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2006 Volume 22 Issue 7
2006, 22(07): 771-776
doi: 10.3866/PKU.WHXB20060701
Abstract:
A series of molecular dynamics simulations for the structure transformation during heating and melting of FCC Ni have been performed with the Tight-binding potential developed by Cleri and Rosato. The simulated melting point of Ni at constant pressure condition is between 1850 K and 1900 K. The static structural informations, such as the radial distribution functions and the distributions of the coordination numbers, have been obtained during the simulation. The calculated diffusion coefficient of the liquid Ni is about 5.02×10−9 m2•s−1 at 1900 K, which is consistent with the experimental result. The possible distortion of local structure of FCC crystal and the relevant changes of the types of the atom pairs (indexed by Honeycutt-Anderesen pair analysis technique) have been analyzed. The distributions of the short-range ordered (SRO) structures of FCC and defective icosahedra at different temperatures are calculated combining the local configuration search and H-A pair analysis methods. It is indicated that after melting a few SRO structures in FCC crystal are remained with distortion to a certain extent. A small quantity of the defective icosahedra in the liquid is also confirmed and their numbers are estimated. It suggested that the geometrical configurations of the local structure in liquid Ni are between the distorted cubooctahedron in FCC and the defective icosahedra.
A series of molecular dynamics simulations for the structure transformation during heating and melting of FCC Ni have been performed with the Tight-binding potential developed by Cleri and Rosato. The simulated melting point of Ni at constant pressure condition is between 1850 K and 1900 K. The static structural informations, such as the radial distribution functions and the distributions of the coordination numbers, have been obtained during the simulation. The calculated diffusion coefficient of the liquid Ni is about 5.02×10−9 m2•s−1 at 1900 K, which is consistent with the experimental result. The possible distortion of local structure of FCC crystal and the relevant changes of the types of the atom pairs (indexed by Honeycutt-Anderesen pair analysis technique) have been analyzed. The distributions of the short-range ordered (SRO) structures of FCC and defective icosahedra at different temperatures are calculated combining the local configuration search and H-A pair analysis methods. It is indicated that after melting a few SRO structures in FCC crystal are remained with distortion to a certain extent. A small quantity of the defective icosahedra in the liquid is also confirmed and their numbers are estimated. It suggested that the geometrical configurations of the local structure in liquid Ni are between the distorted cubooctahedron in FCC and the defective icosahedra.
2006, 22(07): 777-779
doi: 10.3866/PKU.WHXB20060702
Abstract:
A large human phage antibody library was subjected for panning with leukocytes from healthy donors and leukemia patients to select for specific antibodies against leukocytic surface proteins. Recombinant phage particles displaying multiple antibody fragments via pVIII display system were used to prepare high-density phage antibody chips. Leukocyte lysate samples from 3 healthy donors and 3 leukemia patients were labeled with Cy3 fluorescence dye and reacted with the microarrays on the epoxy substrates. Eight sets of specific spots were found to have significantly distinct fluorescence intensities between the two groups of fluorescence profiles. It was demonstrated that phage antibody chips could be used for the recognition of cellular surface proteins.
A large human phage antibody library was subjected for panning with leukocytes from healthy donors and leukemia patients to select for specific antibodies against leukocytic surface proteins. Recombinant phage particles displaying multiple antibody fragments via pVIII display system were used to prepare high-density phage antibody chips. Leukocyte lysate samples from 3 healthy donors and 3 leukemia patients were labeled with Cy3 fluorescence dye and reacted with the microarrays on the epoxy substrates. Eight sets of specific spots were found to have significantly distinct fluorescence intensities between the two groups of fluorescence profiles. It was demonstrated that phage antibody chips could be used for the recognition of cellular surface proteins.
Study on the Characteristics of the Ground States and Excited States of He2+ and He2++ Molecule Ions
2006, 22(07): 780-785
doi: 10.3866/PKU.WHXB20060703
Abstract:
The molecule structures for the ground and low-lying states of He2+ and He2++ are calculated using the SAC/SAC-CI with the basis set CC-PV5Z. The analytical forms of potential energy function are least-squared-fitted from the potential energy and the corresponding spectroscopic data are derived out. For He2+, the obtained spectroscopic data of X2Σu+ are in well agreement with the experimental data and the results for the excited states 2Πu, 4Σu+, and 4Πg, are worked out for the first time. For He2++, the results indicate that only the ground state X1Σg+ and excited states 1Σg+, 1Σu+ among the nine calculated states are bound states. The spectroscopic constants corresponding to these three states are worked out, and the origin of the energy barriers in the ground states X1Σg+ energy curve has been explained using the avoided crossing rules of valence bond model.
The molecule structures for the ground and low-lying states of He2+ and He2++ are calculated using the SAC/SAC-CI with the basis set CC-PV5Z. The analytical forms of potential energy function are least-squared-fitted from the potential energy and the corresponding spectroscopic data are derived out. For He2+, the obtained spectroscopic data of X2Σu+ are in well agreement with the experimental data and the results for the excited states 2Πu, 4Σu+, and 4Πg, are worked out for the first time. For He2++, the results indicate that only the ground state X1Σg+ and excited states 1Σg+, 1Σu+ among the nine calculated states are bound states. The spectroscopic constants corresponding to these three states are worked out, and the origin of the energy barriers in the ground states X1Σg+ energy curve has been explained using the avoided crossing rules of valence bond model.
2006, 22(07): 786-790
doi: 10.1016/S1872-1508(06)60031-4
Abstract:
The thermal decomposition of one kind of biomass in air has been investigated by differential scanning calorimetry (DSC) analyzer. The results indicate that the heating process of samples from ambient temperature to 923 K at low heating rates show two obvious exothermic peaks. According to the decomposition mechanism, the first exothermic step is attributed to oxidative degradation of hemicellulose and cellulose, and the second exothermic step is attributed to lignin degradation and char oxidation. The reaction model of the studied biomass thermal decomposition has been studied by iso-conversional methods and optimization computation. The results suggest that the two-step consecutive reaction model is suitable to describe the exotherm of biomass thermal decomposition in air.
The thermal decomposition of one kind of biomass in air has been investigated by differential scanning calorimetry (DSC) analyzer. The results indicate that the heating process of samples from ambient temperature to 923 K at low heating rates show two obvious exothermic peaks. According to the decomposition mechanism, the first exothermic step is attributed to oxidative degradation of hemicellulose and cellulose, and the second exothermic step is attributed to lignin degradation and char oxidation. The reaction model of the studied biomass thermal decomposition has been studied by iso-conversional methods and optimization computation. The results suggest that the two-step consecutive reaction model is suitable to describe the exotherm of biomass thermal decomposition in air.
2006, 22(07): 791-796
doi: 10.1016/S1872-1508(06)60032-6
Abstract:
Core-shell Ag/TiO2 nanocomposites with different TiO2 concentration were synthesized by the photoreduction method, in the presence of ethanol. The diameter of the nanoparticles, with various TiO2 and Ag content, was determined to be 20~60 nm using a transmission electron microscope(TEM), and the crystal lattice fringes of silver particles were observed. The prepared nanocomposites were characterized by ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffraction (XRD). The intensity and width of the characteristic peak near 420 nm of the Ag nanoparticles increased as the TiO2 or silver concentration was increased. The nonlinear optical properties of thin films of nanocomposites with different TiO2 concentrations were analyzed, using Z-scan technique at the wavelength of 790 nm with a pulse width of 130 fs. Two different nonlinear regimes in nonlinear absorption were found by changing the content of TiO2 : an optical limiting effect at a low concentration, and a sign change at a higher concentration.
Core-shell Ag/TiO2 nanocomposites with different TiO2 concentration were synthesized by the photoreduction method, in the presence of ethanol. The diameter of the nanoparticles, with various TiO2 and Ag content, was determined to be 20~60 nm using a transmission electron microscope(TEM), and the crystal lattice fringes of silver particles were observed. The prepared nanocomposites were characterized by ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffraction (XRD). The intensity and width of the characteristic peak near 420 nm of the Ag nanoparticles increased as the TiO2 or silver concentration was increased. The nonlinear optical properties of thin films of nanocomposites with different TiO2 concentrations were analyzed, using Z-scan technique at the wavelength of 790 nm with a pulse width of 130 fs. Two different nonlinear regimes in nonlinear absorption were found by changing the content of TiO2 : an optical limiting effect at a low concentration, and a sign change at a higher concentration.
2006, 22(07): 797-803
doi: 10.3866/PKU.WHXB20060706
Abstract:
The interconversion process between keto and enol forms of formamide (FM→FA) can be regarded as a model for tautomerization of larger nucleic acid base, which may be responsible for the spontaneous point mutation in DNA. The present paper describes a study of structural tautomer interconversion and the relative stabilizing influences of water for formamide-H2O and the enol form formamidic acid-H2O in aqueous solution. The solvent effects were considered by explicit water molecule within SCRF framework. In the vicinity of formamide (FM) and formamidic acid (FA), three different regions are considered, full geometry optimizations of these complexes were carried out at B3LYP/6-311++G** using self-consistent isodensity polarized continuum model (SCIPCM). The calculated results indicate that water in two of them can protect formamide from tautomerizing, while in the third one works oppositely, exactly the same as the situations in gas phase. However, comparing with the transition in gas phase, the protective and assistive effects induced by the explicit water are greatly altered. The calculated results shed more light on the water′s influence on the proton transfer and offer a new insight into the structural tautomer interconversion of FM.
The interconversion process between keto and enol forms of formamide (FM→FA) can be regarded as a model for tautomerization of larger nucleic acid base, which may be responsible for the spontaneous point mutation in DNA. The present paper describes a study of structural tautomer interconversion and the relative stabilizing influences of water for formamide-H2O and the enol form formamidic acid-H2O in aqueous solution. The solvent effects were considered by explicit water molecule within SCRF framework. In the vicinity of formamide (FM) and formamidic acid (FA), three different regions are considered, full geometry optimizations of these complexes were carried out at B3LYP/6-311++G** using self-consistent isodensity polarized continuum model (SCIPCM). The calculated results indicate that water in two of them can protect formamide from tautomerizing, while in the third one works oppositely, exactly the same as the situations in gas phase. However, comparing with the transition in gas phase, the protective and assistive effects induced by the explicit water are greatly altered. The calculated results shed more light on the water′s influence on the proton transfer and offer a new insight into the structural tautomer interconversion of FM.
2006, 22(07): 804-808
doi: 10.1016/S1872-1508(06)60033-8
Abstract:
Three kinds of MgC2O4•2H2O were prepared by precipitation method with different raw materials, and M with high surface area was obtained via thermal decomposition of MgC2O4•2H2O in different atmospheres. The precursor MgC2O4•2H2O and as-prepared M were characterized by XRD, BET, TEM, and TG-DTA measurements. It was found that using Mg(CH3COO)2•4H2O and H2C2O4•2H2O as the starting materials and calcining the precursor MgC2O4•2H2O in flowing dry gas are key factors to obtain high surface area M . The M prepared at the optimum condition is composed of nanocrystals with a size about 4~5 nm and forms a wormhole-like porous structure with a specific surface of 534 m2•g−1 after calcining at 520 ℃. In addition, the M has od thermal stability, after calcining at 650 ℃ and 800 ℃ for 2 h, its surface area is still 229 m2•g−1 and 134 m2•g−1, respectively.
Three kinds of MgC2O4•2H2O were prepared by precipitation method with different raw materials, and M with high surface area was obtained via thermal decomposition of MgC2O4•2H2O in different atmospheres. The precursor MgC2O4•2H2O and as-prepared M were characterized by XRD, BET, TEM, and TG-DTA measurements. It was found that using Mg(CH3COO)2•4H2O and H2C2O4•2H2O as the starting materials and calcining the precursor MgC2O4•2H2O in flowing dry gas are key factors to obtain high surface area M . The M prepared at the optimum condition is composed of nanocrystals with a size about 4~5 nm and forms a wormhole-like porous structure with a specific surface of 534 m2•g−1 after calcining at 520 ℃. In addition, the M has od thermal stability, after calcining at 650 ℃ and 800 ℃ for 2 h, its surface area is still 229 m2•g−1 and 134 m2•g−1, respectively.
2006, 22(07): 809-814
doi: 10.1016/S1872-1508(06)60034-X
Abstract:
The Ag-MoO3 catalyst for direct gas phase epoxidation of propylene was prepared, and in situ FT-IR technology was used to study the adsorption and reaction behavior of propylene, propylene oxide (PO), and the gaseous mixture of propylene and oxygen on the surfaces of Ag and Ag-MoO3 catalysts. The results indicate that on using single Ag catalyst the selectivity to PO is very low, and Ag-MoO3 is an efficient catalyst for the direct epoxidation of propylene using molecular oxygen as oxidant. The studies of in situ FT-IR show that no chemical reaction occurs, within the range of the experimental temperatures, when propylene is adsorbed on the surface of Ag or Ag-MoO3 catalysts, whereas, the open-ring, polymerization, and coking of PO adsorbed on the Ag or Ag-MoO3 catalysts can occur at higher temperature. The presence of MoO3 in the Ag-MoO3 catalyst can inhibit the open-ring and deep reactions of PO to some extent, despite decreasing its activity, which leads to an increase in the selectivity of PO. The lower reaction temperature and shorter contact time are favorable to inhibit the deep reaction of PO on the surface of the catalyst.
The Ag-MoO3 catalyst for direct gas phase epoxidation of propylene was prepared, and in situ FT-IR technology was used to study the adsorption and reaction behavior of propylene, propylene oxide (PO), and the gaseous mixture of propylene and oxygen on the surfaces of Ag and Ag-MoO3 catalysts. The results indicate that on using single Ag catalyst the selectivity to PO is very low, and Ag-MoO3 is an efficient catalyst for the direct epoxidation of propylene using molecular oxygen as oxidant. The studies of in situ FT-IR show that no chemical reaction occurs, within the range of the experimental temperatures, when propylene is adsorbed on the surface of Ag or Ag-MoO3 catalysts, whereas, the open-ring, polymerization, and coking of PO adsorbed on the Ag or Ag-MoO3 catalysts can occur at higher temperature. The presence of MoO3 in the Ag-MoO3 catalyst can inhibit the open-ring and deep reactions of PO to some extent, despite decreasing its activity, which leads to an increase in the selectivity of PO. The lower reaction temperature and shorter contact time are favorable to inhibit the deep reaction of PO on the surface of the catalyst.
2006, 22(07): 815-819
doi: 10.3866/PKU.WHXB20060709
Abstract:
The performance of NOx oxidation-storage and desorption over Mn/Ba/Al2O3 catalyst were investigated at different temperatures. The catalysts were prepared by equal volume impregnation method and characterized by XRD and TPD. The results showed that Mn/Ba/Al2O3 catalyst had high catalytic activity for NO oxidation and large NOx storage capacity. BaMnO3 was the major active component. Mn could catalyze the oxidation of NO, having certain NOx storage capacity. Ba was the major storage component, NOx were stored with the formation of the nitrate that can be decomposed between 300~600 ℃ to release NOx. When Mn/Ba/Al2O3 was aged at 800 ℃ for 6 h, both the catalylic activity for NO oxidation and the NOx storage capacity were slightly decreased. The catalylic activity for NO oxidation and the NOx storage capacity were hardly affected by low concentration SO2. However, higher concentration SO2 decreased the catalylic activity for NO oxidation and the NOx storage capacity, leading to deactivation of the catalyst.
The performance of NOx oxidation-storage and desorption over Mn/Ba/Al2O3 catalyst were investigated at different temperatures. The catalysts were prepared by equal volume impregnation method and characterized by XRD and TPD. The results showed that Mn/Ba/Al2O3 catalyst had high catalytic activity for NO oxidation and large NOx storage capacity. BaMnO3 was the major active component. Mn could catalyze the oxidation of NO, having certain NOx storage capacity. Ba was the major storage component, NOx were stored with the formation of the nitrate that can be decomposed between 300~600 ℃ to release NOx. When Mn/Ba/Al2O3 was aged at 800 ℃ for 6 h, both the catalylic activity for NO oxidation and the NOx storage capacity were slightly decreased. The catalylic activity for NO oxidation and the NOx storage capacity were hardly affected by low concentration SO2. However, higher concentration SO2 decreased the catalylic activity for NO oxidation and the NOx storage capacity, leading to deactivation of the catalyst.
2006, 22(07): 820-825
doi: 10.3866/PKU.WHXB20060710
Abstract:
The surface geometries of ultrafine silica and its adsorption property for ethanol had been studied by density functional theory using the small cluster model as well as the periodic model. It was found that the method of small cluster model had superiority in some cases, while the periodic model could consider the surface environment of the ultrafine silica in more details. The results indicated that the ethanol molecules were adsorbed on the silica surface mainly through hydrogen bonds, and they favored to act as hydrogen bond acceptors.
The surface geometries of ultrafine silica and its adsorption property for ethanol had been studied by density functional theory using the small cluster model as well as the periodic model. It was found that the method of small cluster model had superiority in some cases, while the periodic model could consider the surface environment of the ultrafine silica in more details. The results indicated that the ethanol molecules were adsorbed on the silica surface mainly through hydrogen bonds, and they favored to act as hydrogen bond acceptors.
2006, 22(07): 826-830
doi: 10.3866/PKU.WHXB20060711
Abstract:
Two thermal polymerization initiators, 2,2′-azobisisobutyronitrile(AIBN) and benzoyl peroxide(BPO), commonly used to prepare gel polymer electrolytes (GPEs) for lithium-ion polymer batteries (LiPBs), were studied by thermogravimetry/differential thermal analysis (TG/DTA). The GPEs prepared with thermal initiators showed different electrochemical performances and had great influence on the performance of LiPBs, such as rate capability, temperature reliability, and cycling performance. An appropriate thermal initiator is selected for the GPE system.
Two thermal polymerization initiators, 2,2′-azobisisobutyronitrile(AIBN) and benzoyl peroxide(BPO), commonly used to prepare gel polymer electrolytes (GPEs) for lithium-ion polymer batteries (LiPBs), were studied by thermogravimetry/differential thermal analysis (TG/DTA). The GPEs prepared with thermal initiators showed different electrochemical performances and had great influence on the performance of LiPBs, such as rate capability, temperature reliability, and cycling performance. An appropriate thermal initiator is selected for the GPE system.
2006, 22(07): 831-835
doi: 10.1016/S1872-1508(06)60035-1
Abstract:
Macroporous material of Al2O3 was prepared through mixing a Al2O3 sol with polystyrene (PS) particles as templates, drying the suspension, and finally calcining it to remove the templates. The measurement obtained from the scanning electron microscopy (SEM) showed that the formed macroporous materials had a vesicle-like structure and most of the voids left by the templates were isolated from each other. The zeta-potential value indicated that the PS spheres carried negative charges, whereas the alumina particles carried positive charges. During the preparation of macroporous Al2O3, the Al2O3 colloidal particles were adsorbed on the surface of the PS particles, and the PS with the shell of Al2O3 particles played the role of templates, resulting in the formation of vesicle-like structures. To avoid the formation of the vesicle-like structure materials, the PS was switched from a negative charge to a positive charge through surface modification with PD (poly (diallyl-dimethyl ammonium chloride)), so that PS spheres carried the same kind of charge as the Al2O3 colloidal particles. The SEM images showed that the macroporous material of Al2O3, prepared using the modified PS spheres as templates, was free from the vesicle-like structure and voids left by the templates were connected through some windows.
Macroporous material of Al2O3 was prepared through mixing a Al2O3 sol with polystyrene (PS) particles as templates, drying the suspension, and finally calcining it to remove the templates. The measurement obtained from the scanning electron microscopy (SEM) showed that the formed macroporous materials had a vesicle-like structure and most of the voids left by the templates were isolated from each other. The zeta-potential value indicated that the PS spheres carried negative charges, whereas the alumina particles carried positive charges. During the preparation of macroporous Al2O3, the Al2O3 colloidal particles were adsorbed on the surface of the PS particles, and the PS with the shell of Al2O3 particles played the role of templates, resulting in the formation of vesicle-like structures. To avoid the formation of the vesicle-like structure materials, the PS was switched from a negative charge to a positive charge through surface modification with PD (poly (diallyl-dimethyl ammonium chloride)), so that PS spheres carried the same kind of charge as the Al2O3 colloidal particles. The SEM images showed that the macroporous material of Al2O3, prepared using the modified PS spheres as templates, was free from the vesicle-like structure and voids left by the templates were connected through some windows.
2006, 22(07): 836-839
doi: 10.1016/S1872-1508(06)60036-3
Abstract:
To design three-dimensional cobalt(II) metal complexes and Schiff base ligands, the geometry was taken from the starting structures based on the crystallographic data. The density functional theory (DFT) B3LYP/6-31g(d)-FF method was used to calculate the second-order nonlinear optical (NLO) properties of open-shell cobalt(II) metal complexes. The results indicated that when compared with the Schiff base ligands, the second-order NLO properties of the metal complexes do not change obviously, the reason being that the NLO responses of cobalt(II) metal complexes are strongly related to intraligand charge transfer transitions. According to the frontier molecular orbitals, the less contribution of Co2+ in determining the NLO responses of metal complexes arises from the action of the bridging moiety in the charge transfer processes.
To design three-dimensional cobalt(II) metal complexes and Schiff base ligands, the geometry was taken from the starting structures based on the crystallographic data. The density functional theory (DFT) B3LYP/6-31g(d)-FF method was used to calculate the second-order nonlinear optical (NLO) properties of open-shell cobalt(II) metal complexes. The results indicated that when compared with the Schiff base ligands, the second-order NLO properties of the metal complexes do not change obviously, the reason being that the NLO responses of cobalt(II) metal complexes are strongly related to intraligand charge transfer transitions. According to the frontier molecular orbitals, the less contribution of Co2+ in determining the NLO responses of metal complexes arises from the action of the bridging moiety in the charge transfer processes.
2006, 22(07): 840-844
doi: 10.1016/S1872-1508(06)60037-5
Abstract:
Nb-doped LiFePO4/C was synthesized using one-step solid-state method. The effect of Nb contents on the electrochemical performance was investigated. The results showed that the electrochemical performances were remarkably promoted. The discharge capacities of Li0.96Nb0.008FePO4/C cathode material were 161, 148, and 132 mAh•g−1 at the charge and discharge rates of 0.5C, 1C, and 2C, respectively. The results of cyclic voltammetry and EIS analyses showed that the resistance and polarization of the LiFePO4/C composite electrode could be effectively decreased by Nb doping, which would improve the electron conductivity of LiFePO4.
Nb-doped LiFePO4/C was synthesized using one-step solid-state method. The effect of Nb contents on the electrochemical performance was investigated. The results showed that the electrochemical performances were remarkably promoted. The discharge capacities of Li0.96Nb0.008FePO4/C cathode material were 161, 148, and 132 mAh•g−1 at the charge and discharge rates of 0.5C, 1C, and 2C, respectively. The results of cyclic voltammetry and EIS analyses showed that the resistance and polarization of the LiFePO4/C composite electrode could be effectively decreased by Nb doping, which would improve the electron conductivity of LiFePO4.
2006, 22(07): 845-850
doi: 10.1016/S1872-1508(06)60038-7
Abstract:
When a quaternary ammonium surfactant has a suitable solubility in a polar solvent, it can induce the phase self-separation of mutually soluble polar and apolar mixed solvents and a stable interface between the two phases can be formed. This phenomenon was attributed to the quaternary ammonium surfactant reaching suitable solubility in the polar solvent and driving out a considerable part of the apolar solvent, in which the surfactant is insoluble. As a result, phase separation appears. Using aqueous surfactant two-phase as reference, we suggest that it be termed as nonaqueous surfactant two-phase (NSTP) and also as two oil phases for short.
When a quaternary ammonium surfactant has a suitable solubility in a polar solvent, it can induce the phase self-separation of mutually soluble polar and apolar mixed solvents and a stable interface between the two phases can be formed. This phenomenon was attributed to the quaternary ammonium surfactant reaching suitable solubility in the polar solvent and driving out a considerable part of the apolar solvent, in which the surfactant is insoluble. As a result, phase separation appears. Using aqueous surfactant two-phase as reference, we suggest that it be termed as nonaqueous surfactant two-phase (NSTP) and also as two oil phases for short.
2006, 22(07): 851-855
doi: 10.3866/PKU.WHXB20060716
Abstract:
Series of Ni-Fe-La0.8Sr0.2Ga0.8Mg0.115Co0.085O3 (LSGMC8.5) composite anodes were prepared and characterized for solid oxide fuel cells (SOFCs) fueled with dimethyl ether (DME). The molar ratio of Ni to Fe was 9:1, 8:2, 7:3, and 5:5, respectively, and the total mass fraction of Ni-Fe in the electrode was 75%. Multiple techniques were applied to study the phase composition, the microstructure of the electrode, and the electrochemical oxidation of DME over the electrode/electrolyte interface. The results demonstrated that increase in the amount of Fe in the electrode improved the sintering activity of the electrode and changed the microstructure of the electrode and electrode/electrolyte interface. The activities for electrochemical oxidation of DME of the electrodes depended strongly on the molar ratio of Ni to Fe, and the electrode with a molar ratio of Ni to Fe at 8:2 exhibited the highest activity. The electrodes showed od activity and stability for DME oxidation, and no obvious coke deposition was observed.
Series of Ni-Fe-La0.8Sr0.2Ga0.8Mg0.115Co0.085O3 (LSGMC8.5) composite anodes were prepared and characterized for solid oxide fuel cells (SOFCs) fueled with dimethyl ether (DME). The molar ratio of Ni to Fe was 9:1, 8:2, 7:3, and 5:5, respectively, and the total mass fraction of Ni-Fe in the electrode was 75%. Multiple techniques were applied to study the phase composition, the microstructure of the electrode, and the electrochemical oxidation of DME over the electrode/electrolyte interface. The results demonstrated that increase in the amount of Fe in the electrode improved the sintering activity of the electrode and changed the microstructure of the electrode and electrode/electrolyte interface. The activities for electrochemical oxidation of DME of the electrodes depended strongly on the molar ratio of Ni to Fe, and the electrode with a molar ratio of Ni to Fe at 8:2 exhibited the highest activity. The electrodes showed od activity and stability for DME oxidation, and no obvious coke deposition was observed.
2006, 22(07): 856-859
doi: 10.3866/PKU.WHXB20060717
Abstract:
A new complex [Ni(phen)3](ClO4)2 was synthesized by transition metal Ni2+ with phen(1,10-phenanthroline). The crystal structure of the complex was determined by X-ray diffraction. The complex crystalizes in monoclinic system, space group P21/n with a=0.9388(2) nm, b=3.0139(5) nm, c=1.2974(2) nm, β=111.054(3)º, V=3.426(1) nm3. Quantum chemistry calculation was performed to the complex by using semi-empirical method with ZINDO/1 of hyperchem 7.0 program package. The optimized structure has been investigated. Atomic charge distribution results provided a od testimony for the coordination condition in the crystal structure.
A new complex [Ni(phen)3](ClO4)2 was synthesized by transition metal Ni2+ with phen(1,10-phenanthroline). The crystal structure of the complex was determined by X-ray diffraction. The complex crystalizes in monoclinic system, space group P21/n with a=0.9388(2) nm, b=3.0139(5) nm, c=1.2974(2) nm, β=111.054(3)º, V=3.426(1) nm3. Quantum chemistry calculation was performed to the complex by using semi-empirical method with ZINDO/1 of hyperchem 7.0 program package. The optimized structure has been investigated. Atomic charge distribution results provided a od testimony for the coordination condition in the crystal structure.
2006, 22(07): 860-863
doi: 10.3866/PKU.WHXB20060718
Abstract:
Sodium-doped lithium silicate as CO2 absorbent at 500 ℃ to 750 ℃ was prepared by high-temperature solid-state reaction. The influence of sodium doping on the crystal structure of the absorbent was studied by X-ray diffraction (XRD). The microscopic morphologies of the absorbents were observed by scanning electron microscopy (SEM). The CO2-absorption capacities were measured by a thermogravimetric analyzer, which showed that sodium doping could improve the CO2-absorption ability of lithium silicate. It was found that the absorbent possessed the best performance when n(SiO2):n(Li2CO3):n(Na2CO3)=1:1.96:0.04. The maximum amount of CO2 absorption arrives at (46±0.6)%(w) in CO2 atmosphere at 700 ℃ within 15 min. Moreover, the CO2 concentration in gas phase influences the rate of CO2 absorption.
Sodium-doped lithium silicate as CO2 absorbent at 500 ℃ to 750 ℃ was prepared by high-temperature solid-state reaction. The influence of sodium doping on the crystal structure of the absorbent was studied by X-ray diffraction (XRD). The microscopic morphologies of the absorbents were observed by scanning electron microscopy (SEM). The CO2-absorption capacities were measured by a thermogravimetric analyzer, which showed that sodium doping could improve the CO2-absorption ability of lithium silicate. It was found that the absorbent possessed the best performance when n(SiO2):n(Li2CO3):n(Na2CO3)=1:1.96:0.04. The maximum amount of CO2 absorption arrives at (46±0.6)%(w) in CO2 atmosphere at 700 ℃ within 15 min. Moreover, the CO2 concentration in gas phase influences the rate of CO2 absorption.
2006, 22(07): 864-867
doi: 10.3866/PKU.WHXB20060719
Abstract:
The potential energy curves of two alkyl iodides, C2H2F3I and n-C3H4F3I, are calculated with B3LYP method and dissociation energies of C—I bond are calculated accurately with B3LYP and MPn(n=2, 3, 4) methods. For dissociation energy, zero point vibration energy (ZPVE) is calculated and basis set superposition error (BSSE) is corrected by counterpoise method. Experimentally, emission spectra of C2H2F3I and n-C3H4F3I have been observed through microwave discharge. Experimental results show that 1315 nm emission spectra can be obtained. Consequently, iodine atom can be generated through dissociation of C—I bond of C2H2F3I and n-C3H4F3I by microwave excitation.
The potential energy curves of two alkyl iodides, C2H2F3I and n-C3H4F3I, are calculated with B3LYP method and dissociation energies of C—I bond are calculated accurately with B3LYP and MPn(n=2, 3, 4) methods. For dissociation energy, zero point vibration energy (ZPVE) is calculated and basis set superposition error (BSSE) is corrected by counterpoise method. Experimentally, emission spectra of C2H2F3I and n-C3H4F3I have been observed through microwave discharge. Experimental results show that 1315 nm emission spectra can be obtained. Consequently, iodine atom can be generated through dissociation of C—I bond of C2H2F3I and n-C3H4F3I by microwave excitation.
2006, 22(07): 868-872
doi: 10.3866/PKU.WHXB20060720
Abstract:
Horseradish peroxidase (HRP) was immobilized on glassy carbon electrode (GCE) surface by konjac glucomannan (KGM). HRP entrapped in the KGM film underwent fast direct transfer-electron reactions in water-organic solvent mixtures. The electrocatalysis of peroxides, such as hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxide, and 2-butanone peroxide, by the immobilized HRP was also explored. Stability and reproducibility of the modified electrode made it possible to determine the organic peroxides.
Horseradish peroxidase (HRP) was immobilized on glassy carbon electrode (GCE) surface by konjac glucomannan (KGM). HRP entrapped in the KGM film underwent fast direct transfer-electron reactions in water-organic solvent mixtures. The electrocatalysis of peroxides, such as hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxide, and 2-butanone peroxide, by the immobilized HRP was also explored. Stability and reproducibility of the modified electrode made it possible to determine the organic peroxides.
2006, 22(07): 873-877
doi: 10.3866/PKU.WHXB20060721
Abstract:
By means of Fourier transform infrared(FTIR) spectroscopy, the structure development of urea-formaldehyde (UF) resins in synthesis process was investigated, and the structural difference of reaction inter-products of urea and formaldehyde was observed in alkaline and acidic media and at different formaldehyde-to-urea molar ratios. With the reaction process of urea and formaldehyde the variation of the FTIR peaks was obvious, the amide II band frequency of FTIR spectra of UF resins shifted gradually from high to low, and more methylols, ether linkages and —NHCH2— were formed. But in the cured UF resins, the contents of methylols, ether linkages, and —NHCH2— decreased. With the increase of the formaldehyde-to-urea molar ratios from 0.5 to 3.0, the amide II band frequency also shifted gradually from high to low, and the contents of ether linkages and —NHCH2— increased in alkaline media, while in stronger acidic media the contents of Uron, methylene linkages, and methylols increased, but the content of —NHCH2— decreased.
By means of Fourier transform infrared(FTIR) spectroscopy, the structure development of urea-formaldehyde (UF) resins in synthesis process was investigated, and the structural difference of reaction inter-products of urea and formaldehyde was observed in alkaline and acidic media and at different formaldehyde-to-urea molar ratios. With the reaction process of urea and formaldehyde the variation of the FTIR peaks was obvious, the amide II band frequency of FTIR spectra of UF resins shifted gradually from high to low, and more methylols, ether linkages and —NHCH2— were formed. But in the cured UF resins, the contents of methylols, ether linkages, and —NHCH2— decreased. With the increase of the formaldehyde-to-urea molar ratios from 0.5 to 3.0, the amide II band frequency also shifted gradually from high to low, and the contents of ether linkages and —NHCH2— increased in alkaline media, while in stronger acidic media the contents of Uron, methylene linkages, and methylols increased, but the content of —NHCH2— decreased.
2006, 22(07): 878-882
doi: 10.3866/PKU.WHXB20060722
Abstract:
Molecular dynamics simulations on amorphous BCN system were carried out in order to investigate the structure character of short-range atomic arrangements, and to analyze the influence of the addition of C on the radial distribution function(RDF) and coordination number of the amorphous system at different temperatures. The results showed that there was little influence of C doping in amorphous BCN on the position of peaks and shape of RDF curves, but some partial RDF peaks shifted to the right contrasting to the PRDF of the amorphous BN. In amorphous BCN system, the added C atoms took partly up the positions of N atoms, reducing the coordination number of B-N atom pairs. There was no phase separation between BN phase and C phase at the simulation condition.
Molecular dynamics simulations on amorphous BCN system were carried out in order to investigate the structure character of short-range atomic arrangements, and to analyze the influence of the addition of C on the radial distribution function(RDF) and coordination number of the amorphous system at different temperatures. The results showed that there was little influence of C doping in amorphous BCN on the position of peaks and shape of RDF curves, but some partial RDF peaks shifted to the right contrasting to the PRDF of the amorphous BN. In amorphous BCN system, the added C atoms took partly up the positions of N atoms, reducing the coordination number of B-N atom pairs. There was no phase separation between BN phase and C phase at the simulation condition.
2006, 22(07): 883-887
doi: 10.3866/PKU.WHXB20060723
Abstract:
Hydrogen peroxide production via cathodic reduction of oxygen on self-made gas diffusion electrode was studied in an undivided system. The effects of mass ratio between graphite and PTFE, cathodic potential, pH, and gas flow rate on hydrogen peroxide output were investigated. When the mass ratio between graphite and PTFE was 2:1, pH=3, Na2SO4 concentration was 0.1 mol•L−1, oxygen flow rate was 0.4 L•min−1, and cathodic potential was −0.55 V (vs SCE), hydrogen peroxide concentration could reach about 60 mg•L−1 after 2 h. It had a od hydrogen peroxide output and current efficiency. The pH values applicable to hydrogen peroxide production could be extended to a wide range in this undivided system and this novel gas diffusion electrode system is expected to be applicable in waste water treatment.
Hydrogen peroxide production via cathodic reduction of oxygen on self-made gas diffusion electrode was studied in an undivided system. The effects of mass ratio between graphite and PTFE, cathodic potential, pH, and gas flow rate on hydrogen peroxide output were investigated. When the mass ratio between graphite and PTFE was 2:1, pH=3, Na2SO4 concentration was 0.1 mol•L−1, oxygen flow rate was 0.4 L•min−1, and cathodic potential was −0.55 V (vs SCE), hydrogen peroxide concentration could reach about 60 mg•L−1 after 2 h. It had a od hydrogen peroxide output and current efficiency. The pH values applicable to hydrogen peroxide production could be extended to a wide range in this undivided system and this novel gas diffusion electrode system is expected to be applicable in waste water treatment.
2006, 22(07): 888-890
doi: 10.3866/PKU.WHXB20060724
Abstract:
The critical phenomena of water + 3-methylpyridine + sodium bromide system, with the mass fractions of sodium bromide, 3-methylpyridine, and water being 0.240, 0.192, and 0.568, respectively, have been studied by measuring refractive indexes in two coexisting phases. It was found that the effective critical exponent was 0.365 near the critical point, which is in well agreement with the Fisher renormalization value. As the distance from the critical point increased, the effective critical exponent decreased from 0.365 to 0.20, but it exhibited crossover from Ising to mean-field critical behavior after the regular term was subtracted.
The critical phenomena of water + 3-methylpyridine + sodium bromide system, with the mass fractions of sodium bromide, 3-methylpyridine, and water being 0.240, 0.192, and 0.568, respectively, have been studied by measuring refractive indexes in two coexisting phases. It was found that the effective critical exponent was 0.365 near the critical point, which is in well agreement with the Fisher renormalization value. As the distance from the critical point increased, the effective critical exponent decreased from 0.365 to 0.20, but it exhibited crossover from Ising to mean-field critical behavior after the regular term was subtracted.
2006, 22(07): 891-894
doi: 10.3866/PKU.WHXB20060725
Abstract:
It is shown here that, by introduction of competitive reaction, the formation of tar in hydroxylation of aromatics can be completely avoided. As a result, higher catalytic selectivity and longer durability of the catalysts are achieved, compared with those of the conventional process for hydroxylation of phenol and benzene with H2O2.
It is shown here that, by introduction of competitive reaction, the formation of tar in hydroxylation of aromatics can be completely avoided. As a result, higher catalytic selectivity and longer durability of the catalysts are achieved, compared with those of the conventional process for hydroxylation of phenol and benzene with H2O2.
2006, 22(07): 895-898
doi: 10.3866/PKU.WHXB20060726
Abstract:
Different contents of Na2WO4 reagents were added to nickel positive electrode to enhance its high temperature performance. The results showed that, compared with blank electrode without Na2WO4, positive nickel electrode with Na2WO4 displayed an improved high temperature charging performance. Under the conditions of 70 ℃ and 1.0%(w) Na2WO4, high temperature charging efficiency over 85% was obtained for nickel positive electrode. Moreover, Na2WO4 was also favorable for the discharging capacity, cycle life, and charge retention. It was also found that, when Na2WO4 was added into nickel positive electrode, the main charging oxidation reaction of Ni(OH)2 was accelerated as well as oxygen extraction over-potential.
Different contents of Na2WO4 reagents were added to nickel positive electrode to enhance its high temperature performance. The results showed that, compared with blank electrode without Na2WO4, positive nickel electrode with Na2WO4 displayed an improved high temperature charging performance. Under the conditions of 70 ℃ and 1.0%(w) Na2WO4, high temperature charging efficiency over 85% was obtained for nickel positive electrode. Moreover, Na2WO4 was also favorable for the discharging capacity, cycle life, and charge retention. It was also found that, when Na2WO4 was added into nickel positive electrode, the main charging oxidation reaction of Ni(OH)2 was accelerated as well as oxygen extraction over-potential.
2006, 22(07): 899-912
doi: 10.3866/PKU.WHXB20060727
Abstract:
Recent progresses in the combinatorial materials science were reviewed. Firstly, the basic concept and history of combinatorial materials science were introduced. Then, the parallel synthesis methods and high throughput characterization techniques for combinatorial materials library were described in detail. The content mainly includes drop-on-demand ink-jet delivery technique, parallel solution combustion synthesis, thin film deposition combined with quaternary or in situ physical mask, imaging techniques, scanning X-ray structure/composition analysis, dielectric/ferroelectric characterization, etc. Finally, several successful examples of screening new materials via combinatorial method were demonstrated. Outlook on this new discipline was also discussed according to our consideration.
Recent progresses in the combinatorial materials science were reviewed. Firstly, the basic concept and history of combinatorial materials science were introduced. Then, the parallel synthesis methods and high throughput characterization techniques for combinatorial materials library were described in detail. The content mainly includes drop-on-demand ink-jet delivery technique, parallel solution combustion synthesis, thin film deposition combined with quaternary or in situ physical mask, imaging techniques, scanning X-ray structure/composition analysis, dielectric/ferroelectric characterization, etc. Finally, several successful examples of screening new materials via combinatorial method were demonstrated. Outlook on this new discipline was also discussed according to our consideration.
