Advanced Materials Research Vols. 284-286

Abstract: Titania nanotube arrays were fabricated in deionize water and glycerol mixed electrolyte containing a certain amount of NH₄F. Three different polishing methods were used for pretreatment of Ti substrates: polished by hand with abrasive paper, by polishing machine, or by chemical polishing fluid (HF:HNO₃=1:4, in volumetric ratio). The morphology of three different samples were imaged by scanning electron microscopy, and their photoelectrical properties were studied as well. Experimental results showed that Titania nanotube arrays grown on the Ti substrate and polished by polishing fluid has highly-ordered and well-defined nanotube structure. The effects of anodization potential and duration on synthesis of highly-ordered TiO₂ nanotubes were also studied in this paper. Both the layer thickness and nanotube diameter linearly increase with the increasing potential. The layer thickness also increases with prolongation of anodization time. By optimizing the preparation conditions, we can successfully control the geometrical structure of TiO₂ nanotube arrays with diameters in the range between 50 and 200 nm and the layer thickness between 800 and 2000 nm.

Abstract: The Vetier (Vetiveria zizanioides) cellulose micro/nano fibrils (VCMNFs) were isolated by high intensity ultrasonication (HIUS). The morphology and diameter distribution of cellulose fiber and micro/nano fibrils were investigated by optical microscopy, scanning electric microscopy (SEM) and laser diameter analysis instrument. The range of diameter distribution of micro/nano fibrils was from 0.24 μm to 426 μm. With the variation of treating amplitude and time by HIUS, the extent of fibrillation and diameter distribution were different. There were significant changes of diameter distribution treated at amplitude of 90% and 30 min or 60 min and the diameter distribution was showed from 7.0 to 80 μm.

Abstract: Carbon-encapsulated copper nanoparticles were synthesized by a carbon arc discharge method. The particles were characterized in detail by transmission electron microscope, high-resolution transmission electron microscopy, thermogravimetric and differential scanning calorimetry. The result showed that the outside graphitic carbon layers effectively prevented unwanted oxidation of the copper inside. The dispersion behaviors and thermal conductivity of Carbon-encapsulated copper nanoparticles in water with different dispersants were investigated under different pH values. The results showed that the dispersion and thermal conductivity enhancements of Carbon-encapsulated copper nanoparticles nanofluids are higher than that of copper nanoparticles.

Abstract: Au/Co₃O₄ catalysts were prepared by a co-precipitation method and characterized by inductively coupled plasma-atomic emission spectrometry (ICP-AES), transmission electron microscope (TEM) and X-ray diffraction (XRD). The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol was investigated over Au/Co₃O₄ catalysts using molecular oxygen as oxidant. These catalysts showed higher activities as compared to the pure Co₃O₄ under the same reaction conditions_.

Abstract: Effect of pH value and dispersant of polyethylene imine (PEI) on dispersion of nano TiN in ethanol liquid was investigated by sedimentation volume and viscosity, surface electric characteristic of particles was measured by Zeta potential. Results showed that pH value and PEI concentration had an important effect on dispersion of nano TiN. Excellent dispersibility was obtained through adjusting PEI amount and pH value. It was found that PEI was an efficient dispersant for nano TiN to disperse in ethanol liquid. The dispersibility follows by electrostatic and space steric stability mechanism.

Abstract: By applying nonequilibrium Green’s function formalism combined first-principles density functional theory, we investigate the electronic transport properties of the azobenzene -based optical molecular switch with different substituents. Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.

Abstract: N-doped TiO₂ powders have been prepared by solvothermal synthesis using TiCl₃ aqueous solution as precursor. The as-synthesized powders are composed of anatase and rutile and show light-yellow in color. The grain size is ranged from 10.3 nm to 19.1 nm by Scherrer's method and the specific surface area is ranged from 21 m²/g to 122 m²/g. X-ray photoelectron spectroscopy (XPS) results indicate that N atoms have been doped into the lattice of TiO₂. Ti-N bonding and radical groups such as ×OH were detected on the surface of the powders. The synthesized N-doped TiO₂ powders shows excellent visible-light photocatalytic activities and their absorption edge have been red-shifted to 560 nm.

Abstract: The nano-indentation response and the friction and wear properties of the CNx/SiC (carbon nitride /silicon carbon) double layer thin films (SiC films as interlayer) deposited on nanocrystalline titanium substrate using magnetron sputtering technique at room temperature were investigated. The results show that the CNx films exhibited a low nano-hardness of 8.0 GPa and Young's modulus of 55.0 GPa but a high hardness-to-modulus ratio of 0.146. As sliding against Si₃N₄ (silicon nitride) ball under Kokubo simulation body fluid (SBF) at room temperature, the CNx films exhibited the superior tribological properties with the friction coefficients of about 0.1 and the special wear rate of about 1.6×10⁻⁶ mm³/Nm.

Abstract: Nanocrystalline MgSeO₃ was synthesized by method of ultrasonic precipitation, and was determined by X-ray powder diffraction patterns and transmission electron microscope. Photocatalyst behavior of MgSeO₃ has been studied by decomposing organic acid black dye.

Abstract: I theoretically investigate the spin Polarization and transmission of the electrons in a nanostructure consisting barriers with periodic, parallel and also anti parallel magnetization .also I investigate polarization when distance between barriers is constant, or is increased, or is decreased periodically. These observable quantities are found to be strongly affected by both the magnetic configuration and the number of the periodic magnetic barriers. When the number of periods increases, in parallel magnetization for periodic increasing distance the polarization is enhanced so in parallel configuration it is better that distance between barriers to be increasing periodically. I investigate Polarization in these configuration in both delta function approximation and modulated magnetic barriers in x direction. This Polarization can be used in spintronics device.