High‐Temperature Strength of Boron Suboxide Ceramic Consolidated by Spark Plasma Sintering

Abstract

The spark plasma sintering (SPS) of B6O ceramics using a highly crystalline boron suboxide powder with a low oxygen deficiency level is reported. The monolithic boron suboxide ceramic exhibited a room‐temperature strength of 300 ± 20 MPa, which is comparable to the strength of monolithic boron carbide. With increasing flexural test temperature, the strength of the boron suboxide ceramics increased to 450 MPa at 1400°C. The increase in strength with the temperature is associated with the unique microstructure of boron suboxide grains, which allows intergranular “brittle” fracture along subgrains even at 1400°C. This suggests that even higher strengths can be achieved.

Ultrafine‐grained B6O–diamond composites with superb mechanical properties

“…In the past, a series of efforts have been devoted to the densification and sintering of B 6 O. Regrettably, due to its low diffusion coefficients and the relatively high vapor pressure at sintering temperatures, full densification of B 6 O is only possible by pressure assisted sintering. The specific method is to heat the B 6 O powder or the mixtures of B and B 2 O 3 powder under a certain pressure to a high temperature of 1700–2200°C for sintering, but even at such a high temperature, the poor sinterability leads to poor fracture toughness (1.7–3.1 MPa m 1/2 ) of the B 6 O ceramics 12–15 . Adding additives is a straightforward approach to improve its sinterability.…”

“…The specific method is to heat the B 6 O powder or the mixtures of B and B 2 O 3 powder under a certain pressure to a high temperature of 1700-2200 • C for sintering, but even at such a high temperature, the poor sinterability leads to poor fracture toughness (1.7-3.1 MPa m 1/2 ) of the B 6 O ceramics. [12][13][14][15] Adding additives is a straightforward approach to improve its sinterability. Experiments in the past have confirmed that adding the alkaline earth, 16 rare earth, 17 alkaline oxides, 18 transition metals 19 and their oxides 20 as additives in B 6 O sintering process can effectively reduce the sintering temperature and is conducive to densification.…”