Cf/SiC陶瓷基复合材料在航天领域的研究与应用

碳纤维增强碳化硅(Cf/SiC)陶瓷基复合材料是近年来发展起来的新型高温结构材料.综述了Cf/SiC陶瓷复合材料的主要制备工艺和氧化防护方面的研究进展,概括介绍了Cf/SiC陶瓷复合材料在航天领域的应用与研究,最后指出了有待解决的问题和研究方向.     

SiCf/SiC陶瓷基复合材料制备技术与性能研究进展

连续SiC纤维增强SiC陶瓷基复合材料(SiCf/SiC)具有良好的高温力学性能、抗氧化性及放射耐受性等,是继Cf/C和Cf/SiC复合材料之后航空航天和原子能等领域最理想的新一代高温结构材料.从原材料、制备技术、微观结构与性能及应用等方面对SiCf/SiC复合材料的最新研究进展进行了综述,并对其发展趋势进行了展望.开发新型制备技术和优化现有技术及采用其联合工艺减低成本,进一步优化材料微观结构提高其使用性能是今后SiCf/SiC复合材料的研究重点.     

T300碳纤维热处理对Cf/SiC复合材料性能的影响

以聚碳硅烷先驱体浸渍裂解工艺制备T300碳纤维增强3D Cf/SiC复合材料,研究了T300碳纤维预先热处理对材料性能的影响.结果表明,热处理能够弱化Cf/SiC复合材料中纤维-基体界面结合,减少碳纤维在复合过程的损伤,显著提高复合材料性能.纤维经热处理后制备的Cf/SiC复合材料弯曲强度和断裂韧性分别从未经处理的154MPa,4.8MPa·m1/2提高到437MPa,20.4 MPa·m1/2.     

Cf/SiC复合材料的应用研究进展

Cf/SiC复合材料充分结合了碳纤维和SiC基体的优势,表现出低密度,高强度,高韧性,耐高温,耐烧蚀,抗冲刷,高硬度和高耐磨性等特点,成为航空航天、军事、能源等领域理想的高温结构材料.目前Cf/SiC复合材料已达到实用化水平,研究重点已转向应用研究.本文主要介绍Cf/SiC复合材料在热结构部件、热防护系统及高温光学部件等领域的研究进展.     

先驱体转化-热压单向Cf/SiC复合材料的高温拉伸蠕变

采用先驱体转化－热压工艺制备了Cf/SiC复合材料，研究了Cf/SiC复合材料的1300－1450℃，蠕变应国90－120MPa下的蠕变性能，考察了温度及应力对复合材料隐态蠕变速率的影响关系。结果表明：Cf/SiC复合材料的稳态蠕变速率在10^-7s^-1量级，蠕变应力指数为1．68，蠕变激活能△Q为99．2kJ.mol^-1；在纤维周围和SiC颗粒晶界之间存在的玻璃相及纤维与其体的界面反应是Cf/SiC复合材料抗蠕变能力退化的主要原因。     

Cf／sic陶瓷基复合材料抗氧化涂层发展现状

综述了制备Cf／SiC陶瓷基复合材料抗氧化涂层体系的发展，Cf／SiC复合材料抗氧化涂层的基本制备工艺，指出了有待解决的问题和今后努力的方向。     

Cf／SiC陶瓷基复合材料制备及性能研究现状

本文综述了Cf／SiC陶瓷基复合材料的研究进展，回顾了碳纤维的发展过程，介绍了Cf／SiC陶瓷基复合材料的制备技术，详细阐述了Cf／SiC陶瓷基复合材料的力学性能与微观结构，分析了提高其断裂强度、断裂韧性的机理。并展望了Cf／SiC陶瓷基复合材料以后的研究重点及发展前景。     

先驱体紫外光固化法制备隔热涂层

以聚硅氮烷先驱体为原料,采用紫外光固化法在Cf/SiC复合材料基体上制备隔热涂层,通过配方的研究和工艺的优化,得到了粘结性良好的多孔隔热涂层.结果表明聚硅氮烷紫外光固化涂层与Cf/SiC复合材料基体相容性良好.二氧化硅填料可降低先驱体转化的体积收缩,提高涂层高温性能.     

碳纤维增强Cu-Ti3SiC2复合材料的研究

采用电镀Cu碳纤维(Cf)与化学镀Cu的Ti3SiC2粉及Cu粉进行湿混,通过真空热压烧结法制备Cf增强的Cu-Ti3SiC2复合材料.研究了其致密度、电阻率、维氏硬度随Cf,Ti3SiC2含量变化的规律.实验结果表明,Ti3SiC2体积含量为20%,Cf体积含量为8%时,制备的Cf增强Cu-Ti3SiC2复合材料综合性能最好.Cf镀Cu和Ti3SiC2镀Cu改善了它们和Cu的润湿性,从而提高了相互之间的结合强度是复合材料获得良好综合性能的基本原因.     

浸渍浆料对先驱体转化C_f/SiC复合材料结构及性能的影响

采用先驱体转化法,以聚碳硅烷/二甲苯、聚碳硅烷/二甲苯/碳化硅粉、聚碳硅烷/交联剂三种浆料体系分别浸渍增强体,裂解制备Cf/SiC复合材料,考察了浸渍浆料体系对Cf/SiC复合材料的结构和性能的影响。研究发现:聚碳硅烷/交联剂浆料制备复合材料所需周期最短,9个周期即可制得密度达1.78g.cm-3、开孔率为4.95%的复合材料;聚碳硅烷/二甲苯/碳化硅粉制备的复合材料密度最大,达1.87g.cm-3,并且制备的复合材料表面平整光洁;聚碳硅烷/二甲苯浆料制备的Cf/SiC复合材料力学性能最好,弯曲强度达455.9MPa,模量达90.6GPa,断裂韧性达18.9MPa.m1/2。研究结果表明,三种常用的浸渍浆料制备的复合材料各有其优点,在各个浸渍周期合理的选用浆料能有效的改善材料结构及性能。     

SiC微粉含量对先驱体转化制备碳纤维布增强碳化硅复合材料性能的影响

以聚碳硅烷(PCS)、二乙烯基苯(DVB)和SiC微粉为原料制备了碳纤维布增强碳化硅复合材料，考察了SiC微粉含量对材料结构与性能的影响。实验表明，SiC微粉含量过低，材料内部存在大的孔洞，容易造成应力集中，导致材料的力学性能较差；而当SiC微粉含量较高时，在制备过程中微粉对碳纤维机械损伤加大，同样导致材料力学性能下降。当SiC微粉含量为30％(质量分数)时，所制备的材料的力学性能较好，其弯曲强度和拉伸强度分别为246．4MPa和72．5MPa。     

Al2O3f+Cf/ZL109混杂复合材料钻削加工性的研究

利用挤压铸造法制备了Al₂O_3f+C_f/ZL109短纤维混杂金属基复合材料,并进行了钻削加工试验研究。考察了Al₂O₃短纤维和C短纤维含量、纤维位向、钻削速度及进给量对钻削力、刀具磨损和钻削精度的影响,并进行了分析。结果表明:以刀具磨损作为衡量标准,该混杂复合材料的钻削加工性次于基体合金。      

Salt-fog corrosion behavior of C/SiC and its effect on ablation resistance

Carbon fiber-reinforced silicon carbide(C/SiC) composites are significantly important candidates for thermal protection materials. The corrosion mechanism of C/SiC composite materials is the basis of their optimization and application. In this study, structural evolution of C/SiC composites fabricated by chemical vapor infiltration was investigated in the salt-fog storage environment. Furthermore, the effect of salt-fog on their ablation behaviors under oxyacetylene flame environment was studied. The ablation morphologies and corrosion mechanisms of C/SiC composites were analyzed and discussed. The results indicated that silica layer with size of c.a. 20 nm was formed on the surface of composite. The extent of corrosion in salt fog was limited, and it had little effect on the ablation behavior of the C/SiC composites,as well on the tensile strength and bending strength.     

Design,Fabrication, Characterization and Simulation of PIP-SiC/SiC Composites

Continuous SiC fiber reinforced SiC matrix composites (SiC/SiC) have been studied and developed for high temperature and fusion applications. Polymer impregnation and pyrolysis (PIP) is a conventional technique for fabricating SiC/SiC composites. In this research, KD-1 SiC fibers were employed as reinforcements, a series of coatings such as pyrocarbon (PyC), SiC and carbon nanotubes (CNTs) were synthesized as interphases, PCS and LPVCS were used as precursors and SiC/SiC composites were prepared via the PIP method. The mechanical properties of the SiC/SiC composites were characterized. Relationship between the interphase shear strength and the fracture toughness of the composites was established. X-ray tomographic scans of the SiC/SiC composites were performed and the closed porosities of the composites were calculated. The compatibility of the SiC/SiC composites with liquid LiPb at 800 °C and 1000 °C was investigated. High-resolution synchrotron X-ray tomography was applied to the SiC/SiC composite and digital volume correlation was employed for Hertzian indentation testing of the SiC/SiC composite. A Cellular Automata integrated with Finite Elements (CAFE) method was developed to account for the effect of microstructure on the fracture behavior of the SiC/SiC composite.     

Effects of microstructure on flexural strength of biomorphic C/SiC composites

Biomorphic C/SiC composites were fabricated from different kinds of wood by liquid silicon infiltration (LSI) following a two-step process. In the first-step, the wood is converted into carbon preforms by pyrolysis in a nitrogen atmosphere. The carbon preforms are then infiltrated by silicon melt at 1,560°C under vacuum to fabricate C/SiC composites. The mechanical properties of the C/SiC composites were characterized by flexural tests at ambient temperature, 1,000, and 1,300°C, and the relationship between mechanical properties and microstructure was analyzed. The flexural strength of the biomorphic composites was strongly dependent on the properties of the carbon preforms and the degree of silicon infiltration. The flexural strength increased with increasing SiC content and bulk density of composite, and with decreasing porosity in the C/SiC composite. An analysis of fractographs of fractured C/SiC composites showed a cleavage type fracture, indicating brittle fracture behavior.     

连续SiC纤维增强金属基复合材料研究进展

SiC纤维增强金属基复合材料具有高的比强度、比刚度、耐腐蚀、耐高温等优异的综合性能,在实际应用中具有广阔的前景。本文主要总结了SiC纤维增强金属基复合材料的研究进展,分别阐述了SiC纤维增强铝基、钛基、铜基、镍基复合材料存在的问题、解决办法及应用现状。最后指出了限制复合材料实际应用的几点因素,包括:成本问题、界面问题、各向异性以及缺少质量检测评估体系。     

微纳米SiC/环氧树脂复合材料的界面和非线性电导特性

以微米和纳米SiC为填料,制备了不同填料配比的微纳米SiC/环氧树脂(EP)复合材料。测试了微纳米SiC/EP复合材料的玻璃化转变温度、室温介电谱和直流电导特性。分析了填料与基体之间的界面对玻璃化转变温度、介电谱及直流电导特性的影响。实验结果表明,在微米和纳米SiC填料的共同掺杂下,随着纳米SiC填料含量的增加,微纳米SiC/EP复合材料的玻璃化转变温度先降低后升高。在相同频率下,微纳米SiC/EP复合材料具有更低的相对介电常数和低频损耗峰幅值。与EP相比,微纳米SiC/EP复合材料具备显著的非线性电导特性。与微米SiC/EP复合材料相比,微纳米SiC/EP复合材料具有更高的非线性指数和阈值电场强度。微纳米SiC/EP复合材料的非线性电导特性与SiC颗粒和EP基体之间的界面区密切相关。      

界面相对3D-SiC/SiC复合材料静态力学性能及内耗特征的影响

采用先驱体浸渍裂解工艺制备无界面、SiC、PyC和PyC/SiC等界面相SiC/SiC复合材料, 研究了SiC/SiC复合材料的微观结构及静态力学性能, 并通过强迫振动法系统分析了界面相对复合材料内耗行为的影响。研究结果表明, 引入界面相有效改善了复合材料的微观结构及力学性能, 并降低了复合材料的内耗。其中, PyC/SiC复相界面中亚层SiC限制了PyC界面相与纤维的结合及塑性形变, 提高了复合材料的力学性能; 同时, 界面相对SiC/SiC复合材料内耗行为有显著影响, 材料内耗水平与界面剪切强度成反比。对比50和350 ℃时的材料内耗变化率发现, 随界面剪切强度增大, 材料内耗呈降低的趋势, 且含有PyC的PyC/SiC界面复合材料具有较低的内耗变化率, 说明PyC/SiC复相界面的SiC/SiC复合材料更适于高温振动环境。     

预制体结构及界面对三维SiC/SiC复合材料拉伸性能的影响

为研究预制体结构及界面对三维编织SiC/SiC复合材料拉伸性能的影响,采用先驱体浸渍裂解法（PIP）分别制备了三维四向和三维五向SiC/SiC复合材料,并引入热解炭/碳化硅（PyC/SiC）复合界面层,进行拉伸性能测试和断口形貌观察。结果表明,三维五向SiC/SiC复合材料拉伸性能优于三维四向SiC/SiC复合材料,三维五向SiC/SiC复合材料的拉伸强度、模量和断裂应变分别是三维四向SiC/SiC复合材料的1.22倍、1.25倍、1.43倍,且比三维四向SiC/SiC复合材料具有更好的强度可靠性。这是由于三维五向SiC/SiC复合材料增加了受力方向的纤维含量,限制了纤维在外力作用下的转动和变形,起到定型和稳固作用。添加PyC/SiC复合界面层,三维五向SiC/SiC复合材料的拉伸强度、模量及断裂应变分别提高了21.7%、15.0%和11.0%。界面的存在可以保护纤维,调节纤维与基体之间的热应力,受力时诱使裂纹偏转和分叉,消耗能量,提高三维五向SiC/SiC复合材料的拉伸性能。