Single crystals of RSeTe2 （R =La, Ce, Pr, Nd） are synthesized using LiC1/RbCI flux. Transport and magnetic properties in the directions parallel and perpendicular to the a-c plane are investigated. We find that the ...Single crystals of RSeTe2 （R =La, Ce, Pr, Nd） are synthesized using LiC1/RbCI flux. Transport and magnetic properties in the directions parallel and perpendicular to the a-c plane are investigated. We find that the resistivity anisotropy P⊥/P∥ lies in the range 486-615 for different compounds at 2K, indicating the highly two-dimensional character. In both the orientations, the charge-density-wave transitions start near Tcow = 284（3）K, 316（3）K, 359（3）K for NdSeTe2, PrSeTe2, CeSeTe2, respectively, with a considerable increase in dc resistivity. While for LaSeTe2, no obvious resistivity anomaly is observed up to 380K. The value of TCDW increases monotonically with the increasing lattice parameters. Below TCDW, slight anomalies can be observed in NdSeTe2, PrSeTe2 and CeSeTe2 with onset temperature at 193（3）K, 161（3）K, 108（3）K, respectively, decreasing as lattice parameters increase. Magnetic susceptibility measurements show that the valence state of rare earth ions are trivalenee in these compounds. Antiferromagnetie-type magnetic order is formed in CeSeTe2 at 2.1 K, while no magnetic transition is observed in PrSeTe2 and NdSeTe2 down to 1.8 K.展开更多
A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion ...A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion of CF4 can be reached initially over NaF-Si-La2O3,NaF-Si-CeO2,NaF-Si-Nd2O3,and NaF-Si-Y2O3 at 850 C.The fresh and used reagents were characterized using XRD and XPS techniques.It was found that the active components of NaF and metal oxides in NaF-Si-CeO2,NaF-Si-Pr6O11,NaF-Si-Nd2O3,and NaF-Si-Y2O3 weretransformed into inert phases of mixed metal fluorides and silicates,respectively,resulting in an ineffective utilization of these de-fluorinatedreagents,whereas no inert phases from NaF and La2O3 can be observed in the used NaF-Si-La2O3,indicating the NaF-Si-La2O3 reagent couldbe utilized more efficiently than the other reagents in CF4 decomposition.展开更多
Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as P...Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity.展开更多
A series of catalysts with (Ce-Zr-La-Pr)O contents range from 0 to 50% in coating and single-palladium loads on substrates were prepared to study effects of (Ce-Zr-La-Pr)O contents on catalytic activities and durabili...A series of catalysts with (Ce-Zr-La-Pr)O contents range from 0 to 50% in coating and single-palladium loads on substrates were prepared to study effects of (Ce-Zr-La-Pr)O contents on catalytic activities and durability by contrasting the characteristics of light-off, A/F and catalytic conversions of the fresh catalysts with that of the aged catalysts. The results show that (Ce-Zr-La-Pr)O can enhance the catalysts light-off characteristics, widen A/F windows and increase catalytic conversions at a certain extent through optimizing physical structural and chemical property of the mixed coating. However, (Ce-Zr-La-Pr)O contents influence greatly on the catalysts activities and durability, and the catalysts with contents ranging from 10% to 30% exhibited better integrative properties in all samples, and 10% was the optical content to make the catalyst performance highest in this thesis. It is indicated that an suitable content of (Ce-Zr-La-Pr)O plays an important role in assisting catalysis, enhancing durability and increasing oxygen storage capability.展开更多
LnVO_(4)(Ln=La,Ce,Pr,Nd,etc.)is an emerging photocatalyst for solving the energy and environmental crisis,due to its suitable band gap,special valence electronic structure,high thermal,and chemical sta-bility,as well ...LnVO_(4)(Ln=La,Ce,Pr,Nd,etc.)is an emerging photocatalyst for solving the energy and environmental crisis,due to its suitable band gap,special valence electronic structure,high thermal,and chemical sta-bility,as well as excellent photocatalytic performance.Although exhibiting great promise,the low solar power employment efficiency of LnVO_(4) materials has limited its further development and application.However,recent breakthroughs have been made in both heightening its photocatalysis efficiency and elu-cidating the essential photocatalytic mechanisms.Therefore,it is important to review and summarize recent research progress on LnVO_(4) nanomaterials and their applications.In this review,we systemat-ically report on and examine recent computational and experimental advances in the modification of LnVO_(4)-based photocatalysts through morphology adjustment,elemental doping,phase structure modula-tion,crystal facet modulation,defect modulation,heterostructure,and beyond.Thereafter,we outline cur-rent promising photocatalytic applications and discuss challenges/expected upcoming research aims for LnVO_(4)-based photocatalysts.Our goal is to furnish guidance for the reasonable design and preparation of highly efficient LnVO_(4)(Ln=La,Ce,Pr,Nd,etc.)-based photocatalytic materials for sundry applications.展开更多
基金Supported by the National Basic Research Program of China under Grant No 2015CB921303the Strategic Priority Research Program(B) of Chinese Academy of Sciences under Grant No XDB07020100
文摘Single crystals of RSeTe2 （R =La, Ce, Pr, Nd） are synthesized using LiC1/RbCI flux. Transport and magnetic properties in the directions parallel and perpendicular to the a-c plane are investigated. We find that the resistivity anisotropy P⊥/P∥ lies in the range 486-615 for different compounds at 2K, indicating the highly two-dimensional character. In both the orientations, the charge-density-wave transitions start near Tcow = 284（3）K, 316（3）K, 359（3）K for NdSeTe2, PrSeTe2, CeSeTe2, respectively, with a considerable increase in dc resistivity. While for LaSeTe2, no obvious resistivity anomaly is observed up to 380K. The value of TCDW increases monotonically with the increasing lattice parameters. Below TCDW, slight anomalies can be observed in NdSeTe2, PrSeTe2 and CeSeTe2 with onset temperature at 193（3）K, 161（3）K, 108（3）K, respectively, decreasing as lattice parameters increase. Magnetic susceptibility measurements show that the valence state of rare earth ions are trivalenee in these compounds. Antiferromagnetie-type magnetic order is formed in CeSeTe2 at 2.1 K, while no magnetic transition is observed in PrSeTe2 and NdSeTe2 down to 1.8 K.
基金supported by the National Natural Science Foundation of China (No. 20976149)
文摘A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion of CF4 can be reached initially over NaF-Si-La2O3,NaF-Si-CeO2,NaF-Si-Nd2O3,and NaF-Si-Y2O3 at 850 C.The fresh and used reagents were characterized using XRD and XPS techniques.It was found that the active components of NaF and metal oxides in NaF-Si-CeO2,NaF-Si-Pr6O11,NaF-Si-Nd2O3,and NaF-Si-Y2O3 weretransformed into inert phases of mixed metal fluorides and silicates,respectively,resulting in an ineffective utilization of these de-fluorinatedreagents,whereas no inert phases from NaF and La2O3 can be observed in the used NaF-Si-La2O3,indicating the NaF-Si-La2O3 reagent couldbe utilized more efficiently than the other reagents in CF4 decomposition.
基金Project supported by the National High Technology Research and Development Programs (863 ) of China (2002 AA321060, 2004AA649040) Yunnan Province Science Technology Program (2004B0028Q)
文摘Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity.
文摘A series of catalysts with (Ce-Zr-La-Pr)O contents range from 0 to 50% in coating and single-palladium loads on substrates were prepared to study effects of (Ce-Zr-La-Pr)O contents on catalytic activities and durability by contrasting the characteristics of light-off, A/F and catalytic conversions of the fresh catalysts with that of the aged catalysts. The results show that (Ce-Zr-La-Pr)O can enhance the catalysts light-off characteristics, widen A/F windows and increase catalytic conversions at a certain extent through optimizing physical structural and chemical property of the mixed coating. However, (Ce-Zr-La-Pr)O contents influence greatly on the catalysts activities and durability, and the catalysts with contents ranging from 10% to 30% exhibited better integrative properties in all samples, and 10% was the optical content to make the catalyst performance highest in this thesis. It is indicated that an suitable content of (Ce-Zr-La-Pr)O plays an important role in assisting catalysis, enhancing durability and increasing oxygen storage capability.
基金National Natural Science Foundation of China(Nos.22076068,8111310014)(China)Global Research Initiative for Sustainable Low-Carbon Unconventional Resources(Canada)University of Calgary’s Canada First Research Excellence Fund(CFREF)program(Canada).
文摘LnVO_(4)(Ln=La,Ce,Pr,Nd,etc.)is an emerging photocatalyst for solving the energy and environmental crisis,due to its suitable band gap,special valence electronic structure,high thermal,and chemical sta-bility,as well as excellent photocatalytic performance.Although exhibiting great promise,the low solar power employment efficiency of LnVO_(4) materials has limited its further development and application.However,recent breakthroughs have been made in both heightening its photocatalysis efficiency and elu-cidating the essential photocatalytic mechanisms.Therefore,it is important to review and summarize recent research progress on LnVO_(4) nanomaterials and their applications.In this review,we systemat-ically report on and examine recent computational and experimental advances in the modification of LnVO_(4)-based photocatalysts through morphology adjustment,elemental doping,phase structure modula-tion,crystal facet modulation,defect modulation,heterostructure,and beyond.Thereafter,we outline cur-rent promising photocatalytic applications and discuss challenges/expected upcoming research aims for LnVO_(4)-based photocatalysts.Our goal is to furnish guidance for the reasonable design and preparation of highly efficient LnVO_(4)(Ln=La,Ce,Pr,Nd,etc.)-based photocatalytic materials for sundry applications.
