J. of Supercritical Fluids 89 (2014) 28–32 Contents lists available at ScienceDirect The Journal of Supercritical Fluids j o ur na l ho me page: www.elsevier.com/locate/supflu Hexafluoroisopropyl alcohol as a new solvent for aerogels preparation Sergey Lermontov a,∗ , Alena Malkova a , Lyudmila Yurkova a , Elena Straumal a , Nadezhda Gubanova b , Alexander Baranchikov c , Mikhail Smirnov d , Viktor Tarasov d , Vyacheslav Buznik e , Vladimir Ivanov c,f a Institute of Physiologically Active Compounds of the Russian Academy of Sciences, 1 Severnij Pr., Chernogolovka, 142432, Russia b National Research Centre “Kurchatov Institute”, B. P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, Leningrad District, 188300, Russia c Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky Av., Moscow, 119991, Russia d Institute of Problems of Chemical Physics of the Russian Academy of Sciences, 1 Prospect Akademika Semenova, Chernogolovka, Moscow Reg., 142432, Russia e “All-Russian Scientific Research Institute of Aviation Materials”, Federal State Unitary Enterprise, State Research Center of the Russian federation, 17 Radio Street, Moscow, 105005, Russia f Tomsk State University, Faculty of Chemistry, 36 Lenin Av., Tomsk, 634050, Russia a r t i c l e i n f o Article history: Received 10 December 2013 Received in revised form 14 February 2014 Accepted 14 February 2014 Keywords: Aerogels Hexafluoroisopropyl alcohol Supercritical drying Silica Alumina Zirconia a b s t r a c t Fluorinated alcohols are claimed to be promising solvents for supercritical drying. A number of metal oxide aerogels (both monoliths and powders) including silica, alumina and zirconia were prepared using hexafluoroisopropyl alcohol. It is shown that the specific surface area of all the aerogels dried in hexaflu- oroisopropyl alcohol is twice that of the aerogels prepared in ethanol. Surface modification of aerogels with fluorinated organic species is shown to take place upon supercritical drying. © 2014 Published by Elsevier B.V. 1. Introduction Aerogels are mesoporous solid materials possessing unique properties including very low bulk density (up to 98% of their volume is air), large specific surface area and high thermal sta- bility among others [1]. Since their discovery in 1931 [2], great efforts were made to develop industrial and domestic applications of aerogels. Nowadays they are used as reusable oil spills adsor- bents [3], CO 2 scavengers [4,5] and water desalination materials [6]. A very large specific surface area makes aerogels promising catalysts and catalyst supports [7–10], energy storage materials [11–14] and hydrogen accumulators for fuel cells [15]. Prepa- ration of graphene–aerogels electroconducting nanocomposites [14,16–18] presents a very promising recent area of application. The most interesting feature of aerogels is their extremely low thermoconductivity up to 0.004 W m -1 K -1 [10]. For instance, organic aerogels are used as thermoinsulators in space explo- ration technologies and in special clothing including sportswear ∗ Corresponding author. Tel.: +7 4965249508; fax: +7 4965249508. E-mail addresses: lermontov52@yandex.ru, lermon@ipac.ac.ru (S. Lermontov). [10]. Great efforts were made to develop the use of aerogels as thermoinsulating windows since high transparency and low thermoconductivity makes aerogels an ideal material for this appli- cation. Aerogels are usually prepared by a sol–gel technique using supercritical drying (SCD) [1]. A solvent removal at a temperature exceeding its critical temperature is a necessary stage of this proce- dure. Thus the critical temperature of the solvent is a key parameter which determines the overall energy consumption in course of SCD as well as the resultant aerogels’ properties. Alcohols and carbon dioxide (CO 2 ) are the most conventional types of SCD fluids for aerogels’ preparation [19]. SCD with CO 2 is widely used since this compound is non-flammable and has a low critical temperature (31 ◦ C). However, SCD with CO 2 requires expensive equipment. On the contrary, SCD in alcohol media is performed using compara- tively low cost equipment, but alcohols are flammable substances, having a higher critical temperature. Little is known about the influence of the nature of supercritical solvent on composition and structural characteristics of aerogels, including specific surface area and porosity. Only a few publica- tions were found concerning the comparative study of the influence of the solvent used for supercritical drying on aerogels’ properties http://dx.doi.org/10.1016/j.supflu.2014.02.011 0896-8446/© 2014 Published by Elsevier B.V.