【作者】 高孟姣；

【导师】 孙晋良；

【作者基本信息】 上海大学 ， 材料学， 2013， 博士

【摘要】 为了提高C/C复合材料的抗氧化、耐烧蚀性能，采用先驱体转化法(PIP)，以含氢聚硅氧烷为先驱体制备了C/C-SiC复合材料。本文对含氢聚硅氧烷的交联固化条件进行了研究，较佳条件为：含氢聚硅氧烷/二乙烯基苯的最佳配比为1/0.5；交联温度为250℃；裂解温度大于1550℃。裂解升温过程中链的断裂和重排主要发生300-800℃，在该温度段，升温速率较慢有利于提高陶瓷产率。密度为1.02、1.21、1.60、1.78g/cm3的C/C复合材料经4次致密化后，制得密度分别为1.24、1.36、1.69、1.84g/cm3的C/C-SiC复合材料，其SiC质量百分含量分别为15.78%、13.14%、5.28%、4.12%。采用H2-O2焰烧蚀法测定了C/C-SiC复合材料的烧蚀率，结果显示：密度分别为1.24、1.36、1.69、1.84g/cm3的C/C-SiC复合材料的线烧蚀率分别为0.00311、0.00222、0.00167、0.00144mm/s，质量烧蚀率分别为0.87、0.58、0.56、0.16mg/s。SiC的加入明显地提高了材料的抗烧蚀性能。对C/C-SiC复合材料在静态空气中进行了氧化实验。C/C-SiC复合材料的氧化失重率低于C/C复合材料，经800℃氧化30分钟后，1.84g/cm3的C/C-SiC复合材料的失重率是1.85g/cm3C/C复合材料的76.31%。SiC的加入明显地提高了材料的抗氧化性能。为了在C/C复合材料基体中引入抗氧化耐烧蚀的难熔金属，本文首次采用电化学法以甲基三氯硅烷、烯丙基氯、环戊二烯和四氯化锆为原料合成合成了含有难熔金属Zr、含有双键的聚硅烷，经测定，含锆聚硅烷中Si、Zr的质量百分含量分别为48.81%、4.11%。研究了含锆聚硅烷交联固化和裂解条件。含锆聚硅烷可以自交联，较佳的交联温度为300℃，其陶瓷产率为82.2%。热重-差热曲线分析表明，在裂解过程中，键的断裂与重排主要发生在400~800℃之间。采用含锆聚硅烷作为浸渍剂，制备了C/C-ZrC-SiC多元陶瓷基复合材料。密度为1.28g/cm3的C/C复合材料经4次浸渍后得到为密度1.69g/cm3的C/C-ZrC-SiC复合材料，密度增加32.03%。测定了1.69g/cm3的C/C-ZrC-SiC复合材料的烧蚀性能，其线烧蚀率为0.00211mm/s，质量烧蚀率为0.518mg/s。其线烧蚀率和质量烧蚀率分别相当于密度1.78g/cm3C/C复合材料的20.6%和31.57%。在C/C复合材料中引入ZrC-SiC复合陶瓷能明显提高C/C复合材料的抗氧化烧蚀性能。烧蚀后的形貌可明显分为烧蚀中心区、烧蚀过渡区、烧蚀边缘区，各区域的烧蚀机理不同。C/C-ZrC-SiC复合材料在500-900℃条件下的氧化失重率低于C/C复合材料的失重率。在900℃氧化30分钟后，C/C-ZrC-SiC复合材料的氧化失重率是同密度C/C复合材料的80.73%。从化学热力学和化学动力学方面分析了C/C-SiC复合材料和C/C-ZrC-SiC复合材料抗烧蚀、抗氧化机理：ZrC、SiC氧化的吉布斯自由能(ΔG)较低，优先于C氧化，在材料表面形成SiO2膜；另外，C/C-ZrC-SiC与C/C-SiC复合材料比C/C复合材料有更高的表观活化能。更多还原

【Abstract】 The precursor infiltration and pyrolysis (PIP) method was used to prepareC/C-SiC composites with hydrogen-containing polysiloxane as precursor, in order toimprove the ablation resistance and oxidation resistance of the C/C composites. Thecross-linking conditions of hydrogen-containing polysiloxane were studied. The bestratio of hydrogen-containing polysiloxane and crosslinker divinylbenzene is1/0.5; thefavorable cross-linking temperature is250℃, and the pyrolysis temperature shouldbe higher than1550℃. In the pyrolysis process, the break and rearrangement of themolecular chains mainly happen at the temperature range of300-800℃. The slowheating rate is preferred to improve the ceramic yield.C/C-SiC composites of1.24,1.36,1.69and1.84g/cm3were prepared through PIPmethod with hydrogen-containing polysiloxane as precursor, the density of the initialC/C composites was1.02,1.21,1.60and1.78g/cm3. After4times PIP process, thecontents of SiC of the above samples were15.78%,13.14%,5.28%and4.12%respectively.The ablation rates of C/C-SiC composites and C/C composites were determinedwith H2-O2flame ablation method. The results demonstrated that: the linear ablationrates of C/C-SiC composites with density of1.24,1.36,1.69and1.84g/cm3were3.11,2.22,1.67and1.44μm/s respectively, and the mass ablation rates were0.87,0.58,0.56and0.16mg/s. The ablation rates were proved that the introduction of SiCappearently improves the ablation resistance of C/C composites.The static air oxidation of C/C-SiC composites shows that the weight loss rates ofC/C-SiC composites with density of1.84g/cm3was76.3%that of C/C-SiCcomposites with density of1.85g/cm3. The fact proves that the addition of SiCsignificantly improves the oxidation resistance of C/C composites, Furthrmore, theanti-oxidation mechanism was analysed from the point of view of chemicalthermodynamics.Zr-containing polysilane was synthesized for the first time throughelectrochemical method, in order to introduce the refractory metal elements into C/Ccomposites, methyl trichlorosilane allyl chloride, cyclopentadiene, and zirconiumtetrachloride was used. The product contains48.8%Si (Wt%) and4.11%Zr.In the process, the crosslinking and pyrolysis condition of Zirconium-containingpolysilane was studied. the study of the crossling condition demonstrated that theZr-containing polysilane can cross-linked by itself, and the best cross-linkedtemperature is300℃, the highest ceramic yield is82.2%. Themogravimetrydifferential thermal curve analysis showed that the cleavage and rearrangement ofbond occur mainly between400~800℃.The C/C-ZrC-SiC composites of1.69g/cm3were produced after PIP for4cycles,using Zr-containing polysilanes as ceramic precursor, the density of the initial C/Ccomposites was1.28g/cm3. The density was increased by32.03%.The ablation property was measured with the H2-O2flame ablation method ofC/C-ZrC-SiC composites of1.69g/cm3, the linear ablation rate was2.11μm/s, andfor the mass ablation rate was0.518mg/s. The results showed that the addition of ZrCand SiC, to a great extent, can improve the anti-ablation properties of the C/Ccomposites. From the ablation morphology, the ablation surface can be divided into the central area, the transitional area and the rim area. The ablation mechanism indifferent regions was proposed.The static air oxidation experiment was done to C/C-ZrC-SiC composites from500to900℃, which showed that the oxidational weight loss rate of C/C-ZrC-SiCcomposites was80.7%that of C/C composites after oxidation for30min at900℃.The additions of ZrC and SiC greatly improve the oxidation resistance of C/Ccomposites. The anti-oxidation mechanism was analyzed.The anti-ablation and anti-oxidation mechanism of C/C-ZrC-SiC and C/C-SiCcomposites was analyzed from the perspective of chemical thermodynamics andchemical kinetics: Gibbs free energy(ΔG) of ZrC and SiC less than that of carbon, andthe oxidation of ZrC and SiC was prior to carbon, in addition, the apparent activationenergy of C/C-ZrC-SiC and C/C-SiC composites is greater than that of C/Ccomposites.更多还原