Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic pr...Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.展开更多
Owing to their unique optical properties and nontoxicity,lead-free halide double perovskite nanocrystals are of interest for widespread applications.Herein,the colloid synthesis and photoluminescenc e property of Ag^(...Owing to their unique optical properties and nontoxicity,lead-free halide double perovskite nanocrystals are of interest for widespread applications.Herein,the colloid synthesis and photoluminescenc e property of Ag^(+)-Eu^(3+)codoped Cs_(2)NaInCl_(6)nanocrystals were investigated.The pe rovskite nanocrystals exhibit a broad warm-white photo luminescence with correlated color temperature(CCT)of 3447 K and color rendering index(CRI)of 90.2,and the means of codoping would improve its optical performance.A fast energy transfer and a long-lived self-trapped excitons state are unveiled by the femtosecond transient absorption spectra.The fast energy transfer from the self-trapped excitons of host nanocrystals to the Eu^(3+)ions is helpful to achieve a broad photoluminescence,and the quantum yield of Cs_(2)NaInCl_(6):0.05Ag^(+)-Eu^(3+)anocrystals can be enha nced to 69.5%.There is a large exciton binding energy and strong electron-phonon interaction in the codoped perovskite nanocrystals.The efficient and excellent air-stable double perovskite nanocrystals would be considered as a single-component phosphor for warm-white lighting.展开更多
Lead-free double perovskites have gained recognition as top luminescent materials due to their environmental friendliness,high chemical stability,structural adjustability,and excellent photoelectric properties.However...Lead-free double perovskites have gained recognition as top luminescent materials due to their environmental friendliness,high chemical stability,structural adjustability,and excellent photoelectric properties.However,the poor modulation of emission restricts their applications,and it is highly desirable to explore stable and efficient double perovskites with multimode luminescence and adjustable spectra for multifunctional photoelectric applications.Herein,the rare earth ions Ln^(3+)(Er^(3+)and Ho^(3+))-doped Cs_(2)NaYCl_(6):Sb^(3+)crystals were synthesized by a simple solvothermal route.The X-ray diffraction pattern(XRD),energy-dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),and elemental mapping images demonstrate that the Sb^(3+),Er^(3+),and Ho^(3+)ions have been homogeneously incorporated into the Cs_(2)NaYCl_(6)crystals.As anticipated,the emissio n spectra of Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)are composed of two bands.One broad blue band derives from self-trapped exciton(STE)in[SbCl_(6)]3-octahedra while another group of emission peaks stems from the f-f transitions of Ln^(3+)ions.The emission colors of Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)phosphors can be tuned in a wide range by modulating the doping concentrations of Ln^(3+)ions.The efficient energy transfer from STE to Ln^(3+)is the key point to achieving the efficient and tunable emissions Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)samples.Interestingly,Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)can also exhibit characteristic up-conversion luminescence of Ln^(3+)under nearinfrared(NIR)excitation besides the down-conversion luminescence,revealing that the materials may have potential applicability in multimode anti-counterfeiting and information encryption applications.Furthermore,the light emitting diodes(LEDs)assembled by Cs_(2)NaYCl_(6):Sb^(3+)and Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)phosphors display dazzling blue,green,and red emissions under a forward bias current,which indicates that the as-obtained double perovskites materials may have great potential in solid-state lighting and optoelectronic devices.展开更多
Although the lead-free halide double perovskites(DPs)have shown great promise for the photocatalytic reduction of CO_(2),the catalytic performance is still far from satisfactory.In this work,lead-free Cs_(2)AgSbX_(6)(...Although the lead-free halide double perovskites(DPs)have shown great promise for the photocatalytic reduction of CO_(2),the catalytic performance is still far from satisfactory.In this work,lead-free Cs_(2)AgSbX_(6)(X=Cl,Br,I)DPs nanocrystals(NCs)are prepared by a modified ligand-assisted reprecipitation(LARP)approach at room temperature.The crystal surface,shape,and optoelectronic properties of the AgSb-based DPs are modified using halogen modulation technique.Moreover,a series of Cs_(2)AgSbX_(6) perovskites NCs are utilized as efficient catalysts for the photocatalytic CO_(2) reduction.Among them,the Cs_(2)AgSbBr_(6) NCs demonstrate the optimal CO_(2) photoreduction activity with CO and CH_(4) evolutions of 366 and 49μmol g^(-1) respectively under 3h irradiation.Additionally,using the in-situ DRIFTS research,the surface reaction intermediates were precisely identified and dynamically tracked.This study suggests the potential of the lead-free halide DPs NCs as an important platform for the practical solar-to-fuel conversions.展开更多
Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge...Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge carriers and inadequate response to near-infrared(NIR)light usually leads to the unsatisfactory photocatalytic efficiency,hindering their application potentials.In this work,a significantly enhanced photothermal catalytic hydrogen evolution reaction over the lead-free perovskite Cs_(3)Bi_(2)Br_(9)/FeS_(2)(CBB/FS)heterostructure is simultaneously verified,where the CBB/FS Z-scheme heterojunctions display the strong stability and superb photothermal catalytic activity.Under the simulated solar irradiation(AM 1.5G),the optimized CBB/FS-5 achieves a photocatalytic hydrogen evolution rate of 31.5 mmol g^(-1)h^(-1),which is 112.6 and 77.1 times higher than that of FS and CBB,respectively,together with an apparent quantum yield of 29.5%at 420 nm.This significantly improved photocatalytic H_(2)evolution can be mainly attributed to the Z-scheme charge transfer and photothermal-assisted synergistically enhanced photocatalytic H_(2)production,and the potential mechanism of the enhanced photocatalytic H_(2)evolution is also proposed by photoelectrochemical characterizations,in situ XPS,EPR spectra,and the DFT calculations.This work provides new insights to the design of high-efficient photothermal catalysts,leading to the sustainable and efficient solutions towards the energy and environmental challenges.展开更多
Metal halide perovskites exhibit promising prospect in light-emitting diodes,solar cells,photodetectors and bioimaging.However,the workhorse of metal halide perovskites relies on toxicity lead element,which severely d...Metal halide perovskites exhibit promising prospect in light-emitting diodes,solar cells,photodetectors and bioimaging.However,the workhorse of metal halide perovskites relies on toxicity lead element,which severely damages human body and environment.Among lead-free perovskites,Cs_(2)NaInCl_(6)double perovskite is one of the most promising candidates because of its great stability and easy synthesis,but suffers inadequate optical performance.Here,we doped Sb^(3+)and Sm^(3+)into Cs_(2)NaInCl_(6)nanocrystals by a hot injection method.Cs_(2)NaInCl_(6):Sb^(3+)exhibits blue emission at 447 nm.Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals simultaneously generate the blue emission of Sb^(3+)and the multiple emissions of Sm^(3+)at 565,602,650 and 710 nm.With the increase of Sm^(3+)feed ratio,the emission color of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)gradually moves to cold white region at(0.27,0.28)in CIE chromaticity diagram and correlated color temperature of 11840 K.This work shows the potential application of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals as a single-component cold white emitter.展开更多
Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelect...Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_(C)) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.展开更多
A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development o...A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development of high-energy-density ceramic-based capacitors.Although significant successes have been achieved in obtaining high energy densities in lead-based ferroelectric ceramics,the utilization of lead-containing ceramies has been restricted due to environmental and health hazards of lead.Lead-free ferroelectric ceramics have garnered tremendous attention and are expected to replace lead-based ceramics in the near future.However,the energy density of lead-free ceramics is still lagging behind that of lead-containing cou.nterparts,severely limiting their applications.Significant efforts have been made to enhance the energy storage performance of lead-free ceramics using multi-scale design strategies,and exciting progress has been achieved in the past decade.This review briefly discusses the energy storage mechanism and fundamental characteristics of a dielectric capacitor,summarizes and compares the state-of-the-art design strategies for high-energy-density lead-free ceramics,and highlights several critical issues and requirements for industrial production.The prospects and challenges of lead-free ceramics for energy storage applications are also discussed.展开更多
A triboelectric nanogenerator(TENG)is a highly potential green energy harvesting technology to power small-scale electronic devices.Enhancing the overall electricity production capacity of TENGs is a primary concern f...A triboelectric nanogenerator(TENG)is a highly potential green energy harvesting technology to power small-scale electronic devices.Enhancing the overall electricity production capacity of TENGs is a primary concern for their utilization as an electricity generator in day-to-day life.Herein,we proposed a lead-free silver niobate(AgNbO_(3)(ANb))microparticles(MPs)-embedded polydimethylsiloxane(PDMS)composite film-based clip-like hybrid nanogenerator(HNG)device,producing an enhanced electrical output from the applied mechanical movements.The ANb MPs with a high dielectric constant were initially synthesized and embedded inside the PDMS polymer matrix.Various HNGs were fabricated utilizing ANb MPs/PDMS composite films/aluminum tape as negative/positive triboelectric films,respectively and operated in contact-separation mode.The electrical output from them was comparatively analyzed to investigate an optimum concentration of the ANb MPs inside the PDMS film.The robust HNG with 5 wt%ANb MPs/PDMS composite film produced the highest electrical output with promising stability.Thereafter,three similar optimized HNGs were fabricated and integrated within a 3D-printed clip-like structure and the electrical output was thoroughly evaluated while combining multiple HNGs as well as from each independent HNG.The clip-like HNG device exhibited an electrical output of 340 V and 20μA that can be further utilized to charge various capacitors and power portable electronics.Owing to the high resilience structure of the clip-like HNG device,it was also demonstrated to harvest biomechanical energy produced by human movements into electricity.The mechanical energy harvesting when the clip-like HNG device was attached to the accelerator pedal of the car and the pedal of a musical piano was successfully demonstrated.展开更多
Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses,lightweight,and mechanical flexibility.Twodimensiona...Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses,lightweight,and mechanical flexibility.Twodimensional(2D)hybrid perovskites have demonstrated excellent promise for assembling dielectric switches,in which the dynamic motions of organic moieties afford driving force to trigger switchable dielectric phase transition.Here,we successfully assembled a new lead-free hybrid double perovskite,(CHA)4Cu Bi Br8(1,CHA=cyclohexylammonium),adopting a typical 2D structural motif,which shows dielectric anisotropy and bistable behaviors during the reversible phase transition near T_(c)=378 K(the Curie temperature).That is,its dielectric constants could be switched and tuned between high-dielectric and low-dielectric states.Structure analyses reveal that the ordered-disordered transformation of the organic CHA+moiety and distortion of inorganic framework account for its phase transition.This result will stimulate further exploration of molecular dielectric switches in this 2D environmentally friendly family.展开更多
Metal halide perovskites(MHP)are potential candidates for the photocatalytic reduction of CO_(2)due to their long photogenerated carrier lifetime and charge diffusion length.However,the conventional long-chain ligand ...Metal halide perovskites(MHP)are potential candidates for the photocatalytic reduction of CO_(2)due to their long photogenerated carrier lifetime and charge diffusion length.However,the conventional long-chain ligand impedes the adsorption and activation of CO_(2)molecules in practical applications.Here,a ligand modulation technology is employed to enhance the photocatalytic CO_(2)reduction activity of lead-free Cs_(2)AgInCl_(6)microcrystals(MCs).The Cs_(2)AgInCl_(6)MCs passivated by Oleic acid(OLA)and Octanoic acid(OCA)are used for photocatalytic CO_(2)reduction.The results show that the surface defects and electronic properties of Cs_(2)AgInCl_(6)MCs can be adjusted through ligand modulation.Compared with the OLA-Cs_(2)AgInCl_(6),the OCA-Cs_(2)AgInCl_(6)catalyst demonstrated a significant improvement in the catalytic yield of CO and CH_(4).The CO and CH_(4)catalytic yields of OCA-Cs_(2)AgInCl_(6)reached 171.88 and34.15μmol g^(-1)h^(-1)which were 2.03 and 12.98 times higher than those of OLA-Cs_(2)AgInCl_(6),and the total electron consumption rate of OCA-Cs_(2)AgInCl_(6)was 615.2μmol g^(-1)h^(-1)which was 3.25 times higher than that of OLA-Cs_(2)AgInCl_(6).Furthermore,in situ diffuse reflectance infrared Fourier transform spectra revealed the enhancement of photocatalytic activity in Cs_(2)AgInCl_(6)MCs induced by ligand modulation.This study illustrates the potential of lead-free Cs_(2)AgInCl_(6)MCs for efficient photocatalytic CO_(2)reduction and provides a ligand modulation strategy for the active promotion of MHP photocatalysts.展开更多
Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.T...Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.The nontoxic cerium-doped lead-free perovskites with intrinsically efficient and short lifetime d–f transitions are a prospective replacement for the toxic Pb^(2+).Here,we demonstrated Ce-doped cesium lanthanide chloride perovskites (Cs_(3)LnCl_(6),Ln=Gd,Y,Lu) synthesized through a facile solution method for the first time.These perovskites exhibit blue-violet emission,which arises from Ce 5d→4f transitions.Among three types of Cs_(3)LnCl_(6) perovskites,Ce:Cs_(3)LuCl_(6) exhibited high photoluminescence quantum yield (PLQY) of 82%and a short excited-state lifetime of approximately 34 ns.When utilized as X-ray scintillators,Ce:Cs_(3)LuCl_(6) crystals display a high light yield of 8120 photons per MeV and a low detection limit of 36.8 n Gy air s^(-1).Importantly,the figure of merit (FoM),representing the ratio of light yield to decay time,reaches 239,which is the highest reported value for lead-free perovskite scintillators up to now.Additionally,the fabrication of perovskite/PMMA films was undertaken for practical demonstrations in X-ray imaging,resulting in the attainment of a resolution of up to 8.38 lp/mm.We anticipate that this work will inspire the utilization of Ce-doped Cs_(3)LnCl_(6) perovskites in ultrafast scintillation applications such as high-energy physics,nuclear reaction monitoring,and dynamic X-ray imaging.展开更多
Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ ...Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.展开更多
Graphite brasses were prepared by graphitizing annealing of cast brasses containing cementite particles,which were in-situ formed during the fasting process.The eutectic cast iron as carbon source was added into commo...Graphite brasses were prepared by graphitizing annealing of cast brasses containing cementite particles,which were in-situ formed during the fasting process.The eutectic cast iron as carbon source was added into common brasses by casting.SEM and EDS were used to analyze the microstructure of graphite brasses,and the relationship between the microstructure and machinability was investigated.The results show that graphite particles are formed by the decomposition of cementite particles in cast brasses.The graphite particles are uniformly dispersed in the brass matrix with the average size of 5.0 μm and the volume fraction of ~1.1%.The machinability in the graphite brass is dramatically increased relative to the common brass,because of the lubricating properties of graphite particles and its role in chip breaking.The workpiece surface of the graphite brasses chips is smooth and burr-free,and the chips of graphite brasses are short（C-shape） and discontinuous,which is much better than that of the long spiral chips of common brasses.展开更多
Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of...Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence.Three-dimensional(3 D)organic-inorganic hybrid lead halide perovskites are promising for direct X-ray detection-they show improved sensitivity compared to conventional X-ray detectors.However,their high and unstable dark current,caused by ion migration and high dark carrier concentration in the 3 D hybrid perovskites,limits their performance and long-term operation stability.Here we report ultrasensitive,stable X-ray detectors made using zero-dimensional(0 D)methylammonium bismuth iodide perovskite(MA3Bi2I9)single crystals.The 0 D crystal structure leads to a high activation energy(Ea)for ion migration(0.46 e V)and is also accompanied by a low dark carrier concentration(~10^6 cm^-3).The X-ray detectors exhibit sensitivity of 10,620μC Gy-1 air cm-2,a limit of detection(Lo D)of 0.62 nG yairs-1,and stable operation even under high applied biases;no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of^23,800 m Gyair,equivalent to>200,000 times the dose required for a single commercial X-ray chest radiograph.Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.展开更多
The Sn9Zn eutectic alloy is the nontoxic lead-free solders alternative having a melting temperature which is closest to that of the eutectic SnPb alloy. In order to improve the properties of SnZn lead-free solders, 0-...The Sn9Zn eutectic alloy is the nontoxic lead-free solders alternative having a melting temperature which is closest to that of the eutectic SnPb alloy. In order to improve the properties of SnZn lead-free solders, 0-0.5 wt.% of rare earth Er was added to the base alloys, and the microstructures were studied. Results showed that the addition of rare earth Er could enhance the wettability of SnZn solders, with 0.08%Er addition, the spreading area gavc an 19.1% increase. And based on the mechanical testing, it was found that the tensile force and shear force of SnZn-xEr solder joints could be improved significantly. Moreover, the oxidation resistance of SnZn0.08Er solder was better than that of SnZn solder, in addition, it was found that trace amounts of rare earth Er could refine the microstructures of SnZn solders, espe- cially for Zn-rich phases, and excessive amount of rare earth Er led to a coarse microstructure.展开更多
Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as ou...Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.展开更多
This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was ...This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was used to characterize the wettability of Sn-9Zn-xP solder alloys to Cu substrates. The oxidation and corrosion behaviors of Sn- 9Zn-xP solder alloys were determined by means of weight gaining, and secondary ion mass spectrometry was used to analyze the oxygen content. The role and mechanism of P in the solder alloys were also discussed. It is found that the addition of P can significantly improve the wettability of the solder alloys. Incorporating P into Sn-9Zn solder alloy obviously decreases the oxygen content and enhances the oxidation and corrosion resistance. Microstructure observations show that an appropriate amount of P can greatly refine coarse rod-like Zn-rich phases in Sn-gZn solder alloy.展开更多
Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction m...Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM） and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 decreased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 ℃ could also be obtained. The piezoelectric constant （d33）, the relative permit-tivity （εr） and the planar electromechanical coupling factor （kp） of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss （tanδ） decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount （x） was 0.2 wt.%, the BCTZ ceramics doped with Li2CO3 （0.6 wt.%） and sintered at 1050 ℃ possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.展开更多
Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achie...Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy,named high-entropy strategy,realizing nearly ten times growth of energy storage density compared with low-entropy material.Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time.The achievement of excellent energy storage properties should be attributed to the enhanced random field,decreased nanodomain size,strong multiple local distortions,and improved breakdown field.Furthermore,the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized.The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics,promoting the development of advanced capacitors.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 22375157 and W2433042)the Key Scientific and Technological Innovation Team of Shaanxi Province(No. 2020TD-001)+1 种基金the Fundamental Research Funds for Central Universities, State Key Laboratory of Electrical Insulation and Power Equipment (No. EIPE23409)the Instrument Analysis Center of Xi’an Jiaotong University for assistance。
文摘Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.
基金Project supported by the National Natural Science Foundation of China(61805134,11974229,22303044)Fundamental Research Program of Shanxi Province(202203021221121)+3 种基金China Postdoctoral Science Foundation(2022M711898)Natural Science Fo undation of Shandong Province(ZR2023QB135)Postdoctoral Innovation Project of Shandong Province(SDCX-ZG-202201004)Graduate Innovation Project in Shanxi Province(2024KY450)。
文摘Owing to their unique optical properties and nontoxicity,lead-free halide double perovskite nanocrystals are of interest for widespread applications.Herein,the colloid synthesis and photoluminescenc e property of Ag^(+)-Eu^(3+)codoped Cs_(2)NaInCl_(6)nanocrystals were investigated.The pe rovskite nanocrystals exhibit a broad warm-white photo luminescence with correlated color temperature(CCT)of 3447 K and color rendering index(CRI)of 90.2,and the means of codoping would improve its optical performance.A fast energy transfer and a long-lived self-trapped excitons state are unveiled by the femtosecond transient absorption spectra.The fast energy transfer from the self-trapped excitons of host nanocrystals to the Eu^(3+)ions is helpful to achieve a broad photoluminescence,and the quantum yield of Cs_(2)NaInCl_(6):0.05Ag^(+)-Eu^(3+)anocrystals can be enha nced to 69.5%.There is a large exciton binding energy and strong electron-phonon interaction in the codoped perovskite nanocrystals.The efficient and excellent air-stable double perovskite nanocrystals would be considered as a single-component phosphor for warm-white lighting.
基金Project supported by the Natural Science Foundation of Hebei Province(B2023201108,B2024201076)Science Fund for Creative Research Groups of Natural Science Foundation of Hebei Province(B2021201038)+3 种基金333 Talent Project Fund of Hebei Province(C20221015)National High-End Foreign Expert Recruitment Plan(G2022003007L)Hebei Province Higher Education Science and Technology Research Project(JZX2023001)Hebei Province Innovation Capability Enhancement Plan Project(22567632H)。
文摘Lead-free double perovskites have gained recognition as top luminescent materials due to their environmental friendliness,high chemical stability,structural adjustability,and excellent photoelectric properties.However,the poor modulation of emission restricts their applications,and it is highly desirable to explore stable and efficient double perovskites with multimode luminescence and adjustable spectra for multifunctional photoelectric applications.Herein,the rare earth ions Ln^(3+)(Er^(3+)and Ho^(3+))-doped Cs_(2)NaYCl_(6):Sb^(3+)crystals were synthesized by a simple solvothermal route.The X-ray diffraction pattern(XRD),energy-dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),and elemental mapping images demonstrate that the Sb^(3+),Er^(3+),and Ho^(3+)ions have been homogeneously incorporated into the Cs_(2)NaYCl_(6)crystals.As anticipated,the emissio n spectra of Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)are composed of two bands.One broad blue band derives from self-trapped exciton(STE)in[SbCl_(6)]3-octahedra while another group of emission peaks stems from the f-f transitions of Ln^(3+)ions.The emission colors of Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)phosphors can be tuned in a wide range by modulating the doping concentrations of Ln^(3+)ions.The efficient energy transfer from STE to Ln^(3+)is the key point to achieving the efficient and tunable emissions Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)samples.Interestingly,Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)can also exhibit characteristic up-conversion luminescence of Ln^(3+)under nearinfrared(NIR)excitation besides the down-conversion luminescence,revealing that the materials may have potential applicability in multimode anti-counterfeiting and information encryption applications.Furthermore,the light emitting diodes(LEDs)assembled by Cs_(2)NaYCl_(6):Sb^(3+)and Cs_(2)NaYCl_(6):Sb^(3+)/Ln^(3+)phosphors display dazzling blue,green,and red emissions under a forward bias current,which indicates that the as-obtained double perovskites materials may have great potential in solid-state lighting and optoelectronic devices.
基金supported by the National Natural Science Foundation of China(62375032,22408362)The China National Postdoctoral Program for Innovative Talents(Certificate Number:BX20230355)+3 种基金The China Postdoctoral Science Foundation(Certificate Number:2024M753165)The Natural Science Foundation of Chongqing(No.CSTB2023TIAD-KPX0017)The Open Fund of the State Key Laboratory of High Field Laser Physics(Shanghai Institute of Optics and Fine Mechanics)Department of Education of Guizhou Province(Guizhou Teaching and Technology[2023]015).
文摘Although the lead-free halide double perovskites(DPs)have shown great promise for the photocatalytic reduction of CO_(2),the catalytic performance is still far from satisfactory.In this work,lead-free Cs_(2)AgSbX_(6)(X=Cl,Br,I)DPs nanocrystals(NCs)are prepared by a modified ligand-assisted reprecipitation(LARP)approach at room temperature.The crystal surface,shape,and optoelectronic properties of the AgSb-based DPs are modified using halogen modulation technique.Moreover,a series of Cs_(2)AgSbX_(6) perovskites NCs are utilized as efficient catalysts for the photocatalytic CO_(2) reduction.Among them,the Cs_(2)AgSbBr_(6) NCs demonstrate the optimal CO_(2) photoreduction activity with CO and CH_(4) evolutions of 366 and 49μmol g^(-1) respectively under 3h irradiation.Additionally,using the in-situ DRIFTS research,the surface reaction intermediates were precisely identified and dynamically tracked.This study suggests the potential of the lead-free halide DPs NCs as an important platform for the practical solar-to-fuel conversions.
基金supported by the National Natural Science Foundation of China(No.52172206)the Project of Science&Technology Office of Jiangsu Province(No.KB20181043)the Talent Research Projects of Qilu University of Technology(Shandong Academy of Sciences)(No.2024RCKY018)。
文摘Photothermal catalysis is a promising technology primarily utilized the solar energy to produce photogenerated e^(-)/h^(+) pairs together with the production of heat energy.However,the inefficient separation of charge carriers and inadequate response to near-infrared(NIR)light usually leads to the unsatisfactory photocatalytic efficiency,hindering their application potentials.In this work,a significantly enhanced photothermal catalytic hydrogen evolution reaction over the lead-free perovskite Cs_(3)Bi_(2)Br_(9)/FeS_(2)(CBB/FS)heterostructure is simultaneously verified,where the CBB/FS Z-scheme heterojunctions display the strong stability and superb photothermal catalytic activity.Under the simulated solar irradiation(AM 1.5G),the optimized CBB/FS-5 achieves a photocatalytic hydrogen evolution rate of 31.5 mmol g^(-1)h^(-1),which is 112.6 and 77.1 times higher than that of FS and CBB,respectively,together with an apparent quantum yield of 29.5%at 420 nm.This significantly improved photocatalytic H_(2)evolution can be mainly attributed to the Z-scheme charge transfer and photothermal-assisted synergistically enhanced photocatalytic H_(2)production,and the potential mechanism of the enhanced photocatalytic H_(2)evolution is also proposed by photoelectrochemical characterizations,in situ XPS,EPR spectra,and the DFT calculations.This work provides new insights to the design of high-efficient photothermal catalysts,leading to the sustainable and efficient solutions towards the energy and environmental challenges.
基金Project supported by the National Natural Science Foundation of China(62104062)the China Postdoctoral Science Foundation(2021M701056)。
文摘Metal halide perovskites exhibit promising prospect in light-emitting diodes,solar cells,photodetectors and bioimaging.However,the workhorse of metal halide perovskites relies on toxicity lead element,which severely damages human body and environment.Among lead-free perovskites,Cs_(2)NaInCl_(6)double perovskite is one of the most promising candidates because of its great stability and easy synthesis,but suffers inadequate optical performance.Here,we doped Sb^(3+)and Sm^(3+)into Cs_(2)NaInCl_(6)nanocrystals by a hot injection method.Cs_(2)NaInCl_(6):Sb^(3+)exhibits blue emission at 447 nm.Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals simultaneously generate the blue emission of Sb^(3+)and the multiple emissions of Sm^(3+)at 565,602,650 and 710 nm.With the increase of Sm^(3+)feed ratio,the emission color of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)gradually moves to cold white region at(0.27,0.28)in CIE chromaticity diagram and correlated color temperature of 11840 K.This work shows the potential application of Cs_(2)NaInCl_(6):Sm^(3+),Sb^(3+)nanocrystals as a single-component cold white emitter.
基金Project supported by the National Natural Science Foundation of China Youth Project (51702317)the Youth Project of the Natural Science Foundation of Jiangxi Provincial Science and Technology (20212BAB214019)the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology (JXUSTQJYX2020004)。
文摘Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_(C)) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.
基金supported by the National Science Foundation of China(No.61631166004)Shenzhen Science and Technology Program(Grant Nos.KQTD20180411143514543 and JCYJ20180504165831308)Guangdong Provincial Key Laboratory Program(Grant No.2021B1212040001)。
文摘A greater number of compact and reliable electrostatic capacitors are in demand due to the Internet of Things boom and rapidly growing complex and integrated electronic systems,continuously promoting the development of high-energy-density ceramic-based capacitors.Although significant successes have been achieved in obtaining high energy densities in lead-based ferroelectric ceramics,the utilization of lead-containing ceramies has been restricted due to environmental and health hazards of lead.Lead-free ferroelectric ceramics have garnered tremendous attention and are expected to replace lead-based ceramics in the near future.However,the energy density of lead-free ceramics is still lagging behind that of lead-containing cou.nterparts,severely limiting their applications.Significant efforts have been made to enhance the energy storage performance of lead-free ceramics using multi-scale design strategies,and exciting progress has been achieved in the past decade.This review briefly discusses the energy storage mechanism and fundamental characteristics of a dielectric capacitor,summarizes and compares the state-of-the-art design strategies for high-energy-density lead-free ceramics,and highlights several critical issues and requirements for industrial production.The prospects and challenges of lead-free ceramics for energy storage applications are also discussed.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(No.2018R1A6A1A03025708 and No.2020M3H2A1076786).
文摘A triboelectric nanogenerator(TENG)is a highly potential green energy harvesting technology to power small-scale electronic devices.Enhancing the overall electricity production capacity of TENGs is a primary concern for their utilization as an electricity generator in day-to-day life.Herein,we proposed a lead-free silver niobate(AgNbO_(3)(ANb))microparticles(MPs)-embedded polydimethylsiloxane(PDMS)composite film-based clip-like hybrid nanogenerator(HNG)device,producing an enhanced electrical output from the applied mechanical movements.The ANb MPs with a high dielectric constant were initially synthesized and embedded inside the PDMS polymer matrix.Various HNGs were fabricated utilizing ANb MPs/PDMS composite films/aluminum tape as negative/positive triboelectric films,respectively and operated in contact-separation mode.The electrical output from them was comparatively analyzed to investigate an optimum concentration of the ANb MPs inside the PDMS film.The robust HNG with 5 wt%ANb MPs/PDMS composite film produced the highest electrical output with promising stability.Thereafter,three similar optimized HNGs were fabricated and integrated within a 3D-printed clip-like structure and the electrical output was thoroughly evaluated while combining multiple HNGs as well as from each independent HNG.The clip-like HNG device exhibited an electrical output of 340 V and 20μA that can be further utilized to charge various capacitors and power portable electronics.Owing to the high resilience structure of the clip-like HNG device,it was also demonstrated to harvest biomechanical energy produced by human movements into electricity.The mechanical energy harvesting when the clip-like HNG device was attached to the accelerator pedal of the car and the pedal of a musical piano was successfully demonstrated.
基金financially supported by National Natural Science Foundation of China(Nos.22125110,22205233,22193042,21833010,21921001,and U21A2069)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(No.ZDBSLY-SLH024)+3 种基金the National Postdoctoral Program for Innovative Talents(No.BX2021315)the National Key Research and Development Program of China(No.2019YFA0210402)the China Postdoctoral Science Fund(No.2022TQ0337)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZR126)。
文摘Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses,lightweight,and mechanical flexibility.Twodimensional(2D)hybrid perovskites have demonstrated excellent promise for assembling dielectric switches,in which the dynamic motions of organic moieties afford driving force to trigger switchable dielectric phase transition.Here,we successfully assembled a new lead-free hybrid double perovskite,(CHA)4Cu Bi Br8(1,CHA=cyclohexylammonium),adopting a typical 2D structural motif,which shows dielectric anisotropy and bistable behaviors during the reversible phase transition near T_(c)=378 K(the Curie temperature).That is,its dielectric constants could be switched and tuned between high-dielectric and low-dielectric states.Structure analyses reveal that the ordered-disordered transformation of the organic CHA+moiety and distortion of inorganic framework account for its phase transition.This result will stimulate further exploration of molecular dielectric switches in this 2D environmentally friendly family.
基金the National Natural Science Foundation of China(Grant No.62375032)the Natural Science Foundation of Chongqing(Grant No.CSTB2023TIADKPX0017)+2 种基金the Open Fund of the State Key Laboratory of High Field Laser Physics(Shanghai Institute of Optics and Fine Mechanics)the China Postdoctoral Science Foundation(Grant No.BX20230355)the Department of Education of Guizhou Province(Guizhou Teaching and Technology[2023]015)。
文摘Metal halide perovskites(MHP)are potential candidates for the photocatalytic reduction of CO_(2)due to their long photogenerated carrier lifetime and charge diffusion length.However,the conventional long-chain ligand impedes the adsorption and activation of CO_(2)molecules in practical applications.Here,a ligand modulation technology is employed to enhance the photocatalytic CO_(2)reduction activity of lead-free Cs_(2)AgInCl_(6)microcrystals(MCs).The Cs_(2)AgInCl_(6)MCs passivated by Oleic acid(OLA)and Octanoic acid(OCA)are used for photocatalytic CO_(2)reduction.The results show that the surface defects and electronic properties of Cs_(2)AgInCl_(6)MCs can be adjusted through ligand modulation.Compared with the OLA-Cs_(2)AgInCl_(6),the OCA-Cs_(2)AgInCl_(6)catalyst demonstrated a significant improvement in the catalytic yield of CO and CH_(4).The CO and CH_(4)catalytic yields of OCA-Cs_(2)AgInCl_(6)reached 171.88 and34.15μmol g^(-1)h^(-1)which were 2.03 and 12.98 times higher than those of OLA-Cs_(2)AgInCl_(6),and the total electron consumption rate of OCA-Cs_(2)AgInCl_(6)was 615.2μmol g^(-1)h^(-1)which was 3.25 times higher than that of OLA-Cs_(2)AgInCl_(6).Furthermore,in situ diffuse reflectance infrared Fourier transform spectra revealed the enhancement of photocatalytic activity in Cs_(2)AgInCl_(6)MCs induced by ligand modulation.This study illustrates the potential of lead-free Cs_(2)AgInCl_(6)MCs for efficient photocatalytic CO_(2)reduction and provides a ligand modulation strategy for the active promotion of MHP photocatalysts.
基金supported by the National Natural Science Foundation of China (Grant Nos. 22075043, 21875034, 12274075, 62375142)。
文摘Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes,low detection limits,and ease of fabrication compared to traditional scintillators.The nontoxic cerium-doped lead-free perovskites with intrinsically efficient and short lifetime d–f transitions are a prospective replacement for the toxic Pb^(2+).Here,we demonstrated Ce-doped cesium lanthanide chloride perovskites (Cs_(3)LnCl_(6),Ln=Gd,Y,Lu) synthesized through a facile solution method for the first time.These perovskites exhibit blue-violet emission,which arises from Ce 5d→4f transitions.Among three types of Cs_(3)LnCl_(6) perovskites,Ce:Cs_(3)LuCl_(6) exhibited high photoluminescence quantum yield (PLQY) of 82%and a short excited-state lifetime of approximately 34 ns.When utilized as X-ray scintillators,Ce:Cs_(3)LuCl_(6) crystals display a high light yield of 8120 photons per MeV and a low detection limit of 36.8 n Gy air s^(-1).Importantly,the figure of merit (FoM),representing the ratio of light yield to decay time,reaches 239,which is the highest reported value for lead-free perovskite scintillators up to now.Additionally,the fabrication of perovskite/PMMA films was undertaken for practical demonstrations in X-ray imaging,resulting in the attainment of a resolution of up to 8.38 lp/mm.We anticipate that this work will inspire the utilization of Ce-doped Cs_(3)LnCl_(6) perovskites in ultrafast scintillation applications such as high-energy physics,nuclear reaction monitoring,and dynamic X-ray imaging.
文摘Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.
基金Projects(51271090,51364036,51471083)supported by the National Natural Science Foundation of ChinaProject(IRT0730)supported by the Program for Changjiang Scholars and Innovative Research Team in University,China+1 种基金Project(NCET-10-0184)supported by the Program for New Century Excellent Talents in University,ChinaProject(20103601110001)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Graphite brasses were prepared by graphitizing annealing of cast brasses containing cementite particles,which were in-situ formed during the fasting process.The eutectic cast iron as carbon source was added into common brasses by casting.SEM and EDS were used to analyze the microstructure of graphite brasses,and the relationship between the microstructure and machinability was investigated.The results show that graphite particles are formed by the decomposition of cementite particles in cast brasses.The graphite particles are uniformly dispersed in the brass matrix with the average size of 5.0 μm and the volume fraction of ~1.1%.The machinability in the graphite brass is dramatically increased relative to the common brass,because of the lubricating properties of graphite particles and its role in chip breaking.The workpiece surface of the graphite brasses chips is smooth and burr-free,and the chips of graphite brasses are short（C-shape） and discontinuous,which is much better than that of the long spiral chips of common brasses.
基金supported by the National Natural Science Foundation of China(Grant nos.21773218,61974063)the Sichuan Province(Grant no.2018JY0206)the China Academy of Engineering Physics(Grant no.YZJJLX2018007)。
文摘Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence.Three-dimensional(3 D)organic-inorganic hybrid lead halide perovskites are promising for direct X-ray detection-they show improved sensitivity compared to conventional X-ray detectors.However,their high and unstable dark current,caused by ion migration and high dark carrier concentration in the 3 D hybrid perovskites,limits their performance and long-term operation stability.Here we report ultrasensitive,stable X-ray detectors made using zero-dimensional(0 D)methylammonium bismuth iodide perovskite(MA3Bi2I9)single crystals.The 0 D crystal structure leads to a high activation energy(Ea)for ion migration(0.46 e V)and is also accompanied by a low dark carrier concentration(~10^6 cm^-3).The X-ray detectors exhibit sensitivity of 10,620μC Gy-1 air cm-2,a limit of detection(Lo D)of 0.62 nG yairs-1,and stable operation even under high applied biases;no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of^23,800 m Gyair,equivalent to>200,000 times the dose required for a single commercial X-ray chest radiograph.Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.
基金Project supported by Provincial Key Lab of Advanced Welding Technology Foundation(JSAWS-11-03)the Xuzhou Normal University Foundation(11XLR16)Natural Science Foundation of Jiangsu Province(BK2012144)
文摘The Sn9Zn eutectic alloy is the nontoxic lead-free solders alternative having a melting temperature which is closest to that of the eutectic SnPb alloy. In order to improve the properties of SnZn lead-free solders, 0-0.5 wt.% of rare earth Er was added to the base alloys, and the microstructures were studied. Results showed that the addition of rare earth Er could enhance the wettability of SnZn solders, with 0.08%Er addition, the spreading area gavc an 19.1% increase. And based on the mechanical testing, it was found that the tensile force and shear force of SnZn-xEr solder joints could be improved significantly. Moreover, the oxidation resistance of SnZn0.08Er solder was better than that of SnZn solder, in addition, it was found that trace amounts of rare earth Er could refine the microstructures of SnZn solders, espe- cially for Zn-rich phases, and excessive amount of rare earth Er led to a coarse microstructure.
文摘Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.
基金supported by the National Natural Science Foundation of China(No.50904035)
文摘This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was used to characterize the wettability of Sn-9Zn-xP solder alloys to Cu substrates. The oxidation and corrosion behaviors of Sn- 9Zn-xP solder alloys were determined by means of weight gaining, and secondary ion mass spectrometry was used to analyze the oxygen content. The role and mechanism of P in the solder alloys were also discussed. It is found that the addition of P can significantly improve the wettability of the solder alloys. Incorporating P into Sn-9Zn solder alloy obviously decreases the oxygen content and enhances the oxidation and corrosion resistance. Microstructure observations show that an appropriate amount of P can greatly refine coarse rod-like Zn-rich phases in Sn-gZn solder alloy.
基金supported by Project of Combination of Producing,Learning and Studying of Guangdong Province and Education Department(2011B090400027)
文摘Ba0.85Ca0.15Ti0.9Zr0.1O3 （BCTZ） lead-free piezoelectric ceramics co-doped with CeO2 （x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%） and Li2CO3 （0.6 wt.%） were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM） and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 decreased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 ℃ could also be obtained. The piezoelectric constant （d33）, the relative permit-tivity （εr） and the planar electromechanical coupling factor （kp） of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss （tanδ） decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount （x） was 0.2 wt.%, the BCTZ ceramics doped with Li2CO3 （0.6 wt.%） and sintered at 1050 ℃ possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.
基金supported by the National Natural Science Foundation of China(Grant Nos.21825102,22235002,52172181,and 22105017)Key R&D Plan of the Ministry of Science and Technology of China(Grant No.2022YFB3204000)。
文摘Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market.Here,an ultrahigh energy storage density of~13.8 J cm^(-3)and a large efficiency of~82.4%are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy,named high-entropy strategy,realizing nearly ten times growth of energy storage density compared with low-entropy material.Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time.The achievement of excellent energy storage properties should be attributed to the enhanced random field,decreased nanodomain size,strong multiple local distortions,and improved breakdown field.Furthermore,the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized.The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics,promoting the development of advanced capacitors.
