纳米ZnO的沉淀法制备、表征及影响因素分析

用Zn(NO₃)₂·6H₂O对作原料、Na₂CO₃作沉淀剂,制得了纳米ZnO粉体.用TG-DSC、XRD和TEM分别对前驱体和纳米ZnO粉体进行了表征.结果表明:所得前驱体在253℃左右分解为六方纤锌矿型纳米ZnO,颗粒大小约为15～20nm,粒径分布窄,基本无团聚,粉体的比表面积为64.12m²·g^-1实验发现,当反应物浓度从2.0mol·L^-1减小至1.0、0.5mol·L^-1时,纳米ZnO粉体的粒径基本无变化,但颗粒间的团聚状态减轻;在用无水乙醇洗涤沉淀前,先用蒸馏水或稀氨水清洗对得到的纳米ZnO粉体的团聚状态没有明显的区别.     

纳米SiO2制备及改性

为了改善纳米SiO2的分散性,用溶胶-凝胶技术制备了纳米SiO2凝胶,并用不同改性剂对粉末进行了表面改性.采用透射电子显微镜(TEM)、X射线衍射(XRD)、粒度分析仪(PSA)、紫外-可见光分光光度计(UV-VS)等分析了纳米SiO2的粒径及分散性.结果表明,正硅酸乙酯的水解和缩合反应条件直接影响纳米SiO2粉体的粒径大小.KH-550硅烷偶联改性剂用量、改性时间等因素对改性效果有明显的影响.当改性剂用量为4.1%(质量分数),改性时间为2h时,可得到高分散性的纳米SiO2粉体.纳米SiO2粉末易发生团聚,只有对其进行表面改性,才能得到疏水性纳米SiO2粉末.     

高能球磨法制备超滤分离膜用钼铜复合粉末

研究高能球磨法制备纳米钼铜复合粉末的主要影响因素,通过扫描电镜和透射电镜分析粉末的形貌及颗粒尺寸.研究结果表明,复合粉的粒度随着球磨时间的延长而减小,但随着球磨时间增加,团聚加剧;通过重力沉降法可以去除浆体中的团聚体,从而获得颗粒分布适合的粉体,10h球磨粉沉降后粉体颗粒尺寸约为50～60nm,20h球磨粉沉降后粉体颗粒尺寸约为20～30nm.     

BaTiO3纳米粉体的制备和性能

采用溶胶-凝胶和溶胶-沉淀的方法合成了立方相纳米BaTiO3粉体．溶胶-凝胶法制备的粉体平均粒径为19nm，颗粒分布均匀、含少量BaCO3．溶胶-沉淀法得到了纯BaTiO3粉，平均粒径为42nm，存在部分团聚．两种方法相比，溶胶-凝胶法的粉体烧结密度较高，介电性能较好．讨论了两种合成方法的晶粒形成机理及对材料微观结构和介电性能的影响．     

纳米ZnO/Ag的制备及其光催化性能

以Zn(CH3COO)2·2H2O和AgNO3为原料,丙烯酰胺为单体,N,N′-亚甲基双丙烯酰胺为交联剂,用高分子凝胶法在较低的温度下制备出纳米ZnO/Ag.对纳米ZnO/Ag的结构和性能进行了表征,并研究了它的光催化活性.结果表明:在这个方法中,利用丙烯酰胺自由基聚合反应,同时利用网络剂有两个活化双健的双功能团效应,将高分子链联结起来构成网络.高分子凝胶形成的极小且均匀的网络限制了ZnO/Ag晶粒之间的团聚.制备出的纳米ZnO/Ag粉料颗粒为球形,未被Ag包覆的纳米ZnO的平均粒径约15 nm,被Ag包覆的纳米ZnO的平均粒径约45 nm.在次甲基蓝水溶液中加入3 g/LZnO/Ag粉料后,次甲基蓝的降解率为100%.沉积贵金属Ag使ZnO纳米粉料的光催化活性得到了很大提高,且可以重复使用.     

纳米AgCl水溶胶的制备与表征

采用沉淀法制备了AgCl纳米粒子水溶胶,对制备水溶胶的条件进行了系统地研究.TEM分析表明,AgCl纳米粒子呈球形,粒径小于30 nm,粒度分布均匀,无明显团聚现象;ED分析表明,AgCl纳米粒子为多晶结构,其中有少量的发育较好的单晶颗粒存在.     

复合纳米ZnO-SnO2粉体的电合成及光催化性能的研究

采用改进的电化学法制备了ZnO-SnO2纳米复合氧化物粉体,通过XRD、FT-IR、TEM等测试手段,对产物的物相组成、粒径大小、形貌等进行了表征;并考察了该纳米复合粉体的光催化活性.结果表明,得到的产物(氧化锌与氧化锡的复合物)颗粒分布均匀、平均粒径约为30～50 nm;该复合氧化物对甲基橙及亚甲基蓝溶液的光催化降解明显优于单纯的ZnO或SnO2;前驱体的焙烧温度以及ZnO和SnO2的复合摩尔比对ZnO-SnO2的光催化活性有较大的影响.     

酸催化剂对溶胶-凝胶法制备TiO2粉末的影响

用钛酸四丁酯为前驱物,无水乙醇为溶剂,乙酰丙酮为稳定剂,浓硝酸、浓盐酸、冰醋酸为催化剂,采用溶胶-凝胶法制备TiO2粉末。分析了在酸性条件下,催化剂的种类和加入量对凝胶时间和TiO2粉末粒径大小的影响。用该方法制备的TiO2纳米粉末,粒径大小为3～20nm。     

溶胶-凝胶法制备钇掺杂氧化锆的工艺研究

论述了用溶胶-凝胶法制备钇掺杂的氧化锆前驱体的过程,系统地研究草酸溶液的浓度、pH值、加热温度以及添加方式对溶胶、凝胶的影响,得出制备氧化锆前驱体的最佳工艺条件:当氧氯化锆溶液与草酸溶液的浓度比为1.25～2,草酸溶液pH值为1～2,加热温度为40～80℃,制得的前驱体溶胶、凝胶均匀,透明.正加方式得到的溶胶淡蓝色透明,较反加方式下的溶胶的胶凝时间短.并对最佳工艺条件制备的粉体进行SEM分析,结果表明,很好地合成了钇掺杂的纳米氧化锆粉体.     

Si基微绝热结构PLZT厚膜红外探测器阵列

介绍了一种制备非致冷红外探测器阵列的新方法,此方法避免了使用传统的微电子机械系统(MEMS)工艺来加工微桥.研究了如何在Si基片表面形成ZnO膜层网格状结构的方法.ZnO纳米粉末和PLZT厚膜采用改进的溶胶-凝胶法制备.表征了ZnO纳米粉末的表面形貌和PLZT厚膜的相组成,测量了 PLZT-8/53/47厚膜的铁电性和热释电性.结果表明,ZnO纳米粉末的粒径为40～70 nm,PLZT-8/53/47厚膜为纯钙钛矿相,其主结晶方向与底电极一致.PLZT-8/53/47厚膜具有优良的热释电性能,其热释电系数p为8.21×10-8C/(cm2·℃),而矫顽场较小,25℃时 Ec为32.0 kV/cm,40℃时 Ec仅为27.8 kV/cm.     

溶胶-凝胶法制备ZnO微粉及对丁烷气敏性研究

以草酸、柠檬酸和柠檬三铵为络合剂,利用溶胶凝胶法制备ZnO微粉。通过实验摸索制备小粒径ZnO的最佳工艺条件,及其性能表征,包括激光光散射粒度分析、X 射线衍射分析、比表面测定。并对ZnO超细粉的气敏性进行研究。     

机械化学法合成纳米ZnO粉体

利用机械化学法合成了单相ZnO粉体,XRD分析结果表明,ZnSO₄/NaOH(mol比)在1/2.1～1/3.0之间均可合成ZnO粒子,ZnO产率在ZnSO₄/NaOH为1/2.5时最大,TEM分析表明,ZnO粒子的粒径在40～80nm范围,对于反应机理,认为是固-固反应中放出的大量的热,使Zn(OH)₂直接转化为ZnO粒子,光吸收性能表明,纳米ZnO粉体的紫外吸收性能(200～400nm)较普通ZnO粉体强得多。     

高分子网络凝胶法制备纳米α-Al2O3粉体

用高分子网络凝胶法制备Ａｌ_２Ｏ_３粉体,通过网络的阻碍作用,阻止Ａｌ_２Ｏ_３的团聚,获得颗粒大小在 １０ｎｍ左右的α－Ａｌ_２Ｏ_３粉体,其煅烧温度比通常低 １００℃．     

A simple sol–gel technique for preparing lanthanum oxide nanopowders

Nanosized lanthanum oxide powders have been prepared by a simple sol–gel technique using commercial lanthanum oxide, nitrate acid and polyethylene glycol (PEG) as the starting materials. The decomposition process of dried gel powders were investigated by differential thermal and thermogravimetric analysis(TG-DSC). The crystalline structures and morphologies of the powders were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The effects of calcination temperature, calcination time, stirring and the concentration of PEG on the particle size were studied. The results show that the calcination temperature and concentration of PEG have obvious influence on the La₂O₃ particle size and agglomeration tendency. At lower calcination temperature the prolongation of calcination time has slight influence on the particle size. Stirring will promote the growth of particles. The weak-agglomerated nanosized powders with the mean particle size less than 40 nm could be obtained by controlling the process condition.     

氧化锌在纸张装裱小麦浆糊中防霉作用的研究

在小麦浆糊(浆糊)里加入氧化锌超细粉(氧化锌),采用培养皿观察法评价防霉效果.讨论了6种商品氧化锌的防霉效果与其微粒大小、形貌之间的关系;考察了氧化锌加入方法、加入量及湿度条件的影响,比较了海泰纳米氧化锌、纳米氧化锌悬浮液及明矾的防霉效果.结果表明:原级粒子为纳米级且分散良好的氧化锌才能表现出很好的防霉作用;先期加入法优于后期加入法;氧化锌加入量越多、粒径越小,防霉效果则越好;在霉菌易于生长条件下,明矾几乎没有防霉效果,而纳米氧化锌悬浮液防霉效果显著.     

Controlled mechanochemically assisted synthesis of ZnO nanopowders in the presence of oxalic acid

In this study, the ZnO nanopowders were synthesized by mechanochemical processing with a successive thermal decomposition reaction. The initial reactants mixture of zinc chloride and oxalic acid was milled from 30 min to 4 h and thermally treated for 1 h at 450 °C. The influence of both, oxalic acid and the duration of milling, on the crystal structure, average crystallite size, average particle size, and the morphology of ZnO nanopowders were investigated. The qualitative analysis was performed using X-ray diffraction and Raman spectroscopy techniques. While the XRD analysis shows perfect long-range order and pure wurtzite structure of the synthesized ZnO powders, Raman spectroscopy indicates a different middle-range order; in addition, according to Raman spectra, it is found that lattice defects and impurities introduced in ZnO crystal structure depend on milling duration, in spite of applied thermal treatment. The particle size distribution was measured by laser diffraction, whereas the morphology of the powders was determined by scanning electron microscopy. Impurity contamination was studied using inductively coupled plasma analysis. The obtained results showed that the applied two-step method is appropriate for the synthesis of high crystalline ZnO nanopowders, with uniform spherical particles with diameter between 20 and 50 nm. Profound effect of aqueous solution of oxalic acid to prevent agglomeration of final product is presented.     

Synthesis of ZnO nanopowder via an aqueous acetate-citrate gelation method

The synthesis of nanoparticulate ZnO via an aqueous carboxylate gelation route is presented. Starting from a solution of zinc acetate with citric acid as a complexing agent, a solid glassy gel is obtained after drying that is converted into a fine powder by calcination. It is found that a very homogeneous precursor is indispensable when preparing very fine particles with a narrow size distribution. Cryo-transmission electron microscopy (Cryo-TEM) investigation is used as a feedback tool to prevent early precipitation during gelation. Study of the thermal decomposition of the gel shows that ZnO is formed before the final decomposition step takes place. After removing the organic backbone, very small oxide particles are found. The influence of the thermal treatment parameters on the particle size is investigated and a particle growth process is found. By a proper adjustment of the final calcination temperature in dry air, the mean particle size can be controlled between ∼11 and 175 nm. It was also seen that even in inert atmosphere, ZnO is formed and that particle morphology is greatly influenced by the calcination atmosphere.     

Production and characterization of ZnO nanocrystals obtained by solochemical processing at different temperatures

The semiconductor zinc oxide (ZnO) has been widely used because it presents exclusive novel physical and chemical properties at the nanometer scale. In this work, ZnO nanocrystals were synthesized via solochemical processing in a few hours without any subsequent treatment. ZnCl2 and NaOH were adopted as synthesis precursors. ZnO production was realized at different reaction temperatures to verify the effect of this parameter on synthesis. The synthesis temperatures studied were 50 degrees C, 70 degrees C and 90 degrees C. The materials obtained at different reaction temperatures were characterized by X-ray diffraction (XRD) and the Rietveld method. The size and morphology of the ZnO particles obtained at 50 degrees C were evaluated by transmission electron microscopy (TEM). ZnO powders have hexagonal wurtzite structure and nanometric-sized crystallites. Microstrain increased and the average crystallite size decreased with the increase in reaction temperature.     

矿物颗粒表面纳米化修饰及其在PP复合材料中的应用

通过化学方法成功地实现了矿物粉体在Ca (OH)₂-H₂O-CO₂ 体系中的表面纳米化修饰, 即在微米级重质碳酸钙、硅灰石粉体表面形核生成粒径均匀的纳米碳酸钙颗粒层。研究表明, 表面纳米化修饰后的矿物粉体表面的粗糙度大大增加, 尖锐的棱角得以钝化, 纳米化修饰后矿物粉体比表面积比原来提高至少200 %以上。将经表面纳米化修饰后的硅灰石粉体在聚丙烯(PP) 中填充应用, 较未经表面纳米化修饰的硅灰石粉体填料, 其抗冲击强度提高65 %以上, 延伸率提高200 %以上。