Investigation on the growth of boron carbide nanowires

Simple methods for preparing boron carbide nanowires have been investigated. The methods involve thermal evaporation of C/B/B2O3 powder precursors in an argon atmosphere with or without metal catalysts. High-purity nanowires (50-200 nm) were obtained by employing a precursor that has C:B:B2O3 molar ratios of 1:2:1. Less carbon content (C:B:B2O3 = 1:8:4) yielded products exhibiting different morphologies ranging from nanowires to platelet crystals. These nanowires were considered to grow via a vapor-solid (VS) mechanism. The addition of an Fe impurity into the precursor changed the growth from a VS mechanism to a vapor-liquid-solid (VLS) one, resulting in nanowires with smaller diameters (10-30 nm). We also found that boron carbide nanowires coated with boron nitride (BN) layers could be easily produced by adding B4N3O2H into the starting materials and then subjecting the material to evaporation under a nitrogen atmosphere. The structural features of these nanowires were characterized by means of transmission electron microscopy.