The multi-staged formation process of titanium oxide nanotubes and its thermal stability

The multi-staged formation process of titanium oxide nanotubes was investigated in detail under a hydrothermal treatment. During the synthesis procedure, an intermediate stage (tree-like structures) was observed before the formation of the titanium oxide layered structures. The layered structure of titanium oxide generally was considered to exfoliate directly from raw TiO₂ materials through the alkaline hydrothermal treatment. The rolling process of the layered structures of titanium oxide was confirmed by TEM observation after the alkaline hydrothermal treatment for the raw TiO₂ materials, followed by washing with 4 M HNO₃ aqueous solution. The thermal stability of the tube products was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The result showed that both the morphology and crystal phase of titanium oxide nanotubes could be retained even after calcination at 650 °C.     

Photocatalytic characteristics of TiO2 nanotubes with different microstructures prepared under different pulse anodizations

In this work, different positive voltages of a pulsed waveform, time intervals and electrolyte stirring were used to prepare by anodization of pure titanium plates, a series of TiO₂ thin films based on nanotubes with different morphologies and dimensions. Electrolyte stirring results in large size TiO₂ nanotubes with uneven surface morphology and less oriented directions. The titanium plates containing the TiO₂ thin films were further annealed at 450 °C for 30 min under air. It was found that only crystalline anatase was formed under this condition. Both methylene blue degradation and antibacterial tests against Escherichia coli were performed to evaluate the photocatalytic performance of these TiO₂ films. Better methylene blue degradation ability was achieved by TiO₂ nanotubes prepared under electrolyte stirring. However, the antibacterial ability of the annealed TiO₂ nanotubes was affected by their inner diameter rather than their length. It is also concluded that the anodized TiO₂ nanotube arrays fabricated in this work are promising for photo-induced methylene blue degradation and bacteria killing applications.     

Nanotubular surface and morphology of Ti-binary and Ti-ternary alloys for biocompatibility

The nanotubular surface of Ti-binary and Ti-ternary alloys for biomaterials has been investigated using various methods of surface characterization. Binary Ti-xNb (x = 10, 20, 30, and 40 wt.%) and ternary Ti-30Ta-xNb (x = 3, 7 and 15 wt.%) alloys were prepared by using the high-purity sponges; Ti, Ta and Zr spheres. The nanotube on the alloy surface was formed in 1.0 M H₃PO₄ with small additions of NaF (0.5 and 0.8 wt.%), using a potentiostat. For cell proliferation, an MC3T3-E1 mouse osteoblast was used. The surface characteristics were investigated using field-emission scanning electron microscope, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy.Binary Ti-xZr alloys had a lamellar and a needle-like structure, whereas, ternary Ti-30Ta-xZr alloys had equiaxed grains with a lamellar martensitic α′ structure. The thickness of the needle-like laths of the α-phase increased as the Zr content increased. The nanotubes formed on the α phase and β phase showed a different size and shape appearance with Zr content. As the Zr content increased from 3 to 40 wt.%, the diameter of the nanotubes in Ti-xZr and Ti-30Ta-xZr alloy decreased from 200 nm to 50 nm. The nanotubular Ti-30Ta-15Zr alloy surface with a diameter of 50 nm provided a good osseointegration; cell proliferation, migration and differentiation.     

Flexible Triboelectric Nanogenerator Based on High Surface Area TiO2 Nanotube Arrays

Triboelectric nanogenerators (TENGs) can harvest mechanical energy through coupling triboelectric effect and electrostatic induction. Typically, TENGs consist of organic materials, however on account of the potentially wide range of applications of TENGs as the self‐powered portable/wearable electronics, biomedical devices, and sensors; semiconductor metal oxide materials can be promising candidates to be incorporating in TENG structure. Here, flexible TENG based on self‐organized TiO₂ nanotube arrays (TNTAs) is fabricated via anodization method. The introduced flexible large area nanotubular electrode is employed as the moving electrode in contact with Kapton film in vertical contact separation mode of TENG. The fabricated TENG can deliver output voltage of 40 V with the current density of 1 μA cm^?2. To evaluate the role of nanostructured interface, its performance has been compared to the thin film flat compact TiO₂ electrode. The results of extracted charge measurements under short circuit condition indicate that larger triboelectric charge density formed in TNTA‐based electrode (about 110 nC per cycle of press and release) is in comparison to 15 nC in flat TiO₂ electrode. Due to the extensive range of applications of TiO₂, the introduced structure can potentially be applicable in various types of self‐powered systems such as photo‐detectors and environmental gas and bio‐sensors.

     

Subtractive methods to form pyrite and sulfide nanostructures of Fe,Co, Ni,Cu and Zn

The low Z metals Fe, Co, Ni, Cu and Zn are Earth abundant, i.e. inexpensive, and their sulfides are of low toxicity. This makes them appealing candidates for materials applications requiring semiconductors or, in the case of CoS₂, a metal since they can potentially be produced in large quantities and low cost. Though of great potential little work has explored how subtractive methods can be used to form nanostructured and/or porous structures in, e.g. FeS₂, CoS₂, NiS, Cu₂S and ZnS.     

Controlled transformation of carbon coating on silicon nanochains into nanotubes of carbon by Joule heating

A method of carbon coating of silicon nanochains is developed for the controlled transformation of silicon nanochains into nanotubes of carbon: the surface of silicon nanochains is coated with hexadecanoic acid by annealing after plasma cleaning. Individual silicon nanochains are heated by applying an electric current using a micro-manipulator for the transformation. The transformation is observed in situ by means of transmission electron microscopy.     

Synthesis and electrophoretic deposition of hydrothermally synthesized multilayer TiO2 nanotubes on conductive filters

TiO₂ nanotubes were synthesized by the decomposition of titanium isopropoxide in water and the calcination at 450 °C for 2 h to form TiO₂ nanoparticles. The synthesized TiO₂ in anatase form nanoparticles were processed hydrothermally in 10 M NaOH solution at 130 °C for 24 h to obtain multilayer TiO₂ nanotubes. TEM analysis revealed that the diameters of the tubes were around 10 nm and they are in the length of 100 nm. Subsequently, colloidal suspensions containing 1% wt. Of TiO2 nanotubes were prepared with TEA and butanol and electrophoretic deposition (EPD) experiments were conducted in order to obtain coatings on Ni and carbon filters using a deposition time of 10 min. and an applied voltage of 65 V. It is also shown that multilayer TiO₂ nanotubes having outer diameter around 10 nm and inner diameters of 4.3 nm can be produced using the described technique. EPD is also shown to be an effective technique to coat three dimensional components, such as Ni and C filters for various applications including water and air purification systems.     

Self-organized TiO2 nanotubes in mixed organic–inorganic electrolytes and their photoelectrochemical performance

The formation of self-organized TiO₂ nanotube array films by electrochemical anodizing titanium foils was investigated in a developed organic–inorganic mixed electrolyte. It was found that the structure and morphology of the TiO₂ nanotube layer were greatly dependent upon the electrolyte composition, anodizing potential and time. Under the optimized electrolyte composition and electrochemical conditions, a controllable, well-ordered TiO₂ nanotube array layer could be fabricated in a short time. The diameters of the as-prepared TiO₂ nanotubes could be adjusted from 20 to 150 nm, and the thickness could be adjusted from a few hundred nanometers to several micrometers. The photoresponse and the photocatalytic activity of the highly ordered TiO₂ nanotube array films were also examined. The nanotube array film with a thickness of about 2.5 μm had the highest incident photon to photocurrent conversion efficiency (IPCE) (34.3%) at the 350 nm wavelength, and had better charge transfer ability under UV light illumination. The photocatalytic experimental results indicated that the 450 °C annealing samples have the highest photodegradation efficiency for methyl orange pollutant.     

铁掺杂TiO2纳米管阵列的制备及其电化学性能

在钛基体上,通过二次阳极氧化法和化学方法制备了不同Fe掺杂浓度的TiO2纳米管阵列,分析了所制备掺杂纳米管阵列的表面形貌、结构及化学组成,研究了其耐腐蚀性能。结果表明,0.05mol/L的Fe(NO3)3溶液浸泡可以不破坏纳米管阵列实现Fe离子高浓度掺杂。过高铁离子浓度溶液掺杂会损坏纳米管表面形貌,且实际Fe离子掺杂浓度低。经过低铁离子浓度溶液浸泡后,纳米管阵列表现出最好的耐腐蚀性。     

TiO2纳米管阵列的制备、改性及应用研究

二氧化钛因其化学性质稳定,无毒,无污染,是环境友好型材料.它的一维纳米材料尤其是二氧化钛纳米管在绿色能源太阳能和环境治理方面有很大的潜在应用价值,激起了全球科学家的兴趣.基于前人对二氧化钛纳米管的研究成果,我们总结了目前的制备方法、改性及其应用方面的研究现状,以期对二氧化钛纳米管的未来研究提供一些知识基础的支持.