Fast Economical Fabrication of Silicon Carbide Mirrors
Advancing Materials and processing to improve satellite optics manufacturing
Engineering is about tradeoffs, and this can be particularly true in the manufacturing of optical mirrors and related structures. In many applications, optical mirrors need to be very precise and able to maintain precision under a variety of changing conditions. In many applications the mirrors need to be light in weight, putting additional demands on production processes and the material from which they are made. And while performance can be critical, cost is still a consideration.
When performance is paramount, compared to metal, glass, or composites, the material of choice is silicon carbide (SiC). SiC is an excellent material for applications requiring superior strength and resistance to deformation because it combines high hardness, high stiffness, low density, high thermal conductivity, and low coefficient of thermal expansion. It resists corrosion and has a long working lifetime.
Various methods for production of SiC parts exist, each with its own strengths and drawbacks:
- Machining block SiC
- Powder metallurgy with either reaction bonding or sintering
- Chemical vapor deposition (CVD)
- Graphite conversion
Graphite conversion combines the relative machinability of graphite with the best qualities of SiC. It further joins the speed of forming a SiC substrate by conversion with the superior optical qualities—fine grain and excellent polishability — of CVD SiC. The result is a “best of all worlds” end-product that can be quickly produced at a reasonable price.