IDEA #7BG92D The Lightweight Silicon Carbide Mirror Of A New Type

THE SCIENCE AND TECHNOLOGY CENTER IN UKRAINE THE LIGHTWEIGHT SILICON CARBIDE MIRROR OF A NEW TYPE Description One of promising materials for space telescopes mirrors is silicon carbide ceramics. Complex of unique silicon carbide ceramic physical properties (small value to the thermal expansion coefficient, high heat conductivity and high spe(cid:28) cific inflexibility) allows expecting results. The main dis(cid:28) advantage of silicon carbide ceramic from the point of view of the optical requirements is remaining porosity. There is a known solution which eliminates such imperfec(cid:28) tions. It is forming of working thin (a few millimeters) layer of ceramics by CVD (Chemical Vapor Deposition) technology, i.e. chemical sedimentation from a vapor phase. The silicon chloride and hydrogen are used in this technol(cid:28) ogy. It is necessary also to provide the package plan for eco(cid:28) logical and production safety in connection with high tox(cid:28) icity of chlorides. In our solution first in the world it is proposed to elaborate technology and construction of sili(cid:28) con carbide mirrors of a new type, at which an upper layer (with the thickness a few millimeters) will be made of glass ceramic material with value of coefficient of thermal expansion near to the silicon carbide ceramics. Glass ceramic materials, similar to Zerodur (SCHOTT, Germany) and Clearceramics (OHARA, Japan), can be diffusively connected with a silicon carbide basic construc(cid:28) tion. In the results of preliminary researches the first frag(cid:28) ment samples of such mirrors were made. Its properties confirm the perspective of the chosen scientific and tech(cid:28) nical approach. Bonding of upper working layer was car(cid:28) ried out by trough nanolayers (thickness of 100 nm order), which are adhesion active to the connected ceramic mate(cid:28) rials. The process of bonding of upper layer with a basis is environmentally clean and does not require application of unique equipment. On the offered technical solution was received DECLARATIVE PATENT (Ukraine) FOR A UTILITY MODEL #9167 "Maslov's Mirror" at 15.09.2005. Innovative Aspect and Main Advantages In the patent we offer mirror in which the silicon carbide basis bonded with the top layer of optical glass ceramics with coefficient of thermal expansion (CTE) close to sili(cid:28) con carbide CTE. Bonding of these parts is made by non(cid:28) polluting nanotechnology, including vacuum sputtering of special coatings (thickness of about 100 nanometers) on connected surfaces, it's contacting and heat treatment for high(cid:28)strength diffusive bonding formation.In other known decisions nonporous top layer is created with the help of CVD (Chemical Vapor Deposition) technology i.e. chemi(cid:28) cal sedimentation from a vapor phase. The silicon chloride and hydrogen are used in this technology. Such production is expensive because of the using of high dimension vacu(cid:28) um oven equipment (process is running at the temperature 24 Fig. 1. Bonding of SiC ceramics (lower details) with Zerodur K20, upper surface is optically polished and coated with alu% minum reflecting coating of more than 1000°C) and necessity of chloride wastes uti(cid:28) lization. It is necessary also to provide the package plan for ecological and production safety in connection with high toxicity of chlorides. Thus the offered new decision has such advantages: – high quality of optical surface; – ecological clearness of manufacturing techniques;(cid:28) opportunity of manufacturing of large(cid:28)sized facilitated mirrors up to 4 (cid:28) 6 m in diameter; – the simplicity of manufacturing due to opportunity of using of the traditional optical manufacturing equipment; – relatively low cost in comparison with analogues. Areas of Application Regardless of foregoing difficulties in a present time silicon carbide mirrors were made on enterprises in the USA, Europe and Japan. The space telescope IRIS (Infrared Imaging Surveyor) were made and launched on an earth orbit in correspondence to the space infra(cid:28)red program in Japan. It is the most prime example of the successful use of silicon carbide ceramic mirrors. Telescope IRIS has a diam(cid:28) eter 700 mm and mass only 8.2 kg. There is forming of working thin (a few millimeters) layer of ceramics by CVD (Chemical Vapor Deposition) technology, i.e. chemical sed(cid:28) imentation from a vapor phase.The new mirror made of composite materials: SiC ceramics (lower details) and glassceramic. This solution may be used in optical and opto(cid:28) electronic industries at manufacture of mirror telescopes. Stage of Development Development phase(cid:28)laboratory tested Contact Details V.Lashkaryov Institute of Semiconductor Physics NASU Maslov Volodymyr Petrovych 41, prospect Nauky, Kyiv 03028, Ukraine Tel/fax +380 (44) 525(cid:28)05(cid:28)55 maslov@isp.kiev.ua; vmaslov1@yahoo.com www.isp.kiev.ua SCIENCE AND INNOVATION. Special Issue, 2007