Showing papers in "Transactions of The Indian Ceramic Society in 1968"
TL;DR: In this paper, the crystallinity in UO2 powders prepared by the ADU route at different calcination temperatures (600°-1600°C) and its influence on their sintering behavior (sintering temperature 1000° -1600°c) in hydrogen were studied by X-ray difiraction techniques.
Abstract: The crystallinity in UO2 powders prepared by the ADU route at different calcination temperatures (600°-1600°C) and its influence on their sintering behaviour (sintering temperature 1000°-1600°C) in hydrogen were studied by X-ray difiraction techniques. Powder patterns were made for the loose powders and back reflection for the sintered pellets. It was noticed that higher the calcination temperature, the greater was the degree of crystallinity developed in the powders and poorer was their sinterability. The crystallinity of the sintered pellets was mainly dependent on the sintering temperature and crystallinity of the original powder and is not directly related to the sintered density. By sintering pellets of poorly crystalline powders at low temperatures (about 1200°C) sintered pellets of near theoretical density but with poorly developed crystallinity could be obtained.
24 citations
TL;DR: In this article, it has been shown that the sinterability of oxides depends on the origin and thermal history of the powders and that the crystallinity of the oxides can be assessed on a comparative basis by determination of the streaming potentials.
Abstract: It has been shown that the sintering behaviour of oxides depends on the origin and thermal history of the powders. Physical characteristics of the powder such as, surface area, particle size etc were not found to be adequate to explain the sintering behaviour. It is also shown that the sinterability is directly related to the crystallinity in the powders. The crystallinity of the powders can be assessed on a comparative basis by determination of the streaming potentials. An apparatus has been set up to determine the streaming potentials of urania powders. It was found that the slope of the streaming potentials vs. velocity of flow plots was a direct indication of the comparative sinterability of the urania powders.
9 citations
TL;DR: In this paper, a study was made on the kinetics of sintering of UO2powders derived from ADU at different calcination temperatures, where the powders were calcined between 500° and 1500°C and the densification characteristics of the pellets made from these were evaluated for different soaking times.
Abstract: A study has been made on the kinetics of sintering of pellets prepared from UO2powders derived from ADU at different calcination temperatures. The powders were calcined between 500° and 1500°C and the densification characteristics of the pellets made from these were evaluated for different soaking times from 10 to 1000 mts at sintering temperatures between 1000° and 1500°C. Data were analysed using the empirical equation where D is the density, C and K are constants and t denotes time.It was found that (i) the progress of sintering, (ii) attainment of limiting densities and (iii) variation in rates of densification at different temperatures and time can be explained on the assumption that material movement (hence densification) is governed by the number, nature and energy of crystalline defects (flaws) in the original powders.
7 citations
TL;DR: The ratio of ignition loss (IL) to the moisture absorption (MA) at a particular relative humidity of a clay mineral has been used as a technique for clay mineral identification as discussed by the authors.
Abstract: The ratio of ignition loss (IL) to the moisture absorption (MA) at a particular relative humidity of a clay mineral has been used as a technique for clay mineral identification. This technique has been employed for studying the mineral components present in some Indian Bentonites. It has been found that if the three main groups of clay minerals are lined up in the order of increasing of particle fineness as kaolinite, illite and montmorillonite, the IL values increased in the reverse order MA, however, followed the same order and increased from Kaolinite to Montmorillonite. Bihar, Rajula, Akli and Hathi-ki-Dhani Bentonites were found to be typically montmorillonitic. Jaipur and Karauli were predominantly illitic.
5 citations
TL;DR: In this paper, a systematic study of the influence of repeated calcination and grinding of stoichiometric mixtures of barium carbonate and titanio and sintering temperatures and soaking periods on the dielectric properties of the barium titanate pellets was made.
Abstract: A systematic study of the influence of (1) repeated calcination and grinding of stoichiometric mixtures of barium carbonate and titanio and (2) sintering temperatures and soaking periods on the dielectric properties of the barium titanate pellets was made. An attempt has been made to correlate the properties with the microstructures which essentially depend on the various factors during the preparation of the samples.
4 citations
TL;DR: In this article, the authors investigated the effect of time and temperature on the rate of volatilisation of ruthenium from simple glasses in the system Na2O-SiO2.
Abstract: Solubility dependence of ruthenium volatilisation from glass at glass forming temperature and the effect of time and temperature on the rate of volatilisation were investigated. Simple glasses in the system Na2O-SiO2 were considered for the study. Volatilisation runs were carried out at different temperatures in an air flow of 118 cm/min and the surface of glass subjected to evaporation was 2.73 sq. cm.The plot of ruthenium volatilisation loss vs solubility at 1100°C showed a direct relation between them upto 38 mole percent Na2O content and the curve was a straight line passing through the origin with a slope of 1.64 X 10-2 mg/ppm. For the glasses, with more Na2O, volatilisation was believed to depend on solubility as well as on oxygen diffusion. Volatilisation at different temperatures showed that it followed the Arrhenius law and the calculated activation energy for evaporation was 18.65 K Cal/mole. Rate of ruthenium volatilisation decreased with time and attained a constant value as soon as ruthenium ...
4 citations
TL;DR: In this paper, the progress in vitreous enamelling of aluminium during the last two decades is summarised and the scope for the development of aluminium enameling industry in India in the light of increased production of aluminium in the next plan period has been emphasised.
Abstract: Progress in vitreous enamelling of aluminium during the last two decades is summarised. Metal pretreatment process, enamel compositions and firing are discussed. Scope for the development of aluminium enamelling industry in India in the light of increased production of aluminium in the next plan period has been emphasised.
4 citations
TL;DR: In this article, the effects of mechanical strength, linear thermal expansion and modulus of elasticity on thermal-shock resistance of alumino-silicate refractories have been studied and the results have been statistically analyzed.
Abstract: The effects of mechanical strength, linear thermal expansion and modulus of elasticity on thermal-shock resistance of alumino-silicate refractories have been studied and the results have been statistically analysed. An equation correlating thermal-shock resistance of these refractories to their strength, thermal expansion and modulus of elasticity has been suggested on the basis of the observations made.
4 citations
TL;DR: In this paper, the authors give an account of the efforts made in the direction of indigenous development and production of lead zirconate titanate type of materials at Armament Research and Development Establishment and describe their characteristics and typical uses.
Abstract: Piezoelectric ceramics—a class of oxidic ferro-electric materials with specific modifications—display excellent electro-mechanical properties for use as transducer elements in the production of high voltages, ultrasonics, wave fiilters, radiation detectors and for pressure measurements. The paper gives an account of the efforts made in the direction of indigenous development and production of lead zirconate titanate type of materials at Armament Research and Development Establishment and describes their characteristics and typical uses.
4 citations
TL;DR: In this paper, a study of the relations between powder properties, sintering treatments and the densification and microstructure development in urania pellets was carried out, and the results revealed that urania pellets of specified density and grain development can be prepared by first attempting to achieve densification, and then continuing the thermal treatments to attain the desired densification.
Abstract: The investigation is aimed at a study of the relations between powder properties, sintering treatments and the densification and microstructure development in urania pellets. Urania powders for this study were prepared from ammonium diuranate by decomposition and reduction at various temperatures, namely, 400°, 600°, 900°, 1200° and 1500°C. Pellets prepared from these powders were sintered at temperatures in the range of 1200° to 1700°C with different soaking periods.The influence of (i) sintering temperatures, (ii) soaking periods at different temperatures, (iii) intermediate soaks at varying time periods at various temperatures, (iv) reheating of prepared sintered pellets and (v) rates of heating during sintering, on the density and microstructure development of pellets was studied in this investigation.The study revealed that urania pellets of specified density and grain development can be prepared by first attempting to achieve densification and then continuing the thermal treatments to attain the des...
3 citations
TL;DR: In this article, the changes in electrical conductivity of sintered urania pellets were measured at room temperature, and an attempt was made to explain changes in conductivity on the basis of crystallinity development in the powders, densification of the compacts and grain growth during sintering.
Abstract: It was considered that the changes in electrical conductivity of pellets of UO2 would be related to the progress of sintering in them. Electrical conductivity of sintered urania pellets was measured at room temperature. Powders of different crystallinity were prepared by calcination of ADU at 600° to 1500°C and the samples were sintered at temperatures between 600° to 1500°C. An attempt was made to explain the changes in conductivity on the basis of crystallinity development in the powders, densification of the compacts and grain-growth during sintering.
TL;DR: In this paper, mineralogical studies of zircon sand from Kerala beach revealed that about 97% of the grains were unaltered, but they appeared to have a lower degree of crystallinity.
Abstract: Mineralogical studies of zircon sand from Kerala beach revealed that about 97% of the grains were unaltered, but they appeared to have a lower degree of crystallinity. About 2% of the grains were found to be partly metamicted. Huttonite (ThSiO4) was found as one of the impurities responsible for the radio activity of the sample.Calcination improved the crystallinity and colour of zircon grains, making them more suitable for use as opacifiers in porcelain glazes. The behaviour of raw and calcined zircon in various types of glazes have been explained.
TL;DR: In this paper, the rates of extraction of Li2O and SiO2 from silicate glasses containing up to 34 mole per cent Li2Os were studied. But, from the composition containing 7 mole per percent Li 2Os, hardly any Li 2O could be extracted, apparently due to entrapment of the lithium silicate phase in a matrix of silica.
Abstract: The rates of extraction of Li2O and SiO2 from silicate glasses containing up to 34 mole per cent Li2O were studied. From the composition containing 7 mole per cent Li2O hardly any Li2O could be extracted, apparently due to entrapment of the lithium silicate phase in a matrix of silica. On raising the Li2O content to 10 mole per cent and above, the separated phase became progressively continuous and the rate of extraction increased sharply. Boro-silicate glasses containing 10 and 12 mole per cent of Li2O and B2O3 respectively, were readily attacked by water due to the presence of a more readily soluble phase. The soluble phase having a probable composition around 1.5 Li2O, 1 B2O3, 1 SiO2, could be selectively extracted from one of the glasses leaving a skeleton containing over 92 per cent SiO2 and hardly any Li2O. Compositions comparatively richer in Li2O and B2O3, disintegrated in water presumbly due to the presence of the insoluble phase as islets in a matrix of soluble boro-silicate phase. Replacing B2O...
TL;DR: In this article, phase transformations of silica in mixtures containing boric oxide and three forms of silicas, namely, amorphous silica, quartz and ordered cristobalite, were studied by the X-ray and DTA methods.
Abstract: Phase transformations of silica in mixtures containing boric oxide and three forms of silica, namely, amorphous silica, quartz and ordered cristobalite, were studied by the X-ray and DTA methods. With 5, 7.5 and 10 wt per cent of boric oxide, amorphous silica readily and completely vitrified at about 1480°C, 1300°C and 1040°C, respectively but not the crystalline forms, even after heating for periods upto 50 hours. The results suggest that with increasing boric oxide content, larger proportions of amorphous silica were directly converted to SiO2-B2O3 glass before any cristobalite could appear.Boric oxide accelerates the formation of tridymite from quartz and cristobalite, but does not permit conversion of quartz to cristobalite. At higher temperatures, quartz was probably transformed to an intermediate amorphous form and then to SiO2-B2O3 glass before any cristobalite could be formed. Starting with either ordered cristobalite or amorphous silica only a particular disordered form of cristobalite, showing α...
TL;DR: In this paper, two glass compositions in Li2O-Al2O3-SiO2 system, one corresponding to β-Spodumene, and the other corresponding to the eutectic at 1026°C were prepared, and studied with respect to their crystallization behaviour.
Abstract: Two glass compositions in Li2O-Al2O3-SiO2 system, one corresponding to β-Spodumene, and the other corresponding to the eutectic at 1026°C were prepared, and studied with respect to their crystallization behaviour. The phases crystallizing on heat treatment at different temperature schedules and for different nucleating agents were identified by X-ray diffraction patterns. In all cases, the major phase present was Li2O.Al2O3.6SiO2. Besides, lithium metasilicate and lithium orthosilicate were also crystallized. DTA technique was used to distinguish the effects of TiO2, and ZrO2 as nucleating agents.
TL;DR: In this paper, a procedure was worked out for decolourisation of clays by reducing-their Fe2O3 content based on these observations, which involved dispersion of the clay suspension, addition of Na2S2O5 in presence of zinc at controlled pH and after completion of the reactions washing the decolouredised clay free of excess salts, filtering and drying An important feature of the process was that no external heating was necessary and it could as such be adopted as an adjunct to a clay washing plant.
Abstract: Dissolution of Fe2O3 from clay suspension by various reducing agents at different pH and temperature was systematically studied Based on these observations a procedure was worked out for decolourisation of clays by reducing-their Fe2O3 content The method developed involved dispersion of the clay suspension, addition of Na2S2O5 in presence of zinc at controlled pH and after completion of the reactions washing the decolourised clay free of excess salts, filtering and drying An important feature of the process was that no external heating was necessary and it could as such be adopted as an adjunct to a clay washing plantClays from different regions were studied In most cases substantial increase in brightness factor was obtained without showing any deterioration in the other properties
TL;DR: In this article, the phase relations obtained in six vertical sections of ternary system CA2 - gehlenite -spinel are described, and the liquid formation and refractoriness of calcium aluminate cements containing geHlenite and spinel are discussed.
Abstract: Phase relations obtained in six vertical sections of ternary system CA2 - gehlenite -spinel are described. Six isothermal sections in the ternary systems CA2 - gehlenite - spinel and CA - gehlenite - spinel are presented. Liquid formation and refractoriness of calcium aluminate cements containing gehlenite and spinel are discussed.
TL;DR: In this paper, the thermal characteristics of four Bull's trench kilns of different designs have been studied and factors responsible for wide variations in the quality of burning, fuel consumption and other performance characteristics have been explained.
Abstract: Thermal characteristics of four Bull's trench kilns of different designs have been studied. Factors responsible for wide variations in the quality of burning, fuel consumption and other performance characteristics have been explained. Thermal balance sheet for each kiln has been presented indicating the quantity of heat utilized in completing different processes and the quantity lost through different sources. Theoretical heat requirements for burning bricks have been calculated and thermal efficiencies of the kilns, calculated on minimum heat requirements, have been compared. It is concluded that the thermal efficiencies being more or less the same in all cases, none of the designs studied, offers distinct advantage over others. Practical suggestions for improving the thermal performance of such kilns have been given.
TL;DR: In Na2O-SiO2 glasses, on substitution of SiO2 by ZrO2, resistance to chemical attack of water, hydrochloric acid and alkalis of different concentrations, increased substantially as mentioned in this paper.
Abstract: In Na2O-SiO2 glasses, on substitution of SiO2 by ZrO2 (upto 1.1% by wt) resistance to chemical attack of water, hydrochloric acid and alkalis of different concentrations, increased substantially.
TL;DR: In this paper, the cation exchange capacities of three kaolinitic clays of Indian origin were determined in connection with the preparation of homoionic forms of the clays for studies on their thermal behaviour.
Abstract: The cation exchange capacities of three kaolinitic clays of Indian origin were determined in connection with the preparation of homoionic forms of the clays for studies on their thermal behaviour. Two inflexion points in the potentiometric titration of H-form of Travancore china clay was noticed, while the other two H-forms of Rajmahal china clay and Ball clay exhibited only one inflexion point. Titration of H-forms of these three clays in methanol-water mixture (methanol+1% water) also showed the same type of behaviour except that the inflexions occurred at lower amounts of alkali than in water. On the basis of the results obtained in this study and evidence available on the subject, the author considers that the two inflexion points in some of the H+—kaolinites may be due to H+ and Al+++ in the exchange complex which, at appropriate concentrations give rise to the individual peaks.
TL;DR: The role of associated clay and non-clayey materials on the nature of their titration curves has been discussed in this paper and it has been observed that their influence is not very markedly manifested on these curves and hence the titration characteristics of these samples have been ascribed as due to interstratified illite-montmorillonite minerals mainly.
Abstract: pH-neutralisation curves of some natural clay samples containing interstratified illite-montmorillonite minerals have been studied. It has been observed that their titration curves are different from those of kaolinite, montmorillonite, illite and their natural mixtures. Unlike these, the titration curves of samples containing interstratified minerals show four inflections at pH ranges 5–6, 7–7.5, 8–9.5 and 10–10.5. The role of associated clay and non-clayey materials on the nature of their titration curves has been discussed. It has been observed that their influence is not very markedly manifested on these curves and hence the titration characteristics of these samples have been ascribed as due to interstratified illite-montmorillonite minerals mainly. Reasons for the polybasic character of their curves have been discussed in relation to the surface area of the samples and their crystal structure.
TL;DR: In this article, the authors measured the mechanical strength, rate of water attack and surface power factor of soda-magnesia, soda-lime and soda-alumina glasses before and after the glass specimens were treated with alkali pyrosulphate at elevated temperatures.
Abstract: The mechanical strength, rate of water attack and surface power factor were measured on soda-magnesia, soda-lime and soda-alumina glasses before and after the glass specimens were treated with alkali pyrosulphate at elevated temperatures. The average transverse strength increased by three to five times after the treatment. The rate of extraction of Na2O and SiO2 by boiling water, as well as the ratio Na2O: SiO2 in the extracts decreased very considerably from the normal values. The surface power factor and the mechanical strength of treated glass specimens did not deteriorate with increasing humidity. The observed improvements in the properties have been ascribed to the formation of a dealkalised and toughened surface layer as a result of the thermo-chemical treatment. The results were discussed in relation to the nature of the thermo-chemical reactions involved and structure of glass.
TL;DR: In this paper, four fire bricks of commercial brand were examined for their hot strength and creep resistance by torsion method and showed that no such relation exists with the apparent porosity.
Abstract: Four fire bricks of commercial brand were examined for their hot strength and creep resistance by torsion method. While a good correlation appears to exist between the underload values and the torsional strength, no such relation exists with the apparent porosity. On the other hand, texture of refractories tends to influence their torsional strength inasmuch as that the coarse grain texture without sufficient viscous matrix is detrimental to its strength. Torsional characteristics of refractories in the range of 1200° to 1400°C indicate the difference in their quality and performance characteristic.
TL;DR: In this article, it was shown that the densities obtained depended on the calcination temperature and increased directly with an increase in either the hot pressing temperature or pressure, and the data was found to be in accord with McClelland's equation.
Abstract: The beryllium oxide obtained by calcination of Be(OH)2 at various temperatures was hot pressed at different temperatures and pressures. The densities obtained depended on the calcination temperature and increased directly with an increase in either the hot pressing temperature or pressure. The data is found to be in accord with McClelland's equation; both the yield stress and activation energy are found to be enhanced with an increase in calcination temperature. It thus appears that the densification during hot pressing of active BeO powders is due to macroscopic material movement (plastic flow) and is directly dependent on the crystallinity of the powder.
TL;DR: In this paper, a new viscometer suitable for measuring the viscosities of relatively fluid silicates, in limited ranges, has been devised, based on the study of forced vertical oscillations of a solid platinum sphere in the melt.
Abstract: A new viscometer suitable for measuring the viscosities of relatively fluid silicates, in limited ranges, has been devised. The method is based on the study of forced vertical oscillations of a solid platinum sphere in the melt. The viscometer has been used to measure the viscosity of Na2O.SiO2-K2O.SiO2 eutectic melt, over the temperature range, 1000°C to 1200°C. The results compare satisfactorily with those reported in the literature.
TL;DR: In this paper, the effects of alkali and alumina on the equilibrium pH were studied and the pH values were found to be highly influenced by the composition of glass and appeared to have a direct relationship with the logarithm of oxygen ion activity.
Abstract: Chemical equilibrium was allowed to attain at the glass solution interface of some commercial and experimental glasses and the pH values measured at equilibrium were compared with the results of alkali extraction from previous investigations. The effects of alkali and alumina on the equilibrium pH were studied. The pH values were found to be highly influenced by the composition of glass and appeared to have a direct relationship with the logarithm of oxygen ion activity. Also it was found that in commercial glasses containing low amounts of MgO, BaO and B2O3 the equilibrium pH appeared to increase linearly with the increasing amount of alkali extraction when the ratio of (moles of alkali oxides—moles of Al2O3) to moles of alkaline earth oxides is more than 1.1. The slope of the plot of log alkali extraction against equilibrium pH was found to be different for different systems.
TL;DR: In this article, Activated Lime-Slag Cement (ALSC) has been used for Indian ceramics, and the authors present a detailed discussion of its application in the Indian Ceramic Society.
Abstract: (1968). Activated Lime-Slag Cement. Transactions of the Indian Ceramic Society: Vol. 27, No. 1, pp. 46-47.