A method for preparing W-Cu composite material by solid-liquid doping co-precipitation
By using a solid-liquid doping co-precipitation method and oxalic acid as a control agent, W-Cu composite materials were prepared, overcoming the problem of insufficient density in traditional methods and obtaining W-Cu materials with high purity, high hardness, and high density.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI UNIV OF TECH
- Filing Date
- 2024-02-02
- Publication Date
- 2026-07-21
AI Technical Summary
Traditional methods are difficult to prepare high-density W-Cu composite materials, and existing powder metallurgy technology has limited performance improvement under the incompatibility of W and Cu.
A homogeneous W-Cu precursor was prepared by using a solid-liquid doping co-precipitation method with the addition of oxalic acid as a process control agent. High-purity and high-density W-Cu composite materials were then prepared by hydrogen reduction and high-temperature hydrogen sintering.
High purity, high hardness, and high density of W-Cu composite materials were achieved, improving the overall performance of the materials.
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Figure CN118048566B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of W-Cu composite material preparation technology, specifically to a method for preparing W-Cu composite materials through solid-liquid doping co-precipitation. The method obtains W-Cu powder with uniform composition and high purity through solid-liquid doping co-precipitation, and then further improves the comprehensive performance of the W-Cu composite material through subsequent sintering. Background Technology
[0002] Due to differences in melting point, electronegativity, and atomic radius between W and Cu, W-Cu composites, which combine the advantages of both W (high melting point, high hardness, low expansion) and Cu (high electrical and thermal conductivity), exhibit excellent thermal and electrical conductivity, high hardness, resistance to arc erosion, and low coefficient of thermal expansion. They are widely used in electrical contact materials, electronic packaging materials, heat sink materials, and functional structural materials. In recent years, with the rapid development of high-tech fields such as microelectronics communications, aerospace, and military engineering, the demand for high-performance W-Cu composites has been increasing.
[0003] Due to the incompatibility of W and Cu, traditional melt infiltration methods are insufficient for preparing high-density W-Cu composites. Powder metallurgy, as an emerging technology, holds promise for improving the various properties of W-Cu composites. The high surface activity and large specific surface area of nanopowders facilitate higher sintering driving forces during low-temperature densification, and the resulting bulk composites exhibit better mechanical properties. Therefore, improving the preparation and molding processes of W-Cu powder can enhance the quality of powder metallurgy products.
[0004] This invention utilizes a solid-liquid doping co-precipitation method and adds oxalic acid as a process control agent to prepare a W-Cu precursor with uniform composition distribution. The precursor powder is then reduced with hydrogen to produce W-Cu powder with uniform composition. Finally, a W-Cu composite material with uniform composition, high purity, high hardness, and high density is prepared by compression molding and high-temperature hydrogen sintering. Summary of the Invention
[0005] This invention utilizes a solid-liquid doping co-precipitation method and modifies the precursor solution environment by adding oxalic acid as a process control agent. This allows the oxalic acid to fully react with W and Cu, thereby improving the purity of the precursor powder. This facilitates the preparation of W-Cu powder with uniform composition, low oxygen content, and good particle size dispersibility via hydrogen reduction. On one hand, hydrogen effectively removes residual oxygen impurities from the W-Cu powder; on the other hand, the long high-temperature holding time allows for sufficient diffusion of W and Cu elements. Finally, high-density W-Cu composite blocks are prepared through molding and high-temperature hydrogen sintering. The main improvement of this invention is in the preparation process, namely, changing from the liquid-liquid doping process commonly used in wet chemical methods to a solid-liquid doping process. Furthermore, the W-Cu composite blocks prepared by the solid-liquid doping co-precipitation method exhibit superior performance compared to those prepared by the liquid-liquid doping method under the same process parameters.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A method for preparing W-Cu composite materials by solid-liquid doping coprecipitation includes the following steps:
[0008] Step 1: Preparation of W-Cu powder
[0009] A certain proportion of ammonium metatungstate or tungsten oxide, copper nitrate or copper oxide, and oxalic acid are dissolved in deionized water, and the solid content of the precursor solution is controlled at 20%-30%. The solution is stirred and heated, and after the solution is completely evaporated, W-Cu precursor is prepared using a drying oven. Then, the W-Cu precursor is thoroughly ground, sieved, and reduced with hydrogen to obtain W-Cu powder.
[0010] When choosing a combination of ammonium metatungstate and copper oxide, the amount of copper oxide added should be 15-20% of the mass of ammonium metatungstate, and the amount of oxalic acid added should be 35-40% of the mass of ammonium metatungstate.
[0011] When choosing a combination of tungsten oxide and copper nitrate, the amount of copper nitrate added should be 58-63% of the mass of tungsten oxide, and the amount of oxalic acid added should be 38-43% of the mass of tungsten oxide.
[0012] Step 2: Molding without molding agent
[0013] A certain amount of W-Cu powder prepared in step one is weighed according to the size requirements of the pressed sample and placed in a steel mold for cold pressing. Then the pressure is released and the W-Cu green block is taken out.
[0014] Step 3: High-temperature hydrogen sintering
[0015] The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified at the same sintering temperature to obtain a W-Cu composite block; finally, the surface of the obtained block is polished to obtain the W-Cu composite material.
[0016] As a preferred technical solution of the present invention, in the preparation method:
[0017] In step one, the stirring and heating temperature is 120-160℃, and the rotation speed is 150-250 r / min. After the solution has completely evaporated, the W-Cu precursor is prepared using a drying oven with a drying temperature of 80-100℃ and a drying time of 12-14 h. The sieve mesh size is 100-200 μm when grinding and sieving. The hydrogen reduction step is as follows: the W-Cu precursor is spread evenly in a sintered boat, which is then placed in a hydrogen reduction furnace. The furnace is vacuum-treated, and then hydrogen is introduced. The temperature is then increased to 930-980℃ at 4-8℃ / min and held for 1-3 h. The temperature is then reduced to 500℃ at 4-10℃ / min, and then cooled to room temperature with the furnace to obtain W-Cu powder.
[0018] In step two, the pressing pressure selected for cold pressing is 200-220 MPa, and the pressure is maintained for 2-4 minutes to obtain a green body with a relative density of 60-68%.
[0019] The sintering densification process in step three is as follows: the pressed W-Cu green block is placed in a tube furnace and hydrogen is introduced. The temperature is increased to 100°C at 5°C / min, then increased to 1000°C at 5-10°C / min, and finally increased to 1350°C at 5°C / min and held for 1-3 hours. The temperature is then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block.
[0020] This invention utilizes a solid-liquid doping coprecipitation method and modifies the precursor solution environment by adding oxalic acid as a process control agent, thereby ensuring that oxalic acid reacts fully with raw materials containing W and Cu elements. The advantages are as follows:
[0021] 1. Sufficient precursor reaction: Directly introducing solid powder containing W or Cu through solid-liquid doping can improve the difference in reaction rates between W and Cu elements during the W-Cu precursor reaction.
[0022] 2. Excellent powder properties: After hydrogen reduction, the W-Cu powder has improved compositional uniformity and purity, as well as lower oxygen impurity content, which is beneficial for molding and high-temperature hydrogen sintering.
[0023] 3. Excellent performance of W-Cu composite material: Hydrogen can effectively remove oxygen impurities in W-Cu powder, and high temperature insulation is conducive to obtaining high density W-Cu composite material.
[0024] 4. This invention ultimately produces a W-Cu composite material with high purity, high hardness, high density, and uniform composition. The W-Cu composite material prepared by the solid-liquid doping co-precipitation method has a relative density as high as 99.3%, a Vickers hardness as high as 305±10 Hv, and a coefficient of thermal expansion of 8.3×10⁻⁶. -6 K. Attached Figure Description
[0025] Figure 1 These are the XRD patterns of W-Cu powder after reduction in Examples 1, 2, and 3.
[0026] Figure 2 a, b, and c are the SEM morphologies of W-Cu powder after reduction in Examples 1, 2, and 4, respectively.
[0027] Figure 3 a, b, c, and d are SEM images of the fracture surfaces of the W-Cu composite materials prepared in Examples 1, 2, 3, and 4, respectively. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.
[0029] Example 1
[0030] A method for preparing a W-Cu composite material includes the following steps:
[0031] Step 1: Preparation of liquid-liquid doping co-precipitation W-Cu powder
[0032] A certain proportion of ammonium metatungstate (AMT, Aladdin, purity ≥99.95%) and copper nitrate (Cu(NO3)2·3H2O, Aladdin, purity ≥99.5%) were dissolved in deionized water. The solution was placed in an oil bath and heated and stirred at 140℃ and 230 r / min. After the solution reacted for 0.5 h, oxalic acid (C2H2O4·2H2O, analytical grade) solution was added. The solid content of the precursor solution was 20-30%. The mixture was heated and stirred until the solution in the oil bath was completely evaporated to obtain the W-Cu precursor. The W-Cu precursor was then dried at 80℃ for 14 h. The dried W-Cu precursor was thoroughly ground and sieved through a 100 μm sieve. The W-Cu precursor was then subjected to hydrogen reduction. The W-Cu precursor was spread evenly in a sintering boat, which was then placed in a hydrogen reduction furnace. The hydrogen reduction furnace was then vacuum-treated, and hydrogen (hydrogen purity ≥ 99.999%, hydrogen flow rate 0.5 L / min) was introduced. The temperature was then increased to 950°C at 5°C / min and held at 950°C for 2 hours. The temperature was then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain W-Cu powder.
[0033] In step one, the amounts of copper nitrate and oxalic acid added are 58.18% and 37.80% of the mass of ammonium metatungstate, respectively.
[0034] Step 2: Molding without molding agent
[0035] Weigh 15g of the W-Cu powder from step one according to the required size of the pressed sample and place it into a steel mold. The medium-cold pressing process is performed with a pressing pressure of 200-220 MPa, which is maintained for 3 minutes to obtain a green blank with a relative density of 60-62%. The pressure is then released to remove the W-Cu green blank block.
[0036] Step 3: High-temperature hydrogen sintering
[0037] The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified under high-temperature hydrogen sintering. The pressed W-Cu green body is placed in a tube furnace and hydrogen (hydrogen purity ≥99.999%, hydrogen flow rate 0.2 L / min) is introduced. The temperature is increased to 100℃ at 5℃ / min, then increased to 1000℃ at 10℃ / min, and finally increased to 1350℃ at 5℃ / min and held for 2 hours. After that, the temperature is reduced to 500℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block. Finally, the surface of the obtained block is polished with sandpaper of gradually increasing fineness (240 grit to 800 grit) to obtain the W-Cu composite material.
[0038] The W-Cu composite material obtained in this embodiment was prepared by liquid-liquid doping co-precipitation method, with a relative density as high as 96.9%, a Vickers hardness as high as 297±10 Hv, and a coefficient of thermal expansion of 8.5×10⁻⁶. -6 K.
[0039] Example 2
[0040] A method for preparing a W-Cu composite material includes the following steps:
[0041] Step 1: Preparation of solid-liquid doped co-precipitated W-Cu powder
[0042] A certain proportion of ammonium metatungstate (AMT, Aladdin, purity ≥99.95%) and copper oxide (CuO, 0.1-0.5 μm, purity ≥99.5%) were dissolved in deionized water. The solution was then heated and stirred in an oil bath at 140℃ and 230 r / min. After 0.5 h of reaction, oxalic acid (C2H2O4·2H2O, analytical grade) solution was added, resulting in a precursor solution with a solid content of 25-29%. The mixture was heated and stirred until the solution in the oil bath was completely evaporated, yielding the W-Cu precursor. The W-Cu precursor was then dried at 80℃ for 14 h. The dried W-Cu precursor was thoroughly ground and sieved through a 100 μm sieve. The W-Cu precursor was then subjected to hydrogen reduction. The W-Cu precursor was spread evenly in a sintering boat, which was then placed in a hydrogen reduction furnace. The hydrogen reduction furnace was then vacuum-treated, and hydrogen (hydrogen purity ≥ 99.999%, hydrogen flow rate 0.5 L / min) was introduced. The temperature was then increased to 950°C at 5°C / min and held at 950°C for 2 hours. The temperature was then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain W-Cu powder.
[0043] In step one, the amounts of copper oxide and oxalic acid added are 19.16% and 37.80% of the mass of ammonium metatungstate, respectively.
[0044] Step 2: Compression Molding
[0045] Weigh 15g of the W-Cu powder from step one according to the required size of the pressed sample and place it into a steel mold. The medium-cold pressing process is performed with a pressing pressure of 200-220 MPa, which is maintained for 3 minutes to obtain a green blank with a relative density of 65-67%. The pressure is then released to remove the W-Cu green blank block.
[0046] Step 3: High-temperature hydrogen sintering
[0047] The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified under high-temperature hydrogen sintering. The pressed W-Cu green body is placed in a tube furnace and hydrogen (hydrogen purity ≥99.999%, hydrogen flow rate 0.2 L / min) is introduced. The temperature is increased to 100℃ at 5℃ / min, then increased to 1000℃ at 10℃ / min, and finally increased to 1350℃ at 5℃ / min and held for 2 hours. After that, the temperature is reduced to 500℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block. Finally, the surface of the obtained block is polished with sandpaper of gradually increasing fineness (240 grit to 800 grit) to obtain the W-Cu composite material.
[0048] The W-Cu composite material obtained in this embodiment was prepared by solid-liquid doping co-precipitation method, with a relative density as high as 84.2%, a Vickers hardness as high as 275±10 Hv, and a coefficient of thermal expansion of 8.6×10⁻⁶. -6 K.
[0049] Example 3
[0050] A method for preparing a W-Cu composite material includes the following steps:
[0051] Step 1: Preparation of solid-liquid doped co-precipitated W-Cu powder
[0052] A certain proportion of tungsten oxide (WO3, 0.1-0.5 μm, purity ≥99.9%) and copper nitrate (Cu(NO3)2·3H2O, Aladdin, purity ≥99.5%) were dissolved in deionized water. The solution was placed in an oil bath and heated and stirred at 140℃ and 230 r / min. After the solution reacted for 0.5 h, oxalic acid (C2H2O4·2H2O, analytical grade) solution was added, and the solid content of the precursor solution was 24-28%. The solution was heated and stirred until it was completely evaporated in the oil bath to obtain the W-Cu precursor. The W-Cu precursor was then dried at 80℃ for 14 h. The dried W-Cu precursor was thoroughly ground and sieved through a 100 μm sieve. The W-Cu precursor was then subjected to hydrogen reduction. The W-Cu precursor was spread evenly in a sintering boat, which was then placed in a hydrogen reduction furnace. The hydrogen reduction furnace was then vacuum-treated, and hydrogen (hydrogen purity ≥ 99.999%, hydrogen flow rate 0.5 L / min) was introduced. The temperature was then increased to 950°C at 5°C / min and held at 950°C for 2 hours. The temperature was then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain W-Cu powder.
[0053] In step one, the amounts of copper nitrate and oxalic acid added are 62.21% and 40.43% of the mass of tungsten oxide, respectively.
[0054] Step 2: Molding without molding agent
[0055] Weigh 15g of the W-Cu powder from step one according to the required size of the pressed sample and place it into a steel mold. The medium-cold pressing process is performed with a pressing pressure of 200-220 MPa, which is maintained for 3 minutes to obtain a green blank with a relative density of 63-65%. The pressure is then released to remove the W-Cu green blank block.
[0056] Step 3: High-temperature hydrogen sintering
[0057] The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified under high-temperature hydrogen sintering. The pressed W-Cu green body is placed in a tube furnace and hydrogen (hydrogen purity ≥99.999%, hydrogen flow rate 0.2 L / min) is introduced. The temperature is increased to 100℃ at 5℃ / min, then increased to 1000℃ at 10℃ / min, and finally increased to 1350℃ at 5℃ / min and held for 2 hours. After that, the temperature is reduced to 500℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block. Finally, the surface of the obtained block is polished with sandpaper of gradually increasing fineness (240 grit to 800 grit) to obtain the W-Cu composite material.
[0058] The W-Cu composite material obtained in this embodiment was prepared by solid-liquid doping co-precipitation method, with a relative density as high as 99.3%, a Vickers hardness as high as 305±10 Hv, and a coefficient of thermal expansion of 8.3×10⁻⁶. -6 K.
[0059] Example 4
[0060] A method for preparing a W-Cu composite material includes the following steps:
[0061] Step 1: Preparation of solid-solid doped co-precipitated W-Cu powder
[0062] A certain proportion of tungsten oxide (WO3, 0.1-0.5 μm, purity ≥99.9%) and copper oxide (CuO, 0.1-0.5 μm, purity ≥99.5%) were dissolved in deionized water. The solution was placed in an oil bath and heated and stirred at 140℃ and 230 r / min. After the solution reacted for 0.5 h, oxalic acid (C2H2O4·2H2O, analytical grade) solution was added, and the solid content of the precursor solution was 20-28%. The solution was heated and stirred until it was completely evaporated in the oil bath to obtain the W-Cu precursor. The W-Cu precursor was then dried at 80℃ for 14 h. The dried W-Cu precursor was thoroughly ground and sieved through a 100 μm sieve. The W-Cu precursor was then subjected to hydrogen reduction. The W-Cu precursor was spread evenly in a sintering boat, which was then placed in a hydrogen reduction furnace. The hydrogen reduction furnace was then vacuum-treated, and hydrogen (hydrogen purity ≥ 99.999%, hydrogen flow rate 0.5 L / min) was introduced. The temperature was then increased to 950°C at 5°C / min and held at 950°C for 2 hours. The temperature was then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain W-Cu powder.
[0063] In step one, the amounts of copper oxide and oxalic acid added are 20.49% and 40.43% of the mass of tungsten oxide, respectively.
[0064] Step 2: Molding without molding agent
[0065] Weigh 15g of the W-Cu powder from step one according to the required size of the pressed sample and place it into a steel mold. The medium-cold pressing process is performed with a pressing pressure of 200-220 MPa, which is maintained for 3 minutes to obtain a green blank with a relative density of 62-64%. The pressure is then released to remove the W-Cu green blank block.
[0066] Step 3: High-temperature hydrogen sintering
[0067] The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified under high-temperature hydrogen sintering. The pressed W-Cu green body is placed in a tube furnace and hydrogen (hydrogen purity ≥99.999%, hydrogen flow rate 0.2 L / min) is introduced. The temperature is increased to 100℃ at 5℃ / min, then increased to 1000℃ at 10℃ / min, and finally increased to 1350℃ at 5℃ / min and held for 2 hours. After that, the temperature is reduced to 500℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block. Finally, the surface of the obtained block is polished with sandpaper of gradually increasing fineness (240 grit to 800 grit) to obtain the W-Cu composite material.
[0068] The W-Cu composite material obtained in this embodiment was prepared by solid-solid doping co-precipitation method, with a relative density as high as 87.9%, a Vickers hardness as high as 281±10 Hv, and a coefficient of thermal expansion of 8.6×10⁻⁶. -6 K.
[0069] Figure 1 These are the XRD patterns of W-Cu powder after reduction in Examples 1, 2, and 3, where the W and Cu peaks are distinct and there are no impurity peaks.
[0070] Figure 2 a, b, and c are the SEM morphologies of W-Cu powder after reduction in Examples 1, 2, and 4, respectively, with the powder particle size reaching submicron.
[0071] Figure 3 a, b, c, and d are SEM images of the fracture surfaces of W-Cu composite materials prepared in Examples 1, 2, 3, and 4, respectively. It can be seen that the fracture surfaces exhibit dimple morphology and good interfacial bonding.
[0072] By comparison, it can be found that the W-Cu composite material prepared by solid-liquid doping co-precipitation method in Example 3 has the advantages of high purity, high hardness, high density and uniform composition.
[0073] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.
Claims
1. A method for preparing W-Cu composite materials by solid-liquid doping co-precipitation, characterized in that, The steps are as follows: Step 1: Preparation of W-Cu powder A certain proportion of ammonium metatungstate or tungsten oxide, copper nitrate or copper oxide, and oxalic acid are dissolved in deionized water, and the solid content of the precursor solution is controlled at 20%-30%. The solution is stirred and heated, and after the solution is completely evaporated, W-Cu precursor is prepared using a drying oven. Then, the W-Cu precursor is thoroughly ground, sieved, and reduced with hydrogen to obtain W-Cu powder. When choosing a combination of ammonium metatungstate and copper oxide, the amount of copper oxide added should be 15-20% of the mass of ammonium metatungstate, and the amount of oxalic acid added should be 35-40% of the mass of ammonium metatungstate. When choosing a combination of tungsten oxide and copper nitrate, the amount of copper nitrate added should be 58-63% of the mass of tungsten oxide, and the amount of oxalic acid added should be 38-43% of the mass of tungsten oxide. The hydrogen reduction step in step one is as follows: W-Cu precursor is spread evenly in a sintering boat, and then the sintering boat is placed in a hydrogen reduction furnace. The hydrogen reduction furnace is vacuum treated and then hydrogen is introduced. The temperature is then raised to 930-980℃ at 4-8℃ / min and held for 1-3 hours. The temperature is then lowered to 500℃ at 4-10℃ / min and then cooled to room temperature with the furnace to obtain W-Cu powder. Step 2: Molding without molding agent A certain amount of W-Cu powder prepared in step one is weighed according to the size requirements of the pressed sample and placed in a steel mold for cold pressing. Then the pressure is released and the W-Cu green block is taken out. Step 3: High-temperature hydrogen sintering The high-density green body obtained in step two, which has no forming agent and low pressing force, is densified at the same sintering temperature to obtain a W-Cu composite block; finally, the surface of the obtained block is polished to obtain the W-Cu composite material.
2. The method as described in claim 1, characterized in that, In step one, the stirring and heating temperature is 120-160℃, and the rotation speed is 150-250r / min.
3. The method as described in claim 1, characterized in that, In step one, after the solution has completely evaporated, the W-Cu precursor is prepared using a drying oven. The drying temperature is set to 80-100℃ and the drying time is 12-14h.
4. The method as described in claim 1, characterized in that, In step one, the mesh size of the sieve during grinding and sieving is 100-200μm.
5. The method as described in claim 1, characterized in that, In step two, the pressing pressure selected for cold pressing is 200-220 MPa, and the pressure is maintained for 2-4 minutes to obtain a green body with a relative density of 60-68%.
6. The method as described in claim 1, characterized in that, The sintering densification process in step three is as follows: the pressed W-Cu green block is placed in a tube furnace and hydrogen is introduced. The temperature is increased to 100°C at 5°C / min, then increased to 1000°C at 5-10°C / min, and finally increased to 1350°C at 5°C / min and held for 1-3 hours. The temperature is then reduced to 500°C at 5°C / min and then cooled to room temperature with the furnace to obtain the W-Cu composite block.