ELSEVIER Materials Chemistry and Physics 49 (1997) 105-109 Glassy carbon from camphor - a natural source Kingsuk Mukhopadhyay, Maheshwar Sharon * Departnlent of Chemistty, Indian Institute of Technology, Powai, Bombay 400 076, India Received 20 May 1996; revised 17 October 1996; accepted 17 October 1996 Abstract Glassy carbon has been synthesized for the first time by a simple pyrolysis experiment. The glassy carbon from camphor has been characterized by XRD, Raman, FTIR, ESR and SEM/AFM techniques. It hasbeenfound that the undoped glassycarbonfilm hasa resistance of less than about 1 fl and has n-type character.However, when it was doped with boron by a conventional vapour growth process,its resistanceincreasedto the range 3.5 a-14.5 kR, depending upon the concentration of boron incorporated, and the resulting material has p-type ChamCter, henceshowing a semiconducting brhaviour unlike the undopedfilm which hasmetallic character. Kelwsords: Camphor; Pyrolysis of camphor; Glassy carbon 1. Introduction Pyrolysis of aromatic/aliphatic hydrocarbons (e.g. ben- zene, acetylene) has yielded graphite/glassy carbon [ 1,2], whereas fast pyrolysis of benzene in the presence of hydrogen and Fe catalyst has yielded conducting carbon fibres [ 31, Recently Sharon et al. have successfully isolated C,, and other members of the fullerene family [ 451, multichannel- multilayered nanotubules [ 6,7] and synthesized diamond- like carbon films [ 81 from camphor, a natural source. As an extension of this work, it was decided to synthesize glassy carbon by the controlled pyrolysis of camphor in an inert ( argon j atmosphere. 2. Experimental technique A self-explanatory apparatus is shown in Fig. 1. The entire system after assembling and keeping camphor in the flask, was flushed with argon for 15 min to ensure the absence of oxygen inside the system before heating the flask. The tem- perature of the flask containing camphor was kept around 50°C. The temperature of the furnace was kept around 1000°C. The alumina boat was kept near the hottest zone of the quartz tube inside the furnace. The flow rate of argon gas was maintained such that 50 g of camphor could be trans- ferred to the furnace in about 2 h. After the experiment, the furnace was cooled to room temperature and the boat was * Corresponding author. 0254-0584/97/$17.00 0 1997 Elsevier Science S.A. All rights reserved HISO254-0584(96)01918-9 removed. A thin film of black conducting carbon coated the boat and some shiny flakes of conducting carbon were found. These flakes were very light and could easily become air- borne. The room temperature resistance of these flakes as well as the thin film deposited on the alumina boat was less than 1 R. Thin films and flakes were characterized by Raman, XRD, FTIR, ESR and SEM were found to be glassy carbon. 3. Results and discussion XRD of the thin film (Fig. 2(a) ) matched well with all the characteristic 20 values of the peaks of glassy carbon [ 91. The observed 28 values of the peaks are compared with the standard JCPDS data for glassy carbon in Table 1. For com- parison, XRD spectra of commercially available glassy car- bon and graphite were also taken. In both cases, the 100% peak has been found at 26.6 (28 value), but for glassy carbon while its intensity was 9000 (Fig. 2(b) ), for graphite it was 35 000 (Fig. 2(c)). In glassy carbon from camphor, the 100% peak appeared at 26.215. This slight variation in 28 values could be due to the difference in alignment of samples or due to the variation in preparing conditions of commercial available samples and the test sample [ lo]. Since XRD patterns of glassy carbon and graphite are reported to be almost the same and the Raman spectra for graphite and glassy carbon are different, Raman spectrum of our film was also taken (Fig. 3). It is reported that Raman spectrum of graphite will show a sharp peak at 1580 cm-‘, while for glassy carbon the peaks will appear around the 1357