A kind of color filler and its preparation method and application in spacecraft high temperature resistant heat control coating

Abstract

The application discloses a kind of color fillers and its preparation method and application in high-temperature-resistant heat control coating, belong to functional materials and heat control material preparation technical field.The application is with ZnCl2 and TiO2 as main raw material, with ZnCl2-NaCl as molten salt raw material, and according to certain proportion, Al2O3, Ga2O3, Gd2O3, Tm2O3, Lu2O3 and other doped element oxides are added, and the doped modified inverse spinel structure zinc titanate powder is prepared, then the space environmental stability is improved by potassium silicate coating, and the color filler applicable to high-temperature-resistant heat control coating is obtained.The preparation method of the application can obtain the color filler with uniform morphology, small particle size and good dispersibility, which provides a good structural basis for its application in high-temperature-resistant heat control coating.The color filler has high hemispherical emittance under high temperature conditions and other characteristics, which can meet the high-temperature heat dissipation demand of spacecraft, and has important significance for the preparation of high-temperature area surface heat control coating for future deep space exploration missions.

Description

Technical Field

[0001] This invention relates to a pigment and filler, its preparation method, and its application in high-temperature thermal control coatings, belonging to the field of functional materials and thermal control materials preparation technology. Background Technology

[0002] Thermal control coatings are an important component of spacecraft thermal control systems, adjusting the solar absorptivity α of the object's surface. s and hemispherical emissivity ε h This allows for the regulation of the thermal equilibrium state of objects, thereby effectively controlling the temperature of spacecraft during radiative heat exchange, maintaining the operating temperature of internal instruments and equipment within the allowable range, and ensuring the stable operation of the spacecraft's internal environment.

[0003] To meet the mission requirements of future deep space exploration, thermal radiators typically need to operate at temperatures above 400°C to achieve efficient heat dissipation. Currently, traditional white paint thermal control coatings, such as S781, SR107-ZK, and KS-ZA, mainly use zinc oxide as a filler. Under conditions of 200–500°C, conductivity and dielectric mechanisms play a major role in the emissivity of zinc oxide, but the emissivity of zinc oxide powder is relatively low, making it difficult to meet the high-temperature heat dissipation requirements of spacecraft.

[0004] Therefore, it is of great significance to provide pigments and fillers suitable for high-temperature thermal control coatings to meet the high-temperature heat dissipation requirements of spacecraft. Summary of the Invention

[0005] In view of the above-mentioned technical problems of pigments and fillers used in existing thermal control coatings, the present invention provides a pigment or filler and its preparation method, and provides its application in high-temperature resistant thermal control coatings.

[0006] The technical solution of the present invention is as follows: One objective of this invention is to provide a method for preparing pigments and fillers, comprising the following steps: (1) Using a mixture of ZnCl2 and TiO2 as the main raw material, ZnCl2-NaCl as the molten salt raw material, and oxides containing doped elements as modifiers, doped modified zinc titanate powder was prepared by molten salt method; (2) The doped and modified zinc titanate powder was coated with potassium silicate by spray drying to obtain pigments and fillers.

[0007] Further specifying, the molar ratio of ZnCl2 to TiO2 in the main raw materials of step (1) is 2:1.

[0008] Furthermore, the ZnCl2 has a purity > 99% and a particle size D50 < 0.5 μm.

[0009] Furthermore, the TiO2 is anatase with a purity > 99% and a particle size D50 < 0.5 μm.

[0010] Further specified, the molar ratio of ZnCl2 to NaCl in the molten salt raw material of step (1) is 1:1.

[0011] Further specifying, the modifier in step (1) is one or a mixture of two of γ-Al2O3, Ga2O3, Gd2O3, Tm2O3, and Lu2O3.

[0012] Furthermore, the modifier has a purity > 99% and a particle size D50 < 2 μm.

[0013] Further specifying, the specific operation process of step (1) is as follows: after mixing the main raw material, molten salt raw material and modifier, the mixture is ball-milled to obtain a mixed powder; the mixed powder is sintered at high temperature, the calcined product is crushed, dissolved in deionized water, and repeatedly rinsed with deionized water until no white precipitate is generated when the washing liquid is tested with silver nitrate reagent; the washed powder is dried to obtain the doped modified zinc titanate powder.

[0014] Furthermore, the ball milling conditions are as follows: the solvent is ethanol or acetone, the rotation speed is 400-800 rpm, the time is 3-5 h, and the drying temperature after ball milling is 60-100℃ for 3-5 h.

[0015] Furthermore, the high-temperature sintering conditions are: a temperature of 1000~1200℃ and a time of 2~4h.

[0016] Further specifying, the specific operation process of step (2) is as follows: the doped and modified zinc titanate powder obtained in step (1) is subjected to air jet pulverization, and the powder with a fineness of 1 to 3 μm is collected by a collector; the powder is homogenized with potassium silicate solution at a temperature of 45 to 55°C and a pressure of 25 to 35 MPa for 20 min; then spray drying is performed at an inlet hot air temperature of 140 to 160°C and an outlet temperature of 70 to 90°C, and the powder particles with a particle size of <3 μm are collected by a filter bag, thus obtaining the pigment and filler.

[0017] A second objective of this invention is to provide a pigment / filler prepared by the above method. Specifically, the pigment / filler is potassium silicate-coated and doped modified zinc titanate powder with an inverse spinel structure.

[0018] A third objective of this invention is to provide applications for the aforementioned pigments and fillers. Specifically, the pigments and fillers are used in the preparation of high-temperature thermal control coatings for spacecraft.

[0019] Beneficial effects: This invention uses ZnCl2 and TiO2 as the main raw materials, ZnCl2-NaCl as the molten salt, and adds dopant oxides such as Al2O3, Ga2O3, Gd2O3, Tm2O3, and Lu2O3 in a certain proportion to prepare doped and modified zinc titanate powder. Subsequently, potassium silicate coating is applied to improve its stability in the space environment, resulting in pigments and fillers applicable to high-temperature thermal control coatings. These pigments and fillers possess characteristics such as high hemispherical emissivity under high-temperature conditions, making them suitable for surface thermal control coatings in high-temperature regions, such as in future deep space exploration missions. Compared with existing pigments and fillers, this invention has at least the following advantages: (1) Among the pigments and fillers prepared in this invention, the doped and modified zinc titanate powder has an inverse spinel structure and good high-temperature stability. Its lattice asymmetry can reduce the recombination frequency of electrons and holes in the charge carriers and increase the photon scattering probability. At the same time, the doping element destroys the lattice periodicity, making the electronic energy state of the impurity local region different from that of the impurity-free region. Therefore, the impurity energy level can appear in the electronic band gap, thereby providing favorable conditions for valence band electron transitions and the interaction between electrons and holes, increasing the concentration of free charge carriers in the crystal, and thus increasing the hemispherical emissivity of the powder. On the other hand, the powder surface coating material is an inorganic silicate material, which helps to improve the spatial environment adaptability of the powder.

[0020] (2) The present invention uses molten salt with a low eutectic point as the reaction medium, wherein ZnCl2 is used as both the main raw material and the molten salt raw material, making the preparation process relatively simple and the synthesis temperature lower; the raw material has a high reaction rate in the molten salt, the required holding time is shorter, and the chemical composition of the obtained product is more uniform.

[0021] (3) The pigments and fillers prepared by the present invention have the advantages of uniform chemical composition, narrow particle size distribution, regular particle morphology, good dispersibility, simple preparation process and easy large-scale production. Attached Figure Description

[0022] Figure 1 The XRD patterns of the pigments and fillers prepared in Examples 1-3 and Comparative Examples 1-3 are shown in comparison. Figure 2 SEM images of the pigments and fillers prepared in Example 1; Figure 3 The hemispherical emissivity is given by the pigments and fillers prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0023] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Several specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention may also be implemented in other ways than those described herein; those skilled in the art can make similar extensions or equivalent substitutions without departing from the inventive concept. Therefore, the invention is not limited to the specific embodiments described below.

[0025] It should be noted that, as used herein, "an embodiment" or "an embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different locations in this specification does not necessarily refer to the same embodiment, nor does it imply that it is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. The materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art; the purity of the solid and liquid reagents used is analytical grade.

[0027] Example 1 The pigments and fillers prepared in this embodiment are carried out according to the following steps: (1) A mixture of ZnCl2 and TiO2 with a molar ratio of 2:1 was used as the main raw material, and a mixture of ZnCl2 and NaCl with a molar ratio of 1:1 was used as the molten salt raw material. γ-Al2O3 with a purity >99% and a particle size D50 <2μm was added and mixed to obtain a preliminary mixed powder. The specific mass ratio of the main raw material, the molten salt raw material, and γ-Al2O3 was 50:100:1.

[0028] (2) The preliminary mixed powder obtained in step (1) was added to a ball mill jar, and acetone was used as the ball milling solvent and ZrO2 grinding balls were used as the ball milling medium. The mixture was ball milled for 3 hours at a speed of 600 rpm. The ball-milled powder was then dried at 80°C for 4 hours.

[0029] (3) The dried mixed powder obtained after step (2) is placed in a corundum crucible and calcined at 1000℃ for 3 hours, and then cooled to room temperature with the furnace temperature. The calcined product is dissolved in deionized water, and then repeatedly rinsed with deionized water. The solution is filtered again after rinsing. This process is repeated 2 to 3 times until no white precipitate is formed in the washing solution when tested with silver nitrate reagent. The washed powder is dried at 90℃ to obtain zinc titanate powder.

[0030] (4) The zinc titanate powder obtained in step (3) is pulverized by airflow and collected by a collector to achieve a fineness of 1~3μm. 100g of zinc titanate powder with a fineness of 1~3μm and 500mL of potassium silicate solution with a concentration of 0.02g / mL are homogenized at 55℃ and 30MPa for 20min. Then, spray drying is performed at an inlet hot air temperature of 140℃ and an outlet temperature of 80℃. The powder with a particle size of <3.0μm is collected through a filter bag, which is the pigment and filler.

[0031] Example 2 The difference between this embodiment and Example 1 is that Ga2O3 with a purity > 99% and a particle size D50 < 2 μm is used to replace γ-Al2O3. The remaining process steps and parameter settings are the same as in Example 1, and pigments and fillers are prepared.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of the main raw material, molten salt raw material and γ-Al2O3 is 50:25:1. The remaining process steps and parameter settings are the same as in Example 1, and pigments and fillers are prepared.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of the main raw material, molten salt raw material and γ-Al2O3 is 10:20:1. The remaining process steps and parameter settings are the same as in Example 1, and pigments and fillers are prepared.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that step (4) was not performed. The remaining process steps and parameter settings are the same as in Example 1, and zinc titanate powder is obtained as a pigment and filler.

[0035] Comparative Example 4 Zinc oxide with a particle size of <3.0μm was used as a pigment and filler.

[0036] Example of effect (1) The microstructure of the pigments and fillers obtained in Examples 1-3 and Comparative Examples 1-3 was characterized. Figure 1 shows the XRD patterns of the pigments and fillers prepared in the examples and comparative examples. As can be seen from Figure 1, the pigments and fillers obtained in Examples 1-3 and Comparative Example 3 all showed characteristic diffraction peaks corresponding to the inverse spinel structure of zinc titanate, and the diffraction peaks were sharp and had high intensity, indicating that the obtained powders had high crystallinity and a relatively stable crystal structure; while the diffraction peaks of the pigments and fillers obtained in Comparative Examples 1-2 differed from the target inverse spinel structure, indicating that they failed to form the same target crystal structure as the examples or had poor crystal phase integrity. It can be seen that the raw material composition and molten salt preparation process used in this invention are conducive to promoting the formation of the doped modified zinc titanate inverse spinel structure, thereby obtaining pigments and fillers with stable crystal structure.

[0037] Figure 2 shows SEM images of the pigments and fillers prepared in Example 1. As can be seen from Figure 2, the pigments and fillers obtained in Example 1 have relatively regular particle morphology and uniform particle distribution, with no obvious large-sized agglomerates. The powder particles have certain packing porosity, which is beneficial for their dispersion and filling in the coating system. The above results indicate that the preparation method of this invention can obtain pigments and fillers with relatively uniform morphology, small particle size, and good dispersibility, providing a good structural basis for their application in high-temperature thermal control coatings.

[0038] (2) The properties of the pigments and fillers obtained in Examples 1-3 and Comparative Examples 1-4 were characterized. Specifically, 50 g of pigments and fillers were mixed with 25 g of potassium silicate solution with a concentration of 0.30 g / mL, 10 g of silica sol and 15 g of deionized water to obtain a thermal control coating; after coating on a pretreated aluminum alloy substrate, the coating was leveled at room temperature for 30 min, cured at 80°C for 2 h, and then heat-treated at 200°C for 2 h to obtain thermal control coatings prepared with the pigments and fillers provided in different examples and comparative examples.

[0039] The solar absorptivity of the thermal control coating was measured using a Perkin Elmer LAMBDA 950 UV-VIS-NIR spectrometer, and the hemispherical emissivity of the pigments and fillers was measured using an AZ Technology TEMP 2000A emissivity meter. The results are shown in Table 1 and [Table data missing]. Figure 3 As shown.

[0040] Table 1

[0041] As shown in Table 1 and Figure 3 above, the solar absorptivity of the samples corresponding to Examples 1-3 are 0.089, 0.082, and 0.090, respectively, all lower than that of Comparative Example 4. Meanwhile, the hemispherical emissivity of Examples 1-3 at 600℃ is 0.83, 0.83, and 0.84, respectively, all higher than that of the Comparative Example. This indicates that the pigments and fillers prepared in this invention are beneficial for reducing the solar absorptivity of the thermal control coating and improving its infrared emission performance. Figure 3 further shows that as the test temperature increases, the hemispherical emissivity of both Example 1 and Comparative Example 1 decreases. However, the hemispherical emissivity of Example 1 is higher than that of Comparative Example 1 at all test temperatures, and the emissivity decay under high-temperature conditions is relatively smaller. Especially at 400℃ and 600℃, Example 1 can still maintain a high hemispherical emissivity, indicating that it has a superior ability to retain high-temperature infrared radiation performance. The above results demonstrate that the potassium silicate-coated doped and modified zinc titanate pigments and fillers prepared in this invention can impart low solar absorptivity and high hemispherical emissivity to the thermal control coating, and have good high-temperature stability, making it suitable for the preparation of high-temperature resistant thermal control coatings for spacecraft.

[0042] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing pigments and fillers, characterized in that, Includes the following steps: Step 1: Using a mixture of ZnCl2 and TiO2 as the main raw material, ZnCl2-NaCl as the molten salt raw material, and oxides containing doped elements as modifiers, doped modified zinc titanate powder is prepared by molten salt method; Step 2: The doped and modified zinc titanate powder is coated with potassium silicate by spray drying to obtain pigments and fillers.

2. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of ZnCl2 to TiO2 in the main raw materials is 2:1; the purity of ZnCl2 is >99% and the particle size D50 is <0.5μm; the TiO2 is anatase crystal form, with a purity >99% and a particle size D50 <0.5μm.

3. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of ZnCl2 to NaCl in the molten salt raw material is 1:

1.

4. The preparation method according to claim 1, characterized in that, The modifier in step 1 is one or a mixture of two of γ-Al2O3, Ga2O3, Gd2O3, Tm2O3, and Lu2O3; the purity of the modifier is >99% and the particle size D50 is <2μm.

5. The preparation method according to any one of claims 1 to 4, characterized in that, Step 1 involves mixing the main raw material, molten salt raw material, and modifier and then ball milling them to obtain a mixed powder. The mixed powder is then sintered at high temperature. The calcined product is pulverized and dissolved in deionized water, and then repeatedly rinsed with deionized water until no white precipitate is formed in the washing solution when tested with silver nitrate reagent. The washed powder is then dried to obtain the doped and modified zinc titanate powder.

6. The preparation method according to claim 5, characterized in that, The ball milling conditions are as follows: solvent is ethanol or acetone, rotation speed is 400-800 rpm, time is 3-5 h, and drying temperature after ball milling is 60-100℃ for 3-5 h.

7. The preparation method according to claim 5, characterized in that, The high-temperature sintering conditions are: temperature 1000~1200℃, time 2~4h.

8. The preparation method according to any one of claims 1 to 4, characterized in that, The operation process of step 2 is as follows: The doped and modified zinc titanate powder obtained in step (1) is pulverized by airflow, and the powder with a fineness of 1~3μm is collected by a collector. The powder and potassium silicate solution are homogenized for 20min at a temperature of 45~55℃ and a pressure of 25~35MPa. Then, the powder is spray-dried at an inlet hot air temperature of 140~160℃ and an outlet temperature of 70~90℃. The powder particles <3μm are collected by a filter bag, which are the pigments and fillers.

9. A pigment or filler prepared by the method according to any one of claims 1 to 8, characterized in that, The pigment / filler is potassium silicate coated and doped modified zinc titanate powder with an inverse spinel structure.

10. An application of the pigment / filler according to claim 9, characterized in that, Used for the preparation of high-temperature resistant thermal control coatings for spacecraft.

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