Energetic Material(TKK-2130)

13/14 Spring Semester

Instructor: Rama OktavianEmail: rama.oktavian86@gmail.comOffice 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