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2004 Volume 21 Issue 9
2004, 21(9): 865-871
Abstract:
This paper reviews recent developments of direct methanol fuel cells(DMFC) in China and other countries in following major aspects:catalyst, proton exchange membrane, membrane electrode assembly, cell structure, and cell performance. The problems in these aspects are discussed, and the development trends and applications of DMFC are suggested.
This paper reviews recent developments of direct methanol fuel cells(DMFC) in China and other countries in following major aspects:catalyst, proton exchange membrane, membrane electrode assembly, cell structure, and cell performance. The problems in these aspects are discussed, and the development trends and applications of DMFC are suggested.
2004, 21(9): 872-877
Abstract:
The rencent progress on BN nanotubes is reviewed. Structure features and synthetic technology, especially chemical-synthesis routes and the corresponding growth mechanism, are summarized. BN nanotubes have a uniform electronic band gap of 5.5 eV, which is independent of tube diameter, chirality, or the number of tube walls. This property is different from that of carbon nanotubes. BN nanotubes can be used to fabricate some BN nanocomposites owing to their high chemical stability and thermal resistibility. BN nanotubes are promoted as a promising hydrogen storage material because of their highly porous structure and light mass density. Theoretical research as well as experimental work on lowering the cost, increasing the yield and purity of BN nanotubes and new application development are intensely pursued.
The rencent progress on BN nanotubes is reviewed. Structure features and synthetic technology, especially chemical-synthesis routes and the corresponding growth mechanism, are summarized. BN nanotubes have a uniform electronic band gap of 5.5 eV, which is independent of tube diameter, chirality, or the number of tube walls. This property is different from that of carbon nanotubes. BN nanotubes can be used to fabricate some BN nanocomposites owing to their high chemical stability and thermal resistibility. BN nanotubes are promoted as a promising hydrogen storage material because of their highly porous structure and light mass density. Theoretical research as well as experimental work on lowering the cost, increasing the yield and purity of BN nanotubes and new application development are intensely pursued.
2004, 21(9): 878-883
Abstract:
Three mesoporous silica materials were chemically bonded with β-cyclodextrin(β-CD) using two different methods. The bonding methods were compared by calculating the bonded amount of β-cyclodextrin. The results indicated that larger bonding amount of β-CD could be obtained by first coupling β-CD with KH-560 and then reacting with silica. The resulting materials were characterized by N2 adsorption measurement and the physical and porous parameters were compared before and after bonding. Surface areas and pore diameters of all the materials decrease after bonding. The bonded materials were evaluated as adsorbents for phenols. The ordered mesoporous silica(MS1) with 1.36 μmol/m2 of β-CD bonded showed the largest adsorption capability towards phenols; its adsorption capacity for 2,4-dinitrophenol was found to be 24.81 mg/g. And the pore structure of the mesoporous silicas can affect the adsorption selectivity of the resulting β-CD bonded adsorbents towards the studied phenols.
Three mesoporous silica materials were chemically bonded with β-cyclodextrin(β-CD) using two different methods. The bonding methods were compared by calculating the bonded amount of β-cyclodextrin. The results indicated that larger bonding amount of β-CD could be obtained by first coupling β-CD with KH-560 and then reacting with silica. The resulting materials were characterized by N2 adsorption measurement and the physical and porous parameters were compared before and after bonding. Surface areas and pore diameters of all the materials decrease after bonding. The bonded materials were evaluated as adsorbents for phenols. The ordered mesoporous silica(MS1) with 1.36 μmol/m2 of β-CD bonded showed the largest adsorption capability towards phenols; its adsorption capacity for 2,4-dinitrophenol was found to be 24.81 mg/g. And the pore structure of the mesoporous silicas can affect the adsorption selectivity of the resulting β-CD bonded adsorbents towards the studied phenols.
2004, 21(9): 884-889
Abstract:
A series of porous PNIPAAm-co-PAAc hydrogels were synthesized by radical copolymerization of (N-isopropylacrylamide)(NIPAAm) and acrylic acid(AAc) using silica particles as a porogent. The dynamic swelling kinetics of the hydrogels pretreated in different buffer solutions have been studied. Experimental results revealed that the swelling rate of the porous hydrogels greatly increased in comparison with nonporous hydrogels due to their porous structure. And although the previous treatment did not affect the equilibrium swelling degree of copolymer hydrogels, a strong influence on their dynamic swelling kinetics was still observed especially for the copolymers with composition of NIPAAm between 30% and 70% mole fraction. When subsequently soaked in a neutral solution with pH=7, these copolymer samples exhibited sigmoidal swelling curves by an autoacceleration mechanism. The dynamic swelling of the copolymer and homopolymer hydrogels at pH=7 after soaking in a solution of the same pH can be described by second-order kinetics.
A series of porous PNIPAAm-co-PAAc hydrogels were synthesized by radical copolymerization of (N-isopropylacrylamide)(NIPAAm) and acrylic acid(AAc) using silica particles as a porogent. The dynamic swelling kinetics of the hydrogels pretreated in different buffer solutions have been studied. Experimental results revealed that the swelling rate of the porous hydrogels greatly increased in comparison with nonporous hydrogels due to their porous structure. And although the previous treatment did not affect the equilibrium swelling degree of copolymer hydrogels, a strong influence on their dynamic swelling kinetics was still observed especially for the copolymers with composition of NIPAAm between 30% and 70% mole fraction. When subsequently soaked in a neutral solution with pH=7, these copolymer samples exhibited sigmoidal swelling curves by an autoacceleration mechanism. The dynamic swelling of the copolymer and homopolymer hydrogels at pH=7 after soaking in a solution of the same pH can be described by second-order kinetics.
2004, 21(9): 890-894
Abstract:
Meth acrylate copolymer latexes containing fluorine have been prepared via emulsion copolymerization of methyl methacrylate(MMA), butyl acrylate(BA) and fluorinated monomers, 2,2,2-trifluoroethyl methacrylate(TFEMA) and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate(HFBMA). FT-IR,1H NMR, 13C NMR and 19F NMR results confirmed the incorporation of fluorinated methacrylate units in the copolymers. The effect of amount of TFEMA, solubilization agent β-cyclodextrin, and polymerization conditions on the reaction rate, particle size and size distribution of latex, as well as on the copolymer properties have been investigated. The results indicated that the reaction rate increased with the increase of the reaction temperature in the range of 55 to 65℃. DSC and TGA results showed the reaction temperature hardly affected the copolymer composition. The contact angles of the copolymer films with fluorine were greater than that of the film without any fluorine moiety, suggesting that the fluorine-containing units in the copolymers are in favor of improvement of the film property.
Meth acrylate copolymer latexes containing fluorine have been prepared via emulsion copolymerization of methyl methacrylate(MMA), butyl acrylate(BA) and fluorinated monomers, 2,2,2-trifluoroethyl methacrylate(TFEMA) and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate(HFBMA). FT-IR,1H NMR, 13C NMR and 19F NMR results confirmed the incorporation of fluorinated methacrylate units in the copolymers. The effect of amount of TFEMA, solubilization agent β-cyclodextrin, and polymerization conditions on the reaction rate, particle size and size distribution of latex, as well as on the copolymer properties have been investigated. The results indicated that the reaction rate increased with the increase of the reaction temperature in the range of 55 to 65℃. DSC and TGA results showed the reaction temperature hardly affected the copolymer composition. The contact angles of the copolymer films with fluorine were greater than that of the film without any fluorine moiety, suggesting that the fluorine-containing units in the copolymers are in favor of improvement of the film property.
2004, 21(9): 895-899
Abstract:
The equilibrium solubilities of CsNO3 in CsNO3-C2H5OH-H2O ternary system at -10℃, 10℃, 30℃ and 50℃ have been studied using a self-made microdevice for solubility determination. The density and refractive index of the solutions were also determined. The equilibrium phase diagram is given and indicates that the equilibrium solid phase is CsNO3. The solubility, density and refractive index of the solution were correlated to the alcohol content according to the experimental equation ln Y=A0+A1x+A2x2+A3x3.
The equilibrium solubilities of CsNO3 in CsNO3-C2H5OH-H2O ternary system at -10℃, 10℃, 30℃ and 50℃ have been studied using a self-made microdevice for solubility determination. The density and refractive index of the solutions were also determined. The equilibrium phase diagram is given and indicates that the equilibrium solid phase is CsNO3. The solubility, density and refractive index of the solution were correlated to the alcohol content according to the experimental equation ln Y=A0+A1x+A2x2+A3x3.
2004, 21(9): 900-904
Abstract:
A room temperature ionic liquid of 3-ethyl-1-methyl-imidazolium tetrafluoroborate (EMIBF4) was prepared by microwave synthesis, and characterized by elemental analysis and FTIR spectrometry. The solid poly (vinylidene-co-hexafluoropropylene)(P(VDF-HFP)) electrolyte with EMIBF4 as a plasticizer had a decompostion temperature of up to 273℃. The electrochemical stability of the resulting polymer electrolyte was studied on different current collectors (Ni, Al, Cu) by cyclic voltagrammetry. The ionic conductivity of polymer electrolyte[0.5 g P(VDF-HFP)/0.5 g EMIBF4/0.01 g LiBF4] was investigated by ac impedance measurement, and the activation energy of ions transition was 7.27 kJ/mol as calculated according to Arrhenius equation.
A room temperature ionic liquid of 3-ethyl-1-methyl-imidazolium tetrafluoroborate (EMIBF4) was prepared by microwave synthesis, and characterized by elemental analysis and FTIR spectrometry. The solid poly (vinylidene-co-hexafluoropropylene)(P(VDF-HFP)) electrolyte with EMIBF4 as a plasticizer had a decompostion temperature of up to 273℃. The electrochemical stability of the resulting polymer electrolyte was studied on different current collectors (Ni, Al, Cu) by cyclic voltagrammetry. The ionic conductivity of polymer electrolyte[0.5 g P(VDF-HFP)/0.5 g EMIBF4/0.01 g LiBF4] was investigated by ac impedance measurement, and the activation energy of ions transition was 7.27 kJ/mol as calculated according to Arrhenius equation.
2004, 21(9): 905-909
Abstract:
The cathode materials for a lithium-ion battery LiNi1-xMnxO2 were prepared by a phase transfer method. XRD, SEM, IR, CV and charging-discharging experiments showed that when n(Li):n(Ni):n(Mn) was 1.24:0.9:0.1, and the intermediate gel powders were heated at 400℃ for 2 h, followed by sintering at 720℃ for 24 h, the redox reversibility of the electrode material was significantly improved; its activity was increased with stead working potential and its first discharging capability achieved 161.8 mA·h/g.
The cathode materials for a lithium-ion battery LiNi1-xMnxO2 were prepared by a phase transfer method. XRD, SEM, IR, CV and charging-discharging experiments showed that when n(Li):n(Ni):n(Mn) was 1.24:0.9:0.1, and the intermediate gel powders were heated at 400℃ for 2 h, followed by sintering at 720℃ for 24 h, the redox reversibility of the electrode material was significantly improved; its activity was increased with stead working potential and its first discharging capability achieved 161.8 mA·h/g.
2004, 21(9): 910-913
Abstract:
Hydrophobic nickel-poly tetrafluoroethlyene(Ni-PTFE) composite electrode has been prepared by constant current and cathodic electroplating with nickel as substrate in a PTFE suspension. The Ni-PTFE electrode was used for electrooxidation of lactic acid to pyruvic acid. The electrochemical characterizations such as polarization curve, cyclic voltammogram and electrode stability have been carried out. The current efficiency of electrooxidation of the electrode with 6.7% mass fraction PTFE coating was 34% and the conversion ratio of electrooxidation of lactic acid was 72%.
Hydrophobic nickel-poly tetrafluoroethlyene(Ni-PTFE) composite electrode has been prepared by constant current and cathodic electroplating with nickel as substrate in a PTFE suspension. The Ni-PTFE electrode was used for electrooxidation of lactic acid to pyruvic acid. The electrochemical characterizations such as polarization curve, cyclic voltammogram and electrode stability have been carried out. The current efficiency of electrooxidation of the electrode with 6.7% mass fraction PTFE coating was 34% and the conversion ratio of electrooxidation of lactic acid was 72%.
2004, 21(9): 914-917
Abstract:
Free-radical dual grafting of maleic anhydride(MAH) and styrene(St) onto granular polypropylene(PP) using supercritical CO2 as a solvent and swelling agent has been studied and PP-g-(MAH-St) prepared. The effect of molar ratio of monomers, swelling temperature and time, reaction time and pressure on the grafting density are discussed. It is found that the St as a co-monomer in the grafting reaction system could significantly enhance the grafting density of PP for MAH and St on PP. The maximum grafting density for PP-g-(MAH-St) in supercritical CO2 fluid under optimal reaction conditions was 10.58%, two times that for PP-g-MAH. The process is simpler than regular graft polymerization processes. The structures and properties of the graft copolymers were characterized by FTIR and DSC. The results indicate that styrene branch chains reduces the Tm of PP from 158℃ to 154℃.
Free-radical dual grafting of maleic anhydride(MAH) and styrene(St) onto granular polypropylene(PP) using supercritical CO2 as a solvent and swelling agent has been studied and PP-g-(MAH-St) prepared. The effect of molar ratio of monomers, swelling temperature and time, reaction time and pressure on the grafting density are discussed. It is found that the St as a co-monomer in the grafting reaction system could significantly enhance the grafting density of PP for MAH and St on PP. The maximum grafting density for PP-g-(MAH-St) in supercritical CO2 fluid under optimal reaction conditions was 10.58%, two times that for PP-g-MAH. The process is simpler than regular graft polymerization processes. The structures and properties of the graft copolymers were characterized by FTIR and DSC. The results indicate that styrene branch chains reduces the Tm of PP from 158℃ to 154℃.
2004, 21(9): 918-922
Abstract:
A silicone modified polyurethane-acrylate(Si-PUA) prepolymer was prepared from 2-hydroxyethyl methacrylate, isophorone diisocyanate, and bis[3-(triethoxysilyl)propyl]amine. The Si-PUA prepolymer exhibits the behavior of Bingham fluids. The polydispersity of the prepolymer was 1.12 by GPC. The curing behavior of the Si-PUA prepolymer was investigated by FTIR and photo-DSC(DPC), tne it was found that the conversion of acrylate double bonds was 56.3% under ultraviolet irradation. The properties of the UV-cured and moisture-cured films were studied by TG and other measurements, and it was found that the UV-cured films were superior to the moisture-cured ones in electrical, physical properties and thermal stability.
A silicone modified polyurethane-acrylate(Si-PUA) prepolymer was prepared from 2-hydroxyethyl methacrylate, isophorone diisocyanate, and bis[3-(triethoxysilyl)propyl]amine. The Si-PUA prepolymer exhibits the behavior of Bingham fluids. The polydispersity of the prepolymer was 1.12 by GPC. The curing behavior of the Si-PUA prepolymer was investigated by FTIR and photo-DSC(DPC), tne it was found that the conversion of acrylate double bonds was 56.3% under ultraviolet irradation. The properties of the UV-cured and moisture-cured films were studied by TG and other measurements, and it was found that the UV-cured films were superior to the moisture-cured ones in electrical, physical properties and thermal stability.
2004, 21(9): 923-927
Abstract:
Non-homogenous condensation of alkylferrocenes with acetone has been carried out in the presence of methyl alcohol and concentrated sulfurric acid. Two series of compounds, 2,2-bis(monoalkylferrocenyl)propanes and 2,2-bis(dialkylferrocenyl)propanes were isolated by column chromatography. It was found the optimal conditions were n(alkylferrocene):n(acetone):n(concentrated sulfuric acid):n(methyl (alcohol)=)1:0.55:2:6.7, reaction time 4~6 h, and reaction temperature 80~90℃. The structures of these compounds were characterized by elemental analysis, IR, and 1H NMR. The electrochemical properties of these compounds were investigated by cyclic voltammetry. The results indicated that the burning-rate catalytic efficiency of the title compounds showed a slow decrease with the increase of the alkyl chain length, and for the alkyl group with same carbon number, the more alkyl groups the stronger the electron repulsion and reducibility, and hense the higher the burning-rate catalytic activity. The effect of the structures, electrochemical properties, and catalytic activity on the burning-rate were also discussed.
Non-homogenous condensation of alkylferrocenes with acetone has been carried out in the presence of methyl alcohol and concentrated sulfurric acid. Two series of compounds, 2,2-bis(monoalkylferrocenyl)propanes and 2,2-bis(dialkylferrocenyl)propanes were isolated by column chromatography. It was found the optimal conditions were n(alkylferrocene):n(acetone):n(concentrated sulfuric acid):n(methyl (alcohol)=)1:0.55:2:6.7, reaction time 4~6 h, and reaction temperature 80~90℃. The structures of these compounds were characterized by elemental analysis, IR, and 1H NMR. The electrochemical properties of these compounds were investigated by cyclic voltammetry. The results indicated that the burning-rate catalytic efficiency of the title compounds showed a slow decrease with the increase of the alkyl chain length, and for the alkyl group with same carbon number, the more alkyl groups the stronger the electron repulsion and reducibility, and hense the higher the burning-rate catalytic activity. The effect of the structures, electrochemical properties, and catalytic activity on the burning-rate were also discussed.
2004, 21(9): 928-931
Abstract:
Chemical groups (-COOH, -OH) on carbon fiber surface were transformed into CF-COCl, which was used as an effective activating group for graft polymerization of MC nylon 6 onto carbon fiber surface. The morphology of the graft nylon 6 on carbon fiber surface was characterized by SEM. The XPS results showed that the grafted carbon fiber has a higher N/C ratio from 0.030 to 0.061 on its surface. The grafting degree was above 2.1%. Grafting of nylon 6 improved the interface interaction between carbon fiber and nylon 6 matrix and increased the ILSS of CF/PA6 composites by 14%.
Chemical groups (-COOH, -OH) on carbon fiber surface were transformed into CF-COCl, which was used as an effective activating group for graft polymerization of MC nylon 6 onto carbon fiber surface. The morphology of the graft nylon 6 on carbon fiber surface was characterized by SEM. The XPS results showed that the grafted carbon fiber has a higher N/C ratio from 0.030 to 0.061 on its surface. The grafting degree was above 2.1%. Grafting of nylon 6 improved the interface interaction between carbon fiber and nylon 6 matrix and increased the ILSS of CF/PA6 composites by 14%.
2004, 21(9): 932-936
Abstract:
The isothermal crystallization behavior and melting characteristics of CF/PA6 composites have been studied by DSC. The results show that the ungrafted carbon fiber in CF/PA6 composites played the role of nucleating agent, which enhances the crystallization rate and increase the apparent crystallization degree of PA6. The grafting CF improved the interface adhesion between PA6 and CF, which prohibits the movement of PA6 molecule thus leading to reduce the crystallization rate and the apparent crystallization degree of PA6. The interphase chemistry property of grafting CF/PA6 composites was similar due to grafting, thus the inducing transcrystallization ability of grafting CF was improved. At lower crystallization temperature, ungrafted CF induces PA6 matrix to form α crystal and inhibits the form of γ crystal, grafting CF enhances the interface interaction between CF and PA6, thus prohibits PA6 from forming stable crystal and produces metastable γ* crystal.At higher crystallization temperature, the induction effect of ungrafted CF declined, and PA6 matrix intended to form γ crystal as the pure PA6, but grafting CF urges PA6 to form metastable γ* crystal as it did at lower crystallization temperature.
The isothermal crystallization behavior and melting characteristics of CF/PA6 composites have been studied by DSC. The results show that the ungrafted carbon fiber in CF/PA6 composites played the role of nucleating agent, which enhances the crystallization rate and increase the apparent crystallization degree of PA6. The grafting CF improved the interface adhesion between PA6 and CF, which prohibits the movement of PA6 molecule thus leading to reduce the crystallization rate and the apparent crystallization degree of PA6. The interphase chemistry property of grafting CF/PA6 composites was similar due to grafting, thus the inducing transcrystallization ability of grafting CF was improved. At lower crystallization temperature, ungrafted CF induces PA6 matrix to form α crystal and inhibits the form of γ crystal, grafting CF enhances the interface interaction between CF and PA6, thus prohibits PA6 from forming stable crystal and produces metastable γ* crystal.At higher crystallization temperature, the induction effect of ungrafted CF declined, and PA6 matrix intended to form γ crystal as the pure PA6, but grafting CF urges PA6 to form metastable γ* crystal as it did at lower crystallization temperature.
2004, 21(9): 937-941
Abstract:
A derivative constant-energy synchronous fluorescence spectroscopy for rapid and simultaneous analysis of four polynuclear aromatic hydrocarbons(PAHs):2,3-benzofluorene, benzo[α]pyrene, 3,4,8,9-dibenzopyrene and 2,3-benzoanthracene has been developed. Only a single scan is needed for the simultaneous identification and quantitative determination of above-mentioned PAHs. The detection limit for 2,3-benzofluorene, benzo[α]pyrene, 3,4,8,9-dibenzopyrene and 2,3-benzoanthracene is 0.22×10-9, 0.52×10-9, 0.46×10-9 and 0.24×10-9 g/mL, respectively. By using this method, the four PAHs in real samples were determined directly and with good results. The recovery of PAHs in tap water, seawater and airborne particulates was 87%~99.5%, 88%~101% and 84%~105% respectively.
A derivative constant-energy synchronous fluorescence spectroscopy for rapid and simultaneous analysis of four polynuclear aromatic hydrocarbons(PAHs):2,3-benzofluorene, benzo[α]pyrene, 3,4,8,9-dibenzopyrene and 2,3-benzoanthracene has been developed. Only a single scan is needed for the simultaneous identification and quantitative determination of above-mentioned PAHs. The detection limit for 2,3-benzofluorene, benzo[α]pyrene, 3,4,8,9-dibenzopyrene and 2,3-benzoanthracene is 0.22×10-9, 0.52×10-9, 0.46×10-9 and 0.24×10-9 g/mL, respectively. By using this method, the four PAHs in real samples were determined directly and with good results. The recovery of PAHs in tap water, seawater and airborne particulates was 87%~99.5%, 88%~101% and 84%~105% respectively.
2004, 21(9): 942-945
Abstract:
The silicon-substituted polysilane(SPS) as a novel class of polysilane was prepared by polymer reaction of polymethylsilane(PMS) with substitution degree being 43% and characterized by FT-IR,1H NMR,29Si CP MAS-NMR, UV and GPC techniques. The polymer is soluble in common organic solvents, and its molecular weight could be increased by crosslinking reaction.
The silicon-substituted polysilane(SPS) as a novel class of polysilane was prepared by polymer reaction of polymethylsilane(PMS) with substitution degree being 43% and characterized by FT-IR,1H NMR,29Si CP MAS-NMR, UV and GPC techniques. The polymer is soluble in common organic solvents, and its molecular weight could be increased by crosslinking reaction.
2004, 21(9): 946-949
Abstract:
The highly ordered mesoporous silica with hexagonal symmetry was synthesized by using an oligomeric surfactant as template under neutral condition. The effect of different molar ratio of surfactant to silicate on the surface structure of the product was studied by small-angle X-ray diffractometry. The results showed that the structure of the resulting product has hexagonal symmetry and the ordering of pore structure increased with the improving of the molar ratio of surfactant to silica. When the molar ratio of surfactant to silica was more than 35, product with high quality could be obtained. The ordering of pore structure was the highest at 1:8 of the ratio of surfactant to silica. Nitrogen adsorption-desorption test indicated that the BET surface and total pore volume of the product increased rapidly with the increase in the molar ratio of surfactant to silica and the type of N2 adsorption isotherm transformed from Ⅱ to Ⅳ at n(surf):n(Si)=1:35. The molar ratio of surfactant to silica hardly showed effect on the most probable pore size and pore wall thickness which was found to be 3.74~3.76 nm and 0.54~0.69 nm, respectively.
The highly ordered mesoporous silica with hexagonal symmetry was synthesized by using an oligomeric surfactant as template under neutral condition. The effect of different molar ratio of surfactant to silicate on the surface structure of the product was studied by small-angle X-ray diffractometry. The results showed that the structure of the resulting product has hexagonal symmetry and the ordering of pore structure increased with the improving of the molar ratio of surfactant to silica. When the molar ratio of surfactant to silica was more than 35, product with high quality could be obtained. The ordering of pore structure was the highest at 1:8 of the ratio of surfactant to silica. Nitrogen adsorption-desorption test indicated that the BET surface and total pore volume of the product increased rapidly with the increase in the molar ratio of surfactant to silica and the type of N2 adsorption isotherm transformed from Ⅱ to Ⅳ at n(surf):n(Si)=1:35. The molar ratio of surfactant to silica hardly showed effect on the most probable pore size and pore wall thickness which was found to be 3.74~3.76 nm and 0.54~0.69 nm, respectively.
2004, 21(9): 950-953
Abstract:
The factors affecting the electrochemical behavior of the 1,4-dihydropyridine group in the 1,4-(dihydropyridine) derivatives were studied by cyclic voltammetry. The results indicated that the dipole moment of the organic solvent showed the largest effect on the electrochemical behavior of the 1,4-dihydropyridine group; the water content in the organic solvent has large effect, and the substituent on the 1,4-dihydropyridine group would influence the electrochemical behavior in a certain extent.
The factors affecting the electrochemical behavior of the 1,4-dihydropyridine group in the 1,4-(dihydropyridine) derivatives were studied by cyclic voltammetry. The results indicated that the dipole moment of the organic solvent showed the largest effect on the electrochemical behavior of the 1,4-dihydropyridine group; the water content in the organic solvent has large effect, and the substituent on the 1,4-dihydropyridine group would influence the electrochemical behavior in a certain extent.
2004, 21(9): 954-957
Abstract:
Highly branched polyesters with linear structure were synthesized from trimellitic anhydride(TMA), epichlorohydrin(ECH), methyl tetrahydrophenyl anhydride(MTHPA) and ethanol. The structure and properties of the polyesters were characterized by1H NMR, FTIR, GPC, rotating viscometery and DSC. The apparent molecular weights of polyesters were in the range of 2 000~3 500 g/mol, depending on the ratio and feeding manners of monomers. The glass transition temperatures of the polyesters were decreased after introduction of MTHPA and ethanol as the linear unit sources.
Highly branched polyesters with linear structure were synthesized from trimellitic anhydride(TMA), epichlorohydrin(ECH), methyl tetrahydrophenyl anhydride(MTHPA) and ethanol. The structure and properties of the polyesters were characterized by1H NMR, FTIR, GPC, rotating viscometery and DSC. The apparent molecular weights of polyesters were in the range of 2 000~3 500 g/mol, depending on the ratio and feeding manners of monomers. The glass transition temperatures of the polyesters were decreased after introduction of MTHPA and ethanol as the linear unit sources.
2004, 21(9): 958-961
Abstract:
The nanometer γ-Al2O3 powders were prepared by a Sol-Gel method and characterized by TEM, XRD, BET and Zeta potential measurements. The diameters of the powders were ranged in 30 nm to 70 nm. The results showed that the powders have strong adsorption capacity towards Pb(Ⅱ), Cd (Ⅱ) and Cr(Ⅵ) ions at a pH value of medium ranging from 6.0 to 7.0. The adsorption isotherms of metal ions on the powders fit Freundlich adsorption equation. The adsorbed metal ions on the powders could be desorbed in 0.1 mol/L HCl solution and the powder could be regenerated and used without loss of its adsorbability.
The nanometer γ-Al2O3 powders were prepared by a Sol-Gel method and characterized by TEM, XRD, BET and Zeta potential measurements. The diameters of the powders were ranged in 30 nm to 70 nm. The results showed that the powders have strong adsorption capacity towards Pb(Ⅱ), Cd (Ⅱ) and Cr(Ⅵ) ions at a pH value of medium ranging from 6.0 to 7.0. The adsorption isotherms of metal ions on the powders fit Freundlich adsorption equation. The adsorbed metal ions on the powders could be desorbed in 0.1 mol/L HCl solution and the powder could be regenerated and used without loss of its adsorbability.
2004, 21(9): 962-965
Abstract:
The structural and morphological investigations of the products PbCO3 by common preparation method showed that the PbCO3 crystal grows very quickly and nanometer PbCO3 could hardly be obtained. The nanometer PbCO3 was synthesized by mixed Pb(CH3COO)2·3H2O and Na2CO3 in 8 000 r/min quick mixing equipment. The influences of material and concentration of reactant on the preparation of nanometer PbCO3 were discussed. The nanoparticles as prepared showed narrow size distribution and the particle sizes of PbCO3 were about 10~30 nm when Pb(NO3)2 was replaced by Pb(CH3COO)2·3H2O as raw material, and the particle sizes of PbCO3 decreased with increasing the concentration of Pb(CH3COO)2·3H2O.
The structural and morphological investigations of the products PbCO3 by common preparation method showed that the PbCO3 crystal grows very quickly and nanometer PbCO3 could hardly be obtained. The nanometer PbCO3 was synthesized by mixed Pb(CH3COO)2·3H2O and Na2CO3 in 8 000 r/min quick mixing equipment. The influences of material and concentration of reactant on the preparation of nanometer PbCO3 were discussed. The nanoparticles as prepared showed narrow size distribution and the particle sizes of PbCO3 were about 10~30 nm when Pb(NO3)2 was replaced by Pb(CH3COO)2·3H2O as raw material, and the particle sizes of PbCO3 decreased with increasing the concentration of Pb(CH3COO)2·3H2O.
2004, 21(9): 966-968
Abstract:
The optimium value of Δν=-1 400 cm-1(Δν=1/λEx-1/λEm) for constant-energy synchronous fluorescence spectrometry was obtained by a series experiments of crude oil, crushed well-rock sand. Based on studying characteristics of constant-energy synchronous fluorescence spectra of various kinds of crude oils and natural gas from large oil fields in our country, the characteristic peak of typical crude oils were proposed. The main emission peak of condensation gas, light oil and dense oil was found at 276 nm, 300 nm and 330 nm respectively.
The optimium value of Δν=-1 400 cm-1(Δν=1/λEx-1/λEm) for constant-energy synchronous fluorescence spectrometry was obtained by a series experiments of crude oil, crushed well-rock sand. Based on studying characteristics of constant-energy synchronous fluorescence spectra of various kinds of crude oils and natural gas from large oil fields in our country, the characteristic peak of typical crude oils were proposed. The main emission peak of condensation gas, light oil and dense oil was found at 276 nm, 300 nm and 330 nm respectively.
2004, 21(9): 969-970
Abstract:
Polyaspartic acid(PASP) was synthesized by polycondensate of L-aspartic acid using H3PO4 as a catalyst. The corrosion inhibition performance of PASP on carbon steel was studied by a rotating hanging slice method. The results showed that the corrosion inhibitory efficiency rose with the increasing of the concentration of PASP. It also indicated that the highest corrosion inhibitory efficiency reached 93% when the concentration of PASP was 100 mg/L. The strong adsorption signal of PASP on the carbon steel surfaces was detected by surface-enhanced Raman scattering(SERS) technique. The results suggested that the high corrosion inhibitory efficiency appeared owing to the chemical adsorption of carboxyl groups in PASP on steel surface.
Polyaspartic acid(PASP) was synthesized by polycondensate of L-aspartic acid using H3PO4 as a catalyst. The corrosion inhibition performance of PASP on carbon steel was studied by a rotating hanging slice method. The results showed that the corrosion inhibitory efficiency rose with the increasing of the concentration of PASP. It also indicated that the highest corrosion inhibitory efficiency reached 93% when the concentration of PASP was 100 mg/L. The strong adsorption signal of PASP on the carbon steel surfaces was detected by surface-enhanced Raman scattering(SERS) technique. The results suggested that the high corrosion inhibitory efficiency appeared owing to the chemical adsorption of carboxyl groups in PASP on steel surface.
2004, 21(9): 971-972
Abstract:
The isomeric mixtures containing trans and cis forms of 4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (3HHA) was produced by hydrogenation of 4-(trans-4'-propylcyclohexyl) benzoic acid (3HPA) at 105℃ and 5 MPa using ruthenium/carbon as catalysts.The isomerization reaction was performed in the absence of solvent at 200℃ when the molar ratio of potassium hydroxide catalyst to 3HHA was 2.0 to 1.0.The product in a mass ratio of trans-4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (trans-3HHA) to cis-4-4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (cis-3HHA) of 98:2 was obtained.
The isomeric mixtures containing trans and cis forms of 4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (3HHA) was produced by hydrogenation of 4-(trans-4'-propylcyclohexyl) benzoic acid (3HPA) at 105℃ and 5 MPa using ruthenium/carbon as catalysts.The isomerization reaction was performed in the absence of solvent at 200℃ when the molar ratio of potassium hydroxide catalyst to 3HHA was 2.0 to 1.0.The product in a mass ratio of trans-4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (trans-3HHA) to cis-4-4-(trans-4'-propylcyclohexyl) cyclohexylcarboxylic acid (cis-3HHA) of 98:2 was obtained.
