Advanced Materials Research Vols. 463-464

Abstract: The microstructure and mechanical properties of ZrO2/Ni functionally graded materials (FGMs) fabricated by powder metallurgy technique were investigated experimentally. The relative density of non-graded composite and functionally graded materials (FGM) was also measured. Microscopic examination exhibits that the material composition and microstructure of the FGMs vary gradually. The distributions of mechanical properties in the FGMs are obtained from the mechanical testing of homogeneous composite samples with different volume fractions of Ni. The results show that the elastic modulus and the bending strength decreases with increasing the nickel content from 0 to 50 % Ni, this is mainly affected by the weakly bonded ceramic/metal interface. Also, it was found that the fracture toughness and the elastic modulus in the FGMs are higher than that of the all non-graded composite.

Abstract: The ternary compound thin films doped with Mn and Nb, Pb(Mn1/3,Nb2/3)O3-PbZrO3- PbTiO3(PMnN-PZ-PT), with the same ratio of PZ/PT=52:48(PZT(52/48)) are fabricated on the heterostructure substrates of SrRuO3(SRO)/Pt(111)/Ti/SiO2/Si(100) by the radio frequency (RF) magnetron sputtering system, in which the quench method is used for the post heat treatments. The ternary compound films exhibit polycrystal phase combined with (001), (101) and (111) orientations with the 6% mole percent mixing ratio of PMnN, in which the (111) directions are the main orientations for non-mixed PZT(52/48) films and 6% mole percent PMnN mixing PZT(52/48) films(6%PMnN-94%PZT(52/48)), and so both of them are epitaxially grown on Silicon substrates with the (111) orientation. The ferroelectricities of the films are studied by the Sawyer Tower circuit, and the results show that the mixing of PMnN seriously improves the ferroelectricities of PZT(52/48), in which the 6% mixed PZT films own the rest polarization intensity , the saturation polarization intensity and the coercive electric-field intensity =139 kV/cm which are distinctly larger than the non-mixed PZT(52/48) films

Abstract: One-ply thick externally pressurized GFRP cylinders were analyzed using computational numerical simulation and analytical method. The main part of the work was to study the critical external pressure to avoid failure in the laminated shells by employing various phenomenological failure criteria. Comparison between ABAQUS FEM simulation results and analytical solutions using MATLAB programming codes proved high accuracy of the analytical approach. Various fiber angles stacking sequences were chosen for optimization analysis. The results did not show any increase in stability as the layer number increased. The results also showed high correlation with corresponding failure criteria. The analytical solutions gave higher accuracy as the number of plies and the total laminate thicknesses were reduced.

Abstract: Integrating germanium on Si is one of the major challenges of epitaxial growth and presents important applicative interest. Recently, SrTiO₃ was adopted as a buffer layer to accommodate the mismatch between Ge and Si. Germanium can take its bulk lattice parameter as soon as the growth begins without threading defects on SrTiO₃ surface. However, the details of Ge adsorption on SrTiO3 surface are not clear. In present work, the electronic structures of Ge deposited on the SrTiO₃ (001) 2×1 Double Layer (DL) TiO₂ surfaces were investigated by means of density functional theory calculations. Several stable adsorption sites are identified. It is found that the germanium adsorption shows site selectivity and causes noticeable surface distortion. The charge transfer from germanium atom to surface contributes to the formation of strong Ge-O bondings and surface metallization.

Abstract: Currently, Pb-free is the primary trend of development for solder alloys, and the existing Pb-free solder alloys are still difficult to replace the traditional tin-lead solder alloys. How to further improve the welding properties of Pb-free solder alloys is the issue we currently faced. In this paper, through melt overheating treatment, the influence of liquid-liquid structure change (LLSC) on the structure and properties of SnZn8Bi3 Pb-free solder alloy has been studied. Experimental results show that the LLSC has obvious effects on the solidification process and solidified microstructure of SnZn8Bi3 alloy: bigger solidification undercooling degree in the solidification process, finer and more dispersed solidification structure, and more importantly, the mechanical and welding properties of the solder alloy have also been obviously improved.

Abstract: Zn-Al composites with carbonized rice husks were prepared by permanent mould. Microstructure and wear property of Zn-Al composites were measured under the condition of as-cast heated at 375 °C and 430 °C corresponding to solid and semi-solid range. The microstructure of as-cast, heated at 375 °C and 430 °C were different. The microstructure of as-cast Zn-Al alloy revealed primary a dendrites (α) and eutectoid α+η (α,rich Al, η rich Zinc)phases. The microstructure of ZA alloy with carbonized rice husks was fine dendrites for heated at 375 °C and second and third dendrites were almost dispersed. After semi-solid treatment, the microstructure of Zn-Al composites presented quasi-round or round and large with time prolonger. The hardness of Zn-Al composites rose with carbonized rice husks and increased slightly by heat treatment. Wear resistance of Zn-Al composites with carbonized rice husks improved significantly and increased with carbonized rice husks. But at the same amount of carbonized rice husks the wear resistance of the composite varied little regardless of being in the state of as-cast or heat treatment.

Abstract: In this work, a boundary element formulation for 2D linear viscoelastic solid polymers subjected to body force of gravity has been presented. Structural analysis of solid polymers is one of the most important subjects in advanced engineering structures. From basic assumptions of the viscoelastic constitutive equations and the weighted residual techniques, a simple but effective boundary element formulation is implemented for standard linear solid (SLS) model. The SLS model provides an approximate representation of observed behavior of a real advanced polymer in its viscoelastic range. This approach avoids the use of relaxation functions and mathematical transformations, and it is able to solve quasistatic viscoelastic problems with any load time-dependence and boundary conditions. Problem of pressurization of thick-walled viscoelastic tanks made of PMMA polymer, which subjected to a body force, is completely analyzed.

Abstract: Mono-crystal diamond was brazed with Ni-Cr alloy in protective atmosphere furnace, SEM and XRD were used to analyze the carbides on the surface of diamond and the phases of diamond after brazing, respectively. The results show that the diamond brazed in protective atmosphere furnace can realize high strength connection; the diamond has clear edges and complete morphology after brazing. On the surface of diamond, the arrangement of Cr₃C₂ is regular, the growth direction of Cr₃C₂ has a certain orientation relationship with the (111) crystal plane of diamond, all the Cr₇C₃ nucleates and grows on the surface of Cr₃C₂, finally, the inner layer is regular arrangement Cr₃C₂ and the external layer is Cr₇C₃.

Abstract: This paper reports that ZnO nanosheet-covered carbon fibers are synthesized by thermal oxidation of zinc films deposited on carbon fiber surfaces. The structure and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectrum. The result shows that all of the cabon fibers are coated ZnO nanosheets. An orange-red emission around 683 nm was found in PL spectrum when the sample prepared at 400 oC for 4 hours in air. I considered that the growth of ZnO nanosheets may be related to the size of substrates and reaction temperature. The orange-red emission was resulted from the interstitial carbon of ZnO-nanosheet-covered fibers, and green emission results from the oxygen vacancies.

Abstract: Phosphorous-containing flame retardant additive for polyethylene terephthalate (PET), hexa(phenylamino)cyclotriphosphazene (HPACP) was synthesized by substitution reaction of hexachlorocyclotriphosphazene (HCCP) with aniline. The melting temperature of HPACP are 279.2°C, and HPACP possesses of favorable thermal stability. Flame-retardant effect of HPACP on PET was investigated by Differential Scanning Calorimetry (DSC) and Limit Oxygen Index (LOI) methods. With the content of flame retardant HPACP increasing, the melting enthalpy of PET reduced, while the melting temperature and onset temperature showed a decreasing tendency. With the weakening of melt dripping phenomenon, LOI of PET/ HPACP flame retardant systems increases with the increase of content of HPACP. LOI of PET containing 10 wt% of HPACP is 28.3.