Showing papers in "Transactions of The Indian Ceramic Society in 1997"
TL;DR: In this paper, the synthesis of Ni-YSZ cermet through a solution chemistry route is discussed, and the Ni concentration is varied between 10 and 60 volume percent (v/o).
Abstract: Porous and electrically conducting Ni-YSZ cermet is used as fuel electrode for solid oxide fuel eel (SOFC). The synthesis of NI-YSZ cermet through a solution chemistry route is discussed in this paper. The Ni concentration is varied between 10 and 60 volume percent (v/o). Porous structure of these cermets is obtained by proper control of sintering schedule. Electrical properties are evaluated as a function of nickel content. At around 30 v/o of Ni a sudden change in electrical conductivity takes place due to formation of a continuous Ni-chain.
5 citations
TL;DR: In this paper, the physicochemical and mineralogical characteristics of different types of clays, available as overburden in lignite deposit at Rajpardi village in Bharuch district in Gujarat were studied with a view to finding out their possible utilisation as replacements of conventional plastic clays in the manufacture of traditional ceramic products.
Abstract: Physicochemical and mineralogical characteristics of different types of clays, available as overburden in lignite deposit at Rajpardi village in Bharuch district in Gujarat were studied with a view to finding out their possible utilisation as replacements of conventional plastic clays in the manufacture of traditional ceramic products.The studies included plastic and dry properties, particle size distribution, chemical analyses, XRD, DTA as well as ceramic properties on the specimens fired at different experimental temperatures. The results showed that the clays were highly plastic in nature as compared to the traditional plastic clays and contained predominantly kaolinite minerals associated with illite/muscovite as minor minerals.
3 citations
TL;DR: In this paper, the physical, chemical, rational, base exchange capacity, pyrometric cone equivalent, petrographical, thermo- chemical and XRD characteristics of all the fractions of the clay were investigated.
Abstract: Kaolinised rocks occurring at the northern part of Mulieh village of Jaintia Hills, Meghalaya were studied with a view to identifying the possible mineralogical set up. The investigation was confined mainly on the crude as well as washed fractions of the clay as obtained from systematic levigation of the crude by gravity sedimentation technique. The study included the finding out of the physical, chemical, rational, base exchange capacity, pyrometric cone equivalent, petrographical, thermo- chemical and XRD characteristics of all the fractions of the clay. The results indicated that the clay in its crude form was primary in origin and contained substantial amount of free quartz, and was kaolinitic in character. On processing by gravity sedimentation the clay was found to be almost free from quartz and contained mineral kaolinite as the predominant phase along with quartz, microcline, muscovite, illite and rutile in minor amounts.
2 citations
TL;DR: In this article, a few compositions in the valence compensated perovskite system have been reported to have relaxor like dielectric behavior, and a few more compositions in this system with 0.20 < x < 0.40 have been prepared by solid state ceramic method and characterized.
Abstract: A few compositions in the valence compensated perovskite system Sr1—xLaxTi1—xCoxO3 have been reported to show relaxor like dielectric behaviour. In order to thoroughly investigate this relaxor like behaviour, a few more compositions in this system with 0.20 < x < 0.40 have been prepared by solid state ceramic method and characterized. All the compositions are single phase solid solution having cubic crystal structure. The microstructure and dielectric behaviour depend on composition. Complex plane impedance and modulus analysis of the electrical data have been made to study the origin of relaxor like behaviour.
2 citations
TL;DR: In this article, a reaction hot pressing of stoichiometric ratios of mixtures of powders of Mo/Si and TiH2/Si without and with reinforcement powders, respectively at 1500°C in vacuum.
Abstract: Molybdenum and titanium silicides (MoSi2 and Ti5Si3) and their composites have been processed by reaction hot pressing of stoichiometric ratios of mixtures of powders of Mo/Si and TiH2/Si without and with reinforcement powders, respectively at 1500°C in vacuum. MoSi2 and Ti5Si3 form in situ by diffusion of Si atoms (in liquid state) under external pressure into the Mo and Ti lattice, respectively, followed by chemical reaction. The processing parameters and particle sizes of the raw materials affect the density, microstructure, grain size and other properties of the composite. In the MoSi2/20 vol% SiC composite, most of the MoSi2/SiC interfaces are atomically abrupt. However, a few interfaces contain a layer of amorphous SiO2 5–8 nm thick Fracture toughness and flexural strengths increase with the decrease in grain sizes. Ti5Si3 and Ti5Si3/20 vol% TiC composite having similar grain size show a higher hardness and fracture toughness in the composite.
2 citations
TL;DR: In this article, a model oil fired ceramic fiber-lined shuttle kiln has been constructed and installed at Santiniketan, Bolepur to meet the demand of small scale industries.
Abstract: The drastic price rise of fuel and the environmentalists' demand on maintaining cleaner environment are forcing the small scale industries to close their units as they are becoming unable to compromise with both the fuel cost and the high installation and maintenance cost of the pollution control equipment. They are looking for alternatives which would be based on cleaner technology. To meet their demand, a model oil fired ceramic fibre-lined shuttle kiln has been constructed and installed at Santiniketan, Bolepur. Its efficiency has been compared with conventional brick-made kiln fired by oil, gas and coal. The outcome is detailed in this paper, which would help the small scale industries to take their future action plan.
2 citations
TL;DR: In this paper, Rajpardi clay, an overburden material of a lignite mine on replacements of extensively used traditional plastic clays like Than and Bikaner, was used in the earthenware type glazed wall tile body composition.
Abstract: The investigation was carried out to incorporate newly tapped Rajpardi clay, an overburden material of a lignite mine on replacements of extensively used traditional plastic clays like Than and Bikaner in the earthenware type glazed wall tile body composition. Test specimens of five different body compositions incorporating Rajpardi clay were prepared and fired at four different test temperatures, viz. 950°, 1050°, 1100° and 1150°C in an electrical furnace. Dry and fired properties like dry shrinkage, dry MOR, fired shrinkage, fired MOR, percent apparent porosity, percent water absorption, bulk density etc were determined and compared with those of the specimens of a traditional earthenware tile body used as a standard composition.
It was observed that the incorporation of Rajpardi clay in the tune of 25 wt% was the optimum condition in achieving the requisite thermo-mechanical properties in wall tile body. A significant increase in the values of dry and fired MOR, as compared to those of the standard composition, was also noticed.
1 citations
TL;DR: Al2O3-SiC composite precursor has been made by dispersing fine SiC particles in a boehmite (AlOOH) matrix at pH 3.5 and slowly flocculating to pH 7.5 by dropwise addition of dilute NH4OH solution while the whole mixture was kept under constant stirring.
Abstract: Al2O3-SiC composite precursor has been made by dispersing fine SiC particles in a boehmite (AlOOH) matrix at pH 3.5 and slowly flocculating to pH 7.5 by dropwise addition of dilute NH4OH solution while the whole mixture was kept under constant stirring. The gel thus obtained is further dried under humid conditions and thermally dehydroxylated below 600°C. This precursor has been further subjected to microwaves having frequency 2.45 GHz and 600 W power under a “Picket Fencing” arrangement and sintered to reasonably higher densities. In a similar way, identical samples have been sintered in an electrical furnace up to 1450°C and the sintered properties are compared.
1 citations
TL;DR: In this article, the physicico-thermal properties of kaolinised rocks occurring at the Northern part of Mulieh village of Jaintia Hills, Meghalaya were studied with a view to find out its possible use in ceramic industry.
Abstract: The physico-thermal properties of kaolinised rocks occurring at the Northern part of Mulieh village of Jaintia Hills, Meghalaya were studied with a view to find out its possible use in ceramic industry. The study was conducted on the crude as well as washed fractions of Grade I and Grade II clays obtained by systematic levigation. The investigation included the determination of unfired physical properties of all the three fractions of the clay leading to the suitability in ceramic industry. The PCE values and the fired characteristics at six different temperatures starting from 1200° to 1450°C at the interval of 50°C of all the three levigated fractions of the clay were determined. The results indicated that the crude clay being non-slaking in nature and contained about 68% residual fraction required proper processing for using it successfully in producing ceramic articles. Grade I clay when mixed with other ceramic raw materials in right proportions may prove promising in the manufacture of ceramic white...
1 citations
TL;DR: In this paper, a diphasic mullite gel (Si/Al = 1/3) was synthesized in situ by hydrolyzing an aqueous solution of silica sol and aluminium salt with the help of NH4OH solution.
Abstract: Diphasic mullite gel (Si/Al=1/3) has been synthesized in.situ by hydrolyzing an aqueous solution of silica sol and aluminium salt with the help of NH4OH solution. It has been characterized by DTA. The formation of Si-Al spinel during non-eqilibrium heating of the gel and its subsequent transformation have been recorded by XRD technique. The result shows that Si—Al spinel crystallizes very slowly at 500°-800°C and then very rapidly at ∼ 1200°C which corresponds with the exhibition of a broad exotherm between 1100° and 1300°C in DTA. Accordingly, this exotherm is attributed to the formation of Si—Al spinel. It suddenly transforms to predominant amount of orthorhombic form of mullite with consequent exhibition of an exotherm at 1320°C in DTA. The residual non-crystalline aluminosilicate phase also crystallizes into mullite and accounts for the second mullitization process in diphasic gel.
1 citations
TL;DR: In this article, five different types of calcined alumina were incorporated in the formulation of mullite shapes to have a compartative study of the materials, and the results indicate that these shapes possess high spalling resistances and improved cold crushing strengths after 25 cycles of spalling test.
Abstract: In the present investigation, five different types of calcined alumina were incorporated in the formulation of mullite shapes to have a compartative study of the materials. The mullite compositions were pneumatically rammed at a pressure of 100 kg.cm−2 and fired at 1420°C for 4 hours. The results indicate mullite shapes possessing high spalling resistances (+ 30 cycles water quenching from 1000°C to room temperature) and improved cold crushing strengths after 25 cycles of spalling test.
TL;DR: In this paper, an attempt was made to fabricate different ceramic items made of common clays and the physical properties of the clay were systematically investigated in detail, both unfired and fired.
Abstract: An attempt was made to fabricate different ceramic items made of common clays. The fast depletion of higher grade china clays and progressive increase in the cost of fuel necessitated the development of ceramic bodies by incorporating abundantly available low-cost, inferior grade ceramic clays fired at a low temperature but without compromising with the desired properties. With preliminary processing, the physical properties of the clay—both unfired and fired, were systematically investigated in detail. The utilisation of the common clay along with other ceramic ingredients in right proportion in the production of various types of semi-vitreous and vitreous articles was found to be quite viable.
TL;DR: In this paper, attempts have been made to compare various high alumina aggregates in making low cement castables for different applications in iron and steel industries, which are generally used for manufacturing different types of furnace like soaking pit, end pusher etc in steel industry.
Abstract: Low cement castables are finding wide use in high temperature application in various industries like steel, foundries, aluminium, cement, ceramic, petrochemical etc. The high alumina based LCC, ULCC are generally used for manufacturing different types of furnace like soaking pit, end pusher etc in steel industry. In the present paper, attempts have been made to compare various high alumina aggregates in making low cement castables for different applications in iron and steel industries.
TL;DR: An attempt has been made to prepare stoichiometric mullite powders by mixing aluminium nitrate and TEOS in different solvents like distilled water, ethanol and methanol as discussed by the authors.
Abstract: An attempt has been made to prepare stoichiometric mullite powders by mixing aluminium nitrate and TEOS in different solvents like distilled water, ethanol and methanol. The sol obtained was spray dried and the powders were calcined in the range 850°-1000°C and sintered at 1600°C. XRD patterns of these powders calcined at 1000°C showed mullite formation in all the solvent systems. Thermal analysis data indicated mullite exotherm below 1000°C. A 10% increase in density was observed on sintering at 1600°C preferentially for methanol derived powder. Fractographs of the sintered mullite generally showed localised densification indicating the inhomo-geneity in the precursor. A controlled hydrolysis of the precursor under different solvent media was indicated to influence the gelation characteristics and bring down the extent of inhomogeneity. A correlation has been presented with respect to history of gelation and the formation of a mullite phase as well as development of sintered microstructure.
TL;DR: In this article, the room temperature (298 K) three-band spectra, which have been splitted to two doublets, reveal Fe2+ ions to be exclusively located at dodecahedral site (IS = 1.303-1.389 mm/s; QS = 3.423-3.822 mm /s).
Abstract: Garnets from high P—T granulite field of Sittampundi, Tamil Nadu were investigated by 57Fe Mossbauer spectroscopy. The room temperature (298 K) three-band spectra, which have been splitted to two doublets, reveal Fe2+ ions to be exclusively located at dodecahedral site (IS = 1.303–1.389 mm/s; QS = 3.423–3.822 mm/s) and Fe3+ at tetrahedral site (IS = 0.0060.163 mm/s; QS = 0.520–0.663 mm/s). The Fe3+/∑Fe ratios vary between 0.073 and 0.150, which indicate its formation at high P—T field. The high values of QS of tetrahedral Fe3+ suggest that the occupied site is very regular with little distortion. The fairly broad line-width (FWHM, 0.455–0.596 mm/s) of Fe3+ doublet may arise from a substitution of some tetrahedral Si by (OH)− group. The strong partition and ordering of Fe2+ and Fe3+ in dodecahedral and tetrahedral sites, having octahedral sites totally free from iron, suggest in a strong measure of slow cooling and recrystallization of garnet through decompression. The presence of tetrahedral Fe3+ strongly...
TL;DR: In this article, the effect of coprecipitated MgO-Al2O3, Mg O-Cr2O 3 and Mg o-Fe 2O3 gel on the strength retainment properties of basic castables has been investigated.
Abstract: The effect of coprecipitated MgO-Al2O3, MgO-Cr2O3 and MgO-Fe2O3 gel on the strength retainment properties of magnesium oxysulphate cement based basic castables has been investigated. Incorporation of MgO-Al2O3 gel is found to be most beneficial for the improvement and retainiment of both the room temperature and high temperature strengths. SEM studies have been conducted to get an idea about the microstructure of castables cured at room temperature and heated at high temperature.
TL;DR: In this paper, the type of chelating agent and the amount of water used for hydrolysis were found to affect crack formation of chelated alkoxide membranes. But they were tested for their integrity using scanning electron microscopy and nitrogen permeability measure-ments.
Abstract: Alumina membranes for gas separation were made using chelated alkoxide, through the sol-gel route. Use of chelated alkoxides prevents the uncontrolled hydrolysis of aluminium alkoxides and gives rise to a modified precursor that gives finer particle size and lower alumina crystallization temperature. However, chelated alkoxide membranes crack extensively. The type of chelating agent and the amount of chelating agent and water used for hydrolysis were found to affect crack formation. Crack-free membranes could be successfully prepared with alkoxide/chelating agent ratios less than 1: 0.75 using ethylacetoacetate as the chelating agent. These membranes were tested for their integrity using scanning electron microscopy and nitrogen permeability measure-ments. Cracked membranes showed considerably high permeability compared to uncracked ones.
TL;DR: In this article, the topochemical sintering of barium hexaferrite utilizing stoichiometric mixtures of BaCO3 and αFe2O3/α-FeOOH raw materials has been investigated with the help of a dilatometer.
Abstract: The topochemical sintering of barium hexaferrite utilizing stoichiometric mixtures of BaCO3 and αFe2O3/α-FeOOH raw materials has been investigated. The densification behaviour of BaO.6Fe2O3 in the temperature range of 1273 to 1573 K is studied with the help of a dilatometer. The nonisothermal dcnsification kinetics is derived from dilatometrie results. A kinetic relation of the type mentioned in the equation In(ΔL/L)0.8 × 1/T2 = K/T + Cis found to be valid in the temperature range of 1323 to 1573 K.The chemical decomposition reactions that are likely to take place during initial heating and final sintering of the green compacts are interpreted from the DTA/TGA plots. The inicrostructural studies of BaO.6Fe2O3 sintered at 1573 K for the time durations of 60, 120 and 240 mins reveal that grain coarsening takes place with the increase of the sintering time. The BaO.6Fe2O3 topochemically sintered at 1473 K for 60 mins showed a miximum magnetic energy product of 0.82 MGOe.
TL;DR: In this article, the physicico-chemical characteristics of kaolinised rocks occurring at the Northern part of Mulieh village of Jaintia Hills in Meghalaya were studied with a view to finding out their possible industrial applications.
Abstract: The physico-chemical characteristics of kaolinised rocks occurring at the Northern part of Mulieh village of Jaintia Hills in Meghalaya were studied with a view to finding out their possible industrial applications. The study was conducted on the washed fraction (Grade I) of the clay as obtained by systematic levigation based on the principle of gravity sedimentation. The investigation included characterization of the clay for its suitability in paper, textile, rubber and insecticide industries as per BIS specification. The clay was further evaluated for its application in the field of ceramic whitewares, and this included definite formulation of various types of ceramic products and finding out the thermo-mechanical properties at different temperatures subject to the requirements of the respective products.
The results indicated that the clay was quite suitable for direct use in paper, textile, rubber and insecticide industry except as a coating material in paper or textile. Due to off- white colour of the clay, its use was restricted in making porcelain tablewares and alike; otherwise it suited well in all the other ceramic applications.