Changes in electrical and microstructural properties of microcrystalline cellulose as function of carbonization temperature Yo-Rhin Rhim a , Dajie Zhang b , D. Howard Fairbrother c , Kevin A. Wepasnick c , Kenneth J. Livi d , Robert J. Bodnar e , Dennis C. Nagle b, * a Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723, USA b Advanced Technology Laboratory, Johns Hopkins University, 810 Wyman Park Drive, Baltimore, MD 21211, USA c Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA d Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA e Department of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, VA 24061, USA ARTICLE INFO Article history: Received 9 February 2009 Accepted 8 November 2009 Available online 13 November 2009 ABSTRACT AC and DC electrical measurements were made to better understand the thermal conver- sion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstruc- tural evolution of cellulose during carbonization. In Region I (250–350 °C), a decrease in overall AC conductivity occurs due to the loss of the polar oxygen-containing functional groups from cellulose molecules. In Region II (400–500 °C), the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III (550–600 °C), a further increase of AC conductivity with increasing heat treatment temperature is observed. In addition, the AC conductivity dem- onstrates a non-linear frequency dependency due to electron hopping, interfacial polariza- tion, and onset of a percolation threshold. In Region IV (610–1000 °C), a frequency independent conductivity (DC conductivity) is observed and continues to increase with heat treatment due to the growth and further percolation of carbon clusters. Finally in Region V (1200–2000 °C), the DC conductivity reaches a plateau with increasing heat treat- ment temperature as the system reaches a fully percolated state. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Electrical properties of various forms of carbon, including graphite, anthracite carbons, carbon nanotubes, and graph- ene materials are of great interest in many technical areas. The electrical properties of carbon materials derived from or- ganic precursors have been studied extensively over the years and have been shown to vary widely depending on the nature of the precursor and the heat treatment temperature (HTT) [1–8]. Microcrystalline cellulose is a basic component of wood that has been highly refined to remove all the inorganic ash. By using this high purity precursor material, more definitive observations could be made on the carbonization mecha- nisms of organic compounds as they are converted to non- graphitizing hard carbons. Since cellulose molecules do not contain any aromatic structures and does not exhibit an intermediate mesophase, they yield highly amorphous carbon even when heated to extremely high HTTs. This study 0008-6223/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2009.11.020 * Corresponding author: Fax: +1 410 516 7249. E-mail address: dnagle@jhu.edu (D.C. Nagle). CARBON 48 (2010) 1012 – 1024 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon