Liquid metal-based microcapsule phase change material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of concrete preparation, and particularly relates to a liquid metal-based microcapsule phase change material and a preparation method and application thereof.The liquid metal-based microcapsule phase change material comprises liquid metal and a polyhydroxy polymer. The liquid metal shows longer effective management time and excellent heat storage capacity within the same volume. The liquid metal has excellent mechanical properties compared to conventional phase change materials. At a relatively low temperature (30-200 DEG C), the liquid metal can be converted into a liquid state similar to flowing water, but still retains the characteristics of the metal. And when the liquid metal is cooled below the melting point, the liquid metal can be quickly converted into a solid state, the strength, rigidity and toughness generally related to the metal are recovered, the enthalpy value is high, and hot cracking is more effectively controlled.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete preparation, and in particular relates to a liquid metal-based microcapsule phase change material and a preparation method and application thereof. Background Art

[0002] Concrete has become the preferred engineering material in contemporary production and construction due to its readily available raw materials, low cost, and stable mechanical properties. However, due to the limited thermal conductivity of cement hydrates, large concrete structures are susceptible to thermal cracking. The large amount of heat released by early cement hydration within a concrete structure causes internal temperature accumulation, while surface temperatures remain low because the heat is efficiently dissipated to the external environment, resulting in thermal stresses driven by the surface-to-interior temperature gradient. Furthermore, drastic temperature fluctuations during the concrete's service life can lead to uneven temperature distribution, resulting in thermal stresses. Once these stresses exceed the concrete's tensile strength, thermal cracks can develop, compromising structural integrity and posing a serious threat to its performance and service life. Numerous attempts have been made to mitigate thermal cracking in concrete structures, such as using low-heat cement and mineral admixtures, pre-embedded cooling water pipes, layered pouring, and surface insulation and maintenance. However, the effectiveness of these methods is limited to their applicability during the pouring phase, and the cumbersome construction process increases complexity, time, and cost. Therefore, further research is urgently needed to effectively limit the initiation and propagation of thermal cracks.

[0003] One feasible measure is to incorporate phase change materials, which can reduce the internal temperature rise to a certain temperature threshold by absorbing the hydration heat released by cement-based materials. In addition, embedded phase change materials not only play a role in the initial casting process of cement-based materials, but also provide continuous and effective temperature regulation during their service life. However, traditional organic / inorganic phase change materials have poor thermal conductivity and mechanical properties, which inevitably leads to a significant loss of thermal and mechanical properties of cement-based materials. This results in a significant reduction in flexural strength, compressive strength, and thermal conductivity. Therefore, there is an urgent need to develop a phase change material concrete that does not affect the basic properties of concrete, so as to fundamentally solve the technical problem of concrete cracking. Summary of the Invention

[0004] The purpose of the present invention is to provide a liquid metal-based microcapsule phase change material, a preparation method and application thereof. After the liquid metal-based microcapsule phase change material is compounded with graphene and applied to concrete, it can effectively improve the thermal conductivity and storage capacity of concrete, thereby reducing the hydration temperature of concrete; improve the flexural strength and toughness of concrete, do not affect the compressive strength of concrete, and reduce the risk of thermal cracking.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a liquid metal-based microcapsule phase change material. The liquid metal-based microcapsule phase change material comprises liquid metal and a polyhydroxy polymer.

[0007] Furthermore, the liquid metal includes a low-melting-point metal or an alloy thereof, and the low-melting-point metal includes any one or more of indium, tin, lead, bismuth, zinc, antimony, cesium, francium, lithium, sodium, potassium or rubidium.

[0008] Furthermore, the liquid metal is a Ni-Bi-Sn alloy, and the mass fraction of the Ni-Bi-Sn alloy is 50-55% Ni, 30-35% Bi and 15-17% Sn.

[0009] Furthermore, the polyhydroxy polymer includes polyolefins and their derivatives.

[0010] The present invention also provides a method for preparing the liquid metal-based microcapsule phase change material, which comprises the steps of preparing the material by adopting a high-speed liquid phase dispersion method.

[0011] Furthermore, the preparation using the high-speed liquid phase dispersion method specifically includes the following steps:

[0012] (1) introducing the liquid metal into the polyhydroxy polymer solution and heating the solution to convert the solid liquid metal into a liquid state to obtain a mixture;

[0013] (2) The mixture obtained in step (1) is stirred at high speed and heated to ensure that the alloy is in liquid state; then the excess solution is poured out, and the obtained tiny droplets are washed and dried to obtain the liquid metal-based microcapsule phase change material.

[0014] Furthermore, the polyhydroxy polymer solution is a 3 wt % polyvinyl alcohol solution; and the shear rate during the high-speed stirring process is 14000 rpm.

[0015] The present invention also provides a high-performance crack-resistant concrete, which contains the liquid metal-based microcapsule phase change material.

[0016] Furthermore, the high-performance crack-resistant concrete also includes graphene.

[0017] The present invention also provides an application of the liquid metal-based microcapsule phase change material in improving the performance of concrete, characterized in that the application includes adding the liquid metal-based microcapsule phase change material and graphene during the preparation of concrete.

[0018] In the present invention, graphene, as a reinforcing material, offers the dual advantages of enhancing mechanical strength and thermal conductivity. Its high thermal conductivity plays a key role in mitigating temperature rise within concrete structures. Therefore, adding graphene to high-performance concrete can synergize with the liquid alloy and graphene to control thermal cracking. Furthermore, graphene can be oriented to reinforce polymer-based composites, forming a well-dispersed structure within the polyvinyl alcohol matrix, with the two materials bonding via hydrogen bonding. The addition of graphene can significantly improve the mechanical properties of polyvinyl alcohol materials.

[0019] Polyvinyl alcohol (PVA) in the present invention is a polyhydroxy polymer with excellent film-forming properties and chemical resistance. While alloys suffer from a common problem inherent in metal materials: susceptibility to corrosion, which makes it difficult to maintain sustained efficiency when used in concrete materials under corrosive environmental conditions, PVA's excellent film-forming properties and chemical resistance can be used for surface pretreatment of concrete aggregates, protecting the alloy metal from corrosion. PVA also provides excellent tensile strength, which can enhance concrete toughness. Furthermore, PVA can help convert Ni-Bi-Sn alloy into small particles by reducing its surface tension, further enhancing the effectiveness of Ni-Bi-Sn alloy in concrete.

[0020] The Ni-Bi-Sn alloy in this invention, as a liquid alloy, exhibits considerable thermal conductivity, minimal volume change, high thermal storage density, and stable performance, making it a promising new phase change material. Pure Ni-Bi-Sn alloy has melting and freezing points of 63.0°C and 56.3°C, respectively, with corresponding enthalpies of 27.9 J / g and 26.8 J / g during the phase change process. This allows the alloy to absorb the heat of cement hydration within the concrete, controlling temperature increases and preventing crack growth.

[0021] The beneficial effects of the present invention are:

[0022] The present invention introduces liquid metal into concrete, and the liquid metal exhibits a longer effective management time and excellent heat storage capacity within the same volume. The advantage of liquid metal over traditional phase change materials is its excellent mechanical properties. At lower temperatures (30-200°C), liquid metal can be transformed into a liquid state similar to flowing water, but still retains metallic properties. When cooled below the melting point, the liquid metal will quickly transform into a solid state, restoring the strength, stiffness and toughness usually associated with metals, with a high enthalpy value and more effective control of thermal cracking. At the same time, the crack-resistant concrete of the graphene and liquid metal-based microcapsule phase change material of the present invention can reduce the hydration temperature and improve its flexural strength and toughness without sacrificing the previous strength. In addition, graphene has high mechanical strength and thermal conductivity, which can slow down the temperature rise in the concrete structure and control thermal cracking through the synergistic use of liquid metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 The figure is a graph showing the flexural strength and compressive strength of cement mortars with different mix ratios in the present invention;

[0025] Figure 2 This is a diagram showing the thermal diffusivity and thermal conductivity of cement mortars with different mix ratios in the present invention. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] The raw materials of the liquid metal-based microcapsule phase change material of the present invention include liquid metal and polyhydroxy polymer, wherein the liquid metal includes a low-melting-point metal or an alloy thereof, and the low-melting-point metal includes any one or more of indium, tin, lead, bismuth, zinc, antimony, cesium, francium, lithium, sodium, potassium or rubidium. When the liquid metal is an alloy, the purity of the alloy is above 95%, and the liquid metal is preferably a Ni-Bi-Sn alloy with a mass fraction of 50-55% Ni, 30-35% Bi and 15-17% Sn; the polyhydroxy polymer includes polyolefins and derivatives thereof, and the polyhydroxy polymer is preferably polyvinyl alcohol.

[0032] The preparation method of the liquid metal-based microcapsule phase change material of the present invention comprises the following steps:

[0033] (1) introducing bulk liquid metal into a polyhydroxy polymer solution and heating the solution to a temperature higher than the melting point of 63° C. to convert the solid liquid metal into a liquid state, thereby obtaining a mixture;

[0034] (2) The mixture obtained in step (1) is stirred at 800-14000 rpm for 3-5 minutes, and heating is maintained during the stirring to ensure that the alloy is in a liquid state; the excess solution is poured out, and the obtained tiny droplets are washed and dried to obtain liquid metal-based phase change material powder.

[0035] The present invention will be further described below by way of examples.

[0036] Example 1

[0037] The raw materials of the liquid metal-based microcapsule phase change material in Example 1 include a Ni-Bi-Sn alloy with a mass fraction of 51.0% Ni, 32.5% Bi and 16.5% Sn, and a polyvinyl alcohol solution.

[0038] In the specific preparation process of the liquid metal-based microcapsule phase change material in this Example 1, the mass ratio of the polyvinyl alcohol solution to the Ni-Bi-Sn alloy was 1:1. Different polyvinyl alcohol solution concentrations and different shear rates were set, and shearing was performed for 3-5 minutes until the polyvinyl alcohol completely wrapped the alloy or no longer wrapped the alloy. Different liquid metal-based microcapsule phase change material samples were prepared, numbered M1-M5 in sequence. The specific samples and related parameters in the preparation process are shown in Table 1.

[0039] Table 1 Preparation parameters of different liquid metal-based microcapsule phase change material samples

[0040]

[0041]

[0042] The results showed that when the PVA solution concentration was 1wt% and the shear rate was 14,000 rpm, the surface of the prepared M1 particles showed obvious uncovered areas. When the PVA solution concentration increased to 5wt%, the dispersion resistance of the Ni-Bi-Sn droplets increased, causing deformation of the prepared M3 particles. At a PVA solution concentration of 3wt% and a shear rate of 8,000 rpm, the M4 particles prepared were mostly elliptical with diameters exceeding 100μm, while the prepared M5 particles were mainly smaller, unevenly distributed, and had low sphericity. When the preparation parameters were set to a PVA solution concentration of 3wt% and a shear rate of 14,000 rpm, the M2 particles produced had a smooth surface and regular sphericity. The M2 particles showed a Gaussian distribution with an average diameter of 36.26μm and a standard deviation of 0.46μm. Therefore, the performance of the liquid metal-based microcapsule phase change material was the best when the PVA solution concentration was 3wt% and the shear rate was 14,000 rpm.

[0043] Example 2

[0044] This example investigates the effects of varying proportions of graphene and the Ni-Bi-Sn alloy-based microcapsule phase-change material M2 prepared in Example 1 on the mechanical and thermal properties of cement mortar by designing five different mixing ratios. The specific mix ratios are shown in Table 2. The water-cement ratio was 0.4, the sand-cement ratio was 2.0, and the graphene content was fixed at 0.3% by weight of cement. The focus of the study was on the volume content of the Ni-Bi-Sn alloy-based microcapsule phase-change material, specifically 0%, 1.6%, 3.2%, and 4.8%.

[0045] Table 2 Mixing ratio of liquid metal-based microcapsule phase change material, graphene and cement mortar (kg / m 3 )

[0046]

[0047] Depend on Figure 1It can be seen that the addition of graphene has a positive impact on the flexural strength of cement mortar. The flexural strength of the CM0F sample was 7.6 MPa at 7 days and 10.5 MPa at 28 days, representing increases of 4.1% and 6.1%, respectively, compared to the CM0 sample. The introduction of Ni-Bi-Sn alloy-based microcapsule phase change material further improved the flexural strength of the cement mortar, but with increasing microcapsule phase change material dosage, the flexural strength showed an initial increase followed by a decrease. Compared to the CM0 sample, the addition of 1.6%, 3.2%, and 4.8% Ni-Bi-Sn alloy-based microcapsule phase change material resulted in increases in flexural strength of 15.2%, 8.3%, and 11.5% at 7 days, and 10.3%, 12.0%, and 7.4% at 28 days, respectively. The 28-day compressive strength of the cement mortars containing 1.6%, 3.2%, and 4.8% microcapsule phase change material decreased by 3.6%, 6.1%, and 12.4%, respectively, compared to the CM0 sample. This reduction is likely attributed to the soft polyvinyl alcohol shell of the Ni-Bi-Sn alloy-based microcapsule phase change material, which leads to weak discontinuities within the cement matrix. However, the percentage reduction is significantly mitigated due to the good mechanical properties and high stiffness of the Ni-Bi-Sn alloy in the solid state and the mechanical reinforcement of the polyvinyl alcohol shell by graphene.

[0048] Depend on Figure 2 It can be seen that the thermal diffusivity of the CM0 sample is 0.43 mm 2 / s, and a thermal conductivity of 1.15 W / (m·K). The incorporation of graphene has a positive impact on the thermal properties of cement mortar, increasing thermal diffusivity and thermal conductivity by 14.1% and 7.2%, respectively. These thermal parameters are further improved by the addition of Ni-Bi-Sn alloy-based microcapsule phase change material, and continue to increase with increasing Ni-Bi-Sn alloy-based microcapsule phase change material dosage.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. A liquid metal-based microcapsule phase change material, characterized in that: The liquid metal-based microcapsule phase change material comprises liquid metal and polyhydroxy polymer.

2. The liquid metal-based microcapsule phase change material according to claim 1, characterized in that: The liquid metal includes a low-melting-point metal or an alloy thereof, and the low-melting-point metal includes any one or more of indium, tin, lead, bismuth, zinc, antimony, cesium, francium, lithium, sodium, potassium or rubidium.

3. The liquid metal-based microcapsule phase change material according to claim 2, characterized in that: The liquid metal is a Ni-Bi-Sn alloy, and the mass fraction of the Ni-Bi-Sn alloy is 50-55% Ni, 30-35% Bi and 15-17% Sn.

4. The liquid metal-based microcapsule phase change material according to claim 1, characterized in that: The polyhydroxy polymer includes polyolefins and their derivatives.

5. The method for preparing a liquid metal-based microcapsule phase change material according to any one of claims 1 to 4, characterized in that: The method comprises the steps of adopting a high-speed liquid phase dispersion method for preparation.

6. The preparation method according to claim 5, wherein The high-speed liquid phase dispersion method for preparation specifically comprises the following steps: (1) introducing the liquid metal according to any one of claims 1 to 3 into the polyhydroxy polymer solution according to any one of claim 1 or claim 4, and heating the liquid metal to convert it into a liquid state to obtain a mixture; (2) The mixture obtained in step (1) is stirred at high speed and heated to ensure that the alloy is in liquid state; then the excess solution is poured out, and the obtained tiny droplets are washed and dried to obtain the liquid metal-based microcapsule phase change material.

7. The preparation method according to claim 6, wherein The polyhydroxy polymer solution is a 3 wt % polyvinyl alcohol solution; and the shear rate during the high-speed stirring process is 14000 rpm.

8. A high performance crack-resistant concrete, characterized in that: The high-performance crack-resistant concrete comprises the liquid metal-based microcapsule phase change material according to any one of claims 1 to 4.

9. The high performance crack-resistant concrete according to claim 8, characterized in that: The high-performance crack-resistant concrete also includes graphene.

10. Use of the liquid metal-based microcapsule phase change material according to any one of claims 1 to 4 in improving concrete performance, characterized in that: The application includes adding the liquid metal-based microcapsule phase change material and graphene during the preparation of concrete.

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