Optimal design of sintered Ce_9Nd_(21)Fe_(bal)B_1 magnets with a low-melting-point (Ce,Nd)-rich phase

A systemic investigation was done on the chemistry and crystal structure of boundary phases in sintered Ce9Nd21FebalB1 （wt%） magnets. Ce2Fe14B is believed to be more soluble in the rare-earth （RE）-rich liquid phase during the sintering process. Thus, the grain size and oxygen content were controlled via low-temperature sintering, resulting in high coercivity and maximum energy products. In addition, Ce formed massive agglomerations at the triple-point junctions, as confirmed by elemental mapping results. Transmission electron micros- copy （TEM） images indicated the presence of （Ce,Nd）Ox phases at grain boundaries. By controlling the composition and optimizing the preparation process, we successfully obtained Ce9Nd21FebalBx sintered magnets; the prepared magnets exhibited a residual induction, coerciv- ity, and energy product of 1.353 T, 759 kA/m, and 342 kJ/m3, respectively.

Effects of substrate temperature and annealing treatment on the microstructure and magnetic characteristics of TbDyFe films

A series of TbDyFe films were prepared by DC magnetron sputtering. The effects of substrate temperature and annealing temperature on the phase structure and the magnetic properties of the sample films were investigated. The an-nealing treatment has a significant influence on the microstructure and the magnetic properties of the sample. The results obtained by XRD indicate that the films deposited at a temperature lower than 525℃ are amorphous and have an easy magnetization direction perpendicular to the film plane. An RFe2 phase is formed in the sample annealed at 550℃ and the residual phases observed are Fe and rare earth oxide. The magnetic properties Hc and Mr/Ms of the film annealed at 550℃ obtain the maximum values,for which the formation of the RFe2 phase is mainly responsible. An annealing treatment leads to a rotation of the sample’s easy axis from being parallel to the film surface to becoming vertical.

Influence of Magnetic Annealing on Properties of SmFe Thin Films

SmFe thin films were prepared by DC magietron sputtering at room temperature and 300 %. The influence of magnetic annealing temperature on the phase structure and magnetic properties was investigated. Results showed that thermal sputtering followed by a heat treatment process helped to obtain a structure with a relatively large fraction of SmFe2. Residual phases observed were α-Fe, Sm2O3, and unknown phases. During the annealing treatment, the intrinsic compressive stress in SmFe films was relieved and could become tensile at higher annealing temperatures. The degree of in-plane anisotropy weakened, and furthermore, the anisotropy transformed into out-of-plane anisotropy.

Magnetic-Field-Induced Strains of Bonded Ni-Mn-Ga Melt-Spun Ribbons

Non-stoichiometric Ni50Mn27 Ga23 polycrystalline ribbons are prepared by melt-spinning technique. The magneticfield-induced strain （MFIS） of Ni-Mn-Ga bulk alloy prepared by bonding the melt-spun ribbons is obtained. The experimental results show that Ni50Mn27Ga23 bonded ribbons exhibit a typical thermal-elastic shape memory effect in the thickness direction. The martensitic transformation strain of bonded ribbons is an expansive strain of about 0.3% without the magnetic field and a contractive strain of about -0.46% at the magnetic field of 1 T. The field can not only enhance the value of the martensitic transformation strain of the bonded ribbons, but can also change the direction of the strain. The bonded ribbons alloy presents negative MFIS and obtains a larger value of the strain though influenced by the adhesive between the ribbons. Therefore, the preparation technique of the Ni-Mn-Ga bulk alloy by bonding melt-spun ribbons is helpful to get rid of the size restriction of the ribbon and to broaden the applications of the ribbons.

Effect of different additives on the properties of lithium alanate

LiAIH4 doped with Ni and Ce（SO4）2 additives and the effect of doping on temperature and hydrogen release were studied by pressure-content-temperature （PCT） experiment and X-ray diffraction （XRD） analysis. It is indicated that doping with Ni induces a significant decrease in temperature in the first step and LiA1H4 doped with 1mol% Ni presents the most absorption of hydrogen. Doping with Ce（S04）2 also causes a marked decrease, while the amount of hydrogen release changes only slightly. The results from X-ray diffraction analysis show that doping does not cause any structural change; Ni and Ce-containing phases are not observed at room temoerature or even at 250℃.

1-D Open-channeled 3-D Supramolecular Frameworks Built with 2,3-Dihydroxybutanedioic Acid (H_4dhbd) and 2,2':6',2'-Terpyridine (tpy)~i

The complex [Cu2（H2dhbd）2（tpy）2]·CH3OH·4H2O 1 （H4dhbd =2,3-dihydroxybutanedioic acid, tpy = 2,2＇：6＇,2＇＇-terpyridine） has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis. The crystal is of triclinic, space groups Pi with a= 8.6859（17）, b = 11.223（2）, c = 12.275（2）A, α = 112.454（3）, β= 98.435（3）, γ = 105.593（3）°, V= 1022.5（3） A^3, Z = 1, C38H42Cu2N6O18, Mr = 997.86, Dc = 1.621 g/cm^3, μ= 1.127 mm^-1, F（000） = 514, T = 293（2） K, the final R = 0.0539 and wR = 0.1394 for 3550 observed reflections with I 〉 2σ（I）. In the dinuclear unit, two Cun atoms are bridged by two H2dhbd chelate anions, forming a 14-membered ring, in which the distance of Cu…Cu atoms is 7.0526（12）A. Adjacent dinuclear units are constituted through π-π interactions and C-H…O hydrogen-bonding interactions, fashioning the final 3-D supramolecular framework with 1-D open channels. Variable-temperature magnetic susceptibility measurement indicates the presence of weak antiferromagnetic exchange interactions between Cu^II ions.

Isocyanide-Based One-Pot Cascade Synthesis of 3-Acyl Isoindolinones

A series of 3-acyl-substituted isoindolinone derivatives were synthesized in a one-pot manner via the reaction of o-bromobenzaldehydes,isocyanides,and carboxylic acids in the presence of palladium catalyst and base. The reaction employing easily available starting materials features simple operation and high efficiency. The mechanistic study showed that the reaction might undergo 1) Pd-catalyzed [3+2] cyclization of o-bromobenzaldehyde with isocyanide and the re-insertion of another molecule of isocyanide,2) addition of carboxylic acid to in situ formed ketenimine followed by a rearrangement relay to give 3,3-diacyl-substituted isoindolinone derivative. Further transformations of the obtained products through decarbonylation could also be realized.

Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties

Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows： （i） Sm1 TM17 ： Br=0. 62 T, jHc=803.7 kA/m, （BH）m= 58.97 kJ/m^3, p=7 Ω· m; （2） NdFeB： Br=0.485 T, jHc=766.33 kA/m, （BH）m=37.96 kJ/m^3, ρ=Ω · m. The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.

Nanotwin-assisted nitridation of quenched FeNi alloy nanopowders for rare-earth-free magnets

L1_(0)-ordered FeNi alloy with a high uniaxial magnetic anisotropy and large magnetic moment is a promising candidate for rare-earth-free permanent magnets applications.However,the synthesis of this chemically ordered phase remains a longstanding challenge because of its low chemical order-disorder transition temperature(200-320℃).Although a non-equilibrium synthetic route based on a nitrogen topotactic reaction has been proposed as a valid approach,the volume fraction and degree of chemical ordering of the product phase are limited.Herein,we propose a promising approach that promotes the efficient formation of L1_(0)-ordered nitride phase in FeNi nanopowders by introducing a quenching treatment during a low-oxygen induction thermal plasma process.The quenched FeNi nanopowders possessed much smaller powder sizes(40.4 vs 74.0 nm),exhibited higher number densities of nanotwins(39.8%vs 24.1%)and formed much larger volume fraction(33.6 wt.%vs 0.6 wt.%)of ordered phase than the unquenched nanopowders.Notably,quenching-induced high-density nanotwins led to the dominant coverage of serrated{001}crystal facets over the surfaces of the FeNi nanopowders.Such unique features substantially accelerated the formation of the L1_(0)-ordered nitride phase in the FeNi nanopowders because the{001}crystallographic orientation had the highest nitrogen diffusivity.This work provides not only a valid synthetic approach for mass production of the L10-ordered nitride phase in FeNi nanopowders but also novel insights into the crystal-defect-assisted nitridation of nanomaterials.

MOF衍生的磷化钴纳米纤维用于电催化氧析出和氢析出反应

高性能催化剂的开发和利用是能源领域的研究热点,其中制备具有高活性面积的一维纳米催化剂是目前的难点.本研究以金属有机框架(MOF)复合纤维为前驱体,通过热处理-磷化过程制备了具有氧析出(OER)和氢析出(HER)双功能特性的CoP纳米纤维.该MOF衍生策略也可以用来制备其他一维纳米材料,如Co_(3)O_(4)纳米纤维、Co/C纤维和CoP/C复合纤维.研究表明,CoP纳米纤维的直径约100 nm,长度可达几微米,具有较高的活性面积.通过Cu掺杂改性可以提高CoP纳米纤维的催化活性,碱性条件下测得其对OER和HER的过电位分别为330和170 mV,可与商业的贵金属催化剂相媲美.该工作也为一维双功能电极催化剂的制备及功能化提供了研究基础.

Base-controlled annulation of tryptamine-derived isocyanides with nitrile imines for access to polycyclic spiroindoline derivatives

An annulation reaction of tryptamine-derived isocyanides with hydrazonyl chlorides in the presence of bases was developed.Controlled by different bases,[1+2+3]annulation and[1+2+3]/[2+3]annulation cascade were realized.In the latter reaction,five new chemical bonds as well as three new heterocycles were formed in one step.It showed extremely high efficiency,relatively broad substrate scope,milder reaction conditions,good tolerance of functional groups and good chemoselectivity.

Microstructure and damping properties of MnCuNiFeCe alloy

Mn-Cu alloys could exhibit high damping ability and excellent mechanical properties after proper heat treatment. In order to reduce the influence of impurity elements on damping capacity of Mn-Cu alloys, rare ele- ment cerium （Ce） was added into MnCuNiFe alloys. It is indicated that the contents of C, S and Si which have adverse effects on the damping capacity decrease and the grains are refined with the Ce content increasing. The microstructure of the MnCuNiFeCe alloy was investigated by X-ray diffraction （XRD）, scanning electron microscope （SEM） and transmission electron microscopy （TEM）. The damping ability （tane） of the alloy was characterized by dynamical mechanical analyzer （DMA）. It is found that the damping ability （tane） retains a very high level which is all above 0.05 from the temperature of -50 to 75 ℃ with the addition of Ce element. It is expected that the Ce alloying MnCuNiFe alloy with refined grains could find wide applications in the field of industry.

Deformation induced Elinvar behavior in Fe-Ni Invar alloy

Fe-Ni alloys exhibiting temperature-independent elastic modulus(Elinvar)and thermal expansion(Invar)properties have found wide and significant applications,such as liquefied natural gas tanks,micrometers,reed relays,hairsprings,etc.[1].Owing to the technical and theoretical importance of Invar and Elinvar effects,the underlying mechanisms of such effects have been

High coercivity Nd-Ce-Fe-B nanostructured ribbons prepared from melt spinning technique

The Ce-substituted(Nd1-xCex)12.2 Fe81.6 B6.2(x=0.0, 0.2, 0.4, 0.6) nanocrystalline ribbons were prepared by annealing amorphous ribbons from melt spinning. It is found that all ribbons are in a multiphase state consisting of a-Fe phase, Nd(Ce)-rich phases and RE2 Fe14 B(RE = Nd, Ce) phases. However, the coercivity of all annealed ribbons can reach a considerably high value without doping any heavy rare earth or other coercivity enhanced elements. A strong intergranular exchange coupling appears in these nanocrystalline ribbons. The Nd12.2 Fe81.6 B6.2 ribbons with multiphase have a coercivity of about 11.3 k Oe, and the coercivity decreases slightly with increasing Ce content. A coercivity of 7.5 kOe can be obtained when60 at% of Nd is replaced by Ce(x = 0.6) due to the grain refinement and the strong intergranular exchange coupling. This provides a practical approach of fabricating high coercivity Ce-substituted Nd-Fe-B materials.

Resolution of a discrepancy of magnetic mechanism for Elinvar anomaly in Fe-Ni based alloys

Fe-Ni based Elinvar alloys performing temperature-independent elastic modulus over a wide temperature range have found wide and significant applications. Although numerous models involved with magnetism have been proposed to explain the Elinvar anomaly, some of the puzzles concerning the anomaly have not been fully understood. In this work, a remarkable discrepancy between the inflection temperature of modulus and the Curie temperature in a typical Fe-Ni-Cr Elinvar alloy was found,challenging the magnetic mechanism for Elinvar anomaly. Microstructural characterization and dynamic mechanical analysis demonstrate the occurrence of a strain glass transition with continuous formation of nanodomains. Accompanying such a transition, the gradual softening in the elastic modulus of austenite offsets the modulus hardening due to the vibrational anharmonicity of nanodomains upon cooling, leading to the Elinvar effect. As a result, the inflection temperature of modulus corresponds to the initiation of nanodomains' formation instead of magnetic transition. Our findings specify the association of Elinvar anomaly with structural aspects, and provide new insights into the mechanism of Elinvar anomaly in Fe-Ni based alloy.

Structure and electrochemical properties of LaMgNi4-xCox(x=0-0.8)hydrogen storage electrode alloys

LaMgNi（4-x）Cox（x = 0-0.8） electrode alloys used for MH/Ni batteries were prepared by induction melting. The structures and electrochemical hydrogen storage properties of the alloys were investigated in detail.X-ray diffraction（XRD） and scanning electron microscopy（SEM） analysis show that LaMgNi4 phase and LaNi5 phase are obtained. The lattice parameters of the two phases increase first and then decrease with Co content increasing.The electrochemical properties of the alloy electrodes were measured by means of simulated battery tests. Results show that the addition of Co does not change the discharge voltage plateau of the alloy electrodes. However, the maximum discharge capacity increases from 319.9 mAh·g^-1（x = 0）to 347.5 mAh·g^-1（x = 0.4） and then decreases to331.7 mAh·g^-1（x = 0.8）. The effects of Co content on electrochemical kinetics of the alloy electrodes were also performed. The high rate dischargeability（HRD） first increases and then decreases with Co content increasing and reaches the maximum value（95.0 %） when x = 0.4. Test results of the electrochemical impedance spectra（EIS）,potentiodynamic polarization curves and constant potential step measurements of the alloy electrodes all demonstrate that when Co content is 0.4 at%, the alloy exhibits the best comprehensive electrochemical properties.

Preparation of Sintered(Ce_(1-x)Nd_x)_(30)Fe_(bal)Cu_(0.1)B_1 Magnets by Blending Powder Method

Magnets with nominal compositions of （ Nd1-x Cex ） 30 Febal Cu0.1 B1 （x = 0, 0.15, 0.3 and 0.4, mass% ） have been fabricated by blending powder method. The remanence （B r）, intrinsic coercivity （He） and maximum en- ergy product （BH） of the RE2Fe14B type magnets deteriorated when Nd was replaced by Ce. The chemical composition and crystal structure of magnet were investigated systemically. Backscattered electron （BSE） and energy dispersive spectroscopy （EDS） results revealed that Ce-rich and Ce-lean matrix grains coexisted in the magnets. The magnetic coupling mechanism among the double hard magnetic phases was discussed. Low melting point RE-Cu phase was in favor of the formation of uniform continuous grain boundary. Transmission electron microscopy （TEM） investigation showed the presence of fcc （Nd,Ce）Ox phase in the grain boundary. When the Ce content was 15% of the total amounts of all the rare earth, the maximum energy product of the sintered magnet was 359.8 kJ/ms.

One-Step Synthesis of Ultrathin Carbon Nanoribbons from Metal–Organic Framework Nanorods for Oxygen Reduction and Zinc–Air Batteries

Two-dimensional(2D)carbon nanostructures play a critical role in energy-related applications,but developing facile and efficient strategies to synthesize these kinds of nanostructures is extremely rare.Herein,ultrathin carbon nanoribbons(CNRibs),with a thickness of 2–6 nm and length over 100 nm,have been strategically fabricated via a one-step pyrolysis of one-dimensional(1D)metal–organic framework nanorods(MOF NRods).Manipulating the diameters of MOF NRods will result in the formation of porous carbon nanostructures in 1D or 2D morphologies.Functional CNRibs with N doping or metal active site immobilization have also been studied.The CNRibs decorated with iron nanoclusters and single atoms have been used as excellent catalysts for the oxygen reduction reaction under both alkaline and acidic conditions,as well as zinc–air batteries.This work gives deep insights into the structural evolution from 1D to 2D morphology,providing an efficient approach to fabricate low-dimensional nanomaterials with controllable morphologies and functionalities for electrochemical applications.

Spherical to truncated octahedral shape transformation of palladium nanocrystals driven by e-beam in aqueous solution

The crystallographic shapes of nano crystals play critical roles in determi ning their physical and chemical properties.Liquid phase synthesis serves as one of the most importa nt approaches for preparing shape-controlled nano crystals,therefore,understa nding the formation mecha nisms of the thermod yn amic equilibrium structures of nano crystals in liquid soluti on is importa nt.Using in situ liquid cell tran smissi on electron microscopy(TEM),we observe for the first time the shape transformation of individual palladium nanocrystals from energy unfavored spherical shapes into equilibrium truncated octahedrons in aqueous solution.Via quantitative analysis of the shape evolution dynamics of an individual Pd nano crystal,we find that about 10%of nano crystal atoms were relocated during the shape tran sformation.The mass tran sport is attributed to the synergetic effect of electron beam irradiation and water environment.

Microstructures and magnetic properties of Sm(Co_(bal)Fe_(0.245)Cu_(0.07)Zr_(0.02))_(7.8)sintered magnet solution-treated at high temperature

Sm(CoFeCuZr)zsintered permanent magnet has been attracting a great deal of attention by virtue of its high-temperature magnetic properties,low temperature coefficient and good corrosion and oxidation resistance.The microstructures and magnetic properties of Sm(Co_(ba1)Fe_(0.245)Cu_(0.07)Zr_(0.02))_(7.8)sintered permanent magnet prepared by a traditional powder metallurgy method were investigated.Tunable magnetic properties,especially the maximum magnetic energy product,(BH)max,were obtained through adjusting solution-treated temperatures.With solution-treated temperature increasing from 1155 to 1195℃,remanence(Br)almost keeps constant and knee point coercivity(Hk),magnetic induction coercivity(H_(cb))and(B_(H))maxfirst increase and then decrease.The intrinsic coercivity(H_(cj))of magnet solution-treated at 1195℃is 738 kA·m^(-1),which is less than 2/5 that of magnet solution-treated at 1183℃(>1927 kA·m^(-1)).The reason that magnet solution-treated at 1195℃shows lower Hcjthan magnet solution-treated at 1183℃is considered to be mainly related to the fact that there are a lot of cells with abnormally small size.In addition,the lattice constant of Sm(Co_(bal)Fe_(0.245)Cu_(0.07)Zr_(0.02))_(7.8)sintered permanent magnet solution-treated at 1195℃,given by indexing highresolution transition electron microscope(HRTEM)results,is considered to be related to the formation of cells with abnormally small size which decreases H_(cj).