Facile fabrication of lightweight mullite fiber/phenolic ablator with low thermal conductivity via ambient pressure impregnation

2021 ◽  
Author(s):  
Xianfeng Jia ◽  
Wenda Song ◽  
Wei Chen ◽  
Cheng Ma ◽  
Jitong Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Ambient Pressure ◽  
Low Thermal Conductivity ◽  
Mullite Fiber ◽  
Facile Fabrication

scholarly journals Silica Aerogel Monoliths Derived from Silica Hydrosol with Various Surfactants

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3192 ◽  
Author(s):  
Dong Chen ◽  
Xiaodong Wang ◽  
Wenhui Ding ◽  
Wenbing Zou ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Silica Aerogel ◽  
Low Cost ◽  
Ambient Pressure ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Low Thermal Conductivity ◽  
Silica Hydrosol ◽  
High Production Cost

Owing to their ultra-low thermal conductivity, silica aerogels are promising thermal insulators; however, their extensive application is limited by their high production cost. Thus, scientists have started to explore low-cost and easy preparation processes of silica aerogels. In this work, a low-cost method was proposed to prepare silica aerogels with industrial silica hydrosol and a subsequent ambient pressure drying (APD) process. Various surfactants (cationic, amphoteric, or anionic) were added to avoid solvent exchange and surface modification during the APD process. The effects of various surfactants on the microstructure, thermal conductivity, and thermal stability of the silica aerogels were studied. The results showed that the silica aerogels prepared with a cationic or anionic surfactant have better thermal stability than that prepared with an amphoteric surfactant. After being heated at 600 °C, the silica aerogel prepared with a cationic surfactant showed the highest specific surface area of 131 m2∙g−1 and the lowest thermal conductivity of 0.038 W∙m−1∙K−1. The obtained low-cost silica aerogel with low thermal conductivity could be widely applied as a thermal insulator for building and industrial energy-saving applications.

scholarly journals Strong and machinable carbon aerogel monoliths with low thermal conductivity prepared via ambient pressure drying

Carbon ◽  
2016 ◽  
Vol 108 ◽  
pp. 551-560 ◽  
Author(s):  
Xianfeng Jia ◽  
Bowen Dai ◽  
Zhaoxian Zhu ◽  
Jitong Wang ◽  
Wenming Qiao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Ambient Pressure ◽  
Carbon Aerogel ◽  
Ambient Pressure Drying ◽  
Low Thermal Conductivity

Low-density graphene/carbon composite aerogels prepared at ambient pressure with high mechanical strength and low thermal conductivity

RSC Advances ◽  
2015 ◽  
Vol 5 (7) ◽  
pp. 5197-5204 ◽  
Author(s):  
Kang Guo ◽  
Zijun Hu ◽  
Huaihe Song ◽  
Xian Du ◽  
Liang Zhong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Compression Strength ◽  
Ambient Pressure ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Low Density ◽  
High Mechanical Strength ◽  
Low Thermal Conductivity ◽  
Composite Aerogels

SEM and TEM pictures show that GNSs can be well-dispersed in a carbon matrix. The resultant composite CAs exhibited high compression strength and extremely low thermal conductivity of 0.028 W m−1 K−1.

scholarly journals Robust Silica–Polyimide Aerogel Blanket for Water-Proof and Flame-Retardant Self-Floating Artificial Island

2021 ◽  
Vol 8 ◽  
Author(s):  
Riyong Liu ◽  
Jin Wang ◽  
Jianhe Liao ◽  
Xuetong Zhang
Keyword(s):  
Thermal Conductivity ◽  
Flame Retardant ◽  
Silica Aerogel ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Three Dimensional ◽  
Ambient Pressure Drying ◽  
Low Density ◽  
Low Thermal Conductivity ◽  
Sol Gel Transition

A robust silica–polyimide (PI) aerogel blanket is designed and synthesized using the PI foam as the matrix and silica aerogel as the filler through an in situ method, where sol–gel transition of silica precursor occurs in pores of the PI foam, followed by the hydrophobization and ambient pressure drying. The density of the aerogel blanket ranges from 0.036 to 0.196 g/cm3, and the low density is directly controlled by tailoring the silica concentration. The specific surface area of the aerogel blanket reaches 728 m2/g. These features of the blanket result in a low thermal conductivity of 0.018 W/mK, which shows a remarkable reduction of 59% compared to that of the PI foam (0.044 W/mK). As a result, a remarkable decrease of 138°C is achieved using the silica blanket as the thermal insulator on a hot plate of approximately 250°C. In addition, the temperature degradation of the blanket is around 500°C, and up to 86% of mass remaining at 900°C is obtained. The blanket is resistant at extremely harsh conditions, e.g., 600°C for 30 min and 1,300°C for 1 min, and no open flame is observed, suggesting a significant flame-retardant of the blanket. Owing to the three-dimensional (3D) porous framework of the PI foam, the silica aerogel is encapsulated in the PI foam and the blanket exhibits strong mechanical property. The silica–PI aerogel can be reversibly compressed for 50 cycles without reduction of strain. The contact angle of the blanket is 153°, which shows a superior waterproof property. Combining with the low density, low thermal conductivity, flame-retardant, and strong mechanical strength, the aerogel blanket has the potential as an artificial island, which is safe (waterproof and flame-retardant), lightweight, comfortable, and easy to be moved.

Structure and Thermoelectric Properties of New Quaternary Tin and Lead Bismuth Selenides, K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1+xSn5-xBi11+xSe22

2000 ◽  
Vol 626 ◽  
Author(s):  
Antje Mrotzek ◽  
Kyoung-Shin Choi ◽  
Duck-Young Chung ◽  
Melissa A. Lane ◽  
John R. Ireland ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Thermoelectric Properties ◽  
Three Dimensional ◽  
Structure Type ◽  
Narrow Gap ◽  
Low Thermal Conductivity ◽  
Seebeck Coefficients ◽  
Metal Atoms ◽  
Anionic Framework

ABSTRACTWe present the structure and thermoelectric properties of the new quaternary selenides K1+xM4–2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22. The compounds K1+xM4-2xBi7+xSe15 (M= Sn, Pb) crystallize isostructural to A1+xPb4-2xSb7+xSe15 with A = K, Rb, while K1-xSn5-xBi11+xSe22 reveals a new structure type. In both structure types fragments of the Bi2Te3-type and the NaCl-type are connected to a three-dimensional anionic framework with K+ ions filled tunnels. The two structures vary by the size of the NaCl-type rods and are closely related to β-K2Bi8Se13 and K2.5Bi8.5Se14. The thermoelectric properties of K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22 were explored on single crystal and ingot samples. These compounds are narrow gap semiconductors and show n-type behavior with moderate Seebeck coefficients. They have very low thermal conductivity due to an extensive disorder of the metal atoms and possible “rattling” K+ ions.

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