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Ageing of wet-synthesized oxide powders. Role of surface carbonation, effect on sintering, restoration

Wet chemical synthesis of precursor oxide ceramics is a method to obtain small particulate powders. Such powders are far more prone to ageing in air than more traditional precursors. Thermogravimetric analysis is used to highlight the species responsible for the ageing of ceramic precursors. Indeed water and carbon dioxide are observed to evolve from aged powders. Ceramics obtained from aged precursors can reach a very low final density with respect to the theoretical value.

Thermal stability and sintering behaviour of hydroxyapatite nanopowders

Hydroxyapatite (HA) nanopowders were synthesised following two different precipitation routes: (a) from calcium nitrate and diammonium hydrogen phosphate solutions and (b) from calcium hydroxide suspension and phosphoric acid solution.

Study of the resistance to washout of PVD coated hot working tool steels

Wear and failure of die casting dies involve a complex interaction between various mechanisms. A CrAlSiN coating system was deposited on the base material, modulating the chemical composition of the chromium or the aluminium-silicon content. A set of the coated specimens was directly analysed through optical and electronic microscopy, so as to assess the overall quality. Other was subjected to a cyclic immersion program in molten aluminium bath. Coating efficiency was determined through electron microscopy analysis. Thermal fatigue was investigated, quantified.

Effect of porosity of cordierite preforms on microstructure and mechanical strength of co-continuous ceramic composites

With the aim of reducing the overall cost of the process, co-continuous metal–ceramic composites were obtained by reactive metal penetration, starting from very low cost cordierite preforms. It was investigated how the preform porosity influences both the residual porosity left in the composites after infiltration and the mechanical properties.