The influence of the deposition parameters on the porosity of thin alumina films electrophoretically deposited on steel from aqueous suspensions was investigated. The effects of the applied voltage, deposition time, suspension temperature and the solid content of the aqueous suspension on the porosity of the obtained alumina films have been determined using optical microscopy coupled with image analysis. It was shown that the lowest film porosity was obtained from a suspension containing 20 wt.% alumina powder at the lowest applied voltage (30 V), for a longer deposition time (10 min) using a suspension temperature of 30 ºC. This behavior can be explained by the smaller amount of hydrogen evolved on the cathode during the electrophoretic deposition process.

Alumina water suspensions have been prepared for thin alumina film deposition on steel. The type and quantity of deflocculant have been determined using zeta potential and viscosimetric measurements. The deposition was performed under the constant deposition voltage between 30 and 250 V. The morphology of electrodeposited alumina films was investigated using the optical microscopy coupled with image analysis, which enables the determination of pore number, percentage of film surface covered by pores and mean pore diameter, and scanning electron microscopy (SEM). It was shown that alumina films of the highest thickness and the lowest porosity can be formed at lower applied voltage and for longer deposition time. The minimum of alumina films porosity, obtained at the lowest deposition voltage of 30 V, can be explained by smaller amount of evolved hydrogen on the cathode during electrodeposition process.

The objective of the present work is to examine the different aspects of the interfaces existing in three and five layers laminar composites. Al2O3, Ni and Ni + Al2O3 (microinfiltrated bonding layer; Ni:Al2O3-25:75 wt% mixture) layers were obtained by tape casting. The characterization of laminated Al2O3 / Ni+- Al2O3 / and Al2O3/ Ni+ Al2O3 / Ni / Ni+ Al2O3 / Al2O3 composites produced by pressureless sintering, included SEM, EDAX, Ro and bending tests examinations. The nature of interface between the individual layers of the composites, as well as nickel particles in alumina matrix (microinfiltrated laminae), has been discussed. Bonding quality, interaction between cracks and nickel particles, laminar composite architecture and thermal residual stresses as well influence the strength of the composites.

On a etudie les possibilites de moulage par injection de SiC en employant differents additifs organiques, a partir de l'examen de la viscosite a haute temperature de differents melanges, c'est a dire en comparant les valeurs de viscosite, dans les memes conditions, ainsi que la dependance en temperature de la viscosite. On a aussi etudie le comportement durant le moulage par injection. Les composants organiques de base entrant dans toutes les formulations sont la paraffine et l'acide stearique, mais on peut aussi ajouter du polyethylene, du poly propylene, de la glycerine, et de l'huile de poisson. Les formulations contenant de la glycerine et du polyethylene ne sont pas fluides dans les conditions etudiees. Les formulations contenant du polypropylene ne peuvent pas etre mises en forme par moulage par injection a 200 °C, et meme a plus haute temperature. Les formulations contenant de l'huile de poisson donnent de bons resultats, mais les meilleurs resultats sont obtenus avec les formulations les plus simples, contenant de la paraffine et de l'acide stearique. On a etudie en detail la viscosite de trois de ces formulations, avec 85-89 % en masse de poudre ceramique (63-71 % en volume). On a etabli qu'il est non seulement possible, mais meme aise, de mettre en oeuvre des melanges contenant un maximum de 89 % en masse de poudre ceramique (71 % en volume), c'est a dire la formulation proche de la concentration critique de phase solide dans un melange pour moulage par injection.

Metal-ceramic-intermetallic multilayered, laminar composites present an attractive group of materials offering a variety of combinations of constituent component properties. Processing of these composites is possible due to a considerable processing flexibility afforded by the powder metallurgy route. In the present paper, the possibility of obtaining laminar composite structures consisting of metal (Ni), ceramic (Al2O3) and intermetallic compound (Ni3Al) layers, has been described. Individual layers were prepared by different techniques. Laminar composites were obtained by hot pressing and standard sintering process.

In this work the quantitative relations between the properties of sintered fused silica (density, mechanical propel-ties, cristobalite content) and slip preparation parameters as well as sintering conditions (milling balls material, temperature and rime of sintering) were established Multifactorial experimental design ,cas used in ol der to obtain rite respective mathematical al models. The response surfaces of these models were analyzed, together with correlations between the compressive and tensile strength and cristobalite content. it was established that the maximum values of mechanical properties for a given material were obtained with 6-8 vol.% of cristobalite in sintered samples.

Frittage et devitrification sont des processus simultanes lors du frittage au-dessus de 1100°C de silice fondue de qualite technique preparee par coulage de barbotine. Cela rend difficile l'obtention d'un materiau a faible porosite et faible teneur en cristobalite. L'article montre les posibilites du pressage chaud pour l'obtention de ce type de materiau. La densification intervient par un mecanisme d'ecoulement visqueux, du moins si la devitrification n'est pas trop prononcee.

An analysis of ceramic slip-casting in porous molds is given in this paper. A new process parameter, called the slip-casting coefficient, is introduced in order to indicate the progression of the slip-casting process, independent of mold shape. Material balances for the solid and liquid phases of ceramic slip, as well as the filtration equation (Carman-Kozeny), are the basis for establishing the mathematical model of slip-casting in porous molds.