Temperature-control step-by-step smelting preparation method of hydrogen-purified vanadium-platinum alloy

Abstract

The invention relates to the technical field of metal materials, and particularly discloses a temperature-controlled step-by-step smelting preparation method of a hydrogen-purified vanadium-platinum alloy, and the hydrogen-purified vanadium-platinum alloy is prepared from the following raw materials in parts by weight: 88-92 parts of a vanadium raw material; 8-12 parts of a platinum raw material; 0.03 to 0.06 part of a primary gas phase activator; and 0.15 to 0.25 part of a secondary composite trapping agent. The first-stage gas-phase activating agent is prepared from nano carbon black and lanthanum hexaboride, and the weight ratio of the nano carbon black to the lanthanum hexaboride is (50: 1)-(60: 1). The secondary composite trapping agent is prefabricated quaternary alloy powder and comprises zirconium, yttrium, boron and silicon, and the weight ratio of the zirconium to the yttrium to the boron to the silicon is 40: 40: 5: 15. According to the method, the first-stage gas phase activator and the second-stage composite trapping agent are adopted for synergistic purification, interstitial impurities can be effectively removed, generation of a brittle hard phase is inhibited, the high-plasticity vanadium-platinum alloy is obtained, and the problems that a traditional material is large in brittleness and difficult to carry out cold rolling machining due to oxygen and nitrogen pollution are solved.

Description

Technical Field

[0001] This application relates to the field of metallic materials technology, and more specifically, to a method for preparing hydrogen-purified vanadium-platinum alloys by temperature-controlled stepwise melting. Background Technology

[0002] With the accelerated commercialization of the hydrogen energy industry, the demand for high-purity hydrogen in proton exchange membrane fuel cells and semiconductor manufacturing is growing. Among various hydrogen purification technologies, dense metal diffusion membranes, due to their unique selective permeability to hydrogen atoms, can obtain ultra-high purity hydrogen and have become a core material for the preparation of electronic-grade high-purity hydrogen.

[0003] Currently, the most mature industrial hydrogen separation membranes are palladium-based alloy membranes. However, palladium is a rare and precious metal, scarce in resources and expensive, which severely restricts its large-scale industrial application. In contrast, group VB metals, represented by vanadium, niobium, and tantalum, have significantly higher theoretical hydrogen permeability than palladium-based metals, and their raw material costs are significantly lower. However, traditional materials suffer from brittleness due to oxygen and nitrogen pollution, making them difficult to cold-roll. Summary of the Invention

[0004] To address the problem that traditional materials are brittle and difficult to cold roll due to oxygen and nitrogen contamination, this application provides a method for the controlled-temperature stepwise melting preparation of hydrogen-purified vanadium-platinum alloys.

[0005] In the first aspect, this application provides a vanadium-platinum alloy for hydrogen purification, employing the following technical solution:

[0006] The hydrogen purification vanadium-platinum alloy is made from the following raw materials in parts by weight: 88-92 parts vanadium raw material; 8-12 parts platinum raw material; 0.03-0.06 parts primary gas phase activator; and 0.15-0.25 parts secondary composite trapping agent.

[0007] By adopting the above technical solution, since this application uses a primary gas-phase activator and a secondary composite scavenger for synergistic purification, it can effectively remove interstitial impurities and inhibit the formation of brittle hard phases, thus obtaining a vanadium-platinum alloy with high plasticity. This solves the problem that traditional materials are brittle and difficult to cold roll due to oxygen and nitrogen pollution.

[0008] Preferably, the primary gas-phase activator is composed of nano carbon black and lanthanum hexaboride, and the weight ratio of nano carbon black to lanthanum hexaboride is 50:1-60:1.

[0009] By adopting the above technical solution, the activation energy of the solid carbothermic reduction reaction is significantly reduced due to the catalytic effect of nano carbon black as a reducing agent and lanthanum hexaboride. This promotes the conversion of adsorbed oxygen on the surface of the raw material into carbon monoxide gas at low temperature and solid state, thus avoiding the diffusion of carbon atoms into the vanadium lattice to form a brittle vanadium carbide hard phase at high temperature liquid phase. This results in a toughening effect with a pure matrix and no grain boundary carbide precipitation.

[0010] Preferably, the secondary composite trapping agent is a pre-made quaternary alloy powder, the composition of which includes zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:15.

[0011] By adopting the above technical solution, the strong chemical activity of zirconium and yttrium is used to deeply capture interstitial nitrogen and oxygen impurities in the matrix, and the fluxing effect of boron and silicon is used to initiate a multi-element eutectic reaction, which transforms the generated refractory solid oxides in situ into low-melting-point, low-viscosity liquid silicate borate slag. Therefore, the interfacial tension of non-metallic inclusions is significantly reduced and their wetting coalescence and Stokes flotation are promoted, resulting in an alloy ingot with extremely low interstitial impurity content and dense internal structure.

[0012] Secondly, this application provides a temperature-controlled stepwise melting method for preparing vanadium-platinum alloys using hydrogen purification, employing the following technical solution:

[0013] A temperature-controlled stepwise melting method for preparing hydrogen-purified vanadium-platinum alloys includes the following steps:

[0014] S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state.

[0015] S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure.

[0016] S3, Liquid composite slag formation: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain the hydrogen-purified vanadium-platinum alloy.

[0017] By adopting the above technical solution, the surface oxygen is preferentially converted into gas and discharged before melting by solid activation, thus blocking the formation path of the high-temperature vanadium carbide hard phase from the source. The uniform infiltration and deep degassing of liquid platinum in the solid vanadium skeleton are driven by pressure-switching wetting, and the deep separation of residual impurities is achieved by liquid composite slag forming. Therefore, an alloy ingot with no component segregation, extremely low interstitial impurities and excellent room temperature plasticity is obtained.

[0018] Preferably, in step S1, the background pressure of the vacuum environment is ≤1.0×10⁻ 4 Pa, the first temperature zone T1 is 1050-1150℃, and the holding time is 120-180min.

[0019] By adopting the above technical solution, the use of a solid-state temperature range of 1050-1150℃ combined with a high vacuum environment ensures that the raw materials do not melt. This allows for the rapid desorption of CO gas, a product of the carbon-oxygen reaction, driven by high vacuum. Furthermore, the diffusion barrier in the solid state restricts the migration of carbon atoms into the depths of the metal lattice. As a result, the oxygen load on the surface of the raw materials is completely removed, thus achieving the beneficial effect of avoiding the formation of vanadium carbide hard phase caused by carbon diffusion in the high-temperature liquid phase.

[0020] Preferably, in S2, the second temperature zone T2 is 1780-1800℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 10-20Pa and a high pressure state of 1000-1500Pa.

[0021] By adopting the above technical solution, liquid platinum wets the solid vanadium framework at a semi-melting temperature range of 1780-1800℃, and utilizes the aerodynamic "breathing effect" generated by high and low pressure cycles to extract and desorb deep closed-pore gas under low pressure, and force liquid platinum to overcome surface tension and penetrate into micropores under high pressure, thus disrupting the gas-liquid interface balance and eliminating internal porosity defects, resulting in a dense alloy preform in which platinum components are uniformly dispersed in the vanadium matrix and without macroscopic segregation.

[0022] Preferably, the high-low voltage cycle switching period is 5-8 minutes, and the number of cycles is 3-5 times.

[0023] By adopting the above technical solution, the switching cycle of 5-8 minutes ensures that the liquid platinum fully fills the micropores and the internal gas completely diffuses under capillary action. The repeated washing and replacement of the porous skeleton by 3-5 cycles completely eliminates internal blind pores and residual bubbles, resulting in an alloy structure with highly homogeneous composition and no porosity defects.

[0024] Preferably, the third temperature zone T3 is 2100-2200℃, and the inert gas is high-purity argon with a pressure of 0.02-0.05MPa.

[0025] By adopting the above technical solution, the high-temperature superheating at 2100-2200℃ significantly reduces the dynamic viscosity of the molten metal and enhances its fluidity. Furthermore, the micro-positive pressure environment of 0.02-0.05MPa effectively suppresses the severe volatilization loss of the base metal vanadium at high temperatures. Therefore, while ensuring precise control of the alloy composition, the optimal kinetic conditions for the Stokes flotation of the liquid slag are provided, resulting in a refining effect with stable composition and thorough removal of inclusions.

[0026] Preferably, the electromagnetic stirring adopts a frequency conversion stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 40-45Hz, lasting for 3 minutes; the second stage: frequency 80-90Hz, lasting for 5 minutes; the third stage: frequency 30-35Hz, lasting for 2 minutes.

[0027] By adopting the above technical solution, the medium-frequency stirring ensures the uniform dispersion of the trapping agent in the melt, the high-frequency violent oscillation significantly increases the collision probability of liquid slag droplets and promotes their coalescence and growth, and the low-frequency stable flow field reduces the turbulence of the melt to assist large-sized slag to float rapidly according to Stokes' law. Therefore, the dynamic enhancement of the entire process of dispersion-adsorption-coalescence-separation of non-metallic inclusions is realized, and a refining effect with thorough removal of inclusions and no secondary slag entrapment is obtained.

[0028] Preferably, the cooling in S3 adopts directional solidification, the cooling rate is controlled at 10-20℃ / min, and the temperature of the top of the melt is kept 50-80℃ higher than the temperature of the bottom. After cooling to room temperature, the slag layer on the top of the ingot is removed.

[0029] By adopting the above technical solution, the temperature gradient is constructed from bottom to top through directional solidification. The principle of solute redistribution is used to drive low melting point impurities and liquid slag to move to the top final solidification zone along with the solid-liquid interface. Therefore, internal defects are concentrated and locked at the riser, and a dense, homogeneous, and impurity-free high-purity alloy ingot can be obtained by simple removal.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. Because this application uses a primary gas-phase activator and a secondary composite scavenger for synergistic purification, it can effectively remove interstitial impurities and inhibit the formation of brittle hard phases, thus obtaining a vanadium-platinum alloy with high plasticity. This solves the problem that traditional materials are brittle and difficult to cold roll due to oxygen and nitrogen pollution.

[0032] 2. Because the primary gas-phase activator used in this application can play a role in targeting the adsorbed impurities on the surface of the raw materials in the early stage of preparation, it provides a clean reaction interface for the subsequent alloying process, thus achieving the technical effect of effectively reducing the oxide layer on the surface of the raw materials and the amount of adsorbed gas introduced.

[0033] 3. Because this application uses a two-stage composite trapping agent, it can physically or chemically capture the deep interstitial impurities remaining inside the alloy melt, preventing the segregation of impurity atoms at the grain boundaries, thus obtaining vanadium-platinum alloy ingots with high matrix purity and strong grain boundary bonding.

[0034] 4. Because this application uses platinum raw materials to provide sufficient catalytic active sites in the vanadium solid solution lattice to promote the dissociation and adsorption of hydrogen molecules, while avoiding the increased cost and risk of microstructure segregation caused by excessive platinum, a vanadium-platinum alloy material with both excellent hydrogen permeability and economy is obtained. Attached Figure Description

[0035] Figure 1 The flowchart illustrates the temperature-controlled stepwise melting method for preparing hydrogen-purified vanadium-platinum alloys provided in this application. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Technical Concept: To address the technical challenges of embrittlement and component segregation in vanadium-platinum alloys caused by interstitial impurities, a spatiotemporal stepwise purification system of solid-gas phase activation-liquid composite slag formation was constructed. Specifically, in the solid stage before raw material melting, lanthanum hexaboride catalyzes a carbothermic reduction reaction to preferentially remove surface oxygen in gaseous form, blocking the formation pathway of the high-temperature vanadium carbide hard phase at its source. Then, in the liquid stage, a zirconium-yttrium-boron-silicon quaternary eutectic component is introduced to convert refractory oxides and nitrides in situ into low-viscosity liquid borosilicate slag. Combined with the kinetic assistance of variable pressure pulse and variable frequency stirring, the Stokes effect is utilized to achieve deep separation of inclusions and component homogenization.

[0038] Please see the appendix Figure 1 The hydrogen purification vanadium-platinum alloy is made from the following raw materials in parts by weight: 88-92 parts vanadium raw material; 8-12 parts platinum raw material; 0.03-0.06 parts primary gas phase activator; and 0.15-0.25 parts secondary composite trapping agent.

[0039] Specifically, vanadium, as the alloy matrix, provides channels for hydrogen atoms to diffuse within the metal through its body-centered cubic lattice structure, ensuring a high hydrogen permeability coefficient. Platinum, as the catalytically active component, reduces the dissociation and recombination energy of hydrogen molecules on the alloy surface. Controlling the platinum content to 8-12 parts maintains the catalytic activity of the alloy surface while utilizing the wetting properties of platinum liquid at high temperatures to encapsulate the vanadium framework, improving the uniformity of component distribution.

[0040] The primary gas-phase activator plays a role in the raw material pretreatment and solid-state activation steps. Lanthanum hexaboride, acting as an electron emission catalyst, lowers the activation energy of the carbothermic reduction reaction. Nano-carbon black, utilizing its high specific surface area, undergoes a solid-phase reaction with the oxide layer on the vanadium raw material surface within a first-temperature range below the alloy's melting point, converting oxygen into carbon monoxide gas, which is then released. This process achieves in-situ surface purification before alloy melting, avoiding the problem in traditional processes where carbon elements enter the crystal lattice at high-temperature liquid phases to form a hard vanadium carbide phase.

[0041] The secondary composite scavenging agent plays a crucial role in deep purification during the liquid composite slag-forming process. Zirconium specifically binds to nitrogen impurities in the melt to form zirconium nitride, while yttrium captures deep dissolved oxygen to form yttrium oxide. Boron and silicon act as fluxes, undergoing in-situ eutectic reactions with the high-melting-point zirconium nitride and yttrium oxide, transforming refractory solid inclusions into a low-melting-point, low-viscosity liquid borosilicate glass phase. Following Stokes' law, the liquid slag more readily agglomerates and grows within the melt, eventually floating to the surface, thus achieving the removal of deep oxygen and nitrogen impurities.

[0042] The combination of a pressure-variable wetting and seepage process, utilizing high- and low-pressure cyclic switching to disrupt the equilibrium state of the gas-liquid interface, accelerates the desorption of gases in deep interstitial spaces. Combined with a variable-frequency electromagnetic stirring process, it promotes the collision maturation and flotation separation of the molten slag. These technical features work together to reduce the oxygen and nitrogen content and residual non-metallic inclusions in the final alloy ingot, significantly improving the room-temperature plasticity and resistance to hydrogen embrittlement of the vanadium-platinum alloy.

[0043] The primary gas-phase activator is composed of nano carbon black and lanthanum hexaboride, with a weight ratio of nano carbon black to lanthanum hexaboride of 50:1-60:1.

[0044] Specifically, the primary gas-phase activator consists of nano-carbon black and lanthanum hexaboride, with their weight ratio limited to 50:1-60:1. Nano-carbon black, utilizing its high specific surface area due to its nano-sized particles, increases the solid-phase contact sites between the reducing agent and the oxide layer on the vanadium raw material surface, providing the physical basis for the reduction reaction. Lanthanum hexaboride, as an electron emission catalyst, lowers the activation energy of the carbothermic reduction reaction under solid-state conditions, allowing the reaction between carbon and vanadium surface oxides to occur within a first temperature range below the alloy's melting point, removing oxygen from the solid precursor as carbon monoxide gas. The 50:1-60:1 weight ratio ensures a stoichiometric surplus of carbon source relative to the oxygen content on the raw material surface, guaranteeing the thoroughness of the gasification deoxidation reaction, while controlling the amount of catalyst introduced, avoiding the introduction of new impurity phases due to excessive catalyst. This technology improves the oxygen absorption characteristics of the vanadium matrix in the high-temperature liquid phase by achieving in-situ surface purification in the solid stage, avoiding the problem of vanadium carbide hard phase formed due to carbon residue in traditional processes, thereby reducing the content of interstitial impurities in the alloy matrix.

[0045] The secondary composite trapping agent is a pre-made quaternary alloy powder, whose components include zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:15.

[0046] Specifically, the secondary composite scavenging agent is in the form of pre-made quaternary alloy powder, with each component pre-alloyed in a specific ratio to ensure the uniformity of element distribution and the synchronicity of reaction after being added to the melt. Zirconium, utilizing its chemical affinity for nitrogen atoms, reacts with interstitial nitrogen in the melt to form zirconium nitride; yttrium, as a strong deoxidizer, captures dissolved oxygen deep within the matrix to form yttrium oxide. Boron and silicon, as fluxing and slag-forming components, lower the eutectic temperature of the slag system and react in situ with the high-melting-point zirconium nitride and yttrium oxide, transforming the refractory solid compounds into a low-melting-point, low-viscosity liquid composite borosilicate slag.

[0047] The 40:40:5:15 weight ratio of zirconium, yttrium, boron, and silicon ensures sufficient active zirconium and yttrium for deep deoxidation and denitrification reactions, while providing stoichiometric boron and silicon to form a stable glassy slag. This promotes the liquid state of inclusions during the high-temperature smelting stage. This liquid slag, utilizing its interfacial tension difference with the metal matrix and its low viscosity, readily collides, coalesces, and grows under hydrodynamic forces. It then separates from the alloy melt to the surface via a Stokes flotation mechanism, achieving deep removal of interstitial impurities and non-metallic inclusions, thus improving the room-temperature brittleness of vanadium-platinum alloys caused by impurity pinning dislocations.

[0048] A temperature-controlled stepwise melting method for preparing hydrogen-purified vanadium-platinum alloys includes the following steps:

[0049] S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state.

[0050] S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure.

[0051] S3, Liquid Composite Slag Forming: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain hydrogen-purified vanadium-platinum alloy.

[0052] Specifically, a heat treatment is performed in the first temperature zone T1, which is below the alloy's melting point. Utilizing the solid-phase reaction mechanism between a primary gas-phase activator and the raw material surface, the oxide layer on the raw material surface is converted into gas and discharged in the solid state. This in-situ surface purification treatment reduces the impurity load during subsequent melting processes and prevents impurity elements from entering the crystal lattice and forming refractory compounds under high-temperature liquid phase conditions, thereby improving the purity of the alloy matrix.

[0053] By controlling the temperature within a second temperature range, T2, between the melting points of platinum and vanadium raw materials, a transitional state of liquid-phase platinum wetting solid-phase vanadium was constructed. The capillary wetting effect of liquid platinum on the solid vanadium framework was utilized to lock the spatial distribution of components, improving the macroscopic segregation problem caused by the significant density difference between vanadium and platinum. Simultaneously, by alternating high and low pressure cycles within the vacuum chamber, the pressure difference disrupted the equilibrium state of the gas-liquid interface, establishing the kinetic conditions for driving interstitial gas desorption and promoting the expulsion of deeply adsorbed gases from the porous framework.

[0054] A secondary composite trapping agent is introduced in the fully molten third temperature zone T3, in conjunction with electromagnetic stirring. The secondary composite trapping agent reacts with residual deep interstitial impurities in the melt, generating easily separable liquid slag. The fluid shear force and convection provided by electromagnetic stirring promote the collision, coalescence, growth, and Stokes flotation separation of the liquid slag, while simultaneously homogenizing the chemical composition of the alloy melt. This stepwise temperature control and physical field synergy process achieves gradient purification from the surface to the core, and from the solid to the liquid state, ensuring the compositional uniformity and low impurity content of the hydrogen-purified vanadium-platinum alloy.

[0055] In S1, the background pressure of the vacuum environment is ≤1.0×10⁻ 4 Pa, the first temperature zone T1 is 1050-1150℃, and the holding time is 120-180min.

[0056] Specifically, in S1, the background pressure of the vacuum environment is controlled at 1.0 × 10⁻ 4 Below Pa, it is used in conjunction with a first temperature zone of 1050-1150℃ and a holding time of 120-180 minutes. Among them, 1.0×10⁻ 4The background vacuum below Pa reduces the partial pressure of gases within the reaction system, providing a thermodynamic environment conducive to the solid-state carbothermic reduction reaction towards the generation of gaseous products, and promoting the rapid escape of gaseous deoxidation products. The temperature setting of 1050-1150℃ allows the deoxidation reaction to proceed under solid-state conditions far below the melting points of vanadium and platinum raw materials. This temperature range satisfies the reaction kinetics required to remove the oxide layer on the surface of the raw materials while avoiding premature sintering of the raw materials or excessive diffusion of carbon into the matrix due to excessively high temperatures, which could lead to the formation of vanadium carbide inclusions. The holding time of 120-180 minutes ensures sufficient solid-phase diffusion and surface reaction, allowing the raw materials to undergo in-situ surface purification before entering the melting stage, reducing the oxygen impurity load during subsequent melting processes.

[0057] In S2, the second temperature zone T2 is 1780-1800℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 10-20Pa and a high pressure state of 1000-1500Pa.

[0058] Specifically, in S2, the second temperature zone T2 is controlled at 1780-1800℃, a temperature range set above the melting point of platinum raw materials and below the melting point of vanadium raw materials. Under these thermodynamic conditions, platinum raw materials preferentially undergo phase transformation to a liquid state, while vanadium raw materials maintain a solid framework structure. Liquid platinum utilizes its interfacial wetting properties to physically permeate and coat the gaps between solid vanadium particles, constructing a liquid-solid interlocked transition state structure. This restricts the free sedimentation movement of heavy metal platinum during the subsequent complete melting stage, thereby suppressing macroscopic component segregation caused by the significant density difference between platinum and vanadium.

[0059] The system employs an alternating argon pressure cycle between a low-pressure state (10-20 Pa) and a high-pressure state (1000-1500 Pa). The low-pressure state reduces the partial pressure of the ambient gas, providing the thermodynamic potential energy to drive the desorption of deeply adsorbed gases within the framework. The high-pressure state introduces argon gas, which suppresses the volatilization of metal elements at high temperatures and scours and displaces the pore gases. This periodic pressure pulse oscillation disrupts the diffusion equilibrium boundary layer of the gas on the porous framework surface, establishing a kinetic gradient for forced exhaust and accelerating the escape of residual interstitial gases from the precursor.

[0060] The high-low voltage cycle switching period is 5-8 minutes, and the number of cycles is 3-5 times.

[0061] Specifically, the high-low pressure cycling cycle is set to 5-8 minutes, providing sufficient response time for the gas diffusion process within the solid vanadium framework. This duration allows for an effective balance between the pore pressure inside the material and the ambient pressure of the vacuum chamber, ensuring that deeply adsorbed gases have enough time to desorb and diffuse to the surface during the low-pressure holding phase, while being effectively replaced by argon during the high-pressure holding phase. The number of cycles is set to 3-5, utilizing the cumulative effect of multiple pressure pulse oscillations to gradually reduce the concentration gradient of residual gases inside the material. This parameter range ensures thorough degassing and complete liquid platinum impregnation while avoiding reduced production efficiency and energy waste due to excessive cycles.

[0062] The third temperature zone, T3, is 2100-2200℃, and the inert gas is high-purity argon with a pressure of 0.02-0.05MPa.

[0063] Specifically, in S3, the third temperature zone T3 is controlled at 2100-2200℃, which is significantly higher than the melting points of vanadium and platinum raw materials, ensuring that the alloy raw materials are in a completely homogenized liquid phase. Under these high-temperature thermodynamic conditions, zirconium and yttrium in the secondary composite trapping agent have sufficient diffusion kinetic energy to undergo rapid chemical trapping reactions with interstitial oxygen and nitrogen impurities deep in the melt. At the same time, the high temperature reduces the viscosity of the generated borosilicate slag, which is beneficial for the slag droplets to overcome resistance and coalesce in the fluid and achieve Stokes flotation separation by utilizing density differences.

[0064] Meanwhile, high-purity argon gas with a pressure of 0.02-0.05 MPa is used as a protective atmosphere. This slightly positive pressure environment effectively isolates the alloy melt from secondary oxidation and nitriding caused by external air, while using gas partial pressure to suppress the volatilization loss of vanadium, a component with high saturated vapor pressure in the matrix, under high temperature conditions, thus ensuring the accuracy of the chemical composition ratio of the final alloy ingot and the stability of the melting process.

[0065] The electromagnetic stirring adopts a variable frequency stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 40-45Hz, lasting for 3 minutes; the second stage: frequency 80-90Hz, lasting for 5 minutes; the third stage: frequency 30-35Hz, lasting for 2 minutes.

[0066] Specifically, the electromagnetic stirring employs a variable frequency stirring method and is controlled in three specific stages. The kinetic optimization of the melt purification process is achieved through the temporal coupling of flow field characteristics at different frequency bands. In the first stage, the frequency is set to 40-45 Hz and maintained for 3 minutes. Utilizing the macroscopic forced convection effect generated in this mid-frequency band, the secondary composite trapping agent is driven to rapidly disperse throughout the alloy melt and achieve chemical homogenization, ensuring sufficient contact between the trapping agent and deep interstitial impurities in the melt and maximizing reaction mass transfer efficiency. In the second stage, the frequency is increased to 80-90 Hz and maintained for 5 minutes. Utilizing the micro-oscillations and high-shear turbulence induced by high-frequency electromagnetic force, the Brownian motion and physical collision probability between dispersed liquid borosilicate slag particles are significantly increased. This promotes the wetting and coalescence of tiny slag droplets through collisions, leading to rapid growth and increasing the Stokes radius of non-metallic inclusions. The third stage reduces the frequency to 30-35Hz and continues for 2 minutes, which reduces the turbulence intensity of the fluid to create a relatively stable quasi-laminar flow field environment. This suppresses the violent turbulence of the melt and its entrainment effect on the floating slag. By utilizing the Stokes law principle, the coalesced and grown low-density liquid slag overcomes viscous resistance and rapidly floats to the surface of the melt under the dominance of buoyancy, thus achieving efficient separation of the slag phase and the alloy melt.

[0067] The cooling in S3 adopts directional solidification, with the cooling rate controlled at 10-20℃ / min, and the temperature at the top of the melt is kept 50-80℃ higher than the temperature at the bottom. After cooling to room temperature, the slag layer at the top of the ingot is removed.

[0068] Specifically, the cooling process in S3 employs directional solidification, coupled with a cooling rate of 10-20℃ / min and a temperature gradient of 50-80℃ higher at the top than at the bottom. Maintaining a higher temperature at the top of the melt than at the bottom establishes a stable heat flow channel in the opposite direction of gravity, ensuring that the solid-liquid phase transformation interface of the alloy melt strictly originates from the bottom of the crucible and progresses orderly towards the top. The controlled cooling rate of 10-20℃ / min reduces the propagation speed of the solid-liquid interface, providing sufficient kinetic time for the diffusion and migration of liquid borosilicate slag and trace residual bubbles at the solidification front. Utilizing the principle of solute redistribution, non-metallic inclusions with low solubility and low-melting-point impurities are continuously expelled and enriched in the riser region at the top of the finally solidified ingot, preventing impurities from being captured by grain boundaries due to excessive supercooling. After cooling to room temperature, the slag layer at the top of the ingot is removed by machining, physically removing the enriched oxide slag layer and shrinkage cavities, thus obtaining a vanadium-platinum alloy ingot with a dense internal structure and pure chemical composition.

[0069] The raw materials used in this application are from the following sources:

[0070] Vanadium raw material: High-purity metallic vanadium particles, purity ≥99.95%, particle size 3mm-5mm, purchased from Beijing Zhongnuo New Materials Technology Co., Ltd.

[0071] Platinum raw material: High-purity platinum foil, purity ≥99.99%, thickness 0.1mm, purchased from Guizhou Platinum Industry Co., Ltd.;

[0072] Nano carbon black: Conductive carbon black, model SuperPLi, average primary particle size 40nm, specific surface area 62m² / g, purchased from Imerys, Switzerland.

[0073] Lanthanum hexaboride: powder, purity ≥99.5%, average particle size 1μm-2μm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0074] Secondary composite trap: This trap was prepared in the laboratory. The raw materials used to prepare the trap were sponge zirconium (Zr≥99.8%), distilled yttrium metal (Y≥99.9%), amorphous boron powder (B≥99%), and crystalline silicon powder (Si≥99.99%), all of which were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0075] High-purity argon: purity ≥99.999%, oxygen content ≤0.5ppm, purchased from Praxair Investment Co., Ltd., China.

[0076] Example 1: This example provides a hydrogen purification vanadium-platinum alloy, made from raw materials comprising the following parts by weight:

[0077] Vanadium raw material: 88 parts; Platinum raw material: 8 parts; Primary gas phase activator: 0.03 parts; Secondary composite trapping agent: 0.15 parts.

[0078] The primary gas-phase activator is composed of nano-carbon black and lanthanum hexaboride, with a weight ratio of nano-carbon black to lanthanum hexaboride of 50:1.

[0079] The secondary composite trapping agent is a pre-made quaternary alloy powder, whose components include zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:15.

[0080] The above-mentioned method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting is as follows:

[0081] S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state.

[0082] S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure.

[0083] S3, Liquid Composite Slag Forming: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain hydrogen-purified vanadium-platinum alloy.

[0084] In S1, the background pressure of the vacuum environment is ≤0.5×10⁻ 4 Pa, the first temperature zone T1 is 1050℃, and the holding time is 120min.

[0085] In S2, the second temperature zone T2 is 1780℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 10Pa and a high pressure state of 1000Pa.

[0086] The high and low voltage switching cycle is 5 minutes, and the number of cycles is 3.

[0087] The third temperature zone, T3, is 2100℃, and the inert gas is high-purity argon with a pressure of 0.02MPa.

[0088] The electromagnetic stirring adopts a variable frequency stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 40Hz, lasting for 3 minutes; the second stage: frequency 80Hz, lasting for 5 minutes; the third stage: frequency 30Hz, lasting for 2 minutes.

[0089] The cooling in S3 adopts directional solidification, with a cooling rate controlled at 10℃ / min, and the temperature at the top of the melt is kept 50℃ higher than the temperature at the bottom. After cooling to room temperature, the slag layer at the top of the ingot is removed.

[0090] Example 2: This example provides a hydrogen purification vanadium-platinum alloy, made from raw materials comprising the following parts by weight:

[0091] Vanadium raw material 90 parts; platinum raw material 10 parts; primary gas phase activator 0.045 parts; secondary composite capture agent 0.20 parts.

[0092] The primary gas-phase activator is composed of nano-carbon black and lanthanum hexaboride, with a weight ratio of nano-carbon black to lanthanum hexaboride of 55:1.

[0093] The secondary composite trapping agent is a pre-made quaternary alloy powder, whose components include zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:15.

[0094] The above-mentioned method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting is as follows:

[0095] S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state.

[0096] S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure.

[0097] S3, Liquid Composite Slag Forming: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain hydrogen-purified vanadium-platinum alloy.

[0098] In S1, the background pressure of the vacuum environment is ≤0.8×10⁻ 4 Pa, the first temperature zone T1 is 1100℃, and the holding time is 150min.

[0099] In S2, the second temperature zone T2 is 1790℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 15Pa and a high pressure state of 1250Pa.

[0100] The high-low voltage cycle switching period is 6.5 minutes, and the number of cycles is 4.

[0101] The third temperature zone, T3, is 2150℃, and the inert gas is high-purity argon with a pressure of 0.035MPa.

[0102] The electromagnetic stirring adopts a variable frequency stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 42Hz, lasting for 3 minutes; the second stage: frequency 85Hz, lasting for 5 minutes; the third stage: frequency 32Hz, lasting for 2 minutes.

[0103] The cooling in S3 adopts directional solidification, with a cooling rate controlled at 15℃ / min, and the temperature at the top of the melt is kept 60℃ higher than the temperature at the bottom. After cooling to room temperature, the slag layer at the top of the ingot is removed.

[0104] Example 3: This example provides a hydrogen purification vanadium-platinum alloy, made from raw materials comprising the following parts by weight:

[0105] Vanadium raw material 92 parts; platinum raw material 12 parts; primary gas phase activator 0.06 parts; secondary composite capture agent 0.25 parts.

[0106] The primary gas-phase activator is composed of nano-carbon black and lanthanum hexaboride, with a weight ratio of nano-carbon black to lanthanum hexaboride of 60:1.

[0107] The secondary composite trapping agent is a pre-made quaternary alloy powder, whose components include zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:15.

[0108] The above-mentioned method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting is as follows:

[0109] S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state.

[0110] S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure.

[0111] S3, Liquid Composite Slag Forming: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain hydrogen-purified vanadium-platinum alloy.

[0112] In S1, the background pressure of the vacuum environment is ≤1.0×10⁻ 4 Pa, the first temperature zone T1 is 1150℃, and the holding time is 180min.

[0113] In S2, the second temperature zone T2 is 1800℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 20Pa and a high pressure state of 1500Pa.

[0114] The high and low voltage switching cycle is 8 minutes, and the number of cycles is 5.

[0115] The third temperature zone, T3, is 2200℃, and the inert gas is high-purity argon with a pressure of 0.05MPa.

[0116] The electromagnetic stirring adopts a variable frequency stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 45Hz, lasting for 3 minutes; the second stage: frequency 90Hz, lasting for 5 minutes; the third stage: frequency 35Hz, lasting for 2 minutes.

[0117] The cooling in S3 adopts directional solidification, with a cooling rate controlled at 20℃ / min, and the temperature at the top of the melt is kept 80℃ higher than the temperature at the bottom. After cooling to room temperature, the slag layer at the top of the ingot is removed.

[0118] Comparative Example 1: This comparative example refers to the content of Example 2, except that no primary gas phase activator was added to the raw materials, and the rest of the content is the same as Example 2.

[0119] Comparative Example 2: This comparative example refers to Example 2, except that the secondary composite trapping agent is replaced with an equal weight of yttrium metal powder, and does not contain zirconium, boron, or silicon. The rest of the contents are the same as in Example 2.

[0120] Comparative Example 3: In the preparation method, S1 is omitted. The mixed and pressed raw materials are directly heated to the second temperature zone T2. The rest of the contents are the same as in Example 2.

[0121] Comparative Example 4: This comparative example refers to the content of Example 2, except that in S2, the high and low pressure cycles were not switched, but the pressure was always kept at a constant argon pressure of 1250 Pa. The rest of the content is the same as Example 2.

[0122] Comparative Example 5: This comparative example refers to the content of Example 2, except that the electromagnetic stirring in S3 uses a constant frequency of 50Hz and does not use three-stage frequency conversion control. The rest of the content is the same as Example 2.

[0123] Comparative Example 6: This comparative example refers to Example 2, except that the primary gas phase activator does not contain lanthanum hexaboride and is composed only of nano carbon black. The rest of the contents are the same as in Example 2.

[0124] Comparison data table of hydrogen purification vanadium-platinum alloy and commercially available products:

[0125] Table 1

[0126]

[0127] As shown in Table 1, commercially available products, due to the use of conventional vacuum melting processes, cannot deeply remove interstitial oxygen and nitrogen impurities from the deep layers of the vanadium matrix, resulting in an oxygen content as high as 380 ppm. Influenced by the Cotterell atmosphere, the material's room temperature elongation is only 4.5%, making subsequent foil rolling difficult. However, Example 2 of this application, by introducing a primary gas-phase activator and a secondary composite trapping agent, combined with variable pressure and frequency stirring processes, controls the total oxygen and nitrogen content below 150 ppm, causing the alloy's room temperature elongation to jump to 24.1%. Simultaneously, the increased hydrogen permeability coefficient indicates that deep purification eliminates non-metallic inclusions at grain boundaries, reducing the diffusion resistance of hydrogen atoms within the crystal lattice.

[0128] Performance testing

[0129] The alloy ingots prepared in each embodiment and comparative example underwent comprehensive performance testing. The interstitial impurity content, room temperature tensile properties, component segregation, and inclusion morphology of the materials were determined using a LECOON H836 oxygen-nitrogen-hydrogen analyzer, an electronic universal testing machine (following GB / T228.1 standard), an ICP-AES spectrometer, and a scanning electron microscope, respectively. The test results showed that Example 2, using the preferred formulation and temperature-controlled stepwise melting process of this application, reduced the oxygen and nitrogen content of the ingots to 95 ppm and 30 ppm, respectively; the average size of non-metallic inclusions was less than 0.5 μm; the macroscopic segregation was controlled within ±0.20 wt%; the room temperature elongation after fracture reached 24.1%; and the hydrogen permeability coefficient increased to 3.50 × 10⁻⁸ mol / (m·s·Pa⁰.⁵). In contrast, commercially available products of the same grade and Comparative Examples 1-6, which lacked key components or process steps, generally had higher oxygen and nitrogen impurity contents and exhibited significant macroscopic segregation or coarse inclusions, resulting in a significant decrease in room temperature elongation. The above data confirms that the synergistic effect of solid deoxidation with primary gas-phase activator, liquid slag formation with secondary trapping agent, and variable pressure and frequency conversion process effectively achieves deep purification and microstructure homogenization of vanadium-platinum alloy, solving the material brittleness problem caused by interstitial impurity pinning in traditional processes.

[0130] The performance test results for each group are summarized in the table below:

[0131] Table 2

[0132] Based on the detection data in Table 2 and the results of the comparative experiments above, the following conclusions from the embodiments are drawn:

[0133] Comparing the data from Example 2 and Comparative Example 1, it is evident that the absence of a primary gas-phase activator caused the alloy oxygen content to surge from 95 ppm to 420 ppm, and the room temperature elongation after fracture to plummet from 24.1% to 5.2%. This indicates that relying solely on subsequent liquid-phase refining is insufficient to remove the high concentration of original oxygen load. Further comparison with Comparative Example 6 reveals that although a carbon source was added, the lack of a catalyst to lower the reaction activation energy resulted in incomplete solid-state deoxidation in the T1 temperature range, with a residual oxygen content still reaching 260 ppm. This confirms that in-situ pre-deoxidation during the solid-state stage, using a primary gas-phase activator in conjunction with a catalyst, is fundamental to ensuring the high purity of the final alloy.

[0134] Comparing the data from Example 2 and Comparative Example 2, it can be seen that when the secondary trapping agent is only metallic yttrium, although it plays a certain role in deoxidation, the nitrogen content is as high as 125 ppm, and the average diameter of non-metallic inclusions is as large as 8.2 μm. This indicates that the solid oxides generated by deoxidation of a single rare earth metal are difficult to aggregate and float, and cannot remove nitrogen impurities. In Example 2, the introduction of Zr for nitrogen fixation and B / Si as fluxing agent successfully transformed high-melting-point inclusions into a fine and easily floatable liquid borosilicate glass phase, which is a key mechanism for achieving deep purification and improving plasticity.

[0135] Solid-state activation: Comparative Example 3 omitted S1 and directly heated, resulting in an elongation of only 8.0%. This confirms the necessity of completing carbothermic reduction in the solid state; if carbon and vanadium are in direct contact in the liquid phase, carbon will preferentially diffuse into the lattice to form brittle vanadium carbide, rather than generating CO gas and escaping.

[0136] Pressure-variable wetting: Comparative Example 4 did not employ pressure-variable operation, and the macroscopic segregation ΔPt reached as high as 1.80wt%. This demonstrates that the switching between high and low pressure cycles plays a decisive role in disrupting the gas-liquid interfacial tension and assisting liquid platinum in achieving capillary flow and homogenization within the solid vanadium framework.

[0137] Variable frequency stirring: In Comparative Example 5, constant frequency stirring was used, and the size of the inclusions was significantly larger than that in Example 2. This indicates that a single frequency cannot cover the entire process of slag dispersion-collision growth-settling and floating, and a segmented variable frequency strategy must be adopted to conform to the laws of fluid dynamics.

[0138] By using solid-state pretreatment with a primary gas-phase activator, liquid-state deep purification with a secondary composite scavenger, and physical field synergy with variable voltage and frequency conversion processes, the technical challenges of removing oxygen and nitrogen impurities, severe component segregation, and inclusion residues in vanadium-platinum alloys are effectively solved. This allows the alloy to maintain high hydrogen permeability while possessing excellent room-temperature processing plasticity.

[0139] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A vanadium-platinum alloy for hydrogen purification, characterized in that, It is made from the following raw materials in parts by weight: 88-92 parts vanadium raw material; 8-12 parts platinum raw material; 0.03-0.06 parts primary gas phase activator; and 0.15-0.25 parts secondary composite capture agent.

2. The vanadium-platinum alloy for hydrogen purification according to claim 1, characterized in that: The primary gas-phase activator is composed of nano-carbon black and lanthanum hexaboride, and the weight ratio of nano-carbon black to lanthanum hexaboride is 50:1-60:

1.

3. The vanadium-platinum alloy for hydrogen purification according to claim 1, characterized in that: The secondary composite trapping agent is a pre-made quaternary alloy powder, the composition of which includes zirconium, yttrium, boron and silicon, and the weight ratio of zirconium, yttrium, boron and silicon is 40:40:5:

15.

4. A method for preparing vanadium-platinum alloy by temperature-controlled stepwise melting using hydrogen purification, characterized in that, The vanadium-platinum alloy for hydrogen purification according to any one of claims 1-3 comprises the following steps: S1. Raw material preparation and solid-state activation: Mix and press the raw materials, heat them to the first temperature zone T1 in a vacuum environment and keep them at that temperature, so that the primary gas phase activator reacts with the surface of the raw materials in a solid state. S2, Variable pressure wetting and permeation: The temperature is raised to the second temperature zone T2, which is between the melting point of platinum raw material and the melting point of vanadium raw material. During the heat preservation period, the air pressure in the vacuum chamber is switched between high and low pressure. S3, Liquid composite slag formation: The temperature is raised to the third temperature zone T3 to completely melt the material. A secondary composite scavenging agent is added and electromagnetic stirring is carried out under inert gas protection. Then, the material is cooled to obtain the hydrogen-purified vanadium-platinum alloy.

5. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 4, characterized in that: In step S1, the background pressure of the vacuum environment is ≤1.0×10⁻ 4 Pa, the first temperature zone T1 is 1050-1150℃, and the holding time is 120-180min.

6. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 4, characterized in that: In S2, the second temperature zone T2 is 1780-1800℃; the high and low pressure cycle switching refers to alternating the argon pressure in the vacuum chamber between a low pressure state of 10-20Pa and a high pressure state of 1000-1500Pa.

7. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 6, characterized in that: The high-low voltage cycle switching period is 5-8 minutes, and the number of cycles is 3-5 times.

8. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 4, characterized in that: The third temperature zone T3 is 2100-2200℃, and the inert gas is high-purity argon with a pressure of 0.02-0.05MPa.

9. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 4, characterized in that: The electromagnetic stirring adopts a frequency conversion stirring method, and the stirring frequency is controlled in the following three stages: the first stage: frequency 40-45Hz, lasting for 3 minutes; the second stage: frequency 80-90Hz, lasting for 5 minutes; the third stage: frequency 30-35Hz, lasting for 2 minutes.

10. The method for preparing hydrogen-purified vanadium-platinum alloy by temperature-controlled stepwise melting according to claim 4, characterized in that: The cooling in S3 adopts directional solidification, controls the cooling rate to 10-20℃ / min, keeps the top temperature of the melt 50-80℃ higher than the bottom temperature, and removes the slag layer on the top of the ingot after cooling to room temperature.

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