Study on the Motion and Heating Behavior of Powder Particles in Radio Frequency Plasma

The study investigated the transient heating and melting behaviors of ceramic powder (cerium dioxide, CeO2) under considering thermal resistance effect in radio frequency (RF) thermal plasma using a three-dimensional plasma particle heating model. The melting behavior of particles with different sizes, different trajectories and the time interval of the particles under thermal resistance effect was analyzed respectively. Furthermore, a dimensionless parameter Biot number is used to characterize the thermal resistance effect of the in-flight particles heating. The results indicate the Biot number is close to or larger than 0.1 in the plasma system, the effect of thermal resistance must be taken into account. This behavior was particularly prominent in the heating process for larger particles, where the Biot number approached 0.1 and the melting time interval is prolonged. Under the thermal resistance effect, the temperature difference of surface and center of particle is more significant for particles with an initial size larger than $30 \mu \mathrm{m}$. Additionally, the particle trajectory is a key factor for the particle heating process which relate to the local temperature surrounding the particle and the surface heat transfer coefficient of the particle. The results could provide a further understanding on particle heating in plasma powder spheroidization and plasma spraying process.