Showing papers in "Transactions of The Indian Ceramic Society in 1974"
TL;DR: In this paper, the transformations of two varieties of high purity quartz were studied at 1400 and 1500°, the determination of quartz being done by DTA, and the transformations were found to be greatly influenced by particle size.
Abstract: The transformations of two varieties of high purity quartz were studied at 1400 and 1500°, the determination of quartz being done by DTA. The transformations were found to be greatly influenced by particle size. The decomposition of fine fractions of quartz followed a spherical model in which the decomposition starting from the surface nucleation centres proceeded towards the interior of the particles. Decomposition of coarse fractions did not accurately follow this model, and their apparent decomposition velocities were much higher than those for the fine fractions, an explanation to which has been sought in a consideration of additional decomposition from interior nucleation centres in the coarse particles. No induction period was observed for the decomposition of any size fraction. The small difference in the transformation rates between the two varieties of quartz was attributed to presence of strain or possible structural defects in one of them.
6 citations
TL;DR: In this article, a hydrous sodium aluminosilicate exhibiting molecular sieving properties was synthesized at 75-120° from gels of various alkali and silica concentrations, and the optimum conditions for complete conversion of a gel into Zeolite ‘A’ crystals have been suggested.
Abstract: Zeolite ‘A’, a hydrous sodium aluminosilicate exhibiting molecular sieving properties, was synthesized at 75–120° from gels of various alkali and silica concentrations. The effects of parameters like gel composition, temperature and agitation of the starting gel have been discussed in brief, and the optimum conditions for complete conversion of a gel into Zeolite ‘A’ crystals have been suggested.
4 citations
TL;DR: In this article, an improved method for the spectrophotometric determination of titanium using chromotropic acid is described, which has been successfully applied to the determination of traces of TiO2 in various ceramic materials such as feldspar, silica bricks, burnt magnesite, chromite and glass.
Abstract: An improved method for the spectrophotometric determination of titanium using chromotropic acid is described. The optical density of Ti-chromotropic acid complex at 470 nm has been found to be independent of pH from 3 to 6. Acetic acid sensitises the optical density of the complex. The interfering effect of Fe(III) up to 200 μg/ml has been overcome by adding 5 mg Fe(III) to both the standard and the test solutions followed by reduction with a mixture of ascorbic and acetic acids at pH 3–4. The photosensitivity of chromotropic acid has been eliminated by preparing the reagent solution in 0.3N H2SO4. The development of Ti-chromotropic acid colour is instantaneous and the optical density does not change for a period of at least 12 hrs. The method has been successfully applied to the determination of traces of TiO2 in various ceramic materials such as feldspar, silica bricks, burnt magnesite, chromite and glass.
3 citations
TL;DR: In this article, the influence of the amount of calcia addition on the sintering characteristics of zirconia and the physical properties of the sintered products has been studied.
Abstract: The influence of the amount of calcia addition on the sintering characteristics of zirconia and the physical properties of the sintered products has been studied. It was noticed that the optimum amount of calcia addition was 0.50 to 0.75 wt% to obtain high density without cracking of the ware. Higher additions of calcia invariably resulted in lowered density. The extent of stabilization was studied by x-ray diffraction and dilatometry.Though the stabilization (conversion to the cubic structure) was not obtained with 0.50 and 0.75 wt% addition of calcia, and the presence of hysteresis loops in the dilatometric curves were noticed in the samples sintered at temperatures up to 1500°, they were found to have sufficent thermal shock resistance to be used as refractory ware.
2 citations
TL;DR: In this article, the authors divided the literature into five sections dealing with polymorphs of silica, raw materials, manufacture, properties and usage, and classified silica refractories as acidic and contain at least 93% SiO2.
Abstract: The paper is divided in 5 sections dealing with polymorphs of silica, raw materials, manufacture, properties and usage.Silica refractories are classified as acidic and contain at least 93% SiO2. This oxide exists in many crystallographic modifications and at least 7 polymorphs plus the vitreous (amorphous) phase are of interest in technology of silica refractories (section-1). The principal raw materials are quartzites, containing 95% or more of SiO2, which are agglomerates of quartz particles cemented or compacted together (section-2). 1–3% lime is used as ceramic bond in the manufacture of silica bricks which, on account of large volume expansion accompanying the phase transformations, must be fired with some care (section-3). The distinguishing properties of silica refractories are (i) tendency to permanent expansion in service (ii) ability to support heavy loads right up to the fusion point (iii) resistance to corrosion attack by iron and calcium oxides, and (iv) excellent thermal shock resistance in ...
2 citations
TL;DR: In this article, it was assumed that the dust accumulation in the roof was acting as insulation altering the thermal gradient and enhancing the liquid migration deeper in the brick and laboratory investigation confirmed this assumption.
Abstract: Roof Cleaning is one of the means adopted by different steel plants throughout the world for increasing the roof life of open hearth furnaces. With the adoption of basic roof in TISCO, it was observed that the roof was getting over-heated and the tabs holding the bricks were getting cut. This resulted in premature failure of roof requiring frequent hot repairs. It was presumed that the dust accumulation in the roof was acting as insulation altering the thermal gradient and enhancing the liquid migration deeper in the brick. Laboratory investigation confirmed this assumption. In TISCO, roof cleaning has been undertaken regularly to overcome this problem which has resulted in improving the roof life considerably. The practice has been extended to the silica roof also with considerable success.
1 citations
TL;DR: In this paper, fire bricks were made from Chittarpur fireclay with the addition of Chakla non-plastic clay grog and calcined Lohardaga bauxite.
Abstract: Firebricks were made from Chittarpur fireclay with the addition of Chakla non-plastic clay grog and calcined Lohardaga bauxite. Chakla clay was calcined both in rotary as well as in intermittent kilns at temperatures around 1350°. Bricks were fired to 1350° for 4 hours and were tested for their properties. Reheat shrinkage was observed on bricks containing intermittent kiln-clay grog, and even with the addition of 25% calcined bauxite in the batch. Bricks containing 70% rotary kiln-clay grog showed slight reheat expansion. Incorporation of finer fractions of calcined bauxite increased firing expansion and reduced reheat expansion. Similar observations were made also with higher calcination temperature of the bauxite. To minimise the reheat expansion of fireclay refractories, it is desirable to avoid calcined bauxite together with rotary kiln-clay grog and to use in case of necessity, only finer fractions of high temperature calcined bauxite.
1 citations
TL;DR: In this article, a process for the extraction of zirconia from Indian Zircon CaCO3 and ZrSiO4 was proposed and the optimum conditions for the production of ZIRconia were suggested and the probable course of reactions with the help of X-ray, microscopic and chemical analysis.
Abstract: With a view to developing a process for the manufacture of zirconia from Indian zircon CaCO3 and ZrSiO4 were used in different molar ratios and fired between 1100–1450° for varied lengths of time. The optimum conditions for the production of zirconia were suggested and the probable course of reactions was investigated with the help of X-ray, microscopic and chemical analysis.
1 citations
TL;DR: In this article, the relationship of specific energy with drying rate, Young's modulus and slip casting rate in plaster moulds was investigated and the results interpreted in the light of available data.
Abstract: Specific energy designating the partial specific Gibbs free energy of water in a clay-water system is a fundamental parameter that can be used by ceramists to study the mechanical properties of this and other similar systems as well as the moisture mobility in them. Various methods available to measure this thermodynamic quantity including a new method based on mercury penetration measurements have been discussed. Variation of coefficient of internal friction with the specific energy has been studied and the results interpreted in the light of the available data on the relationships of specific energy with drying rate, Young's modulus and slip casting rate in plaster moulds.
1 citations
TL;DR: In this article, the effect of forming pressure on the sintering of plate glass was studied at pressures 120,360, 600 and 840 kg/cm2, and the authors found that the porosity and permeability of the specimens studied decrease significantly with increasing forming pressure.
Abstract: Effect of forming pressure on the sintering of plate glass was studied at pressures 120,360, 600 and 840 kg/cm2. Both the rate of sintering and extent of shrinkage slightly increase with increasing forming pressure. The open porosity and permeability of the specimens studied decrease significantly with increasing forming pressure.
1 citations
TL;DR: Semiconducting glazes are used on high voltage insulators to suppress radio interference commonly known as RI as mentioned in this paper, and they are also found very suitable in stabilization of line voltage in industrially polluted and marine areas.
Abstract: Semiconducting glazes are being used on high voltage insulators to suppress radio interference commonly known as RI. They are also found very suitable in stabilization of line voltage in industrially polluted and marine areas. The way in which the semiconducting glaze helps in minimising the two problems of high voltage engineering has been discussed. The development of semiconducting glazes, their characteristics, as also the different techniques of preparation have been elucidated.