利用阳离子吡啶衍生物制备银纳米颗粒及光催化性能研究

摘要：通过二乙烯三胺的还原反应与1-十六烷基溴化吡啶的调控．在室温下化学还原制备均匀单分散的稳定银纳米颗粒。得到的银颗粒尺寸分布在60-90纳米之间。形成银纳米颗粒的反应过程表现出明显的燕山变化,由无色到苍黄色,最终变化到椋黄色。制备的银纳米颗粒对于刚果红与罗丹明B表现出良好的光催化性能。     

水热合成法制备银-氧化锡复合粉体备

采用水热合成法,以亚硫酸钠为还原剂,用硝酸银、氨水和锡酸钠为原料制备银-氧化锡复合粉体,对制备的粉体进行X射线衍射、扫描电镜和能谱分析。结果表明:采用水热合成法可以制备出银-氧化锡颗粒,颗粒近似球形,粒径约为400 nm;该粉体由银和氧化锡两种物相组成,银的衍射峰非常明显,银元素和锡元素在粉体中均匀分布,可以推断银和氧化锡的分布是均匀的。     

晶化时间对水热法制备钛酸铋纳米粉体的研究

采用分析纯Bi(NO3)3·5H2O和TiCl4为原料,以NaOH为矿化剂,在反应温度为230℃的水热条件下,研究了晶化时间对Bi4Ti3O12物相结晶性能的影响。XRD表明在晶化时间不少于240min的条件下,才能合成纯的Bi4Ti3O12单一物相,并随着晶化时间的延长,Bi4Ti3O12的晶粒有所长大。通过红外光谱、比表面积和TEM等性能表征,探讨了钛酸铋的水热合成机理,用原位生成机理和溶解 再结晶机理解释了钛酸铋的水热生长过程。     

化学气相沉积过程各参数对沉积速度和薄膜晶体组织结构的影响

以氢气还原氯化钨沉积纯钨薄膜为例,简述了化学气相沉积法反应的主要原理,叙述了在反应过程中各参数对沉积速率的影响,及各参数对晶体结构的影响。     

水热法合成ZnSe纳米晶及其发光性质的研究

采用水热法在低温下合成了球形的立方相ZnSe纳米晶,研究了水热过程中ZnSe纳米晶的结晶动力学过程。通过在水热反应过程中添加不同量的C17H33COOH,得到了形貌规则、不同粒径的ZnSe纳米晶。水热条件下C17H33COOH能控制纳米晶形貌和分散性的机理为:C17H33COOH分子内部的羧基提升了ZnSe纳米晶的表面完整性,并保护了ZnSe结构内部的非极性烷基,使得ZnSe纳米晶很容易分散在非极性溶剂中,提高了溶液中ZnSe纳米晶的分散性。光谱测试结果表明ZnSe纳米晶的发射光谱随着粒径减小发生蓝移,归因于量子限域效应的增强。     

静电纺制备二氧化锡/碳纳米纤维锂离子电池负极材料的研究进展

二氧化锡纳米材料具有毒性小、成本低、可逆容量高等优点,是当前研究最为广泛的锂离子动力电池负极材料之一。构建与碳复合的二氧化锡基纳米结构是缓解二氧化锡在长时间的嵌/脱锂循环过程中体积膨胀、控制纳米颗粒团聚问题以及增加材料导电性的有效方法。用高效、可控的静电纺丝技术,结合高温煅烧、水热合成、化学沉积等方法,可制备出结构型二氧化锡/碳复合纳米纤维。本文讨论了具有不同碳层分布的均匀型、核壳型及三明治型结构的二氧化锡/碳复合纳米纤维的制备方法,以及不同碳层分布对其锂电性能的改善状况及机理分析。     

玻璃基片中银离子及纳米晶图形电场诱导热转印

利用电场诱导热转印技术,通过电场诱导热扩散和后续热处理分别在硅酸盐玻璃内部获得了银离子与银纳米晶图形.借助XPS、FT-IR、UV-vis研究了银的扩散、析晶机制.结果发现,在直流电场作用下,图形膜中金属银通过电化学反应被氧化为银离子,并沿电力线扩散进入玻璃基体,分别以Ag+和Ag0形式占据Na+空位和填充到玻璃网络间隙.后续热处理过程中部分Ag+还原为Ag,银离子通过扩散、成核、析晶为银纳米晶.EPA和HRTEM等分析表明,玻璃内部获得的金属银离子及银纳米晶图形清晰,银含量最高可达24.5%(质量分数),扩散深度>200μm,银纳米晶体呈面心立方结构,直径为7～15nm.     

镀银铝粉的制备及其机理分析

通过置换反应法制备镀银铝粉时所得到的银层不够致密,为了提升银镀层对铝粉的包覆效果,本文利用扫描电子显微镜、X射线衍射仪观察镀银铝粉的包覆效果和微观结构,并采用电化学工作站对反应过程中铝基体电位的变化进行分析.结果 表明,在活化的铝粉表面依靠铝银之间的置换反应可以使银沉积,但由于电化学微电偶电池效应的存在,仅通过置换反应无法得到致密的镀银层.进一步研究发现,通过添加合适的还原剂来降低置换反应中的微电偶电池效应的影响,可以改善银颗粒的沉积形貌并提高镀银层的致密性,从而降低镀银铝粉的压片电阻.     

氮硫共掺杂碳纳米管的制备及其催化性能研究

采用非原位掺杂方式,将化学气相沉积法生长的碳纳米管阵列在含氮和含硫的气氛下,700~900℃退火,制备了氮硫共掺杂的碳纳米管(NS-CNT)。X射线光电子能谱仪测试证明,通过非原位掺杂方式成功实现了氮和硫在碳纳米管上的掺杂。通过电化学测试研究退火温度对氧还原反应催化活性的影响,电化学测试结果表明,800℃退火所制备样品的氧还原峰电位和起始电位分别为0.873,0.771V,表现出最好的催化活性。通过旋转环盘电极测试发现,样品NS-CNT-800在反应过程中的反应电子数为3.7,说明该样品的反应机理是二电子和四电子反应同时进行,但以四电子反应过程为主,并研究了样品的长时间稳定性。与商业燃料电池所用的Pt/C催化剂相比,NS-CNT-800的稳定性更好,用于燃料电池有明显的优势。     

K_2O-MgO-MgF_2-SiO_2系统固相反应与玻璃析晶相变反应的比较

K_2O-MgO-MgF_2-SiO_2系统与云母型微晶玻璃的化学组成密切相关。作者采用显微结构的研究方法,研究了该系统在不同反应条件下固相反应和玻璃析晶相变反应的历程;根据 X-射线衍射分析结果和玻璃晶化过程中物相的形貌变化,比较了两个反应过程的差异。值得指出,虽然该系统固相反应与玻璃析晶相变反应的过渡相的种类和含量不同,但它们的最终反应产物都是含氟四硅酸云母。     

水热法合成纳米SnO2粉体

以硝酸锡为原料，配成稳定溶液，进行水热反应合成得到了晶粒尺寸只有数纳米的SnO2粉体．以FT—IR，XRD，TEM等分析手段对粉体进行了表征．FT—IR表明所得粉体均已实现了晶化．XRD衍射峰显示为SnO2相，衍射峰宽化明显，且随水热温度的升高宽化变窄，结晶性提高．粉体的晶胞体积随水热温度也呈现规律性变化．TEM表明粒子均为数纳米，粉体的分散性能良好，团聚很少。     

单分散纳米氧化铟锡粉末的水热合成

以金属铟和锡为原料,于碱性环境240℃水热合成12h并经500℃煅烧2h得到了 粒径为70±10nm,比表面积为11 m²／g的高纯氧化铟锡(ITO)粉末.由SEM、激光粒度测试 仪和BET三种方法分析得到的粉末平均粒径相吻合,证明制备的粉末是单分散状态的.研究 还发现,提高铟锡初始浓度和氢氧化钠过量浓度均有利于小粒径单分散ITO粉末的制备,但 过高的氢氧化钠过量浓度会使粉末出现团聚.     

机械镀锌沉积机理的研究

通过蒸发皿模拟试验和生产试验,采用体视显微镜观察了机械镀锌形层过程中金属锌粉在预镀工件表面的吸附、沉积过程,并用光学相机记录了金属锌粉的沉积过程.运用物理化学、电化学的基础理论分析了金属锌粉的沉积机理.分析结果表明,基层建立阶段,金属锌粉和Sn2+发生化学反应;镀层增厚阶段,金属锌粉和M2+发生化学反应;金属锌粉表面化学反应造成的库仑引力和机械镀锌过程玻璃珠冲击介质的碰撞是锌粉沉积的主要原因.     

Single particle model of SnO2 deposition on silver nanoparticles

Silver nanoparticles coated with almost uniform, thin shell of tin oxide are synthesized via a simple colloid chemistry technique, where the reduction of Ag⁴⁺ to Ag⁰ followed by the encapsulation of oxide takes place. The as prepared dispersions of tin oxide coated silver nanocomposite particles display a surface plasmon band, which is significantly red shifted with respect to that of bare Ag. Morphology of the composite nanoparticles was investigated by TEM. Presence of SnO₂ shell on the silver nanoparticles was also supported by XPS results. A theoretical single particle model has been proposed for the formation of tin oxide shell on the silver nanoparticles.     

Preparation of nanostructured tin oxide using a sol-gel process based on tin tetrachloride and ethylene glycol

A sol-gel process starting with tin tetrachloride and ethylene glycol as precursors, has been successfully used to prepare nanostructured tin oxide powders. The molecular structure evolution during the process has been identified using infrared spectroscopy and the underlying reaction mechanisms of the sol-gel process are proposed. Results suggest that the -OHCH₂CH₂OH- prevent Cl^– ions from access to tin ions due to steric effect and hence increase the stability of the sol solution. Ethylene glycol functions not only as a complexion agent to form a polymer network but also as a spacer to modulate the distance between metal ions, preventing metal oxide particles from aggregation during earlier stages of organics removal. Further, conversion of xerogel to tin oxide are studied using thermogravimetric analysis, X-ray diffraction, and electron microscopy. It is found that cassiterite begins to form at a temperature as low as 250 °C when organics start to burn off. However, nanocrystalline tin oxide powders are formed only after the chemically bonded hydroxyl groups are completely removed at about 600 °C.     

Effect of Ag addition on the structural and electrical properties of ITO powder compact

Nanocrystalline ITO-Ag powders were prepared using a coprecipitation method. Surface modified silver nanoparticles were mixed with the indium tin hydroxide precursor before the sintering process. The ITO-Ag nanocomposite powder was formed into pellets by uniaxial pressing process. The effect of addition of silver to the electrical and structural properties of ITO powder compact was studied. The relative density of the metal filled composite ITO-Ag powder compact is higher than the pure ITO powder compact. The result may be attributed to the melted silver eventually fills the void space between agglomerate pores and hence enhances the interconnection between nanocrystalline ITO powders. The crystal phase and particle size of ITO powder and ITO-Ag powder were measured by powder X-ray diffraction and the surface morphology of powder compact was investigated using a scanning electron microscope.     

水热合成纳米氧化锡粉体工艺因素研究

以SnCl4·5H2O和氨水为原料,通过正交实验并借助于XRD、TEM等手段,研究了前驱物浓度、反应温度、保温时间和氨水滴加速率等工艺因素对水热合成纳米SnO2粉体的影响。     

Preparation and characterization of BaSnO<Subscript>3</Subscript> powders by hydrothermal synthesis from tin oxide hydrate gel

BaSnO₃ powders have been prepared from the tin oxide hydrate gel and the Ba(OH)₂ solution via hydrothermal synthesis route. The influence of the process parameters on the characteristics of BaSnO₃ has been studied. A powder with the single-phase of BaSnO₃ can be obtained only when the concentration of Ba(OH)₂ solution is no less than 0.2 M and the ratio of Ba:Sn lies between 1.0 and 1.2. At a hydrothermal temperature of 330 °C or higher, uniform BaSnO₃ powders can be directly prepared through hydrothermal reaction. When the hydrothermal temperature is lower than 250 °C, the as-prepared powder consists of BaSn(OH)₆ that transforms through an amorphous phase into BaSnO₃ by calcination at 260 °C. In the hydrothermal temperature range of 130–250 °C, a higher temperature can promote the crystallization of BaSnO₃, increases its specific surface area and decreases the average particle size. The duration of the hydrothermal reaction affects the morphology of the powder particles. The effects of the nonaqueous solvents on the properties of powders have also been investigated.     

锡催化生长氧化硅纳米线的制备和表征

使用高纯SnO2粉和石墨粉混合物作为锡催化剂的来源,硅片作为硅的来源和产物生长的基底,用化学气相沉积法在硅片上准备了有序排列的氧化硅纳米线组成的微米结构,用扫描电子显微镜(SEM)、X-射线能谱仪(EDX)、透射电子显微镜(TEM)和选区电子衍射谱图(SAED)对其进行了表征.结果表明:直径为5-15 μm,长度达到5...