炭基体结构状态对C/C复合材料抗烧蚀性能的影响

碳基体在C／C复合材料的组成中占有很大的比重，因此炭基体不同的结构状态往往对C／C复合材料的各项性能有显著的影响。本文利用不同的原料和加工工艺制备出了三种具有不同炭基体的C／C复合材料，这三种碳基体分别是热解炭，沥青炭以及解热炭－树脂炭混合炭基体。对这三种材料多项性能的测试结果表明，炭基体的结构状态如石墨化度，炭片层结构的取向度的不同对C／C复合材料的各项性能均有显著的影响；基本趋势是C／C材料的石墨化度越高，材料的导电性能，导热性能以及抗烧蚀性能越好，压缩强度越低。三种炭基体中沥青炭基体沿纤维轴向的取向度最低，其抗烧蚀性能最差。     

热解炭结构对C/C复合材料热物理性能影响

炭布叠层为预制体，采用等温CVI工艺制备出炭/炭（C/C）复合材料。通过调节丙烯与氢气的比例得到热解炭结构分别为粗糙层（RL），光滑层（SL），各向同性（ISO）的三种C/C复合材料，研究了热解炭组织结构对C/C复合材料热导率的影响，讨论了C/C复合材料的导热机理。结果表明：RL织构C/C复合材料的热导率无论是在平行方向还是在垂直方向上都明显高于SL和ISO织构C/C复合材料，在两个方向上，RL织构C/C复合材料的最大热导率比SL织构C/C复合材料分别大41.0%和31.7%，是ISO织构C/C复合材料的2倍多，且3种C/C复合材料的热导率随温度的升高呈现不同的变化趋势。     

基体炭种类对C/C复合材料电导率的影响分析

使用炭毡为增强体分别制备了热解炭基、树脂炭基、沥青炭基和热解炭/树脂炭双基体、树脂炭/沥青炭双基体C/C复合材料,比较研究了复合材料的电导率与不同先驱体含量的关系。结果表明,不同前驱体C/C复合材料电导率有较大的差异,热解炭基C/C复合材料的电导率是沥青炭基C/C复合材料和树脂炭基C/C复合材料电导率近3倍,热解炭和沥青炭双基体C/C复合材料的电导率符合简单并联混合法则,树脂炭和沥青炭双基体C/C复合材料的电导率随树脂炭质量分数的增加而减小。     

针刺成型C／C预制体的研究进展

预制体作为C／C复合材料的增强结构,它的发展必定会推动C／C复合材料应用于更广闾的领域。文章综述了针刺成型C／C预制体技术在国内外研究进展,并概述了影响针刺C／C预制体性能的主要因素,包括炭布、网胎以及针刺工艺参数等,并对我国针刺技术的发展提出了一些建议。     

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。     

致密化工艺对C/C复合材料性能的影响

以三种致密化工艺对2D炭布针刺预制体进行致密，得到三组C／C复合材料，对其进行力学、热学性能检测及微观结构分析，并用C／C复合材料抗热震指标对三种致密化工艺所制备试样的性能进行综合评价，考察并比较了不同致密化工艺对C／C复合材料性能的影响。结果表明，采用化学气相沉积、沥青高压浸渍炭化及树脂常压炭化工艺所制备的RLS试样具有较好的综合性能。     

化学气相沉积致密针刺C/C复合材料的结构及力学性能研究

以T300炭纤维无纬布、网胎为原材料,层叠针刺成型炭纤维预制体,并采用化学气相沉积工艺对预制体进行致密,制成密度为1.55 g/cm3的针刺C/C复合材料。对针刺C/C复合材料的微观结构进行了观察分析,并对材料力学性能进行了测试。结果表明:化学气相沉积致密的针刺C/C复合材料呈现出以层间大量垂直纤维束为节点的类钉板状网状结构,这种特殊结构使材料层间结合更好,材料整个结构更加紧密;针刺C/C复合材料内部纤维被沉积形成的热解炭所包裹,热解炭的织构类型为光滑层(SL)和粗糙层(RL)并存;针刺C/C复合材料的各项力学性能均达到了较高水平,并且高温力学性能比常温力学性能有了很大幅度的提高。     

C/C复合材料CVI致密化过程及影响因素研究进展

综述了C/C复合材料CvI致密化过程中,气相反应、表面反应和扩散共同作用控制热解炭沉积的特点;讨论了沉积温度、气体压力、碳源气体种类、滞留时间、预制体等因素的影响.     

多晶硅炉热场用C/C复合材料的硅化腐蚀失效机理

以2D叠层炭布为增强体的炭/炭（C/C）复合材料作为多晶硅炉用热场盖板,对其在硅液/硅蒸汽共同作用下的硅化腐蚀失效机理进行了研究。通过多功能密度测试仪、扫描电子显微镜（SEM）和X射线衍射仪（XRD）分析了硅化作用对C/C复合材料致密度、微观结构及物相组成的影响,并对侵蚀后的C/C复合材料失效机理进行了分析。结果表明：硅化侵蚀后的C/C复合材料致密度高,存在大量的Si元素,生成了大量的β-SiC,且微观缺陷较多,层间开裂严重,呈现脆性断裂模式。理论分析发现,高温下单位摩尔质量的热解炭和单位摩尔质量的硅发生反应生成单位摩尔质量的SiC后,总体积膨胀约为单位摩尔热解炭体积的6.3倍,不同物相间的热失配导致热应力集中,引起C/C复合材料变形开裂失效,裂纹产生的扩散通道加剧了硅液/硅蒸汽对C/C复合材料的硅化侵蚀作用。     

化学气相渗（CVI）C／SiC复合材料性能控制

本研究用化学气相渗技术制备了四种Ｃ／ＳｉＣ复合材料：在ＣＨ３ＳｉＣｌ３＋Ｈ２（普通）＋Ａｒ（高纯）系统中制各了两种材料：材料Ａ为１Ｋ炭布层叠无热解炭界面层，材料Ｂ为１Ｋ炭布层叠有热解炭界面层；在ＣＨ３ＳｉＣｌ３＋Ｈ２（高纯）＋Ａｒ（高纯）系统中制备了另两种材料：材料Ｃ和材料Ｄ分别为１Ｋ、Ｔ３００炭布层叠有热解炭界面层．分别对其中每两种材料进行了相互比较，研究了骨架纤维、界面层及基体对整个复合材料性能的影响；通过控制上述三方面因素可以对Ｃ／ＳｉＣ复合材料的总体结构进行设计从而控制其材料最终性能。     

C/C多孔体对C/C-SiC复合材料微观结构和弯曲性能的影响

以4种纤维含量相同(32%,体积分数,下同),用化学气相渗透(chemical vapor infiltration,CVI)法制备了4种密度的碳纤维增强碳(carbon fiber reinforced carbon,C/C)多孔体,基体炭含量约20%～50%.利用液相渗硅法(liquid silicon infiltration,LSI)制备了C/C-SiC复合材料,研究了C/C多孔体对所制备的C/C-SiC复合材料微观结构和弯曲性能的影响.结果表明:不同密度的C/C多孔体反应渗硅后,复合材料的物相组成均为SiC,C及单质Si;随着C/C多孔体中基体炭含量的增加,C/C-SiC复合材料中SiC含量逐渐减少而热解炭含量逐渐增加.C/C-SiC复合材料弯曲强度随着材料中残留热解炭含量增加而逐渐增加,热解炭含量为约42%的C/C多孔体所制备的C/C-SiC复合材料的弯曲强度最大,达到320 MPa.     

预制体孔隙结构对炭/炭复合材料ICVI制备工艺的影响

研究了预制体孔隙结构对ICVI工艺致密化过程及基体热解炭微观结构的影响。结果表明：2D针刺炭毡致密化速度高于炭布叠层预制体，1K炭布叠层预制体的致密化速度高于3K炭布叠层；在致密化过程中，热解炭均匀沉积在纤维表面，预制体AS／VR比值变化是导致热解炭微观结构发生改变的根本原因。     

Densification rate and mechanical properties of carbon/carbon composites with layer-designed preform

In this work, carbon fiber needle-punching preforms were designed into two structure according to the density change along the thickness direction. One structure is designed to two layers with low-density layer and high-density layer, and the other is to three layers with low-density exterior layer and high-density interior layer. Then the effect of the preform with different structure on the densification rate and compressive properties of C/C composites was investigated. The results show that both two designed preforms can effectively avoid surface blocking, and lead to the faster densification rate of C/C composites during the chemical vapor infiltration processes. These results are attributable to the change of pore size distribution and pyrocarbon thickness, which was caused by fiber architecture designs. Meanwhile, these structural changes can improve the compressive strength of C/C composites, especially for the three-layer preforms. When the density of preforms is 0.45?g/cm³, C/C composites with three-layer preform has the highest compressive strength. The damage of most C/C composites with two and three-layer preforms is caused by shear or delamination failure, while that of C/C composites with common preforms usually caused by matrix collapse. Cracks in C/C composites with two and three-layer preforms always happened on the low-density layer, and consequently ceased or changed propagation direction in the interface between two layers.     

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     

C/C刹车盘制备工艺的研究

选择整体针刺毡为预制体,致密化工艺采用气相沉积(CVD),以天然气和丙烷的混合气体为原料,制备C/C刹车盘。其热解炭以粗糙体为主,摩擦曲线平稳,没有湿态衰减,沉积时间短。     

The catalytic effect of boric acid on polyacrylonitrile-based carbon fibers and the thermal conductivity of carbon/carbon composites produced from them

The catalytic effect of boric acid on the graphitization and surface structure of polyacrylonitrile-based carbon fibers was investigated by dipping fibers in boric acid before heating at 2500 °C. The thermal conductivity of carbon/carbon composites produced from the modified carbon performs by chemical vapor infiltration was also studied. The results show that the treatment by boric acid has a catalytic-graphitization effect on the fibers that increases the crystallinity and changes the surface state of carbon fibers during high temperature treatment. The modified carbon fibers induce the deposition of pyrocarbon with high crystallinity and an obvious transition interface between the carbon fiber and pyrocarbon during chemical vapor infiltration. By changing the microscopic structure of the carbon fibers, the interface bonding between fibers and pyrocarbon is improved and the microstructure of pyrocarbon is regulated. The thermal conductivity of the carbon/carbon composites is therefore improved, especially that in the direction perpendicular to fiber axis.     

B4C／C复合材料高温氧化过程中的结构变化模型的研究

在用混合磨碎法制备Ｂ４Ｃ／Ｃ复合材料的基础上,考察了不同条件对复合材料氧化失重速率的影响,然后讨论了上述各因素对复合材料抗氧化性能的影响机制,并对复合材料结构与其自愈合功能的性进行了分析,在此基础上建立了复合材料高温氧化过程的结构变化模型。     

Preparation of in situ grown silicon carbide nanofibers radially onto carbon fibers and their effects on the microstructure and flexural properties of carbon/carbon composites

Silicon carbide nanofibers (SiCNFs) used as the second reinforcements of carbon/carbon composites were grown radially on the carbon fiber surface. The microstructure of SiCNFs and their effects on the microstructure and flexural properties of C/C composites were investigated. Results show that there are many defects such as twin crystals and stacking faults in SiCNFs which were grown by catalytic chemical vapor deposition. During the same process, the skin region of carbon fiber has changed. Several SiC layers are formed and the arrangement of the graphite layers around SiC layers is more orderly. In the next chemical vapor infiltration, due to the induction of SiCNFs, the middle textural pyrocarbon were formed firstly and then is the high textural pyrocarbon. The existence of SiCNFs also contributes to the three-phase interface between pyrocarbon, SiCNFs and carbon fibers, resulting in a good bond between carbon fiber and matrix. Those structural changes lead the better flexural properties of SiCNF–C/C composites compared with C/C composites.