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A novel processing route for developing open-cell, microcellular SiC ceramics has been developed. The strategy adopted for making microcellular SiC ceramics involved the following: (i) fabricating a formed body from a mixture of polysiloxane, phenol resin (used as a carbon source), polymer microbeads (used as sacrificial templates), and Al 2 O 3 -Y 2 O 3 (an optional sintering additive); (ii) cross-linking the polysiloxane in the formed body; (iii) transforming the polysiloxane and phenol resin by pyrolysis into silicon oxycarbide and C, respectively; and (iv) synthesizing SiC by carbothermal reduction. By controlling the microbead and additive contents, it was possible to adjust the porosity so that it ranged from 60% to 95%.

Nano‐hafnium diboride powder was synthesized by boro/carborthermal reduction process of HfO2 using a spark plasma sintering (SPS) apparatus. The agglomerated product was found to be 1–2 μm in size, which was composed with small primary particles of 100–200 nm in size. The particle size of HfO2 played an important role to produce the nano‐boride powder. In addition, the grain growth of HfB2 could be effectively suppressed by using SPS due to the fast heating rate. The synthesized powder had a low oxygen content (~0.66 wt%). Excessive B4C and C were necessary during the boro/carborthermal reduction in HfO2 process because of the volatilization of boron as a form of B2O3 and the reduction in residual HfO2.

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