Direct fabrication of poly(p-phenylene terephthalamide) aerogel and its composites with great thermal insulation and infrared stealth

et al. 2021

Adv Funct Materials

145

Thermal camouflage has attracted increasing attention owing to the rapid development of infrared (IR) surveillance technologies. Various materials and systems have been developed to date, but the realization of high-temperature thermal camouflage using ultrathin film/coating remains a great challenge; this is of great significance, especially for IR stealth in military equipment. This work demonstrates a series of ultrathin Ti 3 C 2 T x MXene films (as low as 1 µm) with superior high-temperature indoor/outdoor thermal camouflage performance: wide camouflage temperature range (from below −10 °C to over 500 °C), large reduction in radiation temperature (exceeding 300 °C for objects with temperatures over 500 °C), long-term high-temperature or fire stability, multifunctionality including disguised Joule heating capability, and high electromagnetic interference shielding efficiency. The superior high-temperature thermal camouflage performance of the ultrathin MXene film is attributed to its low mid-IR emissivity (0.19), which is comparable to that of stainless steel but far below that of other 2D nanomaterials, such as graphene. The multifunctional ultrathin MXene films prepared through simple vacuum-assisted filtration provide a feasible method for efficient high-temperature thermal camouflage using ultrathin films, demonstrating the great promise of MXene materials for thermal camouflage, IR stealth, counter-surveillance, and security protection.

Section: Thermal Camouflage Performance Of Mxene Filmsmentioning

confidence: 99%

mentioning

confidence: 99%

Ultrathin Titanium Carbide (MXene) Films for High‐Temperature Thermal Camouflage

Shi

et al. 2021

Adv Funct Materials

145

“…Due to their unique nano-porous nature, ultralight densities, low thermal conductivity, etc., polymer aerogels have received a lot of attention in the fields of thermal insulation, catalysis, waste disposal, and so on. [1][2][3][4] Up to now, there are a DOI: 10.1002/mame.202100645 wide variety of polymer aerogels available, such as those derived from phenolic resins (PR), [5] polybenzoxazines (PBO), [6,7] polyureas (PUA), [8] Kevlarlike polyamides (PPTA), [9,10] polyimides (PI), [11][12][13] polyurethanes (PU), [14] etc. Among them, PI aerogels are very attractive due to their superior mechanical and thermal insulation properties, and can find diverse applications such as extravehicular activity (EVA) suits, thermal protective systems (TPS), submarine sound barrier systems, etc.…”

Section: Introductionmentioning

confidence: 99%

Melamine‐Crosslinked Polyimide Aerogels from Supercritical Ethanol Drying with Improved In‐Use Shape Stability Against Shrinking

Chen

Sun

et al. 2021

Macro Materials & Eng

Polyimide aerogels are promising for diverse applications owing to their nano-porous structure and superior properties. However, the shrinkage of melamine-crosslinked polyimide (MPI) aerogels has greatly compromised their performance in practical applications. In this study, supercritical drying with ethanol rather than CO 2 is employed to enhance their in-use shape stability at high temperatures. The structure, thermal insulation, mechanical strength of the resultant aerogels as well as their shape stability are characterized. Experimental results reveal that the shape stability of MPI aerogels during use is greatly improved thanks to the in-advance baptism of supercritical ethanol drying. The aerogel shrinks by only 2.64 vol.% after being treated at 280 °C for 72 h. Besides, the MPI aerogel shows enhanced compressive strength and can easily support a load more than 20 000 times its own weight. The thermal conductivity of these aerogels varies from 0.034 to 0.046 W m −1 k −1 , indicative of remarkable performance in thermal insulation. In addition, the aerogels that started to decompose at as high as 500 °C also perform well in thermal stability and char forming. It can be envisaged that the developed MPI aerogels with greatly improved in-use shape stability may have broad prospects for thermal insulation at high temperatures.

“…Zhu et al 13 prepared a mechanically robust poly (vinyl alcohol) nanofiber aerogel with low thermal conductivity (0.033 W/(m K)), which can withstand up to 1000 times its own weight. Zhang et al 14 fabricated poly (p-phenylene terephthalamide) aerogels by using the freeze-drying technology, and the aerogels were proved to possess both thermal insulation and mechanical properties with the thermal conductivity as low as 0.083 W/(m K) and the tensile strength being 1.6 MPa.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of light‐weight ultrahigh molecular weight polyethylene films with hybrid porous structure and the thermal insulation properties

Shen

J of Applied Polymer Sci

Jiang³

et al. 2022

According to the infrared stealth mechanism, controlling the surface temperature of objects can effectively hide the infrared radiation and resist the infrared detection. In this paper, a high infrared transparent polymer ultrahigh molecular weight polyethylene (UHMWPE) is selected as the matrix of a thermal insulation material. UHMWPE porous films with high porosity and hybrid pore structure are obtained through the thermal induced phase separation combining with particle leaching method. The film structures with micropores and macropores are adjusted through the variation of the mass ratio of UHMWPE/liquid paraffin, the dosage and the particle size of NaCl. The thermal conductivity of the UHMWPE film is as low as 0.034 W/(m K), while the density is only 54.4 mg/cm 3 . The classical Maxwell-Eucken model is used to discuss the relationship between the pore structure and the thermal conductivity of the films. It is determined that the hybrid porous structure can reduce heat conduction and gas-solid coupling effect simultaneously, thus the thermal conductivity is significantly reduced. Moreover, the porous films exhibited remarkable flexibility and hydrophobicity. Based on these properties, the porous films are highly promising in the field of thermal insulation protection and infrared stealth.