Hegzagonal bor nitrürün erime noktası düşürücü maddeler varlığında sentezi

Hexagonal boron nitride, one of the polymorph of boron nitride is important synthetic products in materials science. It is commercially valuable compound for industrial applications due to its special chemical and physical properties. Therefore, hBN has been the subject of recent interests for twenty years. Some additives are known to catalytically affect the hBN formation. However, they have various functions at high temperature processes; such as a reducing agent, absorption of impurities, and retention of mixture at liquid phase at the melting temperature for a longer time thus increasing interaction at the interface of solids. Also, they are used to control grain size of crystalline solids as in optimum time-temperature conditions during sintering. In this study, hBN was synthesized with the modified O?Connor method in presence of representative metal carbonates, acetates, and hydroxides in different amounts at different temperatures under ammonia atmosphere. Structural properties of the synthesized materials were determined by Fourier Transform Infrared Spectroscopy, (FT-IR), X-Ray Diffraction, (XRD), Scanning Electron Microscopy, (SEM), and Transmission Electron Microscopy, (TEM). FT-IR investigations confirmed the formation hBN and XRD patterns of the samples were indexed as hBN and calculated lattice parameters were very close to reported values of hBN. Addition of representative metal salts (especially lithium and calcium salts) into the reaction mixture decreased the formation temperature of hBN and overcome the internal stress. Also, usages of salts improved the formation of the nano structures at any temperature applied in experiments. The accompanying anions in the fluxing agents did not virtually have significant effect on the crystallization behavior of hBN. Finally, the effect of fluxing agents on the synthesis of hBN was determined that addition of more than 20 % of metal salts into the boron oxide and urea mixture was found optimum for increasing the rate and yield of hBN formation.