Graphene-Reinforced Polymer Derived Ceramic Carbon Fibers

Over the past few decades, there has been a rising demand for new structural aerospace materials with lightweight than single crystals (current generation high temperature material), high strength and modulus (at elevated temperatures), and high thermal stability. The desire has motivated the advance of materials science in high temperature applications. Non-oxide ceramic matrix composites (CMCs) are promising for this application, due to the low density (than metals), remarkable mechanical strength and chemical resistance (at high temperatures) as well as elevated fracture toughness by fiber reinforcement. The microporous and micro-cracked ceramic matrices allow several times higher strainto-failure than monolithic ceramics, which enabled it as one of the optimum structural materials at high temperature, while reinforcement contribution is mainly towards properties such as toughness, electrical conductivity, hardness, thermal expansion, and shock resistance.

Ever since the invention of the polymer-derived ceramic fibers (PDCFs) by Yajima et al in early 1970s, they have been considered as an admirable reinforcement for CMCs due to their improved properties and ease of fabrication. Since polymer-derived ceramic route requires the modeling or shaping of polymer stages, therefore, recent innovations in the polymer fiber fabrication techniques may also be applied to the fabrication of PDCFs. Over the last four decades, silicon-based advanced ceramics with a variety of desirable physical and chemical properties, such as remarkable chemical resistance to the oxidation environment, thermal stability, and mechanical strength at high temperatures, have been designed with the help of straightforward polymer-to-ceramic conversion techniques. The mechanical properties of PDCFs have been reported as high as 2.5 GPa in tensile strength with 300 GPa in modulus that is stable up to 2200°C.

Here, graphene-rich PDC fibers were synthesized via hand-drawing and polymer pyrolysis of a hybrid precursor of graphene oxide, Organosilicon polymer, and poly-acrylic acid (PAA). The introduction of graphene to PAA minimizes the defects and improve the mechanical strength, while PAA improves the spinnability of Organosilicon polymer. Investigations on the structural and compositional development of the fibers are conducted via Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR) and thermo-gravimetric analysis (TGA) to determine the characteristics of the fibers, such as, spinnability of the preceramic precursor slurry, “free carbon” and graphene content after pyrolysis, cross-linking and pyrolysis behavior of the fibers, the effect of incorporation of graphene to the ceramic system, the chemical evolution of the fabricated fibers, and the fiber morphology of the fibers at each production stages.