Strength Characteristics of Silica-Aerogels

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Strength Characteristicsof Silica-Aerogels

• Marissa J. Post
• Senior Project
• Spring 2003
• Advisor Professor Ann Anderson

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Presentation Outline

• Goals
• Background
• What are Aerogels?
• Strengthening Aerogels
• Progress
• Results
• Future Work

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Goals

• Spring Term
• Research strengthening methods
• Fabricate aerogels
• Characterize standard silica-aerogels

• Fall Term
• Apply select strengthening methods
• Compare standard silica-aerogels with
  strengthened aerogels

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Aerogel Characterization

• Porous nanostructure formed of solid silica
• High Porosity
• 90 99 air by volume
• Low Density
• 0.003 0.35 g/cm3
• Low Thermal Conductivity

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Aerogel Applications

• Thermal Insulation
• Walls
• Windows
• Aerospace
• Cosmic dust collectors
• Mars Pathfinder
• Absorption
• Packaging
• Clothing

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Aerogel Fabrication

• Solution
• Precursor Chemical TMOS
• Hydrolyzing Agent H2O
• Solvent Methanol
• Catalyst Ammonia
• Sol-gel
• Aerogel
• Supercritical Extraction

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Aerogel Limitations

• Fragile and Brittle
• Low Compressive Strength
• Low Modulus 2 3 MPa

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Strengthening Aerogels

• Fiber Reinforcement
• Aging and Drying
• Composite Aerogels

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Fiber Reinforcement

• Parmanter and Milstein (1998) compared
  unreinforced aerogels to fiber reinforced
  aerogels
• 68 Silica Fibers 3 mm dia, 1.27 cm length
• 20 Alumina Fibers 2-4 mm dia, 1.27 cm length
• 12 Aluminaborosilicate Fibers 8 mm dia, 1.27 cm
  length
• Mass Percentages 0, 5, 10, and 25
• Densities 40, 50, and 80 kg/m3

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Fiber Reinforcement

• Modulus was the highest for fiber content of 5
  and density of 80 kg/m3
• E 34 MPa
• Modulus increased with increasing density

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Aging and Drying

• Parmenter and Milstein (1998) investigated the
  aging effects on the compressive strength of
  aerogels
• Aged one week
• Aged two months

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Aging and Drying

• Trend of higher modulus with two months of aging
• In one case, the modulus increased from 18 MPa to
  28 MPa with aging for two months

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Composite Aerogels

• Marliere and Woignier (2001) experimented with
  silica soot (aerosil) composite aerogels
• Fumed Silica
• Aerosil weight percentage range 0 70

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Composite Aerogels

• Increased weight percentages of aerosil greatly
  increased the modulus

• 70 aerosil composite increased modulus

by nearly 10-fold
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First Term Progress

• Fabricating Aerogels
• CO2 Supercritical Drying
• Compression Tester
• Designed and machined

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Fabricating Aerogels

• Autoclave

Chiller
CO2 Tank
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Compression Tester

• 7075 Aluminum
• Linear Bearings
• Precision Shafts

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Compression Test
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Compression Test

• Standard Aerogel Sample
• 10 mm cylinder, 6 mm dia
• Approximately 0.0001 lbs
• Aged one year
• Load 13 lbs

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Future Work

• Summer
• Continue aerogel fabrication
• Characterize standard aerogels

• Fall Term
• Apply select strengthening methods
• Characterize compressive strength, porosity, and
  surface area in strengthened aerogels

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Acknowledgements

• Professor Ann Anderson,
• Professor Bucinell,
• Smitesh Bakrania,
• Jason Elbot,
• Jim Howard,
• Roland Pierson