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2002 Volume 18 Issue 4
2002, 18(04): 289-91
doi: 10.3866/PKU.WHXB20020401
Abstract:
The crystal structure of a new charge transfer salt,(ET)2FeCl4 has been predicted by molecular mechanics.Unit crystal electron energies of charge transfer salts of (ET)2FeCl4 family are calculated using density functional theory (DFT).Rationality of the crystal structure is explained by comparing with other two similar charge transfer salts in crystal structure and electron energy.
The crystal structure of a new charge transfer salt,(ET)2FeCl4 has been predicted by molecular mechanics.Unit crystal electron energies of charge transfer salts of (ET)2FeCl4 family are calculated using density functional theory (DFT).Rationality of the crystal structure is explained by comparing with other two similar charge transfer salts in crystal structure and electron energy.
2002, 18(04): 292-296
doi: 10.3866/PKU.WHXB20020402
Abstract:
A series of Eu,Tb complexes were synthesized with derivatives of benzoic acid as the first ligand and phenanthroline or 2,2′bipyridine as the second ligand.The structural characterization of the complexes was performed using elemental analysis,FTIR spectroscopy and UVVis spectroscopy.The photoluminescent behaviors of the complexes were investigated using fluorescent spectroscopy.The results showed that introduction of the second ligand improved the solubility of the complexes significantly.As far as the photoluminescent behaviors was concerned,phenanthroline enhanced the fluorescent intensity of Eu complexes but weakened the fluorescent intensity of Tb complexes; while the fluorescent intensity of Tb complexes increased and the fluorescent intensity of Eu complexes decreased upon coordinating with 2,2bipyridine.In addition,introducing of various substitutions onto the aromatic ring of benzoic acid brought about considerable variation of the fluorescent intensity of the Eu,Tb complexes.
A series of Eu,Tb complexes were synthesized with derivatives of benzoic acid as the first ligand and phenanthroline or 2,2′bipyridine as the second ligand.The structural characterization of the complexes was performed using elemental analysis,FTIR spectroscopy and UVVis spectroscopy.The photoluminescent behaviors of the complexes were investigated using fluorescent spectroscopy.The results showed that introduction of the second ligand improved the solubility of the complexes significantly.As far as the photoluminescent behaviors was concerned,phenanthroline enhanced the fluorescent intensity of Eu complexes but weakened the fluorescent intensity of Tb complexes; while the fluorescent intensity of Tb complexes increased and the fluorescent intensity of Eu complexes decreased upon coordinating with 2,2bipyridine.In addition,introducing of various substitutions onto the aromatic ring of benzoic acid brought about considerable variation of the fluorescent intensity of the Eu,Tb complexes.
2002, 18(04): 297-301
doi: 10.3866/PKU.WHXB20020403
Abstract:
A series of simulation of the evolution of atom clusters in liquid Ni3Al alloy during rapid solidification have been performed under constant pressure and temperature by molecular dynamic simulation technique. TB(tightbinding) potential function has been adopted to describe the interaction between atoms. The structure parameters such as pair correlation function, bonded pairs and polyhedra clusters have been used to characterize the dependence of the type and number of clusters on temperature during rapid cooling process. The cluster structure could be visualized clearly through the conversion of atom coordinates obtained by simulation to threedimension graphical interface. The number of liquid Ni3Al clusters at the temperature of 2 000 K is small and all are made up of diicosahedron; however, it increases rapidly at the cooling rate of 4×1013 K•s－1, and finally,the icosahedra clusters occur at low temperature. The network consists of the icosahedra and diicosahedra clusters forming an amorphous system.
A series of simulation of the evolution of atom clusters in liquid Ni3Al alloy during rapid solidification have been performed under constant pressure and temperature by molecular dynamic simulation technique. TB(tightbinding) potential function has been adopted to describe the interaction between atoms. The structure parameters such as pair correlation function, bonded pairs and polyhedra clusters have been used to characterize the dependence of the type and number of clusters on temperature during rapid cooling process. The cluster structure could be visualized clearly through the conversion of atom coordinates obtained by simulation to threedimension graphical interface. The number of liquid Ni3Al clusters at the temperature of 2 000 K is small and all are made up of diicosahedron; however, it increases rapidly at the cooling rate of 4×1013 K•s－1, and finally,the icosahedra clusters occur at low temperature. The network consists of the icosahedra and diicosahedra clusters forming an amorphous system.
2002, 18(04): 302-306
doi: 10.3866/PKU.WHXB20020404
Abstract:
Using Gaussian 98 program with B3LYP method, ground state equilibrium structure of PuCO was optimized and harmonic frequencies and force constant for the PuCO molecule have been calculated. Analytical potential energy function for PuCO system was derived using manybody expansion method. Molecular reaction dynamics for the collision Pu(7Fg)＋CO(X 1Σ＋,0,0) have been studied based on the analytical potential energy function of PuCO( 7A″) by MonteCarlo quasiclassical trajectory approach. The results for the collision process indicate that the main channel is the complex reaction with no threshold energy for the collision Pu(7Fg)＋CO(0,0). The reactive cross section decreases with increase of relative kinetic energy.
Using Gaussian 98 program with B3LYP method, ground state equilibrium structure of PuCO was optimized and harmonic frequencies and force constant for the PuCO molecule have been calculated. Analytical potential energy function for PuCO system was derived using manybody expansion method. Molecular reaction dynamics for the collision Pu(7Fg)＋CO(X 1Σ＋,0,0) have been studied based on the analytical potential energy function of PuCO( 7A″) by MonteCarlo quasiclassical trajectory approach. The results for the collision process indicate that the main channel is the complex reaction with no threshold energy for the collision Pu(7Fg)＋CO(0,0). The reactive cross section decreases with increase of relative kinetic energy.
2002, 18(04): 307-314
doi: 10.3866/PKU.WHXB20020405
Abstract:
The geometries and electronic structures of methyl nitrate and its dimers have been calculated by DFT method at the B3LYP/631G level and ab initio method at the HF/631G level respectively.The total energies using 6311G and 6311＋＋G basis sets have been calculated.Dimer binding energies at the HF/631G level have been corrected for MP4SDTQ electron correlation.All the binding energies have been corrected by the basis set superposition error (BSSE) and zero point energies (ZPE).Based on the vibrational analysis,the changes of thermodynamic properties at 200～600 K temperatures from mono to dimer have been calculated using the statisticalthermodynamic method.It is found that DFT method gives shorter intermolecular distances in a dimer,larger bond lengths in a molecule,and much smaller binding energies than those given by ab initio method.
The geometries and electronic structures of methyl nitrate and its dimers have been calculated by DFT method at the B3LYP/631G level and ab initio method at the HF/631G level respectively.The total energies using 6311G and 6311＋＋G basis sets have been calculated.Dimer binding energies at the HF/631G level have been corrected for MP4SDTQ electron correlation.All the binding energies have been corrected by the basis set superposition error (BSSE) and zero point energies (ZPE).Based on the vibrational analysis,the changes of thermodynamic properties at 200～600 K temperatures from mono to dimer have been calculated using the statisticalthermodynamic method.It is found that DFT method gives shorter intermolecular distances in a dimer,larger bond lengths in a molecule,and much smaller binding energies than those given by ab initio method.
2002, 18(04): 315-320
doi: 10.3866/PKU.WHXB20020406
Abstract:
Hydrophobicallymodified watersoluble polymers are essentially hydrophilic polymers which also contain a small proportion(up to a few mole percent) of strongly hydrophobic groups, usually in the form of pendant side chains or terminal groups. In recent years, they are attracting much increasing attention because of their unusual rheological and amphipathic properties in the presence of added salt, and potential industrial applications. One of the applications directly relates to clay, for instance, the adsorption of hydrophobic associative polyacrylamide on clay has been studied. However, the interaction of hydrophobicallymodified watersoluble amphoteric polymer with clay has been so far hardly investigated including the adsorption. In the previous paper, the hydrophobicallymodified watersoluble amphoteric cellulosic graft copolymer (carboxymethylcellulose grafting acrylamide and dimethyloctyl(2methacryloxyethyl) ammonium bromide, abbr. CGAO) has been prepared for the first time. In this paper, the adsorption amount (Γ) of CGAO on clay has been investigated as a function of concentration of CGAO and NaCl, temperature, pH, surfactant and clay content by means of the ultraviolet spectrum. The results indicate that Γ tends to increase with the increasing of CGAO concentration, but no saturation of adsorption is observed as in the case of the general polymer; Γ sharply rises up with the increment of NaCl concentration up to 1 mol•L－1; Γ continuously decreases at temperature from 25 ℃ to 60 ℃ or pH from 3.6 to 10.3; Γ exhibits an interesting concave curve with the concentration enhancement of SDS from 0 to 14 mmol•L－1 or CTAB from 0 to 1.3 mmol•L－1; at approximate cmc(critical micelle concentration) of SDS or CTAB, Γ approaches a minimum; and Γ reduces with the increase of clay content from 1 to 5 g•dL－1. CGAO is only adsorbed onto the surface of clay, but not into the intercrystal layer as is verified by the layer distance (d001) of the crystal obtained by Xray diffraction. Laser particle size analysis of clay reveals that CGAO can effectively encapsulate and bridge clay particles,as is also confirmed by the scanning electron microscope, and the complex particle size of clay/CGAO cuts down in the presence of SDS.
Hydrophobicallymodified watersoluble polymers are essentially hydrophilic polymers which also contain a small proportion(up to a few mole percent) of strongly hydrophobic groups, usually in the form of pendant side chains or terminal groups. In recent years, they are attracting much increasing attention because of their unusual rheological and amphipathic properties in the presence of added salt, and potential industrial applications. One of the applications directly relates to clay, for instance, the adsorption of hydrophobic associative polyacrylamide on clay has been studied. However, the interaction of hydrophobicallymodified watersoluble amphoteric polymer with clay has been so far hardly investigated including the adsorption. In the previous paper, the hydrophobicallymodified watersoluble amphoteric cellulosic graft copolymer (carboxymethylcellulose grafting acrylamide and dimethyloctyl(2methacryloxyethyl) ammonium bromide, abbr. CGAO) has been prepared for the first time. In this paper, the adsorption amount (Γ) of CGAO on clay has been investigated as a function of concentration of CGAO and NaCl, temperature, pH, surfactant and clay content by means of the ultraviolet spectrum. The results indicate that Γ tends to increase with the increasing of CGAO concentration, but no saturation of adsorption is observed as in the case of the general polymer; Γ sharply rises up with the increment of NaCl concentration up to 1 mol•L－1; Γ continuously decreases at temperature from 25 ℃ to 60 ℃ or pH from 3.6 to 10.3; Γ exhibits an interesting concave curve with the concentration enhancement of SDS from 0 to 14 mmol•L－1 or CTAB from 0 to 1.3 mmol•L－1; at approximate cmc(critical micelle concentration) of SDS or CTAB, Γ approaches a minimum; and Γ reduces with the increase of clay content from 1 to 5 g•dL－1. CGAO is only adsorbed onto the surface of clay, but not into the intercrystal layer as is verified by the layer distance (d001) of the crystal obtained by Xray diffraction. Laser particle size analysis of clay reveals that CGAO can effectively encapsulate and bridge clay particles,as is also confirmed by the scanning electron microscope, and the complex particle size of clay/CGAO cuts down in the presence of SDS.
2002, 18(04): 321-325
doi: 10.3866/PKU.WHXB20020407
Abstract:
The influence of the addition of ntype semiconductor oxide CeO2 and noble metal Pd to Ni/γAl2O3 catalyst on carbon deposition by CH4 and carbon elimination by CO2 was studied by using a pulse microreaction as well as BET, TPR, CO2TPSR and hydrogen chemisorption techniques. It was found that, the addition of ntype semiconductor CeO2 to Ni/γAl2O3 catalyst could decrease carbon deposition activity of CH4 and increase carbon elimination ability of CO2; the addition of noble metal Pd could further alter the interaction between support Al2O3, promoter CeO2 and active phase Ni, as a result, the performance of resistance to carbon deposition of Ni/γAl2O3 catalyst was improved. At the same time, a new explanation for the above promoting effect was put forward by the models of carbon deposition by CH4 and carbon elimination by CO2 on the NiCePd/γAl2O3 catalyst.
The influence of the addition of ntype semiconductor oxide CeO2 and noble metal Pd to Ni/γAl2O3 catalyst on carbon deposition by CH4 and carbon elimination by CO2 was studied by using a pulse microreaction as well as BET, TPR, CO2TPSR and hydrogen chemisorption techniques. It was found that, the addition of ntype semiconductor CeO2 to Ni/γAl2O3 catalyst could decrease carbon deposition activity of CH4 and increase carbon elimination ability of CO2; the addition of noble metal Pd could further alter the interaction between support Al2O3, promoter CeO2 and active phase Ni, as a result, the performance of resistance to carbon deposition of Ni/γAl2O3 catalyst was improved. At the same time, a new explanation for the above promoting effect was put forward by the models of carbon deposition by CH4 and carbon elimination by CO2 on the NiCePd/γAl2O3 catalyst.
2002, 18(04): 326-331
doi: 10.3866/PKU.WHXB20020408
Abstract:
Both the mechanism of the background generated and the derivation process of Tougaard’s method used for subtracting background in XPS are elucidated briefly,and the Tougaard′s simplest form used for writing the calculation program is presented.To inspect the suitable range to the Tougaard′s method,the most of samples in this research which have not been involved in the measurements by Tougaard are selected,such as PbCl2、TiO2、SnCl2、MoO3、NaCl、NaBr、KI、NaH2PO4、Na2SO4、and SiO2.Of course,in order to compare with the results measured by Tougaard,the pure Au、Ag、Cu and Ni are also selected and measured.The program of Tougaardlike written by ourselves to use the VC language are tried to be applied to subtracting backgrounds of some spectra from fourteen various kinds of sample including metal、transition element and nonmetal.All of results from eighteen typical sets of data are compared successively with those taken from both Shirley′s and straightline′s methods (Fig.3～5 and Table 2,3 respectively).The comparisions of deviation of three experimental methods from the theoretical calculations are also made (Fig.6).Finally,according to our experimental results,it is shown that the Tougaard′s method indeed could give out the more accurate peak area measurements in XPS,i.e.possessing the least deviations from the theoretical calculating value in the three methods used for both subtracting background and measuring the peak area not only suitable for both the noble metal and transition metal,but also for the samples of nonmetal and powder compound.
Both the mechanism of the background generated and the derivation process of Tougaard’s method used for subtracting background in XPS are elucidated briefly,and the Tougaard′s simplest form used for writing the calculation program is presented.To inspect the suitable range to the Tougaard′s method,the most of samples in this research which have not been involved in the measurements by Tougaard are selected,such as PbCl2、TiO2、SnCl2、MoO3、NaCl、NaBr、KI、NaH2PO4、Na2SO4、and SiO2.Of course,in order to compare with the results measured by Tougaard,the pure Au、Ag、Cu and Ni are also selected and measured.The program of Tougaardlike written by ourselves to use the VC language are tried to be applied to subtracting backgrounds of some spectra from fourteen various kinds of sample including metal、transition element and nonmetal.All of results from eighteen typical sets of data are compared successively with those taken from both Shirley′s and straightline′s methods (Fig.3～5 and Table 2,3 respectively).The comparisions of deviation of three experimental methods from the theoretical calculations are also made (Fig.6).Finally,according to our experimental results,it is shown that the Tougaard′s method indeed could give out the more accurate peak area measurements in XPS,i.e.possessing the least deviations from the theoretical calculating value in the three methods used for both subtracting background and measuring the peak area not only suitable for both the noble metal and transition metal,but also for the samples of nonmetal and powder compound.
2002, 18(04): 332-335
doi: 10.3866/PKU.WHXB20020409
Abstract:
The TiO2 and /TiO2 catalysts were prepared by solgel method and charaterized by Xray diffraction, N2 absorption analysis applying BET method, and microwave absorption spectrum. Photocatalytic oxidation of C2H4 in air stream was studied. The results(see Fig.1) showed that the photocatalytic activity of both /TiO2 and TiO2 catalysts was obviously increased under the reaction condition of ultraviolet(UV) combined with microwave(MW). The time resolved UVVis absorption spectrum substantiated that absorptivity of UV of catalysts was effectively enhanced in the presence of microwave field(see Fig.2). The improvement on photocatalytic activity was attributed to the polarization effect of the highly defected catalysts in microwave field, which increased the transition probability of photongenerated electrons and decreased the electronhole recombination on semiconductor surface.
The TiO2 and /TiO2 catalysts were prepared by solgel method and charaterized by Xray diffraction, N2 absorption analysis applying BET method, and microwave absorption spectrum. Photocatalytic oxidation of C2H4 in air stream was studied. The results(see Fig.1) showed that the photocatalytic activity of both /TiO2 and TiO2 catalysts was obviously increased under the reaction condition of ultraviolet(UV) combined with microwave(MW). The time resolved UVVis absorption spectrum substantiated that absorptivity of UV of catalysts was effectively enhanced in the presence of microwave field(see Fig.2). The improvement on photocatalytic activity was attributed to the polarization effect of the highly defected catalysts in microwave field, which increased the transition probability of photongenerated electrons and decreased the electronhole recombination on semiconductor surface.
2002, 18(04): 336-339
doi: 10.3866/PKU.WHXB20020410
Abstract:
Using hightemperature θθ Xray diffractometer,the liquid structure of Fe68Si32 alloy was investigated and the structure factor, radial distribution function, the nearest neighbor distance and coordination number were obtained. In the temperature range of 1250～1450 ℃ the nearest neighbor distance and coordination number of the alloy are 0.259～0.260 nm and 10.3(±0.2), respectively. A visible prepeak atQ=15.5 nm－1 in the structure factor S(Q) of liquid Fe68Si32 alloy is observed. According to the characters of prepeak, an atom model of liquid Fe68Si32 alloy was constructed, namely, ordered bcc Fe3Si clusters form a Fe3Si fcc superstructure unit(DO3) with a shared face. The results of Gaussian separation of RDF for Fe68Si32 alloy at 1250 ℃ agrees well with that of Fe3Si superstructure. The prepeak is related to the correlation between silicon atoms in the superstructure. The Xray diffraction of solid Fe68Si32 alloy showed the existence of Fe3Si phase in the alloy and the peaks agree with that of S(Q), which means the correlation of structure between liquid and solid Fe68Si32 alloy.
Using hightemperature θθ Xray diffractometer,the liquid structure of Fe68Si32 alloy was investigated and the structure factor, radial distribution function, the nearest neighbor distance and coordination number were obtained. In the temperature range of 1250～1450 ℃ the nearest neighbor distance and coordination number of the alloy are 0.259～0.260 nm and 10.3(±0.2), respectively. A visible prepeak atQ=15.5 nm－1 in the structure factor S(Q) of liquid Fe68Si32 alloy is observed. According to the characters of prepeak, an atom model of liquid Fe68Si32 alloy was constructed, namely, ordered bcc Fe3Si clusters form a Fe3Si fcc superstructure unit(DO3) with a shared face. The results of Gaussian separation of RDF for Fe68Si32 alloy at 1250 ℃ agrees well with that of Fe3Si superstructure. The prepeak is related to the correlation between silicon atoms in the superstructure. The Xray diffraction of solid Fe68Si32 alloy showed the existence of Fe3Si phase in the alloy and the peaks agree with that of S(Q), which means the correlation of structure between liquid and solid Fe68Si32 alloy.
2002, 18(04): 340-345
doi: 10.3866/PKU.WHXB20020411
Abstract:
Coke based super activated carbons (SAC) with higher surface area were synthesized by means of KOH thermoactivation.The structure and properties of SAC samples were extensively investigated by TGDTA and N2 adsorption techniques.Simultaneously,insitu TDDTA and quick activation quenching techniques were designed to investigate the activation mechanism of SAC samples.A twostep activation mechanism,which includes radial activation at moderate temperature and transverse activation at higher temperature,respectively,was tentatively postulated.It indicated that K2O,－O－K＋ and －CO－2K＋ might be the active sites of radial activation at moderate temperature and fused K＋O－ and K＋ might be the active centers of transverse activation at higher temperature.Of special is that radial activation at moderate temperature may result in the formation of micropores and that this might be the effective way to improve the micropore distribution of SAC samples.In contrary,the transverse activation at higher temperature would lead to the formation of macropore.The formation of super activated carbons was resulted from the radial activation at moderate temperature and subsequent transverse activation at higher temperature.
Coke based super activated carbons (SAC) with higher surface area were synthesized by means of KOH thermoactivation.The structure and properties of SAC samples were extensively investigated by TGDTA and N2 adsorption techniques.Simultaneously,insitu TDDTA and quick activation quenching techniques were designed to investigate the activation mechanism of SAC samples.A twostep activation mechanism,which includes radial activation at moderate temperature and transverse activation at higher temperature,respectively,was tentatively postulated.It indicated that K2O,－O－K＋ and －CO－2K＋ might be the active sites of radial activation at moderate temperature and fused K＋O－ and K＋ might be the active centers of transverse activation at higher temperature.Of special is that radial activation at moderate temperature may result in the formation of micropores and that this might be the effective way to improve the micropore distribution of SAC samples.In contrary,the transverse activation at higher temperature would lead to the formation of macropore.The formation of super activated carbons was resulted from the radial activation at moderate temperature and subsequent transverse activation at higher temperature.
2002, 18(04): 346-349
doi: 10.3866/PKU.WHXB20020412
Abstract:
The chemically induced dynamic electron polarization(CIDEP) of the antheraquinone(AQ)/ethylene glycol(EG) and AQ/EG/2,2,6,6tetramethylpiperidinyloxyl(TEMPO) systems were investigated using timeresolved ESR spectrometer. In AQ/EG system, the electron spin polarized signal of antheraquinone radical is generated due to hydrogen abstraction from EG(Fig.1), this is a triplet mechanism(TM) accompanied by radical pair mechanism(RPM). On the an addition of TEMPO to the system, the chemically induced dynamic electron polarization signal of TEMPO is also evident, this is a radicaltriplet pair mechanism(RTPM), so in the AQ/EG/TEMPO system,there are competition between RTPM and TM or RPM polarization, along with the change of the concentration of TEMPO in the solution, the signal intensities of antheraquinone radical and TEMPO are changed(Fig.2 and Fig.3), from this competition, the reaction rate of the radicaltriplet pair has been deduced(Table 1).
The chemically induced dynamic electron polarization(CIDEP) of the antheraquinone(AQ)/ethylene glycol(EG) and AQ/EG/2,2,6,6tetramethylpiperidinyloxyl(TEMPO) systems were investigated using timeresolved ESR spectrometer. In AQ/EG system, the electron spin polarized signal of antheraquinone radical is generated due to hydrogen abstraction from EG(Fig.1), this is a triplet mechanism(TM) accompanied by radical pair mechanism(RPM). On the an addition of TEMPO to the system, the chemically induced dynamic electron polarization signal of TEMPO is also evident, this is a radicaltriplet pair mechanism(RTPM), so in the AQ/EG/TEMPO system,there are competition between RTPM and TM or RPM polarization, along with the change of the concentration of TEMPO in the solution, the signal intensities of antheraquinone radical and TEMPO are changed(Fig.2 and Fig.3), from this competition, the reaction rate of the radicaltriplet pair has been deduced(Table 1).
2002, 18(04): 350-354
doi: 10.3866/PKU.WHXB20020413
Abstract:
The scanning microreference electrode (SMRE) technique and scanning electron microscopy (SEM) were applied to investigate the localized corrosion in its early stage of Al 2024T3 alloy.SMRE potential measurements revealed that localized corrosion occurred on the alloy surface immediately after the exposure to 0.01 mol•L－1 NaCl solution at opencircuit potential,which was more negative than the pitting potential.The potential peaks developed with time and reached the maximum after 2 h exposure.Consequently,the heights of potential peaks would decrease and then maintained a stable value for a long time.SEM indicated the initial of localized corrosion was associated with the second phase particles,especially the Al2CuMg (S phase).Three types of corrosion behavior of S phase were observed.
The scanning microreference electrode (SMRE) technique and scanning electron microscopy (SEM) were applied to investigate the localized corrosion in its early stage of Al 2024T3 alloy.SMRE potential measurements revealed that localized corrosion occurred on the alloy surface immediately after the exposure to 0.01 mol•L－1 NaCl solution at opencircuit potential,which was more negative than the pitting potential.The potential peaks developed with time and reached the maximum after 2 h exposure.Consequently,the heights of potential peaks would decrease and then maintained a stable value for a long time.SEM indicated the initial of localized corrosion was associated with the second phase particles,especially the Al2CuMg (S phase).Three types of corrosion behavior of S phase were observed.
2002, 18(04): 355-358
doi: 10.3866/PKU.WHXB20020414
Abstract:
Organic methylmodified silica sols were obtained by Hydrolysis and cocondensation reactions occurred in basecatalyzed system by carefully controlling the solgel process of DDS and TEOS. Both hydrophobic and antireflective silica coating was then prepared by spincoating technique from the modified sols. As a result, the moistureresistant ability of antireflective coating was highly improved. The properties of somodified sols and their effects on the coating were studied using transmission electron micrograph(TEM) and size distribution of particles(SDP) measurements. In addition, comparison was carried out between organically modified and pure silica coating and the results showed that not only the hydrophobicity of the coating was greatly improved by the modification but also the transmittance curve not easily showed multipeaks in the wavelength range of 300～800 nm.
Organic methylmodified silica sols were obtained by Hydrolysis and cocondensation reactions occurred in basecatalyzed system by carefully controlling the solgel process of DDS and TEOS. Both hydrophobic and antireflective silica coating was then prepared by spincoating technique from the modified sols. As a result, the moistureresistant ability of antireflective coating was highly improved. The properties of somodified sols and their effects on the coating were studied using transmission electron micrograph(TEM) and size distribution of particles(SDP) measurements. In addition, comparison was carried out between organically modified and pure silica coating and the results showed that not only the hydrophobicity of the coating was greatly improved by the modification but also the transmittance curve not easily showed multipeaks in the wavelength range of 300～800 nm.
2002, 18(04): 359-363
doi: 10.3866/PKU.WHXB20020415
Abstract:
ld nanowires with 90 nm diameter were prepared by electrodeposition on polycarbonate membrane template. Transmission electron microscope(TEM)results indicated that the surfaces of nanowires were smooth and exhibited single crystal structure. Scanning electron microscopy showed that these ld nanowires had flat roofs and were distributed uniformly on the substrate. The array microstructure of nanowires determined by atomic force microscope(AFM) was consistent with scanning electron microscope(SEM)results. The I－V characteristics of individual nanowire by AFM revealed metallic characteristics with a conductive tip operating in contact mode at room temperature in air.
ld nanowires with 90 nm diameter were prepared by electrodeposition on polycarbonate membrane template. Transmission electron microscope(TEM)results indicated that the surfaces of nanowires were smooth and exhibited single crystal structure. Scanning electron microscopy showed that these ld nanowires had flat roofs and were distributed uniformly on the substrate. The array microstructure of nanowires determined by atomic force microscope(AFM) was consistent with scanning electron microscope(SEM)results. The I－V characteristics of individual nanowire by AFM revealed metallic characteristics with a conductive tip operating in contact mode at room temperature in air.
2002, 18(04): 364-367
doi: 10.3866/PKU.WHXB20020416
Abstract:
Two cobalt complexes with diethylenetriamine(dien) and triethylenetetramine(trien) as ligands were synthesized by solidstate reaction at room temperature. It was found that one mole of complex reacted with two moles of oxygen at room temperature. One mole O2 coordinated to Co complex and formed superoxo type oxygenated complex. The reason of excess oxygen uptake is that the ligand was oxidatively dehydrogenated (－CH2－NH－→－C=N－). That is, molecular oxygen could be activated by the coordination with cobalt complex. Two oxygenated complexes prepared via solidstate reaction were isolated and characterized by elemental analysis, IR, XRD, TG/DTA, NMR and molar conductance.
Two cobalt complexes with diethylenetriamine(dien) and triethylenetetramine(trien) as ligands were synthesized by solidstate reaction at room temperature. It was found that one mole of complex reacted with two moles of oxygen at room temperature. One mole O2 coordinated to Co complex and formed superoxo type oxygenated complex. The reason of excess oxygen uptake is that the ligand was oxidatively dehydrogenated (－CH2－NH－→－C=N－). That is, molecular oxygen could be activated by the coordination with cobalt complex. Two oxygenated complexes prepared via solidstate reaction were isolated and characterized by elemental analysis, IR, XRD, TG/DTA, NMR and molar conductance.
2002, 18(04): 368-371
doi: 10.3866/PKU.WHXB20020417
Abstract:
Anatase TiO2 thin films were obtained on a substrate at lowtemperature by addition of H3BO3 into （NH4）2TiF6 solution supersaturated with anatase nanocrystalline TiO2.Effect of concentration,/H3BO3 molar ratio, deposition time and reaction temperature on the surface structure and performance of deposited thin films were investigated.The transparence ,thickness,crystal structure and image of the deposited films were characterized by XRD,SEM,and UVVis absorption spectroscopy.Photocatalytic activity of the TiO2 thin films was evaluated by degradation of methylene blue.
Anatase TiO2 thin films were obtained on a substrate at lowtemperature by addition of H3BO3 into （NH4）2TiF6 solution supersaturated with anatase nanocrystalline TiO2.Effect of concentration,/H3BO3 molar ratio, deposition time and reaction temperature on the surface structure and performance of deposited thin films were investigated.The transparence ,thickness,crystal structure and image of the deposited films were characterized by XRD,SEM,and UVVis absorption spectroscopy.Photocatalytic activity of the TiO2 thin films was evaluated by degradation of methylene blue.
2002, 18(04): 372-376
doi: 10.3866/PKU.WHXB20020418
Abstract:
The Xray diffraction whole pattern (XDWP) data of semicrystalline poly(ethylene terephthalate) PET2 sample were collected in the symmetric reflection geometry on a diffractometer employing a copper target (Kα wavelength 0.15418 nm )(see Fig.1 ).The XDWP was fitted by combining the Rietveld method and Fourier filtering technique,Rietveld structure refinement for PET2 crystalline phase was performed,the unitcell parameters obtained are a =0.445 nm,b=0.592 nm,c =1.072 nm,α= 99.6(°),β= 116.9(°),γ= 111.9 (°),the density of the crystals is dc = 1.495 g•cm－3(see Table 1) .Meanwhile the XDWP was separated into two parts,CR2 crystalline region and AM2 noncrystalline region in PET2 (see Fig.2).The reduced radial distribution function G2(r) was calculated from AM2 and lead to three main peaks,G21(r) = 0.150 nm,G22(r) = 0.254 nm,G23(r)=0.460 nm which characterize the structure of the noncrystalline phase in PET2 (see Fig.3).The result shows that this combination of techniques is feasible.The auther suggests that the reliability of evaluation on two phases separation and structure analysis in semicrystalline polymer,besides the three criteria to estimate the parameters of the crystalline phase,also depends on other two new physical criteria.Effect of various fitting plans on the results of structure refinement and phase separation were discussed.It is shown that in order to get reliable results it is necessary to have scattering pattern of pure amorphous sample as initial values of background intensity in fitting process. This work discusses how to deal with the difficulties and its possible solutions in applying Rietveld method to polymer structure analysis.
The Xray diffraction whole pattern (XDWP) data of semicrystalline poly(ethylene terephthalate) PET2 sample were collected in the symmetric reflection geometry on a diffractometer employing a copper target (Kα wavelength 0.15418 nm )(see Fig.1 ).The XDWP was fitted by combining the Rietveld method and Fourier filtering technique,Rietveld structure refinement for PET2 crystalline phase was performed,the unitcell parameters obtained are a =0.445 nm,b=0.592 nm,c =1.072 nm,α= 99.6(°),β= 116.9(°),γ= 111.9 (°),the density of the crystals is dc = 1.495 g•cm－3(see Table 1) .Meanwhile the XDWP was separated into two parts,CR2 crystalline region and AM2 noncrystalline region in PET2 (see Fig.2).The reduced radial distribution function G2(r) was calculated from AM2 and lead to three main peaks,G21(r) = 0.150 nm,G22(r) = 0.254 nm,G23(r)=0.460 nm which characterize the structure of the noncrystalline phase in PET2 (see Fig.3).The result shows that this combination of techniques is feasible.The auther suggests that the reliability of evaluation on two phases separation and structure analysis in semicrystalline polymer,besides the three criteria to estimate the parameters of the crystalline phase,also depends on other two new physical criteria.Effect of various fitting plans on the results of structure refinement and phase separation were discussed.It is shown that in order to get reliable results it is necessary to have scattering pattern of pure amorphous sample as initial values of background intensity in fitting process. This work discusses how to deal with the difficulties and its possible solutions in applying Rietveld method to polymer structure analysis.
2002, 18(04): 377-380
doi: 10.3866/PKU.WHXB20020419
Abstract:
A new approach has been developed to obtain the data of solubilization kinetics,in which the micelles are not separated from the solution.The solubilization kinetics of benzene in Pluronic F127 and P123 aqueous micellar solutions have been examined by this method.The results show that the rate of benzene solubilization by both F127 and P123 micelles is significantly fast.Increasing temperature further enhances the rate of benzene solubilization.
A new approach has been developed to obtain the data of solubilization kinetics,in which the micelles are not separated from the solution.The solubilization kinetics of benzene in Pluronic F127 and P123 aqueous micellar solutions have been examined by this method.The results show that the rate of benzene solubilization by both F127 and P123 micelles is significantly fast.Increasing temperature further enhances the rate of benzene solubilization.
2002, 18(04): 381-384
doi: 10.3866/PKU.WHXB20020420
Abstract:
AC impedance analysis is employed to study frequencyresponse characteristics of supercapacitors utilizing carbon nanotube and activated carbon block electrodes.Charge saturation for carbon nanotube occurs at about 250 mHz,but that of activated carbon is not observed in the frequency range of 100 mHz to 100 kHz.There is a 45° line in the complex plane plot of each supercapacitor utilizing both carbon nanotube or activated carbon electrodes. Phase angles of supercapacitors with both kinds of electrodes are far smaller than 90° of pure capacitors.
AC impedance analysis is employed to study frequencyresponse characteristics of supercapacitors utilizing carbon nanotube and activated carbon block electrodes.Charge saturation for carbon nanotube occurs at about 250 mHz,but that of activated carbon is not observed in the frequency range of 100 mHz to 100 kHz.There is a 45° line in the complex plane plot of each supercapacitor utilizing both carbon nanotube or activated carbon electrodes. Phase angles of supercapacitors with both kinds of electrodes are far smaller than 90° of pure capacitors.
