Coating processes – Particles – flakes – or granules coated or encapsulated – Solid encapsulation process utilizing an emulsion or...
Reexamination Certificate
1999-09-16
2001-07-24
Nutter, Nathan M. (Department: 1711)
Coating processes
Particles, flakes, or granules coated or encapsulated
Solid encapsulation process utilizing an emulsion or...
C427S231000, C427S231000, C428S402200, C428S402210, C428S402240, C264S010000, C264S438000
Reexamination Certificate
active
06265025
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method for the production of homogeneous, ultrafine inorganic materials. Specifically, electrohydrodynamic flows are utilized to induce turbulent mixing of fluids containing reactive species, thereby producing non-agglomerated, submicron-sized particles.
BACKGROUND OF INVENTION
Ultrafine particles constitute the key building blocks for diverse advanced structural and functional materials, such as high-performance ceramics and alloys. These advanced materials have tremendous impact in many areas, including catalysts, separations, electronics, energy production processes, and environmental applications. Of particular importance, nanophase ceramic or metallic materials that contain nanosized (<100 nm) particles/grains show dramatically improved performance (mechanical, electrical, optical, magnetic, and/or catalytic). The characteristics of ultrafine particles, i.e., size, morphology, monodispersity, purity, and homogeneity of composition directly determine the properties of the materials that are made from them. Thus, the future application of advanced materials depends on the capability to produce particles with outstanding characteristics.
Currently, there is a strong need for more efficient methods of production of high-quality inorganic particles. Ideally, an instantly reactive, continuous process that generates homogeneous ultrafine particles with controllable characteristics is desired. The primary technologies for synthesis of ultrafine particles are liquid-phase chemical and sol-gel processing, and gas-phase condensation. Most of the production processes for both approaches are conducted in batch mode. Gas-phase reactions typically require extreme conditions such as high vacuum and high temperature and give very slow particle production rate. A few continuous, liquid-phase processes have been developed for production of microspheres from alkoxide; however, these involve relatively slow kinetics during hydrolysis and condensation, typically 30 minutes or more reaction time. In contrast, real metal alkoxides are so reactive that agglomerated solids, rather than dispersed particles, are formed under conditions with rapid reaction kinetics. Thus, controlled hydrolysis/condensation of alkoxides in a batch reactor is the usual approach for the production of monodispersed metal oxide precursor powders.
Tubular-type reactors have been designed for the continuous synthesis of ultrafine ceramic particles such as titania and ferric oxide via hydrolysis and condensation of metal alkoxides. In addition, liquid spraying techniques including electrostatic spraying/atomization and ultrasonic spraying of liquids into gas have been used in ceramic particle production.
SUMMARY OF INVENTION
The present invention solves the above-described problems by providing a method for the production of inorganic particles involving electrohydrodynamic flows to rapidly and efficiently mix two reacting liquid streams in a process. The micromixing induced by this process is very advantageous for reactive systems that generate solid particles. Since the mixture is homogenized very quickly, it is possible to continuously operate with faster reaction rates and yet result in a homogeneous product.
The method of the present invention comprises injecting a first fluid into a first conduit, and injecting a second fluid through a second conduit into the first conduit wherein the second conduit is partially disposed within the first conduit. An electric field is then applied between the two conduits. Either the first fluid or second fluid contains a species reactive with that of the other fluid to induce particle-producing reactions.
More particularly, the first fluid may be introduced continuously into the first conduit, and the first fluid may be miscible, or partially miscible or immiscible with the second fluid. The second conduit may be disposed within the first conduit so that there is an annular space between the second conduit and the first conduit.
The electric field is applied between the second conduit and an electrode placed either on the interior or the exterior of the first conduit. Alternatively, the electric field may be applied between the second conduit and an electrode comprising the first conduit.
Electrodynamic flows inducing turbulent mixing of the first and second fluids are caused by charge injection at the tip of the second conduit.
Particle producing reactions suitable for the present invention include sol-gel reactions, inverse phase precipitations, and chemical reduction reactions.
Other objects, features and advantages of this invention will become apparent upon reading the following detailed description in conjunction with the drawings, photographs, and claims.
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DePaoli David W.
Hu Zhong Cheng
Tsouris Constantinos
Kilpatrick & Stockton LLP
Lockheed Martin Energy Research Corporation
Nutter Nathan M.
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