炭／炭复合材料界面海微观结构的研究

炭纤维增强炭基（炭／炭）复合材料中的界面结构直接影响着炭／炭材料的力学、热物理等各种性能。采用ＳＥＭ、ＴＥＭ等微观观察手段,新几种炭／炭复合材料界面的微观结构进行考察。对观察到炭纤维与基体炭间的界面、同一纤维束中两根纤维间的界面,基体与其他外加物质间的界面、不同取向炭纤维间界面、不同基体前驱体层间的界面等界面类型的细微结构进行了图示分析与讨论。     

热解炭微观结构对炭/炭复合材料力学性能的影响

以PAN基针刺纤维毡为基体,采用等温化学气相渗透技术,在温度1000℃、压力5.0~20.0 kPa条件下制备了2种具有不同微观结构热解炭的炭/炭复合材料,研究了其力学性能与热解炭微观结构的关系. 结果表明,压力8.0 kPa下得到的具有单一低织构热解炭的炭/炭复合材料的断裂强度较高,为86±3 MPa,热解炭与炭纤维间界面结合紧密,加载过程中二者同时断裂,呈现明显的脆性断裂行为;压力10.0~20.0 kPa下得到的具有中织构-高织构-中织构热解炭的炭/炭复合材料的断裂强度稍低,为82±4 MPa,加载过程中材料内部不同织构热解炭间多层次界面通过改变裂纹扩展路径而延缓其扩展速度,断口形貌呈现锯齿状,表现出假塑性断裂特征.     

炭/炭复合材料组分微观结构及热处理研究进展

炭/炭复合材料组分的微观结构具有多样性.不同前驱体的炭纤维的微观结构不同,PAN基炭纤维的结构最精细,有基本炭网面、微原纤、微纤和条带结构共四级结构单元,高温热处理将使微原纤结构消失从而变成三级结构:基本炭网面、微纤和条带结构;沥青基炭纤维中大致有三级结构单元:微域、域和织构;基体材料无论是热解炭还是沥青炭,都有三级结构,基本结构单元(BSU)、小区域分子取向(LMO)、织构;基体/纤维界面的结构很复杂,具有过渡性,界面结构不但有梯度变化,也有织构突变,基体/纤维界面应力同样会影响纤维的表面和内部结构,这种结构变化在高温热处理后更加明显.     

热处理温度对炭/炭复合材料性能的影响

对同一种炭／炭复合材料，经过不同温度热处理后的微观结构、石墨化度、导热系数、抗弯强度和摩擦磨损性能进行了对比研究。试验表明：随着最终热处理温度的提高，易石墨化的热解炭偏振光下光学活性增强，而难石墨化的热解炭微观结构几乎没有变化；炭／炭复合材料的晶粒逐渐长大，层面间距缩小，石墨化度有较大提高；平行炭布方向的导热系数和垂直炭布方向的导热系数均有上升。同时，由于基体炭与炭纤维两者热膨胀系数的差别，热处理温度的提高，降低了基体与增强纤维的的结合强度，使炭／炭复合材料的抗弯强度降低。试验还表明：随着热处理温度的提高，炭／炭复合材料的摩擦表面逐渐形成薄而致密的自润滑膜，摩擦系数在经过一个峰值后趋于平稳状态，磨损量下降明显。经l800℃热处理的质量损失主要是由氧化造成的。     

结构炭/炭复合材料力学性能及微观结构研究

采用四向编织、快速化学气相渗透致密化新工艺制备了炭／炭复合材料,其弯曲强度达３２０ＭＰａ。分析研究了这种材料的力学性能特征。利用ＳＥＭ和高分辨ＴＥＭ分析了基体炭、炭纤维／基体灰界面的精细结构,发现炭纤维呈单根被基体炭包围,基体现灰呈层片状,为二维有序的乱层石墨结构;在炭纤维与基体炭之间存在着过渡相,这一过渡相厚度的约几十纳米,随着与炭纤维之间距离的增大,它们之间形成的夹角由小变大,这一过渡相即为炭     

炭纤维表面特性对炭/炭复合材料力学性能的影响

分别以含有原始上浆剂的聚丙烯腈基炭纤维及其经过高温除胶处理的炭纤维为增强体,通过沥青浸渍、炭化和高温热处理方法获得了炭/炭复合材料,对获得的复合材料中基体炭的结构和材料的力学性能进行了分析。含有原始上浆剂的炭纤维表面含有较多含氧官能团,易与基体炭形成较强结合的界面,基体炭取向受到限制,在纤维轴向呈竹节状断裂,承载过程中基体炭对炭纤维协同承载作用弱,复合材料表现出了较弱的力学性能。经过高温除胶处理的炭纤维表面几乎没有含氧官能团,易于与基体炭形成弱结合界面,基体炭取向受到的约束小,可围绕炭纤维形成"类同心圆"结构。这种状态下形成的基体炭在纤维轴向连续性较好,复合材料的力学性能较高。     

炭/炭复合材料的热物理性能

综述了炭／炭复合材料的热物理性能及其影响因素。炭／炭复合材料热导率的大小由炭纤维的类型、取向、体积分数以及基体的结构类型决定，热处理工艺也对它有很大的影响。炭／炭复合材料的热导率随温度升高一般先升高后降低。炭／炭复合材料在低温时具有负热膨胀系数，影响其这一性能的因素除了坯体结构和基体     

不同炭基体对炭/炭复合材料力学性能的影响

结合化学气相沉积（CVD）和前驱体浸渍裂解工艺,分别以丙烯、糠酮树脂和煤沥青为前驱体制备了密度在1.85g/cm3以上的三维炭/炭（C/C）复合材料,对比研究了沥青炭、热解炭+沥青炭以及热解炭+树脂炭结构（分别为A、B、C组）的等三种不同炭基体C/C复合材料的增密效率与力学性能,采用排水法表征C/C复合材料的孔隙率及密度,利用扫描电镜进行炭基体的微观结构表征,采用万用电子力学试验机进行拉伸强度、压缩强度、剪切强度等力学性能表征。结果表明,在热解炭质量含量相同的前提下,树脂浸渍裂解增密速率低于沥青浸渍裂解工艺,树脂炭基体孔隙率低于沥青炭基体。不同炭基体结构的C/C复合材料力学性能次序为：热解炭+树脂炭双元炭基体最高,纯沥青炭基体次之,热解炭+沥青炭双元炭基体最低,分析原因为热解炭与树脂炭双元炭基体的界面结合强度高,而沥青炭为混乱无序碳结构,热解炭和沥青炭双元炭基体界面结合强度弱,因此力学强度最低。     

基于RPM的炭/炭复合材料人工骨预制体成型技术研究

炭／炭复合材料是一种新型的炭纤维增强的以炭为基体的高性能复合材料，其增强相和基体都由碳元素构成，不仅具有炭材料固有的生物相容性，而且还具有纤维增强复合材料的高强度与高韧性，对其应用于人体组织材料进行了广泛的研究。通过应用RPM技术及快速模具，解决了复杂形状炭／炭复合材料难成型的问题，并对其在生物领域的应用进行了展望。     

固体火箭发动机炭/炭复合材料喉衬烧蚀行为研究

从固体火箭发动机炭/炭复合材料喉衬烧蚀后的形貌和结构特性出发,采用扫描电子显微镜、高分辨透射电子显微镜、元素分析仪等表征分析了炭/炭复合材料烧蚀后的微观结构形貌、纤维损伤程度、纤维和基体的界面结合状态、沉积粒子含量以及喉衬密度等,探究了烧蚀温度、压力及推进剂种类等因素对炭/炭复合材料烧蚀后微观结构的影响,并结合材料的构...     

化学气相渗C／SiC材料结构与性能的研究

采用碳布层叠然后用化学气相渗方法制备了Ｃ／ＳｉＣ复合材料，这种材料纤维与基体间的界面是决策材料力学行为的重要因素，带有热解碳作为界面层的Ｃ／ＳｉＣ材料，在断裂进表现出大范围的脱粘，纤维与周围的基体不同发生断裂，有大量的纤维拨出，断口类似毛刷，无界央层材料表现为脆性平面断口，裂纹直接通过纤维和基体向前扩展，没有发生脱粘。     

纤维含量对C／C复合材料力学性能的影响

研究了炭纤维含量对C/C复合材料力学性能的影响,用扫描电镜（SEM）对材料的断口进行分析,结果表明：当炭纤维的体积分数小于8.3%时,随着炭纤维体积分数的增加,复合材料的抗折强度逐渐升高;之后,随着炭纤维的体积分数的增加,复合材料的抗折强度逐渐下降,短纤维增强C/C复合材料的断口特征为大量纤维拔出,其断裂过程为界面破坏所控制。     

Effect of the fabrication process on the microstructural evolution of carbon fibers and flexural property on C/SiC composites by the NITE method

Nano-infiltration and transient eutectic phase (NITE) SiC matrix composites are designed for application in aerospace propulsion systems, particularly in fasteners and thrusters. A variety of carbon fibers with different properties have been selected as reinforcements for SiC matrix composites. Carbon fibers are known to be stable at high temperatures; however, the effects of high applied pressure at high temperatures on the fiber microstructure evolution and mechanical properties are not well-known. As a scoping study for fabricating NITE C/SiC composites, the behaviors of various carbon fibers in SiC composites. Pitch-based fibers, namely, GRANOX XN-05 and YS-90A, and a polyacrylonitrile-based fiber, namely, TORAYCA T-300B, were selected for matrix reinforcement. The 3-point bending test results indicated pseudo-ductile behaviors in the cases of YS-90A and T-300B fiber reinforcements. Fracture resistance evaluation based on the single-notch bending test indicated that the YS-90A fiber reinforced composite afforded the highest fracture resistance among the three C/SiC composites. The microstructure evolution on YS-90A and T-300B fibers was limited to near the fiber surface. Therefore, YS-90A and T-300B carbon fibers are potential candidates for reinforcement in NITE C/SiC composites.     

THE INFLUENCE OF OXIDATION OF THE FIBERS ON THE TRIBOLOGICAL PROPERTIES OF CARBON FIBER-REINFORCED NYLON COMPOSITES

Three-dimensional braided carbon fiber-reinforced nylon composites (C_3D/MCN) were prepared in order to investigate the influence of oxidation of carbon fibers on the tribological properties of the C_3D/MCN composites. Friction and wear tests of the C_3D/MCN composites with untreated and treated carbon fabric were conducted. The characteristics of the carbon fiber, the interface strength, the hardness, and the worn surface morphologies of the C_3D/MCN composites were analyzed. The results show that the specific surface area of treated carbon fiber was far higher than that of untreated carbon fiber and there formed a functional group of –C=O on the carbon fiber surface after air oxidation. The oxidation of the carbon fibers improved the interface strength between the carbon fibers and the matrix and had little effect on the hardness of the composites. The friction coefficient and wear rate of C_3D/MCN composites with oxidized carbon fibers were apparently lower than those with untreated carbon fibers. In conclusion, the oxidation of the fibers showed good effects on the improvement of the interface strength and the tribological properties of the composites.     

搅拌法制备C/Al复合材料的界面问题

在碳纤维表面镀上一层金属铜镀层,用硼酸对其进行防氧化处理,采用机械搅拌法制取C/Al复合材料。利用扫描电镜、能谱分析和X射线衍射等手段对液态机械搅拌法制备的碳纤维增强铝基复合材料的界面微观结构进行了分析,结果表明,碳纤维表面镀铜,既可有效解决碳纤维与铝的润湿性问题,又可有效地阻挡碳纤维与铝的过度化学反应。硼酸作为保护剂,有效地解决了高温复合时镀铜层的氧化难题。Cu/Al界面生成大量的CuAl₂金属间化合物,C-Cu/Al界面为混合界面：C/Cu界面和C/Al界面。     

Ablation of the carbon/carbon composite nozzle-throats in a small solid rocket motor

Ablation of needled carbon/carbon (C/C) composite nozzle-throats was studied by hot-fire testing in a small solid rocket motor. The composition of the combustion gases was estimated by principle of free energy minimum. The ablation morphology was investigated by scanning electron microscopy. The ablation mechanism of C/C composites was also studied. The results showed that the ablation performance of C/C composites was determined by mechanical breakage of fibers/matrix together with thermal chemical ablation from the heterogeneous reactions on the throat surface. The mechanical breakage of fibers/matrix dominated the ablation of the composites at high pressure based on the calculated ablation rate. Cone-shaped fibers were formed after ablation in high fiber density area; but in low fiber density area, the fibers were peeled off because of the weakened strength after ablation. Meanwhile, the matrix around the fiber bundles was ablated into a shell shape, while the matrix between the cone-shaped fibers might be blown away by the combustion gases. Oxidation of C/C composites led to the formation of the cone-shaped fibers and shell-shaped matrix, as well as the loss of matrix between the cone-shaped fibers. The fiber/matrix fragments on the ablation surface were caused by the mechanical breakage.     

THE INFLUENCE OF OXIDATION OF THE FIBERS ON THE TRIBOLOGICAL PROPERTIES OF CARBON FIBER-REINFORCED NYLON COMPOSITES

Three-dimensional braided carbon fiber-reinforced nylon composites (C_3D/MCN) were prepared in order to investigate the influence of oxidation of carbon fibers on the tribological properties of the C_3D/MCN composites. Friction and wear tests of the C_3D/MCN composites with untreated and treated carbon fabric were conducted. The characteristics of the carbon fiber, the interface strength, the hardness, and the worn surface morphologies of the C_3D/MCN composites were analyzed. The results show that the specific surface area of treated carbon fiber was far higher than that of untreated carbon fiber and there formed a functional group of -C=O on the carbon fiber surface after air oxidation. The oxidation of the carbon fibers improved the interface strength between the carbon fibers and the matrix and had little effect on the hardness of the composites. The friction coefficient and wear rate of C_3D/MCN composites with oxidized carbon fibers were apparently lower than those with untreated carbon fibers. In conclusion, the oxidation of the fibers showed good effects on the improvement of the interface strength and the tribological properties of the composites.     

针刺C/C复合材料拉伸性能和韧性的研究进展

综述了近年来国内外针刺C／C复合材料拉伸性能和韧性研究进展,归纳了影响针刺C／C复合材料拉伸性能和韧性的主要因素,即炭纤维、炭基体、界面和针刺工艺参数等,初步得到了提高材料拉伸性能和韧性的方法：提高针刺C／C材料拉伸性能的方法主要是提高纤维体积分数;提高针刺C／C材料韧性的方法主要是改善致密工艺。在此基础上,对未来的进一步研究进行展望。     

轴棒法C／C复合材料微观结构及性能分析

采用轴棒法4D预制体、煤沥青为前驱体,经过常压、高压相结合的液相浸渍一炭化的致密工艺,制备出高密度轴棒法C／C复合材料。研究了轴棒法C／C复合材料的微观结构及其对轴向室温、高温（2800℃）拉伸破坏形式的影响。结果表明：轴棒法C／C复合材料轴向增强体采用炭棒,出现了一个特殊的界面,即炭棒与基体的“间隙”,主要原因是炭棒内部结合较强和纤维、基体的热膨胀系数不匹配而引起的;间隙的存在,使得轴棒法C／C复合材料的轴向室温、高温拉伸破坏形式出现较大差异,室温拉伸由于界面结合强度弱而引起的炭棒完整的拔出,未起到纤维应有的增强作用;高温拉伸却由于受热膨胀,间隙愈合,界面结合变强,试样从有效部位断裂,纤维增强作用明显提高。     

涂层工艺对C/C复合材料结构和弯曲性能的影响

采用热处理和包埋工艺制备了Ｃ／Ｃ复合材料的ＭｏＳｉ２／ＳｉＣ抗氧化涂层,对组织结构、界面、弯曲断口进行了显微观察,分析了氧化保护涂层及其工艺对其机械性能的影响,结果表明,该工艺在Ｃ／Ｃ复合材料表面生成涂层的同时,使基材内部的界面也被硅化;并且发现,热解炭基体比炭纤维更易与Ｓｉ反应生成ＳｉＣ。Ｃ／Ｃ复合材料经涂层工艺处理后,弯曲强度降低;热处理过程中发生的材料氧化是弯曲强度下降的主要原因