本文選題：碳化硅納米線 + 薄膜�。� 參考：《浙江理工大學》2014年碩士論文

【摘要】：碳化硅(SiC)具有寬禁帶、高硬度、高熱導(dǎo)率、高擊穿場強、高電子遷移率、強抗氧化性和化學穩(wěn)定性等優(yōu)異性能。一維SiC納米材料除保留其本征性質(zhì)外，還由于納米尺寸效應(yīng)、特定的形貌和內(nèi)在的特殊晶體結(jié)構(gòu)及缺陷，在力學、電學和光學等方面展現(xiàn)出更多特異性能。SiC納米線薄膜作為一維SiC納米材料的宏觀體結(jié)構(gòu)，在高溫分離過濾膜、光電催化分解水制氫、催化劑載體、高溫傳感器、納米復(fù)合材料以及新型納米光電器件等領(lǐng)域具有潛在的應(yīng)用前景。 本文采用碳熱還原法，以可膨脹石墨為碳源，金屬硅粉或正硅酸乙酯為硅源，分別以石墨紙和氧化鋁片為納米線生長基底，制備了3C-SiC納米線薄膜；通過X射線衍射儀、場發(fā)射掃描電鏡、透射電鏡等手段表征了產(chǎn)物的物相、形貌及微結(jié)構(gòu)；分析了SiC納米線薄膜的生長機理；利用傅里葉紅外光譜儀、激光拉曼光譜儀、熒光光譜儀等儀器研究了納米線薄膜的成分及光致發(fā)光等性能；并重點研究了納米線薄膜的電化學、光電催化分解水制氫和光催化降解亞甲基藍性能。得到主要結(jié)論如下： 以石墨紙為基底，可膨脹石墨、金屬硅粉為原料通過碳熱還原法合成了SiC納米線薄膜。考察了不同反應(yīng)溫度、保溫時間和原料比例對納米線薄膜的形貌與結(jié)構(gòu)的影響規(guī)律；1500℃下，C/Si摩爾比為2:1，保溫反應(yīng)6h，得到直徑約20nm、長度在幾百微米到厘米量級的納米線構(gòu)成的薄膜，其厚度約100-200μm。分析了石墨紙基SiC納米線薄膜的兩步氣-固生長機理：首先Si和反應(yīng)體系殘余O2反應(yīng)產(chǎn)生SiO氣體， SiO與石墨紙基底的碳反應(yīng)生成SiC晶核，其次，反應(yīng)體系中的SiO與CO氣固反應(yīng)生成SiC不斷沉積在石墨紙基底的晶核上及納米線端部，使納米線沿一維方向生長。 研究了石墨紙基SiC納米線薄膜的電化學性能。采用石墨紙基SiC納米線薄膜作為電化學工作電極，在0.1M H2SO4電解液溶液和10mV s1掃描電壓下，其循環(huán)伏安特性曲線顯示薄膜電極具備良好的電容性能和可逆性。恒流充放電測試表明，該薄膜電極具有優(yōu)異的能量儲存和快速的離子傳輸性能，在電流密度0.2Acm2、0.3Acm2、0.5Acm2、2.0Acm2下比電容分別為25.6mF cm2、37mF cm2、28mF cm2、28mF cm2，充放電2000次后電容性能保持穩(wěn)定。 研究了石墨紙基SiC納米線薄膜光電催化分解水制氫性能。采用石墨紙基SiC納米線薄膜作為光電極，以0.1M H2SO4溶液作為電解液，在500W的可見光照射下，響應(yīng)電流最高達2.8mAcm-2，薄膜電極表面出現(xiàn)明顯的分解水現(xiàn)象，而暗室里響應(yīng)電流較低，薄膜表面無分解水現(xiàn)象。隨著體系中正向電勢增加，響應(yīng)電流增大，分解水制氫效果變得越明顯。采用了反Volmer-Heyrovsky機理闡述該光電催化分解水制氫過程。研究還初步探討了電解液、基底材料、表面負載Pt粒子對電極光電催化作用的影響。 以氧化鋁片為基底，可膨脹石墨、正硅酸乙酯為原料，通過溶膠凝膠-碳熱還原法在氧化鋁基底上制備SiC納米線薄膜，分析了反應(yīng)溫度、保溫時間和原料比例等因素對薄膜生長的影響。1500℃下，C/Si摩爾比為1:1，保溫反應(yīng)6h，所得納米線直徑為20-40nm，薄膜厚度約為80μm。分析了氧化鋁基SiC納米線薄膜的生長機理：干凝膠粉末中SiO2和C直接參與反應(yīng)生成SiO和CO氣體，再以氣-固反應(yīng)模式在氧化鋁表面異相形核和生長。研究了薄膜的光催化降解性能，薄膜在可見光下具有良好的光催化降解性能，光照6h后亞甲基藍的脫色率最大為76%，亞甲基藍分子在光生空穴以及超氧自由基、活化的羥基自由基等基團作用下氧化分解。
[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.
【學位授予單位】：浙江理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TB383.2

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