用SAM检测碳纤维微观元素分布

现代化的表面分析技术在某些领域的应用已得到了很好的效果。在我们的复合材料测试中,只要解决好样品制备、表面清洁及电荷累积的消除诸问题,就使测试成为可能。本文介绍了四种不同工艺生产高强度碳纤维的SAM微区分析的检测结果。由于不同的预氧化碳工艺所得的碳纤维的碳化曲线的均匀度是不大相同的,对照抗拉强度的图表来看碳化均匀性好的碳纤维其抗拉强度也大,沿径向碳的分布是起伏不一,并不象人们所想的是锅底形状的。我们认为碳在径向分布与碳纤维的力学性能有关,测试结果也证实了这一点。从SAM微区分析检测结果来看,对单根碳纤维,我们检测了它的组分和元素分布,提供了一些其它分析手段得不到的新的信息。这种方法使测试复合材料和碳纤维又多了一种先进的可靠的特殊的分析手段和工具。如果能进一步深入研究,必将揭示碳纤维碳化过程的微观性能和宏观的物理、力学机械性能的内在联系。     

木质素基碳纤维制备的研究进展

木质素在自然界中储量丰富,并且可再生、碳含量高,将其应用于碳纤维的制备有着无可比拟的成本优势。简要介绍了木质素基碳纤维的发展进程,详述了硫酸盐木质素、有机溶剂型木质素和蒸汽爆破木质素的来源、结构差异及其碳纤维制备工艺过程进展,通过对比得出硫酸盐木质素是制备低成本碳纤维的最佳木质素原料,同时指出了木质素制备碳纤维的未来研究方向,旨在为木质素制备碳纤维的研究者提供参考。     

碳纤维增强铜基（碳／铜）复合材料的研究现状与展望

概述了国内，外碳／铜复合材料制造工艺，碳纤维与铜合金粉末的混合；碳／铜复合材料的成型工艺等。     

金属粉体对细编穿刺织物的损伤及其微观形态的研究

在C/C复合材料中引入难熔金属化合物,可进一步提高C/C材料超高温抗烧蚀性能,采用细编穿刺工艺成型含金属粉体织物,是制备低烧蚀C/C复合材料一条新的技术途径.讨论了添加金属粉体对细编穿刺织物的性能影响,在碳布和碳纤维中引入纳米、微米级粒径粉体,对碳布和碳纤维进行测试,分析了不同粒径粉体对碳布和碳纤维在工艺过程中损伤情况的影响.并对其进行了分散形貌和微观形态的分析.展示了纳米级粉体引入细编穿刺织物的良好前景.     

金属粉体对细编穿刺织物的损伤及其微观形态的研究EI

在C/C复合材料中引入难熔金属化合物,可进一步提高C/C材料超高温抗烧蚀性能,采用细编穿刺工艺成型含金属粉体织物,是制备低烧蚀C/C复合材料一条新的技术途径.讨论了添加金属粉体对细编穿刺织物的性能影响,在碳布和碳纤维中引入纳米、微米级粒径粉体,对碳布和碳纤维进行测试,分析了不同粒径粉体对碳布和碳纤维在工艺过程中损伤情况的影响.并对其进行了分散形貌和微观形态的分析.展示了纳米级粉体引入细编穿刺织物的良好前景.     

3D混杂梯度结构碳/碳复合材料微观结构和性能研究

采用Z-PIN与粘胶基碳纤维毡、粘胶基碳纤维平纹织物、聚丙烯氰基碳纤维平纹织物制备了3D混杂梯度纤维预制体,多相碳素基体经丙烯等温化学气相渗透(ISO-CVI)和煤焦油沥青高压浸渍碳化(HPIC)复合工艺制备,分析研究了多相碳素基体的组织特征、Z向增强体对粘胶基碳纤维织物碳/碳复合材料(RCC)和聚丙烯氰基碳纤维织物碳/碳复合材料(ACC)层间性能的影响以及失效模式.碳基体的微观组织结构为各向同性层、光滑层和粗糙层多相复合体,粘胶基碳纤维表面和聚丙烯氰基碳纤维表面沉积碳的微观组织存在差异性.采用高密度Z-PIN增强体可提高层间性能40%～60%.失效模式为层间和纤维束内裂纹扩展,基体组织和纤维类型对层间性能的影响很小.     

碳纤维在高温下的结构、性能演变研究

针对碳纤维在碳/碳烧蚀防热复合材料中应用的基础问题,论述了不同碳纤维结构、成分、表面特征,及其力学性能和热物理性能的高温演变规律,揭示了碳纤维灰分含量对碳纤维力学性能和热氧化性能的影响。确定了在碳/碳复合材料复合成型过程中,碳纤维结构受基体碳影响的变化规律和碳纤维表面特征对碳/碳材料宏观力学性能的影响。阐明了碳/碳复合材料中碳纤维的力学性能对纤维发生折断烧蚀的阻碍作用和通过控制碳/碳成型最高温度实现提高性能的途径。     

木质素基碳纤维的制备及应用研究现状

碳纤维具有低密度、高模量等一系列优异性能,具有广泛的应用领域。木质素作为一种丰富的可再生资源在自然界中的含量仅次于纤维素,碳含量高达60%以上,是一种新型的制备碳纤维的理想原料。文中根据纺丝工艺的不同,从前驱体溶液、纺丝参数、预氧化和碳化工艺角度,分别阐述并讨论了木质素基碳纤维的多种制备方法,包括熔融纺丝、湿法纺丝、凝胶纺丝及静电纺丝。并介绍了木质素基碳纤维的应用领域,为今后研究者高效利用木质素资源提供参考。     

2D-C/C复合材料结构与性能的研究进展

2D-C/C复合材料是以二维碳纤维为增强体,以化学气相渗透的热解碳或液相浸渍炭化的树脂碳、沥青碳为基体组成的一种纯碳多相二维结构材料,是一种新型高性能结构功能复合材料,大量运用在航空航天等高新技术领域.目前研究集中于其宏观性能方面,难点在于其组织结构和性能的可控性、可调性.主要介绍了二维碳纤维预制体和针刺碳纤维,基体碳的微观结构和添加剂,纤维/基体界面和界面修饰,以及制备工艺对2D-C/C复合材料性能的影响.结合2D-C/C复合材料的结构特点,概述了2D-C/C复合材料热物理性能、力学性能及氧化烧蚀等行为的各向异性.此外,还展望了其研究发展方向.     

粉末涂层碳纤维制备碳/碳复合材料研究进展

综述了国内外碳/碳复合材料的主要用途和制备方法,通过比较发现粉末预涂层制备碳/碳复合材料是一种低成本、短制备周期的理想方法,它包括基体树脂和碳纤维的选择、碳纤维的表面处理及碳纤维丝束的铺展.采取层压成型制备试样,经高温炭化和石墨化制备碳/碳复合材料.     

SiC fibers with controllable thickness of carbon layer prepared directly by preceramic polymer pyrolysis routes

Continuous SiC fibers with different thickness of carbon layer were prepared through three preceramic polymer pyrolysis routes. To make the carbon layer thickness controllable, a simple improvement by using a ceramic bushing was adopted to retard the deposition of the pyrolytic carbons. Auger electron spectroscopy (AES) analysis reveals that the carbon layer thickness varies from less than 5 nm to 40 nm. The specific resistivity of the fibers increases by 5 orders of magnitude as the carbon layer thickness decreases. All of the fibers exhibit a tensile strength of around 1.8 GPa which is independent of the carbon layer thickness. The formation process of the carbon layer is discussed in three steps: the decomposition, the carbonization and the deposition. The as-received fibers have a potential application as the reinforcement of functional materials.     

炭化条件对木材苯酚液化物碳纤维性能的影响

以木材苯酚液化物为原料,加入六次甲基四胺熔融纺丝后,经甲醛和盐酸溶液固化处理、炭化后得到木材液化物碳纤维。通过纸框拉伸检测法研究了炭化工艺条件对碳纤维力学性能、炭化率等的影响。结果发现:木材液化物碳纤维的力学性能随着炭化温度和炭化时间的增加而显著提高;随着炭化升温速率的增加而逐渐下降。同时,原料中木材/苯酚比越大,其碳纤维的拉伸强度和拉伸模量增幅比例越大,且直径收缩越小。木材液化物碳纤维在合适的炭化条件下拉伸强度、拉伸模量和炭化率可分别达到1.7 GPa、159 GPa和60%。      

碳纤维制造过程中径向差异表征及演变机理

为优化PAN基碳纤维结构,采用AES表征PAN纤维在低温碳化与高温碳化后C,N,O沿纤维径向的分布,并用以阐明预氧化碳化过程径向差异的形成机理.结果表明:预氧丝径向结构不均匀,由外向内氧化程度降低;预氧时物理阻隔与化学阻隔导致径向形成氧浓度梯度,热物理传递与化学反应放热导致径向形成温度梯度.低温碳化时,热物理传递与化学反应放热形成温度梯度加剧了预氧时的径向差异;纤维分3部分,最外层氧含量低,由氧化程度高的预氧皮层外部强烈脱氮脱氧形成,最内层由氧化程度低的预氧芯层转化而成;中间是过渡层,一部分由氧化程度较高的预氧皮层内部少量脱氧脱氮而成,氧含量高,而后过渡到预氧程度低的低含氧量芯部.高碳丝径向组分差异变小,纤维分两部分,外层厚度仅为纤维直径的10%,是碳含量逐渐降低的过渡性皮层,其余部分为组成均一的芯层.     

Bis-<Emphasis Type="Italic">ortho</Emphasis>-diynylarene polymerization as a route to solid and hollow carbon fibers

The preparation, fabrication, and carbonization of bis-ortho-diynylarene (BODA)-derived polymers are described. BODA monomers undergo thermal step-growth polymerization to reactive and processable branched polyarylene intermediates. Well-defined intermediates with controlled conversion, molecular weight and viscosity, along with solution or melt processing allow for control in ultimate carbon structure. Fabrication followed by thermal cure and carbonization results in solid or hollow carbon fiber prototypes with interesting thermal and electrical properties. The BODA polymerization and fiber formation were investigated by differential scanning calorimetry, and gel permeation chromatography. The thermal behavior and stability of fibers was measured by thermogravimetric analysis. The surface crystallinity of fibers was studied by Raman spectroscopy. The conductivity of fibers was measured by a multimeter. The surface morphology and dimensions of the fibers were examined by scanning electron microscopy.     

Carbon fibers modified with carbon nanotubes

Carbon nanotubes were used to modify a polyacrylonitrile (PAN) polymer solution before the manufacture of the carbon fiber precursor. The modified PAN fibers were spun from a dimethylformamide solution containing a small amount of single-walled carbon nanotubes. The fibers were characterized by thermogravimetry and optical and scanning electron microscopy. Structure, morphology, and selected properties of the composite polymeric fibers and the fibers after carbonization are characterized. The mechanical properties of the fibers are examined. It is found that nanotubes in the PAN solution have a strong tendency to form agglomerates that inhibit suitable macromolecular chain orientation of the carbon fiber precursor. Fibers manufactured from such a solution have similar mechanical properties to those from a pure PAN precursor, and after carbonization the resultant carbon fibers are very weak. A comparison of pure carbon fibers and those containing nanotubes reveals slight differences in their structural ordering.     

低温炭化温度梯度对聚丙烯腈预氧纤维结构演变及碳纤维性能的影响

聚丙烯腈(PAN)预氧纤维在低温炭化阶段经热裂解重组而转化为具有乱层石墨结构雏形的低温炭化纤维,此阶段的温度调控对最终碳纤维的结构与性能有着重要影响。采用¹³C固体核磁共振谱图(¹³C-NMR)、拉曼光谱(Raman)、X射线衍射(XRD)和力学性能分析等手段,研究预氧纤维在低温炭化阶段的反应进程、温度梯度调控对预氧纤维的结构演变和碳纤维结构及性能的影响。结果表明:PAN预氧纤维在低温炭化过程中,经450℃热处理后碳结构的支链化程度达到最大值0.99,当处理温度达到550℃后,以芳环链段的重组交联为主要反应。低温炭化温度梯度影响预氧纤维的结构演变进程,当采用350—450—650℃的梯度升温模式时,先经450℃处理的低碳纤维中—C—C基团的¹³C-NMR位移最大,表明纤维内的支化交联反应最多,再经650℃处理的纤维d₀₀₂以及相应高碳纤维的I_A/I_G达到最大,说明其无定形碳相对含量最多,因而最终碳纤维的力学性能最差;当采用350—550—650℃的梯度升温模式时,纤维内裂解与重组交联反应有序开展,低碳和高碳纤维的碳结构更优,最终碳纤维的致密性及力学性能得到提升。     

High‐Modulus Low‐Cost Carbon Fibers from Polyethylene Enabled by Boron Catalyzed Graphitization

Currently, carbon fibers (CFs) from the solution spinning, air oxidation, and carbonization of polyacrylonitrile impose a lower price limit of ≈$10 per lb, limiting the growth in industrial and automotive markets. Polyethylene is a promising precursor to enable a high‐volume industrial grade CF as it is low cost, melt spinnable and has high carbon content. However, sulfonated polyethylene (SPE)‐derived CFs have thus far fallen short of the 200 GPa tensile modulus threshold for industrial applicability. Here, a graphitization process is presented catalyzed by the addition of boron that produces carbon fiber with >400 GPa tensile modulus at 2400 °C. Wide angle X‐ray diffraction collected during carbonization reveals that the presence of boron reduces the onset of graphitization by nearly 400 °C, beginning around 1200 °C. The B‐doped SPE‐CFs herein attain 200 GPa tensile modulus and 2.4 GPa tensile strength at the practical carbonization temperature of 1800 °C.     

Thermal stability of low-oxygen silicon carbide fibers (Hi-Nicalon) in carbon monoxide

The effect of CO treatments on thermal stability of low-oxygen SiC fibers (Hi-Nicalon) was examined at 1273–1773 K using mass change measurements, X-ray diffraction (XRD) analysis, Auger electron spectroscopy (AES) analysis, resistivity measurements, scanning electron microscopy (SEM) observation and tensile tests. The fiber properties remained unchanged by heating below 1573 K. In addition to the grain growth of SiC, reduction of resistivity and degradation of strength above 1573 K, mass loss was observed above 1673 K. AES analysis showed carbon film formation on fiber surfaces at high temperature. The carbon film was formed by the following reaction:CO(g) + SiC(s) = SiO(g) + 2C(s)A Tensile strength of 1.83 GPa was retained even after exposure at 1773 K for 10 h, owing to the suppressing effect of the carbon film on the thermal decomposition of SiC _X O _Y phase.     

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.     

原丝浸渍硼酸对炭纤维结构与性能的影响

聚丙烯腈原丝(3K,1.1dtex)用硼酸进行浸渍,再分别进行间歇式预氧化和炭化。借助元素分析、X射线衍射、红外分析和扫描电镜等表征手段和力学性能测试,研究了硼酸浸渍对原丝结构、预氧化炭化过程及炭纤维结构与性能的影响。结果表明,硼能进入到原丝的内部,但只是物理吸附,在浸渍过程中不改变原丝结构,在预氧化过程,硼钝化了纤维的环化、氧化反应,起始温度推迟2.5℃。在炭化过程中,硼促进了纤维结构的有序化和完善,炭纤维的强度和模量都得到了提高。硼质量分数为1.376×10-4,张力为108 g时,炭纤维抗拉强度为2544 MPa,较同等条件未渗硼的提高约90%。