【作者】 裴新美；

【导师】 陈文；

【作者基本信息】 武汉理工大学 ， 材料学， 2003， 硕士

【摘要】 本文系统地研究了ZnO晶须的控制合成、生长机理及性能。采用简单的气相反应方法，实现了ZnO晶须形态和尺度的控制生长，制备出形态规整、结构均匀的各种ZnO晶须：T-ZnO晶须、一维ZnO晶须和ZnO阵列。ZnO晶须可控生长的关键是控制成核和生长过程，而反应体系的工艺参数决定着成核和生长过程，最终控制ZnO晶须的形貌。 用SEM，TEM，HRTEM对ZnO晶须的形貌和结构进行了分析，结果表明，T-ZnO晶须的生长机理为气—固机理。ZnO晶须的生长模型为八面体孪晶核生长模型，即先通过均匀成核形成八面体孪晶核，然后在四个正(0001)面上优先生长四根针体形成T-ZnO晶须。TEM和HRTEM观察首次给出了八面体孪晶核生长模型的直接证据。沉积在Si基板上的ZnO纳米线和ZnO阵列首先通过非均匀成核，再通过VS生长机理沿[0001]方向择优生长。 在T-ZnO纳米晶须、ZnO纳米线和ZnO阵列室温光致发光谱中均观察到385nm的窄紫外发射峰和495nm处的宽绿光发射峰，紫外发射峰对应于近带边发射，绿光发射峰对应于深能级发射。三种ZnO材料中的紫外峰强度接近，但绿峰强度差别很大：纳米线中的最强，T-ZnO纳米晶须中的次之，ZnO阵列中的最低。绿峰强度的不同取决于其结构中不同浓度的单离子氧空位。将ZnO纳米线在空气中950℃热处理1小时后，绿峰强度大幅度下降，这证明与深能级发射有关的氧空位浓度在热处理后大大降低。通过调节ZnO结构中的氧空位多少，可对ZnO的发光特性进行调控。 在聚丙烯中加入T-ZnO晶须能降低复合材料的电阻率，复合材料导电性提高的机理可归结为网络导电、隧道效应及尖端放电等效应。同时，T-ZnO晶须具有三维立体增强效果，使PP的抗拉强度提高50％。更多还原

【Abstract】 ZnO materials exhibit a wide range of electrical and optical properties that depend sensitively on both shape and size, and are of both fundamental and technological interest. We have demonstrated a simple vapor-phase approach to control growth of ZnO whiskers. Some types of ZnO whiskers with various shape and size, including tetrapod-like ZnO (T-ZnO) whiskers, one-dimensional whiskers (nanowires) and arrays etc., have been obtained by controlled growth process in our laboratory. The key for controlling the shape and size is the level of supersautration that controls ZnO nucleation and growth. The supersaturation in the reaction vessel strongly depends on the processing parameters.The structures of ZnO whiskers have been investigated by means of scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The growth mechanisms of various ZnO whiskers are proposed based on our experimental observations. Results show that T-ZnO whiskers grow in vapor-solid (VS) mechanism. T-ZnO whiskers grow in octa-twin model. Our experimental observation gives the direct evidence to the octahedral multiple twin nucleus model of T-ZnO whisker. ZnO nanowires and arrays deposited on Si substrate also grow in vapor-solid (VS) mechanism.The room temperature PL spectra of the ZnO whiskers show a narrow UV emission at 385nm and a broad green emission at 495nm. The green emission intensity in different structures is different, while their UV emission intensity is nearly the same. The difference in green emission intensity results from the different level of oxygen vacancies in ZnO structures. The green emission intensity in ZnO nanowires is decrease but the UV emission intensity keeps unchanged when the nanowires are annealed at 950℃ for an hour. It is obvious that optical property of the ZnO is tunable by controlling the oxygen vacancy concentration.The electrical resistivity of T-ZnOw/Polypropylene composites is decreased by using T-ZnO whiskers as the conductive additives. The conductive mechanisms are the combine of net conductive, tunnel effect and the charge concentrating effect at the needle’s tips of the whiskers. The tensile strength of the composites is increase 50% compared to the PP matrix.更多还原