Fabrication of fully dense ZrB2- and HfB2-based Ultra High Temperature Ceramics by combining Self-propagating High-temperature Synthesis and Spark Plasma Sintering
AbstractThe Self-propagating High-temperature Synthesis (SHS) technique and the Spark Plasma Sintering (SPS) technology are combined in this work for the fabrication of fully dense MB 2-SiC and MB 2-MC-SiC (M=Zr, Hf) Ultra High Temperature Ceramics (UHTCs). Specifically, Zr or Hf, B 4C, Si, and, for the cases of the ternary systems, graphite powders are first reacted by SHS to successfully form the desired compounds. The resulting powders are then subjected to consolidation by SPS. In particular, by setting a dwell temperature level equal to 1800 °C, a mechanical pressure P=20 MPa, and a non-isothermal heating time t h= 10 min, products with relative densities ≥ 98.5% are obtained for all systems investigated within 30 min of total processing time. The characteristics of the resulting dense UHTCs, i.e. hardness, fracture toughness, and oxidation resistance, are similar to, and in some cases superior than, those related to analogous products synthesized by alternative, less rapid, methods.
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