π-Conjugated donor-acceptor-donor-acceptor-donor(D-A-D-A-D)type pyrenoviologens(PyV^(2+)),with the 2,7 positions of pyrene serving as connection bridges,were synthesized through SN2 reactions.Specifically,pyrenoviolo...π-Conjugated donor-acceptor-donor-acceptor-donor(D-A-D-A-D)type pyrenoviologens(PyV^(2+)),with the 2,7 positions of pyrene serving as connection bridges,were synthesized through SN2 reactions.Specifically,pyrenoviologen 3c was modified with a methylnaphthalene group,while 3a and 3b were modified with methyl and benzyl groups,respectively,for comparison.These pyrenoviologens exhibit reversible redox properties and strong fluorescence emission.Electrochromic devices(ECDs)were prepared using pyrenoviologens as the active materials.Notably,naphthalene-containing pyrenoviologen 3c,with its DA-D-A-D conjugated structure,possesses more stable free radicals,enabling it to maintain the radical color for a longer duration after power loss.A series of color-changing devices were successfully assembled.Due to the strong fluorescence of pyrenoviologens and the unique electron transfer effect between them and picric acid(PA),a sensor film with good selectivity and high sensitivity for PA in aqueous solution was prepared using pyrenoviologens as the fluorescent probe.Specifically,3c exhibited the highest sensitivity to PA due to its lowest energy gap.The introduction of the D-A-D-A-D structure is a strategic approach to enhancing photoelectric performance and broadening the application of viologens.展开更多
Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence ...Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.展开更多
Cold atmospheric plasmas are widely used in biomedicine.Although direct plasma treatments of wounds have been demon-strated,there are still obstacles hampering further clinical adoption,for example,the limited treatme...Cold atmospheric plasmas are widely used in biomedicine.Although direct plasma treatments of wounds have been demon-strated,there are still obstacles hampering further clinical adoption,for example,the limited treatment area,inconsistent ac-tions and risk of thermal injury.In this respect,plasma-activated air(PAA)is proposed and demonstrated for infected wounds treatment as an alternative to the conventional direct plasma treatment.The combination of gliding arc discharge reactor and dielectric barrier discharge reactor produces highly bioactive PAA.In in vitro sterilisation of Staphylococcus aureus,approxi-mately 9-log reduction is achieved after the PAA treatment for 6 min.Bovine serum albumin is added to the S.aureus sus-pension to further simulate the wound exudate to accomplish inactivation of approximately 3-log reduction after 10 min.In vivo experiments show that the PAA treatment of infected wounds significantly reduces the bacterial load and improves the healing rate,revealing an optimal treatment time of 3 min/day.The immunohistochemical and blood biochemical analyses show that the PAA-3 min treatment enhances wound healing by inhibiting the tissue inflammatory response and inducing growth factor production without showing evident systemic toxicity.In conclusion,PAA holds great clinical promise as a safe and effective wound-healing strategy.展开更多
A series of isomeric sandwich-type dysprosiacarboranyl complexes,including[Na(THF)_(5)][3.2'-(THF)_(2)-3.2-Dy(1,2-C_(2)B_(9)H_(11))_(x)(1'7'-C_(2)B_(9)H_(11))_(2-x))(o/m-Dy)and[Na(THF)_(5)][2.2'-(THF)_...A series of isomeric sandwich-type dysprosiacarboranyl complexes,including[Na(THF)_(5)][3.2'-(THF)_(2)-3.2-Dy(1,2-C_(2)B_(9)H_(11))_(x)(1'7'-C_(2)B_(9)H_(11))_(2-x))(o/m-Dy)and[Na(THF)_(5)][2.2'-(THF)_(2)-2.2'-Dy(1,7-C_(2)B_(9)H_(11))2](m-Dy)were synthesized by using the isomeric dicarbollide ligands,namely[nido-7,8-C2BgH_(11)]^(2-)and[nido-7,9-C_(2)B_(9)H_(11)]^(2-).The structural details of o/m-Dy and m-Dy and magnetic dynamics of m-Dy were investigated to compare with the previous study on[Na(THF)_(5)][2.2'-(THF)_(2)-2.2'-Dy(1,2-C_(2)B_(9)H_(11))_(2)]o-Dy.The bending angles of sandwiched dysprosiacarboranes are straightened so as to improve energy bar-riers(U_(eff))from 430(5)to 591(0)K.Magneto-structural correlations show that the introduction of meta-C sites within the π-electron delocalized heterocyclic ring can effectively shorten the Dy-C_(2)B_(3)centroid distance and increase the C_(2)B_(3)centroid...Dy...C_(2)B_(3)centroid bending angle which is attributed to the dif-ferences in electronegativity between C and B atoms on the ring of C_(2)B_(3)^(2-).Therefore,to further enhance the performance of single-molecule magnets(SMMs)on this basis,future endeavors should focus on diminishing the equatorial solvent molecules to make a wider C2B3...Dy...C_(2)B_(3)bending angle.展开更多
The inherent complexities of excitable cardiac,nervous,and skeletal muscle tissues pose great challenges in constructing artificial counterparts that closely resemble their natural bioelectrical,structural,and mechani...The inherent complexities of excitable cardiac,nervous,and skeletal muscle tissues pose great challenges in constructing artificial counterparts that closely resemble their natural bioelectrical,structural,and mechanical properties.Recent advances have increasingly revealed the beneficial impact of bioelectrical microenvironments on cellular behaviors,tissue regeneration,and therapeutic efficacy for excitable tissues.This review aims to unveil the mechanisms by which electrical microenvironments enhance the regeneration and functionality of excitable cells and tissues,considering both endogenous electrical cues from electroactive biomaterials and exogenous electrical stimuli from external electronic systems.We explore the synergistic effects of these electrical microenvironments,combined with structural and mechanical guidance,on the regeneration of excitable tissues using tissue engineering scaffolds.Additionally,the emergence of micro/nanoscale bioelectronics has significantly broadened this field,facilitating intimate interactions between implantable bioelectronics and excitable tissues across cellular,tissue,and organ levels.These interactions enable precise data acquisition and localized modulation of cell and tissue functionalities through intricately designed electronic components according to physiological needs.The integration of tissue engineering and bioelectronics promises optimal outcomes,highlighting a growing trend in developing living tissue construct-bioelectronic hybrids for restoring and monitoring damaged excitable tissues.Furthermore,we envision critical challenges in engineering the next-generation hybrids,focusing on integrated fabrication strategies,the development of ionic conductive biomaterials,and their convergence with biosensors.展开更多
Recent advances in all-inorganic perovskite semiconductors have garnered significant research interest due to their potential for high-performance optoelectronic devices and enhanced stability under harsh environmenta...Recent advances in all-inorganic perovskite semiconductors have garnered significant research interest due to their potential for high-performance optoelectronic devices and enhanced stability under harsh environmental conditions.A deeper understanding of their structural,chemical,and physical properties has driven notable progress in addressing challenges related to electrical characteristics,reproducibility,and long-term operational stability in perovskite-based memristors.These advancements have been realized through composition engineering,dimensionality modulation,thin-film processing,and device optimization.This review concisely summarizes recent developments in all-inorganic perovskite memristors,highlighting their diverse material properties,device performance,and applications in artificial synapses and logic operations.We discuss key resistance-switching mechanisms,optimization strategies,and operational capabilities while outlining remaining challenges and future directions for perovskitebased memory technologies.展开更多
Twelve novel transition-rare-earth metal clusters,formulated as [Ni_(18)Pr_(14)(μ_(3)OH)_(14)(dmpa)_(10)(mmt)_(10)(SO_(4))_(4)(CH_(3)COO)_(16)]·9CH_(3)OH·5H_(2)O(1,H_(3)dmpa=dimethylolpropionic acid,and Hmm...Twelve novel transition-rare-earth metal clusters,formulated as [Ni_(18)Pr_(14)(μ_(3)OH)_(14)(dmpa)_(10)(mmt)_(10)(SO_(4))_(4)(CH_(3)COO)_(16)]·9CH_(3)OH·5H_(2)O(1,H_(3)dmpa=dimethylolpropionic acid,and Hmmt=2-me rcapto-5-methyl-1,3,4-thiadiazole) [Ni_(36)RE_(102)(OH)_(138)(mmt)_(18)(Hdmpa)_(30)(H_(2)dmpa)_(12)(CH_(3)COO)_(72)(NO_(3))_(36)(SO_(4))_(18)(H_(2)O)_(30)]·Br_(6)(RE=Nd(2),Sm(3),Eu(4) and Gd(5))[Ni_(12)RE_(10)(μ_(3)-OH)_(10)(dmpa)_(8)(mmt)_(8)(S(_(4))2(CH_(3)COO)_(8)(H_(2)O)_(4)]·8CH_(3)OH·7H_(2)O(RE = Tb(6),Dy(7),Ho(8),Er(9) and Y(10)) [Ni_(8)Pr_(8)(μ_(3)-OH)_(8)(mmt)_(8)(Hdpga)_(16)(CH3COO)_(8)]·8CH_(3)OH(11,H_(2)dpga=diphe nyl-glycolic acid),and [Ni_(16)Tb_(6)(μ_(3)-OH)_(24)(mmt)_(8)(Hdpga)_(4)(dpga)_(4)(CH_(3)COO)_(2)(NO_(3))_(4)(H_(2)O)_(2)]·12CH_(3)OH·5H_(2)O(12),were synthesized solvothermally by using different ligand combinations and rare earth nitrates.X-ray crystal structure analyses reveal that complexes 1 and 12 possess sandwich-like structure.Compounds 2-5 are isostructural and feature a hexagonal structure,shaped like a "Star of David".Isostructural 6-10 present ring-like structure,as well as the cluster 11.The structural variations of these complexes can be attributed to the effect of lanthanide contraction.Moreover,the template effect of SO_(4)^(2-) anion derived from the slow decomposition of Hmmt ligand also plays a significant role in the formation of cluster skeletons.The insitu mechanism for the generation of sulfate anion is briefly discussed.Meanwhile,the magnetic properties of complexes 2-11 were studied which show typical antiferromagnetic interactions.展开更多
In this study,a series of arylene-bridged bis(benzimidazolium)triflates 1^(–)6^(^(2+))·2[OTf^(–)]were synthesized by grafting differentπ-linkers with benzimidazolium scaffolds.Among them,compound 1^(2+)·2...In this study,a series of arylene-bridged bis(benzimidazolium)triflates 1^(–)6^(^(2+))·2[OTf^(–)]were synthesized by grafting differentπ-linkers with benzimidazolium scaffolds.Among them,compound 1^(2+)·2[OTf^(–)]with anthracene as the linker exhibited remarkable electron transfer capabilities across four distinct redox states.The inclusion of an anthracene unit as theπ-linker contributes to its exceptional redox and optoelectronic characteristics.Consequently,1^(2+)·2[OTf^(–)]was successfully utilized as both an electrochromic molecule in an ECD under applied voltage for the first time,and a highly efficient photocatalyst for the formation of carbon–phosphorus bonds via visible-light-induced cross-dehydrogenative coupling reactions.展开更多
The electrochemical performance of microsupercapacitors with graphene electrodes is reduced by the issue of graphene sheets aggregation,which limits electrolyte ions penetration into electrode.Increasing the space bet...The electrochemical performance of microsupercapacitors with graphene electrodes is reduced by the issue of graphene sheets aggregation,which limits electrolyte ions penetration into electrode.Increasing the space between graphene sheets in electrodes facilitates the electrolyte ions penetration,but sacrifices its electronic conductivity which also influences the charge storage ability.The challenging task is to improve the electrodes’electronic conductivity and ionic diffusion simultaneously,boosting the device’s electrochemical performance.Herein,we experimentally realize the enhancement of both electronic conductivity and ionic diffusion from 2D graphene nanoribbons assisted graphene electrode with porous layer-uponlayer structure,which is tailored by graphene nanoribbons and self-sacrificial templates ethyl cellulose.The designed electrode-based device delivers a high areal capacitance of 71 mF cm^(-2)and areal energy density of 9.83μWh cm^(-2),promising rate performance,outstanding cycling stability with 97%capacitance retention after 20000 cycles,and good mechanical properties.The strategy paves the way for fabricating high-performance graphene-based MSCs.展开更多
Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic pr...Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.展开更多
Due to the ionic feature of the lanthanide ions,to straightly bridge two lanthanide(Ln)ions is rather challenging though this bridging mode is much beneficial to suppress the zero-field quantum tunneling of the magnet...Due to the ionic feature of the lanthanide ions,to straightly bridge two lanthanide(Ln)ions is rather challenging though this bridging mode is much beneficial to suppress the zero-field quantum tunneling of the magnetization(QTM)for single-molecule magnets(SMMs),a kind of nanosized magnetic materials for high-density information storage and magnetic resonance imaging contrast agent.Here we used an unusual terminal amino pyridine ligand which utilizes extensive supramolecular interactions to stabilize such an unusual linear bridging mode and obtained a series of such dimeric Ln(Ⅲ)complexes-{[LnL_(A)(4-NH_(2)py)_(5)]_(2)(μ-Cl)}[BPh_(4)]_(3)(For L_(A)^(-)=1-AdO^(-),1Ln;for L_(A)^(-)=~tBuO^(-),2Ln;Ln=Dy,Gd).More uniquely,the bridging chloride sits in the center of two improper rotation symmetry related Ln(Ⅲ)ions with local C_(5v)symmetry.The dimeric compounds 1Dy and 2Dy exhibit much slower low-temperature magnetic relaxation and thousands of times longer relaxation times at 2 K(τ_(2K)=2706.89 and 1437.05 s for 1Dy and 2Dy)compared to the diluted ones with the approaching magnetic property of the C_(5v)motifs(τ_(2K)=0.77 and 1.29 s for 1Dy@1Y and 2Dy@2Y).Though magnetic interactions mediated via the chloride bridge in both 1Dy and 2Dy are weak and antiferromagnetic,it is still very effective due to such a linear geometry to reduce the QTM effect in SMMs.展开更多
Traditional hemostatic materials are difficult to meet the needs of non-compressible bleeding and for coagulopathic patients.In addition,open wounds are susceptible to infection,and then develop into chronic wounds.Ho...Traditional hemostatic materials are difficult to meet the needs of non-compressible bleeding and for coagulopathic patients.In addition,open wounds are susceptible to infection,and then develop into chronic wounds.However,the development of integrated dressings that do not depend on coagulation pathway and improve the microenvironment of chronic wounds remains a challenge.Inspired by the porous structure and composition of the natural extracellular matrix,adipic dihydrazide modified gelatin(GA),dodecylamine-grafted hyaluronic acid(HD),and MnO_(2) nanozyme(manganese dioxide)@DFO(deferoxamine)@PDA(polydopamine)(MDP)nanoparticles were combined to prepare GA/HD/MDP cryogels through amidation reaction and hydrogen bonding.These cryogels exhibited good fatigue resistance,photothermal antibacterial(about 98%killing ratios of both Escherichia coli and methicillin-resistant Staphylococcus aureus(MRSA)after 3 min near-infrared irradiation),reactive oxygen species scavenging,oxygen release,and angiogenesis properties.Furthermore,in the liver defect model of rats with coagulopathy,the cryogel displayed less bleeding and shorter hemostasis time than commercial gelatin sponge.In MRSA-infected diabetic wounds,the cryogel could decrease wound inflammation and oxidative stress,alleviate the hypoxic environment,promote collagen deposition,and induce vascular regeneration,showing a better repair effect compared with the Tegaderm^(TM)film.These results indicated that GA/HD/MDP cryogels have great potential in non-compressible hemorrhage for coagulopathic patients and in healing infected wounds for diabetic patients.展开更多
Lanthanide-based single-molecule magnets exhibit broad magnetic hysteresis,which manifests as slow magnetic relaxation in strong magnetic fields.However,the origin of the nontrivial hysteresis behaviors remains debate...Lanthanide-based single-molecule magnets exhibit broad magnetic hysteresis,which manifests as slow magnetic relaxation in strong magnetic fields.However,the origin of the nontrivial hysteresis behaviors remains debated.Here,we propose two influential mechanisms:activation of optical-phonon-mediated direct transitions within the ground-state doublet and the resonant Raman process.These discoveries,coupled with the g-factor anisotropy,account for the observed hysteresis behaviors in the regimes of fast magnetic relaxation.Our findings complement the recognized mechanisms used to interpret the magnetic hysteresis of single-molecule magnets.展开更多
Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integra...Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integration.However,the extent of grain and grain boundary contribution to the colossal permittivity of CCTO-based ceramics based on the internal barrier layer capacitor(IBLC)model is still in debate.This affects their electrical performance optimization and real-world applications.In this study,a series of novel lead-free colossal permittivity ceramic s,xLiCuNb_(3)O_(9-)(1-x)CaCu_(3)Ti_(4)O_(12)(LCNOCCTO),were designed and prepared using a solid-phase reaction approach.The colossal permittivity response mechanism of LCNO-CCTO ceramics was further explored by performing the complex impedance spectrum and analyzing the activation energy from the grain and grain boundary contribution viewpoint.As a result,the LCNO-CCTO ceramics present the cubic perovskite structure with the space groups of■.All the LCNOCCTO ceramics exhibit the significantly enhanced colossal permittivity(10^(5))response,and the ceramic with x=0.15 shows the highest permittivity of about 4.64×10^(5)(20 Hz,room temperature)accompanied by a lower grain resistance of 9.61Ωand larger grain activation energy of 0.21 eV.The enhanced colossal permittivity response is primarily attributed to the great electrical response inside grains of LCNO-CCTO ceramics,resulting from a smaller grain resistance.Also importantly,the high-frequency dielectric relaxation characteristics are improved by incorporating the LCNO into CCTO ceramics as an ion form.Accordingly,the LCNO-CCTO ceramics show a suppressed high-frequency dielectric loss.These results can provide a thorough knowledge and useful optimization strategy for developing high-performance colossal permittivity materials.展开更多
Trace Zr addition is essential for achieving desired cellular nanostructure and large coercivity in the pinning-controlled 2:17-type Sm-Co-Fe-Cu-Zr magnets that have served as the strongest high temperature permanent ...Trace Zr addition is essential for achieving desired cellular nanostructure and large coercivity in the pinning-controlled 2:17-type Sm-Co-Fe-Cu-Zr magnets that have served as the strongest high temperature permanent magnets for over 40 years.However,accompanying this is the formation of Zr-rich particles that may deteriorate the hard magnetic properties.Besides the formerly-reported 1:3R Zr-rich platelets,in this work,1–2μm sized Zr6(Co,Fe)23(6:23)particles(Fm 3 m)and 100–200 nm sized 1:3R Zr-rich particles were also found based on combined structural identifications and element mapping analysis.Around such particles,the desired 1:5H cell wall precipitates that provide the strongest pinning force of magnetic domain wall motions are rare,forming the precipitate-free-zones(PFZs).The 1:5H-PFZs and the soft magnetism of both 6:23 and 1:3R Zr-rich particles act as local weak pinning points,which are unfavorable to retain the large magnetization in strong opposite fields and lead to poor squareness.As observed in a Sm25Co45.9Fe19.5Cu5.6Zr4.0(wt.%)magnet,the co-existence of such Zr-rich particles and the associated 1:5H-PFZs leads to a pretty low squareness factor of only 52.89%given the large coercivity of 29.04 kOe.Our findings suggest that careful controlling the Zr content and avoiding its aggregation to form harmful 6:23 and 1:3R Zr-rich particles are essential for achieving high squareness as well as large energy product in the Sm-Co-Fe-Cu-Zr permanent magnets.展开更多
Effects of dopant size on the magnetic properties and corrosion behavior of hot-deformed NdFeB with the intergranular additions of nano-TiC were investigated using X-ray diffraction(XRD),X-ray photoelectron spectromet...Effects of dopant size on the magnetic properties and corrosion behavior of hot-deformed NdFeB with the intergranular additions of nano-TiC were investigated using X-ray diffraction(XRD),X-ray photoelectron spectrometer(XPS),scanning electron microscopy(SEM),electrochemical and magnetic measurement technologies.Additions of 50 nm-TiC,unlike 30 nm- and 40 nm-TiC,are found to increase the magnetic energy product and comprehensive magnetic properties,due in main to the improvement of magnet orientation by more strip-shaped Nd-rich phases.Nano-TiC dopants especially with a size of40 nm can increase the electrochemical corrosion resistance of magnets.It is attributed to the hindrance of additives on the reaction channel formation and their barrier effect on the oxidations of Nd and Fe.For 40 nm-TiC doped magnet,the charge transfer resistance in electric double layer structure reaches 15000 Ω·cm^(2) that is one order of magnitude higher than other cases,which is responsible for the lowe st corrosion current density and accordingly the best anti-corrosion properties.展开更多
The design of alloys with simultaneous high strength and high ductility is still a difficult challenge.Here,we propose a new approach to designing multi-phase alloys with a synergistic combination of strength and duct...The design of alloys with simultaneous high strength and high ductility is still a difficult challenge.Here,we propose a new approach to designing multi-phase alloys with a synergistic combination of strength and ductility by engineering heterogeneous precipitate microstructures through the activation of different transformation mechanisms.Using a two-phase titanium alloy as an example,phase field simulations are carried out firstly to design heat treatment schedules that involve both conventional nucleation and growth and non-conventional pseudospinodal decomposition mechanisms,and the calculated microstructures have been evaluated by crystal plasticity finite element modeling.According to simulations,we then set a two-step heat treatment to produce bimodalα+βmicrostructure in Ti-10V-2Fe-3Al.Further mechanical testing shows that the ductility of the alloy is increased by~50%and the strength is increased by~10%as compared to its unimodal counterpart.Our work may provide a general way to improve the mechanical properties of alloys through multiscale microstructure design.展开更多
The heterogeneous precipitation in the 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets has been found to contain complex formation and dissociation of defects.Though low-temperature pre-aging has been utilized to promote t...The heterogeneous precipitation in the 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets has been found to contain complex formation and dissociation of defects.Though low-temperature pre-aging has been utilized to promote the precipitate nucleation by the enlarged chemical driving force,how the defects evolve after pre-aging and how the possibly changed defects state affects the subsequent precipitation behavior remain unclear.In this work,a model magnet Sm25Co47.9Fe18.5Cu5.6Zr3.0(wt%)was selected to study.Through comparison with the as-solution-treated state,it is found that pre-aging for 2 h at 550℃reduces the defects density,which was characterized by less cell boundaries(i.e.,larger cell size)and less basal stacking faults inside the cells(i.e.,higher 2:17 R ordering degree).Further studies reveal that after aging for the same time(10 h)at the same temperature(830℃),the reduced density of defects by preaging also leads to slower precipitation/phase transformation kinetics when co mpared with the non-preaged one,which was characterized by the lower 2:17 R ordering degree and smaller coercivity for the former.These findings suggest that pre-aging has a strong influence on the density of defects and their evolution during subsequent isothermal aging process,which should be carefully considered to tailor the microstructure and magnetic properties of Sm-Co-Fe-Cu-Zr magnets.展开更多
Well-aligned and uniform Coo.sZno.2Fe204 nanofibers （NFs） are prepared by electrospinning via sol-gel and sub- sequent heat treatment. Each of the as-spun NFs has a diameter of about 300 nm and a smooth surface morp...Well-aligned and uniform Coo.sZno.2Fe204 nanofibers （NFs） are prepared by electrospinning via sol-gel and sub- sequent heat treatment. Each of the as-spun NFs has a diameter of about 300 nm and a smooth surface morphology. The scanning electron microscope （SEM） image shows that the diameter decreases to 70 nm after the Coo.sZno.2Fe204 NF has been annealed at 650℃ for 3 h. The structure and chemical of Co0.8Zn0.2Fe204 NF are investigated by X- ray diffraction （XRD） and energy dispersive X-ray spectroscopy （EDS）, respectively. Single phase cubic spinel structure, Coo.sZno.2Fe204 NF, is successfully obtained after having been calcined at 550 ~C in air for 3 h, and a reduced lattice constant of the Coo.8Zno.2Fe204 NF provides the evidence of effective Zn2＋ substitution. The magnetic measurements show that the substitution of Zn2＋ for Co2＋ , i.e., the introduction of non-magnetic Zn2＋ ions into A sites, can increase the saturation magnetization （Ms） and reduce the coercivity （He）. The obtained Hc results of different samples reveal that the critical single-domain size of the Co0.8Zn0.2Fe204 NF is approximately 44 nm. By doping Zn2＋ with different concentra- tions, the morphologies of Co1-xZnxFe2O4 （0 〈 x 〈 0.5） NFs do not show obvious changes. For magnetic properties, the Ms increases and Hc decreases monotonically, respectively.展开更多
Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt ca...Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenati on of carb on monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffraction, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet transform results give evidenee for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.展开更多
基金supported by the Shaanxi Province Technological Innovation Guidance Special(No.2022QFY08-01)the National Key Research and Development Program of China(No.2021YFB3200702)+5 种基金Natural Science Foundation of China(Nos.22201228,22205172,52203240 and 22175138)China Postdoctoral Science Foundation(Nos.2022M712530,2023T160506,and 2022M712497)Fundamental Research Funds for the Central Universities(No.xzy012022017)Young Talent Fund of Association for Science and Technology in Shaanxi(No.20230624)Shaanxi Province Postdoctoral Science Foundation(No.2023b SHTBZZ04)the Youth Innovation Team of Shaanxi Universities。
文摘π-Conjugated donor-acceptor-donor-acceptor-donor(D-A-D-A-D)type pyrenoviologens(PyV^(2+)),with the 2,7 positions of pyrene serving as connection bridges,were synthesized through SN2 reactions.Specifically,pyrenoviologen 3c was modified with a methylnaphthalene group,while 3a and 3b were modified with methyl and benzyl groups,respectively,for comparison.These pyrenoviologens exhibit reversible redox properties and strong fluorescence emission.Electrochromic devices(ECDs)were prepared using pyrenoviologens as the active materials.Notably,naphthalene-containing pyrenoviologen 3c,with its DA-D-A-D conjugated structure,possesses more stable free radicals,enabling it to maintain the radical color for a longer duration after power loss.A series of color-changing devices were successfully assembled.Due to the strong fluorescence of pyrenoviologens and the unique electron transfer effect between them and picric acid(PA),a sensor film with good selectivity and high sensitivity for PA in aqueous solution was prepared using pyrenoviologens as the fluorescent probe.Specifically,3c exhibited the highest sensitivity to PA due to its lowest energy gap.The introduction of the D-A-D-A-D structure is a strategic approach to enhancing photoelectric performance and broadening the application of viologens.
基金support from the National Key Research and Development Program of China(Grant No.2021YFB3501402)the National Natural Science Foundation of China(Grant Nos.52250313 and 52121001)Yang Liu and Chen Si acknowledge financial support from the National Natural Science Foundation of China(Grant No.12274013).
文摘Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.
基金supported by National Natural Science Foundation of China(Grant 52277231)City University of Hong Kong Donation Research(Grant DON-RMG 9229021)Hong Kong PDFS—RGC Postdoctoral Fellowship Scheme(PDFS2122-1S08).
文摘Cold atmospheric plasmas are widely used in biomedicine.Although direct plasma treatments of wounds have been demon-strated,there are still obstacles hampering further clinical adoption,for example,the limited treatment area,inconsistent ac-tions and risk of thermal injury.In this respect,plasma-activated air(PAA)is proposed and demonstrated for infected wounds treatment as an alternative to the conventional direct plasma treatment.The combination of gliding arc discharge reactor and dielectric barrier discharge reactor produces highly bioactive PAA.In in vitro sterilisation of Staphylococcus aureus,approxi-mately 9-log reduction is achieved after the PAA treatment for 6 min.Bovine serum albumin is added to the S.aureus sus-pension to further simulate the wound exudate to accomplish inactivation of approximately 3-log reduction after 10 min.In vivo experiments show that the PAA treatment of infected wounds significantly reduces the bacterial load and improves the healing rate,revealing an optimal treatment time of 3 min/day.The immunohistochemical and blood biochemical analyses show that the PAA-3 min treatment enhances wound healing by inhibiting the tissue inflammatory response and inducing growth factor production without showing evident systemic toxicity.In conclusion,PAA holds great clinical promise as a safe and effective wound-healing strategy.
基金the National Natural Science Foundation of China(22375157)the Programme of Introducing Talents of Discipline to Universities(B23025)+4 种基金State Key Laboratory of Electrical Insulation and Power Equipment(EIPE23402,EIPE23405)SpecialSupportPlanof ShaanxiProvincefor Young Top-notch Talent,the Fundamental Research Funds for Central Universities(xtr052023002,xzy012023024)the China Postdoctoral Science Foundation(2023M742783)Shaanxi Postdoctoral Science Foundation(2023BSHYDZZ12)the"Scientists+engineers"Team Building Project of Qin Chuang Yuan(2022KXJ-088).
文摘A series of isomeric sandwich-type dysprosiacarboranyl complexes,including[Na(THF)_(5)][3.2'-(THF)_(2)-3.2-Dy(1,2-C_(2)B_(9)H_(11))_(x)(1'7'-C_(2)B_(9)H_(11))_(2-x))(o/m-Dy)and[Na(THF)_(5)][2.2'-(THF)_(2)-2.2'-Dy(1,7-C_(2)B_(9)H_(11))2](m-Dy)were synthesized by using the isomeric dicarbollide ligands,namely[nido-7,8-C2BgH_(11)]^(2-)and[nido-7,9-C_(2)B_(9)H_(11)]^(2-).The structural details of o/m-Dy and m-Dy and magnetic dynamics of m-Dy were investigated to compare with the previous study on[Na(THF)_(5)][2.2'-(THF)_(2)-2.2'-Dy(1,2-C_(2)B_(9)H_(11))_(2)]o-Dy.The bending angles of sandwiched dysprosiacarboranes are straightened so as to improve energy bar-riers(U_(eff))from 430(5)to 591(0)K.Magneto-structural correlations show that the introduction of meta-C sites within the π-electron delocalized heterocyclic ring can effectively shorten the Dy-C_(2)B_(3)centroid distance and increase the C_(2)B_(3)centroid...Dy...C_(2)B_(3)centroid bending angle which is attributed to the dif-ferences in electronegativity between C and B atoms on the ring of C_(2)B_(3)^(2-).Therefore,to further enhance the performance of single-molecule magnets(SMMs)on this basis,future endeavors should focus on diminishing the equatorial solvent molecules to make a wider C2B3...Dy...C_(2)B_(3)bending angle.
基金financially supported by the National Natural Science Foundation of China(Nos.52125501,52405325)the Key Research Project of Shaanxi Province(Nos.2021LLRH-08,2024SF2-GJHX-34)+5 种基金the Program for Innovation Team of Shaanxi Province(No.2023-CX-TD17)the Postdoctoral Fellowship Program of CPSF(No.GZB20230573)the Postdoctoral Project of Shaanxi Province(No.2023BSHYDZZ30)the Basic Research Program of Natural Science in Shaanxi Province(No.2021JQ-906)the China Postdoctoral Science Foundationthe Fundamental Research Funds for the Central Universities。
文摘The inherent complexities of excitable cardiac,nervous,and skeletal muscle tissues pose great challenges in constructing artificial counterparts that closely resemble their natural bioelectrical,structural,and mechanical properties.Recent advances have increasingly revealed the beneficial impact of bioelectrical microenvironments on cellular behaviors,tissue regeneration,and therapeutic efficacy for excitable tissues.This review aims to unveil the mechanisms by which electrical microenvironments enhance the regeneration and functionality of excitable cells and tissues,considering both endogenous electrical cues from electroactive biomaterials and exogenous electrical stimuli from external electronic systems.We explore the synergistic effects of these electrical microenvironments,combined with structural and mechanical guidance,on the regeneration of excitable tissues using tissue engineering scaffolds.Additionally,the emergence of micro/nanoscale bioelectronics has significantly broadened this field,facilitating intimate interactions between implantable bioelectronics and excitable tissues across cellular,tissue,and organ levels.These interactions enable precise data acquisition and localized modulation of cell and tissue functionalities through intricately designed electronic components according to physiological needs.The integration of tissue engineering and bioelectronics promises optimal outcomes,highlighting a growing trend in developing living tissue construct-bioelectronic hybrids for restoring and monitoring damaged excitable tissues.Furthermore,we envision critical challenges in engineering the next-generation hybrids,focusing on integrated fabrication strategies,the development of ionic conductive biomaterials,and their convergence with biosensors.
基金supported by the JST SPRING Grant number JPMJSP2131funded by the Research Fellow Scheme from The Chinese University of Hong KongUniversiti Teknologi Malaysia AJ090000.6700.09453-Tabung Pembayaran Lantikan Skim Prominent Visiting Researcher Scheme JTNCPI。
文摘Recent advances in all-inorganic perovskite semiconductors have garnered significant research interest due to their potential for high-performance optoelectronic devices and enhanced stability under harsh environmental conditions.A deeper understanding of their structural,chemical,and physical properties has driven notable progress in addressing challenges related to electrical characteristics,reproducibility,and long-term operational stability in perovskite-based memristors.These advancements have been realized through composition engineering,dimensionality modulation,thin-film processing,and device optimization.This review concisely summarizes recent developments in all-inorganic perovskite memristors,highlighting their diverse material properties,device performance,and applications in artificial synapses and logic operations.We discuss key resistance-switching mechanisms,optimization strategies,and operational capabilities while outlining remaining challenges and future directions for perovskitebased memory technologies.
基金Project supported by the National Natural Science Foundation of China (21971203)Support Plan of Shaanxi Province for Young Topnotch TalentFundamental Research Funds for Central Universities。
文摘Twelve novel transition-rare-earth metal clusters,formulated as [Ni_(18)Pr_(14)(μ_(3)OH)_(14)(dmpa)_(10)(mmt)_(10)(SO_(4))_(4)(CH_(3)COO)_(16)]·9CH_(3)OH·5H_(2)O(1,H_(3)dmpa=dimethylolpropionic acid,and Hmmt=2-me rcapto-5-methyl-1,3,4-thiadiazole) [Ni_(36)RE_(102)(OH)_(138)(mmt)_(18)(Hdmpa)_(30)(H_(2)dmpa)_(12)(CH_(3)COO)_(72)(NO_(3))_(36)(SO_(4))_(18)(H_(2)O)_(30)]·Br_(6)(RE=Nd(2),Sm(3),Eu(4) and Gd(5))[Ni_(12)RE_(10)(μ_(3)-OH)_(10)(dmpa)_(8)(mmt)_(8)(S(_(4))2(CH_(3)COO)_(8)(H_(2)O)_(4)]·8CH_(3)OH·7H_(2)O(RE = Tb(6),Dy(7),Ho(8),Er(9) and Y(10)) [Ni_(8)Pr_(8)(μ_(3)-OH)_(8)(mmt)_(8)(Hdpga)_(16)(CH3COO)_(8)]·8CH_(3)OH(11,H_(2)dpga=diphe nyl-glycolic acid),and [Ni_(16)Tb_(6)(μ_(3)-OH)_(24)(mmt)_(8)(Hdpga)_(4)(dpga)_(4)(CH_(3)COO)_(2)(NO_(3))_(4)(H_(2)O)_(2)]·12CH_(3)OH·5H_(2)O(12),were synthesized solvothermally by using different ligand combinations and rare earth nitrates.X-ray crystal structure analyses reveal that complexes 1 and 12 possess sandwich-like structure.Compounds 2-5 are isostructural and feature a hexagonal structure,shaped like a "Star of David".Isostructural 6-10 present ring-like structure,as well as the cluster 11.The structural variations of these complexes can be attributed to the effect of lanthanide contraction.Moreover,the template effect of SO_(4)^(2-) anion derived from the slow decomposition of Hmmt ligand also plays a significant role in the formation of cluster skeletons.The insitu mechanism for the generation of sulfate anion is briefly discussed.Meanwhile,the magnetic properties of complexes 2-11 were studied which show typical antiferromagnetic interactions.
基金supported by Natural Science Foundation of China(Nos.22001200,22175138,21875180)。
文摘In this study,a series of arylene-bridged bis(benzimidazolium)triflates 1^(–)6^(^(2+))·2[OTf^(–)]were synthesized by grafting differentπ-linkers with benzimidazolium scaffolds.Among them,compound 1^(2+)·2[OTf^(–)]with anthracene as the linker exhibited remarkable electron transfer capabilities across four distinct redox states.The inclusion of an anthracene unit as theπ-linker contributes to its exceptional redox and optoelectronic characteristics.Consequently,1^(2+)·2[OTf^(–)]was successfully utilized as both an electrochromic molecule in an ECD under applied voltage for the first time,and a highly efficient photocatalyst for the formation of carbon–phosphorus bonds via visible-light-induced cross-dehydrogenative coupling reactions.
基金financially supported by National Natural Science Foundation of China(No.52072297)Key R&D Plan of Shaanxi Province(No.2021GXLH-Z-068)Young Talent Support Plan of Xi'an Jiaotong University
文摘The electrochemical performance of microsupercapacitors with graphene electrodes is reduced by the issue of graphene sheets aggregation,which limits electrolyte ions penetration into electrode.Increasing the space between graphene sheets in electrodes facilitates the electrolyte ions penetration,but sacrifices its electronic conductivity which also influences the charge storage ability.The challenging task is to improve the electrodes’electronic conductivity and ionic diffusion simultaneously,boosting the device’s electrochemical performance.Herein,we experimentally realize the enhancement of both electronic conductivity and ionic diffusion from 2D graphene nanoribbons assisted graphene electrode with porous layer-uponlayer structure,which is tailored by graphene nanoribbons and self-sacrificial templates ethyl cellulose.The designed electrode-based device delivers a high areal capacitance of 71 mF cm^(-2)and areal energy density of 9.83μWh cm^(-2),promising rate performance,outstanding cycling stability with 97%capacitance retention after 20000 cycles,and good mechanical properties.The strategy paves the way for fabricating high-performance graphene-based MSCs.
基金supported by the National Natural Science Foundation of China (Nos. 22375157 and W2433042)the Key Scientific and Technological Innovation Team of Shaanxi Province(No. 2020TD-001)+1 种基金the Fundamental Research Funds for Central Universities, State Key Laboratory of Electrical Insulation and Power Equipment (No. EIPE23409)the Instrument Analysis Center of Xi’an Jiaotong University for assistance。
文摘Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.
基金supported by the National Natural Science Foundation of China(No.22375157)the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23405)+2 种基金the Fundamental Research Funds for Central Universities(No.xtr052023002)the Special Support Plan of Shaanxi Province for Young Top-notch Talentthe Medical-Engineering Cross Project of the First Affiliated Hospital of XJTU(No.QYJC02)。
文摘Due to the ionic feature of the lanthanide ions,to straightly bridge two lanthanide(Ln)ions is rather challenging though this bridging mode is much beneficial to suppress the zero-field quantum tunneling of the magnetization(QTM)for single-molecule magnets(SMMs),a kind of nanosized magnetic materials for high-density information storage and magnetic resonance imaging contrast agent.Here we used an unusual terminal amino pyridine ligand which utilizes extensive supramolecular interactions to stabilize such an unusual linear bridging mode and obtained a series of such dimeric Ln(Ⅲ)complexes-{[LnL_(A)(4-NH_(2)py)_(5)]_(2)(μ-Cl)}[BPh_(4)]_(3)(For L_(A)^(-)=1-AdO^(-),1Ln;for L_(A)^(-)=~tBuO^(-),2Ln;Ln=Dy,Gd).More uniquely,the bridging chloride sits in the center of two improper rotation symmetry related Ln(Ⅲ)ions with local C_(5v)symmetry.The dimeric compounds 1Dy and 2Dy exhibit much slower low-temperature magnetic relaxation and thousands of times longer relaxation times at 2 K(τ_(2K)=2706.89 and 1437.05 s for 1Dy and 2Dy)compared to the diluted ones with the approaching magnetic property of the C_(5v)motifs(τ_(2K)=0.77 and 1.29 s for 1Dy@1Y and 2Dy@2Y).Though magnetic interactions mediated via the chloride bridge in both 1Dy and 2Dy are weak and antiferromagnetic,it is still very effective due to such a linear geometry to reduce the QTM effect in SMMs.
基金jointly supported by the National Natural Science Foundation of China(No.52273149,82171143)Fundamental Research Funds for the Central Universities and the World-Class Universities(Disciplines)Characteristic Development Guidance Funds for the Central Universities.
文摘Traditional hemostatic materials are difficult to meet the needs of non-compressible bleeding and for coagulopathic patients.In addition,open wounds are susceptible to infection,and then develop into chronic wounds.However,the development of integrated dressings that do not depend on coagulation pathway and improve the microenvironment of chronic wounds remains a challenge.Inspired by the porous structure and composition of the natural extracellular matrix,adipic dihydrazide modified gelatin(GA),dodecylamine-grafted hyaluronic acid(HD),and MnO_(2) nanozyme(manganese dioxide)@DFO(deferoxamine)@PDA(polydopamine)(MDP)nanoparticles were combined to prepare GA/HD/MDP cryogels through amidation reaction and hydrogen bonding.These cryogels exhibited good fatigue resistance,photothermal antibacterial(about 98%killing ratios of both Escherichia coli and methicillin-resistant Staphylococcus aureus(MRSA)after 3 min near-infrared irradiation),reactive oxygen species scavenging,oxygen release,and angiogenesis properties.Furthermore,in the liver defect model of rats with coagulopathy,the cryogel displayed less bleeding and shorter hemostasis time than commercial gelatin sponge.In MRSA-infected diabetic wounds,the cryogel could decrease wound inflammation and oxidative stress,alleviate the hypoxic environment,promote collagen deposition,and induce vascular regeneration,showing a better repair effect compared with the Tegaderm^(TM)film.These results indicated that GA/HD/MDP cryogels have great potential in non-compressible hemorrhage for coagulopathic patients and in healing infected wounds for diabetic patients.
基金the support from the Sichuan Normal Universitysupport from the National Natural Science Foundation of China(Grant No.22375157)+1 种基金support from the National Natural Science Foundation of China(Grant Nos.12474122,52171188,51771127,and 52111530143)the Central Government Funds of Guiding Local Scientific and Technological Development for Sichuan Province(Grant No.2021ZYD0025)。
文摘Lanthanide-based single-molecule magnets exhibit broad magnetic hysteresis,which manifests as slow magnetic relaxation in strong magnetic fields.However,the origin of the nontrivial hysteresis behaviors remains debated.Here,we propose two influential mechanisms:activation of optical-phonon-mediated direct transitions within the ground-state doublet and the resonant Raman process.These discoveries,coupled with the g-factor anisotropy,account for the observed hysteresis behaviors in the regimes of fast magnetic relaxation.Our findings complement the recognized mechanisms used to interpret the magnetic hysteresis of single-molecule magnets.
基金financially supported by the National Natural Science Foundation of China(No.52202136)the Natural Science Foundation of Jiangxi Province(No.20232BAB204017)+2 种基金the State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE24203)Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(No.EFMD2024002Z)the Innovation Special Foundation Project for Graduate Students of Nanchang Hangkong University(No.YC2024019)
文摘Copper calcium titanate(CaCu_(3)Ti_(4)O_(12),CCTO)ceramics with colossal permittivity have gained widespread concern because of their potential application in modern electronic devices with miniaturization and integration.However,the extent of grain and grain boundary contribution to the colossal permittivity of CCTO-based ceramics based on the internal barrier layer capacitor(IBLC)model is still in debate.This affects their electrical performance optimization and real-world applications.In this study,a series of novel lead-free colossal permittivity ceramic s,xLiCuNb_(3)O_(9-)(1-x)CaCu_(3)Ti_(4)O_(12)(LCNOCCTO),were designed and prepared using a solid-phase reaction approach.The colossal permittivity response mechanism of LCNO-CCTO ceramics was further explored by performing the complex impedance spectrum and analyzing the activation energy from the grain and grain boundary contribution viewpoint.As a result,the LCNO-CCTO ceramics present the cubic perovskite structure with the space groups of■.All the LCNOCCTO ceramics exhibit the significantly enhanced colossal permittivity(10^(5))response,and the ceramic with x=0.15 shows the highest permittivity of about 4.64×10^(5)(20 Hz,room temperature)accompanied by a lower grain resistance of 9.61Ωand larger grain activation energy of 0.21 eV.The enhanced colossal permittivity response is primarily attributed to the great electrical response inside grains of LCNO-CCTO ceramics,resulting from a smaller grain resistance.Also importantly,the high-frequency dielectric relaxation characteristics are improved by incorporating the LCNO into CCTO ceramics as an ion form.Accordingly,the LCNO-CCTO ceramics show a suppressed high-frequency dielectric loss.These results can provide a thorough knowledge and useful optimization strategy for developing high-performance colossal permittivity materials.
基金supported by the National Natural Science Foundation of China(Nos.51622104,51871174,and 51831006)the Fundamental Research Funds for Central Universities+1 种基金the Young Talent Support Plans of XJTU and Shaanxi Provincethe State Key Laboratory for Mechanical Behavior of Materials。
文摘Trace Zr addition is essential for achieving desired cellular nanostructure and large coercivity in the pinning-controlled 2:17-type Sm-Co-Fe-Cu-Zr magnets that have served as the strongest high temperature permanent magnets for over 40 years.However,accompanying this is the formation of Zr-rich particles that may deteriorate the hard magnetic properties.Besides the formerly-reported 1:3R Zr-rich platelets,in this work,1–2μm sized Zr6(Co,Fe)23(6:23)particles(Fm 3 m)and 100–200 nm sized 1:3R Zr-rich particles were also found based on combined structural identifications and element mapping analysis.Around such particles,the desired 1:5H cell wall precipitates that provide the strongest pinning force of magnetic domain wall motions are rare,forming the precipitate-free-zones(PFZs).The 1:5H-PFZs and the soft magnetism of both 6:23 and 1:3R Zr-rich particles act as local weak pinning points,which are unfavorable to retain the large magnetization in strong opposite fields and lead to poor squareness.As observed in a Sm25Co45.9Fe19.5Cu5.6Zr4.0(wt.%)magnet,the co-existence of such Zr-rich particles and the associated 1:5H-PFZs leads to a pretty low squareness factor of only 52.89%given the large coercivity of 29.04 kOe.Our findings suggest that careful controlling the Zr content and avoiding its aggregation to form harmful 6:23 and 1:3R Zr-rich particles are essential for achieving high squareness as well as large energy product in the Sm-Co-Fe-Cu-Zr permanent magnets.
基金Project supported by the National Natural Science Foundation of China(52174346)Natural Science Foundation of Shandong Province of China(ZR2021ME031)。
文摘Effects of dopant size on the magnetic properties and corrosion behavior of hot-deformed NdFeB with the intergranular additions of nano-TiC were investigated using X-ray diffraction(XRD),X-ray photoelectron spectrometer(XPS),scanning electron microscopy(SEM),electrochemical and magnetic measurement technologies.Additions of 50 nm-TiC,unlike 30 nm- and 40 nm-TiC,are found to increase the magnetic energy product and comprehensive magnetic properties,due in main to the improvement of magnet orientation by more strip-shaped Nd-rich phases.Nano-TiC dopants especially with a size of40 nm can increase the electrochemical corrosion resistance of magnets.It is attributed to the hindrance of additives on the reaction channel formation and their barrier effect on the oxidations of Nd and Fe.For 40 nm-TiC doped magnet,the charge transfer resistance in electric double layer structure reaches 15000 Ω·cm^(2) that is one order of magnitude higher than other cases,which is responsible for the lowe st corrosion current density and accordingly the best anti-corrosion properties.
基金the National Key Research and Development Program of China(No.2016YFB0701302)the National Natural Science Foundation of China(Nos.52171012 and 51931004)“H2”High-Performance Cluster,the internal City University of Hong Kong under the Programs 7004894 and 9380060。
文摘The design of alloys with simultaneous high strength and high ductility is still a difficult challenge.Here,we propose a new approach to designing multi-phase alloys with a synergistic combination of strength and ductility by engineering heterogeneous precipitate microstructures through the activation of different transformation mechanisms.Using a two-phase titanium alloy as an example,phase field simulations are carried out firstly to design heat treatment schedules that involve both conventional nucleation and growth and non-conventional pseudospinodal decomposition mechanisms,and the calculated microstructures have been evaluated by crystal plasticity finite element modeling.According to simulations,we then set a two-step heat treatment to produce bimodalα+βmicrostructure in Ti-10V-2Fe-3Al.Further mechanical testing shows that the ductility of the alloy is increased by~50%and the strength is increased by~10%as compared to its unimodal counterpart.Our work may provide a general way to improve the mechanical properties of alloys through multiscale microstructure design.
基金Project supported by the National Natural Science Foundation of China(52071256,51901170)the fund of Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education,China(MMMM-202003)。
文摘The heterogeneous precipitation in the 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets has been found to contain complex formation and dissociation of defects.Though low-temperature pre-aging has been utilized to promote the precipitate nucleation by the enlarged chemical driving force,how the defects evolve after pre-aging and how the possibly changed defects state affects the subsequent precipitation behavior remain unclear.In this work,a model magnet Sm25Co47.9Fe18.5Cu5.6Zr3.0(wt%)was selected to study.Through comparison with the as-solution-treated state,it is found that pre-aging for 2 h at 550℃reduces the defects density,which was characterized by less cell boundaries(i.e.,larger cell size)and less basal stacking faults inside the cells(i.e.,higher 2:17 R ordering degree).Further studies reveal that after aging for the same time(10 h)at the same temperature(830℃),the reduced density of defects by preaging also leads to slower precipitation/phase transformation kinetics when co mpared with the non-preaged one,which was characterized by the lower 2:17 R ordering degree and smaller coercivity for the former.These findings suggest that pre-aging has a strong influence on the density of defects and their evolution during subsequent isothermal aging process,which should be carefully considered to tailor the microstructure and magnetic properties of Sm-Co-Fe-Cu-Zr magnets.
基金Project supported by the National Natural Science Foundation of China(Grant No.50873047)the Foundation of Gansu Education Department,China(Grant No.0603-02)
文摘Well-aligned and uniform Coo.sZno.2Fe204 nanofibers （NFs） are prepared by electrospinning via sol-gel and sub- sequent heat treatment. Each of the as-spun NFs has a diameter of about 300 nm and a smooth surface morphology. The scanning electron microscope （SEM） image shows that the diameter decreases to 70 nm after the Coo.sZno.2Fe204 NF has been annealed at 650℃ for 3 h. The structure and chemical of Co0.8Zn0.2Fe204 NF are investigated by X- ray diffraction （XRD） and energy dispersive X-ray spectroscopy （EDS）, respectively. Single phase cubic spinel structure, Coo.sZno.2Fe204 NF, is successfully obtained after having been calcined at 550 ~C in air for 3 h, and a reduced lattice constant of the Coo.8Zno.2Fe204 NF provides the evidence of effective Zn2＋ substitution. The magnetic measurements show that the substitution of Zn2＋ for Co2＋ , i.e., the introduction of non-magnetic Zn2＋ ions into A sites, can increase the saturation magnetization （Ms） and reduce the coercivity （He）. The obtained Hc results of different samples reveal that the critical single-domain size of the Co0.8Zn0.2Fe204 NF is approximately 44 nm. By doping Zn2＋ with different concentra- tions, the morphologies of Co1-xZnxFe2O4 （0 〈 x 〈 0.5） NFs do not show obvious changes. For magnetic properties, the Ms increases and Hc decreases monotonically, respectively.
基金the financial support from Joint Fund U1732267 of the National Natural Science Foundation of Chinathe Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)+2 种基金the National Key R&D Program of China(2017YFB0602500)the National Natural Science Foundation of China(Grant no.21503218)DICP DMTO201306(Grant no.DICP DMTO201306)
文摘Cobalt carbide has recently been reported to catalyse the FTO con version of syngas with high selectivity for the production of lower olefins (C2-C4). Clarifying the formation process and atomic structure of cobalt carbide will help understand the catalytic mechanism of FTO. Herein, hydrogenati on of carb on monoxide was investigated for cobalt carbide synthesized from CoMn catalyst, followed by X-ray diffraction, transmission electron microscopy, temperature programmed reaction and in situ X-ray absorption spectroscopy. By monitoring the evolution of cobalt carbide during syngas conversion, the wavelet transform results give evidenee for the formation of the cobalt carbide and clearly demonstrate that the active site of catalysis was cobalt carbide.
