In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in pr...In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.展开更多
The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x...The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.展开更多
Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the...Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the Mg2Ni–Ni–5 mol% Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） composites.The structures and spectrum characteristics of the Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions catalysts were analyzed systemically.XRD results showed that the doped samples exhibited single phase of CeO2 fluorite structure.The cell parameters and cell volumes were increased with increasing the doped content.Raman spectrum revealed that the peak position of F^2g mode shift to higher wavenumbers and the peak corresponding to oxygen vacancies were observed distinctly for the doped samples.UV-Vis technique indicated that the absorption peaks of Eu^3＋ and Nd^3＋ ions appeared; the bandgap energy was decreased linearly.The electrochemical and kinetic properties of the Mg2Ni–Ni–5 mol% Ce1-x（Nd0.5Eu0.5xO2-δ composites were measured.The maximum discharge capacity was increased from 722.3 mA h/g for x = 0.00 to 819.7 mA h/g for x = 0.16,and the cycle stability S20 increased from 25.0%（x = 0.00） to 42.2%（x = 0.20）.The kinetic measurement proved that the catalytic activity of composite surfaces and the hydrogen diffusion rate were improved for the composites with doped catalysts,especially for the composites with x = 0.16 and x = 0.20.The catalysis mechanism was analyzed from the point of microstructure and spectrum features of the Ce1-x（Nd0.5Eu0.5）xO2-δ solid solutions.展开更多
CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive pro...CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.展开更多
The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniq...The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniques. The results show that the addition of Ce-Zr oxides improves the thermal stability of alumina and PdO. The Pd/Ce0.2Zr0.8/Al2O3 exhibits the highest activity and thermal stability for methane combustion.展开更多
基金Project(2009BB4228) supported by the Natural Science Foundation of Chongqing City,ChinaProject(CK2010Z09) supported by the Research Foundation of Chongqing University of Science and Technology,China
文摘In order to reduce the oxidizing and volatilizing caused by Mg element in the traditional methods for synthesizing Mg2Sil-xSnx （x=0.2, 0.4, 0.6, 0.8） solid solutions, microwave irradiation techniques were used in preparing them as thermoelectric materials. Structure and phase composition of the obtained materials were investigated by X-ray diffraction （XRD）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured as a function of temperature from 300 to 750 K. It is found that Mg2Si1-xSnx solid solutions are well formed with excessive content of 5% （molar fraction） Mg from the stoichiometric MgESil.xSnx under microwave irradiation. A maximum dimensionless figure of merit, ZT, of about 0.26 is obtained for Mg2Si1-xSnx solid solutions at about 500 K for x=0.6.
文摘The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.
基金supported by the National Natural Science Foundations of China(51501095,51371094)the Natural Science Foundation of Inner Mongolia(2017MS(LH)0516)
文摘Nanosized Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions（x = 0.00-0.20） were synthesized by means of hydrothermal method.Then the solid solutions were ball milled with Mg2Ni and Ni powders for 20 h to get the Mg2Ni–Ni–5 mol% Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） composites.The structures and spectrum characteristics of the Ce^1-x）（Nd^0.5）Eu^0.5））xO^2-δ） solid solutions catalysts were analyzed systemically.XRD results showed that the doped samples exhibited single phase of CeO2 fluorite structure.The cell parameters and cell volumes were increased with increasing the doped content.Raman spectrum revealed that the peak position of F^2g mode shift to higher wavenumbers and the peak corresponding to oxygen vacancies were observed distinctly for the doped samples.UV-Vis technique indicated that the absorption peaks of Eu^3＋ and Nd^3＋ ions appeared; the bandgap energy was decreased linearly.The electrochemical and kinetic properties of the Mg2Ni–Ni–5 mol% Ce1-x（Nd0.5Eu0.5xO2-δ composites were measured.The maximum discharge capacity was increased from 722.3 mA h/g for x = 0.00 to 819.7 mA h/g for x = 0.16,and the cycle stability S20 increased from 25.0%（x = 0.00） to 42.2%（x = 0.20）.The kinetic measurement proved that the catalytic activity of composite surfaces and the hydrogen diffusion rate were improved for the composites with doped catalysts,especially for the composites with x = 0.16 and x = 0.20.The catalysis mechanism was analyzed from the point of microstructure and spectrum features of the Ce1-x（Nd0.5Eu0.5）xO2-δ solid solutions.
文摘CexZr1-xO2 complex oxides doped by transition metal(Fe, Mn, Cu) were prepared by precipitation method. Thermal stability of samples was characterized by XRD, surface areas were measured by BET method and reductive property was characterized by TPR. The results show that MnO2 can be dispersed in solid solution after calcined at 1273 K, when the loading is 12%, while Fe and Cu is easy to separate from samples at this temperature. Samples doped simultaneously by Fe, Mn or Fe, Cu demonstrated high reactive property at low temperature. The starting reduction temperature are 413 and 373 K, respectively. TPR results also show a broad range of reductive temperature exists in these bi-metal doped samples.
文摘The effects of ceria and zirconium oxides additions to alumina-supported palladium catalysts on methane combustion behavior were investigated. The structure and TPR/TPO properties were studied by XRD, TPR, TPO techniques. The results show that the addition of Ce-Zr oxides improves the thermal stability of alumina and PdO. The Pd/Ce0.2Zr0.8/Al2O3 exhibits the highest activity and thermal stability for methane combustion.
