CeraMat

In many cases the production of advanced ceramics is still limited in reliability and reproducibility of material performances by inadequate technologies. Above all this is due to the fact that a real control of all the microstructure parameters (chemical composition, phases distribution and composition, surface compositional gradients, grain size, etc.), on which the properties of the ceramic mainly depend, has not been yet achieved.

The structure and physicomechanical properties of mortars with added polymer emulsions were compared with those of a pure mortar after curing for 3, 7 and 28 days. No changes were observed in the crystal growth of the hydrated phases. The emulsions did, however, provoke a shift of the pore distribution curve towards higher mean radius values, although this shift became more and more negligible as curing proceeded. Total porosity was more contained when the additive was present, since its fluidifying effect enabled a lower initial water/cement value to be used.

85Al2O3-15ZrO2 (wt%) powders were synthesized by gel precipitation starting from AlCl3 · 6H2O and ZrCl4 solutions and dried by two different methods: (i) by spray-drying and (ii) via a sol-gel route by n-octanol in a pilot plant. The particles by process (i) were spherical granules of diameter 15 μm, and those by process (ii) were microspheres of 25 μm. The powders were characterized in terms of morphology, particle size distribution, surface area, weight loss and crystallization behaviour at different temperatures.

The results of the investigations of thermal behaviour of Li2ZrO3, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min-1 and cooling rate of 2.5 deg·min-1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.

Depending on the preparation temperature and the origin of the raw material, the products obtained by thermal activation of kaolinite lead, by hydrothermal treatment with sodium hydroxide at 102°C, either to zeolite 4A, or to cubic zeolite P, or to a mixture of cubic and tetragonal zeolite P.

(High resolution) TEM and FTIR spectroscopy of in-situ CO adsorption at 300and ∼ 78 K have been used to characterize particle morphology and surface Lewis acidity of three preparations of tetragonal ZrO2 stabilized with Y2O3. Depending on preparation, the starting materials are in the form of individual coin-shaped platelets, or of huge aggregates of small particles. In either case, few low-index crystal planes are most frequently exposed, and the particle edges are irregular.