The densification behavior, microstructure, mechanical, and thermionic emission properties of LaB6‐SiC composite

Abstract

The LaB6‐SiC composite with the different SiC content (0, 15, 30, 36, 50, 90, and 100 wt.%,) was densified by spark plasma sintering. The effects of SiC content on the densification behavior, microstructure, mechanical, and thermionic emission properties of LaB6‐SiC composite were systemically investigated. The results show that all the rapid shrinkage occurred at the heating stage during densification, and LaB6‐36 wt.%SiC composite owned the maximum shrinkage rate of 1.5 mm/min at T = 1798oC. The highest relative density of the composite decreased from 98.18% to 95.01% as the SiC content increased from 15 wt.% to 90 wt.%, under which the morphology of LaB6 grain evaluated from the equiaxed to elongated structure, and LaB6 grain size varied in the range of 5.05–11.42 μm. The similar eutectic structures were observed in the LaB6‐36 wt.% SiC composite because of some LaB6 grains melting. Both the highest fracture toughness of 5.15 ± 0.56 MPa.m1/2 and the highest bending strength of 313 ± 4.7 MPa belonged to the LaB6‐36 wt.% SiC composite, which also exhibited thermionic emission current density of 10.74 A/cm2 and work function of 2.99 eV at T = 1873 K.