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lambda=355nm


lambda=635 nm

Silica Aerogel Rayleigh Scattering

 

 

 

 

 

 

 


Silica aerogel-iron oxide nanocomposites

 

 

High-coercivity ultralight transparent magnets
of Nd2Fe14B: Samples of FeNdB particles embedded in a silica aerogels, isotropically dispersed (a) aligned with a field (b).

 

 

 

 

 

SEM micrographs of porous silica aerogel microparticles

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

What aerogels are?

Aerogels are solid materials with amorphous structure and high open porosity (~95% of its volume is air). Due to this structure they show an ensemble of properties not encountered in any other kind of material:

Aerogels are extremely light (0.004 g/cm3- 0.6 g/cm3)

Aerogels have a high surface area (as big as a soccer field per 1 g of material)

Aerogels are chemically inert

Aerogels are thermal, acoustic and electric insulators (an aerogel panel of 2.5 cm thickness gives the same thermal insulation as 10 double windows). Although carbon aerogels are electrically conductive

Aerogels have very low dielectric constants and refraction indexes

Aerogels are transparent to visible radiation

This particular combination of properties makes aerogels useful in lots of applications and best candidates for many other in the future, for instance:

Thermal insulation, super capacitors, water deionisers, optical sensors for gas detection, pollution filters, reduction of dielectric coupling between conducting layers in chips, absorbents for desiccation, insecticides, dangerous liquids storage vessels, catalysis, impedance adapters for acoustical transducers, sound insulation and absorption, impact protection materials, solidification crucibles, particle detectors,...

How are aerogels obtained?

A gel is formed from a suspension of particles in a liquid (sol) that begin to aggregate one to another forming a capillary network (sol-gel process). When this structure extends over the whole volume of the container we get a gel.

As its name suggests, an aerogel is a gel whose solvent has been replaced by air, maintaining the solid network structure. This is usually achieved by treatments at pressures and temperatures above the critical point of the liquid filling the gel: in such conditions evacuation of the supercritical fluid is done without the liquid-vapour coexistence that would destroy the gel solid network due to surface tension.

The high pressure and temperature conditions (~100 bar and 250 ºC) needed to obtain an aerogel from a gel are reached at the Supercritical Gases Laboratory set by the ICMAB in co-operation with Carburos Metalicos S.A. (link Supercritical Gases Laboratory) http://www.icmab.es/labgs/labgs.html
An alternative process at low temperature can be applied by substituting the solvent by liquid CO2

Aerogel research in our group:

  • Basic Research
    • Influence of the synthesis parameters on the final material: the aim is to be able to control the microstructure of the aerogels.

      Silica Aerogels by Supercritical Extraction
      A. Roig, I. Mata, E. Molins, C. Miravitlles, J. Torras and J. Llibre
      Journal of the European Ceramic Society. 18 (1998) 1141-1143

    • Mechanical properties of aerogels: One of the main drawbacks of silica aerogels is its fragility. Aiming to improve their elasticity, hybrid aerogel composites have been developed.

      Micromechanical Properties of Silica Aerogels
      M. Moner-Girona, A. Roig, E. Molins, E.Martínez and J. Esteve
      Applied Physics Letters 75 5 (1999) 653-655

      Mechanical properties of silica aerogels measured by microindentation: influence of sol-gel processing parameters and carbon addition
      M. Moner-Girona, E. Martínez, A. Roig, J. Esteve and E. Molins
      J. Non.Crystalline Solids 285, 1-3 (2001) 244-250

      Micromechanical properties of carbon-silica aerogel composites
      M. Moner-Girona, E. Martínez, J. Esteve, A. Roig, R. Solanas, and E. Molins
      Applied Physics A 74 1 (2002) 119-122 (rapid communication)

    • Ultrasound properties of aerogels: for the use of aerogel in acoustic impedance matching layers for air coupled piezoelectric transducers.


      T. E. Gómez, F. Montero, M. Moner-Girona, E. Rodríguez, A. Roig, E. Molins, J. R. Rodríguez, S. Vargas, M. Esteves
      2001 IEEE Ultrasonics Symp Proceedings (Atlanta 7-10) (2001)

      Viscoeleasticity of silica aerogels at ultrasonic frequencies
      T. E. Gómez, F. Montero, M. Moner-Girona, E. Rodríguez, A. Roig, E. Molins,
      Applied Physics Letters 81 7 (2002) 1198-1200

     

    • Magnetic Aerogels: synthesis and magnetic characterisation of iron oxide nanocomposite aerogels to be used in heterogeneous catalysis.

      Silica aerogel-iron oxide nanocomposites: structural and magnetic properties
      Ll. Casas, A. Roig, E. Rodríguez, E. Molins, J. Tejada and J. Sort
      J. Non.Crystalline Solids 285, 1-3 (2001) 37-43

      Iron oxide nanoparticles hosted in silica aerogels
      Ll. Casas, A. Roig, E. Molins, J. M. Grenèche, J. Asenjo and J. Tejada
      Applied Physics A 74 (2002) 5, 591-597

      Magnetic Aerogels
      Ll. Casas, A. Roig, M-Moner-Girona, E.Molins, J. Asenjo, J. Tejada and J.M. Grenèche
      NATO ASI-Series: Magnetic Storage Beyond 2000, Series II: Mathematics, Physics and Chemistry-Vol.41, 2001 Kluwer Academic Publishers 2001, Ed. G.C. Hadjipanayis, pp. 391-396.

      Silica aerogel-iron oxide nanocomposites: recoverable catalysts in conjugate additions and in Biginelli reaction
      S. Martínez, M. Messeguer, E. Rodríguez, Ll. Casas, E. Molins, M. Moreno-Mañas, A. Roig and A. Vallribera
      Tetrahedron 59 9 (2003) 1553-1556

      High-coercivity ultralight transparent magnets
      M. Gich, Ll. Casas, A. Roig and E. Molins, J. Sort, S. Suriñach, M.D. Baró, J.S. Muñoz, L. Morellon, M.R. Ibarra, J. Nogués
      Appl. Physics Lett. (acceptat)

    • Porous silica aerogel microparticles: with applications in catalysis, encapsulation of products and chromatographic systems.

      Sol-gel route to direct formation of silica aerogel microparticles using supercritical solvents
      M. Moner-Girona, A. Roig, E. Molins and J. Llibre
      Journal of Sol-Gel Science and Technology (2003) 26, 645–649.

  • Applied Research
    • Aerogels for coatings (Carburos Metálicos & Air Products, 2001-2002)
    • Aerogels as Absorbers (Helwett-Packard, 2000-2001)
    • Aerogels for gas cylinder fillings (Carburos Metálicos 1997-1999)
  • Collaborations
Our group has collaborations in aerogels research with:
  • Joan Esteve-Elena Martínez, Universitat de Barcelona (mechanical properties)
  • Arlon Hunt-Mike Ayers, Lawrence Berkeley National Laboratory (light scattering)
  • Marcial Moreno-Adelina Vallribera, Universitat Autònoma de Barcelona (catalysts)
  • Tomás García-Francisco Montero, Instituto de Acústica CSIC (ultrasound properties)
  • Ulrich-Scubert-Nicola Hüsing, Technical University of Wien (synthesis of hybrid aerogels)

Interesting related websites

This line of research is being developed by the group the Research Professor E. Molins.