纤蛇纹石酸浸及其制备氧化硅纳米线的研究

【作者】 杨艳霞；

【导师】 冯其明；

【作者基本信息】 中南大学 ， 再生材料工程， 2007， 硕士

【摘要】 氧化硅纳米线具有特殊的蓝光光致发光性能，是一种极具应用潜力的一维纳米新材料。本论文从天然矿物纤蛇纹石本身特有的纳米管状结构出发，研究其通过化学分散、酸处理制备纯度高、直径小、长径比大、分散均匀的氧化硅纳米线的方法及其结构和物化性能的表征。论文的主要研究内容和结果如下：（1）纤蛇纹石的化学分散用阴离子表面活性剂Aerosol OT（AOT）来分散纤蛇纹石，采用FTIR、XRD和SEM等方法对分散效果进行检测，研究结果表明：AOT能很好地吸附在纤蛇纹石表面，对其有很好的分散作用，分散后的纤维基本以纳米级的单纤维存在，纤维问间隙明显。（2）纤蛇纹石的盐酸浸出研究通过单因素实验确定了纤蛇纹石的最佳浸出条件。在此条件的基础上，建立了一种液-固相反应纤维状颗粒的宏观动力学模型，并用该模型计算出反应活化能为24.4 kJ／mol，与用等浸出法计算的反应活化能23.6kJ／mol基本吻合；反应活化能的值说明纤蛇纹石的盐酸浸出反应属扩散控制。利用XRF、XRD、FTIR和N₂吸附-脱附等温技术对纤蛇纹石在盐酸浸出过程中的结构变化进行了研究，结果表明：纤蛇纹石中的Fe主要是以Fe²⁺的形式取代八面体中的Mg²⁺，Al则主要以Al³⁺的形式取代四面体中的Si⁴⁺；盐酸主要通过纤蛇纹石柱面方向与其发生反应，随着浸出的进行，纤蛇纹石中的镁和铁等可溶性成分进入溶液，八面体层逐渐消失，硅氧四面体结构层发生扭曲变形，形成最终的无定形氧化硅；纤蛇纹石比表面积和孔容随着浸出率的增大而增大，由吸附-脱附等温线的滞后回线特征判断其结构中主要含缝隙型孔。（3）纤蛇纹石制备氧化硅纳米线将化学分散与盐酸浸出相结合，利用纤蛇纹石制备出了高纯度的氧化硅纳米线，其化学组成为SiO_1.8·0.6H₂O。其结构为无定形，组成单元仍为硅氧四面体，这些四面体在一定程度上保持了六元环结构。氧化硅纳米线基本呈圆管状，表面较为光滑平整、分散性好，长度约十数微米，直径为25～55nm。更多还原

【Abstract】 As a one-dimensional nanostructure material, silica nanowires, which have special blue light emission, will have good potential application in many fields. Considering from the nanotube structure of natural chrysotile, we report the production of silica nanowires with high-purity, low diameter, large scale of length to diameter and well-dispersion using a chemical dispersing and acid leaching route with chrysotile as a source material in this paper. The main points and content of the paper are indicated as following:（1） The chemical dispersal of chrysotileChrysotile was dispersed with anionic surfactant Aerosol OT （AOT）. The dispersal effect was characterized by FTIR, XRD and SEM. The results show that AOT is absorbed onto the chrysotile surface effectively and chrysotile is dispersed into single fibers. The interspace between fibers is obvious.（2） Chrysotile was leached in hydrochloric acidThe optimum leaching conditions were obtained by separate factor conditional experiments. Then we build the overall kinetic model for the fibrous particle in liquid-solid reaction. Based on the model the apparent activation energy of the reaction is 24.4kJ/mol, which is consistent with the 23.6kJ/mol obtained by subsequent leaching. The kinetic result shows that the reaction rate is determined by diffusion.The change of chrysotile structure during the leaching process in hydrochloric acid was researched by XRF, XRD, FTIR and N₂ adsorption-desorption techniques. The results show that Fe mostly in the form of Fe²⁺ ions occupies octahedral sites to subtitute Mg²⁺, and Al ions are mainly in the tetrahedral sites in place of Si⁴⁺. Chrysotile reacted with acid mainly through its cylinder. As leaching, Mg and Fe ions are dissolved, but Si becomes non-crystal silica. The brucite-like sheet disappeares gradually and the silica-like sheet experiences a distortion. The amorphous silica is obtained at last. A continous enhancement of the specific surface area and total pore volume is observed as leaching. The characteristic of hysteresis loop indicates mainly slit-shaped pores. （3） Preparation of silica nanowires from chrysotile by acid leachingBy chemical dispersion and acid leaching, high-purity silica nanowires were prepared from chrysotile. The chemical composition of silica nanowires is SiO_1.8·0.6H₂O. The silica is amorphous. The structure unit of silica nanowires is a SiO₄ tetrahedron, which retains six-member silicon-oxygen rings. The silica nanowires are well-dispersed and have columned morphology and a smooth surface, with lengths over 10μm and diameters of 25～55 nm.更多还原