Research On Iron Removal And Pressureless Sintering Of Boron Carbide Waste

Recently,yield of boron carbide abrasive uesd in sapphire wafer polishing rises sharply due to the rapid development of sapphire industry.Dust generated in boron carbide abrasive production process is difficult to apply because of its ultra-fine particle and low purity.If it can be recycled,it will be good for resources saving and environment protecting.In this paper,boron carbide waste from Yunnan Yuxi Hengyu Technology Co.Ltd.was used as the test materials.In accordance with ideas of chemical leaching of hydrometallurgy firstly,the most suitable conditions of removing iron from boron carbide waste were determined through single factor experiment,and the reaction kinetics analyzed.Then prepare boron carbide product by pressureless sintering according to the principle of pyrometallurgy,the mechanical properties and sintering characteristics of the product were studied to determine the effect of various factors,and improve the sintering process,provide basic data for the industrial recycling of boron carbide waste.Effect of general conditions such as sulfuric acid concentration,leach temperature,liquid-solid ratio on removal rate of iron were studied through single factor experiment.The removal rate and remaining iron content is 89.5%and 0.36%respectively under the optimal conditions of sulfuric acid concentration 30%,leaching temperature 50? liquid-solid ratio 6:1,kinetics of this reaction were analyzed,relationship between reaction rate constant k1 and T in accordance with k1=0.0406 exp(-501.19/T),and the apparent activation energy is 60.28kJ/mol;The removal rate and remaining iron content are 95.2%and 0.165%respectively under the optimal ultrasound-assisted conditions of leaching temperature 50?,ultrasonic power 210W,ultrasonic frequency 45kHz,kinetics of this reaction were analyzed,relationship between reaction rate constant k2 and T in accordance with k2 = 0.2200 exp(-100.44/T),and the apparent activation energy is 120.33kJ/mol.Boron carbide waste purifide were pressureless sintered to be Refractory products with A1 as additive.Effects of sintering temperature on products' performance were studied,pellet in which Al content is 9wt.%sintered at 1400? for 120min,products' compressive strength is 115.4MPa,elastic modulus 1185MPa,flexural strength 41.2MPa,apperant porosity 9.4%,and AlB10 and AIB12 were discovered in its XRD patterns.Effects of sintering time on products' performance were studied,pellet in which A1 content is 9wt.%sintered at 1400? for 90min,products' compressive strength is 108.3MPa,elastic modulus 1055MPa,flexural strength 40MPa,apperant porosity 8.9%;Effects of content of Al on products' performance were studied,pellet in which Al content is 6wt.%sintered at 1400?for 90min,products' compressive strength is 103.7MPa,elastic modulus 1030MPa,flexural strength 44MPa,apperant porosity 12.7%;Conclusion of sintering temperature which has significant effect on the apparent porosity of the product was reached by orthogonal experiment.With boron carbide waste before purification and purified as sintering material respectively,performances of the two kinds of products were compared.The performance of product with waste without purification as sintering material is worse than product with waste purified as materials was found,and the oxygen impurities adversely affect the sintering process.