Density Dependence of Select Properties of Silica Aerogels

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Density Dependence of Select Properties of Silica
Aerogels
A Characterization of Youngs Modulus Thermal
Conductivity
April 2, 2004
Marissa J. Post Professor Ann M. Anderson
Union College Mechanical Engineering ASME
Regional Speaking Competition
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Background
Silica Aerogels
Aerogels are porous nanostructures formed of
solid silica.

• High Porosity
• 90-99 Air by Volume
• Low Density
• 0.003-0.35 g/cm3
• Low Thermal Conductivity
• 0.008-0.017 W/m-K

Some Applications Structural Thermal
Insulation Aerospace Applications
Absorption Applications
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Background
Mechanical Properties
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Fabricating Aerogels

• 1. Mix Solution
• precursor chemical
• hydrolyzing agent
• solvent
• catalyst
• 2. Allow Solution to Gel
• sol-gel
• 3. Dry Gel
• CO2 Supercritical Drying Method
• Rapid Supercritical Extraction Technique
• Natural Drying

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Samples in Study

• Low Density Samples
• CO2 Supercritical Drying Method
• Macroporous
• Nominal Density Samples
• Rapid Supercritical Extraction Technique
• Microporous
• Controlled and Random Samples
• High Density Samples
• Rapid Supercritical Extraction Technique
• Microporous
• Xerogels
• Natural Drying

within 0.003 g/cm3 2.4 error
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Compression Testing
Designing and Machining of Custom Fixture
Conducting Compression Tests using Standard
Instron Machine
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Thermal Conductivity Testing

• Hot Disk Analyzer
• Trapeze
• Sensor Disk
• Balance
• Source Meter
• Computational Unit

Temperature Increase as a Function of Time
Thermal Conductivity
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Results
Youngs Modulus
within 0.03 MPa 3.4 error

• Low and Nominal Density Samples
• Compression in Elastic Region
• Compacting in Strain Hardening Region
• Not Loaded to Failure

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Results
Youngs Modulus

• High Density Xerogel Samples
• Distinct Elastic Region
• Brittle Behavior
• Ultimately Loaded to Failure

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Results
Density Dependence of Youngs Modulus

• Power Law Relationship

E 324?2.69
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Results
Thermal Conductivity

• Within Range Found in Literature
• Wider Range of Densities Required
• Thermal Conductivity Increases after Compression
  Testing

within 0.002 W/m-K 7.8 error
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Summary

• Conducted compression tests to verify power law
  relationship between Youngs Modulus and
  Density
• Performed thermal conductivity tests
• Observed approximately 10 increase in Thermal
  Conductivity after compression testing
• Quantified variance within experimentally
  obtained results

Future Work

• Examine a wider range of densities
• Pin-pointing fabrication procedure for
  repeatability
• Conquering different fabrication methods
• Explore additional properties of aerogels

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Acknowledgements

• Professor Ann M. Anderson
• Professor Ronald B. Bucinell
• Professor Mary Carroll, Smitesh Bakrania, Ben
  Gauthier
• Joel Beal, Bobby Dunton, Jenn Haff, Jason
  Elbot
• Jim Howard, Roland Pierson, Stan Gorski
• University of Virginia

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Density Dependence of Select Properties of Silica
Aerogels
A Characterization of Youngs Modulus Thermal
Conductivity
April 2, 2004
Marissa J. Post Professor Ann M. Anderson
Union College Mechanical Engineering ASME
Regional Speaking Competition