International Journal of Electrical and Computer Engineering (IJECE) Vol. 13, No. 4, August 2023, pp. 3695~3705 ISSN: 2088-8708, DOI: 10.11591/ijece.v13i4.pp3695-3705  3695 Journal homepage: http://ijece.iaescore.com Numerical analysis in Ar-H2 coupled-coil inductively coupled thermal plasma with Si feedstock for stable operation Yulianta Siregar 1 , Yasunori Tanaka 2 1 Department of Electrical Engineering, Universitas Sumatera Utara, Medan, Indonesia 2 Faculty of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa, Japan Article Info ABSTRACT Article history: Received Sep 20, 2022 Revised Dec 12, 2022 Accepted Dec 17, 2022 In nanopowder synthesis, the starting powder to be evaporated is infused in a plasma torch through the upper coil and the lower coil in the coupled model of inductively coupled thermal plasma (coupled-coil inductively coupled thermal plasma (ICTP)). Mixing these evaporated materials to form the coupled ICTP significantly influences the thermodynamic and transport properties. It is essential to understand these complex interactions between coupled ICTP and feedstock evaporation. This research investigated the thermal interactions between silicon raw material powder (Si) with ICTP in coupled 99%Ar/1%H2 through the numerical model developed for the synthesis of Si nanopowder. The feed rate of the Si raw material was set at 0.05, 0.1, and 0.5 g/min. This implies that the increased Si feed is too heavy to vaporize all the injected feed. Keywords: Ar-H2 Coupled coil Inductively coupled thermal plasma Nanoparticle synthesis This is an open access article under the CC BY-SA license. Corresponding Author: Yulianta Siregar Department of Electrical Engineering, Faculty of Engineering, Universitas Sumatera Utara St. Dr. T. Mansur No. 9, Medan City, Sumatera Utara Province, Indonesia Email: julianta_srg@usu.ac.id 1. INTRODUCTION Inductively coupled thermal plasma (ICTP) at high power and high pressure is commonly used as a heat resource and a chemical resource in material handling. Examples are thermal barrier spray coating [1], [2], transparent conductive oxide deposition [3], diamond film deposition [4], [5], and surface transformation [6]. The advantage of ICTP in preparing this material is that ICTP has a high density and high enthalpy of chemical species with a gas temperature of about 10,000 K. In addition, ICTP does not require electrode removal. It can offer clean thermal plasma without any contamination measure for this benefit. The synthesis of nanomaterials is one of the important applications of ICTP, such as nanotubes [7], [8], nanoparticles [9]–[14], fullerenes [15], [16]. In these examples, the ICTP process is generally used by a one coil ICTP close to the plasma torch. Synthesis of nanomaterials in plasma torch, the raw material powder is infusion to be evaporated in ICTP with the high-temperature field. Mix this evaporated material into the cooled ICTP to nucleate and synthesize the nanomaterials. Meanwhile, its effect on the thermodynamic properties and the main plasma transport properties causes changes in temperature and gas flow field and the evaporation rate of raw materials at ICTP. During this treatment, ICTP has a large infusion of raw material powder and causes instability with disruptive effects. In surprising cases, ICTP can be restrained by too heavy an infusion of raw material powder. The solution to this problem, a coupled coil model of inductively coupled thermal plasma (coupled coil-ICTP), has been developed. The coupled coil-ICTP has two different coils in a dielectric cylindrical tube. Research conducted by Siregar et al. [17] on coupled coil-ICTP for injecting raw material powder and