Magnesium Oxide Powder Synthesis in Cathodic Arc Discharge Plasma in an Argon Environment at Atmospheric Pressure

Abstract

Discharges with cathode spots can operate in a wide range of gas pressures. Erosion of the cathode material is an inherent property of such discharges. The erosion products are considered to be ionized atoms and electrically neutral microdroplets. In accordance with this concept, a plasma source based on a pulsed cathodic arc discharge in atmospheric-pressure argon with a current of up to 200 A, a pulse duration of 250 μs, and a pulse repetition rate of 10 Hz was implemented. Using this source, the synthesis of magnesium oxide powder was performed. The chemical composition of the erosion products was determined using the TEM/EDS method and the composition of the gas mixture in which the discharge system operated was evaluated by optical spectrometry. It was shown that particles of the synthesized powder have different morphological features, depending on the nature of the electrical erosion of the cathode material. Micron-sized particles are formed due to the removal of microdroplets from liquid–metal craters on the cathode surface at certain plasma pressures. Submicron particles are produced during the agglomeration of atoms originating from the plasma jets flowing out from cathode spots. These atoms are magnesium ions that are neutralized by collisions with gas particles. The advantages and disadvantages of this synthesis method are discussed in this paper. The reference methods for the powder synthesis of magnesium oxide are compared. The prospects of the studied method from the point of view of its application for obtaining ceramic materials are also evaluated.

Keywords

• magnesium oxide
• nanopowder
• ceramic parts
• atmospheric-pressure discharge
• plasma source
• cathode