Properties and characterization of codeposited boron nitride and carbon materials

The physical properties of carbon-boron nitride (C-BN) prepared from mixtures of BCl3, NH3, and selected hydrocarbons by codeposition methods have been investigated using x-ray diffraction, electron diffraction, transmission electron spectroscopy, x-ray photoelectron spectroscopy, Raman scattering, optical reflectivity, thermal conductivity, thermopower, and electrical resistivity. Taken collectively, the results of these experiments indicate that the compression-annealed C-BN materials studied here consist of separated domains of pyrolytic boronated graphite and pyrolytic boron nitride, while as-deposited samples may possibly be a single-phase mixture of C, B, and N. As-deposited materials containing more than 20% carbon were found to be more highly oriented than unannealed pyrolytic graphite, and the crystallinity of these materials was greatly enhanced by uniaxial compression annealing. Results of the thermal conductivity, thermopower, and electrical resistivity measurements are consistent with a network of turbostratic graphite BN domains with some conduction paths for charge carrier transport between the domains. Increasing the carbon concentration from 20% to 60% leads to an increased linkage between the conducting domains and a percolation conducting network is established.