Abstract: Aluminum alloy 2219 is widely used in aerospace applications since it has a unique combination of good weldability and high specific strength. Furthermore, it can provide a high strength after heat treatment with superior properties in cryogenic environment so they have been widely used for cryogenic fuel tank of space launch vehicles. It is known that solid state welding like friction stir welding can improve the joint properties of this alloy. Friction stir welding is a solid state welding technology which two materials are welded together by the frictional heat due to the rotation of the tool. In this study, friction stir welding was performed on aluminum alloy 2219 sheets. The range of welding parameter is four rotation speeds from 350 to 800 rpm and six travel speeds from 120 to 420 mm/min. The results include the microstructural change after friction stir welding. The microstructure was characterized and material in the stirred zone experience sufficient deformation and heat input which cause the complete dynamic recrystallization. The present work represents the strength at each process condition and the optimum friction stir welding process parameters. The optimum weld efficiency obtained in this study was 76.5 %.
Abstract: The perovskite oxide Bi0.5Na0.5MnxTi1-xO3, Bi0.5Na0.5NbxTi1-xO3, Bi0.5Na0.5 (Mn0.5Nb0.5)xTi1-xO3 and Bi0.5Na0.5TiO3 ceramics (x=0.25%) were prepared via the conventional solid state reaction method. The role of Mn as an acceptor, Nb as a donor and (Mn0.5Nb0.5) substitution at B site in BNT lead-free piezoceramics was investigated. The (Mn0.5Nb0.5) substitution led to the inhibited of reduction of Ti4+ to Ti3+ and gave rise to large defect-dipole clusters containing highly localized electrons which should be responsible for the increase of Tc and Td. The ferroelectric properties and field-induced strains were both improved by Mn-acceptor and (Mn0.5Nb0.5) co-doped. The fatigue-resistant properties of Nb doped BNT ceramics were comparable to BNT ceramics, Mn doped ceramics were found to have significantly improved fatigue-resistant properties, while almost no profound fatigue was observed in BNT-MnNb ceramics after switching over 106 cycles at room temperature.
Abstract: The greenhouse is widely used in agriculture, and its covering material is one of the most important factors that affect its performance. In summer, the inner temperature of the greenhouse is usually too high for people to cultivate plants. In this work, a polymer matrix composite (PMC) was developed to reduce the inner temperature of the greenhouse without affecting the photosynthesis for the growth of plants. The PMC developed in this study was made of LDPE with suitable additives such as pigments, metal oxide etc. The morphology of the covering layer made of the PMC was observed with the atomic force microscopy (AFM). The transmittance of visible light and NIR through the cladding layer was measured with an optical fiber detector and used as the primarily performance index. Finally a simulated greenhouse was used to verify the cooling effect of the cladding layer. Experimental results showed that the PMC developed in this study gave more temperature reduction than that of the commercial PE covering.
Abstract: Photocatalytic degradation kinetics of methylene blue in aqueous solution was systematically investigated using Ti-based composite material as the photocatalyst. The single-variable-at-a-time ( SVAT) method was employed. It studied the individual and synergistic effects of several classical parameters on photocatalytic efficiencies. The kinetic mechanism was systematically explored. The kinetics effects of the doping amount of La and N, calcination temperature and time, light intensity were studied in detail. The factors on the degradation of MB were in accordance with the pseudo first order kinetic model. This kinetic model followed the Langmuir–Hinshelwood model. The best preparation conditions were found in the experiments. It is proved that the Ti-based composite material is an effective adsorbent for the degradation of dye contaminated water.
Abstract: Porous irons with only micropores were produced through powder metallurgy route. Corn starch of small particle size (5-15μm) was utilized to regulate the densification of green compacts. The structural and mechanical properties of porous irons sintered at different temperatures were evaluated. The porosities increased with increasing the starch content, which reduced compressive strength and increased volumetric shrinkage. The compressive yield stress increased with increasing sintering temperature. It was also found that the effect of sintering temperature on the microstructure and compressive properties was more obvious when green compacts were less densified. Moreover, volumetric shrinkage of porous irons without adding starch remains in a quite low level for different sintering temperatures.
Abstract: LiNi1/3Co1/3Mn1/3O2 was prepared by high temperature solid-state method under different synthesis temperature. The structure and morphology of LiNi1/3Co1/3Mn1/3O2 were characterized by Scanning electron microscopy (SEM) and X-ray diffraction (XRD). Electrochemical performance of the cathode material was researched by Land 2001. XRD and SEM results show that the well-crystallized LiNi1/3Co1/3Mn1/3O2 composite with homogeneous small particles was obtained. And the optimum synthetic temperature was 500°C for 5 hour and 900°C for 20 hour. From charge/discharge test, it can be seen that at 0.1C, 0.2C and 0.5C rate, LiNi1/3Co1/3Mn1/3O2 has initial discharge capacities of 178.6mAh/g, 172.9mAh/g and 152.7mAh/g, respectively. The discharge capacities of optimum sample remain above 85% after 43 cycles. This study provides the selection of synthetic temperature via solid state methods.
Abstract: An assembly of diacetylene molecules is necessary to progress a topochemical reaction as UV-irradiated polymerization. In this study, we attempt to regularly assemble 10, 12- pentacosadiynoic acid (PCDA) by freezing the solution, followed by lyophilization. Dried PCDA assembly was easily dispersed in aqueous solution by sonication. Irradiation of UV light can promote polymerization reaction of PCDA judging from a color change of the solution into blue. A color transition of the polyPCDA-dispersed solution from blue to red was observed at approximately 56°C due to distortion of its π-conjugated system. A color transition temperature could be controlled by hybridization with thermosensitive hydroxypropyl cellulose, of which lower critical solution temperature appears around 38-39°C. By synchronizing to coli-globule transition of HPC in aqueous media, blue-red transition response of water-dispersed polyPCDA could be induced by changing conformation of surrounded polymer.
Abstract: The advantages of aluminum alloy are found expression in lightweight and high strength, while bamboo features in density and thermal insulation. It’s necessary to explore composition effect of bamboo-aluminum composite. Specimens were prepared by filling aluminum alloy hollow profile with bamboo blocks, and then stress-time curves were collected in process of compression. Its ultimate strength reached 56 MPa, and residual strength is about 40% of its ultimate strength. The bamboo-aluminum composite has good mechanical properties and reliability for structural components and is worthy of wide applications.
Abstract: А new polyethyleneimine sulfur-containig exchanger network structure with static exchange capacity of 0.1 N solution of HCl 4.7 mEq/g was obtained by polycondensation of glycidyl methacrylate, methyl methacrylate and phosphoric acid. Sorption of copper (II) and zinc (II) ions was studied and investigated in static conditions from model solutions of sulfates of copper and zinc, in dependence on their concentration and pH, as well as their contact time with the ion-exchanger. Found that the magnitude of the sorption capacity of the ion exchanger for ions of copper (II) at pH 3.6 CuSO4 solution is 4.03 mg / g. It has been established that zinc ion (II) is absorbed best by the sorbent at pH 4.06. In these conditions the sorption capacity of the sorbent for copper ions (II) and zinc (II) respectively equal to 0.8225 mmol / g (Cu) and 0.8305 mmol / g (Zn). The sorption ability new sulfur-containing ionite with respect to copper ions (II) and zinc (II) is significantly higher than for industrial ionite of KU-2x8.