Showing papers in "Transactions of The Indian Ceramic Society in 1976"
TL;DR: The influence of morphology of magnesia powders on their sinterability has been studied in this paper, showing that powders derived from acetate, tannate, oxalate, succinate and phthalate were found to retain the regular geometric crystalline shapes of their parent compounds.
Abstract: The influence of morphology of magnesia powders on their sinterability has been studied. Magnesia powders were prepared by calcination of organic salts and their morphology was studied by electron microscopy. Powders derived from acetate, tannate, oxinate and formate were found to have an irregular globular morphology and such powders were found to be highly sinterable. In comparison, powders derived from oxalate, succinate and phthalate were found to retain the regular geometric crystalline shapes of their parent compounds and were found to be poorly sinterable.
4 citations
TL;DR: In this article, X-ray diffraction and optical microscopy were used to identify chabazite-type and gmelinite-type molecular sieve zeolites, which were synthesized in small batches from sodium aluminosilicate gels at and around 100°C.
Abstract: Chabazite-type (R) and gmelinite-type (S) molecular sieve zeolites were synthesized in small batches from sodium aluminosilicate gels at and around 100°C. The materials were identified by X-ray diffraction and optical microscopy. Thermal behaviour and water sorption efficiency of these molecular sieves, specially the latter, as a function of post-synthesis grinding and heat treatment, were studied; the sorption characteristics have been discussed in terms of the available crystallographic information on these materials.
4 citations
TL;DR: In this article, the self-diffusion coefficients of glasses containing bismuth oxide were measured by electron probe microanalysis and the activation energies for these diffusion coefficients lie in the range 0.2 eV-1.4 eV.
Abstract: Sodium ⇌ Silver interdiffusion coefficients in the temperature range 275° to 375°C have been measured for glasses in the system Na2O—B2O3—Bi2O3—SiO2 by electron probe microanalysis. The interdiffusion coefficients are found to be dependent on silver concentration. By analysing the data on the basis of Helfferich's interdiffusion formula, values of self-diffusion coefficients for sodium and silver have been estimated. The activation energies for these diffusion coefficients lie in the range 0.2 eV—1.4 eV. An increase of the alkali content in glasses containing bismuth oxide increases the activation energy for silver self-diffusion coefficient relative to that of sodium. A possible explanation is given in terms of a two-phase structure model of these glasses.
4 citations
TL;DR: The importance and relevance of adopting the technique of fast firing of ceramics to the country's needs have been discussed in this paper, where the advantages, the scope of the technique and the equipment such as kilns, conveyors, controllers etc and the fuels used have been indicated along with the firing schedules followed.
Abstract: The importance and relevance of adopting the technique of fast firing of ceramics to the country's needs have been discussed. The advantages, the scope of the technique and the equipment such as kilns, conveyors, controllers etc and the fuels used have been indicated along with the firing schedules followed.
2 citations
TL;DR: In this paper, a single-decomposition analysis of enamels and frits has been proposed, which enables the determination of seventeen different constituents from a stock solution of single decomposition.
Abstract: A scheme has been worked out for rapid and accurate analysis of enamels and frits. The scheme enables the determination of seventeen different constituents from a stock solution of single decomposition. The stock solution was prepared by decomposing the sample with hydrofluoric and sulphuric acids. Lead and barium were separated as sulphates prior to the determination of other constituents and then lead sulphate was separated from barium sulphate for the first time with EDTA at pH 4.3. Different aliquots were used for determination of sodium and potassium by flame photometry; cadmium and zinc by polarography and traces of iron, chromium, nickel, copper, cobalt and manganese by spectrophotometry. From another aliquot of the stock solution interfering elements were removed by mercury-cathode electrolysis and then zirconium, aluminium, calcium and magnesium were determined by complexometric methods and titanium by the spectrophotometric or polarographic method. Separate samples were decomposed for determinat...
1 citations
TL;DR: In this paper, the crystal chemistry and polymorphism of zirconia is reviewed and its role in stabilizing the cubic polymorph of ZrO2 is discussed with special stress.
Abstract: Zirconia finds wide applications in high temperature technology. The paper reviews the crystal chemistry and polymorphism of zirconia, the knowledge of which is immensely important in its utilization. Solid solution formation of zirconia with various oxides is dealt with at length and its role in stabilizing the cubic polymorph of ZrO2 is discussed with special stress.
1 citations
1 citations
TL;DR: The influence of these dopants in suppressing YOF growth and in promoting YIG growth was thoroughly discussed, and conditions of growth of YIG crystals of fair size and better quality were suggested as discussed by the authors.
Abstract: Crystals of Yttrium iron garnet (YIG) and Yttrium orthoferrite (YOF) were grown from the flux system PbO—PbF2—B2O3 containing minor quantities of alkali and alkaline earth oxides in the melt as dopants. The influence of these dopants in suppressing YOF growth and in promoting YIG growth was thoroughly discussed, and conditions of growth of YIG crystals of fair size and better quality were suggested.
1 citations
TL;DR: Using hot stage electron microscopy, a technique for the in situ study of the thermal decomposition of magnesium hydroxide and the successive stages of the formation of magnesia has been developed.
Abstract: Using hot stage electron microscopy, a technique for the in situ study of the thermal decomposition of magnesium hydroxide and the successive stages of the formation of magnesia has been developed....
1 citations
TL;DR: In this article, the effect of silica in the direct titration of ZrO2 by EDTA in 1N HNO3 has been thoroughly studied; a rapid and accurate method has been developed for the determination of ZRO2 and SiO2 in zirconia bearing materials without separation of any constituent.
Abstract: The effect of silica in the direct titration of ZrO2 by EDTA in 1N HNO3 has been thoroughly studied; a rapid and accurate method has been developed for the determination of ZrO2 and SiO2 in zirconia bearing materials without separation of any constituent. After the decomposition of zircon and zirconia bearing materials with the mixture of KOH and Na2O2 in a nickel crucible, ZrO2 and SiO2 are determined by a complexometric method. The time required for the determination of both the oxides is only four hours; accuracy and reproducibility of results obtained by the method described here are quite satisfactory.
TL;DR: In this paper, the microstructural development in sintered uranium dioxide pellets was studied with reference to origin of the powder and time, temperature and other conditions of sintering.
Abstract: Microstructural development in sintered uranium dioxide pellets was studied with reference to (1) origin of the powder and (2) time, temperature and other conditions of sintering. Changes in the microstructure of the sintered pellets when reheated at temperatures below and above sintering temperature for various periods of time have also been studied. It was found that a judicious choice of the powder with desired characteristics and a judicious choice of optimum conditions for sintering of the powder have to be utilized to attain controlled microstructure. The grain size can be increased and grain development made more perfect by an appropriate thermal treatment of the sintered pellets.
TL;DR: In this article, a comparative study of the properties of the raw materials in their selection has been carried out to have a comparative idea on the properties in the selection of raw materials for structural uses.
Abstract: Petroleum coke calcined at 1000°, 1300° and 1600°C, petroleum coke based dense carbon aggregate developed at NML, two varieties of anthracite coke and two varieties of natural graphite have been studied. Studies on proximate analyses, specific gravity, crushability index, susceptibility to oxidation, X-ray diffraction have been made to have a comparative idea on the properties of the raw materials in their selection. Anthracite coke is found to have inferior properties as compared with dense carbon aggregate and petroleum coke calcines in the case of specific gravity, electrical resistivity and average crystallite size, etc. and a little superior property in the case of susceptibility to oxidation. For structural uses, i.e. furnace blocks, as well as for continuous type soderberg anode, dense carbon aggregate may be found quite suitable.
TL;DR: In this paper, phase transformations of silica were studied at 1400°C employing DTA method for determination of the crystalline forms of the silica, and the consecutive transformation of quartz to tridymite proceeded through metastable cristobalite and intervening transition phases.
Abstract: Catalysed phase transformations of silica were studied at 1400°C employing DTA method for determination of the crystalline forms of silica. The consecutive transformation of quartz to tridymite proceeded through metastable cristobalite and intervening transition phases. The decomposition of quartz in presence of mineralisers that produced liquid phases proceeded with uniform radial velocity, while with those acting in the solid state, the decomposition velocity progressively decreased with time, and the conversion kinetics were in approximate agreement with a phase boundary-controlled and a diffusion-controlled process respectively. The dependence of cristobalite formation rate on the transition phase concentration suggested that development of cristobalite occurred at the nucleation centres distributed inside the whole volume of the transition phase.
TL;DR: In this article, a number of experimental results have been presented to confirm the form-stability of glass tools when used for machining aluminium, and the important elements in the design of cutting tools are the materials of construction and their judicious selection.
Abstract: The important elements in the design of cutting tools are the materials of construction and their judicious selection. Retention of form-stability at elevated temperatures while machining is the fundamental requirement. Glass-ceramics is an upcoming tool material with lower manufacturing cost that can be used for machining of materials. A number of experimental results have been presented to confirm the form-stability of glass tools when used for machining aluminium.
TL;DR: In this paper, a plot of squareness-ratio versus deviationratio data was obtained for the sintering of toroid powder at 1400°C for 4 hours.
Abstract: Magnesium—Manganese ferrite toroids having square loop characteristics were prepared. Ferritisation of the powder was essentially complete at 1150°C within 5 hours in Argon atmosphere. The sintering of toroids was carried out at 1400°C for 4 hours. A plot of squareness-ratio versus deviation-ratio data was similar to that obtained in literature.
TL;DR: In this paper, five types of beryllia powders, one from sulphate, two from hydroxide, and two of as received commercial powders were studied for their densification behaviour and microstructural development with and without a minor addition of 1% Fe2O3.
Abstract: Five types of beryllia powders, one from sulphate, two from hydroxide, and two of as received commercial powders were studied for their densification behaviour and microstructural development with and without a minor addition of 1% Fe2O3. Sinterings were carried out in humid, dry and natural air and vacuum at temperatures between 1200°–1500°C. It is observed that beryllia powders with large surface areas are sensitive towards moisture in the sintering atmosphere resulting in low densification. Densification for these powders is least in moist atmosphere and maximum in vacuum. Fe2O3 addition improved the densities in all the cases; more so in case of larger surface area powders at lower sintering temperatures. The influence of sintering atmosphere, surface area etc can be virtually ignored in the presence of Fe2O3. Even inactive powders resulted in a density of about 90% theoretical at 1500°C in presence of 1% Fe2O3. Further, the iron oxide gets eliminated from the system at higher temperatures and especia...
TL;DR: A critical review of the various methods for the extraction of zirconia has been made in this article, where some of the important uses of this material have also been listed.
Abstract: The position of India with regard to the resources of raw materials for the production of ZrO2 has been discussed. A critical review of the various methods for the extraction of zirconia has been made. Some of the important uses of this material have also been listed.
TL;DR: In this paper, the effectiveness of certain organic binders and the amounts necessary have been examined for the solid extrusion of plasticised alumina as a preliminary step towards preparation of refractory tubes.
Abstract: This investigation deals with the solid extrusion of plasticised alumina as a preliminary step towards preparation of refractory tubes. The effectiveness of certain organic binders, and the amounts necessary have been examined. Sample bars have been prepared from a mix by ram extrusion and some of their physical properties determined. It appears as a result of this study that gum tragacanth is a suitable binder and two per cent would be sufficient for the extrusion of a plasticised mix of alumina fines such as the ones encountered in this investigation.