电化学氧化处理对PAN基炭纤维表面浸润性的影响

以硫酸铵为电解质,对炭纤维进行连续电化学氧化处理,利用反气相色谱(IGC)研究电化学氧化处理前后的表面能变化,并联系SEM、AFM、XRD、Raman、XPS等测试结果综合分析电化学氧化处理对炭纤维表面性能的影响。研究表明,经电化学氧化处理后,纤维沿轴方向表面沟槽加深加宽,薄弱层被剥除,晶格择优取向遭到破坏;纤维表面活性官能团增多,氧和氮含量分别增加了180%和65%,提高了纤维与树脂的粘结性;纤维表面能提高了3.1倍,与树脂的浸润性得到改善;电化学氧化处理后其复合材料的ILSS达109MPa,已可充分满足实际应用需求。     

表面氧化处理对炭纤维及炭／炭复合材料力学性能的影响

采用硝酸表面氧化法，对炭纤维进行表面氧化处理，考察了不同的氧化处理时间、温度和浓度对炭纤维及其炭纤维增强复合材料力学性能的影响，提出适宜的表面氧化处理条件是低温（室温）、浓酸（５０％～６５％），短时间（１５ｍｉｎ～６０ｍｉｎ）。     

炭纤维表面氧化处理对其力学性能的影响

对炭纤维进行表面氧化处理不仅可以改善纤维增强复合材料的界面状况,而且可以改善纤维自身的力学性能.TX-3和HTA纤维的液相(HNO3、H2O2)和电化学表面氧化处理的结果表明,在氧化处理的不同阶段,纤维的抗拉强度和弹性模量表现出不同的升降规律,从纤维表面特性的角度对这一现象的原因进行了解释.电化学表面氧化处理时,电解质的浓度和氧化电流对炭纤维的抗拉强度和弹性模量有显著影响.     

阳极氧化对炭纤维电镀镍的影响

采用阳极氧化法对炭纤维进行连续表面改性,并在其表面进行电镀镍处理,利用扫描电子显微镜(SEM)、X射线衍射(XRD)、热重分析和酸碱滴定等方法研究了炭纤维阳极氧化前后的物理化学结构及对炭纤维电镀镍镀层的影响。结果表明:经过阳极氧化处理后,炭纤维表面的总酸性官能团提高约10倍;炭纤维拉伸强度降低先慢后快;阳极氧化可以改善镀层的生长过程,使镍镀层的生长由(V-W)模式转变为(F-M)模式,并且促使镀层晶粒细晶化,N i晶粒尺寸由14.5nm降为11.2nm,提高了镀镍炭纤维的抗氧化性以及镀层与炭纤维的结合力,阳极氧化后镀镍的炭纤维初始氧化温度较镀镍炭纤维提高了50℃。     

炭纤维表面化学结构对其增强环氧树脂基复合材料性能的影响

采用阳极氧化法对炭纤维的表面进行处理,通过改变氧化程度制备具有不同表面化学结构的炭纤维,并将其作为增强体再制备成复合材料。研究了炭纤维表面化学结构对其增强环氧树脂基复合材料性能的影响。结果表明,阳极氧化处理后炭纤维表面活性大幅提高,O,N元素含量分别由处理前的3.10%,1.12%提高到处理后的13.07%,5.96%;当电流密度低于15A/m2时,O/C,N/C值越高越有利于炭纤维表面与环氧树脂基体之间的界面黏合;在含氧官能团中,-COOH是决定炭纤维/环氧树脂基体间化学键合强度高低的关键因素。     

空气氧化处理对三维编织炭复合材料性能的影响

利用真空浸渍法制得三维编织炭纤维增强环氧复合材料,研究了空气氧化处理前后炭纤维表面状态的变化以及表面处理对三维编织复合材料力学性能的影响。结果表明:空气氧化处理使炭纤维的比表面积和表面粗糙度发生了变化,随着氧化温度和氧化时间的增加,炭纤维的比表面积有不同程度的增加;但同时伴随着炭纤维强度的下降。经450℃-1h空气氧化处理后,复合材料的弯曲强度、弯曲模量和剪切强度分别提高了149%,91%和29%,但冲击强度下降了23%。     

电化学表面处理PAN基炭纤维的表面性能研究

以NH4HCO3为电解质对PAN基炭纤维进行了连续表面处理，并利用X射线光电子能谱(XPS)、X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)和自动电位滴定等方法，系统研究了电化学氧化反应后炭纤维表面石墨微晶尺寸的变化规律，推导出微晶宽度(La)、微晶厚度(Lc)与电流密度(J)之间存在线性天系式；同时，经电化学氧化处理后，炭纤维表面含氧官能团的摩尔分数增加8．54％，表面吸附水的摩尔分数增加5．34％，使其表面由憎液性变为亲液性，这有利于提高炭纤维增强树脂基复合材料(CFRP)的层问剪切强度(ILSS)。     

氧化石墨烯/炭纤维复合增强体的制备及对环氧树脂复合材料界面性能影响

为了改善炭纤维/环氧树脂复合材料的界面性能,以对硝基苯胺为原料,通过两步重氮化还原反应,在炭纤维表面共价接枝氧化石墨烯,制备出氧化石墨烯/炭纤维(GO/CF)复合增强体。研究了反应机理,并对改性前后炭纤维表面的化学结构、微观形貌、表面粗糙度、单丝拉伸强度和炭纤维/环氧树脂复合材料的界面性能等进行了测试分析。结果表明,接枝GO后,炭纤维表面粗糙度增加了188%,单丝拉伸强度提高了13. 2%,断裂伸长率增加12. 1%,界面黏结强度提高了80. 2%。     

XPS,AFM研究沥青基碳纤维电化学表面处理过程的机制

对各向同性沥青基碳纤维进行电化学氧化表面处理,用XPS,AFM分析了碳纤维表面含氧官能团和表面微观形貌的变化过程。实验结果表明:电化学氧化处理是表面碳及其含氧官能团逐步被氧化成羧基和CO₂的过程。氧化处理首先是使碳纤维表面变得更光滑,持续氧化后才会出现沟槽,SEM的分辨率不足以表征碳纤维电化学氧化前后的表面形貌变化,而采用AFM可在纳米尺度上表征碳纤维在电化学氧化过程中的表面形貌变化。AFM和XPS的结合可表征碳纤维电化学氧化表面处理的进程。     

炭纤维阳极氧化对活性污泥固着性能的影响

通过炭纤维电化学表面改性及动态固着代替静态固着,发现好氧池中处理后的聚丙烯腈(PAN)基炭纤维固着能力更好。对改性后炭纤维的表面形貌、表面官能团的种类和含氧官能团的含氧量进行了表征,并根据动、静态固着效果,分析了影响活性污泥固着的关键因素。SEM表面形貌观察表明经过电化学刻蚀后,炭纤维表面粗糙度的增加有利于形成活性污泥的固着。XPS分析显示,电化学表面改性后,C-C键、羧基、羰基等官能团影响活性污泥的表面固着效果,其中羧基的影响最为显著,另外,表面化学吸附氧对活性污泥固着有促进作用。     

用STM研究渗硼改性碳纤维结构与力学性能的相关性

研究了PAN基碳纤维浸渍不同硼化物溶液进行高温热处理后(2500℃)对力学性能的影响。采用扫描隧道显微镜观察了渗硼处理对碳纤维表面微观形态结构的影响,同时还采用X-ray衍射技术分析了渗硼处理对纤维结构参数的影响。结果表明渗硼处理可提高CF的力学性能,采用硼化物A浸渍热处理后CF的模量和强度分别提高了10.3 %和15.3 %。通过STM观察可以很清楚看到渗硼处理可提高CF的择优取向和晶体尺寸,减少表面缺陷。X-ray衍射分析结果与STM一致,渗硼热处理提高了CF的晶体尺寸。      

高温渗硼对炭纤维微观结构的影响

选用日本东邦THA-3K型炭纤维经过硼化物溶液浸渍,然后在1900℃-2500℃温度范围内进行了高温热处理,采用X-ray衍射技术测定了渗硼前后炭纤维晶格参数和取向指数的变化,研究了渗硼对炭纤维力学性能和微观结构的影响,结果表明,渗硼显著地提高了炭纤维的模量,而强度并没有降低,同时增加了晶格尺寸,改善了纤维的结构取向。     

碳纤维增强尼龙1010的力学性能及其对摩擦磨损的影响

用碳纤维填充尼龙1010制备了碳纤维增强尼龙复合材料,并对碳纤维增强尼龙复合材料的力学性能和摩擦学性能进行了实验研究。力学实验结果表明:碳纤维增强使尼龙复合材料的拉伸强度、表面硬度增大,碳纤维增强尼龙材料的拉伸强度在20%碳纤维含量时达到最大值;碳纤维表面处理对尼龙复合材料的拉伸强度有很大影响,碳纤维表面氧化处理提高了碳纤维增强尼龙复合材料的拉伸强度。摩擦磨损实验表明:碳纤维增强尼龙复合材料的摩擦系数和磨损率与其拉伸强度和硬度有密切关系。随着拉伸强度和硬度的提高,尼龙复合材料摩擦系数和磨损率降低;摩擦系数和磨损率与拉伸强度具有反比关系,与材料硬度具有二次方程关系,与碳纤维填充量之间存在负指数变化规律。      

气液双效表面处理方法的应用

炭纤维增强树脂基复合材料（ＣＦＲＰ）是炭纤维应用的主要形式。未表面处理的粘胶基炭纤维所制ＣＦＲＰ力学性能较低,经过气液双效法表面处理后,明显提高了所制ＣＦＲＰ的力学性能,同时,炭纤维本身的抗拉强度和断裂伸长有了较大提高。这种表面处理方法已经应用到炭纤维生产线上。     

电化学改性对PAN基碳纤维表面状态的影响

采用电化学氧化法对聚丙烯腈(PAN) 基碳纤维进行表面改性, 利用扫描电子显微镜(SEM) 、原子力显微镜(AFM) 、X 射线光电子能谱(XPS) 和X 射线衍射(XRD) 对改性后的碳纤维表面状态进行了研究。同时探讨了碳纤维表面状态与其抗拉强度及其复合材料力学性能的关联。研究结果表明, 碳纤维经电化学氧化后, 表面的粗糙度提高了1.1 倍; 表面碳含量降低了9.7 %, 氧含量提高了53.8 %, 氮含量增加了7.5 倍, 羟基和羰基含量也有不同程度的提高; 表面取向指数减小了1.5 %, 表面微晶尺寸减小, 表面活性碳原子数增加了78 %。电化学氧化法的刻蚀作用致使碳纤维拉伸强度降低了8.1 %, 但同时也改善了碳纤维表面的物理性质和化学性质, 提高了碳纤维与树脂间的粘结性, 使复合材料的ILSS 提高26 %。      

Comparison of chemical vapor deposition and chemical grafting for improving the mechanical properties of carbon fiber/epoxy composites with multi-wall carbon nanotubes

By engineering the fiber/matrix interface, the properties of the composite can be changed significantly. In this work, we increased the effective surface area of the fiber/matrix interface, to facilitate additional stress transfer between fibers and matrix, by grafting carbon nanotubes on to carbon fibers (in the form of carbon fabric) by two different methods: (1) chemical vapor deposition (CVD) method and (2) a purely chemical method. With the CVD process, carbon nanotubes (CNT) were directly grown on carbon fiber substrate using chemical vapors. For the chemical method, CNT with carboxyl groups were grafted on functionalized carbon fiber via a chemical reaction. The morphology of CNT/carbon fibers was examined by scanning electron microscope (SEM) which revealed uniform coverage of carbon fibers with CNT in both of CVD method and chemical grafting method. CNT-grafted woven carbon fibers were used to make carbon/epoxy composites, and their mechanical properties were measured using three-point bending and tension tests which showed that those with CNT-grafted carbon fiber reinforcements using the CVD process has 11 % higher tensile strength compared to those containing carbon fibers modified with the chemical method. Also, composites with CNT-grafted carbon fibers with chemical method showed 20 % higher tensile strength compared to composites with unmodified carbon fibers. The results of tensile test revealed that both CVD and chemical grafting could significantly improve the mechanical properties of the carbon fiber composites.     

Optimum dispersion conditions and interfacial modification of carbon fiber and CNT–phenolic composites by atmospheric pressure plasma treatment

Electric resistance measurements were used to determine the optimal dispersion conditions for carbon nanotubes (CNTs) in phenolic resins. Plasma treatment is frequently used to modify carbon fiber surfaces to improve adhesion of the fibers to matrices. Such treatment might also influence carbon fiber tensile strength. In order to determine the effect of atmospheric pressure plasma treatment on carbon fiber tensile strength and interfacial bonding strength, change in tensile strength of the fiber was studied at different gage lengths before and after the plasma treatment. The wettability of carbon fibers was improved significantly after only 10 s of plasma treatment. Such plasma treatment resulted in a decrease in the advancing contact angle from 65° to 28°. Surface energies of carbon fiber and CNT–phenolic composites were measured using the Wilhelmy plate technique, indicating that the work of adhesion between plasma treated carbon fibers and CNT–phenolic composites was higher than it before plasma modification. The interfacial shear strength (IFSS) and apparent modulus were also increased by plasma treatment of the carbon fibers.     

Effect of hot stretching graphitization on the structure and mechanical properties of rayon-based carbon fibers

The influence of hot stretching graphitization on the structure and mechanical properties of rayon-based carbon fibers was studied. It was observed that the Young’s modulus of the treated fibers increased with heat treatment temperature (HTT) and hot stretching stress, to 173 GPa by 158.2 % through hot stretching at 2700 °C under stress of 270 MPa compared to that of the as-received carbon fiber. Meanwhile the tensile strength increased to 1.75 GPa by 73.3 % through hot stretching at 2700 °C under 252 MPa. The field emission scanning electron images showed markedly increased roughness on the external surface and bigger and more compacted granular morphologies on the cross section of the treated fibers with increasing HTT. The preferred orientation of graphitic layers was improved by hot stretching, and the higher the HTT, the stronger the effectiveness of the hot stretching. The crystallite sizes grew and the crystallite interlayer spacing decreased obviously with increasing HTT but changed just slightly with increasing stretching stress. The analysis based on uniform stress model and shear fracture theory proposed that the improvement of tensile strength and Young’s modulus for rayon-based carbon fiber was mainly due to the increased preferred orientation and nearly unchanged shear modulus between planes with increasing HTT during hot stretching graphitization, which was much different from polyacrylonitrile-based carbon fibers.     

The effect of surface modification with carbon nanotubes upon the tensile strength and Weibull modulus of carbon fibers

Carbon fibers are widely used as reinforcements in composite materials because of their high specific strength and modulus. Today, a number of ultrahigh strength polyacrylonitrile (PAN)-based (more than 6?GPa), and ultrahigh modulus pitch-based (more than 900?GPa) carbon fibers have been commercially available. In contrast, carbon nanotube (CNT) with the extremely high tensile strength have attracted attention as reinforcements. An interesting technique to modify the carbon fiber is CNT grafting on the carbon fiber surface. CNT-grafted carbon fibers offer the opportunity to add the potential benefits of nanoscale reinforcement to well-established fibrous composites to create micro-nano multiscale hybrid composites. In the present study, the tensile properties of CNT grown on T1000GB PAN- and K13D pitch-based carbon fibers have been investigated. Single filament tensile test at gauge lengths of 1, 5, and 25?mm were conducted. The effect of gauge length on tensile strength and Weibull modulus of CNT-grafted PAN- and pitch-based carbon fibers were evaluated. It was found that grafting of CNT improves the tensile strength and Weibull modulus of PAN- and pitch-based carbon fibers with longer gauge length (≥5?mm). The results also clearly show that for CNT-grafted and as-received PAN- and pitch-based carbon fibers, there is a linear relation between the Weibull modulus and the average tensile strength on log–log scale.     

碳纤维表面性能的研究

通过此表面、接触角、浸润性、表面能和表面基团的测定,本文较系统地研究了碳纤维表面性能。结果表明经处理后的碳纤维表面的浸润性、此表面、表面能与表面基团含量都增加。就浸润性而论,不论对环氧或水的接触角都随氧化处理时间增加而减少,浸润速度随氧化处理而上升,表面能随氧化处理而提高。特别是表面能中极性组份增加得较为显著,这与表面基团分折结果表明表面含氧极性基团随氧化时间增加而增加的结论是相一致的。另外表面基团含量化学分析的结果与XPS分析的结果基本上一致,因此可以用XPS表面基团分析来代替烦杂的化学分析方法。