CN115651460A - MgO coating for radiation cooling and preparation process thereof - Google Patents
MgO coating for radiation cooling and preparation process thereof Download PDFInfo
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Abstract
The invention discloses a MgO coating for radiation cooling and a preparation process thereof, relating to the technical field of radiation refrigeration, comprising MgO particles, a coating substrate, absolute ethyl alcohol, a defoaming agent and a film-forming auxiliary agent; wherein the MgO particles have a non-uniform particle size distribution; also discloses a preparation process of the MgO coating for radiation cooling, which comprises the following steps: preparing PVA particles into a PVA solution as a coating substrate; mixing MgO particles with a coating substrate, and adding absolute ethyl alcohol for dispersion and stirring to obtain a pre-dispersion coating; carrying out ultrasonic treatment on the pre-dispersed coating, and adding a defoaming agent and a film-forming assistant to obtain a finished coating; the invention adopts MgO particles with different particle sizes as the main component of the coating, the particles with different particle sizes have different sunlight scattering effects on different wave bands, and the coating particles with non-uniform particle size distribution can better realize the reflection of the sunlight in all wave bands; and the PVA solution is used as a solvent of the coating, so that the coating has higher emissivity.
Description
Technical Field
The invention relates to the technical field of radiation refrigeration, in particular to MgO coating for radiation cooling and a preparation process thereof.
Background
The radiation cooling technology is a novel passive cooling technology which reflects most of sunlight and emits infrared heat to outer space with the temperature of 3K through an atmospheric window (8-13 mu m). The high-efficiency green daytime radiation cooling coating which can be produced in a large scale can be prepared, the refrigeration energy consumption can be effectively reduced, and the carbon emission can be reduced. The radiant cooling material is required to have high reflectivity (R > 90%) in the solar band and high emissivity (E > 90%) with atmospheric window fluctuations. Therefore, the preparation of the radiation cooling material which can be produced in a large scale, is efficient, simple in preparation and convenient in construction is the key point and the difficulty for popularizing the novel cooling technology.
The coating exists in a liquid state before construction, can be directly sprayed and blade-coated on the surface of a cooled object, and then is naturally dried to form a solid film without other adhesives, so that the coating is a better application mode of the radiation refrigerating material. The current traditional commercial white coating consists of TiO 2 Particles and acrylates. Due to TiO 2 Higher refractive index of (>2.5 And the inherent ir emissivity of acrylates, commercial coatings exhibit some radiant cooling properties. However, tiO 2 Has an electronic band gap (3.0 eV) smaller than that of ultraviolet light (3.2 eV), and inevitably absorbsUltraviolet light and blue-violet light. Therefore, the solar reflectance of the commercial coating cannot exceed 86%, and the commercial coating cannot be directly applied to radiation cooling of buildings and the like.
Disclosure of Invention
The invention aims to provide an MgO coating for radiation cooling and a preparation process thereof, so as to solve the technical problem of low solar reflectance of commercial coatings in the prior art.
At present, there have been many studies on CaCO 3 、BaSO 4 、Al 2 O 3 The radiation refrigeration coating is made of materials with higher electronic band gap and has good effect. The electronic band gap of the MgO material is 7.2eV, which is higher than the particle band gap of the existing radiation cooling coating, and can ensure lower ultraviolet absorption, and the MgO material has high emissivity at the atmospheric window wave band, so that the MgO material has great daytime radiation cooling potential.
Therefore, the invention provides a MgO coating for radiation cooling and a preparation process thereof, which comprises the following components: mgO particles, a coating substrate, absolute ethyl alcohol, a defoaming agent and a film-forming auxiliary agent;
wherein the particle size distribution of the MgO particles is not uniform.
As an embodiment of the present invention, the coating substrate is a PVA solution.
As an embodiment of the present invention, the MgO coating for radiation cooling is mainly composed of: 0.8 to 1.2 volume parts of PVA solution, 2 volume parts of absolute ethyl alcohol, 0.8 to 1.2 volume parts of MgO particles, a defoaming agent with the volume fraction of 0.3v percent and a film-forming additive with the volume fraction of 0.4v percent.
As an embodiment of the present invention, the MgO coating for radiation cooling consists essentially of: 1 part by volume of PVA solution, 2 parts by volume of absolute ethyl alcohol, 1 part by volume of MgO particles, a defoaming agent with the volume fraction of 0.3v percent and a film-forming assistant with the volume fraction of 0.4v percent.
In one embodiment of the present invention, the MgO particles have a particle size of 0 to 2 μm.
In one embodiment of the present invention, the PVA solution is present in an amount of 8 to 10% by mass.
The invention also provides a preparation process of the MgO coating for radiation cooling, which comprises the following steps:
100, preparing PVA particles into a PVA solution serving as a coating substrate;
step 200, mixing MgO particles with a coating substrate, and adding absolute ethyl alcohol for dispersing and stirring to obtain a pre-dispersed coating;
and 300, carrying out ultrasonic treatment on the pre-dispersed coating, and then adding a defoaming agent and a film-forming assistant to obtain a finished coating product.
As an embodiment of the present invention, in step 100, preparing the PVA solution specifically includes:
placing PVA particles in water, stirring at normal temperature for a first preset time, heating to the first preset temperature, stirring for a second preset time to fully dissolve PVA, and stopping heating and continuing stirring until the PVA solution is recovered to normal temperature to obtain a PVA solution;
wherein the first preset time is 10min;
the first preset temperature is 90 ℃;
the second preset time is 20min.
As an embodiment of the present invention, in step 200, the dispersing and stirring are performed by a high-speed disperser;
wherein the dispersing frequency of the high-speed dispersing machine is 6000r/min-8000r/min, and the dispersing time is 3h.
As an embodiment of the present invention, in step 300, the sonication is achieved by a cell disruptor;
wherein the ultrasonic treatment time is 30min;
the ultrasonic power is 600W;
the ultrasound pause time was set at 2 seconds.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention adopts MgO particles with different particle sizes as the main component of the coating, the particles with different particle sizes have different sunlight scattering effects on different wave bands, and the coating particles with non-uniform particle size distribution can better realize the reflection of the whole wave band of sunlight;
(2) The volume fraction of particles in the coating cannot be increased without limit, so that the spectral characteristic of the solvent is very important, and the PVA solution is used as the solvent of the coating, so that the coating has higher emissivity.
(3) The coating provided by the invention is easy to prepare, the solar light reflectivity R is 95%, the infrared emissivity E is 93%, and the spectral characteristics are obviously superior to those of commercial TiO 2 White paint (R: 80%, E: 90%).
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a graph showing solar reflectance of an MgO coating material prepared in example 1 according to the present invention;
FIG. 2 is an infrared emissivity of a MgO coating prepared in example 1 of the present invention;
FIG. 3 is a scanning electron micrograph of an MgO coating prepared in example 1 of the present invention;
FIG. 4 shows real parts of complex refractive indexes of MgO coatings of different particle sizes;
FIG. 5 shows the imaginary complex refractive index of MgO coating with different particle sizes;
FIG. 6 shows the infrared reflectance of MgO coatings of different particle sizes;
FIG. 7 is a graph showing the scattering coefficient of MgO coatings of different particle sizes;
FIG. 8 is an atmospheric window infrared reflectance of a non-uniform MgO coating;
FIG. 9 is a MgO particle size distribution;
FIG. 10 shows the solar transmittance of PVA.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention.
The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.
All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In view of the fact that there has been much research on CaCO 3 、BaSO 4 、Al 2 O 3 The radiation refrigeration coating is made of materials with higher electronic band gap and has good effect. The electronic band gap of the MgO material is 7.2eV, which is higher than the particle band gap of the prior radiation cooling coating, so that the MgO material can maintain the energyLower ultraviolet absorption is proved, and the MgO material has high emissivity in an atmospheric window wave band and has extremely large daytime radiation cooling potential.
Therefore, the embodiment of the invention provides an MgO coating for radiation cooling and a preparation process thereof, wherein the MgO coating comprises the following components: mgO particles, a coating substrate, absolute ethyl alcohol, a defoaming agent and a film-forming auxiliary agent;
based on the existing components of the radiation refrigeration coating, one of the characteristics of the embodiment of the present invention is that the particle size distribution of the MgO particles is not uniform, i.e., mgO particles of different particle sizes are used as the main component of the coating.
Specifically, the MgO material has a strong phonon resonance effect in a middle infrared band, and after the MgO material exists in a particle form, the surrounding PVA medium weakens the complex refractive index of the MgO, improves the impedance between the MgO material and air, and realizes the high infrared emissivity of the coating. However, mgO particles with different particle sizes have different resonance intensities, different infrared dispersion effects and different degrees of absorption for infrared light in different bands. Therefore, on the basis of considering sunlight reflection, the phonon resonance effect of the MgO particles with different particle sizes in an infrared band is analyzed, and the premise of ensuring the high infrared emissivity of the MgO coating is provided.
The real part and the imaginary part of the complex refractive index are important scales for representing the color radiation and absorption effect of infrared light of the material, and according to Maxwell-Garnett-Mie, the effective dielectric constants of MgO coatings with the particle diameters of 0.5 mu m, 1.0 mu m and 2.0 mu m are respectively calculated, so that the complex refractive index of the coatings under the particle diameters in an atmospheric window is obtained. As shown in fig. 4 and 5. As can be seen from FIG. 4, the smaller the particle size of MgO particles, the more significant the refractive index decay of the coating material, i.e., the stronger the dispersion effect. When the particle size is 0.5 μm, the refractive index of the coating material has a remarkable fluctuation in the atmospheric window band, and the refractive index is suddenly changed from 0.21 to 2.31 in the 11.4 μm-12.5 μm band. Excessive refractive index fluctuations will result in reflection of the infrared light, while appropriate dispersion facilitates absorption of the internal infrared light. As the particle size of the particles increases, the relative change width of the refractive index gradually decreases despite the increase in the number of the refraction peaks, the difference between the peak value and the valley value of the fluctuation curve decreases, and the dispersion effect as a whole decreases. Furthermore, it was found that the refraction peaks at different positions of different particles, i.e. the infrared dispersion of different particle coatings, occur in different wavelength bands.
The imaginary part of the complex index is also known as the absorption coefficient, extinction coefficient, etc. As shown in FIG. 5, the refractive index of the MgO coating material having a particle size of 0.5 μm and a particle size of 1.0 μm is negative. In general, the imaginary part of the refractive index of a material in nature is a real number, but the imaginary part of a "metamaterial" compounded by a plurality of materials can have a negative number condition. It can be found that the MgO coating material with the particle size of 2.0 μm has a broader absorption coefficient spectrum, i.e., has a stronger infrared emissivity in the atmospheric window band.
In order to compare the infrared resonance effect of the coatings with different particle sizes more intuitively, the infrared reflectivity of the coatings with different particle sizes was calculated according to Fresnel theory, as shown in fig. 6. It was found that the MgO coating material having a particle size of 2.0 μm had the smallest reflectance (peak value < 0.3), the coating material having a particle size of 1.0 μm had the second highest reflectance (peak value <0.6, narrow reflection range), and the coating material having a particle size of 2.0 μm had the highest infrared reflectance (peak value <0.6, wide reflection range). Although the reflectivity of the coating is minimized by selecting MgO particles with larger particle size, the IR emissivity of the coating consisting of particles with single particle size is still low in part. Therefore, in order to achieve high ir emissivity of the MgO coating over the whole atmospheric window band, it is also necessary to select a non-uniform distribution of particle sizes.
On the basis that MgO selects particles with different particle sizes, in order to prepare an ideal radiation cooling coating, the ideal particle size distribution of the coating particles needs to be designed according to an optical principle. The MgO coating with different particle size compositions has different spectral characteristics. In the sunlight wave band, the particles with different particle sizes have different sunlight scattering effects on different wave bands, and the coating particles with non-uniform particle size distribution can better realize the reflection of the sunlight in all wave bands. In addition, the scattering and absorption effects of the particles with different particle sizes on infrared light with different wave bands are also greatly different. Wherein the absorption peak of the particles with large particle size (8 μm) in the atmospheric window is wider. Therefore, it is important to ensure the cooling function of the coating material while taking into account the influence of the particle size on the reflection of sunlight and the infrared emission of the coating material.
Therefore, the selection of the MgO particle size in the invention is mainly divided into three steps:
firstly, determining the sunlight scattering characteristics of particles with different particle sizes;
secondly, determining the influence of particles with different particle sizes on the resonance of the infrared band;
and thirdly, determining the particle size distribution of MgO particles according to the theoretical infrared emissivity of the composite coating with non-uniform particle size distribution.
Specifically, the MgO particle scattering effect:
generally, the scattering effect of particles on incident electromagnetic waves is best when the size parameter value of the particles is close to 1. The size parameters of the particles are determined by the particle size of the particles, the refractive index of the surrounding matrix and the wavelength of the incident electromagnetic wave. In order to determine the scattering of particles of incident sunlight in different bands, the scattering coefficients of MgO particles with particle diameters of 0.5 μm, 1.0 μm, 2.0 μm and 3.0 μm were calculated according to Mie theory, and the results are shown in FIG. 7.
The scattering coefficient of MgO particles with a certain particle size tends to increase and then decrease with increasing wavelength. When the incident electromagnetic wave is small, i.e. the particle size is larger than the incident wave (size parameter > 1), absorption mainly occurs between the particles and the wave. When the incident electromagnetic wave is close to the size parameter (size parameter = 1), mie scattering occurs in which forward scattering is stronger than backward scattering, and a scattering coefficient peak occurs. When the incident electromagnetic wave is large, namely the particle size is smaller than that of the incident electromagnetic wave (the size parameter is less than 1), rayleigh scattering occurs, and the scattering image function is distributed more uniformly. In order to realize the reflection of the incident sunlight, the incident light needs to be induced by multiple scattering of particles, and the emergent direction is changed from the incident direction. Thus, mie scattering, which is more forward scattering, is more capable of fulfilling this requirement.
From the calculation results, it is found that the fine particles having a particle size of about 0.5 μm can effectively scatter visible light (0.4 μm to 0.7 μm); the particles with the particle size range of 0.5-2.0 μm can effectively scatter near infrared light. When the particle diameter of the particles exceeds 3.0. Mu.m, the peak of the scattering coefficient is not in the visible light band. Therefore, in order to secure the solar reflection effect of the whole band, the particle size distribution of the MgO particles is mainly concentrated within 2.0 μm, that is, the particle size of the MgO particles is 0 to 2 μm.
Further, it is known from the sunlight scattering effect and the infrared resonance effect of the MgO particles that the MgO particles having a non-uniform particle size distribution are selected to achieve a better effect of cooling by the daytime radiation, and the particle size of the MgO particles is controlled to be as small as possible within a range of 0 μm to 2.0. Mu.m. Generally, for a specific MgO particle preparation condition, a nearly infinite number of MgO particles are prepared, the particle size of which is lognormal distributed.
In order to determine the specific distribution of MgO particle size, the proportion of the MgO particle size of 2 μm or less is limited to 90%, and the probability density function of the MgO particle size distribution is a single variable function, i.e., the variance of the distribution density function can be determined from the desired value.
The infrared reflectivity of the coating is different according to the particle size distribution with different expected values. According to the dielectric constant calculation method and Fresnel equation of the coating with non-uniform distribution particle size, the probability density distribution function is expected to be-0.288, and the reflectance of the coating is the smallest at 0.569 with a variance of about 0.9, as shown in FIG. 8. It can be found that the infrared spectrum distribution in the atmospheric window band is uniform without obvious valleys. In this case, the peak value of the ideal MgO particle size distribution is 0.75 μm, and the actual MgO particle distribution is prepared from the log-normal distribution as shown in FIG. 9. The actual MgO particles have about 90% of their particle size less than 2.0 μm and fit well to the log probability density function curve.
The second characteristic of the embodiment of the invention is that the PVA solution is selected as the coating substrate (solvent).
Specifically, the coating mainly comprises a solute (scattering particles) and a solvent according to a certain proportion. For commercial TiO 2 White coating material in a certain particle concentration range (<30 v%) solar reflectance follows that of TiO 2 The volume fraction of particles increases. When the particle concentration exceeds the threshold of 30v%, the reflectance starts to decrease instead. This is because the scattering particles, which are too dense, are not completely dispersed, and local packing is formed. However, if the paint particles have low solar absorptivity, the absorption of solar light by the matrix of the paint decreases as the concentration continues to increase, and the reflectance of the paint as a whole increases again. MgO has a high electronic band gap (7.6 eV), and absorbs ultraviolet light, blue-violet light, and the likeHas low performance and is a good raw material for preparing radiation cooling materials. The spectral properties of the solvent cannot be taken into account, since the volume fraction of particles in the coating cannot be increased without limit.
Polyvinyl alcohol (PVA) is widely used in the industries of building glue, textile slurry, adhesive, fiber, paper making and the like. Based on its excellent high permeability, film forming property, adhesion, thermal stability, PVA is used as a coating base for MgO radiation cooling coating. FIG. 10 shows the solar transmittance of PVA. As can be seen, PVA has good transmittance (about 0.9) and very low absorptance in all solar bands. In summary, to achieve high solar reflectance, the present study designed MgO radiant cooling coatings with a particle volume fraction of 50v% of the particles.
Since the solubility of PVA in water is limited, it was found in experiments that the problem of incomplete dissolution and poor fluidity is likely to occur with the increase of the content of PVA, and this problem is more obvious when the mass fraction exceeds 10%, and at the same time, the solution viscosity increases and stirring becomes difficult with the increase of the content, so the mass fraction is preferably 10% or less. However, considering the amount of distilled water used and the requirement of more PVA as a substrate to provide infrared emissivity, the PVA concentration should not be too low, otherwise the cooling effect of the coating material is affected, and therefore, the PVA solution is selected to have a mass fraction of 8-10%.
The invention also provides a preparation process of the MgO coating for radiation cooling, which comprises the following steps:
a preparation process of MgO coating comprises the following steps:
1) Stirring PVA particles in water at normal temperature, heating and stirring the mixture, closing heating and continuing stirring the mixture until the PVA solution is recovered to normal temperature after the PVA is fully dissolved, and obtaining the PVA solution with a certain mass fraction.
Wherein, the stirring time at normal temperature is 10min;
the heating temperature is 90 ℃;
heating and stirring for 20min;
the mass fraction is 8-10%.
2) The MgO particles are added into the PVA solvent, and the scattering particles can not be fully dispersed under the solubility of large particles, so that the MgO particles are more easily dispersed without adding absolute ethyl alcohol in the preparation process. Mixing the PVA solution cooled to room temperature, absolute ethyl alcohol and MgO particles according to a certain volume ratio. The prepared coating is placed in a high-speed dispersion machine to be dispersedly stirred for a period of time at a fixed frequency.
Specifically, the volume ratio of the PVA solution to the anhydrous ethanol to the MgO particles is (0.8 to 1.2): 2: (0.8-1.2) feeding.
The frequency of the high-speed dispersion machine is 6000r/min-8000r/min;
the stirring time was 3h.
3) After the high-speed dispersion machine finishes predispersion, the coating is subjected to ultrasonic treatment by using a cell disruption instrument to play a role in further dispersion, and a defoaming agent and a film-forming auxiliary agent are added to increase a defoaming effect and a coating film-forming effect, so that the treated coating is already prepared preliminarily.
Wherein the volume fraction of the defoaming agent is 0.3v%;
the volume fraction of the film-forming aid is 0.4v%;
the ultrasonic treatment time of the coating is 30min;
the ultrasonic power is 600W;
the ultrasound pause time was set at 2 seconds.
Finally, the coating prepared by the embodiment of the invention selects a high-pressure air gun spraying mode during spraying so as to repeatedly spray the coating on the surfaces of buildings, metals and the like to enable the coating to be more uniformly covered, wherein the repeated spraying times are 10-12 times; the coating covering thickness is 140-160 μm.
Example 1
(1) 20ml of deionized water was weighed into a clean beaker using a measuring cylinder, the beaker was placed on a magnetic stirrer, placed into a rotor, and rotated at low speed for 5min without heating. Subsequently, 1.74g of PVA pellets were weighed into a beaker and stirred for a further 10min. Since PVA is insoluble in water at normal temperature, the magnetic stirrer is switched on in a heating mode at a heating temperature of 90 ℃. After the duration time is about 20min, the PVA is fully dissolved, and the heating mode is closed to continue stirring until the PVA solution is set to return to the normal temperature.
(2) The MgO particles with the volume ratio to the PVA solvent of 1 are taken, and under the solubility of large particles, scattering particles can not be fully dispersed, so that absolute ethyl alcohol is not needed to be added in the preparation process, so that the MgO particles are more easily dispersed, and in the spraying process, volatile ethyl alcohol can complete volatilization in the high-speed jet flow process of the coating. The PVA solution cooled to room temperature, absolute ethyl alcohol, and MgO particles were mixed at a volume ratio of 1.
(3) After the high-speed dispersion machine finishes pre-dispersion, 0.3v% of defoaming agent and 0.4v% of film-forming auxiliary agent are added into the coating, so that the defoaming effect and the coating film-forming effect are improved. And then, carrying out ultrasonic treatment on the coating for 30min by using a cell disruptor, wherein the ultrasonic power is 600W, the ultrasonic pause time is set to be 2 seconds, and the coating after ultrasonic treatment is prepared preliminarily.
Detection example 1
The coating prepared in example 1 was sprayed 10 times using a high pressure air gun to obtain a coating layer with a thickness of 150 μm, and the coating layer was measured for solar reflectance and infrared emissivity measured using an ultraviolet-visible-near infrared spectrophotometer (Lambda 750) and observed using a scanning electron microscope (sem), wherein the solar reflectance was measured using a fourier transform infrared spectrometer (vertex 70 v) to measure an emission spectrum of the coating layer in the mid-infrared band, and the morphology of the prepared MgO coating layer was observed using a field scanning electron microscope (sigma hd, ZEISS), and the results of the measurements of example 1 are shown in fig. 1 to 3: the solar reflectance R is 95 percent, the infrared emissivity E is 93 percent, and the spectral characteristics are obviously superior to those of commercial TiO 2 White paint (R: 80%, E: 90%).
Example 2
(1) 20ml of deionized water was weighed into a clean beaker using a measuring cylinder, the beaker was placed on a magnetic stirrer, placed into a rotor, and rotated at low speed for 5min without heating. Subsequently, 1.74g of PVA pellets were weighed into a beaker and stirred for a further 10min. Since PVA is insoluble in water at normal temperature, the magnetic stirrer is switched on in a heating mode at a heating temperature of 90 ℃. After the duration time is about 20min, the PVA is fully dissolved, and the heating mode is closed to continue stirring until the PVA solution is set to return to the normal temperature.
(2) MgO particles with the volume ratio to the PVA solvent of 1.2. The PVA solution cooled to room temperature, absolute ethyl alcohol, and MgO particles were mixed at a volume ratio of 1.2.
(3) After the high-speed dispersion machine finishes pre-dispersion, 0.3v% of defoaming agent and 0.4v% of film-forming auxiliary agent are added into the coating, so that the defoaming effect and the coating film-forming effect are improved. And then, carrying out ultrasonic treatment on the coating for 30min by using a cell disruptor, wherein the ultrasonic power is 600W, the ultrasonic intermittent time is set to be 2 seconds, and the coating after ultrasonic treatment is prepared preliminarily.
Detection example 2
The coating prepared in example 2 was sprayed 10 times using a high pressure air gun to obtain a coating with a thickness of 150 μm, the coating was measured for solar reflectance and infrared emissivity using a scanning electron microscope, wherein the solar reflectance was measured using an ultraviolet-visible-near infrared spectrophotometer (Lambda 750), the emission spectrum of the coating in the mid-infrared band was measured using a fourier transform infrared spectrometer (vertex 70 v), the morphology of the prepared MgO coating was observed using a field scanning electron microscope (sigma hd, ZEISS), and the results showed that the solar reflectance R was 93%, the infrared emissivity E was 93%, and the spectral properties were significantly better than those of commercial TiO 2 The white paint (R: 80%, E: 90%) was inferior to example 1 in effect because of the relatively low MgO concentration.
Example 3
(1) 20ml of deionized water was weighed into a clean beaker using a measuring cylinder, the beaker was placed on a magnetic stirrer, placed into a rotor, and rotated at low speed for 5min without heating. Subsequently, 1.74g of PVA pellets were weighed into a beaker and stirred for a further 10min. Since PVA is insoluble in water at normal temperature, the magnetic stirrer is switched on in a heating mode at a heating temperature of 90 ℃. After the duration time is about 20min, the PVA is fully dissolved, and the heating mode is closed to continue stirring until the PVA solution is set to return to the normal temperature.
(2) The MgO particles with the volume ratio to the PVA solvent of 0.8. The PVA solution cooled to room temperature, absolute ethanol, and MgO particles were mixed at a volume ratio of 0.8.
(3) After the high-speed dispersion machine finishes pre-dispersion, 0.3v% of defoaming agent and 0.4v% of film-forming auxiliary agent are added into the coating, so that the defoaming effect and the coating film-forming effect are improved. And then, carrying out ultrasonic treatment on the coating for 30min by using a cell disruptor, wherein the ultrasonic power is 600W, the ultrasonic intermittent time is set to be 2 seconds, and the coating after ultrasonic treatment is prepared preliminarily.
Detection example 3
The coating prepared in example 3 was sprayed 10 times using a high pressure air gun to obtain a coating with a thickness of 150 μm, the coating was examined for solar reflectance and infrared emissivity using a scanning electron microscope, wherein the solar reflectance was measured using an ultraviolet-visible-near infrared spectrophotometer (Lambda 750), the emission spectrum of the coating in the mid-infrared band was measured using a fourier transform infrared spectrometer (vertex 70 v), the morphology of the prepared MgO coating was observed using a field scanning electron microscope (sigma hd, ZEISS), and the results showed that the solar reflectance R was 95.3%, the infrared emissivity E was 93%, and the spectral properties were significantly better than those of commercial TiO 2 Although the optical properties of the white paint (R: 80% and E: 90%) are slightly improved compared with those of example 1, the viscosity of the paint is slightly reduced, the film forming effect after actual spraying is poorer than that of example I, and the actual application capability is reduced.
As can be seen from the above, the results of the tests of examples 1 to 3 show that the volume ratio of the PVA solution to the absolute ethyl alcohol to the MgO particles is (0.8 to 1.2): 2: (0.8-1.2), spectral characteristics of the coating material preparedAre all significantly superior to commercial TiO 2 The white coating is prepared from a PVA solution, absolute ethyl alcohol and MgO particles in a volume ratio of 1:2:1, the effect is optimal.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. An MgO coating for radiation cooling, comprising the following components: mgO particles, a coating substrate, absolute ethyl alcohol, a defoaming agent and a film-forming auxiliary agent;
wherein the MgO particles have a non-uniform particle size distribution.
2. An MgO coating for radiation cooling according to claim 1, wherein the coating matrix is a PVA solution.
3. MgO coating for radiation cooling according to claim 1, characterized in that it consists essentially of: 0.8 to 1.2 portions of PVA solution, 2 portions of absolute ethyl alcohol, 0.8 to 1.2 portions of MgO particles, a defoaming agent with the volume fraction of 0.3v percent and a film-forming additive with the volume fraction of 0.4v percent.
4. MgO coating for radiation cooling according to claim 3, characterized in that it consists essentially of: 1 part by volume of PVA solution, 2 parts by volume of absolute ethyl alcohol, 1 part by volume of MgO particles, a defoaming agent with the volume fraction of 0.3v percent and a film-forming assistant with the volume fraction of 0.4v percent.
5. MgO coating for radiation cooling according to claim 1, characterized in that the MgO granules have a particle size of 0 to 2 μm.
6. An MgO coating for radiation cooling according to claim 2, characterized in that the PVA solution is present in a mass fraction of 8% to 10%.
7. A preparation process of MgO coating for radiation cooling is characterized by comprising the following steps:
step 100, preparing PVA solution from PVA particles as a coating substrate;
step 200, mixing MgO particles with a coating substrate, and adding absolute ethyl alcohol for dispersing and stirring to obtain a pre-dispersed coating;
and 300, performing ultrasonic treatment on the pre-dispersed coating, and adding a defoaming agent and a film-forming additive to obtain a coating finished product.
8. A process for preparing MgO coating for radiation cooling according to claim 7, wherein in step 100, preparing the PVA solution specifically includes:
placing PVA particles in water, stirring at normal temperature for a first preset time, heating to the first preset temperature, stirring for a second preset time to fully dissolve PVA, and stopping heating and continuing stirring until the PVA solution is recovered to normal temperature to obtain a PVA solution;
wherein the first preset time is 10min;
the first preset temperature is 90 ℃;
the second preset time is 20min.
9. The process for preparing MgO coating material for radiation cooling according to claim 7, wherein in the step 200, the dispersion stirring is performed by a high speed disperser;
wherein the dispersing frequency of the high-speed dispersing machine is 6000r/min-8000r/min, and the dispersing time is 3h.
10. The process for preparing MgO coating material for radiant cooling in accordance with claim 7, wherein the ultrasonic treatment is performed by a cell disruptor in step 300;
wherein the ultrasonic treatment time is 30min;
the ultrasonic power is 600W;
the ultrasound pause time was set at 2 seconds.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117229660A (en) * | 2023-09-18 | 2023-12-15 | 北京建院投资有限责任公司 | Super-cooled composite material and preparation method thereof |
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