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2003 Volume 19 Issue 12
2003, 19(12): 1097-1101
doi: 10.3866/PKU.WHXB20031201
Abstract:
A novel polymer material poly(methyl methacrylate-co-acrylonitrile-co-lithium methacrylate) (PMAML) was synthesized. The polymer electrolytes based on the blend of PMAML and PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) were prepared. The structure of PMAML was characterized by FTIR, and the surface morphology of PMAML/PVDF-HFP membrane was observed by SEM. Gelled polymer electrolytes were obtained by soaking PMAML/PVDF-HFP membrane in electrolyte solution. Ambient temperature conductivity of 2.6×10－3 S•cm－1 was obtained. The interfacial properties between the polymer electrolyte and lithium electrode were investigated by A.C. impedance. The effects of storage time, cyclic voltammetry and constant charge on interfacial impedance were studied. The interfacial resistance between polymer electrolyte and lithium electrode increased with the increasing of storage time. But the interfacial impedance decreased after the surface of lithium was refreshed by means of cyclic voltammetry or constant charge. The retention capability of electrolyte solution and the interfacial stability can be improved by introducing PMAML into PVDF-HFP.
A novel polymer material poly(methyl methacrylate-co-acrylonitrile-co-lithium methacrylate) (PMAML) was synthesized. The polymer electrolytes based on the blend of PMAML and PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) were prepared. The structure of PMAML was characterized by FTIR, and the surface morphology of PMAML/PVDF-HFP membrane was observed by SEM. Gelled polymer electrolytes were obtained by soaking PMAML/PVDF-HFP membrane in electrolyte solution. Ambient temperature conductivity of 2.6×10－3 S•cm－1 was obtained. The interfacial properties between the polymer electrolyte and lithium electrode were investigated by A.C. impedance. The effects of storage time, cyclic voltammetry and constant charge on interfacial impedance were studied. The interfacial resistance between polymer electrolyte and lithium electrode increased with the increasing of storage time. But the interfacial impedance decreased after the surface of lithium was refreshed by means of cyclic voltammetry or constant charge. The retention capability of electrolyte solution and the interfacial stability can be improved by introducing PMAML into PVDF-HFP.
2003, 19(12): 1102-1107
doi: 10.3866/PKU.WHXB20031202
Abstract:
A first-principles density-functional theory method, i.e. the finite-difference pseudopotential density-functional theory in real space and Langevin molecular dynamics annealing technique (PDFMD),is introduced to describe the structures and properties of small sulfur clusters Sn(n=2～8). It is found that the ground state structures of S3, S4, S5, S6, S7 and S8 are C2v, D2h, envelope-shaped Cs, D3d (or boat-shaped C2v), a chair-shaped Cs and D4d symmetry structures, respectively, which are in od agreement with experiment. It is shown that the more the number of atom in the cluster, the more stable it is for small sulfur clusters.
A first-principles density-functional theory method, i.e. the finite-difference pseudopotential density-functional theory in real space and Langevin molecular dynamics annealing technique (PDFMD),is introduced to describe the structures and properties of small sulfur clusters Sn(n=2～8). It is found that the ground state structures of S3, S4, S5, S6, S7 and S8 are C2v, D2h, envelope-shaped Cs, D3d (or boat-shaped C2v), a chair-shaped Cs and D4d symmetry structures, respectively, which are in od agreement with experiment. It is shown that the more the number of atom in the cluster, the more stable it is for small sulfur clusters.
2003, 19(12): 1108-1113
doi: 10.3866/PKU.WHXB20031203
Abstract:
Two minimum energy conformations of DHPs were obtained by molecular mechanics and quantum chemistry calculation. In the studies of 3D-QSAR,comparative molecular fields analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were applied using a data set of 43 DHPs of two-conformations. The results indicate that the models of two-conformations, investigated by the two kinds of 3D-QSAR techniques, are significant and have od predictability. The analysis of steric and electrostatic CoMFA and CoMSIA coefficients contour maps reveals the influence of the structures on biological activity and gives insights to the further design of highly active DHPs compounds.
Two minimum energy conformations of DHPs were obtained by molecular mechanics and quantum chemistry calculation. In the studies of 3D-QSAR,comparative molecular fields analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were applied using a data set of 43 DHPs of two-conformations. The results indicate that the models of two-conformations, investigated by the two kinds of 3D-QSAR techniques, are significant and have od predictability. The analysis of steric and electrostatic CoMFA and CoMSIA coefficients contour maps reveals the influence of the structures on biological activity and gives insights to the further design of highly active DHPs compounds.
2003, 19(12): 1114-1118
doi: 10.3866/PKU.WHXB20031204
Abstract:
The gas phase reaction of Cu plasma and ethanol clusters is studied by the laser ablation-molecular beam(LAMB) method. Six species of clustered complex ions Cu＋(C2H5OH)n, CuO＋(C2H5OH)n, H＋(C2H5OH)n， (C2H5OH)nC2H5O－, (C2H5OH)n(H2O)OH－, (C2H5OH)n(H2O)2OH－(n≤12 ) are observed. Interestingly, the species and sizes of the product clusters vary observably either when the plasma acts on the different parts of the pulsed ethanol beam or when the carrier gas under different pressure is put on. When the laser ablated Cu plasma act on the low density part of the beam, the metal ethanol complex clusters Cu＋(C2H5OH)n and the protonated ethanol clusters H＋(C2H5OH)n are domainant, while the plasma act on the high density part of the beam, however, the H＋(C2H5OH)n turn to be the only discriminable resulting clusters . By comparing the intensities and the cluster sizes of Cu＋(C2H5OH)n with H＋(C2H5OH)n, the formation of Cu＋(C2H5OH)n is considered in company with the evaporation of several ethanol molecules. Under a given pressure and a specific laser delay time, the metal-oxygen-ethanol clusters CuO＋(C2H5OH)n are observed. As the intensity of(C2H5OH)n(H2O)OH－ is much stronger than that of (C2H5OH)nC2H5O－, one can suppose that (C2H5OH)n(H2O)OH－ is much more stable.
The gas phase reaction of Cu plasma and ethanol clusters is studied by the laser ablation-molecular beam(LAMB) method. Six species of clustered complex ions Cu＋(C2H5OH)n, CuO＋(C2H5OH)n, H＋(C2H5OH)n， (C2H5OH)nC2H5O－, (C2H5OH)n(H2O)OH－, (C2H5OH)n(H2O)2OH－(n≤12 ) are observed. Interestingly, the species and sizes of the product clusters vary observably either when the plasma acts on the different parts of the pulsed ethanol beam or when the carrier gas under different pressure is put on. When the laser ablated Cu plasma act on the low density part of the beam, the metal ethanol complex clusters Cu＋(C2H5OH)n and the protonated ethanol clusters H＋(C2H5OH)n are domainant, while the plasma act on the high density part of the beam, however, the H＋(C2H5OH)n turn to be the only discriminable resulting clusters . By comparing the intensities and the cluster sizes of Cu＋(C2H5OH)n with H＋(C2H5OH)n, the formation of Cu＋(C2H5OH)n is considered in company with the evaporation of several ethanol molecules. Under a given pressure and a specific laser delay time, the metal-oxygen-ethanol clusters CuO＋(C2H5OH)n are observed. As the intensity of(C2H5OH)n(H2O)OH－ is much stronger than that of (C2H5OH)nC2H5O－, one can suppose that (C2H5OH)n(H2O)OH－ is much more stable.
2003, 19(12): 1119-1122
doi: 10.3866/PKU.WHXB20031205
Abstract:
Calculations were performed on some low-lying electronic states for Ru2 by using density functional method(B3LYP). The results showed that the ground state of Ru2 is 7Δu with re=228 pm， ωe=338 cm－1 and De=1.92 eV， which are in od agreement with the previous results obtained at high level of theory. We also studied the activation of the nitrogen of Ru2N2 clusters having C2v symmetry, and obtained the calculated properties and energies of different optimized geometries. The results indicated that the activation extent of nitrogen depends on the number of feedback orbitals. In general, the more activated the nitrogen molecule, the higher the system energy. At the same activation situations, the higher the multiplicity, the lower the system energy.
Calculations were performed on some low-lying electronic states for Ru2 by using density functional method(B3LYP). The results showed that the ground state of Ru2 is 7Δu with re=228 pm， ωe=338 cm－1 and De=1.92 eV， which are in od agreement with the previous results obtained at high level of theory. We also studied the activation of the nitrogen of Ru2N2 clusters having C2v symmetry, and obtained the calculated properties and energies of different optimized geometries. The results indicated that the activation extent of nitrogen depends on the number of feedback orbitals. In general, the more activated the nitrogen molecule, the higher the system energy. At the same activation situations, the higher the multiplicity, the lower the system energy.
2003, 19(12): 1123-1126
doi: 10.3866/PKU.WHXB20031206
Abstract:
Surface enhanced Raman spectroscopy(SERS) has been used to study the octadecylamine(ODA) Langmuir monolayers and egg phosphatidylcholine(PC)/ODA mixed monolayers on colloidal silver subphase. The SERS enhancement results from the strong interaction between headgroups of the ODA molecules and silver nanoparticles in subphase. The results of Raman test for PC/ODA mixed monolayers show that the vibrational information of phospholipid molecules can be acquired in situ with surfactant-aided SERS effect. Work based on such systems could expand the application of SERS technique in the study of Langmuir monolayers at the air-water interface.
Surface enhanced Raman spectroscopy(SERS) has been used to study the octadecylamine(ODA) Langmuir monolayers and egg phosphatidylcholine(PC)/ODA mixed monolayers on colloidal silver subphase. The SERS enhancement results from the strong interaction between headgroups of the ODA molecules and silver nanoparticles in subphase. The results of Raman test for PC/ODA mixed monolayers show that the vibrational information of phospholipid molecules can be acquired in situ with surfactant-aided SERS effect. Work based on such systems could expand the application of SERS technique in the study of Langmuir monolayers at the air-water interface.
2003, 19(12): 1127-1132
doi: 10.3866/PKU.WHXB20031207
Abstract:
The effect of cephanone on the first critical micelle concentration (cmc1) and the second critical micelle concentration (cmc2) of CTAB have been studied by methods of conductivity and fluorescence polarization. The aggregation number of CTAB micelles and the distribution coefficient of cephanone between the CTAB micelle and the aqueous phase have been studied through the methods of the static fluorescence and UV spectra, respectively. The results show that with increasing cephanone concentration, cmc1 and cmc2 of CTAB micelle both increase, whereas the aggregation number of micelles and the viscosity of CTAB micelle system both decrease. The results are related to the interaction between cephanone and CTAB and the distribution of cephanone between CTAB micelle and the aqueous phase.
The effect of cephanone on the first critical micelle concentration (cmc1) and the second critical micelle concentration (cmc2) of CTAB have been studied by methods of conductivity and fluorescence polarization. The aggregation number of CTAB micelles and the distribution coefficient of cephanone between the CTAB micelle and the aqueous phase have been studied through the methods of the static fluorescence and UV spectra, respectively. The results show that with increasing cephanone concentration, cmc1 and cmc2 of CTAB micelle both increase, whereas the aggregation number of micelles and the viscosity of CTAB micelle system both decrease. The results are related to the interaction between cephanone and CTAB and the distribution of cephanone between CTAB micelle and the aqueous phase.
2003, 19(12): 1133-1137
doi: 10.3866/PKU.WHXB20031208
Abstract:
A novel inorganic/organic hybrid compound Co(μ2-bpy)V2O6 was synthesized by hydrothermal reaction of CoCl2•6H2O, 4,4′-bipyridine,NH4VO3,and H2O in a molar ratio of 1∶2∶2∶1950 at 170 ℃ for 72 h. The compound crystallized in triclinic space group Pī,with the cell parameters a=0.81599(7) nm, b=0.85826(7) nm, c=1.02031(8) nm, α=87.111(2)°, β=75.305(2)° and γ=74.782(2). As showed by single crystal X-ray diffraction, The crystal structure is constructed with inorganic bimetallic oxide layers, [Co2V4O12]n, and organic 4,4′-bipyridine μ2-ligands.The 4,4′-bipyridine ligands bridge the inorganic layers through N－Co coordination bonds to build up a three dimensional covalent framework with various open micropores. UV-Vis-NIR reflectance spectrum study revealed the nature of a semiconductor with an energy gap of ca.2.0 eV and thermal analysis showed thermal stability below 420 ℃ for the title compound.
A novel inorganic/organic hybrid compound Co(μ2-bpy)V2O6 was synthesized by hydrothermal reaction of CoCl2•6H2O, 4,4′-bipyridine,NH4VO3,and H2O in a molar ratio of 1∶2∶2∶1950 at 170 ℃ for 72 h. The compound crystallized in triclinic space group Pī,with the cell parameters a=0.81599(7) nm, b=0.85826(7) nm, c=1.02031(8) nm, α=87.111(2)°, β=75.305(2)° and γ=74.782(2). As showed by single crystal X-ray diffraction, The crystal structure is constructed with inorganic bimetallic oxide layers, [Co2V4O12]n, and organic 4,4′-bipyridine μ2-ligands.The 4,4′-bipyridine ligands bridge the inorganic layers through N－Co coordination bonds to build up a three dimensional covalent framework with various open micropores. UV-Vis-NIR reflectance spectrum study revealed the nature of a semiconductor with an energy gap of ca.2.0 eV and thermal analysis showed thermal stability below 420 ℃ for the title compound.
2003, 19(12): 1138-1142
doi: 10.3866/PKU.WHXB20031209
Abstract:
Chemical controlling the morphology of the CdS nanocrystals fabricated by hydrothermal method was studied. Different coordination agents were chosen as templates to test their effects on the shape of the produced CdS nanocrystals. It was found that when ethylenediamine or methylamine was employed as the template, CdS nanocrystals display rod-like shapes with a dimension of （20～30）nm×（200～600） nm and （40～50） nm×（200～600） nm, respectively. In contrary, only particles of CdS nanocrystals with an average size of about 30 nm or 20 nm were observed if pyridine or ammonia was used. XRD、TEM、PL(photoluminescence)、Raman spectroscopy and XPS techniques were used to characterize the as produced CdS nanocrystals. Our experimental results suggested that bidentate ligands and high stability constant of the template complex might not be the only critical factors to the growth of CdS nanorods. A complex structure induced growth mechanism was proposed to explain the morphology control of CdS nanocrystals in hydrothermal synthesis.
Chemical controlling the morphology of the CdS nanocrystals fabricated by hydrothermal method was studied. Different coordination agents were chosen as templates to test their effects on the shape of the produced CdS nanocrystals. It was found that when ethylenediamine or methylamine was employed as the template, CdS nanocrystals display rod-like shapes with a dimension of （20～30）nm×（200～600） nm and （40～50） nm×（200～600） nm, respectively. In contrary, only particles of CdS nanocrystals with an average size of about 30 nm or 20 nm were observed if pyridine or ammonia was used. XRD、TEM、PL(photoluminescence)、Raman spectroscopy and XPS techniques were used to characterize the as produced CdS nanocrystals. Our experimental results suggested that bidentate ligands and high stability constant of the template complex might not be the only critical factors to the growth of CdS nanorods. A complex structure induced growth mechanism was proposed to explain the morphology control of CdS nanocrystals in hydrothermal synthesis.
2003, 19(12): 1143-1145
doi: 10.3866/PKU.WHXB20031210
Abstract:
Microcontact printing(μCP) technology has been shown to be an easy,inexpensive and low-cost approach for microfabrication. We inked the poly(dimethylsiloxane) elastomeric stamp by rubbing the stamp gently with 10 mmol•L－1 octadeyl trichlorosilane(OTS) in hexane solution, then applied the dried stamp to cover glasses and the outer surface of tubes. We also micropatterned a glass rod surface by scrolling the rod on the patterned surface of an inked stamp. Patterned substrates were immersed in the silver plating bath for 30 min to selective deposition of silver on OTS free part of the substrates to obtain 2D and quasi-3D microstructure of silver. The microscope images show that microcontact printing technology can fabricate 2D and quasi-3D microstructure rapidly and easily, with high fidelity, which further demonstrates potential application of μCP in microfabrication technology.
Microcontact printing(μCP) technology has been shown to be an easy,inexpensive and low-cost approach for microfabrication. We inked the poly(dimethylsiloxane) elastomeric stamp by rubbing the stamp gently with 10 mmol•L－1 octadeyl trichlorosilane(OTS) in hexane solution, then applied the dried stamp to cover glasses and the outer surface of tubes. We also micropatterned a glass rod surface by scrolling the rod on the patterned surface of an inked stamp. Patterned substrates were immersed in the silver plating bath for 30 min to selective deposition of silver on OTS free part of the substrates to obtain 2D and quasi-3D microstructure of silver. The microscope images show that microcontact printing technology can fabricate 2D and quasi-3D microstructure rapidly and easily, with high fidelity, which further demonstrates potential application of μCP in microfabrication technology.
2003, 19(12): 1146-1149
doi: 10.3866/PKU.WHXB20031211
Abstract:
π－A curve and stability of the monolayer of Eu(DBM)3(DiBut-bpy)/TiO2/AA (arachidic acid) are investigated.TiO2 nanoparticles are obtained by TBT (tetrabutyloxyltitanium) 2D sol-gel process. TiO2 nanoparticles and europium complex were transferred successively onto the solid substrate by Langmuir-Blodgett technique. A novel luminescence thin film was obtained and this film has od mechanic and thermal stability. The linear relationship of UV-visilbe spectra vs the layers of LB film indicates that this composite film is vertically homogeneous. The result of small-angle XRD further demonstrated that this composite film has ordered periodic structure. The effect of TiO2 nanoparticles on the luminescence mechanism of this composite film was discussed.
π－A curve and stability of the monolayer of Eu(DBM)3(DiBut-bpy)/TiO2/AA (arachidic acid) are investigated.TiO2 nanoparticles are obtained by TBT (tetrabutyloxyltitanium) 2D sol-gel process. TiO2 nanoparticles and europium complex were transferred successively onto the solid substrate by Langmuir-Blodgett technique. A novel luminescence thin film was obtained and this film has od mechanic and thermal stability. The linear relationship of UV-visilbe spectra vs the layers of LB film indicates that this composite film is vertically homogeneous. The result of small-angle XRD further demonstrated that this composite film has ordered periodic structure. The effect of TiO2 nanoparticles on the luminescence mechanism of this composite film was discussed.
2003, 19(12): 1150-1153
doi: 10.3866/PKU.WHXB20031212
Abstract:
The solubility and stability of potassium ferrate(VI) and barium ferrate(VI) in 7 mol•L－1 KOH solution were investigated. It was found that the solubility of ferrates (VI) compounds increased and the stability decreased with increasing temperature. The structures and morphology of the potassium ferrate and barium ferrate were examined by IR、XRD and SEM, and the results showed that they were orthorhombic crystal with space group D2h(Pnma) and consisted of sub-micron to nanometer particles(50～165 nm). The discharge results of Zn-BaFeO4 and Zn-K2FeO4 batteries displayed that the former has a double discharge capacity than the latter, and the discharge voltage plateau of the former is 170～220 mV higher than that of the latter.
The solubility and stability of potassium ferrate(VI) and barium ferrate(VI) in 7 mol•L－1 KOH solution were investigated. It was found that the solubility of ferrates (VI) compounds increased and the stability decreased with increasing temperature. The structures and morphology of the potassium ferrate and barium ferrate were examined by IR、XRD and SEM, and the results showed that they were orthorhombic crystal with space group D2h(Pnma) and consisted of sub-micron to nanometer particles(50～165 nm). The discharge results of Zn-BaFeO4 and Zn-K2FeO4 batteries displayed that the former has a double discharge capacity than the latter, and the discharge voltage plateau of the former is 170～220 mV higher than that of the latter.
2003, 19(12): 1154-1158
doi: 10.3866/PKU.WHXB20031213
Abstract:
The paste-coating method is a modified method of coating-pyrogenation. In this new method, Ti-substrate electrode coated by oxides is covered with paste of Sn、Sb hydroxide to decrease the volatilization of the coating component. The preparation conditions for Ti/Sn、Sb oxide electrode by the paste-coating method are investigated. The effect of the amount of SbCl3 added and the sintering temperature on the electrode lifetime and oxygen evolution potential are investigated with EDS, SEM and XRD analysis. The results indicate that the electrode prepared by coating-pyrogenation appears some exposure of TiO2 due to inhomogeneous distribution of coating oxides on its surface, while the one prepared by paste-coating method enhances homogeneity for the same coating thickness. As a result, the electrode exhibits a higher oxygen evolution potential and has a longer lifetime for its higher electro-catalytic activity and the electrochemical stability.
The paste-coating method is a modified method of coating-pyrogenation. In this new method, Ti-substrate electrode coated by oxides is covered with paste of Sn、Sb hydroxide to decrease the volatilization of the coating component. The preparation conditions for Ti/Sn、Sb oxide electrode by the paste-coating method are investigated. The effect of the amount of SbCl3 added and the sintering temperature on the electrode lifetime and oxygen evolution potential are investigated with EDS, SEM and XRD analysis. The results indicate that the electrode prepared by coating-pyrogenation appears some exposure of TiO2 due to inhomogeneous distribution of coating oxides on its surface, while the one prepared by paste-coating method enhances homogeneity for the same coating thickness. As a result, the electrode exhibits a higher oxygen evolution potential and has a longer lifetime for its higher electro-catalytic activity and the electrochemical stability.
2003, 19(12): 1159-1162
doi: 10.3866/PKU.WHXB20031214
Abstract:
Nanosized AgBr/PMMA hybrid material of photochromism was synthesized byin situ polymerization. XRD analyses indicate that the nanosized AgBr/PMMA hybrid materials are amorphous. SEM analyses show that the morphology of the hybrid material varies with the AgBr content in the hybrid materials, and the tenacity fracture of the hybrid material changes into fragility fracture with the increase of AgBr content. EDS reveals that the distributions of both elements of Ag and Br in the hybrid material are homogeneous. The nanosized AgBr/PMMA hybrid material has a photochromic effect.
Nanosized AgBr/PMMA hybrid material of photochromism was synthesized byin situ polymerization. XRD analyses indicate that the nanosized AgBr/PMMA hybrid materials are amorphous. SEM analyses show that the morphology of the hybrid material varies with the AgBr content in the hybrid materials, and the tenacity fracture of the hybrid material changes into fragility fracture with the increase of AgBr content. EDS reveals that the distributions of both elements of Ag and Br in the hybrid material are homogeneous. The nanosized AgBr/PMMA hybrid material has a photochromic effect.
2003, 19(12): 1163-1166
doi: 10.3866/PKU.WHXB20031215
Abstract:
The structure and thermodynamics of liquid Au and AuCu alloys have been simulated using molecular dynamics method based upon the EAM interatomic potential to reveal the influence of the mismatch in atomic size on the glass-forming ability. Under the cooling rate in the range of 4×1012 K•s－1 to 5×1011 K•s－1, the system under es the liquid, super-cooled liquid and solid state processes. Liquid Au always forms the crystal, the higher the cooling rate, the lower the crystallization temperature; while AuCu alloy forms a glass, the higher the cooling rate, the higher the glass transition temperature. The mismatch in atomic size is favorable to the formation of glass.
The structure and thermodynamics of liquid Au and AuCu alloys have been simulated using molecular dynamics method based upon the EAM interatomic potential to reveal the influence of the mismatch in atomic size on the glass-forming ability. Under the cooling rate in the range of 4×1012 K•s－1 to 5×1011 K•s－1, the system under es the liquid, super-cooled liquid and solid state processes. Liquid Au always forms the crystal, the higher the cooling rate, the lower the crystallization temperature; while AuCu alloy forms a glass, the higher the cooling rate, the higher the glass transition temperature. The mismatch in atomic size is favorable to the formation of glass.
2003, 19(12): 1167-1170
doi: 10.3866/PKU.WHXB20031216
Abstract:
The metal-hydride electrode of MH/Ni batteries was modified with a thin conductive film using plasma technology. The experimental results demonstrated that the resistance of the batteries with the modified electrode was decreased by 24％,the discharge capacity was remarkably increased, discharge capacity at 5C (7.5 A) was increased by 200 mA•h and discharge voltage was increased by 0.14 V, the conductive film also restrained the pulverization of the hydrogen storage alloy and the battery with modified electrode exhibited satisfactory durability, the inner pressure of batteries was also decreased . The performance of the batteries showed an obvious improvement.
The metal-hydride electrode of MH/Ni batteries was modified with a thin conductive film using plasma technology. The experimental results demonstrated that the resistance of the batteries with the modified electrode was decreased by 24％,the discharge capacity was remarkably increased, discharge capacity at 5C (7.5 A) was increased by 200 mA•h and discharge voltage was increased by 0.14 V, the conductive film also restrained the pulverization of the hydrogen storage alloy and the battery with modified electrode exhibited satisfactory durability, the inner pressure of batteries was also decreased . The performance of the batteries showed an obvious improvement.
2003, 19(12): 1171-1175
doi: 10.3866/PKU.WHXB20031217
Abstract:
Chemical composition analysis, CEC method, and alkylammonium method were used to study the charge density and distribution of 12 montmorillonite samples coming from different sources. The results show that the total charge of all dioctahedron montmorillonites is between 0.40 to 0.45 eq/[(Al, Si)4O10], but the layer charge and the variable surface charge vary with the ratio of Al/Mg in octahedron. For the montmorillonites with lower layer charge and higher variable surface charge, the occupancy of Al and Mg in the octahedron site is above 1.5 and 0.3～0.4 respectively, while for the montmorillonites with higher layer charge and lower variable surface charge, the occupancy of that is 1.3～1.4 and about 0.3 respectively. Charge that mostly origin from Mg2＋ substituting Al3＋ in octahedron and Al3＋ substituting Si4＋ in tetrahedron is mainly related to Mg content and Al/Mg ratio in montmorillonites. Generally, montmorillonites with higher Mg content have higher charge. The difference of Al/Mg ratio and Fe content accounts for the structural variety, charge and physicochemical property of montmorillonites.
Chemical composition analysis, CEC method, and alkylammonium method were used to study the charge density and distribution of 12 montmorillonite samples coming from different sources. The results show that the total charge of all dioctahedron montmorillonites is between 0.40 to 0.45 eq/[(Al, Si)4O10], but the layer charge and the variable surface charge vary with the ratio of Al/Mg in octahedron. For the montmorillonites with lower layer charge and higher variable surface charge, the occupancy of Al and Mg in the octahedron site is above 1.5 and 0.3～0.4 respectively, while for the montmorillonites with higher layer charge and lower variable surface charge, the occupancy of that is 1.3～1.4 and about 0.3 respectively. Charge that mostly origin from Mg2＋ substituting Al3＋ in octahedron and Al3＋ substituting Si4＋ in tetrahedron is mainly related to Mg content and Al/Mg ratio in montmorillonites. Generally, montmorillonites with higher Mg content have higher charge. The difference of Al/Mg ratio and Fe content accounts for the structural variety, charge and physicochemical property of montmorillonites.
