Advanced Materials Research Vols. 631-632

Abstract: Polypyrrole/montmorillonite (PPy/MMT) particles were synthesized using an oxidative polymerization method. Then the particles were added into polymethyl methacrylate (PMMA) as additives to prepare PPy/MMT/PMMA composite. The structures and properties of the composite were characterized by FT-IR, TGA, X-ray diffraction spectroscopy, and four–probe machine. The relationship between content of PPy/MMT and conductivity was analyzed. The result shows that the amount of PPy/MMT is a key factor for improving the conductivity of composite. Furthermore, dynamic mechanical (DM) properties of composite were studied. When the PPy/MMT content reach 0.2% of composite, the storage modulus, loss function modulus, dissipation factor get highest values.

Abstract: DNA sequencing by nanopore is a technique to detect DNA sequence by making the DNA strain passing through the nanopore material and measureing some characteristic parameters to determine the order of the four kinds of base-pairs. Graphene nanopore research becomes a hotspot for the DNA sequencing technology. In this paper, a kind of novel nanopore on graphene oxide is sculptured with FEB(Focused Electron Beam) to overcome the problem about the high noise for graphene nanopore. By tuning FEB parameters, e.g. the accelerating voltage, the spot number, the exposure time and the amplification factor, sub 10nm nanopores on single layer GO(Graphene Oxide) film will be achieved. At the same time, some challenges are discussed: difficult to get stable size, hard to take TEM pictures and hard to get relatively smaller size.

Abstract: Obtaining photocathodes with high quantum yield has been the focus during the process of photocathode development. With the limitation of basic industrial manufacturing level, the further performance improvement of the negative electron affinity photocathode is subject to the quality of grown material itself. For this reason, according to the band engineering science, we have proposed an exponential-doping structure applied to the active-layer of reflection-mode and transmission-mode AlGaAs/GaAs photocathodes via molecular beam epitaxy technique, to increase the photocathode emission efficiency. A series of theoretical and experimental researches including structure design, material growth, surface cleanness, Cs-O activation and performance evaluation have been carried out to confirm the actual effect of exponential-doping photocathodes. As a result of the built-in electric field, the cathode performance was enhanced for exponential-doping AlGaAs/GaAs photocathodes.

Abstract: For effective bonding of Magnesium alloy, Cu foil was used as the interlayer to conduct the diffusion bonding experiment of AZ31B alloy. The microstructure and properties of the diffusion bonding joint was analyzed by means of SEM, EDS and micro-hardness tester. Experiment results show that compact bonding joint was obtained at the temperature of 480°C, holding time of 30 minutes, pressure of 10 MPa and the vacuum degree of 1.0×10^-2Pa. The bonding joint consists of a interfacial diffusion region which is a mixture of Mg₂Cu, MgCu₂, and Mg(Cu) solid solution, and the transitional zone which is composed of Mg(Cu,Al) solid solution base and Mg₁₇(Al, Cu)₁₂ phase. Within the bonding joint,the micro-hardness shows a step pattern of increasing, which is well accord with the the microstructural feature of the joint.This trial has prove that using Cu as the interlayer is effective to improve the quality of the AZ31B bonding joint.

Abstract: The formed transfer film on the counterpart surface and tribological properties of PTFE composites filled with Al₂O₃ or SiO₂ were investigated in this paper. The results indicated that under the same friction conditions, the friction coefficients of SiO2/PTFE and Al₂O₃/PTFE are very close to each other, but the wear resistance of SiO₂/PTFE is superior to that of Al₂O₃/PTFE. According to the measured data, the micro-hardness and elastic modulus of the transfer film for SiO₂/PTFE are much better than those of Al₂O₃/PTFE. In addition, the interfacial adhesion strength between the transfer film of SiO₂/PTFE and the counterface is higher. It can be proved that the mechanical properties of transfer films for PTFE composites vary with different fillers and the friction transfer film with better adhesion strength and mechanical property is useful to improve the tribological properties of the composite.

Abstract: In this paper, nano TiO₂ loaded on activated carbon fiber(ACF) was prepared by hydrothermal method as TiO₂/ACF photocatalytic.The material crystal structure, the superficial appearance of catalyst, were analyzed and measured by XRD and SEM images.Moreover, it used for photocatalytic oxidation As(Ⅲ).The effect of pH on the oxidation of As(Ⅲ) was studied. The oxidation of As(Ⅲ) efficiency increasing markedly with pH, and the catalytic efficiency is much higher in the alkaline environment than in the acidic environment.

Abstract: To explore the optic properties of transmission-mode GaAs photocathode module, experimental and theoretical values of reflectance and transmittance of photocathode module has been compared. it showns that experemental curves cannot tally with theoretical curves completely. The variation range of initial values of thickness is firstly setted. Modifing transmittance formula by a fitting coefficient A, optical properties is fitted using the method of error control. R-T combined error reduced from 15.2% to 4.9% using R-T combined error control scheme. Optimal fitting values of thickness of photocathode module are obtained, which are d₁ = 110 nm, d₂ = 1019 nm, d₃ = 1491 nm. And the error of total thickness is 2.9%.

Abstract: We have fabricated Aluminum Nitride (AlN) films on the quartz substrates using RF-reactive magnetron sputtering method. The conditions of the films have been performed under different concentration ratios between nitrogen and argon. We have found that all obtained films were transparent in visible wavelength. By using X-ray diffraction (XRD) technique, it was found that the (002), (102) and (103) orientations were shown in XRD patterns. The (002) orientation was dominant when nitrogen concentration (C_N) was at 40%. On the other hand, the refractive index and optical band gap energy of the films were determined as a function of C_N. We have found that the refractive index weakly depended on C_N, while optical band gap energy did not.

Abstract: The sensitization and intergranular corrosion (IGC) behavior of a novel Cr-Mn-N austenitic stainless steel (named as MPMD133) sensitized in the temperature range from 600 oC to 1000oC for 3 hours was investigated by the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The effects of the sensitization temperature on the susceptibility to IGC of MPMD133 were examined in the 0.5M H₂SO₄ +0.01M KSCN electrolyte solution. The results show that the degree of IGC increases as the sensitization temperature increasing till 900oC. Meanwhile it decreases rapidly when the sensitization temperature is elevated up to 1000oC, which is confirmed by the subsequent optical micrographs observation. The XRD analysis reveals that the precipitation of Cr₂₃C₆ leads to chromium depletion along the grain boundaries, consequently results in the susceptibility to IGC.

Abstract: Standard discrete element method does not take the effect of rolling resistance into account. To overcome this shortcoming, a contact model considering rolling resistance is developed and implemented into PFC^2D. Using this contact model, a series of numerical biaxial compression tests are carried out. The results of these numerical simulations show that rolling resistance has remarkable effects on shear strength and shear dilatancy of granular matters, and these trends are agreed with previous studies, which proves that this model works well. Then the effect of rolling resistance on anisotropy of granular matters is studied in this paper. It can be seen that rolling resistance has dramatic effect on the anisotropy of granular matters. The anisotropy of granular matters increases with rolling resistance.