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2003 Volume 19 Issue 3
2003, 19(03): 193-197
doi: 10.3866/PKU.WHXB20030301
Abstract:
The interaction of two NO molecules and NO dimers with Cu2 has been studied at B3LYP/Lanl2DZ level. The results show that the NO molecules and dimers can be stably adsorbed on the adjacent Cu atoms on the copper surface. However, the structure of NO adsorbed on Cu atom with N-down ward is more stable than any other structure in the NO co-adsorption models, and the NO atop adsorption is less stable than the other. On the other hand, the N－N bond is strengthened, while the N-O bond is weakened in the NO dimer adsorption models. It indicates that the formation of NO dimer is favorable to the NO direct decomposition on the copper surface. The Mülliken population analysis shows that the average charge on Cu is 0.66 e, when the singlet state dimer interacts with the copper. It suggests that the bond between the singlet state dimer and the Cu atom is more ionic, and that the N-O bond is more reactive in singlet state dimer. The calculation results reasonably indicate that NO can be directly decomposed via the dimer configurations on the copper surface.
The interaction of two NO molecules and NO dimers with Cu2 has been studied at B3LYP/Lanl2DZ level. The results show that the NO molecules and dimers can be stably adsorbed on the adjacent Cu atoms on the copper surface. However, the structure of NO adsorbed on Cu atom with N-down ward is more stable than any other structure in the NO co-adsorption models, and the NO atop adsorption is less stable than the other. On the other hand, the N－N bond is strengthened, while the N-O bond is weakened in the NO dimer adsorption models. It indicates that the formation of NO dimer is favorable to the NO direct decomposition on the copper surface. The Mülliken population analysis shows that the average charge on Cu is 0.66 e, when the singlet state dimer interacts with the copper. It suggests that the bond between the singlet state dimer and the Cu atom is more ionic, and that the N-O bond is more reactive in singlet state dimer. The calculation results reasonably indicate that NO can be directly decomposed via the dimer configurations on the copper surface.
2003, 19(03): 198-202
doi: 10.3866/PKU.WHXB20030302
Abstract:
Based on the introduction of bonding parameters and quantum numbers, an approved atomic valence named δiY was suggested, and a novel molecular topological index mXY was put forward. The approved atomic valence δiY was recommended relating to such atomic properties as Yang’s electronegative force gauge Yi, electron number of valence shell Zi, number of bonding electrons bi and the main quantum number of valence shell ni. The first order index 1XY was utilized to study quantitatively the structure-property or structure-activity relationship of organic and inorganic compounds. The index was correlated with the selected properties or activities of physicochemical properties, as boil point, heat capacity of liquids, heat capacity of vapors, heats of vaporization, critical temperature and critical pressure, of alkanes, the hydrophobicity parameter of phenyl halides, retention index of gas chromatograph of alkoxyl silicon chlorides, the toxicity of heterocyclic nitrogen-containing compounds, the lattice enthalpy of alkaline halides F bands energy of alkaline halides, and 119Sn Mossbauer shift of tin halides. The results suggested that the proposed index with fairly high and extensive correlation ability could be a useful parameter in QSPR and QSAR research.
Based on the introduction of bonding parameters and quantum numbers, an approved atomic valence named δiY was suggested, and a novel molecular topological index mXY was put forward. The approved atomic valence δiY was recommended relating to such atomic properties as Yang’s electronegative force gauge Yi, electron number of valence shell Zi, number of bonding electrons bi and the main quantum number of valence shell ni. The first order index 1XY was utilized to study quantitatively the structure-property or structure-activity relationship of organic and inorganic compounds. The index was correlated with the selected properties or activities of physicochemical properties, as boil point, heat capacity of liquids, heat capacity of vapors, heats of vaporization, critical temperature and critical pressure, of alkanes, the hydrophobicity parameter of phenyl halides, retention index of gas chromatograph of alkoxyl silicon chlorides, the toxicity of heterocyclic nitrogen-containing compounds, the lattice enthalpy of alkaline halides F bands energy of alkaline halides, and 119Sn Mossbauer shift of tin halides. The results suggested that the proposed index with fairly high and extensive correlation ability could be a useful parameter in QSPR and QSAR research.
2003, 19(03): 203-207
doi: 10.3866/PKU.WHXB20030303
Abstract:
Well spatial-dispersed and high purity silver oxide nanoparticles, whose size can be controlled from 5 nm to 30 nm, were prepared by vacuum thermal evaporation and glow discharge oxidation. To form island and keep samples in darkness are two key points of synthesis. Based on Ag3d and O1s binding energy and the ratio of silver atoms to oxide atoms given by XPS, the sample was confirmed to be Ag2O. X-ray diffraction of Ag2O nano-scale thin films was acquired and the strongest diffraction peaks referred to face (111), (110), (200) and (211) of Ag2O. Absorption spectra of the samples were also studied. The absorption spectrum indicates that band gap of silver oxide is 2.8 eV. After being photo-activated by blue light for a few minutes, intermittent green and yellow photoluminescence from silver oxide nanoparticles were observed with blue excitation. Luminescence from the same region excited by green light is red and also dynamic. This phenomenon was explained by electron transitions to the impurities energy levels induced by photolytic centers（Ag3O, Ag2＋O and Ag3＋O） in silver oxide.
Well spatial-dispersed and high purity silver oxide nanoparticles, whose size can be controlled from 5 nm to 30 nm, were prepared by vacuum thermal evaporation and glow discharge oxidation. To form island and keep samples in darkness are two key points of synthesis. Based on Ag3d and O1s binding energy and the ratio of silver atoms to oxide atoms given by XPS, the sample was confirmed to be Ag2O. X-ray diffraction of Ag2O nano-scale thin films was acquired and the strongest diffraction peaks referred to face (111), (110), (200) and (211) of Ag2O. Absorption spectra of the samples were also studied. The absorption spectrum indicates that band gap of silver oxide is 2.8 eV. After being photo-activated by blue light for a few minutes, intermittent green and yellow photoluminescence from silver oxide nanoparticles were observed with blue excitation. Luminescence from the same region excited by green light is red and also dynamic. This phenomenon was explained by electron transitions to the impurities energy levels induced by photolytic centers（Ag3O, Ag2＋O and Ag3＋O） in silver oxide.
2003, 19(03): 208-211
doi: 10.3866/PKU.WHXB20030304
Abstract:
The title resin was synthesized and the adsorption isotherms of phenol from cyclohexane solution were measured. Values of isosteric adsorption enthalpy, adsorption Gibbs free energy and adsorption entropy were calculated. These values implied a hydrogen-bonding adsorption mechanism. Furthermore, difference of adsorption property for phenol and o-nitrophenol from cyclohexane solution was studied, and the result was in accordance with the hydrogen-bonding mechanism.
The title resin was synthesized and the adsorption isotherms of phenol from cyclohexane solution were measured. Values of isosteric adsorption enthalpy, adsorption Gibbs free energy and adsorption entropy were calculated. These values implied a hydrogen-bonding adsorption mechanism. Furthermore, difference of adsorption property for phenol and o-nitrophenol from cyclohexane solution was studied, and the result was in accordance with the hydrogen-bonding mechanism.
2003, 19(03): 212-215
doi: 10.3866/PKU.WHXB20030305
Abstract:
The hydrothermal reaction processes of MgSO4-NaOH-H2O system with the same raw materials concentration for different reaction time at 160 ℃ have been studied. There are two magnesium oxysulfate compounds obtained by hydrothermal reaction, namely 5Mg(OH)2•MgSO4•2H2O(MOS) whisker and Mg(OH)2•2MgSO4•2H2O crystal. The compounds were characterized by chemical analysis, XRD, FT-IR and SEM. The 5Mg(OH)2•MgSO4•2H2O whisker is a metastable phase in MgSO4-NaOH-H2O system at 160 ℃,whereas the Mg(OH)2•2MgSO4•2H2O crystal is the stable phase.
The hydrothermal reaction processes of MgSO4-NaOH-H2O system with the same raw materials concentration for different reaction time at 160 ℃ have been studied. There are two magnesium oxysulfate compounds obtained by hydrothermal reaction, namely 5Mg(OH)2•MgSO4•2H2O(MOS) whisker and Mg(OH)2•2MgSO4•2H2O crystal. The compounds were characterized by chemical analysis, XRD, FT-IR and SEM. The 5Mg(OH)2•MgSO4•2H2O whisker is a metastable phase in MgSO4-NaOH-H2O system at 160 ℃,whereas the Mg(OH)2•2MgSO4•2H2O crystal is the stable phase.
2003, 19(03): 216-220
doi: 10.3866/PKU.WHXB20030306
Abstract:
Si, Zr-substituted aluminumphosphate zeolites were synthesized by hydrothermal method. XRD data indicated that they bear the same AEL structure with APO-11 zeolite. Of interest is that the crystal shape of SAPO-11 and APO-11 all are sphere-like, while ZAPO-11 exists as bar-like. Simultaneously, the introduction of heteroatoms in APO-11 skeleton could lead to the positive modification of acidity and micropore features. SAPO-11 showed higher acidity and ZAPO-11 possessed less micropore volume. Of special is that SAPO-11 with Si/Al =0.15 is the optimum shape-selective catalyst of skeletal isomerization of butene. The isomerization effect factors, such as butene partial pressure, temperature, were also extensively investigated. Of special is that the inconsistency in concentration changes between product isobutene and by-product, C3 and C5, was continually occurred while the reaction parameters were accordingly changed. It indicated that isobutene is shape-selectively formed via mono-imolecule mechanism, while the by-products C3 and C5 are mainly formed via bimolecular mechanism.
Si, Zr-substituted aluminumphosphate zeolites were synthesized by hydrothermal method. XRD data indicated that they bear the same AEL structure with APO-11 zeolite. Of interest is that the crystal shape of SAPO-11 and APO-11 all are sphere-like, while ZAPO-11 exists as bar-like. Simultaneously, the introduction of heteroatoms in APO-11 skeleton could lead to the positive modification of acidity and micropore features. SAPO-11 showed higher acidity and ZAPO-11 possessed less micropore volume. Of special is that SAPO-11 with Si/Al =0.15 is the optimum shape-selective catalyst of skeletal isomerization of butene. The isomerization effect factors, such as butene partial pressure, temperature, were also extensively investigated. Of special is that the inconsistency in concentration changes between product isobutene and by-product, C3 and C5, was continually occurred while the reaction parameters were accordingly changed. It indicated that isobutene is shape-selectively formed via mono-imolecule mechanism, while the by-products C3 and C5 are mainly formed via bimolecular mechanism.
2003, 19(03): 221-225
doi: 10.3866/PKU.WHXB20030307
Abstract:
The adsorption of two representative N-nitrosamines with larger molecular volume than the pore size of zeolites, N-nitrosohexamethyleneimine (NHMI) and N’-nitrosonornicotine (NNN) on zeolite KA and NaA were investigated in this article, in order to explore how the small pore zeolites adsorb and separate those guest molecules with bigger volume. Both NHMI and NNN could be adsorbed on NaA or KA zeolites and degraded in the process of temperature programmed surface reaction (TPSR), though the pore size of adsorbent was much smaller than the molecular size of the adsorbate. Several possible adsorption models of NHMI and NNN were assumed and discussed on the basis of simulation for the structure of N-nitrosamines, but only the insertion of －N－N=O group in the channel of zeolites was found to be the feasible one in accordance with the experiments of adsorption and TPSR. Through such insertion-adsorption, many pollutant species with big molecular size in the environment can thus be adsorbed and separated by use of zeolite molecular sieve materials.
The adsorption of two representative N-nitrosamines with larger molecular volume than the pore size of zeolites, N-nitrosohexamethyleneimine (NHMI) and N’-nitrosonornicotine (NNN) on zeolite KA and NaA were investigated in this article, in order to explore how the small pore zeolites adsorb and separate those guest molecules with bigger volume. Both NHMI and NNN could be adsorbed on NaA or KA zeolites and degraded in the process of temperature programmed surface reaction (TPSR), though the pore size of adsorbent was much smaller than the molecular size of the adsorbate. Several possible adsorption models of NHMI and NNN were assumed and discussed on the basis of simulation for the structure of N-nitrosamines, but only the insertion of －N－N=O group in the channel of zeolites was found to be the feasible one in accordance with the experiments of adsorption and TPSR. Through such insertion-adsorption, many pollutant species with big molecular size in the environment can thus be adsorbed and separated by use of zeolite molecular sieve materials.
2003, 19(03): 226-229
doi: 10.3866/PKU.WHXB20030308
Abstract:
A series of rare earth complex oxides, i.e. (Y1-xGdx)3Al5O12 : Ce3＋, (Y1-xLux)3Al5O12:Ce3＋, (Y1-xLax)3Al5O12:Ce3＋, (Y1-xYbx)3Al5O12:Ce3＋and (Y1-xTbx)3Al5O12:Ce3＋, have been prepared, and their luminescent properties were studied. Particular attention was paid to (Y1-xGdx)3Al5O12:Ce3＋ and (Y1-xLux)3Al5O12:Ce3＋systems because of their promising luminescent properties. X-ray powder diffraction patterns show that both systems have garnet structure, and the lattice constants vary smoothly with the compositions. The emission spectra of Ce3＋ in both systems are a broad band located at about 540 nm. The emission transition shows a red shift in (Y1-xGdx)3Al5O12:Ce3＋ system, and a blue shift also observed in (Y1-xLux)3Al5O12:Ce3＋system. This phenomenon could be interpreted with the configuration coordination model. The shift of the emission spectra in these systems provides the new option to improve the performance of white LED device.
A series of rare earth complex oxides, i.e. (Y1-xGdx)3Al5O12 : Ce3＋, (Y1-xLux)3Al5O12:Ce3＋, (Y1-xLax)3Al5O12:Ce3＋, (Y1-xYbx)3Al5O12:Ce3＋and (Y1-xTbx)3Al5O12:Ce3＋, have been prepared, and their luminescent properties were studied. Particular attention was paid to (Y1-xGdx)3Al5O12:Ce3＋ and (Y1-xLux)3Al5O12:Ce3＋systems because of their promising luminescent properties. X-ray powder diffraction patterns show that both systems have garnet structure, and the lattice constants vary smoothly with the compositions. The emission spectra of Ce3＋ in both systems are a broad band located at about 540 nm. The emission transition shows a red shift in (Y1-xGdx)3Al5O12:Ce3＋ system, and a blue shift also observed in (Y1-xLux)3Al5O12:Ce3＋system. This phenomenon could be interpreted with the configuration coordination model. The shift of the emission spectra in these systems provides the new option to improve the performance of white LED device.
2003, 19(03): 230-232
doi: 10.3866/PKU.WHXB20030309
Abstract:
Standard Gibbs energies of transfer, GtΘ, of In(Ⅲ) from water to aqueous sucrose and aqueous glucose solutions(mass fraction of sucrose and glucose w=0, 0.10, 0.20, 0.30, 0.40 and 0.50) have been determined by polarography at (298±1) K. In aqueous sucrose and glucose solutions containing 5.0×10－2 mol•L－1 LiClO4, the reversible half-wave potential and the diffusion coefficients for In(Ⅲ) have been determined respectively. Values of GtΘ, obtained from the reversible half-wave potentials vs the ferrocene electrode scale, are negative and decrease with increasing concentration of sucrose and glucose, indicating increasing stability of In(Ⅲ) in sucrose-water and glucose-water solutions. The GtΘ values were split into electrostatic and chemical contributions. The decreased chemical contribution shows that the mixtures are more basic than pure water. The experimental results are discussed in terms of solute-solvent and solute-solute interactions in the ternary systems.
Standard Gibbs energies of transfer, GtΘ, of In(Ⅲ) from water to aqueous sucrose and aqueous glucose solutions(mass fraction of sucrose and glucose w=0, 0.10, 0.20, 0.30, 0.40 and 0.50) have been determined by polarography at (298±1) K. In aqueous sucrose and glucose solutions containing 5.0×10－2 mol•L－1 LiClO4, the reversible half-wave potential and the diffusion coefficients for In(Ⅲ) have been determined respectively. Values of GtΘ, obtained from the reversible half-wave potentials vs the ferrocene electrode scale, are negative and decrease with increasing concentration of sucrose and glucose, indicating increasing stability of In(Ⅲ) in sucrose-water and glucose-water solutions. The GtΘ values were split into electrostatic and chemical contributions. The decreased chemical contribution shows that the mixtures are more basic than pure water. The experimental results are discussed in terms of solute-solvent and solute-solute interactions in the ternary systems.
2003, 19(03): 233-236
doi: 10.3866/PKU.WHXB20030310
Abstract:
The technique of nanometer scale manipulation is very important in constructing nano-structures and nano-devices.By using atomic force microscope in contact mode, we have accomplished many kinds of controllable manipulations on single wall carbon nanotubes, including bending, cutting and splitting of nanotube bundles, etc. The results of the manipulation depend on the interaction between tip and nanotubes as well as between substrate and nanotubes. When nanotubes are fixed to some extent on the substrate surface, it will be easier to accomplish manipulations; when the force from the tip is stronger, bundles of nanotube can be splitted.
The technique of nanometer scale manipulation is very important in constructing nano-structures and nano-devices.By using atomic force microscope in contact mode, we have accomplished many kinds of controllable manipulations on single wall carbon nanotubes, including bending, cutting and splitting of nanotube bundles, etc. The results of the manipulation depend on the interaction between tip and nanotubes as well as between substrate and nanotubes. When nanotubes are fixed to some extent on the substrate surface, it will be easier to accomplish manipulations; when the force from the tip is stronger, bundles of nanotube can be splitted.
2003, 19(03): 237-241
doi: 10.3866/PKU.WHXB20030311
Abstract:
In a mixture of Ru(dpphen)32+ and stearic acid (SA),the ratio of Ru(dpphen)32+ :SA=1:2 is the only best one and any excess of Ru(dpphen)32+ or SA is not favorable for the deposition of mixed monolayer and LB films. If variation of the composition of Ru(dpphen)32+ in LB films is needed, some non-functional “surface ions" must be introduced to replace Ru(dpphen)32+ partially. The octadecyltrichlorosilane (OTS) was used to replace Ru(dpphen)32+ successfully. The threshold concentration of Ru(dpphen)32+ in mixing SA-OTS- Ru(dpphen)32+ on pure water and forming Ru(dpphen)32+ controlled LB films was studied. OTS can form crosslinked network monolayer on pure water, on interfusing SA, crosslinked network is destroyed gradually. Increase of concentration of SA, till SA/OTS=3:1,there is no crosslinked network in the monolayer and is favorable for the stable and condensed mixed monolayer and LB films deposition. Ru(dpphen)32+/OTS/SA forms three component mixed monolayer, Ru(dpphen)32+/OTS are surface ions. It is availably to prevent OTS from crosslinking when Ru(dpphen)32+ is mixed. Ru(dpphen)32+/SA and OTS/SA are uniformly mixed. By changing the mixing ratios of Ru(dpphen)32+/SA and OTS/SA, component of Ru(dpphen)32+ will be controlled accurately and can lead the deposition of stable and condensed mixed monolayer for LB films.
In a mixture of Ru(dpphen)32+ and stearic acid (SA),the ratio of Ru(dpphen)32+ :SA=1:2 is the only best one and any excess of Ru(dpphen)32+ or SA is not favorable for the deposition of mixed monolayer and LB films. If variation of the composition of Ru(dpphen)32+ in LB films is needed, some non-functional “surface ions" must be introduced to replace Ru(dpphen)32+ partially. The octadecyltrichlorosilane (OTS) was used to replace Ru(dpphen)32+ successfully. The threshold concentration of Ru(dpphen)32+ in mixing SA-OTS- Ru(dpphen)32+ on pure water and forming Ru(dpphen)32+ controlled LB films was studied. OTS can form crosslinked network monolayer on pure water, on interfusing SA, crosslinked network is destroyed gradually. Increase of concentration of SA, till SA/OTS=3:1,there is no crosslinked network in the monolayer and is favorable for the stable and condensed mixed monolayer and LB films deposition. Ru(dpphen)32+/OTS/SA forms three component mixed monolayer, Ru(dpphen)32+/OTS are surface ions. It is availably to prevent OTS from crosslinking when Ru(dpphen)32+ is mixed. Ru(dpphen)32+/SA and OTS/SA are uniformly mixed. By changing the mixing ratios of Ru(dpphen)32+/SA and OTS/SA, component of Ru(dpphen)32+ will be controlled accurately and can lead the deposition of stable and condensed mixed monolayer for LB films.
2003, 19(03): 242-245
doi: 10.3866/PKU.WHXB20030312
Abstract:
A method based on a genetic al rithm was used to determine the lowest energy structure of an atomic cluster in an arbitrary model potential. The method operated on a population of candidate structures to produce new candidates with lower energies, and finally the lowest energy structure can be obtained. We applied the genetic al rithm to a tight-binding (TB) model potential for aluminum clusters. With this potential, the al rithm efficiently found the lowest energy structures of Al6, Al8, Al9, Al10 clusters starting from a random atomic collection of atoms. The lowest energy structures of Al6, Al8, Al9, Al10 were found to adopt four forms of Bernal polyhedron. The density function theory (DFT) calculation was also done and the result shows that the four geometries are the minimums on the potential surface.
A method based on a genetic al rithm was used to determine the lowest energy structure of an atomic cluster in an arbitrary model potential. The method operated on a population of candidate structures to produce new candidates with lower energies, and finally the lowest energy structure can be obtained. We applied the genetic al rithm to a tight-binding (TB) model potential for aluminum clusters. With this potential, the al rithm efficiently found the lowest energy structures of Al6, Al8, Al9, Al10 clusters starting from a random atomic collection of atoms. The lowest energy structures of Al6, Al8, Al9, Al10 were found to adopt four forms of Bernal polyhedron. The density function theory (DFT) calculation was also done and the result shows that the four geometries are the minimums on the potential surface.
2003, 19(03): 246-250
doi: 10.3866/PKU.WHXB20030313
Abstract:
The catalytic activity of several SnO2 based catalysts for methane combustion in the presence of 200×10－6（φ,volume fraction） SO2 were tested. The results showed that among these samples studied SnCrO possessed the highest resistance to sulphur poisoning, while the catalytic activity of SnCuO and SnCoO samples decreased significantly. XRD, BET, XPS, FT-IR and DTA-TG techniques were employed to characterize the samples before and after reaction in SO2, and it was found that the thermal stability of the respective metal sulfates played an important role in the combustions of methane in the presence of SO2. At 500 ℃,Co2(SO4)3 and CuSO4 are stable but Cr2(SO4)3 can decompose, therefore, during the reaction in 200×10－6（φ） SO2, SnCrO sample only adsorbs a small amount of SO42- ions on its surface and the activity remains almost unchanged, which is the reason for the highest resistance of SnCrO sample to sulphur poisoning.
The catalytic activity of several SnO2 based catalysts for methane combustion in the presence of 200×10－6（φ,volume fraction） SO2 were tested. The results showed that among these samples studied SnCrO possessed the highest resistance to sulphur poisoning, while the catalytic activity of SnCuO and SnCoO samples decreased significantly. XRD, BET, XPS, FT-IR and DTA-TG techniques were employed to characterize the samples before and after reaction in SO2, and it was found that the thermal stability of the respective metal sulfates played an important role in the combustions of methane in the presence of SO2. At 500 ℃,Co2(SO4)3 and CuSO4 are stable but Cr2(SO4)3 can decompose, therefore, during the reaction in 200×10－6（φ） SO2, SnCrO sample only adsorbs a small amount of SO42- ions on its surface and the activity remains almost unchanged, which is the reason for the highest resistance of SnCrO sample to sulphur poisoning.
2003, 19(03): 251-255
doi: 10.3866/PKU.WHXB20030314
Abstract:
On a composite surfactant template(Brij35 and PEG), ordered mesoporous TiO2 was synthesized successfully. The formation of the ordered mesoporous TiO2 was analyzed by continuously monitoring the conductivity and viscosity during the reaction process, the ordered mesoporous TiO2 formed was characterized by XRD, HRTEM, SEM, FT-IR and N2 adsorption and desorption methods. The results indicated that ordered mesoporous TiO2 was of a hexa nal packed structure, at a temperature below 400 ℃, ordered mesoporous TiO2 has a higher thermal stability and a higher surface area of 252 m2•g－1,the mesoporous pore diameter was uniform with a value of 3.4 nm and the crystal was in anatase phase. After TiO2 was calcined at 500 ℃, ordered mesoporous structure was destroyed somewhat, and the formation of rutile phase appeared. The results also showed that liquid crystal template played a key role for the reaction, especially in a high polar media, in which non-polar carbon-hydrogen chain easily coagulated forming micelle, and TBOT gathered around the micelle formed, when they were acted by acid, reaction took place gradually to generate ordered mesoporous structure TiO2. It was found that taking efficient measures to control the hydrolysis and condensation processes of the reaction was the key of forming ordered mesoporous structure TiO2.
On a composite surfactant template(Brij35 and PEG), ordered mesoporous TiO2 was synthesized successfully. The formation of the ordered mesoporous TiO2 was analyzed by continuously monitoring the conductivity and viscosity during the reaction process, the ordered mesoporous TiO2 formed was characterized by XRD, HRTEM, SEM, FT-IR and N2 adsorption and desorption methods. The results indicated that ordered mesoporous TiO2 was of a hexa nal packed structure, at a temperature below 400 ℃, ordered mesoporous TiO2 has a higher thermal stability and a higher surface area of 252 m2•g－1,the mesoporous pore diameter was uniform with a value of 3.4 nm and the crystal was in anatase phase. After TiO2 was calcined at 500 ℃, ordered mesoporous structure was destroyed somewhat, and the formation of rutile phase appeared. The results also showed that liquid crystal template played a key role for the reaction, especially in a high polar media, in which non-polar carbon-hydrogen chain easily coagulated forming micelle, and TBOT gathered around the micelle formed, when they were acted by acid, reaction took place gradually to generate ordered mesoporous structure TiO2. It was found that taking efficient measures to control the hydrolysis and condensation processes of the reaction was the key of forming ordered mesoporous structure TiO2.
2003, 19(03): 256-259
doi: 10.3866/PKU.WHXB20030315
Abstract:
In the alkali/surfactant/polymer (ASP) flooding technology to enhance oil recovery, the unmatched alkali and polymer have serious influence on the study of composition of displacing system and application of ASP flooding. For the condition of Daqing oil field, the rheologic behavior of ASP solution has been systematically studied by using HAAK rheometer. The results show that the viscoelasticity of ASP solution decreases obviously with the addtion of alkali (see Fig.1). By using AFM, the effect of alkali on the molecular configuration of polymer has been studied. In obsence of alkali, polymer molecules stretch out themselves in liquid phase. But polymer molecules huddle up by adding alkali. The higher alkali concentration is the compacter curly clew of polymer molecules. With low alkali concentration (mass fraction 0.3％),polymer molecules cannot extent fully and exist in aggregation of multi-molecules(see Fig.5).
In the alkali/surfactant/polymer (ASP) flooding technology to enhance oil recovery, the unmatched alkali and polymer have serious influence on the study of composition of displacing system and application of ASP flooding. For the condition of Daqing oil field, the rheologic behavior of ASP solution has been systematically studied by using HAAK rheometer. The results show that the viscoelasticity of ASP solution decreases obviously with the addtion of alkali (see Fig.1). By using AFM, the effect of alkali on the molecular configuration of polymer has been studied. In obsence of alkali, polymer molecules stretch out themselves in liquid phase. But polymer molecules huddle up by adding alkali. The higher alkali concentration is the compacter curly clew of polymer molecules. With low alkali concentration (mass fraction 0.3％),polymer molecules cannot extent fully and exist in aggregation of multi-molecules(see Fig.5).
2003, 19(03): 260-264
doi: 10.3866/PKU.WHXB20030316
Abstract:
Visible Chemiluminescence in the region of 380～500 nm was measured from the reaction of O( 3P ) atoms with carbon disulfide under various pressures using crossed molecular beam apparatus. The emission spectra were assigned to 3B1→ 1A1 transition of gaseous sulfur dioxide molecules. 3B1 state of sulfur dioxide is mainly composed of vibrational ground state and excited vibrational state of bending vibrational mode, vibrational band progressions in the lower state of bending modes and stretching modes were observed. The spectra under various pressures and the reaction mechanism were discussed. It was proposed that 3B1 state of sulfur dioxide was produced from multistage processes.
Visible Chemiluminescence in the region of 380～500 nm was measured from the reaction of O( 3P ) atoms with carbon disulfide under various pressures using crossed molecular beam apparatus. The emission spectra were assigned to 3B1→ 1A1 transition of gaseous sulfur dioxide molecules. 3B1 state of sulfur dioxide is mainly composed of vibrational ground state and excited vibrational state of bending vibrational mode, vibrational band progressions in the lower state of bending modes and stretching modes were observed. The spectra under various pressures and the reaction mechanism were discussed. It was proposed that 3B1 state of sulfur dioxide was produced from multistage processes.
2003, 19(03): 265-267
doi: 10.3866/PKU.WHXB20030317
Abstract:
Direct current electro-deposition was applied to add Nickel to the nano-scale holes of porous Alumina template prepared by two-step anodic oxidation. The structure and magnetic performance of Ni-Al2O3 array system were investigated by electron microscope, X-Ray and vibration sample magnetometer. The results indicated that the regularity of the holes’ arrangement in the porous Alumina membrane by two-step anodic oxidation was obviously better than that by one-step anodic oxidation. Nickel was in single crystal state in the nanochannal array system and had definite crystall selective-orientation. The array had obvious magnetic anisotropy, and was promising for perpendicular magnetic recording medium.
Direct current electro-deposition was applied to add Nickel to the nano-scale holes of porous Alumina template prepared by two-step anodic oxidation. The structure and magnetic performance of Ni-Al2O3 array system were investigated by electron microscope, X-Ray and vibration sample magnetometer. The results indicated that the regularity of the holes’ arrangement in the porous Alumina membrane by two-step anodic oxidation was obviously better than that by one-step anodic oxidation. Nickel was in single crystal state in the nanochannal array system and had definite crystall selective-orientation. The array had obvious magnetic anisotropy, and was promising for perpendicular magnetic recording medium.
2003, 19(03): 268-271
doi: 10.3866/PKU.WHXB20030318
Abstract:
The proton exchange of the benzoquinone radicals obtained from the laser photolysis of p-benzoquinone in ethylene glycol/water system was investigated by using time-resolved ESR(TRESR)spectrometer. The dependence of the TRESR spectra upon the pH value of the mixed solution was studied. In neutral solution, six superfine emission lines were observed and were attributed to radical BQH•, while the pH value of the solution changed to ～2.0, five emission superfine lines were observed and were assigned to cation BQH＋. For BQH＋, the decay rates differ in the superfine lines, lines involving greater fraction of the nuclear spin states decayed with slower rates than those involving smaller ones owing to the variation of the resonance position in the proton exchange.
The proton exchange of the benzoquinone radicals obtained from the laser photolysis of p-benzoquinone in ethylene glycol/water system was investigated by using time-resolved ESR(TRESR)spectrometer. The dependence of the TRESR spectra upon the pH value of the mixed solution was studied. In neutral solution, six superfine emission lines were observed and were attributed to radical BQH•, while the pH value of the solution changed to ～2.0, five emission superfine lines were observed and were assigned to cation BQH＋. For BQH＋, the decay rates differ in the superfine lines, lines involving greater fraction of the nuclear spin states decayed with slower rates than those involving smaller ones owing to the variation of the resonance position in the proton exchange.
2003, 19(03): 272-274
doi: 10.3866/PKU.WHXB20030319
Abstract:
The gas-solid heterogeneous reaction between X2 (X=Cl, Br) and A CN has been investigated under the condition of super vacuum, HeI photoelectron spectroscopy (PES) indicates that XNCO was produced, and we deduce that an inter mediate complex in this process was formed, i.e. the generation of new-bond and the broken of old-bond were ing simultaneously.
The gas-solid heterogeneous reaction between X2 (X=Cl, Br) and A CN has been investigated under the condition of super vacuum, HeI photoelectron spectroscopy (PES) indicates that XNCO was produced, and we deduce that an inter mediate complex in this process was formed, i.e. the generation of new-bond and the broken of old-bond were ing simultaneously.
2003, 19(03): 275-277
doi: 10.3866/PKU.WHXB20030320
Abstract:
Nanocrystalline oxide compound Ba(Zn1－xCox)2Fe16O27 has been synthesized using PEG gel method. The products are characterized by means of X-ray powder diffraction analysis. Based on a two-layer structure, the Ba(Zn1－xCox)2Fe16O27 powder is integrated with the traditional microwave absorbing material, iron particle, to form the absorbing coatings. The experimental result indicates that the composite materials have a od absorbing property. The absorptive mechanism of nanocrystalline material has also been discussed.
Nanocrystalline oxide compound Ba(Zn1－xCox)2Fe16O27 has been synthesized using PEG gel method. The products are characterized by means of X-ray powder diffraction analysis. Based on a two-layer structure, the Ba(Zn1－xCox)2Fe16O27 powder is integrated with the traditional microwave absorbing material, iron particle, to form the absorbing coatings. The experimental result indicates that the composite materials have a od absorbing property. The absorptive mechanism of nanocrystalline material has also been discussed.
2003, 19(03): 278-282
doi: 10.3866/PKU.WHXB20030321
Abstract:
Artificial graphite samples with different particle size ranging from 13 to 80 μm were prepared by sieving method. The lithium intercalation performances of these samples were investigated. The results showed that the particle size had distinct effect on lithium intercalation performances of graphite. When particle size of graphite decreased gradually from 80 μm to 13 μm, the irreversible capacity loss of graphite increased about 10％. However, the reversible capacity increased with the decrease of particle size until the latter reached 20 μm with which the graphite had the highest capacity. When the particle size decreased from 20 μm, the reversible capacity decreased also. It suggested that neither large nor small graphite particle is suitable for reversible lithium intercalation. The medium graphite particles have the optimum reversible capacity. The Brunauer-Emmett-Teller (BET) surface area was measured and it increased with the decrease of particle size. This trend could explain the change of lithium intercalation performances of graphite with particle size.
Artificial graphite samples with different particle size ranging from 13 to 80 μm were prepared by sieving method. The lithium intercalation performances of these samples were investigated. The results showed that the particle size had distinct effect on lithium intercalation performances of graphite. When particle size of graphite decreased gradually from 80 μm to 13 μm, the irreversible capacity loss of graphite increased about 10％. However, the reversible capacity increased with the decrease of particle size until the latter reached 20 μm with which the graphite had the highest capacity. When the particle size decreased from 20 μm, the reversible capacity decreased also. It suggested that neither large nor small graphite particle is suitable for reversible lithium intercalation. The medium graphite particles have the optimum reversible capacity. The Brunauer-Emmett-Teller (BET) surface area was measured and it increased with the decrease of particle size. This trend could explain the change of lithium intercalation performances of graphite with particle size.
2003, 19(03): 283-285
doi: 10.3866/PKU.WHXB20030322
Abstract:
Copper p-toluenesulfonate was synthesized and has been applied to the electrochemical test for the first time. This salt can lose all its hydrated water easily and the dehydrated salt does not deliquesce in air. Hence, the copper p-toluenesulfonate is suitable to the electrochemical studies in organic solvents. The cyclic voltammetry, chronoamperometry and potential-time curve after galvanostatic electrolysis were used to study the electro-reduction of Cu(II) on Pt electrode in Cu (p-CH3C6H4SO3)2＋TBAP＋DMSO. The electro-reduction of Cu (II) to Cu proceeds by two steps: Cu (II)＋e = Cu (I), Cu (I)＋e = Cu. The first step is reversible. The diffusion coefficient of Cu(II) in DMSO is determined as 1.0×10－6 cm2•s－1 at 301 K.
Copper p-toluenesulfonate was synthesized and has been applied to the electrochemical test for the first time. This salt can lose all its hydrated water easily and the dehydrated salt does not deliquesce in air. Hence, the copper p-toluenesulfonate is suitable to the electrochemical studies in organic solvents. The cyclic voltammetry, chronoamperometry and potential-time curve after galvanostatic electrolysis were used to study the electro-reduction of Cu(II) on Pt electrode in Cu (p-CH3C6H4SO3)2＋TBAP＋DMSO. The electro-reduction of Cu (II) to Cu proceeds by two steps: Cu (II)＋e = Cu (I), Cu (I)＋e = Cu. The first step is reversible. The diffusion coefficient of Cu(II) in DMSO is determined as 1.0×10－6 cm2•s－1 at 301 K.
2003, 19(03): 286-288
doi: 10.3866/PKU.WHXB20030323
Abstract:
The nanophase MnO2 was synthesized by solid-phase reaction as electrode material for electrochemical supercapacitor and the MnO2 electrode was tested by cyclic voltammetry(CV),electrochemical impedance spectrometry (EIS) and constant charge-discharge curves. The result shows that MnO2 electrode has od performance of faradic pseudocapacitance in 1mol•L－1 KOH between －0.1 and 0.6 V(vs Hg/H ). The electrode can provide a specific capacitance of 240.25 to 325.21 F•g－1 at different current densities. After 5000 cycles of constant charge-discharge the capacitance reduces no more than 10％.
The nanophase MnO2 was synthesized by solid-phase reaction as electrode material for electrochemical supercapacitor and the MnO2 electrode was tested by cyclic voltammetry(CV),electrochemical impedance spectrometry (EIS) and constant charge-discharge curves. The result shows that MnO2 electrode has od performance of faradic pseudocapacitance in 1mol•L－1 KOH between －0.1 and 0.6 V(vs Hg/H ). The electrode can provide a specific capacitance of 240.25 to 325.21 F•g－1 at different current densities. After 5000 cycles of constant charge-discharge the capacitance reduces no more than 10％.
