The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(...The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)and atom probe tomography(APT)to investigate the structural and local chemical information of LPSO phases formed in Mg-Ni-Y/Sm ternary alloys after extended isothermal annealing.Depending on the alloying elements and their concentrations,Mg-Ni-Y/Sm develops a two-phase LPSO+α-Mg structure in which the LPSO phase contains defects,hybrid LPSO structure,and Mg insertions.HAADF-STEM and APT indicate non-stoichiometric LPSO with incomplete Ni_(6)(Y/Sm)_(8) clusters.In addition,the APT quantitatively determines the local composition of LPSO and confirms the presence of Ni within the Mg bonding layers.These results provide insight into a better understanding of the structure and hydrolysis properties of LPSO-Mg alloys.展开更多
采用固相法合成了中温固体氧化物燃料电池（IT-SOFCs）阴极材料La Bi Mn2O6,并利用X射线衍射（XRD）和电化学阻抗谱（EIS）进行表征。结果表明该材料与电解质Ce0.7Bi0.3O1.85（CBO）在1 000℃烧结12 h不发生反应。交流阻抗和直流极化测...采用固相法合成了中温固体氧化物燃料电池（IT-SOFCs）阴极材料La Bi Mn2O6,并利用X射线衍射（XRD）和电化学阻抗谱（EIS）进行表征。结果表明该材料与电解质Ce0.7Bi0.3O1.85（CBO）在1 000℃烧结12 h不发生反应。交流阻抗和直流极化测试结果发现,阴极极化电阻随测试温度的增加而逐渐减小,700℃空气中的极化电阻为0.71Ω·cm2;氧分压测试结果显示,在600～700℃范围内,电极反应的速率控制步骤为电极上发生的电荷转移反应。电极过电位为85 m V时,700℃的阴极电流密度达到216 m A·cm-2,表明La Bi Mn2O6是一种潜在的中温固体氧化物燃料电池（IT-SOFCs）阴极材料。展开更多
The chemical and electrochemical stability of lanthanide nickelates La2 NiO4+δ(LNO),Pr2 NiO4+δ(PNO)and their mixed compounds La(2-x)PrxNiO4+δ(LPNOs)with x=0.5,1 or 1.5 is reported.The aim is to promote these materi...The chemical and electrochemical stability of lanthanide nickelates La2 NiO4+δ(LNO),Pr2 NiO4+δ(PNO)and their mixed compounds La(2-x)PrxNiO4+δ(LPNOs)with x=0.5,1 or 1.5 is reported.The aim is to promote these materials as efficient electrodes for solid oxide fuel cell(SOFC)and/or solid oxide electrolysis cell(SOEC).La2 NiO4+δand La1.5Pr0.5NiO4+δcompounds are chemically very stable as powders over one month in the temperature range 600-800℃,while the other materials rich in praseodymium progressively decompose into various perovskite-deriving components with additional Pr6 O11.Despite their uneven properties,all these materials are quite efficient and sustainable as electrodes on top of gadolinium doped ceria(GDCBL)//yttrium doped zirconia(8 YSZ)electrolyte,for one month at 700℃without polarization.Under polarization(300 mA·cm-2),the electrochemical performances of LNO,PNO and La1.5Pr0.5NiO4+δ(LP5 NO)quickly degrade in SOFC mode,i.e.for the oxygen reduction reaction,while they show durability in SOEC mode,i.e.for the oxide oxidation reaction.展开更多
As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs la...As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining(i.e.defects on edges and tapered sidewalls).The evolution of edge sharpness(edge transition width)and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed.Through decreasing the angle of incidence(AOI)from 0◦to−5◦,the edge transition width could be reduced to below 10µm but at the cost of increased sidewall tapers.Furthermore,by analyzing lateral and vertical ablation behaviors,a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls.The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications.The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions.Both mm-scale diameters and depths were realized with dimensional precisions below 10µm and surface roughness below 1µm.This research establishes a novel strategy to finely control the fs laser machining process,enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.展开更多
The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion ...The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion coefficient compatible with chip materials while still ensuring the reliability of the power modules.Metal matrix composites,especially copper matrix composites,containing carbon fibers,carbon nanofibers,or diamond are considered very promising as the next generation of thermalmanagement materials in power electronic packages.These composites exhibit enhanced thermal properties,as compared to pure copper,combined with lower density.This paper presents powder metallurgy and hot uniaxial pressing fabrication techniques for copper/carbon composite materials which promise to be efficient heat-dissipation materials for power electronic modules.Thermal analyses clearly indicate that interfacial treatments are required in these composites to achieve high thermal and thermomechanical properties.Control of interfaces(through a novel reinforcement surface treatment,the addition of a carbide-forming element inside the copper powders,and processing methods),when selected carefully and processed properly,will form the right chemical/mechanical bonding between copper and carbon,enhancing all of the desired thermal and thermomechanical properties while minimizing the deleterious effects.This paper outlines a variety of methods and interfacial materials that achieve these goals.展开更多
The hydrolysis of Mg-based materials appears to be an ideal solution for clean energy production.Green hydrogen was produced by the hydrolysis reaction of a"standard"AZ91 alloy(called AZ91 in the following)i...The hydrolysis of Mg-based materials appears to be an ideal solution for clean energy production.Green hydrogen was produced by the hydrolysis reaction of a"standard"AZ91 alloy(called AZ91 in the following)in"model"seawater solution.Two milling speeds(i.e.250 rpm and 350 rpm)were tested to enhance the reactivity of AZ91.Graphite and AlCl_(3)were used as ball milling additives.Milling at higher rotational speed is more energetic,hence it ameliorates the most the hydrolysis performance of AZ91.Comparing both milling additives,AlCl_(3)enhances the most the hydrolysis of AZ91 with a generation of 65%of its theoretical H_(2)generation capacity.The best material was obtained by milling AZ91 at 350 rpm with graphite for 2 h followed by a further milling with AlCl_(3)for 2h-a yield of 75%of its theoretical H_(2)generation capacity was reached within a few minutes.The corrosion behavior of milled AZ91 was investigated by anodic polarization and electrochemical impedance spectroscopy(EIS).The calculated electrochemical parameters from EIS fitting of two materials milled under different conditions but with the same milling additive are approximately the same.This suggests that,in order to fully evaluate the reactivity of AZ91,hydrolysis,anodic polarization and EIS must be considered.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 report the formation of colloidal polymers consisting of disk-like silica nanoparticles(NPs)with polystyrene(PS)chains at the bottom of their two cavities assembled through reduction of the solvent quality for the ...We report the formation of colloidal polymers consisting of disk-like silica nanoparticles(NPs)with polystyrene(PS)chains at the bottom of their two cavities assembled through reduction of the solvent quality for the PS chains and linked by hydrophobic associations.We show that this NPs assembly exhibits a two-stage process involving reaction-controlled polymerization and diffusion-controlled polymerization.Colloidal polymer networks are produced by the incorporation of three-patch NPs,which serve as branching points between the colloidal chains.By co-assembling preformed homopolymers composed of patchy NPs of different sizes or surface chemical groups,block copolymers are also achieved.This study provides insight into the process of self-assembly of two-patch NPs by precisely designing the components to generate colloidal analogues of linear macromolecular chains.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
New lead-free compositions of AMO_(3)perovskite type were synthesized in the BaTi_(1-x)(Nb_(1/2)Sc_(1/2))_(x)O_(3)(0≤x≤1)system,with regards to the comparable electronic configurations of the various 6-coordinated c...New lead-free compositions of AMO_(3)perovskite type were synthesized in the BaTi_(1-x)(Nb_(1/2)Sc_(1/2))_(x)O_(3)(0≤x≤1)system,with regards to the comparable electronic configurations of the various 6-coordinated cations.Special solid state reaction was used.The effect of the repla-cement of titanium by scandium and niobium in the B-site on structural and dielectric properties was investigated.For this,we have used X-ray diffraction and dielectric characterizations.Dielectric measurements performed on ceramics with 0≤x≤0.25 composition revealed that the small change in composition from BaTiO_(3)has a strong infuence on the dielectric properties:fast decreasing of the ferroelectric transition temperature for low values of x and evolution from classical ferroelectric for 0≤x≤0.075 to relaxor behavior for 0.075<x≤0.25.展开更多
Three types of BaTiO3 core-amorphous nanoshell composite ceramics were processed from the same core-shell powder by standard sintering,spark-plasma sintering and two-step sintering techniques and characterized by XRD,...Three types of BaTiO3 core-amorphous nanoshell composite ceramics were processed from the same core-shell powder by standard sintering,spark-plasma sintering and two-step sintering techniques and characterized by XRD,HRSEM and broadband dielectric spectroscopy in the frequency range 10^(3)-10^(13)Hz including the THz and IR range.The samples differed by porosity and by the amount of interdiffusion from the cores to shells,in correlation with their increasing porosity.The dielectric spectra were also calculated using suitable models based on effective medium approximation.The measurements revealed a strong dielectric dispersion below the THz range,which cannot be explained by the modeling,and whose strength was in correlation with the degree of interdiffusion.It is assigned to an effect of the interdiffusion layers,giving rise to a strong interfacial polarization.It appears that the high-frequency dielectric spectroscopy is an extremely sensitive tool for detection of any gradient layers and sample inhomogeneities even in dielectric materials with negligible conductivity.展开更多
Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro–nanostructure.Controlling the architecture of multi-materials at different scales is still challenging and provi...Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro–nanostructure.Controlling the architecture of multi-materials at different scales is still challenging and provides a great opportunity to broaden the range of functionalities in the field of ferroelectric-based ceramics.We used the potentialities of Spark Plasma Sintering(SPS)to control a number of key parameters regarding the properties:anisotropy,interfaces,grain size and strain effects.The flexibility of the wet and supercritical chemistry routes associated with the versatility of SPS allowed designing newferroelectric composite ceramics at different scales.These approaches are illustrated through various examples based on our work on ferroelectric/dielectric composites.展开更多
Here we present the ability of Nd^(3+)-doped zinc-phosphate glasses to be shaped into rectangular core fibers.At first,the physico-chemical properties of the developed P_(2)O_(5)-based materials are investigated for d...Here we present the ability of Nd^(3+)-doped zinc-phosphate glasses to be shaped into rectangular core fibers.At first,the physico-chemical properties of the developed P_(2)O_(5)-based materials are investigated for different concentrations of neo-dymium oxide and core and cladding glass compositions are selected for further fiber development.A modified stack-and-draw technique is used to produce multimode large rectangular-core optical fibers.Self-guided nonlinear effects acting as spatial beam reshaping processes occurring in these newly-developed photonic structures lead to the generation of spectral broadenings in the visible and near-infrared spectral domains.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the financial support provided by ANR(Project ANR-22-PEHY-0007)DGA(French Direction Générale des Armées,2018600045)Région Nouvelle Aquitaine(agreement 2018–1R10126).
文摘The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)and atom probe tomography(APT)to investigate the structural and local chemical information of LPSO phases formed in Mg-Ni-Y/Sm ternary alloys after extended isothermal annealing.Depending on the alloying elements and their concentrations,Mg-Ni-Y/Sm develops a two-phase LPSO+α-Mg structure in which the LPSO phase contains defects,hybrid LPSO structure,and Mg insertions.HAADF-STEM and APT indicate non-stoichiometric LPSO with incomplete Ni_(6)(Y/Sm)_(8) clusters.In addition,the APT quantitatively determines the local composition of LPSO and confirms the presence of Ni within the Mg bonding layers.These results provide insight into a better understanding of the structure and hydrolysis properties of LPSO-Mg alloys.
文摘采用固相法合成了中温固体氧化物燃料电池（IT-SOFCs）阴极材料La Bi Mn2O6,并利用X射线衍射（XRD）和电化学阻抗谱（EIS）进行表征。结果表明该材料与电解质Ce0.7Bi0.3O1.85（CBO）在1 000℃烧结12 h不发生反应。交流阻抗和直流极化测试结果发现,阴极极化电阻随测试温度的增加而逐渐减小,700℃空气中的极化电阻为0.71Ω·cm2;氧分压测试结果显示,在600～700℃范围内,电极反应的速率控制步骤为电极上发生的电荷转移反应。电极过电位为85 m V时,700℃的阴极电流密度达到216 m A·cm-2,表明La Bi Mn2O6是一种潜在的中温固体氧化物燃料电池（IT-SOFCs）阴极材料。
基金PEREN project(reference:ANR-2011-PREG-016–05)the ECOREVE project(reference:ANR-18-CE05-0036-01)the Agence Nationale de la Recherche(A.N.R.,France)for supporting these scientific works and for the financial support。
文摘The chemical and electrochemical stability of lanthanide nickelates La2 NiO4+δ(LNO),Pr2 NiO4+δ(PNO)and their mixed compounds La(2-x)PrxNiO4+δ(LPNOs)with x=0.5,1 or 1.5 is reported.The aim is to promote these materials as efficient electrodes for solid oxide fuel cell(SOFC)and/or solid oxide electrolysis cell(SOEC).La2 NiO4+δand La1.5Pr0.5NiO4+δcompounds are chemically very stable as powders over one month in the temperature range 600-800℃,while the other materials rich in praseodymium progressively decompose into various perovskite-deriving components with additional Pr6 O11.Despite their uneven properties,all these materials are quite efficient and sustainable as electrodes on top of gadolinium doped ceria(GDCBL)//yttrium doped zirconia(8 YSZ)electrolyte,for one month at 700℃without polarization.Under polarization(300 mA·cm-2),the electrochemical performances of LNO,PNO and La1.5Pr0.5NiO4+δ(LP5 NO)quickly degrade in SOFC mode,i.e.for the oxygen reduction reaction,while they show durability in SOEC mode,i.e.for the oxide oxidation reaction.
基金This study was supported by the National Science Foundation(CMMI 1826392)and the Nebraska Center for Energy Sci-ences Research(NCESR)The research was performed in part in the Nebraska Nanoscale Facility:National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Mater-ials and Nanoscience,which are supported by the National Sci-ence Foundation under Award ECCS:1542182,and the Neb-raska Research Initiative.
文摘As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining(i.e.defects on edges and tapered sidewalls).The evolution of edge sharpness(edge transition width)and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed.Through decreasing the angle of incidence(AOI)from 0◦to−5◦,the edge transition width could be reduced to below 10µm but at the cost of increased sidewall tapers.Furthermore,by analyzing lateral and vertical ablation behaviors,a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls.The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications.The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions.Both mm-scale diameters and depths were realized with dimensional precisions below 10µm and surface roughness below 1µm.This research establishes a novel strategy to finely control the fs laser machining process,enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.
文摘The increase in both power and packing densities in power electronic devices has led to an increase in the market demand for effective heat-dissipating materials with a high thermal conductivity and thermal expansion coefficient compatible with chip materials while still ensuring the reliability of the power modules.Metal matrix composites,especially copper matrix composites,containing carbon fibers,carbon nanofibers,or diamond are considered very promising as the next generation of thermalmanagement materials in power electronic packages.These composites exhibit enhanced thermal properties,as compared to pure copper,combined with lower density.This paper presents powder metallurgy and hot uniaxial pressing fabrication techniques for copper/carbon composite materials which promise to be efficient heat-dissipation materials for power electronic modules.Thermal analyses clearly indicate that interfacial treatments are required in these composites to achieve high thermal and thermomechanical properties.Control of interfaces(through a novel reinforcement surface treatment,the addition of a carbide-forming element inside the copper powders,and processing methods),when selected carefully and processed properly,will form the right chemical/mechanical bonding between copper and carbon,enhancing all of the desired thermal and thermomechanical properties while minimizing the deleterious effects.This paper outlines a variety of methods and interfacial materials that achieve these goals.
基金financially supported by the AZM&SAADE Associationthe Lebanese University(Scientific research support program)+1 种基金the Lebanese Council of Scientific Research(CNRSL)Bordeaux foundation
文摘The hydrolysis of Mg-based materials appears to be an ideal solution for clean energy production.Green hydrogen was produced by the hydrolysis reaction of a"standard"AZ91 alloy(called AZ91 in the following)in"model"seawater solution.Two milling speeds(i.e.250 rpm and 350 rpm)were tested to enhance the reactivity of AZ91.Graphite and AlCl_(3)were used as ball milling additives.Milling at higher rotational speed is more energetic,hence it ameliorates the most the hydrolysis performance of AZ91.Comparing both milling additives,AlCl_(3)enhances the most the hydrolysis of AZ91 with a generation of 65%of its theoretical H_(2)generation capacity.The best material was obtained by milling AZ91 at 350 rpm with graphite for 2 h followed by a further milling with AlCl_(3)for 2h-a yield of 75%of its theoretical H_(2)generation capacity was reached within a few minutes.The corrosion behavior of milled AZ91 was investigated by anodic polarization and electrochemical impedance spectroscopy(EIS).The calculated electrochemical parameters from EIS fitting of two materials milled under different conditions but with the same milling additive are approximately the same.This suggests that,in order to fully evaluate the reactivity of AZ91,hydrolysis,anodic polarization and EIS must be considered.
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.
基金the CNRS through the MITI interdisciplinary programs (Action MITI: Nouveaux Materiaux 2020 and 2021)financially supported by the National Key Research and Development Program of China (2022YFB3602903, 2021YFB3602703, and 2022YFB3606504)+4 种基金the National Natural Science Foundation of China (62204107 and 12204229)Guangdong Basic and Applied Basic Research Foundation (2022A1515011614)Shenzhen Science and Technology Program (JCYJ20220818100411025)Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting (ZDSYS201707281632549)Pingshan District Innovation Platform Project of Shenzhen Hi-tech Zone Development Special Plan in 2022 (29853M-KCJ-2023-002-01)。
基金This work was supported by the Agence Nationale de la Recherche(ENLARgER project,No.ANR-15-CE09-0010)the LabEx AMADEus(No.ANR-10-LABX-42)IdEx Bordeaux(No.ANR-10-IDEX-03-02)。
文摘We report the formation of colloidal polymers consisting of disk-like silica nanoparticles(NPs)with polystyrene(PS)chains at the bottom of their two cavities assembled through reduction of the solvent quality for the PS chains and linked by hydrophobic associations.We show that this NPs assembly exhibits a two-stage process involving reaction-controlled polymerization and diffusion-controlled polymerization.Colloidal polymer networks are produced by the incorporation of three-patch NPs,which serve as branching points between the colloidal chains.By co-assembling preformed homopolymers composed of patchy NPs of different sizes or surface chemical groups,block copolymers are also achieved.This study provides insight into the process of self-assembly of two-patch NPs by precisely designing the components to generate colloidal analogues of linear macromolecular chains.
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.
文摘New lead-free compositions of AMO_(3)perovskite type were synthesized in the BaTi_(1-x)(Nb_(1/2)Sc_(1/2))_(x)O_(3)(0≤x≤1)system,with regards to the comparable electronic configurations of the various 6-coordinated cations.Special solid state reaction was used.The effect of the repla-cement of titanium by scandium and niobium in the B-site on structural and dielectric properties was investigated.For this,we have used X-ray diffraction and dielectric characterizations.Dielectric measurements performed on ceramics with 0≤x≤0.25 composition revealed that the small change in composition from BaTiO_(3)has a strong infuence on the dielectric properties:fast decreasing of the ferroelectric transition temperature for low values of x and evolution from classical ferroelectric for 0≤x≤0.075 to relaxor behavior for 0.075<x≤0.25.
基金supported by the Academy of Sci-ences of the Czech Republic(project AVOZ 10100520)the Czech Science Foundation(project 202/09/0430)by COST action MP904.
文摘Three types of BaTiO3 core-amorphous nanoshell composite ceramics were processed from the same core-shell powder by standard sintering,spark-plasma sintering and two-step sintering techniques and characterized by XRD,HRSEM and broadband dielectric spectroscopy in the frequency range 10^(3)-10^(13)Hz including the THz and IR range.The samples differed by porosity and by the amount of interdiffusion from the cores to shells,in correlation with their increasing porosity.The dielectric spectra were also calculated using suitable models based on effective medium approximation.The measurements revealed a strong dielectric dispersion below the THz range,which cannot be explained by the modeling,and whose strength was in correlation with the degree of interdiffusion.It is assigned to an effect of the interdiffusion layers,giving rise to a strong interfacial polarization.It appears that the high-frequency dielectric spectroscopy is an extremely sensitive tool for detection of any gradient layers and sample inhomogeneities even in dielectric materials with negligible conductivity.
基金Financial support from the French National Center for Scientific Research(CNRS),the Conseil Regional d'Aquitaine,and the National Research Agency(ANR)(Projects NANO4F(ANR-05-JCJC-0169)ARCHIFUN(ANR-12-BS08–009)are gratefully acknowledged.
文摘Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro–nanostructure.Controlling the architecture of multi-materials at different scales is still challenging and provides a great opportunity to broaden the range of functionalities in the field of ferroelectric-based ceramics.We used the potentialities of Spark Plasma Sintering(SPS)to control a number of key parameters regarding the properties:anisotropy,interfaces,grain size and strain effects.The flexibility of the wet and supercritical chemistry routes associated with the versatility of SPS allowed designing newferroelectric composite ceramics at different scales.These approaches are illustrated through various examples based on our work on ferroelectric/dielectric composites.
文摘Here we present the ability of Nd^(3+)-doped zinc-phosphate glasses to be shaped into rectangular core fibers.At first,the physico-chemical properties of the developed P_(2)O_(5)-based materials are investigated for different concentrations of neo-dymium oxide and core and cladding glass compositions are selected for further fiber development.A modified stack-and-draw technique is used to produce multimode large rectangular-core optical fibers.Self-guided nonlinear effects acting as spatial beam reshaping processes occurring in these newly-developed photonic structures lead to the generation of spectral broadenings in the visible and near-infrared spectral domains.
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.
