By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model f...By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-ΣXiC multicomponent structural steels(Xi=Mn,Si,Mo,Cr,Ni or Ti,etc)was suggested.The comparison of the calculated Ae3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square(RMS)error between them are only 0.71% and 8.92 K,respectively.However,the deviations between the same measured data and the values calculated from the superelement model are as high as 1.86% and 23.83 K,respectively.It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated Ae3 temperatures are in good agreement with the experimental data.展开更多
As rolled microstructure and mechanical properties of a new kind of grain boundary allotriomorphic ferrite/granular bainite duplex steel plate and its crack propagation behavior were investigated in comparison with s...As rolled microstructure and mechanical properties of a new kind of grain boundary allotriomorphic ferrite/granular bainite duplex steel plate and its crack propagation behavior were investigated in comparison with simple granular bainitic steel plate. These new duplex plate steels possess better combination of strength and toughness than granular bainite plate steels under the conditions of conventional rolling and air cooling. The observation of fatigue crack propagation behaviors showed that the existence of proper grain boundary allotriomorphic ferrite increases the compatible deformation ability of duplex microstructure and leads to the formation of crack branching and curving route, and it has an evidently blunting effect on microcrack tip and results in higher impact toughness. In addition, the new duplex steel plate also has good weldability as hot rolled high strength low alloy structural steel.展开更多
The accurate establishment of a ferrite transformation start temperature model is crucial to design a reasonable controlled rolling process and ensure uniform microstructure in aluminum bearing dual-phase steel.The me...The accurate establishment of a ferrite transformation start temperature model is crucial to design a reasonable controlled rolling process and ensure uniform microstructure in aluminum bearing dual-phase steel.The measurements of the expansion-temperature curves of aluminum bearing dual-phase steel under continuous cooling and isothermal conditions are presented,utilizing a dynamic transformation dilatometer experiment.Based on these expansion-temperature curves,the start temperature and incubation time of ferrite transformation were determined,elucidating the influence of process parameters on both the incubation time and the start temperature of ferrite transformation.By integrating metallurgical principles with measured incubation time of ferrite transformation,and considering the effects of temperature and strain,a fitting model for the variation in volume free energy during ferrite nucleation was derived.Building upon this foundation,a high-precision incubation time of ferrite transformation mathematical model for the experimental steel was established.To more accurately calculate the start temperature of ferrite transformation under continuous cooling conditions,the Scheil’s additivity rule was modified to account for the effects of deformation and cooling rate.The results indicate that the modification coefficient decreases with increasing the cooling rate and strain,thereby significantly improving the accuracy of calculating the starting temperature of ferrite transformation using the modified additivity rule.展开更多
To realize the application of electromagnetic wave absorption(EWA)devices in humid marine environments,bifunctional EWA materials with better EWA capacities and anticorrosion properties have great exploration signific...To realize the application of electromagnetic wave absorption(EWA)devices in humid marine environments,bifunctional EWA materials with better EWA capacities and anticorrosion properties have great exploration significance and systematic research re-quirements.By utilizing the low-cost and excellent magnetic and stable chemical characteristics of barium ferrite(BaFe_(12)O_(19))and using the high dielectric loss and excellent chemical inertia of nanocarbon clusters,a new type of nanocomposites with carbon nanoclusters en-capsulating BaFe_(12)O_(19)was designed and synthesized by combining an impregnation method and a high-temperature calcination strategy.Furthermore,Ce-Mn ions were introduced into the BaFe_(12)O_(19)lattice to improve the dielectric and magnetic properties of BaFe_(12)O_(19)cores significantly,and the energy band structure of the doped lattice and the orders of Ce replacing Fe sites were calculated.Benefiting from Ce-Mn ion doping and carbon nanocluster encapsulation,the composite material exhibited excellent dual functionality of corrosion resist-ance and EWA.When BaCe_(0.2)Mn_(0.3)Fe_(11.5)O_(19)-C(BCM-C)was calcined at 600°C,the minimum reflection loss of-20.1 dB was achieved at 14.43 GHz.The Ku band’s effective absorption bandwidth of 4.25 GHz was achieved at an absorber thickness of only 1.3 mm.The BCM-C/polydimethylsiloxane coating had excellent corrosion resistance in the simulated marine environment(3.5wt%NaCl solution).The|Z|0.01Hz value of BCM-C remained at 106Ω·cm^(2)after 12 soaking days.The successful preparation of the BaFe_(12)O_(19)composite en-capsulated with carbon nanoclusters provides new insights into the preparation of multifunctional absorbent materials and the fabrication of absorbent devices applied in humid marine environments in the future.展开更多
In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The ...In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The microstructure and solidification kinetics of the two as-cast grades were in situ observed by high temperature confocal laser scanning microscopy(HT-CLSM).There are significant differences in the as-cast microstructures of the two 316L stainless steel compositions.In L-316L steel,ferrite morphology appears as the short rods with a ferrite content of 6.98%,forming a dual-phase microstructure consisting of austenite and ferrite.Conversely,in H-316L steel,the ferrite appears as discontinuous network structures with a content of 4.41%,forming a microstructure composed of austenite and sigma(σ)phase.The alloying elements in H-316L steel exhibit a complex distribution,with Ni and Mo enriching at the austenite grain boundaries.HT-CLSM experiments provide the real-time observation of the solidification processes of both 316L specimens and reveal distinct solidification modes:L-316L steel solidifies in an FA mode,whereas H-316L steel solidifies in an AF mode.These differences result in ferrite and austenite predominantly serving as the nucleation and growth phases,respectively.The solidification mode observed by experiments is similar to the thermodynamic calculation results.The L-316L steel solidified in the FA mode and showed minimal element segregation,which lead to a direct transformation of ferrite to austenite phase(δ→γ)during phase transformation after solidification.Besides,the H-316L steel solidified in the AF mode and showed severe element segregation,which lead to Mo enrichment at grain boundaries and transformation of ferrite into sigma and austenite phases through the eutectoid reaction(δ→σ+γ).展开更多
High-entropy design is attracting growing interest as it offers unique structures and unprecedented application potential for ma-terials.In this article,a novel high-entropy ferrite(CoNi)_(x/2)(CuZnAl)_((1-x)/3)Fe_(2)...High-entropy design is attracting growing interest as it offers unique structures and unprecedented application potential for ma-terials.In this article,a novel high-entropy ferrite(CoNi)_(x/2)(CuZnAl)_((1-x)/3)Fe_(2)O_(4)(x=0.25,0.34,0.40,0.50)with a single spinel phase of space group Fd3m was successfully developed by the solid-state reaction method.By tuning the Co-Ni content,the magnetic properties of the material,especially the coercivity,changed regularly,and the microwave absorption properties were improved.In particular,the ef-fective absorption bandwidth of the material increased from 4.8 to 7.2 GHz,and the matched thickness decreased from 3.9 to 2.3 mm,while the minimum reflection loss remained below-20 dB.This study provides a practical method for modifying the properties of fer-rites used to absorb electromagnetic waves.展开更多
W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high...W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high-temperature resistance,and excellent chemical stability.However,the poor dielectric loss of magnetic ferrites hampers their utilization,hindering enhancement in their EMW-absorption performance.Developing efficient strategies that improve the EMW-absorption performance of ferrite is highly desired but re-mains challenging.Here,an efficient strategy substituting Ba^(2+)with rare earth La^(3+)in W-type ferrite was proposed for the preparation of novel La-substituted ferrites(Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)).The influences of La^(3+)substitution on ferrites’EMW-absorption performance and the dissipative mechanism toward EMW were systematically explored and discussed.La^(3+)efficiently induced lattice defects,enhanced defect-induced polarization,and slightly reduced the ferrites’bandgap,enhancing the dielectric properties of the ferrites.La^(3+)also enhanced the ferromagnetic resonance loss and strengthened magnetic properties.These effects considerably improved the EMW-absorption perform-ance of Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)compared with pure W-type ferrites.When x=0.2,the best EMW-absorption performance was achieved with a minimum reflection loss of-55.6 dB and effective absorption bandwidth(EAB)of 3.44 GHz.展开更多
With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance elec...With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.展开更多
Calcium ferrite(CF)is recognized as a potential green and efficient functional material because of its advantages of magnetism,electrochemistry,catalysis,and biocompatibility in the fields of materials chemistry,envir...Calcium ferrite(CF)is recognized as a potential green and efficient functional material because of its advantages of magnetism,electrochemistry,catalysis,and biocompatibility in the fields of materials chemistry,environmental engineering,and biomedicine.There-fore,the obtained research results need to be systematically summarized,and new perspectives on CF and its composite materials need to be analyzed.Based on the presented studies of CF and its composite materials,the types and structures of the crystal are summarized.In addition,the current application technologies and theoretical mechanisms with various properties in different fields are elucidated.Moreover,the various preparation methods of CF and its composite materials are elaborated in detail.Most importantly,the advantages and disadvantages of the synthesis methods of CF and its composite materials are discussed,and the existing problems and emerging challenges in practical production are identified.Furthermore,the key future research directions of CF and its composite materials have been prospected from the potential application technologies to provide references for its synthesis and efficient utilization.展开更多
Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultane...Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultaneously promotes the formation of coarse ferrite and expands the two-phase(α+γ)intercritical temperature range.Thus,increasing the Al content for higher weight reduction inevitably leads to ferrite formation and impedes further strengthening.To achieve both high strength and duc-tility while incorporating ferrite,it is crucial to elucidate the effects of ferrite fraction,size,and dis-tribution on mechanical properties and deformation behavior,particularly in relation to phase interac-tions.In this study,three model steels were developed through controlled annealing temperatures,pro-ducing distinct triplex microstructures comprising ferrite,martensite,and retained austenite(RA).The role of each phase in strain partitioning was investigated using ex-situ microscopic digital image cor-relation and electron back-scattered diffraction analysis.Key findings reveal that the martensitic matrix ensures an ultrahigh strength level(1758 MPa),while a moderate fraction(∼17%)and homogeneous dis-tribution of intercritical-ferrite(IC-ferrite)enable sustainable strain-hardening behavior by delaying the transformation-induced plasticity(TRIP)effect.Strain partitioning into IC-ferrite reduces local strains in the martensitic matrix,preventing early exhaustion of the TRIP effect and facilitating ductile fracture behavior.This strategy leverages the presence of ferrite,offering significant advantages for applications requiring both ultrahigh strength and ductility.展开更多
The substantial influences of Mo contents varying from 0 to 0.26 and 0.50 wt.%on the microstructural evolution and MX(M=Nb,V and Mo;X=C and N)precipitation characteristics of Nb–V–N microalloyed steels processed by ...The substantial influences of Mo contents varying from 0 to 0.26 and 0.50 wt.%on the microstructural evolution and MX(M=Nb,V and Mo;X=C and N)precipitation characteristics of Nb–V–N microalloyed steels processed by hot deformation and continuous cooling were studied using a Gleeble 3800 thermomechanical simulator.Metallographic analysis showed that the ferrite microstructure transformed from polygonal ferrite(PF)in 0Mo steel to both acicular ferrite(AF)and PF in 0.26Mo and 0.50Mo steels,and AF content first increased and then decreased.The thermodynamic calculations and the experimental results proved that the quantity of solid solution of Mo in austenite obviously increased,which reduced the austenite(γ)to ferrite(α)transformation temperature,consequently promoting AF formation in 0.26Mo steel and bainite transformation in 0.50Mo steel.Moreover,the submicron Nb-rich MX particles that precipitated at the temperature of the austenite region further induced AF heterogeneous nucleation with an orientation relationship of(100)_(MX)//(100)_(Ferrite)and[■][001]Ferrite.The interphase precipitation of the nanosized V-rich MX particles with Mo partitioning that precipitated duringγ→αtransformation exhibited a Baker–Nutting orientation relationship of(100)_(MX)//(100)Ferrite and[001]_(MX)//[■]_(Ferrite)with respect to the ferrite matrix.With increasing Mo content from 0 to 0.26 and 0.50 wt.%,the sheet spacing decreased from 46.9–49.0 to 34.6–38.6 and 25.7–28.0 nm,respectively,which evidently hindered dislocation movement and greatly enhanced precipitation strengthening.Furthermore,facilitating AF formation and interphase precipitation was beneficial to improving steel properties,and the optimal Mo content was 0.26 wt.%.展开更多
The phase volume fraction has an important role in the match of the strength and plasticity of dual phase steel.The different bainite contents(18–53 vol.%)in polygonal ferrite and bainite(PF+B)dual phase steel were o...The phase volume fraction has an important role in the match of the strength and plasticity of dual phase steel.The different bainite contents(18–53 vol.%)in polygonal ferrite and bainite(PF+B)dual phase steel were obtained by controlling the relaxation finish temperature during the rolling process.The effect of bainite volume fraction on the tensile deformability was systematically investigated via experiments and crystal plasticity finite element model(CPFEM)simulation.The experimental results showed that the steel showed optimal strain hardenability and strength–plasticity matching when the bainite reached 35%.The 3D-CPFEM models with the same grain size and texture characters were established to clarify the influence of stress/strain distribution on PF+B dual phase steel with different bainite contents.The simulation results indicated that an appropriate increase in the bainite content(18%–35%)did not affect the interphase strain difference,but increased the stress distribution in both phases,as a result of enhancing the coordinated deformability of two phases and improving the strength–plasticity matching.When the bainite content increased to 53%,the stress/strain difference between the two phases was greatly increased,and plastic damage between the two phases was caused by the reduction of the coordinated deformability.展开更多
The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic si...The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic simulations, we investigate recently synthesized ultrathin perovskite bismuth ferrite(BFO) films. Our numerical results reveal that, at the monolayer limit, the ferroelectricity of BFO is missing because the octahedral distortions are constrained. However, the monolayer bismuth ferrite is a topological antiferromagnetic metal with tunable bimeron magnetic structure. The dual topologically non-trivial characteristics make monolayer bismuth ferrite a multifunctional building block in future spintronic devices.展开更多
Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs...Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs.In this paper,the citrate-nitrate auto-combustion method was applied for the formation of Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4);(0≤x≤0.1;step 0.02)(CZNL)nanoferrites.Although the substitution process entails the replacement of a small ion with a larger one,the lattice constant and crystallite size does not exhibit a consistent incremental pattern.This behavior is justified and discussed.The size of all the CZNL ferrite nanoparticles is in the range of 8-12 nm,and the lattice constant is in the range of 8.6230 to 8.4865 nm.The morphological analysis conducted using field emission-scanning electron microscopy(FE-SEM)reveals that the CZNL exhibits agglomerated spherical morphology.The energy dispersive X-ray spectrameter(EDAX)analysis was employed to confirm the elemental composition of CZNL nanoferrites.Since the process entails the substitution of Fe^(3+)magnetic ions with nonmagnetic ions La^(3+),the magnetic parameters of CZNL nanoferrites show a general decreasing trend as predicted.At 20 K,saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x=0.0-41.295 emu/g at x=0.1,the smallest value of 37.87 emu/g is recorded at x=0.06.the highest coercivity(H_(c)=125.9 Oe)and remanence(M_(r)=13.32 emu/g)are recorded for x=0.08 and x=0.04 nanoferrite,respectvely.The band gap of all the CZNL nanoferrites was determined using the Kubelka-Munk function and Tauc plot for direct permitted transitions.La doping modifies the band gap(within 1.86-1.75 eV),increases light absorption,induces efficient e/h separation and charge migration to Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4)surfaces.The nanoferrite Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)achieves a degradation efficiency of 97.3%for methylene blue(MB)dye removal after just 60 min.After five recycling processes,the nanocatalyst Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)is degraded by 95.83%,resulting in a negligible1.51%decrease in photocatalytic activity efficiency.The new Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)has exceptional photocatalytic activity and remarkable stability,making it a promising candidate for applications in wastewater treatment.展开更多
Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.I...Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.In this study,a nonisothermal crystallization thermodynamics behavior of C-F-xA and C-F-xM systems was examined using differential scanning calorimetry,and a phase identification and microstructure analysis for C-F-xA and C-F-xM systems were carried out by X-ray diffraction and scanning electron microscopy.Results showed that in C-F-2A and C-F-2M systems,the increased cooling rates promoted the precipitation of CaFe_(2)O_(4)(CF)but inhibited the formation of Ca_(2)Fe_(2)O_(5)(C2F).In addition,C-F-2A system exhibited a lower theoretical initial crystallization temperature(1566 K)compared to the C-F system(1578 K).This temperature further decreases to 1554 K and 1528 K in the C-F-4A and C-F-8A systems,respectively.However,in C-F-xM system,the increased MgO content raised the crystallization temperature.This is because that the enhanced precipitation of MF(a spinel phase mainly comprised Fe_(3)O_(4)and MgFe_(2)O_(4))and C2F phases suppressed the CF precipitation reaction.In kinetic calculations,the Ozawa method revealed the apparent activation energies of the C-F-2A and C-F-2M systems.Malek's method revealed that the crystallization process in C-F-2A system initially followed a logarithmic law(lnαor lnα2),later transitioning to a reaction order law((1-α)-1or(1-α)^(-1/2),n=2/3)or the lnα2function of the exponential law.In C-F-2M system,it consistently followed the sequencef(α)=(1-α)^(2)(αis the crystallization conversion rate;n is the Avrami constant;?(α)is the differential equations for the model function of C_(2)F and CF crystallization processes).展开更多
The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications ...The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz.In this study,we prepared Z-type Ba_(3)Co_(1.6−x)Zn_(x)Cu_(0.4)Fe_(24)O_(41)hexaferrites using the sol-gel auto-combustion method.By changing the ratio of Co and Zn ions,the magnetocrystalline anisotropy of ferrite is further ma-nipulated,resulting in significant changes in their magnetic resonance frequency and intensity.Ba_(3)Zn_(1.6)Cu_(0.4)Fe_(24)O_(41)with high-frequency resonance achieved the lowest reflectivity of−72.18 dB at 15.56 GHz,while Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)with stronger loss obtained the widest bandwidth of 4.93 GHz(6.14-11.07).Additionally,we investigated surface wave suppression properties previously overlooked.Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)can achieve a larger attenuation at low frequency under low thickness,which has an excellent effect on reducing backscattering.This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.展开更多
The present work reports the structural,optical,dielectric,and electrical properties of Eu-Er substituted M-type Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19)(x=0.0.05,0.1,0.15,and 0.2)hexaferrites synthesized by sol-g...The present work reports the structural,optical,dielectric,and electrical properties of Eu-Er substituted M-type Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19)(x=0.0.05,0.1,0.15,and 0.2)hexaferrites synthesized by sol-gel combustion method.The hexagonal structure of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples was confirmed from X-ray diffraction(XRD)analysis.The values of lattice parameters of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19)samples are increased as compared to Ba_(0.5)Sr_(0.5)Fe_(12)O_(19) sample.This increase in the value of lattice parameters is attributed to the substitution of larger cations(Eu^(3+)and Er^(3+))in place of smaller cations(Fe^(3+)ions).The crystallite sizes of the Ba0.5Sr0.5EuxErxFe12-2x019 samples also increase due to the substitution of larger cations.The force constants(K_o and K_t)increases with increasing Eu-Er concentration.The octahedral cluster shifts towards the higher wavenumber side whereas the tetrahedral cluster shifts towards the lower wavenumber side due to Eu-Er substitution in the Fourier transform infrared(FTIR)spectra.The photoluminescence(PL)emission spectra for the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples are observed at 365 nm.The dielectric dispersion in the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples can be understood by Koop's theory and Maxwell-Wagner type of inte rfacial polarization.Using Jonscher's power law and the co rrelated barrier hopping(CBH)model,the frequency and temperature-dependent be haviour of ac conductivity of Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples are described.The temperature-dependent behaviour of the dc conductivity of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples is explained by the variable range hopping(VRH)model.The Motto temperature of the sample varies from 4.55×10^(9) to 2.31×10^(8) K.The estimated maximum barrier height(WM)of the compound varies from 0.6603 to 0.1199 eV.The temperature coefficient and activation energy of the samples were also calculated as a function of Eu-Er concentration.展开更多
Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406...Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406Å,while crystallite sizes were estimated to range between 55.20 and 31.40 nm using the Scherrer method.The different functional groups were found to correlate with various ab-sorption bands using Fourier transform infrared(FTIR)spectroscopy.Five active modes were identified by Raman spectroscopy,reveal-ing vibration modes of O2-ions at tetrahedral and octahedral locations.The ferromagnetic hysteresis loop was observed in all the synthes-ized samples,which can be explained by Neel’s model.The results showed that AC conductivity decreased with increasing Mn^(2+)content at the Fe^(2+)site,while the dielectric constant and dielectric loss increased with increasing frequency.Furthermore,the saturation magnetiz-ation(Ms),remnant magnetization(M_(r)),and coercivity(H_(c))all showed declining trends with the increase in Mn^(2+)doping.Finally,the CoMn_(0.20)Fe_(1.8)O_(4) samples showed Ms and M_(r) values ranging from 73.12 to 66.84 emu/g and from 37.77 to 51.89 emu/g,respectively,while Hc values ranged from 1939 to 1312 Oe,after which coercivity increased.Thus,the CoMn_(0.20)Fe_(1.8)O_(4) sample can be considered a prom-ising candidate for magnetic applications.展开更多
Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversio...Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversion.The incorporation of rare earth metal ferrites into heterojunction photocatalytic systems enhances light absorption,charge separation and photocatalytic efficiency.This review comprehensively discusses some common types of rare earth metal ferrites such as LaFeO_(3),GdFeO_(3),SmFeO_(3),PrFeO_(3)and CeFeO_(3)and their properties as photocatalysts.The photocatalytic pollutants removal and energy conversion mechanisms are discussed in detail and various types of heterojunctions reported in literature based on rare earth metal ferrites and their synthetic routes are also explored.The recent key findings and advances in the heterojunctions based on these rare earth metal ferrites for the pollutants removal and energy conversion applications are summarized.Despite notable progress in enhancing photocatalytic efficiency and stability,several challenges remain.Current research highlights improvements in material synthesis and performance,but issues such as high production costs,scalable synthesis and limited long-term stability persist.Future directions should focus on exploring uncharted applications,novel material combinations and enhancing the practical implementation of these heterojunctions to fully exploit their potential in environmental and energy technologies.展开更多
Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorp...Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorption properties has not been thoroughly investigated.In this study,based on ferrites,we controlled the micros tructural morphology by doping with light rare earth element Nd,and then formed heterogeneous structures through composite polypyrrole to enhance its performance.The structural changes in neodymium-doped ferrites and their corresponding variations in performance were systematically analyzed.The results indicate that Nd^(3+)ions doping has a pronounced effect on the microstructure of ferrites,significantly improving their dielectric loss capability for electromagnetic waves.The sample with optimal performance,Sr_(0.75)Nd_(0.25)Co_(2)Fe_(16)O_(27)@PPy,has a value of minimum reflection loss that can reach-63.11 dB,and the effective absorption bandwidth achieves 6.40 GHz at2.27 mm.This study provides instructive thinking for the structural manipulation of MA materials.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50075053)
文摘By introducing aparameter of difference in ferrite formation temperature between binary Fe-C and multicomponent system,and referring to the thermodynamic model for Fe-C binary system,a simplified thermodynamic model for pro-eutectoid ferrite formation in Fe-ΣXiC multicomponent structural steels(Xi=Mn,Si,Mo,Cr,Ni or Ti,etc)was suggested.The comparison of the calculated Ae3 temperatures with the measured data of steels 42 shows that the relative standard deviation and root-mean-square(RMS)error between them are only 0.71% and 8.92 K,respectively.However,the deviations between the same measured data and the values calculated from the superelement model are as high as 1.86% and 23.83 K,respectively.It can be concluded that the simplified thermodynamic model for pro-eutectoid ferrite formation in multicomponent structural steels is acceptable and the calculated Ae3 temperatures are in good agreement with the experimental data.
基金Item Sponsored by National Natural Science Foundation of China(50075053)
文摘As rolled microstructure and mechanical properties of a new kind of grain boundary allotriomorphic ferrite/granular bainite duplex steel plate and its crack propagation behavior were investigated in comparison with simple granular bainitic steel plate. These new duplex plate steels possess better combination of strength and toughness than granular bainite plate steels under the conditions of conventional rolling and air cooling. The observation of fatigue crack propagation behaviors showed that the existence of proper grain boundary allotriomorphic ferrite increases the compatible deformation ability of duplex microstructure and leads to the formation of crack branching and curving route, and it has an evidently blunting effect on microcrack tip and results in higher impact toughness. In addition, the new duplex steel plate also has good weldability as hot rolled high strength low alloy structural steel.
基金supported by the National Science and Technology Major Project-Intelligent Manufacturing Systems And Robots(2025ZD1602200)the National Key Research and Development Program of China(Grant No.2022YFB3304800).
文摘The accurate establishment of a ferrite transformation start temperature model is crucial to design a reasonable controlled rolling process and ensure uniform microstructure in aluminum bearing dual-phase steel.The measurements of the expansion-temperature curves of aluminum bearing dual-phase steel under continuous cooling and isothermal conditions are presented,utilizing a dynamic transformation dilatometer experiment.Based on these expansion-temperature curves,the start temperature and incubation time of ferrite transformation were determined,elucidating the influence of process parameters on both the incubation time and the start temperature of ferrite transformation.By integrating metallurgical principles with measured incubation time of ferrite transformation,and considering the effects of temperature and strain,a fitting model for the variation in volume free energy during ferrite nucleation was derived.Building upon this foundation,a high-precision incubation time of ferrite transformation mathematical model for the experimental steel was established.To more accurately calculate the start temperature of ferrite transformation under continuous cooling conditions,the Scheil’s additivity rule was modified to account for the effects of deformation and cooling rate.The results indicate that the modification coefficient decreases with increasing the cooling rate and strain,thereby significantly improving the accuracy of calculating the starting temperature of ferrite transformation using the modified additivity rule.
基金supported by the National Key R&D Program of China(Nos.2022YFB3504804 and 2023YFF0718303)the National Natural Science Foundation of China(Nos.51871219,52071324,52031014,and 52401255)+1 种基金Science and Technology Project of Shenyang City(No.22-101-0-27)Liaoning Institute of Science and Technology Doctoral Initiation Fund Project(No.2307B19).
文摘To realize the application of electromagnetic wave absorption(EWA)devices in humid marine environments,bifunctional EWA materials with better EWA capacities and anticorrosion properties have great exploration significance and systematic research re-quirements.By utilizing the low-cost and excellent magnetic and stable chemical characteristics of barium ferrite(BaFe_(12)O_(19))and using the high dielectric loss and excellent chemical inertia of nanocarbon clusters,a new type of nanocomposites with carbon nanoclusters en-capsulating BaFe_(12)O_(19)was designed and synthesized by combining an impregnation method and a high-temperature calcination strategy.Furthermore,Ce-Mn ions were introduced into the BaFe_(12)O_(19)lattice to improve the dielectric and magnetic properties of BaFe_(12)O_(19)cores significantly,and the energy band structure of the doped lattice and the orders of Ce replacing Fe sites were calculated.Benefiting from Ce-Mn ion doping and carbon nanocluster encapsulation,the composite material exhibited excellent dual functionality of corrosion resist-ance and EWA.When BaCe_(0.2)Mn_(0.3)Fe_(11.5)O_(19)-C(BCM-C)was calcined at 600°C,the minimum reflection loss of-20.1 dB was achieved at 14.43 GHz.The Ku band’s effective absorption bandwidth of 4.25 GHz was achieved at an absorber thickness of only 1.3 mm.The BCM-C/polydimethylsiloxane coating had excellent corrosion resistance in the simulated marine environment(3.5wt%NaCl solution).The|Z|0.01Hz value of BCM-C remained at 106Ω·cm^(2)after 12 soaking days.The successful preparation of the BaFe_(12)O_(19)composite en-capsulated with carbon nanoclusters provides new insights into the preparation of multifunctional absorbent materials and the fabrication of absorbent devices applied in humid marine environments in the future.
基金support of the Research Project Supported by Shanxi Scholarship Council of China(2022-040)"Chunhui Plan"Collaborative Research Project by the Ministry of Education of China(HZKY20220507)+2 种基金National Natural Science Foundation of China(52104338)Applied Fundamental Research Programs of Shanxi Province(202303021221036)Shandong Postdoctoral Science Foundation(SDCX-ZG-202303027,SDBX2023054).
文摘In 316L austenitic stainless steel,the presence of ferrite phase severely affects the non-magnetic properties.316L austenitic stainless steel with low-alloy type(L-316L)and high-alloy type(H-316L)has been studied.The microstructure and solidification kinetics of the two as-cast grades were in situ observed by high temperature confocal laser scanning microscopy(HT-CLSM).There are significant differences in the as-cast microstructures of the two 316L stainless steel compositions.In L-316L steel,ferrite morphology appears as the short rods with a ferrite content of 6.98%,forming a dual-phase microstructure consisting of austenite and ferrite.Conversely,in H-316L steel,the ferrite appears as discontinuous network structures with a content of 4.41%,forming a microstructure composed of austenite and sigma(σ)phase.The alloying elements in H-316L steel exhibit a complex distribution,with Ni and Mo enriching at the austenite grain boundaries.HT-CLSM experiments provide the real-time observation of the solidification processes of both 316L specimens and reveal distinct solidification modes:L-316L steel solidifies in an FA mode,whereas H-316L steel solidifies in an AF mode.These differences result in ferrite and austenite predominantly serving as the nucleation and growth phases,respectively.The solidification mode observed by experiments is similar to the thermodynamic calculation results.The L-316L steel solidified in the FA mode and showed minimal element segregation,which lead to a direct transformation of ferrite to austenite phase(δ→γ)during phase transformation after solidification.Besides,the H-316L steel solidified in the AF mode and showed severe element segregation,which lead to Mo enrichment at grain boundaries and transformation of ferrite into sigma and austenite phases through the eutectoid reaction(δ→σ+γ).
基金supported by the National Natural Science Foundation of China(No.52371231)the Key Research and Development Program of Shanxi Province,China(No.202102030201006)+1 种基金the Central Government Guides Local Science and Technology Development Special Fund Project(No.YDZJSX2022B003),the Natural Science Foundation of Shanxi Province,China(No.202203021212205)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(No.2022L074).
文摘High-entropy design is attracting growing interest as it offers unique structures and unprecedented application potential for ma-terials.In this article,a novel high-entropy ferrite(CoNi)_(x/2)(CuZnAl)_((1-x)/3)Fe_(2)O_(4)(x=0.25,0.34,0.40,0.50)with a single spinel phase of space group Fd3m was successfully developed by the solid-state reaction method.By tuning the Co-Ni content,the magnetic properties of the material,especially the coercivity,changed regularly,and the microwave absorption properties were improved.In particular,the ef-fective absorption bandwidth of the material increased from 4.8 to 7.2 GHz,and the matched thickness decreased from 3.9 to 2.3 mm,while the minimum reflection loss remained below-20 dB.This study provides a practical method for modifying the properties of fer-rites used to absorb electromagnetic waves.
基金financially supported by the National Key R&D Program of China(No.2021YFB3502500)the Natur-al Science Foundation of Shandong Province,China(No.2022HYYQ-014)+5 种基金the“20 Clauses about Colleges and Uni-versities(new)”(Independent Training of Innovation Team)Program of Jinan,China(No.2021GXRC036)the Provin-cial Key Research and Development Program of Shandong,China(No.2021ZLGX01)the National Natural Science Foundation of China(No.22375115)the Joint Laboratory project of Electromagnetic Structure Technology(No.637-2022-70-F-037)the Discipline Construction Expenditure for Distinguished Young Scholars of Shandong University,China(No.31370089963141)the Qilu Young Scholar Program of Shandong University,China(No.31370082163127).
文摘W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high-temperature resistance,and excellent chemical stability.However,the poor dielectric loss of magnetic ferrites hampers their utilization,hindering enhancement in their EMW-absorption performance.Developing efficient strategies that improve the EMW-absorption performance of ferrite is highly desired but re-mains challenging.Here,an efficient strategy substituting Ba^(2+)with rare earth La^(3+)in W-type ferrite was proposed for the preparation of novel La-substituted ferrites(Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)).The influences of La^(3+)substitution on ferrites’EMW-absorption performance and the dissipative mechanism toward EMW were systematically explored and discussed.La^(3+)efficiently induced lattice defects,enhanced defect-induced polarization,and slightly reduced the ferrites’bandgap,enhancing the dielectric properties of the ferrites.La^(3+)also enhanced the ferromagnetic resonance loss and strengthened magnetic properties.These effects considerably improved the EMW-absorption perform-ance of Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)compared with pure W-type ferrites.When x=0.2,the best EMW-absorption performance was achieved with a minimum reflection loss of-55.6 dB and effective absorption bandwidth(EAB)of 3.44 GHz.
基金supported by the National Natural Science Foundation of China(No.52377026)Taishan Scholars and Young Experts Program of Shandong Province,China(No.tsqn202103057)the Natural Science Foundation of Shandong Province,China(No.ZR2024ME046).
文摘With the booming development of electronic information science and 5G communication technology,electromagnetic radi-ation pollution poses a huge threat and damage to humanity.Developing novel and high-performance electromagnetic wave(EMW)ab-sorbers is an effective method to solve the above issue and has attracted the attention of many researchers.As a typical magnetic material,ferrite plays an important role in the design of high-performance EMW absorbers,and related research focuses on diversified synthesis methods,strong absorption performance,and refined microstructure development.Herein,we focus on the synthesis of ferrites and their composites and introduce recent advances in the high-temperature solid-phase method,sol-gel method,chemical coprecipitation method,and solvent thermal method in the preparation of high-performance EMW absorbers.This review aims to help researchers understand the advantages and disadvantages of ferrite-based EMW absorbers fabricated through these methods.It also provides important guidance and reference for researchers to design high-performance EMW absorption materials based on ferrite.
基金supported by the National Natural Science Foundation of China(No.51574105)the Science and Technology Program of Hebei Province,China(No.23564101D)+2 种基金the Natural Science Foundation of Hebei Province,China(No.E2021209147)the Key Research Project of North China University of Science and Technology(No.ZD-ST-202308)the Postgraduate Innovation Funding Project of Hebei Province,China(No.CXZZBS2024135).
文摘Calcium ferrite(CF)is recognized as a potential green and efficient functional material because of its advantages of magnetism,electrochemistry,catalysis,and biocompatibility in the fields of materials chemistry,environmental engineering,and biomedicine.There-fore,the obtained research results need to be systematically summarized,and new perspectives on CF and its composite materials need to be analyzed.Based on the presented studies of CF and its composite materials,the types and structures of the crystal are summarized.In addition,the current application technologies and theoretical mechanisms with various properties in different fields are elucidated.Moreover,the various preparation methods of CF and its composite materials are elaborated in detail.Most importantly,the advantages and disadvantages of the synthesis methods of CF and its composite materials are discussed,and the existing problems and emerging challenges in practical production are identified.Furthermore,the key future research directions of CF and its composite materials have been prospected from the potential application technologies to provide references for its synthesis and efficient utilization.
基金financially supported by Korea Institute for Advancement of Technology(KIAT)grant funded by the Ko-rea Government(MOTIE)(HRD Program for Industrial Innova-tion)(P0023676)the National Research Foundation of Ko-rea(NRF)grant funded by the Korea government(MSIT)(NRF-2022R1A5A1030054,RS-2023-00281508,NRF-RS-2024-00345498).
文摘Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultaneously promotes the formation of coarse ferrite and expands the two-phase(α+γ)intercritical temperature range.Thus,increasing the Al content for higher weight reduction inevitably leads to ferrite formation and impedes further strengthening.To achieve both high strength and duc-tility while incorporating ferrite,it is crucial to elucidate the effects of ferrite fraction,size,and dis-tribution on mechanical properties and deformation behavior,particularly in relation to phase interac-tions.In this study,three model steels were developed through controlled annealing temperatures,pro-ducing distinct triplex microstructures comprising ferrite,martensite,and retained austenite(RA).The role of each phase in strain partitioning was investigated using ex-situ microscopic digital image cor-relation and electron back-scattered diffraction analysis.Key findings reveal that the martensitic matrix ensures an ultrahigh strength level(1758 MPa),while a moderate fraction(∼17%)and homogeneous dis-tribution of intercritical-ferrite(IC-ferrite)enable sustainable strain-hardening behavior by delaying the transformation-induced plasticity(TRIP)effect.Strain partitioning into IC-ferrite reduces local strains in the martensitic matrix,preventing early exhaustion of the TRIP effect and facilitating ductile fracture behavior.This strategy leverages the presence of ferrite,offering significant advantages for applications requiring both ultrahigh strength and ductility.
基金supported by the National Natural Science Foundation of China(Grant No.52104333)the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(Grant No.NJYT24070)+1 种基金the Natural Science Foundation of Inner Mongolia(Grant No.2024MS05029)the Research Project of Carbon Peak and Carbon Neutrality in Universities of Inner Mongolia Autonomous Region(Grant No.STZX202316).
文摘The substantial influences of Mo contents varying from 0 to 0.26 and 0.50 wt.%on the microstructural evolution and MX(M=Nb,V and Mo;X=C and N)precipitation characteristics of Nb–V–N microalloyed steels processed by hot deformation and continuous cooling were studied using a Gleeble 3800 thermomechanical simulator.Metallographic analysis showed that the ferrite microstructure transformed from polygonal ferrite(PF)in 0Mo steel to both acicular ferrite(AF)and PF in 0.26Mo and 0.50Mo steels,and AF content first increased and then decreased.The thermodynamic calculations and the experimental results proved that the quantity of solid solution of Mo in austenite obviously increased,which reduced the austenite(γ)to ferrite(α)transformation temperature,consequently promoting AF formation in 0.26Mo steel and bainite transformation in 0.50Mo steel.Moreover,the submicron Nb-rich MX particles that precipitated at the temperature of the austenite region further induced AF heterogeneous nucleation with an orientation relationship of(100)_(MX)//(100)_(Ferrite)and[■][001]Ferrite.The interphase precipitation of the nanosized V-rich MX particles with Mo partitioning that precipitated duringγ→αtransformation exhibited a Baker–Nutting orientation relationship of(100)_(MX)//(100)Ferrite and[001]_(MX)//[■]_(Ferrite)with respect to the ferrite matrix.With increasing Mo content from 0 to 0.26 and 0.50 wt.%,the sheet spacing decreased from 46.9–49.0 to 34.6–38.6 and 25.7–28.0 nm,respectively,which evidently hindered dislocation movement and greatly enhanced precipitation strengthening.Furthermore,facilitating AF formation and interphase precipitation was beneficial to improving steel properties,and the optimal Mo content was 0.26 wt.%.
基金supported by the Project of Liaoning Marine Economic Development(Development of high strength pipeline steel for submarine oil and gas transmission)State Key Laboratory of Metal Material for Marine Equipment and Application Funding(No.SKLMEA-K202205).
文摘The phase volume fraction has an important role in the match of the strength and plasticity of dual phase steel.The different bainite contents(18–53 vol.%)in polygonal ferrite and bainite(PF+B)dual phase steel were obtained by controlling the relaxation finish temperature during the rolling process.The effect of bainite volume fraction on the tensile deformability was systematically investigated via experiments and crystal plasticity finite element model(CPFEM)simulation.The experimental results showed that the steel showed optimal strain hardenability and strength–plasticity matching when the bainite reached 35%.The 3D-CPFEM models with the same grain size and texture characters were established to clarify the influence of stress/strain distribution on PF+B dual phase steel with different bainite contents.The simulation results indicated that an appropriate increase in the bainite content(18%–35%)did not affect the interphase strain difference,but increased the stress distribution in both phases,as a result of enhancing the coordinated deformability of two phases and improving the strength–plasticity matching.When the bainite content increased to 53%,the stress/strain difference between the two phases was greatly increased,and plastic damage between the two phases was caused by the reduction of the coordinated deformability.
基金supported by the National Natural Science Foundation of China (Grant No. 12174382)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDB0460000 and XDB28000000)the Innovation Program for Quantum Science and Technology (Grant Nos. 2024ZD0300104 and 2021ZD0302600)。
文摘The competition between dimensionality and ordering in multiferroic materials is of great interest for both fundamental physics and potential applications. Combining first-principles calculations with micromagnetic simulations, we investigate recently synthesized ultrathin perovskite bismuth ferrite(BFO) films. Our numerical results reveal that, at the monolayer limit, the ferroelectricity of BFO is missing because the octahedral distortions are constrained. However, the monolayer bismuth ferrite is a topological antiferromagnetic metal with tunable bimeron magnetic structure. The dual topologically non-trivial characteristics make monolayer bismuth ferrite a multifunctional building block in future spintronic devices.
文摘Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs.In this paper,the citrate-nitrate auto-combustion method was applied for the formation of Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4);(0≤x≤0.1;step 0.02)(CZNL)nanoferrites.Although the substitution process entails the replacement of a small ion with a larger one,the lattice constant and crystallite size does not exhibit a consistent incremental pattern.This behavior is justified and discussed.The size of all the CZNL ferrite nanoparticles is in the range of 8-12 nm,and the lattice constant is in the range of 8.6230 to 8.4865 nm.The morphological analysis conducted using field emission-scanning electron microscopy(FE-SEM)reveals that the CZNL exhibits agglomerated spherical morphology.The energy dispersive X-ray spectrameter(EDAX)analysis was employed to confirm the elemental composition of CZNL nanoferrites.Since the process entails the substitution of Fe^(3+)magnetic ions with nonmagnetic ions La^(3+),the magnetic parameters of CZNL nanoferrites show a general decreasing trend as predicted.At 20 K,saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x=0.0-41.295 emu/g at x=0.1,the smallest value of 37.87 emu/g is recorded at x=0.06.the highest coercivity(H_(c)=125.9 Oe)and remanence(M_(r)=13.32 emu/g)are recorded for x=0.08 and x=0.04 nanoferrite,respectvely.The band gap of all the CZNL nanoferrites was determined using the Kubelka-Munk function and Tauc plot for direct permitted transitions.La doping modifies the band gap(within 1.86-1.75 eV),increases light absorption,induces efficient e/h separation and charge migration to Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4)surfaces.The nanoferrite Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)achieves a degradation efficiency of 97.3%for methylene blue(MB)dye removal after just 60 min.After five recycling processes,the nanocatalyst Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)is degraded by 95.83%,resulting in a negligible1.51%decrease in photocatalytic activity efficiency.The new Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)has exceptional photocatalytic activity and remarkable stability,making it a promising candidate for applications in wastewater treatment.
基金financially supported by the National Natural Science Foundation of China(Nos.52204331 and 52374315)the Major Industrial Innovation Plan of Anhui Provincial Development and the Reform Commission,China(No.AHZDCYCX-LSDT2023-01)。
文摘Al_(2)O_(3)and MgO serve as the primary gangue components in sintered ores,and they are critical for the formation of CaO-Fe_(2)O_(3)-xAl_(2)O_(3)(wt%,C-F-xA)and CaO-Fe_(2)O_(3)-xM gO(wt%,C-F-xM)systems,respectively.In this study,a nonisothermal crystallization thermodynamics behavior of C-F-xA and C-F-xM systems was examined using differential scanning calorimetry,and a phase identification and microstructure analysis for C-F-xA and C-F-xM systems were carried out by X-ray diffraction and scanning electron microscopy.Results showed that in C-F-2A and C-F-2M systems,the increased cooling rates promoted the precipitation of CaFe_(2)O_(4)(CF)but inhibited the formation of Ca_(2)Fe_(2)O_(5)(C2F).In addition,C-F-2A system exhibited a lower theoretical initial crystallization temperature(1566 K)compared to the C-F system(1578 K).This temperature further decreases to 1554 K and 1528 K in the C-F-4A and C-F-8A systems,respectively.However,in C-F-xM system,the increased MgO content raised the crystallization temperature.This is because that the enhanced precipitation of MF(a spinel phase mainly comprised Fe_(3)O_(4)and MgFe_(2)O_(4))and C2F phases suppressed the CF precipitation reaction.In kinetic calculations,the Ozawa method revealed the apparent activation energies of the C-F-2A and C-F-2M systems.Malek's method revealed that the crystallization process in C-F-2A system initially followed a logarithmic law(lnαor lnα2),later transitioning to a reaction order law((1-α)-1or(1-α)^(-1/2),n=2/3)or the lnα2function of the exponential law.In C-F-2M system,it consistently followed the sequencef(α)=(1-α)^(2)(αis the crystallization conversion rate;n is the Avrami constant;?(α)is the differential equations for the model function of C_(2)F and CF crystallization processes).
基金supported by the National Natural Science Foundation of China(No.62371222)the Defense Industrial Technology Development Program(No.JCKY2023605C002)thePriority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(No.ZHD202305).
文摘The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz.In this study,we prepared Z-type Ba_(3)Co_(1.6−x)Zn_(x)Cu_(0.4)Fe_(24)O_(41)hexaferrites using the sol-gel auto-combustion method.By changing the ratio of Co and Zn ions,the magnetocrystalline anisotropy of ferrite is further ma-nipulated,resulting in significant changes in their magnetic resonance frequency and intensity.Ba_(3)Zn_(1.6)Cu_(0.4)Fe_(24)O_(41)with high-frequency resonance achieved the lowest reflectivity of−72.18 dB at 15.56 GHz,while Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)with stronger loss obtained the widest bandwidth of 4.93 GHz(6.14-11.07).Additionally,we investigated surface wave suppression properties previously overlooked.Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)can achieve a larger attenuation at low frequency under low thickness,which has an excellent effect on reducing backscattering.This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.
文摘The present work reports the structural,optical,dielectric,and electrical properties of Eu-Er substituted M-type Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19)(x=0.0.05,0.1,0.15,and 0.2)hexaferrites synthesized by sol-gel combustion method.The hexagonal structure of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples was confirmed from X-ray diffraction(XRD)analysis.The values of lattice parameters of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19)samples are increased as compared to Ba_(0.5)Sr_(0.5)Fe_(12)O_(19) sample.This increase in the value of lattice parameters is attributed to the substitution of larger cations(Eu^(3+)and Er^(3+))in place of smaller cations(Fe^(3+)ions).The crystallite sizes of the Ba0.5Sr0.5EuxErxFe12-2x019 samples also increase due to the substitution of larger cations.The force constants(K_o and K_t)increases with increasing Eu-Er concentration.The octahedral cluster shifts towards the higher wavenumber side whereas the tetrahedral cluster shifts towards the lower wavenumber side due to Eu-Er substitution in the Fourier transform infrared(FTIR)spectra.The photoluminescence(PL)emission spectra for the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples are observed at 365 nm.The dielectric dispersion in the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples can be understood by Koop's theory and Maxwell-Wagner type of inte rfacial polarization.Using Jonscher's power law and the co rrelated barrier hopping(CBH)model,the frequency and temperature-dependent be haviour of ac conductivity of Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples are described.The temperature-dependent behaviour of the dc conductivity of the Ba_(0.5)Sr_(0.5)Eu_(x)Er_(x)Fe_(12-2x)O_(19) samples is explained by the variable range hopping(VRH)model.The Motto temperature of the sample varies from 4.55×10^(9) to 2.31×10^(8) K.The estimated maximum barrier height(WM)of the compound varies from 0.6603 to 0.1199 eV.The temperature coefficient and activation energy of the samples were also calculated as a function of Eu-Er concentration.
文摘Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406Å,while crystallite sizes were estimated to range between 55.20 and 31.40 nm using the Scherrer method.The different functional groups were found to correlate with various ab-sorption bands using Fourier transform infrared(FTIR)spectroscopy.Five active modes were identified by Raman spectroscopy,reveal-ing vibration modes of O2-ions at tetrahedral and octahedral locations.The ferromagnetic hysteresis loop was observed in all the synthes-ized samples,which can be explained by Neel’s model.The results showed that AC conductivity decreased with increasing Mn^(2+)content at the Fe^(2+)site,while the dielectric constant and dielectric loss increased with increasing frequency.Furthermore,the saturation magnetiz-ation(Ms),remnant magnetization(M_(r)),and coercivity(H_(c))all showed declining trends with the increase in Mn^(2+)doping.Finally,the CoMn_(0.20)Fe_(1.8)O_(4) samples showed Ms and M_(r) values ranging from 73.12 to 66.84 emu/g and from 37.77 to 51.89 emu/g,respectively,while Hc values ranged from 1939 to 1312 Oe,after which coercivity increased.Thus,the CoMn_(0.20)Fe_(1.8)O_(4) sample can be considered a prom-ising candidate for magnetic applications.
文摘Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversion.The incorporation of rare earth metal ferrites into heterojunction photocatalytic systems enhances light absorption,charge separation and photocatalytic efficiency.This review comprehensively discusses some common types of rare earth metal ferrites such as LaFeO_(3),GdFeO_(3),SmFeO_(3),PrFeO_(3)and CeFeO_(3)and their properties as photocatalysts.The photocatalytic pollutants removal and energy conversion mechanisms are discussed in detail and various types of heterojunctions reported in literature based on rare earth metal ferrites and their synthetic routes are also explored.The recent key findings and advances in the heterojunctions based on these rare earth metal ferrites for the pollutants removal and energy conversion applications are summarized.Despite notable progress in enhancing photocatalytic efficiency and stability,several challenges remain.Current research highlights improvements in material synthesis and performance,but issues such as high production costs,scalable synthesis and limited long-term stability persist.Future directions should focus on exploring uncharted applications,novel material combinations and enhancing the practical implementation of these heterojunctions to fully exploit their potential in environmental and energy technologies.
基金financially supported by the National Natural Science Foundation of China(Nos.52273267 and 22271155)
文摘Structural manipulation plays a crucial role in material design,exerting a significant influence on various aspects of material performance.However,the impact of material microstructure on electromagnetic waves absorption properties has not been thoroughly investigated.In this study,based on ferrites,we controlled the micros tructural morphology by doping with light rare earth element Nd,and then formed heterogeneous structures through composite polypyrrole to enhance its performance.The structural changes in neodymium-doped ferrites and their corresponding variations in performance were systematically analyzed.The results indicate that Nd^(3+)ions doping has a pronounced effect on the microstructure of ferrites,significantly improving their dielectric loss capability for electromagnetic waves.The sample with optimal performance,Sr_(0.75)Nd_(0.25)Co_(2)Fe_(16)O_(27)@PPy,has a value of minimum reflection loss that can reach-63.11 dB,and the effective absorption bandwidth achieves 6.40 GHz at2.27 mm.This study provides instructive thinking for the structural manipulation of MA materials.
