A new theory was formulated for analyzing the cyclic fatigue behavior of ceramics by combining the multi-modal Weibull distribution function with slow crack growth law (S. C. G.). Using an internal pressure testing machine, static and fatigue tests were performed on cylindrical alumina specimens. Statistical data analysis showed that cyclic stress reduces the number of cycles to failure. Intergranular fracture was dominant on fatigue fractured surfaces. The semi-length of the crack at branching has been best correlated with the peak applied stress in the cyclic fatigue test. The least of the number of cycles to failure was ensured for the specimens passing through the pre-loading proof test.
In order to investigate the effects of diffusion and convection on the melt mixing of semiconductors, experiments under microgravity in space and 1-g on earth were conducted. Sandwich combinations of In/GaSb/Sb solids closed in a BN cylinder were heated up to 733° C in space and 744° C on earth, and they were then cooled rapidly. In both samples, many needle crystals were distributed in the whole area. It was observed that the melt mixing in space was controlled by diffusion which was represented with an error function, and the diffusion coefficient of indium was given by a value of 2.4×10 -4 cm 2 / s. In the earth sample, however, the indium concentration distribution followed an exponential curve. This indicated that both factors, diffusion and thermal convection, have contributed to the mixing of semiconductor melts.
Abstract A mixing experiment of multicomponents melts was performed using a uniform temperature furnace in the Second International Microgravity Laboratories (IML‐2) mission. Growth morphologies and Ga concentration profiles were analyzed for the samples with the compositional ratio of 0.5 In–0.5 Ga–1.0 Sb grown under microgravity and on earth. The sample with free surface grown under microgravity was nearly spherical in shape, except some parts with projections. Ga was dispersed homogeneously in the bulk because the mixing was enhanced by Marangoni convection due to the concentration gradient. On the other hand, the sample grown on earth was a double cylindrical shape with different diameters, and Ga concentration decreased from top to bottom, showing clearly the effect of gravity. Many needle crystals were formed in both space and earth samples due to rapid cooling. The average size of the needle crystals grown in space was larger than that of the earth sample.
