Carbon coatings have been applied to silica lightguide fibers for many years in order to provide hermeticity to both water and H2. While there was a flurry of activity in this technology in the late 80’s and early 90’s, it appears that these coatings are little used today. The reasons for this are the increased cost associated with their use, the perception that they are unnecessary, and perhaps most important, the lack of complete understanding and control of their properties. In this paper we will review the history, preparation, structure and properties of these coatings in an effort to clarify some of the issues surrounding their production and use.
|