Heat-conducting intelligent insulating material with nonlinear volt-ampere characteristic, preparation method and application thereof

Abstract

The invention relates to a heat-conducting intelligent insulating material with nonlinear volt-ampere characteristics, a preparation method and application thereof, and belongs to the technical field of insulating materials. The intelligent insulating material comprises a polymer matrix and a SiC nanofiber felt in the polymer matrix, the volume fraction of the SiC nanofiber felt is 0.5%-2% of that of the polymer matrix, and the SiC nanofiber felt is formed by stacking and assembling SiC nanofibers which are approximately in the same direction; the SiC nanofibers are arranged in parallel or vertically in the polymer matrix. According to the scheme provided by the invention, the heat conduction path of the intelligent insulating material can be optimized, 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, and the composite material is endowed with low-field-insulation and high-field-conduction electric field self-adaptive regulation and control capability through the nonlinear volt-ampere characteristics; and the problem of aging breakdown when the composite material is faced with an electric field distortion phenomenon is relieved.

Description

Technical Field

[0001] This application relates to the technical field of insulating materials, and particularly to an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of industries such as 5G, 6G, artificial intelligence, and automotive electronics, high-power semiconductor devices (such as SiC MOSFETs, GaN MOSFETs, etc.) are all developing towards miniaturization, high integration, and high power density. The working temperature can reach up to more than 200°C, and the thermal failure of their packaging materials has become the primary problem hindering the performance and lifespan of electronic devices. For example, for the thermal interface material connecting the radiator and the device, the heat conduction ability in the out-of-plane direction is particularly important, which also poses higher requirements for the thermal management ability of the packaging material in a specific direction. In addition, phenomena such as electric field distortion and partial discharge also occur in high-power density semiconductor devices, ultimately leading to dielectric breakdown and insulation failure. Summary of the Invention

[0003] One of the purposes of this application is to avoid the deficiencies of the prior art and provide an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics, which can optimize the heat conduction path of the intelligent insulating material, taking into account the high heat conduction and non-linear volt-ampere characteristics of the material. It not only solves the problem of low heat dissipation efficiency of the packaging material, but also endows the composite material with the ability of electric field self-adaptive regulation of low-field insulation and high-field conduction through non-linear volt-ampere characteristics, alleviating the aging breakdown problem of the composite material when facing the electric field distortion phenomenon.

[0004] Another purpose of this application is to provide a preparation method of an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics.

[0005] The third purpose of this application is to provide an application of an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics in electronic packaging materials and insulation of high-voltage electrical equipment.

[0006] One of the purposes of this application is achieved through the following technical solutions:

[0007] Provide an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics, including a polymer matrix and a SiC nanofiber mat inside it. The volume fraction of the SiC nanofiber mat is 0.5% - 2% of the polymer matrix, and the SiC nanofiber mat is assembled by stacking SiC nanofibers in generally the same direction; the SiC nanofiber mat is arranged parallel or perpendicular in the polymer matrix.

[0008] In some embodiments, 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-1,4-polybutadiene rubber, isoprene rubber, neoprene 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 epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and alicyclic epoxy resin;

[0011] The curing agent is any one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride;

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

[0013] Advantages of an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics according to the present application:

[0014] (1) The intelligent insulating material with heat conduction and non-linear volt-ampere characteristics provided by the present application is formed by overlapping SiC nanofibers to form a SiC nanofiber mat with a horizontal orientation or a vertical orientation. When the SiC nanofiber mat is filled with a polymer matrix at a volume fraction of 0.3% to 2%, the SiC nanofibers of the intelligent insulating material with a horizontal orientation structure extend horizontally and are interconnected with each other, and a lateral heat conduction path can be formed, acting as an in-plane heat conduction path; while the SiC nanofibers of the intelligent insulating material with a vertical orientation structure are cross-connected vertically, and a longitudinal heat conduction path can be formed, acting as an out-of-plane heat conduction path, having the advantages of low filling, short path, high heat conduction, and low thermal resistance.

[0015] (2) For the intelligent insulating material with heat conduction and non-linear volt-ampere characteristics provided by the present application, the SiC nanofiber mat forms a three-dimensional conduction path with close contact. When local electric field unevenness occurs and partial discharge occurs, the intelligent insulating material with a horizontal or vertical orientation structure acts as a charge release path and conducts and releases quickly along the extension direction of the SiC nanofiber mat. Compared with the existing randomly oriented SiC nanofibers, it has a faster response speed and release speed.

[0016] The second object of the present application is achieved by the following technical solutions:

[0017] A preparation method of the above-mentioned heat-conducting intelligent insulating material with non-linear volt-ampere characteristics includes the following steps:

[0018] (1) Add polycarbosilane and polyethylene oxide into chloroform and mix evenly to obtain a SiC polymer precursor solution;

[0019] (2) Perform high-voltage electrospinning orientation treatment on the SiC polymer precursor solution, collect it through a substrate to obtain a polymer flexible fiber felt with nanofibers extending substantially in the same direction, cut it into pieces after peeling off the polymer flexible fiber felt to obtain a sheet-like fiber felt, and perform curing and sintering treatment after stacking and assembling the sheet-like fiber felt to obtain a SiC nanofiber felt;

[0020] (3) Mix the epoxy resin matrix, curing agent and latent agent and stir evenly, immerse the SiC nanofiber felt in the epoxy resin mixture until it is completely penetrated, and then transfer it to a high-temperature vacuum drying oven to continuously evacuate;

[0021] (4) Take out the SiC nanofiber felt completely impregnated with epoxy resin and transfer it to a constant-temperature air-circulating drying oven for gradient temperature curing to prepare a heat-conducting intelligent insulating material with non-linear volt-ampere characteristics.

[0022] In some embodiments, the addition ratio of the polycarbosilane, polyethylene oxide and chloroform is (1 g - 2 g):(0.2 g - 0.4 g):10 mL, 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 40 kV;

[0024] The stacking and assembling specifically is: several sheet-like fiber felts are stacked in sequence in the horizontal direction or in sequence in the vertical direction.

[0025] In some embodiments, the curing specifically is: put the sheet-like fiber felt after stacking and assembling into an oven for high-temperature oxidation treatment, the high-temperature oxidation temperature is 200 °C, and the curing time is 2 hours;

[0026] The sintering specifically is: transfer the sheet-like fiber after curing treatment of stacking and assembling to a high-temperature atmosphere tube furnace, and perform high-temperature sintering in an inert gas atmosphere, the sintering temperature is 1600 °C, the heating rate is 5 °C / min, the heat preservation time is 2 hours, and the cooling rate is 10 °C / min.

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

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

[0029] The vacuum drying temperature is 80 °C, and the continuous vacuum pumping time is 12 hours;

[0030] The gradient temperature curing specifically is:

[0031] Perform the first-stage curing treatment, the second-stage curing treatment and the third-stage curing treatment in sequence. The curing temperature of the first-stage curing treatment is 120 °C, and the curing time is 2 hours; the curing temperature of the second-stage curing treatment is 145 °C, and the curing time is 3 hours; the curing temperature of the third-stage curing treatment is 165 °C, and the curing time is 2 hours.

[0032] The preparation method of the thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics provided by this application may include the following

[0033] Beneficial effects:

[0034] For the preparation method of the thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics provided by this application, a mixed solution of polycarbosilane and polyethylene oxide is subjected to high-voltage electrospinning orientation treatment. By orientation, a SiC nanofiber mat with fibers oriented substantially in the same direction is obtained. More uniform arrangement of SiC nanofibers can improve the heat flux after connection between SiC nanofibers, enabling it to achieve high thermal conductivity effect under the filling of 0.5% to 2% volume fraction, ensuring the processability of the material and good mechanical strength. Compared with the prior art, it greatly reduces the ineffective connection between SiC nanofibers and the disordered and long heat conduction path.

[0035] The third object of this application is achieved through the following technical solutions:

[0036] Provide the application of the above-mentioned thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics in electronic packaging materials and insulation of high-voltage electrical equipment.

[0037] The technical solutions provided by this application may include the following beneficial effects:

[0038] For the thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics provided by this application, the horizontally oriented structure has a higher threshold field strength, while the vertically oriented structure has a more stable non-linear coefficient, enabling this intelligent insulating material to be applied in electronic packaging materials and insulation of high-voltage electrical equipment under different working conditions, improving the insulation level of high-voltage electrical equipment and regulating the spatial electric field distribution of high-voltage electrical equipment, ensuring the safe and stable operation of electrical equipment. Description of the Drawings

[0039] The above and other objects, features, and advantages of the present application will become more apparent by describing the exemplary embodiments of the present application in more detail with reference to the accompanying drawings, in which, in the exemplary embodiments of the present application, the same reference numerals generally represent the same components.

[0040] Figure 1 SEM image of the intelligent insulating material prepared for Example 1;

[0041] Figure 2 SEM image of the intelligent insulating material prepared for Example 5;

[0042] Figure 3 Nonlinear volt-ampere characteristic curves of the intelligent insulating materials prepared for Examples 1-8. Specific embodiments

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

[0044] Related research has found that doping high-thermal-conductivity semiconductor fillers in a polymer matrix can achieve the nonlinear volt-ampere characteristics and high-efficiency thermal management capabilities of insulating materials. However, at low filling amounts, the efficiency of improving the thermal conductivity of the composite material is low, it is difficult to solve the heat accumulation problem caused by high leakage current at the electric field distortion, and it is easy to cause the failure of the package insulation thermal breakdown. Moreover, the nonlinear volt-ampere characteristics are weak and cannot quickly relieve the problem of local high electric fields. While a higher filling amount reduces the processability and mechanical strength of the material, the filler distribution is random, which greatly increases the cost. Therefore, it is crucial to balance the nonlinear volt-ampere characteristics and high-thermal-conductivity performance of the composite material through structural orientation design.

[0045] To solve the above problems, the present invention provides an intelligent insulating material with thermal conductivity and nonlinear volt-ampere characteristics, a preparation method thereof, and an application thereof.

[0046] The following further describes the present invention in detail with reference to embodiments. There are no particular restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0047] There are no particular restrictions on the purity of all raw materials of the present invention. The present invention preferably uses analytical pure or conventional purity used in the resin material field.

[0048] In a typical embodiment of the present invention, there is provided an intelligent insulating material that is thermally conductive and has non-linear volt-ampere characteristics. It can optimize the heat conduction path of the intelligent insulating material, and has both high thermal conductivity and non-linear volt-ampere characteristics. It not only solves the problem of low heat dissipation efficiency of the encapsulation material, but also endows the composite material with the ability of electric field self-adaptive regulation of low-field insulation and high-field conduction through non-linear volt-ampere characteristics, alleviating the aging breakdown problem of the composite material when facing the electric field distortion phenomenon.

[0049] In one embodiment of the present invention, there is provided an intelligent insulating material that is thermally conductive and has non-linear volt-ampere characteristics. The intelligent insulating material includes a polymer matrix and a SiC nanofiber mat inside it. The volume fraction of the SiC nanofiber mat is 0.5% - 2% of the polymer matrix, and the SiC nanofiber mat is assembled by stacking SiC nanofibers in substantially the same direction; the SiC nanofibers are arranged parallel or perpendicular to each other in the polymer matrix.

[0050] Furthermore, the above 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-1,4-polybutadiene rubber, isoprene rubber, chloroprene rubber, and natural rubber. This polymer matrix has universality, and different types of polymer substrates can be used for the intelligent insulating material 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 epoxy resin, bisphenol F epoxy resin, polyphenolic glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and alicyclic epoxy resin;

[0052] The curing agent is any one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride;

[0053] The latent 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, and 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 thinning and performance improvement. Overheating of electronic devices will seriously affect the reliability and service life of products. The extremely low thermal conductivity of epoxy resin (about 0.2 W / (m·K)) is no longer suitable for the usage environment of current electronic components. The epoxy resin described in the present invention includes any one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, and alicyclic epoxy resin. Typical but non-limiting examples of the combinations are: the combination of bisphenol A epoxy resin and bisphenol F epoxy resin, the combination of bisphenol F epoxy resin and phenolic epoxy resin, the combination of polyphenol glycidyl ether epoxy resin and aliphatic glycidyl ether epoxy resin, or the combination of bisphenol A epoxy resin, bisphenol F epoxy resin, and alicyclic epoxy resin, etc.

[0055] There is no particular limitation on the addition amount of the curing agent in the present invention. In order to improve the dispersion and properties of the composite material in the present invention, 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 latent agent described in 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 even more specifically preferably neodymium acetylacetonate. The mass ratio of the latent 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 preparation method of a thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics is provided, which is characterized in that the preparation method includes:

[0058] (1) Polycarbosilane and polyethylene oxide are added to chloroform and mixed evenly to obtain a SiC polymer precursor solution;

[0059] (2) The SiC polymer precursor solution is subjected to high-voltage electrospinning orientation treatment, and a polymer flexible fiber mat with nanofibers extending substantially in the same direction is collected through a substrate. After peeling the polymer flexible fiber mat, it is cut into pieces to obtain a sheet-like fiber mat. After stacking and assembling the sheet-like fiber mat, curing and sintering treatments are carried out to obtain a SiC nanofiber mat;

[0060] (3) Mix the epoxy resin matrix, curing agent, and latent agent and stir evenly. Immerse the SiC nanofiber mat in the epoxy resin mixture until it is completely penetrated, and then transfer it to a high-temperature vacuum drying oven for continuous vacuum pumping;

[0061] (4) Take out the SiC nanofiber mat completely impregnated with epoxy resin and transfer it to a constant-temperature forced-air drying oven for gradient temperature curing to prepare a thermally conductive and intelligent insulating material with non-linear volt-ampere characteristics.

[0062] The electrospinning described in the present invention can be a method well-known to those skilled in the art without special limitations. In this embodiment, the orientation setting of the SiC nanofibers can be carried out in the following ways, such as the collector improvement method, the field-induced electrospinning method, the parallel electrode collector method, and the electrospinning solution improvement method.

[0063] Among them, the working principle of obtaining oriented electrospinning by improving the collector in the collector improvement method is to use a roller-shaped collector and utilize its high-speed rotation to stretch the polymer jet, thereby obtaining oriented nanofibers.

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

[0065] Among them, the parallel electrode electrospinning method is to collect the electrospinning between two parallel conductive strips (for example: metal or highly doped silicon). The distance between the parallel electrodes can be from a few hundred micrometers to several centimeters.

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

[0067] It can be understood that limited by the existing technical level of electrospinning, it is impossible to achieve completely co-oriented SiC nanofibers.

[0068] The immersion described in the present invention means that the SiC nanofiber mat is completely immersed in the epoxy resin mixture. To improve the dispersion and composite material properties in the present invention, after the SiC nanofiber mat is completely immersed in the epoxy resin mixture, the container containing the epoxy resin mixture can be placed in a vacuum chamber for vacuum treatment to remove the bubbles in the epoxy resin mixture. The pressure of the vacuum treatment is 0.01 - 0.07 MPa, more preferably 0.02 - 0.06 MPa, and most preferably 0.03 - 0.05 MPa.

[0069] The nanofiber mat impregnated with epoxy resin is taken out specifically within a certain period of immersion. Those skilled in the art can select the immersion time of the nanofiber mat according to the types 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] Further, the addition ratio of the above-mentioned polycarbosilane, polyethylene oxide, and chloroform is (1 g to 2 g): (0.2 g to 0.4 g): 10 mL, the stirring time is 6 hours, and the stirring temperature is room temperature.

[0071] Further, the voltage of the above-mentioned high-voltage electrospinning is 40 kV;

[0072] The stacking and assembly specifically is: a plurality of sheet-shaped fiber mats are stacked in sequence in the horizontal direction or stacked in sequence in the vertical direction.

[0073] Further, the above-mentioned curing specifically is: the sheet-shaped fiber mats after stacking and assembly are put into an oven for high-temperature oxidation treatment, the high-temperature oxidation temperature is 200 °C, and the curing time is 2 hours;

[0074] The sintering specifically is: the sheet-shaped fiber mats after stacking and assembly are transferred to a high-temperature atmosphere tube furnace after curing treatment, and high-temperature sintering is carried out under an inert gas atmosphere. The sintering temperature is 1600 °C, the heating rate is 5 °C / min, the holding time is 2 hours, and the cooling rate is 10 °C / min.

[0075] Further, the number of the above-mentioned plurality of sheet-shaped fiber mats stacked in sequence in the horizontal direction or stacked in sequence in the vertical direction is 5n, where n is a natural number, and the thickness of the sheet-shaped fiber mat is 50 to 100 μm.

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

[0077] The vacuum drying temperature is 80 °C, and the continuous vacuum pumping time is 12 hours;

[0078] The gradient temperature rise curing specifically is:

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

[0080] In another embodiment of the present invention, there is provided an application of the intelligent insulating material with heat conduction and non-linear volt-ampere characteristics provided in the above embodiment in electronic packaging materials. In the electronic packaging materials, SiC nanofiber structures with horizontal or vertical orientations are used as heat-conducting materials for the polymer matrix. The horizontally oriented structure has a higher threshold field strength, while the vertically oriented structure has a more stable non-linear coefficient, enabling the intelligent insulating material of the present application to be applied to electronic packaging materials under different working conditions and the insulation of high-voltage electrical equipment, improving the insulation level of high-voltage electrical equipment and regulating the spatial electric field distribution of high-voltage electrical equipment, and ensuring the safe and stable operation of electrical equipment.

[0081] To further illustrate the present invention, the following describes in detail the intelligent insulating material with heat conduction and non-linear volt-ampere characteristics and its preparation method provided by the present invention in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, giving detailed implementation manners and specific operation processes, only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0082] Example 1

[0083] A preparation method of an intelligent insulating material with heat conduction and non-linear volt-ampere characteristics:

[0084] 1. Add 1 g of polycarbosilane and 0.2 g of polyethylene oxide into chloroform and stir at room temperature for 6 hours 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 of electrospinning is 40 kV. Cut the obtained polymer flexible fiber mat into pieces to obtain a sheet-like fiber mat, and then stack it horizontally;

[0085] 2. Put the stacked sheet-like fiber mats into a drying oven and cure at a temperature of 200 °C for 2 hours. Then transfer them to a high-temperature atmosphere tube furnace and sinter at a temperature of 1600 °C under the protection of an argon atmosphere. The heating rate is 5 °C / min, the holding time is 2 hours, and the cooling rate is 10 °C / min to obtain a SiC nanofiber mat with aligned orientation;

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

[0087] 4. Take 3.4 g of the above epoxy resin mixture and 56 mg of the prepared SiC nanofiber mat with aligned orientation. Horizontally immerse it in the above epoxy resin mixture until it is completely penetrated. Then transfer the mixed system to a high-temperature vacuum drying oven and continuously evacuate. The vacuum drying temperature is 80 °C, and the continuous evacuation time is 12 hours until no bubbles emerge. Then transfer it to a stainless steel mold and cure it at a temperature of 120 °C for 2 hours, then cure it at a temperature of 145 °C for 3 hours, and finally cure it at a temperature of 165 °C for 2 hours to prepare an intelligent insulating material containing 0.5 vol% SiC nanofiber mat.

[0088] Example 2

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

[0090] Example 3

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

[0092] Example 4

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

[0094] Example 5

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

[0096] Example 6

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

[0098] Example 7

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

[0100] Example 8

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

[0102] This application conducts SEM tests on the above Examples 1 and 5, as specifically shown in Figure 1 and Figure 2 .

[0103] Specifically, a field emission scanning electron microscope (Merlin, Zeiss) was used to characterize epoxy resin composites with parallel and vertically aligned SiC nanofiber mats. For the smart insulation materials stacked in parallel, in order to clearly observe the internally parallel SiC nanofibers, liquid nitrogen was used to brittlely fracture the smart insulation materials. The cross-sectional SEM images after brittle fracture, Figure 1 As shown in the SEM image of the smart insulation material prepared in Example 1, it can be clearly observed that the nanofibers in the nanofiber mat with a parallel arrangement structure are exposed on the cross-sectional surface. The SiC nanofibers are interconnected with each other, forming a good lateral conduction path, which can act as an efficient in-plane heat conduction path. For the smart insulation material with a vertically aligned structure, Figure 2 As shown in the SEM image of the smart insulation material prepared in Example 5, it can be seen that the SiC nanofiber mats are all in the vertical direction. Vertically aligned nanofibers can be clearly observed on the material surface. There is a well-filled and cured epoxy resin matrix between the fibers, and no obvious interfacial defects are present. Moreover, the nanofibers form a closely contacted linear conduction path. Therefore, when local electric field non-uniformity occurs and local discharge takes place, it can act as a complete charge release path and conduct and release quickly along the arrangement direction. Similarly, due to the formation of a good longitudinal conduction path, it can act as an efficient out-of-plane heat conduction path.

[0104] The present application also measured the non-linear volt-ampere characteristics, non-linear coefficient, threshold field strength, in-plane thermal conductivity, and out-of-plane thermal conductivity of the smart insulation materials prepared in the above respective examples. Specifically, see Figure 3 Table 1 and Table 2.

[0105] Table 1 Non-linear coefficient, threshold field strength, in-plane thermal conductivity, and out-of-plane thermal conductivity of insulation materials with parallel-aligned SiC nanofiber mats at different volume fractions

[0106]

[0107] Table 2 Non-linear coefficient, threshold field strength, in-plane thermal conductivity, and out-of-plane thermal conductivity of insulation materials with vertically aligned SiC nanofiber mats at different volume fractions

[0108]

[0109] Specifically, the non-linear volt-ampere characteristics and their characteristic parameters (non-linear coefficient and threshold field strength) and thermal conductivity are as shown in Figure 2 Table 1 and Table 2.

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

[0111] The bulk density ρ of the material was measured by the drainage method using an electronic balance.

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

[0113] It can be seen from Figure 3 that there is voltage equalization of epoxy resin with high resistance between the parallel-aligned nanofiber mats. Under the above volume fraction, the threshold field strength of the epoxy resin composite material with a parallel-aligned structure is higher and the nonlinear coefficient is smaller. However, under the parallel-aligned structure design, the nonlinear coefficient of the epoxy resin composite material fluctuates greatly between different volume fractions, and the stability is worse. While under the vertical-aligned structure design, the epoxy resin composite material has a top-down connected conduction path inside, which significantly enhances the stability of the nonlinear volt-ampere characteristics of the composite material, and the nonlinear coefficients under different volume fractions are all stable between 9.2 and 9.6. According to the thermal conductivity test results of the two materials in Table 1 and Table 2, it can be found that the parallel-aligned specimens and the vertical-aligned specimens each have a relatively high in-plane thermal conductivity and out-of-plane thermal conductivity, which is also closely related to their respective internal structure designs and heat conduction paths. The above test results all provide new material preparation methods for the application of high thermal conductivity intelligent epoxy resin composite materials in different scenarios.

[0114] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technologies in the market, or to enable other ordinary skill in the art in the technical field to understand the embodiments disclosed herein.

Claims

1. A thermally conductive intelligent insulating material having nonlinear volt-ampere characteristics, characterized in that: The invention comprises a polymer matrix and SiC nanofiber felt inside the polymer matrix, 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 SiC nanofibers in roughly the same direction; the SiC nanofibers are arranged in parallel or vertically in the polymer matrix.

2. The heat-conductive smart insulating material having 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, butadiene rubber, isoprene rubber, chloroprene rubber and natural rubber.

3. The heat-conductive smart insulating material having nonlinear volt-ampere characteristics according to claim 2, characterized in that: The epoxy resin comprises an epoxy resin matrix, a curing agent and a latent agent; The epoxy resin matrix is ​​any one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin and alicyclic epoxy resin; The curing agent is any one of methyl hexahydrophthalic anhydride and methyl tetrahydrophthalic anhydride; The latent agent is any one of neodymium acetylacetonate, 2-methylimidazole and 2-ethyl-4-methylimidazole.

4. A method for preparing a heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises: (1) adding polycarbosilane and polyethylene oxide into chloroform and mixing them evenly to prepare a SiC polymer precursor solution; (2) subjecting the SiC polymer precursor solution to high-voltage electrospinning orientation treatment, collecting the polymer flexible fiber felt with nanofibers extending in roughly the same direction through a substrate, peeling off the polymer flexible fiber felt and cutting it into sheets to obtain a sheet-like fiber felt, and stacking and assembling the sheet-like fiber felt and then curing and sintering it to obtain a SiC nanofiber felt; (3) mixing and uniformly stirring the epoxy resin matrix, the curing agent and the latent agent, immersing the SiC nanofiber felt in the epoxy resin mixture until it is completely penetrated, and then transferring it to a high-temperature vacuum drying oven and continuously evacuating the vacuum; (4) The SiC nanofiber felt completely impregnated with epoxy resin is taken out and transferred to a constant temperature forced air drying oven for gradient temperature curing to prepare a thermally conductive intelligent insulating material with nonlinear volt-ampere characteristics.

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

6. The method for preparing the heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics according to claim 4, characterized in that: The voltage of the high-voltage electrospinning is 40 kV; The stacking assembly specifically includes: a plurality of sheet-like fiber felts are stacked in sequence in a horizontal direction or in sequence in a vertical direction.

7. The method for preparing the heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics according to claim 6, characterized in that: The curing is specifically as follows: the stacked and assembled sheet-like fiber felt is placed in an oven for high-temperature oxidation treatment, the high-temperature oxidation temperature is 200° C., and the curing time is 2 hours; The sintering is specifically as follows: the stacked and assembled sheet fibers are cured and then transferred to a high-temperature atmosphere tubular furnace for high-temperature sintering in an inert gas atmosphere, with a sintering temperature of 1600°C, a heating rate of 5°C / min, a holding time of 2 hours, and a cooling rate of 10°C / min.

8. The method for preparing the heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics according to claim 7, characterized in that: The number of the plurality of sheet-like fiber felts stacked in sequence in the horizontal direction or in sequence in the vertical direction is 5n, where n is a natural number, and the thickness of the sheet-like fiber felt is 50-100 μm.

9. The method for preparing the heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics 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°C, and the stirring time is 1 hour; The vacuum drying temperature is 80°C and the vacuuming time is 12 hours; The gradient temperature rise curing is specifically as follows: The first stage curing treatment, the second stage curing treatment and the third stage curing treatment are performed in sequence. The curing temperature of the first stage curing treatment is 120°C and the curing time is 2 hours; the curing temperature of the second stage curing treatment is 145°C and the curing time is 3 hours; the curing temperature of the third stage curing treatment is 165°C and the curing time is 2 hours.

10. Application of the heat-conductive intelligent insulating material having nonlinear volt-ampere characteristics as claimed in any one of claims 1 to 4 in electronic packaging materials and insulation of high-voltage electrical equipment.

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