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This paper describes the purification of diatomaceous earth mined in the Ankara region of Turkey. The diatomaceous earth was found to be essentially amorphous, but a small amount of crystalline illite, K0.7Al2(Si,Al)4O10(OH)2, was present in it. The complete chemical composition of the material was 74.4% SiO2, 14.55% Al2O3, 3.62% Fe2O3, 1.55% CaO, 1.37% MgO, 2.44% K2O and 0.72%Na2O. In connection with the purification of the diatomite, two different processing routes were planned: (i) leaching of the diatomaceous earth directly in cold acidic solutions of HCl; (ii) leaching of the diatomaceous earth directly by using hot 1 and 2 N HCl. It was found that all of the undesirable elements in the composition of the diatomaceous earth were dissolved when treated at about 100°C with acidic solutions prepared using 1 and 2 N HCl for various leaching times. Under several cold acid concentrations, varying from 1 N to 5 N HCl, however, only a small amount of silica is dissolved, while significantly reducing the contribution of undesirable aluminium, calcium, magnesium, iron and alkaline elements.

This paper describes the microstructural and mechanical properties of injection moulded 17-4 PH stainless steel gas and water atomised powder. Gas and water atomised stainless steel powders were injection moulded with wax based binder. The critical powder loading for injection moulding were 62 . 5 and 55 vol.-% for gas and water atomised powders respectively. Binder debinding was performed using solvent and thermal method. After dedinding the samples were sintered at different temperatures for 1 h in pure H 2 . Metallographic studies were conducted to determine to extend densification and the corresponding microstructural changes. The results show that gas atomised powder could be sintered to a maximum (98 . 7%) of theoretical density, and water atomised powder could be sintered to a maximum (97 . 08%) of theoretical density. Maximum tensile strength was obtained for gas atomised powder sintered at 1350uC. The tensile strength of the water atomised powder sintered at the same temperature was lower owing to higher porosity. Finally, mechanical tests show that the water atomised powder has lower mechanical properties than gas atomised powder.