Electrochemical vapor deposition (EVD) of oxygen ion conducting and mixed conducting, oxygen-ionic/electronic, oxide layers is achieved at near atmospheric pressure process conditions by employing metals and metal compounds for removal and/or recovery of the free halogen byproduct of the EVD reaction. The metals and metal compounds are employed as solids, vapors, and as oxides in intimate mixture with carbon directly within the deposition zone together with the substrates to be coated. The process leads to significant cost reduction, for instance, in the fabrication of thin layers of solid oxygen ion conducting electrolytes, for fuel cells, gas separators, and gas sensors, when compared to state-of-the-art EVD processes which are conducted under vacuum conditions.
A method for depositing solid electrolyte layer includes the steps of depositing a solid electrolyte layer on an electrode substrate by an electrophoretic deposition process, firing the solid electrolyte layer at a temperature of 1,300.degree. C. or less, and depositing another electrolyte layer on the fired solid electrolyte layer by a CVD-EVD process. In accordance with the method, thin and sufficiently dense solid electrolyte layers which are suitable for solid electrolyte fuel cells can be easily produced.
An integrated system for producing high purity silicon dioxide comprising: a) a source of an oxygen-containing feed gas containing at least one impurity, b) an oxygen transport membrane cell containing an oxygen-selective transport membrane that has a cathode side and an opposing anode side, the membrane being at an elevated temperature effective for separation of oxygen in the feed gas from the impurity by transporting oxygen ions from the oxygen-containing feed gas through the membrane to the anode to form a purified oxygen permeate on the anodeside, while retaining an essentially oxygen-depleted, impurity-containing retentate on the cathode side, c) a passageway from the source (a) to the cathode side of the membrane cell, d) a silicon source, and e) a silicon oxidation furnace, in communication with the anode side of the membrane cell, for reaction of the purified oxygen permeate with silicon from the silicon source, at an elevated reaction temperature effective for the reaction, in order to produce the high purity silicon dioxide.
The present invention provides a solid oxide fuel cell which contains an anode, a cathode, and an electrolyte, where at least one of the electrode contains a wash-coat composition that improves the performance of the solid oxide fuel cell. Also provided is a method for making the solid oxide fuel cell.
Novel solid oxide fuel cell (SOFC) article and method of manufacture with improved properties at lower costs. The structural features and methods involve fabricating an anode (i.e., fuel electrode); applying a cermet electrolyte, which includes a mixture of ceramic and electrochemically active substances, and applying a cathodic layer. The cermet electrolyte containing a small amount of transition metal reduces the thermal expansion mismatch with the anode, and allows for a graded structure of the electrochemically active substances across the anode/electrolyte structure. Under operating conditions, a dense electrolyte and metal oxide sub-layer exist on the oxidized side (cathode side); while the other side of the electrolyte (reducing side) is made of a porous sub-layer containing transition metal. The tailoring of the amounts of metal present in the anode and the cermet electrolyte allows for greater power output and enhanced electrochemical performance, while maintaining the structural integrity and reliability of the SOFC.
