Journal of Alloys and Compounds 434–435 (2007) 854–857 Structural properties of some transition metal highly doped carbon aerogels L.C. Cotet a , M. Baia b , L. Baia b , I.C. Popescu a , V. Cosoveanu a , E. Indrea c , J. Popp d , V. Danciu a,∗ a Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, 400028 Cluj-Napoca, 11, Arany Janos, Romania b Babes-Bolyai University, Faculty of Physics, 400084 Cluj-Napoca, M. Kogalniceanu 1, Romania c National Institute for Research and Development of Isotopic and Molecular Technologies, 400293 Cluj-Napoca, 71-103 Donath, Romania d Institute of Physical Chemistry, Friedrich Schiller University of Jena, Helmholtzweg 4, 07743 Jena, Germany Available online 6 October 2006 Abstract Structural characterization of transition metal highly doped carbon aerogels obtained through the sol–gel polymerization process of the formalde- hyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by metal ions exchange using Ni(II) and Cu(II) aqueous solutions, supercritical drying with liquid CO 2 and carbonization at 1050 ◦ C under inert atmosphere has been performed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy were used and it was found that the metal-containing phase is more homogeneously distributed in Cu-doped carbon aerogels. The presence of the metal species determines both the growth of graphitic nanoribbons and the change of framework of the interconnected carbon particles. © 2006 Elsevier B.V. All rights reserved. Keywords: Carbon aerogels; Sol–gel synthesis; TEM; X-ray diffraction; Raman spectroscopy 1. Introduction Carbon aerogels are a new class of nanoporous materials with controllable and interesting structural properties such as low mass densities, high surface areas, continuous porosities [1–3] and moreover, they offer the possibility to incorporate metallic species in the carbon framework [4]. In the last decade many efforts have been devoted to increase the graphitization of carbon aerogels in order to enhance their electrical conductivity. It was reported [5,6] that transition metals incorporated into the carbon aerogels structure seem to be the best catalysts for graphitization of carbon aerogels. Recently, carbon aerogels doped with Ni and Cu have been prepared by sol–gel polymerization of formaldehyde with potas- sium salt of 2,4-dihydroxybenzoic acid followed by an ion- exchange process between K + doped gel and Ni(II), Cu(II) ion aqueous solutions [7,8]. The resulted metal-doped gels have been dried in supercritical conditions with liquid CO 2 and then ∗ Corresponding author. E-mail address: vdanciu@chem.ubbcluj.ro (V. Danciu). pyrolyzed in high temperature and inert atmosphere resulting in a monolithic metal-doped carbon aerogel (Me-DCA). In the present study, our interest was focused on finding the structural properties of the obtained Ni and Cu highly doped car- bon aerogels by applying complementary investigation methods like transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The structural analysis regard- ing the crystalline nature of graphitic and metallic state of Ni and Cu doped aerogels was performed in comparison with the data obtained for the K-doped carbon aerogel, which is considered throughout of this study as the blank carbon aerogel sample. 2. Experimental 2.1. Sample preparation The metal-doped aerogels were prepared by K 2 CO 3 addition to a 2,4- dihydroxybenzoic acid demineralised water suspension (acid/K 2 CO 3 molar ratio was 0.5 and acid/water, 0.03 g/cm 3 ), under vigorous stirring. After 30 min, when all the acid is neutralised, the solution becomes clear and after another 30 min, 37% formaldehyde (F) and then K 2 CO 3 as catalyst (acid/formaldehyde and acid/catalyst molar ratios was 2 and 100, respectively) were added to the solution. The resulting solution was placed into tightly closed glass moulds (7 cm-length × 1 cm-internal diameter) and cured for 1 day at room temperature 0925-8388/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2006.08.100