A fly ash of a coal-fired power plant was examined by XRD, XRF and SEM to determine the crystalline phases and their constituent components. The fly ash was calcined at 600" in air to remove residual C, and based on the results of the XRF analysis alumina powder was added to achieve the stoichiometric composition of the aluminium silicate mullite. The powders were mixed, ball milled, sieved, and rectangular compacts were prepared at pressures of 200 MPa, and sintered at up to 1600" in air. The quartz transformed at 1200" to cristobalite, and mullitization started by the reaction of cristobalite with a-AlzOs at about 1300". The mullitization was completed at 1400", and the crystallization of the mullite increased with higher temperatures. It was demonstrated that low density mullite ceramics with low porosity could be fabricated in this way at sintering temperatures of 1500" from coal fly ash and alumina. The fracture strength of the mullite ceramics could be controlled by the mullite grain shape and size, and the addition of 3Y-PSZ powders inhibited grain growth and enhanced the fracture strength.
SPACE HEATING AND COOLING
02lO1695 A study on the energy performance of three schemes for widening application of water-cooled airconditioning systems in Hong Kong