Microstructural evolution of mullite nanofibrous aerogels with different ice crystal growth inhibitors

Abstract

Mullite nanofibrous aerogels with low density, low thermal conductivity and high service temperature (as high as 1400 °C) was fabricated by the freeze-casting method, and two different kinds of ice crystal growth inhibitors, glycerol as the cryoprotector and agarose as the gel-former, were adopted respectively to influence the growth of ice crystal, thereby adjusting the sample microstructure (including the pore size and the pore distribution). The addition of glycerol could influence the growth of the ice crystal, leading to the pore structure changing from the cellular pores to the spherical pores and the decrease of the large pore size, consequently resulting in the increase of the sample density and compressive strength. The addition of agarose could inhibit the growth of the ice crystal due to the formation of gel network, resulting in the disappearance of the large pores (cellular pores). The sample with high agarose content exhibited a relatively high compressive strength of 252.41 kPa due to high density and uniform pore structure. The research of this work provides an effective method to regulate the properties of nanofibrous aerogel to meet the demand of different applications.