The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was ex...The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...展开更多
Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and ther...Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and thermogravimetric analyses.Their catalytic properties were investigated in ozone(O3)decomposition reaction.Results show that the small amount of rare earth metal Ce added during Mn-Fe(FM) mixed-oxide synthesis greatly improves the catalytic performance in O3 decomposition.Among the prepared catalysts.the C0.04(FM)0.96 mixed-oxide catalyst exhibits the highest catalytic activity and stability.The O3 conversion over C0.04(FM)0.96 is 98% after 24 h reaction at 25℃ under dry condition,and that over FM decreases to 90% after 16 h reaction.At 0℃,the O3 conversion over C0.04(FM)0.96 is 95% after 7 h reaction under dry condition.and that over FM slows down to 70%.Under humid condition(RH 65%),the O3 conversion over C0.04(FM)0.96 is 63% after 6.5 h reaction at 25℃.while that over FM decreases to 55%.When Ce is doped into Mn-Fe mixed oxides,the small amount of Ce enters the crystal lattice of MnO2.and partial Fe is separated to form Fe2O3.This changes cause lattice distortion and increase defects and enable the as-synthesized Ce-Fe-Mn ternary mixed-oxide catalysts to acquire additional oxygen vacancies and increase their specific surface area,thereby increasing the number of reaction sites and enhancing the catalytic performance of the catalysts for O3 decomposition.展开更多
In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and ...In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and coercivity H(cj)of Ce-Fe-B sintered magnet are improved from 6.76 to 9.13 MGOe by 35.1%,and from 1.44 to 1.67 kOe by 16.0%,respectively,via adding 5 wt%liquid phase alloy of Ce(35.58)Fe(57.47)Cu6 B(0.95)(at%).Compared with the magnet without Cerich alloy addition,the volume fraction of the grain-boundary phase with low melting point increases in the magnet with Ce-rich alloy additio n,which is be ne ficial to imp roving the microstructure and promoting the coercivity enhancement of the magnet.In the Ce-Fe-B magnet with Ce-rich alloy addition,Cu and Ce enrich in the grain boundaries of the magnet after annealing,therefore the as-annealed magnet has a higher coercivity than the as-sintered magnet.A distinct Fe-rich layer with the average thickness of 60 nm is found in the grain boundaries in the magnet without Ce-rich alloy addition,but it seems that Fe-rich phase disappears in the magnet with Ce-rich alloy addition.The present work suggests that the further improvement of coercivity in the Ce-Fe-B sintered magnets is expectable by designing the composition and structure of added liquid phase alloys.展开更多
Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temp...Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1~）.5 was able to produce syngas with high selectivity in high-temperature range （800-900 ~C）, and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation oc- curred at beginning following with selective oxidation later. Ce~_xFexO2~ oxygen carriers （x5_0.5） were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selec- tivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe＊ activated CeO2 and Ce3＋ activated iron oxides （FeOm）, and those chemical interaction greatly enhanced the oxygen mobility and selectivity.展开更多
The Ce;Fe;B thin films with a notable out-of-plane c-axis texture were prepared by DC magnetron sputtering on a Ta buffer layer. The morphological and magnetic properties were investigated. The thickness of the magnet...The Ce;Fe;B thin films with a notable out-of-plane c-axis texture were prepared by DC magnetron sputtering on a Ta buffer layer. The morphological and magnetic properties were investigated. The thickness of the magnetic layer had a dramatic effect on the formation of Ce;Fe;B phase,and excellent magnetic properties(H;≈4.25 kOe, M;/M;≈0.81) were observed for the Ce-Fe-B film with the thickness d;= 200 nm. The results of the hysteresis loops for Ce-Fe-B film（d;= 200 nm） at various measured temperatures show that a decoupling between the hard and the soft phases is observed at low temperatures, which is due to the regions with quite low anisotropy provided by the a-Fe. Moreover. it is clear that significantly various magnetization behaviors between the films with d;= 200 and 300 nm were observed with a similar trend due to the existence of the a-Fe soft phase.展开更多
基金Project supported by the National Natural Science Foundation of China (50574046, 50774038)the Research Fund for the Doctoral Program of Higher Education of China (20095314120005)+1 种基金the Natural Science Foundation of Yunnan Province (2008E030M) the Foundation of Kun-ming University of Science and Technology (KKZ3200927010)
文摘The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...
基金supported by the National Natural Science Foundation of China(21506194,21676255)the Natural Science Foundation of Zhejiang Province(Y16B070011)the Commission of Science and Technology of Zhejiang province(2017C03007,2017C33106).
文摘Ce-modified Mn-Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction,Raman,N2 adsorption-desorption,infrared spectra H2 temperature-programmed reduction and thermogravimetric analyses.Their catalytic properties were investigated in ozone(O3)decomposition reaction.Results show that the small amount of rare earth metal Ce added during Mn-Fe(FM) mixed-oxide synthesis greatly improves the catalytic performance in O3 decomposition.Among the prepared catalysts.the C0.04(FM)0.96 mixed-oxide catalyst exhibits the highest catalytic activity and stability.The O3 conversion over C0.04(FM)0.96 is 98% after 24 h reaction at 25℃ under dry condition,and that over FM decreases to 90% after 16 h reaction.At 0℃,the O3 conversion over C0.04(FM)0.96 is 95% after 7 h reaction under dry condition.and that over FM slows down to 70%.Under humid condition(RH 65%),the O3 conversion over C0.04(FM)0.96 is 63% after 6.5 h reaction at 25℃.while that over FM decreases to 55%.When Ce is doped into Mn-Fe mixed oxides,the small amount of Ce enters the crystal lattice of MnO2.and partial Fe is separated to form Fe2O3.This changes cause lattice distortion and increase defects and enable the as-synthesized Ce-Fe-Mn ternary mixed-oxide catalysts to acquire additional oxygen vacancies and increase their specific surface area,thereby increasing the number of reaction sites and enhancing the catalytic performance of the catalysts for O3 decomposition.
基金Project supported by the National Natural Science Foundation of China(51590882)the Plan of National Key Research and Development of China(2016YFB0700903)
文摘In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and coercivity H(cj)of Ce-Fe-B sintered magnet are improved from 6.76 to 9.13 MGOe by 35.1%,and from 1.44 to 1.67 kOe by 16.0%,respectively,via adding 5 wt%liquid phase alloy of Ce(35.58)Fe(57.47)Cu6 B(0.95)(at%).Compared with the magnet without Cerich alloy addition,the volume fraction of the grain-boundary phase with low melting point increases in the magnet with Ce-rich alloy additio n,which is be ne ficial to imp roving the microstructure and promoting the coercivity enhancement of the magnet.In the Ce-Fe-B magnet with Ce-rich alloy addition,Cu and Ce enrich in the grain boundaries of the magnet after annealing,therefore the as-annealed magnet has a higher coercivity than the as-sintered magnet.A distinct Fe-rich layer with the average thickness of 60 nm is found in the grain boundaries in the magnet without Ce-rich alloy addition,but it seems that Fe-rich phase disappears in the magnet with Ce-rich alloy addition.The present work suggests that the further improvement of coercivity in the Ce-Fe-B sintered magnets is expectable by designing the composition and structure of added liquid phase alloys.
基金Project supported by National Natural Science Foundation of China(51204083,51374004,51104074,51174105,51306084)the Applied Basic Research Program of Yunnan Province(2012FD016)the Candidate Talents Training Fund of Yunnan Province(2012HB009)
文摘Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1~）.5 was able to produce syngas with high selectivity in high-temperature range （800-900 ~C）, and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation oc- curred at beginning following with selective oxidation later. Ce~_xFexO2~ oxygen carriers （x5_0.5） were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selec- tivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe＊ activated CeO2 and Ce3＋ activated iron oxides （FeOm）, and those chemical interaction greatly enhanced the oxygen mobility and selectivity.
基金supported by the Major State Basic Research Development Program of China(2014CB643701)the General Program of the National Natural Science Foundation of China(51571064)
文摘The Ce;Fe;B thin films with a notable out-of-plane c-axis texture were prepared by DC magnetron sputtering on a Ta buffer layer. The morphological and magnetic properties were investigated. The thickness of the magnetic layer had a dramatic effect on the formation of Ce;Fe;B phase,and excellent magnetic properties(H;≈4.25 kOe, M;/M;≈0.81) were observed for the Ce-Fe-B film with the thickness d;= 200 nm. The results of the hysteresis loops for Ce-Fe-B film（d;= 200 nm） at various measured temperatures show that a decoupling between the hard and the soft phases is observed at low temperatures, which is due to the regions with quite low anisotropy provided by the a-Fe. Moreover. it is clear that significantly various magnetization behaviors between the films with d;= 200 and 300 nm were observed with a similar trend due to the existence of the a-Fe soft phase.
