An expanding human population and technological progress demand clean and effective energy-storing systems.Within the realm of energy-storing devices,supercapacitors(SCs)have grabbed huge focus owing to their high-pow...An expanding human population and technological progress demand clean and effective energy-storing systems.Within the realm of energy-storing devices,supercapacitors(SCs)have grabbed huge focus owing to their high-power density,unique cycling stability,and fast charging discharging capabilities.Electrode material has a prominent impact on the effectiveness of SCs.Several types of electrode materials have been used,encompassing varied metal oxides,activated carbon,conducting polymers,and MOFs.Metal organic frameworks(MOFs)are considered emerging electrode candidates,which could be ascribed to the tunable porosity,large surface areas,and designed morphology.This review shows a detailed analysis of various mono-,bi-,and tri-metallic MOFs along with derivatives in SC applications,their structural characteristics,and synthetic strategies.It also critically evaluates MOFs potential to boost the SC's energy density,power density,stability,and conductivity.Also,it underscores their significance in the establishment of future-oriented energy storage applications.展开更多
A highly branched polycarbosilane bearing allyl groups has been prepared by a one-pot synthesis with chloromethyltrichlorosilane, chloromethylmethyldichlorosilane and allyl chloride as the starting materials. The resu...A highly branched polycarbosilane bearing allyl groups has been prepared by a one-pot synthesis with chloromethyltrichlorosilane, chloromethylmethyldichlorosilane and allyl chloride as the starting materials. The resultant polymer, with the approximate formula [SiH1.2(CH3)0.71(CH2CHCH2)0.09CH2]n, has been characterized by 1H, 13C, and 29Si NMR, GPC, TG and elemental analysis. It could be cross-linked thermally at 170 °C in the absence of oxygen. Pyrolysis of the polymer gave a ceramic with a yield of about 70%.展开更多
High temperature deformation characteristics of a semiaustenitic grade of precipitation-hardening stain- less steels were investigated by conducting hot compression tests at temperatures of 900--1 100 ℃ and strain ra...High temperature deformation characteristics of a semiaustenitic grade of precipitation-hardening stain- less steels were investigated by conducting hot compression tests at temperatures of 900--1 100 ℃ and strain rates of 0. 001--1 s^-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization （DRX） was responsible for flow softening. The correlation between critical strain for initiation of DRX and de- formation parameters including temperature and strain rate, and therefore, Zener-Hollomon parameter （Z） was studied. Metallographic observation was performed to determine the as-deformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed.展开更多
Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good print...Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good printability with various SLM parameters and the as-built HEA samples achieve a reliable forming quality.Despite the slight evaporation of Mn,energy dispersive spectrometer mapping and Xray diffraction results show that the as-built HEA has a homogeneous chemical distribution and presents a single face-centred-cubic(fcc)phase,indicating successful in-situ alloying.The study has verified the feasibility of using blended powder to prepare high-quality HEA by SLM.展开更多
The effect of vanadium （V） addition on the mechanical properties of a Cr-Ni-Mo-Cu-Ti stainless steel was studied and its influence on microstructural changes was also investigated. Results indicate that the structur...The effect of vanadium （V） addition on the mechanical properties of a Cr-Ni-Mo-Cu-Ti stainless steel was studied and its influence on microstructural changes was also investigated. Results indicate that the structure of the solution-treated specimens mainly comprises of austenite-martensite, and adding V leads to the formation of a consid erable amount of ferrite. Under this condition, austenite phase is not mechanically stable, and transforms to martensite by plastic deformation. The addition of 0.5% - 1.0% （in mass percent） of V increases the hardness and the strength of the 80% cold rolled and aged steel, without any effect on ductility. Improvement in mechanical properties is presumably attributed to the formation of a small amount of ferrite in the primary structure, and the formation of certain precipitates is accelerated by the addition of V during aging. By contrast, excessive V decreases the strength and ductility simultaneously. This is due to the strong effect of ferrite formation compared to the beneficial effect of precipitation. The loss of ductility caused by adding higher amount of V is due to the formation of ferrite phases which in turn are suitable nucleation sites for crack propagation.展开更多
MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were in...MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.展开更多
Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds sta...Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure （R3c space group） and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies （A1） and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field （M-H） shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO6 envi- ronment due to shift in the 6Alg→4T2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.展开更多
In the present work, selective methanation of carbon monoxide in hydrogen rich stream was investigated over Ni/CeO2 nanocatalysts. The obtained results revealed that increasing in nickel loading decreased the BET surf...In the present work, selective methanation of carbon monoxide in hydrogen rich stream was investigated over Ni/CeO2 nanocatalysts. The obtained results revealed that increasing in nickel loading decreased the BET surface area, pore vohune and nickel dispersion. The 25%Ni/CeO2 with a NiO crystal size of 12 nm exhibited the highest activity in CO methanation reaction and reached to maximum CO conversion and CH4 selectivity at temperatures above 230 ℃. The catalytic results revealed that CO selective methanation well progressed at lower temperatures while CO2 methanation was completely suppressed until CO conversion reached to maximum value.展开更多
Ultra-high strength Al alloy system was developed by cryorolling and the contribution of various strengthening mechanisms to the overall yield strength of the system was evaluated. Cryorolling of Al-4%Cu-3%TiB2 in sit...Ultra-high strength Al alloy system was developed by cryorolling and the contribution of various strengthening mechanisms to the overall yield strength of the system was evaluated. Cryorolling of Al-4%Cu-3%TiB2 in situ composite followed by short annealing at 175 ℃ and ageing at 125℃ resulted in an ultra-high yield strength of about 800 MPa with 9%total elongation. The strengthening contributions form solid solution strengthening, grain refinement, dislocation strengthening, precipitation hardening and dispersion strengthening were evaluated using standard equations. It was estimated that the maximum contribution was from grain refinement due to cryorolling followed by precipitation and dispersion strengthening.展开更多
Mesoporous CuFe2O4 solid solution nanopowders with high specific surface areas were synthesized by a novel, very simple and inexpensive sol-gel route using propylene oxide as gelation agent, and used as the catalyst i...Mesoporous CuFe2O4 solid solution nanopowders with high specific surface areas were synthesized by a novel, very simple and inexpensive sol-gel route using propylene oxide as gelation agent, and used as the catalyst in low temperature CO oxidation. The samples were characterized by X-ray diffraction, N2 adsorption-desorption, thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and temperature-programmed reduction. The results revealed that the samples have a nanocrystalline structure with crystals in the range of 10 to 25 nm, and that all the catalysts have mesoporous pores. The addition of Cu into iron oxide affected its structural and catalytic properties. The sample containing 15 mol% Cu showed the highest specific surface area and catalytic activity, and showed high catalytic stability in low temperature CO oxidation.展开更多
Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly ...Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8＋δ （Bi2212） and YBa2Cu3O7-x （YBCO） along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the （100） plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a （110） surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.展开更多
Thermodynamic analysis was applied to study combined partial oxidation and carbon dioxide reforming of methane in view of carbon formation. The equilibrium calculations employing the Gibbs energy minimization were per...Thermodynamic analysis was applied to study combined partial oxidation and carbon dioxide reforming of methane in view of carbon formation. The equilibrium calculations employing the Gibbs energy minimization were performed upon wide ranges of pressure （1-25 atm）, temperature （600-1300 K）, carbon dioxide to methane ratio （0-2） and oxygen to methane ratio （0-1）. The thermodynamic results were compared with the results obtained over a Ru supported catalyst. The results revealed that by increasing the reaction pressure methane conversion decreased. Also it was found that the atmospheric pressure is the preferable pressure for both dry reforming and partial oxidation of methane and increasing the temperature caused increases in both activity of carbon and conversion of methane. The results clearly showed that the addition of O2 to the feed mixture could lead to a reduction of carbon deposition.展开更多
A series of nanocrystalline γ-alumina are synthesized by different procedures, namely, thermal decomposition method （sample A）, precipita-tion method （sample B） and sol-gel method using sucrose and hexadecyltrime...A series of nanocrystalline γ-alumina are synthesized by different procedures, namely, thermal decomposition method （sample A）, precipita-tion method （sample B） and sol-gel method using sucrose and hexadecyltrimethyl ammonium bromide （CTAB） as templates （samples C and D, respectively）. Textural and acidic properties of γ-alumina samples are characterized by XRD, N2 adsorption-desorption and NH3-TPD techniques. Vapor-phase dehydration of methanol into dimethyl ether is carried out over these samples. Among them, sample C shows the highest catalytic activity. NH3-TPD analysis reveals that the sample with smaller crystallite size possesses higher concentration of medium acidic sites and consequently higher catalytic activity. Thermal decomposition method leads to decrease in both surface area and moderate acidity, therefore it is the cause of lower catalytic activity.展开更多
The hydrothermal aging of poly（ethylene terephthalate） （PET） was investigated at 70-95 ℃. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy （FTIR） was proposed....The hydrothermal aging of poly（ethylene terephthalate） （PET） was investigated at 70-95 ℃. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy （FTIR） was proposed. The spectra during the hydrothermal aging were measured using attenuated total reflection accessory （ATR）. Peak resolving of carbonyl regions was performed, and the ratio of two groups of bands representing carboxylic acids and esters respectively were calculated to show the hydrolysis degree of ester groups in PET. The acid/ester ratio shows exactly the same trend as the average chain scission number per unit mass at various temperatures and thus can be used as a parameter to characterize the hydrolysis and random chain scission of PET. This method related to the hydrolysis mechanism directly, is simple, fast and convenient compared to the traditional methods such as viscometry, end-group titration and size exclusion chromatography （SEC）. It may also be useful in hydrolysis characterization of other polyesters.展开更多
In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesiz...In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption, H2 chemisorption, temperature-programmed reduction （TPR）, temperature-programmed oxidation （TPO）, temperature- programmed desorption （TPD） and transmission and scanning electron microscopies （TEM, SEM） techniques. The obtained results showed that the catalyst support has a nanocrystalline structure （crystal size： about 5 nm） with a high specific surface area （175 m2 g-1） and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.展开更多
The role of water in CO oxidation was investigated on Pd/CeO2 with different morphologies(rods(R),cubes(C)and octahedrons(O)).Compared with the absence of water,CO oxidation activity increases 2 times in the presence ...The role of water in CO oxidation was investigated on Pd/CeO2 with different morphologies(rods(R),cubes(C)and octahedrons(O)).Compared with the absence of water,CO oxidation activity increases 2 times in the presence of water on Pd/CeO2-C;but a decrease is found on Pd/CeO2-R.Catalyst characterization reveals that Pd is mainly in the form of solid solution(PdxCe1-xO2-σ)on Pd/CeO2-R and a mixture of metal and PdxCe1-xO2-σsolid solution on Pd/CeO2-C.The strong interaction between Pd and CeO2-R results in the form of stable bidentate carbonates species;while the relatively weak interaction between Pd and CeO2-C leads to the produce of unstable monodentate carbonates species.The effects of water on CO oxidation activity closely relate with the Pd chemical state and the types of carbonates species.Water restrains CO adsorption on PdxCe1-xO2-σsolid solution,but it has negligent effects on metallic Pd species.In the presence of water,bidentate carbonates species remains stable but the decrease in the amount of monodentate carbonates species is observed.展开更多
文摘An expanding human population and technological progress demand clean and effective energy-storing systems.Within the realm of energy-storing devices,supercapacitors(SCs)have grabbed huge focus owing to their high-power density,unique cycling stability,and fast charging discharging capabilities.Electrode material has a prominent impact on the effectiveness of SCs.Several types of electrode materials have been used,encompassing varied metal oxides,activated carbon,conducting polymers,and MOFs.Metal organic frameworks(MOFs)are considered emerging electrode candidates,which could be ascribed to the tunable porosity,large surface areas,and designed morphology.This review shows a detailed analysis of various mono-,bi-,and tri-metallic MOFs along with derivatives in SC applications,their structural characteristics,and synthetic strategies.It also critically evaluates MOFs potential to boost the SC's energy density,power density,stability,and conductivity.Also,it underscores their significance in the establishment of future-oriented energy storage applications.
文摘A highly branched polycarbosilane bearing allyl groups has been prepared by a one-pot synthesis with chloromethyltrichlorosilane, chloromethylmethyldichlorosilane and allyl chloride as the starting materials. The resultant polymer, with the approximate formula [SiH1.2(CH3)0.71(CH2CHCH2)0.09CH2]n, has been characterized by 1H, 13C, and 29Si NMR, GPC, TG and elemental analysis. It could be cross-linked thermally at 170 °C in the absence of oxygen. Pyrolysis of the polymer gave a ceramic with a yield of about 70%.
文摘High temperature deformation characteristics of a semiaustenitic grade of precipitation-hardening stain- less steels were investigated by conducting hot compression tests at temperatures of 900--1 100 ℃ and strain rates of 0. 001--1 s^-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization （DRX） was responsible for flow softening. The correlation between critical strain for initiation of DRX and de- formation parameters including temperature and strain rate, and therefore, Zener-Hollomon parameter （Z） was studied. Metallographic observation was performed to determine the as-deformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed.
基金supported financially by the Shenzhen ScienceandTechnologyInnovationCommission(Nos.ZDSYS201703031748354 and JCYJ20170817110358927)the Science and Technology Planning Project of Guangdong Province of China(No.2017B090911003)the Natural Science Foundation of Guangdong Province(No.2016A030313756)。
文摘Quasi-equiatomic Co Cr Fe Mn Ni high entropy alloy(HEA)has been in-situ alloyed by selective laser melting(SLM)from a blend of Co Cr Fe Ni pre-alloyed powder and Mn elemental powder.The blended powder shows good printability with various SLM parameters and the as-built HEA samples achieve a reliable forming quality.Despite the slight evaporation of Mn,energy dispersive spectrometer mapping and Xray diffraction results show that the as-built HEA has a homogeneous chemical distribution and presents a single face-centred-cubic(fcc)phase,indicating successful in-situ alloying.The study has verified the feasibility of using blended powder to prepare high-quality HEA by SLM.
文摘The effect of vanadium （V） addition on the mechanical properties of a Cr-Ni-Mo-Cu-Ti stainless steel was studied and its influence on microstructural changes was also investigated. Results indicate that the structure of the solution-treated specimens mainly comprises of austenite-martensite, and adding V leads to the formation of a consid erable amount of ferrite. Under this condition, austenite phase is not mechanically stable, and transforms to martensite by plastic deformation. The addition of 0.5% - 1.0% （in mass percent） of V increases the hardness and the strength of the 80% cold rolled and aged steel, without any effect on ductility. Improvement in mechanical properties is presumably attributed to the formation of a small amount of ferrite in the primary structure, and the formation of certain precipitates is accelerated by the addition of V during aging. By contrast, excessive V decreases the strength and ductility simultaneously. This is due to the strong effect of ferrite formation compared to the beneficial effect of precipitation. The loss of ductility caused by adding higher amount of V is due to the formation of ferrite phases which in turn are suitable nucleation sites for crack propagation.
基金supported by the University of Kashan(Grant No.158426/16)
文摘MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.
基金supported by Department of Science and Technology (DST),Government of India under Fast Track Scheme (SR/FTP/PS-065/2011)
文摘Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure （R3c space group） and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies （A1） and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field （M-H） shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO6 envi- ronment due to shift in the 6Alg→4T2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.
基金supported by the Iran National Science Foundation(INSF)(91052908)
文摘In the present work, selective methanation of carbon monoxide in hydrogen rich stream was investigated over Ni/CeO2 nanocatalysts. The obtained results revealed that increasing in nickel loading decreased the BET surface area, pore vohune and nickel dispersion. The 25%Ni/CeO2 with a NiO crystal size of 12 nm exhibited the highest activity in CO methanation reaction and reached to maximum CO conversion and CH4 selectivity at temperatures above 230 ℃. The catalytic results revealed that CO selective methanation well progressed at lower temperatures while CO2 methanation was completely suppressed until CO conversion reached to maximum value.
基金the Department of Science & Technology (DST) for their financial support for carrying out this research through Fast Track Scheme (DST Sanction No: SR/FT/ET-005/2008)Technical Education Quality Improvement Programme (TEQIP)
文摘Ultra-high strength Al alloy system was developed by cryorolling and the contribution of various strengthening mechanisms to the overall yield strength of the system was evaluated. Cryorolling of Al-4%Cu-3%TiB2 in situ composite followed by short annealing at 175 ℃ and ageing at 125℃ resulted in an ultra-high yield strength of about 800 MPa with 9%total elongation. The strengthening contributions form solid solution strengthening, grain refinement, dislocation strengthening, precipitation hardening and dispersion strengthening were evaluated using standard equations. It was estimated that the maximum contribution was from grain refinement due to cryorolling followed by precipitation and dispersion strengthening.
文摘Mesoporous CuFe2O4 solid solution nanopowders with high specific surface areas were synthesized by a novel, very simple and inexpensive sol-gel route using propylene oxide as gelation agent, and used as the catalyst in low temperature CO oxidation. The samples were characterized by X-ray diffraction, N2 adsorption-desorption, thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and temperature-programmed reduction. The results revealed that the samples have a nanocrystalline structure with crystals in the range of 10 to 25 nm, and that all the catalysts have mesoporous pores. The addition of Cu into iron oxide affected its structural and catalytic properties. The sample containing 15 mol% Cu showed the highest specific surface area and catalytic activity, and showed high catalytic stability in low temperature CO oxidation.
基金Supported by the National Natural Science Foundation of Chinathe National Key Research and Development Program of China under Grant No 2016YFA0300203
文摘Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8＋δ （Bi2212） and YBa2Cu3O7-x （YBCO） along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the （100） plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a （110） surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.
基金supported by University of Kashan(Grant No.158426/5)
文摘Thermodynamic analysis was applied to study combined partial oxidation and carbon dioxide reforming of methane in view of carbon formation. The equilibrium calculations employing the Gibbs energy minimization were performed upon wide ranges of pressure （1-25 atm）, temperature （600-1300 K）, carbon dioxide to methane ratio （0-2） and oxygen to methane ratio （0-1）. The thermodynamic results were compared with the results obtained over a Ru supported catalyst. The results revealed that by increasing the reaction pressure methane conversion decreased. Also it was found that the atmospheric pressure is the preferable pressure for both dry reforming and partial oxidation of methane and increasing the temperature caused increases in both activity of carbon and conversion of methane. The results clearly showed that the addition of O2 to the feed mixture could lead to a reduction of carbon deposition.
基金supported by the Petrochemical Research & Technology Company of National Petrochemical Company in Iran
文摘A series of nanocrystalline γ-alumina are synthesized by different procedures, namely, thermal decomposition method （sample A）, precipita-tion method （sample B） and sol-gel method using sucrose and hexadecyltrimethyl ammonium bromide （CTAB） as templates （samples C and D, respectively）. Textural and acidic properties of γ-alumina samples are characterized by XRD, N2 adsorption-desorption and NH3-TPD techniques. Vapor-phase dehydration of methanol into dimethyl ether is carried out over these samples. Among them, sample C shows the highest catalytic activity. NH3-TPD analysis reveals that the sample with smaller crystallite size possesses higher concentration of medium acidic sites and consequently higher catalytic activity. Thermal decomposition method leads to decrease in both surface area and moderate acidity, therefore it is the cause of lower catalytic activity.
文摘The hydrothermal aging of poly（ethylene terephthalate） （PET） was investigated at 70-95 ℃. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy （FTIR） was proposed. The spectra during the hydrothermal aging were measured using attenuated total reflection accessory （ATR）. Peak resolving of carbonyl regions was performed, and the ratio of two groups of bands representing carboxylic acids and esters respectively were calculated to show the hydrolysis degree of ester groups in PET. The acid/ester ratio shows exactly the same trend as the average chain scission number per unit mass at various temperatures and thus can be used as a parameter to characterize the hydrolysis and random chain scission of PET. This method related to the hydrolysis mechanism directly, is simple, fast and convenient compared to the traditional methods such as viscometry, end-group titration and size exclusion chromatography （SEC）. It may also be useful in hydrolysis characterization of other polyesters.
文摘In this paper dry reforming of methane （DRM） was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction （XRD）, N2 adsorption, H2 chemisorption, temperature-programmed reduction （TPR）, temperature-programmed oxidation （TPO）, temperature- programmed desorption （TPD） and transmission and scanning electron microscopies （TEM, SEM） techniques. The obtained results showed that the catalyst support has a nanocrystalline structure （crystal size： about 5 nm） with a high specific surface area （175 m2 g-1） and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.
基金Project supported financially by the National Key Research and Development Program of China(2016YFC0204300)the National Natural Science Foundation of China(21976057,21922602)the Shanghai“Pujiang”Program(18PJD011)。
文摘The role of water in CO oxidation was investigated on Pd/CeO2 with different morphologies(rods(R),cubes(C)and octahedrons(O)).Compared with the absence of water,CO oxidation activity increases 2 times in the presence of water on Pd/CeO2-C;but a decrease is found on Pd/CeO2-R.Catalyst characterization reveals that Pd is mainly in the form of solid solution(PdxCe1-xO2-σ)on Pd/CeO2-R and a mixture of metal and PdxCe1-xO2-σsolid solution on Pd/CeO2-C.The strong interaction between Pd and CeO2-R results in the form of stable bidentate carbonates species;while the relatively weak interaction between Pd and CeO2-C leads to the produce of unstable monodentate carbonates species.The effects of water on CO oxidation activity closely relate with the Pd chemical state and the types of carbonates species.Water restrains CO adsorption on PdxCe1-xO2-σsolid solution,but it has negligent effects on metallic Pd species.In the presence of water,bidentate carbonates species remains stable but the decrease in the amount of monodentate carbonates species is observed.
