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2002 Volume 18 Issue 11
2002, 18(11): 962-966
doi: 10.3866/PKU.WHXB20021101
Abstract:
The adsorption of cetyl trimethylammonium bromide (CTAB) at a smooth surface of SiO2 film was determined by ellipsometry. The result is in agreement with a two steps model. Its monolayer and bilayer adsorption occurred at different concentrations. The adsorption is consistant with the wettability change of the film surface. The wettability of a silica gel powder was determined by a modified Washburn equation expressed as contact angles. The interfacial tension (γ) between the dodecane and the dilute CTAB aqueous solution was obtained using the pendant method. The relationship between the wettability of the powder surface, the critical micelle concentration (CMC) of CTAB and the mimic oil recovery of the resident oil on the powder surface has been explored. It has been found that od residual oil could be achieved by surface wettability changes at normal interfacial tensions (100～102 mN•m－1) and no formation of emulsion (see Table 4).
The adsorption of cetyl trimethylammonium bromide (CTAB) at a smooth surface of SiO2 film was determined by ellipsometry. The result is in agreement with a two steps model. Its monolayer and bilayer adsorption occurred at different concentrations. The adsorption is consistant with the wettability change of the film surface. The wettability of a silica gel powder was determined by a modified Washburn equation expressed as contact angles. The interfacial tension (γ) between the dodecane and the dilute CTAB aqueous solution was obtained using the pendant method. The relationship between the wettability of the powder surface, the critical micelle concentration (CMC) of CTAB and the mimic oil recovery of the resident oil on the powder surface has been explored. It has been found that od residual oil could be achieved by surface wettability changes at normal interfacial tensions (100～102 mN•m－1) and no formation of emulsion (see Table 4).
2002, 18(11): 967-972
doi: 10.3866/PKU.WHXB20021102
Abstract:
The Morse’s type interaction potential between two C60 molecules has been obtained according to the properties of FCC C60 crystal, such as heat of sublimation, lattice constants, and so on. The expression is as follows: u(r)=30.05 exp[－24.96(r－1.005)]－60.10 exp[－12.48(r－1.005)] Using the Morse’s type interaction potential, energy of surface of (100)plane has been calculated, the value is 7.46×10－2 J•m－2. The second virial coefficients have been obtained from the potential in the range of 650 to 4500 K (Table 2). Lattice vibration has been studied (Fig.2), distribution of state-densities of FCC C60 lattice vibrations has been gained (Fig.3) based on the potential. Stability of C60 crystal at different crystal structures has also discussed here.
The Morse’s type interaction potential between two C60 molecules has been obtained according to the properties of FCC C60 crystal, such as heat of sublimation, lattice constants, and so on. The expression is as follows: u(r)=30.05 exp[－24.96(r－1.005)]－60.10 exp[－12.48(r－1.005)] Using the Morse’s type interaction potential, energy of surface of (100)plane has been calculated, the value is 7.46×10－2 J•m－2. The second virial coefficients have been obtained from the potential in the range of 650 to 4500 K (Table 2). Lattice vibration has been studied (Fig.2), distribution of state-densities of FCC C60 lattice vibrations has been gained (Fig.3) based on the potential. Stability of C60 crystal at different crystal structures has also discussed here.
2002, 18(11): 973-978
doi: 10.3866/PKU.WHXB20021103
Abstract:
Cu electrodeposits with highly preferred orientations were obtained from H2SO4-CuSO4 electrolytic solution. XRD results indicated that at current densities 1.0～6.0 A•dm－2 and 15.0 A•dm－2,the obtained Cu electrodeposits were respectively shown in (220) and (111) highly preferred orientations. The value of texture coefficient of Cu electrodeposited at a stationary current density was increased with its thickness. SEM results revealed that the surface morphology of the electrodeposits with (220) texture obtained at 4.0 A•dm－2 appeared in network combined with needle crystals, and texture with (111) at 15.0 A•dm－2 in hexa nal pyramid. The changes of the preferred orientation effected by current density were mainly attributed to the competitions between the grains growing direction and the rate during Cu electro crystallization.
Cu electrodeposits with highly preferred orientations were obtained from H2SO4-CuSO4 electrolytic solution. XRD results indicated that at current densities 1.0～6.0 A•dm－2 and 15.0 A•dm－2,the obtained Cu electrodeposits were respectively shown in (220) and (111) highly preferred orientations. The value of texture coefficient of Cu electrodeposited at a stationary current density was increased with its thickness. SEM results revealed that the surface morphology of the electrodeposits with (220) texture obtained at 4.0 A•dm－2 appeared in network combined with needle crystals, and texture with (111) at 15.0 A•dm－2 in hexa nal pyramid. The changes of the preferred orientation effected by current density were mainly attributed to the competitions between the grains growing direction and the rate during Cu electro crystallization.
2002, 18(11): 979-984
doi: 10.3866/PKU.WHXB20021104
Abstract:
A new liquid membrane oscillator has been discovered experimentally, in the reaction of producing soap between the two phases of oil and water, pH oscillations appeared near the interface lasting a long time with large amplitude. When the system of W/O two phases was changed by three phases of W1/O/W2, the amplitude changed from pH 0.50 to pH 2.88. The constitution of the liquid membrane oscillator is two aqueous solutions of CTAB and NaOH, respectively and an oil phase of kerosene solution of oleic acid. In addition, obvious oscillations of electric potential and conductivity have also been discovered in the liquid membrane oscillator. In order to probe the oscillation mechanism more deeply, the effect of concentration, the change of position and kind of electrodes, as well as auxiliary experiments have been carried out and a generalizated mechanism has been given. The mechanism pointed out that under the condition of membrane reaction carrying to some extent, when the reaction rate is proportion to diffusion velocity, a regular periodic phenomenon could be produced. A comparison between simulation of experimental curves and mechanistic formula was also engaged. On the base of mono valence soap oscillator, various kinds of higher valence ones were formed by substitution or addition of transition metals. The change of pH, electric potential and conductivity during the reaction were monitored. With comparison study of the same kind of chemical oscillators, some conclusions were obtained from the consideration of the coordination between metal and acid radical.
A new liquid membrane oscillator has been discovered experimentally, in the reaction of producing soap between the two phases of oil and water, pH oscillations appeared near the interface lasting a long time with large amplitude. When the system of W/O two phases was changed by three phases of W1/O/W2, the amplitude changed from pH 0.50 to pH 2.88. The constitution of the liquid membrane oscillator is two aqueous solutions of CTAB and NaOH, respectively and an oil phase of kerosene solution of oleic acid. In addition, obvious oscillations of electric potential and conductivity have also been discovered in the liquid membrane oscillator. In order to probe the oscillation mechanism more deeply, the effect of concentration, the change of position and kind of electrodes, as well as auxiliary experiments have been carried out and a generalizated mechanism has been given. The mechanism pointed out that under the condition of membrane reaction carrying to some extent, when the reaction rate is proportion to diffusion velocity, a regular periodic phenomenon could be produced. A comparison between simulation of experimental curves and mechanistic formula was also engaged. On the base of mono valence soap oscillator, various kinds of higher valence ones were formed by substitution or addition of transition metals. The change of pH, electric potential and conductivity during the reaction were monitored. With comparison study of the same kind of chemical oscillators, some conclusions were obtained from the consideration of the coordination between metal and acid radical.
2002, 18(11): 985-988
doi: 10.3866/PKU.WHXB20021105
Abstract:
Characteristics and change rule of an electrode process can be reflected by in-situ graze ellipsometric parameters. The mathematical and physical model of the graze ellipsometry has been put forward by combining the model of diffusion layer in electrochemical reaction with graze ellipsometry experiments. The physicochemical meaning of ellipsometry parameters Δ and Ψ has been explained. The diffusion layer near the electrode is equivalent to a phase retarder and an amplitude absorber. The influence of the concentration of electroactive substance and diameter of spot of the incidence light on Δ and Ψ is discussed with reference to experiment results.
Characteristics and change rule of an electrode process can be reflected by in-situ graze ellipsometric parameters. The mathematical and physical model of the graze ellipsometry has been put forward by combining the model of diffusion layer in electrochemical reaction with graze ellipsometry experiments. The physicochemical meaning of ellipsometry parameters Δ and Ψ has been explained. The diffusion layer near the electrode is equivalent to a phase retarder and an amplitude absorber. The influence of the concentration of electroactive substance and diameter of spot of the incidence light on Δ and Ψ is discussed with reference to experiment results.
2002, 18(11): 989-993
doi: 10.3866/PKU.WHXB20021106
Abstract:
Electrochemical in situ step-scan time-resolved microscope FTIR spectroscopy (in situ SS-TR-MFTIRS) was successively established, for the first time in the present work, by using a step-scan FTIR instrument (Nexus 870 FTIR spectrometer) and an IR microscope (IR-plane advantage microscope). A homemade signal synchronizer was used to generate polarization potential that is in accordance with the signal-time-sequence of step-scan time-resolved spectral data collection. Due to the use of a nanostructured microelectrode of Pt and the enhancement of IR absorption, a character of abnormal infrared effects of the nanostructured Pt surface, IR determination sensitivity of surface species was significantly increased, and the rate of responding to a polarizing potential of electrode surface in a thin-layer IR cell was remarkably improved. Adsorption of CO on nanostructured Pt microelectrode(Φ=0.2 mm)in sulfuric acid solutions was investigated by using the present new technique, and a spectral time-resolution as fast as 50 μs has been achieved. From the variation versus t of the band center of linear-bonded CO(see Fig.7) that is measured from in situ SS-TR-MFTIR spectra, the cell constant (τ=R1Cd) of an electrochemical thin-layer IR cell of external reflection mode, which is employed widely in studies of electrochemical in situ IR spectroscopy, has been determined to be 0.65 ms. In comparison with the τ of 40 ms for a conventional Pt disk electrode (Φ=6.0 mm),the use of a Pt microelectrode has reduced dramatically the thin-layer IR cell constant to about 61 times. The results obtained in the current paper is of importance in illustrating the success of establishing the in situ SS-TR-MFTIRS, and demonstrating the powerful capability of the in situ SS-TR-MFTIRS for studies of fast dynamic processes of electrode and kinetics of reactions taking place at solid/liquid interfaces as well.
Electrochemical in situ step-scan time-resolved microscope FTIR spectroscopy (in situ SS-TR-MFTIRS) was successively established, for the first time in the present work, by using a step-scan FTIR instrument (Nexus 870 FTIR spectrometer) and an IR microscope (IR-plane advantage microscope). A homemade signal synchronizer was used to generate polarization potential that is in accordance with the signal-time-sequence of step-scan time-resolved spectral data collection. Due to the use of a nanostructured microelectrode of Pt and the enhancement of IR absorption, a character of abnormal infrared effects of the nanostructured Pt surface, IR determination sensitivity of surface species was significantly increased, and the rate of responding to a polarizing potential of electrode surface in a thin-layer IR cell was remarkably improved. Adsorption of CO on nanostructured Pt microelectrode(Φ=0.2 mm)in sulfuric acid solutions was investigated by using the present new technique, and a spectral time-resolution as fast as 50 μs has been achieved. From the variation versus t of the band center of linear-bonded CO(see Fig.7) that is measured from in situ SS-TR-MFTIR spectra, the cell constant (τ=R1Cd) of an electrochemical thin-layer IR cell of external reflection mode, which is employed widely in studies of electrochemical in situ IR spectroscopy, has been determined to be 0.65 ms. In comparison with the τ of 40 ms for a conventional Pt disk electrode (Φ=6.0 mm),the use of a Pt microelectrode has reduced dramatically the thin-layer IR cell constant to about 61 times. The results obtained in the current paper is of importance in illustrating the success of establishing the in situ SS-TR-MFTIRS, and demonstrating the powerful capability of the in situ SS-TR-MFTIRS for studies of fast dynamic processes of electrode and kinetics of reactions taking place at solid/liquid interfaces as well.
2002, 18(11): 994-997
doi: 10.3866/PKU.WHXB20021107
Abstract:
The white powder of magnesium L-threonate was obtained by extracting with alcohol the concentrated solution obtained from the reaction between L-threonic acid solution prepared by double decomposition reaction of calcium L-threonate with oxalic acid and superfluous magnesium oxide at 80 ℃. The composition of the new compound was determined by chemical and elemental analyses and its formula fits Mg(C4H7O5)2•H2O, the IR spectra indicated that Mg2＋ in the compound coordinates to oxygen atom of the carboxyl group, while the proton of the carboxyl group is dissociated, it was assumed that the coordination number of Mg2＋ was 4 . The results of TG－DTG showed that the compound had fairish stability, the intermediate and final product of the thermal decomposition of the compound are Mg(C4H7O5)2, Mg(CH3COO)2 and M , respectively. The constant volume combustion energy of the compound, ΔcE, was determined as (－10 407.34±4.67) kJ•mol－1 by a precise rotating-bomb calorimeter at 298.15 K, its standard enthalpies of combustion, ΔcHm, and standard enthalpies of formation, ΔfHm, were calculated as(－3 249.49±1.46) kJ•mol－1 and (－2 786.23±1.84) kJ•mol－1, respectively.
The white powder of magnesium L-threonate was obtained by extracting with alcohol the concentrated solution obtained from the reaction between L-threonic acid solution prepared by double decomposition reaction of calcium L-threonate with oxalic acid and superfluous magnesium oxide at 80 ℃. The composition of the new compound was determined by chemical and elemental analyses and its formula fits Mg(C4H7O5)2•H2O, the IR spectra indicated that Mg2＋ in the compound coordinates to oxygen atom of the carboxyl group, while the proton of the carboxyl group is dissociated, it was assumed that the coordination number of Mg2＋ was 4 . The results of TG－DTG showed that the compound had fairish stability, the intermediate and final product of the thermal decomposition of the compound are Mg(C4H7O5)2, Mg(CH3COO)2 and M , respectively. The constant volume combustion energy of the compound, ΔcE, was determined as (－10 407.34±4.67) kJ•mol－1 by a precise rotating-bomb calorimeter at 298.15 K, its standard enthalpies of combustion, ΔcHm, and standard enthalpies of formation, ΔfHm, were calculated as(－3 249.49±1.46) kJ•mol－1 and (－2 786.23±1.84) kJ•mol－1, respectively.
2002, 18(11): 998-1004
doi: 10.3866/PKU.WHXB20021108
Abstract:
The 4A, 13X and LSX were ion exchanged by Ca2＋ in water solution, and the adsorption isotherms and breakthrough curves of these zeolites were measured at 25 ℃. The data demonstrate that the 4A, 13X and LSX ion-exchanged by Ca2＋ have higher adsorption capacity of N2 than the original ones, but the adsorption capacity of Ar for Ca2＋ exchanged zeolites is almost the same as that of the original ones. It is clear that these Ca2＋ exchanged zeolites have better adsorption selectivity for N2 than for Ar. From breakthrough curves it is known that the zeolites have a suitable pressure for adsorption separation of N2 and Ar. In the pressure range we studied, the best pressure is about 0.6 MPa. The adsorption capacities of N2 and Ar for the gas mixtures can be obtained from the breakthrough curves. Compared with the adsorption capacity of pure N2 and Ar, it can be found that nitrogen in the mixtures has a large effect on the ar n adsorption capacity of the zeolites, which have higher adsorption separation selectivity for N2 and Ar.
The 4A, 13X and LSX were ion exchanged by Ca2＋ in water solution, and the adsorption isotherms and breakthrough curves of these zeolites were measured at 25 ℃. The data demonstrate that the 4A, 13X and LSX ion-exchanged by Ca2＋ have higher adsorption capacity of N2 than the original ones, but the adsorption capacity of Ar for Ca2＋ exchanged zeolites is almost the same as that of the original ones. It is clear that these Ca2＋ exchanged zeolites have better adsorption selectivity for N2 than for Ar. From breakthrough curves it is known that the zeolites have a suitable pressure for adsorption separation of N2 and Ar. In the pressure range we studied, the best pressure is about 0.6 MPa. The adsorption capacities of N2 and Ar for the gas mixtures can be obtained from the breakthrough curves. Compared with the adsorption capacity of pure N2 and Ar, it can be found that nitrogen in the mixtures has a large effect on the ar n adsorption capacity of the zeolites, which have higher adsorption separation selectivity for N2 and Ar.
2002, 18(11): 1005-1008
doi: 10.3866/PKU.WHXB20021109
Abstract:
The spherical nano-particles of AgI were prepared from Ag complexes. Diameter of AgI could be controlled to within 20 to 100 nm. The prerequisite of covering of Y(OH)CO3,obtained by the hydrolysis of Y(NO3)3 in the presence of urea, on the pre-existing spherical AgI particles was that the surface of pre-existing particles must be charged negatively. The results were effected by some factors, such as concentration of Ag complexes, Y(NO3)3,urea and pre-existing particles, reaction time, aging temperature, as evidenced by X-ray diffraction, TEM of particle experiments. The hollow particles of Y(OH)CO3 (see Fig.5) were prepared by the coordination reaction which dissolved the pre-existing particles of AgI in Na2S2O3 concentrated solutions.
The spherical nano-particles of AgI were prepared from Ag complexes. Diameter of AgI could be controlled to within 20 to 100 nm. The prerequisite of covering of Y(OH)CO3,obtained by the hydrolysis of Y(NO3)3 in the presence of urea, on the pre-existing spherical AgI particles was that the surface of pre-existing particles must be charged negatively. The results were effected by some factors, such as concentration of Ag complexes, Y(NO3)3,urea and pre-existing particles, reaction time, aging temperature, as evidenced by X-ray diffraction, TEM of particle experiments. The hollow particles of Y(OH)CO3 (see Fig.5) were prepared by the coordination reaction which dissolved the pre-existing particles of AgI in Na2S2O3 concentrated solutions.
2002, 18(11): 1009-1013
doi: 10.3866/PKU.WHXB20021110
Abstract:
The effects of four kinds of anti-tumor compounds, taxol, carboplatin, ZYZ (the extractive from gleditsia), F43 (the extractive from squamocin), on the assembly and melting denaturation of tubulin in vitro were studied by turbidity and differential scanning calorimetry. The experimental results show that taxol and ZYZ enhance the assembly of tubulin, while carboplatin and F43 have no effect on the assembly of tubulin when the concentrations of all four kinds of compounds are 15 μmol•L－1.At the same time, taxol and ZYZ can make the melting points of tubuin rise, while the melting points of tubuin don't change in the presence of carboplatin and F43.The different interaction mechanisms of the compounds and tubulin have been discussed according to the above experimental results.
The effects of four kinds of anti-tumor compounds, taxol, carboplatin, ZYZ (the extractive from gleditsia), F43 (the extractive from squamocin), on the assembly and melting denaturation of tubulin in vitro were studied by turbidity and differential scanning calorimetry. The experimental results show that taxol and ZYZ enhance the assembly of tubulin, while carboplatin and F43 have no effect on the assembly of tubulin when the concentrations of all four kinds of compounds are 15 μmol•L－1.At the same time, taxol and ZYZ can make the melting points of tubuin rise, while the melting points of tubuin don't change in the presence of carboplatin and F43.The different interaction mechanisms of the compounds and tubulin have been discussed according to the above experimental results.
2002, 18(11): 1014-1017
doi: 10.3866/PKU.WHXB20021111
Abstract:
The electrode of nanothin film of TiO2 was prepared by electrodeposition method on ITO surface. Electrochemical behavior of ITO/TiO2 electrode under UV illumination was investigated using the methods of cyclic voltammetry and AC impedance spectroscopy. A new oxidative peak appeared at 0.15 V when the TiO2 electrode was illuminated less than 253.7 nm lights. It belongs to a new species of photo induced Ti3＋. The complex-plane impedance plots for ITO/TiO2 electrode in a solution containing Na2SO4 at open circuit potential exhibit semicircular shapes. The apparent resistance decreased when the electrode was irradiated by UV light. It is confirmed that a new species was produced when the electrode of nanofilm TiO2 under 253.7 nm light irradiation. The open-circuit potential of an electro deposition TiO2 film electrode varied regularly with light on and off. This result shows that the TiO2 electrode has the typical characteristics of n-type semiconductors. It also indicates that photo-induced Ti3＋ is not stable in the solution.
The electrode of nanothin film of TiO2 was prepared by electrodeposition method on ITO surface. Electrochemical behavior of ITO/TiO2 electrode under UV illumination was investigated using the methods of cyclic voltammetry and AC impedance spectroscopy. A new oxidative peak appeared at 0.15 V when the TiO2 electrode was illuminated less than 253.7 nm lights. It belongs to a new species of photo induced Ti3＋. The complex-plane impedance plots for ITO/TiO2 electrode in a solution containing Na2SO4 at open circuit potential exhibit semicircular shapes. The apparent resistance decreased when the electrode was irradiated by UV light. It is confirmed that a new species was produced when the electrode of nanofilm TiO2 under 253.7 nm light irradiation. The open-circuit potential of an electro deposition TiO2 film electrode varied regularly with light on and off. This result shows that the TiO2 electrode has the typical characteristics of n-type semiconductors. It also indicates that photo-induced Ti3＋ is not stable in the solution.
2002, 18(11): 1018-1022
doi: 10.3866/PKU.WHXB20021112
Abstract:
A sol-gel method was employed to prepare Mn-substituted barium hexaaluminate catalysts for methane combustion. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods, as well as the incorporation of Ba, Mn, on properties of the catalysts were investigated by means of N2adsorption, TG－DTA and X-ray diffraction. The supercritical drying method could maintain a higher specific surface area of the samples and suppress the transformation into α-Al2O3 at elevated temperatures. The introduction of Mn oxides could promote the transformation into hex aluminates during calcinations. BaMnAl11O19 catalyst dried by SCD method has a specific surface area of 35.1 m2•g－1 and an activity with T10％ (temperature for 10％ methane conversion) of 500 ℃ under the condition of 0.1 MPa and 40000 h－1 GHSV.
A sol-gel method was employed to prepare Mn-substituted barium hexaaluminate catalysts for methane combustion. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods, as well as the incorporation of Ba, Mn, on properties of the catalysts were investigated by means of N2adsorption, TG－DTA and X-ray diffraction. The supercritical drying method could maintain a higher specific surface area of the samples and suppress the transformation into α-Al2O3 at elevated temperatures. The introduction of Mn oxides could promote the transformation into hex aluminates during calcinations. BaMnAl11O19 catalyst dried by SCD method has a specific surface area of 35.1 m2•g－1 and an activity with T10％ (temperature for 10％ methane conversion) of 500 ℃ under the condition of 0.1 MPa and 40000 h－1 GHSV.
2002, 18(11): 1023-1028
doi: 10.3866/PKU.WHXB20021113
Abstract:
The weight-loss and electrochemical methods were used to investigate the corrosion behavior of metallic zinc in phosphoric acid solutions with or without dodecyl amine(DDA). The corrosion rate expressions were formulated and the corresponding kinetic parameters and thermodynamic constants were calculated. From the results of electron spectroscopy for chemical analysis (XPS), it was found that, over the temperature range of 40～70 ℃, zinc showed od self corrosion inhibition due to the coverage of Zn(OH)x produced. On the other hand, in the temperature range of 30～40 ℃, since DDA-H3PO4 and several other compounds were adsorbed on zinc surface, DDA exhibited powerful corrosion inhibition. The mechanism for corrosion inhibition was discussed by the adsorption theory.
The weight-loss and electrochemical methods were used to investigate the corrosion behavior of metallic zinc in phosphoric acid solutions with or without dodecyl amine(DDA). The corrosion rate expressions were formulated and the corresponding kinetic parameters and thermodynamic constants were calculated. From the results of electron spectroscopy for chemical analysis (XPS), it was found that, over the temperature range of 40～70 ℃, zinc showed od self corrosion inhibition due to the coverage of Zn(OH)x produced. On the other hand, in the temperature range of 30～40 ℃, since DDA-H3PO4 and several other compounds were adsorbed on zinc surface, DDA exhibited powerful corrosion inhibition. The mechanism for corrosion inhibition was discussed by the adsorption theory.
2002, 18(11): 1029-1032
doi: 10.3866/PKU.WHXB20021114
Abstract:
The Ni-W gradient deposit with nanostructure was prepared by controlling the bath temperature and current density. The plating bath contained sodium tungsten, nickel sulfate and citrate, and the preparation was undertaken at various current densities. X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) indicate that crystallite size of the deposit decreases from 10.9nm to 1.5nm and lattice strain increases with the increase of W content in the direction of deposition. The structure of the deposit changes from crystalline to amorphous gradually with associated increase in lattice strain. These show that the deposit is gradient with nanostructure. Furthermore, the strain distribution in the Ni-W gradient deposit studied by the digital-image correlation method can eliminate the mismatch of expansion coefficients at the interface, thus relaxing the thermal stresses of the materials.
The Ni-W gradient deposit with nanostructure was prepared by controlling the bath temperature and current density. The plating bath contained sodium tungsten, nickel sulfate and citrate, and the preparation was undertaken at various current densities. X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) indicate that crystallite size of the deposit decreases from 10.9nm to 1.5nm and lattice strain increases with the increase of W content in the direction of deposition. The structure of the deposit changes from crystalline to amorphous gradually with associated increase in lattice strain. These show that the deposit is gradient with nanostructure. Furthermore, the strain distribution in the Ni-W gradient deposit studied by the digital-image correlation method can eliminate the mismatch of expansion coefficients at the interface, thus relaxing the thermal stresses of the materials.
2002, 18(11): 1033-1037
doi: 10.3866/PKU.WHXB20021115
Abstract:
110 keV Fe＋ ion beams supplied by 200 kV ion injector were implanted into film samples of L(＋)-cysteine hydrochloride monohydrate. The dose was 2.5×1016 ions•cm-2.After the implantation, the film samples were scraped down and simply mixed together in the solid state. The samples before and after ion implantation were tested on FTIR, HPLC and ESI-FTMS spectroscope respectively. The two results of FTIR spectroscopic tests of the ion-implanted samples were different, which showed that radiolysis might have taken place at different sites of the film. But there is certain similarity between the two results in that they both showed the damages of the amino, carboxyl and sulfhydryl groups, and so on, of the original molecules and the formation of new nitro groups. The formation of many new molecules with various molecular weights was determined by HPLC and FTMS analysis and radiolysis of amino acid derivatives induced by the irradiation of 110 keV Fe＋ ion beams was confirmed.
110 keV Fe＋ ion beams supplied by 200 kV ion injector were implanted into film samples of L(＋)-cysteine hydrochloride monohydrate. The dose was 2.5×1016 ions•cm-2.After the implantation, the film samples were scraped down and simply mixed together in the solid state. The samples before and after ion implantation were tested on FTIR, HPLC and ESI-FTMS spectroscope respectively. The two results of FTIR spectroscopic tests of the ion-implanted samples were different, which showed that radiolysis might have taken place at different sites of the film. But there is certain similarity between the two results in that they both showed the damages of the amino, carboxyl and sulfhydryl groups, and so on, of the original molecules and the formation of new nitro groups. The formation of many new molecules with various molecular weights was determined by HPLC and FTMS analysis and radiolysis of amino acid derivatives induced by the irradiation of 110 keV Fe＋ ion beams was confirmed.
2002, 18(11): 1038-1042
doi: 10.3866/PKU.WHXB20021116
Abstract:
Oxidation of Mn(II) to Mn(Ⅲ) and reduction of Mn(Ⅲ) on platinum electrode in sulphuric acid were investigated by cyclic voltammetry as a function of the Mn(II) concentration ,acid concentration, scan rate, temperature and convection. It was found that oxidation of Mn(II) and reduction of Mn(Ⅲ) were mass transfer controlled. High temperature and stirring enhanced the oxidation rate of Mn(II) to Mn(Ⅲ).Increase of acid concentration or Mn(II) concentration favours the stability of Mn(Ⅲ), i.e. inhibits the disproportionation and hydrolysis of Mn(Ⅲ).
Oxidation of Mn(II) to Mn(Ⅲ) and reduction of Mn(Ⅲ) on platinum electrode in sulphuric acid were investigated by cyclic voltammetry as a function of the Mn(II) concentration ,acid concentration, scan rate, temperature and convection. It was found that oxidation of Mn(II) and reduction of Mn(Ⅲ) were mass transfer controlled. High temperature and stirring enhanced the oxidation rate of Mn(II) to Mn(Ⅲ).Increase of acid concentration or Mn(II) concentration favours the stability of Mn(Ⅲ), i.e. inhibits the disproportionation and hydrolysis of Mn(Ⅲ).
2002, 18(11): 1043-1047
doi: 10.3866/PKU.WHXB20021117
Abstract:
Water based gels, comprising Xanthan gum(XC) cross linked with cross linking agent, such as trivalent chromic ions(Cr(Ⅲ)), are now finding widespread use for near well-bore water and gas shut-off in the oil industry. The study on the rheology of gel is very important to understand and to improve the in-situ application of the gels technology. In this paper the viscoelasticity of the systems of XC cross-linked with Cr(Ⅲ) in the presence of dodecyl-oxypropyl-β-hydroxyl-trimethyl-ammonium bromide(C12NBr) has been investigated. The viscoelasticity measurements were performed on a RS 75 controlled stress rheometer(Haake Co.)operating in an oscillating mode. Determination of the G′ and G″ vs shear stress was performed at a fixed frequency of 1.0 Hz and the moduli vs frequency relationsbip were determined at a fixed shear stress of 1 Pa. For the XC aqueous solution, the storage (i.e., elastic) modulus G′ could not be measured under the experimental condition. For the cross linking system G′ value increased it was and always larger than the G″ value at shear stress less than 0.5 Pa, i.e., the gelling system has more solid or elastic properties. The elasticity of gel is weakened and its viscosity is enhanced in the presence of C12NBr. The main effect of the addition of C12NBr to XC gel is to destroy the network structure of the gel. It is resulted from the binding between C12NBr and XC, i.e., cross linking agent Cr(Ⅲ)was replaced by C12N＋. This is testified by binding isotherom of C12NBr on XC.
Water based gels, comprising Xanthan gum(XC) cross linked with cross linking agent, such as trivalent chromic ions(Cr(Ⅲ)), are now finding widespread use for near well-bore water and gas shut-off in the oil industry. The study on the rheology of gel is very important to understand and to improve the in-situ application of the gels technology. In this paper the viscoelasticity of the systems of XC cross-linked with Cr(Ⅲ) in the presence of dodecyl-oxypropyl-β-hydroxyl-trimethyl-ammonium bromide(C12NBr) has been investigated. The viscoelasticity measurements were performed on a RS 75 controlled stress rheometer(Haake Co.)operating in an oscillating mode. Determination of the G′ and G″ vs shear stress was performed at a fixed frequency of 1.0 Hz and the moduli vs frequency relationsbip were determined at a fixed shear stress of 1 Pa. For the XC aqueous solution, the storage (i.e., elastic) modulus G′ could not be measured under the experimental condition. For the cross linking system G′ value increased it was and always larger than the G″ value at shear stress less than 0.5 Pa, i.e., the gelling system has more solid or elastic properties. The elasticity of gel is weakened and its viscosity is enhanced in the presence of C12NBr. The main effect of the addition of C12NBr to XC gel is to destroy the network structure of the gel. It is resulted from the binding between C12NBr and XC, i.e., cross linking agent Cr(Ⅲ)was replaced by C12N＋. This is testified by binding isotherom of C12NBr on XC.
2002, 18(11): 1048-1051
doi: 10.3866/PKU.WHXB20021118
Abstract:
The promotional effects of NOx on the gas-phase oxidation of methane have been studied in the absence of solid catalysts. NOx showed an obvious catalytic activity for the partial oxidation of methane to carbon monoxide, even under strong oxidizing conditions (O2/CH4=5).The addition of 0.005％～0.2％ NO in the CH4-O2 system decreased the reaction temperatures by 200～300 ℃.Formaldehyde and ethylene were also observed in the products, and their relative concentrations were partially controlled by reaction conditions.
The promotional effects of NOx on the gas-phase oxidation of methane have been studied in the absence of solid catalysts. NOx showed an obvious catalytic activity for the partial oxidation of methane to carbon monoxide, even under strong oxidizing conditions (O2/CH4=5).The addition of 0.005％～0.2％ NO in the CH4-O2 system decreased the reaction temperatures by 200～300 ℃.Formaldehyde and ethylene were also observed in the products, and their relative concentrations were partially controlled by reaction conditions.
2002, 18(11): 1052-1056
doi: 10.3866/PKU.WHXB20021119
Abstract:
An empirical solvation model based on atom-weighted accessible surface areas was reported. This solvation model is based on atom-weighted solvent accessible surface area (SAWSA). The parameterization procedure for different kind of atoms was performed as follows: firstly, the atoms in a molecule were defined to different atom types based on SMARTS language; then, solvent accessible surface area for each atom was calculated; finally, a genetic al rithm (GA) was applied to optimize the solvation parameters for different atom types. The SAWSA model was applied to predict the aqueous salvation free energies for 18 proteins. The solvation free energies predicted by the SAWSA model show high linear correlation (r=0.99) with those predicted by PB/SA. The calculated results indicate that the SAWSA model bears significant predicted ability to small organic molecules and proteins.
An empirical solvation model based on atom-weighted accessible surface areas was reported. This solvation model is based on atom-weighted solvent accessible surface area (SAWSA). The parameterization procedure for different kind of atoms was performed as follows: firstly, the atoms in a molecule were defined to different atom types based on SMARTS language; then, solvent accessible surface area for each atom was calculated; finally, a genetic al rithm (GA) was applied to optimize the solvation parameters for different atom types. The SAWSA model was applied to predict the aqueous salvation free energies for 18 proteins. The solvation free energies predicted by the SAWSA model show high linear correlation (r=0.99) with those predicted by PB/SA. The calculated results indicate that the SAWSA model bears significant predicted ability to small organic molecules and proteins.
