Nanocrystalline material development for high-power inductors

Self Cite

We report on new high-saturation induction, high-temperature nanocomposite alloys with reduced glass formers. The amounts of the magnetic transition metals and early transition metal growth inhibitors were systematically varied to determine trade-offs between higher inductions and fine microstructures with consequently lower magnetic losses. Alloys of nominal composition ͑Fe 65 Co 35 ͒ 79.5+x Nb 4−x B 13 Si 2 Cu 1.5 ͑x=0-4͒ were cast into a 28 mm wide, 20 m thick ribbon from which toroidal cores were wound. Inductions and magnetic losses were measured after nanocrystallization and stress relief. We report technical magnetic properties: permeability, maximum induction, remanence ratio, coercive field, and high frequency magnetic losses as a function of composition and annealing temperature for these alloys. Of note is the development of maximum inductions in excess of 1.76 T in cores made of alloys with the x = 4 composition and maximum inductions in excess of 1.67 T in alloys with the x = 3 composition, which also exhibit power losses smaller than 10 W/kg at 0.2 T induction levels in 20 kHz fields. We discuss optimization of induction with chemistry and correlate the microstructures with losses.

Section: Introductionmentioning

confidence: 99%

“…1 This requires soft magnetic materials that operate at high temperatures with high inductions and low losses. Systems can be made smaller and lighter by size and weight reductions of the magnetic passive components.…”

Section: Introductionmentioning

confidence: 99%

Increased induction in FeCo-based nanocomposite materials with reduced early transition metal growth inhibitors

Miller

Leary

Kernion

et al. 2010

Self Cite

“…Miniaturization of power electronic components demands highly efficient magnetic materials that can be used in power transformers and converters. 1 These materials must have thermal stability and good high temperature magnetic properties to facilitate good performance in severe environments. Several newly developed Fe based soft magnetic nanocomposites exhibit low thermal stability.…”

Section: Introductionmentioning

confidence: 99%

Effect of P addition on nanocrystallization and high temperature magnetic properties of low B and Nb containing FeCo nanocomposites

Roy¹,

Shen²,

Kernion³

et al. 2012

The P content dependencies of the nanocrystallization behaviors and high temperature magnetic properties of the Fe 54.6 Co 29.4 Si 2.8 (B 0.8ÀY P Y ) 14 Nb 1 Cu 1 (Y ¼ 0, 0.2, and 0.3) alloys have been investigated. Alloys were prepared by melt spinning and subsequently annealed in an argon atmosphere to induce nanocrystallization. P addition increases primary crystallization temperature (Tx 1 ), thermal stability (DTx), and activation energy (Q JMA ) for secondary crystallization in as-cast alloys. The saturation induction (B s ) of 1.68 T for as-cast P free alloy decreases continuously with the addition of P. However, the soft magnetic properties are enhanced for P added alloys. The XRD pattern reveals that grain refinement increases with increasing P contents. Alloys annealed at 430 C confirm primary nanocrystallization of a-FeCo in the amorphous matrix, while annealing at 550 C causes secondary crystallization of other non-magnetic phases as well. The magnetic moment of as-cast and annealed alloys, measured by vibrating sample magnetometry (VSM), has minimum values at two temperatures, labeled Tc 1 , Tc 2 , prior to secondary crystallization, corresponding to the ferromagnetic transitions of as-quenched amorphous and residual amorphous phase, respectively. The stabilization of amorphous phase delays primary crystallization, resulting in increase of Tc 1 for P-rich as-cast alloys.

“…[6][7][8] These graded mechanisms should be based on the fact that amorphous solids are thermodynamically metastable and amorphous to-crystalline phase transformation will be stimulated if sufficient energy to drive this process is supplied. Thermal annealing is a common method to ahead these transformations.…”

mentioning

confidence: 99%

“…[2][3][4][5] In the case of magnetic materials, high-performance means operating at high frequency, high power densities, and high temperatures in extreme environments. [6][7][8] These applications require soft magnetic materials not only preserving excellent conductivity, high permeability and saturation magnetization, low coercivity, low eddy-current losses, and high Curie temperatures [6][7][8][9] but also the necessary mechanical strength (i.e., toughness) for processing.…”

mentioning

confidence: 99%

Low temperature magnetic behaviour of glass-covered magnetic microwires with gradient nanocrystalline microstructure

Serrano

Hernando

Marı́n

2014

Slow nanocrystallization driving dynamics can be affected by the combination of two factors: sample residual stresses and sample geometry. This effect is evidenced at the initial stages of nanocrystallization of amorphous CoFeSiBCuNb magnetic microwires. Transmission electron microscopy observations indicate how crystallization at temperatures between 730 and 780 K results in a graded microstructure where the crystallization at the surface skin of the microwire, which remains almost amorphous, differs from that of the middle, where elongated grains are observed, and inner regions. However, samples annealed at higher temperatures present a homogeneous microstructure. The effect of gradient microstructure on magnetic properties has been also analyzed and a loss of bistable magnetic behaviour at low temperatures, from that obtained in the amorphous and fully nanocrystallized sample, has been observed and ascribed to changes in sign of magnetostriction for measuring temperatures below 100 K. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4862540] High performance materials are those essential to important modern applications as ultra-sensitive sensors, actuators and transducers, space power generators, high density magnetic storage media, electromagnetic waves shielding, etc., that should work in extreme environments. However, the full advantage that these materials can provide is strongly dependent on composition and microstructure.1 On the other hand, the concept of gradient materials that refer to the introduction of engineered chemical composition and/or microstructure parameter profiles has been used to tailor materials with desired properties and has gained much attention due to their potential applications. [2][3][4][5] In the case of magnetic materials, high-performance means operating at high frequency, high power densities, and high temperatures in extreme environments.6-8 These applications require soft magnetic materials not only preserving excellent conductivity, high permeability and saturation magnetization, low coercivity, low eddy-current losses, and high Curie temperatures 6-9 but also the necessary mechanical strength (i.e., toughness) for processing.Nanocrystallization from the amorphous state has become a promising method currently available for producing desirable amorphous-nanocrystalline structures with high magnetic characteristics but, generally, these processes involve mechanical properties deterioration associated to embrittlement and ultimate rupture strength decrease. 10Consequently, new graded processes, focused to obtain high-performance nanocrystalline magnetic materials with superior mechanical properties combined with excellent magnetic and/or electronic properties, are going on. [6][7][8] These graded mechanisms should be based on the fact that amorphous solids are thermodynamically metastable and amorphous to-crystalline phase transformation will be stimulated if sufficient energy to drive this process is supplied. Thermal annealing is a common method to ahead these tra...