Synthesis of Nanomaterials—From Nanoparticles to Low-Dimensional Structures Using Thermal Plasma

Thermal plasma is an extremely high-temperature fluid exceeding 10,000K, consisting of electrons and heavy particles such as ions and neutral atoms. Approximately 5-10% of the plasma-forming gas molecules are ionized, producing highly reactive chemical species such as radicals. In addition, due to the steep temperature gradient from the core of the highest temperature region to the tail of the plasma jet, it provides a high-enthalpy medium with a quenching rate of 10⁴-10⁶ K/s. It allows to occur for thermodynamically non-equilibrium or high activation energy chemical reactions. These extreme conditions enable the synthesis of unique nanomaterials that cannot be produced in typical low-temperature or slow-reaction environments.<br/>Among various nanomaterials, thermal plasma is particularly advantageous for synthesizing nitrides, borides, carbides, and their composites. Not only can they have unique chemical compositions, but they can also form unique structures, such as nanotubes(e.g. Carbon nanotubes and Boron nitride nanotubes) as low-dimensional nanomaterials and nanocomposites with dispersed cores that are completely different from traditional core-shell structures. Thermal plasma is generally categorized by power sources, DC(Direct current) and RF(Radio frequency). We primarily utilize thermal plasma with a DC power source to maximize the quenching rate and miniaturize the synthesis volume. This presentation aims to review the current state of nanomaterial synthesis and production using thermal plasma by sharing research results in synthesizing various nanomaterials. Additionally, it will suggest the limitations required to be overcome for further commercialization or improved TRL.