Advanced Materials Research Vols. 284-286

Abstract: V-MCM-41 molecular sieve with high vanadium content has been prepared by the atrane route. Gas phase partial oxidation of toluene to benzaldehyde on the V-MCM-41 molecular sieves catalysts was studied. The structure and characteristic of catalyst were characterized by means of XRD, UV-vis and so on. The experimental results showed that the vanadium content in the framework related to mole ratio of silica to vanadium. The vanadium content in the framework was the highest, when the mole ratio of Si to V was 30. And the vanadium in the framework may be active centers of catalytic oxidation of toluene to benzaldehyde. Under the condition of atmospheric pressure, mole ratio of Si to V 30, space velocity 800 h^-1, n(air):n(toluene)=5 and reaction temperature 450°C，the conversion of toluene, selectivity to benzaldehyde and its yield were 20.8%, 41.8% and 8.7% respectively.

Abstract: The microencapsulated phase change material (PCM) slurry is a kind of mixture with the PCM microcapsule particles and water. The actual PCM in the microcapsule is composed of several kinds of paraffin waxes (mainly nonadecane), and the membrane is a type of melamine resin. This study is focused on preparation, characterization, and thermal properties of the microencapsulated (PCM) slurry. The microencapsulated PCM particles are prepared by in-situ polymerization method. Four different levels of mass concentration C_m of the PCM will be used such as C_m=10%, 20%, 30% and 40%, respectively. The diameter of the particles is distributed in the range of 0µm~4.5µm, and most (61%) of them occur in the range of 0.5µm~1.5µm. The average volumetric diameter of the PCM microcapsule particle is about 0.78µm. And the average membrane thickness is about 11nm.Thermal properties of the microencapsulated PCM slurry are determined using differential scanning calorimeter (DSC). From DSC analysis, the melting and freezing temperatures and the latent heats of C_m=30% are measured as 38°C and 25°C, and 37.9 kJ/kg, respectively. The rheological properties are measured by a rotating cylinder type of rheometer, which the slurry shows the pseudo plastic non-Newtonian fluid behavior with the power-law fluid index n.

Abstract: Using the specially designed mechanochemical ball-mill equipment, the ultramicro molybdenum nitride powders were prepared from pure molybdenum powders in ammonia atmosphere at room temperature by high-energy ball milling. The results show that the mass ratio of grinding media to powder was 4:1 and after milling for 30 h, the Mo₂N of fcc structure was obtained, and the average particle size of powders was around 100 nm. It is found that the chemisorption of ammonia onto the fresh molybdenum surfaces created by milling was the predominant process during solid–gas reaction，and the change of Mo electronic undersaturation induced by the grain refining also accelerated the bonding between Mo and N. The coating was formed on the 40Cr steel base using plasma spray method by mix Ni60 alloy powders and ultramicro Mo₂N powders of 5wt%, 10wt% and 15wt%, respectively. Coating abrasion test under the condition of dry-grinding , 2h wear time and 300N test load showed that the wear-resisting property of coating added with ultramicro Mo₂N powders could be improved greatly, and the wear-resisting property of coating increased with the increase of Mo₂N content. In the abrasion process, the evenly distributed ultramicro Mo₂N particles play the dispersion strengthening and self-lubricating role in the coating.

Abstract: In this paper, the properties of chitosan (CS) nanoparticles (CS NPs) and Bovine Serum Albumin (BSA) loaded chitosan nanoparticles (BSA-loaded CS NPs) prepared with sodium tripolyphosphate (TPP) at different pH values were discussed. In addition, BSA encapsulation efficiency, zeta potentials and size of CS NPs and BSA-loaded CS NPs were characterized. The results indicated that sizes of CS NPs presented “V” change along with increase of pH values, while the size of BSA-loaded CS NPs showed “U” shape change. BSA encapsulation efficiency reached the biggest value when the pH value was 5.5. Zeta potentials of CS NPs and BSA-loaded CS NPs kept going down when the pH values were increasing, and positive potential of CS-loaded BSA CS NPs became higher than that of CS NPS when the pH value was more than 5.5. BSA-loaded CS NPs prepared at pH 5.5 exhibited regular and close to spherical in shape under transmission electron microscopy (TEM) sight.

Abstract: Zinc oxide (ZnO) microrods were grown by the floating zone method, the as-grown ZnO microrods have uniform size. Scanning electron microscope image reveals that the ZnO microrods are grown with a hexagonal structure, well faceted ends and side surfaces. Most of ZnO microrods have diameters of about 20-30 mm and lengths of about 1-2 mm. Polarizing microscopy image of ZnO microrods shows that they have high crystal quality. The X-Ray diffraction pattern shows that microrods have vertical orientation and the crystal structure of ZnO is wurtzite type. At low exciting intensity, ultra violet range emission was found and the growth process of ZnO microrods was discussed.

Abstract: The nano-sized silver particles were prepared by flow-levitation technique firstly, and then the particles were compacted with warm-vacuum-compaction method to fabricate the nanocrystalline silver with average grain size of 18.5 nm. The influences of experimental parameters, such as pressure, temperature and pressure duration, upon the density and microhardness of the nanocrystalline silver were investigated in detail. The experimental results show that both the density and microhardness of the nanocrystalline silver increase significantly with higher pressure or elevated temperature, while the duration of pressure has a little effect to the density. The average microhardness of the as-prepared nanocrystalline silver is 1.25 GPa, which is 3 times higher than that of coarse-grained silver.

Abstract: Basing on the introduction of Multidisciplinary Design Optimization (MDO), Multidisciplinary Design Optimization method based on iSIGHT is given, which includes one general process model and one optimization algorithm. Optimization of one bearing is selected as one example. According to its application, it approves that MDO methods can solve practical engineering problems more effectively because of comprehensive consideration of the internal problems in all disciplines.

Abstract: The inorganic electrophoretic particles easily sedimentate and are not preferably dispersed in medium because their density is relatively big. Spheric and hollow TiOB_2B particles were prepared against the core-shell polymer latex particles via a simple wet-chemistry route, using Ti(OBu)B_4B as a precursor. The particles¢ morphology was observed by atom force microscopy (AFM) images, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The products were characterized by X-ray Diffraction (XRD) and TEM. TEM showed spheric and hollow particles with a diameter around 290 nm. The density (in the atmospheric pressure, 20°C) of TiOB_{2 B}was 2.21 g∙mLP^-1P. Results showed that hollow framework could reduce the density of particles. The Zeta potentials were determined by micro-electrophoresis apparatus. TiOB_2B particles had good electrophoretic property, and the Zeta potential was 5.25 mV.

Abstract: TiO₂ thin films were prepared successfully by dip-coating technique and sol-gel method on quartz glass plate. The photocatalytic properties of the fabricated TiO₂ thin films to decompose the Methyl orange(MO) solution with or wihtout ultrasonic vibrations were investigated. Experimental results showed that TiO₂ thin films had best photocatalytic properties when it was coated four layers and calcined at 500°C. The sonophotocatalytic technology is more effective for the decomposition of methyl orange than single TiO₂ photocatalytic,the degradation rate increased by 35%.In addition,the degradation rate is affected by reaction time, the impact of ultrasonic power.

Abstract: CuCr₂O₄ nanopowders were successfully prepared by co-precipitation technique from alcohol-aqueous system and applied for photo-anodes of dye-sensitized solar cells (DSSCs). The synthesized CuCr₂O₄ particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectrum (UV-vis) and thermo-gravimetric/differential Scanning Calorimetry (TG-DSC). It was shown that, with the sintering temperature of 1000 °C and the amount of PEG-400 of 1.5 wt % , the size of primary crystal grain was about 48 nm. The CuCr₂O₄/TiO₂ composite exhibit high absorption ability in the spectral range 600 ~ 900 nm, which leading to a much higher conversion efficiency (η) of the solar cell in comparison with the pure TiO₂ film electrode.