A comparative study of production methods for nuclear-grade boron carbide powder

Two industrial-scale methods for synthesizing nuclear-grade boron carbide (B4C) powder have been investigated and compared: direct synthesis from elements and carbothermal reduction. A series of experiments using different boron (isotopically enriched 10B and 11B) and carbon sources (carbon black and graphite powder) has been conducted. The synthesized powders have been analyzed for their chemical composition, purity, morphology, and particle size distribution. It was found that the carbothermal reduction, while producing chemically pure boron carbide, results in significant loss of boron due to the volatility of boron oxides, leading to a boron-deficient product with elongated, platelet-shaped particles. In contrast, direct synthesis from elements enables precise control over the B/C ratio and produces powders with polyhedral particles. However, the products of the direct synthesis method are often contaminated with impurities from the raw boron material, requiring subsequent mechanochemical treatment to achieve nuclear-grade purity. Both methods face challenges with morphological heterogeneity when scaled up, primarily due to temperature gradients within large powder volumes, which can also be addressed by mechanochemical treatment. As for loss of isotopic boron in the carbothermal process, it is 25–35%, while in direct synthesis it is 5–6%.