Antiferromagnets offer great potential for high-speed data processing applications,as they can expend spintronic devices from a static storage and gigahertz frequency range to the terahertz range.However,their zero ne...Antiferromagnets offer great potential for high-speed data processing applications,as they can expend spintronic devices from a static storage and gigahertz frequency range to the terahertz range.However,their zero net magnetization makes them difficult to manipulate and detect.In recent years,there has been a lot of attention given to the ultrafast manipulation of magnetic order using ultra-short single laser pulses,but it remains unknown whether a similar scenario can be observed in antiferromagnets.In this work,we demonstrate the manipulation of antiferromagnets with a single femtosecond laser pulse in perpendicular exchange-biased Co/Ir Mn/Co Gd trilayers.We study the dual exchange bias interlayer interaction in quasi-static conditions and competition in ultrafast antiferromagnet rearrangement.Our results show that,compared to conventional ferromagnetic/antiferromagnetic systems,the Ir Mn antiferromagnet can be ultrafast and efficiently manipulated by the coupled Co Gd ferrimagnetic layer,which paves the way for potential energy-efficient spintronic devices.展开更多
We present an effective approach for fabricating nanowell arrays in a one-step laser process with promising applications for the storage and detection of chemical or biological elements.Biocompatible thin films of met...We present an effective approach for fabricating nanowell arrays in a one-step laser process with promising applications for the storage and detection of chemical or biological elements.Biocompatible thin films of metallic glasses are manufactured with a selected composition of Zr_(65)Cu_(35),known to exhibit remarkable mechanical properties and glass forming ability.Dense nanowell arrays spontaneously form in the ultrafast laser irradiation spot with dimensions down to 20 nm.The flared shape observed by transmission electron microscopy is ideal to ensure chemical or biological material immobilization into the nanowells.This also indicates that the localization of the cavitation-induced nanopores can be tuned by the density and size of the initial nanometric interstice from the columnar structure of films deposited by magnetron sputtering.In addition to the topographic functionalization,the laser-irradiated amorphous material exhibits structural changes analyzed by spectroscopic techniques at the nanoscale such as energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy.Results reveal structural changes consisting of nanocrystals of monoclinic zirconia that grow within the amorphous matrix.The mechanism is driven by local oxidation process catalyzed by extreme temperature and pressure conditions estimated by an atomistic simulation of the laser-induced nanowell formation.展开更多
The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The recons...The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The reconstruction suffers a significant immediate error that is not rapidly damped.It is demonstrated that even though no reflections occur inside the hollow region causing the blind area,the higher probing frequencies that propagate through it carry information that can be used to estimate its properties.The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1 D,with special attention paid to the frequency band where they are dominant.A database of perturbation signals was simulated onfive-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge.The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it.展开更多
A LiBr/LiOH non-eutectic mixture shows a potentially outstanding heat energy density of 800 J/g at a constant temperature,which makes it a very promising candidate for heat storage applications around 300℃.However,sa...A LiBr/LiOH non-eutectic mixture shows a potentially outstanding heat energy density of 800 J/g at a constant temperature,which makes it a very promising candidate for heat storage applications around 300℃.However,salt-based phase change materials are known for their too low thermal conductivity which can question the thermal storage systems effective feasibility.The objective here is to infiltrate a carbon felt of high porosity(>93%)with the LiBr/LiOH mixture to anticipate this deficiency.The device has to be adapted according to the properties and the characteristics of the studied storage and host materials.The developed procedure for the carbon felt infiltration with the synthesized binary system is presented.The optimised working conditions allow(1)minimizing the interaction time duration between the quartz tube and the salt-based mixture and,(2)verifying the good chemical compatibility of the mixture with the host matrix after infiltration.展开更多
We investigated the phase transformation sequence,kinetics,and microstructural evolutions during heating,isothermal treatment,and continuous cooling of the metastable Ti–B19 alloy.On the basis of these results,we sum...We investigated the phase transformation sequence,kinetics,and microstructural evolutions during heating,isothermal treatment,and continuous cooling of the metastable Ti–B19 alloy.On the basis of these results,we summarized the phase transformation characteristics of this kind of alloys,especially the metastable b-Ti alloy.We also analyzed and discussed the possibility of describing the size,morphology,and distribution of precipitates as well as the possibility of and complications in establishing relationships among the chemical composition,microstructure,processing parameters,and properties of the metastable Ti–B19 alloy.展开更多
Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT)lead-free ceramics demonstrated excellent dielectric,ferroelectric,and piezoelectric properties at the morphotropic phase boundary(MPB).So far,to study the effect of morphological chang...Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT)lead-free ceramics demonstrated excellent dielectric,ferroelectric,and piezoelectric properties at the morphotropic phase boundary(MPB).So far,to study the effect of morphological changes on dielectric and ferroelectric properties in lead-free BCZT ceramics,researchers have mostly focused on the influence of spherical grain shape change.In this study,BCZT ceramics with rod-like grains and aspect ratio of about 10 were synthesized by surfactant-assisted solvothermal route.X-ray diffraction(XRD)and selected area electron diffraction(SAED)performed at room temperature confirm the crystallization of pure perovskite with tetragonal symmetry.Scanning electron microscopy(SEM)image showed that BCZT ceramics have kept the 1D rod-like grains with an average aspect ratio of about 4.Rod-like BCZT ceramics exhibit enhanced dielectric ferroelectric(εr=11,906,tanδ=0.014,Pr=6.01μC/cm^2,and Ec=2.46 kV/cm),and electrocaloric properties(ΔT=0.492 K andz=0.289(K×mm)/kV at 17 kV/cm)with respect to spherical BCZT ceramics.Therefore,rod-like BCZT lead-free ceramics have good potential to be used in solid-state refrigeration technology.展开更多
The first carbon aerogels prepared by autocondensation of condensed(flavonoid)tannin,a cheap renewable resource extracted from Mimosa barks,are presented.Mixing aqueous solutions of tannin and sodium silicate indeed p...The first carbon aerogels prepared by autocondensation of condensed(flavonoid)tannin,a cheap renewable resource extracted from Mimosa barks,are presented.Mixing aqueous solutions of tannin and sodium silicate indeed produced the very fast gelation of tannins,thus leading to organic hydrogels which were first converted into organic aerogels by supercritical drying,and then into carbon aerogels after pyrolysis at 900℃.Subsequent dissolution of the silica nanoparticles thus formed within the carbon structure further increased significantly the porosity of the materials.Silica thus appeared to be both the gelation catalyst and a pore-directing agent.In this work,the influence on the porosity of the silica/tannin ratio and of the nature of the etching agent used for removing the silica was thoroughly investigated by combining several techniques.The conditions for producing either the most porous materials or those with the highest surface areas were identified and discussed.展开更多
The synthesis of CdO, Ag2O (5nm) and Ag (~20~30 nm) nano-objects is achieved simultaneously by nanosecond-pulsed discharges in liquid nitrogen between one cadmium electrode and one silver electrode. Oxidation occurs w...The synthesis of CdO, Ag2O (5nm) and Ag (~20~30 nm) nano-objects is achieved simultaneously by nanosecond-pulsed discharges in liquid nitrogen between one cadmium electrode and one silver electrode. Oxidation occurs when liquid nitrogen is fully evaporated and nanoparticles are in contact with the air. No alloy is formed, whatever the conditions, even though both elements are present simultaneously, as showed by timeresolved optical emission spectroscopy. This lack of reactivity between elements is attributed to the high pressure within the discharge that keeps each metallic vapor around the electrode it comes from. Each element exhibits a specific behavior. Cubic Cd particles, formed at 4 kV, get elongated with filamentary tips when the applied voltage reaches 7 and 10 kV. Cd wires are formed by assembly in liquid nitrogen of Cd nanoparticles driven by dipole assembly, and not by dielectrophoresis. On the contrary, silver spherical particles get assembled into 2D dendritic structures. The anisotropic growth of these structures is assumed to be due to the existence of pressure gradients.展开更多
The eco-responsible lead-free piezoelectric ceramics have been intensively searched for more than adecade, however, the final goal to replace toxic ceramics like lead zirconate titanate (PZT) with lead-freecompounds, ...The eco-responsible lead-free piezoelectric ceramics have been intensively searched for more than adecade, however, the final goal to replace toxic ceramics like lead zirconate titanate (PZT) with lead-freecompounds, having comparable or even better performance has not yet been reached. In this road, thelead-free ceramics Ba_(0.85)Ca_(0.15)Zr_(0.1)Ti_(0.9)O_(3) (BCZT), possessing excellent dielectric, ferroelectric, andpiezoelectric properties are regarded as serious candidates for the PZT replacement. Besides, nano-structuring BCZT is of paramount importance to enhance these functionalities even more. Here, BCZTmultipodes are designed by template-growth hydrothermal synthesis using hydrogen zirconate titanatenanowires. We demonstrate that the fabricated BCZT multipodes exhibit high dielectric permittivity of5300 with a temperature stability coefficient of ±5.9% between 20 and 140℃. A significant recoveredenergy density of 315.0 mJ/cm^(3) with high thermal stability and high energy storage efficiency of 87.4%,and enhanced large-signal piezoelectric coefficient d^(*)_(33) (310 pm/V) are found. Compared to the tradi-tional BCZT ceramics reported in the literature, relying on high-temperature processing, our sampleexhibits boosted energy storage parameters at a much lower temperature. These outcomes may offer anew strategy to tailor eco-responsible relaxor ferroelectrics toward superior energy storage performancefor ceramic capacitor applications.展开更多
基金National Key Research and Development Program of China(Grant No.2022YFB4400200)the National Natural Science Foundation of China(Grant Nos.12104030,12104031,and 61627813)+10 种基金the Program of Introducing Talents of Discipline to Universities(Grant No.B16001)the Beijing Municipal Science and Technology Project(Grant No.Z201100004220002)China Postdoctoral Science Foundation(Grant No.2022M710320)China Scholarship Councilsupported by the ANR-15-CE24-0009 UMAMI and the ANR-20-CE09-0013by the Institute Carnot ICEEL for the project“Optic-switch”and Matelasby the Région Grand Estby the Metropole Grand Nancyby the impact project LUE-N4Spart of the French PIA project“Lorraine Universitéd’Excellence,”reference ANR-15-IDEX-04-LUEby the“FEDERFSE Lorraine et Massif Vosges 2014-2020,”a European Union Program。
文摘Antiferromagnets offer great potential for high-speed data processing applications,as they can expend spintronic devices from a static storage and gigahertz frequency range to the terahertz range.However,their zero net magnetization makes them difficult to manipulate and detect.In recent years,there has been a lot of attention given to the ultrafast manipulation of magnetic order using ultra-short single laser pulses,but it remains unknown whether a similar scenario can be observed in antiferromagnets.In this work,we demonstrate the manipulation of antiferromagnets with a single femtosecond laser pulse in perpendicular exchange-biased Co/Ir Mn/Co Gd trilayers.We study the dual exchange bias interlayer interaction in quasi-static conditions and competition in ultrafast antiferromagnet rearrangement.Our results show that,compared to conventional ferromagnetic/antiferromagnetic systems,the Ir Mn antiferromagnet can be ultrafast and efficiently manipulated by the coupled Co Gd ferrimagnetic layer,which paves the way for potential energy-efficient spintronic devices.
基金supported by the ANR project MEGALIT(ANR-18-CE08)the project FORMEL of the Pack Ambition Research program of the Auvergne Rhône-Alpes RegionOpen access funding provided by Shanghai Jiao Tong University
文摘We present an effective approach for fabricating nanowell arrays in a one-step laser process with promising applications for the storage and detection of chemical or biological elements.Biocompatible thin films of metallic glasses are manufactured with a selected composition of Zr_(65)Cu_(35),known to exhibit remarkable mechanical properties and glass forming ability.Dense nanowell arrays spontaneously form in the ultrafast laser irradiation spot with dimensions down to 20 nm.The flared shape observed by transmission electron microscopy is ideal to ensure chemical or biological material immobilization into the nanowells.This also indicates that the localization of the cavitation-induced nanopores can be tuned by the density and size of the initial nanometric interstice from the columnar structure of films deposited by magnetron sputtering.In addition to the topographic functionalization,the laser-irradiated amorphous material exhibits structural changes analyzed by spectroscopic techniques at the nanoscale such as energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy.Results reveal structural changes consisting of nanocrystals of monoclinic zirconia that grow within the amorphous matrix.The mechanism is driven by local oxidation process catalyzed by extreme temperature and pressure conditions estimated by an atomistic simulation of the laser-induced nanowell formation.
基金carried out with the support of the Brazilian National Council for Scientific and Technological Development(CNPq)under the Science Without Borders programme,within the framework of the French Federation for Magnetic Fusion Studies(FR-FCM)and of the EUROfusion consortium with funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No.633053part-funded by the RCUK Energy Programme grant number EP/P012450/1。
文摘The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The reconstruction suffers a significant immediate error that is not rapidly damped.It is demonstrated that even though no reflections occur inside the hollow region causing the blind area,the higher probing frequencies that propagate through it carry information that can be used to estimate its properties.The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1 D,with special attention paid to the frequency band where they are dominant.A database of perturbation signals was simulated onfive-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge.The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it.
文摘A LiBr/LiOH non-eutectic mixture shows a potentially outstanding heat energy density of 800 J/g at a constant temperature,which makes it a very promising candidate for heat storage applications around 300℃.However,salt-based phase change materials are known for their too low thermal conductivity which can question the thermal storage systems effective feasibility.The objective here is to infiltrate a carbon felt of high porosity(>93%)with the LiBr/LiOH mixture to anticipate this deficiency.The device has to be adapted according to the properties and the characteristics of the studied storage and host materials.The developed procedure for the carbon felt infiltration with the synthesized binary system is presented.The optimised working conditions allow(1)minimizing the interaction time duration between the quartz tube and the salt-based mixture and,(2)verifying the good chemical compatibility of the mixture with the host matrix after infiltration.
文摘We investigated the phase transformation sequence,kinetics,and microstructural evolutions during heating,isothermal treatment,and continuous cooling of the metastable Ti–B19 alloy.On the basis of these results,we summarized the phase transformation characteristics of this kind of alloys,especially the metastable b-Ti alloy.We also analyzed and discussed the possibility of describing the size,morphology,and distribution of precipitates as well as the possibility of and complications in establishing relationships among the chemical composition,microstructure,processing parameters,and properties of the metastable Ti–B19 alloy.
基金The authors gratefully acknowledge the generous financial support of CNRST Priority Program(PPR 15/2015)Slovenian Research Agency Program(P1-0125)European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant Agreement(No.778072).
文摘Ba0.85Ca0.15Zr0.10Ti0.90O3(BCZT)lead-free ceramics demonstrated excellent dielectric,ferroelectric,and piezoelectric properties at the morphotropic phase boundary(MPB).So far,to study the effect of morphological changes on dielectric and ferroelectric properties in lead-free BCZT ceramics,researchers have mostly focused on the influence of spherical grain shape change.In this study,BCZT ceramics with rod-like grains and aspect ratio of about 10 were synthesized by surfactant-assisted solvothermal route.X-ray diffraction(XRD)and selected area electron diffraction(SAED)performed at room temperature confirm the crystallization of pure perovskite with tetragonal symmetry.Scanning electron microscopy(SEM)image showed that BCZT ceramics have kept the 1D rod-like grains with an average aspect ratio of about 4.Rod-like BCZT ceramics exhibit enhanced dielectric ferroelectric(εr=11,906,tanδ=0.014,Pr=6.01μC/cm^2,and Ec=2.46 kV/cm),and electrocaloric properties(ΔT=0.492 K andz=0.289(K×mm)/kV at 17 kV/cm)with respect to spherical BCZT ceramics.Therefore,rod-like BCZT lead-free ceramics have good potential to be used in solid-state refrigeration technology.
基金The authors gratefully acknowledge the financial support of the CPER 2007–2013“Structuration du Pole de Competitivite Fibres Grand’Est”(Competitiveness Fibre Cluster,France)through local(Conseil General des Vosges),regional(Region Lorraine)national(DRRT and FNADT)and European(FEDER,France)funds.
文摘The first carbon aerogels prepared by autocondensation of condensed(flavonoid)tannin,a cheap renewable resource extracted from Mimosa barks,are presented.Mixing aqueous solutions of tannin and sodium silicate indeed produced the very fast gelation of tannins,thus leading to organic hydrogels which were first converted into organic aerogels by supercritical drying,and then into carbon aerogels after pyrolysis at 900℃.Subsequent dissolution of the silica nanoparticles thus formed within the carbon structure further increased significantly the porosity of the materials.Silica thus appeared to be both the gelation catalyst and a pore-directing agent.In this work,the influence on the porosity of the silica/tannin ratio and of the nature of the etching agent used for removing the silica was thoroughly investigated by combining several techniques.The conditions for producing either the most porous materials or those with the highest surface areas were identified and discussed.
文摘The synthesis of CdO, Ag2O (5nm) and Ag (~20~30 nm) nano-objects is achieved simultaneously by nanosecond-pulsed discharges in liquid nitrogen between one cadmium electrode and one silver electrode. Oxidation occurs when liquid nitrogen is fully evaporated and nanoparticles are in contact with the air. No alloy is formed, whatever the conditions, even though both elements are present simultaneously, as showed by timeresolved optical emission spectroscopy. This lack of reactivity between elements is attributed to the high pressure within the discharge that keeps each metallic vapor around the electrode it comes from. Each element exhibits a specific behavior. Cubic Cd particles, formed at 4 kV, get elongated with filamentary tips when the applied voltage reaches 7 and 10 kV. Cd wires are formed by assembly in liquid nitrogen of Cd nanoparticles driven by dipole assembly, and not by dielectrophoresis. On the contrary, silver spherical particles get assembled into 2D dendritic structures. The anisotropic growth of these structures is assumed to be due to the existence of pressure gradients.
基金The authors gratefully acknowledge the generous financial support of the European Union Horizon 2020 Research and Inno-vation actions MSCA-RISE-ENGIMA(No.778072)MSCA-RISE-MELON(No.872631)Z.K.,B.R.,D.V.,and M.S.acknowledge the Slovenian Research Agency program P1-0125 and P2-0091.
文摘The eco-responsible lead-free piezoelectric ceramics have been intensively searched for more than adecade, however, the final goal to replace toxic ceramics like lead zirconate titanate (PZT) with lead-freecompounds, having comparable or even better performance has not yet been reached. In this road, thelead-free ceramics Ba_(0.85)Ca_(0.15)Zr_(0.1)Ti_(0.9)O_(3) (BCZT), possessing excellent dielectric, ferroelectric, andpiezoelectric properties are regarded as serious candidates for the PZT replacement. Besides, nano-structuring BCZT is of paramount importance to enhance these functionalities even more. Here, BCZTmultipodes are designed by template-growth hydrothermal synthesis using hydrogen zirconate titanatenanowires. We demonstrate that the fabricated BCZT multipodes exhibit high dielectric permittivity of5300 with a temperature stability coefficient of ±5.9% between 20 and 140℃. A significant recoveredenergy density of 315.0 mJ/cm^(3) with high thermal stability and high energy storage efficiency of 87.4%,and enhanced large-signal piezoelectric coefficient d^(*)_(33) (310 pm/V) are found. Compared to the tradi-tional BCZT ceramics reported in the literature, relying on high-temperature processing, our sampleexhibits boosted energy storage parameters at a much lower temperature. These outcomes may offer anew strategy to tailor eco-responsible relaxor ferroelectrics toward superior energy storage performancefor ceramic capacitor applications.
