Magnetic Nanocomposite Materials for High Temperature Applications

Presented by:

Vahidreza Bitarafhaghighi Ravinder Singh

Advisor:

Dr. Zhanhu John Guo

Spring, 2013

Agenda

1- paper review2-background Nanocomposites Magnetization3- thermal decoupling4- results5- conclusion

Why Nano?

Nanoscale materials can have properties that are unrealizable in

bulk materials

Making a material nanoscale can change its

• Melting temperature• Magnetization• Ability to hold charge

• Structure• Chemical reactivity• … among other

things

What is a magnet?

Mr Hc Ms µ

Characterization

Figure from: Magnetic Nanocomposite Materials for High Temperature Applications, F. Johnson, et al.http://neon.mems.cmu.edu/mchenry/mchenry2/Publications/172.PDF

6

Types of Magnets

Ferromagnetic materials the magnetic moments of neighboring atoms align resulting in a net magnetic moment.

Paramagnetic materials are randomly oriented due to Brownian motion, except in the presence of external magnetic field.

B

Paramagnetism

M

H

H = 0H

H

H = 0

Ferromagnetism

H = 0H

H

H

M

H

9

Superparamagnetic

Combination of paramagnetic and ferromagnetic properties Made of nano-sized (<20nm) ferrous magnetic particles, but affected by Brownian

Motion. They will align in the presence of an

external magnetic field.Magnetite naturally found in human

body

Hergt, Rudolf. Journal of Physics: Condensed Matter v18 2006 s2919-2934

Curie Temperature

Historical Background

FINEMET (Fe73.5Si13.5B9Nb3Cu1) 1988An extension of common Fe-Si-B alloy with Cu and NbNANOPERM (Fe88Zr7B4Cu1) 1990Higher saturation inductionHITPERM (Fe88Co44Zr7B4Cu1) 1998The key distinction is the substitution of Co for Fe

The amorphous and crystalline phases have distinct behaviors Ribbons made for the experiment:Fe44Co44Zr3.5Nb3.5B4Cu1(Fe:Co 50:50)Fe57.2Co30.8Zr3.5Nb3.5B4Cu1(Fe:Co 65:35)Which are a modification of the original HITPERM

Thermal Decoupling

Results

Brillouin function

Randomized anisotropy

Anisotropy is the property of the material by virtue of which its physical properties like absorbance, refractive index, conductivity, magnetism, etc. are dependent on the direction in which they are measured.

Applications

Transformers: Miniaturization and

efficiency requirements demand the reduction of size and mass of the core materials in transformer.

Operating temperatures may increase as power electronic systems become more densely populated with components.

Applications

DC-DC power converters: These converters use

magnetic transformers and inductors along with active circuit elements to convert voltage levels.

The Low Ms and Tc of ferrite materials, which are presently used, limits the miniaturization potential of converters

Conclusion

Nanocomposite magnetic materials have been developed as an evolution of amorphous magnetic alloys. These alloys display low Hc and power loss . HITPERM alloys, based on the FeCo system, offer high Ms and Tc. Hitperm has shown to have the highest interparticle decoupling temperatures yet observed. These properties show promise for increasing efficiency and component packing density in power electronic applications.

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