Nanoengineering Super Heat-Resistant, Strong Alumina Aerogels

Abstract

Because of ultralow thermal conductivity, excellent catalytic activity, and better heat resistance than silica aerogel, alumina-based aerogel has drawn great interest as thermal insulators and catalysts. However, it is too fragile and sinters above 1000°C (it shrinks drastically, >50%, and leaves the surface area as low as 10−70 m 2 /g at 1300°C), which badly limits its high-temperature applications. Herein, super heat-resistant, strong alumina aerogels are prepared via a novel acetone-aniline in situ water formation (ISWF) method combined with novel modification techniques: supercritical fluid modification (SCFM) and hexamethyldisilazane gas phase modification. The heat resistance of alumina aerogel is enhanced up to 1300°C via this method. The shrinkage of the optimized alumina aerogel is reduced to as low as 1 and 5% and the corresponding surface area reaches up to 152−261 and 125−136 m 2 /g after being heated to 1200 and 1300°C for 2 h, respectively. The strength is significantly increased by more than 120% through SCFM. It also exhibits excellent thermal insulation properties at temperatures up to 1300°C. This may significantly contribute to their practical ultrahigh-temperature applications in thermal insulations, catalysts, catalyst supports, etc.

Ultralight nanofibre-assembled cellular aerogels with superelasticity and multifunctionality

“…Plotting the relative compressive modulus (E/E s ) of various fabricated FIBER NFAs versus their relative density (r/r s ) revealed that the modulus scaled as E/E s B(r/r s ) 2 (Fig. 3a), indicating a cellulardominated mechanical behaviour similar to that of open-cell cellular foams 10,44 . This scaling law also affects the structural stability of self-supporting cellular materials, imposing a lower bound on density 7,9 .…”

Strong and resilient alumina nanotube and CNT/alumina hybrid foams with tuneable elastic properties

“…3,5,6 Furthermore, these techniques afford little control over cellular architecture such as pore size and distribution, particularly for very low densities (#20 mg cm À3 ). Alternatively, there has been growing interest in the development of novel methods to produce mesoporous metal oxide materials with ordered architectures.…”

“…11,28 Even the highest density demonstrated in this work (39 mg cm À3 ), is lower than that of alumina aerogels fabricated using sol-gel methods. 3,5,6 Thermogravimetric analysis, provided in Fig. 2, revealed that alumina coated CNTFs exhibited good thermal stability with minimal weight loss at low temperature.…”

Heat-resistant, strong titania aerogels achieved by supercritical deposition

“…The titania wet gels were prepared via an ISWF method according to the following three steps [18]. First, TBO was dissolved in ethanol at room temperature.…”

“…Sanli and Erkey have reported monolithic composites of silica aerogels by reactive supercritical deposition of hydroxylterminated poly (dimethylsiloxane) during CO 2 supercritical fluid drying [17]. We have successfully prepared heat-resistant, strong alumina aerogels via a supercritical fluid modification method performed during high-temperature ethanol supercritical fluid drying [18].…”