Showing papers in "Transactions of The Indian Ceramic Society in 1989"
TL;DR: In this paper, five samples of a conventional stoneware composition have been prepared with variations in grinding time and a body mix having identical composition but produced under factory conditions was also collected for the study.
Abstract: Five-samples of a conventional stoneware composition have been prepared with variations in grinding time. A body mix having identical composition but produced under factory conditions was also collected for the study. Physico-chemical characteristics of raw materials used in the body mix were evaluated. Physical and fired properties of prepared body samples fired at various test temperatures were measured and their relationship with the particle size of mixed bodies was examined. It was observed that the gradual reduction in particle size of the mixed bodies improved the fired properties with the gradual increase in test temperatures until vitrification. On optimization of properties, it emerged that the conventional white stonewares containing particles in the range of 60 to 65% below 10 micron not only matured at a lesser temperature than that of the factory body containing about 50% particles below 10 micron, but also had improved ceramic properties and were found suitable for successful industrial pro...
8 citations
TL;DR: In this paper, a strong bond is maintained between periclase grains and magnesium aluminate hydrate (MAH) which does not weaken during the gradual decomposition of the latter.
Abstract: Magnesium aluminate hydrate (MAH) which is synthesized as a gelly like material, retains its combined water over a wide range of temperature and undergoes a series of changes with the rise of temperature. A strong bond is maintained between periclase grains and MAH which does not weaken during the gradual decomposition of the latter. By analogy with the mechanism postulated in the phosphate bond, formation of contacts between grains and the bond during hardening of the binder may involve hydrogen bonds. The strength in the so-called “weak zone” is maintained by generation of anion and cation vacancies in the binder, producing a reactive non-stoichiometric spinel, which interacts in the solid state with periclase grains.
7 citations
TL;DR: In this paper, the most important modes of chemical attack on concrete, which include chloride ion penetration, sulphate attack, and carbonation attack, are reviewed and the roles of pozzolanic substances such as silica fume, fly ash and slag in reducing deterioration in concrete are described.
Abstract: Deterioration in concrete not only affects the aesthetic beauty of the structure, but also is highly important from the point of view of durability Despite concerted efforts of scientists and technologists to solve this problem, concrete deterioration continues to exist on a global scaleThe paper reviews the most important modes of chemical attack on concrete, which include chloride ion penetration, sulphate attack and carbonation The possible mechanisms of attack are discussed The roles of pozzolanic substances, such as silica fume, fly ash and slag in reducing deterioration in concrete are described with reference to some of the findings of different workers over the last few years
5 citations
TL;DR: In this article, the absorption characteristics of Mn3+ ion in alkali borate and alkali silicate glasses were investigated and it was found that the absorption maximum was more towards the longer wavelengths with increasing ionic radii of the alkali ions and the results were discussed in the light of ligand field approach.
Abstract: Absorption characteristics of Mn3+ ion in alkali borate and alkali silicate glasses were investigated. The absorption maximum due to Mn3+ ion was found to shift more towards the longer wavelengths with increasing ionic radii of the alkali ions and the results were discussed in the light of ligand field approach.
3 citations
TL;DR: In this paper, the compaction characteristics of different silicon carbide and carbon powders and the optimum compaction pressures for bringing about proper reaction of silicon vapour and particulate carbon were studied and evaluated.
Abstract: In reaction sintering of silicon carbide, newly formed grains bind the already existing grains in a compact of silicon carbide and carbon mixture under heating in an atmosphere of silicon vapour. Powders of silicon carbide were prepared and characterized for specific surface area, average particle size and size distribution. The compaction characteristics of the mixtures of different silicon carbide and carbon powders and the optimum compaction pressures for bringing about proper “siliciding” (reaction of silicon vapour and particulate carbon) were studied and evaluated. Siliciding studies were carried out in the temperature range of 1500°–2000°C in argon atmosphere at pressures from 760 torr to 10−1 torr. The sintered specimens were characterized for bulk density by water displacement method and completion of reaction by X-ray diffraction. Sintered densities of the order of 80–85% of the theoretical value could be obtained by optimizing argon partial pressure and increasing the reaction temperature to 20...
2 citations
TL;DR: In this article, a spectrophotometric method was developed for the determination of trace amounts of silica in barium titanate and zirconia ceramics based on the formation of molybdosilicic acid, its preconcentration on polyurethane foam, elution in acetone (acetone: HCl = 99:1) and reduction to molybdenum blue form.
Abstract: A spectrophotometric method has been developed for the determination of trace amounts of silica in barium titanate and zirconia ceramics based on the formation of molybdosilicic acid, its preconcentration on polyurethane foam, elution in acetone (acetone: HCl = 99:1) and reduction to molybdenum blue form. The method is applicable up to 2 μg Si/ml. The minimum that was detected by this method was 5.0 ng Si/ml. The method yielded agreeable results.
2 citations
TL;DR: In this paper, reaction sintering of zircon and mullite at relatively low temperatures was used to construct zirco-mullite ceramics, and the strength of the composites was found to have improved by annealing.
Abstract: Zirco-mullite ceramics have been prepared by reaction sintering of zircon and mullite at relatively low temperatures. The strength of the composites was found to have improved by annealing.
2 citations
TL;DR: In this paper, a mixture of pure zirconia and yttria was prepared by sol-gel transformation followed by calcination techniques, and the powders were characterized for their purity, chemical homogeneity, thermal behaviour, particle size, surface area, crystallite size and content of the tetragonal and monoclinic phases.
Abstract: Powders of pure zirconia and zirconia containing 3 mol% yttria were prepared by sol-gel transformation followed by calcination techniques. The powders were characterized for their purity, chemical homogeneity, thermal behaviour, particle size, surface area, crystallite size and content of the tetragonal and monoclinic phases. The results show that as-prepared powders were of high purity, chemically homogeneous, X-ray amorphous and contained sub-micron particles. Addition of yttria increased the temperature stability of the tetragonal phase, while the critical crystallite size for the transformation remained unchanged. Yttria stabilized zirconia powders could be hot- pressed to 97% theoretical density at 1450°C and the sintered body consisted of uniform 0.70 μm grains having about 45% tetragonal phase.
2 citations
TL;DR: In this paper, the effect of incorporating yttria stabilized zirconia on fracture toughness and other related mechanical properties of high alumina ceramics was studied, including porosity, density, fired shrinkage, microhardness, transverse rupture strength and fracture toughness.
Abstract: The effect of incorporating yttria stabilized zirconia on fracture toughness and other related mechanical properties of high alumina ceramics was studied. The experiments were so designed as to allow study of the effect of sintering at various temperatures with different periods of soaking on some of the properties. It was shown that the transverse rupture strength and fracture toughness were largely dependent on the percentage and crystalline phases of ZrO2 present and also on the sintering temperature.
The properties studied included porosity, density, fired shrinkage, microhardness, transverse rupture strength and fracture toughness. SEM was deployed for characterization of the resulting microstructure. An attempt was made towards characterization of the resulting phases due to supposedly two different mechanisms.
1 citations
TL;DR: In this paper, a solution of hydrated thoria was precipitated from aqueous solution of Th(NO3)4·6H2O with concentrated ammonia, and X-ray and electron diffraction showed the precipitate to be amorphous.
Abstract: Hydrated thoria was precipitated from aqueous solution of Th(NO3)4·6H2O with concentrated ammonia. X-ray and electron diffraction showed the precipitate to be amorphous. TE micrographs showed the individual particle sizes to be in the range 50–100 A with larger agglomerates of the order of 1000–3000 A. X-ray line broadening indicated average crystallite sizes in the range 17 to 394 A for the powders calcined between 300° and 800°C. Infrared spectra showed absorption bands of OH, NO and NO2 radicals in the amorphous as well as calcined materials, their intensities decreasing at higher calcination temperatures. Green pellets of ThO2 powder pressed in the range 27.2–109.5 KN.cm−2 gave green densities in the range 3.34–4.92 gm.cm−3 and isothermal sintering of the compacts in the temperature range of 1233°–1509°C for 1.5–9 hrs yielded densities in the range 72–96% of theoretical.
1 citations
TL;DR: The physical, chemical and mineralogical characters of twelve pyrophyllite samples collected from three states, namely, Uttar Pradesh, Madhya Pradesh and Rajasthan are described in this article.
Abstract: The physical, chemical and mineralogical characters of twelve pyrophyllite samples collected from three states, namely, Uttar Pradesh, Madhya Pradesh and Rajasthan are described. The investigations show that the deposits mainly fall into three categories: low, medium and high alkali content pyrophyllites. Possible utilization for these three categories of pyrophyllites have been mentioned.
TL;DR: In this article, the authors deal with the study of production of metallic glasses, their properties and technological applications, and their use in the field of mechanical engineering and also in electrical and electronic components.
Abstract: Metallic glasses are materials produced by rapid cooling of metallic melts avoiding crystallization. The excellent combination of mechanical, electrical and chemical properties of these disordered materials find their extensive use not only in the field of mechanical engineering but also in electrical and electronic components. This paper deals with the study of production of metallic glasses, their properties and technological applications.
TL;DR: In this paper, dilute hydrochloric acid (0.4 M) of known volume was used to estimate pozzolana content in portland polysilicon (PPC).
Abstract: Determination of pozzolana content in portland pozzolana cement (PPC) by the hydrochloric acid extraction technique has been already investigated. In the existing methods the varying degree of dissolution of pozzolana contents causes its over- or underestimation. This could be eliminated by using dilute hydrochloric acid (0.4 M) of known volume. In the suggested method, errors due to the extraction of ordinary portland cement (OPC) fraction and other constituents of pozzolana were successfully minimized. These conditions can be adopted to different types of pozzolana even in the absence of original ingredients used in the PPC and estimation can be completed in 3–4 hrs by taking 4 samples at a time. The results obtained are reasonably accurate (within ± 2.5% error).
TL;DR: Strontium hexaferrite was prepared from coprecipitated strontium iron complex obtained from metal chloride solutions in the presence of ammonium carbonate as discussed by the authors, which was prepared in the ranges pH 7.5-10, dilution 0.001-0.001M and an increase with pH when other variables were held constant.
Abstract: Strontium hexaferrite was prepared from coprecipitated strontium iron complex obtained from metal chloride solutions in the presence of ammonium carbonate. Coprecipitation parameters were varied in the ranges pH 7.5–10, dilution 0.001–0.5 moles Fe in solution and Fe/Sr ratio 11–25. X-ray diffraction indicated crystalline SrCO3 and amorphous hydroxide of iron in the precipitate. Transmission electron micrographs indicated decrease in particle size with decrease in concentration of Fe, (600 A at 0.04M to 55 A at 0.001M) and an increase with pH (400 A at pH 7.0 to 840 A at pH 9.0) when other variables were held constant. Lattice parameters of the hexaferrite showed c0 = 23.13 A (23.05 A) and a0 = 5.880 A (5.885 A) with published values in parentheses. Ferritization of powders was carried out in the range 1000°-1200°C after precalcination at 800°C. Magnetic studies indicated highest σs, the saturation moment at 61.3 emu.gm−1 for polycrystalline material (74.3 reported for single crystal) at room temperature f...
TL;DR: The influence of 5 to 15% substitution of copper by Ti, Fe and Zn on the superconducting transition temperature of YBa2Cu3O7 has been studied through resistivity measurements.
Abstract: The influence of 5 to 15% substitution of copper by Ti, Fe and Zn on the superconducting transition temperature of YBa2Cu3O7 has been studied through resistivity measurements. Tc is found to be reduced gradually due to Ti substitution. Fe and Zn substitutions have very pronounced effect on Tc and superconductivity is destroyed at 15% substitution in both these cases. Possible reasons for the observed behaviour are discussed.
TL;DR: In this paper, the preparation and properties of self-bonded silicon carbide (SBSC) rods are presented, including Young's modulus, bulk modulus and rigidity modulus.
Abstract: The preparation and properties of self-bonded silicon carbide (SBSC) are presented. The properties include Young's modulus (E), bulk modulus (μ), rigidity modulus (K), Poisson's ratio (σ) and electrical resistivity (ρ). E, μ and K for SBSC rods pressed at 76 MN.m−2 were found to be 0.329, 0.422 and 0.122 GN.m−2 respectively and ρ for the above rods varied from 0.42 to 0.22 ohm.cm at room temperature and 1000°C respectively with a minimum at 600°C.
TL;DR: In this paper, the melting conditions of photochromic glasses of the ophthalmic variety were investigated and the results indicated the formation of AgCl1-x Brx type crystallites with sizes ranging from 100 to 500 A during heat treatment of the glass.
Abstract: Melting conditions of photochromic glasses of the ophthalmic variety were investigated Melting consisted of two parts, viz a pyrex type glass and then a photochromic composition with the premelted glass The method followed suppressed the loss of halides from the molten glass by reducing the melting time Alkali-halide-saturated air cover over the melt surface was found necessary to make the glass photochromic Ophthalmic specifications were attained by replacing part of the alkalis by PbO and BaO for matching index and Abbe values Absorption studies indicated the formation of AgCl1-x Brx type crystallites with sizes ranging from 100 to 500 A during heat treatment of the glass
TL;DR: In this article, various methods for enriching CaO content in lime from shaft kilns are described, such as water and air elutriation, exposure to air, manual scrapping of lumps and sprinkling water on the lumps.
Abstract: Various methods for enriching CaO content in lime from shaft kilns are described. Methods adopted in this work include water and air elutriation, exposure to air, manual scrapping of lumps and sprinkling water on the lumps. It is shown that lime containing 40–60% CaO can be enriched to corresponding Ca(OH)2 of 80–85%.
TL;DR: In this article, the thermal stability of monocalcium aluminate hydrate in relation to titania was studied by thermogravi-metry and the dehydration rate curves obtained at different temperatures in the range 100°-400°C followed formal first order kinetics.
Abstract: Monocalcium aluminate, a major hydraulic phase of high-alumina cements, hydrates to form metastable CAH10 which finally converts to stable C3AH6 and AH3. The thermal stability of monocalcium aluminate hydrate in relation to titania was studied by thermogravi- metry. The dehydration rate curves obtained at different temperatures in the range 100°–400°C followed formal first order kinetics. The activation energy values of the dehydration reactions were determined and found to be dependent on the titania content. Six per cent titania has beneficial role on the thermal stability of the hydrated monocalcium aluminate.
TL;DR: In this article, the effects of silicate boundary phase provided by monticellite (CaMgSiO4) decomposition in situ on the sintering behaviour of magnesium oxide powder compacts have been studied.
Abstract: The effects of silicate boundary phase provided by monticellite (CaMgSiO4) decomposition in situ on the sintering behaviour of magnesium oxide powder compacts have been studied. The parameteis include median particle size, nature and quantity of silicate liquids and thermal treatments.Inadequate amount of viscous liquid formation at 1490°C due to peritectic reaction of monticellite (CMS) seemed to hinder the densificaron in magnesia-monticellite system. On the other hand, complete melting of monticellite at 1650°C enhanced densification to 3.16 gm.cm−3 from 2.75 gm.cm −3 at 1490°C for samples containing 12% CMS. Under the conditions of sintering, liquid formation followed by particle rearrangement played the principal role in densification.
TL;DR: Two mica schists and three talc minerals from Jhabua and Dhar districts of Madhya Pradesh hare been studied using DTA and TGA techniques Structural changes accompanying dehydration and thermal transformations in different silicate minerals have been studied Suitability of these minerals as additive for filling and reinforcement in polymer and in alloys has been assessed SEM micrographs of the heat treated minerals are presented as mentioned in this paper.
Abstract: Two mica schists and three talc minerals from Jhabua and Dhar districts of Madhya Pradesh hare been studied using DTA and TGA techniques Structural changes accompanying dehydration and thermal transformations in different silicate minerals have been studied Suitability of these minerals as additive for filling and reinforcement in polymer and in Al-alloy has been assessed SEM micrographs of the heat treated minerals are presented
TL;DR: In this paper, surface modified kaolinite particles were used for the preparation of Clay-polyethylene (CPM) composites using a thermal decomposition-hydration-redecomposition technique.
Abstract: Clay-polyethylene particulate composites were prepared using surface modified kaolinite particles. The modification was achieved by a thermal decomposition-hydration-redecomposition technique. Properties such as density, porosity, tensile properties, abrasive wear and dielectric properties of the composites containing 0.05–0.2 volume fraction of surface modified kaolinite were measured and compared to those containing untreated kaolinite. It was observed that composites containing surface modified kaolinite showed improvements in the above properties compared to the composites containing untreated ones. The microstructural observations on the polished surface of the composites indicated a fairly uniform distribution of the particles with less agglomeration in case of the surface modified kaolinite composites as compared to those containing unmodified particles.
TL;DR: In this article, the newly employed Mossbauer spectroscopic technique has been evaluated with respect to other methods and the premise employed involves the significant relationships of particle size with relaxation time, showing exponential relationship, hyperfine field and recoil-free fraction, showing corresponding linear decrease, and line width, showing inverse relationship.
Abstract: Quantitative estimation of particle size of crystalline materials is commonly made by, among others, scanning electron microscopy (SEM)/transmission electron microscopy (TEM), X-ray diffraction (XRD) etc. In this paper, the newly employed Mossbauer spectroscopic technique has been evaluated with respect to other methods. The premise employed involves the significant relationships of particle size with (a) relaxation time, showing exponential relationship, (b) hyperfine field and recoil-free fraction, showing corresponding linear decrease, and (c) line width, showing inverse relationship.
TL;DR: In this paper, the effect of powder preparation on the mechanical properties of partially stabilized zirconia has been studied and it has been observed that fracture toughness, transverse rupture strength, microhardness etc improved with the improvement in the powder preparation method.
Abstract: The effect of method of powder preparation on the mechanical properties of partially stabilized zirconia has been studied. Zirconia powder doped with 3 mol% of yttria was prepared by three different methods, viz. mechanical method, modified mechanical method and co-precipitation method. It has been observed that fracture toughness, transverse rupture strength, microhardness etc improved with the improvement in the powder preparation method.
TL;DR: In this paper, the powder was separated, dried and reduced in H2 at 500°C for 4 hours and the nickel content was 30 wt% and its density 9.46 gm.
Abstract: Thoria powder of—100 to +170 mesh prepared by crushing presintered compacts was soaked with nickel salt by digestion in an aqueous solution of Ni(NO3)2·7H2O for 1 hr at 80°C followed by dropwise addition of Na2CO3 when the reaction was completed. The powder was separated, dried and reduced in H2 at 500°C for 4 hours. The nickel content of the powder was 30 wt% and its density 9.46 gm.cm−3. It was mixed with ferritic stainless steel (SS) powder of—100 mesh into 4 compositions (0, 30, 45 and 60% by wt thoria and balance SS) and hot pressed into pellets of 12.7 mm dia × 8 mm ht at 1030°C to relative densities ranging from 96 to 86% of theoretical. Optical micrographs of polished surfaces indicate SS matrix as continuous with discrete pore and thoria powder phases and that the coatings are continuous with the matrix. Compressive tests on Instron Material Tester determined 0.2% proof stress, deformation, modulus of elasticity and ultimate strength at room temperature. Brinell hardness was determined at room te...
TL;DR: In this paper, the possibility of the use of carbonized rice husk as a fuel for black meal process of cement making is investigated, and it is observed that about 50% of the energy required for clinkerization in the black-meal process can be saved via substitution by the carbonized husk.
Abstract: The possibility of the use of carbonized rice husk as a fuel for black meal process of cement making is investigated. It is observed that about 50% of the energy required for clinkerization in the black meal process can be saved via substitution by the carbonized husk. Cements produced by using higher percentage of carbonized husk, although found to be of higher free lime in the clinkers, exhibit higher compressive strength. The reasons for such behaviour are discussed in the paper.