Sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material and preparation method thereof
By combining sodium acetate trihydrate-lotus root starch with carbon nanofibers, the problems of thermal conductivity and phase separation in inorganic phase change energy storage materials were solved, achieving efficient thermal energy storage and stability while reducing preparation costs.
Patent Information
- Application Number
- CN202511583591.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-23
AI Technical Summary
Existing inorganic phase change energy storage materials suffer from poor thermal conductivity, severe phase separation, high supercooling, and poor thermal cycling stability. Furthermore, existing thermally conductive fillers are expensive, complex to synthesize, and thickeners are difficult to degrade, resulting in high costs.
A composite phase change material was prepared by combining sodium acetate trihydrate-lotus root starch with carbon nanofibers. The carbon nanofibers were dried and lotus root starch and nucleating agent were added. The composite phase change material was prepared by ambient temperature and pressure and negative pressure vacuum impregnation process. Lotus root starch is a renewable resource that is inexpensive and easy to degrade, while carbon nanofibers are used as thermally conductive reinforcing fillers.
It achieves high thermal conductivity, good stability after multiple thermal cycles, large latent heat, simple manufacturing process, low cost, high packaging capacity, and strong liquid leakage prevention capability.
Smart Images
Figure CN121379534A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of phase change materials, in particular to a sodium acetate trihydrate-konjac flour / carbon nanofiber composite phase change material and a preparation method thereof. BACKGROUND
[0002] The increasing consumption of non-renewable resources such as petroleum and the problems such as the emission of greenhouse gases make it urgent to develop efficient energy storage technology. Phase change energy storage materials can store and release energy through the change of the phase state of the material, and through relative temperature control, the energy can be converted in different time and space, thereby improving the utilization efficiency of energy. In recent years, the preparation and application of high-performance energy storage composite phase change materials in various renewable energy systems have attracted widespread discussion and research. Inorganic phase change materials have suitable phase change temperature and high phase change latent heat, and have the advantages of non-toxicity, wide source, low cost and easy availability, and have wide application prospects in fields such as household hot water, building heating, electronic device thermal management and the like. However, inorganic phase change energy storage materials have poor thermal conductivity, and there are serious problems of phase separation and supercooling, which further hinder their practical application.
[0003] Improving the thermal conductivity of the composite phase change material is one of the important indicators for evaluating the overall performance. Compared with other carbon-based thermal conductive materials, the thermal conductivity of carbon nanofiber is close to that of metal aluminum and copper, it is easy to prepare and low in price, and it has strong resistance to corrosion and chemical erosion, and it is considered to be an ideal filler for phase change composites. Previous studies have shown that the addition of 4% carbon nanofiber makes the thermal conductivity of paraffin / carbon nanofiber composite material reach 0.33 W / (m·K), which is increased by about 137% compared with the thermal conductivity of pure paraffin (0.24 W / (m·K)). Wang et al. added potassium hydroxide to the surface of carbon nanofiber to modify the surface of the carbon nanofiber, and the thermal conductivity of the carbon nanofiber was increased by 239.2%.
[0004] The problem of phase separation of inorganic phase change energy storage materials is generally solved by adding a thickening agent. Li et al. screened 0.5% hydroxyethyl cellulose to add CaCl2·6H2O-MgCl2·6H2O eutectic salt, and the phase change temperature is 21.4℃ and the phase change enthalpy is 102.3J / g, and the phase separation is effectively inhibited. Hee et al. proposed that 2wt.% to 4wt.% of sodium carboxymethyl cellulose is used as a thickening agent, and the phase separation of inorganic hydrated salt (Na2SO4·10H2O, Na2HPO4·12H2O, Na2CO3·10H2O) is effectively inhibited, and there is no adverse effect on the heat storage performance of the hydrated salt phase change material. Duan et al. used a surfactant OP-10 to enhance the bond energy between expanded graphite and hydrated salt energy storage materials, and the hydrated salt is not easy to leak after being liquefied.
[0005] Existing technologies often have the following drawbacks: (1) The thermally conductive fillers used often have problems such as high price, complex synthesis methods and complex composite methods with phase change materials; (2) The thickeners used are often synthetic polymers that are difficult to degrade, have uncontrollable viscosity, and are costly; (3) The prepared composite phase change energy storage material has low encapsulation capacity, poor liquid leakage prevention capability, and low comprehensive latent heat. Summary of the Invention
[0006] The purpose of this invention is to address the problems of easy phase separation, low latent heat of phase change, high supercooling, and low thermal conductivity in existing hydrated salt composite phase change materials, and to provide a sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material and its preparation method. This phase change material possesses ideal overall latent heat and high thermal conductivity, while also exhibiting stability under multiple thermal cycles. The preparation method is simple and mild, making it highly valuable for industrial production.
[0007] The technical solution adopted to achieve the purpose of this invention is: A method for preparing a sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material includes the following steps: Step 1: Dry the carbon nanofibers; Step 2: After heating sodium acetate trihydrate to melt (the melting temperature of sodium acetate trihydrate is 60~80℃), add lotus root starch to the molten sodium acetate trihydrate and stir to obtain sodium acetate trihydrate-lotus root starch system; Step 3: The carbon nanofibers dried in Step 1 (as thermally conductive reinforcing filler and encapsulation material) are added to the system obtained in Step 2 for impregnation. After impregnation, the phase change material is removed and liquid leakage is performed to obtain sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material.
[0008] In the above technical solution, in step 2, the mass of lotus root powder added is 1% to 5% of the mass of sodium acetate trihydrate, the stirring time after adding lotus root powder is 0.5 to 3 hours, and the stirring temperature is 60 to 80℃.
[0009] In the above technical solution, after obtaining the sodium acetate trihydrate-lotus root starch system in step 2, a nucleating agent is added and stirred evenly. The nucleating agent is used to reduce the supercooling of the phase change material.
[0010] In the above technical solution, in step 2, the nucleating agent is one or more of Na2HPO4·12H2O, Na2SiO3·9H2O, or nano Cr2O3.
[0011] In the above technical solution, in the step 2, the added mass of the nucleating agent is 1%-3% of the mass of sodium acetate trihydrate, the stirring time after adding the nucleating agent is 0.5-2h, and the stirring temperature is 60-80 DEG C.
[0012] In the above technical solution, in the step 3, the added mass of the carbon nanofiber is 2%-8% of the mass of sodium acetate trihydrate.
[0013] In the above technical solution, in the step 3, when impregnating, normal temperature and pressure impregnation is first carried out, and then negative pressure vacuum impregnation is carried out.
[0014] In the above technical solution, the normal temperature and pressure impregnation time is 1-2.5h; the pressure of the negative pressure vacuum impregnation is-0.8~-0.5MPa, the temperature is 60-80 DEG C, and the time is 5-20min.
[0015] In the above technical solution, in the step 3, when the liquid leaks, the phase change material is placed on the filter paper, the film is sealed, and the liquid leakage is carried out in the oven, the liquid leakage temperature is 60-80 DEG C, and the filter paper is replaced during the period until no leakage trace is observed to complete the liquid leakage.
[0016] Another aspect of the application also includes the sodium acetate trihydrate-lotus root powder / carbon nanofiber composite phase change material obtained by the preparation method.
[0017] Compared with the prior art, the beneficial effects of the application are: 1. The heat-conducting filler used in the application is easy to prepare and has high cost performance; the lotus root starch used is a renewable resource and can be naturally degraded in the environment, and the price is 1 / 3-1 / 2 of that of synthetic polymer materials, and does not need complex purification treatment, and has certain biocompatibility.
[0018] 2. The preparation process of the composite phase change material prepared in the application is simple, the cost is low, and the obtained sodium acetate trihydrate-lotus root powder / carbon nanofiber composite phase change energy storage material has the advantages of large comprehensive latent heat, high thermal conductivity and good thermal cycle performance. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 Fig. 1 (a), (b) and (c) are SEM images of CNF, SAT / CNF and SAT-LRS / CNF, respectively. 3.0 Fig. 2 (a) and (b) are XRD and FT-IR spectra of the composite phase change material and its components.
[0020] Figure 2 Fig. 2 (a) and (b) are XRD and FT-IR spectra of the composite phase change material and its components.
[0021] Figure 3The DSC curves of (a) SAT, SAT / CNF and SAT-LRS / CNF, (b) the relationship between LRS ratio and the enthalpy of SAT-LRS / CNF.
[0022] Figure 4 The phase separation state of SAT after adding 1wt.%-5wt.% LRS.
[0023] Figure 5 The step cooling curves of SAT-LRS system with (a) Na2HPO4·12H2O (DPD), (b) Na2SiO3·9H2O (SMN) and (c) nano Cr2O3 (CS) as nucleating agent, respectively.
[0024] Figure 6 The thermal conductivity of SAT, SAT / CNF and SAT-LRS 3.0 -DPD 1.5 / CNF.
[0025] Figure 7 The DSC curves of SAT-LRS 3.0 -DPD 1.5 / CNF before and after 100 thermal cycles. DETAILED DESCRIPTION
[0026] The application will be further described below in conjunction with specific examples. It should be understood that the specific examples described herein merely serve to explain the application and are not intended to limit the application.
[0027] Example 1 A preparation method of a sodium acetate trihydrate-konjac flour / carbon nanofiber composite phase change material, comprising the following steps: Step 1, carbon nanofiber (CNF) is placed in a drying box and dried at 60℃ for 30 min; Step 2, sodium acetate trihydrate (SAT) is heated and melted, 3wt.% of konjac flour (LRS) is added to the molten sodium acetate trihydrate, and a magnetic stirrer is used for continuous stirring during the process, the stirring time is 1.5h, and the stirring temperature is 72℃, to obtain a gel state of sodium acetate trihydrate-konjac flour (SAT-LRS); Step 3, to the system obtained in step 2, add the carbon nanofiber after drying in step 1 as a heat-conducting reinforcing filler and encapsulating material, the addition amount of carbon nanofiber (CNF) is 6 wt.% of the mass of sodium acetate trihydrate (SAT), after soaking for half an hour, the sample is obtained by negative pressure vacuum impregnation, the pressure during negative pressure vacuum impregnation is -0.8 MPa, the temperature is 80°C, and the negative pressure vacuum impregnation time is 15 min. Finally, the sample is placed on filter paper, sealed with plastic wrap, and subjected to liquid leakage in a 60°C oven. After the leakage is completed, the sodium acetate trihydrate-lotus root powder / carbon nanofiber composite phase change material is obtained, denoted as SAT-LRS / CNF. 3.0 / CNF.
[0028] From Figure 1 (a), it can be seen that CNF has irregular gaps and pore structures, which are conducive to the large space of hydrated salt encapsulation. However, from Figure 1 (b), it can be seen that the hydrophobicity of CNF leads to partial leakage of SAT in the liquid leakage test. From Figure 1 (c), it can be seen that the hydrophilic groups of LRS improve the hydrophobicity of CNF, enhance the encapsulation ability and adhesion ability of CNF, so that the pores constructed by CNF are more filled with hydrated salt.
[0029] Example 2 According to the method of example 1, the addition amount of lotus root powder (LRS) in step 2 is changed to 1 wt.%, 2 wt.%, 4 wt.% and 5 wt.% respectively, and the obtained sodium acetate trihydrate-lotus root powder / carbon nanofiber composite phase change material is denoted as SAT-LRS / CNF, SAT-LRS / CNF, SAT-LRS / CNF and SAT-LRS / CNF respectively. 1.0 / CNF, SAT-LRS 2.0 / CNF, SAT-LRS 4.0 / CNF and SAT-LRS 5.0 / CNF.
[0030] The heat of the sodium acetate trihydrate-lotus root powder / carbon nanofiber composite phase change material obtained in example 1 and example 2 is analyzed, as shown in the solid-liquid phase change temperature and latent heat parameters of each phase change material in table 1. With the increase of the proportion of LRS, the heat of SAT-LRS / CNF shows an initial increase and then a downward trend, as shown in Figure 3 (b). When the proportion of LRS exceeds 3.0 wt.%, the melting enthalpy of CPCM (SAT-LRS / CNF composite phase change material) decreases with the increase of the proportion of LRS.
[0031] Table 1. Melting peak temperature TM, phase change enthalpy and encapsulation rate of SAT, SAT / CNF and SAT-LRS / CNF.
[0032] As shown in Table 1 and Figure 3 The melting enthalpy of SAT is -221.9 J / g, and the phase transition temperature is 63.85℃. The enthalpy of SAT / CNF is -110.9 / g, and the encapsulation capacity is 500%; while the maximum enthalpy of SAT-LRS 3.0 / CNF is -207.1 J / g, which is 1.9 times higher than that of SAT / CNF, and the encapsulation efficiency reaches 93.3%. This result shows that the addition of LRS effectively improves the melting enthalpy of CPCMs. The performance enhancement is due to the hydrophilic groups of LRS changing the hydrophobicity of CNF, reducing the liquid leakage of hydrated salt, and improving the overall thermal energy storage performance.
[0033] Example 3 A preparation method of a sodium acetate trihydrate-taro / carbon nanofiber composite phase change material, comprising the following steps: Step 1, carbon nanofiber (CNF) is placed in a drying box at 60℃ for 30min; Step 2, sodium acetate trihydrate (SAT) is heated to melt, a certain amount of taro (LRS) is added to the molten sodium acetate trihydrate, and the magnetic stirrer is continuously stirred during the process, the stirring time is 2h, and the stirring temperature is 720℃, to obtain a gel state of sodium acetate trihydrate-taro (SAT-LRS); a certain amount of nucleating agent is added and stirred, the stirring time is 0.5h, and the stirring temperature is 72℃ Step 3, carbon nanofiber (CNF) after drying treatment in step 1 is added to the system obtained in step 2 as a heat-conducting reinforcing filler and an encapsulating material, the addition amount of carbon nanofiber (CNF) is 6wt.% of the mass of sodium acetate trihydrate (SAT), after half an hour of immersion, the sample is obtained by negative pressure vacuum impregnation, the pressure during negative pressure vacuum impregnation is -0.8MPa, the temperature is 80℃, and the negative pressure vacuum impregnation time is 15min. Finally, the sample is placed on filter paper, sealed with plastic wrap, and subjected to liquid leakage in a 60℃ oven, and after the leakage is completed, the sodium acetate trihydrate-taro / carbon nanofiber composite phase change material is obtained.
[0034] When the addition amount of taro in step 2 is 3% of the mass of sodium acetate trihydrate (SAT), and the nucleating agent selected is DPD with an addition amount of 1.5% of the mass of sodium acetate trihydrate (SAT), the obtained sodium acetate trihydrate-taro / carbon nanofiber composite phase change material is denoted as SAT-LRS 3.0 -DPD 1.5 / CNF.
[0035] When the addition amount of taro in step 2 is 1% of the mass of sodium acetate trihydrate (SAT), and the nucleating agent selected is DPD with an addition amount of 2.5% of the mass of sodium acetate trihydrate (SAT), the obtained sodium acetate trihydrate-taro / carbon nanofiber composite phase change material is denoted as SAT-LRS 1.0 -DPD2.5 / CNF.
[0036] SAT-LRS obtained in Example 2 3.0 -DPD 1.5 / CNF and SAT-LRS 1.0 -DPD 2.5 / CNF was used for XRD and FT-IR spectral analysis, such as Figure 2 As shown, no new peaks were observed in the XRD and FT-IR spectra of the SAT CPCM. This indicates good chemical compatibility among the components, the absence of new substances, and minimal physical interactions between the components. Figure 2 As can be seen in (b), the stretching vibration peak of OH in the FT-IR spectrum of SAT CPCM shifts to the left to 3430.16 cm⁻¹. -1 This indicates that hydrogen bonds have formed between SAT and LRS.
[0037] The optimal addition amount of carbon nanofibers (CNF) was validated: Sodium acetate trihydrate (SAT) was heated to melt, and a certain amount of lotus root starch (LRS) was added to the molten sodium acetate trihydrate. The mixture was continuously stirred with a magnetic stirrer for 2 hours at a temperature of 70°C to obtain a gel-like sodium acetate trihydrate-lotus root starch (SAT-LRS). The SAT-LRS obtained when the added amount of lotus root starch (LRS) was 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, and 5 wt.% were respectively denoted as SAT-LRS. 1.0 SAT-LRS 2.0 SAT-LRS 3.0 SAT-LRS 4.0 SAT-LRS 5.0 ,Depend on Figure 4 It is evident that the addition of LRS reduces the fluidity of molten PCM, and the strong interaction between LRS and hydrated salt enhances the water-holding capacity of the hydrated salt. This effectively alleviates the phase separation of SAT.
[0038] The nucleating agent and its optimal dosage were validated: Sodium acetate trihydrate (SAT) was heated to melt, and 3 wt.% lotus root starch (LRS) was added to the molten sodium acetate trihydrate. The mixture was continuously stirred with a magnetic stirrer for 2 hours at 70°C to obtain a gel-like sodium acetate trihydrate-lotus root starch (SAT-LRS). A certain amount of nucleating agent was then added, and the mixture was stirred for 0.5 hours at 70°C to obtain SAT-LRS. 3.0 - Nucleating agent (DPD / SMN / CS) system.
[0039] In this embodiment, Na2HPO4·12H2O (DPD), Na2SiO3·9H2O (SMN) and nano-Cr2O3 (CS) were used as nucleating agents, and DPD, SMN and CS were introduced at a ratio of 1.0%, 1.5% and 2.0% of the mass of SAT, respectively. The obtained phase change materials were denoted as SAT-LRS 3.0 -DPD 1.0 , SAT-LRS 3.0 -DPD 1.5 , SAT-LRS 3.0 -DPD 2.0 , SAT-LRS 3.0 -SMN 1.0 , SAT-LRS 3.0 -SMN 1.5 , SAT-LRS 3.0 -SMN 2.0 , SAT-LRS 3.0 -CS 1.0 , SAT-LRS 3.0 -CS 1.5 , SAT-LRS 3.0 -CS 2.0 .
[0040] The performance of the phase change materials is shown in Table 2 and Figure 5 2 wt.% of SMN reduced the supercooling degree (△T = T2-T1) of SAT to 5.31 ℃. The same proportion of CS helped SAT to obtain a supercooling degree of 4 ℃. At the same time, 1.5% of DPD showed the best effect △T = 1.5. It is shown that DPD is an effective nucleating agent for SAT, which can effectively reduce the supercooling of SAT.
[0041] Table 2. Initial temperature (T1), end temperature (T2) and supercooling degree (△T) of phase change of SAT-LRS3.0 system with different nucleating proportions.
[0042] Test Example 1 Since the addition ratio of LRS is 3.0 wt.%, DPD is used as a nucleating agent and the addition amount is 1.5 wt.%, the phase change system shows excellent performance, so the performance of SAT-LRS3.0-DPD 1.5 / CNF is tested.
[0043] Figure 6 SAT, SAT / CNF, SAT-LRS 3.0 -DPD 1.5Thermal conductivity of SAT-LRS / CNF. From the figure, it can be seen that 6 wt.% of CNF increases the thermal conductivity of SAT from 0.609 W / (m·K) to 1.812 W / (m·K), nearly 3 times. However, due to the disordered molecular arrangement and weak intermolecular bonds of LRS, LRS has a negative effect on the thermal conductivity of CPCM. Nevertheless, SAT-LRS 3.0 -DPD 1.5 The thermal conductivity of SAT-LRS / CNF is still 1.95 times that of pure SAT. It shows that CNF is an excellent encapsulation matrix, which effectively improves the thermal conductivity of CPCM.
[0044] Figure 7 SAT-LRS 3.0 -DPD 1.5 DSC curves of SAT-LRS / CNF before and after 100 thermal cycles. From the figure, it can be seen that SAT-LRS 3.0 -DPD 1.5 After 100 thermal cycles, the latent heat of SAT-LRS / CNF decreases slightly from 204.7 J / g to 190.6 J / g, with an enthalpy loss of 6%, indicating its good thermal stability. It shows that the hydrogen-bonding network formed by LRS and the porous structure constructed by CNF synergistically reduce liquid leakage and phase separation.
[0045] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.
Claims
1. A method for preparing sodium acetate trihydrate-sago / carbon nanofiber composite phase change material, characterized in that, The method comprises the following steps: Step 1, drying treatment of carbon nanofiber; Step 2, heating and melting sodium acetate trihydrate, then adding lotus root starch into the molten sodium acetate trihydrate, and stirring to obtain a sodium acetate trihydrate-lotus root starch system; Step 3, immersing the carbon nanofiber subjected to the drying treatment in the system obtained in Step 2, and taking out the phase change material after the immersion is completed to perform liquid leakage, thereby obtaining a sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material.
2. The production method according to claim 1, wherein In Step 2, the added mass of the lotus root starch is 1% to 5% of the mass of the sodium acetate trihydrate, and the stirring time after the lotus root starch is added is 0.5 to 3 hours, and the stirring temperature is 60 to 80°C.
3. The production method according to claim 1, wherein In Step 2, after the sodium acetate trihydrate-lotus root starch system is obtained, a nucleating agent is then added and stirred uniformly, and the nucleating agent is used to reduce the supercooling degree of the phase change material.
4. The production method according to claim 3, wherein In Step 2, the nucleating agent is one or more of Na2HPO4·12H2O, Na2SiO3·9H2O or nano-Cr2O3.
5. The production method according to claim 3, wherein In Step 2, the added mass of the nucleating agent is 1% to 3% of the mass of the sodium acetate trihydrate, and the stirring time after the nucleating agent is added is 0.5 to 2 hours, and the stirring temperature is 60 to 80°C.
6. The production method according to claim 1, wherein In Step 3, the added mass of the carbon nanofiber is 2% to 8% of the mass of the sodium acetate trihydrate.
7. The method of claim 1, wherein the method is characterized by, In Step 3, during the immersion, normal temperature and pressure immersion is first performed, and then negative pressure vacuum immersion is performed.
8. The method of claim 1, wherein The normal temperature and pressure immersion time is 1 to 2.5 hours, the pressure of the negative pressure vacuum immersion is -0.8 to -0.5 MPa, the temperature is 60 to 80°C, and the time is 5 to 20 minutes.
9. The method of claim 1, wherein In Step 3, during the liquid leakage, the phase change material is placed on filter paper, and the film is sealed and subjected to liquid leakage in an oven, the liquid leakage temperature is 60 to 80°C, the filter paper is replaced constantly during the liquid leakage, and the liquid leakage is completed when no leakage trace is observed.
10. A sodium acetate trihydrate-lotus root starch / carbon nanofiber composite phase change material obtained by the preparation method according to any one of claims 1 to 9.