Applied Mechanics and Materials Vol. 492

Abstract: μc-Si:H thin films have been deposited on the 7059 glass substrate by RF-PECVD. Effects of film thickness on structure and properties of Si thin films were investigated by XRDRamanUV-Vis and precision multimeter. Experimental results indicated that uniform dense microcrystalline silicon thin films can be prepared by rf-PECVD, silicon thin films transferred from a-Si:H to μc-Si:H along with film thickness increased. For μc-Si:H, XRD spectrum occurred (111)(220) and (331) peak, grain size and crystalline volume fraction increased with thickness enhanced, arrived at 82%; optical band gap of μc-Si:H is 2.0~2.36eV and decreased when thickness increased, the transmittance was added firstly and then reduced with film thickness increased, the transmittance curve occurred redshift;the photosensitivity of the thin films was improved firstly and then decreased with thickness increased, which was highest at 104 quantity in the transition zone from a-Si:H to μc-Si:H.

Abstract: Six interatomic potentials based on Buckingham potential form for yttria-stablized zirconia have been critically assessed by predicting lattice constants, dielectric constants, and elastic properties using the mean-field approach. The content of Y₂O₃ is set to the range from 8 to 24 mol%. It has been found out that no potential can reproduce all the fundamental properties. Taking all the simulation and comparison results into consideration, the potential of Butler (1981) displays the highest fidelity, and the potential of Lewis (1985) shows the widest range of applicability.

Abstract: The direct electrochemical reduction of solid titanium dioxide (TiO₂) is conducted in [BMIM]BF₄-CaCl₂ ionic liquid (IL) at 100 °C using sintered TiO₂ as cathode and graphite rod as anode at an electrolysis potential of 3.2 V. Cyclic voltammetry is used to investigate the mechanism and feasibility of the direct electrochemical reduction of solid TiO₂ in [BMIM]BF₄-CaCl₂ IL at 100 °C. The surface morphologies of the cathode are examined by scanning electron microscopy（SEM）. The crystal phase structure of the cathode is examined using a D8 Advance X-ray diffractometer(XRD). The results indicate that the direct electrochemical reduction of solid TiO₂ in [BMIM]BF₄-CaCl₂ IL is feasible. A significant increase in conductivity is obtained by doping graphite into the cathode, thereby enhancing deoxidation. TiO₂ reduction is conducted step by step, from outside to inside, and from high to low valence variation.

Abstract: Polycrystalline ferrites powders samples: Ni_0.6Cu_0.4Fe₂O₄ were synthesized by using metal nitrates and freshly extracted egg white, all the samples were sintered at 500°C,520°C, 550°C, 580°C and 600°C for 3h,6h,9h, respectively. The better synthesis conditions were investigated by analyzed the effect of sintering temperature and soaking time on structural, grain size and magnetic properties using X-ray diffraction (XRD), laser grain size analyzer (LPSA) and vibrating sample magnetometer (VSM). From the above analysis, the better synthesis conditions is set two insulation work steps: First at 240°C for 1h, then heating to 440°C for 2h, finally sintering at between 520°C and 550°C for 6h.

Abstract: To overcome the overcoming of agglomeration and reclamation of nanoparticulate materials, it is imperative to synthesize nanosized materials with other morphologies. Fe₃O₄ nanotubes were synthesized by using anodized aluminum oxide as template under microwave assistance by tuning the deposition mechanism in this work. The obtained nanotubes were characterized by the means of XRD and SEM. Its magnetic property was also investigated. Results show that tubes are of the spinel structure, a layer of about 30 nm Fe₃O₄ was deposited attaching to the AAO wall, and the nanotubes possess good magnetic performance.

Abstract: Pure Ni coating and multi-layered Ni-P coatings were deposited on sintered NdFeB magnets by ion beam sputtering and electroless plating to improve the corrosion resistance of magnets, respectively. The structure and preferred growth orientation, surface morphology, the adhesive strength between coatings and magnets, and corrosion properties of samples were investigated by XRD, SEM, high-low temperature shock test and potentiodynamic polarization curves, respectively. It was found that electroless Ni-P coatings are amorphous with nodules distributed, Ni coating deposited by ion beam sputtering is crystalline and spherical Ni grains are densely packed. Ni coating deposited by ion beam sputtering can provide better protection for sintered NdFeB than that of electroless Ni-P coating.

Abstract: In present work, two conductive filler (carbon fiber with Nickel (Ni) coatings and carbon fiber with Nickel/Fe₃O₄ nanoparticle (Ni/Fe₃O₄-NPs) composite coatings) were prepared by electrodeposition. Microstructure observation indicated that the coatings were deposited uniformly on the surface of fiber. Vibrating sample magnetometer (VSM) and electromagnetic interference (EMI) shielding test showed that the two conductive filler has good saturation magnetization and EMI shielding effectiveness.The conductive filler of carbon fiber with Ni/Fe₃O₄-NPs composite coatings was more excellent. They are promising for application in electromagnetic shielding materials.

Abstract: The electronic structure of ZnO is calculated by using an accurate full-potential linear plane-wave based on the density function theory and WIN2K package. The curves of energy band and density of states of ZnO are gained. The energy gap is 0.9eV that is better some of the computed results by theory approaches and smaller than the experimental value obtained by X spectra. After analyzing it is known that the coulomb repulsion between 3d state of Zn and 2p state of O is very strong leading to the increase in the energy of O2p and the energy gap become smaller.

Abstract: Porous titanium dioxide film is an important photocatalyst. To bridge the gap between the application and traditional preparation of porous TiO₂ film, an approach was developed to achieve porous TiO₂ film by oxidization. SEM and XRD were used to characterize the morphologies and crystalline structure. Photodegradation of methyl orange was performed to investigate the photovoltaic performance. The results reveal: (i) the film obtained by oxidization has irregular porous structure with many protuberances on its surface, pore diameter ranging from 20 to 300 nm, and an average thickness of 40 μm, while that fabricated by potential anodization was highlyordered with pore diameter of about 50 nm and thickness of about 6 μm; (ii) the former has anatase structure after being calcined, while the latter contains anatase and titanium; and (iii) the former has higher adsorption and photocatalytic activity than the latter.

Abstract: A glass powder of the SiO₂-Al₂O₃-K₂O-Na₂O system was added to fused silica particles to form composite green compacts by tape casting. This procedure was able to lower the sintering temperature of the fused silica particles making the composites suitable for being co-fired with the silver-palladium (Ag-Pd) paste commonly used as a conductive circuit in several microwave applications. The resulting new ceramic composite with the composition of 50 wt% fused silica and 50 wt% glass (brand name: TC-3) had a low dielectric constant and a low loss tangent of 2.7 and 2.5-3.7 x10^-3 , respectively, and was able to be co-fired with the Ag-Pd conductive paste at the temperature of 895 °C, resulting in a potential low temperature co-fired ceramic (LTCC) system for microwave applications.