Amorphous Amorphous Nanocomposite Nanocomposite MaterialsMaterials

Presented by: Presented by:

Renée E. GordonRenée E. Gordon

Advisor: Advisor: Professor Michael Professor Michael McHenryMcHenryGraduate Student: Graduate Student: Changyong UmChangyong Um

Melt Spinning Process

• Amorphous Nanocomposite Material.– FINEMET, NANOPERM, and

HITPERM.– Nanocrystals are embedded in an

amorphous matrix.• Rapid Solidification Technique.

– Cooling rate: 1 Million Kelvin per second. (106 K/sec)

• Produces Amorphous Metastable Material.– Material is not stable at higher

temperatures.– If occurs, material is thermally

activated and can turn to Crystalline phase.

• Application: Inductive Component of electronic devices.

– Good soft magnetic properties.

•Indenter is only 100nm in size.

•Area of Berkovich Tip :

•θ = 65.3° (semi-angle of Berkovich indenter)

•hp= plastic depth of penetration

•Berkovich Hardness:

Nano-Indentation

22 tan)33( phA

)(5.24 2ph

PH

Theory

• Begins Fully Amorphous.• Gradually becomes paramagnetic (losing magnetic change).• Crystallization begins at ~500oC.

– Increase in magnetization.

• Curie Temperature of Nanocrystalline phase: 610oC.• Note there are 2 different Curie temperatures.

0

20

40

60

80

100

120

140

160

0 100 200 300 400 500 600 700 800 900

Temperature (oC)

Mag

neti

zati

on

(em

u/g

)

Curie transition

Primary crystallization onset temperature

Nanocrystalline Curie Temperature

FINEMET

Theory

• Increase in annealing temperature increases the rate of crystallization.

• Morphology Index (n) can be determined from Johnson-Mehl-Avrami Kinetic model.

• This (n) indicates the mechanism and dimension of nucleation and growth.

• Volume Fraction Transformed:

– koJMA= rate constant coefficient

– QJMA= activation energy

• Volume fracture increase is proportional to the magnetization increase.

Isothermal Magnetization Kinetic Dataof FINEMET

RT

QkTk JMAoJMA exp)(

Results

• Shows Hardness as a function of Volume Fraction that has been Crystallized.

• When crystallization occurs, nanocrystals form.

• These nanocrystals are harder than the amorphous matrix.

• The more nanocrystals, the harder the overall material.

• Fully Amorphous, Hardness=7-8 GPa.

• Saturated (top right), Hardness=14 GPa.

• HITPERM expected to act similar to FINEMET and NANOPERM.

Results

• Thickness-Dependent Magnetization Curve (from VSM).

• Increased thickness results in slower crystallization.

• As thickness decreases crystallization occurs faster.

• 100 nm reading has “noise”. • 70-80% Volume Fraction of the

material crystallizes.

NANOPERM

AcknowledgementsAcknowledgements

•Changyong UmChangyong Um•Professor McHenryProfessor McHenry•MRSECMRSEC•Wright Patterson Air Force BaseWright Patterson Air Force Base•Magnetics, A Division of Spang and Co.Magnetics, A Division of Spang and Co.

Thank you for your Thank you for your time.time.

Questions and Comments.Questions and Comments.

Extras

• Composition of HITPERM:

– (Fe,Co)88M7B4Cu1 ; (M=Zr,Nb,Hf)

• Composition of NANOPERM:

– Fe88Zr7B4Cu1

• Composition of FINEMET:

– Fe73.5Si13.5B9Nb3Cu1