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Abstract Attempts to prepare NdFe 9 Si 2 by arc-melting and annealing produce α-Fe(Si), Nd 2 (Fe, Si) 17 and NdFe 2 Si 2 . As an alternative, we have produced amorphous samples by melt spinning. Amorphous NdFe 9 Si 2 has a Curie... more
Abstract Attempts to prepare NdFe 9 Si 2 by arc-melting and annealing produce α-Fe(Si), Nd 2 (Fe, Si) 17 and NdFe 2 Si 2 . As an alternative, we have produced amorphous samples by melt spinning. Amorphous NdFe 9 Si 2 has a Curie temperature of 405(5) K and an average 57 Fe hyperfine field of 18.2(3) T, at 295 K. The amorphous phase undergoes two-stage crystallization with peak temperatures of 897 and 924 K, ultimately producing Nd 2 (Fe, Si) 17 and BCC α-Fe(Si)-A2.
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Research Interests: Engineering, Materials Engineering, Condensed Matter Physics, Materials Science, Nanomaterials Characterization, and 15 moreMagnetic Materials, Dilute Magnetic Semiconductors, Nanoparticle, Applied Physics, Nanomaterials, Magnetism, Mathematical Sciences, Applied, Ball Mill, CHEMICAL SCIENCES, Calcination, Diamagnetism, Magnetization, Ferromagnetism, and Alloys
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Research Interests: Engineering, Materials Engineering, Condensed Matter Physics, Materials Science, Nanomaterials Characterization, and 15 moreMagnetic Materials, Dilute Magnetic Semiconductors, Applied Physics, Nanomaterials, Nanoparticles, Nanotechnology, Mathematical Sciences, Applied, Nanoscience, Physical sciences, Ball Mill, CHEMICAL SCIENCES, Magnetization, Ferromagnetism, and Alloys
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Ultra-Rapid Annealing (URA) is an effective means of producing Fe-rich nanocrystalline soft magnetic materials with desirable soft magnetic properties. However, compared to existing annealing techniques, URA presents many unique... more
Ultra-Rapid Annealing (URA) is an effective means of producing Fe-rich nanocrystalline soft magnetic materials with desirable soft magnetic properties. However, compared to existing annealing techniques, URA presents many unique processing challenges that have so far limited its scalability. In this study, a novel Continuous Ultra-Rapid Annealing (CURA) technique is introduced. This technique is based on a reel-to-reel process and is considered suitable for industrial-scale production. The effectiveness of CURA is evaluated by comparing the microstructural and magnetic properties of a heating-rate-sensitive nanocrystalline (Fe0.8Co0.2)86B14 alloy produced by URA and CURA. It is seen that both techniques produce comparable soft magnetic properties and that the continuous annealing process is stable after a short settling time. A proof-of-concept electric motor containing a CURA prepared nanocrystalline stator core is also demonstrated and compared to an equivalent motor with a Fe-Si ...
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Soft magnetic materials are key materials for the magnetic cores used in motors and generators. To improve the energy efficiency of magnetic cores, it is important to understand the mechanism of energy loss under oscillating magnetic... more
Soft magnetic materials are key materials for the magnetic cores used in motors and generators. To improve the energy efficiency of magnetic cores, it is important to understand the mechanism of energy loss under oscillating magnetic fields. Here, we clarify the mechanism of energy loss in nanocrystalline soft magnetic materials (NSMMs), which are candidates for energy-efficient magnetic cores. To investigate the energy loss of an NSMM, it is necessary to consider the interaction between the magnetization and the crystal lattice, i.e., magnetostriction. However, the random distributions of crystalline axes in nanocrystals hinder magnetostriction calculation. We developed a micromagnetic simulation program by formulating the effective fields due to magnetostriction in randomly oriented nanocrystallites. We performed micromagnetic simulations of NSMMs under an oscillating magnetic field and found that the magnetic energy of the moving domain wall dissipates into the elastic energy of ...
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Materials with 1st order antiferromagnetic (AFM) to high-magnetization (MM) phase transition known for their inverse magnetocaloric effect, abrupt rise in magnetization and magnetoelastic coupling, are promising for application in... more
Materials with 1st order antiferromagnetic (AFM) to high-magnetization (MM) phase transition known for their inverse magnetocaloric effect, abrupt rise in magnetization and magnetoelastic coupling, are promising for application in combined simultaneous diagnosis and targeted cancer therapy. A therapy that combines alternating-current (ac) and direct-current (dc) magnetic fields for simultaneous magnetic hyperthermia therapy (MHT) and magnetic resonance imaging (MRI), using same magnetic particles for heating and as contrast agents. We report a proof-of-concept study on the induction heating ability of 1st order metamagnetic material with moderate specific absorption rates (SAR) and no tendency for agglomeration, for potential MHT and MRI cancer therapy. CoMnSi, a metamagnetic antiferromagnet (MM) was used in this study because of its desirable ability to rapidly switch from a low to high magnetization state in an applied dc bias field condition without particle agglomeration on fiel...
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While suitable texture has been developed in Nd2Fe14B/α-Fe nanocomposites via thermomechanical processing methods such as die upsetting by incorporating low melting point eutectic Nd-Cu additives, significant grain coarsening occurs... more
While suitable texture has been developed in Nd2Fe14B/α-Fe nanocomposites via thermomechanical processing methods such as die upsetting by incorporating low melting point eutectic Nd-Cu additives, significant grain coarsening occurs during this process due to the high temperature and long timescales involved, resulting in a loss of exchange coupling. Equal channel angular pressing (ECAP) is a severe plastic deformation technique which has been successfully used to produce a suitable texture in single-phase Nd2Fe14B at temperatures on the order of 500°C while preserving grain sizes on the order of 20-30nm. We investigate the development of texture in a commercial Nd2Fe14B/α-Fe nanocomposite alloy with added Nd90Cu10 produced via ECAP and then characterise it using texture x-ray diffraction and magnetic measurements. It is found that initial texture can be developed in this nanocomposite system at T = 520°C via ECAP. The average grain size of Nd2Fe14B as measured via X-ray diffraction...
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Nanocrystalline soft magnetic materials are known to be prepared by primary crystallization of Fe-based amorphous precursors. Since the crystallization reaction is exothermic, the amorphous precursor may experience a temporary rise in its... more
Nanocrystalline soft magnetic materials are known to be prepared by primary crystallization of Fe-based amorphous precursors. Since the crystallization reaction is exothermic, the amorphous precursor may experience a temporary rise in its temperature relative to its surroundings during the process of nanocrystallization. Given the typical latent heat of primary crystallization (∼ 100 kJ/kg), this temperature rise may exceed hundreds of degrees if not adequately controlled and thus, lead to the formation of unwanted magnetically hard compounds. This effect is generally small for isolated ribbons annealed with a moderate heating rate. However, the recent adoption of high heating rates and short annealing times has caused the self-heating effect to become relevant even for small sample sizes. In this work, the effect of self-heating on the microstructure and magnetic properties of nanocrystalline Fe86B14 is investigated. It is found that magnetically hard Fe-B compounds cannot be avoid...
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Five percent Fe-doped InO films were deposited using a pulsed laser deposition system. X-ray diffraction and transmission electron microscopy analysis show that the films deposited under oxygen partial pressures of 10 and 10 Torr are... more
Five percent Fe-doped InO films were deposited using a pulsed laser deposition system. X-ray diffraction and transmission electron microscopy analysis show that the films deposited under oxygen partial pressures of 10 and 10 Torr are uniform without clusters or secondary phases. However, the film deposited under 10 Torr has a Fe-rich phase at the interface. Magnetic measurements demonstrate that the magnetization of the films increases with decreasing oxygen partial pressure. Muon spin relaxation (μSR) analysis indicates that the volume fractions of the ferromagnetic phases in PO = 10, 10, and 10 Torr-deposited samples are 23, 49, and 68%, respectively, suggesting that clusters or secondary phases may not be the origin of the ferromagnetism and that the ferromagnetism is not carrier-mediated. We propose that the formation of magnetic bound polarons is the origin of the ferromagnetism. In addition, both μSR and polarized neutron scattering demonstrate that the Fe-rich phase at the in...
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Metal–organic frameworks (MOFs), with their intriguing network structures, large internal surface areas, and tunable pore properties offer the perfect yet largely unexplored alternative for selective adsorption of oxygen.
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MoS2 nanosheets were doped with vanadium (V) with a variety of concentrations using a hydrothermal method. Raman, X-ray photoelectron spectroscopy, and electron paramagnetic resonance results indicate the effective substitutional doping... more
MoS2 nanosheets were doped with vanadium (V) with a variety of concentrations using a hydrothermal method. Raman, X-ray photoelectron spectroscopy, and electron paramagnetic resonance results indicate the effective substitutional doping in MoS2. Without V doping, oxides such as MoO2 and MoO3 have been observed, whereas with 5 at% V doping, the oxide disappeared. Magnetic measurements show that room temperature ferromagnetism has been induced by V doping. Magnetization tends to increase with the increased V doping concentration. A very large coercivity up to 1.87 kOe has been observed in 5 at% vanadium doped MoS2, which may attribute to a combination effect of localized charge transfer between V and S ions, pinning effect due to the in-between defects, stress induced by doping, and shape anisotropy due to two-dimensional nature of MoS2 ribbons.
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The rapid synthesis of metal organic frameworks (MOFs) is one important feature necessary to aid their wide adoption. Most synthetic methods involve the heating of large amounts of solvent to promote the extended framework growth. Here,... more
The rapid synthesis of metal organic frameworks (MOFs) is one important feature necessary to aid their wide adoption. Most synthetic methods involve the heating of large amounts of solvent to promote the extended framework growth. Here, we report the establishment of Magnetic Induction Framework Synthesis (MIFS), where elevated temperatures are provided locally at a surface through induction heating of a magnetic nanoparticle. MOFs are found to grow at orders of magnitude higher rates with MIFS compared to that of conventional synthesis. The resulting magnetic framework composites (MFCs) exhibit the controlled yield and particle size depending on the reaction conditions. The presence of well-distributed magnetic nanoparticles within MFCs allows the induction heating to be further used to promote desorption of captured CO2, with 98.4 % able to be released. Moreover, MIFS is applicable to the synthesis of a broad range of MFCs, with five other MOF composites also successfully prepared.
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Research Interests: Engineering, Materials Engineering, Condensed Matter Physics, Materials Science, Nanomaterials Characterization, and 12 moreMagnetic Materials, Dilute Magnetic Semiconductors, Applied Physics, Nanomaterials, Nanoparticles, Nanotechnology, Mathematical Sciences, Applied, Nanoscience, Physical sciences, Ball Mill, and Alloys
Magnetic small-angle neutron scattering is employed to investigate the magnetic interactions in (Fe0.7Ni0.3)86B14 alloy, a HiB-NANOPERM-type soft magnetic nanocrystalline material, which exhibits an ultrafine microstructure with an... more
Magnetic small-angle neutron scattering is employed to investigate the magnetic interactions in (Fe0.7Ni0.3)86B14 alloy, a HiB-NANOPERM-type soft magnetic nanocrystalline material, which exhibits an ultrafine microstructure with an average grain size below 10 nm. The neutron data reveal a significant spin-misalignment scattering which is mainly related to the jump of the longitudinal magnetization at internal particle–matrix interfaces. The field dependence of the neutron data can be well described by micromagnetic small-angle neutron scattering theory. In particular, the theory explains the `clover-leaf-type' angular anisotropy observed in the purely magnetic neutron scattering cross section. The presented neutron data analysis also provides access to the magnetic interaction parameters, such as the exchange-stiffness constant, which plays a crucial role towards the optimization of the magnetic softness of Fe-based nanocrystalline materials.
We demonstrate a magnetocaloric ferrofluid based on a gadolinium saturated liquid metal matrix, using a gallium-based liquid metal alloy as the solvent and suspension medium. The material is liquid at room temperature, while exhibiting... more
We demonstrate a magnetocaloric ferrofluid based on a gadolinium saturated liquid metal matrix, using a gallium-based liquid metal alloy as the solvent and suspension medium. The material is liquid at room temperature, while exhibiting spontaneous magnetization and a large magnetocaloric effect. The magnetic properties were attributed to the formation of gadolinium nanoparticles suspended within the liquid gallium alloy, which acts as a reaction solvent during the nanoparticle synthesis. High nanoparticle weight fractions exceeding 2% could be suspended within the liquid metal matrix. The liquid metal ferrofluid shows promise for magnetocaloric cooling due to its high thermal conductivity and its liquid nature. Magnetic and thermoanalytic characterizations reveal that the developed material remains liquid within the temperature window required for domestic refrigeration purposes, which enables future fluidic magnetocaloric devices. Additionally, the observed formation of nanometer-s...
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ABSTRACT We plated Fe–Ni films from a citric-acid-based plating bath and evaluated the effect of pH value in the bath on the magnetic properties and the productivities of the films. In this study, the pH value of the bath was controlled... more
ABSTRACT We plated Fe–Ni films from a citric-acid-based plating bath and evaluated the effect of pH value in the bath on the magnetic properties and the productivities of the films. In this study, the pH value of the bath was controlled from 0.5 to 3.6 by the addition of hydrochloric acid or sodium citrate. The electrodeposited Fe–Ni film with the Fe content of approximately 22 at.% prepared at high pH ($>$3) tends to show large coercivity ($>100~hbox{A/m}$), rough surface and relatively high cathode efficiency ($>$70%) whereas the films prepared at low pH ($<$1) tend to show low coercivities ($<50~hbox{A/m}$), smooth surfaces and low cathode efficiencies ($<$60%). The ${hbox{Fe}}_{22}{hbox{Ni}}_{78}$ film prepared from the bath without the pH adjuster of a hydrochloric acid or a sodium citrate shows low coercivity of 25 A/m, smooth surface and relatively high cathode efficiency of 65%. Since low coercivity, smooth surface and high cathode efficiency are important factors for mass-producing Fe–Ni films, we concluded that a citric-acid-based bath with pH range from 1 to 3 is suitable for electrodeposition of soft magnetic Fe–Ni films.
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Superparamagnetic particles have attracted a lot of interest due to their relatively high saturation magnetization, zero remanence and zero coercivity. These properties render such particles suitable for a range of applications, such as... more
Superparamagnetic particles have attracted a lot of interest due to their relatively high saturation magnetization, zero remanence and zero coercivity. These properties render such particles suitable for a range of applications, such as cell sorting and targeted drug ...
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Dodecanethiol capped Ag nanoparticles (NPs) have been independently synthesized by the well-known Brust method under the same physical-chemical conditions. The obtained NP present similar sizes ( ∼ 2 nm) but different magnetic behaviors.... more
Dodecanethiol capped Ag nanoparticles (NPs) have been independently synthesized by the well-known Brust method under the same physical-chemical conditions. The obtained NP present similar sizes ( ∼ 2 nm) but different magnetic behaviors. The extended x-ray absorption fine structure analyses at the K-edge of Ag did not reveal any noticeable structural nor topological differences among the samples. In clear contrast with the structure provided for thiol capped ferromagnetic Au NPs, the analysis also brings out the existence of Ag–S bonds in a diffuse region surrounding a reduced Ag core where the magnetism of the Ag NPs would be located.
Research Interests: Engineering, Synthesis of nanoparticles, Nanomaterials Characterization, Magnetic Materials, Applied Physics, and 11 moreNanoparticles, Nanotechnology, Nanocrystalline Material, Silver Nanoparticles, Mathematical Sciences, Applied, Nanoscience, Physical sciences, X ray Absorption, extended x-ray absorption fine structure (EXAFS), and Fine Particles
Small-angle scattering of X-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering curve from an assembly of... more
Small-angle scattering of X-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering curve from an assembly of particles. The Guinier law has originally been derived for nonmagnetic particle-matrix-type systems and it is successfully employed for the estimation of particle sizes in various scientific domains (e.g. soft-matter physics, biology, colloidal chemistry, materials science). An important prerequisite for it to apply is the presence of a discontinuous interface separating particles and matrix. Here, the Guinier law is introduced for the case of magnetic small-angle neutron scattering and its applicability is experimentally demonstrated for the example of nanocrystalline cobalt. It is well known that the magnetic microstructure of nanocrystalline ferromagnets is highly nonuniform on the nanometre length scale and characterized by a spectrum of continuously var...
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The huge energy requirement for industrial separations of chemical mixtures has necessitated the need for the development of energy efficient and alternative separation techniques in order to mitigate the negative environmental impacts... more
The huge energy requirement for industrial separations of chemical mixtures has necessitated the need for the development of energy efficient and alternative separation techniques in order to mitigate the negative environmental impacts associated with greenhouse gas emissions from fossil fuel combustions for energy generation. A promising approach involves the use of magnetic framework composites (MFCs) for gas capture and release via localised magnetic induction heating in a process known as magnetic induction swing adsorption (MISA). This feature article presents an overview of the mechanism of induction heating of magnetic nanoparticles, incorporation of the nanoparticles into metal organic frameworks to form MFCs and the potential of deploying MFCs for the mitigation of greenhouse gas emissions using the MISA process. We also present an overview of the potential energy savings as a result of the efficiency of magnetic induction heating and we give a perspective on the future dir...
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A Fe3O4/Cu- ceramic system converted into a magnetic HKUST-1 composite was used as a recyclable catalyst for one-pot cascade and hydrogenation reactions.