activated surface sintering process for the densification of ceramic and metal composite bodies at low temperatures

摘要

activated surface sintering process for the densification of ceramic and metallic composite bodies at low temperatures. The invention describes a new material engineering technique which promotes sintering of ceramic shaped powders and cermets and ceramic-ceramics composites at lower temperatures than usual. The process can be employed in a multitude of materials, including those containing ceramics such as alumina, zirconia, titania, uranium and mixed oxides such as titanates, zirconates and others. Several modes of operation are included and exemplified, whose theoretical and practical bases rest on the coating of the original ceramic particles of interest with metallic or ceramic additives, according to the projected morphologies, leading to the blocking of the surface diffusion in these particles. The process thus performed preserves the specific surface during the heating phase of sintering, promoting densification at lower temperatures. The additives are subsequently removed during heating exposing the original preserved high-sintered ceramic surfaces capable of activating densification at lower temperatures in the range of 600 198 c to 1300 198 c. The ssa surface activated sintering process utilizes preferably oxidizing atmospheres imposed on the sintering chamber as well as additives that form protective liquid phases during the process. The obtaining processes and compositions of these composite powders are integrated with sintering techniques.