Formation of Two-Dimensional Nanomaterials of Boron Carbides

A simple chemical vapor deposition in a graphite crucible was employed in the development of two-dimensional nanomaterials of boron carbide. The sole starting material was B 2 O 3 powder, and the deposition was undertaken on a chemically and thermally stable insulating template, graphitic boron nitride. The majority of the boron carbide products (B 4 C structure, R 3̄ m ) exhibit a beltlike morphology with lateral dimensions of 5−10 μm (in width) and 50−100 μm (in length), while the thickness is in the nanoscale range (20−100 nm). Transmission electron microscopy revealed a strong dependence of growth morphology on the number ( n ) of different {1,−1,−1} surfaces appearing during the crystal growth. The dimensionality of the boron carbide crystallites can be described by (3 − n ); for example, the appearance of a sole ( n = 1) {1,−1,−1} surface leads to a two-dimensional material while zero-dimensional particles, i.e., icosahedral quasicrystals, appear when n = 3. Growth morphology can possibly be controlled via controlling the temperature and the vapor pressure of the starting source.