Pr / W co-doped Bi2MoO6 green pigment as well as preparation method and application thereof

Abstract

The invention discloses a Pr / W co-doped Bi2MoO6 green pigment as well as a preparation method and application thereof, and compared with bismuth molybdate (a * =-2.28 to-8.87) which is singly doped with praseodymium oxide, the Pr / W co-doped Bi2MoO6 has an excellent green hue (a * =-6.13 to-12.38). The near-infrared solar reflectivity of all pigment samples is more than 80%, and the temperature difference between the Bi < 1.95-x > Pr < x > W < 0.05 > MoO < 6 + delta > pigment coating and a blank galvanized sheet can reach 10.3 DEG C after the pigment samples are irradiated by an infrared lamp for 30 minutes in a heat insulation experiment. The color difference value E * of a pigment sample is far less than 5 after an acid-base test, so that the pigment disclosed by the invention has good chemical stability in acid and base, is expected to replace a green pigment containing toxic metals, and thus, can be used as a cold pigment to show huge application potential in the aspect of architectural coatings.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic oxide pigments, and particularly relates to a Pr / W co-doped Bi2MoO6 green pigment, a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of economy, people's living standards have been greatly improved, and the rapid development of urbanization has led to an increase in the number of buildings and a decrease in vegetation coverage. The outer walls and roofs of buildings absorb solar radiation, causing the ground temperature to rise, so the temperature in the city center is generally 3-5℃ higher than in the suburbs, which easily causes the urban heat island effect (UHI). The heat island effect reduces people's living comfort and increases the energy consumption of air conditioners in summer, further exacerbating the UHI effect. Related studies have shown that building energy consumption accounts for more than 30% of total energy consumption in China, and the proportion is still on the rise, of which 20% of energy consumption comes from cooling equipment in summer. In order to solve this environmental problem, many technologies have been used to alleviate the heat island effect, among which, coating the outer walls and roofs of buildings with high near-infrared reflectivity coatings can effectively reduce the surface temperature of the outer walls and roofs of buildings, thereby reducing energy consumption to effectively alleviate the heat island effect.

[0003] Sunlight is composed of different wavelengths of visible light and non-visible light, of which 5% of solar radiation is distributed in the ultraviolet region (200-400 nm), 43% in the visible light region (400-700 nm), and 52% in the near-infrared (NIR) region (700-2500 nm). Therefore, it has become a hot topic with practical significance to research and develop a new type of functional pigment to specifically absorb or reflect a part of the light in the visible light region, thereby presenting a certain color while meeting the demand for the color of the pigment, and at the same time having a high reflectivity in the near-infrared region to reflect most of the infrared light and achieve the purpose of cooling.

[0004] Green inorganic pigments with bright color are one of the most lacking inorganic colored pigments in China, but green pigments are widely used, such as green camouflage clothing or equipment, which can play a hiding role and thus a protective role. However, the traditional inorganic green pigments on the current market have the following problems: first, most of them perform poorly in near-infrared reflectivity, thereby limiting their heat insulation effect in actual application. Second, more seriously, traditional pigments often contain a series of toxic heavy metal ions, such as lead (Pb 2+ ), cadmium (Cd 2+ ), cobalt (Co 2+ ) and chromium (Cr 6+). These heavy metal ions can have serious adverse effects on human health in the case of long-term contact or inhalation of excessive amounts. In addition, the release of these heavy metal ions also causes great harm to the environment. Thadsanee Thongkanluang et al. synthesized green pigment Cr2O3-TiO2-Al2O3-V2O5 with high near-infrared reflectivity, which has a near-infrared solar reflectivity of 82.8%, and this material is suitable for ceramic-based roofs. Yin Zhang's team synthesized low-cobalt-content Zn 0.98 Co 0.02 O green pigment by co-precipitation method. The results show that this green pigment not only retains the wurtzite structure of zinc oxide, but also has the best green tone (a* = -17.25). The room temperature of the roof coating sample in the heat insulation experiment is nearly 10℃ lower than that using ordinary pigments, indicating that the synthesized pigment has good thermal stability, high near-infrared reflectivity, chemical stability and low cobalt nitrate content (1.92wt%).

[0005] Bismuth molybdate (Bi2MoO6) as a N-type semiconductor has a unique layered structure, mainly composed of (Bi2O2) 2+ layers and (MoO4) 2- layers alternately, which makes Bi2MoO6 show unique physical and chemical properties. In addition, different compositions and structures provide a variety of choices for its application fields. The chemical formula of bismuth molybdate composite oxide is Bi2O3·nMoO3, where n is 3, 2, 1, corresponding to the three crystal structures found, namely α-Bi2Mo3O 12 , β-Bi2MoO9 and γ-B i2 MoO6. Studies have found that there are differences in crystal structure and band position among the above three crystal forms, and the charge between the electronic layers of the γ-Bi2MoO6 phase has an electrostatic effect, which promotes charge separation, and the chemical properties of Bi2MoO6 are relatively stable. It is reported that the rare earth ions doped Bi2MoO6 can effectively adjust its color, such as Han Aijun's team modified Bi2WO6 by Mo doping to prepare bismuth molybdate composite oxide with good near-infrared reflectivity, heat insulation capacity and good chemical stability and thermal stability. Shuang Liu et al. synthesized a series of environmentally friendly yellow near-infrared reflective pigments Bi 2-x Er x MoO6 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) by high-temperature solid-state method, which has high NIR reflectivity and heat preservation performance. So far, rare earth-containing high NIR reflective pigments have attracted great interest from researchers due to their low toxicity to rare earth elements, rich spectral properties and magnetic properties. SUMMARY

[0006] To improve the above technical problems, the present application provides a near-infrared reflective pigment, the chemical formula of which is: Bi 2.0-x-y Pr x W y MoO 6+δ , wherein: Pr, W are doping elements, x represents the doping molar amount of Pr, 0.1≤x≤0.5; exemplarily, x is 0.1, 0.2, 0.3, 0.4, 0.5; y represents the doping molar amount of W, 0.01≤y≤0.05; exemplarily, y is 0.01, 0.02, 0.03, 0.04, 0.05; and δ is charge balancing.

[0007] According to an embodiment of the present application, the near-infrared reflective pigment is monoclinic crystal system, and the space group is P21 / c (14).

[0008] According to an embodiment of the present application, the average particle size of the near-infrared reflective pigment is 1-50 μm, preferably 1-10 μm, and exemplarily 2 μm, 3 μm, 5 μm, 8 μm, 10 μm.

[0009] According to an embodiment of the present application, the average near-infrared reflectivity of the near-infrared reflective pigment is greater than 85%, for example, 85-95%, and exemplarily 85%, 90%, 92%, 95%.

[0010] According to an embodiment of the present application, the near-infrared reflective pigment is prepared by a solid phase sintering method from raw materials including Bi source, Pr source, W source and Mo source.

[0011] According to an embodiment of the present application, the Bi source is provided by a compound containing Bi element; for example, provided by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing Bi element; and preferably provided by oxides (for example Bi2O3) containing Bi element.

[0012] According to an embodiment of the present application, the Pr source is provided by a compound containing Pr element; for example, provided by oxides (for example Pr6O 11 ) containing Pr element.

[0013] According to an embodiment of the present application, the W source is provided by a compound containing W element; for example, provided by oxides (for example WO3) containing W element.

[0014] According to an embodiment of the present application, the Mo source is provided by a compound containing Mo element; for example, provided by oxides (for example MoO3) containing Mo element.

[0015] According to an embodiment of the present application, the near-infrared reflective pigment can be Bi 1.85 Pr 0.1 W0.05 MoO 6+δ , Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ , Bi 1.65 Pr 0.3 W 0.05 MoO 6+δ , Bi 1.55 Pr 0.4 W 0.05 MoO 6+δ or Bi 1.45 Pr 0.4 W 0.05 MoO 6+δ .

[0016] According to an embodiment of the present application, the color of the near-infrared reflective pigment is green.

[0017] The present application also provides a preparation method of the above-mentioned near-infrared reflective pigment, comprising the following steps: mixing the stoichiometric ratio of each element in the chemical formula Bi 2.0-x-y Pr x W y MoO 6+δ (0.1≤x≤0.5, 0.01≤y≤0.05) by using a Bi source, a Pr source, a W source and a Mo source as raw materials, and obtaining the near-infrared reflective pigment by using solid phase sintering.

[0018] According to an embodiment of the present application, the Bi source, the Pr source, the W source and the Mo source have the meanings as described above.

[0019] According to an embodiment of the present application, the solid phase sintering uses secondary calcination treatment, the temperature of the primary calcination is 600-800℃, and exemplary temperatures are 600℃, 700℃ and 800℃; the time of the primary calcination is 0.5-2h, and exemplary times are 0.5h, 1h and 2h.

[0020] The temperature of the secondary calcination is 800-1000℃, and exemplary temperatures are 800℃, 900℃ and 1000℃; the time of the secondary calcination is 1-3h, and exemplary times are 1h, 2h and 3h.

[0021] According to an embodiment of the present application, the heating rate of the solid phase sintering (including the heating rate of the primary calcination and the secondary calcination) is 1-10℃ / min, and exemplary heating rates are 1℃ / min, 5℃ / min and 8℃ / min.

[0022] According to an embodiment of the present application, before the solid phase sintering treatment, the method further comprises a step of grinding the raw materials. For example, the grinding can be wet grinding; preferably, the medium used for grinding can be at least one of acetone, water and ethanol, and preferably acetone.

[0023] According to an embodiment of the present application, the preparation method further comprises drying the milled raw material. For example, the drying temperature is 40-60°C, and exemplary values are 40°C, 50°C, and 60°C. Further, the drying time can be 0.5-2h, and exemplary values are 0.5h, 1.5h, and 2h.

[0024] According to an embodiment of the present application, the preparation method further comprises cooling the prepared calcined sample after the solid phase sintering is completed. For example, the cooling rate is 1-10°C / min, and exemplary values are 1°C / min, 5°C / min, and 10°C / min.

[0025] According to an embodiment of the present application, the preparation method further comprises milling the cooled calcined sample. Preferably, the average particle size of the milled calcined sample is 1-50μm, preferably 1-10μm, and exemplary values are 2μm, 3μm, 5μm, 8μm, and 10μm.

[0026] According to an exemplary embodiment of the present application, the preparation method comprises the following steps: taking Bi, Pr, W, and Mo sources in stoichiometric ratios of Bi 2.0-x- y Pr x W y MoO 6+δ (0.1≤x≤0.5, 0.01≤y≤0.05) in turn, adding a grinding medium (e.g. acetone) to mill, then drying and solid phase sintering the milled mixture to obtain a calcined sample, and milling the calcined sample again to obtain the near-infrared reflective pigment.

[0027] The present application also provides applications of the above-mentioned near-infrared reflective pigment in the fields of green camouflage clothing or equipment, cosmetics, building materials, paints, plastics, vehicle decks, aerospace, oil storage tanks, or inks, etc.

[0028] Preferably, the near-infrared reflective pigment can be used in high-reflectivity paints, such as for preparing chemical product storage tank paints, vehicle and ship heat insulation paints, metal plate heat insulation paints, communication base station heat insulation paints, or building exterior wall paints, etc.

[0029] The present application also provides a coating layer containing or prepared from the above-mentioned near-infrared reflective pigment.

[0030] Advantages of the present application:

[0031] The present application successfully synthesizes a series of non-toxic and environment-friendly Bi2MoO6 doped with rare earth ions green pigments by adopting a solid-phase synthesis method.The pigments of the present application have bright color and high near-infrared reflectivity, and can replace traditional inorganic green pigments containing heavy metal ions.In addition, it is unexpectedly found that the coating coated with the pigments of the present application can significantly reduce the surface temperature, and the temperature difference between the blank galvanized sheet coated with the pigments of the present application and the blank galvanized sheet without the pigments of the present application can be as high as 10.3℃. This finding means that the coating prepared by using the pigments of the present application can effectively reduce the indoor temperature, so as to improve the comfort of people's living environment, thereby having a broad application prospect in the field of heat insulation and energy saving. The pigments prepared by the present application do not contain heavy metals, have excellent color and performance characteristics, and are expected to become an environment-friendly green pigment, so as to be widely applied in the fields of building and coating, and contribute to the promotion of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 (b) is Bi 2-x Pr x MoO 6+δ XRD diffraction pattern of Bi2MoO6 doped with Pr (x=0-0.6); Figure 1 (b) is Bi 1.95- x Pr x W 0.05 MoO 6+δ XRD diffraction pattern of Bi2MoO6 doped with Pr (x=0.1-0.5).

[0033] Figure 2 (b) is Bi 1.95-x Pr x W 0.05 MoO 6+δ SEM image of Bi2MoO6 doped with Pr (x=0.1-0.5) pigments.

[0034] Figure 3 (b) is Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ EDS spectrum and element distribution map of Bi2MoO6 doped with Pr pigments.

[0035] Figure 4 (b) is Bi 1.95-x Pr x W 0.05 MoO 6+δ Particle size distribution map of Bi2MoO6 doped with Pr (x=0.1-0.5) pigments.

[0036] Figure 5 (b) is Bi 1.95-x Pr x W 0.05 MoO 6+δUV-visible reflectance and absorption spectra of the pigments (x = 0.1-0.5).

[0037] Figure 6 Bi 1.95-x Pr x W 0.05 MoO 6+δ Absorption edge of the pigments (x = 0.1-0.5).

[0038] Figure 7 Bi 1.95-x Pr x W 0.05 MoO 6+δ CIE 1931 chromaticity diagram of the pigments.

[0039] Figure 8 Bi 2-x Pr x MoO 6+δ Near-infrared reflectance and near-infrared solar reflectance of the pigments (x = 0-0.5); Figure 8 Bi 1.95-x Pr x W 0.05 MoO 6+δ Near-infrared reflectance and near-infrared solar reflectance of the pigments (x = 0.1-0.5).

[0040] Figure 9 Temperature experiment diagram of the synthesized pigment coating and the blank coating.

[0041] Figure 10 Bi 1.9-x Pr x W 0.1 MoO 6+δ XRD spectrum of the pigments (x = 0.1-0.5).

[0042] Figure 11 Performance diagram of the praseodymium / tungsten co-doped Bi2MoO6 green pigment of the present application. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be further described in detail below in combination with specific embodiments. It should be understood that the following embodiments are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0044] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0045] MoO3 of 99.99% purity and WO3 of 99.9% purity were purchased from Adamas-beta (Shanghai) Co. Ltd, Bi2O3 and Pr6O 11 were purchased from Aladdin Reagent (Shanghai) Co. Ltd. All the above reagents were used directly without further purification. Deionized water was used throughout the process.

[0046] Examples 1-18

[0047] Praseodymium / Tungsten co-doped Bi2MoO6 green pigment Bi 1.95-x Pr x W 0.05 MoO 6+δ (x = 0-0.5), Bi 2-x Pr x MoO 6+δ (x = 0-0.6), Bi 1.9-x Pr x W 0.1 MoO 6+δ (x = 0.1-0.5) were synthesized by solid state synthesis method. The difference between each example is the type and amount of raw materials used. Table 1 lists the type and amount of raw materials used in each example.

[0048] A method for preparing praseodymium oxide doped Bi2MoO6 green powder, comprising the following steps:

[0049] (1) Weigh each oxide (Bi2O3, MoO3 and Pr6O 11 ) according to the stoichiometric ratio and mix well. Then pour the mixture into an agate mortar and wet mill in acetone medium until the acetone evaporates, repeating this operation 2-3 times.

[0050] (2) Put the above treated powder into an oven at 60°C and dry for 120 minutes. Then pour the completely dried powder into a corundum crucible and put it into a muffle furnace for high temperature reaction (the experimental procedure is: heat to 700°C at a rate of 8°C / min and maintain for 60 minutes, then continue to heat to 900°C at a rate of 8°C / min, react for 120 min), after completion, cool to room temperature at a rate of 5°C / min. Wet mill the reacted sample again in an agate mortar in acetone medium for 2-3 times, dry and obtain the desired praseodymium doped pigment sample Bi 2-x Pr x MoO 6+δ .

[0051] (3) In order to improve the color of the pigment sample, the above pigment sample Bi 2-x Prx MoO 6+δ On the basis of the above, WO3 was further doped: the pigment sample obtained in step (2) and WO3 were weighed according to the stoichiometric ratio, and then the mixture was poured into an agate mortar and wet ground in an acetone medium until the acetone evaporated, and this operation was repeated 2-3 times; the powder thus treated was dried in an oven at 60°C for 120 minutes, and then the completely dry powder was poured into a corundum crucible and placed in a muffle furnace for high-temperature reaction (the experimental procedure was: heating to 700°C at a rate of 8°C / min and maintaining for 60 minutes, and then continuing to heat to 900°C at a rate of 8°C / min, for 120 min), and after completion, cooling to room temperature at a rate of 5°C / min. The reacted sample was again wet ground in an agate mortar in an acetone medium 2-3 times, and dried, to obtain praseodymium / tungsten co-doped Bi2MoO6 green powder Bi 1.95- x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5), Bi 1.9-x Pr x W 0.1 MoO 6+δ (x = 0.1-0.5).

[0052] Table 1 Preparation parameters for examples 1-18

[0053]

[0054] Note: "-" in the table means not added.

[0055] The cell parameters and phase information of the pigment samples synthesized in this example were determined using a Rigaku Miniflex 600 X-ray diffractometer (Cu-Ka target). The XRD test was performed on the sample at a scan speed of 8° / θ, a scan step of 0.02°, and a scan range of 5-50°, under test conditions of a voltage and current of 40 kV and 15 mA, respectively, to obtain the diffraction spectrum data.

[0056] The surface morphology characteristics and particle size of the pigment samples were observed using a field emission scanning electron microscope (SEM, SU1510, Hitachi), and the chemical composition and element distribution of the pigment samples were analyzed using energy dispersive X-ray spectroscopy (EDS).

[0057] The pigment powder was pre-dispersed in anhydrous ethanol, and the particle size and particle size distribution of the pigment powder were tested using a Brookhaven multi-angle particle size high-sensitivity Zeta potential analyzer.

[0058] The absorption spectrum and reflectance spectrum of the pigment sample were determined using a UV-visible near-infrared spectrophotometer (UV).

[0059] The reflectance and absorption spectra of the pigment samples were tested in the wavelength range of 200-2500 nm using barium sulfate (BaS04) as a baseline standard, and the NIR solar reflectance (R*) of the samples in the wavelength range of 700-2500 nm was calculated by the following equation (1):

[0060]

[0061] In the above equation, r(λ) and i(λ) represent the reflectance measured at 700-2500 nm and the solar spectrum irradiance (W-m -2 ·nm -1 ) of the ASTM G173-03 standard, respectively.

[0062] The band gap value (Eg) of the sample was calculated according to the following equation:

[0063]

[0064] In the equation, λ represents the absorption edge in the UV-Vis spectral region.

[0065] The absorption limit is defined by the Kubelka-Munk equation as follows:

[0066]

[0067] where R represents the reflectance of the pigment sample in the UV-Vis region. The tangent of the line drawn with (F(R)) 2 as the ordinate and hv as the abscissa intersects the abscissa at the band gap of the pigment sample.

[0068] The color coordinates of the pigment sample were described using the CIE L*a*b* (1931) color space system. The spectrophotometer CS-580A produced by Hangzhou Caipu Technology Co., Ltd. was used to measure under D65 standard light and a 10° standard observer angle. In this system, L* represents the brightness, ranging from 0 (black) to 100 (white); a* represents the green-red characteristics of the synthetic pigment, with negative values indicating green and positive values indicating red; and b* is used to represent the blue-yellow color of the pigment, with negative values indicating blue and positive values indicating yellow. The range of a* and b* is between -128 and +128. In addition, the parameter C* represents the color saturation of the sample, and the parameter H° (0-360°) represents the hue angle, which can be used to determine the color interval in which the sample is located. The definitions of C* and H° are as follows:

[0069]

[0070] H° = arctan(b * / a * ) (5)

[0071] The chemical stability of the pigment is one of the measures of the durability of the pigment in practical application, and the change of the L*a*b* value of the pigment after soaking in different acid (HCl, H2SO4, HNO3) and base (NaOH, NH3·H2O) solutions is recorded as ΔE* to determine whether the pigment is suitable for application in practical production.

[0072] The prepared pigment and the glaze are uniformly mixed at a mass ratio of 1:1.5, and are evenly coated on a 10cm*10cm rectangular galvanized sheet, and are finally naturally air-dried to obtain a pigment coating plate with a thickness of 100-120μm. The thermocouple thermometer probe is placed at the intersection of the diagonal lines of the galvanized sheet, and the distance between the galvanized sheet and the infrared lamp is kept at 25cm. Then the galvanized sheet coated with different pigments is irradiated under the infrared lamp for a period of time, and the temperature change of the galvanized sheet coated with different pigments after irradiation for 0min, 1min, 4min, 7min, 10min, 20min, 30min, 60min and 90min is recorded respectively to determine whether the prepared pigment sample material is a qualified heat insulation material.

[0073] Phase structure analysis

[0074] The microcrystal composition and structure of the Bi 2- x Pr x MoO 6+δ (x=0-0.6) and Bi 1.95-x Pr x W 0.05 MoO 6+δ (x=0.1-0.5) pigment samples prepared in Examples 7-13 after calcination at 900℃ were characterized by X-ray diffraction, and the results are shown in Figs. Figure 1 (a) and (b), respectively. As can be seen from Figs. Figure 1 , all the characteristic peaks of the pure Bi2MoO6 and the doped modified pigment samples correspond to standard card No. 82-2067, and all the doped samples are monoclinic with a space group of P21 / c(14). The strong and sharp main diffraction peaks in the XRD spectrum indicate that the crystallinity of the pigment powder is high, and there are no main diffraction peaks of MoO3, Bi2O3, Pr6O 11 , CeO2 or WO3 in the spectrum. This indicates that the Bi 2-x Pr x MoO 6+δ (x=0-0.6), Bi 1.95-x Pr x W 0.05 MoO 6+δ(x = 0.1-0.5) solid solution has been completely formed. According to Bragg's law, the characteristic diffraction peak of the sample will shift after the formation of the solid solution. The movement of the XRD characteristic peak is directly related to the lattice expansion at high temperature. In the present application, smaller radius Substitution, the lattice shrinks to a certain extent, and the crystal plane moves to a large angle. And through the enlarged view of 2θ (27.1°-27.9°), it can be observed that the (341) crystal plane (27.25°) and the (-341) crystal plane (27.41°) move to a higher angle, and the peak intensity of the (341) crystal plane increases, and the diffraction peak of the (-341) crystal plane is slightly weakened. According to Bragg's law, the characteristic diffraction peak of the sample will shift after the formation of the solid solution. From Figure 1 It can be seen from (a) that when the doping amount of praseodymium oxide is 0.6, a small peak of unreacted Bi2O3 appears, indicating that the doping concentration of praseodymium oxide has been saturated, which is not conducive to the crystallization of the solid solution. Therefore, in order to make the pigment maintain its high crystallinity and purity at the same time, the doping amount of praseodymium oxide in the present application is preferably not more than 0.5 (i.e. x≤0.5).

[0075] In order to investigate the effect of the doping amount of WO3 on the performance of Pr, W co-doped Bi2MoO6 pigment, the inventors prepared Bi 1.9-x Pr x W 0.1 MoO 6+δ (x = 0.1-0.5) pigment, and its X-ray diffraction pattern is shown in Figure 10 It can be seen from the figure that when the doping amount of WO3 is 0.1, a small peak of unreacted Bi2O3 appears in the product, indicating that the doping concentration of WO3 is saturated, which is not conducive to the crystallization of the solid solution. Therefore, in order to make the pigment maintain its high crystallinity and purity at the same time, the doping amount of WO3 in the present application is preferably not more than 0.05 (i.e. y≤0.05).

[0076] In summary, in order to make the pigment maintain its high crystallinity and purity at the same time, the doping amount of praseodymium oxide in the present application is preferably not more than 0.5 (i.e. x≤0.5), and the doping amount of WO3 is determined to be not more than 0.05 (i.e. y≤0.05).

[0077] Morphology analysis

[0078] The surface morphology characteristics and particle size of Bi 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) were observed using a field emission scanning electron microscope (SEM), and the results are shown in Figure 2As shown in the figure, the Pr and W co-doped pigment samples exhibit irregular morphologies, which may be related to the synthesis method. Scanning electron microscopy (SEM) images reveal that the samples prepared in this invention all exhibit a certain degree of agglomeration, with the most pronounced agglomeration occurring when the Pr doping concentration is 0.5%. The agglomerated particles are of uneven size, ranging from 1 μm to 50 μm.

[0079] The chemical composition and elemental distribution of pigment samples were analyzed using energy-dispersive X-ray spectroscopy (EDS). This invention investigated Bi prepared with a Pr doping concentration of 0.2%. 1.75 Pr 0.2 W 0.05 MoO 6+δ EDS and X-ray dot matrix images of the pigment samples are shown below. Figure 3 As shown in the figure, the results demonstrate that this invention introduces Pr and W elements into Bi₂MoO₆, and the quantitative results are almost consistent with the stoichiometric coefficients of the theoretical composition, thus further illustrating that Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ The solid solution has been basically formed.

[0080] The smoothness of the coating surface is closely related to the particle size of the powder, which is one of the important factors affecting the performance of pigment coatings. Figure 4 for Bi 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) Particle size distribution of pigments, from Figure 4 It can be clearly observed that the Bi of the present invention 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) The particle size distribution of the pigment samples was mostly concentrated around 2 μm, exhibiting a relatively uniform characteristic. We recorded the Bi... 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) Particle size data of pigment samples, including the values ​​of D10, D50 and D90. For details, please refer to Table 2 below.

[0081] Table 2Bi 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1 - 0.5) D10, D50, D90 of the pigment

[0082]

[0083] Further observation of the D50 changes of pigment powders at different doping concentrations in Table 2 reveals that as the Pr doping concentration increases, Bi... 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) The average diameter of the pigment particles gradually increases. Of particular note is that when the Pr doping concentration reaches 0.5%, significant agglomeration of the sample particles occurs, leading to a substantial increase in particle size. This result is consistent with the findings obtained from scanning electron microscopy (SEM) analysis.

[0084] Analysis of UV-Vis reflectance and color characteristics

[0085] Color performance is considered an important property of pigment powders. 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) The ultraviolet-visible reflectance and absorption spectra of pigments related to their color properties are as follows: Figure 5 As shown in (a) and (b), by observing the absorption bands or peaks of the powder in the ultraviolet-visible spectrum, it can be seen that samples with different doping concentrations have very weak absorption in the green wavelength range (495nm-570nm), that is, there are few absorption features in the green wavelength range, and the absorption of green light is weak. Therefore, most of the green light will be reflected back. Therefore, the Bi of this invention... 1.95-x Pr x W 0.05 MoO 6+δ (x = 0.1-0.5) The pigment sample appears green.

[0086] The reflectance in the ultraviolet-visible region determines the color properties of the powder. Figure 6 Bi with different doping concentrations is calculated using the Kubelka-Munk (KM) formula. 1.95-x Pr x W 0.05 MoO 6+δ The bandgap curve is calculated using equation (1), with hv as the horizontal coordinate and [F(R)*hv]¹ / ² as the vertical coordinate. The intersection of the tangent line with the curve and the x-axis is the bandgap width. Figure 6 As shown, with increasing Pr doping concentration, the Eg value of the pigment sample first increased from 3.15 eV to 3.18 eV, and then decreased to 3.14 eV. The valence band (VB) of bismuth molybdate is mainly composed of 6s orbitals of Bi atoms and 2p orbitals of O atoms undergoing energy level hybridization, while its conduction band (CB) is mainly composed of 5d orbitals of Mo atoms. This implies that W in the solid solution... 6+The 5d orbital of W atom is empty and the interaction between 2p orbital of O atom and the 5d orbital of W atom is strengthened; this in turn slightly reduces the energy of the band gap, i.e. the change trend of the chromaticity of the sample and the change trend of the band gap width are consistent. In addition, it can be seen from Table 2 that the band gap of all the pigment samples is not in the range of near-infrared radiation energy (0.5-1.8 eV), thus it is illustrated that all the pigment samples synthesized by the present application have high near-infrared reflectivity. Figure 6

[0087] Color performance analysis

[0088] The color properties of the pigment samples are characterized by the chromaticity coordinates of CIE1931. Table 3 summarizes the L*a*b* parameters of Bi 2-x Pr x MoO 6+δ (x=0-0.5) pigment samples.

[0089] Table 3 Bi 2-x Pr x MoO 6+δ Color coordinates, band gap width and reflectivity of Bi

[0090]

[0091] It can be observed from the above table that the brightness value L* is generally increased after the addition of Pr6O 11 , which illustrates that the brightness of the pigment is improved. With the increase of the Pr6O 11 doping amount, the brightness first increases and then decreases, but overall the brightness of the pigment is bright. The a* value related to the green color change decreases from -2.28 to -8.87, and the smaller the a* value, the greener the sample, which means that the sample will have more obvious green color. Especially when x=0.5, the green color value reaches the minimum value -8.87, and at this time the color saturation C* is relatively high, C*=28.35.

[0092] In order to further improve the color performance of the pigment, on the basis of the above Bi 2-x Pr x MoO 6+δ WO3 is further doped to prepare Pr / Ta co-doped Bi2MoO6 pigment samples Bi 1.95-x Pr x W 0.05 MoO 6+δ (x=0.1-0.5). Table 4 details the L*a*b* parameters of the pigment samples.

[0093] Table 4 Bi 1.95-x Pr x W 0.05 MoO​6+δ Pigment color coordinates, band gap, and reflectance

[0094]

[0095] Table 4 shows a slight decrease in pigment brightness, indicating a darker color. The a* value decreased from -6.13 to -12.38, reaching its lowest value of -12.38 when x = 0.4, with a color saturation of 31.17. This is similar to the effect of only doping Pr6O. 11 Compared to pigments, the present invention simultaneously dops with Pr6O 11 The green value of the pigment generally decreased after praseodymium / tungsten co-doping, indicating that the pigment became greener, thus proving that the color performance of the pigment was significantly improved after praseodymium / tungsten co-doping. Figure 7 Bi1.95-xPrxW0.05MoO 6+δ The CIE 1931 chromaticity coordinate diagram of the pigment (x = 0.1-0.5) shows that the changes in its L*a*b* parameters are consistent with the observations in the pigment optical photographs.

[0096] Near-infrared reflectance analysis

[0097] The thermal insulation performance of pigment samples can be predicted using near-infrared reflectance. To study Bi... 2-x Pr x MoO 6+δ (x=0-0.5), Bi 1.95-x Pr x W 0.05 MoO 6+δ The near-infrared (NIR) reflectance properties of the pigment (x = 0.1-0.5) were measured, with the reflectance of the pigment in the 700-2500 nm range tested. From... Figure 8 As can be seen in (a) and Table 5 below, with Pr6O 11 With increasing doping concentration, Bi 2- x Pr x MoO 6+δ The continuous decrease in the near-infrared reflectance of the pigment indirectly indicates a decline in its heat insulation performance. To improve the pigment's color performance while maintaining its NIR reflectance, this invention further dops it with WO3. Figure 8 As can be seen from (c) and Table 6 below, with Pr6O 11 With increasing doping concentration, Bi 1.95-x Pr x W 0.05 MoO 6+δ The near-infrared reflectance of the pigment decreases slightly when the doping concentration x is 0.4. 1.95-x Pr x W 0.05 MoO6+δ The NIR reflectance of pigments is the lowest. Synthetic pigment Bi 2-x Pr x MoO 6+δ (x = 0-0.5), Bi 1.95-x Pr x W 0.05 MoO 6+δ The near-infrared solar reflectance curve of the pigments of Bi Figure 8 The color performance of the pigments is shown in (b) and (d) of FIG. 8. According to the color performance analysis of the pigments, the pigments doped with Pr6O 11 and WO3 have brighter green color, especially when the content of praseodymium oxide is 0.2, the green value a* is -11.55, and the color saturation C* is 29.47. At this time, the color performance of the pigments is superior, which can meet the aesthetic requirements of people on color, and the pigments have high near-infrared reflectance (R = 87.84%, R* = 92.82%). Table 7 shows the comparison of the synthetic pigment samples and other green pigments.

[0098] Table 5 Bi 2-x Pr x MoO 6+δ The near-infrared reflectance and the near-infrared solar reflectance of the pigments

[0099]

[0100] Table 6 Bi 1.95-x Pr x W 0.05 MoO 6+δ The near-infrared reflectance and the near-infrared solar reflectance of the pigments

[0101]

[0102]

[0103] Table 7 Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ Comparison of the color performance and the near-infrared reflectance of the pigments with other green pigments

[0104]

[0105] Note: 1, Co 0.1 Zn 0.9O) for application in NIR radiation reflectance, J. Alloys Compd., 780 (2019) 17-24 reports the synthesis. x Zn 1- x O) for application in NIR radiation reflectance, J. Alloys Compd., 780 (2019) 17-24 reports the synthesis.

[0106] 2、Zn 0.96 Co 0.04 O) for application in NIR radiation reflectance, J. Alloys Compd., 780 (2019) 17-24 reports the synthesis.

[0107] 3、(Cr,V)-ZrSiO4 by J. Yu, F. Jiang, J. Liu, T. Wang, X. Zhang, Q. Zhang, R. Zhang, Q. Wu, Q. Hu, Y. Yu, G. Feng, Coloring and near-infrared reflection performance of low-temperature synthesized novel (Cr,V)-ZrSiO4 jewel green pigments, Ceram. Int., 49 (2023) 38602-38613 reports the synthesis.

[0108] 4. YInCuO-ZnO was synthesized as reported in the literature M. Fedel, A. Rosati, M. Bertasini, S. Rossi, Cu doped YInO3-ZnO green colored NIR reflective pigments: Synthesis and application in PMMA based cool-roof coatings, Prog. Org. Coat., 182 (2023) 107708.

[0109] 5. Iron oxide green pigment was synthesized as reported in the literature M. Xu, G. Pan, Q. Shen, Y. Guo, M. Zhou, Q. Liang, The color rendering and near infrared reflection properties of coated iron oxide green pigments, Appl. Surf. Sci, 641 (2023) 158525.

[0110] 6. Cr2O3-TiO2-Al2O3-V2O5 was synthesized as reported in the literature T. Thongkanluang, T. Kittiauchawal, P. Limsuwan, Preparation and characterization of Cr2O3-TiO2-Al2O3-V2O5 green pigment, Ceram. Int., 37 (2011) 543-548.

[0111] 7. Y3Al 4.9 Cr 0.1 O 12 was synthesized as reported in the literature C. Chen, A. Han, M. Ye, X. Chen, J. Wang, Near-infrared solar reflectance and chromaticity properties of novel green ceramic pigment Cr-doped Y3Al5O 12 , J. Solid State Chem., 307 (2022)

[0112] 122873.

[0113] In summary, the green pigment Bi 1.95-x Pr x W 0.05 MoO6+δ (x=0.1-0.5) has excellent near-infrared reflection performance, can reflect most of the solar radiation, thereby effectively reducing the heat accumulation on the material, and it can be predicted that the pigment has the potential as a cool pigment in the field of ceramics, building. And on the basis of comprehensive consideration of the color and reflectivity performance of the pigment, it is unexpectedly found that when the doping amount of praseodymium oxide is 0.2 and the doping amount of tungsten oxide is 0.05, the pigment sample is monoclinic, and there is no impurity peak of the oxide, and the crystallinity is high. Among them, the pigment powder Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ It has the characteristics of bright color, high reflectivity and excellent stability in color, near-infrared reflectivity (R=87.84%) and chemical stability.

[0114] Thermal insulation experiment

[0115] The thermal insulation experiment can truly reflect the thermal insulation of the pigment in actual application. The prepared Bi 1.95- x Pr x W 0.05 MoO 6+δ (x=0.2) and the glaze are mixed uniformly in a mass ratio of 1:1.5 and coated on a galvanized sheet, and then naturally air-dried. The galvanized sheet without coating any pigment is used as a blank control, the room temperature is used as the environmental temperature, the air circulation is maintained, and the initial temperatures of the two galvanized sheets are kept consistent. The temperatures of the galvanized sheet coated with the pigment and the blank galvanized sheet are measured by using a thermocouple thermometer, T1 and T2 are the temperatures of the Bi 1.95-x Pr x W 0.05 MoO 6+δ (x=0.2) pigment coating and the blank galvanized sheet, the temperature difference AT=T2-T1, and the results are shown in Figure 9 From the figure, it can be seen that during the entire irradiation process, the temperature of the sample coating is always lower than that of the blank galvanized sheet. At the beginning of irradiation, the temperature difference between the two is relatively small, and as the irradiation time is prolonged, the temperature difference between the galvanized sheet coated with the pigment and the blank galvanized sheet gradually increases. When the irradiation time is 60 min, the temperature difference reaches a maximum value of 10.3℃. After irradiation for 60 minutes, the temperature difference is stable at 10.3℃. Moreover, compared with the blank galvanized sheet, the temperature rising trend of the galvanized sheet coated with the pigment is relatively slow during the entire experiment, which indicates that the coating of the pigment can effectively reduce the temperature. The reason for this result may be that the Bi 1.95-x Pr x W 0.05 MoO 6+δThe pigment has high near-infrared reflectivity, and most of the heat can be reflected, and the heat is accumulated on the surface of the blank galvanized plate, so that the temperature rapidly rises. The above experimental results further show that the Bi 1.95-x Pr x W 0.05 MoO 6+δ The pigment has excellent heat insulation performance, and therefore can be applied in the field of environmental protection building as a "cool" pigment to improve the living comfort of people while reducing energy loss.

[0116] The chemical stability of the pigment is particularly important in actual life and production, and is one of the standards for judging whether the pigment is durable. In order to explore the chemical stability of the pigment, the Bi 1.95-x Pr x W 0.05 MoO 6+δ (x=0.2) pigment was respectively immersed in 2% acid (HCl, HNO3, H2SO4) and alkali (NaOH, NH3·H2O) for two hours, and the change of L*a*b* value of the pigment was recorded respectively, and the results are shown in Table 8. The color difference value ΔE* represents the change of the color of the pigment before and after immersion, and the smaller the ΔE*, the smaller the change of the color of the pigment, that is, the pigment has good chemical stability in acid and alkali. Generally, ΔE*≤1, which means that the color of the pigment has not changed, and the naked eye cannot distinguish it; when ΔE*≤5, it means that the change of the pigment is not large, and the pigment has good acid and alkali resistance; when ΔE*>5, it means that the color of the pigment has changed greatly, and the pigment is not stable in acid and alkali, and cannot maintain the original performance, so as to affect the use of the pigment.

[0117] Table 8: L*a*b* color difference coordinates and total color difference value of the pigment powder

[0118]

[0119] ΔE*=[(△L*) 2 +(△a*) 2 +(△b*) 2 ] 1 / 2

[0120] From the data in Table 7, it can be known that the color difference value ΔE* of the Bi 1.95-x Pr x W 0.05 MoO 6+δ (x=0.2) pigment of the present application is much smaller than 5, especially after being immersed in HNO3 and NaOH, the ΔE* is less than 1, which means that the color of the pigment has not changed, and the original performance can be maintained. In summary, it can be considered that the acid and alkali solution has little effect on the Bi 1.95-x Pr x W 0.05 MoO 6+δ The color of the pigment (x=0.2) is less affected, which indicates that the pigment has excellent acid and alkali resistance, and thus has good chemical stability in a natural environment.

[0121] The above describes embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A near infrared reflecting pigment, characterized in that, The chemical general formula of the pigment is: Bi 2.0-x-y Pr x W y MoO 6+δ , wherein: Pr, W are doping elements, x represents the doping molar amount of Pr, 0.1≤x≤0.5; y represents the doping molar amount of W, 0.01≤y≤0.05; and δ is charge balancing.

2. The near infrared reflecting pigment of claim 1, wherein The near-infrared reflective pigment is monoclinic, and the space group is P21 / c (14). Preferably, the average particle size of the near-infrared reflective pigment is 1-50 μm, preferably 1-10 μm. Preferably, the average near-infrared reflectivity of the near-infrared reflective pigment is greater than 85%, for example, 85-95%.

3. The near infrared reflective pigment according to claim 1 or 2, wherein The near-infrared reflective pigment is prepared by a solid-phase sintering method from raw materials including a Bi source, a Pr source, a W source and a Mo source.

4. The near infrared reflecting pigment of claim 3, wherein The Bi source is provided by at least one of carbonates, oxides, chlorides, nitrates and sulfates containing Bi elements. Preferably, the Pr source is provided by oxides containing Pr elements. Preferably, the W source is provided by oxides containing W elements. Preferably, the Mo source is provided by oxides containing Mo elements.

5. The near infrared reflecting pigment according to any one of claims 1 to 4, wherein The near-infrared reflective pigment can be Bi 1.85 Pr 0.1 W 0.05 MoO 6+δ , Bi 1.75 Pr 0.2 W 0.05 MoO 6+δ , Bi 1.65 Pr 0.3 W 0.05 MoO 6+δ , Bi 1.55 Pr 0.4 W 0.05 MoO 6+δ , or Bi 1.45 Pr 0.4 W 0.05 MoO 6+ .

6. A process for the preparation of near infrared reflecting pigments according to any one of claims 1 to 5, characterized in that The preparation method comprises the following steps: taking a Bi source, a Pr source, a W source and a Mo source as raw materials, mixing stoichiometric ratios of elements in a chemical formula Bi 2.0-x-y Pr x W y MoO 6+δ (0.1≤x≤0.5, 0.01≤y≤0.05) by solid phase sintering to obtain the near-infrared reflective pigment.

7. The production method according to claim 6, wherein The solid-phase sintering adopts a two-stage calcination process, the temperature of the first-stage calcination is 600-800 ℃, the time of the first-stage calcination is 0.5-2 h, the temperature of the second-stage calcination is 800-1000 ℃, and the time of the second-stage calcination is 1-3 h.

8. The production method according to claim 6 or 7, characterized by, The preparation method comprises the following steps: taking the stoichiometric ratio of each element in the chemical formula Bi 2.0-x-y Pr x W y MoO 6+δ (0.1≤x≤0.5, 0.01≤y≤0.05) in turn, adding grinding medium for grinding, then drying the ground mixture, solid phase sintering treatment, and grinding the obtained calcined sample to obtain the near-infrared reflective pigment.

9. Use of the near-infrared reflective pigment according to any one of claims 1-5 in the fields of green camouflage clothing or equipment, cosmetics, building materials, paints, plastics, vehicle decks, aerospace, oil tank storage tanks or inks, etc.

10. A coating characterized in that, It contains the near-infrared reflective pigment according to any one of claims 1-5 or is prepared from the near-infrared reflective pigment according to any one of claims 1-5.

Images