CN116004197A - Preparation method of porous carbon matrix, composite phase change material and preparation method thereof - Google Patents
Preparation method of porous carbon matrix, composite phase change material and preparation method thereof Download PDFInfo
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- CN116004197A CN116004197A CN202310115630.2A CN202310115630A CN116004197A CN 116004197 A CN116004197 A CN 116004197A CN 202310115630 A CN202310115630 A CN 202310115630A CN 116004197 A CN116004197 A CN 116004197A
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Abstract
The invention provides a preparation method of a porous carbon matrix, a composite phase change material and a preparation method thereof, belonging to the technical field of new energy materials, wherein the preparation method of the composite phase change material comprises the following steps: stirring and mixing the easily-decomposable material and the high-heat-conductivity material according to a preset mass ratio; placing the mixture into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure; placing the pressed material into a constant temperature drying oven for drying to obtain a porous carbon matrix; placing excessive filling material into a square container, and putting the square container into a constant-temperature drying oven to completely melt the square container into liquid; placing the dried material into a container, and simultaneously placing the container into a vacuum drying box for vacuum adsorption; placing the container containing the composite material at a preset temperature to cool the container; and removing superfluous materials on the surface to obtain the composite phase change material. The preparation method has simple steps and low cost. Due to the design of the porous carbon matrix, the composite phase change material has the characteristics of high heat conduction and leakage resistance.
Description
Technical Field
The invention belongs to the technical field of new energy materials, and particularly relates to a preparation method of a porous carbon matrix, a composite phase change material and a preparation method of the composite phase change material.
Background
The phase change material is used as an energy storage material, realizes energy storage and release through the phase change process, and has obvious competitive advantages in the fields of heat management and energy storage. At present, organic phase change materials such as paraffin, fatty acid, polyethylene glycol and the like are widely studied and used in the field of low-temperature heat storage, but the defects of the organic phase change materials limit the further application of the organic phase change materials, including the problems of low heat conductivity of the organic phase change materials and leakage of liquid phase change materials during solid-liquid phase change. In order to solve the problems, it is critical to add a heat conductive filler to the phase change material to improve the thermal conductivity and leakage resistance of the composite material. According to the distribution characteristics of the heat conducting filler in the material, the heat conducting filler can be divided into ordered distribution and disordered distribution. The disordered distribution is mainly accompanied by random distribution of heat conducting particles in the composite material, so that the heat transfer resistance is increased, and the heat conductivity improvement degree is limited; in contrast, the ordered distribution of the heat conducting filler can form a relatively complete passage in the composite material, so that a path is provided for heat transfer, the overall heat conductivity of the composite material is greatly improved, and the leakage resistance of the composite material is improved.
In the related art, carbon substances such as expanded graphite, graphene, graphite powder and the like are utilized to be stirred and mixed with a phase change material, so that a composite material with heat conduction and leakage resistance is prepared, but the heat conductivity improvement degree is limited.
Disclosure of Invention
In order to solve the problem of limited enhancement degree of thermal conductivity of a composite material in the related art, the invention provides a preparation method of a porous carbon matrix, a composite phase-change material and a preparation method thereof, wherein the technical scheme is as follows:
in a first aspect, there is provided a method of preparing a porous carbon matrix, the method comprising:
step 1, stirring and mixing an easily-decomposable material and a high-heat-conductivity material according to a preset mass ratio;
step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
and 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain the porous carbon matrix.
Wherein, in the step 2, the range of the pressing pressure is 20-40 MPa, and the range of the pressing time is 5-15 min.
In the step 3, the drying temperature is 70-90 ℃ and the drying time is 4 hours.
Wherein the easily-decomposable material is ammonium bicarbonate, the high-heat-conductivity material is graphite powder, and the dosage ratio of the graphite powder to the ammonium bicarbonate is (5-2.5 g) (5-7.5 g).
In a second aspect, a method for preparing a composite phase change material is provided, the method comprising:
step 1, stirring and mixing an easily-decomposable material and a high-heat-conductivity material according to a preset mass ratio;
step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
step 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain a porous carbon matrix;
step 4, taking excessive filling materials in a container, and putting the container in a constant-temperature drying oven to completely melt the material into liquid;
step 5, placing the material obtained by drying in the step 3 into the container obtained in the step 4, and simultaneously placing the material into a vacuum drying oven for vacuum adsorption;
step 6, placing the container filled with the composite material in the step 5 at a preset temperature to cool the container;
and 7, removing superfluous materials on the surface of the material obtained in the step 6 to obtain the composite phase change material.
Wherein the easily-decomposable material is ammonium bicarbonate, the high-heat-conductivity material is graphite powder, the filling material is paraffin, and the dosage ratio of the graphite powder to the ammonium bicarbonate to the paraffin is (5-2.5 g) to (5-7.5 g) to (10 g).
Wherein, in the step 4, the heating temperature is in the range of 60-75 ℃ and the heating time is in the range of 30-50 min.
In the step 5, the vacuumizing pressure is 65-75 ℃, the temperature is-0.1 MPa, and the time is 1-2 h.
Wherein, in the step 6, the cooling temperature is in the range of 30-25 ℃.
In a third aspect, there is provided a composite phase change material derived from a porous carbon matrix prepared by the method of any one of the first aspects.
The preparation method of the composite phase-change material provided by the invention has the advantages of simple steps and low cost. Because the composite phase change material comprises a porous carbon matrix, the prepared composite phase change material has the characteristics of high heat conduction and leakage resistance, and has certain advantages in the fields of heat dissipation and thermal management.
Drawings
FIG. 1 is a flow chart of a method for preparing a porous carbon substrate according to an embodiment of the present invention;
FIG. 2 is an SEM image of a porous carbon matrix and composite phase change material according to one embodiment of the present invention;
FIG. 3 is a graph of thermal conductivity versus thermal conductivity enhancement rate for composite phase change materials at different graphite volume fractions;
FIG. 4 is a leakage image of pure paraffin wax and the composite phase change material of the present invention.
Detailed Description
The invention is described in further detail below with reference to specific embodiments and figures.
The invention provides a preparation method of a porous carbon matrix, which comprises the following steps:
step 1, stirring and mixing an easily-decomposable material and a high-heat-conductivity material according to a preset mass ratio;
step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
and 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain the porous carbon matrix.
The method of the invention is now described by taking the easily decomposable material as ammonium bicarbonate and the high heat conductive material as graphite powder as an example. According to an embodiment of the present invention, as shown in fig. 1, a method for preparing a porous carbon substrate is provided, which includes the following steps:
step 1, stirring and mixing ammonium bicarbonate and graphite powder according to a preset mass ratio;
ammonium bicarbonate for forming the porous structure of the matrix.
Graphite powder is used for constructing a matrix heat conduction network.
Illustratively, the dosage ratio of graphite powder to ammonium bicarbonate is (5-2.5 g): 5-7.5 g.
Step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
in the step 2, the range of the pressing pressure is 20-40 MPa, and the range of the pressing time is 5-15 min. Preferably, the pressing pressure and the pressing time are respectively 30MPa and 10min, the pressing pressure is 30MPa, and the pressing time is 10min, so that the integrity of the material can be well maintained.
And 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain the porous carbon matrix.
In the step 3, the drying temperature is 70-90 ℃ and the drying time is 4 hours. Preferably, the drying temperature is 80 ℃, and the drying temperature of 80 ℃ can lead the easily-decomposed material to be fully decomposed by heating.
Fig. 2 (a) and fig. 2 (b) are SEM images of a porous carbon matrix, the porous carbon matrix is prepared by utilizing the characteristic that ammonium bicarbonate is easy to decompose when heated, the porous structure of the porous carbon matrix provides adsorption space for a phase change material, and the pore wall formed by graphite powder provides a path for heat transfer.
Exemplary, embodiments of the present invention also provide a composite phase change material, including: porous carbon matrix and paraffin wax.
Wherein the chemical component of the porous carbon matrix is carbon, and the paraffin is mainly hydrocarbon mixture.
The porous carbon matrix is obtained by mixing ammonium bicarbonate and graphite powder, and after the graphite powder and the ammonium bicarbonate are stirred and mixed according to a preset mass ratio, the mixture is subjected to preset pressure forming by a tablet press, and then the mixture is placed into a constant temperature drying oven for drying for a preset period of time, so that the porous carbon matrix is obtained. The parameters of the graphite powder are as follows: the purity was 99.95% and the particle size was 325 mesh.
For example, in one implementation, the mass ratio of graphite powder to ammonium bicarbonate may be 1:1, or 1:2, or 1:3.
Illustratively, in one implementation, the parameters of paraffin are: the melting point is 54-58 ℃ and the density is 0.84g/cm 3 。
According to the embodiment of the invention, the characteristic that ammonium bicarbonate is easy to decompose is mainly utilized, after stirring, cold pressing and drying are carried out on the ammonium bicarbonate and graphite powder, gas generated by decomposition overflows from the inside of the material to form a porous characteristic, so that the porous material is prepared, and after vacuum adsorption on the porous material, the high-heat-conductivity composite phase-change material is prepared.
The embodiment of the invention also provides a preparation method of the composite phase change material, which comprises the following steps of:
step 1, stirring and mixing ammonium bicarbonate and graphite powder according to a preset mass ratio;
ammonium bicarbonate for forming the porous structure of the matrix.
Graphite powder is used for constructing a matrix heat conduction network.
Step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
in the step 2, the range of the pressing pressure is 20-40 MPa, and the range of the pressing time is 5-15 min. Preferably, the pressing pressure and the pressing time are 30MPa and 10min respectively, and the parameters can better maintain the integrity of the material.
Step 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain a porous carbon matrix;
in the step 3, the drying temperature is 70-90 ℃ and the drying time is 4 hours. Preferably, the drying temperature is 80 ℃, a parameter which enables the ammonium bicarbonate to decompose sufficiently thermally.
Step 4, taking excessive paraffin into a container such as a square plastic box, and putting the container into a constant-temperature drying box to completely melt the paraffin into liquid;
paraffin is a heat storage medium.
In the step 4, the heating temperature is 60-75 ℃ and the heating time is 30-50 min. Preferably, the heating temperature and the heating time are respectively 70 ℃ and 45min, and the parameters can lead the solid paraffin to be completely melted into liquid.
Step 5, placing the material obtained by drying in the step 3 into the container obtained in the step 4, and simultaneously placing the material into a vacuum drying oven for vacuum adsorption;
in the step 5, the vacuumizing temperature is 65-75 ℃, the pressure is-0.1 MPa, and the time is 1-2 h. Preferably, the evacuation temperature and time are 70 ℃ and 1.5 hours, respectively, which parameters enable the liquid paraffin to be fully infiltrated into the porous carbon matrix.
Step 6, placing the container filled with the composite material in the step 5 at a preset temperature to cool the container;
the cooling temperature is in the range of 30-25 ℃. Preferably, the cooling temperature is 25 ℃, a parameter which enables the composite material to be sufficiently cooled.
And 7, removing superfluous materials on the surface of the material obtained in the step 6 to obtain the composite phase change material.
Wherein the dosage ratio of graphite powder, ammonium bicarbonate and paraffin is (5-2.5 g): (5-7.5 g): 10g.
According to the embodiment of the invention, after stirring and mixing graphite powder and ammonium bicarbonate according to a certain mass ratio, a certain pressure is applied to a tablet press for forming, the tablet press is placed into a constant-temperature drying oven for drying for a certain time, a porous carbon matrix is obtained, and finally, the porous carbon matrix and liquid paraffin are subjected to vacuum adsorption to prepare the paraffin/porous carbon composite phase change material.
Fig. 2 (c) and fig. 2 (d) are SEM images of the composite phase change material, and after the porous carbon matrix adsorbs paraffin, the internal pores of the material are filled with paraffin, so that the composite phase change material with certain performance is prepared.
FIG. 3 is a graph showing the thermal conductivity and the thermal conductivity enhancement rate of the composite phase-change material under different graphite volume fractions, wherein the thermal conductivity of the composite phase-change material is greatly improved by adding a porous carbon matrix, the volume fraction of graphite powder is from 15.40% to 35.72%, the thermal conductivity of the composite phase-change material is from 7.48W/(m.K) to 19.20W/(m.K), and the thermal conductivity enhancement rate is from 28.92 to 76.08, so that the thermal conductivity of the composite material is greatly improved.
FIG. 4 is a leakage image of pure paraffin wax and the composite phase change material of the present invention. The pure paraffin sample and the composite phase-change material are placed in a constant-temperature drying oven at 80 ℃, images before and after 30 minutes of the experiment are shot, and after the pure paraffin sample is completely melted into liquid, the composite phase-change material can still maintain a stable shape, and has excellent anti-leakage performance.
According to the invention, by adding ammonium bicarbonate, a certain porous structure is formed in the material after the ammonium bicarbonate is heated and decomposed, a path is provided for heat transfer, and meanwhile, the formed porous carbon material also shows a certain adsorption performance. The composite phase change material finally obtained by soaking the paraffin has high heat conductivity coefficient, good leakage resistance and certain circulation stability.
Referring to tables 1 to 3, table 1 shows the thermal conductivity of the composite phase change material at the graphite volume fraction of the melt blending method of 0.4W/(m·k) for paraffin wax in the related art, table 2 shows the thermal conductivity of the composite phase change material at the graphite volume fraction of the compression molding method of 1.4W/(m·k) for bakelite in the related art, and table 3 shows the thermal conductivity of the composite phase change material at the graphite volume fraction of the cold press drying method of 0.25W/(m·k) for paraffin wax in the embodiment of the present invention. It can be obtained that the thermal conductivity of the composite phase change material in the embodiment of the invention is higher than that of the composite phase change material under a certain graphite volume fraction in the related technology.
Table 1 thermal conductivity of composite phase change materials at graphite volume fraction of melt blending process
Table 2 thermal conductivity of composite phase change materials at graphite volume fraction for compression molding
TABLE 3 thermal conductivity of composite phase change materials of the examples of this invention
It should be noted that in the embodiment of the invention, the porous structure is formed by cold pressing and drying of the easily-decomposable material ammonium bicarbonate and the high-heat-conductivity material graphite powder. The easily decomposable material in the invention can also be sodium bicarbonate and the like; the high heat conduction material can also be aluminum nitride, silicon carbide, copper powder and the like; the filler may be solid-liquid phase transition materials such as higher aliphatic hydrocarbons, fatty acids and esters thereof, or materials with low heat conductivity such as epoxy resin, other than paraffin. The present invention is not particularly limited to the easily decomposable material, the highly thermally conductive material and the filler material.
The preparation method of the composite phase change material provided by the embodiment of the invention has the advantages of simple steps and low cost. Because the composite phase change material comprises a porous carbon matrix, the prepared composite phase change material has the characteristics of high heat conduction and leakage resistance, and has certain advantages in the fields of heat dissipation and thermal management.
The foregoing has outlined rather broadly the more detailed description of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present invention may be better understood. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. In addition, the invention is not fully described in the conventional technology.
Claims (10)
1. A method of preparing a porous carbon substrate, the method comprising:
step 1, stirring and mixing an easily-decomposable material and a high-heat-conductivity material according to a preset mass ratio;
step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
and 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain the porous carbon matrix.
2. The method according to claim 1, wherein in step 2, the pressing pressure is in the range of 20 to 40MPa and the pressing time is in the range of 5 to 15min.
3. The method according to claim 1, wherein in step 3, the drying temperature is in the range of 70 to 90 ℃ and the drying time is 4 hours.
4. The method of claim 1, wherein the readily decomposable material is ammonium bicarbonate, the highly thermally conductive material is graphite powder, and the ratio of graphite powder to ammonium bicarbonate is between 5 and 2.5g, and between 5 and 7.5 g.
5. A method of preparing a composite phase change material, the method comprising:
step 1, stirring and mixing an easily-decomposable material and a high-heat-conductivity material according to a preset mass ratio;
step 2, placing the mixture obtained in the step 1 into a die, and pressing for a preset time and forming by using a tablet press under a preset pressure;
step 3, placing the pressed material obtained in the step 2 into a constant-temperature drying oven for drying to obtain a porous carbon matrix;
step 4, taking excessive filling materials in a container, and putting the container in a constant-temperature drying oven to completely melt the material into liquid;
step 5, placing the material obtained by drying in the step 3 into the container obtained in the step 4, and simultaneously placing the material into a vacuum drying oven for vacuum adsorption;
step 6, placing the container filled with the composite material in the step 5 at a preset temperature to cool the container;
and 7, removing superfluous materials on the surface of the material obtained in the step 6 to obtain the composite phase change material.
6. The method according to claim 5, wherein the easily decomposable material is ammonium bicarbonate, the high heat-conducting material is graphite powder, the filling material is paraffin wax, and the dosage ratio of the graphite powder to the ammonium bicarbonate to the paraffin wax is (5-2.5 g): (5-7.5 g): 10g.
7. The method according to claim 5, wherein in step 4, the heating temperature is in the range of 60 to 75 ℃ and the heating time is in the range of 30 to 50 minutes.
8. The method according to claim 5, wherein in step 5, the evacuation temperature is 65 to 75 ℃, the pressure is-0.1 MPa, and the time is 1 to 2 hours.
9. The method according to claim 5, wherein in step 6, the cooling temperature is in the range of 30-25 ℃.
10. A composite phase change material, characterized in that it is obtained from a porous carbon matrix, which is produced by the method according to any one of claims 1 to 4.
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