13/14 Spring Semester
Energetic Material
(TKK-2130)
Instructor: Rama Oktavian
Email: rama.oktavian86@gmail.com
Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Outlines
1. Aerogel
2. Types of Aerogel
3. Aerogel synthesis process
4. Aerogels application
5. Recent status of aerogel
Aerogel
What is Aerogel ?
A classic silica aerogel monolith (image credit Prof. C.
Jeffrey Brinker)
Aerogel
What is Aerogel ?
A Nanostructured
Material with Fascinating
Properties and Unlimited
Applications
Aerogel
What is Aerogel ?
• Is essentially the solid
framework of a gel
• A class of porous, solid
materials that exhibit
extreme material
properties
• Aerogels are derived
from gels–effectively the
solid structure of a wet
gel
• Aerogels were first
created by Samuel
Stephens Kistler in 1951
An aerogel is an open-celled, mesoporous,
solid foam that is composed of a network of
interconnected nanostructures and that
exhibits a porosity (non-solid volume) of no
less than 50%.
Aerogel
Aerogel’s properties
• extreme low densities
(which range from
0.0011 to ~0.5 g cm-3)
• Very good thermal
insulator
• High specific surface
area
• Lowest dielectric
constant
Aerogel
Aerogel
Aerogel is nanotechnology
 A nanometer is
1 billionth
of a meter.
 A hair is 80,000
nm wide.
 Aerogel is a glass foam with
bubbles 10 nm wide.
Aerogel
Aerogel
What are aerogels made of?
• Silica
• Most of the transition metal oxides (for example, iron oxide)
• Most of the lanthanide and actinide metal oxides (for example, praseodymium
oxide)
• Several main group metal oxides (for example, tin oxide)
• Organic polymers (such as resorcinol-formaldehyde, phenol-formaldehyde,
polyacrylates, polystyrenes, polyurethanes, and epoxies)
• Biological polymers (such as gelatin, pectin, and agar agar)
• Semiconductor nanostructures (such as cadmium selenide quantum dots)
• Carbon
• Carbon nanotubes, and
• Metals (such as copper and gold)
Aerogel
Silica aerogel
• high specific surface area (500–1200 m2/g)
• high porosity (80–99.8%)
• low density (∼0.003 g/cm3)
• high thermal insulation value (0.005 W/mK)
• ultra low dielectric constant (k= 1.0–2.0)
• low index of refraction (∼1.05)
Silica Aerogel
Source materials
• Water glass
• Na2SiO3
• silicon alkoxides (e.g. Si(OMe)4)
Precursors
Catalyst
• Tetramethoxysilane (TMOS)
• Tetraethoxysilane (TEOS)
• Methyltriethoxysilane (MTES)
• Methyltrimethoxysilane (MTMS)
• H2O
Solvent
• Alcohol group
• Ionic liquid
Silica Aerogel
Precursors
a starting compound for preparation of a
colloid (or sol).
• Tetramethoxysilane (TMOS)
• Tetraethoxysilane (TEOS)
• Methyltriethoxysilane (MTES)
• Methyltrimethoxysilane (MTMS)
Silica Aerogel
Synthesis
• Gel preparation
• Aging of the gel
• Drying of the gel
Silica Aerogel
Gel preparation
• The silica gel is obtained by sol–gel process
a process in which solid nanoparticles dispersed
in a liquid (a sol) agglomerate together to form a
continuous three-dimensional network extending
throughout the liquid (a gel).
Silica Aerogel
Gel preparation
• Sol-gel reaction
Silica Aerogel
Gel preparation
• Gelation
With time the polycondensation of silicon
alkoxide produces colloidal particles that
link together to become a 3-D network
Silica Aerogel
Aging of the gel
With time after gelation the solid network
immersed in the pore liquor continues to
evolve.
The gel prepared in the first step is aged in
its mother solution. This aging process
strengthens the gel.
Bulk density and pore size are influenced
by concentration aging solution and aging
time
Silica Aerogel
Aging of the gel
Polycondensation – reactions continue to
increase network
Syneresis – spontaneous shrinkage;
continues until gel is a solid mass
Coarsening –small particles grow initially
and act as “nutrients” for bigger crystals
Silica Aerogel
Factors Affecting Chemistry
• H2O/Si Molar Ratios
• Temperature and Time
• pH
• Catalyst
Silica Aerogel
Drying
This is where the liquid within the gel is
removed, leaving only the linked aerogel
network.
• Supercritical drying
• Ambient pressure drying
• Freeze drying
Silica Aerogel
Supercritical drying
Silica Aerogel
Supercritical drying procedure
compressing and heating the sol-gel above the critical pressure and
temperature of the solvent
decompressing it down to atmospheric pressure
cooling it down to room temperature
Silica Aerogel
Supercritical drying procedure for silica aerogel in ethanol
sol-gel is placed in the autoclave and charged with additional ethanol
the system is then pressurized to at least 5-6 MPa with CO2
and cooled to 5-10°C.
Supercritical fluid is flushed through the vessel until ethanol has been totally
removed from the vessel and from within the gel.
Carbon Aerogel
Properties of carbon aerogels
 Lowest density solid
 Thermal conductivity of .03 W/m-K
 Surface area of up to 1200 m2 / g
 Capacitance of 100-200 F/g
 Up to 99.9% air
 Power densities up to 20 kW/kg
 Energy densities up to 325 kJ/kg
 Low index of refraction
 1/2000 to 1/5000 the size of normal ultra-capacitors
 Brittle
Carbon Aerogel
How is it made?
Step 1:
 Organic aerogels
– Formed with a formaldehyde solution
– Resorcinol is used as catalyst
– Dried in methanol for 3-5 days
– Super critical CO2 drying
Carbon Aerogel
How is it made?
Step 2:
 Pyrolysis
– Requires an inert gas
– Organic aerogel is placed into a furnace at 1100° C
– Converts the organic molecules into carbon
Aerogel
Application
 Thermal insulation
 Supercapacitors
 Filter and absorption media
 Energy storage
 Lithium battery (carbon aerogel)
Aerogel
Application in energy-related sector
Source:
Vladimir Anikeev,Maohong Fan. 2014. Supercritical fluid for energy and environmental application.
Elsevier
Recent status of Aerogel
• It’s your job to find the recent status and
development of aerogel including the most recent
and promising technology for aerogel synthesis
• Show me the most recent development of aerogels
application in energy and chemical process sector