The morphology and formation mechanism of the substructure of martensite in TC21 alloy was investigated by XRD and TEM. The results showed that the martensitic transformation from β to α＂ occurs upon quenching afte...The morphology and formation mechanism of the substructure of martensite in TC21 alloy was investigated by XRD and TEM. The results showed that the martensitic transformation from β to α＂ occurs upon quenching after solution treatment between 960-1000 ℃. The antiphase boundary （APB）-like structure was observed clearly in the α＂ martensite plates. The APB-like contrasts exist along the （001） and （020） planes of α＂ martensite. This APB-like structure of α＂ martensite was identified as a kind of stacking fault with an APB-like morphology induced by martensitic transformation and not by order/disorder transition. During martensitic transformation, martensitic domains nucleate and grow, eventually encounter each other, resulting in the formation of the APBdike contrast.展开更多
Revealing the magnetic coupling nature of boundary defects is crucial for in-depth understanding of the behavior and properties of magnetic materials and devices.Here,magnetite(i.e.,Fe_(3)O_(4))thin films were grown e...Revealing the magnetic coupling nature of boundary defects is crucial for in-depth understanding of the behavior and properties of magnetic materials and devices.Here,magnetite(i.e.,Fe_(3)O_(4))thin films were grown epitaxially on(100)SrTiOsingle-crystal substrates by pulsed laser deposition.Atomic-scale scanning transmission electron microscopy characterizations reveal that three types of antiphase boundaries(APBs)are formed in the Fe_(3)O_(4)thin film.They are the(100)APB that is formed on the(100)plane with a crystal translation of(1/4)a[011^(-)],the typeⅠand typeⅡ(110)APBs that are both formed on the(110)plane with the same crystal translation of(1/4)a[101]but different terminated atomic planes.The typeⅠ(110)APB is terminated at the atomic plane with mixed tetrahedral-and octahedral-sites Fe atoms,the typeⅡ(110)APB is terminated at the octahedral-site Fe plane.First-principles calculations reveal that the(100)APB and the typeⅠ(110)APB tend to form the ferromagnetic coupling that will not decrease the spin polarization of Fe_(3)O_(4)films,while the typeⅡ(110)APB prefers to form the antiferromagnetic coupling that will degrade the magnetic properties.The magnetic coupling modes of the APBs are closely related to the Fe-O-Fe bond angles across the boundaries.展开更多
Antiphase boundaries(APBs)are intrinsic defects in Fe_(3)O_(4) films that significantly alter their magnetic and transport properties compared to the bulk material due to antiferromagnetic interactions across these bo...Antiphase boundaries(APBs)are intrinsic defects in Fe_(3)O_(4) films that significantly alter their magnetic and transport properties compared to the bulk material due to antiferromagnetic interactions across these boundaries.In the study,we realize ferromagnetically coupled APBs in spinel ferrite by cation disorder and oxygen vacancy defects.Ni and Zn are introduced into Fe_(3)O_(4) to form Ni and NiZn ferrites and cation disorder is found in the two ferrites with Ni and Zn occupied in both octahedral and tetrahedral sites.This disorder transforms the ferrites from semiconductors into half-metals,characterized by a nonzero majority spin density of states(DOS)and a zero minority spin DOS at Fermi level.The stacking fault of the cations(Fe,Ni,Zn)at the APB induces excess negative charges,leading to the formation of oxygen vacancies as charge compensators.These vacancies disrupt the antiferromagnetic superexchange interactions,preventing spin polarization reversal across the APB,thereby enabling ferromagnetic coupling.This work provides insights into tuning the magnetic properties of APBs in spinel ferrites through defect engineering and cation manipulation.展开更多
Clarifying how spinel inversion affects the magnetic coupling nature at antiphase boundaries(APBs)is crucial for understanding the intriguing magnetic behaviors of spinel ferrites.Here,MgFe_(2)O_(4) films with an inve...Clarifying how spinel inversion affects the magnetic coupling nature at antiphase boundaries(APBs)is crucial for understanding the intriguing magnetic behaviors of spinel ferrites.Here,MgFe_(2)O_(4) films with an inversion coefficient of 2/3 are grown on MgO substrates using pulsed laser deposition(PLD).In-vestigations by state-of-the-art transmission electron microscopy suggest that two types of APBs are formed on the MgFe_(2)O_(4){110}crystal planes.The typeⅠand typeⅡAPBs have the crystal translation of(1/4)a[110]+(1/6)a[1(1)2]and(1/4)a[110]at the boundary,respectively.First-principles calculations reveal that both typeⅠand typeⅡAPBs tend to form antiferromagnetic coupling when the inversion co-efficient in MgFe_(2)O_(4) is zero.When the inversion coefficient rises to 2/3 due to the occupation of Mg^(2+)cations in octahedral sites,the magnetic coupling at the typeⅠAPBs changes to the ferromagnetic cou-pling,while the typeⅡAPBs still remain the antiferromagnetic one.The magnetic coupling modes of the APBs are closely related to the Fe-O-Fe superexchange interaction across the boundaries.Our findings clarify the atomistic mechanism of how spinel inversion affects the magnetic properties of spinel ferrites,which will promote the applications of magnetoelectricity materials with partial inversion.展开更多
For realizing the goals of“carbon peak”and“carbon neutrality”,lithium-ion batteries(LIB)with LiFePO_(4)as the cathode material have been widely applied.However,this has also led to a large number of spent lithium-...For realizing the goals of“carbon peak”and“carbon neutrality”,lithium-ion batteries(LIB)with LiFePO_(4)as the cathode material have been widely applied.However,this has also led to a large number of spent lithium-ion batteries,and the safe disposal of spent lithium-ion batteries is an urgent issue.Currently,the main reason for the capacity decay of LiFePO_(4)materials is the Li deficiency and the formation of the Fe^(3+)phase.In order to address this issue,we performed high-temperature calcination of the discarded lithium iron phosphate cathode material in a carbon dioxide environment to reduce or partially remove the carbon coating on its surface.Subsequently,mechanical grinding was conducted to ensure thorough mixing of the lithium source with the discarded lithium iron phosphate.The reaction between CO_(2)and the carbon coating produced a reducing atmosphere,reducing Fe^(3+)to Fe^(2+)and thereby reducing the content of Fe^(3+).The Fe^(3+)content in the repaired LiFePO_(4)material is reduced.The crystal structure of spent LiFePO_(4)cathode materials was repaired more completely compare with the traditional pretreatment method,and the repaired LiFePO_(4)material shows good electrochemical performance and cycling stability.Under 0.1 C conditions,the initial capacity can reach 149.1 m Ah/g.It can be reintroduced for commercial use.展开更多
Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder ...Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the enrichment of V and depletion of Ni and A1, the ordered APDB with phase-shift vector of a/2[100] transforms into a thin disordered phase layer. Whereas at the APDB with phase shift vector of a/2[110], which remains ordered with temporal evolution, Ni and A1 enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of DO22 phase, and the formation of disordered phase layer accelerates the growth of DO22 phase. The disordered phase caused by order-disordered transition of the APDB can be considered as the transient phase along the precipitation path of DO22 phase.展开更多
The phase transformation of θ’’→θ’ in an Al-5.7 Cu alloy was investigated by aberration-corrected scanning transmission electron microscopy, and the tranformation mode of θ’’→θ’ during aging treatment was ...The phase transformation of θ’’→θ’ in an Al-5.7 Cu alloy was investigated by aberration-corrected scanning transmission electron microscopy, and the tranformation mode of θ’’→θ’ during aging treatment was clarified. In the presence of the θ’ phases, θ’ was found to be formed by in-situ transformation fromθ’’ with the same plate shape, size and broad faces. The transformation starts from multiple sites within the θ’ precipitate and the whole θ’ phase finally forms as the preferential θ’ sections grow and connect with each other. Antiphase domain boundaries are also found in some θ’ precipitates when the disregistry exists between different θ’ sections.展开更多
The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase an...The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.展开更多
Microstructural properties of spinel Li Fe5O8(LFO)films grown on(001)-oriented Sr TiO3(STO)substrates have been investigated at the atomic-scale by advanced electron microscopy techniques.Two types of orientation rela...Microstructural properties of spinel Li Fe5O8(LFO)films grown on(001)-oriented Sr TiO3(STO)substrates have been investigated at the atomic-scale by advanced electron microscopy techniques.Two types of orientation relationship(OR)between the LFO films and the STO substrates have been determined,cube-on-cube and(111)[ī10]LFO//(111)[1ī0]STO.Antiphase boundaries(APBs)and three types of twin boundaries(TBs)form within the LFO films,and the propagation of TBs and APBs results in their complex interactions.In most cases,interactions between TBs and APBs change the type of TBs and terminate the propagation of APBs since the APBs introduce a displacement vector of(a/4)110 into the TBs.In addition,the interactions between two coherent TBs are observed to generate the incoherent TB.The epitaxial strain of the LFO/STO(001)heterosystem can be released by the formation of TBs and APBs in the films and misfit dislocations at the interface.Considering that the magnetic coupling across the APBs and TBs can lead to novel physical properties,the appearance of APBs and TBs with a high density in the LFO films would affect the magnetic properties of the films.展开更多
基金Project (2011AA030101) supported by the High-tech Research and Development Program of China
文摘The morphology and formation mechanism of the substructure of martensite in TC21 alloy was investigated by XRD and TEM. The results showed that the martensitic transformation from β to α＂ occurs upon quenching after solution treatment between 960-1000 ℃. The antiphase boundary （APB）-like structure was observed clearly in the α＂ martensite plates. The APB-like contrasts exist along the （001） and （020） planes of α＂ martensite. This APB-like structure of α＂ martensite was identified as a kind of stacking fault with an APB-like morphology induced by martensitic transformation and not by order/disorder transition. During martensitic transformation, martensitic domains nucleate and grow, eventually encounter each other, resulting in the formation of the APBdike contrast.
基金supported by the National Natural Science Foundation of China(Nos.51771200,51971224,51801215)LiaoNing Revitalization Talents Program(No.XLYC1802088)+1 种基金the Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-JSC027)Ji Hua Laboratory Project X210141TL210 for cooperation。
文摘Revealing the magnetic coupling nature of boundary defects is crucial for in-depth understanding of the behavior and properties of magnetic materials and devices.Here,magnetite(i.e.,Fe_(3)O_(4))thin films were grown epitaxially on(100)SrTiOsingle-crystal substrates by pulsed laser deposition.Atomic-scale scanning transmission electron microscopy characterizations reveal that three types of antiphase boundaries(APBs)are formed in the Fe_(3)O_(4)thin film.They are the(100)APB that is formed on the(100)plane with a crystal translation of(1/4)a[011^(-)],the typeⅠand typeⅡ(110)APBs that are both formed on the(110)plane with the same crystal translation of(1/4)a[101]but different terminated atomic planes.The typeⅠ(110)APB is terminated at the atomic plane with mixed tetrahedral-and octahedral-sites Fe atoms,the typeⅡ(110)APB is terminated at the octahedral-site Fe plane.First-principles calculations reveal that the(100)APB and the typeⅠ(110)APB tend to form the ferromagnetic coupling that will not decrease the spin polarization of Fe_(3)O_(4)films,while the typeⅡ(110)APB prefers to form the antiferromagnetic coupling that will degrade the magnetic properties.The magnetic coupling modes of the APBs are closely related to the Fe-O-Fe bond angles across the boundaries.
基金financially supported by the National Science Fund for Distinguished Young Scholars(No.52225312)the Na-tional Natural Science Foundation of China(Nos.11904068 and 52272292)the Zhejiang Provincial Natural Science Foundation(No.LY23A040009).
文摘Antiphase boundaries(APBs)are intrinsic defects in Fe_(3)O_(4) films that significantly alter their magnetic and transport properties compared to the bulk material due to antiferromagnetic interactions across these boundaries.In the study,we realize ferromagnetically coupled APBs in spinel ferrite by cation disorder and oxygen vacancy defects.Ni and Zn are introduced into Fe_(3)O_(4) to form Ni and NiZn ferrites and cation disorder is found in the two ferrites with Ni and Zn occupied in both octahedral and tetrahedral sites.This disorder transforms the ferrites from semiconductors into half-metals,characterized by a nonzero majority spin density of states(DOS)and a zero minority spin DOS at Fermi level.The stacking fault of the cations(Fe,Ni,Zn)at the APB induces excess negative charges,leading to the formation of oxygen vacancies as charge compensators.These vacancies disrupt the antiferromagnetic superexchange interactions,preventing spin polarization reversal across the APB,thereby enabling ferromagnetic coupling.This work provides insights into tuning the magnetic properties of APBs in spinel ferrites through defect engineering and cation manipulation.
基金supported by the National Natural Science Foundation of China(Nos.52125101 and 52271015)Guangdong Major Project of Basic Research,China(No.2021B0301030003)Jihua Laboratory(No.X210141TL210).
文摘Clarifying how spinel inversion affects the magnetic coupling nature at antiphase boundaries(APBs)is crucial for understanding the intriguing magnetic behaviors of spinel ferrites.Here,MgFe_(2)O_(4) films with an inversion coefficient of 2/3 are grown on MgO substrates using pulsed laser deposition(PLD).In-vestigations by state-of-the-art transmission electron microscopy suggest that two types of APBs are formed on the MgFe_(2)O_(4){110}crystal planes.The typeⅠand typeⅡAPBs have the crystal translation of(1/4)a[110]+(1/6)a[1(1)2]and(1/4)a[110]at the boundary,respectively.First-principles calculations reveal that both typeⅠand typeⅡAPBs tend to form antiferromagnetic coupling when the inversion co-efficient in MgFe_(2)O_(4) is zero.When the inversion coefficient rises to 2/3 due to the occupation of Mg^(2+)cations in octahedral sites,the magnetic coupling at the typeⅠAPBs changes to the ferromagnetic cou-pling,while the typeⅡAPBs still remain the antiferromagnetic one.The magnetic coupling modes of the APBs are closely related to the Fe-O-Fe superexchange interaction across the boundaries.Our findings clarify the atomistic mechanism of how spinel inversion affects the magnetic properties of spinel ferrites,which will promote the applications of magnetoelectricity materials with partial inversion.
基金supported by Heilongjiang Province Key R&D Program(No.GA22A014)。
文摘For realizing the goals of“carbon peak”and“carbon neutrality”,lithium-ion batteries(LIB)with LiFePO_(4)as the cathode material have been widely applied.However,this has also led to a large number of spent lithium-ion batteries,and the safe disposal of spent lithium-ion batteries is an urgent issue.Currently,the main reason for the capacity decay of LiFePO_(4)materials is the Li deficiency and the formation of the Fe^(3+)phase.In order to address this issue,we performed high-temperature calcination of the discarded lithium iron phosphate cathode material in a carbon dioxide environment to reduce or partially remove the carbon coating on its surface.Subsequently,mechanical grinding was conducted to ensure thorough mixing of the lithium source with the discarded lithium iron phosphate.The reaction between CO_(2)and the carbon coating produced a reducing atmosphere,reducing Fe^(3+)to Fe^(2+)and thereby reducing the content of Fe^(3+).The Fe^(3+)content in the repaired LiFePO_(4)material is reduced.The crystal structure of spent LiFePO_(4)cathode materials was repaired more completely compare with the traditional pretreatment method,and the repaired LiFePO_(4)material shows good electrochemical performance and cycling stability.Under 0.1 C conditions,the initial capacity can reach 149.1 m Ah/g.It can be reintroduced for commercial use.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50941020, 10902086, 50875217,and 20903075)the Natural Science Foundation of Shaanxi Province (Grant Nos.SJ08-ZT05 and SJ08-B14)the Doctorate Foundation of Northwest Polytechnical University (Grant No.CX200905)
文摘Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the enrichment of V and depletion of Ni and A1, the ordered APDB with phase-shift vector of a/2[100] transforms into a thin disordered phase layer. Whereas at the APDB with phase shift vector of a/2[110], which remains ordered with temporal evolution, Ni and A1 enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of DO22 phase, and the formation of disordered phase layer accelerates the growth of DO22 phase. The disordered phase caused by order-disordered transition of the APDB can be considered as the transient phase along the precipitation path of DO22 phase.
基金supported by the National Natural Science Foundation of China (No. 11227403)Cyrus Tang Center for Sensor Materials and Applications
文摘The phase transformation of θ’’→θ’ in an Al-5.7 Cu alloy was investigated by aberration-corrected scanning transmission electron microscopy, and the tranformation mode of θ’’→θ’ during aging treatment was clarified. In the presence of the θ’ phases, θ’ was found to be formed by in-situ transformation fromθ’’ with the same plate shape, size and broad faces. The transformation starts from multiple sites within the θ’ precipitate and the whole θ’ phase finally forms as the preferential θ’ sections grow and connect with each other. Antiphase domain boundaries are also found in some θ’ precipitates when the disregistry exists between different θ’ sections.
文摘The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.
基金financially supported by the National Basic Research Program of China(No.2015CB654903)the National Natural Science Foundation of China(Nos.51471169 and 51390472).
文摘Microstructural properties of spinel Li Fe5O8(LFO)films grown on(001)-oriented Sr TiO3(STO)substrates have been investigated at the atomic-scale by advanced electron microscopy techniques.Two types of orientation relationship(OR)between the LFO films and the STO substrates have been determined,cube-on-cube and(111)[ī10]LFO//(111)[1ī0]STO.Antiphase boundaries(APBs)and three types of twin boundaries(TBs)form within the LFO films,and the propagation of TBs and APBs results in their complex interactions.In most cases,interactions between TBs and APBs change the type of TBs and terminate the propagation of APBs since the APBs introduce a displacement vector of(a/4)110 into the TBs.In addition,the interactions between two coherent TBs are observed to generate the incoherent TB.The epitaxial strain of the LFO/STO(001)heterosystem can be released by the formation of TBs and APBs in the films and misfit dislocations at the interface.Considering that the magnetic coupling across the APBs and TBs can lead to novel physical properties,the appearance of APBs and TBs with a high density in the LFO films would affect the magnetic properties of the films.
