Key Engineering Materials Vols. 609-610

Abstract: Micro-arc oxidation (MAO) coating was prepared in different electrolyte compositions on 6063 alloy and its characterizations were detected by X-ray diffractometer (XRD), scanning electric microscope (SEM), energy dispersive X-ray spectrometer (EDX) and Vickers hardness tester. Friction and wear behaviors of the coatings were tested without lubrication and the abrasion loss was measured after the friction test. The results showed that the MAO coatings, presenting rough and porous surface and high hardness, mainly consisted of α-Al₂O₃ and γ-Al₂O₃ phases. The composition of electrolytic solution had great influence on the coating morphology and its mechanical performance. Compared with the coating prepared in silicate and borate solutions, the coating prepared in aluminate solution had not only denser and smoother surface but also higher micro-hardness value and better abrasion resistance.

Abstract: Mesophase pitch and natural graphite flake were applied as raw materials to prepare the graphite materials by a hot-pressing technique at a relatively low temperature. In this work, the effect of mean size of natural graphite flake on physical properties and microstructure of the graphite materials were investigated. X-ray analyses, field emission scanning electron microscopy and polarized light microscopy observations indicate that the graphite blocks have highly preferred structural orientation perpendicular to the hot-pressing direction. Results shows that the graphite materials have a low electrical resistivity of 2.45μΩ·m and a high thermal conductivity of 498 W/m·K ,as well as a high bending strength of 26.71 MPa when the mean size of graphite flake in raw materials was 425μm.

Abstract: Taking antimony powder with 75μm of average particle size as raw material, the antimony nanoparticles were synthesized by mechanical ball milling. Crystalline structure, morphology and particle size of the antimony nanoparticles were characterized by XRD, TEM and FT-IR. The effect of milling mediums and ball milling speed on results antimony nanoparticles were studied using dry grinding and wet grinding methods. The results show that the antimony nanoparticles can be prepared successfully by wet process of ball milling. When the ball milling speed is 150 r/min and the milling mediums is a composites of distilled water and OP-10, the best antimony nanoparticles were prepared, which is high dispersibility and the average particle size is 10 nm.

Abstract: In the paper, the TiO₂ nanomaterials adopted the microcrystalline cellulose as the template by the template method and sol-gel method was prepared. Through the infrared spectrometer (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), the surface morphology, composition and the type of the samples were characterized respectively. The influence of the macro morphology of TiO₂ photocatalytic performance to use the reaction of decolorization and degradation of methyl orange as model was analyzed. The results showed that TiO₂ which was produced by the template of sallix fiber was Rod-shaped and the average diameter size of nanocomposite structure was 20.592 nm, which can provide a new method of producing other morphology of TiO₂.

Abstract: Single-phase delafossite type Mg-doped copper-chromium oxide thin films were prepared on c-sapphire, quartz glass and n-Si substrates by direct current (DC) magnetron sputtering using a CuCr_0.97Mg_0.03O₂ (CCMO) ceramic target, followed by post annealing at 800 °C in a nitrogen atmosphere. X-ray diffraction (XRD) revealed that the film deposited on c-plane sapphire was highly c-axis oriented, while the films on quartz glass and Si only showed weak (0 1 2) peak. The transparencies of the films on c-sapphire and quartz glass were over 60 % in the visible light region and the direct bandgap of both films were estimated to be 3.16 eV. The in-plane resistivities were 0.24 Ωcm and 7.68 Ωcm for the crystallized films on c-sapphire and quartz glass, respectively. The electrical property of the formed CCMO/n-Si junction was found to be rectifying with a ratio of ~15 at ±2 V.

Abstract: In this paper, nanocrystalline VO₂ thin film is fabricated by a kind method of two steps and its phase transition characteristics are investigated. The two-step method contains low-temperature reactive ion sputtering and post-annealing, and its process parameters determine the phase transition properties of fabricated VO₂ thin film. With optimized process parameters, VO₂ thin film with nanocrystalline structure can be successfully fabricated and has excellent phase transition performance for smart glass and optical switch.

Abstract: A post-drying thermal annealing method is proposed to successfully fabricate micro-/nanostructures with 9,10-diphenylanthracene (DPA). Through varying operating temperature, different morphologies from 0-D to 3-D of pure DPA self-assembly were achieved and studied by SEM, XRD and PL spectra. The morphology transformation mechanism was also investigated. These results indicate that varying annealing temperature is an effective way to control the supramolecular architectures of DPA. In addition, such in situ fabrication on a substrate will provide possibility for manufacture of electronic devices which normally require surface deposition of nanomaterials.

Abstract: In this paper, the microprism reflective structure is optimized by theoretical research and simulation calculations, and based on the current technology of V-shaped diamond blade manufacturing mode, an improved microprism retroreflective material is designed. By adjusting the intensity distribution and angle of the light cone, we can control the style of light cone which is formed by the reflected light for optimal reflective effect. The microprism reflective structure contains the positive unit and negative unit. The negative unit relative to the positive unit is rotated 60° for producing phase superposition to reduce the non-uniform of the material orientation. Cutting along a straight line by V-shaped diamond blade, the technology creates a plurality of higher-precision and smaller reflective elements and enhances the retroreflective performance. Meanwhile, the overall processing technology which reduces labor force greatly is beneficial to the cost control and highly practical during the fabrication process. Keywords: microprism retroreflective material, improvement and optimization

Abstract: Tetraethyl orthosilicate (TEOS), butyl titanate [Ti (OBu)₄] and aluminium isopropoxide were used as molecular precursor of ternary nanoSiO₂-Al₂O₃-TiO₂ materials. The influences of temperature and the dosage of compounds on the characteristic of ternary nanomaterials were investigated. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to investigate the characteristics of the nanomaterials synthesized by the sol-gel method. In addition, the adsorption of nanomaterials for different kinds of surfactants was also studied. Results revealed that the influences of temperature, compounds dosages and water on the size of ternary nanomaterials had a significant impact. With the increase of ammonia dosage, the concentration of the OH^- ion became higer, and system showed a faster reaction rate. The higer temperature of the system was, the larger size of the ternary nanomaterials was. Moreover, the higer tempreature woule also lead to divide into layer and precipitate. Optimal parameters can be chosen to prepare monodispersed ternary nanoSiO₂-Al₂O₃-TiO₂ materials. Results also showed that the surface characteristic of ternary nanoSiO₂-Al₂O₃-TiO₂ particles differed from nanosilica, which manifested in forms of the adsorption dosage of surfactants.

Abstract: Nanosized NaY molecular sieves with high crystallinity was synthesized using sodium silicate solution (industrial water glass) without the presence of additive via dynamic hydrothermal method. The influences of aging time of the seed-gel, the temperature and route of gelation, and the alkalinity of the feed-stock gel on the grain size, relative crystallinity and framework SiO₂/Al₂O₃ ratios of NaY nanoparticles were investigated by XRD(X-ray diffraction, XRD), SEM(Scanning electron microscope, SEM) and TEM(Transmission electron microscope, TEM). The results shown that the grain size could be effectively controlled by adding seed-gel of aging at 20°C for 4 days, and adopting the gelation route of putting sodium silicate solution into NaAlO₂ and NaOH mixed solution. The grain size and framework SiO₂/Al₂O₃ ratios decreased with reducing the alkalinity of synthetic system. The nanoNaY products with the grain size at a range of 82-105 nm and the framework SiO₂/Al₂O₃ ratios at 3.9-4.0 could be synthesized by optimizing the synthesis conditions.