Highly reflective super white hollow powder, preparation method and application thereof

Abstract

The application relates to a kind of high-reflective super-white hollow powder and a preparation method and application thereof, and belongs to the field of thermal control coating.The application aims to solve the problems of existing preparation of hollow spherical ZrO2, such as high requirement for raw materials, complex process, often requiring high temperature and high pressure environment, harsh requirement for equipment, high production cost, easy to produce secondary pollution, and being not conducive to industrial production and the like.By growing hydroxide on the surface of SiO2, then through calcination and etching treatment, high-reflective ZrO2 hollow spherical super-white powder is obtained.The process of the application is simple, environment-friendly, easy to produce and low in cost, the prepared high-reflective super-white hollow powder is high in purity, uniform in particle and complete in structure, and has great market advantage.The high-reflective super-white hollow powder prepared by the application has good dispersibility in potassium silicate resin, and the inorganic thermal control coating obtained by spraying method has excellent thermal control performance, the solar absorption ratio is 0.118, the radiation absorption ratio is less than 0.2, and the thermal control performance requirement of low radiation absorption ratio coating is met.

Description

Technical Field

[0001] This invention belongs to the field of thermal control coatings, specifically, it relates to a high-reflectivity ultra-white hollow powder, its preparation method, and its application. Background Technology

[0002] Low absorptivity-to-radiance ratio (LARR) thermal control coatings, as one of the main means of passive thermal control in spacecraft, are an important component of spacecraft thermal control systems. They can regulate the solar absorptivity of the material surface (…). α s ) and infrared emissivity ( ε This allows for precise temperature control of spacecraft to ensure a normal operating environment inside the spacecraft. Ideally, the absolute surface temperature T of an object in space is proportional to... α s and ε The ratio, that is, through regulation α s / ε It can achieve the control of thermal balance of an object. Thermal control coatings can be divided into inorganic white paint and organic white paint according to the type of adhesive. Compared with organic white paint, inorganic white paint has excellent optical properties, moderate substrate adhesion strength and good high temperature resistance, so it has an irreplaceable role.

[0003] Hollow spherical ZrO2 pigment is a non-metallic oxide pigment with a hollow structure. A low-absorption-to-radius ratio inorganic thermal control coating is prepared by adding hollow spherical ZrO2 pigment to potassium silicate resin. The thermal control coating reflects light by utilizing the scattering of sunlight by the hollow spherical ZrO2 pigment. Hollow spherical ZrO2 pigment has attracted much attention due to its excellent chemical stability, high refractive index, and wide bandgap.

[0004] The traditional methods for preparing hollow spherical ZrO2 mainly include solid-phase and liquid-phase methods. The traditional solid-phase method for preparing hollow spherical ZrO2 has the following problems: (1) Based on the direct mixing of solid raw materials, it essentially relies on mechanical force (such as ball milling) for crushing and mixing, making it difficult to directly form a regular hollow spherical morphology; (2) In order to ensure sufficient reaction and uniform mixing, the reaction process needs to be carried out at a high temperature, which needs to reach above 900℃, and the product has a wide particle size distribution, uneven particle size, and serious agglomeration phenomenon; (3) In order to meet its application requirements, additional crushing and classification steps are usually required to improve it, which can easily cause the shell to break or the morphology to be damaged, thus reducing its chemical resistance. Generally speaking, the copper chromium black pigment prepared by the traditional liquid-phase method is superior to that prepared by the traditional solid-phase method in terms of purity and uniformity. However, the traditional liquid-phase method for preparing hollow spherical ZrO2 also has obvious shortcomings, such as high raw material requirements, complex process, often requiring high temperature and high pressure environment, demanding equipment requirements, long reaction time, high production cost, and easy to generate secondary pollution, which is not conducive to industrial production.

[0005] Therefore, there is an urgent need to develop a high-reflectivity ultra-white hollow powder that is simple to prepare, environmentally friendly, easy to scale up, and has superior optical performance. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a high-reflectivity ultra-white hollow powder, its preparation method, and its application.

[0007] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a high-reflectivity ultra-white hollow powder, characterized in that the powder material is ZrO2, it is in the form of hollow spheres, and it is prepared according to the following steps: Step 1: Mix anhydrous ethanol, deionized water and NH3·H2O, stir until uniform, add Si(OC2H5)4 dropwise, continue stirring, centrifuge and wash until neutral, dry to obtain SiO2 template; Step 2: Place the SiO2 template and C 16 H 35 N was ultrasonically dispersed in anhydrous ethanol, then NH3·H2O was added and stirred until homogeneous. C was then gradually added. 16 H 36 O4Zr was stirred and reacted until the reaction was complete. After washing, centrifuging, drying and calcining, SiO2@ZrO2 was obtained. Step 3: At a certain temperature, SiO2@ZrO2 is fully dispersed in deionized water, and then NaOH solution is added dropwise while continuously stirring. After complete etching, the mixture is washed, centrifuged until neutral, and dried to obtain high-reflectivity ultra-white hollow powder.

[0008] Further specifying, in step 1, the volume ratio of anhydrous ethanol, deionized water and NH3·H2O is (90~100):20:9, and the volume ratio of anhydrous ethanol and Si(OC2H5)4 is (90~100):5.

[0009] To further specify, in step 1, after adding Si(OC2H5)4, the mixture is stirred for 10 hours.

[0010] Further specifying, in step 2, the SiO2 template and C 16 H 35 The mass ratio of N is (4~5):5.

[0011] Further specifying, in step 2, NH3·H2O and C 16 H 36 The volume ratio of O4Zr is 3:(5~6).

[0012] To further specify, in step 2, after adding C...16 H 36 O4Zr was stirred for 4 hours.

[0013] Further specifying, in step 2, calcination is carried out at 700℃~800℃ for 6 hours.

[0014] Further specifying, in step 3, the temperature is 60℃~70℃.

[0015] Further specifying, in step 3, the mass ratio of SiO2@ZrO2 to NaOH is 5:(4~8), and the concentration of the NaOH solution is 1 mol·L⁻¹. -1 ~2mol·L -1 .

[0016] To further specify, in step 3, the mixture is stirred for 6 hours after the NaOH solution is added.

[0017] In addition, the use of the above-mentioned high-reflectivity ultra-white hollow powder or the preparation of high-reflectivity ultra-white hollow powder by any of the above-described methods is also provided, in the application of thermal control coatings.

[0018] Further specifying, the thermal control coating is prepared according to the following steps: Dissolve 21g~22g of potassium silicate resin in 10g~12g of deionized water and stir until uniform. Then add 0.1g~0.2g of magnesium aluminum silicate and continue stirring. Subsequently, add 16g of high-reflectivity ultra-white hollow powder and stir until uniform to obtain a sprayable thermal control coating. Spray the coating onto the treated aluminum alloy substrate using air spraying technology and cure at 100℃~120℃ for 2~3 hours.

[0019] This invention prepares a SiO2 template at room temperature using a sol-gel method, then loads a non-metallic hydroxide onto the SiO2, and calcines it to obtain SiO2@ZrO2. Subsequently, it is etched to prepare high-reflectivity ZrO2 hollow spherical ultra-white powder.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention obtains high-reflectivity ZrO2 hollow spherical ultra-white powder by growing hydroxide on the surface of a SiO2 template, followed by calcination and etching. The preparation process provided by this invention is simple, environmentally friendly, easy to produce, and inexpensive. The prepared hollow spherical ZrO2 pigment has high purity, uniform particles, and a complete structure, giving it a significant market advantage. The high-reflectivity ZrO2 hollow spherical ultra-white powder prepared by this invention has a large specific surface area, excellent refractive index, and the special hollow spherical structure increases surface light scattering, enhancing its ability to reflect sunlight.

[0021] The high-reflectivity ZrO2 hollow spherical ultra-white powder prepared by this invention has good dispersibility in potassium silicate resin. The inorganic thermal control coating obtained by spraying has excellent thermal control performance, with a solar absorptivity of 0.118 and an absorptivity of less than 0.2, which meets the thermal control performance requirements of low absorptivity coatings.

[0022] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope image of the hollow spherical ZrO2 pigment prepared in Example 1; Figure 2 This is an X-ray diffraction pattern of the hollow spherical ZrO2 pigment prepared in Example 1; Figure 3 The ultraviolet-visible-near-infrared reflectance spectrum of the hollow spherical ZrO2 / potassium silicate coating prepared in Example 1; Figure 4 The image shows the ultraviolet-visible-near-infrared reflectance spectrum of the hollow spherical ZrO2 / potassium silicate coating prepared in Example 1. Detailed Implementation

[0024] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Unless otherwise specified, all raw materials used in the examples were commercially purchased.

[0026] Transmission electron microscopy (TEM): The morphology and size of the prepared hollow spherical ZrO2 were analyzed using TEM. The transmission electron microscope was a Tecnai G2F30, manufactured by FEI Corporation, USA.

[0027] X-ray diffraction (XRD): X-ray diffraction is used to analyze the phase composition of hollow spherical ZrO2 and characterize its crystal structure. The excitation source is a Cu target K. α X-ray, scanning range is 2 θ =10 70°.

[0028] Ultraviolet-Visible-Near Infrared Diffuse Reflectance Spectroscopy: The solar reflectance of the samples was measured using a PerkinElmer Lambda 950 ultraviolet-visible-near infrared diffuse reflectance spectrometer. The test range was set to 200-2500 nm with a resolution of 0.1 nm. The system was initialized with 100% reflectance using a BaSO4 standard white plate to ensure the accuracy of the test results. Subsequently, the samples to be tested were placed in the test window, and their reflectance at different wavelengths was measured to obtain the ultraviolet-visible-near infrared diffuse reflectance spectrum in the wavelength range of 200–2500 nm.

[0029] Coating emissivity test: The emissivity of the sample was tested using a TEMP 2000A emissivity meter.

[0030] Example 1 The steps for preparing high-reflectance ZrO2 hollow spherical ultra-white powder in this embodiment are as follows: Step 1, Preparation of SiO2 template: 200 mL of anhydrous ethanol, 40 mL of deionized water, and 18 mL of ammonia (NH3·H2O) were mixed and stirred at room temperature for 30 min. Then, 10 mL of tetraethyl orthosilicate (Si(OC2H5)4) was added dropwise, and stirring was continued for 10 h to obtain a milky white solution. The solution was washed with deionized water and ethanol by centrifugation at 6000 r for 8 min until neutral. Then, it was dried at 80 °C for 6 h to obtain the SiO2 template.

[0031] Step 2, Preparation of SiO2@ZrO2: 0.8g SiO2 template and 1g C 16 H 35 N was ultrasonically dispersed in 200 mL of ethanol, and 3 mL of NH3·H2O was added and stirred continuously for 30 min. Then, 5 mL of HCl was gradually added. 16 H 36 After stirring the O4Zr solution for another 4 hours, a milky white solution was obtained. The solution was washed with ethanol 3-4 times and dried at 70℃ for 8 hours. Then, it was calcined at 800℃ for 6 hours at a heating rate of 5℃ / min to obtain SiO2@ZrO2.

[0032] Step 3, Preparation of hollow spherical ZrO2: 1 g of SiO2@ZrO2 was dispersed in 100 mL of deionized water at 70 °C with stirring. Then, 7.5 mL of 2 mol·L⁻¹ sodium chloride solution was added dropwise. -1 The NaOH solution was continuously stirred for 6 hours. The resulting solution was washed with deionized water, centrifuged until neutral, and dried at 80°C for 12 hours to finally obtain hollow spherical ZrO2 pigment.

[0033] The microstructure of the prepared high-reflectance ultrawhite hollow powder was characterized, and its surface TEM image is shown below. Figure 1 As shown. By Figure 1 It can be seen that all particles have a typical hollow structure with complete structure and uniform particle size distribution, which proves that hollow spherical ZrO2 powder was successfully prepared.

[0034] X-ray diffraction analysis was performed on the prepared high-reflectance ultrawhite hollow powder, and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that the XRD pattern of the prepared hollow spherical ZrO2 shows three strong peaks of monoclinic ZrO2, and the diffraction peaks are sharp and there are no other impurity peaks. This proves that the prepared hollow spherical ZrO2 has high purity and good crystallinity.

[0035] Preparation of hollow spherical ZrO2 / potassium silicate coating: Weigh 21.6g of potassium silicate resin and dissolve it in 10.0g of deionized water. Disperse and stir at 500rpm for 5min to make it uniform. Then add 0.1g of magnesium aluminum silicate and continue stirring for 30min. Then add 16g of hollow spherical ZrO2 pigment and disperse and stir at 1200rpm for 2h to obtain a sprayable thermal control coating. Spray the coating onto the treated aluminum alloy substrate using air spraying technology and cure at 120℃ for 2h to obtain a hollow spherical ZrO2 / potassium silicate thermal control coating with a thickness of 125μm.

[0036] The prepared hollow spherical ZrO2 / potassium silicate coating was subjected to ultraviolet light. visible Near-infrared diffuse reflectance spectroscopy testing, the ultraviolet-visible near-infrared diffuse reflectance spectrum in the 200-2500 nm range is as follows: Figure 3 As shown. By Figure 3 It can be seen that in ultraviolet light... visible In the near-infrared range, the solar absorptivity of the white thermal control coating with hollow spherical ZrO2 pigment is 0.118, which proves that the hollow spherical ZrO2 / potassium silicate coating has good performance in reflecting sunlight.

[0037] The emissivity of the prepared hollow spherical ZrO2 / potassium silicate coating was tested, and the emissivity spectrum in the range of 3-35 μm is as follows: Figure 4 As shown. By Figure 4 It can be seen that the emissivity of the hollow spherical ZrO2 / potassium silicate coating is 0.940, which proves that the coating has good emission performance. Based on the solar absorptivity and emissivity obtained above, the absorptivity-to-radiation ratio of the thermal control coating is calculated to be 0.125, which is less than 0.2, meeting the thermal control performance requirements of low absorptivity-to-radiation ratio coatings.

[0038] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A high-reflectivity ultra-white hollow powder, characterized in that, The powder material is ZrO2 and is in the form of hollow spheres.

2. The method for preparing high-reflectivity ultra-white hollow powder as described in claim 1, characterized in that, Includes the following steps: Step 1: Mix anhydrous ethanol, deionized water and NH3·H2O, stir until uniform, add Si(OC2H5)4 dropwise, continue stirring, centrifuge and wash until neutral, dry to obtain SiO2 template; Step 2: Place the SiO2 template and C 16 H 35 N was ultrasonically dispersed in anhydrous ethanol, then NH3·H2O was added and stirred until homogeneous. C was then gradually added. 16 H 36 O4Zr was stirred and reacted until the reaction was complete. After washing, centrifuging, drying and calcining, SiO2@ZrO2 was obtained. Step 3: At a certain temperature, SiO2@ZrO2 is fully dispersed in deionized water, and then NaOH solution is added dropwise while continuously stirring. After complete etching, the mixture is washed, centrifuged until neutral, and dried to obtain high-reflectivity ultra-white hollow powder.

3. The method according to claim 2, characterized in that, In step 1, the volume ratio of anhydrous ethanol, deionized water and NH3·H2O is (90~100):20:9, and the volume ratio of anhydrous ethanol and Si(OC2H5)4 is (90~100):

5.

4. The method according to claim 2, characterized in that, SiO2 template and C 16 H 35 The mass ratio of N is (4~5):

5.

5. The method according to claim 2, characterized in that, NH3·H2O and C 16 H 36 The volume ratio of O4Zr is 3:(5~6).

6. The method according to claim 2, characterized in that, Calcination at 700℃~800℃.

7. The method according to claim 2, characterized in that, The specific temperature is 60℃~70℃.

8. The method according to claim 2, characterized in that, The mass ratio of SiO2@ZrO2 to NaOH is 10:(4~8), and the concentration of NaOH solution is 1~2 mol·L. -1 .

9. An application of the high-reflectivity ultra-white hollow powder according to claim 1 or the high-reflectivity ultra-white hollow powder prepared by the method according to any one of claims 2-8, characterized in that, Application in the preparation of thermal control coatings.

10. The application according to claim 9, characterized in that, The thermal control coating is prepared according to the following steps: Dissolve 21g~22g of potassium silicate resin in 10g~12g of deionized water and stir until uniform. Then add 0.1g~0.2g of magnesium aluminum silicate and continue stirring. Subsequently, add 16g of ultra-white reflective powder and stir until uniform to obtain a sprayable thermal control coating. Spray the coating onto the treated aluminum alloy substrate using air spraying technology and cure at 100℃~120℃ for 2~3 hours.

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