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Nanotwinning and Directed Alloying to Enhance the Strength and Ductility of Superhard Materials
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Yidi Shen, Qi An, Xiaokun Yang, William A. Goddard III
Superhard materials, such as boron carbide (B4C), boron suboxide (B6O), boron subphosphide (B12P2), and related materials, have been examined extensively using both theory and experiments because of unique properties such as low density, superhardness, high chemical inertness, and resistance to wear.13–16 The combination of these properties makes them excellent candidates for engineering applications such as cutting tools, body armors for soldiers, and additives in manufacturing process. However, their low fracture toughness prevents their extended engineering applications. In particular, B4C exhibits anomalous brittle failure when subjected to hypervelocity impact.17,18
Synthesis of boron suboxide (B6O) with alkaline earth metal oxide materials with improved properties
Published in Particulate Science and Technology, 2019
E. N. Ogunmuyiwa, O. T. Johnson, I. Sigalas
The boron-rich compound with a structure based on a rigid three-dimensional, α-rhombohedra boron network includes boron carbide (B4C) and boron suboxide (B6O1-x, nominally B6O). The B6O structure (space group R m) consists of B12 icosahedral units connected through oxygen by mostly covalent bonds (Kobayashi et al. 1993) and like B4C, it can be nonstoichiometric. B6O-based materials are known as the hardest materials after diamond and cubic boron nitride with a hardness of 45 GPa measured on monocrystals (He et al. 2002). In addition to this hardness, the fracture toughness of this material (B6O single crystal) was found to be 4.5 MPa.m0.5, which approaches that of single crystal diamond at 5 MPa.m0.5 and is significantly better than that of single crystal cubic boron nitride (cBN) at 2.8 MPa.m0.5 (Brookes 1986). The combination of high hardness, the possibility of cheaper production cost, and production without the need for high pressure, unlike diamond and cBN, make B6O-based materials a good candidate for cutting tools and other applications where abrasive wear resistance is important.