Study On The Preparation And Properties Of Uniform Boron Carbide Powder With Smaller Size

Boron carbide is an important inorganic ceramic material.High-temperature carbothermal reduction is a main synthesis way to synthesize boron carbide.However,the as-prepared boron carbide particle is always in larger size,and the carbothermal reduction temperature is higher.Developing new synthesis process for boron carbide with smaller size at relative lower temperature has great industrial application value.In this thesis,we developed an improved carbothermal process using cellulose as organic carbon resources to synthesize uniform B4C particles in fine-grained size.The improvement of the proposed carbothermal processes lies in two points:(i)we use immiscible hexane/water solvents to obtain high-dispersed boric acid(BA),which promotes the esterification of BA with organic carbon;(ii)the boron oxide/carbon resources are ground sufficiently before high-temperature carbonization.The purpose of these two procedures is to increase the homogeneity of precursors,and their effects on the final crystalline structure and morphology of B4C are studied systematically.The results show that uniform fine-grained B4C in about 4μm is successfully fabricated,indicating the homogeneity of precursors can effectively meliorate the B4C powder in a smaller size.Considering the p-type semiconductor nature and the excellent electronic properties of B4C,the photoelectrochemical and photoelectrocatalytic performances of as-prepared fine-grained B4C was studied in detail for the first time to the best of our knowledge.The EIS spectra of the B4C powder was measured,and the smaller arc radius on the EIS Nynquist plot of the fine-grained B4C indicated the higher separation efficiency of photogenerated electron-hole pairs.The B4C powder also present good absorption responses in both UV and visible light range,indicating the good UV-VIS light response ability.The Photoelectrocatalytic(PEC)water reduction for hydrogen production were conducted under 300 W Xe lamp irradiation using the electrolyte of 0.5 mol L-1 of Na2SO4.The hydrogen generation capacity within 5 h reached 70 μmol cm-2,which data is higher than some of reported carbon-based materials.The good photoelectrocatalytic stability implied the extended application prospect of these fine-gained B4C powder in photoelectrochemical researches.