Showing papers by "Pedro José Sánchez-Soto published in 2001"

Effect of grinding and water vapour on the particle size of kaolinite and pyrophyllite

Abstract: The increase in specific surface of kaolinite (K) and pyrophyllite (P) induced by dry grinding in an oscillatory mill, proceeded during storage in water vapour The average particle thickness, δ, changed from 42 nm (K) and 66 nm (P) in the original materials to 12 nm (K) and 20 nm (P) after water sorption (20 days at relative humidity RH = 10, at room temperature and pressure) and to similar values of 13 nm (K) and 16 nm (P) after grinding for 10 min (in agreement with some published data), The action of water molecules on ground clays (at the conditions indicated) resulted in a further decrease in δ, In pyrophyllite, prolonged grinding (30 min) and prolonged action of water molecules (36 days) caused a particle collapse After pre-storing at RH = 05 the successive decrease in δ at RH = 10 was smaller

Fabrication of Layered Mullite-SiAlON-SiC Composites from a Preform by Nitridation and Oxidation

Abstract: A composite was prepared from a prior preform by chemical processing of reactive precursor powders synthesized from coprecipitated mixtures of an aluminium silicate and aluminium hydroxide, which was prepared using aluminium salts in solution and a diamine as base precipitant and coupling chemical agent. This is also the organic source for carbothermal reduction. The powder was compacted by cold-pressing and the preform thermally treated under nitrogen flow to facilitate nitridation and carbothermal reduction. A subsequent controlled oxidation process was used to prepare the composite. The final sintered composite comprised layers of mullite, mullite and alumina, β-SiAlON and silicon carbide. The presence of particles (mullite-sialon) and fibres (sialon-silicon carbide) in the composites was considered very attractive from the point of view of mechanical, thermal and electrical behaviour.