查看更多>>摘要：We report on the structural,magnetic,and magnetocaloric properties of EuRhO3 powders.The oxidation states of Eu and Rh ions were studied using X-ray photoelectron spectroscopy(XPS).It is found that the Eu ions are mainly in the divalent oxidation state while the Rh ions have+4 state.EuRhO3 powders are found to be antiferromagnetic with a second order magnetic transition at Néel temperature(TN=2.9 K).Analysis of the magnetic susceptibility versus temperature data in terms of the Curie-Weiss law:(x=C/(T-θw))for T＞TN,yields θw=-3.1 K and effective magnetic moment μeff exp=7.72 μB,which is close to the theoretical value μeff theo=7.94 μB.The magnetic entropy change(-△SM),was determined by employing the thermodynamic Maxwell's relation.At μ0H=5 T and near TN,(-△SMMax)and relative cooling power(RCP)exhibit large values of 33.7 J/(kg-K)and 238 J/kg,respectively.The large magnitude of-△SM and RCP show that the EuRhO3 compound could be a potential candidate to be used in cryogenic magnetic refrigeration.
查看更多>>摘要：Lithium-sulfur(Li-S)batteries have generated significant attention due to their high theoretical specific capacity and energy density among a host of energy storage power devices.Nevertheless,the lithium polysulfide dissolution shuttle that occurs within Li-S batteries will lead to capacity deterioration and inadequate cycling stability.In the paper,we proposed a measure to deal with the above problems by modifying the separator with Nd2O3/graphene composite in Li-S batteries.Graphene's special chemical properties and structural qualities make it an excellent choice for Li-S batteries.Meanwhile,Nd2O3 has a strong binding affinity with lithium polysulfide due to its low electronegativity,which exhibits Lewis's acidity and forms strong interactions with lithium polysulfide,which is strongly Lewis basic.By utilizing these advantageous properties,Li-S batteries assembling Nd2O3-decorated reduced graphite oxide modified polypropylene separators(Nd2O3/RGO/PP)demonstrate outstanding electrochemical perfor-mance,including a mere 0.0525％capacity attenuation rate under 2C during 1000 cycles and with exceptional rate performance of 614 mAh/g even at 3C.This study presents valuable knowledge for effectively modifying separators using rare earth oxides to incorporate graphene,ultimately promoting the practical application of Li-S batteries.
查看更多>>摘要：We investigated the effect of additional doping with Ce on the ionic conductivity of the Nb-doped Li7La3Zr2O12(LLZO)garnet ceramics using a combination of experimental and modeling approaches.Our results indicate that Ce doping can alter lattice parameters of the LLZNO,leading to the enhanced lithium ionic conductivity.The Ce,Nb co-doped LLZO(LLZNCO)structure with composition Li6.5La3Zr1.5-xNb..5CexO12(x=0.125)exhibits a lower activation energy(Ea=0.39 eV)than Li6.5La3Zr1.5Nb0.5O12(LLZNO)(Ea=0.41 eV).Furthermore,Ce doping leads to an increase in Li+con-ductivity from 6.4 × 10-4 to 7 × 10-4 S/cm at room temperature.In addition,we discuss the diffusivity and conductivity of our samples using ab initio molecular dynamics simulations and propose possible mechanisms to explain the enhanced Li-ion conductivity caused by co-doping with Ce and Nb.Our re-sults demonstrate that the LLZNCO ceramics are promising candidates for potential solid-state electro-lytes for Li-ion batteries.
查看更多>>摘要：Lead-free ferroelectric ceramics,0.67Bi1-xEuxFeO3-0.33BaTiO3(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction.The effect of Eu3+doping on the microstructure,dielectric properties,ferro-electric 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 Eu3+reduces the Fe2+content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d33*)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(Tc)of 414 ℃.The unipolar strain and d33*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.
Laura KhudayshInas A.AhmedSyeda Rabia EjazSajjad Ahmad Khan...
1755-1763页
查看更多>>摘要：Spinel ferrites exhibit exceptional magnetic properties,making them a distinctive class of magnetic materials.The sol-gel technique was utilized for the synthesis of spinel ferrites with the chemical for-mula Co0.6Sr0.4CexFe2-xO4.Following that,a comprehensive X-ray diffraction analysis unveiled the crystalline cubic structure of the synthesized materials.Through the utilization of the M-H loop approach,the ferromagnetic attributes of ferrites were assessed,and the assimilation of rare earth el-ements led to substantial enhancements in saturation magnetization,remanence,and coercivity.Spinel ferrites with a high concentration of rare earth elements have improved direct current resistivity and activation energy.The logarithm of a material's resistance increased from 5.29 to 8.12 Q·cm as cerium is added.With a change in the amount of cerium,the activation energy goes up from 0.19 to 0.29.By changing the frequency from 5.5 to 9.5 GHz,the dielectric characteristics were determined.As the fre-quency goes up,the dielectric constant goes down.Spinel ferrites that have been made better in every way can be used in high-frequency applications.
查看更多>>摘要：The recovery of yttrium is proposed by applying a solid-liquid extraction process using di-2-ethyl hexylphosphoric acid(D2EHPA)as extracting agent.The extracting agents were supported on a macro porous polymeric resin XAD-7(solid phase).Yttrium ions extraction and discharge tests were performed,firstly from a synthetic aqueous solution of 100 mg/L Y(liquid phase)at 25 ℃ with stirring.The effects of pH of aqueous solutions bearing yttrium,volume fraction of extracting agents and the solid/liquid(S/L)ratio on the yttrium recovery were studied.The most favorable conditions for yttrium ions extraction are:20 vol％D2EHPA functionalized resin,pH=1.5 and an S/L ratio of 10 mg/mL.The discharge of yttrium ions was done under the same conditions of extraction stage,using a 2 mol/L[H2SO4]as stripping so-lution.Up to 80％yttrium is extracted,while 75％yttrium is recovered in the striping solution.In all experiments,the reaction equilibrium is reached after 20 min,and the kinetics for the extraction stage was determined as a second-order model.Also,experiments were carried out to discharge the yttrium-loaded resins,and it has been determined that the best pH value to strip the Y ions is 1.5.Cyclic tests of extraction and discharge for yttrium ions show that the functionalized resin can work at least five cycles without decreasing its efficiency.Finally,the proposed process was tested in a real solution with Y ions from a waste fluorescent lamp powder leached in H2SO4,demonstrating the ability to effectively recover yttrium,separating it from various metals from the studied residue.
查看更多>>摘要：Viewing the problem of high energy consumption in the process of recovering rare earths from rare earth molten salt electrolysis slag,an environmentally friendly and low carbon process by sub-molten salt decomposition was developed.The thermodynamic analysis of sub-molten salt reaction indicates that the recovery of rare earths from the slag using sub-molten salt medium is thermodynamically feasible.In this process,the rare earth fluoride and lithium in the slag are almost transformed into rare earth hy-droxide,sodium fluoride and lithium hydroxide,fluorine and lithium are transferred into the washing solution,and the rare earths in the residues can be leached into solution by acid leaching.Under the optimum reaction conditions of reaction temperature 200 ℃,reaction time 3 h,NaOH initial concen-tration 80％,NaOH-Slag mass ratio 3:1,the leaching efficiency of rare earths,fluorine and lithium can reach to 99.05％,98.23％and 99.22％.After evaporation,the fluorine and lithium in the washing solution can be obtained in the forms of sodium fluoride and lithium fluoride,the recovery efficiency reach 95.5％and 92.8％,respectively.The RE oxides(99.53％)can be obtained from the leaching solution after pre-cipitation and roasting.
查看更多>>摘要：In the process of extracting ion-absorbed rare earth ore(IREO),the production of radioactive waste is a major environmental concern.To address this issue,MoS2 was used to modify ion-absorbed rare earth tailings(RET)to synthesize a novel MoS2@RET composite material for the effective handling of radio-active waste generated in IREO separation industry.The composite material was thoroughly character-ized using various analytical techniques,including X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),thermogravimetry(TG),Fourier-transform infrared(FTIR),scanning electron mi-croscopy(SEM),Brunauer-Emmett-Teller(BET)and energy dispersive spectroscopy(EDS).By optimizing the operating parameters,the optimal experimental conditions were determined to be pH=3,contact time=60 min,liquid-solid ratio=6 g/L,and initial concentration=150 mg/L The adsorption data fitted well with the pseudo second-order rate model.The thermodynamic parameters concerning the adsorption of Th(Ⅳ)were analyzed and computed.Langmuir isotherm model is a more fitting choice for the adsorption process compared to the Freundlich isotherm model.MoS2@RET was used in the acid leachate of IREO waste residue,achieving the separation of Th and rare earth successfully.The mecha-nism of Th(Ⅳ)adsorption by MoS2@RET was investigated,revealing that the adsorption process involves electrostatic interactions,chemical bonding,and redox reactions.The above research results indicate that MoS2@RET composite materials have application potential in the sustainable treatment of IREO radio-active waste.
查看更多>>摘要：The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)imaging and first-principles calculations of density-functional theory.Eleven possible interfacial models were constructed according to the different terminations of the LPSO phase,and the corre-sponding interfacial energies were calculated,from which the four most stable structures(Ter1-MgY-hollow,Ter2-Zn-hollow,Ter3-MgYⅡ-hollow and Ter4-Mg-bridge)were obtained.The interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations,and the most stable interfacial structure was evaluated.Ter1-MgY-hollow and Ter2-Zn-hollow have the lowest interfacial energies in the range of-0.7 eV＜△µY＜-0.6 eV,where fluctuating change of state is the minimized and the interface is the most stable.The separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the interface.The calculation results show that the maximum interfacial separation work is 1.45 J/m2 for the interface model of a-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.
查看更多>>摘要：Rare earth elements and transition metals have been found to improve the hydrogen storage charac-teristics of magnesium-based alloys.This study investigated the Mg-Ho-Fe(MHF)ternary alloy prepared using the vacuum induction melting technique.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),pressure-composition-temperature(PCT),and differ-ential scanning calorimetry(DSC)were used to analyze the alloy's phase transitions,microstructure,thermodynamics,and kinetic properties.The results reveal that the Mg98Ho1.5Fe0.5 alloy forms a solid solution with Ho and Fe in the magnesium matrix.Upon hydrogen absorption,the activated alloy transforms into a mixture of Mg/MgH2 phases and nanoscale HoH2 phases.Notably,only the MgH2 phase decomposes during hydrogen desorption,while the HoH2 phase remains unchanged,exhibiting a pos-itive catalytic effect.The alloy demonstrates excellent hydrogen absorption kinetics,achieving a capacity of 5.56 wt％H2 within 10 min at 360 ℃,owing to the combined catalytic effects of Ho and Fe.The activation energy for hydrogen desorption is found to be 135.87 kJ/mol,which is lower than that of the activation energies of pure MgH2 and MgFe alloys,indicating an enhancement in desorption kinetics.Moreover,the enthalpy and entropy changes for hydrogen absorption and desorption are determined to be-70.51 kJ/mol H2,-125.62 J/(K·mol)H2,72.83 kJ/mol H2,and 128.95 J/(K·mol)H2,respectively.Furthermore,it is worth noting that the thermodynamic properties of the alloy are improved due to the catalytic effect of Ho and Fe.
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