The enthalpy change of reaction of zinc chloride with L-α-histidine in thetemperature range of 25-50 ℃ has been determined by a microcalorimeter. On the basis ofexperimental and calculated results, three thermodynam...The enthalpy change of reaction of zinc chloride with L-α-histidine in thetemperature range of 25-50 ℃ has been determined by a microcalorimeter. On the basis ofexperimental and calculated results, three thermodynamics parameters (the activation enthalpy, theactivation entropy, the activation free energy), the rate constant and three kinetic parameters (theactivation energy, the pre-exponential constant and the reaction order) of the reaction, and thestandard enthalpy of formation of Zn(His)^(2+) (aq.) are obtained. The results showed that the titlereaction easily took place at the studied temperature.展开更多
Terbium- and yttrium-group rare earths form β-complexes with CPApC in acidic medium. The sensitivities for determination of these rare earths by this reaction depend on their ionic radii. Cerium- or terbium-group rar...Terbium- and yttrium-group rare earths form β-complexes with CPApC in acidic medium. The sensitivities for determination of these rare earths by this reaction depend on their ionic radii. Cerium- or terbium-group rare earth in the presence of yttrium-group element produces the cocolouration effect which remarkably sensitizes the reaction. Yb-CPApC-Eu complex has a molar composition of 1:4:2 and gives a molar absorptivity of 2. 02 ×10~5 L·mol^(-1)·cm^(-1) at 746 nm for Eu. It is found that the closer the lengths of ionic radii of the rare earths are, the greater will be the cocolouration effect.展开更多
The present investigation is concerned with the reaction of barium and iron nitrates mixtures using three different molar ratios, 1:1 (Ⅰ), 1:2 (Ⅱ) and 2:1 (Ⅲ) at different temperatures as pointed out from the DTA d...The present investigation is concerned with the reaction of barium and iron nitrates mixtures using three different molar ratios, 1:1 (Ⅰ), 1:2 (Ⅱ) and 2:1 (Ⅲ) at different temperatures as pointed out from the DTA data. The reaction products exhibit 12 compounds namely, Ba(NO3)2, αFe2O3, Fe3O4, BaFeO3, BaFeO2.9, hexagonal BaFeO3-x, tetragonal BaFeO3-x, BaFe2O4, αBaFe2O4, Ba2Fe6O11, Ba5Fe14O26 and BaFe12O19. The formation of these products depend on the molar ratio between the reactants and the reaction temperature. The reaction products were studied by DTA and TG techniques and characterized by X-ray diffraction patterns, magnetic susceptibility data and scanning electron microscopy, SEM.展开更多
To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretre...To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.展开更多
Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity amo...Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.展开更多
The formation enthalpy of complex nickel(Ⅱ) histidine(His) in water was determined by means of microcalorimetry in the temperature range of 298 15-323 15 K. The standard enthalpy of the formation of Ni(His) 2...The formation enthalpy of complex nickel(Ⅱ) histidine(His) in water was determined by means of microcalorimetry in the temperature range of 298 15-323 15 K. The standard enthalpy of the formation of Ni(His) 2+ 2(aq) was calculated. On the basis of the experimental and the calculated results, three thermodynamic parameters(the activation enthalpy, the activation entropy and the activation free energy), the rate constants, three kinetic parameters(the apparent activation energy, the pre exponential constant and the reaction order) of the formation reaction of the title complex were obtained.展开更多
Control of the spatiotemporal patterns near the codimension-three Turing–Hopf–Wave bifurcations is studied by using time-delayed feedback in a three-variable Brusselator model. Linear stability analysis of the syste...Control of the spatiotemporal patterns near the codimension-three Turing–Hopf–Wave bifurcations is studied by using time-delayed feedback in a three-variable Brusselator model. Linear stability analysis of the system shows that the competition among the Turing-, Hopf- and Wave-modes, the wavenumber, and the oscillation frequency of patterns can be controlled by changing the feedback parameters. The role of the feedback intensity Pu played on controlling the pattern competition is equivalent to that of Pw, but opposite to that of Pv. The role of the feedback intensity Pu played on controlling the wavenumber and oscillation frequency of patterns is equivalent to that of Pv, but opposite to that of Pw. When the intensities of feedback are applied equally, changing the delayed time could not alter the competition among these modes, however, it can control the oscillation frequency of patterns. The analytical results are verified by two-dimensional （2D） numerical simulations.展开更多
Small-molecule electrooxidation-boosted water electrolysis(WE)is an energy-saving method for hydrogen(H2)production.Herein,PdPt bimetallenes(PdPt BMLs)are obtained through the simple galvanic replacement reaction.PdPt...Small-molecule electrooxidation-boosted water electrolysis(WE)is an energy-saving method for hydrogen(H2)production.Herein,PdPt bimetallenes(PdPt BMLs)are obtained through the simple galvanic replacement reaction.PdPt BMLs reveal 2.93-fold enhancement in intrinsic electroactivity and 4.53-fold enhancement in mass electroactivity for the formate oxidation reaction(FOR)with respect to Pd metallenes(Pd MLs)at 0.50 V potential due to the synergistic effect.Meanwhile,the introduction of Pt atoms also considerably increases the electroactivity of PdPt BMLs for hydrogen evolution reaction(HER)with respect to Pd MLs in an alkaline medium,which even exceeds that with the use of commercial Pt nanocrystals.Inspired by the outstanding FOR and HER electroactivity of bifunctional PdPt BMLs,a two-electrode FOR-boosted WE system(FOR-WE)is constructed by using PdPt BMLs as the cathode and the anode.The FOR-WE system only requires an operational voltage of 0.31 V to achieve H2 production,which is 1.48 V lower than that(ca.1.79 V)with the use of the traditional WE system.展开更多
Based on the full optimized molecular geometric structure at 6-311＋＋G＊＊ level,the density（ρ）,detonation velocity（D）,and detonation pressure（P） for a new furazan-based energetic macrocycle compound,hexakis[1...Based on the full optimized molecular geometric structure at 6-311＋＋G＊＊ level,the density（ρ）,detonation velocity（D）,and detonation pressure（P） for a new furazan-based energetic macrocycle compound,hexakis[1,2,5]oxadi-azole[3,4-c：3＇,4＇-e;3＇＇,4＇＇-g：3＇＇＇,4＇＇＇-k：3＇＇＇＇,4＇＇＇＇-m：3＇＇＇＇＇,4＇＇＇＇＇-o][1,2,9,10]-tetraazacyclohexadecine,were investigated to verify its capacity as high energy density material（HEDM）. The infrared spectrum was also predicted. The heat of formation（HOF） was calculated using designed isodesmic reaction. The calculation on the bond dissociation energies（BDEs） was done and the pyrolysis mechanism of the compound was studied. The result shows that the N3–O1 bond in the ring may be the weakest one and the ring cleavage is possible to happen in thermal decomposition. The condensed phase HOF and the crystal density were also calculated for the title compound. The detonation data show that it can be considered as a potential HEDM. These results would provide basic information for the molecular design of novel high energy materials.展开更多
A new three-dimensional coordination polymer, [Ho（5-nip）（phen）（NO3）（DMF）] （5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline）, was prepared and characterized by single crystal X-ray diffraction, ele...A new three-dimensional coordination polymer, [Ho（5-nip）（phen）（NO3）（DMF）] （5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline）, was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the title complex crystallizes in space group P2/m with a= 1.0906（3） nm, b =1.2804 （3） nm, c= 1.6987（4） nm, β=91.400（5）°, Z=4, Dc= 1.931 Mg/m^3, F（000）= 1352. Each Ho（Ⅲ） ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO3 anion, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π-π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three-dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 ℃. Its enthalpy change of formation of the reaction in liquid-phase in solvent DMF was measured using an RD496-Ⅲ type microcalorimeter with a value of （-11.016±0.184） kJ·mol^-1.展开更多
The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with L--histidine in water were determined by a microcalorimeter at...The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with L--histidine in water were determined by a microcalorimeter at 298.15—323.15 K. The standard enthalpy of formation of 32Cr(His)+(aq) and 22M(His)+(aq) (M=Mn, Fe, Co, Ni and Cu) were calculated. Based on the thermodynamic and kinetic equations of the reactions, three thermody-namic parameters (the activation enthalpy, the activation entropy, the activation free energy), the rate constants, and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) are obtained. The solid complexes of CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with histidine were prepared and identified as Cr(His)2Cl3H2O, Mn(His)2Cl24H2O, Fe(His)2Cl2H2O, Co(His)2Cl2H2O, Ni(His)2Cl2H2O and Cu(His)2Cl2H2O by chemical and elemental analyses. The bonding characteristics of these complexes were char-acterized by IR as well. The results showed that, with the atomic number increasing, three thermodynamic parame-ters, GD!, HD! and SD! of the complexation reaction of these metal chlorides with L-a-histidine in water present an analogy regularity.展开更多
This paper has improved Hickman's nonadiabatic collision model by substituting Hickman's constant velocity classical straight line trajectory approximation with the solution of motion equation mR=-dV(R)/dR, an...This paper has improved Hickman's nonadiabatic collision model by substituting Hickman's constant velocity classical straight line trajectory approximation with the solution of motion equation mR=-dV(R)/dR, and has calculated the cross sections of ion-pair formation Cs+O2 -Cs++O2- with the improved nonadiabatic collision model (INCM). A comparison of our results with other theoretical and experimental results has been made.展开更多
Thermal decomposition of supported magnesium formate has been studied by gas chro- matography.The reaction paths of decomposition of supported magnesium formate depend on the nature of the supports.For Mg(HCO_2)_2/HZS...Thermal decomposition of supported magnesium formate has been studied by gas chro- matography.The reaction paths of decomposition of supported magnesium formate depend on the nature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst to give CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanation reaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leads to the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears after modified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2^- takes place on the surface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of CO and only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the first peak of CO_2 arises from the reaction of surface Mg^(2+) with HCO_2^- from dissociated Mg(HCO_2)_2.展开更多
The effects of the chiral substituents attached to silicon on the stereoselectivity of the reactions of C-centered chiral silicon compounds wm examined. The investigation was focused on the asymmetric C—C bond format...The effects of the chiral substituents attached to silicon on the stereoselectivity of the reactions of C-centered chiral silicon compounds wm examined. The investigation was focused on the asymmetric C—C bond formation reaction of chiral allylsilanes and α-silylallyl anions with aldehydes. The functionalities of the substituents on silicon can be manipulated to improve the stereoselectivities of the reactions remote from silicon atom.展开更多
The widespread commercial application of direct formate fuel cell(DFFC)is limited by the lack of efficient electrocatalysts for the formate oxidation reaction(FOR).AgPdCo hollow nanospheres(H-NSs)with jagged surfaces ...The widespread commercial application of direct formate fuel cell(DFFC)is limited by the lack of efficient electrocatalysts for the formate oxidation reaction(FOR).AgPdCo hollow nanospheres(H-NSs)with jagged surfaces are successfully synthesized via a facile method involving the wet-chemical synthesis of AgPdCo nanospheres(NSs)and galvanic replacement reaction between Pd salt and AgPdCo NSs.Surpassing Ag_(30)Pd_(69)Co_(1) NSs and most of previously reported electrocatalysts,Ag_(9)Pd_(90)Co_(1) H-NSs exhibit extremely high FOR activity with a peak current density of 3.08 A·mg_(Pd)^(−1).Apart from the competitive activity,Ag_(9)Pd_(90)Co_(1) H-NSs show greatly improved chronoamperometric and cycling stability,whereby the current density retains about 0.24 A·mg_(Pd)^(−1) after 3,600 s electrocatalysis and the mass activity maintains 54.06%of the initial value after 500 cycles.The unique hollow nanosphere and synergistic effect are responsible for the enhanced activity and stability.This study will provide new clues for the development of outstanding electrocatalysts.展开更多
基金theNationalNaturalScienceFoundationofChina (No .2 98710 2 3)andNaturalScienceFoundationofShaanxiProvince
文摘The enthalpy change of reaction of zinc chloride with L-α-histidine in thetemperature range of 25-50 ℃ has been determined by a microcalorimeter. On the basis ofexperimental and calculated results, three thermodynamics parameters (the activation enthalpy, theactivation entropy, the activation free energy), the rate constant and three kinetic parameters (theactivation energy, the pre-exponential constant and the reaction order) of the reaction, and thestandard enthalpy of formation of Zn(His)^(2+) (aq.) are obtained. The results showed that the titlereaction easily took place at the studied temperature.
文摘Terbium- and yttrium-group rare earths form β-complexes with CPApC in acidic medium. The sensitivities for determination of these rare earths by this reaction depend on their ionic radii. Cerium- or terbium-group rare earth in the presence of yttrium-group element produces the cocolouration effect which remarkably sensitizes the reaction. Yb-CPApC-Eu complex has a molar composition of 1:4:2 and gives a molar absorptivity of 2. 02 ×10~5 L·mol^(-1)·cm^(-1) at 746 nm for Eu. It is found that the closer the lengths of ionic radii of the rare earths are, the greater will be the cocolouration effect.
文摘The present investigation is concerned with the reaction of barium and iron nitrates mixtures using three different molar ratios, 1:1 (Ⅰ), 1:2 (Ⅱ) and 2:1 (Ⅲ) at different temperatures as pointed out from the DTA data. The reaction products exhibit 12 compounds namely, Ba(NO3)2, αFe2O3, Fe3O4, BaFeO3, BaFeO2.9, hexagonal BaFeO3-x, tetragonal BaFeO3-x, BaFe2O4, αBaFe2O4, Ba2Fe6O11, Ba5Fe14O26 and BaFe12O19. The formation of these products depend on the molar ratio between the reactants and the reaction temperature. The reaction products were studied by DTA and TG techniques and characterized by X-ray diffraction patterns, magnetic susceptibility data and scanning electron microscopy, SEM.
基金National Natural Science Foundation of China(52071274)Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating,a micro-arc oxidation pretreatment was employed to construct a Ta_(2)O_(5)ceramic layer on the Ta12W alloy surface.Subsequently,a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate.Comparative studies were conducted on the microstructure,phase composition,and isothermal oxidation resistance(at 1600℃)of the as-prepared coatings with and without the micro-arc oxidation ceramic layer.The results show that the Ta_(2)O_(5)layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V.After microarc oxidation pretreatment,the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers:an upper layer dominated by Ti_(5)Si_(3),Ta_(5)Si_(3),and ZrSi;a middle layer dominated by TaSi_(2);a coating/substrate interfacial reaction layer dominated by Ta_(5)Si_(3).Both the Si-Cr-Ti-Zr coatings with and without the Ta_(2)O_(5)ceramic layer do not fail after isothermal oxidation at 1600℃for 5 h.Notably,the addition of the Ta2O5 ceramic layer reduces the high-temperature oxidation rate of the coating.
文摘Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.
基金Supported by the National Natural Science Foundation of China(No.2 0 170 36 )
文摘The formation enthalpy of complex nickel(Ⅱ) histidine(His) in water was determined by means of microcalorimetry in the temperature range of 298 15-323 15 K. The standard enthalpy of the formation of Ni(His) 2+ 2(aq) was calculated. On the basis of the experimental and the calculated results, three thermodynamic parameters(the activation enthalpy, the activation entropy and the activation free energy), the rate constants, three kinetic parameters(the apparent activation energy, the pre exponential constant and the reaction order) of the formation reaction of the title complex were obtained.
基金Project supported by the National Nature Science Foundation of China(Grant No.11205044)the Fundamental Research Funds for the Central Universities(Grant No.10ML40)
文摘Control of the spatiotemporal patterns near the codimension-three Turing–Hopf–Wave bifurcations is studied by using time-delayed feedback in a three-variable Brusselator model. Linear stability analysis of the system shows that the competition among the Turing-, Hopf- and Wave-modes, the wavenumber, and the oscillation frequency of patterns can be controlled by changing the feedback parameters. The role of the feedback intensity Pu played on controlling the pattern competition is equivalent to that of Pw, but opposite to that of Pv. The role of the feedback intensity Pu played on controlling the wavenumber and oscillation frequency of patterns is equivalent to that of Pv, but opposite to that of Pw. When the intensities of feedback are applied equally, changing the delayed time could not alter the competition among these modes, however, it can control the oscillation frequency of patterns. The analytical results are verified by two-dimensional （2D） numerical simulations.
基金the National Natural Science Foundation of China(22272103)the Shenzhen Stable Supporting Program(20220716001753001 and SZWD2021015)+3 种基金the University Engineering Research Center of Crystal Growth and Applications of Guangdong Province(2020GCZX005)the Science and Technology Innovation Team of Shaanxi Province(2023-CX-TD-27 and 2022TD-35)the Fundamental Research Funds for the Central Universities(GK202202001)the 111 Project(B14041).
文摘Small-molecule electrooxidation-boosted water electrolysis(WE)is an energy-saving method for hydrogen(H2)production.Herein,PdPt bimetallenes(PdPt BMLs)are obtained through the simple galvanic replacement reaction.PdPt BMLs reveal 2.93-fold enhancement in intrinsic electroactivity and 4.53-fold enhancement in mass electroactivity for the formate oxidation reaction(FOR)with respect to Pd metallenes(Pd MLs)at 0.50 V potential due to the synergistic effect.Meanwhile,the introduction of Pt atoms also considerably increases the electroactivity of PdPt BMLs for hydrogen evolution reaction(HER)with respect to Pd MLs in an alkaline medium,which even exceeds that with the use of commercial Pt nanocrystals.Inspired by the outstanding FOR and HER electroactivity of bifunctional PdPt BMLs,a two-electrode FOR-boosted WE system(FOR-WE)is constructed by using PdPt BMLs as the cathode and the anode.The FOR-WE system only requires an operational voltage of 0.31 V to achieve H2 production,which is 1.48 V lower than that(ca.1.79 V)with the use of the traditional WE system.
基金supported by the National Natural Science Foundation of China(No.U1304111)the Program for Science&Technology Innovation Talents in Universities of Henan Province(No.14HASTIT039)the Innovation Team of Henan University of Science and Technology(2015XTD001)
文摘Based on the full optimized molecular geometric structure at 6-311＋＋G＊＊ level,the density（ρ）,detonation velocity（D）,and detonation pressure（P） for a new furazan-based energetic macrocycle compound,hexakis[1,2,5]oxadi-azole[3,4-c：3＇,4＇-e;3＇＇,4＇＇-g：3＇＇＇,4＇＇＇-k：3＇＇＇＇,4＇＇＇＇-m：3＇＇＇＇＇,4＇＇＇＇＇-o][1,2,9,10]-tetraazacyclohexadecine,were investigated to verify its capacity as high energy density material（HEDM）. The infrared spectrum was also predicted. The heat of formation（HOF） was calculated using designed isodesmic reaction. The calculation on the bond dissociation energies（BDEs） was done and the pyrolysis mechanism of the compound was studied. The result shows that the N3–O1 bond in the ring may be the weakest one and the ring cleavage is possible to happen in thermal decomposition. The condensed phase HOF and the crystal density were also calculated for the title compound. The detonation data show that it can be considered as a potential HEDM. These results would provide basic information for the molecular design of novel high energy materials.
基金Project supported by the National Natural Science Foundation of China （No. 20471047） and the Natural Science Foundation of Shaanxi Province （Nos. FF05201 and FF05203）.
文摘A new three-dimensional coordination polymer, [Ho（5-nip）（phen）（NO3）（DMF）] （5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline）, was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the title complex crystallizes in space group P2/m with a= 1.0906（3） nm, b =1.2804 （3） nm, c= 1.6987（4） nm, β=91.400（5）°, Z=4, Dc= 1.931 Mg/m^3, F（000）= 1352. Each Ho（Ⅲ） ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO3 anion, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π-π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three-dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 ℃. Its enthalpy change of formation of the reaction in liquid-phase in solvent DMF was measured using an RD496-Ⅲ type microcalorimeter with a value of （-11.016±0.184） kJ·mol^-1.
基金Projected supported by the National Natural Science Foundation of China (Nos. 299871032 and 20171036) and the National Natural Science Foun-dation of Shaanxi Province (No. FF02328).
文摘The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with L--histidine in water were determined by a microcalorimeter at 298.15—323.15 K. The standard enthalpy of formation of 32Cr(His)+(aq) and 22M(His)+(aq) (M=Mn, Fe, Co, Ni and Cu) were calculated. Based on the thermodynamic and kinetic equations of the reactions, three thermody-namic parameters (the activation enthalpy, the activation entropy, the activation free energy), the rate constants, and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) are obtained. The solid complexes of CrCl3, MnCl2, FeCl2, CoCl2, NiCl2 and CuCl2 with histidine were prepared and identified as Cr(His)2Cl3H2O, Mn(His)2Cl24H2O, Fe(His)2Cl2H2O, Co(His)2Cl2H2O, Ni(His)2Cl2H2O and Cu(His)2Cl2H2O by chemical and elemental analyses. The bonding characteristics of these complexes were char-acterized by IR as well. The results showed that, with the atomic number increasing, three thermodynamic parame-ters, GD!, HD! and SD! of the complexation reaction of these metal chlorides with L-a-histidine in water present an analogy regularity.
基金Project supported by the National Natural Science Foundation of China and the Special DoctoralFund of the Chinese Education Committee.
文摘This paper has improved Hickman's nonadiabatic collision model by substituting Hickman's constant velocity classical straight line trajectory approximation with the solution of motion equation mR=-dV(R)/dR, and has calculated the cross sections of ion-pair formation Cs+O2 -Cs++O2- with the improved nonadiabatic collision model (INCM). A comparison of our results with other theoretical and experimental results has been made.
基金Project supported by Fok Ying Tung Education Foundation and the State Education Commission of China(FEYUT).
文摘Thermal decomposition of supported magnesium formate has been studied by gas chro- matography.The reaction paths of decomposition of supported magnesium formate depend on the nature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst to give CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanation reaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leads to the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears after modified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2^- takes place on the surface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of CO and only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the first peak of CO_2 arises from the reaction of surface Mg^(2+) with HCO_2^- from dissociated Mg(HCO_2)_2.
文摘The effects of the chiral substituents attached to silicon on the stereoselectivity of the reactions of C-centered chiral silicon compounds wm examined. The investigation was focused on the asymmetric C—C bond formation reaction of chiral allylsilanes and α-silylallyl anions with aldehydes. The functionalities of the substituents on silicon can be manipulated to improve the stereoselectivities of the reactions remote from silicon atom.
基金This work was supported by the National Natural Science Foundation of China(Nos.51874243,51271148,and 50971100)the Research Fund of State Key Laboratory of Solidification Processing(NPU),China(No.2020-TS-02)+1 种基金the Project of Transformation of Scientific and Technological Achievements of NWPU(No.19-2017)the Open Fund of State Key Laboratory of Advanced Technology for Material Synthesis and Processing(Wuhan University of Technology,No.2018KF-18).
文摘The widespread commercial application of direct formate fuel cell(DFFC)is limited by the lack of efficient electrocatalysts for the formate oxidation reaction(FOR).AgPdCo hollow nanospheres(H-NSs)with jagged surfaces are successfully synthesized via a facile method involving the wet-chemical synthesis of AgPdCo nanospheres(NSs)and galvanic replacement reaction between Pd salt and AgPdCo NSs.Surpassing Ag_(30)Pd_(69)Co_(1) NSs and most of previously reported electrocatalysts,Ag_(9)Pd_(90)Co_(1) H-NSs exhibit extremely high FOR activity with a peak current density of 3.08 A·mg_(Pd)^(−1).Apart from the competitive activity,Ag_(9)Pd_(90)Co_(1) H-NSs show greatly improved chronoamperometric and cycling stability,whereby the current density retains about 0.24 A·mg_(Pd)^(−1) after 3,600 s electrocatalysis and the mass activity maintains 54.06%of the initial value after 500 cycles.The unique hollow nanosphere and synergistic effect are responsible for the enhanced activity and stability.This study will provide new clues for the development of outstanding electrocatalysts.
