Carbon foam derived from pitches modified with mineral acids by a low pressure foaming process B. Tsyntsarski a, * , B. Petrova a , T. Budinova a , N. Petrov a , M. Krzesinska b , S. Pusz b , J. Majewska b , P. Tzvetkov c a Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev str., BL. 9, Bulgaria b Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Marii Curie-Sklodowskiej 34, PL-41819 Zabrze, Poland c Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev str., BL. 11, Bulgaria ARTICLE INFO Article history: Received 11 March 2010 Accepted 24 May 2010 Available online 27 May 2010 ABSTRACT Carbon foams with an anisotropic texture and high mechanical strength were produced using precursors obtained after thermo-oxidation treatment of commercial coal–tar pitch with H 2 SO 4 and HNO 3 . The investigations of the relation between the properties of the pre- cursor and the structure of obtained foam indicate, that the composition and softening point of the pitch precursor significantly affect the foaming process, foam structure and foam mechanical strength. The composition and properties of the modified pitches allow foam formation at relatively low pressure and fast heating rate during the foaming process without a stabilization treatment. The foaming process of pitch-based carbon foams, pre- treatment of the precursors, and the properties of resultant foams are discussed in this paper. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The unique properties, which mainly depend on the precur- sor features and synthesis conditions, make carbon foams ultra-high performance engineering materials, and deter- mine their many potential applications in numerous indus- tries [1,2]: shipbuilding – living space modules, above deck structures, bulkheads; aerospace – aerospace modules, opti- cal benches and lightweight mirrors, rocket nozzles and mo- tors, thermal protection systems, composite tooling, heat transfer systems, radar adsorbing and antennae system; en- ergy – fuel cells, battery electrodes, nuclear shields, rods for nuclear reactors; automobile – catalytic converters, brakes, bumpers; defence-related – insensitive munitions, shields and body lightweight armour; medical – bone surgery mate- rial, prosthetics, tooth implants; architecture – insulation, fire proof blocks, shields and coatings, safe rooms, heating and cooling units; abrasives – for polishing of glass and met- als, for paint removal, in cosmetics; filters for hazardous conditions; electronics – processor radiators, radio frequency shields [1,2]. Initially, carbon foams were fabricated by carbonization of polymeric foams [3–6]. The development of carbon foams synthesis – on the base of coal–tar pitch [7,8], petroleum pitch [7,9], synthetic pitch from organics [10–15], coals [7,16,17] as well as from biomass materials like cork [18], olive stones [19], melanine [20] – provides an economical path for produc- tion of lightweight carbon materials. The effect of the precur- sor on the structure and properties of obtained foams is of great importance, so this issue is under extensive investiga- tions [4,10]. When the starting material is mesophase pitch, the final product is carbon foam with cellular graphitic liga- ment microstructure, similarly to that in high-tech carbon fi- bers, ensuring isotropic material properties – high stiffness and high thermal conductivity graphitic foams [1,10,12,13]. The properties of synthetic pitch can be adjusted to obtain suitable foaming precursor that can be foamed directly without pre-treatment. In this relation commercial coal–tar 0008-6223/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2010.05.048 * Corresponding author: Fax: +359 2 87 00 225. E-mail addresses: goriva@orgchm.bas.bg, boykotsyntsarski@yahoo.com (B. Tsyntsarski). CARBON 48 (2010) 3523 – 3530 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon