A preparation method of a porous copper foam material with high thermal conductivity and heat dissipation

Abstract

The present invention relates to the technical field of metal foam preparation, and in particular to a method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps: S1, preparing two mixtures containing copper powder and additives, and mixing them with polystyrene microspheres and modified polystyrene microspheres respectively to obtain mixtures A and B; S2, placing mixture B into a mold C, isostatically pressing, and obtaining a green body X; S3, placing green body X into a mold D, and then filling mixture A into the pores between green body X and mold D, isostatically pressing, and obtaining green body Y; S4, pre-sintering and sintering green body Y under an inert protective gas atmosphere to obtain a novel porous copper foam material with high thermal conductivity and heat dissipation. The porous copper foam material of the present invention is prepared by adopting a microsphere calcination process, has high porosity and impact resistance, and excellent thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of foam metal preparation, and in particular to a method for preparing a novel porous foam metal copper material with high thermal conductivity and heat dissipation. Background Art

[0002] As electronic devices develop towards high performance, miniaturization and integration, the power density of chips and electronic components continues to increase, and the heat dissipation problem becomes increasingly prominent. Porous copper foam materials have broad application prospects in the field of electronic equipment heat dissipation due to their light weight, large specific surface area and good thermal conductivity.

[0003] At present, the methods for preparing porous foamed copper metal materials mainly include powder metallurgy, melt foaming, electrodeposition and metal deposition. Among them, the powder metallurgy method forms a porous structure by mixing metal powder with a foaming agent and then heating and sintering. Although this method has a relatively simple process, the porosity of the resulting product is low, the pore size distribution is uneven, and the mechanical strength is poor; the melt foaming method is to add a foaming agent to the molten metal and prepare the foamed metal through the bubble formation and solidification process, but this method has problems such as difficulty in process control and unstable product quality; the electrodeposition method obtains a porous structure by electrodepositing copper metal on a porous template and then removing the template. This method can accurately control the pore size and distribution, but has disadvantages such as a long preparation cycle and high cost; the metal deposition method uses chemical vapor deposition or physical vapor deposition to deposit metal on the template surface. Although a higher porosity can be obtained, the equipment requirements are high and it is difficult to achieve large-scale production.

[0004] Announcement No. CN107552796B discloses "A method for preparing foam metal by stacking resin microspheres". This method first prepares a PMMA hollow microsphere, stacks the PMMA hollow microspheres, and then fills them with a slurry prepared by mixing metal powder and water. After drying, sintering and curing, foam metal is obtained. The porosity and size of the foam metal prepared by this method are effectively controlled, and the compressive resistance is enhanced. However, the foam metal prepared by this method cannot be applied to some solid-state battery fields with harsh conditions.

[0005] Therefore, there is an urgent need to develop a new method for preparing porous foam metal copper materials to solve the problems existing in the existing technology, such as poor mechanical properties and narrow application range. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation. The copper foam material is prepared by adopting a microsphere calcination process, has high porosity and impact resistance, and excellent thermal conductivity.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps:

[0009] S1. preparing two mixtures containing copper powder and additives, and mixing them with polystyrene microspheres and modified polystyrene microspheres to obtain mixture A and mixture B, respectively;

[0010] S2, the mixed material B is placed in a mold C and isostatically pressed to obtain a green body X;

[0011] S3, placing the green body X into the mold D, then filling the mixed material A into the gap between the green body X and the mold D, and isostatically pressing to obtain the green body Y;

[0012] S4. Under an inert protective gas atmosphere, pre-sintering and sintering the green body Y to obtain a new type of porous foam metal copper material with high thermal conductivity and heat dissipation.

[0013] In the past, foam metal materials were often mixed with a single sodium chloride and calcined to prepare foam metal copper materials. Although this method is simple in process, the resulting product has low porosity and poor impact resistance, resulting in a narrow range of application for the product. Therefore, it is necessary to improve its process. Previously, a preparation process for foam metal was disclosed in the CN105903968A patent. It was prepared by mixing, refining, calendering, pre-drying, finishing, sintering, cleaning, drying, slicing and other processes, which reduced production time and improved processing accuracy. As the company's research and development continues to deepen, it was found that the performance of the foam metal material in the aforementioned application still has room for improvement, so that the foam metal can be applied to the field of solid-state batteries with more stringent conditions, and prevent the foam metal from cracking due to poor mechanical properties during the pressurized packaging process, affecting battery performance.

[0014] The present application first mixes a composite pore-forming agent, an additive and copper powder with polystyrene microspheres and modified polystyrene microspheres of different particle sizes, and then presses a mixed material B containing modified polystyrene microspheres with smaller particle sizes into a green body X, and then fills and composite-presses a mixed material A containing polystyrene microspheres with larger particle sizes to obtain a green body Y. In this process, the outer layer of the mixed material B is wrapped and compacted by the mixed material A. Under specific conditions, the green body Y is calcined step by step using a microsphere calcination process. First, during the two-stage pre-calcination process, the polystyrene microspheres in the outermost layer of the first calcination process decompose to produce pores. Then, when the temperature is increased again, the modified polystyrene microspheres in the inner layer will begin to decompose and produce gas. Due to the presence of larger pores in the outer layer, internal aggregation and expansion will not occur, resulting in uneven pores in the internal structure of the foam metal. Finally, a foam metal with a gradient pore size distribution is formed. When the outer layer structure is impacted or squeezed, it can undergo slight elastic deformation to absorb energy. The inner layer structure has a high density and acts as a rigid support, thereby improving the stability of the structure, thereby improving the impact resistance and compressive resistance of the foam metal.

[0015] In some embodiments, the mass ratio of the copper powder, the additive, and the polystyrene microspheres is 1:(0.2-0.6):(0.1-0.3).

[0016] In some embodiments, the width of the mold C is greater than the width of the mold D.

[0017] In some embodiments, the average particle size of the polystyrene microspheres is 30-50 μm; the average particle size of the modified polystyrene microspheres is 20-30 μm.

[0018] The present application regulates the average particle size of polystyrene microspheres and modified polystyrene microspheres, enabling the metal foam to form a foamed metal copper material with a pore gradient distribution during the preparation process. In conjunction with a specific preparation process, the problem of uneven pore size distribution caused by microspheres of different particle sizes can be prevented. At the same time, the presence of a gradient pore distribution can improve the thermal conductivity of the metal foam. The reason may be that the large-diameter pores can improve the convective heat transfer performance of the material, and the small-diameter pores can enhance the thermal conduction path. The synergistic effect of the two improves the thermal conductivity of the material.

[0019] In some embodiments, the method for preparing the modified polystyrene microspheres comprises the following steps:

[0020] A1. Acryloyl chloride and melamine were mixed and added to the first solvent and the acid binding agent, and stirred at room temperature for 2 to 4 hours. Epichlorohydrin was then added and stirred at the same temperature for 3 to 5 hours. After the reaction was completed, the organic phase was extracted and concentrated under reduced pressure, and the compound represented by formula I was obtained by column chromatography.

[0021] (I);

[0022] A2. Under an inert protective gas atmosphere, styrene, divinylbenzene, and the compound represented by formula I in step A1 are mixed and added to a second solvent. An initiator is added, and the temperature is raised to 70-90°C and stirred at a constant temperature for 12-14 hours. After the reaction is completed, the mixture is centrifuged, filtered, washed, dried, and placed at 170-200°C for 1-3 hours to obtain modified polystyrene microspheres.

[0023] In some embodiments, the molar ratio of acryloyl chloride, melamine, epichlorohydrin and acid binding agent is (0.8-1):1:(2-2.3):(3.4-4).

[0024] Preferably, the molar ratio of acryloyl chloride, melamine, epichlorohydrin and acid binding agent is 0.9:1:2.2:3.7.

[0025] The present application can prevent the modified polystyrene microspheres from undergoing cross-linking and increasing the microsphere particle size by regulating the molar ratio of acryloyl chloride, melamine, epichlorohydrin and acid-binding agent, which is not conducive to the preparation of a foam metal material with a pore size distribution that increases from the inside to the outside. In addition, it can also prevent the decomposition temperature of the modified polystyrene microspheres and the polystyrene microspheres from being similar, thereby preventing the gas generated by the decomposition of the internal microspheres during the preparation process from being discharged in time, reducing the structural strength of the foam metal and causing uneven pore distribution within the foam metal.

[0026] In some embodiments, in step A2, the molar ratio of styrene, divinylbenzene and the compound represented by formula I is 1:(0.2-0.4):(0.3-0.6).

[0027] Preferably, in step A2, the molar ratio of styrene, divinylbenzene and the compound represented by formula I is 1:0.3:0.4.

[0028] In some embodiments, the method for preparing the additive comprises the following steps:

[0029] B1. Ball mill the kaolin at 500 rpm for 1-2 h to obtain activated kaolin with an average particle size of 1-2 μm.

[0030] B2. Soak the activated kaolin in step B1 in dimethyl sulfoxide for 22 to 24 hours, then add cetyltrimethylammonium bromide, raise the temperature to 60 to 80° C., and soak at this temperature for 4 to 8 hours. Filter to obtain intercalated modified kaolin.

[0031] B3. Soak the intercalated modified kaolin in step B2 in an ethanol dispersion of heptafluorodecyltrimethoxysilane and carboxylated carbon nanotubes, raise the temperature to 55-65° C. and stir at this temperature for 4-8 hours. After the reaction is completed, centrifuge and filter, and dry to obtain the product.

[0032] During the study, the present application found that kaolin will generate mullite phase during high-temperature sintering to enhance the mechanical properties of foamed metal. However, the compatibility between conventional kaolin and copper powder is poor and agglomeration is easily generated. The present application modifies kaolin. On the one hand, the modified kaolin is pretreated with dimethyl sulfoxide and hexadecyltrimethylammonium bromide to increase the spacing between kaolin intercalations, so that carboxylated carbon nanotubes can effectively enter between kaolin intercalations. At the same time, the synergistic addition of heptadecafluorodecyltrimethoxysilane can form a multi-level micro-nano hydrophobic structure, thereby enhancing the compatibility between the modified kaolin and copper powder. At the same time, the carboxylated carbon nanotubes can enter the intercalations of kaolin, enhance the mechanical strength of each intercalation, and further improve the mechanical properties and thermal conductivity of the foamed metal.

[0033] In some embodiments, in step B2, the mass ratio of the activated kaolin, dimethyl sulfoxide, and cetyltrimethylammonium bromide is 1:(5-8):(1-1.5).

[0034] Preferably, in step B2, the mass ratio of the activated kaolin, dimethyl sulfoxide and cetyltrimethylammonium bromide is 1:6:1.3.

[0035] In some embodiments, in step B3, the mass ratio of the heptadecafluorodecyltrimethoxysilane to the carboxylated carbon nanotubes is 1:(0.2-0.7).

[0036] Preferably, in step B3, the mass ratio of the heptadecafluorodecyltrimethoxysilane to the carboxylated carbon nanotubes is 1:0.5.

[0037] In some embodiments, in step S4, the pre-sintering is specifically performed as follows: first heating the temperature to 300-400°C at a heating rate of 5-10°C / min, keeping the temperature for 1-2 hours, then heating the temperature to 500-700°C at a heating rate of 5-10°C / min, and keeping the temperature for 0.5-1.5 hours.

[0038] In some embodiments, in step S4, the sintering temperature is 800-950° C. and the sintering time is 3-4 hours.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The porous foamed copper metal material of the present invention is prepared by adopting a microsphere calcination process, has a gradient pore size distribution structure, and has high porosity and impact resistance, as well as excellent thermal conductivity.

[0041] (2) The modified polystyrene microspheres of the present invention contain a large number of epoxy groups in their structure, which increases the decomposition temperature of the modified polystyrene microspheres and enables them to decompose later than the polystyrene microspheres. When the polystyrene microspheres with larger particle sizes first decompose in the outer layer of the foam metal to form a larger pore structure, the modified polystyrene microspheres with slightly smaller particle sizes then decompose in the interior to form gases that can be discharged smoothly, preventing the risk of gas accumulation increasing the size of the inner pore size. At the same time, it can also prevent the internal structure of the foam metal from cracking due to pressure, resulting in a decrease in mechanical strength.

[0042] (3) The additive of the present invention is prepared by pre-treating modified kaolin with dimethyl sulfoxide and hexadecyltrimethylammonium bromide, thereby increasing the spacing between kaolin intercalations and enabling carboxylated carbon nanotubes to effectively enter between kaolin intercalations. Subsequently, the additive is combined with heptadecafluorodecyltrimethoxysilane to form a multi-level micro-nano hydrophobic structure, thereby enhancing the compatibility between the modified kaolin and copper powder. At the same time, the carboxylated carbon nanotubes can enter the intercalations of kaolin, thereby enhancing the mechanical strength of each intercalation and further improving the mechanical properties and thermal conductivity of the foam metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the structure of green body Y prepared in Example 1;

[0044] Figure 2 Schematic diagram of the structure of the green body X prepared in Example 1;

[0045] Figure 3 is the H NMR spectrum of the compound of formula I obtained in Preparation Example 1;

[0046] Figure 4 This is the H NMR spectrum of the compound represented by Formula II obtained in Preparation Example 2. DETAILED DESCRIPTION

[0047] 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.

[0048] 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.

[0049] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally 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 be used in the practice or testing of the present invention. Various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention, as will be apparent to those skilled in the art. Other embodiments obtained from the present invention description will be apparent to those skilled in the art. This application description and examples are exemplary only.

[0050] Among them, polystyrene microspheres were purchased from Zhongke Leiming (Beijing) Technology Co., Ltd.

[0051] Preparation Example 1

[0052] The preparation method of modified polystyrene microspheres comprises the following steps:

[0053] A1. 270 mmol of acryloyl chloride and 300 mmol of melamine were mixed and added to 550 mL of toluene and 1110 mmol of sodium bicarbonate. The mixture was stirred at room temperature for 3 h. Subsequently, 630 mmol of epichlorohydrin was added and the mixture was stirred at room temperature for 4 h. After the reaction was completed, the mixture was extracted and the organic phase was concentrated under reduced pressure. The compound represented by formula I was obtained by column chromatography.

[0054] (I) (See attached H NMR spectrum Figure 3 );

[0055] A2. Under N2 atmosphere, 750 mmol of styrene, 225 mmol of divinylbenzene, and 300 mmol of the compound represented by formula I in step A1 were mixed and added to 1 L of tetrahydrofuran, and 1 g of azobisisobutyronitrile was added. The temperature was raised to 80°C and stirred at this temperature for 13 hours. After the reaction was completed, the mixture was centrifuged, filtered, washed, dried, and placed at 180°C for 2 hours to obtain modified polystyrene microspheres.

[0056] Preparation Example 2

[0057] The preparation method of modified polystyrene microspheres comprises the following steps:

[0058] A1. 630 mmol of acryloyl chloride and 300 mmol of melamine were mixed and added to 550 mL of toluene and 1110 mmol of sodium bicarbonate. The mixture was stirred at room temperature for 3 h. Subsequently, 270 mmol of epichlorohydrin was added and the mixture was stirred at room temperature for 4 h. After the reaction was completed, the mixture was extracted and the organic phase was concentrated under reduced pressure. The compound represented by formula II was obtained by column chromatography.

[0059] (II) (See attached H NMR spectrum Figure 4 );

[0060] A2. Under N2 atmosphere, 750 mmol of styrene, 225 mmol of divinylbenzene, and 300 mmol of the compound represented by formula II in step A1 were mixed and added to 1 L of tetrahydrofuran, and 1 g of azobisisobutyronitrile was added. The temperature was raised to 80°C and stirred at this temperature for 13 hours. After the reaction was completed, the mixture was centrifuged, filtered, washed, dried, and placed at 180°C for 2 hours to obtain modified polystyrene microspheres.

[0061] Preparation Example 3

[0062] The preparation method of modified polystyrene microspheres is the same as that of Preparation Example 1, except that in step A2, the amount of the compound represented by formula I is 200 mmol.

[0063] Preparation Example 4

[0064] The preparation method of the additive comprises the following steps:

[0065] B1. Ball mill the kaolin at 500 rpm for 1.5 h to obtain activated kaolin with an average particle size of 2 μm;

[0066] B2, soaking 10g of the activated kaolin prepared in step B1 in 60g of dimethyl sulfoxide for 23h, then adding 13g of hexadecyltrimethylammonium bromide, heating to 70°C and soaking at this temperature for 6h, and filtering to obtain intercalated modified kaolin;

[0067] B3. Soak 10 g of the intercalated modified kaolin prepared in step B2 in 300 mL of an ethanol dispersion containing 10 g of heptadecafluorodecyltrimethoxysilane and 5 g of carboxylated carbon nanotubes. Heat the mixture to 60° C. and stir for 6 h. After the reaction is complete, centrifuge and filter, and dry to obtain the product.

[0068] Preparation Example 5

[0069] The preparation method and specific implementation manner of the additive are the same as those of Preparation Example 3, except that cetyltrimethylammonium bromide is not added.

[0070] Preparation Example 6

[0071] The preparation method of the additive is the same as that of Preparation Example 3, except that the operation steps of step B2 are as follows: soaking 10g of the activated kaolin in step B1 in a mixture of 60g of dimethyl sulfoxide and 13g of hexadecyltrimethylammonium bromide for 24h, filtering, and obtaining the additive.

[0072] Example 1

[0073] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps:

[0074] S1. Two mixtures containing 100 g of copper powder and 40 g of an additive were mixed with 20 g of polystyrene microspheres having an average particle size of 40 μm and 20 g of modified polystyrene microspheres having an average particle size of 25 μm, respectively, to obtain mixed materials A and mixed material B;

[0075] S2. The mixed material B is placed into the mold C and isostatically pressed to obtain a green body X (see attached Figure 2 );

[0076] S3. Place the green body X into the mold D, then fill the gap between the green body X and the mold D with the mixed material A, and perform isostatic pressing to obtain the green body Y (see attached). Figure 1 );

[0077] S4. Pre-sintering the green body Y in a N2 atmosphere and sintering it at 900°C for 3.5h to obtain a novel porous copper foam material with high thermal conductivity and heat dissipation.

[0078] The width of mold C is greater than the width of mold D.

[0079] The specific operation steps of pre-sintering are as follows: first, heat up to 350°C at a heating rate of 7°C / min, keep warm for 1.5 hours, then heat up to 600°C at a heating rate of 7°C / min, keep warm for 1 hour.

[0080] The modified polystyrene microspheres were prepared by Preparation Example 1, and the additives were prepared by Preparation Example 4.

[0081] Example 2

[0082] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps:

[0083] S1. Two mixtures containing 100 g of copper powder and 20 g of an additive were mixed with 10 g of polystyrene microspheres having an average particle size of 50 μm and 10 g of modified polystyrene microspheres having an average particle size of 30 μm, respectively, to obtain mixed materials A and mixed material B;

[0084] S2, the mixed material B is placed in a mold C and isostatically pressed to obtain a green body X;

[0085] S3, placing the green body X into the mold D, then filling the mixed material A into the gap between the green body X and the mold D, and isostatically pressing to obtain the green body Y;

[0086] S4. Pre-sinter the green body Y in a N2 atmosphere and sinter it at 800°C for 4h to obtain a new type of porous foam metal copper material with high thermal conductivity and heat dissipation.

[0087] The width of mold C is greater than the width of mold D.

[0088] The specific operation steps of pre-sintering are as follows: first, heat up to 300°C at a heating rate of 5°C / min, keep warm for 2 hours, then heat up to 500°C at a heating rate of 5°C / min, keep warm for 1.5 hours.

[0089] The modified polystyrene microspheres were prepared by Preparation Example 1, and the additives were prepared by Preparation Example 4.

[0090] Example 3

[0091] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps:

[0092] S1. Two mixtures containing 100 g of copper powder and 60 g of an additive were mixed with 30 g of polystyrene microspheres having an average particle size of 30 μm and 30 g of modified polystyrene microspheres having an average particle size of 20 μm, respectively, to obtain mixed materials A and mixed material B;

[0093] S2, the mixed material B is placed in a mold C and isostatically pressed to obtain a green body X;

[0094] S3, placing the green body X into the mold D, then filling the mixed material A into the gap between the green body X and the mold D, and isostatically pressing to obtain the green body Y;

[0095] S4. Pre-sintering the green body Y in a N2 atmosphere and sintering it at 950°C for 3h to obtain a novel porous copper foam material with high thermal conductivity and heat dissipation.

[0096] The width of mold C is greater than the width of mold D.

[0097] The specific operation steps of pre-sintering are as follows: first, heat up to 400°C at a heating rate of 10°C / min, keep warm for 1 hour, then heat up to 700°C at a heating rate of 10°C / min, keep warm for 0.5 hour.

[0098] The modified polystyrene microspheres were prepared by Preparation Example 1, and the additives were prepared by Preparation Example 4.

[0099] Example 4

[0100] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that the modified polystyrene microspheres are prepared by Preparation Example 2.

[0101] Example 5

[0102] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that the modified polystyrene microspheres are prepared according to Preparation Example 3.

[0103] Example 6

[0104] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that the additive is prepared by Preparation Example 5.

[0105] Example 7

[0106] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that the additive is prepared by Preparation Example 6.

[0107] Example 8

[0108] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that the specific operation steps of pre-sintering are as follows: heating to 600°C at a heating rate of 10°C / min and keeping warm for 1.5 hours.

[0109] Comparative Example 1

[0110] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation, comprising the following steps:

[0111] S1, mixing 100 g of copper powder and 40 g of an additive, and then mixing with 20 g of polystyrene microspheres having an average particle size of 40 μm to obtain a mixture A;

[0112] S2, isostatically pressing the mixed material A to obtain a green body M;

[0113] S4. Pre-sinter the green body M in a N2 atmosphere and sinter it at 900°C for 3.5h to obtain a novel porous copper foam material with high thermal conductivity and heat dissipation.

[0114] The specific operation steps of pre-sintering are as follows: heating to 350° C. at a heating rate of 7° C. / min and keeping the temperature for 1.5 h.

[0115] The additive was prepared according to Preparation Example 4.

[0116] Comparative Example 2

[0117] A method for preparing a novel porous copper foam material with high thermal conductivity and heat dissipation is disclosed. The specific implementation method is the same as that of Example 1, except that kaolin of equal mass is used instead of the additive.

[0118] Performance testing:

[0119] (1) Thermal conductivity: The porous copper foam was made into a cylindrical sample with a diameter of 12.7 mm, and the thermal conductivity of the sample was tested using a laser thermal conductivity meter;

[0120] (2) Porosity: The porosity of porous copper foam was tested by gas adsorption method (BET method);

[0121] (3) Compression test: The compression resistance of porous copper foam was tested with reference to the test method of GB / T 31930-2015 standard;

[0122] (4) Impact resistance test: Refer to the GB / T 229-2020 standard test, make the porous copper foam into a standard part with a thickness of 200 mm, and use a 0.5 kg metal ball to vertically impact the standard part at a speed of 300 km / h to observe the dent condition.

[0123] The porous copper foams of the embodiments and comparative examples were tested according to the above method. The test results are shown in Table 1.

[0124] Table 1

[0125]

[0126] According to the data in Table 1, the porous copper foam materials prepared in Examples 1 to 3 have high porosity, thermal conductivity and compressive strength, and good impact resistance. In Example 4, due to the change in the molar ratio of acryloyl chloride, melamine, epichlorohydrin and acid binding agent, cross-linking occurs during the preparation of modified polystyrene microspheres, resulting in an increase in particle size, thereby weakening the pore size gradient distribution effect of the copper foam, and reducing the thermal conductivity, compressive strength and impact strength. In Example 5, due to the change in the molar ratio of styrene, divinylbenzene and the chemical compound shown in Formula I, the modified polystyrene microspheres undergo cross-linking, resulting in an increase in particle size. The molar ratio of the compound, the content of epoxy groups and amide groups in the modified polystyrene microsphere structure is reduced, resulting in a decrease in the high temperature resistance of the modified polystyrene microspheres, a poor effect of forming a gradient pore size distribution, and a disadvantage of improving the compressive strength and impact strength of the foam metal; in Example 6, due to the lack of the addition of hexadecyltrimethylammonium bromide, the single dimethyl sulfoxide has a weak performance in expanding the interlayer spacing of the kaolin intercalation, resulting in a decrease in the amount of copper powder and carboxylated carbon nanotubes intercalated into the kaolin, thereby reducing the compressive strength and impact strength of the internal structure of the foam metal copper; at the same time, the embodiment In Example 7, due to the change in the preparation method of the additive, when dimethyl sulfoxide and cetyltrimethylammonium bromide were used to modify kaolin, the two competed for the active sites of kaolin and a competitive adsorption phenomenon occurred. Cetyltrimethylammonium bromide would hinder dimethyl sulfoxide from entering deeper into the kaolin to expand the interlayer spacing, thereby deteriorating the adsorption capacity and dispersibility of kaolin, thereby weakening the thermal conductivity, compressive strength and impact strength of the foamed copper metal. In Example 8, due to the change in the pre-sintering method, the structural effect of the gradient pore size distribution of the foamed metal was deteriorated, resulting in a significant decrease in the porosity of the foamed metal, while the compressive strength and impact strength decreased. In Comparative Example 1, due to the lack of modified polystyrene microspheres in the preparation process of the foamed copper metal, the porosity and thermal conductivity of the foamed copper metal were reduced, and the impact strength and compressive strength were slightly enhanced. In Comparative Example 2, due to the use of equal mass kaolin instead of the additive, its dispersibility and adsorption capacity in the system were poor, resulting in an uneven pore size distribution of the foamed copper metal, thereby reducing the thermal conductivity, compressive strength and impact strength of the foamed copper metal.

[0127] Finally, it should be noted that the above specific implementation methods 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 examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a porous copper foam material with high thermal conductivity and heat dissipation, characterized in that: The steps include: S1. preparing two mixtures containing copper powder and additives, and mixing them with polystyrene microspheres and modified polystyrene microspheres to obtain mixture A and mixture B, respectively; S2, the mixed material B is placed in a mold C and isostatically pressed to obtain a green body X; S3, placing the green body X into the mold D, then filling the mixed material A into the gap between the green body X and the mold D, and isostatically pressing to obtain the green body Y; S4. Pre-sintering and sintering the green body Y in an inert protective gas atmosphere to obtain a novel porous copper foam material with high thermal conductivity and heat dissipation; The preparation method of the modified polystyrene microspheres comprises the following steps: A1. Acryloyl chloride and melamine were mixed and added to the first solvent and the acid binding agent, and stirred at room temperature for 2 to 4 hours. Epichlorohydrin was then added and stirred at the same temperature for 3 to 5 hours. After the reaction was completed, the organic phase was extracted and concentrated under reduced pressure, and the compound represented by formula I was obtained by column chromatography. （Ⅰ）； A2. Under an inert protective gas atmosphere, styrene, divinylbenzene, and the compound represented by Formula I in step A1 are mixed and added to a second solvent, an initiator is added, and the temperature is raised to 70-90°C and stirred for 12-14 hours. After the reaction is completed, the mixture is centrifuged, filtered, washed, dried, and placed at 170-200°C for 1-3 hours to obtain modified polystyrene microspheres; The preparation method of the additive comprises the following steps: B1. Ball mill the kaolin at 500 rpm for 1-2 h to obtain activated kaolin with an average particle size of 1-2 μm. B2. Soak the activated kaolin in step B1 in dimethyl sulfoxide for 22 to 24 hours, then add cetyltrimethylammonium bromide, raise the temperature to 60 to 80° C., and soak at this temperature for 4 to 8 hours. Filter to obtain intercalated modified kaolin. B3. Soak the intercalated modified kaolin in step B2 in an ethanol dispersion of heptafluorodecyltrimethoxysilane and carboxylated carbon nanotubes, raise the temperature to 55-65° C. and stir at this temperature for 4-8 hours. After the reaction is completed, centrifuge and filter, and dry to obtain the product.

2. The method for preparing the porous copper foam material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: The average particle size of the polystyrene microspheres is 30-50 μm; the average particle size of the modified polystyrene microspheres is 20-30 μm.

3. The method for preparing the porous copper foam material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: The molar ratio of the acryloyl chloride, melamine, epichlorohydrin and acid binding agent is (0.8-1):1:(2-2.3):(3.4-4).

4. The method for preparing the porous foamed copper metal material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: In step A2, the molar ratio of styrene, divinylbenzene and the compound represented by formula I is 1:(0.2-0.4):(0.3-0.6).

5. The method for preparing the porous foam copper material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: In step B2, the mass ratio of the activated kaolin, dimethyl sulfoxide and cetyltrimethylammonium bromide is 1:(5-8):(1-1.5).

6. The method for preparing the porous foamed copper material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: In step B3, the mass ratio of the heptadecafluorodecyltrimethoxysilane to the carboxylated carbon nanotubes is 1:(0.2-0.7).

7. The method for preparing a porous copper foam material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: In step S4, the specific operation of the pre-sintering is: first heating the temperature to 300-400°C at a heating rate of 5-10°C / min, keeping the temperature for 1-2 hours, then heating the temperature to 500-700°C at a heating rate of 5-10°C / min, keeping the temperature for 0.5-1.5 hours.

8. The method for preparing the porous foamed copper metal material with high thermal conductivity and heat dissipation according to claim 1, characterized in that: In step S4, the sintering temperature is 800-950° C. and the sintering time is 3-4 hours.

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