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Journal ArticleDOI

Studies on Liquid-Phase Sintering of MgO-China Clay Compacts

01 Jan 1983-Transactions of The Indian Ceramic Society (Taylor & Francis)-Vol. 42, Iss: 6, pp 158-163
TL;DR: In this paper, a study on liquid phase sintering was carried out on different MgO-china clay compacts containing 4, 8, 12, 16 and 20% by weight of china clay.
Abstract: Studies on liquid-phase sintering were carried out on different MgO-china clay compacts containing 4, 8, 12, 16 and 20% by weight of china clay. Initial particle size of the powders taken was—45 microns. The green compacts of 1.25 cm dia were cold pressed at a constant pressure of 1600 kg/cm2 and sintered in a high temperature gas fired furnace in oxidising atmosphere at 1600°, 1650° and 1700°c for 0 to 8 hours. The rates of densification showed that MgO-12 wt % china clay compacts sintered at 1700°c for 4 hours, attained a maximum value of bulk density, i.e. 3.56 gm/cc. This value was 99.44% of the theoretical density. The same compacts, when sintered at 1650° and 1600°c for 4 hours, resulted in maximum values of bulk density, i.e. 3.53 and 3.44 gm/cc respectively. These values were 98.60 and 96.08% of the theoretical density. The values of apparent porosity of these sintered compacts were found to be 1.10, 3.50 and 5.20% respectively.For studying the kinetics of sintering, experimental data were analyse...
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Journal ArticleDOI
TL;DR: In this paper, the driving force leading to densification during sintering in the presence of a liquid phase and the material transport phenomena have been analyzed and relationships for the densification rate during the rearrangement process, the solution-precipitation process, and the final coalescence process have been determined.
Abstract: The driving force leading to densification during sintering in the presence of a liquid phase and the material transport phenomena have been analyzed and relationships for the densification rate during the rearrangement process, the solution-precipitation process, and the final coalescence process have been determined. These relationships allow an experimental determination of the mechanism of sintering in the presence of a liquid phase on the basis of the time, particle size and temperature dependence of the densification rate. In addition, they allow direct calculations of densification rates to be made for certain simple systems for which property data are available.

918 citations

Journal ArticleDOI
TL;DR: Theoretical estimations of the sintering rate are in reasonable agreement with experimental measurements as discussed by the authors, which is consistent with the observed microstructure changes in several systems and the rate of densification of magnesium oxide, titanium carbide, and tungsten carbide.
Abstract: Observations of microstructure changes in several systems and the rate of densification during sintering of magnesium oxide, titanium carbide, and tungsten carbide in the presence of a liquid phase indicate that the densification rate is controlled by diffusion through a liquid film between particles. Dependence of the sintering rate on time, particle size, and temperature are in agreement with predictions. Theoretical estimations of the sintering rate are in reasonable agreement with experimental measurements.

98 citations

Journal ArticleDOI
TL;DR: In this paper, 14 selected metal ions were added to magnesium basic carbonate, and the MgO obtained after calcining was fired at various temperatures to determine the effect of the additives on the sintering behavior.
Abstract: Fourteen selected metal ions were added to magnesium basic carbonate, and the MgO obtained after calcining was fired at various temperatures to determine the effect of the additives on the sintering behavior. The magnesia without additives showed rapid increase in density with firing temperature near 1200° C. The majority of the additives caused increased density, at a given firing treatment, but some were without effect and one (Cr) dramatically inhibited sintering in certain percentages. It is believed that most of the additives which aided sintering did so by entering into the magnesia lattice and creating defects, although at least one (V) clearly promoted sintering by liquid formation.

43 citations

Journal ArticleDOI
TL;DR: In this article, a reagent-grade magnesium oxide containing 0.5% lithium chloride was used as an additive to the original surface area and particle size of the MgO.
Abstract: The addition of 0.25% or more of certain lithium compounds, particularly the halides, facilitates the pressing and sintering of reactive forms of high-purity magnesium oxide. Densities up to 3.46 gm. per cm.3 have been obtained at 1400°C. with reagent-grade magnesium oxide containing 0.5% lithium chloride as an additive. The effectiveness of lithium salts as sintering catalysts for magnesium oxide depends on the original surface area and particle size of the MgO. After autoclaving at 150 lb. per sq. in. gauge for 2 hours, samples of MgO sintered at 1400°C. with 0.5%of LiCl showed a water absorption comparable to that of fused magnesium oxide. Similar samples of lithium-treated periclase had about the same resistance to attack by a NaOH-FeO melt as pure MgO fired at 1800° to 1850°C.

41 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of calcining temperatures on the sinter ability of high-purity magnesia powders was investigated, and it was suggested that proper calcinations might also facilitate the preparation of dense ceramics of other oxides.
Abstract: The effect of calcining temperatures on the sinter ability of high-purity magnesia powders was investigated. A marked decrease in the density of sintered (fired) compacts occurred when petro-graphically identifiable periclase was formed in calcining. By employing proper heat-treatment in calcining the powder, ceramic bodies with zero apparent porosities were obtained at sintering temperatures as low as 1650°C. It is suggested that proper calcinations might also facilitate the preparation of dense ceramics of other oxides.

27 citations