The volume resistivity of the spacecraft thermal control coating is tested by referring to the standard GB/T1410-2006, and the test conditions are as follows:

test voltage 100V;

TABLE 3 conductivity of coatings

Vacuum gassing property test

Vacuum bleed test was performed with reference to standard GJB2704A-2006, under the following conditions:

sample pretreatment: maintaining at 23+ -1deg.C and humidity 45%RH+ -10%RH for 24 hr; the heated temperature of the sample is 125+/-1 ℃; the collection temperature of the condensable volatile is 25 ℃; the test pressure is less than or equal to 7 multiplied by 10^-3 Pa; the heat preservation time is 24 hours;

balance test sensitivity: l μg.

Testing to calculate Total Mass Loss (TML), condensable Volatiles (CVCM) of the material in vacuum; as shown in table 3.

TABLE 4 vacuum gassing performance of coatings

Sample numbering	Example 1	Example 2	Example 3	Example 4	Comparative example 1	Comparative example 2
							TML	0.84	0.76	0.72	0.77	0.076	0.067
CVCM	0.010	0.011	0.016	0.012	0.012	0.013

Thermal cycle testing

The method adopts a temperature impact box (model ZTS010, shanghai up to environmental test equipment Co., ltd.) and under the standard requirement of GJB2704A-2006, the test conditions are as follows after 100 times of thermal cycles at the temperature ranging fromminus 100 ℃ to plus 100 ℃ under the normal atmospheric condition:

test temperature: the high temperature end temperature is-196 ℃, and the low temperature end temperature is-100 ℃; cycling for 100 times; temperature control error: high temperature + -5 ℃ and low temperature + -10 ℃; the thermal cycling device should have two constant temperature zones of different temperatures, with the sample 10s being transferred from one constant temperature zone to the other; preserving heat for 10min at the high temperature and low temperature ends to ensure that the temperature of the test piece is the same as the ambient temperature; dehumidifying measures should be taken during the test to prevent frosting on the surface of the test piece.

The test results of example 4 are shown in fig. 4: the modified coating has good appearance after 100 times of high-temperature heat cycle at-196 ℃ to +100 ℃, stable optical performance and good adhesive force, and meets the technical index requirement.

In combination with table 1, table 2 and test results, the properties of the high reflectivity inorganic thermal control coating of the present invention are as follows:

appearance: white, even coating surface, no bubble, no crack, no peeling and no falling off;

thickness: 100 μm to 150 μm;

solar absorption ratio: 0.08-0.16;

hemispherical emissivity: 0.91-0.92;

the volume resistivity is less than or equal to 1 multiplied by 10⁷ Ω·m

Thermal cycle test: after the coating meets the high-temperature low-temperature heat cycle test for 100 times at the temperature of minus 196 ℃ to plus 100 ℃, the phenomena of cracking, peeling, foaming and color change are avoided, the optical performance is stable, and the adhesive force is good;

vacuum air release performance: all satisfy TML <1%, CVCM <0.1%.

In conclusion, the high-reflectivity inorganic thermal control coating has good coating adhesive force on the basis of ensuring good thermal control performance (solar absorption ratio and hemispherical emissivity) of the coating, is simple and easy to learn in coating construction, has strong feasibility, and has good adhesive force after being subjected to 100-time temperature impact test at-196 ℃ to +100 ℃.

The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention.

Claims

1. A high reflectance filler, characterized in that it is prepared by the steps of: respectively weighing nano zinc oxide and silica sol, and carrying out ultrasonic and high-speed stirring to obtain a mixed solution of the nano zinc oxide and the silica sol; centrifuging and drying to obtain nano-scale mixed powder; sintering to obtain filler particles with high reflectivity.

2. The high reflectance filler according to claim 1, wherein the ratio of nano zinc oxide to 30% silica sol is 4:2-4:5; the ultrasonic treatment is carried out for 0.5 to 2 hours; the high-speed stirring is 300-500r/min.

3. The high reflectance filler according to claim 1, wherein the nano zinc oxide has a particle size of between 30 and 200nm; the silica sol is one or more of acidic silica sol, neutral silica sol and alkaline silica sol.

4. The high-reflectivity filler of claim 1, characterized in that the centrifugation speed is 6000-8000r/min and the centrifugation time is 5-10min; the drying temperature is 100-120 ℃ and the drying time is 12-24 hours; the sintering temperature is 600-1200 ℃ and the sintering time is 1-3h.

5. A method for preparing a high-reflectivity inorganic thermal control coating, which is characterized by comprising the following steps:

s2, preparing a coating: taking the modified high-modulus potassium silicate resin solution as a binder, adding the high-reflectivity filler according to any one of claims 1-4, adding a solvent, and uniformly mixing and stirring to obtain a finish paint;

6. The method of producing a high reflectance inorganic thermal control coating according to claim 5, wherein in step S1, the ratio of low modulus potassium silicate to silica sol is 2:2-2:6; the reaction temperature of the stirring reaction is 30-60 ℃, and the stirring speed is 1000-1500r/min; the modulus of the high modulus potassium silicate solution is 3.0-5.0.

7. The method for preparing the high-reflectivity inorganic thermal control coating according to claim 5, wherein in the step S1, the organic modification is to add deionized water into a high-modulus potassium silicate solution to dilute the solution to 30% by mass, and the silane coupling agent accounting for 0.2% -0.8% of the total mass is adopted for mixed modification; the silane coupling agent is one or more of KH550, KH560 and KH 570.

8. The method for preparing a high-reflectivity inorganic thermal control coating according to claim 5, wherein in step S2, the mass ratio of the binder to the filler is 10:3-10:9; the stirring speed of the mixing and stirring is 800-1200 r/min.

9. The method for preparing a high-reflectivity inorganic thermal control coating according to claim 5, wherein deionized water is added as a solvent in step S2; the viscosity of the finish paint measured by the four-viscosity meter is 14-17 s.

10. The method for preparing a high-reflectivity inorganic thermal control coating according to claim 5, wherein in the step S3, the standing time is 6-12 hours, the curing temperature is 60-100 ℃, and the curing time is 12-24 hours; the thickness of the high-reflectivity inorganic thermal control coating is 100-150 mu m.