Rare earth element doped composite phase change material and preparation method thereof

Abstract

The invention discloses a rare earth element doped composite phase change material and a preparation method thereof. The preparation method comprises the following steps: mixing yttrium nitrate with a dysprosium nitrate solution, adjusting the pH value to 10, and heating and precipitating to prepare rare earth doped nanoparticles; the preparation method comprises the following steps: dissolving a polyurethane prepolymer and a rare earth coordination compound in dimethylformamide, and stirring to form a uniform solution; melting paraffin, adding nanoparticles and a surfactant, and carrying out ultrasonic dispersion; mixing the mixture with a disulfide bond-containing polyurethane solution, and adding a cross-linking agent to form a precursor; and finally, carrying out microencapsulation on the melamine-formaldehyde resin to obtain the composite material. The latent heat capacity of the material reaches 175-182J / g, the thermal conductivity is 0.40-0.46 W / (m.K), the mechanical strength is 11.8-12.5 MPa, and the thermal cycle stability is 93-96%.

Description

Technical Field

[0001] The present invention relates to the technical field of composite phase change materials, and in particular to a rare earth element-doped composite phase change material and a preparation method thereof. Background Art

[0002] Phase change materials (PCMs) have been widely used in building energy conservation, electronic device thermal management, solar energy utilization, and textiles due to their excellent performance in thermal energy storage and management. Rare earth element-doped phase change materials have attracted much attention due to their combined thermal energy storage and optical functions. In recent years, with the development of materials science, researchers have been able to dope rare earth elements (such as Eu 3+ 、Tb 3+ 、Yb 3+ ) or combined with nanostructures (such as metal organic frameworks, nanoparticles) have significantly improved the latent heat storage capacity and optical properties of phase change materials. For example, rare earth-doped composite phase change materials have achieved thermal-optical dual-functional applications through up-conversion or down-conversion luminescence mechanisms, expanding their potential in sensors and smart devices. In addition, advances in preparation methods such as microencapsulation technology, nanocomposite technology and interface optimization have further improved the thermal conductivity and phase change stability of phase change materials. However, existing technologies mainly focus on improving a single performance (such as latent heat or luminescence efficiency), and research on the long-term performance and multifunctional integration of materials under complex working conditions is still insufficient, especially the mechanical and chemical stability issues under repeated thermal cycles have not been fully resolved.

[0003] Despite the significant technological progress mentioned above, existing rare earth doped composite phase change materials still face several key technical bottlenecks in practical applications, especially in the process of repeated thermal cycling, which is prone to mechanical degradation and phase separation, resulting in a significant shortening of the material's service life. Specifically, organic phase change materials (such as paraffin wax, fatty acids) often produce microcracks or pores due to molecular chain rearrangement or interfacial stress accumulation after multiple solid-liquid phase changes, reducing mechanical strength; inorganic phase change materials (such as hydrated salts) cause latent heat efficiency to decay due to phase separation or supercooling. Existing technologies attempt to alleviate these problems by adding reinforcing phases or optimizing packaging structures, but these methods often sacrifice thermal conductivity or latent heat capacity, and lack targeted solutions to the fundamental mechanisms of mechanical degradation (such as interface fatigue and molecular migration). In addition, the heterogeneous interface introduced by rare earth doping may further aggravate phase separation or stress concentration, especially under long-term thermal cycling, where the uneven distribution of doping elements may induce local performance degradation. In response to the above shortcomings, the present invention proposes a rare earth element doped composite phase change material and a preparation method thereof. Summary of the Invention

[0004] The present application provides a method for preparing a rare earth element-doped composite phase change material, comprising the following technical steps:

[0005] Step S1. Mixing yttrium nitrate with a rare earth precursor solution, adjusting the pH to 10 to form a precipitate, heating and cooling the mixture, and centrifuging the product to obtain rare earth-doped nanoparticles;

[0006] Step S2. The polyurethane prepolymer and the rare earth coordination compound are added to dimethylformamide and stirred under a nitrogen atmosphere to form a uniform solution;

[0007] Step S3. Melting the phase change material, adding rare earth-doped nanoparticles, dispersing the nanoparticles using ultrasonic oscillation, and adding a surfactant;

[0008] Step S4. Mixing the mixture of the phase change material and the nanoparticles with the self-healing polymer solution, adding a crosslinking agent and continuing to stir to form a viscous composite precursor;

[0009] Step S5. Mix the melamine-formaldehyde resin with deionized water, adjust the pH to 4.5, and add the complex precursor dropwise to the shell forming solution under high-speed stirring to react and form microcapsules.

[0010] As a preferred technical solution for a method for preparing a rare earth element-doped composite phase change material, in step S1, the rare earth precursor solution is a dysprosium nitrate solution, and the yttrium nitrate and the dysprosium nitrate solution are mixed in a molar ratio of 95:5 to 95:15.

[0011] As a preferred technical solution for a method for preparing a rare earth element-doped composite phase change material, in step S2, the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine.

[0012] As a preferred technical solution for the preparation of a rare earth element-doped composite phase change material, in step S3, the rare earth-doped nanoparticles account for 2 wt % to 5 wt % of the phase change material.

[0013] As a preferred technical solution for the preparation of a rare earth element-doped composite phase change material, in step S3, the phase change material is paraffin, the surfactant is polysorbate, sodium lauryl sulfate or, and the surfactant accounts for 0.1% to 0.4% of the mass of the phase change material.

[0014] As a preferred technical solution for the preparation of a rare earth element-doped composite phase change material, in step S4, the self-healing polymer is a polyurethane containing disulfide bonds, the cross-linking agent is hexamethylene diisocyanate, and the cross-linking agent accounts for 1wt% to 2wt% of the polyurethane containing disulfide bonds.

[0015] As a preferred technical solution for the preparation of a rare earth element-doped composite phase change material, in step S4, the phase change material-nanoparticle mixture is mixed with a disulfide bond-containing polyurethane solution in a mass ratio of 70:20 to 70:40.

[0016] As a preferred technical solution for the preparation of a rare earth element-doped composite phase change material, in step S5, the mass ratio of the melamine-formaldehyde resin to deionized water is 1:5-1:10.

[0017] The rare earth element doped composite phase change material and its preparation method provided by the present invention have significant beneficial effects. By introducing rare earth nanoparticles co-doped with yttrium nitrate and dysprosium nitrate (molar ratio 95:5 to 95:15), combined with disulfide bond-containing polyurethane self-healing polymer and melamine-formaldehyde resin microencapsulation technology, the material exhibits excellent latent heat capacity (175-182 J / g), high thermal conductivity (0.40-0.46 W / (m·K)), excellent mechanical strength (11.8-12.5 MPa) and outstanding thermal cycling stability (93-96% retention rate, 1000 cycles). Rare earth doping enhances thermal and optical properties, microencapsulation effectively prevents leakage and phase separation of phase change materials, and self-healing polymers improve long-term mechanical durability. These characteristics give the material broad application prospects in the fields of building energy conservation, thermal management of electronic devices and smart devices, which are significantly superior to traditional phase change materials. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0021] Example

[0022] Example 1

[0023] Example 1 provides a method for preparing a rare earth element-doped composite phase change material, comprising the following technical steps:

[0024] Step S1. Yttrium nitrate and dysprosium nitrate solutions were mixed in a molar ratio of 95:5, 1 mol / L sodium hydroxide was added dropwise, and the pH was adjusted to 10 to form a precipitate. The mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 200°C for 10 hours. After cooling, the product was centrifuged, washed with ethanol and deionized water, and dried at 80°C for 6 hours to obtain rare earth-doped nanoparticles.

[0025] Step S2. The polyurethane prepolymer and the rare earth coordination compound are dissolved in dimethylformamide (DMF) in a mass ratio of 2:1, wherein the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine, and stirred at 60°C for 2 hours under a nitrogen atmosphere to form a uniform solution;

[0026] Step S3. Paraffin was melted at 70°C, and 5 wt% of rare earth-doped nanoparticles were added to the paraffin. The nanoparticles were dispersed using ultrasonic oscillation (frequency: 20 kHz, power: 150 W, time: 30 minutes) for 30 minutes. The temperature was maintained at 70°C, and 0.1 wt% of polysorbate was added.

[0027] Step S4. The phase change material-nanoparticle mixture and the disulfide bond-containing polyurethane solution are mixed in a mass ratio of 70:30 and stirred at 500 rpm at 60°C for 1 hour to achieve uniformity. A crosslinker (e.g., hexamethylene diisocyanate) is added at 1 wt% of the disulfide bond-containing polyurethane to initiate polymerization. Stirring is continued for 30 minutes to form a viscous composite precursor.

[0028] Step S5. Melamine-formaldehyde resin and deionized water were mixed in a mass ratio of 1:10, the pH was adjusted to 4.5 with acetic acid, and the complex precursor was added dropwise to the shell forming solution under high-speed stirring at 55°C and 1000 rpm. The reaction was continued for 3 hours to form microcapsules.

[0029] Example 2

[0030] Example 2 provides a method for preparing a rare earth element-doped composite phase change material, comprising the following technical steps:

[0031] Step S1. Yttrium nitrate and dysprosium nitrate solutions were mixed in a molar ratio of 95:15, 1 mol / L sodium hydroxide was added dropwise, and the pH was adjusted to 10 to form a precipitate. The mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 150°C for 8 hours. After cooling, the product was centrifuged, washed with ethanol and deionized water, and dried at 80°C for 6 hours to obtain rare earth-doped nanoparticles;

[0032] Step S2. The polyurethane prepolymer and the rare earth coordination compound are dissolved in dimethylformamide (DMF) in a mass ratio of 1:1, wherein the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine, and stirred at 60°C for 2 hours under a nitrogen atmosphere to form a uniform solution;

[0033] Step S3. Melt paraffin at 70°C, add 2 wt% of rare earth-doped nanoparticles to the paraffin, and disperse the nanoparticles using ultrasonic oscillation (frequency: 40 kHz, power: 100 W, time: 10 minutes) for 30 minutes. Maintain the temperature at 70°C, and add 0.4 wt% of sodium lauryl sulfate to the paraffin.

[0034] Step S4. The phase change material-nanoparticle mixture and the disulfide bond-containing polyurethane solution are mixed in a mass ratio of 70:40 and stirred at 500 rpm at 60°C for 1 hour to achieve uniformity. A crosslinker (e.g., hexamethylene diisocyanate) is added to initiate polymerization, and stirring is continued for 30 minutes to form a viscous composite precursor.

[0035] Step S5. Melamine-formaldehyde resin and deionized water were mixed in a mass ratio of 1:10, the pH was adjusted to 4.5 with acetic acid, and the complex precursor was added dropwise to the shell forming solution under high-speed stirring at 55°C and 2000 rpm. The reaction was continued for 3 hours to form microcapsules.

[0036] Example 3

[0037] Example 3 provides a method for preparing a rare earth element-doped composite phase change material, comprising the following technical steps:

[0038] Step S1. Yttrium nitrate and dysprosium nitrate solutions were mixed in a molar ratio of 95:8, 1 mol / L sodium hydroxide was added dropwise, and the pH was adjusted to 10 to form a precipitate. The mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 150°C for 15 hours. After cooling, the product was centrifuged, washed with ethanol and deionized water, and dried at 80°C for 8 hours to obtain rare earth-doped nanoparticles.

[0039] Step S2. The polyurethane prepolymer and the rare earth coordination compound are dissolved in dimethylformamide (DMF) in a mass ratio of 2:1, wherein the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine, and stirred at 60°C for 2 hours under a nitrogen atmosphere to form a uniform solution;

[0040] Step S3. Melt paraffin at 70°C, add 2 wt% of rare earth-doped nanoparticles to the paraffin, and disperse the nanoparticles using ultrasonic oscillation (frequency: 40 kHz, power: 100 W, time: 10 minutes) for 30 minutes. Maintain the temperature at 70°C, and add 0.3 wt% of polyvinylpyrrolidone to the paraffin.

[0041] Step S4. The phase change material-nanoparticle mixture and the disulfide bond-containing polyurethane solution are mixed in a mass ratio of 70:30 and stirred at 500 rpm at 60°C for 1 hour to achieve uniformity. A crosslinker (e.g., hexamethylene diisocyanate) is added to initiate polymerization, accounting for 2 wt% of the disulfide bond-containing polyurethane solution. Stirring is continued for 30 minutes to form a viscous composite precursor.

[0042] Step S5. Melamine-formaldehyde resin and deionized water were mixed in a mass ratio of 1:8, the pH was adjusted to 4.5 with acetic acid, and the complex precursor was added dropwise to the shell forming solution under high-speed stirring at 55°C and 1500 rpm. The reaction was continued for 3 hours to form microcapsules.

[0043] Example 4

[0044] Example 4 provides a method for preparing a rare earth element-doped composite phase change material, comprising the following technical steps:

[0045] Step S1. Yttrium nitrate and dysprosium nitrate solutions were mixed in a molar ratio of 95:10, 1 mol / L sodium hydroxide was added dropwise, and the pH was adjusted to 10 to form a precipitate. The mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 180°C for 15 hours. After cooling, the product was centrifuged, washed with ethanol and deionized water, and dried at 80°C for 8 hours to obtain rare earth-doped nanoparticles;

[0046] Step S2. The polyurethane prepolymer and the rare earth coordination compound are dissolved in dimethylformamide (DMF) in a mass ratio of 3:1, wherein the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine, and stirred at 60°C for 2 hours under a nitrogen atmosphere to form a uniform solution;

[0047] Step S3. Melt paraffin at 70°C, add 5 wt% of rare earth-doped nanoparticles to the paraffin, and disperse the nanoparticles using ultrasonic oscillation (frequency: 40 kHz, power: 100 W, time: 10 minutes) for 30 minutes. Maintain the temperature at 70°C, and add 0.4 wt% of polyvinylpyrrolidone to the paraffin.

[0048] Step S4. The phase change material-nanoparticle mixture and the disulfide bond-containing polyurethane solution are mixed in a mass ratio of 70:30 and stirred at 500 rpm at 60°C for 1 hour to achieve uniformity. A crosslinker (e.g., hexamethylene diisocyanate) is added to initiate polymerization, and stirring is continued for 30 minutes to form a viscous composite precursor.

[0049] Step S5. Melamine-formaldehyde resin and deionized water were mixed in a mass ratio of 1:10, the pH was adjusted to 4.5 with acetic acid, and the complex precursor was added dropwise to the shell forming solution under high-speed stirring at 55°C and 1500 rpm. The reaction was continued for 3 hours to form microcapsules.

[0050] Control Example

[0051] Comparative Example 1: Composite Phase Change Material without Rare Earth Doped Nanoparticles

[0052] Step S1: Omit the preparation of rare earth-doped nanoparticles and jump directly to step S2.

[0053] Step S2: According to the conditions of Example 1, the polyurethane prepolymer and the rare earth coordination compound (LaCl3 and 2,2'-bipyridine chelate) were dissolved in dimethylformamide (DMF) at a mass ratio of 2:1, and stirred at 60°C for 2 hours under a nitrogen atmosphere to form a uniform solution.

[0054] Step S3: melt paraffin at 70° C., add 0.1 wt % polysorbate as a surfactant (without rare earth-doped nanoparticles), and stir evenly.

[0055] Step S4: paraffin wax and disulfide bond-containing polyurethane solution were mixed in a mass ratio of 70:30, stirred at 500 rpm at 60° C. for 1 hour, 1 wt % hexamethylene diisocyanate was added as a cross-linking agent, and stirring was continued for 30 minutes to form a viscous composite precursor.

[0056] Step S5: Melamine-formaldehyde resin and deionized water were mixed in a mass ratio of 1:10, the pH was adjusted to 4.5 with acetic acid, and the complex precursor was added dropwise to the shell forming solution under high-speed stirring at 55°C and 1000 rpm. The mixture was reacted for 3 hours to form microcapsules.

[0057] Comparative Example 2: Using ordinary polyurethane instead of polyurethane containing disulfide bonds

[0058] Step S1: According to the conditions of Example 1, yttrium nitrate and dysprosium nitrate solution were mixed in a molar ratio of 95:5, the pH was adjusted to 10, and the mixture was heated at 200° C. for 10 hours. The mixture was centrifuged, washed, and dried to obtain rare earth-doped nanoparticles.

[0059] Step S2: As in Example 1, the polyurethane prepolymer and the rare earth coordination compound (LaCl 3 and 2,2'-bipyridine chelate) were dissolved in DMF at a mass ratio of 2:1 and stirred at 60° C. for 2 hours under a nitrogen atmosphere.

[0060] Step S3: melt paraffin at 70° C., add 5 wt % of rare earth-doped nanoparticles, perform ultrasonic oscillation (20 kHz, 150 W, 30 minutes), and add 0.1 wt % of polysorbate.

[0061] Step S4: The phase change material-nanoparticle mixture was mixed with a common polyurethane solution (without disulfide bonds) in a mass ratio of 70:30, stirred at 500 rpm at 60° C. for 1 hour, 1 wt % hexamethylene diisocyanate was added, and stirring was continued for 30 minutes to form a composite precursor.

[0062] Step S5: As in Example 1, melamine-formaldehyde resin and deionized water were mixed at a mass ratio of 1:10, the pH was adjusted to 4.5, and the mixture was stirred at 55° C. and 1000 rpm. The precursor was added dropwise and reacted for 3 hours to form microcapsules.

[0063] Control Example 3: No microencapsulation

[0064] Steps S1-S4: Prepare completely according to the steps of Example 1, that is, prepare rare earth doped nanoparticles, rare earth coordination compound solution, phase change material-nanoparticle mixture, and mix them with disulfide bond-containing polyurethane solution to form a composite precursor.

[0065] Step S5: The microencapsulation step is omitted, and the composite precursor obtained in step S4 is directly dried in vacuum at 60° C. for 6 hours to obtain a solid composite phase change material.

[0066] Comparative Example 4: Using a single rare earth element (without dysprosium nitrate doping)

[0067] Step S1: Using only yttrium nitrate solution (without dysprosium nitrate), 1 mol / L sodium hydroxide was added dropwise, the pH was adjusted to 10, and the solution was heated at 200°C for 10 hours, centrifuged, washed, and dried at 80°C for 6 hours to obtain single rare earth (yttrium) nanoparticles.

[0068] Steps S2-S5: The steps of Example 1 are completely followed, i.e., rare earth coordination compounds, disulfide bond-containing polyurethane, microencapsulation and other processes are used. The only difference is that single rare earth (yttrium) nanoparticles (5 wt%) are added in step S3.

[0069] Performance testing methods

[0070] 1. Latent heat capacity (ΔH): measures the material’s ability to store heat;

[0071] 2. Phase transition temperature (Tm): reflects the operating temperature range of the material;

[0072] 3. Thermal conductivity (k): affects heat transfer efficiency;

[0073] 4. Mechanical strength (σ): evaluates the durability of the material under repeated thermal cycles;

[0074] 5. Thermal Cycle Stability (ΔH Retention): Evaluates the performance retention of a material after multiple thermal cycles;

[0075] Table 1

[0076]

[0077]

[0078] Combining Examples 1 to 4 and Table 1, it can be seen that the latent heat capacity of the rare earth element doped composite phase change materials of Examples 1 to 4 is 175-182 J / g, and the phase transition temperature is

[0079] The material has a temperature of 54.8-55.2℃, a thermal conductivity of 0.40-0.46W / (m·K), a mechanical strength of 11.8-12.5MPa and a thermal cycling stability of 93-96%. The synergistic effect of rare earth-doped nanoparticles (yttrium nitrate and dysprosium nitrate) and disulfide bond-containing polyurethane enhances the heat transfer efficiency and mechanical stability. The microencapsulation technology further improves the material's interface stability and resistance to thermal cycling degradation.

[0080] Combining Example 1, Comparative Example 1, and Table 1, it can be seen that the rare earth element-doped composite phase change material of Example 1 is superior to Comparative Example 1 (latent heat capacity 170 J / g, phase transition temperature 54.5°C, thermal conductivity 0.30 W / (m·K), mechanical strength 10.5 MPa, and thermal cycling stability 85%) in terms of latent heat capacity (180 J / g), phase transition temperature (55.0°C), thermal conductivity (0.45 W / (m·K)), mechanical strength (12.5 MPa), and thermal cycling stability (95%). Specifically, Example 1 has a 10 J / g higher latent heat capacity, a 50% increase in thermal conductivity, a 19% increase in mechanical strength, and a 10% increase in thermal cycling stability. This is because Example 1 introduces rare earth-doped nanoparticles (yttrium nitrate to dysprosium nitrate in a 95:5 molar ratio), which enhance heat transfer efficiency and interface stability through ultrasonic dispersion and microencapsulation technology. The rare earth element doping also optimizes the thermal and optical properties of the material. In contrast, the control example 1 omitted the rare earth doped nanoparticles, resulting in lower thermal conductivity and latent heat capacity, and the lack of synergistic effect of rare earth elements significantly reduced the mechanical strength and long-term thermal cycling stability.

[0081] Combining Example 1, Control Example 2 and Table 1, it can be seen that the rare earth element doped composite phase change material of Example 1 is superior to Control Example 2 (latent heat capacity 176 J / g, phase transition temperature 55.0°C, thermal conductivity 0.43 W / (m·K)), mechanical strength (12.5 MPa) and thermal cycling stability (95%) in terms of latent heat capacity (180 J / g), phase transition temperature 55.0°C, thermal conductivity 0.43 W / (m·K), mechanical strength 8.5 MPa, thermal cycling stability 80%). The reason is that Example 1 uses a polyurethane containing disulfide bonds as a self-healing polymer, whose dynamic chemical bonds can repair microcracks during thermal cycling, enhance mechanical durability and interface stability, and rare earth doped nanoparticles (yttrium nitrate and dysprosium nitrate) further optimize heat transfer and structural stability. In contrast, Control Example 2 uses ordinary polyurethane, which lacks self-healing function, resulting in a significant decrease in mechanical strength and thermal cycling stability. Although the thermal conductivity is still high due to rare earth doping, the overall performance is limited.

[0082] Combining Example 1, Comparative Example 3, and Table 1, it can be seen that the rare earth element-doped composite phase change material of Example 1 significantly outperforms Comparative Example 3 (latent heat capacity 165 J / g, phase transition temperature 54.7°C, thermal conductivity 0.38 W / (m·K), mechanical strength 9.0 MPa, and thermal cycling stability 75%) in terms of latent heat capacity (180 J / g), phase transition temperature (55.0°C), thermal conductivity (0.45 W / (m·K)), mechanical strength (12.5 MPa), and thermal cycling stability (95%). Specifically, Example 1 has a 15 J / g higher latent heat capacity, an 18.4% increase in thermal conductivity, a 38.9% increase in mechanical strength, and a 26.7% increase in thermal cycling stability. This is because Example 1 effectively encapsulates the phase change material and rare earth-doped nanoparticles through microencapsulation technology (melamine-formaldehyde resin shell layer), enhancing interfacial stability and resistance to phase separation. The self-healing properties of the disulfide bond-containing polyurethane further improve the material's durability during thermal cycling. In contrast, the control example 3 omitted the microencapsulation step, which resulted in the phase change material being prone to leakage and phase separation during repeated thermal cycles, and the dispersion stability of the rare earth-doped nanoparticles decreased, thereby significantly reducing the latent heat capacity, thermal conductivity, mechanical strength and thermal cycle stability.

[0083] Combining Example 1, Comparative Example 4, and Table 1, it can be seen that the rare earth element-doped composite phase change material of Example 1 is superior to Comparative Example 4 (latent heat capacity 178 J / g, phase transition temperature 55.0°C, thermal conductivity 0.35 W / (m·K), mechanical strength 11.5 MPa, and thermal cycling stability 90%) in terms of latent heat capacity (180 J / g), phase transition temperature (55.0°C), thermal conductivity (0.45 W / (m·K)), mechanical strength (12.5 MPa), and thermal cycling stability (95%). Specifically, Example 1 has a slightly higher latent heat capacity of 2 J / g, a significant increase in thermal conductivity by 28.6%, an increase in mechanical strength by 8.7%, and an improvement in thermal cycling stability by 5.6%. The reason is that Example 1 uses rare earth nanoparticles co-doped with yttrium nitrate and dysprosium nitrate (95:5 molar ratio). The dysprosium doping enhances the thermal and optical properties of the material through a synergistic effect, improving thermal conductivity and structural stability, while the self-healing properties of microencapsulation and disulfide bond-containing polyurethane further consolidate long-term performance. In contrast, Control Example 4 uses only a single rare earth (yttrium) nanoparticle, lacking the synergistic effect of dysprosium, resulting in lower thermal conductivity. The singleness of the doping element limits interface optimization and thermal cycle stability, and the mechanical strength and latent heat capacity are also slightly inferior to those of Example 1.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth element-doped composite phase change material, characterized in that: The following technical steps are included: Step S1. Mixing yttrium nitrate with a rare earth precursor solution, adjusting the pH to 10 to form a precipitate, heating and cooling the mixture, and centrifuging the product to obtain rare earth-doped nanoparticles; Step S2. The polyurethane prepolymer and the rare earth coordination compound are added to dimethylformamide and stirred under a nitrogen atmosphere to form a uniform solution; Step S3. Melting the phase change material, adding rare earth-doped nanoparticles, dispersing the nanoparticles using ultrasonic oscillation, and adding a surfactant; Step S4. Mixing the mixture of the phase change material and the nanoparticles with the self-healing polymer solution, adding a crosslinking agent and continuing to stir to form a viscous composite precursor; Step S5. Mix the melamine-formaldehyde resin with deionized water, adjust the pH to 4.5, and add the complex precursor dropwise to the shell forming solution under high-speed stirring to react and form microcapsules.

2. The method for preparing a rare earth element-doped composite phase change material according to claim 1, wherein: In step S1 , the rare earth precursor solution is a dysprosium nitrate solution, and the yttrium nitrate and the dysprosium nitrate solution are mixed in a molar ratio of 95:5 to 95:

15.

3. The method for preparing a rare earth element-doped composite phase change material according to claim 1, wherein: In step S2, the rare earth coordination compound is a chelate synthesized by coordination of LaCl3 and 2,2'-bipyridine.

4. The method for preparing a rare earth element-doped composite phase change material according to claim 1, wherein: In step S3 , the rare earth-doped nanoparticles account for 2 wt % to 5 wt % of the phase change material.

5. The method for preparing a rare earth element-doped composite phase change material according to claim 1, wherein: In step S3, the phase change material is paraffin, the surfactant is polysorbate, sodium lauryl sulfate or, and the surfactant accounts for 0.1% to 0.4% of the mass of the phase change material.

6. The method for preparing a rare earth element-doped composite phase change material according to claim 1, wherein: In step S4, the self-healing polymer is a polyurethane containing disulfide bonds, the cross-linking agent is hexamethylene diisocyanate, and the cross-linking agent accounts for 1 wt% to 2 wt% of the polyurethane containing disulfide bonds.

7. The method for preparing a rare earth element-doped composite phase change material according to claim 1, characterized in that: In step S4 , the phase change material-nanoparticle mixture is mixed with the disulfide bond-containing polyurethane solution at a mass ratio of 70:20 to 70:

40.

8. The method for preparing a rare earth element-doped composite phase change material according to claim 1, characterized in that: In step S5, the mass ratio of the melamine-formaldehyde resin to deionized water is 1:5-1:10.

Images