聚丙烯腈基碳纤维高温石墨化综述

针对高模量碳纤维制备的关键工艺环节,综述总结了石墨化的基本工艺和石墨化高温处理过程纤维组成、结构的变化以及对最终碳纤维力学性能的影响,以期为我国高强高模碳纤维研发提供借鉴。综述结果表明,一步法石墨化高温处理有利于保持纤维的高强度特性,该工业化技术具有发展潜力;1 800℃前后纤维密度为先降后升;随着纤维对石墨晶体结构逐渐完善,层间距减少,模量提高;催化石墨化以及强磁场或射线处理可促使纤维石墨晶体结构的完善,但不易工业化实施;石墨化过程中适施应力是一项保持纤维强度和提高模量的有效措施。     

低温石墨化对碳纤维性能的影响

使用高温石墨化炉对实验室自制的高强中模碳纤维进行连续石墨化处理,制备得到了强度4.86 GPa、模量541 GPa的高强高模碳纤维,并详细研究了石墨化处理过程中主要工艺参数对碳纤维结构与性能的影响。研究结果探索掌握了低温石墨化(1 600~2 200℃)过程中,不同处理温度对碳纤维密度、拉伸强度、拉伸模量等性能的影响规律。     

PAN基高模量碳纤维成型过程中的结构性能关联性

以实验室自制T800级聚丙烯腈（PAN）基高强中模碳纤维为原料，经连续石墨化处理得到M50J级、M55J级高模量碳纤维，以X射线衍射（XRD）、Raman光谱为表征手段研究了高强碳纤维向高模量碳纤维转变过程中石墨微晶、取向、微孔含量、石墨化度等石墨特征结构的演变规律，并开展了PAN基碳纤维石墨特征结构与力学性能的关联性研究。研究结果表明：在高强碳纤维向高模量碳纤维转变过程中，随着石墨微晶层间距d ₀₀₂的下降以及石墨微晶堆砌厚度L _c的增加，碳纤维的拉伸模量逐渐提升；石墨微晶层间距和微晶取向是影响碳纤维拉伸强度的两个主要因素，石墨微晶层间距d ₀₀₂值增加、石墨微晶取向越高，纤维拉伸强度也越高；在高模量碳纤维的成型过程中，纤维内部微孔含量随着石墨化程度的提高而降低；经过高温石墨化处理后，碳纤维的拉伸强度会随着Raman光谱中无序结构D峰和石墨特征结构G峰积分强度比值I _D /I _G的下降而下降。     

高温石墨化对碳纤维结构的影响

使用高温石墨化炉对实验室自制的高强中模碳纤维进行连续石墨化处理,制备得到了强度4.86 GPa、模量541 GPa的高强高模碳纤维,并详细研究了石墨化处理过程中主要工艺参数对碳纤维结构与性能的影响。研究结果探讨掌握了高温石墨化(2 500℃)处理前后碳纤维微观结构的演变规律。     

碳纤维八面体骨架增强泡沫复合结构的制备及力学性能分析

设计了一种不需加装面板的碳纤维八面体骨架增强泡沫复合结构,介绍了碳纤维八面体骨架增强泡沫复合结构的制作工艺。分别从实验测试以及理论分析两个方面,获得了碳纤维八面体骨架增强泡沫复合结构的抗压强度及压缩模量等力学性能。研究结果表明:受边界效应影响,碳纤维八面体骨架增强泡沫复合结构的抗压强度及压缩模量明显降低,实测抗压强度介于理论最大值与最小值,压缩模量甚至低于最小值。对比其他类型的碳纤维-泡沫复合结构,碳纤维八面体骨架增强泡沫复合结构在抗压强度与压缩模量上具有一定优势。碳纤维八面体骨架增强泡沫复合结构具有近乎各向同性的力学性能,密度低于水,耐腐蚀性高,在航海领域的应用前景广泛。     

PAN基碳纤维连续石墨化过程中的取向性

利用XRD研究了PAN基碳纤维在连续高温石墨化和热牵伸石墨化过程中纤维内石墨微晶沿纤维轴择优取向性的变化。结果表明：碳纤维中石墨微晶的择优取向性随石墨化温度的提高和热牵伸的增大而增加。两种工艺中纤维的拉伸模量均随微晶取向性的增加而增大,但在获得相同的模量下其取向参数却不同;碳纤维的拉伸模量不仅仅取决于石墨微晶的择优取向,而且与晶体的大小有关。另外,经过3000℃的高温处理后,纤维的择优取向参数Z仅为14.71°,说明纤维中乱层石墨的层面仍没有高度取向。     

聚丙烯腈基高强高模石墨纤维结构研究

以聚丙烯腈纤维为先驱体,经连续热稳定化、碳化处理,制备出T800级碳纤维;进一步经连续石墨化处理后,制备出M50J级石墨纤维。采用SEM、元素分析、XRD和Raman等手段表征了碳纤维截面形貌、化学组成、石墨微晶及取向等结构。与进口M50J石墨纤维相比,国产M50J级碳纤维模量与其相当,但有更高的拉伸强度;同时两者间碳含量和石墨微晶尺寸相当,但国产纤维具有更高的取向程度和石墨化程度。M50J级碳纤维比T800级碳纤维具有更高的碳含量、更完善的石墨微晶结构及取向程度。     

碳纤维高温热处理技术进展

从高温热处理技术方面介绍了碳纤维在石墨化过程中微观结构的变化和宏观力学性能的改变。综述了高温、热牵伸、催化、压力、渗碳、外加磁场等条件在碳纤维石墨化过程中的研究与进展,并对高性能石墨纤维的制造技术和研究发展进行了展望。指出优化石墨化条件、创新制造工艺、降低生产成本、进一步提高石墨纤维的性能将成为今后研究的重点和发展方向。     

文摘

聚丙烯腑基碳纤维高温石墨化综述[刊,中],卢天豪。陆文睛。童元建//高科技纤维与应用,2013,38（3）：46-53．74针对高模量炭纤维制备的关键工艺环节,综述总结了石墨化的基本工艺和石墨化高温处理过程纤维组成、结构的变化以及对最终炭纤维力学性能的影响,以期为我国高强高模炭纤维研发提供借鉴。综述结果表明,一步法石墨化高温处理有利于保持纤维的高强度特性,该工业化技术具有发展潜力：1800℃前后纤维密度为先降后升;随着纤维对石墨晶体结构逐渐完善．层间距减少。模量提高;催化石墨化以及强磁场或射线处理可促使纤维石墨晶体结构的完善,但不易工业化实施：石墨化过程中适施应力是一项保持纤维强度和提高模量的有效措施。     

高强高模PAN基石墨纤维的制备研究

以国产T800级PAN基碳纤维为原料,通过调整石墨化温度和牵伸率,制备出拉伸强度3.8 GPa和拉伸模量450 GPa的石墨纤维。研究发现,拉伸模量随石墨化处理的温度升高和牵伸比的增加而提高,而其拉伸强度随牵伸比的增加而下降。进一步分析石墨化处理过程中纤维微观结构参数发现,微观有序化和高取向是制备高强高模石墨纤维的关键。     

高性能沥青基碳纤维制造——氧化碳化石墨化

本文论述了用于制造高性能碳纤维的中介相沥青初生纤维的氧化稳定化、碳化与石墨化过程及其对最终碳纤维力学性能与电导性能的影响;讨论了氧化碳化与石墨化温度、升温速率、中介相沥青原料种类与氧化稳定化程度、石墨化程度、抗张强度与模量、电阻率、纤维结构的关系;指出了五种加速氧化稳定化进程的有效措施。     

Graphitization thermal treatment of carbon nanofibers

Carbon nanofibers (CNFs) and carbon nanotubes have revolutionized the world of the nanotechnology due to their excellent mechanical, electrical and thermal properties. CNFs are graphitic fibers made of stacks of graphene layers aligned perpendicular, tilted or parallel to the fiber axis, thus resulting in different microstructures. Post-production treatments can be applied to CNFs to improve their performance in several applications. Among them, the heat treatment at high temperature to achieve the transformation of the CNFs into graphite (graphitization) or graphitized CNFs (graphitization heat treatment) has been studied in detail. This review covers the literature on this topic for the last 20 years, analyzing the structural and textural changes shown by the CNFs during graphitization, and how these changes influence their mechanical and electrical properties. Different techniques, particularly, high-resolution transmission electron microscopy, have allowed to determine the microstructure of these nanofilaments. A survey of the applications of graphitized CNFs is provided, these including additives for polymer reinforcement in composites, anodes in lithium-ion batteries, catalyst supports in fuel cells, hydrogen storage and others such as potential biosensors and catalysts in diverse reactions. In this regard, special emphasis is placed on the advantages (or disadvantages) of using graphitized CNFs instead of as-grown CNFs.     

The electronic and structural characteristics of carbon fibers from mesophase pitch

The electronic properties (resistivity, magnetoresistance, and electron spin resonance) of mesophase pitch-based carbon fibers have been studied in relation to the fiber structure and processing conditions. Reproducible correlations between the electronic properties and the structure demonstrate that the electronic properties are a sensitive indicator of the degree of graphite order in the fibers. Fibers having radial transverse structure are more easily graphitized than fibers with random transverse structure. The effect of differences in the thermosetting procedure is relatively unimportant. The ultimate degree of graphitization attainable by these fibers is comparable to that of similarly heat-treated pyrolytic carbons, whereas PAN-based carbon fibers are ultimately capable only of properties comparable to pitch-based fibers treated in the 1700–2300°C range.     

Analysis of carbon fiber structure based on dynamic laser Raman spectroscopy

The in-plane modulus and inter layer shear modulus are the intrinsic properties determining the carbon fiber's characterization, but could not be gotten for a single sample. With the addition of dynamic Raman spectra, the parameters are obtained from five carbon fibers individually, which interpret perfectly that the Young's modulus and conductivities are not consistent according to the normal views. The mesophase pitch-based graphitized carbon fiber has thermal conductivity of 635 Wm⁻¹ K⁻¹, much higher than 78 Wm⁻¹ K⁻¹ of the polyacrylonitrile graphitized carbon fiber, even the modulus of the latter is higher than the former. The Young's modulus of polyacrylonitrile carbon fiber and rayon-based graphitized carbon fiber are 260 and 140 GPa; however, their thermal conductivities are lower than 1.0 Wm⁻¹ K⁻¹. With these two intrinsic properties, the structure of a carbon fiber can be understood clearly, so that the properties can be enhanced accordingly.     

Raman spectrum of modified PAN-based carbon fibers during graphitization

Graphite fibers were developed from polyacrylonitrile (PAN) fibers which were modified with potassium permanganate. After the transitional temperature, the formation of graphite structures commenced, the crystals increased in thickness, and the preferred orientation of the fiber crystals increased. The Raman specific absorption peak of noncrystalline carbon layers (1360 cm⁻¹) weakened with the increase in the graphitization temperature, whereas the degree of graphitization rose. The results of this analysis indicate that manganese has the effect of catalyzing graphitization, thus increasing the mechanical properties of the graphite fibers. © 1996 John Wiley & Sons, Inc.     

激光石墨化过程中激光功率和牵伸力对聚丙烯腈基碳纤维化学结构和微观结构的影响

采用自制的高温激光石墨化平台对聚丙烯腈（PAN）基碳纤维进行石墨化处理,分别在不同激光功率和不同牵伸力条件下制备了多种碳纤维实验样品,利用拉曼光谱和XRD射线衍射研究了不同条件下碳纤维样品的化学结构和微观结构。结果表明：在牵伸力不变时,随着激光功率的增大,碳纤维石墨化程度提高,当激光功率增大到一定值时,单方面继续提高激光功率对于提高碳纤维石墨化程度的影响将变小;在激光功率一定时,随着牵伸力的增大,石墨微晶尺寸L_c、L_a均逐渐增大,而d₀₀₂和取向角逐渐减小,在激光石墨化过程中,施加一定的牵伸力可以促使碳纤维中的石墨微晶沿纤维轴方向择优取向,改善微晶尺寸、减少石墨微晶层间距、提高微晶堆砌层数。     

Mechanical tests of a three-dimensionally-reinforced carbon-carbon composite material

A tightly woven block consisting of high modulus graphite fiber yarns in a three-dimensional array was repeatedly impregnated with a series of low viscosity polymer resins, each reimpregnation being followed by a 1540°C carbonization process. After thirteen reimpregnations and carbonizations, the densified block was graphitized at 2650°C. Strength and modulus properties were measured after the seventh and thirteenth carbonizations, and after graphitization, by cutting test specimens from the block. These properties are compared with microphotographs of cross sections of the block taken at various process stages. The influence of the anisotropic thermal expansion characteristics of the composite on the variations in mechanical properties is discussed.     

Rapid and low-cost carbon/carbon composites by using graphite slurry impregnated prepregs

A rapid and low-cost carbon/carbon (C/C) composites preparation method is proposed: graphite prepreg-coated carbon fiber fabric (CFF) is formed by hot pressing, followed by hot isostatic pressing and high temperature graphitization, to prepare C/C composite with low porosity and high crystallinity. In this method, the carbon fiber (CF) mass fraction can be precisely regulated in the range of 40–95% by the impregnation process conditions of CFF in graphite prepreg. The graphite particles in the preform were graphitized and bonded with CFF by high temperature graphitization. Finally, a ZrO₂ anti-ablative layer was applied using sol-gel method. The results show that when the CF mass fraction is 50%, the C/C composite with a crystallinity of 92.21 and a porosity of 3.47% can be obtained, with mass ablation rate of 0.23 mg/s and density of 1.62 g/m³. The method can prepare C/C composites with uniform density and high ablation resistance.