Advanced Materials Research Vols. 562-564

Abstract: A coarse-grained force field for poly (methylmethacrylate-b-2-vinyl pyridine) is developed based on the Iterative Boltzmann Inversion method. The proposed coarse-grained model, successfully reproduced the properties of the polymer melts obtained from atomistic simulations, may provide an efficient way to study their mechanical properties and self-assembly behaviors.

Abstract: Zinc whiskers threaten the safety of electronic components due to their electrical conductivity. Factors that control zinc whisker growth are still unknown. The aim of this study was to investigate the effect of current density (1.5, 2.25 and 3.0 A/dm2) on the formation of zinc whiskers, and to relate this to the microstructure of the deposit. Scanning Electron Microscopy (SEM) analyses show that the surface morphologies of deposits became rougher when current density increased; however, nodule density increased from 25/mm2 to 53/mm2 when current density increased from 1.5 to 2.25 A/dm2, and it decreased to 24/mm2 when current density increased to 3.0 A/dm2. X-ray diffraction analyses (XRD) show that the preferred orientation of deposits remain when current densities increased from 1.5 to 2.25 A/dm2, while it changed to when current density increased to 3.0 A/dm2. Results show that zinc coatings electroplated at 2.25 A/dm2 may have greater risk of whisker growth then that electroplated at 1.5 or 3.0 A/dm2.

Abstract: The shape-memory effect (SME) and corrosion resistance of an Fe-20Mn-5Si-10Cr-5Ni- 0.7V-0.2C alloy, before and after aging, were investigated. The results showed that VC precipitation and bending temperatures obviously affect the alloy’s SME. Nearly perfect SME (90.2% of initial 4% bend) was achieved when the 2h aged sample was deformed at 223K. At the meantime, the electrochemical impedance spectroscopy (EIS) showed that the alloy, aged for 2h to 4h, exhibited the worst corrosion resistance in the research system related with the fine VC precipitates. The morphology and distribution of VC were observed by SEM.

Abstract: In a deformation progress of a polyvinyl chloride sheet, the coupled deforming heat is recorded by a thermal infrared imager. In order to have a real-time study for the variation regularity of the deforming temperature field distribution, all infrared images are imported into MATLAB software as digital data through a dynamic link routine compiled based on MATLAB and Windows. By utilizing a gradient-based transition region extraction algorithm and an interpolation algorithm, the high-resolution recognized and reconstructed infrared images are obtained from original blurring images recorded in thermal infrared imager. The variations of temperature distribution are studied combining with the test data based on MATLAB.

Abstract: Structural and optical properties of MgxZn1-xO (x=0.23) thin films grown by radio frequency (R.F.) magnetron sputtering and annealed with different temperature (from 100°C to 400°C) are reported. The films were single-phase, highly c-axis oriented and wurtzite structure. The transmission spectra, recorded in the visible range, reveal a high transmission coefficient (about 95 %) in the obtained films. Besides, when the annealing temperature is 100°C, the crystalline grains are smooth, compact and uniformly distributed. As the annealing temperature increases from 100°C to 400°C, the crystalline grains get larger, but the annealing temperature does not influence optical transmittance obviously.

Abstract: Fuzzy ball material which imitating the structure of bacteria have been tested and developed as a new lost circulation material. The fuzzy plugging theory include three pressure distribution methods: the pressure decomposition filling mechanism, the pressure reducing filling mechanism and the pressure support filling mechanism. Fuzzy ball material relies on its own particular structure, achieving full-size sealing and self-adjustment to match the porous media. Fuzzy ball working fluids can be prepared without auxiliary equipment and its non-weighted density is 0.85~1.0g/cm3. Its density can be up to 1.2g/cm3 when it is weighted by inert materials to meet the need of near/under balanced drilling. Indoor test showed that novel working fluids have significant inhibitive capacity and sealing characteristic. There are three properties of fuzzy three ball working fluids: inhibitive capacity, anti-temperature capacity and sealing characteristic. Fuzzy ball working fluid has been successful applied in hundreds of wells to solve the problems such as collapse, severe losses and etc.

Abstract: Reduction product of nitrite by Spherical sponge iron (SSI) was investigated through static state experiment combined with E-pH diagram of Fe-N-H2O system. In a certain range of pH and redox potential, the speciation of iron include Fe0, Fe2+, Fe3+, Fe(OH)₂ and Fe(OH)₃, and the speciation of N was NO₂, NO₃-, N₂, NH₄+ or NH₃ as the initial speciation of N was nitrite. pH in solution increased to above 10 in 6min because of rapid erosion battery reaction of zero-valent iron. Moreover, the E value in solution declined quickly to the minimum and then increased slightly because of dissolution of oxygen from atmosphere. It was suggested that ammonium was the finial product during the reduction of nitrite by SSI. Nitrite removal from wastewater was related with escape of ammonia, which was gas state of ammonium, when the water solution was alkaline.

Abstract: This paper focuses on the microstructure change of bionic units, processed by the bionic laser, on vermicular cast iron, during the thermal fatigue tests. The results show that the microstructure of bionic units is uneven, and the thermal fatigue first occurs in the region with coarser microstructure on the surface of bionic units; the thermal fatigue failure mode of the bionic units is oxidizing, fracturing and peeling layer by layer.

Abstract: Silver-incorporated titania (Ag/TiO₂) nano-membrane were formed on the surface of domestic ceramic substrates by a sol-gel method with the use of tetrabutyl titanate and silver nitrate as precursors, acetyl acetone and nitric acid as a catalytic inhibitor, absolute ethyl alcohol as the solvent. In the same way, titanium dioxide (TiO₂) films were also prepared on the same ceramic substrates. The surface morphology and the crystal structure of the Ag/TiO₂ nano-membrane obtained through the method mentioned with different calcination treatment have been discussed by XRD, SEM, DRS and FTIR respectively. Compared with TiO₂ nano-membrane, the XRD analysis shows that no significant shift in the crystal structure is presented because of silver ion-doping. From SEM and EDS, it is shown that spheric silver particles are spread on the surface of the nano-membrane and the insights into the compositions were provided by FTIR. DRS analysis showed that the red shift of the fundamental absorption edge of titania could be caused by silver ion-doping.

Abstract: Silicon nitride powders were prepared via direct nitridation of silicon powders diluted with -Si₃ N₄ at atmospheric pressure. The nitridation temperature and time were ranged from1623K to 1823K and from 0 minute to 20 minutes respectively. Based on the relations between the conversion rate of silicon and the time at different temperatures, and using shrinking core model, a simple model for the reaction between silicon and nitrogen was derived. The model showed that the relations between the conversion rate of silicon and the time displayed asymptotic exponential conversion trend. Using this model, the kinetics parameters of nitridation of silicon powder at atmospheric pressure were calculated, including pre-exponential factor in Arrhenius equation, activation energy, effective diffusion coefficient, and the formula of the reaction rate constant.