2023 article

Spatially Directed Pyrolysis via Thermally Morphing Surface Adducts

Du, C., Gregory, P., Jamadgni, D. U., Pauls, A. M., Chang, J. J., Dorn, R. W., … Thuo, M. (2023, August 9). ANGEWANDTE CHEMIE-INTERNATIONAL EDITION.

By: C. Du*, P. Gregory*, D. Jamadgni n, A. Pauls n, J. Chang n, R. Dorn*, A. Martin n, E. Foster*, A. Rossini*, M. Thuo n

co-author countries: Canada 🇨🇦 United States of America 🇺🇸
author keywords: Carbon Tubes; Morphing Surfaces; Surface Reactions; Thermal Degradation; Directed Pyrolysis
Source: Web Of Science
Added: August 21, 2023

Combustion is often difficult to spatially direct or tune associated kinetics-hence a run-away reaction. Coupling pyrolytic chemical transformation to mass transport and reaction rates (Damköhler number), however, we spatially directed ignition with concomitant switch from combustion to pyrolysis (low oxidant). A 'surface-then-core' order in ignition, with concomitant change in burning rate,is therefore established. Herein, alkysilanes grafted onto cellulose fibers are pyrolyzed into non-flammable SiO2 terminating surface ignition propagation, hence stalling flame propagating. Sustaining high temperatures, however, triggers ignition in the bulk of the fibers but under restricted gas flow (oxidant and/or waste) hence significantly low rate of ignition propagation and pyrolysis compared to open flame (Liñán's equation). This leads to inside-out thermal degradation and, with felicitous choice of conditions, formation of graphitic tubes. Given the temperature dependence, imbibing fibers with an exothermically oxidizing synthon (MnCl2 ) or a heat sink (KCl) abets or inhibits pyrolysis leading to tuneable wall thickness. We apply this approach to create magnetic, paramagnetic, or oxide containing carbon fibers. Given the surface sensitivity, we illustrate fabrication of nm- and μm-diameter tubes from appropriately sized fibers.