阳极氧化法制备TiO2纳米管阵列

采用阳极氧化法在乙二醇体系电解液中制备TiO2纳米管阵列,获得了长度为15~20μm的底端纳米管与顶端纳米线的新型复合结构。讨论了电解液中不同含水量对该复合结构形成的影响,并采用两步阳极氧化法对该结构的形成机理进行了分析。结果表明,当乙二醇体系电解液含有0.4%(质量分数)NH4F和2%(体积分数)H2O时,电解液腐蚀速度适中,纳米管上端部分被选择性腐蚀,最终形成纳米管与纳米线的复合结构。     

TiO2纳米管晶型对钛生物活性的影响

利用阳极氧化法在HF电解液体系中制备了高有序TiO2纳米管。样品分别在400和600℃下热处理后,得到锐钛矿和金红石两种晶型的TiO2纳米管。对样品进行了表征,将样品浸泡于模拟体液中,观察表面HA沉积情况,并进行体外细胞毒性实验以探讨样品的生物相容性。结果发现,400和600℃退火处理的纳米管样品生物活性高于未退火处理样品,400℃退火处理纳米管活性高于600℃退火处理纳米管。由于不同后处理条件下制备的纳米管形貌相似,仅为晶型不同,故推断出锐钛矿型TiO2生物活性最好,金红石型TiO2次之,无定型TiO2生物活性相对最差。     

TiO2纳米管阵列的制备工艺对其光催化性能的影响

采用阳极氧化法,在醇(丙三醇、乙二醇)-水-NH4F电解液体系中制备高度有序的TiO2纳米管阵列。采用场发射扫描电子显微镜(SEM)、X射线衍射仪(XRD)对TiO2纳米管阵列的形貌和晶型结构进行表征,讨论了阳极氧化法制备工艺(阳极氧化电压、氧化时间、电解液)对TiO2纳米管的形貌、结构及其甲基橙光催化降解性能的影响;分析了退火温度对TiO2阵列的物相及其光催化性能的影响。研究结果表明,采用高电压、增加氧化时间有利于TiO2纳米管阵列光催化的提高,在其它参数相同的情况下,采用丙三醇作为电解液制备获得的TiO2纳米管阵列较乙二醇体系具有更加优异的光催化性能。     

玻璃基底TiO2纳米管阵列的制备及其光电性能研究

提高二氧化钛纳米管阵列电极的机械稳定性,改善电极的透光性能,有助于提高其光电催化性能,拓展电极的应用范围.通过室温射频溅射方法在玻璃基底上溅射一层金属钛膜,然后在含0.5%HF的电解液,10V阳极氧化电压下进行阳极氧化,得到玻璃基TiO2纳米管阵列电极.扫描电子显微镜和X射线衍射分析表明,玻璃基表面形成了孔径为20～30nm,管长约130nm排列有序的锐钛矿型TiO2纳米管阵列.光电性能测试表明,玻璃基TiO2纳米管阵列与金属钛基TiO2纳米管阵列表现出相似的光电催化性能,明显优于磁控溅射制备的TiO2薄膜.     

TiO2纳米管的结构特征对其光电催化性能的影响

研究了利用电化学阳极氧化法在不同的氧化电压和氧化时间条件下制备的TiO2纳米管(TNT)的结构特征对其光电催化性能的影响。运用场发射扫描电子显微镜,X射线衍射和X射线光电子能谱分析等手段对其进行表征,考察了其光电化学性质,研究了具有不同纳米结构特征的TiO2纳米管降解甲基橙染料废水的反应动力学性能。结果表明,TiO2纳米管的长径比对其光电催化性能影响最大。其管长和管径随着氧化电压和氧化时间的增大而增大,壁厚随着氧化电压的增大而减小。在其管长为25.85μm、壁厚为10.23nm、长径比为178、粗糙系数为175的条件下具有最大光电流密度4.8×10-2 mA/cm2,对甲基橙(MO)光电催化降解拟一级反应动力学常数达到最大值2.26×10-3/min。     

金属掺杂对纳米管TiO2光催化性能的影响

利用水热法,以Degussa P-25TiO2粉末为原料,AlCl3、Fe(NO3)3·9H2O和ZnCl2为掺杂剂合成金属掺杂纳米管TiO2,并采用透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和BET比表面积分析对催化剂进行表征。结果表明,掺杂金属分别以Al 3+、Fe3+和Zn2+的形式存在。随着煅烧温度的增高,样品的比表面积逐渐降低,锐钛矿含量先增大后减小;金属掺杂后,催化剂比表面积略有降低,锐钛矿含量略有增大。考察紫外光催化臭氧化工艺中TiO2降解腐植酸标志物的催化效果,结果表明,450℃煅烧未掺杂纳米管TiO2对腐植酸的催化降解效率为44%,较P-25TiO2粉末提高了11%;金属掺杂后催化效果提升明显,550℃煅烧Fe掺杂纳米管TiO2的催化效果最为显著,腐植酸去除率达77%。     

TiO2纳米管阵列膜的制备及对304不锈钢的光生阴极保护效应

应用电化学阳极氧化法在Ti表面构筑不同的TiO2纳米管阵列膜。采用XRD、SEM、XPS表征薄膜的结构、形貌和组成。通过电化学阻抗谱及电位随时间变化的测试,考察TiO2薄膜的光生阴极保护效应。结果表明薄膜主要由锐钛矿型的TiO2纳米管阵列组成,当304不锈钢耦连于紫外光照下的TiO2薄膜电极时,其界面反应电阻变小,电极电位显著降低,说明TiO2纳米管薄膜能够对不锈钢产生良好光生阴极保护效应,特别是掺Fe的TiO2薄膜在光照时可使不锈钢电位降低约450mV,而且在暗态时也能较长时间保持对不锈钢的阴极保护作用。     

三电极体系制备TiO2纳米管

利用电化学阳极氧化法在乙二醇和氟化铵溶液三电极体系中阳极氧化纯钛箔,制备出具有双面结构的TiO2阵列纳米管。研究了不同电压和电解液含水量对纳米管形貌的影响,通过扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析了TiO2纳米管阵列的微观形貌及物相。     

TiO2纳米管阵列薄膜的水热晶化

首先在KF和乙二醇的混合溶液中利用阳极氧化技术在钛基底表面制得了一层排列整齐、形貌均一的TiO₂纳米管阵列薄膜,然后将制得的薄膜进行水热处理,通过扫描电子显微镜、X射线衍射仪等表征手段研究了水热处理温度和时间对TiO₂纳米管阵列薄膜表面形貌、结晶度以及管状结构的影响。结果表明:水热处理即使在较短的时间内（如3 h）也可在较低温度下（如210℃）使TiO₂纳米管阵列薄膜由无定形转变为锐钛矿型结构;提高水热处理温度或延长水热处理时间均可提高薄膜的结晶度,但同时纳米管管壁结晶度增加会使管内径变小甚至堵塞,从而破坏管状结构。     

TiO2纳米管阵列阳极氧化制备的研究进展

综述了TiO2纳米管阵列的阳极氧化制备研究进展,尤其是制备机理、阳极氧化电压、电解液组成对其形貌的影响。此外,展望了TiO2纳米管阵列的研究前景,提出了其工业化生产工艺的研究方向和充分利用其空腔管阵结构进行改性的研究思路。     

Enhanced photoelectrocatalytic activity in TiO2 nanotube arrays modified with TiO2 nanoparticles

The use of TiO₂ nanotube arrays fabricated by anode oxidation of titanium sheets as a photoelectrocatalyst is limited by low surface activity owing to passive crystallization post-treatment. We report here on a vacuum assisted filling route for modifying TiO₂ nanotube arrays using high-activity anatase TiO₂ nanoparticles as a filling. Photoelectrocatalytic degradation experiments show that a nearly 4-fold activity enhancement in photoelectrocatalysis is achieved and good photoelectrocatalytic stability is kept after the nanotube arrays are filled with the high-activity TiO₂ nanoparticles. The remarkable enhancement in photoelectrocatalysis is ascribed to the key modification of the TiO₂ nanotube arrays using the high-activity TiO₂ nanoparticles. Our findings provide an insight into designing excellent photoelectrocatalysts by filling TNAs with available high-activity TiO₂ nanoparticles.     

TiO2纳米管的制备及光催化性能研究

以氟化铵水溶液为电解质,采用阳极氧化法,在钛片基体上制备出TiO2纳米管阵列.用FESEM、XRD等测试方法对样品进行表征,采用UV-1800型紫外-可见分光光度计检测TiO2纳米管对甲基橙的光催化性能.结果表明,氧化电压为50V,氧化时间为10h,煅烧温度为500℃时得到的TiO2纳米管对甲基橙的降解效果最好.     

Ag2S quantum dots-sensitized TiO2 nanotube array photoelectrodes

Ag₂S quantum dots (QDs) were deposited on ordered TiO₂ nanotube arrays (TNTAs) using a sequential chemical bath deposition (S-CBD) approach. AgNO₃ and thiourea were used as the precursor materials of Ag⁺ and S²⁻ ions, respectively. The decoration of Ag₂S QDs significantly shifted the absorption spectrum of the TNTAs to visible light region. As a result, Ag₂S QDs-sensitized TNTAs exhibited much higher photocurrent density than pure TNTAs under visible light irradiation.     

Photocatalytic reduction of methylene blue by TiO2 nanotube arrays: effects of TiO2 crystalline phase

TiO₂ nanotube arrays were synthesized by anodization of Ti metal sheets followed by thermal annealing at elevated temperatures from 400 to 600 °C. Scanning electron microscopic measurements showed that dense arrays of nanotubes were produced with the inner diameter about 100 nm, wall thickness 35 nm, and length about 10 μm. X-ray diffraction measurements showed that the as-prepared nanotubes were largely amorphous, whereas thermal annealing led to the formation of well-defined anatase crystalline phase. More interestingly, at 470 °C, the brookite crystalline phase also started to emerge, which became better defined at 500 °C and disappeared eventually at higher temperatures, a phenomenon that has not been observed previously in TiO₂ nanotube arrays prepared by anodization. The impacts of the TiO₂ nanocrystalline structure on the photocatalytic activity were then examined by using the reduction of methylene blue in water as an illustrating example. Upon exposure to UV lights, the visible absorption profiles of methylene blue exhibited apparent diminishment. Based on these spectrophotometric measurements, the corresponding pseudo-first-order rate constant was estimated, and the sample thermally annealed at 500 °C was found to exhibit the highest activity. The strong correlation between the TiO₂ crystalline characteristics and photocatalytic performance suggests that the synergistic coupling of the anatase and brookite crystalline domains led to effective charge separation upon photoirradiation and hence improved photocatalytic activity, most probably as a consequence of the vectorial displacement at the nanoscale junctions between these crystalline grains that impeded the dynamics of electron–hole recombination. These results demonstrate the significance of nanoscale engineering in the manipulation of oxide photocatalytic performance.     

Investigation on solar photocatalytic activity of TiO2 loaded composite: TiO2/Eggshell, TiO2/Clamshell and TiO2/CaCO3

The TiO₂/Eggshell, TiO₂/Clamshell and TiO₂/CaCO₃ loaded composites were prepared by sol-gel method and characterized by XRD and SEM. Their photocatalytic activities were measured through the degradation of Acid Red B under solar light irradiation. The influences of TiO₂ loaded content, heat-treated temperature and time on the photocatalytic activities were reviewed. The effects of irradiation time and dye initial concentration on the photocatalytic degradation were also investigated. The results showed that the photocatalytic activity can be greatly enhanced by appropriate TiO₂ loaded content.     

The influence of ultrasound on the formation of TiO2 nanotube arrays

Electrochemically anodized TiO₂ nanotube (NT) arrays on Ti foils have been in great interests recently attributing to the wide applications. The net growth rate of TiO₂ NT array is determined by electrochemical etching of Ti foil and chemical dissolution of the formed TiO₂ NTs. While the TiO₂ NT growth becomes a diffusion controlled process after certain growth time. Here, we report the influence of ultrasound on the growth process of TiO₂ NT arrays. The results indicate that ultrasound can significantly alter the relative rates of these reactions and adjust the geometries of the TiO₂ NT arrays.     

Electron field emission from the carbon-doped TiO2 nanotube arrays

The field-emission characteristics of the carbon-doped TiO₂ nanotube arrays (TNAs), which can be obtained by a heat treatment of the as-fabricated TNAs under a continuous argon and acetylene flux, were investigated. The morphology, crystalline structure, and composition of the as-grown specimens were characterized by the use of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the samples' turn-on electric field is reduced from 21.9 to 5.0 V/μm and the field-emission current density rapidly reaches about 9.0 mA/cm² at 11.8 V/μm after carbon doping. The dramatically improved field-emission characteristics would be mainly attributed to the reduced work function and the enhanced conductivity due to the carbon doping into TNAs.     

碳纳米管修饰LaFeO3/TiO2复合材料的光催化性能与机理

采用超声辅助溶胶凝胶法制备了LaFeO₃颗粒,进一步以碳纳米管(CNTs)为基底和钛酸丁酯为前体,通过一步水热法煅烧合成CNTs/TiO₂/LaFeO₃(CTF)三元异质结光催化复合材料。通过扫描电子显微镜(SEM)、X射线衍射分析(XRD)、氮气吸附-解吸等温线(BET)、紫外-可见分光光度计(UV-Vis)、光致发光光谱(PL)等表征手段对材料的形貌与特征结构、比表面积和孔径结构以及光学特征进行了分析,并在紫外光下通过降解活性黑五(RB5)测试样品的光催化性能。结果表明,以CNTs作为载体,能够有效提升LaFeO₃/TiO₂复合材料的光催化性能。当CNTs在复合材料中的质量占比为5%时,150 W汞灯照射下RB5的50 min去除率可达99.5%。CNTs一方面通过增加复合材料的比较面积为催化反应的进行提供了更多的活性位点,更为重要的是,CNTs作为光生载流子传输的通道加快了电荷分离效率,提升了复合材料的降解能力和催化反应动力学进程。     

Investigations on the self-organized growth of TiO2 nanotube arrays by anodic oxidization

The formation mechanism of a thin film of self organized TiO₂ nanotube arrays prepared by anodic oxidization of a pure titanium sheet in electrolyte solutions containing potassium fluoride and sulfate was investigated through near-real time monitoring the anode mass, the current density, and the surface topography during the anodization. Energy dispersive X-ray spectrometry was used to monitor the surface composition change during the anodization. The titanium surface was first electrochemically oxidized to form a layer of dense oxide under which nanotubes were originated. With the protection of the oxide layer, long nanotubes could be formed in electrolyte solutions with relatively high pH. The surface composition analysis indicates that the nanotubes were not totally oxidized to TiO₂. However, no other elements but Ti and O were found in the oxide film. This work reveals a way to fabricate long nanotubes with defined sizes.     

Field emission from the structure of well-aligned TiO2/Ti nanotube arrays

Well-aligned TiO₂/Ti nanotube arrays were synthesized by anodic oxidation of titanium foil in 0.5 wt.% HF in various anodization voltages. The images of filed emission scanning electron microscopy indicate that the nanotubes structure parameters, such as diameter, wall thickness and density, can be controlled by adjusting the anodization voltage. The peaks at 25.3° and 48.0° of X-ray diffraction pattern illuminate that the TiO₂ nanotube arrays annealed at 500 °C are mainly in anatase phase. The filed emission (FE) properties of the samples were investigated. A turn-on electric field 7.8 V/µm, a field enhancement factors approximately 870 and a highest FE current density 3.4 mA/cm² were obtained. The emission current (2.3 mA/cm² at 18.8 V/µm) was quite stable within 480 min. The results show that the FE properties of TiO₂/Ti have much relation to the structure parameters.