Recent development of new inductively coupled thermal plasmas for materials processing

Abstract

This paper explains recent developments in the field of inductively coupled thermal plasmas (ICTP or ITP) used for materials processing. Inductive coupling technique is important to produce thermal plasma with high gas temperature at high pressures. Conventional cylindrical ICTP was developed originally in the 1960s by T. Reed. It remains widely used for different materials processing today, with almost identical configuration to the original version. Through some revision and improved functionalization, ICTPs of several kinds such as DC-RF hybrid ICTP have also been developed. They are also widely adopted for processing of various materials because of their various benefits. Inductively coupled plasma at low pressures are not treated herein: only thermal plasma with high enthalpy. One is modulated induction thermal plasma (MITP), which has a function of controlling the temperature and chemical active fields in the time domain. Another development in ICTP includes changes in the ICTP configuration such as a planar-ICTP and loop-ICTP. These were developed for large-area materials processing.

Numerical study of nanoparticle formation in two-coil tandem-type modulated induction thermal plasmas with simultaneous modulation of upper- and lower-coil currents

“…For synthesis of numerous NPs, we first developed the PMITP + TCFF method [42]. The PMITP is sustained by the coil current amplitude-modulated into a rectangular waveform.…”

“…Furthermore, we developed two-coil tandem type MITP for NPs [25,26,28,42]. Tandem MITP consists of twoindependent coils surrounding one plasma torch.…”

“…The frequencies of the upper-coil current and lower-coil current were set respectively to 430 and 300 kHz. These frequencies of the upper-coil and the lowercoil currents were determined experimentally and theoretically to reduce mutual inductive coupling between the two coils [25,26,28,42]. Both coil currents were modulated into rectangular waveforms with the time-averaged power of 10 kW under modulation condition.…”

“…The modulation cycle of the coil current was set at 20 ms with on-time of 10 ms and off-time of 10 ms. This modulation cycle was used because the current modulation in 10 ms order can perturb the temperature and gas flow fields in the ICTP [42]. The SCLs for upper-coil and lower-coil currents were set to (i) 100%SCL upper -100%SCL lower , (ii)100%SCL upper -0%SCL lower , and (iii) 70%SCL upper -0%SCL upper .…”

Combined simulation of micro and nanoparticles in RF inductively coupled plasma torches with the variations of metallic species and feeding nozzle location

“…Although RF-ICP torches do not have contamination by electrodes, a drastic increase in the electrical conductivity can occur due to the metallic species. 33) Therefore, the electrical conductivity is fitted as below where fitting s is the fitted electrical conductivity as a function of the temperature below 9000 K, and general s is the electrical conductivity without consideration of metallic vapor contamination. 34) The major effect of metallic vapor contamination is the increased electrical conductivity at a temperature lower than 9000 K. 22) Therefore, other effects of metallic vapor are ignored in this study.…”