Abstract
We report nearly full densification of polycrystalline rhombohedral beta(β)-boron without the addition of sintering aids via spark plasma sintering(SPS).The analytical aberration corrected transmission elec-tron microscope observations have revealed in-situ growth of nanocrystalline boron-rich oxide precipi-tates that contain approximately 4 at.％of oxygen and beget the densification of β-boron.Further elec-tron energy loss spectroscopy and diffraction analysis confirmed that the newly formed boron-rich oxide(nominally B96O4)structure with B-O σ-bonding belongs to space group R3m.Depth sensitive nanoin-dentation showed boron-rich oxide phase has a hardness of about 41±2 GPa,which is 10％higher than that of β-boron matrix.The estimated hardness and fracture toughness of β-boron were approximately 31 GPa and 2.2 MPa m1/2,respectively,using Vickers microindentation,which falls in the range of those commercially used boron carbides.These results suggest that the enhanced densification and mechanical properties arise from the newly formed boron-rich oxide in β-boron during SPS experiments.
基金项目
National Science Foun-dation China(51850410501)
seed funding from the School of Materials Science and Engineering at Shanghai Jiao Tong University China)KMRis partially sup(QN20200009025)
NETL
NSTL
维普
万方数据