Rheological Measurements in Titania Gels Synthesized from Reverse Micelles

Abstract

TiO₂ sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant W _o = [H₂O]/[AOT] and changing R = [H₂O]/[Ti(BuO)₄]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol-gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters (G′, G″ and η?) as a function of time at different frequencies.

The possibility to apply standard percolation theory was discussed. The application of two alternative growth models-either “fractal growth model” or “nearly linear growth model”-has been analysed.     

CNTs/TiO2多孔复合膜的组装及光催化性能

提出了一种在掺氟的SnO2(FTO)导电玻璃上组装碳纳米管(CNTs)/Fe-Ni/TiO2多孔复合膜光催化剂的新方法.采用喷涂热解法(SPD)将掺杂镍和铁的含有嵌段聚合物P123的二氧化钛前驱体溶胶涂覆在FTO导电玻璃上,制备Fe-Ni/TiO2多孔膜,再采用化学气相沉积法(CVD)在Fe-Ni/TiO2膜上原位生长CNTs,得到CNTs/Fe-Ni/TiO2多孔复合膜光催化剂.CNTs/Fe-Ni/TiO2复合膜具有多级孔结构特征,在TiO2表面原位生长的CNTs不但具有较好的石墨化结构,且CNTs较均匀地分布在整个膜层的孔中.考察了CNTs/Fe-Ni/TiO2复合膜光催化剂的结构和性能,并通过降解甲基橙溶液评价了复合膜的光催化活性.结果表明,CNTs的复合及铁和镍的掺杂等改性显著提高了TiO2膜材料的光催化活性.     

Influence of O2 Plasma on Surface Properties of PC-TiO2 Nanocomposite Film

In this work, polycarbonate-TiO₂ nanocomposite films were prepared with different percentages. The aim was to consider the effect of O₂ LF plasma (50 Hz) on the hydrophilicity, surface energy, and surface morphology of polycarbonate and polycarbonate-TiO₂ nanocomposite. Structure of samples was determined by using X-ray diffraction analysis. In comparison with the reference sample, the samples’ structure did not change after plasma treatment. Surface properties of polycarbonate and polycarbonate-TiO₂ nanocomposite films were studied by X-ray photoelectron spectroscopy (XPS), contact angle measurement, atomic force microscopy (AFM), and Vickers microhardness tester. XPS analysis showed that the surface of samples became more oxidized due to plasma treatment. The water contact angle significantly decreased from 88° to 15° after plasma treatment. It was observed that the hardness of the nanocomposite films was not modified after plasma treatment.     

Two-Dimensional Sol-Gel Synthesis of Ultrathin Zirconia and Hetero-Layered Titania/Zirconia Films

Synthesis of ZrO₂ and hetero-layered TiO₂/ZrO₂ ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C₁₈AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C₁₈AA was spread on the water surface, Zr-based gel films stabilized with C₁₈AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO₂ ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C₁₈AA]. Well-organized hetero-multilayers composed of ultrathin TiO₂ and ZrO₂ layers could be fabricated by the alternate deposition of C₁₈AA-stabilized Ti- and Zr-gel films.     

LB技术制备SnO2-TiO2无机交替纳米薄膜

采用LB技术将SnO₂纳米粒子和TiO₂纳米粒子组装进花生酸的交替多层膜，通过热处理除去膜中的有机成分后，采用红外光谱、紫外可见光谱、X-光电子能谱、低角X-射线衍射、原子力显微镜以及扫描电子显微镜等手段对处理后的膜进行了形貌、组成和结构表征，表明制得的是SnO₂纳米粒子-TiO₂纳米粒子无机-无机交替的均匀的纳米薄膜。     

Silver Nanoparticles Filling in TiO2 Hollow Nanofibers by Coaxial Electrospinning

This study investigated the coaxial electrospinning process of silver filling in TiO₂ ultrafine hollow fibers using polyvinyl pyrrolidone (PVP) sol/titanium n-butyloxide (Ti(OC₄H₉)₄) and PVP sol/silver nanoparticles as pore-directing agents. The bicomponent fibers were heat treated at 200 °C and calcined at 600 °C. Silver particles having diameters of 5 to 40 nm were deposited on the inner surface of the long hollow TiO₂ nanofibers (outer diameter of 150.300 nm) with mesoporous walls (thickness of 10.20 nm). The morphological structure of the filled ultrafine hollow fibers has been studied by means of infrared (IR) spectrum, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The diameters and wall thicknesses of the hollow fibers could be tuned by adjusting the electrospinning parameters. Compared with other nanostructured TiO₂ materials, such as mesoporous Ag-TiO₂ blending fibers, TiO₂ hollow nanofibers, TiO₂ nanofibers, and TiO₂ powders, the silver filled TiO₂ hollow fibers exhibited a higher photocatalytic activity toward the degradation of methylene blue.     

载银二氧化钛纳米管表面pH敏感膜构建及其抑菌特性

采用表面涂覆硅烷偶联剂KH550、两步光接枝、阳极氧化等方法,在钛表面成功制备出一种pH型敏感膜覆盖的载银二氧化钛(TiO2)纳米管阵列。利用扫描电镜(SEM)、透射电镜(TEM)、能谱分析(EDS)、原子吸收光谱(AAS)对该pH敏感膜覆盖的载银TiO2纳米管阵列理化性能进行了表征,采用抑菌环实验定性考察了样品的抗菌特性,并计算其抑菌率。结果表明,含银离子溶液在毛细管力作用下大量进入TiO2纳米管中,并在pH型敏感膜的调控下,使银离子在不同pH环境下具备不同的释放行为,从而达到良好的控释效果;载银TiO2纳米管的抑菌率与银离子负载量成正比,且抗菌性能持久。     

载银二氧化钛纳米管表面pH敏感膜构建及其抑菌特性

采用表面涂覆硅烷偶联剂KH550、两步光接枝、阳极氧化等方法,在钛表面成功制备出一种pH型敏感膜覆盖的载银二氧化钛（TiO₂）纳米管阵列。利用扫描电镜（SEM）、透射电镜（TEM）、能谱分析（EDS）、原子吸收光谱（AAS）对该pH敏感膜覆盖的载银TiO₂纳米管阵列理化性能进行了表征,采用抑菌环实验定性考察了样品的抗菌特性,并计算其抑菌率。结果表明,含银离子溶液在毛细管力作用下大量进入TiO₂纳米管中,并在pH型敏感膜的调控下,使银离子在不同pH环境下具备不同的释放行为,从而达到良好的控释效果;载银TiO₂纳米管的抑菌率与银离子负载量成正比,且抗菌性能持久。     

正钛酸胶溶法制纳米TiO2薄膜及性能表征

The Nanometer TiO₂ thin film was prepared by sol method with titanic acid precursor from industrial TiOSO₄ solution. The characters of the sol and the factors affecting sol formation were investigated by ζ electricity potential. The crystalline structure, particle size, appearance shape and photo-catalytic activity were characterized by XRD, SEM, TEM and spectrophotometer. The study show: (1) pH value and HNO₃concentration effected importantly on the forming process and stability of the sol. The thermodynamic condition for forming sol is pH=0.5～1.5. The lower the HNO₃concentration,the more stable the sol. The ζ electricity potential of the sol, with 5% HNO₃as gluing reagent, was up to 48 mV, and shelf life of the sol could more than 10 months. (2) The film, made from the sol and crystallized at 400 ℃, had the characters of anatase structure and crystal size of 18.5 nm by XRD analysis. The SEM imagines show that TiO₂ film was with the characteristics of tight surface structure, The TEM imagine showed the mean particle size is about 20 nm. The photo-degrading test data indicate that the photo-degrading rate to methyl orange solution of 20 mg·L^-1 was more than 84% in 5 hours.     

水热法制备TiO_2纳米线薄膜的光生阴极保护性能

应用水热法在钛箔表面制备TiO2纳米线薄膜,采用场发射扫描电子显微镜、X射线衍射和紫外-可见分光光度法对薄膜进行表征,用电极电位和电化学阻抗谱考察TiO2光生阴极保护性能.结果表明:薄膜由纵横交错的锐钛矿型TiO2纳米线组成,纳米线的直径约10nm.在150℃下反应6h生成的TiO2纳米线薄膜在0.3mol·L-1 Na2SO4溶液和0.3mol·L-1 Na2SO4+0.5mol·L-1 HCOOH混合溶液中对与TiO2薄膜耦连的403不锈钢均有良好的阴极保护效应.TiO2膜所在溶液中含有HCOOH时,可使耦连的403不锈钢在0.5mol·L-1 NaCl溶液中电极电位负移约545mV,界面反应电阻显著变小,表明电解质溶液加入HCOOH可以增强TiO2纳米线薄膜对403不锈钢的光生阴极保护效应.     

表面活性剂对染料敏化太阳能电池光电性能的提高

在硝酸/醋酸(HNO₃/HAc)的水溶液中分别加入十二烷基苯磺酸钠(DBS)、十六烷基三甲基溴化铵(CTAB)、吐温20等不同类型的表面活性剂来水解钛酸四正丁酯制得前驱体溶液,通过水热法制备纳晶TiO₂,并组装成染料敏化太阳能电池(DSSC)。通过XRD、SEM和UV-Vis对纳晶TiO₂薄膜进行表征,并对DSSC进行光电流-光电压(I-V)曲线的测试,研究了不同类型的表面活性剂和不同浓度的CTAB对DSSC光电性能的影响。结果表明：加入阳离子表面活性剂CTAB时提高了DSSC的光电性能,而加入阴离子表面活性剂DBS和非离子表面活性剂吐温20时,DSSC的光电性能反而降低。随着CTAB浓度的增加,电池的光电性能先提高后下降,当c_CTAB=0.08 mol·L^-1时,DSSC的光电转化效率最高为5.76%,比不添加表面活性剂制备的纳晶TiO₂所组装的DSSC的光电转化效率提高了约18%。     

硫化物/Ru(II)络合物复合敏化TiO2纳米多孔膜

用光电化学方法研究了ＣｄＳ,ＰｄＳ和Ｒ１１Ｌ２（ＮＣＳ）２,（Ｌ＝２,２′－ｂｉｐｙｄｉｎｅ－４,４′－ｄｉｃａｒｂｏｘｙｌｉｃａｃｉｄ）复合敏化ＴｉＯ２纳米晶电极的光电化学行为,结果表明,采用复合敏化比用Ｒ１１（ＩＩ）络合物单独敏化ＴｉＯ２纳米晶电极效果好,大大提高了光电转换效率,主要原因是采用复合敏化,可防止ＴｉＯ２导带上由光注入产生的电子的反向转移,避免了电子的损失。     

氢氟酸腐蚀对α-Fe2O3薄膜光解水电极光电化学性质的影响

使用溶胶-凝胶法制备了α-Fe₂O₃薄膜,研究了氢氟酸腐蚀薄膜表面对其光电化学性质的影响. 实验发现,薄膜表面的孔洞和间隙随着氢氟酸浸蚀时间的增长而发生变化. 氢氟酸浸蚀5 min,α-Fe₂O₃电极的光电流降低;随后随浸蚀时间增加而迅速增加;当浸蚀时间大于15 min时,其光电流再次下降,但对浸蚀过的样品再次退火可以使光电流大幅增加. 通过电化学交流阻抗谱、拉曼和X射线光电子能谱分析,提出了两个影响光电流的因素：氢氟酸表面浸蚀造成薄膜表面的多孔性和结晶度降低. 为此,通过示意图解释了结合浸蚀和退火后处理两个步骤来增强α-Fe₂O₃薄膜光解水电极光电活性的原理. 相对于初始的α-Fe₂O₃电极,浸蚀并且再退火处理后,其光电性质更加稳定.     

High Photocatalytic Activity of F-Doped TiO2 Film on Glass

The photoreactivity of sol-gel (SG)-TiO₂ films was enhanced significantly with addition of a small amount of trifluoroacetic acid (TFA) into the starting solution. The promoting effect was confirmed in two separate experiments of the methylsiloxane monolayer oxidation and the photocurrent measurements. The results of film characterization indicated that the absorption coefficient for ultraviolet light ( < 360 nm) increases due to film densification and the crystallinity is improved upon F doping. The improvement in the photoreactivity was ultimately attributed to the increase in the rate at which the photogenerated charge carriers reach the surface in the photostationary state.     

High photocatalytic activity and stability for decomposition of gaseous acetaldehyde on TiO2/Al2O3 composite films coated on foam nickel substrates by sol-gel processes

A set of anatase titanium dioxide (TiO₂) films coated on foam nickel that modified by Al₂O₃ films as transition layer (indicated as TiO₂/Al₂O₃ films) were synthesized via sol-gel route. The bulk and surface properties of the TiO₂/Al₂O₃ films were characterized by thermal gravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and BET. The photocatalytic activities of TiO₂/Al₂O₃ films were investigated based on the degradation of gaseous acetaldehyde under ultraviolet (UV) irradiation. The foam nickel is a promising substrate material in practical applications because of its excellent hydrodynamic properties for gas passing. The TiO₂/Al₂O₃ composite films showed much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than the onefold TiO₂ films. The significant enhancement in photocatalytic activity and stability can be ascribed to the coating of Al₂O₃ transition layer, which concentrates the target substances around TiO₂ particles and increases the specific surface area (SSA) of the substrate (the SSAs of bare foam nickel and Al₂O₃ modified foam nickel are 0.12 and 113.7 m²/g, respectively) to provide more sites for TiO₂ loading.     

Dielectric properties and I-V characteristics of (Pb<Subscript>0.4</Subscript>Sr<Subscript>0.6</Subscript>)TiO<Subscript>3</Subscript> thin films improved by TiO<Subscript>2</Subscript> buffer layers

A TiO₂ thin buffer layer was introduced between the (Pb_0.4Sr_0.6)TiO₃ (PST) film and the Pt/Ti/SiO₂/Si substrate in an attempt to improve their electrical properties. Both TiO₂ and PST layers were prepared by a chemical solution deposition method. It was found that the TiO₂ buffer layer increased the (100)/(001) preferred orientation of PST and decreased the surface roughness of the films, leading to an enhancement in electrical properties including an increase in dielectric constant and in its tunability by DC voltage, as well as a decrease in dielectric loss and leakage current density. At an optimized thickness of the TiO₂ buffer layer deposited using 0.02 mol/l TiO₂ sol, the 330-nm-thick PST films had a dielectric constant, loss and tunability of 1126, 0.044 and 60.7% at 10 kHz, respectively, while the leakage current density was 1.95 × 10⁻⁶ A/cm² at 100 kV/cm.     

ZnO-聚苯胺复合膜的制备和性能研究

利用溶胶-凝胶法在Au膜、聚苯胺膜(PANI)和ITO(导电玻璃)基体上制备ZnO纳米微粒膜,初步研究了该微粒膜的形貌,结构和紫外-可见吸收等性质.结果表明,PANI的孔洞结构抑制了ZnO颗粒的团聚,因此,ZnO-PANI复合膜的紫外-可见吸收光谱和荧光光谱相对于ZnO-Au微粒膜有一定程度的蓝移.光电流谱研究同时表明,ZnO-聚苯胺复合膜有望在光电化学方面得到应用.     

Cellular Patterns in Organic-Inorganic Hybrid Film

The formation of cellular patterns, known as Bénard cell, was investigated in organic-inorganic hybrid films under various conditions. The cells were observed in undoped-hybrid films, and its origin was attributed to the convection of TiO₂ nanoparticles formed in the aging process of the sol. These cells showed the particular properties such as the difference between the center and its surrounding: the center showed a lower refractive index than that of the surrounding, a valley at the center with mountain-like surroundings, and a hydrophobic center and hydrophilic surrounding. How the cell patterns were formed depended on the conditions such as the atmospheric humidity and the gravity. It should be also noted that the cells on a silica glass substrate remained after 1000°C heating.     

Titania supported copper catalysts for methanol synthesis from carbon dioxide

The effect of co-catalyst (ZnO or ZrO₂) has been tested for hydrogenation of CO₂ on CuO/TiO₂ and CuO/Al₂O₃. CuO−ZnO/TiO₂ catalyst showed the highest activity for methanol synthesis. Kinetic parameters were also determined.     

Effects of UV-irradiation on the formation of oxide thin films from chemically modified metal-alkoxides

The effects of UV-irradiation on the properties of ZrO₂ and TiO₂ gel films prepared from corresponding metal-butoxides modified with acetylacetone (AcAc) or benzoylacetone (BzAc) have been studied. It was found that the chelate bonds of -diketones remaining in the gel films were dissociated by the UV-irradiation. The UV-irradiation also changed the properties of the gel films such as solubility; the solubility in acidic solutions was decreased for ZrO₂ gel films modified with AcAc and TiO₂ gel films modified with BzAc became insoluble in alcohol. Based on these findings, a new fine-patterning process has been established, which enables us to make fine-patterns of ZrO₂ and TiO₂ films on a variety of substrates.