Advanced Materials Research Vols. 328-330

Abstract: Although the zinc-aluminum alloy has gotten substantial increase in terms of strength and friction characteristics than the traditional zinc alloy, it has limitation in the operating temperature and speed. In order to further improve the frictional characteristic and expand its application range, we adopted the inexpensive zinc-aluminum alloy of ZA27 reinforced by TiC nano-particles to replace the traditional bronze alloys (ZQSn6-6-3) to produce bearing bush. And through its dynamic performance of the finite element analysis to prove particle reinforced ZA27 bearing bush has good dynamic performance.

Abstract: Microstructure in the welding zone, mechanical and electro-chemical corrosion properties of high matching T91/T23 heterology heat-resisting steel welding joint were investigated. Experimental result shows that good welding joint was made by high matching and argon tungsten arc process. Micro-structure of the weld metal was tempering lath martensite with coarsing crystal grain. Microstructure in the HAZ of T23 steel side was mainly granular bainite and lath bainite; micro-structure of HAZ at T91 steel side was mainly tempered sorbite and tempered martensite. Hardness nearbynearby the fusion zone of T91 steel was the highese, and weak carbon migration were found nearby the fusion zone of T23 steel side weld junction. Corrosion resistance properties by turns of from large to small were: welded joint, T91 base metal , T23 base metal.

Abstract: Geopolymer, produced by the reaction of fly ash with an alkaline activator (mixture of Na₂SiO₃ and NaOH solutions), is an alternative to the use of ordinary Portland cement (OPC) in the construction industry. However, there are salient parameters that affecting the compressive strength of geopolymer. In this research, the effects of various NaOH molarities, Na₂SiO₃/NaOH ratios, fly ash/alkaline activator, and curing temperature to the strength of geopolymer paste fly ash were studied. Tests were carried out on 50 x 50 x 50 mm cube geopolymer specimens. Compression tests were conducted on the seventh day of testing for all samples. The test results revealed that a 12 M NaOH solution produced the highest compressive strength for the geopolymer. The combination mass ratios of fly ash/alkaline activator and Na₂SiO₃/NaOH of 2.0 and 2.5, respectively, produced the highest compressive strength after seven days. Geopolymer samples cured at 60 °C produced compressive strength as high as 70 MPa.

Abstract: A method was developed to predict numerically the dent depth of composite laminates subjected to quasi-static indentation. A progressive damage analysis was conducted for composite laminates under quasi-static transverse compressive loading by using a strain based Hashin and Yeh failure criteria as well as the FEM, and a series of degraded elastic constants of the damaged zone were drawn from the numerical results. The effective elastic constants of the damaged zone of the laminates were reevaluated according to Sun’s explicit expression. Finally, the dent depth vs. indentation force curve was predicted based on Swanson’s contact theory. The numerical simulations on the static indentation tests of T700/BA9912, T700S/5228 and T700/QY9511 laminates were done via this method. The numerical results agree well with the test data in the terms of the contact force and the corresponding dent depth.

Abstract: Wear resistance of Zn-Al alloys declines sharply at high-speed overload, or poor lubrication, friction interface adhering. It is necessary to further improve the properties of Zn-Al alloys. Silicon were added into Zn-Al alloys as reinforcement (Si from 3%, 5% to 7%) and modified with mixed salt (sodiums, CaF2 and KCl ) and mixed rare earth(La and Ce oxides).Research determined the hardness, tensile toughness, wear quantities (at room and high temperature), observed the microstructure of alloys, analyzed the modification mechanism of modifier on silicon ,and selected a better sample for testing of high temperature wear resistance and high speed friction- rotating. The results show that silicon phases are significantly modified from sheet to spheroid, the properties are further improved because of silicon as hard phase in alloys, especially, the high temperature properties increases greatly, adhering temperature increases from below 170°C to above 250°C.

Abstract: Wind power is emerging as a particularly attractive form of renewable energy. Dielectric Electric Active Polymers (DEAP) has shown great potential as actuator materials. Their predomination has been shown to operate in transforming mechani­cal to electrical energy in a generator mode. This work investigates the principle of wind power dielectric electro active polymer generator, simulation and experimental verification of the phenomenon. Dielectric Electro Active Polymer have proved to provide electrical energy with density as high as 1.5J.g^-1.This value is very important compared to the density available with piezoelectric polymer (0.3J.g^-1). The prototype has been set up on the DEAP wind power generator in the article. It is a membrane with an area of 1.5 m² and 30μm in thickness, which is fabricated by Danfoss PolyPower A/S using smart compliant electrode technology in conjunction with a silicone elastomer. In the last part of this article, experimental results are detailed with our prototype for wind application.

Abstract: Using nano-TiO₂ particles obtained by hydrolysis of titanium oxysulfate (TiOSO₄) as the precursor, and polystyrene (PS) spheres as the template, TiO₂ hollow spheres were successfully deposited on CPTi substrates through layer-by-layer self-assembly technology. After ultraviolet light (UV) irradiation, the TiO₂ coatings were soaked in simulated body fluid (SBF) to explore their bioactivities. The effects of UV irradiation time and UV irradiation media on the bioactivities of nano TiO₂ coatings were investigated. The results show that bone-like apatite can be formed on the surface of nano TiO₂ coating irradiated by UV, and this reveals that the irradiated coating has good bioactivity. The amount of apatite formed on the surface of the coating increases with the increase of UV irradiation time. UV-irradiated media also influence the bioactivity of the coating. The bioactivities of nano TiO₂ coatings irradiated in air and SBF are better than that in water.

Abstract: Bi-2212 superconducting phase was synthesized via sol-gel method, and the experimental parameters such as the concentration of precursor solution and heat treatment temperature were adjusted to find the optimal conditions. Metal nitrates were adopted as the starting materials and ethylenediaminetetracetic acid (EDTA) as chelating agent. Precursor solutions and gel with different concentration were obtained through the addition of different content of distilled water as solvent followed by heating at certain temperature to form grey powders. Afterwards, the powders were sintered at different temperature for 10 hours, respectively. X-ray diffraction (XRD) was adopted to investigate the phase purity and crystallinity of the sample derived. Results reveal that the optimized precursor solution concentration is 27% and the optimized sintering temperature is 850°C.

Abstract: To realize the functions of infrared transparent as well as radar double– pass Band, A Y loop and Y slot compound element Frequency Selective Surface (FSS) structure is proposed, which takes an infrared transparent inductive mesh as a substrate. The proposed structure is analyzed based on Galerkin spectral method. The transitivity of infrared (3um-5um) as well as the radar double passed band with two resonance frequencies (31GHz and 54GHz) is discussed. The result reveals that this structure has function of infrared transparent as well as stable radar double–band filter with effective shielding effect on S-band and C-band radar electromagnetic waves. The design with multiple passband is suitable for radar/IR composite guidance and it also offers a kind of new thinking way of design for multi-mode compound guidance systems.

Abstract: FeVO4 photocatalysts were synthesized by complexing Sol-Gel method using citric acid as chelate and characterized with X-ray diffraction (XRD), scanning electron microsoope(SEM, specific surface area (BET). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange (MO) solution under visible light. It was found that the sample prepared with the molar ratio of citric acid to metal inons be 2:1, pH=7 and calcinated under 750°C for 4 hours was pure triclinic FeVO4 phase. In the experimental conditions used, the FeVO4 calcined at 750°C had highest photocatalytic activity with the photodegradation rate was about 85% or so in 150min under 250W halogen lamp.