Nanowerk August 14, 2023
High-temperature flames can be difficult to control how it interacts with the material being processed. An international team of researchers (USA – Iowa State University, North Carolina State University, Ames National Laboratory, Canada) developed a technique that utilizes a molecule-thin protective layer to control how the flame’s heat interacts with the material allowing users to finely tune the characteristics of the processed material. They pyrolyzed alkysilanes grafted onto cellulose fibers into non-flammable SiO2 terminating surface ignition propagation, hence stalling flame propagating. Sustaining high temperatures, however, triggered gnition in the bulk of the fibers but under restricted gas flow resulted in significantly low rate of ignition propagation and pyrolysis compared to open flame. This could lead 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) inhibited pyrolysis leading to tunable wall thickness. They applied this approach to create magnetic, paramagnetic, or oxide containing carbon fibers. They illustrated fabrication of nm- and μm-diameter tubes from appropriately sized fibers… read more. TECHNICAL ARTICLE
