Grain boundary restructuring and La/Ce/Y application in Nd–Fe–B magnets

Since the 1980 s, Nd–Fe–B with largest energy product(BH)max approaching the theoretical limit has become the landmark of permanent magnetic material.The application spectrum for Nd–Fe–B continues to expand over time both in the industrial and commercial sectors, which leads to growing research interests for solving the long-standing drawbacks of Nd–Fe–B, i.e., poor corrosion resistance, low coercivity, high Dy/Tb and low La/Ce/Y consumption.Concerning the above obstacles, we aim to present the novel grain boundary restructuring(GBR) approach, from GB design, processing, to structure evolution and property evaluation with a focus on the corrosion and coercivity mechanism of the restructured 2:14:1-typed magnets.Starting with an introduction to the fundamental of GBR, two representative examples,high-electrode-potential(Pr, Nd)32.5Fe62.0Cu5.5 and low-melting-point Dy71.5Fe28.5, are given with detailed descriptions of the advantages of GBR to enhance the intrinsic anti-corrosion stability and to strengthen the coercivity at low Dy consumption.Microstructure–property correlations are established to understand the critical importance of regulating the restructured GB phase to maximize the all-round performance of the 2:14:1-typed permanent magnets.Aiming at sustainable and balanced development of rare earth(RE) industry, the proceeding section proposes new prototypes of La–Ce and Y–Ce co-substitutions with dual benefits of stabilizing the 2:14:1 tetragonal phase and strengthening the intrinsic hard magnetism.The findings of additional REFe2 intergranular phase delight that the GBR approach also opens up a new horizon of research and application to develop high-performance La/Ce/Y-rich permanent magnets with deliberately tailored GB phase.

Enhanced magnetic properties in chemically inhomogeneous Nd-Dy-Fe-B sintered magnets by multi-main-phase process

Homogeneous substitution of Dy for Nd in the hard magnetic 2:14:1 phase can effectively enhance coercivity to ensure the high temperature operation,however,inevitably deteriorate remanence at expense.In this work,we performed a comparative investigation of the two magnets prepared by multimain-phase(co-sintering Nd_(2)Fe_(14)B and(Nd,Dy)_(2)Fe_(14)B powders)and single-main-phase(sintering(Nd,Dy)_(2)Fe_(14)B powders)approaches.The comparative investigation reveals that at the same Dy substitution level(2.16 wt%),such chemically inhomogeneous multi-main-phase magnet possesses better roomtemperature magnetic properties as well as thermal stability than those of the single-main-phase one with homogenous Dy distribution in the matrix grains.Room-temperature magnetic properties H_(Cj)=1664 kA/m,B_(r)=1.33 T and(BH)_(max)=350.4 kJ/m^(3)for the multi-main-phase magnet are all better than those for the single-main-phase magnet with H_(Cj)=1536 kA/m,B_(r)=1.29 T and(BH)_(max)=318.4 kj/m^(3).In addition,over the temperature range from 295 to 423 K,both the temperature coefficients of coercivity and remanence for the multi-main-phase magnet are also lower than that for the single-main-phase magnet.Such superior magnetic performance is attributed to the short-range magnetic interactions inside individual 2:14:1 phase grains and the long-range magnetostatic interactions between adjacent grains with inhomogeneous Dy distribution.Our work provides a feasible approach of enhancing coercivity and retaining energy product simultaneously in the Nd-Dy-Fe-B permanent magnets.

Enhanced damping capacity of ferromagnetic Fe-Ga alloys by introducing structural defects

The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy,and the associated damping capacity is proportional to the magnetostriction constant.In contrast,here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2-3 times through introducing structural defects including interfacial dislocations and stacking faults,despite that these defects deteriorate the magnetostriction.These structural defects were introduced by aging the BCC(body-centered-cubic)solution-treated precursor,for which the formation of mechanically harder FCT(face-centered-tetragonal)and/or FCC(face-centered-cubic)phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants.The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy.These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.

Role of primary Zr-rich particles on microstructure and magnetic properties of 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets

Trace Zr addition is essential for achieving desired cellular nanostructure and large coercivity in the pinning-controlled 2:17-type Sm-Co-Fe-Cu-Zr magnets that have served as the strongest high temperature permanent magnets for over 40 years.However,accompanying this is the formation of Zr-rich particles that may deteriorate the hard magnetic properties.Besides the formerly-reported 1:3R Zr-rich platelets,in this work,1–2μm sized Zr6(Co,Fe)23(6:23)particles(Fm 3 m)and 100–200 nm sized 1:3R Zr-rich particles were also found based on combined structural identifications and element mapping analysis.Around such particles,the desired 1:5H cell wall precipitates that provide the strongest pinning force of magnetic domain wall motions are rare,forming the precipitate-free-zones(PFZs).The 1:5H-PFZs and the soft magnetism of both 6:23 and 1:3R Zr-rich particles act as local weak pinning points,which are unfavorable to retain the large magnetization in strong opposite fields and lead to poor squareness.As observed in a Sm25Co45.9Fe19.5Cu5.6Zr4.0(wt.%)magnet,the co-existence of such Zr-rich particles and the associated 1:5H-PFZs leads to a pretty low squareness factor of only 52.89%given the large coercivity of 29.04 kOe.Our findings suggest that careful controlling the Zr content and avoiding its aggregation to form harmful 6:23 and 1:3R Zr-rich particles are essential for achieving high squareness as well as large energy product in the Sm-Co-Fe-Cu-Zr permanent magnets.

Shortened processing duration of high-performance Sm-Co-Fe-Cu-Zr magnets by stress-aging

Simultaneously achieving high energy product and high coercivity in the 2:17-type Sm-Co-Fe-Cu-Zr high temperature magnets has been closely relied on long-term isothermal aging to develop complete cellu-lar nanostructure.In this work,we report a novel stress-aging approach that can substantially shorten the aging time to fabricate high-performance Sm-Co-Fe-Cu-Zr magnets.As exhibited by a model magnet Sm_(25) Co_(50.2) Fe_(16.2) Cu_(5.6) Zr_(3.0)(wt.%),applying 90 MPa compressive stress can shorten the aging time from 20 h for conventional isothermal aging to 10 h at the same aging temperature for achieving nearly equiv-alent magnetic performance.Further comparative study between the 10 h-aged samples under stress-containing and stress-free conditions revealed that the stress not only promotes the precipitation of the cell boundary phase that are essential for enhancing the coercivity but also accelerates the dissociation of the cell edge defects that are detrimental to squareness factor,without destroying the[001]crystal-lographic texture.Such microstructural improvements enable the achievement of high-performance with maximum energy product of∼30 MGOe and coercivity above 35 kOe at reduced aging time.

Effects of pre-aging on defects evolution and magnetic properties of Sm-Co-Fe-Cu-Zr magnets

The heterogeneous precipitation in the 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets has been found to contain complex formation and dissociation of defects.Though low-temperature pre-aging has been utilized to promote the precipitate nucleation by the enlarged chemical driving force,how the defects evolve after pre-aging and how the possibly changed defects state affects the subsequent precipitation behavior remain unclear.In this work,a model magnet Sm25Co47.9Fe18.5Cu5.6Zr3.0(wt%)was selected to study.Through comparison with the as-solution-treated state,it is found that pre-aging for 2 h at 550℃reduces the defects density,which was characterized by less cell boundaries(i.e.,larger cell size)and less basal stacking faults inside the cells(i.e.,higher 2:17 R ordering degree).Further studies reveal that after aging for the same time(10 h)at the same temperature(830℃),the reduced density of defects by preaging also leads to slower precipitation/phase transformation kinetics when co mpared with the non-preaged one,which was characterized by the lower 2:17 R ordering degree and smaller coercivity for the former.These findings suggest that pre-aging has a strong influence on the density of defects and their evolution during subsequent isothermal aging process,which should be carefully considered to tailor the microstructure and magnetic properties of Sm-Co-Fe-Cu-Zr magnets.

Revisiting the pinning sites in 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets

It is still an open debate whether the 1:5 H cell boundaries(CBs)or the intersections of 1:3 R platelets and1:5 H CBs are the strong pining sites for the cellular nanostructured 2:17-type Sm-Co-Fe-Cu-Zr high temperature permanent magnets despite that they have been widely applied in advanced industries since 1970 s.Herein,through tuning the volume fraction of Zr-enriched 1:3 R platelets by varying the second-step aging time,the pinning behavior in a model magnet Sm_(2.5)Co_(44.9)Fe_(21.5)Cu_(5.6)Zr_(3.0)(wt%)was investigated.The results show that the volume fraction of 1:3 R platelets can be effectively enlarged without changing the cell size(i.e.the volume fraction of CBs)by extending the aging time at 400℃.Micro scopic TEM characterizations co mbined with macro scopic magnetic measurements reveals that the locally thickened 1:3 R platelets after long-term second-step aging reduce the effective pinning area by interrupting the magnetic domain walls at CBs,weakening the average pinning strength and the coercivity of the magnet.Consequently,our work supports that the 1:5 H CBs act as the dominating pinning sites instead of the intersections of 1:3 R platelets and 1:5 H CBs,which may provide an important insight towards understanding the hard magnetism of pinning-controlled permanent magnets.

Exchange interaction and demagnetization process of high-abundance rare-earth magnets sintered using dual alloy method

The 2:14:1-type rare-earth(RE)-Fe-B permanent magnets prepared by the dual alloy method have been found to possess much superior magnetic properties to those prepared by the single alloy method,providing an appealing route to promote the utilization of high-abundance RE elements Ce and La and balance the use of the RE source.However,the relationship between magnetic interactions among different 2:14:1 main phases and superior magnetic properties is still unclear.In this study,we investigated the magnetic interactions and reversal field distribution in these magnets using first-order reversal curve(FORC)images.The FORC images showed that(Nd,Pr)27.8(La,Ce)2.7FebalM1.4B1.0(S-9)and(Nd,Pr)19.5(La,Ce)11.0FebalM1.4B1.0(S-36)have the characteristics of multiple main phases.The reverse magnetic fields corresponding to the soft and hard main phases,as well as the associated exchange coupling,were highly dependent on the La Ce content.The higher the La Ce content,the weaker the exchange coupling and the more asynchronous the demagnetization process.In addition,the FORC images indicated that the magnetization reversal process also varies with La Ce content,where the nucleation and propagation of reversed domains dominant in the S-9 magnet,while the domain propagation in the S-36 magnet is considerably suppressed.Additional micromagnetic simulations also revealed that the coercivity and exchange coupling of multi-main-phase magnets decrease with increasing La Ce content,correlating well with the experimental results.These findings may not only contribute to a better understanding of the complex magnetic interactions between the soft and hard phases and how they affect macroscopic magnetic properties but also help in improving the magnetic performance of the RE-Fe-B magnets with high La Ce content.

Formation mechanism of partial stacking faults by incompletemixed-mode phase transformation: A case study of Fe-Ga alloys

Partial stacking faults(PSFs) formed by incomplete mixed-mode phase transformation have been found to exhibit unfixed slip distance of closely-packed planes unlike those of the deformation-induced stacking faults(SFs) with fixed distance. Though engineering PSFs can yield appealing properties, such as the enhanced damping capacity, understanding of the interaction between lattice distortion and atomic diffusion and their influences on forming PSFs is still far from being clear. Herein we performed a case study on aged Fe-Ga alloy that undergoes a mixed-mode phase transformation from body-centered cubic(BCC)to ordered face-centered cubic(FCC). The TEM investigations showed that the faulted {111}-FCC distance of the PSFs is shorter than a/6<112> of the typical {111}-<112> SFs in deformed FCC materials and the PSFs have disordered Fe and Ga arrangements. Further studies revealed that such PSFs will not be completely dissociated at FCC twin boundaries(TBs) even after long term isothermal aging. Consequently,the formation of PSFs can be ascribed to the transformation-dependent atomic ordering and lattice shear strain of the parent BCC lattice, where the diffusion-controlled glides of the PSFs-associated dislocations will accelerate atomic diffusions due to the dislocation-pipe effect along <112>-FCC direction, but may hinder the atomic diffusions across the {111}-FCC TBs due to the retarding effect. This study may add important insight into the defects process during mixed-mode phase transformation and broaden the knowledge of the interaction between concurrently-happened lattice distortion and atomic diffusion.

Enhanced Magnetostriction of a Narrow Hysteresis Tb_(0.26)Dy_(0.54)Ho_(0.20)Fe_2 Alloy

In this work, a magnetic annealing method used to enhance the magnetostrictive property of a narrow hysteresis alloy Tb0.26Dyo.saHo0.20Fe2 is reported. Cylindrical-rod shaped specimen with 〈110〉 crystal orientation was fabricated using zone-melting unidirectional solidification technique, followed by annealing in a transverse magnetic field of 366 kA/m. The crystal orientation and bi-phase solidified morphology can be retained after magnetic annealing. A high magnetostriction of 1.508×10^-3 was obtained in the magnetically annealed specimen, which is 25.2% larger than the untreated one. Simultaneously, the magnetostriction hysteresis width is slightly enlarged from 4.45 to 6.36 kA/m, which is still much lower than that of the Ho-free Tbo.3Dy0.TFe2 alloy. The additional anisotropy which is induced by magnetic annealing, as reflected by the magnetic hysteresis loops, is responsible for the enhancement of magnetostrictive performance.

Epigenetics and environmental health

Epigenetic modifications including DNA methylation,histone modifications,chromatin remodeling,and RNA modifications complicate gene regulation and heredity and profoundly impact various physiological and pathological processes.In recent years,accumulating evidence indicates that epigenetics is vulnerable to environmental changes and regulates the growth,development,and diseases of individuals by affecting chromatin activity and regulating gene expression.Environmental exposure or induced epigenetic changes can regulate the state of development and lead to developmental disorders,aging,cardiovascular disease,Alzheimer's disease,cancers,and so on.However,epigenetic modifications are reversible.The use of specific epigenetic inhibitors targeting epigenetic changes in response to environmental exposure is useful in disease therapy.Here,we provide an overview of the role of epigenetics in various diseases.Furthermore,we summarize the mechanism of epigenetic alterations induced by different environmental exposures,the influence of different environmental exposures,and the crosstalk between environmental variation epigenetics,and genes that are implicated in the body's health.However,the interaction of multiple factors and epigenetics in regulating the initiation and progression of various diseases complicates clinical treatments.We discuss some commonly used epigenetic drugs targeting epigenetic modifications and methods to prevent or relieve various diseases regulated by environmental exposure and epigenetics through diet.

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE_(3),AlRE2 and AlRE_(3).The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE_(3),Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.

Promoting the La solution in 2:14:1-type compound:Resultant chemical deviation and microstructural nanoheterogeneity

RE_(2)Fe_(14)B-based(RE,rare earth)permanent magnets containing abundant and cheap La/Ce have attracted intense attention recently.In comparison with Ce that can fully replace Nd in the 2:14:1 lattice,La substitution for Nd has long been limited at a low level.Here we present that through doping La35 Ce65 alloy with the La/Ce ratio in natural mineral,stable 2:14:1 phase can be maintained at 1273 K within the entire substitution range of[(La_(35)Ce_(65))、(Pr_(20)Nd_(80))_(1-x)]_(2.14)Fe_(14)B(0.6≤x≤1.0,at.%),as verified by composition analysis,microstructural characterization and magnetic measurements.Interestingly,the promoted La solution in 2:14:1 phase induces two unique findings upon coexisting La-Ce-Pr-Nd:i)Compared to Ce that fits well with the nominal concentration,La deviates noticeably from the nominal one;ii)Nanoscale spinodal-decomposition-like phase separation is observed due to different solubilities of La-Ce-Pr-Nd elements in 2:14:1 phase.Above joint effects induce higher Curie temperature than estimation based on the rule of mixture,which delights the prospect of La_(35)Ce_(65)alloy in developing low-cost permanent materials.

JARID2 coordinates with the NuRD complex to facilitate breast tumorigenesis through response to adipocyte-derived leptin

Background Proteins containing the Jumonji C(JmjC)domain participated in tumorigenesis and cancer progression.However,the mechanisms underlying this effect are still poorly understood.Our objective was to investigate the role of Jumonji and the AT-rich interaction domain-containing 2(JARID2)—a JmjC family protein—in breast cancer,as well as its latent association with obesity.Methods Immunohistochemistry,The Cancer Genome Atlas,Gene Expression Omnibus,and other databases were used to analyze the expression of JARID2 in breast cancer cells.Growth curve,5-ethynyl-2-deoxyuridine(EdU),colony formation,and cell invasion experiments were used to detect whether JARID2 affected breast cancer cell proliferation and invasion.Spheroidization-based experiments and xenotumor transplantation in NOD/SCID mice were used to examine the association between JARID2 and breast cancer stemness.RNA-sequencing,Kyoto Encyclopedia of Genes and Genomes,and Gene Set Enrichment Analysis were used to identify the cell processes in which JARID2 participates.Immunoaffinity purification and silver staining mass spectrometry were conducted to search for proteins that might interact with JARID2.The results were further verified using co-immunoprecipitation and glutathione S-transferase(GST)pull-down experiments.Using chromatin immunoprecipitation(ChIP)sequencing,we sought the target genes that JARID2 and metastasis-associated protein 1(MTA1)jointly regulated;the results were validated by ChIP-PCR,quantitative ChIP(qChIP)and ChIP-reChIP assays.A coculture experiment was used to explore the interactions between breast cancer cells and adipocytes.Results In this study,we found that JARID2 was highly expressed in multiple types of cancer including breast cancer.JARID2 promoted glycolysis,lipid metabolism,proliferation,invasion,and stemness of breast cancer cells.Furthermore,JARID2 physically interacted with the nucleosome remodeling and deacetylase(NuRD)complex,transcriptionally repressing a series of tumor suppressor genes such as BRCA2 DNA repair associated(BRCA2),RB transcriptional corepressor 1(RB1),and inositol polyphosphate-4-phosphatase type II B(INPP4B).Additionally,JARID2 expression was regulated by the obesity-associated adipokine leptin via Janus kinase 2/signal transducer and activator of transcription 3(JAK2/STAT3)pathway in the breast cancer microenvironment.Analysis of various online databases also indicated that JARID2/MTA1 was associated with a poor prognosis of breast cancer.Conclusion Our data indicated that JARID2 promoted breast tumorigenesis and development,confirming JARID2 as a target for cancer treatment.

Molecular deconvolution of the neutralizing antibodies in duced by an in activated SARS-CoV-2 virus vaccine

Dear Editor,The rapid emerge nee and persistence of the pan demic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has had enormous impacts on global health and the economy.Effective vaccines against SARS-CoV-2 are urgently needed to control the coronavirus disease 2019(COVID-19)pandemic,and multiple vaccines have been found to be efficacious in preventing symptomatic COVID-19(Polack et al.,2020;Wu et al.,2020;Jones and Roy,2021).