Substitution of silicon within the rhombohedral boron carbide (B4C) crystal lattice through high-energy ball-milling

摘要: Boron carbide (B4C) is a ceramic with structure composed of B12 or B11C icosahedra bonded to each other and three (C and/or B)-atom chains. Despite its excellent hardness, B4C fails catastrophically under shock loading, but substituting elements into lattice sites may change possibly improve mechanical properties. Density functional theory calculations elemental inclusions in the most abundant polytypes boron carbide, B12-CCC, B12-CBC, B11Cp-CBC, predict that preferential substitution site for metallic (Be, Mg Al) chain center atom non-metallic (N, P S) it generally end three-atom B4C's rhombohedral crystal lattice. However, Si, semi-metal, seems prefer B12-CCC icosahedral polar both B12-CBC B11Cp-CBC. As first step testing feasibility substitutions experimentally, Si atoms were incorporated at low temperatures (∼200–400 °C) by high-energy ball-milling. High-resolution transmission electron microscopy showed uniformly dispersed product, magnitude expansion Rietveld analysis X-ray diffraction data analyzed determine likely B4C. Further corroborative evidence was obtained from spin resonance spectroscopy, magic-angle spinning nuclear magnetic photoelectron spectroscopy Raman characterizations samples. Thus, simple, top-down approach manipulating chemistry presented potential generating materials tailored properties broad range applications.