阳极氧化制备工艺对TiO_2纳米管阵列显微形貌的影响

为改善TiO_2纳米管阵列结构有序性和形貌完整性,以NH4F-丙三醇-水溶液为电解液,采用一次阳极氧化法和二次阳极氧化法在Ti片表面制备TiO_2纳米管阵列,借助扫描电子显微镜和原子力显微镜,研究一次阳极氧化电压、二次阳极氧化法制备过程中阳极氧化电压和一次阳极氧化时间以及退火温度对TiO_2纳米管阵列显微形貌的影响。结果表明,采用一次阳极氧化法在5~25 V电压下阳极氧化Ti片120 min后均可制得有序排列的TiO_2纳米管阵列,纳米管外侧面具有"竹节状"结构特征,纳米管平均管径和管间距随氧化电压升高而增大;一次阳极氧化法在20 V/120 min下制得的TiO_2纳米管阵列相对较优,其表面平整度高。在相同氧化电压下采用二次阳极氧化法制备TiO_2纳米管阵列不能有效改善阵列的有序程度和表面平整度。600℃退火会促进TiO_2纳米管层/钛金属界面处的热氧化物层生长。     

基于两步法阳极氧化的TiO_2纳米管阵列制备研究

采用低浓度的无机溶剂HF溶液(0.05%,质量分数)对溅射在硅基底上的400 nm钛薄膜进行阳极氧化制备TiO_2纳米管阵列,并利用SEM对制备出的TiO_2纳米管阵列进行表征。实验结果表明,通过优化阳极氧化电压幅值、电压施加方式和氧化时间,均可有效控制纳米管阵列的尺寸和形貌。首先施加0.5 V的低电压28 min,在低浓度的HF溶液中阳极氧化钛薄膜制备TiO_2纳米管阵列,其管径可达120 nm左右。在此基础上,对电压施加方式进行改进,提出两步法施加电压方式,并优化氧化时间,在硅基底钛薄膜上制备出管径为100~270 nm结构紧密有序的TiO_2纳米管阵列,明显优于钛薄膜在有机电解液中氧化制备的管径为70~100 nm的TiO_2纳米管阵列。     

择优取向对氢化TiO2纳米管阵列电化学性能的影响

氢化TiO_2纳米管阵列具有良好的电化学性能,通过构筑TiO_2001取向结构可进一步提高氢化TiO_2纳米管阵列的电化学性能。本研究以Ti为基底,通过调节阳极氧化法醇-水配比及高温退火工艺的方法制备了具有不同取向程度的锐钛矿型TiO_2纳米管阵列,并对具有不同取向度的TiO_2纳米管阵列进行相同工艺参数电化学氢化处理,利用SEM、XPS、XRD、TEM及电化学测试等表征手段研究了制备工艺对取向结构的影响以及取向结构对氢化TiO_2纳米管阵列电化学性能的影响规律和作用机理。具有高度001择优取向结构的氢化TiO_2纳米管阵列放电比容量达到了17.31mF·cm~(-2),其优异的电化学性能主要归功于氢化与取向结构的协同效应。     

TiO_2纳米管阵列的制备及其光催化产氢活性研究

采用阳极氧化法在乙二醇电解液中制备了高度有序的TiO2纳米管阵列,分别通过SEM、EDX表征其形貌及元素组成,并探讨了TiO2纳米管的生长过程。结果表明,TiO2纳米管的形成过程是一个由纳米多孔膜结构向独立有序的纳米管阵列转变的过程。同时以TiO2纳米管为光阳极,采用双室光电化学池制氢体系,利用光照TiO2产生的光电压与双室电解液pH差产生的化学偏压的协同效应可达到水的分解电压,充分实现高效率、低能耗制氢的目标。无外加电压及牺牲剂条件下,TiO2纳米管的光电流密度为6.51 m A/cm2,光照1 h产氢量高达108.9μmol/cm2。     

铝合金微弧氧化膜纳米TiO_2掺杂机理研究

在含有纳米TiO_2的电解液中对铝合金进行微弧氧化处理,用以研究掺杂纳米TiO_2对铝合金微弧氧化成膜机理及性能的影响。利用扫描电镜(SEM)观察微弧氧化膜形貌,能谱仪(EDS)分析膜层Ti、Al、O等元素含量,X射线衍射仪(XRD)分析相组成,测定膜厚、硬度和氧化液中TiO_2表面电荷,建立了掺杂改性模型。结果表明,加入纳米TiO_2后,氧化初期电压随TiO_2添加量增加逐渐升高、5min后电压逐渐降低;氧化膜表面孔洞数量和尺寸减小,成膜效率、膜层致密度和表面疏松层硬度提高。纳米TiO_2在氧化膜表面均匀分布,截面不均匀分布。氧化膜主要由γ-Al_2O_3、Mullite和少量Si组成。     

用乳酸溶液为电解质制备TiO2纳米管阵列

为了开发自组织阳极氧化制备TiO2纳米管阵列的新体系,以乳酸／NH4F混合溶液为电解质,研究了阳极氧化制备TiO2纳米管阵列的影响因素及形成机理。采用X射线衍射（XRD）和扫描电子显微镜（SEM）对样品进行检测,并通过观察阳极氧化过程中的电流-时间变化曲线,探讨TiO2纳米管阵列的形成机理。结果表明：阳极氧化电压、时间及电解质溶液的黏度是影响TiO2纳米管阵列结构和形貌的主要因素,在40V阳极氧化电压下,制备出平均管径高达180nm的纳米管,所获得的TiO2纳米管阵列为无定型结构,300℃热处理以后转变为锐钛矿型TiO2。     

有机电解液中钛基材表面TiO2纳米管阵列生长机制的研究

采用恒压阳极氧化法在有机电解液(NH4F/甘油、NH4F/乙二醇)中制备TiO2纳米管阵列,研究了阳极氧化电压、时间、电解液成分对纳米管阵列形貌、生长过程的影响,并提出了有机电解液中TiO2纳米管阵列的生长机制.研究表明:有机电解液中,获得纳米管阵列的电压范围更为宽泛,纳米管的生长时间也更长;在不同含水量的有机电解液中,可以制备出形貌不同的纳米管阵列;有机溶剂的高粘度、低含氧量提高了纳米管生长速度的同时控制着纳米管的腐蚀速度,因此在有机电解液中可以制备更大长径比的TiO2纳米管阵列;乙二醇电解液中纳米管的生长速度大于甘油电解液,并可制各出64μm的TiO2纳米管阵列.     

氧化钛纳米管阵列的表面聚集控制及光电化学特性

采用阳极氧化法在有机介质中制备垂直排列的厚度达百微米的TiO2纳米管阵列,重点考察TiO2纳米管表面形貌特性的控制,以期从微观修饰角度来提高TiO2纳米管阵列膜的光电化学性能;在此基础上,考察不同处理条件下的TiO2纳米管阵列膜的光电化学特性。实验结果表明:采用无水乙醇作为超声液并结合二次蒸馏水进行漂洗能彻底清除纳米管表面聚集堵塞部分,得到清洁、规整有序的纳米管阵列表面,且不破坏纳米管阵列膜的最佳超声振动时间为20～30s。在对纳米管阵列的表面形貌特性进行控制后,采用一步阳极氧化法+无水乙醇超声制备的样品经500℃退火在全谱段的光转换效率达到1.48%,证实对纳米管阵列的表面形貌特性实施控制能有效提高其光电化学性能。     

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。     

高长径比TiO_2纳米管阵列的制备及其电致变色与光电化学性能

采用NH4F-DMSO-甘油-H2O溶液体系的电化学阳极氧化法,经高温热处理后,在金属钛基板上制备了有序的Ti O2纳米管阵列薄膜。通过计时安培法、循环伏安曲线、光照开路电位谱和瞬态光电流谱技术对纳米管阵列电极的电致变色及光电化学特性进行了研究。结果表明,Ti O2纳米管为混晶组成,阵列薄膜具有大比表面积和高长径比。纳米管阵列电极具有稳定的阴极电致变色效应,快速的着色/褪色反应时间。与Ti O2纳米多孔膜电极相比,Ti O2纳米管阵列电极的光电流及光照开路电压都显著增加。     

Preparation of titanium dioxide nanotube arrays on titanium mesh by anodization in (NH4)2SO4/NH4F electrolyte

The self‐organized titanium dioxide (TiO₂) nanotube arrays on titanium mesh were prepared by electrochemical anodization with the neutral electrolyte containing ammonium sulfate and ammonium fluoride in a two‐electrode electrochemical cell. The effects of the fluoride ion concentration, the anodic potential, and the oxidation time on the formation of the titanium dioxide nanostructures on titanium mesh with complex geometry were investigated. The anodized titanium mesh was characterized by field emission scanning electron microscope and in situ high temperature X‐ray diffraction. The results show that the titanium dioxide nanotube arrays are grown in a radially outward direction around the titanium wire. The optimized anodization condition for preparing titanium dioxide nanotube arrays with superior architecture on the titanium mesh is 0.5 wt% of ammonium fluoride, 20 V of applied potential, and 20 min of oxidation time. The amorphous titanium dioxide nanotubes on titanium mesh turn to anatase phase at 400 °C and further to rutile phase at 650 °C.     

Au负载N掺杂TiO2纳米管阵列的制备及其性能

TiO₂ 纳米管阵列较大的禁带宽度是导致其光催化效率较低的重要原因,采用磁控溅射、阳极氧化以及气氛退火相结合的方法对 TNAs 改性后制备了 Au 负载 N 掺杂 TiO₂ 纳米管阵列(Au@ N-TNAs),然后以甲基橙为目标污染物, 进一步分析了 Au@ N-TNAs 在不同 Au 负载量时光降解效率的变化情况。 采用 SEM、XRD、TEM 和 X 射线光电子能谱 (XPS)等对 Au 和 N 在 Au@ N-TNAs 中的存在形式进行表征和分析,发现 Au 主要是负载在 TiO₂ 纳米管阵列上,而 N 元素则是以掺杂的方式进入 TiO₂ 纳米管阵列的晶格中。 此外,在光降解试验中发现通过 Au 负载与 N 掺杂相结合的方法对 TiO₂ 纳米管阵列进行复合改性后,TiO₂ 纳米管阵列的光催化效率得到显著提升,其中 20s-Au@ N-TNAs 具有最佳的光降解效率。 但 Ti-N 薄膜中间的 Au 层太厚时会影响阳极氧化过程中 TiO₂ 纳米管阵列的生长,而且过量的 Au 在退火处理时很难及时地扩散均匀,进而使得改性后的 TiO₂ 纳米管阵列(40s-Au@ N-TNAs)的光催化效率明显降低。     

Chemical state and ultra-fine structure analysis of biocompatible TiO<Subscript>2</Subscript> nanotube-type oxide film formed on titanium substrate

TiO₂ nanotube-type oxide film on Ti substrate has been fabricated using an electrochemical method, and the chemical bonding state, ultra-fine structures, and surface characteristics of the TiO₂ nanotube layer have been investigated. The formation and growth of a self-organized nanotube layer can be achieved directly by anodization in NH₄-containing electrolytes. The diameter, length, and wall thickness of the nanotube are significantly affected by anodizing conditions such as applied voltage, current density, and anodizing time. The length limiting factor of nanotube growth was found to be the diffusion of ionic species in the electrolyte. XRD investigations revealed that annealed nanotubes have anatase and rutile structure, and some Ti-peaks from the Ti substrate were observed. From the compositional analysis of TiO₂ nanotubes layer using Energy Dispersive Spectroscopy (EDS), Ti, O, and P elements were obtained in the wall nanotube layer. For incorporated P-containing in the TiO₂ nanotube layer, various chemical states were presented, which were revealed mostly in the forms of H₂PO₄, HPO₄ ^2-, and PO₄ ^3-.     

Influence of electrolyte and anodic potentials on morphology of titania nanotubes

The effects of electrolyte and applied potentials on TiO₂ nanotube morphologies were investigated. The specific surface area of the TiO₂ nanotubes was measured to be 57 m²/g for titania nanotubes formed in HF, and 147 m²/g formed in organic electrolyte, respectively. The results of adsorption-desorption isotherms agree with the morphology of TiO₂ nanotubes. The length and average diameter of nanotubes were influenced by electrolyte and anodic potentials. The multilayered TiO₂ nanotube arrays can be fabricated by changing the electrolyte composition during anodization.     

Rapid anodic oxidation of highly ordered TiO2 nanotube arrays

Highly ordered TiO₂ nanotube arrays prepared by anodic oxidation have attracted increasing research interests due to their promising applications in many scientific areas. To the best of our knowledge, a factor limiting the application of TiO₂ nanotube arrays was their long sustaining reaction time by anodic oxidation, usually lasting 6-12 h and even longer when synthesizing thicker nanotubular layers. In the present paper, we reported for the first time a facile but effective approach to accelerate the anodic formation of TiO₂ nanotube arrays by proper addition of sodium carbonate (Na₂CO₃) into the anodization electrolyte. We adopted the 0.3 M NH₄F + 0.03 M Na₂CO₃ + EG (ethylene glycol) + 3.0 vol.% H₂O electrolyte and the average growth rate of the nanotubes achieved in our experiments could be accelerated to 1100 nm/min. The possible mechanism of the rapid electrochemical process was also presented.     

Self-aligned TiO2 nanotube arrays produced by air-cathode as electrode

Air-cathodes were used to produce TiO₂ nanotube arrays. The effects of pH, voltage and degradation of air-cathode in tailoring the morphologies of TiO₂ nanotube arrays were investigated. Preliminary results show that TiO₂ nanotubes could be formed and are comparable to those produced by platinum electrodes under similar conditions. The lengths and diameters of TiO₂ nanotube arrays obtained are in the range of 1.0-2.2 μm and 40-150 nm, respectively. It is found that the rate of formation of the nanotubes is closely related to the pH of the solution. Air-cathodes are found to have relative low values of mass loss rates.     

非晶TiO2 纳米管形貌对其作为超级电容器电化学性能的影响

采用改进的两步电化学阳极氧化和电化学氢化法制备了不同管径、长度和壁厚的氢化无定型TiO₂纳米管阵列（H@am-TNAs）。结果表明,电化学氢化对TiO₂纳米管阵列的结构影响不大。经过电化学氢化后,纳米管在100 mV·s^-1时的比电容为4.05 mF·cm^-2,比未氢化的管长和管径相同的TiO₂纳米管的比电容大20倍。纳米管的比电容不仅与管长有关,还受管径的影响。通过指数函数拟合,纳米管的长径比呈线性关系。面积电容/长径比达到0.056,几乎相当于锐钛矿相TiO₂纳米管。阳极化处理后的纳米管具有最小的电荷转移阻力和最佳的离子扩散/输运动力学,具有最高的面积容量。此外,为了研究H@am-TNAs纳米管的电化学性能的润湿性,相同的H@am-TNAs电极在C-V和C-P测试前,在电解液中浸泡不同时间,结果表明,比电容随着浸泡时间的增加而减小。     

Characteristics of N-doped TiO2 nanotube arrays by N2-plasma for visible light-driven photocatalysis

N-doped TiO₂ nanotube arrays were prepared by electrochemical anode oxidation of Ti foil followed by treatment with N₂-plasma and subsequent annealed under Ar atmosphere. The morphologies, composition and optical properties of N-doped TiO₂ nanotube arrays were characterized using field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectrometer (XRD), Photoluminescence (PL) and UV-vis diffusion reflection spectroscopy (UV-vis DRS). Methylene blue (MB) solution was utilized as the degradation model to evaluate the photocatalytic activity of the samples under visible light irradiation. The results suggested N₂-plasma treatment created doping of nitrogen onto the surface of photoelectrodes successfully and the N-doped TiO₂ nanotube arrays display a significantly enhancement of the photocatalytic activity comparing with the pure TiO₂ nanotube arrays under the visible light irradiation.     

Highly ordered self-organized TiO2 nanotube arrays prepared by a multi-step anodic oxidation process

Highly ordered TiO₂ nanotube arrays were prepared using a self-templating multi-step anodic oxidation process in a fluoride-containing electrolyte. The microstructures, chemical compositions, and phases of the self-organized TiO₂ nanotube arrays were analyzed by FESEM, XPS, and XRD, respectively. Hexagonal packing density in TiO₂ nanotube arrays significantly improved after the the multi-step anodic oxidation. The area densities of the hexagonal TiO₂ nanotube arrays increased approximately 3 times from the first to second step in the anodic oxidation steps process (4.9 μm⁻² to 16.4 μm⁻²), but there was no difference between the second and third step (16.4 μm⁻² to 16.0 μm⁻²). The as-anodized TiO₂ nanotube array had an amorphous structure and it transformed to an anatase phase during the annealing process at 450 °C for 1 h. The as-anodized TiO₂ nanotube arrays adsorbed the fluoride, hydrocarbon groups (CH), hydroxyl groups (OH, C-OH), and carboxyl groups (O = C-OH) on their surfaces.     

Formation behavior of anodic TiO2 nanombes in fluoride containing electrolytes

TiO₂ nanotube layers can be formed with titanium in the electrolytes containing fluoride by electrochemical method. The role of fluoride ion, the crystallinity of the anodic oxide, and the chemical state were investigated. The results show the anodic film is composed of oxide and a little amount of hydroxide. The presence of F⁻ ions leads to chemical dissolution of Ti oxide layer and prevents hydroxide precipitation. Consequently, chemical dissolution rate increases with increasing the fluoride content in the range of 0–2% (in mass fraction) because F⁻ ions in electrolyte attack the interface and allow the ions of the electrolyte to easily penetrate into the interface. The as-anodized TiO₂ nanotubes exhibit an amorphous structure. Thermally treated nanotubes are composed of mixtures of the anatase and rutile phases.