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1992 Volume 8 Issue 3
1992, 8(03): 289-292
doi: 10.3866/PKU.WHXB19920301
Abstract:
A simple reaction model; A+B→C+D, B+C→2B,D→A, is shown to be able to exhibit a pitchfork bifurcation of stationary states in a continuous stirred tank reactor (CSTR). To be different from the well-known Schlogl model, the present model involves only mono-and bimolecular reaction steps and without an assumption of pool chemicals which may cause an inequality of total mass for different states in system and, in turn, some problems for comparison of thermodynamic properties for different states.
A simple reaction model; A+B→C+D, B+C→2B,D→A, is shown to be able to exhibit a pitchfork bifurcation of stationary states in a continuous stirred tank reactor (CSTR). To be different from the well-known Schlogl model, the present model involves only mono-and bimolecular reaction steps and without an assumption of pool chemicals which may cause an inequality of total mass for different states in system and, in turn, some problems for comparison of thermodynamic properties for different states.
1992, 8(03): 293-295
doi: 10.3866/PKU.WHXB19920302
Abstract:
In this paper a chamber-reactor that makes it possible to investigate the kineties of catalytic reaction with simultaneous X-ray diffraction phase analysis of the catalyst during the reaction is described. Two samples, the phase trasformations of quartz powder during temperature variation and the reduction of CuO with H_2 were investigated by this chamber reactor. An analysis of XRD spectrum leads to the conclusion that use of a Beryllium window have some special advantages.
In this paper a chamber-reactor that makes it possible to investigate the kineties of catalytic reaction with simultaneous X-ray diffraction phase analysis of the catalyst during the reaction is described. Two samples, the phase trasformations of quartz powder during temperature variation and the reduction of CuO with H_2 were investigated by this chamber reactor. An analysis of XRD spectrum leads to the conclusion that use of a Beryllium window have some special advantages.
1992, 8(03): 296-300
doi: 10.3866/PKU.WHXB19920303
Abstract:
In our previous work we have found that the 2223 phase is formed more rapidly and the structural stability can be enhanced by doping high valence cation(Sn~(4+)、Sb~(5+)、V~(5+)、W~(6+)、Mo~(6+) etc.) in the Bi(Pb)SrCaCuO system. In this paper the effects of high valence cations doped on the phase formation and the crystal structure are discussed further.
The Aurivillus building and rocksalt building unit coexist in the Bi double layers. The structural variety strongly affects the structural stability. Owing to Pb~(2+) addition the probability of Aurivillus building is increased, the stability of 2223 phase can be promoted. However, the structure is still not stable, since the addition of Pb~(2+) has decreased the valence state of Bi site and the oxygen positions are not fully occupied. By doping high valence cation, especially, when the valence of Pb_x~(2+)M_y~(n+) equals to +3 the structure of the 2223 phase can be stabilized. This result has been observed with examining elemental content of 2223 phase.
The melting point of the grain boundaries are much lower after doping high valence cations, therefore the ion diffusion is more rapid and acceleration of the 2223 phase formation is observed.
In our previous work we have found that the 2223 phase is formed more rapidly and the structural stability can be enhanced by doping high valence cation(Sn~(4+)、Sb~(5+)、V~(5+)、W~(6+)、Mo~(6+) etc.) in the Bi(Pb)SrCaCuO system. In this paper the effects of high valence cations doped on the phase formation and the crystal structure are discussed further.
The Aurivillus building and rocksalt building unit coexist in the Bi double layers. The structural variety strongly affects the structural stability. Owing to Pb~(2+) addition the probability of Aurivillus building is increased, the stability of 2223 phase can be promoted. However, the structure is still not stable, since the addition of Pb~(2+) has decreased the valence state of Bi site and the oxygen positions are not fully occupied. By doping high valence cation, especially, when the valence of Pb_x~(2+)M_y~(n+) equals to +3 the structure of the 2223 phase can be stabilized. This result has been observed with examining elemental content of 2223 phase.
The melting point of the grain boundaries are much lower after doping high valence cations, therefore the ion diffusion is more rapid and acceleration of the 2223 phase formation is observed.
1992, 8(03): 301-303
doi: 10.3866/PKU.WHXB19920304
Abstract:
1992, 8(03): 304-306
doi: 10.3866/PKU.WHXB19920305
Abstract:
The pH dependence of ultraviolet absorption spectra of an aqueous bilayer membrane composed of single-chain ammonium amphiphile containing a Schiff base, has been studied at 10 and 35 ℃, which are below and above the liquid crystalline to gel phase transition (T_c=32 ℃) of the neutral solution, respectively. At 10 ℃, increasing acidity of the solution facilitates the formation of H-aggregate. At 10 ℃, the H-aggregate increases with the decrease of pH value in the range of pH 13.0-10.0. Further increase of acididy leads to the protonation of the Schiff base and thus partially disintegrates the aggregate.
The pH dependence of ultraviolet absorption spectra of an aqueous bilayer membrane composed of single-chain ammonium amphiphile containing a Schiff base, has been studied at 10 and 35 ℃, which are below and above the liquid crystalline to gel phase transition (T_c=32 ℃) of the neutral solution, respectively. At 10 ℃, increasing acidity of the solution facilitates the formation of H-aggregate. At 10 ℃, the H-aggregate increases with the decrease of pH value in the range of pH 13.0-10.0. Further increase of acididy leads to the protonation of the Schiff base and thus partially disintegrates the aggregate.
1992, 8(03): 307-312
doi: 10.3866/PKU.WHXB19920306
Abstract:
Kashiwagi used semiortho nalized orbitals as basis set in quantum chemicalcal culations and proposed a scheme in which two-electron integrals containing ortho nalized orbital pairs were neglected, but the same kind of one-electron integrals were reserved. We proposed in this paper that one-electron integrals containing ortho- nalized orbital pairs should be neglected too. This improvement makes the calcu-lations more accurate, because nuclear attractive energy is approximately equal to electron repulsive energy in a system. We use simpler orbitals to evaluate threeand four-center integrals, while keeping charge conservation. These two improvements can save a lot of computer time in approximate ab initio calculations.
Kashiwagi used semiortho nalized orbitals as basis set in quantum chemicalcal culations and proposed a scheme in which two-electron integrals containing ortho nalized orbital pairs were neglected, but the same kind of one-electron integrals were reserved. We proposed in this paper that one-electron integrals containing ortho- nalized orbital pairs should be neglected too. This improvement makes the calcu-lations more accurate, because nuclear attractive energy is approximately equal to electron repulsive energy in a system. We use simpler orbitals to evaluate threeand four-center integrals, while keeping charge conservation. These two improvements can save a lot of computer time in approximate ab initio calculations.
1992, 8(03): 313-320
doi: 10.3866/PKU.WHXB19920307
Abstract:
Adsorption and reaction of acetonitrile (CH_3CN) and benzonitrile (C_6H_5CN) on clean and oxygen covered Cu(111) and Pd(100) surface have been studied by HREELS. At 198 K the CH_3CN molecule rehybridized and chemisorbed on Cu(111) and Pd(100) by di-σ-bonds with carbon and nitrogen atom parallelly to the surface. The chemisorbed species, CH_3-C=N, showing a week loss at 196 meV. The HREEL spectra of C_6H_5CN adsorbed on Pd(100) and Cu(111) are indicative of molecularly adsorbed C_6H_5CN, with the ring plane and the CN group parallelled to the surface at 198 K. The preadsorption of oxygen enhancing the adsorption of CH_3CN and C_6H_5CN on Pd(100) surface was not found. The adsorption of C_6H_5CN on oxygen covered Cu(111) surface results in species with a strong mode at 173 meV, suggesting an N-bonded oxide (—C=N=O). Similar reaction with CH_3CN is supposed.
Adsorption and reaction of acetonitrile (CH_3CN) and benzonitrile (C_6H_5CN) on clean and oxygen covered Cu(111) and Pd(100) surface have been studied by HREELS. At 198 K the CH_3CN molecule rehybridized and chemisorbed on Cu(111) and Pd(100) by di-σ-bonds with carbon and nitrogen atom parallelly to the surface. The chemisorbed species, CH_3-C=N, showing a week loss at 196 meV. The HREEL spectra of C_6H_5CN adsorbed on Pd(100) and Cu(111) are indicative of molecularly adsorbed C_6H_5CN, with the ring plane and the CN group parallelled to the surface at 198 K. The preadsorption of oxygen enhancing the adsorption of CH_3CN and C_6H_5CN on Pd(100) surface was not found. The adsorption of C_6H_5CN on oxygen covered Cu(111) surface results in species with a strong mode at 173 meV, suggesting an N-bonded oxide (—C=N=O). Similar reaction with CH_3CN is supposed.
1992, 8(03): 321-325
doi: 10.3866/PKU.WHXB19920308
Abstract:
An investigation of the adsorption of NO on reduced Co-Mo/Al_2O_3 and Ru-Co-Mo/Al_2O_3 catalysts has been performed by using IR and MS spectros-copies, and it was found that two IR bands appeared at 1895 and 1880 cm~(-1) in the IR spectra and three peaks exhibited at 353, 423 and 473 K in the TPD-MS profiles. These are attributed to the various Co-sites on the surface of catalysts.Comparing Co-Mo/Al_2O_3 catalyst with Ru-Co-Mo/Al_2O_3 it was found that the addition of Ru in Ru-Co-Mo/Al_2O_3 markedly led to an increase of the rate and amount for NO adsorption, which may indicate that the HDS activity of Ru-Co-Mo/Al_2O_3 was much higher than that of Co-Mo/Al_2O_3 catalyst.
An investigation of the adsorption of NO on reduced Co-Mo/Al_2O_3 and Ru-Co-Mo/Al_2O_3 catalysts has been performed by using IR and MS spectros-copies, and it was found that two IR bands appeared at 1895 and 1880 cm~(-1) in the IR spectra and three peaks exhibited at 353, 423 and 473 K in the TPD-MS profiles. These are attributed to the various Co-sites on the surface of catalysts.Comparing Co-Mo/Al_2O_3 catalyst with Ru-Co-Mo/Al_2O_3 it was found that the addition of Ru in Ru-Co-Mo/Al_2O_3 markedly led to an increase of the rate and amount for NO adsorption, which may indicate that the HDS activity of Ru-Co-Mo/Al_2O_3 was much higher than that of Co-Mo/Al_2O_3 catalyst.
1992, 8(03): 326-331
doi: 10.3866/PKU.WHXB19920309
Abstract:
Implantation of light-induced Co ions from Co(NO_3)_2 solution (≥0. 10 mol·cm~(-3)) into Ti anodic oxide film was observed and studied by photocurrent spectroscopy and XPS technique. The results show that implantation could not take place at film/solution interface without illumination. But the Co ions at film/solution interface excited by illuminating can overcome the interface barrier and the TiO_2 lattice energy and into the tetrahedral interstitial sites and/or octahedral interstitial sites in TiO_2 lattice. The implanted Co ions can interact with the O~(2-) ions in the lattice and probably form tetracoordinated compound of Co with typical blue color and hexacoordinated compound of Co with typical pink color. The quantum efficiency for photoelectric conversion of Ti anodic film decreases with very high doping concentration of Co ions.
Implantation of light-induced Co ions from Co(NO_3)_2 solution (≥0. 10 mol·cm~(-3)) into Ti anodic oxide film was observed and studied by photocurrent spectroscopy and XPS technique. The results show that implantation could not take place at film/solution interface without illumination. But the Co ions at film/solution interface excited by illuminating can overcome the interface barrier and the TiO_2 lattice energy and into the tetrahedral interstitial sites and/or octahedral interstitial sites in TiO_2 lattice. The implanted Co ions can interact with the O~(2-) ions in the lattice and probably form tetracoordinated compound of Co with typical blue color and hexacoordinated compound of Co with typical pink color. The quantum efficiency for photoelectric conversion of Ti anodic film decreases with very high doping concentration of Co ions.
1992, 8(03): 332-338
doi: 10.3866/PKU.WHXB19920310
Abstract:
In this paper, UV and CD spectra of bilirubin and bile salts-bilirubin in aqueous solution have been simulated by. means of "PPP-SCF-CI-DV", quantum chemical programme, in order to clarify the conformations of bilirubin and its complexes with bile salts. The torsional angles between two dipyrrole chromophores of bilirubin were pos-tulated changing from 104° to 112°, after binding with bile salts and the intramole-cularly hydrogen bonded states of bilirubin still are kept; the separation between two absorption peakes in both UV and CD spectrum increases in presence of bile salts, it is interpreted by that one dipyrrole chromophores of billrubin are combined with bile salts mainly; the difference of CD spectrum which are produced by dihydroxy and trihydroxy bile salts may be explained by enantio-selective binding.
In this paper, UV and CD spectra of bilirubin and bile salts-bilirubin in aqueous solution have been simulated by. means of "PPP-SCF-CI-DV", quantum chemical programme, in order to clarify the conformations of bilirubin and its complexes with bile salts. The torsional angles between two dipyrrole chromophores of bilirubin were pos-tulated changing from 104° to 112°, after binding with bile salts and the intramole-cularly hydrogen bonded states of bilirubin still are kept; the separation between two absorption peakes in both UV and CD spectrum increases in presence of bile salts, it is interpreted by that one dipyrrole chromophores of billrubin are combined with bile salts mainly; the difference of CD spectrum which are produced by dihydroxy and trihydroxy bile salts may be explained by enantio-selective binding.
1992, 8(03): 339-344
doi: 10.3866/PKU.WHXB19920311
Abstract:
Vanadium has been introduced into high-silica zeolites by heating the physical mixture of V_2O_5 and H-Mordenite or H-ZSM-5 in an airflow containing water vapor. XRD, LRS, BIE and FTIR results suggest that ion exchange occurs between protons of zeolite and the (VO)~(3+) formed during preparation. ESR results show these are two different coordination structures for the vanadyl species entered into HM or H-ZSM-5, i.e. The compressed hexacoordinated octahedral and the pentacoordinated with pyramidic symmetry.
Vanadium has been introduced into high-silica zeolites by heating the physical mixture of V_2O_5 and H-Mordenite or H-ZSM-5 in an airflow containing water vapor. XRD, LRS, BIE and FTIR results suggest that ion exchange occurs between protons of zeolite and the (VO)~(3+) formed during preparation. ESR results show these are two different coordination structures for the vanadyl species entered into HM or H-ZSM-5, i.e. The compressed hexacoordinated octahedral and the pentacoordinated with pyramidic symmetry.
1992, 8(03): 345-351
doi: 10.3866/PKU.WHXB19920312
Abstract:
In this article, a simple and efficient al rithm has been designed for reconstructing ESR image, on the basis of projection profile principle, which can be used to plot contour, stereograph and dispersal-point distribution graph of the sample sipn density distribution on a cross-section. As an example, the ESR image of paramagnetic defect centers in quartz Dewar due to UV-irradiation was given to illustratethe appli-cation of the al rithm.
In this article, a simple and efficient al rithm has been designed for reconstructing ESR image, on the basis of projection profile principle, which can be used to plot contour, stereograph and dispersal-point distribution graph of the sample sipn density distribution on a cross-section. As an example, the ESR image of paramagnetic defect centers in quartz Dewar due to UV-irradiation was given to illustratethe appli-cation of the al rithm.
1992, 8(03): 352-357
doi: 10.3866/PKU.WHXB19920313
Abstract:
The interaction between polyacrylamide (PAM) and sodium dodecyl sulfonate (R_(12)SO_3Na) in NaCl solution and in NaCl-R_4OH solution have been studied by viscosity measurements. The electro-viscous effect was found, that is, the reduced viscosity of PAM-R_(12)SO_3Na solution increases with the decrease of the concentration of PAM. These results are interpreted in terms of the formation of polymer-micelle aggregate formed by the binding between the PAM and the R_(12)SO_3Na micelle.
The interaction between polyacrylamide (PAM) and sodium dodecyl sulfonate (R_(12)SO_3Na) in NaCl solution and in NaCl-R_4OH solution have been studied by viscosity measurements. The electro-viscous effect was found, that is, the reduced viscosity of PAM-R_(12)SO_3Na solution increases with the decrease of the concentration of PAM. These results are interpreted in terms of the formation of polymer-micelle aggregate formed by the binding between the PAM and the R_(12)SO_3Na micelle.
1992, 8(03): 358-363
doi: 10.3866/PKU.WHXB19920314
Abstract:
The IR spectra of n-C_(16)H_(33)OH/n-C_6H_(14)(n-hexadecanol/n-hexane) system in seven different alcohol concentrations (0.01-0.20 mol·L~(-1)) were measured and analysed by combined Fourier self-deconyolution and curve-fitting methods. The types of associa-tion in the system can be identified and their distribution can be evaluated.
The IR spectra of n-C_(16)H_(33)OH/n-C_6H_(14)(n-hexadecanol/n-hexane) system in seven different alcohol concentrations (0.01-0.20 mol·L~(-1)) were measured and analysed by combined Fourier self-deconyolution and curve-fitting methods. The types of associa-tion in the system can be identified and their distribution can be evaluated.
1992, 8(03): 364-369
doi: 10.3866/PKU.WHXB19920315
Abstract:
The charge transport of Fe(Ⅱ/Ⅲ) ions within the Nafion film and in solutions has theoretically been derived. The diffusion coefficients and standard rate constants of Fe(Ⅱ/Ⅲ) ions in the film were evaluated to be 2.9×10~(-7) cm~2·s~(-1) and 1.1×10~(-3) cm·s~(-1), respectively, by analyzing the system impedance based on the small amplitude potential step. Obtained value of k°′ is less than an order of magnitude to uncoated electrodes, which is correlated with large diffusion rate of Fe(Ⅱ/Ⅲ) ions within the Nafion film. Effects of electrode potentials and concentrations of supporting electrolytes on the system impedances have been discussed. Results are reasonably agreed with theoretical derivations.
The charge transport of Fe(Ⅱ/Ⅲ) ions within the Nafion film and in solutions has theoretically been derived. The diffusion coefficients and standard rate constants of Fe(Ⅱ/Ⅲ) ions in the film were evaluated to be 2.9×10~(-7) cm~2·s~(-1) and 1.1×10~(-3) cm·s~(-1), respectively, by analyzing the system impedance based on the small amplitude potential step. Obtained value of k°′ is less than an order of magnitude to uncoated electrodes, which is correlated with large diffusion rate of Fe(Ⅱ/Ⅲ) ions within the Nafion film. Effects of electrode potentials and concentrations of supporting electrolytes on the system impedances have been discussed. Results are reasonably agreed with theoretical derivations.
1992, 8(03): 370-375
doi: 10.3866/PKU.WHXB19920316
Abstract:
Sulfonated EPDM ionomers containing Na~+, Mg~(2+), Zn~(2+) and Al~(3+) have been synthesized and identified with IR spectra. Dynamic mechanical analyses showed that the ionic groups in ionomers have been aggregated to mutiplets instead of clusters. Ther-mogravimetry showed that the thermal stability of the ionomers is in an order as Na>Zn>Mg>Al.
Viscometric behaviors of ionomers in xylene-5% hexanol mixed solvent are quite different from that of EPDM owing to the interaction between ionic groups. The strength of interaction of metallic ions with -SO_3~- is in the order Na>Mg>Zn. This fact was interpreted by considering the different hexanol-solvation ability of different metallic ions and the stability of the solvation layer around them.
Sulfonated EPDM ionomers containing Na~+, Mg~(2+), Zn~(2+) and Al~(3+) have been synthesized and identified with IR spectra. Dynamic mechanical analyses showed that the ionic groups in ionomers have been aggregated to mutiplets instead of clusters. Ther-mogravimetry showed that the thermal stability of the ionomers is in an order as Na>Zn>Mg>Al.
Viscometric behaviors of ionomers in xylene-5% hexanol mixed solvent are quite different from that of EPDM owing to the interaction between ionic groups. The strength of interaction of metallic ions with -SO_3~- is in the order Na>Mg>Zn. This fact was interpreted by considering the different hexanol-solvation ability of different metallic ions and the stability of the solvation layer around them.
1992, 8(03): 376-382
doi: 10.3866/PKU.WHXB19920317
Abstract:
Theoretical investigations have been made on the monomolecular adsorption of carbon monoxide on aluminum clusters Al_n(n=1-10, 12, 13). The equilibrium adsorption positions and the binding energies of various CO sites have been evaluated by using the quantum chemical method of CNDO/2 with properly choosing the optimal geometries of aluminum clusters from the reported data. The results reveal that the adsorption of CO on Al_n remarkably depends upon the number of metal atoms in the cluster and exhibits a notable "magic number" behavior, viz. the adsorption energies on Al_2, Al_6 and Al_(12) appear in particularly large values, which are in encouraging agreement with the experimental observations and that predicted by our Extended Electron-Shell Model proposed previously. The analysis of the electronic structure of Al_(12) and Al_(13) puts the model on a still solid basis. It can also be seen that such a size-dependence es down with the increasing cluster size and the behavior of cluster gradually approaches to that of bulk aluminum.
Theoretical investigations have been made on the monomolecular adsorption of carbon monoxide on aluminum clusters Al_n(n=1-10, 12, 13). The equilibrium adsorption positions and the binding energies of various CO sites have been evaluated by using the quantum chemical method of CNDO/2 with properly choosing the optimal geometries of aluminum clusters from the reported data. The results reveal that the adsorption of CO on Al_n remarkably depends upon the number of metal atoms in the cluster and exhibits a notable "magic number" behavior, viz. the adsorption energies on Al_2, Al_6 and Al_(12) appear in particularly large values, which are in encouraging agreement with the experimental observations and that predicted by our Extended Electron-Shell Model proposed previously. The analysis of the electronic structure of Al_(12) and Al_(13) puts the model on a still solid basis. It can also be seen that such a size-dependence es down with the increasing cluster size and the behavior of cluster gradually approaches to that of bulk aluminum.
1992, 8(03): 383-388
doi: 10.3866/PKU.WHXB19920318
Abstract:
We measured the optical emission spectra (OES) of glow discharged plasma of methane in the diamond-like carbon film deposition and analyzed the relationship between the OES and the deposition parameters, such as rf power, gas pressure and the distances from the lower electrode.
The infrared absorption of films were also measured and the results of infrared absorption were compared with that of OES measurement.
We measured the optical emission spectra (OES) of glow discharged plasma of methane in the diamond-like carbon film deposition and analyzed the relationship between the OES and the deposition parameters, such as rf power, gas pressure and the distances from the lower electrode.
The infrared absorption of films were also measured and the results of infrared absorption were compared with that of OES measurement.
1992, 8(03): 389-393
doi: 10.3866/PKU.WHXB19920319
Abstract:
In this paper, according to UV and CD experiments of nine different bile saltbilirubin-Ca~(2+) ternary systems, a conformational model of the resulted ternary complexes was suggested. In order to clarify their conformations, UV and CD spectra of these ternary complexes have been simulated by means of "PPP-SCG-CI-DV", quantum chemical programme. Six optimum conformations may be grouped into two types, for which the results are in agreement with that of the spectroscopic experiments obtained. Based on them, the chiralities shown in CD spectra of nine different bile salt-bilirubin-Ca~(2+) complexes were explained.
In this paper, according to UV and CD experiments of nine different bile saltbilirubin-Ca~(2+) ternary systems, a conformational model of the resulted ternary complexes was suggested. In order to clarify their conformations, UV and CD spectra of these ternary complexes have been simulated by means of "PPP-SCG-CI-DV", quantum chemical programme. Six optimum conformations may be grouped into two types, for which the results are in agreement with that of the spectroscopic experiments obtained. Based on them, the chiralities shown in CD spectra of nine different bile salt-bilirubin-Ca~(2+) complexes were explained.
1992, 8(03): 394-397
doi: 10.3866/PKU.WHXB19920320
Abstract:
The molecular orientation and thermal stability of the Langmuir-Blodgett film of Cd salt of 10, 12-tricosadiynoic acid was studied using linear dichroism FT-IR spectroscopy. It was found that orientation angles between the transition moments of major characteristic groups in the film and the substrate surface normal line N are different. A molecular configuration like that of folding chain was evaluated, the closer to the hydrophobic end the more small the orientation angle is, this satisfies structural stability of LB films. The experiments on thermal stabiliyt showed that the structural stability of the LB film mainly depends on the hydrocarbon chain. After heated the tilt of the hydrocarbon chain was most serious and was irreversible on cooling back to the original room temperature.
The molecular orientation and thermal stability of the Langmuir-Blodgett film of Cd salt of 10, 12-tricosadiynoic acid was studied using linear dichroism FT-IR spectroscopy. It was found that orientation angles between the transition moments of major characteristic groups in the film and the substrate surface normal line N are different. A molecular configuration like that of folding chain was evaluated, the closer to the hydrophobic end the more small the orientation angle is, this satisfies structural stability of LB films. The experiments on thermal stabiliyt showed that the structural stability of the LB film mainly depends on the hydrocarbon chain. After heated the tilt of the hydrocarbon chain was most serious and was irreversible on cooling back to the original room temperature.
1992, 8(03): 398-400
doi: 10.3866/PKU.WHXB19920321
Abstract:
SERRS of copper tetrakis(2,4-ditert-penthyl phenoxy) Phthalocyanine LB monolayer on Ag island film and RRS of the compound in solid state have been obtained. On comparison between the spectra, it is proposed that the macrocycle of the molecule on the Ag substrate is oriented parallel to the surface.
SERRS of copper tetrakis(2,4-ditert-penthyl phenoxy) Phthalocyanine LB monolayer on Ag island film and RRS of the compound in solid state have been obtained. On comparison between the spectra, it is proposed that the macrocycle of the molecule on the Ag substrate is oriented parallel to the surface.
1992, 8(03): 401-404
doi: 10.3866/PKU.WHXB19920322
Abstract:
Ion implantation method was used for the doping of mild steel substrates with Ni and Mo. The mild steel was bombarded with 1×10~(16) ions·cm~(-2) of Ni and Mo. The resulting catalysts were tested with respect to their activity for the electrochemical H~+-reduction. The results indicate that implanted mild steel exhibit low hydrogen overvoltage (130～160 mV, 20～60 A·dm~(-2) in 30 wt% KOH at 25 ℃) and excellent stability. The Ni and Mo bombardments lead to a much more active in comparison with untreated mild steel. Ion beam mixing is less effective than ion implantation in this case. By XPS the shifts of electron bonding energies for Ni_(2p) and Mo_(3d) were observed for implanted mild steel with respect to the corresponding Ni and Mo. The electrocatalytic activity of implanted substrates was explained provisionally by an interaction between implanted metals in mild steel.
Ion implantation method was used for the doping of mild steel substrates with Ni and Mo. The mild steel was bombarded with 1×10~(16) ions·cm~(-2) of Ni and Mo. The resulting catalysts were tested with respect to their activity for the electrochemical H~+-reduction. The results indicate that implanted mild steel exhibit low hydrogen overvoltage (130～160 mV, 20～60 A·dm~(-2) in 30 wt% KOH at 25 ℃) and excellent stability. The Ni and Mo bombardments lead to a much more active in comparison with untreated mild steel. Ion beam mixing is less effective than ion implantation in this case. By XPS the shifts of electron bonding energies for Ni_(2p) and Mo_(3d) were observed for implanted mild steel with respect to the corresponding Ni and Mo. The electrocatalytic activity of implanted substrates was explained provisionally by an interaction between implanted metals in mild steel.
1992, 8(03): 405-409
doi: 10.3866/PKU.WHXB19920323
Abstract:
The photophysical behavior of titled compound has been studied. Results show that the fluorescence spectra and the fluorescence quantum yields depend strongly on the polarity and the viscosity of solvents. The rate constants of the radiation and ra-diationless decay processes of the excited compound were calculated. A comparative study has been carried out between compounds which possess binding and unbinding structures respectively.
The photophysical behavior of titled compound has been studied. Results show that the fluorescence spectra and the fluorescence quantum yields depend strongly on the polarity and the viscosity of solvents. The rate constants of the radiation and ra-diationless decay processes of the excited compound were calculated. A comparative study has been carried out between compounds which possess binding and unbinding structures respectively.
1992, 8(03): 410-412
doi: 10.3866/PKU.WHXB19920324
Abstract:
Anthracene and phenanthrene have been analyzed on a self-built laser probe time-of-flight mass spectrometer. Although both compounds have the same molecular formular, their positive and negative ion mass spectra recorded on the spectrometer are very different. These differences are discussed and contributed to their different structure. The study also demonstrates the power of the instrument in structure ana lysis and laser plasma studies.
Anthracene and phenanthrene have been analyzed on a self-built laser probe time-of-flight mass spectrometer. Although both compounds have the same molecular formular, their positive and negative ion mass spectra recorded on the spectrometer are very different. These differences are discussed and contributed to their different structure. The study also demonstrates the power of the instrument in structure ana lysis and laser plasma studies.
1992, 8(03): 413-417
doi: 10.3866/PKU.WHXB19920325
Abstract:
Interfacial tension is important in various industry processes, particularly in petroleum recovery where low or ultralow interfacial tension between oil and water bring about great benefit. For the measurement of interfacial tension, serveral kinds of method can be used. Those depending on size and shape of liquid drop including se-ssile drop, pendant drop and sprinning drop methods are suitable. Among them, se-ssile drop method has the advantage of simple equipment and procedure. Usually, the radius of drop equator is necessary for sessile drop method. Hence a drop with contice. In systems of low or ultralow interfacial tension, it is seldom to form a contact angle larger than 90°. This had been a restriction for the application of sessile drop method. In this work, procedures for obtaining interfacial tension from size and shape with small contact angle (<90°) was provided. od precision of this method was shown by applying to typical system (butanol/water). Comparasons of it with other methods have been made.
Interfacial tension is important in various industry processes, particularly in petroleum recovery where low or ultralow interfacial tension between oil and water bring about great benefit. For the measurement of interfacial tension, serveral kinds of method can be used. Those depending on size and shape of liquid drop including se-ssile drop, pendant drop and sprinning drop methods are suitable. Among them, se-ssile drop method has the advantage of simple equipment and procedure. Usually, the radius of drop equator is necessary for sessile drop method. Hence a drop with contice. In systems of low or ultralow interfacial tension, it is seldom to form a contact angle larger than 90°. This had been a restriction for the application of sessile drop method. In this work, procedures for obtaining interfacial tension from size and shape with small contact angle (<90°) was provided. od precision of this method was shown by applying to typical system (butanol/water). Comparasons of it with other methods have been made.
1992, 8(03): 418-423
doi: 10.3866/PKU.WHXB19920326
Abstract:
The passivation behavior and the pitting process at the fixed potentials for Ni electrode in Na_2SO_4-borax-borate buffer solution have been studied with alternating current(AC) impedance technique. For the passivation in the Cl~--free buffer solution the maximum of impedance moduli |Z| and the minimum of capacitances C_(dl) appeared at the potential of -0.2 V (vs. Hg/H ), because both the thickness of passive film and the rate of anodic dissolution increased with rising potential. As the pitting went on in the Cl~--containing buffer solutions at the fixed potentials, |Z| at low fretrations of 0.1, 0.05, 0.01 mol·L~(-1) and the fixed potentials of 0.2, 0.7, 0.7 V, respectively, are discussed.
The passivation behavior and the pitting process at the fixed potentials for Ni electrode in Na_2SO_4-borax-borate buffer solution have been studied with alternating current(AC) impedance technique. For the passivation in the Cl~--free buffer solution the maximum of impedance moduli |Z| and the minimum of capacitances C_(dl) appeared at the potential of -0.2 V (vs. Hg/H ), because both the thickness of passive film and the rate of anodic dissolution increased with rising potential. As the pitting went on in the Cl~--containing buffer solutions at the fixed potentials, |Z| at low fretrations of 0.1, 0.05, 0.01 mol·L~(-1) and the fixed potentials of 0.2, 0.7, 0.7 V, respectively, are discussed.
1992, 8(03): 424-428
doi: 10.3866/PKU.WHXB19920327
Abstract:
In this work it is proved that the expression for steady state reversible voltammetric waves of a microelectrode is independent of the electrode geometry, provided that the migration of species O and R, the natural convection and the ohmic drop of the solution are neglected.
In this work it is proved that the expression for steady state reversible voltammetric waves of a microelectrode is independent of the electrode geometry, provided that the migration of species O and R, the natural convection and the ohmic drop of the solution are neglected.
1992, 8(03): 429-431
doi: 10.3866/PKU.WHXB19920328
Abstract:
The relation between the broadening of X-ray diffraction peaks and their structure factor, for γ-and η-Aluminas, was studied. Comparison showed that the structure factor of the broad peaks result primarily from the Aluminium atoms. Thus, The structue imperfection of γ-and η-Aluminas is interpreted in terms of incomplete rearrangment of Aluminium atoms.
The relation between the broadening of X-ray diffraction peaks and their structure factor, for γ-and η-Aluminas, was studied. Comparison showed that the structure factor of the broad peaks result primarily from the Aluminium atoms. Thus, The structue imperfection of γ-and η-Aluminas is interpreted in terms of incomplete rearrangment of Aluminium atoms.
