Advanced Materials Research Vols. 393-395

Abstract: Coating and gradient structure can improve the quality of products, but growth-induced stress generates in the forming process of the coating and the gradient structure due to the existence of the defects and metastable phase. The existence of growth-induced stress can conversely affect the quality of the product, even lead to cracking and product failure. This paper shows the model of stress calculation according to the crystal structure’s defect theory.

Abstract: A high-definition imaging and processing system is presented, which consists of a color CMOS image sensor, SRAM, CPLD and DSP. The CPLD implements the logic and timing control to the system. SRAM stores the image data, and DSP controls the image acquisition system through the SCCB. The timing sequence of the CMOS image sensor OV9620 is analyzed. The imaging part and the high speed image data memory unit are designed. The hardware design of the imaging system and processing algorithm are given. Because the CMOS digital cameras use color filter arrays to sample different spectral components, such as red, green, and blue, at the location of each pixel only one color sample is taken, and the other colors must be interpolated from neighboring samples. We use the edge-oriented adaptive interpolation algorithm for the edge pixels and bilinear interpolation algorithm for the non-edge pixels to improve the visual image quality. This method can get high processing speed, decrease the computational complexity, and effectively preserve the image edges.

Abstract: Defect structure of ZnO determines the optoelectronic characteristics of ZnO crystal and film. The identification and modulation of the defect structure is the foundation of the manufacture of optoelectronic devices. Although a good deal of research has been carried out about intrinsic defects and doping defects in ZnO, it is difficult to obtain a conclusive result accepted by all. In the paper, ZnO film is prepared by sol-gel method and the defect structure is expressed by photoluminescent (PL) spectroscopy. Based on some basic rules the intrinsic defect structure of ZnO is confirmed and the interaction of impurity Li and intrinsic defect is discussed. At the same time, some new electronic levels are proposed. It is surprising that although there are fourteen peaks in PL spectra of ZnO film, almost all the peaks can be identified by these basic rules.

Abstract: A stable magnetic field was applied during hot press molding of low-density polyethylene (LDPE)/carbon black (CB)/ carbon nanotube (CNT) composites and HDPE/CB/nickel powder composites. The effect of magnetic field treatment on the temperature-sensing property of LDPE-based positive temperature coefficient (PTC) composites was investigated. Experimental results indicate that the magnetic field treatment can lead to an alignment of CNT and nickel powder in LDPE along the direction of the applied external magnetic field. The alignment of these filler particles can endow the composites with low room-temperature resistivity and high PTC intensity when the concentration of CB is decreased. The alignment also can significantly improve mechanical property and processability of the composites. Compared with CNT, nickel powder with strong magnetism has more sensitive response to external magnetic field and is much easier to align in LDPE. Addition of nickel powder is beneficial for developing PTC composites with excellent comprehensive properties.

Abstract: Polyvinylidene fluoride (PVDF)/Carbon nanotubes (CNTs) and PVDF/Organo-modified layered silicates (OMLSs) nano-composites were prepared by phase inversion technique. Maleic anhydride grafted PVDF (PVDF-MAH), were used to fine tune the interface. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to characterize the nanocomposites. Elastic modulus and creep resistance of the PVDF nanocomposites were evaluated according to ASTM D-638. The results showed that both CNTs and OMLSs were good candidates to reinforce the PVDF and the addition of PVDF-MAH enhanced the interface between nanoparticles and PVDF, leading to further increase of mechanical property.

Abstract: This paper studies the influence of adhesive dimensions on the transverse free vibration of the single-lap adhesive cantilevered beams. The researches are performed by employing software ansys .Efficient analytic results of natural frequencies and mode shapes of transverse free vibration of the beams are provided, corresponding to different adhesive dimensions of bonded thicknesses and bondlines length. Bondlines length has more significant influence on the transverse natural frequencies and the lap joint’s mode shapes of the beams than bonded thickness. The transverse natural frequencies decrease with a decrease in the bondlines length of adhesive, but do not appear to variation observably with a decrease in the bonded thickness. Bondlines length shorting, the lap joint has a sharper mode shape. Simultaneously, the lap joint of even mode shapes influences the dynamic response of the beams significantly. These results indicate a local crack in adhesive layers because of the existence of stress concentration.

Abstract: In order to reduce production cost of making H2, one of the key points was to reduce Pt loading in Pt/C catalytic electrode. In our study, a new type of Pt/C membrane electrodes, PtCu-LaOx/C composite structure, was manufactured by Ion Beam Sputtering (IBS) technology. These membrane electrodes were treated by different annealing temperature in vacuum furnace, and by different time in different concentration H2SO4 solution. The hydrogen evolution properties of these electrodes were tested by tri-electrode system, and were calculated results of their exchange current density (i0), decomposition voltage (Ed) and active specific surface area (ESA). It was found that PtCu-LaOx composite membrane electrodes with Pt loading less than 0.045mg•cm-2 (the electrode area) undergone treatment, whose Ed, i0 and ESA was -0.264(V vs SCE), 4.111mA•cm2 and 75.8926m2•g-1 respectively in balanced condition.

Abstract: The double perovskite Sr2FeMnO6 has been synthesized by the solid-state reaction method. X-ray diffraction and subsequent Rietveld refinement confirm that Sr2FeMnO6 has the double-perovskite structure with a cubic cell (a=7.726 Å) and space group Fm3m (No. 225) . The appearance of the superlattice reflection (111) indicates that Fe and Mn atoms alternatively occupy the center of oxygen octahedron in an ordered way. Based on magnetization hysteresis curve and ESR measurements, a ferrimagnetic to paramagnetic phase transition for the double perovskite Sr2FeMnO6 was observed, and the Neel temperature was determined to be TN ~475K. In paramagnetic phase above TN, the value of gyromagnetic factor was determined to be very close to 2.

Abstract: Magnetorheological(MR) materials, which consist of magnetic particles in a non-magnetic medium can be divided into three kinds: MR fluid, MR foam and MR elastomer (MRE),MRE is a new branch of MR materials whose mechanical property can be changed quickly and reversibly by the application of an external magnetic field[1]. In this paper, the new research, typical modeling and various experiments will be reviewed and discussed. So far MREs have been used in tons of scientific filed owing to their significant advantages and MREs will have more promising applications.

Abstract: studies were carried out to determine the principles of mechanical equipment coordination for large cross-section tunnel construction in combination with the tunnel construction practices within the sections under the charge of China Railway First Group Co., Ltd. on Wuhan-Guangzhou PDL and with a view to optimize the allocation of resources and improve the efficiency of large cross-section tunnel construction. Directed to different procedures such as excavation, support, waterproofing, drainage and lining, the mechanical equipment coordination and operation mode of large cross-section tunnels on the passenger dedicated line were established and the mechanized working faces were formed, which provide experience and reference for the large cross-section tunnel construction of passenger dedicated lines.