Kedar Nath Maiti

Effect of rice husk ash in whiteware compositions

Quartz was progressively replaced by ground active silica obtained from rice husk ash (RHA) in a traditional whiteware composition and the effect of this replacement on the vitrification behaviour and mechanical and thermal properties in relation to the microstructure of specimens has been investigated. It has been found that the complete replacement of quartz by RHA drastically reduced both the maturing temperature and the percentage of thermal expansion, and increased the strength marginally. The improvement in the properties is attributed to sharp changes in the microstructural features as a result of significant reduction in the content of quartz phase and the simultaneous increase in glassy phase.

Effect of glass-ceramics and sillimanite sand additions on microstructure and properties of porcelain

Both quartz and feldspar were progressively replaced by ground sillimanite sand and glass-ceramics in a classical porcelain composition and the effect of these replacements on the vitrification behaviour and mechanical and thermal properties in relation to the microstructure of specimens has been investigated. Progressive additions of sillimanite sand and crystallising glasses leading to the complete replacement of quartz and feldspar increased the strength, toughness and modulus significantly, and drastically reduced the per cent thermal expansion in the composition. The improvement in the properties is attributed to dramatic changes in the microstructural features as a result of significant reduction in the content of glassy phase and the simultaneous increase in crystalline phases such as mullite, sillimanite and cordierite.

Effect of Particle Size on the Vitrification Temperature and Fired Properties of Conventional White Stonewares

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...

Appropriate Technologies in Low Cost Ceramics for Small and Tiny Sector Industries: A Progress Report from CG & CRI

This article presents an account of the progress made by CG & CRI in developing some appropriate technologies for the small and tiny scale pottery industries of the country. Special stress has been laid in these technologies on the meaningful use of low grade raw materials in the manufacture of rural sanitaryware, unglazed flooring and facing tiles and low maturing white stonewares with matching glazes. In addition, an energy efficient low thermal mass down draught kiln was also designed and developed in this programme for reducing firing cost. Transfer of these technologies through training-cum-demonstration programmes has been described.

Development of glazed wall tiles through optimal utilization of fly ash

This Investigation was carried out to incorporate fly ash, a waste material generated from thermal power stations, as a replacement of sandstone and to some extent feldspar in the earthenware type glazed wall tile body composition. Test specimens of eight different body compositions incorporating fly ash were prepared and fired at five different test temperatures, viz., 1000°, 1050°, 1100°, 1150° and 1200°C in an electrical furnace. Dry and fired properties like dry MOR, fired shrinkage, fired MOR, apparent porosity, water absorption, bulk density, thermal expansion of the optimized body and glaze 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 fly ash in the tune of 30 wt% was the optimum In achieving the requisite thermo-mechanical properties In wall tile body.

Effect of Firing Schedule on the Properties of Flooring Tiles

The mechanical properties of flooring tiles fired in a conventional down draft kiln were compared with those produced commercially following the fast firing schedules. It has been observed that the conventional long firing operation favours dissolution of quartz, recrystallization of the secondary mullite and reduction in the amount of closed pores in the structure, thus enhancing the strength and toughness of the body as well as the resistance towards abrasion of the glazed surface.

Physico-chemical characterization of Ukrainian and Indian plastic clays - A comparative study

The chemistry, mineralogy, plastic and dry properties, thermo-mechanical characteristics and rheological properties of imported Ukrainian clay vis-à-vis three Indian plastic clays have been investigated. The presence of illite, poor crystallinity, high degree of disordered kaolinite, lower colouring oxides content, high plasticity and finer particle size present in the Ukrainian clay are found to be the key contributors to its unique characteristics.

Effects of fly ash addition on thermomechanical properties of earthenware wall tile compositions

Abstract The effect of fly ash addition as a substitution of sand stone on the thermomechanical properties of traditional earthenware wall tile composition was studied. Considerable improvement (8.0 to 18.6%) in mechanical strength was observed on replacement of quartz by fly ash up to the complete replacement in the biscuit firing temperature range of 1050 and 1150°C. The increase in strength may be attributed to the gradual decrease in stresses in the fired bodies due to the decrease in the content of sand stone. There is a significant reduction in percentage thermal expansion of body mixes at 600°C in the samples fired at 1100°C due to gradual replacement of sand stone by fly ash in the compositions. This would make the body mixes more thermal shock resistant in comparison to the reference body. Moreover, this investigation showed promising result and encouraged the utilisation of waste material like fly ash in the production of value added traditional ceramic products like earthenware glazed wall tile with improved thermomechanical properties.

Studies on Cordierite-Mullite Body—Part II: Effect of Sillimanite Sand in a Cordierite Composition

Beach sand sillimanite was substituted for china clay and fireclay grog in a standard cordierite body mix containing 60% china clay, 20% fireclay grog (IS-6 grade) and 20% talc. The specimens were fired at different temperatures ranged from 1200 to 1340°C with 2 h dwelling time at respective peak temperatures. The addition of 40 wt% sillimanite in the standard composition was found to improve the mechanical properties and to reduce the coefficient of thermal expansion from 25.7 × 10−7 to 20.43 × 10−7 at 500°C and 25.20 × 10−7 to 21.34 × 10−7 at 1000 C. The reduction in the coefficient of thermal expansion value of the body mix containing 40 wt% sillimanite was due to the presence of cordierite and mullite and/or sillimanite phases in the composition. The final body also showed enhanced fired strength from 147.67 kg.cm−2 to 241.90 kg.cm−2 after firing at 1340 C. The thermal shock resistance of the developed body mix containing 40 wt% sillimanite. measured in terms of percent loss of MOE after repeated thermal shock at gradually enhanced temperatures in water quenching, was found to be more than two times higher than that of the standard cordierite composition.

Evaluation and Utilization of Rajpardi Clay in the Production of Traditional Ceramics: Part—I: Physicochemical Characteristics of Rajpardi Clays

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.