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Three-dimensional interconnected alumina/ steel metal matrix composites (MMCs) were produced by pressureless Ti-activated melt infiltration method using three types of Al 2 O 3 powder with different sizes and shapes. By partial sintering during infiltration an interpenetrating ceramic network was realised. The effect of the ceramic particle size and shape on the resulting ceramic network, volume % fraction and the MMC properties is presented. The MMCs were characterised for mechanical properties at room temperature and elevated temperature. An increase in flexural strength and Young's modulus with decreasing particle size has been observed. In addition, the effect of the volume of ceramic content and the surface finish of the MMCs on the wear behaviour is shown.

The effect of different sintering additives on the high temperature oxidation and corrosion behaviour of Si3N4 ceramics is investigated. A corrosion furnace was set up which allows testing of ceramic discs at test temperatures upto 1500°C. It was possible to conduct tests under ambient oxygen conditions, or with increased water vapour as well as testing with corrosive gases such as HCl or SO2. Si3N4 was prepared with MgO, Al2O3, Y2O3 and Al2O3+Y2O3 sintering additives. These discs were subjected to different oxidation and corrosion test conditions at temperatures of 1200°C and 1500°C for upto 128 h. The effects that the different corrosion enviroments have on the corrosion resistance of the Si3N4 materials are presented.

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