CN114958033B - High near infrared reflection color pigment and application thereof - Google Patents

Abstract

The invention relates to the technical field of pigments and discloses a high near-infrared reflective color pigment and its application. The general chemical formula of the pigment is: LiAl _1‑x M _x (MoO _{4 + δ} ) ₂ , and the doping amount x is 0 -0.4; prepared by solid phase reaction method from raw materials including Li source, Al source, Mo source and M source. The invention meets people's aesthetic needs for multiple colors; the synthesized pigment has high near-infrared reflectivity (R%), and the color and reflectivity of the pigment can be controlled by changing the doping concentration, and can be used as a High-performance "cold" materials are used in building facades, vehicle and boat exteriors or in paint can coatings.

Description

A kind of high near-infrared reflective color pigment and its application

Technical field

The present invention relates to the technical field of pigments, and in particular to a high near-infrared reflective color pigment and its application.

Background technique

With the rapid development of economy and technology, the process of urbanization has accelerated. The use of asphalt, glass and other materials and air conditioning have made the temperature in the city center 3-5°C higher than that in surrounding areas. A large amount of energy consumption and heat accumulation have produced the "urban heat island effect". The urban heat island effect has become a topic of great concern. It has potential impacts on energy consumption and vegetation growth, and may even cause certain adverse effects on residents' lives and human health. harm. The urban heat island effect is closely related to factors such as building density and vegetation area. If buildings can emit more sunlight, more energy will be saved and the "urban heat island effect" will be alleviated. Therefore, how to effectively block the heat transfer of sunlight on building surfaces and roofs has received widespread attention.

The use of ceramic pigments with high near-infrared reflectivity can effectively reflect solar energy at 700-2500nm (52%), thereby reducing energy consumption and slowing down the urban heat island effect. Generally speaking, most traditional inorganic pigments contain toxic heavy metal elements and have single colors, which cannot meet people's aesthetic requirements for building materials. Changing the color and reflective properties of pigments through doping has become a research hotspot for researchers. Doping transition metals or rare earth elements is an effective means to change the color of pigments. Commonly used chromophores mainly include Fe, Cr, Bi and RE, etc. At present, many researchers have studied various colors that can be used in architecture. Surface inorganic pigments, such as LiRE(MoO ₄ ) ₂ , Y _3-x Ce _x Al ₅ O ₁₂ , Sr _1-x RE _x CuSi ₄ O _10+δ (RE=Pr, Nd, Sm), etc., can replace traditional Architectural Coatings. Therefore, studying and preparing pigments that can not only exhibit high near-infrared reflectivity but also meet the diversity of colors is an urgent technical problem that needs to be solved in this field.

Contents of the invention

The purpose of the present invention is to provide a high near-infrared reflective color pigment and its application. The synthetic pigment has low toxic metal content, high near-infrared reflectivity and more diverse colors.

In order to achieve the above technical objectives and achieve the above technical effects, the present invention discloses a high near-infrared reflective color pigment. The general chemical formula of the pigment is:

LiAl _1-x M _x (MoO _4+δ ) ₂ ;

Wherein: M is selected from at least one of Fe, Pr, Ho, Nd, Er and Ce.

Wherein, the value range of x in the general chemical formula is: 0<x≤0.4.

Wherein, the pigment has a triclinic crystal structure of P-1 space group.

Wherein, the pigment is prepared by a solid phase reaction method from raw materials including Li source, Al source, Mo source and M source.

The invention also discloses a method for preparing high near-infrared reflective color pigments, which includes the following steps:

Step 1: Weigh the raw materials of Li source, Al source, Mo source and M source according to the stoichiometric ratio of each element in LiAl _1-x M _x (MoO _4+δ ) ₂ ;

Step 2: Mix the raw materials weighed in step 1 and grind them in an agate mortar. Add acetone as the wet grinding medium until the acetone evaporates. Repeat the operation 3-5 times to obtain mixed powder;

Step 3: Dry the mixed powder ground in Step 2 in an air oven to obtain dried powder;

Step 4: Put the powder from Step 3 into the crucible, roast it in a muffle furnace, heat it from room temperature to 400°C, react for 2 hours, then raise the temperature to 650°C again, and keep it warm for 4 hours to obtain a sample;

Step 5: Grind the sample obtained in Step 4 3-5 times to obtain colored pigments.

Wherein, the Li source is provided by at least one of carbonate and molybdate containing Li element;

The M source is provided by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing M elements;

The Al source is provided by at least one of oxides, chlorides, nitrates and sulfates containing Al elements;

The Mo source is provided by an oxide or molybdate containing Mo element.

Preferably, the Li source is provided by carbonate containing Li element;

The M source is provided by an oxide containing M element;

The Al source is provided by an oxide containing Al element;

The Mo source is provided by an oxide containing Mo element.

The invention also discloses the application of a high near-infrared reflective color pigment in building exterior wall coatings, vehicle and ship exterior coatings, and paint can coatings.

The invention has the following beneficial effects:

(1) A series of LiAl(MoO ₄ ) ₂ near-infrared reflective pigments doped with Fe, Pr, Ho, Nd, Er, and Ce are provided. The pigments are successfully transformed by doping with Fe, Pr, Ho, Nd, Er, and Ce elements. The color changes from white to green, lavender, pink, yellow and other colors, which can meet people's aesthetic needs for a variety of colors;

(2) The pigment synthesized in the present invention has high near-infrared reflectivity (R%). By changing the doping concentration, the color and reflectivity of the pigment can be controlled, and it can be used as a high-performance "cold" material. In the field of building exterior walls, vehicle and ship exteriors or paint can coatings.

Description of drawings

Figure 1 is the XRD diffraction pattern of (a) LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment synthesized in Example 3 of the present invention, x=0-0.4; (b) 2θ=26.0°-27.5° Partial enlargement of the XRD diffraction pattern.

Figure 2 is an SEM image of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ (x=0-0.4) pigment synthesized in Example 3 of the present invention.

Figure 3 is a particle size distribution diagram of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ (x=0-0.4) pigment synthesized in Example 3 of the present invention.

Figure 4 is the absorption spectrum of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ (x=0-0.4) pigment synthesized in Example 4 of the present invention, and the inset is the ultraviolet-visible reflection spectrum.

Figure 5 is an absorption limit diagram of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ (x=0-0.4) compound synthesized in Example 4 of the present invention.

Figure 6 is a colorimetric parameter diagram of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ pigment synthesized in Example 4 of the present invention.

Figure 7 is a near-infrared reflectance diagram of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ pigment synthesized in Example 4 of the present invention.

Figure 8 is a near-infrared solar reflectance diagram of the LiAl _{1-x Fex} (MoO _4+δ ) ₂ pigment synthesized in Example 4 of the present invention.

Figure 9 is a graph showing changes in L*a*b* of the LiAl _1-x M _x (MoO _4+δ ) ₂ (M=Fe, Pr, Ho, Nd, Er, Ce) pigment synthesized in Example 5 of the present invention.

Figure 10 is a physical diagram of the pigment synthesized in Example 5 of the present invention.

Figure 11 is a near-infrared reflectance diagram of the LiAl _0.8 M _0.2 (MoO ₄ ) ₂ (M=Pr, Ho, Nd, Er, Ce) pigment synthesized in Example 5 of the present invention.

Figure 12 Infrared images of LiAl _0.8 Fe _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ synthesized in Example 5 of the present invention and mixed with alkyd resin on galvanized plates with or without TiO _2- based coating at different times. Heated infrared thermography, where ① and ③ are galvanized sheets not coated with TiO ₂ , ② and ④ are galvanized sheets coated with TiO ₂ , ① and ② are coated with LiAl _0.8 Fe _0.2 ( Galvanized sheets with MoO ₄ ) ₂ pigment, ③ and ④ are galvanized sheets coated with LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ pigment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Example 1

The invention provides a high near-infrared reflective color pigment LiAl _1-x M _x (MoO _4+δ ) ₂ ; wherein the M source is the corresponding oxide of Fe, Pr, Ho, Nd, Er, and Ce.

The pigment LiAl _1-x M _x (MoO _4+δ ) ₂ has a triclinic crystal structure of the P-1 space group.

The pigment is prepared by a solid-phase reaction method from raw materials including Li source, Al source, Mo source, and M source.

Example 2

The invention provides a method for preparing the high near-infrared reflective color pigment LiAl _1-x M _x (MoO _4+δ ) ₂ in Example 1, which includes the following steps:

Step 1: Weigh the raw materials of Li source, Al source, Mo source and M source according to the stoichiometric ratio of each element in LiAl _1-x M _x (MoO _4+δ ) ₂ ;

Step 2: Mix the raw materials weighed in step 1 and grind them in an agate mortar. Add acetone as the wet grinding medium until the acetone evaporates. Repeat the operation 3-5 times to obtain mixed powder;

Step 3: Dry the mixed powder ground in Step 2 in an air oven to obtain dried powder;

Step 4: Put the powder from Step 3 into the crucible, roast it in a muffle furnace, heat it from room temperature to 400°C, react for 2 hours, then raise the temperature to 650°C again, and keep it warm for 4 hours to obtain a sample;

Step 5: Grind the sample obtained in Step 4 3-5 times to obtain colored pigments.

in:

The Li source is provided by at least one of carbonate and molybdate containing Li element;

The M source is provided by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing M elements;

The Al source is provided by at least one of oxides, chlorides, nitrates and sulfates containing Al elements;

The Mo source is provided by an oxide or molybdate containing Mo element.

Preferably, the Li source is provided by carbonate containing Li element;

The M source is provided by an oxide containing M element;

The Al source is provided by an oxide containing Al element;

The Mo source is provided by an oxide containing Mo element.

Example 3

In order to further study the influence of different doping amounts x on the crystal structure of high near-infrared reflective color pigments, this example prepared LiAl _{1 - x F} Pigment, the value range of the doping amount x is: 0<x≤0.4, the results are shown in Figure 1 and Table 1.

Table 1 Unit cell parameters and strains of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment

Figure 1 shows that the main peak shapes of five samples with different doping concentrations match well with the standard card of LiAl(MoO ₄ ) ₂ (PDF No. 72-0753), indicating that the samples have better crystallinity at the calcination temperature of 650°C. Lithium aluminum molybdate belongs to the triclinic crystal structure and the space group is P-1. As the doping concentration increases, the (020) peak and (002) peak of the LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment sample The relative intensity of the peaks is slightly different. The relative intensity difference between the strongest diffraction peak (002) and the weaker (002) peak begins to decrease, and the crystal plane (002) moves to a lower angle. When the doping concentration is 0.4, the intensities of the (020) and (002) peaks are basically the same. The above shows that lithium aluminum molybdate crystal forms with different Fe doping concentrations will grow directionally, and the morphologies of various pigments may be different.

Table 1 shows the unit cell parameters and other information of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4). It can be seen from the above table that the introduction of Fe ³⁺ will affect the increase in the unit cell volume of the sample, which is mainly due to the ionic radius of Fe ³⁺ (coordination number CN is 6) replaces the ionic radius of /> Al ³⁺ (coordination number CN is 6) increases the volume of the unit cell and shifts the diffraction peak to a low angle.

It can be observed from Figure 2 that the morphology of LiAl(MoO ₄ ) ₂ with different Fe doping concentrations has obvious crystal faces when the calcination temperature is 650°C, indicating that the solid solution has good crystallinity. The sample particles with different doping concentrations all exhibit irregular polyhedrons and different particle sizes, and are accompanied by agglomeration.

Figure 3 shows the particle size distribution of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment. Table 2 lists the detailed information of D10, D50 and D90 of the pigment samples.

Table 2 D10, D50, D90 of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment powder

sample D10 D50 D90 x=0 125.36 247.31 487.89 x=0.1 386.58 729.61 1377.02 x=0.2 339.90 634.73 1185.29 x=0.3 278.79 512.30 941.40 x=0.4 287.33 537.89 106.96

From the particle size distribution diagram, it can be observed that the particle sizes of all samples are normally distributed and evenly distributed. The D10, D50, and D90 of the undoped LiAl(MoO ₄ ) ₂ sample are 125.36nm, 247.31nm, and 487.89nm respectively. The effective particle diameter D50 of other samples is larger than that of the undoped sample, ranging from 500-750nm. Good particle size distribution is the guarantee for uniform distribution and pure color of later coatings.

Example 4

In order to further study the optical properties of the pigments of the present invention, this example uses the LiAl _{1-x Fex} (MoO _4+δ ) ₂ (x=0-0.4) pigment prepared in Example 2 and Example 3 as the object. The absorption spectrum was characterized and analyzed, and the results are shown in Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Table 3, and Table 4.

Figure 4 shows the absorption spectrum and UV-visible reflection spectrum of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment. The prepared LiAl _1-x Fe _x (MoO _4+δ ) _{The 2} sample has a high reflectivity in the visible light region of 380-700nm, which means that the color of the LiAl _1-x Fe _x (MoO _4+δ ) ₂ sample will tend to be light.

As the doping amount of Fe ³⁺ increases, the visible light reflectance gradually decreases. The absorbance of the pure LiAl(MoO ₄ ) ₂ sample at 270-400 nm shows a sharp decrease trend. The incorporation of Fe ³⁺ ions makes The inflection point of the band moves toward the longer length of the band. All samples have strong absorbance in the ultraviolet and blue light regions, so the color of the LiAl _1-x Fe _x (MoO _4+δ ) ₂ sample will gradually change from white to yellow-green.

Table 3 lists the L*a*b* value and bandgap width Eg of LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment. It can be observed from the table that the L* value decreased from 97.22 to 89.15, that is It shows that the brightness of the pigment has been reduced.

Table 3 Color coordinates and bandgap width of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment

sample L* a* b* C* H° Eg(eV) x=0 97.22 -1.20 2.39 2.67 63.34 3.89 x=0.1 95.14 -2.48 9.19 9.52 74.90 3.24 x=0.2 92.83 -4.07 14.93 15.47 74.75 3.14 x=0.3 90.91 -5.13 20.26 20.90 75.79 3.07 x=0.4 89.15 -5.89 25.36 26.04 76.92 3.03

Figure 5 is the absorption limit diagram of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) compound. The absorption limit of LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment changes with Fe concentration. The increased red shift makes the bandgap width Eg become smaller, and Eg decreases from 3.89eV to 3.03eV. The change in bandgap width may be due to the introduction of Fe _3d orbitals between Al _3p and O _2p orbitals, which reduces the force between the two orbitals. In addition, Fe ³⁺ ions will undergo dd transitions, mainly at 430nm and 480- ⁶ A ₁ → ⁴ E, ⁴ A ₁ transition mode at 650nm.

Figure 6 Colorimetric parameters of the synthesized LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment, showing the changes in the L*a*b* parameters of the pigment. When x=0, the L* value is 97.22, Close to white.

As the Fe doping concentration increases, the a* value decreases from -1.20 to -5.89, indicating that the color of the pigment is greener, but the increase is small; the b* value increases from 2.39 to 25.36, indicating that the color of the pigment is yellowish, with an increase of larger. The saturation C* value increases from 2.67 to 26.04, indicating that the color of the pigment is fuller. The hue angle H° of all color samples is in the yellow zone (70-105°), so the color presented is yellow.

Figure 7 shows the near-infrared reflectance of the synthesized LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment, and Figure 8 shows the near-infrared solar reflection of the synthesized LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment. Rate chart, Table 4 shows the reflectance, average reflectance and near-infrared solar reflectance of the synthesized LiAl _1-x Fe _x (MoO _4+δ ) ₂ pigment at 1100nm.

Table 4 Near-infrared reflectance and near-infrared solar reflectance of LiAl _1-x Fe _x (MoO _4+δ ) ₂ (x=0-0.4) pigment at 1100nm

sample R%(1100nm) R% R*% x=0 90.38 96.40 92.18 x=0.1 92.77 98.34 94.19 x=0.2 90.16 98.31 92.27 x=0.3 87.94 96.85 89.84 x=0.4 87.12 95.51 88.76

The results show that the reflectance of Fe-doped LiAl(MoO ₄ ) ₂ pigment changes compared to the undoped sample.

The reflectance of the pigment (x=0.1-0.2) at 1100nm decreases from 92.77% to 87.12% as the doping amount increases, and the average near-infrared reflectance increases from 96.40% to 98.34%, and then decreases from 98.34% to 95.51 %; the near-infrared solar reflectance increases from 92.18% to 94.19%, and then gradually decreases to 88.76%.

The above shows that Fe doping can improve the reflective properties of pigments, and increasing the doping concentration will also reduce the reflectivity. Compared with traditional pigments, the prepared LiAl _1-x F _x (MoO _4+δ ) ₂ pigment has better reflective properties.

The R*% of NiTiO ₃ @TiO ₂ is about 60%, the R*% of BiPr _0.5 Cr _0.5 TiO ₃ is 91.5%, Y ₃ Al _5-x Fe _x O ₁₂ (x=0.0, 0.5, 1.0, 1.5, 2.0 , 3.0) series of pigments have an R*% between 68.08-86.47%. Compared with yellow-green pigments with similar colors, the near-solar reflectance of the synthesized LiAl _0.8 Fe _0.2 (MoO _4+δ ) ₂ pigment is as high as 92.27%.

Example 5

In order to further characterize the color of the synthesized pigment under specific usage conditions, this example uses LiAl _1-x M _x (MoO _4+δ ) ₂ (M=Fe, Pr, Ho, synthesized in Example 1 and Example 2, _{Nd , Er , Ce ; _ _ _ x} Ho _x (MoO _4+δ ) ₂ , LiAl _1-x Nd _x (MoO _4+δ ) ₂ , LiAl _1-x Er _x (MoO _4+δ ) ₂ , LiAl _{1- x Ce} ) ₂ .

Figure 9 shows the changes in L*a*b* of LiAl _1-x M _x (MoO _4+δ ) ₂ (M=Fe, Pr, Ho, Nd, Er, Ce) pigment synthesized by calcining at 650°C for 4 hours. , Figure 10 is a physical picture of the synthetic pigment, and Table 5 is the relevant information of the L*a*b* value.

The color of LiAl _1-x Pr _x (MoO _4+δ ) ₂ pigment is green. As the Pr doping concentration increases, the color gradually deepens. Its L* values are all above 95, and the red-green degree a* value ranges from -3.60 becomes -5.60, and the b* value increases from 9.30 to 12.29.

The color of LiAl _1-x Nd _x (MoO _4+δ ) ₂ pigment is lavender, the brightness L* value decreases from 92.88 to 86.19 as the Nd concentration increases, the a* value increases from -2.08 to 0.42, and the b* value It slowly decreases to -3.99 from x=0.1 to 0.3, and drops sharply to -9.23 when x=0.4.

The color of LiAl _1-x Er _x (MoO _4+δ ) ₂ pigment is pink, the brightness L* is between 94-96, the a* value gradually increases from 3.88 to 8.95, and the b* value is in the range of -0.72-0.14.

The above three color pigments are cold color pigments.

LiAl _1-x Ho _x (MoO _4+δ ) ₂ and LiAl _1-x Ce _x (MoO _4+δ ) ₂ pigments are both yellow warm-color pigments.

The brightness L* value of LiAl _1-x Ho _x (MoO _4+δ ) ₂ pigment is higher than that of LiAl _1-x Ce _x (MoO _4+δ ) ₂ pigment, indicating that LiAl _{1- x} Ho _x (MoO _4+δ ) ₂ The pigment color is lighter; the yellow-green degree b* value of the LiAl _{1 -x Ce x (} MoO _{4+δ ) 2} pigment is larger _, indicating that the LiAl _1-x Ce _x (MoO _4+δ ) ₂ pigment has a deeper yellow color.

The a* value of LiAl _1-x Ho _x (MoO _4+δ ) ₂ pigment varies between -2.98 and -3.10, and that of LiAl _1-x Ce _x (MoO _4+δ ) ₂ pigment is -1.17 -Changes before 5.95.

Table 5 L*a*b* values of synthetic pigments

The above results show that different doping metal elements will cause the white powder LiAl(MoO ₄ ) ₂ to show various colors. The research of the present invention has enriched the chromatogram of near-infrared reflective inorganic pigments and can satisfy modern people's demand for diverse colors. sexual needs.

Figure 11 shows the near-infrared reflectance diagram of LiAl _0.8 M _0.2 (MoO ₄ ) ₂ (M=Pr, Ho, Nd, Er, Ce) pigment. Table 6 shows the near-infrared reflectance of LiAl _0.8 M _0.2 (MoO ₄ ) ₂ (M=Pr, Calculated data of near-infrared reflectance and near-infrared solar reflectance of Ho, Nd, Er, Ce) pigments.

Table 6 Near-infrared reflectance and near-infrared solar reflectance of LiAl _0.8 M _0.2 (MoO ₄ ) ₂ (M=Pr, Ho, Nd, Er, Ce) pigment

sample R%(1100nm) R*% E LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ 90.48 90.29 3.67 LiAl _0.8 Nd _0.2 (MoO ₄ ) ₂ 90.23 87.83 3.81 LiAl _0.8 Er _0.2 (MoO ₄ ) ₂ 96.57 95.67 3.83 LiAl _0.8 Ho _0.2 (MoO ₄ ) ₂ 91.72 92.29 3.77 LiAl _0.8 Ce _0.2 (MoO ₄ ) ₂ 99.09 98.05 3.56

It can be seen that the reflection of cold color pigments, such as green LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ , lavender LiAl _0.8 Nd _0.2 (MoO ₄ ) ₂ and pink LiAl _0.8 Er _0.2 (MoO ₄ ) ₂ at 1100nm The rates are 90.48%, 90.23% and 96.57% respectively, and the near-infrared solar reflectance R*% is as high as 90.29%, 87.83% and 95.67%; among the warm color pigments, LiAl _0.8 Ho _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Ce _0.2 ( The R*% of MoO ₄ ) ₂ are 92.29% and 98.05% respectively. It can reflect most of the solar energy, can be used as a near-infrared reflective material, and expand its application in heat insulation.

Example 6

In order to further characterize the usability of the synthesized pigments in actual coatings under specific usage conditions, this example uses the LiAl _0.8 Fe _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ pigments synthesized in Example 5 as the experimental objects. The following experiments were conducted.

Pigments containing high solar reflectivity in the paint will largely reflect the infrared part of the sun that generates heat to achieve energy-saving cooling. In order to evaluate the applicability of the designed pigments, the designed and developed LiAl _0.8 Fe _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ pigments were coated on galvanized plates with or without TiO ₂ for infrared heat radiation.

During the coating process, the pigment and alkyd resin are mixed evenly in a ratio of 1:1.5 to make a water-based metal anti-rust paint decorative coating, which is coated on a 10cm × 8cm galvanized plate. The plates were naturally dried and then dispersed on the heat shielding plate. The QNix 8500 thickness gauge was used to measure the thickness of the coating. The thickness of each coating was measured to be approximately 110-120 μm.

The image of the smear is collected by an infrared thermal imaging camera. The shooting time interval is 3 minutes. The temperature recording mode is set to the highest temperature point marking mode. The distance between the galvanized plate and the infrared light is maintained at 25cm. In the thermal imaging experiment, the galvanized plate The total exposure time under an infrared lamp with a power of 100w is 10min.

Figure 12 shows that the highest temperature point has always been on the LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ sample without TiO ₂ substrate ③. Within the same thermal radiation time interval, the temperature increase rate of the smear surface gradually slowed down, rapidly rising from the initial 42.7°C to 54.8°C, and then slowly rising to 65.8°C. The surface temperature of the smear without TiO ₂ base is higher than that of the smear with TiO ₂ base, indicating that TiO ₂ can improve the reflectivity of the smear.

For LiAl _0.8 Fe _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ smears (① and ③) without TiO ₂ substrate, the surface temperature of ① is 5 to 6°C lower than that of ③, mainly because Since the near-infrared reflectivity of LiAl _0.8 Fe _0.2 (MoO ₄ ) ₂ is higher than that of LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ , it can reflect more infrared radiation heat. Generally speaking, both pigments have good near-infrared reflection properties and can be used as a type of cold-color inorganic pigments with high near-infrared reflection.

In summary, the present invention provides a high near-infrared reflective color pigment for use in building exterior wall coatings, vehicle and boat exterior coatings, and paint can coatings. The pigment has high near-infrared reflectivity, LiAl _1-x M _x (MoO _4+δ ) ₂ (M=Fe, Pr, Ho, Nd, Er, Ce) pigments present colors such as yellow-green, green, lavender, pink, and yellow, and have rich color properties.

When the doping element is Fe, all samples with doped amounts are triclinic. At lower doping concentrations, the Fe-doped sample pigments have higher near-infrared reflectivity (x=0.2, R%=98.13 ), as the doping concentration increases, the color of all sample pigments deepens.

The R% of LiAl _0.8 Pr _0.2 (MoO ₄ ) ₂ , LiAl _0.8 Nd _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Er _0.2 (MoO ₄ ) ₂ pigments at 1100nm are 90.48%, 90.23% and 96.57% respectively, R*% As high as 90.29%, 87.83% and 95.67%. Among warm color pigments, the R*% of LiAl _0.8 Ho _0.2 (MoO ₄ ) ₂ and LiAl _0.8 Ce _0.2 (MoO ₄ ) ₂ are 92.29% and 98.05% respectively. The excellent reflective properties make all the prepared pigments have good thermal insulation properties and can be used as a new type of "cold" pigment.

The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description and drawings of the present invention, or directly or indirectly applied to other related technologies fields are equally included in the scope of patent protection of the present invention.

Claims (5)

1. A high near infrared reflective color pigment, characterized by: the chemical general formula of the pigment is as follows:

LiAl _1-x M _x (MoO _4+δ ) _2，

the M is at least one of Fe, pr, ho, nd, er and Ce;

the value range of x is as follows: x is more than 0 and less than or equal to 0.4;

wherein, the pigment is prepared from raw materials including Li source, al source, mo source and M source by a solid phase reaction method:

the preparation method comprises the following steps:

step 1: according to LiAl _1-x M _x (MoO _4+δ ) ₂ The stoichiometric ratio of each element of the raw materials of a Li source, an Al source, a Mo source and an M source is weighed;

step 2: mixing the raw materials weighed in the step 1, adding the raw materials into an agate mortar for grinding, adding acetone as a wet grinding medium until the acetone volatilizes, and repeating the operation for 3-5 times to obtain mixed powder;

step 3: drying the mixed powder ground in the step 2 in an air oven to obtain dried powder;

step 4: placing the powder obtained in the step 3 into a crucible, roasting in a muffle furnace, heating to 400 ℃ from room temperature, reacting for 2 hours, heating to 650 ℃ again, and preserving heat for 4 hours to obtain a sample;

step 5: grinding the sample obtained in the step 4 for 3-5 times to obtain the color pigment.

2. The high near infrared reflective color pigment of claim 1, wherein: the pigment has a triclinic structure of the P-1 space group.

3. The high near infrared reflective color pigment of claim 1, wherein:

the Li source is provided by at least one of carbonate and molybdate containing Li element;

the M source is provided by at least one of carbonate, oxide, chloride, nitrate and sulfate containing M element;

the Al source is provided by at least one of oxides, chlorides, nitrates and sulfates containing Al elements;

the Mo source is provided by oxide or molybdate containing Mo element.

4. The high near infrared reflective color pigment of claim 1, wherein:

the Li source is provided by carbonate containing Li element;

the M source is provided by an oxide containing M element;

the Al source is provided by oxide containing Al element;

the Mo source is provided by oxide containing Mo element.

5. Use of the highly near infrared reflective color pigments according to any of claims 1 to 4 in exterior wall coatings for buildings, exterior coatings for vehicles and ships, paint can coatings.