A method for preparing a high-performance W-Cu composite material doped with HfO2
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI UNIV OF TECH
- Filing Date
- 2024-02-17
- Publication Date
- 2026-07-21
Smart Images
Figure CN118048547B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rare earth oxide-doped W-Cu composite material preparation technology, specifically to a method for preparing a high-performance W-Cu composite material doped with HfO2. Background Technology
[0002] In recent decades, metal matrix composites have attracted widespread attention in high-tech fields such as microelectronics, aerospace, and military engineering due to their excellent comprehensive properties. Among them, the emerging W-Cu composite material combines the unique performance advantages of W and Cu, and often exhibits good mechanical and electrical properties by changing the composition ratio of W and Cu elements and adjusting the microstructure.
[0003] Currently, W-Cu composites occupy an important position among metal matrix composites, and are widely used as electrical contact materials in high-voltage vacuum switches, and as electronic packaging materials and heat sink materials in large-scale integrated circuits and high-power heat dissipation devices. In these applications, the performance requirements for W-Cu composites are gradually increasing. Based on most current research findings, the main research direction for W-Cu composites is to pursue higher density and more uniform microstructure to achieve better overall performance.
[0004] Powder metallurgy, as a key technology for preparing W-Cu composites, lies in obtaining W-Cu composite powders with uniformly distributed fine W particles. Methods for preparing nano-W-Cu composite powders have been reported by most research institutes both domestically and internationally. The most commonly used methods include mechanical alloying, sol-gel method, co-precipitation method, and spray drying. Mechanical alloying easily introduces other impurity elements and the resulting powder is prone to agglomeration. The wet chemical method achieves uniform distribution of the two metal phases in the W-Cu composite powder through uniform mixing of salt solutions. It also requires lower reaction temperatures, is simpler to operate, and has higher production efficiency. W-Cu composite powders with uniform composition and small particle size prepared by this technology hold promise for industrial production in the future.
[0005] However, wet chemical methods result in problems such as tungsten (W) particle agglomeration and growth, and microstructure inhomogeneity during sintering. Generally, the smaller the grain size of W-Cu composite powder, the higher its sintering activity. Therefore, preparing ultrafine W-Cu powder with high sintering activity is crucial. Recent studies have mostly focused on adding thermally stable rare earth oxides as dispersing reinforcing phases to suppress disordered agglomeration and growth of powder particles, thereby refining the grain size of W-Cu composites. This is of great significance for improving the mechanical properties of W-Cu composites and broadening their application range. Summary of the Invention
[0006] To solve the above-mentioned technical problems, this invention uses spray drying and adds oxalic acid as a process control agent to synthesize W-Cu precursors with different contents of rare earth oxide HfO2. Then, W-Cu composite powder with uniform composition distribution is produced by hydrogen reduction. Finally, W-Cu composite material with low W-W connectivity, more uniform microstructure, high density, high hardness, and high flexural strength is prepared by high-temperature hydrogen sintering.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] A method for preparing a high-performance W-Cu composite material doped with HfO2 is disclosed. First, a wet chemical method is used, and oxalic acid is added as a precipitant to create an acidic environment in the precursor solution. This allows the oxalic acid to fully react with ammonium metatungstate, copper nitrate trihydrate, and hafnium tetrachloride, thereby improving the performance of the spherical precursor prepared by spray drying. This improves the compositional uniformity of the W-Cu composite powder after hydrogen reduction. During hydrogen reduction, HfO2 second-phase particles are successfully and uniformly dispersed into the W-Cu composite powder. Then, high-temperature hydrogen sintering promotes the full and uniform distribution of fine HfO2 particles in the W-Cu composite material, effectively suppressing the agglomeration and growth of W particles on the surface and in the W / Cu interface gaps, reducing the connectivity of W and W, and resulting in a W-Cu composite material exhibiting high overall performance.
[0009] As a preferred technical solution of the present invention, the specific steps of the preparation method are as follows:
[0010] Step 1: Preparation of HfO2-doped W-Cu precursor
[0011] A certain proportion of ammonium metatungstate, copper nitrate trihydrate, and hafnium tetrachloride were dissolved in deionized water and poured into a glass reactor. The solution was mixed evenly by stirring with an electric rod and sonicating with an ultrasonic rod. Then, oxalic acid was added as a precipitant to allow the solution to react in an acidic environment. The entire process was carried out at an oil bath temperature of 120℃ for 6 hours, and the solid content of the precursor solution was 20%-36%. Subsequently, the mixed solution was sent to the atomizer of the spray drying tower by a peristaltic pump for spray drying. The spray drying parameters were set as follows: inlet air temperature 230-250℃, atomizer speed 22000 r / min.
[0012] In step one, the amounts of copper nitrate trihydrate, oxalic acid, and hafnium tetrachloride added are 89.76%, 24.06%, and 0.70-1.42% of the mass of ammonium metatungstate, respectively.
[0013] Step 2: Preparation of HfO2-doped W-Cu composite bulk material
[0014] The W-Cu precursor was then reduced with hydrogen. The W-Cu precursor was spread evenly in a sintering boat and heated to 900℃ in a hydrogen atmosphere in a pusher-type reduction furnace and held for 2 hours. The sintering boat was then removed and cooled to room temperature to obtain HfO2-doped W-Cu composite powder. The HfO2-doped W-Cu composite powder was sieved through a 100-mesh sieve, and 15-20g of the sieved powder was weighed and placed in a steel mold for molding. The selected pressing pressure was 400MPa, and the pressure was maintained for 2-4 minutes. Then the pressure was released and the HfO2-doped W-Cu green block was taken out.
[0015] Step 3: High-temperature hydrogen sintering
[0016] The pressed block was sintered with hydrogen at high temperature. The block was laid flat in a sintering boat, which was then placed in a tube furnace. The tube furnace was evacuated, and then hydrogen was introduced. The temperature was then increased to 1250-1400℃ at 5-10℃ / min and held for 1-2 hours. The temperature was then reduced to 480-520℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain a W-Cu composite material with HfO2 doping and a certain strength.
[0017] The HfO2-doped W-Cu composite material obtained by the present invention using a wet chemical method combined with high-temperature hydrogen sintering has the following advantages:
[0018] 1. Uniformly distributed W-Cu precursor with small particle size: By adding oxalic acid as a precipitant to make the precursor solution acidic, the oxalic acid reacts fully with ammonium metatungstate, copper nitrate trihydrate and hafnium tetrachloride. The precursor is then prepared by spray drying technology to obtain a spherical W-Cu precursor with uniformly distributed composition and small particle size.
[0019] 2. Uniform distribution of HfO2 second-phase particles: By reducing the W-Cu precursor with hydrogen, the HfO2 second-phase particles were successfully and uniformly introduced into the W-Cu composite powder during the reduction process, which is beneficial to suppress the growth of W grains during the subsequent high-temperature sintering process.
[0020] 3. Reduced connectivity of WW: High-temperature liquid-phase sintering promotes the full and uniform distribution of fine HfO2 particles in the W-Cu composite material, effectively suppressing the agglomeration and growth of W particles on the surface of W particles and in the gaps between W / Cu interfaces, thus reducing the connectivity of WW. The average grain size of the composite material is 0.5-1.2 μm, with a uniform microstructure, enhancing the bonding force between the phases. The fine HfO2 particles are more difficult to detach than W particles, thereby increasing the fracture strength of the W-Cu composite material.
[0021] 4. The HfO2-doped W-Cu composite material exhibits high comprehensive performance: After testing, the relative density of the HfO2-doped W-Cu composite material after high-temperature sintering reached 97.74%, the maximum Vickers hardness reached 338 HV, the flexural strength reached 826 MPa, and the thermal conductivity was 209 W / (m·K). Attached Figure Description
[0022] Figure 1 a, b, and c are SEM images of the W-Cu composite powders doped with HfO2 in Examples 2 and 3, and undoped with HfO2 in Example 1, respectively; d is the EDS energy spectrum of the W-Cu composite powder doped with HfO2 in Example 2.
[0023] Figure 2 a and b are scanning electron microscope images of the fracture surfaces of W-Cu composite materials doped with HfO2 in Examples 2 and 3, respectively.
[0024] Figure 3 a and b are scanning electron microscope images of the W-Cu composite material without doping in Example 1 and with HfO2 doping in Example 2, respectively.
[0025] Figure 4 The hardness of the W-Cu composite materials doped with HfO2 in Examples 2 and 3 and undoped with HfO2 in Example 1 is given.
[0026] Figure 5 The relative densities are those of the W-Cu composite materials doped with HfO2 in Examples 2 and 3 and undoped with HfO2 in Example 1.
[0027] Figure 6 The bending strength of the W-Cu composite materials doped with HfO2 in Examples 2 and 3 and undoped with HfO2 in Example 1 is given. 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 high-performance W-Cu composite material includes the following steps.
[0031] Step 1: Preparation of W-Cu precursor
[0032] A certain proportion of ammonium metatungstate (AMT, Aladdin, purity ≥99.95%) and copper nitrate trihydrate (Cu(NO3)2·3H2O, Aladdin, purity ≥99.5%) were dissolved in deionized water and poured into a glass reactor. The solutions were mixed uniformly by stirring with an electric stirrer and sonicating with an ultrasonic stirrer. Then, oxalic acid (C2H2O4·2H2O, analytical grade) was added as a precipitant to allow the solution to react in an acidic environment. The entire process was carried out at an oil bath temperature of 120℃ for 6 hours, and the solid content of the precursor solution was 30%. Subsequently, the mixed solution was sent to the atomizer of the spray drying tower by a peristaltic pump for spray drying. The spray drying parameters were set as follows: inlet air temperature 250℃, atomizer speed 22000 r / min.
[0033] In step one, the amounts of copper nitrate trihydrate and oxalic acid added are 89.76% and 24.06% of the mass of ammonium metatungstate, respectively.
[0034] Step 2: Preparation of W-Cu composite bulk material
[0035] The W-Cu precursor was then reduced with hydrogen. The W-Cu precursor was spread evenly in a burning boat and reduced in a pusher-type furnace under a hydrogen atmosphere (hydrogen purity ≥ 99.999%, hydrogen flow rate 8 m³ / s). 3 The furnace temperature was raised to 900℃ and held for 2 hours. The furnace was then removed and cooled to room temperature to obtain W-Cu composite powder. The W-Cu composite powder was sieved through a 100-mesh sieve, and 15g of the sieved powder was weighed and placed into a steel mold. The medium-pressure molding process was carried out with a selected pressing pressure of 400 MPa, which was maintained for 2 minutes. Then the pressure was released and the W-Cu green block was removed.
[0036] Step 3: High-temperature hydrogen sintering
[0037] The pressed blocks are sintered with hydrogen at high temperature. The blocks are laid flat in a firing boat, which is then placed in a tube furnace. The tube furnace is evacuated, and then hydrogen gas (hydrogen purity ≥ 99.999%, hydrogen flow rate 2 m³ / h) is introduced. 3 The temperature is increased to 1400℃ at 10℃ / min and held for 1 hour. Then the temperature is decreased to 500℃ at 5℃ / min and then cooled to room temperature in the furnace to obtain a W-Cu composite material with a certain strength.
[0038] Example 2
[0039] A method for preparing a high-performance W-Cu composite material doped with HfO2 includes the following steps:
[0040] Step 1: Preparation of HfO2-doped W-Cu precursor
[0041] A certain proportion of ammonium metatungstate (AMT, Aladdin, purity ≥99.95%), copper nitrate trihydrate (Cu(NO3)2·3H2O, Aladdin, purity ≥99.5%), and hafnium tetrachloride (HfCl4, analytical grade) were dissolved in deionized water and poured into a glass reactor. The solutions were mixed uniformly by electric stirring and ultrasonication. Then, oxalic acid (C2H2O4·2H2O, analytical grade) was added as a precipitant to allow the solution to react in an acidic environment. The entire process was carried out at an oil bath temperature of 120℃ for 6 hours, and the solid content of the precursor solution was 30%. Subsequently, the mixed solution was sent to the atomizer of the spray drying tower by a peristaltic pump for spray drying. The spray drying parameters were set as follows: inlet air temperature 250℃, atomizer speed 22000 r / min.
[0042] In step one, the amounts of copper nitrate trihydrate, oxalic acid, and hafnium tetrachloride added are 89.76%, 24.06%, and 0.70% of the mass of ammonium metatungstate, respectively.
[0043] Step 2: Preparation of HfO2-doped W-Cu composite bulk material
[0044] The W-Cu precursor was then reduced with hydrogen. The W-Cu precursor was spread evenly in a burning boat and reduced in a pusher-type furnace under a hydrogen atmosphere (hydrogen purity ≥ 99.999%, hydrogen flow rate 8 m³ / s). 3 The furnace temperature was raised to 900℃ and held for 2 hours. The furnace was then removed and cooled to room temperature to obtain HfO2-doped W-Cu composite powder. The HfO2-doped W-Cu composite powder was sieved through a 100-mesh sieve, and 15g of the sieved powder was weighed and placed into a steel mold. The medium-pressure molding process was carried out at a pressure of 400 MPa, which was maintained for 2 minutes. Then the pressure was released to remove the W-Cu green block doped with HfO2.
[0045] Step 3: High-temperature hydrogen sintering
[0046] The pressed blocks are sintered with hydrogen at high temperature. The blocks are laid flat in a firing boat, which is then placed in a tube furnace. The tube furnace is evacuated, and then hydrogen gas (hydrogen purity ≥ 99.999%, hydrogen flow rate 2 m³ / h) is introduced. 3 The temperature is increased to 1400℃ at 10℃ / min and held for 1 hour. Then the temperature is decreased to 500℃ at 5℃ / min and then cooled to room temperature in the furnace to obtain a W-Cu composite material with HfO2 doping with a certain strength.
[0047] Example 3
[0048] A method for preparing a high-performance W-Cu composite material doped with HfO2 includes the following steps:
[0049] Step 1: Preparation of HfO2-doped W-Cu precursor
[0050] A certain proportion of ammonium metatungstate (AMT, Aladdin, purity ≥99.95%), copper nitrate trihydrate (Cu(NO3)2·3H2O, Aladdin, purity ≥99.5%), and hafnium tetrachloride (HfCl4, analytical grade) were dissolved in deionized water and poured into a glass reactor. The solutions were mixed uniformly by electric stirring and ultrasonication. Then, oxalic acid (C2H2O4·2H2O, analytical grade) was added as a precipitant to allow the solution to react in an acidic environment. The entire process was carried out at an oil bath temperature of 120℃ for 6 hours, and the solid content of the precursor solution was 30%. Subsequently, the mixed solution was sent to the atomizer of the spray drying tower by a peristaltic pump for spray drying. The spray drying parameters were set as follows: inlet air temperature 250℃, atomizer speed 22000 r / min.
[0051] In step one, the amounts of copper nitrate trihydrate, oxalic acid, and hafnium tetrachloride added are 89.76%, 24.06%, and 1.42% of the mass of ammonium metatungstate, respectively.
[0052] Step 2: Preparation of HfO2-doped W-Cu composite bulk material
[0053] The W-Cu precursor was then reduced with hydrogen. The W-Cu precursor was spread evenly in a burning boat and reduced in a pusher-type furnace under a hydrogen atmosphere (hydrogen purity ≥ 99.999%, hydrogen flow rate 8 m³ / s). 3 The furnace temperature was raised to 900℃ and held for 2 hours. The furnace was then removed and cooled to room temperature to obtain HfO2-doped W-Cu composite powder. The HfO2-doped W-Cu composite powder was sieved through a 100-mesh sieve, and 15g of the sieved powder was weighed and placed into a steel mold. The medium-pressure molding process was carried out at a pressure of 400 MPa, which was maintained for 2 minutes. Then the pressure was released to remove the W-Cu green block doped with HfO2.
[0054] Step 3: High-temperature hydrogen sintering
[0055] The pressed blocks are sintered with hydrogen at high temperature. The blocks are laid flat in a firing boat, which is then placed in a tube furnace. The tube furnace is evacuated, and then hydrogen gas (hydrogen purity ≥ 99.999%, hydrogen flow rate 2 m³ / h) is introduced. 3 The temperature is increased to 1400℃ at 10℃ / min and held for 1 hour. Then the temperature is decreased to 500℃ at 5℃ / min and then cooled to room temperature in the furnace to obtain a W-Cu composite material with HfO2 doping with a certain strength.
[0056] Figure 1The images show scanning electron microscope (SEM) images of the morphology of W-Cu composite powders in Example 1 (undoped) and Examples 2 and 3 (doped with HfO2), and an EDS (energy dispersive spectroscopy) image of the W-Cu composite powder in Example 2 (doped with HfO2). The surface of the doped W-Cu composite powder has fine, bright phase particles attached. With increasing doping concentration, the bright phase gradually increases and is uniformly and diffusely distributed on the surface of the matrix phase. Comparison of SEM images at the same magnification shows that the W-Cu powder doped with HfO2 particles contains more fine particles, which are more widely distributed than the undoped powder. EDS analysis of the SEM images reveals the presence of W, Cu, Hf, and O elements.
[0057] Figure 2 a and b are scanning electron microscope images of the fracture surfaces of the HfO2-doped W-Cu composite materials in Examples 2 and 3, respectively. Small HfO2 particles are present on the surface of W particles, at the W / Cu interface, and encapsulated by the Cu network. This presence can block the contact between W and W, reduce W / Cu connectivity, result in a uniform microstructure, and enhance the bonding force between the phases. The small size of the HfO2 particles makes them more difficult to detach than W particles, thus increasing the fracture strength of the W-Cu composite.
[0058] Figure 3 a and b are scanning electron microscope images of the undoped W-Cu composite material in Example 1 and the HfO2-doped W-Cu composite material in Example 2, respectively. The comparison revealed that the W-Cu composite material doped with HfO2 exhibited reduced W-W connectivity. This is because the uniform distribution of HfO2 particles during sintering inhibited the coarsening of W grains, making W-W contact difficult and reducing W-W connectivity.
[0059] Figure 4 , 5 Figures 6 and 7 represent the hardness, relative density, and flexural strength of the HfO2-doped W-Cu composites in Examples 2 and 3, and the undoped W-Cu composites in Example 1, respectively. As shown in the figures, the undoped W-Cu composite prepared in Example 1 has a relative density of 97.17%, a Vickers hardness of 303 HV, and a flexural strength of 747 MPa. The HfO2-doped W-Cu composite prepared in Example 2 has a relative density of 97.74%, a Vickers hardness of 338 HV, and a flexural strength of 826 MPa. The HfO2-doped W-Cu composite prepared in Example 3 has a relative density of 96.82%, a Vickers hardness of 323 HV, and a flexural strength of 793 MPa. Therefore, the HfO2-doped W-Cu composites exhibit higher overall performance.
[0060] 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 a high-performance W-Cu composite material doped with HfO2, characterized in that, First, a wet chemical method was used, and oxalic acid was added as a precipitant to create an acidic environment in the precursor solution. This allowed the oxalic acid to fully react with ammonium metatungstate, copper nitrate trihydrate, and hafnium tetrachloride, thereby improving the properties of the spherical precursor prepared by spray drying. This improved the compositional uniformity of the W-Cu composite powder after hydrogen reduction. During the hydrogen reduction process, HfO2 second-phase particles were successfully and uniformly dispersed into the W-Cu composite powder. Then, high-temperature hydrogen sintering was used to promote the full and uniform distribution of fine HfO2 particles in the W-Cu composite material. This effectively suppressed the agglomeration and growth of W particles on the surface of W particles and in the gaps between W and Cu, reducing the connectivity of W and Cu. As a result, the prepared W-Cu composite material exhibited higher overall performance. The specific steps are as follows: Step 1: Preparation of HfO2-doped W-Cu precursor A certain proportion of ammonium metatungstate, copper nitrate trihydrate, and hafnium tetrachloride were dissolved in deionized water and poured into a glass reactor. The solution was mixed evenly by stirring with an electric rod and sonicating with an ultrasonic rod. Then, oxalic acid was added as a precipitant to allow the solution to react in an acidic environment. The entire process was carried out at an oil bath temperature of 120℃ for 6 hours, and the solid content of the precursor solution was 20%-36%. Subsequently, the mixed solution was sent to the atomizer of the spray drying tower by a peristaltic pump for spray drying. The spray drying parameters were set as follows: inlet air temperature 230-250℃, atomizer speed 22000 r / min. In step one, the amounts of copper nitrate trihydrate, oxalic acid, and hafnium tetrachloride added are 89.76%, 24.06%, and 0.70-1.42% of the mass of ammonium metatungstate, respectively. Step 2: Preparation of HfO2-doped W-Cu composite bulk The W-Cu precursor was then reduced with hydrogen. The W-Cu precursor was spread evenly in a sintering boat and heated to 900℃ in a hydrogen atmosphere in a pusher-type reduction furnace and held for 2 hours. The sintering boat was then removed and cooled to room temperature to obtain HfO2-doped W-Cu composite powder. The HfO2-doped W-Cu composite powder was sieved through a 100-mesh sieve, and 15-20g of the sieved powder was weighed and placed in a steel mold for molding. The selected pressing pressure was 400MPa, and the pressure was maintained for 2-4 minutes. Then the pressure was released and the HfO2-doped W-Cu green block was taken out. Step 3: High-temperature hydrogen sintering The pressed block was sintered with hydrogen at high temperature. The block was laid flat in a sintering boat, which was then placed in a tube furnace. The tube furnace was evacuated, and then hydrogen was introduced. The temperature was then increased to 1250-1400℃ at 5-10℃ / min and held for 1-2 hours. The temperature was then reduced to 480-520℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain a W-Cu composite material with HfO2 doping and a certain strength.
2. The high-performance W-Cu composite material doped with HfO2 prepared by the method described in claim 1, characterized in that, The average grain size of the composite material is 0.5-1.2 μm.