CaO fluorescent color-changing drying agent as well as preparation method and use method thereof

Abstract

The invention relates to a CaO fluorescent color-changing drying agent and a preparation method and a use method thereof, and the preparation method comprises the following steps: weighing raw materials CaCO3, Eu2O3, Bi2O3 and Li2CO3 according to the mass ratio of 100: (1-4): (0.5-2): (1.5-6), adding absolute ethyl alcohol as a grinding aid, fully and uniformly grinding, and drying to obtain a precursor; placing the precursor in a calcining box, setting 1000-1300 DEG C as a calcining temperature, and performing high-temperature sintering for 3-5 hours; after sintering, cooling and grinding to obtain a calcium oxide fluorescent powder sample, namely the CaO fluorescent color-changing drying agent. The CaO fluorescent color-changing drying agent disclosed by the invention can be used in an ultraviolet environment, and the water absorption capacity of the drying agent can be judged by observing the color of fluorescence with naked eyes by utilizing the change of the emission peak position and the emission peak intensity of photoluminescence of the calcium oxide fluorescent powder when the environment humidity is changed.

Description

Technical Field

[0001] The present invention relates to the technical field of desiccants, and in particular to a CaO fluorescent color-changing desiccant and a preparation method and a use method thereof. Background Art

[0002] Desiccant is a dehumidifier that absorbs moisture from the atmosphere. It physically absorbs water molecules into its own structure or chemically absorbs water molecules and changes its chemical structure to another substance. It is suitable for preventing instruments, meters, electrical equipment, medicines, food, textiles and other packaging items from getting damp.

[0003] Calcium oxide desiccant is widely used in packaged food due to its good drying effect and low production cost. Calcium oxide desiccant has fast adsorption speed, strong adsorption capacity, is non-toxic, tasteless, pollution-free, and harmless to the human body. For example, a high specific surface area calcium oxide desiccant and its preparation method provided in the Chinese invention patent with publication number CN110773110B, the high specific surface area calcium oxide desiccant has higher water absorption. However, the existing calcium oxide desiccant only has the drying function, and there is no function to show whether it can also have water absorption characteristics.

[0004] On the other hand, color-developing desiccants such as silica gel desiccants are desiccants that change with water absorption. This type of desiccant is often used to keep sealed containers dry, and at the same time indicates whether it is ineffective by changing its own color. However, this type of desiccant can only show clear color changes under white light, and is generally used for drying needs in daily environments.

[0005] For some scenarios that require ultraviolet irradiation environment and maintain a certain degree of dryness, such as some special plant growth environments and the preservation of some insulating organic matter, a desiccant that can be excited by ultraviolet light to develop color is required.

[0006] Therefore, the present invention provides a CaO fluorescent color-changing desiccant and a preparation method and a use method thereof to solve the above problems. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a CaO fluorescent color-changing desiccant and a preparation method and a use method thereof. The desiccant can judge the water absorption of the desiccant and evaluate the environmental humidity by observing the color change of the desiccant with the naked eye in an ultraviolet irradiation environment.

[0008] In order to solve the above technical problems, the technical solution of the present invention is: a preparation method of a CaO fluorescent color-changing desiccant, the innovation of which is that the preparation method comprises the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 according to the molar ratio of 100:1~4:0.5~2:1.5~6, add anhydrous ethanol as a grinding aid, grind them evenly, and then dry them to obtain a precursor; (2) Place the precursor in a calcination box, set the calcination temperature to 1000-1300°C, and sinter at high temperature for 3-5 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

[0009] Furthermore, in step (1), the molar ratio of the raw materials CaCO3, Eu2O3, Bi2O3 and Li2CO3 is 100:1:0.5:1.5.

[0010] Furthermore, among the raw materials, the purity requirement of CaCO3 and Li2CO3 is AR, the purity requirement of Eu2O3 is 4N, and the purity requirement of Bi2O3 is 4N.

[0011] The chemical formula of the CaO fluorescent color-changing desiccant prepared by the preparation method is CaO: 0.02-0.08Eu, 0.01-0.04Bi.

[0012] The method for using the above-mentioned CaO fluorescent color-changing desiccant is as follows: placing the CaO fluorescent color-changing desiccant in an ultraviolet light environment, observing the luminescent chromaticity of the CaO fluorescent color-changing desiccant to determine the amount of water absorbed by the desiccant, and evaluating the ambient humidity according to the chromaticity / humidity calibration curve.

[0013] Furthermore, the luminescent chromaticity of the CaO fluorescent color-changing desiccant varies from orange to purple-red.

[0014] Furthermore, the maximum temperature of the use environment of the CaO fluorescent color-changing desiccant is 500°C.

[0015] Furthermore, the method for obtaining the chromaticity / humidity calibration curve is as follows: placing the CaO fluorescent color-changing desiccant in a container to keep it in a fluffy state and in full contact with the environment, building a test light path, using an excitation light source as ultraviolet light with an excitation wavelength of 250-370 nm, changing the ambient humidity by adjusting the ambient water vapor concentration, using a micro grating spectrometer to measure and obtain fluorescence spectra under different humidity, using the fluorescence spectrum to calculate the corresponding chromaticity coordinates, and obtaining the chromaticity / humidity calibration curve.

[0016] Furthermore, the excitation light source is ultraviolet light with an excitation wavelength of 320 nm.

[0017] Furthermore, the CaO fluorescent color-changing desiccant is placed in a carrier for use, and the carrier includes an alumina ceramic heating plate and a heating circuit.

[0018] The advantages of the present invention are: (1) The CaO fluorescent color-changing desiccant of the present invention combines the characteristics of the existing fluorescent powder that the luminescence changes with humidity and the advantages of the color-changing desiccant, and adopts CaO: 0.02~0.08Eu, 0.01~0.04Bi phosphor, wherein Eu is used as the luminescence center and Bi is the energy transfer center, which can enhance the luminescence intensity of the calcium oxide phosphor. Meanwhile, Bi can also be used as an auxiliary material for the sintering of calcium oxide to improve the sintering efficiency. The CaO fluorescent color-changing desiccant can be used in ultraviolet environment. The change of the emission peak position and the emission peak intensity of the photoluminescence of the calcium oxide phosphor when the ambient humidity changes is utilized, and the water absorption of the desiccant can be judged by observing the fluorescence color with the naked eye.

[0019] (2) The preparation method of the CaO fluorescent color-changing desiccant of the present invention is simple and convenient. Its matrix is ​​mainly derived from calcium carbonate powder. Calcium carbonate has the advantages of low price, stable chemical properties, easy control of particle size and morphology, high output and yield, and is suitable for large-scale industrial production.

[0020] (3) The CaO fluorescent color-changing desiccant of the present invention emits obvious light when used in an ultraviolet environment, and the light emission changes significantly under continuous water absorption.

[0021] (4) When the CaO fluorescent color-changing desiccant of the present invention is used, the chromaticity coordinates at different humidity levels are calibrated by a spectrometer to obtain a chromaticity / humidity calibration curve. The user of the desiccant can estimate the ambient humidity by visually judging the calibration curve.

[0022] (5) The CaO fluorescent color-changing desiccant of the present invention is placed in a heatable carrier when in use. After the desiccant is saturated with water after being used for a period of time, the carrier can be directly used for heating and dehumidification, so that the desiccant can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] Figure 1 This is the SEM image of CaO fluorescent color-changing desiccant.

[0025] Figure 2 The fluorescence spectra of CaO fluorescent color-changing desiccant at different humidity levels.

[0026] Figure 3 This is the fluorescence chromaticity diagram of CaO fluorescent color-changing desiccant at different humidity.

[0027] Figure 4 This is the chromaticity / humidity calibration curve of CaO fluorescent color-changing desiccant at different humidity levels.

[0028] Figure 5Schematic diagram of the use of CaO fluorescent color-changing desiccant. DETAILED DESCRIPTION

[0029] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0030] Example 1 This embodiment provides a method for preparing a CaO fluorescent color-changing desiccant, comprising the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 in a molar ratio of 100:1:0.5:1.5. The purity requirements for CaCO3 and Li2CO3 are AR, the purity requirement for Eu2O3 is 4N, the purity requirement for Bi2O3 is 4N, and the purity requirement for Eu 3+ As an activator, Bi 3+ As a sensitizer, Li2CO3 is a co-solvent and charge compensator. The raw material mixture is placed in a mortar, anhydrous ethanol is added as a grinding aid, and the mixture is fully and evenly ground. After drying, the precursor can be obtained; (2) placing the precursor in a calcination box, setting the calcination temperature to 1150°C, and sintering at high temperature for 4 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

[0031] The chemical formula of the CaO fluorescent color-changing desiccant prepared by the preparation method of this embodiment is CaO: 0.02Eu, 0.01Bi. The SEM image of the CaO fluorescent color-changing desiccant is as follows: Figure 1 shown.

[0032] Example 2 This embodiment provides a method for preparing a CaO fluorescent color-changing desiccant, comprising the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 in a molar ratio of 100:2:1:3. The purity requirements for CaCO3 and Li2CO3 are AR, the purity requirement for Eu2O3 is 4N, the purity requirement for Bi2O3 is 4N, and the purity requirement for Eu2O3 is 4N. 3+ As an activator, Bi 3+ As a sensitizer, Li2CO3 is a co-solvent and charge compensator. The raw material mixture is placed in a mortar, anhydrous ethanol is added as a grinding aid, and the mixture is fully and evenly ground. After drying, the precursor can be obtained; (2) placing the precursor in a calcination box, setting the calcination temperature at 1200°C, and sintering at high temperature for 4.5 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

[0033] The chemical formula of the CaO fluorescent color-changing desiccant prepared by the preparation method of this embodiment is CaO: 0.04Eu, 0.02Bi.

[0034] Example 3 This embodiment provides a method for preparing a CaO fluorescent color-changing desiccant, comprising the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 in a molar ratio of 100:3:1.5:4.5, where the purity requirements for CaCO3 and Li2CO3 are AR, the purity requirement for Eu2O3 is 4N, the purity requirement for Bi2O3 is 4N, and the purity requirement for Eu 3+ As an activator, Bi 3+ As a sensitizer, Li2CO3 is a co-solvent and charge compensator. The raw material mixture is placed in a mortar, anhydrous ethanol is added as a grinding aid, and the mixture is fully and evenly ground. After drying, the precursor can be obtained; (2) placing the precursor in a calcination box, setting the calcination temperature at 1000°C, and sintering at high temperature for 5 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

[0035] The chemical formula of the CaO fluorescent color-changing desiccant prepared by the preparation method of this embodiment is CaO: 0.06Eu, 0.03Bi.

[0036] Example 4 This embodiment provides a method for preparing a CaO fluorescent color-changing desiccant, comprising the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 in a molar ratio of 100:4:2:6. The purity requirements for CaCO3 and Li2CO3 are AR, the purity requirement for Eu2O3 is 4N, the purity requirement for Bi2O3 is 4N, and the purity requirement for Eu2O3 is 4N. 3+ As an activator, Bi 3+ As a sensitizer, Li2CO3 is a co-solvent and charge compensator. The raw material mixture is placed in a mortar, anhydrous ethanol is added as a grinding aid, and the mixture is fully and evenly ground. After drying, the precursor can be obtained; (2) placing the precursor in a calcination box, setting the calcination temperature at 1300°C, and sintering at high temperature for 3 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

[0037] The chemical formula of the CaO fluorescent color-changing desiccant prepared by the preparation method of this embodiment is CaO: 0.08Eu, 0.04Bi.

[0038] Example 5 This embodiment provides a method for using the CaO fluorescent color-changing desiccant: before use, the CaO fluorescent color-changing desiccant is placed in a carrier in advance, such as Figure 5 As shown, the carrier includes an alumina ceramic heating plate 3 and a heating circuit. The heating circuit is connected to the alumina ceramic heating plate 3 and can be heated to a maximum of 500°C. The top surface of the alumina ceramic heating plate 3 has a frame 4. The CaO fluorescent color-changing desiccant 2 is laid inside the frame 4 on the alumina ceramic heating plate 3. For long-term humid weather, the heating function of the carrier can be used to heat and dehumidify the desiccant at regular intervals to achieve the recycling of the desiccant. When the CaO fluorescent color-changing desiccant is in use, the CaO fluorescent color-changing desiccant is placed in the carrier and then placed in an ultraviolet light environment. It is irradiated by an ultraviolet light source 1, and the luminescent chromaticity of the CaO fluorescent color-changing desiccant is observed to determine the water absorption of the desiccant, and the environmental humidity is evaluated according to the chromaticity / humidity calibration curve.

[0039] Among them, the maximum temperature of the use environment of CaO fluorescent color-changing desiccant is 500°C, the ultraviolet light environment needs to be ≤500°C, and the luminescent chromaticity of CaO fluorescent color-changing desiccant varies from orange to purple-red.

[0040] The method for obtaining the chromaticity / humidity calibration curve is as follows: put the CaO fluorescent color-changing desiccant into a container to keep it in a fluffy state and in full contact with the environment, build a test light path, the excitation light source is ultraviolet light with an excitation wavelength of 250-370nm, and the optimal excitation wavelength is 320nm. The ambient humidity is changed by adjusting the ambient water vapor concentration. In this embodiment, three humidity levels of 10%, 40% and 70% are selected, and a portable micro-grating spectrometer is used to measure and obtain the fluorescence spectra under different humidity levels, such as Figure 2 As shown, the corresponding chromaticity coordinates are calculated using the fluorescence spectrum, as shown in Figure 3 As shown, the chromaticity coordinates at different humidity are used to form a chromaticity / humidity calibration curve, such as Figure 4 The chromaticity / humidity calibration curve combined with the chromaticity diagram can guide users of fluorescent desiccant to judge the ambient humidity based on the fluorescent color.

[0041] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a CaO fluorescent color-changing desiccant, characterized in that: The preparation method comprises the following steps: (1) Weigh the raw materials CaCO3, Eu2O3, Bi2O3, and Li2CO3 according to the molar ratio of 100:1~4:0.5~2:1.5~6, add anhydrous ethanol as a grinding aid, grind them evenly, and then dry them to obtain a precursor; (2) Place the precursor in a calcination box, set the calcination temperature to 1000-1300°C, and sinter at high temperature for 3-5 hours; (3) After sintering, the mixture is cooled and ground to obtain a calcium oxide phosphor sample, that is, a CaO fluorescent color-changing desiccant.

2. The method for preparing the CaO fluorescent color-changing desiccant according to claim 1, characterized in that: In the step (1), the molar ratio of the raw materials CaCO3, Eu2O3, Bi2O3 and Li2CO3 is 100:1:0.5:1.

5.

3. The method for preparing the CaO fluorescent color-changing desiccant according to claim 1, characterized in that: Among the raw materials, the purity requirement of CaCO3 and Li2CO3 is AR, the purity requirement of Eu2O3 is 4N, and the purity requirement of Bi2O3 is 4N.

4. A CaO fluorescent color-changing desiccant prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The chemical formula of the CaO fluorescent color-changing desiccant is CaO: 0.02-0.08Eu, 0.01-0.04Bi.

5. A method for using the CaO fluorescent color-changing desiccant according to claim 4, characterized in that: The method of use is as follows: placing the CaO fluorescent color-changing desiccant in an ultraviolet light environment, observing the luminescent chromaticity of the CaO fluorescent color-changing desiccant to determine the amount of water absorbed by the desiccant, and evaluating the environmental humidity according to a chromaticity / humidity calibration curve.

6. The method for using the CaO fluorescent color-changing desiccant according to claim 5, characterized in that: The luminescent chromaticity of the CaO fluorescent color-changing desiccant varies from orange to purple-red.

7. The method for using the CaO fluorescent color-changing desiccant according to claim 5, characterized in that: The maximum temperature of the use environment of the CaO fluorescent color-changing desiccant is 500°C.

8. The method for using the CaO fluorescent color-changing desiccant according to claim 5, characterized in that: The method for obtaining the chromaticity / humidity calibration curve is as follows: putting the CaO fluorescent color-changing desiccant into a container to keep it in a fluffy state and in full contact with the environment, building a test light path, using ultraviolet light with an excitation wavelength of 250-370 nm as the excitation light source, changing the ambient humidity by adjusting the ambient water vapor concentration, using a micro grating spectrometer to measure and obtain fluorescence spectra under different humidity, and using the fluorescence spectra to calculate the corresponding chromaticity coordinates to obtain the chromaticity / humidity calibration curve.

9. The method for using the CaO fluorescent color-changing desiccant according to claim 8, characterized in that: The excitation light source is ultraviolet light with an excitation wavelength of 320 nm.

10. The method for using the CaO fluorescent color-changing desiccant according to claim 5, characterized in that: The CaO fluorescent color-changing desiccant is placed in a carrier for use, and the carrier includes an alumina ceramic heating plate and a heating circuit.

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