Aluminum(Al)-ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium.Nonetheless,given the nascent stage of advancement in Al-io...Aluminum(Al)-ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium.Nonetheless,given the nascent stage of advancement in Al-ion batteries(AIBs),attaining electrode materials that can leverage both intercalation capacity and structural stability remains challenging.Herein,we demonstrate a C3N4-derived layered N,S heteroatom-doped carbon,obtained at different pyrolysis temperatures,as a cathode material for AIBs,encompassing the diffusion-controlled intercalation and surface-induced capacity with ultrahigh reversibility.The developed layered N,S-doped corbon(N,S-C)cathode,synthesized at 900℃,delivers a specific capacity of 330 mAhg^(-1)with a relatively high coulombic efficiency of~85%after 500 cycles under a current density of 0.5 A g^(-1).Owing to its reinforced adsorption capability and enlarged interlayer spacing by doping N and S heteroatoms,the N,S-C900 cathode demonstrates outstanding energy storage capacity with excellent rate performance(61 mAhg^(-1)at 20 A g^(-1))and ultrahigh reversibility(90 mAhg^(-1)at 5Ag^(-1)after 10000cycles).展开更多
Free-standing and fexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)are crucial to the development of wearable Zn-air rec...Free-standing and fexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)are crucial to the development of wearable Zn-air rechargeable batteries.In this work,we synthesize a fexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition(CVD)and acidic etching processes.Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface,which consequentially boosts both the ORR and OER activities,as well as catalytic durability.First-principles density functional theory(DFT)calculations reveal the synergetic effects between the Ni and the N-doped graphene;namely,the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene,and in turn the graphene-covering layers enhance the stability of Ni.Thanks to the better protection from the triple graphene shells,our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials.It is reasonable to expect that such freestanding trimodal graphene/Ni would be promising in many fexible energy conversion/storage devices.展开更多
Purpose： This study aims to investigate and compare celebrity and ordinary users＇ behaviors on Sina Weibo. Design/methodology/approach： Data was collected from 12,555 ordinary users and 2,467 celebrity users on Sin...Purpose： This study aims to investigate and compare celebrity and ordinary users＇ behaviors on Sina Weibo. Design/methodology/approach： Data was collected from 12,555 ordinary users and 2,467 celebrity users on Sina Weibo. Correlation and regression analysis was performed on users＇ number of followings, number of followers and number of posts. Findings： The results revealed significant difference between famous and ordinary users＇ behaviors on Sina Weibo. We found correlation among ordinary users＇ number of followings, number of followers and number of posts, but for celebrity users, only their number of followings and number of posts are related with each other. For both ordinary and celebrity users, their number of followings significantly affects how many posts they publish. Research limitations： We only carried out our investigation on Sina Weibo and the findings need to be further verified on other microblogging platforms. Practical implications： This research is useful for microblogging service providers to understand different types of users and promote the continuous use of their services. Originality/value： This research delivers valuable insights into understanding of the characteristics of different types of microbloggers and the ways to increase user viscosity.展开更多
Solid-state lithium batteries using composite polymer electrolytes(CPEs)have attracted much attention owing to their higher safety compared to liquid electrolytes and flexibility compared to ceramic electrolytes.Howev...Solid-state lithium batteries using composite polymer electrolytes(CPEs)have attracted much attention owing to their higher safety compared to liquid electrolytes and flexibility compared to ceramic electrolytes.However,their unsatisfactory lithium-ion conductivity still limits their development.Herein,a high ion conductive CPE with multiple continuous lithium pathways is designed.This new electrolyte consists of poly(vinylidene fluorideco-hexafluoropropylene)(PVDF-HFP)and lithiated X type zeolite(Li-X),which possesses a high ionic conductivity(1.98×10^(-4)S/cm),high lithium transference number(t_(Li^(+))=0.55),wide electrochemical window(4.7 V),and excellent stability against the lithium anode.Density functional theory(DFT)calculation confirms that the Lewis acid sites in zeolite can graft with N,N-dimethylformamide(DMF)and PVDF-HFP chains,resulting in decreased crystallinity of polymer and providing rapid Li+transmission channels.When used in a full cell,the solid Li|Li-X-3%|LiFePO_(4) cell displays excellent cycling stability and rate performance at room temperature and 60℃.Furthermore,pouch cells with the Li-X-3%electrolyte exhibit brilliant safety under extreme conditions,such as folding and cutting.Thus,this proposed zeolite-PVDF-HFP CPE represents a promising potential in the application of making a safer,higher performing,and flexible solid-state lithium battery.展开更多
Zinc-based degradable metals are considered one of the most promising biodegradable materials due to their moderate corrosion rate,excellent mechanical properties,and good biocompatibility.In this work,biodegradable Z...Zinc-based degradable metals are considered one of the most promising biodegradable materials due to their moderate corrosion rate,excellent mechanical properties,and good biocompatibility.In this work,biodegradable Zn-0.4Mn-0.8Li alloy was fabricated and rolled in multiple passes at different tem peratures.As the hot rolling temperature increases,the grain size of Zn-0.4Mn-0.8Li alloy was found to increase cor-respondingly.Further,a multi-scale structure with the coexistence of coarse grains and fine grains was obtained.The results demonstrated that the mechanical strength and corrosion resistance were improved by increasing the rolled temperature.It was observed that Zn-0.4Mn-0.8Li alloy with a total reduction of 90%after hot rolling at 325℃ exhibited excellent mechanical and corrosion properties.The cooperation of multi-scale microstructure and twinning was found to improve the strength and guarantee the duc-tility of Zn-0.4Mn-0.8Li alloy significantly so that the 325℃ hot-rolled Zn-0.4Mn-0.8Li alloy has optimal comprehensive properties.Further,yield strength,ultimate tensile strength,and elongation were found to be 449.7±5.3 MPa,505.1±6.5 MPa,and 40.5%±7.5%,respectively.Meanwhile,Zn-0.4Mn-0.8Li al-loy via 325℃ hot-rolled processes also exhibited excellent corrosion resistance.The corrosion current density and corrosion potential were found to be 8.8×10-5 mA cm^(-2)and−0.929 V,respectively.The preliminary study indicates that Zn-0.4Mn-0.8Li alloy is a promising candidate material for medical de-vice applications.展开更多
A typical G-phase strengthened ferritic model alloy(1Ti:Fe-20Cr-3Ni-1Ti-3Si,wt.%)has been carefully studied using both advanced experimental(EBSD,TEM and APT)and theoretical(DFT)techniques.During the classic“solid so...A typical G-phase strengthened ferritic model alloy(1Ti:Fe-20Cr-3Ni-1Ti-3Si,wt.%)has been carefully studied using both advanced experimental(EBSD,TEM and APT)and theoretical(DFT)techniques.During the classic“solid solution and aging”process,the superfine(Fe,Ni)_(2)TiSi-L2_(1)particles densely precipitate within the ferritic grain and subsequently transform into the(Ni,Fe)_(16)Ti_(6)Si_(7)-G phase.In the meanwhile,the elemental segregation at grain boundaries and the resulting precipitation of a large amount of the(Ni,Fe)_(16)Ti_(6)Si_(7)-G phase are also observed.These nanoscale microstructural evolutions result in a remarkable increase in hardness(100-300 HV)and severe embrittlement.When the“cold rolling and aging”process is used,the brittle fracture is effectively suppressed without loss of nano-precipitation strengthening ef-fect.Superhigh yield strength of 1700 MPa with 4%elongation at break is achieved.This key improvement in mechanical properties is mainly attributed to the pre-cold rolling process which effectively avoids the dense precipitation of the G-phase at the grain boundary.These findings could shed light on the further exploration of the precipitation site via optimal processing strategies.展开更多
Realizing high performance in both n-type and p-type materials is essential for designing efficient ther-moelectric devices.However,the doping bottleneck is often encountered,i.e.,only one type of conduction can be re...Realizing high performance in both n-type and p-type materials is essential for designing efficient ther-moelectric devices.However,the doping bottleneck is often encountered,i.e.,only one type of conduction can be realized.As one example,p-type CdSb with high thermoelectric performance has been discovered for several decades,while its n-type counterpart has rarely been reported.In this work,the calculated band structure of CdSb demonstrates that the valley degeneracy is as large as ten for the conduction band,and it is only two for the valence band.Therefore,the n-type CdSb can potentially realize an ex-ceptional thermoelectric performance.Experimentally,the n-type conduction has been successfully real-ized by tuning the stoichiometry of CdSb.By further doping indium at the Cd site,an improved room-temperature electron concentration has been achieved.Band modeling predicts an optimal electron con-centration of∼2.0×1019 cm−3,which is higher than the current experimental values.Therefore,future optimization of the n-type CdSb should mainly focus on identifying practical approaches to optimize the electron concentration.展开更多
The interfaces between in-situ Al3Ti particles and magnesium(Mg)matrix are crucial role in highperformance titanium(Ti)reinforced AZ31 alloy.Herein,the interfaces between Al3Ti particles and the Mg matrix are fabricat...The interfaces between in-situ Al3Ti particles and magnesium(Mg)matrix are crucial role in highperformance titanium(Ti)reinforced AZ31 alloy.Herein,the interfaces between Al3Ti particles and the Mg matrix are fabricated and investigated using advanced characterization tools and first-principles calculations.The orientation relationship(OR)and atomic interface structure between the Al_(3)Ti particles and matrix are characterized using a high-resolution transmission electron microscope.The OR is determined to be(1010)Mg//(001)Al3Ti;[1213]Mg//[100]Al3Ti.Based on the characterized OR,the interface properties(including atomic structure,work of adhesion,interface energy,and fracture mechanism)are investigated using first-principles calculations.The relaxed interface structure indicates that the TiAl-terminated bridge site configurations(MT1)and hollow site configurations(HCP1)are unstable and would convert into other bridge site configurations(MT).Furthermore,the work of adhesion and interface energy suggests that Al-terminated hollow site configurations(HCP)and bridge site configurations(MT)are more stable than other configurations.In addition,the calculations of work of fracture show that fracture of the interfaces with Al-MT1,Al-HCP,and TiAl-MT configurations may initiate from bulk Mg interior.The findings may help to understand and tailor the deformation mechanisms and mechanical properties of Ti-reinforced Mg alloys.展开更多
The thermoelectric parameters are essentially governed by electron and phonon transport.Since the carrier scattering mechanism plays a decisive role in electron transport,it is of great significance for the electrical...The thermoelectric parameters are essentially governed by electron and phonon transport.Since the carrier scattering mechanism plays a decisive role in electron transport,it is of great significance for the electrical properties of thermoelectric materials.As a typical example,the defect-dominated carrier scattering mechanism can significantly impact the room-temperature electron mobility of n-type Mg_(3)Sb_(2)-based materials.However,the origin of such a defect scattering mechanism is still controversial.Herein,the existence of the Mg vacancies and Mg interstitials has been identified by synchrotron powder X-ray diffraction.The relationship among the point defects,chemical compositions,and synthesis conditions in Mg_(3)Sb_(2)-based materials has been revealed.By further introducing the point defects without affecting the grain size via neutron irradiation,the thermally activated electrical conductivity can be reproduced.Our results demonstrate that the point defects scattering of electrons is important in the n-type Mg_(3)Sb_(2)-based materials.展开更多
Carbon-based material has been regarded as one of the most promising electrode materials for potassium-ion batteries(PIBs).However,the battery performance based on reported porous carbon electrodes is still unsatisfac...Carbon-based material has been regarded as one of the most promising electrode materials for potassium-ion batteries(PIBs).However,the battery performance based on reported porous carbon electrodes is still unsatisfactory,while the in-depth K-ion storage mechanism remains relatively ambiguous.Herein,we propose a facile“in situ self-template bubbling”method for synthesizing interlayer-tuned hierarchically porous carbon with different metallic ions,which delivers superior K-ion storage performance,especially the high reversible capacity(360.6 mAh·g^(−1)@0.05 A·g^(−1)),excellent rate capability(158.6 mAh·g^(−1)@10.0 A·g^(−1))and ultralong high-rate cycling stability(82.8%capacity retention after 2,000 cycles at 5.0 A·g^(−1)).Theoretical simulation reveals the correlations between interlayer distance and K-ion diffusion kinetics.Experimentally,deliberately designed consecutive cyclic voltammetry(CV)measurements,ex situ Raman tests,galvanostatic intermittent titration technique(GITT)method decipher the origin of the excellent rate performance by disentangling the synergistic effect of interlayer and pore-structure engineering.Considering the facile preparation strategy,superior electrochemical performance and insightful mechanism investigations,this work may deepen the fundamental understandings of carbon-based PIBs and related energy storage devices like sodium-ion batteries,aluminum-ion batteries,electrochemical capacitors,and dual-ion batteries.展开更多
1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large differ...1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb.In this paper,we adjust the covalently bonded network of MgeSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb.The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity.Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn,the maximum ZT value of ~0.8 at 773 K is achieved in YbMg_(0.9)Zn_(1.1)Sb_(2) which is~100% enhancement compared with that of YbMg_(2)Sb_(2).展开更多
The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N co...The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.展开更多
The solubility range of interstitial Ni in the ZrNi1+xSn half-Heusler phase is a controversial issue,but it has an impact on the thermoelectric properties.In this study,two isothermal section phase diagrams of the Zr-...The solubility range of interstitial Ni in the ZrNi1+xSn half-Heusler phase is a controversial issue,but it has an impact on the thermoelectric properties.In this study,two isothermal section phase diagrams of the Zr-Ni-Sn ternary system at 973K and 1173 K were experimentally constructed based on the binary phase diagrams of Zr-Ni,Zr-Sn,and Ni-Sn.The thermodynamic equilibrium phases were obtained after a long time of heating treatment on the raw alloys prepared by levitation melting.Solubilities of x<0:07 at 973 K and x<0:13 at 1173 K were clearly indicated.An intermediate-Heusler phase with a partly filled Ni void was observed,which is believed to be beneficial to the lowered lattice thermal conductivity.The highest ZT value~0:71 at 973 K was obtained for ZrNi_(1.11)Sn_(1.04).The phase boundary mapping provides an important instruction for the further optimization of ZrNiSn-based materials and other systems.展开更多
hermoelectric materials can be potentially applied to waste heat recovery and solid-state cooling because they allow a direct energy conversion between heat and electricity and vice versa.The accelerated materials des...hermoelectric materials can be potentially applied to waste heat recovery and solid-state cooling because they allow a direct energy conversion between heat and electricity and vice versa.The accelerated materials design based on machine learning has enabled the systematic discovery of promising materials.Herein we proposed a successful strategy to discover and design a series of promising half-Heusler thermoelectric materials through the iterative combination of unsupervised machine learning with the labeled known half-Heusler thermoelectric materials.Subsequently,optimized zT values of~0.5 at 925 K for p-type Sc_(0.7)Y_(0.3)NiSb_(0.97)Sn_(0.03)and~0.3 at 778 K for n-type Sc_(0.65)Y_(0.3)Ti_(0.05)NiSb were experimentally achieved on the same parent ScNiSb.展开更多
Recently, the design of core-shell hierarchical architecture plays an important role in improving the electrochemical performance of Prussian blue analogue cathodes(PBAs). Unfortunately, the inconvenient stepwise prep...Recently, the design of core-shell hierarchical architecture plays an important role in improving the electrochemical performance of Prussian blue analogue cathodes(PBAs). Unfortunately, the inconvenient stepwise preparation and the strict lattice-matching requirement have restricted the development of coreshell PBAs. Herein, we demonstrate a one-step synthesis strategy to synthesize core-shell manganese hexacyanoferrate(MnFeHCF@MnFeHCF) for the first time. And the formation mechanism of the core-shell hierarchical architecture is investigated by first-principles calculations. It is found that the as-obtained Mn FeHCF@MnFeHCF act out the superior intrinsic natures, which not only can obtain a larger specific surface area and lower Fe(CN)_(6) vacancies but also can activate more Na-storage sites. Compared with the manganese hexacyanoferrate(MnHCF), the iron hexacyanoferrate(FeHCF), and even the traditional coreshell nickel hexacyanoferrate(FeHCF@NiHCF) prepared by a stepwise method, the Mn Fe HCF@MnFeHCF demonstrates a superior rate performance, which achieves a high capacity of 131 mAh g^(−1) at 50 mA g^(−1) and delivers a considerable discharge capacity of about 100 mAh g^(−1) even at 1600 mA g^(−1). Meantime, the capacity retention can reach up to nearly 80% after 500 cycles. The improved performances could be mainly originated from two aspects: on the one hand, Mn substitution is helpful to enhance the material conductivity;on the other hand, the core-shell structure with matched lattice parameters is more favorable to enhance the diffusion coefficient of sodium ions. Beside, the structural transformation of MnFeHCF@MnFeHCF upon the extraction/insertion of sodium ions is instrumental in releasing the interior stress and effectively maintaining the integrity of the crystal structure.展开更多
TiFe0.5Ni0.5Sb-based half-Heusler compounds have the intrinsic low lattice thermal conductivity and the adjustable band structure.Inspired by the previously reports to achieve both p-and n-type components by tuning th...TiFe0.5Ni0.5Sb-based half-Heusler compounds have the intrinsic low lattice thermal conductivity and the adjustable band structure.Inspired by the previously reports to achieve both p-and n-type components by tuning the ratio of Fe and Ni based on the same parent TiFe0.5Ni0.5Sb,we selected Co as the amphoteric dopants to prepare both n-type and p-type pseudo-ternary Ti(Fe,Co,Ni)Sb-based halfHeusler alloys.The carrier concentration,as well as the density of states effective mass was significantly increased by Co doping,contributing to the enhanced power factor of 1.80 mW m^(-1) K^(-2) for n-type TiFe0.3Co_(0.2)Ni_(0.5)Sb and 2.21 mW m^(-1) K^(-2) for p-type TiFe_(0.5)Co_(0.15)Ni_(0.35)Sb at 973 K.Combined with the further decreased lattice thermal conductivity due to the strain field and mass fluctuation scattering induced by alloying Hf on the Ti site,peak ZTs of 0.65 in n-type Ti0.8Hf_(0.2)Fe_(0.3)Co_(0.2)Ni_(0.5)Sb and 0.85 in ptype Ti0.8Hf_(0.2)Fe_(0.5)Co_(0.15)Ni_(0.35)Sb were achieved at 973 K,which is of great significance for the thermoelectric power generation applications.展开更多
Controlling the distribution of solar spectrum in different bands would boost the energy harvesting efficiency and optimize the energy dispatchability.1D photonic crystal with intrinsic optical band gap can be used to...Controlling the distribution of solar spectrum in different bands would boost the energy harvesting efficiency and optimize the energy dispatchability.1D photonic crystal with intrinsic optical band gap can be used to split the solar spectrum for hybrid photovoltaic/thermal solar applications.Here,we designed an efficient solar spectrum optical filter based on a cermet layer,Si/SiO_(2)1D photonic crystal,and top heterostructure layer.Compared with 1D photonic crystal structure,the 1D photonic crystal heterostructure with top YSZ layer can realize the reflectance of greater than 92%in PV band and the low average reflectance in two thermal bands by tuning the effective impedance of multilayer films.The enhanced reflectance in PV band results from the huge mismatching of impedance between free space and the heterostructure structure.The top dielectric layer can also be extended to other oxides.展开更多
Shape memory alloys can recover the deformed shape due to their superelasticity or shape memory effect. In this study, a novel Cu-Al-Mn-Fe shape memory single crystal is reported. The results show that it has excellen...Shape memory alloys can recover the deformed shape due to their superelasticity or shape memory effect. In this study, a novel Cu-Al-Mn-Fe shape memory single crystal is reported. The results show that it has excellent superelasticity and shape memory effect simultaneously when deformed at room temperature, as well as tunably wide response temperature range with near-zero interval of reverse phase transformation. When deforming one single crystal at room temperature, it not only possesses full superelasticity of 7%, but also tunable shape memory effects up to 8.8 %. The full shape recovery during heating exhibits near-zero response interval and tunably wide response temperature range of 166 K depending on the deformation. The functional characteristics of the alloys result from the controllable reverse phase transformation hinging on the stabilization of stress-induced martensite. This class of Cu-Al-Mn-Fe alloy may be used as both superelastic materials, and shape memory materials with wide working temperature range as high-sensitive detector, driver or sensor.展开更多
Zintl-phase compounds have great potential in thermoelectric applications owing to their“phonon glasselectron crystal”(PGEC)structures.In this paper,a new Zintlphase thermoelectric material Ba Ag Sb is reported.Ba d...Zintl-phase compounds have great potential in thermoelectric applications owing to their“phonon glasselectron crystal”(PGEC)structures.In this paper,a new Zintlphase thermoelectric material Ba Ag Sb is reported.Ba deficiency increased the carrier concentration,and then suppressed the intrinsic excitation.The peak ZT value of Ba_(0.98)Ag Sb reached~0.56 at 773 K.Moreover,Eu alloying at Ba site not only lowered the lattice thermal conductivity by inducing point-defect scattering,but also improved the electrical properties by increasing the carrier mobility.Finally,a peak ZT of~0.73 was achieved in Ba_(0.78)Eu_(0.2)Ag Sb.展开更多
基金the financial support from the National Natural Science Foundation of China(Grand No.52203092)an SSF Synergy Program(EM16-0004)the National Academic Infrastructure for Supercomputing in Sweden(NAISS)funded by the Swedish Research Council through grant agreement no.202206725
文摘Aluminum(Al)-ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium.Nonetheless,given the nascent stage of advancement in Al-ion batteries(AIBs),attaining electrode materials that can leverage both intercalation capacity and structural stability remains challenging.Herein,we demonstrate a C3N4-derived layered N,S heteroatom-doped carbon,obtained at different pyrolysis temperatures,as a cathode material for AIBs,encompassing the diffusion-controlled intercalation and surface-induced capacity with ultrahigh reversibility.The developed layered N,S-doped corbon(N,S-C)cathode,synthesized at 900℃,delivers a specific capacity of 330 mAhg^(-1)with a relatively high coulombic efficiency of~85%after 500 cycles under a current density of 0.5 A g^(-1).Owing to its reinforced adsorption capability and enlarged interlayer spacing by doping N and S heteroatoms,the N,S-C900 cathode demonstrates outstanding energy storage capacity with excellent rate performance(61 mAhg^(-1)at 20 A g^(-1))and ultrahigh reversibility(90 mAhg^(-1)at 5Ag^(-1)after 10000cycles).
基金financially supported by the Development and Reform Commission of Shenzhen Municipalitythe National Natural Science Foundation of China(Grant Nos.51702031,51871077)+1 种基金the Shenzhen Fundamental Research Program(Grant Nos.JCYJ20180306171644942,JCYJ20180507184623297,KQJSCX20180328165656256)the Innovation Project from Harbin Institute of Technology。
文摘Free-standing and fexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction(ORR)and the oxygen evolution reaction(OER)are crucial to the development of wearable Zn-air rechargeable batteries.In this work,we synthesize a fexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition(CVD)and acidic etching processes.Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface,which consequentially boosts both the ORR and OER activities,as well as catalytic durability.First-principles density functional theory(DFT)calculations reveal the synergetic effects between the Ni and the N-doped graphene;namely,the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene,and in turn the graphene-covering layers enhance the stability of Ni.Thanks to the better protection from the triple graphene shells,our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials.It is reasonable to expect that such freestanding trimodal graphene/Ni would be promising in many fexible energy conversion/storage devices.
文摘Purpose： This study aims to investigate and compare celebrity and ordinary users＇ behaviors on Sina Weibo. Design/methodology/approach： Data was collected from 12,555 ordinary users and 2,467 celebrity users on Sina Weibo. Correlation and regression analysis was performed on users＇ number of followings, number of followers and number of posts. Findings： The results revealed significant difference between famous and ordinary users＇ behaviors on Sina Weibo. We found correlation among ordinary users＇ number of followings, number of followers and number of posts, but for celebrity users, only their number of followings and number of posts are related with each other. For both ordinary and celebrity users, their number of followings significantly affects how many posts they publish. Research limitations： We only carried out our investigation on Sina Weibo and the findings need to be further verified on other microblogging platforms. Practical implications： This research is useful for microblogging service providers to understand different types of users and promote the continuous use of their services. Originality/value： This research delivers valuable insights into understanding of the characteristics of different types of microbloggers and the ways to increase user viscosity.
基金This work was supported by the Stable Supporting Fund of Shenzhen(No.GXWD20201230155427003-20200728114835006).
文摘Solid-state lithium batteries using composite polymer electrolytes(CPEs)have attracted much attention owing to their higher safety compared to liquid electrolytes and flexibility compared to ceramic electrolytes.However,their unsatisfactory lithium-ion conductivity still limits their development.Herein,a high ion conductive CPE with multiple continuous lithium pathways is designed.This new electrolyte consists of poly(vinylidene fluorideco-hexafluoropropylene)(PVDF-HFP)and lithiated X type zeolite(Li-X),which possesses a high ionic conductivity(1.98×10^(-4)S/cm),high lithium transference number(t_(Li^(+))=0.55),wide electrochemical window(4.7 V),and excellent stability against the lithium anode.Density functional theory(DFT)calculation confirms that the Lewis acid sites in zeolite can graft with N,N-dimethylformamide(DMF)and PVDF-HFP chains,resulting in decreased crystallinity of polymer and providing rapid Li+transmission channels.When used in a full cell,the solid Li|Li-X-3%|LiFePO_(4) cell displays excellent cycling stability and rate performance at room temperature and 60℃.Furthermore,pouch cells with the Li-X-3%electrolyte exhibit brilliant safety under extreme conditions,such as folding and cutting.Thus,this proposed zeolite-PVDF-HFP CPE represents a promising potential in the application of making a safer,higher performing,and flexible solid-state lithium battery.
基金The work was financially supported by the National Natural Science Foundation of China(No.51871077)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012626)+1 种基金the Shenzhen Knowledge Innovation Plan-Fundamental Research(Discipline Distribution)(No.JCYJ20180507184623297)the Startup Foundation from Shenzhen and Startup Foundation from Harbin Institute of Technology(Shenzhen),and the Development and Reform Commission of Shenzhen Municipality Shenzhen R&D Center for Al-based Hydrogen Hydrolysis Materials(No.ZX20190229).
文摘Zinc-based degradable metals are considered one of the most promising biodegradable materials due to their moderate corrosion rate,excellent mechanical properties,and good biocompatibility.In this work,biodegradable Zn-0.4Mn-0.8Li alloy was fabricated and rolled in multiple passes at different tem peratures.As the hot rolling temperature increases,the grain size of Zn-0.4Mn-0.8Li alloy was found to increase cor-respondingly.Further,a multi-scale structure with the coexistence of coarse grains and fine grains was obtained.The results demonstrated that the mechanical strength and corrosion resistance were improved by increasing the rolled temperature.It was observed that Zn-0.4Mn-0.8Li alloy with a total reduction of 90%after hot rolling at 325℃ exhibited excellent mechanical and corrosion properties.The cooperation of multi-scale microstructure and twinning was found to improve the strength and guarantee the duc-tility of Zn-0.4Mn-0.8Li alloy significantly so that the 325℃ hot-rolled Zn-0.4Mn-0.8Li alloy has optimal comprehensive properties.Further,yield strength,ultimate tensile strength,and elongation were found to be 449.7±5.3 MPa,505.1±6.5 MPa,and 40.5%±7.5%,respectively.Meanwhile,Zn-0.4Mn-0.8Li al-loy via 325℃ hot-rolled processes also exhibited excellent corrosion resistance.The corrosion current density and corrosion potential were found to be 8.8×10-5 mA cm^(-2)and−0.929 V,respectively.The preliminary study indicates that Zn-0.4Mn-0.8Li alloy is a promising candidate material for medical de-vice applications.
基金This work was financially funded by the National Natural Science Foundation of China(Nos.51971082 and 52001098)the National Post-doctoral Program for Innovative Talents(No.BX20200103)the China Post-doctoral Science Foundation(No.2020M681092).The authors would like to thank Dr.Ivan Povstugar at ZEA-。
文摘A typical G-phase strengthened ferritic model alloy(1Ti:Fe-20Cr-3Ni-1Ti-3Si,wt.%)has been carefully studied using both advanced experimental(EBSD,TEM and APT)and theoretical(DFT)techniques.During the classic“solid solution and aging”process,the superfine(Fe,Ni)_(2)TiSi-L2_(1)particles densely precipitate within the ferritic grain and subsequently transform into the(Ni,Fe)_(16)Ti_(6)Si_(7)-G phase.In the meanwhile,the elemental segregation at grain boundaries and the resulting precipitation of a large amount of the(Ni,Fe)_(16)Ti_(6)Si_(7)-G phase are also observed.These nanoscale microstructural evolutions result in a remarkable increase in hardness(100-300 HV)and severe embrittlement.When the“cold rolling and aging”process is used,the brittle fracture is effectively suppressed without loss of nano-precipitation strengthening ef-fect.Superhigh yield strength of 1700 MPa with 4%elongation at break is achieved.This key improvement in mechanical properties is mainly attributed to the pre-cold rolling process which effectively avoids the dense precipitation of the G-phase at the grain boundary.These findings could shed light on the further exploration of the precipitation site via optimal processing strategies.
基金supported by the Shenzhen Science and Tech-nology Program (No.KQTD20200820113045081)the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology.J.M.acknowledges the financial support from the National Natural Science Foundation of China (No.52101248)+6 种基金Shenzhen fundamental research projects (No.JCYJ20210324132808020)the start-up funding of Shenzhen,and the start-up funding of Harbin Institute of Technology (Shenzhen).Q.Z.acknowledges the financial support from the National Nat-ural Science Foundation of China (Nos.52172194 and 51971081)the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province of China (No.2020B1515020023)the Natural Science Foundation for Distinguished Young Scholars of Shenzhen (No.RCJC20210609103733073)the Key Project of Shenzhen Fundamental Research Projects (No.JCYJ20200109113418655)F.C.acknowledges the financial support from the National Natural Science Foundation of China (No.51871081)H.L.acknowledges the financial support from the National Natural Science Foundation of China (No.62174044).
文摘Realizing high performance in both n-type and p-type materials is essential for designing efficient ther-moelectric devices.However,the doping bottleneck is often encountered,i.e.,only one type of conduction can be realized.As one example,p-type CdSb with high thermoelectric performance has been discovered for several decades,while its n-type counterpart has rarely been reported.In this work,the calculated band structure of CdSb demonstrates that the valley degeneracy is as large as ten for the conduction band,and it is only two for the valence band.Therefore,the n-type CdSb can potentially realize an ex-ceptional thermoelectric performance.Experimentally,the n-type conduction has been successfully real-ized by tuning the stoichiometry of CdSb.By further doping indium at the Cd site,an improved room-temperature electron concentration has been achieved.Band modeling predicts an optimal electron con-centration of∼2.0×1019 cm−3,which is higher than the current experimental values.Therefore,future optimization of the n-type CdSb should mainly focus on identifying practical approaches to optimize the electron concentration.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030006)the financial support from the open research fund of Songshan Lake Materials Laboratory(2021SLABFK06)and start-up funding from Harbin Institute of Technology(Shenzhen).
文摘The interfaces between in-situ Al3Ti particles and magnesium(Mg)matrix are crucial role in highperformance titanium(Ti)reinforced AZ31 alloy.Herein,the interfaces between Al3Ti particles and the Mg matrix are fabricated and investigated using advanced characterization tools and first-principles calculations.The orientation relationship(OR)and atomic interface structure between the Al_(3)Ti particles and matrix are characterized using a high-resolution transmission electron microscope.The OR is determined to be(1010)Mg//(001)Al3Ti;[1213]Mg//[100]Al3Ti.Based on the characterized OR,the interface properties(including atomic structure,work of adhesion,interface energy,and fracture mechanism)are investigated using first-principles calculations.The relaxed interface structure indicates that the TiAl-terminated bridge site configurations(MT1)and hollow site configurations(HCP1)are unstable and would convert into other bridge site configurations(MT).Furthermore,the work of adhesion and interface energy suggests that Al-terminated hollow site configurations(HCP)and bridge site configurations(MT)are more stable than other configurations.In addition,the calculations of work of fracture show that fracture of the interfaces with Al-MT1,Al-HCP,and TiAl-MT configurations may initiate from bulk Mg interior.The findings may help to understand and tailor the deformation mechanisms and mechanical properties of Ti-reinforced Mg alloys.
基金supported by the Shenzhen Science and Technology Program(KQTD20200820113045081)the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology.Q.Z.acknowledges the financial support from the National Natural Science Foundation of China(52172194,51971081)+7 种基金the Natural Science Foundation of Guangdong Province for Distinguished Young Scholars of China(2020B1515020023)the Natural Science Foundation for Distinguished Young Scholars of Shenzhen(RCJC20210609103733073)the Key Project of Shenzhen Fundamental Research Projects(JCYJ20200109113418655)F.C.acknowledges the financial support from the National Natural Science Foundation of China(51871081)J.M.acknowledges the financial support from the National Natural Science Foundation of China(52101248)the Shenzhen Fundamental Research Projects(JCYJ20210324132808020)the Start-Up Funding of Shenzhen,and the Start-Up Funding of Harbin Institute of Technology(Shenzhen).Y.M.W.acknowledges the financial support from the National Natural Science Foundation of China(12074409)H.Y.and Y.C.are grateful for the support of the Environment and Conservation Fund(69/2018)and the Research Computing Facilities offered by ITS,HKU.We thank Dr.Tiancheng Yi for his kind help in the neutron irradiation experiment.
文摘The thermoelectric parameters are essentially governed by electron and phonon transport.Since the carrier scattering mechanism plays a decisive role in electron transport,it is of great significance for the electrical properties of thermoelectric materials.As a typical example,the defect-dominated carrier scattering mechanism can significantly impact the room-temperature electron mobility of n-type Mg_(3)Sb_(2)-based materials.However,the origin of such a defect scattering mechanism is still controversial.Herein,the existence of the Mg vacancies and Mg interstitials has been identified by synchrotron powder X-ray diffraction.The relationship among the point defects,chemical compositions,and synthesis conditions in Mg_(3)Sb_(2)-based materials has been revealed.By further introducing the point defects without affecting the grain size via neutron irradiation,the thermally activated electrical conductivity can be reproduced.Our results demonstrate that the point defects scattering of electrons is important in the n-type Mg_(3)Sb_(2)-based materials.
基金This work was supported by School Research Startup Expenses of Harbin Institute of Technology(Shenzhen)(No.DD29100027)the National Natural Science Foundation of China(No.52002094)+2 种基金Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110756)China Postdoctoral Science Foundation(No.2019M661276)High-level Talents’Discipline Construction Fund of Shandong University(No.31370089963078).
文摘Carbon-based material has been regarded as one of the most promising electrode materials for potassium-ion batteries(PIBs).However,the battery performance based on reported porous carbon electrodes is still unsatisfactory,while the in-depth K-ion storage mechanism remains relatively ambiguous.Herein,we propose a facile“in situ self-template bubbling”method for synthesizing interlayer-tuned hierarchically porous carbon with different metallic ions,which delivers superior K-ion storage performance,especially the high reversible capacity(360.6 mAh·g^(−1)@0.05 A·g^(−1)),excellent rate capability(158.6 mAh·g^(−1)@10.0 A·g^(−1))and ultralong high-rate cycling stability(82.8%capacity retention after 2,000 cycles at 5.0 A·g^(−1)).Theoretical simulation reveals the correlations between interlayer distance and K-ion diffusion kinetics.Experimentally,deliberately designed consecutive cyclic voltammetry(CV)measurements,ex situ Raman tests,galvanostatic intermittent titration technique(GITT)method decipher the origin of the excellent rate performance by disentangling the synergistic effect of interlayer and pore-structure engineering.Considering the facile preparation strategy,superior electrochemical performance and insightful mechanism investigations,this work may deepen the fundamental understandings of carbon-based PIBs and related energy storage devices like sodium-ion batteries,aluminum-ion batteries,electrochemical capacitors,and dual-ion batteries.
基金funded by the National Natural Science Foundation of China(11674078,24401019,51871077,and 51871081)the National Nature Science Foundation of Guangdong Province of China(2018A0303130033)+3 种基金Shenzhen fundamental research projects(JCYJ20170811155832192,JCYJ20160608161000821)Shenzhen Science and Technology Innovation Plan(KQISCX20180328165435202,JQJSCX20180328165656256)Startup Foundation from ShenzhenStartup Foundation from Harbin Institute of Technology(Shenzhen).
文摘1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications.However,YbMg_(2)Sb_(2) is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb.In this paper,we adjust the covalently bonded network of MgeSb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb.The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity.Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn,the maximum ZT value of ~0.8 at 773 K is achieved in YbMg_(0.9)Zn_(1.1)Sb_(2) which is~100% enhancement compared with that of YbMg_(2)Sb_(2).
基金financially supported by the National Natural Science Foundation of China(No.51771158)the Development and Reform Commission of Shenzhen Municipality(No.ZX20190229)。
文摘The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.
基金This work was funded by the National Natural Science Foundation of China(51971081,11674078,and 51871081)the National Key Research&Development Program of China(2017YFA0303600)+2 种基金the National Natural Science Foundation of Guangdong Province of China(2018A0303130033)Shenzhen Fundamental Research Projects(JCYJ20170811155832192)Shenzhen Science and Technology Innovation Plan(KQISCX20180328165435202).
文摘The solubility range of interstitial Ni in the ZrNi1+xSn half-Heusler phase is a controversial issue,but it has an impact on the thermoelectric properties.In this study,two isothermal section phase diagrams of the Zr-Ni-Sn ternary system at 973K and 1173 K were experimentally constructed based on the binary phase diagrams of Zr-Ni,Zr-Sn,and Ni-Sn.The thermodynamic equilibrium phases were obtained after a long time of heating treatment on the raw alloys prepared by levitation melting.Solubilities of x<0:07 at 973 K and x<0:13 at 1173 K were clearly indicated.An intermediate-Heusler phase with a partly filled Ni void was observed,which is believed to be beneficial to the lowered lattice thermal conductivity.The highest ZT value~0:71 at 973 K was obtained for ZrNi_(1.11)Sn_(1.04).The phase boundary mapping provides an important instruction for the further optimization of ZrNiSn-based materials and other systems.
基金This work was funded by the National Key R&D Program of China(No.2020YFB0704503)the National Natural Science Foundation of China(51871081,51971081,and 51971082)+2 种基金the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province of China(2020B1515020023)Shenzhen Science and Technology Program(KQTD20200820113045081)Key Project of Shenzhen Fundamental Research Projects(JCYJ20200109113418655).
文摘hermoelectric materials can be potentially applied to waste heat recovery and solid-state cooling because they allow a direct energy conversion between heat and electricity and vice versa.The accelerated materials design based on machine learning has enabled the systematic discovery of promising materials.Herein we proposed a successful strategy to discover and design a series of promising half-Heusler thermoelectric materials through the iterative combination of unsupervised machine learning with the labeled known half-Heusler thermoelectric materials.Subsequently,optimized zT values of~0.5 at 925 K for p-type Sc_(0.7)Y_(0.3)NiSb_(0.97)Sn_(0.03)and~0.3 at 778 K for n-type Sc_(0.65)Y_(0.3)Ti_(0.05)NiSb were experimentally achieved on the same parent ScNiSb.
基金supported by the National Natural Science Foundation of China(Nos.51771158 and 11975191)the Guangdong Natural Science Foundation(No.2018A030313721)the Shenzhen International Collaboration Project(No.GJHZ20180928155621530).
文摘Recently, the design of core-shell hierarchical architecture plays an important role in improving the electrochemical performance of Prussian blue analogue cathodes(PBAs). Unfortunately, the inconvenient stepwise preparation and the strict lattice-matching requirement have restricted the development of coreshell PBAs. Herein, we demonstrate a one-step synthesis strategy to synthesize core-shell manganese hexacyanoferrate(MnFeHCF@MnFeHCF) for the first time. And the formation mechanism of the core-shell hierarchical architecture is investigated by first-principles calculations. It is found that the as-obtained Mn FeHCF@MnFeHCF act out the superior intrinsic natures, which not only can obtain a larger specific surface area and lower Fe(CN)_(6) vacancies but also can activate more Na-storage sites. Compared with the manganese hexacyanoferrate(MnHCF), the iron hexacyanoferrate(FeHCF), and even the traditional coreshell nickel hexacyanoferrate(FeHCF@NiHCF) prepared by a stepwise method, the Mn Fe HCF@MnFeHCF demonstrates a superior rate performance, which achieves a high capacity of 131 mAh g^(−1) at 50 mA g^(−1) and delivers a considerable discharge capacity of about 100 mAh g^(−1) even at 1600 mA g^(−1). Meantime, the capacity retention can reach up to nearly 80% after 500 cycles. The improved performances could be mainly originated from two aspects: on the one hand, Mn substitution is helpful to enhance the material conductivity;on the other hand, the core-shell structure with matched lattice parameters is more favorable to enhance the diffusion coefficient of sodium ions. Beside, the structural transformation of MnFeHCF@MnFeHCF upon the extraction/insertion of sodium ions is instrumental in releasing the interior stress and effectively maintaining the integrity of the crystal structure.
基金the National Natural Science Foundation of China(51971081,11674078,and 51871081)the Cheung Kong Scholar Reward Program Young Scholar Program of China(Q2018239)+2 种基金the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province of China(2020B1515020023)the China Scholarship Council project,the Natural Science Foundation of Guangdong Province of China(2018A0303130033)Shenzhen Science and Technology Innovation Plan(KQJSCX20180328165435202).
文摘TiFe0.5Ni0.5Sb-based half-Heusler compounds have the intrinsic low lattice thermal conductivity and the adjustable band structure.Inspired by the previously reports to achieve both p-and n-type components by tuning the ratio of Fe and Ni based on the same parent TiFe0.5Ni0.5Sb,we selected Co as the amphoteric dopants to prepare both n-type and p-type pseudo-ternary Ti(Fe,Co,Ni)Sb-based halfHeusler alloys.The carrier concentration,as well as the density of states effective mass was significantly increased by Co doping,contributing to the enhanced power factor of 1.80 mW m^(-1) K^(-2) for n-type TiFe0.3Co_(0.2)Ni_(0.5)Sb and 2.21 mW m^(-1) K^(-2) for p-type TiFe_(0.5)Co_(0.15)Ni_(0.35)Sb at 973 K.Combined with the further decreased lattice thermal conductivity due to the strain field and mass fluctuation scattering induced by alloying Hf on the Ti site,peak ZTs of 0.65 in n-type Ti0.8Hf_(0.2)Fe_(0.3)Co_(0.2)Ni_(0.5)Sb and 0.85 in ptype Ti0.8Hf_(0.2)Fe_(0.5)Co_(0.15)Ni_(0.35)Sb were achieved at 973 K,which is of great significance for the thermoelectric power generation applications.
基金the National Natural Science Foundation of China(51871081,11674078 and 51971081)the Natural Science Foundation of Guangdong Province of China(2018A0303130033)+1 种基金Shenzhen Fundamental Research Project(JCYJ20170811155832192)Natural Scientific Research Innovation Foundation in Harbin Institute of Technology(HIT.NSRIF.2020060).
文摘Controlling the distribution of solar spectrum in different bands would boost the energy harvesting efficiency and optimize the energy dispatchability.1D photonic crystal with intrinsic optical band gap can be used to split the solar spectrum for hybrid photovoltaic/thermal solar applications.Here,we designed an efficient solar spectrum optical filter based on a cermet layer,Si/SiO_(2)1D photonic crystal,and top heterostructure layer.Compared with 1D photonic crystal structure,the 1D photonic crystal heterostructure with top YSZ layer can realize the reflectance of greater than 92%in PV band and the low average reflectance in two thermal bands by tuning the effective impedance of multilayer films.The enhanced reflectance in PV band results from the huge mismatching of impedance between free space and the heterostructure structure.The top dielectric layer can also be extended to other oxides.
基金financially supported by the National Natural Science Foundation of China (No. 51971185)the National Key R&D Program of China (No. 2017YFB0702901)。
文摘Shape memory alloys can recover the deformed shape due to their superelasticity or shape memory effect. In this study, a novel Cu-Al-Mn-Fe shape memory single crystal is reported. The results show that it has excellent superelasticity and shape memory effect simultaneously when deformed at room temperature, as well as tunably wide response temperature range with near-zero interval of reverse phase transformation. When deforming one single crystal at room temperature, it not only possesses full superelasticity of 7%, but also tunable shape memory effects up to 8.8 %. The full shape recovery during heating exhibits near-zero response interval and tunably wide response temperature range of 166 K depending on the deformation. The functional characteristics of the alloys result from the controllable reverse phase transformation hinging on the stabilization of stress-induced martensite. This class of Cu-Al-Mn-Fe alloy may be used as both superelastic materials, and shape memory materials with wide working temperature range as high-sensitive detector, driver or sensor.
基金supported by the National Natural Science Foundation of China (51871081, 11674078, 51971081, and 52001339)the Cheung Kong Scholar Reward Program Young Scholar Program of China (Q2018239)+3 种基金the Natural Science Foundation of Guangdong Province of China (2018A0303130033)the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province (2020B1515020023)Shenzhen Science and Technology Innovation Plan (KQJSCX20180328165435202 and JCYJ20180307154619840)the National Key Research and Development Program of China (2017YFA0303600)
文摘Zintl-phase compounds have great potential in thermoelectric applications owing to their“phonon glasselectron crystal”(PGEC)structures.In this paper,a new Zintlphase thermoelectric material Ba Ag Sb is reported.Ba deficiency increased the carrier concentration,and then suppressed the intrinsic excitation.The peak ZT value of Ba_(0.98)Ag Sb reached~0.56 at 773 K.Moreover,Eu alloying at Ba site not only lowered the lattice thermal conductivity by inducing point-defect scattering,but also improved the electrical properties by increasing the carrier mobility.Finally,a peak ZT of~0.73 was achieved in Ba_(0.78)Eu_(0.2)Ag Sb.
