炭纤维表面处理及结构与性能的研究

【作者】 许林；

【导师】 肖鹏；

【作者基本信息】 中南大学 ， 材料学， 2008， 硕士

【摘要】 炭纤维的力学、热学、化学和电学等综合性能优异,是一种很有发展前景的高性能增强材料。炭纤维增强炭基复合材料和陶瓷基复合材料被广泛应用于航空、航天、交通运输、能源、环保等高新技术领域。未经过表面处理的炭纤维表面能低,表面呈现憎水性,缺乏有化学活性的官能团,限制了炭纤维复合材料高性能的发挥。本文采用液相氧化、电化学氧化、化学镀镍和化学气相生长纳米炭纤维等方法对炭纤维表面进行改性处理,改变其表面结构和形貌,增大比表面积,改善炭纤维的力学性能,提高抗氧化性能,以期进一步改善炭纤维复合材料的性能。主要结论如下:1、随着硝酸氧化时间的延长,HTA炭纤维的比表面积先有明显的增加,在氧化5min时,达到最大值14.11 m²/g,而后减小。TX-3炭纤维的比表面积刚开始略有减少,而后明显的增加,在氧化10min时,达到最大值6.613 m²/g,最后又减小。平均孔径的变化趋势刚好与比表面积的趋势相反,HTA炭纤维在20min达到最大值9.683nm;TX-3炭纤维在15min达到最大值13.44nm。2、经过双氧水氧化后,TX-3炭纤维的拉伸强度最大下降9%左右,HTA炭纤维的拉伸强度最大提高13%左右,两种纤维的弹性模量都会降低。随着硝酸氧化时间的延长,TX-3的拉伸强度会先下降,后增加,在氧化10min达到最大,为2.68Gpa,提高了4.8%,最后趋于稳定值。HTA炭纤维的拉伸强度先增加,再减小,然后又有所增加,在20min达到最大,为3.29GPa,提高了11.5%,最后同样趋于稳定值。3、分别对HTA炭纤维和TX-3炭纤维进行电化学改性表面处理,通过正交试验发现,HTA炭纤维最佳参数组合为:电解质浓度15%,电流强度20mA,氧化时间60s,此时拉伸强度为3.41GPa,提高了15.6%,弹性模量为189 GPa,下降了9.1%。TX-3炭纤维最佳参数组合为:电解质浓度15%,电流强度30mA,氧化时间40s,此时拉伸强度为2.70GPa,提高了5.5%,弹性模量为189 GPa,提高了4.4%。4、用化学镀镍的方法,可以在炭纤维的表面镀上一层连续均匀致密化的镍磷合金薄层,镀层呈玉米颗粒状生长和扩展。化学镀镍提高了纤维的实际拉伸强度,但纤维的弹性模量减小。高温氧化时,Ni-P合金和氧化生成的新相NiO和Ni₃（PO₄）₂在炭纤维表面形成一层保护膜,可减缓炭纤维氧化的速度,提高炭纤维的抗氧化性能。5、采用电镀的方法在炭纤维表面沉积纳米Ni单质颗粒作为化学气相沉积原位生长纳米炭纤维的催化剂。沉积温度在化学气相沉积生长纳米炭纤维过程中起着至关重要作用,最佳温度为900℃左右;而沉积时间的长短决定了纳米炭纤维的直径。其最佳工艺条件为:C₃H₆的流量为30ml/min,H₂的流量为200ml/min,N₂的流量为400ml/min,沉积压力保持在700-1000Pa,沉积温度为900℃,沉积时间为4h。更多还原

【Abstract】 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.更多还原