Vapor Deposition Process for the Manufacture of Coated Particles

Abstract

A process for conducting vapor phase deposition is disclosed. The process separates a series of reactions through a sequence of reaction reservoirs. In some particular embodiments, the reactor includes a reactive precursor reservoir beneath a powder reservoir separated by valve means. A reactive precursor is charged into the reactive precursor reservoir and a powder is charged into the powder reservoir. The pressures are adjusted so that the pressure in the reactive precursor reservoir is higher than that of the powder reservoir. The valve means is opened, and the vapor phase reactant fluidized the powder and coats its surface. The powder falls into the reactive precursor reservoir. The apparatus permits vapor phase deposition processes to be performed semi-continuously.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. patent application Ser. No. 13 / 069,452, filed Mar. 23, 2011, which claims priority benefit of U.S. Provisional Patent Application No. 61 / 316,410, filed 23 Mar. 2010, all of which are incorporated herein by reference in their entirety.BACKGROUND OF THE INVENTION[0002]The incorporation of particles from millimeter-scale down to nanometers in size is ubiquitous in end-use products produced in industrial-scale quantities. A significant percentage of the particles used across all industries require that the surfaces be coated with a shell, layer, film, or other coating, ranging from sub-nanometer to hundreds of micrometers in thickness. For a variety of reasons, each sector or industry has determined that the incorporation of coated particles into the end-use product provides enough value-add in the performance of the product that the cost associated with each coating process is justified. Vapor deposit...

AI Technical Summary

Benefits of technology

The invention provides a simplified apparatus for vapor deposition processes that can be performed in a semi-continuous manner. This apparatus allows for a higher throughput of coated particles, resulting in higher quality products that can be produced for similar or lower capital costs. The apparatus can be used in processes such as atomic layer deposition and chemical vapor deposition, and can be easily adapted to high production rates or different thicknesses of coatings. Overall, the invention improves production efficiency and allows for greater control over the coating process.

Problems solved by technology

Batch processes have significant inefficiencies when operated at large scale, for several reasons.

Equipment failures and maintenance add to this downtime.

Process equipment tends to be very large and expensive in batch processes.

The need to operate these processes under vacuum adds greatly to equipment costs, especially as equipment size increases.

Because of this, equipment costs for batch processes tend to increase faster than operating capacity.

Another problem that occurs as the process equipment becomes larger is that it becomes more difficult to maintain uniform reaction conditions throughout the vessel.

It is also difficult to adequately fluidize a large mass of particles, specifically nanoparticles.

Issues such as these can lead to inconsistencies and defects in the coated product.

This represents yet another problem for a batch operation.

The batch particle ALD process inherently incurs additional down-time due to more frequent periodic cleaning requirements, and the reaction vessels cannot be used for multiple film types when cross-contamination could be problematic.

With larger vessels, localized process conditions, including internal bed heating, pressure gradients, mechanical agitation to break up nanoparticle aggregates, and diffusion limitations amongst others, become more difficult to control.

There is a practical maximum reaction vessel size when performing ALD processes on fine and ultra-fine particles, which limits the annual throughput for a single batch reactor operating continually, where the time duration of the process producing a given amount of coated materials equals the up-time plus down-time.

There is a practical maximum allowable capital expense to fabricate a particle ALD production facility, which effectively limits the number of batch reactors that operate identical processes in parallel.

With these constraints, there are practical throughput limitations that prohibit the integration of some particle ALD processes at the industrial scale.

For a traditional batch CVD process, the primary methods of controlling reactions are limited to reactant exposure time and operating conditions such as process temperatures and pressures.

The batch particle CVD process inherently has limited opportunity to prevent unwanted gas-phase side reactions.

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