The U.S. Bureau of Mines evaluated the physical properties of ceramic particulate composites made from titanium nitride (tin), alumina (al2o3), and aluminum nitride (aln) as part of a program to meet the high-performance demands on structural materials for new and emerging technologies. Samples containing from 20 to 80 wt pct tin were pressed and fired, and their composition, vickers hardness, modulus of rupture (mor), and fracture toughness were determined. X- ray diffraction and scanning electron microscope (sem) analyses showed that, depending on the amount of tin added, the microstructure of the samples consisted of either a titanium- aluminum-oxynitride (tialon) particulate in a spinel matrix or a spinel particulate in a tialon matrix. The best results of the physical tests were achieved on a mixture of 40 wt pct tin, 30 wt pct al2o3, and 30 wt pct aln. Sintering aids were added in 1- and 3- mol-pct increments to the 40-30-30 mixture to determine their effect on microstructure and physical properties. Results of an analysis of variance on a 4 by 4 factorial analysis showed significant effects on density, mor, and vickers hardness.