Improvement of the Thermal Insulation Performance of Silica Aerogel by Proper Heat Treatment: Microporous Structures Changes and Pyrolysis Mechanism

Abstract

A simple heat treatment method was used to optimize the three-dimensional network structure of the hydrophobic aerogel, and during the heat treatment process at 200–1000 °C, the thermal conductivity of the aerogel reached the lowest to 0.02240 W/m·K between 250 °C and 300 °C, which was mainly due to the optimization of microstructure and pyrolysis of surface groups. Further Fluent heat-transfer simulation also confirmed the above results. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was used to finely measure the pyrolysis process of aerogels, and the pyrolysis process of aerogel was divided into four stages. (I) Until 419 °C, as the temperature continued to rise, surface methyl groups were oxidized to form hydroxyl. (II) As the temperature reached to 232 °C, the oxidation proceeded. In addition, inside the aerogel, because of lacking oxygen, the reaction produced CH4 and C–Si bonds would form. (III) After 283 °C, Si–OH groups began to condense to form Si–O–Si, which optimized the three-dimensional network structures to be beneficial to improve the thermal insulation performance of silica aerogel. (IV) When it reached 547 °C, the chemical reaction was terminated, and all the primary particles gradually fused into secondary particles and sintered to form clusters.

Self-catalyzed Gelling Synthesis of Aerogels with Inorganic and Organic Nanocomponents for Thermal Insulation and CO2 Capture

“…From the XRD pattern (Figure a and Figures S1 and S2), there is a weak and broad diffraction peak at 21.2°, which indicates that OIHAs composed of organic and inorganic components are amorphous Figure b displays the FT-IR pattern features of OIHA-2.…”

“…From the XRD pattern (Figure 2a and Figures S1 and S2), there is a weak and broad diffraction peak at 21.2°, which indicates that OIHAs composed of organic and inorganic components are amorphous. 37 Figure 2b displays the FT-IR pattern features of OIHA-2. The peak located at 2980 cm −1 corresponds to the stretching vibration adsorption of C−H groups, and peaks at 3432 and 1646 cm −1 correspond to the N−H bond from BTPA.…”

Synthesis, characterization, and application of silica aerogel thin films prepared via surface derivatization: A comprehensive study on micro-silica nanofilms for enhanced photoelectric conversion efficiency in photovoltaic solar cells

“…These peaks yield relative atomic concentrations of approximately 17% for carbon (C), 28% for oxygen (O), and a compelling 55% for silicon (Si), thereby consolidating the elemental foundation of the material. A noteworthy observation is the characteristic C 1s peak at 285 eV, which is indicative of the presence of carbon atoms in methyl (-CH3) functional groups [23,24]. These groups are most likely incorporated during the surface derivatization processes, serving as a testament to the material's engineered surface chemistry.…”

Heat-Treated Aramid Pulp/Silica Aerogel Composites with Improved Thermal Stability and Thermal Insulation

“…In this regard, Li et al [ 37 ] improved the thermal stability of hydrophobic silica aerogels to ~590 °C using heat treatment in an argon atmosphere at 700 °C, which greatly enhanced the thermal safety of silica aerogels. It can be seen that heat treatment is worth trying for adjusting the thermal properties of silica aerogels [ 38 ].…”