Ultralight carbon nanofoam from naphtalene-mediated hydrothermal sucrose carbonization Shelby Taylor Mitchell a , Natalie Frese b , Armin G € olzh € auser b , Amanda Bowers a , Klaus Sattler a, * a Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, HI 96822, USA b Faculty of Physics, University of Bielefeld, D-33501 Bielefeld, Germany article info Article history: Received 5 May 2015 Received in revised form 27 July 2015 Accepted 2 August 2015 Available online 7 August 2015 abstract We report experimental studies of carbon nanofoam produced using a hydrothermal autoclave reactor with a sucrose solution and a small added amount of naphthalene. The foam has an average density of 85 mg/cc and is uniform in its appearance. He-ion microscopy (HeIM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the foam samples. These show good con- sistency in the micro/nanostructure as well as in the elemental constitution. The vibrational and electron core-level studies suggest an open cellular structure with curved graphene walls and basal-plane oxide groups. We conclude that naphthalene-assisted hydrothermal processing of sucrose is a useful method to produce high-quality carbon nanofoams. © 2015 Elsevier Ltd. All rights reserved. 1. . Introduction Nanofoams from various materials have been synthesized in recent years. Among these are nanofoams from chemical elements such as copper [1], silicon [2], nickel [3], gold [4], and silica [5]. Also, various types of polymeric nanofoams have been produced since their first synthesis in 1994 [6]. In addition, nanocomposite foams have been investigated [7] which are interesting due to their su- perior mechanical and thermal properties. Cu-nanofoams were studied with respect to their possible use in energy applications [1]. There is an intense interest in nanocarbon for a variety of en- gineering applications. Nanocarbon materials are thermodynami- cally stable in different polymorphs which can adopt a wide range of crystalline and non-crystalline structures with very interesting properties. This is because of carbon's ability to form sp 1 - (poly- meric-type), sp 2 - (graphite-like), and sp 3 - (diamond-like) hybrid- ized bonds. Noncrystalline carbons usually are intermediate between diamond and graphite since they contain variable amounts of sp 3 -and sp 2 etype atoms. Hybrid graphite-diamond structures have been theoretically developed [8], in particular for the understanding of glassy carbons, carbon blacks, and diamond- like carbon films [9]. The properties of these materials depend very strongly on the sp 3 /sp 2 ratio [10]. Mass densities typically range from ~3.5 gcm 3 for diamond to about 1 gcm 3 for noncrystalline carbon films. Carbon nanofoam (CNFM) was first produced in 2002 by high- repetition-rate laser ablation of a glassy carbon target in an Argon atmosphere [11]. The foams were found to have very low densities and high electrical resistivity. Carbon nanofoam has been consid- ered as a potential hydrogen storage material [12] and as cathode materials for metal-air batteries [13]. It was found that this material contains both sp 2 and sp 3 bonded carbon atoms. It was suggested that the foams consist of graphite-like sheets with hyperbolic curvature, similar to the structure of “schwarzite”. Surprisingly, ferromagnetism was found for some of the foams up to 90 K, with a narrow hysteresis curve and a high saturation magnetization [14]. Also, catalytic applications have been reported using carbon nanofoams [15]. Atomistic simulations of carbon nanofoams reveal a low-density nanoporous material [16]. A nanofoam-related structure has also been suggested for carbon nanotube aerogels [17]. Such carbon structures with complex topology related to the coexistence of both sp 2 and sp 3 hybridized atoms, have attracted considerable interest in recent years [18]. Porous carbon materials are usually produced by chemical [19,20] or physical [21] routes. Among these, the mesoporous and nanoporous carbons are attractive materials for a number of different applications, such as methane gas storage [22], hydrogen storage [23], as electrodes in supercapacitors [24,25], and as * Corresponding author. E-mail address: sattler@hawaii.edu (K. Sattler). Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon http://dx.doi.org/10.1016/j.carbon.2015.08.001 0008-6223/© 2015 Elsevier Ltd. All rights reserved. Carbon 95 (2015) 434e441