醇盐水解法制备二氧化钛纳米粉体

利用控制醇盐水解的方法，分析采用正丁醇共沸蒸馏和乙醇洗涤这两种工艺，详细研究了超细二氧化钛粉体的制备过程，采和ＸＲＤ、ＴＥＤ、ＢＥＴ、ＴＧ和ＤＴＡ等方面对用直接沉淀、正丁醇共沸和乙醇洗涤三种方法获得的粉体进行了表征。发现用直接沉淀和乙醇洗涤法均能获得团聚少、颗粒在１５ｎｍ左右的粉体，且乙醇洗涤能进一步减少粉体的团聚，但共沸蒸馏反而增加了粉体的团聚度。     

Photocatalytic hydrogen evolution with fibrous titania prepared by the solvothermal reactions of protonic layered tetratitanate (H2Ti4O9)

Various titania such as monoclinic titania, anatase and rutile were prepared via the heat treatment of protonic layered tetratitanate. The microstructure and hydrogen evolution activity of titania changed significantly depending on the reaction conditions. Generally, the hydrogen evolution activity of titania prepared by solvothermal reactions in water and alcohols at 200–325°C was much higher than that prepared by calcination in air. The solvothermal reactions using methanol and ethanol were much more efficient in increasing the hydrogen evolution activity than when water was used. When the titania formed by the solvothermal reaction in methanol was heated in air, the hydrogen evolution activity decreased with increasing temperature; however, the powders possessed higher hydrogen evolution activity than those produced directly by calcining the protonic layered tetratitanate at the same temperature without a solvothermal treatment.     

TiCl3、TiCl4共水解制备金红石相氧化钛粉体

通过TiCl3、TiCl4共同水解可以制备出金红石相的氧化钛粉体．改变原料浓度可以控制产物的形貌，较高浓度下得到300—500nm的球状颗粒，由许多细小晶粒组成；较低浓度下得到纳米针状颗粒．提高TiCl3的浓度可以使晶粒尺寸有所减小．     

Controlled chemical precipitation of titania for membrane applications—effect of heat treatment and fabrication conditions on its performance

Controlled chemical precipitation method was used to obtain nanosized titania (TiO₂) powders. XRD, DTA/TGA/DTG techniques were employed for phase analysis and to know the thermal changes taking place in precipitated precursor during heating. The effect of processing and fabrication conditions viz. calcination temperature, mold pressure and sintering temperature/time on membranes prepared from this titania powder was studied using permeability measurements. The bulk porosity, average pore size and permeability were found to decrease with increase in the molding pressure. However, an increase in the sintering period increases the bubble point and brings the diameter of the larger pores nearer to that of the average pore.     

Direct precipitation of lead zirconate titanate by the hydrothermal method

Direct precipitation of fine powders of lead zirconate titanate (PZT) in the complete range of solid solution, is investigated under hydrothermal conditions, starting from lead oxide and titania/zirconia mixed gels. The perovskite phase is formed in the temperature range of 165 – 340°C. Sequence of the hydrothermal reactions is studied by identifying the intermediate phases. The initial formation of PbO: TiO₂ solid solution is followed by the reaction of the same with the remaining mixed gels giving rise to X-ray amorphous PZT phase. Further, through crystallite growth, the X-ray crystalline PZT is formed. This method can be extended for the preparation of PLZT powder as well. The resulting powders are sinterable to high density ceramics.     

有机表面修饰温度对纳米二氧化钛微结构的影响

首先制备出纳米二氧化钛水分散液, 然后通过蒸馏的方法, 把纳米二氧化钛粒子由水分散液转移到溶有硬脂酸的甲苯溶液中, 以确保纳米二氧化钛在有机相中进行表面修饰. 然后升温到不同的温度, 利用硬脂酸对纳米二氧化钛进行有机表面修饰, 研究了有机表面修饰温度对纳米二氧化钛微结构的影响. 采用红外光谱(FT IR)、X 射线光电子能谱（XPS）、热分析(TG DTG)、X 射线粉末衍射（XRD）和透射电镜(TEM)等对有机表面修饰前后的纳米二氧化钛进行分析表征. 结果表明, 硬脂酸与纳米二氧化钛表面之间存在双齿配位方式的化学键作用, 硬脂酸在纳米二氧化钛表面形成了均匀的单分子化学修饰层. 随着表面修饰温度的升高, 纳米二氧化钛的晶粒逐渐长大, 硬脂酸在纳米二氧化钛表面的化学包覆量逐渐下降, 硬脂酸分子间排列更加紧密, 硬脂酸包覆层由1nm变为2～3nm. 表面修饰温度对硬脂酸与纳米二氧化钛表面的结合方式影响不大.     

TiCl3、TiCl4共水解制备金红石相氧化钛粉体

通过TiCl₃、TiCl₄共同水解可以制备出金红石相的氧化钛粉体.改变原料浓度可 以控制产物的形貌,较高浓度下得到300—500nm的球状颗粒,由许多细小晶粒组成;较低浓 度下得到纳米针状颗粒.提高TiCl₃的浓度可以使晶粒尺寸有所减小.     

Hierarchical macro-mesoporous structures in the system TiO2–Al2O3, obtained by hydrothermal synthesis using Tween-20® as a directing agent

Macro-mesoporous powders of titania, alumina, and mixed titania–20%alumina systems were obtained by hydrothermal synthesis employing surfactant Tween-20^® as structural directing agent in order to promote the textural properties of titania. The effect of the alumina in the titania phase and on textural properties was analyzed. The obtained powders presented a macroporous channel structure that was characterized by X-ray diffractometry, scanning and transmission electron microscopy, N₂ adsorption–desorption analysis, pore size distribution, Fourier transform infrared spectrometry, and thermogravimetric analysis. It was found that alumina content retarded the anatase phase crystallization and increased the Brunauer–Emmet–Teller surface area from 136 to 210 m²/g. The powders calcined at 400 °C are thermally stable and possess an interconnected macro-mesoporous hierarchical structure; the results indicate that this synthesis can be employed to prepare mixed titania–alumina with good textural properties.     

溶胶-凝胶法制备二元炭质-TiO_2气凝胶前驱体

以炭质水性中间相和四氯化钛为原料 ,分别制取了炭质溶胶 -凝胶和钛溶胶 -凝胶 ,然后将二者充分搅拌混合后 ,再进行超临界干燥制得了二元炭质 /二氧化钛气凝胶粉末前驱体。利用 FT- IR,XRD和 TEM技术对二元炭质 /氧化钛粉末进行了表征。研究结果表明 ,二元炭质 /氧化钛粉末具有小于 10 nm的颗粒尺寸 ,炭和氧化钛混合均匀且具有较高的比表面和疏松的表观结构。     

乙醇/水复合溶剂中纳米CaF2的沉淀制备及表征

用纯水溶剂和水/乙醇复合溶剂沉淀制备了不同粒径的CaF2纳米粉体.用FSEM和XRD对沉淀粉体的粒径和形貌进行了观测.研究发现,使用复合溶剂减小了产物纳米CaF2的粒径,从纯水溶液制备的51nm减小到1:4复合溶剂的20nm,并且沉淀粒径随复合溶剂中乙醇含量升高而减小.结果表明,复合溶剂是沉淀制备纳米粉体中控制粒径的有效手段.     

Solvothermal synthesis of visible light responsive nitrogen-doped titania nanocrystals

Nitrogen ion-doped titania nanoparticles were obtained by the homogeneous precipitation in hexamethylenetetramine-titanium trichloride mixed solution followed by heat treatment in the solution at desired temperatures. After that the sample powders obtained were calcined in air at desired temperatures. Various phases of titania such as anatase, rutile and brookite were obtained depending on the reaction condition. Crystallite size, specific surface area and color also greatly changed as 5-50 nm, 20--200 m²·g^-1 and light gray-yellow, respectively, depending on the solvent, pH, etc. The products after calcination around 400°C were yellow indicating doping with nitrogen ion. Photocatalytic activity for the oxidative decomposition of NO in air atmosphere was also evaluated by using a continuous flow system with 1 ppm NO gas, where the high pressure mercury arcs filtered using various filters were irradiated. All colored titania nanoparticles showed photocatalytic activity under visible light irradiation for the oxidative decomposition of nitrogen monoxide in air. Especially, the nanoparticles of anatase type nitrogen-doped titania obtained by the homogeneous precipitation using hexamethylenetetramine-methanol aqueous solution around 200°C showed excellent photocatalytic activity under visible light irradiation.     

Homogeneous (co)precipitation of inorganic salts for synthesis of monodispersed barium titanate particles

Various processes of coprecipitation or crystallization of inorganicsalts of barium and titanium from homogeneous solutions were studiedin this work. In particular, barium hydroxide and barium chloridesalt as well as titanium tetrachloride were used as the startingmaterials for dielectric-tuning homogeneous precipitation in mixedsolvents of isopropanol and water. Hydroxypropylcellulose was used asa steric dispersant. Evaluations of size, shape, and composition ofsynthesized particles were made using scanning electron microscopy,high-temperature X-ray diffractometry, and differential thermalanalysis. Results show that salt concentration, pH, and reaction timeare important in determining the morphology and composition of thefinal powder. The titania particles from dielectric-tuningprecipitation are perfect microspheres with narrow size distribution(near monodispersed), while the particles from barium salts areflake-like, irregular in shape and size. Instead of particlescontaining uniform compositions of barium and titanium compounds,dielectric-tuning coprecipitation yielded powders of two separatedphases, i.e., monodispersed titania microspheres (1 m) coated onbarium chloride salt flakes. Titanium-rich barium titanate wasobtained after calcination of coprecipitated powders. However,preliminary results show that the titania particles obtained bydielectric-tuning precipitation can be hydrothermally converted toBaTiO₃ particles that are fully crystallized after calcination above950°C.     

制备条件对TiO2纳米管晶型影响研究

用不同TiO2作原料,在一般水热法和微波法条件下,制备TiO2纳米管,通过TEM、XRD等表征手段,研究了影响合成TiO2纳米管晶型的因素,提出了影响纳米管晶型结构的机理.结果表明,利用不同的原料在一定制备条件下可制得单一晶型的TiO2纳米管.     

共沸蒸馏法制备超细氧化铝粉体及其表征

用改进的溶胶－凝胶法（ｓｏｌ－ｇｅｌ）制备了单分散纳米级Ａｌ_２Ｏ_３粉体,研究了不同干燥方法对产品粒子性能的影响．结果表明,共沸蒸馏法能够有效地对氢氧化铝凝胶脱水,防止了硬团聚体的形成．在１１５０℃的温度下煅烧,可制得尺寸分布均匀、呈球形的α－Ａｌ_２Ｏ_３超细粉体,其平均粒径为６８ｎｍ．以透射电镜（ＴＥＭ）、Ｘ射线衍射（ＸＲＤ）、热重（ＴＧ）、差热（ＤＴＡ）、比表面测定（ＢＥＴ）等手段对所得的超细Ａｌ_２Ｏ_３粉体进行了表征．     

Comparison of reductive dechlorination of p-chlorophenol using Fe0 and nanosized Fe0

Chlorophenols, as a kind of important contaminants in groundwater, are toxic and difficult to biodegrade. Laboratory tests were conducted to examine zero-valent iron as an enhancing agent in the dechlorination of chlorinated organic compounds. Nanoscale iron particles were synthesized from common precursors KBH(4) and FeSO(4). Batch experiments were performed to investigate the reduction of p-chlorophenol (4-CP) by both common Fe(0) and nanoscale Fe(0). Comparison of 300 mesh/100 mesh/commercial reductive iron powders showed that size of iron particles played an important role in reduction process. Initial concentration and pretreatment of iron particles also influenced the chlorination rate. Nanoscale Fe(0) offered much more advantages for treatment of 4-CP compared with common iron particles, such as stability and durability. And they can be used to treat contaminants in groundwater over a long time. Among different parts of synthesized nanoscale iron particle solution, the very fine particles were the major agent for treatment of pollutants. As for preservation of nanoscale Fe(0), ethanol was recommended.     

Morphology Controlling of the Ultrafine Cerium Dioxide (CeO2) Precursor

The synthesis of ultrafine cerium dioxide precursor via homogeneous precipitation was studied. Mixed aqueous solution of anhydrous cerium nitrate and urea was first heated to 85℃ for 2 h, and the prepared suspension was then aged at room temperature for various periods of time. White precipitate was finally collected by centrifuging and washed with distilled water and anhydrous ethanol. The obtained cerium dioxide (CeO2) precursor was observed with SEM. It was found that the morphology and size of the precursor were strongly affected by aging time and stirring conditions (with or without stirring). The precipitated fine spherical particles of the precursor changed their shape from ellipse to slice or directly to slice. Fine spherical monodispersed (300 nm) precursor powders could be obtained by controlling the aging time. Stirring the solution also could change the reaction process and thus the morphology and size of the precursor were changed.     

A micro-Raman study of iron-titanium oxides obtained by sol-gel synthesis

Iron-Titanium mixed oxides in powders and thin films on glass substrates have been prepared at different composition by using the sol-gel method. The thermal evolution, revealing the formation of different crystalline phases, has been followed by means of the micro-Raman spectroscopy. Pseudobrookite was the only crystalline phase found involving both iron and titanium. The differences in the thermal behavior between powders and films and the influence of iron as impurity in the crystallization process of the titania were also studied.     

Role of the nature of support on the structure of Au-Rh bimetallic nanoparticles

Au, Rh, and Au-Rh clusters were studied on Al₂O₃, TiO₂ powders and titania nanowire by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). On the XP spectra of the Au-Rh/TiO₂ and Au-Rh/Al₂O₃ powders and wires the binding energy of the Au 4f emission was practically unaffected by the presence of Rh, the position of Rh 3d remained also constant on alumina, while it shifted to lower binding energy with gold admixture on titania. New emission for Rh 3d at 309.2 eV and for Au 4f at 85.6 eV developed on titania wire case. The bands due to Rho-CO and (Rho)₂-CO were observed on IR spectra of titania supported bimetallic samples. The peak due to Rh⁺-(CO)₂ was less intense on bimetallic nanowire. All three bands however are intense on Au-Rh/Al₂O₃. The results were interpreted by electron donation from titania through gold to rhodium. “Core-shell” bimetallic structures are supposed on Au-Rh/titania wire.     

四氯化钛水解法制备纳米氧化钛超细粉体

研究了改变溶液的酸碱度来控制ＴｉＣｌ４水解,制备锐钛上超细ＴｉＯ２纳米粉体的过程,采用ＸＲＤ,ＴＥＭ、ＳＡＥＤ和ＴＧ－ＤＴＡ等方法对所得粉体进行了表征,发现水解后的沉淀经真空干燥后,不用任何热处理,室温下即有锐钛矿相存在,其原始粒径约为３．８ｎｍ,粉体于４００℃煅烧２ｈ,可得到平均粒径为７ｎｍ的纯钛矿相纳米氧化钛粉体。