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HATA, Toshimitsu

IMAMURA, Yuji

ISHIMARU, Kengo

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Title<Preliminary>Surface Characterization of Wood Charcoalunder Different Carbonization ConditionsAuthor(s)ISHIMARU, Kengo; HATA, Toshimitsu; IMAMURA, YujiCitationWood research : bulletin of the Wood Research Institute KyotoUniversity (2002), 89: 31-32Issue Date2002-09-30URL http://hdl.handle.net/2433/53114RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityPreliminarySurface Characterization of Wood Charcoal underDifferent Carbonization Conditions*lKengo ISHIMARU*2, Toshimitsu HATA *2 and Yuji IMAMURA*3(Received May 31, 2002)Keywords: wood charcoal, surface chemical structure, carbonization condition, XPSIntroductionThe characteristic functions of wood charcoal ofelectrical conductivity and adsorptive property areconsidered to be affected by its microstructure whichchanges according to carbonization conditions such ascarbonized temperature, heating rate and atmosphere.The microstructure of wood carbon is considered to bedrastically changed at 500 to 800°C and electron micro-scopic studies have shown that various nano-carbonstructures such as C60 fullerene, onion-like and diamondstructure were formed in wood charcoal around thesetemperature ranges 1-3). These findings showed a closerelation between the function and microstructure of woodcharcoal.The chemical structure such as type of functional groupand chemical bond of wood charcoal during carbonizationis also thought to be related to its characteristic propertiesand functions. X-ray photoelectron spectroscopy (XPS)is a powerful tool for analyzing the surface characteristicsof wood charcoal due to its good surface sensitivity andability to provide structural analysis for chemicalbonding4 ).In this paper, the effects of carbonization conditionssuch as the carbonized temperature, heating rate andreaction time on the surface chemical structure of woodcharcoal were studied by XPS.Materials and MethodsOven-dried chips of sugi sapwood (Cryptomeria japonica)were carbonized in a laboratory-scale furnace. Rawsamples were heated at the heating rate of 2, 4, 8°C/min.up to the target temperatures of 500, 600, 700 and 800°C ina nitrogen gas atmosphere, maintained at thesetemperatures for 1 or 3 hr, and then cooled down to roomternpera ture.All carbonized samples were powdered and dried at105°C for 24 hr for analysis by XPS. XPS spectra wereobtained by AXIS-HS [Shimadzu/KRATOS] using anMgKa (1253.6eV) X-ray source operated at 150W in avacuum of 3-5 X 10-9 Torr. High-resolution scans of Cis*1 A part of this research was presented at the 28th AnnualMeeting of the Carbon Society ofJapan (Kiryuu, December,2001) and at the 52th Annual Meeting of Japan WoodResearch Society (Gifu, April, 2002).*2 Laboratory of Wood Composite.*3 Laboratory of Deterioration Control.were performed with the pass energy adjusted to 20 eV.Results and DiscussionThe FWHM (full width at half maximum) values of theCis spectrum, which indicate the degree of carbonizationand the order of laminated hexagonal carbon layers ofcarbon materials5), are shown in Fig. 1. It is said that theFWHM of C Is spectra narrows with the development ofcarbonization and the lattice structure of hexagonal carbonlayers. The FWHM values of the wood charcoalprepared in this experiment decreased up to 700°C ofcarbonized temperature. However, FWHM was notsignifican tly different among the various heating rates andreaction times. The development of the carbonizationstage and the formation of laminated hexagonal carbonlayers was assumed to progress up to 700°C in all samples.A curve fitting of the C Is spectrum was carried out bynon-linear least squares curve fitting with Gaussiandistribution and Shirley background subtractiGn. Thespectra were fitted to six peaks4,6). The binding energy ofC-C was assigned at 284.6 eV and of C-H was shifted to+0.5-0.8 eV from the C-C peak. In addition to the C-Cand C-H, the spectra were fitted to three peaks of oxygen-containing groups, with chemical shifts of + 1.4-1.8 eV2.01.9S- 1.8~(/)() 1.74-0 1.6~:r:~ 1.51.41.3500 600 700 800Carbonized temperature(OC)Fig. 1. Effects of carbonized temperature on the FWHMof CIs spectrum of wood charcoal at differentheating rates and reaction times. Legend: 0;heating rate of 2°C/min, .; heating rate of4°C/min, L:::.; heating rate of 8°C/min, 0;heating rate of 4°C/min and reaction time of 3 hr.- 31-WOOD RESEARCH No. 89 (2002)o500 600 700 800Carbonized temperature(OC)Effects of carbonized temperature on the Qxygenconcentration, obtained by curve fitting of CIsspectrum of wood charcoal at different heatingrates and reaction times. Legend: see Fig. 1.50.........~'-" 40c:0i~+J 30c:Q)0c:0 200c:Q)tID>- 10><0Fig. 3.700 800Carbonized temperature(OC)Changes of the peak area ratio of aromaticscarbon (C-C) obtained from the curve fitting of. CIs spectrum with Gaussian distribution atdifferent carbonized temperatures, heating ratesand reaction times. Legend: see Fig. 1.70.........~ 60'-"0I0 50'+-00 40i~ 30«JQ)~ 20«J.::t:.«J 10Q)CL0500 600Fig. 2.(01), +2.8-3.2 eV (02) and +4.3-4.7 eV (03), and+ 6.4-6.8 eV for 'Plasmon. These assignments of thefunctional groups are normally used to 01 for C-OH, 02for C =0 and 03 for COOH, for which proof theassignment of the chemical shifts to each functional groupis underway.The effects of the carbonized temperature and theheating rate on the peak area ratio of C-C are evaluated inFig. 2. With increases in the carbonized temperaturefrom 500 to 700°C, the peak area ratios ofC-C increased inall' the carbonization conditions. While the peak arearatio ofC-C increased with the increase of the reaction timefrom 500 to 600°C" little difference was observed in thepeak area of C-C by changing the heating rates.The oxygen concentration of wood charcoal decreasedwith the increase of the carbonized temperature (Fig. 3).The heating rate and reaction time affected the oxygenconcentration below the carbonized temperatures of 700°C,however, no significant difference was observed above700°C a;mong the various heating rates and reaction times.It is expected that the chemical structure of woodcharcoal with aliphatic and oxygen-containing componentsmainly changes to the framework of hexagonal carbonlayers at temperatures up to 700°C, and the development ~fthe order of the laminated hexagonal carbon layers occursmainly at temperatures above 700°C. The carbonizationconditions of the heating rate and reaction time influen,cethe changes of the chemical structure in the range of50o-600°C, but do not significantly affect the chemicaistructures at 70o-BOO°C.Reference1) M. SHIBUYA, M. KATO, M. OZAWA, P.H. FANG and E.OSAWA: Fullerene Science and Technology, 7(2), 181-193 (1999).2) T. HATA, Y. IMAMURA, E. KOBAYASHI, K. YAMANE and K.KIKUCHI: J. Wood Sci., 46, 89-92' (2000).3) K. ISHIMARU, T. VYSTAVEL, P. BRONSVELD, T. HATA, Y.IMAMURA and J.D. HOSSON: ibid, 47, 414-416 (2001).4) K. NISHIMIYA, T. HATA, Y. IMAMURA and S. ISHIHARA: ibid,44, 56-61 (1998).5) T. TAKAHAGI and A. ISHITANI: Carbon, 26(3), 389-396(1988).6) H. DARMSTADT, C. Roy and S. KALIAGUINE: ibid, 32(8),1399-1406 (1994).- 32-

<Preliminary>Surface Characterization of Wood Charcoal under Different Carbonization Conditions

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<Preliminary>Surface Characterization of Wood Charcoal under Different Carbonization Conditions

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