乙二醇表面改性纳米二氧化钛的制备及其对水性聚氨酯的改性

以乙二醇(EG)和钛酸四丁酯(TBOT)为原料,采用原位表面修饰方法成功制备了乙二醇表面改性纳米TiO2(EG-TiO2);利用傅立叶红外光谱仪、X射线衍射仪、透射电子显微镜表征了其结构,采用热重分析仪测定了其热稳定性.结果表明,经表面修饰的纳米二氧化钛在水性聚氨酯皮革涂饰剂(WPU)基体中分散良好;将EG-TiO2添加到WPU中能显著提高其抗紫外线性能、热稳定性及耐磨性能.     

二氧化钛纳米材料的非均相光催化本质及表面改性

非均相光催化过程是指多相多尺度体系在光辐射作用下发生的一个复杂的催化过程,被认为最有潜力解决环境污染和能源短缺问题的绿色及可再生的技术之一。在目前已经报道的各种非均相光催化剂中, TiO2纳米材料被证实是应用最广泛、光催化效果最好的催化剂,是当前国际材料、环境和能源等领域的研究前沿和热点,高性能TiO2基光催化材料的设计及改性一直是该领域的难点,其关键问题主要为：如何增强TiO2的表面光催化量子效率、促进光生载流子分离和拓展其可见光响应范围。尽管已经有很多关于TiO2光催化的综述,但大多综述集中在高性能TiO2的制备及各种改性策略研究,而对各种改性策略与光催化分子机理之间的关系阐述较少。为此,本文深入分析了TiO2纳米材料的非均相光催化本质并总结了各种表面改性策略。首先从热力学角度阐明TiO2的热力学能带能够确保其实现各种典型光催化反应(包括光催化降解、CO2还原及光解水),证实其广泛应用的可行性。然后,对TiO2光生载流子的动力学基础进行总结,证实快速的广生载流子复合以及较慢的表面化学反应动力学是限制其光催化活性提高的关键制约性因素。于此同时,对TiO2纳米材料的表面Zeta点位、超亲水性、超强酸光催化剂制备(表面羟基取代)等重要的表面化学性质也进行了详细阐述。从而可以初步得出如下结论：表面改性是设计高性能TiO2光催化材料的重中之重,并将各种改性策略浓缩在6个方面：表面掺杂和敏化,构建表面异质结,负载纳米助催化剂,增加可利用的比表面剂,利用表面氟效应以及暴露高活性晶面等。显然,表面掺杂和敏化可以减小TiO2纳米材料的禁带宽度,从而大幅拓宽其可见光吸收范围及光催化效率。而构建紧密的表面异质结可以创建界面电场,不仅可以促进光生电荷分离效率,而且可以有效提高界面电荷转移效率,最终实现异质结的高光催化效率。负载纳米助催化剂则可以大幅加快表面化学反速率,降低光生载流子的表面复合并增加其利用率,并有可能减少不期望的表面逆反应,从而实现光催化活性提升。增加可利用的比表面剂,可以有效提升光催化剂与吸附质之间的有效接触面积,缩短了载流子的传输距离以及通过多次反射与折射提升光能的利用率,从而全方位地提升TiO2纳米材料的光催化活性。对TiO2纳米材料表面进行氟化,可以增加光生羟基自由基的速率以及浓度,并可以通过调节TiO2表面酸碱性而控制其光催化选择性,从而实现高效高选择性光催化。最后,通过暴露TiO2纳米材料的高活性晶面,也可以促进光生载流子分离、增加吸附性能或羟基自由基生成速率,从而获得高光催化效率。另外,这些表面改性策略的协同效应仍是较有前景的TiO2纳米光催化剂改性技术,值得深入研究。同时,深入的光催化分子机理探索仍然是必须的,其不仅有助于发现影响TiO2纳米材料光催化活性提高的关键性制约因素,而且也可以指导开发新型的TiO2纳米光催化剂改性技术。总而言之,通过总结TiO2纳米材料在光催化、表面化学及表面改性等方面的重要进展,可为设计高效的TiO2基及非TiO2基光催化剂并应用于太阳燃料生产、环境修复、有机合成及相关的领域(如太阳能电池、热催、分离和纯化)等提供新的思路。     

H3PO4改性纳米TiO2气相光催化降解正己烷

利用钛酸丁酯水解浸渍方法制备了几种不同浓度H3PO4改性的TiO2纳米复合粉体材料并作了XRD、BET等表征，以正己烷的气相光催化氧化降解为探针反应研究了H3PO4改性TiO2催化剂的光催化活性，并和未改性TiO2及商品TiO2 Degussa P-25作了比较．结果表明，H3PO4改性能够显著地细化TiO2的晶粒度，增大TiO2的比表面积，同时，适量掺杂H3PO4对TiO2的光催化活性也有较大的促进作用．H3PO4作为掺杂物有优于NH4H2PO4之处．     

氮掺杂改性二氧化钛光催化剂的研究进展

综述了近年来国内外利用氮掺杂改性二氧化钛的光催化剂性能、提高可见光的利用效率的最新研究进展;分析和讨论了氮掺杂二氧化钛的制备方法、理论计算和结构模型、掺杂机理等;总结了氮掺杂改性二氧化钛存在的问题,同时讨论了今后的研究方向.     

二氧化钛微粒存在下表面活性剂光催化分解机理的研究

半导体微粒子(二氧化钦等)在光照射下产生强烈的氧化能力,可以把水和空气中的许多难分解有毒有机污染物氧化分解为二氧化碳、水等无机物。该方法分解速度快、除净度高,有着很大的应用前景^[1~3]。在过去几年里,我们广泛地报导了在二氧化钦半导体微粒子催化下表面活性剂^[3,4]、农药^[5]氰化物困等环境污染物的光催化分解。烷基、芳香基及含氧碳氢基团可被氧化分解为二氧化碳和水^[4];有机化合物中的卤素^[5]、磷川、硫^[8]氮^[9]原子分别被光分解为卤素离子、磷酸根离子、硫酸根、按和硝酸根离子。因多相光催化反应十分复杂,目前对光催化分解过程,特别是中间化合物的生成及其浓度变化了解很少,甚至连光致电子及空穴的反应也并不十分明确。     

二氧化钛表面光学特性与光催化活性的关系

本文考察了二氧化钛经氢气氛热处理后对其光催化降解苯酚活性的影响。结果ＤＲＳ，ＦＳ，ＸＲＤ等研究手段，发现二氧化钛光催化降解苯酚的活性与其光学特性（吸收光能力和荧光发射强度）有较好的一致性，而光学特性来自表面态。由此，提出了二氧化钛光学表面态的概念，认为与光催化活性密切相关的二氧化钛光学表面态的性质，是由这些钛羟基和低价钛的数量及比例决定的。     

硅烷偶联剂改性的二氧化钛光催化降解气相苯

 用硅烷偶联剂KH-570对二氧化钛光催化剂进行了改性,制备了一种新型光催化剂. 以苯作为 模拟气体,在静态反应装置中考察了该催化剂的光催化性能. 结果表明,KH-570能显著提高 二氧化钛对气相苯的光催化降解性能,其转化率是纯二氧化钛的2.5倍. 采用红外光谱和X射线光电子能谱对催化剂进行了表征.     

乙酰丙酮金属配合物的制备及催化性能研究

制备了各种乙酰丙酮金属配合物催化剂。通过扫描电镜、热重等测试手段对催化剂形貌和性质进行了表征,并初步探讨了反应机理。以酯交换法催化合成甲基丙烯酸二甲氨基乙酯反应为对象,考察了乙酰丙酮金属配合物催化剂的用量、反应时间和反应温度等对产物产率的影响。     

共沉淀法制备氧化硅改性的纳米二氧化钛及其性质

采用共沉淀法合成了氧化硅改性的具有高比表面积的纳米二氧化钛.氧化硅的添加提高了二氧化钛纳米颗粒的热稳定性能,有效地抑制了纳米二氧化钛的颗粒增长、团聚和锐钛向金红石的晶型转换.光催化降解亚甲基蓝证明,样品具有较高的光催化活性,而且随着氧化硅添加量的增加,光催化活性提高.     

纳米碳酸钙的表面改性研究

纳米产品(材料)是当今世界高科技产品之一.纳米碳酸钙作为粉体产品中的一种,以高纯、超细、改性和功能性为标志,广泛应用于橡胶、塑料、造纸、油墨、涂料、医药、化妆品等各行各业[1-2].主要用作填充材料,因粒度超细、分散性好,可以增加填充量,降低制品成本,改善制品性能,提高制品档次,拓宽制品使用范围.近年来,随着CaCO3的超细化、结构复杂化及表面改性技术的发展,极大地提高了它的应用价值.对不同形态的超细CaCO3制备技术的研究,已成为许多先进国家竞相开发的热点[3-5].     

Synthesis of nanosized titanium dioxide from tetrabutoxytitanium

Mesoporous TiO₂ has been obtained by template synthesis. The introduction of a surfactant in the hydrolysis of tetrabutoxytitanium in aqueous ethanol allows the structure of the resulting material to be controlled. The amorphous TiO₂ resulting from hydrolysis turns into anatase on being calcined at 300°C. As determined by X-ray diffraction, the anatase crystallite size is 70 nm in the presence of the highest surfactant concentration examined and 210 nm in the absence of a surfactant. Amorphous materials have been characterized by electron microscopy and differential thermal analysis. The ultimate benzene adsorption value has been determined for calcined mesoporous TiO₂.     

Physicochemical and photocatalytic properties of nanosized titanium dioxide deposited on silicon dioxide microspheres

The synthesis of SiO₂ core-TiO₂ shell composites from a titanium dioxide sol and a suspension of microspherical silicon dioxide is described. The main factors ensuring the formation of a composite with a preset morphology are the size and charge of the TiO₂ sol particles (10–45 nm) and silicon dioxide core particles (300–700 nm), the pH values of the suspensions of the starting components and the resulting composite, and the proportions and way of mixing of the siliconand titanium-containing components. The SiO₂ core-TiO₂ shell composites show high photocatalytic activity in the degradation of Rhodamine FL-BM dye (rate constant of k = 0.0813 min⁻¹) and are much more active than precipitated TiO₂ powder (k = 0.0022 min⁻¹). The activity of the composite is determined by the calcination temperature (700–800°C), by the proportion and accessibility of the active component (TiO₂), and by the presence of a dopant (P₂O₅).     

纳米二氧化钛光催化降解喹啉动力学

利用溶胶-凝胶法制备纳米二氧化钛光催化剂,探讨了其光催化降解废水中典型含氮杂环化合物喹啉的动力学行为。实验条件下,TiO₂光催化降解喹啉的反应为准一级反应,可用Langmuir-Hinshelwood动力学模型描述,其表达式为r=0.296kc_t/(1+0.296c_t),其中,lnk =-0.411 1lnc₀+2.278。     

Surface states of titanium dioxide nanoparticles modified with enediol ligands

Control of surface states of titanium dioxide nanoparticles using 2-(3,4-dihydroxyphenyl)ethylamine (dopamine) and 3,4-dihydrophenylacetic acid, which act as ligands to the undercoordinated surface sites (carrier traps), is demonstrated by electrochemical techniques. The deepest traps were found to be most reactive and are selectively removed by the addition of the ligands which enhances the kinetics of electron accumulation in the film. Furthermore, a shift in the Fermi level to more positive potentials was detected for electrodes modified with the negatively charged ligand (3,4-dihydrophenylacetic acid) compared to that of electrodes modified with the positively charged ligand (dopamine). The presence of the negative charge on the ligand also contributed to the underpotential of hydrogen evolution on 3,4-dihydrophenylacetic acid-modified electrodes.     

机械力化学反应法制备纳米金红石型二氧化钛的研究

以Ti (C4H9O)4 和 C2H2O4·2H2O 为原料在室温下利用机械力化学反应法制备前驱体,利用热重-微商热重法(TG-DTG)决定前驱体的分解温度,通过在特定温度下对前驱体进行热分解得到TiO2.利用XRD,SEM,ZETA 电位粒度分析仪以及紫外光谱仪对所得样品物相,形貌,粒度和光学性能进行分析和表征.结果显示所得粉体微观形貌为球形,其直径(＞ 95%)小于60nm,粒径较小的粉体对紫外线UVA波段的吸收效果较好.     

Preparation and properties of a new composite photocatalyst based on nanosized titanium dioxide

The use of photocatalysts supported on adsorbents is receiving substantial attention. Supporting TiO₂ with zeolites is found to be one of the best solutions to increase the efficiency of TiO₂-based photocatalysts. This work was focused on simple preparation of a TiO₂/Na-ZSM-5 composite catalyst by the solid state dispersion (SSD) method and its modification with an organic photosensitizer — polythiophene (PT). Using the XRD diffractometry, structure of the new composite catalyst was proved. Beside this composite catalyst, mechanical mixtures of TiO₂-based catalysts with Na-ZSM-5 zeolite were prepared. The efficiency of all five available photocatalysts (TiO₂, TiO₂-PT, mechanical mixture of TiO₂ + Na-ZSM-5, mechanical mixture of TiO₂-PT + Na-ZSM-5, and the modified SSD-PT composite) on photodegradation of 4-chlorophenol was compared. By measuring the formation of chloride ions and decreasing the 4-chlorophenol concentration at two different initial concentrations of 4-chlorophenol in the basic aqueous solution, the photoefficiency and adsorption properties of our photocatalysts were determined. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Mechanical and thermal properties of nanosized titanium dioxide filled rigid poly(vinyl chloride)

Nano-sized rod-like titanium dioxide (TiO2) filled rigid poly(vinyl chloride) (PVC) nanocomposites were prepared by using injection-molding method. Vicat, Charpy impact and tensile tests as well as thermogravimetric and dynamic mechanical analyses were used to characterize the structure and properties of the nanocomposites. The results showed that nano-TiO2 could improve Vicat softening temperature and also improve thermal stability of PVC during the stages of dehydrochlorination and formation of carbonaceous conjugated polyene sequences, which can be ascribed to restriction of the nanoparticles on the segmental relaxation as being evidenced by raises in glass transition and β-relaxation temperatures of PVC upon filling TiO2. Addition of TiO2 nanoparticles less than 40 phr (parts per hundreds of resin) could significantly improve impact strength of the composites while the TiO2 agglomeration at high contents leads to a reduction in impact toughness.     

Surface modification of titanium with thermally treated polydimethylsiloxane coating and the effect on resin to titanium adhesion

In this study, titanium surface modification by a thermal treatment using a polydimethylsiloxane (PDMS) coating was investigated. The surfaces of four titanium samples were surface treated by polishing, sandblasting, and coating with a PDMS with a thermal treatment at 800 and 1100 °C. The titanium surfaces were characterized by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy. The effect of the surface treatments on adhesion of resin to titanium was assessed by shear adhesion strength test. XPS analysis showed that there was a change of elemental composition of titanium surfaces after surface treatment. Binding energy shifts for Si2p and O1s were observed after sandblasting and thermally treated PDMS. Therefore, chemical states of Si and O were changed. Atomic force microscopy analysis revealed that the surface topography of the Ti samples was different, and surface roughness was increased after sandblasting and thermal treatment of PDMS coating. Shear adhesion strength test results showed that the adhesion between resin and titanium is affected by the treatment temperature of PDMS coating. The highest adhesion is obtained at 1100 °C (14.7 ± 1.57 MPa). Copyright © 2014 John Wiley & Sons, Ltd.     

Inorganic polarography in organic solvents-III Analytical applications of metal-acetylacetonate complexes in toluene

Indium and palladium are determined polarographically with a dropping mercury electrode in a toluene phase, following extraction as the acetylacetonates from aqueous solutions containing 2-10 ppm of the metals (or 0.1-0.5 ppm with a greater ratio of sample volume to solvent volume). Of 31 elements examined, only Co(III), Cr(III), Cu(II), Fe(III), In, Mo(VI), Pd and Ti(IV) gave extractable complexes with reduction waves in the available potential range. Specificity for palladium is obtained by extraction at pH 0.5, and for indium at pH 9 m the presence of cyanide and ascorbic acid as masking agents.