Fabrication and microstructure evolution of monolithic bridged polysilsesquioxane-derived SiC ceramic aerogels

Ding, Chengxi; Hu, Dongxiao; He, Xinrui; Lai, Yifan; Shao, Gaofeng

doi:10.1016/j.ceramint.2022.05.259

Cited by 16 publications

(4 citation statements)

References 28 publications

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“…36 (2) Hydrolytic co-polycondensation of the resultant precursor and MTMS in the presence of acetic acid catalyst combined with solvent replacement and vacuum drying to obtain BPSi aerogel (Figure C-E). 37,38 (3) Polymer-to-ceramic conversion process was realized by the pyrolysis of BPSi aerogel at 1000 • C to afford lightweight SiOCN aerogel with the density of 0.155 g/cm 3 (Figure 1F). Compared with the sol-gel transformation process based on hydrosilylation reaction, the hydrolytic co-polycondensation-triggered gelation circumvents the need for harsh synthetic conditions and high-cost noble metal catalysts.…”

Section: Resultsmentioning

confidence: 99%

Bridged polysilsesquioxane‐derived SiOCN ceramic aerogels for microwave absorption

Shao

Ding

et al. 2022

J Am Ceram Soc.

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The development of high‐performance microwave absorption materials in harsh environment is highly desirable but challenging. Herein, lightweight silicon oxycarbonitride (SiOCN) ceramic aerogels were fabricated by the pyrolysis of bridged polysilsesquioxane aerogels, which was presynthesized by a sol–gel method followed by vacuum drying. The structural order and content of free carbon phase determined by pyrolysis temperature play a critical role in modulating the impedance matching and attenuation capacity. The as‐prepared SiOCN aerogel pyrolyzed at 1000°C achieves a minimal reflection loss of −64.2 dB at 8.96 GHz and a broad bandwidth of 5.4 GHz at a low thickness of 2.15 mm. The hierarchical pore structure, abundant heterogeneous amorphous SiOCN/free carbon interfaces, and conductive free carbon phase benefit the superior absorption performance by forming good impedance matching, multiple scattering, interface polarization, and conduction losses. This work provides an insight for the rational design of polymer‐derived ceramic aerogel‐based microwave absorption materials for potential application under extreme conditions such as high‐temperature and oxidation environments.

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Section: Resultsmentioning

confidence: 99%

Bridged polysilsesquioxane‐derived SiOCN ceramic aerogels for microwave absorption

Shao

Ding

et al. 2022

J Am Ceram Soc.

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“…For instance, they tend to be brittle and fragile, making them prone to cracking or breaking under compression. 12,13 Additionally, the fabrication process for these materials can be complex and expensive, limiting their availability in the intermediate temperature areas.…”

Section: Introductionmentioning

confidence: 99%

“…However, there are also some disadvantages associated with elastic ceramic aerogels. For instance, they tend to be brittle and fragile, making them prone to cracking or breaking under compression. , Additionally, the fabrication process for these materials can be complex and expensive, limiting their availability in the intermediate temperature areas. Recent research has suggested that organic aerogels, such as chitosan aerogels, − cellulose aerogels, , gelatin aerogels, and polyimide aerogels (PIAs), have better mechanical properties compared to inorganic aerogels.…”

Section: Introductionmentioning

confidence: 99%

Mechanically Robust Nanoporous Polyimide/Silica Aerogels for Thermal Superinsulation of Aircraft

Zhang

Wang

et al. 2023

ACS Appl. Nano Mater.

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Polyimide aerogels (PIAs) are thermally insulating materials that possess various advantages, such as exceptionally high temperature resistance and low thermal conductivity, which make them great potential candidate materials to be applied in the area of thermal protection. However, under harsh mechanical stresses, the macro- and microscopic structural stability of PIAs may be compromised due to shrinkage/collapse, leading to performance degradation. Herein, we propose a homogeneous organic/inorganic hybrid formation strategy for constructing nanoporous polyimide/silica aerogels (PIAs-A) with exceptional mechanical strength and ultralow thermal conductivity. The results obtained indicate that PIAs-A have an optimal three-dimensional nanoporous network structure with a pore size distribution mainly within the range of 10–20 nm. Monitoring the temperature evolution of the material’s cold surface showed that it remained at a low temperature of 37.5 °C even when the material was placed against a hot surface of 150 °C. The residual mechanical strengths of the aerogels remained at a superior level (with strength degradation being less than 9%) after exposure to ultralow and high-temperature atmospheres. Furthermore, compressive stress values at 3% strain exceeded previously reported values for PIAs by 625 and 733% at −50 and 100 °C, respectively. Meanwhile, our aerogels displayed flame resistance even when exposed to a heat source of approximately 1200 °C, possessed favorable hydrophobic properties, and maintained dimensional stability up to 504 °C. The robust mechanical and thermal insulation properties of PIAs-A make them a promising substitute material for thermal superinsulation in aircraft.

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“…Aerogel microspheres can be synthesized by ball dropping, W/O (water-in-oil) emulsion, and jet cutting methods. ,− Silica aerogel microspheres were commonly synthesized by a W/O emulsion method using silicon alkoxide as a precursor. The formation of silica aerogel microspheres via a water-in-oil emulsion method is achieved by pouring the aqueous silica sol into a continuous oil phase along with continuous stirring.…”

Section: Introductionmentioning

confidence: 99%

Development of Regular Hydrophobic Silica Aerogel Microspheres for Efficient Oil Adsorption

et al. 2022

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The objective of this research was to develop new hydrophobic silica aerogel microspheres (HSAMs) with water glass and hexmethyldisilazane for oil adsorption. The effects of the hexmethyldisilazane concentration and drying method on the structure and organic liquid adsorption capacity were investigated. The hexmethyldisilazane concentration of the modification solution did not influence the microstructure and pore structure in a noteworthy manner, which depended more on the drying method. Vacuum drying led to more volume shrinkage of the silica gel microsphere (SGM) than supercritical CO 2 drying, thus resulting in a larger apparent density, lower pore volume, narrower pore size distribution, and more compact network. Owing to the large pore volume and pore size, the HSAMs synthesized via supercritical CO 2 drying had a larger organic liquid adsorption capacity. The adsorption capacities of the HSAMs with pore volumes of 4.04−6.44 cm 3 /g for colza oil, vacuum pump oil, and hexane are up to 18.3, 18.9, and 11.8 g/g, respectively, higher than for their state-of-the-art counterparts. The new sorbent preparation method is facile, cost-effective, safe, and ecofriendly, and the resulting HSAMs are exceptional in capacity, stability, and regenerability.

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Fabrication and microstructure evolution of monolithic bridged polysilsesquioxane-derived SiC ceramic aerogels

Cited by 16 publications

References 28 publications

Bridged polysilsesquioxane‐derived SiOCN ceramic aerogels for microwave absorption

Bridged polysilsesquioxane‐derived SiOCN ceramic aerogels for microwave absorption

Mechanically Robust Nanoporous Polyimide/Silica Aerogels for Thermal Superinsulation of Aircraft

Development of Regular Hydrophobic Silica Aerogel Microspheres for Efficient Oil Adsorption

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