Synthesis Of H-BN And Preparation And Structural Characterization Of G-C₃N₄/SnO Composites

As a nitride material with a layered stack of graphite sheets,hexagonal boron nitride（h-BN）and graphite phase carbon nitride（g-C₃N₄）have good chemical inertness and thermal stability,adjustable band gap structure,good thermal conductivity,biocompatibility,and more unexpected physicochemical properties.h-BN and g-C₃N₄ have potential applications in semiconductors,bioimaging,adsorption,photoelectrocatalysis,optoelectronic devices,etc.In this paper,the following studies were carried out around two nitrides,h-BN and g-C₃N₄（1）h-BN nanopower were obtain in a N₂ atmosphere via mechanical mixing using boric acid and melamine as raw materials.The effects of n（H₃BO₃）/n（C₃H₆N₆）ratio and calcination temperature on the yield,purity,crystallinity and particle size of h-BN samples were studied.The results show that when n（H₃BO₃）/n（C₃H₆N₆）is4.0:1,it is first kept at 1000℃for 2 h and raised to 1400℃for 2 h to obtain a diameter of not more than 250 nm,a thickness of about 50 nm,a yield of about 25%and a purity of more than 97%.Compared with the traditional high-temperature method,this method has no solid by-products,and the post-treatment is simple and environmentally friendly,which is in line with the green development concept.（2）Using boric acid and melamine as main raw materials,the precursors were prepared by microwave reaction,and different morphology h-BN samples were prepared by reacting at 1000°C for 3 h in N₂ atmosphere.The results show that:○1Compared with the dry drying method,the sample size obtained by freeze drying is significantly smaller;○2Compared with the sample without surfactant,the sample with surfactant added in the preparation of precursor was more distinct in contour and smaller in size.○3The NaCl-KCl molten salt method not only promotes crystal growth,but also makes the morphology of the sample diverse.In addition,the h-BN obtained by the method has good adsorption capacity for methylene blue,and the adsorption rate of 10 min is as high as 91%or more.（3）g-C₃N₄/SnO composites were prepared by solid-phase grinding assisted ultrasonic method using stannous chloride,bicarbonate and g-C₃N₄ as raw materials.The results show that the synthesis of SnO can be promoted by doping g-C₃N₄ in the raw materials.After doping the proper amount of g-C₃N₄ in the raw material,although the morphology of the SnO nanosheet is not changed,the photocatalytic performance of SnO is greatly improved.The g-C₃N₄/SnO sample with g-C₃N₄ content of 7.66wt%has the best visible light catalytic performance,which can degrade 96.5%methylene blue in 4 h and 98%methyl orange in 80 min.