Improved method for producing ceramic powders: An R&D 100 Award winner
September 24, 1992
RICHLAND, Wash. –
Researchers at the U.S. Department of Energy's Pacific Northwest Laboratory were recently recognized for technological excellence by Research and Development magazine. PNL researchers Larry A. Chick, Larry R. Pederson, Greg J. Exarhos, Lambert J. Bates and Gary D. Maupin received an R&D 100 Award for developing a unique technology for producing ultrafine ceramic powders that improve the manufacture of solid oxide fuel cells and many other important products.
The award is for one of the top 100 technological achievements of 1992 as determined in R&D magazine's annual competition. R&D magazine conducts the competition to honor the most promising new products, processes, materials or software developed worldwide. Awards are based on a product's technical significance, uniqueness and usefulness. This is the 30th year of the competition.
"The production of solid oxide fuel cells, chemical sensors and many other valuable ceramic products depends upon the availability of very fine ceramic particles that are chemically homogeneous and of high purity," Larry said, "PNL's unique glycine-nitrate process enhances that availability."
The PNL process produces the desired powders by preparing a preliminary solution containing the amino acid glycine and metal nitrates, mixed at the molecular level and combined with water. This solution is heated to drive off the free water. The resulting foam self-ignites at temperatures near 200 degrees Celsius and burns at temperatures as high as 1450 degrees Celsius (depending upon the mix of the solution.) Through burning, the metal ions in the solution are converted to an ash composed of microscopic ceramic powders of the desired oxide composition. These powders can be consolidated and sintered (heated without melting) to make uniformly dense ceramic parts.
Because combustion is complete and occurs very rapidly at high temperatures, the PNL process produces purer products (fewer carbon impurities) than other methods such as the amorphous citrate process. PNL's glycine-nitrate process also produces a powder that is up to 30 times greater in specific surface area than the product of the citrate process. The higher surface area is created by the extremely small particles achieved with the PNL process. These small particles are more chemically active than coarser ones and can be sintered at lower temperatures. Powders produced by the new method are exceptionally uniform, a significant improvement over current methods.
In addition to the technical improvements of the PNL process, the ability to use lower sintering temperatures and elimination of the need for extensive milling (by virtue of smaller and more uniform particle size) can lead to considerable cost savings in producing solid oxide fuel cells and many other ceramic-based products.
Tags: Energy, Fuel Cells