Extreme temperature stability of thermally insulating graphene-mesoporous-silicon nanocomposite

Abstract

We demonstrate the thermal stability and thermal insulation of graphene-mesoporous-silicon nanocomposites (GPSNC). By comparing the morphology of GPSNC carbonized at 650 °C as-formed to that after annealing, we show that this nanocomposite remains stable at temperatures as high as 1050 °C due to the presence of a few monolayers of graphene coating on the pore walls. This does not only make this material compatible with most thermal processes but also suggests applications in harsh high temperature environments. The thermal conductivity of GPSNCs carbonized at temperatures in the 500 °C-800 °C range is determined through Raman spectroscopy measurements. They indicate that the thermal conductivity of the composite is lower than that of silicon, with a value of 13 ± 1 W mK at room temperature, and not affected by the thin graphene layer, suggesting a role of the high concentration of carbon related-defects as indicated by the high intensity of the D-band compared to G-band of the Raman spectra. This morphological stability at high temperature combined with a high thermal insulation make GPSNC a promising candidate for a broad range of applications including microelectromechanical systems and thermal effect microsystems such as flow sensors or IR detectors. Finally, at 120 °C, the thermal conductivity remains equal to that at room temperature, attesting to the potential of using our nanocomposite in devices that operate at high temperatures such as microreactors for distributed chemical conversion, solid oxide fuel cells, thermoelectric devices or thermal micromotors.

Structural, optical and terahertz properties of graphene-mesoporous silicon nanocomposites

“…Raman spectra taken at different spots on the samples surface as well as Raman spectra of previously reported GPSi-nCs show similar values of I D / I G ratio to ours, owing to a relatively uniform graphene coating. Based on gravimetric analysis, ref. 20 estimated the coating thickness to 2–3 monolayers for graphene deposition temperature between 650 °C and 800 °C.…”

“…Because the pore sizes lie in the same range as the crystallite dimensions, the porous network can serve as a template for growing nanostructures. This advantage was used in previous works 19,20 to synthetize a new type of porous silicon nanocomposites named graphenemesoporous silicon nanocomposites (GPSi-nCs). These nanocomposites consist of a free-standing mesoporous silicon membrane whose external and pore surface is covered with fewlayer graphene coating by thermal carbonization.…”

“…These nanocomposites consist of a free-standing mesoporous silicon membrane whose external and pore surface is covered with fewlayer graphene coating by thermal carbonization. It was shown that this graphene coating enhanced signicantly the mechanical exibility of the porous silicon matrix and thermally insulated the porous structure against extreme temperatures as high as 1050 C. 20 The carbonization of porous silicon was also shown to stabilize the surface chemistry by replacement of terminal Si-H bonds with much more stable Si-C bonds. 21 The stable chemical properties of these nanostructures as well as the possibility to functionalize their surface with organic or biological molecules make them attractive for optical sensing and optoelectronic applications.…”

Integration of 3D nanographene into mesoporous germanium

“…Furthermore, as noticed on similar material as mesoporous silicon, the number of layer is estimated at 2-3 layers and the growth is self-limiting catalytic reaction. 15,41 Considering all these information, we call the carbon coating studied here, nanographene.…”

Mechanical Strength of Graphene Reinforced Geopolymer Nanocomposites: A Review

“…For the geopolymer composites cured under steam condition, the obtained Si:Al ratio and K:Al ratio is closer to the designed composition than the same geopolymer composites that are cured in room temperature, which indicates a higher formation of aluminosilicate gel from the material source (Kani and Allahverdi, 2009). Graphene also is famously known for its unique thermal properties, as reported by many (Kolhatkar et al, 2018;Phiri et al, 2018;Liu et al, 2019). The thermal properties of graphene are related to its anisotropic bonding and effective heat transfer by lattice vibrations.…”