二氧化钛纳米材料的制备与结构表征及杀菌性能

IMR OpenIR

	二氧化钛纳米材料的制备与结构表征及杀菌性能
	尚振岗
学位类型	博士
导师	尚建库
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料物理与化学
关键词	Tio2纳米线热蒸镀 Tion薄膜微波晶化透射电镜表征杀菌性能 Tio2 Nanowire Thermal Evaporation Tion Film Microwave Crystallization Tem Characterization Bactericidal Property.
摘要	"半导体二氧化钛（TiO2）纳米材料在环境修复、绿色能源和微电子等领域有广泛的应用前景，然而在实际应用中存在诸多限制，如：禁带宽度大、只能吸收紫外光,纳米颗粒粉末易团聚、难回收，更重要的是纳米颗粒之间过多晶界的存在使电子-空穴的传输性能变得很差，大幅降低了材料的光催化或光伏性能。因而，本论文的研究工作集中在以下两方面以改善TiO2的实用性能：单晶TiO2纳米线的制备及结构表征和杀菌性能；高氮掺杂非晶TiO2薄膜的制备及结构表征和杀菌性能。首先以Au为催化剂，通过调整热蒸镀温度和蒸镀原料的种类，在Ti板上可控地生长出不同形态的TiO2纳米材料。结果表明，这些不同形态的纳米材料都是金红石相TiO2单晶。以Ti及TiO粉为蒸镀源、在850°C得到蠕虫状纳米线，900°C及以上温度得到直线状纳米线；无蒸镀源时、900°C得到纳米片，1000°C和1050°C得到大量的直线状纳米线。在所有的直线状纳米线的产物中，发现极少量的端部呈链球状的纳米线。实验中还发现，固态Au颗粒对TiO2纳米线的生长仍然具备催化作用；另外，Ti基底的固态相变对TiO2产物的形态有重要影响。基于此分析讨论得出高温时纳米线的生长过程遵循经典的气-液-固（VLS）理论；但在低温时纳米线的生长则可用Ti基底的固态原子扩散来解释较为合理。其次，利用透射电镜对不同形态的TiO2纳米材料进行了详细的结构表征。主要结果如下：不同形态的TiO2纳米线都是单晶，且生长方向都是Rutile[110]。直线状纳米线的横截面呈现六边形结构且暴露面为{110}和{112}。实验中发现一种Au与TiO2纳米线之间的取向关系为：(-111)Au// (010)TiO2，[211] Au //[101] TiO2。分析确定了TiO2纳米片的上下表面为{110}晶面。然后研究了氮掺杂TiO2（TiON）非晶薄膜在微波场中的晶化行为。与普通热退火相比，微波可以使非晶TiON薄膜在非常短的时间内晶化，并且薄膜的氮含量高、晶化程度好。微波加热温度对TiON薄膜的微观结构影响很大，500°C及以上在20s内即可获得由贯穿整个薄膜厚度的大晶粒组成的TiON薄膜，而在450°C加热120s却只能得到由尺寸为几个纳米的晶粒组成的薄膜。最后，对比研究了不同TiO2纳米材料的杀菌性能。热蒸镀法制备的各种形态TiO2纳米材料中，其光催化活性由高到低依次为纳米片、蠕虫状纳米线、直纳米线和多晶颗粒膜。多晶颗粒膜的杀菌性能最差，可能是由于其较大的晶粒尺寸（约500nm）而导致催化活性下降造成的；纳米片的杀菌性能最好，分析认为与其{110}暴露面所占比重较大有关。微波晶化TiON薄膜可见光杀菌性能优于同等温度下普通热处理TiON薄膜。由于微波晶化TiON薄膜的含N量高、晶化度好，其可见光杀菌性能优于同等温度下普通热处理的TiON薄膜。"
其他摘要	"Titanium dioxide has found wide applications in environmental and energy related fields because of its semiconductor photocatalytic properties. However, to take good advantage of the semiconductor properties of TiO2 requires a well-developed crystal structure. This is especially important for nano-sized photocatalysts where crystalline defects or noncrystalline regions could become a significant fraction of the total volume of the nanostructures so that the nanosized photocatalysts may suffer from a serious loss of the semiconductor properties. In this study, nanocrystals were made in two forms of nanostructures, a one-dimensional nanowire, and a two-dimensional thin film. The microstructures and properties of the nanocrystals were characterized. Firstly, a large quantity of TiO2 nanomaterials with various morphologies were synthesized by a thermal evaporation method, using a bulk Ti plate pre-coated with a thin Au layer as the substrate. At a deposition temperature from 850°C to 1050°C, all deposition products were rutile TiO2. With Ti or TiO as the evaporation sources, worm-like nanowires were obtained at 850°C, while straight ones were got at and above 900°C. Without evaporation sources, the products at 900°C were nanoslices, while nanowires were synthesized at 1000°C and 1050°C. In addition, it was found that Au particles in the solid state are still effective as catalysts for the growth of TiO2 nanowires, and the resulted morphologies of TiO2 products have direct relationship with the solid state transformation of Ti substrate. The growth of worm-like TiO2 nanowires at low temperature (850°C at least) was discussed basing on the solid state diffusion of Ti atoms from the Ti substrate, and the synthesis of straight TiO2 nanowires at 1050°C could be explained by the classical vapor-liquid-solid (VLS) mechanism. Secondly, microstructural characterization of the above obtained TiO2 nanomaterials was carried mainly using transmission electron microscopy (TEM). Nanowires with different morphologies, including straight nanowires, nanochains and worm-like nanowires are all single rutile crystals grown in the <110> crystallography direction. The cross-section of the straight nanowires obtained at 1050°C was a solid hexagon with {110} and {112} as the external surfaces. The appearance of {112} faces with higher surface tension in straight nanowires implies that the growth of TiO2 nanowire is not a thermodynamic equilibrium process. The worm-like nanowires expose {110} and {100} surfaces viewed from rutile [001] direction, while the nanochains seldomly observed on the top of straight nanowires present {101} faces in [111] direction, although both of their three-dimensional morphologies still remain unclear at the present. The catalyst Au particles have a distorted quasi-truncated-octahedron morphology theoretically enclosed by {111} and {100} faces. Between Au particle and TiO2 nanowire the following orientation relationship was observed with a mismatch of 2.45% between Au (-111) and TiO2 (010) planes: (-111)Au // (010)TiO2, and [211] Au // [101] TiO2. Then, the crystallization behavior of the amorphous TiON film on Si substrate was invesgated. Compared with the conventional thermal annealing, TiON film with a much higher nitrogen concentration and better crystallinity could be obtained by microwave annealing in a much shorter time. The optimum annealing parameters of microwave irradiation are 500°C within 20s. Increase of annealing temperature and irradiation time resulted in the decrease of nitrogen concentration within the film. The crystallized TiON film has an anatase but not a rutile structure at the annealing temperature up to 800°C. Finally, bactericidal properties of various TiO2 nanomaterials were comparatively studied. The bactericidal ability of nanomaterials obtained by thermal evaporation method inceases in sequence of TiO2 polycyrstal films, straight nanowires, worm-like nanowire and nanosclices.The bad performance of polycyrstal films may be due to their large crystal sized of about 500nm. The nanoslice had the best bactericidal ability which colud be attributue to their rutile {110} surfaces.The visible light bactericidal ability of TiON films on Si (100) has been enhanced by 22% through microwave annealing (500°C, 20s) in comparison with the conventional heat treatment at the same temperature (500°C, 300s), owing to a higher nitrogen concentration and a better crystallinity in the microwave annealed film."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64423
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	尚振岗. 二氧化钛纳米材料的制备与结构表征及杀菌性能[D]. 北京. 中国科学院金属研究所,2012.