RCLD法制备碳表面Si化物涂层的研究

发布时间：2018-06-19 17:16

  本文选题：化学液相沉积法 + C/Si化物复合材料　； 参考：《济南大学》2011年硕士论文

【摘要】：碳材料具有优良的耐化学腐蚀、耐热、良好的导热性、低电阻率、抗辐射、导热、降噪、减震等一系列力学和电学性能,已成为目前国际上新型技术研究领域中重点开发和研究的一种新材料,被广泛应用于国防军事、航空航天等尖端领域及医疗、交通以及器械等民用领域。但是碳材料在高温下非常容易被氧化,导致其各项性能下降。因此,对碳材料的抗氧化研究具有重要的意义。 快速制备工艺与结构性能的关系是决定C/Si化物复合材料研究及发展的关键因素。本研究采用煤油为碳源、正硅酸乙酯为硅原,根据快速化学液相沉积工艺在不同实验条件下制备C/Si化物复合材料。本文以理论分析与工艺试验为基础,结合材料的微观表征、致密化机理、抗氧化性能,对制备C/Si化物复合材料的工艺参数进行了系统研究。主要研究内容和结果如下: (1)研究了预制体的表面处理、预制体的直径、电压电流、保温时间等工艺参数对复合材料微观结构的影响。表面处理后制备的Si化物涂层与预制体之间结合紧密,形成良好的梯度过渡。直径为7mm的预制体制备的Si化物层与基体结合良好,涂层内无明显缺陷。随着电压电流的增大,涂层表面的颗粒越大,在电压、电流分别为54V、86A时得到的Si化物涂层颗粒排列致密,表面光滑。保温时间为3h,制备的涂层厚度在120μm左右。制备的Si化物涂层经XRD分析可知,涂层内同时存在SiC及无定形态的SiO_2。 (2)探讨了快速化学液相沉积工艺的机理,分析表明:置于在液态前躯体内的预制体,在制备涂层过程中存在的由内而外的温度梯度及连续的浓度梯度,是快速制备复合材料的关键,同时,沉积过程是化学动力控制机制和扩散相互转变的过程,并通过作图模拟了沉积界面。 (3)通过分析表明,氧气分子在沉积层表面裂纹以及沉积缺陷内的扩散均属于混合型扩散。用质量损失率表征C/Si化物复合材料的氧化行为。随着温度的升高,复合材料的氧化质量损失逐渐升高。抗氧化性能测试表明,C/Si化物复合材料在900℃下静态空气中氧化10h后质量损失率仅为15.4%。 (4)研究了C/Si化物复合材料的氧化行为、氧化模式和氧化机理。C/Si化物复合材料的氧化行为受涂层内的裂纹和沉积缺陷控制。在400℃～700℃内,C/Si化物复合材料的氧化速度由C-O2的反应控制。在700℃～900℃内,氧化速度由氧通过沉积缺陷和涂层内的微裂纹控制。温度在900℃～1200之间,氧化速度由氧通过沉积缺陷的扩散控制。在1200℃以上,氧化速度由于涂层表面产生的气泡急剧加快。
[Abstract]:Carbon materials have excellent chemical corrosion resistance, heat resistance, good thermal conductivity, low resistivity, radiation resistance, thermal conductivity, noise reduction, shock absorption and a series of mechanical and electrical properties. It has become a new material in the field of new technology research in the world. It is widely used in the fields of national defense, aviation and aerospace, medical treatment, transportation, equipment and other civil fields. However, carbon materials are easily oxidized at high temperature, which results in the degradation of their properties. Therefore, it is of great significance to study the oxidation resistance of carbon materials. The relationship between the rapid preparation process and the structure and properties is the key factor to determine the research and development of C / Si composites. Using kerosene as carbon source and ethyl orthosilicate as silicogen, C / Si composites were prepared by rapid chemical liquid deposition under different experimental conditions. On the basis of theoretical analysis and technological tests, the process parameters of C / Si composites were systematically studied in this paper, combining with the microscopic characterization, densification mechanism and oxidation resistance of C / Si composites. The main contents and results are as follows: 1) the effects of surface treatment, diameter, voltage and current, and holding time of the preform on the microstructure of the composite were studied. After surface treatment, the Si coating is bonded closely with the preform, and a good gradient transition is formed. The silicide layer prepared by the 7mm preform binds well to the substrate, and there is no obvious defect in the coating. With the increase of voltage and current, the particles on the surface of the coating become larger. When the voltage and current are 54V / 86A, the particles of the coating are compact and the surface is smooth. The coating thickness is about 120 渭 m when the holding time is 3 h. XRD analysis showed that sic and amorphous Sio _ 2 in the coating existed simultaneously. The mechanism of rapid chemical liquid deposition was discussed. The results showed that the preform was placed in the liquid front body. The temperature gradient from inside to outside and the continuous concentration gradient in the process of coating preparation are the key to the rapid preparation of composite materials. At the same time, the deposition process is the process of chemical dynamic control mechanism and diffusion mutual transformation. The results show that the diffusion of oxygen molecules in the surface cracks and defects is mixed diffusion. The oxidation behavior of C / Si composites was characterized by mass loss rate. With the increase of temperature, the mass loss of oxidation increases gradually. The oxidation resistance test showed that the mass loss rate of C / Si composites was only 15.4g after oxidation in static air at 900 鈩，

本文编号：2040663