Pressure controlled droplet spraying (PCDS) method for forming particles of compound materials from melts

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is related to commonly assigned, co-pending U.S. patent application Ser. No. 12 / 185,369, entitled “A Reacted Particle Deposition (RPD) Method for Forming a Compound Semi-Conductor Thin-film, filed Aug. 4, 2008, which is incorporated by reference herein in its entirety.FIELD OF INVENTION[0002]The present invention relates to a method of forming particles, including nanoparticles, of compound materials with controlled composition.BACKGROUND OF THE INVENTION[0003]The formation and properties of nanoparticles are areas of intense scientific research, having a wide variety of potential applications in biomedical, optical, electronic and structural material fields. Particles, with dimensions between 1-100 nanometers (nm) are typically identified as nanoparticles. The properties of nanoparticles fall in the range between those of bulk materials and atomic or molecular structures. While a bulk material typically exhibits constant ...

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for forming compositionally homogeneous particles. The method involves forming a homogeneous 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 homogeneous melt and cooled under a second pressure sufficient to prevent substantial vaporization of the constituent materials until the homogeneous particles formed have stabilized. The homogeneous particles may comprise nanoparticles. The first pressure may arise from an inert gas, while the second pressure may arise from an inert gas or a reactive gas. The generating and cooling steps may be performed in a melting vessel, droplet generation vehicle, and particle generation vehicle, respectively. The temperature and pressure may be controlled and monitored in the melting vessel, droplet generation vehicle, and the particle generation vehicle. The gas composition may be controlled and monitored in the melting vessel, droplet generation vehicle, and the particle generation vehicle. The homogeneous melt may be formed from a solid body that is melted in a droplet generation vehicle that generates the droplets. The homogeneous melt may be transported from the melting vessel to the droplet generation vehicle by a gravitational feed, a pressurized feed, or a combination of both. The method may also involve applying the droplets to a substrate under a second pressure sufficient to prevent substantial vaporization of the constituent materials so that a homogeneous layer is formed. The plurality of homogeneous layers may form a preform structure.

Problems solved by technology

Ball-milling is sometimes considered a “dirty” process because of a potential for contamination from the ball-milling components and processes.

For given manufacturing objectives, including cost or rate of production, the processing time required to achieve very small nanoparticles may become restrictive.

Addressable compositions are restricted by the availability of suitable precursor materials.

A common limitation of the flame pyrolysis, plasma spraying and gas aggregation methods for nanoparticle formation is a difficulty in achieving compositional control which precludes the possibility of appropriately processing of compound nanoparticles which are comprised of multiple elements which exhibit significantly different tendencies to vaporize, or separate, during processing.

This also limits their usefulness for applications where it is highly beneficial, or essential, to achieve precise compositional control of the nanoparticles.

One limiting factor is the difficulty in forming nanoparticles of materials which exhibit a preferred loss of constituents during processing.

None of the references or techniques cited above provides a suitable method for generating such compound semiconductor nanoparticles.

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