Amorphous Nanocomposite Materials Presented by: Renée E. Gordon Advisor: Professor Michael McHenry...
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Transcript of Amorphous Nanocomposite Materials Presented by: Renée E. Gordon Advisor: Professor Michael McHenry...
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