Reverse infiltration preparation method of low-cost high-density diamond copper-based composite material

Abstract

The invention discloses a reverse infiltration preparation method of a low-cost and high-density diamond copper-based composite material. The reverse infiltration preparation method comprises the following steps: step 1, cleaning and drying industrial processing waste diamond crushed aggregates; step 2, mixing the diamond crushed aggregates in the step 1 with copper powder, and carrying out first sintering to obtain a composite material green body; 3, under the condition that a mold is not needed, the composite material blank is subjected to second-time sintering at the temperature higher than the copper melting point, in the process that the composite material blank is continuously thinned during second-time sintering, copper is continuously melted and seeps out of gaps of the diamond blank, and the reverse infiltration diamond copper-based composite material is obtained; the technology of combining warm-pressing sintering with discharge plasma reverse infiltration is adopted, the diamond crushed aggregates and the copper powder are used as raw materials, and compared with diamond ball materials, on the premise that the heat conduction performance is not obviously reduced, the material utilization rate is greatly increased, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, and particularly relates to a low-cost, high-density diamond copper-based composite material preparation method by reverse melting infiltration. Background Technology

[0002] Existing preparation technologies (such as traditional melt infiltration and powder metallurgy) generally use diamond polyhedral particles, single crystal particles, and spherical particles as reinforcing phase raw materials to ensure particle flowability and preform formability. Diamond spherical particles require multiple processing steps such as crushing, shaping, and fine grinding, and their market price is typically 2000-7000 yuan / kg. However, diamond scraps generated in the diamond processing industry (such as cutting waste and grinding slag), although having the same chemical composition and crystal structure as the spherical particles, and with a particle size that can be controlled within 5-100μm through simple sieving, are irregular in shape (mostly angular). Existing processes make it difficult to mix them with other materials and prepare high-density preforms, resulting in these scraps being treated as waste for a long time, with a price of only 300-800 yuan / kg that has not been effectively utilized. This "choosing the expensive over the cheap" approach to raw material selection increases the raw material cost of this composite material by nearly 10 times, making the high raw material cost a significant factor restricting its large-scale application.

[0003] Traditional forward melting infiltration (using a diamond preform as a framework, with liquid copper seeping into the preform's pores from top to bottom) is one of the mainstream manufacturing processes, but it has two major problems: First, to ensure that the molten copper fully fills the pores, the preform needs to be treated at high temperature (usually above 1100℃) and high pressure (10-50MPa), which is not only energy-intensive and expensive (requiring a dedicated high-temperature and high-pressure melting infiltration furnace), but may also cause the diamond to undergo graphitization at high temperatures, reducing the material's thermal conductivity; second, the tiny pores between diamond particles (especially the fine particle region with a particle size of less than 5μm) are prone to forming "unmelted defects" due to insufficient fluidity of the molten copper, resulting in a composite material density generally below 94%, seriously affecting thermal conductivity. The production cost of this process varies depending on the production scale, ranging from approximately 1500-3000 yuan per kilogram.

[0004] While powder metallurgy (mixing diamond powder and copper powder, pressing them into shape, and then sintering) can reduce the pressure requirements of the equipment, it requires the addition of active metal powders such as nickel and chromium as interfacial binders (usually accounting for 5%-15%) to achieve effective bonding between particles. The introduction of these precious metals will increase the cost of raw materials by 30%-50%. In addition, it is difficult to completely eliminate the voids between powder particles during the sintering process. Even with hot isostatic pressing, the density of the composite material is difficult to exceed 96%. Moreover, the processing cost of hot isostatic pressing equipment (about 2,000 yuan / piece) is much higher than that of ordinary melting and infiltration equipment, making it unsuitable for large-scale production. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, high-density diamond / copper matrix composite material preparation method via reverse melt infiltration, so as to reduce production costs and improve the density and thermal conductivity of the diamond / copper matrix composite material.

[0006] This invention employs the following technical solution: a low-cost, high-density diamond-copper matrix composite material preparation method via reverse melt infiltration, characterized by comprising: Step 1: Clean and dry the diamond scraps, which are industrial processing waste; Step 2: Mix the diamond scrap from Step 1 with copper powder and perform the first sintering to obtain a composite material blank; Step 3: Without the need for a mold, the composite material blank is sintered a second time at a temperature higher than the melting point of copper. During the second sintering, as the composite material blank becomes thinner, copper continuously melts and seeps out from the gaps in the diamond blank. Sintering is stopped when the thickness of the composite material blank after the second sintering is 80% of the thickness of the initial composite material blank, resulting in a reverse-melting diamond copper-based composite material.

[0007] The beneficial effects of this invention are: This invention employs a combination of warm-pressure sintering and spark plasma reverse melting infiltration technology, using diamond scrap and copper powder as raw materials. Compared with diamond spheres, it significantly improves material utilization and reduces production costs without significantly reducing thermal conductivity. Compared with traditional melting infiltration, production costs are greatly reduced, and production costs can be controlled below 800 yuan per kilogram. This invention combines warm-press sintering with spark plasma reverse melting infiltration technology, using diamond scrap and copper powder as raw materials, to achieve stable preparation of high-density, high-thermal-conductivity diamond-copper matrix composite materials. Compared with existing methods that use traditional melting infiltration or single sintering processes, this invention has a reasonable process route, strong controllability, and can effectively improve the comprehensive performance of the materials. Attached Figure Description

[0008] Figure 1 This is a cross-sectional scan of the fracture surface of the diamond-copper composite material obtained in Example 1; Figure 2 This is a cross-sectional scan of the fracture surface of the diamond-copper composite material obtained in Example 2; Figure 3 This is a cross-sectional scan of the fracture surface of the diamond-copper composite material obtained in Example 3; Figure 4 This is a cross-sectional scan of the diamond-copper composite material obtained in Example 4. Detailed Implementation

[0009] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0010] This invention discloses a low-cost, high-density diamond-copper matrix composite material preparation method via reverse melt infiltration, such as... Figure 1 As shown, it includes steps 1-3.

[0011] Step 1: Clean and dry the industrial processing waste diamond fragments; when cleaning the diamond fragments, use alcohol for ultrasonic cleaning for 15 minutes to remove organic matter and grease from the diamond surface.

[0012] The process uses low-cost industrial diamond scrap, ensuring the low cost of raw materials, which is in stark contrast to the high-cost raw materials widely used in the market, such as diamond polyhedral particles, single crystal particles, and spherical particles.

[0013] In step 1, the particle size of the industrial processing waste diamond fragments is one or a mixture of several of the following: 20μm, 40μm, 60μm, 80μm, and 100μm.

[0014] The thickness of the composite preform that is sintered for the second time can be determined by the displacement of the pressure head of the sintering equipment.

[0015] Step 2: Mix the diamond scrap from Step 1 with copper powder and perform a first sintering to obtain a composite material blank; the particle size of the copper powder in Step 2 is 10μm. When mixing diamond scrap and copper powder in Step 2, the volume ratio of diamond scrap is 20%-50%, and the remainder is copper powder.

[0016] Step 3: Without the need for a mold, the composite material blank is sintered a second time at a temperature higher than the melting point of copper. During the second sintering, as the composite material blank becomes thinner, copper continuously melts and seeps out from the gaps in the diamond blank. Sintering is stopped when the thickness of the composite material blank after the second sintering is 80% of the thickness of the initial composite material blank, resulting in a reverse-melting diamond copper-based composite material.

[0017] Step 3 specifically involves: High-temperature, high-pressure sintering above the melting point of copper is performed without the need for molds. During the sintering process, the sintered sample becomes thinner, and molten copper seeps out from the gaps in the diamond scrap and flows to the outside of the sintered sample. By controlling the sintering time and temperature, a diamond-copper matrix composite material reinforced with high volume fraction diamond scrap is finally obtained.

[0018] In a conventional melting and infiltration process, a diamond framework is first prepared, and then copper is infiltrated at a high temperature above the melting point. The resulting composite material often contains obvious voids, which greatly weakens the performance of copper-diamond high thermal conductivity composite materials that are extremely sensitive to porosity.

[0019] The reverse melting and infiltration method proposed in this invention first utilizes the high plasticity of copper to solidify low-cost diamond scrap into a uniform and highly dense composite material preform. Then, an excess copper is melted and infiltrated out of the preform through a high-temperature process. After this process, the diamond scrap maintains its high density within the preform and achieves a high volume fraction, thus achieving high density at a low cost. This ultimately yields a low-cost, high-thermal-conductivity copper-diamond composite material. In conventional melting and infiltration, copper is infiltrated from the outside in; in the reverse melting and infiltration method proposed in this invention, copper is infiltrated from the inside out, effectively solving the practical engineering problems of poor flowability and poor densification caused by the irregular shape of the diamond scrap.

[0020] The first sintering conditions in step 2 are: vacuum degree ≤ 4.5 × 10⁻⁶ -3 Pa, pressure is 20MPa, and the temperature is 600℃ for 10 minutes.

[0021] The conditions for the second sintering in step 3 are: vacuum degree ≤ 4.5 × 10⁻⁶ -3 The temperature was 1250-1300℃, the sintering time was 30 min, and the pressure was 25 MPa.

[0022] This invention differs from traditional melt infiltration processes. It does not require a pre-fabricated diamond framework. Instead, it thoroughly mixes diamond fragments with copper powder, then heats the mixture for a very short time to melt the copper powder, filling the gaps between the copper and diamond fragment particles. This allows the diamond to fully bond with the copper matrix. Some of the melted copper seeps out of the blank, and under negative pressure, air is expelled to prevent the formation of bubbles. This ensures that the diamond and copper matrix are fully bonded, forming a composite material with extremely high density. Furthermore, the volume percentage of diamond fragment particles in the composite material is significantly increased, resulting in a highly dense and thermally conductive copper-diamond composite material.

[0023] Compared to the diamond spheres widely used in existing technologies, this invention selects diamond shavings as the reinforcing phase. While ensuring that the thermal conductivity of the composite material is not significantly reduced, it greatly improves the utilization rate of raw materials and reduces the use of high-cost diamond spheres, thereby lowering the material preparation cost from the source. Simultaneously, combined with the spark plasma reverse melting process, it is possible to achieve full wetting and filling of the copper matrix with diamond under lower energy consumption conditions. Compared to traditional high-temperature melting processes, the overall production cost is significantly reduced, and the material preparation cost can be controlled below 800 yuan / kg, demonstrating a clear economic advantage.

[0024] Example 1

[0025] The required diamond crushing particle size is 20μm, the copper powder particle size is 10μm, the copper powder volume percentage is 80%, and the diamond crushing particle size percentage is 20%, resulting in a composite material with a diamond volume percentage of 55%.

[0026] Step 1: Place the diamond fragments into a beaker containing alcohol for ultrasonic cleaning, and then dry the cleaned diamonds.

[0027] Step 2: Place the diamond fragments and copper powder from Step 1 in the same container and mix thoroughly. Pour the mixed diamond and copper powder into a 30mm diameter graphite mold, place it in a hot-pressing sintering furnace, evacuate the furnace, and set the relevant process parameters for warm-pressing sintering. The sintering conditions are: vacuum degree of 4.5 × 10⁻⁶. -3 Pa, pressure of 20MPa, when the temperature reaches 600℃, keep it at that temperature for 10 minutes.

[0028] Step 3: The warm-pressed sample is removed and subjected to rapid liquid-phase sintering in a spark plasma sintering furnace at a set temperature to achieve reverse melting and infiltration, obtaining a composite material with a diamond volume fraction of approximately 55%. The conditions for the second sintering are: vacuum degree of 4.5 × 10⁻⁶. -3 The temperature was set at 1250-1300℃, the sintering time was 30 minutes, and the pressure was 25 MPa.

[0029] The cross-sectional scanning image of the diamond-copper composite material obtained in this embodiment is as follows: Figure 1 As shown.

[0030] Example 2

[0031] This embodiment is the same as Embodiment 1, except that: The required diamond scrap has a particle size of 40 μm, and the copper powder has a particle size of 10 μm. The copper powder has a volume percentage of 70%, and the diamond scrap has a volume percentage of 30%, resulting in a composite material with a diamond volume percentage of approximately 58%. The cross-sectional scanning image of the diamond-copper matrix composite material obtained in this embodiment is shown below. Figure 2 As shown.

[0032] Example 3

[0033] This embodiment is the same as Embodiment 1, except that: The required diamond scrap has a particle size of 60 μm, and the copper powder has a particle size of 10 μm. The copper powder has a volume percentage of 60%, and the diamond scrap has a volume percentage of 40%, resulting in a composite material with a diamond volume percentage of 63%. The cross-sectional scanning image of the diamond-copper matrix composite material obtained in this embodiment is shown below. Figure 3 As shown.

[0034] Example 4

[0035] This embodiment is the same as Embodiment 1, except that: The required diamond scrap has a particle size of 80 μm, and the copper powder has a particle size of 10 μm. The copper powder volume percentage is 50%, and the diamond scrap volume percentage is 50%, resulting in a composite material with a diamond volume percentage of 66%. The cross-sectional scanning image of the diamond-copper matrix composite material obtained in this embodiment is shown below. Figure 4 As shown.

[0036] The density and thermal conductivity of the diamond-copper composite materials prepared in Examples 1-4 were tested, and the specific results are shown in Table 1.

[0037] Table 1

[0038] By controlling the average particle size of diamond scrap, the density and thermal conductivity of the composite material were synergistically improved. Data shows that as the average particle size of the diamond scrap increases, the diamond framework structure becomes more stable, and the filling effect of the copper matrix is ​​improved, thus simultaneously increasing the density and thermal conductivity of the composite material. When the average particle size of the diamond scrap reaches 80 μm, the resulting diamond-copper matrix composite material achieves a density of 97.75% and a thermal conductivity of 798 W / m·K, meeting the performance requirements of high-power electronic devices for heat dissipation materials.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-cost, high-density diamond-copper matrix composite material preparation method via reverse melt infiltration, characterized in that, include: Step 1: Clean and dry the diamond scraps, which are industrial processing waste; Step 2: Mix the diamond scrap from Step 1 with copper powder and perform the first sintering to obtain a composite material blank; Step 3: Without the need for a mold, the composite material blank is sintered a second time at a temperature higher than the melting point of copper. During the second sintering, as the composite material blank becomes thinner, copper continuously melts and seeps out from the gaps in the diamond blank. Sintering is stopped when the thickness of the composite material blank after the second sintering is 80% of the thickness of the initial composite material blank, resulting in a reverse-melting diamond copper-based composite material.

2. The method for preparing a low-cost, high-density diamond-copper matrix composite material by reverse melt infiltration according to claim 1, characterized in that, In step 2, when mixing diamond scrap with copper powder, the volume ratio of diamond scrap is 20%-50%.

3. The method according to claim 1, wherein the method is characterized by, In step 1, the particle size of the industrial processing waste diamond fragments is 20μm, 40μm, 60μm, 80μm or 100μm.

4. The method according to claim 1, wherein the method is characterized by, The copper powder in step 2 has a particle size of 10 μm.

5. The method according to claim 1, wherein the method is characterized by, The first sintering condition in step 2 is: vacuum degree ≤ 4.5 × 10 -3 pa, pressure is 20 MPa, and the temperature is kept for 10 min when the temperature reaches 600℃.

6. The method according to claim 1, wherein the method is a low cost high density diamond copper matrix composite material reverse infiltration preparation method, characterized in that, The conditions for the second sintering in step 3 are: vacuum degree ≤ 4.5 × 10⁻⁶ -3 The temperature was 1250-1300℃, the sintering time was 30 min, and the pressure was 25 MPa.

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