The Soret effect in laser chemical vapor-deposited carbon fibers

Laser chemical vapor deposition (LCVD) is the process by which free standing fibers additively deposit from the gas-to-solid phase under a laser focal point. In this letter, we address how the mixing of disparate molecular weight precursors facilitate changes in the growth and fiber structure using the Soret effect. The Soret effect causes lighter particles to migrate to warmer regions and heavier particles to migrate to cooler regions in a reaction. Using ethylene mixed with helium, the reaction rate, temperature, activation energy, and morphology for a series of carbon fibers are compared. It was found that the onset of the Soret effect bypasses specific growth regimes, reduces the extent of graphitization, and creates morphological variations within the carbon fiber core. These results highlight the potential use of the Soret effect as a means for tailoring LCVD fiber processing.