Design of the4 ceramic-metal composites with gradient concentration of metal particles
Mikołaj Szafran*,Ewa Bobryk*, Katarzyna Konopka** *Politechnika Warszawska, Wydział Chemiczny, ul. Noakowskiego 3, 00-664 Warszawa **Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Quarterly No. 3, 2005 pages 10-15
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abstract In the paper the design of ceramic-metal composites with gradient concentration of metal particles is presented. As a method of composites fabrication the slip casting method was chosen. The process of metal particles sedimentation under gravitation force and magnetic field was used to achieve the gradient concentration of metal particles. In slip casting method the mixture of powders with addition of liquidizers, surface active agents and binders is prepared. Process of metal particles with higher density than the density of ceramic powder sedimentation under gravity force is possible when the distance between the ceramic powder particles are bigger than the size of metal particles (Fig. 2). In the paper the calculations of the distances between the particles are presented. Moreover, the correlation between the size of metal particles and the distance between ceramic particles is described. In calculations the assumption was made that there is regular distribution of free particles. Results showed that the distance between the particles decreases together with the decrease of average size of particles and with increase of concentration of solid phase in slip casting (Tab. 1, Fig. 3). Experimental results confirmed the calculations. The composites Al2O3-Fe were prepared. The Al2O3 powder with average diameter equal to 0.5 μm and density equal to 3.926 g/cm3 was used. The average size of Fe powder was equal to 4 μm, and its density was equal to 7.81 g/cm3. In case of slip casting with 40 volume % of alumina powder no gradient concentration in composites was noticed. Gradient concentration of iron particles is possible when the size of Fe particles in slip casting is lower than the distance between the Al2O3 particles. In such a situation when gradient concentration of metal particles can not be obtained by sedimentation method i.e. when the size of metal particles is equal or bigger than the distance between the particles, the magnetic force might be used. Magnetic force leads to gradient concentration of metal particles, moreover the metal particles are situated along the line of magnetic field. Key words: ceramic-metal composites, gradient materials, slip casting