Study On Efficient Purification Process And Influencing Factors Of Carbon Fiber Felt

Silicon are the core of the semiconductor industry and the photovoltaic industry.High-purity carbon fiber felt is an important material in the thermal field of monocrystalline silicon furnaces.When carbon fiber felt is used as an insulation material,the metal impurities(MIs)in it will gradually escape in a high-temperature environment.Into the silicon crystal,it affects the electrical parameters of the silicon single crystal,making the quality of the silicon wafer poor,and it cannot meet the requirements of the photovoltaic industry and the semiconductor industry.In order to obtain high-quality silicon wafers,which are mainly clean thermal field materials,it is particularly important to remove the MIs in the high-purification treatment of carbon fiber felt.Because PAN carbon felt is the main variety produced in China and the price is low,this article takes PAN carbon felt as the object,mainly discusses the high-purification treatment process and influencing factors of carbon fiber felt,using SEM,XRD,Raman,element analyzer,ICP-AES for testing.Using the purification process of ultrasonic pickling and microwave heat treatment,the effect of the type of acid and the treatment time on the purification effect,as well as the influence on the morphology and oxidation resistance of the felt material,was explored.The order of the purification effect of sulfuric acid on 13 metal impurities of Al,K,Ca,Na,Fe,Ti,Cu,Mg,Li,Cr,V,Co,Ni is:HCl>HNO3>H2SO4;Destroy the fiber surface structure to a certain extent.When three acids are used as purifying agents,the damage to the fiber surface is:HCl<H2SO4<HNO3.Using methyl chloride as the function by the purification process of microwave heat treatment,explore the effect of the type of purifier and microwave heat treatment time on the purification effect,as well as the influence on the morphology,structure and anti-oxidation performance of the felt material;discussed the chlorination The purification mechanism of methane,through kinetics and thermodynamics research,analyzed the pyrolysis reaction of CHCl3 and CH2Cl2,the reaction with MIs,the possibility of reaction and the temperature conditions,and theoretical analysis and experiments proved that the purification effect of CHCl3 is better than CH2Cl2?Using CHCl3 and CH2Cl2 as function,after microwave heat treatment,the surface of the fiber changes from smooth to pore structure,which is caused by the escape of metal chloride and the etching of oxygen and water vapor generated by the reaction.The pore structure can be the subsequent reaction gas The diffusion provides access,but too much pore structure will reduce the oxidation resistance of the material;Using CHCl3 as function,by changing the microwave heat treatment time,it was found that the purification effect was the best when the heat treatment time was 15 minutes and the fiber structure was less damaged.A better purification effect can be achieved at 700?,and the Mis content is reduced to The purification rate is 77.1ppm and the purification rate is 67.4%,which improves the high temperature and long time-consuming disadvantages of the traditional high-temperature chemical treatment method.For the relatively removed Al,a two-step method is adopted for treatment.Firstly,microwave heat treatment is performed with methyl chloride as a purifying agent,and then a second high temperature heat treatment at 2800? is performed to compare the changes of various indicators before and after high temperature heat treatment;The growth of graphite-like crystallites can promote the growth of crystal grains,which reduces the interplanar spacing,increases the stacking thickness,increases the degree of ordering,increases the degree of graphitization,and improves the oxidation resistance of the high-purity carbon felt;the presence of MIs elements Catalyzes the oxidation of carbon felt.After removing MIs,the active sites for oxidation reaction can be reduced,and the oxidation resistance of the obtained high-purity carbon felt is improved;the second high temperature treatment can increase the grain size and further promote order The improvement of the degree of chemical conversion improves the oxidation resistance of the high-purity carbon felt;the second high-temperature treatment will further enhance the purification effect.Holding at 2800? for 10 minutes can reduce the MIs content to 24.9ppm,and the purification rate reaches 89.47%.