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Alternative TitleDesign and Preparation of Nanostructures and Study on Properties of Ionic Liquids in High Magnetic F
Thesis Advisor张香平 ; 张海涛
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword磁性离子液体   强磁场   高温反应装置   枝状金纳米材料   磁性催化剂
Abstract在强磁场环境下进行科学研究已经引起科研工作者的广泛关注,研究强磁场作用后出现的新现象,揭示反应规律,有利于控制物质在原子尺度上定向运动,调控强磁场中的物理化学反应。对于由正负离子组成的离子液体来说,强磁场能够激发其响应,因此通过调控外加磁场强度和离子液体磁化强度,有望调控离子液体物性,进而改变其参与反应的速率、选择性、转化率、产物形貌等。基于上述背景,本论文的主要工作如下: 1.在磁性离子液体1-丁基-3-甲基咪唑四氯化铁盐(BmimFeCl4)中使用油胺还原氯化金成功制备出枝状金纳米材料。与其他制备方法相比,该方法更加简单:反应物少、步骤少。实验结果表明,BmimFeCl4和油胺的物质的量比(r)对产物的形貌起着决定性作用。当r从0变到0.5时,球形颗粒表面开始向不同的方向生长枝,形成枝状立体结构,枝的直径大约在20~40 nm之间,长度在200~300 nm之间,长径比约为10。r增大到2时,金纳米材料从枝状结构转变成花状结构,表面生成径向长度达到了200 nm的片层结构。比值进一步增大到12时,产物内核直径远远大于表面凸起的长度,生成表面粗糙的类球体。枝状材料最佳制备温度是65 ℃,升高反应温度后产物多为不规则颗粒。同时发现强磁场对产物形貌影响不明显。与花状纳米颗粒(knor=1018 min-1g-1)相比,枝状纳米颗粒(knor=2381 min-1g-1)显示出优良的催化性能。 2.研制在强磁场环境中使用的高温装置,为在强磁场中进行化学反应提供适宜的反应环境。研制过程中选用特种不锈钢和石英材料避免材料对磁场影响,采用水冷炉壁避免热量扩散对强磁体影响,使用直流电加热不对磁场发生器产生干扰。在强磁场环境中应用该高温反应装置水热法制备Fe3O4,发现强磁场对颗粒形貌影响明显;成功制备了一种结构完整的壳/壳/核结构的Fe3O4@SiO2@HNbMoO6磁载催化剂,各种分析手段证明强酸性固体酸HNbMoO6可以牢固地负载在Fe3O4@SiO2磁载体上,具有较强的磁感应强度和良好的磁回收性能。 3.合成两种常规的离子液体HmimNTF2和OmimNTF2,研究它们在强磁场中的粘度变化规律,并对其有机溶剂二元体系的密度和粘度进行了测量、计算和拟合。研究发现:强磁场中,HmimNTF2和OmimNTF2粘度呈下降趋势;离子液体-有机溶剂二元体系的超摩尔体积依据有机溶剂的结构不同而分为正负两种,与氮甲基吡咯烷酮的超摩尔体积为正,与乙醇的超摩尔体积为负;离子液体-有机溶剂二元体系的超摩尔粘度为负,说明低粘度有机溶剂加入使得离子液体体系粘度降低。
Other AbstractIt have attracted considerable interest in a strong magnetic field environment for scientific research. Finding new phenomenon in the magnetic field, and revealing the reaction regularity, it is beneficial to control matter moving at the atomic scale and regulate the physical and chemical reaction in strong magnetic field. For ionic liquids composed of positive and negative ions, strong magnetic field can stimulate its response, so it is expected to regulation of ionic liquid property by regulating magnetic field strength and ionic liquid magnetization, thus change the reaction rate and selectivity, conversion rate, morphology of the product, etc. Based on the above background, the main work of this paper is as follows: 1. Au nanostructures were successfully synthesized by reducing chloroauric acid with oleylamine in1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl4). This method is more easy, less reactants and steps compared to other methods for preparetion of branched gold nanostructures. Results reveal that the size and shape are mostly determined by the molar ratio of BmimFeCl4 to oleylamine. When r changes from 0 to 0.5, branches begins to grow from spherical particle surface in different directions for a stereoscopic dendritic structure. These branches have an average diameter of 20~40 nm , length of 200~300 nm and the length to diameter ratio of about 10.When r increases to 2, gold nanomaterials from dendritic structure into a flower structure, generated on the surface of the radial length to 200 nm lamella structure. And ratio is further increased to 12, the core diameter is more than the length of the bump on the surface of product.The best temperture of prepration of branched gold nanostructures is 65 ℃, and the product , formed at 100 ℃, was a mixture of irregular particles and spherical particles with an average size of about 150 nm. And effect of magnetic field for nanostructures is not obvious.Branched nanostructures (knor=2381 min-1g-1) show improved catalytic activities compared with flake-shaped nanostructures (knor=1018 min-1g-1). 2. The situ reacted equipment at high tempreture in high magnetic field has been designed and established, for providing a suitable reaction conditions for chemical reaction in a strong magnetic field. Using special stainless steel and silica material to avoid influence magnetic field, using water-cooled furnace wall to prevent the spread of heat impact the strong magnets, using a direct current heating for not disturbing magnetic field generator. Effect of high magnetic field on preparation of Fe3O4 has been studied. Then shell/shell/nuclear magnetically responsive catalyst, named Fe3O4@SiO2@HNbMoO6 were successfully synthesized, which consist of a magnetic core surrounded by HNbMoO6 shell. The magnetic core (Fe3O4 nanoparticles) was modified with silica as inert isolating layer. The phase composition, morphology, surface properties and magnetic properties of the composite particles were characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). It has strong magnetic induction intensity and good magnetic recovery performance. 3. HmimNTF2 and OmimNTF2 were synthesized and characterized, and the binary mixture systems of ionic liquids + organic solvents have been tested, calculated and fitted. The results indicate that their viscosity a downward trend in strong magnetic field the binary mixture’s excess molar volumes are positive or negative according to the different organic solvents. The cyclic organic solvent, such as NMP, makes the excess molar volume positive, and chain organic solvent, such as ethanol, makes the excess molar volumes negative. It can be explained that NMP is a cyclic organic molecule interacted with HmimNTF2 or OmimNTF2 as molecule with molecule. However ethanol is a chain-shaped molecule that can be dispersed into ionic liquid easily. Ionic liquids and organic solvents of binary system Moore viscosity is negative, and viscosity of ionic liquid system is reduced after low viscosity organic solvent added.
Document Type学位论文
Recommended Citation
GB/T 7714
张树恒. 强磁性环境中材料合成及离子液体物性研究[D]. 中国科学院研究生院,2013.
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