Investigation of Microstructural Evolution in Needle Cokes during Heat Treatment by Synchrotron Radiation SAXS and WAXS

Needle coke is a porous carbon material that is easy to graphitize. Its porous and microcrystalline structure has an important influence on its macroscopic properties. In this study, coal-based and petroleum-based needle cokes were subjected to high-temperature heat treatment (ranging from 500 to 2800 °C). Synchrotron radiation small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) techniques were employed to analyze needle coke samples’ pore and microcrystalline structures at various heat treatment temperatures. The results demonstrated that the SAXS and WAXS scattering patterns of needle coke exhibited isotropic characteristics. The high-temperature heat treatment of needle coke can be categorized into two distinct stages: calcination (500 °C–1200 °C) and graphitization (1200 °C–2800 °C). During these stages, significant changes were observed in specific surface area, porosity, pore distribution, and microcrystal size. The variations of the electrical conductivity of the two types of needle coke with the heat treatment temperature were also studied. This study reveals the microstructure changes of needle coke during high-temperature heat treatment and provides a reference for regulating the pore and microcrystalline structure.