Structure formation of TiB2-TiC-B4C-C hetero-modulus ceramics via reaction hot pressing

The densification kinetics and structure of TiB2-TiC-C, TiB2-C and TiB2-B4C-C hetero-modulus ceramics produced via reaction hot-pressing of B4C and TiС precursors are investigated. The reaction begins at 1100°C with boron carbide decomposition and progresses in two main stages which can be predominantly determined by the boron atoms to TiC grains diffusion mechanisms. The solid phase grain boundary diffusion starts at 1100°C and effective gas phase transport finalises the reaction at temperatures above 1400°C. Two distinctive waves of the charge consolidation allow densifying investigated refractory materials at 1900°C and 30MPa during 16 minutes. The reaction is shown to define the features of the composite structure: submicron TiB2 particles and faceted voids in B4C matrix, flake-like graphite and TiB2 inclusions in TiC matrix. High concentration of carbon atoms (~ 10 at.%) in synthesized diboride titanium grains have been observed

Effect of Yttrium Oxide Impurities on the Structure and Properties of Metallic Hafnium

The influence of yttrium oxide impurity content of 0 to 0.4 wt.% on the structure and microhardness metal hafniuminvestigated. It is shown that grain size decreases and the Microhardness of hafnium increases monotonically with increasing content of impurities, while increasing Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; content more than 0.3 wt.% is cracking material.Keywords: yttrium oxide, hafnium, microhardness, optical microscopy.</p