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The thermal decomposition of the ferric and nickel acetate salts has been followed. It was found that the heating rate affects the decomposition steps. For a heating rate of 1 K min -I the product is either Fe203 or NiO. For a higher heating rate the suboxides are obtained and reoxidized again on further heating. The decomposition of the mixed salt is an overlap of the DTA for the separate salts but the decomposition reactions are shifted to lower temperatures.

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Cr 3 B 4 cermets cemented by cobalt and iron as a metallic b inder up to 20 wt% were prepared by hot pressing at 1500 and 1800℃ under a pressure of 14 and 41 MPa for 1hr. The binder addition enhanced the densification of Cr 3 B 4 cermets due to the formation of liquid metal and its flow into the pores. It is also found that the temperature and pressure have a pronounced effect on densificat ion. The densification of Cr 3 B 4 is enhanced by the addition of cobalt and iron due to the liquid phase format ion, therefore, the hardness and fracture toughness were improved, to a certain extent. A composite with a both high Vickers hardness of 35.98 GPa and a modest fracture toughness of 2.5 MPa.m 1/2 could be obtained by the addition of 8 wt% cobalt at 1500 o C and 14 MPa. There is an overgrowth of the boride grains which surly reduces the hardness but has less impact on the fracture toughness.