Showing papers in "Transactions of The Indian Ceramic Society in 1992"
TL;DR: In this article, two samples of China clay received from Darugiri area of East Garo Hills, Meghalaya were studied to identify their mineralogical characteristics, and the results indicated that China No. 1 in its crude form contained a good amount of free quartz whereas clay No. 2 as such was purer in form so far as free quartz was concerned.
Abstract: Two samples of China clay received from Darugiri area of East Garo Hills, Meghalaya were studied to identify their mineralogical characteristics. The studies conducted on the crude as well as washed fractions of both the clays included physical, chemical, thermochemical, petrographical, bec, PCE and XRD analysis. Results indicated that clay No. 1 in its crude form contained a good amount of free quartz whereas clay No. 2 as such was purer in form so far as free quartz was concerned. Both the clays were predominantly kaolinitic in nature.
5 citations
TL;DR: The vast deposits of Mokhdumnagar china clay from Birbhum district of West Bengal have been characterised from mineralogical and ceramic points of view with the object of evaluating its suitability in the ceramic and other allied industries as discussed by the authors.
Abstract: The vast deposits of Mokhdumnagar china clay from Birbhum district of West Bengal has been characterised from mineralogical and ceramic points of view with the object of evaluating its suitability in the ceramic and other allied industries. The study includes examination of the general characteristics, chemical, mineralogical and physical properties of the clay both in the crude and washed form. Washing the crude clay resulted in two types of beneficiated clays, Grade I and Grade II. Investigations have also been made by incorporating the clay in some typical ceramic body compositions. The results reveal that the clay is essentially kaolinitic in nature and being only moderately plastic, requires incorporation of at least 10–20% of ball clay to allow its utilization in the pottery industry except in the manufacture of white porcelain. The Grade II clay however, may be used in making stoneware, earthenware or wall tiles with slight alteration in compositions. The clay Grade I may be more or less suitable in paper industry as a filler, in rubber industry and in insecticide industry.
3 citations
2 citations
TL;DR: In this article, the optical absorption edges of the gels obtained after heating at 500° and 700°C showed progressive shifts towards longer wavelengths with increasing Zn2+; the optical band gap recorded a corresponding decrease, suggesting this to be an effect of formation of nonbridging Si-O-Zn groups.
Abstract: Doped silica sols were prepared via hydrolysis and poly-condensation reactions involving Si(OC2H5)4 and water in which 0.5–10 mol% equivalent of ZnO was added through Zn(NO3)2.6H2O. Gelation was found to be progressively accelerated with increasing amount of Zn2+ which was suggested to link the silicate polymeric clusters via terminal SiO− groups. Activation energies of the overall process of gelation (calculated from gelling times at 10°, 30°, 40° and 50°C) showed significant drop with increasing dopant content.
Optical absorption edges of the gels obtained after heating at 500° and 700°C showed progressive shifts towards longer wavelengths with Increasing Zn2+; the optical band gap recorded a corresponding decrease, suggesting this to be an effect of formation of non-bridging Si-O-Zn groups. Another kind of non-bridging group, namely Si-OH, was found by Infrared spectroscopy to decrease in amount with increase In the temperature of heating.
2 citations
TL;DR: In this article, a spectrophotometric method has been developed for determination of small amounts of lead in glass and some ceramic raw materials, which obeys Beer's law from 0.1 to 2.5 μg Pb at 500 nm.
Abstract: A spectrophotometric method has been developed for determination of small amounts of lead in glass and some ceramic raw materials. The method involves selective separation of lead with 5.85 × 10−5M dithizone and 7.5 × 10−2M KCN at pH∼10 followed by elution of the complex with acetone and making it alkaline with 0.2 ml of 2.5M NH3 in a total volume of 10 ml. The method obeys Beer's law from 0.1 to 2.5 μg Pb.ml−1 at 500 nm. Correlation coefficient calculated from the linearity curve is 0.99. Interferences due tp Cu(II), Co(II), Ni (II), Zn(II), Cd(II), Mn(III) and Fe (II) have been eliminated automatically by using KCN. Effect of Fe(III) could be eliminated by extraction with MIBK prior to the separation of lead. The developed method has been standardized against National Bureau of Standards opal glass sample (NBS 91). Standard deviation of the results has been found to be ±0.0021.
2 citations
TL;DR: A review of the general technical aspects on constituents, manufacturing methods in brief, properties, durability and scope of commercial applications is given in this article, where the authors also discuss the application of GRC composites in the building industry.
Abstract: With the advent of new types of alkali resistant glass fibres and advances in cement matrix formulation, the application of Glass Fibre Reinforced Cement (GRC) composites has been extended in a big way. GRC, as it stands today, is not just one composite, but a generic name covering a wide range of materials and the developments are taking place at a rapid pace. In the building industry of India, GRC would help broaden the entrepreneur's technological base with the diversity of its application for replacement of traditional and naturally occurring materials such as timber, asbestos, sheet metal etc. The article is a review of the general technical aspects on constituents, manufacturing methods in brief, properties, durability and scope of commercial applications.
1 citations
TL;DR: In this article, the sintering and grain growth of natural Indian Magnesite as a function of added titania have been studied in the range 0.05 to 0.50wt% TiO2 with respect to the natural magnesite.
Abstract: The sintering and grain growth of natural Indian magnesite as a function of added titania have been studied in the range 0.05 to 0.50wt% TiO2 with respect to the natural magnesite. Grain sizes in fired compacts have been measured with the aid of an optical microscope on thin and polished sections. The activation energy for grain growth in magnesites with and without added titania has been calculated from the increase in average grain diameter as a function of firing temperature and time. A higher activation energy of 607 kJ/mol has been observed in the case of natural cryptocrystalline magnesite from Salem with 0.20 to 0.50wt% titania addition when compared to the activation energy of 293 kJ/mol in natural coarse crystalline magnesite from Almora with 0.50wt% added titania in the original magnesite. The higher activation energy is attributed to change in the mechanism of sintering due to the addition of titania.
1 citations
TL;DR: In this paper, four samples of sandstone collected from Anjar taluka of Kachch district, Gujarat State, India were studied to develop applicable beneficiation routes, the sandstones were friable in nature, off white to white in colour, assaying from 90 to 96% silica content, with minor amounts of Al2O3 (1.5 to 5.0%), CaO (0.90 to 3.40%), trace amounts of TiO2 (0.,13 to 0.28%) and iron oxides (0,10 to 0.,35%).
Abstract: Four samples of sandstone collected from Anjar taluka of Kachch district, Gujarat State, India were studied to develop applicable beneficiation routes. The sandstones were friable in nature, off white to white in colour, assaying from 90 to 96% silica content, with minor amounts of Al2O3 (1.5 to 5.0%), CaO (0.90 to 3.40%), trace amounts of TiO2 (0.13 to 0.28%) and iron oxides (0.10 to 0.35%). Petrography and XRD analyses revealed clay, feldspar and calcite as the major impurities. The samples were crushed and sieved into various size fractions. Sizing followed by attrition scrubbing with water as medium brought down the iron content from 0.17 to 0.10%. Scrubbing with mild alkali/acid medium further reduced it. The most impure sandstone sample was further investigated to explore the possibility of beneficiation. After sizing the crushed sand with a nest of sieves, the coarse sand fraction retained on 500 μm sieve was attrition ground with pebbles and sieved again. The ground sand along with the medium fraction passing through 500 μm sieve but retained on 125 μm sieve was scrubbed with water. The Iron content was brought down to 0.05% with further chemical treatment. The resultant sandstone product conformed to Grade I glass sand of the relevant Indian Standards Specification.
1 citations
TL;DR: In this article, the effect of additives on the workability and water retentivity of cement-sand mortar has been studied by mixing 0.5 to 3.0% tartaric acid, dextrine, ammonium chloride and sodium bicarbonate.
Abstract: The effect of additives on the workability and water retentivity of cement-sand mortar has been studied by mixing 0.5 to 3.0% tartaric acid, dextrine, ammonium chloride and sodium bicarbonate by we...
1 citations
TL;DR: In this article, synthetic mullite prepared from clay alumina mixture was sintered around 1400°C and at 1600°C to obtain controlled porosity, and mechanical strength was evaluated by compressive test measurements at room temperature.
Abstract: Synthetic mullite prepared from clay alumina mixture was sintered around 1400°C and at 1600°C to obtain controlled porosity. The sintered compacts were subjected to thermal shock between 1400°C and room temperature, and mechanical strength was evaluated by compressive test measurements at room temperature.The porous (∼20% OP) samples showed densification during thermal shocks. The compressive strength increased up to five thermal cycles and decreased thereafter. The least porous (0.5 to 6% OP) samples retained the strength during thermal shocks while impervious (<0.5% OP) samples showed steady increase in strength. The samples sintered at 1600°C, though impervious, had low strength and cracked after five thermal cycles due to the separation of glassy phase from the matrix resulting in conchoidal fracture.
1 citations
TL;DR: In this paper, a single fired low temperature (1090°C) relatively fast-fired (7-8 hours) crockery body containing wollastonite was developed.
Abstract: A single fired low temperature (1090°C) relatively fast-fired (7–8 hours) crockery body containing wollastonite was developed. Vitrification characteristics, strength, water absorption, microstructure and crystalline phases present were studied.
TL;DR: In this article, a montmorlllonite-octadecylammonium intercalation compound has been prepared by treating sodium montmorillonite with alcoholic solution of octadecyclamine hydrochloride.
Abstract: A montmorlllonite-octadecylammonium intercalation compound has been prepared by treating sodium montmorillonite with alcoholic solution of octadecylamine hydrochloride. The XRD analysis of the compound prepared showed that the basal spacing increases from 12.5 A to 16.0 A. This suggests that octadecylammonium is intercalated in the interlayer space of montmorillonite. This fact has been supplemented by the IR spectra of the complex which shows the characteristic bands corresponding to—CH3, -CH2, and—NH+3 groups of alkylammonium ion.
TL;DR: In this paper, the electronic structures of Fe3+ co-coordination in iron oxide/hydroxide phases are evaluated from Self Consistent Field Xα Scattered Wave (SCF-Xα -SW) molecular orbital calculations on the octahedral (FeO6)9- clusters and/or trigonally distorted (Fe6) 9- clusters.
Abstract: The electronic structures of Fe3+ co-ordination in iron oxide/hydroxide phases are evaluated from Self Consistent Field Xα Scattered—Wave (SCF-Xα -SW) molecular orbital calculations on the octahedral (FeO6)9- clusters and/or trigonally distorted (FeO6)9- clusters. The electronic structures can be studied directly from the diffuse reflectance, specular reflectance and optical absorption methods. In α-Fe2O3 (haematite) pairs of face sharing polyhedra of (FeO6)9- share the edges and corners with each other to form sheets of (FeO6)9- polyhedra perpendicular to c-axis. This causes a strong trigonal distortion of (FeO6)9- polyhedra and results in two triatomic clusters of O2- ions around a central Fe3+ ion. In haematite, most of the electronic transitions are caused by ligand field transition and are intensified by the pair excitation (double exciton).
TL;DR: In this paper, the mechanical properties and microstructures of partially stabilized zirconia (Y-PSZ) ceramics containing 3.5, 4.0 and 5.0 mol% Y2O3 were examined.
Abstract: Yttria—partially stabilized zirconia (Y—PSZ) ceramics containing 3.5, 4.0 and 5.0 mol% Y2O3 were fabricated from commercial grade zirconia powder by dry pressing and normal sintering at 1600°C. The mechanical properties and microstructures of such materials were examined. Mechanical properties, both strength and fracture toughness, deteriorated with increasing yttria content. XRD revealed the presence of both tetragonal and monoclinic phases in the sintered materials and with decreasing yttria content, the tetragonal phase increased. Vickers' microhardness values differed slightly among the three compositions.
TL;DR: In this paper, real and imaginary parts of complex permeability, μ' and μ'' and quality factor Q were determined in the frequency range 100-2000 kHz using impedance bridge on toroidal samples.
Abstract: Manganese-zinc-ferrous ferrites of estimated structural compositions Zn0.216Mn0.706Fe0.078Fe204 and Zn0.197Mn0.683 Fe0.120Fe2O4 were ferritized at 1120° and 1090°C using air atmosphere during heating and soaking periods and argon atmosphere during cooling. This ferritized powder after grinding to ≅ 5 μm was pressed into toroid and cylindrical pellets. Sintering of shapes was done in air at temperatures of 1220° and 1250°C and for a soaking periods of 6 hours, while the heating and cooling were done in air and argon respectively. Lattice parameters were determined by the X-ray method; the values ranged between 4.487 and 4.497 A for materials ferritized under different conditions. Real and imaginary parts of complex permeability, μ' and μ″ and quality factor Q were determined in the frequency range 100–2000 kHz using impedance bridge on toroidal samples. The values varied in the range 370–648 (for μ'), 30–54 (for μ″) and 7–16 (for Q) at 100 kHz. The permeability at 100 kHz range was 373–651 against the expe...
TL;DR: In this article, Li2O-P2O5-SIO2 system with additions of CaO, MgO, and B2O3 have been described.
Abstract: Studies on development and property evaluation of extra-white glass tiles In Li2O-P2O5-SIO2 system with additions of CaO, MgO and B2O3 have been described. The glass possessed fair working characteristics and corrosion of sillimanite pots during melting was insignificant. On controlled heat-treatment, glasses possessing high mechanical strength and good resistance to attack of acid and alkaline water were obtained. The principal crystal phases appearing at crystallisation temperature were indentified as lithium meta-and di-sillcate.
TL;DR: In this paper, the formation processes and size control of particles of refractory nitrides and carbides by vapour-phase reaction (CVD) method and their sintering behavior are discussed.
Abstract: As technology advances, need for fine, homogeneous powders has increased. Among many new powder preparation techniques, the vapour phase reaction method is receiving increasing attention as the preparation technique of powders of refractory oxides and non-oxides. Powders produced by vapour phase techniques can be characterized by high discreteness and ultrafineness. In the present paper, the formation processes and size control of particles of refractory nitrides and carbides by vapour-phase reaction (CVD) method and their sintering behaviour are discussed.The formation processes of particles of the carbides and nitrides can be divided into: (a) formation of adduct particles of reactants and their thermal decomposition into carbide or nitride, (b) formation of nuclei of carbide or nitride and their growth, and (c) formation of metal particles and their nitridation or carburization. The particle sizes which range from 0.01 to 0.5 μm can be controlled by manipulating the reaction conditions. Ultrafine CVD p...
TL;DR: In this paper, a spectrophotometric method was described for the determination of minor or trace amount of copper and silver when present together in special glasses, which involves selective extraction of copper dithizonate on polyurethane foam after masking of silver with chloride.
Abstract: A spectrophotometric method has been described for the determination of minor or trace amount of copper and silver when present together in special glasses. The method involves selective extraction of copper dithizonate on polyurethane foam after masking of silver with chloride. Silver is extracted in ammoniacal medium after masking of copper with EDTA. Both the complexes, i.e. copper and silver dithizonates are eluted from foam with acetone. Determinations are carried out spectrophotometrically. Beer's law is obeyed for the concentration range of 0.05–2.5 μg Cu/ml at 550 nm and 0.10–6.0 μg Ag/ml at 500 nm. The method yields agreeable results.
TL;DR: The chemical industry is quite capable of supplying high purity ceramic precursors on the largest scale, whether as powders, colloidal slurries or preceramic polymers as discussed by the authors.
Abstract: The chemical industry is quite capable of supplying high purity ceramic precursors on the largest scale, whether as powders, colloidal slurries or preceramic polymers. Particularly interesting, now that “high-tech” ceramics are already entering automobiles in Japan, and will soon be demanded everywhere on a massive scale for automobiles and trucks, is the case of silicon nitride. On the basis of its physical properties, it had been proposed 36 years ago to be a prime candidate material for engine applications. However, due to the nature of the socio-technical-political set-up, the economic, large-scale, high purity powder synthesis, the without-which-nothing, was not addressed in the USA.Lack of market so far is the main reason why the chemical engineering aspects of ceramic precursors have not been sufficiently emphasized, but, with the recent developments, it will be interesting to see how the community adjusts as major improvements in the way materials innovation† (information openness and flexibility ...