Advanced Materials Research Vols. 150-151

Abstract: Both tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly and reach the maximum values as their EGMC contents approach an optimum value of 6 wt%. The melt shear viscosity values of PLAxEGMCy resins measured at varying shear rates are significantly higher than those of the PLA resin and increase consistently with their EGMC contents. FT-IR analysis suggest that the carboxylic acid groups of PLA molecules react with the epoxy groups of EGMC molecules during the reactive-extrusion processes of PLAxEGMCy specimens. Further DMA and morphological analysis of PLAxEGMCy specimens reveal that EGMC molecules are phase-separated with PLA molecules at EGMC contents equal to or more than 2 wt%, since distinguished phase-separated EGMC droplets and tanδ transitions were found on fracture surfaces and tanδ curves of PLAxEGMCy specimens, respectively. Possible reasons accounting for the above interesting properties of the PLA/EGMC specimens are proposed in this study.

Abstract: Copper matrix composites reinforced with 3D-SiC network (15v% and 20v% SiC) were fabricated by squeezing copper alloy into 3D-SiC network preforms. The thermo-physical properties of the copper matrix composites were investigated. The specific heat capacities of the composites were about 0.39~0.50 J•g-1•K-1. The coefficients of thermal expansion (CTEs) of the composites were found to be lower than 6.9×10-6 -1 at Room Temperature. The composites exhibited high thermal stability for 3D-SiC network advent. The thermal conductivity of the composites was in the range of 50~80W•m−1•K−1. The thermo-physical properties of Cu matrix composites had a great relationship with the structures of 3D-SiC network preforms. The thermal conductivity of the composites decreased with an increase in the volume fraction of SiC or the structures of the limbs changing compacted, but the CTEs were not completely according this rule.

Abstract: Polymers imprinted with (S)-(-)-1,1’-bi (2-naphthol) and (R)-(+)-1,1’-bi (2-naphthol) have been prepared by non-covalent imprinting. A combinational procedure was used to optimize the functional monomer and crosslinker. A copolymer of 2-vinylpyridine and divinylbenzene resulted in the best chiral recognition. The ratio of template to functional monomer and solvent in the pre-polymerization mixture were also optimized. The imprinted polymers were used as stationary phases in high-performance liquid chromatography (HPLC). The molecularly imprinted polymers (MIPs) were more selective when prepared using a less polar solvent. Effective separations of the enantiomers of racemic (±)-1, 1’-Bi (2-naphthol) were achieved by use of acetonitrile as mobile phase; no cross-selectivity was observed. Interactions between functional monomers and template were investigated by 1H NMR spectroscopy. The results suggest that hydrogen-bonding between the functional monomer and the template and π-π stacking interaction between the cross-linker and the template may contribute to chiral recognition.

Abstract: The computer simulation of the structural evolutions of Al nanowires on cooling has been carried out based on the embedded atom method potential. The infinite Al nanowire was modeled by super-cell with a one-dimensionally periodical boundary condition along the [001] direction. The simulation results indicate that the microstructure of Al nanowires changed from amorphous to helical multi-shelled structure along with the drops of cooling rate. The helical multi-shelled structure possesses some features of amorphous structure, but it is more stable than the later. Moreover, the Al nanowires still keep the helical multi-shelled structure even if the cooling rate decreased to 1010 K/s.

Abstract: Lead rubber bearing (LRB) is a new type of earthquake-resistance rubber bearings, formed by inserting lead-core into ordinary laminated rubber bearing, vertical supporting, horizontal displacement and hysteretic damping are hung in single unit together. For lead-core can dissipate seismic energy and increase stiffness under load simultaneously, and most of the requirements of the Seismic isolation system can be satisfied, the material-device has been found widespread application prospect in bridge engineering. Hysteretic behaviors, ductility, and energy dissipation of LRB are mainly determined by some dynamical parameters such as characteristic intensity of LRB, post-yield, pre-yield stiffness and so on. Equivalent linear model of hysteretic characteristics, computational method and the varying range of dynamic parameters of LRB are presented. Dynamic responses of high-speed railway bridge fabricated LRB are calculated, and calculation results are compared with those fabricated common bearings, factors which influence seismic isolation are analyzed.

Abstract: Na2SO4 solution was impregnated into rice straws, then the straws impregnated with Na2SO4 was cemented using water glass and molded to shaped phase change plate. The plate was subsequently inserted into the concrete bricks with rectangular holes, assembled as phase change bricks. The latent heat of phase change of the plate was measured by DSC, the microstructure of the plate was observed by SEM, and the heat insulating property of the brick was investigated. The results are as follows. The rice straws can encapsulate 2 times Na2SO4•10H2O in mass and the phase change heat of the plate is 121 J/g. The microstructure shows that the rice straws and hardened water glass play an encapsulating action for the package of Na2SO4•10H2O. The weight loss of the plate was 0.9% after 30 times of phase change cycles. For the concrete bricks (size: 240×240×115 mm) inserted with phase change plates, when the heated surface temperature was 80 oC and the initial cold surface temperature was 14.5 oC, the needed time that the cold surface temperature rose to 25 oC was 17 h, which was 6.5 h and 9 h longer than the concrete bricks inserted with rice straw plates and the original concrete bricks, respectively. When the heating was maintained for 5 h and 8 h, the cold surface temperature increased by only 1.4 oC and 3.9 oC and the temperature difference between the cold surface and hot surface was 64.1 oC and 61.6 oC. This study provides a new way for the encapsulation of phase change materials and its application in construction.

Abstract: First-principles study of elastic modulus, shear modulus and some other elastic parameters of TiN and NbN are reported using the plane-wave pseudopotential density functional theory method in this paper. The calculated lattice and elastic constants are in good agreement with the experimental data and other theoretical results. The band structure and density of states of these two compounds were obtained, which show that the mainly contribution on pseudopotential calculations of the density of states of TiN is Ti-3d orbital and N-2p orbital, while TiN is the Nb-4d orbit and B-2p orbit, TiN with higher conductivity; Pugh empirical criterion shows that TiN and NbN are both brittle compounds, and NbN is more brittle than TiN.

Abstract: In recent years, the problem of contaminated source water is increasingly outstanding with the rapid development of industry，agriculture and population. Especially, the eutrophication of river and lake is severer. The modified clay was studied to remove algae in lake type raw water in which average concentrations of turbidity, TN, TP and Chl-a were 33NTU, 4.002 mg/L, 0.263mg/L and 29.02 mg/m3. The results showed that the average removal efficiency of turbidity, TN, TP and Chl-a were 88.53%、26.61%、87.45% and 87.97% respectively when the dosage of modified clay was 0.8 g/L.

Abstract: In this paper, the typical cold work die steel Cr12MoV was used as substrate material for vanadizing treatment. And the coating structure and bonding strength were studied. Moreover, comparison experiment of wear resistance between the coating and the substrate material was performed, and based on the experiment results, wear failure mechanism of vanadizing layer was analyzed. The results showed that vanadium carbide coating is dense, with fine grain structure and high bonding strength. These features help to improve the wear resistance of coatings. Comparision of wear performance between coating and substrate showed that vanadizing surface layer can significantly improve wear resistance of substrate material. Friction coefficient decreased from the 0.48 to 0.33 and wear weight loss decreased by 95%. Wear Failure analysis showed that the vanadium carbide layer of the wear mechanism is fatigue spalling wear.

Abstract: As a new long-span space system, the prestressed arch-supported reticulate shell structure performs the advantages of reticulated shell and prestressed structure. The construction process, large span/depth ratio and small critical load of long-span space structure, can lead to obvious stress excess of tensile steel, especially when prestressed arches are used in truss arch and reticulated shell combined structure. However, no research was conducted on how the residual stress in the steel affects the structure stability. Thus, the dynamic behavior of some actual structure is simulated numerically through modal analysis by ANSYS in this paper. The results show that, for prestressed arch-supported reticulate shell structure, the vibration frequency increases with the whole stiffness, and the prestress can improve obviously the buckling ultimate load. There is great difference in vibration modes for different structure styles. This kind of hybrid structure conducts good whole performance, and may be used widely in the near future.