An intelligent insulating material with heat conduction and nonlinear volt-ampere characteristic, a preparation method and applications thereof

Abstract

The application relates to a heat-conducting intelligent insulation material with nonlinear volt-ampere characteristics, a preparation method and application thereof, and belongs to the technical field of insulation materials. The intelligent insulation material comprises a polymer matrix and SiC nanofiber felt in the polymer matrix, the volume fraction of the SiC nanofiber felt is 0.5%-2% of the polymer matrix, the SiC nanofiber felt is assembled by roughly same-direction SiC nanofibers, and the SiC nanofibers are arranged in parallel or vertically in the polymer matrix. The scheme provided by the application can optimize the heat conduction path of the intelligent insulation material, and the high heat conduction and nonlinear volt-ampere characteristics of the material are considered, the problem of low heat dissipation efficiency of the packaging material is solved, the composite material is endowed with the electric field self-adaptive regulation and control ability of low-field insulation and high-field conduction through the nonlinear volt-ampere characteristics, and the aging breakdown problem of the composite material when facing the electric field distortion phenomenon is relieved.

Description

Technical Field

[0001] This application relates to the field of insulating materials technology, and in particular to a thermally conductive smart insulating material with nonlinear current-voltage characteristics, its preparation method, and its application. Background Technology

[0002] With the rapid development of industries such as 5G, 6G, artificial intelligence, and automotive electronics, high-power semiconductor devices (such as SiC MOSFETs and GaN MOSFETs) are evolving towards miniaturization, high integration, and high power density, with operating temperatures reaching over 200°C. Thermal failure of their packaging materials has become a primary obstacle to the performance and lifespan of electronic devices. For example, the out-of-plane thermal conductivity of the thermal interface material connecting the heat sink and the device is particularly important, which places higher demands on the thermal management capabilities of the packaging material in specific directions. Furthermore, high-power-density semiconductor devices also experience phenomena such as electric field distortion and partial discharge, ultimately leading to dielectric breakdown and insulation failure. Summary of the Invention

[0003] One of the objectives of this application is to provide a smart insulating material with thermal conductivity and nonlinear volt-ampere characteristics to overcome the shortcomings of the prior art. This material can optimize the heat conduction path of the smart insulating material, taking into account both the high thermal conductivity and nonlinear volt-ampere characteristics of the material. It not only solves the problem of low heat dissipation efficiency of the encapsulation material, but also endows the composite material with the ability to adaptively control the electric field for low-field insulation and high-field conduction through the nonlinear volt-ampere characteristics, thereby alleviating the aging and breakdown problem of the composite material when facing electric field distortion.

[0004] The second objective of this application is to provide a method for preparing a smart insulating material that is thermally conductive and has nonlinear current-voltage characteristics.

[0005] The third objective of this application is to provide a smart insulating material with thermal conductivity and nonlinear current-voltage characteristics for use in electronic packaging materials and insulation of high-voltage electrical equipment.

[0006] One of the objectives of this application is achieved through the following technical solution:

[0007] A smart insulating material with thermal conductivity and nonlinear current-voltage characteristics is provided, comprising a polymer matrix and a SiC nanofiber felt inside it, wherein the volume fraction of the SiC nanofiber felt is 0.5% to 2% of the polymer matrix, and the SiC nanofiber felt is assembled by stacking approximately homo-oriented SiC nanofibers; the SiC nanofiber felt is arranged in parallel or perpendicular arrangement in the polymer matrix.

[0008] In some embodiments, the polymer matrix includes at least one selected from epoxy resin, polyimide, polyethylene terephthalate, polydimethylsiloxane, polyurethane, polyvinylidene fluoride, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polyethylene, polystyrene, polypropylene, polymethyl methacrylate, polyamide, polyoxymethylene, polycarbonate, styrene-butadiene rubber, silicone rubber, cis-butadiene rubber, isoprene rubber, chloroprene rubber, and natural rubber.

[0009] In some embodiments, the epoxy resin includes an epoxy resin matrix, a curing agent, and a latent agent;

[0010] The epoxy resin is any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin and alicyclic epoxy resin.

[0011] The curing agent is either methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride;

[0012] The luring agent is any one of neodymium acetylacetonate, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

[0013] The beneficial effects of the intelligent insulating material with thermal conductivity and nonlinear current-voltage characteristics proposed in this application are as follows:

[0014] (1) The intelligent insulating material with thermal conductivity and nonlinear current-voltage characteristics provided in this application is formed by overlapping SiC nanofibers to form SiC nanofiber felt with horizontal or vertical orientation. With the SiC nanofiber felt filled with a polymer matrix of 0.3% to 2% by volume, the SiC nanofibers of the intelligent insulating material with horizontal orientation extend horizontally and are interwoven with each other, which can form a transverse heat conduction path and act as an in-plane heat conduction path; while the SiC nanofibers of the intelligent insulating material with vertical orientation are cross-connected vertically, which can form a longitudinal heat conduction path and act as an out-of-plane heat conduction path. It has the advantages of low filling, short path, high thermal conductivity and low thermal resistance.

[0015] (2) The intelligent insulating material provided in this application, which is thermally conductive and has nonlinear current-voltage characteristics, forms a three-dimensional conduction path with close contact in the SiC nanofiber felt. When local electric field inhomogeneity occurs, resulting in partial discharge, the intelligent insulating material with horizontal or vertical orientation structure acts as a charge release path and is rapidly conducted and released along the extension direction of the SiC nanofiber felt. Compared with the existing irregular and non-oriented SiC nanofibers, it has a faster response speed and release speed.

[0016] The second objective of this application is achieved through the following technical solution:

[0017] A method for preparing the aforementioned thermally conductive and nonlinear current-voltage characteristic smart insulating material is provided, comprising the following steps:

[0018] (1) Add polycarbosilane and polyoxyethylene to chloroform and mix evenly to prepare SiC polymer precursor solution;

[0019] (2) The SiC polymer precursor solution is subjected to high voltage electrospinning orientation treatment, and polymer flexible fiber mat with nanofibers extending in roughly the same direction is collected through a substrate. After peeling off the polymer flexible fiber mat, it is cut into sheets to obtain sheet fiber mat. The sheet fiber mat is stacked and assembled, and then cured and sintered to obtain SiC nanofiber mat.

[0020] (3) Mix the epoxy resin matrix, curing agent and luring agent and stir evenly. Immerse the SiC nanofiber felt in the epoxy resin mixture until it is completely penetrated. Then transfer it to a high-temperature vacuum drying oven and continue to evacuate the vacuum.

[0021] (4) The SiC nanofiber felt that is completely impregnated with epoxy resin is taken out and transferred to a constant temperature drying oven for gradient temperature curing to prepare a smart insulating material with thermal conductivity and nonlinear volt-ampere characteristics.

[0022] In some embodiments, the ratio of the added polycarbosilane, polyethylene oxide and chloroform is (1g~2g):(0.2g~0.4g):10mL, the stirring time is 6 hours, and the stirring temperature is room temperature.

[0023] In some embodiments, the voltage of the high-voltage electrospinning is 40kV;

[0024] The stacking assembly specifically involves stacking several sheet-like fiber felts sequentially in the horizontal direction or in the vertical direction.

[0025] In some embodiments, the curing specifically involves placing the stacked and assembled sheet fiber felt into an oven for high-temperature oxidation treatment, wherein the high-temperature oxidation temperature is 200°C and the curing time is 2 hours.

[0026] The sintering process specifically involves: after the stacked and assembled sheet fibers are cured, they are transferred to a high-temperature atmosphere tube furnace and sintered at high temperature in an inert gas atmosphere. The sintering temperature is 1600℃, the heating rate is 5℃ / min, the holding time is 2 hours, and the cooling rate is 10℃ / min.

[0027] In some embodiments, the number of the plurality of sheet-like fiber felts stacked sequentially in the horizontal direction or in the vertical direction is 5n, where n is a natural number, and the thickness of the sheet-like fiber felts is 50 to 100 μm.

[0028] In some embodiments, the weight ratio of the epoxy resin, curing agent, and latent agent is 100g:(90g-120g):(0.5g-1g); the stirring temperature is 40-80°C, and the stirring time is 1 hour.

[0029] The vacuum drying temperature is 80℃, and the continuous vacuuming time is 12 hours;

[0030] The gradient temperature curing process specifically involves:

[0031] The first stage of curing treatment, the second stage of curing treatment, and the third stage of curing treatment are performed sequentially. The curing temperature of the first stage of curing treatment is 120°C and the curing time is 2 hours; the curing temperature of the second stage of curing treatment is 145°C and the curing time is 3 hours; and the curing temperature of the third stage of curing treatment is 165°C and the curing time is 2 hours.

[0032] The method for preparing the thermally conductive and nonlinear volt-ampere-current characteristic smart insulating material provided in this application may include the following:

[0033] Beneficial effects:

[0034] The method for preparing a thermally conductive and nonlinear volt-ampere intelligent insulating material provided in this application involves high-voltage electrospinning and orientation treatment of a mixed solution of polycarbosilane and polyethylene oxide. This orientation process yields SiC nanofiber mats with approximately identical fiber orientations. The relatively uniform arrangement of SiC nanofibers improves the heat flux after the connection between SiC nanofibers, enabling high thermal conductivity with a filling volume fraction of 0.5% to 2%. This ensures the processability and good mechanical strength of the material. Compared with existing technologies, this method significantly reduces ineffective connections between SiC nanofibers and disordered, lengthy heat conduction paths.

[0035] The third objective of this application is achieved through the following technical solution:

[0036] This provides the application of the aforementioned thermally conductive and nonlinear volt-ampere characteristics of intelligent insulating materials in electronic packaging materials and insulation of high-voltage electrical equipment.

[0037] The technical solution provided in this application may include the following beneficial effects:

[0038] The intelligent insulating material provided in this application, which is thermally conductive and has nonlinear current-voltage characteristics, has a higher threshold field strength in its horizontally oriented structure and a more stable nonlinear coefficient in its vertically oriented structure. This enables the intelligent insulating material to be used in electronic packaging materials and high-voltage electrical equipment insulation under different operating conditions. It can improve the insulation level of high-voltage electrical equipment and regulate the spatial electric field distribution of high-voltage electrical equipment, thereby ensuring the safe and stable operation of electrical equipment. Attached Figure Description

[0039] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments of this application taken in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of this application.

[0040] Figure 1 SEM image of the smart insulating material prepared in Example 1;

[0041] Figure 2 SEM image of the smart insulating material prepared in Example 5;

[0042] Figure 3 The nonlinear current-voltage characteristic curves of the smart insulating materials prepared in Examples 1-8 are shown. Detailed Implementation

[0043] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0044] Related research has found that doping polymer matrices with high thermal conductivity semiconductor fillers can achieve nonlinear current-voltage characteristics and efficient thermal management capabilities in insulating materials. However, low filler content results in low efficiency in improving the thermal conductivity of composite materials, making it difficult to address the heat accumulation problem caused by high leakage current at electric field distortion points, which can easily lead to thermal breakdown failure of the encapsulated insulation. Furthermore, the weak nonlinear current-voltage characteristics cannot quickly alleviate the problem of localized high electric fields. Higher filler content reduces the material's processability and mechanical strength, and the random distribution of fillers significantly increases costs. Therefore, it is crucial to find a structural orientation design that balances the nonlinear current-voltage characteristics and high thermal conductivity of composite materials.

[0045] To address the above problems, this invention provides a thermally conductive smart insulating material with nonlinear current-voltage characteristics, its preparation method, and its applications.

[0046] The present invention will be further described in detail below with reference to the embodiments. There are no special restrictions on the source of all raw materials used in the present invention. They can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0047] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity used in the field of resin materials.

[0048] In a typical embodiment of the present invention, a smart insulating material with thermal conductivity and nonlinear volt-ampere characteristics is provided. This material can optimize the heat conduction path of the smart insulating material and has both high thermal conductivity and nonlinear volt-ampere characteristics. It not only solves the problem of low heat dissipation efficiency of encapsulation materials, but also endows the composite material with the ability to adaptively control the electric field for low-field insulation and high-field conduction through nonlinear volt-ampere characteristics, thereby alleviating the aging and breakdown problem of composite materials when facing electric field distortion.

[0049] In one embodiment of the present invention, a smart insulating material with thermal conductivity and nonlinear current-voltage characteristics is provided. The smart insulating material includes a polymer matrix and a SiC nanofiber felt inside it. The volume fraction of the SiC nanofiber felt is 0.5% to 2% of the polymer matrix. The SiC nanofiber felt is assembled by stacking approximately homo-oriented SiC nanofibers. The SiC nanofibers are arranged in parallel or perpendicular arrangement in the polymer matrix.

[0050] Furthermore, the aforementioned polymer matrix includes at least one selected from epoxy resin, polyimide, polyethylene terephthalate, polydimethylsiloxane, polyurethane, polyvinylidene fluoride, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polyethylene, polystyrene, polypropylene, polymethyl methacrylate, polyamide, polyoxymethylene, polycarbonate, styrene-butadiene rubber, silicone rubber, cis-butadiene rubber, isoprene rubber, chloroprene rubber, and natural rubber. This polymer matrix is ​​universally applicable; different types of polymer substrates can be used in the smart insulating materials of the embodiments of the present invention. Specifically, in a preferred embodiment, the polymer matrix is ​​selected as epoxy resin.

[0051] Furthermore, the epoxy resin includes an epoxy resin matrix, a curing agent, and a latent agent; the epoxy resin is any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and alicyclic epoxy resin.

[0052] The curing agent is either methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride;

[0053] The luring agent is any one of neodymium acetylacetonate, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

[0054] Epoxy resin (EP) is a type of thermosetting resin with excellent mechanical properties, dimensional stability, and electrical insulation. It has been widely used in electronic packaging fields such as adhesives, casting materials, and coatings. With the rapid development of electronic technology, the heat generated by electronic components increases exponentially with the reduction in size and the improvement of performance. Overheating of electronic equipment can seriously affect the reliability and service life of products. The extremely low thermal conductivity of epoxy resin (approximately 0.2 W / (mk)) is no longer suitable for the current operating environment of electronic components. The epoxy resin described in this invention includes any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyphenolic glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and alicyclic epoxy resin. Typical but non-limiting examples of the combination include: a combination of bisphenol A type epoxy resin and bisphenol F type epoxy resin, a combination of bisphenol F type epoxy resin and phenolic epoxy resin, a combination of polyphenolic glycidyl ether epoxy resin and aliphatic glycidyl ether epoxy resin, or a combination of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin, etc.

[0055] The present invention does not impose any particular limitation on the amount of curing agent added. In order to improve the dispersion and composite material performance, the mass ratio of the curing agent to the epoxy resin is preferably 100:(90-120), more preferably 100:(95-110), and even more preferably 100:(100-105).

[0056] The luring agent of the present invention preferably includes one or more of neodymium acetylacetonate, 2-methylimidazole, and 2-ethyl-4-methylimidazole, more preferably neodymium acetylacetonate and 2-ethyl-4-methylimidazole, and more specifically neodymium acetylacetonate. The mass ratio of the luring agent to the epoxy resin is preferably 100:(0.5-1), more preferably 100:(0.7-0.8).

[0057] In another embodiment of the present invention, a method for preparing a smart insulating material that is thermally conductive and has nonlinear current-voltage characteristics is provided, characterized in that the preparation method includes:

[0058] (1) Add polycarbosilane and polyoxyethylene to chloroform and mix evenly to prepare SiC polymer precursor solution;

[0059] (2) The SiC polymer precursor solution is subjected to high voltage electrospinning orientation treatment, and polymer flexible fiber mat with nanofibers extending in roughly the same direction is collected through a substrate. After peeling off the polymer flexible fiber mat, it is cut into sheets to obtain sheet fiber mat. The sheet fiber mat is stacked and assembled, and then cured and sintered to obtain SiC nanofiber mat.

[0060] (3) Mix the epoxy resin matrix, curing agent and luring agent and stir evenly. Immerse the SiC nanofiber felt in the epoxy resin mixture until it is completely penetrated. Then transfer it to a high-temperature vacuum drying oven and continue to evacuate the vacuum.

[0061] (4) The SiC nanofiber felt that is completely impregnated with epoxy resin is taken out and transferred to a constant temperature drying oven for gradient temperature curing to prepare a smart insulating material with thermal conductivity and nonlinear volt-ampere characteristics.

[0062] The electrospinning method described in this invention can be any method well known to those skilled in the art and is not particularly limited. In this embodiment, the orientation of SiC nanofibers can be achieved through methods such as improved collection devices, field-induced spinning, parallel electrode collectors, and improved electrospinning solutions.

[0063] Among them, the improved collection device method obtains the working principle of oriented electrospinning by improving the collection device. It adopts a roller-shaped collector and uses its high-speed rotation to stretch the polymer jet, thereby obtaining oriented nanofibers.

[0064] Among them, field-induced spinning is a method that induces the orientation of electrospinning by applying an external magnetic or electric field to both sides of the collector.

[0065] Among them, the parallel electrode spinning method involves collecting electrospun fibers between two parallel conductive strips (e.g., metal or highly doped silicon). The distance between the parallel electrodes can range from hundreds of micrometers to several centimeters.

[0066] Among them, the electrospinning solution improvement method is to add a solution with a low dielectric constant to the electrospinning solution to prepare a solution with low charge induction, thereby eliminating the bending instability of electrospinning during electrospinning and promoting the formation of a stable and low-speed forward-moving electrospinning jet.

[0067] Understandably, due to the limitations of current electrospinning technology, it is impossible to achieve completely unidirectional SiC nanofibers.

[0068] The immersion described in this invention refers to completely submerging the SiC nanofiber felt in the epoxy resin mixture. To improve dispersion and composite material properties, after the SiC nanofiber felt is completely submerged in the epoxy resin mixture, the container containing the epoxy resin mixture can be placed in a vacuum chamber for vacuum treatment to remove air bubbles from the epoxy resin mixture. The vacuum treatment pressure is 0.01–0.07 MPa, more preferably 0.02–0.06 MPa, and most preferably 0.03–0.05 MPa.

[0069] The present invention describes the removal of the epoxy resin-impregnated nanofiber felt, specifically by removing the nanofiber felt after a certain period of immersion. Those skilled in the art can select the immersion time of the nanofiber felt based on the type of epoxy resin, curing agent, and latent agent, as well as the curing agent of the curing agent. The immersion time described in the present invention is preferably 3 to 12 hours, more preferably 5 to 10 hours, and most preferably 6 to 8 hours.

[0070] Furthermore, the ratio of the above-mentioned polycarbosilane, polyethylene oxide and chloroform is (1g~2g):(0.2g~0.4g):10mL, the stirring time is 6 hours, and the stirring temperature is room temperature.

[0071] Furthermore, the voltage of the aforementioned high-voltage electrospinning is 40kV;

[0072] The stacking assembly specifically involves stacking several sheet-like fiber felts sequentially in the horizontal direction or in the vertical direction.

[0073] Furthermore, the above-mentioned curing specifically involves: placing the stacked and assembled sheet fiber felt into an oven for high-temperature oxidation treatment, wherein the high-temperature oxidation temperature is 200°C and the curing time is 2 hours;

[0074] The sintering process specifically involves: after the stacked and assembled sheet fiber felt is cured, it is transferred to a high-temperature atmosphere tube furnace and sintered at high temperature in an inert gas atmosphere. The sintering temperature is 1600℃, the heating rate is 5℃ / min, the holding time is 2 hours, and the cooling rate is 10℃ / min.

[0075] Furthermore, the number of the aforementioned sheet-like fiber felts stacked sequentially in the horizontal direction or in the vertical direction is 5n, where n is a natural number, and the thickness of the sheet-like fiber felts is 50–100 μm.

[0076] Furthermore, the weight ratio of epoxy resin, curing agent, and latent agent is 100g:(90g~120g):(0.5g~1g); the stirring temperature is 40~80℃, and the stirring time is 1 hour;

[0077] The vacuum drying temperature is 80℃, and the continuous vacuuming time is 12 hours;

[0078] The gradient temperature curing process specifically involves:

[0079] The first stage of curing treatment, the second stage of curing treatment, and the third stage of curing treatment are performed sequentially. The curing temperature of the first stage of curing treatment is 120°C and the curing time is 2 hours; the curing temperature of the second stage of curing treatment is 145°C and the curing time is 3 hours; and the curing temperature of the third stage of curing treatment is 165°C and the curing time is 2 hours.

[0080] In another embodiment of the present invention, an application of the thermally conductive and nonlinear current-voltage characteristic smart insulating material provided in the above embodiments is provided in electronic packaging materials. In the electronic packaging material, horizontally oriented or vertically oriented SiC nanofiber structures are used as the thermally conductive material of the polymer matrix. The horizontally oriented structure has a higher threshold field strength, while the vertically oriented structure has a more stable nonlinear coefficient. This allows the smart insulating material of this application to be used in electronic packaging materials under different operating conditions and in the insulation of high-voltage electrical equipment. It can improve the insulation level of high-voltage electrical equipment and regulate the spatial electric field distribution of high-voltage electrical equipment, ensuring the safe and stable operation of electrical equipment.

[0081] To further illustrate the present invention, the following detailed description of the intelligent insulating material with thermal conductivity and nonlinear current-voltage characteristics and its preparation method provided by the present invention is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0082] Example 1

[0083] A method for preparing a thermally conductive smart insulating material with nonlinear current-voltage characteristics:

[0084] 1. Add 1g of polycarbosilane and 0.2g of polyethylene oxide to chloroform and stir for 6 hours at room temperature to obtain a SiC polymer precursor solution. Then, put the SiC polymer precursor solution into an electrospinning machine for high-voltage electrospinning orientation treatment. The applied voltage for electrospinning is 40kV. Cut the obtained polymer flexible fiber felt into sheets to obtain sheet fiber felt, and then stack them horizontally.

[0085] 2. The stacked sheet fiber felt was placed in a drying oven and cured at 200℃ for 2 hours. Then it was transferred to a high-temperature atmosphere tube furnace and sintered at 1600℃ under the protection of argon atmosphere. The heating rate was 5℃ / min, the holding time was 2 hours, and the cooling rate was 10℃ / min to obtain SiC nanofiber felt with the same orientation.

[0086] 3. Stir 100 parts by weight of bisphenol A epoxy resin, 70 parts by weight of methyltetrahydrophthalic anhydride and 0.5 parts by weight of triethylamine at 60°C for 1 hour.

[0087] 4. Take 3.4g of the above epoxy resin mixture and 56mg of the prepared SiC nanofiber felt with the same orientation, and horizontally immerse them in the above epoxy resin mixture until they are completely penetrated. Then transfer the mixture to a high-temperature vacuum drying oven and continuously evacuate it. The vacuum drying temperature is 80℃ and the vacuum time is 12 hours until no bubbles emerge. Then transfer it to a stainless steel mold and cure it at 120℃ for 2 hours, then at 145℃ for 3 hours, and finally at 165℃ for 2 hours to prepare a smart insulating material containing 0.5 vol% SiC nanofiber felt.

[0088] Example 2

[0089] The difference from Example 1 is that the amount of SiC nanofiber mat with co-orientation is 112 mg.

[0090] Example 3

[0091] The difference from Example 1 is that the amount of SiC nanofiber mat with co-orientation is 168 mg.

[0092] Example 4

[0093] The difference from Example 1 is that the amount of SiC nanofiber mat with co-orientation is 224 mg.

[0094] Example 5

[0095] The difference from Example 1 is that the SiC nanofiber felt with the same orientation is vertically immersed in the epoxy resin mixture.

[0096] Example 6

[0097] The difference from Example 2 is that the SiC nanofiber felt with the same orientation is vertically immersed in the epoxy resin mixture.

[0098] Example 7

[0099] The difference from Example 3 is that the SiC nanofiber felt with the same orientation is vertically immersed in the epoxy resin mixture.

[0100] Example 8

[0101] The difference from Example 4 is that the SiC nanofiber felt with the same orientation is vertically immersed in the epoxy resin mixture.

[0102] This application performs SEM tests on Embodiments 1 and 5 described above, as detailed in [link to details]. Figure 1 and Figure 2 .

[0103] Specifically, field emission scanning electron microscopy (Merlin, Zeiss) was used to characterize epoxy resin composites with parallel and perpendicularly aligned SiC nanofiber mats. For the parallel-stacked smart insulation material, liquid nitrogen was used to induce brittle fracture in order to clearly observe the internal parallel-aligned SiC nanofibers. The cross-sectional SEM images after brittle fracture are shown below. Figure 1 The SEM image of the smart insulating material prepared in Example 1 clearly shows that the nanofibers in the parallel-aligned nanofiber felt are exposed at the cross-sectional surface. The SiC nanofibers are interwoven, forming good lateral conductive paths, which can serve as efficient in-plane heat conduction pathways. For the smart insulating material with a vertically aligned structure... Figure 2 The image shows an SEM image of the smart insulating material prepared in Example 5. It can be seen that the SiC nanofiber felt is entirely vertically aligned, and vertically arranged nanofibers are clearly visible on the material surface. The fibers are filled with a well-cured epoxy resin matrix, with no obvious interface defects. Furthermore, the nanofibers form a tightly contacted linear conduction path. Therefore, when local electric field inhomogeneity occurs, leading to partial discharge, this path can serve as a complete charge release path, rapidly conducting and releasing the charge along the alignment direction. Similarly, due to the well-formed longitudinal conduction path, it can act as an efficient out-of-plane heat conduction pathway.

[0104] This application also analyzed the nonlinear current-voltage characteristics, nonlinear coefficient, threshold field strength, in-plane thermal conductivity, and out-of-plane thermal conductivity of the smart insulating materials prepared in the above embodiments, as detailed in [see details]. Figure 3 Tables 1 and 2.

[0105] Table 1. Nonlinear coefficients, threshold field strengths, in-plane thermal conductivity, and out-of-plane thermal conductivity of insulating materials with different volume fractions under parallel arrangement of SiC nanofiber mats.

[0106]

[0107] Table 2. Nonlinear coefficients, threshold field strengths, in-plane thermal conductivity, and out-of-plane thermal conductivity of insulating materials with different volume fractions under vertically aligned SiC nanofiber mats.

[0108]

[0109] Specifically, the nonlinear current-voltage characteristics and their characteristic parameters (nonlinear coefficient and threshold field strength) and thermal conductivity are as follows: Figure 2 As shown in Tables 1 and 2.

[0110] Among them, the thermal conductivity was tested using a NETZSCH LFA 467 laser scattering thermal conductivity meter from Germany to measure the thermal diffusivity α of the composite material in different directions.

[0111] The bulk density ρ of the material was tested using an electronic balance via the water displacement method.

[0112] The specific heat Cp of the material is measured using the DSC (sapphire method); the thermal conductivity λ of the composite material is calculated using the formula λ=α×ρ×Cp, W / (m·K).

[0113] Depend on Figure 3 It is known that the parallel-arranged nanofiber felts are uniformly pressured by high-resistivity epoxy resin. At the aforementioned volume fractions, the epoxy resin composite material with the parallel arrangement structure exhibits a higher threshold field strength and a smaller nonlinear coefficient. However, under the parallel arrangement structure design, the nonlinear coefficient of the epoxy resin composite material fluctuates significantly between different volume fractions, resulting in poorer stability. In contrast, the epoxy resin composite material with a vertical arrangement structure has a top-to-bottom connected conduction path, significantly enhancing the stability of the composite material's nonlinear current-voltage characteristics. The nonlinear coefficient at different volume fractions remains stable between 9.2 and 9.6. According to the thermal conductivity test results of the two materials in Tables 1 and 2, both the parallel-arranged and vertically arranged samples possess high in-plane and out-of-plane thermal conductivity, which is closely related to their respective internal structural designs and heat conduction paths. These test results provide a new material preparation method for the application of high thermal conductivity intelligent epoxy resin composite materials in different scenarios.

[0114] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A thermally conductive smart insulating material with nonlinear current-voltage characteristics, characterized in that, The invention comprises a polymer matrix and a SiC nanofiber mat within it, wherein the volume fraction of the SiC nanofiber mat is 0.5% to 2% of the polymer matrix, and the SiC nanofiber mat is assembled by stacking approximately homo-oriented SiC nanofibers; the SiC nanofibers are arranged in parallel or perpendicular arrangement within the polymer matrix.

2. The intelligent insulating material with thermal conductivity and nonlinear volt-ampere characteristics according to claim 1, characterized in that, The polymer matrix includes at least one of epoxy resin, polyimide, polyethylene terephthalate, polydimethylsiloxane, polyurethane, polyvinylidene fluoride, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polyethylene, polystyrene, polypropylene, polymethyl methacrylate, polyamide, polyoxymethylene, polycarbonate, styrene-butadiene rubber, silicone rubber, cis-butadiene rubber, isoprene rubber, chloroprene rubber, and natural rubber.

3. The intelligent insulating material with thermal conductivity and nonlinear volt-ampere characteristics according to claim 2, characterized in that, The epoxy resin includes an epoxy resin matrix, a curing agent, and a latent agent; The epoxy resin matrix is ​​any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyphenol type glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin and alicyclic epoxy resin. The curing agent is either methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride; The luring agent is any one of neodymium acetylacetonate, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

4. A method for preparing a smart insulating material with thermal conductivity and nonlinear current-voltage characteristics as described in any one of claims 1 to 3, characterized in that, The preparation method includes: (1) Add polycarbosilane and polyoxyethylene to chloroform and mix evenly to prepare SiC polymer precursor solution; (2) The SiC polymer precursor solution is subjected to high voltage electrospinning orientation treatment, and polymer flexible fiber mat with nanofibers extending in roughly the same direction is collected through a substrate. After peeling off the polymer flexible fiber mat, it is cut into sheets to obtain sheet fiber mat. The sheet fiber mat is stacked and assembled, and then cured and sintered to obtain SiC nanofiber mat. (3) Mix the epoxy resin matrix, curing agent and luring agent and stir evenly. Immerse the SiC nanofiber felt in the epoxy resin mixture until it is completely penetrated. Then transfer it to a high-temperature vacuum drying oven and continue to evacuate the vacuum. (4) The SiC nanofiber felt that is completely impregnated with epoxy resin is taken out and transferred to a constant temperature drying oven for gradient temperature curing to prepare a smart insulating material with thermal conductivity and nonlinear volt-ampere characteristics.

5. The method for preparing the thermally conductive and nonlinear volt-ampere characteristic smart insulating material according to claim 4, characterized in that, The ratio of the amount of polycarbosilane, polyethylene oxide and chloroform added is (1g~2g):(0.2g~0.4g):10mL, the stirring time is 6 hours and the stirring temperature is room temperature.

6. The method for preparing the thermally conductive and nonlinear volt-ampere characteristic smart insulating material according to claim 4, characterized in that, The voltage of the high-voltage electrospinning is 40kV; The stacking assembly specifically involves stacking several sheet-like fiber felts sequentially in the horizontal direction or in the vertical direction.

7. The method for preparing the thermally conductive and nonlinear volt-ampere characteristic smart insulating material according to claim 6, characterized in that, The curing process specifically involves placing the stacked and assembled sheet fiber felt into an oven for high-temperature oxidation treatment. The high-temperature oxidation temperature is 200°C, and the curing time is 2 hours. The sintering process specifically involves: after the stacked and assembled sheet fibers are cured, they are transferred to a high-temperature atmosphere tube furnace and sintered at high temperature in an inert gas atmosphere. The sintering temperature is 1600℃, the heating rate is 5℃ / min, the holding time is 2 hours, and the cooling rate is 10℃ / min.

8. The method for preparing the thermally conductive and nonlinear volt-ampere characteristic smart insulating material according to claim 7, characterized in that, The number of sheet-like fiber mats stacked sequentially in the horizontal direction or in the vertical direction is 5n, where n is a natural number, and the thickness of the sheet-like fiber mats is 50-100μm.

9. The method for preparing the thermally conductive and nonlinear volt-ampere characteristic smart insulating material according to claim 5, characterized in that, The weight ratio of the epoxy resin, curing agent, and latent agent is 100g:(90g~120g):(0.5g~1g); the stirring temperature is 40~80℃, and the stirring time is 1 hour; The vacuum drying temperature is 80℃, and the continuous vacuuming time is 12 hours; The gradient temperature curing process specifically involves: The first stage of curing treatment, the second stage of curing treatment, and the third stage of curing treatment are performed sequentially. The curing temperature of the first stage of curing treatment is 120°C and the curing time is 2 hours; the curing temperature of the second stage of curing treatment is 145°C and the curing time is 3 hours; and the curing temperature of the third stage of curing treatment is 165°C and the curing time is 2 hours.

10. The application of a thermally conductive and nonlinear volt-ampere characteristic smart insulating material as described in any one of claims 1 to 4 in electronic packaging materials and insulation of high-voltage electrical equipment.

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