The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed...The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.展开更多
A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-co...A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.展开更多
The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate （K2S2O8） in acidic media is satisfa...The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate （K2S2O8） in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.展开更多
Pure K2Ti4O9 whiskers were prepared by KDC（Kneading-Drying-Calcination） method with TiO2 and K2CO3 as raw materials. The influences of TiO2/K2CO3 molar ratio（RT/K）, calcination temperature（TC） and cooling proces...Pure K2Ti4O9 whiskers were prepared by KDC（Kneading-Drying-Calcination） method with TiO2 and K2CO3 as raw materials. The influences of TiO2/K2CO3 molar ratio（RT/K）, calcination temperature（TC） and cooling process on phase composition and morphology of the whiskers were investigated by TG-DSC（thermo gravimetric-differential scanning calorimeter）, XRD（X-ray diffraction）, and SEM（scanning electron microscope）. Pure K2Ti4O9 potassium titanate whiskers with large length-diameter ratio（r）（over 250） can be obtained at RT/K = 2.9 and TC = 950 ℃.展开更多
β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate s...β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate stabilizer KI, and reacted at room temperature for 5 h to produce a ferrate-containing cake. The cake is dried to give a water-free dried potassium ferrate (VI).展开更多
For improving its hydrophilicity and biocompatibility,and preserving filament mechanical properties at the same time,polyglycolic acid( PGA) filament was modified by potassium dichromate solution with different proces...For improving its hydrophilicity and biocompatibility,and preserving filament mechanical properties at the same time,polyglycolic acid( PGA) filament was modified by potassium dichromate solution with different processing time. Breaking force and water contact angle were tested. Surface changes before and after surface modifications were tested with scanning electron microscopy(SEM). Furthermore,differential scanning calorimeter(DSC) and Fourier transform infrared spectrometry(FTIR) were used to analyze the changes of molecular structure and functional group. Experimental results showed that 6 min was the most suitable time for improving hydrophilicity of PGA filament and preserving its mechanical properties.展开更多
The complex K_3H_4GeW_9V_3O_(40)·8H_2O crystallized in a monocliinie system with space group P2, Mr=2784.67, a=11.099(3), b=16.452(4), c=13.534(4) , β=108.14(2)°, Z=2,V=2348.49 ~3, F(000):2456, μ=239.7cm^(...The complex K_3H_4GeW_9V_3O_(40)·8H_2O crystallized in a monocliinie system with space group P2, Mr=2784.67, a=11.099(3), b=16.452(4), c=13.534(4) , β=108.14(2)°, Z=2,V=2348.49 ~3, F(000):2456, μ=239.7cm^(-1), De=3.932 g/cm^3. The final R=0.083 for 4528 non-zero reflexions. The structure of anions GeW_9V_3O_(40)~and GeW_9O_(34)~belongs to A-type.展开更多
文摘The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.
基金financially supported by the National Natural Science Foundation of China(21173195)~~
文摘A series of K-promoted Pt/Al2O3 catalysts were tested for CO oxidation. It was found that the addition of K significantly enhanced the activity. A detailed kinetic study showed that the activation energies of the K-containing catalysts were lower than those of the K-free ones, particularly for catalysts with high Pt contents （51.6 k）/mol for 0.42K-2.0Pt/Al2O3 and 6：3.6 kJ/mol for 2.0Pt/Al2O3 ）. The CO reaction orders were higher for the K-containing catalysts （about -0.2） than for the K-free ones （about -0.5）, with the former having much lower equilibrium constants for CO adsorption than the latter. In situ Fourier-transform infrared spectroscopy showed that surface CO desorption from the 0.42K-2.0Pt/Al2O3 catalyst was easier than from 2.0Pt/Al2O3. The promoting effect of K was therefore caused by weakening of the interactions between CO and surface Pt atoms. This decreased coverage of the catalyst with CO and facilitated competitive O2 chemisorption on the Pt surface, and significantly lowered the reaction barrier between chemisorbed CO and O2 species.
基金support and purchase of Hewlett-Packard 6890 GC-Hewlett-Packard 5973N MSD instrument.
文摘The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate （K2S2O8） in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.
基金Funded by the Natural Science Foundation Key Project of Hubei Province(No.2011CDA060)
文摘Pure K2Ti4O9 whiskers were prepared by KDC（Kneading-Drying-Calcination） method with TiO2 and K2CO3 as raw materials. The influences of TiO2/K2CO3 molar ratio（RT/K）, calcination temperature（TC） and cooling process on phase composition and morphology of the whiskers were investigated by TG-DSC（thermo gravimetric-differential scanning calorimeter）, XRD（X-ray diffraction）, and SEM（scanning electron microscope）. Pure K2Ti4O9 potassium titanate whiskers with large length-diameter ratio（r）（over 250） can be obtained at RT/K = 2.9 and TC = 950 ℃.
文摘β-Fe2O3·H2O is prepared by reacting FeCl3, K2CO3, an oxidizing agent HIO4 and a metal chelating agent K3PO4 at 65~ 70℃. The prepared β-Fe2O3' H2O is introduced into the mixture of KOH, KOCl and a ferrate stabilizer KI, and reacted at room temperature for 5 h to produce a ferrate-containing cake. The cake is dried to give a water-free dried potassium ferrate (VI).
基金Shanghai Municipality Science and Technology Commission,China(No.12DZ1940300)
文摘For improving its hydrophilicity and biocompatibility,and preserving filament mechanical properties at the same time,polyglycolic acid( PGA) filament was modified by potassium dichromate solution with different processing time. Breaking force and water contact angle were tested. Surface changes before and after surface modifications were tested with scanning electron microscopy(SEM). Furthermore,differential scanning calorimeter(DSC) and Fourier transform infrared spectrometry(FTIR) were used to analyze the changes of molecular structure and functional group. Experimental results showed that 6 min was the most suitable time for improving hydrophilicity of PGA filament and preserving its mechanical properties.
文摘The complex K_3H_4GeW_9V_3O_(40)·8H_2O crystallized in a monocliinie system with space group P2, Mr=2784.67, a=11.099(3), b=16.452(4), c=13.534(4) , β=108.14(2)°, Z=2,V=2348.49 ~3, F(000):2456, μ=239.7cm^(-1), De=3.932 g/cm^3. The final R=0.083 for 4528 non-zero reflexions. The structure of anions GeW_9V_3O_(40)~and GeW_9O_(34)~belongs to A-type.
