Ce–Zr solid solution(CexZr1-xO2,CZO)was prepared by the citric acid sol–gel method.The CZO was then used as a support for Pd/CZO catalysts for the oxidative carbonylation of phenol to diphenyl carbonate.The Pd/CZO c...Ce–Zr solid solution(CexZr1-xO2,CZO)was prepared by the citric acid sol–gel method.The CZO was then used as a support for Pd/CZO catalysts for the oxidative carbonylation of phenol to diphenyl carbonate.The Pd/CZO catalyst showed enhanced activity and diphenyl carbonate selectivity compared with the Pd/CeO2 catalyst.The catalytic performance of Pd/CZO was influenced by the calcination temperature of the CZO support.X-ray diffraction,scanning electron microscopy,N2 adsorption–desorption measurements,X-ray photoelectron spectroscopy and H2 temperature-programmed reduction measurements were used to investigate the effects of Zr doping and calcination temperature.The catalytic performance of Pd/CZO and Pd/CeO2 for the oxidative carbonylation of phenol was affected by several factors,including the specific surface area,Ce^3+and/or oxygen vacancy content,oxygen species type and Pd(II)content of the catalyst.All these properties were influenced by Zr doping and the calcination temperature of the CZO support.展开更多
The Sm–Zr–Fe–Co–Ti quinary-alloys with ThMn12 structure has attracted wide attention for ultra-high intrinsic magnetic properties,showing potentiality to be developed into rare-earth permanent magnets.The Ti eleme...The Sm–Zr–Fe–Co–Ti quinary-alloys with ThMn12 structure has attracted wide attention for ultra-high intrinsic magnetic properties,showing potentiality to be developed into rare-earth permanent magnets.The Ti element in alloys is crucial for phase stability and magnetic properties,and lower Ti content can increase intrinsic magnetic properties but reduce phase stability.In this study,the 1:12 single-phase melt-spun ribbons with low Ti content was successfully prepared using a rapid solidification non-equilibrium method for the Sm1.1Zr_(0.2)Fe_(9.2)Co_(2.3)Ti_(0.5) quinary-alloy.However,this non-equilibrium ribbon did not achieve good magnetic hardening due to the uneven microstructure and microstrain.Then,annealing was carried out to eliminate micro-strain and homogenize microstructure,therefore,remanence and coercivity were significantly improved even the precipitation of a small amount of a-Fe phase which were not conducive to coercivity.The remanence of 86.1 emu/g and coercivity of 151 kA/m was achieved when annealing at 850℃ for 45 min.After hot pressing,under the action of high temperature and pressure,a small portion of ThMn12 phases in the magnet decompose into Sm-rich phases and a-Fe,while remanence of 4.02 kGs(1 Gs=10^(-4) T),and coercivity of 1.12 kOe(1 Oe=79.5775 A·m^(-1))were still acquired.Our findings can provide reference for exploring practical permanent magnets made of 1:12 type quinary-alloys.展开更多
Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would indu...Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would induce bulk structure degradation and interfacial environment deterioration,and the absence of Co element reduces the lithium diffusion kinetics,severely limiting the performance liberation of this kind of cathodes.Herein,a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi_(0.9)Mn_(0.1)O_(2)(NM91)cathode.On the one hand,the Ti/Zr co-doping weakens the Li^(+)/Ni^(2+)mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti^(4+)and Zr^(4+),increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases.On the other hand,they enhance the lattice oxygen stability because of the strong Ti-O and Zr-O bonds,inhibiting the undesired H3 phase transition and lattice oxygen loss,improving the bulk structure and cathode-electrolyte interface stability.As a result,the Ti/Zr co-doped NM91(NMTZ)exhibits a 91.2%capacity retention rate after 100 cycles,while that of NM91 is only82.9%.Also,the NMTZ displays better rate performance than NM91 with output capacities of 115 and93 mA h g^(-1)at a high current density of 5 C,respectively.Moreover,the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg^(-1),making the ultra-high nickel cobaltfree lithium layered oxide cathode closer to practical applications.展开更多
Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-s...Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.展开更多
The oxidation behavior of Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys at 800 °C for exposure time up to 100 h was examined. It is shown that oxidation rate of experimental alloys obeys the parabolic kinetics. Ti?22Al...The oxidation behavior of Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys at 800 °C for exposure time up to 100 h was examined. It is shown that oxidation rate of experimental alloys obeys the parabolic kinetics. Ti?22Al?26Nb?1Zr alloy demonstrates more excellent oxidation resistance than the other two alloys. The main oxidation products are TiO2, Al2O3 and AlNbO4 phases for all these alloys. For the Ti?22Al?26Nb?1Zr alloy, Zr addition can modify the growth mechanism of oxide scale, which can effectively hinder the diffusion of oxygen. Whereas, reaction of Zr with oxygen leads to the formation of ZrO2 precipitates for the Ti?22Al?21Nb?6Zr alloy, which promotes the oxygen ingress into the substrate. Meanwhile, oxidation affected zones, including internal-oxidation layer and oxygen-enriched zone, are present beneath the outmost oxide scale. The difference in these zones is derived from the phase constitution in the starting Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys.展开更多
The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and diff...The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and differential scanning calorimeter （DSC） methods. The results show that severe dendritic segregation exists in the experimental alloy ingot. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varies periodically. The main secondary phase is Al2Cu. The overburnt temperature of the alloy is 520 °C. The second phases are gradually dissolved into the matrix, and the grain boundaries become spare and thin during homogenization with increasing temperature or prolonging holding time. Homogenization can be described by a constitutive equation in exponential function. The suitable homogenization treatment for the alloy is （510 °C, 18 h）, which agrees well with the results of homogenization kinetic analysis.展开更多
The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were...The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.展开更多
Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied ...Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 ℃ using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick （Nb,X）Si2 outer layer and a thin （Ti,Nb）5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 ℃ in air.展开更多
The hot compression deformation behavior of Cu−3Ti−0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble−3500 thermal-mechanical simulator at temperatures from 700 to ...The hot compression deformation behavior of Cu−3Ti−0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble−3500 thermal-mechanical simulator at temperatures from 700 to 850℃ with the strain rates between 0.001 and 1 s^−1.The results show that work hardening,dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation.The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol.The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result,and the hot processing maps are established based on the dynamic material model.The optimal hot deformation temperature range is between 775 and 850℃ and the strain rate range is between 0.001 and 0.01 s^−1.展开更多
基金supported by the National Natural Science Foundation of China(21776057)the Natural Science Foundation of Tianjin City(Nos.17JCYBJC20100,18JCYBJC21500)the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Hebei Province(CL201605)。
文摘Ce–Zr solid solution(CexZr1-xO2,CZO)was prepared by the citric acid sol–gel method.The CZO was then used as a support for Pd/CZO catalysts for the oxidative carbonylation of phenol to diphenyl carbonate.The Pd/CZO catalyst showed enhanced activity and diphenyl carbonate selectivity compared with the Pd/CeO2 catalyst.The catalytic performance of Pd/CZO was influenced by the calcination temperature of the CZO support.X-ray diffraction,scanning electron microscopy,N2 adsorption–desorption measurements,X-ray photoelectron spectroscopy and H2 temperature-programmed reduction measurements were used to investigate the effects of Zr doping and calcination temperature.The catalytic performance of Pd/CZO and Pd/CeO2 for the oxidative carbonylation of phenol was affected by several factors,including the specific surface area,Ce^3+and/or oxygen vacancy content,oxygen species type and Pd(II)content of the catalyst.All these properties were influenced by Zr doping and the calcination temperature of the CZO support.
基金the National Key Research and De-velopment Program of China(Grant No.2021YFB3500300)the National Natural Science Foundation of China(Grant No.51931007)the Program of Top Disciplines Construc-tion in Beijing(Grant No.PXM2019014204500031).
文摘The Sm–Zr–Fe–Co–Ti quinary-alloys with ThMn12 structure has attracted wide attention for ultra-high intrinsic magnetic properties,showing potentiality to be developed into rare-earth permanent magnets.The Ti element in alloys is crucial for phase stability and magnetic properties,and lower Ti content can increase intrinsic magnetic properties but reduce phase stability.In this study,the 1:12 single-phase melt-spun ribbons with low Ti content was successfully prepared using a rapid solidification non-equilibrium method for the Sm1.1Zr_(0.2)Fe_(9.2)Co_(2.3)Ti_(0.5) quinary-alloy.However,this non-equilibrium ribbon did not achieve good magnetic hardening due to the uneven microstructure and microstrain.Then,annealing was carried out to eliminate micro-strain and homogenize microstructure,therefore,remanence and coercivity were significantly improved even the precipitation of a small amount of a-Fe phase which were not conducive to coercivity.The remanence of 86.1 emu/g and coercivity of 151 kA/m was achieved when annealing at 850℃ for 45 min.After hot pressing,under the action of high temperature and pressure,a small portion of ThMn12 phases in the magnet decompose into Sm-rich phases and a-Fe,while remanence of 4.02 kGs(1 Gs=10^(-4) T),and coercivity of 1.12 kOe(1 Oe=79.5775 A·m^(-1))were still acquired.Our findings can provide reference for exploring practical permanent magnets made of 1:12 type quinary-alloys.
基金funded by the Key R&D Program of Jilin Province(20220201132GX)the Key R&D Program of Hubei Province(2022BAA084)the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization(RERU2023008)。
文摘Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would induce bulk structure degradation and interfacial environment deterioration,and the absence of Co element reduces the lithium diffusion kinetics,severely limiting the performance liberation of this kind of cathodes.Herein,a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi_(0.9)Mn_(0.1)O_(2)(NM91)cathode.On the one hand,the Ti/Zr co-doping weakens the Li^(+)/Ni^(2+)mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti^(4+)and Zr^(4+),increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases.On the other hand,they enhance the lattice oxygen stability because of the strong Ti-O and Zr-O bonds,inhibiting the undesired H3 phase transition and lattice oxygen loss,improving the bulk structure and cathode-electrolyte interface stability.As a result,the Ti/Zr co-doped NM91(NMTZ)exhibits a 91.2%capacity retention rate after 100 cycles,while that of NM91 is only82.9%.Also,the NMTZ displays better rate performance than NM91 with output capacities of 115 and93 mA h g^(-1)at a high current density of 5 C,respectively.Moreover,the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg^(-1),making the ultra-high nickel cobaltfree lithium layered oxide cathode closer to practical applications.
基金Project(2011B050400007)supported by the International Cooperation Program of Guangdong Province,China
文摘Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.
基金Project(2011CB605503)supported by the National Basic Research Program of China
文摘The oxidation behavior of Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys at 800 °C for exposure time up to 100 h was examined. It is shown that oxidation rate of experimental alloys obeys the parabolic kinetics. Ti?22Al?26Nb?1Zr alloy demonstrates more excellent oxidation resistance than the other two alloys. The main oxidation products are TiO2, Al2O3 and AlNbO4 phases for all these alloys. For the Ti?22Al?26Nb?1Zr alloy, Zr addition can modify the growth mechanism of oxide scale, which can effectively hinder the diffusion of oxygen. Whereas, reaction of Zr with oxygen leads to the formation of ZrO2 precipitates for the Ti?22Al?21Nb?6Zr alloy, which promotes the oxygen ingress into the substrate. Meanwhile, oxidation affected zones, including internal-oxidation layer and oxygen-enriched zone, are present beneath the outmost oxide scale. The difference in these zones is derived from the phase constitution in the starting Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys.
文摘The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDX）, and differential scanning calorimeter （DSC） methods. The results show that severe dendritic segregation exists in the experimental alloy ingot. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varies periodically. The main secondary phase is Al2Cu. The overburnt temperature of the alloy is 520 °C. The second phases are gradually dissolved into the matrix, and the grain boundaries become spare and thin during homogenization with increasing temperature or prolonging holding time. Homogenization can be described by a constitutive equation in exponential function. The suitable homogenization treatment for the alloy is （510 °C, 18 h）, which agrees well with the results of homogenization kinetic analysis.
基金the Foundation of Wuhan University of Science and Technology
文摘The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.
基金Projects(51371145,51431003,U1435201,51401166)supported by the National Natural Science Foundation of ChinaProject(B080401)supported by the Programme of Introducing Talents of Discipline to Universities,China
文摘Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 ℃ using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick （Nb,X）Si2 outer layer and a thin （Ti,Nb）5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 ℃ in air.
基金Project(2016YFB0301300)supported by the National Key Research and Development Program of ChinaProject(U1637210)supported by the National Natural Science Foundation of China+1 种基金Project(2019B10088)supported by the Technology Research Program of Ningbo,ChinaProject supported by State Key Laboratory of Powder Metallurgy,Central South University,China。
文摘The hot compression deformation behavior of Cu−3Ti−0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble−3500 thermal-mechanical simulator at temperatures from 700 to 850℃ with the strain rates between 0.001 and 1 s^−1.The results show that work hardening,dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation.The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol.The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result,and the hot processing maps are established based on the dynamic material model.The optimal hot deformation temperature range is between 775 and 850℃ and the strain rate range is between 0.001 and 0.01 s^−1.
