阅读说明：本技术 一种高导热低膨胀超薄片金刚石-金属基复合材料及其制备方法和应用 (High-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material and preparation method and application thereof ) 是由 魏秋平 周科朝 马莉 黄开塘 李俊 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种高导热低膨胀超薄片金刚石-金属基复合材料及其制备方法和应用,所述一种高导热金刚石/金属基复合材料包含核壳结构掺杂金刚石、金属基材料,所述核壳结构掺杂金刚石包含金刚石、金刚石表面改性层,所述金刚石表面改性层从内至外依次包括金刚石过渡层,掺杂金刚石外壳层；所述金刚石-金属基复合材料的厚度在0.1mm～1mm。其制备方法是采用气体压力辅助熔渗工艺技术,以高纯气体为压力源,作用在熔融液态金属基表面,实现金刚石与金属基材料高密度复合；本发明能够有效地克服渗透过程中的毛细管力,实现高压渗流成型,使材料导热系数高,热膨胀系数可调,均匀性更好,可靠性更高。(The invention discloses a high-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material and a preparation method and application thereof, wherein the high-thermal-conductivity diamond/metal-based composite material comprises a core-shell structure doped diamond and a metal-based material, the core-shell structure doped diamond comprises a diamond and a diamond surface modification layer, and the diamond surface modification layer sequentially comprises a diamond transition layer and a doped diamond outer shell layer from inside to outside; the thickness of the diamond-metal matrix composite material is 0.1 mm-1 mm. The preparation method adopts a gas pressure auxiliary infiltration process technology, takes high-purity gas as a pressure source and acts on the surface of a molten liquid metal base to realize high-density compounding of the diamond and the metal base material; the invention can effectively overcome the capillary force in the permeation process, realize high-pressure seepage forming, and ensure that the material has high heat conductivity coefficient, adjustable thermal expansion coefficient, better uniformity and higher reliability.)

1. A high-thermal-conductivity low-expansion ultrathin diamond-metal matrix composite material is characterized in that: the diamond core-shell structure doped diamond coating comprises a metal matrix and core-shell structure doped diamonds dispersed in the metal matrix, wherein the core-shell structure doped diamonds comprise diamond particles and a diamond surface modification layer, and the diamond surface modification layer sequentially comprises a diamond transition layer and a doped diamond outer shell layer from inside to outside; the thickness of the diamond-metal matrix composite material is 0.1 mm-1 mm.

2. The high thermal conductivity low expansion ultrathin diamond-metal matrix composite material as claimed in claim 1, wherein: the volume fraction of the core-shell structure doped diamond in the diamond/metal matrix composite material is 30-80%.

3. The high thermal conductivity low expansion ultra-thin sheet diamond-metal matrix composite of claim 1, wherein: the particle size of the diamond particles is 50-500 mu m, and the diamond particles are of single crystal structures; the thickness of the diamond transition layer is 5 nm-2 mu m, and the diamond transition layer is of a polycrystalline structure.

4. The high thermal conductivity low expansion ultrathin diamond-metal matrix composite material as claimed in claim 1, wherein: the thickness of the doped diamond outer shell layer is 5 nm-100 mu m, the doping mode comprises one or more combinations of constant doping, multi-layer variable doping and gradient doping, and the doping elements are selected from one or more of boron, nitrogen, phosphorus and lithium.

5. The high thermal conductivity low expansion ultrathin diamond-metal matrix composite material as claimed in claim 1, wherein: the diamond surface modification layer also comprises at least one of a coating layer, a porous layer and a modification layer, wherein the coating layer is a chemical vapor deposition boron film arranged on the surface of the doped diamond shell layer, and the thickness of the chemical vapor deposition boron film is 10nm-200 μm; the porous layer is formed by etching the surface of the doped diamond shell layer into a porous structure, and the modification layer is the outermost layer of the diamond surface modification layer and comprises one or more combinations of metal modification, carbon material modification and organic matter modification.

6. The high thermal conductivity low expansion ultrathin diamond-metal matrix composite material as claimed in claim 1, wherein: the metal in the metal matrix comprises a main metal and an additive, the main metal is selected from one of Cu, Al, Ag, Ti, Mg and Zn, the additive is selected from at least one of lanthanum, cerium, neodymium, europium, gadolinium, dysprosium, holmium, ytterbium, lutetium, yttrium and scandium, and the addition amount of the additive is 0.05-1% of the mass of the main metal.

7. The method for preparing a high thermal conductivity low expansion ultrathin diamond-metal matrix composite material as claimed in any one of claims 1 to 6, wherein the method comprises the following steps: placing the core-shell structure doped diamond and a metal ingot in a mold in a non-contact manner, vacuumizing to 100Pa, heating to melt the metal ingot, continuously preserving the temperature of the obtained melt until the temperature is uniform, and then introducing protective atmosphere for pressurization so as to enable the melt to permeate into pores formed between the diamond reinforcement bodies, thereby obtaining the diamond-metal matrix composite material.

8. The method for preparing the high-thermal-conductivity low-expansion ultrathin diamond-metal matrix composite material as claimed in claim 7, wherein the method comprises the following steps: the heating temperature is 300-1450 ℃, and the heating rate is 5-15 ℃/min.

9. The method for preparing the high-thermal-conductivity low-expansion ultrathin diamond-metal matrix composite material as claimed in claim 7, wherein the method comprises the following steps: the protective atmosphere is selected from N₂The atmosphere is one of an Ar atmosphere, the pressure of the protective atmosphere is 2-15 Mpa, and the pressure maintaining time is 10-120 min.

10. Use of a high thermal conductivity low expansion ultra thin sheet diamond-metal matrix composite material according to any one of claims 1-6, characterized in that: the diamond-metal matrix composite material is applied as an electronic packaging material.

Technical Field

The invention belongs to the field of composite materials, and particularly relates to a high-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material as well as a preparation method and application thereof.

Background

With the rapid development of science and technology, the power and integration of electronic equipment applied to various fields such as aerospace, military, industry, national production and the like are higher and higher, and the heat dissipation problem becomes an important factor for restricting the development of the industries. Especially, in the coming of 5G communication era, the integration degree of electronic and semi-finished devices is increased geometrically, which makes the heat density of electronic devices increase rapidly, and researches show that the failure rate of electronic components is about doubled every 10 ℃ rise in temperature, and in addition, 55% of failures in electronic equipment are caused by overhigh temperature of electronic devices and lack of reliable and comprehensive temperature control measures.

The thermal conductivity of diamond is 2200W/(mK), the thermal expansion coefficient (8.6 multiplied by 10 < -7 >/K < -1 >) and the density (3.52g/cm3) are very high, and when the diamond is used as a reinforcement material for an electronic packaging material, the composite material has high thermal conductivity and simultaneously meets the requirements of low expansion coefficient and light weight.

The diamond and the metal-based material are combined, so that the excellent heat-conducting property and mechanical property of the diamond and the metal-based material are fully exerted, and the diamond/metal-based composite material with higher heat conductivity and matched thermal expansion coefficient is prepared, and is also one of the most potential electronic packaging materials at present.

However, although the diamond particles used in the prior art have high thermal conductivity at room temperature, the diamond particles have poor thermal stability at high temperature, are easy to graphitize, have defects such as cracks on the surface of the diamond, have high interfacial energy between the diamond and metal, and have poor affinity.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a high-thermal-conductivity low-expansion ultrathin diamond-metal matrix composite material, and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme,

the invention relates to a high-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material which is composed of a metal matrix and core-shell structure doped diamonds dispersed in the metal matrix, wherein the core-shell structure doped diamonds are composed of diamond particles and a diamond surface modification layer, and the diamond surface modification layer sequentially comprises a diamond transition layer and a doped diamond outer shell layer from inside to outside; the thickness of the diamond-metal matrix composite material is 0.1 mm-1 mm.

With the rapid development of electronic equipment towards high performance, miniaturization and high integration, the power density of electronic components is continuously increased, the heat productivity of unit volume is larger and larger, the heat dissipation problem becomes one of the technical bottlenecks restricting the development of electronic information industry, and the development of ultrathin metal-based composite materials with high heat conduction, low thermal expansion and light weight becomes the key for determining the development of related industries. The invention provides a high-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material, which not only has high thermal conductivity and low thermal expansion coefficient, but also can meet the requirements of miniaturized semiconductor packaging materials.

In a preferred scheme, the volume fraction of the core-shell structure doped diamond in the diamond/metal matrix composite material is 30-80%.

Preferably, the diamond particles have a particle size of 50 to 500 μm, and the diamond particles have a single crystal structure.

Preferably, the thickness of the diamond transition layer is 5 nm-2 μm, and the diamond transition layer is of a polycrystalline structure.

The diamond reinforcement body of the invention takes diamond particles as a core, a polycrystalline diamond transition layer is firstly arranged on the surface of the diamond particles, and then a doped diamond outer shell layer is arranged, wherein the high-purity polycrystalline diamond transition layer grows in situ on the single crystal diamond particles, and the original performances of the single crystal diamond, such as high thermal conductivity, high hardness, high wear resistance and the like, are maintained. The doped diamond outer shell layer grows on the polycrystalline diamond coating in situ, the purpose of doping is to solve the problem of interface combination of diamond and metal, and the doped diamond film can improve the wettability of diamond and metal. In addition, the diamond surface modification layer is arranged on the outer surface of the single crystal diamond particles, so that the isolation and protection effects on the diamond particles can be achieved, and the diamond can be protected from graphitization, oxidation reaction and other chemical reactions at a high temperature; meanwhile, the bonding capacity of the bonding agent to the diamond is improved, the modified layer plays a role of a bonding bridge between the bonding agent and the diamond, and the wettability of the diamond and matrix metal is improved; and the strength of the diamond particles is improved, the coating plays roles of reinforcement and toughening, and the surface defects and microcracks of the diamond are overcome. The tiny holes can be compensated by the modified layer, and the strength is improved.

In the present invention, the diamond particles may be either pure single crystal diamond prepared by a high temperature and high pressure method or natural single crystal diamond.

Preferably, the thickness of the doped diamond outer shell layer is 5 nm-100 μm, the doping mode comprises one or more combinations of constant doping, multi-layer variable doping and gradient doping, and the doping element is one or more selected from boron, nitrogen, phosphorus and lithium.

Preferably, the doping mode of the doped diamond outer shell layer is gradient doping, and the gradient doping mode is that the concentration of doping elements is increased from 0ppm from inside to outside to 3000-30000 ppm.

According to the preferred scheme, the preparation process of the core-shell structure doped diamond comprises the steps of depositing a polycrystalline diamond transition layer on the surface of diamond particles in a chemical deposition mode, and growing a doped diamond outer shell layer on the surface of the polycrystalline diamond transition layer in a hot wire chemical vapor deposition mode.

Further preferably, the process of growing the doped diamond outer shell layer by hot wire chemical vapor deposition comprises the following steps: the mass flow ratio of the introduced gas is hydrogen: methane: doping gas source 97: 2: 0.1 to 0.7, the growth pressure is 2 to 5Kpa, the growth temperature is 800-850 ℃, the growth frequency is 2 to 6 times, the carrier particles are taken out after each growth, the growth is continued after the carrier particles are shaken, the time of single growth is 1 to 20 hours, and the doping gas source is selected from at least one of ammonia gas, phosphine and borane.

More preferably, when the doping mode of the doped diamond outer shell layer is gradient doping, the gas flow is introduced in three sections, and the mass flow ratio of the introduced gas in the first section is CH₄:H₂Doping gas source is 2:97: 0.1-0.25; the mass flow rate of the introduced gas in the second stage is CH₄:H₂Doping gas source is 2:97: 0.3-0.45; in the third stage, the mass flow rate of the introduced gas is CH₄:H₂Doping gas source 2:97: 0.5-0.6.

Preferably, the diamond surface modification layer further comprises at least one of a coating layer, a porous layer and a modification layer, wherein the coating layer is a chemical vapor deposition boron film arranged on the surface of the doped diamond outer shell layer, and the thickness of the chemical vapor deposition boron film is 10nm-200 μm; the porous layer is formed by etching the surface of the shell layer into a porous structure, and the modification layer is the outermost layer of the diamond surface modification layer and comprises one or more combinations of metal modification, carbon material modification and organic matter modification.

In actual operation, the porous layer can be etched by one or more combination techniques of plasma etching, high-temperature oxidation etching and nano metal nano particle etching.

Preferably, the metal in the metal matrix comprises a main metal and an additive, the main metal is selected from one of Cu, Al, Ag, Ti, Mg and Zn, the additive is selected from at least one of lanthanum, cerium, neodymium, europium, gadolinium, dysprosium, holmium, ytterbium, lutetium, yttrium and scandium, and the addition amount of the additive is 0.05-1% of the mass of the main metal.

In the invention, a small amount of rare earth elements are added into the metal matrix, so that the crystal grains of the matrix can be refined, the interface between the diamond and the matrix can be purified, the reaction between carbide in the matrix and the diamond can be promoted, the bonding condition of the metal matrix and the diamond can be improved, and the interface bonding state of the matrix and the diamond can be improved.

In the present invention, the finished structure of the diamond/metal matrix composite is not limited, i.e. the finished structure may be a regular structure, or may be a special-shaped structure with multiple sizes or special sizes.

The invention discloses a preparation method of a high-thermal-conductivity low-expansion ultrathin diamond-metal matrix composite material, which comprises the following steps: the method comprises the following steps: placing the diamond reinforcement bodies and the metal ingots in a mold in a non-contact manner, vacuumizing to be lower than 100Pa, heating to melt the metal ingots, continuously preserving the temperature of the obtained melt until the temperature is uniform, and then introducing protective atmosphere for pressurization so as to enable the melt to permeate into pores formed between the diamond reinforcement bodies, thereby obtaining the diamond/metal matrix composite material.

The preparation method of the invention adopts a gas pressure auxiliary infiltration process technology, takes high-purity gas as a pressure source and acts on the surface of the molten liquid metal base to realize the high-density compounding of the diamond and the metal base material. The inventor finds that compared with technologies such as Spark Plasma Sintering (SPS), powder metallurgy, high temperature and high pressure, the diamond/metal matrix composite material prepared by the atmosphere pressurization infiltration technology has low porosity and compact microstructure, because the gas pressure can effectively overcome the capillary force in infiltration. The inherent capillary forces prevent the molten metal solution from entering the interstices between the diamond enhanced bodies. Low porosity is important, especially in heat transfer processes where void-free interfaces can reduce phonon scattering. To promote high thermal conductivity of the composite material.

Preferably, the vacuum degree is 10-100 pa.

In the preferred scheme, the heating temperature is 300-1450 ℃, and the heating rate is 5-15 ℃/min.

Preferably, the protective atmosphere is selected from N₂The atmosphere is one of an Ar atmosphere, the pressure of the protective atmosphere is 2-15 Mpa, and the pressure maintaining time is 10-120 min.

The invention relates to an application of a high-thermal-conductivity low-expansion ultrathin diamond-metal-based composite material, which is applied as an electronic packaging material.

Advantageous effects

The diamond reinforcement body of the invention takes diamond particles as a core, a polycrystalline diamond coating is firstly arranged on the surface of the diamond particles, and then a doped diamond shell layer is arranged, wherein the high-purity polycrystalline diamond coating grows in situ on the single crystal diamond particles, and the original performances of the single crystal diamond, such as high thermal conductivity, high hardness, high wear resistance and the like, are kept. The doped diamond shell coating grows in situ and is a polycrystalline diamond coating, the purpose of doping is to solve the problem of interface bonding between diamond and metal, and the doped diamond film can improve the wettability of the diamond and the metal. In addition, the diamond surface modification layer is arranged on the outer surface of the single crystal diamond particles, so that the isolation and protection effects on the diamond particles can be achieved, and the diamond can be protected from graphitization, oxidation reaction and other chemical reactions at a high temperature; meanwhile, the bonding capacity of the bonding agent to the diamond is improved, the modified layer plays a role of a bonding bridge between the bonding agent and the diamond, and the wettability of the diamond and matrix metal is improved; and the strength of the diamond particles is improved, the coating plays roles of reinforcement and toughening, and the surface defects and microcracks of the diamond are overcome. The tiny holes can be compensated by the modified layer, and the strength is improved.

The preparation method of the invention adopts a gas pressure auxiliary infiltration process technology, takes high-purity gas as a pressure source and acts on the surface of the molten liquid metal base to realize the high-density compounding of the diamond and the metal base material. The inventor finds that compared with technologies such as Spark Plasma Sintering (SPS), powder metallurgy, high temperature and high pressure, the diamond/metal matrix composite material prepared by the atmosphere pressurization infiltration technology has low porosity and compact microstructure, because the gas pressure can effectively overcome the capillary force in infiltration. The inherent capillary forces prevent the molten metal solution from entering the interstices between the diamond enhanced bodies. Low porosity is important, especially in heat transfer processes where void-free interfaces can reduce phonon scattering. To promote high thermal conductivity of the composite material.

In conclusion, the diamond-metal matrix composite material prepared by the invention has the characteristics of high thermal conductivity and low thermal expansion coefficient, and can meet the requirements of thermal management materials with more and more strict requirements on thermal conductivity and thermal expansion coefficient.

Detailed description of the preferred embodiments

Example 1

Preparation of diamond reinforcement

Using 200 μm single crystal diamond particles as raw material, firstly depositing a polycrystalline diamond transition layer on the surface of the diamond particles by chemical deposition, the process comprises: the mass flow ratio of introduced atmosphere is CH₄:H₂And (2) 98 times of growth, wherein the time of each growth is 20min, and finally the polycrystalline diamond transition layer with the maximum thickness of 400nm is obtained.

And then adopting hot filament chemical vapor deposition to grow a doped diamond outer shell layer on the surface of the polycrystalline diamond transition layer to obtain the diamond reinforcement body. Deposition process parameters: the distance of the hot wire is 10mm, the growth temperature of the hot wire with the thickness of 0.5mm is 850 ℃, the deposition pressure is 3KPa, and the thickness of the diamond film is 2 mu m by controlling the deposition time; the mass flow ratio of the passing gas is CH in the chemical vapor deposition₄:H₂:B₂H₆The growth pressure is 3Kpa, the growth times are 2 times, the carrier particles are taken out every time of growth, after the carrier particles are shaken, the growth is continued, and the time of single growth is 1 h.

Composition of diamond reinforcement and metal

Putting the diamond reinforcement body and metal ingots of Cu, lanthanum and cerium into a mold with the thickness of 0.5mm together, assembling, wherein the diamond reinforcement body is not in contact with the metal ingots of Cu, lanthanum and cerium, the metal ingots of Cu, lanthanum and cerium are positioned above the diamond reinforcement body, a channel inlet is arranged between the metal ingots of Cu, lanthanum and cerium, the mass sum of lanthanum and cerium is 0.1 percent of Cu, putting the assembled mold into a graphite crucible for mold loading, and then putting the whole workpiece into a heating zone in a furnace body of a metal pressure infiltration device; after the vacuum degree of the equipment is lower than 100Pa, starting a heating program to heat the furnace body to 1150 ℃ at a heating rate of 10 ℃/min, reaching the infiltration temperature above the metal melting point so as to melt the metal ingot, and preserving heat for a period of time to ensure that the metal ingot is fully melted and the temperature of each part in the furnace body is uniform; and then introducing high-purity gas to pressurize the furnace body to 6Mpa, so that the molten metal liquid overcomes the capillary action and infiltrates into holes between the diamond reinforcement bodies, and the composite material with the thickness of 0.5mm is obtained. In the composite material obtained by the invention, the volume fraction of the diamond particles is 65%.

The properties of the obtained composite material are detected as follows: the thermal conductivity is 650W/mK; coefficient of thermal expansion of 6.5X 10^-6K; the density is less than 6g/cm³(ii) a The surface roughness is less than or equal to 3.2 um; the use of the polymer in the packaging material can be carried out at a temperature ranging from-50 to 400 ℃.

Example 2

Preparation of diamond reinforcement

Using 200 μm single crystal diamond particles as raw material, firstly depositing a polycrystalline diamond transition layer on the surface of the diamond particles by chemical deposition, the process comprises: the mass flow ratio of introduced atmosphere is CH₄:H₂And (2) 98 times of growth, wherein the time of each growth is 20min, and finally the polycrystalline diamond transition layer with the maximum thickness of 400nm is obtained.

And then adopting hot filament chemical vapor deposition to grow a doped diamond outer shell layer on the surface of the polycrystalline diamond transition layer to obtain the diamond reinforcement body. Deposition process parameters: the distance of the hot wire is 10mm, the growth temperature of the hot wire with the thickness of 0.5mm is 850 ℃, the deposition pressure is 3KPa, and the thickness of the diamond film is 3 mu m by controlling the deposition time; during the chemical vapor deposition, three-stage growth deposition is carried out, and during the first-stage deposition, the mass flow ratio of introduced gas is CH₄:H₂:B₂H₆2:97: 0.15; the mass flow ratio of the introduced gas in the second section of deposition is CH₄:H₂:B₂H₆2:97:0.35 sccm; third stage sinkThe mass flow rate of the introduced gas is CH during the time accumulation₄:H₂:B₂H₆2:97: 0.55; the growth pressure is 3Kpa, the carrier particles are taken out every time of growth, the growth is continued after the carrier particles are shaken, and the time of single growth is 1 h.

And then etching the doped diamond outer shell layer into a porous structure by adopting plasma, wherein the process conditions are that a tubular furnace provided with a plasma device is used, the temperature is 800 ℃, the vacuum degree is below 0pa, the gas flow is 35sccm under the assistance of hydrogen atmosphere or oxygen atmosphere, and the etching time is 60min, so that the porous modified layer is obtained.

Putting the diamond reinforcement body and a CuB alloy ingot, a lanthanum metal ingot and a cerium metal ingot into a mold with the thickness of 0.5mm for assembly, wherein the diamond reinforcement body is not in contact with the CuB alloy ingot, the lanthanum metal ingot and the cerium metal ingot, the CuB alloy ingot, the lanthanum metal ingot and the cerium metal ingot are positioned above the diamond reinforcement body, a channel inlet is arranged between the CuB alloy ingot, the lanthanum metal ingot and the cerium metal ingot, the mass sum of the lanthanum and the cerium metal is 0.1 percent of that of the CuB alloy, putting the assembled mold into a graphite crucible for mold loading, and then loading the whole workpiece into a heating zone in a furnace body of a metal pressure infiltration device; after the vacuum degree of the equipment is lower than 100Pa, starting a heating program to heat the furnace body to 1150 ℃ at a heating rate of 10 ℃/min, reaching the infiltration temperature above the metal melting point to melt the metal ingot, and preserving heat for a period of time to ensure that the metal ingot is fully melted and the temperature of each part in the furnace body is uniform; and then introducing high-purity gas to pressurize the furnace body to 8Mpa, so that the molten metal liquid overcomes the capillary action and infiltrates into the holes of the reinforcement body, and the composite material with the thickness of 0.5mm is obtained. In the composite material obtained by the invention, the volume fraction of the diamond particles is 70%.

The properties of the obtained composite material are detected as follows: the thermal conductivity is 750W/mK; coefficient of thermal expansion of 5X 10^-6K; the density is less than 6g/cm³(ii) a The surface roughness is less than or equal to 3.2 um; the use of the polymer in the packaging material can be carried out at a temperature ranging from-50 to 400 ℃.

Example 3

Preparation of diamond reinforcement

Using 200 μm single crystal diamond particles as raw material, firstly adopting chemistryThe deposition mode is to deposit a polycrystalline diamond transition layer on the surface of diamond particles, and the process comprises the following steps: the mass flow ratio of introduced atmosphere is CH₄:H₂And (2) 98 times of growth, wherein the time of each growth is 20min, and finally the polycrystalline diamond transition layer with the maximum thickness of 400nm is obtained.

And then adopting hot filament chemical vapor deposition to grow a doped diamond outer shell layer on the surface of the polycrystalline diamond transition layer to obtain the diamond reinforcement body. Deposition process parameters: the distance of the hot wire is 10mm, the growth temperature of the hot wire with the thickness of 0.5mm is 850 ℃, the deposition pressure is 3KPa, and the thickness of the diamond film is 2 mu m by controlling the deposition time; the mass flow ratio of the passing gas is CH in the chemical vapor deposition₄:H₂:B₂H₆The growth pressure is 3Kpa, the growth times are 2 times, the carrier particles are taken out every time of growth, after the carrier particles are shaken, the growth is continued, and the time of single growth is 1 h.

Then carrying out chemical vapor deposition of a boron film on the surface of the doped diamond shell layer, wherein the process comprises the following steps: deposition process parameters: the distance between the hot wires is 30mm, the temperature is 800 ℃, the deposition pressure is 3KPa, and the thickness of the diamond film is 10um by controlling the deposition time; the mass flow ratio of the passing gas is H in the chemical vapor deposition₂:B₂H₆And (5) 2 times of deposition, taking out the carrier particles, shaking the carrier particles, and continuing to grow for 4 hours.

Composition of diamond reinforcement and metal

Putting the diamond reinforcement body and Al metal ingots, lanthanum and cerium metal ingots into a mold with the thickness of 0.5mm for assembly, wherein the diamond reinforcement body is not in contact with the Al metal ingots, the lanthanum and the cerium metal ingots, the Al metal ingots, the lanthanum and the cerium metal ingots are positioned above the diamond reinforcement body, a channel inlet is arranged between the diamond reinforcement body and the Al metal ingots, the mass sum of the lanthanum and the cerium is 0.1 percent of the Al, putting the assembled mold into a graphite crucible for mold filling, and then putting the whole workpiece into a heating zone in a furnace body of a metal pressure infiltration device; after the vacuum degree of the equipment is lower than 100Pa, starting a heating program to heat the furnace body to 750 ℃ at a heating rate of 10 ℃/min, reaching the infiltration temperature above the metal melting point to melt the metal ingot, and preserving heat for a period of time to ensure that the metal ingot is fully melted and the temperature of each part in the furnace body is uniform; and then introducing high-purity gas to pressurize the furnace body to 8Mpa, so that the molten metal liquid overcomes the capillary action and infiltrates into the holes of the reinforcement body, and the composite material with the thickness of 0.5mm is obtained.

In the composite material obtained by the invention, the volume fraction of the diamond particles is 65%.

The properties of the obtained composite material are detected as follows: the thermal conductivity is 600W/mK; coefficient of thermal expansion of 5.6X 10^-6K; density 3.2g/cm³(ii) a The surface roughness is less than or equal to 3.2 um; the use of the polymer in the packaging material can be carried out at a temperature ranging from-50 ℃ to 300 ℃.

Example 4

Preparation of diamond reinforcement

Using 200 μm single crystal diamond particles as raw material, firstly depositing a polycrystalline diamond transition layer on the surface of the diamond particles by chemical deposition, the process comprises: the mass flow ratio of introduced atmosphere is CH₄:H₂And (2) 98 times of growth, wherein the time of each growth is 20min, and finally the polycrystalline diamond transition layer with the maximum thickness of 400nm is obtained.

And then adopting hot filament chemical vapor deposition to grow a doped diamond outer shell layer on the surface of the polycrystalline diamond transition layer to obtain the diamond reinforcement body. Deposition process parameters: the distance of the hot wire is 10mm, the growth temperature of the hot wire with the thickness of 0.5mm is 850 ℃, the deposition pressure is 3KPa, and the thickness of the diamond film is 3 mu m by controlling the deposition time; during the chemical vapor deposition, three-stage growth deposition is carried out, and during the first-stage deposition, the mass flow ratio of introduced gas is CH₄:H₂:B₂H₆2:97: 0.15; the mass flow ratio of the introduced gas in the second section of deposition is CH₄:H₂:B₂H₆2:97:0.35 sccm; during the third stage deposition, the mass flow ratio of the introduced gas is CH₄:H₂:B₂H₆2:97: 0.55; the growth pressure is 3Kpa, the carrier particles are taken out every time of growth, the growth is continued after the carrier particles are shaken, and the time of single growth is 1 h.

And then etching the doped diamond outer shell layer into a porous structure by adopting plasma, wherein the process conditions are that a tubular furnace provided with a plasma device is used, the temperature is 800 ℃, the vacuum degree is below 0pa, the gas flow is 35sccm under the assistance of hydrogen atmosphere or oxygen atmosphere, and the etching time is 60min, so that the porous modified layer is obtained.

Then, metal modification is carried out through a physical vapor deposition technology, wherein the flow rate of a high-purity argon atmosphere is 30sccm, the vacuum degree is 0.5-1 Pa, the temperature is 473KK, the power is 200W, and the sputtering time is 10 min; the thickness is 1 um;

putting the diamond reinforcement body and silver metal ingots, lanthanum and cerium metal ingots into a mold with the thickness of 0.5mm for assembly, wherein the diamond reinforcement body is not in contact with the silver metal ingots, the lanthanum and the cerium metal ingots, the silver metal ingots, the lanthanum and the cerium metal ingots are positioned above the diamond reinforcement body, a channel inlet is arranged between the silver metal ingots, the lanthanum and the cerium metal ingots, the mass sum of the lanthanum and the cerium is 0.1 percent of the silver, putting the assembled mold into a graphite crucible for mold filling, and then putting the whole workpiece into a heating zone in a furnace body of a metal pressure infiltration device; after the vacuum degree of the equipment is lower than 100Pa, starting a heating program to heat the furnace body to 1050 ℃ at a heating rate of 10 ℃/min, reaching the infiltration temperature above the metal melting point to melt the metal ingot, and preserving heat for a period of time to ensure that the metal ingot is fully melted and the temperature of each part in the furnace body is uniform; and then introducing high-purity gas to pressurize the furnace body to 10Mpa, so that the molten metal liquid overcomes the capillary action and infiltrates into the holes of the reinforcement body, and the composite material with the thickness of 0.5mm is obtained. In the composite material obtained by the invention, the volume fraction of the diamond particles is 70%.

The properties of the obtained composite material are detected as follows: the thermal conductivity is 750W/mK; coefficient of thermal expansion 4X 10^-6K; the density is less than 7g/cm³(ii) a The use of the polymer in the packaging material can be carried out at a temperature ranging from-50 to 400 ℃.

Comparative example 1

The other conditions are the same as those of the example 1, and only the core-shell structure doped diamond is not provided with the diamond transition layer, and the diamond/metal matrix composite material which is not provided with the transition layer has weak bonding strength, weak wettability, easy oxidation of the surface, easy carbonization at high temperature and weak ablation resistance.