The preparation of high-entropy(HE)ceramics with designed composition is essential for verifying the formability models and evaluating the properties of the ceramics.However,inevitable oxygen contamination in non-oxid...The preparation of high-entropy(HE)ceramics with designed composition is essential for verifying the formability models and evaluating the properties of the ceramics.However,inevitable oxygen contamination in non-oxide ceramics will result in the formation of metal oxide impurity phases remaining in the specimen or even escaping from the specimen during the sintering process,making the elemental compositions of the HE phase deviated from the designed ones.In this work,the preparation and thermodynamic analysis during the processing of equiatomic 9-cation HE carbide(HEC9)ceramics of the IVB,VB,and VIB groups were studied focusing on the removing of the inevitable oxygen impurity existed in the starting carbide powders and the oxygen contamination during the powder mixing processing.The results demonstrate that densification by spark plasma sintering(SPS)by directly using the mixed powders of the corresponding single-component carbides will inhibit the oxygen-removing carbothermal reduction reactions,and most of the oxide impurities will remain in the sample as(Zr,Hf)O_(2)phase.Pretreatment of the mixed powders at high temperatures in vacuum will remove most part of the oxygen impurity but result in a remarkable escape of gaseous Cr owing to the oxygen-removing reaction between Cr_(3)C_(2)and various oxide impurities.It is found that graphite addition enhances the oxygen-removing effect and simultaneously prevents the escape of gaseous Cr.On the other hand,although WC,VC,and Mo2C can also act as oxygen-removing agents,there is no metal-containing gaseous substance formation in the temperature range of this study.By using the heat-treated powders with added graphite,equiatomic HEC9 ceramics were successfully prepared by SPS.展开更多
Sustainable development has long been recognized as one of the most critical issues in today’s energy and environment-conscious society.It has never been more urgent to recycle and reuse the end-of-life cathode mater...Sustainable development has long been recognized as one of the most critical issues in today’s energy and environment-conscious society.It has never been more urgent to recycle and reuse the end-of-life cathode materials.Here,this work systematically investigates the structure-critical degradation mechanism of polycrystalline LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)(NCM),combining experimental characterization and DFT simulations.Targeting the key degradation factors,a synergistic repair strategy based on deep mechanochemical activation and heat treatment was successfully proposed to direct regenerate the degradedNCMmaterial.Studies indicate the induction and promotion of synergistic repair technique on the reconstruction of particlemorphology,the recovery of the chemical composition and crystal structure,and the favorable transformation of the impurities phase in the failed materials.In particular,the synergistic repair process induces a gradient distribution of LiF and further enables partial fluorine doping into the NCM surface,forming abundant oxygen vacancies and increasing the content of highly reactive Ni2+.Benefiting from the comprehensive treatment for the multi-scale and multi-form degradation behaviors,the repaired material exhibits a capacity of 176.8 mA h g^(-1)at 0.1 C,which is comparable to the corresponding commercial material(172.8 mA h g^(-1)).The satisfactory capacity of the recovered cathode proves that it is an effective direct renovating strategy.展开更多
The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.T...The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.The 1.2 wt%Al showed the lowest corrosion rate,which was mainly attributed to the weakening of the cathode efect caused by the increase of the Al and the decrease of the Fe in the precipitated phase.Refned grains,stronger basal surface texture and higher corrosion potential deriving from the higher Al content of the matrix also further enhanced the corrosion resistance of the matrix.展开更多
Y-Si compounds with the composition of Y:Si = 1:2 were fabricated using Yttrium and Silicon raw powders with low and high purity in various atmospheres and temperatures. Although the latest Y-Si phase diagram shows th...Y-Si compounds with the composition of Y:Si = 1:2 were fabricated using Yttrium and Silicon raw powders with low and high purity in various atmospheres and temperatures. Although the latest Y-Si phase diagram shows that the α- and β-YSi<sub>2</sub> phases are the stable phases for the stoichiometric composition of Y:Si = 1:2, the current experimental results suggest that the high temperature phase with the hexagonal structure, β-Y<sub>3</sub>Si<sub>5</sub>, would be the stable phase for this composition, and that the high temperature phase with the orthorhombic structure, β-YSi<sub>2</sub>, would be the meta-stable phase with high oxygen impurity content. It was demonstrated that YSi<sub>2</sub> powders possess much superior chemical stability than Yttrium metal. It was found that the best dispersing solvent was 2-propanol for YSi<sub>2</sub> powder.展开更多
Based on a discrete phase model, the numerical simulation is carried out for the flow fields of different size calcium carbo- nate suspensions in the ultrasonic heat meter body. The flow characteristics and the impuri...Based on a discrete phase model, the numerical simulation is carried out for the flow fields of different size calcium carbo- nate suspensions in the ultrasonic heat meter body. The flow characteristics and the impurity distribution in the ultrasonic heat meter body are analyzed. The errors of the ultrasonic heat meter in measuring calcium carbonate suspensions of particles of 10 micrometers and the causes are analyzed by simulation and experiment. Results show the effects of the impurities on the value of the k coeffi- cient and the sound attenuation on the reflection path due to the particle distribution are the two main factors that influence the mea- surement accuracy.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.52032001 and 51872045).
文摘The preparation of high-entropy(HE)ceramics with designed composition is essential for verifying the formability models and evaluating the properties of the ceramics.However,inevitable oxygen contamination in non-oxide ceramics will result in the formation of metal oxide impurity phases remaining in the specimen or even escaping from the specimen during the sintering process,making the elemental compositions of the HE phase deviated from the designed ones.In this work,the preparation and thermodynamic analysis during the processing of equiatomic 9-cation HE carbide(HEC9)ceramics of the IVB,VB,and VIB groups were studied focusing on the removing of the inevitable oxygen impurity existed in the starting carbide powders and the oxygen contamination during the powder mixing processing.The results demonstrate that densification by spark plasma sintering(SPS)by directly using the mixed powders of the corresponding single-component carbides will inhibit the oxygen-removing carbothermal reduction reactions,and most of the oxide impurities will remain in the sample as(Zr,Hf)O_(2)phase.Pretreatment of the mixed powders at high temperatures in vacuum will remove most part of the oxygen impurity but result in a remarkable escape of gaseous Cr owing to the oxygen-removing reaction between Cr_(3)C_(2)and various oxide impurities.It is found that graphite addition enhances the oxygen-removing effect and simultaneously prevents the escape of gaseous Cr.On the other hand,although WC,VC,and Mo2C can also act as oxygen-removing agents,there is no metal-containing gaseous substance formation in the temperature range of this study.By using the heat-treated powders with added graphite,equiatomic HEC9 ceramics were successfully prepared by SPS.
基金National Natural Science Foundation of China,Grant/Award Number:52074098the State Grid Heilongjiang Electric Power Co.,Ltd.,Technology Project Funding,Grant/Award Number:52243723000C+1 种基金Foundation of Key Program of Sci-Tech Innovation in Ningbo,Grant/Award Number:2019B10114Natural Science Foundation of Heilongjiang Province,Grant/Award Number:YQ2021E039。
文摘Sustainable development has long been recognized as one of the most critical issues in today’s energy and environment-conscious society.It has never been more urgent to recycle and reuse the end-of-life cathode materials.Here,this work systematically investigates the structure-critical degradation mechanism of polycrystalline LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)(NCM),combining experimental characterization and DFT simulations.Targeting the key degradation factors,a synergistic repair strategy based on deep mechanochemical activation and heat treatment was successfully proposed to direct regenerate the degradedNCMmaterial.Studies indicate the induction and promotion of synergistic repair technique on the reconstruction of particlemorphology,the recovery of the chemical composition and crystal structure,and the favorable transformation of the impurities phase in the failed materials.In particular,the synergistic repair process induces a gradient distribution of LiF and further enables partial fluorine doping into the NCM surface,forming abundant oxygen vacancies and increasing the content of highly reactive Ni2+.Benefiting from the comprehensive treatment for the multi-scale and multi-form degradation behaviors,the repaired material exhibits a capacity of 176.8 mA h g^(-1)at 0.1 C,which is comparable to the corresponding commercial material(172.8 mA h g^(-1)).The satisfactory capacity of the recovered cathode proves that it is an effective direct renovating strategy.
基金supported by the National Natural Science Foundation of China(No.51804130)the Key Research and Development Projects of Science and Technology Development Plan of Jilin Province(No.20180201054GX)the Graduate Innovation Fund of Jilin University(Nos.101832020CX241,101832020CX242).
文摘The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.The 1.2 wt%Al showed the lowest corrosion rate,which was mainly attributed to the weakening of the cathode efect caused by the increase of the Al and the decrease of the Fe in the precipitated phase.Refned grains,stronger basal surface texture and higher corrosion potential deriving from the higher Al content of the matrix also further enhanced the corrosion resistance of the matrix.
文摘Y-Si compounds with the composition of Y:Si = 1:2 were fabricated using Yttrium and Silicon raw powders with low and high purity in various atmospheres and temperatures. Although the latest Y-Si phase diagram shows that the α- and β-YSi<sub>2</sub> phases are the stable phases for the stoichiometric composition of Y:Si = 1:2, the current experimental results suggest that the high temperature phase with the hexagonal structure, β-Y<sub>3</sub>Si<sub>5</sub>, would be the stable phase for this composition, and that the high temperature phase with the orthorhombic structure, β-YSi<sub>2</sub>, would be the meta-stable phase with high oxygen impurity content. It was demonstrated that YSi<sub>2</sub> powders possess much superior chemical stability than Yttrium metal. It was found that the best dispersing solvent was 2-propanol for YSi<sub>2</sub> powder.
基金Project supported by the National Natural Science Foundation of China(Grant No.51276102)
文摘Based on a discrete phase model, the numerical simulation is carried out for the flow fields of different size calcium carbo- nate suspensions in the ultrasonic heat meter body. The flow characteristics and the impurity distribution in the ultrasonic heat meter body are analyzed. The errors of the ultrasonic heat meter in measuring calcium carbonate suspensions of particles of 10 micrometers and the causes are analyzed by simulation and experiment. Results show the effects of the impurities on the value of the k coeffi- cient and the sound attenuation on the reflection path due to the particle distribution are the two main factors that influence the mea- surement accuracy.
