Study On B-C-N And B-C Compounds Synthesized By Solvothermal Method

In this thesis, B-C-N and B-C compounds were prepared by solvothermalsynthesis. In three different reaction systems, we have successfully preparedB-C-N compound and two kinds of B-C compounds. Some rules on theexperimental conditions and results were mainly investigated in the system ofCCl₄ and Ca₃B₂N₄ as raw materials. On the other hand, elementary explorationhas also been performed for the other two experiments of preparing B-Ccompounds from the two systems of BBr₃ + CCl₄ and C₃N₆H₆ + BBr₃,respectively.The phase forms, chemical compositions, structures, morphology andchemical bonds of the prepared samples are characterized by XRD, TEM, EELS,SEM, EDS and FTIR.The results indicated that B-C-N compound has been successfullysynthesized by the reaction of carbon tetrachloride(CCl₄) and calcium boronnitride(Ca₃B₂N₄) between 350 ℃ and 550 ℃. The XRD results showed thatthe B-C-N compound has a hexagonal structure. EELS analysis were carried outunder TEM, which revealed that the prepared samples were composed ofhexagonal B-C-N compound, h-BN, graphite, and amorphous carbon. Furtheranalysis on the B-C-N particles indicate that the composition is uneven, thecarbon content in the B-C-N particles is about 1¹1 at%, so the chemical form isdenoted as B(C_xN_1-x) (x=0.04⁰.22). Except for B-N bonds, B-C and C-N bondsare also detected by FTIR. The results given by EELS and FTIR have confirmedthat the chemical combination occur between the three elements of B, C and N.The possible crystal structure and band structure of the hexagonal B(C_xN_1-x)compound were studied by first principles calculations, the B(C_xN_1-x) crystalmay show metallicity.B-C compounds have been successfully prepared from BBr₃ and CCl₄using sodium as co-reductant at low-temperature condition. The analysis byEELS reveals that the prepared sample is mainly composed of rhombohedralboron carbide with the carbon content varying from 8 at% to 12 at%. Thiscontent is consistent with that of B4C.A polycrystalline B-C compound has been prepared from BBr3 and C3N6H6,with existing of ammonium sulphate at low temperature. The results indicatethat the sample has hexagonal structure and the carbon content is about 15²9at%.