Advanced Materials Research Vols. 295-297

Abstract: The main feature of this article is the investigation on the influence of temperature, relative humidity, film thickness on permeability of PET packaging film, the analysis of perm-selectivity of the packaging films for oxygen gas and carbon dioxide gas, and the evaluation on experimental formulas of water vapor, O₂ and CO₂ gas permeating rates on the basis of gas molecular osmotic reaction kinetics and regression analysis. The comparison between experimental studies and calculation indicates that: (1) with increment of ambient temperature water vapor, O₂ and CO₂ permeating rate of PET films and PET/Al film also rise, and the logarithm of water vapor, O₂ and CO₂ gas permeating rates has linear relation with the reciprocal of thermodynamic temperature, and (2) the influence of relative humidity on water vapor permeating rate of PET film with thickness 12µm is the least, and that of PET film with thickness 20µm and PET/Al film with thickness 18µm is a little obvious. (3) The PET films hold remarkable perm-selectivity for O₂ and CO₂ gas, and CO₂ gas permeating rate is about two times of O₂ gas, yet O₂ and CO₂ gas permeating rates of PET/Al film are both very low and have small difference, so the PET/Al film has better barrier performance than the PET film.

Abstract: We have investigated the deposition of silicon films on SiO₂ patterned Si(111) substrates by atmospheric pressure chemical vapor deposition (APCVD) under standard condition. Oxidized silicon wafers with different sizes of circular and striated patterns were used as substrates for deposition of 35 μm silicon films. The influence of surface morphologies of substrates on epitaxial Si films has been discussed. The crystalline structures of the epitaxial Si films rely on the prepatterned substrates. Triangular prism-shaped grains have been obtained after depositing silicon film on substrates with circular patterns. While different size polycrystalline silicon grains appear on surfaces of Si films grown on SiO₂ regions of substrates along the axis of striated patterns. Twins defects were observed in epitaxial Si films grown on SiO₂ layers of the pretreated substrates.

Abstract: In this paper, three-layer biaxial weft knitted fabric(TBWK) made of carbon fiber as inserted yarns and polyester yarns as knitted yarns , which is a kind of non-crimp fabric, has been impregnated with epoxy via RTM technique. The bending properties of the TBWK fabric reinforced composite materials with different fiber volume fraction have been investigated. The bending strength of TBWK reinforced composites with fiber volume fraction of 48.8% can reach 821.1 MPa. The results show that this kind of composites has good bending properties, and load - deflection curve shows obvious linear features.

Abstract: There are many kinds of pre-crosslinking gel being used at present, but their high temperature resisting performance are poor. The general temperature resisting capacity is only about 120°C. Aiming at the poor resistance to high temperature of current pre-crosslinking gel , an anti-high temperature pre-crosslinking polymer gel is developed in this paper. Experimental results show that this product has appropriate swelling ability, better anti-extruding strength, better deformability and elasticity. The temperature resisting capacity in freshwater can reach as high as 150°C,and it still has comparatively higher strength after high temperature treatment.

Abstract: Microstructural characterization of Al-Cu-Mg-Ag alloy ageing at low and elevated temperature were investigated by differential scanning calorimeter (DSC) and transmission electron microscopy (TEM). The results show that the precipitation sequence is significantly influenced by the ageing temperature. With prolonging of ageing at 65°C, G.P. zones on the plane of {100}α separates out with no precipitation of Ω phase. After 10h ageing at 160°C,the phase of Ω separates out and dominant the microstructure, while a small quantity of θ′separates out as well.

Abstract: This paper presents several methods usually used for measuring cable tension in cable-stayed bridges, especially frequency vibration method. Taken two different length stay-cables under given tension forces in a real cable-stayed bridge as an example, different modeling methods in finite element methods (FEM) were used to solve their natural vibration frequencies. The results by FEM were compared with those from other available theoretical predicting method. It was found that FEM based on tightening string model is more suitable for a long stay-cable. For a short stay-cable under given tension force, beam bending stiffness can be ignored in predicting its first five natural frequencies using a hinged beam model in FEM. While the predicted lower frequency using clamped beam FEM model is more accurate and reasonable.

Abstract: In this study, reductive dechlorination of DDT compounds by zero-valent iron in Jiangxi red soil was investigated. DDT compounds were effectively dechlorinated by zero-valent iron. The pseudo-first-order kinetic model for 2,4¢-DDT and 4,4¢-DDT reduction with zero-valent iron was proposed. The reaction rate constants for 2,4¢-DDT and 4,4¢-DDT were 1.19´10^-2 (min^-1) and 1.44´10^-2 (min^-1), respectively. The dechlorination of 2,4¢-DDT and 4,4¢-DDT were mainly affected by the specific surface area of iron. The data from the variable-pH experiments (between 3.6 and 8.8) suggested that pH does not play a role in the rate-determination step.

Abstract: To achieve high-gain C-band waveguide amplifiers with integrated configuration, bent channel structures (S-, U-, and F-bend) based on buried Er³⁺/Yb³⁺ codoped phosphate glass waveguide channel fabricated by field-assisted annealing (FAA) have been designed in a 4´4 cm2 substrate. Using simulated-bend method, the optimal radius for the curved structure is derived to be 1.00 cm with loss coefficient of 0.0045 dB/cm. In the wavelength range of 1520-1575 nm, obvious gain enhancement for the bent structure waveguides is anticipated, and for the F-bend waveguide, the net gain at 1534 nm wavelength is derived to be 43.95 dB, which is much higher than the value of 26.67 and 13.20 dB in the U- and S-bend waveguides, respectively, and over three times higher than that of the straight one. The simulation results indicate that the bent structure designing is beneficial in obtaining high signal gain in buried Er³⁺/Yb³⁺ codoped phosphate glass waveguides, which lays the foundation for the further design and fabrication of integrated devices.

Abstract: To obtain a new method to improve hydrodynamic bearing carrying capacity, hydrodynamic journal bearing’s characteristics as well as the current study direction are analyzed. According to the calculation of general cylindrical hydrodynamic journal bearing, the mathematic model for sinusoidal surface hydrodynamic bearing’s carrying capacity is established. It is used to calculate, analyze and compare these two bearings’ carrying capacity with example. The bearing, which has the characteristic of sinusoidal surface, has stronger carrying capacity than general cylindrical hydrodynamic bearing. What’s more, the improvement is more obvious when the number of waves is 3, also it has wider carrying area. Compared with other journal bearings, the journal bearing with sinusoidal surfaces has stronger carrying capacity, smaller friction moment and longer life-span. Therefore, it has extensive prospect.

Abstract: As a kind of the high strength low alloy steel (HSLA), 30CrMoSi has been used widely in some industrial fields. However, just like some HSLA, this steel also faces some problems when it is welded, especially such problem as cold cracking in the welded joints. In this paper, the cold welding cracks and microstructure of the joints of 30CrMoSi steel were studied by scanning electron microscopy (SEM) and optical microscopy (OM), and a method called welding with trailing impacting and rolling (WTIR) was utilized to solve the problem mentioned above by decreasing the residual welding stress which is one main factor to lead to cold welding crack in the joint of HSLA. The crack-free joints of 30CrMoSi steel were obtained by using proper parameters.