CN111020329A - Method for preparing porous tungsten material based on W-Fe-C system corrosion method - Google Patents
Method for preparing porous tungsten material based on W-Fe-C system corrosion method Download PDFInfo
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- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 title claims abstract description 153
- 229910052721 tungsten Inorganic materials 0.000 title claims abstract description 126
- 239000010937 tungsten Substances 0.000 title claims abstract description 126
- 238000000034 method Methods 0.000 title claims abstract description 64
- 239000000463 material Substances 0.000 title claims abstract description 62
- 230000007797 corrosion Effects 0.000 title claims abstract description 22
- 238000005260 corrosion Methods 0.000 title claims abstract description 22
- 229910017112 Fe—C Inorganic materials 0.000 title claims abstract description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 76
- 238000005245 sintering Methods 0.000 claims abstract description 62
- 239000011148 porous material Substances 0.000 claims abstract description 45
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910001145 Ferrotungsten Inorganic materials 0.000 claims abstract description 25
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 229910052742 iron Inorganic materials 0.000 claims abstract description 17
- 239000002131 composite material Substances 0.000 claims abstract description 16
- 239000011812 mixed powder Substances 0.000 claims abstract description 15
- 238000000498 ball milling Methods 0.000 claims abstract description 12
- 238000001272 pressureless sintering Methods 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000009826 distribution Methods 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 9
- 238000000227 grinding Methods 0.000 claims abstract description 7
- 238000009766 low-temperature sintering Methods 0.000 claims abstract description 6
- 238000011049 filling Methods 0.000 claims abstract description 3
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 3
- 239000010439 graphite Substances 0.000 claims abstract description 3
- 239000002245 particle Substances 0.000 claims description 39
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
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- 239000002184 metal Substances 0.000 claims description 11
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- 229910021641 deionized water Inorganic materials 0.000 claims description 8
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- 238000002490 spark plasma sintering Methods 0.000 claims description 4
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- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000004913 activation Effects 0.000 description 3
- 238000001479 atomic absorption spectroscopy Methods 0.000 description 3
- GXBKELQWVXYOPN-UHFFFAOYSA-N iron tungsten Chemical compound [W][Fe][W] GXBKELQWVXYOPN-UHFFFAOYSA-N 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 238000010345 tape casting Methods 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000007767 bonding agent Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
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- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- BQPIGGFYSBELGY-UHFFFAOYSA-N mercury(2+) Chemical compound [Hg+2] BQPIGGFYSBELGY-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
- C22C27/04—Alloys based on tungsten or molybdenum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/11—Making porous workpieces or articles
- B22F3/114—Making porous workpieces or articles the porous products being formed by impregnation
-
- 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
- C22C1/08—Alloys with open or closed pores
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
- B22F2003/1051—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding by electric discharge
Abstract
The invention relates to a method for preparing a porous tungsten material based on a W-Fe-C system corrosion method, which comprises the following specific steps: 1) forming a composite block by low-temperature sintering: uniformly ball-milling tungsten powder, iron powder and carbon powder to obtain mixed powder, filling the mixed powder into a graphite grinding tool, and sintering by adopting discharge plasma to obtain a ferrotungsten block; 2) and (3) corroding iron in the base material by using a chemical corrosion method: putting the ferrotungsten block into an excessive dilute sulfuric acid solution, and heating the dilute sulfuric acid solution to 40-80 ℃ to obtain a porous tungsten green body with a micron pore size; 3) preparing porous tungsten by high-temperature sintering: and (3) carrying out vacuum pressureless sintering on the porous tungsten green body obtained in the step 3) to obtain the porous tungsten material. The porous tungsten material provided by the invention has the advantages of uniform pore distribution, consistent structure, no obvious defect, porosity of 25.8-78%, pore diameter of 1-10 mu m and wide application.
Description
Technical Field
The invention belongs to the technical field of porous metal materials, and particularly relates to a method for preparing a porous tungsten material based on a W-Fe-C system corrosion method.
Background
The porous metal has the characteristics of low relative density, high specific strength, large specific surface area, strong permeability, good energy absorption and the like, and is a multifunctional material integrating mechanical properties, thermal properties, acoustic properties and electrical properties.
The porous tungsten has excellent thermal, electrical and mechanical properties, is widely used in the fields of modern communication technology, electronic computers, space development, medicine and health, photosensitive materials, photoelectric materials, energy materials, catalyst materials and the like, and is particularly used as a porous cathode with high current density, an emitter for charging an electron emission material in an ion engine, a vaporizer for separating mercury gas from liquid in a mercury ion rocket engine, a high-temperature fluid filter, an electronic packaging material and the like.
However, the very high melting point and the very high density of tungsten make it difficult to prepare porous materials by conventional preparation methods. The conventional sintering method, the activation sintering method, the freezing casting method, the organic matrix slurry dipping drying sintering method and the like are commonly used at present. The sintering temperature of the traditional non-densification sintering method is 1500-; the complex phase activation sintering method with the addition of aluminum or nickel can obviously reduce the sintering temperature and promote the sintering of tungsten particles, but the pore structure is controlled by the morphology of the particles and the pretreatment process of raw materials; the slurry of the freeze casting method is firstly solidified at low temperature, then treated at high temperature to remove organic additives and sintered at the same time, but the control of the pore structure is not accurate enough, and the slurry is often used for preparing a large-aperture porous structure.
In order to improve the disadvantages of the conventional methods, there are many researchers who have adopted a new method for preparing porous tungsten. Patent application
CN103774184A discloses a method for preparing porous tungsten by electrolysis, which utilizes the characteristic that tungsten is electrolyzed in a molten salt solution under the electrochemical action, adopts an alternating current power supply and a direct current power supply to electrolyze tungsten metal in an additive-containing NaOH solution to prepare the porous tungsten, and the porous tungsten prepared by the method has uniform pore size distribution, uncontrollable pore size and low porosity. Patent CN107234241A discloses a method for preparing porous tungsten by taking NaCl as a pore-forming agent and a tape casting method, wherein NaCl is used as the pore-forming agent to control porosity and pore structure, then the tape casting method is used to overcome huge density difference among particles to obtain uniform particle distribution, residual C generated by organic matters added in the tape casting process reacts with W, and sintering temperature is remarkably reduced, and the porous tungsten prepared by the method comprises pore diameters of two specifications. The pore diameter of the existing reported method for preparing porous tungsten can not be controlled in a larger porosity range, and pores with regular morphology can be obtained.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for preparing porous tungsten by using Fe as a pore-forming agent and a structure stabilizer simultaneously and combining a corrosion method and secondary sintering, wherein the porous tungsten prepared by the method has the advantages of regular pore appearance, concentrated pore size distribution, controllable pore size and porosity.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the method for preparing the porous tungsten material based on the W-Fe-C system corrosion method comprises the following specific steps:
1) forming a composite block by low-temperature sintering: uniformly ball-milling tungsten powder, iron powder and carbon powder to obtain mixed powder, filling the mixed powder into a graphite grinding tool, and performing Spark Plasma Sintering (SPS) to obtain a ferrotungsten block (W-Fe-C base material);
2) and (3) corroding iron in the base material by using a chemical corrosion method: putting the ferrotungsten block obtained in the step 1) into an excessive dilute sulfuric acid solution, heating the dilute sulfuric acid solution to 40-80 ℃, taking out the metal block when no bubbles are generated, repeatedly washing the metal block by using absolute ethyl alcohol and deionized water, and then drying to obtain a porous tungsten green body with a micron pore diameter;
3) preparing porous tungsten by high-temperature sintering: and (3) carrying out vacuum pressureless sintering on the porous tungsten green body obtained in the step 3) to obtain the porous tungsten material.
According to the scheme, the molar parts of the tungsten powder and the iron powder in the mixed powder in the step 1) are as follows: 20-60 parts of tungsten powder, 40-80 parts of iron powder, and 100 parts of tungsten powder and iron powder in total, wherein the using amount of the carbon powder is 0.01-0.2% of the total mass of the tungsten powder and the iron powder.
According to the scheme, the ball milling process conditions in the step 1) are as follows: ball milling is carried out for 12-24 h at the speed of 150-300 r/min.
According to the scheme, the purity of the iron powder in the step 1) is more than 99.99%, and the particle size is 5-10 microns; the purity of the tungsten powder is more than 99.99%, and the particle size is 1-3 mu m; the purity of the carbon powder is more than 99.99%, and the particle size is 30-50 nm.
According to the scheme, the conditions of the spark plasma sintering in the step 1) are as follows: sintering under a vacuum condition, wherein the sintering temperature is 800-1000 ℃, the sintering time is 2-10 min, and the sintering pressure is 10-30 MPa.
According to the scheme, the mass concentration of the dilute sulfuric acid solution in the step 2) is 2-10%.
According to the scheme, the vacuum pressureless sintering process conditions in the step 3) are as follows: under the vacuum condition, the temperature is increased from room temperature to 1300-1500 ℃ at the temperature increasing rate of 5-10/min, and the heat preservation time is 1-2 h.
The invention also comprises the porous tungsten material prepared by the method, wherein the porous tungsten material has uniform pore distribution and consistent structure, the porosity is 25.8-78%, the pore diameter is 1-10 mu m, and the density is 4.26-14.36 g/cm3。
The sintering temperature of tungsten exceeds 1600 ℃, the pore-forming agent is difficult to be applied to pore-forming of the tungsten-based porous material, the pore-forming process and the sintering process are respectively realized by two-step sintering, so that the pore-forming is carried out at a lower temperature (900 ℃) and the sintering is carried out at a high temperature (1300-1700 ℃), and the problem that the common pore-forming agent cannot be used at the high temperature is solved.
The invention can form W-Fe-C network under low temperature sintering (discharge plasma sintering) by adding a small amount of C, bonding W particles, improving the structural stability of green body, in addition, making the particle size of tungsten powder smaller than that of iron powder to form a structure that iron particles are wrapped by tungsten particles, which is more favorable for ensuring the uniformity of pore diameter after corrosion, meanwhile, the pore structure of porous tungsten is regulated and controlled by changing the content and particle size distribution of iron powder, micron porous tungsten block bodies with uniform pore distribution, controllable pore size and porosity can be obtained by chemical corrosion deferrization, and a small amount of iron element is still in the porous tungsten green body after chemical corrosion, the solid-dissolved trace iron preferentially forms local liquid phase in the subsequent sintering process, thereby promoting the interaction and mass transfer among particles, improving the sintering effect and obviously reducing the sintering temperature.
The invention has the beneficial effects that: 1. the method adopts a low-temperature sintering method to prepare the W-Fe-C base material, then utilizes a chemical corrosion method to corrode iron in the base material, and then utilizes a high-temperature sintering method to obtain the porous tungsten material with regular micron-sized pores and controllable pore size within a larger porosity range, and utilizes the metastable carbide in the system as a bonding agent, so that no additional bonding agent is needed to be added, unnecessary impurities are prevented from being introduced, the metastable carbide can be gradually decomposed in the high-temperature sintering process, iron elements can be gradually segregated and flow out from a porous framework, and finally the iron content of the porous tungsten framework is lower than 1 wt%. The porous green body bonded by the carbide is stable and does not have local collapse, so the pore structure formed by the pore-forming agent can be completely preserved and solidified in subsequent sintering, and the pore structure and the porosity can be well controlled. 2. The porous tungsten material provided by the invention has uniform pore distribution, consistent structure and no obvious defect, the porosity is 25.8-78%, the pore diameter is 1-10 mu m,
the density is 4.26 to 14.36g/cm3And has wide application.
Drawings
FIG. 1 is a sectional SEM photograph of a low-temperature sintered composite block prepared in example 3 of the present invention;
FIG. 2 is an SEM image of a green porous tungsten body prepared in example 3;
FIG. 3 is an SEM image of the porous tungsten material prepared in example 3;
FIG. 4 is an SEM image of the porous tungsten material prepared in example 3;
FIG. 5 is an XRD pattern of a green porous tungsten body prepared in example 3;
fig. 6 is an XRD pattern of the porous tungsten material prepared in example 3.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings.
The invention adopts SPS discharge activation sintering tungsten powder, iron powder and carbon powder mixed powder to obtain a ferrotungsten block, then the ferrotungsten block is cleaned and immersed into dilute sulfuric acid solution for selective corrosion, iron in the block is dissolved away, thereby obtaining three-dimensional network-shaped porous tungsten green bodies bonded by ferrotungsten carbide among particles, finally the green bodies are placed into a hot pressing furnace for vacuum pressureless sintering, so that the particles are sintered to form a stable pore wall structure, thereby obtaining the porous tungsten block with high porosity. The defects that the existing porous tungsten is difficult to prepare and the structure is difficult to control are overcome, so that the prepared porous tungsten has high porosity, the structure is easy to control, the strength is high, and more possibilities are provided for preparing the porous tungsten by a corrosion method. The invention can produce products with large size, has simple process and low cost and is easy for industrialization.
Example 1
The embodiment provides a preparation method of a porous tungsten material, which comprises the following steps:
tungsten powder (purity 99.99%, average particle diameter 1 μm) and iron powder (purity 99.99%, average particle diameter 10 μm) were mixed at a molar ratio of 20: 80, then adding nano C powder (the purity is 99.99 percent and the average grain diameter is 30nm) accounting for 0.01 percent of the total mass of the tungsten powder and the iron powder,ball-milling the mixed powder on a light low-energy ball mill for 12 hours at a speed of 150 revolutions per minute to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at a low temperature, vacuumizing the furnace, wherein the sintering temperature is 800 ℃, the heat preservation time is 10min, and the sintering pressure is 20MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4And putting the container in a water bath, heating to 50 ℃, preserving heat, observing bubbles generated by reaction of active metallic iron in the container and a sulfuric acid solution, generating no bubbles in the solution after 15 hours, taking out the block, repeatedly washing and drying the block by using alcohol and deionized water to obtain a porous tungsten green body, taking a small amount of the porous tungsten green body, grinding the porous tungsten green body, and performing an atomic absorption spectrum test to obtain a Fe element of 5 wt%. Carrying out vacuum pressureless sintering on the porous tungsten green body, heating to 1300 ℃ from room temperature at the heating rate of 10 ℃/min under the vacuum condition, and preserving the heat for 1h to obtain the porous tungsten material, wherein the porosity of the obtained porous tungsten material is 78%, and the sample density is 4.26g/cm3The pore size distribution is in the range of 8-9 μm, atomic absorption spectroscopy and X-ray diffraction tests are carried out on a porous tungsten material sample, the content of Fe element after sintering is 1 wt%, and the XRD diffraction peak shows that the sample is basically pure tungsten phase.
Example 2
The embodiment provides a preparation method of micron-sized porous tungsten, which comprises the following steps:
tungsten powder (purity 99.99%, average particle diameter 3 μm) and iron powder (purity 99.99%, average particle diameter 5 μm) were mixed in a molar ratio of 60: 40, adding nano C powder (the purity is 99.99 percent and the average particle size is 50nm) accounting for 0.05 percent of the total mass of the tungsten powder and the iron powder, and ball-milling the mixed powder on a light low-energy ball mill for 12 hours at the speed of 200 r/min to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at low temperature, vacuumizing the furnace, wherein the sintering temperature is 900 ℃, the heat preservation time is 10min, and the sintering pressure is 20MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4In the solution, the solution is added with a solvent,and placing the container in a water bath kettle, heating to 50 ℃ and preserving heat. The time is recorded. Observing bubbles generated by the reaction of the active metal iron in the container and the sulfuric acid solution, finding that no bubbles are generated in the solution after 15 hours, then taking out the block, and repeatedly washing and drying the block by using alcohol and deionized water to obtain the porous tungsten green body. A small amount of the porous tungsten green compact was ground and subjected to atomic absorption spectroscopy to determine that the Fe element was 6 wt%. Vacuum pressureless sintering is carried out on the porous tungsten green body, the temperature is raised to 1300 ℃ from room temperature at the temperature rise rate of 5 ℃/min under the vacuum condition, the heat is preserved for 1h, the porous tungsten material is obtained, the porosity of the obtained porous tungsten material is 40.2 percent, the pore diameter is distributed in the range of 3-4 mu m, and the density is 11.41g/cm3And carrying out atomic absorption spectrum and X-ray diffraction tests on a porous tungsten material sample, wherein the content of Fe element in the sintered porous tungsten material is 1 wt%, and the test sample is basically a pure tungsten phase according to an XRD diffraction peak.
Example 3
The embodiment provides a preparation method of micron-sized porous tungsten, which comprises the following steps:
tungsten powder (purity 99.99%, 2 μm) and iron powder (purity 99.99%, 7 μm) were mixed in a molar ratio of 40: 60, adding nano C powder (the purity is 99.99 percent and the average particle size is 40nm) accounting for 0.1 percent of the total mass of the tungsten powder and the iron powder, and ball-milling the mixed powder on a light low-energy ball mill for 18 hours at 200 revolutions per minute to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at low temperature, vacuumizing the furnace, wherein the sintering temperature is 900 ℃, the heat preservation time is 10min, and the sintering pressure is 20MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4Putting the container in a water bath kettle, heating to 50 deg.C, and keeping the temperature. The time is recorded. Observing bubbles generated by the reaction of the active metal iron in the container and the sulfuric acid solution, finding that no bubbles are generated in the solution after 15h, then taking out the block, repeatedly washing and drying the block by using alcohol and deionized water to obtain a porous tungsten green body, taking a small amount of porous tungsten green body, grinding the porous tungsten green body, and performing atomic absorption spectrum test to obtain the Fe element of 5 wt%. Vacuum of porous tungsten green bodyPressureless sintering, heating from room temperature to 1500 deg.C at a heating rate of 10 deg.C/min under vacuum condition, and maintaining for 2h to obtain porous tungsten material with porosity of 34.2%, pore diameter distribution of 3-4 μm, and density of 12.70g/cm3And carrying out atomic absorption spectrum and X-ray diffraction tests on a porous tungsten material sample, wherein the content of Fe element in the sintered porous tungsten material is 1 wt%, and the test sample is basically a pure tungsten phase according to an XRD diffraction peak.
As shown in fig. 1, which is a cross-sectional microscopic structure diagram of the ferrotungsten block prepared in this embodiment, it can be seen that there are certain gaps between particles in the prepared ferrotungsten block, and there are certain neck connections between ferrotungsten particles.
As shown in fig. 2, which is an SEM image of the porous tungsten green compact obtained in this example, it can be seen from the figure that the pore structure is stable, there is no significant deformation and collapse, the pore size is similar to the size of the pore-forming agent Fe, about 5 to 7 μm, the particle size is about 1 μm, nano-sheet-like substances exist between particles, and XRD and TEM prove that such substances are tungsten iron tungsten carbide, and there is significant diffusion of Fe and C on the tungsten particles.
As shown in fig. 3 and fig. 4, SEM images of the porous tungsten material prepared in this embodiment under different multiples show that the prepared porous tungsten material has uniform pores and consistent structure, ligament pores are in a bicontinuous structure, the pores are connected to each other and have a through-hole structure, and the pore size is in the range of 4-5 μm.
Fig. 5 is an XRD chart of the porous tungsten green compact prepared in this example, and fig. 6 is an X-ray diffraction pattern of the porous tungsten material prepared in this example, from which it can be seen that the porous tungsten green compact has an obvious diffraction peak of tungsten-iron-tungsten carbide, which proves that in the first step of low-temperature sintering, a certain in-situ reaction occurs between the three elements of tungsten-iron-carbon, and tungsten-iron-tungsten carbide is generated on the contact surface of the particles, thereby solidifying the porous structure of the green compact and stabilizing the porous tungsten green compact. After subsequent vacuum pressureless sintering, the diffraction peak of ferrotungsten carbide of the porous tungsten material is obviously reduced, which proves that the substance is decomposed in the sintering process, and the decomposed iron phase is melted out from the matrix.
Example 4
The embodiment provides a preparation method of micron-sized porous tungsten, which comprises the following steps:
tungsten powder (purity 99.99%, average particle size 2 μm) and iron powder (purity 99.99%, average particle size 6 μm) were mixed at a molar ratio of 30: 70, adding nano C powder (the purity is 99.99 percent and the average particle size is 30nm) accounting for 0.2 percent of the total mass of the tungsten powder and the iron powder, and ball-milling the mixed powder on a light low-energy ball mill for 18 hours at the speed of 300 revolutions per minute to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at low temperature, vacuumizing the furnace, wherein the sintering temperature is 900 ℃, the heat preservation time is 10min, and the sintering pressure is 20MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4Putting the container in a water bath kettle, heating to 50 deg.C, and keeping the temperature. The time is recorded. Observing bubbles generated by the reaction of the active metal iron in the container and the sulfuric acid solution, finding that no bubbles are generated in the solution after 15 hours, then taking out the block, and repeatedly washing and drying the block by using alcohol and deionized water to obtain the porous tungsten green body. A small amount of the porous tungsten green compact was ground and subjected to atomic absorption spectroscopy to determine that the Fe element content was 5 wt%. Vacuum pressureless sintering is carried out on the porous tungsten green body, the temperature is raised to 1400 ℃ from room temperature at the temperature raising rate of 8 ℃/min under the vacuum condition, the heat is preserved for 2 hours, the porous tungsten material is obtained, the porosity of the obtained porous tungsten material is 58.9 percent, the pore diameter is distributed in the range of 5-6 mu m, and the density is 7.93g/cm3And carrying out atomic absorption spectrum and X-ray diffraction tests on a porous tungsten material sample, wherein the content of Fe element in the sintered porous tungsten material is 1 wt%, and the sample is basically a pure tungsten phase according to an XRD diffraction peak.
Example 5
The embodiment provides a preparation method of micron-sized porous tungsten, which comprises the following steps:
tungsten powder (purity 99.99%, average particle diameter 1 μm) and iron powder (purity 99.99%, average particle diameter 7 μm) were mixed at a molar ratio of 50: 50, then adding nano C powder (with purity of 99.99% and average particle size of 50nm) accounting for 0.15% of total mass of the tungsten powder and the iron powder, and mixingBall-milling the mixed powder on a light low-energy ball mill for 12 hours at the speed of 300 r/min to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at low temperature, vacuumizing the furnace, wherein the sintering temperature is 900 ℃, the heat preservation time is 10min, and the sintering pressure is 20MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4Putting the container in a water bath kettle, heating to 50 deg.C, and keeping the temperature. The time is recorded. Observing bubbles generated by the reaction of the active metal iron in the container and the sulfuric acid solution, finding that no bubbles are generated in the solution after 15h, then taking out the block, repeatedly washing and drying the block by using alcohol and deionized water to obtain a porous tungsten green body, taking a small amount of porous tungsten green body, grinding the porous tungsten green body, and performing an atomic absorption spectrum test to obtain the Fe element content of 4 wt%. Carrying out vacuum pressureless sintering on the porous tungsten green body, heating to 1500 ℃ from room temperature at the heating rate of 8 ℃/min under the vacuum condition, and preserving heat for 2h to obtain the porous tungsten material, wherein the porosity of the obtained porous tungsten material is 25.8%, the pore diameter is distributed in the range of 4-5 mu m, and the density is 14.36g/cm3And carrying out atomic absorption spectrum and X-ray diffraction tests on the porous tungsten material sample, wherein the content of the Fe element after sintering is 1 wt%, and the XRD diffraction peak shows that the test sample is basically a pure tungsten phase.
Example 6
The embodiment provides a preparation method of micron-sized porous tungsten, which comprises the following steps:
tungsten powder (purity 99.99%, average particle diameter 1 μm) and iron powder (purity 99.99%, average particle diameter 10 μm) were mixed at a molar ratio of 35: 65, adding nano C powder (the purity is 99.99 percent and the average particle size is 40nm) accounting for 0.01 percent of the total mass of the tungsten powder and the iron powder, and ball-milling the mixed powder on a light low-energy ball mill for 18 hours at the speed of 150 revolutions per minute to uniformly mix the composite powder; sintering the composite powder in a discharge plasma sintering furnace at low temperature, vacuumizing the furnace, wherein the sintering temperature is 900 ℃, the heat preservation time is 10min, and the sintering pressure is 30MPa to obtain a ferrotungsten block; h is prepared at a concentration of 5 wt%2SO4Solution, putting clean ferrotungsten block into excessive H2SO4Putting the container in a water bath kettle, heating to 50 deg.C, and keeping the temperature. The time is recorded. Observing bubbles generated by the reaction of the active metal iron in the container and the sulfuric acid solution, finding that no bubbles are generated in the solution after 15h, then taking out the block, repeatedly washing and drying the block by using alcohol and deionized water to obtain a porous tungsten green body, taking a small amount of porous tungsten green body, grinding the porous tungsten green body, and performing an atomic absorption spectrum test to obtain the Fe element content of 4 wt%. Carrying out vacuum pressureless sintering on the porous tungsten green body, heating to 1500 ℃ from room temperature at the heating rate of 10 ℃/min under the vacuum condition, and preserving heat for 2h to obtain the porous tungsten material, wherein the porosity of the obtained porous tungsten material is 43.5%, the pore diameter is distributed in the range of 6-7 mu m, and the density is 10.90g/cm3And carrying out atomic absorption spectrum and X-ray diffraction tests on a porous tungsten material sample, wherein the content of Fe element in the sintered porous tungsten material is 1 wt%, and the test sample is basically a pure tungsten phase according to an XRD diffraction peak.
The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is rather exhaustive, but not to be construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (8)
1. A method for preparing a porous tungsten material based on a W-Fe-C system corrosion method is characterized by comprising the following specific steps:
1) forming a composite block by low-temperature sintering: uniformly ball-milling tungsten powder, iron powder and carbon powder to obtain mixed powder, filling the mixed powder into a graphite grinding tool, and sintering by adopting discharge plasma to obtain a ferrotungsten block;
2) and (3) corroding iron in the base material by using a chemical corrosion method: putting the ferrotungsten block obtained in the step 1) into an excessive dilute sulfuric acid solution, heating the dilute sulfuric acid solution to 40-80 ℃, taking out the metal block when no bubbles are generated, repeatedly washing the metal block by using absolute ethyl alcohol and deionized water, and then drying to obtain a porous tungsten green body with a micron pore diameter;
3) preparing porous tungsten by high-temperature sintering: and (3) carrying out vacuum pressureless sintering on the porous tungsten green body obtained in the step 3) to obtain the porous tungsten material.
2. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the molar parts of the tungsten powder and the iron powder in the mixed powder of the step 1) are as follows: 20-60 parts of tungsten powder, 40-80 parts of iron powder, and 100 parts of tungsten powder and iron powder in total, wherein the using amount of the carbon powder is 0.01-0.2% of the total mass of the tungsten powder and the iron powder.
3. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the ball milling process conditions in the step 1) are as follows: ball milling is carried out for 12-24 h at the speed of 150-300 r/min.
4. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the purity of the iron powder in the step 1) is more than 99.99%, and the particle size is 5-10 μm; the purity of the tungsten powder is more than 99.99%, and the particle size is 1-3 mu m; the purity of the carbon powder is more than 99.99%, and the particle size is 30-50 nm.
5. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the conditions of the spark plasma sintering in the step 1) are as follows: sintering under a vacuum condition, wherein the sintering temperature is 800-1000 ℃, the sintering time is 2-10 min, and the sintering pressure is 10-30 MPa.
6. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the mass concentration of the dilute sulfuric acid solution in the step 2) is 2-10%.
7. The method for preparing the porous tungsten material based on the W-Fe-C system corrosion method according to claim 1, wherein the vacuum pressureless sintering process conditions in the step 3) are as follows: under the vacuum condition, the temperature is increased from room temperature to 1300-1500 ℃ at the temperature increasing rate of 5-10/min, and the heat preservation time is 1-2 h.
8. The porous tungsten material prepared by the method according to any one of claims 1 to 7, wherein the porous tungsten material has uniform pore distribution, uniform structure, porosity of 25.8-78%, pore diameter of 1-10 μm, and density of 4.26-14.36 g/cm3。
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