The present study examined changes in surface shape and pore size observed in carbon black particles isothermally oxidized in an air atmosphere according to their burn-off ratio. Carbon black materials were fed into a horizontal tubular furnace in an air atmosphere when the inside temperature reached 600 °C. Subsequently, while changing the isothermal oxidation time, carbon black samples with different burn-off ratios were obtained, i.e., 10.5, 20.0, 30.4, 41.0, 49.9, 59.8, 71.1, and 81.0%. The scanning electron microscope analysis revealed that the observed carbon black particles were in the form of aggregated primary particles, and that there was no change in the particle size of these primary particles as the burn-off process proceeded. The latter observation supported the observation that pores were formed in the carbon black samples during the burn-off process. Notably, the Brunauer–Emmett–Teller analysis exhibited hysteresis curves, indicating that the corresponding adsorption isotherms were of IV-type. It was also found that the area of the hysteresis curves increased as the burn-off process proceeded. The specific surface area of the raw carbon black sample was 58.00 m2/g, while that of the 81.0% sample was about 4.1 times the figure at 240.27 m2/g. The total pore volume VT was 0.17 cm3/g for the raw sample, and it was much higher for the 81.0% sample at 0.58 cm3/g. The transmission electron microscope analysis showed that the raw carbon black particles had a spherical shape with a smooth surface, but inner pores were not observed. In the 49.9% sample, pores with a size of about 5 nm were observed inside carbon black particles. Notably, the size of the pores observed in the 81.0% sample was about 20 nm and the large pores were created by the collapsing and merging of the smaller pores by oxidation.

Surface shape and pore size change in carbon blacks isothermally oxidized in air atmosphere according to burn-off ratio
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
            2.1.1 Preparation of carbon black
        2.2 Characterization of carbon black
            2.2.1 Characterization of carbon black by SEM
            2.2.2 Characterization of carbon black by gas adsorption apparatus
            2.2.3 Characterization of carbon black by TEM
    3 Results and discussion
        3.1 SEM analysis and morphological features of carbon black
        3.2 BET analysis
        3.3 TEM analysis
    4 Conclusions
    Acknowledgements 
    References

• Sang Min Lee(School of Materials Science and Engineering, Kumoh National Institute of Technology)
• Jae Ho Lee(School of Materials Science and Engineering, Kumoh National Institute of Technology)
• Gibeop Nam(Advanced Material Research Center (AMRC), School of Materials Science and Engineering, Kumoh NationalInstitute of Technology)
• Suk Hwan Kim(School of Materials Science and Engineering, Kumoh National Institute of Technology)
• Jongbok Kim(School of Materials Science and Engineering, Kumoh National Institute of Technology)
• Jae Seung Roh(School of Materials Science and Engineering, Kumoh National Institute of Technology)