Advanced Materials Research Vol. 499

Abstract: Mg-6Al-0.3Mn-0.9Y (mass fraction, %) magnesium alloy was prepared by metal mould casting. The as-cast ingot was homogenized, and then hot-rolled with total thickness reduction of 70%. Further annealing treatment was carried out on the hot-rolled sample. Microstructure and mechanical properties of the studied alloy in as-cast, hot rolled and annealed states were investigated. Results showed that main phases of the as-cast sample were composed of α-Mg, Mg₁₇Al₁₂ and Al₂Y. Average grain size was about 9 μm after hot rolling and annealing treatment. It is found that the optimal annealed parameters for the Mg-6Al-0.3Mn-0.9Y alloy should be 350 °C for annealed temperature and 30 min for the corresponding time, respectively. Tensile test results showed that ultimate tensile strength, yield strength and elongation of the annealed sample were 261 MPa, 149 MPa and 32%, respectively. Compared with those of the as-cast sample, they were enhanced by 36%, 140% and 146% correspondingly.

Abstract: Severe plastic deformation can be introduced on the surface of metallic materials, and nanostructured surface layer is induced, which incorporates the surface modification technique with nanomaterials. The severe plastic deformation method-Supersonic Particles Bombarding (SSPB) was used to treat the anealled 40Cr steel. The surface microstructure and area where is about 50μm away from the top suface of 40Cr steel after SSPB treatment were characterized by transmission electron microscopy (TEM). Wear resisting property lubricated by liquid paraffin (LP)+0.3%ZDDP of SSPB sample was studied. Equiaxed nanocrystallites with random crystallographic orientation were obtained on the top surface of SSPB treated 40Cr steel. Ferrite and pearlite were deformed severely at the depth about 50μm away from the top suface, and cementite in the pearlite shows plasticity. Wear loss of polished SSPB sample is the lowest and that of untreated sample is the biggest.

Abstract: A series of cross-linked fluorinated waterborne shape memory polyurethaneurea (PUU) ionomers were synthesized from polycaprolactone diol, perfluoropolyether diol (PFPE), dimethylolproionic acid, isophorone diisocyanate, ethylenediamine (EDA) and diethylenetriamine (DETA). The effect of PFPE content in the soft segment and the degree of cross-linking on the molecular structure and the properties of for these PUU films was examined and studied. Differential scanning calorimetry showed that the transition temperature for these Tm type shape memory PUU could be facially tuned by PFPE weight percentage and EDA/DETA ratio in the range between 30°C to 50°C, in the vicinity of body temperature. The dependence of their properties on hydrogen-bonds evaluated by FT-IR was also discussed.

Abstract: Mesoporous sulfur, aluminium doped TiO₂ materials (S-Al-TiO₂, S-TiO₂, Al-TiO₂) have been synthesized by solid-state reaction route. The textural properties of the samples are monitored by the X-ray diffraction (XRD), Scanning electron micrography (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible light spectroscopy (UV-Vis) and N₂-physisorption. Moreover, compared with the pure TiO₂, the photodecomposition properties of methylene blue (MB) irradiated with ultraviolet and visible light are presented on the doped TiO₂ materials. It is shown that TiO₂ doped by sulfur and /or aluminium are mesoporous materials, and the S and Al enter into the crystal lattice of TiO₂. At 298K, the rule of pseudo-first-order reaction and excellent visible light catalytic activity are obtained in the photodecomposition of MB on the S-Al-TiO₂, S-TiO₂, Al-TiO₂ and pure TiO₂ materials. Interestingly, the reaction rate constant of MB on the S-Al-TiO₂ meso- porous nanomaterial is 11.40 times irradiated with the ultraviolet than that with visible light irradiation. But there is 1.42 times corresponding to the pure TiO₂. Within 50 min, ultraviolet degradation rate of MB over the S-Al-TiO₂ is 98.5%.

Abstract: Electrostatic layer-by-layer (LbL) self-assembly is widely used in sequential adsorption of nanometer-thick monolayers of oppositely charged polyelectrolytes to form a multi-layer film with molecular-level control over the architecture. To offer functional material for the potential application, this paper exploits PDDA and PSS as polycation and polyanion for LbL self-assembly to fabricate polyelectrolyte nanocomposite films. The preparation and film-growing mechanism is investigated under the influences of multi-factor such as polyelectrolyte concentration, ionic strength, and assembling duration using quartz crystal microbalance (QCM). The research results indicate the formation mechanism of multi-layer PDDA/PSS films and offer fundamental basis for the optimum preparation of polyelectrolyte films.

Abstract: In this study, a numerical model was built to simulate the self-piercing riveting (SPR) process using commercial LS-DYNA finite element code. The difficulties in numerical simulation of the SPR process, such as large deformation and fracture, were resolved by the use of an explicit solution process combined with the r-adaptive meshing method. The model was applied to joining two sheets of 6061 aluminium alloy. The effects of die geometry, rivet material properties and the adaptive step size in numerical calculation were studied, using 6061 aluminum sheets as a model system. The simulation agrees well with the experimental results in terms of geometric characterisitcs of the cross-sections of the joints formed.

Abstract: Using three natural graphites with different particle size, 35, 50 and 80 mesh, as raw materials, expandable graphites were prepared by intercalating, water-washing and drying the natural graphites. The products were characterized by X-ray diffraction, Infrared spectroscopy, scanning electron microscope and Raman spectroscopy. Results show that the structure of expandable graphite is affected strongly by the particle size of natural graphite. With increasing the particle size of natural graphite, for expandable graphite, the expansion degree of graphite flakes along the c-axis and the relative ratio of intercalating agents increase, while the structural disorder increases.

Abstract: Young's modulus is one of the most fundamental parameter to depict the elasticity of a given material. It determines the basic elastic deformation capacity of a structure under a bear load. When the diameter of nanocrystals is in the scale of several nanometers, the Young's modulus is quite different from that of bulk. In order to determine elastic deformation capacity of nanocrystals, it is necessary to study the size dependent Young's modulus. Based on above consideration, a simple thermodynamic model is developed for size dependent Young's modulus of nanocrystals according to the “universal” binding energy curve and Laplace-Young equation. According to this model, the Young's modulus of several FCC metallic films is predicted and the Young's modulus increases with the size reduction. The prediction is agreed with computer simulation results.

Abstract: A series of blend films of cellulose and chitosan were prepared from 1-ethyl-3-methyl imidazole acetate ([Emim] Ac) by coagulating with ethanol. Structure, mechanical properties, thermal stability and antibacterial properties were investigated. The results showed that there were strong interactions and good compatibility between cellulose and chitosan in blend films. The blend films possess good mechanical properties and thermal stability, and the existence of chitosan endows blend films with antimicrobial property.

Abstract: The CaCO₃-polyethylene (PE) film was prepared by filling method, and the filling amount of calcium carbonate in film was 20%(w/w). The effects of natural weathering, ultraviolet light irradiation on the tensile strength, breaking elongation and molecular weight of the CaCO₃-PE film was investigated comparing with the photosensitizer-PE film. After being located in the open air for 30 d, the average tensile strength, average breaking elongation and the mean molecular weight of CaCO₃-PE film decreased 80.6%, 99.3% and 25.3%, respectively, as for the photosensitizer-PE film, the corresponding items decreased 18.8%, 45.0% and 11.7%, respectively. After ultraviolet light irradiation for 120 h, the average tensile strength of CaCO₃-PE film decreased 29.9%, the average tensile strength of the photosensitizer-PE film, however, increased 20.5%. The average breaking elongation of CaCO₃-PE film and photosensitizer-PE film decreased 97.3% and 84.1% respectively, the mean molecular weight of both films decreased 66.7% and 26.6% respectively. After covered by soil for 200 d, the weight loss of the CaCO₃-PE film and photosensitizer-PE was 2.15% and 0.22%, respectively. The results showed that the degradability of CaCO₃-PE film is superior to the photosensitizer-PE film.