Preparation method of ternary hybrid micro-nanoparticle / encapsulated flame-retardant heat-conducting epoxy composite with branch-leaf structure

Abstract

The application discloses a preparation method of a ternary hybrid micro-nano particle / encapsulated flame-retardant heat-conducting epoxy composite material with a branch-leaf structure, and belongs to the technical field of micro-nano particle modified hybrid and preparation of flame-retardant heat-conducting composite materials. The application provides a preparation method of an encapsulated epoxy composite material with a branch-leaf structure hybrid nano particle, in which boron nitride nano sheets with excellent heat-conducting and flame-retardant properties are selected as leaf structures, the surfaces of the boron nitride nano sheets are modified by aluminum oxide microspheres with excellent heat-conducting properties, and silicon carbide nano wires with excellent heat-conducting properties are selected as branch structures, so that the branch-leaf structure hybrid nano particle is constructed, and the encapsulated epoxy resin composite material with excellent heat-conducting and flame-retardant properties is prepared.

Description

Technical Field

[0001] This invention relates to a method for preparing a flame-retardant and thermally conductive epoxy composite material with a ternary hybrid micro / nanoparticle / encapsulation structure that mimics the structure of branches and leaves, belonging to the technical field of micro / nanoparticle modification and hybridization and the preparation of flame-retardant and thermally conductive composite materials. Background Technology

[0002] Epoxy resin materials used for encapsulation serve as sealing bodies for integrated circuits, providing mechanical support, sealing protection, and heat dissipation, playing a crucial role in printed circuit boards. However, they still have shortcomings in meeting the requirements of flame retardancy, high heat resistance, and high thermal conductivity in the 5G field, namely, poor thermal conductivity (thermal conductivity ≈ 0.2 W·m). -1 ·K -1 Its inherent flammability is a disadvantage.

[0003] Boron nitride is valued for its excellent thermal conductivity (250–300 W·m). -1 K -1 Boron nitride (BN) hybrid nanofillers, with their excellent insulation, high temperature resistance, chemical resistance, and low density, are ideal fillers for preparing thermally conductive epoxy resin materials. Furthermore, the addition of BN hybrid nanofillers helps improve the thermal stability of epoxy resins; the nanofillers are dense and continuous, exhibiting a tortuous path effect in the composite material, which can prevent oxygen and flammable molecules from penetrating deep into the material. In addition, BN has high thermal conductivity, allowing excessively high localized heat to be quickly conducted to the rest of the material, resulting in good heat dispersion and thus improving the flame retardant properties of the material.

[0004] Improving the thermal conductivity of polymer composites requires maximizing the formation of a thermally conductive network within the material, which necessitates a high filler content. However, high filler content can deteriorate the molding processability of epoxy resins and reduce their mechanical properties. Therefore, developing novel boron nitride hybrid materials to reduce filler usage and improve the dispersibility and thermal conductivity of nanoparticles is a pressing challenge in the field of high thermal conductivity epoxy composites.

[0005] Currently, most hybrid filler systems are achieved through simple physical mixing of two or more thermally conductive particles of different sizes, resulting in weak interactions between them. Furthermore, the interfacial thermal resistance between the inorganic filler and the polymer matrix is ​​a key factor hindering the development of thermally conductive composites with a filled polymer matrix. Therefore, the preparation of a material that simultaneously possesses excellent thermal conductivity, flame retardancy, thermal stability, and dielectric properties has extremely high practical and economic value. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for preparing a ternary hybrid micro / nanoparticle / encapsulation epoxy composite material with a simulated branch and leaf structure. This method selects boron nitride nanosheets with excellent thermal conductivity and flame retardancy as the leaf structure, modifies the surface of the boron nitride nanosheets with alumina microspheres that also possess excellent thermal conductivity, and selects silicon carbide nanowires with excellent thermal conductivity as the branch structure to construct a simulated branch and leaf structure hybrid nanoparticle, thereby preparing an epoxy resin composite material for encapsulation that possesses both excellent thermal conductivity and flame retardancy.

[0007] The first objective of this invention is to provide a method for preparing ternary hybrid micro / nanoparticles (Al2O3@BNNS@SiC, hereinafter referred to as ternary hybrid micro / nanoparticles) with a branch-like structure, comprising the following steps:

[0008] (1) Mix the ethanol aqueous solution of silanized boron nitride nanosheets, the ethanol aqueous solution of silanized silicon carbide nanocrystals and the ethanol aqueous solution of silanized alumina microspheres and sonicate to obtain a mixed solution; the mass ratio of silanized silicon carbide nanocrystals, silanized boron nitride nanosheets and silanized alumina microspheres in the mixed solution is 1:1~4:1~12.

[0009] (2) Adjust the pH of the mixed solution, react, cool, and centrifuge to obtain Al2O3@BNNS@SiC ternary hybrid micro-nanoparticles with a branch-leaf structure.

[0010] In one embodiment, in the mixed solution of step (1), the mass ratio of silanized silicon carbide nanowhiskers, silanized boron nitride nanosheets and silanized alumina microspheres is 1:1 to 4:1 to 12.

[0011] In one embodiment, the reaction in step (2) is refluxed at 60-80°C, 90-110°C, and 110-130°C for 1-2 hours, and then refluxed at 100-150°C for 1-2 hours.

[0012] A second objective of this invention is to provide ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC prepared by any of the methods described above.

[0013] A third objective of this invention is to provide a method for preparing epoxy resin-based thermally conductive composite materials, using ternary hybrid micro / nanoparticles as thermally conductive fillers, the method comprising the steps of:

[0014] TGDDM type epoxy resin, curing agent MTHPA, curing accelerator 2-ethyl-4-methylimidazolium and thermally conductive filler are mixed and homogenized to obtain a homogeneous material; the homogeneous material is cured to obtain an epoxy resin-based thermally conductive composite material.

[0015] The amount of thermally conductive filler added is 20-35 wt% of the epoxy resin-based thermally conductive composite material;

[0016] The preparation method of the ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC is as follows:

[0017] (1) Mix the ethanol aqueous solution of silanized boron nitride nanosheets, the ethanol aqueous solution of silanized silicon carbide nanocrystals and the ethanol aqueous solution of silanized alumina microspheres and sonicate to obtain a mixed solution; the mass ratio of silanized silicon carbide nanocrystals, silanized boron nitride nanosheets and silanized alumina microspheres in the mixed solution is 1:1~4:1~12.

[0018] (2) Adjust the pH of the mixed solution, react, cool, and centrifuge to obtain ternary hybrid micro-nano particles.

[0019] In one embodiment, the mass ratio of TGDDM type epoxy resin to curing agent MTHPA is 10:3 to 5, and 2-ethyl-4-methylimidazolium accounts for 1.5 to 2.5 wt% of the epoxy system.

[0020] In one embodiment, the mixture is homogenized at atmospheric pressure and 800–1200 rpm for 100–120 s, and then mixed under vacuum conditions at 1000–1200 rpm for 80–100 s.

[0021] A fourth object of the present invention is to provide an epoxy resin-based thermally conductive composite material prepared by any of the above methods.

[0022] The fifth objective of this invention is to provide a method for simultaneously improving the thermal conductivity, thermal stability, flame retardancy, and dielectric properties of epoxy resin-based thermally conductive composite materials, using ternary hybrid micro / nanoparticles (Al2O3@BNNS@SiC) as thermally conductive fillers. The method includes the following steps:

[0023] TGDDM type epoxy resin, curing agent MTHPA, curing accelerator 2-ethyl-4-methylimidazolium and thermally conductive filler are mixed and homogenized to obtain a homogeneous material; the homogeneous material is cured to obtain an epoxy resin-based thermally conductive composite material.

[0024] The amount of thermally conductive filler added is 20-35 wt% of the epoxy resin-based thermally conductive composite material;

[0025] The preparation method of ternary hybrid micro / nanoparticles is as follows:

[0026] (1) Mix the ethanol aqueous solution of silanized boron nitride nanosheets, the ethanol aqueous solution of silanized silicon carbide nanocrystals and the ethanol aqueous solution of silanized alumina microspheres and sonicate to obtain a mixed solution; the mass ratio of silanized silicon carbide nanocrystals, silanized boron nitride nanosheets and silanized alumina microspheres in the mixed solution is 1:1~4:1~12.

[0027] (2) Adjust the pH of the mixed solution, react, cool, and centrifuge to obtain ternary hybrid micro-nano particles.

[0028] The sixth object of the present invention is to provide the application of any of the above-described methods or the above-described ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC or the above-described epoxy resin-based thermally conductive composite materials in the fields of aerospace and electronic communications.

[0029] Beneficial effects of the present invention

[0030] This invention provides a method for preparing a hybrid nanoparticle / encapsulation epoxy composite material with a branch-leaf structure. The method selects boron nitride nanosheets with excellent thermal conductivity and flame retardancy as the leaf structure, modifies the surface of the boron nitride nanosheets with alumina microspheres that also have excellent thermal conductivity, and selects silicon carbide nanowires with excellent thermal conductivity as the branch structure to construct a hybrid nanoparticle with a branch-leaf structure, thereby preparing an epoxy resin composite material for encapsulation with excellent thermal conductivity and flame retardancy.

[0031] Specifically:

[0032] (1) Based on chemical grafting modification technology, this invention prepares hybrid nanoparticles with a branch-like structure through structural regulation, which improves the dispersibility of single boron nitride nanomaterials and helps to build a micro-nano bridging thermal insulation network in the matrix, thereby improving the processability and thermal conductivity of the material at low addition levels.

[0033] (2) Ternary hybrid micro- and nano-particles improve the problem of excessive addition of thermally conductive particles in single-addition systems and the inability of blended systems to effectively form a thermally conductive network, thus effectively improving the thermal conductivity of the material. At the same time, they have a physical barrier effect of gas barrier.

[0034] (3) The epoxy resin-based thermally conductive composite material EP / 35% ABS (i.e., Al2O3@BNNS@SiC added at a rate of 35 wt%) prepared by the present invention using ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC has a thermal conductivity of 1.262 W·m. -1 ·K -1 It is 615.6% of EP (i.e., without the addition of Al2O3@BNNS@SiC);

[0035] Under a nitrogen atmosphere, the LOI of EP / 35% ABS increased from 21.5% to 50.5% compared to EP, and the PHRR decreased by 39.4% compared to EP.

[0036] The dielectric constant of EP / 35%ABS is higher than that of EP at all frequencies, and the dielectric loss is lower than that of EP. Attached Figure Description

[0037] Figure 1The images show the microstructures of the hybrid nanoparticles; (a) Al2O3@BNNS with a mass ratio of 1:1; (b) Al2O3@BNNS with a mass ratio of 2:1; (c) Al2O3@BNNS with a mass ratio of 3:1; (d) BNNS@SiC with a mass ratio of 2:1; (e) BNNS@SiC with a mass ratio of 3:1; (f) BNNS@SiC with a mass ratio of 4:1; and (gi) Al2O3@BNNS@SiC with a mass ratio of 1:3:6.

[0038] Figure 2 The infrared curves before and after modification of three nanoparticles are shown; (a) is BN; (b) is Al2O3@BNNS@SiC.

[0039] Figure 3 The chemical composition of Al2O3@BNNS@SiC was analyzed; (a) is the elemental spectrum of the Al2O3@BNNS@SiC sample; (b) is the XPS spectrum of C1s; (c) is the XPS spectrum of N1s; (d) is the XPS spectrum of Al2p; (e) is the XPS spectrum of B1s; and (f) is the XPS spectrum of Si2p.

[0040] Figure 4 The thermal conductivity of different composite materials is shown in Figure 1. (a) shows epoxy resin with different mass ratios of Al2O3@BNNS; (b) shows epoxy resin with different mass ratios of BNNS@SiC; (c) compares the thermal conductivity of different amounts of Al2O3@BNNS@SiC added to the epoxy resin; and (d) shows samples with different thermal conductivity modifications.

[0041] Figure 5 The results of thermogravimetric analysis of EP and its thermally modified samples are shown; (a) is the TG curve; (b) is the DTG curve.

[0042] Figure 6 Limiting oxygen index (LOI) and MCC test results for EP and its thermally modified samples; where (a) is the LOI result and (b) is the MCC result.

[0043] Figure 7 Dielectric properties of EP and EP / 35% ABS were tested; where (a) is the dielectric constant and (b) is the dielectric loss. Detailed Implementation

[0044] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0045] This invention modifies the surface of nanofillers to reduce phonon scattering at the interface between the filler and the matrix, improves the interfacial compatibility between the nanofiller and the polymer matrix, and uses different silane coupling agents to modify different nanofillers to hybridize the two nanofillers together, increase the contact between the fillers, give full play to the advantages of each filler, and more effectively construct thermal conductivity pathways.

[0046] Raw materials used in the examples:

[0047] Boron nitride (BN), 1-2 μm, purchased from Shanghai Aladdin Biochemical Co., Ltd.

[0048] Alumina (Al2O3), 100nm, purchased from Qinghe County Kete New Materials Technology Co., Ltd.

[0049] Silicon carbide (SiC), 3-5μm, purchased from Nangong Bole Metal Materials Co., Ltd.

[0050] Sodium hydroxide (NaOH), specification AR, ≥96%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0051] 3-Aminopropyltriethoxysilane (APTES), ≥99%, purchased from Shanghai Aladdin Biochemical Co., Ltd.

[0052] 3-Glycidyloxypropyltrimethoxysilane (GPTMS), specification ≥97%, purchased from Shanghai Aladdin Biochemical Co., Ltd.

[0053] Tetraglycidyl dimethyl diphenylamine (TGDDM), ≥99%, purchased from Shanghai Huayi Holdings Group Co., Ltd.

[0054] Methyltetrahydrophthalic anhydride (MTHPA), ≥99%, purchased from Shanghai Huayi Holdings Group Co., Ltd.

[0055] 2-Ethyl-4-methylimidazole, specification ≥96%, purchased from Shanghai Aladdin Biochemical Co., Ltd.

[0056] Sulfuric acid (H2SO4), grade AR, 95%–98%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0057] Hydrogen peroxide (H2O2), with an AR rating of ≥30%, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0058] Anhydrous ethanol, with an AR rating of ≥99.7%, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0059] Test method:

[0060] 1. Scanning Electron Microscope (SEM)

[0061] The morphology of BNNS, Al2O3, SiC, and their hybrid samples Al2O3@BNNS, BNNS@SiC, and Al2O3@BNNS@SiC was observed using a Hitachi SU8100 field emission scanning electron microscope (Hitachi, Japan). Before observation, the samples underwent gold sputtering treatment, and the accelerating voltage was 4 kV.

[0062] 2. Fourier Transform Infrared Absorption Spectroscopy (FTIR) Analysis

[0063] The structures of BNNS, Al2O3, SiC, and their hybrid Al2O3@BNNS@SiC before and after modification were characterized using a Nicolet Is 10 Fourier transform infrared spectrometer (Thermo Electron Scientific Instruments, USA) by attenuated total reflectance testing. The testing range was 4000-500 cm⁻¹. -1 .

[0064] 3. X-ray photoelectron spectroscopy (XPS) analysis

[0065] The elemental composition of Al2O3@BNNS@SiC was analyzed using an Axis supra-type X-ray photoelectron spectrometer (Kratos, UK).

[0066] 4. Laser Thermal Apparatus (LFA)

[0067] The thermal conductivity of different modified composite materials was measured at room temperature using a NETZSCH LFA457 laser thermal conductivity meter, and calculated using formula 2.1:

[0068] TC=α×ρ×C P

[0069] In the formula, α is the thermal diffusivity, m² / s; C P ρ is the specific heat capacity, J / g·K; ρ is the density, g·cm³. -3 The sample has a diameter of 12.7 mm and a thickness of 1 mm.

[0070] 5. Thermal stability analysis (TGA)

[0071] EP, EP / 35% ABS, EP / 35% AB, EP / 35% BS, and EP / 35% BNNS samples were tested using a Q500 thermogravimetric analyzer (TA Instruments, USA) under a nitrogen atmosphere. The sample testing temperature range was 20–700 °C, the heating rate was 20 °C / min, and the gas flow rate was set to 50 mL / min.

[0072] 6. Limiting Oxygen Index (LOI) Analysis

[0073] The limiting oxygen index of EP, EP / 35% ABS, and EP / 35% BNNS samples was measured using an HC-2 oxygen index meter according to the national standard GB / T 5454-1997. The sample size was 100mm × 6.5mm × 3.0mm.

[0074] 7. Micro Combustion Calorimeter (MCC) Analysis

[0075] The heat release rate of EP, EP / 35% ABS, EP / 35% BNNS, Al2O3@BNNS, and BNNS@SiC samples was evaluated using an FTT micro combustion calorimeter (Fire Testing Technology, UK). The test temperature ranged from 0 to 700℃, and the heating rate was 1℃ / s.

[0076] 8. Dielectric property analysis

[0077] The dielectric constant (DC) and dielectric loss (DL) of EP and EP / 35% ABS at different frequencies were measured using a ZJD-C type dielectric constant and dielectric loss tester. The experimental voltage was 1V, the sampling time was 3s / sample, and the time interval was 3min.

[0078] Example 1: Preparation of ternary hybrid micro / nanoparticles

[0079] 1. Modified boron nitride nanosheets

[0080] 15g of boron nitride (h-BN) was placed in a zirconia ball mill jar, and 1.5g of NaOH was added to assist in ball milling. The mixture was ball milled at 300rpm for 90min using a planetary ball mill to obtain boron nitride nanosheets (BNNS). At the same time, 750mL of a 5mol / L NaOH solution was prepared. The obtained BNNS and NaOH solution were transferred to a three-necked flask and refluxed in an oil bath at 120℃ for 12h. After cooling and filtering, the solution was washed with deionized water to completely remove residual NaOH until the solution was neutral, and hydroxylated BNNS was obtained. The product was named BNNS-OH.

[0081] Weigh 50g of APTES (3-aminopropyltriethoxysilane) and add it to 700mL of ethanol-water solution (the volume ratio of anhydrous ethanol to deionized water is 6:4, and this ratio of mixed solution is used in all examples). After ultrasonic hydrolysis for 30min, add BNNS-OH and ultrasonically disperse it evenly. Then transfer it to a three-necked flask, add acetic acid to adjust the pH to 4.5-5, reflux in an oil bath at 80℃ for 12h, and filter to obtain silanized boron nitride nanosheets, named APTES-BNNS.

[0082] 2. Modified silicon carbide nanocrystals

[0083] Before silanization, 10 g of SiC was added to 300 mL of a mixed solution of H2SO4 and H2O2 (H2O2:H2SO4 volume ratio 1:4), acidified and stirred for 3 h, and then washed until neutral. The product was labeled as g-SiC.

[0084] Weigh 33g of GPTMS (3-glycidyl etheroxypropyltriethoxysilane) and add it to a mixed solution of 700mL of deionized water and anhydrous ethanol. After ultrasonic hydrolysis for 30min, add g-SiC and ultrasonically disperse it evenly. Then transfer it to a three-necked flask, add acetic acid to adjust the pH to 4.5-5, reflux in an oil bath at 80℃ for 12h, and filter to obtain silanized silicon carbide nanocrystals, named GPTMS-SiC.

[0085] 3. Modified alumina microspheres

[0086] Weigh 50g of GPTMS and add it to a mixed solution of 700mL of deionized water and anhydrous ethanol. After ultrasonic hydrolysis for 30min, add 15g of Al2O3 and ultrasonically disperse it evenly. Then transfer it to a three-necked flask, add acetic acid to adjust the pH to 4.5-5, reflux in an oil bath at 80℃ for 12h, and centrifuge to obtain silanized alumina microspheres, named GPTMS-Al2O3.

[0087] 4. Preparation of ternary hybrid micro / nanoparticles with branch-leaf-like structure

[0088] Take 2g of GPTMS-SiC, 6g of APTES-BNNS and 12g of GPTMS-Al2O3 prepared in steps 1, 2 and 3 respectively and add them to 80mL, 240mL and 480mL of ethanol aqueous solution. Disperse them evenly by ultrasonication. After mixing the three, continue to ultrasonicate until they are evenly mixed to obtain a mixed solution.

[0089] The mixed solution was transferred to a three-necked flask, and acetic acid was added to adjust the pH to 4.5–5. After reflux at 70℃, 100℃, and 120℃ for 2 hours, the mixture was placed in an oven and reacted at 150℃ under high pressure for 1 hour. After cooling, the mixture was centrifuged to obtain ternary hybrid "branch and leaf" structure thermally conductive nanoparticles, which were named ternary hybrid micro-nanoparticles with imitation branch and leaf structure, namely Al2O3@BNNS@SiC(ABS).

[0090] 5. Following the method in section 4, GPTMS-Al2O3 and APTES-BNNS were mixed at mass ratios of 1:1, 2:1, and 3:1 to prepare binary hybrid nanoparticles Al2O3@BNNS(AB); APTES-BNNS and GPTMS-SiC were mixed at mass ratios of 2:1, 3:1, and 4:1 to prepare binary hybrid nanoparticles BNNS@SiC(BS).

[0091] Example 2: Characterization of Hybrid Nanoparticles

[0092] The Al2O3@BNNS@SiC(ABS) prepared in Example 1 was characterized as follows:

[0093] (1) Observation of morphology using scanning electron microscopy

[0094] The morphology of the ternary hybrid micro / nanoparticles and binary hybrid nanoparticles prepared in Example 1 was observed, and the results are as follows: Figure 1 As shown.

[0095] The results show that for the binary hybrid nanoparticles Al2O3@BNNS, Al2O3 can be uniformly grafted onto the surface of boron nitride nanosheets (BNNS). When the mass ratio is 1:1, Al2O3 is sparsely dispersed on the BNNS surface. This dispersion is not conducive to the construction of an effective interconnection network between nanoparticles and hinders heat transfer. When the mass ratio is increased to 3:1, Al2O3 is over-coated on the BNNS surface.

[0096] Given that Al2O3 has a lower thermal conductivity than BNNS, excessive Al2O3 can shield the thermal conductivity advantage of BNNS, limiting its thermal conductivity performance. Therefore, a mass ratio of 2:1 is chosen, resulting in uniform and appropriate grafting of Al2O3 onto the BNNS surface. This approach not only constructs a good particle network but also fully preserves the thermal conductivity advantage of BNNS, which is most beneficial for improving the thermal conductivity of the matrix.

[0097] For the binary hybrid nanoparticles BNNS@SiC, relatively uniform and complete "branch" structures were successfully constructed in samples with mass ratios of 2:1 and 3:1. In the sample with a mass ratio of 3:1, BNNS achieved a more complete coating on the surface of silicon carbide (SiC). This structural characteristic greatly promoted the formation of thermally conductive pathways, which was very beneficial for heat conduction. However, when the mass ratio of BNNS to SiC increased to 4:1, BNNS exhibited a disordered stacking state on the SiC surface. This disordered stacking led to a significant increase in interfacial thermal resistance, thereby hindering effective heat conduction.

[0098] For the ternary hybrid micro / nanoparticle Al2O3@BNNS@SiC, it can be seen that the three nanoparticles coat each other, forming a uniform "branch-leaf" structure of nanoparticles, which proves the successful synthesis of ternary hybrid micro / nanoparticles from the microscopic morphology.

[0099] (2) FTIR test

[0100] Fourier transform infrared spectroscopy was used to test the hydroxylated and silanized boron nitride (BNNS) samples with Al2O3@BNNS@SiC. The infrared results for the original boron nitride (h-BN), hydroxylated boron nitride (BNNS-OH), and silanized boron nitride (APTES-BNNS) are as follows: Figure 2 As shown in (a) in the figure.

[0101] 3435cm in the picture -1 The characteristic peak at 1700 cm⁻¹ corresponds to the stretching vibration of -OH. It can be seen that BNNS-OH exhibits the highest intensity due to hydroxylation, while h-BN also produces a characteristic peak here due to hygroscopicity in air. APTES-BNNS, however, consumes some of the -OH during silanization, resulting in a lower intensity. -1 This corresponds to the in-plane vibration of NH, 1026 cm. -1 The peak at this point corresponds to the stretching vibration peak of the Si-O bond, proving the successful modification of BNNS by APTES.

[0102] The infrared spectrum of Al2O3@BNNS@SiC is as follows: Figure 2 As shown in (b) of the figure, characteristic peaks of -OH, Si-O and BN are present. In addition, there is also an 800 cm⁻¹ peak in the figure. -1 The Si-C vibrational peak, and the 640 cm⁻¹ peak. -1 The stretching vibration peak of Al-O, and also at 600 cm⁻¹. -1 The presence of Al-O-Si peaks at the site confirms the grafting and modification of the material.

[0103] (3) XPS test

[0104] The chemical composition of the ternary hybrid sample Al2O3@BNNS@SiC was analyzed by elemental analysis, and the results are as follows: Figure 3 As shown.

[0105] Figure 3 (a) in the figure is the elemental spectrum of the Al2O3@BNNS@SiC sample. It can be seen that characteristic peaks corresponding to O1s, N1s, C1s, B1s, Si2p and Al2p appear at 532.8eV, 397.8eV, 284.8eV, 190.8eV, 100.8eV and 74.8eV. Figure 3 In the figure, (d) represents the XPS spectrum of Al2p. The peaks at 74.9 eV and 73.3 eV correspond to the characteristic peaks of Al-OB and Al-B, respectively, proving the successful grafting of Al2O3 with BNNS. Figure 3 The 191.1 eV in (e) corresponds to the BO bond, proving the successful modification of BNNS. The XPS spectrum of Si2p is as follows: Figure 3As shown in (f), 102.5 eV corresponds to the Si-O-Si bond, and 100.8 eV corresponds to the Si-OB bond, proving the successful modification of SiC and the successful grafting with BNNS. XPS spectra prove the successful hybridization grafting of the three nanoparticles with Al2O3@BNNS@SiC.

[0106] Example 3: Preparation of epoxy resin-based thermally conductive composite material

[0107] 1. Preparation of epoxy resin-based thermally conductive composite materials

[0108] The ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC (ABS), binary hybrid nanoparticles Al2O3@BNNS (AB, containing 1:1, 2:1, and 3:1), and binary hybrid nanoparticles BNNS@SiC (BS, containing 2:1, 3:1, and 4:1) prepared in Example 1, as well as modified particles GPTMS-Al2O3 (A), APTES-BNNS (B), and GPTMS-SiC (S), were used as thermally conductive fillers to prepare epoxy resin-based thermally conductive composite materials. The steps are as follows:

[0109] Weigh the thermally conductive filler according to Table 1, and mix it with TGDDM type epoxy resin, curing agent MTHPA, and curing accelerator 2-ethyl-4-methylimidazol after preheating at 100℃ for 5 min and homogenizing.

[0110] The mass ratio of epoxy resin to MTHPA is 10:3.7, and 2-ethyl-4-methylimidazolium accounts for 2 wt% of the epoxy system. The homogenization conditions are: mixing at 1000 rpm for 120 s under normal pressure and mixing at 1200 rpm for 80 s under vacuum to obtain a homogeneous material.

[0111] The homogeneous material was introduced into a polytetrafluoroethylene mold and cured in stages by heating. First, it was cured at 100℃ for 2 hours, then the temperature was raised to 120℃ and 150℃ for 2 hours respectively, and finally cured at 180℃ for 2 hours to prepare epoxy resin-based thermally conductive composite materials, namely EP, EP / 20%ABS, EP / 25%ABS, EP / 30%ABS, EP / 35%ABS, EP / 35%AB (1:1), EP / 35%AB (2:1), EP / 35%AB (3:1), EP / 35%BS (2:1), EP / 35%BS (3:1), EP / 35%BS (4:1), EP / 35%BNNS, and EP / 35%ABS (the three raw materials were added directly without grafting).

[0112] Table 1 Formula

[0113]

[0114] 2. Performance Testing

[0115] (1) Thermal conductivity

[0116] The epoxy resin-based thermally conductive composite material prepared in step 1 was tested for its thermal conductivity, and the results are as follows. Figure 4 As shown.

[0117] Figure 4 As can be seen from (a) above, the epoxy resin modified with filler at a mass ratio of Al2O3 to BNNS of 2:1 achieved the highest thermal conductivity, reaching 1.182 W·m. -1 ·K -1 Correspondingly, the thermal conductivity of the epoxy resin added in Al2O3@BNNS at mass ratios of 1:1 and 3:1 were 1.104 W·m. -1 ·K -1 and 0.998 W·m -1 ·K -1 This is consistent with the analysis of the graft morphology under electron microscopy, and moderately uniform grafting helps to improve thermal conductivity.

[0118] Figure 4 As can be seen from (b), the improved thermal conductivity of epoxy resin by BNNS@SiC particles with mass ratios of 2:1, 3:1, and 4:1 reached 1.087 W·m. -1 ·K -1 1.153 W·m -1 ·K -1 0.965 W·m -1 ·K -1 Among them, the BNNS@SiC particles with a mass ratio of 3:1 achieved the best thermal conductivity among the three ratios due to the formation of their more complete "branch" structure.

[0119] Figure 4 As shown in (c), the concentrations of ternary thermally conductive particles added were 20wt%, 25wt%, 30wt%, 35wt%, and 40wt%. However, the sample with 40wt% addition experienced a sharp increase in system viscosity during preparation, making molding difficult. Among these, the thermal conductivity increased with increasing addition amount, with EP / 35% ABS exhibiting the highest thermal conductivity at 1.262 W·m. -1 ·K -1 It achieved a pure EP thermal conductivity of 0.205 W·m. -1 ·K -1 It has a thermal conductivity of 615.6%, indicating strong thermal conductivity potential.

[0120] Figure 4As shown in (d) and Table 2, a horizontal comparison of the thermal conductivity of EP / 35%BNNS, EP / 35%AB, EP / 35%BS, EP / 35%BAS, and EP / 35%ABS reveals that epoxy resin with single nanoparticles exhibits the worst thermal conductivity. EP / 35%BAS, due to the weak interaction between its blended nanoparticles, shows a weaker improvement in thermal conductivity compared to hybrid particles. EP / 35%ABS, with its multi-scale "branch" structure, is more conducive to constructing thermal conductive pathways, thereby improving the thermal conductivity of the material.

[0121] Table 2 Thermal conductivity properties

[0122] EP 0.205±0.003 EP / 35% BNNS 1.015±0.002 EP / 35%AB 1.182±0.002 EP / 35%BS 1.153±0.002 EP / 35% ABS 1.262±0.004 EP / 35% ABS 1.073±0.002

[0123] (2) Thermal stability

[0124] EP, EP / 35% BNNS, EP / 35% AB, EP / 35% BS, EP / 35% ABS, and EP / 35% ABS were tested for their thermal stability. Thermogravimetric analysis (TGA) was performed on them under nitrogen atmosphere. The thermogravimetric results are as follows. Figure 5 As shown in Table 3.

[0125] The results showed that both EP with added thermally conductive nanoparticles and pure EP exhibited a single-stage degradation process under a nitrogen atmosphere, but their thermal stability changed significantly, with an increased initial thermal degradation temperature and a higher Tg for EP / 35% ABS. -10％ The temperature reached 388.5℃, indicating that the addition of thermally conductive nanoparticles improved the thermal stability of the EP matrix. This trend also significantly improved the thermal stability of the material in the high-temperature region. The char residue of EP / 35% ABS increased from 7.6% of pure EP to 42.2%. The thermally modified samples showed the same thermal degradation trend as EP / 35% ABS, and their corresponding T... -10％ T max The results are similar, and the char residue is significantly higher than that of pure EP. Considering both the high thermal stability and char residue, it can be inferred that the thermally conductive nanoparticles possess certain flame-retardant potential.

[0126] Table 3 Thermal stability results

[0127] EP 329.2 348.3 7.6 EP / 35% BNNS 396.3 411.2 41.4 EP / 35%AB 388.9 407.4 38.0 EP / 35%BS 388.8 410.2 39.5 EP / 35% ABS 388.5 408.5 42.2

[0128] (3) Flame retardancy

[0129] EP, EP / 35% BNNS, EP / 35% AB, EP / 35% BS, EP / 35% ABS, and EP / 35% ABS were tested, and their flame retardant properties were characterized by LOI and MCC tests.

[0130] The fire safety performance of EP and its thermally modified materials was evaluated using the limiting oxygen index. The test results are as follows: Figure 6 As shown in Table 4.

[0131] The results showed that the LOI value of pure EP was only 21.5%, indicating its high flammability. When 35 wt% BNNS was added, the sheet-like nanoparticles acted as a physical barrier, reducing the oxygen diffusion rate, thus increasing the LOI value to 48%. Furthermore, the hybrid nanoparticles formed a more interconnected network in the composite material, strengthening the barrier effect. Consequently, the LOI values ​​of EP / 35%AB, EP / 35%BS, and EP / 35%ABS increased to 49.5%, 49%, and 50.5%, respectively, demonstrating that the addition of nanoparticles improved the fire safety performance of the materials.

[0132] Flame retardancy was further tested using MCC (Medium-to-Chip Corrosion Control). MCC testing requires only a small sample size (1-10 mg), and the results are as follows: Figure 6 As shown in Table 4.

[0133] The results showed that the PHRR of EP / 35% ABS reached 259 W / g, a decrease of approximately 39.4% compared to pure EP. This is partly due to the barrier effect of nanoparticles in the composite material, which can form a char layer and isolate the exchange of small combustible molecules within the composite.

[90] On the other hand, due to the excellent thermal conductivity of nanoparticles, the heat generated during combustion can be quickly conducted within the material, thus delaying the release of heat.

[0134] Similarly, the PHRR decrease of the EP / 35%BNNS, EP / 35%AB, and EP / 35%BS samples was similar to that of the EP / 35%ABS sample, but the PHRR decrease of the EP / 35%ABS sample was the largest, demonstrating that the better the connectivity of the hybrid thermally conductive nanoparticles in the composite material, the better their barrier effect. The MCC results prove that nanoparticles can reduce the heat release of the material and reduce its fire hazard.

[0135] Table 4 Flame retardancy results

[0136] EP 21.5 427.7±12.3 EP / 35% BNNS 48 274.7±8.4 EP / 35%AB 49.5 259.2±7.7 EP / 35%BS 49 281.5±7.3 EP / 35% ABS 50.5 259±6.8

[0137] (4) Dielectric properties

[0138] Dielectric constant and dielectric loss are key factors influencing the selection of epoxy resins in modern electronic packaging. Appropriate parameters help reduce heat generation and signal propagation time in electronic devices at high operating frequencies. EP and EP / 35% ABS were tested for their dielectric properties, and the results are as follows: Figure 7 As shown in Table 5.

[0139] The results show that the dielectric constant of both materials decreases with increasing frequency, and the dielectric constant of EP / 35%ABS is always higher than that of pure EP. This is because an interfacial polarization effect is formed at the interface between Al2O3@BNNS@SiC and EP, which increases the dielectric constant without creating a conductive channel. This improves the material's resistance to electrical breakdown at high frequencies while also providing insulation, thus enhancing the material's electrical safety performance.

[0140] Furthermore, it can be seen that the dielectric loss of EP and EP / 35%ABS increases with frequency, but the dielectric loss of EP / 35%ABS is always lower than that of pure EP. This means that the signal energy attenuation is smaller when transmitted in EP / 35%ABS, and its communication efficiency is higher. In addition, dielectric loss generates heat, causing local heating of the material, which can lead to thermal stress, material aging, or even thermal breakdown. The addition of Al2O3@BNNS@SiC filler not only reduces dielectric loss and heat generation, but its excellent thermal conductivity can also transfer heat more quickly, ensuring the safe and efficient operation of electronic devices.

[0141] Table 5 Dielectric constant and dielectric loss values

[0142]

[0143]

[0144] The data above show that as the amount of Al2O3@BNNS@SiC (mass ratio 6:3:1) added to the epoxy resin increases, the thermal conductivity of EP increases from the original 0.205 W·m. -1 ·K -1 Rising to 1.262 W·m of EP / 35% ABS -1 ·K -1 This is 615.6% of EP;

[0145] Under a nitrogen atmosphere, the addition of thermally conductive nanoparticles significantly improved the thermal stability of epoxy resin (EP), with the highest char residue of EP / 35% ABS reaching 42.2%. The LOI of EP / 35% ABS increased from 21.5% for EP to 50.5%. With the addition of thermally conductive nanoparticles to the epoxy resin, its barrier effect was also enhanced; due to the isolation of oxygen, the LOI values ​​of other systems also showed a significant increase. In MCC testing, the PHRR of EP / 35% ABS decreased by 39.4% compared to EP.

[0146] Meanwhile, the dielectric constant of EP / 35%ABS is higher than that of EP at all frequencies, and the dielectric loss is lower than that of EP. The thermally conductive nanoparticles effectively improve the electrical breakdown resistance and signal transmission capability of the epoxy resin used for encapsulation.

[0147] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing ternary hybrid micro / nanoparticles with a branch-leaf-like structure, characterized in that, Including the following steps: (1) Mix the aqueous solution of silanized boron nitride nanosheets, the aqueous solution of silanized silicon carbide nanocrystals, and the aqueous solution of silanized alumina microspheres in ethanol and sonicate to obtain a mixed solution; the mass ratio of silanized silicon carbide nanocrystals, silanized boron nitride nanosheets and silanized alumina microspheres in the mixed solution is 1:1~4:1~12. (2) Adjust the pH of the mixed solution, react, cool, and centrifuge to obtain Al2O3@BNNS@SiC ternary hybrid micro / nanoparticles with a branch-leaf structure.

2. The method according to claim 1, characterized in that, In step (2), the reaction is refluxed at 60~80 ℃, 90~110 ℃, and 110~130 ℃ for 1~2 h, and then refluxed at 100~150 ℃ for 1~2 h.

3. The method according to claim 1, characterized in that, In step (2), the reaction is carried out at 100~150 ℃ for 1~3 h.

4. The ternary hybrid micro / nanoparticles Al2O3@BNNS@SiC with a branch-like structure prepared by the method according to any one of claims 1 to 3.

5. A method for preparing epoxy resin-based thermally conductive composite materials, characterized in that, The method using Al2O3@BNNS@SiC ternary hybrid micro / nanoparticles with a branch-like structure as a thermally conductive filler includes the following steps: TGDDM type epoxy resin, curing agent MTHPA, curing accelerator 2-ethyl-4-methylimidazolium and thermally conductive filler are mixed and homogenized to obtain a homogeneous material; the homogeneous material is cured to obtain an epoxy resin-based thermally conductive composite material. The amount of thermally conductive filler added is 20~35 wt% of the epoxy resin-based thermally conductive composite material. The preparation method of the ternary hybrid micro / nanoparticle Al2O3@BNNS@SiC with a branch-leaf-like structure is as follows: (1) Mix the aqueous solution of silanized boron nitride nanosheets, the aqueous solution of silanized silicon carbide nanocrystals, and the aqueous solution of silanized alumina microspheres in ethanol and sonicate to obtain a mixed solution; the mass ratio of silanized silicon carbide nanocrystals, silanized boron nitride nanosheets and silanized alumina microspheres in the mixed solution is 1:1~3:4~6. (2) Adjust the pH of the mixed solution, react, cool, and centrifuge to obtain Al2O3@BNNS@SiC ternary hybrid micro / nanoparticles with a branch-leaf structure.

6. The method according to claim 5, characterized in that, The mass ratio of TGDDM type epoxy resin to curing agent MTHPA is 10:3~5, and 2-ethyl-4-methylimidazolium accounts for 1.5~2.5 wt% of the epoxy system.

7. The method according to claim 5, characterized in that, Under homogeneous atmospheric pressure, the mixture is stirred at 800~1200 rpm for 100~120s, and then stirred under vacuum at 1000~1200 rpm for 80~100s.

8. The epoxy resin-based thermally conductive composite material prepared by the method according to any one of claims 5 to 7.

9. The application of the ternary hybrid micro / nanoparticle Al2O3@BNNS@SiC with a branch-like structure as described in claim 4 or the epoxy resin-based thermally conductive composite material as described in claim 8 in the fields of aerospace and electronic communications.

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