Aluminum bioavailability from the approved food additive leavening agent acidic sodium aluminum phosphate, incorporated into a baked good, is lower than from water
#4 - Is it possible to braze ceramics.pdf
The development of karst is a complex system driven by the dissolution of a host rock and the subsequent removal of dissolved matter by moving water. It is the process that, at various stages, initiates or triggers associated processes including erosion, collapse and subsidence. The dissolution of sulphate rocks proceeds by different mechanisms and at different rates to those associated with the dissolution of carbonate rocks. For each rock type different factors influence the process. This chapter is an attempt to summarise the present knowledge of the dissolution chemistty and kinetics of gypsum and anhydrite. These are important for the genetic interpretation of karst features in these rocks. The gypsum-anhydrite-gypsum transitions and recrystallization processes are also addressed, because of their importance to karst development. Many studies have been undertaken on the solubility and dissolution of sulphate minerals, in the context of construction engineering and karst processes. Important works include these of Laptev (1939), Kuznetzov (1947), Shternina (1949), Zdanovsky (1956), Sokolov (1962), Zverev (1967), Lui & Nancollas (1971), Blount & Dickson (1973), Mel'nikova & Moshkina (1973), Wigley (1973), Gorbunova (1977), James & Lupton (1978), Kushnir (1988). The most comprehensive recent account is that of James (1992).
The dissolution and conversion of gypsum and anhydrite
A series of copolymer containing sulfonyl and carboxyl units were synthesized and used in combination with a bisvinyl ether monomer in the form of thin film. It was found that the polymer matrix became completely insoluble in aqueous solution after baked at low temperature around 100 oC and then turned to be highly soluble in aqueous solution, even in neutral water, when exposed to high temperature above 200 oC. Systematic investigations by using DSC, TG and FTS and a homemade apparatus for monitoring film thickness change in dissolving revealed that the insolubilization at low temperature was enabled by thermally induced crosslinking between vinyl group of the bisvinyl ether monomer and carboxyl group of the copolymer and the solubilization at high temperature was the result of acidcatalyzed decrosslinking. The sulfonyl group of the copolymer acted as a thermal acid generator. Preliminary imaging experiments showed that this polymer matrix could be possibly applied in thermal laser imaging.
A Novel Polymer Matrix Capable of Crosslinking and Decrosslinking Upon Thermal Irradiation
Wu et al. - A Novel Polymer Matrix Capable of Crosslinking and.pdf
Abstract : Freeze-form Extrusion Fabrication (FEF) is an environmentally friendly solid freeform fabrication method that uses aqueous pastes to fabricate ceramic-based components. The process uses only small quantities (2 to 4 vol.%) of organic binder. Using the FEF process, 3-D ceramic components have been fabricated from aluminum oxide (Al2O3) by extrusion deposition of Al2O3 paste in a layer-by-layer manner utilizing a 3-D gantry controlled by a computer using Labview software. Sintered samples have achieved 98% of their theoretical density, demonstrating the feasibility of the FEF process.
FREEZE-FORM EXTRUSION FABRICATION OF ALUMINA COMPONENTS USING AQUEOUS PASTE (PREPRINT)
"According to Sofie’s work [Sofie], 6 vol.% of glycerol will effectively optimize water crystallization to avoid large elongated crystal formation"
A combination of rapid prototyping processes (3D Systems ' stereolithography and Sanders Prototyping's ModelMaker) are combined with gelcasting to produce high quality silicon nitride components that were performance tested under simulated use conditions. Two types of aerospace components were produced, a low-force rocket thruster and a simulated airfoil section. The rocket was tested in a test stand using varying mixtures of H2 and O2, whereas the simulated airfoil was tested by subjecting it to a 0.3 Mach jet-fuel burner flame. Both parts performed successfully, demonstrating the usefulness of the rapid prototyping in efforts to effect materials substitution. In addition, the simulated airfoil was used to explore the possibility of applying thermal/environmental barrier coatings and providing for internal cooling of ceramic parts. It is concluded that this strategy for processing offers the ceramic engineer all the flexibility normally associated with investment casting of superalloys.
PRODUCTION STRATEGIES FOR PRODUCTION-QUALITY PARTS FOR AEROSPACE APPLICATIONS
A series of low-toxicity gelcasting systems has been developed. The reagents used in these systems have very low acute toxicity. The new systems perform at least as well as, and in some cases better than, the original acrylamide-based system. The development of these systems is described herein, including the search for new gel compositions, the study of suspensions made with the new gel precursor solutions, and pyrolysis of the dried gels and gelcast parts. Applications of the new gelcasting systems include complex silicon nitride parts, large-diameter rings, rapid prototyping by green machining, and metal-powder gel casting.
Development of Low-Toxicity Gelcasting Systems
Mechanical properties and transition temperatures of cross-linked oriented gelatin
Mechanical properties and transition temperatures .pdf
This invention is concerned with the production of glass-ceramic articles from glasses within the Li2O-FeO-Al2O3-SiO2 system which, when nucleated with TiO2 or a combination of TiO2 and ZrO2 and exposed to carefully-defined heat treatments, will crystallize in situ to bodies having highly-durable integral surfaces exhibiting distinctly metallic lusters. The lustrous surfaces are reflective to visible light and, when developed upon previously polished surfaces, can produce mirror-like finishes with good color and spatial reproduction of reflected images. On slightly irregular or non-planar surfaces as, for example, fractured or as-poured surfaces, an appearance similar to metal plating is observed.
Glass-ceramic articles with reflective surfaces
Classifications C03B32/02: Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles C03C10/0027: Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
Microwave sintering of transparent alumina
Great shots of grain boundaries, 0.05% MgO had substantial effect on grain structure. Acetone solvent, 'ultrapure hydrogen atmosphere'.
The article describes a new method which increases radiation heat transfer of furnace refractory linings. The method, which is the application of a high emissivity coating, results partly in energy savings, partly increases gas tightness and life span of the lining. As heating time is decreased, the method also makes the operation of the furnace more flexible. Application of ENECOAT furnace coating increases the emissivity of ceramic fibre insulations by 45 %, while that of shamotte by 20 %. The phenomenon is illustrated by infrared thermograms. Industrial applications are also referred to.
ENERGY CONSERVATION THROUGH INCREASED EMISSIVITY IN FURNACES
Periodica Polytechnica Mechanical Engineering
Abstract. In this study, aluminum nitride films were formed on aluminum substrates by gas nitriding in order to improve their low emissivities. To accomplish this, aluminum alloys were subjected to nitriding conditions at 773 and 823 K for 0–5 h, using alumina and magnesium powders. The resulting aluminum nitride films were several micrometers thick and the films were dark brown or black. The surface structures of the aluminum nitride films were investigated using a scanning electron microscope, which showed fine acicular aluminum nitride nodules with diameters on the order of several micrometers. Emissivities were evaluated at 298 K using Fourier transform infrared spectroscopy, in a wavelength range of 2–14 µm. Total emissivities at temperatures between 323 and 383 K were estimated from emissivity results obtained at 298 K. It was subsequently found that emissivity decreases with increasing wavelength and an emissivity of 0.80 was observed at a wavelength of 2 µm. Total emissivity was 0.49 % at 298 K and was in excess of 0.50 between 323 and 383 K.
Surface Structure and Emissivity of Aluminum Nitride Films
The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles (solid, hollow, and core-shell spherical), the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.
Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications
International Journal of Minerals, Metallurgy, and Materials
Normal spectral emittance measurements were made on a two-layer ceramic thermal barrier coating system developed at the NASA Lewis Research Center. This system consists of a metal substrate, a NiCrAlY bond coating, and a yttria-stabilized ceramic coating. The normal spectral emittance was used to calculate the thermal radiation properties of hemispherical total absorptance and emittance of the NASA coating system. The normal spectral emittance of the coating system was obtained at a single bond coating thickness of 0.010 centimeter, at ceramic coating thicknesses of zero to 0 . 0 7 6 centimeter, at wavelengths of 0.4 to 14.6 micrometers and at temperatures of 300 to 1590 K. These data were transformed into hemispherical total emittance values and correlated with respect to ceramic coating thickness and temperature using multiple regression curve fitting techniques. Equations were obtained which can be easily used by a designer to calculate the coating system hemispherical total absorptance a t temperatures of 700 to 2800 K and the coating system hemispherical total emittance at ternperatures of 700 to 1590 K. The data show that the NASA coating system is highly reflective and therefore can significantly reduce radiation heat loads on cooled gas turbine engine components. Calculation of the radiant heat transfer within the nonisothermal, translucent ceramic coating material shows that a designer, with little loss of accuracy, can use the gas-side ceramic coating surface temperature in heat transfer analysis of radiation head loads on the coating system.
Emittance and absorptance of NASA ceramic thermal barrier coating system
Ceramics Articles @ Ceramics Made Easy: How to Cast Wax in a Plaster Mold (About Ceramic Molds)
Gelatin Manufacturers Institute of America Members as of January 2012
VAPOR PRESSURE OF COPPER OXIDE AND OF COPPER
Journal of the American Chemical Society
Fire Ratings Of Engineering Plastics - About Plastics
The use of water-based systems represents an interesting alternative to the widespread non-aqueous tape-casting but the low strength of water-based binders generally limits their applicability. A tapecasting slurry is a complex system where each organic component has a substantial eflect on the rheological behaviour. In this study the eflect of the dispersant and binders in alumina aqueous tapecasting slurries were characterized with electrophoretic mobility and rheological measurements. In aqueous medium, a 4,5-dihydroxy-1,3_benzenedisulfonic acid, wasfound to be a very eflective dispersant for alumina. The amount of dispersant required to achieve a minimum of viscosity was equal to 0.2 wt%. Two aqueous emulsions of acrylic polymers were used as binders. These binders strongly aflect the rheology of the suspensions. The best conditions to obtain a homogeneous stable slurry with a high powder loading suitable for tapecasting were determined in terms of order of component addition, rheological behaviour and ageing of the suspensions. Acrylic binders should act through a cohesive mechanism and lead to green tapes with good mechanical strength. Published by Elsevier Science Limited.
Aqueous suspensions for tape-casting based on acrylic binders
2.3.1 Zeta-potential experiments Electrokinetic measurements provide information on the magnitude of the electrostatic forces of repulsion between ceramic particles. Zeta potential values of the alumina particle charges in the suspensions were measured using an Electrokinetic Sonic Amplitude (ESA) measurement apparatus (Model ESA 8000 Matec). This technique is based upon the acoustic wave which is generated by the respective motion of the electric double-layer ions and of the charged particles submitted to a high frequency alternating electric field (1 MHz). This motion generates a sound wave at the same frequency as the electric field with an amplitude proportional to the electrostatic potential at the shear plane where the zeta potential is defined, to the particle concentration and to the amplitude of the applied electric field. The ultrasonic signal is detected and converted to a voltage (ESA) by a piezoelectric transducer. In the case of our suspensions, the ESA data are directly proportional to the zeta potential, then the curves of variations of the electrokinetic properties in function of pH and/or dispersant amounts will be presented with ESA values as the Y axis.
Pagnoux et al. - 1998 - Aqueous suspensions for tape-casting based on acry.pdf
Cookbook for Do-it-yourself Transformer Design
Elektronik - Cookbook for Do-it-yourself Transformer Design.pdf
Sorption of ethyl acetate and d-limonene in poly(lactide) polymers
Journal of the Science of Food and Agriculture
Auras et al_2006_Sorption of ethyl acetate and d-limonene in poly(lactide) polymers.pdf
Poly(lactic acid) (PLA) films have a great interest for the food packaging. But the interaction between the food and the packaging must be investigated. The gas and aroma barrier properties of PLA were analysed and the influence of PLA crystallinity on these properties was studied because of processing conditions. The crystallinity seems to have no effect on helium and oxygen barrier properties but ethyl acetate as aroma compound has a plasticizing effect on the PLA film.
Influences of the crystallisation rate on thermal and barrier properties of polylactide acid (PLA) food packaging films
International Journal of Material Forming
Discusses Tg after ethyl acetate exposure
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Agar Agar – The Vegan Gelatin Alternative
"Agar is a great medium for scientists and biologists needing an inert substance to grow bacteria and fungus; agar is great for this because it stays in gel form at temperatures that would melt gelatin; gelatin turns liquid at 37 C whereas agar doesn’t melt until it reaches 85 C."
Different from the oxidation kinetics of other nitrides, the oxide layer on AlN can easily reach tens of micrometers at a temperature above 1200 ℃. In the present study, the oxidation mechanism of AlN is investigated through microstructure observation. The analysis indicates that the oxide layer is full of small pores. The formation of pores generates additional surface area to induce further reaction. The reaction thus controls the oxidation in the temperature range from 1050 to 1350 ℃. The oxidation rate becomes slow as the oxide layer reaches a critical thickness.
Oxidation mechanism of aluminum nitride revisited
Agar does not seem to be an ideal binder for gelcasting. The high viscosity mandates small concentrations of binder, so green strength is very poor. High temperatures are required to prevent gelation.
Lattice Energy Calculator (Semester 2 Study Vacation)
A large quantity of white gas containing titanium dioxide and hydrogen chloride was generated unexpectedly during an experiment in a chemical laboratory. Fourteen students and staff complained of nausea, dyspnea, or respiratory irritation immediately after inhaling the gas. On arrival at Saint Luke's International Hospital, more than half of the patients presented with low-grade fever. Symptoms spontaneously resolved soon after admission, although the low-grade fever persisted until the following morning. Low-grade fever after inhalation exposure is not explicable by hydrogen chloride inhalation and therefore appeared to be caused by titanium dioxide inhalation, manifesting as metal fume fever. Titanium dioxide is thought to have no remarkable human toxicity and is considered to be safe clinically. To our knowledge, this is the first report of titanium dioxide inhalation as the potential cause of metal fume fever in humans. Correlations between the degree of fever and quantity and concentration of inhaled titanium dioxide remain to be determined.
Acute group poisoning by titanium dioxide: inhalation exposure may cause metal fume fever
Acute group poisoning by titanium dioxide
The American Journal of Emergency Medicine
Understanding isolator standards and certification to meet safety requirements
Implementation of a Single-Phase Electronic Watt-Hour Meter Using the MSP430AFE2xx
Download scientific diagram | Tensile strength of PVA fiber at various temperatures [9]. from publication: Engineered Cementitious Composites for Modern Civil Engineering Structures in Hot Arid Coastal Climatic Conditions | Engineered Cementitious Composite (ECC) is an exclusive type of cement mixture with unique composition of low volume fibers and different composites so as to impart high ductility, high tensile strength besides ability to repair. Conventional concrete and fiber reinforced... | Arid, Civil Engineering and Climate | ResearchGate, the professional network for scientists.
Fig. 1. Tensile strength of PVA fiber at various temperatures [9].
THERMAL PERFORMANCE OF CRYOGENIC MULTILAYER INSULATION AT VARIOUS LAYER SPACINGS
Johnson - THERMAL PERFORMANCE OF CRYOGENIC MULTILAYER INSULA.pdf
The combined radiation/conduction heat transfer in high-temperature multilayer insulations for typical reentry of reusable launch vehicles from low Earth orbit was investigated experimentally and numerically. The high-temperature multilayer insulation investigated consisted of gold-coated reflective foils separated by alumina fibrous insulation spacers. The steady-state heat transfer through four multilayer insulation configurations was investigated experimentally over the temperature range of 300-1300 K and environmental pressure range of 1.33 × 10-5-101.32 kPa. It was shown that including the reflective foils reduced the effective thermal conductivity compared to fibrous insulation sample at 1.5 times the density of the multilayer sample. A finite volume numerical model was developed to solve the governing combined radiation/conduction heat transfer equations. The radiation heat transfer in the fibrous insulation spacers was modeled using the modified two-flux approximation assuming anisotropic scattering and gray medium. The numerical model was validated by comparison with steady-state experimental data. The root mean square deviation between the predicted and measured effective thermal conductivity of the samples was 9.5%.
HEAT TRANSFER IN HIGH-TEMPERATURE MULTILAYER INSULATION
Daryabeigi et al. - HEAT TRANSFER IN HIGH-TEMPERATURE MULTILAYER INSUL.pdf
Technology & Engineering / Chemical & Biochemical
Technology & Engineering / Textiles & Polymers
This book exclusively focuses on the science and fundamentals of polymer gels, as well as the numerous advantages that polymer gel-based materials offer. It presents a comprehensive collection of chapters on the recent advances and developments in the core science and fundamentals of both synthetic and natural polymer-based gels, and pays particular attention to applications in the various research fields of biomedicine and engineering. Key topics addressed include: polysaccharide-based gels and their fundamentals; stimuli-responsive polymer gels; polymer gels applied to enzyme and cell immobilization; chitosan-based gels for cancer therapy; natural polymeric and gelling agents; radiation dosimetry; polymeric gels as vehicles for enhanced drug delivery across the skin; transport in and through gel; and polymer gel nanocomposites and functional gels. The book’s extensive and highly topical coverage will appeal to researchers working in a broad range of fields in industry and academia alike.
Alginate crosslinking is reversible with sodium citrate chelator.
Rigidity of Two-Component Hydrogels Prepared from Alginate and Poly(ethylene glycol)−Diamines
Properties of silicon carbide ceramics from gelcasting and pressureless sintering
THE HYDRATION OF MAGNESIUM OXIDE WITH DIFFERENT REACTIVITIES BY WATER AND MAGNESIUM ACETATE
MgO + Citric acid = magnesium citrate
Aphane - THE HYDRATION OF MAGNESIUM OXIDE WITH DIFFERENT RE.pdf
Copyright © 1965 John Wiley & Sons, Inc.
Ultraviolet-induced crosslinking of the film of polyvinyl alcohol with different degrees of polymerization was investigated in air at 25°C. in the presence of sodium benzoate as a sensitizer. Crosslinking is always accompanied by photolysis of the sensitizer. In the absence of the sensitizer, no crosslinking occurred. The gel content increased with irradiation time, and tended to a limiting value, depending on the initial sensitizer concentration. The final gel content increased as a function of the initial amount of sodium benzoate. A plot of solubility (S + S1/2) against the reciprocal of the concentration of sensitizer converted gives a straight line in each case. The number of crosslinks is directly related to the number of sensitizer molecules destroyed. The crosslinking occurred predominantly, and main-chain scission was negligible. This result is in marked contrast to the effect of ionizing radiation, since the ionizing radiation causes only degradation under the identical conditions. This ultraviolet method was applied successfully to the crosslinking of water-soluble cellulose derivatives, such as methyl cellulose and sodium carboxymethyl cellulose.
Ultraviolet-induced crosslinking of poly(vinyl alcohol) in the presence of sensitizers
Takakura et al_1965_Ultraviolet-induced crosslinking of poly (vinyl alcohol) in the presence of.pdf
Takakura et al. - 1965 - Ultraviolet-induced crosslinking of poly(vinyl alc.pdf
Abstract , A novel and simple method for gelcasting of alumina was developed using a nontoxic and water-soluble copolymer of isobutylene and maleic anhydride (commercially called Isobam). In this method, there is requirement of only a small amount of Isobam (0.3 wt%) and neither initiators nor dispersants are needed for preparation and gelation of a 50 vol% solids loaded alumina slurry. The gelation rate increased with increasing solids loading but decreased with increasing Isobam content. A typical gelation time was 38 min for the slurry containing 50 vol% solids loading and 0.3 wt% Isobam. The resultant wet gel was strong enough to allow reversible bending and twisting. This simple gelling system is attractive for wet forming of ceramics because only a single additive, which acts as both dispersant and gelling agent at room temperature in air, is used.
Room-temperature gelcasting of alumina with a water-soluble copolymer
Three methods for in situ cross-linking of polyvinyl alcohol films for application as ion-conducting membranes in potassium hydroxide electrolyte
Philipp and Hsu - Three methods for in situ cross-linking of polyvin.pdf
New crosslinked cast films based on poly(vinyl alcohol): Preparation and physico-chemical properties
Crosslinking of polymers by the effect of ultraviolet radiation Crosslinking of polyvinyl alcohol) in the presence of terephthalic aldehyde
Polavka et al. - 1980 - Crosslinking of polymers by the effect of ultravio.pdf
In situ citric acid crosslinking of alginate/polyvinyl alcohol electrospun nanofibers
Intermediate compositions enable synergised, strong-and-tough dual-physical double-network hydrogels of dispersion-induced rigid, ionic alginate-networks interlocking with global ductile, hydrogen-bonded poly(vinyl alcohol)-network. , Strong and tough poly(vinyl alcohol) (PVA)/alginate hydrogen-bonded-ionic dual-physical double-network (DN) hydrogels have been successfully prepared by a facile route of a freeze–thaw (25–25–25 °C) cycle followed by concentrated (1.0 mol L −1 of) aqueous-Ca 2+ immersion of PVA/Na alginate (SA) mixed aqueous solutions. It was found that, at mole ratios of the PVA- to SA repeat units of 20/1 to 80/1, the DN gels likely evolved a semi-interpenetrating polymer network (IPN) morphology of rigid alginate networks dispersed in while interlocking with ductile PVA network to accomplish DN synergy that gave their high strength and toughness, where the high alginate rigidity originated probably from its dense cross-link induced syneresis and dispersion along crosslink-defective voids to result in little internal stress concentration. Tentatively mechanistically, as the 20/1–80/1 DN gels were stretched steadily, their mechanical response was gradually differentiated into distinct synergistic states: the sparsely hydrogen-bonded PVA served as a ductile matrix to bear small fractions of the established stresses at its large elongations; whereas the densely ionically ( i.e. Ca 2+ ) cross-linked alginate functioned as a rigid skeleton to sustain the remaining larger stresses upon its smaller local strains. Promisingly, this ductile-rigid matrix-skeleton synergistic mechanism of semi-IPN morphology may be universally extended to all A/B DN hydrogels of large A–B rigidity (or cross-link density) contrast, whether the cross-link nature of network(s) A or B is covalent, ionic, hydrogen bonded or van der Waals interacted. The strong and tough DN gels also displayed satisfactory self-recovery of viscoelastic behaviour, in that their Young's modulus and dissipated energy in the uniaxial tensile mode and dynamic storage and loss moduli in the oscillatory shear mode all recovered significantly from non-linear viscoelastic regimes despite different degrees of failure to revert to (quasi)linear viscoelasticity.
Strong, tough and mechanically self-recoverable poly(vinyl alcohol)/alginate dual-physical double-network hydrogels with large cross-link density contrast
Li et al. - 2018 - Strong, tough and mechanically self-recoverable po.pdf
A new cell immobilization technique is described in which polyvinyl alcohol is crosslinked with boric acid, with the addition of a small amount of calcium alginate. The presence of the calcium alginate improves the surface properties of the beads, preventing agglomeration. A pure culture of phenol-degrading Pseudomonas was immobilized in the PVA-alginate beads. Phenol was successfully degraded in a fluidized bed of the beads, indicating that cell viability was maintained following the immobilization procedure. The PVA-alginate beads proved to be very strong and durable, with no noticeable degradation of the beads after 2 weeks of continuous operation of the fluidized bed.
Cell immobilization using PVA crosslinked with boric acid
Polyvinyl alcohol, (PVA) was prepared using polyvinyl acetate emulsion (manufactured by Al-Jihad factory, That-Al-Sawary Company) as a local raw material. In this investigation, polyvinyl acetate emulsion was converted to solid form by coagulation the polymer from its emulsion using sodium sulphate salt as coagulant aid, then alcoholyzed the solid polyvinyl acetate in methanol using sodium hydroxide as catalyst, polyvinyl alcohol produced by this method is a dry, white to yellow powder.
Preparation of Polyvinyl Alcohol from Local Raw Material
Haweel and Ammar - 2008 - Preparation of Polyvinyl Alcohol from Local Raw Ma.pdf
This paper is concerned with the cross-linking of poly(vinyl alcohol) (PVA) using maleic acid as the cross-linker. The curative (maleic acid) dose and the curing temperature and time were varied between 2.5 and 60% (w/w), 120 and 160 -C and 30 and 120 min, respectively. From a thorough swelling study in both hot and cold water (percentage swelling, gel content, swelling ratio, etc-) the optimum curative dose and curing conditions have been evaluated. The molecular weight between the cross-links exhibited a sharp fall up to a maleic acid dose of 20% (w/w). A comparative evaluation of maleic acid cross-linked and heat-treated PVA ﬁlms has been done. Better heat stability for maleic acid cross-linked PVA was observed from thermogravimetric analysis. A shift in glass transition temperature was observed for both heat-treated and maleic acid treated PVA compared with the virgin one. IR spectroscopic study indicated the presence of an ester linkage and an oleﬁnic double bond in maleic acid treated and heat-treated PVA ﬁlms, respectively. Maleic acid crosslinked PVA is quite stable in different polar and nonpolar solvents. A deﬁnite structural pattern has been observed in maleic acid cross-linked PVA ﬁlms through scanning electron microscopy.
Studies On The Crosslinking Of Poly (Vinyl Alcohol)
Gohil et al. - 2006 - Studies On The Crosslinking Of Poly (Vinyl Alcohol.pdf
Submicrometer alumina suspensions, dispersed in aqueous acidic solutions of polyvinyl alcohol (PVA) and 2,5-dimethoxy-2,5-dihydrofuran, have been evaluated for suitability as a cross-linkable binder system for casting complex-shaped ceramic components. Suspensions of up to 50 vol% solids have rheological behavior, which is suitable for pouring and filling molds. Complex-shaped green bodies are then formed by heating the suspension in the mold for a period of time (typically 15–60 min) at moderate temperature (60°–80°C) to gel the suspension. High green densities (58%–62% of full density) can be obtained. The dried green bodies have strength in excess of 1 MPa and may be readily machined. No more than 1–3 wt% PVA per weight of alumina is necessary, ensuring burnout that minimizes generation of flaws. The ceramic components can be fired to >96% of full density when fired for 2 h at 1400°–1450°C. Cross-linkable PVA may receive more widespread acceptance in ceramic processing than previous gelcasting formulations because PVA is already a common processing additive.
Cross-linked Polyvinyl Alcohol as a Binder for Gelcasting and Green Machining
Chabert et al. - 2008 - Cross-linked Polyvinyl Alcohol as a Binder for Gel.pdf
Copyright © 2001 John Wiley & Sons, Inc.
Poly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); their swelling characteristics and tensile strength were also determined. The DSC results for the gels displayed depressions of the melting and crystallization temperatures, as well as a decrease of the heat of fusion, when compared to those of PVA free of crosslinker. The DMA analysis revealed that: (1) The glass transition temperature of the wet PVA was lower than that of the dry one, indicating that the water had a plasticizing effect. (2) The gels had a lower glass transition temperature than PVA. (3) The glass transition temperature of the wet gels increased with increasing crosslink density. Possible explanations are provided for these observations. Whereas the thermogravimetric curves of PVA exhibited a single degradation peak, two degradation peaks were detected for the crosslinked PVA. The wet PVA and PVA gels displayed lower tensile strengths and higher elongations than the dried ones. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1816–1823, 2001
On the viscoelastic properties of poly(vinyl alcohol) and chemically crosslinked poly(vinyl alcohol)
The glass-transition temperature (Tg) is a fundamental property of all organic binders, It is illustrated with polyethylene glycol (PEG)-plasticized polyvinyl alcohol (PVA) binder systems that densification is enhanced when the binder Tg, is below the pressing temperature. This is a result of the increased deformability of the binder system and the decrease in the granule strength. Because of the reduction in the binder film strength with increasing PEG content, increasing the PEG content to lower the binder Tg, results in reductions in the compact green strength.
Effect of Glass-Transition Temperature of Polyethylene Glycol-Plasticized Polyvinyl Alcohol on Granule Compaction
Gel-Free Process of Saponification of Polyvinyl Acetate in Water–Alcohol Media
International Polymer Science and Technology
Boiko et al. - 2003 - Gel-Free Process of Saponification of Polyvinyl Ac.pdf
In recent years, a technological breakthrough in the pharmaceutical and biomedical fields have been reflected in the development of more complex, safe and effective dosage forms to improve the administration, delivery, disposition and stability of drugs, as well as at creating more biocompatible and biodegradable materials. As a result, modified release devices and functional coatings which improve the effectiveness and efficacy of drugs have been generated. This advancement has been achieved by physical or chemical modification of natural or semisynthetic polymers which stabilize and protect drugs against harsh environmental factors. Therefore, the development of novel excipients with a high functionality and robustness has become an important quest. Among these materials, polyvinyl alcohol is one of the most versatile and biocompatible, since by chemical or physical modification its properties are modulated, improving drug stability, drug targeting, and ensures patient compliance. Freezing-thawing cycles, heat treatment and formation of composites are the most significant physical modifications to improve the performance of polyvinyl alcohol. On the other hand, the chemical modifications by cross-linking with aldehydes, carboxylic acids, sodium tetraborate, epichlorohydrin have enhanced the physical and mechanical properties, such as the oil sorption ability, oxygen and waterproof characteristics, mechanical strength, drug diffusion and rate of swelling.
A review of polyvinyl alcohol derivatives: Promising materials for pharmaceutical and biomedical applications
Crosslinking reactions are one of the most commonly used techniques to improve physical properties of polyvinyl alcohol (PVA). Commonly used crosslinkers for these reactions are di-functional compounds, such as glutaraldehyde and glyoxal. The hydroxyl groups of PVA react with aldehydes via formation of acetal bonds hence corsslinking could take place. Quantitative analysis of glyoxal crosslined PVA will be described in this report. A convenient FTIR method has been established to analyze degree of crosslinking in PVA. Analysis by 1H NMR spectroscopy methods will also be described.
Crosslinking reaction of poly(vinyl alcohol) with glyoxal
Characteristics of poly(vinyl alcohol) films crosslinked by cinnamaldehyde with improved transparency and water resistance
Originally developed in the late 1960s, anodic bonding, also known as electrostatic bonding, field-assisted bonding or Mallory bonding, has become one of the most important silicon packaging techniques. Despite its industrial relevance the bonding mechanism is mainly only qualitatively understood and is almost solely applied to the bonding of silicon to Pyrex glass. The objective of the present paper is to review the current state of knowledge of the anodic bonding process. Possible material combinations and current scientific and industrial applications of this bonding technique are reviewed. The various aspects of the bonding process, such as the creation of intimate contact, the cation movement in the glass and the interfacial chemical reactions, are discussed in detail and related to the external current measured during bonding to describe the bonding process quantitatively. A better understanding of the process itself should help not only to improve the process control and the quality of devices, but also to broaden the application of this successful bonding technique to more challenging designs, to smaller device sizes and to systems other than silicon–Pyrex glass.
Knowles and van Helvoort - 2006 - Anodic bonding.pdf
Gelatine Handbook: Theory and Industrial Practice
This is a truly magnificent book. It contains 350 pages of nothing but gelatine. It begins with a rousing and exhaustive traipse through the history of gelatin, containing such chapters as 1.1.3 Pure Luxury for Kings and Aristocrats and 1.1.5 Suddenly, Medicines No Longer Had a Bitter Taste One wonders if the authors paused to giggle every few sentences. Chapter 3 has a list of all organic gels.
Schrieber and Gareis - 2007 - Gelatine Handbook Theory and Industrial Practice.pdf
Injection moulding in water is receiving great interest for the low-cost production of near-net-shaped ceramic parts. In this technique, aqueous suspensions are gelated in the presence of a low concentration of gelling additive. In this work, alumina bodies are injection moulded in water by adding 1 wt.% agarose. The agarose is incorporated to the previously dispersed slurry and the blend is then milled in a ball mill. Agarose dissolves upon heating, but the dispersed slurry maintains stability up to 708C. Rheological behaviour is studied as a function of temperature for the ceramic slurry with and without agarose. The injected parts show a homogeneous microstructure without binder agglomerates. q 2001 Elsevier Science B.V. All rights reserved.
Aqueous injection moulding of alumina using agarose
Millán et al. - 2001 - Aqueous injection moulding of alumina using agaros.pdf
Patterned negative-tone images on the polymer film have been prepared based on the photoinduced crosslinking of water soluble poly(vinyl alcohol) (PVA) in the presence of various alcohols. Irradiation of a polymer film containing PVA, a photoacid generator and an alcohol as a crosslinker with 254-nm UV through a photomask followed post-exposure bake (PEB) allowed generation of negative-tone relief images at 5 µm resolution in the polymer film. Among various alcohols tested, aromatic alcohols such as pyrogallol and resorcinol were found to be superior to aliphatic alcohols such as sucrose and inositol in terms of resist sensitivity.
Alcohol-Assisted Photocrosslinking of Poly(vinyl alcohol) for Water-Soluble Photoresists
Shim and Kim - Alcohol-Assisted Photocrosslinking of Poly(vinyl a.pdf
DeTox additive makes Ethylene Glycol safe That's pretty neat!
Sciencemadness Discussion Board - purification of manganese dioxide from batteries - Powered by XMB 1.9.11
<span style="color: #000000; font-family: Arial; font-size: 12px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #fffbe8; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">Having said that, in <strong style="color: #000000; font-family: Arial; font-size: 12px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #fffbe8; text-decoration-style: initial; text-decoration-color: initial;">spent<span style="color: #000000; font-family: Arial; font-size: 12px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #fffbe8; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> alkaline batteries the Mn will be no longer as MnO2 but also as lower oxides because that's what using the batteries does to the initial MnO2. So you would have to sacrifice new batteries.
We map the ultrasonic (8 MHz) speed and attenuation of edible-grade gelatin in water, exploring the key dependencies on temperature, concentration and time. The ultrasonic signatures of the sol-gel transition, confirmed by rheological measurements, and incomplete gel formation at low concentrations, enable a phase diagram of the system to be constructed. Sensitivity is also demonstrated to the kinetics of gel formation and melting, and associated hysteresis effects upon cyclic temperature sweeps. Furthermore, simple acoustic models of the sol and gel state enable estimation of the speed of sound and compressibility of gelatin. Our results demonstrate the potential of ultrasonic measurements to characterise the structure and visco-elasticity of gelatin hydrogels.
Ultrasonic study of the gelation of gelatin: phase diagram, hysteresis and kinetics
Ultrasonic study of the gelation of gelatin
Parker_Povey_2012_Ultrasonic study of the gelation of gelatin.pdf
Gelcasting is a novel method for molding ceramic powder based on a synthesis of concepts derived from traditional ceramics and polymer chemistry. Gelcasting of alumina is described in this paper. The process is based on the in situ polymerization of acrylamide monomers as the setting mechanism for forming the green body. It has the following features: slurries with high solids loading and low viscosity (1.8 Pa·s at 62 vol% solids), dried bodies containing less than 4 wt% binder, and the ability to fabricate complex-shaped bodies.
Rheology of Cross‐Linked Chitosan–Alumina Suspensions Used for a New Gelcasting Process - Johnson - 2002 - Journal of the American Ceramic Society - Wiley Online Library
The rheological behavior of a low-toxicity, aqueous, Al2O3–chitosan–2,5-dimethoxy-2,5-dihydrofuran (DHF) system was examined over a temperature range of 20°–98°C. At room temperature, a high-volume-fraction solids, shear-thinning suspension was produced. The suspension remained in a liquidlike state for ∼24 h. By contrast, at elevated temperatures, DHF became active as a cross-linking agent for chitosan, and a rapid transition from liquidlike to solidlike suspension behavior was apparent. The rate of gelation and the gel strength increased with increased temperature and increased DHF concentration. Gelation occurred at pH 1.4–4.5, which is a complex function of pH. At pH above ∼4, rapid gelation was not possible because of the low-pH solution conditions required for the cross-linking reaction. An examination of the strength and shape-forming properties of several Al2O3–chitosan–DHF systems showed them to be suitable for production of strong, reliable, complex-shaped ceramic components. In particular, small, dense Al2O3 pseudorotors were formed and found to be of sufficient strength for mold removal and subsequent handling. In all formulations examined, chitosan concentrations of <0.5 wt% (by weight of ceramic) were required; therefore, the need for a discrete binder burnout process was eliminated.
Rheology of Cross-Linked Chitosan–Alumina Suspensions Used for a New Gelcasting Process
Gelcasting: From laboratory development to
Oak Ridge National Lab., TN (United States)
Gelcasting: from laboratory development toward industrial production
Methods currently used to prepare fiber-reinforced, high-temperatureresistant polyphenylquinoxaline (PPQ) composites employ extremely viscous, low-solid-content solutions of high-molecular-weight PPQ polymers. An improved approach, described in this report, consists of impregnating the fiber with a solution of the appropriate monomers instead of a solution of previously synthesized high-molecular-weight polymers. Polymerization of the monomers occurs in situ on the fiber during the solvent removal and curing stages. The in situ polymerization approach greatly simplifies the fabrication of PPQ - graphite fiber composites. The use of low-viscosity, monomeric-type solutions facilitates fiber wetting, permits a high solid content, and eliminates the need for prior polymer synthesis.
IN SITU POLYMERIZATION OF MONOMERS FOR POLYPHENYLQUINOXALINE -
Method for molding ceramic powders using a water-based gel casting
Abstract: The present study reports green electrospinning of polyvinyl alcohol (PVA) / citric acid nanofiber membranes, and the membranes were then crosslinked by heat treatment. The electric conductivity of the PVA aqueous solution increases rapidly and the growth slows down along with the increase of citric acid content. The viscosity of 13 wt % PVA aqueous solutions with citric acid had a small increase and remained stable in one week, which was suitable for electrospinning fibers. Porous, interconnected nonwoven nanofiber membranes were electrospun from a thoroughly mixing of PVA / citric acid aqueous solution. The membranes were then heat treated at 140 oC for 2 h. The postelectrospinning crosslinked nanofiber membranes were insoluble in water, while the non-crosslinked electrospun nanofiber membranes dissolved instantaneously. FT-IR spectrum, X-ray diffraction, and DSC thermograms reveal that crosslinking of PVA nanofiber membranes occurred through esterfication reaction during heat treatment.
Green electrospinning and crosslinking of polyvinyl alcohol / citric acid
Creative Commons Attribution-ShareAlike License
Starch gelatinization is a process of breaking down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water. This irreversibly dissolves the starch granule in water. Water acts as a plasticizer. Three main processes happen to the starch granule: granule swelling, crystallite or double helical melting, and amylose leaching. During heating, water is first absorbed in the amorphous space of starch, which leads to a swelling phenomenon. Water then enters via amorphous regions the tightly bound areas of double helical structures of amylopectin. At ambient temperatures these crystalline regions do not allow water to enter. Heat causes such regions to become diffuse, the amylose chains begin to dissolve, to separate into an amorphous form and the number and size of crystalline regions decreases. Under the microscope in polarized light starch loses its birefringence and its extinction cross. Penetration of water thus increases the randomness in the starch granule structure, and causes swelling; eventually amylose molecules leach into the surrounding water and the granule structure disintegrates.The gelatinization temperature of starch depends upon plant type and the amount of water present, pH, types and concentration of salt, sugar, fat and protein in the recipe, as well as starch derivatisation technology are used. Some types of unmodified native starches start swelling at 55 °C, other types at 85 °C. The gelatinization temperature of modified starch depends on, for example, the degree of cross-linking, acid treatment, or acetylation. Gel temperature can also be modified by genetic manipulation of starch synthase genes. Gelatinization temperature also depends on the amount of damaged starch granules; these will swell faster. Damaged starch can be produced, for example, during the wheat milling process, or when drying the starch cake in a starch plant. There is an inverse correlation between gelatinization temperature and glycemic index. High amylose starches require more energy to break up bonds to gelatinize into starch molecules. Gelatinization improves the availability of starch for amylase hydrolysis. So gelatinization of starch is used constantly in cooking to make the starch digestible or to thicken/bind water in roux, sauce, or soup.
Hydrogels represent a class of high water content polymers with physical or chemical crosslinks. Their physical properties are similar to soft tissues. Cross linking is a stabilization process in polymer chemistry which leads to multidimensional extension of polymeric chain resulting in network structure. Cross-link is a bond which links one polymer chain to other. It can be ionic or covalent. Cross linking changes a liquid polymer into ‘solid’ or ‘gel’ by restricting the ability of movement. When polymer chains are linked together by cross-links, they lose some of their ability to move as individual polymer chains. A liquid polymer (where the chains are freely flowing) can be turned into a ‘solid’ or ‘gel’ by cross-linking the chains together. Cross linking increases the molecular mass of a polymer. Cross-linked polymers are important because they are mechanically strong and resistant to heat, wear and attack by solvents. However, the drawback associated with cross-linked polymers is that they are relatively inflexible when it comes to their processing properties because they are insoluble and infusible.
Table 1 is a great chart of crosslinkers - not exhaustive, though, some missing. Polyethylene can be crosslinked by Silane. I'll get right on that, thanks.
Polyvinyl acetate (PVA, PVAc, poly(ethenyl ethanoate): best known as wood glue, white glue, carpenter's glue, school glue, Elmer's glue in the US, or PVA glue) is an aliphatic rubbery synthetic polymer with the formula (C4H6O2)n. It belongs to the polyvinyl ester family, with the general formula -[RCOOCHCH2]-. It is a type of thermoplastic.
"<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">PVAc emulsions such as <a class="mw-redirect" style="text-decoration: none; color: #0b0080; background: none #ffffff; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;" title="Elmer's Glue-All" href="https://en.wikipedia.org/wiki/Elmer%27s_Glue-All">Elmer's Glue-All<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> contain polyvinyl alcohol as a protective colloid."
Science made alive: Chemistry/Experiments
Fabrication of transparent Y2O3 ceramics via aqueous gelcasting
Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N¢N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densiﬁcation and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum ﬂexural strength, as high as 81.32 MPa, but, simultaneously, a high coefﬁcient of linear expansion (2.56 9 10À6/K at 800°C) and dramatically reduced residual ﬂexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar ﬂexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 9 10À3 (at 1 MHz).
Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting
Wan et al. - 2014 - Effect of Sintering Temperature on the Properties .pdf
Gelcasting of alumina suspensions containing nanoparticles with glycerol monoacrylate
Polysaccharide (glucose-derived polymer), made with acrylic acid and glycidiol.
Glass-to-metal seals are a very important element of the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass encapsulated semiconductor diodes, reed switches, pressure tight glass windows in metal cases, and metal or ceramic packages of electronic components. Properly done, such a seal is hermetic (vacuum tight, good electrical insulation, special optical properties e.g. UV lamps). To achieve such a seal, two properties must hold: The molten glass must be capable of wetting the metal, in order to form a tight bond, and The thermal expansion of the glass and metal must be closely matched so that the seal remains solid as the assembly cools.Thinking for example about a metal wire in a glass bulb sealing, the metal glass contact can break if the CTEs (coefficient of thermal expansion) are not well aligned. For the case that the CTE of the metal is larger than the CTE of the glass, the sealing shows a high probability to break upon cooling. By lowering the temperature, the metal wire shrinks more than the glass does, leading to a strong tensile force on the glass, which finally lead to breakage. On the other hand, if the CTE of the glass is larger than the CTE of the metal wire, the seal will tighten upon cooling since compression force is applied on the glass. According to all requirements that need to be fulfilled and the strong necessity to align the CTE of both materials, there only a few companies offering specialty glass for glass-metal sealing. Such as SCHOTT AG and Morgan Advanced Materials.
<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">copper...to improve the bonding to glass, the oxide layer should be borated; this is achieved by e.g. dipping the hot part into a concentrated solution of <a style="text-decoration: none; color: #0b0080; background: none #ffffff; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;" title="Borax" href="https://en.wikipedia.org/wiki/Borax">borax<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> and then heating it again for certain time. This treatment stabilizes the oxide layer by forming a thin protective layer of <a style="text-decoration: none; color: #0b0080; background: none #ffffff; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;" title="Sodium borate" href="https://en.wikipedia.org/wiki/Sodium_borate">sodium borate<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> on its surface, so the oxide does not grow too thick during subsequent handling and joining. The layer should have uniform deep red to purple sheen.<sup id="cite_ref-elmatpack_3-0" class="reference" style="line-height: 1; unicode-bidi: isolate; white-space: nowrap; font-weight: 400; font-style: normal; font-size: 11.2px; color: #222222; font-family: sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;">[3]<sup id="cite_ref-handbeltube_4-0" class="reference" style="line-height: 1; unicode-bidi: isolate; white-space: nowrap; font-weight: 400; font-style: normal; font-size: 11.2px; color: #222222; font-family: sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;">[4]<span style="color: #222222; font-family: sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> The boron oxide from the borated layer diffuses into glass and lowers its melting point. The oxidation occurs by oxygen diffusing through the molten borate layer and forming copper(I) oxide, while formation of copper(II) oxide is inhibited.<sup id="cite_ref-vacsealtec_2-1" class="reference" style="line-height: 1; unicode-bidi: isolate; white-space: nowrap; font-weight: 400; font-style: normal; font-size: 11.2px; color: #222222; font-family: sans-serif; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: #ffffff; text-decoration-style: initial; text-decoration-color: initial;">[2]
Ceramic insulation/multifoil composite for thermal protection of reentry spacecraft
Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric in nature, i.e., it has both basic and acidic properties. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide or alumina (Al2O3), the latter of which is also amphoteric. These compounds together are the major components of the aluminium ore bauxite.
Aluminum hydroxide is soluble in solutions with a high pH, then decomposes back to aluminum at 400c. Might be useful for casting aluminum? Could also be useful for creating ultrafine aluminum powder or oxide powder. Aluminum hydroxide can form a weak hydrogel. Neat!
Library Catalog: kristilynglass.com Section: Creations
To use compact disks (CDs) or DVDs as tops on my "aurora" decorative pill organizers, as shown above, I had to experiment with various ways to cut the CDs
_eprint: https://ceramics.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1151-2916.1996.tb08006.x
The interaction between citric acid and alumina in aqueous solution is characterized. Adsorption isotherms of the dispersant on the alumina surface, electrophoretic mobility of the alumina particles as a function of the citric acid concentration, and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy of the citratealumina surface complex have been used. The adsorption behavior of citric acid is dependent on the pH of the suspension and the concentration of the citric acid. The maximum amount of citric acid adsorbed on the alumina surface, 2.17 μ.mol/m2 at pH 3, decreases to 1.17 μmol/m2 at pH 8. The adsorption of citrate causes a highly negatively charged powder surface and a shift of the isoelectric point (IEP) to lower pH values. The IEP of alumina can be fixed at any pH value between 9 and 3 by proper adjustment of the citric acid concentration. In situ ATR-FTIR spectroscopy of the citrate-alumina surface complex gives evidence for a direct interaction between the carboxylate groups of the citrate and the surface aluminum(III) atoms. The rheological properties of alumina suspensions are studied as a function of the citric acid concentration. The data obtained from the viscosity and dynamic electrophoretic measurements correlate well and allow the construction of a stability map of alumina suspensions stabilized with citric acid. The influence of citric acid on the viscosity is discussed using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The interaction potential between the particles is determined by the citrate adsorbed on the surface, leading to a negative particle charge, and the citrate anions remaining in the solution, resulting in an increase of the ionic strength. The adsorption of citric acid also creates a steric barrier that inhibits the complete mutual approach of the individual alumina particles.
Citric Acid—A Dispersant for Aqueous Alumina Suspensions
LTCC Thick Film Process Characterization
LTCC Thick Film Process Characterization.pdf
Evolution and application of the Kyropoulos crystal growth method
Sintering of Alumina at Temperatures of 1400 C. and Below
Cutler et al_1957_Sintering of Alumina at Temperatures of 1400 C.pdf
Demystifying the role of sintering additives with ‘‘complexion’’
Dillon_Harmer_2008_Demystifying the role of sintering additives with ‘‘complexion’’.pdf
Contents Introduction Experimental procedure Results and discussion Conclusions References
A physical model for the drying of gelcast ceramics
Vacuum pumps and systems: A review of current practice
Giles - VACUUM PUMPS AND SYSTEMS A REVIEW OF CURRENT PRAC.pdf
Field-assisted sintering technology/spark plasma sintering: mechanisms, materials, and technology developments
Guillon et al_2014_Field-assisted sintering technology-spark plasma sintering.pdf
Brazing ceramic oxides to metals at low temperatures
Effect of MgO additive on microstructure of Al2O3
Harun et al_2012_Effect of MgO additive on microstructure of Al2O3.pdf
Electrically conductive alumina & carbon nanocomposites prepared by spark plasma sintering
Journal of Applied Pharmaceutical Science
In-Situ UV-Photopolymerized PVA-g-GMA Hydrogels for Biomedical Applications: I. Synthesis, Characterizations and Grafting Optimization
Journal of sol-gel science and technology
Evolution of porosity by freeze casting and sintering of sol-gel derived ceramics
Koch et al. - Evolution of Porosity by Freeze Casting and Sinter.pdf
The Thermodynamics of the Silica/Silicon-Oxygen Vapor System
Krieger_1965_The Thermodynamics of the Silica-Silicon-Oxygen Vapor System.pdf
Aluminum Nitride, a Refractory for Aluminum to 2000Â° C
Luks_1942_Vitreous high alumina porcelain.pdf
NP℡_Processing of Ceramic Parts – Pressing.pdf
Mechanical Properties and Performance of Engineering Ceramics and Composites: A Collection of Papers Presented at the 29th International Conference on Advanced Ceramics and Composites, Jan 23-28, 2005, Cocoa Beach, FL
NDE for characterizing oxidation damage in reinforced carbon-carbon used on the NASA space shuttle thermal protection system
A new gel casting of ceramics by reaction of sodium alginate and calcium iodate at increased temperatures
Xie et al. - A new gel casting of ceramics by reaction of sodiu.pdf
Yoder et al_2015_Carbon Structure Hazard Control.pdf
Contents Figures Tables Definitions Acronyms Executive Summary 1.0 INTRODUCTION 1.1 Background 1.2 Carbon Composite Materials 1.3 Controls 2.0 HAZARDS 2.1 Types of Hazards 2.2 Reinforcement Fiber 2.3 Dust 2.4 Inhalation 2.5 Skin Contact 2.6 Eyes 2.7 Ingestion 2.8 Electrical 2.9 Other Associated Hazards 2.9.1 Combustion 2.9.2 Solvents 3.0 OPERATIONS 3.1 General Handling 3.2 Manufacturing (Finishing and/or Machining) 3.3 Catastrophic Event 3.3.1 Small Scale Catastrophic Event 3.3.2 Large Scale Catastrophic Event 3.3.3 Catastrophic Event Involving Fire 3.4 Analysis 3.4.1 Vehicle, Structure, or Fiber Level Forensics 3.4.2 Vehicle, Structure, or Fiber Level Forensics Involving Fire 4.0 HAZARD CONTROLS 4.1 Handling 4.2 Manufacturing (Finishing and/or Machining) 4.3 Control and Containment (Catastrophic Event) 4.3.1 Wet Containment 4.3.2 Dry Containment 4.4 Forensic Analysis 4.4.1 Laboratory 4.4.2 Service/Field Environments 4.5 Displays 4.6 Storage 5.0 FIRST AID 6.0 DISPOSAL 7.0 REFERENCES DISTRIBUTION
Wax-based binder for low-ressure injection molding and the robust production of ceramic parts
Zorzi et al_2003_Wax-based binder for low-ressure injection molding and the robust production of.pdf
Bulk Diffusion in Alumina: Solving the Corundum Conundrum
Hine et al. - Bulk Diffusion in Alumina Solving the Corundum Co.pdf
Article 61- Discovering a Material That's Harder Than Diamond
Field-Assisted Bonding of Beta-Alumina to Metals
Dunn - 1979 - Field-Assisted Bonding of Beta-Alumina to Metals.pdf
50 years progress in crystal growth: a reprint collection
Feigelson - 2004 - 50 years progress in crystal growth a reprint col.pdf
A single-level multigrid algorithm is developed in which coarse-grid correction is performed on the fine grid. This negates the need for coarse grid storage allocation resulting in easy programmability. The algorithm differs from unigrid in that it mimics multigrid V(0, v) cycles which effectively overcomes the inefficiency of the unigrid technique.
Journal of Computational and Applied Mathematics
Hunt - 1988 - Single-level multigrid.pdf
Treatise on Materials Science & Technology
Brook - 1976 - Controlled Grain Growth.pdf
This chapter gives an introduction to low-energy beam transport systems, and discusses the typically used magnetostatic elements (solenoid, dipoles and quadrupoles) and electrostatic elements (einzel lens, dipoles and quadrupoles). The ion beam emittance, beam space-charge eﬀects and the physics of ion source extraction are introduced. Typical computer codes for analysing and designing ion optical systems are mentioned, and the trajectory tracking method most often used for extraction simulations is described in more detail.
Comment: presented at the CERN Accelerator School CAS 2012: Ion Sources, Senec, 29 May - 8 June 2012
Kalvas - Beam Extraction and Transport.pdf
EVALUATION OF BINDERS FOR MACHINABLE UNFIRED CERAMICS
Teter - 1965 - EVALUATION OF BINDERS FOR MACHINABLE UNFIRED CERAM.pdf
Proceedings of the American Academy of Arts and Sciences
Langley - 1880 - The Bolometer and Radiant Energy.pdf
Langley_1880_The Bolometer and Radiant Energy.pdf
Contents 342 343 344 345 346 347 348 349 350 [351] 352 [353] 354 355 356 357 358
This paper presents the design and control of a rotary servo actuated by a shape memory alloy (SMA) wire. A new rotary servo device using Nitinol type of SMA wire is designed and fabricated in this study. This new rotary actuator utilizes a Nitinol wire wound on a threaded non-conductive rotor.
Design and control of a Nitinol wire actuated rotary servo
Song - 2007 - Design and control of a Nitinol wire actuated rota.pdf
In the present work, we studied the addition of sodium alginate, a natural innoxious polymer, to coagulate alumina slurry in the fabrication of an Al2O3 green body. Calcium iodate was added into the alumina suspension that was dispersed in a sodium alginate solution. The slurry was stable at room temperature but it solidified with increasing temperature. A slurry of 50 vol.% alumina ceramic powder, 1 wt.% calcium iodate and 1 wt.% sodium alginate solidified after being heated at 60 jC for 1 h. In addition to this process, a chelator was used to control the gelation behavior. Associated with the effect of the chelator, the consolidation reaction rate was delayed to longer than 30 min. The gelling properties of the sodium alginate solution and the resultant alumina slurry were analyzed. The rheological behavior of the slurry was examined. Appropriate forming processes were determined. Near-net-shaped green bodies were produced. The resultant green body has uniform structure and smooth surface, and the bonding strength is as high as 8.0 MPa.
Fabrication of alumina green body through gelcasting process using alginate
Jia et al. - 2003 - Fabrication of alumina green body through gelcasti.pdf
57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
American Institute of Aeronautics and Astronautics
NARloy-Z alloy (Cu-3%Ag-0.5%Zr) is a state of the art alloy currently used for fabricating rocket engine combustion chamber liners. Research conducted at NASA-MSFC and Penn State –Applied Research Laboratory has shown that thermal conductivity of NARloy-Z can be increased significantly by adding diamonds to form a composite (NARloy-Z-D). NARloy-Z-D is also lighter than NARloy-Z. These attributes make this advanced composite material an ideal candidate for fabricating combustion chamber liner for an advanced rocket engine. Increased thermal conductivity will directly translate into increased turbopump power and increased chamber pressure for improved thrust and specific impulse. This paper describes the process development for fabricating a subscale high thermal conductivity NARloy-Z-D combustion chamber liner using Field Assisted Sintering Technology (FAST). The FAST process uses a mixture of NARloy-Z and diamond powders which is sintered under pressure at elevated temperatures. Several challenges were encountered, i.e., segregation of diamonds, machining the super hard NARloy-Z-D composite, net shape fabrication and nondestructive examination. The paper describes how these challenges were addressed. Diamonds coated with copper (CuD) appear to give the best results. A near net shape subscale combustion chamber liner is being fabricated by diffusion bonding cylindrical rings of NARloy-Z-CuD using the FAST process.
Fabrication of High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner for Advanced Rocket Engines
Bhat et al. - 2016 - Fabrication of High Thermal Conductivity NARloy-Z-.pdf
Alumina casting based on gelation of gelatine
Chen et al. - 1999 - Alumina casting based on gelation of gelatine.pdf
SiC reinforced graphite composites were prepared via introducing carbide silicon into the natural graphite flakes (NGF) by hot-pressing process. Their physical and mechanical properties, including density, open porosity, ﬂexural strength, and friction behavior were investigated. The addition of 30vol% SiC increased the bending strength of composites materials to 127 MPa, 2 times higher than 60 MPa of commercial pure graphite block. What was particularly interesting was that the as-obtained graphite composite with 30vol% SiC kept the same low friction coefﬁcient of about 0.1 as pure graphite, and the wear resistance of composites increased.
A simple way to prepare silicon carbide reinforced graphite composite lubricating materials
Journal of Wuhan University of Technology-Mater. Sci. Ed.
Han et al. - 2015 - A simple way to prepare silicon carbide reinforced.pdf
Bubble Nucleation During Oxidation of SiC
Raj and Terauds - 2015 - Bubble Nucleation During Oxidation of SiC.pdf
A novel optoacoustic phantom made of polyvinyl chloride-plastisol (PVCP) for optoacoustic studies is described. The optical and acoustic properties of PVCP were measured. Titanium dioxide (TiO2) powder and black plastic colour (BPC) were used to introduce scattering and absorption, respectively, in the phantoms. The optical absorption coefﬁcient (µa) at 1064 nm was determined using an optoacoustic method, while diffuse reﬂectance measurements were used to obtain the optical reduced scattering coefﬁcient (µs). These optical properties were calculated to be µa = (12.818 ± 0.001)ABPC cm−1 and µs = (2.6 ± 0.2)STiO2 + (1.4 ± 0.1) cm−1, where ABPC is the BPC per cent volume concentration, and STiO2 is the TiO2 volume concentration (mg mL−1). The speed of sound in PVCP was measured to be (1.40 ± 0.02) × 103 m s−1 using the pulse echo transmit receive method, with an acoustic attenuation of (0.56 ± 1.01)fM(1H.5z1±0.06) (dB cm−1) in the frequency range of 0.61–1.25 MHz, and a density, calculated by measuring the displacement of water, of 1.00 ± 0.04 g cm−3. The speed of sound and density of PVCP are similar to tissue, and together with the user-adjustable optical properties, make this material well suited for developing tissue-equivalent phantoms for biomedical optoacoustics.
Optical and acoustic properties at 1064 nm of polyvinyl chloride-plastisol for use as a tissue phantom in biomedical optoacoustics
Spirou et al. - 2005 - Optical and acoustic properties at 1064 nm of poly.pdf
The alumina nanopowder was synthesized via the sol–gel method. u-Alumina with crystallite size in the range of 25–110 nm was crystallized by calcination of the powder at 900 8C for 1 h. Sodium alginate, a natural innoxious polymer, was applied for in situ forming process of an Al2O3 green body, using calcium phosphate as a solidiﬁer agent. Sodium hexa metaphosphate was also utilized as a chelator. Rheological and gelation behaviors of resultant slurry were analyzed. The viscosity of slurries with 15 vol.% alumina and 1.8 vol.% calcium phosphate dispersed by 1 wt.% sodium alginate solution, was less than 800 mPa s. The green bodies from the gelcasting process were dried at room temperature for 36 h and pressureless sintered at 1500 8C for 3 h. A uniform microstructure without huge grain growth was revealed by SEM.
Gelcasting of alumina nanopowders based on gelation of sodium alginate
Akhondi et al. - 2009 - Gelcasting of alumina nanopowders based on gelatio.pdf
In situ rheological techniques are used to characterize and investigate the structure–property relationships for a two-step photoinitiated alginate crosslinking system. , We examine the gelation of alginate undergoing ionic crosslinking upon ultraviolet (UV) irradiation using in situ dynamic rheology. Hydrogels are formed by combining alginate with calcium carbonate (CaCO 3 ) particles and a photoacid generator (PAG). The PAG is photolyzed upon UV irradiation, resulting in the release of free calcium ions for ionic crosslinking. The viscous and elastic moduli during gelation are monitored as a function of the UV irradiation intensity, exposure time, alginate concentration, and the ratio between alginate and calcium carbonate. Gel time decreases as irradiation intensity increases because a larger concentration of PAG is photolyzed. Interestingly, dark curing, the continuing growth of microstructure in the absence of UV light, is observed. In some instances, the sample transitions from a solution to a gel during the dark curing phase. Additionally, when exposed to constant UV irradiation after the dark curing phase, samples reach the same plateau modulus as samples exposed to constant UV without dark curing, implying that dark curing does not affect the gelation mechanism. We believe the presence of dark curing is the result of the acidic environment persisting within the sample, allowing CaCO 3 to dissociate, thereby releasing free Ca 2+ ions capable of binding with the available appropriate ionic blocks of the polymer chains. The growth of microstructure is then detected if the activation barrier has been crossed to release sufficient calcium ions. In this regard, we calculate a value of 30 J that represents the activation energy required to initiate gelation.
Photo-activated ionic gelation of alginate hydrogel: real-time rheological monitoring of the two-step crosslinking mechanism
Photo-activated ionic gelation of alginate hydrogel
Higham et al. - 2014 - Photo-activated ionic gelation of alginate hydroge.pdf
The electrical conductivity, r, of silicon carbide (SiC) composites and ﬁbers was measured for temperatures between 20 and 1000 °C in order to estimate the magnitude of magnetohydrodynamic eﬀects for liquid metal blankets and a SiC composite structure. Two types of composites were tested: the ﬁrst type had a matrix made by chemical vapor inﬁltration (CVI), the second type had a matrix made by polymer-impregnation-pyrolysis (PIP). The electrical conductivity of these materials diﬀered by more than an order of magnitude, 650 (Xm)À1 for CVI and 22 (Xm)À1 for PIP composites at 1000 °C. This diﬀerence is attributed to the diﬀerent carbon content of the materials. Several CVI composite samples were irradiated in HFR Petten to doses of 1, 2 and 5 dpa at 750 °C. The thermal conductivity, after 1 dpa, dropped below 30% of the unirradiated value, the drop in electrical conductivity was much smaller.
Electrical conductivity of silicon carbide composites and fibers
Scholz et al. - 2002 - Electrical conductivity of silicon carbide composi.pdf
Silicon Carbide Films by Laser Pyrolysis of Polycarbosilane
Colombo et al. - 2001 - Silicon Carbide Films by Laser Pyrolysis of Polyca.pdf
Blocher et al. - 1957 - CARBIDE COATINGS ON GRAPHITE.pdf
Egg White as an Environmentally Friendly Low-Cost Binder for Gelcasting of Ceramics
Dhara and Bhargava - 2001 - Egg White as an Environmentally Friendly Low-Cost .pdf
The oxidation of SiC-protected carbon/carbon through machined slots and naturally occurring craze cracks in the SiC was studied. The slot and crack geometries were characterized, and the subsurface oxidation of the carbon/carbon substrate at temperatures of 1000 to 1300 °C in air was assessed using weight change, x-ray computed tomography, and optical microscopy of sections. Rate constants were derived from these measurements and compared with a two-step diffusion control model of carbon oxidation. Oxidation kinetic measurements on both the specimens with machined slots and with naturally occurring craze cracks showed good agreement with the model.
Oxidation through coating cracks of SiC-protected carbon/carbon
Jacobson et al. - 2008 - Oxidation through coating cracks of SiC-protected .pdf
Electrophoretic deposition of aqueous alumina slips
Ferrari and Moreno - 1997 - Electrophoretic deposition of aqueous alumina slip.pdf
In this study, coated reinforced carbon-carbon (RCC) samples of similar structure and composition as that from the NASA space shuttle orbiter’s thermal protection system were fabricated with slots in their coating simulating craze cracks. These specimens were used to study oxidation damage detection and characterization using NDE methods. These specimens were heat treated in air at 1143 and 1200 °C to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1 to 3 mm. Single-sided NDE methods were used since they might be practical for on-wing inspection, while x-ray micro-computed tomography (CT) was used to measure cavity sizes in order to validate oxidation models under development for carbon-carbon materials. An RCC sample having a naturallycracked coating and subsequent oxidation damage was also studied with x-ray micro-CT. This effort is a follow-on study to one that characterized NDE methods for assessing oxidation damage in an RCC sample with drilled holes in the coating. The results of that study are briefly reviewed in this article as well. Additionally, a short discussion on the future role of simulation to aid in these studies is provided.
NDE for Characterizing Oxidation Damage in Reinforced Carbon-Carbon
Roth et al. - 2010 - NDE for Characterizing Oxidation Damage in Reinfor.pdf
The results of studies on the application of new water-dispersible binders such as poly(acrylic-styrene), poly(acrylic-allyl ether) for die and isostatic pressing and tape casting of Al2O3 ceramics are presented. The properties of these acrylic polymers were modified by insertion of selected amphiphilic macromonomers into the polymer chains. These amphiphilic macromonomers, due to the proper ratio of the hydrophilic to hydrophobic fragments, play the role of not only an internal plasticizer, but they also modify the adhesion of such binders to the ceramic powder particles. The influence of chemical structure of these copolymers on the properties of alumina ceramics is discussed. The investigations on properties of alumina ceramics obtained by gelcasting method using new water soluble acrylic monomers containing hydroxyl groups in their chemical structure as well as by direct coagulation casting method using polymeric flocculants are also presented and discussed.
New Polymeric Binders in Ceramic Processing
DOI 10.4028/www.scientific.net/AST.45.453
Szafran and Rokicki - 2006 - New Polymeric Binders in Ceramic Processing.pdf
The different steps in the preparation of aluminium nitride powder by carbothermal nitridation of alumina are described. The parameters influencing the kinetics of the basic transformation of the oxide are listed and illustrated. The reaction rate depends on the degree of homogeneity of the solid mixture of raw materials or, adversely, is controlled by the composition of the gaseous phase surrounding the solid reactants. Due to the availability of oxide powders and carbon sources an optimization is possible.
Aluminium nitride by carbothermal nitridation
Bachelard and Joubert - 1989 - Aluminium nitride by carbothermal nitridation.pdf
Number: 12 Publisher: Multidisciplinary Digital Publishing Institute
The chemical environment and the internal conditions of the furnaces and ladles are extremely aggressive for the refractories, so metallurgical industries demand refractory linings with greater durability and resistance to avoid unforeseen stoppages and to reduce the changes of the furnace lining. Therefore, the current work aims to evaluate the impact of the additions of ZrO2-nanoparticles (1, 3, and 5 wt. %) in magnesia-based bricks. A comparative study of the physical and chemical properties in bricks obtained using two cold pressing techniques (uniaxial and isostatic pressing) and two sintering temperatures (1550 and 1650 °C) was carried out. The microstructure and crystalline phase characteristics obtained after the heat treatments and the slag corrosion test was studied using scanning electron microscopy/electron dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The results reveal that the sample with 5 wt. % of ZrO2 nanoparticles (obtained by cold isostatic pressing and sintering at 1650 °C) has the lowest porosity and greatest resistance to penetration of blast furnace slag.
MgO Refractory Doped with ZrO2 Nanoparticles: Influence of Cold Isostatic and Uniaxial Pressing and Sintering Temperature in the Physical and Chemical Properties
MgO Refractory Doped with ZrO2 Nanoparticles
Because of the presence of grain boundaries in polycrystalline materials, the energy decrease due to elimination of free surface area does not go totally into driving the densification process. Part of the energy decrease goes into driving the grain growth process, leading to a reduction in the driving force for densification.
Awesome use of the Schrodinger wave equation!
Generally, owing to tautomerism of vinyl alcohol monomer, poly(vinyl alcohol) (PVA) cannot be obtained by direct polymerization but it can be obtained by the saponification of poly(vinyl ester) precursors such as poly(vinyl acetate) (PVAc). In this study, to obtain high-molecular-weight (HMW) PVA with high yield through a one-batch method, we tried continuous saponification of PVAc prepared by suspension polymerization of vinyl acetate (VAc). We controlled various polymerization conditions, such as polymerization temperature, initiator concentration, suspending agent concentration, agitation speed, and VAc/water ratio, and obtained PVAc with a maximum conversion of VAc into PVAc of over 95–98%. PVA beads having various molecular parameters were prepared by continuous saponification of PVAc microspheres. Despite our employing a one-batch process, a maximum degree of saponification of 99.9% could be obtained. Continuous heterogeneous saponification of prepared PVAc yielded HMW PVA having a number-average degree of polymerization of 2,500–5,500, a syndiotactic diad content of 51–52%, and degree of saponification of 85.0–99.9%.
Synthesis of high-molecular-weight poly(vinyl alcohol) with high yield by novel one-batch suspension polymerization of vinyl acetate and saponification
Purpose – The purpose of this paper is to study the microwave interactions in polymer thick ﬁlm resistors, namely, polyvinyl chloride (PVC)-graphite thick ﬁlm resistors, and its applications in trimming of these resistors. Design/methodology/approach – We applied microwave radiation in the form of pulses of various pulse durations and with different powers to polymer thick ﬁlm resistors and observed the variation of resistance of these resistors with microwave radiation. Findings – The paper ﬁnds that microwave radiation can be used for trimming of polymer thick ﬁlm resistors. Research limitations/implications – The research implication of this paper is that polymer thick ﬁlm resistors can be trimmed practically using this method. Practical implications – The practical implication of this paper is that we can trim the polymer thick ﬁlm resistors, namely, PVC-graphite thick ﬁlm resistor, by using this method. Originality/value – The value of the paper is in showing that microwave radiation can be used to trim downwards in the case of high-value resistors and trim upwards in the case of low-value resistors.
The effect of microwave radiation on polyvinyl chloride-graphite thick film resistors
Venkatasubrahmanayam et al. - 2014 - The effect of microwave radiation on polyvinyl chl.pdf
Journal of Composite Materials - J COMPOS MATER
A natural polyol was prepared from castor oil by alcoholysis with triethanolamine. The oil and the oil-based polyol were characterized by infrared spectroscopy and through the analytical determination of their functional groups, both techniques indicating that the hydroxyl content increased significantly after the alcoholysis reaction. The modified oil was subsequently used as the polyol component in the formulation of rigid polyurethane foams. Wood flour was chosen to be incorporated as filler in these materials. Physical, thermal, and mechanical properties of the neat and reinforced foams were measured, analyzed, and compared to a reference commercial system. The chemical reaction between wood flour and isocyanate strongly affected the composites’ response to thermo-gravimetric tests. Compression modulus and yield strength decreased as wood flour content increased. The effect of the foam density on the compression properties was also investigated.
Polyurethane Foams Obtained from Castor Oil-based Polyol and Filled with Wood Flour
Mosiewicki et al_2009_Polyurethane Foams Obtained from Castor Oil-based Polyol and Filled with Wood.pdf
Publisher: Taylor & Francis _eprint: https://doi.org/10.1080/19476337.2010.523902
Films from three different bloom strength were prepared and dried at three different temperatures (20 °C, 40 °C and 60 °C) to investigate whether the differences in ordering and aggregation during film formation, under controlled drying conditions, reflect changes in their mechanical properties. Results showed that Young's modulus (E) was not significantly (p ≤ 0.05) influenced by the drying regime because it remained around 3.0 GPa. Film A-270 dried at 20 °C showed higher fracture properties when compared with the same sample dried at 40 °C and 60 °C. Brittleness followed: 60 °C > 40 °C > 20 °C. A-100 was sensitive to 60 °C because there was no formation of a continuous network. Films with higher bloom index showed improved fracture properties, it followed A-270 > A-160 > A-100. Films reflected lower degree of crystallinity (∼0%) as the drying temperature increased; the higher the crystallinity (∼33%), the better the fracture properties. Films formed at 40 °C and 60 °C showed mostly an amorphous structure. Películas con tres diferentes grados de firmeza de gel fueron elaborados y secados a tres diferentes temperaturas (20 °C, 40 °C y 60 °C) para investigar si las diferencias en reorganización y agregación durante la formación de película bajo condiciones de secado controladas refleja cambios en sus propiedades mecánicas. Los resultados mostraron que el módulo de Young (E) de las películas no fue influenciado significativamente (p ≤ 0,05) por el régimen de secado debido a que éste permaneció alrededor de 3,0 GPa. La película A-270 secado a 20 °C mostró mejores propiedades de fractura en comparación a la misma muestra pero secada a 40 °C y 60°. La rigidez en películas siguió la tendencia: 60 °C > 40 °C > 20 °C. A-100 fue sensitiva a 60 °C porque no hubo formación de una red continua. Las películas con alto nivel de firmeza de gel mostró mejores propiedades de fractura, esta tendencia mostró A-270>A-160>A-100. Las películas reflejaron bajo grado de cristalinidad (∼0%) mientras que la temperatura de secado se incrementaba, cuanto más alta la cristalinidad (∼33%) mejores fueron las propiedades de fractura. Películas formadas a 40 °C y 60 °C mostraron una estructura amorfa.
The effect of drying temperature on mechanical properties of pig skin gelatin films El efecto de la temperatura de secado sobre las propiedades mecánicas de películas de gelatina de cerdo
Aguirre-Alvarez et al_2011_The effect of drying temperature on mechanical properties of pig skin gelatin.pdf
Gelatin gelcasting of ceramic components
Journal of Materials Processing Technology
A novel visible light-crosslinkable porcine gelatin was prepared for gelation and micropatterning. The preparation employed a photo-oxidation-induced crosslinking mechanism. First, furfuryl groups were incorporated into the gelatin. Second, the modified gelatin was mixed in water with Rose Bengal, which is a visible light sensitizer. Irradiation by visible light solidified the aqueous solution. In addition, when the solution was cast on a plate, dried and photo-irradiated in the presence of a photomask a micropattern was formed that matched the micropattern on the photomask. The gelatin-immobilized regions enhanced cell adhesion. It was also confirmed that the gelatin incorporating furfuryl and Rose Bengal have no significant toxicity. The photo-crosslinkable gelatin was employed as a direct pulp capping material in the dental field. Considering these results, this system could be useful as a new type of visible light-induced crosslinkable biosealant.
Visible light-induced crosslinkable gelatin
A new kind of gelation process for forming a ceramic green body is discussed. The forming method is based on a process in which gelatine, enzyme (urease) and urea are used. Urea is employed to prevent attraction between gelatine molecules when the dissolved hot gelatine solution cools down for preparing a well-dispersed suspension by ball milling and degassing at ambient conditions. After urease is added into the suspension, gelatine molecules attract each other and form three-dimensional network through hydrogen bonding due to urea decomposition by urease. Slurry containing alumina and gelatin could be consolidated in situ by the above gelation process at room temperature. A green body with homogeneous microstructure and smooth surface was obtained.
A novel casting forming for ceramics by gelatine and enzyme catalysis
_eprint: https://ceramics.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1151-2916.2001.tb00860.x
Freeze-drying concepts were utilized in the shape forming of alumina parts by pressureless slip molding using aqueous slurries. A water solidification modifier, glycerol, was utilized to eliminate the defects associated with the expansion and ceramic particle rejection of water during freezing. Castable alumina slurries with solids loading up to 60 vol% were prepared and characterized using viscosity and zeta-potential measurements with and without glycerol additions. Frozen parts were dried under vacuum by sublimation of ice to obtain net-shape green bodies. The combined effects of high-solids-loading slurries, >57.5 vol%, and glycerol additions were essential for freeze casting to achieve highly dense alumina bodies with a uniform microstructure.
Freeze Casting of Aqueous Alumina Slurries with Glycerol
© 2014 The American Ceramic Society and Wiley Periodicals, Inc
_eprint: https://ceramics.onlinelibrary.wiley.com/doi/pdf/10.1111/ijag.12060
Gelcasting is a colloidal processing method for fabricating high-strength and complex shape ceramic green bodies. However, industry has been reluctant to use the gelcasting technique because the most commonly used gel, acrylamide (AM), is a neurotoxin. Here, we report an attempt at the gelcasting of fused silica glass using a natural and nontoxic gel, glutinous rice flour (GRF) as binder. The GRF-based aqueous system was found to behave excellently in the gelcasting process. Flexural strength of fused silica green bodies solidified with only 3 wt% GRF is up to 11.87 MPa. Bulk density and flexural strength of fused silica glass sintered at 1275 °C are 1.75 g/cm3 and 47.02 MPa, respectively.
Study on Gelcasting of Fused Silica Glass Using Glutinous Rice Flour as Binder
International Journal of Applied Glass Science
Wan et al_2014_Study on Gelcasting of Fused Silica Glass Using Glutinous Rice Flour as Binder.pdf
© 2008, The Author(s). Journal compilation © 2008, Blackwell Publishing
_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1745-4603.2008.00140.x
Rice flour dispersions, under suitable conditions of processing, can form a gel. The effect of concentration of solids (10–18%) and time (0–75 min) of processing on textural attributes, and viscoelasticity were investigated along with sensory attributes. The textural attribute determined is gel strength, while viscoelasticity was determined in terms of mechanical spectra like storage modulus (G′), loss modulus (G″), complex viscosity (η*) and loss factor (tan δ) during a frequency sweep varying from 0.01 to 40 Hz at a constant stress of 25 Pa. Microstructural observation indicates the swelling of starch granules in the beginning of heating, while damaged granule and leached-out materials are visible at the end of the gelling process. Desirability function analysis has been applied to obtain a rice gel with acceptable textural attributes; a solid concentration of 15.2% and a heating time of 75 min can lead to the development of a gel with a satisfaction level of 0.6. PRACTICAL APPLICATIONS Rice flour gels in the form of hard-set gels, porridges and spreads are popular in several parts of the world particularly for feeding of infants and children. The application of the present study lies in understanding the role of major processing variables on the quality attributes and viscoelasticity of a product, characterization of cooked gels and for developing rice flour-based food gels. The findings may also be extended for the development of other cereal-based gels.
Gelling Behavior of Rice Flour Dispersions at Different Concentrations of Solids and Time of Heating
_eprint: https://ceramics.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1551-2916.2011.04557.x
An improved ceramic processing method, thermoresponsive gelcasting, has been developed. The method uses a rapid thermoresponsive gel system to solve the problem of inefficient drying within the conventional gelcasting procedure. The gel system of poly(N-isopropylacrylamide) gel containing poly-(ethylene oxide) graft chains with a freely mobile end was taken as an example for thermoresponsive gelcasting of alumina. The gelling behavior of organic aqueous solution was evaluated. The slurries (solids loading, 50 vol%) with the new gelcasting system were prepared. The wetting ceramic parts were almost completely dried in 70 min at 50°C. The microstructure of the green body is homogeneous. The flexural strength of the sintered ceramics is 282 ± 37 MPa with a theoretical density of 97.6%.
Thermoresponsive Gelcasting: Improved Drying of Gelcast Bodies
Conventional methods in drying ceramic parts, using dry air or gas with particular conditions of humidity and temperature, is usually confronted with many difficulties. Non-uniform and differential drying in various regions due to the solvent gradient, induces structural and residual stresses which cause defects, such as cracking, warpage, bending and the other malformations, which make the articles useless. These malformations can be minimised or eliminated by using the liquid desiccant drying method due to the release of residual stresses. In this work, gelcast green parts have been brought in contact with an appropriate liquid desiccant with the purpose of withdrawing above 30 wt.% solvent in a reasonable period of time, i.e. 3 h. The effects of factors such as loading level of ceramic powders, liquid desiccant concentration and its gradient, effective thickness and geometry of parts and type of liquid desiccant solution (aqueous or non-aqueous), on the drying rate were studied. Lower solid content in the gel, higher liquid desiccant concentration and lower effective thickness of parts, increase the drying rate. Decrease of aspect ratio in cylindrical parts changes the diffusion mechanism from radial to longitudinal direction. Drying of parts in aqueous solution of PEG1000 is more homogeneous than the non-aqueous one, but drying rate of parts in non-aqueous solution of PEG1000 is greater than the aqueous one.
Drying of gelcast ceramic parts via the liquid desiccant method
Glutinous rice flour (GRF) and glutinous rice starch (GRS) were modified by dry-heat treatment and their rheological, thermal properties and freeze-thaw stability were evaluated. Compared with the native GRF and GRS, the water-holding ability of modified GRF and GRS were enhanced. Both the onset and peak temperatures of the modified samples increased while the endothermic enthalpy change decreased significantly (p < 0.05). Meanwhile, dry heating remarkably increased the apparent viscosities of both GRF and GRS. Importantly, compared with GRS samples, the storage modulus (G') and loss modulus (G") values of modified GRF increased more greatly and the tanδ values decreased more remarkably, indicating that the dry-heat treatment showed more impact on the GRF and a higher viscoelasticity compared with GRS. Our results suggest the dry-heat treatment of GRF is a more effective method than that of GRS, which omits the complex and tedious process for purifying GRS, and thereby has more practical applications in the food industry.
Functional Properties of Glutinous Rice Flour by Dry-Heat Treatment
Qin et al_2016_Functional Properties of Glutinous Rice Flour by Dry-Heat Treatment.pdf
CaCu3Ti4O12 (CCTO) ceramics with desirable dielectric properties were prepared by a green gelcasting forming method combined with pressureless sintering. A non-toxic natural macromolecule, glutinous rice flour (GRF) was used as the gelling agent for the gelcasting process. The significant parameter, namely, the dosage of gelling agent was carefully studied so as to optimize the gelcasting process. The results showed that the dosage of GRF had evident effect on both gelcasting process and the final dielectric properties of CCTO ceramics. CCTO ceramics from the green body solidified with 3.5 wt% GRF showed relatively optimal dielectric properties, namely a dielectric constant up to 1.60 × 104 and a loss of only 0.063 (at 1 kHz test frequency). CCTO ceramics fabricated by this green gelcasting method have superior dielectric properties compared with that of the ceramics obtained by the dry pressing method.
Green gelcasting of CaCu3Ti4O12 ceramics
Journal of Materials Science: Materials in Electronics
Number: 4 Publisher: Molecular Diversity Preservation International
Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers are available. In the present paper, only water soluble polymers are described. They have been explained in two categories (1) synthetic and (2) natural. Drug polymer conjugates, block copolymers, hydrogels and other water soluble drug polymer complexes have also been explained. The general properties and applications of different water soluble polymers in the formulation of different dosage forms, novel delivery systems and biomedical applications will be discussed.
Water Soluble Polymers for Pharmaceutical Applications
Kadajji_Betageri_2011_Water Soluble Polymers for Pharmaceutical Applications.pdf
New Trends and Developments in Automotive System Engineering
Powder Injection Moulding - An Alternative Processing Method for Automotive Items
Hausnerova - 2011 - Powder Injection Moulding - An Alternative Process.pdf
Preparation of Al203 Ceramics by Low Pressure Injection Molding
Miyamoto and Taguchi - Preparation of Al203 Ceramics by Low Pressure Inje.pdf
Number: 6 Publisher: Multidisciplinary Digital Publishing Institute
We have fabricated Cu-based micropatterns in an ambient environment using femtosecond laser direct writing to reduce a glyoxylic acid Cu complex spin-coated onto a glass substrate. To do this, we scanned a train of focused femtosecond laser pulses over the complex film in air, following which the non-irradiated complex was removed by rinsing the substrates with ethanol. A minimum line width of 6.1 µm was obtained at a laser-pulse energy of 0.156 nJ and scanning speeds of 500 and 1000 µm/s. This line width is significantly smaller than that obtained in previous work using a CO2 laser. In addition, the lines are electrically conducting. However, the minimum resistivity of the line pattern was 2.43 × 10−6 Ω·m, which is ~10 times greater than that of the pattern formed using the CO2 laser. An X-ray diffraction analysis suggests that the balance between reduction and re-oxidation of the glyoxylic acid Cu complex determines the nature of the highly reduced Cu patterns in the ambient air.
Direct Writing of Copper Micropatterns Using Near-Infrared Femtosecond Laser-Pulse-Induced Reduction of Glyoxylic Acid Copper Complex
Mizoshiri et al_2019_Direct Writing of Copper Micropatterns Using Near-Infrared Femtosecond.pdf
The reduction of partially- and fully-oxidized Cu films was carried out by vacuum annealing, and the reduction mechanisms were investigated in situ by XPS. For a partially-oxidized Cu film, CuO was reduced to Cu2O around 380K, and the Cu2O concentration decreased with increasing annealing temperature and fell below the XPS detection limit at 673K. For a fully-oxidized Cu film, CuO started to form Cu2O around 473K, and Cu began to appear at 673K. The results for a partially-oxidized film are interpreted in terms of oxygen diffusion into bulk Cu rather than oxygen desorption into vacuum.
Copper oxide reduction through vacuum annealing
Lee et al_2003_Copper oxide reduction through vacuum annealing.pdf
Contents Introduction Experimental procedures Results Discussion Conclusion Acknowledgements References
Oxidation and reduction of copper oxide thin films
Li et al_1991_Oxidation and reduction of copper oxide thin films.pdf
The aim of the present paper is to demonstrate that the existence of a bulky sintered material, with the required properties for a potential application (called hereafter active material), does not necessarily mean a straightforward manufacturing of a corresponding functional planar thick-ﬁlm device with the required properties. Many problems have to be solved at the level of each element of the micro-assembly, namely the substrate, the electrodes, the heating resistor, and of course the active material. Moreover, for a reliability approach, physico-chemical interactions in the whole micro-assembly have to be considered. Examples drawn from our own experience in the area, deal with super-thick copper pads, varistors, PZT-based pyroelectric sensors, semiconductor oxide gas sensors, zirconia oxygen sensors . . ..
Screen-printed thick-films: From materials to functional devices
Ménil et al. - 2005 - Screen-printed thick-films From materials to func.pdf
A screen-printable copper paste has been developed by Dow Corning to replace the standard screen-printable silver paste for use in front busbars for solar cells. Solar cells produced with these ‘passivated copper busbars’ have shown increased conversion efficiency due to an improved device operating voltage and current while maintaining a similar fill factor when compared to cells with standard ‘fired-through’ silver busbars. In addition to the improved cell efficiency, the use of copper paste may provide major cost savings compared to the use of silver, potentially giving a very significant reduction in cost per Watt. 60-cell modules have been produced at Trina Solar with passivated copper busbars, showing similar performance to the reference modules with silver busbars. Module reliability has been shown to be well in excess of the IEC 61215 standard requirements.
Passivated Busbars from Screen-printed Low-temperature Copper Paste
Wood et al. - 2014 - Passivated Busbars from Screen-printed Low-tempera.pdf
Nonvacuum, Maskless Fabrication of a Flexible Metal Grid Transparent Conductor by Low-Temperature Selective Laser Sintering of Nanoparticle Ink
1988., IEEE MTT-S International Microwave Symposium Digest
An overview of microwave sintering is presented, and the basic theory for the design of impedance applicators is derived. Examples of applicators for ribbon materials and rods are developed and sintering results are presented. The problems imposed by radiation loss and plasma breakdown are examined and their solution by use of thermally reflecting high-pressure cavities are described. A basic system for sintering with feedback control of surface temperature is discussed.<>
Number: 1 Publisher: Nature Publishing Group
We developed an ultra-high speed photonic sintering method involving flash white light (FWL) combined with near infrared (NIR) and deep UV light irradiation to produce highly conductive copper nano-ink film. Flash white light irradiation energy and the power of NIR/deep UV were optimized to obtain high conductivity Cu films. Several microscopic and spectroscopic characterization techniques such as scanning electron microscopy (SEM), a x-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize the Cu nano-films. Optimally sintered Cu nano-ink films produced using a deep UV-assisted flash white light sintering technique had the lowest resistivity (7.62 μΩ·cm), which was only 4.5-fold higher than that of bulk Cu film (1.68 μΩ•cm).
All-photonic drying and sintering process via flash white light combined with deep-UV and near-infrared irradiation for highly conductive copper nano-ink
Hwang et al_2016_All-photonic drying and sintering process via flash white light combined with.pdf
New electroless copper plating bath using sodium hypophosphite as reductant: Surface Engineering: Vol 28, No 5
tex.ids: lazicInfluenceDepositionParameters2004
The influence of the deposition parameters on the porosity of thin alumina films electrophoretically deposited on steel from aqueous suspensions was investigated. The effects of the applied voltage, deposition time, suspension temperature and the solid content of the aqueous suspension on the porosity of the obtained alumina films have been determined using optical microscopy coupled with image analysis. It was shown that the lowest film porosity was obtained from a suspension containing 20 wt.% alumina powder at the lowest applied voltage (30 V), for a longer deposition time (10 min) using a suspension temperature of 30 ºC. This behavior can be explained by the smaller amount of hydrogen evolved on the cathode during the electrophoretic deposition process.
The influence of the deposition parameters on the porosity of thin alumina films on steel
Lazic et al_2004_The influence of the deposition parameters on the porosity of thin alumina.pdf
Lazic et al. - 2004 - The influence of the deposition parameters on the .pdf
_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1151-2916.1959.tb14066.x
In commercial practice, where temperatures are low, a number of commercially available materials are satisfactory as a container for molten aluminum. None of these, however, resists attack by aluminum in the temperature range 1800° to 2000°C. An investigation was conducted to find a material completely inert to aluminum at these high temperatures. Aluminum nitride emerged as the material that was inert to aluminum and showed satisfactory properties as a ceramic material. A method of preparing high-purity AIN by striking a d.-c. arc between two high-purity aluminum electrodes in a nitrogen atmosphere is described. A refractory having excellent strength and low porosity was achieved by hydrostatic pressing and firing at high temperatures. The mechanical, electrical, thermal, and chemical properties of the refractory are discussed.
Aluminum Nitride, a Refractory for Aluminum to 2000°C.
Conference Name: IRE Transactions on Component Parts
Metal and ceramic parts are sealed by introducing a molten solder or by inserting a thin sheet of metal that will form a reactive alloy. A wide choice of materials can be used, including many that seal at high temperatures with little metallic evaporation. Materials can be used that can be predegassed at temperatures considerably above those used for final sealing. The seals can be made in vacuum or in an inert gas. The parts can be stacked one on the other so that a multiplicity of seals can be made at the same time. By using a metal such as titanium, and ceramic parts having an expansion characteristic similar to that of titanium, seals can be made that are strong and can operate for many hours at temperatures as high as 800°C.
Sealing Metal and Ceramic Parts by Forming Reactive Alloys
Nickel is anot(her metal that alloys readily with titanium. Fig. 4 shows the Ni-Ti constitution diagram. It will be noted that about eleven per cent nickel will reduce the melting point of titanium from approximately 1700°C to 955°C. Three eutectic points are present: 955”C, llOO”C, and 1285°C at 30, 66, and 84 per cent nickel. Successful seals have been made in the range of temperatures from 955°C to 1300°C by using nickel parts with titanium shims, and from 955°C to 1100°C by using titanium parts with nickel shims. https://electrontubestore.com/index.php?main_page=shopping_cart
Multipurpose electric furnace system.[for use in Apollo-Soyuz Test Program]
The next factor investigated was the suitability of Kanthal A-1 as heater material. Although this material is suitable for use to 1325 C in air, at least one reference does not recommend its use in vacuum at temperatures over 1000°C. This warning is founded in the rapid evaporation of a component (chromium?) from the alloy and verified by tests we performed on bare wires in ultra-high vacuum. Sample filaments burned out after two hours or less at a surface temperature of 1200°C. The heater winding, however, is NOT a bare wire operating in ultra-high vacuum.