ADVANCED MATERIALS BY CHEMICAL VAPOR DEPOSITION TECHNIQUES

SILICON CARBIDE (SIC) IS AN EXCELLENT MATERIAL FOR THE MANUFACTURE OF HIGH RESOLUTION AND HIGH EFFICIENCY GRATINGS.GRATINGS MADE FROM THIS MATERIAL ARE PARTICULARLY SUITABLE FOR HOSTILE ENVIRONMENTS SUCH AS PLASMA FUSION EXPERIMENTS. THEY WOULD BE RESISTANT TO HIGH ENERGY RADIATION, BE CHEMICALLY INERT, HAVE A HIGH THERMAL CONDUCTIVITY AND A LOWTHERMAL EXPANSION COEFFICIENT, AND THEY ARE POLISHABLE TO A HIGH SURFACE FIGURE FOR GOOD REFLECTIVITY. SILICON CARBIDE IS ALSO STRONG AND HARD. CONVENTIONAL TECHNIQUES, SUCH AS RULING AND PHOTOETCHING, ARE NOT SUITABLE FOR THE PRODUCTIONOF GRATINGS FROM SIC. WE PROPOSE TO TEST THE FEASIBILITY OFMAKING SUCH GRATINGS BY THE PROCESS OF REPLICATION DURING CHEMICAL VAPOR DEPOSITION. THE REPLICATION CONCEPT WILL BE TESTED ON SMALL SAMPLES USING A VARIETY OF MANDRELS WHOSE THERMAL PROPERTIES ARE CLOSELY MATCHED TO THOSE SIC. THE DEGREE OF REPLICATION WILL BE ESTABLISHED BY SENSITIVE OPTICAL MEASUREMENTS OF BOTH THE MANDREL AND THE REPLICATED MATERIAL. THE POTENTIAL FOR SCALING THIS TECHNOLOGICAL APPROACH TO LARGE SIZE GRATINGS WILL BE INVESTIGATED.