Synthesis And Characterion Of BN And AlN Nanocrystals

BN and AlN nano-materials have excellent physical and chemical properties, which make them pop materials studied in the world. The traditional methods of preparation with complex technics and high reaction temperature are difficult to be controled; Some methods even required more expensive equipment. To solve these problems, in this paper, BN and AlN nano-materials we tried to be synthesized at moderate temperature by solvothermal method.In a typical procedure, reactants were added into a stainless steel autoclave in N2 atmosphere. The autoclave sealed was reacted in a resistance furnace, then it was cooled to room temperature. At last an appropriate post-processing of the resultant products, BN and AlN nanocrystals were obtained. The structure and composition were characterized by X-ray diffraction (XRD),infrared absorption spectrum (FTIR) ,and selective area electron diffraction (SAED) and so on; The particle size and morphologies were observed by transmission electron microscope (TEM); The optical properties were tested by photoluminescence spectrum (PL).Hexagonal boron nitride nanocrystals were successfully synthesized at 400℃by an anhydrous acetonitrile-thermal method using three different experimental methods. The results showed that, different nitrogen and boron sources played a key role on the morphologies of hexagonal boron nitride nanocrystals. Needle-like crystalmorphologies were prepared by NaN3 and BBr3 as the reactants; Under the same experimental conditions, multiplex needle-like,flake-like,tube-like and grain-like crystalmorphologies were prepared by NaN3 and B powder as the reactants. Meanwhile, the crystallization effect was much better than the former; Most grain-like crystalmorphologies were prepared by KHB,NH4Cl and Li3N (little) as the reactants. Furthermore, as it was shown from the photoluminescence (PL) spectras, the as-prepared boron nitride with different crystalmorphology had different emission peaks. However, all the products had a strong visible emission peak appears at the 580 nm (λ=325 nm), which definitely indicated bathochromic shift.Hexagonal aluminium nitride nanocrystals were obtained at 400℃using three different experimental programs by a xylene-thermal method. The characterization results indicate that grain-like crystalmorphologies were mainly prepared using NaN3 as the nitrogen sources, and the crystallization effect of product was enhanced by adding the hexadecyl trimethyl ammonium bromide (CTAB) as the surfactant; Under the same experimental conditions, block-like and grain-like crystalmorphologies were mainly prepared using Li3N as the nitrogen sources. The PL spectra of the products have showed that the as-prepared AlN with three different experimental methods both emit a strong visible luminescence at 440 nm (λ=290 nm), which indicates some certain optical properties.