Evaporation of zirconia in an inductively coupled plasma

An inductively coupled plasma was studied to assess the feasibility of plasma flash evaporation of high-melting materials. The evaporation time of zirconia particles in a thermal plasma of 10,000 K was estimated to be 90 and 560 mu s for spherical particles with radii of 5 and 12.5 mu m, respectively. An inductively coupled argon-hydrogen plasma was generated with a power of 30 kW at a frequency of 4 MHz. Its temperature as inferred from intensity ratios of spectral lines of singly ionised Zr amounted to between 7000 and 8600 K, depending on pressure, thus allowing for the existence of zirconia vapour. By laser light scattering it was shown that zirconia particles with a maximum diameter of 12 mu m could be vaporised at a rate of at least 200 mg/min, if the hydrogen fraction of the argon-hydrogen plasma was sufficiently high.