Energetic Material (TKK-2130) 13/14 Spring Semester Instructor: Rama Oktavian Email: [email protected] Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Feb 26, 2016
Energetic Material(TKK-2130)
13/14 Spring Semester
Instructor: Rama OktavianEmail: [email protected] 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
AerogelWhat is Aerogel ?
A classic silica aerogel monolith (image credit Prof. C. Jeffrey Brinker)
AerogelWhat is Aerogel ?
A Nanostructured Material with Fascinating Properties and Unlimited Applications
AerogelWhat 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%.
AerogelAerogel’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
AerogelAerogel 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
AerogelWhat 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)
AerogelSilica aerogel
• high specific surface area (500–1200 m2/g)
• high porosity (80–99.8%)
• low density ( 0.003 g/cm∼ 3)
• high thermal insulation value (0.005 W/mK)
• ultra low dielectric constant (k= 1.0–2.0)
• low index of refraction ( 1.05)∼
Silica AerogelSource materials
• Water glass
• Na2SiO3
• silicon alkoxides (e.g. Si(OMe)4)
Precursors• Tetramethoxysilane (TMOS)
• Tetraethoxysilane (TEOS)
• Methyltriethoxysilane (MTES)
• Methyltrimethoxysilane (MTMS)
Catalyst
• Alcohol group
• Ionic liquid
• H2O Solvent
Silica AerogelPrecursors
• Tetramethoxysilane (TMOS)
• Tetraethoxysilane (TEOS)
• Methyltriethoxysilane (MTES)
• Methyltrimethoxysilane (MTMS)
a starting compound for preparation of a colloid (or sol).
Silica AerogelSynthesis
• Gel preparation
• Aging of the gel
• Drying of the gel
Silica AerogelGel 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 AerogelGel preparation
• Sol-gel reaction
Silica AerogelGel preparation
• Gelation
With time the polycondensation of silicon alkoxide produces colloidal particles that link together to become a 3-D network
Silica AerogelAging 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 AerogelAging 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 AerogelFactors Affecting Chemistry
• H2O/Si Molar Ratios
• Temperature and Time
• pH
• Catalyst
Silica AerogelDrying
• Supercritical drying
• Ambient pressure drying
• Freeze drying
This is where the liquid within the gel is removed, leaving only the linked aerogel network.
Silica AerogelSupercritical drying
Silica AerogelSupercritical 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 AerogelSupercritical 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 CO2and 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 AerogelProperties 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 AerogelHow is it made?
Organic aerogels– Formed with a formaldehyde solution– Resorcinol is used as catalyst– Dried in methanol for 3-5 days– Super critical CO2 drying
Step 1:
Carbon AerogelHow is it made?
Pyrolysis– Requires an inert gas– Organic aerogel is placed into a furnace at 1100° C – Converts the organic molecules into carbon
Step 2:
AerogelApplication
Thermal insulation Supercapacitors Filter and absorption media Energy storage Lithium battery (carbon aerogel)
AerogelApplication 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