Advanced Materials Research Vols. 239-242

Abstract: Salt fog corrosion test was employed to observe the corrosion behavior of welded joint of 7N01-T4 aluminum alloy of high-speed train. Tensile strength and hardness change after corrosion were tested and micro morphology was observed by metalloscope and LCSM. The results indicated that HAZ was the most sensitive corrosion zone in welded joint of 7N01-T4 in chlorinated moisture environment. Influenced by the heat-input of welding, the grains of HAZ were coarsening and inhomogeneous. A corrosion cell between welding seam with high Mg content and HAZ with high Zn content formed. HAZ corroded preferentially as anode, and the dissolving of zinc-rich phase in grain boundary resulted in the extending of corrosion crack along grain boundaries.

Abstract: Different morphology of Cu₂O crystals were fabricated by electrochemical deposition using ITO and ITO/nano-TiO₂ as working electrode. The effect of different KCl concentrations on the microstructure and surface morphology of Cu₂O thin films were studied and the morphology controlled mechanism was also discussed. When the concentration of KCl was 7mmol/L, the shape of Cu₂O crystals evolved from dentrite to similar cube on the ITO matrix. When the concentration of KCl was 5mmol/L, the shape of Cu₂O crystals evolves from regular octahedron ({111} preferred orientation) to truncated cube ({100} preferred orientation) on the ITO/nano-TiO₂ matrix. The results also indicate that the substrates played a key role in the particle size control.

Abstract: An electrochemical sensor modified with tetra-(N-phenylpyrazole)-porphyrin/b- cyclodextrin/carbon nanotube (TPPyPh/b-CD/CNT) film was fabricated for determination of hemoglobin (Hb) in this paper. The electrochemical behavior of the proposed sensor was investigated by cyclic voltammetry (CV). TPPyPh has been shown preferably for the fabrication of electrochemical sensor. The peak currents decreased significantly with the increase of the Hb concentration in solution. The response mechanism of TPPyPh/b-CD/CNT film for Hb was suggested to be based on the coordinated interaction between Hb and TPPyPh. It showed excellent selectivity for the determination of Hb in PBS.

Abstract: Al doped ZnO films have been prepared by dc magnetron sputtering. These films were annealed in different atmosphere and temperature. The crystal structures were analyzed by x-ray diffraction (XRD), and the magnetic properties were measured by a Physical Properties Measurement System (PPMS) with the magnetic field paralleled to the films plane. The results show the microstructure and magnetic properties were influenced by annealing atmosphere. Compared to the films annealed in vacuum, the films annealed in air shows obvious room temperature ferromagnetism, the magnetic moment increases about an order of magnitude. The room temperature ferromagnetism may be associated with a charge transfer between Al and Zn and the variational position of Al in ZnO films in different annealing ambience.

Abstract: A series of Fe³⁺-dopped polyaniline (Fe³⁺/PANI) nanomaterials with different morphologies and a higher conductivity were successfully synthesized using a simple and static interfacial polymerization by using FeCl₃ as both oxidant catalyst and dopant. The effect of surfactants CTAB and SDS and the concentration of FeCl₃ on the morphology and conductivity of Fe³⁺/PANI nanomaterial were investigated. The samples were characterized by Transmission Electron Microscopy (TEM), SDY-4 probes conductivity meter, X-ray Diffractometry (XRD), Energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy techniques. TEM’s results showed that their morphologies changed with the type of the surfactant and the concentration of FeCl₃. Introducing surfactants CTAB and SDS into Fe³⁺/PANI remarkably improved the conductivity of the material. The conductivities of CTAB/Fe³⁺/PANI and SDS /Fe³⁺/PANI nanomaterials were respectively about 4.8×10^-2 and 1.3×10^-2 S/cm while the conductivity of Fe³⁺/PANI was found to be 1.5×10^-4 S/cm. The different morphology and high conductivity may be ascribed to the mutual effects of the surfactant and oxidant.

Abstract: In this study, chitosan was modified by acrylamide and acrylonitrile when NaHSO₃-K₂S₂O₈ as initiator under N₂. Chitosan-acrylamide-acrylonitrile ternary graft copolymer was synthesized on the use of radical polymerization mechanism. The optimal experimental conditions for the preparation are obtained by orthogonal experiments: the reaction temperature 65°C, the reaction time 6.5h, the concentration of NaHSO₃ 3mmol/L, the concentration of K₂S₂O₈ 4.5mmol/L, and the ratio of m(chitosan):m(acrylamide):m(acrylonitrile) was 1:6:4. Under such conditions, the average graft ratio and the graft efficiency could achieve 852.455% and 85.260% respectively. Chitosan and chitosan-acrylamide-acrylonitrile ternary graft copolymer were then characterized by means of XRD and SEM, and the graft mechanism was explored preliminary as well. The results showed that chitosan was modified successfully by graft polymerization, and the surface property and the strength of the product were also improved obviously.

Abstract: In order to solve the shortcomings of current engineering methods for parameters adjustment that can only deal with them according to single requirement of system and can not optimize them in the whole range, as well as the standard genetic algorithm is prone to premature convergence, therefore, an improved PID parameters adjustment method based on self-adaptive genetic algorithm was proposed. This approach enables crossover and mutation probability automatically change along with the fitness value, not only can it maintain the population diversity, but also can ensure the convergence of the algorithm. A comparison of the dynamic response between the traditional PID control and the PID control based on self-adaptive genetic algorithm was made. Simulation results show that the latter has much superiority.

Abstract: Phase-pure Eu³⁺ doped Gd₂Sn₂O₇ nanocrystals have been successfully synthesized via a co-precipitation processes combined with hydrothermal treatment. The crystal structure, particle size, morphologies, composition, and photoluminescence properties of the as-synthesized products were investigated by XRD, SEM, TEM, EDS and PL. The samples were single-phase cubic pyrochlore-type nanocrystals with a typical size of about 30 - 60 nm. All the samples exhibited irregular flower like secondary nanostructure assembled by primary nanoparticles. Photoluminescence properties of Gd₂Sn₂O₇:Eu³⁺ were investigated, and the results revealed that the as-synthesized materials displayed intense and prevailing emission located at 580 - 630 nm. The excitation spectra indicated that an energy transfer from Gd³⁺ to Eu³⁺ occurred. Meanwhile, the concentration quenching phenomenon was observed in Gd₂Sn₂O₇:Eu³⁺nanocrystals.

Abstract: Chitosan/cellulose acetate multimicrospheres (CCAM) were prepared by the method of W/O/W emulsion with no toxic reagents and had the size interval of 200--280µm. It was investigated as an ideal alternative to enhancement the adsorption of water-soluble dyes from wastewater. The correlation coefficients of adsorption isotherm showed that the Freundlich model was comparable to the Langmuir model. The 1/n was lower than 1.0, indicating that malachite green was favorably adsorbed by CCAM. Furthermore, the amount of malachite green absorbed steeply increased with increasing time and reached plateau values within 2 h and increased with increasing of initial concentration of malachite green from 5 to 25 mg/g.

Abstract: The surface of SiC particles were modified by electroless plating. To avoid complicated activation and sensitization process before nickel-phosphorus chemical plating, a special process was adopted in experiment. After experiments, the metallographic structure was characterized by using SEM and EDS, respectively. The results show that SiC particles modified by Ni-P alloy are obtained after a simple and specific process of SiC particles activation.