高温热处理对炭 /炭复合材料湿态摩擦性能的影响

研究了高温热处理工艺对快速定向扩散化学气相渗透炭／炭复合材料在湿态下的摩擦磨损性能的影响。实验选择了4种不同的高温热处理工艺，用于比较其对炭／炭复合材料微观结构及湿态下的摩擦磨损性能的影响。分析结果表明湿度对炭／炭复合材料的摩擦性能有显著的影响，在湿态下它的摩擦系数明显低于正常干态下的摩擦系数并且随着刹车压力和刹车惯量的增加下降得更快；高温热处理工艺对炭／炭复合材料微观结构有显著影响，通过改变炭／炭复合材料微观结构，适当的高温热处理工艺可以改善湿态下炭／炭复合材料摩擦磨损性能。结果表明，最适合的热处理温度为2000℃，在2000℃下热处理的炭／炭复合材料有足够的摩擦系数，并且湿度对其摩擦磨损性能影响较其他3种热处理工艺的炭／炭复合材料小。     

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。     

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     

炭纳米纤维添加剂对炭/炭复合材料力学性能影响

采用等温CVI工艺制备出5种不同炭纳米纤维含量（质量分数分别为0，5％，10％，15％和20％）的炭／炭复合材料。发现添加炭纳米纤维的炭／炭复合材料具有很高的力学性能，在加入炭纳米纤维为5％时，相对于没有添加炭纳米纤维的炭／炭复合材料，弯曲强度增大了76．3％，弹性模量增大了55．5％，但添加量增大到20％时，强度和模量都逐渐降低。     

预制体结构对炭／炭复合材料力学性能影响

四种用于制备炭／炭（C／C）复合材料的预制体，即1K发布叠层坯体（1#坯体），3K发布叠层坯体（4#坯体），发市 炭纸叠层坯体（2#坯体），特殊炭毡 发布叠层坯体（3#坯本），并探索了预制体结构对C／C复合材料力学性能影响．研究表明：用1#坯体制备的C／C复合材料弯曲强度最高，2#坏体制备的材料弯曲强度最低，随著炭纤维（CF）体积含量的增加，用四种坯体制备的材料弯曲强度增大。确定了弯曲强度的优化配方．     

炭/炭复合刹车材料的防氧化技术研究进展

从炭／炭复合材料氧化特点、抗氧化要求出发，综述了基体改性技术和涂层技术，对炭／炭复合材料防氧化研究进展进行了详细的介绍，提出了对其高温抗氧化研究方向的一些观点。     

炭／炭U型加热器的制备与性能

研究了炭布与薄网胎交替叠层针刺制成准三向结构U型加热体预制体,经糠酮树脂浸渍／炭化致密工艺,并通过真空高温处理制备了炭／炭复合材料U型加热器。结果表明,其弯曲强度为122MPa,压缩强度182MPa,层间剪切强度为14．9MPa。其电阻值可达到0．10～0．21Ω。在多晶硅氢化炉中应用寿命达到6个月～9个月,凸显出高电阻值和长使用寿命的两大特色。     

炭毡/炭复合材料的氧化防护

以磷酸和氢氧化铝为原料，配制了不同P／Al摩尔比的酸式磷酸盐溶液，通过浸溃法，对炭毡／炭复合材料的氧化防护进行了研究。结果表明，提高P／Al摩尔比可以增加材料抗氧化性。经P／A1摩尔比23：1的溶液浸溃，800□热处理后的炭毡／炭复合材料在600□下氧化几乎没有失重。     

炭/炭复合材料的摩擦磨损性能及应用

论述了炭／炭复合材料的特点，结合该材料在飞机刹车盘中的具体应用，讨论了炭／炭复合材料在不同环境气氛下的摩擦磨损行为及其影响因素，并阐明了炭／炭复合材料的研究现状和尚需解决的问题。     

炭/炭复合材料在 X射线下可视化处理研究

炭／炭复合材料作为种植体在X射线下几乎是透明的，通过在炭／炭复合材料中添加金属钨可以解决炭／炭复合材料在X射线下的可视化问题。用浸渍法将可溶性钨酸盐浸渍到炭／炭复合材料的孔隙中，300℃下将钨酸盐转变成三氧化钨，在540～660℃下、氢气气氛中将三氧化钨还原成金属钨。研究结果表明，用浸渍法可将可溶性钨酸盐浸渍到炭／炭复合材料的孔隙中，将浸入炭／炭复合材料中的钨酸盐还原成金属钨可以在一定程度上改善炭／炭复合材料在X射线下的可视性。经过10次可溶性钨酸盐浸渍处理后，炭／炭复合材料中的金属钨含量可达到3．23％．在X光片中表现出的密度与人牙标本的根部近似。     

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     

Effects of high-temperature heat treatment on the mechanical properties of unidirectional carbon fiber reinforced geopolymer composites

Unidirectional carbon fiber reinforced geopolymer composite (C_uf/geopolymer) is prepared by a simple ultrasonic-assisted slurry infiltration method, and then heat treated at elevated temperatures. Effects of high-temperature heat treatment on the microstructure and mechanical properties of the composites are studied. Mechanical properties and fracture behavior are correlated with their microstructure evolution including fiber/matrix interface change. When the composites are heat treated in a temperature range from 1100 to 1300 °C, it is found that mechanical properties can be greatly improved. For the composite heat treated at 1100 °C, flexural strength, work of fracture and Young's modulus reach their highest values increasing by 76%, 15% and 75%, respectively, relative to their original state before heat treatment. The property improvement can be attributed to the densified and crystallized matrix, and the enhanced fiber/matrix interface bonding based on the fine-integrity of carbon fibers. In contrast, for composite heat treated at 1400 °C, the mechanical properties lower substantially and it tends to fracture in a very brittle manner owing to the seriously degraded carbon fibers together with matrix melting and crystal phases dissolve.     

Influence of adding Mesocarbon Microbeads into C/C composites on microstructure and properties during carbonization

This work tests the effect on microstructure, flexural strength, flexural moduli, plus the electrical and thermal conductivity of carbon/carbon composites with Mesocarbon Microbeads (MCMBs) content ranging 0–30% by weight during carbonization. These composites were reinforced by oxidative PAN Base fiber felts, and matrix precursor was resol‐type‐phenolic resin. MCMBs with a weight fraction of 0–30% were added to the matrix to elucidate the effect. Liquid‐phase impregnation was applied to reinforce matrix carbon. Cured composites were stabilized at 230°C, then heat‐treated at 400, 600, 800, 900 and 1000°C for carbonization. The measured flexural strength after heat‐treated at 1000°C was 51.20, 49.59, 43.55, and 38.76 MPa for MCMBs with 0, 10, 20, and 30% added to composites; mean flexural moduli were l.73, 1.24, 0.73, and 0.57 MPa, respectively. Adding MCMBs reduced both strength and modulus because of cracks and avoids caused by different shrinkage between resin and MCMBs; adding 30 wt % MCMBs raised thermal conductivity of C/C composites from 1.55 to 1.78 W/mK and reduced electric resistivity from 1.8 × 10^?2 to 5.97 × 10^?3 Ω cm. effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3102–3110, 2006     

The effect of pyrolysis on the properties of stabilized PAN fabric reinforced phenolic resins for 2D carbon/carbon composites

Two-dimensional (2D) carbon/carbon composites were prepared with phenol-formaldehyde resin and a commercial stabilized PAN fabric. The effect of pyrolysis on the microstructure and flexural strength of the composites during the carbonization process was studied. The interaction between fabric and matrix inhibited the decomposition and the thermal fragmentation, leading to a higher carbon yield for the final composition. Because of the formation of strong bonding in the fiber/matrix interface, the composites made with stabilized PAN fabric showed catastrophic failure and low flexural strength below carbonization temperatures of 600°C. Above 600°C, the flexural strength of the composites increased with the increase in the carbonization temperatures, even when the fracture behavior showed catastrophic failure.     

针刺碳纤维增强莫来石基复合材料的制备及性能

采用溶胶-凝胶法制备了针刺碳纤维增强莫来石基复合材料。借助于TG-DTA和XRD对合成凝胶的莫来石化过程进行研究,结果表明,在热处理过程中,凝胶在920°C左右形成铝硅尖晶石,1198°C左右形成莫来石。研究了烧结温度对复合材料性能的影响,结果表明,烧结温度为1500°C制备的复合材料弯曲强度最高,达到142.2 MPa,断裂韧性为8.77 MPa·m~(1/2)。借助于对复合材料微观结构的观察对复合材料力学性能的变化进行了解释。     

热处理气氛对AIN／SiCw（Y2O3—SiO2）复合材料性能的影响

将ＡＩＮ／ＳｉＣｗ（Ｙ２Ｏ３－ＳｉＯ２）复合材料在氧气氛和氮气氛下进行热处理,研究热处理气氛对材料性能的影响,并利用ＸＲＤ、ＥＰＡ、ＳＥＭ和ＨＲＥＭ等技术分析了材料的相组成、显微结构和粒界相。结果表明：该材料在１３００℃空气中热处理,材料性能得到改善,材料的断裂强度和韧性增长幅度明显大于氮气气氛下的热处理。在空气中氧化处理对Ｙ２Ｏ３－ＳｉＯ２组成靠近其低共熔点组成的试样具有良好的增强增韧作用,可有     

碳纳米管定向排列增强碳纤维/环氧树脂复合材料制备及力学性能

采用高频电场诱导法制备了碳纳米管定向有序填充的碳纤维/环氧树脂复合材料。研究了电场频率对复合材料力学性能的影响规律,对复合材料的显微形貌进行观察。结果表明:在富树脂区碳纳米管沿着电场方向存在明显的有序排列现象;高频电场诱导后复合材料的层间剪切强度最大提高28.9%,压缩强度提高28.83%,弯曲强度提升15.01%,断口粗糙度增加,树脂与碳纤维的界面结合状态改善。     

Heat treatment effects on microstructure and properties of CVI SiC/SiC composites with Sylramic™-iBN SiC fibers

Chemical-vapor-infiltrated (CVI) SiC/SiC composites with Sylramic?-iBN SiC fibers and CVI carbon, BN, and a combination of BN/C interface coating were heat treated in 0.1-MPa argon or 6.9-MPa N₂ at temperatures to 1800 °C for exposure times up to 100 hr. The effects of thermal treatment on constituent microstructures, in-plane tensile properties, in-plane and through-the-thickness thermal conductivities, and creep behavior of the composites were investigated. Results indicate that heat treatment affected stoichiometry of the CVI SiC matrix and interface coating microstructure, depending on the interface coating composition and heat treatment conditions. Heat treatment of the composites with CVI BN interface in argon caused some degradation of in-plane properties due to the decrease in interface shear strength, but it improved creep resistance significantly. In-plane tensile property loss in the composites can be avoided by modifying the interface composition and heat treatment conditions.     

一种低粘度双马树脂及其复合材料的性能研究

对一种适用于RTM工艺的低粘度双马树脂QY8911-Ⅳ进行了研究,考察了树脂体系的粘度特性和固化特性,并对不同后固化温度下的树脂固化物的耐热性、力学性能及吸水性等进行了全面考察。结果表明,该树脂体系具有粘度低(80℃为200mPa·s)、固化收缩小(1%)、耐热性好(T_g为260℃)、力学性能好(弯曲强度为170 MPa、冲击强度为20 kJ/m~2)和吸水率低(0.39%)等特点。选择合适的注射工艺和固化工艺,以此树脂为基体,采用RTM工艺,制备出了碳布增强的复合材料,并对其力学性能进行了测试,其弯曲强度和冲击强度分别为754 MPa和110.9 kJ/m~2。