Long-afterglow self-luminous material based on multi-element rare earth synergistic sensitization and preparation method of long-afterglow self-luminous material

Abstract

The invention discloses a long-afterglow self-luminous material based on multi-element rare earth synergistic sensitization and a preparation method thereof. SrAlO is used as a matrix, trap level distribution is optimized through ternary rare earth synergistic doping according to the molar ratio of Eu to Dy to Nd being 1: (0.4-0.6): (0.2-0.4), and a ZnO nanorod array is grown on the surface of a light-emitting core in an in-situ epitaxial mode to improve the light extraction efficiency; and a hydrophobic modified SiO core-shell coating layer with an ordered mesoporous channel is combined, and oxygen diffusion is promoted by utilizing a nanopore channel so as to accelerate trap regeneration and synchronously inhibit non-radiative recombination. The afterglow time of the material is not less than 8 hours, and the afterglow retention rate after aging at 60 DEG C is not less than 80%. A solid-phase synthesis process and red mud / fly ash industrial solid waste raw materials are adopted, and the carbon emission intensity is smaller than or equal to 6 kgCO / kg. The material can be widely applied to the fields of green traffic infrastructures such as expressways and tunnels.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic luminescent materials, and particularly relates to a low-carbon and environmentally friendly long-afterglow self-luminescent material for road marking paint and a preparation method thereof, and is particularly suitable for complex climate scenes such as expressways, tunnels, and mountainous roads. BACKGROUND

[0002] With the acceleration of global urbanization and the continuous growth of the number of motor vehicles, the problem of road traffic safety at night is becoming increasingly prominent. Statistics show that the death rate of traffic accidents at night is nearly 3 times higher than that during the day, and insufficient visibility is one of the main factors leading to accidents. The traditional road marking system mainly relies on retroreflective materials to achieve night visibility, but its optical performance is limited by the angle and intensity of the incident light source, and the visible distance sharply decreases to less than 30% under complex weather conditions such as rain and fog. To break through this technical limitation, road marking materials with self-luminescent characteristics have gradually become a research hotspot in the field of traffic engineering.

[0003] In the prior art, the schemes for realizing active light emission of road markings mainly include electroluminescent and photoluminescent systems. The electroluminescent system is represented by LED embedded marking, which realizes high-brightness display through a semiconductor light-emitting diode and has been successfully applied to special road sections such as tunnels and bridges. However, this technology has significant defects: first, its power consumption is serious, leading to a sharp increase in operating costs; second, the failure rate of the complex circuit system under repeated vehicle loads exceeds 5% per year; and most importantly, in remote areas or disaster emergency scenarios, power supply interruption will directly lead to system failure. These technical and economic defects seriously restrict the large-scale application of electroluminescent markings. The photoluminescent material system exhibits unique advantages due to its zero-energy consumption characteristics. The first-generation product uses zinc sulfide-based fluorescent powder, but its afterglow time can only last for 2-3 hours, which cannot meet the whole-night lighting demand. The second-generation strontium aluminate system (SrAl2O4:Eu²⁺, Dy³⁺) extends the afterglow time to 3-4 hours through rare earth ion doping, but still has four major technical bottlenecks in practical applications: first, the environmental stability is insufficient, with a 40% decay in luminous intensity at 50°C high-temperature environment; second, it is highly sensitive to water vapor, and surface hydroxylation leads to trap energy level failure when the relative humidity is >80%; third, the carbon emission intensity of the traditional carbon thermal reduction synthesis process is as high as 8 kg CO2 / kg; and most importantly, the high-end long-afterglow material market has been monopolized by Japanese Nemoto and German OSRAM for a long time, and there is a generational gap in key indicators such as weather resistance and luminous efficiency for domestic materials.

[0004] Based on this, the application proposes a new long afterglow road marking material system, which constructs a gradient trap energy level through Eu2+ / Dy3+ / Nd3+ ternary rare earth synergistic sensitization, at the same time, ZnO nanochannel promotes oxygen diffusion to make the trap regeneration rate, combined with plasma enhanced chemical vapor deposition to prepare a hydrophobic SiO2 protective layer, while maintaining the afterglow performance of more than 8 hours, reducing the performance fluctuation rate of the material in extreme environment. The technical scheme not only solves the environmental stability problem of the traditional photoluminescence material, but also reduces the carbon emission intensity to 6kg CO2 / kg by using the supercritical CO2 assisted synthesis process, which provides key technical support for the development of sustainable intelligent transportation infrastructure. SUMMARY

[0005] The technical problem to be solved is to provide a high-performance long afterglow self-luminous material and a green preparation method thereof, aiming to solve the three key technical problems of the existing strontium aluminate system material: insufficient material afterglow time, poor high-temperature stability, high production energy consumption and low industrial solid waste resource utilization rate.

[0006] Technical scheme: A long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, characterized in that: taking SrAl2O4 as a matrix, doping Eu2+, Dy3+ and Nd3+ ternary rare earth ions to form a luminescent core to be coated, the molar ratio of Eu2+, Dy3+ and Nd3+ is 1:(0.4-0.6):(0.2-0.4), ZnO nanocolumn array is grown in situ on the surface of the luminescent core, and a hydrophobic modified SiO2 shell layer is coated on the surface of the ZnO nanocolumn, the thickness of the SiO2 shell layer is 50-100 nm.

[0007] The preparation method of the above long afterglow self-luminous material based on multi-element rare earth synergistic sensitization comprises the following steps: S1. Using a supercritical CO2 assisted solid phase synthesis method, mixing raw materials according to the ratio; after cooling, a luminescent core to be coated is obtained; S2. Coating zinc oxide nanocolumns on the luminescent core obtained in step S1 to obtain SrAl2O4:Eu2+, Dy3+, Nd3+@ZnO nanocolumn core-shell precursor; S3. Using plasma enhanced chemical vapor deposition technology to deposit a SiO2 shell layer on the surface of the SrAl2O4:Eu2+, Dy3+, Nd3+@ZnO nanocolumn core-shell precursor prepared in step S2, then immersing the coated material in a silane coupling agent solution for reaction, washing and drying to obtain a long afterglow self-luminous material.

[0008] The preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the supercritical CO2 parameters of 8-10 MPa of pressure, 300-500 ℃ of reaction temperature, and 3-5 h of reaction time.

[0009] Preferably, the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the method of coating the zinc oxide nanocolumns outside the light-emitting core comprising the following steps: S11. The light-emitting core is immersed in a 0.05-0.2 M zinc acetate ethanol solution, and a seed layer is baked at 60-100 ℃; S12. The seed layer of step S11 is placed in a reaction solution containing 0.05 M zinc nitrate and 0.05 M hexamethylenetetramine with a pH of 10-11, and a powder is obtained by growing at 60-120 ℃ for 2 h; S13. After centrifugal cleaning, the SrAl2O4:Eu2+, Dy3+, Nd3+@ZnO nanocolumn core-shell precursor is obtained by annealing at 300-500 ℃ for 1-3 h.

[0010] The preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the deposition parameters of 1:(1-3) of SiH4 / O2 flow ratio, 20-50 min of deposition time, 0.5-2 wt% of concentration of octadecyltrimethoxysilane as the silane coupling agent, 60-80 ℃ of reaction temperature, 1-3 h of reaction time, ethanol washing, 50-100 ℃ of drying treatment, and formation of a hydrophobic functional SiO2 coating layer.

[0011] The long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the light-emitting core further doped with red mud / pulverized fuel ash as a functional filler, and the addition amount is 5-30 wt% relative to the total mass of the material and the particle size is ≤5 μm.

[0012] Preferably, the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the preparation method of the functional filler comprising the following steps: S111. The red mud / pulverized fuel ash is dried at 200-300 ℃ in an inert atmosphere for 1.5-2.5 h; S112. The dried red mud / pulverized fuel ash of step S111 is placed in a ball mill and ball milled at a speed of 200-500 rpm for 2-5 h; S113. The powder obtained in step S112 is mixed and ground with the light-emitting core raw material at a mass ratio of (5-30):100.

[0013] The long afterglow self-luminous material based on multi-element rare earth synergistic sensitization has the characteristics that the average diameter of the ZnO nanocolumn is 80-100 nm, the average height is 240-300 nm, and the average area density is 20-30 per mu square.

[0014] The long afterglow self-luminous material based on multi-element rare earth synergistic sensitization is applied to road marking paint, tunnel indication sign, building escape passage or safety emergency identification.

[0015] Beneficial effects: The long afterglow self-luminous material has the following advantages: 1. The long afterglow self-luminous material breaks through the traditional process, adopts high-speed shearing dispersion-supercritical fluid technology to pretreat raw materials, combines plasma enhanced chemical vapor deposition to in-situ epitaxial growth of ZnO nanocolumn array on the surface of a light-emitting core, and directly constructs a gradient trap energy level core-shell structure. The process avoids high-temperature carbon thermal reduction, forms a tangled energy level network through mechanical-physical synergy, improves the light scattering efficiency by more than 30% by using the photonic crystal effect of the ZnO nanocolumn, and significantly enhances the light-generated electron capture and storage capacity. Meanwhile, the high-speed shearing dispersion process makes the red mud / coal ash functional filler uniformly distributed in the light-emitting core matrix, and through the dispersion strengthening and interface stress transmission effect of the rigid particles, the impact strength of the material is improved; 2. The long afterglow self-luminous material is based on ternary rare earth synergistic modification of strontium aluminate matrix, improves the ultraviolet-visible light conversion efficiency through the ZnO nanocolumn array, accelerates the oxygen diffusion through the nanopore of the hydrophobic mesoporous SiO2 shell layer to improve the trap regeneration rate, and further optimizes the energy level matching through the carrier capture auxiliary effect of the Fe2O3 / Al2O3 porous framework in the red mud / coal ash functional filler, so that the synergistic breakthrough of the light absorption efficiency ≥80% and the afterglow retention rate ≥80% at 60 DEG C is realized; 3. The long afterglow self-luminous material is physically modified through ZnO hydrothermal epitaxial growth and supercritical CO2 assisted coating, and the use of organic solvents and heavy metal additives is completely avoided throughout the process. The low-temperature construction of the nanocolumn array and the utilization of solid waste reduce the raw material cost by 20%, and the addition of the red mud / coal ash filler significantly enhances the mechanical properties of the material, the active silicon aluminum components in the filler are bonded with the matrix in solid phase, and the crack propagation is inhibited; the mesoporous-nanocolumn synergistic structure prolongs the service life of the material, reduces the carbon footprint by 30% in the whole life cycle, and realizes the double improvement of environmental and economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 ZnO parameters affect the intensity of afterglow; Figure 2 Different critical states affect the afterglow time; Figure 3 The relationship between the afterglow retention rate and the soaking time. DETAILED DESCRIPTION

[0017] The application will be further described in connection with the following examples, which are intended to be illustrative only and not limiting of the application. The application provides a long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, characterized by: taking SrAl2O4 as a matrix, doping Eu²⁺, Dy³⁺ and Nd³⁺ ternary rare earth ions to form a luminescent core to be coated, the molar ratio of Eu²⁺, Dy³⁺ and Nd³⁺ being 1:(0.4-0.6):(0.2-0.4), growing ZnO nanocolumn arrays on the surface of the luminescent core in situ epitaxy, and coating a hydrophobic modified SiO2 shell layer on the surface of the ZnO nanocolumn, the thickness of the SiO2 shell layer being 50-100 nm. The material constructs a gradient trap level system through the synergistic effect of the ternary rare earth ions: Eu²⁺ as a luminescent center (4f 6 5d¹→4f 7 transition), the quantum efficiency of the 4f-5d electronic transition of which is improved under the conversion assistance of ultraviolet-visible light of the ZnO nanocolumn; Dy³⁺ forms a 0.45-0.6 eV shallow trap, which is coupled with a ZnO surface oxygen vacancy (Vo⁺ / Vo²⁺) to improve the electron storage density; Nd³⁺ constructs a 0.8-1.0 eV deep trap, which realizes an afterglow of >8 h under the electron injection from the ZnO conduction band (-4.19 eV) to SrAl2O4 (-4.05 eV); the ZnO nanocolumn array has a wide band gap (~3.2 eV) and can efficiently convert ultraviolet photons to match the absorption band of Eu²⁺; the periodic structure produces Mie scattering, so that the light absorption efficiency is improved. The hydrophobic SiO2 coating layer prevents H2O / O2 erosion; at the same time, the alkyl chain hydrophobic modification inhibits the condensation of surface water vapor; finally, the material has an afterglow retention rate ≥80% in a 60℃ humid heat environment.

[0018] The preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization described above comprises the following steps: S1. Using a supercritical CO2 assisted solid phase synthesis method, mixing raw materials according to the ratio; after cooling, obtaining a luminescent core to be coated; S2. Coating a zinc oxide nanocolumn on the luminescent core obtained in step S1 to obtain a SrAl2O4:Eu²⁺, Dy³⁺, Nd³⁺@ZnO nanocolumn core-shell precursor; S3. Using a plasma enhanced chemical vapor deposition technology to deposit a SiO2 shell layer on the surface of the SrAl2O4:Eu²⁺, Dy³⁺, Nd³⁺@ZnO nanocolumn core-shell precursor prepared in step S2, then immersing the coated material in a silane coupling agent solution for reaction, washing and drying to obtain a long afterglow self-luminous material.

[0019] S1 of the above steps realizes atomic-level uniform doping of rare earth ions in the SrAl2O4 matrix, and the supercritical fluid has high diffusivity and solvation capacity, which breaks the agglomeration of raw materials at the sub-micron scale, so that Eu²⁺ / Dy³⁺ / Nd³⁺ occupies the lattice site accurately according to 1:(0.4-0.6):(0.2-0.4), and forms a deeply matched cooperative trap level network; S2 of the above steps constructs a photonic crystal structure on the surface of the light-emitting core, and the periodic arrangement enhances the ultraviolet-visible light conversion efficiency through Bragg scattering, and the gradient energy band structure formed at the nanorod / matrix interface drives the directional injection of photo-generated electrons into the Dy³⁺ deep trap; In S3 of the above steps, SiH4 / O2 plasma fills mesoporous SiO2 in the gap between the nanorods, and the nanopores accelerate the diffusion of environmental oxygen to the trap center, so that the electron capture / release kinetics rate is improved by 50%; the octadecyltrimethoxysilane hydrophobic layer passivates the surface hydroxyl group through the —CH3 group, blocks the hydrolysis erosion of H2O on SrAl2O4, and realizes the synergistic regulation of afterglow lifetime and environmental stability.

[0020] In one embodiment, the preparation method of the long-afterglow self-luminescent material adopts a supercritical CO2-assisted solid-phase synthesis method to mix raw materials according to a ratio; the parameters meet the following conditions: the pressure is 8-10 MPa, the reaction temperature is 300-500 ℃, and the reaction time is 3-5 h, and after cooling, a light-emitting core to be coated is obtained. The supercritical CO2 has the unique property of high diffusivity of gas, and under the condition of 8-10 MPa pressure, the supercritical CO2 can deeply penetrate into the gap between the raw material particles, significantly promoting the atomic-level uniform mixing of the reactants. When the temperature rises to 300-500 ℃, ion diffusion is accelerated, and the lattice energy is reduced through the solvation effect. This special reaction environment greatly reduces the high temperature required by the traditional solid-phase method, and the precursor material can be obtained within 3-5 h. Through a simple pressure reduction operation, CO2 can be completely recovered, and the entire process does not require the participation of organic solvents, which not only greatly reduces energy consumption, but also controls the carbon emission intensity below 6 kg CO2 / kg.

[0021] In one embodiment, the method for coating the light-emitting core with zinc oxide nanorods comprises the following steps: S11. Immersing the light-emitting core into a 0.05-0.2M zinc acetate ethanol solution and baking at 60-100 ℃ to form a seed layer.

[0022] S12. Placing the seed layer of step S11 into a reaction solution containing 0.05M zinc nitrate and 0.05M hexamethylenetetramine with a pH of 10-11, and growing at 60-120 ℃ for 2 h to obtain a powder; S13. Centrifuging and washing the powder of step S12, and then annealing at 300-500 ℃ for 1-3 h.

[0023] The preparation method realizes efficient long afterglow luminescence through three steps: first, the luminescent core is immersed in a 0.05-0.2M zinc acetate ethanol solution, and a ZnO seed crystal layer is formed by baking at 60-100°C. This process builds a uniform nanocrystal core through a sol-gel reaction, laying the foundation for directional growth; second, the core is hydrothermally grown in a reaction solution containing 0.05M zinc nitrate and 0.05M hexamethylenetetramine at 60-120°C for 2 hours. The use of hexamethylenetetramine to slow down the release of OH⁻ promotes the self-assembly of ZnO into a nanocolumn structure along the

[001] crystal direction, and the high aspect ratio morphology gives excellent light waveguide effect; finally, after centrifugal cleaning, the core is gradient annealed at 300-500°C for 1-3 hours. The low-temperature stage eliminates crystal defects, and the high-temperature stage activates rare earth doping ions (such as Eu²⁺ / Dy³⁺), building a deep matching electron trap energy level in the ZnO lattice.

[0024] In one embodiment, the deposition parameters in step S3 are: SiH4 / O2 flow ratio 1:(1-3), deposition time 20-50 min; the silane coupling agent is octadecyltrimethoxysilane / ethanol solution, and the reaction parameters are: 0.5-2 wt% octadecyltrimethoxysilane / ethanol solution, reaction at 60-80°C for 1-3 hours, washed with ethanol and dried at 50-100°C. A hydrophobic functional SiO2 coating layer is formed. The octadecyltrimethoxysilane ethanol solution is used for surface modification, and at 60-80°C, the methoxy groups in the octadecyltrimethoxysilane molecules undergo condensation reaction with the SiO2 surface hydroxyl groups, and the long-chain alkyl groups arrange outward to form a hydrophobic monolayer. By controlling the concentration of octadecyltrimethoxysilane and the reaction time, the surface modification density can be accurately controlled, and finally a hydrophobic surface with a water contact angle greater than 120° is obtained.

[0025] In one embodiment, the luminescent core is also doped with red mud / fly ash as functional filler, and the addition amount is 5-30 wt% relative to the total mass of the material, and the particle size is ≤5 μm.

[0026] Preferably, the pretreatment method of red mud / fly ash comprises the following steps: S111. Dry the red mud / fly ash at 200-300°C for 1.5-2.5 hours; S112. Put the dried red mud / fly ash from step S111 into a ball mill and mill at a speed of 200-500 rpm for 2-5 hours; S113. Mix the red mud powder / fly ash obtained in step S112 with rare earth raw materials in a mass ratio of (5-30):100, and grind to a uniform mixture.

[0027] In one embodiment, by introducing the pretreated red mud / fly ash as a functional component, efficient resource utilization of industrial solid waste is achieved. The pretreatment process includes three key steps: first, dry treatment at 200-300℃ for 1.5-2.5h to effectively remove the combined water and volatile impurities in the raw materials; then ball milling at 200-500rpm for 2-5h to ensure that the particle size is controlled below 5μm and the ideal surface activity is obtained; finally, accurately proportioning with rare earth raw materials at a mass ratio of 5-30:100, and achieving uniform dispersion through thorough grinding. The pretreated red mud / fly ash particles not only can be used as a structure stabilizer to improve the mechanical properties of the material, but also contain trace metal oxides that can be used as auxiliary luminescence centers to produce a synergistic effect with rare earth ions.

[0028] In one embodiment, the diameter of the ZnO nanorod is 80-100 nm, the height is 240-300 nm, and the surface density is 20-30 rods / μm². Among them, the ZnO nanorod diameter of 80-100 nm excites Mie resonance to improve the light absorption rate to 80%; the height of 240-300 nm constructs a resonant cavity to improve the quantum efficiency; the surface density of 20-30 rods / μm² forms a Dy³⁺, Nd³⁺ gradient trap, and the afterglow is more than 8h. This design not only maintains the afterglow for more than 8h, but also significantly reduces production costs and environmental load. Based on these characteristics, the material is particularly suitable for application scenarios such as road marking paint, tunnel indication signs, and building escape passages, and its persistent and stable luminescent performance can ensure reliable visual guidance in the event of power failure or insufficient visibility, greatly improving the safety assurance capability in night and emergency situations.

[0029] Embodiment 1

[0030] A long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, characterized in that: SrAl2O4 is used as a matrix, doped with Eu²⁺, Dy³⁺ and Nd³⁺ ternary rare earth ions to form a luminescent core to be coated, the molar ratio of Eu²⁺, Dy³⁺ and Nd³⁺ is 1:0.5:0.3, ZnO nanorod arrays are in-situ epitaxially grown on the surface of the luminescent core, and a hydrophobic modified SiO2 shell layer is coated on the surface of the ZnO nanorod, the thickness of the SiO2 shell layer is 80 nm. And the final raw material molar ratio is SrAl2O4:Eu²⁺:Dy³⁺:Nd³⁺=1:0.01:0.005:0.003.

[0031] The preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization described above, comprising the following steps: S1. mixing the raw materials according to the ratio by using a supercritical CO2 assisted solid phase synthesis method; the parameters meet: pressure 8MPa, reaction temperature 320℃, reaction time 4h, and after cooling, the luminescent core to be coated is obtained.

[0032] S2. The luminescent core obtained in step S1 is immersed in a 0.1 M zinc acetate ethanol solution, and baked at 80°C to form a seed layer; then put into a reaction solution containing 0.05 M zinc nitrate and 0.05 M hexamethylenetetramine with pH = 10.5, and grown at 90°C for 2 h; finally, after centrifugal cleaning, annealing at 450°C for 1 h to obtain SrAl2O4:Eu²⁺, Dy³⁺, Nd³⁺@ZnO nanorod core-shell precursor.

[0033] S3. A SiO2 shell layer is deposited on the surface of the SrAl2O4:Eu²⁺, Dy³⁺, Nd³⁺@ZnO nanorod core-shell precursor prepared in step S2 by plasma-enhanced chemical vapor deposition technology, with a SiH4 / O2 flow ratio of 1:2, and a deposition time of 30 min; then the coated material is immersed in 1 wt% octadecyltrimethoxysilane at 80°C for 2 h, and after ethanol washing and drying at 60°C, a long-afterglow luminescent material with a hydrophobic surface is obtained.

[0034] The long-afterglow self-luminescent material described above: red mud / fly ash is doped in the raw material, and the addition amount is 5 wt% relative to the total mass of the material, and the particle size is ≤5 μm.

[0035] Preferably, the pretreatment method of the red mud / fly ash comprises the following steps: S111. The red mud / fly ash is dried at 250°C for 2 h; S112. The dried red mud / fly ash of step S111 is placed in a ball mill and ball milled at a speed of 300 rpm for 3 h; S113. The red mud powder / fly ash obtained in step S112 is mixed with rare earth raw materials at a mass ratio of 5:100, and ground to a uniform mixture.

[0036] Preferably, the diameter of the ZnO nanorod is 80 nm, the height is 250 nm, and the surface density is 25 / μm².

[0037] Example 2

[0038] Example 2 differs from Example 1 in that: a preparation method of a long-afterglow self-luminescent material based on multi-element rare earth synergistic sensitization, the material uses SrAl2O4 as the matrix, doped with Eu²⁺, Dy³⁺, and Nd³⁺ ternary rare earth ions, with a molar ratio of Eu²⁺:Dy³⁺:Nd³⁺ = 1:0.4:0.3.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 is that the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is SrAl2O4 as the substrate, doped with Eu2+, Dy3+, Nd3+ ternary rare earth ions, the molar ratio is Eu2+:Dy3+:Nd3+=1:0.6:0.3.

[0041] Example 4

[0042] The difference between Example 4 and Example 1 is that the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is SrAl2O4 as the substrate, doped with Eu2+, Dy3+, Nd3+ ternary rare earth ions, the molar ratio is Eu2+:Dy3+:Nd3+=1:0.5:0.2.

[0043] Example 5

[0044] The difference between Example 5 and Example 1 is that the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is SrAl2O4 as the substrate, doped with Eu2+, Dy3+, Nd3+ ternary rare earth ions, the molar ratio is Eu2+:Dy3+:Nd3+=1:0.5:0.4.

[0045] Example 6

[0046] The difference between Example 6 and Example 1 is that the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is SrAl2O4 as the substrate, doped with Eu2+, Dy3+, Nd3+ ternary rare earth ions, the molar ratio is Eu2+:Dy3+:Nd3+=1:0.4:0.4.

[0047] Example 7

[0048] The difference between Example 7 and Example 1 is that the preparation method of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is SrAl2O4 as the substrate, doped with Eu2+, Dy3+, Nd3+ ternary rare earth ions, the molar ratio is Eu2+:Dy3+:Nd3+=1:0.6:0.2.

[0049] Example 8

[0050] The difference between Example 8 and Example 1 is that the supercritical CO2 assisted solid phase synthesis method is used to mix the raw materials according to the ratio; the parameters meet: the pressure is 10 MPa, the reaction temperature is 500 DEG C, the reaction time is 5 h, and the luminescent core to be coated is obtained after cooling.

[0051] Example 9

[0052] Example 9 differs from Example 1 in that the raw materials are mixed in proportion by using a supercritical CO2 assisted solid phase synthesis method; the parameters meet: the pressure is 10 MPa, the reaction temperature is 300°C, the reaction time is 3 h, and the obtained luminescent core to be coated is cooled.

[0053] Example 10

[0054] Example 10 differs from Example 1 in that the SiH4 / O2 flow ratio in step S3 is 1:1, and the deposition time is 20 min; then the coated material is immersed in a 0.5 wt% octadecyltrimethoxysilane / ethanol solution, reacted at 60°C for 1 h, washed with ethanol, and dried at 60°C to obtain a long afterglow luminescent material with a hydrophobic surface.

[0055] Example 11

[0056] Example 11 differs from Example 1 in that the SiH4 / O2 flow ratio in step S3 is 1:1, and the deposition time is 20 min; then the coated material is immersed in a 0.5 wt% octadecyltrimethoxysilane / ethanol solution, reacted at 60°C for 1 h, washed with ethanol, and dried at 60°C to obtain a long afterglow luminescent material with a hydrophobic surface.

[0057] Example 12

[0058] Example 12 differs from Example 1 in that red mud / fly ash is added as a functional filler in the raw materials, with an addition amount of 10 wt% relative to the total mass of the material, and the particle size is ≤5 μm.

[0059] Example 13

[0060] Example 13 differs from Example 1 in that red mud / fly ash is added as a functional filler in the raw materials, with an addition amount of 5 wt% relative to the total mass of the material, and the particle size is ≥5 μm.

[0061] Example 14

[0062] Example 14 differs from Example 1 in that in the step S113 of the pretreatment method of red mud / fly ash, the red mud powder / fly ash is mixed with the rare earth raw material in a mass ratio of 10:100, and ground into a uniform mixture.

[0063] Example 15

[0064] Example 15 differs from Example 1 in that the diameter of the ZnO nanorod is 90 nm, the height is 240 nm, and the areal density is 25 roots / μm².

[0065] Example 16

[0066] Example 16 differs from Example 1 in that the ZnO nanopillar has a diameter of 100 nm, a height of 300 nm, and a surface density of 30 per μm².

[0067] Comparative Example 1 Comparative Example 1 differs from Example 1 in that a preparation method of a long afterglow self-luminescent material based on multi-element rare earth synergistic sensitization is used, the material has a SrAl2O4 matrix, is doped with Eu2+, Dy3+, and Nd3+ ternary rare earth ions, and has a molar ratio of Eu2+:Dy3+:Nd3+=1:0.1:0.1.

[0068] Comparative Example 2 Comparative Example 2 differs from Example 1 in that a preparation method of a long afterglow self-luminescent material based on multi-element rare earth synergistic sensitization is used, the material has a SrAl2O4 matrix, is doped with Eu2+, Dy3+, and Nd3+ ternary rare earth ions, and has a molar ratio of Eu2+:Dy3+:Nd3+=1:1:1.

[0069] Comparative Example 3 Comparative Example 3 differs from Example 1 in that a supercritical CO2 assisted solid phase synthesis method is used to mix the raw materials according to the ratio; the parameters satisfy: a pressure of 1 MPa, a reaction temperature of 100°C, a reaction time of 1 h, and the luminescent core to be coated is obtained after cooling.

[0070] Comparative Example 4 Comparative Example 4 differs from Example 1 in that a supercritical CO2 assisted solid phase synthesis method is used to mix the raw materials according to the ratio; the parameters satisfy: a pressure of 20 MPa, a reaction temperature of 800°C, a reaction time of 4 h, and the luminescent core to be coated is obtained after cooling.

[0071] Comparative Example 5 Comparative Example 5 differs from Example 1 in that the surface of the long afterglow self-luminescent material is not hydrophobically modified.

[0072] Comparative Example 6 Comparative Example 6 differs from Example 1 in that red mud / fly ash is added to the above-mentioned raw materials as a functional filler, the amount of addition is 50 wt% relative to the total mass of the material, and the particle size satisfies ≤5 μm.

[0073] Comparative Example 7 Comparative Example 7 differs from Example 1 in that red mud / fly ash is added to the raw materials as a functional filler without pretreatment.

[0074] Comparative Example 8 Comparative Example 8 differs from Example 1 in that red mud / fly ash is not added to the above-mentioned raw materials as a functional filler.

[0075] Comparative Example 9 The difference between Comparative Example 9 and Example 1 is that: a preparation method of a long afterglow self-luminous material based on multi-element rare earth synergistic sensitization, the material is based on SrAl2O4 as a substrate, only doped with Eu²⁺ and Dy³⁺ two-element rare earth ions, and the molar ratio is Eu²⁺:Dy³⁺=1:0.5.

[0076] Comparative Example 10 The difference between Comparative Example 10 and Example 1 is that: the supercritical CO2 assisted solid phase synthesis method is not used, and the high temperature calcination method is used.

[0077] Comparative Example 11 The difference between Comparative Example 11 and Example 1 is that: the diameter of the ZnO nanocolumn is 500 nm, the height is 600 nm, and the surface density is 10 roots / μm².

[0078] Comparative Example 12 The difference between Comparative Example 12 and Example 1 is that: the diameter of the ZnO nanocolumn is 50 nm, the height is 100 nm, and the surface density is 50 roots / μm².

[0079] Comparative Example 13 The difference between Comparative Example 13 and Example 1 is that: the luminescent core is not coated with a zinc oxide nanocolumn array.

[0080] Performance test: Test Example 1 Afterglow time test: six samples of Example 1 were placed in natural light outdoors, and the irradiation time was 30 min, 1 h, 2 h, 4 h, 6 h and 8 h, respectively. Then the samples were immediately transferred to an electromagnetic shielding darkroom, and the background light intensity of the darkroom was not higher than 0.01 mcd / m 2 . A calibrated Topcon BM-7A low light brightness meter was used to continuously monitor the afterglow decay, and the detection sensitivity of the equipment reached 10⁻ 6 cd / m², and the test distance was fixed at 30 cm. The data acquisition adopts a segmented strategy: the decay trend is recorded at a high frequency of 10 min intervals for the first 2 h, and then it is continuously tracked at a 1 h interval for 8 h, and the data is averaged for 5 times. As can be seen from Table 1, irradiation for 4 h can meet the night lighting function, and the measured intensity at the 8 h node reaches 12.8 mcd / m 2 , which confirms that the 1.05 eV deep trap level constructed by Nd³⁺ dominates the long-term luminescence; and the 8 h intensity is 2.1 mcd / m 2 , and the performance improvement rate of the application reaches 293%.

[0081] Table 1 is the test result of the luminescent performance Main performance / irradiation time 30 min 1h 2 h 4 h 6 h 8 h Persistence brightness (mcd / m 2 ) 90 160 200 240 260 300 Afterglow time / h 2.1 6.4 7.2 9.4 12.3 12.8 Among them, from Figure 1It can be seen that the addition of ZnO has a certain good effect on the retention rate of afterglow intensity, because ZnO forms a Type-II heterojunction with the SrAl2O4 interface, and when the ZnO parameter reaches a certain limit, the 8h intensity loss is 27-33%, the photonic crystal periodicity is destroyed, non-radiative recombination is induced, and when there is no ZnO (Comparative Example 13), the 8h intensity drops by 65.9% to 4.2 mcd / m², because the photonic band gap disappears, the spontaneous radiation rate increases to 89% of free space, causing more than 60% radiation loss.

[0082] At the same time, from Table 2, it can be seen that in general, Example 1 (and Examples 2 to 7) demonstrates that SrAl2O4:Eu²⁺, Dy³⁺, Nd³⁺ is an excellent luminescent material with long afterglow time and stable luminescent properties, significantly longer than the classic representative substance and the comparative example due to improper proportioning, resulting in poor effect.

[0083] Table 2 is a comparison of afterglow time Category Classical representative substance Luminescence color Afterglow time / h Main emission peak / nm Sulfide ZnS: Cu, Co Yellow-green 2 530 Silicate [Ca1-xSrx]SiO3:Eu 2+ , Dy 3+ ]]> Blue 4 470 Aluminate SrAl2O4:Eu 2+ , Dy 3+ ]]> Yellow-green 4.2 520 Example 1 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.3 520 Example 2 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.2 520 Example 3 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.1 520 Example 4 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.0 520 Example 5 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.3 520 Example 6 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.2 520 Example 7 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 8.1 520 Comparative Example 1 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 5 520 Comparative Example 2 [Ca1-xSrx]Al2O4:Eu2+,Dy3+,Nd3+ Yellow-green 5.2 520 Comparative Example 9 [Ca1-xSrx]Al2O4:Eu2+,Dy3+ Yellow-green 4.5 520 At the same time, the influence of the supercritical CO2 assisted solid phase synthesis method on the afterglow time retention is explored, from Figure 2 It can be seen that the supercritical CO2 assisted pressure and temperature have a great influence on the retention length of afterglow time, and it can be concluded that at 8 MPa, the reaction temperature is 320°C, and the reaction time is 4 h, the afterglow retention time is the longest, and the afterglow time of the supercritical CO2 assisted solid phase method is lower than that of Comparative Example 5 using the high temperature solid phase method, the reason is that its core principle is: to avoid high temperature defects by using low temperature and high diffusion characteristics, to inhibit non-radiative recombination by in-situ surface passivation, and to precisely construct deep traps (Nd³⁺ density increased by 253%). In contrast, the high temperature solid phase method causes the afterglow time to decrease by 50.4% due to phase change, volatilization, and vacancy defects.

[0084] Test Example 2 High-temperature stability test: The high-temperature stability test from Table 3 shows that after aging at 60°C for 72 h and recovering for 24 h, the initial afterglow intensity retention rate of the sample of Example 1, which was added with 5 wt% of red mud fly ash with a particle size of ≤5 μm, dried at 250°C for 2 h, ball-milled at 300 rpm for 3 h, and mixed and ground at a mass ratio of red mud powder to rare earth raw material of 5:100, reached 82.3%, and the average value of five repetitions was stable and reliable. Under the same test conditions, the time length of the afterglow intensity of the aged sample maintaining above 10 mcd / m² was still 6.8 h, and the intensity at 8 h was maintained at 10.5 mcd / m², confirming that the Nd³⁺ deep trap level was structurally stable without thermal quenching in a high-temperature environment. The comparative groups showed significant degradation: the retention rate of Example 12 with a red mud content of 10 wt% decreased to 76.1%, and excessive red mud caused interfacial thermal stress; the retention rate of Example 13 with a particle size of ≥5 μm was only 69.5%, and coarse particles damaged the dispersion and thermal conductivity; the retention rate of Example 14 with a red mud to rare earth ratio of 10:100 decreased to 74.8%, and excessive rare earth led to amorphous phase impurities; the retention rate of Comparative Example 6 with a content of 50 wt% decreased to 43.2%, and the super-high content collapsed the matrix structure; the retention rate of Comparative Example 7 without pretreatment was only 58.6%, and residual water vapor and sodium ions induced high-temperature hydrolysis; and the afterglow retention rate of Comparative Example 8 without the addition of functional materials decreased to 33.4%. The key influencing factors can be attributed to the synergistic effect of low red mud fly ash content, fine particle size, and standard pretreatment process.

[0085] Table 3: Afterglow retention rate under different red mud / fly ash addition conditions Group Red mud / fly ash content Particle size requirement Afterglow retention rate (72 h / 60°C) Example 1 5 wt% ≤ 5 μm 82.3% Example 12 10 wt% ≤ 5 μm 76.1% Example 13 5 wt% ≥ 5 μm 69.5% Example 14 5 wt% ≤ 5 μm 74.8% Comparative Example 6 50 wt% ≤ 5 μm 43.2% Comparative Example 7 5 wt% ≤ 5 μm 58.6% Comparative Example 8 / / 33.4% Test Example 3 Environmental safety requirement test: The material passed the strict volatile organic compound quantitative test, and the VOC content measured value was less than 45 g / L, lower than the standard specified threshold limit value of 50 grams per liter, indicating that the substance release risk was in the industry-leading safe interval. In terms of carbon footprint accounting, based on the ISO 14067 life cycle assessment method, combined with the whole process data collection from raw material mining, synthesis manufacturing to finished product packaging, the carbon emission intensity of each kilogram of product was measured to be 5.8 kilograms of carbon dioxide equivalent, which was significantly reduced by 32% compared with the traditional strontium aluminate europium and dysprosium phosphor benchmark value of 8.5 kilograms of carbon dioxide equivalent. In addition, the heavy metal migration test met the safety standards, and harmful elements such as lead, cadmium, and mercury were not detected, indicating that it had both ecological safety and industrial sustainability, fully meeting the requirements of green building material certification.

[0086] Test Example 4 Water resistance analysis: All samples were accelerated by a constant temperature water bath at 40°C and sampled for detection at regular intervals. For example, Figure 3As shown, the raw material without surface treatment completely lost the afterglow performance after 168 h immersion, while the comparative example 5 with only SiO2 coating still maintained 41% afterglow intensity retention, confirming that the inorganic coating layer can provide a basic physical barrier. Under the same coating conditions, the sample modified by octadecyltrimethoxysilane made the 168 h retention rate increase from 41% to 87%, indicating that the successful grafting of long-chain alkyl effectively blocked the penetration of water molecules. When the optimized process combination was used, i.e. the SiH4 / O2 flow ratio was increased to 1:3 and the deposition time was 50 min, combined with high concentration 2 wt% octadecyltrimethoxysilane modification, example 11 exhibited the highest retention rate of 94%, indicating that the synergistic effect of thickening the coating layer and dense alkyl chains significantly strengthened the water resistance stability. The contact angle test in Table 4 further confirmed the modification effect: the contact angles of all hydrophobic treated samples were more than 128°, confirming that a stable hydrophobic layer was formed on the surface; among them, the contact angle of the 2 wt% high concentration modified sample reached 152°, reaching the super-hydrophobic state, which was significantly better than the 128° of the 0.5 wt% modified sample.

[0087] Table 4: Influence of surface coating on hydrophobic performance Group Contact angle Comparative Example 5 35° Example 10 142° Example 1 128° Example 11 152° Obviously, the above examples are only examples for clearly illustrating, but not limitation of the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application. A long afterglow self-luminous material based on multi-element rare earth synergistic sensitization and a preparation method thereof.

Claims

1. A long-afterglow self-luminescent material based on multi-element rare earth synergistic sensitization, characterized in that: Using SrAl2O4 as a matrix, ternary rare earth ions of Eu²⁺, Dy³⁺, and Nd³⁺ are doped to form a luminescent core to be coated. The molar ratio of Eu²⁺, Dy³⁺, and Nd³⁺ is 1:(0.4-0.6):(0.2-0.4). ZnO nanopillar arrays are epitaxially grown in situ on the surface of the luminescent core, and a hydrophobic modified SiO2 shell is coated on the surface of the ZnO nanopillars. The thickness of the SiO2 shell is 50-100 nm.

2. The method for preparing long-afterglow self-luminescent materials based on multi-element rare earth synergistic sensitization according to claim 1, characterized in that, Includes the following steps: S1. A supercritical CO2-assisted solid-phase synthesis method is used, and raw materials are mixed according to the specified ratio; After cooling, the luminescent core to be coated is obtained; S2. The luminescent core obtained in step S1 is coated with zinc oxide nanopillars to obtain the SrAl2O4:Eu²⁺,Dy³⁺,Nd³⁺@ZnO nanopillar core-shell precursor; S3. A SiO2 shell layer is deposited on the surface of the SrAl2O4:Eu²⁺,Dy³⁺,Nd³⁺@ZnO nanopillar core-shell precursor obtained in step S2 using plasma-enhanced chemical vapor deposition. The coating material is then immersed in a silane coupling agent solution for reaction, washed, and dried to obtain a long afterglow self-luminescent material.

3. The method for preparing long-afterglow self-luminescent materials based on multi-element rare earth synergistic sensitization according to claim 2, characterized in that: The parameters for the supercritical CO2 are: pressure of 8-10 MPa, reaction temperature of 300-500℃, and reaction time of 3-5 h.

4. The method for preparing long-afterglow self-luminescent materials based on multi-element rare earth synergistic sensitization according to claim 2, characterized in that, The method for coating zinc oxide nanopillars around a luminescent core includes the following steps: S11. Immerse the luminescent nucleus in a 0.05~0.2M zinc acetate ethanol solution and bake at 60~100℃ to form a seed crystal layer; S12. Place the seed crystal layer from step S11 into a reaction solution containing 0.05M zinc nitrate and 0.05M hexamethylenetetramine at pH=10-11 and grow at 60~120℃ for 2 h to obtain powder. S13. After centrifuging and washing the powder from step S12, anneal it at 300~500℃ for 1~3h to obtain SrAl2O4:Eu²⁺,Dy³⁺,Nd³⁺@ZnO nanopillar core-shell precursor.

5. The method for preparing long-afterglow self-luminescent materials based on multi-element rare earth synergistic sensitization according to claim 2, characterized in that: In step S3, the deposition parameters are: SiH4 / O2 flow ratio 1:(1-3), deposition time 20-50 min; the silane coupling agent is octadecyltrimethoxysilane with a concentration of 0.5-2 wt%, and the reaction parameters are: reaction at 60-80℃ for 1-3 h, followed by washing with ethanol and drying at 50-100℃ to form a hydrophobic functionalized SiO2 coating layer.

6. The long-afterglow self-luminescent material based on multi-element rare earth synergistic sensitization according to claim 1, characterized in that: The luminescent core is also mixed with red mud / fly ash as a functional filler, with an addition amount of 5-30 wt% relative to the total mass of the material and a particle size ≤5 μm.

7. The long-afterglow self-luminescent material based on multi-element rare earth synergistic sensitization according to claim 6, characterized in that, The preparation method of the functional filler includes the following steps: S111. Dry the red mud / fly ash at 200~300℃ under an inert atmosphere for 1.5~2.5 h; S112. Place the dried red mud / fly ash from step S111 into a ball mill and ball mill at 200~500 rpm for 2~5 hours; S113. Mix and grind the powder obtained in step S112 with the luminescent core material at a mass ratio of (5-30):

100.

8. The long-afterglow self-luminescent material based on multi-element rare earth synergistic sensitization according to claim 1, characterized in that: The ZnO nanopillars have an average diameter of 80-100 nm, an average height of 240-300 nm, and an average areal density of 20-30 nanopillars / μm².

9. The application of the long afterglow self-luminous material based on multi-element rare earth synergistic sensitization as described in claim 1 in road marking paint, tunnel signage, building escape routes, or safety emergency signs.

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