查看更多>>摘要：The high-temperature magnetic performance and microstructure of Sm1-xGdx(CobalFe0.09Cu0.09Zr0.025)7.2(x=0.3,0.5)magnets were investigated.With the isothermal aging time decreasing from 11 to 3 h,the temperature coefficient of intrinsic coercivity in the temperature range of 25-500 ℃,β25-500 c,was optimized from-0.167％/℃ to-0.112％/℃ for x=0.3 magnets.The noticeable enhancement(～33％)of temperature stability is correlated with the increased content of 1∶5H cell boundary phase and its relatively high Curie temperature as well.However,for the x=0.5 magnet,it is found that the presence of Sm5Co19 phases and wider nanotwin variants hinder the formation of 1∶5H cell boundary phase.The insufficient 1∶5H is not beneficial to the proper redistribution of Cu in cell boundary,making the x=0.5 magnet difficult to achieve higher temperature stability.Consequently,the approach of adjusting the isothermal aging process can offer guidance for attaining superior magnetic performance in the tem-perature range from 25 to 500 ℃ for Gd-substituted Sm2Co17-type magnets.
查看更多>>摘要：The synthesis of size-controlled Sm2Fe17 magnetic particles is a prerequisite for the fabrication of high-performance Sm2Fe17N3 permanent magnetic materials.Here,Sm2Fe17 was synthesized using a cost-effective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm2Fe17.The effects of reduction-diffusion reaction temper-ature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt％of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm2Fe17 particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm2Fe17N3 material was successfully obtained.This study could be useful for the devel-opment of high-performance Sm2Fe17N3 magnetic materials utilizing reduction-diffusion technology.
查看更多>>摘要：The magnetic properties and magnetic phase transition critical behavior of Gd3Ga5O12 single crystals subjected to high-pressure heat treatment were investigated.The results show that high-pressure heat treatment reduces the Curie temperature and magnetization of the sample.Under a magnetic field change of 5 T,the maximum isothermal magnetic entropy of the sample is approximately 19.73 J/(kg·K).High-pressure heat treatment increases the phase transition temperature range and leads to an increase in the magnetic refrigeration power.Both Gd3Ga5O12 single crystals and the high-pressure heat-treated sample undergo a second-order phase transition.The critical behavior of the samples aligns with the mean field model acquired via critical model fitting.This indicates that the samples exhibit long-range exchange interactions in the system near the Curie temperature.Thus,this material can be used as a magnetic refrigerant for low-temperature applications.
查看更多>>摘要：The significant rise of ultra-violet(UV)radiation and pathogenic infectious bacteria poses a serious threat to global health.Numerous researchers'interests are attracted by novel materials with strong UV-blocking ability,antibacterial activity and low toxicity to other species.In this case,a simple wet chemical method with different annealing temperatures(400,500,and 600 ℃)was employed to create highly effective rare earth(Sm)-doped ZnO nanorods.The(101)plane of wurtzite ZnO shifts towards a lower angle with increasing annealing temperature,according to the X-ray diffraction(XRD)study findings,which additionally establishes the consequence of lattice expansion.Occurrence of doublet peaks of Sm 3d(Sm 3d5/2 and Sm 3d3/2)in the X-ray photoelectron spectroscopy(XPS)spectrum clearly validates the substitution of Sm3+ions in the 500 ℃-annealed samples.The 500 ℃-annealed nanorods exhibit combined performances of the wide band gap,improved UV absorbance,and vivid green luminescent emission(563 nm).Additionally,the nanorods have favorable UV-blocking execution of 96％for UVA at 360 nm,92％for UVB at 320 nm,and 57％for UVC at 225 nm,which is greater than the majority of ZnO-related materials that have been reported up to this date.Sm doping is also appropriate for improving bacterial inhibition against the two studied strains(Escherichia coli and Staphylococcus aureus),in addition to the intriguing features discussed above.Furthermore,with maximum inhibition zone diameters of 20±0.72 and 18±0.57 mm,respectively,these nanorods exhibit high inhibitory action against E.coli and S.aureus bacterial strains.The rare earth-doped material developed during the current experiment,which was annealed at 500 ℃,could potentially serve as an effective replacement for UV-blocking and antibacterial material,especially for biomedical applications.
查看更多>>摘要：The present study focuses on the synthesis and characterization of lanthanum(La3+)-doped calcium nanoferrites(CaLaxFe2-xO4;x=0.025,0.050,0.075 and 0.100)using the sonochemical method.Various techniques were employed to analyze the effect of La3+infusion.Raman spectroscopy confirms the presence of active A1g,T2g and Eg modes in the CaLaxFe2-xO4 nanoferrite,indicating the formation of an active ferrite system.The introduction of La3+doping results in a significant increase in the band gap energy,rendering the nanoferrites insulating(3.23-3.57 eV).At higher frequencies,the impedance studies reveal minimal losses and better AC conductivity,pointing to improved dielectric characteristics.At higher frequencies,the Q-factor of La-doped calcium nanoferrites shows lower electromagnetic losses.The M-H curve exhibits ferromagnetic behavior,with La3+-doped calcium nanoferrites displaying a saturation magnetization ranging from 12.72 to 18.10 emu/g.The incorporation of La3+also induces enhanced electrical polarization,leading to notable dielectric loss and increased absorption of electromagnetic waves.Consequently,these CaLaxFe2-xO4 nanoferrites demonstrate potential as effective microwave ab-sorbers across a wide frequency range,with significant shielding absorption observed at 8.8-9.1 GHz.
查看更多>>摘要：Employing the spin-polarized density functional theory(DFT),we investigated the magnetic and optical properties of buckled arsenene(β-As)after doping a whole series of lanthanide(Ln)atoms.Our results demonstrate that Ln atoms can be stably doped into the single layer arsenene.Upon doping Ln atoms,La,Ce,Pr,Nd,Gd,Dy and Lu@arsenene behave dilute magnetic semiconductor(DMS)properties,while the Pm,Sm,Eu,Ho,Er and Tm@arsenene show half metallic characteristics.Most of Ln@arsenene systems favor the long-range ferromagnetic ordering.The maximum of Ln-doped systems'magnetic moments and magnetic anisotropy energy(MAE)can reach 8 μB and 7.48 meV,respectively.The doping of Ln atoms into arsenene improves the optical responses in visible and infrared regions.Strain can alter the magnetic coupling between Sm and the neighboring As atoms and reduce the system's magnetic moment.Besides,strain can improve the MAE of these systems,accompanied by the change of the easy magnetization of Sm@arsenene.Furthermore,compressive and tensile strains effectively improve the optical responses in visible and ultraviolet region,respectively.Based on the obtained results,we believe that the Ln@arsenene monolayer has application prospects in photoelectronics and spintronics such as high-density memory devices.
查看更多>>摘要：Twelve novel transition-rare-earth metal clusters,formulated as[Ni18Pr14(μ3OH)14(dmpa)10(mmt)10(SO4)4(CH3COO)16]·9CH3OH·5H2O(1,H3dmpa=dimethylolpropionic acid,and Hmmt=2-mercapto-5-methyl-1,3,4-thiadiazole)[Ni36RE102(OH)138(mmt)18(Hdmpa)30(H2dmpa)12(CH3COO)72(NO3)36(SO4)18(H2O)30]·Br6(RE=Nd(2),Sm(3),Eu(4)and Gd(5))[Ni12RE10(μ3-OH)10(dmpa)8(mmt)8(SO4)2(CH3COO)8(H2O)4]·8CH3OH·7H2O(RE=Tb(6),Dy(7),Ho(8),Er(9)and Y(10))[Ni8Pr8(μ3-OH)8(mmt)8(Hdpga)16(CH3COO)8]·8CH3OH(11,H2dpga=diphenyl-glycolic acid),and[Ni16Tb6(μ3-OH)24(mmt)8(Hdpga)4(dpga)4(CH3COO)2(NO3)4(H2O)2]·12CH3OH·5H2O(12),were synthesized sol-vothermally by using different ligand combinations and rare earth nitrates.X-ray crystal structure an-alyses reveal that complexes 1 and 12 possess sandwich-like structure.Compounds 2-5 are isostructural and feature a hexagonal structure,shaped like a"Star of David".Isostructural 6-10 present ring-like structure,as well as the cluster 11.The structural variations of these complexes can be attributed to the effect of lanthanide contraction.Moreover,the template effect of SO42-anion derived from the slow decomposition of Hmmt ligand also plays a significant role in the formation of cluster skeletons.The in-situ mechanism for the generation of sulfate anion is briefly discussed.Meanwhile,the magnetic properties of complexes 2-11 were studied which show typical antiferromagnetic interactions.
查看更多>>摘要：The efficient enrichment and separation of rare earth elements(REEs)from sulfate leachates of ion-adsorption type rare earth ore(IATREO)is still a challenge.This work presents a novel extractant 2-(bis((2-ethylhexyl)oxy)phosphoryl)-2-hydroxyacetic acid(HPOAc)for the selective extraction and effi-cient enrichment of REEs from sulfate leachates of IATREO.HPOAc exhibits higher extraction ability for all fifteen REEs(Ⅲ)than naphthenic acid(NA)at pHini=1.56.Furthermore,it has no drawbacks of di-(2-ethylhexyl)phosphoric acid(P204)and 2-ethylhexyl phosphoric acid mono-2-ethylhexylester(P507)such as weak extraction ability towards light REEs(Ⅲ)and high stripping acidity for heavy REEs(Ⅲ).It has better separation performance for metal ion impurities than P204 and P507,especially for the typical impurity Al(Ⅲ).Furthermore,the HPOAc system has better phase separation behavior and extraction phenomena.A simulated operation with two-stage counter-current extraction and single-stage stripping of REEs was carried out using unsaponified HPOAc.The recovery of REEs reaches 98.7％.The concen-tration of REEs increases from 0.44 to 130.35 g/L,indicating a nearly 300-fold increase.Furthermore,the content of REEs increases from 77.8 wt％to 97.6 wt％.So HPOAc has the potential to selectively recover REEs from sulfate leachates of IATREO.
查看更多>>摘要：Sc and Y are key rare earth elements and are widely used in lamp phosphors,lasers and high-performance alloys.However,highly efficient extraction and separation of Sc3+and Y3+is laborious,harmful,slow,and costly,strongly necessitating more efficient extraction and separation techniques.Here,we produced hydrated Sc3+-and hydrated Y3+-controlled graphene oxide(GO)membranes and find that both hydrated cations were completely self-rejected by the membrane.By combining this self-rejection effect of the larger hydrated Y3+-controlled GO membrane and the rapid passage of the membrane through the smaller hydrated Sc3+,we proposed a strategy to separate Sc3+and Y3+by using a hydrated Y3+-controlled GO membrane.The experimental results show that the permeation rate of Sc3+exceeds that of Y3+when the separation factor reaches 4.02,which can be attributed to the interlayer sieving effects of the GO membrane.Our finding illustrates the use of a forward osmosis process with a GO membrane for the efficient separation of Sc3+and Y3+by interlayer sieving,which provides a new effective and eco-friendly method for the separation of rare earth elements.
查看更多>>摘要：Water quality has been found to significantly influence the flotation operations due to the alteration of surface properties of minerals.The effect of cations on the flotation of RE minerals has been studied,however,there are still very limited information regarding the effect of anions.The present study examined the impact of specific anions such as Cl-,SO42-,and HCO3 on the flotation performance of rare earth(RE)ore.This study integrates flotation experiments,rheology measurements,entrainment ex-periments,zeta potential measurements and settling experiments.It is observed that an increase in the concentration of these anions lead to a decrease in the recovery of RE minerals and an increase in the recovery of FeO minerals and thus negatively affecting flotation efficiency.This adverse effect is most pronounced with Cl-and least noticeable with HCO3.An increase in the non-selective entrainment of gangue minerals is observed when the flotation pulp has higher viscosity.The reduction in the zeta potential of fine particles in the presence of these results in a higher pulp viscosity due to increased attractive forces between particles.These findings were verified by settling experiments and calculations based on the DLVO theory.
NETL
NSTL
万方数据