Spherulites and phase separation in plasma-dissociated zircon

Plasma dissociation of zircon with concurrent in-flight removal of silica

“…7 shows the EDS spectrum of dissociated zircon without carbon at 25 kW. The spherulitic growth pattern of zirconia crystals observed in the silica glass matrix agrees well with previously reported plasma dissociated zircon microstructures [6][7][8][9][10][11][12]. Silica was present in the amorphous phase due to the high quench rate and could not be detected by XRD.…”

“…For more than a half century, numerous efforts have been made throughout the globe to reduce the operating cost and to enhance the dissociation efficiency by means of designing novel plasma torches, thermal plasma assisted high temperature furnaces and different combination of plasma forming gases, etc. [6][7][8][9][10][11][12][13]. Preliminary experimental investigations by Yugeswaran et al showed that replacing expensive argon by air as the plasma gas resulted in substantial cost savings.…”

Microstructural and analytical analysis of plasma dissociated zircon

“…Figure 2 shows a PDZ particle consisting entirely of zirconia spherulites in a silica matrix. Spherulites are non-crystallographic branching arms that extend in all directions [7]. The observed morphologies has been previously described, [7,8], and will be discussed.…”

“…Spherulites are non-crystallographic branching arms that extend in all directions [7]. The observed morphologies has been previously described, [7,8], and will be discussed. According to the phase diagram of the ZrO 2 -SiO 2 system based on the work of Butterman and Foster [9], the zirconia which has dissociated out of the zircon will be stable in the tetragonal or cubic crystal structure.…”

“…The ZrO 2 -SiO 2 phase diagram from McPherson and Shafer [7] shows that molten zircon could enter the miscibility gap if cooled rapidly to inhibit the formation of zirconia crystals. In this gap the zircon separates into a zirconia rich and silica rich liquid.…”