Nanoparticles Enhance Polymeric Composites

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Nanoparticles Enhance Polymeric Composites
A study of the mechanical properties of
nanocomposites

• By Alex Arguelles
• Graduate Student Mentor Hengyu Wang
• Faculty Advisor Dr. Min Zou
• Monday, July 21, 2008 130pm

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Presentation Outline

• Background information
• Research objectives
• Sample description
• Experiment details
• Results
• Conclusions

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BackgroundPolymethyl methacrylate (PMMA) is a
versatile substance

• Common uses of polymethyl methacrylate
• A glass alternative called Plexiglas
• Superglue
• Hard drives
• Photo resistors
• Dentures and artificial nails
• Nanocomposites enhance the properties of PMMA
• Pros Light weight (lighter than glass), easy to
  form
• Cons Not hard enough, wears easily

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Research Objectives

• Investigate the effects of nanoparticle
  concentrations on mechanical properties of
  cadmium selenide (CdSe)/PMMA nanocomposites
• Elastic modulus
• Hardness
• Creep
• Deformation behavior

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Sample Description

• CdSe/PMMA composites were prepared using a
  solution-based technique (in collaboration with
  Dr. Andrew Wang)
• Samples investigated
• 2 µm thick
• PMMA (control)
• 0.1 wt CdSe in PMMA
• 1 wt CdSe in PMMA
• 10 wt CdSe in PMMA

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Indentation Instrument
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Indentation Test Details

• Berkovich tip was used
• Tip area function was calibrated up to 200 nm
  depth
• Loading rate effect was studied
• Holding time effect was studied
• Indentation tests were performed
• At various loads 20 µN to 220 µN
• Fixed loading rate 10 µN/s
• Fixed holding time 20 sec
• 10 measurements for each load on each sample
• Scanning probe microscope (SPM) imaging before
  and after indents 3 each for 20 µN and 220 µN
  indents

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Loading Rate Effect Has Limited Effect
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Holding Time Of Up To 20 Seconds Impacts Results
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SPM Surface Characterization
0.1
PMMA
Ra 1.12 nm RMS 1.26 nm P-V 51.14 nm
Ra 0.88 nm RMS 1.05 nm P-V 19.34 nm
1
10
Ra 1.01 nm RMS 1.28 nm P-V 17.36 nm
Ra 27.39 nm RMS 33.92 nm P-V 226.93 nm
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SPM Images of Indented Surface (20µN)
0.1
PMMA
Depth 12 nm Pile-Up 1.4 nm
Depth 9 nm Pile-Up 1.3 nm
1
10
Depth 8 nm Pile-Up 1.2 nm
Depth 7 nm Pile-Up 0.7 nm
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SPM Images of Indented Surface (220µN)
0.1
PMMA
Depth 38 nm Pile-Up 3.2 nm
Depth 33 nm Pile-Up 3 nm
1
10
Depth 31 nm Pile-Up 2.6 nm
Depth 23 nm Pile-Up 1.3 nm
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Concentration vs. Pile-up and Indentation Depth
(20µN)
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Concentration vs. Pile-up and Indentation Depth
(220µN)
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Youngs Modulus Increases with Increasing
Concentrations of Quantum Dots
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Hardness Results
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Comparison Between Samples
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Conclusions

• As the concentration of quantum dots increases,
  both the Youngs Modulus and Hardness increase
• Different loading rates will affect indentation
  loading curves but have little impact on
  unloading curves, therefore the loading rate will
  not affect the E and H results
• Different holding times have significant effects
  on E and H results, however, after 20 seconds
  there is little incremental creep
• An increasing percentage of quantum dots will
  decrease the pile-up and indentation depths
• An increase in quantum dots will increase the
  roughness of the sample and also the peak to
  valley distance
• Although the E and H results look promising,
  further testing of polymeric nanocomposites is
  required to determine real life applications

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Questions?
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Indentation Data Analysis Method

• Hardness is measured by dividing the maximum load
  by the contact area. Contact area is measured
  from the indentation depth and the calibrated tip
  shape.
• Youngs modulus is related to the slope of the
  initial part of the unloading curve.