碳化硅纳米线薄膜的制备及其性能研究

发布时间：2018-05-20 00:03

本文选题：碳化硅纳米线 + 薄膜　；参考：《浙江理工大学》2014年硕士论文

【摘要】：碳化硅(SiC)具有宽禁带、高硬度、高热导率、高击穿场强、高电子迁移率、强抗氧化性和化学稳定性等优异性能。一维SiC纳米材料除保留其本征性质外，还由于纳米尺寸效应、特定的形貌和内在的特殊晶体结构及缺陷，在力学、电学和光学等方面展现出更多特异性能。SiC纳米线薄膜作为一维SiC纳米材料的宏观体结构，在高温分离过滤膜、光电催化分解水制氢、催化剂载体、高温传感器、纳米复合材料以及新型纳米光电器件等领域具有潜在的应用前景。本文采用碳热还原法，以可膨胀石墨为碳源，金属硅粉或正硅酸乙酯为硅源，分别以石墨纸和氧化铝片为纳米线生长基底，制备了3C-SiC纳米线薄膜；通过X射线衍射仪、场发射扫描电镜、透射电镜等手段表征了产物的物相、形貌及微结构；分析了SiC纳米线薄膜的生长机理；利用傅里叶红外光谱仪、激光拉曼光谱仪、荧光光谱仪等仪器研究了纳米线薄膜的成分及光致发光等性能；并重点研究了纳米线薄膜的电化学、光电催化分解水制氢和光催化降解亚甲基蓝性能。得到主要结论如下：以石墨纸为基底，可膨胀石墨、金属硅粉为原料通过碳热还原法合成了SiC纳米线薄膜。考察了不同反应温度、保温时间和原料比例对纳米线薄膜的形貌与结构的影响规律；1500℃下，C/Si摩尔比为2:1，保温反应6h，得到直径约20nm、长度在几百微米到厘米量级的纳米线构成的薄膜，其厚度约100-200μm。分析了石墨纸基SiC纳米线薄膜的两步气-固生长机理：首先Si和反应体系残余O2反应产生SiO气体， SiO与石墨纸基底的碳反应生成SiC晶核，其次，反应体系中的SiO与CO气固反应生成SiC不断沉积在石墨纸基底的晶核上及纳米线端部，使纳米线沿一维方向生长。研究了石墨纸基SiC纳米线薄膜的电化学性能。采用石墨纸基SiC纳米线薄膜作为电化学工作电极，在0.1M H2SO4电解液溶液和10mV s1扫描电压下，其循环伏安特性曲线显示薄膜电极具备良好的电容性能和可逆性。恒流充放电测试表明，该薄膜电极具有优异的能量储存和快速的离子传输性能，在电流密度0.2Acm2、0.3Acm2、0.5Acm2、2.0Acm2下比电容分别为25.6mF cm2、37mF cm2、28mF cm2、28mF cm2，充放电2000次后电容性能保持稳定。研究了石墨纸基SiC纳米线薄膜光电催化分解水制氢性能。采用石墨纸基SiC纳米线薄膜作为光电极，以0.1M H2SO4溶液作为电解液，在500W的可见光照射下，响应电流最高达2.8mAcm-2，薄膜电极表面出现明显的分解水现象，而暗室里响应电流较低，薄膜表面无分解水现象。随着体系中正向电势增加，响应电流增大，分解水制氢效果变得越明显。采用了反Volmer-Heyrovsky机理阐述该光电催化分解水制氢过程。研究还初步探讨了电解液、基底材料、表面负载Pt粒子对电极光电催化作用的影响。以氧化铝片为基底，可膨胀石墨、正硅酸乙酯为原料，通过溶胶凝胶-碳热还原法在氧化铝基底上制备SiC纳米线薄膜，分析了反应温度、保温时间和原料比例等因素对薄膜生长的影响。1500℃下，C/Si摩尔比为1:1，保温反应6h，所得纳米线直径为20-40nm，薄膜厚度约为80μm。分析了氧化铝基SiC纳米线薄膜的生长机理：干凝胶粉末中SiO2和C直接参与反应生成SiO和CO气体，再以气-固反应模式在氧化铝表面异相形核和生长。研究了薄膜的光催化降解性能，薄膜在可见光下具有良好的光催化降解性能，光照6h后亚甲基蓝的脱色率最大为76%，亚甲基蓝分子在光生空穴以及超氧自由基、活化的羟基自由基等基团作用下氧化分解。
[Abstract]:Silicon carbide (SiC) has excellent properties such as wide band gap, high hardness, high thermal conductivity, high breakdown field strength, high electron mobility, strong antioxidant and chemical stability. One dimensional SiC nanomaterials, in addition to their intrinsic properties, are also due to nano size effects, specific morphologies and special crystal structures and defects within them, in mechanics, electricity and optics. More specific properties of.SiC nanowires are shown as the macroscopic structure of one dimensional SiC nanomaterials, which have potential applications in the fields of high temperature separation of filter membrane, photoelectrochemical catalytic decomposition of hydrogen, catalyst carrier, high temperature sensor, nanocomposite and new nano optoelectronic devices.
In this paper, the 3C-SiC nanowire film was prepared with expandable graphite as the carbon source, metal silicon powder or ethyl orthosilicate as the silicon source. The nanowire films were prepared with graphite paper and alumina as nanowires respectively. The phase, morphology and microstructure of the products were characterized by X ray diffractometer, field emission scanning electron microscope and transmission mirror. The growth mechanism of SiC nanowires was analyzed. The components and photoluminescence properties of nanowire films were studied by Fourier transform infrared spectrometer, laser Raman spectrometer, fluorescence spectrometer and other instruments. The electrochemistry of Nanowire Films, the photocatalytic decomposition of water and the photocatalytic degradation of methylene blue were studied. The main conclusions are as follows:
SiC nanowire thin film was synthesized by carbon thermo reduction method with graphite paper as the base, expandable graphite and metal silicon powder as raw material. The influence of different reaction temperature, heat preservation time and raw material ratio on the morphology and structure of nanowire thin film was investigated. At 1500, the C/Si molar ratio was 2:1 and the heat preservation reaction was 6h, the diameter was about 20nm and the length was several hundred. The thin film composed of nanowires of micron to centimeter, whose thickness is about 100-200 M., analyses the two step gas solid growth mechanism of the graphite paper based SiC nanowire thin film: first Si and the residual O2 reaction of the reaction system produce SiO gas, SiO and the carbon reaction of the graphite paper substrate to produce the SiC crystal nucleus, and the SiO and CO gas solid reaction in the reaction system generates SiC. It is deposited on the core of graphite paper and the ends of nanowires, so that nanowires grow along one-dimensional direction.
The electrochemical performance of the graphite paper based SiC nanowire thin film was studied. The graphite based SiC nanowire film was used as the electrochemical working electrode. The cyclic voltammetry curves showed that the film electrode had good capacitance and reversibility under the 0.1M H2SO4 electrolyte solution and the 10mV S1 scanning voltage. The electrode has excellent energy storage and rapid ion transmission performance. Under the current density 0.2Acm2,0.3Acm2,0.5Acm2,2.0Acm2, the specific capacitance is 25.6mF cm2,37mF cm2,28mF cm2,28mF cm2 respectively. After charging and discharging for 2000 times, the capacitance performance is stable.
The performance of hydrogen production by photo catalytic decomposition of graphite paper based SiC nanowire thin film is studied. Using graphite paper based SiC nanowire film as photoelectric pole and 0.1M H2SO4 solution as electrolyte, the response current is up to 2.8mAcm-2 under the visible light of 500W, and the apparent decomposition water phenomenon appears on the surface of the film electrode, while the response current is low in the dark room. There is no water decomposition on the surface of the film. With the increase of the positive potential in the system and the increase of the response current, the effect of the decomposition of water to hydrogen production becomes more obvious. The photoelectrocatalytic decomposition water hydrogen production process is described with the anti Volmer-Heyrovsky mechanism. The effect of the electrolyte, substrate and surface load Pt particles on the photoelectrocatalysis of the electrode is also discussed. Ringing.
The SiC nanowire thin film was prepared on alumina substrate by using alumina as the substrate, expandable graphite and ethyl orthosilicate as raw material. The influence of the reaction temperature, heat preservation time and raw material ratio on the growth of the film was analyzed by the sol-gel carbon thermal reduction method. The C/ Si molar ratio was 1:1 and the thermal insulation reaction was 6h. The diameter of the nanowires was the diameter of the nanowires. 20-40nm, the film thickness is about 80 mu m., the growth mechanism of the alumina based SiC nanowire thin film is analyzed. The SiO2 and C in the dry gel powder are directly involved in the reaction to produce SiO and CO gases, and then the heterogeneous nucleation and growth on the surface of alumina. The photocatalytic degradation properties of the films are studied. The films have good light under visible light. Catalytic degradation performance, the maximum decolorization rate of methylene blue after 6h is 76%, and methylene blue molecules are oxidized by oxygen free radicals, superoxide radicals, activated hydroxyl radicals and other groups.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB383.2

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