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Titanium/hydroxyapatite (HAP) composites are candidate materials for biomedical applications as implants and hard tissue substitutes since they combine the good mechanical properties and biocompatibility of Ti with the excellent HAP bioactivity and osteointegration. In powder metallurgy processing of these composites, HAP decomposition promoted by Ti during powder sintering is found. In a previous work Ti-50v%HAP greens of 60% theoretical density (dT) were vacuum sintered at 1150 °C and formation of CaO and Ca4O(PO4)2 (TTCP) resulting from the HAP decomposition, as well as Ti4P3 at the Ti/HAP interfaces was obtained. In the present work those composites are compared with similar ones processed from TiH2 as a substitute for Ti which were also vacuum sintered at 1150 °C from greens with 60 to 86%dT. For the lower %dT, the compounds formed were CaO, TTCP and Ti4P3 and for the higher %dT ones, besides those same products, CaTiO3, Ti5P3 and a phase containing Ti, Ca and P were detected

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The aim of the present research work was to study the effect of mixing aluminum hydroxide sludges with wastes resulting from the cutting and polishing of dimensional stones, which have high content of alumino-silicates, in order to develop mullite. This study shows that, after sintering different mixtures to temperatures up to 1300ºC, there is an important increase of secondary mullite phase in the resultant material, particularly in the mixes 2:1 (alumina:silica ratio) simultaneously with a significant decrease of silica phases. The presence of important quantities of -alumina was also detected with the increasing of sintering temperature. Therefore the product obtained after sintering was a composite of mullite and alumina. The mullitisation behaviour was studied using X-ray diffraction and microstructural analysis, which have confirmed the increase of mullite attaining a maximum when the sintering temperature was 1270ºC. The composite formed during sintering was responsible for a flexure modulus higher than 100 MPa, with a Weibull Modulus typical of technical ceramics, without degrading other properties, like water absorption. The new developed material was found to be inert after leaching tests carried out according to DIN standard 38414.