In the present study, a coal-based pitch containing 12.1% quinoline insoluble (QI) underwent isothermal heat treatment, and changes in the mesophase microstructure were analyzed for the heat treatment duration. The nuclei creation and growth rate of mesophase were affected by the distribution of QI particles in the pitch. The growth process could be explained in four regions through the mesophase area fraction. During the carbonization of carbon blocks, mesophase formation was induced in the binder phase. The physical properties of carbon blocks were measured as a function of residence time. As residence time increased, bulk density decreased and porosity increased, but electrical conductivity increased. It was determined that forming a mesophase in the binder phase during carbonization reduced the size of large pores in carbon block and improved the connectivity between particles, thereby increasing electrical conductivity. These results are expected to show greater improvement in electrical properties after graphitization.

Effect of mesophase formation from quinoline insoluble-containing coal tar pitch on physical properties of carbon blocks
    Abstract
    1 Introduction
    2 Experimental procedures
        2.1 Raw materials and isothermal heat treatment
        2.2 Microstructural analysis
        2.3 Fabrication of carbon block
        2.4 Properties analysis of carbon block
    3 Results and discussion
        3.1 TGA analysis
        3.2 Microstructural analysis
        3.3 Microstructural growth stage according to mesophase fraction variation
        3.4 Properties of carbon blocks
    4 Conclusions
    Acknowledgements 
    References

• Jung‑Jin Kim(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea)
• Sang‑Hye Lee(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea)
• U‑Sang Youn(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea)
• Sun‑Ung Gwon(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea)
• Tae‑Sub Byun(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea)
• Jae‑Seung Roh(School of Materials Science and Engineering, Kumoh National Institute of Technology, Daehak‑ro 61, Gumi, South Korea) Corresponding author