A curable thermally conductive silicone gel and a method for preparing the same

Abstract

The present application relates to a kind of solidifiable heat-conducting silica gel and its preparation method.The preparation raw materials of the solidifiable heat-conducting silica gel include the following components by weight fraction:vinyl silicone oil 100 parts,hydrogen-containing silicone oil 10~15 parts,three-peak compound modified diamond 3000~4000 parts,platinum gold catalyst 0.15~0.3 parts,inhibitor 0.2~0.6 parts and fumed silica 1.5~2.5 parts;The three-peak particle size distribution of the three-peak compound modified diamond is D50 particle size >100 μm and ≤200 μm, D50 particle size ≥50 μm and ≤100 μm and D50 particle size ≥0.5 μm and ≤1 μm respectively.The solidifiable heat-conducting silica gel provided by the present application can provide high thermal conductivity,realize chemical curing and shaping,while ensuring long-term stability and reliability.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive materials technology, and in particular to a curable thermally conductive silicone gel and its preparation method. Background Technology

[0002] As electronic devices evolve towards higher power, higher integration, and miniaturization, the heat generated by electronic components is increasing dramatically, severely impacting the reliability and lifespan of these devices. To address this issue, thermal interface materials play a crucial role in the heat dissipation systems of electronic devices. Currently, thermal interface materials mainly include thermal grease, thermal pads, and thermal adhesives. Among these, thermal gels have become one of the most widely used interface thermal conductive materials due to their excellent storage stability, high thermal conductivity, high reliability, and the ability to achieve efficient automated dispensing processes.

[0003] However, existing thermal conductive materials still have many shortcomings. Traditional thermal greases, due to their purely physical mixture structure, tend to leak oil, delaminate, and dry out and powder under prolonged high temperatures, resulting in significant performance degradation after about two years of use. While ordinary curing gels offer improved stability and lifespan, their thermal conductivity is low (typically only 6-8 W / m·K), failing to meet the 5G era's requirements of 10-18 W / m·K or even higher. Furthermore, although phase change materials have the advantage of strong temperature stability, their extremely poor matrix thermal conductivity and lack of a dense thermal network make them prone to leakage and contamination of printed circuit boards (PCBs). They also cannot maintain their shape for extended periods, making it difficult to meet the long-term reliability requirements of high-end electronics.

[0004] Therefore, there is a need to develop a thermally conductive material that can provide high thermal conductivity, achieve chemical curing and shaping, and ensure long-term stability and reliability. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a curable thermally conductive silicone gel and its preparation method. The curable thermally conductive silicone gel provides high thermal conductivity, achieves chemical curing and shaping, and ensures long-term stability and reliability.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a curable thermally conductive silicone gel, wherein the raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts of vinyl silicone oil, 10-15 parts of hydrogen-containing silicone oil (e.g., 11, 12, 13, or 14 parts, etc.), 3000-4000 parts of tri-peaked modified diamond (e.g., 3200, 3400, 3600, or 3800 parts, etc.), and 0.15-0.3 parts of platinum catalyst (e.g., 0. The modified diamond comprises 17 parts, 0.20 parts, 0.23 parts, 0.26 parts, or 0.28 parts, etc.), 0.2-0.6 parts of inhibitor (e.g., 0.25 parts, 0.30 parts, 0.35 parts, 0.40 parts, 0.45 parts, 0.50 parts, or 0.55 parts, etc.), and 1.5-2.5 parts of fumed silica (e.g., 1.6 parts, 1.8 parts, 2.0 parts, 2.2 parts, or 2.4 parts, etc.); the particle size distribution of the modified diamond in the three-peak compound is D50 particle size > 100. μm and ≤200 μm (e.g., 105 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm or 190 μm, etc.), D50 particle size ≥50 μm and ≤100 μm (e.g., 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm or 95 μm, etc.) and D50 particle size ≥0.5 μm and ≤1 μm (e.g., 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm or 0.95 μm, etc.).

[0007] In this invention, the three-peak particle size distribution of the modified diamond with three-peak composite refers to the D50 particle size of the three diamonds used in the preparation of the modified diamond with three-peak composite.

[0008] Diamond is a material with high thermal conductivity, but diamond fillers with a single particle size have problems such as large voids, low filling rate, and high interfacial thermal resistance. It is difficult to achieve both high thermal conductivity and long-term stability when filling it in a silicon matrix. The modified diamond with a three-peak composite structure described in this invention is prepared from three types of diamond with different particle sizes as thermally conductive fillers. A composite coupling agent is also added for surface modification, which increases the compatibility with the silicon matrix composed of vinyl silicone oil and hydrogen-containing silicone oil. This allows the diamond to be uniformly dispersed to form a dense thermally conductive network, which can significantly improve the thermal conductivity.

[0009] In this invention, the vinyl silicone oil and hydrogen-containing silicone oil can undergo a hydrosilylation reaction under the action of a platinum catalyst to achieve chemical curing; and overcome the shortcomings of insufficient thermal conductivity of ordinary curing gels, achieving long-term stability and effectively solving the problem of excessively high transient temperature of electronic components under high power operation.

[0010] Preferably, the tri-peaked modified diamond comprises tri-peaked modified diamond with a composite coupling agent.

[0011] Preferably, the tri-peaked composite coupling agent modified diamond comprises a first composite coupling agent modified diamond, a second composite coupling agent modified diamond, and a third composite coupling agent modified diamond.

[0012] Preferably, the raw materials for preparing the composite coupling agent modified first diamond include a composite coupling agent and a first diamond. The mass of the composite coupling agent is 0.03% to 0.06% of the mass of the first diamond (e.g., 0.035%, 0.04%, 0.045%, 0.05%, or 0.055%). The first diamond is a diamond with a D50 particle size >100 μm and ≤200 μm (e.g., 105 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, or 190 μm).

[0013] Preferably, the raw materials for preparing the composite coupling agent modified second diamond include a composite coupling agent and a second diamond. The mass of the composite coupling agent is 0.03% to 0.06% of the mass of the second diamond (e.g., 0.035%, 0.04%, 0.045%, 0.05%, or 0.055%). The second diamond is a diamond with a D50 particle size ≥ 50 μm and ≤ 100 μm (e.g., 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, or 95 μm).

[0014] Preferably, the raw materials for preparing the composite coupling agent modified third diamond include a composite coupling agent and a third diamond. The mass of the composite coupling agent is 0.03% to 0.06% of the mass of the third diamond (e.g., 0.035%, 0.04%, 0.045%, 0.05%, or 0.055%). The third diamond is a diamond with a D50 particle size ≥ 0.5 μm and ≤ 1 μm (e.g., 0.55 μm, 0.60 μm, 0.65 μm, 0.70 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.90 μm, or 0.95 μm).

[0015] Preferably, the three-peaked composite coupling agent modified diamond comprises the following components by mass percentage: 60%~75% (e.g., 62%, 64%, 66%, 68%, 70%, 72% or 74%) of composite coupling agent modified first diamond, 15%~25% (e.g., 16%, 18%, 20%, 22% or 24%) of composite coupling agent modified second diamond, and 5%~15% (e.g., 6%, 8%, 10%, 12% or 14%) of composite coupling agent modified third diamond.

[0016] Preferably, the composite coupling agents in the raw materials for preparing the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent each independently include a silane coupling agent and a titanate coupling agent in a mass ratio of (3~4):1 (e.g., 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, or 3.9:1, etc.).

[0017] Preferably, the silane coupling agent comprises 3-methacryloyloxypropyltrimethoxysilane.

[0018] Preferably, the inhibitor comprises alkynol and / or triphenylpyrrole.

[0019] In a second aspect, the present invention provides a method for preparing a curable thermally conductive silicone gel as described in the first aspect, the method comprising the following steps: mixing vinyl silicone oil, hydrogen-containing silicone oil, modified diamond with a three-peak compound, platinum catalyst, inhibitor and fumed silica to obtain the curable thermally conductive silicone gel.

[0020] Preferably, the three-peaked modified diamond comprises a first diamond modified by a composite coupling agent, a second diamond modified by a composite coupling agent, and a third diamond modified by a composite coupling agent.

[0021] Preferably, the first diamond modified by the composite coupling agent is prepared by the following method: the first diamond is graphitized, ball-milled, treated with oxygen plasma, and then mixed with the composite coupling agent to obtain the first diamond modified by the composite coupling agent.

[0022] Preferably, the composite coupling agent modified second diamond is prepared by the following method: the second diamond is graphitized, ball-milled, treated with oxygen plasma, and then mixed with the composite coupling agent to obtain the composite coupling agent modified second diamond.

[0023] Preferably, the composite coupling agent modified third diamond is prepared by the following method: the third diamond is treated with oxygen plasma and then mixed with the composite coupling agent to obtain the composite coupling agent modified third diamond.

[0024] In this invention, the graphitization process involves graphitizing the edges and corners of the diamond. Since diamonds are hexagonal octahedral, their edges experience significant heat accumulation during graphitization and are preferentially graphitized. After graphitization, excess graphite is removed by ball milling to facilitate rapid sphericalization of the diamond.

[0025] In this invention, the oxygen plasma treatment etches the diamond surface, introducing a large number of oxygen-containing active groups, such as hydroxyl and carboxyl groups. This provides chemical bonding sites, enabling the composite coupling agents, silane coupling agents and titanate coupling agents, to form a chemical bond with the diamond, rather than simple physical adsorption. Oxygen plasma treatment also eliminates the inert carbon layer on the diamond surface, improving the compatibility of diamond with vinyl silicone oils, etc. Furthermore, oxygen plasma treatment helps reduce the surface energy of the diamond, inhibits the agglomeration of smaller diamond particles, reduces air gaps within the system, and helps to reduce interfacial defects between the diamond and the silicon matrix composed of vinyl silicone oil and hydrogen-containing silicone oil, thereby reducing interfacial thermal resistance and establishing a continuous and complete thermal conductivity pathway. The combination of oxygen plasma treatment and surface modification with composite coupling agents significantly improves the compatibility of diamond with the silicon matrix.

[0026] Preferably, the graphitization treatment temperature in the preparation of the composite coupling agent modified first diamond and the composite coupling agent modified second diamond is independently 700~850℃ (e.g. 720℃, 740℃, 760℃, 780℃, 800℃, 820℃ or 840℃, etc.), and the graphitization treatment time is independently 10~22 min (e.g. 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min or 21 min, etc.).

[0027] Preferably, the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, after the graphitization treatment, each independently includes acid washing with aqua regia and alkali washing until neutral.

[0028] In this invention, the purpose of acid washing with aqua regia after graphitization is to remove residual graphite.

[0029] Preferably, in the preparation of the composite coupling agent modified first diamond and the composite coupling agent modified second diamond, the ball milling media used for ball milling each independently include a first grinding ball, a second grinding ball, and a third grinding ball, wherein the diameter of the first grinding ball is greater than the diameter of the second grinding ball, and the diameter of the third grinding ball is greater than the diameter of the third grinding ball.

[0030] Preferably, the diameter of the first grinding ball is 2.5~3.5 mm (e.g., 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm or 3.4 mm, etc.), the diameter of the second grinding ball is 1.5~2.5 mm (e.g., 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm or 2.4 mm, etc.), and the diameter of the third grinding ball is 0.5~1.5 mm (e.g., 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm or 1.4 mm, etc.).

[0031] Preferably, the first grinding ball, the second grinding ball, and the third grinding ball each independently comprise a zirconia ball and / or a diamond polycrystalline polygonal ball.

[0032] Preferably, based on the total mass of the grinding media as 100%, the mass of the first grinding ball is 35%~45% (e.g., 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, or 44%), the mass of the second grinding ball is 25%~35% (e.g., 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, or 34%), and the mass of the third grinding ball is 25%~35% (e.g., 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, or 34%).

[0033] Preferably, in the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, the ball-to-material ratio of the ball milling is independently (10~20):1, for example, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1 or 19:1, etc.

[0034] Preferably, the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent each includes, independently, acid washing and water washing until neutral after ball milling.

[0035] In this invention, the acid washing after ball milling in the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent is used to remove any possible metal residues to reduce impurities. These metal residues may originate from the diamond production process, breakage during ball milling, and metal exposure.

[0036] Preferably, the power of the oxygen plasma treatment in the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent is independently 50~100 W, for example 55 W, 60 W, 65 W, 70 W, 75 W, 80 W, 85 W, 90 W, or 95 W.

[0037] Preferably, the oxygen plasma treatment time in the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent is independently 20~30 min, for example 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, or 29 min.

[0038] Preferably, the pressure of oxygen plasma treatment in the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent is independently 0.1~0.5 Pa, for example 0.15 Pa, 0.20 Pa, 0.25 Pa, 0.30 Pa, 0.35 Pa, 0.40 Pa, or 0.45 Pa.

[0039] Preferably, the oxygen plasma treatment temperature in the preparation of the composite coupling agent modified first diamond, composite coupling agent modified second diamond and composite coupling agent modified third diamond is independently 20~30℃, for example 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃ or 29℃, etc.

[0040] Preferably, the mixing in the preparation of the composite coupling agent modified first diamond, composite coupling agent modified second diamond, and composite coupling agent modified third diamond each independently includes stirring and mixing. The stirring and mixing temperature is 60~80℃ (e.g., 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, or 78℃, etc.), the stirring and mixing speed is 300~1000 rpm (e.g., 350 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, or 900 rpm, etc.), and the stirring and mixing time is 2~3 h (e.g., 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, or 2.9 h, etc.).

[0041] Preferably, the preparation method includes the following steps: (1) Pre-treating the first diamond, the second diamond, and the third diamond and then mixing them with a composite coupling agent to prepare composite coupling agent modified first diamond, composite coupling agent modified second diamond, and composite coupling agent modified third diamond; (2) Mixing vinyl silicone oil, inhibitor, and fumed silica to obtain a base gel; (3) Mixing the composite coupling agent modified first diamond, composite coupling agent modified second diamond, composite coupling agent modified third diamond, the base gel obtained in step (1), hydrogen-containing silicone oil, and platinum catalyst, vacuum degassing, and thermal curing to obtain the curable thermally conductive silicone gel; Steps (1) and (2) are performed in any order, or simultaneously.

[0042] Preferably, the mixing in steps (2) and (3) is carried out independently under vacuum conditions, wherein the vacuum degree is ≤0.1MPa, for example 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa or 0.09 MPa, etc.

[0043] Preferably, the mixing in step (2) includes stirring, the temperature of stirring is 20~30℃ (e.g., 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃ or 29℃, etc.), the speed of stirring is 500~1000rpm (e.g., 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm or 950 rpm, etc.), and the time of stirring is 15~30 min (e.g., 16 min, 18 min, 20 min, 22 min, 24 min, 26 min or 28 min, etc.).

[0044] Preferably, the mixing in step (3) includes mixing the first diamond modified with the composite coupling agent with the base adhesive at a speed of 1000-1500 rpm (e.g., 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, or 1450 rpm, etc.) for 10-15 min (e.g., 10.5 min, 11.0 min, 11.5 min, 12.0 min, 12.5 min, 13.0 min, 13.5 min, or 14.0 min, etc.) under a temperature of 20-30℃ (e.g., 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, or 29℃, etc.) for 10-15 min (e.g., 10.5 min, 11.0 min, 11.5 min, 12.0 min, 12.5 min, 13.0 min, 13.5 min, or 14.0 min, etc.) for 10-15 min (e.g., 10.5 ...5 min, or 14.0 min, etc.) for 10-15 min (e.g., 10.5 min, 11.5 min, 12.0 min, 12.5 min, 13.5 min Add the composite coupling agent-modified third diamond at 500-1000 rpm (e.g., 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, or 900 rpm) and stir for 15-20 min (e.g., 15.5 min, 16.0 min, 16.5 min, 17.0 min, 17.5 min, 18.0 min, 18.5 min, or 19.0 min) for 1200-1500 rpm (e.g., 1220 rpm, 1250 rpm, 1280 rpm, 1300 rpm, 1330 rpm, or 1360 rpm). Stir and mix at speeds of 1390 rpm, 1420 rpm, or 1450 rpm, etc., for 15 to 20 minutes (e.g., 15.5 min, 16.0 min, 16.5 min, 17.0 min, 17.5 min, 18.0 min, 18.5 min, or 19.0 min, etc.).

[0045] Preferably, the vacuum degree of vacuum degassing in step (3) is ≤0.1MPa (e.g., 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa or 0.09 MPa, etc.), and the vacuum degassing time is 45~60 min (e.g., 46 min, 48 min, 50 min, 52 min, 54 min, 56 min or 58 min, etc.).

[0046] Preferably, the heat curing temperature is 80~110℃ (e.g., 85℃, 90℃, 95℃, 100℃ or 105℃, etc.), and the heat curing time is 15~40 min (e.g., 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min or 38 min, etc.).

[0047] Compared with the prior art, the present invention has at least the following beneficial effects: The curable thermally conductive silicone gel of this invention provides both high thermal conductivity and chemical curing, while ensuring long-term stability and reliability. The thixotropic index of the adhesive solution before thermal curing is 3-7, preferably 3.2-4.3. The thermal conductivity of the curable thermally conductive silicone gel is ≥9.6 W / m·K, and the interfacial thermal resistance at a thickness of 200 μm is ≤0.26℃·cm. 2 The curable thermally conductive silicone gel has a Shore OO hardness of 20~35, an interfacial thermal resistance change rate of <19% after 50 cycles of high and low temperature cycling from -40 to 180℃, and a thermal conductivity decay rate of <20% after 1000 h of long-term aging. Preferably, the thermal conductivity of the curable thermally conductive silicone gel is ≥13 W / m·K, and the interfacial thermal resistance at a thickness of 200 μm is ≤0.15℃·cm. 2 / W, Shore OO hardness is 20~35, the interfacial thermal resistance change rate after 50 cycles of high and low temperature (-40~180℃) is <5%, and the thermal conductivity decay rate after 1000h long-term aging is <5%. Detailed Implementation

[0048] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0049] Unless otherwise specified, the materials and equipment involved in the following detailed embodiments are all conventional materials and equipment in the art and will not affect the technical effects of the present invention.

[0050] Unless otherwise specified, all reagents and raw materials used in the following examples and comparative examples are commercially available products. Some raw material information is as follows: Vinyl silicone oil: Model VS450L, manufactured by Shanghai Jingri New Materials Technology Co., Ltd. Hydrogen-containing silicone oil: Model DH007, manufactured by Shanghai Jingri New Materials Technology Co., Ltd. Platinum catalyst: Model PL2000, manufactured by Zijun Chemical. Inhibitor: Model HR, manufactured by Zijun Chemical.

[0051] Example 1 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts of vinyl silicone oil, 12 parts of hydrogen-containing silicone oil, 3000 parts of diamond modified with a three-peak composite coupling agent, 0.2 parts of platinum catalyst, 0.4 parts of inhibitor, and 2 parts of fumed silica.

[0052] The raw materials for preparing the above-mentioned three-peaked composite coupling agent modified diamond include a first diamond (D50 particle size of 150 μm), a second diamond (D50 particle size of 80 μm), a third diamond (D50 particle size of 0.8 μm), and a composite coupling agent.

[0053] The aforementioned composite coupling agent is a 3-methacryloyloxypropyltrimethoxysilane and titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate) in a mass ratio of 3:1.

[0054] The preparation method of the curable thermally conductive silicone gel includes the following steps: (1) The first diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, acid-washed with aqua regia for 60 min, washed with 5% sodium hydroxide aqueous solution until neutral (pH=7), and then dry-milled using a planetary ball mill. The milling media consisted of 30% of the first grinding balls (3 mm in diameter), 30% of the second grinding balls (2 mm in diameter), and 30% of the third grinding balls (1 mm in diameter) in a mass ratio of 40:30:30. The first, second, and third grinding balls were all zirconia balls, and the ball-to-material ratio for each grinding ball was 10:1. The powder obtained from the ball milling was screened using an 80-mesh sieve, and then washed with 28% dilute nitric acid (deionized water as solvent) to remove metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. The powder was then placed in a plasma treatment device for oxygen plasma treatment at a power of 50 W and a pressure of 0.3 W. The first diamond was treated at 30°C for 20 min, then mixed with a composite coupling agent at 60°C for 2 h at 300 rpm. The mass of the composite coupling agent was 0.05% of the mass of the first diamond, thus obtaining the first diamond modified with the composite coupling agent.

[0055] The second diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, then acid-washed with aqua regia for 60 min, and washed with a 5% sodium hydroxide aqueous solution until neutral (pH=7). It was then dry-milled using a planetary ball mill with a grinding media consisting of 3 mm diameter first grinding balls, 2 mm diameter second grinding balls, and 1 mm diameter third grinding balls in a 40:30:30 mass ratio. All three grinding balls were zirconia balls, with each having a ball-to-material ratio of 10:1. The resulting powder was sieved through a 200-mesh sieve, then washed with 28% dilute nitric acid (using deionized water as solvent) to remove any potential metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. Finally, it was subjected to oxygen plasma treatment in a plasma treatment device at a power of 50 W, a pressure of 0.3 Pa, a temperature of 30℃, and a treatment time of 20 minutes. The mixture was stirred at 60°C for 2 hours with a composite coupling agent at a speed of 500 rpm. The mass of the composite coupling agent was 0.05% of the mass of the second diamond, thus obtaining the composite coupling agent-modified second diamond.

[0056] The third diamond was placed in a plasma treatment device for oxygen plasma treatment at a power of 50W, a pressure of 0.3 Pa, a temperature of 30℃, and a treatment time of 20 min. Then, it was mixed with a composite coupling agent at 60℃ for 2 h at a speed of 1000 rpm. The mass of the composite coupling agent was 0.05% of the mass of the third diamond, thus obtaining the composite coupling agent modified third diamond.

[0057] (2) Under a vacuum of 0.1 MPa, vinyl silicone oil, inhibitor and fumed silica were stirred and mixed at 20°C for 15 min at a stirring speed of 800 rpm to obtain the base adhesive.

[0058] (3) Under a vacuum of 0.1 MPa, the first diamond modified by the composite coupling agent obtained in step (1) and the base adhesive obtained in step (2) are dispersed at 20°C and 1500 rpm for 10 min. The second diamond modified by the composite coupling agent obtained in step (1) is added and dispersed at 20°C and 1500 rpm for 10 min. The third diamond modified by the composite coupling agent obtained in step (1) is added and dispersed at 20°C and 800 rpm for 15 min. Based on the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent being 100%, the mass of the first diamond modified by the composite coupling agent is 70%, the mass of the second diamond modified by the composite coupling agent is 20%, and the mass of the third diamond modified by the composite coupling agent is 10%. Then, hydrogen-containing silicone oil and platinum catalyst are added and dispersed at 20°C and 1200 rpm for 15 min. The gel was vacuum degassed for 45 minutes under a vacuum of -0.095 MPa, heated to 100°C at a heating rate of 3°C / min, and then cured at 100°C for 20 minutes to obtain the curable thermally conductive silicone gel.

[0059] Example 2 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts of vinyl silicone oil, 10 parts of hydrogen-containing silicone oil, 3500 parts of diamond modified with a three-peak composite coupling agent, 0.3 parts of platinum catalyst, 0.6 parts of inhibitor, and 2.5 parts of fumed silica.

[0060] The raw materials for preparing the above-mentioned three-peaked composite coupling agent modified diamond include a first diamond (D50 particle size of 120 μm), a second diamond (D50 particle size of 50 μm), a third diamond (D50 particle size of 0.5 μm), and a composite coupling agent.

[0061] The aforementioned composite coupling agent is a coupling agent of 3-methacryloyloxypropyltrimethoxysilane and titanate (isopropyltris(diisooctyl pyrophosphate) titanate) with a mass ratio of 3.5:1.

[0062] The preparation method of the curable thermally conductive silicone gel includes the following steps: (1) Graphitized diamond with a D50 particle size of 120 μm was subjected to graphitization treatment at 800℃ for 20 min to achieve graphitized edges, followed by acid washing with aqua regia for 60 min, and then washing with a 5% sodium hydroxide aqueous solution until neutral (pH=7). The diamond was then dry-milled using a planetary ball mill. The milling media consisted of a first grinding ball (3 mm in diameter), a second grinding ball (2 mm in diameter), and a third grinding ball (1 mm in diameter) with a mass ratio of 40:30:30. The first, second, and third grinding balls are all zirconia balls, and the ball-to-powder ratio for each is 12:1. The powder obtained from ball milling is screened using a 300-mesh sieve, and then washed with 28% dilute nitric acid (solvent deionized water) to remove any possible metal residues. After washing with deionized water until neutral (pH=7), the powder is dried in a vacuum drying oven at 120°C for 3 hours to remove surface adsorbed moisture. It is then placed in a plasma treatment device for oxygen plasma treatment at a power of 70W, a pressure of 0.2Pa, a temperature of 25°C, and a treatment time of 20 minutes. Then, it is mixed with a composite coupling agent at 63°C for 2.5 hours at a speed of 300 rpm. The mass of the composite coupling agent is 0.03% of the mass of the first diamond, thus obtaining the first diamond modified with the composite coupling agent.

[0063] The second diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, followed by acid washing with aqua regia for 60 min. After washing with a 5% sodium hydroxide aqueous solution until neutral (pH=7), it was dry-milled using a planetary ball mill. The milling media consisted of a 40:30:30 ratio of 30% for the first (3 mm diameter), 2 mm diameter, and 1 mm diameter grinding balls. All three grinding balls were zirconia balls, with an independent ball-to-material ratio of 12:1 for each. The resulting powder was sieved through a 250-mesh sieve, then washed with 28% dilute nitric acid (using deionized water as solvent) to remove any potential metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. Finally, it was subjected to oxygen plasma treatment at a power of 70 W, a pressure of 0.2 Pa, a temperature of 25℃, and a treatment time of 20 minutes. The mixture was stirred at 63°C for 2.5 h with a composite coupling agent at a speed of 500 rpm. The mass of the composite coupling agent was 0.03% of the mass of the second diamond, thus obtaining the composite coupling agent-modified second diamond.

[0064] The third diamond was placed in a plasma treatment device for oxygen plasma treatment at a power of 70W, a pressure of 0.2 Pa, a temperature of 25℃, and a treatment time of 20 min. Then, it was mixed with a composite coupling agent at 63℃ for 2.5 h at a rotation speed of 1000 rpm. The mass of the composite coupling agent was 0.03% of the mass of the third diamond, thus obtaining the composite coupling agent modified third diamond.

[0065] (2) Under a vacuum of 0.1 MPa, vinyl silicone oil, inhibitor and fumed silica were stirred and mixed at 20°C for 20 min at a stirring speed of 500 rpm to obtain the base adhesive.

[0066] (3) Under a vacuum of 0.1 MPa, the first diamond modified by the composite coupling agent prepared in step (1) and the base adhesive prepared in step (2) are dispersed at 20°C and 1000 rpm for 12 min. The second diamond modified by the composite coupling agent prepared in step (1) is added and dispersed at 20°C and 1000 rpm for 12 min. The third diamond modified by the composite coupling agent prepared in step (1) is added and dispersed at 20°C and 500 rpm for 17 min. Based on the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent being 100%, the mass of the first diamond modified by the composite coupling agent is 60%, the mass of the second diamond modified by the composite coupling agent is 25%, and the mass of the third diamond modified by the composite coupling agent is 15%. Then, hydrogen-containing silicone oil and platinum catalyst are added and dispersed at 20°C and 1500 rpm for 15 min. The gel was vacuum degassed for 50 minutes at a vacuum degree of -0.095 MPa, heated to 80°C at a heating rate of 2°C / min, and then cured at 80°C for 40 minutes to obtain the curable thermally conductive silicone gel.

[0067] Example 3 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts of vinyl silicone oil, 15 parts of hydrogen-containing silicone oil, 4000 parts of diamond modified with a three-peak composite coupling agent, 0.15 parts of platinum catalyst, 0.2 parts of inhibitor, and 1.5 parts of fumed silica.

[0068] The raw materials for preparing the above-mentioned three-peaked composite coupling agent modified diamond include first diamond (D50 particle size of 200 μm), second diamond (D50 particle size of 100 μm), third diamond (D50 particle size of 1 μm) and composite coupling agent.

[0069] The aforementioned composite coupling agent is a 3-methacryloyloxypropyltrimethoxysilane and titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate) in a mass ratio of 3:1.

[0070] The preparation method of the curable thermally conductive silicone gel includes the following steps: (1) The first diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, acid-washed with aqua regia for 60 min, washed with 5% sodium hydroxide aqueous solution until neutral (pH=7), and then dry-milled using a planetary ball mill. The milling media consisted of 30% of the first grinding balls (3 mm in diameter), 30% of the second grinding balls (2 mm in diameter), and 30% of the third grinding balls (1 mm in diameter) in a mass ratio of 40:30:30. The first, second, and third grinding balls were all zirconia balls, and the ball-to-material ratio for each grinding ball was 15:1. The powder obtained from the ball milling was screened using a 60-mesh sieve, and then washed with 28% dilute nitric acid (deionized water as solvent) to remove any possible metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. The powder was then placed in a plasma treatment device for oxygen plasma treatment at a power of 70 W and a pressure of 0.3 W. The first diamond was treated at 25°C for 25 min, and then mixed with a composite coupling agent at 70°C for 2.5 h at a speed of 300 rpm. The mass of the composite coupling agent was 0.06% of the mass of the first diamond, thus obtaining the first diamond modified by the composite coupling agent.

[0071] The second diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, then acid-washed with aqua regia for 60 min, and washed with a 5% sodium hydroxide aqueous solution until neutral (pH=7). It was then dry-milled using a planetary ball mill with a grinding media consisting of 3 mm diameter first grinding balls, 2 mm diameter second grinding balls, and 1 mm diameter third grinding balls in a mass ratio of 40:30:30. All three grinding balls were zirconia balls, with an independent ball-to-material ratio of 15:1 for each. The resulting powder was sieved through a 160-mesh sieve, then washed with 28% dilute nitric acid (using deionized water as solvent) to remove any potential metal residues. After washing with deionized water until neutral (pH=7), it was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. Finally, it was subjected to oxygen plasma treatment in a plasma treatment device with a power of 70 W, a pressure of 0.3 Pa, a temperature of 25℃, and a treatment time of 25 seconds. The mixture was stirred at 70°C for 2.5 h with a composite coupling agent at a speed of 500 rpm. The mass of the composite coupling agent was 0.06% of the mass of the second diamond, thus obtaining the composite coupling agent-modified second diamond.

[0072] The third diamond was placed in a plasma treatment device for oxygen plasma treatment at a power of 70W, a pressure of 0.3 Pa, a temperature of 25℃, and a treatment time of 25 min. Then, it was mixed with a composite coupling agent at 70℃ for 2.5 h at a speed of 1000 rpm. The mass of the composite coupling agent was 0.06% of the mass of the third diamond, thus obtaining the composite coupling agent modified third diamond.

[0073] (2) Under a vacuum of 0.1 MPa, vinyl silicone oil, inhibitor and fumed silica were stirred and mixed at 25°C for 25 min at a stirring speed of 800 rpm to obtain the base adhesive.

[0074] (3) Under a vacuum of 0.1 MPa, the first diamond modified by the composite coupling agent obtained in step (1) and the base adhesive obtained in step (2) are dispersed at 25°C and 2000 rpm for 15 min. The second diamond modified by the composite coupling agent obtained in step (1) is added and dispersed at 25°C and 2000 rpm for 15 min. The third diamond modified by the composite coupling agent obtained in step (1) is added and dispersed at 25°C and 1000 rpm for 20 min. Taking the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent as 100%, the mass of the first diamond modified by the composite coupling agent is 75%, the mass of the second diamond modified by the composite coupling agent is 20%, and the mass of the third diamond modified by the composite coupling agent is 5%. Then, hydrogen-containing silicone oil and platinum catalyst are added and dispersed at 25°C and 1200 rpm for 20 min. The gel was vacuum degassed for 50 minutes under a vacuum of -0.095 MPa, heated to 90°C at a heating rate of 3°C / min, and then cured at 90°C for 30 minutes to obtain the curable thermally conductive silicone gel.

[0075] Example 4 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts of vinyl silicone oil, 15 parts of hydrogen-containing silicone oil, 3800 parts of diamond modified with a three-peak composite coupling agent, 0.2 parts of platinum catalyst, 0.2 parts of inhibitor, and 1.5 parts of fumed silica.

[0076] The raw materials for preparing the above-mentioned three-peaked composite coupling agent modified diamond include a first diamond (D50 particle size of 180 μm), a second diamond (D50 particle size of 80 μm), a third diamond (D50 particle size of 0.6 μm), and a composite coupling agent.

[0077] The aforementioned composite coupling agent is a 3-methacryloyloxypropyltrimethoxysilane and titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate) in a mass ratio of 3:1.

[0078] The preparation method of the curable thermally conductive silicone gel includes the following steps: (1) The first diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, acid-washed with aqua regia for 60 min, washed with 5% sodium hydroxide aqueous solution until neutral (pH=7), and then dry-milled using a planetary ball mill. The milling media consisted of 30% of the first grinding balls (3 mm in diameter), 30% of the second grinding balls (2 mm in diameter), and 30% of the third grinding balls (1 mm in diameter) in a mass ratio of 40:30:30. The first, second, and third grinding balls were all zirconia balls, and the ball-to-material ratio for each grinding ball was 20:1. The powder obtained from the ball milling was screened using a 60-mesh sieve, and then washed with 28% dilute nitric acid (deionized water as solvent) to remove any possible metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. The powder was then placed in a plasma treatment device for oxygen plasma treatment at a power of 70 W and a pressure of 0.3 W. The first diamond was prepared by mixing the composite coupling agent at 80°C for 3 hours at 25°C for 25 minutes, and then stirring at 300 rpm for 3 hours. The mass of the composite coupling agent was 0.05% of the mass of the first diamond.

[0079] The second diamond was graphitized at 800℃ for 20 min to achieve graphitized edges, followed by acid washing with aqua regia for 60 min. After washing with a 5% sodium hydroxide aqueous solution until neutral (pH=7), it was dry-milled using a planetary ball mill. The milling media consisted of a 40:30:30 ratio of 30% for the first, second, and third grinding balls (30% by mass), all of which were zirconia balls, with an independent ball-to-material ratio of 20:1 for each. The resulting powder was sieved through a 160-mesh sieve, then washed with 28% dilute nitric acid (using deionized water as solvent) to remove any potential metal residues. After washing with deionized water until neutral (pH=7), the powder was dried in a vacuum drying oven at 120℃ for 3 h to remove surface adsorbed moisture. Finally, it was subjected to oxygen plasma treatment at a power of 70 W, a pressure of 0.3 Pa, a temperature of 25℃, and a treatment time of 25 seconds. The mixture was stirred at 80°C for 3 hours with a composite coupling agent at a speed of 500 rpm. The mass of the composite coupling agent was 0.05% of the mass of the second diamond, thus obtaining the composite coupling agent-modified second diamond.

[0080] The third diamond was placed in a plasma treatment device for oxygen plasma treatment at a power of 70W, a pressure of 0.3 Pa, a temperature of 25℃, and a treatment time of 25 min. Then, it was mixed with a composite coupling agent at 80℃ for 3 h at a speed of 1000 rpm. The mass of the composite coupling agent was 0.05% of the mass of the third diamond, thus obtaining the composite coupling agent modified third diamond.

[0081] (2) Under a vacuum of 0.1 MPa, vinyl silicone oil, inhibitor and fumed silica were stirred and mixed at 30°C for 30 min at a stirring speed of 800 rpm to obtain the base adhesive.

[0082] (3) Under a vacuum of 0.1 MPa, the first diamond modified by the composite coupling agent obtained in step (1) and the base adhesive obtained in step (2) are dispersed at 30°C and 2000 rpm for 15 min. Then, the second diamond modified by the composite coupling agent is added and dispersed at 30°C and 2000 rpm for 15 min. Taking the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent as 100%, the mass of the first diamond modified by the composite coupling agent is 72%, the mass of the second diamond modified by the composite coupling agent is 20%, and the mass of the third diamond modified by the composite coupling agent is 8%. Then, the third diamond modified by the composite coupling agent is added and dispersed at 30°C and 1000 rpm for 20 min. Then, hydrogen-containing silicone oil and platinum catalyst are added and dispersed at 30°C and 1200 rpm for 15 min. Vacuum degassing was performed under a vacuum of MPa for 60 min, followed by heating to 90°C at a heating rate of 5°C / min, and then curing at 90°C for 30 min to obtain the curable thermally conductive silicone gel.

[0083] Example 5 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Embodiment 1 is that the composite coupling agent is a 4:1 mass ratio of 3-methacryloyloxypropyltrimethoxysilane and a titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate), and the other conditions are the same as in Embodiment 1.

[0084] Example 6 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Embodiment 1 is that the composite coupling agent is a 3-methacryloyloxypropyltrimethoxysilane and a titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate) in a mass ratio of 5:1. Other conditions are the same as in Embodiment 1.

[0085] Example 7 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Embodiment 1 is that the composite coupling agent is a 2:1 mass ratio of 3-methacryloyloxypropyltrimethoxysilane and a titanate coupling agent (isopropyltris(diisooctyl pyrophosphate) titanate), and the other conditions are the same as in Embodiment 1.

[0086] Example 8 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Embodiment 1 is that, based on the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent as 100%, the mass of the first diamond modified by the composite coupling agent is 55%, the mass of the second diamond modified by the composite coupling agent is 30%, and the mass of the third diamond modified by the composite coupling agent is 15%. Other conditions are the same as in Embodiment 1.

[0087] Example 9 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Embodiment 1 is that, based on the total mass of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent being 100%, the mass of the first diamond modified by the composite coupling agent is 82%, the mass of the second diamond modified by the composite coupling agent is 12%, and the mass of the third diamond modified by the composite coupling agent is 6%. Other conditions are the same as in Embodiment 1.

[0088] Example 10 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference from Embodiment 1 is that the first, second, and third diamonds are not subjected to oxygen plasma treatment. The preparation of the composite coupling agent-modified third diamond is adjusted to involve mixing the third diamond and the composite coupling agent at 60°C for 2 hours at a speed of 1000 rpm, with the mass of the composite coupling agent being 0.05% of the mass of the third diamond, thus obtaining the composite coupling agent-modified third diamond. Other conditions are the same as in Embodiment 1.

[0089] Example 11 This embodiment provides a curable thermally conductive silicone gel and its preparation method. The difference between this embodiment and Example 1 is that 3-methacryloyloxypropyltrimethoxysilane is replaced with the same mass of γ-aminopropyltriethoxysilane (KH-550). Other conditions are the same as in Example 1.

[0090] Comparative Example 1 This comparative example provides a curable thermally conductive silicone gel and its preparation method. The difference between this example and Example 1 is that the D50 particle size of the first diamond is adjusted to 30 μm. Other conditions are the same as in Example 1.

[0091] Comparative Example 2 This comparative example provides a curable thermally conductive silicone gel and its preparation method. The difference between this and Example 1 is that the three-peaked composite coupling agent modified diamond is replaced with the same mass of two-peaked composite coupling agent modified diamond. The raw materials for preparing the three-peaked composite coupling agent modified diamond include a second diamond (D50 particle size of 80 μm), a third diamond (D50 particle size of 0.8 μm), and a composite coupling agent. Step (3) in the preparation method does not include the step of dispersing the first diamond modified with the composite coupling agent. With the total mass of the second and third diamonds modified with the composite coupling agent as 100%, the mass of the second diamond modified with the composite coupling agent is 67% and the mass of the third diamond modified with the composite coupling agent is 33%. Other conditions are the same as in Example 1.

[0092] Comparative Example 3 This comparative example provides a curable thermally conductive silicone gel and its preparation method. The difference between this example and Example 1 is that the three-peaked composite coupling agent modified diamond is replaced with the same mass of two-peaked composite coupling agent modified diamond. The raw materials for preparing the three-peaked composite coupling agent modified diamond include a first diamond (D50 particle size of 150 μm), a third diamond (D50 particle size of 0.8 μm), and a composite coupling agent. Step (3) in the preparation method does not include the step of dispersing the second diamond modified with the composite coupling agent. Taking the total mass of the first and third diamonds modified with the composite coupling agent as 100%, the mass of the first diamond modified with the composite coupling agent is 87.5% and the mass of the third diamond modified with the composite coupling agent is 12.5%. Other conditions are the same as in Example 1.

[0093] Comparative Example 4 This comparative example provides a curable thermally conductive silicone gel and its preparation method. The difference between this example and Example 1 is that the three-peaked composite coupling agent modified diamond is replaced with the same mass of two-peaked composite coupling agent modified diamond. The raw materials for preparing the three-peaked composite coupling agent modified diamond include a first diamond (D50 particle size of 150 μm), a second diamond (D50 particle size of 80 μm), and a composite coupling agent. Step (3) in the preparation method does not include the step of dispersing the third diamond modified by the composite coupling agent. Taking the total mass of the first and second diamonds modified by the composite coupling agent as 100%, the mass of the first diamond modified by the composite coupling agent is 77.8%, and the mass of the second diamond modified by the composite coupling agent is 22.2%. Other conditions are the same as in Example 1.

[0094] The following performance tests were conducted on the cured thermally conductive silicone gels provided in Examples 1-11 and Comparative Examples 1-4.

[0095] (1) Thermal conductivity: The thermal conductivity of the cured thermally conductive silicone gel was tested using a DRL-III thermal flow method thermal conductivity tester according to ASTM D5470 standard. The test pressure was set to 50 psi and the test temperature was kept constant at 25℃. Each sample was tested 5 times, and the arithmetic mean was taken as the final thermal conductivity result. The unit is W / m·K.

[0096] (2) Interfacial thermal resistance: The interfacial thermal resistance of the cured thermally conductive silicone gel was tested using a DRL-III thermal conductivity tester according to ASTM D5470 standard. The sample thickness was uniformly controlled at 200 μm, the test pressure at 50 psi, and the ambient temperature at 25 ℃. Five sets of samples were tested in parallel for each group of samples. After removing outliers, the average value was taken. The unit is ℃·cm. 2 / W.

[0097] (3) Shore OO hardness: The Shore OO hardness of the cured thermally conductive silicone gel was tested using a Shore OO type hardness tester according to the ASTM D2240 standard. The sample was placed flat on a hard horizontal platform, and the hardness tester probe was pressed vertically down on the sample surface. Five different points were selected for testing each sample. The values ​​were read after standing for 10 seconds, and the average value was finally taken to obtain the Shore OO hardness.

[0098] (5) High and low temperature cycling performance: The cured thermally conductive silicone gel was subjected to high and low temperature cycling treatment using a programmable high and low temperature alternating test chamber. The heating and cooling rate was uniformly set to 10℃ / min. The high and low temperature cycling range was -40℃ (holding for 30min) to 180℃ (holding for 30min). The duration of a single cycle was 60min, and the cycle was repeated 50 times. After the cycle was completed, the sample was cooled to room temperature (25℃) and the interfacial thermal resistance at a thickness of 200μm was tested again.

[0099] Formula for calculating the rate of change of interfacial thermal resistance: Rate of change of interfacial thermal resistance = (Interfacial thermal resistance after cycling - Interfacial thermal resistance before cycling) / Interfacial thermal resistance before cycling × 100%.

[0100] (6) Aging resistance: The cured thermally conductive silicone gel was aged in a high-temperature hot air aging test chamber. The aging conditions were set at 150℃ and constant pressure air for 1000 h. After aging, the appearance of the sample was observed to see if there was oil seepage, drying, cracking or powdering. The change in thermal conductivity of the sample before and after aging was tested, and thermal conductivity was used as the core evaluation index.

[0101] The formula for calculating the thermal conductivity degradation rate is: Thermal conductivity degradation rate = (thermal conductivity before aging - thermal conductivity after aging) / thermal conductivity before aging × 100%.

[0102] (7) Thixotropic index: The thixotropic index of the adhesive liquid before thermal curing of the thermally conductive silicone gel was tested using a rotational rheometer. At room temperature of 25°C, the viscosity of the system was tested at shear rates of 1 rpm and 10 rpm respectively. Thixotropic index = viscosity at 1 rpm / viscosity at 10 rpm. The higher the thixotropic index, the better the anti-flow performance of the material and the better the effect of automatic dispensing process.

[0103] The test results are shown in Tables 1 and 2.

[0104] Table 1 Table 2 According to the test results in Tables 1 and 2, the thixotropic index of the curable thermally conductive silicone gel prepared in Examples 1-11 before thermal curing is 3-7, the thermal conductivity of the cured curable thermally conductive silicone gel is ≥9.6 W / m·K, and the interfacial thermal resistance at a thickness of 200 μm is ≤0.253℃·cm. 2 / W, Shore OO hardness is 21~33, the interfacial thermal resistance change rate after 50 cycles of high and low temperature (-40~180℃) is ≤18.3%, and the thermal conductivity decay rate after 1000 h of long-term aging is ≤19.2%.

[0105] Compared to Example 1, if the mass ratio of silane coupling agent to titanate coupling agent is too high (Example 6), the proportion of titanate coupling agent is too low, resulting in a significant decrease in the wetting and deagglomeration ability of diamond, severe diamond agglomeration, and a large number of voids inside the cured thermally conductive silicone gel, leading to the breakage of thermal conductivity pathways. Simultaneously, excessive silane coupling agent exists as small molecules free in the silicon matrix, easily generating trace amounts of small molecules that volatilize during aging. The thermal conductivity of the resulting cured thermally conductive silicone gel decreases significantly, while the interfacial thermal resistance increases significantly. After 1000 hours of high-temperature aging at 150°C, the rate of thermal conductivity degradation increases, and the rate of change in interfacial thermal resistance increases after high and low temperature cycling. The viscosity of the adhesive before curing increases, the thixotropic index increases, the dispensing fluidity deteriorates, and the overall performance deteriorates.

[0106] Compared to Example 1, if the mass ratio of silane coupling agent to titanate coupling agent is too low (Example 7), the proportion of titanate coupling agent is too high. Excessive long pyrophosphate flexible branches (diisooctyl pyrophosphate) in the titanate coupling agent easily isolate vinyl silicone oil molecules, significantly hindering the hydrosilylation crosslinking reaction. The platinum catalytic activity is slightly inhibited by the excessive titanate coupling agent, resulting in incomplete surface curing. Simultaneously, the excessive titanate coupling agent leads to a decrease in the compatibility between diamond and the silicon matrix composed of vinyl silicone oil and hydrogen-containing silicone oil. Performance: The surface of the prepared cured thermally conductive silicone gel is slightly sticky, the crosslinking density is reduced, and the Shore hardness decreases. After 1000 hours of high-temperature aging at 150°C, the rate of thermal conductivity decay increases; after high and low temperature cycling, the rate of change in interfacial thermal resistance increases; the crosslinking integrity decreases; and the thermal cycling resistance and long-term reliability deteriorate. Therefore, it can be concluded that the curable thermally conductive silicone gel and the cured thermally conductive silicone gel prepared by controlling the mass ratio of silane coupling agent to titanate coupling agent to be (3~4):1 have better performance.

[0107] A comparison of Examples 1 with Examples 8 and 9 shows that the present invention, by controlling the three-peaked composite coupling agent modified diamond to include the following components by mass percentage: 60%~75% composite coupling agent modified first diamond, 15%~25% composite coupling agent modified second diamond, and 5%~15% composite coupling agent modified third diamond, produces a curable thermally conductive silicone gel with better thermal conductivity, high and low temperature cycling resistance, and aging resistance.

[0108] Compared to Example 1, without oxygen plasma treatment (Example 10), the diamond surface is highly inert, the composite coupling agent has a poor modification effect on the diamond, and the bonding strength is low. It relies only on physical adsorption on the diamond surface, which leads to the diamond being prone to agglomeration and clumping, increasing the porosity of the powder, and reducing the thermal conductivity due to air blocking the thermal conduction path. The diamond has poor compatibility with silicone oil, and the viscosity of the curable thermally conductive silicone gel increases under the same filling amount, with a high thixotropic index, poor flowability of automatic dispensing, and easy clogging of needles and internal air entrapment. During high and low temperature cycling and aging, the composite coupling agent layer on the diamond surface is very easy to fall off, and gaps and voids appear at the interface between the diamond and the silicon matrix composed of vinyl silicone oil and hydrogen-containing silicone oil, increasing the rate of change of interfacial thermal resistance and the rate of decay of thermal conductivity.

[0109] Compared to Example 1, if 3-methacryloyloxypropyltrimethoxysilane is replaced with the same mass of γ-aminopropyltriethoxysilane (Example 11), the matrix is ​​a hydrosilylation curing system of vinyl silicone oil and hydrogen-containing silicone oil under platinum catalyst catalysis. The side chain of 3-methacryloyloxypropyltrimethoxysilane has carbon-carbon double bonds, which match the functional group structure of vinyl silicone oil. During the curing process catalyzed by platinum catalyst, it can directly participate in the hydrosilylation crosslinking reaction and chemically bond into the organosilicon three-dimensional network. At the same time, the hydrolyzed terminal hydroxyl groups can firmly bind to the hydroxyl groups on the surface of diamond after oxygen plasma treatment and activation. One end is connected to diamond and the other end is fixed in the organosilicon three-dimensional network. The interfacial bonding force is extremely strong, there are no free small molecules, and it does not poison the platinum catalyst. γ-aminopropyltriethoxysilane, as an aminosilane coupling agent, has active amino groups at its molecular end. These amino groups cause partial deactivation of the platinum catalyst, resulting in a decrease in crosslinking density. Consequently, the cured thermally conductive silicone gel exhibits a sticky surface and incomplete internal curing. Furthermore, lacking carbon-carbon double bonds, it cannot participate in the crosslinking reaction of the silicone matrix composed of vinyl silicone oil and hydrogen-containing silicone oil. This leads to decreased interfacial bonding and compatibility, increased interfacial porosity, a significant increase in interfacial thermal resistance, and a marked decrease in overall thermal conductivity. Simultaneously, the excessive polarity of the amino groups exacerbates the increase in viscosity of the curable thermally conductive silicone gel system. This makes it difficult to achieve uniform dispersion and, at the same addition amount, increases the viscosity of the curable thermally conductive silicone gel, causing the thixotropic index to deviate from the optimal range and resulting in poor flowability during automatic dispensing. During high and low temperature cycling and aging processes, the interface between diamond and the silicone matrix composed of vinyl silicone oil and hydrogen-containing silicone oil is prone to peeling, leading to an increased rate of change in interfacial thermal resistance and a higher rate of decay in thermal conductivity. Therefore, it can be seen that the preferred silane coupling agent is a combination of 3-methacryloyloxypropyltrimethoxysilane and titanate coupling agent, which produces curable thermally conductive silicone gels and cured thermally conductive silicone gels with better performance.

[0110] A comparison of Example 1 and Comparative Examples 1-4 shows that using a three-peaked modified diamond, and controlling the three-peak particle size distribution of the modified diamond to be D50 particle size > 100 μm and ≤ 200 μm, D50 particle size ≥ 50 μm and ≤ 100 μm, and D50 particle size ≥ 0.5 μm and ≤ 1 μm, results in curable thermally conductive silicone gels and cured thermally conductive silicone gels with better performance.

[0111] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A curable thermally conductive silicone gel, characterized in that, The raw materials for preparing the curable thermally conductive silicone gel include the following components by weight: 100 parts vinyl silicone oil, 10-15 parts hydrogen-containing silicone oil, 3000-4000 parts modified diamond with three-peak compound, 0.15-0.3 parts platinum catalyst, 0.2-0.6 parts inhibitor, and 1.5-2.5 parts fumed silica; The three-peaked modified diamond has three-peaked particle size distributions, namely D50 particle size > 100 μm and ≤ 200 μm, D50 particle size ≥ 50 μm and ≤ 100 μm, and D50 particle size ≥ 0.5 μm and ≤ 1 μm.

2. The curable thermally conductive silicone gel according to claim 1, characterized in that, The tri-peaked modified diamond includes tri-peaked modified diamond with a composite coupling agent. Preferably, the three-peaked composite coupling agent modified diamond comprises a first composite coupling agent modified diamond, a second composite coupling agent modified diamond, and a third composite coupling agent modified diamond. Preferably, the raw materials for preparing the composite coupling agent modified first diamond include a composite coupling agent and a first diamond, wherein the mass of the composite coupling agent is 0.03% to 0.06% of the mass of the first diamond, and the first diamond is a diamond with a D50 particle size > 100 μm and ≤ 200 μm. Preferably, the raw materials for preparing the composite coupling agent modified second diamond include a composite coupling agent and a second diamond, wherein the mass of the composite coupling agent is 0.03% to 0.06% of the mass of the second diamond, and the second diamond is a diamond with a D50 particle size ≥ 50 μm and ≤ 100 μm. Preferably, the raw materials for preparing the composite coupling agent modified third diamond include a composite coupling agent and a third diamond, wherein the mass of the composite coupling agent is 0.03% to 0.06% of the mass of the third diamond, and the third diamond is a diamond with a D50 particle size ≥ 0.5 μm and ≤ 1 μm.

3. The curable thermally conductive silicone gel according to claim 2, characterized in that, The three-peaked composite coupling agent modified diamond comprises the following components by mass percentage: 60%~75% composite coupling agent modified first diamond, 15%~25% composite coupling agent modified second diamond, and 5%~15% composite coupling agent modified third diamond.

4. The curable thermally conductive silicone gel according to claim 2 or 3, characterized in that, The composite coupling agents used in the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent each independently include a silane coupling agent and a titanate coupling agent in a mass ratio of (3~4):

1. Preferably, the silane coupling agent comprises a vinylsilane coupling agent; Preferably, the vinyl silane coupling agent comprises 3-methacryloyloxypropyltrimethoxysilane.

5. The curable thermally conductive silicone gel according to any one of claims 1 to 4, characterized in that, The inhibitors include alkynols and / or triphenylpyrroles.

6. A method for preparing a curable thermally conductive silicone gel as described in any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: mixing vinyl silicone oil, hydrogen-containing silicone oil, modified diamond with three peaks, platinum catalyst, inhibitor and fumed silica to obtain the curable thermally conductive silicone gel.

7. The preparation method according to claim 6, characterized in that, The three-peaked modified diamond comprises a first diamond modified by a composite coupling agent, a second diamond modified by a composite coupling agent, and a third diamond modified by a composite coupling agent. Preferably, the first diamond modified by the composite coupling agent is prepared by the following method: the first diamond is graphitized, ball-milled, treated with oxygen plasma, and then mixed with the composite coupling agent to obtain the first diamond modified by the composite coupling agent. Preferably, the composite coupling agent modified second diamond is prepared by the following method: the second diamond is graphitized, ball-milled, treated with oxygen plasma, and then mixed with the composite coupling agent to obtain the composite coupling agent modified second diamond; Preferably, the composite coupling agent modified third diamond is prepared by the following method: the third diamond is treated with oxygen plasma and then mixed with the composite coupling agent to obtain the composite coupling agent modified third diamond.

8. The preparation method according to claim 7, characterized in that, In the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, the graphitization treatment temperature is independently 700~850℃ and the graphitization treatment time is independently 10~22 min. Preferably, the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, after the graphitization treatment, each independently includes acid washing with aqua regia and alkali washing until neutral. Preferably, in the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, the ball milling media used in the ball milling each independently include a first grinding ball, a second grinding ball and a third grinding ball, wherein the diameter of the first grinding ball is greater than the diameter of the second grinding ball and the diameter of the third grinding ball. Preferably, the diameter of the first grinding ball is 2.5~3.5 mm, the diameter of the second grinding ball is 1.5~2.5 mm, and the diameter of the third grinding ball is 0.5~1.5 mm. Preferably, the first grinding ball, the second grinding ball, and the third grinding ball each independently comprise zirconia balls and / or diamond polycrystalline polygonal spheres; Preferably, based on the total mass of the grinding media as 100%, the mass of the first grinding ball is 35%~45%, the mass of the second grinding ball is 25%~35%, and the mass of the third grinding ball is 25%~35%. Preferably, in the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, the ball-to-material ratio of the ball milling is independently (10~20):1; Preferably, the preparation of the first diamond modified by the composite coupling agent and the second diamond modified by the composite coupling agent, after ball milling, each independently includes acid washing and water washing until neutral.

9. The preparation method according to claim 7 or 8, characterized in that, In the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent, the power of the oxygen plasma treatment is independently 50~100 W, the pressure of the oxygen plasma treatment is independently 0.1~0.5 Pa, the temperature of the oxygen plasma treatment is independently 20~30℃, and the time of the oxygen plasma treatment is independently 20~30 min. Preferably, in the preparation of the first diamond modified by the composite coupling agent, the second diamond modified by the composite coupling agent, and the third diamond modified by the composite coupling agent, the mixing each independently includes stirring and mixing, the stirring and mixing temperature is 60~80℃, the stirring and mixing speed is 300~1000 rpm, and the stirring and mixing time is 2~3 h.

10. The preparation method according to claim 6, characterized in that, The mixture then undergoes heat curing, with the heat curing temperature being 80~110℃ and the heat curing time being 15~40 min.

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