CN109295335B - Modified expanded graphite-graphite/copper composite material and preparation method thereof - Google Patents
Modified expanded graphite-graphite/copper composite material and preparation method thereof Download PDFInfo
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- CN109295335B CN109295335B CN201811241587.XA CN201811241587A CN109295335B CN 109295335 B CN109295335 B CN 109295335B CN 201811241587 A CN201811241587 A CN 201811241587A CN 109295335 B CN109295335 B CN 109295335B
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- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 190
- 239000010439 graphite Substances 0.000 title claims abstract description 190
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 97
- 239000010949 copper Substances 0.000 title claims abstract description 77
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 77
- 239000002131 composite material Substances 0.000 title claims abstract description 74
- 238000002360 preparation method Methods 0.000 title abstract description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 169
- 238000007747 plating Methods 0.000 claims abstract description 35
- 238000000034 method Methods 0.000 claims abstract description 23
- 238000005245 sintering Methods 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 238000003825 pressing Methods 0.000 claims abstract description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 21
- 229910017604 nitric acid Inorganic materials 0.000 claims description 21
- 239000000126 substance Substances 0.000 claims description 18
- 238000011282 treatment Methods 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 15
- 239000011812 mixed powder Substances 0.000 claims description 14
- 238000005406 washing Methods 0.000 claims description 13
- 230000007935 neutral effect Effects 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 9
- 238000001914 filtration Methods 0.000 claims description 7
- 238000010992 reflux Methods 0.000 claims description 7
- 230000003213 activating effect Effects 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 230000001235 sensitizing effect Effects 0.000 claims description 6
- 230000001590 oxidative effect Effects 0.000 claims description 5
- 230000004913 activation Effects 0.000 claims description 4
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 3
- 206010070834 Sensitisation Diseases 0.000 claims description 3
- 230000008313 sensitization Effects 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000000748 compression moulding Methods 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- 238000000465 moulding Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000005303 weighing Methods 0.000 abstract description 21
- 239000000463 material Substances 0.000 abstract description 10
- 230000003647 oxidation Effects 0.000 abstract description 6
- 238000007254 oxidation reaction Methods 0.000 abstract description 6
- 230000004048 modification Effects 0.000 abstract description 5
- 238000012986 modification Methods 0.000 abstract description 5
- 238000011161 development Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 20
- 238000012360 testing method Methods 0.000 description 18
- 238000001816 cooling Methods 0.000 description 15
- 239000000843 powder Substances 0.000 description 14
- 239000010410 layer Substances 0.000 description 10
- 230000009977 dual effect Effects 0.000 description 9
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- 238000005452 bending Methods 0.000 description 6
- 238000004321 preservation Methods 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000001050 lubricating effect Effects 0.000 description 3
- 238000012876 topography Methods 0.000 description 3
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- AHADSRNLHOHMQK-UHFFFAOYSA-N methylidenecopper Chemical compound [Cu].[C] AHADSRNLHOHMQK-UHFFFAOYSA-N 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
-
- B22F1/0003—
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/18—Pretreatment of the material to be coated
- C23C18/1851—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material
- C23C18/1872—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment
- C23C18/1886—Multistep pretreatment
- C23C18/1889—Multistep pretreatment with use of metal first
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/38—Coating with copper
- C23C18/40—Coating with copper using reducing agents
- C23C18/405—Formaldehyde
Abstract
The invention discloses a method for preparing a modified expanded graphite-graphite/copper composite material by replacing graphite with a small amount of expanded graphite subjected to oxidation modification and then copper plating modification. The preparation method of the composite material comprises the steps of weighing a small amount of modified expanded graphite, graphite powder and electrolytic copper powder, uniformly mixing, pressing and sintering to obtain the composite material. The modified expanded graphite-graphite/copper composite material prepared by the invention has excellent conductivity, excellent frictional wear performance, smaller friction coefficient and lower wear rate. The composite material has excellent conductivity and more excellent friction and wear performance due to the addition of the modified expanded graphite. And the preparation method is simple, the cost is low, and the electric contact material has a good development prospect.
Description
Technical Field
The invention belongs to the technical field of electric contact materials, and particularly relates to a modified expanded graphite-graphite/copper composite material and a preparation method thereof.
Technical Field
The graphite/copper composite material has excellent heat conductivity and electric conductivity of copper and excellent lubricating property of graphite, so that the graphite/copper composite material is widely applied to the field of electric contact materials for rail transit, electronics and electricians and the like. However, since the wettability of graphite and copper is poor, the wetting angle exceeds 140 degrees even under high temperature conditions, the difference of the thermal expansion coefficients is large, the bonding strength between the graphite and the copper is low, the graphite and the copper can be bonded only through mechanical interlocking in the composite material, cracks are easily generated at the joint of two phases under cyclic stress and extend along the graphite phase or the joint of the two phases, and severe fatigue wear is caused. In the high copper phase composite material, the lubricating effect of the graphite cannot be fully exerted due to the low content of the graphite, so that the composite material has a high friction coefficient and a high wear rate.
At present, a great deal of research is carried out on improving the graphite/copper interface bonding by a method of plating copper on the graphite surface and then performing powder metallurgy pressing sintering, but the problem of poor wettability of copper and graphite in the case of plating copper on the graphite surface is that a uniform graphite copper plating layer with strong bonding property with graphite is difficult to obtain, so that the graphite/copper interface bonding condition cannot be essentially improved.
Patent CN102694329A discloses a process of mixing, pressing and sintering graphite, a binder and a copper-plated carbon material, wherein the addition of the binder can help the material to be formed, but greatly affects the conductivity and friction performance of the material, resulting in high wear rate.
In order to improve the problem of the interface between copper and graphite, patent CN16424713A firstly plates nickel on the surface of graphite, and then plates copper, which can improve the wettability of the copper-carbon composite material and improve the interface, but the addition of nickel will also affect the conductivity of the material, and at the same time, the process will be more complicated and the preparation cost will be increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a modified expanded graphite-graphite/copper composite material with good conductivity, small friction coefficient and low wear rate and a preparation method thereof. The preparation method provided by the invention has the advantages of simple process, easily-controlled parameters and low cost.
The invention relates to a modified expanded graphite-graphite/copper composite material, which comprises the following components in percentage by mass: 0.5-5% of modified expanded graphite; 5% -39.5% of graphite powder and 60% -90% of copper powder, wherein the modified expanded graphite is obtained by oxidizing expanded graphite and plating copper on the surface.
The modified expanded graphite is originally used for replacing equivalent graphite, the expanded graphite has excellent wettability, the distance between expanded graphite layers is large, the interlayer binding force is weak, and the expanded graphite is easy to fall off between the layers under the action of stress in the friction process and is flatly paved on the friction surface to form a complete friction layer, so that the friction coefficient of the material is reduced. The expanded graphite is modified by oxidation, the surface is plated with copper, the bonding effect between a graphite phase and a copper phase is effectively improved, and the worm-shaped modified expanded graphite with large particle size is beneficial to forming a more complete three-dimensional network copper structure in the composite material. The obtained composite material has excellent friction and wear properties.
The inventors found that the addition amount of the modified expanded graphite has a great influence on the performance of the composite material, that the addition amount of the modified expanded graphite is too small to improve the combination of the graphite phase and the copper phase, and that the addition amount of the modified expanded graphite is too large to cause a great reduction in the performance of the composite material.
In a preferred scheme, the composite material comprises the following components in percentage by mass: 0.5-5% of modified expanded graphite; 15 to 29.5 percent of graphite powder and 70 to 80 percent of copper powder.
As a further preferable scheme, the composite material comprises the following components in percentage by mass: 0.5-2% of modified expanded graphite; 18 to 29.5 percent of graphite powder and 70 to 80 percent of copper powder.
The inventor finds that when the content of the modified expanded graphite in the composite material is controlled to be 0.5-2%, the obtained composite material has excellent friction and wear properties.
As a further preferable scheme, the composite material comprises the following components in percentage by mass: 1-2% of modified expanded graphite; 18-19% of graphite powder and 80% of copper powder.
Preferably, the diameter of the expanded graphite is 50-150 μm, and the length of the expanded graphite is 300-1000 μm.
In a preferred scheme, the preparation method of the modified expanded graphite comprises the following steps of; adding the expanded graphite into a nitric acid solution, refluxing for 4-8 hours at 80-100 ℃, filtering, washing to be neutral, drying to obtain oxidized expanded graphite, and then carrying out surface copper plating on the oxidized expanded graphite to obtain the modified expanded graphite.
As a further preferable scheme, the solid-liquid mass volume ratio of the expanded graphite to the nitric acid solution is 1-4 g: 100 mL.
In a further preferable embodiment, the mass fraction of the nitric acid solution is 65 to 68%.
As a further preferable scheme, after the oxidation treatment of the expanded graphite, sensitization treatment and activation treatment are carried out, and then surface copper plating is carried out in a chemical plating mode;
said sensitizationThe treatment process comprises the following steps: placing the oxidized expanded graphite in a sensitizing treatment solution, sensitizing for 20-40 min, and washing to be neutral to obtain sensitized expanded graphite; the sensitizing treatment solution is SnCl with the concentration of 5g/L and the pH of 1.5-22A solution;
the activating treatment process comprises the following steps: placing the sensitized expanded graphite in an activation treatment solution, activating for 20-40 min, and washing with water to be neutral to obtain activated expanded graphite; the activating treatment solution is PbCl with the concentration of 0.05g/L and the pH of 1.5-22A solution;
the chemical plating comprises the following steps: placing the activated expanded graphite in a chemical plating solution with the pH value of 12.5-13 for chemical plating for 1-4 h at the temperature of 40-60 ℃ to obtain the copper-plated expanded graphite, wherein the chemical plating solution comprises the following components: 12-16 g/LCuSO4∙5H2O、5～10g/L CH2O、20～21g/L EDTA、14～18/L NaKC4H4O6∙4H2O。
Preferably, the copper powder is electrolytic copper powder, and the particle size of the copper powder is 200-300 meshes.
In a preferred scheme, the particle size of the graphite powder is less than or equal to 100 meshes.
The invention relates to a preparation method of a modified expanded graphite-graphite/copper composite material, which comprises the steps of mixing modified expanded graphite, graphite powder and copper powder according to a designed proportion to obtain mixed powder, then pressing and molding the mixed powder to obtain a pressed sample, and sintering the pressed sample at 700-900 ℃ for 2-3 hours under the protection of a non-oxidizing atmosphere to obtain the modified expanded graphite-graphite/copper composite material.
In the preferable scheme, the pressure of the compression molding is 300-400 MPa, and the pressure maintaining time is 30-60 s.
In the preferred scheme, the sintering temperature rise rate is less than or equal to 2 ℃/min.
Further preferably, the sintering temperature rise rate is 1 to 1.5 ℃/min.
The inventor finds that the temperature rise rate needs to be controlled well for obtaining the compact composite material, and if the temperature rise rate is too high, the product is cracked, so that the mechanical property of the material is greatly reduced.
Preferably, the non-oxidizing atmosphere is an ammonia gas atmosphere and/or a nitrogen gas atmosphere.
The invention has the beneficial effects that:
in the invention, a small amount of modified expanded graphite is used for replacing graphite to prepare the modified expanded graphite-graphite/copper composite material, so that the excellent conductivity of the composite material is ensured, the friction and wear properties of the high-copper phase graphite/copper composite material are effectively improved, and the friction coefficient and wear rate of the composite material are reduced. The obtained modified expanded graphite-graphite/copper composite material is an electric contact material with development prospect.
The preparation method has the advantages of simple preparation process, easily-controlled parameters, low requirement on required equipment and low preparation cost, and is suitable for large-scale industrial production.
The invention uses a small amount of expanded graphite with larger grain diameter and smaller density to replace a small amount of graphite, and fully exerts the lubricating effect of the graphite phase. In order to solve the problem of weak bonding effect between two phases, the expanded graphite is subjected to oxidation modification, surface copper plating and other treatments. The distance between the expanded graphite layers is large, the binding force between the layers is weak, and the expanded graphite layers are easy to fall off between the layers under the action of stress in the friction process and are flatly paved on the friction surface to form a complete friction layer, so that the friction coefficient of the material is reduced. Copper plating on the surface of the expanded graphite effectively improves the bonding effect between the graphite phase and the copper phase, and the vermicular copper-plated expanded graphite with large particle size is beneficial to forming a more complete three-dimensional network copper structure in the composite material.
Drawings
FIG. 1 is an SEM topography for the modified expanded graphite used in example 1. It can be seen from the figure that the copper has been successfully plated uniformly on the surface of the expanded graphite;
FIG. 2 is a micro-topography of the composite material of example 1. When the content of the expanded graphite is low, the expanded graphite is not obvious on the surface of the composite material, and copper phases are tightly combined;
FIG. 3 is a micro-topography of the composite material of example 2. When the content of the expanded graphite is higher, a larger C phase can be observed on the surface of the composite material, and the expanded graphite is large in particle size.
Detailed Description
The present invention is further illustrated by the following specific examples, which are implemented on the premise of the technical solution of the present invention, and the protection scope of the present invention is not limited by these examples.
In the following examples, the following procedures were used for chemical plating:
placing the oxidized expanded graphite in SnCl with the concentration of 5g/L and the pH value of 22Sensitizing the solution for 30min, and washing the solution to be neutral to obtain sensitized expanded graphite; then the sensitized expanded graphite is put into PbCl with the concentration of 0.05g/L and the pH value of 22Activating in the solution for 30min, and washing with water to neutrality to obtain activated expanded graphite; and then placing the activated expanded graphite in a chemical plating solution with the pH value of 12.5-13 for chemical plating for 2 hours at the temperature of 40-60 ℃ to obtain the copper-plated expanded graphite with a uniform copper-plated layer, wherein the chemical plating solution comprises the following components: 16g/LCuSO4∙5H2O、7g/L CH2O、20g/L EDTA、16/L NaKC4H4O6∙4H2O。
Example 1:
(1) weighing 3g of expandable graphite with the average diameter of 75 microns and the average length of 750 microns in a graphite box, carrying out heat preservation and expansion in a muffle furnace for 30s at 900 ℃ in air atmosphere, taking out, and naturally cooling to room temperature to obtain expanded graphite;
(2) placing the expanded graphite obtained in the step (1) in a round-bottom flask, and mixing the expanded graphite: concentrated nitric acid 1 g: weighing concentrated nitric acid (mass fraction is 68%) in a proportion of 100mL, refluxing for 4h at 100 ℃, taking out the concentrated nitric acid from a flask, cooling to room temperature, filtering and washing the expanded graphite to be neutral, and obtaining oxidized expanded graphite;
(3) uniformly plating copper on the surface of the oxidized expanded graphite obtained in the step (2) by using a chemical plating method, and drying and reducing to obtain copper-plated expanded graphite, namely modified expanded graphite;
(4) according to mass ratio of mGraphite (II)：mCopper powder：mModified expanded graphiteWeighing the powder according to the proportion of 19:80:1, and uniformly mixing to obtain mixed powder; wherein the copper powder has a particle size of 300 meshes and is in the form of stoneThe particle size of the ink powder is 100 meshes;
(5) weighing 20g of the mixed powder obtained in the step (4) in a mould, maintaining the pressure for 30s under the pressure of 300MPa, placing the pressed sample in a sintering furnace under the protection of ammonia gas, setting the setting procedure that the sintering furnace is heated to 760 ℃ at the speed of 1.2 ℃/min, then preserving the temperature for 2h, cooling to room temperature along with the furnace, and taking out the sample to obtain the copper-plated expanded graphite-graphite/copper composite material;
(6) the composite material prepared above has a density of 4.482g/cm3Bending strength of 28.5MPa and resistivity of 3.59X 10-7Ω·m。
(7) The friction and wear performance of the composite material is inspected on an HRS-2M high-speed reciprocating friction tester, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.21 and the wear rate was found to be 1.4X 10-3mm3/N·m。
Example 2
(1) Weighing 3g of expandable graphite with the average diameter of 75 microns and the average length of 750 microns in a graphite box, carrying out heat preservation and expansion in a muffle furnace for 30s at 900 ℃ in air atmosphere, taking out, and naturally cooling to room temperature to obtain expanded graphite;
(2) placing the expanded graphite obtained in the step (1) in a round-bottom flask, and mixing the expanded graphite: concentrated nitric acid 1 g: weighing concentrated nitric acid (mass fraction is 68%) in a proportion of 100mL, refluxing for 4h at 100 ℃, taking out the concentrated nitric acid from a flask, cooling to room temperature, filtering and washing the expanded graphite to be neutral, and obtaining oxidized expanded graphite;
(3) uniformly plating copper on the surface of the oxidized expanded graphite obtained in the step (2) by using a chemical plating method, and drying and reducing to obtain copper-plated expanded graphite, namely modified expanded graphite;
(4) according to mass ratio of mGraphite (II)：mCopper powder：mModified expanded graphiteWeighing the powder according to the ratio of 18:80:2, and uniformly mixing to obtain mixed powder; wherein the particle size of the copper powder is 300 meshes, and the particle size of the graphite powder is 100 meshes;
(5) weighing 20g of the mixed powder obtained in the step (4) in a mould, maintaining the pressure for 30s under the pressure of 300MPa, placing the pressed sample in a sintering furnace under the protection of ammonia gas, setting the setting procedure that the sintering furnace is kept at the temperature of 1.2 ℃/min to 760 ℃ for 2h, cooling the sample to room temperature along with the furnace, and taking out the sample to obtain the copper-plated expanded graphite-graphite/copper composite material;
(6) the composite material prepared above has a density of 4.067g/cm3Bending strength of 29.2MPa and resistivity of 2.83X 10-7Ω·m。
(7) The friction and wear performance of the composite material is inspected on an HRS-2M high-speed reciprocating friction tester, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.19 and the wear rate was found to be 1.2X 10-3mm3/N·m。
Example 3:
(1) weighing 3g of expandable graphite with the average diameter of 75 microns and the average length of 750 microns in a graphite box, carrying out heat preservation and expansion in a muffle furnace for 30s at 900 ℃ in air atmosphere, taking out, and naturally cooling to room temperature to obtain expanded graphite;
(2) placing the expanded graphite obtained in the step (1) in a round-bottom flask, and mixing the expanded graphite: concentrated nitric acid 1 g: weighing concentrated nitric acid (the mass fraction is 65%) in a proportion of 100mL, refluxing for 4h at 100 ℃, taking out the concentrated nitric acid from a flask, cooling to room temperature, filtering and washing the expanded graphite to be neutral to obtain oxidized expanded graphite;
(3) uniformly plating copper on the surface of the oxidized expanded graphite obtained in the step (2) by using a chemical plating method, and drying and reducing to obtain copper-plated expanded graphite, namely modified expanded graphite;
(4) according to mass ratio of mGraphite (II)：mCopper powder：mModified expanded graphiteWeighing the powder according to the proportion of 29.5:70:0.5, and uniformly mixing to obtain mixed powder; wherein the particle size of the copper powder is 300 meshes, and the particle size of the graphite powder is 100 meshes;
(5) weighing 20g of the mixed powder obtained in the step (4) in a mould, maintaining the pressure for 30s under the pressure of 300MPa, placing the pressed sample in a sintering furnace under the protection of ammonia gas, setting the setting procedure that the sintering furnace is heated to 760 ℃ at the speed of about 1.2 ℃/min, then preserving the temperature for 2h, cooling to room temperature along with the furnace, and taking out the sample to obtain the copper-plated expanded graphite-graphite/copper composite material;
(6) the density of the composite material prepared in the above is 3.906g/cm3Bending strength of 25.4MPa and resistivity of 6.52X 10-7Ω·m。
(7) The friction and wear performance of the composite material is inspected on an HRS-2M high-speed reciprocating friction tester, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.21 and the wear rate was found to be 2.36X 10-3mm3/N·m。
Example 4
(1) Weighing 3g of expandable graphite with the average diameter of 75 microns and the average length of 750 microns in a graphite box, carrying out heat preservation and expansion in a muffle furnace for 30s at 900 ℃ in air atmosphere, taking out, and naturally cooling to room temperature to obtain expanded graphite;
(2) placing the expanded graphite obtained in the step (1) in a round-bottom flask, and mixing the expanded graphite: concentrated nitric acid 1 g: weighing concentrated nitric acid (the mass fraction is 65%) in a proportion of 100mL, refluxing for 4h at 100 ℃, taking out the concentrated nitric acid from a flask, cooling to room temperature, filtering and washing the expanded graphite to be neutral to obtain oxidized expanded graphite;
(3) uniformly plating copper on the surface of the oxidized expanded graphite obtained in the step (2) by using a chemical plating method, and drying and reducing to obtain copper-plated expanded graphite, namely modified expanded graphite;
(4) according to mass ratio of mGraphite (II)：mCopper powder：mModified expanded graphiteWeighing the powder according to the proportion of 15:80:5, and uniformly mixing to obtain mixed powder; wherein the particle size of the copper powder is 300 meshes, and the particle size of the graphite powder is 100 meshes;
(5) weighing 20g of the mixed powder obtained in the step (4) in a mould, maintaining the pressure for 30s under the pressure of 300MPa, placing the pressed sample in a sintering furnace under the protection of ammonia gas, setting the setting procedure that the sintering furnace is heated to 760 ℃ at the speed of about 1.2 ℃/min, then preserving the temperature for 2h, cooling to room temperature along with the furnace, and taking out the sample to obtain the copper-plated expanded graphite-graphite/copper composite material;
(6) the density of the composite material prepared above was 4.258g/cm3Bending strength of 29MPa and resistivity of 2.26X 10-7Ω·m
(7) The friction and wear performance of the composite material is inspected on an HRS-2M high-speed reciprocating friction tester, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.22 and the wear rate was found to be 2.0X 10-3mm3/N·m。
Comparative example 1
(1) This comparative example was conducted under the same conditions as in example 1 except that the expanded graphite was not modified, and m wasGraphite (II)：mCopper powder：mExpanded graphite＝19:80:1；
(2) The density of the composite material obtained in this comparative example was measured to be 3.962g/cm3Flexural strength of 27.2MPa and resistivity of 3.51X 10-7Ω·m。
(3) The composite material obtained by the comparative example is examined on an HRS-2M type high-speed reciprocating friction tester for the friction and wear performance of the composite material, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.22 and the wear rate was found to be 1.9X 10-3mm3/N·m。
Comparative example 2
(1) Weighing a proper amount of 3g of expandable graphite in a graphite box, carrying out heat preservation and expansion in a muffle furnace for 30s at 900 ℃ in air atmosphere, taking out, and naturally cooling to room temperature to obtain the expandable graphite;
(2) placing the expanded graphite obtained in the step (1) in a round-bottom flask, and mixing the expanded graphite: concentrated nitric acid 1 g: weighing concentrated nitric acid in a proportion of 100mL, refluxing for 4h at 100 ℃, taking out the concentrated nitric acid from a flask, cooling to room temperature, filtering and washing the expanded graphite to be neutral to obtain oxidized expanded graphite;
(3) according to mass ratio of mGraphite (II)：mCopper powder：mOxidized expanded graphiteWeighing the powder according to the proportion of 19:80:0.5, and uniformly mixing to obtain mixed powder;
(4) weighing 20g of the mixed powder obtained in the step (3) in a mould, maintaining the pressure for 30s under the pressure of 300MPa, placing the pressed sample in a sintering furnace under the protection of ammonia gas, setting the procedure that the sintering furnace slowly rises to 760 ℃, preserving the heat for 2h, cooling to room temperature along with the furnace, and taking out the sample to obtain the copper-plated expanded graphite-graphite/copper composite material;
(5) the composite material prepared above has a density of 3.968g/cm3Flexural strength of 27.4MPa and resistivity of 3.62X 10-7Ω·m。
(6) The friction and wear performance of the composite material is inspected on an HRS-2M high-speed reciprocating friction tester, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.24 and the wear rate was 1.92X 10-3mm3/N·m。
Comparative example 3
(1) This comparative example was conducted under the same conditions as those in example 1 except that the expanded graphite was modified by oxidation only and was not plated with copper, andgraphite (II)：mCopper powder：mOxidized expanded graphite＝19:80:1；
(2) The density of the composite material obtained in this comparative example was measured to be 3.936g/cm3Flexural strength of 27.2MPa and resistivity of 3.51X 10-7Ω·m。
(3) The composite material obtained by the comparative example is examined on an HRS-2M type high-speed reciprocating friction tester for the friction and wear performance of the composite material, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.22 and the wear rate was found to be 1.8X 10-3mm3/N·m。
Comparative example 4
(1) The comparative example is identical to the comparative example 3 in other conditions except that the expanded graphite is subjected to oxidation treatment and then ball milling modification without copper plating modification.
(2) The density of the composite material obtained in this comparative example was measured to be 3.962g/cm3Bending strength of 24.8MPa and resistivity of 1.449 × 10-6Ω·m。
(3) The composite material obtained by the comparative example is examined on an HRS-2M type high-speed reciprocating friction tester for the friction and wear performance of the composite material, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.34 and the wear rate was found to be 7.3X 10-3mm3/N·m。
Comparative example 5
(1) This comparative example was conducted under the same conditions as in example 3 except that the expanded graphite was not modified and m wasGraphite (II)：mCopper powder：mExpanded graphite＝29.5:70:0.5；
(2) The density of the composite material obtained in this comparative example was measured to be 3.947g/cm3Bending strength of 23.1MPa and resistivity of 1.549 × 10-6Ω·m。
(3) The composite material obtained by the comparative example is examined on an HRS-2M type high-speed reciprocating friction tester for the friction and wear performance of the composite material, the running speed is 0.1M/s, the test load is 10N, the test time is 30min, and the dual ball is red copper. The friction coefficient was found to be 0.22 and the wear rate was found to be 3.12X 10-3mm3/N·m。
Comparative example 6
The comparative example is the same as the example 1 in other conditions, only the temperature is raised at 2.5 ℃/min, so that the obtained composite material has obvious defects, and clear cracks can be seen by observing the appearance of a sample. Poor mechanical property and low strength.
Claims (5)
1. A modified expanded graphite-graphite/copper composite material is characterized in that: the composite material comprises the following components in percentage by mass: 0.5-5% of modified expanded graphite; 5% -39.5% of graphite powder and 60% -90% of copper powder, wherein the modified expanded graphite is obtained by oxidizing expanded graphite and plating copper on the surface; the diameter of the expanded graphite is 50-150 mu m, and the length of the expanded graphite is 300-1000 mu m;
adding expanded graphite into a nitric acid solution, refluxing for 4-8 h at 80-100 ℃, filtering, washing to be neutral, drying to obtain oxidized expanded graphite, and then carrying out surface copper plating on the oxidized expanded graphite to obtain the modified expanded graphite;
the solid-liquid mass volume ratio of the expanded graphite to the nitric acid solution is 1-4 g: 100mL, wherein the mass fraction of the nitric acid solution is 65-68%;
the oxidized expanded graphite is subjected to sensitization and activation treatment, and then surface copper plating is carried out in a chemical plating mode; the process of the sensitization treatment comprises the following steps: placing the oxidized expanded graphite in a sensitizing treatment solution, sensitizing for 10-20 min, and washing to be neutral to obtain sensitized expanded graphite; the sensitizing treatment solution is SnCl with the concentration of 5g/L and the pH of 1.5-22A solution; the activating treatment process comprises the following steps: placing the sensitized expanded graphite in an activation treatment solution, activating for 10-20 min, and washing with water to be neutral to obtain activated expanded graphite; the activating treatment solution is PbCl with the concentration of 0.05g/L and the pH of 1.5-22A solution; the chemical plating comprises the following steps: placing the activated expanded graphite in a chemical plating solution with the pH value of 12.5-13 for chemical plating for 1-4 h at the temperature of 40-60 ℃ to obtain the copper-plated expanded graphite, wherein the chemical plating solution comprises the following components: 12-16 g/LCuSO4∙5H2O、5～10g/L CH2O、20～21g/L EDTANa2、14～18/L NaKC4H4O6∙4H2O；
The copper powder is electrolytic copper powder, and the particle size of the copper powder is 200-300 meshes; the particle size of the graphite powder is less than or equal to 100 meshes.
2. The modified expanded graphite-graphite/copper composite material according to claim 1, wherein: the composite material comprises the following components in percentage by mass: 0.5-5% of modified expanded graphite; 15 to 29.5 percent of graphite powder and 70 to 80 percent of copper powder.
3. A process for preparing a modified expanded graphite-graphite/copper composite material according to any one of claims 1 to 2, characterized in that: mixing the modified expanded graphite, graphite powder and copper powder according to a designed proportion to obtain mixed powder, then pressing and molding the mixed powder to obtain a pressed sample, and sintering the pressed sample at 700-900 ℃ for 2-3 h under the protection of non-oxidizing atmosphere to obtain the modified expanded graphite-graphite/copper composite material.
4. The method for preparing a modified expanded graphite-graphite/copper composite material according to claim 3, wherein: the pressure of the compression molding is 300-400 MPa, and the pressure maintaining time is 30-60 s.
5. The method for preparing a modified expanded graphite-graphite/copper composite material according to claim 3, wherein: the sintering temperature rise rate is less than or equal to 2 ℃/min.
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