A temperature monitoring material with photochromic properties, its preparation and application

Abstract

This invention relates to a temperature monitoring material with photochromic properties, its preparation, and its application, belonging to the interdisciplinary field of temperature monitoring and sensing technology. The chemical formula of this dosimeter material is CaF2:xNa. + The material is first uniformly ground manually or mechanically, then dried by baking or air drying, and finally pressed into a preform. After sintering, a temperature monitoring material with photochromic properties is obtained. The prepared product exhibits excellent performance in terms of tissue equivalence, temperature response speed, cost control, and portability. It has a temperature response range of 50-200℃, and the temperature information can be intuitively read through visually perceptible color changes, making it suitable for large-scale preparation and a wide range of applications.

Description

Technical Field

[0001] This invention relates to a temperature monitoring material with photochromic properties, its preparation and application, and belongs to the interdisciplinary field of temperature monitoring and sensing technology. Background Technology

[0002] In recent years, with the development of technologies such as high-precision manufacturing, energy storage management, biomedicine, and aerospace, higher demands have been placed on the accurate monitoring and rapid response of ambient temperature. Especially in fields such as human body surface monitoring, heat dissipation control of electronic devices, and safety protection for high-temperature operations, temperature detection technology has become a crucial means to ensure stable system operation and personal safety. To achieve more efficient and intuitive temperature assessment, functional materials with visualized temperature response capabilities are gradually becoming a research hotspot.

[0003] Currently, common temperature detection methods include thermocouples, infrared thermometers, and electronic temperature sensors. While these devices offer advantages in temperature measurement accuracy, they generally suffer from drawbacks such as high cost, complex structure, strong dependence on power supply, and sensitivity to the operating environment, making it difficult to meet the demands of new applications requiring portability, passivity, and visualization. In contrast, photochromic temperature indicator materials, due to their visually intuitive response process, fast response speed, simple structure, and lack of power supply requirements, have become an ideal choice for visualized temperature detection, particularly suitable for extreme environments, high-temperature scenarios, and flexible wearable devices.

[0004] Most reported temperature visualization materials are based on organic dyes or liquid crystal systems, such as cholesteric liquid crystals, thermochromic inks, and polymer-dye complexes. While these materials possess some color-changing response capability, they typically suffer from poor stability, easy aging, narrow response windows, complex processing, and poor environmental adaptability, limiting their application in scenarios with high reliability requirements. Especially when monitoring biological tissues, human-worn devices, or the surfaces of complex industrial equipment, materials must possess comprehensive properties including high sensitivity, good repeatability, high tissue equivalence, structural stability, and ease of preparation. Therefore, there is an urgent need to develop an inorganic temperature-responsive color-changing material with low cost, good reversibility, clear visualization, and strong thermal stability for next-generation visualized temperature detection. Summary of the Invention

[0005] The first objective of this invention is to provide a temperature monitoring material with photochromic properties, which can undergo significant color changes during temperature changes, thereby enabling intuitive and visual indication of temperature information.

[0006] The second objective of this invention is to provide a method for preparing a temperature monitoring material with photochromic properties. This method is simple, has good repeatability, and the prepared temperature indicator material has advantages such as high yield and good stability, making it suitable for large-scale production and application.

[0007] The third objective of this invention is to provide applications of the temperature monitoring material with photochromic properties in fields such as environmental temperature monitoring, personal protective equipment, thermal management of electronic devices, or biological surface temperature indication, especially suitable for passive temperature visualization monitoring scenarios that do not require power.

[0008] The technical solution of this invention: a temperature monitoring material with photochromic properties, characterized in that: the chemical formula of the dosimeter material is CaF2:xNa + Where 0.00≤x≤0.03.

[0009] The method for preparing the temperature monitoring material with photochromic properties is characterized by: firstly, a material containing Na... + The raw materials and calcium fluoride are mixed in stoichiometric ratio, then mechanically activated and dried to form a blank, and finally sintered to obtain a temperature monitoring material with photochromic properties.

[0010] The raw material containing Na+ is sodium fluoride.

[0011] The preparation method of the temperature monitoring material with photochromic properties includes the following steps: (1) Mechanical activation: The raw materials prepared in proportion are mechanically activated by planetary ball milling or manual grinding to obtain activated raw materials; (2) Drying: The activated raw material obtained in step (1) is dried. The drying process is carried out by drying oven or air drying. (3) Preform formation: The dried raw material obtained in step (2) is mixed with polyvinyl alcohol (PVA) at a ratio of 50:1 and granulated to obtain a mixed raw material; then it is placed in a mold and pressed with a pressure of 10-20 MPa for 200-400 seconds to obtain a preform. (4) Sintering: The preform obtained in step (3) is sintered; sintering is carried out by high temperature calcination or microwave-assisted sintering to finally obtain the precursor; (5) Sample preparation: The precursor and anhydrous ethanol are mixed in a ratio of 1:4, and then ground and dried to obtain a temperature monitoring material with photochromic properties.

[0012] In step (1), when using a planetary ball mill, the rotation speed is 300-800 rpm and the duration is 6-12 hours, the resulting raw material particle size is 10-100 nm; when using manual grinding, the time is 20-60 minutes, and the resulting raw material particle size is 1-10 µm.

[0013] In step (2), the temperature setting range of the drying oven is 50-80℃ and the drying time is 10-20 minutes; natural air drying takes 30-50 minutes at room temperature.

[0014] In step (3), during the mixing and granulation, the mixed raw materials are pressed for 200-400 seconds at a pressure of 10-20 MPa.

[0015] Step (4) The high-temperature calcination process during sintering is as follows: calcination is carried out in a high-temperature furnace with programmed temperature rise at a rate of 2-7℃ / min, from room temperature to 600-800℃, followed by holding for 6-9 hours, and then naturally cooling to room temperature after the holding period. The microwave-assisted sintering process is as follows: 10-20g of carbon powder is used to absorb microwaves, and the carbon powder combustion provides the temperature to sinter the preform. The frequency is 2.45GHz, the microwave power is 800-1200w, and the sintering time is 15-25min. After sintering, it is naturally cooled.

[0016] The application of the temperature monitoring material with photochromic properties involves making the material into a temperature sensor, which serves as a monitoring device for temperature changes.

[0017] Furthermore, when applied to environments with different temperatures, the monitor's color changes provide a visual indication of the temperature.

[0018] Furthermore, under different temperature environments, the temperature response information of the monitor can be read from the photochromic color. The monitor changes color from blue to purple to pink and finally to yellow at different temperatures, and has a temperature response range of 50-200℃.

[0019] The beneficial effects of this invention: This invention provides a temperature monitoring material based on photochromism, specifically CaF2:xNa... + The temperature sensing material can exhibit a continuous color change from blue to purple to pink to yellow under different ambient temperatures. It has a sensitive temperature response, is easy to identify with the naked eye, and facilitates quick judgment of changes in ambient temperature, thus possessing excellent visual detection performance.

[0020] The temperature monitoring material provided by this invention, in addition to the intuitive identification of color changes, also exhibits a regular shift in its reflectance spectrum with temperature changes, enabling quantitative temperature readings through spectral analysis, thus combining qualitative observation and quantitative monitoring functions.

[0021] The temperature monitoring material provided by this invention is prepared by two methods: microwave heating sintering and high-temperature furnace programmed temperature rise. The process is mature, the equipment requirements are low, and it is easy to scale up production. At the same time, the raw materials used are abundant and inexpensive, which is conducive to its widespread application.

[0022] The temperature monitoring material provided by this invention has a color response caused by temperature changes that does not require an external power supply or electronic system, making it particularly suitable for applications such as on-site temperature indication, field detection, or personalized visual temperature-sensing tags. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a comparison between the X-ray diffraction pattern of the temperature monitoring device prepared in Example 2 of the present invention and the standard card PDF#75-0363; Figure 2 This is a comparison between the X-ray diffraction pattern of the temperature monitoring device prepared in Example 3 of the present invention and the standard card PDF#75-0363; Figure 3 These are diffuse reflectance spectra of the temperature monitoring device prepared in Embodiment 3 of the present invention under X-ray irradiation for different times; Figure 4 These are photochromic photographs of the temperature monitoring device prepared in Embodiment 3 of the present invention under X-ray irradiation for different durations; Figure 5 The diffuse reflectance spectrum of the temperature monitoring device prepared in Example 3 of this invention was obtained by irradiating it with 254 nm for different times after 20 min of X-ray irradiation. Figure 6 These are photographs of the temperature monitoring device prepared in Example 3 of the present invention after 20 minutes of X-ray irradiation and 254 nm irradiation for different times to remove color. Figure 7 This is a stability test of the temperature monitoring device prepared in Embodiment 3 of the present invention during 10 cycles of color fading; Figure 8 This is the reflectance variation spectrum of the temperature monitoring device prepared in Example 3 of the present invention at 50-225℃; Figure 9 The temperature monitoring device prepared in Example 3 of this invention exhibits reflectance changes in 11 different temperature ranges during fading at 50-225℃. Figure 10 This is an image showing the color change of the temperature monitoring device prepared in Embodiment 3 of the present invention after being fully irradiated with X-rays. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.01 and put them into a ball mill jar. Add anhydrous ethanol to disperse them and manually grind for 40 minutes to mechanically activate the raw materials. (2) Place the activated raw materials indoors to air dry naturally for 50 minutes to achieve drying; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 15 MPa for 300 seconds. (4) Finally, the preform is placed in a tube furnace for sintering. The heating rate is 5℃ / min, and the temperature is 700℃ for synthesis. The holding time is 4h. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0026] Example 2 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and put them into a ball mill jar. Add anhydrous ethanol to disperse them and manually grind for 40 minutes to mechanically activate the raw materials. (2) Place the activated raw materials indoors to air dry naturally for 50 minutes to achieve drying; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 15 MPa for 300 seconds. (4) Finally, the preform is placed in a tube furnace for sintering. The heating rate is 5℃ / min, and the temperature is 700℃ for synthesis. The holding time is 4h. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0027] Example 3 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and put them into a ball mill jar and add anhydrous ethanol for dispersion. Mechanical activation is performed using a planetary ball mill with the program set to 500rpm for 10h. (2) Place the activated raw material in an oven at 80°C for 10 minutes to dry it; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 10 MPa for 400 seconds. (4) Finally, the embryo is placed in a crucible, wrapped with carbon powder, and then placed in a microwave oven for sintering. The microwave power is 800W and the time is 20min. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0028] Example 4 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.03 and put them into a ball mill jar and add anhydrous ethanol for dispersion. Use a planetary ball mill for mechanical activation. The program is set to 800rpm and lasts for 6h. (2) The activated raw materials are dried in an oven at 50°C for 20 minutes; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 20 MPa for 200 seconds. (4) Finally, the preform is placed in a tube furnace for sintering. The heating rate is 3℃ / min, and the temperature is 800℃ for synthesis. The holding time is 3h. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0029] Example 5 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and put them into a ball mill jar. Add anhydrous ethanol to disperse them and use a planetary ball mill for mechanical activation. The program is set to 300rpm and lasts for 12h. (2) Place the activated raw materials indoors to air dry naturally for 30 minutes to achieve drying; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 15 MPa for 300 seconds. (4) Finally, the embryo is placed in a crucible, wrapped with carbon powder, and then placed in a microwave oven for sintering. The microwave power is 1000W and the time is 15min. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0030] Example 6 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and put them into a ball mill jar. Add anhydrous ethanol to disperse them and manually grind for 60 minutes to mechanically activate the raw materials. (2) The activated raw materials are dried in an oven at 70°C for 15 minutes; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 15 MPa for 300 seconds. (4) Finally, the embryo is placed in a crucible, wrapped with carbon powder, and then placed in a microwave oven for sintering. The microwave power is 600W and the time is 30min. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0031] Example 7 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and place them in a mortar and disperse them in anhydrous ethanol. Manually grind for 20 minutes to mechanically activate the raw materials. (2) Place the activated raw materials indoors to air dry naturally for 40 minutes to achieve drying; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 15 MPa for 300 seconds. (4) Finally, the preform is placed in a tube furnace for sintering. The heating rate is 6℃ / min, and the temperature is 600℃ for synthesis. The holding time is 6h. After the reaction is completed, the furnace is cooled to room temperature to obtain the target sample.

[0032] Example 8 The present invention discloses a method for preparing a photochromic temperature monitoring material, which specifically includes the following steps: (1) Weigh 5g of CaF2 and NaF raw materials in a molar ratio of 1:0.02 and put them into a ball mill jar. Add anhydrous ethanol to disperse them and use a planetary ball mill for mechanical activation. The program is set to 700rpm and lasts for 5h. (2) The activated raw materials are dried in an oven at 70°C for 15 minutes; (3) PVA is added to the dried powder for granulation. After grinding into uniform fine particles, the mixture is pressed into a preform by a tablet press at a pressure of 10 MPa for 400 seconds. (4) Finally, the embryo is placed in a crucible, wrapped with carbon powder, and then placed in a microwave oven for sintering. The microwave power is 700W and the time is 25min. After the reaction is completed, the target sample is obtained by cooling the furnace to room temperature.

[0033] Results Analysis Figure 1 It is the CaF2:Na obtained in Example 2 +The XRD pattern of the sample, such as Figure 1 As shown, the synthesized CaF2:Na + The XRD (X-ray diffraction) pattern and standard diffraction card PDF#75-0363 were used as references for comparison to verify CaF2:Na + The synthesis process. The results obtained are as follows. Figure 1 As shown, the XRD data of the product corresponded one-to-one with the standard diffraction card without any impurity peaks, and the sample always maintained a pure phase, indicating that the sample could be successfully synthesized under these synthesis conditions.

[0034] Figure 2 It is the CaF2:Na obtained in Example 3 + The XRD pattern of the sample, such as Figure 2 As shown, the synthesized CaF2:Na + The standard diffraction card PDF#75-0363 was used as a reference for comparison to verify the synthesis of CaF2. The XRD data of the product corresponded to the standard diffraction card, indicating that the sample could be successfully synthesized under these conditions.

[0035] Figure 3 These are diffuse reflectance spectra of the sample obtained in Example 3 of this invention under X-ray irradiation for different durations. Under X-ray irradiation, the reflectance of the sample obtained in Example 3 gradually changes, such as... Figure 3 As shown, the reflectance of the sample changed by 53.6% after irradiation for 20 minutes, with the change occurring at 395 and 600 nm. The photochromic performance of the sample obtained in Example 3 (53.6%) was significantly better than that of Example 2 (41.2%), therefore, the sample from Example 3 was used for performance testing and applications in all subsequent tests. Figure 4 These are photochromic photographs of the sample obtained in Example 3 of this invention under different X-ray irradiation times. As the irradiation time gradually increases, the sample color changes from the initial white to light blue (irradiation for 5 min) and then to dark blue (irradiation for 20 min).

[0036] Figure 5 The diffuse reflectance spectra of the CaF2 sample obtained in Example 3 of this invention after complete photochromism and fading under 254nm irradiation for different times demonstrate the sample's recyclability. Figure 5 As shown, after being irradiated with 254nm light, the reflectivity of the sample gradually returned to its initial state from the change caused by photochromism.

[0037] Figure 6 The CaF2:Na obtained in Example 3 of this invention +The images show the fading of the sample after complete photochromism by irradiation at 254 nm for different times. The images show that the sample gradually returns to its initial state from a completely dark blue after irradiation at 254 nm.

[0038] Figure 7 The CaF2:Na obtained in Example 3 of this invention + Stability test of the sample in 10 cycles of color fading, CaF2:Na + The sample maintained good color-changing properties even after 10 staining (X-ray irradiation) and 10 fading (254nm irradiation), which demonstrates that the sample has good thermal stability and reusability under common environmental conditions.

[0039] Figure 8 The CaF2:Na obtained in Example 3 of this invention + The reflectance change spectrum of the sample after complete photochromism at 50-225℃; such as... Figure 8 As shown, the reflectance spectrum of this material exhibits a regular shift with temperature changes, allowing for quantitative temperature readings through spectral analysis, thus possessing both qualitative observation and quantitative monitoring functions.

[0040] Figure 9 The temperature monitoring device prepared in Example 3 of this invention exhibits reflectance changes in 11 different temperature ranges during fading at 50-225℃; for example... Figure 9 As shown, the reflectivity of the sample changes significantly during gradual heating, and this change can be further subdivided into specific temperature ranges. Within different temperature ranges, such as 50-80℃, 150-160℃, and 200-225℃, the color center of the sample changes significantly with temperature. Based on this characteristic, a specific temperature range can be obtained according to the specific reflectivity changes of the sample.

[0041] Figure 10 The CaF2:Na obtained in Example 3 of this invention + Images showing the color change of a sample after complete photochromism, ranging from 50-225℃, as a function of temperature. The sample exhibits a continuous color change from blue to purple to pink to yellow at different ambient temperatures, demonstrating sensitive temperature response, intuitive visual identification, and easy and rapid judgment of ambient temperature changes, thus possessing excellent visual detection performance.

[0042] In summary, this invention provides a photochromic temperature monitoring material, specifically CaF2:Na... +The temperature-sensing material exhibits a continuous color change from blue to purple to pink to yellow under varying ambient temperatures. It demonstrates sensitive temperature response, is easily identifiable to the naked eye, and facilitates rapid assessment of environmental temperature changes, exhibiting excellent visual detection performance. Beyond the intuitive color change, the material's reflectance spectrum shows a regular shift with temperature, allowing for quantitative temperature readings through spectral analysis, thus combining qualitative observation with quantitative monitoring. The material is prepared using two sintering methods: microwave heating and programmed high-temperature furnace heating. These mature processes require minimal equipment and are easily mass-produced. Furthermore, the abundant and inexpensive raw materials facilitate widespread application. Its temperature-induced color response requires no external power supply or electronic system, making it particularly suitable for applications such as on-site temperature indication, field monitoring, or personalized visual temperature-sensing tags.

[0043] The present invention has been described in detail with reference to the foregoing embodiments. Those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A temperature monitoring material with photochromic properties, characterized in that: The chemical formula of the dosimeter material is CaF2:xNa. + Where 0.00≤x≤0.

03.

2. The method for preparing the temperature monitoring material with photochromic properties as described in claim 1, characterized in that: First, include Na + The raw materials and calcium fluoride are mixed in stoichiometric ratio, then mechanically activated and dried to form a blank, and finally sintered to obtain a temperature monitoring material with photochromic properties.

3. The method for preparing the temperature monitoring material with photochromic properties as described in claim 3, characterized in that: The containing Na + The raw material is sodium fluoride.

4. The method for preparing the temperature monitoring material with photochromic properties as described in claim 3, characterized in that... The specific steps are as follows: (1) Mechanical activation: The raw materials prepared in proportion are mechanically activated by planetary ball milling or manual grinding to obtain activated raw materials; (2) Drying: The activated raw material obtained in step (1) is dried. The drying process is carried out by drying oven or air drying. (3) Preform formation: The dried raw material obtained in step (2) is mixed with polyvinyl alcohol (PVA) at a ratio of 50:1 and granulated to obtain a mixed raw material; then it is placed in a mold and pressed with a pressure of 10-20 MPa for 200-400 seconds to obtain a preform. (4) Sintering: The preform obtained in step (3) is sintered; sintering is carried out by high temperature calcination or microwave-assisted sintering to finally obtain the precursor; (5) Sample preparation: The precursor and anhydrous ethanol are mixed in a ratio of 1:4, and then ground and dried to obtain a temperature monitoring material with photochromic properties.

5. The method for preparing the temperature monitoring material with photochromic properties as described in claim 4, characterized in that: In step (1), when using a planetary ball mill, the rotation speed is 300-800 rpm and the duration is 6-12 hours, the resulting raw material particle size is 10-100 nm; when using manual grinding, the time is 20-60 minutes, and the resulting raw material particle size is 1-10 µm.

6. The method for preparing the temperature monitoring material with photochromic properties as described in claim 4, characterized in that: In step (2), the temperature setting range of the drying oven is 50-80℃ and the drying time is 10-20min; natural air drying takes 30-50min at room temperature.

7. The method for preparing the temperature monitoring material with photochromic properties as described in claim 4, characterized in that: In step (3), during the mixing and granulation, the mixed raw materials are pressed for 200-400 seconds at a pressure of 10-20 MPa.

8. The method for preparing the temperature monitoring material with photochromic properties as described in claim 5, characterized in that: Step (4) The high-temperature calcination process during sintering is as follows: calcination is carried out in a high-temperature furnace with programmed temperature rise at a rate of 2-7℃ / min, from room temperature to 600-800℃, followed by holding for 6-9 hours, and then naturally cooling to room temperature after the holding period. The microwave-assisted sintering process is as follows: 10-20g of carbon powder is used to absorb microwaves, and the carbon powder combustion provides the temperature to sinter the preform. The frequency is 2.45GHz, the microwave power is 800-1200w, and the sintering time is 15-25min. After sintering, it is naturally cooled.

9. The application of the temperature monitoring material with photochromic properties as described in claim 8, characterized in that: The material is made into a temperature sensor, which serves as a monitoring device for temperature changes.

10. The application of the temperature monitoring material with photochromic properties as described in claim 9, characterized in that: When used in environments with different temperatures, the monitor's color changes provide a visual indication of the temperature. Furthermore, under different temperature environments, the temperature response information of the monitor can be read from the photochromic color. The monitor changes color from blue to purple to pink and finally to yellow at different temperatures, and has a temperature response range of 50-200℃.

Images