The Study Of Microstructure And Adsorptivity Of Hexagonal Boron Nitride

Abstract of Thesis:h-BN materials has significant potential applications in the fields of hydrogen storage materials, catalyst carriers and environmental protection, etc, owing to its excellent mechanical properties, stability chemical and resistance to oxidation and high thermal conductivity, etc. But until now, h-BN materials has not been widely used in these fields. The main reason for this is that there is no method of synthesizing h-BN with different microstructures and high adsorptivity. Therefore, it is very important to study the microstructure and adsorptivity of h-BN materials.In this paper, the effect of the composition ratio of boron sources on the microstructure and adsorptivity of h-BN powders was studied in both sides of not adding soft templates and adding soft templates respectively. And, the choice of the composition ratio of boron sources is 1:0, 1:0.5, 1:1, 1:2, 1:3. h-BN material were characterized by XRD, SEM, TEM and the automatic porosity locator. The experimental results indicated that h-BN powders with different microstructures were synthesized by different composition ratios. Then the different microstructures included the flakiness, the solid sphere, the hollow sphere, the mesoporous microballoon and so on. And, according to the adsorptivity of the h-BN, it was relatively best that the composition ratio of boron sources was 1:1 under the experimental conditions.The effect of soft templates on the microstructure and adsorptivity of h-BN powders was studied. Two kinds of surface active agents were used as soft templates which were CTAC and DTAC. h-BN powders were characterized by XRD, SEM, TEM and the automatic porosity locator. The experimental results indicated that h-BN powders with different microstructures were synthesized by different amount of substances CTAC and DTAC. And the different microstructures included the flakiness, the sphere, the hollow sphere, the pie, the mesoporous microballoon and so on. And, according to the adsorptivity of the h-BN, when 1.5g DTAC was used as the soft templates that the adsorptivity of h-BN material was relatively best under the experimental conditions.The effect of nitriding temperatures on the microstructure and adsorptivity of h-BN powders was studied. h-BN materials were characterized by XRD, SEM, TEM and the automatic porosity locator. The experimental results indicated that h-BN powders with different microstructures were synthesized by different nitriding temperatures. Then, according to the adsorptivity of the h-BN, when the nitriding temperatures was 675°C that the adsorptivity of h-BN material was relatively best under the experimental conditions. At this experiment conditions, the adsorption capacity of the high purity h-BN powders was 276.02 cm3 / g (STP) by the best proportion and the best synthesizing technology. The innovation of this paper was that the soft template technology was applied to the synthesis of h-BN. So, the mesoporous and hollow h-BN materials with the high surface and high adsorptivity was obtained, and the theoretical foundation was established for the development and utilization of h-BN materials.