Surface engineering of carbon fiber via upcycling of waste gases generated during carbon fiber production: A sustainable approach towards high-performance composites

Carbon fiber (CF) prevails as a cutting-edge material, however, considerable waste gases produced in its production place a tremendous burden on the industry and environment. Our previous study proposed a “two-birds-one-stone” strategy to simultaneously convert the gaseous effluents into carbon nanotubes (CNT) and produce multifunctional CNT@CF materials. However, the challenges in the management of iron nanocatalysts and the containment of side effects on the performance of CF composites have significantly affected the scalability of this technique. In the present work, we developed a further comprehensive understanding of cobalt and nickel-based metallic CFs as new catalysts to obtain more controlled and effective catalytic properties and subsequently extend the better performance of CF composite. In-situ capture and solidification of gases generated from the carbonization step of CF production process created more novel CNTs in the tip- and base-growth model. The CNTs with tip-growth model exhibited a better enhancement effect than the base-growth model on the interfacial properties of composites with up to 57% and 54% improvement in interfacial and inter-laminar shear strength, respectively. Moreover, new insights regarding the evolution mechanism of CNTs were provided through qualitative and quantitative analysis of the gas emissions reduction and recycling efficiency, supported by density functional theory. In this work, more available practical parameters governing the catalytic properties of metallic CF provide additional efficiency of gas waste recovery, diversity of CNTs, and potential for emerging applications, which delivers a more comprehensive guarantee for the implementation of this technology on the CF production line in the next step.