1995

Alloys with a cobalt binder content in the range from 3 to 15 wt.% were studied. The carbides grain size also range between 0.7 and 5 μm. Mechanical properties, such as transverse rupture strength and hardness, were tested. The residual porosity and the micro structure were accurately observed by optical microscopy and the carbide grain size was estimated using an optical image analyser.

Amorphous precursors of LaNbO4 have been prepared by coprecipitation and mechanical alloying. Powder characteristics before and after calcination were studied by thermogravimetric analysis, differential thermal analysis, Fourier transform-infrared spectroscopy and X-ray diffraction, and the crystallographic changes during thermal treatment were documented by high-temperature X-ray diffraction.

Lithium metazirconate is a candidate in fusion reactor designs as a tritium-breeding material. An amorphous powder was synthesized by gelling zirconium propylate and lithium acetate: after heat treatment at 900 °C, pure Li2ZrO3-l was obtained. Preliminary tests made on sintered pellets, obtained from this powder, demonstrated an appropriate tritium release at low temperature, when the sample porosity was about 20% and the mean pore radius 3 μm. The subject of this paper was to realize a good compromise between mechanical properties and the spread porosity, necessary for tritium diffusion.

This work deals with the development of a new type of product, a catalytic filter, which could be used for treating flue gases, coupling particulate filtration and catalytic abatement of noxious gases. The first step of this project concerned the coating of the pore walls of a ceramic candle filter (made of α Al2O3) with a high specific surface area phase (i.e. a transition alumina). This layer will act as a catalyst support. The coating was obtained by impregnation of the porous support and subsequent calcination, using three different precursors.

Dry pressing is the most common industrial shaping process for ceramic pieces. Sol-gel powders are of high reactivity, but very often agglomeration-aggregation phenomena limit this advantage by inducing poor compaction behaviour. Consequently the goal of sol-gel powder research - to obtain full densification at very low sintering temperature, is not achieved. With the intention of showing the influence of sol-gel powders, specific characteristics on pressing, compaction diagrams and green body characteristics of two experimental zirconia sol-gel powders have been determined.

This paper deals with the preparation and the characterization of ceramic porous filters whose pores were deposited with a γ-Al2O3 layer via the so-called "urea method", in order to increase their specific surface area. Once activated with a suitable catalytic principle, these filters can find a potential application in flue gas cleaning according to a combined action: mechanical particulate removal + catalytic abatement of chemical pollutants (nitrogen oxides volatile organic compounds, etc.).