The efficient extraction of sodium(Na^(+))and lithium(Li^(+))from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries.However,coexisting cations such as divale...The efficient extraction of sodium(Na^(+))and lithium(Li^(+))from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries.However,coexisting cations such as divalent calcium(Ca^(2+))and magnesium(Mg^(2+))ions are at the subnanometer scale in diameter,similar to target monovalent ions,making ion separation a great challenge.Here,we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH_(2)membranes on the surface of anodic aluminum oxide.Such membranes contain angstrom-scale(~7Å)channels for the entrance of small monovalent ions and water molecules,endowing the selectivities for monovalent cations over divalent cations and water over salt molecules.The resulting high-connectivity MIL-53(Al)-NH_(2)membranes exhibit excellent ion separation performance(a selectivity of 121.42 for Na^(+)/Ca^(2+)and 93.81 for Li^(+)/Mg^(2+))and desalination performance(a water/salt selectivity of up to 5196).This work highlights metal–organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.展开更多
The electronic packaging shell of high silicon carbide （54%SiC, volume fraction） aluminum-based composites was produced by liquid-solid separation technique. The characteristics of distribution and morphology of SiC...The electronic packaging shell of high silicon carbide （54%SiC, volume fraction） aluminum-based composites was produced by liquid-solid separation technique. The characteristics of distribution and morphology of SiC as well as the shell’s fracture surface were examined by optical microscopy and scanning electron microscopy, and the thermo-physical and mechanical properties of the shell were also tested. The results show that Al matrix has a net-like structure while SiC is uniformly distributed in the Al matrix. The SiCp/Al composites have a low density of 2.93 g/cm^3, and its relative density is 98.7%. Thermal conductivity of the composites is 175 W/（·K）, coefficient of thermal expansion （CTE） is 10.3×10^-6 K-1 （25-400 ℃）, compressive strength is 496 MPa, bending strength is 404.5 MPa, and the main fracture mode is brittle fracture of SiC particles accompanied by ductile fracture of Al matrix.Its thermal conductivity is higher than that of Si/Al alloy, and its CTE matches with that of the chip material.展开更多
Double glow plasma surface metallurgy technique was used to fabricate a Fe?Al?Cr?Nb alloyed layer onto the surface of the 45 steel. The microstructures and composition of th?eA Fl?eCr?Nb alloyed layer were analyzed by...Double glow plasma surface metallurgy technique was used to fabricate a Fe?Al?Cr?Nb alloyed layer onto the surface of the 45 steel. The microstructures and composition of th?eA Fl?eCr?Nb alloyed layer were analyzed by scanning electronic microscopy, X-ray diffraction and energy dispersive spectroscopy. The results indicate thatthe 20 μm alloyed layer is homogeneous and compact. The alloyed elements exhibit a gradient distribution along the cross section. Microhardness and nanoindentation tests imply that the surface hardness of the alloyed layer reaches HV 580, which is almost 2.8 times that of the substrate. Compared with the substrate, the alloyed layer has a much smaller displacement and a larger elastic modulus. According to the friction and wear tests at room temperature, the? FeAl?Cr?Nb alloyed layer has lower friction coefficient and less wear mass, implying that the Fe?Al?Cr?Nb alloyed layer can effectively improve the surface hardness and wear resistance of the substrate.展开更多
The effect of arc-ultrasound on microstructures and mechanical properties of SiCp/6061A1 MMCs joints produced by arc-ultrasound plasma arc ＂in-situ＂ alloy-welding with different excitation frequencies was investigat...The effect of arc-ultrasound on microstructures and mechanical properties of SiCp/6061A1 MMCs joints produced by arc-ultrasound plasma arc ＂in-situ＂ alloy-welding with different excitation frequencies was investigated, in which argon-nitrogen mixture was used as plasma gas, Ti wire as filler and the arc-ultrasound was produced by modulating the plasma arc with high frequency. The results show that arc-ultrasound could refine the new reinforced composites such as TiC, TiN significantly, and improve their distribution greatly. And new phase A13Ti becomes finer and less. The test results of mechanical properties indicate that the maximum tensile strength of welded joints is gained when the excitation frequency is 50 kHz, and the maximum is 225 MPa, raising by about 7% comoared with conventional nlasma arc welding （PAW） （20q MPa）.展开更多
Melt-spun Al75-xSi25Crx （x=2, 4, 7, 10, mole fraction, %） alloys were investigated as anode materials for lithium-ion batteries. The as-quenched ribbons consist of nano-grains and metallic glass. The electrochemical...Melt-spun Al75-xSi25Crx （x=2, 4, 7, 10, mole fraction, %） alloys were investigated as anode materials for lithium-ion batteries. The as-quenched ribbons consist of nano-grains and metallic glass. The electrochemical measurements reveal that an activation behavior is exhibited in the anodes. The specific capacity of the A173Si25Cr2 anodes can reach a maximum of 1119 mA.h/g and maintain at 586 mA·hg after 30 cycles. A more stable cycle performance is shown and a capacity loss is only 24% over 30 cycles for Al71Si25Cr4. The intermetallic compounds with Li cannot be detected in the lithiated anodes. After the ribbons were annealed, the specific capacities become much lower due to the formation of inert Al13SiaCr4, and an A1Li phase can be tested in the lithiated anodes. The Cr dissolved in the non-equilibrium alloys causes low lithiation activity and strong structure stability, which could be the main reason of the activation and a restriction of structure evolution.展开更多
Si/Al composites with different Si contents for electronic packaging were prepared by spark plasma sintering （SPS） technique. Properties of the composites were investigated, including density, thermal conductivity, ...Si/Al composites with different Si contents for electronic packaging were prepared by spark plasma sintering （SPS） technique. Properties of the composites were investigated, including density, thermal conductivity, coefficient of thermal expansion and flexural strength. The effects of the Si content on microstructure and thermal and mechanical properties of the composites were studied. The results show that the Si/Al composites consist of Si and Al components and Al uniformly distributes among Si grains. The relative density of the Si/Al composites gradually increases with the decrease of Si content and reaches 98.0% when the Si content is 50%. The thermal conductivity, the coefficient of thermal expansion and the flexural strength of the composite all decrease with the increase of the Si content, and an optimal matching of them is obtained when the Si content is 60%（volume fraction）.展开更多
To address the limitations of the separate fluoride removal or detection in the existing materials,herein,amino-decorated metal organic frameworks NH_(2)-MIL-53(Al)have been succinctly fabricated by a sol-hydrothermal...To address the limitations of the separate fluoride removal or detection in the existing materials,herein,amino-decorated metal organic frameworks NH_(2)-MIL-53(Al)have been succinctly fabricated by a sol-hydrothermal method for simultaneous removal and determination of fluoride.As a consequence,the proposed NH_(2)-MIL-53(Al)features high uptake capacity(202.5 mg/g)as well as fast adsorption rate,being capable of treating 5 ppm of fluoride solution to below the permitted threshold in drinking water within 15 min.Specifically,the specific binding between fluoride and NH_(2)-MIL-53(Al)results in the release of fluorescent ligand NH2-BDC,conducive to the determination of fluoride via a concentration-dependent fluorescence enhancement effect.As expected,the resulting NH_(2)-MIL-53(Al)sensor exhibits selective and sensitive detection(with the detection limit of 0.31μmol/L)toward fluoride accompanied with a wide response interval(0.5-100μmol/L).More importantly,the developed sensor can be utilized for fluoride detection in practical water systems with satisfying recoveries from 89.6% to 116.1%,confirming its feasibility in monitoring the practical fluoride-contaminated waters.展开更多
This study aimed at improving the tribological and thermal properties of Al alloy using CNTs and Nb nanopowder as reinforcements and spark plasma sintering(SPS)as the fabrication method.The SPS was conducted at 630℃,...This study aimed at improving the tribological and thermal properties of Al alloy using CNTs and Nb nanopowder as reinforcements and spark plasma sintering(SPS)as the fabrication method.The SPS was conducted at 630℃,30 MPa,10 min,and 200℃/min.The tribology test was run with ball-on-disc tribometer using steel ball as the counter body.And the thermal test was processed with thermogravimetric analyzer(TGA)and laser flash apparatus(LFA).Results showed that the addition of 8 wt.%CNTs and 8 wt.%Nb reinforcements respectively decreased the coefficient of friction(COF)of the composite by 79%.The wear volume of the composite was decreased by 23%,and so was the wear rate.However,the thermal conductivity of the composite was equally improved by 44%.The tribology improvement was stimulated by a C film generated by CNTs and a protective Nb2O5 formed by Nb nanopowder.The thermal conductivity was improved by the grain refining property of Nb and the high thermal conductivity of CNTs.Therefore,these results indicated that Al-CNTs-Nb composite is a robust material for high transmission conductor capable of reducing sag and ensuring the durability of the composite.展开更多
Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,...Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.展开更多
The reaction diffusion between Fe and Al during spark plasma sintering(SPS)was studied.Microstructural evolution wasinvestigated by X-ray diffraction(XRD)and scanning electron microscopy(SEM)and the sintering kinetics...The reaction diffusion between Fe and Al during spark plasma sintering(SPS)was studied.Microstructural evolution wasinvestigated by X-ray diffraction(XRD)and scanning electron microscopy(SEM)and the sintering kinetics was disclosed.The maininterphase of the SPS sample was Fe2Al5at773-873K.Ball-milling enabled a large number of lattice defects and grain boundariesthus the reaction kinetics was accelerated,although the direct current can also promote those defects.After milling,the phasetransformation kinetics was improved from0.207before mill to4.56×10-3.Besides,this work provided more details for thegeneration of Joule heating.The resistance offered to the electric path was considered to be the source of Joule heating,andparticularly the resistance offered by the different contact interfaces of die,punch,graphite foil and the sample played a leading rolefor the generation of Joule heating during spark plasma sintering.展开更多
To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pre...To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over the whole process. The difference between the positive voltages of non-etched and etched specimens decreases gradually with the increase of processing time. The pretreatment exhibits much less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min-1and the energy consumption is decreased from 6.30 to 4.36 k W·h·μm-1·m-2. At the same time, both mullite and amorphous Si O2 contents are decreased in the coating.展开更多
Surface organometallic chemistry (SOMC) is a recently developing research field. It is of great significance for the quantitative modification, restoration of solid surface, identification of the physical and chemical...Surface organometallic chemistry (SOMC) is a recently developing research field. It is of great significance for the quantitative modification, restoration of solid surface, identification of the physical and chemical nature of surface and the preparation of new catalyst. The production of R 3 Sn-O-MCM-41 (R 3 SnM) was obtained by heating tributyltin chloride and Al-MCM-41 mixture at 170 °C for 5 h under stirring in nitrogen atmosphere. The composition, structure and surface physical and chemical properties of the samples were characterized by inductively coupled plasma mass spectrometry (ICP-MS), 13 C, 119 Sn, 29 Si and 27 Al solid state NMR (nuclear magnetic resonance) spectra, in-situ pyridine infrared spectroscopy (Py-IR), N 2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), etc. The results of ICP and organic elemental analysis shows that the grafting yield w Sn was 6.46% for R 3 SnM. H 0 (the negative logarithm of the acid concentration)and the number of acid sites for R 3 SnM respectively were 2.77-0.99 and 4.8 mmol·g-1 by the Hammett method. N 2 adsorption-desorption, XRD, TEM analysis showed that R 3 SnM with ordered hexagonal mesopore structure, resulted in the decease of surface areas and pore size as well as the increase of mesoporous volume and surface acidity, as compared to Al-MCM-41. R 3 SnM was used in the synthesis of isoamyl acetate. The yield of isoamyl acetate was 96% when n(isoamyl alcohol)︰n(acetic acid) 1.0︰1.0, 3 R SnM w 5%, 138 °C for 5 h. The catalyst can be reused and the yield of 86% can be attained when catalyst was reused five times at the same catalytic conditions.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(WK2060000030)USTC Research Funds of the Double First Class Initiative(YD2060002022)Major Science and Technology Innovation Projects in Shandong Province(2022CXGC020415).
文摘The efficient extraction of sodium(Na^(+))and lithium(Li^(+))from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries.However,coexisting cations such as divalent calcium(Ca^(2+))and magnesium(Mg^(2+))ions are at the subnanometer scale in diameter,similar to target monovalent ions,making ion separation a great challenge.Here,we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH_(2)membranes on the surface of anodic aluminum oxide.Such membranes contain angstrom-scale(~7Å)channels for the entrance of small monovalent ions and water molecules,endowing the selectivities for monovalent cations over divalent cations and water over salt molecules.The resulting high-connectivity MIL-53(Al)-NH_(2)membranes exhibit excellent ion separation performance(a selectivity of 121.42 for Na^(+)/Ca^(2+)and 93.81 for Li^(+)/Mg^(2+))and desalination performance(a water/salt selectivity of up to 5196).This work highlights metal–organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.
文摘The electronic packaging shell of high silicon carbide （54%SiC, volume fraction） aluminum-based composites was produced by liquid-solid separation technique. The characteristics of distribution and morphology of SiC as well as the shell’s fracture surface were examined by optical microscopy and scanning electron microscopy, and the thermo-physical and mechanical properties of the shell were also tested. The results show that Al matrix has a net-like structure while SiC is uniformly distributed in the Al matrix. The SiCp/Al composites have a low density of 2.93 g/cm^3, and its relative density is 98.7%. Thermal conductivity of the composites is 175 W/（·K）, coefficient of thermal expansion （CTE） is 10.3×10^-6 K-1 （25-400 ℃）, compressive strength is 496 MPa, bending strength is 404.5 MPa, and the main fracture mode is brittle fracture of SiC particles accompanied by ductile fracture of Al matrix.Its thermal conductivity is higher than that of Si/Al alloy, and its CTE matches with that of the chip material.
基金Project(51371097)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Double glow plasma surface metallurgy technique was used to fabricate a Fe?Al?Cr?Nb alloyed layer onto the surface of the 45 steel. The microstructures and composition of th?eA Fl?eCr?Nb alloyed layer were analyzed by scanning electronic microscopy, X-ray diffraction and energy dispersive spectroscopy. The results indicate thatthe 20 μm alloyed layer is homogeneous and compact. The alloyed elements exhibit a gradient distribution along the cross section. Microhardness and nanoindentation tests imply that the surface hardness of the alloyed layer reaches HV 580, which is almost 2.8 times that of the substrate. Compared with the substrate, the alloyed layer has a much smaller displacement and a larger elastic modulus. According to the friction and wear tests at room temperature, the? FeAl?Cr?Nb alloyed layer has lower friction coefficient and less wear mass, implying that the Fe?Al?Cr?Nb alloyed layer can effectively improve the surface hardness and wear resistance of the substrate.
基金Project (09003)supported by the Open Research Fund of State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, ChinaProject (JSAWT-07-04 ) supported by Provincial Key Research Fund of Advanced Welding Technology, Jiangsu University of Science and Technology, China
文摘The effect of arc-ultrasound on microstructures and mechanical properties of SiCp/6061A1 MMCs joints produced by arc-ultrasound plasma arc ＂in-situ＂ alloy-welding with different excitation frequencies was investigated, in which argon-nitrogen mixture was used as plasma gas, Ti wire as filler and the arc-ultrasound was produced by modulating the plasma arc with high frequency. The results show that arc-ultrasound could refine the new reinforced composites such as TiC, TiN significantly, and improve their distribution greatly. And new phase A13Ti becomes finer and less. The test results of mechanical properties indicate that the maximum tensile strength of welded joints is gained when the excitation frequency is 50 kHz, and the maximum is 225 MPa, raising by about 7% comoared with conventional nlasma arc welding （PAW） （20q MPa）.
基金Projects (50871081,51002117,51071117) supported by the National Natural Science Foundation of China
文摘Melt-spun Al75-xSi25Crx （x=2, 4, 7, 10, mole fraction, %） alloys were investigated as anode materials for lithium-ion batteries. The as-quenched ribbons consist of nano-grains and metallic glass. The electrochemical measurements reveal that an activation behavior is exhibited in the anodes. The specific capacity of the A173Si25Cr2 anodes can reach a maximum of 1119 mA.h/g and maintain at 586 mA·hg after 30 cycles. A more stable cycle performance is shown and a capacity loss is only 24% over 30 cycles for Al71Si25Cr4. The intermetallic compounds with Li cannot be detected in the lithiated anodes. After the ribbons were annealed, the specific capacities become much lower due to the formation of inert Al13SiaCr4, and an A1Li phase can be tested in the lithiated anodes. The Cr dissolved in the non-equilibrium alloys causes low lithiation activity and strong structure stability, which could be the main reason of the activation and a restriction of structure evolution.
基金Project (51374039) supported by the National Natural Science Foundation of ChinaProject (613135) supported by National Security Basic Research Program of China
文摘Si/Al composites with different Si contents for electronic packaging were prepared by spark plasma sintering （SPS） technique. Properties of the composites were investigated, including density, thermal conductivity, coefficient of thermal expansion and flexural strength. The effects of the Si content on microstructure and thermal and mechanical properties of the composites were studied. The results show that the Si/Al composites consist of Si and Al components and Al uniformly distributes among Si grains. The relative density of the Si/Al composites gradually increases with the decrease of Si content and reaches 98.0% when the Si content is 50%. The thermal conductivity, the coefficient of thermal expansion and the flexural strength of the composite all decrease with the increase of the Si content, and an optimal matching of them is obtained when the Si content is 60%（volume fraction）.
基金supported by the National Key R&D Program of China(No.2017YFA0207202)the National Natural Science Foundation of China(No.51572263,No.51772299,No.41701259).
文摘To address the limitations of the separate fluoride removal or detection in the existing materials,herein,amino-decorated metal organic frameworks NH_(2)-MIL-53(Al)have been succinctly fabricated by a sol-hydrothermal method for simultaneous removal and determination of fluoride.As a consequence,the proposed NH_(2)-MIL-53(Al)features high uptake capacity(202.5 mg/g)as well as fast adsorption rate,being capable of treating 5 ppm of fluoride solution to below the permitted threshold in drinking water within 15 min.Specifically,the specific binding between fluoride and NH_(2)-MIL-53(Al)results in the release of fluorescent ligand NH2-BDC,conducive to the determination of fluoride via a concentration-dependent fluorescence enhancement effect.As expected,the resulting NH_(2)-MIL-53(Al)sensor exhibits selective and sensitive detection(with the detection limit of 0.31μmol/L)toward fluoride accompanied with a wide response interval(0.5-100μmol/L).More importantly,the developed sensor can be utilized for fluoride detection in practical water systems with satisfying recoveries from 89.6% to 116.1%,confirming its feasibility in monitoring the practical fluoride-contaminated waters.
基金Centre for Energy and Electric Power (CEEP), Tshwane University of Technology, Pretoria, NRF and DHET for providing financial aid to this project
文摘This study aimed at improving the tribological and thermal properties of Al alloy using CNTs and Nb nanopowder as reinforcements and spark plasma sintering(SPS)as the fabrication method.The SPS was conducted at 630℃,30 MPa,10 min,and 200℃/min.The tribology test was run with ball-on-disc tribometer using steel ball as the counter body.And the thermal test was processed with thermogravimetric analyzer(TGA)and laser flash apparatus(LFA).Results showed that the addition of 8 wt.%CNTs and 8 wt.%Nb reinforcements respectively decreased the coefficient of friction(COF)of the composite by 79%.The wear volume of the composite was decreased by 23%,and so was the wear rate.However,the thermal conductivity of the composite was equally improved by 44%.The tribology improvement was stimulated by a C film generated by CNTs and a protective Nb2O5 formed by Nb nanopowder.The thermal conductivity was improved by the grain refining property of Nb and the high thermal conductivity of CNTs.Therefore,these results indicated that Al-CNTs-Nb composite is a robust material for high transmission conductor capable of reducing sag and ensuring the durability of the composite.
基金Project(18JS060) supported by the Shaanxi Key Laboratory of Nano-materials and Technology,ChinaProject(2018JQ5087) supported by Natural Science Basic Research Plan of Shaanxi Province,China。
文摘Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.
基金Projects(51474245,51571214)supported by the National Natural Science Foundation of ChinaProjects(2015GK3004,2015JC3006)supported by the Science and Technology Project of Hunan Province,China+3 种基金Project(2016YFB1100101)supported by the National Key Research and Development Program,ChinaProject(K1502003-11)supported by the Changsha Municipal Major Science and Technology Program,ChinaProject(CSUZC2015030)supported by the Open-End Fund for the Valuable and Precision Instruments of CSU,ChinaProjects(2015CX004,2016CX003)supported by the Project of Innovation-driven Plan in CSU,China
文摘The reaction diffusion between Fe and Al during spark plasma sintering(SPS)was studied.Microstructural evolution wasinvestigated by X-ray diffraction(XRD)and scanning electron microscopy(SEM)and the sintering kinetics was disclosed.The maininterphase of the SPS sample was Fe2Al5at773-873K.Ball-milling enabled a large number of lattice defects and grain boundariesthus the reaction kinetics was accelerated,although the direct current can also promote those defects.After milling,the phasetransformation kinetics was improved from0.207before mill to4.56×10-3.Besides,this work provided more details for thegeneration of Joule heating.The resistance offered to the electric path was considered to be the source of Joule heating,andparticularly the resistance offered by the different contact interfaces of die,punch,graphite foil and the sample played a leading rolefor the generation of Joule heating during spark plasma sintering.
基金Supported by the Natural Science Foundation of Guangdong Province,China(S2013010015211)
文摘To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over the whole process. The difference between the positive voltages of non-etched and etched specimens decreases gradually with the increase of processing time. The pretreatment exhibits much less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min-1and the energy consumption is decreased from 6.30 to 4.36 k W·h·μm-1·m-2. At the same time, both mullite and amorphous Si O2 contents are decreased in the coating.
基金Supported by the National Science Foundation of Heilongjiang Province (B201010)the Education Department of Heilongjiang Province (12511595)
文摘Surface organometallic chemistry (SOMC) is a recently developing research field. It is of great significance for the quantitative modification, restoration of solid surface, identification of the physical and chemical nature of surface and the preparation of new catalyst. The production of R 3 Sn-O-MCM-41 (R 3 SnM) was obtained by heating tributyltin chloride and Al-MCM-41 mixture at 170 °C for 5 h under stirring in nitrogen atmosphere. The composition, structure and surface physical and chemical properties of the samples were characterized by inductively coupled plasma mass spectrometry (ICP-MS), 13 C, 119 Sn, 29 Si and 27 Al solid state NMR (nuclear magnetic resonance) spectra, in-situ pyridine infrared spectroscopy (Py-IR), N 2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), etc. The results of ICP and organic elemental analysis shows that the grafting yield w Sn was 6.46% for R 3 SnM. H 0 (the negative logarithm of the acid concentration)and the number of acid sites for R 3 SnM respectively were 2.77-0.99 and 4.8 mmol·g-1 by the Hammett method. N 2 adsorption-desorption, XRD, TEM analysis showed that R 3 SnM with ordered hexagonal mesopore structure, resulted in the decease of surface areas and pore size as well as the increase of mesoporous volume and surface acidity, as compared to Al-MCM-41. R 3 SnM was used in the synthesis of isoamyl acetate. The yield of isoamyl acetate was 96% when n(isoamyl alcohol)︰n(acetic acid) 1.0︰1.0, 3 R SnM w 5%, 138 °C for 5 h. The catalyst can be reused and the yield of 86% can be attained when catalyst was reused five times at the same catalytic conditions.
