Advanced Materials Research Vols. 476-478

Abstract: β-Sialon/ZrO2 composites were prepared using 10 wt. % β-Sialon powder (where the z =1, 2, 3, respectively) and 90 wt. % ZrO2 powder as the starting materials. The effects of the Z value of β-Sialon on the bulk density, apparent porosity, water absorption rate, room temperature modulus of rupture, thermal shock resistance, microstructure and composition of the composites were investigated. The microstructure of sintered specimens was analyzed by scanning electron microscope (SEM), and X-Ray diffraction (XRD). The results revealed that with increase of the Z value of β–Sialon, bulk density gradually increased, apparent porosity and water absorption rate gradually decreased. The specimen possessed a maximum MOR (71.46MPa) when the z=2. In carbon embedded condition, the residual strength ratio of the specimen reached 60% and the lowest thermal expansion rate was obtained (0.55%) when the z=1. The phase compositions were cubic ZrO2 (c-ZrO2) and monoclinic ZrO2 (m-ZrO2). β-Sialon/ZrO2 composites exhibited overall optimum performance when the z equals 2

Abstract: By means of the reactive magnetron sputtering method, a series of Nb–Si–N composite films with different Si contents were deposited in an Ar, N2 and SiH4 mixture atmosphere. These films’ chemical composition, phase formation, microstructure and mechanical properties were characterized by the energy dispersive spectroscopy, X-ray diffraction, transmission electron microcopy, atomic force microscopy and nanoindentation. In the Nb–Si–N films, 3 distinct concentration regions have been observed depending on the Si content. Based on the three concentration regions, a three-step model is proposed for the film formation of the Nb–Si–N thin films. This model correlates nanoscale structures with macroscopic properties of the films.

Abstract: Vanadiunm carbide (V8C7) nanopowders were prepared by the solution-derived precursor method, ammonium vanadate (NH4VO3) and glucose (C6H12O6) were used as raw materials. The samples were characterized by TG-DTA, XRD and SEM. The results show that the weight of the sample reduces rapidly before 600°C (about 25 wt.%), but it changes very slowly (about 1.0 wt.%) after 600°C. The DTA curve mainly includes 5 endothermic peaks and an exothermic peak which are corresponding to the peaks of 110°C, 300°C, 348°C, 677°C, 1000°C and 509°C, respectively. When the carbon content between 24 wt.% and 30 wt.%, the samples mainly consist of V2O3 and VC1−X (1−X = 0.66–0.88). When the carbon content is 32 wt.%, the sample includes a main phase (V8C7) and a second phase (V2O3). When the carbon content reaches to 36 wt.%, the single-phase V8C7 powder can be obtained. The SEM results show that major powders exhibit good dispersion and are mainly composed of particles with a mean diameter of ~200 nm.

Abstract: Sliver nanoparticles were synthesized in organic phase through two-phase reaction procedure using DMF as a reducing agent and oleate as a ligand without addition of phase transfer agent.

Abstract: The face strain and interlaminar stress of bamboo plywood were studied through finite-element analysis (FEA). The study results showed that under the action of centralized cross line load, the upper face strain (compression strain) of the board gradually increased and the lower face strain (tensile strain) gradually decreased from the middle section to two ends of the board. The stress components（σz、τxz、τyz）between the each two layer, in the thickness direction, were symmetrical on the plane y＝37.5mm，and reached maximum nearby the free edges, but were nearly zero in the board. Within the limit of small deformation，the stress components between the each two layer, in the thickness direction, increased linearly with the load increasing, which resulted in the interlaminar cracking of the product at the free edges.

Abstract: The effect of supercritical carbon dioxide emulsion (Sc-CO2-E) on the smooth and microhardness of nickel film electroplated using Watts bath was studied in this paper. Morphology of nickel film electroplated with Sc-CO2-E was found much uniform. Microhardness of nickel film electroplated with Sc-CO2-E was higher than that of nickel film electroplated through conventional method. A increasing of microhardness was found for nickel film electroplated through Sc-CO2-E when increasing experimental pressure from 12 to 18 MPa, and the smooth of nickel film be promoted. This was because of higher hydrogen solubility and higher mobility in Sc-CO2-E. Grain size of nickel film electroplated with Sc-CO2-E was found to be refinement.

Abstract: An optical-electronic system for Faraday rotation measurement is designed and constructed to evaluate the verdet constant of magnetic -optical glasses. The works include the optical bench setup and development of software. PbO-Bi2O3-B2O3 glasses systems were fabricated and characterized by using the self-constructed optical bench and the obtained Verdet constants @632.8nm for glass PBB1 was verified by using a commercial powermeter (as detector). The developed measurement system showed characteristics of low cost, small size and accurate.

Abstract: The influence of different negative current density on oxidation film thickness and dense layer thickness was studied. According to the results and experimental phenomenon，the negative current was adjusted steply, and the dense layer with high rates for 70% of micro-arc oxidation film was achieved. EDS and X-ray diffraction were used to analyse the composition and phase structure of the surface layer and the dense layer of oxide film .The friction coefficient and wear of the surface layer and the dense layer of oxide film were measured by wear machine measurement ,and were compared with hard anode oxidation film. The results show that the oxidation film thickness and the dense layer thickness increase with the rising of negative current density.The micro sparks can be avoided out, through adjusting negative current and a high dense layer of MAO film is got .The dense layer of MAO film contains only oxygen and aluminum elements, so it can not be effected by the electrolyte composition .The alpha Al2O3 level of the dense layer is higher than that of the surface layer, and the friction coefficient and abrasion loss of the dense layer is the lowest among the surface layer and hard anode oxidation film.

Abstract: Grain size, shape and orientation play an important role on the deformability of micro workpiece as the geometrical dimensions approach to a characteristic scale in micro-forming process. This paper addresses the three-dimensional (3D) finite element (FE) model with weighed centroidal voronoi diagram (WCVD). Steady-state grains are generated when the voronoi generating points approach the grain centroid utilising a simplex integration algorithm. As a result of the centroidal process, the topological features of grains advance the uniform and steady state gradually, which may cause a decrease of interfacial energy. The grain size distribution is compared between the 3D domain and random cross-sectional plan. The effects of centroidal process on the distributions of grain size and number of grain corners, facet and edge are analysed.

Abstract: The catalytic reforming of methane with carbon dioxide using Pd promoter on 1% Ni/20%TiO2-P25+80%α-Al2O3 was investigated. An experimental study was carried out using the catalyst prepared by impregnation method. The catalysts were dried at 120°C and calcined at 900°C. The reforming reactions were carried out using CO2/CH4/N2 feed ratio of 5/5/1, F/W=44 ml/min.gcat and reaction temperature of 700°C. The effect of nominal load of Pd ranging from 0.0 to 0.48 was studied by evaluating catalyst activity, stability, coke and (H2/CO) ratio. The prepared catalysts were tested in micro reactor at atmospheric pressure. The effluents were analyzed using an online gas chromatography equipped with a thermal conductivity detector. EDS and TGA for the fresh and spent catalysts were evaluated. Results indicate that the addition of small amounts of Pd is preferable in terms of activity and carbon deposition than higher Pd loading. For instance, 0.01%Pd gives a conversion of 78.4 for CH4 and 4.9% deactivation factor. While, 0.48%Pd gives a conversion of 75.6 for CH4 and 29.9% deactivation factor. Thus higher loading of Pd causes the catalyst to show poor performance with lower conversion and higher carbon formations. It can be concluded that Pd promoter has an optimal concentration with respect to the active metal of the catalyst beyond which the performance deteriorates.