Sintering behavior of SiO2 aerogel composites reinforced by mullite fibers via in-situ rapid heating TEM observations

Cai, Huafei; Feng, Jian; Qu, Chao; Zhang, Sizhao; Li, Liangjun; Feng, Jing

doi:10.1016/j.jeurceramsoc.2019.09.014

Cited by 40 publications

(25 citation statements)

References 58 publications

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“…The SiZrNOC f /SiO 2 ACs were fabricated through a similar method described in Ref. [18], which were used to evaluate the thermal insulation performance of the SiZrNOC NFMs.…”

Section: Preparation Of Amorphous Sizrnoc Nfmsmentioning

confidence: 99%

Robust, fire-resistant, and thermal-stable SiZrNOC nanofiber membranes with amorphous microstructure for high-temperature thermal superinsulation

ZHANG¹,

Xu²,

Jiang³

et al. 2023

Journal of Advanced Ceramics

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Ceramic nanofibers with robust mechanical properties, high-temperature resistance, and superior thermal insulation performance are promising thermal insulators used under extreme conditions. However, developing of ceramic fibers with both low solid thermal conductivity (λ s ) and low infrared radiation thermal conductivity (λ r ) is still a great challenge. Herein, according to the Ioffe-Regel limit theory, we report a novel SiZrNOC nanofiber membrane (NFM) with a typically amorphous structure by combining the electrospinning method and high-temperature pyrolysis technique in a NH 3 atmosphere. The prepared SiZrNOC NFM has a high tensile strength (1.98±0.09 MPa), excellent thermal stability (1100 ℃ in air), and superior thermal insulation performance. The thermal conductivity of SiZrNOC NFM was 0.112 W•m −1 •K −1 at 1000 ℃, which is obviously lower than that of the traditional ceramic fiber membranes (> 0.2 W•m −1 •K −1 at 1000 ℃). In addition, the prepared SiZrNOC NFM-reinforced SiO 2 aerogel composites (SiZrNOC f /SiO 2 ACs) exhibited ultralow thermal conductivity of 0.044 W•m −1 •K −1 at 1000 ℃, which was the lowest value for SiO 2 -based aerogel composites ever reported. Such superior thermal insulation performance of SiZrNOC NFMs was mainly due to significant decreasing of solid heat conduction and thermal radiation by the fancy amorphous microstructure and high infrared shielding compositions. This work not only provides a promising high-temperature thermal insulator, but also offers a novel route to develop other high-performance thermal insulating materials.

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“…The SiZrNOC f /SiO 2 ACs were fabricated through a similar method described in Ref. [18], which were used to evaluate the thermal insulation performance of the SiZrNOC NFMs.…”

Section: Preparation Of Amorphous Sizrnoc Nfmsmentioning

confidence: 99%

Robust, fire-resistant, and thermal-stable SiZrNOC nanofiber membranes with amorphous microstructure for high-temperature thermal superinsulation

ZHANG¹,

Xu²,

Jiang³

et al. 2023

Journal of Advanced Ceramics

Self Cite

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“…Confirmation of this assumption would require a chemical analysis of the bubble structure which was not performed in this work. Silica aerogels have been shown to sinter through a viscous sintering mechanism which is controlled by the viscosity of the silica at the sintering temperature, pore size, and pore size distribution (Scherer et al, 1998, Cai et al, 2020. The melting temperature of silica is known to be 1983 K, based on the flame temperature (Tf) over the cooling air mixture temperature (Tm), reported in Table 1, for silica should fall within the range of 0.73 to 1.02; well within the range for sintering to occur.…”

Section: Materials Analysismentioning

confidence: 99%

Experimental Evaluation of Using Silica Aerogels as the Thermal Insulator for Combustor Liners

Pyo¹,

Robertson²,

Yun³

et al. 2020

Proceedings of Global Power &Amp; Propulsion Society

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An experimental study was conducted for evaluating the feasibility of using silica aerogel as thermal insulator for combustor liners. Aerogels are a superior material for minimizing heat flux to the metal structure of the combustion liner due to their low thermal conductivity. In this study, a conical natural gas fired swirling-flame combustor was utilized for reproducing the combustion environment that's typical to a gas turbine combustor. The silica aerogel blanket was attached to the inner side of a perforated combustor liner. Temperature distribution on the outer side of the combustion liner was measured using a calibrated thermal infrared (IR) camera. To minimize the uncertainty in steel surface emissivity due to surface oxidation at elevated temperatures, designated areas on the metal surface were coated with a ceramic cement whose emissivity was carefully determined. To create a protective cooling film over the aerogel surface, cooling air was supplied from the back side of the perforated metal liner and was allowed to penetrate the silica aerogel blanket to be discharged to the combustor. As the combustor was operated at a fixed equivalence ratio of 0.83, cooling air flow rates were varied to evaluate the effectiveness of transpiration cooling on the aerogel blanket as various cooling flow rates. The measured evolutions of temperature distribution confirmed thermal equilibriums for every test condition with transpiration cooling. The measured temperature distribution of metal liner demonstrated superior thermal insulation of aerogel blanket under the protection of cooling film with a temperature difference as high as 1580 K between combustion products temperature and the metal liner temperature on the back side. In addition, silica aerogel samples were examined before and after the combustion tests to understand their material degradation exposing to a typical gas turbine combustor environment using high-resolution scanning electron microscope (SEM). Test results suggest multiple degradation mechanisms to the silica aerogel blanket samples from the combustion tests. The material analysis suggests that improvements can be made to the silica aerogel blankets for a more resilient thermal insulator, for example, by replacing glass fibers in silica aerogels.

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“…Confirmation of this assumption would require a chemical analysis of the bubble structure which was not performed in this work. Silica aerogels have been shown to sinter through a viscous sintering mechanism which is controlled by the viscosity of the silica at the sintering temperature, pore size, and pore size distribution (Scherer et al, 1998;Cai et al, 2020). The melting temperature of silica is known to be 1983 K, based on the flame temperature (T f ) over the cooling air mixture temperature (T m ), reported in Table 1, for silica should fall within the range of 0.73 to 1.02; well within the range for sintering to occur.…”

Section: Materials Analysismentioning

confidence: 99%

Experimental Evaluation of Using Silica Aerogels as the Thermal Insulator for Combustor Liners

Pyo

Robertson

Yun

et al. 2020

J. Glob. Power Propuls. Soc.

View full text Add to dashboard Cite

An experimental study was conducted for evaluating the feasibility of using silica aerogel as thermal insulator for combustor liners. Aerogels are a superior material for minimizing heat flux to the metal structure of the combustion liner due to their low thermal conductivity. In this study, a conical natural gas fired swirling-flame combustor was utilized for reproducing the combustion environment that's typical to a gas turbine combustor. The silica aerogel blanket was attached to the inner side of a perforated combustor liner. Temperature distribution on the outer side of the combustion liner was measured using a calibrated thermal infrared (IR) camera. To minimize the uncertainty in steel surface emissivity due to surface oxidation at elevated temperatures, designated areas on the metal surface were coated with a ceramic cement whose emissivity was carefully determined. To create a protective cooling film over the aerogel surface, cooling air was supplied from the back side of the perforated metal liner and was allowed to penetrate the silica aerogel blanket to be discharged to the combustor. As the combustor was operated at a fixed equivalence ratio of 0.83, cooling air flow rates were varied to evaluate the effectiveness of transpiration cooling on the aerogel blanket as various cooling flow rates. The measured evolutions of temperature distribution confirmed thermal equilibriums for every test condition with transpiration cooling. The measured temperature distribution of metal liner demonstrated superior thermal insulation of aerogel blanket under the protection of cooling film with a temperature difference as high as 1,580 K between combustion products temperature and the metal liner temperature on the back side. In addition, silica aerogel samples were examined before and after the combustion tests to understand their material degradation exposing to a typical gas turbine combustor environment using high-resolution scanning electron microscope (SEM). Test results suggest multiple degradation mechanisms to the silica aerogel blanket samples from the combustion tests. The material analysis suggests that improvements can be made to the silica aerogel blankets for a more resilient thermal insulator, for example, by replacing glass fibres in silica aerogels.

show abstract

Sintering behavior of SiO2 aerogel composites reinforced by mullite fibers via in-situ rapid heating TEM observations

Cited by 40 publications

References 58 publications

Robust, fire-resistant, and thermal-stable SiZrNOC nanofiber membranes with amorphous microstructure for high-temperature thermal superinsulation

Robust, fire-resistant, and thermal-stable SiZrNOC nanofiber membranes with amorphous microstructure for high-temperature thermal superinsulation

Experimental Evaluation of Using Silica Aerogels as the Thermal Insulator for Combustor Liners

Experimental Evaluation of Using Silica Aerogels as the Thermal Insulator for Combustor Liners

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