Sb-doped SnO2(ATO)-(CeO2-TiO2) thin Films were deposited on glass substrates using the mixed solution including CeO2-TiO2 precursor and ATO particles by sol-gel dip coating process.ATO particles were prepared using lo...Sb-doped SnO2(ATO)-(CeO2-TiO2) thin Films were deposited on glass substrates using the mixed solution including CeO2-TiO2 precursor and ATO particles by sol-gel dip coating process.ATO particles were prepared using low-temperature hydrothermal process.The mixed molar ratio of ATO to(CeO2-TiO2) vs the properties of CeO2-TiO2 thin film was investigated.The optical properties of the films were characterized by UV-visible transmission and infrared reflection spectra,the sheet resistance of ATO particles and films were measured by rubber sheeter(MYI-50) and four-point probe(HisuperGroup Inc,SDY-5),the surface morphology and structure of the films were analyzed using 3D Digitale Mikroskop and X-ray diffraction(XRD),respectively.The results showed that the ATO precursor solution lost weight completely at about 500 oC,and the ATO particles was obtained,which indicated the same rutile lattice structure as SnO2.The glass substrates coated with ATO-(CeO2-TiO2) thin films showed better properties in antistatic electricity(104-106 Ω/),shielding UV(almost 100%),visible light transmission(70%) and infrared reflection(】30%).展开更多
Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscalin...Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.展开更多
In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice...In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice,forming solid solutions.The catalysts were then used for the selective catalytic reduction(SCR)of NO by CO.The Cu‐doped catalyst exhibited the highest SCR activity;it had a T50(i.e.,50%NO conversion)of only 83°C and a T90(i.e.,90%NO conversion)of 126°C.Such an activity was also higher than in many state‐of‐the‐art catalysts.In situ diffuse reflectance Fourier transform infrared spectroscopy suggested that the MOx‐CeO2 catalysts(M=Co and Fe)mainly followed an Eley‐Rideal reaction mechanism for CO‐SCR.In contrast,a Langmuir‐Hinshelwood SCR reaction mechanism occurred in CuO‐CeO2 owing to the presence of Cu+species,which ensured effective adsorption of CO.This explains why CuO‐CeO2 exhibited the highest activity with regard to the SCR of NO by CO.展开更多
Mesoporous CeO2 was first synthesized by hydrothermal method,and then used to synthesize different contents of CuO)x/CeO2(x:molar ratio of Cu to Ce) by deposition-precipitation method.These materials were characterize...Mesoporous CeO2 was first synthesized by hydrothermal method,and then used to synthesize different contents of CuO)x/CeO2(x:molar ratio of Cu to Ce) by deposition-precipitation method.These materials were characterized by X-ray diffraction(XRD),N2 adsorption and desorption,H2 temperature programmed reduction(H2-TPR) and O2 temperature programmed desorption(O2-TPD) to study the crystal structure,surface area,and the mechanism of CO oxidation.The results show that,on XRD patterns,no evidence of CuO diffraction peaks is present until Cu loading is increased to 20%.The BET surface area decreases noticeably with the increase of Cu content.Compared with other samples,the better reducibility and activity oxygen species of(CuO)10%/CeO2coincide with its better catalytic activity.展开更多
The morphology effect of Zr-doped CeOwas studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zrdoped CeOnanor...The morphology effect of Zr-doped CeOwas studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zrdoped CeOnanorods exhibited the highest catalytic performance（yield of styrene oxide and TOF value）followed by nanoparticles and nanocubes. For the Zr-doped CeOnanorods, the apparent activation energy is 56.3 k J/mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes（73.3 and 93.4 k J/mol）. The high resolution transmission electron microscopy results indicated that（100） and（110） crystal planes are predominantly exposed for Zr-doped CeOnanorods while（100）and（111） for nanocubes,（111） for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeOnanorods is mainly attributed to the higher percentage of Cespecies and more oxygen vacancies, which are associated with their exposed（100） and（110） crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeOnanorods did not lose its initial high catalytic activity after five successive recycles.展开更多
The Sr2 CeO4:Ln3+(Ln=Eu,Dy)fine phosphor particles were prepared by a facile wet chemical approach,in which the consecutive hydrothermal-combustion reaction was performed.The doping of Ln3+into Sr2 CeO4 has little inf...The Sr2 CeO4:Ln3+(Ln=Eu,Dy)fine phosphor particles were prepared by a facile wet chemical approach,in which the consecutive hydrothermal-combustion reaction was performed.The doping of Ln3+into Sr2 CeO4 has little influence on the structure of host,and the as-prepared samples display wellcrystallized spherical or elliptical shape with an average particle size at about 100-200 nm.For Eu3+ions-doped Sr2 CeO4,with the increase of Eu3+-doping concentration,the blue light emission band with the maximum at 468 nm originating from a Ce4+→O2-charge transfer of the host decreases obviously and the characteristic red light emission of Eu3+(5 D0→7 F2 transition at 618 nm)is enhanced gradually.Simultaneously,the fluorescent lifetime of the broadband emission of Sr2 CeO4 decreases with the doping of Eu3+,indicating an efficient energy transfer from the host to the doping Eu3+ions.The ene rgy transfer efficiency from the host to Eu3+was investigated in detail,and the emitting color of Sr2 CeO4:Eu3+can be easily tuned from blue to red by varying the doping concentration of Eu3+ions.Moreover,the luminescence of Dy3+-doped Sr2 CeO4 was also studied.Similar energy transfer pheno menon can be observed,and the incorporation of Dy3+into Sr2 CeO4 host leads to the characteristic emission of 4 F9/2→6 H15/2(488 nm,blue light)and 4 F9/2→6 H13/2(574 nm,yellow light)of Dy3+.The Sr2 CeO4:Ln3+fine particles with tunable luminescence are quite beneficial for its potential applications in the optoelectronic fields.展开更多
A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral ...A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral phase,morphology,and optical performances of the synthesized catalyst samples were characterized by XRF,XRD,SEM,UV-Vis DRS,and so on.XRD and SEM results show that calcium silicate hydrate(Ca1.5SiO3.5·xH2O)mineral phase is formed in the carrier sample,and the prepared catalyst specimens are made up of approximately 50 nm particles.After 6 hours of xenon lamp irradiation,the catalyst supported on V-doped 8wt%CeO_(2) exhibits the highest photocatalytic hydrogen production activity(8292μmol/g),which is attributed to the interaction between the V-doped CeO_(2) active components and FeO existed in catalyst carrier.A possible photocatalytic decomposition of water for hydrogen production mechanism over the V-8CeO_(2)/AC catalyst was proposed.展开更多
Propylene,a readily accessible and economically viable light olefin,has garnered substantial interest for its potential conversion into valuable higher olefins through oligomerization processes.The distribution of pro...Propylene,a readily accessible and economically viable light olefin,has garnered substantial interest for its potential conversion into valuable higher olefins through oligomerization processes.The distribution of products is profoundly influenced by the catalyst structure.In this study,Fe_(2)O_(3)-doped NiSO_(4)/Al_(2)O_(3) catalysts have been meticulously developed to facilitate the selective trimerization of propylene under mild conditions.Significantly,the 0.25Fe_(2)O_(3)-NiSO_(4)/Al_(2)O_(3) catalyst demonstrates an enhanced reaction rate(48.5 mmol_(C3)/(g_(cat).·h)),alongside a high yield of C9(~32.2%),significantly surpassing the performance of the NiSO_(4)/Al_(2)O_(3) catalyst(C9:~24.1%).The incorporation of Fe_(2)O_(3) modifies the migration process of sulfate ions,altering the Lewis acidity of the electron-deficient Ni and Fe sites on the catalyst and resulting a shift in product distribution from a Schulz-Flory distribution to a Poisson distribution.This shift is primarily ascribed to the heightened energy barrier for theβ-H elimination reaction in the C6 alkyl intermediates on the doped catalyst,further promoting polymerization to yield a greater quantity of Type II C9.Furthermore,the validation of the Cossee-Arlman mechanism within the reaction pathway has been confirmed.It is noteworthy that the 0.25Fe_(2)O_(3)-NiSO_(4)/Al_(2)O_(3) catalyst exhibits remarkable stability exceeding 80 h in the selective trimerization of propylene.These research findings significantly enhance our understanding of the mechanisms underlying olefin oligomerization reactions and provide invaluable insights for the development of more effective catalysts.展开更多
The electrical properties of TiO2-based varistor ceramics with different amount of CeO2 were investigated by measuring the properties of V-I, permittivity, density and boundary defect barriers. It is found that an opt...The electrical properties of TiO2-based varistor ceramics with different amount of CeO2 were investigated by measuring the properties of V-I, permittivity, density and boundary defect barriers. It is found that an optimal composition doped with 0.7% CeO2 exhibits the highest nonlinear coefficient of 10.5, the highest breakdown voltage of 12.77 V·mm^-1, the ultrahigh permittivity of 82900（measured at 1 kHz）, and the highest density of 4.15 g·cm^-3, which is consistent with the highest and narrowest grain-boundary defect barriers. In order to illustrate the grain boundary barriers formation in TiO2-Nb2O5-MnCO3-CeO2 varistor, an grain-boundary defect barrier model was also introduced.展开更多
The N and C doping effects on the crystal structures, electronic and optical properties of fluorite structure CeO2 have been investigated using the first-principles calculation. Co-doping these two elements results in...The N and C doping effects on the crystal structures, electronic and optical properties of fluorite structure CeO2 have been investigated using the first-principles calculation. Co-doping these two elements results in the local lattice distortion and volume expansion of CeO2. Compared with the energy hand structure of pure CeO2, some local energy levels appear in the forbidden band, which may facilitate the light absorption. Moreover, the enhanced photo-catalytic properties of CeO2 were explained through the absorption spectra and the selection rule of the band-to-band transitions.展开更多
The role of ceria doping (0.75 - 3 mol%) on solid-solid interactions between ferric and cobaltic oxides was investigated. The investigated solids were characterized by TGA, DTA, XRD and HRTEM. The results revealed tha...The role of ceria doping (0.75 - 3 mol%) on solid-solid interactions between ferric and cobaltic oxides was investigated. The investigated solids were characterized by TGA, DTA, XRD and HRTEM. The results revealed that ceria much enhanced the formation of nanosized CoFe2O4 (10 - 30 nm). The stimulation effect of ceria towards cobalt ferrite formation was evidenced from analysis of DTA and XRD investigations. In fact, the area of endothermic peak located at 575℃- 680℃ relative to solid-solid interaction between ferric and cobaltic oxide increased by increasing the dopant concentration. This treatment decreased the activation energy of formation of the produced ferrite from 33 - 9.2 kJ/mol upon doping with 3 mol% CeO2. HRTEM analysis revealed the formation of homogenous nanosized CoFe2O4. The formation effect of ceria dopant towards the formation of CoFe2O4 has been tentatively attributed to an effective increase in the mobility of the reacting cations.展开更多
The catalytic activity measurement for the NO+CO reaction over CuO/CeO\-2/\%γ\%\|Al\-2O\-3 catalysts at a low\|temperature(200 ℃) shows that the activity is strongly related to ceria loading amount, and both surface...The catalytic activity measurement for the NO+CO reaction over CuO/CeO\-2/\%γ\%\|Al\-2O\-3 catalysts at a low\|temperature(200 ℃) shows that the activity is strongly related to ceria loading amount, and both surface dispersed ceria species and crystalline CeO\-2 shows a significant enhancement on the activity. The effect of ceria species is contributed to their promoting the reduction of copper oxide species.展开更多
基金Project supported by the Changjiang Scholars and Innovative Research Team in University
文摘Sb-doped SnO2(ATO)-(CeO2-TiO2) thin Films were deposited on glass substrates using the mixed solution including CeO2-TiO2 precursor and ATO particles by sol-gel dip coating process.ATO particles were prepared using low-temperature hydrothermal process.The mixed molar ratio of ATO to(CeO2-TiO2) vs the properties of CeO2-TiO2 thin film was investigated.The optical properties of the films were characterized by UV-visible transmission and infrared reflection spectra,the sheet resistance of ATO particles and films were measured by rubber sheeter(MYI-50) and four-point probe(HisuperGroup Inc,SDY-5),the surface morphology and structure of the films were analyzed using 3D Digitale Mikroskop and X-ray diffraction(XRD),respectively.The results showed that the ATO precursor solution lost weight completely at about 500 oC,and the ATO particles was obtained,which indicated the same rutile lattice structure as SnO2.The glass substrates coated with ATO-(CeO2-TiO2) thin films showed better properties in antistatic electricity(104-106 Ω/),shielding UV(almost 100%),visible light transmission(70%) and infrared reflection(】30%).
基金financially supported by the National Key R&D Program of China (No. 2018YFB1502203-1)the Guangdong Basic and Applied Basic Research Foundation (No. 2021B1515120087)the Stable Supporting Fund of Shenzhen, China (No. GXWD20201230155427003-202007 28114835006)
文摘Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.
文摘In the present study,we synthesized CeO2 catalysts doped with various transition metals(M=Co,Fe,or Cu)using a supercritical water hydrothermal route,which led to the incorporation of the metal ions in the CeO2 lattice,forming solid solutions.The catalysts were then used for the selective catalytic reduction(SCR)of NO by CO.The Cu‐doped catalyst exhibited the highest SCR activity;it had a T50(i.e.,50%NO conversion)of only 83°C and a T90(i.e.,90%NO conversion)of 126°C.Such an activity was also higher than in many state‐of‐the‐art catalysts.In situ diffuse reflectance Fourier transform infrared spectroscopy suggested that the MOx‐CeO2 catalysts(M=Co and Fe)mainly followed an Eley‐Rideal reaction mechanism for CO‐SCR.In contrast,a Langmuir‐Hinshelwood SCR reaction mechanism occurred in CuO‐CeO2 owing to the presence of Cu+species,which ensured effective adsorption of CO.This explains why CuO‐CeO2 exhibited the highest activity with regard to the SCR of NO by CO.
基金Project(2011FZ030)supported by the Natural Science Foundation of Yunnan Province,ChinaProjects(2011144,2011221)supported by Analysis and Test Foundation of Kunming University of Science and Technology,China
文摘Mesoporous CeO2 was first synthesized by hydrothermal method,and then used to synthesize different contents of CuO)x/CeO2(x:molar ratio of Cu to Ce) by deposition-precipitation method.These materials were characterized by X-ray diffraction(XRD),N2 adsorption and desorption,H2 temperature programmed reduction(H2-TPR) and O2 temperature programmed desorption(O2-TPD) to study the crystal structure,surface area,and the mechanism of CO oxidation.The results show that,on XRD patterns,no evidence of CuO diffraction peaks is present until Cu loading is increased to 20%.The BET surface area decreases noticeably with the increase of Cu content.Compared with other samples,the better reducibility and activity oxygen species of(CuO)10%/CeO2coincide with its better catalytic activity.
基金the financial support from NNSFC(Project 21373054,21303023,21173052)the Natural Science Foundation of Shanghai Science and Technology Committee(08DZ2270500)
文摘The morphology effect of Zr-doped CeOwas studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zrdoped CeOnanorods exhibited the highest catalytic performance（yield of styrene oxide and TOF value）followed by nanoparticles and nanocubes. For the Zr-doped CeOnanorods, the apparent activation energy is 56.3 k J/mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes（73.3 and 93.4 k J/mol）. The high resolution transmission electron microscopy results indicated that（100） and（110） crystal planes are predominantly exposed for Zr-doped CeOnanorods while（100）and（111） for nanocubes,（111） for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeOnanorods is mainly attributed to the higher percentage of Cespecies and more oxygen vacancies, which are associated with their exposed（100） and（110） crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeOnanorods did not lose its initial high catalytic activity after five successive recycles.
基金Project supported by National Natural Science Foundation of China(51972097)This work was financially supported by the Science Foundation of Hebei Normal University,China(L2019K11).This work was also financially supported by the project WINLEDS—POCI-01-0145-FEDER-030351 and developed within the scope of the project CICECO-Aveiro Institute of Materials,FCT Ref.UID/CTM/50011/2019,financed by national funds through the FCT/MCTES.
文摘The Sr2 CeO4:Ln3+(Ln=Eu,Dy)fine phosphor particles were prepared by a facile wet chemical approach,in which the consecutive hydrothermal-combustion reaction was performed.The doping of Ln3+into Sr2 CeO4 has little influence on the structure of host,and the as-prepared samples display wellcrystallized spherical or elliptical shape with an average particle size at about 100-200 nm.For Eu3+ions-doped Sr2 CeO4,with the increase of Eu3+-doping concentration,the blue light emission band with the maximum at 468 nm originating from a Ce4+→O2-charge transfer of the host decreases obviously and the characteristic red light emission of Eu3+(5 D0→7 F2 transition at 618 nm)is enhanced gradually.Simultaneously,the fluorescent lifetime of the broadband emission of Sr2 CeO4 decreases with the doping of Eu3+,indicating an efficient energy transfer from the host to the doping Eu3+ions.The ene rgy transfer efficiency from the host to Eu3+was investigated in detail,and the emitting color of Sr2 CeO4:Eu3+can be easily tuned from blue to red by varying the doping concentration of Eu3+ions.Moreover,the luminescence of Dy3+-doped Sr2 CeO4 was also studied.Similar energy transfer pheno menon can be observed,and the incorporation of Dy3+into Sr2 CeO4 host leads to the characteristic emission of 4 F9/2→6 H15/2(488 nm,blue light)and 4 F9/2→6 H13/2(574 nm,yellow light)of Dy3+.The Sr2 CeO4:Ln3+fine particles with tunable luminescence are quite beneficial for its potential applications in the optoelectronic fields.
基金Funded by the National Natural Science Foundation of China(No.51372197)the Basic Research Plan of Natural Science of Shaanxi Province(No.2020JQ-754)+4 种基金the Key Innovation Team of Shaanxi Province(No.2014KCT-04)the Special Project of Shaanxi Province(No.19JK0490)the Construction and Promotion of Highlevel Achievements in Material Science and Engineering Discipline of Xi’an University of Science and Technology(No.2040519061)the Study on Preparation and Properties of New Solid-wastebased Cementitious Materials(No.6000190120)the Xi’an University of Science and Technology Doctoral Start-up Project(No.2018QDJ011)。
文摘A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral phase,morphology,and optical performances of the synthesized catalyst samples were characterized by XRF,XRD,SEM,UV-Vis DRS,and so on.XRD and SEM results show that calcium silicate hydrate(Ca1.5SiO3.5·xH2O)mineral phase is formed in the carrier sample,and the prepared catalyst specimens are made up of approximately 50 nm particles.After 6 hours of xenon lamp irradiation,the catalyst supported on V-doped 8wt%CeO_(2) exhibits the highest photocatalytic hydrogen production activity(8292μmol/g),which is attributed to the interaction between the V-doped CeO_(2) active components and FeO existed in catalyst carrier.A possible photocatalytic decomposition of water for hydrogen production mechanism over the V-8CeO_(2)/AC catalyst was proposed.
文摘Propylene,a readily accessible and economically viable light olefin,has garnered substantial interest for its potential conversion into valuable higher olefins through oligomerization processes.The distribution of products is profoundly influenced by the catalyst structure.In this study,Fe_(2)O_(3)-doped NiSO_(4)/Al_(2)O_(3) catalysts have been meticulously developed to facilitate the selective trimerization of propylene under mild conditions.Significantly,the 0.25Fe_(2)O_(3)-NiSO_(4)/Al_(2)O_(3) catalyst demonstrates an enhanced reaction rate(48.5 mmol_(C3)/(g_(cat).·h)),alongside a high yield of C9(~32.2%),significantly surpassing the performance of the NiSO_(4)/Al_(2)O_(3) catalyst(C9:~24.1%).The incorporation of Fe_(2)O_(3) modifies the migration process of sulfate ions,altering the Lewis acidity of the electron-deficient Ni and Fe sites on the catalyst and resulting a shift in product distribution from a Schulz-Flory distribution to a Poisson distribution.This shift is primarily ascribed to the heightened energy barrier for theβ-H elimination reaction in the C6 alkyl intermediates on the doped catalyst,further promoting polymerization to yield a greater quantity of Type II C9.Furthermore,the validation of the Cossee-Arlman mechanism within the reaction pathway has been confirmed.It is noteworthy that the 0.25Fe_(2)O_(3)-NiSO_(4)/Al_(2)O_(3) catalyst exhibits remarkable stability exceeding 80 h in the selective trimerization of propylene.These research findings significantly enhance our understanding of the mechanisms underlying olefin oligomerization reactions and provide invaluable insights for the development of more effective catalysts.
文摘The electrical properties of TiO2-based varistor ceramics with different amount of CeO2 were investigated by measuring the properties of V-I, permittivity, density and boundary defect barriers. It is found that an optimal composition doped with 0.7% CeO2 exhibits the highest nonlinear coefficient of 10.5, the highest breakdown voltage of 12.77 V·mm^-1, the ultrahigh permittivity of 82900（measured at 1 kHz）, and the highest density of 4.15 g·cm^-3, which is consistent with the highest and narrowest grain-boundary defect barriers. In order to illustrate the grain boundary barriers formation in TiO2-Nb2O5-MnCO3-CeO2 varistor, an grain-boundary defect barrier model was also introduced.
基金Project supported by the National Natural Science Foundation of China(Grant No.61306098)
文摘The N and C doping effects on the crystal structures, electronic and optical properties of fluorite structure CeO2 have been investigated using the first-principles calculation. Co-doping these two elements results in the local lattice distortion and volume expansion of CeO2. Compared with the energy hand structure of pure CeO2, some local energy levels appear in the forbidden band, which may facilitate the light absorption. Moreover, the enhanced photo-catalytic properties of CeO2 were explained through the absorption spectra and the selection rule of the band-to-band transitions.
文摘The role of ceria doping (0.75 - 3 mol%) on solid-solid interactions between ferric and cobaltic oxides was investigated. The investigated solids were characterized by TGA, DTA, XRD and HRTEM. The results revealed that ceria much enhanced the formation of nanosized CoFe2O4 (10 - 30 nm). The stimulation effect of ceria towards cobalt ferrite formation was evidenced from analysis of DTA and XRD investigations. In fact, the area of endothermic peak located at 575℃- 680℃ relative to solid-solid interaction between ferric and cobaltic oxide increased by increasing the dopant concentration. This treatment decreased the activation energy of formation of the produced ferrite from 33 - 9.2 kJ/mol upon doping with 3 mol% CeO2. HRTEM analysis revealed the formation of homogenous nanosized CoFe2O4. The formation effect of ceria dopant towards the formation of CoFe2O4 has been tentatively attributed to an effective increase in the mobility of the reacting cations.
文摘The catalytic activity measurement for the NO+CO reaction over CuO/CeO\-2/\%γ\%\|Al\-2O\-3 catalysts at a low\|temperature(200 ℃) shows that the activity is strongly related to ceria loading amount, and both surface dispersed ceria species and crystalline CeO\-2 shows a significant enhancement on the activity. The effect of ceria species is contributed to their promoting the reduction of copper oxide species.
