Graphite-copper uniform layered composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a graphite-copper uniform layered composite material. The preparation method comprises the following steps: plating a metal coating on the surface of a graphite flake; preparing slurry from the product, a freezing medium and a binder; solidifying the obtained slurry at a fixed liquid-solid interface solidification speed by using a freezing casting method; freeze-drying the solidified slurry to obtain a layered porous graphite skeleton green body; and degreasing and sintering the layered graphite skeleton green body, and infiltrating copper to obtain the graphite-copper uniform layered composite material. The invention further discloses a graphite / copper uniform layered composite material, the volume fraction of copper in the composite material is 30%-70%, the thermal conductivity is 400-650 W / (m.K), and the thermal expansion coefficient is (0-3) * 10 <-6 > / K. According to the graphite-copper uniform layered composite material prepared by adopting the ice template-infiltration method, the orientation height of a graphite sheet layer is consistent, and the graphite-copper uniform layered composite material has a low and adjustable thermal expansion coefficient and a high heat conductivity coefficient.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a method for preparing a graphite-copper uniform layered composite material. The invention also relates to the graphite-copper uniform layered composite material. Background Art

[0002] With the rapid advancement of modern science and technology and information technology, semiconductor devices and circuits are moving towards higher power, higher integration, and smaller size, leading to a gradual increase in chip heat generation. Electronic packaging materials support and protect chips, dissipating heat from electronic components and playing a crucial role in ensuring the proper function of these devices. In addition to excellent thermal conductivity, electronic packaging materials must also have a similar coefficient of thermal expansion to that of the chip to prevent chip cracking due to excessive thermal stress, thereby improving the reliability of electronic products. This makes the development of new electronic packaging materials with low thermal expansion and high thermal conductivity of great practical significance.

[0003] Copper has higher thermal conductivity and good processing properties, but its thermal expansion coefficient is higher and cannot be well matched with semiconductor electronic devices. Graphite is in a layered structure, with properties such as ultra-high thermal conductivity, lower thermal expansion coefficient, and even a negative thermal expansion coefficient in its planar direction. Therefore, high thermal conductivity graphite is selected as a reinforcing phase and is compounded with metallic copper by a suitable process to obtain a novel copper-based composite material for electronic packaging with good thermal conductivity, low thermal expansion coefficient and adjustable thermal conductivity. However, conventional preparation methods such as discharge plasma method, hot pressing sintering method, etc. are more difficult to prepare a graphite-copper uniform layered composite material with a high degree of graphite sheet orientation. For example, the Chinese invention patent with publication number CN103924119A discloses a super-high thermal conductivity graphite flake / copper composite material and a preparation method thereof, which is formed by extruding a graphite flake-containing slurry so that the graphite flakes are oriented in the matrix, but the graphite flakes that deviate from the oriented arrangement direction account for a higher proportion. Therefore, it is urgent to find a new method for preparing a graphite-copper uniform layered composite material. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a graphite-copper uniform layered composite material. The graphite flakes in the composite material prepared by the method have highly consistent orientation.

[0005] Another object of the present invention is to provide the above-mentioned graphite-copper uniform layered composite material.

[0006] The technical solution adopted by the present invention is a method for preparing a graphite-copper uniform layered composite material, comprising the following steps: Step 1, coating a metal coating on the surface of graphite flakes to obtain surface-modified graphite flakes; Step 2, preparing a slurry of the surface-modified graphite flakes, a freezing medium, and a binder; Step 3, using a freeze casting method to directionally solidify the slurry to obtain a directional porous green body; Step 4, freeze-drying the oriented porous green body to obtain a layered porous graphite skeleton green body; Step 5, degreasing and sintering the layered porous graphite skeleton green body to obtain a layered porous graphite skeleton; Step 6: Infiltrating copper into the layered porous graphite skeleton to obtain a graphite-copper uniform layered composite material.

[0007] The present invention is also characterized in that: In step 1, the graphite flakes are natural graphite flakes with an average diameter of 300~800 , thickness is 10~100 .

[0008] In step 1, the metal coating is at least one of Ti, Cr, W, Mo, Zr or V, and the coating thickness is 400~600nm.

[0009] In step 2, the freezing medium is at least one of camphene and tert-butyl alcohol; The binder is at least one of polyvinyl alcohol, polyvinyl butyral, and polyethylene glycol.

[0010] In step 2, the mass percentage of the surface-modified graphite flakes is 30% to 80%, the mass percentage of the binder is 0.1% to 5%, and the remainder is the freezing medium. The sum of the mass percentages of the above components is 100%.

[0011] Specifically, step 3 is to inject the slurry into the mold, perform unidirectional freezing by freeze casting, control the freezing speed of the freezing front to maintain at 0.1~2.0mm / min, and obtain a layered porous graphite skeleton green body after the slurry is completely solidified.

[0012] The vacuum degree of freeze drying in step 4 is not greater than 100 Pa, and the drying time is 24h~48h.

[0013] The sintering temperature in step 5 is 1100° C. to 1500° C., and high-purity nitrogen is continuously introduced during the sintering process.

[0014] In step 6, the volume ratio of copper to the layered porous graphite skeleton is (3-7): (7-3), the infiltration temperature is 1150°C-1400°C, and the temperature is kept for 1h-8h. High-purity nitrogen is continuously introduced during the infiltration process.

[0015] The technical solution adopted by the present invention is that a graphite-copper uniform layered composite material comprises graphite flakes coated with a metal coating on the surface, and the graphite flakes are infiltrated with copper with a volume fraction of 30% to 70%. The thermal conductivity of the composite material is 400 to 650 W / (m·K), and the thermal expansion coefficient is (0 to 3)×10 -6 / K.

[0016] The beneficial effects of the present invention are: The method of the present invention first performs surface modification on graphite flakes, and then uses a freeze casting-melt infiltration method to obtain a graphite-copper uniform layered composite material. By introducing a coating into the graphite flake matrix, the interface bonding between the graphite and copper is improved, and the prepared composite material has a tight interface bonding and lower interface thermal resistance. At the same time, the graphite flakes are oriented in the freeze casting process, and the thermal conductivity of the composite material shows obvious anisotropy, showing high thermal conductivity and low thermal expansion characteristics in the layered direction, which can meet the requirements of directional heat dissipation type electronic packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the microstructure of the graphite-copper uniform layered composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The preparation method of the uniform layered composite material of the present invention comprises the following steps: Step 1: Prepare natural graphite flakes with an average diameter of 300~800 , thickness is 10~100 The graphite flakes are surface-plated with at least one of Ti, Cr, W, Mo, Zr, or V using a salt bath plating method, with a coating thickness of 400 to 600 nm. The salt bath medium is one of BaCl2-NaCl, NaCl-NaF, LiCl-KCl, or NaCl-KCl, to obtain surface-modified graphite flakes.

[0020] Step 2, mixing the surface-modified graphite flakes, a freezing medium, and a binder to form a slurry; Among them, the mass percentage of surface-modified graphite flakes is 30% to 80%, the mass percentage of the binder is 0.1% to 5%, and the balance is the freezing medium. The sum of the mass percentages of the three raw materials is 100%.

[0021] The freezing medium is at least one of camphene and tert-butyl alcohol; the binder is at least one of polyvinyl alcohol, polyvinyl butyral and polyethylene glycol.

[0022] Step 3, performing directional solidification treatment on the slurry obtained in step 2 using a freeze casting method to obtain a green body; Specifically, the slurry prepared in step 2 is injected into the mold, and unidirectional freezing is performed by freeze casting. The freezing speed of the freezing front is controlled to be maintained at 0.1~2.0mm / min. After the slurry is completely solidified, the solidified green body is taken out from the mold.

[0023] Step 4, freeze-drying the green body of step 3 to obtain a layered porous graphite skeleton green body; Specifically, freeze drying is performed using a freeze dryer, the freeze drying vacuum degree is set to ≤100 Pa, the drying time is 24h~48h, and after drying is completed, a layered porous graphite skeleton green body is obtained.

[0024] Step 5: Degreasing and sintering the layered porous graphite skeleton green body obtained in step 4 at a sintering temperature of 1100° C. to 1500° C., continuously introducing high-purity nitrogen during the sintering process to obtain a layered porous graphite skeleton having a porosity of 30% to 70%.

[0025] Step 6, infiltrating Cu into the layered porous graphite skeleton in a volume ratio of (3-7): (7-3), with an infiltration temperature of 1150°C-1400°C and holding temperature for 1h-8h. During the infiltration process, high-purity nitrogen is continuously introduced to obtain a graphite-copper uniform layered composite material.

[0026] Example 1 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 300 , thickness is 10 The graphite flakes are surface-plated with Ti by salt bath plating. The salt bath medium is NaCl-KCl. The thickness of the Ti coating is 500 nm. After completion, surface-modified graphite flakes are obtained.

[0027] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 50%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0028] Step 3: Pour the prepared slurry into the mold, control the liquid-solid interface solidification rate to maintain at 0.10 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0029] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0030] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1450° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 40%.

[0031] Step 6: Take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 4:6, infiltrate Cu into the layered porous graphite skeleton, the infiltration temperature is 1300°C, and the temperature is kept for 3 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0032] like Figure 1 As shown, the graphite flakes in the prepared graphite-copper uniform layered composite maintain a relatively intact flaky morphology and are evenly distributed within the matrix. Most of the flakes are parallel to each other, overlapping to form a layered network and a stacked structure with the matrix. The copper phase continuously fills the pores of the graphite network, forming a continuous metal matrix. Simultaneously, the plated metal layer forms a transition zone at the graphite-copper interface. Atomic diffusion and chemical bonding in this region further strengthen the bond between the two phases, optimizing the mechanical and physical properties of the composite.

[0033] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 40%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 583 W / (m·K) and the thermal expansion coefficient was 0.78×10 -6 / K.

[0034] Example 2 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 500 , thickness is 100 The graphite flakes are surface-plated with Cr by salt bath plating. The salt bath medium is NaCl-KCl. The thickness of the Cr coating is 450nm. After completion, surface-modified graphite flakes are obtained.

[0035] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 60%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0036] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 0.2 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0037] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0038] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1350° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 50%.

[0039] Step 6: take copper and the layered porous graphite skeleton obtained in step 5 at a volume ratio of 5:5, infiltrate Cu into the layered porous graphite skeleton, and the infiltration temperature is 1250° C. for 2 hours. During the infiltration process, high-purity nitrogen is continuously introduced to obtain a graphite-copper uniform layered composite material.

[0040] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 50%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 516 W / (m·K) and the thermal expansion coefficient was 1.68×10 -6 / K.

[0041] Example 3 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 800 , thickness is 60 The graphite flakes are surface-coated with Mo using a salt bath plating method. The salt bath medium is NaCl-KCl, and the Mo coating thickness is 400 nm. After completion, surface-modified graphite flakes are obtained.

[0042] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 60%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0043] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 0.15 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0044] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a uniform layered porous graphite skeleton green body is obtained.

[0045] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1450° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 50%.

[0046] Step 6: take copper and the layered porous graphite skeleton obtained in step 5 at a volume ratio of 5:5, infiltrate Cu into the layered porous graphite skeleton, and the infiltration temperature is 1250° C. for 2 hours. During the infiltration process, high-purity nitrogen is continuously introduced to obtain a graphite-copper uniform layered composite material.

[0047] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 50%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 545 W / (m·K) and the thermal expansion coefficient was 1.05×10 -6 / K.

[0048] Example 4 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 400 , thickness is 90 The graphite flakes are surface-coated with W by salt bath plating. The salt bath medium is NaCl-KCl. The W coating thickness is 550nm. After completion, surface-modified graphite flakes are obtained.

[0049] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 80%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0050] Step 3: Pour the prepared slurry into the mold, control the liquid-solid interface solidification rate to maintain at 0.10 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0051] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0052] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1350° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 70%.

[0053] Step 6: Take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 7:3, infiltrate Cu into the layered porous graphite skeleton, and the infiltration temperature is 1200°C. The temperature is kept for 2 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0054] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 70%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 400 W / (m·K) and the thermal expansion coefficient was 3×10 -6 / K.

[0055] Example 5 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 900 , thickness is 20 The graphite flakes are plated with V on the surface by salt bath plating. The salt bath medium is NaCl-KCl. The thickness of the V coating is 500nm. After completion, surface-modified graphite flakes are obtained.

[0056] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 70%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0057] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 0.15 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0058] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0059] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1300° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 60%.

[0060] Step 6: take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 6:4, infiltrate Cu into the layered porous graphite skeleton, the infiltration temperature is 1250° C., and the temperature is kept for 2 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0061] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 60%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 524 W / (m·K) and the thermal expansion coefficient was 2.5×10 -6 / K.

[0062] Example 6 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 500 , thickness is 60 The graphite flakes are plated with Zr on the surface by salt bath plating method. The salt bath medium is NaCl-KCl. The thickness of the Zr coating is 400nm. After completion, surface-modified graphite flakes are obtained.

[0063] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 70%, and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0064] Step 3: Pour the prepared slurry into the mold, control the liquid-solid interface solidification rate to maintain at 0.10 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0065] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0066] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1450° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 60%.

[0067] Step 6: take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 6:4, infiltrate Cu into the layered porous graphite skeleton, the infiltration temperature is 1200°C, and the temperature is kept for 3 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0068] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 60%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 515 W / (m·K) and the thermal expansion coefficient was 1.7×10 -6 / K.

[0069] Example 7 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 500 , thickness is 60 The graphite flakes are plated with Zr on the surface by salt bath plating method. The salt bath medium is LiCl-KCl. The thickness of the Zr coating is 450nm. After completion, surface-modified graphite flakes are obtained.

[0070] Step 2, using surface-modified graphite flakes, polyvinyl butyral and camphene as raw materials, stirring the three raw materials to form a slurry, the sum of the mass percentages of the three raw materials is 100%, wherein the mass percentage of the surface-modified graphite flakes is 30%, and the mass percentage of polyvinyl butyral is 5%.

[0071] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 2.0 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0072] Step 4: Place the solidified slurry obtained in step 3 in a freeze dryer, set the freeze drying vacuum degree to 100 Pa, and the drying time to 24 hours. After completion, a uniform layered porous graphite skeleton green body is obtained, and the porosity of the uniform layered porous graphite skeleton green body is 55%.

[0073] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a temperature of 1100°C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton. Step 6: Take copper and the layered porous graphite skeleton obtained in step 5 at a volume ratio of 5.5:4.5, infiltrate Cu into the layered porous graphite skeleton, and the infiltration temperature is 1400° C. for 8 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0074] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 55%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 575W / (m·K) and the thermal expansion coefficient was 0.95×10 -6 / K.

[0075] Example 8 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 500 , thickness is 60 The graphite flakes are surface-plated with Ti using a salt bath plating method. The salt bath medium is BaCl2-NaCl, and the thickness of the Ti coating is 600nm. After completion, surface-modified graphite flakes are obtained.

[0076] Step 2, using surface-modified graphite flakes, polyethylene glycol and camphene as raw materials, stirring the three raw materials to form a slurry, the sum of the mass percentages of the three raw materials is 100%, wherein the mass percentage of the surface-modified graphite flakes is 40%, and the mass percentage of polyethylene glycol is 0.1%.

[0077] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 2.0 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0078] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 50 Pa and the drying time to 36 hours. After completion, a uniform layered porous graphite skeleton green body is obtained, and the porosity of the uniform layered porous graphite skeleton green body is 65%.

[0079] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1500° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton.

[0080] Step 6: Take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 6.5:3.5, infiltrate Cu into the layered porous graphite skeleton, the infiltration temperature is 1150°C, and the temperature is kept for 1 hour. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0081] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 65%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 615 W / (m·K) and the thermal expansion coefficient was 0.54×10 -6 / K.

[0082] Example 9 A method for preparing a graphite-copper uniform layered composite material, the specific process is as follows: Step 1: Prepare an average diameter of 300 , thickness is 10 The graphite flakes are surface-plated with Ti by salt bath plating. The salt bath medium is NaCl-KCl. The thickness of the Ti coating is 500 nm. After completion, surface-modified graphite flakes are obtained.

[0083] Step 2: Using surface-modified graphite flakes, polyvinyl alcohol (PVA), and tert-butyl alcohol as raw materials, the three raw materials are stirred to form a slurry, wherein the sum of the mass percentages of the three raw materials is 100%, of which the mass percentage of the surface-modified graphite flakes is 50% and the mass percentage of polyvinyl alcohol (PVA) is 2%.

[0084] Step 3: Pour the prepared slurry into the mold, control the solidification rate of the liquid-solid interface to maintain at 2.0 mm / min through the freeze casting method, and take out the slurry after it is completely solidified.

[0085] Step 4: placing the solidified slurry obtained in step 3 in a freeze dryer, setting the freeze drying vacuum degree to 1 Pa and the drying time to 48 hours. After completion, a layered porous graphite skeleton green body is obtained.

[0086] Step 5: Degrease and sinter the graphite skeleton green body obtained in step 4 at a sintering temperature of 1450° C. High-purity nitrogen is continuously introduced during the sintering process to obtain a layered porous graphite skeleton having a porosity of 30%.

[0087] Step 6: Take copper and the layered porous graphite skeleton obtained in step 5 in a volume ratio of 3:7, infiltrate Cu into the layered porous graphite skeleton, and the infiltration temperature is 1300°C for 3 hours. High-purity nitrogen is continuously introduced during the infiltration process to obtain a graphite-copper uniform layered composite material.

[0088] The volume fraction of Cu phase in the graphite-copper uniform layered composite material was detected to be 30%. At the same time, the thermal conductivity of the graphite-copper uniform layered composite material was 650 W / (m·K) and the thermal expansion coefficient was 0×10 -6 / K.

Claims

1. A method for preparing a graphite-copper uniform layered composite material, characterized in that: The following steps are involved: Step 1, coating a metal coating on the surface of graphite flakes to obtain surface-modified graphite flakes; Step 2, preparing a slurry of the surface-modified graphite flakes, a freezing medium, and a binder; Step 3, performing a directional solidification treatment on the slurry using a freeze casting method to obtain a directional porous green body; Step 4, freeze-drying the oriented porous green body to obtain a layered porous graphite skeleton green body; Step 5, degreasing and sintering the layered porous graphite skeleton green body to obtain a layered porous graphite skeleton; Step 6: Infiltrating copper into the layered porous graphite skeleton to obtain a graphite-copper uniform layered composite material.

2. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: In step 1, the graphite flakes are natural graphite flakes, and the average diameter of the graphite flakes is 300 to 800 mm. , thickness is 10~100 .

3. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: In step 1, the metal coating is at least one of Ti, Cr, W, Mo, Zr or V, and the coating thickness is 400-600 nm.

4. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: In the step 2, the freezing medium is at least one of camphene and tert-butyl alcohol; The binder is at least one of polyvinyl alcohol, polyvinyl butyral, and polyethylene glycol.

5. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: In the step 2, the mass percentage of the surface-modified graphite flakes is 30% to 80%, the mass percentage of the binder is 0.1% to 5%, and the remainder is the freezing medium. The sum of the mass percentages of the above components is 100%.

6. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: Specifically, step 3 includes injecting the slurry into a mold, performing unidirectional freezing by freeze casting, controlling the freezing speed of the freezing front to maintain at 0.1-2.0 mm / min, and obtaining a layered porous graphite skeleton green body after the slurry is completely solidified.

7. The method for preparing a graphite-copper uniform layered composite material according to claim 1, wherein: The vacuum degree of freeze drying in step 4 is not greater than 100 Pa, and the drying time is 24h~48h.

8. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: The sintering temperature in step 5 is 1100° C. to 1500° C., and high-purity nitrogen is continuously introduced during the sintering process.

9. The method for preparing the graphite-copper uniform layered composite material according to claim 1, wherein: In step 6, the volume ratio of copper to the layered porous graphite skeleton is (3-7): (7-3), the infiltration temperature is 1150° C.-1400° C., and the temperature is kept for 1 h-8 h. High-purity nitrogen is continuously introduced during the infiltration process.

10. A graphite-copper uniform layered composite material, characterized in that: The graphite-copper uniform layered composite material prepared by the method for preparing the graphite-copper uniform layered composite material according to any one of claims 1 to 9 comprises graphite flakes coated with a metal coating on the surface, wherein the graphite flakes are infiltrated with copper having a volume fraction of 30% to 70%, and the thermal conductivity of the composite material is 400 to 650 W / (m·K) and the thermal expansion coefficient is (0 to 3)×10 -6 / K.

Images