交替电解促进PAN基炭纤维的催化石墨化

介绍了一种简单的在硼酸和氯化镍溶液中交替电解的方法来促进PAN基炭纤维的催化石墨化,并考察了热处理温度和电解液中氯化镍的浓度对PAN基炭纤维催化石墨化的影响.纤维的形貌和结构变化分别采用扫描电子显微镜(SEM)和X射线衍射(XRD)进行表征.结果表明:通过交替电解处理,可以有效地破坏炭纤维的组织结构,并同步实现催化剂硼酸和镍在炭纤维上的分散和沉积.交替电解处理过的炭纤维经2 400℃热处理l h后,其石墨化度明显提高,达到85%,Le为15 nm.     

B_4C催化剂对PAN基炭纤维径向结构和性能的影响

采用机械混合法将纳米B4C催化剂均匀地分散在自制纺丝液中,经预氧化、低温炭化、高温炭化处理后,分析硼元素在PAN基炭纤维径向上的分布。并通过扫描电子显微镜(SEM)、俄歇电子扫描(AES)、X射线光电子扫描(XPS)、傅里叶变换红外光谱仪(FT-IR)、拉曼光谱仪(Raman)以及X射线衍射(XRD)等测试方法观察并研究了炭纤维表面形貌和结构的变化以及硼的催化石墨化效应。实验结果表明:添加B4C催化剂可以提高炭纤维的径向均匀程度,弱化皮芯结构,提高整体的石墨化度。     

高温处理对PAN基炭纤维热稳定性的影响

将2种PAN基炭纤维经3次2 500℃高温处理,研究了不同次数处理后炭纤维的晶格参数、灰分含量以及炭纤维在静态和流动空气中的热稳定性。结果表明高温处理能改善PAN基炭纤维的石墨微晶结构,减少灰分含量;随着高温处理次数的增加,炭纤维在静态空气和流动空气中的氧化失重率降低,热稳定性提高。     

激光隧道炉炭纤维超高温石墨化处理方法

为突破现有炭纤维石墨化炉温度低、能耗高的技术瓶颈,提出一种采用激光加热技术的炭纤维超高温石墨化方法,并研制一套炭纤维超高温石墨化激光隧道炉实验装置。利用激光在氩气气氛中照射PAN基炭纤维进行石墨化处理,根据Raman光谱和X射线衍射分析(XRD)对激光石墨化处理的炭纤维试样的化学结构和微晶结构进行表征。结果表明,激光隧道炉超高温热处理的炭纤维无序碳含量和晶面间距大幅减小,晶粒尺寸变大,石墨化程度有显著提升,验证了该设备和方法的可行性;通过调整工艺参数可实现3 000℃超高温条件下石墨纤维连续生产的可控制备。     

在石墨化过程中采用热牵伸法制备高性能PAN基炭纤维

对PAN基炭纤维（PANCF）石墨化处理过程中采用热牵伸的工艺进行了初步探讨。实验结果表明：适当张力的热牵伸可以得到高模高强的炭纤维。本文还对热牵伸改善炭纤维力学性能的原因进行了讨论。     

酚醛树脂炭含量对炭纸组织结构和性能的影响

对预制PAN基炭纤维纸进行树脂浸渍、模压和高温热处理,制备燃料电池用炭纸。借助SEM和XRD等技术研究了炭纸的微观结构和石墨化度。分别用压差法、四探针电阻法和拉伸测试测得炭纸的透气率、面电阻率和拉伸强度。结果表明:增加PF树脂炭含量可以提高炭纸的体积密度和拉伸强度,但导致透气性能下降。树脂炭含量的增加也有助于炭纸形成发达的三维网络状结构,炭纸的导电性能得到改善,炭纸整体石墨化趋势有一定的加强。当PF树脂炭含量为54%时,炭纸透气率为2050mL·mm/(cm2·h·mmAq),密度为0.48g/cm3,面电阻率21.1mΩ·cm,石墨化度58%,抗拉强度达到15MPa,基本满足炭纸的应用要求。     

日本聚丙烯腈基炭纤维的研制及生产近况

我国家科委组成的炭纤维考察团,应日本高分子学会的邀请,对日本炭纤维及其复合材料进行为期三周的考察。本文主要介绍日本有关聚丙烯腈(PAN)基炭纤维对原丝的要求、预氧化炭化及表面处理的一些基本看法;着重介绍日本主要PAN基炭纤维生产厂,如东丽、日本炭、东邦及三菱公司的近期发现概况。一、供生产炭纤维用的聚丙烯腈长丝日本专家们一致认为,供炭化用的聚丙烯腈原丝与民用产品不同,甚至生产不同性能的炭纤维对PAN长丝的要求也不一样。从化学结构来说,聚丙烯腈纯聚体的结构规整,有利于形成六元环的似石墨结构。因此纯聚长丝是比较合适的,但纯聚体不易成纤,易微纤化     

C／C复合材料石墨化度的研究

用XRD多重分离软件分别对不同热处理温度下C／C复合材料进行衍射分峰处理,得出该材料由三种不同组元构成,即树脂炭、炭纤维和热解炭,并求出各组元的石墨化度值及所占比例,进而得到试样的加权平均石墨化度。用光学显微镜对试样表面进行分析证明了三种组元的存在,讨论了热处理温度与石墨化度的关系。     

几种PAN基炭纤维的氧化特性研究

通过氧化实验，X射线衍射分析和扫描电子显微分析，初步研究了PNA基炭纤维的氧化特性，结果表明，PAN基炭纤维的氧化特性与其表面形貌和微晶参数密切相关，炭纤维表面的沟槽，坑洞越多，石墨微晶参数d002值越大，其氧化失重率越大，即抗氧化性越差。     

文摘

<正>KCl对酚醛树脂炭化生长碳纤维的影响[刊,中]/吴小贤,李红霞,刘国齐,等//耐火材料,2015,49(1):1-5为了促进酚醛树脂在炭化过程中的石墨化,以工业液态酚醛树脂为碳源,微米尺度的KCl为催化剂,经混合、六亚甲基四胺固化处理后,在埋炭1 000℃保温3 h热处理条件下,研究了KCl添加量(掺入酚醛树脂质量的1%、3%、5%和7%)对树脂炭的物相、微观结构的影响及炭纤维的生长机制。结果表明:KCl催化后提高了树脂炭的石墨化程度,树脂炭中原位生长较多炭纤维和片状炭,炭纤维直径为30~200nm,长度可达10~20μm;KCl最优添加量为5%(质量分数),     

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。     

Catalytic graphitization of electroless Ni-P coated PAN-based carbon fibers

Catalytic graphitization of electroless Ni-P coated PAN-based carbon fibers is reported. PAN-based carbon fibers with and without electroless Ni-P coatings were heat treated and the structural changes were followed by X-ray diffraction and Raman spectroscopy, both of which indicate that the graphitization of PAN-based carbon fibers was enhanced in the presence of the coating. The graphitization was shown to be better for electroless Ni-P coated PAN-based carbon fibers heat treated at 1400 °C than for uncoated fibers heat treated at 2400 °C.     

Synergistic catalytic effect of Ti-B on the graphitization of polyacrylonitrile-based carbon fibers

A novel carbon fiber pretreatment is proposed. PAN-based carbon fibers are first anodized in a H₃PO₄ electrolyte to achieve an active surface, and then coated with Ti-B catalyst by immersion of the carbon fibers in a uniformly dispersed H₃BO₃-doped TiO₂ sol. The as-treated carbon fibers are then graphitized at 2400 °C for 2 h. The effects of the anodization and the Ti-B catalyst on the graphitization are investigated.     

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.     

Catalytic graphitization of fibrous and particulate carbons

Catalytic graphitization of carbon fibers, carbon black and anisopropic mesophase spheres by chromia and chromium compounds was studied to examine the influences of the amount of catalyst, procedures of catalyst dispersion and heating on the extent of graphitization. Catalyst addition as a liquid solution provided better dispersion than mixing of powdered catalyst with the carbons by grinding, and permitted graphitization of intact carbon fibers. However, the catalytic action caused restructuring of the fibers and the carbon black. Sequential heat treatments at temperatures < 2000°C were more effective for graphitization than higher temperature treatments in which the catalyst sublimed. In all cases the amount of graphitization increased sharply with the amount of catalyst. The mechanism of catalytic graphitization is briefly discussed.     

Graphitization of carbon fibre/ glassy carbon composites

Carbon fibre/glassy carbon composites were prepared by aligning unidirectionally in furfuryl alcohol condensate the PAN-based carbon fibres treated at different temperatures and with different degrees of stretching. The graphitization of the composites was found to start at the boundary between the fibres and glassy carbon matrix, and to proceed into the matrix. This is considered to be due to the stress accumulation at the boundary caused by a large shrinkage of the matrix. The carbon fibres remain nongraphitized even after a heat-treatment at 2800°C. The composites heat-treated at high temperature (2800°C) are found to show a high overall degree of graphitization, unexpected on basis of the known graphitization behavior of carbon fibres and of glassy carbon, and a high degree of uniaxial preferred orientation of crystallites.     

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。     

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.     

Transmission electron microscopy study of the microstructure of unidirectional C/C composites fabricated by catalytic chemical vapor infiltration

Unidirectional carbon/carbon (C/C) composites were fabricated by catalytic chemical vapor infiltration, using electroless Ni–P as catalyst. Transmission electron microscopy (TEM) investigations indicate that the catalyst particles (100–800 nm) in the pyrocarbon (PyC) matrix are composed of Ni₃P and Ni phases, but only the Ni₃P phase was observed in the tiny catalyst particles (<50 nm) in carbon fibers. The catalyst particles in the matrix were encapsulated by high-textured PyC shells, in which openings were observed. The thicknesses of the medium-textured PyC in the composites (720–850 nm) are greater than in conventional C/C composites (660–740 nm), but have no significant difference in texture degree. Catalysts were partially extruded out of the PyC shells and migrated into the carbon fibers, leading to the catalytic graphitization of the carbon fibers, and their structural homogeneity was destroyed. Based on the TEM observation, a dissolution/precipitation mechanism was proposed for the catalytic graphitization of carbon fibers, and a dissolution/precipitation/encapsulation/fracture/extrusion mechanism was proposed for the encapsulation of catalyst particles.