Hard Magnetic Nanoparticles and Nanocomposites

1999 ◽  
Vol 577 ◽  
Author(s):  
Anit Giri ◽  
Krishna Chowdary ◽  
Sara A. Majetich
Keyword(s):  
High Performance ◽  
Permanent Magnets ◽  
Characteristic Length ◽  
Alloy Nanoparticles ◽  
Feco Alloy ◽  
Random Anisotropy ◽  
Sample Density ◽  
Anisotropy Model ◽  
Feco Nanoparticles ◽  
Exchange Length

ABSTRACTMany high performance permanent magnets are nanostructured materials. The magnetic properties of nanoparticles are discussed in terms of characteristic length scales, including the maximum monodomain size and the exchange length. Experimental results for ball milled SmCo5 nanoparticles are presented, showing deviations from idealized behavior. Because of the short exchange length, this can be understood in terms of independent nucleation of reverse domains in grains within larger particles. With a much longer exchange length, FeCo alloy nanoparticles show reduced coercivity in a high density compact, in accordance with the random anisotropy model. The SmCo5 and FeCo nanoparticles were mixed and compacted in an attempt to make an exchange spring nanocomposite. However, significant exchange between the hard and soft phases was not observed because the sample density was too low. Processing considerations for improved co-compaction of these nanoparticles are discussed.

Robust FeCo nanoparticles embedded in a N-doped porous carbon framework for high oxygen conversion catalytic activity in alkaline and acidic media

2018 ◽  
Vol 6 (46) ◽  
pp. 23445-23456 ◽  
Author(s):  
Xuan-Wen Gao ◽  
Junghoon Yang ◽  
Kyeongse Song ◽  
Wen-Bin Luo ◽  
Shi-Xue Dou ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Porous Carbon ◽  
Graphitic Carbon ◽  
Alloy Nanoparticles ◽  
Feco Alloy ◽  
Acidic Media ◽  
Highly Active ◽  
Carbon Framework ◽  
Feco Nanoparticles ◽  
Oxygen Conversion

FeCo alloy nanoparticles were nucleated onto graphitic carbon layers through the pyrolysis of polydopamine (PDA) sub-micrometer spheres to form a highly active electrocatalytic system that exhibits excellent oxygen conversion catalytic activity in both alkaline and acidic media.

Synthesis of FeCo Alloy Nanoparticles for Electromagnetic Absorber by Polyol Method

2020 ◽  
Vol 20 (8) ◽  
pp. 4926-4932
Author(s):  
Dae Seok Seo ◽  
Jong Hwan Park ◽  
Jae Chul Ro ◽  
Kyung Sub Lee ◽  
Su Jung Suh
Keyword(s):  
Electron Microscopy ◽  
Synthesis Temperature ◽  
Alloy Nanoparticles ◽  
Feco Alloy ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Optimized Conditions ◽  
Feco Nanoparticles

The correlations among magnetic properties, synthesis temperature, and composition of FeCo nanoparticles were investigated herein. Fe80Co20 alloy nanoparticles synthesized at different temperatures (383, 393, 403, 413, 428, and 443 K) showed variable compositions and aggregation degrees of the FeCo nanoparticles. Under the optimized conditions of synthesis temperature of 403 K and duration of 1 h, FeCo nanoparticles were synthesized at molar ratios of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9. The FeCo alloy nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometer, fourier transform infrared, and network analyzer. With increasing Co content, the extent of aggregation increased. The cobalt ferrite phase was detected under some conditions, and all FeCo nanoparticles showed high saturation magnetization and low coercive forces. The prepared FeCo nanoparticles exhibited high permeability at a high frequency range.

scholarly journals Investigation on the La Replacement and Little Additive Modification of High-Performance Permanent Magnetic Strontium-Ferrite

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1034
Author(s):  
Ching-Chien Huang ◽  
Chin-Chieh Mo ◽  
Guan-Ming Chen ◽  
Hsiao-Hsuan Hsu ◽  
Guo-Jiun Shu
Keyword(s):  
High Performance ◽  
Single Phase ◽  
Permanent Magnets ◽  
High Efficiency ◽  
Cobalt Content ◽  
Preparation Condition ◽  
Milling Process ◽  
Experimental Parameters ◽  
La Substitution ◽  
Hard Magnets

In this work, an experiment was carried out to investigate the preparation condition of anisotropic, Fe-deficient, M-type Sr ferrite with optimum magnetic and physical properties by changing experimental parameters, such as the La substitution amount and little additive modification during fine milling process. The compositions of the calcined ferrites were chosen according to the stoichiometry LaxSr1-xFe12-2xO19, where M-type single-phase calcined powder was synthesized with a composition of x = 0.30. The effect of CaCO3, SiO2, and Co3O4 inter-additives on the Sr ferrite was also discussed in order to obtain low-temperature sintered magnets. The magnetic properties of Br = 4608 Gauss, bHc = 3650 Oe, iHc = 3765 Oe, and (BH)max = 5.23 MGOe were obtained for Sr ferrite hard magnets with low cobalt content at 1.7 wt%, which will eventually be used as high-end permanent magnets for the high-efficiency motor application in automobiles with Br > 4600 ± 50 G and iHc > 3600 ± 50 Oe.

scholarly journals Alloying effect on the order–disorder transformation in tetragonal FeNi

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Li-Yun Tian ◽  
Oliver Gutfleisch ◽  
Olle Eriksson ◽  
Levente Vitos
Keyword(s):  
Transition Temperature ◽  
High Performance ◽  
Density Functional ◽  
Permanent Magnets ◽  
Positive Impact ◽  
Design Strategies ◽  
Alloying Effect ◽  
Functional Theory ◽  
Disorder Transition ◽  
Disorder Transition Temperature

AbstractTetragonal ($${\hbox{L1}}_{0}$$ L1 0 ) FeNi is a promising material for high-performance rare-earth-free permanent magnets. Pure tetragonal FeNi is very difficult to synthesize due to its low chemical order–disorder transition temperature ($$\approx {593}$$ ≈ 593  K), and thus one must consider alternative non-equilibrium processing routes and alloy design strategies that make the formation of tetragonal FeNi feasible. In this paper, we investigate by density functional theory as implemented in the exact muffin-tin orbitals method whether alloying FeNi with a suitable element can have a positive impact on the phase formation and ordering properties while largely maintaining its attractive intrinsic magnetic properties. We find that small amount of non-magnetic (Al and Ti) or magnetic (Cr and Co) elements increase the order–disorder transition temperature. Adding Mo to the Co-doped system further enhances the ordering temperature while the Curie temperature is decreased only by a few degrees. Our results show that alloying is a viable route to stabilizing the ordered tetragonal phase of FeNi.

scholarly journals A Novel High Performance Discrete Flux Integrator for Control Algorithms of Fast Rotating AC Machines

2021 ◽  
Vol 11 (5) ◽  
pp. 2150
Author(s):  
Claudio Rossi ◽  
Alessio Pilati ◽  
Marco Bertoldi
Keyword(s):  
High Performance ◽  
Permanent Magnets ◽  
Machine Model ◽  
Ac Machines ◽  
Fast Calculation ◽  
Calculation Time ◽  
Digital Implementation ◽  
Rotating Speed ◽  
Interior Permanent Magnets ◽  
Accuracy Performance

This paper deals with the digital implementation of a motor control algorithm based on a unified machine model, thus usable with every traditional electric machine type (induction, brushless with interior permanent magnets, surface permanent magnets or pure reluctance). Starting from the machine equations in matrix form in continuous time, the paper exposes their discrete time transformation, suitable for digital implementation. Since the solution of these equations requires integration, the virtual division of the calculation time in sub-intervals is proposed to make the calculations more accurate. Optimization of this solver enables faster runs and higher precision especially when high rotating speed requires fast calculation time. The proposed solver is presented at different implementation levels, and its speed and accuracy performance are compared with standard solvers.

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