Low Cost Dome Fabrication

The current method for producing dome blanks for multimode optics involves spray drying powders, followed by isopressing around metal mandrels. Yield losses during spray drying, and excess material requirements in the pressing step represent a significant portion of the final part cost. Slurry casting processes represent an alternative to isopressing, and in the case of hemispherical domes, are particularly well suited. Both slip casting and gel casting provide the opportunity to prepare domes at near-net shape with minimal yield loss. The fine particle size of the current Spinel powders pose a particular difficulty in slip/gel casting. Issues related to poor dewatering, cracking and low green densities all affect the value of these processes. We propose herein to develop a freeze casting method suitable for producing hemispherical domes of suitable optical quality from spinel powders. Freeze casting has all the advantages of gel casting, but further includes opportunities for net shape fabrication of dense green ceramic components. The Phase I work will include demonstration of technology to produce relevant dome articles. Phase II will demonstrate repeatability and include cost-benefits and producibility studies. Surmet is already working closely with prime contractors to produce ALON and spinel domes and optical components for near-term missile systems. This will facilitate insertion of this technology rapidly at conclusion of Phase II effort.