Preparation and magnetic hardening of low Ti content(Sm,Zr)(Fe,Co,Ti)_(12) magnets by rapid solidification non-equilibrium method

The Sm–Zr–Fe–Co–Ti quinary-alloys with ThMn12 structure has attracted wide attention for ultra-high intrinsic magnetic properties,showing potentiality to be developed into rare-earth permanent magnets.The Ti element in alloys is crucial for phase stability and magnetic properties,and lower Ti content can increase intrinsic magnetic properties but reduce phase stability.In this study,the 1:12 single-phase melt-spun ribbons with low Ti content was successfully prepared using a rapid solidification non-equilibrium method for the Sm1.1Zr_(0.2)Fe_(9.2)Co_(2.3)Ti_(0.5) quinary-alloy.However,this non-equilibrium ribbon did not achieve good magnetic hardening due to the uneven microstructure and microstrain.Then,annealing was carried out to eliminate micro-strain and homogenize microstructure,therefore,remanence and coercivity were significantly improved even the precipitation of a small amount of a-Fe phase which were not conducive to coercivity.The remanence of 86.1 emu/g and coercivity of 151 kA/m was achieved when annealing at 850℃ for 45 min.After hot pressing,under the action of high temperature and pressure,a small portion of ThMn12 phases in the magnet decompose into Sm-rich phases and a-Fe,while remanence of 4.02 kGs(1 Gs=10^(-4) T),and coercivity of 1.12 kOe(1 Oe=79.5775 A·m^(-1))were still acquired.Our findings can provide reference for exploring practical permanent magnets made of 1:12 type quinary-alloys.

Comparative DNA methylation reveals epigenetic adaptation to high altitude in snub-nosed monkeys

DNA methylation plays a crucial role in environmental adaptations.Here,using whole-genome bisulfite sequencing,we generated comprehensive genome-wide DNA methylation profiles for the high-altitude Yunnan snub-nosed monkey(Rhinopithecus bieti)and the closely related golden snub-nosed monkey(R.roxellana).Our findings indicated a slight increase in overall DNA methylation levels in golden snub-nosed monkeys compared to Yunnan snub-nosed monkeys,suggesting a higher prevalence of hypermethylated genomic regions in the former.Comparative genomic methylation analysis demonstrated that genes associated with differentially methylated regions were involved in membrane fusion,vesicular formation and trafficking,hemoglobin function,cell cycle regulation,and neuronal differentiation.These results suggest that the high-altitude-related epigenetic modifications are extensive,involving a complete adaptation process from the inhibition of single Ca^(2+)channel proteins to multiple proteins collaboratively enhancing vesicular function or inhibiting cell differentiation and proliferation.Functional assays demonstrated that overexpression or down-regulation of candidate genes,such as SNX10,TIMELESS,and CACYBP,influenced cell viability under stress conditions.Overall,this research suggests that comparing DNA methylation across closely related species can identify novel candidate genomic regions and genes associated with local adaptations,thereby deepening our understanding of the mechanisms underlying environmental adaptations.

Improved mammalian family phylogeny using gap-rare multiple sequence alignment:A timetree of extant placentals and marsupials

The timing of mammalian diversification in relation to the Cretaceous-Paleogene(KPg)mass extinction continues to be a subject of substantial debate.Previous studies have either focused on limited taxonomic samples with available whole-genome data or relied on short sequence alignments coupled with extensive species samples.In the present study,we improved an existing dataset from the landmark study of Meredith et al.(2011)by filling in missing fragments and further generated another dataset containing 120 taxa and 98 exonic markers.Using these two datasets,we then constructed phylogenies for extant mammalian families,providing improved resolution of many conflicting relationships.Moreover,the timetrees generated,which were calibrated using appropriate molecular clock models and multiple fossil records,indicated that the interordinal diversification of placental mammals initiated before the Late Cretaceous period.Additionally,intraordinal diversification of both extant placental and marsupial lineages accelerated after the KPg boundary,supporting the hypothesis that the availability of numerous vacant ecological niches subsequent to the mass extinction event facilitated rapid diversification.Thus,our results support a scenario of placental radiation characterized by both basal cladogenesis and active interordinal divergences spanning from the Late Cretaceous into the Paleogene.

Multiple modes of perpendicular magnetization switching scheme in single spin-orbit torque device

Spin-orbit torque(SOT)has been considered as one of the promising technologies for the next-generation magnetic random access memory(MRAM).So far,SOT has been widely utilized for inducing various modes of magnetization switching.However,it is a challenge that so many multiple modes of magnetization switching are integrated together.Here we propose a method of implementing both unipolar switching and bipolar switching of the perpendicular magnetization within a single SOT device.The mode of switching can be easily changed by tuning the amplitude of the applied current.We show that the field-like torque plays an important role in switching process.The field-like torque induces the precession of the magnetization in the case of unipolar switching,however,the field-like torque helps to generate an effective zcomponent torque in the case of bipolar switching.In addition,the influence of key parameters on the mode of switching is discussed,including the field-like torque strength,the bias field,and the current density.Our proposal can be used to design novel reconfigurable logic circuits in the near future.

Primary lymphoblastic B-cell lymphoma of the stomach:A case report

Primary stomach lymphoblastic B-cell lymphoma (B-LBL) is a rare tumor. We describe a primary stomach B-LBL in a 38 years old female who presented with nonspecific complaints of fatigue and vomiting for 2 mo. Gastrofiberscopy revealed a large gastric ulcer, which was successfully resected. Pathology showed a lymphoblastic cell lymphoma arising from the stomach, and there was no evidence of disease at any extrastomach site. Immunohistochemical staining and gene rearrangement studies supported that the stomach tumor was a clonal B-cell lymphoma. Therefore, the diagnosis of B-LBL was made based on the stomach specimen.

Coercivity,microstructure,and thermal stability of sintered Nd-Fe-B magnets by grain boundary diffusion with TbH3 nanoparticles

Grain boundary diffusion technique with TbH3 nanoparticles was applied to fabricate Tb-less sintered NdFe-B permanent magnets with high coercivity. The magnetic properties and microstructure of magnets were systematically studied. The coercivity and remanence of grain boundary diffusion magnet are improved by 112% and reduced by 26% compared with those of the original magnet, respectively. Meanwhile, both the remanence temperature coefficient（α） and the coercivity temperature coefficient（β） of the magnets are improved after diffusion treatment. Microstructure shows that Tb element enriches in the surface region of Nd2Fe（14）B grains and is expected to exist as（Nd,Tb）2Fe（14）B phase. Thus, the magneto-crystalline anisotropy field of the magnet improves remarkably. As a result, the sintered Nd-FeB magnets by grain boundary diffusion with TbH3 nanoparticles exhibit enhanced coercivity.

Enhancement of corrosion resistance in sintered Nd-Fe-B permanent magnet doping with different CuZn5 contents

Nd-Fe-B permanent magnets doped with CuZn5 powders were prepared via conventional sintered method. The effects of CuZn5 contents on magnetic properties and corrosion resistance of the magnets were sys- tematically studied. It shows that the remanence, coercivity, and maximum energy product decrease gradually with the increase in CuZn5 doping content. The magnet＇s corrosion kinetics in autoclaves environment and its electrochemical properties in electrolytes were also examined. It is interesting to see that the weight loss of 3.5 wt% and 4.5 wt% CuZn5 powders doping magnets is only 1 and 0 mg.cm^-2 after autoclaves test at 121 ℃, 2 × 10^5 Pa for 500 h, respectively, which is much lower than that of the magnets without CuZn5 doping. Electrochemical results show that the CuZn5 powders doping magnets display more positive corrosion potential （Eoorr） and lower corrosion current density （Icorr） than those of the original magnets without CuZn5 doping in sulphuric acid electrolyte and distilled water. It is, therefore, concluded that doping CuZn5 powders is a promising way to enhance the corrosion resistance of sintered Nd-Fe-B magnets.

High-temperature magnetic properties of anisotropic Mn Bi/Nd Fe B hybrid bonded magnets

Anisotropic MnBi/NdFeB （MnBi contents of 0 wt%, 20 wt%, 40 wt%, 60 wt%, 80 wt%, and 100 wt%） hybrid bonded magnets were prepared by molding compression using MnBi powders and commercial hydro-genation disproportionation desorption and recombination （HDDR） NdFeB powders. Magnetic measurements at room temperature show that with MnBi content increasing, the magnetic properties of the MnBi/NdFeB hybrid bonded magnets all decrease gradually, while the density of the hybrid magnets improves almost linearly. In a temperature range of 293-398 K, the coercivity temperature coefficient of the hybrid magnets improves gradually from -0.59 %.K^-1 for the pure NdFeB bonded magnet to -0.32 %.K^-1 for the hybrid bonded magnet with 80 wt% MnBi, and the pure MnBi bonded magnet exhibits a positive coercivity temperature coefficient of 0.61%-K^-1.

Microstructure and magnetic properties of SmCo_(5) sintered magnets

SmCo_(5)sintered magnets with good thermal stability are mainly used in high-temperature field.In this study,two types of SmCo_(5) powders with different nominal z values were mixed and synthesized into SmCo_(5) magnets by the traditional powder metallurgy method.The magnetic properties of the SmCo_(5) sintered magnet are maximum energy product of(BH)_(max)=172.29 kJ·m^(-3),remanence of B_(r)=7.47×10^(5)A·m^(-1)and coercivity of H_(ci)=2.42 T.The results show that there are three coexisting phases in the magnet,which are SmCo_(5)phase,Sm_(2)Co_(7)phase and Sm_(2)O_(3)phase.The microstructural observation indicates that the average grain size in the magnet is about 8μm,and the high coercivity of this magnet is attributed to these fine grains.X-ray diffraction(XRD)and electron backscatter diffraction(EBSD)results indicate that the magnet has a well-aligned(00l)orientation texture.

Origin of low coercivity of high La-Ce-containing Nd-Fe-B sintered magnets

The origin of low coercivity of high La-Cecontaining Nd-Fe-B sintered magnets was analyzed based on characterization of the microstructure,magnetic domain structure,and magnetization reversal process.It can be found that the coercivity of magnet decreases sharply and the ratio value of coercivity(H_(cj))to anisotropic field(H_(A))is below the theoretical value when the amount of La-Ce substitution for Nd is more than 40 wt%.The grain boundaries with poor magnetic isolation in the high La-Cecontaining Nd-Fe-B sintered magnets play an important role in reducing the coercivity of the magnet.In addition,a larger proportion of the reversible portions can be found for the magnet with a large content of La-Ce,which will lead to the low performance of the magnet.

Influence of angle of attack on a combined opposing jet and platelet transpiration cooling blunt nose in hypersonic vehicle

Flying condition with angle of attack is inevitable in a hypersonic vehicle,and it may influence the thermal protection system(TPS)performance of opposing jet and its combinations.A 3D Navier–Stokes equation and shear stress transfer(SST)k-ωmodel with compressible correction are employed to simulate the angle of attack characteristics of a blunt body with opposing jet and platelet transpiration TPS.The flowfield and heat flux transfer for angles of attack 0°,3°,6°with jet pressure ratio PR=0.1 and 0°,6°,12°with PR=0.2 are obtained.Numerical results show that the flowfield is no longer symmetrical with the effect of the angle of attack.The flowfield and heat transfer in windward and leeward performed adversely.The recompression shock wave in windward is strengthened,which increases local temperature and strengthens heat transfer.The opposing jet fails in thermal protection when the angle of attack reaches critical value;however,the critical angle of attack can be promoted by increasing PR.Finally,the transpiration gas can strengthen the cooling efficiency of windward,thereby,increasing the critical angle of attack.

Numerical simulation of single roller melt spinning for NdFeB alloy based on finite element method

The numerical simulation model of single roller melt spinning for rapid quenching process of NdFeB alloy was built,and the vacuum chamber,cooling roller and sample were taken into account as a system.The existing mature technology was in order to verify the correctness of simulation.The rapid quenching ribbons with different roll speeds were used as the simulation objects.The results of the numerical simulation and experiments show that the validity of the model has been testified and the reasons of the formation of complete quenching ribbons and by-product have been explained.The experimental thickness of the ribbons is proportional to the theoretical thickness.In the same spray condition,with the roll speed increasing,the thickness decreases linearly.At the speed range of25-30 m·s^(-1),the simulated calculation date is close to the experimental date,which can be considered as an ideal technological parameter.

Low-cost Sm0.7Y0.3Co5 sintered magnet produced by traditional powder metallurgical techniques

RCo5(R=rare earth)sintered magnets have good temperature stability,so it is still widely used in high temperature field.In this paper,by the method of adding liquid phase SmCo1.7 to the main phase,Sm0.7Y0.3Co5 magnet was prepared by traditional powder metallurgical process.The results show the presence of a main phase RCo5,a minor phase R2 Co7,and a R-rich phase in the magnet.Contrasting the results of the XRD(X-ray diffraction)in random and oriented directions,the magnet has a well-aligned(00l)orientated texture,which is consistent with the result of the electron backscattered diffraction(EBSD).The Sm0.7Y0.3Co5 sintered magnet has good magnetic properties as remanence(Br)is 0.96 T,the coercivity(Hcj)is 1201.96 kA·m-1,and maximum magnetic energy product((BH)max)is 175.16 kJ m-3.

Coercivity enhancement mechanism of Tb-diffusion Nd-Fe-B sintered magnets studied by magneto-optical Kerr optical microscope

The coercivity,microstructure,and magnetic domain structure of Nd-Fe-B sintered magnets by grain boundary diffusion process(GBDP) with TbH3 nanoparticles were systematically investigated.Compared to the original magnet,the coercivity(Hci) of the GBDP magnets improved from 1702 to 2374 kA·m^(-1) with few remanence reduced from 1.338 to 1.281 T.Electron probe microanalysis(EPMA) analysis showed that Tb diffused along grain boundary,mainly concentrated in the boundary layer of the main phase,and formed a core-shell structure.Magneto-optical Kerr optical microscope(MOKE) analysis showed that there were two types of magnetic domain reversal in one grain:gradual reversal(GR) and abrupt reversal(AR).When the applied field decreased from saturated magnetic field,the reversal magnetic domain nucleated and then spread over the whole grain gradually,which was called GR.However,some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis loops.When the applied field increased above Hh,reversed magnetic domain would suddenly appear and occupy most of the area of the grain,which was called AR.That is because AR grains have higher reversed magnetic domain nucleation field(HRN2) than GR grains(HRN1).After GBDP,the area of AR region increased obviously and GR region decreased accordingly,indicating that the core-shell structure could change GR grain into AR grain.The coreshell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tbrich shell.Therefore,large AR area led to high coercivity.

Effect of oxygen enrichment on sintering behavior of high proportion vanadium-titanium magnesite concentrates

To achieve high-efficiency utilization of complex and unmanageable iron-containing minerals,the effects of oxygen enrichment on productivity,yield,flame front speed,exhaust gas peak temperature,and desulphurization reaction of the vanadium-titanium magnetite sintering process as well as sinter tumble index and mineralogy were clarified,with oxygen enrichment concentrations ranging from 21 to 29 vol.%.Results indicated that with increasing the oxygen enrichment concentration from 21 to 27 vol.%,the flame front speed increased from 30.3 to 40.0 mm min^(-1),the yield enhanced from 72%to 77%,and the productivity augmented from 1.83 to 2.67t m^(-2)h^(-1);in the meantime,the tumble index was improved from 73.7%to 77.9%,and the exhaust gas peak temperature rose from 376.4 to 484.8℃.The main reason for the improvement in sintering properties was the increased combustibility of fuels and the generation of proper liquid phase that improved the permeability of the packed bed.The improved sinter strength is mainly due to the increase in the phase fraction of silico-ferrites of calcium and aluminium.In addition,oxygen enrichment sintering could significantly increase the desulphurization level of vanadium-titanium magnetite sinter and the rate of desulphurization reaction during sintering process.

Preface

In the post-Moore era,the further reduction of the energy consumption of computing systems cannot be achieved by transistor scaling.Multiple alternative paths are now being actively explored for continuous improvement in energy efficiency,including novel device research and novel computer architecture research.Meanwhile,it is noticed that many applications we widely use today are error-tolerant,that is,a controlled amount of errors occurred in their internal computation do not affect their application-level quality.