【作者】 荣怀苹；

【导师】 余木火；

【作者基本信息】 东华大学 ， 材料学， 2013， 博士

【摘要】 碳纤维增强树脂基复合材料己经在航空航天、汽车、船舶、石油、化工等行业得到了广泛的应用,然而碳纤维表面惰性大、活性官能团少,导致其与基体的界面粘结性差,很大程度上影响了复合材料整体的力学性能,限制了其应用范围。由微米尺度的传统碳纤维与纳米尺度的碳纳米管复合而成的增强材料-碳纳米管/碳纤维多尺度增强体可以明显改善复合材料的界面性能,进而提高复合材料的整体性能,因而成为近年来研究的热点。碳纤维除了上述被用作结构增强型材料以外,碳纤维由于其优良的电性能等因素,近年来作为载体在功能材料等领域也受到了广泛的研究。碳纤维由于其低密度和良好的导电特性等优势,以碳纤维为基体的改性材料在电磁屏蔽和吸收方面也有优异的表现,被越来越多的作为吸波材料的基体材料。碳纤维本身具有优异的介电损耗性能,可单独作为吸波剂制备轻质吸波材料,因此,具有磁性无机纳米涂层的碳纤维有望成为具有结构增强性能的新型吸波材料。本论文主要从碳纤维的表面改性入手,在碳纤维的表面及纳米粒子表面引入反应较强的活性点,使碳纤维与纳米粒子通过化学或者物理作用有效地结合,从而实现碳纤维复合材料的高性能化及高功能化。(1)本论文采用一种化学修饰的方法将碳纳米管修饰在碳纤维表面。混酸处理后的碳纳米管被分散在聚乙烯醇溶液中,碳纤维浸渍在分散有碳纳米管的聚乙烯醇溶液中。碳纤维在氮气的保护下经过高温处理,在其表面形成了少量胺基基团。带有羧基基团的碳纳米管与含有胺基基团的碳纤维通过羧基与胺基的缩合反应,将碳纳米管修饰在了碳纤维的表面。通过傅里叶变换红外光谱、X光电子能谱仪、场发射电镜,以及拉曼光谱分析对化学修饰碳纳米管的碳纤维进行了分析表征。由力学性能分析得知,化学修饰碳纳米管的碳纤维其单丝的拉伸强度比初始碳纤维单丝的拉伸强度提高了15%。这进一步证明了在碳纤维表面修饰碳纳米管,能够修复碳纤维的表面缺陷,减少由缺陷引起的应力集中现象,最终提高了碳纤维的拉伸强度。(2)本论文通过化学气相沉积(CVD)法分别在碳纤维(Carbon fiber)、碳布(carbon cloth)和碳纸(carbon paper)表面原位生长了不同形貌的碳纳米管。该方法通过将催化剂前驱体二茂铁溶解在碳源二甲苯中通过高温分解碳源来实现碳纳米管在碳纤维表面的取向生长。通过固定催化剂种类、催化剂浓度、反应时间等反应条件,研究反应温度的变化对碳纤维表面生长的碳纳米管表面形貌的影响,最终得出适宜碳纳米管生长的最佳反应温度,并且通过拉曼光谱分析了碳纤维表面生长碳纳米管以后的杂化结构。(3)碳纳米管及其碳纤维具有优异的性能,可以作为高性能复合材料的增强体而成为研究的热点。但是碳纤维表面呈惰性,与基体粘结性差,限制了复合材料性能的提高,且碳纤维与碳纳米管的表面均缺少活性官能团,与复合材料的相容性较差,这些都成为制约二者应用的一个重要因素,为改善复合材料的界面性能,对二者进行了表面改性。本论文通过化学修饰的方法以及气相沉积的方法在碳纤维表面修饰碳纳米管来改善碳纤维的表面性能。并且分析对比了由两种方法制备的碳纤维复合材料的结构及其力学性能。由扫描电镜照片得知用化学方法修饰的碳纳米管以及气相沉积方法生长的碳纳米管都均匀覆盖在碳纤维的表面。由力学性能测试对比分析了由两种方法制备的碳纤维/碳纳米管/环氧树脂复合材料的拉伸性能。用CVD方法制备的碳纤维/碳纳米管/环氧树脂复合材料的拉伸强度比用化学修饰方法制备的碳纤维/碳纳米管/环氧树脂复合材料的拉伸强度提高了11%,这说明用CVD方法制备的碳纤维/碳纳米管/环氧树脂复合材料比用化学修饰方法制备的的碳纤维/碳纳米管/环氧树脂复合材料具有更优异的力学性能。而且用化学修饰方法制备的碳纤维/碳纳米管/环氧树脂复合材料的拉伸强度比相同条件下的没有修饰碳纳米管的碳纤维的拉伸强度提高了20%,这说明碳纤维表面修饰碳纳米管后,能够大大改善树脂基体和碳纤维的界面结合,提高了碳纤维复合材料的整体性能。(4)本论文在前文研究的基础上,进一步研究了如何将纳米微晶纤维素与碳纳米管这种两种纳米粒子修饰在高性能碳纤维的表面,这是以前的研究工作者从未开展过的工作。该研究的主要内容是将纳米微晶纤维素作为化学修饰反应的中间体,首先将酰氯化的碳纳米管修饰在带有大量羟基的纳米微晶纤维素的表面,然后将酰氯化的碳纤维与上一步反应后剩余的纳米微晶纤维素的羟基基团相互反应。这样就成功的实现了在碳纤维表面化学修饰了碳纳米管与纳米微晶纤维素两种纳米粒子。(5)本论文在前文研究的基础上,进一步在碳纤维表面修饰了铁磁性纳米粒子,实现了碳纤维的高功能化。通过一种环境保护的溶胶凝胶方法在碳纤维的表面制备了均一可控、致密度高、磁响应较强的磁性三氧化二铁纳米粒子的涂层,并且由该方法制备的磁性三氧化二铁纳米粒子的涂层能够均匀的覆盖在碳纤维的表面。由X射线光电子能谱、傅里叶变换红外光谱仪、X射线衍射、扫描电镜等多种分析测试方法分析了磁性复合物的结构和形态。由扫描电镜照片观察得知,磁性三氧化二铁纳米粒子可以均匀的涂覆在碳纤维的表面,其平均直径为10nm。对碳纤维织物表面涂层铁磁性纳米粒子的磁性能进行了表征,进一步验证了通过溶胶凝胶方法在碳纤维表面涂层铁磁性纳米粒子以后具有优异的铁磁性。该研究对后续碳纤维吸波复合材料的设计和应用具有重要意义。更多还原

【Abstract】 Carbon fiber reinforced polymer composites have been widely used in many field such as aerospace industry. Automotive industry, steamship industry, Petroleum industry and chemical industry. The cohesive force between carbon fibers (CFs) and the matrix is weak because the CFs has small active specific surface area, low surface energy, and lipophobic suface. It much limites the applications of carbon fibers reinforced composites. To improve the adhesion behavior of the carbon fiber/matrix interface, grafting carbon nanotubes (CNTs) onto the carbon fibers to design a CNT/CF multi-scale structure has become a hot spot in recent years and attracted more and more attention.(1) A novel method is developed for grafting multiwall carbon nanotubes (MWNTs) onto the surface of polyacrylonitrile-based high strength (T300GB) carbon fiber. Functionalized MWNTs were well dispersed in the PVA solution and the carbon fiber was dip-coated in this solution. After heat treatment of the coated carbon fiber under a nitrogen atmosphere, MWNTs with carboxyl groups were grafted onto the functionalized carbon fiber via chemical interaction. The resulting materials were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Raman spectrum and mechanical testing. FESEM observations revealed uniform coverage of carbon nanotubes on carbon fiber. The carbon fiber grafted with MWNTs improved the tensile strength by15%with respect to the pristine carbon fiber. These results are supportive of good interfacial bonding between the carbon nanotubes (CNTs) and carbon fibre. The introduction of MWNTs onto the surface of carbon fiber may help to remedy the surface defects and reduce stress concentrations, resulting in improved tensile strength of the carbon fiber.(2) The main purpose of this paper is focused on the growth of carbon nanotube on the surface of carbon fiber, carbon cloth and carbon paper with different morphologies by chemical vapor deposition (CVD) method. In this process, the metal catalyst ferrocene was dissolved in a liquid hydrocarbon, Xylene, to form a feed solution. This solution was delivered by a syringe pump to an injection tube and dispersed into a stream of hydrogen and helium. This vapor was transported into a hot quartz tube reactor. Aligned carbon nanotubes were grown on the carbon fiber surface at680℃.(3) Because of their noticeable mechanical, chemical and physical properties, carbon nanotubes (CNTs) and carbon fibers (CF) are attracted wide attention as reinforcement for composites. However, both of them have poor wettability and absorption with most polymers because their surface is non-polar and compound of highly crystallized graphitic basal planes with inert structures. In order to improve the performance of composites, we used chemical method to modify CNT and CF surface. And after that, the composites’performances were studied. The interfacial bonding strength between fibers and polymer matrices is low, therefore, good mechanical performance of composites cannot be ensured. We use the chemical method and chemical vapor deposition to modify the carbon fiber surface. The morphology of CNT/carbon fibers was examined by scanning electron microscope (SEM). SEM observation revealed uniform coverage of carbon fibers with carbon nanotubes in both of CVD method and chemical 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 has11%higher tensile strength compared to those containing carbon fibers modified with the chemical method. Also, composites with CNT grafted carbon fibers with chemical method showed20%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.(4) In the here proposed work we intend to investigate systematically of grafting carbon nanotube (CNTs) and nanocrystal cellulose (NCC) onto carbon fiber surface (CF). The main goal is to make CNTs-NCC-CF using NCC as a bridging molecule between CNT and CF. Grafting secondary materials onto carbon fibers and carbon nanotubes is often limited by the low reactivity of graphitic carbon and there is strong demand to create novel grafting methods using functional groups. One desirable functional group is a carboxylic acid, which strongly interacts with many organic and inorganic materials. Another advantage is that the carboxylic acid group can be modified and also be used as an active group to bind CNT, NCC and CF’s together.(5) Carbon fiber (CF) microwave absorption materials are multifunctional composites with high strength and modulus; good carry capacity, excellent electrical property and reflection loss characteristic, which are increasingly, recognized and practical structural absorption composites. The magnetization modification of carbon fiber is an important way to enhance the microwave absorption property of carbon fiber filled composites. In this paper, a novel environmentally friendly method was proposed for decorating carbon fiber with y-Fe2O3magnetic nanoparticles (maghemite) that aim to develop new functional nanomaterials with good magnetic properties. It was found that excellent uniformity of γ-Fe2O3nanoparticle layers were obtained on carbon materials’ surface. The structure and morphology of the magnetic composites have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and Raman spectra. The SEM images showed that a complete and uniform y-Fe2O3nanoparticle coating was formed on carbon materials at600℃, and the average diameter of the γ-Fe2O3nanoparticles on the surface was about10nm. The surface properties of y-Fe2O3nanoparticles detached from carbon fibers/γ-Fe2O3composite have been analyzed by XPS and FTIR. The uniformity of y-Fe2O3coating on the surface of carbon materials have improved magnetic and microwave absorption properties of the base materials. This research had great significance for the design and application of microwave absorption materials.更多还原