Prepare SiBNC Coating On Carbon Fibers And Sibnc Composite Via Polymer Derived

Composite materials made of a ceramic-based matrix reinforced by carbon fibers appear to be attractive candidate for aerospace applications and automobile industry.Owning to the low density,such materials could effectively combine high specific strength and stiffness with high temperature resistance,high damping capacity and a near-zero coefficient of thermal expansion.But there is a series of interface problems between the reinforcement of carbon fibers and matrix materials.It is the most effective method to enhance the interfacial wettability,prevent interface diffusion and enhance the oxidation resistance ability of the reinforcement by preparing coatings on carbon fiber surface.SiBNC has a good property of high temperature oxidation resistance,formatting an oxidation layer on the surface in high temperature.There are many means of coating on carbon fiber surface,such as CVD,Sol-Gel and polymer derived.Polymer derived method is fit for industrial production to prepare coatings on carbon fiber surface because of the simple technology,the low cost and easily operating.This paper discussed the developing of the technology about carbon fiber.The application of CF in the field of military and spaceflight are also discussed in detail.Process for preparation of SiBNC coating on carbon fiber surface is established.Crosslink and pyrolysis of the polymer,relation between concentration of polymer solution and the coatings were studied in this paper.The crystal structure,phase composition,surface morphology and anti-oxidation property of coating were characterized and analysis by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive X-ray(EDS),and thermal gravimetric(TG).The mechanical properties of coating fiber were test by XQ-1C fiber tensile apparatus.We have explored the preparation of the carbon fiber reinforced SiBNC composite.The main results are as follow:1.Gel content quickly rose to more than 90%when temperature at 200 ℃.With the increase of crosslinking temperature,gel content are rising.gel content and ceramic yield increase slowly above 240 ℃.2.Activation energy of the first stage is 161.39 kJ/mol at Pyrolysis process.The pyrolysis mechanism function of this stage is Avrami-Erofeev,and Si-C、C-N and C-C bonds mainly ruptured in this stage.Activation energy of the second stage is 379.42 kJ/mol.The pyrolysis mechanism function of this stage is Avrami-Erofeev.The pyrolysis reaction of the second stage is controlled by one-dimensional diffusion.3.The coating is uniform from concentration of 0.01%～30%prepared via polymer derived.We can see the coating has certain thickness is about 30～150 nm.4.There is a litter influence on strength of coating carbon fiber when prepare coating from different concentrations.From low concentration,it has keep the basic mechanical properties of original carbon fiber.Coating cycle has certain influence on the strength of the coated carbon fiber.5.The oxidation energy of coated carbon fiber were 167.52 kJ/mo,178.42 kJ/mol,and 163.19 kJ/mol,corresponding to 5%,0.5%,0.05%,.But the oxidation energy of uncoated carbon fiber is just 87.29 kJ/mol.6.Explore SiBNC composites reinforced by carbon fiber,we discovery that composite full density through precursor crosslinking at 240℃ for 3h,pressing under 150 MPa at 220 ℃.