Advanced Materials Research Vols. 79-82

Abstract: Circular lining is used widely in structure design. In this paper, the method of Green’s function is used to investigate the problem of far field solution of circular lining and linear crack impacted by incident SH-wave. Firstly, a Green’s function is constructed, which is a fundamental solution of displacement field for an elastic space possessing a circular lining while bearing out-of-plane harmonic line source force at any point; Secondly, in terms of the solution of SH-wave’s scattering by an elastic space with circular lining, anti-plane stresses which are the same in quantity but opposite in direction to those mentioned before, are loaded at the region where the linear crack is in existent actually; Finally, the expressions of displacement and stress are given when the circular lining and linear crack exist at the same time. Then, the far field of scattered wave is studied. The results can be applied in the study of fracture, and undamaged frame crack detection.

Abstract: Lotus effect is well-known to be governed by chemical properties and nanotextures of the surfaces. In this paper, a method with two-steps treatment technology was applied to develop the superhydrophobic polyvinylidene fruoride(PVDF) membrane with the property of anti-contamination and self-cleaning. First, the PVDF membrane was treated by oxygen plasma so as to get the reactive groups. Second, this film was deposited by perfluoroalkylethyl acrylate precursor/Ar gas via plasma-enhanced chemical vapor deposition (PECVD). The modified film surface exhibited ultra water-repellent ability, showing that the water contact angles was larger than 150 °and the dynamic contact angles was usually lower than 5°.

Abstract: The constitutive equations relating cross-sectional loads(forces and moments)to cross-sectional displacements(stretching, bending, twisting) of thin-walled laminated beams with integral shape memory alloy (SMA)active fibers was presented. The variational asymptotic method was used to formulate the force- deformation relationships equations, accounting for the presence of active SMA fibers distributed along the cross-section of the beam. The constitutive relationships for evaluation of the properties of a hybrid SMA composite ply were obtained following the rule of mixtures. The analytical expressions of the actuation components for the active beam were derived based on Tanaka’s constitutive equation and Lin’s linear phase transformation kinetics for SMA fiber. The general form of constitutive relation was applied to the case of stretching-twist coupling, corresponding to Circumferentially Uniform Stiffness (CUS). The present analysis extended the previous work done for modeling generic passive thin-walled laminated beams. Numerical results shown that significant stretching and twisting deflection occur during the phase transformation due to SMA actuation. The effects of temperature on structural response behavior during phase transformation from martensite to austenite are significant. The effects of the volume fraction of the SMA fiber, the martensitic residual strain and ply angle were also addressed

Abstract: The laser surface alloying(LSA) technique was firstly used to form wear resistant layers on nodular cast iron rolls with two different powders, A: NiCr-Cr3C2 and B: C-B-W-Cr. The microstructure, element distribution and phases of the layers were investigated. Results indicate that the alloying layers had pores and cracks, as well as a metallurgical bonding with the substrates. For layers with powder A, as the thickness of the pre-layers decreased, the numbers of pores and cracks of the LSA layers decreased but the thicknesses of them were close. Phases were barely influenced by the thickness of the pre-layer, while the content of them were affected. For layers with powder B, as the laser specific energy increased, the numbers of pores and cracks in the LSA layers decreased and the thicknesses of them increased. The microstructure in the layers with different powders was different.

Abstract: In the paper, tungsten carbide (WC) particles can be in-situ synthesized by applying electromagnetic field to the system consisting of tungsten wires and gray cast iron melt at 1573 K. The microstructures and wear-resistant properties of composites reinforced by both WC particles and the residual tungsten wires were investigated by XRD, SEM, EDS, micro-hardness and pin-on-disc wear measurements. The results show that, with enhancing frequencies of electromagnetic field from 0 to 5 KHz, the amounts of in-situ WC particles increased and of the residual tungsten wires gradually decreased until tungsten wires completely reacted. Due to the higher hardness of in-situ WCp(2100-2231HV0.1) and the strong interfacial bonding, the composites displayed an excellent wear-resistant properties. When the frequency was 5 kHz, the wear loss for the composite fabricated was optimal and 2.69 times lower than that of reference samples.

Abstract: Experiments using a planar metal disc flyer driven by explosives and a cylindrical chamber was designed to synthesize cubic silicon nitride with the mixtures of α-Si3N4 and copper powders as starting materials. The ratio of transformation from α-Si3N4 to γ-Si3N4 approached to 80% percent at 45 GPa pressures and 4000K temperatures. The purity of γ-Si3N4 reached 100% after the synthesized samples were treated with hydrofluoric acid at 440K for 9-10h. High pressure sintering was carried out with a DS6×800A link-type cubic anvil apparatus at a pressure of 5.7GPa and calculated temperature of 1370-1670K over the course of 15 minutes. The result showed that γ-Si3N4 was completely transformed into β-Si3N4 at 5.7GPa, 1420-1670k and was partly transformed into β-Si3N4 at 5.7 GPa, 1370k. Micro-analysis indicated that the typical microstructure of sintered Si3N4 was elongated β-Si3N4 rod crystals in disordered orientation, the highest relative density of the sintered samples was 99.06% and Vickers hardness of them was 21.15GPa.

Abstract: In this study, thermal post-buckling behaviors and linear flutter analysis of Functionally Graded(FG) panels with structural damping under a supersonic airflow are investigated. First-order shear deformation theory (FSDT) is applied to model the panel, and the von-Karman strain-displacement relations are adopted to consider the geometric nonlinearity. In addition, the damping is modeled as the Rayleigh damping, and the first-order piston theory is applied for the supersonic aerodynamic load.

Abstract: A supramolecular compound, Co(C5H4NCOO)2(H2O)2∙2H2O was hydrothermally synthesized and characterized by elemental analysis, infrared spectra, UV-vis spectra. Elemental analysis result shows that the mass percent of C is 38.36%; H, 4.32% and N, 7.50%. Infrared spectra show that the main absorption peak is near 3396 cm-1, which is attributed to the O-H stretching vibration absorption. Also there are some absorption peaks at 1599, 1551, 1420, 1384 cm-1, which are attributed to the pyridine vibration absorption. UV spectrum for the compound shows strong absorption peaks at 203 and 259 nm, which are similar to isoniazid. X-ray diffraction data indicate that the compound is monoclinic, P21 / c space group. The cyclic voltammograms indicate that the compound decreases the rate of oxygen reduction reaction (ORR) and induces the ORR more difficult in aqueous solutions. The electrochemical behavior suggests that the compound possesses the potential application for corrosion in aqueous environment.

Abstract: Two new microporous polyoxomolybdates of (NH4)2[γ-Mo8O26] (Compound I) and (NH4)2[Mo4O13] (Compound II) were synthesized hydrothermally and characterized by elemental analysis, infra-red, TG analysis and single-crystal X-ray diffraction. In the synthesis process, we found that both organic template and transition metal salt play crucial roles in the formation of crystals. Cyclic voltammetry was used to study their electrochemical properties. The results reveal that the two compounds possess electrochemical activity in 0.2M H2SO4+Na2SO4 ( pH=1 ) solution and three multi-electron transferred redox reaction (I-I´, II-II´ and III-III´) processes were obtained. The first two redox reactions (I-I´, II-II´) are reversible reaction processes but another one (III-III´) is not. The electrochemical properties of the two compounds indicate their great potential applications in electroanalysis and electrocatalysis.

Abstract: The SiC/Cu composite was prepared by the method, which is patented in China, casting the metal into the SiC skeleton in a special furnace at 1160°C by pressure, caused by pressure difference between pressured gas and vacuum. During the preparation, the SiC decomposed. The carbon precipitated and the silicon, which has well affinity with the metal, formed silicon-copper compounds as Cu4Si, gathering in the silicon-copper interface area, identified by means of EDS and XRD. The mechanism of the solid reaction was discussed and the microstructure and morphology was studied by means of optical devices, SEM, EDS and XRD as well. And the diffusion coefficient was calculated.