Polymer Nanocomposites for Electronic Device Applications

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Polymer Nanocomposites for Electronic Device
Applications
Zhanhu John Guo, Ph.D.Assistant Professor
Integrated Composites Lab (ICL)Chemical
Engineering DepartmentLamar University,
Beaumont, Texas http//dept.lamar.edu/zhanhu
September 4, 2008
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Outline

• Introduction
• Polymer Nanocomposite Fabrication Methodology
• -- Particle surface
  functionalization in neutral solution
• -- Surface initiated
  polymerization (SIP)
• -- Monomer-stabilization-method
  (MSM)
• Polymer Nanocomposite Applications
• -- Giant magnetoresistive
  (GMR) sensor
• -- Microwave absorber
• Summary and Conclusions
• Future Plans
• Acknowledgements

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Composites and Polymer Nanocomposites

• Composites Two or more materials with different
  properties remain separate and distinct on a
  macroscopic level within one unity.

Boeing 787 Dreamliner 50 wt composite
Polymer Nanocomposites

• Lightweight (compared to metal)
• High mechanical properties (compared to pure
  resin)
• Unique physical properties

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Polymer Nanocomposite Fabrication Classifications

• Ex-situ methods

- Dispersing NPs into an organic polymeric
solution1

• In-situ methods

- Monomer polymerization in the presence of
NPs2 - NP formation in the polymer matrix
(Guo/LSU) 3
1. Baker et al., J. Magn. Magn. Mater. 280,
412-418 (2004) 2. Fang et al., J. Appl. Phys.,
91, 8816-8818 (2002) 3. Guo et al., J. Mater.
Chem., 16, 1772-1777 (2006)
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Nanoparticles/Polymer Interactions

• Strong (covalent attachment)

- Covalent bond

• Weak (physical absorption)

Entanglement

• van der Waals force
• Hydrogen bonding
• Electrostatic interaction
• Steric interaction force
• Lewis acid-base interaction

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Challenges of Nanocomposite Fabrication
30 nm SiC NPs

• Particle agglomeration
• Particle/polymer interaction

Surface-Initiated-Polymerization (SIP)
(Currently used byNorthrop Grumman Co.)
Direct-Mixing (DM) (Formally used by Northrop
Grumman Co.)
Epoxy
DM
Rodgers et al., Macromolecular Materials
Engineering, 290, 423-429 (2005) Guo et al.,
Composites Science and Technology, 68,
164-170 (2008)
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Why Nanoparticles?
Interest in iron-group nanoparticles

• Enhanced coercivity (Hc) (data storage)
• Catalyst for CNT/fiber synthesis
• Isotropic properties (compared to wire/tube)

Challenges

• A noble metal shell1-4
• Polymer5

• Easy oxidation (metal)
• Particle agglomeration

• Particle functionalization

• OConnor et al., J. Solid Sate Chem., 159, 26
  (2001)/Journal of Applied Physics, 91, 8195
  (2002)
• Kauzlarich et al., Journal of Applied Physics,
  95, 6804 (2004)
• Guo Podlaha et al., Electrochemical and Solid
  State Letters, 10(12) E31-E35 (2007)
• Guo Podlaha et al., Journal of the
  Electrochemical Society, 152(1) D1-D5 (2005)
• Guo Podlaha et al., Journal of Materials
  Chemistry, 16, 1772-1777 (2006).

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Description of Magnetic Properties
Magnetization, M
Important parameters
Tb Blocking temperature Ms Saturation
magnetization Mr Remanent magnetization Hc
Coercivity
Tb
ZFC
superparamagnetic
ferromagnetic
T
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Polymer Nanocomposite Fabrication Methodology
Iron oxide
Metal
Nanophase tech., inc.
Quantumsphere. Inc.
23 nm
20 nm
How to fabricate magnetic polymer nanocomposites?

• Particle surface functionalization

• Surface-initiated-polymerization (SIP)

• Monomer-stabilization-method (MSM)

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Composite Fabrication Method I Particle
Functionalization by Coupling Agent

• Curable at room temperature
• Good mechanical properties
• High stability to chemicals and moisture

Why vinyl ester?

• Automotive parts
• Marine systems (submarine)

Applications

• Reported in Frost Sullivan
• Contacted by 3M Company, Texas

Guo et al., Journal of Materials Chemistry, 16,
2800-2808 (2006) alumina-VE. Guo et al., Journal
of Materials Chemistry, 17,806-813 (2007)
ZnO-VE. Guo et al., Composites Science and
Technology, 67,2036-2044 (2007) CuO-VE. Guo et
al., Composites Science and Technology, in press
(2008) Fe2O3-VE
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Why Coupling Agent/Surfactant?
Chemical Structure of vinyl ester resin (VE) (a)
styrene and (b) vinyl ester
No chemical bonding!
Bi-functional groups
Nanocomposite structure
Purposes of Coupling Agent/Surfactant 1)
Favor nanoparticle dispersion 2) Minimize
void percentage 3) Improve linkage between
NPs and matrix
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Guo Pereira Choi Wang Hahn, Journal of
Materials Chemistry, 16, 2800 (2006).
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Functionalization Methods in Literature

• pH4 acidic alcoholic solution (Kim et al., 2004)
• ? From Pourbaix diagram,
• NPs are stable in between 4.25
• High temperature at the silane toluene refluxing
  point
• (Abboud et al., 1997)

Kim et al, J. Appl. Polym. Sci., 91, 1898
(2004) Pourbaix, Atlas of Electrochemical
Equilibria in Aqueous Solution (1974) Abbound et
al., J. Mater. Chem., 7, 1527 (1997)
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Experimental Functionalization of Nanoparticles
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
MeOH
H2O
MeOH
MeOH
H2O
H2O
MeOH
H2O
H2O
MeOH
MeOH
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
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Nanocomposite Fabrication
As-received NPs
Functionalized NPs

• Uniform dispersion
• Good particle/polymer bond

• Particle agglomeration
• Voids (poor interaction)

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Guo Pereira Choi Wang Hahn, Journal of
Materials Chemistry, 16, 2800 (2006).
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Functionalization Effect on Mechanical Properties
15 wt nanoparticle loading
Tensile strength
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39.2 MPa
- 25
Youngs modulus

• Particle dispersion
• Particle/polymer interaction

Guo Lei Li Ng and Hahn, Composites Science and
Technology, in press (2008)
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Patent Pending
Method II Surface-Initiated-Polymerization (SIP)
Direct mixing (DM) method
Highly flexible
Why polyurethane?

• Coating
• Corrosion
• Aerospace engineering

Applications
Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007) Guo Kim
Lei Pereira Sugar Hahn, Composites Science and
Technology, 68,164 (2008)
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Surface-Initiated-Polymerization (SIP) Process
Physically absorbed moisture
Step 1.
NP
5.05 g
NP
NP

NP
Catalyst 1.03g Promoter 1.42 g THF 30 ml
Physical chemical adsorption of catalyst
promoter
Ultrasonic bath 30 min
Step 2.
PU
7.7 g
PU monomers
Ultrasonic bath 6 hours
Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007)
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Surface-Initiated-Polymerization (SIP) Process
(contd)
Step 3.
THF
NP/PU Composite
SIP NP/PU
Aluminum Mold 3 days
Hot Press 130 oC 10 minutes

• Mechanism

Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007)
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Characterization TGA/DTG of Nanocomposites
Thermogravimetric Analysis (TGA)
Derivative Thermal Gravimetric (DTG)
Particle dispersion quality
Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007)
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Particle Dispersion Investigation by SEM

• No obvious agglomeration.
• SIP method yielded high-quality composites.

Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007)
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Mechanical Properties
65 wt

• ASTM D412
• Crosshead speed 15mm/min.

Guo Park Wei Pereira Moldovan Karki Young
Hahn, Nanotechnology, 18, 335704 (2007)
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Technical Disclosure Submitted
Method III Monomer Stabilization Method
Suitable for reactive metal nanoparticles
Advantages

• No need for particle functionalization
• Strong chemical bonding
• Improved particle dispersion

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Mechanisms of Monomer-stabilization-method
Polyurethane
Vinyl-ester resin
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Fe NPs Effect on Vinyl-ester Resin Curing DSC
Differential Scanning Calorimetry (DSC)
10 oC/min
NPs favor a lower temperature curing process!
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Polymer Nanocomposite Application I Giant
Magnetoresistance (GMR) Sensor
Funded Proposals

• UC-Discovery Grant (2006/7)
• QuantumSphere Research Grant (2006/7)
• UC-Discovery Renewal Grant (2007/8)

Patent Pending
Licensed to QuantumSphere. Inc.
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GMR History
The Nobel Prize in Physics 2007
"for the discovery of Giant Magnetoresistance"
Dr. Peter Grünberg
Dr. Albert Fert
Germany
France
1970 thin film technique development 1988 first
GMR phenomena found in multilayer structure 1997
first read-out technology based on GMR effect
http//nobelprize.org/nobel_prizes/physics/laureat
es/2007/press.html
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GMR Principle of Operation
Multilayer structure (a) antiferromagnetic domain
orientation, H0
(b) parallel
magnetic domain with a field.
Granular structure (a) antiferromagnetic domain
orientation, H0
(b) parallel
magnetic domain with a field.
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GMR Applications

• Recording and storage information systems
• -- Hard disk
• -- GMR computer memory chips
• Angular and rotating sensor in automotive system
• Biological detection
• Optical IR detection

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Why Granular Polymer GMR?

• Polymer
• Multifunctional groups of polymer matrix

• Applicable in harsh environments
• Flexibility and processability
• Isotropic properties
• No extra packaging needed

• Specific molecular targeting bio-application

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Particle Dispersion in Fe-PU nanocomposite
Guo Park Hahn Wei Moldovan, Karki Young,
Applied Physics Letters, 90, 053111 (2007)
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TEM of Annealed Fe/PU Composites
Iron NPs were embedded in conductive carbon matrix
Guo Park Hahn Wei Moldovan, Karki Young,
Applied Physics Letters, 90, 053111 (2007)
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Magnetic Properties of Fe/PU Nanocomposites
d

• Particle loading
• Annealing condition

coercivity
Guo Park Hahn Wei Moldovan, Karki Young,
Applied Physics Letters, 90, 053111 (2007)
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GMR Sensor Structure and Measurement

• Cold press 10, 000 psi
• Silver paint for electrode connections

GMR sensor geometry and measurement
where R(0) and R(H) resistance at zero and any
applied field H.
Temperature can be controlled from 5 K to RT or
higher.
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GMR Sensor in Annealed Fe/PU Nanocomposites
Electron Transport
RT 7.3
Ln(R) k T(-1/2)
130 K 14
Interparticle tunneling/hopping conduction
mechanism.
Guo Park Hahn Wei Moldovan, Karki Young,
Applied Physics Letters, 90, 053111 (2007)
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GMR Sensor in Annealed Fe/VER Nanocomposites
_at_ RT
Electron Transport
Ln(R) k T(-1/2)
8.5 !!
Interparticle tunneling/hopping conduction
mechanism.
d
Submitted
Particle loading effect inter-particle distance
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Co-Au Core-Shell Nanoparticulate System
Displacement Reaction
Fresh NPs

• Size 2.7 nm ? 0.5 nm
• Shell 0.7 nm

• Metallic conduction mechanism
• Small GMR at 10 K

Guo Moldovan Young Henry Podlaha
Electrochemical and Solid State Letters, 10(12)
E31-E35 (2007).
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Annealed Co-Au Core-Shell Nanoparticulate System
Sample annealed
1.5 at 10 K No GMR at RT
Guo Moldovan Young Henry Podlaha
Electrochemical and Solid State Letters, 10(12)
E31-E35 (2007).
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Reported GMR
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Reported GMR
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Polymer Nanocomposite Application
II Electromagnetic Wave Absorber

• Current absorber materials

• Polymer Nanocomposite

• Improve microwave absorption
• Reduce the weight

• Applications

• Electromagnetic shielding for aircraft
• Wireless communications.

Guo Park Hahn Wei Moldovan, Karki Young, J.
Applied Physics, 10, 09M511(2007)
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Microwave Absorption Evaluation
MBRL metal back reflection loss
Z normalized impedance of the material over
air d microwave absorber layer thickness ?
wave-length in free space er and mr relative
permittivity and permeability of absorber

• 10 dB 90 Reduction
• 20 dB 99 Reduction

Requirement 20 dB loss at 10 GHz
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Microwave Absorption Measurement Setup
Microwave absorber dimensions outer diameter
7.00 mm inner diameter 3.04 mm
e0 and m0 complex permittivity and permeability
of air er and mr complex permittivity and
permeability of absorber
Nicolson and Ross, IEEE Trans. Instrum. Meas.
IM-19, 377 (1970).
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Complex Permittivity

• Higher permittivity
• The presence of oxide in Fe particles
• The formation of particle-chain

Bold Real, Thin imaginary
FeNP-PU, 65 wt
Fe NPs
Real, FeNP-PU
CIP-PU, 79 wt
Real, CIP-PU
Guo Park Hahn Wei Moldovan, Karki Young, J.
Applied Physics, 10, 09M511(2007)
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Complex Permeability
Real, CIP-PU
Real, FeNP-PU
Lower permeability in FeNP/PU composites, low
magnetization
Guo Park Hahn Wei Moldovan, Karki Young, J.
Applied Physics, 10, 09M511(2007)
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Microwave Absorber Evaluation

• Weight reduction of 38 for discrete frequency at
  10 GHz
• Potential to save weight with improved metal NPs

Guo Park Hahn Wei Moldovan, Karki Young, J.
Applied Physics, 10, 09M511(2007)
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Summary and Conclusions

• Three methods to fabricate high-quality
  nanocomposites
• Particle functionalization in neutral
  solution
• Surface-initiated-polymerization (SIP)
  method adopted by NGC
• Monomer-stabilization-method (MSM)
• Particle functionalization has dramatic effect
  on mechanical
• properties
• Particle loading has an effect on the magnetic
  properties/GMR
• performance
• GMR achieved in annealed composites
• 7.3 at room temperature in Fe/PU system
• 8.5 at room temperature in Fe/VER
  system
• Much lighter microwave absorber was designed

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