Segregation in Titanium Dioxide Co‐Doped with Indium and Niobium

This work reports the effect of oxygen activity on surface segregation for TiO₂ co‐doped with two cations, indium and niobium (0.076 at.% In + 0.103 at.% Nb). In this work, we studied the effect of annealing at 1273 K in the gas phase of controlled oxygen activity on surface segregation of both ions. The applied oxygen activity included pure oxygen, p(O₂) = 100 kPa, and argon, p(O₂) = 10 Pa. The segregation‐induced concentration gradients were determined using both secondary ion mass spectrometry and X‐ray photoelectron spectroscopy. The obtained results indicate that annealing of the studied TiO₂ specimens in argon results in cooperative segregation of both ions leading to the formation of a surface structure involving comparative concentrations of both cations. However, annealing in oxygen results in preferential segregation of indium leading to the formation of a In₂TiO₅‐type surface structure. The obtained results are considered in terms of the effect of multicomponent segregation on processing of the surface layer with controlled properties that are desired for specific applications. The present work indicates that oxygen activity may be used as the parameter in surface engineering of the solid solution.     

Surface Segregation of Niobium and Tantalum in Titanium Dioxide. Overview

Segregation in crystals results in surface layer enrichment of selected lattice elements. The present work considers the phenomenon of segregation in solid solutions of TiO₂ doped with donor‐type elements, such as niobium and tantalum. The focus is on the effect of oxygen activity on segregation at elevated temperatures. It is shown that the effect of oxygen activity on the segregation‐induced enrichment may be used for engineering of oxide materials in general and TiO₂‐based materials in particular with controlled surface composition that is required to achieve the desired reactivity and photoreactivity for energy conversion in general and solar energy conversion in particular. The development of the related surface engineering procedures requires correct determination of oxygen activity during processing and the segregation‐induced concentration gradients within the surface layer.     

可见光响应型非金属掺杂TiO2的研究进展

综述了各种非金属(N、S、C、B)掺杂TiO2在可见光范围的响应,以及N和F共掺杂TiO2、N和La^3 共掺杂TiO2、B与Ni2O3复合的制备及其光催化性能的研究进展。     

Pb2+掺杂TiO2的光催化性能研究

以钛酸丁酯和硝酸铅为原料,用溶胶-凝胶法制备了Pb2+掺杂纳米TiO2粉体,讨论了不同掺杂浓度、不同热处理温度样品在催化降解刚果红染料实验中的光催化活性,分析了Pb2+掺杂TiO2样品的相组成、晶胞参数和晶粒大小对光催化活性的影响.结果表明:Pb2+掺杂能够使锐钛矿向金红石的转变温度向高温方向移动,并且细化了晶粒,实验最佳掺杂浓度为100∶2.0,最佳热处理温度为700℃;Pb2+掺杂的TiO2的锐钛矿相是影响光催化活性的决定性因素.     

Fe3+掺杂TiO2光催化自洁玻璃的研制

采用溶胶—凝胶法和浸渍提拉法在普通钠钙玻璃表面负载了一层纯TiO2。膜或掺杂不同量的Fe3 件的TiO2膜，经灼烧后制备了具有自洁功能的新型玻璃。通过以邻苯二酚紫作为有机污染模拟物的光催化对比实验发现，掺杂适量的Fe3^ 件可以有效的提高光催化效率，过量掺杂则反而降低光催化活性，最佳掺杂量约为1．5%。掺杂1．5％的Fe3^ 件后，紫外一可见吸收光谱的吸收峰增强了大约1倍，而且吸收范围红移了大约30nm。同时对灼烧温度和灼烧时间进行了研究，确定了较优化的制备条件。     

Performance Evaluation of Doped Titanium Oxide for Low‐Voltage Applications

Varistors are the electronic devices which are used in various industries to protect the electrical and electronic systems from sudden surges. In this research, the electrical properties of titanium dioxide (TiO₂) doped with tantalum pentoxide (Ta₂O₅), tungsten trioxide (WO₃), cobalt oxide (Co₃O₄), and bismuth oxide (Bi₂O₃) and fired at different temperatures were investigated for low‐voltage applications. The adequate amount of dopants at suitable sintering temperature had beneficial effect in improving the properties of TiO₂. The relative density was found to be more than 97% of theoretical density when samples sintered between 1300°C and 1400°C for all composition compared to undoped samples. On the other hand, the addition of dopants enhanced hardness and compressive strength of varistor disks. The average grain size was also increased with the dopants system, making it suitable for low‐voltage application. Furthermore, the current–voltage characteristic of the TiO₂ revealed a significantly high value of nonlinearity of 19.6. A high dielectric constant of 10⁴ with minimum dissipation factor of 0.002852 at 1 kHz was also obtained, thereby making it suitable for low‐voltage application.     

硅胶负载F掺杂TiO_2的制备与性能评价

利用水热法,以硅胶为载体、以Ti（SO4）2为钛源、NaF为氟源制备了具有良好性能的＂硅胶负载氟掺杂二氧化钛＂（FTS）光催化剂。考察了氟投加量、焙烧温度及钛硅比对光催化活性的影响。利用X射线晶体粉末衍射（XRD）,比表面积分析（BET）和紫外可见漫反射光谱（DRS）等表征手段对样品进行表征。结果表明,氟投加量为30%、钛硅比为1/1、焙烧温度为200℃时制备的FTS具有最佳的光催化活性,其比表面积为81.40 m2/g。氟掺杂二氧化钛（FT）经硅胶负载后,其表面孔结构发生了变化,并且热稳定性增加。苯酚降解实验表明：与FT相比,FTS以0.53 g/g的二氧化钛含量却体现更高光催化活性。     

N掺杂锐钛矿二氧化钛光响应红移的模拟计算

利用密度泛函理论(DFT),采用平面波超软赝势方法,模拟计算了掺N锐钛矿相TiO2对能隙、Fermi能级、态密度的影响,以探讨其可见光活性的机理。计算结果表明:表面HOMO和LUMO分别主要由Ti的3d轨道和O、N的2p轨道构成,掺杂出现的N2S态增加了N掺杂的稳定性。并发现N掺杂从两个方面使TiO2材料的带隙变窄:一为N掺杂使Fermi能级移入价带,使带隙变窄;二为在价带的上方引入了独立的能级,在导带下方引入一个宽为0.9 eV左右的能带,这两个掺杂能级使其禁带减小。     

可见光响应的Fe^3＋修饰纳米TiO2光催化降解氮氧化物研究

为了在光催化转化氮氧化物的反应中利用可见光,以Fe（NO3）·9H2O作为Fe^3＋源,采用浸渍的方法,制备了Fe^3＋修饰的纳米TiO2。经XRD分析表明,搀杂和煅烧过程没有改变TiO2的晶型。由XRD和XPS图谱可知,Fe^3＋在TiO2表面形成Ti—O—Fe键。催化剂的UV-Vis漫反射光谱显示,Fe^3＋修饰TiO2催化剂的吸收光谱发生了一定程度的红移,在可见光区有一定的吸收。Fe^3＋修饰TiO2催化在蓝光照射下对NOx有一定的转化而且在模拟自然光下NOx的转化效率也有所提高。合适的Fe^3＋修饰量对修饰过程非常重要,Fe^3＋/Ti^4＋摩尔比为0.2%并在600℃下煅烧1.0 h的催化剂在可见光下转化NOx的活性最高。     

掺偶氮苯二氧化钛基复合薄膜的制备及光开关性能

通过低温溶胶-凝胶技术结合旋涂法制备了掺偶氮苯二氧化钛基有机-无机复合薄膜.研究了不同热处理温度对复合薄膜的表面形貌、传输模式、折射率与厚度和光化学结构特性的影响.结果表明:该复合薄膜在低于300℃的热处理温度时表面光滑致密、折射率可调,是良好的光波导材料.通过测试样品在365 nm紫外光和450 nm可见光照射下的吸...     

UV‐Cured Polysiloxane Epoxy Coatings Containing Titanium Dioxide as Photosensitive Semiconductor

UV‐cured polysiloxane epoxy coatings containing titanium dioxide were prepared by means of a cationic photopolymerization process. A good distribution of the inorganic filler was achieved within the polymeric network with an average size dimension of around 500 nm. UV‐vis analysis performed on organic dye (methylene blue) stained coatings showed a high efficiency of the titania photocatalytic activity: a complete degradation of the dye on the coating surface is reached after 60 min of UV irradiation without affecting the matrix photo‐degradation.

     

钛精矿中二氧化钛的测定

介绍了一种直接测定钛精矿中的二氧化钛的含量的新方法。拟定在不经分离沉淀的情况下，采用H2SO4-HNO3-HF熔矿，H2O2光度法测定钛精矿中的二氧化钛，用国家一级标准物质GBW07224(ωTiO2为10．63％)和GBW07225(ωTiO2为9．72％)进行了精密度实验，RSD(n=6)为8．33％、6．59％。加标准回收试验结果TiO2的回收率为99．34％～101．4％。经国家标准物质验证，测定结果与标准值相符，方法适用于1％～70％之间的二氧化钛测定。     

Surface Characterization and Biocompatibility of Selenium‐Doped Hydroxyapatite Coating on Titanium Alloy

Selenium‐doped hydroxyapatite (HA) was biomimetically coated on Ti6Al4V plates with the aim of combining the anticancer and antibacterial properties of selenium with the biocompatibility and bioactivity of HA. For the coating process, the composition of 1.5 × SBF (solution with ion concentrations at 1.5 times that of simulated body fluid, SBF) was modified to include 0.15 mM selenate (SeO₄^2?) ion. The selenium‐doped HA coating was characterized by several methods, such as scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy. The cytotoxicity of selenium on osteoblast and osteosarcoma cells was determined. The coating was shown to inhibit the growth of Staphylococcus epidermidis.     

Solar‐Assisted Photocatalytic Degradation of Benzoic Acid Using Titanium Dioxide as a Photocatalyst

The photocatalytic degradation of benzoic acid using titanium dioxide (Degussa P‐25) as a photocatalyst has been studied. The effects of various anions, which are common in industrial wastewater, and of the initial pH were also studied. The effect of the presence of low concentration of cations was also studied. From the intermediates detected a photocatalytic degradation pathway for benzoic acid has been proposed.     

Sintering Rates for Pristine and Doped Titanium Dioxide Determined Using a Tandem Differential Mobility Analyzer System

Sintering rates of pristine and V-doped TiO ₂ were obtained using a tandem DMA system. A range of experiments were conducted to first map out the variation of mobility size of a monodisperse (by mobility) agglomerate with time at three fixed temperatures. Using relationships of the surface area to the mobility size, the sintering equation was solved to determine the activation energy and pre-exponential factor. The value of the activation energy was 236 (± 46) kJ/mol for pristine TiO ₂ and 363 (± 1) kJ/mol for V-doped TiO ₂ . The corresponding pre-exponential factors were 7.22 × 10 ¹⁹ and 2.22 × 10 ¹² s/m ⁴ K, respectively. These values were then used to predict changes in mobility diameter at different temperatures, and good agreement was obtained with measurements. Possible reasons for faster sintering rates of V-TiO ₂ relative to pristine TiO ₂ were conjectured.     

钛白粉及金红石中TiO2的置换配位滴定

本文提出了测定钛白粉和金红石中二氧化钛的简易置换配位滴定法，向含有钛离子和其它阳离子的溶液中加入过量的环己烷二胺四乙酸（ＤＣＴＡ），以二甲酚橙（ＸＯ）为指示剂，用乙酸锌标准溶液返滴定过量的ＤＣＴＡ，然后以氟化物分解Ｔｉ（ＩＶ）－ＤＣＴＡ配合物，释放出的ＤＣＴＡ，用乙酸锌标准溶液滴定，本法终点变化敏锐，具有很好的精密度和准确度。     

氯化法钛白综述

钛白粉生产工艺有硫酸法和氯化法两种,氯化法钛白粉生产比硫酸法生产流程短、工序少、可采用连续化生产,产品质量好,三废排放量少,因此氯化法钛白粉生产发展迅速.本文详细分析了国外和国内氯化钛白的发展分析历程和不同技术路径发展情况,并介绍了氯化钛白不同结构沸腾氯化炉的优缺点,以及氧化工序中三氯化铝发生装置,氧化系统防疤、除疤技...     

Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst

The photocatalytic oxidation of 4‐methoxybenzyl alcohol to p‐anisaldehyde (PAA) was performed in water with organic‐free suspensions of home‐prepared and commercial titanium dioxide (TiO₂) catalysts. The nanostructured TiO₂ samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl₄), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4‐methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116 %. A comparison with two commercial TiO₂ samples showed that all the home‐prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by‐products present were traces of 4‐methoxybenzoic acid and aliphatic products, carbon dioxide being the other main oxidation product.     

钛白粉市场分析

2009年世界钛白粉生产商85家,我国占其中65家;世界钛白粉产能618万t/a,我国却只占其中150万t/a,而且只有一套3万t/a氯化法生产装置,其余均采用硫酸法,高档的金红石型钛白粉不能生产。这一切至2010年底将得到改变,产能将达到210万t/a,成为全球第一,但仍以硫酸法为主。国家鼓励高品位钛原料的氯化法钛白粉生产工艺开发。钛白粉企业优胜劣汰不可避免。