Densification of Nano-Sized Boron Carbide

by Shupe, John

Boron carbide nano-powders, singly-doped over a range of compositions, were pressurelessly-sintered at identical temperature and atmospheric conditions in a dif- ferential dilatometer to investigate sintering behavior. Samples that achieved relative densities greater than 93% of theoretical density were post-HIPed. Post-HIPing re- sulted in an increase in relative density as well as an increase in Vicker's hardness. To optimize the sintering behavior, nano-powders with multiple dopants were prepared based on the results of single dopant experiments. These powders were studied using the same heating schedule as the single dopant samples. The powder with optimized composition was selected, and 44.45 mm diameter disks were pressed to determine the e¢çects of sample size. Powder composition #166 with Al, Ti, W and Mg additions was processed using di¢çerent methods in order to create defect-free green bodies after uniaxial press- ing. The 44.45 mm diameter compacts were heat-treated to remove organics and B2O3 coatings on particles and then encapsulated in an evacuated fused silica am- pule. Encapsulated samples were HIPed at temperatures below the coarsening region observed in the dilatometric traces of multiply-doped nano-powders. The E-HIPed sample showed a relative density of 96% with a limited extent of nano-sized grain microstructure.