Al2O3-atZnS: Mn core-shell structured mechanoluminescent material as well as preparation method and application thereof

Abstract

The invention discloses an Al2O3-coated ZnS: Mn core-shell structured mechanoluminescent material and a preparation method and application thereof, and belongs to the technical field of mechanoluminescent materials, the material is composed of a core layer and a shell layer, the core layer is a ZnS: Mn mechanoluminescent material, the raw materials comprise 98 parts by mass of ZnS and 2 parts by mass of manganese carbonate, the Mn ion doping amount is 1-4% of the molar weight of ZnS, the shell layer is Al2O3, the surface of the core layer is uniformly coated with the Al2O3, and the core layer is coated with the ZnS: Mn core-shell structured mechanoluminescent material. The catalyst is formed by an acetic acid-sodium acetate buffer solution, an aluminum sulfate solution and a sodium hydroxide solution through a precipitation-calcination reaction. The preparation method comprises the steps of core layer sintering, buffer solution dispersion, shell layer precursor deposition and post-treatment, an aluminum sulfate solution is dropwise added at the speed of 3-5 ml / min, and finally the core-shell structure is formed through calcination at the temperature of 300 DEG C for 2 h. According to the invention, through Al2O3 shell layer modification, the mechanoluminescence performance and environmental stability of the ZnS: Mn material are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of mechanoluminescent materials technology, and in particular to an Al2O3@ZnS:Mn core-shell structure mechanoluminescent material, its preparation method, and its applications. Background Technology

[0002] Methorax materials are a class of materials that emit light under mechanical stress. Due to their unique luminescent properties, they are widely used in various fields such as stress sensing, structural health monitoring, anti-counterfeiting labeling, and visual pressure monitoring. Especially in aerospace, construction engineering, and intelligent equipment, methorax materials can reflect the stress state applied by the external environment in real time through luminescent signals, playing a role in monitoring and early warning.

[0003] Currently, these materials can be classified into various types based on their luminescence mechanism and composition, including zinc sulfide (ZnS), copper sulfide (CuS), and manganese sulfide (MnS). Among them, manganese-doped zinc sulfide (ZnS:Mn) has become the most widely used mechanoluminescent material due to its excellent luminescence efficiency, good chemical stability, and long lifespan. ZnS:Mn materials not only have high photoluminescence efficiency but also exhibit strong light intensity and long duration of mechanoluminescence, thus dominating high-performance mechanoluminescence applications. Existing technical solutions mainly employ surface coating modification to enhance the stability of ZnS:Mn materials. These coating materials can effectively prevent the ZnS matrix from contacting moisture or oxygen in the environment, thereby delaying the hydrolysis or oxidation process of the material. However, the existing conventional coating layers (such as SiO2) have insufficient bonding strength with the ZnS matrix and are easily peeled off under stress, thus affecting the material's lifespan and mechanoluminescence effect. Furthermore, traditional coating materials typically have limited impact on the luminescence properties of ZnS:Mn and cannot significantly improve its stability and luminescence intensity when exposed to extreme environments for extended periods.

[0004] Therefore, there is an urgent need to develop a novel coated ZnS:Mn material with high stability and strong luminescence intensity. This new material not only needs to maintain its original luminescent properties while improving its resistance to oxidation and hydrolysis under humid and high-temperature environments, but also needs to ensure good adhesion between the coating layer and the ZnS:Mn matrix to prevent delamination during long-term use. Summary of the Invention

[0005] The purpose of this invention is to provide an Al2O3@ZnS:Mn core-shell structured mechanoluminescent material, its preparation method, and its application, in order to solve the above-mentioned problems.

[0006] This invention provides an Al2O3@ZnS:Mn core-shell structured mechanoluminescent material, comprising a core layer and a shell layer; the core layer is a wurtzite-structured ZnS:Mn mechanoluminescent material, the raw material composition of the core layer is 98 parts by mass of ZnS and 2 parts by mass of Mn source, the Mn source is manganese carbonate, and the Mn ion doping amount is 1% to 4% of the molar amount of ZnS, the Mn in the core layer... 2+ Replacing Zn in the ZnS lattice 2+ The core layer is located at a position that forms a mechanoluminescent center; the shell layer is Al2O3, which is uniformly coated on the surface of the core layer, and the shell layer thickness is 5-50 nm.

[0007] Preferably, the ZnS has an analytical purity ≥99.99%, and the manganese carbonate has an analytical purity ≥99.95%. Zinc sulfide with an analytical purity ≥99.99% is selected as the matrix material, forming the main crystal lattice of the mechanoluminescent material. Manganese carbonate with an analytical purity ≥99.95% is selected as the manganese source, which decomposes during the high-temperature synthesis process, allowing manganese ions to enter the zinc sulfide lattice, replacing zinc ions and forming luminescent centers.

[0008] Preferably, the raw materials for preparing the shell include acetate-sodium acetate buffer, aluminum sulfate solution, and sodium hydroxide solution, wherein the pH of the acetate-sodium acetate buffer is 5, and the shell is prepared by Al... 3+ With OH - The reaction produces Al(OH)3 precipitate, which is then calcined at 300℃ for 2 hours to transform into Al2O3, forming the core layer. The Al(OH)3 precipitate is uniformly deposited on the surface of the core layer. The acetate-sodium acetate buffer solution stabilizes the solution pH. It adjusts the surface charge or chemical state of the ZnS:Mn powder, making it easier to disperse in the solution and preventing agglomeration; it provides a suitable acid-base environment for subsequent chemical reactions, preventing drastic pH changes from affecting reaction selectivity or product structure; it maintains the stability of the suspension, ensuring uniform dispersion of powder particles and laying the foundation for the uniformity of the subsequent coating layer. Aluminum sulfate solution is the source of aluminum ions, and its core function is to provide "precursor ions" for the coating layer. The aluminum sulfate solution is slowly added dropwise using a syringe pump, allowing Al... 3+ Evenly dispersed in the suspension, and reacted with subsequently added OH- - The reaction produces Al(OH)3 precipitate. Sodium hydroxide solution is a strong base; its function is to adjust the pH to neutral and provide OH-. - It reacts with aluminum sulfate: The reaction product is eventually converted into an Al2O3 coating layer by calcination (300℃), achieving surface modification of ZnS:Mn.

[0009] A method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material as described above is provided, comprising the following steps: S1. Core layer preparation: 98 parts by mass of ZnS, 2 parts by mass of manganese carbonate and anhydrous ethanol were mixed and wet-ground until uniform. After natural drying, the mixture was placed in a corundum crucible and sintered at 1050℃ for 4 hours under a nitrogen atmosphere. After cooling to room temperature, it was ground into powder to obtain ZnS:Mn metronic luminescent powder. S2. Buffer Dispersion: Prepare an acetate-sodium acetate buffer solution with a pH of 5. Add the ZnS:Mn mechanoluminescent powder obtained in step S1 to the buffer solution, controlling the mass ratio of powder to buffer solution to be 1:5, and stir to form a uniform suspension. At pH 5, the ZnS:Mn particles have an appropriate amount of negative charge on their surface, which helps to repel the particles, reduce aggregation, and enhance their dispersibility. Simultaneously, the negatively charged particle surface can more easily adsorb Al from the solution. 3+ Ions provide ideal active sites for the subsequent uniform deposition of Al(OH)3. This ensures good particle dispersion in solution and creates favorable conditions for the uniform deposition of the alumina coating, thereby improving the coating effect.

[0010] S3, Deposition of shell precursor: Prepare a 0.1 mol / L Al2(SO4)3 solution, add the Al2(SO4)3 solution dropwise to the suspension described in step S2, keep stirring, and react at 70°C for 1 h after the addition is complete; S4. Post-processing: After the reaction is complete, NaOH solution is added dropwise to adjust the system to neutrality. The mixture is then allowed to stand, filtered, washed, and dried. The product is then calcined at 300℃ for 2 hours, cooled, and ground into powder to obtain Al2O3@ZnS:Mn core-shell structure mechanoluminescent material.

[0011] Preferably, the wet grinding time in step S1 is based on the complete and uniform mixing of the raw materials, and the natural drying temperature is room temperature.

[0012] Preferably, in step S3, the Al2(SO4)3 solution is added dropwise to the suspension described in step S2 at a rate of 3 ml / min to 5 ml / min.

[0013] Preferably, the Al2O3 shell accounts for 15% to 20% of the mass of the core-shell material. In steps S3 and S4, a dual-path synchronous dropping method is used to add the Al2(SO4)3 solution at a rate of 3 ml / min to 5 ml / min, and the NaOH solution is added simultaneously to maintain the pH value of the reaction system between 5.0 and 7.0.

[0014] An application of the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material as described above, applied in structural health detection, includes the following steps: (1) Preparation of composite material: The Al2O3@ZnS:Mn core-shell structure mechanoluminescent material is mixed with a transparent polymer matrix to prepare a mechanoluminescent composite film or coating, wherein the mass fraction of the material in the composite material is 5% to 30%; (2) Sample placement: The film or coating obtained in step (1) is pasted or coated onto the surface of the engineering structure or key components to be monitored; (3) Stress monitoring: When the structure to be monitored is subjected to stress, the composite material emits visible light. The intensity, distribution and changes of the light emission are monitored by photoelectric sensor or CCD camera to assess the stress concentration, fatigue damage or crack propagation of the structure in real time, so as to realize structural health monitoring.

[0015] Preferably, the transparent polymer matrix in step (1) is one or more of epoxy resin, silicone rubber or polyurethane.

[0016] Preferably, the engineering structure to be monitored in step (2) includes bridges, buildings, dams, or wind turbine blades.

[0017] Therefore, the present invention employs the above-mentioned Al2O3@ZnS:Mn core-shell structure mechanoluminescent material, its preparation method, and its application, which have the following beneficial effects: (1) Significantly Improved Stability: The material of this invention effectively isolates moisture and oxygen through an alumina (Al2O3) coating layer, solving the problem of performance degradation caused by hydrolysis or oxidation of ZnS:Mn materials in humid or high-temperature environments, and significantly improving the long-term stability of the material under harsh environments. Compared with traditional SiO2 coating technology, choosing Al2O3 as the coating layer has stronger interfacial bonding force. The bonding force between alumina and the zinc sulfide (ZnS) matrix is ​​better than that of SiO2, and it can adhere more firmly to the ZnS surface, thereby reducing the peeling phenomenon of the coating layer under stress. In addition, the chemical and thermal stability of Al2O3 is also better than that of SiO2, which can better resist the influence of the external environment and improve the stability of the material under high temperature and humid conditions.

[0018] (2) Enhanced luminescence performance: The heterostructure formed by the alumina coating layer and the ZnS:Mn core layer significantly optimizes the stress transfer efficiency, thereby improving the mechanoluminescence intensity of the material. Compared with the uncoated sample, it shows a more obvious performance improvement, overcoming the problem that the traditional coating technology has limited effect on improving luminescence performance.

[0019] (3) Simple and efficient process: The preparation method adopts a mild liquid phase deposition method for coating, the coating thickness is controllable (5-50nm), the process is simple and easy to scale up production, and solves the problems of insufficient bonding force between conventional coating layers and substrates and easy peeling.

[0020] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0021] To better understand the above technical solutions, a detailed description of the specific implementation methods will be provided below. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0023] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0024] This invention provides an Al2O3@ZnS:Mn core-shell structured mechanoluminescent material, comprising a core layer and a shell layer; the core layer is a wurtzite-structured ZnS:Mn mechanoluminescent material, the raw material composition of the core layer is 98 parts by mass of ZnS and 2 parts by mass of Mn source, the Mn source is manganese carbonate, and the Mn ion doping amount is 1% to 4% of the molar amount of ZnS, the Mn in the core layer... 2+ Replacing Zn in the ZnS lattice 2+ The core layer is located at a position that forms a mechanoluminescent center; the shell layer is Al2O3, which is uniformly coated on the surface of the core layer, and the shell layer thickness is 5-50 nm.

[0025] To further optimize the above technical solution, the ZnS has an analytical purity ≥99.99%, and the manganese carbonate has an analytical purity ≥99.95%. Zinc sulfide with an analytical purity ≥99.99% is selected as the matrix material, forming the main crystal lattice of the mechanoluminescent material. Manganese carbonate with an analytical purity ≥99.95% is selected as the manganese source, which decomposes during the high-temperature synthesis process, allowing manganese ions to enter the zinc sulfide lattice, replacing zinc ions and forming luminescent centers.

[0026] To further optimize the above technical solution, the raw materials for preparing the shell include acetate-sodium acetate buffer, aluminum sulfate solution, and sodium hydroxide solution. The pH of the acetate-sodium acetate buffer is 5. The shell is prepared using Al... 3+ With OH - The reaction produces Al(OH)3 precipitate, which is then calcined at 300℃ for 2 hours to transform into Al2O3, forming the core layer. The Al(OH)3 precipitate is uniformly deposited on the surface of the core layer. The acetate-sodium acetate buffer solution stabilizes the solution pH. It adjusts the surface charge or chemical state of the ZnS:Mn powder, making it easier to disperse in the solution and preventing agglomeration; it provides a suitable acid-base environment for subsequent chemical reactions, preventing drastic pH changes from affecting reaction selectivity or product structure; it maintains the stability of the suspension, ensuring uniform dispersion of powder particles and laying the foundation for the uniformity of the subsequent coating layer. Aluminum sulfate solution is the source of aluminum ions, and its core function is to provide "precursor ions" for the coating layer. The aluminum sulfate solution is slowly added dropwise using a syringe pump, allowing Al... 3+ Evenly dispersed in the suspension, and reacted with subsequently added OH- - The reaction produces Al(OH)3 precipitate. Sodium hydroxide solution is a strong base; its function is to adjust the pH to neutral and provide OH-. - It reacts with aluminum sulfate: The reaction product is eventually converted into an Al2O3 coating layer by calcination (300℃), achieving surface modification of ZnS:Mn.

[0027] A method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material as described above is provided, comprising the following steps: S1. Core layer preparation: 98 parts by mass of ZnS, 2 parts by mass of manganese carbonate and anhydrous ethanol were mixed and wet-ground until uniform. After natural drying, the mixture was placed in a corundum crucible and sintered at 1050℃ for 4 hours under a nitrogen atmosphere. After cooling to room temperature, it was ground into powder to obtain ZnS:Mn metronic luminescent powder. S2. Buffer Dispersion: Prepare an acetate-sodium acetate buffer solution with a pH of 5. Add the ZnS:Mn mechanoluminescent powder obtained in step S1 to the buffer solution, controlling the mass ratio of powder to buffer solution to be 1:5, and stir to form a uniform suspension. At pH 5, the ZnS:Mn particles have an appropriate amount of negative charge on their surface, which helps to repel the particles, reduce aggregation, and enhance their dispersibility. Simultaneously, the negatively charged particle surface can more easily adsorb Al from the solution. 3+ Ions provide ideal active sites for the subsequent uniform deposition of Al(OH)3. This ensures good particle dispersion in solution and creates favorable conditions for the uniform deposition of the alumina coating, thereby improving the coating effect.

[0028] S3, Deposition of shell precursor: Prepare a 0.1 mol / L Al2(SO4)3 solution, add the Al2(SO4)3 solution dropwise to the suspension described in step S2, keep stirring, and react at 70°C for 1 h after the addition is complete; S4. Post-processing: After the reaction is complete, NaOH solution is added dropwise to adjust the system to neutrality. The mixture is then allowed to stand, filtered, washed, and dried. The product is then calcined at 300℃ for 2 hours, cooled, and ground into powder to obtain Al2O3@ZnS:Mn core-shell structure mechanoluminescent material.

[0029] To further optimize the above technical solution, the wet grinding time in step S1 is based on the raw materials being completely and evenly mixed, and the natural drying temperature is room temperature.

[0030] To further optimize the above technical solution, in step S3, the Al2(SO4)3 solution is added dropwise to the suspension described in step S2 at a rate of 3 ml / min to 5 ml / min.

[0031] To further optimize the above technical solution, the Al2O3 shell accounts for 15% to 20% of the mass of the core-shell material. In steps S3 and S4, a dual-path synchronous dropping method is adopted, in which the Al2(SO4)3 solution is added dropwise at a rate of 3 ml / min to 5 ml / min, and the NaOH solution is added dropwise simultaneously to maintain the pH value of the reaction system between 5.0 and 7.0.

[0032] An application of the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material as described above, applied in structural health detection, includes the following steps: (1) Preparation of composite material: The Al2O3@ZnS:Mn core-shell structure mechanoluminescent material is mixed with a transparent polymer matrix to prepare a mechanoluminescent composite film or coating, wherein the mass fraction of the material in the composite material is 5% to 30%; (2) Sample placement: The film or coating obtained in step (1) is pasted or coated onto the surface of the engineering structure or key components to be monitored; (3) Stress monitoring: When the structure to be monitored is subjected to stress, the composite material emits visible light. The intensity, distribution and changes of the light emission are monitored by photoelectric sensor or CCD camera to assess the stress concentration, fatigue damage or crack propagation of the structure in real time, so as to realize structural health monitoring.

[0033] To further optimize the above technical solution, the transparent polymer matrix in step (1) is one or more of epoxy resin, silicone rubber or polyurethane.

[0034] To further optimize the above technical solution, the engineering structure to be monitored in step (2) includes bridges, buildings, dams or wind turbine blades.

[0035] To more clearly and in detail introduce the Al2O3@ZnS:Mn core-shell structure mechanoluminescent material, its preparation method, and its application provided by the embodiments of the present invention, the following description will be based on specific embodiments.

[0036] Example 1 Preparation and application of Al2O3@ZnS:Mn materials with 1% Mn ion doping: In the raw material preparation stage, 98g of ZnS powder with an analytical purity ≥99.99% and 0.43g of manganese carbonate with an analytical purity ≥99.95% were selected. The calculated Mn ion doping amount was 1% of the molar amount of ZnS. Anhydrous ethanol, acetic acid, sodium acetate, aluminum sulfate, sodium hydroxide, and deionized water were also prepared. For core layer preparation, ZnS and manganese carbonate were placed in a planetary ball mill, 50mL of anhydrous ethanol was added, and the mixture was wet-milled at 300r / min for 2.5h until homogeneous. After natural drying at room temperature, the mixture was transferred to a corundum crucible and placed in a tube furnace. High-purity nitrogen was introduced for protection, and the temperature was raised to 1050℃ at 5℃ / min and held for 4h for sintering. After cooling to room temperature, the mixture was ground into ZnS:Mn powder.

[0037] In the buffer dispersion step, an acetate-sodium acetate buffer solution with pH=5 was prepared. 1.2g of acetate and 8.2g of sodium acetate were dissolved in 200mL of deionized water. 10g of ZnS:Mn powder was added to 50g of buffer solution at a mass ratio of 1:5, and stirred to form a homogeneous suspension. For shell precursor deposition, a 0.1mol / L Al2(SO4)3 solution was prepared and added dropwise to the suspension at a rate of 3ml / min to 5ml / min using a syringe pump. The mixture was reacted at 70℃ for 1h with stirring. In the post-treatment stage, 0.1mol / L NaOH was added dropwise to adjust to neutrality. After standing for 2h, the mixture was filtered, washed four times alternately with deionized water and anhydrous ethanol, vacuum dried at 70℃ for 5h, calcined at 300℃ for 2h (heating rate 3℃ / min), and then cooled and ground to obtain Al2O3@ZnS:Mn core-shell material.

[0038] In application verification, epoxy resin was selected as the transparent matrix, and a composite film was prepared at a material mass fraction of 5%: 20g epoxy resin, 5g curing agent, and 1.3g core-shell material. The film was cured at 60℃ for 2 hours to obtain a 0.5mm thick film. The film was adhered to key stress areas of the bridge concrete piers, and monitoring was performed using a CCD camera and photoelectric sensors. When the bridge was under traffic, the luminescence intensity of the film in the stress concentration areas of the piers increased significantly, showing a linear correlation with stress. When simulating micro-cracks, the luminescence intensity at the crack locations increased sharply, allowing for real-time assessment of structural damage and verifying the effectiveness of the application.

[0039] Example 2 Preparation and application of Al2O3@ZnS:Mn materials with 4% Mn ion doping: The raw materials selected were 98g ZnS (purity ≥99.99%) and 4.3g manganese carbonate (purity ≥99.95%), with Mn ion doping amount of 4% of the molar amount of ZnS. Core layer preparation: The raw materials were mixed with 50mL of anhydrous ethanol, wet-milled at 350r / min for 2h, naturally dried at room temperature for 8h, sintered at 1050℃ for 4h under nitrogen atmosphere in a corundum crucible, and then ground into 180 mesh ZnS:Mn powder after cooling.

[0040] Buffer dispersion: Prepare an acetate-sodium acetate buffer solution with pH=5. Add 10g of ZnS:Mn powder to 50g of buffer solution and stir at 450r / min for 25min to form a suspension. Shell deposition: Add 0.1mol / L Al2(SO4)3 solution dropwise at a rate of 4ml / min and react at 70℃ for 1h. Post-treatment: Adjust to neutral with NaOH, let stand for 3h, filter, wash alternately 5 times, dry at 80℃ for 4h, and calcine at 300℃ for 2h to obtain the core-shell material.

[0041] In terms of application, polyurethane was selected as the transparent matrix, and a coating was prepared at a material mass fraction of 30%: 15g polyurethane and 7.5g core-shell material. After being stirred evenly, the mixture was applied to the surface of a building steel structure beam with a coating thickness of 0.6mm. During monitoring, the steel structure beam was subjected to stress, and the luminescence distribution of the coating was consistent with the stress distribution. Long-term monitoring showed that the luminescence performance of the coating was stable and could effectively capture structural fatigue damage, meeting the needs of building structural health monitoring.

[0042] Example 3 Preparation and application of Al2O3@ZnS:Mn materials with aluminum sulfate dropping rate of 4 ml / min for dam structure monitoring: The raw materials used were 98g ZnS and 2g manganese carbonate, with Mn ion doping amounting to 2.3% of the molar amount of ZnS. Core layer preparation: The raw materials were mixed with 50mL of anhydrous ethanol, wet-milled at 300r / min for 2h, dried at room temperature for 10h, sintered at 1050℃ under nitrogen atmosphere for 4h, and then cooled and ground into 150 mesh powder.

[0043] Buffer dispersion: 10g ZnS:Mn powder was dispersed in an acetate-sodium acetate buffer solution (pH=5) at a mass ratio of 1:5 and stirred at 400 rpm for 30 min. Shell deposition: 0.1 mol / L Al2(SO4)3 solution was added dropwise at a rate of 4 ml / min, and the reaction was carried out at 70℃ for 1 h to ensure the deposition of Al. 3+ Uniform dispersion. Post-treatment: neutralize with NaOH, stand for 2 hours, filter and wash 5 times, dry at 70℃ for 5 hours, and calcine at 300℃ for 2 hours to obtain the core-shell material.

[0044] Application in dam concrete surface monitoring: A composite material coating was prepared using silicone rubber as the matrix, with a material mass fraction of 15%, and applied to the concrete surface of the dam spillway (coating area 15cm × 15cm). When water flows through the spillway, the concrete is subjected to stress by the water flow pressure, and the coating's luminescence intensity responds in real time to changes in pressure. When simulating the expansion of concrete cracks, the luminescent area extends along the crack, allowing for precise location of damage and providing an effective monitoring method for dam structural safety.

[0045] Example 4 Preparation of silicone rubber-based composite materials and their application in wind turbine blade monitoring: In the material preparation stage, the Mn ion doping concentration was 2.3%, and the aluminum sulfate dropping rate was 4 ml / min. Al2O3@ZnS:Mn core-shell material was prepared according to the core process of Example 3 to ensure uniform shell coating and stable mechanoluminescence performance. In the application stage, the compatibility with the silicone rubber matrix was verified: 20 g of silicone rubber and 5 g of curing agent were weighed and mixed evenly, and 3 g of core-shell material (mass fraction 12%) was added. After stirring until no bubbles were present, a 0.4 mm thick composite film was prepared by molding and cured at 60℃ for 3 hours. The film was then adhered to the critical stress area (the part of the blade prone to fatigue damage) on the leading edge of the wind turbine blade using a special adhesive, with an adhesion area of ​​8 cm × 12 cm, ensuring a tight fit between the film and the blade surface. During blade rotation testing, when the blade was subjected to airflow load and stress, the film emitted obvious visible light, and the light distribution was captured in real time by a high-speed CCD camera. Tests revealed that the luminescence intensity in the stress concentration area at the leading edge of the blade was higher than that in other areas, and it fluctuated regularly with changes in rotational speed (stress changes). When simulating micro-cracks (0.05 mm wide) on the blade surface, the luminescence intensity at the cracks increased sharply, which can quickly identify early damage and meet the dynamic health monitoring needs of wind turbine blades. Furthermore, the silicone rubber matrix has good flexibility and can adapt to the bending deformation of the blade. After long-term monitoring, the film did not peel off or crack, and its stability meets the requirements of practical applications.

[0046] Example 5 Preparation and performance verification of Al2O3@ZnS:Mn material with 18% coating using a dual-path synchronous dropping method: The raw materials used were 98g ZnS and 2g manganese carbonate, with Mn ion doping amounting to 2.3% of the molar amount of ZnS. Core layer preparation: The raw materials were mixed with 50mL of anhydrous ethanol, wet-milled at 300r / min for 2h, dried at room temperature for 10h, sintered at 1050℃ under nitrogen atmosphere for 4h, and then cooled and ground into 150 mesh powder.

[0047] Buffer dispersion: Prepare an acetate-sodium acetate buffer solution with pH=5. Add 10g of ZnS:Mn powder to 50g of buffer solution at a mass ratio of 1:5 and stir to form a homogeneous suspension. For shell deposition, a dual-channel synchronous dropping method is used: a dual-channel constant flow pump is used. Line A adds 0.1mol / L Al2(SO4)3 solution at a rate of 4ml / min, while line B simultaneously adds 0.1mol / L NaOH solution. During the dropping process, the pH is monitored using a pH meter, and the NaOH dropping rate is dynamically adjusted to maintain a stable pH value between 6.0±0.2. By controlling the total amount of aluminum sulfate added, the final Al2O3 shell mass is ensured to account for 18% of the total mass of the core-shell structure (i.e., the alumina coating is 18%). After the dropping is complete, the reaction is carried out at 70℃ for 1 hour. Post-treatment: Neutralize with NaOH, stand for 2 hours, filter and wash 5 times, dry at 70℃ for 5 hours, and calcine at 300℃ for 2 hours to obtain core-shell material.

[0048] In application verification, epoxy resin was selected as the transparent matrix, and a composite film was prepared at a material mass fraction of 5%: 20g epoxy resin, 5g curing agent, and 1.3g core-shell material. The film was cured at 60℃ for 2 hours to obtain a 0.5mm thick film. The film was then applied to a dam spillway under pressure and microcrack propagation scenarios. When stress concentration occurred in the steel beam under load, a CCD camera monitored a linear increase in the brightness of the luminous area with increasing stress. At the instant of simulated crack initiation, the crack tip emitted a high-brightness light signal due to the sudden stress change, enabling rapid identification of early damage.

[0049] Therefore, this invention employs the aforementioned Al2O3@ZnS:Mn core-shell structure mechanoluminescent material, its preparation method, and its application. By effectively isolating moisture and oxygen through an alumina coating layer, it solves the problem of performance degradation caused by hydrolysis or oxidation of ZnS:Mn materials under humid or high-temperature environments, significantly improving the long-term stability of the material under harsh conditions. Compared with traditional SiO2 coating technology, choosing Al2O3 as the coating layer provides stronger interfacial bonding. The bonding force between alumina and the zinc sulfide matrix is ​​superior to that of SiO2, allowing for more robust adhesion to the ZnS surface, thus reducing the peeling phenomenon of the coating layer under stress. Furthermore, Al2O3 exhibits better chemical and thermal stability than SiO2, better resisting the influence of the external environment and improving the material's stability under high-temperature and humid conditions. The heterogeneous structure formed by the alumina coating layer and the ZnS:Mn core layer significantly optimizes stress transfer efficiency, thereby enhancing the mechanoluminescence intensity of the material. Compared to uncoated samples, it shows a more significant performance improvement, overcoming the limited improvement in luminescence performance in traditional coating technologies. The preparation method uses a mild liquid phase deposition method for coating, and the coating thickness is controllable (5-50nm). The process is simple and easy to scale up, solving the problems of insufficient adhesion between conventional coating layers and substrates and easy peeling.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An Al2O3@ZnS:Mn core-shell structured mechanoluminescent material, characterized in that, It includes a core layer and a shell layer; the core layer is a wurtzite-structured ZnS:Mn mechanoluminescent material, the raw material composition of the core layer is 98 parts by mass of ZnS and 2 parts by mass of Mn source, the Mn source is manganese carbonate, and the Mn ion doping amount is 1% to 4% of the molar amount of ZnS, the Mn in the core layer 2+ Replacing Zn in the ZnS lattice 2+ The core layer is located at a position that forms a mechanoluminescent center; the shell layer is Al2O3, which is uniformly coated on the surface of the core layer, and the shell layer thickness is 5-50 nm.

2. The Al2O3@ZnS:Mn core-shell structure mechanoluminescent material according to claim 1, characterized in that, The ZnS has an analytical purity of ≥99.99%, and the manganese carbonate has an analytical purity of ≥99.95%.

3. The Al2O3@ZnS:Mn core-shell structure mechanoluminescent material according to claim 1, characterized in that, The raw materials for preparing the shell include acetate-sodium acetate buffer, aluminum sulfate solution, and sodium hydroxide solution. The pH of the acetate-sodium acetate buffer is 5. The shell is prepared by Al... 3+ With OH - The reaction produces Al(OH)3 precipitate, which is then calcined at 300℃ for 2 hours to transform into Al2O3. The Al(OH)3 precipitate is uniformly deposited on the surface of the core layer.

4. A method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Core layer preparation: 98 parts by mass of ZnS, 2 parts by mass of manganese carbonate and anhydrous ethanol were mixed and wet-ground until uniform. After natural drying, the mixture was placed in a corundum crucible and sintered at 1050℃ for 4 hours under a nitrogen atmosphere. After cooling to room temperature, it was ground into powder to obtain ZnS:Mn metronic luminescent powder. S2, Buffer Dispersion: Prepare an acetate-sodium acetate buffer solution with a pH of 5, add the ZnS:Mn mechanoluminescent powder obtained in step S1 to the buffer solution, control the mass ratio of powder to buffer solution to be 1:5, and stir to form a uniform suspension; S3, Deposition of shell precursor: Prepare a 0.1 mol / L Al2(SO4)3 solution, add the Al2(SO4)3 solution dropwise to the suspension described in step S2, keep stirring, and react at 70°C for 1 h after the addition is complete; S4. Post-processing: After the reaction is complete, NaOH solution is added dropwise to adjust the system to neutrality. The mixture is then allowed to stand, filtered, washed, and dried. The product is then calcined at 300℃ for 2 hours, cooled, and ground into powder to obtain Al2O3@ZnS:Mn core-shell structure mechanoluminescent material.

5. The method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material according to claim 4, characterized in that, The wet grinding time in step S1 is based on the complete and uniform mixing of the raw materials, and the natural drying temperature is room temperature.

6. The method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material according to claim 4, characterized in that, In step S3, the Al2(SO4)3 solution is added dropwise to the suspension described in step S2 at a rate of 3 ml / min to 5 ml / min.

7. The method for preparing the Al2O3@ZnS:Mn core-shell structured mechanoluminescent material according to claim 4, characterized in that, The Al2O3 shell accounts for 15% to 20% of the mass of the core-shell material. In steps S3 and S4, the Al2(SO4)3 solution is added dropwise at a rate of 3 ml / min to 5 ml / min using a dual-path synchronous dropping method, while the NaOH solution is added dropwise simultaneously to maintain the pH value of the reaction system between 5.0 and 7.

0.

8. An application of the Al2O3@ZnS:Mn core-shell structure mechanoluminescent material as described in any one of claims 1-3, characterized in that, When applied to structural health monitoring, the following steps are included: (1) Preparation of composite material: The Al2O3@ZnS:Mn core-shell structure mechanoluminescent material is mixed with a transparent polymer matrix to prepare a mechanoluminescent composite film or coating, wherein the mass fraction of the material in the composite material is 5% to 30%; (2) Sample placement: The film or coating obtained in step (1) is pasted or coated onto the surface of the engineering structure or key components to be monitored; (3) Stress monitoring: When the structure to be monitored is subjected to stress, the composite material emits visible light. The intensity, distribution and changes of the light emission are monitored by photoelectric sensor or CCD camera to assess the stress concentration, fatigue damage or crack propagation of the structure in real time, so as to realize structural health monitoring.

9. The application of the Al2O3@ZnS:Mn core-shell structure mechanoluminescent material according to claim 8, characterized in that, The transparent polymer matrix mentioned in step (1) is one or more of epoxy resin, silicone rubber or polyurethane.

10. The application of the Al2O3@ZnS:Mn core-shell structure mechanoluminescent material according to claim 8, characterized in that, The engineering structure to be monitored in step (2) includes bridges, buildings, dams, or wind turbine blades.