Carbon Fiber Surface Treatment And The Structure And Properties

Carbon fiber(CF)is a kind of high performance reinforcing material which has developing prospect because of its excellent properties such as mechanics,thermology,chemistry and electricity.CF reinforcing C/C and C/SiC composites have big application prospect,and widely used in field of aviation,astronautics,transportation,energy and so on.CF without any surface treatment can limit the composites' properties due to the low surface energy,hydrophobic property and the lack of active functional groups.In this research work,CF with modification treatment by some methods including liquid-phase oxidation,electrochemical,electroless nickel plating and growing nano-CF by chemical vapor deposition(CVD), have variational structure and appearance,more surface area,better mechanical properties,and higher oxidation resistance,which further improve the performance of compound materials with carbon fiber.1,Along with the increase of oxidation time by nitric acid,the HTA-CF's surface area increases firstly,then reduces.When the oxidized time is 5min,the surface area gets to the maximize of 14.11 m²/g.The TX-3 CF's surface area started to have reduction,then obvious increase, finally reduces.When the oxidized time is 10min,the surface area gets to the maximize of 6.613 m²/g.The average aperture changed tendency is opposite than that of the surface area.The HTA-CF's average aperture maximizing 9.683nm at 20min and the TX-3 CF's average aperture maximizing 13.44nm at 15min.2,After oxidation by hydrogen peroxide,the TX-3 CF's tensile strength drop most by 9%,and the HTA CF's tensile strength enhance most by 13%,meanwhile both CF's elastic modulus reduce.Along with the nitric acid oxidation time's extension,TX-3 CF's tensile strength obviously reduces firstly,then increases.When the oxidized time is 10min,the tensile strength maximizing 2.68GPa,improving 4.8%and tends to stable finally;HTA CF's tensile strength increases firstly,then reduces,then increases.When the oxidized time is 20min,the tensile strength maximizing 3.29GPa,improving 11.5%,finally it also tends the stable value. 3,The HTA and TX-3 CF are modified by electrochemistry separately.Through orthogonal experiment,it can be seen that the HTA CF's optimum parameter combination is that:electrolyte density is 15%, current intensity is 20mA,electro-oxidation time is 60s.The tensile strength is 3.41GPa,improving 15.6%and the elastic modulus is 189 GPa,descending 9.1%.The TX-3 CF's optimum parameter combination is that:electrolyte density is 15%,current intensity is 30mA, electro-oxidation time is 40s.The tensile strength is 2.70GPa,improving 5.5%and the elastic modulus is 189 GPa,improving 4.4%.4,Electroless deposition technique is used to deposit a layer of nickel-phosphorus alloy on the CF's surface,and the layer is continual, even and compact.The layer grows and expands with granular corn.After plating nickel on the CF,it can enhance the CF's actual tensile strength, and reduce the CF's elastic modulus.When high temperature oxidation, Ni-P alloy,NiO and Ni₃(PO₄)₂ producted by oxidation formed a protective layer on the CF.These all can decreased the oxidation speed of carbon fiber and enhance its high temperature anti-oxidation properties.5,Electroplating is used to deposit the nanometer Ni on the CF's surface,which is the catalyst to grow nanometer CF by CVD.The deposition temperature plays an important role in growing nanometer CF by CVD,and the best temperature is about 900℃.The deposition time affects the nanometer CF's diameter.The optimal process conditions is as follows:C₃H₆ dosage 30ml/min,H₂ dosage 200ml/min,N₂ dosage 400ml/min,press 700-1000Pa,temperature 900℃and time 4h.