Synthesis And Characterization Of B-C Compounds

B-C system is a huge system, including a variety of compounds. Boron-rich B-C compounds possess high-hardness, good anti-oxidation property, high chemical stability, excellent thermoelectric properties and high neutron absorption, thus it has been applied to many fileds. There have been some achievements in theory of carbon-rich B-C compounds, which possess semi-conductive or conductive, anti-oxidized property, hydrogen storage capability, but such research has only been carried out by a few people. In this paper, based on the experimental and theoretical overview of B-C compounds, B-C compounds were successfully synthesized using organic precursor, which was prepared from sucrose and boric acid through chemical combination, in vacuum sinter furnace with different catalyst. The phase forms, morphology, chemical compositions and bond structures of pyrolyzed products were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and fourier transform infrared spectroscopy (FTIR). The influence of process parameters on product was discussed. Thermo-properties and electron-properties of B-C compounds are studied. With magnesium oxide catalyst, turbo-graphite like BC5 compouds was synthesized at pyrolysis temperature in the range of 500℃~1200℃for 30min~120min. The obtained compounds were irregular lumps which were about 30μm~170μm. FTIR measurement indicates that B-C, C=C bonds exist in BC5 compouds. Both the increased of pyrolyzed temperature and prolonged pyrolyzed time are benefitial to improve crystalline. In nitrogen, it performed well in thermal stability, which becomes better with the increase of crystalline, and it possed good anti-oxidized property.With ferrum catalyst, turbo-graphite like BC5 compouds is synthesized at pyrolysis temperatures in the range of 500℃~1000℃after pyrolysis for 15min~60min. The obtained compounds are irregular lumps which are about 30μm~170μm. FTIR measurement indicates that B-C, C=C bonds exist in BC5 compouds. To obtain crystal product, both increased pyrolyzed temperature and prolonged pyrolyzed time are needed. It performed good thermal stability in nitrogen.With ferrum-nickel alloy catalyst, turbo-graphite like BC5 compound was synthesized at pyrolysis temperatures 800℃and 1000℃. Hexagonal crystal BC5 compound was synthesized at 1200℃after pyrolyzed for 30min, and its lattice parameters were a=0.2427nm, c=0.6803nm; and the product was synthesized at 1200℃after pyrolyzed for 60min, whose crystalline is higher,its lattice parameters were a=0.2432nm, c=0.6794nm, and its size is about 1μm~3μm, like layers on the surface. FTIR measurement indicates that B-C, C=C bonds exist in BC5 crystal. Ferrum-nickel alloy was suitable to synthesis B-C compounds. In nitrogen, turbo-graphite like BC5 performed well thermal stability and crystal BC5 possessed well anti-oxidization. Resistivity test of BC5 with four probe method show that turbo-graphite like BC5 possessed semi-conduction; however, hexagonal crystal BC5 compound possessed metallic conductive property. Experimental result is consistent with theoretical calculations.