O.N. Emelianova, A.N. Bolshakova, E.P. Kudryavtseva, N.A. Yashtulov

In this paper the objects of study are the potassium and lithium high-modulus liquid glass (LG), which are solutions of polymer electrolytes consisting of hydrated alkali metal cations and polysilicate anions, having low degree of polymerization, and high-purity silica sols. The increase of modulus and reduction of impurities in LG make them indispensable for bonding thin pigmented coatings, in particular thermal control coatings (TCC) with high reflectivity and resistance to radiation for spacecraft. Potassium LG with modulus range from 3,2 to 5,0 and lithium LG with modulus range between 2,9 and 3,6 are obtained by direct hydrothermal synthesis in a single stage. The different types of raw materials were considered, and, finally, the best siliceous materials with high solubility in alkalis are selected to produce high-purity liquid glass. The optimal modulus ranges and concentrations of the major components in LG solutions were found, which providing the rheology of dispersing pigments during coatings formation. Special attention is paid to the analysis of the LG impurities composition, in particular, to the coloring impurities level determination providing the necessary optical performance of TCC. Types of silicate binders, being a basis of developed and used in space technology TCC class "solar reflectors (more than 20 recipes), are described. The technological scheme and technology of silicate binders with productivity up to 5.2 tn. per year are described, which allow to meet the needs of the space industry. The possibility of affecting the quality of TCC is shown by modification of silicate binder synthesis conditions: the raw silica selection, temperature and time of synthesis, the alkali cation and modulus of silicate solution selection, and the size regulation of obtained silicate anions in solution. It is shown that the use of high-purity silica sols in synthesis allows to maximize modulus (over 10) of lithium silicate. A presence of nanoparticles in solutions of alkali silicates is detected and their size distribution is defined by photon-correlation analysis using particle analyzer Malvern Zetasizer S: the maximum contribution of particles with a size of 4.65 nm is observed for potassium silicate and 42 nm for lithium silica sols. The advantage of lithium silicate binders for TCC spacecraft due to the larger sizes of silicate anions is shown.