Jianling Zhao

In situ templated synthesis of anatase single-crystal nanotube arrays

Anatase single-crystal nanotubes were obtained using an in situ templated method. First, highly ordered titania arrays were formed through an anodization process in H(3)PO(4) electrolytes containing 0.5 wt% HF. Under optimized conditions titania nanotubes with a diameter of up to 100 nm and a length of up to 1.1 microm were prepared. Second, the crystallization and stability of the titania nanotubes were studied in air at elevated temperatures. Anatase single-crystal nanotubes were fabricated after annealing the sample in air at 450 degrees C. The anatase single-crystal structure was verified by selected area diffraction pattern and HRTEM images.

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.

Mechanism study of self-organized TiO2 nanotube arrays by anodization

Based on analysis of the current–time curve and observation of surface morphology including top, cross-section, bottom and substrate views by scanning electron microscopy (SEM), a new growth, dissolution–breakdown model, of self-organized titania nanotube arrays is presented. By this model, many phenomena raised during anodization are explained, such as the sharp decrease of current in initial period, current transient, occurring of ridges on tube walls, and formation of not pores but tubes etc. Furthermore, the reason for the occurrence of a porous structure, the balance between internal energy and surface energy, was proposed too. This study may also shed light on the formation of porous oxide films on other valve metals.

Blue emitting BCNO phosphors with high quantum yields

The blue emitting BCNO phosphors with high quantum yields were prepared at 625 °C using boric acid, melamine and hexamethylenetetramine as raw materials. The BCNO phosphors have turbostratic boron nitride structure and consist of nanocrystallites 5 nm in size. The emission and excitation spectra can be tuned by the contents of raw materials and sintering temperatures. The quantum yields of BCNO phosphors can be up to 99% with increasing boric acid. The FTIR spectra suggested that the quantum yield can be improved with increasing strength of B–N and B–N–B bonds, and formation of B–O–B bonds, while it decreased with enhancement of CC bonds. The emission decay curves indicated that the decay process was related to two luminescence centers corresponding to carbon and oxygen impurities. In addition, the high temperature emission spectra disclosed that the nitrogen vacancy would participate in the blue light emission process at a certain heating temperature. The blue emitting BCNO phosphors with high quantum yields have great potential application in luminescence and display areas.

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.

Spectral properties and luminescence mechanism of red emitting BCNO phosphors

Red emitting (λem = 620 nm) BCNO phosphors were synthesized at 650 °C with solid state reaction method using boric acid and hexamethy lenetetramine as raw materials. The BCNO phosphors have turbostratic boron nitride structure and particle sizes are in micro scale. Carbon and oxygen elements were bonded to boron and nitrogen to form BCNO phosphors. The emission peaks were shifted from blue light (420–470 nm) to red light (590–620 nm) with increasing sintering temperature, heating time and the ratio of boric acid to hexamethy lenetetramine, which was induced by partially formed BCNO and completely formed BCNO phosphors. The decay curves and emission spectra indicated that the red emission was induced by two luminescence centers, corresponding to longer lifetime τ1 and short lifetime τ2. The ultraviolet visible absorption spectra disclosed that the optical band gap was changed from 1.75 eV to 2.0 eV with different preparation conditions. The high temperature emission spectra suggested that the nitrogen defects levels served as electron traps and attended the red emission. The luminescence mechanism of BCNO phosphors was stated by a simplified energy level diagram. The red emission BCNO phosphors have good thermal stability and great potential application on lighting, display, solar cell and biomedical fields.

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.

Synthesis of nanoporous spheres of cubic gallium oxynitride and their lithium ion intercalation properties

Cubic spinel structured gallium oxynitride has been synthesized through the reaction of metallic gallium and water in the presence of organic ethylenediamine. The relative content of the mixed solvent of water and ethylenediamine controls the product morphology and structure. A novel well-defined nanoporous structure has finally been obtained, whose large surface area and peculiar surface chemistry will generate novel physical and chemical properties. As an example, lithium intercalation properties for prospective applications in lithium ion batteries are demonstrated in this work.