Thermal insulation with 2D materials: liquid phase exfoliated vermiculite functional nanosheets
Iwona Janica1, Stefano Del Buffa2, Agnieszka Mikołajczak3
1Faculty of Chemistry, Adam Mickiewicz University in Poznań, Umultowska 89b, 61-614 Poznań, Poland and Centre for Advanced Technologies, Adam Mickiewicz University, Umultowska 89c, 61-614 Poznań, Poland. ciesielski@unistra.fr and Université de Strasbourg, CNRS, ISIS, 8 allée Gaspard Monge, 67000 Strasbourg, France. samori@unistra.fr.
Nanoscale
|December 6, 2018
Summary
Researchers exfoliated phyllosilicates into 2D nanosheets using ultrasound and shear-mixing. Ultrasound yielded more single-layer nanosheets with higher surface area, achieving ultra-low thermal conductivity for printable insulators.
Area of Science:
- Materials Science
- Nanotechnology
- Geochemistry
Background:
- Phyllosilicates, like vermiculite, are layered materials with useful thermal properties.
- Current applications are limited to their crystalline form, hindering versatile use.
- Liquid-phase exfoliation offers a route to 2D nanosheets for inks and dispersions.
Purpose of the Study:
- To develop a method for producing 2D clay nanosheets from low-cost vermiculite.
- To compare ultrasound-assisted exfoliation with shear-mixing for nanosheet production.
- To investigate the impact of exfoliation on the thermal conductivity of vermiculite.
Main Methods:
- Liquid-phase exfoliation of multiphasic vermiculite using ultrasound and shear-mixing in mild acidic aqueous solutions.
- Characterization of exfoliated nanosheets via granulometry, X-Ray Diffraction (XRD), specific surface area, and Atomic Force Microscopy (AFM).
- Measurement of thermal conductivity of raw and exfoliated materials.
Main Results:
- Both ultrasound and shear-mixing produced mono- and few-layer clay nanosheets.
- Ultrasound-assisted exfoliation yielded more mono- and bi-layer flakes and higher specific surface area.
- Exfoliated vermiculite exhibited a 25% decrease in thermal conductivity, reaching the ultra-low regime (<0.1 W m-1 K-1).
Conclusions:
- Ultrasound-assisted exfoliation is more effective for producing high-quality vermiculite nanosheets.
- Structural changes during exfoliation significantly reduce thermal conductivity.
- This method enables the development of printable thermal insulator inks and dispersions.
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