Showing papers in "Transactions of The Indian Ceramic Society in 1982"
TL;DR: In this paper, thermal analysis of clay-H3PO4 system was studied in view of beneficial effect of clay in phosphate bond by way of increasing workability and reducing the moisture sensitivity.
Abstract: Thermal analyses of clay-H3PO4 system were studied in view of beneficial effect of clay in phosphate bond by way of increasing workability and reducing the moisture sensitivity.The various properties of clay and H3PO4 were taken to obtain P2O5/A12O3 molar ratios from 0.5 to 3.0. The results of thermal analyses show that the clay attacks phosphoric acid at as low as 200°-220°C and the product depends upon the P2O5/A12O3 ratios and the temperature of reaction. The A1(H2PO4)3, A12(H2P2O7)3, A1(PO3)3, A1(PO4) and silico-phosphates are the major products. With the higher concentration of P2O5 there is a tendency to form silico-phosphates.
7 citations
TL;DR: In this paper, a simple and rapid complexometric method for stepwise titration of calcium and magnesium, when present in unfavourable ratios, has been successfully worked out, which is based on the direct titrations of calcium of pH 12 with EDTA, using thymolphthaleincalcein indicator.
Abstract: A simple and rapid complexometric method for stepwise titration of calcium and magnesium, when present in unfavourable ratios, has been successfully worked out. The method is based on the direct titration of calcium of pH 12 with EDTA, using thymolphthaleincalcein indicator. The adsorption of metallochromic indicator and any Ca2+ has been prevented by the prior addition of titan yellow which masks magnesium by lake formation. Glycerine is also added as a protective colloid to stabilize the lake and to prevent coprecipitation of Ca(OH)2. After dissolution of the lake in HC1 acid, subsequent addition of ascorbic acid, then ammonia and ammonia buffer, for controlling the pH at 10, Mg is determined in the same aliquot by direct titration with EDTA using Eriochrome Black T indicator. The method has been successfully applied for the determination of calcium oxide and magnesium oxide in magnesite, dolomite, asbestos and other lime and magnesia bearing materials.
4 citations
TL;DR: In this article, high alumina ceramics are used as insulating materials in high voltage electrical application and they exhibit excellent dielectric properties along with high electrical resistivity and high thermal shock resistance and mechanical strength.
Abstract: High alumina ceramics are used as insulating materials in high voltage electrical application. Thin plates of alumina (≈ 1 mm) are found highly suitable in miniaturised electronic systems. They exhibit excellent dielectric properties along with high electrical resistivity and high thermal shock resistance and mechanical strength.Initial investigations were carried out for the development of high alumina substrates with alumina content above 90% with a view to get complete vitrification at commercially attainable temperatures in the range 1400°-1500°C. The data presented include the properties like porosity, density, dielectric loss, dielectric constant, microstructures of ‘as-fired surface’ and the surface characteristics of the substrates developed. The influence of various compositions and sintering treatments on surface characteristics has been studied by SEM.
3 citations
TL;DR: In this paper, it has been confirmed by X-ray, IR spectroscopy and magnetic susceptibility measurements that the first exothermic peak corresponds to the crystallization of α-FeOOH while the second peak at 315°C correspond to the formation of α2O3 and the third one is due to a change in crystallite size of the specimen.
Abstract: The decomposition sequence of the pure and mixed hydroxides of iron(III) and nickel(II) containing 0–50 mol% of NiO and the formation of a ferrite phase have been studied using various experimental techniques. DTA plots of pure ferric hydroxide exhibit one endothermic peak at 130° and three exothermic peaks at 210°, 315° and 430°C. It has been confirmed by X-ray, IR spectroscopy and magnetic susceptibility measurements that the first exothermic peak corresponds to the crystallization of α-FeOOH while the second exothermic peak at 315°C corresponds to the formation of α-Fe2O3 and the third one is due to a change in crystallite size of the specimen.The positions of the endothermic peak at 130° and the two exothermic peaks at 210° and 315°C of ferric hydroxide do not vary significantly with the addition of NiO to the ferric oxide. However, there is a shift in the exothermic peak at 430°C. The magnetic measurements of the mixed oxide specimens indicate the possible formation of the ferrite phase within 550°C ...
3 citations
3 citations
TL;DR: In this paper, the rheological behavior of clay pastes from 20 clay samples at various moisture contents, close to liquid limit consistency have been carried out, and from the results, the magnitude of thixotropic break-down at liquid-limit consistency has been determined.
Abstract: Investigations on the rheological behaviour of clay pastes from 20 clay samples at various moisture contents, close to liquid limit consistency have been carried out, and from the results, the magnitude of thixotro- pic break-down at liquid limit consistency has been determined. The magnitude of thixotropic break-down at liquid limit has been found to vary within a narrow range of 3.4 to 4.6 sq cm. A method to determine liquid limit of clays has also been worked out from these studies. The liquid limit values obtained by the above method and from other standard classical methods compare well within a variation of 1 to 2 per cent.
2 citations
TL;DR: In this paper, the suitability of the sand for the glass industry was examined chemically and petrographically, and some beneficiation work was carried out to investigate the use of the raw sand available at Surajdewal.
Abstract: The raw sand available at Surajdewal was examined chemically and petrographically and some beneficiation work was carried out to investigate the suitability of the sand for the glass industry. The sand, as such, corresponds to Grade 3 of IS: 488-1963. During beneficiation it was observed that washing with water lowered the iron content, bringing the sand almost equivalent to Grade 2, and on leaching with 1 H2S04 the sand was found to be in conformity with Grade 1. The coarseness of the sand was reduced through grinding and this led to significant improvement in particle size distribution, ali preferred by the glass industry. Trial melting wa11 carried out with untreated and different grades of treated sands. The results were found to be encouraging for utilization in the glass industry. © 1982 Taylor & Francis Group, LLC.
2 citations
TL;DR: In this article, the results of some experiments on the application of sodium ion selective glass electrode in the development, quality control and production of high purity reactive alumina required by the electronic and ceramic industries are presented.
Abstract: The paper deals with the method and results of some experiments on the application of sodium ion selective glass electrode in the development, quality control and production of high purity reactive alumina required by the electronic and ceramic industries. The free soda and structural soda were determined by means of the sodium ion selective glass electrode at different stages of development and production of reactive alumina. Some of the results obtained compared very satisfactorily with the results given by flame photometry. The investigation shows the efficacy of the ion electrode system and its scope of utilization in other fields of applications.
2 citations
2 citations
TL;DR: In this paper, a pure alkali alumino-silicate hydrosol has been synthesized by the wet interaction of alkali silicate and alkali aluminine solution under specific experimental conditions.
Abstract: Pure alkali alumino-silicate hydrosol has been synthesized by the wet interaction of alkali silicate and alkali aluminate solution under specific experimental conditions. It was converted to different cationic forms. The cation exchange behaviour, the most important property, by which it can be differentiated from the other sols has been studied with respect to variation of the nature and concentration of cations. Under equilibrium condition, the nature of the exchange concentration relationship did not show any change in their nature, but the sequences of the cations, specially the divalent ones, were found to be dependent on the nature of both the exchanging and exchangeable cations.
1 citations
TL;DR: In this paper, the mineralogical characterizations of some Indian vermiculites and chlorites are reported, and significant differences in X-ray and thermal properties are observed, presumably due to presence of mixed layer minerals and/or other contaminations.
Abstract: Mineralogical characterizations of some Indian vermiculites and chlorites are reported. Significant differences in X-ray and thermal properties are observed. Such anomalies of the properties are presumably due to presence of mixed layer minerals and/or other contaminations.
TL;DR: In this paper, the acceleration voltage recommended is 15 kV and the sample should not be polished as it risks to cause structural disorganization, and a few representative micrographs of vermiculite mineral are presented for comparison.
Abstract: Because of the poor crystalline nature and presence of interlayer water molecules in many phyllosilicates, special pre-treatment as well as analytical procedures are required. One of these procedures consists of lyophilizing the sample before analysis. It is stressed that phyllosilicate samples should not be polished as it risks to cause structural disorganization. The acceleration voltage recommended is 15 kV. Few representative micrographs of vermiculite mineral are presented for comparison.
TL;DR: In this article, the initial rate of hydration was observed to be high, however, it slowed down gradually due to the resistance by the hydrated layer to the diffusion of water.
Abstract: Portland-pozzolanic cements were prepared by gradual replacement of Portland cement by pozzolana. Calcined common clay and china clay were used as two different pozzolanas. Sulphated Portland-pozzolanic cements were prepared by incorporating gypsum. Hydration values were measured on curing these cements separately in water and in 5% MgSO4, solution. On water-curing the initial rate of hydration was observed to be high, it slowed down gradually due to the resistance by the hydrated layer to the diffusion of water. Samples containing china clay hydrated more because of the availability of alumina for the formation of hydrated compounds.
TL;DR: In this paper, conditions of carbon deposition via breakdown of ethyl alcohol during its evaporation out of ethoxysilanol gels were studied, and it was inferred from the obtained information that the breakdown reaction of alcohol, occurring in this temperature range, was an initiating, rather than a precursory step of carbon formation.
Abstract: Conditions of carbon deposition via break-down of ethyl alcohol during its evaporation out of ethoxysilanol gels were studied. In the heat-treatment step for gel-glass conversion, the heating rate in the temperature range of 150°-200°C was found to be critical for the decomposition of alcohol and deposition of carbon. It was inferred from the obtained information that the break-down reaction of alcohol, occurring in this temperature range, was an initiating, rather than a precursory step of carbon formation. Some possible break-down reactions were enumerated and one of the likely routes to carbon formation was indicated.
TL;DR: In this article, the results of using a sodium ion selective glass electrode for assessing the chemical durability of six different types of glass containers have been shown and discussed, and the results were compared with those obtained by titration, where the equivalent Na+ figures had been calculated from the ml of HCI consumed for the same.
Abstract: Chemical durability of glass containers are generally determined by means of volumetric titration in terms of millilitres of N/100 HCI consumed for titrating the aqueous extracts of the glass samples, as prescribed by IS and other similar specifications. In the present paper, the method and results of using sodium ion selective glass electrode for assessing the chemical durability of six different types of glass containers have been shown and discussed. From the extracts of the respective glasses prepared by slightly modified IS method, the Na+ contents in ppm were found out by the sodium ion selective glass electrode and the results were compared with those obtained by titration, where the equivalent Na+ figures had been calculated from the ml of HCI consumed for the same. © 1982 Taylor & Francis Group, LLC.
TL;DR: X-ray line profile analysis of magnesia powders derived from three parent compounds (hydroxide, carbonate and oxalate) at various calcination temperatures ranging between 400° and 1200°C was carried out using Warren and Averbach's method to evaluate strain and effective domain size as mentioned in this paper.
Abstract: X-ray line profile analysis of magnesia powders derived from three parent compounds—hydroxide, carbonate and oxalate—at various calcination temperatures ranging between 400° and 1200°C was carried out using Warren and Averbach's method to evaluate strain and effective domain size. The percentage degree of crystallinity was calculated using crystallinity index method of Wakelin, Virgin and Crystal. It has been found that residual microstrains are absent in these magnesia powders and the line broadening was only due to the small crystallite size. The parent compound influences the changes occurring during calcination and ultimately the powder properties such as degree of crystallinity, the crystallite size and the particle size etc which in turn influence the sinterability of these powders.
TL;DR: In this article, the advantages of using ceramics over glasses and those of using alumina over other materials in ceramic to metal seal assemblies are discussed, as well as the various property requirements of alumina for the above applications and for single and multilayer substrates.
Abstract: The various applications of alumina ceramics to the electronic industry are discussed. The emphasis has been mainly on the application in vacuum tubes and solid state devices. The advantages of using ceramics over glasses and those of using alumina over other ceramics in ceramic to metal seal assemblies are discussed. The various property requirements of alumina ceramics for the above applications as well as for single and multilayer substrates are reviewed.
TL;DR: In this paper, the thixotropic coefficient of various clays at liquid limit consistency has been further extended for the determination of liquid limit for red, black and alluvial clays.
Abstract: Studies on the application of rheological properties of clay pastes from red, black and alluvial clays for the determination of liquid limit have been further extended to determine the thixotropic coefficient of various clays at liquid limit consistency. The thixotropic co-efficient at liquid limit consistency, irrespective of clay mineral composition varies in a narrow range of 0.7 to 1.50. At this consistency, the Bingham yield stress and thixotropic area also vary in a narrow range. The plot between thixotropic co-efficient and moisture content at liquid limit of various clays holds two linear relationships: (i) for plastic clays having liquid limit above 50 and (ii) for lean clays having liquid limit below 50±2. The small variations occurring in thixo-tropic co-efficient at liquid limit consistency have been attributed to the nature of exchangeable and adsorbed ions, organic matter, non-clay fractions, surface roughness on sand and silt particles etc.
TL;DR: In this article, the authors studied the sintering of tin dioxide with additives, viz. of MnO2, CuO, ZnO and Li2CO3, under non-isothermal condition.
Abstract: Enhanced sintering of tin dioxide with additives, viz. of MnO2, CuO, ZnO and Li2CO3, has been studied under non-isothermal condition. The kinetics of sintering has been studied under constant heating rate of 5°, 10° and 15°C per minute.With the additive MnO2, different shrinkage curves were obtained for three heating rates. The kinetic parameters were calculated for this system and the predominant sintering mechanism was found to be dependent on both temperature and the stages of sintering. It was evident from the values of kinetic parameters that both viscous flow and volume diffusion mechanisms were operating simultaneously; although at lower heating rate, predominnat contribution of viscous flow was evident.
TL;DR: In this paper, thermal decomposition characteristics of bauxite minerals were studied thermogravimetrically and the energies (E) of activation of the decomposition processes were calculated by Flynn and Wall's method.
Abstract: Thermal decomposition characteristics of bauxite minerals were studied thermogravimetrically and the energies (E) of activation of the decomposition processes were calculated by Flynn and Wall's method. The observed values showed wide variations due to compositional differences. Accessory minerals associated with the ores influenced dehydroxylation reactions.
TL;DR: In this article, the X-ray microprobe technique has been used for determination of trace elements in vermiculites, and the results showed that it is very effective in determining the structure of the vermicule.
Abstract: Factors intervening in evaluating various microstructural characteristics of clay minerals by X-ray microprobe technique, are elucidated. Three vermiculite minerals of different origin have been studied by both wave-length and energy-dispersive X-ray microprobes following the novel pretreatment and analytical procedures. X-ray images, presented here for vermiculites, heat treated at lower temperatures, indicate homogeneity in elemental distribution. On the other hand, samples which are treated at higher temperatures, show heterogeneity in elemental distribution. Variations in elemental distribution with rise in temperature have been explained in terms of the changes occurring in the structure of the mineral. It is shown here that X-ray microprobe technique is very effective in determination of trace elements in clay mineral.
TL;DR: In this article, the physical and chemical properties of checker bricks have been analyzed along with their mineralogical constituents and compressive creep characteristics have also been evaluated in TISCO.
Abstract: Currently, the stoves of blast furnaces are operated at a higher temperature for increasing productivity. Consequently, the demand on the quality of checker bricks has increased. In TISCO, the blast furnaces are operated at a hot blast temperature of 900°C. An attempt has been made to evaluate the refractories available from indigenous sources. Various physical and chemical properties of the bricks have been analysed along with their mineralogical constituents. Compressive creep characteristics have also been evaluated.
TL;DR: In this article, the structural changes on acid treatment of clays have been explained in terms of their mineral content and structural differences, including substitution of substituted aluminium atoms in the silica layers.
Abstract: Two bentonite samples from Gujarat have been investigated for elucidation of their structures and constituents. Physico-chemical analyses and infra-red, X-ray and thermal studies have been carried out, on raw as well as acid treated clay samples, to understand the structural changes on acid treatment of clays. Different degrees of swelling shown by the clays have been explained in terms of their mineral content and structural differences. Both high-swelling and low-swelling bentonites have montmorillonites as the chief mineral constituent; however, the latter has some amounts of quartz and kaolinite as impurities. Low-swelling bentonite has considerable amount of substituted aluminium atoms in the silica layers.
TL;DR: In this article, an attempt was made to use sand as a lining material in steel ladles to reduce the consumption of refractories and also to save time in relining.
Abstract: In recent years, sand slinging process is being used for lining ladles in steel plants. The slung mixes are made from naturally occurring sands or mixture of synthetic grains with suitable binders.In our country, ladle bricks constitute a major tonnage of fireclay bricks in the steel plants. An attempt was made to use sand as lining material in steel ladles to reduce the consumption of refractories and also to save time in relining.Work was undertaken to develop sand slinging mixes of proper composition utilizing indigenous sand. The mixes were tried in steel ladles, used for transferring blown metal from bessemer shop and hot metal from mixer to open hearth furnaces.
TL;DR: In this paper, two clays from the Cannanore district of Kerala have been assessed, both from mineralogical and ceramic point of view, with the objective of evaluating their suitability in the pottery industry.
Abstract: Two clays from Cannanore district of Kerala have been assessed, both from mineralogical and ceramic point of view, with the objective of evaluating their suitability in the pottery industry. The study included the examination of the chemical, mineralogical and physicochemical characteristics of the clays. From the results it has been confirmed that these two clays can easily be used in ceramic industry where fired colour is not so important. For whiteware industry, however, it re-requires some processing or some opacifying glaze meterials.