Showing papers in "Transactions of The Indian Ceramic Society in 1983"
TL;DR: In this paper, the enhanced sintering of tin dioxide with additives, viz. MnO2, CuO, ZnO, Li2CO3 and Sb2O3 has been studied under isothermal condition.
Abstract: The enhanced sintering of tin dioxide with additives, viz. MnO2, CuO, ZnO, Li2CO3 and Sb2O3 has been studied under isothermal condition. The efficiency of different additives in attaining higher density is discussed in terms of grain growth and pore morphology studied by SEM fractograph.The time exponents of the kinetic equation and activation energies are calculated from isothermal sintering data for various systems and these parameters are used to interpret the sintering mechanism for different additives. It has been found that different mechanisms are predominant in different systems and in some cases it depends on sintering temperature also. From SEM fractograph it appears that due to pore trapping within the grains it is not possible to attain higher density.
32 citations
TL;DR: In this article, it is observed that additions up to 5 wt % of various decomposable and non-decomposable stabilizers like CaCO3 MgCO3, Y2O3 and CaF2 result in formation of cubic zirconia phase from 15 to 90% between 1000° and 1200°C.
Abstract: Usefulness of pure zirconia as a refractory material becomes limited due to phase transformation which results in volume changes. These phase transfromations can be suppressed by various stabilizers.It is observed that additions up to 5 wt % of various decomposable and non-decomposable stabilizers like CaCO3 MgCO3, Y2O3 and CaF2 result in formation of cubic zirconia phase from 15 to 90% between 1000° and 1200°C. However, the formation of cubic phase more than 35%, seems to be affecting the sinterability. Properties like densification, microstructure, cubic phase formed have been studied with these stabilizers.Data obtained reveals that nature of stabilizers and amount of cubic phase formed are factors influencing the densification and microstructure of resultant partially stabilized zirconia.
5 citations
TL;DR: In this article, the influence of amount of calcia addition and calcination temperature on the sintering characteristics of zirconia was studied by X-ray diffraction.
Abstract: The influence of amount of calcia addition and calcination temperature on the sintering characteristics of zirconia was studied. The extent of stabilization was studied by X-ray diffraction. It was noticed that the optimum amount of calcia addition to obtain high density without cracking was 0.50 to 0.75 wt%. Higher amount of calcia addition and higher calcination temperature resulted in lowered density.Stabilization of zirconia with calcia addition, i.e. the formation of cubic phase, is found to be a function of amount of calcia added. The cubic solid solution formation took place mainly between 1000° and 1200°c. With the addition of 5.0 wt% of CaO, about 85% of cubic phase is formed at 1200°C and 100% at 1700°C.
5 citations
TL;DR: When soda-lime-silica glass is heated in contact with zinc chloride and lead nitrate, it is observed that ZnZ+ and PbZ+ ions are introduced in surface layers of the glass (up to 101-') and average ZnO content up to 41-' from the surface is as high as 5.5 as mentioned in this paper.
Abstract: When soda-lime-silica glass is heated in contact with zinc chloride and lead nitrate melts around strain point of the glass, it is observed that ZnZ+ and PbZ+ ions are introduced in surface layers of the glass (up to 101-'). Average ZnO content up to 41-' from the surface is as high as 5.5 . Depletion of Ca 2+ ions is also observed. The phenomenon of bivalent ion exchange in glass is ascribed to the higher ionic field strengths of ZnZ+ and Pb2+ in comparison to CaZ+, SEM studies of the thermo-chemically treated samples also reveal compositional changes in the surface layers whereas X-ray diffraction patterns do not indicate the presence of any crystalline phase. © 1983 Taylor and Francis Group, LLC.
4 citations
TL;DR: In this paper, thin, transparent coatings of amorphous Si02 and Al203 were deposited on soda lime glass substrates by the dip technique, using organometallic precursor sols.
Abstract: Thin, transparent coatings of amorphous Si02 and Al203 were deposited on soda lime glass substrates by the dip technique, using organometallic precursor sols. The water content of the sol was found to influence its wetting behaviour, low values of H20: Si(OC2H6), being preferred for Si02 and high values of H20: AI(OC, H9B)3 for Al20a coatings of sufficient uniformity and clarity. Expulsion of volatiles and polycondensation of the coated material were allowed to take place via (i) an initial baking step at 90°-l00°C and (ii) a final heating step at 350°-500°C according to the sol composition. The procedure yielded homogeneous, highly transparent coatings, showing 84-93 transmission of the visible runge of wavelengths. © 1983 Taylor and Francis Group, LLC.
4 citations
TL;DR: In this article, it has been shown that finely divided metal particles (15-100 A) can be formed in the interlayer space of clay minerals or in the structural voids of zeolite under suitable conditions and these can serve for storing hydrogen.
Abstract: Advantages of using hydrogen as a source of energy and silicate materials for its storage, in place of metal hydrides, have been explained. The silicates studied are vermiculites (from France, Spain and artificially prepared), montmorillonite, chlorite (USA) and zeolites (artificially prepared). It has been shown that finely divided metal particles (15–100 A) can be formed in the interlayer space of clay minerals or in the structural voids of zeolite under suitable conditions and these can serve for storing hydrogen.
3 citations
TL;DR: In this article, the thermal decomposition reactions of homoionic clay minerals, viz. vermiculite, in air in the temperature range 30°-1000°C by thermo-analytical methods are reported.
Abstract: The thermal decomposition reactions of some homoionic clay minerals, viz. vermiculite, in air in the temperature range 30°-1000°C by thermo-analytical methods are reported. The reaction kinetic of isothermal dehydration and dehydroxylation is found to obey first order reaction rate.
3 citations
TL;DR: In this article, three plastic fireclays, namely, Mohuamilan and Chittorpur from Bihar and Barachatarma from West Bengal have been taken to study their physico-chemical properties which include chemical analysis, plasticity, particle-size analysis, base exchange capacity, differential thermal analysis, X-ray diffraction, drying and firing characteristics etc.
Abstract: Three plastic fireclays, namely, Mohuamilan and Chittorpur from Bihar and Barachatarma from West Bengal have been taken to study their physico-chemical properties which include chemical analysis, plasticity, particle-size analysis, base exchange capacity, differential thermal analysis, X-ray diffraction, drying and firing characteristics etc. Results indicate that Barachatarma clay is better than the other two clays with respect to plastic property. Owing to the undesirable fired colour, none of the clays can be used where the colour of the product governs the quality of the same.
3 citations
TL;DR: In this article, the effect of CaO and CaF2 additions and calcination temperature on densification and stabilization was studied by thermal cycling between 1200° and 700°C (lower range) and 1400° and 600°c (higher range) up to 25 thermal cycles.
Abstract: The phase transformations in zirconia take place between 900°-1000° and 1200°c while heating, and between 1000° and 800°–600°C while cooling causing material movement. Hence, effect of amount of CaO and CaF2 additions and calcination temperature on densification and stabilization was studied by thermal cycling between 1200° and 700°C (lower range) and 1400° and 700°c (higher range) up to 25 thermal cycles.It was observed that higher densification can be obtained by thermal cycling at lower temperature compared to the temperature required in normal sintering process, particularly so, with CaO additions. High density was attained with CaO additions up to 2 % compared to equivalent amount of CaF2 additions in the lower temperature range. In general, uncalcined compositions attained high density which decreased with increasing calcination temperature. Thermal cycling promoted stabilization. The reaction was almost completed within 5 thermal cycles.
2 citations
TL;DR: In this article, the sintering of Al2O3 in the presence of (CaO+FeO3) and CaO was investigated at various temperatures (1300°-1600°C) and times (up to 300 minutes).
Abstract: Investigations were carried out on sintering of Al2O3 in presence of (CaO+Fe2O3) and CaO.Fe2O3 synthesized at 1150°c for 50 minutes Effects of different amounts, viz. 0.001, 0.003, 0.005 and 0.01 moles of (CaO+Fe2O3) and CaO.Fe2O3 per 100 gm of Al2O3 on the sintering of alumina were studied at various temperatures (1300°—1600°C) and times (up to 300 minutes). The study revealed that 0.005 moles of (Ca0+Fe2O3) and CaO.Fe2O3 gave maximum densification of alumina at 1600°c.
2 citations
TL;DR: In this article, the authors studied ring formation in a Magnesite Rotary Kiln and found that the ring formation can be traced back to the formation of rings in a ring-shaped ring.
Abstract: (1983). Study of Ring Formations in a Magnesite Rotary Kiln. Transactions of the Indian Ceramic Society: Vol. 42, No. 5, pp. 134-134.
TL;DR: The magnetic saturation moment σs (emu/gm) was determined at room temperature using a vibrating sample magnetometer at a maximum field of 6.5 koes as discussed by the authors.
Abstract: Ni0.5 Zn0.5 Fe2 O4 powder was prepared by standard ceramic methods at precalcination and ferritisation temperatures of 800° and 1250°C respectively. The ferrite was doped with oxides of titanium, zirconium and niobium in nominal weight percentages of 0.5, 1,2,5 and 10 of the respective oxides. Lattice parameter values and pycnometric densities of the doped samples were determined. The magnetic saturation moment σs (emu/gm) was determined at room temperature using a vibrating sample magnetometer at a maximum field of 6.5 koes. The base ferrite had a density of 5.258 gm/ml, a lattice parameter of 8.3974 A and a σs value of 71.44 emu/gm. Titanium doped ferrites showed a sharp fall in lattice parameter up to 0.0240 mole fraction followed by a monotonic rise at higher concentrations. The density value first increased and then decreased monotonically. Zirconium and niobium were slightly soluble up to 0.089 and 0.0012 mole fractions respectively as indicated by a constancy of the lattice parameters (at 8.399 A f...
TL;DR: In this paper, the Fourier co-efficients of the diffraction profile were used to calculate the total variance of the line of a single reflection, which is the result of convolution of the particle size and defect profiles.
Abstract: Phyllitous clay minerals, in general, contain two specific structure defects, viz. layer shift and variability of interlayer spacings. Methods developed earlier for quantitative studies of these defects in kaolinites and halloysites and their dehydration products were based on the variance of the single reflection. These techniques were, however, based on the assumption that the principle of additivity of variances due to defect and particle size profiles was valid. In the present study, the total variance of the line has been calculated, using the principle of convolution directly from the Fourier co-efficients of the diffraction profile which is assumed to be the result of convolution of the particle size and defect profiles. By this new approach, the previous techniques have been considerably modified with several new terms appearing in the final expressions. These modified techniques have been applied to study the layer disorders quantitatively in several phyllosilicates and their dehydration products...
TL;DR: In this article, the fired properties of mixtures of zircon and alumina have been studied on the samples made in the laboratory out of mixture of fused alumina grains used as grog grains, calcined at temperatures of about 1520°C.
Abstract: The fired properties of mixtures of zircon and alumina have been studied on the samples made in the laboratory out of mixtures of zircon sand and fused alumina, used as grog grains. It was observed that the properties of samples were very much improved when fused alumina grains were used instead of grog grains, calcined at temperatures of about 1520°C.
TL;DR: In this paper, the molar proportion of 3:1, 1:1 and 1:2 mixes of CaCO3 and Al2O3 were heated at different temperatures for various reaction times and the unreacted lime contents were determined.
Abstract: Mixes of CaCO3 and Al2O3 in the molar proportion of 3:1,1:1 and 1:2 respectively, were heated at different temperatures for various reaction times and the unreacted lime contents were determined. Phases formed in the reaction mixes have been studied by X-ray diffractograms of the partially reacted samples. Data show that lime is consumed in the three mixes before the equilibrium phase C3A, CA or CA2 is formed. The lime reactivity is in the sequence of CA2 < CA < C3A reaction mixes.*
TL;DR: In this paper, the authors investigated the thermoluminescence behavior of sintered thoria samples with respect to bulk density, sintering atmosphere and the radiation dose, and found that the glow curves have peaks around 100°, 146°, 215° and 266°C with 215°C as the most intense one.
Abstract: The phenomenon of thermoluminescence has been frequently employed to obtain information concerning the defects in ionic solids. Present paper reports the results of an investigation on thermoluminescence behaviour of sintered thoria samples with respect to bulk density, sintering atmosphere and the radiation dose.TL glow curves have peaks around 100°, 146°, 215° and 266°C with 215°C as the most intense one. Intensity as well as peak resolution improved with density. All the peaks are found to saturate at about the same γ-radiation dose. Emission centres are assigned to be associated with the variable valence transition metal impurities unintentionally incorporated in ThO2 lattice.
TL;DR: In this article, a dynamic method based on hot-wire technique for determining thermal conductivity of different insulating materials in block-form bas been developed, which is designed and fabricated to suit the purpose.
Abstract: A dynamic method based on hot-wire technique for determining thermal conductivity of different insulating materials in block-form bas been developed. The circuit is designed and fabricated to suit the purpose. A number of samples having known bulk density and thermal conductivity values are collected to assess the merit of the set-up by comparing the known values of the bricks with those measured by this set-up. © Taylor & Francis Group, LLC.
TL;DR: In this paper, the authors describe how effective gunning could be used as an intermediate measure for maintaining various sections, particularly severe wear areas of mixer and open hearth linings during campaign running.
Abstract: Prolonged campaign life and low maintenance cost play a significant part in the economical operation of steel making furnaces. Uninterrupted services of hot metal mixer and open hearth furnace are essential for augmenting ingot steel production. Since refractories in different parts of mixer and open hearth furnace do not wear at similar rates, some sections of the linings have to be repaired or replaced, if maximum life is to be obtained from the remainder of the linings.In recent years, gunning of refractories for hot repairs of the linings of mixer and open hearth furnace is gaining importance over conventional practice of repairing with the bricks to balance the life of primary brick lining and to maximise the utilization of the entire lining, and thus help lengthening the campaign life.The paper describes as to how effective gunning could be used as an intermediate measure for maintaining various sections, particularly severe wear areas of mixer and open hearth linings during campaign running. Mainte...
TL;DR: In this article, the use of GC, GC/MS and HPLC are also becoming common to characterize health and safety related problems in thermal applications, and the standard deviation and coeficient of determinations are mentioned.
Abstract: Methods have been developed for analysis of alumino-silicate and magnesia-chrome materials by X-ray fluorescence by fusing the materials into a glass disc and then analyzing the components by irradiating with X-rays. Lithium tetraborate has been used for alumino-silicates, and sodium hexametaphosphate along with lithium metaborate has been used for chrome-magnesia materials. Addition of La2O3 as a heavy absorber has been eliminated in both cases by using programmes for inter-elemental corrections by the computer. Calibration lines made from available standards have been made and their standard deviation and coeficient of determinations are mentioned. To cope with the changes in refractory technology, thermal analysis equipment have been used to solve problems related to change in thermal applications. DTA and TGA have been used extensively and some specific applications have been mentioned. The use of GC, GC/MS and HPLC are also becoming common to characterize health and safety related problems.
TL;DR: In this article, the authors described the characterization and rehydration of the clay from Bikaner district of Rajasthan and found that the clay contained predominantly montmorillonite with kaolinite and quartz as impurities.
Abstract: The paper embodies characterization and rehydration of the clay from Bikaner district of Rajasthan. DTA and XRD indicated that the clay contained predominantly montmorillonite with kaolinite and quartz as impurities. The behaviour of the clay on dehydroxylation was found similar to an ‘abnormal montmorillonite’. DTA and TGA study suggested that the clay regained lost water completely on rehydration after being heat-treated up to 400°c, but the rehydration was comparatively poor when the clay was heated at higher temperatures. Maximum water adsorption was noticed for the sample heat-treated at 200°C.
TL;DR: In this paper, a study on liquid phase sintering was carried out on different MgO-china clay compacts containing 4, 8, 12, 16 and 20% by weight of china clay.
Abstract: Studies on liquid-phase sintering were carried out on different MgO-china clay compacts containing 4, 8, 12, 16 and 20% by weight of china clay. Initial particle size of the powders taken was—45 microns. The green compacts of 1.25 cm dia were cold pressed at a constant pressure of 1600 kg/cm2 and sintered in a high temperature gas fired furnace in oxidising atmosphere at 1600°, 1650° and 1700°c for 0 to 8 hours. The rates of densification showed that MgO-12 wt % china clay compacts sintered at 1700°c for 4 hours, attained a maximum value of bulk density, i.e. 3.56 gm/cc. This value was 99.44% of the theoretical density. The same compacts, when sintered at 1650° and 1600°c for 4 hours, resulted in maximum values of bulk density, i.e. 3.53 and 3.44 gm/cc respectively. These values were 98.60 and 96.08% of the theoretical density. The values of apparent porosity of these sintered compacts were found to be 1.10, 3.50 and 5.20% respectively.For studying the kinetics of sintering, experimental data were analyse...
TL;DR: In this article, the usefulness of a refractory clay depends very much on the quantity of free silica (quartz) in the clay and has to be determined before the clay is mined.
Abstract: The usefulness of a refractory clay depends very much on the quantity of free silica (quartz) in the clay and has to be determined before the clay is mined. It has been found that the quartz content can be correlated with loss on ignition (LOI), Pyrometric Cone Equivalent (PCE), water of plasticity and Bulk Specific Gravity (BSG) and calcining temperature of the clay. All these correlations indicate that a suitable clay should not contain more than 20–25% quartz for refractory use.
TL;DR: In this paper, an attempt has been made to prepare PCB with glass-bonded material developed at the Institute of Electronics and Information Technology (TEIT), in view of a unique combination of mechanical, thermal and electrical desirability and also for low cost of production.
Abstract: PCB fabric-ations are, at present, limited within varieties of reinforced plastic laminates. In special cases, ceramic substrates of alumina aud beryllia are also used. Glass-bonded mica also holds a good potentiality as a PCB material, especially in view of a unique combination of mechanical, thermal and electrical desirability and also for low cost of production. An attempt has been made to prepare PCB with glass-bonded material developed at the Institute. © 1983 Taylor & Francis Group, LLC.
TL;DR: Worrall et al. as mentioned in this paper used Stoke's Law to determine the specific surface areas of quite a number of clays used in this country in the whiteware industry, and the results have been discussed.
Abstract: Clays, both china and plastic, dominate the ultimate performance of the whiteware. industry. The rheology of clay-water systems/pastes is governed by the finer fractions or the colloidal particles. The evaluation of the clay fineness using Stoke's Law is time consuming for the whiteware manufacturer, especially in the small-scale sector in this country, who desires quick information which need not be very accurate. Clay minerals have the characteristics of absorbing certain ions and retaining them in an exchangeable state, i.e. these ions are exchangeable for other ions by treatment in an aqueous solution. Worrall developed a method using the above information. The method is inexpensive, quick and accurate enough for practical purposes. The method has been used to determine the specific surface areas of quite a number of clays used in this country in the whiteware Industry. To ascertain the efficacy of the method, clays douched with sulphuric and phosphoric acids were evaluated and results have been discussed. © 1983 Taylor & Francis Group, LLC.
TL;DR: The effect of cation valency on the value of equivalent counterion supply at maximum exchange has been discussed for zeolites NaA, NaX and NaY in this paper, and it has been suggested that the valency dependence of diffusion was much stronger in the zeolite than in the solution.
Abstract: The effect of cation valency on the value of equivalent counterion supply at maximum exchange has been discussed for zeolites NaA, NaX and NaY. It has been suggested that the valency dependence of diffusion was much stronger in the zeolite than in the solution. © 1983 Taylor & Francis Group, LLC.
TL;DR: In this paper, a certain amount of pozzolana can be mixed with Portland cement to yield pozzolanic cements and thus the mixture becomes economic as well as inter-reactive.
Abstract: In this review pozzolanic cements have been discussed. A certain amount of pozzolana can be mixed with Portland cement to yield pozzolanic cements and thus the mixture becomes economic as well as inter-reactive. The specific advantages are its better strength, improved workability, less heat of hydration, less shrinkage and greater resistance to chemical attack and cracking. The improvement of properties as well as their mechanisms have teen discussed.