碳／碳复合材料

一、前言碳纤维增强碳基体的复合材料,在工业上通常称做碳/碳复合材料(也用符号C/C表示),人们为了提高碳和石墨的强度,以便能够利用这些材料的优良耐高温性能,即在2500℃高温下的热稳定性、抗热震性以及利用这些材料做成的高性能工程零部件而不断地研究开发C/C复合材料的。     

碳毡/碳复合材料超高温力学性能实验研究

利用改进的快速通电加热测试技术,模拟碳毡／碳复合材料的超高温工作环境,对其高温下的拉伸、压缩力学性能进行了全面的测试,并计算了材料在不同温度下的抗热应力系数．结果表明,材料的模量和强度在一定范围内随温度的升高而增加．材料的拉伸性能ＸＹ向优于Ｚ向,而压缩性能Ｚ向优于ＸＹ向．材料的抗热震性能随温度升高变化平稳,ＸＹ向的抗热震性能优于Ｚ向．     

碳纤维增强TiC复合材料的抗热震性能

通过测量力学性能和热物理性能,研究了热压烧结碳纤维增强TiC复合材料（Cf/TiC,20vo%碳纤维）的抗热震性能。结果表明,碳纤维加入到TiC基体中,提高了复合材料的抗弯强度和断裂韧性,降低了复合材料的弹性模量和热膨胀系数,进而使得复合材料的抗热震断裂参数R,抗热震损伤参数R^TV和裂纹稳定性参数RST都得以提高,复合材料热震残留强度在热震温差超过900℃后迅速下降。复合材料热扩散率的提高有利于抗热稳定性能的提高,复合材料增强机理是纤维承载。韧化机理是纤维桥联和纤维拔出。     

镁碳材料抗热震性测试评价方法

整体塞棒棒头普遍采用具有优异抗熔钢侵蚀性的镁碳材料,但是由于镁碳材料抗热震性差,从而容易导致塞棒在使用过程中出现掉头、掉块现象,严重影响了钢厂的连铸生产过程.研究探索适宜镁碳材料抗热震性测试评价法,并制作具有优异抗热震性的镁碳材料对保证整体塞棒安全使用性至关重要.因此,本试验通过采用不同配方镁碳棒头材料对比研究水急冷法和浸钢法抗热震性试验方法,从而探索出适宜镁碳材料抗热震性测试评价方法.     

C/SiC/Si-Mo-Cr复合涂层碳/碳复合材料力学性能研究

采用包埋法和涂刷法在碳/碳复合材料表面制备了一种新型的C/SiC/Si-Mo-Cr复合高温抗氧化涂层. 借助XRD和SEM等测试手段对所制备复合涂层的微观结构进行了表征, 采用三点弯曲试验研究了涂层处理及热震试验对碳/碳复合材料力学性能的影响规律. 结果表明: 制备的多相涂层结构致密, 涂层后碳/碳复合材料弯曲强度有所增大, 断裂特征由假塑性向脆性转变. 涂层试样经1500℃至室温20次热震后, 涂层试样的弯曲强度降低, 塑性增强.     

高性能针刺碳/碳复合材料的制备与性能

为获得高性能针刺碳/碳复合材料, 拓展其应用领域, 通过优化针刺工艺参数, 设计并研制了不同结构参数的针刺预制体。采用沥青高压致密化工艺将针刺预制体制备成一系列针刺碳/碳复合材料, 研究了针刺碳/碳复合材料的微观结构、力学性能和热物理性能。结果表明, 针刺预制体的针刺深度、针刺密度以及短/长纤维配比等对碳/碳复合材料的力学性能和热物理性能影响显著。当针刺深度为12 mm、针刺密度为22针/cm ²、短/长纤维比例为1.0 : 4.8时, 针刺碳/碳复合材料表现出优良的综合性能, 拉伸、压缩、弯曲、面内剪切和层间剪切强度分别达到207、228、285、54和28 MPa。     

SiC/MoSi2-Si-Cr-B/玻璃涂层碳/碳复合材料抗氧化行为研究

采用两步包埋法及料浆涂刷-烧结法在二维碳布叠层碳/碳复合材料表面依次制备了SiC/MoSi2-Si-Cr-B包埋涂层及磷酸盐玻璃外涂层,研究了其在950℃静态空气环境中自由状态的抗热震、防氧化性能及不同弯曲变形状态下的防氧化性能,并借助X射线衍射分析仪及扫描电子显微镜对涂层试样的组成成分及微观组织形貌进行了分析.结果表明:950℃自由状态下该涂层体系的氧化失重率为负值,抗热震、防氧化效果良好;磷酸盐玻璃层在950℃软化熔融呈粘流态,可填补涂层内的裂纹和孔洞,阻止氧的入侵,有效提高了涂层整体的抗热震及抗氧化性能;但弯曲变形状态下,涂层试样的氧化失重率随形变量的增加而提高,形变会在一定程度上降低碳/碳复合材料抗氧化涂层的保护效果,加速材料的氧化失效.     

超高温本体抗氧化碳/碳复合材料研究

通过向碳/碳复合材料基体中掺杂难熔金属化合物,研制出了一类集碳/碳材料优异的高温力学、热物理性能和超高温陶瓷材料非烧蚀性能于一体的超高温本体抗氧化碳/碳复合材料。攻克了难熔金属化合物在复合材料中分布以及组元与碳纤维反应控制关键技术,提高了复合材料的力学性能。静态和动态高频等离子风洞超高温本体抗氧化试验表明,在驻点温度达到2 500℃,600 s烧蚀后烧蚀量仅为碳/碳复合材料的1/5,给出了超高温本体抗氧化碳/碳复合材料氧化烧蚀抑制机理。     

碳/碳复合材料MoSi2涂层的防氧化研究

研究了碳/碳复合材料MoSi₂防氧化涂层的性能.结果表明,MoSi₂涂层系统具有1500℃长时间防氧化作用,在1500℃时,带涂层的碳/碳复合材料长时间氧化失重速率稳定在2.43×10-5g/m2·s,242小时的氧化失重为0.57%,该质量损失表现为涂层系统自身蒸发损耗;同时,MoSi₂涂层具有良好的自愈性和抗热震性.     

基于第一抗热震因子的BN纳米管/Si_3N_4复合材料抗热震性能评价

利用Kingery抗热震断裂理论构建了BN纳米管(BNNTs)强韧化陶瓷复合材料的第一抗热震因子模型,通过真空热压烧结法制备了四组BNNTs含量分别为0.5wt%、1.0wt%、1.5wt%和2.0wt%的BNNTs/Si_3N_4复合材料,并采用水浴淬冷法和三点弯曲法测试了复合材料的抗热震性能(震后弯曲强度和临界热震断裂温差)。测试结果验证了在急剧加热和急剧冷却条件下第一抗热震因子模型的正确性。结果表明:添加BNNTs使BNNTs/Si_3N_4复合材料第一抗热震因子增大,抗热震性能提升。分布在晶界上的BNNTs起到裂纹钉扎、桥联和裂纹偏转作用,增加了裂纹扩展的阻力;纳米管孔隙的存在改变了裂纹扩展路径,提高了BNNTs/Si_3N_4的断裂韧度,从而有效提高了其抗热震断裂能力。     

AlN添加量对BN基复合陶瓷热学性能与抗热震性的影响

以BN、SiO₂、AlN为原料, 采用热压工艺制备出BN基复合陶瓷。研究了AlN添加量对复合陶瓷热学与抗热震性能的影响。结果表明: 随着AlN添加量的增加, 复合陶瓷的热膨胀系数呈现先降低后升高的趋势。当AlN的添加量为5vol%时, 复合陶瓷的平均热膨胀系数最小, 为2.22×10^-6/K; 复合陶瓷的热导率则随着AlN添加量的增加呈先升高后降低的趋势, 当AlN的添加量为10vol%时达到最大值。未添加AlN的复合陶瓷热震后的残余强度随着热震温差的增大而升高; 随着AlN的引入, 复合陶瓷热震后的残余强度呈下降的趋势。对于添加5vol%AlN的复合陶瓷, 经1100℃热震后其残余强度为219.7 MPa, 强度保持率为88.9%, 抗热震性良好。     

Experimental description of thermomechanical properties of carbon fiber-reinforced TiC matrix composites

Titanium carbide ceramic is a good potential material used in high temperature environment for its good strength, erosion resistance and thermal stability. Unfortunately, the low thermal shock resistance and low fracture toughness are the well-known impediments to its application as high temperature structure components. In order to extend the application of TiC ceramics at high temperature, 20 vol.% short carbon fiber was added into TiC matrix to improve the thermomechanical properties. With the incorporation of carbon fiber, the thermal expansion coefficient of TiC composites was decreased and the thermal conductivity was increased slightly below 900 °C. The flexural strength was improved from 471 MPa for monolithic TiC to 593 MPa for TiC composites, and the strengthening effect of carbon fiber became more prominent at high temperatures. The addition of fiber decreased the elastic modulus of TiC composite. The elastic modulus of the composite decreased with increasing temperature. The improvement of high temperature strength and thermal conductivity and the decrease of thermal expansion will benefit the application of TiC composites in high temperature environment where the temperature usually varies.     

微波烧结制备ZrO2-AlN复合陶瓷的微观结构与性能研究

氧化锆(ZrO₂)陶瓷具有出色的机械性能, 但其应用受到低热导率(Thermal Conductivity, TC)的限制。本研究设计并通过微波烧结制备了高热导率氧化锆-氮化铝(AlN)复合陶瓷, 优化制备条件后, 抑制了两种物质之间的反应, 获得了致密的复合陶瓷(相对密度>99%), 详细研究了该复合陶瓷的组织演变、热学性能和力学性能。研究结果表明, 随着AlN含量的增加, 复合陶瓷的室温下热导率、热扩散系数和热容增加, 分别达到41.3 W/(m·K)、15.2 mm²/s和0.6 J/(g·K)。这种具有高热导率和抗热震性的ZrO₂-AlN复合复合陶瓷在能源系统的高温热交换材料领域具有广阔的应用前景。     

Thermal shock behaviour of unidirectional, 0°/90°, and 2-D woven fibre-reinforced CVI SiC matrix composites

The thermal shock behaviour of NicalonTM fibre-reinforced chemical vapour infiltrated SiC matrix composites with three different types of fibre architecture, unidirectional, 0°/90°, and 2-D woven, has been studied using the water quench technique. Thermal shock induced damage was characterized by the destructive four-point flexure technique and the nondestructive technique of Young's modulus measurement by the dynamic resonance method. It was shown that the unidirectional and 0°/90° composites did not possess satisfactory mechanical properties or resistance to thermal shock because these fibre architectures prevented the composites from attaining high density during infiltration. Excess carbon coating was also found in the unidirectional and 0°/90° composites. Oxidation of this carbon coating contributed to the property degradation at high quench temperature difference. By contrast, the composite with 2-D woven fibre architecture created using the 0°/30°/60° cloth lay-up showed superior mechanical properties and thermal shock resistance. The nondestructive technique of Young's modulus measurement by the dynamic resonance method was successfully used in detecting the thermal shock damage.     

Aluminium nitride-molybdenum ceramic matrix composites possessing high thermal shock resistance

Aluminium nitride-molybdenum ceramic matrix composites were produced by hotpressing a mixture of AlN and Mo powders. Thermal shock resistance of a composite (AM25) which contained 25 vol.% of metallic phase dispersed in the AlN matrix, was studied in order to verify the influence of metallic phase additional on the thermal properties. Results showed that AM25 possess a critical temperature difference (ΔT_c) for thermal shock of about 550°C compared to a mean value of 350°C measured in the case of pure hot pressed AlN. This improvement in thermal shock resistance was attributed to better mechanical properties and higher thermal conductivity of AM25 as compared to pure AlN.     

Thermal shock resistance of laminated ceramic matrix composites

The thermal shock resistance capability of laminated ceramic matrix composites is investigated through the study of three-dimensional transient thermal stresses and laminate failure mechanisms. A (–45°/45°)_s SiC/borosilicate glass laminate is utilized as a reference composite system to demonstrate the analytical results. The maximum allowable temperature change, T _max, has been taken as a measure of the thermal shock resistance capability of composites. The effects of fibre orientation, volume fraction, thermal expansion coefficient. Young's modulus, and thermal conductivity on the thermal shock resistance capability, expressed in terms of the maximum allowable temperature change, T _max, have been assessed. Numerical computations are also performed for six composite systems.     

PAN-based carbon fibers/PMMA composites: thermal, dielectric, and DC electrical properties

The study deals with thermal, dielectric, and DC electrical properties of polyacrylonitrile (PAN)-based carbon fibers/poly(methyl methacrylate) composites. The polymer composites contain 0, 5, 10, 20 and 30 wt.% PAN-based carbon fibers. The thermal conductivity was studied as a function of filler content and temperature. It was found that the thermal conductivity is enhanced by addition of carbon fibers concentration and temperature. The dielectric properties were determined using impedance measurements. The results showed that the dielectric constant and dielectric loss are decreased with frequency, and increased with both temperature and fibers content. The DC electrical conductivity, temperature coefficient of resistance, and activation energy were studied as a function of fibers concentration in the temperature ranges 30–110?°C. It was found that the composites exhibit negative temperature coefficient of resistivity and enhancement of electrical conductivity with increasing temperature and carbon fibers concentration. The observed increase in the DC conductivity was explained according to the approach of conductive paths and connections between the carbon fibers.     

碳纤维-AlN/聚醚醚酮复合材料的制备与性能

以聚醚醚酮(PEEK)为基体树脂、碳纤维(CF)和氮化铝(AlN)为填料,通过模压成型的方法制备了抗静电耐热型CF-AlN/PEEK复合材料。采用高阻计、导热系数测定仪、热失重、差示扫描量热仪和SEM研究了CF-AlN/PEEK复合材料的抗静电性能、热性能、力学性能以及降温速率对复合材料性能的影响,并探讨了后期热处理对力学性能的影响。结果表明:当CF和AlN的质量分数均为10%时,CF-AlN/PEEK复合材料的性能较优,其表面电阻率达到108 Ω,比PEEK的表面电阻率提高了6个数量级;导热系数为0.418 W·(m·K)-1,初始分解温度高达573℃;拉伸强度提高了40.4%;降温速率越低,复合材料的熔点越高;后期热处理会影响CF-AlN/PEEK复合材料的力学性能,在270℃下热处理2 h,其拉伸强度可达146 MPa,表明在生产过程中,加工温度是影响复合材料性能的因素之一。      

Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC–AlON composites over a temperature range between 175 °C and 275 °C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC–AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 °C in the monolithic AlON to 225 °C in the SiC–AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC–AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge-like characteristics, crack deflection, and crack branching in the SiC–AlON composites.     

烧结温度对包混/复合添加工艺制备多孔SiC陶瓷性能的影响

采用包混工艺合成了核壳结构的先驱体粉体,并引入一定量Al2O3、SiO2和Y2O3复合添加剂,通过成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;分析了样品的物相、表面形貌、孔隙率、热导率、热膨胀系数、抗弯强度和抗热震性能。结果表明,在较低的烧结温度下制得了多孔碳化硅陶瓷,在1650℃烧结的多孔碳化硅陶瓷综合性能较好。