【作者】 王哲；

【导师】 黄玉东；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2007， 博士

【摘要】 分别以石英、纳米二氧化硅粒子和纳米二氧化硅/碳化聚苯胺（GPANI）三种材料作为基底,采用化学气相沉积（CVD）法制备多壁碳纳米管,在一定程度上实现了碳纳米管微观结构及聚集状态的控制,控制作用体现在:在石英基底上生长出碳纳米管的阵列,进而又在该阵列上生长出多层碳纳米管阵列;以纳米二氧化硅控制Fe催化剂的空间尺寸,从而实现了直径分布较窄的碳纳米管的快速生长;通过改变生长促进剂噻吩的浓度和碳源注入速度等因素,在纳米二氧化硅的协助下,制备出竹节状碳纳米管,并且实现了竹节碳层密度在一定程度上的可控生长;制备了纳米二氧化硅/碳化聚苯胺复合基底,使纳米二氧化硅处于镶嵌状态,从而实现了竹节状碳纳米管薄膜的快速生长,竹节状碳纳米管的生长密度受到纳米二氧化硅表面分布密度的控制。使用扫描电镜（SEM）、透射电镜（TEM）对上述碳纳米管的形态和结构进行了表征和分析。并在此基础上,结合X射线光电子能谱（XPS）和X射线能谱仪元素分析（EDS）对碳纳米管的生长机理进行了研究,初步推测了竹节状碳纳米管的生长机理。分析了空气氧化和混酸氧化两种纯化方法对碳纳米管结构的影响,针对所制备的碳纳米管提出了纯化方法。通过经氢氟酸浸泡和450℃空气氧化30min两步处理,得到了高纯度的碳纳米管。使用体积比为3:1的浓硫酸与浓硝酸于60℃条件下对碳纳米管进行混酸氧化,通过SEM、红外光谱（FTIR）对纯化效果进行了分析,结果表明,随着氧化时间的延长,碳纳米管被不同程度裁短,并使管壁上生成羧基和羟基。使用热重分析（TGA）和拉曼（Raman）光谱对碳纳米管进行了缺陷分析,发现竹节状碳纳米管具有较多的缺陷。碳纳米管的场发射性能测试与丝网印刷浆料的研究结合进行,在氧化铟锡（ITO）导电玻璃表面牢固形成碳纳米管/低熔点玻璃复合薄膜。场发射性能测试结果表明,由于缺陷作用,竹节状碳纳米管的场发射性能远高于普通结构的碳纳米管。采用激光刻蚀技术在ITO玻璃衬底上制备出碳纳米短管薄膜。SEM和TEM测试显示碳纳米管被激光截短,管壁变得粗糙不平。Raman光谱分析说明石墨层晶格结构发生了扭曲和混乱。该薄膜具有一定的场发射性能和电子发射稳定性。本研究还制备了一种新的场发射材料碳化聚苯胺。通过对不同条件制备的碳化聚苯胺进行场发射测试,确定了合理的反应条件为:60¹00MPa压片,900℃下氢气热处理2h。XRD、SEM、TEM、Raman光谱和XPS分析表明:碳化聚苯胺是一种氮掺杂的非晶态碳材料,其场发射性能主要来源于:表面纳米级的凸起结构;sp²C结构中包含一定量的sp³C;适量的氮掺杂使表面势垒降低,降低了电子溢出功。研究了在碳化聚苯胺基底上原位生长碳纳米管制备场发射阴极材料的方法。采用旋转蒸发—高温还原法实现了Fe/SiO₂催化剂的快速制备,将该催化剂沉积在碳化聚苯胺基底表面的空隙中,采用低压化学气相沉积法（LPCVD）生长碳纳米管,结果表明:在碳纳米管生长的同时,部分碳原子在孔隙中沉积使孔隙封闭,从而使碳纳米管的根部牢固固定在基底上。因此赋予该材料很强的场发射稳定性。对在纳米二氧化硅/碳化聚苯胺复合基底上生长竹节状碳纳米管薄膜进行了分析和表征。场发射性能测试结果表明,该阴极材料具有很低的开启电场强度和阈值电场强度,并表现出较强的场发射稳定性。更多还原

【Abstract】 In this stduy, multi-wall carbon nanotubes （MWNTs） were prepared with chemical vapor deposition （CVD） on three substrates: quartz, nano-SiO₂ and nanoSiO₂/ Graphitized Polyaniline （GPANI）, respectively. To some extent, the micro-structure of resulted carbon nanotubes were controlled, i.e.: 1) the array of carbon nanotubes was formed on quartz, and then multi-layer carbon nanotubes further grew on this array; 2) the narrow distribution carbon nanotubes grew rapidly by using nano-SiO₂ to control Fe catalyst space; 3) by changing experiment factors（such as the concentration of the promoter thiophene, the inject rate of carbon source） and with the aid of nano-SiO₂, the bamboo-like carbon nanotubes was synthesized with the control of bamboo joint carbon layer intensity; 4) the insertion state nano-SiO₂ on the composite substrate of nano-SiO₂/ GPANI made bamboo-like nanotubes film grow much faster. Therefore, the intensity of bamboo-like carbon nanotubes was controlled by the distribution （intensity） of nano-SiO₂ at the surface.The micro-structure of above carbon nanotubes were analyzed with scanning electron microscope （SEM） and transmission electron microscopy （TEM）. With the combination of X-ray photoelectron spectroscopy analysis （XPS） and X-ray microanalysis （EDS）, the growing mechanism of bamboo-like carbon nanotubes was investigated tentatively.The thermal gravimetric analysis （TGA） and Raman spectrum indicated there were many defects on the bamboo-like carbon nanotubes.The effects of purifying methods, air oxidation and mixed-acid oxidation, on the structure of carbon nanotubes were analyzed. The moderate method of the two-step treatment was proposed. The resulted carbon nanotubes was rinsed in HF and oxidized in the air at 430℃for 30 min. The high purified carbon nanotubes was obtained in the expense of slight damage of the structure of the carbon nanotubes. And then oil of vitriol and dense nitric acid （volume ratio for 3:1） oxidated CNTs at 60℃, the result of SEM and TEM analyses showed that the CNTs were cut into short,and the shell of the tubes produced carboxyl and hydroxy with oxidization time. The carbon nanotubes/low melting point glass composite film was formed tightly on the surface of the ITO glass. The study of the carbon nanotube field emission performance with the aid of screen printing paste indicated that, due to the defect of resulted carbon nanotubes, the field emission performance of bamboo-like carbon nanotubes was higher that of common carbon nanotubes.The short carbon nanotubes film was prepared with laser sculpture technology. The result of SEM and TEM analyses showed that the CNTs were truncated and the tube became rough. Raman spectra showed that the carbon layer crystal lattice structure was contorted and disordered. The film possessed field emission properties and electronic emission stability.A new field emission material, GPANI, was prepared at different reaction conditions. The results of field emission tests indicated that the optimum reaction conditions were: pressure under 60-100MPa,then treated with hydrogen under 900℃for 2h. XRD, SEM, TEM, Raman spectra and XPS results indicated that GPANI was a kind of N-doped amorphous carbon material, its field emission performance resulted from that the surface containing convex structure and the sp²C structure containing sp³C,and the appropriate N-doped structure would decrease the surface potential barrier which improved the field emission performance.The preparation of field emission cathode material for in situ growing the carbon nanotube on the GPANI substrate was also studied. The rapid preparation of Fe/SiO2 catalyst was realized with rotation evaporation and high temperature reduction. Once this catalyst was deposited in the gap of the surface of GPANI substrate, the carbon nanotubes would grow by low pressure chemical vapor deposition （LPCVD）. The results indicated that the gap was closed by partial carbon atoms during the deposition when the carbon nanotubes grew, which made the root of the carbon nanotubes fixed firmly on the substrate. Therefore, this material possessed perfect field emission stability. Finally, the study of growing the bamboo-like carbon nanotubess film on composite substrate of nano-SiO2/GPANI was carried out, then the resulted film was use as field emission cathode material. The result showed that this material had low turn-on filed strength and threshold field strength, and good field emission properties.更多还原