After obtaining the precursor fiber, the next step is to stabilize it. The intermediate step regulates the quality of carbon fibers. Additionally, the carbon fiber yield should be ascertained . During stabilization, precursor fibers are mostly heated to 200-300°C in air. The main purpose of this process is to crosslink lignin macromolecules and prepare a structure that can prevent fiber melting during carbonization at higher temperatures . The fibers can be damaged if the stabilization process is too harsh . The stabilization conditions significantly influence the properties of stabilized lignin fibers, particularly their chemical, structural, and mechanical properties . Understanding the structural and chemical alterations that take place during stabilization can be challenging because the thermal stability of precursor fibers is determined by the composition and nature of the monomers, and the stabilization process is not uniform during the diffusion and reaction of oxygen .