Nd2Fe14B/α-Fe纳米晶双相复合稀土永磁合金的磁性研究

采用单辊熔体快淬法将名义成分为Nd7.5Fe92.5-xBx(x=4．5，5．5，6．5，7．5at．％)的母合金制备成Nd2Fe14B／α—Fe纳米晶双相复合稀土永磁合金薄带．对母合金和合金薄带的磁性能进行对比分析，并分别讨论了合金中硼含量与快淬速度对合金薄带磁性能及薄带厚度的影响．     

非晶晶化对Nd2Fe14B/α-Fe纳米复合材料磁性能的影响

用熔体快淬 晶化处理(RQC)工艺制备了Nd2Fe14B/α-Fe纳米复合材料,研究晶化热处理温度和时间对Nd7.5Fe86B6.5纳米复合材料磁性能的影响.结果表明: 快淬速度为25m/s时制备的Nd7.5Fe86B6.5合金薄带的最佳热处理工艺为700℃保温10min; 快淬速度为30m/s时制备的Nd7.5Fe86B6.5合金薄带的最佳热处理工艺为700℃保温15min,并达到最佳磁性能; 在相同晶化温度下,非晶化程度越高的样品,所需的晶化时间越长; 晶化热处理时不仅要完全消除磁体内的非晶相,而且要使晶粒的尺寸尽可能的小.     

纳米复相α-Fe /Nd2Fe14B材料电磁波吸收性能研究

采用熔体快淬及晶化退火工艺制备了Nd2Fe14B/α-Fe纳米晶双相材料,对该材料在0.5～18GHz频段的复介电常数、复磁导率进行了测试,其磁谱表现为驰豫型特征。由于磁损耗和介电损耗的共同作用,纳米复相Nd2Fe14B/α-Fe吸波材料在9～17GHz具有良好的吸波性能,其匹配厚度为1.6～2.5mm。     

纳米复相α-Fe／Nd2Fe144B材料电磁波吸收性能研究

采用熔体快淬及晶化退火工艺制备了Nd2Fe14B／α-Fe纳米晶双相材料，对该材料在0．5-18GHz频段的复介电常数、复磁导率进行了测试，其磁谱表现为驰豫型特征。由于磁损耗和介电损耗的共同作用，纳米复相Nd2Fe14B／α-Fe吸波材料在9—17GHz具有良好的吸波性能，其匹配厚度为1．6-2．5mm。     

Nb对快淬Nd10Fe84B6合金微观组织和磁性能的影响

研究了添加Nb对快淬Nd10Fe84B6合金磁性能、微观组织和晶化温度的影响.结果表明:添加Nb可以提高快淬态合金中非晶相的热稳定性,减小最佳退火温度和晶化起始温度之间的温度差,抑制热处理时α-Fe和Nd2Fe14B晶粒的预先析出和长大,有效细化了晶粒,提高磁性能.快淬Nd10Fe83Nb1B6合金经过715℃热处理10 min,磁性能达到Br=0.90 T,iHc=750 kA/m,(BH)max=120 kJ/m3,较之Nd10Fe84B6合金,内禀矫顽力提高了25%,最大磁能积提高了14%.     

Pr2Fe14B／α—Fe纳米复合永磁的淬态组织对回火时相变过程和磁性的影响

纳米复合永磁材料的原始淬态组织对最终的显微组织结构和磁性有着决定性的影响,为了弄清其影响规律,研究了成分为Pr7Fe88B5的双相纳米复合永磁材料的淬态组织在回火时相转变的过程和晶化后的组织结构及磁性。X射线谱和Mossbauer谱的研究结果表明,在不同辊速下制得的快淬带样品的组织结构是不同的。原始淬态组织的不同导致回火时的不同相变过程,它们分别是（1）非晶相Am Pr2Fe14B α-Fe→Pr2Fe14B α-Fe;（2）非晶相Am α-Fe→(Am)′ α-Fe→α-Fe 1:7相＋Pr2Fe14B→Pr2Fe14B α-Fe;(3)Am→Am′＋α－Fe→1:7相＋α-Fe→Pr2Fe14B α-Fe。虽然样品最终的相组成均为α-Fe和Pr2Fe14B,但不同原始态的样品晶化后的显微组织和磁性并不同相同。     

快淬速度对Nd2Fe14B/α-Fe纳米晶双相复合稀土永磁材料相结构和磁性能的影响

采用熔体快淬法在不同快淬速度下制备了Nd8Fe86B6合金中Nd2Fe14B/α-Fe双相复合纳米晶薄带．用X射线衍射仪（XRD）和振动样品磁强计（VSM）测量了薄带的相结构和磁性能．结果表明：Nd8Fe86B6合金的最佳快淬速度为18m/s，在此条件下制备的合金薄带平均晶粒尺寸细小．综合磁性能好；合金薄带的平均晶粒尺寸为24．4nm，磁性能为Br=0．69T。Br/Bs=0．66。Hc=296．1kA/m．     

Fe-Cu-Nb-Si-B快淬带的组织、磁性及微区力学性能

采用单辊熔体快淬法制备宽6~8 mm、厚30~40μm的Fe78.3Cu0.6Nb2.6Si9.5B9合金薄带.其直流磁性能为:饱和磁感应强度Bs=1.06 T,剩磁Br=0.39 T,矫顽力Hc=3.53 A/m,最大磁导率μm=2.43 m H/m;交流磁性能为:铁损P0.5 T/1 k Hz=22.2 W/kg,P0.2 T/100 k Hz=864 W/kg,对应的有效磁导率μe分别为833和1225.场发射高分辨扫描电镜观察发现,不同工艺参数制备的快淬带因晶化程度不同,对应的断口形貌特点也不同,非晶相和纳米晶复合的合金带断口可见镜面区和雾状区、周期性褶皱、河流状花样等,而晶化接近完全的合金带呈沿晶断裂.纳米力学探针研究表明,非晶相和纳米晶复合的合金带的微区硬度和弹性模量低于晶化接近完全的合金带.基于Luborsky法,利用自行设计的装置测量断裂应变,对材料的韧性进行半定量分析.     

Nd~(3+)的稳定能与晶场参数及磁交换作用的关系

基于单离子模型,通过对Nd3+磁晶各向异性哈密顿数值的求解,研究了温度趋于0 K时,Nd3+离子稳定能与晶场参数及磁交换作用的关系.结果表明,对于强磁物质(如NdCo5,Nd2Co17,Nd2Fe14B等),Nd3+贡献的稳定能与晶场参数B20近似成正比,而对磁交换作用的变化不敏感.     

Zr和Nb掺杂对Nd2Fe14B/α-Fe纳米复合永磁薄带显微组织和磁性能的影响

比较了Zr,Nb掺杂对Nd8.60Fe80.80Cu0.3Zr2-xNbxB8.30(x=0,1,2)交换耦合纳米复合永磁薄带相组成、显微结构和磁性能的影响. 结果表明:Zr和Nb均能有效地抑制晶粒的长大. Zr与B结合生成ZrB2,消耗了合金中部分B元素,导致合金中硬磁性相N2Fe14B含量的减少. 与Zr相比,Nb能更有效地抑制晶粒长大,提高样品磁滞回线的方形度. 仅掺杂Nb的晶化样品Nd8.60Fe8 0.80Cu0.3Nb2B8.30具有最佳的磁性能:Br=0.89T,H ci=479.1kA·m-1,(BH)max=107.4kJ·m-3.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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