Ultrafine-grained(Sm_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Zr_(2)O_(7)high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for ...Ultrafine-grained(Sm_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Zr_(2)O_(7)high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for the first time.The as-sintered samples exhibit a good microstructure with a grain size of 220 nm and a relative density of 96.8%,which yield excellent comprehensive mechanical properties with a high Vickers hardness of 12.5 GPa and a high fracture toughness of 3.4 MPa·m1/2.In addition,the as-sintered samples possess a good thermostability with the grain growth rate of 30 nm/h,and a low thermal conductivity of 1.57 W·m^(-1)·℃^(-1)at room temperature.The superior mechanical and thermal properties are primarily attributed to the“high-entropy”and grain-refinement effects and good interface bonding.展开更多
The incorporation of therapeutic-capable ions into bioactive glasses(BGs),either based on silica(SBGs)or phosphate(PBGs),is currently envisaged as a proficient path for facilitating bone regeneration.Inconjunction wit...The incorporation of therapeutic-capable ions into bioactive glasses(BGs),either based on silica(SBGs)or phosphate(PBGs),is currently envisaged as a proficient path for facilitating bone regeneration.Inconjunction with this view,the single and complementary structural and bio-functional roles of CuO andGa_(2)O_(3)(in the 2e5 mol%range)were assessed,by deriving a series of SBG and PBG formulations startingfrom the parent glass systems,FastOs®BG e 38.5SiO2d36.1CaOd5.6P2O5d19.2MgOd0.6CaF2,and50.0P2O5d35.0CaOd10.0Na_(2)Od5.0 Fe2O_(3)(mol%),respectively,using the process of melt-quenching.The inter-linked physico-chemistry e biological response of BGs was assessed in search of bio-functional triggers.Further light was shed on the structural role e as network former or modifier e ofCu and Ga,immersed in SBG and PBG matrices.The preliminary biological performance was surveyedin vitro by quantification of Cu and Ga ion release under homeostatic conditions,cytocompatibility assays(in fibroblast cell cultures)and antibacterial tests(against Staphylococcus aureus).The similar(Cu)anddissimilar(Ga)structural roles in the SBG and PBG vitreous networks governed their release.Namely,Cuions were leached in similar concentrations(ranging from 10e35 ppm and 50e110 ppm at BG doses of 5and 50 mg/mL,respectively)for both type of BGs,while the release of Ga ions was 1e2 orders ofmagnitude lower in the case of SBGs(i.e.,0.2e6 ppm)compared to PBGs(i.e.,9e135 ppm).This wasattributed to the network modifier role of Cu in both types of BGs,and conversely,to the network former(SBGs)and network modifier(PBGs)roles of Ga.All glasses were cytocompatible at a dose of 5 mg/mL,while at the same concentration the antimicrobial efficiency was found to be accentuated by the coupledrelease of Cu and Ga ions from SBG.By collective assessment,the most prominent candidate material forthe further development of implant coatings and bone graft substitutes was delineated as the38.5SiO2d34.1CaOd5.6P2O5d16.2MgOd0.6CaF2d2.0CuOd3.0Ga_(2)O_(3)(mol%)SBG system,which yiel-ded moderate Cu and Ga ion release,excellent cytocompatibility and marked antibacterial efficacy.展开更多
Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great po...Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great potential,as it has been applied to obtain a high thermoelectric figure of merit,but the microscopic mechanisms involved have yet to be fully explored.In this study,we focus on r-GeTe,a lowtemperature phase of GeTe,and investigate the pressure effects on the electronic structure,electrical transport properties and anharmonic lattice dynamics based on density functional theory(DFT),the Boltzmann transport equations(BTEs)and perturbation theory.Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation.The corresponding electrical transport properties are compared with those obtained from previous experiments.Hydrostatic pressure is shown to increase valley degeneracy,decrease the band effective mass and enhance the electrical transport property.At the same time,the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure.This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.展开更多
We report that oxygen vacancies have a profound impact on phase separation and thermoelectric properties of ITO films grown at room temperature.Oxygen vacancies in non-stoichiometric In1.8Sn0.2O2.5 films aided the for...We report that oxygen vacancies have a profound impact on phase separation and thermoelectric properties of ITO films grown at room temperature.Oxygen vacancies in non-stoichiometric In1.8Sn0.2O2.5 films aided the formation of In-rich metallic clusters.It yields a high electrical conductivity s=1540 Scm1 and Seebeck coefficient|a|=27.2 mVK1,which resulted in the highest power factor(a2 s=113.8 mW m1 K2)but low optical transmission(Top-25%).An increase in oxygen partial pressure resulted in stochiometric In1.8Sn0.2O3 films which improved the optical transparency by 300%(Top-75.4%),but power factor was reduced by-85%due to a decrease in a and s.A decrease in a was due to the lack of energy filtering of charge carriers in the stoichiometric ITO film which did not have In-rich metallic clusters.XPS results showed that the valence band energy shifts with a change in oxygen partial pressure due to a decrease in carrier density,which implied a change in Fermi energy due to the reverse Moss-Burstein effect.Our results showed that phase separation can be obtained in nanocomposite ITO films by tuning their stoichiometry simply by varying the oxygen partial pressure during deposition of thermoelectric materials at low temperatures.展开更多
MOFs are among the most popular precursors and templates for deriving various porous materials,where the derivatives can inherit a large surface area,abundant active sites for targeted functionalities and a high degre...MOFs are among the most popular precursors and templates for deriving various porous materials,where the derivatives can inherit a large surface area,abundant active sites for targeted functionalities and a high degree of porosity inherited from their parent MOFs.Those unique structural features make them promising candidates in multiple applications.More interestingly,the structure and properties of these MOF derivatives can be modulated by the choice of the parent MOFs and the design in the conversion process.In this overview,the transformation pathways from MOFs into their porous derivatives,the principles underlying these transformations,and the behavior of the MOF components in the transition process are discussed.Recently,there has been tremendous progress in preserving and enhancing the surface area,the amount of active sites and the level of porosity of the MOF-derived materials for targeted applications,from the perspectives of both customizing the parent MOFs and tailoring the transformation process.To develop the rationally designed MOF-derived materials and thus to elucidate the precursor-process-product correlations,some typical examples of the MOF derivatives applied in electrochemical energy storage and conversion,water treatment,gas sensing,and biomedicine are discussed to demonstrate the effectiveness of the key design strategies.展开更多
Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to leadbased perovskite halides.Recently,single-crystalline double perovskite halides were synthesized,and their intrigui...Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to leadbased perovskite halides.Recently,single-crystalline double perovskite halides were synthesized,and their intriguing functional properties were demonstrated.Despite such pioneering works,lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic devices.Here,we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic scale.We avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal synthesis.The suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility further.Our design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.展开更多
The screening of novel materials with good performance and the modelling of quantitative structureactivity relationships(QSARs),among other issues,are hot topics in the field of materials science.Traditional experimen...The screening of novel materials with good performance and the modelling of quantitative structureactivity relationships(QSARs),among other issues,are hot topics in the field of materials science.Traditional experiments and computational modelling often consume tremendous time and resources and are limited by their experimental conditions and theoretical foundations.Thus,it is imperative to develop a new method of accelerating the discovery and design process for novel materials.Recently,materials discovery and design using machine learning have been receiving increasing attention and have achieved great improvements in both time efficiency and prediction accuracy.In this review,we first outline the typical mode of and basic procedures for applying machine learning in materials science,and we classify and compare the main algorithms.Then,the current research status is reviewed with regard to applications of machine learning in material property prediction,in new materials discovery and for other purposes.Finally,we discuss problems related to machine learning in materials science,propose possible solutions,and forecast potential directions of future research.By directly combining computational studies with experiments,we hope to provide insight into the parameters that affect the properties of materials,thereby enabling more efficient and target-oriented research on materials discovery and design.展开更多
Although VB-Group transition metal disulfides(TMDs)VS_(2)nanomaterials with specific electronic properties and multiphase microstructures have shown fascinating potential in the field of electro-magnetic wave(EMW)abso...Although VB-Group transition metal disulfides(TMDs)VS_(2)nanomaterials with specific electronic properties and multiphase microstructures have shown fascinating potential in the field of electro-magnetic wave(EMW)absorption,the efficient utilization of VS_(2)is limited by the technical bottleneck of its narrow effective absorption bandwidth(EAB)which is attributed to environmental instability and a deficient electromagnetic(EM)loss mechanism.In order to fully exploit the maximal utilization values of VS_(2)nanomaterials for EMW absorption through mitigating the chemical instability and optimizing the EM parameters,biomass-based glucose derived carbon(GDC)like sugar-coating has been decorated on the surface of stacked VS_(2)nanosheets via a facile hydrothermal method,followed by high-temperature carbonization.As a result,the modulation of doping amount of glucose injection solution(Glucose)could effectively manipulate the encapsulation degree of GDC coating on VS_(2)nanosheets,further imple-menting the EM response mechanisms of the VS_(2)/GDC hybrids(coupling effect of conductive loss,interfacial polarization,relaxation,dipole polarization,defect engineering and multiple reflections and absorptions)through regulating the conductivity and constructing multi-interface heterostructures,as reflected by the enhanced EMW absorption performance to a great extent.The minimum reflection loss(Rmin)of VS_(2)/GDC hybrids could reach52.8 dB with a thickness of 2.7 mm at 12.2 GHz.Surprisingly,compared with pristine VS_(2),the EAB of the VS_(2)/GDC hybrids increased from 2.0 to 5.7 GHz,while their environmental stability was effectively enhanced by virtue of GDC doping.Obviously,this work provides a promising candidate to realize frequency band tunability of EMW absorbers with exceptional perfor-mance and environmental stability.展开更多
Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and ...Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge.Here,we report a strategy that high contents of medium-polar ester group and end-group(St)modification are introduced into a biode-gradable polymer polylactic acid(PLA)to synergistically reduce the loss and enhance Ue and charge-discharge efficiency(h).The resultant St-modified PLA polymer(PLA-St)exhibits an Ue of 6.5 J/cm^(3)with an ultra-high h(95.4%),far outperforming the best reported dielectric polymers.It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer,which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance.In addition,the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500000 charge-discharge cycles.This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density,low loss,and long-term stability.展开更多
Sodium ion hybrid capacitors(SIHCs)are regarded as advanced power supply systems.Nevertheless,the kinetics imbalance of cathode and anode suppresses the further performance improvement of SIHCs.The carbonaceous anode ...Sodium ion hybrid capacitors(SIHCs)are regarded as advanced power supply systems.Nevertheless,the kinetics imbalance of cathode and anode suppresses the further performance improvement of SIHCs.The carbonaceous anode materials are promising and many strategies have been utilized to increase the capacity of sloping region or accelerate the reaction rate of plateau region.However,it is still challenging to simultaneously realize high mesopore/micropore volume ratio,large interlayer distance(>0.37 nm),and abundant and favorable heteroatoms-doping by a simple method.Herein,we report N,P,O ternarydoped mesoporous carbon(PNPOC-T,T=700,800 or 900)with large interlayer distance(~0.4 nm)as anode materials.The PNPOC-T were prepared by a simple in-situ polymerization of aniline and phytic acid on the exfoliated graphitic nitrogen carbide(g-C3N4)and subsequent carbonization.The obtained PNPOC-800 exhibits an excellent rate performance(101.5 mA·h·g^(-1) at 20 A·g^(-1)),which can be attributed to the high surface-controlled capacitive behavior ratio and rapid ion diffusion.The optimum SIHCs display a high energy density of 105.48 W·h·kg^(-1) and a high power density of 13.59 kW$kg1.Furthermore,the capacitance retention rate of SIHCs can reach 87.43%after 9000 cycles at 1 A·g^(-1).展开更多
By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x...By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x)exhibits rich and interesting variations in crystal structure,mechanical and thermoelectric transport properties.However,Te alloying obviously introduces extremely large order-disorder distributions of cations and anions,leading to quite complicated crystal structures and thermoelectric properties.Detailed composition-structure-performance correlation of Ag_(2)S_(1-x)Te_(x)still remains to be established.In this work,we designed and prepared a series of Ag_(2)S_(1-x)Te_(x)(x=0-0.3)materials with low Te content.We discovered that the monoclinic-to-cubic phase transition occurs around x=0.16 at room temperature.Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition,which is analyzed based on the thermodynamic principles.Compared with the monoclinic counterparts,the cubic-structured phases are more ductile and softer in mechanical properties.In addition,the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance.A maximum zT=0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag_(2)S_(0.7)Te_(0.3).This work provides a useful guidance for designing Ag_(2)S-based alloys with enhanced plasticity and high thermoelectric performance.展开更多
In this work, different amount of Cr_(2)O_(3) (x - 0e0.3 wt%) as dopant were doped into the Aurivillius-typecompound Bi2.8Gd0.2TiNbO9 (BGTN), such a kind of Gd/Cr co-doped Bi3TiNbO9 ceramics with improvedelectrical pr...In this work, different amount of Cr_(2)O_(3) (x - 0e0.3 wt%) as dopant were doped into the Aurivillius-typecompound Bi2.8Gd0.2TiNbO9 (BGTN), such a kind of Gd/Cr co-doped Bi3TiNbO9 ceramics with improvedelectrical properties were synthesized by the convenient solid-state reaction route. The substitution of Cr^(3+) for Ti^(4+) at B-site induced the lattice distortion of pseduo-perovskite layer. Fewer Cr_(2)O_(3) dopant(x<0.2) resulted in the grain refinement of ceramics. After Cr_(2)O_(3) was added into BGTN, TC decreased tothe vicinity of 908 ℃. Below TC, the relaxed dielectric response resulted from charge carriers hoppinginduced another board dielectric permittivity peak, whose starting temperature shifts toward lower sidegradually with increase of x. The values of Eacon calculated from the Arrhenius relationship betweenconductivity and temperature indicated the intrinsic conduction at high temperature is dominated by thelong-range migration of doubly ionized oxygen vacancies. Moderate Cr_(2)O_(3) dopant (x=0.1e0.25) areconducive to the enhancement of piezoelectric property and thermal stability. The sample with x=0.2 achieved both a high T_(C)~903 - C and a high d_(33)~18 pC/N at the same time. Also, its d33 can retain 80% ofthe initial value after the sample was annealed at 800 - C for 4 h.展开更多
Electrochromic devices(ECDs)can regulate the indoor solar radiation by adjusting optical transmissive properties,showing great commercial potential and important social value of green energy saving.However,the unsafet...Electrochromic devices(ECDs)can regulate the indoor solar radiation by adjusting optical transmissive properties,showing great commercial potential and important social value of green energy saving.However,the unsafety and high cost of Li^(+) based electrolyte hinder the large-scale and industrialized production of ECDs.Other metal ions have been used as electrolyte ions,but they are rarely reported in all solid state ECDs.In this study,MgF_(2) film is used as the solid electrolyte to construct all solid state ECD with the structure of glass/ITO/WO_(3)/MgF_(2)/NiO/ITO.The ECD shows the large optical modulation(~83%at 820 nm,with 100 s durations)and fast response(19.2 s for bleaching and 8.3 s for coloring,with 25 s durations).Moreover,the ECD achieves the extreme transmittance value of colored states Tc=0%,which can give an absolute private state.This work not only indicates that MgF_(2) film can be an alternative to Lit based electrolyte in all solid state ECDs,but also broadens the applications of all solid state EC smart windows to private buildings.展开更多
Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect ...Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect in one single material is always the key issue.Herein,we systematically investigate the Co_(3)NiNb_(2)O_(9),including the characterization of its crystalline structure,magnetism,specific heat,and pyroelectric properties.It is revealed that Co_(3)NiNb_(2)O_(9) exhibits a remarkable ME response below the magnetic phase transition temperature of TN-32 K.On one hand,the magnetic field-induced electric polarization is observed below TN while it is non-ferroelectric at no magnetic field.The evaluated ME coefficient is as large as 21.2 ps/m.On the other hand,the magnetization is significantly modulated by the applied electric field,with the inverse ME coefficient being 14.1 ps/m.The observed ME responses suggest a stable ME mutual control by the magnetic or electric field in Co_(3)NiNb_(2)O_(9).展开更多
A nanocomposite of polyaniline/graphene(PAN/GN)was prepared using reverse-phase polymerization.The nanocomposite material was dropcast onto a glassy carbon electrode(GCE).Then,a single-stranded DNA(ssDNA)probe for HIV...A nanocomposite of polyaniline/graphene(PAN/GN)was prepared using reverse-phase polymerization.The nanocomposite material was dropcast onto a glassy carbon electrode(GCE).Then,a single-stranded DNA(ssDNA)probe for HIV-1 gene detection was immobilized on the modified electrode,and the negative charged phosphate backbone of the HIV-1 was bound to the modified electrode surface via p-p*stacking interactions.The hybridization between the ssDNA probe and the target HIV-1 formed doublestranded DNA(dsDNA),and the electron transfer resistance of the electrode was measured using impedimetric studies with a[Fe(CN)6]^(3-/4-)redox couple.Under the optimized experimental conditions,the change of the impedance value was linearly related to the logarithm of the concentration of HIV genes in the range from 5.0×10^(-16)M to 1.0×10^(-10)M(R=0.9930),and the HIV sensor exhibited a lower detection limit of 1.0×10^(-16)M(S/N=3).The results show that this biosensor presented wonderful selectivity,sensitivity and specificity for HIV-1 gene detection.Thus,this biosensor provides a new method for the detection of HIV gene fragments.展开更多
Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties...Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties are poor.Here,the thermoelectric performance of Mg_(3)Sb_(2) under the effect of biaxial strain is investigated by using first-principles method and Boltzmann transport theory.The application of biaxial strain enables tuning the band structure of Mg_(3)Sb_(2) in such a way that the band degeneracy of both the conduction band and valence band increases.As the biaxial strain increases,the Seebeck coefficient of ptype Mg_(3)Sb_(2) has a remarkable increase,leading to a significant improvement in power factor.This is mainly ascribed to the achievement of valence band orbital degeneracy.Meanwhile,the lattice thermal conductivity exhibits very slight biaxial strain dependence within the strain range considered in this work,which increases from 1.28 to 1.62 W m^(-1) K^(-1) at 300 K.Finally,the highest ZT of p-type Mg_(3)Sb_(2) at 700 K can be up to 2.6 along the in-plane direction under-2.5%biaxial strain,which is almost three times that of the unstrained counterpart.The realization of high thermoelectric performance of p-type Mg_(3)Sb_(2) will promote its practical applications as thermoelectric generators.展开更多
The adhesion and wetting between metal and ceramic is a basic problem in materials science and engineering.For example,past materials selection for metal-ceramic composites has relied on random trials and heuristics d...The adhesion and wetting between metal and ceramic is a basic problem in materials science and engineering.For example,past materials selection for metal-ceramic composites has relied on random trials and heuristics due to a limited understanding of their adhesion;the large chemical/structural variability that such interfaces can have hinders the identification of the governing factors.Here based on literature data,we have developed a database with~1,000 experimentally measured wetting angles at different temperatures and atmospheric conditions,and come up with a model for the wettability of ionocovalent ceramics(ICs)by metals using a machine learning(ML)algorithm.The random forest model uses the testing temperature and~40 features generated based on the chemical compositions of the metal and the ceramic as predictors and exhibits strong predictive power with an R^(2) of~0.86.Moreover,this model and the featurization code are integrated into a single computational pipeline to enable(1)predicting metal-IC wettability of interest and(2)high-throughput searching of ICs with the desired wettability by certain metals in the entire Inorganic Crystallographic Structure Database.As a demonstration of this pipeline,the wettability of a Li-ion and electron insulator(LEI),CaO,by molten Li is estimated and compared with ab initio molecular dynamics simulation result.This ML pipeline can serve as a practical tool for methodical design of materials in systems where certain metalceramic wettability is desired.展开更多
Lead-free ceramic capacitors have the application prospect in the dielectric pulse power system due to the advantages of large dielectric constant,lower dielectric loss and good temperature stability.Never-theless,mos...Lead-free ceramic capacitors have the application prospect in the dielectric pulse power system due to the advantages of large dielectric constant,lower dielectric loss and good temperature stability.Never-theless,most reported dielectric ceramics have limitation of realizing large energy storage density(W_(rec))and high energy storage efficiency(h)simultaneously due to the low breakdown electric field(E_(b)),low maximum polarization and large remanent polarization(P_(r)).These issues above can be settled by raising the bulk resistivity of dielectric ceramics and optimizing domain structure.Therefore,we designed a new system by doping(Bi_(0.5)Na_(0.5))_(0.7)Sr_(0.3)TiO_(3) into 0.9NaNbO_(3)-0.1Bi(Ni_(0.5)Zr_(0.5))O_(3) ceramics,which simulta-neously obtained a higher bulk resistivity by decreasing the grain size and achieved a smaller P_(r) by optimizing domain structure,thus the better E_(b) of 530 kV/cm and W_(rec) of 6.43 J/cm^(3) were achieved,h was improved from 34%to 82%.Besides,the 0.4BNST ceramics show excellent temperature,frequency and fatigue stability under the conditions of 20-180℃,1-100 Hz and 104 cycles,respectively.Mean-while,superior power density(P_(D)=107 MW/cm^(3)),large current density(C_(D)=1070 A/cm^(2))and discharge speed(1.025 m s)were achieved in 0.4BNST ceramic.Finally,the charge-discharge performance displayed good temperature stability in the temperature range of 30℃-180℃.The above results indicated that the ceramics have potential practical value in the field of energy storage capacitor.展开更多
Percolating composites with negative permittivity can be promising candidates for metamaterials.Herein,novel all-organic composite films containing of random coil polypyrrole(PPy)and poly(-vinylidene fluoride)(PVDF)ar...Percolating composites with negative permittivity can be promising candidates for metamaterials.Herein,novel all-organic composite films containing of random coil polypyrrole(PPy)and poly(-vinylidene fluoride)(PVDF)are fabricated via a solution casting method.The random coil PPy is prepared by oxidative template assembly approach for the first time.The experimental result indicates that the negative permittivity is easily adjusted through controlling the random coil PPy contents.Especially,the random coil PPy contents exceeded 7 wt% the negative permittivity appear attributed to the formation of 3D interconnected PPy network.This facile approach not only opens a new way to preparing negative permittivity of all-organic composite films,but also points out a route to facilitate the practical applications of metamaterials.展开更多
Epsilon-negative materials with high thermal conductivity and low electrical conductivity are of great importance for high power microwave devices.In this work,BaTiO_(3)/Cu composites,as a class of epsilonnegative mat...Epsilon-negative materials with high thermal conductivity and low electrical conductivity are of great importance for high power microwave devices.In this work,BaTiO_(3)/Cu composites,as a class of epsilonnegative materials,are rationally designed to achieve a high thermal conductivity yet maintaining the electrical insulative character.Negative permittivity behavior induced by dielectric resonance and plasma oscillation is observed in these BaTiO_(3)/Cu composites,which can be explained by the Lorentz and Drude model respectively.An outstanding absorption ability is achieved near the zero-cross point of the permittivity.Benefiting from the positive temperature coefficient of resistance and the weak temperature dependence of thermal conductivity in BaTiO_(3)/Cu composites,sample containing 22.3 vol% of Cu content exhibits a thermal conductivity of up to 17.7 W/(m·k)and an electrical conductivity down to 0.0022(Ω cm)^(-1) at 150℃.Therefore,BaTiO_(3)/Cu composite is a promising candidate for applications in electromagnetic attenuation and thermal management.展开更多
基金support from the National Key Research and Development Program of China(No.2021YFA0715801)the National Natural Science Foundation of China(No.51972116 and 52122204)+1 种基金the,Guangzhou Basic and Applied Basic Research Foundation(No.202201010632)the China Postdoctoral Science Foundation(2021M691051).
文摘Ultrafine-grained(Sm_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Zr_(2)O_(7)high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for the first time.The as-sintered samples exhibit a good microstructure with a grain size of 220 nm and a relative density of 96.8%,which yield excellent comprehensive mechanical properties with a high Vickers hardness of 12.5 GPa and a high fracture toughness of 3.4 MPa·m1/2.In addition,the as-sintered samples possess a good thermostability with the grain growth rate of 30 nm/h,and a low thermal conductivity of 1.57 W·m^(-1)·℃^(-1)at room temperature.The superior mechanical and thermal properties are primarily attributed to the“high-entropy”and grain-refinement effects and good interface bonding.
文摘The incorporation of therapeutic-capable ions into bioactive glasses(BGs),either based on silica(SBGs)or phosphate(PBGs),is currently envisaged as a proficient path for facilitating bone regeneration.Inconjunction with this view,the single and complementary structural and bio-functional roles of CuO andGa_(2)O_(3)(in the 2e5 mol%range)were assessed,by deriving a series of SBG and PBG formulations startingfrom the parent glass systems,FastOs®BG e 38.5SiO2d36.1CaOd5.6P2O5d19.2MgOd0.6CaF2,and50.0P2O5d35.0CaOd10.0Na_(2)Od5.0 Fe2O_(3)(mol%),respectively,using the process of melt-quenching.The inter-linked physico-chemistry e biological response of BGs was assessed in search of bio-functional triggers.Further light was shed on the structural role e as network former or modifier e ofCu and Ga,immersed in SBG and PBG matrices.The preliminary biological performance was surveyedin vitro by quantification of Cu and Ga ion release under homeostatic conditions,cytocompatibility assays(in fibroblast cell cultures)and antibacterial tests(against Staphylococcus aureus).The similar(Cu)anddissimilar(Ga)structural roles in the SBG and PBG vitreous networks governed their release.Namely,Cuions were leached in similar concentrations(ranging from 10e35 ppm and 50e110 ppm at BG doses of 5and 50 mg/mL,respectively)for both type of BGs,while the release of Ga ions was 1e2 orders ofmagnitude lower in the case of SBGs(i.e.,0.2e6 ppm)compared to PBGs(i.e.,9e135 ppm).This wasattributed to the network modifier role of Cu in both types of BGs,and conversely,to the network former(SBGs)and network modifier(PBGs)roles of Ga.All glasses were cytocompatible at a dose of 5 mg/mL,while at the same concentration the antimicrobial efficiency was found to be accentuated by the coupledrelease of Cu and Ga ions from SBG.By collective assessment,the most prominent candidate material forthe further development of implant coatings and bone graft substitutes was delineated as the38.5SiO2d34.1CaOd5.6P2O5d16.2MgOd0.6CaF2d2.0CuOd3.0Ga_(2)O_(3)(mol%)SBG system,which yiel-ded moderate Cu and Ga ion release,excellent cytocompatibility and marked antibacterial efficacy.
基金supported by the Research Grants Council of Hong Kong(17201019)the National Natural Science Foundation of China(11934007,11874194and 11874313)+3 种基金the Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(NO.2018B030322001)the Science and Technology Innovation Committee Foundation of Shenzhen(KQTD2016022619565991)the Zhejiang Provincial Natural Science Foundation(LR19A040001)SL acknowledges the support from the startup fund of Nanjing University of Posts and Telecommunications(NY220096).
文摘Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport.As a nontraditional method,pressure has shown great potential,as it has been applied to obtain a high thermoelectric figure of merit,but the microscopic mechanisms involved have yet to be fully explored.In this study,we focus on r-GeTe,a lowtemperature phase of GeTe,and investigate the pressure effects on the electronic structure,electrical transport properties and anharmonic lattice dynamics based on density functional theory(DFT),the Boltzmann transport equations(BTEs)and perturbation theory.Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation.The corresponding electrical transport properties are compared with those obtained from previous experiments.Hydrostatic pressure is shown to increase valley degeneracy,decrease the band effective mass and enhance the electrical transport property.At the same time,the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure.This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.
基金the Ministry of Business,Innovation and Employment(MBIE),New Zealand(contract#C05X1802).TM acknowledges support from JST Mirai Program JPMJMI19A1.
文摘We report that oxygen vacancies have a profound impact on phase separation and thermoelectric properties of ITO films grown at room temperature.Oxygen vacancies in non-stoichiometric In1.8Sn0.2O2.5 films aided the formation of In-rich metallic clusters.It yields a high electrical conductivity s=1540 Scm1 and Seebeck coefficient|a|=27.2 mVK1,which resulted in the highest power factor(a2 s=113.8 mW m1 K2)but low optical transmission(Top-25%).An increase in oxygen partial pressure resulted in stochiometric In1.8Sn0.2O3 films which improved the optical transparency by 300%(Top-75.4%),but power factor was reduced by-85%due to a decrease in a and s.A decrease in a was due to the lack of energy filtering of charge carriers in the stoichiometric ITO film which did not have In-rich metallic clusters.XPS results showed that the valence band energy shifts with a change in oxygen partial pressure due to a decrease in carrier density,which implied a change in Fermi energy due to the reverse Moss-Burstein effect.Our results showed that phase separation can be obtained in nanocomposite ITO films by tuning their stoichiometry simply by varying the oxygen partial pressure during deposition of thermoelectric materials at low temperatures.
基金the National Research Foundation(NRF)Singapore for funding under NRF-CRP17-2017-01(R-284-000-165-281)for the research conducted at the National University of Singapore.
文摘MOFs are among the most popular precursors and templates for deriving various porous materials,where the derivatives can inherit a large surface area,abundant active sites for targeted functionalities and a high degree of porosity inherited from their parent MOFs.Those unique structural features make them promising candidates in multiple applications.More interestingly,the structure and properties of these MOF derivatives can be modulated by the choice of the parent MOFs and the design in the conversion process.In this overview,the transformation pathways from MOFs into their porous derivatives,the principles underlying these transformations,and the behavior of the MOF components in the transition process are discussed.Recently,there has been tremendous progress in preserving and enhancing the surface area,the amount of active sites and the level of porosity of the MOF-derived materials for targeted applications,from the perspectives of both customizing the parent MOFs and tailoring the transformation process.To develop the rationally designed MOF-derived materials and thus to elucidate the precursor-process-product correlations,some typical examples of the MOF derivatives applied in electrochemical energy storage and conversion,water treatment,gas sensing,and biomedicine are discussed to demonstrate the effectiveness of the key design strategies.
基金the National Research Foundation of Korea(NRF)grants funded by the Ministry of Science and ICT(NRF-2020R1F1A1057220)the Ministry of Education(NRF-2019R1A6A1A11053838)+4 种基金C.W.A acknowledges the support by Basic Science Research Program through the NRF funded the Ministry of Science and ICT(NRF-2018R1A2B6009210)Y.H.H.acknowledges the support by the NRF of Korea(NRF-2019R1I1A3A01063856)H.Y.J.acknowledges the support from Creative Materials Discovery Program(NRF-2016M3D1A1900035)Y.-H.S.acknowledges the support by Basic Science Research Programthrough the NRF funded the Ministry of Science and ICT(NRF-2018R1A2B6005159)Experiments at PLS-II were supported in part by MSICT and POSTECH.
文摘Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to leadbased perovskite halides.Recently,single-crystalline double perovskite halides were synthesized,and their intriguing functional properties were demonstrated.Despite such pioneering works,lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic devices.Here,we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic scale.We avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal synthesis.The suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility further.Our design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U1630134,51622207 and 51372228)the National Key Research and Development Program of China(Grant Nos.2017YFB0701600 and 2017YFB0701500)+2 种基金the Shanghai Institute of Materials Genome from the Shanghai Municipal Science and Technology Commission(Grant No.14DZ2261200)the Shanghai Municipal Education Commission(Grant No.14ZZ099)the Natural Science Foundation of Shanghai(Grant No.16ZR1411200).
文摘The screening of novel materials with good performance and the modelling of quantitative structureactivity relationships(QSARs),among other issues,are hot topics in the field of materials science.Traditional experiments and computational modelling often consume tremendous time and resources and are limited by their experimental conditions and theoretical foundations.Thus,it is imperative to develop a new method of accelerating the discovery and design process for novel materials.Recently,materials discovery and design using machine learning have been receiving increasing attention and have achieved great improvements in both time efficiency and prediction accuracy.In this review,we first outline the typical mode of and basic procedures for applying machine learning in materials science,and we classify and compare the main algorithms.Then,the current research status is reviewed with regard to applications of machine learning in material property prediction,in new materials discovery and for other purposes.Finally,we discuss problems related to machine learning in materials science,propose possible solutions,and forecast potential directions of future research.By directly combining computational studies with experiments,we hope to provide insight into the parameters that affect the properties of materials,thereby enabling more efficient and target-oriented research on materials discovery and design.
基金supported by the National Natural Science Foundation of China(52102368,52072192,51977009)Regional Joint Fund for Basic Research and Applied Basic Research of Guangdong Province(No.2020SA001515110905).
文摘Although VB-Group transition metal disulfides(TMDs)VS_(2)nanomaterials with specific electronic properties and multiphase microstructures have shown fascinating potential in the field of electro-magnetic wave(EMW)absorption,the efficient utilization of VS_(2)is limited by the technical bottleneck of its narrow effective absorption bandwidth(EAB)which is attributed to environmental instability and a deficient electromagnetic(EM)loss mechanism.In order to fully exploit the maximal utilization values of VS_(2)nanomaterials for EMW absorption through mitigating the chemical instability and optimizing the EM parameters,biomass-based glucose derived carbon(GDC)like sugar-coating has been decorated on the surface of stacked VS_(2)nanosheets via a facile hydrothermal method,followed by high-temperature carbonization.As a result,the modulation of doping amount of glucose injection solution(Glucose)could effectively manipulate the encapsulation degree of GDC coating on VS_(2)nanosheets,further imple-menting the EM response mechanisms of the VS_(2)/GDC hybrids(coupling effect of conductive loss,interfacial polarization,relaxation,dipole polarization,defect engineering and multiple reflections and absorptions)through regulating the conductivity and constructing multi-interface heterostructures,as reflected by the enhanced EMW absorption performance to a great extent.The minimum reflection loss(Rmin)of VS_(2)/GDC hybrids could reach52.8 dB with a thickness of 2.7 mm at 12.2 GHz.Surprisingly,compared with pristine VS_(2),the EAB of the VS_(2)/GDC hybrids increased from 2.0 to 5.7 GHz,while their environmental stability was effectively enhanced by virtue of GDC doping.Obviously,this work provides a promising candidate to realize frequency band tunability of EMW absorbers with exceptional perfor-mance and environmental stability.
基金supported by National Key Research&Development Program(No.2021YFB3800603)National Natural Science Foundation of China(No.92066208)+1 种基金Shenzhen Science and Technology Program(Nos.KQTD20180411143514543,JCYJ20180504165831308)Guangdong Natural Science Foundation(No.2020A1515011043).
文摘Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge.Here,we report a strategy that high contents of medium-polar ester group and end-group(St)modification are introduced into a biode-gradable polymer polylactic acid(PLA)to synergistically reduce the loss and enhance Ue and charge-discharge efficiency(h).The resultant St-modified PLA polymer(PLA-St)exhibits an Ue of 6.5 J/cm^(3)with an ultra-high h(95.4%),far outperforming the best reported dielectric polymers.It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer,which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance.In addition,the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500000 charge-discharge cycles.This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density,low loss,and long-term stability.
基金supported by the National Nature Science Foundation of China(Nos.52172047,51972191)and the National Key Research and Development Program of China(No.2021YFA1200800).
文摘Sodium ion hybrid capacitors(SIHCs)are regarded as advanced power supply systems.Nevertheless,the kinetics imbalance of cathode and anode suppresses the further performance improvement of SIHCs.The carbonaceous anode materials are promising and many strategies have been utilized to increase the capacity of sloping region or accelerate the reaction rate of plateau region.However,it is still challenging to simultaneously realize high mesopore/micropore volume ratio,large interlayer distance(>0.37 nm),and abundant and favorable heteroatoms-doping by a simple method.Herein,we report N,P,O ternarydoped mesoporous carbon(PNPOC-T,T=700,800 or 900)with large interlayer distance(~0.4 nm)as anode materials.The PNPOC-T were prepared by a simple in-situ polymerization of aniline and phytic acid on the exfoliated graphitic nitrogen carbide(g-C3N4)and subsequent carbonization.The obtained PNPOC-800 exhibits an excellent rate performance(101.5 mA·h·g^(-1) at 20 A·g^(-1)),which can be attributed to the high surface-controlled capacitive behavior ratio and rapid ion diffusion.The optimum SIHCs display a high energy density of 105.48 W·h·kg^(-1) and a high power density of 13.59 kW$kg1.Furthermore,the capacitance retention rate of SIHCs can reach 87.43%after 9000 cycles at 1 A·g^(-1).
基金This work is supported by the National Key Research and Development Program of China(2018YFB0703600)National Natural Science Foundation of China(91963208,51625205,51961135106,51802333)+2 种基金the CAS-DOE Program of Chinese Academy of Sciences(121631KYSB20180060)the Shanghai Government(20JC1415100)the Swedish Research Council(VR 2018e06030).
文摘By virtue of the excellent plasticity and tunable transport properties,Ag_(2)S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications.Among them,Ag_(2)S_(1-x)Te_(x)exhibits rich and interesting variations in crystal structure,mechanical and thermoelectric transport properties.However,Te alloying obviously introduces extremely large order-disorder distributions of cations and anions,leading to quite complicated crystal structures and thermoelectric properties.Detailed composition-structure-performance correlation of Ag_(2)S_(1-x)Te_(x)still remains to be established.In this work,we designed and prepared a series of Ag_(2)S_(1-x)Te_(x)(x=0-0.3)materials with low Te content.We discovered that the monoclinic-to-cubic phase transition occurs around x=0.16 at room temperature.Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition,which is analyzed based on the thermodynamic principles.Compared with the monoclinic counterparts,the cubic-structured phases are more ductile and softer in mechanical properties.In addition,the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance.A maximum zT=0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag_(2)S_(0.7)Te_(0.3).This work provides a useful guidance for designing Ag_(2)S-based alloys with enhanced plasticity and high thermoelectric performance.
基金This work was supported by the National Natural ScienceFoundation of China (Grant No. 11702037, 51932010)China Post-doctoral Science Foundation Funded Project (Grant No.2017M623025)Opening foundation from the Key Laboratory ofDeep Earth Science and Engineering (Sichuan University), Ministryof Education (Grant No. 202007).
文摘In this work, different amount of Cr_(2)O_(3) (x - 0e0.3 wt%) as dopant were doped into the Aurivillius-typecompound Bi2.8Gd0.2TiNbO9 (BGTN), such a kind of Gd/Cr co-doped Bi3TiNbO9 ceramics with improvedelectrical properties were synthesized by the convenient solid-state reaction route. The substitution of Cr^(3+) for Ti^(4+) at B-site induced the lattice distortion of pseduo-perovskite layer. Fewer Cr_(2)O_(3) dopant(x<0.2) resulted in the grain refinement of ceramics. After Cr_(2)O_(3) was added into BGTN, TC decreased tothe vicinity of 908 ℃. Below TC, the relaxed dielectric response resulted from charge carriers hoppinginduced another board dielectric permittivity peak, whose starting temperature shifts toward lower sidegradually with increase of x. The values of Eacon calculated from the Arrhenius relationship betweenconductivity and temperature indicated the intrinsic conduction at high temperature is dominated by thelong-range migration of doubly ionized oxygen vacancies. Moderate Cr_(2)O_(3) dopant (x=0.1e0.25) areconducive to the enhancement of piezoelectric property and thermal stability. The sample with x=0.2 achieved both a high T_(C)~903 - C and a high d_(33)~18 pC/N at the same time. Also, its d33 can retain 80% ofthe initial value after the sample was annealed at 800 - C for 4 h.
基金We thank,National Key Research&Development Program(2016YFB0303903,2016YFE0201600)National Natural Science Foundation of China(52002097)Foundation of Equipment Development Department(6220914010901).
文摘Electrochromic devices(ECDs)can regulate the indoor solar radiation by adjusting optical transmissive properties,showing great commercial potential and important social value of green energy saving.However,the unsafety and high cost of Li^(+) based electrolyte hinder the large-scale and industrialized production of ECDs.Other metal ions have been used as electrolyte ions,but they are rarely reported in all solid state ECDs.In this study,MgF_(2) film is used as the solid electrolyte to construct all solid state ECD with the structure of glass/ITO/WO_(3)/MgF_(2)/NiO/ITO.The ECD shows the large optical modulation(~83%at 820 nm,with 100 s durations)and fast response(19.2 s for bleaching and 8.3 s for coloring,with 25 s durations).Moreover,the ECD achieves the extreme transmittance value of colored states Tc=0%,which can give an absolute private state.This work not only indicates that MgF_(2) film can be an alternative to Lit based electrolyte in all solid state ECDs,but also broadens the applications of all solid state EC smart windows to private buildings.
基金supported by the National Key Research Projects of China[Grant No.2016YFA0300101]the National Natural Science Foundation of China[Grant Nos.12074111,11804088,11704109,51431006]the Research Project of Hubei Provincial Department of Education[Grant No.B2018146].
文摘Magnetoelectric(ME)materials have caught worldwide attentions owing to their potential technological applications in ME switching devices or high-density data storage.However,realizing a sufficiently strong ME effect in one single material is always the key issue.Herein,we systematically investigate the Co_(3)NiNb_(2)O_(9),including the characterization of its crystalline structure,magnetism,specific heat,and pyroelectric properties.It is revealed that Co_(3)NiNb_(2)O_(9) exhibits a remarkable ME response below the magnetic phase transition temperature of TN-32 K.On one hand,the magnetic field-induced electric polarization is observed below TN while it is non-ferroelectric at no magnetic field.The evaluated ME coefficient is as large as 21.2 ps/m.On the other hand,the magnetization is significantly modulated by the applied electric field,with the inverse ME coefficient being 14.1 ps/m.The observed ME responses suggest a stable ME mutual control by the magnetic or electric field in Co_(3)NiNb_(2)O_(9).
基金Financial support from the Science Foundation of“131”Leading Talents Project of Shanxi Province,the National Science Foundation of China(No.21576230)the Scientific Research Foundation of Yuncheng University,China(Nos.YKU2014015 and CY-2015012)are gratefully acknowledged.
文摘A nanocomposite of polyaniline/graphene(PAN/GN)was prepared using reverse-phase polymerization.The nanocomposite material was dropcast onto a glassy carbon electrode(GCE).Then,a single-stranded DNA(ssDNA)probe for HIV-1 gene detection was immobilized on the modified electrode,and the negative charged phosphate backbone of the HIV-1 was bound to the modified electrode surface via p-p*stacking interactions.The hybridization between the ssDNA probe and the target HIV-1 formed doublestranded DNA(dsDNA),and the electron transfer resistance of the electrode was measured using impedimetric studies with a[Fe(CN)6]^(3-/4-)redox couple.Under the optimized experimental conditions,the change of the impedance value was linearly related to the logarithm of the concentration of HIV genes in the range from 5.0×10^(-16)M to 1.0×10^(-10)M(R=0.9930),and the HIV sensor exhibited a lower detection limit of 1.0×10^(-16)M(S/N=3).The results show that this biosensor presented wonderful selectivity,sensitivity and specificity for HIV-1 gene detection.Thus,this biosensor provides a new method for the detection of HIV gene fragments.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.11775163,12175166,12175079the National Key R&D Program of China(2019YFA0210003).
文摘Mg_(3)Sb_(2) as a Zintl compound is a promising thermoelectric material with the intrinsically low lattice thermal conductivity and excellent n-type electrical properties,but its p-type electrical transport properties are poor.Here,the thermoelectric performance of Mg_(3)Sb_(2) under the effect of biaxial strain is investigated by using first-principles method and Boltzmann transport theory.The application of biaxial strain enables tuning the band structure of Mg_(3)Sb_(2) in such a way that the band degeneracy of both the conduction band and valence band increases.As the biaxial strain increases,the Seebeck coefficient of ptype Mg_(3)Sb_(2) has a remarkable increase,leading to a significant improvement in power factor.This is mainly ascribed to the achievement of valence band orbital degeneracy.Meanwhile,the lattice thermal conductivity exhibits very slight biaxial strain dependence within the strain range considered in this work,which increases from 1.28 to 1.62 W m^(-1) K^(-1) at 300 K.Finally,the highest ZT of p-type Mg_(3)Sb_(2) at 700 K can be up to 2.6 along the in-plane direction under-2.5%biaxial strain,which is almost three times that of the unstrained counterpart.The realization of high thermoelectric performance of p-type Mg_(3)Sb_(2) will promote its practical applications as thermoelectric generators.
基金financially supported by the Samsung Advanced Institute of Technologyfinancial support by the Kwanjeong Scholarship。
文摘The adhesion and wetting between metal and ceramic is a basic problem in materials science and engineering.For example,past materials selection for metal-ceramic composites has relied on random trials and heuristics due to a limited understanding of their adhesion;the large chemical/structural variability that such interfaces can have hinders the identification of the governing factors.Here based on literature data,we have developed a database with~1,000 experimentally measured wetting angles at different temperatures and atmospheric conditions,and come up with a model for the wettability of ionocovalent ceramics(ICs)by metals using a machine learning(ML)algorithm.The random forest model uses the testing temperature and~40 features generated based on the chemical compositions of the metal and the ceramic as predictors and exhibits strong predictive power with an R^(2) of~0.86.Moreover,this model and the featurization code are integrated into a single computational pipeline to enable(1)predicting metal-IC wettability of interest and(2)high-throughput searching of ICs with the desired wettability by certain metals in the entire Inorganic Crystallographic Structure Database.As a demonstration of this pipeline,the wettability of a Li-ion and electron insulator(LEI),CaO,by molten Li is estimated and compared with ab initio molecular dynamics simulation result.This ML pipeline can serve as a practical tool for methodical design of materials in systems where certain metalceramic wettability is desired.
基金This work was supported by Natural Science Foundation of China(Nos.12064007 and 61761015)Natural Science Foundation of Guangxi(Nos.2018GXNSFFA050001,2017GXNSFDA198027 and 2017GXNSFFA198011)High Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes.
文摘Lead-free ceramic capacitors have the application prospect in the dielectric pulse power system due to the advantages of large dielectric constant,lower dielectric loss and good temperature stability.Never-theless,most reported dielectric ceramics have limitation of realizing large energy storage density(W_(rec))and high energy storage efficiency(h)simultaneously due to the low breakdown electric field(E_(b)),low maximum polarization and large remanent polarization(P_(r)).These issues above can be settled by raising the bulk resistivity of dielectric ceramics and optimizing domain structure.Therefore,we designed a new system by doping(Bi_(0.5)Na_(0.5))_(0.7)Sr_(0.3)TiO_(3) into 0.9NaNbO_(3)-0.1Bi(Ni_(0.5)Zr_(0.5))O_(3) ceramics,which simulta-neously obtained a higher bulk resistivity by decreasing the grain size and achieved a smaller P_(r) by optimizing domain structure,thus the better E_(b) of 530 kV/cm and W_(rec) of 6.43 J/cm^(3) were achieved,h was improved from 34%to 82%.Besides,the 0.4BNST ceramics show excellent temperature,frequency and fatigue stability under the conditions of 20-180℃,1-100 Hz and 104 cycles,respectively.Mean-while,superior power density(P_(D)=107 MW/cm^(3)),large current density(C_(D)=1070 A/cm^(2))and discharge speed(1.025 m s)were achieved in 0.4BNST ceramic.Finally,the charge-discharge performance displayed good temperature stability in the temperature range of 30℃-180℃.The above results indicated that the ceramics have potential practical value in the field of energy storage capacitor.
基金supported by the Ministry of Science and Technology of China through 973-project under Grant(2015CB654601)National Nature Science Foundation of China(51902167)+1 种基金Fund in Ningbo UniversityKey Laboratory of Engineering Dielectrics and Its Application(Harbin University of Science and Technology),Ministry of Education.
文摘Percolating composites with negative permittivity can be promising candidates for metamaterials.Herein,novel all-organic composite films containing of random coil polypyrrole(PPy)and poly(-vinylidene fluoride)(PVDF)are fabricated via a solution casting method.The random coil PPy is prepared by oxidative template assembly approach for the first time.The experimental result indicates that the negative permittivity is easily adjusted through controlling the random coil PPy contents.Especially,the random coil PPy contents exceeded 7 wt% the negative permittivity appear attributed to the formation of 3D interconnected PPy network.This facile approach not only opens a new way to preparing negative permittivity of all-organic composite films,but also points out a route to facilitate the practical applications of metamaterials.
基金supported by the National Natural Science Foundation of China(Grant No.51601105,No.51803119,No.51871146)the Innovation Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-10-E00053)+2 种基金Chenguang Program supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(Grant No.18CG56)the support of National Research Foundation Singapore(NRF-CRP17-2017-01),for research conducted at National University of Singaporethe support from the China Scholarship Council.
文摘Epsilon-negative materials with high thermal conductivity and low electrical conductivity are of great importance for high power microwave devices.In this work,BaTiO_(3)/Cu composites,as a class of epsilonnegative materials,are rationally designed to achieve a high thermal conductivity yet maintaining the electrical insulative character.Negative permittivity behavior induced by dielectric resonance and plasma oscillation is observed in these BaTiO_(3)/Cu composites,which can be explained by the Lorentz and Drude model respectively.An outstanding absorption ability is achieved near the zero-cross point of the permittivity.Benefiting from the positive temperature coefficient of resistance and the weak temperature dependence of thermal conductivity in BaTiO_(3)/Cu composites,sample containing 22.3 vol% of Cu content exhibits a thermal conductivity of up to 17.7 W/(m·k)and an electrical conductivity down to 0.0022(Ω cm)^(-1) at 150℃.Therefore,BaTiO_(3)/Cu composite is a promising candidate for applications in electromagnetic attenuation and thermal management.
