The 1：1 water model of a twin-roll strip caster was set up based on the Froude number and the Reynolds number similarity criteria. A new type metal delivery system was designed for the twin-roll strip caster. The lev...The 1：1 water model of a twin-roll strip caster was set up based on the Froude number and the Reynolds number similarity criteria. A new type metal delivery system was designed for the twin-roll strip caster. The level fluctuation and the fluid flow in the pool of the water model were measured using the level detector and the 3D-LDV （laser Doppler velocimetry） technology. It is shown that a wedged delivery system can produce the desirable level fluctuation and even fluid flow distribution in the pool Numerical simulations for the water model were performed. Comparisons between the numerical and physical simulation results show good agreement near the side dams.展开更多
Background: Results from experimental and clinical studies have shown that mechanical ventilation or/and hyperoxia may aggravate a pre-existing lung injury or even cause lung injury in healthy lungs by affecting the e...Background: Results from experimental and clinical studies have shown that mechanical ventilation or/and hyperoxia may aggravate a pre-existing lung injury or even cause lung injury in healthy lungs by affecting the expression of MMP-9, but the MMP-9 effects are controversial. How are MMP-9 regulated when multicausative factors of injury such as different FiO2, PIP, and respiratory time (RT) impose simultaneously on lungs? Methods: Newborn New Zealand white rabbits were randomly allocated to an unventilated air control group or to one of the 2 × 3 × 3 ventilation strategies by using a factorial design, with different FiO2, PIP, and RT. Then, lung wet-to-dry ratio (W/D), lung histopathology scores, transmission electron microscope, and cells in BALF were analyzed in these different groups. MMP-9 levels were studied by immunohistochemistry and ELISA. Results: MMP-9 levels were significantly different among 3 PIP ventilation regimes (F = 7.215) and MPIP group was the highest among 3 PIP groups. The lung histopathology score in 100% oxygen was significantly higher than in 45% oxygen group (F = 9.037) and MPIP group was the lowest among 3 PIP groups (F = 57.515) and RT 6 h was more serious than RT 1 h. MMP-9 positively correlated with monocytes, but negatively correlated with neutrophils and lung injury histopathology scores. Conclusions: Different PIP and FiO2 exert simultaneously on newborn lung in newborn rabbits ventilation, only mechanical stretch stimulation affects MMP-9 synthesis. Advisable mechanical stretch can promote MMP-9 expression and has protective role in lung in VILI. HPIP causes barotraumas and LPIP induces atelectrauma.展开更多
With the deepening understanding for the concept of sustainable development,the utilization of minerals is no longer limited to the traditional way.In this study,an environment friendly method for preparing Fe-Al_(2)O...With the deepening understanding for the concept of sustainable development,the utilization of minerals is no longer limited to the traditional way.In this study,an environment friendly method for preparing Fe-Al_(2)O_(3)composites by using natural minerals was investigated.Additionally,the effects of CeO_(2)on the properties of composites were studied.The mechanical properties of Fe-Al_(2)O_(3)composites prepared by natural minerals are affected by the brittleness of glass phase.The strength and toughness of the glass phase in the composite are improved successfully by using rare earth oxides,indicating that the natural rare earths in Bayan Obo minerals have an enhanced influence on the properties of composite materials.The results show that the properties of glass phase can be significantly improved by addition of CeO_(2).At the optimal addition of 3 wt%CeO_(2),the composite achieves the density of 4.21 g/cm^(3),flexural strength of 401 MPa,Vickers hardness of 13.07 GPa and fracture toughness of 6.58 MPa·m^(1/2).The composite has excellent mechanical properties,which can be used in engineering as a cheap structural material.This study aims at reducing waste emissions,improving energy efficiencies and avoiding waste of rare earth resources during the preparation of composite materials.展开更多
In this paper,CeO2 with a pore size of 2-4 nm was synthesized by hydrothermal method.The CeO2 modified graphene-supported Pt catalyst was prepared by the microwave-assisted ethylene glycol reduction chloroplatinic aci...In this paper,CeO2 with a pore size of 2-4 nm was synthesized by hydrothermal method.The CeO2 modified graphene-supported Pt catalyst was prepared by the microwave-assisted ethylene glycol reduction chloroplatinic acid method,and the effect of the addition of CeO2 prepared by different hydrothermal reaction time on the catalytic performance of Pt-based catalysts was investigated.The microstructures of CeO2 and catalysts were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),specific surface area and pore size analyzer(BET),scanning electron microscopy(SEM)and electron spectroscopy(EDAX),transmission electron microscopy(TEM),and the catalysts electrochemical performance was tested by electrochemical workstation.The results show that the catalytic performance of the four catalysts with CeO2 is better than that of the catalyst without CeO2.Adding CeO2 with a specific surface area of 120.15 m2/g prepared by hydrothermal reaction time of 39 h to Pt/C synthesis catalyst,its electrocatalytic performance,stability and resistance to poisoning are the best.The electrochemical active surface area is 102.83 m2/g,the peak current density of ethanol oxidation is 757.17 A/g and steady-state current density of 1100 s is 108.17 A/g which shows the lowest activation energy for ethanol oxidation reaction.When the cyclic voltammogram is scanned for 500 cycles,the oxidation peak current density retention rate is 87.74%.展开更多
Rare earth Er^(3+)doped(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)(x=0.1,0.2,and 0.3)ceramic samples were synthesized using a solid state reaction method.The microstructure and thermal properties of these ceramics were investigat...Rare earth Er^(3+)doped(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)(x=0.1,0.2,and 0.3)ceramic samples were synthesized using a solid state reaction method.The microstructure and thermal properties of these ceramics were investigated to evaluate their potential as thermal barrier coating materials.The results show that ceramics are compact with regular-shaped grains of 1-5μm size.(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)has a pyrochlore structure mainly determined by ionic radius ratio,but the ordering degree decreases with increase of the Er_(2)O_(3)content.There is no phase transformation from 1000 to 1200℃,and the(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)ceramics exhibit excellent phase stability during thermal treatment at 1200℃for 100 h and 1400℃for 50 h.The thermal conductivities of dense(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)ceramics range from 1.52 to 1.59 W/(m·K),which is lower than that of Sm_(2)Zr_(2)O_(7),and decrease as the Er2O3content increases.Besides,the thermal expansion coefficient of(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)is higher than that of Sm_(2)Zr_(2)O_(7).展开更多
Er_(x)Ti_(0.1)Zr_(0.9-x)O_(2-1.5 x)(x=0.04,0.05,0.06,0.07,0.08) ceramics were synthesized by a solid-state reaction method.The influence of the Er^(3+) addition on the phase composition,Vickers hardness,fracture tough...Er_(x)Ti_(0.1)Zr_(0.9-x)O_(2-1.5 x)(x=0.04,0.05,0.06,0.07,0.08) ceramics were synthesized by a solid-state reaction method.The influence of the Er^(3+) addition on the phase composition,Vickers hardness,fracture toughness,and thermal conductivity of this ceramic material was investigated.The X-ray diffraction results reveal that the c-ZrO_(2) content increases from 1.85 vol% to 33.89 vol%,and the percentage of t-ZrO_(2) decreases from 98.15 vol% to 66.11 vol% with the increase in Er^(3+) content from 4 mol% to 8 mol%.Moreover,the addition of Er^(3+) is beneficial to the volume expansion of the unit cell.At the same time,the incorporation of Er^(3+) weakens the coordination of oxygen ions around the metal cations,resulting in a corresponding decrease in the tetragonality of the t-ZrO_(2).The Vickers hardness and fracture toughness of the Er_(x)Ti_(0.1)Zr_(0.9-x)O_(2-1.5)_(x) ceramics show increasing and decreasing trends,respectively.The thermal conductivity has a significant decline due to point defects caused by the Er^(3+) doping.The 8 ETZ ceramic exhibits the highest Vickers hardness(12.7 GPa),the lowest fracture toughness(7.6 MPa·m^(1/2)),and the lowest average thermal conductivity(1.85 W/(m·K)) in the temperature range of 200-1000℃.All of the above properties are higher than those of the Y_(2)O_(3)-stabilized ZrO_(2) ceramic.展开更多
La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)is recognized as one of the most promising cathode materials for the highly-desired intermediatetemperature solid oxide fuel cell(IT-SOFC)technology.However,it is still ch...La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)is recognized as one of the most promising cathode materials for the highly-desired intermediatetemperature solid oxide fuel cell(IT-SOFC)technology.However,it is still challenged by polarization losses due to reduced operation temperatures.In this work,a series of Ba^(2+)-doped La0.6-xBaxSr0.4Co0.2Fe0.8O3-δ(LBSCFx,x=0.05,0.10,0.15,and 0.20)materials are successfully synthesized and their electrochemical performances are evaluated as a cathode for IT-SOFC technology.The study shows that,compared to the un-doped LSCF,the Ba^(2+)-doped LBSCF possess higher electrical conductivities at 500-800℃ and display lower polarization resistances to oxygen adsorption/dissociation.As a result,the Ni-SDC|SDC|LBSCF0.20 cell(SDC=samarium-doped cerium,Sm_(0.2)Ce_(0.8)O_(1.9))delivers a high maximum power density of 0.704 W/cm^(2)at 750℃,which is>30%higher than the Ni-SDC|SDC|LSCF cell.This work reveals that Ba^(2+)-doping is effective in enhancing oxygen catalytic activity of LSCF-based cathode materials,demonstrating a new and commercial-feasible strategy in developing high performance cathode materials for the IT-SOFC technology.展开更多
To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel(430 SS)as bipolar plates for direct formic acid fuel cells(DFAFCs),a Nb_(0.8)Zr_(0.2) layer has been successfully synthesized...To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel(430 SS)as bipolar plates for direct formic acid fuel cells(DFAFCs),a Nb_(0.8)Zr_(0.2) layer has been successfully synthesized via the pulsed laser deposition(PLD)technique on the surface of 430 SS.This Nb_(0.8)Zr_(0.2) layer is smooth,uniform,and comparatively compact without any surface flaw and micropore.Investigation under the simulated anodic environment of DFAFCs(0.05 M H_(2)SO_(4)+2 ppm HF+10 M HCOOH at 70℃)shows that the corrosion resistance of 430 SS is obviously ameliorated after the PLD modification.In addition,the interfacial contact resistance of Nb_(0.8)Zr_(0.2)-430 SS(6.0 mΩcm^(2))is much smaller than that of bare 430 SS(151.3 mΩcm^(2))at the clamping force of 140 N cm^(-2).Besides,diff erent from the highly increased interfacial contact resistance of bare 430 SS,the Nb_(0.8)Zr_(0.2)-430 SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.展开更多
The existence form and effect of La on the phase composition,morphology,recombination of photocarriers,and optical absorptivity of La-F codoped TiO2 were investigated.Experimental results indicate that all the phase c...The existence form and effect of La on the phase composition,morphology,recombination of photocarriers,and optical absorptivity of La-F codoped TiO2 were investigated.Experimental results indicate that all the phase composition of samples is anatase TiO2,the grain sizes decrease with the increasing of La content The catalysts have a well-defined spherical structure with an average size of 12-14 nm,and the doping elements are uniformly dispersed.Compared with pure TiO2,the absorption edge of La1.5F5-TiO2 red shifts from 388 to 437 nm,accordingly the energy gap(Eg) reduces from 32 to 2.84 eV,Besides,the recombination rate of electron-holes in La1.5F5-TiO2 is the weakest among the prepared samples,and the specific surface area of La1.5F5-TiO2 reaches 105.27 m2/g.The apparent reaction rate constant k of La1.5F5-TiO2 for methylene blue(MB) degradation under visible light obtained from the apparent first-order model achieves 0.0166±0.52 min-1,which is greater than 0.0033±0.09 min 1 of TiO2.Moreover,high-resolution transmission electron microscopy(HRTEM) observation reveals that there coexist La2O3 particles in the co-doped TiO2.展开更多
The influences of equimolar substitution of yttria by gadolinia on the phase constituent and stability for Y203- Ta2Os-Zr02 ceramics have been investigated. The ceramics with the Gd content lower than 8 tool% exhibit ...The influences of equimolar substitution of yttria by gadolinia on the phase constituent and stability for Y203- Ta2Os-Zr02 ceramics have been investigated. The ceramics with the Gd content lower than 8 tool% exhibit pure tetragonal phase as well as high tetragonal phase stability. However, the high Gd containing ceramics consist of t-Zr02, m-Zr02 and monoclinic GdTa04 and show complicated phase evolution behaviors. The fractions of monoclinic Zr02 and GdTa04 increase with increasing Gd content, indicating that the excessive substitution of Gd for Y results in a reduction in the tetragonal phase stability. In addition, the lower Gd containing ceramics show an almost invariable tetragonality, while the higher Gd containing ceramics reveal a composition-dependent tetragonality. Accordingly, an association of the tetragonal phase stability and tetragonality with the Gd concentration is established, which provides us a clue to understand the phase stability of these ceramics.展开更多
基金This work was financially supported by the National Natural Science Foundation of Inner Mongolia of China (No.200408020715).
文摘The 1：1 water model of a twin-roll strip caster was set up based on the Froude number and the Reynolds number similarity criteria. A new type metal delivery system was designed for the twin-roll strip caster. The level fluctuation and the fluid flow in the pool of the water model were measured using the level detector and the 3D-LDV （laser Doppler velocimetry） technology. It is shown that a wedged delivery system can produce the desirable level fluctuation and even fluid flow distribution in the pool Numerical simulations for the water model were performed. Comparisons between the numerical and physical simulation results show good agreement near the side dams.
文摘Background: Results from experimental and clinical studies have shown that mechanical ventilation or/and hyperoxia may aggravate a pre-existing lung injury or even cause lung injury in healthy lungs by affecting the expression of MMP-9, but the MMP-9 effects are controversial. How are MMP-9 regulated when multicausative factors of injury such as different FiO2, PIP, and respiratory time (RT) impose simultaneously on lungs? Methods: Newborn New Zealand white rabbits were randomly allocated to an unventilated air control group or to one of the 2 × 3 × 3 ventilation strategies by using a factorial design, with different FiO2, PIP, and RT. Then, lung wet-to-dry ratio (W/D), lung histopathology scores, transmission electron microscope, and cells in BALF were analyzed in these different groups. MMP-9 levels were studied by immunohistochemistry and ELISA. Results: MMP-9 levels were significantly different among 3 PIP ventilation regimes (F = 7.215) and MPIP group was the highest among 3 PIP groups. The lung histopathology score in 100% oxygen was significantly higher than in 45% oxygen group (F = 9.037) and MPIP group was the lowest among 3 PIP groups (F = 57.515) and RT 6 h was more serious than RT 1 h. MMP-9 positively correlated with monocytes, but negatively correlated with neutrophils and lung injury histopathology scores. Conclusions: Different PIP and FiO2 exert simultaneously on newborn lung in newborn rabbits ventilation, only mechanical stretch stimulation affects MMP-9 synthesis. Advisable mechanical stretch can promote MMP-9 expression and has protective role in lung in VILI. HPIP causes barotraumas and LPIP induces atelectrauma.
基金supported by the National Key R&D Program of China(2020YFC1909105)。
文摘With the deepening understanding for the concept of sustainable development,the utilization of minerals is no longer limited to the traditional way.In this study,an environment friendly method for preparing Fe-Al_(2)O_(3)composites by using natural minerals was investigated.Additionally,the effects of CeO_(2)on the properties of composites were studied.The mechanical properties of Fe-Al_(2)O_(3)composites prepared by natural minerals are affected by the brittleness of glass phase.The strength and toughness of the glass phase in the composite are improved successfully by using rare earth oxides,indicating that the natural rare earths in Bayan Obo minerals have an enhanced influence on the properties of composite materials.The results show that the properties of glass phase can be significantly improved by addition of CeO_(2).At the optimal addition of 3 wt%CeO_(2),the composite achieves the density of 4.21 g/cm^(3),flexural strength of 401 MPa,Vickers hardness of 13.07 GPa and fracture toughness of 6.58 MPa·m^(1/2).The composite has excellent mechanical properties,which can be used in engineering as a cheap structural material.This study aims at reducing waste emissions,improving energy efficiencies and avoiding waste of rare earth resources during the preparation of composite materials.
基金Project supported by the National Natural Science Foundation of China(51474133,51864040)the Natural Science Foundation of Inner Mongolia Autonomous Region(2018LH02006).
文摘In this paper,CeO2 with a pore size of 2-4 nm was synthesized by hydrothermal method.The CeO2 modified graphene-supported Pt catalyst was prepared by the microwave-assisted ethylene glycol reduction chloroplatinic acid method,and the effect of the addition of CeO2 prepared by different hydrothermal reaction time on the catalytic performance of Pt-based catalysts was investigated.The microstructures of CeO2 and catalysts were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),specific surface area and pore size analyzer(BET),scanning electron microscopy(SEM)and electron spectroscopy(EDAX),transmission electron microscopy(TEM),and the catalysts electrochemical performance was tested by electrochemical workstation.The results show that the catalytic performance of the four catalysts with CeO2 is better than that of the catalyst without CeO2.Adding CeO2 with a specific surface area of 120.15 m2/g prepared by hydrothermal reaction time of 39 h to Pt/C synthesis catalyst,its electrocatalytic performance,stability and resistance to poisoning are the best.The electrochemical active surface area is 102.83 m2/g,the peak current density of ethanol oxidation is 757.17 A/g and steady-state current density of 1100 s is 108.17 A/g which shows the lowest activation energy for ethanol oxidation reaction.When the cyclic voltammogram is scanned for 500 cycles,the oxidation peak current density retention rate is 87.74%.
基金Project supported by the National High Technology Research and Development Program of China(2015AA034403)National Natural Science Foundation of China(51762036)The Science and Technology Program of Inner Mongolia(2019)。
文摘Rare earth Er^(3+)doped(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)(x=0.1,0.2,and 0.3)ceramic samples were synthesized using a solid state reaction method.The microstructure and thermal properties of these ceramics were investigated to evaluate their potential as thermal barrier coating materials.The results show that ceramics are compact with regular-shaped grains of 1-5μm size.(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)has a pyrochlore structure mainly determined by ionic radius ratio,but the ordering degree decreases with increase of the Er_(2)O_(3)content.There is no phase transformation from 1000 to 1200℃,and the(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)ceramics exhibit excellent phase stability during thermal treatment at 1200℃for 100 h and 1400℃for 50 h.The thermal conductivities of dense(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)ceramics range from 1.52 to 1.59 W/(m·K),which is lower than that of Sm_(2)Zr_(2)O_(7),and decrease as the Er2O3content increases.Besides,the thermal expansion coefficient of(Sm_(1-x)Er_(x))_(2)Zr_(2)O_(7)is higher than that of Sm_(2)Zr_(2)O_(7).
基金Project supported by the National High Technology Research and Development Program of China(2015AA034403)the National Natural Science Foundation of China(Grant No.51762036)。
文摘Er_(x)Ti_(0.1)Zr_(0.9-x)O_(2-1.5 x)(x=0.04,0.05,0.06,0.07,0.08) ceramics were synthesized by a solid-state reaction method.The influence of the Er^(3+) addition on the phase composition,Vickers hardness,fracture toughness,and thermal conductivity of this ceramic material was investigated.The X-ray diffraction results reveal that the c-ZrO_(2) content increases from 1.85 vol% to 33.89 vol%,and the percentage of t-ZrO_(2) decreases from 98.15 vol% to 66.11 vol% with the increase in Er^(3+) content from 4 mol% to 8 mol%.Moreover,the addition of Er^(3+) is beneficial to the volume expansion of the unit cell.At the same time,the incorporation of Er^(3+) weakens the coordination of oxygen ions around the metal cations,resulting in a corresponding decrease in the tetragonality of the t-ZrO_(2).The Vickers hardness and fracture toughness of the Er_(x)Ti_(0.1)Zr_(0.9-x)O_(2-1.5)_(x) ceramics show increasing and decreasing trends,respectively.The thermal conductivity has a significant decline due to point defects caused by the Er^(3+) doping.The 8 ETZ ceramic exhibits the highest Vickers hardness(12.7 GPa),the lowest fracture toughness(7.6 MPa·m^(1/2)),and the lowest average thermal conductivity(1.85 W/(m·K)) in the temperature range of 200-1000℃.All of the above properties are higher than those of the Y_(2)O_(3)-stabilized ZrO_(2) ceramic.
基金The project was supported by the National Natural Science Foundation of China(No.51974167)XRD,SEM and TEM examinations were assisted by the Center of Laboratory,Inner Monglia University of Science and Technology.
文摘La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)is recognized as one of the most promising cathode materials for the highly-desired intermediatetemperature solid oxide fuel cell(IT-SOFC)technology.However,it is still challenged by polarization losses due to reduced operation temperatures.In this work,a series of Ba^(2+)-doped La0.6-xBaxSr0.4Co0.2Fe0.8O3-δ(LBSCFx,x=0.05,0.10,0.15,and 0.20)materials are successfully synthesized and their electrochemical performances are evaluated as a cathode for IT-SOFC technology.The study shows that,compared to the un-doped LSCF,the Ba^(2+)-doped LBSCF possess higher electrical conductivities at 500-800℃ and display lower polarization resistances to oxygen adsorption/dissociation.As a result,the Ni-SDC|SDC|LBSCF0.20 cell(SDC=samarium-doped cerium,Sm_(0.2)Ce_(0.8)O_(1.9))delivers a high maximum power density of 0.704 W/cm^(2)at 750℃,which is>30%higher than the Ni-SDC|SDC|LSCF cell.This work reveals that Ba^(2+)-doping is effective in enhancing oxygen catalytic activity of LSCF-based cathode materials,demonstrating a new and commercial-feasible strategy in developing high performance cathode materials for the IT-SOFC technology.
基金financially supported by the National Natural Science Foundation of China(Nos.51962027,51974167,21968022,and 21868022)the Natural Science Foundation of Inner Mongolia(No.2019BS02002)+1 种基金the Project of Science Foundation of the Educational Department of Inner Mongolia(No.NJZY19135)the Inner Mongolia University of Science and Technology Innovation Fund(No.2019QDL-B23)。
文摘To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel(430 SS)as bipolar plates for direct formic acid fuel cells(DFAFCs),a Nb_(0.8)Zr_(0.2) layer has been successfully synthesized via the pulsed laser deposition(PLD)technique on the surface of 430 SS.This Nb_(0.8)Zr_(0.2) layer is smooth,uniform,and comparatively compact without any surface flaw and micropore.Investigation under the simulated anodic environment of DFAFCs(0.05 M H_(2)SO_(4)+2 ppm HF+10 M HCOOH at 70℃)shows that the corrosion resistance of 430 SS is obviously ameliorated after the PLD modification.In addition,the interfacial contact resistance of Nb_(0.8)Zr_(0.2)-430 SS(6.0 mΩcm^(2))is much smaller than that of bare 430 SS(151.3 mΩcm^(2))at the clamping force of 140 N cm^(-2).Besides,diff erent from the highly increased interfacial contact resistance of bare 430 SS,the Nb_(0.8)Zr_(0.2)-430 SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.
基金Project supported by the Natural Science Foundation of China(21407084,51474133)
文摘The existence form and effect of La on the phase composition,morphology,recombination of photocarriers,and optical absorptivity of La-F codoped TiO2 were investigated.Experimental results indicate that all the phase composition of samples is anatase TiO2,the grain sizes decrease with the increasing of La content The catalysts have a well-defined spherical structure with an average size of 12-14 nm,and the doping elements are uniformly dispersed.Compared with pure TiO2,the absorption edge of La1.5F5-TiO2 red shifts from 388 to 437 nm,accordingly the energy gap(Eg) reduces from 32 to 2.84 eV,Besides,the recombination rate of electron-holes in La1.5F5-TiO2 is the weakest among the prepared samples,and the specific surface area of La1.5F5-TiO2 reaches 105.27 m2/g.The apparent reaction rate constant k of La1.5F5-TiO2 for methylene blue(MB) degradation under visible light obtained from the apparent first-order model achieves 0.0166±0.52 min-1,which is greater than 0.0033±0.09 min 1 of TiO2.Moreover,high-resolution transmission electron microscopy(HRTEM) observation reveals that there coexist La2O3 particles in the co-doped TiO2.
基金the financial support for this research by the National Natural Science Foundation of China under Grant No.50974074the Program for New Century Excellent Talents in University under Grant No.NCET-10-0910the Natural Science Foundation of Inner Mongolia under Grant No.2011ZD09
文摘The influences of equimolar substitution of yttria by gadolinia on the phase constituent and stability for Y203- Ta2Os-Zr02 ceramics have been investigated. The ceramics with the Gd content lower than 8 tool% exhibit pure tetragonal phase as well as high tetragonal phase stability. However, the high Gd containing ceramics consist of t-Zr02, m-Zr02 and monoclinic GdTa04 and show complicated phase evolution behaviors. The fractions of monoclinic Zr02 and GdTa04 increase with increasing Gd content, indicating that the excessive substitution of Gd for Y results in a reduction in the tetragonal phase stability. In addition, the lower Gd containing ceramics show an almost invariable tetragonality, while the higher Gd containing ceramics reveal a composition-dependent tetragonality. Accordingly, an association of the tetragonal phase stability and tetragonality with the Gd concentration is established, which provides us a clue to understand the phase stability of these ceramics.
