Improved photovoltaic performance of dye-sensitized solar cells by carbon-ion implantation of tri-layer titania film electrodes

TiO2tri-layer structure films were modified by C-ions implantation for improving the photovoltaic performance of dye-sensitized solar cells(DSSCs), in which the structure of TiO2 changes from rutile to anatase and the sizes of TiO2 particles increase. The optimal concentration of ions implantation for C-implanted cells is 19 1015 atom cm-2,and the maximum conversion efficiency of 5.32 % is achieved(luminous intensity of 1 sun, light irradiance of AM1.5G),which is 25.2 % higher than that of unimplanted cell. The significant improvement in conversion efficiency by carbonion implantation is contributed to reducing charge recombination and enhancing the light-harvesting ability, as indicated from incident photon-to-collected electron conversion efficiency(IPCE) and ultraviolet-visible(UV-Vis) measurements. Furthermore, the charge carrier's lifetime in the trilayer titania films is prolonged after carbon-ion implantations.     

电泳法制备择优取向钛酸薄膜

以钛酸的纳米单片层为前驱体,采用电泳沉积法在Pt极板上制备择优取向钛酸薄膜,并通过热处理使其转换成TiO2薄膜。考察了悬浮介质和沉积电压对钛酸薄膜形貌及结构的影响,通过XRD、SEM对薄膜进行了表征。结果表明:在乙醇:水为1:1的悬浮介质中沉积制得的钛酸薄膜均匀、平整、致密,具有很强的b轴取向;薄膜的厚度随电压的升高而增厚;经500℃热处理后,钛酸薄膜转变成具有(101)择优取向的锐钛矿相结构的TiO2薄膜,颗粒尺寸分布均匀,平均粒度约40nm。     

Photocatalytic Active Titania Thin Films through Oxidation of Metallic Ti in Aqueous H2O2 Solutions Containing Various Block Copolymers

利用添加了嵌段共聚物P123、F127及硝酸的双氧水溶液直接氧化钛金属基体制备不同纳米形貌TiO2光催化薄膜。采用X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见漫反射光谱(UV-VisDRS)等技术分析样品的微观结构和形貌,以光催化降解若丹明B测定薄膜的光催化性能。结果表明,Ti-H2O2反应体系中仅添加嵌段共聚物的薄膜结晶呈树枝状,加入硝酸后薄膜形成纳米花结构。450oC热处理后,薄膜为锐钛矿与金红石的混晶结构,平均晶粒尺寸在12～20nm之间。薄膜的间接禁带宽度为2.65～2.85eV,显著低于TiO2块体。添加P123获得的薄膜的光催化性能优于添加F127的薄膜。     

Ti-H2O2反应添加嵌段共聚物制备光催化活性的TiO2薄膜

利用添加了嵌段共聚物P123、F127及硝酸的双氧水溶液直接氧化钛金属基体制备不同纳米形貌TiO2光催化薄膜.采用X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见漫反射光谱(UV-Vis DRS)等技术分析样品的微观结构和形貌,以光催化降解若丹明B测定薄膜的光催化性能.结果表明,Ti-H2O2反应体系中仅添加嵌段共聚物的薄膜结晶呈树枝状,加入硝酸后薄膜形成纳米花结构.450℃C热处理后,薄膜为锐钛矿与金红石的混晶结构,平均晶粒尺寸在12～20 nm之间.薄膜的间接禁带宽度为2.65～2.85 eV,显著低于TiO2块体.添加P123获得的薄膜的光催化性能优于添加F127的薄膜.     

Structural Characterization and Corrosion Behavior of Stainless Steel Coated With Sol-Gel Titania

Sol-gel titania films were prepared from hydrolysis and condensation of titanium (IV) isopropoxide. Diethanolamine was used as chelant agent in titania synthesis. 316L stainless steel substrates were dip-coated at three different withdrawal speeds (6, 30, and 60 mm/min) and heated up to 400 °C. Thermogravimetry and differential thermal analyses of the titania gel solution evinced a continuous mass loss for temperatures up to 800 °C. The transition of anatase to the rutile phase begins at 610-650 °C, being the rutile transformation completed at 900 °C. The thicknesses of the films were determined as a function of the heat treatment and withdrawal speed. It was observed that their thicknesses varied from 130 to 770 nm. Scanning electron microscopy images of the composites revealed the glass-like microstructure of the films. The obtained sol-gel films were also characterized by energy dispersive spectroscopy. The chemical evolution of the films as a function of the heating temperature was evaluated by Fourier transform infrared spectroscopy (specular reflectance method). After performing the adhesion tests, the adherence of the titania films to the stainless steel substrate was excellent, rated 5B according to ASTM 3359. The hardness of the ceramic films obtained was measured by the Knoop microindentation hardness test with a 10 g load. We observed that the titania film became harder than the steel substrate when it was heated above 400 °C. The corrosion rates of the titania/steel composites, determined from potentiodynamic curves, were two orders of magnitude lower than that of the bare stainless steel. The presence of the sol-gel titania film contributed to the increase of the corrosion potential in ca. 650 mV and the passivation potential in ca. 720 mV.     

粒子型TiO_2溶胶和薄膜的制备与性能

利用纳米TiO2粉体制备粒子型TiO2纳米溶胶,并采用浸渍提拉法在普通玻璃表面制备TiO2纳米薄膜。研究粒子型溶胶的胶体特性以及薄膜的表观形貌、透光性、亲水性和光催化性能。结果表明:粒子型TiO2纳米溶胶的常温晶相为锐钛矿相,500℃以后逐步向金红石相转变;TiO2纳米薄膜具有良好的可见光透过性,强的紫外吸收能力,从而具有很好的紫外光光催化性能,同时还具有一定的可见光响应和亲水性能。     

Thermal stability of sol–gel p-type Al–N codoped ZnO films and electric properties of nanostructured ZnO homojunctions fabricated by spin-coating them on ZnO nanorods

The thermal stability of sol–gel p-type Al–N codoped ZnO films was investigated by high-resolution X-ray photoelectron spectroscopy (XPS). XPS revealed the chemical bonding states and solubility of N-related complex defects in the ZnO films. The concentrations of N_O and (NC)_O varied with annealing temperature, which led to the change in conduction between p-type and n-type. Variable-temperature Hall-effect measurement showed that N_O acted as a shallow acceptor, with its energy level locating at ～114 meV above the valance band maximum. Transmission electron microscopy confirmed the presence of undesired carbon clusters as a graphite state in the ZnO films. In order for Al–N codoped ZnO films to exhibit p-type conductivity, samples could only be annealed in a certain range of temperatures. A hybrid structure with nanostructured ZnO homojunctions was fabricated by spin-coating the p-type Al–N codoped ZnO film on an n-type ZnO nanorod array (ZNA). The hybrid nanostructure was demonstrated to possess rectification behavior characteristic of a p–n junction. The leakage current of the nanostructured ZnO homojunctions was smaller by a factor of 2 than that of the film-based ZnO homojunction at a reverse bias of 5 V. The p-type ZnO film/n-type ZNA structure can be applied as a versatile p–n optoelectronic device.     

Surface treatment of NiTi shape memory alloy by modified advanced oxidation process

A modified advanced oxidation process(AOP) utilizing a UV/electrochemically-generated peroxide system was used to fabricate titania films on chemically polished NiTi shape memory alloy(SMA). The microstructure and biomedical properties of the film were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), inductively-coupled plasma mass spectrometry(ICPMS), hemolysis analysis, and blood platelet adhesion test. It is found that the modified AOP has a high processing effectiveness and can result in the formation of a dense titania film with a Ni-free zone near its top surface. In comparison, Ni can still be detected on the outer NiTi surface by the conventional AOP using the UV/H2O2 system. The depth profiles of O, Ni, Ti show that the film possesses a smooth graded interface structure next to the NiTi substrate and this structure enhances the mechanical stability of titania film. The titania film can dramatically reduce toxic Ni ion release and also improve the hemolysis resistance and thromboresistance of biomedical NiTi SMA.     

Biomimetic apatite induction of P-containing titania formed by micro-arc oxidation before and after hydrothermal treatment

Phosphorous (P)-containing titania films were prepared by micro-arc oxidation (MAO) of titanium (Ti) in an electrolyte containing β-glycerol phosphate disodium salt pentahydrate (β-GP, C₃H₇Na₂O₆P^.5H₂O), and their apatite inducing ability in a simulated body fluid (SBF) was investigated. Macro-porous titania films were formed, consisting of only anatase phase, and the P content in the films increased up to 8 at.% with an increasing applied voltage. During hydrothermal treatment, the P in the films was diffused out to the surface and hydrolyzed to form the hydrogen phosphate (HPO₄²⁻) group. When immersed in SBF, no apatite was induced in any of the P-containing MAO specimens for up to 28 days. However, after a hydrothermal treatment at 250 °C, apatite was induced on the titania surfaces as early as 9 h immersion, and the entire exposed surface was covered with the apatite globules after 36 h immersion, which was much faster than the apatite induction on Ca-containing titania. The higher apatite-inducing ability of P-containing titania after hydrothermal treatment was believed to be due to the crystal structure (anatase) and presence of HPO₄²⁻ group on the surface.     

Properties of composite films of titania nanofibers and Safranin O dye

Titania (TiO₂) nanofibers and composite thin films of titania nanofibers and Safranin O dye (SAF) were studied. TiO₂ nanofibers were prepared by electrospinning technique from titanium tetra-isopropoxide precursor solution in ethanol. Surface topology of the nanofibers was observed using scanning electron microscopy (SEM), their crystal structure was studied by X-ray diffraction (XRD) and the chemical composition by X-ray photoelectron spectroscopy (XPS). Properties of the TiO₂ nanofibers were studied in dependence on the values of relative air humidity in the range from 15% to 55%. It was necessary to maintain the relative humidity lower than 30% during electrospinning in order to obtain high quality nanofiber films. The average minimum diameter of the as-prepared TiO₂ nanofibers was found to be around 100 nm. Nanofiber diameter diminishes to about 50 nm after annealing at 420 °C for 1 h. The as-prepared titania nanofiber films were completely amorphous while anatase crystal phase was detected in the films after annealing. In order to prepare the composite films, solution of SAF dye with poly(vinylpyrrolidone) in ethanol/water was dropped off on the prepared titania nanofibers surface. Opto-electrical properties of SAF dye and the resulting nanocomposite films were studied by UV–Vis spectroscopy and current–voltage characteristics. Safranin O is characterized by two strong absorption peaks; one at 274 nm and a wide band with splitting between 420 nm and 600 nm. The optical energy band gap of titania nanofibers was estimated from the UV–Vis measurements to be 3.4 eV. The charge transport in the composite films is influenced by the space charge limited currents due to the very high resistance of the materials.     

时间参数对复合氧化法制备多孔二氧化钛涂层结构的影响

为了分析微弧氧化时间对复合氧化法(即预氧化和微弧氧化复合法)制备的二氧化钛涂层结构和形貌的影响，采用X射线衍射、SEM及附带的能谱(EDS)对涂层的结构、形貌和元素组成进行了分析，采用MH-3型硬度计对涂层表面的硬度进行了测试。结果表明：微弧氧化时间是影响复合氧化法制备多孔二氧化钛表面涂层形貌、结构、硬度和钙磷原子比的主要因素之一。随着微弧氧化时间的延长，涂层表面的微孔孔径增加，凹凸起伏变得明显，涂层中金红石相增加，锐钛矿相减少，表面硬度增加，钙磷原子比也发生了变化。可控制微弧氧化时间得到结构较为理想的多孔二氧化钛梯度涂层。     

Preparation of TiO2 nanotube on glass by anodization of Ti films at room temperature

In order to fabricate titania nanotubes on glass substrate, Ti thin films (700-900 nm) were first deposited by radio-frequency(RF) magnetron sputtering and then anodized in an aqueous HF electrolyte solution at room temperature. The morphology and structure of the nanotubes were identified by means of field emission scanning electron microscopy(FE-SEM) and X-ray diffractometry(XRD). The effects of anodization parameters (concentration of electrolyte, applied voltage) on nanotube morphology were comprehensively investigated. The results show that the dense and crystalline Ti film can be obtained on the unheated glass substrate under the sputtering power of 150 W, and the anodization current and voltage play significant roles in the formation of titania nanotube with different tube sizes.     

溅射参数对钛膜结构及其TiO_2纳米管制备的影响

采用射频磁控溅射在玻璃基片上制备了参数不同的钛膜,并选取钛膜在HF水溶液中恒压阳极氧化得到TiO2纳米管阵列。结果表明：溅射压强从0．1Pa升至1．5Pa,薄膜致密度显著下降,溅射压强以0．5Pa为宜;溅射功率为105W,溅射速率约为0．23nm／s,溅射时间延长,薄膜厚度线性增加;衬底预热有利于提高膜的致密度和结晶性能,在衬底温度低于300℃时,钛晶粒在（002）晶面择优生长,当升温到更高温度时,（010）峰、（011）峰出现且强度升高,而（002）峰的强度降低;在室温下,当溅射功率小于150W时,薄膜具有较高密度,晶粒生长各向异性,增至167W时,钛晶粒在（002）晶面择优生长,呈明显柱状六方晶表面形态,且晶界有明显孔洞存在,致密度下降。将溅射功率为150W,工作压力为0．5Pa,溅射时间为1h条件下所制备的钛膜在氧化电压为10V、电解液为0．5％（质量分数,下同）HF水溶液中室温阳极氧化,得到高规整度的TiO2纳米管阵列。     

Surface characteristics and phase transformation of highly ordered TiO<Subscript>2</Subscript> nanotubes

Highly ordered TiO₂ nanotubes with 85 μm length were fabricated by the electrochemical method for 17 h at 60 V in an ethylene glycol/0.5 % NH₄F/5 % water mixture solution. The nanotube arrangements and surface morphologies of the anodic titania films were clearly dependent on the electrolytes used in the fabrication process. The activation energy for the transformation from an amorphous to anatase structure was evaluated using differential scanning calorimetry (DSC) results and a Kissinger plot. The activation energy for anatase transformation on the anodic titania nanotubular film was estimated to be 208.9 kJ/mol.     

Surface and interface analysis of HAP/TiO2 composite films on Ti6Al4V

The composite films constituted of hydroxyapatite (HAP) submicron particles embedded in the gel composed of the titania nanoparticles were prepared on commercial Ti6Al4V plates with titania buffer layer obtained by a spin-coating technique. The films were annealed in air at 450 ℃, 550 ℃ and 650 ℃, respectively. The phase formation, surface morphology, andinterfacial microstructure of the films were investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy (FT-IR), field emission-scanning electron microscopy(FE-SEM) and energy dispersive X-ray (EDS) analysis. The results show that the as-prepared films are all well-crystallized, dense,homogeneous, and there was a close interfacial bond between the film and the substrate. The results of adhesion test indicate that there is a good bonding strength between the film and the substrate. The bone-like apatite formation on the surface of the films after immersion in acellular simulatedbody fluid(SBF) validated their bioactivities.     

Structural and mechanical properties of nanostructured TiO2 thin films deposited by RF sputtering

This study mainly aims to evaluate the effects of substrate temperatures on the mechanical properties of TiO₂ thin films deposited on glass substrates by radio-frequency (RF) magnetron sputtering. All titania films possess anatase structure having a nodular morphology. AES results reveal that Si and Na ions from glass diffuse into TiO₂ films at higher substrate temperatures. Micro-scratch and wear tests were conducted to evaluate their mechanical and tribological properties. The adhesion critical loads of TiO₂ films deposited at room temperature, 200 and 300 °C are found to be 1.51, 1.54 and 1.08 N, respectively. Scratch hardness also increases from 11.5 to 13.6 GPa with increasing temperature. The wear track width decreases with substrate temperature indicating an improved wear resistance at higher temperatures.     

Effect of polyethyleneimine on the growth of ZnO nanorod arrays and their application in dye-sensitized solar cells

A series of oriented hexagonal wurtzite ZnO nanorod-array films were grown on fluorine-doped tin oxide (FTO) coated glass substrates by chemical process. The effect of polyethyleneimine (PEI) on the structure and micro-morphology of ZnO nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) was analyzed. It was found that with the addition of PEI in growth solution, the ZnO nanorods became smaller in diameter and longer in length and hence the dye absorption and the photovoltaic performance of DSSCs were improved. A power conversion efficiency of 2.30% had been achieved on a DSSC based on a 7.9 μm-long nanorod array film prepared by a growth solution containing the PEI.     

TiO2-Bioactive Glass Nanostructure Composite Films Produced by a Sol-Gel Method: In Vitro Behavior and UV-Enhanced Bioactivity

The aim of this study is to develop TiO₂, titania, -based composite films for 316 stainless steel substrate and to improve their apatite-forming activity. A series of sol-gel derived bioactive glass (49S) and bioactive glass (49S)-TiO₂ films were deposited on the 316L stainless steel substrates by the spin-coating method. Amorphous bioactive glass (49S) film and polycrystalline titania-bioactive glass composite films were obtained after annealing the deposited layers at 600 °C. The microstructure and in vitro bioactivity of the composite films as well as the effect of titania nanopowder content and ultra violet (UV) irradiation on the in vitro bioactivity were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). While bioactivity tests are often carried out within 28-day periods, SEM and EDS data show that, after soaking in SBF for just 7 days, the prepared composite surfaces are covered with an apatite layer. The grown apatite layer consists of spherulites formed by nanosized needle-like aggregates. Fourier transform infrared spectroscopy investigations confirm apatite formation and suggest that the formed apatite is carbonated.     

A method to improve mechanical properties of glass plates by surface-coating titania nanofilms with sol-gel technique

The present work aims to improve mechanical properties of glass plates by coating homogeneous Ce⁴⁺-doped titania films on them with the sol-gel technique. The mechanical properties of coated glass plates and the film microstructure were characterized by using advanced equipments such as X-ray diffractometer, atomic force microscope, X-ray photoelectron spectrometer, nano-indenter and mechanical tester. Experimental results show that, the coated films, with a thickness of 20-100 nm and with a main phase of anatase, firmly adhere to the glass plates by sintering at 450 °C for 2 h. Their mechanical properties such as Young's modulus, strength, fracture toughness and microhardness are increased with the increase of film thickness and significantly increased by Ce⁴⁺ doping titania. Moreover, Ce⁴⁺ doping inhibits the crystallization of rutile phase and decreases anatase granularity. The effects of coating titania films and Ce⁴⁺-doping titania on mechanical properties of glasses are correlated to presence of chemical combinations between film and glass interface, decrease of surface roughness and anatase granularity, as well as reduction of the density of microcracks on the glass surface.     

纯钛表面二氧化钛纳米管阵列结构特征的研究

采用阳极氧化技术在纯Ti表面制备出有序的TiO2纳米管阵列,并通过SEM,XRD,XPS对TiO2纳米管阵列进行表征。结果表明,阳极氧化时间对纳米管的形成有较大的影响。在外加电压为20V,阳极氧化时间为20min时,可制备出长度约480nm、内径约89.90nm、壁厚约7.4nm的TiO2纳米管阵列。经450℃热处理后,可得到锐钛矿型的TiO2纳米管阵列,钛元素以Ti4+氧化态处于八面体的环境中,Ti2p3/2的结合能为459.3eV。