| Carbon fiber reinforced carbon is a carbon matrix,which is composed of carbon fiber and its fabric,also known as carbon/carbon composite.This material has many advantages when be compared with other materials:low proportion,low coefficient of thermal expansion,high thermal conductivity,mild and high modulus.Compared with many other materials,when the temperature is increased,the softening reduced mechanical properties.C/C composite materials,a prominent feature is that with the increase in temperature,the mechanical properties of the rise,especially in recent years,C/C composite materials have been widely used in aerospace,nuclear industry,biological medicine,Daily transportation,such as production and life,and many other fields.However,because its constituent element also is carbon,therefore the C/C composite material also has the carbon element common shortcoming in the high temperature environment.In the air atmosphere more than 573 k,C/C composite can be oxidized,and the quality of 2-5%percent will loss,the corresponding mechanical properties will lose more than 40.The loss of mechanical properties will seriously affect the application of C/C composites in high temperature field.In this paper,an antioxidant coating is used to prolong the antioxidant time of C/C composites.In this study,Si C coating was prepared by a electromagnetic induction heating method.The possibility of producing single SiC coating by four technological factors such as induced current,concentration of circulating suspensions,addition of silica sol and circulating liquid volume in unit time was discussed,and the Si C-Y2Si2O7 composite coating and Si C-MoSi2/Borosilicate were prepared on the basis of the method.Glass composite coating,it is proved that the electromagnetic induction heating method can be used as a coating preparation method to prepare the carbon/C composite coating,and through X-ray diffraction?X-ray diffraction,XRD?,scanning electron microscope and other methods to test the composition of the coating,Structure and its antioxidant properties were analyzed,and the results were as follows:?1?Preparation of a single SiC optimal oxidation resistance coating process parameters are:electromagnetic induction current size of 480 A,Si C slurry particle concentration of 3.5 g/L,silica sol volume per unit volume of the suspension is 15 mL/L,the suspension liquid is deionized water and the circulating suspension volume flow rate per unit time is maintained at 200mL/min.The carbon/carbon composite Si C coating prepared under the optimum process is resistant to oxidation for 142 h in a static aerobic atmosphere of 1773K.The mass loss is about 2.78%,and its oxidation weight loss rate is 0.26×10-3g cm-2·h-1.SiC samples in the high temperature static oxidation experiments,mainly by the three stages,the first stage is the initial period of oxidation,the organic matter of the coating volatilizes and decomposes,SiC and oxygen react to generate gas phase escape.The second stage is the oxidation stabilization period.The coating surface is covered with molten SiO2,and the defects are also compensated by Si O2.The third stage is the period of oxidation failure.The continuous volatilization of SiO2 leads to the loss of its defect-repairing ability,and oxygen enters the depth of the coating until Reaction with the carbon/carbon matrix ultimately results in failure of the carbon/carbon composite to be oxidized by oxygen.?2?SiC-yttrium silicate composite coating was prepared by electromagnetic induction heating.The influence of the different proportions of different SiC and barium silicate materials on the coating surface,fracture morphology,and oxidation resistance was investigated.Finally,the electromagnetic induction heating method was established when the ratio of SiC to yttrium silicate was 1:4.The composite coating obtained has the best performance.Compared to a single SiC coating,the 37%of mass loss is the most important criterion for assessing its oxidation resistance in a 1773 K static aerobic atmosphere.Finally,the oxidation resistance of the composite coating reached.228 h.?3?A Mo Si2/Borosilicate galss composite coating was prepared on the outer surface of a carbon/carbon composite SiC coating by using electromagnetic induction heating combined with hot impregnation.The effects of different silica sol additions on the surface,fracture morphology and oxidation resistance of the coating were investigated.The best process parameters were:the coating prepared by hot dipping with a volume ratio of distilled water to silica sol of 3:1.The layer performance is the best,compared to a single Si C coating,in the 1773 K static aerobic atmosphere,the mass loss of3%is the most assessment of its antioxidant capacity standards,the final composite coating antioxidant time reached 276 h,the unit The mass loss of the area was 0.50×10-2 g·cm-2,and the oxidation rate at the same time was 0.18×104g·cm-2·h-1.The experiment temperature of static oxidation resistance for SiC-Mo Si2/Borosilicate Glass composite coating specimen is 1773 K.At last,SiO2 generated volatilization continuously resulted in the loss of its ability to compensate until the failure of carbon/carbon composites. |
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