Thermal Conductivity of Lofty Nonwovens in Space and Planetary Vacuum Environment

Tang, Henry H.; Orndoff, Evelyne; Trevino, Luis

doi:10.4271/2001-01-2166

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…Because the atmospheric surface pressure on Mars averages around 6 Torr, MLI is not suitable as insulation . Of a variety of materials considered in a recent study, only aerogel fiber composites were found to be effective candidates for Mars surface suit insulation , although they tended to shed silica particles at unacceptable levels .…”

Section: Introductionmentioning

confidence: 94%

Epoxy Reinforced Aerogels Made Using a Streamlined Process

Meador

Scherzer

Vivod

et al. 2010

ACS Appl. Mater. Interfaces

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Reinforcing silica aerogels by conformally coating the nanoskeleton with a polymer has been demonstrated to be an effective way to improve mechanical properties. In addition, the mesoporosity and low thermal conductivity is maintained, making this robust form of aerogel an enabling material for a variety of aerospace applications. However, the process for making the aerogels can be quite long, involving production of the gel, solvent exchanges, and diffusion of monomer, followed by more solvent exchanges and supercritical fluid extraction. This paper for the first time compares a synthetic scheme that shortens the process to make epoxy reinforced aerogels by eliminating monomer diffusion and half of the solvent washes to the previously described diffusion-controlled process. The ethanol-soluble epoxy monomers are included in the initial step of the sol−gel process without interfering with gelation of the starting silanes. Notably, properties of aerogels made using a low amount of amine reactive sites have properties similar to those previously reported that used the longer diffusion controlled process, whereas higher amounts of amine sites produce less desirable monoliths with much higher density and lower surface areas.

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Section: Introductionmentioning

confidence: 94%

Epoxy Reinforced Aerogels Made Using a Streamlined Process

Meador

Scherzer

Vivod

et al. 2010

ACS Appl. Mater. Interfaces

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“…Aerogel composites are the only materials that come close to meeting the requirements for EVA suit insulation. However, current aerogel composites flake apart under rigorous cyclic loading−unloading tests and lose insulation quality over time. , Robust aerogel composites are also considered as the baseline insulation materials of inflatable decelerators for entry, descent, and landing (EDL) applications . Inflatable decelerators are proposed to slow spacecraft for planetary EDL .…”

Section: Introductionmentioning

confidence: 99%

Tailoring Mechanical Properties of Aerogels for Aerospace Applications

Randall

Meador

Jana

2011

ACS Appl. Mater. Interfaces

507

327

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Silica aerogels are highly porous solid materials consisting of three-dimensional networks of silica particles and are typically obtained by removing the liquid in silica gels under supercritical conditions. Several unique attributes such as extremely low thermal conductivity and low density make silica aerogels excellent candidates in the quest for thermal insulation materials used in space missions. However, native silica aerogels are fragile at relatively low stresses. More durable aerogels with higher strength and stiffness are obtained by proper selection of silane precursors and by reinforcement with polymers. This paper first presents a brief review of the literature on methods of silica aerogel reinforcement and then discusses our recent activities in improving not only the strength but also the elastic response of polymer-reinforced silica aerogels. Several alkyl-linked bis-silanes were used in promoting flexibility of the silica networks in conjunction with polymer reinforcement by epoxy.

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“…[ 4 ] NASA pioneered the use of aerogels as efficient insulating materials on several Mars rovers and spacecraft parts, such as the insulation assembly of Rover Mars batteries, the outer surface of vehicle decelerators, [ 5 ] etc., and is also advancing their application in extra‐vehicular insulating suits. [ 6 ] Oxide ceramic aerogels have currently been the most rapidly developed in high‐temperature insulation; however, due to the restrictions of crystallization‐induced pulverization, large thermal expansion, and relatively low operating temperatures, for example, SiO 2 (650 °C), [ 7 ] ZrO 2 (1100 °C), [ 8 ] Al 2 O 3 (1300 °C), [ 9 ] and mullite (1400 °C), these aerogels and their composites suffer from severe strength deterioration and catastrophic structural failure during significant temperature gradient changes or long‐term high‐temperature exposure. [ 10 ] Conversely, carbon aerogels (CAs) maintain their mesoporous structure despite heat treatment over 2500 °C under a vacuum or inert atmosphere, showing favorable thermal stability at ultra‐high temperatures.…”

Section: Introductionmentioning

confidence: 99%

Superelastic Carbon Aerogels: An Emerging Material for Advanced Thermal Protection in Extreme Environments

Chang

Cheng

Zhang

et al. 2023

Adv Funct Materials

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speed airflow scouring. Accordingly, the thermal protection system (TPS) must be applied on their surface to cope with the integrated heat load accumulated during flight. [2] The lightweight nature of TPS is critical in addressing the criteria for ultralong-range combat military weapons with high sound speeds and load capacities while considering the production cost in check. Kistler of Stanford University first proposed the concept of aerogel in 1931, [3] which was fabricated by exchanging the liquid in a wet gel by gas whilst guaranteeing that the internal structure did not collapse, becoming one of the lightest solid materials known to date. The abundance of internal nanoscale pore size and highly tortuous pore structure determine aerogel's excellent thermally insulation performance, with the thermal conductivity as low as 0.005 W m −1 K −1 . [4] NASA pioneered the use of aerogels as efficient insulating materials on several Mars rovers and spacecraft parts, such as the insulation assembly of Rover Mars batteries, the outer surface of vehicle decelerators, [5] etc., and is also advancing their application in extra-vehicular insulating suits. [6] Oxide ceramic aerogels have currently been the most rapidly developed in high-temperature insulation; however, due to the restrictions of crystallization-induced pulverization, large thermal expansion, and relatively low operating temperatures, for example, SiO 2 (650 °C), [7] ZrO 2 (1100 °C), [8] Al 2 O 3 (1300 °C), [9] and mullite (1400 °C), these aerogels and their composites suffer from severe strength deterioration and catastrophic structural failure during significant temperature gradient changes or long-term high-temperature exposure. [10] Conversely, carbon aerogels (CAs) maintain their mesoporous structure despite heat treatment over 2500 °C under a vacuum or inert atmosphere, showing favorable thermal stability at ultra-high temperatures. [11] In addition, they also have a much higher specific extinction coefficient (190 m 2 kg −1 ) than others (e.g., SiO 2 aerogel with 20 m 2 kg −1 ), which leads to lower radiative thermal conductivities. [12] Therefore, CAs are anticipated to be up-and-coming candidates for the TPS of hypersonic vehicles in conditions of severe heat flow density and ultra-high temperatures.The terms of CAs initially referred to carbonaceous substances that exist as 3D monoliths macroscopically and

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Thermal Conductivity of Lofty Nonwovens in Space and Planetary Vacuum Environment

Cited by 4 publications

References 1 publication

Epoxy Reinforced Aerogels Made Using a Streamlined Process

Epoxy Reinforced Aerogels Made Using a Streamlined Process

Tailoring Mechanical Properties of Aerogels for Aerospace Applications

Superelastic Carbon Aerogels: An Emerging Material for Advanced Thermal Protection in Extreme Environments

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