Nanocomposite Ribbons Research Articles

Magnetic properties of gadolinium and/or dysprosium substituted Sm–Co nanocomposite ribbons

The present study reported the influence of heavy rare-earth elements (Gd and/or Dy) on Sm-Co-based melt-spun ribbons. Microstructure and magnetic properties of Sm-Co-based (Sm1–xRExCo5) ternary and quaternary systems were investigated. The X-ray diffraction, Auger spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses reveal the presence of the 1:5H and 2:17R phases in the as-spun ribbons. A high-temperature magnetic measurement reports a Curie temperature (TC) at ∼825 and ∼869 K in Sm0.6Gd0.4Co5 (ribbon A) and Sm0.6Gd0.3Dy0.1Co5 (ribbon B), respectively. A low-temperature magnetic measurement on Sm0.6Gd0.3Dy0.1Co5 ribbons exhibits a type-2 SR (spin reorientation) behaviour at ∼72 K, which arises due to the presence of the DyCo5 phase. Room temperature magnetic measurements reveal that overall magnetic measurement (OMP) is about 24 and 29.9 for ribbons A and B, respectively. Consequently, the comparative investigations profess that ribbon B shows better magnetic performance due to Dy addition with reduced grain size. This observation indicates that the Gd and Dy substituted Sm–Co magnet can be a potential magnet for high-temperature applications.

A combined study on microstructure, microchemistry and magnetic behavior of (Sm0.12Co0.88)95Hf1B4 nano-composite ribbons by electron microscopy and atom probe tomography

In this work, Hf and B modified ribbon produced by RSP (rapid solidification process) method have been studied to investigate the microstructure, phase formation and magnetic properties of the Sm-Co-based alloy. (Sm0.12Co0.88)95Hf1B4 ribbon has been synthesized and annealed at various temperatures (700 °C, 800 °C & 900 °C) to analyze the effect of temperature on magnetic properties and structure. X-ray diffraction (XRD) phase analysis has confirmed the 1:7 H phase as a significant phase in the as-spun ribbon. A combination of 1:5 H and 2:17 R phases were found in the ribbon annealed at 900 °C due to disorder-order transformation upon heat treatment. The development of ordered structure and grain growth upon annealing at 800 °C and 900 °C have deteriorated the magnetic properties. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) analysis also revealed the grain growth and the development of the ordered 2:17 R structure upon annealing. The ribbon annealed at 700 °C showed better magnetic properties, Hc≈ 8.6 kOe, Mr ≈ 49 emu/g and (BH)max≈ 5.63 MGOe with an average grain size of ∼149 ± 5 nm. TC of the as-spun ribbon was found to be ⁓750 °C, and the temperature co-efficient of magnetization (α) and coercivity (β) were about − 0.008 and − 0.161%/°C, respectively. The APT analysis confirmed the fine borides in both as-spun and annealed (700 °C & 900 °C) ribbons.

Strength distributions of laminated FeNi-based metal amorphous nanocomposite ribbons

Metal Amorphous Nanocomposite (MANC) materials offer low losses at high magnetic switching frequency, enabling high power density motors with increased rotational speed. While MANCs have high strength, they are brittle. The use of motor components such as a rotor consisting of brittle material presents a reliability concern. Here, a promising MANC alloy is subjected to tensile tests and failure is observed with high-speed photography. A method is developed to prepare tensile specimens of laminated MANC and epoxy layers, simulating the stacking of an epoxy-impregnated tape-wound core. Tensile tests are conducted for single layer ribbon and for five- and ten-layer stacks of laminated material with thin layers of thermosetting epoxy. Failure distributions are shown to have increasing Weibull modulus with increasing layer count. The composite MANC material system is modeled using chain-of-bundles models. Using a k-failure model, we show that single ribbon strength distribution data can be used to predict well the failure distribution of laminated stacks. The agreement occurs when the assumed ineffective length, over which load is recovered in a failed layer, is comparable to the observed interlaminar separation length.

Enhancement of magnetic properties of Sm-Co nano composite ribbons by heavy lanthanide doping

Sm-Co magnets becoming more and more interesting among research community since 1950′s due to its essential role in space and transport industry to be used in some precious instruments such as, sensors, actuators, motors, and gyroscope. The combination of Rare-earth (RE) and Transition metal (TM) is an ideal combination to make a high-performance magnet, as the RE provides the high magneto crystalline anisotropy (HA) and the TM provides the high magnetization (Ms) and high Curie temperature (Tc). SmCo5 compound possesses Tc as high as ∼ 700 °C. Previous studies have reported that HRE (Gd, Dy, Er and Ho) could be used as a temperature compensation material as unpaired 4f electrons in shell gives rise to maximum magnetic moment. In this study, effect of lanthanides (HREs - Gd and/ Dy) on microstructure and magnetic properties of Sm-Co-based rapidly solidified alloy ribbons have been reported. Phase analyses confirmed the presence of 1:5H phase which was prevalent along with a fraction of 2:17R phase in all the alloy ribbons. Hc value was increased from 10.9 to 13.3 kOe (1.09 to 13.3 T) and Br value was increased from 12.5 to 16.2 kG (1.25 to 1.62 T) with Dysprosium addition.

Analysis of surface roughness and oxidation of FeNi-based metal amorphous nanocomposite alloys

We report on a systematic investigation of newly developed (Fe 70 Ni 30 ) 80 Nb 4 B 14 Si 2 metal amorphous nanocomposites (MANCs) and the factors affecting their surface roughness, including oxide formation and phase evolution during the nanocrystallization process. Analysis of surface roughness using atomic force microscopy (AFM) revealed an average roughness of 9.33 nm after heat treatment compared with as-cast amorphous ribbons, which exhibited a roughness of 4.21 nm. A surface oxide layer thickness has been determined using X-ray photoelectron spectroscopy (XPS). For samples annealed at 400 °C for 1 h, 450 °C for 1 h, and 550 °C for 3 h in air, the average surface oxide layer thickness was determined to be 10.9, 11.7, and 54.4 nm, respectively. It was observed that oxygen is enriched at the outermost surface and decreases rapidly as the XPS sputtering depth increases. Fe-oxide appeared as a predominant metal oxide at the top surface, followed by the presence of Nb oxide. A boron content increase was observed at the interface between the top surface oxide layer and the bulk of the sample. A protective surface oxide layer on FeNi-MANCs, such as observed in this work, can provide sufficient electrical insulation to reduce interlaminate eddy current losses and lower overall losses in magnetic components. • Surface roughness and oxidation of FeNi-based metal amorphous nanocomposites. • Surface roughness in amorphous ribbon using atomic force microscopy (AFM). • Crystallization and activation energies in metal amorphous nanocomposite ribbons. • Phase fractions in metal amorphous nanocomposite ribbons. • Surface oxides partitioning in amorphous and nanocrystalline alloys.

Effect of heat treatment on magnetic properties of nanocomposite Nd-lean Nd7Fe73B20 ribbons

Effect of heat treatment on magnetic properties of nanocomposite Nd-lean Nd7Fe73B20 ribbons

Effect of Wheel Speed on Magnetic Properties of Nd10Fe85−xCoxB5 (x = 0 to 40) Nanocomposite Ribbons

Nd2Fe14B/Fe(Co) nanocomposite ribbons were successfully fabricated by the melt-spinning technique. Nd10Fe85−xCoxB5 (x = 0, 10, 20, 30, and 40) prealloys were used as starting materials, and the wheel speed was varied from 10 m/s to 20 m/s. The effects of substitution of Fe by Co and the wheel speed were investigated to enable direct preparation of high-performance nanocomposite ribbons. It was found that the optimal wheel speed depended on the Co content in the ribbons. The highest energy product (BH)max of the as-spun ribbons reached 144.3 kJ/m3 when using the optimal speed of 16 m/s for Nd10Fe65Co20B5. By annealing the ribbons at 873 K and 973 K for 30 min, the magnetic properties of the Nd10Fe65Co20B5 nanocomposite ribbons obtained at a speed of 20 m/s were significantly improved. The microstructure and magnetic properties of the prepared ribbons are discussed in detail.

High Thermoelectric Power Factor of Si–Mg2Si Nanocomposite Ribbons Synthesized by Melt Spinning

Si has been considered as a promising thermoelectric material because of its many advantages, such as its nontoxic characteristics and abundance. In this study, the concept of modulation doping is ...

Electromagnetic interference shielding effectiveness of amorphous and nanocomposite soft magnetic ribbons

The electromagnetic interference shielding effectiveness (EMI SE) of amorphous and annealed melt-spun ribbons having typical composition of Co72.5Si12.5B15, (Fe0.65Co0.35)83Si1.3B11.7Nb3Cu1, Fe80Si8B12 and Fe83Si2B13Nb2 were studied in the 0.2–8.5 GHz microwave range. The amorphous nature of the as-quenched ribbons was confirmed by X-ray diffraction patterns and differential scanning calorimetry (DSC). The flexible electromagnetic wave absorber ribbons of CoSiB, FeSiB, and FeCoSiBNbCu based alloys exhibit ∼99.99% attenuation of electromagnetic waves in the entire 0.2–8.5 GHz (L, S and C-band) range. Both as-quenched and annealed amorphous ribbons of Co72.5Si12.5B15 and Fe80Si8B12 are electromagnetically active and total electromagnetic shielding effectiveness (SET) of ribbons found to be ∼36 dB, ∼34 dB throughout the test range. The EMI shielding properties deteriorates for FeCoSiBNbCu and FeSiBNb based nanocomposite ribbons achieved by in-situ crystallization annealing. The electromagnetic shielding of magnetic ribbons is effected mainly by absorption mechanism due to high electrical resistivity and magnetic permeability. The CoSiB and FeSiB melt-spun ribbons can be a potential magnetic filler for military and stealth applications in L, S and C-band range.

Thermal profile shaping and loss impacts of strain annealing on magnetic ribbon cores

Abstract

Thermal Behavior and Magnetic Properties of Nd-Fe-B Based Exchange Spring Nanocomposites Nd<sub>4-x</sub>Tb<sub>x</sub>Fe<sub>83.5</sub>Co<sub>5</sub>Cu<sub>0.5</sub>Nb<sub>1</sub>B<sub>6</sub> (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) Melt-Spun Ribbons

Co-rich Nd-Fe-B nanocomposite ribbons with Tb substituted have been fabricated by single roller melt spinning technique of Nd4-xTbxFe83.5Co5Cu0.5Nb1B6 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) alloys in an argon (Ar) atmosphere at a circumferential speed of 40 m/s. According to the differential scanning calorimeter (DSC) traces the nanocomposite samples have been annealed at different temperatures like 675°C, 687°C, 700°C, 712°C and 725°C for 10 min. Crystallization behavior was studied by X-ray diffraction in which it was found that the XRD patterns are characterized by broad diffused pattern which demonstrate the amorphous state of materials. The ribbon samples were also characterized by vibration sample magnetometer (VSM) and Mossbauer spectroscopy at as-cast and annealed condition. Co-rich and Tb substitution has significantly enhanced the value of coercivity (Hc) and maximum energy product (BH)max. Highest value of Hc and (BH)max has been obtained as 2.36 kOe and 6.11 MGOe for the sample annealed at 700°C for 10 min with higher concentration of Tb. The M-H hysteresis loops show extremely soft natures which do not possess any area. We have found reduced remanent ratio (Mr/Ms) up to 0.49 at optimal annealing temperature 700°C. However, with the annealing of the samples in the above mentioned temperature, evolution of large coercivity was observed due to the formation of exchange couple hard and soft nanocrystal composites. We have investigated the variation of Curie temperature (Tc) with annealing temperature of the melt spun ribbon samples. Mossbauer spectroscopy was carried out to study the hyperfine parameters such as hyperfine field, hyperfine field distribution for full width half maximum (FWHM) and isomer shift of Fe species of these two phases.

Nd–Fe–B Thick-Film Magnets Prepared by High Laser Energy Density

Recently, we reported a PLD(Pulsed Laser Deposition)-fabricated isotropic nano-composite thick film magnets with dispersed α-Fe+Nd-Fe-B structure by using the laser energy density (LED) above 10 J/cm2 [1] whose magnetic properties were superior compared with those previously reported α-Fe+Nd-Fe-B nano-composite films prepared by LED lower than 1 J/cm2 [2]. However, the (BH) max value of a film prepared by LED≧10 J/cm2 was inferior to those of isotropic RE (Nd or Pr)-Fe-B/α-Fe nano-composite ribbons with (BH) max above 130 kJ/m3 [3,4]. Furthermore, in order to apply the nano-composite films prepared by the high laser energy density to a miniaturized device, further enhancement in magnetic properties is required [4]. An investigation on the formation of dispersed α-Fe + Nd-Fe-B structure is also indispensable to advance the preparation of a PLD-fabricated thick-film magnet. This contribution reports the improvement in (BH) max by controlling the film composition. In addition, the formation of microstructure of each film prepared by the high laser energy density was examined as a function of deposition time.

A study on the magnetic properties of melt spun Co-Hf-Zr-B nanocomposite ribbons

Magnetic properties of melt spun Co86.5Hf11.5-xZrxB2 (x = 0–5) ribbons have been investigated. For the ribbons spun at the wheel speed of 40 m/s, hard magnetic properties with high energy product ((BH)max) of 34.4–52.8 kJ/m3 and intrinsic coercivity (iHc) of 176–216 kA/m were obtained for x = 0–2, but soft magnetic behavior was observed for x = 3–5 due to the appearance of the amorphous phase. By annealing the ribbons with x = 3–5, hard magnetic properties were improved arisen from the formation of magnetically hard phase. The variation of magnetic properties for Co86.5Hf11.5−xZrxB2 ribbons was correlated to microstructure change. Proper Zr substitution for Hf was helpful in refining the grain size from 10–35 nm for x = 0 to 5–15 nm for x = 1, and thus improving the magnetic properties effectively. The optimal hard magnetic properties of Co86.5Hf10.5Zr1B2 ribbons might be originated from the fine magnetically hard Co11(Hf, Zr)2 phase, and the exchange coupling effect among grains and/or with the face-center-cubic Co phase.

Crystallization kinetics and magnetization behavior of RE3.5Fe66.5Co10B20 (RE = Pr, Nd) nanocomposite ribbons

The influence of hard magnetic phase on the crystallization kinetics and magnetization behavior in nanocomposite RE3.5Fe66.5Co10B20 (RE = Pr, Nd) ribbons prepared by melt-spinning was studied. Differential scanning calorimeter (DSC) measurement of the as-cast melt-spun amorphous ribbons during the crystallization process shows that precipitation energy of Pr2Fe14B phase is higher than that for Nd2Fe14B phase, confirmed by X-ray diffraction (XRD) patterns. It can be explained by the different radii of Pr and Nd atoms. Scanning electron microscopy (SEM) images indicate that the average grain size in Pr3.5Fe66.5Co10B20 ribbon is smaller than that in Nd3.5Fe66.5Co10B20, resulting in an enhancement of exchange coupling between hard and soft phases. It is responsible for the better hard magnetic properties in Pr3.5Fe66.5Co10B20. In addition, the process of magnetization reversal of nanocomposite RE3.5Fe66.5Co10B20 (RE = Pr, Nd) ribbons was discussed in detail by the recoil loops.

The Effect of External Magnetic Field on Microstructure and Magnetic Properties of Melt-Spun Nd-Fe-B/Fe-Co Nanocomposite Ribbons

The ribbons Nd2Fe14B/Fe-Co were prepared with the nominal composition Nd16Fe76B8/40% wt. Fe65Co35by the conventional and the developed magnetic field-assisted melt-spinning (MFMS) techniques. Both ribbons are nanocomposites with the smooth single-phase-like magnetization loops. The 0.32 T magnetic field perpendicular to the wheel surface and assisting the melt-spinning process reduces the grain size inside the ribbon, increases the texture of the ribbon, improves the exchange coupling, and, in sequence, increases the energy product(BH)maxof the isotropic powdered samples of MFMS ribbon in ~9% by comparison with that of the ribbon melt-spun conventionally. The grain size reduction effect caused by the assisted magnetic field has also been described quantitatively. The MFMS technique seems to be promising for producing high-performance nanocomposite ribbons.

Effect of magnetic fields on melt-spun Nd2Fe14B-based ribbons

The effect of a magnetic field on microstructure and magnetic properties of Nd2Fe14B-based melt-spun ribbons is investigated. The magnetic field was applied in perpendicular or parallel direction to the ribbon plane during quench with a field strength up to several kilo Oersteds. The XRD patterns and TEM graphs show a strong grain size reduction upon the magnetic field application. The magnetic field also enhances the (00l) texture of ribbons when the field is perpendicular to the ribbon plane. The refined microstructure with significantly reduced grain size leads to enhanced magnetic exchange interactions between the hard and soft phases in the Nd2Fe14B/Fe nanocomposite ribbons. This magnetic field-assisted melt-spinning technique is promising for producing nanocomposite magnets with enhanced energy density.

Effects of Ga addition on structural and magnetic properties of nanocomposite Nd-Fe-B-Ti-C thick ribbons

Rapidly solidified Nd9Fe73B12.6C1.4Ti4-xGax (x = 0, 0.5, 1) thick ribbons were prepared by melt spinning technique at a surface speed (vs) of 5 m/s. The influences of Gallium doping on the glass-forming ability (GFA), microstructure and magnetic properties of alloys were investigated. The coercivity of Nd-Fe-B-Ti-C nanocomposite alloy thick ribbons can be dramatically enhanced by 0.5 at. % Ga addition in a low cooling-rate regime, attributing to the weakened exchange coupling interaction and grain refinement. The results of XRD showed that the GFA of Nd-Fe-B-Ti-C alloy was enhanced by the Ga addition. Therefore, Gallium addition is effective to refine grain and improve the glass-forming ability, which provides the possibility to obtain the high performance of magnetic properties by using strip casting (SC) method.

Structure and magnetic properties of Pr10(Fe,Co,Ni)84B6 nanocomposite alloys

Nanocomposite ribbons with composition Pr10(Fe1-2xCoxNix)84B6 (x = 0.0, 0.05, 0.10, and 0.15) were prepared by melt-spinning. All melt-spun ribbons are composed of a fine mixture of 2:14:1 and bcc-(Fe,Co,Ni) phases with an additional soft phase (Pr2Fe23B3-based) for x = 0.10 and 0.15. The room temperature coercivity decreases from 7.4 to 2 kOe with Co and Ni substitutions likely due to the decrease of the magnetocrystalline anisotropy of the 2:14:1 phase and the increase of the amount of the soft phases. Saturation magnetization increases slightly while remanence and (BH)max show a slight decrease for x up to 0.10 and then they drop quickly. The intergranular exchange coupling is strong for x ≤ 0.10 but it is reduced significantly for x = 0.15 due to the substantial increase of the volume and size of the soft phases. Thermomagnetic measurements showed a significant increase of the Curie temperature of the 2:14:1 phase from 290 °C for x = 0 to 485 °C for x = 0.15. High temperature hysteresis loop measurements showed improved temperature dependence of remanence and coercivity for x = 0.05.

Synthesis and characterization of Nd4+xFe72Co5Ga2B17−x nanocomposite ribbons

A series of alloys with compositions of Nd4 + xFe72Co5Ga2B17−x, where x = 0–10, were prepared by rapid solidification. Annealing the as-spun alloys above primary crystallization (Tx1) formed nanocomposite ribbons. While x-ray diffraction measurements showed the annealed alloys to be nanocrystalline, the phases present in each alloy were found to vary with Nd content. The alloys with x = 0, 7.5, and 10 contained a majority fraction of the Nd2Fe14B phase, along with Fe3B, α-Fe, and/or Nd2Fe23B3 phases. These alloys showed room temperature coercivities and remanent magnetizations of 199, 446, and 1034 kA/m and 120, 82, and 70 A m2/kg, respectively. The x = 5 and 7.5 samples were primarily made up of Nd2Fe23B3, and therefore, showed little coercivity. At elevated temperatures, the presence of Co and Ga were found to increase the coercivity of the Nd2Fe14B phase.

First order reversal curve analysis on NdFeB nanocomposite ribbons subjected to Joule heating treatments

Amorphous precursors with composition Nd4.5Fe72−xCo3+xCr2Al1B17.5 (x=0, 2, 7, 12) were thermally treated by the Joule heating technique with a linearly varying electrical current. The crystallization kinetics was followed by monitoring the resistance of the ribbons during the heating up to the final applied current. Crystallized nanostructured phases coexist with an amorphous matrix, as it was observed by means of Mössbauer Spectroscopy and X-ray diffraction.The irreversible magnetic response of the Joule heated ribbons was analyzed by the First Order Reversal Curves (FORC) diagram technique. For the optimal treatments, associated with the higher maximum energy products for each sample composition, it was found that the main interaction is of a strongly dipolar characteristic. Over annealed samples show a FORC diagram that gives into account of softening, due to grain growth, for those phases precipitated at the first crystallization stage. When it is measured at 20K, the hardest magnetic sample (Fe=72at.%, Co=3at.%, Ifinal=0.5A), exhibits a diagram with characteristics corresponding to dipolar interactions of soft phases. This fact is consistent with an enhancement of the exchange length due to the increase in the soft phase stiffness as it is expected at low temperatures.