Jungho Song’s research while affiliated with University of Seoul and other places

Aerosol processing is gaining much interest in fabricating particles for various applications due to its easy application and good control of particle characteristics. In this study, spherical alumina particles were prepared using a transferred arc plasma aerosol system with argon shield gas and nitrogen carrier gas. The operating conditions for spheroidization were controlled by comparing the particle heating and particle residence times in plasma to obtain the calculated critical particle size. Nitrogen fractions (10%–63%) and plasma powers (1–2.5 kW) were used as control parameters to verify the process design for the average injected particle sizes of 10 μm and 100 μm. The spherical particle sizes were examined by using field-emission scanning electron microscopy. Results showed that the particle size limits for melting(dP,LM) and vaporization(dP,LV) increased with increasing plasma power. Higher plasma power is required to fabricate spherical shapes from larger injected particles at nitrogen fractions of 10% and 63% because of the longer residence time needed to reach the melting state of the raw materials.

Control of the particle size distribution of fabricated alumina nanoparticles from general alumina powder with a large geometric standard deviation (GSD) was studied. A thermophoretic separator was used to control the GSD of the nanoparticles, and unevaporated and primary particles were separated to yield a small GSD. The fabricated nanoparticles were characterized by field emission scanning electron microscopy (FESEM) and a scanning mobility particle sizer (SMPS). We confirmed that the GSD of the nanoparticles was controlled by the thermophoretic separator. A temperature difference between 79 K and 151 K was applied to the thermophoretic separator for control of the nanoparticle GSD. The GSD of the fabricated alumina nanoparticles was improved from 1.74 to 1.44.

The nanoparticle production process in a transferred arc plasma system was studied. The plasma temperature, particle heating time, and particle residence time in plasma were calculated using heat and mass balance with a lumped capacitance method. We analyzed the nanoparticle production characteristics based on different operating conditions by comparing the particle vaporization time with the particle residence time in the plasma. The limit size for particle vaporization was derived. With higher plasma power, the nanoparticle production rate increased and the energy consumption rate decreased. It was confirmed that the energy consumption rate reaches an optimal point according to the plasma power. Experiments to determine the nanoparticle production rate according to plasma power were also conducted and the experimental data were compared with numerical values. The results show that the error rate between the numerical values and experimental data was approximately ±18%. Therefore, the developed model which was studied could be useful for designing nanoparticle production process using a transferred arc plasma system because of its simple approach.