Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_...Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_(4)(Z=S,Se)in a systematic manner is essential for the strategic advancement of spin polarized current in a spintronic device.In this recent study,the WIEN2K code was employed to comprehensively analyze these properties.The calculated lattice constants,obtained using the generalized gradient approximation(GGAsol-PBE),closely match experimental findings of the similar family compounds.The examination of the stability of ferromagnetic states in the ground state involves comparing energies between anti-ferromagnetic and ferromagnetic states.Moreover,an assessment of the stability of the cubic phase in both spinels was conducted using analyses of the phonon dispersion curve,formation energy and Born stability criteria.The ductility characteristics were examined through the calculation of Poisson's and Pugh's ratios.Furthermore,details regarding the density of states,spin polarization,ex-change coupling and Curie temperature were provided to explore the characteristics associated with ferromagnetism.Potential optoelectronic applications were proposed,leveraging the direct band gaps of 1.4 and 1.0 eV for HgNd_(2)Z_(4)(Z=S,Se)respectively,within the visible spectrum.Particularly noteworthy is the effective light absorption of HgNd2Se4 in the visible range,characterized by prominent peaks that facilitate the transition of electrons from the valence band(VB)to the conduction band(CB).Additionally,the study extends to thermoelectric characteristics,determining various factors such as Seebeck coef-ficient(S),figure of merit(ZT),electrical and thermal conductivities of the evaluated spinels.展开更多
Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done wi...Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done with Perdew-Burke-Ehrenzorf(PBE)sol-generalized gradient approximation(GGA)to calculate the lattice constant of both spinels comparable to experimental data.In addition,Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase.For ferromagnetic(FM)state stability,we also calculated the energy differences among FM,antiferromagnetic(AFM),and non-magnetic(NM)states.Additionally,Curie temperatures of ferromagnetic phases were also estimated.We used Trans-Blaha improved BeckeJohnson(TB-mBJ)potential functional for electronics as well as magnetic characteristics,which lead to the consistent explanation of half-metallic ferromagnetism,representing the whole band-occupancy in material with exact detail of density of states(DOS).The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS.Further,spin magnetic moment was explained in terms of anion,cation,and sharing charge on studied spinels.In addition,the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.展开更多
The densification and microstructure of different spinelized magnesium aluminate spinels（MAS） were studied adding Sc_2O_3 as additive. Sintered products were then characterized in terms of densification, phase analy...The densification and microstructure of different spinelized magnesium aluminate spinels（MAS） were studied adding Sc_2O_3 as additive. Sintered products were then characterized in terms of densification, phase analysis, quantitative elemental analysis and microstructure. The results show that Sc_2O_3 is found to be beneficial for the densification of MAS. Sc_2O_3 has a more significant effect on the densification of partially spinelized MAS batch than that of fully spinelized MAS batch. At the sintering temperature of 1650 °C, the bulk density of sintered products of partially spinelized powders increases by 0.243 g/cm3 as the Sc_2O_3 content increases from 0 to 4%（mass fraction） and that of fully spinelized powder increases by 0.14 g/cm3. Compared with the sintered samples prepared from the fully spinelized powder, the sintered samples using the partially spinelized powders as raw materials have more compact microstructures.展开更多
The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Car...The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.展开更多
New types of refractory materials need to be developed for designing the man-made ledge of the Hall-Heroult cell for aluminum electrolysis, which are currently constructed by frozen ledge.Magnesium aluminate spinel （...New types of refractory materials need to be developed for designing the man-made ledge of the Hall-Heroult cell for aluminum electrolysis, which are currently constructed by frozen ledge.Magnesium aluminate spinel （MAS） as potential candidate materials was prepared by two-step sintering. The densification and grain growth of the MAS wereinvestigatedbytheArchimedes drainage method and scanning electron microscope （SEM）. All the specimens were corroded in aNa3AlF6-AlF3-CaF2-Al2O3bath to assess the corrosion resistance. The results show that a MAS material with a high relative density of 99.2% and ahomogeneous microstructure is achieved under two-step sintering conditions. The corrosion mechanisms of MAS inNa3AlF6-AlF3-CaF2-Al2O3 bathare mainly proposed by dissolution of MAS, formation of aluminum oxide, and diffusion of fluorides. The MAS prepared by two-step sintering exhibits good corrosion resistance to theNa3AlF6-AlF3-CaF2-Al2O3bath.展开更多
A series of manganese spinels LiMn2-yMeyO4 （Me = Li, A1, Mg） were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of A1 can exhibit discharge capacity in the 5 V r...A series of manganese spinels LiMn2-yMeyO4 （Me = Li, A1, Mg） were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of A1 can exhibit discharge capacity in the 5 V region, but spinels doped with Mg do not exhibit any 5 V discharge capacity. It is also observed that the 5 V discharge capacity of Li/A1 doped spinels will be greatly suppressed once calcinated at temperatures above 900 ℃ in preparation. It is suggested that the 5 V discharge capacity of Li/A1 doped spinels may be originated from the special chemical/structural characteristics of spinel phases containing Li or high content of A1 prepared at temperatures below 900 ℃.展开更多
Listwaenite,carbonate-talc schist,and serpentinite of Sartohay ophioliticmélange,Xinjiang,northwestern China,contain variably altered chromian spinels.During the hydrothermal alteration from serpentinite to listw...Listwaenite,carbonate-talc schist,and serpentinite of Sartohay ophioliticmélange,Xinjiang,northwestern China,contain variably altered chromian spinels.During the hydrothermal alteration from serpentinite to listwaenite展开更多
LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such...LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface morphology.TEM images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.展开更多
From the UV?Vis absorption spectra,the FT-IR absorption spectra and the Raman spectra,it is deduced that Co ionsprimarily occupy the tetrahedral(A)site,with a minor number of them entering into the octahedral(B)site i...From the UV?Vis absorption spectra,the FT-IR absorption spectra and the Raman spectra,it is deduced that Co ionsprimarily occupy the tetrahedral(A)site,with a minor number of them entering into the octahedral(B)site in the Ni1?xCoxCr2O4compounds.The origin of the position disorder of the Co ions is consistent with the similar ionic radii of the Co ion(0.65?)and theCr ion(0.62?)at B site.The FT-IR peak at about510cm?1shifts towards high frequency side with the increasing cobalt content.Itis resulted from the reduction of the cation?oxygen distance in the octahedron by the replacement of the Ni2+with the Co2+ions.Themagnetic measurement shows that Curie temperatures(TC)are75and90K for the compounds with x=0.2and0.8,respectively.展开更多
With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH s...With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH snorkel lining.High purity dead burned magnesia,fused magnesia and sintered spinel were used as raw materials and sulfite pulp waste as the binder,specimens of the refractories in the Mg0-Al_(2)O_(3) system were prepared for the purpose of investigating the influences in terms of the addition of three kinds of spinels,with Al_(2)O_(3) 50%,66% and 78%,by mass,respectively,and the size of MA50 spinel on properties of the specimens.Relatively superior comprehensive properties can be achieved when 16%of MA50 spinel with sizes under 1mm is adopted.展开更多
A rigid-ion model is used to calculate the force constants and effective dynamical charges of sulphide and selenide spinels. The Raman and infrared phonon modes of normal cubic sulphide spinels MCr2S4 （M = Mn, Co, Fe...A rigid-ion model is used to calculate the force constants and effective dynamical charges of sulphide and selenide spinels. The Raman and infrared phonon modes of normal cubic sulphide spinels MCr2S4 （M = Mn, Co, Fe, Hg, Zn, and Cd） and selenide spinels MCr2Se4 （M = Hg, Zn, and Cd） are calculated at the first Brillouin zone-centre using above model, The significant outcome of the present work is （i） the interatomic interaction between Cr-S （Se） dominates over the Cr-S（Se） and S-S（Se-Se） type of interatomic interactions, （ii） the effective dynamical charges of the bivalent metal ions are nearly zero, and （iii） the selenide spinels are less ionic than the sulphide spinels and the ionicity decreases as MnCr2S4 〉 FeCr2S4 〉 CoCr2S4 〉 and CdOr2C4 〉 ZnCr2C4 〉 HgCr2C4 （C = S and Se）. The zone-center phonon frequencies, calculated using these parameters, are found to be in very good agreement with the observed results.展开更多
: The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships betw...: The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships between major elements of spinels are discussed. The equilibrium temperatures, pressures and oxygen fugacities of spinels and their coexisting olivines, orthopyroxenes and clinopyroxenes have been determined using the Brey—kohler's T—P calculation methods (1990) and Ballhaus' fo2 calculation method (1991). The relationships between the composition and the equilibrium temperatures, pressures or oxygen fugacities of spinels in peridotite xenoliths from the basalts and the stable field of the spinels in the upper mantle have been shown.展开更多
Detailed mineralogical and gemological records were conducted on 340 unheated spinels from the Horana, Eheliyagoda, Ratnapura, and Okkampatiya mining areas in Sri Lanka. The color of Sri Lankan spinel varies greatly: ...Detailed mineralogical and gemological records were conducted on 340 unheated spinels from the Horana, Eheliyagoda, Ratnapura, and Okkampatiya mining areas in Sri Lanka. The color of Sri Lankan spinel varies greatly: in addition to the mainstream pink to purple pink, green and blue can also be seen. Compared with spinel from other regions such as Myanmar, Vietnam, and Tanzania, Sri Lanka's spinel has more abundant inclusions: several mining areas generally have inclusions such as dolomite, apatite, zircon, and chondrodite. Minerals such as graphite and forsterite are also found in spinel produced in the Horana region;graphite and rutile have been found in spinel produced in the Okkamptiya region. Partially healed fissures are most common in spinel in the Okkampatiya mining area;Unlike Vietnamese spinel, dislocations and growth structures are almost absent in Sri Lankan spinel. The LA-ICP-MS analysis results showed that there were no significant differences among the mining areas. LA-ICP-MS analysis of 5 Sri Lankan cobalt blue spinels showed a variation of 11 to 120 ppm in this chromogenic element. The UV visible absorption spectrum results show that Sri Lankan spinel has a combination spectra with variable ratios of the spectral components Cr 3+ , V 3+ and Fe 2+ from pink to red, orange, purple to purple, and blue-green. The results of infrared spectroscopy and laser Raman spectroscopy analysis showed that all samples showed no indications for heat treatment.展开更多
Fabrics of five spinel peridotites collected from Baker Rocks in northern Victoria Land,Antarctica,were investigated to elucidate the evolution of the lithospheric mantle surrounding the Transantarctic Mountains.Analy...Fabrics of five spinel peridotites collected from Baker Rocks in northern Victoria Land,Antarctica,were investigated to elucidate the evolution of the lithospheric mantle surrounding the Transantarctic Mountains.Analyses revealed the development of crystallographic preferred orientations(CPOs),a slight decrease in mean grain size and J-index across varying proportions of clinopyroxene,and interlobate to amoeboid textures.These findings indicate that dislocation creep is the dominant deformation mechanism for the analyzed samples.展开更多
The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly unders...The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates.In this study,we prepared two Zn-Al spinel oxide catalysts via coprecipitation(ZnAl-C)and hydrothermal(ZnAl-H)methods,and conducted a comparative investigation in the CO_(2)hydrogenation reaction.Surprisingly,under similar conditions,ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H.Comprehensive characterizations using X-ray diffraction(XRD),Raman spectroscopy and electron paramagnetic resonance(EPR)unveiled that ZnAl-C catalyst had abundant ZnO species on its surface,and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies,which are crucial for CO_(2)adsorption and activation.Additionally,state-of-the-art solid-state nuclear magnetic resonance(NMR)techniques,including ex-situ and in-situ NMR analyses,confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species,which was readily hydrogenated to methanol and DME.These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediates for CO_(2)-to-methanol hydrogenation reaction,which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst.These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.展开更多
Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,sy...Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,synthesized via cation exchange and calcination oxidation.These catalysts exhibit excellent efficacy in the electrocatalytic conversion of lignin model compounds,specifically 2-phenoxy-1-phenylethanol,into nitrogen-containing aromatics,achieving high conversion rates and selectivities.These catalysts were synthesized via a cation exchange and calcination oxidation process,using Prussian blue nanocubes as precursors.The porous architecture and polymetallic composition of the NiCo_(2)O_(4)spinel demonstrated superior performance in electrocatalytic oxidative coupling,achieving a 99.2 wt%conversion rate of the 2-phenoxy-1-phenylethanol with selectivities of 37.5 wt%for quinoline derivatives and 31.5 wt%for phenol.Key innovations include the development of a sustainable one-pot synthesis method for quinoline derivatives,the elucidation of a multistage reaction pathway involving CAO bond cleavage,hydroxyaldol condensation,and CAN bond formation,and a deeper mechanistic understanding derived from DFT simulations.This work establishes a new strategy for lignin valorization,offering a sustainable route to produce high-value nitrogen-containing aromatics from renewable biomass under mild conditions,without the need for additional reagents.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
Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully...Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene.The CuMn_(2)O_(4)sample exhibited the best catalytic performance,the conversion of benzene reached 100%at 350℃,and toluene conversion reached 100%at 250℃.XRD,N_(2)adsorption-desorption,HRTEM-EDS,ED-XRF,Raman spectroscopy,H_(2)-TPR,NH_(3)-TPD,O_(2)-TPD and XPS were used to characterize the physical and chemical properties of MMn_(2)O_(4)catalysts.The excellent redox properties,high concentration of surface Mn4+,and adsorption of oxygen species over the CuMn_(2)O_(4)sample facilitated the simultaneous and efficient removal of benzene and toluene.Additionally,in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene.Notably,as an effective catalytic material,spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene,providing some insight for the development of efficient multicomponent VOC catalysts.展开更多
Electroplating sludge(ES),a byproduct of the electroplating industry,is a significant environmental concern due to its high content of soluble heavy metals(HMs).The significance of spinel formation from ES lies in its...Electroplating sludge(ES),a byproduct of the electroplating industry,is a significant environmental concern due to its high content of soluble heavy metals(HMs).The significance of spinel formation from ES lies in its potential for HMs enrichment and environmental remediation,offering a sustainable solution for hazardous waste management.The article delves into themultifaceted recycling of HMs-rich spinel fromES,encompassing its synthesis,metal enrichment,and thermodynamic stability.The pyro-metallurgical and hydrometallurgical processes for spinel synthesis were discussed,with a focus on the critical role of thermodynamic data in predicting the stability and formation of spinel structures.The crystallographic and magnetic properties of spinels,with their applications in environmental remediation and energy storage are highlighted.The article provides a comprehensive reviewon the recycling of HMs-rich spinel fromES,offering a means to recycle HMs,mitigate ecological harm,and contribute to a circular economy through the recovery and application of valuable materials.The selective leaching of metals from ES also faces challenges,which was limited by the separation,purification steps and high energy consumption.This high energy consumption is a significant operational cost and also contributes to environmental concerns related to carbon emissions.It is essential to address the challenges through continued research and development,improved technologies,and supportive regulatory frameworks.展开更多
In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to in...In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to investigate the structural,morphological,dielectric and magnetic properties of the prepared samples.X-ray diffraction(XRD)result suggests that face-centered cube spinel nanocrystalline structure is formed.Crystallite size of the SrFe_(2)O_(4)decreases with rising of Tb ratio.The morphology,shape and size of the SrFe_(2)O_(4)were examined by scanning electron microscopy(SEM)analysis and results reveal inhomogeneous distributions of the nanostructures with high agglomeration.The electrical resistivity of the SrFe_(2)O_(4)increases with rising of Tb ratio,which is confirmed from the cyclic voltammetry.It is observed that dielectric constant of all the samples decreases with the increasing frequency range.It is determined that the dielectric constants of the spinel ferrites are frequency dependent and decrease with increasing the frequency of applied electric field.The magnetic behavior of SrFe_(2)O_(4)with different ratios of Tb was studied and it is found that the saturation magnetization values of samples decrease with increase in the substitution of Tb^(3+)at octahedral sites for Fe^(3+).This decrease in the values of M_(s) is also attributed to spin at surface of nanoparticles.展开更多
基金the Deanship of Scientific Research at King Khalid University for funding this work through large group Research Project under grant number RGP2/450/44。
文摘Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_(4)(Z=S,Se)in a systematic manner is essential for the strategic advancement of spin polarized current in a spintronic device.In this recent study,the WIEN2K code was employed to comprehensively analyze these properties.The calculated lattice constants,obtained using the generalized gradient approximation(GGAsol-PBE),closely match experimental findings of the similar family compounds.The examination of the stability of ferromagnetic states in the ground state involves comparing energies between anti-ferromagnetic and ferromagnetic states.Moreover,an assessment of the stability of the cubic phase in both spinels was conducted using analyses of the phonon dispersion curve,formation energy and Born stability criteria.The ductility characteristics were examined through the calculation of Poisson's and Pugh's ratios.Furthermore,details regarding the density of states,spin polarization,ex-change coupling and Curie temperature were provided to explore the characteristics associated with ferromagnetism.Potential optoelectronic applications were proposed,leveraging the direct band gaps of 1.4 and 1.0 eV for HgNd_(2)Z_(4)(Z=S,Se)respectively,within the visible spectrum.Particularly noteworthy is the effective light absorption of HgNd2Se4 in the visible range,characterized by prominent peaks that facilitate the transition of electrons from the valence band(VB)to the conduction band(CB).Additionally,the study extends to thermoelectric characteristics,determining various factors such as Seebeck coef-ficient(S),figure of merit(ZT),electrical and thermal conductivities of the evaluated spinels.
基金the Deanship of Scientific Research at King Khalid University for funding this work through the small Groups Project under grant number(R.G.P.1/153/43)。
文摘Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done with Perdew-Burke-Ehrenzorf(PBE)sol-generalized gradient approximation(GGA)to calculate the lattice constant of both spinels comparable to experimental data.In addition,Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase.For ferromagnetic(FM)state stability,we also calculated the energy differences among FM,antiferromagnetic(AFM),and non-magnetic(NM)states.Additionally,Curie temperatures of ferromagnetic phases were also estimated.We used Trans-Blaha improved BeckeJohnson(TB-mBJ)potential functional for electronics as well as magnetic characteristics,which lead to the consistent explanation of half-metallic ferromagnetism,representing the whole band-occupancy in material with exact detail of density of states(DOS).The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS.Further,spin magnetic moment was explained in terms of anion,cation,and sharing charge on studied spinels.In addition,the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.
基金Project(51374240) supported by the National Natural Science Foundation of ChinaProject(2012BAE08B02) supported by the National Science and Technology Pillar Program of China
文摘The densification and microstructure of different spinelized magnesium aluminate spinels（MAS） were studied adding Sc_2O_3 as additive. Sintered products were then characterized in terms of densification, phase analysis, quantitative elemental analysis and microstructure. The results show that Sc_2O_3 is found to be beneficial for the densification of MAS. Sc_2O_3 has a more significant effect on the densification of partially spinelized MAS batch than that of fully spinelized MAS batch. At the sintering temperature of 1650 °C, the bulk density of sintered products of partially spinelized powders increases by 0.243 g/cm3 as the Sc_2O_3 content increases from 0 to 4%（mass fraction） and that of fully spinelized powder increases by 0.14 g/cm3. Compared with the sintered samples prepared from the fully spinelized powder, the sintered samples using the partially spinelized powders as raw materials have more compact microstructures.
文摘The magnetic properties of inverse ferrite Fe_(3+) Fe_(3+)Co_(2+) O^(2-)_4, Fe^(3+) Fe^(3+)Cu^(2+) O^2_(-4), Fe^(3+) Fe^(3+)Fe^(2+) O^2_(-4),and Fe^(3+) Fe^(3+)Ni^(2+) O^(2-)_4spinels have been studied using Monte Carlo simulation. We have also calculated the critical and Curie Weiss temperatures from the thermal magnetizations and inverse of magnetic susceptibilities for each system.Magnetic hysteresis cycles have been found for the four systems. Finally, we found the critical exponents associated with magnetization, magnetic susceptibility, and external magnetic field. Our results of critical and Curie Weiss temperatures are similar to those obtained by experiment results. The critical exponents are similar to those of known 3 D-Ising model.
基金Project(51374240)supported by the National Natural Science Foundation of ChinaProject(2012BAE08B02)supported by the National Science and Technology Pillar Program of China
文摘New types of refractory materials need to be developed for designing the man-made ledge of the Hall-Heroult cell for aluminum electrolysis, which are currently constructed by frozen ledge.Magnesium aluminate spinel （MAS） as potential candidate materials was prepared by two-step sintering. The densification and grain growth of the MAS wereinvestigatedbytheArchimedes drainage method and scanning electron microscope （SEM）. All the specimens were corroded in aNa3AlF6-AlF3-CaF2-Al2O3bath to assess the corrosion resistance. The results show that a MAS material with a high relative density of 99.2% and ahomogeneous microstructure is achieved under two-step sintering conditions. The corrosion mechanisms of MAS inNa3AlF6-AlF3-CaF2-Al2O3 bathare mainly proposed by dissolution of MAS, formation of aluminum oxide, and diffusion of fluorides. The MAS prepared by two-step sintering exhibits good corrosion resistance to theNa3AlF6-AlF3-CaF2-Al2O3bath.
基金Funded partly by the Fundamental Research Funds for the Central Universities (No.WHUT-2012-Ia-029)the Foundation of the Ministry of Education of China for Returned Scholars (No.2007-24)
文摘A series of manganese spinels LiMn2-yMeyO4 （Me = Li, A1, Mg） were prepared and examined by XRD and electrochemical methods. The spinels doped with Li or high content of A1 can exhibit discharge capacity in the 5 V region, but spinels doped with Mg do not exhibit any 5 V discharge capacity. It is also observed that the 5 V discharge capacity of Li/A1 doped spinels will be greatly suppressed once calcinated at temperatures above 900 ℃ in preparation. It is suggested that the 5 V discharge capacity of Li/A1 doped spinels may be originated from the special chemical/structural characteristics of spinel phases containing Li or high content of A1 prepared at temperatures below 900 ℃.
文摘Listwaenite,carbonate-talc schist,and serpentinite of Sartohay ophioliticmélange,Xinjiang,northwestern China,contain variably altered chromian spinels.During the hydrothermal alteration from serpentinite to listwaenite
基金support given under the "Brain Pool Program of the Korean Federation of Science and Technology Societies" (KOFST), Republic of South Koreasupported by the Human Resources Development Program (No. 20124010203270) of the Korea Institute of Energy Technology EvaluationPlanning (KETEP) grant funded by the Korea Government Ministry of Trade, Industry and Energy
文摘LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface morphology.TEM images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.
基金Project(11264024)supported by the National Natural Science Foundation of ChinaProjects(2015MS0102,2015MS0524)supported by Natural Science Foundation of Inner Mongolia,China
文摘From the UV?Vis absorption spectra,the FT-IR absorption spectra and the Raman spectra,it is deduced that Co ionsprimarily occupy the tetrahedral(A)site,with a minor number of them entering into the octahedral(B)site in the Ni1?xCoxCr2O4compounds.The origin of the position disorder of the Co ions is consistent with the similar ionic radii of the Co ion(0.65?)and theCr ion(0.62?)at B site.The FT-IR peak at about510cm?1shifts towards high frequency side with the increasing cobalt content.Itis resulted from the reduction of the cation?oxygen distance in the octahedron by the replacement of the Ni2+with the Co2+ions.Themagnetic measurement shows that Curie temperatures(TC)are75and90K for the compounds with x=0.2and0.8,respectively.
文摘With satisfactory high temperature properties,thermal shock resistance and mechanical properties,refractories in the MgO-Al_(2)O_(3) system have become promising alternative to MgO-Cr_(2)O_(3) counterpart used as RH snorkel lining.High purity dead burned magnesia,fused magnesia and sintered spinel were used as raw materials and sulfite pulp waste as the binder,specimens of the refractories in the Mg0-Al_(2)O_(3) system were prepared for the purpose of investigating the influences in terms of the addition of three kinds of spinels,with Al_(2)O_(3) 50%,66% and 78%,by mass,respectively,and the size of MA50 spinel on properties of the specimens.Relatively superior comprehensive properties can be achieved when 16%of MA50 spinel with sizes under 1mm is adopted.
文摘A rigid-ion model is used to calculate the force constants and effective dynamical charges of sulphide and selenide spinels. The Raman and infrared phonon modes of normal cubic sulphide spinels MCr2S4 （M = Mn, Co, Fe, Hg, Zn, and Cd） and selenide spinels MCr2Se4 （M = Hg, Zn, and Cd） are calculated at the first Brillouin zone-centre using above model, The significant outcome of the present work is （i） the interatomic interaction between Cr-S （Se） dominates over the Cr-S（Se） and S-S（Se-Se） type of interatomic interactions, （ii） the effective dynamical charges of the bivalent metal ions are nearly zero, and （iii） the selenide spinels are less ionic than the sulphide spinels and the ionicity decreases as MnCr2S4 〉 FeCr2S4 〉 CoCr2S4 〉 and CdOr2C4 〉 ZnCr2C4 〉 HgCr2C4 （C = S and Se）. The zone-center phonon frequencies, calculated using these parameters, are found to be in very good agreement with the observed results.
文摘: The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships between major elements of spinels are discussed. The equilibrium temperatures, pressures and oxygen fugacities of spinels and their coexisting olivines, orthopyroxenes and clinopyroxenes have been determined using the Brey—kohler's T—P calculation methods (1990) and Ballhaus' fo2 calculation method (1991). The relationships between the composition and the equilibrium temperatures, pressures or oxygen fugacities of spinels in peridotite xenoliths from the basalts and the stable field of the spinels in the upper mantle have been shown.
文摘Detailed mineralogical and gemological records were conducted on 340 unheated spinels from the Horana, Eheliyagoda, Ratnapura, and Okkampatiya mining areas in Sri Lanka. The color of Sri Lankan spinel varies greatly: in addition to the mainstream pink to purple pink, green and blue can also be seen. Compared with spinel from other regions such as Myanmar, Vietnam, and Tanzania, Sri Lanka's spinel has more abundant inclusions: several mining areas generally have inclusions such as dolomite, apatite, zircon, and chondrodite. Minerals such as graphite and forsterite are also found in spinel produced in the Horana region;graphite and rutile have been found in spinel produced in the Okkamptiya region. Partially healed fissures are most common in spinel in the Okkampatiya mining area;Unlike Vietnamese spinel, dislocations and growth structures are almost absent in Sri Lankan spinel. The LA-ICP-MS analysis results showed that there were no significant differences among the mining areas. LA-ICP-MS analysis of 5 Sri Lankan cobalt blue spinels showed a variation of 11 to 120 ppm in this chromogenic element. The UV visible absorption spectrum results show that Sri Lankan spinel has a combination spectra with variable ratios of the spectral components Cr 3+ , V 3+ and Fe 2+ from pink to red, orange, purple to purple, and blue-green. The results of infrared spectroscopy and laser Raman spectroscopy analysis showed that all samples showed no indications for heat treatment.
基金supported by the Korea Polar Research Institute project PE24050.
文摘Fabrics of five spinel peridotites collected from Baker Rocks in northern Victoria Land,Antarctica,were investigated to elucidate the evolution of the lithospheric mantle surrounding the Transantarctic Mountains.Analyses revealed the development of crystallographic preferred orientations(CPOs),a slight decrease in mean grain size and J-index across varying proportions of clinopyroxene,and interlobate to amoeboid textures.These findings indicate that dislocation creep is the dominant deformation mechanism for the analyzed samples.
基金financially National Key R&D Program of China(No.2022YFA1504800)National Natural Science Foundation of China(Grant No.22325405,22372160,22321002)+1 种基金Liaoning Revitalization Talents Program(XLYC1807207)DICP I202104。
文摘The Zn-Al spinel oxide stands out as one of the most active catalysts for high-temperature methanol synthesis from CO_(2)hydrogenation.However,the structure–activity relationship of the reaction remains poorly understood due to challenges in atomic-level structural characterizations and analysis of reaction intermediates.In this study,we prepared two Zn-Al spinel oxide catalysts via coprecipitation(ZnAl-C)and hydrothermal(ZnAl-H)methods,and conducted a comparative investigation in the CO_(2)hydrogenation reaction.Surprisingly,under similar conditions,ZnAl-C exhibited significantly higher selectivity towards methanol and DME compared to ZnAl-H.Comprehensive characterizations using X-ray diffraction(XRD),Raman spectroscopy and electron paramagnetic resonance(EPR)unveiled that ZnAl-C catalyst had abundant ZnO species on its surface,and the interaction between the ZnO species and its ZnAl spinel oxide matrix led to the formation of oxygen vacancies,which are crucial for CO_(2)adsorption and activation.Additionally,state-of-the-art solid-state nuclear magnetic resonance(NMR)techniques,including ex-situ and in-situ NMR analyses,confirmed that the surface ZnO facilitates the formation of unique highly reactive interfacial formate species,which was readily hydrogenated to methanol and DME.These insights elucidate the promotion effects of ZnO on the ZnAl spinel oxide in regulating active sites and reactive intermediates for CO_(2)-to-methanol hydrogenation reaction,which is further evidenced by the significant enhancement in methanol and DME selectivity observed upon loading ZnO onto the ZnAl-H catalyst.These molecular-level mechanism understandings reinforce the idea of optimizing the ZnO-ZnAl interface through tailored synthesis methods to achieve activity-selectivity balance.
基金National Natural Science Foundation of China (U23A6005 and 22078069)Project funded by China Postdoctoral Science Foundation (GZB20230172 and 2023M740748)。
文摘Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,synthesized via cation exchange and calcination oxidation.These catalysts exhibit excellent efficacy in the electrocatalytic conversion of lignin model compounds,specifically 2-phenoxy-1-phenylethanol,into nitrogen-containing aromatics,achieving high conversion rates and selectivities.These catalysts were synthesized via a cation exchange and calcination oxidation process,using Prussian blue nanocubes as precursors.The porous architecture and polymetallic composition of the NiCo_(2)O_(4)spinel demonstrated superior performance in electrocatalytic oxidative coupling,achieving a 99.2 wt%conversion rate of the 2-phenoxy-1-phenylethanol with selectivities of 37.5 wt%for quinoline derivatives and 31.5 wt%for phenol.Key innovations include the development of a sustainable one-pot synthesis method for quinoline derivatives,the elucidation of a multistage reaction pathway involving CAO bond cleavage,hydroxyaldol condensation,and CAN bond formation,and a deeper mechanistic understanding derived from DFT simulations.This work establishes a new strategy for lignin valorization,offering a sustainable route to produce high-value nitrogen-containing aromatics from renewable biomass under mild conditions,without the need for additional reagents.
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supported by the National Natural Science Foundation of China(Nos.22206146,22006079,and U21A20524)the Fundamental Research Funds for the Central Universities,the Youth Innovation Promotion Association of Chinese Academy of Sciences,the Fundamental Research Program of Shanxi Province(No.202103021223280)+1 种基金the Special Fund for Science and Technology Innovation Teams of Shanxi Province(No.202204051002026)the Natural Science Foundation of Shandong Province(No.ZR2021QB133).
文摘Owing to the complexity of multicomponent gases,developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging.The spinel MMn_(2)O_(4)(M=Co,Ni,or Cu)catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene.The CuMn_(2)O_(4)sample exhibited the best catalytic performance,the conversion of benzene reached 100%at 350℃,and toluene conversion reached 100%at 250℃.XRD,N_(2)adsorption-desorption,HRTEM-EDS,ED-XRF,Raman spectroscopy,H_(2)-TPR,NH_(3)-TPD,O_(2)-TPD and XPS were used to characterize the physical and chemical properties of MMn_(2)O_(4)catalysts.The excellent redox properties,high concentration of surface Mn4+,and adsorption of oxygen species over the CuMn_(2)O_(4)sample facilitated the simultaneous and efficient removal of benzene and toluene.Additionally,in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene.Notably,as an effective catalytic material,spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene,providing some insight for the development of efficient multicomponent VOC catalysts.
基金supported by the National Natural Science Foundation of China(Nos.52370158 and 22006053)Guangzhou Science and Technology Plan Project(No.2024A04J0821)Guangdong Provincial Education Science Planning Project(Higher Education Special Project)(No.2023GXJK108).
文摘Electroplating sludge(ES),a byproduct of the electroplating industry,is a significant environmental concern due to its high content of soluble heavy metals(HMs).The significance of spinel formation from ES lies in its potential for HMs enrichment and environmental remediation,offering a sustainable solution for hazardous waste management.The article delves into themultifaceted recycling of HMs-rich spinel fromES,encompassing its synthesis,metal enrichment,and thermodynamic stability.The pyro-metallurgical and hydrometallurgical processes for spinel synthesis were discussed,with a focus on the critical role of thermodynamic data in predicting the stability and formation of spinel structures.The crystallographic and magnetic properties of spinels,with their applications in environmental remediation and energy storage are highlighted.The article provides a comprehensive reviewon the recycling of HMs-rich spinel fromES,offering a means to recycle HMs,mitigate ecological harm,and contribute to a circular economy through the recovery and application of valuable materials.The selective leaching of metals from ES also faces challenges,which was limited by the separation,purification steps and high energy consumption.This high energy consumption is a significant operational cost and also contributes to environmental concerns related to carbon emissions.It is essential to address the challenges through continued research and development,improved technologies,and supportive regulatory frameworks.
基金the Deanship of Scientific Research at King Khalid University for funding this work through Large Groups Project under(RGP.2/111/44)。
文摘In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to investigate the structural,morphological,dielectric and magnetic properties of the prepared samples.X-ray diffraction(XRD)result suggests that face-centered cube spinel nanocrystalline structure is formed.Crystallite size of the SrFe_(2)O_(4)decreases with rising of Tb ratio.The morphology,shape and size of the SrFe_(2)O_(4)were examined by scanning electron microscopy(SEM)analysis and results reveal inhomogeneous distributions of the nanostructures with high agglomeration.The electrical resistivity of the SrFe_(2)O_(4)increases with rising of Tb ratio,which is confirmed from the cyclic voltammetry.It is observed that dielectric constant of all the samples decreases with the increasing frequency range.It is determined that the dielectric constants of the spinel ferrites are frequency dependent and decrease with increasing the frequency of applied electric field.The magnetic behavior of SrFe_(2)O_(4)with different ratios of Tb was studied and it is found that the saturation magnetization values of samples decrease with increase in the substitution of Tb^(3+)at octahedral sites for Fe^(3+).This decrease in the values of M_(s) is also attributed to spin at surface of nanoparticles.
