Sintering of boron carbide and boron carbide-silicon carbide two-phase materials and their properties

• Published in: Journal of nuclear materials Vol. 152; no. 2; pp. 154 - 162
• Main Author: Thevenot, F
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.1988
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/0022-3115(88)90321-2

Boron carbide is a high-technological ceramic material (it is used for lightweight armor, neutron absorbers, wear pieces, etc.). Hot pressing (2200°C, 40 MPa, Ar atmosphere) and recently high isostatic pressing, are the best known ways for industrial preparation of boron carbide items. Pressureless sintering using metallic, inorganic, B + C, additives is not successful, since, despite having a high density, impurities remain present. Pressureless sintering of boron carbide (or silicon carbide composite) using free carbon addition, produced by in-situ pyrolysis of a Novolaque-type phenol-formaldehyde resin (≈ 9 wt%), is now possible in industry. A promising new method is the use of organic precursors, e.g. polycarbosilane with a small amount of phenolic resin, giving CSi and C by in-situ pyrolysis; the resulting boron carbide ceramics have high density (> 92%) and contain no free carbon and a small amount of SiC (≈ 5 wt%). The mechanical properties of sintered B 4C are close to those of hot-pressed; the SiC dispersion in a B 4C matrix has no toughening effect.