Compositions: ceramic – Ceramic compositions – Refractory
Reexamination Certificate
1999-10-15
2001-02-27
Bell, Bruce F. (Department: 1741)
Compositions: ceramic
Ceramic compositions
Refractory
C501S152000, C429S006000, C429S006000, C429S006000, C429S006000, C252S062200, C264S068000
Reexamination Certificate
active
06194335
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electrochemical devices, and more particularly, the invention relates to electrochemical devices using one or more ceramic elements.
BACKGROUND OF THE INVENTION
Electrochemical processes can remove oxygen from air by ionizing oxygen molecules on one surface of an electrolyte and then transporting the oxygen ions through a solid electrolyte. The oxygen molecules are then reformed on an opposite electrolyte surface. An electric potential is applied to a suitable catalyzing electrode coating applied to the surface of the electrolyte. The electrode coating is porous to oxygen molecules and acts to dissociate oxygen molecules into oxygen ions at its interface with the electrolyte. The oxygen ions are transported through the electrolyte to the opposite surface, which is also coated with a catalyzing electrode and electrically charged with the opposite electric potential which removes the excess electrons from the oxygen ions, and the oxygen molecules are reformed.
Although electrochemical devices are generally known there are significant disadvantages associated with using known devices as oxygen generators. For example, in the fuel cells described in U.S. Pat. Nos. 4,640,875 and 5,306,574, the individual electrodes are made from a ceramic material while the manifold into which each of the electrodes is inserted is made from stainless steel. This structure is difficult and expensive to manufacture because many parts must be assembled. More importantly, the electrochemical device operates at high temperatures, typically between 700-1000° C., and the different coefficients of thermal expansion between the stainless steel and the ceramic frequently cause cracks and thus leakage between the ceramic electrode and the stainless steel manifold. This leakage can be especially severe if a high pressure is developed within the electrochemical device. For example, oxygen generators capable of producing at oxygen at high pressures of 2000 psi are unknown to the inventors.
Further in both of these electrochemical devices, whether the device is used as an oxygen generator or as a fuel cell, the electrical interconnections used to form a series-parallel array between the electrodes require direct contact of the outer peripheries of the individual electrodes. The interconnection arrangement is expensive to manufacture, less reliable in operation, and reduces the surface area available for electrochemical exchange.
It is, therefore, an object of the present invention to provide a ceramic electrolyte element which can be formed and used in an electrochemical device.
It is another object of the invention to provide a ceramic electrolyte element having a configuration which provides for an increased active surface area per unit volume and weight of ceramic material.
It is yet a further object of the invention to provide a composition including an electrolyte and a binder which can be injection molded to form a ceramic electrolyte element.
Another object of this invention is to provide a ceramic electrochemical device wherein the electrical connections connecting the electrodes are simplified.
A further object of this invention is to provide an electrochemical device capable of delivering oxygen at 2000 psi or greater.
Still another object of this invention is to provide a ceramic electrochemical device which is of a modular configuration and thereby provides a simple “building block” approach to meet differing requirements for amounts of oxygen to be generated.
SUMMARY OF THE INVENTION
These and other objects of the present invention are achieved by providing a ceramic element which can be injection molded from an electrolyte and a binder. The ceramic element includes a tube support portion and a plurality of tubes extending from the tube support portion. The plurality of tubes are arranged in rows and columns. A plurality of vias extend from one surface of the tube support portion to an opposite surface of the tube support portion. The ceramic element is coated with an electrically conductive coating and a current collector coating. The vias are coated with the electrically conductive coating and plugged. After the coatings are removed in selected areas of the ceramic element, the tubes of the ceramic element form a series-parallel array because tubes in the same column are connected in parallel electrically and tubes in adjacent rows are connected in series electrically. Two ceramic elements are sealed together to form a modular electrochemical device. The electrochemical device can be either an oxygen generator or a fuel cell. Oxygen generating capacity can be increased by manifolding together two or more modular oxygen generators.
These and other objects are achieved by providing a one-piece ionically conductive ceramic electrolyte element including a tube support portion having first and second surfaces and a plurality of tube portions extending from the first surface. The tube portions each have a closed end and an open end. The second surface is at least partially open to the atmosphere. The open ends of the plurality of tube portions being open to the atmosphere through the second surface.
In another aspect of the invention these and other objects are achieved by an electrochemical device including a first ceramic element having a support member and an array of elongated members extending from the support member. A second ceramic element is adjacent the first ceramic element. A seal is between the first ceramic element and the second ceramic element. The first ceramic element, the second ceramic element and the seal form a pressure tight chamber therebetween. The elongated members are open to the chamber.
In another aspect of the invention these and other objects are achieved by a method of generating oxygen including forming an oxygen generator having a first electrode and a second electrode. Electric current is supplied at a first polarity to the first electrode and electric current is supplied at a second polarity to the second electrode. Oxygen pressure is built within the oxygen generator. The oxygen is output at 2000 psi or higher.
In another aspect of the invention these and other objects are achieved by a ceramic module product produced by a method comprising mixing a ceramic powder and a binder. The mixed ceramic powder and binder are injection molded into a ceramic module having a support portion and a plurality of projecting portions extending therefrom.
A number of module assemblies can have their output ports connected together to form a system of greater capacity.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from following detailed description, wherein only the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings are to be regarded as illustrative in nature, and not as restrictive.
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Crome Victor Paul
Hart Russell Frank
Sehlin Scott Richard
Bell Bruce F.
Litton Systems Inc.
Lowe Hauptman Gopstein Gilman & Berner
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