PRESSURE CONTROLLED DROPLET SPRAYING (PCDS) METHOD FOR FORMING PARTICLES OF COMPOUND MATERIALS FROM MELTS
A method and apparatus of forming compositionally homogeneous particles is provided. The method includes forming a homogenous melt from a plurality of constituent materials under a first pressure sufficient to prevent substantial vaporization of the constituent materials. Droplets are generated from the homogenous melt. The droplets are cooled under a second pressure sufficient to prevent substantial vaporization of the constituent materials at least until the homogeneous particles formed therefrom have stabilized.
1 . A method of forming compositionally homogeneous particles, comprising:
(i) forming a homogenous melt from a plurality of constituent materials under a first pressure sufficient to prevent substantial vaporization of the constituent materials;
(ii) generating droplets from the homogenous melt; and
(iii) cooling droplets under a second pressure sufficient to prevent substantial vaporization of the constituent materials at least until the homogeneous particles formed therefrom have stabilized.
2 . The method of claim 1 wherein the homogenous particles comprise nanoparticles.
3 . The method of claim 1 wherein the homogenous melt is formed above its liquidus temperature.
4 . The method of claim 1 wherein the first pressure arises from an inert gas.
5 . The method of claim 1 wherein the second pressure arises from an inert gas.
6 . The method of claim 1 wherein the second pressure arises from a reactive gas.
7 . The method of claim 1 wherein generating the droplets further comprises mixing the homogenous melt with a high pressure inert gas stream while maintaining the homogeneous melt at an elevated temperature at least until the droplets are formed.
8 . The method of claim 1 wherein generating the droplets is performed using a spray nozzle.
9 . The method of claim 1 wherein steps (i), (ii) and (iii) are performed in a melting vessel, droplet generation vehicle and particle generation vehicle, respectively.
10 . The method of claim 9 further comprising controlling and monitoring temperature in the melting vessel, droplet generation vehicle, or the particle generation vehicle.
11 . The method of claim 9 further comprising controlling and monitoring temperature in the melting vessel, droplet generation vehicle and the particle generation vehicle.
12 . The method of claim 9 further comprising controlling and monitoring pressure in the melting vessel, droplet generation vehicle, or the particle generation vehicle.
13 . The method of claim 9 further comprising controlling and monitoring pressure in the melting vessel, droplet generation vehicle and the particle generation vehicle.
14 . The method of claim 9 further comprising controlling and monitoring gas composition in the melting vessel, droplet generation vehicle, or the particle generation vehicle.
15 . The method of claim 9 further comprising controlling and monitoring gas composition in the melting vessel, droplet generation vehicle and the particle generation vehicle.
16 . The method of claim 1 wherein the homogeneous melt is formed from a solid body that is melted in a droplet generation vehicle that generates the droplets.
17 . The method of claim 9 further comprising siphoning the homogenous melt from the melting vessel to the droplet generation vehicle.
18 . The method of claim 9 further comprising transporting the homogenous melt from the melting vessel to the droplet generation vehicle by a gravitational feed extending from the melting vessel.
19 . The method of claim 9 further comprising transporting the homogenous melt from the melting vessel to the droplet generation vehicle by a pressurized feed extending from the melting vessel.
20 . A method of forming compositionally homogeneous layers, comprising:
forming a homogenous melt from a plurality of constituent materials under a first pressure sufficient to prevent substantial vaporization of the constituent materials;
generating droplets from the homogenous melt; and
applying the droplets to a substrate under a second pressure sufficient to prevent substantial vaporization of the constituent materials so that a homogenous layer is formed upon cooling.
21 . The method of claim 20 further comprising applying the droplets to the substrate under the second pressure so that a plurality of homogenous layers is formed.
22 . The method of claim 21 wherein the plurality of homogenous layers forms a preform structure.