Fabrication Of Coated Carbon Fiber And Preparation Of Composites

Carbon fiber reinforced ceramic composites is widely used as structural materials,because of their excellent comprehensive performance,such as the high strength,high hardness,wear resistance corrosion resistance and certain toughness.The big difference between ceramics and carbon fiber in structure and coefficient of thermal expansion,lead to poor combination and interface.So preparation of certain interlayer will improve the problem,which can decrease the difference.Preparation technology of alumina ceramic coating is simple and varied,what's more,which will improve the wettability between carbon fiber and matrix composite materials and increase the resistance of oxidation at high temperature.Therefore,the research about preparation of alumina ceramic coating on carbon fiber shows important academic value and application value.In this article,we studied how the media and surfactant impact the stability of suspension in water and ethanol system,which prepared by ball milling and ultrasonic dispersing using nanometer particles of alumina,lead to optimal combination of suspension components used for electrophoretic deposition:the:100 mL anhydrous ethanol,5wt%of nano Al₂O₃ powder,10wt%Y₂O₃?relative to Al₂O₃?,0.3wt%polyethylene imine?PEI?and 0.5wt%polyethylene butyral?PVB?.With the help of double anode system,we prepared alumina coating layer with thickness of about 2.5?m on woven carbon fiber at the DC voltage of 20 V,and electrophoretic deposition for 20 min,which was dense,uniform and completely coated.SPS technology will be used to sinter the carbon fiber coated with alumina,and preliminary got two-dimensional woven carbon fiber reinforced alumina composites.Among them,the binder PVB can effectively improve the coating thickness and uniformity;Extension of the deposition time and increasing the solid content of Al₂O₃can effectively improve the morphology and thickness of alumina coating.In addition,after adding sintering additives Y₂O₃,two eutectic phases,Y3Al5O12 and Y5Al3O12,were found in composites around the fiber,which benefit to the sintering of Al₂O₃substrate and homogenization of composites.Besides,acetylacetone?AcAcH?was used as chelating agent of aluminum tri-sec-butoxide,which helped to prepare sol.By heterogeneous condensation and dip coating method,gel coating of aluminum compounds was prepared on the powder of carbon fiber and continuous fiber,respectively.The composition of gel prepared in this way was C15H21AlO6 namely aluminum acetylacetonate,while AlO?OH?prepared without addtion of chelating agent.The two gels can completely decompose into gamma Al₂O₃ after heat treatment of 500?for 1 h,thus coating of alumina ceramics was prepared on carbon fiber.The coating thickness on carbon fiber prepared by this way was associated with sol concentration and reaction time.And the number of dip coating will largely affect the coating thickness and uniformity.