Mechanical properties of submicronic and nanometric boron carbides obtained by Spark Plasma Sintering: Influence of B/C ratio and oxygen content

Abstract

Boron carbide samples exhibiting nanometric and submicronic microstructure were sintered by Spark Plasma Sintering to investigate the effect of grain size on mechanical properties. The mechanical properties of sintered monoliths were characterized at the grain and macroscopic scales. Although nanostructured material exhibits finer grains than the submicronic material (i.e. mean diameter of 82 vs. 474 nm), its apparent rigidity and hardness are found to be reduced by 6.8 % and 8.4 % respectively. This contradiction with the Hall-Petch law is linked to the chemical compositions of both materials, which show significant difference in terms of B/C ratio and higher structural oxygen content especially for nanostructured material.

Effect of powder purification by heat-treatment on the creep behaviour of dense boron carbide monoliths

“…B/C < 4), they have highlighted that hardness and toughness also decreases due to the presence of free carbon as secondary phase located at grain boundaries. In addition, in previous works [12,13], we have shown that the presence of structural oxygen in boron carbide lattice, leading to a boron oxycarbide phase, induces a decrease in both hardness and elastic properties for oxygen content higher than 2 wt.%. Some studies have highlighted the benefit effect of impurities removing from starting powder on elasticity and hardness of boron carbide monoliths sintered by Spark Plasma Sintering (SPS), displayed in Table 1.…”

“…According to literature, the mechanical properties of full dense monoliths depend on variation of chemical composition, i.e. carbide stoichiometry and presence of secondary phases such as free carbon [11][12][13]. Niihara et al [11] emphasized that, for a B/C ratio higher than 4, increasing B content in boron carbide plates obtained by chemical vapor deposition resulted in reduction of hardness and toughness, which was attributed to reduction of bond strength in the boron carbide structure.…”

Structural modifications of boron carbide irradiated by swift heavy ions

“…The powder sintering was carried out from a commercial (H.C. Starck) submicrometric powder HD 20 of boron carbide with a purity of 99.5%, an average diameter of 400 nm and a specific area of 24 m 2 •g − 1 [22][23] . Powder has been densified without sintering additives using SPS facility (Fuji-Syntex, Dr Sinter 825, Japan) under dynamic vacuum.…”

Boron-Rich Boron Carbide Nanoparticles as a Carrier in Boron Neutron Capture Therapy: Their Influence on Tumor and Immune Phagocytic Cells

“…Boron carbide is a covalent material characterized by a high melting point, relatively low density, and high chemical resistance; when in the form of dense polycrystals, it is characterized by a high Young modulus, extreme hardness, and good mechanical properties [1][2][3]. Such properties are suitable for boron carbide applications in components resistant to abrasion in ball mills, nozzles, parts of machinery, and equipment and as parts of antiballistic armor.…”