Template-free Synthesis Of High-yield White Graphene Foam And Its Application

Porous boron nitride not only have the property of high temperature resistance, high thermal conductivity, low coefficient of friction, but also have unique characteristics of high specific surface. These characters make the porous boron nitride has great potential application value in the field of catalyst support, hydrogen storage material and filler of materials. The preparation of material is the precondition of research its performance and promoting its application. The methods to prepare the porous boron nitride mainly contains hydrothermal synthesis method, template method, organic precursor decomposition method and aerogel technology, but the synthesis process of these methods are generally complex and low production, this greatly limits the application and development of porous boron nitride materials. Therefore, seeking a simple and suitable preparation method to prepare porous hexagonal boron nitride with high yield, high quality, high specific surface area and unique pore size distribution is of great significance. In this paper, we use a simple, template-free, one-step method to synthesis the porous hexagonal boron nitride with different microstructure. Study its properties, and put them into application in the field of catalyst support, hydrogen storage material and filler of materials.The precursors of ammonia borane, the vesicant of thiourea, thiosemicarbazide can prepare white foam porous boron nitride by a simple thermal decomposition reaction with the yield up to 68%, the density low to 2.05 mg cm-3, which is far lower than theoretical density of commercial boron nitride(2.27 g cm-3), this ultra-light porous boron nitride materials can freely stand on a dandelion flower without bending. Thiourea as vesicant, the sample is mainly composed of irregular frame and large area of lamellar structure with three-dimensional porous structure, the product is marked as ABSN. The HRTEM shows ABSN product with porous structure on the lamellar structure, thickness can be single, double, three layers of atom thick. Nitrogen adsorption results show that the specific surface area of 681 m2 g-1, average pore size of 1.5 and 32 nm. Thiosemicarbazide as vesicant, the sample with three branch, four branch connected porous fibrous network, the product is marked as ABSD. SEM show fibre length can reach hundreds of micrometer. Nitrogen adsorption results show that the specific surface area of 128 m2 g-1, average pore size of 15 nm.Polyethylene glycol as the reaction solution, silver nitrate as raw materials, ABSN as catalyst carrier, synthesise the Ag/ABSN catalyst by the method of ultraviolet radiation. Ag/ABSN catalyst show good catalytic performance for methanol oxidation, T50?T95 is only 50 oC, 110 oC, respectively, which is far lower than the Ag/?-Al2O3 catalyst corresponding to the value of 110 oC and 180 oC. Ag/ABSN catalyst shows good stability at high temperature.ABSN products as adsorbent, the adsorption capacity of organic solvents and oil can be achieved to 70-191 g g-1, complete the absorption in instantaneous and can be recycled many times. The adsorption of methylene blue, methyl orange dye can be completed more than 80% within 5 min, the maximum adsorption capacity nearly 500 mg g-1.ABSD products as polymer filler, SD 184 as base material, the ABSD/SD 184 composite materials with different contents of ABSD can be synthesize by thermosetting molding process. With the increase of boron nitride fiber content,the heat resistance of the ABSD/SD 184 composite increased gradually; 1 wt% ABSD/SD 184 composites with 83% transmittance at 600 nm; 5 wt% ABSD/SD 184 composites with mechanical strength of 96 MPa, modulus elasticity of 3.46 GPa; the thermal conductivity of 50 wt % ABSD/SD 184 composites can reach to 114.7 W m-1 K-1.