SUPERINSULATING AEROGELS Arriving on the Construction Market

Transcription

1 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? Properties & Types Silica aerogel Production & Properties Silica aerogel in construction Windows, Blankets & Renders Though Aerogels: Hybrid Aerogels Nanocomposites Flexible Aerogels: Aerogel Blankets 1

2 What s an Aerogel? An aerogel is an open-celled, mesoporous, solid foam that is composed of a network of interconnected nanostructures, exhibiting a porosity of no less than 50%. Aerogels are the dry, low-density, porous solid framework of a gel. Aerogels (aka, frozen smoke) are the lowest density solid materials ever produced, with densities around 20g/L (only 15x heavier than air). Composed of up to 99.98vol% air. Surface areas of m 2 /g. Most aerogels have 90 to 99.9% porosity and contain mesopores (2 to 50 nm in diameter) as well as micropores (below 2 nm in diameter). Types of Aerogel Silica aerogel The most common type Semiconductor Aerogels Photoluminescent aerogels from metal chalcogenide (CdS, PbSe, etc) Metal Oxide Aerogels Alumina, Titania, Zirconia clear, scattering white/blue (like Silica) Iron oxide - rust red or yellow, opaque Chromia - deep green or deep blue, opaque Vandia - olive green, opaque Neodymium oxide - purple, clear Samarium oxide - yellow, clear Erbium oxide - pink, clear Metal Aerogels Organic and Carbon Aerogels Organic aerogels can be made from polymers such as formaldehyde resins, polyacrylamides, polyacrylates, polyurethanes, epoxies, etc. Carbon aerogels obtained by pyrolysis used used in fast-charging supercapacitors (3200 m 2 /g). 2

3 Silica Aerogel Preparation: The Sol-Gel Method Hydrolysis Silica Gel Formation (alkoxide technique) acid or basic catalysis Reactive silanol groups Condensation Water condensation Alcohol condensation Silica Aerogel Preparation Silica Gel Formation (alkoxide technique) 3

4 Silica Aerogel Preparation Obtaining an aerogel Solvent extraction Drying the wet gel (containing solvent, etc) without destroying the pore structure: Supercritical drying (usually with CO 2 ) Subcritical drying (by solvent exchange) Control of surface tension to limit damage by capillary stress. Silica Aerogel Properties Records held by some specially-formulated silica aerogels: Lowest density solid ( 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 4

5 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). Crocker Museum, Sacramento, CA Broad Art Museum, Michigan State University Convent of Fra Angelico, Louvain La Neuve 5

6 Silica Aerogel in Construction Transparent Window Insulation Interior walls Exterior walls Roof Floor Double interior/exterior insulation with 9mm aerogel blanket of 400yr old building to achieve passive heating status (no heating/cooling required) Silica Aerogel in Construction Transparent Window Insulation Interior walls Exterior walls Roof Floor 9mm aerogel blanket replaced 50 mm mineral wood insulation 6

7 Silica Aerogel in Construction Transparent Window Insulation Interior walls Exterior walls Roof Floor 9mm aerogel blanket installed instead of 4 cm conventional insulation Super thermal insulators Super sound insulators Not so super mechanical properties Low compressive strength High susceptibility to fracture 7

8 Though Aerogels: Hybrid Aerogels Nanocomposites Super thermal insulators Super sound insulators AIRSILTEX Air Silica Latex Hybrid Aerogels nanocomposites with water-dispersed polymeric nanoparticles Flexible and mechanically strong films Usedincoatings Polymer nanoparticles as impact modifiers Rubbery cross-linked low T g core Trimethoxisilane reactive shell (binds to sílica) Farinha, J.P.S. et al. Patented: US ; BR ; JP ; US ; EP ; AU ; etc. 8

9 LIGHT AIRSILTEX INSULATOR STRONG Mechanical properties of the hybrid aerogel nanocomposite Hybrid aerogel nanocomposite with 3 wt% PNP Bicontinuous distribution of particles (D 100 nm) and pores (D 10 nm). Porosity > 80%. Silica aerogel Stress-strain curves for unidirectional compression. SEM Farinha, J.P.S. et al, J. Materials Chemistry 2007, 17, 2195; Chemistry of Materials 2007, 19, 2603; Langmuir 2007, 23, 5727 BUT NOT FLEXIBLE 9

10 Possible Strategies 1 Hybrid Aerogel powder Insulation bag or matrix 2 Flexible fibre Hybrid aerogel coating Flexible Aerogel insulator Silica network Polymer nanoparticles Flexible Hybrid Aerogel Flexible fibre 10

11 Preparation SILICA PRECURSOR SOLUTION HYDROLYSIS Fibre(Process 1) POLYMER DISPERSION CONDENSATION Fibre (Process 2) GEL AGING WASHING SUBCRITICAL DRYING Properties Latex 2%; Glass or polyester fibre 28% Fiber well coated Good Flexibility ρ env in aerogel range Good thermic insulation Thickness: 0.5±0.2 mm ρ env = 367 ±81 kg m -3 ρ sup = 184 ±17 g m -2 K = 8.13 mwm -1 K -1 Hydrophobicity Farinha, J.P.S., J. Materials Chemistry A 2013, 1, PCT patent pending. 11

12 Acknowledgments CQFM-IN / IST-UL Prof. Gaspar Martinho Prof. Laura Ilharco Dra Alexandra Fidalgo Acknowledgments Ana Tristany Interfaces, acrylic on canvas, 1.5 m x 1.5 m 12