Method of processing materials using an inductively coupled plasma

Claim 1

A method of making fine powder in a gas-free environment using an electrically conductive ceramic or metal starting material which is initially in solid form comprising: a. providing inductively coupled plasma apparatus comprising: (1) an electrical induction coil having a central longitudinal axis; (2) a dielectric tubular enclosure centered coaxially on said axis and located inside said coil; (3) a segmented metal radiation shield which is grounded and centered coaxially on said axis inside said enclosure, said shield consisting of a plurality of elongate fluid-cooled metal shield segments extending parallel to said axis, said segments being disposed in a circular arrangement adjacent the interior surface of said enclosure and being substantially equally spaced apart circumferentially such that said shield has a generally tubular configuration, and said shield segments being shaped in cross section so as to occlude line-of-sight transmission of light through said radiation shield; and (4) an outlet for material processed in said plasma apparatus; b. placing said starting material within said radiation shield; c. evacuating said tubular enclosure; d. heating said starting material by use of said induction coil to vaporize said starting material and to form a plasma from the resulting vapor; and e. utilizing a powder collection surface adjacent to said outlet of said plasma apparatus to collect material emanating from said outlet.

Claim 2

A method of making fine powder in a gas-free environment using an electrically conductive ceramic or metal starting material which is initially in solid form comprising: a. providing inductively coupled plasma apparatus comprising: (1) an electrical induction coil having a central longitudinal axis; (2) a dielectric tubular enclosure centered coaxially on said axis and located inside said coil; (3) a segmented metal radiation shield which is grounded and centered coaxially on said axis inside said enclosure, said shield consisting of a plurality of elongate fluid-cooled metal shield segments extending parallel to said axis, said segments being disposed in a circular arrangement adjacent the interior surface of said enclosure and being substantially equally spaced apart circumferentially such that said shield has a generally tubular configuration, and said shield segments being shaped in cross section so as to occlude line-of-sight transmission of light through said radiation shield; and (4) an outlet for material processed in said plasma apparatus; b. placing said starting material within said radiation shield; c. evacuating said tubular enclosure; d. heating said starting material by use of said induction coil to vaporize said starting material and to form a plasma from the resulting vapor; and e. utilizing a powder collection surface adjacent to said outlet of said plasma apparatus to collect material emanating from said outlet.