微波辐射下纳米ZnO的合成研究

在微波辐射下用草酸二甲酯和硝酸锌为原料,在油包水型微乳液的水核中进行均匀沉淀反应制备出纳米ZnO。用DTA-TGA、XRD和TEM等对产物进行了表征,并考察了微波辐射功率对ZnO纳米的收率和平均粒径的影响作用。结果表明:将0.002 mol的表面活性剂NP-9和17 mL正己醇加入70 mL正庚烷中,再加入8 mL 0.02mol/L草酸二甲酯和0.015 mol/L硝酸锌的混合水溶液,制成微乳液,以功率为50~250 W的微波辐射40 m in,经分离得到草酸锌;将所得草酸锌在500℃焙烧1 h,能够得到纳米ZnO;纳米ZnO为六方晶体,外形近于球形,具有很窄的粒径分布。随着微波辐射功率的增大,纳米ZnO的收率增大,其平均粒径也变大。     

SDS/正丁醇/正庚烷/水微乳液稳定性分析及应用

研究了十二烷基硫酸钠(SDS)/正丁醇/正庚烷/水(或氯化镁与硝酸铝混合水溶液或氢氧化钠溶液)四组分形成稳定微乳液的条件。考察了表面活性剂与助表面活性剂的质量比、温度、pH值、盐浓度对该体系稳定性的影响及水与表面活性剂的摩尔比(ωo)对水核粒径的影响。结果表明,m(SDS)∶m(正丁醇)=4∶6时,反相微乳液最稳定,对温度变化不敏感,pH值为7～13时,具有较好的稳定性,随着镁铝混合盐溶液浓度的增加,反相微乳区域急剧缩小,水核粒径随着ωo增大而增大,在稳定微乳液区域内制备了分布较均匀,尺寸范围30～70 nm的粒状纳米颗粒。     

微乳液法制备无定形纳米二氧化硅

采用Triton X-100／正己醇／环己烷／氨水体系配制反相微乳液，在碱性条件下正硅酸乙酯在反相微乳液中发生受控水解，合成了具有无定形结构的球形二氧化硅纳米粒子。通过红外光谱（FT-IR）、X衍射（XRD）、透射电镜（TEM）分别对样品的结构及形貌尺寸进行了表征和分析。结果表明：改变表面活性剂加入量可以得到不同粒径（50～110nm）、不同粒度分布及不同分散程度的球形二氧化硅纳米粒子。随着表面活性剂在微乳液中体积分数的增大，二氧化硅纳米粒子的粒径先减小后增大，团聚程度也呈现先减小后增大的趋势。当表面活性剂在微乳液体系中的体积分数为20％时，所合成的二氧化硅纳米粒子粒径最小（50nm），粒度均匀且呈现出良好的分散性。     

微乳液水核结构对铟纳米粒子分散形态的影响

在环己烷／正己醇／水／乳化剂微乳液中。通过脉冲激光制得并观查到了球形，扁球形，六边形及棒状分散形态的铟纳米粒子。考查了不同水核的红外光谱图，利用透射电镜，观查到了铟纳米粒子的不同分散形态。     

微乳液水核结构对铟纳米粒子分散形态的影响

在环己烷/正己醇／水／乳化剂微乳液中,通过脉冲激光制得并观察到了球形、扁球形、六边形及棒状分散形态的铟纳米粒子。考察了不同水核的红外光谱图,利用透射电镜,观察到了铟纳米粒子的不同分散形态。     

基于相图法的W/O型微乳液体系稳定性分析

以辛基苯基聚氧乙烯醚(TX-10)、十二烷基磺酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)为表面活性剂,以正戊醇、正己醇和正庚醇为助表面活性剂,以正戊烷为油相,制备了油包水型(W/O)微乳液.用相图法分析了微乳液体系的热力学稳定性,计算了水核半径的大小,并考察了影响微乳液W/O区域范围的各种因素.结果表明:这几种微乳液体系在实验条件下能自发形成:微乳液的水核半径处于纳米量级,可作为制备纳米粒子的超微反应器;以TX-10为表面活性剂时,水核可以包容更多的水分子,微乳液的W/O区域较大;而以CTAB为表面活性剂时,由于其极性头之间的空间和静电排斥作用强,微乳液的W/O区域最小;以硝酸镧溶液作为分散相时,微乳液的W/O区域变化较小;随着温度的升高,微乳液的W/O区域显著减小.     

不同醇对微乳液体系结构参数的影响及纳米BaF2的制备

采用稀释法测定了十六烷基三甲基溴化铵(CTAB)/醇/正庚烷/水四组分微乳液体系在不同醇时体系的结构参数。结果表明:随着醇碳原子数的增加,微乳液体系的结构参数水内核半径Rw、颗粒有效半径Re、界面层厚度l、平均聚集数珔n以及吉布斯自由能-ΔG0c→i增加,而颗粒总数Nd以及分散相所占的总界面面积Ad减小。采用CTAB/正丁醇/正庚烷/水微乳液体系制备了纳米BaF2。经SEM和XRD表征,BaF2为均匀的球形纳米粒子,粒径39 nm左右。     

纳米光触媒的合成工艺及其应用研究

以硫酸氧钛为原料通过常温水解沉淀及水热处理制备了纳米光触媒乳液.考察了水解pH值、稳定剂、氧化剂、热处理温度及热处理时间等条件对该乳液的光催化性能的影响.XRD和TEM检测结果表明:光触媒乳液中纳米TiO2颗粒晶体结构为锐钛型,平均粒径为10 nm.光催化活性评价表明:当水解溶液的pH值=8,以柠檬酸为稳定剂,在100 ℃下水热处理6 h后获得的纳米光触媒乳液具有最佳光催化活性.     

复合掺杂的纳米二氧化锡粒子的制备与表征

分别采用微乳液法（辛基酚聚氧乙烯醚＋正己醇／环己烷／水组成的微乳液体系）和柠檬酸溶胶-凝胶法制备了镁与铈、锌、锆复合掺杂的纳米二氧化锡颗粒，通过热分析（TG-DTA）、X射线衍射（XRD）、比表面积测定（BET）、红外吸收光谱（FT-IR）和紫外-可见光谱（Uv-Vis）对其结构进行表征。结果表明，两种方法制备的产物均为金红石结构，微乳液法制备的颗粒较后者具有较小的晶粒粒径、较大的比表面积和紫外吸收边；复合掺杂后，样品的粒径减小，比表面积增大，样品的紫外-可见吸收发生红移；其中，镁-铈复合掺杂的样品具有最小的晶粒粒径和最大的比表面积，分别为4．53nm和78．50m^2／g；复合掺杂能够抑制二氧化锡颗粒生长，增大其比表面积。     

W/O微乳液技术与纳米粒子的控制合成

分析了W／O微乳液的形成机理、结构特征以及用W／O微乳液法合成纳米粒子的基本原理。讨论了制备条件如水与表面活性剂的比值,反应物、表面活性剂、助表面活性剂的浓度以及焙烧条件对纳米粒子特征的影响。指出应该加强对纳米粒子生成反应动力学的研究,加强微乳液法与其它纳米粒子制备技术的耦合研究,并注意改善非极性溶剂和表面活性剂的回收率以降低制备成本。     

硅酸乙酯为原料反相微乳液法制备纳米二氧化硅

采用NP-5/环己烷/去离子水体系制备反相微乳液,绘制了该体系的三元相图,并以正硅酸乙酯(TEOS)为原料,在碱性条件下受控水解反应制备了纳米SiO2粒子,探讨了[n(水)∶n(表面活性剂)](用R表示)和[n(水)∶n(TEOS)](用H表示)对SiO2纳米粒子粒径的影响。通过扫描电镜(SEM)和激光粒度仪对样品形貌和粒子大小和粒径分布进行了表征。结果显示:扫描电镜下观察到的SiO2粒子为无定型球形颗粒,粒径在200～500 nm的范围,激光粒度仪分析得到的平均粒径随着R和H的增大而增大。     

微乳法制备棒状ZnO材料及其光催化性能

采用浊度法绘制十六烷基三甲基溴化铵(CTAB)/正丁醇/环己烷/硝酸锌或草酸铵水溶液体系的拟三元相图,确定微乳液稳定区域最大时CTAB与正丁醇的质量比为1∶1。在此条件下,选择m(CTAB+正丁醇)∶m(环己烷)=3∶7,以硝酸锌和草酸铵为原料,采用微乳法制备ZnO的前驱体二水合草酸锌,然后通过煅烧得到ZnO样品。考察水与CTAB的摩尔比(R)和反应物浓度对ZnO材料结构、形貌、光学性质和光催化性能的影响。实验结果表明:ZnO样品为纯的六方纤锌矿结构晶体,形貌均为棒状,且样品的尺寸随R值和反应物浓度的不同而不同。在300 W汞灯紫外光照射下,ZnO样品对亚甲基蓝溶液均具有较好的光催化性能,光催化反应过程符合准一级反应动力学。其中,在反应物浓度为0.15 mol/L,R=15条件下制备的ZnO样品在光照90 min时可使亚甲基蓝的降解率达到97.0%,且降解反应速率常数k最大,其光催化性能最好。     

Low-Temperature Synthesis of Zinc Oxide Nanoparticles

Crystalline zinc oxide nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and hexamethylenetetramine (HMT) at 60°C and 80°C. Transmission electron microscopy and X-ray diffraction show that the ZnO nanoparticles of diameters ranging from 15–33 nm and 25–43 nm long are formed. Aspect ratio is observed to range from 1.18 to 1.74 at 60°C and 1.22 to 1.70 at 80°C as the HMT to zinc nitrate concentration ratio increases from 10 to 150. Nanoparticle size decreases as the concentration of HMT increases. Much larger ZnO particles are formed with ammonium hydroxide as a hydrolysis agent without HMT. In summary, HMT is an ammonium-hydroxide source in the reaction, a surfactant for retaining nanosize, and not necessarily a template for ZnO nucleation.     

微乳液中纳米ZnS、CdS微粒的合成与表征

以乙酸锌、硝酸镉和硫化钠为原料,室温下,采用微乳液法合成ZnS、CdS纳米粒子。利用rIEM、XRD、Raman、UV-Vis和PL等检测手段对产物进行表征。结果表明,合成的zns纳米晶粒径在25m左右,为立方β-Zns晶相;ω值对合成纳米cds的形貌和粒径产生重要影响,纳米Cds粒径为5nm左右,在紫外吸收光谱和荧光发射光谱上均表现出明显的特征,可作为荧光量子点使用。     

微波辅助制备纳米ZnO及其光催化降解染料的性能

以硝酸锌、氢氧化钠为原料,聚乙二醇400(PEG 400)为溶剂,采用微波加热共沉淀法制备纳米ZnO,并采用X射线衍射、场发射电镜及紫外-可见漫反射对样品进行表征;考察纳米ZnO对结晶紫(CV)及刚果红(CR)的光催化降解性能,以λ=365nm的紫外光为光源,考察了催化剂投加量、染液浓度、pH值以及催化时间对催化效率的影响。实验结果表明,在较少的投加量下,纳米ZnO对50mg/L的CV和CR染液的降解率可分别达到98.8%和97.4%,pH值对两种染料的光催化效果影响不大。CR及CV染液的光催化降解均符合一级动 力学。     

Nanosized TiO2 synthesis by EbCDAB microemulsion

BACKGROUND: Microemulsion is the easiest and cleanest of the popular methods of synthesizing nanomaterial. This work investigated the possibility of forming a single‐phase microemulsion using ethanediyl‐α,β‐bis (cetyldimethylammonium bromide), termed EbCDAB, in a n‐hexanol/water system, and looked for the best scale of microemulsion to synthesize TiO₂ to give the best cleaning of organic pollution. RESULTS: Results confirm that EbCDAB, n‐hexanol and water form a microemulsion system, and this system is an effective way to synthesize nanoparticles of TiO₂. Photo catalysis experiments showed sample E_6?3 to be the best catalyst, and it decomposed 82% of Methyl Orange (10 mg L^?1) in 60 min under UV‐light irradiation. E_6?3 had 1.4 times higher activity than the commercial P25. Analyses using transmission electron microscopy (TEM), X‐ray diffraction (XRD), thermographic differential scanning calorimetry (TG‐DSC) and Fourier transform infrared microscopy (FT‐IR), showed that particles of E_6?3 were of size around 11 nm and of anatase phase. CONCLUSION: The best microemulsion was found to have weight ratio n‐hexanol:EbCDAB:water of 6:3:1. At this ratio, TiO₂ nanoparticles were easily produced. Copyright © 2010 Society of Chemical Industry     

Preparation and characterisation of BaTiO3 nanopowder by microwave assisted microemulsion method

Through the microwave assisted reverse microemulsion method, BaTiO₃ nanopowders are prepared in 10 min by selecting water/OP-10/hexanol/cyclohexane reverse microemulsion system, Ba(NO₃)₂ and tetrabutyl titanate as reactants. The effect of reaction temperature, reaction time, concentration of reactants and molar ratio of water and surfactant on the reaction was studied, and the prepared powders were characterised by X-ray diffraction, TEM and X-ray fluorescence analysis. The results show that cubic phase BaTiO₃ powders of particle size about 50–80 nm with uniform distribution and good dispersion were prepared under atmospheric pressure in 10 min at 65°C. The method has characteristics of lower reaction temperature, shorter reaction time, smaller particle size, narrow particle size distribution and good particle dispersion.     

Preparation and photocatalytic kinetics of nano-ZnO powders by precipitation stripping process

Ultra-fine zinc oxalate powders were prepared through a precipitation stripping method with bis(2-ethylhexyl) phosphate (HDEHP) diluted by tetrachloride carbon as the extractant, and oxalic acid ethanol aqueous solution as the re-extractant and precipitator. Zinc oxide powders were obtained by decomposing zinc oxalate powders at 450°C. The prepared zinc oxide powders were characterized by transmission electron microscope (TEM), Scanning electron microscope (SEM), Thermogravimetric analysis (TG), X-ray diffraction (XRD) and Fourier transmission infrared (FT-IR) spectrum. The photocatalytic performance of methylene blue by zinc oxide was studied based on the Langmuir model and Photo-Layer model. The results show that some zinc oxide powders were micro-multipore materials with hexagonal crystal. The particle size was around 32 nm. The photocatalytic process was the control step in the chemical reaction. The photo catalytic process followed pseudo-first order kinetics and •OH concentration inside the photo-layer in different reaction condition were calculated according to the Photo-Layer model.