【作者】 邹光龙；

【导师】 陈卫祥； 刘润；

【作者基本信息】 浙江大学 ， 物理化学， 2007， 博士

【摘要】 无机纳米材料尺寸、形状相关的物理性质为材料的潜在应用提供了广阔的空间,而构筑结构复杂的纳米粒子进一步提升了它们的功能。本论文以氢氧化镁和氧化锌为研究对象,旨在探索其复杂的微/纳米结构的有效液相化学合成途径,并通过控制合成条件来控制产物的微观形貌。电沉积技术是一种液相电化学沉积方法,已被广泛地用来制备不同纳米薄膜以及氧化物、金属硫化物和氢氧化物等薄膜。电沉积通常在室温条件下操作,沉积的量由Faraday定律控制,并可通过改变沉积电位、电流密度、溶液组成等控制膜的厚度及结构:此外,电沉积技术工艺简单、价格低廉,是一种经济的沉积方法。化学液相沉积类似化学气相沉积技术,将含有构成薄膜成分的一种或几种化合物和单质通过液相供给基片表面,产生化学反应而形成不挥发的固态膜层或材料的方法。其基本要求是基片表面必须有异相的化学反应。该方法具有薄膜沉积速率适中、沉积温度低、可在任何形状和大小的基片上沉积,膜的组成和晶型易于通过沉积条件精确控制等优点。氢氧化镁作为一种重要的无机功能材料,被广泛地用于复合材料中无卤防火阻燃填充剂,催化剂、添加剂和陶瓷前驱体。纯品氢氧化镁为六方晶系或无定形片状晶体,是一种无机弱碱类产品,因其具备较强的缓沖性能、较高的活性和吸附能力、处理使用安全以及无腐蚀性、无毒、无害等诸多独特性能,因此被称为“绿色安全中和剂”、“环境友好阻燃剂”以及“第三种碱”。氧化锌作为是一种重要的直接宽禁带半导体,因其无毒、廉价和化学稳定性并具有优良光、电和化学性质。因此被广泛用于光电子、涂料、化装品、催化剂和气体传感器等领域。本论文的主要工作对氢氧化镁和氧化锌微/纳米结构的新颖软化学合成及其表征进行了较为系统的研究,并取得了以下主要创新性研究成果:1.采用简单分子辅助化学液相沉积的方法,在近室温和室温条件下分别在甲酰胺水溶液和氨基乙酸水溶液中合成了层状和三维花状微/纳米结构的氢氧化镁。比较系统地考察了反应物浓度、反应时间、反应温度对氢氧化镁微/纳米结构的影响。初步研究了形成这种特殊微/纳米结构的可能机理。该方法具有反应条件温和,反应参数可调控,不引入外来杂质等优点。2.采用阴极还原电沉积的方法,室温下直接在硝酸镁水溶液中沉积得到一层均匀的氢氧化镁薄膜。该膜是由纳米壁构成的均匀网络结构。通过XRD、TG/DSC、FT-IR等物理手段确认所得产物为介观层状氢氧化镁,具有类似分子筛和水滑石层状结构;其次,考虑了两种不同的添加剂(醋酸钠和水溶性离子液体)对电沉积氢氧化镁微结构的影响。在此基础上比较系统地考察了添加剂浓度、沉积时间和沉积电压对所沉积薄膜的影响。并初步阐述了添加剂对所沉积薄膜的作用机理。3.采用非水溶液电沉积金属锌膜,然后对其在常压空气中煆烧得到了具有(002)取向加强的氧化锌薄膜。系统地考查了热氧化温度、沉积电位、热处理时间、不同锌盐前驱体对所得薄膜的影响。4.采用简单化学液相沉积的方法,在近室温条件下分别在甲酰胺水溶液和溴酸钾水溶液中合成了纳米棒/管构成的海蛰状和纺锤形氧化锌微/纳米结构。考察了反应物浓度对氧化钠微/纳米结构及其荧光性质的影响,并对所形成的特殊微/纳米结构的可能机理作了初步的探讨;其次,研究了柠檬酸三钠添加剂在甲酰胺水溶液液相化学氧化金属锌箔沉积氧化锌微/纳米结构的影响;再次,考察了不同衬底在六次甲基四胺-硝酸锌体系中对沉积氧化锌纳米结构的影响。该方法具有反应条件温和,反应参数可调控,可一步湿法直接合成氧化锌新颖微/纳米结构等优点。本论文提出了用简单液相化学沉积及其电沉积的方法制备特殊微/纳米结构的氢氧化镁和氧化锌。这些方法在制备金属氧化物和金属氢氧化物特殊结构具有方法简便,可操作性强等优点,并且所得的薄膜比其它方法制得的薄膜更具有厚度均匀、附着力强、方便控制材料的尺寸和形状等优点。更多还原

【Abstract】 The ability to control and manipulate the physical and chemical properties of materials as we desired is one of the challenging issues in chemistry and materials science.The size- and shape-dependent physical properties of inorganic nanoparticles provide tunable materials with broad potential applications,and the fabrication of structurally complex nanoparticles further enhances their functionality.This dissertation aims at searching for effective solution routes to synthesize complex micro/nanostructured magnesium hydroxide and zinc oxide,control the morphology of the products by adjusting the reaction conditions.Elelctrodeposition has evolved recently to a simple and effective liquid phase method for fabrication of homogenous thin layers of insoluble materials,such as metal,ceramics,metal sulfide and metal hydroxide.Electrodeposition usually operates at room temperature and the quantity of deposition is determined by Faraday law,which is very suitable for preparing thin films.Thickness and structure of films can be precisely controlled by electrochemical parameters on conductive substrate of complex shapes,such as deposition potential,current density and solution composition.Moreover,electrodeposition is an economical deposition method due to simple process and inexpensive equipment.The chemical-liquid-deposition process,an analogue to the widely used chemical-vapor-deposition technique,has been well developed for production of insoluble solid films or materials through continuous supply,transport,and chemical reaction of film constituent in a liquid phase.Its basic requirement is heterogeneous chemical reaction on the substrate surface.This method has several merits:（a） appropriate deposition rates can be easily obtained;（b）operation can be achieved at low temperature at ambient conditions;（c）relatively uniform films can be formed on substrates of complex shapes and different size;（d）composition and crystallite of films can be precisely controlled by deposition conditions.Magnesium hydroxide is widely used as halogen-free flame retardant filler in composites materials,catalysis,and additive in refractory and paint,precursor for ceramics.Pure magnesium hydroxide,hexagonal or amorphous platelet crystal,is an inorganic weak alkali product.Due to its relatively strong buffer capacity,high activity and adsorption ability,safe disposal and treatment,magnesium hydroxide is considered to green and safe neutralization agent,environment friendly fire-retardant and the third alkaline while being noncorrosive,nontoxic and nonpoisonous.Znic oxide,an important direct n-type semiconductor with a band gap of 3.37 eV and a large exciton binding energy of 60 meV,and a high efficiency of exciton recombination at room temperature,has excellent optical,chemical,and electrical properties while being nontoxic,inexpensive,and chemically stable.ZnO has attracted considerable attention recently for various potential applications in optoelectronics,paints,cosmetics,catalysis and gas sensor.The main work of this thesis is systematically study on novel soft synthesis and characterization of micro/nanostructured magnesium hydroxide and zinc oxide.The details are given as follows:1.Lamellar-like and 3D flower-like Mg（OH）₂ were synthesized in formamide and glycine aqueous solution at near room temperature and room temperature through simple molecule assisted chemical-liquid-deposition process.Effects of reactant concentration,time and temperature on micro/nanostructured magnesium hydroxide were systematically investigated.The possible formation mechanism of these special micro/nanostructures was also discussed.The convenient,self-seeding growth of Mg（OH）₂ nanostructure not only has an attractive economical,but also avoids the incorporation of exotic metals and metals oxides as catalysts or seed particles, respectively.The exclusion of exotic metal catalysts and counterions（from Mg salt involved in other wet-chemical approaches）is very crucial for fabricating reliable and exquisite materials without unintentional properties.2.Uniform magnesium hydroxide thin film was obtained from directly electrolysis of magnesium nitrate aqueous solution at room temperature.The film with net-like was built up of nanowall.The as-synthesized magnesium hydroxide with highly textural lamellar mesostructure analogue to zeolite and layered double hydroxide was confirmed by XRD、TG/DSC、FT-IR techniques.Secondly,effects of sodium acetate and water-soluble ionic liquid additives on electrodeposited magnesium hydroxide microstructure were studied,then the influence of synthesis parameters on the morphological characteristics and size of magnesium hydroxide thin films deposited from nitrate bath was investigated,such as concentration of additive,duration and applied potential.A possible interaction mechanism responsible for morphologies evolution of thin films was preliminarily elucidated.3.A novel route was developed to prepare the polycrystalline ZnO thin films with（002）orientation enhancement by air annealing of zinc metallic films electrodeposited from nonaqueous solution without using any catalyst and template. Effects of annealing temperature,applied potential,annealing duration,different zinc salt precursor on thin films were systematically conducted.4.Urchin-like built up of nanorod/tube and spindle-like ZnO were synthesized in formamide and potassium bromate aqueous solution at near room temperature through simple chemical-liquid-deposition process.Effects of reactant concentration on zinc oxide micro/nanostructures and photofluorescence was carried out.The possible formation mechanisms of these unique micro/nanostructures were also presented.Secondly,effects of trisodium citrate additive on chemical-liquid-deposition zinc oxide nano/microstructure were executed.Finally,the influence of different substrate on the nature of zinc oxide grown from zinc nitrate and hexamethylenetetramine system through chemical-bath-deposition process was investigated.Novel micro/nanostructured zinc oxide can be directly obtained by simply adjusting reaction parameters at ambient conditions.In this thesis,unique micro/nanostructured magnesium hydroxide and zinc oxide were fabricated through simple chemical-liquid-deposition and cathodic electrodeposition.These methods have advantage over convenient,easy to operation. Moreover,the as-synthesized films were uniform thickness,good adhesion and well tailoring of shape and size compared with other methods.更多还原