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  Synthesis and Effective Thermal Conductivity Measurements of Hollow Mesoporous SiO2 Spheres for Heat‐Insulating Applications

Winkelmann, F., Albert, R., & Felderhoff, M. (2021). Synthesis and Effective Thermal Conductivity Measurements of Hollow Mesoporous SiO2 Spheres for Heat‐Insulating Applications. Energy Technology, 9(5): 2001048. doi:10.1002/ente.202001048.

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 Creators:
Winkelmann, Frederik1, Author           
Albert, Rene1, Author           
Felderhoff, Michael1, Author           
Affiliations:
1Research Group Felderhoff, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_3027887              

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Free keywords: effective thermal conductivity; mesoporous hollow spheres; packed beads; silica nanoparticles; soft templating; transient plane source methods
 Abstract: Mesoporous silica hollow spheres are an excellent model system to investigate the thermal conductivity for an efficient heat‐insulating material with respect to its geometry. Four different monodisperse silica hollow spheres are synthesized via a three‐step synthesis consisting of emulsifier‐free emulsion polymerization, modified Stöber condensation process, and subsequent calcination. In this approach, cetyltrimethylammonium bromide (CTAB) is used as a structure directing component to produce a highly porous silica shell. The systematic investigations of the effective thermal conductivity (ETC) allow distinguishing the respective conduction pathways, such as solid conduction and gas conduction. The carried out thermal conductivity measurements reveal for all four samples promising low ETC values of ≈36 mW m−1 K−1 at 1013 mbar and 35 °C. In vacuum (0.03 mbar) all four samples showed, independent of shell thickness and inner diameter, a comparable reduced ETC of about 10 mW m−1 K−1. The comparison with previous studies on unstructured silica hollow spheres indicates that the solid state conductivity within the bulk is more dependent on the contact strengths and the number of contacts than on the thermal conductivity within the silica material, as the scattering probability of phonons is not influenced by an increased density of defects.

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Language(s): eng - English
 Dates: 2020-12-012021-03-222021-05-04
 Publication Status: Published online
 Pages: 9
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1002/ente.202001048
 Degree: -

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Title: Energy Technology
  Abbreviation : Energy Technol.
Source Genre: Journal
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Publ. Info: Weinheim : Wiley-VCH
Pages: - Volume / Issue: 9 (5) Sequence Number: 2001048 Start / End Page: - Identifier: ISSN: 2194-4296
CoNE: https://pure.mpg.de/cone/journals/resource/21944296