Consolidation of Nanograin Ceramics

Nano and small grain ceramics offer the potential for improved mechanical strength over their larger grain counterparts. The proposed program will demonstrate the feasibility of consolidating nanoparticle dispersions of high purity yttria (Y2O3) to produce transparent fine grain (< 1 µm) dual-mode material for missile domes and windows. Reported IR transparent yttria results showed insufficient strength to withstand the stresses imposed by the application conditions. CeraNova has developed techniques for shaping and densifying nanoparticle alumina to produce transparent polycrystalline alumina with grain size 400-700 nm, excellent transmittance in MWIR (3-5µm), and mechanical properties superior to sapphire. These techniques, and previous experience gained from Phase I efforts on transparent yttria, will be applied to the proposed program. The Phase II program will utilize dispersions of yttria-based nanoparticulates. CeraNova¡¦s proposed approach involves shape-forming and consolidation of particle dispersions and a two-stage densification process (sintering and HIP) to achieve full density and control grain growth. Phase I work has resulted in transmittance ~78% in the 3-5µm region for 1.4mm thick disks. Phase II will build on the Phase I results to improve transmission over a broader range, and greatly increase the mechanical strength by limiting grain size to less than one micron.