Composite coating material with piezoluminescence function and application for lubrication failure detection

Abstract

The application discloses a composite coating material with force-induced luminescence function and lubrication failure detection application, relates to the technical field of material lubrication monitoring, and the composite coating material takes epoxy resin as a continuous phase matrix, dopes zinc sulfide copper activated luminescent powder (ZnS:Cu) as a luminescent functional phase, and polytetrafluoroethylene (PTFE) powder as a wear-resistant and lubricating enhanced phase, wherein the mass ratio of the ZnS:Cu luminescent powder and the PTFE powder is 2:1, the mass ratio of the ZnS:Cu luminescent powder and the epoxy resin matrix is 3:10; the ZnS:Cu luminescent powder has a particle size of 28-30 microns and is coated with an Al2O3 thin layer on the surface, and the average particle size of the PTFE powder is 3 microns. A double-mode luminescent coating can be formed by constructing an electrode / driving structure, and the double-mode luminescent coating has force-induced luminescence and electroluminescence functions. After color powder is added to the original components, white light emission can be realized under friction luminescence and electroluminescence, the double-mode luminescent coating is suitable for various metal friction pairs, supports remote monitoring and fault early warning, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of material lubrication monitoring technology, specifically to composite coating materials with mechanoluminescence function and their application in lubrication failure detection. Background Technology

[0002] Mechanoluminescence (ML) refers to the phenomenon where materials directly convert mechanical energy into light energy under mechanical stress such as friction and compression. It has significant research value in the fields of energy conversion and condition monitoring. In industrial settings, mechanical friction causes approximately one-third of primary energy to be lost as frictional heat. Lubricating oil, as a core medium for reducing friction and wear in mechanical equipment, suffers from deterioration that directly leads to a chain reaction of problems, including increased wear of friction pairs and equipment failure. Existing lubricating oil condition monitoring methods mainly include oil sampling and analysis, viscosity detection, and online sensor monitoring. Current technologies combine mechanoluminescent materials such as ZnS:Cu with polytetrafluoroethylene (PTFE) to provide feedback on lubrication status through triboluminescence signals. Zinc sulfide-based mechanoluminescent materials have been applied to stress distribution visualization, and electroluminescent zinc sulfide materials are widely used in the display field. However, the integration of these materials with friction condition monitoring remains relatively weak.

[0003] Existing lubricating oil condition monitoring technologies have significant limitations and are difficult to match actual engineering needs. Traditional methods such as oil sampling and analysis, and external sensor monitoring generally suffer from problems such as long detection cycles, the need for downtime operation, and reliance on additional equipment. They also fail to reflect the true local condition of the friction contact interface, and have drawbacks such as response lag and complex deployment. The research on "intelligent lubrication / self-monitoring lubrication materials" that has emerged in recent years has mostly focused on solid lubricating blocks or composite material structures, failing to achieve engineering applications that can be directly coated on metal surfaces and are not suitable for the service scenarios of real mechanical friction pairs.

[0004] The insufficient stability of existing mechanoluminescent materials and coatings under wear-resistant conditions further restricts their engineering application. Currently, most mechanoluminescent materials use flexible elastomers such as silicone rubber or low-hardness polymers as matrices. While these can meet the requirements for stress transmission and repetitive luminescence, their inherent strength, hardness, and resistance to cutting and wear are weak, making them unable to withstand the high contact stress and continuous sliding friction of metal friction pairs. This easily leads to surface wear and interfacial delamination, causing luminescence signal drift or even failure. In summary, the industry currently lacks an engineered mechanoluminescent coating solution that is simple to prepare, can be directly coated onto metal surfaces, exhibits excellent wear resistance and stability, and can generate a strong signal response to lubricant failure. Related technologies still have significant shortcomings in practical applications.

[0005] To address the aforementioned problems, this invention proposes a composite coating material with mechanoluminescence function and its application in lubrication failure detection, aiming to overcome the bottlenecks of existing technologies. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a composite coating material with mechanoluminescence function and its application in lubrication failure detection. This solution achieves intuitive, in-situ detection of whether lubricating oil is in an effective lubrication state or has failed by utilizing changes in mechanoluminescence intensity generated during friction. This provides a simple and reliable new approach for assessing and providing early warning of the operating status of mechanical equipment.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a composite coating material with mechanoluminescence function, wherein epoxy resin is used as the continuous phase matrix, zinc copper sulfide activated luminescent powder (ZnS:Cu) is used as the luminescent functional phase, and polytetrafluoroethylene (PTFE) powder is used as the wear-resistant and lubrication-enhancing phase. The mass ratio of ZnS:Cu luminescent powder to PTFE powder is 2:1, and the mass ratio of ZnS:Cu luminescent powder to epoxy resin matrix is ​​3:10. The particle size of ZnS:Cu luminescent powder is 28-30 micrometers, and the surface is coated with a thin layer of Al2O3. The average particle size of PTFE powder is 3 micrometers.

[0008] Preferably, the epoxy resin matrix is ​​selected from either a two-component AB glue-curing epoxy resin or an ultraviolet (UV) light-curing epoxy resin; wherein, the two-component AB glue-curing epoxy resin is made by mixing type A glue and type B glue in a mass ratio of 3:1, and the curing time at room temperature is 48 hours; the UV light-curing epoxy resin is cured after being irradiated by a 65W ultraviolet lamp for 10 to 15 minutes.

[0009] Preferably, the A-type adhesive of the two-component AB-curable epoxy resin comprises 90% epoxy resin (CAS No. 38891-59-7) and 10% diluent (CAS No. 37206-20-5) by mass; the B-type adhesive comprises 30% polypropylene glycol bis(2-aminopropyl ether) (CAS No. 9046-10-0), 28% alicyclic amine (CAS No. 6864-37-5), 7% epoxy resin (CAS No. 38891-59-7), 34.6% diluent (CAS No. 37206-20-5), and 34.6% defoamer (CAS No. 9003-13-8) by mass.

[0010] Preferably, the UV-curable epoxy resin comprises 55–75% by mass of polyurethane resin (CAS No. 9009-54-5, EC No. 210-898-8), 10–30% by mass of acrylic monomer (CAS No. 868-77-9, EC No. 212-782-2), and 10% by mass of dimethylchlorosilane (CAS No. 68611-44-9, EC No. 271-893-4).

[0011] A method for preparing a composite coating material with mechanoluminescence function includes the following steps:

[0012] S1, Pretreatment of experimental materials: The experimental equipment was immersed in anhydrous ethanol for ultrasonic cleaning, then rinsed with deionized water and dried with an air gun; ZnS:Cu luminescent powder and PTFE powder were heated and dried. S2, Functional powder mixing: Weigh ZnS:Cu luminescent powder and PTFE powder at a mass ratio of 2:1, place them in a centrifuge tube and mix them thoroughly with a shaker to obtain uniformly dispersed ZnS:Cu / PTFE mixed powder; S3, preparation of composite system: The mixed powder obtained in S2 is mixed with epoxy resin matrix at a mass ratio of ZnS:Cu luminescent powder to epoxy resin of 3:10. It is first initially stirred, moistened and dispersed by glass rod, and then transferred to centrifuge tube and stirred evenly by shaker. S4, Degassing treatment: Pour the composite system obtained in S3 into a silicone mold and place it in a vacuum drying oven for degassing for 20 minutes; S5, Curing and Molding: If using a two-component AB glue-curing epoxy resin, apply the composite system evenly to the metal surface and allow it to dry and cure at room temperature for 48 hours; if using a UV-curing epoxy resin, apply the composite system evenly to the metal surface and irradiate it with a 65W UV lamp for 15 minutes at room temperature. If the ambient temperature is low, the irradiation time can be appropriately increased to prevent incomplete curing. After cooling, it will be molded.

[0013] The coating method for composite coating materials with mechanoluminescence function achieves coating thickness control using any of the following methods: (1) Apply by scraping or hand to form a coating with a thickness of 0.5–3 mm; (2) Coating the mold frame or limiting structure to form a regular coating with a thickness of 1–5 mm; (3) Apply multiple layers and cure each layer, with each layer having a thickness of 0.2–1 mm, to form a composite coating with a thickness of 1–5 mm. (4) Inject or fill the pre-made grooves or structural grooves on the metal surface to form a wear-resistant luminescent layer with a thickness of 2–10 mm.

[0014] The application of a composite coating material with mechanoluminescence function in the failure detection of lubricating oil on metal surfaces involves applying the composite coating to the surface of a metal friction pair. By monitoring the changes in the mechanoluminescence intensity of the coating during friction, the effective and failed states of the lubricating oil can be determined in situ and in real time. When the lubricating oil is effective, the triboluminescence intensity of the coating is low and stable. When the lubricating oil fails, the triboluminescence intensity of the coating is significantly enhanced, with a difference in intensity exceeding 20 times. Experimental data shows a clear positive correlation between triboluminescence intensity and sliding speed and load. Under normal lubricating oil conditions, the triboluminescence intensity is low and stable. However, when the lubricating oil fails, the decrease in the oil film's load-bearing capacity leads to increased friction and intensified contact stress, resulting in a significant increase in triboluminescence intensity. Therefore, by monitoring the changes in triboluminescence intensity in real time, the effective and failed states of the lubricating oil can be effectively reflected.

[0015] Preferably, the metal friction pair includes any one of bearings, gears, sliding guides, sealing end faces, sliders / guides, and couplings.

[0016] Preferably, the light emission signal of the coating is collected by any one of photoelectric sensor, optical wireless communication device, fiber optic sensor or photomultiplier tube, and after signal conversion, it is transmitted to the monitoring system through wireless transmission module or wired communication, which can provide a signal basis for remote status monitoring and early warning.

[0017] A dual-mode luminescent coating is provided, in which an electrode / driving structure is constructed in a composite coating material with mechanoluminescence function, so that the coating has both mechanoluminescence and electroluminescence functions. In the electroluminescence mode, white light emission can be achieved through RGB three-primary-color synthesis technology.

[0018] Compared with the prior art, the composite coating material with mechanoluminescence function and its application in lubrication failure detection provided by the present invention have the following beneficial effects: I. Breakthrough in in-situ real-time visualization of monitoring methods; Existing lubricating oil condition monitoring technologies mostly rely on indirect methods such as oil sampling and analysis and external sensors, which suffer from problems such as long detection cycles, the need for downtime operation, and difficulty in reflecting the true state of local contact interfaces. This invention directly coats a mechanoluminescent wear-resistant coating onto the metal surface. By utilizing the significant changes in the coating's luminescence intensity during friction, it achieves in-situ differentiation between the effective and failed states of the lubricating oil. It requires no complex external equipment, no downtime for sampling, and can capture changes in the lubrication state of the friction interface in real time, making the monitoring process intuitive and visible. This solves the pain points of traditional technologies, such as slow response and complex deployment.

[0019] II. The material system balances wear resistance and luminescence stability; Existing mechanoluminescent materials mostly use flexible elastomers or low-hardness polymers as matrices. Under the high contact stress and long-term sliding conditions of metal friction pairs, they are prone to wear, scratches, and interfacial delamination, making it difficult to balance continuous luminescence response and long-term wear resistance. This invention innovatively uses epoxy resin as the continuous phase, combined with a ZnS:Cu luminescent functional phase and a PTFE wear-resistant and lubricating reinforcing phase, to construct a three-phase synergistic system. The epoxy resin provides good matrix strength and adhesion, PTFE effectively reduces the coefficient of friction and improves wear resistance stability, and Al2O3-coated ZnS:Cu particles ensure the stability of luminescence performance, enabling the coating to work stably for a long time under real engineering conditions of high speed and certain load, overcoming the limitations of existing materials in engineering applications.

[0020] Third, the signal interpretation is accurate, reliable, and highly recognizable; Existing research shows insufficient correlation between luminescence signals and lubrication status, with insignificant differences in signal intensity, leading to significant interpretation difficulties. This invention optimizes material composition and controls the process to achieve a low and stable luminescence intensity in the coating when the lubricating oil is effective, while a significant increase in luminescence intensity occurs after lubricating oil failure due to enhanced mechanical stimulation caused by the change in interfacial friction state. The difference between the two can reach approximately 20 times, demonstrating strong interpretability. Furthermore, it explicitly uses luminescence intensity, intensity ratio, or a threshold as the judgment criteria, ensuring a clear and unified standard for lubrication status identification and avoiding the problems of signal ambiguity and high misjudgment rates in traditional monitoring methods.

[0021] IV. It has a wide range of applications and strong scalability; Existing technologies are mostly designed for specific working conditions or single functions, limiting their application scope and lacking flexibility. This invention is applicable to various mechanical components such as bearings, gears, and sliding guides. The coating preparation process is simple and low-cost, supporting multiple coating methods such as scraping, mold coating, and layer coating, and the coating thickness can be adjusted according to requirements. In addition to the basic mechanoluminescence monitoring function, it can be expanded to construct a dual-mode luminescent coating of "mechanoluminescence and electroluminescence," accommodating both passive monitoring and active lighting needs. It is compatible with various detection and transmission schemes such as remote real-time monitoring, optical wireless communication, and fiber optic sensing, and is particularly suitable for scenarios where wiring is not possible and electromagnetic interference resistance is high, possessing stronger engineering practical value and expansion potential. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 The triboluminescence detection device of this invention: the left figure shows the mechanical system, and the right figure is a schematic diagram of the Shamrock SR-303i spectrometer from Andor Technologies, UK. Figure 3 This is a schematic diagram of the photoluminescence phenomenon of the material under ultraviolet light irradiation according to the present invention; Figure 4 The triboluminescence intensity diagrams of this invention are as follows: (a) triboluminescence intensity before lubricant failure and (b) triboluminescence intensity after lubricant failure. Figure 5 This is a schematic diagram of the surface friction of the material before and after the lubricant fails according to the present invention; Figure 6 This is the spectrum of triboluminescence of the present invention; Figure 7 This is a schematic diagram showing the overall triboelectric emission detection system of the present invention; Figure 8 The triboluminescence phenomenon under high load in this invention is shown in: (a) a physical image of triboluminescence; (b) a schematic diagram of triboluminescence spectrum measurement. Figure 9 This is a schematic diagram of material wear in this invention; Figure 10 The electroluminescence spectra at different frequencies under 300V are shown in the figure. Figure 11 This is a photograph of the coating material of the present invention covering the surface of a titanium alloy. Figure 12 This is a schematic diagram of the surface potential of the friction interface before and after the lubricant fails, according to the present invention. Figure 13 This is a schematic diagram of the electroluminescent device structure of the present invention, wherein the upper electrode is an ITO thin film, the light-emitting insulating layer is a coating material, the lower electrode is a copper foil, and the bottom insulating layer is a glass sheet; Figure 14 This is a fitted curve of the relationship between light intensity and sliding speed in this invention (each data point is the average of three experimental data). Figure 15 This is a schematic diagram illustrating the relationship between light intensity and sliding speed under a fixed load according to the present invention; Figure 16 This is a curve showing the fitting relationship between light intensity and load in this invention (each data point is the average of three experimental data points). Figure 17 This is the spectrum of white light emitted by friction after color adjustment according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0025] Please refer to the example. Figures 1 to 17 As shown: To address the problems mentioned in the technical solutions, this application provides a composite coating material with mechanoluminescence function and its application in lubrication failure detection. The specific implementation process is as follows: The composite material of the present invention comprises the following components: Matrix material: epoxy resin and its curing system, including at least two optional implementation methods: Implementation Scheme 1: Two-component AB adhesive-curable epoxy resin (components shown in Tables 1 and 2): Mix epoxy resin type A and type B at a mass ratio of 3:1 and cure at room temperature for approximately 48 hours. Table 1: Composition of Epoxy Resin A (Type 204)

[0026] Table 2: Composition of Epoxy Resin B (Type 204)

[0027] Implementation Scheme 2, UV-curable epoxy resin (components shown in Table 3): It cures rapidly under UV irradiation, with a curing time of approximately 10–15 minutes, and is suitable for rapid film formation or layered curing construction.

[0028] Table 3: Composition of UV Epoxy Resin (U226 Light-Curing Adhesive)

[0029] The luminescent functional phase: D502CTZnS:Cu luminescent particles from Shanghai Keyan Optoelectronic Technology Co., Ltd., with a particle size between 28 and 30 micrometers, are used. These particles are coated with a transparent Al2O3 thin layer to prevent water and oxygen penetration and the reaction with ZnS, thus reducing deliquescence and improving the surface hardness and modulus of the particles, providing chemical and mechanical protection for ZnS:Cu.

[0030] Wear-resistant and lubrication-enhancing phase: Shanghai Maclean Biochemical Technology Co., Ltd. p875333 PTFE micro powder with an average particle size of 3 micrometers was used.

[0031] The specific implementation process is as follows: Before preparing the test samples, beakers, tweezers, spatulas, and other experimental supplies were cleaned. If impurities were present on the surface of the supplies, they could contaminate the samples and affect the experimental results. Therefore, the supplies were first immersed in anhydrous ethanol solution and sonicated to remove surface organic matter. After sonication, they were rinsed with deionized water and finally dried with an air gun to reduce the adsorption of airborne dust and impurities on the surface of the experimental items. Simultaneously, the powder used in the experiment was heated and dried to prevent the powder from absorbing water, which could lead to unstable experimental results.

[0032] First, weigh the ZnS:Cu luminescent powder and PTFE powder at a mass ratio of 2:1 and add them to a centrifuge tube. Then, place the tube in a shaker and mix thoroughly to ensure that the two powders are evenly dispersed.

[0033] Subsequently, type A and type B epoxy resins were mixed at a mass ratio of 3:1 to prepare epoxy resin adhesive, which was then added to another centrifuge tube and stirred until the system was homogeneous using a shaker.

[0034] Next, the uniformly mixed ZnS:Cu / PTFE powder and epoxy resin were mixed at a mass ratio of ZnS:Cu powder to epoxy resin of 3:10. The mixture was first stirred in a silicone mold with a glass rod to fully wet and initially disperse the powder. Then, the mixture was transferred to a centrifuge tube and stirred again in a shaker to obtain a uniformly dispersed composite system.

[0035] The obtained mixture is poured into a silicone mold and placed in a vacuum drying oven. The air pressure is reduced to decrease the number of air bubbles in the mixture. After vacuum drying for 20 minutes, the coating material is obtained.

[0036] Curing method: Apply the material evenly to the metal surface and let it dry and cure indoors for 48 hours.

[0037] The coating method and thickness control are as follows: (1) Apply by scraping or hand application (scraper / wipe) to form a coating of about 0.5–3 mm thickness; (2) Apply coating using a mold frame or limiting structure to form a regular coating of about 1–5 mm thickness; (3) The coating is applied in multiple layers and cured layer by layer, with each layer being approximately 0.2–1 mm thick, resulting in a composite coating of 1–5 mm thickness. Composite coating materials with mechanoluminescence function and their application in lubrication failure detection (4) Inject or fill the composite material into a prefabricated groove or structural groove on the metal surface to form a wear-resistant luminescent layer of about 2–10 mm thick.

[0038] The different curing methods are as follows: AB-curable epoxy resins are suitable for overall curing of millimeter-thick and thicker coatings because they do not rely on light penetration. After curing, the coating has good consistency in the thickness direction, which is beneficial to long-term wear resistance and stability. Its curing degree and mechanical properties are mainly affected by curing time and post-curing conditions.

[0039] UV-curable epoxy resins cure quickly, forming a film within 10–15 minutes, making them suitable for rapid application and layered coating. They also establish surface hardness rapidly, which helps improve the wear resistance and scratch resistance of the coating surface. However, for thick coatings, it is preferable to use layered curing or a combination of curing and post-curing processes to avoid uneven performance caused by curing gradients.

[0040] The experimental setup and results are as follows: The triboluminescence detection device used in this experiment consists of three main parts: (1) Mechanical system, which includes a positioning platform and a rotating platform. The positioning platform and the rotating platform work together to achieve contact friction of the friction pair materials to produce a light-emitting phenomenon.

[0041] (2) Control system, including force control system and speed control system. Force control system is used to regulate the loading pressure of the upper friction pair; speed control system is used to regulate the rotation speed of the lower friction pair.

[0042] (3) Measurement System: The measurement system includes a force measurement system and an optical measurement system. The force measurement system is used to collect the downward pressure and friction signals in real time; the optical measurement system is used to measure the light intensity and spectrum of triboluminescence. It should be noted that triboluminescence is a specific manifestation of mechanoluminescence. To avoid interference from ambient light, the entire device is placed in a dark box. A physical diagram of the device is shown below. Figure 2 .

[0043] The specific principle is explained as follows: During friction, due to the relative motion of the contact interfaces, a large number of electrons transfer from one friction surface to another; this process is called triboelectrification. Triboelectrification leads to significant charge separation at the contact interfaces. When the separated surfaces separate again, these charges form a strong local electric field. This local electric field excites charge carriers inside the material or at the interface to undergo transitions and recombination, thereby releasing energy in the form of photons and achieving luminescence.

[0044] Specifically, the electrification process during triboelectricity creates a localized potential difference and enhanced electric field region on the material surface. In doped phosphors such as ZnS:Cu, this electric field can induce the release of electrons from deep-level traps and their recombination with holes, thereby causing the luminescent centers to emit visible light. This electric field-driven carrier release and recombination mechanism is a significant contributing factor to triboelectric luminescence, and it works synergistically with traditional mechanisms such as piezoelectricity and fracture electric fields.

[0045] Compared to many traditional mechanoluminescent material designs (which typically require significant material fracture, crack propagation, or contact fatigue before releasing enough electrons to emit light), the excitation mechanism described above, arising from triboelectricity, exhibits a lower trigger threshold and higher sensitivity. This is because triboelectricity can rapidly generate significant changes in surface potential under relatively small contact stress and sliding conditions, thereby triggering a luminescent response, without relying on macroscopic cracks or damage. This makes luminescent systems employing triboelectric mechanisms exhibit higher sensitivity and lower damage in applications such as detecting changes in lubrication state, microscopic flicker at contact interfaces, and early warning of frictional damage.

[0046] Therefore, compared to strategies that require significant material damage to produce luminescence, material systems based on triboelectric-electric field-induced luminescence can output detectable light signals with lower mechanical stimulation, thereby enabling early, low-damage, and highly sensitive monitoring of lubricant failure, interfacial shear changes, and deterioration of friction conditions. This is also one of the key innovative advantages of this invention compared to existing technologies, as it has less impact on the rubbed material and provides more sensitive detection.

[0047] Since ZnS is a direct bandgap semiconductor, its intrinsic bandgap is approximately 3.66 eV. When doped with copper ions, copper acts as an "activator" entering the ZnS lattice, replacing the positions of zinc ions, thereby altering the material's band structure. When the ZnS:Cu phosphor is irradiated with ultraviolet (UV) light, it absorbs the energy of the UV light, causing electrons within the material to transition from the valence band to the conduction band or excited state, and subsequently return to the ground state through various pathways. + The energy difference between the t2 level formed in ZnS and the valence band of ZnS corresponds to an energy difference of about 2.3–2.5 eV, and the wavelength corresponding to this is the green region (about 500–520 nm).

[0048] Therefore, as Figure 3 As shown, the coating material emits uniform green light under ultraviolet light irradiation, proving that the luminescent powder is uniformly and effectively doped into the epoxy resin.

[0049] Under the same load and rotation speed, when there is an effective lubricating oil film on the coating surface, the friction coefficient is lower, the actual contact stress and shear stimulation acting on the coating are significantly reduced, and the mechanoluminescence response of ZnS:Cu particles is weaker. When lubricating oil fails due to shear degradation, oxidation, or contamination during long-term friction, the oil film's load-bearing capacity decreases, and the interfacial friction state changes from fluid lubrication / boundary lubrication to dry friction or severe boundary lubrication. This causes the coating to withstand stronger mechanical stimulation, thereby significantly enhancing the mechanoluminescence response.

[0050] like Figure 4(a) shows that under the same load and rotational speed conditions, the triboluminescence intensity is low and stable when lubricating oil is present on the coating surface. The failure condition is simulated by removing the surface lubricating oil film, as shown in Figure (a). Figure 4 (b) At this point, the triboluminescence intensity of the material is significantly stronger than that when the lubricating oil is present, and the intensity gradually increases with the increase of friction time. Therefore, the triboluminescence intensity or its ratio can be used as a criterion for determining whether the lubricating oil has failed. Simultaneously, we use a three-dimensional force sensor to detect the magnitude of the frictional force on the material surface before and after lubricating oil failure (e.g., ...). Figure 5 As shown in the figure, it can be clearly seen that when the lubricating oil fails, the friction on the surface of the composite material increases rapidly and is significantly greater than when the lubricating oil is present.

[0051] The triboluminescence spectrum was measured using an SR-303i spectrometer. The upper friction pair consisted of quartz spheres, and the lower friction pair consisted of an epoxy resin-based PTFE & ZnS:Cu composite material. Figure 6 As shown, its triboluminescence spectrum exhibits a single characteristic peak at approximately 500 nm, consistent with the characteristic emission peak of ZnS:Cu. This indicates that the luminescence originates from electronic transitions at the luminescent centers of ZnS:Cu.

[0052] To investigate whether the luminescence performance of the coating material is affected under high loads, this experiment employed the integrated triboeing detection system from Tsinghua University (e.g., [system name missing]). Figure 7 As shown), this system features a high-vacuum triboelectric launch cavity capable of achieving multi-atmosphere, wide-temperature-range environmental control, and can achieve 10 6 The system incorporates parameters such as mbar high vacuum, four controllable gas atmospheres, temperature regulation from -100 to 250℃, and stable frictional motion experiments under loads ranging from 1 to 10N, used to simulate scenarios in some real-world engineering situations. Experiments conducted under a 10N load and a rotational speed of 700 r / min revealed a distinct green glow at the friction point. Figure 8 As shown, the wear marks were light and there were no obvious signs of damage after the experiment (e.g. Figure 9 By changing the friction pair material, using zirconia spheres, stainless steel spheres, and copper spheres to simulate the friction materials in actual engineering, a stable luminescence phenomenon can be achieved.

[0053] By utilizing RGB three-primary-color white light synthesis technology, white light is generated by mixing three monochromatic lights: red (615-620nm), green (530-540nm), and blue (460-470nm). This modulates the emission color of the coating material, enabling it to emit white light under triboluminescence conditions, thereby improving the selectivity of the coating material's emission color. Figure 17 As shown.

[0054] from Figure 12It can be clearly seen that when there is lubricating oil at the friction interface, the surface electrostatic potential of the material is low and changes slowly, corresponding to the stage of weak light intensity and insignificant change in the light intensity diagram. However, when the lubricating oil fails, the surface potential increases rapidly, corresponding to the stage of rapid increase in light intensity in the light intensity diagram. Figure 4 As shown, this demonstrates that triboelectricity is a key reason for the luminescence of the coating material during friction.

[0055] (The measurement was performed using a Trek electrometer. The measurement principle is that the probe electrode undergoes periodic mechanical vibration near the surface to be measured, causing the capacitance between the probe and the surface to change periodically, thereby modulating the surface potential signal into an AC signal for amplification and measurement.) Furthermore, by combining the relationship between relative sliding speed, load, and triboluminescence intensity, real-time monitoring of lubricating oil failure conditions can be achieved. When sliding speed and load increase, the significant increase in triboluminescence intensity not only reflects changes in frictional contact stress but also provides a direct and quantifiable indication of lubricating oil failure. Specifically, this invention establishes a mathematical model between triboluminescence intensity and sliding speed and load based on experimental data; the specific formula is as follows:

[0056] In the formula, (F is the load size in g, x is the light intensity in cps), and the fitting coefficient is 0.996;

[0057] In the formula, (v is the sliding speed in mm / s, x is the light intensity in cps) the fitting coefficient is 0.98573; To this end, we used the following method to measure the luminous intensity at different sliding speeds: First, the lower disk was kept stationary while the noise signal was measured. Then, the sliding speed was sequentially accelerated to specific values ​​under a fixed load. The measurement time for each speed was kept within 100 seconds. Figure 14 and Figure 15 The experimental results show that the intensity of triboluminescence increases monotonically with the increase of relative sliding speed, and the measured value of triboluminescence intensity remains basically unchanged under the same fixed sliding speed. Figure 16 The experimental results show that the intensity of triboluminescence increases monotonically with the increase of load, and the measured value of triboluminescence intensity remains basically unchanged under the same load.

[0058] It should be noted that the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite coating material with mechanoluminescence function, characterized in that, Using epoxy resin as the continuous phase matrix, zinc-copper sulfide activated luminescent powder (ZnS:Cu) is used as the luminescent functional phase, and polytetrafluoroethylene (PTFE) powder is used as the wear-resistant and lubrication-enhancing phase. The mass ratio of ZnS:Cu luminescent powder to PTFE powder is 2:1, and the mass ratio of ZnS:Cu luminescent powder to epoxy resin matrix is ​​3:

10. The particle size of ZnS:Cu luminescent powder is 28-30 micrometers, and the surface is coated with a thin layer of Al2O3. The average particle size of PTFE powder is 3 micrometers.

2. The composite coating material with mechanoluminescence function according to claim 1, characterized in that, The epoxy resin matrix is ​​selected from either a two-component AB glue-curable epoxy resin or an ultraviolet (UV) light-curable epoxy resin; wherein, the two-component AB glue-curable epoxy resin is made by mixing type A glue and type B glue in a mass ratio of 3:1, and the curing time at room temperature is 48h; the ultraviolet light-curable epoxy resin is cured after being irradiated by a 65W ultraviolet lamp for 10~15min at room temperature.

3. The composite coating material with mechanoluminescence function according to claim 2, characterized in that, The two-component AB adhesive-curable epoxy resin comprises: Type A adhesive containing 90% epoxy resin and 10% diluent by mass; and Type B adhesive containing 30% polypropylene glycol bis(2-aminopropyl ether), 28% alicyclic amine, 7% epoxy resin, 34.6% diluent, and 34.6% defoamer by mass.

4. The composite coating material with mechanoluminescence function according to claim 2, characterized in that, The UV-curable epoxy resin comprises 55–75% polyurethane resin, 10–30% acrylic monomer and 10% dimethylchlorosilane by mass fraction.

5. A method for preparing a composite coating material with mechanoluminescence function as described in any one of claims 1-4, characterized in that, Includes the following steps: S1, Pretreatment of experimental materials: The experimental equipment was immersed in anhydrous ethanol for ultrasonic cleaning, then rinsed with deionized water and dried with an air gun; ZnS:Cu luminescent powder and PTFE powder were heated and dried. S2, Functional powder mixing: Weigh ZnS:Cu luminescent powder and PTFE powder at a mass ratio of 2:1, place them in a centrifuge tube and mix them thoroughly with a shaker to obtain uniformly dispersed ZnS:Cu / PTFE mixed powder; S3, preparation of composite system: The mixed powder obtained in S2 is mixed with epoxy resin matrix at a mass ratio of ZnS:Cu luminescent powder to epoxy resin of 3:

10. It is first initially stirred, moistened and dispersed by glass rod, and then transferred to centrifuge tube and stirred evenly by shaker. S4, Degassing treatment: Pour the composite system obtained in S3 into a silicone mold and place it in a vacuum drying oven for degassing for 20 minutes; S5, Curing and Molding: If using a two-component AB adhesive-curing epoxy resin, apply the composite system evenly to the metal surface and allow it to dry and cure at room temperature for 48 hours. If using a UV-curing epoxy resin, apply the composite system evenly to the metal surface, irradiate with a 65W UV lamp at room temperature for 15 minutes, and allow it to cool before molding. If the curing environment temperature is low, the UV lamp irradiation time can be appropriately extended.

6. A method for coating a composite coating material with mechanoluminescence function as described in any one of claims 1-4, characterized in that, Coating thickness control can be achieved using any of the following methods: (1) Apply by scraping or hand to form a coating with a thickness of 0.5–3 mm; (2) Coating the mold frame or limiting structure to form a regular coating with a thickness of 1–5 mm; (3) Apply multiple layers and cure each layer, with each layer having a thickness of 0.2–1 mm, to form a composite coating with a thickness of 1–5 mm. (4) Inject or fill the pre-made grooves or structural grooves on the metal surface to form a wear-resistant luminescent layer with a thickness of 2–10 mm.

7. The application of a composite coating material with mechanoluminescence function as described in any one of claims 1-4 in the detection of lubricating oil failure on metal surfaces, characterized in that, The composite coating is applied to the surface of the metal friction pair. By monitoring the change in the triboluminescence intensity of the coating during the friction process, the effective and ineffective states of the lubricating oil can be determined in situ and in real time. When the lubricating oil is effective, the triboluminescence intensity of the coating is low and stable.

8. The application of the composite coating material with mechanoluminescence function according to claim 7 in the detection of lubricating oil failure on metal surfaces, characterized in that, The metal friction pair includes any one of the following: bearing, gear, sliding guide rail, sealing end face, slider / guide rail, and coupling.

9. The application of the composite coating material with mechanoluminescence function according to claim 7 in the detection of lubricating oil failure on metal surfaces, characterized in that, By using any one of photoelectric sensors, optical wireless communication devices, fiber optic sensors, or photomultiplier tubes to collect the luminous signals of the coating, and then transmitting them to the monitoring system via a wireless transmission module or wired communication after signal conversion, a signal basis can be provided for remote status monitoring and early warning.

10. A dual-mode luminescent coating, characterized in that, An electrode / driving structure is constructed in the composite coating material with mechanoluminescence function as described in claim 1, so that the coating has both mechanoluminescence and electroluminescence functions.

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