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SUPERINSULATING AEROGELS

Arriving on the Construction Market

José Paulo Farinha

INSTITUTO SUPERIOR TÉCNICO

CENTRO DE QUÍMICA-FÍSICA MOLECULAR

INSTITUTE OF NANOSCIENCE AND NANOTECHNOLOGY

AEROGELS in the Construction Market

What’s an Aerogel?

Silica aerogel

Properties & Types

Silica aerogel in construction

Windows, Blankets & Renders

Though Aerogels: Hybrid Aerogels Nanocomposites

Flexible Aerogels: Aerogel Blankets

Production & Properties

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What’s an Aerogel?

An aerogel is an open-celled, mesoporous,solid foam that is composed of a network ofinterconnected nanostructures, exhibiting aporosity of no less than 50%.

Most aerogels have 90 to 99.9% porosityand contain mesopores (2 to 50 nm indiameter) as well as micropores (below 2nm in diameter).

• Aerogels are the dry, low-density,porous solid framework of a gel.

• Aerogels (aka, frozen smoke) arethe lowest density solid materialsever produced, with densitiesaround 20g/L (only 15x heavierthan air). Composed of up to99.98vol% air.

• Surface areas of 100-1000m2/g.

Types of Aerogel

Silica aerogel

The most common type

Organic and Carbon AerogelsOrganic aerogels can be made from polymerssuch as formaldehyde resins, polyacrylamides,polyacrylates, polyurethanes, epoxies, etc.

Carbon aerogels obtained by pyrolysis used usedin fast-charging supercapacitors (3200 m2/g).

Metal Oxide AerogelsAlumina, Titania, Zirconia – clear, scattering white/blue (like Silica)Iron oxide - rust red or yellow, opaqueChromia - deep green or deep blue, opaqueVandia - olive green, opaqueNeodymium oxide - purple, clearSamarium oxide - yellow, clearErbium oxide - pink, clear

Semiconductor AerogelsPhotoluminescent aerogels from metal chalcogenide (CdS, PbSe, etc)

Metal Aerogels

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Silica Aerogel Preparation: The Sol-Gel Method

Reactive “silanol” groups

Hydrolysis

acid or basic catalysis

Condensation

Water condensation

Alcohol condensation

Silica Gel Formation (alkoxide technique)

Silica Gel Formation (alkoxide technique)

Silica Aerogel Preparation

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Obtaining an aerogel

Silica Aerogel Preparation

Drying the wet gel (containing solvent, etc)without destroying the pore structure:

• Supercritical drying (usually with CO2)

• Subcritical drying (by solvent exchange)

Control of surface tension to limit damage by capillary stress.

Solvent extraction

Silica Aerogel Properties

Records held by some specially-formulated silica aerogels :

• Lowest density solid (0.0011 g cm-3)

• Lowest optical index of refraction (1.002)

• Lowest thermal conductivity at atmospheric pressure(0.016 W m-1 K-1)

• Lowest speed of sound through a material (70 m s-1)

• Lowest dielectric constant from 3 to 40 GHz (1.008)

Super thermal insulators

Super sound insulators

Not so super mechanical properties…

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Silica Aerogel Insulation

• Insulation of the Mars exploration rovers

• High-temperature systems

• Cryogenics

• Subsea oil pipelines

• Winter clothing

• Construction

Temperature change >110ºC

Silica Aerogel in Construction

• Transparent Window Insulation

• Interior walls

• Exterior walls

• Roof

• Floor Thermal efficiency, noise

reduction and diffused light

(90% transmission).

Broad Art Museum, Michigan State University

Convent of Fra Angelico, Louvain La Neuve

Crocker Museum, Sacramento, CA

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Silica Aerogel in Construction

• Transparent Window Insulation

• Interior walls

• Exterior walls

• Roof

• Floor

Double interior/exterior insulation with9mm aerogel blanket of 400yr old buildingto achieve passive heating status (noheating/cooling required)

Silica Aerogel in Construction

• Transparent Window Insulation

• Interior walls

• Exterior walls

• Roof

• Floor

9mm aerogel blanket replaced50 mm mineral wood insulation

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Silica Aerogel in Construction

• Transparent Window Insulation

• Interior walls

• Exterior walls

• Roof

• Floor 9mm aerogel blanket installed insteadof 4 cm conventional insulation

• Low compressive strength

• High susceptibility to fracture

Super thermal insulators

Super sound insulators

Not so super mechanical properties…

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Super thermal insulators

Super sound insulators

Though Aerogels: Hybrid Aerogels Nanocomposites

AIRSILTEX

Silica LatexAir

Hybrid Aerogels nanocomposites withwater-dispersed polymeric nanoparticles

• Flexible and mechanically strong films

• Used in coatings

Polymer nanoparticles as impact modifiers

Rubberycross-linkedlow Tg core

Trimethoxisilanereactive shell (binds to sílica)

Farinha, J.P.S. et al. Patented: US7737189 2010; BR200607020 2009; JP2008537570 2008; US2008188575 2008; EP1879690 2008; AU2006231371 2006; etc.

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AIRSILTEXLIGHT

STRONG

INSULATOR

Hybrid aerogel nanocomposite with 3 wt% PNP

SEM

Silica aerogel

Stress-strain curves for unidirectional compression.

Farinha, J.P.S. et al, J. Materials Chemistry 2007, 17, 2195; Chemistry of Materials 2007, 19, 2603; Langmuir 2007, 23, 5727

Bicontinuous distribution of particles (D ≈100 nm) and pores (D ≈10 nm).Porosity > 80%.

Mechanical properties of the hybrid aerogel nanocomposite

…BUT NOT FLEXIBLE

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Possible Strategies

1

2

powderInsulation bag

or matrix

Flexible Aerogelinsulator

Flexible fibre

Hybrid aerogelcoating

Hybrid Aerogel

Flexible fibre

Polymernanoparticles

Silicanetwork

Flexible Hybrid Aerogel

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CONDENSATION

Fibre (Process 2)

SUBCRITICALDRYING

HYDROLYSIS

Fibre (Process 1)

GEL AGING WASHING

SILICA

PRECURSOR

SOLUTION

POLYMER

DISPERSION

Preparation

Properties

Thickness: 0.5±0.2 mm

ρenv = 367 ±81 kg m-3

ρsup = 184 ±17 g m-2

K = 8.13 mWm-1K-1

Latex 2%; Glass or polyester fibre 28%

Fiber well coated

Good Flexibility

ρenv in aerogel range

Good thermic insulation

Hydrophobicity

Farinha, J.P.S., J. Materials Chemistry A2013, 1, 12044-12052. PCT patent pending.

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CQFM-IN / IST-UL

Prof. Gaspar Martinho

Prof. Laura Ilharco

Dra Alexandra Fidalgo

Acknowledgments

Interfaces, acrylic on canvas, 1.5 m x 1.5 m

Acknowledgments

Ana Tristany

www.anatristany.com