Manas Kamal Haldar

Synthesis and densification of magnesium aluminate spinel: effect of MgO reactivity

Stoichiometric magnesium aluminate spinel was synthesized by reaction sintering of alumina with caustic and sintered magnesia. The volume expansion of 5-7% during MgAl2O4 formation was utilized to identify the starting temperature of spinel formation and densification by high temperature dilatometry. The magnesia reactivity was determined by measurement of crystallite size and specific surface area. Caustic magnesia and sintered magnesia behave differently vis-A-vis phase formation and densification of spinel. Densification of stoichiometric Mag-Al spinel was carried out between 1650 and 1750 degreesC. Attempts were made to correlate the MgO reactivity with microstructure and densification of spinel

Properties of zirconia–mullite composites prepared from beach sand sillimanite

Abstract Zirconia–mullite composites were prepared from beach sand sillimanite in the presence of magnesia as an additive. The raw materials were attrition milled. Samples were isostatically pressed and sintered in the temperature range of 1500–1600 °C with 2 h of soaking. The resulting composites were characterized in terms of densification, thermal expansion, martensite start ( M s ) temperature. The presence of magnesia changes the value of thermal expansion coefficient. The mechanical and thermomechanical properties, namely flexural strength and thermal spalling of the sintered composites, were characterized and effect of magnesia on it is discussed. The microstructural characterization of the sintered samples through scanning electron microscopy has shown that mullite and zirconia are the two major phases in the microstructure.

Effect of Addition of Titania doped Preformed Spinel in High Alumina Castables

Magnesium aluminate spinel aggregate was prepared by reaction sintering technique from its constituent oxides in a single firing process and the aggregate was used to develop alumina spinel castable. Different compositions were studied with variation in spinel content between 16 and 20 wt%. Other constituents used were WTA aggregates, bauxite aggregates, high alumina cements and additives. Developed castable was characterized for various properties both at dried and fired conditions.