CN113136169A - Hydrated salt-porous material composite based on hydrogel coating and preparation method and application thereof - Google Patents
Hydrated salt-porous material composite based on hydrogel coating and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a hydrated salt-porous material composite based on hydrogel coating and a preparation method and application thereof. The hydrogel endows the hydrated salt-porous material composite with good plasticity and elasticity and effective heat absorption and release cycle stability.
Description
Technical Field
The invention relates to the technical field of phase change energy storage materials, in particular to a hydrated salt-porous material composite based on hydrogel coating and a preparation method and application thereof.
Background
The phase-change energy storage technology is an effective means for improving the utilization efficiency of energy by absorbing or releasing a large amount of heat energy in the phase-change process of materials so as to play a role in controlling temperature and storing energy, solving the contradiction that the energy supply and demand are unbalanced in time and space distribution. The method has important application value and wide application prospect in a plurality of fields such as aerospace, solar energy utilization, industrial waste heat recovery, heating and air conditioning, medical engineering, military engineering, heat storage building, extreme environment clothing and the like. The composition of the hydrated salt and the porous material is an important phase-change energy storage material, but the deterioration of the hydrated salt and the porous material in the long-term application process further influences the service life of the composite material, and the composition of the hydrogel and the phase-change material can effectively solve the problems.
The hydrogel is compounded with the phase-change material in two ways:
1. as a framework for the porous material. The hydrogel phase-change material with the temperature response effect is prepared by mixing lithium nitrate trihydrate and polyvinyl alcohol by Karimineghlani, etc. of the university of agricultural workers in Texas, wherein the lithium nitrate trihydrate is distributed in a network of the polyvinyl alcohol, the highest mass proportion of the polyvinyl alcohol is 15 percent, the polyvinyl alcohol plays the role of a soft porous material, and the gel-sol transition of the system can be induced by the rise and fall of the temperature. (Valeriya Chernikova, Omar Yang, Osama Shekhah, Mohamed Eddaoudi, Khaled N.Salama, Atemperateure-responsive poly (vinyl alcohol) gel for controlling flexibility of an organic phase change material, J.Material.chem.A, 2017,5,12474-
Dried inorganic three-dimensional network silica gel powder is firstly prepared by Nippon paint (China) Limited Guoshan and the like, and is compounded with a polyethylene glycol phase change material to obtain an interpenetrating network hybrid shape-stabilized phase change material, and the silica gel is used as a rigid porous framework material to coat polyethylene glycol. (Guo Ping, Wu Yongwen, Miao Yongzhi, Zhang hong, a preparation method of interpenetrating network hybridization shape-stabilized phase change material, Nippon paint (China) Co., Ltd., application No. 201610826478.9, inventive patent)
2. As a thickening agent. Zhang Yelong, Nanjing alloy energy materials Limited and the like disclose a medium and low temperature hydrated sulfate composite phase-change material and a preparation method thereof, wherein silica gel, carboxymethyl cellulose or bentonite are used as a thickening agent, the highest dosage of the thickening agent is 1 wt%, and the thickening agent is mixed with a hydrated salt composite system to prepare the composite phase-change energy storage material. (Zhangye Long, Dingyulong, Jia Xuan, Zhao Weijie, Lu Ming gang, a hydrated sulfate composite phase-change material and its preparation method, Nanjing Kui energy materials Co., Ltd., application No. 201810923845.6, inventive patent)
The highest mass proportion of the thickener is 4%, and the thickener CMC is found to be capable of inhibiting the phase separation process of the calcium chloride hexahydrate phase change material, so that the cycle performance of the calcium chloride hexahydrate phase change material is improved. However, the addition of excessive CMC increases the consistency of the calcium chloride hexahydrate solution, so that water molecules and calcium chloride molecules in the calcium chloride hexahydrate solution cannot be sufficiently combined together during temperature reduction, and heat in the calcium chloride hexahydrate solution cannot be sufficiently released. (Majiang Wei, Wang hong Li Kai, Song Dan, xu hong Jun.) the research on the properties of calcium chloride hexahydrate suitable for greenhouse applications. agricultural research, 2013(7):211-216)
The porous material can relieve the leakage problem and the phase separation problem in the phase change process by coating the hydrated salt (adsorbed and fixed in the pore channels) at one time, but the hydrated salt-porous material complex system still has the obvious performance deterioration problem in the long-term application process due to the existence of the open pore channels and the wall climbing phenomenon. Therefore, it is necessary to carry out secondary coating on the hydrated salt-porous material composite phase-change material, especially to block the open pore channel structure.
For a porous material-phase change material composite system, the secondary coating technology mainly comprises high polymer in-situ polymerization, adsorption coating and the like. The polymer in-situ polymerization process comprises mixing a polymer monomer with the hydrated salt-porous material composite system, polymerizing the polymer monomer by applying external field conditions (such as ultraviolet illumination, heating, initiator addition and the like), and coating the polymer monomer on the surface of the hydrated salt-porous material composite system to form secondary coating. The adsorption coating process is characterized in that a coating layer substance is dissolved in a solvent and is mixed with a hydrated salt-porous material composite system, the used solvent is not mutually soluble with a phase-change material, the coating layer substance is easily adsorbed by the porous material, an adsorption coating layer is finally formed on the surface of the porous material, and the open pore channel structure of the porous material is not changed.
The polymer coating layer formed by the polymer in-situ polymerization process can cause the reduction of the overall heat-conducting property of the material, and the polymer coating layer is difficult to uniformly coat on the surface of an irregular porous material, and more seriously, the polymer coating layer is easy to break in the application process of the phase-change material, so that the coating effect is greatly weakened. The adsorption coating process requires a large amount of volatile solvents to be tested for drying removal after the coating is formed, and the adsorption coating process cannot change the open pore structure of the porous material.
The existing secondary coating technology has a disposable blocking effect on the open pore channel of the hydrated salt-porous material composite phase change energy storage material, has no long-term sustainability, and cannot be repaired in situ once a coating layer is damaged in the using process; the existing secondary coating technology is complex in process and high in cost, and is not favorable for reducing the production cost of the phase change energy storage material and promoting the industrial application of the phase change energy storage material.
The xerogel is taken as a porous material and is directly compounded with the hydrated salt phase-change material to form primary coating. The hydrogel is used as a thickening agent for a hydrated salt phase-change energy storage material system, the essence of the thickening effect is that the three-dimensional network structure formed by the hydrogel can inhibit the uneven sedimentation of hydrated salt crystals, the direct action of high-concentration hydrated salt solution and the gel can cause the thickening efficiency of the gel to be remarkably reduced, and even insoluble precipitates are generated, so that the thickening is ineffective. In addition, the thickener can combine metal ions in the hydrated salt, so that the proportion of effective components capable of phase change in the phase change material is reduced, and the latent heat is reduced.
Disclosure of Invention
The invention aims to provide a hydrated salt-porous material composite based on hydrogel coating, aiming at the technical defects of high process cost in the preparation process of a hydrated salt-porous material composite phase change energy storage system and performance attenuation problem in the long-term application process in the prior art.
Another object of the present invention is to provide a method for preparing the hydrogel coating-based hydrated salt-porous material composite.
The invention also aims to provide application of the hydrogel-coated hydrated salt-porous material composite as a phase change energy storage material.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a hydrated salt-porous material composite based on hydrogel coating, wherein a hydrogel system completely covers the hydrated salt-porous material composite, the hydrated salt-porous material composite comprises a porous material and a hydrated salt system adsorbed in open cells of the porous material, and the hydrated salt exposed at the open ends of the open cells has salting-out effect with hydrogel in the hydrogel system to form insoluble precipitates in situ so as to seal the open ends.
In the composite, the hydrogel forms a complete coating on the hydrated salt-porous material composite particles.
In the above technical solution, the hydrogel system is a hydrogel or a hydrogel added with an antioxidant, and the antioxidant includes, but is not limited to, vitamin or tyrosine. The antioxidant has the functions of reducing the oxidation of the organic gelling agent in the hydrogel and prolonging the service life of the organic gelling agent, namely, the organic gelling agent can maintain stable gelling performance for a long time, and the performance of the hydrogel containing the organic gelling agent is not degraded. The mass of the antioxidant is 0.1-0.5 wt% of the mass of the hydrogel, and more preferably, the mass of the antioxidant accounts for about 0.2% of the total mass of the hydrogel system.
In the technical scheme, the mass ratio of the hydrogel system to the hydrated salt-porous material composite is 15: 85-50: 50. The mass range ratio of the hydrated salt system to the porous material is (70-80) to (10-20).
In the above technical solution, the hydrated salt system is a hydrated salt or a mixture of a hydrated salt and a nucleating agent. The nucleating agent is not limited. The nucleating agent can reduce the supercooling degree of the hydrated salt, is generally added in an amount of not more than 5 percent, is directly mixed with the hydrated salt and can be uniformly dispersed in a system at best. The nucleating agent used in the hydrated salt system is selected based on experience and experimental results.
In the above technical scheme, the hydrated salt includes, but is not limited to, one of the following and a mixture of more than one of the following: hydrated magnesium chloride, hydrated calcium chloride, barium hydroxide octahydrate, sodium sulfate decahydrate, sodium carbonate dodecahydrate or magnesium nitrate hexahydrate.
In the above technical solution, the porous material includes, but is not limited to, porous silicon, expanded graphite, expanded vermiculite, porous carbon or expanded perlite. The particle size of the porous material is 100-400 meshes.
In the above technical scheme, the hydrogel is an inorganic gel or an organic gel.
In the above technical solution, the inorganic gel includes, but is not limited to, one of the following and a mixture of more than one of the following: montmorillonite, bentonite or silica gel; the organogel includes but is not limited to one or a mixture of more than one of the following: polyacrylic acid, starch, polyvinyl alcohol, carboxyl cellulose, sodium carboxyl cellulose, agar, polysaccharide, xanthan gum, gelatin, chitosan, cellulose ether, sodium alginate or polyurethane.
In the above technical solution, the hydrogel coating-based hydrated salt-porous material composite is prepared by the following steps:
step 1, directly mixing a hydrogel system with a hydrated salt-porous material compound;
or the gel-forming substance and the hydrated salt-porous material compound are uniformly mixed and then added with water to form gel;
or the hydrosol and the hydrated salt-porous material compound are mixed and then partially dehydrated to form gel;
or further comprises step 2, removing excess hydrogel by squeezing, high speed centrifugation, sol heat filtration, etc.
Whether the hydrogel is dehydrated and the degree of dehydration depend on the application, and partial and complete dehydration of the hydrogel does not affect the coating performance of the hydrogel-porous material composite. Good flexibility can be kept when the powder is not dehydrated, and the powder can be conveniently compounded with powder materials after dehydration.
In the above technical solutions, the mixing includes, but is not limited to, mixing in one or more ways, such as ultrasonic, vigorous stirring or heating.
In another aspect of the invention, the application of the hydrogel-coated hydrated salt-porous material composite as a phase change energy storage material is also included.
In the technical scheme, the melting point of the hydrated salt-porous material compound coated by the hydrogel is 23-31 ℃, the phase change enthalpy is 35-120J/g, and the heat conductivity coefficient is 0.45-5.0 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 0.5-2% after 1000 times of circulation.
In another aspect of the invention, the application of the hydrogel-coated hydrated salt-porous material composite as a material with plasticity and elasticity for phase change and energy storage is also included.
In the technical scheme, the hydrogel-coated hydrated salt-porous material composite can be stretched to 1.05-1.25 times of the original length and compressed to 80% -95% of the original volume. Has good plasticity and elasticity.
In another aspect of the present invention, a method for preparing a hydrogel-coated hydrated salt-porous material composite comprises the following steps:
the hydrogel system is directly mixed with the hydrated salt-porous material composite;
or the gel-forming substance and the hydrated salt-porous material compound are uniformly mixed and then added with water to form gel;
or the hydrosol is mixed with the hydrated salt-porous material composite and then is partially dehydrated to form gel.
In the technical scheme, the mixing is one or any combination of ultrasonic mixing, violent stirring mixing or heating mixing.
In the above technical solution, the hydrated salt-porous material composite is prepared by one of the following methods:
a, normal-pressure melting and mixing: the hydrated salt system melted under normal pressure enters the pore channels of the porous material by virtue of the capillary action;
b, negative pressure pore channel suction: mixing a hydrated salt system and a porous material, putting the mixture into a container, vacuumizing the container in a closed environment, heating and melting the mixture, continuously vacuumizing the container in the melting process, and quickly putting air into the container after melting to promote more of the melted hydrated salt system to enter the inside of a pore channel of the porous material;
c, putting the porous material into a closed container, vacuumizing, and then introducing a molten hydrated salt system;
d, after the porous material is mixed with the molten hydrated salt system, assisting ultrasonic exhaust to promote the exhaust of gas in the pore channel and adsorbed gas on the outer wall of the pore channel;
and E, after the porous material and the molten hydrated salt system are mixed, introducing gas into the closed container, increasing the pressure in the container, and promoting the molten hydrated salt system to enter the inside of the pore channel of the porous material.
The adsorption of the hydrated salt system on the outer wall of the pore channel can be reduced through the five modes, so that more hydrated salt systems enter the pore channel of the porous material, and the coating of the precipitator on the outer wall of the porous material is reduced. The consumption of the hydrate salt adsorbed on the outer wall to the precipitator can be reduced, and the effective content of the hydrate salt capable of playing the heat storage and release functions in the composite system can be increased.
When the hydrogel system is excessive, step 2 is included, and excessive hydrogel is removed by extrusion, high-speed centrifugation or sol heat filtration;
when dehydration is needed, the method comprises the following steps: dehydrating by freeze-drying.
Compared with the prior art, the invention has the beneficial effects that:
1. the coating of the porous material greatly reduces the direct contact area of the hydrated salt and the hydrogel, and the salting-out and precipitation effects of the hydrated salt on the hydrogel are only limited to the open ends of the porous material pore channels, so that the selective plugging of the open pore channels can be realized at lower cost, and the good coating effect on the hydrated salt is achieved.
2. Different from the prior art of completely coating the hydrated salt-porous material composite system particles, the secondary coating is selective coating, the hydrogel only has salting-out effect with the hydrated salt exposed at the open end of the porous material, the generated precipitate is deposited at the open end of the pore channel in situ, and the hydrated salt in the pore channel is blocked and coated.
3. The hydrogel disclosed by the invention is easy to deform, can be converted into a sol state under heating or violent stirring, and can be used for fully coating a hydrated salt-porous material composite.
4. The coating structure in the prior art cannot be repaired in use after being formed, and the damaged coating layer is failed. The hydrogel can repair a new open port formed by the damage of the original coating layer at any time to form a new coating layer and a new blocking structure, and the coating and blocking effects on the opening end of the channel have long-term sustainability.
5. The hydrogel endows the composite system with certain elasticity and buffering capacity, so that the damage rate of the hydrated salt-porous material particles compounded in the system caused by friction, vibration, impact and the like in the long-term application process is greatly reduced, and the long-term stability of the structure and the performance of the hydrated salt-porous material particles is ensured.
6. The raw materials are cheap and easy to obtain, the process is simple, and the hydrogel disclosed by the invention is common chemical raw materials and is cheap and easy to obtain; the coating process only needs to mix the hydrogel and the hydrated salt-porous material composite system, and does not need additional processes such as induced polymerization and solidification.
7. The hydrogel of the invention endows the complex system with good plasticity and elasticity, provides great convenience for the subsequent processing and application of the gel-hydrated salt-porous material complex system and the modular development of the phase-change energy storage material, and is suitable for preparing phase-change energy storage modules with various complex shapes and filling energy storage containers with various complex shapes.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
Weighing calcium chloride hexahydrate (serving as hydrated salt), nucleating agent strontium chloride hexahydrate and expanded graphite (serving as a porous material) according to the weight ratio of 87:1:12, wherein the particle size of the expanded graphite is 100 meshes, uniformly mixing, melting the calcium chloride hexahydrate phase-change material at the temperature of 40-50 ℃ to ensure that the calcium chloride hexahydrate phase-change material is uniformly and fully absorbed by the expanded graphite, and cooling to room temperature (or below 25 ℃) to obtain the calcium chloride hexahydrate phase-change material-expanded graphite composite.
Preparing hydrogel containing 0.05 wt% of vitamin (as antioxidant), 10 wt% of sodium carboxymethylcellulose and the balance of water, mixing the prepared hydrogel and the calcium chloride hexahydrate phase-change material-expanded graphite composite, wherein the mass ratio of the hydrogel to the calcium chloride hexahydrate phase-change material-expanded graphite composite is 15:85, stirring at a high speed to fully mix the hydrogel and the calcium chloride hexahydrate phase-change material-expanded graphite composite, and carefully controlling the mixing process to avoid air mixing as much as possible. The hydrogel-calcium chloride hexahydrate-expanded graphite composite phase change energy storage material is prepared and sealed for later use.
Through measurement and calculation, the melting point of the phase change energy storage material is 27 ℃, the phase change enthalpy is 120J/g, and the heat conductivity coefficient is 5.0 W.m-1·K-1(25.0 ℃) and phase change enthalpy is attenuated by 1% after 1000 times of circulation. The phase change energy storage material can be stretched to 1.05 times of the original length and compressed to 95% of the original volume.
Comparative example 1
Weighing calcium chloride hexahydrate (serving as hydrated salt), nucleating agent strontium chloride hexahydrate and expanded graphite (serving as a porous material) according to the weight ratio of 87:1:12, wherein the particle size of the expanded graphite is 100 meshes, uniformly mixing, melting the calcium chloride hexahydrate phase-change material at the temperature of 40-50 ℃ to ensure that the calcium chloride hexahydrate phase-change material is uniformly and fully absorbed by the expanded graphite, and cooling to room temperature (or below 25 ℃) to obtain the calcium chloride hexahydrate phase-change material-expanded graphite composite.
The melting point of the calcium chloride hexahydrate phase-change material-expanded graphite compound is 27 ℃, the phase-change enthalpy is 140J/g, and the heat conductivity coefficient is 6.0 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 30 to 50 percent after 1000 times of circulation. The phase change energy storage material has no plasticity and elasticity.
Example 2
Weighing a sodium sulfate decahydrate phase-change material (as a hydrate salt), a nucleating agent borax and expanded vermiculite (as a porous material) according to a weight ratio of 78.5:1.5:20, wherein the particle size of the expanded vermiculite is 200 meshes, uniformly mixing, melting the sodium sulfate decahydrate phase-change material at a temperature of 50-60 ℃ to ensure that the sodium sulfate decahydrate phase-change material is uniformly and fully absorbed by the expanded vermiculite, and cooling to room temperature (below 25 ℃) to obtain the sodium sulfate decahydrate phase-change material-expanded vermiculite compound for later use.
Grinding and mixing xanthan gum, glucose and sodium montmorillonite with the prepared sodium sulfate decahydrate phase change material-expanded vermiculite compound, wherein the mass ratio of the xanthan gum, the glucose, the sodium montmorillonite to the sodium sulfate decahydrate phase change material-expanded vermiculite compound is 4:0.05:4: 37; after mixing well, adding a proper amount of water, stirring to gelatinize the mixture, wherein the mass ratio of the hydrogel to the sodium sulfate decahydrate phase change material-expanded vermiculite compound is about 35: 65. The prepared hydrogel-sodium sulfate decahydrate-expanded vermiculite composite phase change energy storage material is sealed for later use.
Through measurement and calculation, the melting point of the phase change energy storage material is 31 ℃, the phase change enthalpy is 90J/g, and the heat conductivity coefficient is 0.45 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 2% after 1000 times of circulation. The phase change energy storage material can be stretched to 1.10 times of the original length and compressed to 85% of the original volume.
Comparative example 2
Weighing a sodium sulfate decahydrate phase-change material (as a hydrated salt), a nucleating agent borax and expanded vermiculite (as a porous material) according to a weight ratio of 78.5:1.5:20, wherein the particle size of the expanded vermiculite is 200 meshes, uniformly mixing, melting the sodium sulfate decahydrate phase-change material at a temperature of 50-60 ℃ to ensure that the sodium sulfate decahydrate phase-change material is uniformly and fully absorbed by the expanded vermiculite, and cooling to room temperature (below 25 ℃) to obtain the sodium sulfate decahydrate phase-change material-expanded vermiculite composite.
The melting point of the sodium sulfate decahydrate phase-change material-expanded vermiculite compound is 31 ℃, the phase-change enthalpy is 150J/g, and the heat conductivity coefficient is 0.55 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 70 to 80 percent after 1000 times of circulation. The phase change energy storage material has no plasticity and elasticity.
Example 3
Weighing magnesium chloride hexahydrate and calcium chloride hexahydrate (serving as hydrated salt) according to the weight ratio of 50:50 to prepare a magnesium chloride hexahydrate-calcium chloride hexahydrate hydrated salt phase-change material (serving as a porous material), wherein the weight ratio of the magnesium chloride hexahydrate to the calcium chloride hexahydrate is 83: 2: 15 weighing the magnesium chloride hexahydrate-calcium chloride hexahydrate hydrated salt phase-change material, the nucleating agent barium hydroxide octahydrate and porous carbon, wherein the granularity of the porous carbon is 400 meshes, uniformly mixing, uniformly and fully absorbing the hydrated salt phase-change material by the porous carbon at the temperature of 40-50 ℃, and cooling to below 20 ℃ to obtain the magnesium chloride hexahydrate-calcium chloride hexahydrate-porous carbon composite.
Preparing hydrosol containing 15 wt% of silicon dioxide, 1 wt% of nano-metal zinc powder and 5 wt% of polyacrylic acid, mixing the hydrosol with magnesium chloride hexahydrate-calcium chloride hexahydrate-porous carbon composite in a mass ratio of 2:1, uniformly mixing, freeze-drying to remove part of water, heating and unfreezing to obtain hydrogel-magnesium chloride hexahydrate-calcium chloride hexahydrate-porous carbon composite phase change energy storage material, and sealing for later use.
Through measurement and calculation, the melting point of the phase change energy storage material is 23 ℃, the phase change enthalpy is 35J/g, and the heat conductivity coefficient is 3.50 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 0.5 percent after 1000 times of circulation. The phase change energy storage material can be stretched to 1.25 times of the original length and compressed to 80% of the original volume.
Comparative example 3
Weighing magnesium chloride hexahydrate and calcium chloride hexahydrate according to the weight ratio of 50:50 to prepare a magnesium chloride hexahydrate-calcium chloride hexahydrate hydrated salt phase-change material, wherein the weight ratio of the magnesium chloride hexahydrate to the calcium chloride hexahydrate is 83: 2: 15 weighing the magnesium chloride hexahydrate-calcium chloride hexahydrate hydrated salt phase-change material, the nucleating agent barium hydroxide octahydrate and porous carbon, wherein the granularity of the porous carbon is 400 meshes, uniformly mixing, uniformly and fully absorbing the hydrated salt phase-change material by the porous carbon at the temperature of 40-50 ℃, and cooling to below 20 ℃ to obtain the magnesium chloride hexahydrate-calcium chloride hexahydrate-porous carbon composite.
The melting point of the magnesium chloride hexahydrate-calcium chloride hexahydrate-porous carbon composite is 23 ℃, the phase change enthalpy is 45J/g, and the heat conductivity coefficient is 3.0 W.m-1·K-1(25.0 ℃) and the phase change enthalpy is attenuated by 60 to 80 percent after 1000 times of circulation. The phase change energy storage material has no plasticity and elasticity.
The hydrogel coating-based hydrated salt-porous material composites of the present invention were prepared and exhibited substantially the same properties as examples 1-3, with process parameter adjustments made in accordance with the present disclosure.
As can be seen from the above examples and comparative examples, the hydrogel-coated hydrated salt-porous material composite has a significantly reduced decay in enthalpy of phase transition after 1000 cycles, which has better stability of heat absorption and release cycles, compared to the uncoated hydrated salt-porous material composite.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (12)
1. A hydrogel-coated hydrated salt-porous material composite is characterized in that a hydrogel system completely covers the hydrated salt-porous material composite, the hydrated salt-porous material composite comprises a porous material and a hydrated salt system adsorbed in open cells of the porous material, and the hydrated salt exposed at the open ends of the open cells has a salting-out effect with hydrogel in the hydrogel system to form insoluble precipitates in situ so as to seal the open ends.
2. The hydrogel-coated hydrated salt-porous material composite as claimed in claim 1, wherein the mass ratio of the hydrogel system to the hydrated salt-porous material composite is 15:85 to 50:50, and the mass ratio of the hydrated salt system to the porous material is (70 to 80): (10 to 20).
3. The hydrogel-coated hydrated salt-porous material composite as claimed in claim 1, wherein the hydrogel system is a hydrogel or a hydrogel added with an antioxidant, the antioxidant is vitamin or tyrosine, and the antioxidant is 0.1 wt% to 0.5 wt% of the hydrogel;
the hydrated salt system is a hydrated salt or a mixture of the hydrated salt and a nucleating agent, and the mass of the nucleating agent is less than or equal to 5% of that of the hydrated salt phase;
the hydrated salt is one or a mixture of hydrated magnesium chloride, hydrated calcium chloride, barium hydroxide octahydrate, sodium sulfate decahydrate, sodium carbonate dodecahydrate or magnesium nitrate hexahydrate in any proportion;
the porous material comprises but is not limited to porous silicon, expanded graphite, expanded vermiculite, porous carbon or expanded perlite, and the particle size of the porous material is 100-400 meshes.
4. The hydrogel-coated hydrated salt-porous material composite of claim 1, wherein the hydrogel is an inorganic gel or an organic gel;
the inorganic gel is one of montmorillonite, bentonite or silica gel or a mixture of any proportion;
the organic gel is one or a mixture of polyacrylic acid, starch, polyvinyl alcohol, carboxyl cellulose, sodium carboxyl cellulose, agar, polysaccharide, xanthan gum, gelatin, chitose, cellulose ether, sodium alginate or polyurethane in any proportion.
5. The hydrogel coated hydrated salt-porous material composite of claim 1, prepared by the steps of:
the hydrogel system is directly mixed with the hydrated salt-porous material composite;
or the gel-forming substance and the hydrated salt-porous material compound are uniformly mixed and then added with water to form gel;
or the hydrosol is mixed with the hydrated salt-porous material composite and then is partially dehydrated to form gel.
6. The hydrogel coated hydrated salt-porous material composite of claim 5,
or further comprising a step of removing excess hydrogel and/or a dehydration step;
the mixing is one or any combination mode of ultrasonic mixing, violent stirring mixing or heating mixing;
the hydrated salt-porous material composite is prepared by one of the following methods:
a, normal-pressure melting and mixing: the hydrated salt system melted under normal pressure enters the pore channels of the porous material by virtue of the capillary action;
b, negative pressure pore channel suction: mixing a hydrated salt system and a porous material, putting the mixture into a container, vacuumizing the container in a closed environment, heating and melting the mixture, continuously vacuumizing the container in the melting process, and quickly putting air into the container after melting to promote more of the melted hydrated salt system to enter the inside of a pore channel of the porous material;
c, putting the porous material into a closed container, vacuumizing, and then introducing a molten hydrated salt system;
d, after the porous material is mixed with the molten hydrated salt system, assisting ultrasonic exhaust to promote the exhaust of gas in the pore channel and adsorbed gas on the outer wall of the pore channel;
and E, after the porous material and the molten hydrated salt system are mixed, introducing gas into the closed container, increasing the pressure in the container, and promoting the molten hydrated salt system to enter the inside of the pore channel of the porous material.
7. Use of the hydrogel-coated hydrated salt-porous material composite as defined in any one of claims 1 to 6 as a phase change energy storage material.
8. The use according to claim 7, wherein the hydrogel-coated hydrated salt-porous material composite has a melting point of 23 to 31 ℃, an enthalpy of phase transition of 35 to 120J/g, and a thermal conductivity of 0.45 to 5.0W-m at 25.0 ℃-1·K-1And after 1000 times of circulation, the phase change enthalpy is attenuated by 0.5-2%.
9. Use according to claim 7, wherein the hydrogel-coated hydrated salt-porous material composite is used as a material having plastic and elastic phase change energy storage properties.
10. The use of claim 9, wherein the hydrogel coated hydrated salt-porous material composite is stretched to 1.05 to 1.25 times its original length and compressed to 80 to 95% of its original volume.
11. A preparation method of a hydrated salt-porous material composite based on hydrogel coating is characterized by comprising the following steps:
the hydrogel system is directly mixed with the hydrated salt-porous material composite;
or the gel-forming substance and the hydrated salt-porous material compound are uniformly mixed and then added with water to form gel;
or the hydrosol and the hydrated salt-porous material compound are mixed and then partially dehydrated to form gel;
and obtaining a hydrated salt-porous material composite coated by the hydrogel system, wherein the mass ratio of the hydrogel system to the hydrated salt-porous material composite is 15: 85-50: 50.
12. The preparation method according to claim 11, wherein the mixing is one or any combination of ultrasonic mixing, intensive stirring mixing or heating mixing;
the hydrated salt-porous material composite is prepared by one of the following methods:
a, normal-pressure melting and mixing: the hydrated salt system melted under normal pressure enters the pore channels of the porous material by virtue of the capillary action;
b, negative pressure pore channel suction: mixing a hydrated salt system and a porous material, putting the mixture into a container, vacuumizing the container in a closed environment, heating and melting the mixture, continuously vacuumizing the container in the melting process, and quickly putting air into the container after melting to promote more of the melted hydrated salt system to enter the inside of a pore channel of the porous material;
c, putting the porous material into a closed container, vacuumizing, and then introducing a molten hydrated salt system;
d, after the porous material is mixed with the molten hydrated salt system, assisting ultrasonic exhaust to promote the exhaust of gas in the pore channel and adsorbed gas on the outer wall of the pore channel;
e, after the porous material and the molten hydrated salt system are mixed, introducing gas into the closed container, increasing the pressure in the container, and promoting the molten hydrated salt system to enter the inside of the pore channel of the porous material;
when the hydrogel system is excessive, step 2 is included, and excessive hydrogel is removed by extrusion, high-speed centrifugation or sol heat filtration;
when dehydration is needed, the method comprises the following steps: dehydrating by freeze-drying.
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