Influence of the Mechanical Alloying Parameters on the Elaboration of Sic/Al Nanocomposite Powders

The paper presents the experimental work regarding the elaboration of some nanocomposite powders with higher SiC content. For the research, three types of mixtures were prepared: 90SiC-10Al, 70SiC-30Al and 60SiC-40Al using mechanical alloying (MA) technique. The MA was carried out in a vario planetary ball mill Pulverisette 4 for 5 hours using different conditions: - the shock mode (the main disk speed 400 rpm and the planets speed -800 rpm); - the friction mode (the main disk speed 400 rpm and the planets speed 800 rpm). The resulting mixtures was investigated by scanning electron microscopie (SEM), X-ray diffraction pattern (RDX), energy dispersive X-ray analysis (EDAX) and particle size distribution. After 5 hours of MA it is observed that the mixture obtained in the friction mode conditions have a homogenous structure and the particle size distribution is better than the particle size distribution of the mixture obtained in the shock mode conditions.

Flow Phenomena of Partially Enclosed Rotating Disks

The flow of air in the space between a rotating disk and a stationary side wall placed parallel to its surface has been investigated over a range of Reynolds numbers from 3 × 105 to 6 × 106 at clearance-to-diameter ratios from 0.0125 to 0.0625. When the size of the stationary side wall was larger than the diameter of the rotating disk the flow in the gap was found to be periodic; several distinct and separate inflow and outflow regions were observed to rotate in the same direction as the disk, but at a slower speed. The number of flow regions was found to be a function of the disk speed and the gap size. The frictional torque on the housing was also measured and the effect of source flow on the flow pattern was studied qualitatively.