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MICVD法制备热解炭的结构及其电学性质研究

发布时间:2018-05-10 17:25

  本文选题:微波工艺 + 热解炭 ; 参考:《深圳大学》2017年硕士论文


【摘要】:热解炭(PyC)材料具有优良的机械、物理性能和良好的生物特性,广泛用于核能、航天航空、电能和生物医学工程等领域。本课题组研究了不同维度的炭炭复合材料的热电性质,发现基体PyC结构是影响其热电性质的关键。因此研究PyC的微观织构及其与热电性质之间的相互联系具有重要意义。论文在课题组前期关于微波化学气相渗透工艺研究的基础上,提出了使用微波恒温恒压化学气相沉积法(MICVD)制备PyC工艺;采用自行设计的微波加热沉积装置,研究了在不同工艺条件下制备的多种微观结构PyC及其电学性质,进一步探讨了PyC的微观结构、电输运性质、热解炭生长机理和工艺参数之间的相互关系。本论文主要研究内容如下:研究了MICVD工艺制备不同形貌和微观织构的PyC。通过控制工艺参数,如沉积温度、碳源分压比、腔体总压以及滞留时间,可以实现多种微观织构PyC的制备。通过偏光显微镜(PLM)、X射线衍射(XRD)、扫描电镜(SEM)等手段表征PyC的结构。结果表明,当PyC微观织构有序性逐渐降低(即从高织构到中织构,再到低织构和无定型碳)时,PyC的石墨微晶尺寸La、Lc在逐渐减小,层间距d002在逐渐增大,取向性变差。研究了沉积时间对PyC结构的影响,结果表明沉积时间对PyC结构基本没有影响。通过对PyC微观结构及形貌的分析,探讨了MICVD工艺制备PyC的生长过程,提出了PyC的岛状-层状生长模式。在沉积温度1200℃,腔体总压50KPa条件下,得到了高织构PyC,且最高沉积速率可达到108μm/h。采用热电性能测试仪(ZEM)和综合物性测量系统(PPMS)等研究了不同结构PyC的电输运性质。结果表明,PyC均表现出以空穴为主要载流子的导电特性。随着PyC有序度的提高,其载流子浓度、载流子迁移率及电导率都在逐渐增大,磁电阻及霍尔系数在逐渐减小,Seebeck系数先减小后增大,高织构PyC具有最好的电输运性能。采用MICVD工艺,以碳化硅多孔陶瓷为基体,可制备出炭微米管,其直径约5μm,壁厚约500nm,微观组织结构为高织构PyC,比表面为1.5483 m2/g,比容量为40 F/g,表现出了一定的电容特性。
[Abstract]:Pyrolytic carbon (PyC) has excellent mechanical, physical properties and good biological properties. It is widely used in nuclear energy, aerospace, electrical energy and biomedical engineering. The research group has studied the thermoelectric properties of carbon carbon composites in different dimensions, and found that the structure of the matrix PyC is the key to influence the thermoelectric properties of the carbon carbon composites. Therefore, the microstructure of PyC is studied. The relationship between texture and its thermoelectric properties is of great significance. On the basis of the research on the microwave chemical vapor infiltration process in the earlier period of the project, the paper proposed the preparation of PyC by microwave constant temperature constant pressure chemical vapor deposition (MICVD), and the self designed micro wave heating and deposition device was used to study the different process conditions. A variety of microstructure PyC and its electrical properties were prepared. The microstructure, electrical transport properties, growth mechanism and technological parameters of PyC were further discussed. The main contents of this paper are as follows: the study of the process parameters for the preparation of different morphologies and microstructure of PyC. by MICVD process, such as deposition temperature, is studied. The carbon source pressure ratio, the total pressure of the cavity and the retention time can be used to prepare a variety of microtextured PyC. The structure of PyC is characterized by polarizing microscope (PLM), X ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that when the microstructure of the PyC microstructure is gradually reduced (from high texture to medium texture, then to low texture and amorphous carbon), Py The size of the graphite microcrystal of C is La, the Lc is gradually reduced, the spacing of D002 is gradually increasing and the orientation is worse. The effect of deposition time on the structure of PyC has been studied. The results show that the deposition time has no effect on the structure of PyC. By analyzing the microstructure and morphology of PyC, the growth process of PyC in MICVD process is discussed, and the island layer of PyC is proposed. Under the condition of the deposition temperature of 1200 and the total pressure of 50KPa, the high texture PyC is obtained, and the highest deposition rate can reach 108 m/h.. The electrical transport properties of the different structure PyC are studied by the thermoelectric performance tester (ZEM) and the comprehensive physical measurement system (PPMS). The results show that the PyC shows the conductance of the main carrier as the hole. With the increase of the order of PyC, the carrier concentration, carrier mobility and electrical conductivity are increasing gradually, the magnetoresistance and Holzer coefficient gradually decrease, the Seebeck coefficient decreases first and then increases, and the high texture PyC has the best electrical transport properties. The carbon microtubules can be prepared by MICVD process. Its diameter is about 5 m, the wall thickness is about 500nm, the microstructure is high texture PyC, the specific surface is 1.5483 m2/g, the specific capacity is 40 F/g, showing a certain capacitance characteristic.

【学位授予单位】:深圳大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TQ127.11

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