Advanced Materials Research Vols. 150-151

Abstract: In this paper, the chromium-free passivation solution was prepared by organic / inorganic process. The surface morphology and corrosion resistance of the composite films were investigated by scanning electron microscopy (SEM), atomic force microscope (AFM), and electrochemical impedance spectroscopy (EIS). The chromium-free passivation film was immersed in 3.5% NaCl solution, and the EIS changed with the immersed time. The results showed that the total impedance of chromium-free passivation film increased more than one order of magnitude compared with the galvanized steel, which is the same as that of chromate passivation film.With immersed time increasing, the impedance decreased, and the impedance stabilized after 8h. AFM and SEM results indicated that the film surface that was very flat was uniformly suspended by a lot of solid particles, in which the little hollow portion was 8nm. The framework structure of the film was cross-linked by resin emulsion and organic silane. After 96h NSS test, the galvanized steel surface appeared only a little pitting corrosion, which proved that corrosion resistance of galvanized steel increased obviously by the chromium-free passivation.

Abstract: Nanocomposites of polyacrylonitrile (PAN) and Organophilic alpha-zirconium phosphate (OZrP) were prepared by gelation/crystallization. OZrP was prepared using cetyl trimethyl ammonium bromide (CTAB). The structure of PAN/OZrP nanocomposites was characterized by X-ray diffractometry (XRD) and high resolution transmission electron microscopy (HRTEM). The results showed that an intercalated or exfoliated structure was formed. Thermogravimetric analysis (TGA) was applied to characterize thermal stability property, which indicated that the thermal stability of PAN/OZrP nanocomposites was improved compared with that of pure PAN. HRTEM and Laser Raman spectroscopy were used to analyze the microstructure of the chars of PAN/OZrP nanocomposites.

Abstract: The electrochemical behaviors of several chlorophenols were investigated on boron-doped diamond thin film electrode. 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol solutions were prepared as the electrolyte. Such four chlorophenols with various number of chlorine atoms in the benzene ring were studied by cyclic voltammetry at different scan rates between –1V to 2.5V (vs. MSE). The results indicated that the reactions of the 2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol at the diamond electrode are irreversible and under diffusion control. The irreversible trend increases as the number of the chlorine atoms decreases. However, the activity of the boron-doped diamond film electrode is not affected by the number of the chlorine atom. Different from the three chlorophenols, fouling of the electrode appears in pentachlorophenol solutions.

Abstract: The effects of thermal cycling and freezing after water absorption on tensile properties of green composites were examined. Jute fiber and matrix were used as the reinforcement and the matrix. The thermal fatigue was conducted as a fatigue test. Heating and freezing process are performed alternately for 0.5h, 1h and 24h during 10 cycles, heating and freezing temperature were 60 and -20 . In a freezing after water absorption, the damage by an expansion of water was examined. The freezing after the water absorption during 1-5 days was performed in a day under the environment of -20 . In thermal cycling, tensile strength and modulus were significantly decreased as the time passes. In 24h-treated test, the decrease rates of tensile strength and modulus were about 50 % compared with that of room temperature. In freezing after water absorption, tensile strength and modulus were decrease compared with that of the room temperature.

Abstract: In order to characterize the curing behavior of low molar ratio urea-formaldehyde (UF) resin, the curing time and thermal analysis in curing reaction of the UF resins and the bonding strength and formaldehyde emission of plywood bonded by five kinds of low molar ratio UF resins with six different curing agents were studied. The results indicated that the UF resins with the molar ratio of formaldehyde to urea more than 1.0 could get reasonable curing time. The heat enthalpy of UF resins significantly increased with the enhancing the acidity of curing agent. The plywood manufactured by the UF resins with 1.1 molar ratio showed much higher bonding strength and lower formaldehyde emission.

Abstract: In order to reduce traffic accidents in tunnel, a type of new road material with excellent skid resistance and multicolour which was abbreviated to TSRM was studied in this paper, and its properties were analyzed and characterized by means of testing its cohesive force, shearing strength, water stability, chemistry stability and skid-resistance on the basis of the former studies. Based on large amount of indoor tests, technical standards for components of TSRM were put forward. The curing mechanism of TSRM was probed into in this paper. The results verified that the comprehensive properties of TSRM were excellent, and it has a high friction factor and good texture depth. With the result that TSRM was fit for tunnel paving.

Abstract: The effect of elements such as Ti, Al, Hf, Zr and B on hot tearing susceptibility during directional solidification was explored by tube-like samples with thickness of 1.0 mm, 1.5mm and 2.0mm in wall. Results of SEM of elements on solidification of casting Ni-based superalloys were presented. The influential extent among the investigated elements is found to be: the largest is Ti, then Zr, B and Al, and Hf is the smallest. Titanium promotes the formation of (γ+γ´) eutectic, increases sizes of the eutectic. Increasing Al content results in the size of γ+γ´ eutectic and the number of γ´. Increasing Zr content promotes γ+γ´ eutectic.Varying B content shows little microstructural evolution.

Abstract: Copper matrix composites with different La2O3 content were fabricated by powder metallurgy method. Sliding wear behavior of the Cu-La2O3 composites was carried out by using a pin-on-disk wear tester under dry sliding conditions at a constant sliding speed of 20 m/s. The results showed that the wear rate of the composites was significantly lower than that of pure copper. The friction coefficient and wear rate of Cu matrix composites decreased significantly by incorporation of La2O3 particles. For determination of the wear mechanisms of the composites, the worn surfaces were examined using scanning electron microscopy. It is found that the main wear mechanisms of the sintered copper-La2O3 composites were oxidation wear and adhesive wear.

Abstract: The geometric structures and electronic properties of Si doped Fen (n=2-7) clusters have been systematically studied at the BPW91 level in density-functional theory (DFT). Calculated results show that an Si impurity does not change the ground-state structure of small iron clusters and prefers to occupy surface site bonding with iron atoms as many as possible. The second-order energy difference and the vertical ionization potential show that n=4 and 6 are magic numbers within the size range studied, but the maximum value occurs at n=4 for the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital(LUMO). It is found that the hybridization intensity between Si and Fe atoms is relevant to the stability of clusters.

Abstract: A new kind of latent curing agent (LCA) for epoxy resin was synthesized by the reaction of Ethylenediamine with Butylacrylate in equal molar ratios, and the chemical structure and thermal property of the LCA were studied with FTIR and TGA, respectively. Moreover, LCA was also used to modify the epoxy sizing agent for high modulus carbon fiber. The results show that the wettability of sized carbon fiber tends to increase due to the increase of the polymer film on the surface of the carbon fiber, and interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 78MPa, which is increased by 8.6% compared with the composites reinforced by high modulus carbon fiber with unmodified sizing agent, indicating that using LCA modified epoxy resin as polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.