Apparatus and method for powder spheroidisation by microwave-induced plasma

A method to make spheroids from a powder precursor by a microwave-induced plasma, comprising the step of forming a plasma torch in a plasma tube by coupling a process gas flow with a microwave radiation, and further comprising the steps of:

• carrying the powder precursor into the plasma torch by means of the process gas acting as a carrier gas, in order to make spheroids from the powder precursor by in-flight melting;
• and
• cooling the plasma tube from outside by injecting compressed air into a microwave cavity that surrounds the plasma tube.

An apparatus for powder spheroidisation by microwave-induced plasma, comprising a microwave generator, a microwave cavity, a waveguide connecting the microwave generator to the microwave cavity, a plasma tube partially located in the microwave cavity, a powder supply connected to the plasma tube to feed a powder precursor flow thereinto, a gas supply connected to the plasma tube to feed a process gas flow thereinto, in order to form a plasma torch in the plasma tube by coupling the process gas flow with a microwave radiation, a compressed air supply, and a waveguide short circuit connected to the microwave cavity, the waveguide short circuit comprising at least one opening for the compressed air so that the compressed air can cool the plasma tube from outside, the gas supply being connected to the powder supply to let the process gas carry the powder precursor into the plasma tube, and so into the plasma torch in order to make spheroids from the powder precursor by in-flight melting.