Developing high efficient Pd-based electrocatalysts for oxygen reduction reaction(ORR) is still challenging for alkaline membrane fuel cell,since the strong oxygen adsorption energy and easy agglomerative intrinsic pr...Developing high efficient Pd-based electrocatalysts for oxygen reduction reaction(ORR) is still challenging for alkaline membrane fuel cell,since the strong oxygen adsorption energy and easy agglomerative intrinsic properties. In order to simultaneously solve these problems, Pd/Co_(3)O_(4)–N–C multidimensional materials with porous structures is designed as the ORR catalysts. In details, the ZIF-67 with polyhedral structure was firstly synthesized and then annealed at high-temperature to prepare the N-doped Co_(3)O_(4)carbon-based material, which was used to homogeneously confine Pd nanoparticles and obtained the Pd/Co_(3)O_(4)–N–C series catalysts. The formation of Co–N and C–N bond could provide efficient active sites for ORR. Simultaneously, the strong electronic interaction in the interface between the Pd and N-doped Co_(3)O_(4)could disperse and avoid the agglomeration of Pd nanoparticles and ensure the exposure of active sites, which is crucial to lower the energy barrier toward ORR and substantially enhance the ORR kinetics. Hence, the Pd/Co_(3)O_(4)–N–C nanocompounds exhibited excellent ORR catalytic performance, ideal Pd mass activity, and durability in 0.1 mol L-1KOH solution compared with Co_(3)O_(4)–N–C and Pd/C. The scalable synthesis method, relatively low cost, and excellent electrochemical ORR performance indicated that the obtained Pd/Co_(3)O_(4)–N–C electrocatalyst had the potential for application on fuel cells.展开更多
The load partitioning between the magnesium and titanium phases in an extruded Mg-15%Ti(vol.%) composite from room temperature up to 300 ℃ using synchrotron radiation diffraction during in-situ compression tests. Dur...The load partitioning between the magnesium and titanium phases in an extruded Mg-15%Ti(vol.%) composite from room temperature up to 300 ℃ using synchrotron radiation diffraction during in-situ compression tests. During compression, the magnesium matrix composite deforms mainly by the activation of the extension twinning system up to 200 ℃. The volume fraction of twins increases with the plastic strain but decrease with the compression temperature. Hard titanium particles bear an additional load transferred by the soft magnesium matrix from room temperature up to 300 ℃. This effect is amplified after yield stress during plastic deformation. Additionally, twins within magnesium grains behaves as an additional reinforcement at low temperature(below 200 ℃) inducing an increase in the work hardening of the composite.展开更多
In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major rea...In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.展开更多
Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical act...Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.展开更多
It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing ...It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.展开更多
A novel quadripolymer scale inhibitor poly-maleic anhydride-acrylic acid-acrylamide-sodium methallyl sulfonate(PMAAS)was synthesized by solution polymerization with maleic anhydride(MA),acrylic acid(AA), acrylamide(AM...A novel quadripolymer scale inhibitor poly-maleic anhydride-acrylic acid-acrylamide-sodium methallyl sulfonate(PMAAS)was synthesized by solution polymerization with maleic anhydride(MA),acrylic acid(AA), acrylamide(AM),sodium methallyl sulfonate(SMAS),etc.IR spectrum shows that PMAAS contains carbonyl, hydroxyl,phosphatic and sulfonic acid group.SEM indicates that PMAAS blocks the normal growth of scale CaCO3 and CaSO4 crystals.The influences of PMAAS concentration,Ca 2+ concentration,temperature and pH value of the system on the inhibition efficiency are investigated.The inhibition efficiency of PMAAS is superior to com- mercial inhibitors T-225 and XF-192.展开更多
We report a newly found strong disturbing effect orAl addition to the intensity ratios of blue and green emissions from single host full-colour phosphor of Ba3MgSi2-xAlxO8:0.02Eu^2+, 0.1Mn^2+ for near-UV excited wh...We report a newly found strong disturbing effect orAl addition to the intensity ratios of blue and green emissions from single host full-colour phosphor of Ba3MgSi2-xAlxO8:0.02Eu^2+, 0.1Mn^2+ for near-UV excited white light. The phase-pure silicate phosphor in the size of around 4μm is prepared by salt-assisted spray pyrolysis route, having three-colour emissions at the wavelength peak values of 437nm, 500 nm and 608 nm simultaneously under the excitation of 375 nm. The amount variation orAl ion added to the phosphor host results in a drastic change of the intensity ratio between green and blue emissions, while the intensity of red light keeps unchanged. As a consequence, the combination of three colours lies in the white light region and can be tuned by precisely controlled addition oral content. The Raman spectroscopy verifies the modifying effect oral ion to the tetrahedral network in silicate hosts. We assume that by addition of Al ion, the amount of those two kinds of Eu^2+ substituting for those two kinds of Ba^2+ lattice sites with distinct energy levels of blue and green featured emissions can be adjusted to contribute to diversification of the ratios of blue and green emissions.展开更多
The crystallization, microstructure, and soft magnetic properties of Fe52Co34Hf7B6Cul alloy are studied. Amorphous Fe52Co34Hf7B6Cul alloys are first treated by a pulsed magnetic field with a medium frequency, and then...The crystallization, microstructure, and soft magnetic properties of Fe52Co34Hf7B6Cul alloy are studied. Amorphous Fe52Co34Hf7B6Cul alloys are first treated by a pulsed magnetic field with a medium frequency, and then annealed at 100 ℃-400 ℃ for 30 min in a vacuum. The rise in temperature during the treatment by a pulsed magnetic field is measured by a non-contact infrared thermometer. The soft magnetic properties of specimens are measured by a vibrating sample magnetometer (VSM). The microstructure changes of specimens are observed by a MSssbauer spectroscopy and transmission electron microscope (TEM). The results show the medium-frequency pulsating magnetic field will pro- mote nanocrystallization of the amorphous alloy with a lower temperature rise. The nanocrystalline phase is (α-Fe(Co) with bcc crystal structure, and the grain size is about 10 nm. After vacuum annealing at 100 ℃ for 30 min, scattering nanocrystalline phases become more uniform, the coercive force and the saturation magnetization of the specimens are 41.98 A/m and 185.15 emu/g.展开更多
The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refr...The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented.展开更多
We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-...We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-rich), the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2+] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2+ emission. The maximum intensity for the luminescence of Mn^2+ emission is observed at the ratio of [S^2-]/[Zn^2+] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2+ ions incorporated into ZnS lattices.展开更多
A new 1D coordination polymer [Co(bpp)3Cl2(H2O)2]n 1 (bpp = 1,3-bis(4-pyridyl)-propane) was synthesized and characterized by elemental analysis,IR spectrum and single-crystal X-ray diffraction. The crystal bel...A new 1D coordination polymer [Co(bpp)3Cl2(H2O)2]n 1 (bpp = 1,3-bis(4-pyridyl)-propane) was synthesized and characterized by elemental analysis,IR spectrum and single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system,space group Ibca with a = 16.569(9),b = 17.240(10),c = 27.087(16) ,V = 7738(8) 3,Z = 8,Dc = 1.306 g/cm3,Mr = 760.65,λ(MoKa) = 0.71073 ,μ = 0.623 mm1,F(000) = 3192,the final R = 0.0678 and wR = 0.2011. The Co(II) atom is coordinated in a slightly distorted octahedral CoN4Cl2 geometry by two Cl atoms in the axial positions,four N atoms from the two bridging bpp ligands and two pendant bpp ligands. The CoN4Cl2 octahedra are connected by the bridging bpp ligands to form a 1D neutral coordination polymer chain. The chains are linked by face-to-face π-π interactions between adjacent pendant bpp ligands to give rise to a 3D supramolecular architecture. The photoluminescent investigation indicates that the emission of 1 is attributed to ligand-centered emission. The variable-temperature magnetic susceptibility measurement shows weak antiferromagnetic behavior in the coπmplex.展开更多
A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in ...A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) ?, V = 11711(4) ?3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm?1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I). The crystal structure is composed of [{Cu(en)2}HPW12O40]2? anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions. The anionic [{Cu(en)2}HPW12O40]2? is formed by the mixed valance {HPWVI11WVO40}3? Keggin unit covalently linked by a {Cu(en)2}+ group.展开更多
The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply.Supercapacitors are high-power devices,particularly suitable for public transportati...The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply.Supercapacitors are high-power devices,particularly suitable for public transportation since they can easily store breaking energy due to their high-rate charging ability.Additionally,they can function with two carbon electrodes,which is an advantage due to the abundance of carbon in biomass and other waste materials(i.e.,plastic waste).Newly developed supercapacitive nanocarbons display extremely narrow micropores(<0.8 nm),as it increases drastically the capacitance in aqueous electrolytes.Here,we present a strategy to produce low-cost flexible microporous electrodes with extremely high power density(>100 kW kg^(-1)),using fourty times less activating agent than traditionnal chemically activated carbons.We also demonstrate that the affinity between the carbon and the electrolyte is of paramount importance to maintain rapid ionic diffusion in narrow micropores.Finally,this facile synthesis method shows that low-cost and bio-based free-standing electrode materials with reliable supercapacitive performances can be used in electrochemistry.展开更多
Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,wh...Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,which leads to co-migration of transition metal ions and oxygen vacancies,causing structural instability.In this work,we propose a pre-activation strategy driven by chemical impregnation to modulate the chemical state of surface lattice oxygen,thus regulating the structural and electrochemical properties of the cathodes.In-situ X-ray diffraction confirms that materials based on activated oxygen configuration have higher structural stability.More importantly,this novel efficient strategy endows the cathodes having a lower surface charge transfer barrier and higher Li+transfer kinetics characteristic and ameliorates its inherent issues.The optimized cathode exhibits excellent electrochemical performance:after 300 cycles,high capacity(from 238 m Ah g^(-1)to 193 m Ah g^(-1)at 1 C)and low voltage attenuation(168 mV)are obtained.Overall,this modulated surface lattice oxygen strategy improves the electrochemical activity and structural stability,providing an innovative idea to obtain high-capacity Co-free Li-rich cathodes for next-generation Li-ion batteries.展开更多
A theoretical model that takes into account the flee-volume aided cooperative shearing of shear transformation zones (STZs) is developed to quantitatively understand the ductile-to-brittle transition (DBT) of meta...A theoretical model that takes into account the flee-volume aided cooperative shearing of shear transformation zones (STZs) is developed to quantitatively understand the ductile-to-brittle transition (DBT) of metallic glasses. The STZ dilatational strain is defined as the ratio of STZ-activated free volume to STZ volume itself. The model demonstrates that the STZ dilatational strain will increase drastically and exceed the characteristic shear strain of STZ as temperature decreases below a critical value. This critical temperature is in good agreement with the experimentally measured DBT temperature. Our results suggest that the DBT of metallic glasses is underpinned by the transition of atomic-cluster motions from STZ-tvpe rearrangements to dilatational processes (termed tension transformation zones (TrZs)).展开更多
This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,th...This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.展开更多
This paper studies the isotopic effect of Cl2^+ rovibronic spectra in the A^2Лu (Ω = 1/2)-X^2Лg (Ω = 1/2) system. Based on the experimental results of the molecular constants of ^35Cl2^+, it calculates the v...This paper studies the isotopic effect of Cl2^+ rovibronic spectra in the A^2Лu (Ω = 1/2)-X^2Лg (Ω = 1/2) system. Based on the experimental results of the molecular constants of ^35Cl2^+, it calculates the vibrational isotope shifts of the (2, 7) and (3, 7) band between the isotopic species ^35C12^+, ^35Cl^37Cl + and ^37Cl2^+, and estimates the rotational constants of both A^2Лu and X^2Лg states for the minor isotopic species ^35Cl^37Cl+ and ^37Cl2^+. The experimental results of the spectrum of 35Cl37Cl-1- (3, 7) band proves the above mentioned theoretical calculation. The molecular constants and thus resultant rovibronic spectrum for ^37Cl2^+ were predicted, which will be helpful for further experimental investigation.展开更多
An electrochemical technique has been introduced and applied to fabricate superconducting MgB2 films in molten salts. MgCl2, Mg(BO2)2, NaCl, and KCl were used as electrolyte, graphite was used as the anode, and copp...An electrochemical technique has been introduced and applied to fabricate superconducting MgB2 films in molten salts. MgCl2, Mg(BO2)2, NaCl, and KCl were used as electrolyte, graphite was used as the anode, and copper was used as the cathode, respectively. X-ray diffraction (XRD) analysis was chosen to investigate the phase composition and crystallinity of the films at different electrolysis temperatures. Stan- dard four-probe technique and SQUID were applied to investigate the temperature dependence of resistance (R-T) properties and magnetic properties of the films, respectively. The results indicate that MgB2 films have been fabricated on the copper cathodes, and superconducting transition takes place close to 50 K.展开更多
Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation pro...Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation process,the material’s surface and microstructure are being changed by stresses induced by machining.Hence degradable metal implants need to be fully characterized in terms of the influence of machining on the resulting microstructure and corrosion performance.In this study,micro-computed tomography(μCT)is used for the quantification of the degradation rate of biodegradable implants.To our best knowledge,for the first time quantitative measures are introduced to describe the degradation homogeneity in 3D.This information enables a prediction in terms of implant stability during the degradation in the body.Two magnesium gadolinium alloys,Mg-5Gd and Mg-10 Gd(all alloy compositions are given in weight%unless otherwise stated),in the shape of M2 headless screws have been investigated for their microstructure and their degradation performance up to 56 days.During the microstructure investigations particular attention was paid to the localized deformation of the alloys,due to the machining process.In vitro immersion testing was performed to assess the degradation performance quantified by subsequent weight loss and volume loss(usingμCT)measurements.Although differences were observed in the degree of screw’s near surface microstructure being influenced from machining,the degradation rates of both materials appeared to be suitable for application in orthopedic implants.From the degradation homogeneity point of view no obvious contrast was detected between both alloys.However,the higher degradation depth ratios between the crests and roots of Mg-5Gd ratios may indicated a less homogeneous degradation of the screws of these alloys on contract to the ones made of Mg-10Gd alloys.Due to its lower degradation rates,its more homogeneous microstructure,its weaker texture and better degradation performance extruded Mg-10Gd emerged more suitable as implant material than Mg-5Gd.展开更多
xMoO2-(1-x)α-Fe2O3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successfully synthesized by mechanochemical activation of MoO2 and α-Fe2O3 mixtures for 0 - 12 hours of ball milling time. X-ray p...xMoO2-(1-x)α-Fe2O3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successfully synthesized by mechanochemical activation of MoO2 and α-Fe2O3 mixtures for 0 - 12 hours of ball milling time. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of the molybdenum dioxide-hematite nanoparticle system under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the crystallite size and lattice parameters as function of milling times and indicated the presence of Mo-substituted hematite and Fe-doped molybdenum dioxide at long milling times. The Mössbauer studies yielded the magnetic hyperfine fields and the relative abundance of a quadrupole-split doublet as function of the milling time for all molar concentrations involved. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in a magnetic field of 200 Oe.展开更多
基金funded by National Natural Science Foundation of China (21975129)Natural Science Foundation of Jiangsu Province (BK20190759)+1 种基金Nanjing Forestry UniversityPostgraduate Research & Practice Innovation Program of Jiangsu Province (SJCX21_0337)。
文摘Developing high efficient Pd-based electrocatalysts for oxygen reduction reaction(ORR) is still challenging for alkaline membrane fuel cell,since the strong oxygen adsorption energy and easy agglomerative intrinsic properties. In order to simultaneously solve these problems, Pd/Co_(3)O_(4)–N–C multidimensional materials with porous structures is designed as the ORR catalysts. In details, the ZIF-67 with polyhedral structure was firstly synthesized and then annealed at high-temperature to prepare the N-doped Co_(3)O_(4)carbon-based material, which was used to homogeneously confine Pd nanoparticles and obtained the Pd/Co_(3)O_(4)–N–C series catalysts. The formation of Co–N and C–N bond could provide efficient active sites for ORR. Simultaneously, the strong electronic interaction in the interface between the Pd and N-doped Co_(3)O_(4)could disperse and avoid the agglomeration of Pd nanoparticles and ensure the exposure of active sites, which is crucial to lower the energy barrier toward ORR and substantially enhance the ORR kinetics. Hence, the Pd/Co_(3)O_(4)–N–C nanocompounds exhibited excellent ORR catalytic performance, ideal Pd mass activity, and durability in 0.1 mol L-1KOH solution compared with Co_(3)O_(4)–N–C and Pd/C. The scalable synthesis method, relatively low cost, and excellent electrochemical ORR performance indicated that the obtained Pd/Co_(3)O_(4)–N–C electrocatalyst had the potential for application on fuel cells.
基金financial support of the Spanish Ministry of Economy and Competitiveness under project number MAT2016-78850-Rprovision of beamtime at the P07 beamline of the Petra Ⅲ synchrotron facility under the project I-20170054EC。
文摘The load partitioning between the magnesium and titanium phases in an extruded Mg-15%Ti(vol.%) composite from room temperature up to 300 ℃ using synchrotron radiation diffraction during in-situ compression tests. During compression, the magnesium matrix composite deforms mainly by the activation of the extension twinning system up to 200 ℃. The volume fraction of twins increases with the plastic strain but decrease with the compression temperature. Hard titanium particles bear an additional load transferred by the soft magnesium matrix from room temperature up to 300 ℃. This effect is amplified after yield stress during plastic deformation. Additionally, twins within magnesium grains behaves as an additional reinforcement at low temperature(below 200 ℃) inducing an increase in the work hardening of the composite.
基金supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020the financial support of the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant No.771146 TOUGHIT)funded within the AIT’s strategic research portfolio 2022 and by the European Commission within the framework INTERREG V-A Austria–Czech Republic in the project“ReMaP“(Interreg project no.ATCZ229)。
文摘In recent years,wire-arc directed energy deposition(wa DED),which is also commonly known as wire-arc additive manufacturing(WAAM),has emerged as a promising new fabrication technique for magnesium alloys.The major reason for this is the possibility of producing parts with a complex geometry as well as a fine-grained microstructure.While the process has been shown to be applicable for Mg-Al-Zn alloys,there is still a lack of knowledge in terms of the influence of the WAAM process on the age-hardening response.Consequently,this study deals with the aging response of a WAAM AZ91 alloy.In order to fully understand the mechanisms during aging,first,the as-built condition was analyzed by means of high-energy X-ray diffraction(HEXRD)and scanning electron microscopy.These investigations revealed a finegrained,equiaxed microstructure with adjacent areas of alternating Al content.Subsequently,the difference between single-and double-step aging as well as conventional and direct aging was studied on the as-built WAAM AZ91 alloy for the first time.The aging response during the various heat treatments was monitored via in situ HEXRD experiments.Corroborating electron microscopy and hardness studies were conducted.The results showed that the application of a double-step aging heat treatment at 325℃with pre-aging at 250℃slightly improves the mechanical properties when compared to the single-step heat treatment at 325℃.However,the hardness decreases considerably after the pre-aging step.Thus,aging at lower temperatures is preferable within the investigated temperature range of 250-325℃.Moreover,no significant difference between the conventionally aged and directly aged samples was found.Lastly,the specimens showed enhanced precipitation kinetics during aging as compared to cast samples.This could be attributed to a higher amount of nucleation sites and the particular temperature profile of the solution heat treatment.
文摘Mixed-oxide nanostructures of the type xGd<sub>2</sub>O<sub>3</sub>-(1-x)α-Fe<sub>2</sub>O<sub>3</sub> (x=0.1, 0.3, 0.5 and 0.7) were synthesized by mechanochemical activation for ball milling times of 0, 2, 4, 8 and 12 hours. The systems were subsequently analyzed by Mӧssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The magnetic hyperfine field was studied as function of ball milling time for all sextets involved and found to be consistent with the formation of a limited solid solution in the systems investigated. The end-product was the gadolinium perovskite, represented by a doublet whose abundance was derived as function of the milling time. The XRPD patterns recorded for the equimolar composition were dominated by the diffraction peaks of GdFeO<sub>3</sub> after 12 hours of milling. The hysteresis loops were recorded at 300 and 5 K in an applied magnetic field of 5 T and were interpreted as a superposition of paramagnetic behavior of gadolinium oxide and weak ferromagnetic behavior of hematite and gadolinium perovskite. The Morin transition of hematite was inferred from zero-field-cooling-field-cooling (ZFC-FC) curves measured with a magnetic field of 200 Oe in the 5-300 K temperature range and was found to depend on the ball milling time. Optical diffuse reflectance spectra showed that the compounds were semiconductors with an optical band gap of 2.1 eV.
基金financially supported by the National Natural Science Foundation of China(52372191)the Natural Science Foundation of Xiamen,China(3502Z202372036)+1 种基金the China Postdoctoral Science Foundation(2022TQ0282)the support of the High-Performance Computing Center(HPCC)at Harbin Institute of Technology on first-principles calculations。
文摘It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.
基金Supported by the National Natural Science Foundation of China (No.50082003) and the Provincial Natural Science Foundation of Fujian (No.E0210023).
文摘A novel quadripolymer scale inhibitor poly-maleic anhydride-acrylic acid-acrylamide-sodium methallyl sulfonate(PMAAS)was synthesized by solution polymerization with maleic anhydride(MA),acrylic acid(AA), acrylamide(AM),sodium methallyl sulfonate(SMAS),etc.IR spectrum shows that PMAAS contains carbonyl, hydroxyl,phosphatic and sulfonic acid group.SEM indicates that PMAAS blocks the normal growth of scale CaCO3 and CaSO4 crystals.The influences of PMAAS concentration,Ca 2+ concentration,temperature and pH value of the system on the inhibition efficiency are investigated.The inhibition efficiency of PMAAS is superior to com- mercial inhibitors T-225 and XF-192.
基金Supported by the National Natural Science Foundation of China under Grant No 50364002, and the Tianjin Natural Science Foundation (06YFJMJC02300).
文摘We report a newly found strong disturbing effect orAl addition to the intensity ratios of blue and green emissions from single host full-colour phosphor of Ba3MgSi2-xAlxO8:0.02Eu^2+, 0.1Mn^2+ for near-UV excited white light. The phase-pure silicate phosphor in the size of around 4μm is prepared by salt-assisted spray pyrolysis route, having three-colour emissions at the wavelength peak values of 437nm, 500 nm and 608 nm simultaneously under the excitation of 375 nm. The amount variation orAl ion added to the phosphor host results in a drastic change of the intensity ratio between green and blue emissions, while the intensity of red light keeps unchanged. As a consequence, the combination of three colours lies in the white light region and can be tuned by precisely controlled addition oral content. The Raman spectroscopy verifies the modifying effect oral ion to the tetrahedral network in silicate hosts. We assume that by addition of Al ion, the amount of those two kinds of Eu^2+ substituting for those two kinds of Ba^2+ lattice sites with distinct energy levels of blue and green featured emissions can be adjusted to contribute to diversification of the ratios of blue and green emissions.
基金Project supported by the National Natural Science Foundation of China(Grant No.50771025)
文摘The crystallization, microstructure, and soft magnetic properties of Fe52Co34Hf7B6Cul alloy are studied. Amorphous Fe52Co34Hf7B6Cul alloys are first treated by a pulsed magnetic field with a medium frequency, and then annealed at 100 ℃-400 ℃ for 30 min in a vacuum. The rise in temperature during the treatment by a pulsed magnetic field is measured by a non-contact infrared thermometer. The soft magnetic properties of specimens are measured by a vibrating sample magnetometer (VSM). The microstructure changes of specimens are observed by a MSssbauer spectroscopy and transmission electron microscope (TEM). The results show the medium-frequency pulsating magnetic field will pro- mote nanocrystallization of the amorphous alloy with a lower temperature rise. The nanocrystalline phase is (α-Fe(Co) with bcc crystal structure, and the grain size is about 10 nm. After vacuum annealing at 100 ℃ for 30 min, scattering nanocrystalline phases become more uniform, the coercive force and the saturation magnetization of the specimens are 41.98 A/m and 185.15 emu/g.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374081 and 11004044)the Fundamental Research Funds for the Central Universities+4 种基金China(Grant Nos.N150905001L1509006and N140901001)the Japan Society for the Promotion of Science Postdoctoral Fellowships for Foreign Researchers(Grant No.P10060)the Alexander von Humboldt(Av H)Foundation(Research stipend to L.Li)
文摘The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively in- vestigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented.
基金Supported by the National Natural Science Foundation of China under Grant No 10674074, and the Tianjin Natural Science Foundation under Grant Nos 06TXTJJC14601 and 07JCYBJC06400.
文摘We investigate the influence of precursor molar ratio of [S^2-]/[Zn^2+] on particle size and photoluminescence (PL) of ZnS:Mn^2+ nanocrystMs. By changing the [S^2-]/[Zn^2+] ratio from 0.6 (Zn-rich) to 2.0 (S-rich), the particle size increases from nearly 2. 7nm to about 4.Ohm. The increase in the ratio of [S^2-]/[Zn^2+] cadses a decrease of PL emission intensity of ZnS host while a distinct increase of Mn^2+ emission. The maximum intensity for the luminescence of Mn^2+ emission is observed at the ratio of [S^2-]/[Zn^2+] ≈ 1.5. The possible mechanism for the results is discussed by filling of S^2- vacancies and the increase of Mn^2+ ions incorporated into ZnS lattices.
基金supported by the National High Technology Research and Development Program of China (863 Program) (No. SQ2008AA03Z2470974)the National Natural Science Foundation of China (Nos. 50572030 and 50372022)the Young Talent Program of Fujian Province (No. 2007F3060)
文摘A new 1D coordination polymer [Co(bpp)3Cl2(H2O)2]n 1 (bpp = 1,3-bis(4-pyridyl)-propane) was synthesized and characterized by elemental analysis,IR spectrum and single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system,space group Ibca with a = 16.569(9),b = 17.240(10),c = 27.087(16) ,V = 7738(8) 3,Z = 8,Dc = 1.306 g/cm3,Mr = 760.65,λ(MoKa) = 0.71073 ,μ = 0.623 mm1,F(000) = 3192,the final R = 0.0678 and wR = 0.2011. The Co(II) atom is coordinated in a slightly distorted octahedral CoN4Cl2 geometry by two Cl atoms in the axial positions,four N atoms from the two bridging bpp ligands and two pendant bpp ligands. The CoN4Cl2 octahedra are connected by the bridging bpp ligands to form a 1D neutral coordination polymer chain. The chains are linked by face-to-face π-π interactions between adjacent pendant bpp ligands to give rise to a 3D supramolecular architecture. The photoluminescent investigation indicates that the emission of 1 is attributed to ligand-centered emission. The variable-temperature magnetic susceptibility measurement shows weak antiferromagnetic behavior in the coπmplex.
基金This work was supported by the Natural Science Foundation of Fujian Province (No. E0420001) and the Science Foundation of Huaqiao University (No. 03HZR9)
文摘A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) ?, V = 11711(4) ?3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm?1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I). The crystal structure is composed of [{Cu(en)2}HPW12O40]2? anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions. The anionic [{Cu(en)2}HPW12O40]2? is formed by the mixed valance {HPWVI11WVO40}3? Keggin unit covalently linked by a {Cu(en)2}+ group.
基金supported by the Engineering and Physical Sciences Research Council (EPSRC)。
文摘The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply.Supercapacitors are high-power devices,particularly suitable for public transportation since they can easily store breaking energy due to their high-rate charging ability.Additionally,they can function with two carbon electrodes,which is an advantage due to the abundance of carbon in biomass and other waste materials(i.e.,plastic waste).Newly developed supercapacitive nanocarbons display extremely narrow micropores(<0.8 nm),as it increases drastically the capacitance in aqueous electrolytes.Here,we present a strategy to produce low-cost flexible microporous electrodes with extremely high power density(>100 kW kg^(-1)),using fourty times less activating agent than traditionnal chemically activated carbons.We also demonstrate that the affinity between the carbon and the electrolyte is of paramount importance to maintain rapid ionic diffusion in narrow micropores.Finally,this facile synthesis method shows that low-cost and bio-based free-standing electrode materials with reliable supercapacitive performances can be used in electrochemistry.
基金the National Natural Science Foundation of China(51902072 and 22075062)the Heilongjiang Touyan Team(HITTY-20190033)+2 种基金the Heilongjiang Province“hundred million”project science and technology major special projects(2019ZX09A02)the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology No.2020DX11)the Fundamental Research Funds for the Central Universities(FRFCU5710051922)。
文摘Co-free Li-rich layered oxide cathodes have drawn much attention owing to their low cost and high energy density.Nevertheless,anion oxidation of oxygen leads to oxygen peroxidation during the first charging process,which leads to co-migration of transition metal ions and oxygen vacancies,causing structural instability.In this work,we propose a pre-activation strategy driven by chemical impregnation to modulate the chemical state of surface lattice oxygen,thus regulating the structural and electrochemical properties of the cathodes.In-situ X-ray diffraction confirms that materials based on activated oxygen configuration have higher structural stability.More importantly,this novel efficient strategy endows the cathodes having a lower surface charge transfer barrier and higher Li+transfer kinetics characteristic and ameliorates its inherent issues.The optimized cathode exhibits excellent electrochemical performance:after 300 cycles,high capacity(from 238 m Ah g^(-1)to 193 m Ah g^(-1)at 1 C)and low voltage attenuation(168 mV)are obtained.Overall,this modulated surface lattice oxygen strategy improves the electrochemical activity and structural stability,providing an innovative idea to obtain high-capacity Co-free Li-rich cathodes for next-generation Li-ion batteries.
基金supported by the National Nature Science Foundation of China (Grant Nos.11522221,11372315,11472287,and 51171138)the National Basic Research Program of China (Grant No.2012CB937500)+1 种基金the CAS/SAFEA International Partnership Program for Creative Research Teamspartially also by DFG
文摘A theoretical model that takes into account the flee-volume aided cooperative shearing of shear transformation zones (STZs) is developed to quantitatively understand the ductile-to-brittle transition (DBT) of metallic glasses. The STZ dilatational strain is defined as the ratio of STZ-activated free volume to STZ volume itself. The model demonstrates that the STZ dilatational strain will increase drastically and exceed the characteristic shear strain of STZ as temperature decreases below a critical value. This critical temperature is in good agreement with the experimentally measured DBT temperature. Our results suggest that the DBT of metallic glasses is underpinned by the transition of atomic-cluster motions from STZ-tvpe rearrangements to dilatational processes (termed tension transformation zones (TrZs)).
基金China Scholarship Council for the award of fellowship and funding (No. 201708510113)。
文摘This work reports the influence of alumina fiber reinforcement of an AZ91Nd MMC(metal matrix composite)on the PEO coating formation process in a sodium phosphate-based electrolyte.By comparison with the pure AZ91Nd,the evolution of alumina fiber during the processing and the characteristics of the resultant PEO coating were investigated.The voltage response as a function of processing time was changed.Lower voltage in the presence of alumina fiber is responsible for the lower coating thickness.The morphology and phase composition of the coatings are also influenced by the incorporation of the fiber.Firstly,the fiber is embedded in the coating and interrupts the continuity of the coating.With increasing processing time,the fiber is found to be reactively incorporated in the coating.The intention to produce a MgAl_(2)O_(4)containing coating is achieved and it is mainly accumulated near the coating surface.However,due to the low number of fibers,the Al content is overall still low and only near to the fibers the MgAl_(2)O_(4)spinel phase can form.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10434060 and 10574045)the National Key Basic Research and Development Program of China (Grant No 2006CB921604)+2 种基金the Basic Key Program of Shanghai Municipality(Grant Nos 07JC14017 and 07dz22025)State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics of China (Grant No T152616)State Key Laboratory of Precision Spectroscopy and Department of Education of Zhejiang Province of China (Grant No Y200701718)
文摘This paper studies the isotopic effect of Cl2^+ rovibronic spectra in the A^2Лu (Ω = 1/2)-X^2Лg (Ω = 1/2) system. Based on the experimental results of the molecular constants of ^35Cl2^+, it calculates the vibrational isotope shifts of the (2, 7) and (3, 7) band between the isotopic species ^35C12^+, ^35Cl^37Cl + and ^37Cl2^+, and estimates the rotational constants of both A^2Лu and X^2Лg states for the minor isotopic species ^35Cl^37Cl+ and ^37Cl2^+. The experimental results of the spectrum of 35Cl37Cl-1- (3, 7) band proves the above mentioned theoretical calculation. The molecular constants and thus resultant rovibronic spectrum for ^37Cl2^+ were predicted, which will be helpful for further experimental investigation.
基金the Research Foundation of Science and Technology PlanProject in Liaoning Province of China (Nos.20060623 and 2006402049).
文摘An electrochemical technique has been introduced and applied to fabricate superconducting MgB2 films in molten salts. MgCl2, Mg(BO2)2, NaCl, and KCl were used as electrolyte, graphite was used as the anode, and copper was used as the cathode, respectively. X-ray diffraction (XRD) analysis was chosen to investigate the phase composition and crystallinity of the films at different electrolysis temperatures. Stan- dard four-probe technique and SQUID were applied to investigate the temperature dependence of resistance (R-T) properties and magnetic properties of the films, respectively. The results indicate that MgB2 films have been fabricated on the copper cathodes, and superconducting transition takes place close to 50 K.
基金carried out within the Synchro Load project(BMBF project number 05K16CGA)which is funded by the Röntgen-Angström Cluster(RAC),a bilateral research collaboration of the Swedish government and the German Federal Ministry of Education and Research(BMBF)the project Mg Bone(BMBF project number 05K16CGB)
文摘Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing applications.During the implant preparation process,the material’s surface and microstructure are being changed by stresses induced by machining.Hence degradable metal implants need to be fully characterized in terms of the influence of machining on the resulting microstructure and corrosion performance.In this study,micro-computed tomography(μCT)is used for the quantification of the degradation rate of biodegradable implants.To our best knowledge,for the first time quantitative measures are introduced to describe the degradation homogeneity in 3D.This information enables a prediction in terms of implant stability during the degradation in the body.Two magnesium gadolinium alloys,Mg-5Gd and Mg-10 Gd(all alloy compositions are given in weight%unless otherwise stated),in the shape of M2 headless screws have been investigated for their microstructure and their degradation performance up to 56 days.During the microstructure investigations particular attention was paid to the localized deformation of the alloys,due to the machining process.In vitro immersion testing was performed to assess the degradation performance quantified by subsequent weight loss and volume loss(usingμCT)measurements.Although differences were observed in the degree of screw’s near surface microstructure being influenced from machining,the degradation rates of both materials appeared to be suitable for application in orthopedic implants.From the degradation homogeneity point of view no obvious contrast was detected between both alloys.However,the higher degradation depth ratios between the crests and roots of Mg-5Gd ratios may indicated a less homogeneous degradation of the screws of these alloys on contract to the ones made of Mg-10Gd alloys.Due to its lower degradation rates,its more homogeneous microstructure,its weaker texture and better degradation performance extruded Mg-10Gd emerged more suitable as implant material than Mg-5Gd.
文摘xMoO2-(1-x)α-Fe2O3 nanoparticle system with molarities x = 0.1, 0.3, 0.5 and 0.7 was successfully synthesized by mechanochemical activation of MoO2 and α-Fe2O3 mixtures for 0 - 12 hours of ball milling time. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of the molybdenum dioxide-hematite nanoparticle system under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the crystallite size and lattice parameters as function of milling times and indicated the presence of Mo-substituted hematite and Fe-doped molybdenum dioxide at long milling times. The Mössbauer studies yielded the magnetic hyperfine fields and the relative abundance of a quadrupole-split doublet as function of the milling time for all molar concentrations involved. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in a magnetic field of 200 Oe.