Composite filler and its preparation method and application

Abstract

The present invention provides a composite filler, a preparation method thereof, and an application thereof. The raw materials for preparing the composite filler include titanium dioxide, graphene, a dispersant, and a silicate. The preparation method comprises the following steps: (1) mixing titanium dioxide, a silicate, and a solvent, and performing a modification treatment to obtain a mixture A containing modified titanium dioxide; mixing graphene, a dispersant, and a solvent to obtain a mixture B; and (2) mixing the mixture A and the mixture B, and drying them to obtain the composite filler. In the present invention, by designing the raw materials for preparing the composite filler, a thermally conductive composite filler having an isotropic thermally conductive 3D network, high emissivity, and good environmental adaptability is constructed.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal conductive fillers, and in particular relates to a composite filler and a preparation method and application thereof. Background Art

[0002] Titanium suboxide is a polycrystalline inorganic material composed of two valence states of titanium oxide in the magneli phase. Its crystal structure is stable and it has excellent properties such as high electrical conductivity, acid resistance, acid resistance and wear resistance. So far, research on titanium suboxide has mainly focused on two aspects: electrode materials and black pigments. Since the thermal conductivity of titanium suboxide is only 10-20W·m - 1 K -1 Compared with most metal oxides, they are not materials with high thermal conductivity. Therefore, there are few reports on research in the field of thermal conductive materials including heat dissipation films, thermal interface materials and thermal grease.

[0003] There are three main ways of heat conduction, including heat conduction, heat convection and heat radiation; among them, heat conduction and heat radiation are properties of the material itself, are highly controllable, and are the main directions of current heat transfer research. The main components of heat-related composite materials include an organic binder base and a filler part. Graphene has become a hot topic in the field of thermal conductive coating filler research due to its high emissivity and high thermal conductivity (5300W / m·K) close to that of a black body. However, the limitations of two-dimensional materials in longitudinal heat transfer are not conducive to graphene exerting its thermal conductivity. Currently, it is commonly used to reduce graphene agglomeration and increase graphene dispersion by adding silica, silicon powder, metal powder and metal oxides, thereby improving the longitudinal thermal conductivity of two-dimensional graphene.

[0004] CN107903751A discloses a graphene heat dissipation coating and a preparation method, wherein the graphene heat dissipation coating comprises, by weight percentage, 35-55% of resin, 1-15% of graphene, 5-10% of functional filler, 0.5-1.5% of leveling agent, 0.05-0.2% of defoaming agent, 1-3% of dispersant, 3-10% of colorant and 10-40% of solvent; the graphene is one or more of N-type high-purity graphene and functional graphene, and the functional filler is one or more of aluminum nitride, carbon fiber, spherical nano-alumina and alumina fiber. In this technical solution, high-heat dissipation and high-radiation N-type high-purity graphene, functional graphene with high radiation dielectric loss, and functional fillers are combined in a specific mass ratio, so that the structure of graphene radiation and filler forms a non-gravity stacking bridging structure. The internal spatial defects of the coating increase, giving the coating better directional heat transfer performance. At the same time, the spatial infrared radiation area is increased, so that the radiation emissivity and radiation absorption rate achieve the optimal radiation effect, enhance infrared thermal radiation, form a coating with high radiation and high heat transfer performance, and achieve a uniform heat effect of the substrate facing the coating.

[0005] CN114163851A discloses a graphene heat dissipation slurry and its preparation method. The graphene heat dissipation slurry comprises, by weight, 25-80 parts of graphene, 15-50 parts of acrylate, 5-35 parts of thermally conductive filler, 10-40 parts of solvent, 0.01-10 parts of resin acid, and 0.01-3 parts of an additive. The thermally conductive filler is at least one of graphite, fullerene, carbon black, carbon nanotubes, carbon fiber, silicon nitride, aluminum nitride, silicon carbide, aluminum, copper, silver, carbon steel, silicon, aluminum oxide, or magnesium oxide. This technical solution utilizes a linear acrylate modified with a resin acid as a polymer binder to improve the adhesion of the coating. This invention can more effectively reduce the volume occupied by macromolecules, thinning the coating, thereby increasing crosslinking density, making the graphene powder or thermally conductive filler more compact, more easily forming a thermal pathway, and improving thermal conductivity.

[0006] Considering the heat dissipation requirements and environmental adaptability of heat dissipation fillers, existing composite fillers struggle to achieve both the required thermal conductivity network, high emissivity, and environmental adaptability. Therefore, developing a thermally conductive composite filler with an efficient thermal conductivity network, high emissivity, and good environmental adaptability has become a pressing technical challenge. Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention aims to provide a composite filler, its preparation method, and its application. By designing the raw materials for preparing the composite filler, the present invention further utilizes silicate to surface-modify titanium dioxide. The interaction between the silicate and graphene enhances the bonding between the graphene and titanium dioxide, thereby constructing an isotropic thermally conductive 3D network. This mitigates the limitations of graphene's two-dimensional thermal conductivity, resulting in a thermally conductive composite filler with a highly efficient thermally conductive network, high emissivity, and excellent environmental adaptability.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a composite filler, wherein raw materials for preparing the composite filler include titanium dioxide, graphene, a dispersant, and a silicate.

[0010] Graphene has become a hot topic in the field of thermal conductive coating fillers due to its high emissivity and thermal conductivity (5300 W / m·K), which is close to that of a black body. However, the limitations of two-dimensional materials in longitudinal heat transfer hinder the full utilization of graphene's thermal conductivity.

[0011] The present invention designs raw materials for preparing the composite filler, further adopts silicate to modify the surface of titanium dioxide (Ti4O7), and conjugates the dispersant with graphene to uniformly disperse the graphene and prevent graphene from agglomerating. At the same time, the interaction between the silicate and the graphene improves the bonding force between the graphene and titanium dioxide, thereby constructing an isotropic thermally conductive 3D network and improving the limitations of the two-dimensional thermal conductivity of graphene. Thus, a thermally conductive composite filler with an efficient thermally conductive network, high emissivity and good environmental adaptability is obtained.

[0012] At the same time, titanium dioxide has good wear resistance and acid and alkali resistance. On the basis of increasing the corrosion protection effect of the organic matrix, it can further enhance the tolerance and environmental adaptability of the composite filler, providing a certain guarantee for expanding the scope of use of the thermal conductive filler.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical solution of the present invention, the mass ratio of titanium dioxide and graphene is 1:(0.2-2.5), for example, it can be 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2 or 1:2.5, etc.

[0015] In the present invention, by controlling the mass ratio of titanium dioxide and graphene within a specific range, an isotropic thermally conductive 3D network can be constructed, resulting in a thermally conductive composite filler with an efficient thermally conductive network, high emissivity, and good environmental adaptability. If the mass ratio of titanium dioxide and graphene is too small, it is not conducive to the formation of an isotropic thermally conductive 3D network, resulting in poor heat dissipation effect of the composite filler; if the mass ratio of titanium dioxide and graphene is too large, due to the low intrinsic thermal conductivity of titanium dioxide, which is 10-20 W·m -1 K -1 , resulting in poor thermal conductivity of the prepared composite filler.

[0016] Preferably, based on the mass percentage of the titanium oxide being 100%, the mass percentage of the dispersant is 3-15%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, etc.

[0017] In the present invention, by controlling the amount of dispersant within a specific range, a better dispersion effect of graphene can be achieved. If the amount of dispersant is too small, the graphene dispersion effect is poor, the graphene is easily agglomerated, and the thermal conductivity of the final composite filler is poor. If the amount of dispersant is too large, the dispersant has no positive effect on the dispersion of graphene.

[0018] Preferably, based on the mass content of the titanium oxide being 100%, the mass percentage of the silicate is 2-10% (for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.), and more preferably 4-8%.

[0019] In the present invention, by controlling the amount of silicate within a specific range, titanium dioxide can be surface activated and serve as a "bridge" connecting titanium dioxide and graphene, improving the bonding between the two, thereby producing a composite filler with excellent thermal conductivity. If the amount of silicate is too small, the modification effect on titanium dioxide is poor, and the thermal conductivity of the resulting composite filler is poor. If the amount of silicate is too large, the thermal conductivity is reduced.

[0020] As a preferred technical solution of the present invention, the average particle size of the titanium oxide is 15 to 25 μm, for example, it can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm or 25 μm.

[0021] Preferably, the graphene is prepared by an oxidation-reduction method.

[0022] In the present invention, graphene prepared by an oxidation-reduction method is selected as a raw material, so that the graphene surface has oxygen-containing groups. The oxygen-containing groups on the graphene surface interact with the silicate-modified titanium dioxide particles to improve the bonding force between the graphene and the titanium dioxide.

[0023] The preparation method of graphene is as follows: 0.4~0.6mg·mL -1 Hydrazine hydrate is added to a graphene oxide solution, wherein the mass ratio of graphene oxide to hydrazine hydrate is 10:(6-8), the mixture is placed in a water bath at 80-95° C. and stirred and heated for 1-2 hours, filtered, the filter cake is collected, and then dried at 80-100° C. for 8-12 hours.

[0024] The concentration of graphene oxide in the graphene oxide solution can be 0.4 mg mL -1 , 0.42mg·mL -1 , 0.44 mg·mL -1 , 0.46mg·mL -1 , 0.48mg·mL -1 , 0.5mg·mL -1 , 0.52mg·mL -1 , 0.54mg·mL -1 , 0.56mg·mL -1 , 0.58mg·mL -1 or 0.6 mg mL -1 wait.

[0025] The mass ratio of graphene oxide to hydrazine hydrate can be 10:6, 10:6.3, 10:6.6, 10:6.8, 10:7, 10:7.2, 10:7.5, 10:7.8 or 10:8, etc.

[0026] The temperature of the water bath heating can be 80°C, 81°C, 84°C, 86°C, 88°C, 90°C, 92°C or 95°C, etc.

[0027] The heating time can be 1 hour, 1.5 hours or 2 hours, etc.

[0028] The drying temperature can be 80°C, 81°C, 84°C, 86°C, 88°C, 90°C, 92°C, 95°C, 98°C or 100°C, etc.

[0029] The drying time can be 8h, 9h, 10h, 11h or 12h, etc.

[0030] Preferably, the number of layers of the graphene is 3-15 layers, for example, it can be 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers, 11 layers, 12 layers, 13 layers, 14 layers or 15 layers.

[0031] As a preferred technical solution of the present invention, the dispersant is selected from any one of dispersant NNO, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone (PVP), rhodamine 6G, and protoporphyrin, or a combination of at least two thereof.

[0032] Preferably, the silicate has the structural formula shown in the following formula I:

[0033]

[0034] wherein R1-R4 are each independently selected from a C1-C5 alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group);

[0035] Preferably, the silicate is selected from any one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate or pentyl orthosilicate, or a combination of at least two thereof.

[0036] As a preferred technical solution of the present invention, the raw materials for preparing the composite filler also include a solvent.

[0037] Preferably, the solvent is selected from any one of ethanol, water or acetic acid, or a combination of at least two thereof.

[0038] In a second aspect, the present invention provides a method for preparing the composite filler according to the first aspect, the method comprising the following steps:

[0039] (1) mixing titanium dioxide, a silicate, and a solvent, and performing a modification treatment to obtain a mixture A containing modified titanium dioxide;

[0040] mixing graphene, a dispersant, and a solvent to obtain a mixture B;

[0041] (2) Mixing the mixture A and the mixture B, and drying them to obtain the composite filler.

[0042] In the present invention, titanium dioxide is surface-modified by using silicate to obtain modified titanium dioxide, graphene is evenly dispersed by using a dispersant, and then the silicate groups on the surface of the titanium dioxide interact with the graphene to improve the bonding force between the titanium dioxide and the graphene. At the same time, the titanium dioxide is dispersed between the graphene to construct an isotropic thermally conductive 3D network, thereby obtaining a thermally conductive composite filler with an efficient thermally conductive network, high emissivity and good environmental adaptability.

[0043] As a preferred technical solution of the present invention, the solvent in the mixture A includes ethanol and / or acetic acid;

[0044] Preferably, the solvent includes ethanol and acetic acid, and the volume ratio of ethanol to acetic acid is 1:(1-2), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0045] Preferably, the temperature of the modification treatment is room temperature.

[0046] Preferably, the modification treatment time is 44 to 50 hours, for example, 44 hours, 45 hours, 46 hours, 47 hours, 48 ​​hours, 49 hours or 50 hours.

[0047] Preferably, the solvent in the mixture B includes water and / or ethanol.

[0048] Preferably, the mixing temperature for obtaining the mixture B is room temperature.

[0049] Preferably, the mixing time for obtaining the mixture B is 34 to 40 hours, for example, 34 hours, 35 hours, 36 hours, 37 hours, 38 hours, 39 hours or 40 hours.

[0050] As a preferred technical solution of the present invention, the mixing time in step (2) is 70 to 75 hours, for example, it can be 70 hours, 71 hours, 72 hours, 73 hours, 74 hours or 750 hours.

[0051] Preferably, the mixing temperature in step (2) is room temperature.

[0052] Preferably, the drying method in step (2) includes freeze drying.

[0053] Preferably, the drying time in step (2) is 12 to 18 hours, for example, it can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours or 18 hours.

[0054] In the present invention, the preparation method of the composite filler specifically comprises the following steps:

[0055] (1) titanium dioxide, a silicate, and a solvent are mixed and subjected to a modification treatment at room temperature for 44 to 50 hours to obtain a mixture A containing modified titanium dioxide;

[0056] Mixing graphene, a dispersant, and water at room temperature for 34 to 40 hours to obtain a mixture B;

[0057] (2) Mixing mixture A and mixture B at room temperature for 70 to 75 hours, and then freeze-drying for 12 to 18 hours to obtain the composite filler.

[0058] In a third aspect, the present invention provides a thermally conductive coating, which comprises the following components in parts by weight: 1-5 parts of the composite filler as described in the first aspect and 24 parts of a binder.

[0059] In the present invention, by controlling the mass ratio of the composite filler to the binder within a specific range, the resulting thermally conductive coating exhibits both good thermal conductivity and low powder shedding. Excessive amounts of composite filler can lead to powder shedding, which does not meet application requirements. Excessive amounts of composite filler can result in poor thermal conductivity.

[0060] There is no particular limitation on the specific selection of the adhesive in the present invention, and any adhesive commonly used in the art is applicable, including but not limited to adhesive DC184.

[0061] The present invention does not impose any particular limitation on the preparation method of the thermal conductive coating, which illustratively includes but is not limited to: uniformly mixing the composite filler and the binder to obtain the thermal conductive coating.

[0062] The thermal conductive coating can be prepared by the thermal conductive coating provided by the present invention, and its preparation method illustratively includes but is not limited to: coating the thermal conductive coating on either side of a substrate and then drying to obtain the thermal conductive coating.

[0063] In a fourth aspect, the present invention provides a use of the composite filler as described in the first aspect and the thermal conductive coating as described in the third aspect in a thermal conductive coating, a thermal conductive interface material and a heat sink.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] The present invention designs the raw materials for preparing the composite filler, further controls the mass ratio of titanium dioxide and graphene in the raw materials for preparing the composite filler within a specific range, controls the amount of silicate used within a specific range, and simultaneously uses graphene with oxygen-containing groups on the surface to construct a composite filler with an isotropic thermally conductive 3D network, thereby improving the limitations of the two-dimensional thermal conductivity of graphene and obtaining a thermally conductive composite filler with an efficient thermally conductive network, high emissivity, and good environmental adaptability. The thermal conductivity of the thermally conductive film prepared from the composite filler is 5.593 to 6.727 W·m -1 K -1 , the heat dissipation effect is 18.55~25.03%. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a scanning electron microscope photograph of titanium dioxide used in Example 1 of the present invention;

[0067] Figure 2 This is a transmission electron microscope photograph of the composite filler provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0068] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0069] The sources of some components in the following examples and comparative examples are as follows:

[0070] Titanium dioxide: Longxing Titanium Industry, purity 99%;

[0071] Graphene oxide: Sichuan Hengli Shengtai Graphene Technology Co., Ltd., 1.5 layers, 4 μm flake diameter;

[0072] Dispersant NNO: Shanghai MacLean Biochemical Technology Co., Ltd., 95%;

[0073] Dispersant sodium dodecylbenzenesulfonate: Shanghai MacLean Biochemical Technology Co., Ltd., 95%;

[0074] Polyvinylpyrrolidone (PVP): Shanghai MacLean Biochemical Technology Co., Ltd., with a degree of polymerization of 58,000.

[0075] Example 1

[0076] This embodiment provides a composite filler and a preparation method thereof. The raw materials for preparing the composite filler include the following components in parts by weight:

[0077] 10 parts of titanium dioxide, 5 parts of graphene, 0.8 parts of dispersant NNO and 0.4 parts of ethyl orthosilicate.

[0078] The preparation method of the composite filler is as follows:

[0079] (1) titanium dioxide (10 parts), tetraethyl orthosilicate (0.4 parts) and a solvent (250 parts, composed of ethanol and acetic acid in a volume ratio of 1:1.4) were mixed and subjected to a modification treatment at room temperature for 48 hours to obtain a mixture A containing modified titanium dioxide;

[0080] Graphene (5 parts), dispersant NNO (0.8 parts) and water (250 parts) were mixed at room temperature for 38 h to obtain mixture B;

[0081] (2) Mixture A and mixture B were mixed at room temperature for 48 hours, and then freeze-dried for 15 hours to obtain the composite filler.

[0082] The structure of titanium dioxide was characterized by scanning electron microscopy. Figure 1 As shown by Figure 1 It can be seen that titanium dioxide has a network structure, which is conducive to building a continuous heat conduction network.

[0083] The structure of the composite filler was tested and characterized using a transmission electron microscope. The test results are as follows: Figure 2 As shown. Figure 2 It can be seen that in this embodiment, by designing the raw materials for preparing the composite filler, a uniformly dispersed composite filler is obtained, wherein the graphene is distributed in the pores of the titanium dioxide.

[0084] Example 2

[0085] This embodiment provides a composite filler and a preparation method thereof. The raw materials for preparing the composite filler include the following components in parts by weight:

[0086] 10 parts of titanium oxide, 15 parts of graphene, 1 part of dispersant sodium dodecylbenzenesulfonate and 0.5 parts of ethyl orthosilicate.

[0087] The preparation method of the composite filler is as follows:

[0088] (1) titanium dioxide (10 parts), tetraethyl orthosilicate (0.5 parts) and a solvent (250 parts, composed of ethanol and acetic acid in a volume ratio of 1:1.4) were mixed and subjected to a modification treatment at room temperature for 44 hours to obtain a mixture A containing modified titanium dioxide;

[0089] Graphene (15 parts), dispersant sodium dodecylbenzenesulfonate (1 part) and water (300 parts) were mixed at room temperature for 40 hours to obtain mixture B;

[0090] (2) Mixture A and mixture B were mixed at room temperature for 10 hours, and then freeze-dried for 15 hours to obtain the composite filler.

[0091] Example 3

[0092] This embodiment provides a composite filler and a preparation method thereof. The raw materials for preparing the composite filler include the following components in parts by weight:

[0093] 10 parts of titanium dioxide, 3 parts of graphene, 0.3 parts of rhodamine 6G and 0.8 parts of ethyl orthosilicate.

[0094] The preparation method of the composite filler is as follows:

[0095] (1) titanium dioxide (10 parts), tetraethyl orthosilicate (0.8 parts) and a solvent (250 parts, composed of ethanol and acetic acid in a volume ratio of 1:1) were mixed and subjected to a modification treatment at room temperature for 48 hours to obtain a mixture A containing modified titanium dioxide;

[0096] Graphene (3 parts), rhodamine 6G (0.3 parts) and water (200 parts) were mixed at room temperature for 38 h to obtain mixture B;

[0097] (2) Mixture A and mixture B were mixed at room temperature for 70 hours, and then freeze-dried for 18 hours to obtain the composite filler.

[0098] Example 4

[0099] This embodiment provides a composite filler and a preparation method thereof. The raw materials for preparing the composite filler include the following components in parts by weight:

[0100] 10 parts of titanium dioxide, 50 parts of graphene, 1.5 parts of PVP and 0.2 parts of tetraethyl orthosilicate.

[0101] The preparation method of the composite filler is as follows:

[0102] (1) titanium dioxide (10 parts), ethyl orthosilicate (0.2 parts) and ethanol (250 parts) were mixed and subjected to a modification treatment at room temperature for 50 hours to obtain a mixture A containing modified titanium dioxide;

[0103] Graphene (50 parts), PVP (1.5 parts) and water (500 parts) were mixed at room temperature for 34 h to obtain mixture B;

[0104] (2) Mixture A and mixture B were mixed at room temperature for 75 hours, and then freeze-dried for 12 hours to obtain the composite filler.

[0105] Example 5

[0106] This embodiment provides a composite filler and a preparation method thereof. The raw materials for preparing the composite filler include the following components in parts by weight:

[0107] 10 parts of titanium dioxide, 30 parts of graphene, 1.2 parts of protoporphyrin and 1 part of tetraethyl orthosilicate.

[0108] The preparation method of the composite filler is as follows:

[0109] (1) titanium dioxide (10 parts), tetraethyl orthosilicate (1 part) and a solvent (250 parts, composed of ethanol and acetic acid in a volume ratio of 1:1.5) were mixed and subjected to a modification treatment at room temperature for 44 hours to obtain a mixture A containing modified titanium dioxide;

[0110] Graphene (30 parts), protoporphyrin (1.2 parts) and water (400 parts) were mixed at room temperature for 40 hours to obtain mixture B;

[0111] (2) Mixture A and mixture B were mixed at room temperature for 70 hours, and then freeze-dried for 15 hours to obtain the composite filler.

[0112] Example 6

[0113] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of graphene in the raw materials for preparing the composite filler is 2 parts, and other conditions are the same as those in Example 1.

[0114] Example 7

[0115] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight proportion of graphene in the raw materials for preparing the composite filler is 20 parts, and other conditions are the same as those in Example 1.

[0116] Example 8

[0117] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight proportion of graphene in the raw materials for preparing the composite filler is 25 parts, and other conditions are the same as those in Example 1.

[0118] Example 9

[0119] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of graphene in the raw materials for preparing the composite filler is 1 part, and other conditions are the same as those in Example 1.

[0120] Example 10

[0121] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of ethyl orthosilicate in the raw materials for preparing the composite filler is 0.2 parts, and other conditions are the same as those in Example 1.

[0122] Example 11

[0123] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of ethyl orthosilicate in the raw materials for preparing the composite filler is 0.7 parts, and other conditions are the same as those in Example 1.

[0124] Example 12

[0125] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of ethyl orthosilicate in the raw materials for preparing the composite filler is 1 part, and other conditions are the same as those in Example 1.

[0126] Example 13

[0127] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of ethyl orthosilicate in the raw materials for preparing the composite filler is 0.1 parts, and other conditions are the same as those in Example 1.

[0128] Example 14

[0129] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the weight portion of ethyl orthosilicate in the raw materials for preparing the composite filler is 1.2 parts, and other conditions are the same as those in Example 1.

[0130] Example 15

[0131] This embodiment provides a composite filler and a preparation method thereof. The only difference from Example 1 is that the graphene in Example 1 is replaced by graphene without oxygen-containing groups on the surface (graphene synthesized by combustion method, purchased from the Institute of Chemistry and Physics). Other conditions are the same as those in Example 1.

[0132] Comparative Example 1

[0133] This comparative example provides a composite filler and a preparation method thereof, wherein the composite filler comprises the following components in parts by weight:

[0134] 10 parts of titanium oxide, 15 parts of graphene, and 1 part of sodium dodecylbenzenesulfonate.

[0135] The preparation method of the composite filler is as follows:

[0136] (1) Graphene, sodium dodecylbenzenesulfonate, and water (300 parts) were mixed at room temperature for 38 hours to obtain a mixture;

[0137] (2) The mixture was mixed with titanium dioxide at room temperature for 72 hours and then freeze-dried for 15 hours to obtain the composite filler.

[0138] Comparative Example 2

[0139] This comparative example provides a composite filler and a preparation method thereof, wherein the composite filler comprises the following components in parts by weight:

[0140] 10 parts of titanium dioxide, 5 parts of graphene and 0.4 parts of tetraethyl orthosilicate.

[0141] The preparation method of the composite filler is as follows:

[0142] (1) titanium dioxide, ethyl orthosilicate, and a solvent (250 parts, composed of ethanol and acetic acid in a volume ratio of 1:1.4) were mixed and subjected to a modification treatment at room temperature for 48 hours to obtain a mixture A containing modified titanium dioxide;

[0143] (2) Mixture A and graphene were mixed at room temperature for 72 hours, and then freeze-dried for 15 hours to obtain the composite filler.

[0144] Comparative Example 3

[0145] This comparative example provides a composite filler and a preparation method thereof, wherein the composite filler comprises the following components in parts by weight:

[0146] 5 parts of boron nitride, 10 parts of graphene, and 0.8 parts of rhodamine 6G.

[0147] The preparation method of the composite filler is as follows:

[0148] (1) Graphene, rhodamine 6G, and water (300 parts) were mixed at room temperature for 38 hours to obtain a mixture;

[0149] (2) The mixture was mixed with boron nitride at room temperature for 72 hours, and then freeze-dried for 15 hours to obtain the composite filler.

[0150] The composite fillers provided in the above examples and comparative examples were used to prepare a thermally conductive film, and the performance of the thermally conductive film was tested. The preparation method of the thermally conductive film is as follows:

[0151] The composite filler (2 parts) and the binder (24 parts) provided in the above examples and comparative examples were respectively mixed evenly, evenly coated on a substrate (aluminum alloy 6061) using a spray gun, and heated and cured to obtain the thermal conductive film.

[0152] The performance test method for thermal conductive film is as follows:

[0153] Thermal conductivity: Thermal conductivity was measured in air at room temperature using a Hot Disk TPS 2500S.

[0154] Heat dissipation effect: The temperature of the film surface was measured using a K-type thermocouple on a 15 cm × 25 cm long and wide heating platform with 560 W stable heating.

[0155] The performance test results are shown in Table 1 below:

[0156] Table 1

[0157]

[0158]

[0159] As can be seen from the above table, the present invention designs the raw materials for preparing the composite filler, further controls the mass ratio of titanium dioxide and graphene in the raw materials for preparing the composite filler within a specific range, controls the amount of silicate within a specific range, and uses graphene with oxygen-containing groups on the surface to construct a composite filler with an isotropic thermal conductive 3D network, thereby improving the limitations of the two-dimensional thermal conductivity of graphene, and thus obtaining a thermally conductive composite filler with an efficient thermal conductive network, high emissivity and good environmental adaptability. The thermal conductivity of the thermally conductive film prepared from the composite filler is 5.593 to 6.727 W·m -1 K -1 , the heat dissipation effect is 18.55~25.03%.

[0160] The present invention can further improve the thermal conductivity and heat dissipation effect of the thermal conductive film by further optimizing the amount of silicate, and its thermal conductivity is ≥6.102W·m -1 K -1 , specifically 6.102~6.727W·m -1 K -1 , the heat dissipation effect is ≥20.09%, specifically 20.09~25.03%.

[0161] Compared with Example 1, if the mass ratio of titanium dioxide to graphene in the composite filler is too small (Examples 4-5) or too large (Example 9), the thermal conductivity of the prepared composite filler is poor.

[0162] Compared with Example 1, if the amount of silicate in the composite filler is too small (Example 13), its modification of titanium dioxide is poor, and it is difficult to construct a 3D thermal conductive network, and the thermal conductivity of the composite filler prepared thereby is poor; if the amount of silicate in the composite filler is too large (Example 14), it will cause waste of raw materials.

[0163] Compared with Example 1, if graphene without oxygen-containing groups on the surface is selected (Example 15), the silica surface modified with silicate is difficult to interact with the graphene without oxygen-containing groups on the surface, and it is difficult to construct a 3D thermal conductive network. The thermal conductivity of the composite filler prepared in this way is poor.

[0164] Compared with Example 1, if the raw materials for preparing the composite filler do not contain silicate (Comparative Example 1), it is difficult to build an interactive "bridge" between titanium dioxide and graphene, the bonding force between titanium dioxide and graphene is poor, and the performance of the prepared composite filler is poor; if the raw materials for preparing the composite filler do not contain a dispersant (Comparative Example 2), graphene is easy to agglomerate, and the thermal conductivity of the prepared composite filler is poor; if the modified titanium dioxide in the composite filler is replaced with boron nitride (Comparative Example 3), it is difficult to obtain a 3D thermal conductive network, and the thermal conductivity of the obtained composite filler is also poor.

[0165] In summary, the present invention designs the raw materials for preparing the composite filler, further controls the mass ratio of titanium dioxide and graphene in the raw materials for preparing the composite filler within a specific range, and controls the amount of silicate within a specific range. At the same time, graphene with oxygen-containing groups on the surface is used to construct a composite filler with an isotropic thermal conductive 3D network, thereby improving the limitations of graphene's two-dimensional thermal conductivity, and thus obtaining a thermally conductive composite filler with an efficient thermal conductive network, high emissivity and good environmental adaptability.

[0166] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed process flow of the present invention, but the present invention is not limited to the above-described detailed process flow, that is, it does not mean that the present invention must rely on the above-described detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A composite filler, characterized in that: The raw materials for preparing the composite filler include titanium dioxide, graphene, a dispersant and silicate; The mass ratio of the titanium dioxide to the graphene is 1:(0.2-2.5); Based on the mass content of the titanium oxide being 100%, the mass percentage of the dispersant is 3-15%; Based on the mass percentage of the titanium oxide being 100%, the mass percentage of the silicate is 2-10%; The average particle size of the titanium oxide is 15 to 25 μm; The graphene is prepared by an oxidation-reduction method; The silicate has the structural formula shown in the following formula I: Wherein, R1-R4 are each independently selected from C1-C5 alkyl groups.

2. The composite filler according to claim 1, characterized in that Based on the mass percentage of the titanium oxide being 100%, the mass percentage of the silicate is 4-8%.

3. The composite filler according to claim 1, characterized in that The number of layers of the graphene is 3-15.

4. The composite filler according to claim 1, characterized in that The dispersant is selected from any one of dispersant NNO, dispersant sodium dodecylbenzenesulfonate, polyvinyl pyrrolidone, rhodamine 6G, and protoporphyrin, or a combination of at least two thereof.

5. The composite filler according to claim 1, characterized in that The silicate is selected from any one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate or pentyl orthosilicate, or a combination of at least two thereof.

6. The composite filler according to claim 1, characterized in that The raw materials for preparing the composite filler also include a solvent.

7. The composite filler according to claim 6, characterized in that The solvent is selected from any one of ethanol, water or acetic acid, or a combination of at least two thereof.

8. A method for preparing a composite filler according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) mixing titanium dioxide, a silicate, and a solvent, and performing a modification treatment to obtain a mixture A containing modified titanium dioxide; mixing graphene, a dispersant, and a solvent to obtain a mixture B; (2) Mixing the mixture A and the mixture B, and drying them to obtain the composite filler.

9. The preparation method according to claim 8, characterized in that The solvent in the mixture A includes ethanol and / or acetic acid.

10. The preparation method according to claim 9, characterized in that The solvent in the mixture A includes ethanol and acetic acid, and the volume ratio of the ethanol to the acetic acid is 1:(1-2).

11. The preparation method according to claim 8, characterized in that The modification treatment time is 44 to 50 hours.

12. The preparation method according to claim 8, characterized in that The mixing time for obtaining the mixture B is 34 to 40 hours.

13. The preparation method according to claim 8, characterized in that The mixing time in step (2) is 70 to 75 hours.

14. The preparation method according to claim 8, characterized in that The drying method in step (2) includes freeze drying.

15. The preparation method according to claim 8, characterized in that The drying time in step (2) is 12 to 18 hours.

16. A thermal conductive coating, characterized in that: The thermal conductive coating comprises the following components in parts by weight: 1-5 parts of the composite filler according to any one of claims 1 to 7 and 24 parts of the binder.

17. Use of the composite filler according to any one of claims 1 to 7 or the thermally conductive coating according to claim 16 in a thermally conductive coating, a thermally conductive interface material and a heat sink.

Images