CN117567877B

CN117567877B - Rare earth-based reflective filler slurry for radiation refrigeration coating and preparation method thereof

Info

Publication number: CN117567877B
Application number: CN202410041725.9A
Authority: CN
Inventors: 吴德平; 张俊辉; 潘文龙; 邓杰; 金文龙; 邓冰; 刘虎威; 颜世强; 宋军; 张骞
Original assignee: Zhongxi Yitu Technology Development Co ltd; Institute of Multipurpose Utilization of Mineral Resources Chinese Academy of Geological Sciences
Current assignee: Zhongxi Yitu Technology Development Co ltd; Institute of Multipurpose Utilization of Mineral Resources Chinese Academy of Geological Sciences
Priority date: 2024-01-11
Filing date: 2024-01-11
Publication date: 2024-04-05
Anticipated expiration: 2044-01-11
Also published as: CN117567877A

Abstract

The invention relates to the technical field of coating materials, in particular to rare earth-based reflective filler slurry for radiation refrigeration coating and a preparation method thereof. The slurry comprises the following raw materials in parts by weight: 20-35 parts of germanium oxide, 25-36 parts of niobium oxide, 13-20 parts of rare earth oxide and 16-35 parts of selenium oxide. The preparation method of the slurry comprises the following steps: mixing the raw materials and then crushing; sintering the crushed powder, and then quenching the sintered melt with cold water to obtain crude product powder; adding a solvent into the crude product powder for grinding to obtain slurry A1, slurry A2 and slurry A3 with different particle sizes; adding water into the crude product powder for grinding, then carrying out atomization drying, and sintering again to obtain powder, wherein the powder is dispersed in a solvent to obtain A4 slurry; and mixing the slurry A1, the slurry A2, the slurry A3 and the slurry A4 to obtain the composite material. The slurry has low production cost, higher window emissivity and reflectivity, and can effectively reduce the surface temperature of an object when being coated on the surface of the object.

Description

Rare earth-based reflective filler slurry for radiation refrigeration coating and preparation method thereof

Technical Field

The invention relates to the technical field of coating materials, in particular to rare earth-based reflective filler slurry for radiation refrigeration coating and a preparation method thereof.

Background

The demand of the whole society for energy-saving building materials is increasing, and among a plurality of energy-saving building materials, the radiation refrigeration coating is an emerging coating product in recent years. The coating product has both high sunlight reflecting effect and high 'atmospheric window' emitting effect. The high sunlight reflection performance can reduce the incidence of sunlight energy, and the high emission performance of the atmospheric window can emit heat into the outer space in the form of 8-13 micron heat radiation, so that the heat dissipation and refrigeration effects are realized. After the radiation refrigeration paint is painted on the wall surface, the incidence of external energy in the building can be effectively reduced, thereby realizing the effects of energy conservation and consumption reduction.

The core material of the radiation refrigeration paint is functional filler in the paint layer. In the prior art, two types of fillers are generally used to realize the radiation refrigeration function, and the first type of material is sunlight reflective filler. Among these fillers, titanium dioxide is the most commonly used solar reflective filler with the best combination of properties, but it absorbs ultraviolet light resulting in a low overall reflectance. The second type of material is an emission type filler, and common emission type fillers are silicon dioxide microspheres and glass microspheres, and the materials have good emission performance in a 9.2-micrometer far infrared band. But emissive materials can reduce the solids content of the reflective filler in the coating, further resulting in a reduction in the reflectivity of the coating.

The traditional radiation refrigeration paint contains resin components, such as the radiation refrigeration paint disclosed in CN202211068033.0, CN201910607455.2, CN201911055405.4 and the like, and the resin components can enhance the intensity of the paint, however, the resin can absorb infrared rays in sunlight and reduce the solar reflectance of the paint, so that the solar reflectance of the traditional radiation refrigeration paint is not high, and the self-curing and other failure problems of the resin occur in the long-time storage process are caused.

In view of the foregoing, there is a need for a radiation refrigeration slurry with high window emissivity and high reflectivity without adding resin components.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide rare earth-based low-cost slurry for reflective filler for radiation refrigeration coating, so as to at least achieve the effects of high window emissivity and high reflectivity of the slurry.

The aim of the invention is realized by the following technical scheme:

slurry for rare earth-based reflective filler for radiation refrigeration coating:

the raw materials comprise, by weight, 20-35 parts of germanium oxide, 25-36 parts of niobium oxide, 13-20 parts of rare earth oxide and 16-35 parts of selenium oxide.

The rare earth oxide is lanthanum oxide and cerium oxide;

and/or, the weight ratio of the lanthanum oxide to the cerium oxide is 25-35:65-75.

Notably, high reflectivity properties require materials that have both high refractive indices and low ultraviolet absorption. In the prior art, the titanium dioxide material has high refractive index, but the final sunlight reflection effect is lower due to strong ultraviolet absorption. Materials such as barium sulfate and calcium carbonate have low ultraviolet absorptivity, but lower refractive index, so that the reflection performance is still insufficient under the same solid content condition. The glass material prepared from gallium and niobium can realize high refractive index and high ultraviolet reflection performance. However, the gallium materials selected in this method are extremely expensive and are not suitable for low cost industrial production. Based on the method, the method selects the oxides of niobium, germanium and selenium as basic raw materials, uses germanium and selenium with similar element properties but cheaper price to replace expensive gallium, and realizes high infrared reflection performance with low cost after the germanium and the selenium are prepared into amorphous materials.

The preparation method of the slurry comprises the following steps:

s1: mixing the germanium oxide, the niobium oxide, the rare earth oxide and the selenium oxide and then crushing;

s2: carrying out first sintering on the crushed powder at high temperature, and then quenching the sintered melt in cold water to obtain crude product powder;

s3: adding solvent into the crude product powder for grinding to obtain A1 slurry with the granularity of 15-25 mu m, A2 slurry with the granularity of 5-10 mu m and A3 slurry with the granularity of 0.3-0.7 mu m respectively;

s4: adding water into the coarse product powder for grinding, then carrying out atomization drying, and carrying out second sintering at high temperature, wherein the obtained powder is dispersed in a solvent to obtain A4 slurry;

s5: and mixing the A1 slurry, the A2 slurry, the A3 slurry and the A4 slurry to obtain the composite material.

Notably, the nature of the filler to reflect infrared light is Mie scattering with the incident light. Generally, large particle fillers have a good reflection effect on infrared rays having a longer wavelength, and small particle filler particles have a good reflection effect on incident light having a shorter wavelength. In the prior art, the used filler is always subjected to a uniform ball milling or sand milling process, so that the obtained slurry has uniform particle size, good reflection effect on incident light with a certain wavelength and poor spectral reflection performance on total sunlight. In the method, through process control, powder materials are firstly processed into intermediate raw materials with certain particle sizes, then the powder with various particle size distributions is proportioned according to certain content, and finally the filler products with a plurality of particle size distributions are obtained.

Further, in the step S2, the granularity of the crushed powder is 30-40 meshes, namely-30 meshes to +40 meshes.

Further, in step S2, the temperature of the first sintering is 1400-1430 ℃;

and/or the time of the first sintering is 4-4.5h.

Further, in step S4, the particle size of the ground coarse product powder is 1-5 μm.

Further, in step S4, the temperature of the second sintering is 1220-1250 ℃;

and/or the second sintering time is 20-30min.

Further, in step S5, the weight ratio of the A1 slurry, the A2 slurry, the A3 slurry, and the A4 slurry is 1:0.8-1.3:0.4-0.6:0.1-0.2.

It is noted that the filler particle size can affect not only the reflective properties of the filler as a whole, but also the emission properties of the filler. The radiation refrigeration paint is additionally added with a filler with specific particle size and special morphology, and the emissivity can be further improved by utilizing the photon enhancement effect of the filler on infrared rays of atmospheric window wavebands.

Further, in steps S4 and S5, the solvent includes water or butyl acetate;

for the slurry for the water-based paint, the solvent is water; for the slurry for the oil-type paint, the solvent is butyl acetate;

and/or the solid content of the A1 slurry, the A2 slurry, the A3 slurry and the A4 slurry is 30-40%.

Furthermore, the slurry can be used as a raw material of a traditional paint, and can be processed into the paint by mixing with a traditional resin material, so that the paint has complementarity with the traditional paint.

The application provides a special material which can be directly painted on the wall surface as a functional layer paint. Compared with the traditional radiation refrigeration paint, the paint does not contain resin components, and can be directly used as a functional layer to be painted on the wall surface, thereby fundamentally avoiding the absorption of resin to infrared rays and ensuring the highest sunlight reflection effect of the coating. Secondly, because the size of the material particles in the slurry used in the application is multi-scale and multi-distributed, the functional interlayer particles are stacked more tightly after the slurry is coated on the wall surface. Meanwhile, the special electronic layer structure on the surface of the rare earth material can enable hydrogen bonds to be formed among particles more easily, so that the bonding between particles of the functional layer and between the functional layer and the wall surface is improved, and the functional layer can be ensured to have enough strength even if no resin exists. Meanwhile, the use of resin is avoided, so that the stability of the material is greatly improved.

The beneficial effects of the invention are as follows:

1. the slurry has the advantages of low cost of raw materials, high window emissivity and high reflectivity; can be used for preparing paint products or can be directly used as functional layer paint to be painted on the wall surface; can also be used as raw material of paint products for preparing other paint products. The slurry is environment-friendly, is coated on the surfaces of fabrics, building outer walls, roofs and petroleum storage tanks, and can effectively reduce the surface temperature of objects.

2. The emissivity of the 'atmospheric window' of the slurry for the radiation refrigeration coating is up to 96%, and the reflection effect of ultraviolet-visible-infrared light is up to 92%.

Drawings

FIG. 1 is an XRD diffraction spectrum of a powder material in experimental example 1;

FIG. 2 shows the reflectance test results of the slurry in Experimental example 1;

FIG. 3 is a graph showing the result of the forbidden bandwidth test in experimental example 1;

fig. 4 is an SEM photograph of the A4 slurry in example 1.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to the accompanying drawings, but the scope of the present invention is not limited to the following description.

Example 1

20 parts of germanium oxide, 26 parts of niobium oxide, 16 parts of cerium oxide and 30 parts of selenium oxide. After fully mixing the raw materials, adding a certain amount of water into a planetary ball mill for wet milling, wherein the ball milling speed is 400 rpm, the milling time is 12 hours, the ratio of large balls to small balls is 3:4:3, and the air in a cavity is: feed liquid: the volume ratio of the balls is controlled to be 1:1:1. After completion of the grinding, the grinding beads were filtered with a 40-mesh screen to obtain a coarse grinding slurry. And (5) fully drying the coarse grinding slurry in a 90-degree oven to obtain a precursor sample of the plate-formed block. And (3) putting the massive precursor sample into a powder crusher again to be crushed into powder, so as to obtain the precursor powder which is uniformly mixed.

The precursor powder is filled into a corundum crucible, and the temperature is raised and heated in a smelting furnace with stirring, wherein the temperature raising program is as follows: the first stage, the temperature interval is 50-400 ℃ and the time is 35 minutes; the second stage, the temperature interval is 400-400 ℃ and the time is 30 minutes; the third section is 400-900 ℃ and the time is 1 hour; the fourth section is 900-1400 ℃ and the time is 2 hours; the fifth section is at constant temperature of 1400 ℃ for 4 hours; the procedure is then terminated. After the fifth section is insulated for 3 hours, the corundum stirring paddle is downwards detected into the feed liquid, the corundum stirring paddle is slowly stirred at the speed of 60 revolutions per minute for 30 minutes, and then the stirring paddle is lifted. After the temperature-raising program is finished, directly pouring the feed liquid into water for cold quenching treatment, and filtering the powder in the water to obtain coarse powder.

Preparing a coarse material powder solution with 40% content, wherein the content of a dispersing agent is 12%, the dispersing agent is BYK111 type dispersing agent, water is used as a solvent, 60 parts of ultrapure water is added, and the coarse material mixed solution is obtained after full mixing. 10 kg of coarse powder solution is put into a sand mill for sand milling, the particle size of grinding balls is 0.5 and mm, and the particle size of primary slurry is detected by a laser particle sizer every 15 minutes until slurry with the target particle size is obtained. By strictly controlling the particle diameter, slurry A1 having D50 at 21 μm, slurry A2 having D50 at 6.2 μm, and slurry A3 having D50 at 0.45 μm were prepared, respectively.

Preparing a coarse powder solution with 40% content by taking water as a solvent, adding 13% BYK111 dispersing agent, grinding the slurry in a sand mill, monitoring the particle size until the particle size is 1-10 mu m, and measuring the D50 particle size to be 3.2 mu m after finishing grinding. The slurry was poured into the feed bottle of a spray dryer, the spray temperature was set at 150 degrees, and the atomizer flow rate was empirically adjusted until a powder vortex was formed. And (3) injecting the obtained fine powder into a suspension sintering furnace, setting the sintering degree to 1250 ℃, and fully sintering to obtain spherical powder.

The obtained spherical powder is reconfigured into a solution with 30 percent of content, the solvent is ultrapure water, 5 percent of BYK111 dispersing agent is added again, and the mixture is fully stirred by a disc stirrer, wherein the spherical powder is poured into the solution in batches under the stirring condition, and after the solution becomes uniform bubble-free emulsion, the solution is poured out for preservation and is named as A4. In the solution A4, the powder form was observed by SEM electron microscopy as shown in FIG. 4.

Four slurries were mixed in mass ratio A1: a2: a3: a4 =1: 1:0.5: mixing in a proportion of 0.15 to finally obtain the finished slurry.

Example 2

35 parts of germanium oxide, 35 parts of niobium oxide, 20 parts of cerium oxide and 16 parts of selenium oxide are taken. After fully mixing the raw materials, adding a certain amount of water into a planetary ball mill for wet milling, wherein the ball milling speed is 400 rpm, the milling time is 12 hours, the ratio of large balls to small balls is 3:4:3, and the air in a cavity is: feed liquid: the volume ratio of the balls is controlled to be 1:1:1. After completion of the grinding, the grinding beads were filtered with a 40-mesh screen to obtain a coarse grinding slurry. And (5) fully drying the coarse grinding slurry in a 90-degree oven to obtain a precursor sample of the plate-formed block. And (3) putting the massive precursor sample into a powder crusher again to be crushed into powder, so as to obtain the precursor powder which is uniformly mixed.

The obtained spherical powder is reconfigured into a solution with 30 percent of content, the solvent is ultrapure water, 5 percent of BYK111 dispersing agent is added again, and the mixture is fully stirred by a disc stirrer, wherein the spherical powder is poured into the solution in batches under the stirring condition, and after the solution becomes uniform bubble-free emulsion, the solution is poured out for preservation and is named as A4.

Four slurries were mixed in mass ratio A1: a2: a3: a4 =1: 0.8:0.4: mixing in a proportion of 0.2 to finally obtain the finished slurry.

Experimental example 1

The XRD test was performed on the coarse powder of example 1, and the results are shown in fig. 1 of the specification, and it is clear from the results that the material structure is truly amorphous. For the reflection performance test, the slurry is prepared into a coating sample for testing, specifically, the aqueous acrylic resin 30 g with the solid content of 35 percent is taken, the finished slurry is 60 g, a proper amount of water is added to adjust the viscosity of the coating, the coating is uniformly coated on the surface of an aluminum sheet, after the resin is completely cured and dried, the reflection effect is tested by an ultraviolet-visible-infrared spectrophotometer, and the reflection effect can reach 92 percent as shown in an attached drawing 2 of the specification. The band result is calculated according to equation 1:

formula 1: (αhνm=a (hν -Eg);

wherein alpha is the absorptivity of the powder to the incident light. V is the frequency of the incident photon, h is the Planck constant, A is the proportionality constant, eg is the band gap, and m is a constant value. For direct bandgap semiconductor materials, m is equal to 2, and for indirect bandgap semiconductor materials, m=0.5.

As shown in the figure 3 of the specification, the forbidden bandwidth reaches 3.6 and eV, which is 2.7-2.8 eV higher than that of titanium white. The emissivity data of the slurry are tested by an IR-1 hemispherical emissivity tester, and the emissivity of a window at the position of 8-14 mu m is measured to be 0.96 at 25 ℃, so that excellent emissivity performance is shown.

Comparative example 1

A radiation refrigeration slurry was prepared in the same manner as in example 1 except that rare earth oxide was not added to the raw material. The specific method comprises the following steps:

20 parts of germanium oxide, 26 parts of niobium oxide and 30 parts of selenium oxide are taken. After fully mixing the raw materials, adding a certain amount of water into a planetary ball mill for wet milling, wherein the ball milling speed is 400 rpm, the milling time is 12 hours, the ratio of large balls to small balls is 3:4:3, and the air in a cavity is: feed liquid: the volume ratio of the balls is controlled to be 1:1:1. After completion of the grinding, the grinding beads were filtered with a 40-mesh screen to obtain a coarse grinding slurry. And (5) fully drying the coarse grinding slurry in a 90-degree oven to obtain a precursor sample of the plate-formed block. And (3) putting the massive precursor sample into a powder crusher again to be crushed into powder, so as to obtain the precursor powder which is uniformly mixed.

A 40% strength coarse powder solution is prepared, wherein the dispersant content is 12%, BYK111 dispersant is selected as the dispersant, and the solvent depends on the final paint product requirement. For the slurry for the water-based paint, the solvent is water; for oil-type coatings, the solvent is butyl acetate. 10 kg of coarse powder solution is put into a sand mill for sand milling, the particle size of grinding balls is 0.5 and mm, and the particle size of primary slurry is detected by a laser particle sizer every 15 minutes until slurry with the target particle size is obtained. By strictly controlling the particle diameter, slurry A1 having D50 at 21 μm, slurry A2 having D50 at 6.2 μm, and slurry A3 having D50 at 0.45 μm were prepared, respectively.

The obtained spherical powder is reconfigured into a solution with 30 percent of content, the solvent is kept consistent with the A1 slurry, 5 percent of BYK111 dispersing agent is added again, and the mixture is fully stirred by a disc stirrer, wherein the spherical powder is poured into the solution in batches under the stirring condition, and after the solution becomes uniform bubble-free emulsion, the solution is poured out for storage and named as A4. Four slurries were mixed in mass ratio A1: a2: a3: a4 =1:1: 0.5: mixing in a proportion of 0.15 to finally obtain the finished slurry.

Comparative example 2

A radiation refrigeration slurry was prepared, the method being identical to example 1, except that only slurry A1 of d50=21 μm was used for the preparation. The specific method comprises the following steps:

A 40% strength coarse powder solution is prepared, wherein the dispersant content is 12%, BYK111 dispersant is selected as the dispersant, and the solvent depends on the final paint product requirement. For the slurry for the water-based paint, the solvent is water; for oil-type coatings, the solvent is butyl acetate. 10 kg of coarse powder solution is put into a sand mill for sand milling, the particle size of grinding balls is 0.5 and mm, and the particle size of primary slurry is detected by a laser particle sizer every 15 minutes until slurry with the target particle size is obtained. By strictly controlling the particle diameter, slurry A1 having D50 of 21 μm was prepared.

The obtained spherical powder is reconfigured into a solution with 30 percent of content, the solvent is kept consistent with the A1 slurry, 5 percent of BYK111 dispersing agent is added again, and the mixture is fully stirred by a disc stirrer, wherein the spherical powder is poured into the solution in batches under the stirring condition, and after the solution becomes uniform bubble-free emulsion, the solution is poured out for storage and named as A4. Mixing two slurries according to a mass ratio A1: a4 =2.5: mixing in a proportion of 0.15 to finally obtain the finished slurry.

Comparative example 3

A radiation refrigeration slurry was prepared, the method being identical to example 1, except that only slurry A1 of d50=0.45 μm was used for the preparation. The specific method comprises the following steps:

A 40% strength coarse powder solution is prepared, wherein the dispersant content is 12%, BYK111 dispersant is selected as the dispersant, and the solvent depends on the final paint product requirement. For the slurry for the water-based paint, the solvent is water; for oil-type coatings, the solvent is butyl acetate. 10 kg of coarse powder solution is put into a sand mill for sand milling, the particle size of grinding balls is 0.5 and mm, and the particle size of primary slurry is detected by a laser particle sizer every 15 minutes until slurry with the target particle size is obtained. By strictly controlling the particle diameter, slurry A1 having a D50 of 0.45 μm was prepared.

Comparative example 4

A radiation refrigeration slurry was prepared in the same manner as in example 1 except that spherical powder was replaced with silica microbeads. The specific method comprises the following steps:

The silica microbeads are prepared into a 30% solution, the solvent is selected to be consistent with the A1 slurry, 5% BYK111 dispersing agent is added again, the solution is fully stirred by a disc stirrer, spherical powder is poured into the solution in batches under the stirring condition, and after the solution becomes uniform bubble-free emulsion, the solution is poured out for storage and named as A4. Four slurries were mixed in mass ratio A1: a2: a3: a4 =1: 1:0.5: mixing in a proportion of 0.15 to finally obtain the finished slurry.

Experimental example 2

Comparative examples 1-4 and examples 1-2 were taken for reflectance performance testing and emissivity testing as follows:

the slurry was prepared into a coating sample for testing, and for comparison of experimental data with conventional coatings, the slurry was used as a raw material, and a resin was added to the slurry to prepare a coating for testing. The specific method is that the general aqueous acrylic resin 30 g with the solid content of 35 percent and the finished product slurry 60 g are taken, and a proper amount of water is added to adjust the viscosity of the paint, thus obtaining the paint 5-8. After the pastes and paints 5 to 8 of comparative examples 1 to 4 were uniformly applied to the surface of the aluminum sheet, after the resin was completely cured and dried, the reflection effect was measured with an ultraviolet-visible-infrared spectrophotometer (energy band result was calculated according to formula 1), and the window emissivity data was measured with an IR-1 type hemispherical emissivity tester. The results are shown in Table 1;

TABLE 1

	Reflection effect (%)	Window emissivity (%)
			Example 1	92.0	96
Example 2	92.2	96
			Comparative example 1	89.1	78
Comparative example 2	82.3	92
			Comparative example 3	83.6	93
Comparative example 4	85.4	94
			Coating 5	87.5	81
Coating 6	80.4	92
			Coating 7	81.7	92
Coating 8	84.4	93

The foregoing is merely a preferred embodiment of the invention, and it is to be understood that the invention is not limited to the form disclosed herein but is not to be construed as excluding other embodiments, but is capable of numerous other combinations, modifications and environments and is capable of modifications within the scope of the inventive concept, either as taught or as a matter of routine skill or knowledge in the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims

1. A rare earth-based reflective filler slurry for radiation refrigeration paint, characterized in that:

the raw materials comprise, by weight, 20-35 parts of germanium oxide, 25-36 parts of niobium oxide, 13-20 parts of rare earth oxide and 16-35 parts of selenium oxide;

the rare earth oxide is lanthanum oxide and cerium oxide;

the weight ratio of the lanthanum oxide to the cerium oxide is 25-35:65-75;

the preparation method of the slurry comprises the following steps:

2. The slurry according to claim 1, wherein: in the step S2, the particle size of the crushed powder is 30-40 meshes.

3. The slurry according to claim 1, wherein: in the step S2, the temperature of the first sintering is 1400-1430 ℃;

the time of the first sintering is 4-4.5h.

4. The slurry according to claim 1, wherein: in step S3, the particle size is a median particle size.

5. The slurry according to claim 1, wherein: in the step S4, the granularity of the ground coarse product powder is 1-5 mu m.

6. The slurry according to claim 1, wherein: in the step S4, the temperature of the second sintering is 1220-1250 ℃;

the second sintering time is 20-30min.

7. The slurry according to claim 1, wherein: in step S5, the weight ratio of the A1 slurry, the A2 slurry, the A3 slurry and the A4 slurry is 1:0.8-1.3:0.4-0.6:0.1-0.2.

8. The slurry according to claim 1, wherein: in steps S4 and S5, the solvent includes water or butyl acetate; the solid content of the A1 slurry, the A2 slurry, the A3 slurry and the A4 slurry is 30-40%.