查看更多>>摘要：SmCo based films with excellent intrinsic magnetic properties have promising applications in micro-electro-mechanical system(MEMS).However,due to the complexity of phase composition and uncon-trollable crystallization degree of SmCo hard magnetic phase in the film,both the coercivity(Hc)and remanence(Mr)of films are difficult to enhance simultaneously.In this paper,SmCo based films were deposited with a Cr underlayer and capping layer on single crystal Si substrates via magnetron sputtering process.The effects of annealing parameters and Sm/Co atomic ratio on the phase structure and coer-civity of films are discussed.By adjusting the Sm/Co atomic ratio from 1∶5 to 1∶4,Co soft magnetic phase disappears and the single phase SmCo5 is obtained,leading to the increase of coercivity of the films from 30 to 34 kOe.The influence of deposition temperature and Cu doping on magnetic properties of SmCo based films was investigated.When the deposition temperature increases from room temperature to 250 ℃,the coercivity will further increase from 34 to 51 kOe.However,a severe kink is observed in the demagnetization curves due to the poor exchanged coupling.An analysis of transmission electron mi-croscopy(TEM)confirms that the average size of non-hard magnetic amorphous phase exceeds the effective exchanged coupling length of SmCo5,which contributes to the decoupling and low remanence ratio.Therefore,doping Cu and applying a post-annealing process can significantly improve the crys-tallization degree of the films.Both the coercivity and the remanence ratio of the demagnetization curves are greatly enhanced.We propose a plausible strategy to prepare the SmCo based films with high coercivity and remanence ratio by temperature and chemical optimization,which can be utilized in high performed MEMS devices.
查看更多>>摘要：On account of the complicated magnetic exchange interactions between lanthanide ions,binuclear lanthanide complexes have broad application prospect in the field of single-molecule magnets.There-fore,it is necessary to develop reasonable bridging ligands to manipulate the directional assembly of binuclear lanthanide complexes.Herein,we selected the macrocyclic ligand LN8O2 to build up two new dilanthanide complexes[Ln2(LN8O2)(OpyO)2(H2O)2](NO3)2(1-Ln,Ln=Dy,Tb;LN8O2=hexamethyl-tet-raaza-dioxe-dipyrazolacycloicosaphane-2,9,12,19-tetraene;OpyOH=2-pyridinol-1-oxide).Dynamic magnetic studies show that 1-Dy exhibits slow relaxation behavior under a 1 kOe applied field.Further fitting analysis of relaxation times gives the effective energy barrier of 38.2 cm-1,and reveals that the slow magnetic relaxation behavior is dominated by the Orbach and Raman processes.High-resolution luminescence emission spectrum indicates the energy gap of 36.8 cm-1 between the ground state and the first excited state,consistent with the magnetic measurement results.1-Tb exhibits brilliant char-acteristic green light emission under UV light excitation.The absolute quantum yield of 1-Tb is 44.8％,and its first-order fitted decay lifetime is 779.21 μs at room temperature.This study provides the way for directional construction of high-performance molecular materials with magnetic and optical dual-function.
Muhammad JavedAyaz Arif KhanJamal KazmiNaeem Akbar b...
1304-1316页
查看更多>>摘要：The polycrystalline GdCrO3(GCO)perovskite orthochromite was synthesized by the sol-gel auto-combustion method.The Rietveld refined X-ray diffraction(XRD)profile of GCO confirms that the orthorhombic phase crystallizes in perovskite crystal structure with space group Pbnm.The transmission electron microscopy and selected area electron diffraction divulge the polycrystalline nature of the perovskite chromite.The field emission scanning electron microscopy(FESEM)images reveal the microstructural polyhedral growth of grains separated by sharp grain boundaries.The chemical states of the ions present in the compound were investigated by X-ray photoelectron spectroscopy(XPS)studies,and the electrical pathways were identified.Complex impedance studies were carried out in the experimental frequency and temperature ranges of 40 Hz-4 MHz and 178-408 K,respectively.The equivalent circuit model(RGQG)(RGBQGB)resolves the impedance response into two contributions originating from the intra-grain and inter-granular micro-constituents of the material.The electrical conduction mechanism is based on the Mott variable range hopping model.The complex electric modulus studies demonstrate the short-and long-range mobility of the charge carriers and rule out the presence of electrode effects on the dielectric relaxation mechanism of the material.The decreasing pattern of dielectric permittivity with frequency is explained by the Maxwell-Wagner type of polari-zation.The frequency dependence of the loss factor exhibits the presence of thermally activated relax-ation time distribution in the material.
查看更多>>摘要：The investigation of Sm-Ce doping on structure,conduction,and dielectric response of Bi2Ca2-2xSmxCexCoO6(x=0.000,0.025,0.050,0.075)(BCSCCO)are presented.All the specimens were synthesized by a facile synthesis technique named the co-precipitation route.X-ray diffraction(XRD)reveals that BCSCCO crystallizes into one phase with space group P21/m.The crystallite size,dislocation density,lattice parameters,lattice strain,unit cell volume,and bulk density were determined using XRD data.The structural properties of Bi2Ca2CoO6 were examined using calculations based on the density functional theory.Theoretical and experimental values discrepancy is less than 1％.A scanning electron microscope was used for performing a microstructural analysis.The SEM images demonstrate the ho-mogeneous distribution of grains with a range of sizes(0.054-0.090 μm).The alternating current(ac)conductivity,dielectric permittivity,and tangent loss were also studied as a function of frequency(20 Hz-3 MHz)at different temperatures(100-500 ℃).All synthesized samples were examined using non-linear Debye's function to determine their spreading factor and relaxation time.The specimen with the lowest crystallite size(～23 nm)exhibits a high dielectric permittivity(～3.80 × 106).The conduction mechanism was examined in the studied samples with the use of Jonscher's power law.The power law indicates that the BCSCCO(x=0.000,0.025)follows correlated barrier hopping,whereas the x=0.050 and 0.075 compositions follow non-overlapping polaron tunneling.The studied specimen Bi2Ca1.90Sm0.050Ce0.050CoO6 with the highest density(～5.65 g/cm3)displays a high electrical conductivity(～46.1 S/cm).These findings correspond to those published for ceramics made from calcium cobaltite using solid-state reactions(5.0-26.0 S/cm).
Varnitha ManikantanGovindaraj Sri VaralakshmiUjma Ashapak TamboliArchana Sumohan Pillai...
1328-1336页
查看更多>>摘要：Interest in metal nanoparticles as nanoscale drug-carrying vehicles has been increasing.In such an aspect,lanthanide metal nanoparticles are particularly intriguing.Herein,we report praseodymium nanoparticles as a novel anticancer therapeutic transporting agent.The material was made as a com-posite with the supramolecular host polymer,poly-β-cyclodextrin.The praseodymium nanorods were characterized using standard analytical techniques,including X-ray diffraction(XRD),X-ray photoelec-tron spectroscopy(XPS),and thermogravimetric analysis(TGA).In addition,they were imaged using transmission electron microscopy.The nanostructures are a long rod-shaped material with 2.0±0.1 μm in length and 230±10 nm in width.The material shows a saturation magnetization value above 30 emu/g with a coercivity value of 130 Oe.The nanocarrier is freighted with the drug 5-fluorouracil,and the encapsulation efficiency is 76.09％.The drug release is continuous from the nanocarrier(polymer-con-taining praseodymium nanoparticles)and proceeds for above 250 h.The in vitro cytotoxicities of the blank nanocarrier and the 5-fluorouracil-loaded one are deduced by testing them on MCF-7 and Vero(non-cancerous)cell lines.The cytotoxicity on the cancerous cell lines is observed,whereas the non-cancerous cells are unaffected.The IC50 values on the cell lines are reported.
查看更多>>摘要：Developing a biomaterial for wound healing applications is still a challenge.Herein,dysprosium oxide(Dy2O3),aluminum oxide(Al2O3),and graphene oxide(GO)were embedded in cast films based on polycaprolactone(PCL)to be examined for wound dressing usage.Different techniques were used to characterize the fabricated films including X-ray diffraction(XRD),Fourier transform infrared spectros-copy(FTIR),Raman,and scanning electron microscopy(SEM),besides their biological activity.The thermogravimetric analysis(TGA)exhibits high thermal stability as the scaffold weight decreases slightly to 98.6％after raising the temperature from room temperature to 280 ℃.The cell viability was investi-gated and it is shown that the viable cells grow up to approximately 93％at 75 μg/mL.Meanwhile,the cell attachment shows excellent behavior as the cells attach on most of the surface of the modified PCL which shows high biocompatibility.
查看更多>>摘要：The doping of the spinel ferrites with selective cations usually improves the properties of the parent ferrite.The effect of Co2+/Gd3+co-substitution on the microstructure,optical,and magnetic properties of Cu1-xCoxFe2-xGdxO4 prepared by the citrate-nitrate auto-combustion synthesis was investigated.Char-acterization of the samples was performed with powder X-ray diffraction(XRD),Raman and Fourier-transform infrared(FTIR)spectroscopy,field-emission scanning electron microscopy,X-ray energy-dispersive spectroscopy,UV-Vis spectroscopy,and a vibrating sample magnetometer.The results of XRD,Raman,and FTIR analysis show a gradual structural phase transition from a tetragonal(I41/amd)structure to a cubic(Fd(3-)m)structure.The bandgap energy of the studied samples is in a range of 1.57-1.75 eV with a minimum in sample x=0.06 and then increases.Magnetic investigations show that the presence of Co2+/Gd3+cations in an octahedral site of the copper ferrite structure could increase saturation magnetization and coercive field from 567.9 Oe and 23.62 emu/g to 929.4 Oe and 28.27 emu/g,respectively.
查看更多>>摘要：High-temperature calcination is effective in improving the leaching characteristics of rare earth elements(REEs)from conventional REE-bearing minerals by transforming them into more leachable forms.However,the recovery of contaminants such as Al,Fe,and Ca also increases significantly.The objective of the study was to maximize the REE extraction while minimizing the concentration of contaminant ions(Al,Ca,and Fe)in the leach solution.Representative density fractions of the coarse refuse from the Baker and Fire Clay seam coal refuse were pulverized to a top size of 180 μm and used as a feedstock for the study.All the samples generated from thermal treatment were leached at 1％(w/v)using 1.2 mol/L sulfuric acid at 75 ℃ for 2 h.Test results from a parametric program based on a Box-Behnken design were used for modeling and optimization of three operating parameters associated with the lab-scale calci-nation process.The parameters included temperature(400-800 ℃),ramp rate(2-10℃/min)and holding time(0-120 min).It was determined that the calcination temperature was the most significant parameter influencing REE recovery.The majority of the heavy rare earth elements(HREEs)were found to be present in an insoluble form in the calcination products and were marginally affected by thermal treatment.A strong correlation between light rare earth elements recovery(LREEs)and Al suggested a possible association with clays.The optimum operating conditions for high REE recovery with comparatively lower contaminant concentration for 1.6 specific gravity float and 2.2 sink fractions of Baker and Fire Clay seam material were determined to be at 776,800 ℃ and 407,800 ℃,calcining temperatures,respectively.A higher optimum temperature of 1.6 float fraction of Baker seam relative to Fire Clay seam material was due to elevated pyrite concentration in Baker seam material.Thermal treatment at 400 ℃ converted pyrite into a soluble intermedium iron oxide,resulting in a high Fe content in the leachate.Calcining at 776 ℃ converted most of the soluble iron oxide into insoluble a-hematite,considerably reducing the Fe concentration in the solution.
Widya RositaIndra PerdanaI Made BendiyasaFerian Anggara...
1366-1374页
查看更多>>摘要：In this decade,coal fly ash(CFA)is considered a potential secondary source of rare earth elements(REEs).However,most REEs in coal fly ash are encapsulated in aluminosilicate glass,making it challenging to recover them through acid leaching.In this study,a sequential alkaline-organic acid leaching was developed for the recovery of REEs from CFA.The effect of alkaline leaching using NaOH solution on the destructive ability of aluminosilicate glass,as well as the mineralogy and morphology changes of the resulting coal fly ash,was first studied.Furthermore,the effectiveness of alkaline leaching on the re-covery ability of REEs through organic acid leaching was evaluated.The results show that the maximum leaching efficiency for Si and Al,which was obtained at the optimum alkaline leaching conditions,namely NaOH concentration of 10 mol/L,reaction temperature of 65 ℃,liquid/solid(L/S)ratio of 10 mL/g,and reaction time of 90 min,is 28％and 32％,respectively.The digestion reaction with NaOH lixiviants also causes coal fly ash to become more porous,making it advantageous in the organic acid-leaching process at the REEs recovery stage.The utilization of the desilicated residue produced from the diges-tion process in acid leaching effectively increases the overall REEs recovery from 32.2％to 77.6％.
查看更多>>摘要：This study investigated the leaching of scandium from a Sc-bearing silicate ore.The Sc concentrate obtained by beneficiation pre-enrichment has 1.03 × 10-4 wt％Sc and 14.66 wt％Fe.The main Sc-bearing minerals are limonite,chlorite,sericite,and hornblende,in the form of isomorphism.High-pressure leaching(HPL)with sulfuric acid(98 wt％)and NaF was used to dispose this samples.The Sc leaching efficiency of 91.82％was obtained under the optimum conditions,which are pressure of 5.0 × 105 Pa,A/O value of 1.1,L/S value of 1.8,NaF dosage of 2 wt％,at 130 ℃ for 6 h.The X-ray diffraction(XRD)and scanning electron microscopy(SEM)results show that the residue is mainly quartz phase in the multi-hole shape.Compared with ordinary leaching for silicate,high-pressure leaching has significant ad-vantages in saving acid and energy consumption.
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