In-flight diagnostics of thermal treatment of powders in induction plasmas

In-flight measurements of principal particle parameters of size, velocity and temperature are made for nickel powders with mean diameter of 76 μm processed in a 3-MHz inductively coupled r.f. plasma torch. The diagnostic technique used for the simultaneous measurement of the three particle parameters is based on the real time observation of a particle through its own emission of Plank's radiation. Measurements are carried out in the plasma plume, at a distance of 340 mm downstream from the point of injection of the powder for different plasma power and pressure conditions of 10, 20 kW and 170, 340 torr, respectively. Cross-correlation analysis between the measured particle parameters shows the particle under plasma processing has higher surface temperature when its size is small and velocity is low