RU2421490C1 - Thermostatic coating of "solar reflector" class - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: coating contains silicate binder, filler and distilled water. The silicate binder is lithium or sodium glass. The filler is a salt of an alkaline-earth element BaSO₄ and a barium or lithium aluminate additive. The coating composition has application life of 3-5 weeks. The coating can be easily applied and has solar radiation absorption capacity (As)_kon not greater than 0.33 when used for 15 years.

EFFECT: coating has low degree of deterioration of optical properties, low gas release, good adhesion to a substrate in outer space conditions, and electroconductive properties.

3 tbl, 3 ex

Description

The invention relates to the field of space materials science and optical technology and can be used in passive and active thermal control systems of spacecraft operating in orbits with a high intensity of ionizing radiation (electron, proton and UV radiation) with an active coexistence period (CAC) of 15 years or more. A temperature-controlled coating (TRP) is applied to the outer surfaces of the spacecraft (SC).

Currently, for spacecraft operating in geostationary orbits (GSO) and highly elliptical orbits (VEO), TRP based on optical glass plates K 208 ZhTsPI 750540.001 TU (industry document) are used, which are square quartz plates with a side of 20-40 mm and 100-200 microns thick with a sprayed layer of silver, which are manually glued to the outer surface of the radiator. Such coatings have good initial optical characteristics (As = 0.1 ÷ 0.12; ε≤0.9) and high resistance to ionizing radiation.

However, these coatings have a number of significant disadvantages:

- the cost of TRP is more than 200,000 rubles / m ² ;

- coatings are dielectrics, to remove static electricity, a thin transparent electrically conductive layer is applied to the outer surface of the TRP, which is not resistant to prolonged exposure to ionizing radiation;

- coatings are fragile, easily damaged in the manufacture of thermal radiators and are difficult to repair if it is necessary to replace radiator elements;

- coatings are time-consuming to manufacture and low-tech when used;

- the glue used for gluing plates of K 208 optical glass to the substrate does not meet the requirements of GOST R 50109-92 for gas evolution and is not resistant to the effects of PCF (thermal drops and ionizing radiation).

A number of TRP coatings are known (patents RU 2168189, G02B 1/10, RU 2331553 BG4G 1/58, RU 02036208, C09D 1/02, RU 2290422, C09D 5/24, RU 2248954, С04В 41/87), which are devoid of the above disadvantages but they have low resistance to the complex effects of space factors (PCF) (electron, proton and UV radiation, thermal drops in vacuum), which makes it impossible to use them on spacecraft with a long term of operation in high orbits (GSO and VEO).

It is known TRP (RF patent 2248954, С04 В 41/87) composition, wt.%:

zirconium (IV) oxide modified 33-53 potassium metasilicate with a module of at least 4,5 at a density of 1.185-1.195 g / cm ³ 24-30 distilled water 23-37

with an initial coefficient of absorption of solar radiation As≤0.12-0.13 and a coefficient As after 3 years of operation (with UV irradiation) - 0.22.

This coating is used on spacecraft operating in low orbits with a life of 3-5 years. The coating does not have good adhesion to the substrate and the antistatic (electrical conductive) properties presented to the materials of the outer surfaces of spacecraft operating in high orbits.

The closest as a prototype (RF patent 2036208, C09D1 / 2) can serve as a composition of the following composition, wt.%:

potassium silicate aqueous solution with a module of 3.8-4.1 58-65 zirconium titanate 35-47

The composition is used to obtain TRP with the coefficients:

As 0.09-0.12 ε (coefficient of thermal radiation) not less than 0.92

Change in As (ΔAs) under the action of a dose of ultraviolet radiation of the sun equal to 50 equivalent to sunny days 0.02-0.04, viability of the composition is not more than 10 hours. Table 3.

The task is the development of TRP with a low degree of degradation of optical characteristics, low gas evolution, good adhesion to the substrate under the conditions of PCF and having conductive properties for spacecraft operating in orbits with a high intensity of ionizing radiation (GSO and VEO).

The expected technical result is to improve technological properties - the viability of the composition up to 3-5 weeks, an easy method of coating.

The essence of the invention lies in the fact that the thermoregulatory coating of the "solar reflectors" class includes a silicate binder, fillers, distilled water, while the silicate binder contains lithium or sodium glass, the filler contains the salt of the alkaline earth element BaSO ₄ , as well as the addition of aluminate barium or lithium in mass parts:

lithium or sodium glass 29.42-33.78 Baso ₄ 43,44-42,28 lithium aluminate or barium aluminate 3.39-3.61 distilled water 22.07-23.53

Method for preparing the composition: components are loaded into a porcelain ball mill with porcelain balls: BaSO ₄ , distilled water, lithium glass with a module of 2.9-3.5 and a density of 1.153 ÷ 1.190 g / m ³ or sodium glass with a module of 25 ÷ 30 and a density 1.133-1.135 g / m ³ and the addition of lithium aluminate or barium aluminate are dispersed for 5-10 hours. The resulting dispersion is poured with simultaneous filtration through gauze. The coating is carried out with a spray gun. Table 1 shows the content of the components in the composition. Table 2 shows the properties of the coating depending on the content of fillers.

Example 1

Baso ₄ 42.28 lithium aluminate 3.52 lithium glass (with module 3.0 and density 1,156) 31.30 distilled water 22.90

Example 2

Baso ₄ 40.76 barium aluminate 3.39 lithium glass (with module 3.0 and density 1,156) 33.78 distilled water 22.07

Example 3

Baso ₄ 41.2 barium aluminate 3.4 sodium glass (with module 26 and density 1,135) 33.26 distilled water 22.14

The developed TRP paint and varnish possesses the following characteristics:

- the cost of coverage is less than 10 thousand rubles / m ² ;

- the coating is technologically advanced, easy to apply and repair in case of accidental damage;

- the equipment existing at the enterprises is used for coating, i.e. creation (or retrofitting) of new production sites is not required;

- materials on which the coating is applied - aluminum alloys of the type AMg-6, D16, V-95;

- the temperature-controlled coating meets the requirements of GOST R 50109-92 for gas evolution (actual loss of coating mass (RPM) is not more than 1.0%, the content of volatile condensing substances (LKV) is 0.1%);

- initial optical characteristics of the TRP: As = 0.10 ÷ 0.12 ε = 0.93 ÷ 0.95.

The coating retains its properties after exposure to PCF acting on GSO, while the absorption coefficient of solar radiation (A _S ) _kon after 15 years of operation on GSO does not exceed 0.33.

The specific volume electrical resistivity of the TRP does not exceed 10 ⁶ Ohm · m.

The mass of one square meter of coverage is not more than 300 g.

Adhesive coating properties:

- breaking stress at separation from the surface - not less than 1.5 MPa (15 kg / cm ² ) according to GOST 14760-69;

- adhesion of the coating to the surface by method 4 according to GOST 15140-78 - no more than 2 points; At the operating temperature of the TRP Texp = ± 100 ° C, the adhesion of the coating to the surface by method 4 according to GOST 15140-78 is no more than 2 points.

The change in the coefficient A _s when exposed to UV radiation for 50 equivalent sunny days does not exceed 0.03. However, the main damaging factor for radiation-hazardous orbits (GSO, GSO) are proton and electron radiation. The new coating has a solar absorption coefficient (A _S ) _con . after a complex effect of the factors of outer space (proton, electron and UV radiation) does not exceed 0.33 when operating for 15 years. Such radiation resistance does not have any known Russian or foreign TRP.

Table 1 Name of components The content of components in the composition one 2 3 four 5 1. Alkaline earth salt of BaSO ₄ 43.12 43,44 40.76 42.28 45.58 2. Additive lithium aluminate or barium aluminate 2,35 3.61 3.39 3.52 2.09 3. Lithium glass with a module of 2.9 ÷ 3.5 and a density of 1.153 ÷ 1.190 g / m ³ or sodium glass with a module of 25 ÷ 30 and a density of 1.133-1.135 4. distilled water 31.79 29.42 33.78 31.30 28.49 22.74 23.53 22.07 22.90 23.84

table 2 The name of indicators The content of components in the composition one 2 3 four 5 Coating thickness, microns 130 125 140 110 The coating is brittle, cracks, chipping Coefficient As, no more 0.14 0.10 0.12 0.11 Coefficient ε, not less 0.93 0.94 0.93 0.94 The specific volume electronic resistance ρ _v , Ohm · m l, 4 · 10 ⁶ 1 · 10 ⁶ 0.5 · 10 ⁶ 0.4-10 ^b Adhesion to aluminum alloys according to GOST 15140-78, score 2-3 1-2 1-2 1-2 four

Table 3 Options TRP Proposed Prototype Coefficient As 0,1-0,12 0.09-0.12 Coefficient ε 0.93-0.94 > 0.92 Conductivity, ρ _v , Ohm · m. ≤10 ⁶ not conductive ΔAs after exposure:
electrons, protons and UV radiation (15 years of GSO, VEO) 0.21-0.23 does not meet modern requirements - UV radiation for 50 equivalent sunny days no more than 0,03 0.02-0.04 As final after 15 years of operation no more than 0,33 does not meet modern requirements

Claims (1)

Thermoregulatory coating of the “solar reflectors” class, including silicate binder, fillers, distilled water, characterized in that it contains lithium or sodium glass as a silicate binder, BaSO ₄ alkaline earth element salt, an addition of barium or lithium aluminate, wt. .:
silicate binder 29.42-33.78 Baso ₄ 42.28-43.44 additive 3.39-3.61 distilled water 22.07-23.53