Non-destructive evaluation of strength and residual stress for weldments using continuous indentation technique

TiO₂ photocatalysts are attractive and promising materials due to their excellent properties such as high photocatalytic activity, stability and non-toxicity. Therefore, TiO₂ photocatalyst has applied into various fields such as environmental purifications. The major forms of TiO₂ photocatalysts are fine particles in order to obtain high surface areas. In order to fabricate commercial applications, the coating procedures using binder chemicals must be employed. However, the fine TiO₂ particles slightly scattered at the surface, since most particles are buried in binder chemicals, leading to obtaining poor photocatalytic activity. TiO₂ films can be easily formed on a metallic titanium substrate by anodization. However, the amorphous TiO₂ films with no photocatalytic activities are usually obtained in conventional anodization. We have successfully obtained the high performance photocatalytic TiO₂ films by using combined treatment of pre-nitridation and anodization. The photocatalytic TiO₂ films show the high photocatalytic activities to decompose the various volatile organic compounds such as trichloroethylene, isopropyl alcohol, acetaldehyde, and so on.     

Preparation of Sn4+-Doped Titanium Dioxide Photocatalytic Films on 304 Stainless Steel by Duplex Treatment

Sn⁴⁺-doped titanium dioxide photocatalytic films were synthesized on 304 stainless steel (SS) by a duplex treatment. The SS substrates were alloyed with titanium (Ti) through cathodic-arc ion plating followed by a microarc oxidation (MAO) treatment in different electrolytes. Field-emission scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy were used to characterize the films surface morphology, crystalline phase, and composition, respectively. Photocatalytic activity was measured using an UV-Vis spectrophotometer. It was found that the films with a porous structure are mainly composed of TiO₂, which exists in an anatase and rutile state. Furthermore, small quantities of SnO₂ have been found in the Sn⁴⁺-doped titanium dioxide films. The fraction of anatase varies with the MAO time and electrolytes, whereas the pore size remains the similar with the same MAO current intensity and density and the surface roughness increases slightly with increasing MAO time. It was also found that the photocatalytic activity of the Sn⁴⁺-doped porous film improved, and the film synthesized with a shorter MAO time in a lower Na₂SnO₃-containing electrolyte is superior to the films with longer MAO times and higher Na₂SnO₃ concentrations.     

Preparation and photocatalytic properties of sillenite Bi12TiO20 films

Sillenite Bi₁₂TiO₂₀ thin films with high photocatalytic activity have been successfully fabricated by means of chemical solution decomposition, and characterized by X-ray diffraction, energy-dispersive spectroscopy, atomic force microscopy, scanning electron microscopy and UV-Vis spectrophotometry. The photocatalytic activity of Bi₁₂TiO₂₀ thin films has been evaluated by photodegrading methyl orange solution and the effect of processing conditions on the photocatalytic activity has been studied in detail.     

无模板剂的溶胶-水热法合成具有可见光响应的氮掺杂混晶 TiO2(锐钛矿/金红石/板钛矿)纳米棒束

采用无模板剂的溶胶-水热法制备了具有可见光响应的N掺杂锐钛矿/金红石/板钛矿型TiO_2(N-TiO_2)纳米棒束,并利用X射线衍射(XRD)、透射电镜(TEM)、紫外-可见光漫反射光谱(UV-Vis DRS)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段对获得的样品进行了表征。以甲基橙为模型反应物,评价了N-TiO_2纳米棒束的光催化活性。表征结果结合光催化活性评价结果显示,与P25-TiO_2相比,N掺杂、混晶及纳米棒束之间的协同作用是所制备的混晶N-TiO_2纳米棒束具有良好光催化活性的主要原因,并对混晶N-TiO_2纳米棒束光催化降解甲基橙的机理进行了探讨。     

Fe掺杂TiO2纳米材料的合成及光催化性能

以钛酸丁酯为钛源,Fe(NO3)3·9H2O为铁源,采用溶胶-凝胶法制备Fe/TiO2纳米粉体,利用溶胶结合静电纺丝技术制备Fe/TiO2纳米纤维,从材料改性及形貌改善两个角度共同提高TiO2纳米材料的光催化活性及实用性。借助XRD、SEM、TEM等分析技术,探究了Fe/TiO2纳米材料在可见光区的光催化活性,分析了煅烧温度及掺铁量对Fe/TiO2纳米材料光催化性能的影响。结果显示,铁的掺入及形貌的改善有助于提高TiO2的光催化性能。     

氧化参数对TiO_2纳米管结构及双室光电化学池产氢性能的影响

采用乙二醇电解液,在不同氧化电压、氧化时间条件下通过阳极氧化纯钛片制备了一系列TiO_2纳米管阵列薄膜。使用场发射扫描电镜(FESEM)表征TiO_2纳米管的表面、断面形貌,探讨氧化时间及氧化电压对纳米管生长速率的影响。同时通过电化学方法测试TiO_2纳米管的光电化学性能,以无外加电压下双室光电化学池中的产氢量考察其光催化活性。结果表明,相比延长氧化时间,提高氧化电压更容易获得高长/径比的TiO_2纳米管阵列,同时可显著提高TiO_2纳米管的光电流、光电转换效率及产氢量。     

Morphology and photocatalytic activity of highly oriented mixed phase titanium dioxide thin films

Thin TiO₂ films on quartz substrates were prepared by spin coating of undoped and metal-ion-doped Sol-Gel precursors. These films were characterised by Scanning Electron Microscopy, Laser Raman Microspectroscopy, X-ray Diffraction and UV-Vis Transmission. The photocatalytic performances of the films were assessed by the photo-degradation of methylene-blue in aqueous solution under UV irradiation. Films exhibited a high degree of orientation and a thermal stabilization of the anatase phase as a result of substrate effects. In the absence of dopants, the rutile phase formed as parallel bands in the anatase which broadened as the transformation progressed. TiO₂ films doped or co-doped with transition metals exhibited the formation of rutile in segregated clusters at temperatures under ~ 800 °C as a result of increased levels of oxygen vacancies. Photocatalytic activity of the films synthesised in this work was low as likely a result of poor TiO₂ surface contact with dye molecules in the solution. The presence of transition metal dopants appears detrimental to photocatalytic activity while the performance of mixed phase films was not observed to differ significantly from single phase material.     

Microstructure characterization and photocatalytic activity of mesoporous TiO2 films with ultrafine anatase nanocrystallites

A series of mesoporous TiO₂ films on borosilicate glass with ultrafine anatase nanocrystallites were successfully synthesized using a non-acidic sol gel preparation route, which involves the use of nonionic surfactant Tween 20 as template through a self assembly pathway. The microstructure of these TiO₂ films was characterized by XRD, SEM, HR-TEM, UV-Vis spectroscopy, and N₂ adsorption-desorption isotherm analysis. Their photocatalytic activities were investigated by using creatinine as a model organic contaminate in water. It was found that all mesoporous TiO₂ films prepared with Tween 20 exhibited a partially ordered mesoporous structure. The photocatalytic activity of the TiO₂ films could be remarkably improved by increasing Tween 20 loading in the sol at the range of 50% (v/v), which yielded large amount of catalyst (anatase) on the glass support and enhanced specific surface area. The optimum Tween 20 loading was 50% (v/v) in the sol, above which good adhesion between TiO₂ films and borosilicate glass could not be maintained. The final TiO₂ film (Tween 20: final sol = 50%,v/v) exhibits high BET surface area (∼ 120 m²/g) and pore volume (0.1554 cm³/g), ultrafine anatase nanocrystallinity (7 nm), uniform and crack free surface morphology, and improved photocatalytic activity.     

Deposition of titanium dioxide from TTIP by plasma enhanced and remote plasma enhanced chemical vapor deposition

Photocatalytic materials, and especially titanium dioxide, have gained wide popularity in recent years in reason of their interesting properties which can be useful in various fields of application, in particular as self-cleaning materials. When submitted to an illumination (in most cases UV-light), the surface of a photocatalytic material becomes chemically active and simultaneously displays a photo-generated hydrophilic activity (PSH effect).Classically, photocatalytic properties are displayed by crystalline titanium dioxide. In this paper we detail the chemical vapor deposition of TiO₂ carried out in two experimental set-ups: one is plasma enhanced reactor and the other is remote plasma enhanced reactor. Both experiments were carried out with titanium(IV) isopropoxide (TTIP). Titanium(IV) tetrachloride (TiCl₄) and titanium(IV) ethoxide (TEOT) were also used in the first setup.In RF-diode plasma reactor, titanium dioxide films were deposited in amorphous form and crystallization of amorphous films was obtained with the help of thermal post-treatments, since seeding and under-layers appeared unable to trigger the crystallization of films. In the remote plasma CVD reactor, allowing high plasma density and ion energy, deposition of crystalline anatase titanium dioxide was achieved at a deposition temperature of 400 °C.Conclusions are presented and suggest control mechanisms for the stoichiometry of titanium dioxide films.     

Ba0.5Sr0.5TiO3铁电薄膜的微弧氧化成膜研究

以0.2 mol/L Ba(OH)2+0.2 mol/L Sr(OH)2溶液为电解液,采用微弧氧化法,在Ti板表面原位生长铁电薄膜,并对薄膜的物相构成、元素分布情况、截面结构及介电性能进行表征。结果表明:该工艺下制备的薄膜主要由四方相Ba0.5Sr0.5TiO3构成,薄膜致密层内,Ba,Sr,Ti和O元素分布都较均匀,但在微弧氧化孔洞附近存在含量波动;该薄膜在1 kHz下的介电常数较优,为411.3。最后对微弧氧化沉积铁电薄膜的成膜过程进行了分析,提出了微弧氧化过程中可能存在的化学反应。     

Micro-arc oxidation of TC4 substrates to fabricate TiO2/YAG:Ce compound films with enhanced photocatalytic activity

This paper introduces a process for “in situ” preparing TiO₂ photocatalytic film compounded with YAG:Ce³⁺ semiconductor upon titanium alloy by using micro-arc oxidation (MAO). The surface morphology, chemical compositions, phase structures and photocatalytic properties of the films were characterized and measured by field emission gun scanning electron microscope (FEG-SEM), energy-dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD), electro-chemical workstation and UV-vis spectrophotometer. The results show that the YAG:Ce³⁺ semiconductor particles which were added in the electrolyte had been homogenously compounded within the TiO₂ film during MAO. Compared with the pure TiO₂ film, the compounded film exhibited much larger specific surface area, stronger absorption in the visible light and higher photo-generated current density, which improves the photocatalytic property markedly. It is expected that MAO will provide a simple, economic and promising approach for preparing a superior photocatalytic TiO₂ film.     

SnO2@TiO2核-壳纳米线的制备及其光催化性能研究

本文通过固-液-气(VLS)生长机制,利用化学气相沉积法(CVD)制备SnO₂纳米线。利用原子层沉积(ALD)以钛酸四异丙酯为前驱体在SnO₂纳米线表面沉积不同厚度的TiO₂壳层,形成SnO₂@TiO₂核-壳纳米线结构。通过中间Al₂O₃插层,分别制备出金红石和锐钛矿两种不同晶型的TiO₂,从而制备出两种不同复合结构的SnO₂@TiO₂核-壳纳米线。实验研究该复合结构中TiO₂的厚度与晶型对紫外光下光催化降解甲基橙溶液活性的影响。     

Influence of fluorine on the structure and photocatalytic activity of TiO2 film prepared in tungstate-electrolyte via micro-arc oxidation

TiO₂ films were prepared on pure titanium substrate via micro-arc oxidation (MAO) technique in tungstate-electrolyte. The influence of fluorine ion concentration in electrolyte on the microstructure and photocatalytic activity of TiO₂ films was investigated. The results showed that the porosity, element content and phase composition of TiO₂ films were affected by fluorine ion concentration in electrolyte. The number of pores, the content of tungsten and the content of anatase phase all increased when appropriate fluorine ion was added into the electrolyte. Thus, the photocatalytic activity of TiO₂ films could be promoted by adding appropriate fluorine ion into the electrolyte. The addition of fluorine ion did not alter the iso-electric points of TiO₂ films. It was confirmed by UV–Vis spectrophotometer that the photocatalytic activity of the film prepared in electrolyte containing 2 g/L NaF was higher than that of the films prepared in other electrolytes during the degradation of methyl orange.     

Preparation of large scale photocatalytic TiO2 films by the sol-gel process

Nanocrystalline titanium dioxide films were formed on frosted and clear borosilicate glass with a large surface area (12 × 22 cm) using doctor blade and spray coating techniques. The films were subjected to a high temperature treatment at 550 °C. X-ray diffraction (XRD) analysis indicated that the TiO₂ films contain only the anatase phase. Optical microscopy was used to determine the morphology changes after the deposition of each layer. Scanning electron microscopy (SEM) was used to study the films surface morphology. The large scale TiO₂ films produced showed a high photocatalytic activity which was evaluated by the degradation of methyl orange (MO) in aqueous solution (10 mg L^− 1) under illumination of a UV light source with an overall irradiance of 0.9 mW cm^− 2. UV-visible spectrophotometry was used to monitor the degradation of MO through the decrease of the main absorbance peak at 464 nm. The results demonstrated that a complete decomposition of MO could be achieved after 2 h of UV irradiation.     

Influence of V~(5+) Ions on Photocatalytic Activity of TiO_2 Films Prepared by Micro-plasma Oxidation Method

Microporous titanium dioxide thin films have been fabricated on titanium plates by the micro-plasma oxidation method with the electrolyte of Na3PO4+Na2B4O7. The influence of V5+ ions addition in the electrolyte on the photocatalytic activities was investigated. A kind of typical textile industry pollutant (methylene blue) was used to evaluate the photo-catalytic activity of the films. The results showed that this activity of the films had been improved by adding V5+ ions into the electrolyte solution. The removal of methylene blue reaches 90% for 60 min when V5+ ions addition concentrate is 0.3 g/L. X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques were applied to characterize the modified films. Experimental results show that the improvement in activity was related to the forming of titanium dioxide lattice distortion, which could accept more photoexcitated holes and produce more strong surface free radicals to oxidate adsorptive molecules.     

Synthesis and photocatalytic properties of InVO4 sol containing nanocrystals by mild hydrothermal processing

The precursor precipitation of InVO₄ was synthesized by co-precipitation using indium trichloride (InCl₃), ammonium metavanadate (NH₄VO₃) and ammonia (NH₃H₂O) as raw materials. The InVO₄ sols with orthorhombic phase were obtained by hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). The precursor and sol of InVO₄ were characterized by X-ray diffraction (XRD), Fourier Transform Infra-red spectra (FT-IR), scanning electron microscopy (SEM) measurements. The XRD patterns indicate that the InVO₄ precursor is amorphous phase, InVO₄ sol contains orthorhombic InVO₄ nanocrystals. The results also reveal that the pH value of the reaction mixture and reaction temperature play important roles to the target phase. InVO₄-TiO₂.thin films on glass slides were prepared by the dip-coating method from the composite sol. The photocatalytic properties of the InVO₄-TiO₂ thin films were investigated by the photocatalytic degradation of methyl orange solution. The results indicate that it has better photocatalytic activities than pure TiO₂ thin films or pure InVO₄ thin films with UV light.     

纳米颗粒增强TiO_2涂层的制备及其防污性能

为提高二氧化钛涂层的防污性能,采用KH-550硅烷改性锐钛矿型TiO_2颗粒,并充分分散于二氧化钛凝胶涂层中。通过降解亚甲基蓝溶液、细菌贴附试验、藻类贴附试验,分别评价了涂层的光催化性能、抗菌性能及抗藻类附着性能,并利用激光共聚焦显微镜及扫描电子显微镜对藻类在涂层表面的附着情况进行分析。结果表明,添加TiO_2纳米颗粒涂层的防污性能较未添加TiO_2纳米颗粒涂层有较大程度的提高。添加粒径为5~10 nm TiO_2颗粒的二氧化钛涂层对小球藻、三角褐指藻及小新月菱形藻的附着降低率分别达到了92.1%、71.5%和62.1%,相较于纯二氧化钛涂层对3种藻类的附着降低率分别提高了29.7%、68.4%和43.5%。TiO_2颗粒的加入可以有效地提高涂层的光催化性能,光催化使得涂层具有亲水、抗菌及自清洁的性能进而有利于提高涂层的防污性能。     

g-C3N4/TiO2纳米管阵列的制备及光催化性能的研究

目的 获得在可见光下光催化活性较好,且可回收、可重复利用的光催化材料。方法 在钛基底上采用阳极氧化法制备TiO2纳米管阵列（TiO2 NTAs）,将TiO2 NTAs在10%尿素溶液中浸渍不同时间后,在氮气保护下高温热分解,制备g-C3N4/TiO2 NTAs复合薄膜。采用XRD、SEM、TEM对复合薄膜进行物相及形貌的表征,在可见光照射下,通过亚甲基蓝溶液的催化降解实验来评估复合薄膜的光催化活性。结果 在10%尿素溶液中浸渍不同时间后所获得的g-C3N4/TiO2 NTAs样品,其可见光催化活性均较纯TiO2 NTAs有所提高,而且随浸渍时间的增加,其可见光催化活性依次增加。浸渍时间为6 h的g-C3N4/TiO2 NTAs样品,在可见光下的光催化活性最高,在120 min内对亚甲基蓝的降解率可达73%。继续增加浸渍时间,所获得的TiO2 NTAs样品的可见光催化活性有所降低。结论 g-C3N4与TiO2 NTAs复合,可以有效提高TiO2 NTAs的光催化活性,其原因是g-C3N4的复合提高了载流子的传递效率,同时也提高了对可见光的吸收。     

Roles of titanium dioxide and ion-doped titanium dioxide on photocatalytic degradation of organic pollutants (phenolic compounds and dyes) in aqueous solutions: A review

Water pollution by organic pollutants is an ever increasing problem for the global concerns. This paper presents a critical review on the abatement of organic pollutants, dyes and phenolic compounds in particular, using photocatalytic reaction by titanium dioxide (TiO₂). Mechanism of photocatalytic reaction is briefly discussed. A detailed search of published reports on the advancement in photocatalytic degradation of organic pollutants in wastewater by doping titanium dioxide with foreign species such as metal and non-metal component has also been carried out and analyzed in this paper.     

Modification of Parylene film-coated glass with TiO2 nanoparticles and its photocatalytic properties

A titania film was deposited on Parylene-coated glass by a one-step, ultrasound-assisted procedure. The TiO₂ nanoparticles formed during the sonochemical hydrolysis of Ti(i-OPr)₄ were thrown to the surface and strongly attached to the Parylene substrate. By using different solvents (water, ethanol or their mixture) and reagent concentrations, the thickness, uniformity and crystallinity of the deposited layer were regulated. PVP was used to stabilize the highly homogeneous distribution of TiO₂ nanocrystals on the Parylene surface. The morphology and structure of the coated films were characterized by physical and chemical methods such as: X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), and optical spectroscopy. The photocatalytic activity of the titania-modified Parylene film in the photo discoloration of methylene blue was demonstrated. The experimental results revealed a correlation between the uniformity of the nanostructured anatase titania film and its photocatalytic properties.