Letter to the Editor Synthesis and characterization of carbon fiber/silica aerogel nanocomposites Ślosarczyk Agnieszka a, ⁎, Strauchmann Wojciech a , Ziółkowski Piotr a , Jakubowska Paulina b a Poznan University of Technology, Institute of Structural Engineering, Poland b Poznan University of Technology, Institute of Chemical Technology, Poland abstract article info Article history: Received 5 January 2015 Received in revised form 13 February 2015 Accepted 15 February 2015 Available online xxxx Keywords: Silica aerogel; Sol–gel synthesis; Carbon fibers; Chemical modification Nanoporous silica aerogel–carbon fiber composites were prepared via a sol–gel process by surface modification at ambient pressure. Oxidizing modification of the carbon microfibers improved the adhesion between hydrophilic silica gel and the carbon material surface. Suggested solution contributed to the blocking of hydroxide bonds of silica gel via reaction with the oxidized carbon material surface, which lowered the contraction of gel volume during its drying in atmospheric pressure and led to the more stable structure. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Receiving good structural parameters of aerogel does not improve the main drawback of silica aerogels, which is their brittleness. One of the ways to improve the aerogel brittleness is the use of fibers. Never- theless, there are very few articles on the synthesis of nanocomposites as silica aerogel-fibers. First research on this subject was conducted in 1990's [1]. Paramenter and Milstein modified silica aerogel with silica fibers, alumina fibers and aluminaborosilicate fibers. Those fibers are characterized by a relatively high mass density, which significantly changes the density of the created nanocomposites. Research proved that applied fibers considerably limited the contraction of silica aerogel, but they lowered its mechanical parameters, such as compressive strength and elastic modulus. Much better parameters were achieved by Meador and co-workers while modifying silica aerogel with much lighter carbon nanofibers and di-isocyanate [2]. In the case of this solu- tion an improvement of compressive strength by 5% was achieved. However, Zhang and co-workers were the first to apply polypropylene fibers as silica aerogel component [3]. They used polypropylene fibers 12 mm long obtaining good structural properties of silica aerogel with- out significant changes in its density. A drawback of hitherto solutions for this type of modification was the lack of fiber surface modification and lack of chemical bonding between fibers and silica gel. The main aim of presented studies was to form the silica aerogel– carbon fiber nanocomposites with more durable structure. The syn- thesis of aerogel and its composites with carbon fibers was performed in two-step sol–gel process using the drying in atmospheric pressure. The chemical modification of carbon fibers in nitric acid was carried out to enhance the adhesion between carbon fibers and silica aerogel skeleton. In addition, the chemical modification of aerogel nanocom- posites in TMCS/n-hexane mixture was performed. The structure and temperature stability of silica aerogel–carbon fiber composites were tested through the following methods: BET analysis, thermogravimetric measurements TGA and Fourier Transform Infrared Spectroscopy FTIR. 2. Materials and methods As the precursor of silica aerogel synthesis the tetramethylsilane TMOS (Sigma-Aldrich) in methanol solution (CHEMPUR) was used. The catalyst of reaction was the aqueous solution of ammonium with the concentration of 29–30% (Sigma-Aldrich). The chemical modi- fication of silica aerogel was performed using the trimethylchlorosilane TMCS (Sigma-Aldrich) and n-hexane (CHEMPUR). As component of silica aerogel–carbon fiber composites, low-modulus carbon fibers from coal-tar pitch with density of 1.64 g/cm 3 were used (OsakaGas Corp.). Carbon fibers have the diameter of 13 μm and length of 700 μm, and are characterized by shape factor of L/d = 50. They have a low graphitization level and small specific surface area 0.96 m 2 /g (according the BET meth- od) with very small micropore content (0.0009 cm 3 /g). The physical and chemical characterization of synthesized nano- materials was performed by the using of BET and thermo-gravimetric analysis. Surface area and pore volume of aerogel composites were esti- mated based on adsorption isotherms in low-temperature nitrogen sorp- tion in the temperature of 77 K using the equation of BET isotherm and analyzer ASAP 2010 (Micrometrics). Thermo-gravimetric analysis of Journal of Non-Crystalline Solids 416 (2015) 1–3 ⁎ Corresponding author at: Piotrowo 5 str., 60–965 Poznan, Poland. E-mail address: agnieszka.slosarczyk@put.poznan.pl (Ś. Agnieszka). http://dx.doi.org/10.1016/j.jnoncrysol.2015.02.013 0022-3093/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol LETTER TO THE EDITOR