This is review study of silica aerogel, represents a meticulous exploration of the properties, applications, and synthesis methods of silica aerogels.

1. A COMPREHENSIVE REVIEW
ON SILICA AEROGEL
BS RESEARCH THESIS

2. OUTLINES
1) Introduction
2) Properties
3) Preparation of Silica Aerogel
4) SiO2 Formation Reactions
5) Characterization Techniques
6) Applications
7) Conclusion

3. INTRODUCTION

4. INTRODUCTION
Properties
Thermal Insulation
 Ultra-low thermal conductivity
Transparency
 Transparent to Visible and IR
Porosity
 Highly Porous
 Large surface area
 Pore diameter is in the range 2 – 5 nm
Hydrophobicity
 Hydrophobic due to the presence of
(OH-) groups on their polar surfaces
 Can be modified
Silica Aerogel
 “Frozen Smoke” or “Blue Smoke”
 Lightest Solid Material
 Samuel Kistler ~ 1930s first time developed
aerogels using SCD method
Density
 Extremely low density ~ (0.001 – 0.35) g/cm3
Composition
 Comprising approximately 95-99% air
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5. PREPARATION OF SILICA AEROGEL
Evaporation
Gel
Solution
Precursor
Aerogel
Extraction of
Solvent (Drying)
Hydrolysis
Condensation
(Gelation)
Aging
Xerogel
Sol-Gel Method
Precursor: Tetramethylorthosilicate
(TMOS) Si(CH3O)4 or
tetraethylorthosilicate (TEOS)
Si(C2H5O)4.
Gelation: At room temperature.
(6 – 36 hours)
Aging: (hours or days), 50 to 80 °C.
Drying: SCD (at 31.1 °C temperature and
above 72 atm pressure for several hours).

6. SiO2 FORMATION REACTIONS
HYDROLYSIS
Si (OR)4 + 4H2O ⇌ Si(OH)4 + 4ROH
Where R = Vinyl, Alkyl , Aryl groups
CONDENSATION
◂ Water Condensation
≡ Si(OH) + (OH)Si ≡ ⇌ ≡ Si − O − Si ≡ + H2O
◂ Alcohol Condensation
≡ Si(OH) + (OCH3)Si ≡ ⇌ ≡ Si − O − Si ≡ + CH3OH
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7. CHARACTERIZATION TECHNIQUES
SEM Image TEM Image
a b (Max Resolution)

8. X-RAY DIFFRACTION (XRD) OF SILICA AEROGELS
 No Sharp Peaks (Amorphous Nature)
 The XRD pattern typically shows a broad,
hump, also known as the amorphous halo.
 Disordered, non-repeating structure of the
amorphous silica network.
 Introducing metal nanoparticles or organic
compounds could lead to additional features
in the XRD pattern.
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9. OPTICAL PROPERTIES
 The refractive index is (1.01–1.22)
at visible wavelengths.
 Transparent to visible and IR
radiation.
 In UV region, the refractive index
increases, and the material
becomes more dispersive.

10. MECHANICAL TESTING
 Stress - Strain curve is almost linear for
pure cellulose aerogel.
 The composite aerogel is more flexible
and more strain is produced by applying
small stress.
 J. Caiet et al,. studied the mechanical
properties of pure cellulose aerogel (1,3)
and cellulose silica composite aerogel
(2,4).
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11. THERMAL CONDUCTIVITY MEASUREMENT
(Radiative Transfer Equation) (Radiative Transfer Equation)
(Equation) (Equation)

12. THERMAL CONDUCTIVITY MEASUREMENT
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13. Tablet project
Show and explain
your web, app or
software projects
using these gadget
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ACCOUSTIC PROPERTIES
20 mm thickness absorption
is increasing linearly with
frequency up to 2 kHz.
After up to 4 kHz it
decreases.
10 mm thickness the
absorption is nearly linear
until 4 kHz.
40 mm thickness graph is
linear up to ~ 1 kHz, and a
small decrease is observed
between 1 and 2 kHz, but
after 3 kHz it is almost
constant.

14. APPLICATIONS
 Thermal Insulation
 Sound Insulation
 Oil Spill Cleanup
 Aerospace and Aviation
 Electronics and Sensors
 Catalysis
 Solar Collectors
 Energy Efficiency
 Environmental Sensors
 Chromatography and Adsorption
 Drug Delivery
 Lightweight Composites
 Biomedical Applications
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15. Conclusion
 Ultra-light solid composition, consisting of 95-99% air.
 Minimal density and unique porosity.
 Properties vary based on precursors, aging, drying methods, and composites.
 Lack of periodicity in SiO2 molecule arrangement due to amorphous nature.
 Shape and geometry influenced by antecedents in the sol-gel process.
 Aging times and drying methods have a major impact on product characteristics.
 Ongoing researches on low cost organic hybrid aerogels.
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16. THANKS!
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