乙二醇辅助水热法合成氧化物纳米结构及表征

【作者】 李慎重；

【导师】 杨德仁； 阙端麟；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2005， 硕士

【摘要】 纳米材料和纳米结构是当今新材料领域中十分重要的研究对象,特别是一维纳米材料由于其新颖的物理、化学和生物学特性以及在纳米器件中的潜在用途成为当今纳米技术的研究热点。就一维纳米材料的合成而言,水热法由于设备简单,成本较低,可控性好,制备的材料纯度高、结晶好等优点,被认为是未来制备纳米材料最具有潜力的方法之一。本文在传统水热和溶剂热方法的基础上,提出了乙二醇辅助水热法新工艺,成功合成出铜氧化物和氧化铁纳米材料的新结构一枝状纳米结构。其中取得的主要创新结果如下:采用乙二醇辅助水热法合成了CuO枝状纳米结构和Cu2O花状纳米结构,无乙二醇作辅助剂的条件下,直接水热合成了CuO片状纳米结构,由此可知,乙二醇对枝状纳米结构的形成起决定作用。研究指出,辅助剂乙二醇为10ml左右时合成枝状结构,为20-40ml时形成花状结构;形成枝状纳米结构的pH值范围为8-10;温度为200℃时,纳米结构结晶较好。通过上述三种纳米结构合成过程的对比,提出了枝状纳米结构的形成机理。通过乙二醇辅助水热法还成功合成了FeOOH枝状纳米结构,再经350℃热处理,得到Fe2O3枝状纳米结构。无乙二醇辅助剂的条件下,直接水热合成了片状FeOOH纳米结构,同样经350℃热处理后,得到Fe2O3片状纳米结构。研究发现,上述两种结构只能在碱性或中性条件下制备得到,而在酸性溶液中,乙二醇不再具有辅助剂的作用,水热合成的是Fe2O3纳米颗粒,其粒径约40nm,同时还发现,粒径大小跟反应源浓度有正对应关系,反应源浓度较高时,合成的Fe2O3纳米颗粒粒径随之增大。实验对上述制得的不同形貌Fe2O3纳米结构进行各种性能测试。对其紫外可见吸收谱的测试分析表明,随Fe2O3纳米结构尺寸减小,其吸收峰发生明显蓝移。通过对合成的不同形貌Fe2O3磁滋回线的测试分析,发现随Fe2O3纳米结构尺寸减小,矫顽力和余磁随之减小,而饱和磁化强度则增加。更多还原

【Abstract】 Nanostructures with various morphologies have attracted great interests due to their significant potential applications. One-dimensional nanomaterials have received intensive interests due to their novel physical, chemical, and biological properties as well as the potential applications in nanodevices. Comparing to other methods, hydrothermal method has been widely employed to prepare one-dimensional nanomaterials due to its advantages of low temperature, simplicity, and large-scale production.In this paper, the novel Ethylene Glycol （EG） assisted hydrothermal method is used to prepare the novel dendrite-like CuO and FeOOH nanostructures successfully. The main results are the following:The dendrite-like CuO and flower-like Cu₂O nanostructures have been synthesized by EG-assisted hydrothermal route. When no EG in the hydrothermal solution, flake-like CuO nanostructures is obtained. The results of the experiments indicate that EG is critical to the preparation of the dendrite-like nanostructures and at the same time it is found that EG is an assistor only when pH value of the hydrothermal solution is within an appropriate range. Moreover, EG is not only an assistor but also has the ability of reducing under the certain pH value. If low quantity of EG is added into the solution, the dendrite-like nanostructures can be prepared, but when with high quantity of EG addition, flower-like and cubic Cu₂O nanostructures are achieved. Based on that, the effects of reaction conditions including the quantity of EG, pH value, reaction temperature and the source concentrations on the morphology and phase of the resulting products are further studied, at the same time, the mechanism of such dendrite-like nanostructures is preliminary presented. Such results will probably be helpful to the controllable fabrication of various nanostructures.Similarly, during the preparation of FeOOH nanostructures, when no EG theflake-like FeOOH nanostructures are synthesized, otherwise, if EG is introduced into the hydrothermal solution, dendrite-like FeOOH can also be fabricated. After the annealing of FeOOH, the corresponding Fe₂O₃ nanostructures are obtained. When the pH value is low in the hydrothermal solution, the product synthesized is Fe₂O₃ nanoparticles. Further investigation shows that the higher the resource concentration is, the larger the nanoparticles are.The UV-vis absorption spectra of the Fe₂O₃ nanostructures with various morphologies show that with the size decrease of the nanoparticles there is blue-shift to the absorption peaks. The magnetization curves of the Fe₂O₃ nanostructures with various morphologies indicate that the morphology has great effects on the magnetic properties of the Fe₂O₃ nanostructures. With the size increase of the Fe₂O₃ nanostructures, the coercive force and residual magnetism are reduced, but the saturation magnetization increases.更多还原