High-uniformity rare earth oxide doped tungsten material and preparation method and application thereof
By employing steps such as pressing, hydrogen sintering, rare earth salt solution impregnation, and freeze drying, the uniformity and controllability issues of rare earth oxide-doped tungsten materials were resolved. This resulted in highly uniform dispersion and precise doping of rare earth oxides, improving the mechanical properties and purity of the materials, making them suitable for extreme working conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-20
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies for preparing rare earth oxide-doped tungsten materials suffer from poor uniformity, low controllability, and impurity contamination, making it difficult to achieve highly uniform dispersion of the rare earth phase and precise control of the doping amount.
By employing pressing molding, sintering under hydrogen atmosphere, pressurized impregnation with rare earth salt solution, freeze drying, and reduction densification sintering, and by accurately calculating the concentration of rare earth salt solution and controlling process parameters, highly uniform dispersion of rare earth oxides and precise control of doping amount can be achieved.
This study achieves highly dispersed distribution of rare earth oxides at the nano/submicron scale in tungsten materials, improving the room temperature toughness and high temperature strength of the materials, avoiding pollution and energy consumption problems during long-term mechanical alloying processes, and meeting the performance requirements of extreme working conditions.
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Figure CN121780923A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of refractory metal composite material preparation technology, specifically relating to a highly uniform rare earth oxide-doped tungsten material, its preparation method, and its application. Background Technology
[0002] Tungsten and tungsten alloys are widely used in high-end fields such as military, aerospace, nuclear industry, and electronic information due to their high melting point, high density, high thermal conductivity, and good high-temperature strength. However, pure tungsten has disadvantages such as high room temperature brittleness, low recrystallization temperature, and rapid grain growth at high temperatures, which seriously limit its reliability and service life. Doping with rare earth oxides is an effective way to improve the performance of tungsten materials. Rare earth oxides can pin grain boundaries and refine grains, significantly improving the recrystallization temperature, high-temperature strength, and creep resistance of the material. Currently, the mainstream method for preparing rare earth oxide-doped tungsten materials is mechanical alloying, which involves long-term ball milling and mixing of tungsten powder with rare earth oxide powder or rare earth precursor salts, followed by molding and sintering. However, this method has obvious drawbacks: 1. Poor uniformity: Mechanical mixing makes it difficult to achieve uniform dispersion at the nanoscale, easily leading to component segregation and rare earth phase agglomeration; 2. Low controllability: Component separation easily occurs during mixing and molding, resulting in large fluctuations in the composition of the final product; 3. Introduction of impurities: Long-term ball milling easily introduces contamination into the grinding balls and the jar, and is energy-intensive and inefficient. Therefore, developing a preparation method that can achieve highly uniform dispersion of rare earth phases, precise control of doping amount and simple process has become an urgent technical problem to be solved in this field. Summary of the Invention
[0003] The purpose of this invention is to provide a highly uniform rare-earth oxide-doped tungsten material, its preparation method, and its applications. The preparation method provided by this invention can achieve highly uniform dispersion of the rare-earth phase, precise and controllable doping amount, and is simple in process.
[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a highly uniform rare-earth oxide-doped tungsten material, comprising the following steps: (1) Tungsten powder is pressed into shape to obtain a blank; (2) The blank obtained in step (1) is sintered in a hydrogen atmosphere to obtain a foamed tungsten skeleton; (3) The foamed tungsten skeleton obtained in step (2) is impregnated under pressure in a rare earth salt solution and then freeze-dried to obtain a rare earth-doped foamed tungsten skeleton. The concentration of the rare earth salt solution is calculated according to Formula I: Formula I, In Equation I, y represents the mass of rare earth salt corresponding to the target doping amount of rare earth oxide in the highly uniform rare earth oxide-doped tungsten material; V 通孔 The volume of the through-holes in the tungsten foam skeleton; (4) The rare earth doped foam tungsten skeleton obtained in step (3) is successively reduced and densified by sintering to obtain a highly uniform rare earth oxide doped tungsten material.
[0005] Preferably, the sintering temperature in step (2) is 1200~1700℃, and the sintering holding time is 60~180min.
[0006] Preferably, in step (2), the total porosity of the foamed tungsten skeleton is 12-45%, and the open porosity of the foamed tungsten skeleton accounts for more than 95% of the total porosity.
[0007] Preferably, the rare earth salt in the rare earth salt solution in step (3) includes one or more of rare earth nitrates, rare earth acetates and rare earth hydrochlorides; the rare earths in the rare earth salt include one or more of La, Y, Ce and Gd.
[0008] Preferably, the pressure for pressure impregnation in step (3) is 1~10MPa, and the pressure holding time for pressure impregnation is 30~60min.
[0009] Preferably, in step (3), the freeze-drying temperature is ≤-30℃, the freeze-drying time is 12~48h, and the freeze-drying vacuum degree is ≤10Pa.
[0010] Preferably, the reduction temperature in step (4) is 500~1000℃, and the reduction holding time is 1~5h.
[0011] Preferably, the densification sintering temperature in step (4) is 2200~2400℃, and the densification sintering holding time is 1~4h.
[0012] The present invention also provides a highly uniform rare earth oxide-doped tungsten material prepared by the preparation method described in the above technical solution.
[0013] The present invention also provides the application of the highly uniform rare earth oxide-doped tungsten material described above in the preparation of diamond tungsten wire, rare earth tungsten electrodes, radiation shielding and heat load resistant components for nuclear fusion devices, high-temperature components for aerospace engines, and semiconductor heat treatment furnace devices.
[0014] This invention provides a method for preparing a highly uniform rare earth oxide-doped tungsten material, comprising the following steps: (1) pressing tungsten powder into a blank; (2) sintering the blank obtained in step (1) under a hydrogen atmosphere to obtain a foamed tungsten skeleton; (3) impregnating the foamed tungsten skeleton obtained in step (2) under pressure in a rare earth salt solution, and then freeze-drying it to obtain a rare earth-doped foamed tungsten skeleton; the concentration of the rare earth salt solution is calculated according to formula I: Formula I, In Equation I, y represents the mass of rare earth salt corresponding to the target doping amount of rare earth oxide in the highly uniform rare earth oxide-doped tungsten material; V 通孔 (3) The volume of the through holes in the foamed tungsten skeleton; (4) The rare earth doped foamed tungsten skeleton obtained in step (3) is successively reduced and densified by sintering to obtain a highly uniform rare earth oxide doped tungsten material. The present invention accurately calculates and controls the concentration of rare earth salt solution based on the volume of the through holes in the foamed tungsten skeleton and the target rare earth oxide doping amount, which can achieve precise and linear control of rare earth doping amount. The composition control is simple and reliable. By freeze drying, the composition migration in the conventional drying process is avoided, and the initial uniform distribution of rare earth at the atomic level is achieved. After subsequent sintering, the rare earth oxides in the final material are highly dispersed at the nano / submicron scale, strongly pinning the grain boundaries and obtaining an ultrafine grain structure. Thus, the material has excellent room temperature toughness, high temperature strength and extremely high recrystallization temperature. It avoids the long mechanical alloying process, has low energy consumption and high efficiency, and avoids the pollution caused by ball milling. The product has high purity, and the prepared material can meet the stringent requirements of extreme working conditions such as diamond wire tungsten wire, high-performance electrode, and nuclear fusion reactor for material performance. Attached Figure Description
[0015] Figure 1 A process flow diagram of the preparation method of highly uniform rare earth oxide-doped tungsten material provided by the present invention; Figure 2 This is a schematic diagram of the pore structure of the foamed tungsten skeleton prepared according to the present invention; Figure 3 The image shows the morphology of the lanthanum oxide-doped tungsten material prepared in Example 1. Figure 4 The image shows the morphology of the lanthanum oxide-doped tungsten material prepared in Example 2. Figure 5 This is a morphology diagram of the yttrium oxide-doped tungsten material prepared in Example 3. Detailed Implementation
[0016] This invention provides a method for preparing a highly uniform rare-earth oxide-doped tungsten material, comprising the following steps: (1) Tungsten powder is pressed into shape to obtain a blank; (2) The blank obtained in step (1) is sintered in a hydrogen atmosphere to obtain a foamed tungsten skeleton; (3) The foamed tungsten skeleton obtained in step (2) is impregnated under pressure in a rare earth salt solution and then freeze-dried to obtain a rare earth-doped foamed tungsten skeleton. The concentration of the rare earth salt solution is calculated according to Formula I: Formula I, In Equation I, y represents the mass of rare earth salt corresponding to the target doping amount of rare earth oxide in the highly uniform rare earth oxide-doped tungsten material; V 通孔 The volume of the through-holes in the tungsten foam skeleton; (4) The rare earth doped foam tungsten skeleton obtained in step (3) is successively reduced and densified by sintering to obtain a highly uniform rare earth oxide doped tungsten material.
[0017] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.
[0018] This invention involves pressing tungsten powder into a blank.
[0019] In one embodiment, the tungsten powder can have a mesh size of 150-325 mesh or 150-250 mesh; the tungsten powder has a density of D... 10 It can be 0.8μm, D 50 It can be 1μm, D 90 The particle size can be 1.1 μm. The tungsten powder of the above particle size used in this invention has a more uniform particle size, which is more conducive to forming the foam tungsten skeleton with the required total porosity and open porosity in the subsequent process.
[0020] When the particle size of the tungsten powder is not within the above-mentioned range, the present invention preferably involves sequentially crushing and sieving the tungsten powder to obtain tungsten powder of the desired particle size. The present invention does not impose any special limitations on the crushing and sieving operations; any technical solution well-known to those skilled in the art can be used to ensure that the particle size of the tungsten powder is within the desired range.
[0021] In this invention, the compression molding is preferably die molding or isostatic pressing; the pressure of the die molding is preferably 240~320MPa; the holding time of the die molding is preferably 5~20s; the pressure of the isostatic pressing is preferably 200~220MPa; and the holding time of the isostatic pressing is preferably 2~5min.
[0022] In one embodiment, the compression molding is performed in a rubber mold. The present invention does not impose any special limitations on the shape and size of the blank; it can be determined according to actual needs.
[0023] After obtaining the blank, the present invention sintersulates the blank in a hydrogen atmosphere to obtain a foamed tungsten skeleton.
[0024] In this invention, the sintering temperature is preferably 1200~1700℃; the sintering holding time is preferably 60~180min. As one embodiment, the sintering temperature can specifically be 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1520℃, 1550℃, 1600℃, 1650℃, or 1700℃; the sintering holding time can specifically be 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, or 180min. This invention, by performing incomplete sintering of the green body at the above temperatures and times, can obtain a three-dimensional foamed tungsten skeleton with the desired total porosity and extremely high through-porosity, providing channels and containers for the subsequent uniform impregnation of rare earth salt solutions.
[0025] After sintering, the present invention preferably cools the sintered product to obtain a foamed tungsten skeleton.
[0026] The present invention does not impose any special limitations on the cooling operation; any cooling technique known to those skilled in the art can be used to cool the material to room temperature.
[0027] In this invention, the total porosity of the tungsten foam skeleton is preferably 12-45%; the open porosity of the tungsten foam skeleton is preferably more than 95% of the total porosity. As one embodiment, the total porosity of the tungsten foam skeleton can specifically be 12%, 13%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 27%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 42.3%, 44%, or 45%; the open porosity of the tungsten foam skeleton can be 95%, 96%, 97%, 98%, or 99% of the total porosity.
[0028] After obtaining the foamed tungsten skeleton, the present invention impregnates the foamed tungsten skeleton under pressure in a rare earth salt solution, and then freeze-dries it to obtain a rare earth-doped foamed tungsten skeleton.
[0029] In this invention, the rare earth salt in the rare earth salt solution preferably includes one or more of rare earth nitrates, rare earth acetates, and rare earth hydrochlorides; the rare earth elements in the rare earth salt preferably include one or more of La, Y, Ce, and Gd. As one embodiment, the rare earth salt may specifically be lanthanum nitrate hexahydrate or yttrium nitrate hexahydrate.
[0030] In this invention, the solvent in the rare earth salt solution is preferably high-purity water.
[0031] In this invention, the concentration of the rare earth salt solution is calculated according to Formula I: Formula I, In Equation I, y represents the mass of rare earth salt corresponding to the target doping amount of rare earth oxide in the highly uniform rare earth oxide-doped tungsten material; V 通孔 Let V be the volume of the through-holes in the tungsten foam skeleton.
[0032] In this invention, the V 通孔 =V 孔 ×P 通孔 Among them, V 孔 The total pore volume of the foamed tungsten skeleton is in cm³. 3 ;P 通孔 , where represents the porosity of the foamed tungsten skeleton.
[0033] In this invention, the V 孔 =V 泡沫钨骨架 ×P 总孔 V 泡沫钨骨架 Let be the geometric volume of the foamed tungsten skeleton, in cm. 3 ;P 总孔 is the total porosity of the foamed tungsten skeleton, %.
[0034] In this invention, the volume V of the foamed tungsten skeleton 钨 =V 泡沫钨骨架 -V 孔 .
[0035] In this invention, the mass m of the foamed tungsten skeleton 钨 =ρ 钨 ×V 钨 , where ρ 钨 The density of tungsten is 19.35 g / cm³. 3 .
[0036] This invention calculates the mass x of rare earth oxides based on the target doping amount of rare earth oxides in rare earth oxide-doped tungsten materials, and then calculates the mass y of rare earth salts based on the mass x of rare earth oxides.
[0037] In this invention, the mass x of the rare earth oxide is calculated according to Formula II: Formula II.
[0038] In this invention, the mass y of the rare earth salt is calculated according to formula III: Formula III.
[0039] This invention allows for precise calculation and control of the concentration of rare earth salt solution based on the pore volume of the foamed tungsten skeleton and the target rare earth oxide doping amount, enabling precise and linear control of the rare earth doping amount, and providing simple and reliable composition control.
[0040] The present invention does not have a special limitation on the amount of rare earth salt solution used, as long as the rare earth salt solution can submerge the foamed tungsten skeleton and completely fill the through holes of the foamed tungsten skeleton.
[0041] In this invention, the pressure of the pressure impregnation is preferably 1~10 MPa; the holding time of the pressure impregnation is preferably 30~60 min. As one embodiment, the pressure of the pressure impregnation can specifically be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, or 10 MPa; the holding time of the pressure impregnation can specifically be 30 min, 40 min, 50 min, or 60 min. This invention, by performing pressure impregnation and controlling the pressure and time of the pressure impregnation, can force the rare earth salt solution into the through-holes of the foamed tungsten skeleton, ensuring that the through-holes are completely filled.
[0042] In one embodiment, the pressure impregnation is carried out in a pressure impregnation apparatus. Preferably, the pressure impregnation apparatus is evacuated before the rare earth salt solution is added and pressure impregnation is performed.
[0043] After pressure impregnation is completed, the present invention preferably removes the pressure-impregnated foam tungsten skeleton, then freezes it in liquid nitrogen, and then freeze-dries it.
[0044] In this invention, the freezing time in liquid nitrogen is preferably 5 to 30 minutes.
[0045] In this invention, the freeze-drying temperature is preferably ≤-30℃; the freeze-drying time is preferably 12~48h; and the freeze-drying vacuum degree is preferably ≤10Pa. As one embodiment, the freeze-drying temperature can specifically be -30℃, -40℃, -50℃, -60℃, -70℃, -80℃, -90℃, or -100℃; and the freeze-drying time can specifically be 12h, 15h, 18h, 20h, 25h, 30h, 35h, 40h, 45h, or 48h. This invention does not have a specific limitation on the specific value of the freeze-drying vacuum degree, as long as it is ≤10Pa. This invention uses freeze-drying to instantly solidify the water in the pores, and then directly sublimates it under a high vacuum environment, thereby avoiding the migration and crystallization segregation of rare earth salts caused by capillary forces during liquid water drying, and fixing rare earth atoms in situ on the foamed tungsten framework in a highly dispersed state.
[0046] After obtaining the rare earth-doped foamed tungsten framework, the present invention sequentially reduces and densifies the rare earth-doped foamed tungsten framework to obtain a highly uniform rare earth oxide-doped tungsten material.
[0047] In this invention, the reduction temperature is preferably 500~1000℃; the holding time for reduction is preferably 1~5h; the reduction is carried out in a hydrogen atmosphere; and the rate of heating to the reduction temperature is preferably 4~6℃ / min. As one embodiment, the reduction temperature can specifically be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, or 1000℃; the holding time for reduction can specifically be 1h, 2h, 3h, 4h, or 5h; and the rate of heating to the reduction temperature can specifically be 5℃ / min. This invention performs reduction and controls the reduction temperature and time to ensure that rare earth salts are fully reduced to nano-sized rare earth oxide particles.
[0048] In this invention, the reduction can be carried out in stages. As one embodiment, the reduction can be: heating to 150~200℃ and holding for 0.5~1.5h, then heating to 500~1000℃ and holding for 1~5h.
[0049] In this invention, the densification sintering temperature is preferably 2200~2400℃; the densification sintering holding time is preferably 1~4h; the densification sintering is carried out in a hydrogen atmosphere; and the heating rate to the densification sintering temperature is preferably 9~11℃ / min. As one embodiment, the densification sintering temperature can specifically be 2200℃, 2250℃, 2300℃, 2350℃, or 2400℃; the densification sintering holding time can specifically be 1h, 2h, 3h, or 4h; and the heating rate to the densification sintering temperature can specifically be 10℃ / min. This invention controls the densification sintering temperature and time to densify the tungsten matrix, while simultaneously firmly anchoring rare earth oxide particles within the tungsten grain boundaries or grains, forming a dispersed strengthening phase.
[0050] The present invention controls the preparation method and parameters to achieve a highly dispersed distribution of rare earth oxides with high distribution uniformity. At the same time, the rare earth doping amount can be precisely controlled, resulting in low energy consumption, high efficiency, high product purity, and excellent mechanical properties of the prepared material.
[0051] The process flow diagram of the preparation method of highly uniform rare earth oxide-doped tungsten material provided by this invention is as follows: Figure 1 As shown.
[0052] A schematic diagram of the pore structure of the foamed tungsten skeleton prepared by this invention is shown below. Figure 2 As shown. From Figure 2As can be seen, the pores of the foamed tungsten skeleton include through pores and closed pores. The rare earth salt solution is pressed into the through pores of the foamed tungsten skeleton by the pressure impregnation method, but not into the closed pores.
[0053] The present invention also provides a highly uniform rare earth oxide-doped tungsten material prepared by the preparation method described in the above technical solution.
[0054] The present invention also provides the application of the highly uniform rare earth oxide-doped tungsten material described above in the preparation of diamond tungsten wire, rare earth tungsten electrodes, radiation shielding and heat load resistant components for nuclear fusion devices, high-temperature components for aerospace engines, and semiconductor heat treatment furnace devices.
[0055] The present invention does not impose any special limitations on the operation of the application, and any technical solution known to those skilled in the art can be used.
[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0057] Example 1 A method for preparing a highly uniform lanthanum oxide-doped tungsten material is as follows: the target doping amount of lanthanum oxide is 0.6 wt%. (1) Take pure tungsten powder with an average particle size of 2.4 μm, crush it by air flow, and pass it through 150 mesh and 325 mesh sieves to obtain 150~325 mesh tungsten powder. Put it into a rubber mold and press it under 210 MPa for 4 min to obtain a blank. (2) The blank obtained in step (1) is placed in a molybdenum wire sintering furnace with hydrogen gas and sintered at 1500℃ for 60 min. After cooling, a foam tungsten skeleton with a total porosity of 27% and a through-porosity of 97% of the total porosity is obtained. (3) Lanthanum nitrate hexahydrate and high-purity water were mixed to obtain a lanthanum nitrate solution with a concentration of 649 g / L. The foamed tungsten skeleton obtained in step (2) was placed in a pressure immersion device. After vacuuming, the lanthanum nitrate solution was injected to cover the foamed tungsten skeleton. A pressure of 5 MPa was applied and held for 30 min. After taking it out, it was immediately placed in liquid nitrogen for freezing for 20 min. Then it was transferred to a freeze dryer and vacuum dried for 24 h at -50℃ and vacuum degree <10 Pa to obtain a rare earth doped foamed tungsten skeleton. (4) The rare earth-doped foamed tungsten skeleton obtained in step (3) is placed in a hydrogen sintering furnace. Under hydrogen protection, the temperature is increased to 160℃ at 5℃ / min and held for 1h, then increased to 600℃ and held for 2h, and then increased to 2400℃ at 10℃ / min and held for 2h. The furnace is then cooled to obtain lanthanum oxide-doped tungsten material.
[0058] The morphology of the lanthanum oxide-doped tungsten material prepared in Example 1 is shown in the figure below. Figure 3 As shown.
[0059] Testing revealed that the density of the lanthanum oxide-doped tungsten material prepared in Example 1 reached 97% of the theoretical density. The lanthanum oxide content was tested at three different locations on the sample, and the results were 0.60 wt%, 0.62 wt%, and 0.62 wt%. The lanthanum oxide was uniformly distributed without agglomeration, and the average grain size was 21.8 μm.
[0060] Example 2 A method for preparing a highly uniform lanthanum oxide-doped tungsten material is as follows: the target doping amount of lanthanum oxide is 2.0 wt%; (1) Take pure tungsten powder with a particle size of 3.5 μm from FSSS, crush it by ball milling, and pass it through 150 mesh and 250 mesh sieves to obtain 150~250 mesh tungsten powder. Put it into a rubber mold and press it isostatically at 200 MPa for 5 min to obtain a blank. (2) The blank obtained in step (1) is placed in a molybdenum wire sintering furnace with hydrogen gas and sintered at 1450℃ for 90 min. After cooling, a foam tungsten skeleton with a total porosity of 42.3% and a through-pore rate of 99% of the total porosity is obtained. (3) Lanthanum nitrate hexahydrate and high-purity water were mixed to obtain a lanthanum nitrate solution with a concentration of 1085 g / L. The foamed tungsten skeleton obtained in step (2) was placed in a pressure immersion device. After vacuuming, the lanthanum nitrate solution was injected to cover the foamed tungsten skeleton. A pressure of 2 MPa was applied and held for 40 min. After taking it out, it was immediately placed in liquid nitrogen for freezing for 15 min. Then it was transferred to a freeze dryer and vacuum dried for 22 h at -50℃ and vacuum degree <10 Pa to obtain a rare earth doped foamed tungsten skeleton. (4) The rare earth-doped foamed tungsten skeleton obtained in step (3) is placed in a hydrogen sintering furnace. Under hydrogen protection, the temperature is increased to 180℃ at 5℃ / min and held for 1h, then increased to 680℃ and held for 1.5h, and then increased to 2320℃ at 10℃ / min and held for 2.5h. The furnace is then cooled to obtain lanthanum oxide-doped tungsten material.
[0061] The morphology of the lanthanum oxide-doped tungsten material prepared in Example 2 is shown in the figure below. Figure 4 As shown.
[0062] Testing revealed that the density of the lanthanum oxide-doped tungsten material prepared in Example 2 reached 96% of the theoretical density. The lanthanum oxide content was tested at three different locations on the sample, and the results were 2.0 wt%, 2.01 wt%, and 2.01 wt%, respectively. The lanthanum oxide content was uniformly distributed, with no agglomeration, and the average grain size was 25.2 μm.
[0063] Example 3 A method for preparing a highly uniform yttrium oxide-doped tungsten material is as follows: the target doping amount of yttrium oxide is 1.0 wt%; (1) Pure tungsten powder with an average particle size of 1 μm was crushed and sieved to obtain a narrow particle size distribution (D). 10 It is 0.8μm, D 50 1μm, D 90 Tungsten powder (1.1 μm) was loaded into a rubber mold and isostatically pressed at 220 MPa for 3 minutes to obtain a blank. (2) The blank obtained in step (1) is placed in a molybdenum wire sintering furnace with hydrogen gas and sintered at 1520℃ for 70 min. After cooling, a foam tungsten skeleton with a total porosity of 20% and a through-porosity of 95% of the total porosity is obtained. (3) Mix yttrium nitrate hexahydrate and high-purity water to obtain a yttrium nitrate solution with a concentration of 2008 g / L. Place the foamed tungsten skeleton obtained in step (2) in a pressure immersion device. After evacuation, inject yttrium nitrate solution to cover the foamed tungsten skeleton. Apply a pressure of 8 MPa and hold for 60 min. After taking it out, immediately immerse it in liquid nitrogen for 10 min and then transfer it to a freeze dryer. Vacuum dry for 12 h at -100℃ and vacuum degree <10 Pa to obtain a rare earth doped foamed tungsten skeleton. (4) The rare earth-doped foamed tungsten skeleton obtained in step (3) is placed in a hydrogen sintering furnace. Under hydrogen protection, the temperature is increased to 550℃ at 5℃ / min and held for 3 hours. Then, the temperature is increased to 2300℃ at 10℃ / min and held for 4 hours. The furnace is then cooled to obtain yttrium oxide-doped tungsten material.
[0064] The morphology of the yttrium oxide-doped tungsten material prepared in Example 3 is shown in the figure below. Figure 5 As shown.
[0065] Testing showed that the density of the yttrium oxide-doped tungsten material prepared in Example 3 reached 96% of the theoretical density. The yttrium oxide content was tested at three different locations on the sample, and the results were 0.99wt%, 1.00wt%, and 1.00wt%, respectively. The yttrium oxide content was uniformly distributed, with no agglomeration, and the average grain size was 12.2μm.
[0066] Comparative Example 1 A method for preparing lanthanum oxide-doped tungsten material is as follows: The material is prepared using a traditional powder metallurgy method, with a target lanthanum oxide doping amount of 0.6 wt%. (1) Take pure tungsten powder with an average particle size of 2.4 μm, crush it by air flow, and pass it through 150 mesh and 325 mesh sieves to obtain 150~325 mesh tungsten powder. Weigh 0.6 wt% lanthanum oxide and mix the tungsten powder with lanthanum oxide by ball milling. The ball milling time is 8 h, the ball-to-material ratio is 5:1, and the total weight ratio of alcohol to powder is 100 mL: 1000 g. The mixed powder is vacuum dried for 6 h at a temperature of 65 °C. (2) The mixed powder obtained in step (1) is loaded into a rubber mold and isostatically pressed at 210 MPa for 4 min to obtain a blank; (3) The blank obtained in step (2) is placed in a hydrogen sintering furnace. Under hydrogen protection, the temperature is increased to 160°C at 5°C / min and held for 1 hour, then increased to 600°C and held for 2 hours, and then increased to 2400°C at 10°C / min and held for 2 hours. The blank is then cooled with the furnace to obtain lanthanum oxide doped tungsten material.
[0067] Testing revealed that the density of the lanthanum oxide-doped tungsten material prepared in Comparative Example 1 reached 95.6% of the theoretical density. The lanthanum oxide content at different locations on the sample was measured, and the results were 0.51 wt%, 0.59 wt%, and 0.55 wt%, respectively. This indicates that the lanthanum oxide distribution in the lanthanum oxide-doped tungsten material prepared by this method is uneven.
[0068] In summary, the preparation method provided by this invention achieves a highly uniform distribution of rare earth oxides.
[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a highly uniform rare earth oxide-doped tungsten material, comprising the following steps: (1) Tungsten powder is pressed into shape to obtain a blank; (2) The blank obtained in step (1) is sintered in a hydrogen atmosphere to obtain a foamed tungsten skeleton; (3) The foamed tungsten skeleton obtained in step (2) is impregnated under pressure in a rare earth salt solution and then freeze-dried to obtain a rare earth-doped foamed tungsten skeleton. The concentration of the rare earth salt solution is calculated according to Formula I: Formula I, In Equation I, y represents the mass of rare earth salt corresponding to the target doping amount of rare earth oxide in the highly uniform rare earth oxide-doped tungsten material; V 通孔 The volume of the through-holes in the tungsten foam skeleton; (4) The rare earth doped foam tungsten skeleton obtained in step (3) is successively reduced and densified by sintering to obtain a highly uniform rare earth oxide doped tungsten material.
2. The preparation method according to claim 1, characterized in that, The sintering temperature in step (2) is 1200~1700℃, and the sintering holding time is 60~180min.
3. The preparation method according to claim 1, characterized in that, In step (2), the total porosity of the foamed tungsten skeleton is 12-45%, and the open porosity of the foamed tungsten skeleton accounts for more than 95% of the total porosity.
4. The preparation method according to claim 1, characterized in that, The rare earth salts in the rare earth salt solution in step (3) include one or more of rare earth nitrates, rare earth acetates and rare earth hydrochlorides; the rare earths in the rare earth salts include one or more of La, Y, Ce and Gd.
5. The preparation method according to claim 1, characterized in that, The pressure for impregnation in step (3) is 1~10MPa, and the holding time for impregnation is 30~60min.
6. The preparation method according to claim 1, characterized in that, In step (3), the freeze-drying temperature is ≤-30℃, the freeze-drying time is 12~48h, and the freeze-drying vacuum degree is ≤10Pa.
7. The preparation method according to claim 1, characterized in that, The reduction temperature in step (4) is 500~1000℃, and the reduction holding time is 1~5h.
8. The preparation method according to claim 1, characterized in that, The densification sintering temperature in step (4) is 2200~2400℃, and the densification sintering holding time is 1~4h.
9. The highly uniform rare earth oxide-doped tungsten material prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the highly uniform rare earth oxide-doped tungsten material of claim 9 in the preparation of diamond wire tungsten wire, rare earth tungsten electrodes, radiation shielding and heat load resistant components for nuclear fusion devices, high-temperature components for aerospace engines, and semiconductor heat treatment furnace devices.