C/C多孔体热处理温度对C/C-SiC复合材料微观结构和热学性能的影响

以针刺网胎无纬布为预制体,采用化学气相渗透(CVI)、压力浸渍树脂/炭化(PIC)及反应熔体浸渗法(RMI)等组合工艺快速制备C/C-SiC复合材料。研究了C/C多孔体的高温热处理温度对C/C-SiC复合材料微观结构和热学性能的影响,结果表明:多孔体经高温热处理后密度有所减小而孔隙率增大;相较于1800℃热处理,多孔体经2200℃热处理后制备的C/C-SiC复合材料密度更大(ρ=2.12g/cm3),孔隙率更低(η=2.7%),SiC基体含量更高(ω=41.11%);C/C-SiC复合材料的比热容和平均热膨胀系数随着温度的升高而增大,而热扩散系数和导热系数随着温度的升高不断减小;多孔体经2200℃热处理后制备的C/C-SiC复合材料X-Y向具有更大的导热系数和更小的热膨胀系数,其室温下的导热系数为83.120W/(m·K),室温~1000℃的平均热膨胀系数为1.608×10-6/℃。     

三维针刺CFRP复合材料的制备及显微结构研究

以三维针刺碳毡作为预制体,采用树脂浸渍-热压固化工艺快速制备了碳纤维增强树脂基复合材料(CFRP)。通过光学和扫描电子显微镜观察了材料的显微结构,使用阿基米德方法测定材料的密度和气孔率,并利用压汞仪分析了材料的孔隙分布。结果表明,树脂浸渍-热压固化是一种理想的制备CFRP复合材料的方法,制备出的材料密度可达1.45 g/cm3,孔隙率仅为3%,且孔隙主要为由热应力引起的纤维束内贯穿裂纹和基体-纤维界面脱粘两类。     

C/SiC-MoSi2复合材料微结构和力学行为研究

以三维针刺碳毡作为预制体,先采用树脂单向加压浸渍-热解工艺制备出C/C多孔体,然后采用反应熔体浸渗法将Si-Mo合金浸渗到C/C多孔体中制备C/SiC-MoSi2复合材料.对C/SiC-MoSi2复合材料的物相组成、显微结构以及力学性能进行了研究.结果表明,该复合材料由C、SiC、MoSi2和Si组成;生成的SiC和M...     

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。     

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.     

高温热处理对C/C复合刹车材料摩擦磨损性能影响的研究

分析讨论了高温热处理温度对C/C复合刹车材料石墨化度及摩擦磨损性能的影响规律。研究表明:通过化学气相沉积法制备的C/C复合刹车材料热解碳结构与最终热处理温度无关,均呈现典型的粗糙型结构;从裂解态至2600℃热处理状态,C/C复合刹车材料石墨化度由7.3%提升至67.2%,对应综合导热系数由11.3 W·m~(-1)·k~(-1)增加至50.1 W·m~(-1)·k~(-1);材料摩擦系数随着刹车压力、单位面积能载和速度的升高呈现出逐渐降低的趋势,且相同条件下,石墨化度越高,摩擦系数及磨损率越高。     

C/C多孔体的制备及其对C/C-SiC-Si复合材料的影响

C／C—SiC—Si材料是一种新型的复合材料。本文通过反应熔渗法将液态硅渗入C／C多孔体中得到致密的C／C—SiC—Si复合材料。重点研究了制备C／C多孔体的树脂浸渍裂解法，并测定了在不同浸渍次数下得到的不同的C／C多孔体的体积密度和气孔率，用扫描电镜观察了其形貌，讨论了不同的C／C多孔体对C／C—SiC—Si复合材料最终形貌的影响。     

针刺炭纤维预制体结构单元对C/C复合材料性能的影响

采用6K炭纤维无纬布/网胎交替叠层及12K炭纤维无纬布/网胎交替叠层,在针刺工艺,致密化、热处理工艺完全相同的情况下,制备了密度为1.8g/cm3的热解炭/树脂炭双元基体的两种C/C复合材料产品,考察了针刺预制体结构单元对C/C复合材料性能的影响.结果表明,两种C/C复合材料的热学（垂直方向导热系数）、电学性能及石墨化度基本相当;而针刺6K炭纤维无纬布/网胎预制体C/C复合材料的拉伸、弯曲、压缩、层间剪切强度分别为127MPa,189MPa,263MPa,24.6MPa;其平行方向导热系数为54.6W/m＆#183;K,比常规针刺12K炭纤维无纬布/网胎预制体C/C复合材料相应提高了38％,32.2％,32.8％,38.9％,21％,彰显了细化针刺预制体结构单元对C/C复合材料力学性能的显著影响.     

致密工艺对C/C复合材料摩擦性能的影响

采用针刺全炭纤维网胎无纬布整体结构预制体为骨架，经化学气相沉积（CVD）、树脂浸溃（RD固化致密及炭化、石墨化制得C／C复合材料。研究了粗糙层（RL）和树脂炭（RC）对摩擦性能的影响。结果表明，RL结构的C／C复合材料的摩擦性能较好，稳定性较高，是用作飞机刹车材料的前提；采用CVD＋RI制备且石墨化后的C／C复合材料具有优良的摩擦磨损特性；CVD试样的密度较低时，摩擦系数较高，但磨损较大，较难形成完整的摩擦膜。     

炭化压力对编织C/C复合材料致密过程及结构的影响

通过浸渍/高压炭化工艺在不同炭化压力下制备了高温煤沥青炭块及沥青基炭/炭（C/C）复合材料,并研究了不同炭化压力环境下对其密度和孔隙的影响.结果表明,随着炭化压力增大,沥青炭体积密度明显增加,孔隙填充效果明显改善;在编织C/C材料的致密过程中,压力越大其孔隙越小,分布越均匀,故产品致密效果越好.     

Microstructure and elastic properties of individual components of C/C composites

Carbon fiber reinforced carbon matrix (C/C) composites are often used for structural and frictional applications at a wide range of temperatures due to their excellent mechanical and thermal properties. Tailoring of mechanical properties through optimization of microstructure is critical for achieving maximum composite performance. This article addresses the evolution of the fiber and matrix microstructure and related nano-mechanical properties in two different C/C composites after being subjected to heat treatment at temperatures between 1800 and 2400 °C. Microstructure and corresponding nano-mechanical properties of C/C composites were studied using Polarized Light Microscopy (PLM), High-Resolution Transmission Electron Microscopy (HRTEM) and nanoindentation techniques. Increased heat treatment temperature (HTT) led to formation of a better-organized microstructure of fiber and matrix and also to formation of thermal cracks. The elastic modulus of rough laminar CVI pyrocarbon decreased from 18 to 12 GPa with increased HTT. In contrast, the isotropic CVI pyrocarbon and charred resin matrix displayed only a slight change of elastic modulus. The elastic modulus of PAN fiber increased from 18 to 34 GPa, indicating the development of a better-organized microstructure in the fiber-axial direction.     

炭/炭复合材料用浸渍剂残炭率研究

研究了两种炭/炭复合材料液相致密用高效、安全的浸渍剂.一种为混合树脂体系,即氨酚醛树脂与树脂B混合且不添加其他任何固化剂;一种为利用新型固化剂C取代磷酸作为糠酮树脂的固化剂.结果表明,混合树脂与纯氨酚醛树脂浸渍剂相比较,其残炭率提高约10％;当混合树脂体系中树脂B的质量分数为30％～50％时,具有较好的残炭率;新型固化剂C作为糠酮树脂固化剂时,其残炭率与磷酸作为固化剂时相当,且安全性更高,具有取代磷酸作为糠酮树脂固化剂的可能性.     

The effect of heat treatment on tensile properties of 2D C/SiC composites

Two-dimensional (2D) carbon fiber reinforced silicon carbide (C/SiC) composites with different initial strength were prepared by chemical vapor infiltration (CVI). After tensile property testing, results exhibited that as the heat-treatment temperature (HTT) increases to 1900°C, the tensile strength and toughness of the low strength specimen (LSS) increased by 110% and 530%, while the high strength specimen (HSS) increased by 5.4% and 550%, respectively. As observed from morphologies, the heat treatment increases the graphitization of the amorphous PyC interphase, which leads to the weakening of interfacial bonding strength (IBS). Meanwhile, the defects arising from heat treatment cause thermal residual stress relaxation. Therefore, the tensile strength and toughness of LSS with relatively high initial IBS increase significantly as HTT increases. For HSS with moderate initial IBS, the heat treatment slightly improves the tensile strength, but significantly improves the toughness. Consequently, the post-heat-treatment tensile properties of 2D C/SiC composites can be regulated by varying HTTs and different initial strength.     

Effect of preform and carbon matrix on bending strength of Cf/Cu/C composites

Aiming to obtain composites with appropriate mechanical properties for pantograph sliders, copper mesh modified carbon/carbon (C_f/Cu/C) composites were prepared by chemical vapor infiltration (CVI) in C₃H₆ +?N₂ atmosphere and impregnation-carbonization (I-C) with furan resin. In this paper, C_f/Cu/C composites with two kinds of preforms and carbon matrixes were obtained. The effect of preforms and carbon matrixes on bending strength was investigated. The results indicated that the bending strength of carbon fiber/copper mesh reinforced pyrolytic carbon matrix composites was about 181.39–195.43?MPa, while that reinforced resin carbon matrix composites had the worst bending strength around 54.45–57.04?MPa, in terms of the same preform. The bending strength of C_f/Cu/C composites in the parallel orientation and vertical orientation were also similar. As for C_f/Cu/C composites with the same carbon matrix, the bending strength of C_f/Cu/C composites with non-woven fiber/fiber web/copper mesh type preform was higher than that with fiber web/copper mesh type preform. However, the bending strength of carbon fiber/copper mesh reinforced resin carbon matrix composites showed the opposite trend, and its reasons were analyzed and discussed taking advantage of the fracture mechanisms.     

空间望远镜用C/SiC镜面研制综述

综述了空间望远镜的主镜用高强度、高表面精度、低热膨胀系数的低温（约4K）用镜面的制备和检测过程.日本将Φ710mm的高强度反应烧结SiC材料已用于红外望远镜镜面.在短切炭纤维增强C/C复合材料毛坯的基础上进行液相硅渗透（LSI）而制备的C/SiC复合材料在光学镜面方面具有更大的优势.通过提高C/C复合材料毛坯中沥青基炭纤维体积分数及控制硅化速度,可有效地提高LSI-C/SiC复合材料的机械性能和表面光学精度;通过不同规格的炭纤维的混杂化,可使C/SiC复合材料热膨胀系数的各向异性降低至小于4％的差异.SiC、Si-SiC浆料涂层处理可有效地提高表面精度至2 nm rms的极高要求.     

轴棒法C／C复合材料室温及高温拉伸性能研究

研究了轴棒法C／C复合材料在室温及高温下的轴向拉伸性能,并用扫描电镜观察了高温拉伸试样的断口形貌。结果表明,轴棒法C／C复合材料在室温及高温下的断裂模式不同,且高温下的拉伸强度高于室温下的拉伸强度;以常压炭化结束的C／C复合材料开孔率变大,室温及高温下的拉伸强度小于以高压炭化结束的C／C复合材料。     

加压焙烧法制备短纤维增强C/C复合材料

采用加压焙烧工艺制备了短纤维增强C／C复合材料，研究了基体材料配比及纤维含量对其力学性能的影响，结果发现，基体材料中粘接剂沥青的最佳含量为30w%，当炭纤维含量小于8．3vol%时，随着炭纤维含量的增加，复合材料的抗折强度逐渐升高，之后，随着炭纤维的体积含量的增加，复合材料的抗折强度有所下降。     

Electrical properties of C/C and C/C-SiC ceramic fibre composites

The electrical properties of carbon/carbon (C/C) and carbon/carbon-silicon carbide (C/C-SiC) ceramic composites were measured. The results show that the capacitance decreases rapidly with an increase in frequency and it becomes constant above a frequency of 500 kHz, whereas the dissipation factor increases with increasing frequency. C/C-SiC composites give higher value than C/C composites due to the presence of microcracks.     

Comparative study of interphase evolution in polysiloxane resin-derived matrix containing carbon micro and nanofibers during thermal treatment

The work presents the results of research on composite materials made of silicon-containing polymer-derived ceramic matrix composites (PDC-Cs) and nanocomposites (PDC-NCs). Carbon micro and nanofibers (CFs and CNFs) were used as reinforcements. The interactions between carbon micro and nanofibers and polysiloxane matrix, as well as interphase evolution mechanism in composite samples during their heating to 1000 °C were studied. CF/resin and CNF/resin composites were prepared via liquid precursor infiltration process of unidirectionally aligned fibers. After heating to 700 °C–800 °C, decomposition of the resin in the presence of CNFs led to the formation of fiber/organic-inorganic composites with pseudo-plastic properties and improved oxidation resistance compared to as-prepared fiber/resin composites. The most favourable mechanical properties and oxidation resistance were obtained for composites and nanocomposites containing the maximum amount of carbon nanoparticles precipitated in the SiOC matrix during the heat treatment at 800 °C. The precipitated carbon phase improves fiber/matrix adhesion of composites.