Applied Mechanics and Materials Vol. 628

Abstract: Adsorbent composites comprising of inorganic clay/sodium lignosulfonate graft-polymerized with acrylamide and maleic anhydride were synthesized by free radical solution copolymerization. The synthesized copolymers presented high adsorption capacity when the monomer ratio of acrylamide to maleic anhydride was 3:2 and montmrillonite was introduced as inorganic clay. The equilibrium adsorption of Pb²⁺ on these copolymers was well represented by Langmuir model which indicated that the Pb²⁺ adsorption was a monolayer chemical adsorption. The calculated adsorption capacity of the copolymers could reach a maximum of 176.70 mg/g for Pb²⁺ and 24.95 mg/g for Cu²⁺. In addition, these copolymers could selectively remove Pb²⁺ from Pb²⁺/Cu²⁺ binary solution and the maximum selective coefficient of Pb²⁺ to Cu²⁺ was 11.939.

Abstract: The microstructure and mechanical properties of friction stir welded Al-Zn-Mg-Cu alloy sheet were investigated by means of hardness and tensile tests, optical microscope and scanning electron microscope. The hardness profile of the weld exhibits a W shape with the lowest value in the thermo-mechanically affected zone on the advancing side. The tensile strength and elongation of the weld are about 71% and 72% that of the base material. In the nugget zone, there are a number of fine recrystallized grains and dispersed precipitates at grain boundaries. In the thermo-mechanically affected zone, the grain size is not uniform and there are a number of precipitates at grain boundaries. In the heat affected zone, the grain structure is similar to the base material.

Abstract: Adsorbent composites comprising of bentonite/sodium lignosulfonate graft-polymerized with acrylamide (BLPAM) were synthesized. Results showed that the optimized preparation conditions within the experimental range were as follows: the mass ratio of acrylamide to sodium lignosulfonate was 14, the pH of the reaction medium was 4.0, the mass concentrations of the initiator and cross-linker were 0.45% and 0.30%, respectively. The Pb²⁺ adsorption capacity of the as-prepared BLPAM was 0.161mmol/g.

Abstract: Catalyst by different carriers prepared of carbon dioxide conversion sequence is: Ni/TiO₂ > Ni/γ-Al₂O₃ > Ni/MgO > Ni/SiO₂. Second metal, Co, Mn, Cu, La and Ce, was significantly enhanced the activity of methanation nickel-based catalysts in the carbon dioxide methanation reaction, but second metal of Cu was bad for the activity of methanation. The 10%Ni/Al2O3 and 2.5%Ce-10%Ni/Al2O3 catalysts were characterized by TG and H2-TPR，it was revealed to Ce which is benefit for reduce NiO reduction temperature and the optimal reduction temperature of the catalysts in between 400°C and 500 °C

Abstract: Acoustic emission signals were continuously monitored during corrosion fatigue crack propagation for X52 steel in 3.5% NaCl and AZ31 magnesium alloy in 0.1%NaCl solution. There are different microstructure and corrosion fatigue crack propagation mechanism for X52 steel and AZ31B magnesium alloy. Combined with the existing research results of LY12CZ and 7075-T6 aluminum alloys, the acoustic emission waveform parameter, the frequency centroid ratio, was tried to use as a criterion to distinguish the corrosion fatigue crack propagation mechanism for anodic dissolution and hydrogen embrittlement. The results also show that the nature of the acoustic emission source determines the main characteristics of the signal parameters and waveforms, and little to do with the experimental material.

Abstract: The effects of mole ratio of formaldehyde and melamine (F/M), solution pH, reaction temperature and time on the foaming melamine-formaldehyde resin (MF resin) with caprolactam as modifier were investigated by orthogonal experiment design where the solid content and the viscosity of the resin, the density and the size uniformity of the foam resin were used as performance evaluation parameters. The results had shown that the optimal conditions for preparing the foaming MF resin were F/M= 3.25, pH=8.0, T=90°C, t=45min. The MF resin prepared under the optimal conditions could be foamed well and its storage time was prolonged to 16 days. The structure and thermal properties of MF resin under the optimal conditions were investigated.

Abstract: 3-Difluoroaminomethyl-3-methyl oxetane (DFAMO) was synthesized via the process of bromination, cyclization, ammonification, amino protection and fluorination with a total yield of 43% and GC purity of 96%. DFAMO was characterized by 1H, 19F, 13C nuclear magnetic resonance (NMR), fourier transform infra red (FTIR) and element analysis. The homopolymer of 3-difluoroaminomethyl-3-methyloxetane (PDFAMO), considered as energetic binder to be used in solid propellants and polymer bonded explosives, with a number-average molecular weight (Mn) about 3000 was synthesized via cationic ring-opening polymerization using boron trifluoride etherate (BTFE) as Lewis acid catalyst, 1,4-butanediol (BDO) as initiator and 1,2-dichloroethane (DCE) as aprotic solvent. The effects of BTFE/BDO feeding molar ratio and temperature of the polymerization reaction were discussed. The structure of PDFAMO was characterized by 1H and 19F NMR.

Abstract: The effect of doping different content of Mn into ammonium paratungstate (APT) on the production of tungsten products was studied systematically. The calcination of APT, reduction of WO₃ and carbonization of W were studied in sequence.The phase composition, powder morphology, existence form and distribution of Mn were analyzed by X-ray diffraction, scanning electron microscope and transmission electron microscope, respectively. The results showed that Mn converted from MnCl₂ to Mn²⁺WO₄ during reduction process. And then Mn²⁺WO₄ converted to Mn₅C₂ in the process of carbonization. Besides, Mn finally existed as the form of (Mn, W) C solid solution and Mn₅C₂. The distribution of Mn was always in the low contrast areas.

Abstract: Under the bad environment, high polymer wear-resistant material has more superior erosion wear resistant performance than metal. It can replace wear-resistant metal material partly. In this paper, high polymer wear-resistant coat has been prepared with the epoxy resin, low molecular polyamide, nanoAl₂O₃ coupling agent. The shear strength and wear resistant test has been carried out under different elements content, and the test curve of coat is given. The results are analyzed. By the experiment result, the optimum coat formula is: low molecular polyamide content is 60% relative to E – 51; and the content of MoS₂ is 12%. The result shows that the coat erosion wear resistance is 9 times of 45# steel under the best recipe. The coat is used to repair a worn mortar pump impeller, and the effect is obvious.