Thermal Gelation for Synthesis of Surface-Modified Silica Aerogel Powders

Lee, Kyoung-Jin; Lee, Jae Min; Nam, Ki Sun; Hwang, Hae Jin

doi:10.3390/gels7040242

Cited by 10 publications

(6 citation statements)

References 31 publications

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“…The FTIR spectra for treated powders are shown in Figure 3 . The bands that are typical of Si-O vibrations are visible in the recorded spectra and are identical to those that have been described in the literature [ 16 , 17 , 18 , 19 , 20 , 21 ]. Small bands at 560 cm −1 or 568 cm −1 may be attributed to the vibration of the Si-O-Zn bonds, whereas the main bands at 1273 cm −1 , 1080 cm −1 , 1114 cm −1 , 793 cm −1 , and 467 cm −1 are assigned to Si-O-Si bonds in networks and chains.…”

Section: Resultssupporting

confidence: 81%

The Influence of Gel Preparation and Thermal Treatment on the Optical Properties of SiO2-ZnO Powders Obtained by Sol–Gel Method

Mocioiu

Vladut

Atkinson

et al. 2022

Gels

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The effect of gel preparation and heat treatment on the structural and optical properties of SiO2-ZnO materials prepared by the sol–gel method was investigated. Zinc acetate dehydrate, TEOS (tetraethylortosilicate), ethanol, distillated water and HCl were used as a starting material, solvent and catalyst, respectively. Four powders (G1–G4) were prepared in different ways from the starting materials mentioned above. The method of adding Zn precursors during the synthesis differed from one another. For the G1 synthesis, only Zn acetate powder was employed; for the G2 synthesis, Zn acetate was dissolved in distilled water; and for the G3 synthesis, Zn acetate was dissolved in ethanol. When synthesizing G4, TEOS was added last, after Zn acetate had been combined with water and ethanol. The SiO2-ZnO materials were dried at 200 °C and then heat-treated at 700 °C and 900 °C. All samples were investigated by X-ray diffraction and infrared spectroscopy in order to investigate their structure. SEM measurements were performed to investigate the morphology of materials. Optical properties were influenced by gel preparation and heat treatments. A reflectance of over 60% was obtained for G3 and G4 powders, while for G1 and G2, the reflectance was below 30%. In conclusion, synthesis steps and heat treatment can control the structure and properties of the powders.

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Section: Resultssupporting

confidence: 81%

The Influence of Gel Preparation and Thermal Treatment on the Optical Properties of SiO2-ZnO Powders Obtained by Sol–Gel Method

Mocioiu

Vladut

Atkinson

et al. 2022

Gels

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“…These results indicate that the fluorine-containing monomer of PI reduces the surface energy of materials as well as microstructure increases in surface roughness, therefore allowing the water droplets to slide away when the sample is slightly tilted. Based on the Wenzel’s model [ 48 , 49 , 50 ], the chemical composition and geometrical microstructure both influence the wettability, as the thermodynamic equilibrium (Equation (4)) shows:

…”

Section: Resultsmentioning

confidence: 99%

Robust, Fire-Retardant, and Water-Resistant Wood/Polyimide Composite Aerogels with a Hierarchical Pore Structure for Thermal Insulation

Chen

Pan

et al. 2023

Gels

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The use of energy-saving materials is an effective strategy for decreasing energy consumption and carbon emission. Wood is a type of biomass material with a natural hierarchical structure, which results in its high thermal insulation. It has been widely used in construction. However, developing wood-based materials without flammability and dimensional instability is still a challenge. Herein, we developed a wood/polyimide composite aerogel with a well-preserved hierarchical pore structure and dense hydrogen bonds inside, resulting in its excellent chemical compatibility and strong interfacial interactions between its two components. This novel wood-based composite was fabricated by removing most hemicellulose and lignin from natural wood, followed by the fast impregnation using an ‘in situ gel’ process. The introduction of polyimide into delignified wood substantially improved its mechanical properties, with the compression resistance being improved by over five times. Notably, the thermal conductivity coefficient of the developed composite was approximately half that of natural wood. Furthermore, the composite exhibited excellent fire-retardancy, hydrophobicity, thermal insulation, and mechanical properties. This study provides a novel method for wood modification, which not only aids interfacial compatibility between wood and polyimide but also retains the properties of the two components. The developed composite can effectively reduce energy consumption, making it promising for practical and complex thermal insulation applications.

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“…This makes their direct use or hybridization with other materials difficult, which seriously limits the application of silica aerogel in many fields [18][19][20][21]. Moreover, the repeated modification process to transfer hydrophilicity to the hydrophobic surface of the silica aerogel monolith is tedious and requires an extremely long processing time [22].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, due to the tiny volume of the silica aerogel powders, the modification and drying process is easier and faster, which effectively decreases the fabrication time. A few silica aerogel powders have been recently reported with various methods for rapid synthesis [22]. Pan et al reported a method to synthesize superhydrophobic (θ = 162 • ) aerogel powders at ambient pressure using a water-glass-based sol-gel method with a technological process of mechanical crushing and filtration [28].…”

Section: Introductionmentioning

confidence: 99%

Eco-Friendly Fabrication of Highly Stable Silica Aerogel Microspheres with Core–Shell Structure

Cai

et al. 2023

Polymers

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Silica aerogel microspheres show great potential in various fields as fillings in different materials. It is important to diversify and optimize the fabrication methodology for silica aerogel microspheres (SAMS). This paper presents an eco-friendly synthetic technique for producing functional silica aerogel microspheres with a core–shell structure. Mixing silica sol with commercial silicone oil containing olefin polydimethylsiloxane (PDMS) resulted in a homogeneous emulsion with silica sol droplets dispersed in the oil. After gelation, the droplets were transformed into silica hydrogel or alcogel microspheres and coated with the polymerization of the olefin groups. Microspheres with silica aerogel as their core and polydimethylsiloxane as their shell were obtained after separation and drying. The sphere size distribution was regulated by controlling the emulsion process. The surface hydrophobicity was enhanced by grafting methyl groups onto the shell. The obtained silica aerogel microspheres have low thermal conductivity, high hydrophobicity, and excellent stability. The synthetic technique reported here is expected to be beneficial for the development of highly robust silica aerogel material.

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Thermal Gelation for Synthesis of Surface-Modified Silica Aerogel Powders

Cited by 10 publications

References 31 publications

The Influence of Gel Preparation and Thermal Treatment on the Optical Properties of SiO2-ZnO Powders Obtained by Sol–Gel Method

The Influence of Gel Preparation and Thermal Treatment on the Optical Properties of SiO2-ZnO Powders Obtained by Sol–Gel Method

Robust, Fire-Retardant, and Water-Resistant Wood/Polyimide Composite Aerogels with a Hierarchical Pore Structure for Thermal Insulation

Eco-Friendly Fabrication of Highly Stable Silica Aerogel Microspheres with Core–Shell Structure

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