Xixin Wang

Reinforcement of denture base PMMA with ZrO(2) nanotubes.

In the research described, ZrO2 nanotubes were prepared by anodization. The morphologies, crystal structure, etc. were characterised by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Fourier transform infrared spectroscopy (FTIR). ZrO2 nanotubes were pre-stirred with the denture base PMMA powder by a mechanical blender and mixed with MMA liquid to fabricate reinforced composites. The composites were tested by an electromechanical universal testing machine to study the influences of contents and surface-treatment effect on the reinforcement. The ZrO2 nanoparticles were also investigated for comparative purposes. Results indicated that ZrO2 nanotubes had a better reinforcement effect than ZrO2 nanoparticles, and surface-treatment would lower the reinforcement effect of the ZrO2 nanotubes which itself was significantly different from that of the ZrO2 nanoparticles. The flexural strength of the composite was maximised when 2.0wt% untreated ZrO2 nanotubes were added.

Degradation of methyl orange through synergistic effect of zirconia nanotubes and ultrasonic wave.

Zirconia nanotubes with a length of 25 μm, inner diameter of 80 nm, and wall thickness of 35 nm were prepared by anodization method in mixture of formamide and glycerol (volume ratio = 1:1) containing 1 wt% NH(4)F and 1 wt% H(2)O. Experiments showed that zirconia nanotubes and ultrasonic wave had synergistic degradation effect for methyl orange and the efficiency of ultrasonic wave increased by more than 7 times. The decolorization percentage was influenced by pH value of the solution. Methyl orange was easy to be degraded in acidic solution. The decolorization percentage of methyl orange reached 97.6% when degraded for 8h in 20mg/L methyl orange solution with optimal pH value 2. The reason of synergistic degradation effect for methyl orange might be that adsorption of methyl orange onto zirconia nanotubes resulted in the easy degradation of the methyl orange through ultrasonic wave.

Outstanding supercapacitive properties of Mn-doped TiO2 micro/nanostructure porous film prepared by anodization method

Mn-doped TiO2 micro/nanostructure porous film was prepared by anodizing a Ti-Mn alloy. The film annealed at 300 °C yields the highest areal capacitance of 1451.3 mF/cm2 at a current density of 3 mA/cm2 when used as a high-performance supercapacitor electrode. Areal capacitance retention is 63.7% when the current density increases from 3 to 20 mA/cm2, and the capacitance retention is 88.1% after 5,000 cycles. The superior areal capacitance of the porous film is derived from the brush-like metal substrate, which could greatly increase the contact area, improve the charge transport ability at the oxide layer/metal substrate interface, and thereby significantly enhance the electrochemical activities toward high performance energy storage. Additionally, the effects of manganese content and specific surface area of the porous film on the supercapacitive performance were also investigated in this work.

Catalytic activity of ZrO 2 nanotube arrays prepared by anodization method

ZrO2 nanotube arrays were prepared by anodization method in aqueous electrolyte containing (NH4)2SO4 and NH4F. The morphology and structure of nanotube arrays were characterized through scanning electron microscope, X-ray diffraction, and infrared spectra analysis. The zirconia nanotube arrays were used as catalyst in esterification reaction. The effects of calcination temperature and electrolyte concentration on catalytic esterification activity have been investigated in detail. Experiments indicate that nanotube arrays have highest catalytic activity when the concentration of (NH4)2SO4 is 1 mol/L, the concentration of NH4F is 1 wt%, and the calcination temperature is 400°C. Esterification reaction yield of as much as 97% could be obtained under optimal conditions.

Photoelectrochemical Activities of W-Doped Titania Nanotube Arrays Fabricated by Anodization

Titania nanotube arrays and W-doped (containing 3-wt% W) titania nanotube arrays were obtained using a direct anodization method in ethylene glycol electrolyte containing 0.5-wt% HF at 60 V. Anneal was conducted to get anatase crystals. The microstructure and crystal structure of the nanotubes were characterized by scanning electron microscopy and X-ray diffraction. The ultraviolet-visible diffuse reflectance spectra of the annealed samples show that the addition of W led to the red shift of absorbance edge and a decrease of bandgap energy for about 0.14 ev. The photoelectrochemical behavior of these samples has been also studied. Results show that photocurrent densities of W-doped titania nanotube arrays were much larger than that of the undoped sample.

Preparation and Growth Mechanism of Niobium Oxide Microcones by the Anodization Method

The formation of niobium oxide microcones on niobium substrates was investigated in HF electrolytes. The microstructure of the layers depends strongly on the HF concentration, the formation potential, and the anodization time. Microcones can be formed under a range of experimental conditions. Electrochemical determination and scanning electron microscopy indicate the microcones were formed due to the fast expansion of the oxide volume and the electric break under electric field. X-ray diffraction results verify the formation of Nb 2 O 5 . A possible growth mechanism has also been presented on the basis of experiments.

Causes for the Formation of Titania Nanotubes During Anodization

Titania nanotube arrays were prepared in the electrolyte containing dimethyl sulphoxide and HF through anodization method and the morphology and composition of the nanotube arrays were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The causes for the formation of nanotubes have been discussed according to the experimental results. Nanopores are formed firstly at the early stage of anodization, O2- ion needed to oxidize the titanium metal below the pore wall must diffuse inward from both sides of the pore wall. Because of the different diffusion resistances, O2- concentrations are different at different positions of the interface between titanium metal and pore wall, leading to different oxide compositions. As a result, the surface of pore wall is mainly composed of high valence oxide TiO2, while the middle of pore wall is mainly composed of suboxides, such as Ti2O3 and TiO. The pore wall would crack easily at the middle low strength suboxides due to temperature changes during anodization, which results in the conversion of nanopores into nanotubes. The selective dissolution of suboxides in the electrolyte leads to the formation of gaps between nanotubes.

Preparation and photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays

Zr–Sm (3 at.% Sm) alloy was prepared through a powder metallurgical method. Sm3+-doped ZrO2 nanotube arrays have been achieved directly by anodizing the Zr–Sm alloy. The effects of electrolyte and annealing temperature on the morphologies and structures of the nanotube arrays were studied. The photoluminescence properties of Sm3+-doped ZrO2 nanotube arrays prepared in aqueous solution and formamide + glycerol solution were studied in detail as well. Results show that tetragonal ZrO2 promoted the photoluminescence efficiency of this system. Under excitation at 407 nm, the sample prepared in aqueous solution annealed at 600 °C displayed the strongest emission peak at 571 nm, corresponding to the 4G5/2 → 6H5/2 samarium transition.

Influence of Mass and Heat Transfer on Morphologies of Metal Oxide Nanochannel Arrays Prepared by Anodization Method

We discuss the influence of mass and heat transfer on the morphologies of Al, Ti, and Zr nanochannel arrays during anodization process. When these metals are anodized, the nanopores are firstly formed at the metal surface, and the nonuniform distribution of mass transfer in the pores results in the increase of pore depth. The nonuniform temperature distribution and the downward movement of reaction interface lead to the temperature changes and the generation of microcracks inside the pore wall, which results in the conversion of nanopores into nanotubes. The low-valency oxides also make the middle of the pore wall crack easily. The morphologies during metal anodization depend greatly on the temperature at the reaction interface. At low interface temperature, it appears to form the nanopores more easily, and, at high interface temperature, it is more propitious to form the nanotube structure. Many factors including resistivity, thermal conductivity, oxidizing reaction heat, and electric field strength (or current density) affect the reaction interface temperature.

Cu/Ni nanoparticles supported on TiO2(B) nanotubes as hydrogen generation photocatalysts via hydrolysis of ammonia borane

TiO2(B) nanotubes (NTs) were used as carriers to support metal Cu/Ni nanoparticles for the catalytic hydrolysis of ammonia borane (NH3BH3, AB) under visible light. The TiO2 NTs were first prepared by the hydrothermal method and subsequently loaded with Cu/Ni metal nanoparticles by the impregnation reduction method. The structure, morphology, and chemical composition of the as-obtained catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), inductively coupled plasma emission spectroscopy (ICP), and ultraviolet–visible spectroscopy (UV-Vis). The characterization results revealed that the metal nanoparticles were uniformly loaded on the surface of the TiO2 NTs, while the band gap of the catalyst was reduced significantly from 3.22 to 2.68 eV. The catalysts showed an excellent photocatalytic performance towards the hydrolysis of AB for H2 production. Thus, the H2 production rate of Cu0.64Ni0.36-TiO2 NTs reached 5763.86 mL g−1 min−1, with a total turnover frequency (TOF) of 15.90 mol H2 (mol cat)−1 min−1 for a loading volume of metal particles of 5.25 wt%. The results presented herein demonstrate that TiO2(B) can be a potential photocatalyst for effective H2 production, and also provide a cheap and effective approach to improve the light-to-H2 energy conversion.