EFFECT OF THE HEATING RATE ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CARBON FIBERS DURING PRE-CARBONIZATION

摘要

In recent decades, carbon fibers (CFs) have been widely used as reinforcement in high-performance composite because of its preeminent mechanical strength, low density and thermo and chemical stability. They are prepared from polyacrylonitrile (PAN) precursor fibers through the thermal treatments of stabilization and carbonization. Carbonization is carried out in an inert atmosphere at the highest heating temperature of 1000~1600°C, during which non-carbon elements are driven off and weight of fibers lose largely and at last stabilized fibers of high molecular weight polymer become inorganic carbonaceous fibrous materials of high performance [1]. Modern carbonization practice is to pass stabilized fibers through an increasing temperature profile giving a total residence time of only a few minutes .To avoid thermal shock of fibers, low temperature heat treatment carbonization, which is called pre-carbonization process. In this work, the thermal chemical reaction, evolution of microstructure and defects of thermal stabilized polyacrylonitrile (PAN) fibers during pre-carbonization (400~800°C) were investigated by XRD and NMR. It focused on the effects of heating rate of the pre-carbonization on the morphological structure and mechanical properties of carbon fibers.