Applied Mechanics and Materials Vol. 470

Abstract: A series of high molecular weight，readily soluble conjugated copolymers derived from 9,9-dioctylfluorene (DOF) and 4,7-di(3- hexylthien-2-yl)-2,1,3-benzothiadiazole (DHTBT) were designed and synthesized by a palladium-catalyzed Suzuki coupling reaction with different ratios of DOF to DHTBT. Thermal stability, solubility, absorption spectra, photoluminescent spectra and electrochemical of the copolymers were investigated in detail. In the solid film, these copolymers showed saturated red light. These properties made them potential soluble red light-emitting candidates for polymer light-emitting diodes.

Abstract: The luminescence investigations on the calcinated zinc tungstate nanopowder (ZnWO₄ NP) synthesized by microwave-assisted synthesis are presented using photoluminescence (PL) and time-resolved photoluminescence (TRPL) analyses. The X-ray diffraction (XRD) patterns exhibit that the significant wolframite structure of ZnWO₄ NP can be detected at calcination temperatures above 300 °C. The 12 K PL and TRPL results demonstrated that the deformation of WO₆ octahedra is responsible for the low-energy side of PL spectra and dominate the red-shifted PL spectra with increasing calcination temperatures.

Abstract: 1Cr13 stainless steel was pre-coated on the surface of 6061 aluminum for electron beam alloying, then the microstructure and properties of the modified layer was discussed and analyzed. Using Scanning electron microscopy (SEM), EDAX energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and other analytical testing methods to analyze the microstructure and phase composition of the modified layer; Using the HX-1000TM automatic turret micro-hardness tester and HSR-2M high-speed reciprocating friction and wear tester to respectively measure its hardness and wear, finally to analyze the modification effect. The results showed that: between the alloyed layer and the substrate obtains a good metallurgical bonding; the modified layer organization composes mainly of martensite and Al-Fe compounds, and has fine grain; the hardness of the strengthening layer is about 4 times that of the substrate, and its wear resistance is a quarter of the matrixs.

Abstract: Aqueous polyurethane(PU) polyols were synthesized from polyester polyol, toluene diisocyanate(TDI), dimethylolbutyric acid (DMBA) and diethanolamine(DEA). The structure of PU polyol and resulting polyurethane film were confirmed by the Fourier Transform Infrared Spectroscopy (FT-IR). The effects of NCO/OH and DMBA content on the particle size of PU polyol and resulting polyurethane films, which formed by the mixture of PU polyol and water-dispersible polyisocyanate, was investigated by dynamic light scattering analysis, dynamic mechanical analysis and measurement of the mechanical properties.The results show the increase in DMBA content or NCO:OH ratio may be used to decrease the particle size of aqueous polyurethane polyol, increase the Tg for two-component aqueous PU film and maybe adjust the mechanical properties of resulting film.

Abstract: The polyimide foam (PIF) was prepared by the foaming of precursor derived from dimethyl ester of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-diaminodiphenyl methane (MDA). The structure and properties of polymers were investigated by FTIR, ¹H NMR, TG, DSC, SEM and mechanical testing. The findings show the PIF developed is of glass transition temperature of about 309°C, weight loss 5wt% at 517°C, density of 0.0018 g/cm³, cell structure of about 150μm, open-cell of 20%, thermal conductivity of 0.0277W/cm·K suitable for thermal insulation foam.

Abstract: This paper mainly describes a novel biodegradable material poly (butylene carbonate) (PBC) to blending toughing modification for polylactic acid (PLA), and prepared the PBC/PLA biodegradable film) of improved toughness. To research the effect of thermol performance and mechanical properties (tensile strength and breaking elongation rate) through Fourier transform infrared spectroscopy (FTIR), differential thermal scanning calorimetry analysis (DSC) and tensile testing to expound different ratio of PBC and additive plasticizer, (lubricant and chain extender) .

Abstract: The monodisperse functional Polystyrene/Silica (PS/silica) microsphere has been successfully prepared via suspension polymerization followed by the modified silica composite phenylethylene method. The FTIR, SEM, EDS and BEI were used to characterize the structure and composition of monodisperse functional PS/Silica microspheres. The results indicated that the dosage of silica modifier affect the compatibility of the modified silica and phenyl ethylene. The several modified silica would synergistically impact on the morphology and performance of products corresponding to distinguish formation mechanisms. The thermal stability and compressive strength performance had been improved compared with polystyrene (PS).The weight loss of PS/Silica microspheres were less than polystyrene (PS) which weightlessness ratio is 96.92 wt %. The compressive strength of PS/Silica microspheres was almost two times as many as pure PS microspheres. The formation mechanism of monodisperse functional PS/Silica microsphere was developed ahead according to the results of FTIR, SEM, EDS and BEI under various polymerization conditions.

Abstract: Both quasi-static compressive tests and dynamic loading tests on the open-cell aluminum foam made of 6061 aluminum alloy were firstly conducted. The Split Hopkinson Pressure Bar (SHPB) apparatus was used to perform the dynamic loading tests. The rate-dependent constitutive model for the open-cell aluminum foam was then studied. Based on the empirical constitutive model proposed by Sherwood for polyurethane foam, a new function was found to analyze the three-stage characteristic of quasi-static stress-strain curve of the aluminum foam. Moreover, the temperature softening was also modified. Thus a new strain rate hardening constitutive model coupled with temperature softening for the open-cell aluminum foam was obtained. Finally, both Taylor impact tests and finite element analysis (FEA) were conducted to verify the new constitutive model and the results show that the model was reliable.

Abstract: The grade of the TiO₂ in the crude ore is 5.84%, the grade of the iron is 28.38%, and the form of the TiO₂ mainly is ilmenite. Because of the TiO₂ dense symbiosis with the iron, so the difficulty of the study is the effective separation of TiO₂ and iron. After testing we decided take the process of grinding the crude ore, then get the iron concentrate through the high gradient magnetic separation. After tailing by the spiral chute, the concentrate through the shaker for the final selection of titanium concentrates. As a result, we attained satisfying selecting targets through closed-circuit test: The grade of TiO₂ is 45.38% and the recovery is 70.64% in the TiO₂ concentrate. The grade of iron is 57.42% and recovery is 63.80% in iron concentrate.

Abstract: A task of a refractory oxide copper ore in Yunnan has been studied, the grade of copper is 2.76% in crude ore. This ore has high oxidation and deep combination, the oxidation ratio is 42.32% and the combination ratio is 33.01%, so it is difficult oxide copper. Because the sulfide copper in crude ore containing 21.27%, so by experimental research, we decided to adopt the process of floating copper sulfides, and then sulfide oxide copper. In the flotation of oxidized copper minerals, we take the process of desliming, the copper minerals have recycled efficiently, while making a small precious metal--silver has been associated enrichment. Through closed-circuit test, we obtained the final concentrate, which the grade of copper is 20.38%, the recovery of copper is 65.44% and the grade of silver is 80.15g/t.