用TiO2，ZnO及Fe2O3纳米粒子光催化氧化庚烷的反应

 制备了三种n－型半导体氧化物TiO2，ZnO和Fe2O3纳米粒子，用X射线衍射和N2吸附技术分别对它们的结构及比表面积进行了表征．考察了三种氧化物粒子对庚烷的气相光催化氧化反应的催化活性．研究表明，对于同种催化剂，随着焙烧温度的升高，催化剂的粒径增大，比表 面积减小，光催化活性下降．三种催化剂纳米粒子的光催化活性顺序为TiO2（锐钛矿）＞ZnO＞Fe2O3，金红石型TiO2粒子的催化活性低于ZnO粒子．结合能带理论探讨了三种催化剂光催化活性差异的原因．     

Pd/ZnO和Ag/ZnO复合纳米粒子的制备、表征及光催化活性

 用焙烧前驱物碱式碳酸锌的方法制备了ZnO纳米粒子，采用光还原沉积贵金属的方法制备了Pd／ZnO和Ag／ZnO复合纳米粒子，并利用ICP，XRD，TEM和XPS等测试技术对样品进行了表征，初步探讨了贵金属在ZnO纳米粒子表面形成原子簇的原因．以光催化氧化气相正庚烷为模型反应，考察了样品的光催化活性以及贵金属沉积量对催化剂活性的影响．结果表明：沉积适量的贵金属，ZnO纳米粒子光催化剂的活性大幅度提高．同时，深入探讨了表面沉积贵金属的ZnO纳米粒子光催化剂活性有所提高的内在原因．     

乙烷在纳米氧化镍上温和氧化脱氢制乙烯

用溶胶-凝胶法制备的纳米氧化镍具有较好的乙烷氧化脱氢低温反应活性．380℃下焙烧的NiO粒子大小在8nm左右，与大尺寸氧化镍相比，获得相同收率时反应温度大约下降125℃．并通过BEY，TPR，TPD，XPS等手段对不同焙烧温度的氧化镍催化剂进行表征，研究其粒子大小与对氧的活化能力及反应活性的关联．     

纳米WO_3的制备工艺探讨与结构表征

通过气液反应制备了纳米WO3光催化剂,并用紫外吸收光谱、粉末X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、能量散射谱(EDS)等手段对催化剂进行了表征.讨论了乙二醇加入量和表面活性剂十二烷基苯磺酸钠对催化剂粒度大小和形貌的影响.结果表明:当水和乙二醇的比例为25∶75时所得WO3粒径为30 nm左右.在此比例条件下加入0.1 g表面活性剂十二烷基苯磺酸钠,可制得片状WO3,粒径约为80 nm.对自制的两种纳米WO3光催化剂在紫外光照射时降解苯酚的活性进行了初步探讨,两者的催化性能均明显优于商品WO3.     

中空介孔三氧化钨微球载钯催化剂的甲酸氧化电催化性能(英文)

采用喷雾干燥法和焙烧处理制备中空介孔三氧化钨微球(HMTTS),在其表面进一步负载活性成分Pd,得到纳米Pd/HMTTS复合催化剂.采用X射线粉末衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)等对催化剂的形貌和晶型结构进行了表征.结果表明,Pd纳米粒子为面心立方晶体结构,均匀地分布在HMTTS表面.采用循环伏安和计时电流法研究了在酸性溶液中Pd/HMTTS催化剂对甲酸的电催化氧化性能,结果表明Pd/HMTTS催化剂比普通的三氧化钨载钯催化剂(Pd/WO3)对甲酸呈现出更高的电催化氧化活性和稳定性.HMTTS独特的中空介孔结构和表面特性以及氢溢流效应有利于甲酸在钯表面的直接脱氢氧化过程的发生.     

Pr~(3+)掺杂的TiO_2纳米粉体的表面特性和光催化活性

利用酸催化的溶胶-凝胶法制备了纯的和不同Pr3+掺杂量的TiO2纳米粉体.以亚甲基蓝(MB)溶液的光催化降解为探针反应,评价了它们的光催化活性.利用XRD和BET技术研究了Pr3+掺杂量和焙烧温度对TiO2纳米粉体的相结构、晶粒尺寸和表面织构特性的影响,并用XPS和SPS技术研究了Pr3+掺杂的TiO2纳米粉体的表面组成和表面光伏特性,探讨了Pr3+掺杂提高纳米TiO2的光催化活性的机制.结果表明:适量Pr3+掺杂能显著提高纳米TiO2的光催化活性.当Pr3+掺杂量为1.25%(以Pr3+/TiO2质量比计),焙烧温度为600℃时,制得粉体的光催化活性最佳.Pr3+掺杂强烈地抑制TiO2由锐钛矿相向金红石相的转变,减小晶粒尺寸,增大比表面积,增加表面羟基和吸附氧的含量,提高光生电子和空穴的分离效率,改善粉体表面的光吸收性能,上述因素均有利于光催化活性的提高.     

Pd/WO3-ZrO2催化剂的结构对乙烯直接氧化制乙酸的影响

利用浸渍法制备了一系列具有不同W/Zr比和不同WO3-ZrO2焙烧温度的1%pd/WO3-ZrO2催化剂.通过X射线衍射、N2吸附、氨程序升温吸附、吡啶吸附红外光谱和程序升温还原方法表征了催化剂的晶体结构、表面状态以及酸性.结果表明,制备条件对W和Pd的表面状态具有很人的影响.随着W/Zr比的增加和焙烧温度的提高,催化剂表而的WOx经历了从聚钨酸物种到聚钨酸/WO3晶体共存再到WO3品体颗粒的转化.W/Zr比为0.2且焙烧湍度为1073K的催化剂具有最多的聚钨酸物种,而该催化剂具有最好的活性.因此,聚钨酸物种的最决定了催化剂的活性.Pd的分散状态只依赖于WO3-ZrO2的焙烧温度.Pd物种分散性好,则乙酸选择性高,而分散性差的人颗粒Pd会导致乙烯的燃烧反应.     

以钛氧有机物为前驱物制备具有高光催化活性的纳米二氧化钛晶体

 纳米二氧化钛的制备方法及前驱物的差别影响其光催化活性．将20ml钛酸丁酯及30ml乙酐在密闭容器中与50ml环己烷混合，在70～85℃反应30min，生成微细的非晶钛氧有机物；经FT－IR和TGA分析，该物质被确认为计量式是TiOOOCCH3）2和TiO（OC4H9）（OOCCH3）的混合体．该钛氧有机物前驱物经焙烧后得到具有高光催化活性的纳米二氧化钛晶体．表征结果表明，钛氧有机物在焙烧过程中，其表面的吸附物及键合有机基团在400℃以前发生脱附和氧化分解；在389～405℃间形成锐钛矿型晶体，在600℃出现金红石晶型；600℃焙烧3h所得样品的比表面积为86m2／g，其二次粒子呈200～300nm条形体，孔隙大于20nm；单分散粒子为球形单晶，粒径为22nm；表面物理吸附水量为1．21％，加热至800℃时失重1．48％，粉体稳定纯净．光催化实验结果表明，以钛氧有机物为前驱物制备的纳米二氧化钛晶体具有高的光催化活性，光降解丁基罗丹明溶液的反应速率常数约为溶胶－凝胶法制备的催化剂样品的4倍．表面氧空缺和一定量的表面羟基可能是粉体具有高光催化活性的重要因素．     

钕掺杂对纳米TiO2光催化分解水制氢活性的影响

 采用溶胶-凝胶法制备了一系列纳米TiO2和掺杂Nd3+ 的纳米TiO2光催化剂,并通过XRD, UV-Vis, TEM和N2吸附等技术对其进行了表征和分析,考察了样品光催化分解水制氢的活性. 结果表明, Nd3+的掺杂使TiO2的相变温度从600 ℃提高到800 ℃, 同时有效抑制了TiO2的粒径增长,提高了粒子的分散性和样品的比表面积, Nd3+掺杂量越大,催化剂的比表面积越大. 掺杂Nd3+ 后, TiO2的光催化制氢活性提高,本实验中Nd3+的最佳掺杂量为0.1%, 此时催化剂的活性比未掺杂TiO2提高了3.5倍. 随着焙烧温度升高, TiO2和Nd3+/TiO2样品的光催化活性均下降,但同时一定量的金红石相与锐钛矿相共存所产生的协同效应也使样品的光催化活性有所提高.     

掺氮纳米炭球担载高分散钯纳米催化剂的制备及其苯甲醇氧化性能(英文)

负载型贵金属纳米催化剂中的金属纳米粒子易发生团聚或流失,因此提高金属活性组分的分散性和稳定性很重要。我们报道了一种制备高分散钯纳米催化剂的方法,通过浸泡法将氯钯酸前驱体负载到苯并噁嗪聚合物上,再经过惰性气氛一步热解得到纳米炭球担载钯催化剂.催化剂性能通过温和条件下苯甲醇氧化反应进行评价.经过500℃热处理制备的催化剂,从TEM图可以看出Pd纳米粒子均匀分散在载体上,尺寸大小约为3 nm,这是由于载体和钯活性组分的配位作用有利于提高钯纳米粒子的分散性和稳定性.通过调控金属负载量及负载时间,尽可能地实现活性组分分布在载体外表面,制备的催化剂上最高TOF为690 h-1.此催化剂同时具有较好的循环稳定性,失活后的催化剂经过200℃焙烧即可实现再生.     

焙烧温度对ZnO粉体结晶及光学性能的影响

以草酸铵和醋酸锌为原料,采用直接沉淀法制备ZnO粉体,考察了焙烧温度对粉体结晶和光学性能的影响。 采用热重分析（TGA-DTA）、X射线衍射、紫外-可见漫反射（UV-Vis）、荧光分光光度计（FS）和扫描电子显微镜（SEM）等方法对样品进行了分析。 结果表明,制备的前驱物为C2O4Zn·2H2O,最低焙烧温度400 ℃,随着焙烧温度的提高,粉体结晶度提高,一次粒径增大;600 ℃焙烧后有较强紫外发光峰,粉体由200 nm的粒子排列成层叠状;900 ℃焙烧后有较强可见发光峰,粉体粒子大于500 nm,团聚严重;粉体有较强的紫外吸收,吸收峰有蓝移。     

锂离子电池正极材料LiMn2O4的合成与晶体结构（英）

Spinel LiMn₂O₄ powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn₂O₄ powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn₂O₄ powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol.     

Polyacrylamide gel method: synthesis and property of BeO nanopowders

Effects of monomer (AM) concentration, monomer/crosslinker (AM/MBAM) ratio and salt concentration on the thermal behavior of precursor gel and the properties of BeO nanopowder synthesized by polyacrylamide gel method were investigated. The decomposition process of precursor gel was also studied. The decomposition process of precursor gel is that, first, the extraction of free and crystallized water, and then the thermal degradation of polymeric network under temperature higher than 600 °C, final, the decomposition of nanoscale beryllium sulfate to BeO nanopowder. As the monomer concentration increases, the calcination temperature of precursor gel decreases due to more compact network structure of gel and thus smaller size of salt in nanocaves in gel. The average particle size of nanopowder reduces correspondingly. The AM/MBAM ratio also has significant effect on the thermal behavior of precursor gel and the average particle size of product. When the ratio of AM to MBAM is 6, the calcination temperature of precursor gel is the lowest, the average particle size of powders is the smallest, because the network structures of gel is the tightest and thus the sizes of salts in precursor gels are the smallest. As the AM/MBAM ratio deviates from this value, the network structures of gel becomes looser and thus the size of salt in precursor gel becomes larger, so the calcination temperature increases and the average particle size of powders becomes larger certainly. For the same reason, both the calcination temperature and the average particle size of powders increases with increasing the salt concentration. The synthesis conditions have no effect on the particle size distribution of the final product due to the natural random distribution of porosity in gel.     

Effect of synthesis method variables on particle size in the preparation of homogeneous doped nano ZnO material

Homogeneous doped ZnO nanoparticles were synthesised by the Pechini method. A statistical experimental design was used to study the effects of the synthesis method variables on the particle size. The variables were the molar ratios of the reagents and the calcination temperature. The results indicated that the calcination temperature was the only factor that had a significant effect on the particle size. The particle size of ZnO varied between 16 and 76 nm with calcination temperatures of 400–800 °C. The homogeneity was studied by the ICP-MS technique, and the powders were found to be highly homogeneous.     

焙烧温度对甲硫醇催化剂K_2WO_4/Al_2O_3结构和性能的影响

研究了焙烧温度对溶胶-凝胶法制备的甲硫醇催化剂K2WO4/Al2O3的表面结构和催化性能的影响.表征结果显示,K2WO4在Al2O3上分散得较好,在450和550oC焙烧的催化剂颗粒大小均匀,无明显团聚现象.随着焙烧温度的升高,催化剂的比表面积减小,表面钨物种与Al2O3的相互作用减弱,与碱物种的相互作用增强,酸碱强度降低.K2WO4/Al2O3表面不含质子酸.催化剂活性与其比表面积及表面的共轭酸碱对密切相关.评价结果表明,在550oC焙烧而制得的催化剂活性最高.     

NiO/WO3/TiO2-Al2O3催化剂上正庚烷的临氢异构化

采用溶胶凝胶法制备了TiO2-Al2O3复合载体,用分步浸渍法制备了NiO/WO3/TiO2-Al2O3催化剂。 在常压连续流动固定床反应器上考察了NiO/WO3/TiO2-Al2O3对正庚烷临氢异构化反应的催化性能。 研究了催化剂中WO3含量、Ni含量、焙烧温度和还原温度及催化反应温度对临氢异构化反应的影响。 采用XRD和BET方法对催化剂进行了表征。 结果表明,当w(WO3)=25%、w(Ni)=10%时,所制备的NiO/WO3/TiO2-Al2O3催化剂对正庚烷异构化反应的催化性能最好,活性可达15.50%,选择性可达84.06%。     

Hydrothermal Synthesis of Pb_(1-1.5x)La_xZr_(0.5)Ti_(0.5)O_3 (x = 0.01-0.06) Nanocrystallites

Lanthanum doped lead zirconate titanate (PLZT) ceramics display excellent electrooptic and photostriction properties because of the existence of cavities in the perovskite structure1-3. The PLZT powders are conventionally prepared by solid state reaction4-5, and the wet chemical methods such as sol-gel techniques are then introduced6-7. However, the homogeneity, morphology and size of the particles, which greatly affect the sinterability and the property of the resulting ceramics, are dif…     

The Effect of Alcohol Solvents on the Porosity and Phase Composition of Titania

Bimodally porous titania powders were made by hydrolysis of titanium tetraisopropoxide (TTIP) dissolved in various alcohols (methanol, ethanol, isopropanol, and sec-butanol). The specific surface area (SSA) of the powders dried at 150 degrees C ranged from 332 to 624 m(2)/g as determined by nitrogen adsorption. At excess alcohol concentration, the SSA of the dried powders decreased in the order of sec-butanol, iso-propanol, ethanol, and methanol at a constant alcohol/TTIP molar ratio. The pore size distribution was bimodal with fine intraparticle pore diameters at 1-6 nm and larger interparticle pore diameters at 30-120 nm as determined by nitrogen adsorption isotherms. The average intraparticle pore diameter decreased with increasing alcohol concentration for methanol and ethanol, while it was rather constant at 3.3 nm, irrespective of alcohol concentration for iso-propanol and sec-butanol. The evolution of particle phase composition was determined by X-ray diffraction ranging from amorphous to crystalline anatase and rutile largely proportional to the calcination temperature and to a lesser extent on the type and concentration of alcohols. Copyright 2000 Academic Press.     

喷雾-胶凝法制备超细莫来石粉末

以水玻璃和硝酸铝为原料 ,通过喷雾 -胶凝法和共沸蒸馏技术制备莫来石前驱粉体 ,然后煅烧得到超细莫来石粉末 .用TG -DTA、XRD、TEM及BET研究了莫来石前驱粉体在煅烧过程中的热学性质、物相与比表面变化及颗粒大小与形貌变化 ,并对所制得的莫来石粉进行了表征 .结果表明 ,莫来石前驱粉体经 130 0℃煅烧 1h可制得粒径为 2 5nm～ 4 0nm ,比表面积为 4 2 5m2 /g的莫来石超细粉 ;煅烧过程中的物相变化次序为 :勃姆石 +非晶态SiO2 →非晶态Al2 O3 +非晶态SiO2 →γ -Al2 O3 +非晶态SiO2 → 3Al2 O3 ·2SiO2 .