煅烧温度对二氧化钛纳米晶性能的影响

研究了不同煅烧温度下,锐钛矿相、混晶和金红石相二氧化钛纳米晶的 粒径、比表面积和吸收光谱的变化。经相同的温度煅烧后,金红石相二氧化钛纳米晶的生长速率和比表面积下降速率均大大高于锐钛矿相,表明高温反应或煅烧难以获得金红石相纳米晶,真空热处理的金红石相二氧化钛纳米晶可以保持较高的比表面积和较小的粒径,但易导致非化学配比、晶格缺陷并降低了粉体的性能。     

Visible Light Induced Photocatalysis of Cerium Ion Modified Titania Sol and Nanocrystallites

The cerium ion(Ce4+) doped titania sol and nanocrystallites were prepared by chemical coprecipitation-peptization and hydrothermal synthesis methods, respectively. The X-ray diffraction pattern shows that Ce4+-TiO2 xerogel powder has semicrystalline structure and thermal sintering sample has crystalline structure. Ce4+-TiO2 nanocrystallites are composed of the major anatase phase titania (88.82 wt pct) and a small amount of crystalline cerium titanate. AFM micrograph shows that primary particle size of well-dispersed ultrafine sol particles is below 15 nm in diameter. The particle sizes are 30 nm for xerogel sample and 70 nm for nanocrystallites sample, which is different from the estimated values (2.41 nm and 4.53 nm) by XRD Scherrer's formula. The difference is mainly due to aggregation of nanocrystallites. The experimental results exhibit that photocatalysts of Ce4+-TiO2 sol and nanocrystallites have the ability to photodegrade reactive brilliant red dye (X-3B ) under visible light irradiation with t     

TiO2纳米微晶的RF-PCVD法制备及表征

以TiCl4为原料,采用高频等离子化学气相沉积(RF-PCVD)法制备了TiO2纳米微晶,考察了控制粒径大小及晶相转化的关键操作条件.借助XPS、TEM、XRD、BET等技术对颗粒的化学组成、形貌、晶相结构等进行了表征.研究表明:所得TiO2纳米微晶大部分为球形体颗粒,粒径30～50 nm,单分散性良好;颗粒中锐钛相和金红石相两相共存,结晶完整;金红石相含量在26.7%～53.6%之间可调.     

Synthesis of nanocrystalline TiO2 at 100 °C

A simple gel to crystal conversion route has been followed for the preparation of TiO₂ at 80–100 °C under refluxing conditions. Freshly prepared titanium hydroxide gel is allowed to crystallize under refluxing and stirring conditions for 6–12 h. Formation of nanocrystallites of anatase is confirmed by X-ray diffraction (XRD) study. The anatase phase converts into rutile when calcined at 700 °C for 12 h. Raman scattering experiments were also performed to confirm both anatase and rutile phases. Transmission electron microscope (TEM) investigations revealed that the average particle size is 10 nm for the anatase phase whereas it is 35 nm for the rutile polymorph.     

Sol-Gel法制备纳米TiO2过程中水解pH值的影响及其性能表征

采用钛酸四异丙酯[Ti(i-OC3H7)4]水解法制备纳米TiO2粉体，水解过程中有很多参数对纳米TiO2的特征产生影响，通过控制制备过程中的水解pH值，可以得到不同粒径和不同晶型的纳米TiO2粉体，本文主要探讨了纳米TiO2晶型转变的条件和晶粒度Dhkl随pH值变化的趋势，并利用XRD，TEM对粉体颗粒的形貌，大小，物相组成进行分析，XRD分析研究表明，纳米的A→R相变和水解pH值密切相关。     

双微乳液法制备掺杂Fe~(3+)的纳米TiO_2及其光催化性能

为了研究双微乳液法在制备纳米级光催化剂的应用,以TiCl4和NH3.H2O为原料,采用十六烷基三甲基溴化铵-正丁醇-环己烷-水微乳体系制备Fe3+掺杂纳米TiO2,对粉末的晶体结构进行X射线衍射表征,并以其对p-甲酚的降解考察其光催化活性。结果表明,在较小的掺杂量时,Fe3+掺杂量的提高可以提高TiO2的光催化活性,进一步提高掺杂量将引起光催化活性的降低;掺杂Fe3+可导致纳米TiO2的粒径减小;Fe3+的半径较小以及Fe2O3的熔点较低均有利于TiO2从锐钛矿向金红石的相变;当Fe3+掺杂摩尔分数为0.06%,煅烧温度为550℃时,纳米TiO2的光催化活性最高,此时形成TiO2的锐钛矿和金红石相的混晶;乳液中含水量也会影响晶相的组成和粒径大小,随着含水量增加产物中出现了一定比例的金红石相。     

二氧化钛纳米晶的光催化活性研究

以苯酚的光催化降解为模型反应,研究了锐钛矿相和金红石相二氧化钛纳米晶（７￣４０ｎｍ）的光催化活性。与市售的氧化钛相比,两种晶相的纳米氧化钛均有很高的光催化活性,锐钛矿相氧化钛对苯酚的深度矿化有更高的选择性。ＴｉＯ２吸附的水及羟基会降低氧化钛的光催化活性。由于粒径减小使氧化钛的吸收带边界蓝移,粒径小的氧化钛有更高的催化活性,粒径〈１５ｎｍ时,显示出量子尺寸效应。     

Optimized method for preparation of TiO2 nanoparticles dispersion for biological study

The objective of the present study was to develop a practical method to prepare a stable dispersion of TiO2 nanoparticles for biological studies. To address this matter a variety of different approaches for suspension of nanoparticles were conducted. TiO2 (rutile/anatase) dispersions were prepared in distilled water following by treated with different ultrasound energies and various dispersion stabilizers (1.0% carboxymethyl cellulose, 0.5% hydroxypropyl methyl cellulose K4M, 100% fetal bovine serum, and 2.5% bovine serum albumin). The average size of dispersed TiO2 (rutile/anatase) nanoparticles was measured by dynamic light scattering device. Agglomerate sizes of TiO2 in distilled water and 100% FBS were estimated using TEM analysis. Sedimentation rate of TiO2 (rutile/anatase) nanoparticles in dispersion was monitored by optical absorbance detection. In vitro cytotoxicity of various stabilizers in 16-HBE cells was measured using MTT assay. The optimized process for preparation of TiO2 (rutile/anatase) nanoparticles dispersion was first to vibrate the nanoparticles by vortex and disperse particles by ultrasonic vibration in distilled water, then to add dispersion stabilizers to the dispersion, and finally to sonicate the nanoparticles in dispersion. TiO2 (rutile/anatase) nanoparticles were disaggregated sufficiently with an ultrasound energy of 33 W for 10 min. The formation of TiO2 (rutile/anatase) agglomerates in distilled water was decreased obviously by addition of 1.0% CMC, 0.5% HPMC K4M, 100% FBS and 2.5% BSA. For the benefit of cell growth, FBS is the most suitable stabilizer for preparation of TiO2 (rutile/anatase) particle dispersions and subsequent investigation of the in vivo and in vitro behavior of TiO2 (rutile/anatase) nanoparticles. This method is practicable to prepare a stable dispersion of TiO2 (rutile/anatase) nanoparticles for at least 120 h.     

The catalytic oxidation of aromatic hydrocarbons over supported metal oxide

The catalytic activity of metals (Cu, Mn, Fe, V, Mo, Co, Ni, Zn)/gamma-Al2O3 was investigated to bring about the complete oxidation of benzene, toluene and xylene (BTX). Among them, Cu/gamma-Al2O3 was found to be the most promising catalyst based on activity. X-ray diffraction (XRD), Brunauer Emmett Teller method (BET), electron probe X-ray micro analysis (EPMA) and temperature programmed reduction (TPR) by H2 were used to characterize a series of supported copper catalysts. Increasing the calcination temperature resulted in decreasing the specific surface areas of catalysts and, subsequently, the catalytic activity. Copper loadings on gamma-Al2O3 had a great effect on catalytic activity, and 5 wt.% Cu/gamma-Al2O3 catalyst was observed to be the most active, which might be contributed to the well-dispersed copper surface phase. Using TiO2 (anatase), TiO2 (rutile), SiO2 (I) and SiO2 (II) as support instead of gamma-Al2O3, the activity sequence of 5 wt.% Cu with respect to the support was gamma-Al2O3 > TiO2 (rutile) > TiO2 (anatase)>SiO2 (I) > SiO2 (II), and this appeared to be correlated with the distribution of copper on support rather than with the specific surface area of the catalyst. The smaller particle size of copper, due to its high dispersion on support, had a positive effect on catalytic activity. The activity of 5 wt.% Cu/gamma-Al2O3 with respect to the VOC molecule was observed to follow this sequence: toluene > xylene > benzene. Increasing the reactant concentration exerted an inhibiting effect on the catalytic activity.     

甲烷燃烧法合成纳米二氧化钛的试验研究

以甲烷为燃料、空气为氧化剂、TiC14为原料,采用燃烧法合成了纳米二氧化钛,利用扫描电镜和X射线衍射对制备出的纳米TiO2颗粒产品的颗粒尺寸分布和物相组成进行了表征,通过调节甲烷、空气、载气的流量,并通过热电偶测量火焰温度,制备出不同操作工况下的纳米TiO2产品,讨论了工艺参数对颗粒特性的影响。结果表明,获得的纳米TiO2粒径主要分布在50～70nm,产品中大部分为锐钛矿相,含有少量的金红石相。     

Ce-TiO2光催化剂的制备与性能研究

采用溶胶-凝胶法制备了稀土Ce离子掺杂的纳米TiO2光催化剂(Ce-TiO2),通过XRD、FT-IR、UV-Vis、PL、Nano-sizer纳米粒度分析仪等对Ce-TiO2样品进行了表征和分析,并以亚甲基蓝(MB)作为目标降解物,考察了不同掺杂浓度及经不同温度热处理后的Ce-TiO2样品对MB的光催化降解效果,结果表明所制备样品的晶型均为锐钛矿相和金红石相的混晶相,Ce离子的掺杂拓展了TiO2在可见光区的光谱响应范围,提高了TiO2光催化活性。当pH值为1.5,Ce的掺杂量为n(Ce)∶n(TiO2)=1∶300,热处理温度为600℃条件下制备的样品其催化活性显著高于Degussa P25。     

气相燃烧合成二氧化钛纳米颗粒

建立了CO气相燃烧合成纳米颗粒材料技术 ,利用TiCl4 气相氧化合成粒度小于 10 0nm纯金红石或锐钛和金红石混合相的TiO2 颗粒。混合温度升高、TiCl4 进料量减小、停留时间缩短时 ,二氧化钛颗粒粒度减小。随混合温度升高、TiCl4 进料增大以及停留时间延长 ,TiO2 颗粒中金红石含量增大。在反应物中加入AlCl3 作为晶型调节剂时 ,金红石含量增大。     

镍、硫共掺杂纳米TiO2的制备及其可见光催化性能

为提高纳米TiO2的可见光催化活性,采用沉淀-浸渍法制备了一种新型Ni和S共掺杂TiO2纳米复合光催化剂.通过紫外-可见(UV-Vis-)漫反射、X-射线衍射(XRD)、透射电子显微镜(TEM)和X-荧光(EDX)等手段对其结晶形态、晶粒尺寸、元素掺杂量和吸光性能等进行了表征.结果显示,催化剂Ni/S/TiO2为锐钛矿晶相,平均粒径约为6～7nm,比表面积高达260.42m2/g,感光范围可拓展到可见光区,且与纯TiO2,S掺杂TiO2和Ni掺杂TiO2相比,光催化剂Ni/S/TiO2的颗粒粒径更小,比表面积更大,光吸收边红移程度更显著.以活性艳蓝198染料溶液为模拟废水,以氙光灯为光源,对光催化剂Ni/S/TiO2的催化活性进行了评价.结果表明,Ni/S/TiO2具有比纯TiO2、S掺杂TiO2和Ni掺杂TiO2更高的可见光催化活性,氙光灯照射120min,活性艳蓝198降解率可达到98.5%.     

纳米二氧化钛粉体晶相控制实验研究

在水解－沉淀法制备纳米TiO2粉体的过程中，使用不同的沉淀剂获得了晶相不同的纳米TiO2粉体，使用混合沉淀剂，通过控制沉淀剂的比例，制备了晶相组成（金红石与锐钛矿比例）不同的纳米TiO2多晶粉体，采用相同的粉体制备工艺，不同的后续处理工艺，探讨了锐钛矿向金红石转变的相变温度，经分析研究后认为，水解－沉淀法制备的纳米粉体中的锐钛矿向金红石红转变的温度为500－800℃，完全转变的温度在800℃以上；纳米TiO2多晶粉体的晶相组成不仅与沉淀剂的种类，混合沉淀剂中沉淀剂的比例和粉体的煅烧温度有关，而且与粉体的后续处理工艺和粉体表面界面相的稳定性有关。     

Effect of Flame Conditions on Crystalline Structure of TiO2 in Liquid Flame Spraying

Nanostructured TiO2 is a most promising functional ceramic owing to its potential utilization in photocatalytical, optical and electrical applications. Nanostructured TiO2 coating was deposited through thermal spraying with liquid feedstock. Two types of crystalline structures were present in the synthesized TiO2 coating including anatase phase and rutile phase.The effect of spray flame conditions on the crystalline structure was investigated in order to control the crystalline structure of the coating. The results showed that spray distance, flame power and precursor concentration in the liquid feedstock significantly influenced phase constitutions and grain size in the coating. Anatase phase was formed at spray distance from 150 to 250mm, while rutile phase was evidently observed in the coating deposited at 100 mm. The results suggested that anatase phase was firstly formed in the coating, and rutile phase resulted from the transformation of the deposited anatase phase. The phase transformation from anatase to rutile occurred through the annealing effect of spraying flame. The control of the phase formation can be realized through flame condition and spray distance.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

纳米TiO2粉晶的XRD研究

用溶胶－凝胶法制备了纳米ＴｉＯ２粉晶,对不同温度自理的系列粉末用Ｘ射线衍射进行了研究,发现所得粉晶随热处理温度的不同发生了从锐钛矿到金红石相的转变。对系列粉晶进行了Ｘ射线衍射点阵参量计算,结合所得的晶粒度和微结构参数,发现纳米ＴｉＯ２粉晶组元中存在着晶格畸变。     

二氧化钛催化剂晶型调控技术的研究进展

综述二氧化钛由锐钛矿向金红石晶型转变调控技术的最新成果,分析温度、氧化物和以及离子掺杂对实现晶型转变的影响规律,重点研究氧化物和离子掺杂对晶型转变的影响。结果显示:复合金属氧化物熔点低于TiO2熔点时,可促进锐钛矿型TiO2向金红石型转变;而金属氧化物熔点高于TiO2熔点时,可阻碍晶型转变;掺杂离子的离子半径、化合价、离子大小对二氧化钛晶型转变及催化性能有明显的影响,当掺杂金属离子半径大于或小于Ti4+半径,使得锐钛矿型TiO2更稳定;当掺杂离子的半径与Ti4+半径相近时,有利于锐钛矿型向金红石型转变,而体积较小的低价阴离子有利于金红石型二氧化钛的的生成,体积较大的高价阴离子则有利于锐钛矿型二氧化钛的的生成;阴阳离子共掺杂可以有效地调控二氧化钛晶型转变,并且能够提高TiO2的光催化活性。探讨二氧化钛多晶之间的协同作用,并基于二氧化钛掺杂改性的计算模拟,指出今后的发展方向。     

Fabrication and characterization of highly crystalline and stable phase-pure rutile nanowires

A homogeneous thin layer of TiO2 has been successfully coated on the surface of multiwalled carbon nanotubes (MWCNTs), which were produced by catalytic chemical vapor decomposition method, via an in situ sol-gel method. The obtained MWCNT-TiO2 composite materials were heat treated in air at high temperatures, attempting to produce highly crystalline pure rutile nanowires. Through comprehensive characterization obtained by scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX), and X-ray powder diffraction (XRD), the effect of heat treatment on crystallization and phase transformation was discussed, and the effect of absence of MWCNTs on the morphology of pure rutile nanowires was analyzed. Both anatase and rutile phases exist after heat treatment in 700 degrees C while only rutile phase exists after heat treatment in 800 degrees C. The crystal size of rutile is formed to be significantly larger than that of anatase, and the hollow tubular structure is found to be destroyed which resulted in nanowire structure.     

Effects of TiO2 nanorod length and post-annealing on the electrical properties of TiO2 nanobarbed fiber structures

TiO2 nanobarbed fiber (NBF) structures consisting of TiO2 nanorods (NRs) on TiO2 nanofibers (NFs) were fabricated. The mean length and diameter of the TiO2 NRs grown for 6 h was 1.38 microm and 71 nm, respectively. One NR was connected to other NRs and the junction points between the TiO2 NRs increased with increasing TiO2 NR length. The crystal structure of the TiO2 NFs and NRs was rutile and anatase, respectively. After post-annealing, only the intensity of the TiO2 NBF peaks increased without any significant structural changes. Raman spectroscopy showed that the TiO2 NBF structure consisted of anatase (TiO2 NFs) and rutile (TiO2 NRs). The bandgap of the TiO2 NBF structure prepared during a TiO2 NR growth time from 0 to 6 h decreased from 3.23 eV to 3.10 eV. The conductivity of the TiO2 NBFs with longer NRs was enhanced by post-annealing.