Spark plasma sintering of Zr- and Hf-borides with decreasing amounts of MoSi2 as sintering aid.

• ZrB2- and HfB2-based composites contg. 1, 3, and 9 vol.% MoSi2 as sintering aid were densified by spark plasma sintering at temps. ranging from 1700 to 1950, with an applied pressure of 100 MPa. As-received ZrB2 and HfB2 powders were also sintered at temps. in the range of 2100-2200. Fully dense samples were obtained between 1750 and 1850 when MoSi2 was added. As-received ZrB2 powder was sintered to 98% at 2100. The microstructural features were investigated by SEM-EDS technique. SciC was detected in all the doped compns. along with significant amts. of oxide species (Hf/ZrO2 and SiO2). Vickers hardness and fracture toughness were measured by indentation technique on polished sections. The effect of the MoSi2 content on densification, microstructure, and mech. properties is discussed.

Nyckelord

Spark plasma sintering

Borides

Hfb2

XrB2

MoSi2.

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