HfC/SiC nanocomposites were fabricated via the reactive spark plasma sintering (R‐SPS) of a nano‐HfC powder and HfSi2‐C sintering additives. The densification temperature decreased to 1750°C as the additive content increased. XRD analysis indicated the formation of pure HfC–(19.3–33.8 vol%) SiC within the sintered composites without residual silicide or oxide phases or secondary nonoxide phases. Ultrafine and homogeneously distributed HfC (470 nm) and SiC (300 nm) grains were obtained in the dense composites using nano‐HfC powder through the high‐energy ball‐milling of the raw powders and R‐SPS. Grain growth was further suppressed by the low‐temperature sintering using R‐SPS. No amorphous phase was identified at the grain boundary. The maximum Vickers hardness, Young's modulus, and fracture toughness values of the HfC/SiC nanocomposites were 22 GPa, 292 GPa, and 2.44 MPa·m1/2, respectively.

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.

Dispersion conditions of ZrB 2 powder in water were investigated using poly(ethyleneimine) (PEI) as a dispersant. Pulverization of ZrB 2 powder to submicrometer size was difficult and a substantial amount of large particles remained after an intensive planatery milling for 72 h. The isoelectric point (IEP) of ZrB 2 powder was measured to be pH 5.8 by electrophoresis, which shifted to pH 6.2 after milling. The application of PEI changed the IEP of the boride slurry to BpH 11. Well-dispersed aqueous ZrB 2 slurries with a high solid loading (up to 45 vol%) were fabricated at pH 6.5-7.5 by the application of 1.5 wt% PEI.N. Jacobson-contributing editor

A new technique for the homogeneous infiltration of concentrated and viscous ceramic filler slurries into stacked 2D‐woven fabrics has been developed by introducing a flexible mold. The inner space of the mold expanded during slurry infiltration, which enhanced penetration of the viscous slurry into the woven fabric layers. The subsequent precursor impregnation and pyrolysis process yielded fiber‐reinforced ceramic composites with scarce macropores between the fabric layers.