A method for low-temperature drying of a microchannel template of a porous zirconia dispersed tungsten material

Abstract

The application relates to the technical field of material preparation, and discloses a micro-channel template low-temperature drying preparation method of porous zirconium oxide dispersed tungsten material, which comprises the following steps: biomass micro-channel template preparation, tungsten precursor solution loading, zirconium oxide sol gradient permeation, low-temperature conformal drying, gradient heat treatment forming and surface closed hole strengthening treatment. In the application, the micro-channel directional regulation and control technology of the biomass template is combined with the axial pressure impregnation of the tungsten precursor solution to form a uniform loading layer on the inner wall of the micro-channel, so that the through permeation of the precursor in the three-dimensional pore network is realized; meanwhile, the step-by-step impregnation method is used to induce the in-situ controllable hydrolysis of the zirconium salt solution and a precipitating agent, so that the zirconium oxide sol grows along the channel wall layer by layer and spontaneously embeds in the gap between the tungsten matrix, thereby not only eliminating the risk of local component segregation, but also constructing a multi-stage symbiotic interface structure, and strengthening the pinning and crack resistance effect and the structural stability of the dispersed phase.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, specifically to a method for preparing porous zirconia dispersed tungsten materials by low-temperature drying of microchannel templates. Background Technology

[0002] Porous tungsten is a metallic material with a controllable pore structure formed through advanced preparation technology. This material is prepared using selective laser melting 3D printing technology, pore-forming agent method and solution combustion synthesis and other processes, which breaks through the technical limitations of low porosity in traditional powder metallurgy. Porous tungsten material has the characteristics of high melting point and boiling point and low vapor pressure of tungsten, and is widely used in aerospace, power electronics and metallurgical industries and other extreme environment fields.

[0003] Currently, due to the natural differences in the microstructure of plant stems during the preparation of biomass microchannel templates, it is impossible to precisely control the degree of collapse and deformation of the cellulose skeleton during the delignification process. This results in the dispersion of microchannel pore size distribution exceeding the process tolerance range, leading to regional uneven penetration depth in the subsequent tungsten precursor solution loading stage.

[0004] Therefore, a low-temperature drying method for preparing microchannel templates of porous zirconia-dispersed tungsten materials is proposed to solve the above problems. Summary of the Invention

[0005] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing porous zirconia dispersed tungsten materials using microchannel templates through low-temperature drying, thus solving the problems mentioned in the background section.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying, comprising the following steps: Step 1: Preparation of biomass microchannel templates. Plant stems are selected as the substrate and are crushed and sieved to obtain biomass particles with a particle size of 50-200μm. The particles are then subjected to delignification treatment, surface activation and microchannel directional regulation. Step 2: Tungsten precursor solution loading. The biomass template treated in Step 1 is immersed in a tungsten precursor solution, with the immersion pressure controlled at 0.1-0.5 MPa and the immersion time at 2-4 h. Step 3: Zirconia sol gradient infiltration. A step-by-step impregnation method is used. First, a zirconium salt solution is injected to fill the microchannels, and then a precipitant is added to initiate in-situ hydrolysis to form a zirconium oxide sol layer. Step 4: Low-temperature conformal drying, freeze-drying for 12-36 hours in an environment with humidity of 30%-50% and temperature of -20℃-0℃, simultaneously achieving ice crystal template support and directional solvent evaporation; Step 5: Gradient heat treatment molding, segmented heating under hydrogen atmosphere: the first stage is 200-400℃ for 1-2h to remove the template, the second stage is 800-1200℃ for 3-5h to achieve densification of the tungsten matrix, and the third stage is 1400-1600℃ for 1-3h to induce the dispersion distribution of zirconium oxide phase transformation. Step 6: Surface pore-closure strengthening treatment. A nano-tungsten layer with a thickness of 50-200nm is deposited on the material surface using pulsed magnetron sputtering to fill the surface pores.

[0007] Preferably, in step one, the delignification treatment uses a sodium chlorite-acetic acid mixture with a pH of 3.5-4.5, reacting at 70-90℃ for 4-8 hours, achieving a delignification rate ≥85%. Surface activation is achieved through low-temperature oxygen plasma treatment at a power of 300-500W for 10-30 minutes, increasing the hydroxyl density on the template surface. The microchannel directional control is assisted by an axial electrostatic field with a field strength of 1-3 kV / cm.

[0008] Preferably, the tungsten precursor solution in step two is prepared from the following components in mass percentage: Ammonium metatungstate: 20-30 wt%, ammonium citrate: 5-10 wt%, polyvinylpyrrolidone: 1-3 wt%, ethylene glycol: 10-15 wt%, balance: deionized water; The solution viscosity was controlled at 25℃, 15-25 mPa·s, and the pH value was adjusted to 2.0-3.0.

[0009] Preferably, the specific operation of the zirconium oxide sol gradient infiltration in step three is as follows: Inject a 0.5-1.5 mol / L solution of zirconium oxynitrate into the microchannel and let it stand for 30-60 minutes. Add a mixture of ammonia and ethanol as a precipitant at a volume ratio of 1:1 at a dropping rate of 0.1-0.5 mL / min to initiate a hydrolysis reaction and generate zirconium hydroxide gel. Add yttrium oxide stabilizer, The molar ratio is 3-8%, and the sol is uniformly distributed by ultrasonic vibration at a frequency of 40kHz and a power of 200W.

[0010] Preferably, in step four, low-temperature conformal drying: During the pre-freezing stage, the temperature is lowered to -40℃ at a rate of 5-10℃ / min and kept at that temperature for 2 hours to form dendritic ice crystals. During the sublimation drying stage, the vacuum degree is ≤10Pa, and the temperature is raised to -20℃-0℃. The directional growth of ice crystals controls the pore size to be 5-20μm. During the drying stage, the temperature is raised to 25-35℃ to remove bound water.

[0011] Preferably, step four, prior to low-temperature conformal drying, further includes ultrasonic pre-structuring treatment: The biomass template loaded with the precursor was placed in an ultrasonic field with a frequency of 18-25 kHz for 10-30 minutes, and the ultrasonic power density was controlled at [value missing]. Maintain the solution temperature at 5-15℃ during treatment; The ultrasound direction is parallel to the microchannel axis, inducing sol particles to align along the channel wall to form a pre-textured layer.

[0012] Preferably, in step five, the gradient heat treatment: The first stage heating rate is 2-5℃ / min, and the hydrogen flow rate is 50-100mL / min; The second stage introduces tungsten carbide seed crystals with a particle size of 0.1-0.5 μm and an addition amount of 0.5-2 wt% to inhibit abnormal growth of tungsten grains. The third stage involves rapid quenching at a cooling rate ≥100℃ / s, causing zirconia to precipitate as a tetragonal phase. It is diffusely distributed, with a phase content of ≥80%.

[0013] Preferably, the zirconium oxide dispersed phase satisfies: The particle size distribution is 50-300nm, with a gradient transition, 50-100nm on the surface and 200-300nm in the core; Bonding energy with tungsten matrix interface A W-Zr-O transition layer with a thickness of 2-5 nm is formed at the interface.

[0014] Preferably, in step six, surface pore-closure strengthening: The sputtering target is made of pure tungsten with a purity of ≥99.95%; Process parameters: pulse frequency 10-50kHz, duty cycle 30-70%, argon pressure 0.5-2Pa; After deposition, the internal stress is eliminated by annealing at 400-600℃ for 1 hour.

[0015] Preferably, the plant stem is selected from at least one of reeds, wheat straw or bamboo shavings, and its microchannel aspect ratio is controlled to be 10:1-50:1, with a porosity ≥85%.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a method for preparing porous zirconia-dispersed tungsten materials by low-temperature drying of microchannel templates, which has the following beneficial effects: 1. In this invention, a uniform loading layer is formed on the inner wall of the microchannel by combining the microchannel directional control technology of biomass template with the axial pressure impregnation of tungsten precursor solution, thereby achieving the permeability of the precursor in the three-dimensional pore network. At the same time, the stepwise impregnation method induces the in-situ controllable hydrolysis of zirconium salt solution and precipitant, which promotes the growth of zirconium oxide sol along the channel wall and its spontaneous embedding into the gaps of the tungsten matrix. This not only eliminates the risk of local component segregation, but also constructs a multi-level symbiotic interface structure, which enhances the pinning and crack-resistant effect and structural stability of the dispersed phase.

[0017] 2. In this invention, a synergistic mechanism of low-temperature conformal drying and ultrasonic pre-structuring is adopted. The collapse and deformation of the pores are suppressed by the directional support of the ice crystal template, and the axial ultrasonic field is used to drive the orderly arrangement of sol particles. During the solvent sublimation stage, multi-level through-pores are spontaneously constructed. Combined with the segmented temperature control strategy of hydrogen atmosphere in gradient heat treatment, a triple synergy of mild decomposition of biological template, seed-guided grain refinement and stable dispersion of zirconium oxide phase transformation is achieved. This achieves the matching of matrix densification and second phase precipitation dynamics, improving the strength and toughness of the material and its high-temperature service reliability.

[0018] 3. In this invention, surface pore strengthening is achieved by pulsed magnetron sputtering technology. The pulse modulation characteristics of high-energy particle beams enable dynamic adaptation between the deposition rate of nano-tungsten layer and pore morphology. The nanoscale pore-closed layer constructed in situ forms a continuous grain boundary bridging network after annealing. This structure not only physically seals surface pore defects, but also forms a cross-scale protection system with the internal multi-level pore structure and zirconium oxide dispersed phase, improving the surface integrity and environmental corrosion resistance of the material. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for preparing a porous zirconia-dispersed tungsten material using a microchannel template at low temperature, according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: A method for preparing a microchannel template of porous zirconia-dispersed tungsten material by low-temperature drying, comprising the following steps: Step 1: Preparation of biomass microchannel template. Plant stems were selected as the substrate and were crushed and sieved to obtain biomass particles with a particle size of 50 μm. The particles were then subjected to delignification treatment, surface activation and microchannel directional regulation. Step 2: Tungsten precursor solution loading. The biomass template treated in Step 1 is immersed in the tungsten precursor solution, with the immersion pressure controlled at 0.1 MPa and the immersion time at 2 h. Step 3: Zirconia sol gradient infiltration. A step-by-step impregnation method is used. First, a zirconium salt solution is injected to fill the microchannels, and then a precipitant is added to initiate in-situ hydrolysis to form a zirconium oxide sol layer. Step 4: Low-temperature conformal drying, freeze-drying at 30% humidity and -20℃ for 12 hours to simultaneously achieve ice crystal template support and solvent directional evaporation; Step 5: Gradient heat treatment molding, segmented heating under hydrogen atmosphere: the first stage is to hold at 200℃ for 1 hour to remove the template, the second stage is to hold at 800℃ for 3 hours to achieve densification of the tungsten matrix, and the third stage is to hold at 1400℃ for 1 hour to induce the dispersion distribution of zirconium oxide phase transformation. Step 6: Surface pore-closure strengthening treatment. A nano-tungsten layer with a thickness of 50 nm is deposited on the material surface using pulsed magnetron sputtering to fill the surface pores.

[0022] In step one, the delignification treatment uses a sodium chlorite-acetic acid mixture with a pH of 3.5, reacting at 70℃ for 4 hours, achieving a delignification rate ≥85%. Surface activation is achieved through low-temperature oxygen plasma treatment at 300W for 10 minutes, increasing the hydroxyl density on the template surface. The microchannel directional control is assisted by an axial electrostatic field with a field strength of 1 kV / cm.

[0023] In step two, the tungsten precursor solution is prepared from the following components in the following mass percentages: Ammonium metatungstate: 20wt%, ammonium citrate: 5wt%, polyvinylpyrrolidone: 1wt%, ethylene glycol: 10wt%, balance: deionized water; The solution viscosity was controlled at 25℃ and 15 mPa·s, and the pH value was adjusted to 2.0.

[0024] The specific operation of zirconium oxide sol gradient infiltration in step three is as follows: A 0.5 mol / L solution of zirconium oxynitrate was injected into the microchannel and allowed to stand for 30 min. A mixture of ammonia and ethanol as a precipitant was added dropwise at a volume ratio of 1:1 and a dropping rate of 0.1 mL / min to initiate a hydrolysis reaction and generate zirconium hydroxide gel. Add yttrium oxide stabilizer, The sol is uniformly distributed by ultrasonic vibration at a frequency of 40kHz and a power of 200W with a molar ratio of 3%.

[0025] Step four: Low-temperature conformal drying During the pre-freezing stage, the temperature was lowered to -40℃ at a rate of 5℃ / min and kept at that temperature for 2 hours to form dendritic ice crystals. During the sublimation drying stage, the vacuum degree is ≤10Pa, the temperature is raised to -20℃, and the directional growth of ice crystals controls the pore size to 5μm. During the drying stage, the temperature is raised to 25°C to remove bound water.

[0026] Step four, prior to low-temperature conformal drying, also includes ultrasonic pre-structuring treatment: The biomass template loaded with the precursor was placed in an ultrasonic field with a frequency of 18 kHz for 10 min, and the ultrasonic power density was controlled at [value missing]. Maintain the solution temperature at 5℃ during treatment; The ultrasound direction is parallel to the microchannel axis, inducing sol particles to align along the channel wall to form a pre-textured layer.

[0027] In step five, during gradient heat treatment: The first stage heating rate is 2℃ / min, and the hydrogen flow rate is 50mL / min; The second stage introduces tungsten carbide seed crystals with a particle size of 0.1 μm and an addition amount of 0.5 wt% to inhibit abnormal growth of tungsten grains. The third stage involves rapid quenching at a cooling rate ≥100℃ / s, causing zirconia to precipitate as a tetragonal phase. It is diffusely distributed, with a phase content of ≥80%.

[0028] Zirconia dispersed phase satisfies: The particle size distribution is 50nm, with a gradient transition, 50nm on the surface and 200nm in the core; Bonding energy with tungsten matrix interface A W-Zr-O transition layer with a thickness of 2nm is formed at the interface.

[0029] Step six: Surface closed-pore strengthening: The sputtering target is made of pure tungsten with a purity of ≥99.95%; Process parameters: pulse frequency 10kHz, duty cycle 30%, argon pressure 0.5Pa; After deposition, the internal stress is eliminated by annealing at 400℃ for 1 hour.

[0030] The plant stems are selected from at least one of reeds, wheat straw, or bamboo shavings, and the aspect ratio of the microchannels is controlled to be 10:1 with a porosity ≥85%.

[0031] Example 2: A method for preparing a microchannel template of porous zirconia-dispersed tungsten material by low-temperature drying, comprising the following steps: Step 1: Preparation of biomass microchannel template. Plant stems were selected as the substrate and obtained by crushing and sieving biomass particles with a particle size of 150μm. The particles were then subjected to delignification treatment, surface activation and microchannel directional regulation. Step 2: Tungsten precursor solution loading. The biomass template treated in Step 1 is immersed in a tungsten precursor solution, with the immersion pressure controlled at 0.3 MPa and the immersion time at 3 h. Step 3: Zirconia sol gradient infiltration. A step-by-step impregnation method is used. First, a zirconium salt solution is injected to fill the microchannels, and then a precipitant is added to initiate in-situ hydrolysis to form a zirconium oxide sol layer. Step 4: Low-temperature conformal drying, freeze-drying for 24 hours at 40% humidity and -10℃, simultaneously achieving ice crystal template support and solvent directional evaporation; Step 5: Gradient heat treatment molding, segmented heating under hydrogen atmosphere: the first stage is to hold at 300℃ for 1.5h to remove the template, the second stage is to hold at 1000℃ for 4h to achieve densification of the tungsten matrix, and the third stage is to hold at 1500℃ for 2h to induce the dispersion distribution of zirconium oxide phase transformation. Step 6: Surface pore-closure strengthening treatment. A nano-tungsten layer with a thickness of 150 nm is deposited on the material surface using pulsed magnetron sputtering to fill the surface pores.

[0032] In step one, the delignification treatment uses a sodium chlorite-acetic acid mixture with a pH of 4.0, reacting at 80℃ for 6 hours, achieving a delignification rate ≥85%. Surface activation is achieved through low-temperature oxygen plasma treatment at 400W for 20 minutes, increasing the hydroxyl density on the template surface. The microchannel directional control is assisted by an axial electrostatic field with a field strength of 2kV / cm.

[0033] In step two, the tungsten precursor solution is prepared from the following components in the following mass percentages: Ammonium metatungstate: 25wt%, ammonium citrate: 8wt%, polyvinylpyrrolidone: 2wt%, ethylene glycol: 12wt%, balance: deionized water; The solution viscosity was controlled at 25℃ and 20 mPa·s, and the pH value was adjusted to 2.5.

[0034] The specific operation of zirconium oxide sol gradient infiltration in step three is as follows: A 1.0 mol / L solution of zirconium oxynitrate was injected into the microchannel and allowed to stand for 45 min. A mixture of ammonia and ethanol as a precipitant was added dropwise at a volume ratio of 1:1 and a dropping rate of 0.3 mL / min to initiate a hydrolysis reaction and generate zirconium hydroxide gel. Add yttrium oxide stabilizer, The sol is uniformly distributed by ultrasonic vibration at a frequency of 40kHz and a power of 200W with a molar ratio of 5%.

[0035] Step four: Low-temperature conformal drying During the pre-freezing stage, the temperature was lowered to -40℃ at a rate of 8℃ / min and kept at that temperature for 2 hours to form dendritic ice crystals. During the sublimation drying stage, the vacuum degree is ≤10Pa, the temperature is raised to -10℃, and the directional growth of ice crystals controls the pore size to 15μm. During the drying stage, the temperature is raised to 30℃ to remove bound water.

[0036] Step four, prior to low-temperature conformal drying, also includes ultrasonic pre-structuring treatment: The biomass template loaded with the precursor was placed in an ultrasonic field with a frequency of 22 kHz for 20 min, and the ultrasonic power density was controlled at [value missing]. Maintain the solution temperature at 10℃ during treatment; The ultrasound direction is parallel to the microchannel axis, inducing sol particles to align along the channel wall to form a pre-textured layer.

[0037] In step five, during gradient heat treatment: The first stage heating rate is 3℃ / min, and the hydrogen flow rate is 80mL / min; The second stage introduces tungsten carbide seed crystals with a particle size of 0.3 μm and an addition amount of 1.5 wt% to inhibit abnormal growth of tungsten grains. The third stage involves rapid quenching at a cooling rate ≥100℃ / s, causing zirconia to precipitate as a tetragonal phase. It is diffusely distributed, with a phase content of ≥80%.

[0038] Zirconia dispersed phase satisfies: The particle size distribution is 200nm, with a gradient transition, 70nm on the surface and 25nm in the core; Bonding energy with tungsten matrix interface A W-Zr-O transition layer with a thickness of 3nm is formed at the interface.

[0039] Step six: Surface closed-pore strengthening: The sputtering target is made of pure tungsten with a purity of ≥99.95%; Process parameters: pulse frequency 35kHz, duty cycle 50%, argon pressure 1.5Pa; After deposition, the internal stress is eliminated by annealing at 500℃ for 1 hour.

[0040] The plant stems are selected from at least one of reeds, wheat straw, or bamboo shavings, and the aspect ratio of the microchannels is controlled to be 30:1 with a porosity ≥85%.

[0041] Example 3: A method for preparing a microchannel template of porous zirconia-dispersed tungsten material by low-temperature drying, comprising the following steps: Step 1: Preparation of biomass microchannel template. Plant stems were selected as the substrate and were crushed and sieved to obtain biomass particles with a particle size of 200 μm. The particles were then subjected to delignification treatment, surface activation and microchannel directional regulation. Step 2: Tungsten precursor solution loading. The biomass template treated in Step 1 is immersed in a tungsten precursor solution, with the immersion pressure controlled at 0.5 MPa and the immersion time at 4 h. Step 3: Zirconia sol gradient infiltration. A step-by-step impregnation method is used. First, a zirconium salt solution is injected to fill the microchannels, and then a precipitant is added to initiate in-situ hydrolysis to form a zirconium oxide sol layer. Step 4: Low-temperature conformal drying, freeze-drying at 50% humidity and 0℃ for 36 hours to simultaneously achieve ice crystal template support and solvent directional evaporation; Step 5: Gradient heat treatment molding, segmented heating under hydrogen atmosphere: the first stage is to hold at 400℃ for 2 hours to remove the template, the second stage is to hold at 1200℃ for 5 hours to achieve densification of the tungsten matrix, and the third stage is to hold at 1600℃ for 3 hours to induce the dispersion distribution of zirconium oxide phase transformation. Step 6: Surface pore-closure strengthening treatment. A nano-tungsten layer with a thickness of 200 nm is deposited on the material surface using pulsed magnetron sputtering to fill the surface pores.

[0042] In step one, the delignification treatment uses a sodium chlorite-acetic acid mixture with a pH of 4.5, reacting at 90℃ for 8 hours, achieving a delignification rate ≥85%. Surface activation is achieved through low-temperature oxygen plasma treatment at 500W for 30 minutes, increasing the hydroxyl density on the template surface. The microchannel directional control is assisted by an axial electrostatic field with a field strength of 3kV / cm.

[0043] In step two, the tungsten precursor solution is prepared from the following components in the following mass percentages: Ammonium metatungstate: 30wt%, ammonium citrate: 10wt%, polyvinylpyrrolidone: 3wt%, ethylene glycol: 15wt%, balance: deionized water; The solution viscosity was controlled at 25℃ and 25 mPa·s, and the pH value was adjusted to 3.0.

[0044] The specific operation of zirconium oxide sol gradient infiltration in step three is as follows: A 1.5 mol / L solution of zirconium oxynitrate was injected into the microchannel and allowed to stand for 60 min. A mixture of ammonia and ethanol as a precipitant was added dropwise at a volume ratio of 1:1 and a dropping rate of 0.5 mL / min to initiate a hydrolysis reaction and generate zirconium hydroxide gel. Add yttrium oxide stabilizer, The sol is uniformly distributed by ultrasonic vibration at a frequency of 40kHz and a power of 200W with a molar ratio of 8%.

[0045] Step four: Low-temperature conformal drying During the pre-freezing stage, the temperature was lowered to -40℃ at a rate of 10℃ / min and kept at that temperature for 2 hours to form dendritic ice crystals. During the sublimation drying stage, the vacuum degree is ≤10Pa, the temperature is raised to 0℃, and the directional growth of ice crystals controls the pore size to 20μm. During the drying stage, the temperature is raised to 35°C to remove bound water.

[0046] Step four, prior to low-temperature conformal drying, also includes ultrasonic pre-structuring treatment: The biomass template loaded with the precursor was placed in an ultrasonic field with a frequency of 25 kHz for 30 min, and the ultrasonic power density was controlled at [value missing]. Maintain the solution temperature at 15℃ during treatment; The ultrasound direction is parallel to the microchannel axis, inducing sol particles to align along the channel wall to form a pre-textured layer.

[0047] In step five, during gradient heat treatment: The first stage heating rate is 5℃ / min, and the hydrogen flow rate is 100mL / min; The second stage introduces tungsten carbide seed crystals with a particle size of 0.5 μm and an addition amount of 2 wt% to inhibit abnormal growth of tungsten grains. The third stage involves rapid quenching at a cooling rate ≥100℃ / s, causing zirconia to precipitate as a tetragonal phase. It is diffusely distributed, with a phase content of ≥80%.

[0048] Zirconia dispersed phase satisfies: The particle size distribution is 300nm, with a gradient transition, 100nm on the surface and 300nm in the core; Bonding energy with tungsten matrix interface A W-Zr-O transition layer with a thickness of 5nm is formed at the interface.

[0049] Step six: Surface closed-pore strengthening: The sputtering target is made of pure tungsten with a purity of ≥99.95%; Process parameters: pulse frequency 50kHz, duty cycle 70%, argon pressure 2Pa; After deposition, the internal stress is eliminated by annealing at 600℃ for 1 hour.

[0050] The plant stems are selected from at least one of reeds, wheat straw, or bamboo shavings, and the aspect ratio of the microchannels is controlled to be 50:1 with a porosity ≥85%.

[0051] Comparative Example 1 differs from Example 1 in that: axial electrostatic field-assisted directional control was not used in the preparation of the biomass microchannel template in this comparative example.

[0052] Comparative Example 2 differs from Example 2 in that: this comparative example did not undergo ultrasonic pre-structuring treatment before low-temperature conformal drying.

[0053] Comparative Example 3 differs from Example 3 in that tungsten carbide seeds were not introduced in the second stage of gradient heat treatment in this comparative example.

[0054] Comparative Example 4 differs from Example 1 in that constant DC magnetron sputtering is used instead of pulsed magnetron sputtering in the surface closed-pore strengthening treatment.

[0055] The porous zirconia-dispersed tungsten materials prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and methods are as follows: Pore ​​structure testing involves observing the cross-sectional morphology of the material under a scanning electron microscope, using image analysis software to measure the pore size distribution and pore penetration rate of macropores, mesopores, and micropores, and calculating the proportion of the three levels of porosity. For the high-temperature oxidation test, the sample was placed in a muffle furnace and heated to 1200℃ at a rate of 10℃ / min in air atmosphere and held for 100 hours. After cooling to room temperature, the mass change was measured using a precision balance and the weight gain per unit area was calculated. Thermal shock stability test: The sample was placed in a tube furnace and rapidly immersed in room temperature water from 1200℃ under argon protection. The cooling rate was ≥200℃ / s. After 50 cycles, the zirconium phase transformation ratio was detected by X-ray diffraction and the residual strength retention rate was measured by the three-point bending method. Strength testing was conducted using a universal testing machine. Three-point bending tests were performed at room temperature and 1000℃, with a span of 30mm and a loading rate of 0.5mm / min. The maximum load was recorded and the bending strength was calculated.

[0056] The test data of the porous zirconium oxide dispersed tungsten materials prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below; By comparing and analyzing the data in the table, it can be seen that the porous zirconia dispersed tungsten materials prepared by the process in Examples 1-3 have better performance than the materials prepared by the process in Comparative Examples 1-4. This indicates that by combining the microchannel directional control technology of biomass template with the axial pressure impregnation of tungsten precursor solution, a uniform loading layer is formed on the inner wall of the microchannel, realizing the permeability of the precursor in the three-dimensional pore network. At the same time, by inducing the in-situ controllable hydrolysis of zirconium salt solution and precipitant by stepwise impregnation method, the zirconia sol grows layer by layer along the channel wall and spontaneously intercalates into the gaps of the tungsten matrix. This not only eliminates the risk of local component segregation, but also constructs a multi-level symbiotic interface structure, which strengthens the pinning and crack-resistant effect and structural stability of the dispersed phase. A synergistic mechanism of low-temperature conformal drying and ultrasonic pre-structuring is employed. Icy crystal templates provide directional support to suppress pore collapse and deformation, while axial ultrasonic fields drive the orderly arrangement of sol particles, spontaneously constructing multi-level interconnected channels during solvent sublimation. Combined with a segmented temperature control strategy using hydrogen atmosphere in gradient heat treatment, a triple synergy is achieved: gentle decomposition of the biological template, seed-guided grain refinement, and stable dispersion of zirconia phase transformation. This matches the matrix densification with the second-phase precipitation dynamics, improving the material's strength, toughness, and high-temperature service reliability. Surface pore-closure strengthening utilizes pulsed magnetron sputtering technology. The pulse modulation characteristics of high-energy particle beams enable dynamic adaptation between the deposition rate of the nano-tungsten layer and the pore morphology. The in-situ constructed nanoscale pore-closure layer, after annealing, forms a continuous grain boundary bridging network. This structure not only physically seals surface open-pore defects but also forms a cross-scale protection system with the internal multi-level pore structure and zirconia dispersed phase, improving the material's surface integrity and environmental corrosion resistance.

[0057] This demonstrates that the microchannel template low-temperature drying preparation method provided by the present invention, through the synergistic process of biological template-sol-gel infiltration-low-temperature drying-gradient heat treatment-surface strengthening, enables porous zirconia dispersed tungsten materials to simultaneously obtain high porosity, excellent high-temperature stability and outstanding mechanical strength, and has industrialization value and market promotion prospects in the extreme working conditions of nuclear reactor lining and high-temperature filtration systems.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a microchannel template of porous zirconia-dispersed tungsten material by low-temperature drying, characterized in that: Includes the following steps: Step 1: Preparation of biomass microchannel templates. Plant stems are selected as the substrate and are crushed and sieved to obtain biomass particles with a particle size of 50-200μm. The particles are then subjected to delignification treatment, surface activation and microchannel directional regulation. Step 2: Tungsten precursor solution loading. The biomass template treated in Step 1 is immersed in a tungsten precursor solution, with the immersion pressure controlled at 0.1-0.5 MPa and the immersion time at 2-4 h. Step 3: Zirconia sol gradient infiltration. A step-by-step impregnation method is used. First, a zirconium salt solution is injected to fill the microchannels, and then a precipitant is added to initiate in-situ hydrolysis to form a zirconium oxide sol layer. Step 4: Low-temperature conformal drying, freeze-drying for 12-36 hours in an environment with humidity of 30%-50% and temperature of -20℃-0℃, simultaneously achieving ice crystal template support and directional solvent evaporation; Step 5: Gradient heat treatment molding, segmented heating under hydrogen atmosphere: the first stage is 200-400℃ for 1-2h to remove the template, the second stage is 800-1200℃ for 3-5h to achieve densification of the tungsten matrix, and the third stage is 1400-1600℃ for 1-3h to induce the dispersion distribution of zirconium oxide phase transformation. Step 6: Surface pore-closure strengthening treatment. A nano-tungsten layer with a thickness of 50-200nm is deposited on the material surface using pulsed magnetron sputtering to fill the surface pores.

2. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: In step one, the delignification treatment uses a sodium chlorite-acetic acid mixture with a pH of 3.5-4.5, reacts at 70-90℃ for 4-8 hours, and achieves a delignification rate of ≥85%. Surface activation is achieved through low-temperature oxygen plasma treatment with a power of 300-500W and a treatment time of 10-30 minutes. Microchannel directional control is assisted by an axial electrostatic field with a field strength of 1-3kV / cm.

3. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: The tungsten precursor solution in step two is prepared by the following components in the following mass percentages: Ammonium metatungstate: 20-30 wt%, ammonium citrate: 5-10 wt%, polyvinylpyrrolidone: 1-3 wt%, ethylene glycol: 10-15 wt%, balance: deionized water; The solution viscosity was controlled at 25℃, 15-25 mPa·s, and the pH value was adjusted to 2.0-3.

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4. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: The specific operation of the zirconium oxide sol gradient infiltration in step three is as follows: Inject a 0.5-1.5 mol / L solution of zirconium oxynitrate into the microchannel and let it stand for 30-60 minutes. Add a mixture of ammonia and ethanol as a precipitant at a volume ratio of 1:1 at a dropping rate of 0.1-0.5 mL / min to initiate a hydrolysis reaction and generate zirconium hydroxide gel. Add yttrium oxide stabilizer, The molar ratio is 3-8%, and the sol is uniformly distributed by ultrasonic vibration at a frequency of 40kHz and a power of 200W.

5. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: In step four, low-temperature conformal drying: During the pre-freezing stage, the temperature is lowered to -40℃ at a rate of 5-10℃ / min and kept at that temperature for 2 hours to form dendritic ice crystals. During the sublimation drying stage, the vacuum degree is ≤10Pa, and the temperature is raised to -20℃-0℃. The directional growth of ice crystals controls the pore size to be 5-20μm. During the drying stage, the temperature is raised to 25-35℃ to remove bound water.

6. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: Step four, prior to low-temperature conformal drying, also includes ultrasonic pre-structuring treatment: The biomass template loaded with the precursor was placed in an ultrasonic field with a frequency of 18-25 kHz for 10-30 minutes, and the ultrasonic power density was controlled at [value missing]. Maintain the solution temperature at 5-15℃ during treatment; The ultrasound direction is parallel to the microchannel axis, inducing sol particles to align along the channel wall to form a pre-textured layer.

7. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: In step five, gradient heat treatment: The first stage heating rate is 2-5℃ / min, and the hydrogen flow rate is 50-100mL / min; The second stage introduces tungsten carbide seed crystals with a particle size of 0.1-0.5 μm and an addition amount of 0.5-2 wt% to inhibit abnormal growth of tungsten grains. The third stage involves rapid quenching at a cooling rate ≥100℃ / s, causing zirconia to precipitate as a tetragonal phase. It is diffusely distributed, with a phase content of ≥80%.

8. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: The zirconium oxide dispersed phase satisfies: The particle size distribution is 50-300nm, with a gradient transition, 50-100nm on the surface and 200-300nm in the core; Bonding energy with tungsten matrix interface A W-Zr-O transition layer with a thickness of 2-5 nm is formed at the interface.

9. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: In step six, surface pore-closure strengthening: The sputtering target is made of pure tungsten with a purity of ≥99.95%; Process parameters: pulse frequency 10-50kHz, duty cycle 30-70%, argon pressure 0.5-2Pa; After deposition, the internal stress is eliminated by annealing at 400-600℃ for 1 hour.

10. The method for preparing a microchannel template for porous zirconia-dispersed tungsten material by low-temperature drying according to claim 1, characterized in that: The plant stem is selected from at least one of reeds, wheat straw or bamboo shavings, and its microchannel aspect ratio is controlled to be 10:1-50:1, with a porosity ≥85%.

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