Method of making composite particles with tailored surface characteristics

Abstract

The invention describes a procedure to make metal containing composite particles and composite particle suspensions. The procedure is versatile and can produce particles with a variety of particle sizes and compositions. For some applications the metal composite particles can provide the functionality of wholly metallic particles including configurations where the metal is located on the particle surface. Such metals have application in a wide variety of fields, including accomplishing electrochemical reduction and catalysis.

Description

[0001] The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract Nos. 68-D-03-033 and EP-D-04-059 awarded by the Environmental Protection Agency (EPA).BACKGROUND [0002] Materials have properties that can be ascribed to either surface or bulk characteristics. These parameters include catalytic activity, electrical and thermal conductivity, optical, electronic, chemical and mechanical properties. Particles with metallic exteriors of tailored compositions and thickness can exploit these properties while providing control over other properties such and density, material cost and particle behavior. [0003] Such metals have application in a wide variety of fields, including but not limited to water treatment, remediation, diagnostic medicine, drug delivery, and cosmetics. For example, zero valent metals may be useful as fillers, such as those f...

AI Technical Summary

Benefits of technology

[0014] The present invention is a cost-effective and scalable technique for producing sub-micrometer and nanocrystalline zero valent metal particles and particle suspensions by depositing metal onto the surface of a host particle. The particles typically offer a surface area of greater than 5 m2 / g and can be inexpensively produced on a large scale. Moreover the particles have reactivity superior to currently available microscale metal particles.

Problems solved by technology

It is difficult or impossible to transport coarse microscale particles through the subsoil as the particles settle rapidly and are strained or filtered before they reach the contaminant phase.

The large particle size makes this product unsuitable for many applications including in-situ remediation, for example.

This is a slow and expensive process that results in material having very limited commercial use.

The particles also have residual boron that is undesirable for some applications.

Aggregated particles still provide a high surface area but behave like coarse particles when injected underground and offer less than ideal sub-surface mobility.

Although less expensive than chemically precipitated product, this product is also prohibitively expensive for most applications.

This product is also aggregated with less than ideal underground mobility.

This procedure also offers the disadvantages of expensive chemical precursors and difficulties in scaling the process.

This consumes the iron prematurely and can also lead to the formation of solid surface deposits of water insoluble metal hydroxides (show in equation (5)), oxides, and oxyhydroxides.

These non-metallic substances can prematurely passivate the particle surface and inhibit reactivity.

This methodology is ineffective for producing discreet, sub-micrometer or nanoscale particles, since iron is ductile at room temperature and does not become brittle unless cooled to cryogenic temperatures.

These are poorly suited for remediation applications.

To date, there is no cost-effective and easy way to manufacture large quantities of the high surface area zero valent metal particles of the type described herein, such particles having a wide variety of uses in a large number of fields.

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