[20a-E317-1~9] 9.2 Nanoparticles, Nanowires and Nanosheets

▲ [20a-E317-4] Oxidization of Molybdenum Nanoparticles in Mixed Gases at a Constant Oxygen Partial Pressure by Pulsed Wire Discharge

〇(M2)Ngo Minh Chu¹, Nguyen Duy Hieu¹, Thi Mai Dung Do¹, Tadachika Nakayama¹, Koichi Niihara¹ (1.Extreme Energy-Density Research Institute, Nagaoka University of Technology)

Keywords:Molybdenum oxides, Nanoparticles, Pulsed wire discharge

Molybdenum is a transition metal with a very high melting point and very low thermal expansion. Mo and its compounds have many applications in coatings, electronic devices, optical devices, and being used for radioactive application in the synthesis of ⁹⁹Mo from MoO₃ to fabricate technetium (Tc). To study deeply about this material, MoC has been synthesized successfully by using pulsed wire discharge (PWD) method in mixture gases of argon and kerosene. In this research, with the purpose of understanding how Mo oxides are formed in PWD. Some experiments have been carried out, where Mo wire of 0.25 mm in diameter with 25 mm in length was used. The experiments were implemented in oxygen partial pressure of 25 kPa, and different total pressures were applied by adding nitrogen gas; the charged voltage for the capacitors of PWD was constant, 6 kV. X-ray diffraction (XRD) measurements were used to identify phases in the samples. The different results were observed by changing total pressure. With only 25 kPa of oxygen gas, entire Mo was oxidized completely. However, when keeping the same partial pressure of O₂ and increasing total pressure by adding N₂, the Mo volume fraction increased. To observe the samples, field emission scanning electron microscopy (FE-SEM) was used, and particle size distribution was calculated in each condition by FE-SEM images. From the voltage and current waveforms, the formation of β- and α-MoO₃ phases have been explained by the cooling speed of Mo vapor/plasma.