Advances in beryllium optical technology utilizing spherical powder

摘要

Beryllium has been used as an optical and structural material for astronomical/IR telescope applications for the past 20 years. Some of the most recent applications have been for the VLT (Very Large Telescope) M2 secondary mirror, SIRTF (Space Infrared Telescope Facility), plus many other space based IR sensors. The traditional forms and optical grades of the material, I-70H and I-220H, are well characterized from a mechanical and thermal standpoint over a wide range of temperatures. Beryllium's limiting factor's for astronomical and/or IR telescopes has been traditionally two fold: cryogenic stability and perceived higher cost than some of the other material options, such as glass, silicon carbide, and some composites. To address those two factors, Brush Wellman has developed a new optical grade of Beryllium produced by gas atomization (spherical powder) called O-30. This paper will detail the development of this grade of Beryllium, with emphasis on the cryogenic properties of the material from a thermal and mechanical view. It will also report on the results of the optical polishing/thermal cycling work done under government sponsored contracts. Finally the paper will describe the process of producing Near Net Shape parts utilizing O-30 spherical powder in order to reduce manufacturing cost and schedule.