Zirconium Micro-Arc Oxidation as a Method for Producing Heat Insulation Elements in Spacecraft

• Published in: Nauka i obrazovanie (Moskva) Vol. 14; no. 8; pp. 162 - 178
• Main Authors: Shatalov, Valeri, Shtokal, Alexander, Rykov, Eugeniy, Dobrosovestnov, Konstantin, Bazhenova, Olga, Rozhkova, Tatiana
• Format: Journal Article
• Language: English; Russian
• Published: MGTU im. N.È. Baumana 03.08.2014
• Subjects: gas generation; micro-arc oxidation; thermal conductivity; zirconium
• ISSN: 1994-0408; 1994-0408
• DOI: 10.7463/0814.0724519

Application of coatings on the surface of materials as well as their composition and structure control in the near-surface layer enables us to use properties of base material and modified layers in the most rational and profitable way and save expensive and rare metals and alloys.The space telescope of T-170M will be the main tool of the international space observatory "Spektr-UF".It is being understood that the main mirror shade, which is in the outer space and has a considerable height will act as a radiator cooling a unit (cage) of the main mirror. Therefore it is necessary to create heat insulation between the shade of the main mirror and the frame of the main mirror unit. From the thermal calculations a detail to provide heat insulation must possess thermal conductivity, at most, 2,5 and a conditional limit of fluidity for compression, at least, 125 MPas to ensure that the shade diaphragms position of the main mirror is stable with respect to the optical system of telescope.Considering that oxide of zirconium possesses one of the lowest thermal conductivities among oxides of metals, it is offered to use zirconium, as a material of base, and to put the MAO-covering (micro-arc oxide) on its surface.As a result of studying the features of MAO-coverings on zirconium it is:1) found that the composite material consisting of zirconium and MAO-covering on it, has low thermal conductivity (less than 2 ), and thus, because of small oxide layer thickness against the thickness of base material, possesses the mechanical properties which are slightly different from the pure zirconium ones;2) found that the composite material possesses the low gas release, allowing its use in the outer space conditions; the material processed in two electrolytes i.e. phosphate and acid ones has the lowest gas release;3) found that with growing thickness of MAO-covering its porosity decreases, thus the average pore diameter grows thereby leading to increasing thermal conductivity of MAO-covering. Therefore it is inexpedient to use thick MAO-coverings. Besides, adhesion between the covering and the base decreases;4) advisable to use a stack of thin washers in case it is necessary to apply the heat insulation of considerable thickness.