Graphitization of Oak-Tree-Based White Charcoals by High Temperature Heat Treatment

• Published in: The Korean journal of chemical engineering Vol. 41; no. 6; pp. 1841 - 1849
• Main Authors: Park, Young-Nam, Lee, Jae Jun, Kwac, Lee-Ku, Ryu, Seung Kon, Kim, Hong-Gun
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.06.2024; Springer Nature B.V; 한국화학공학회
• Subjects: Adsorption; Argon; Biotechnology; Catalysis; Charcoal; Chemistry; Chemistry and Materials Science; Crystallites; Diffraction patterns; Electron microscopy; Graphite; Graphitization; Heat treatment; High temperature; Hysteresis; Industrial Chemistry/Chemical Engineering; Interlayers; Isotherms; Low pressure; Materials Science; Microscopy; Original Article; Pore size; Raman spectroscopy; Temperature; 화학공학; Charcoals; Microporosity; Adsorption isotherms; Surface morphology; Graphitization
• ISSN: 0256-1115; 1975-7220
• DOI: 10.1007/s11814-024-00138-w

Oak-tree-based white charcoals were subjected to high-temperature heat treatment at up to 2400 °C to analyze changes in their surface morphology and internal structure using scanning electron microscopy and transmission electron microscopy. When the treatment temperature was increased, micropores became smaller and disappeared, but macropores and mesopores remained, resulting in an increase in average pore size. At treatment temperatures of 2000 °C or higher, all the pores disappeared and the internal structure changed into a dense graphite-like structure. The X-ray diffraction patterns of charcoals heat-treated at 1800 °C or higher in an argon atmosphere exhibited a sharp peak near 2 θ  = 26.5°, and Raman spectroscopy showed clear D and 2D bands near 1360 and 2680 cm −1 , respectively, indicating that carbon graphite crystals were developing. At 2400 °C for 10 min., the interlayer distances ( d 002 and d 100 ), L c and L a of the graphite crystallites were 0.34, 0.21, 23.00, and 6.13 nm, respectively. The presence of the D band and the I G /( I G  +  I D ) ratio confirmed that the newly developed structure was turbostratic. The Brunauer–Emmett–Teller (BET) adsorption isotherm of the as-received charcoals exhibited peculiar characteristics in which Types I and IV were mixed. This result is due to low-pressure hysteresis, in which nitrogen is embedded in the crevices of charcoal during adsorption and is hardly desorbed during desorption. This low-pressure hysteresis disappeared as increasing the temperature, the adsorption isotherm of charcoal treated at 2400 °C was Type II, and the specific surface area was 8.45 m 2 /g, indicating that the charcoal was completely transformed to nonporous graphite.