Seeded texture development in aluminum nitride-silicon carbide platelet composites

Michael Scott Sandlin, Purdue University

Abstract

Aluminum nitride-silicon carbide platelet composites were selected to investigate seeded bulk texture development by a growth-related mechanism. AlN and SiC form a solid solution at elevated temperatures, have high surface energies, which encourages coalescence during sintering, and they share several epitaxial relationships. In addition, SiC platelets have high aspect ratios making them amenable to texture manipulation during green state processing. Polycrystalline AlN specimens containing 15 and 30 volume percent SiC seed particles were fabricated by slip-casting followed by hot-pressing at 1800$\sp\circ$C. These processing steps result in oriented platelets in a nearly random matrix. Samples were then annealed for 0 to 18 hours at 2150$\sp\circ$C under nitrogen. Quantitative texture measurements of the AlN and SiC basal poles, and powder diffraction measurements were performed using neutron and x-ray diffraction. Optical microscopy and electron microscopy were used in conjunction with texture analysis to elucidate texture development mechanisms. The results indicate that SiC platelets effectively "seed" AlN-SiC alloy textures by a coalescence and growth mechanism during annealing. Texture intensification does not occur in AlN specimens without SiC platelet additions, or in specimens containing non-oriented SiC powder. The most effective seeding was observed in specimens containing 15 volume percent SiC platelets.

Degree

Ph.D.

Advisors

Bowman, Purdue University.

Subject Area

Materials science

COinS