A dealloying method, a porous metal preparation method and system

Abstract

The present application belongs to the technical field of porous metal preparation, and more particularly relates to a dealloying method, a porous metal preparation method and a system. A radio frequency power is applied to an alloy precursor to make a protective gas discharge form an atmospheric pressure radio frequency plasma, and the alloy precursor is dealloyed by the atmospheric pressure radio frequency plasma. During the dealloying process, on the one hand, the alloy precursor is rapidly heated by the atmospheric pressure radio frequency plasma to cause non-equilibrium melting of the alloy precursor, so that the alloy is in a solid-liquid coexisting state; on the other hand, the strong electric field generated by the plasma sheath on the surface of the alloy precursor separates the melted part of the alloy precursor from the alloy precursor, so that the alloy is dealloyed, and a porous metal is prepared. The method is simple and easy to implement, time-saving and efficient, has low equipment cost, and can be processed on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of porous metal preparation technology, and more specifically, relates to a dealloying method, a method and system for preparing porous metals. Background Technology

[0002] Porous metal materials, especially nanoporous metal materials (pore size less than micrometers), have excellent characteristics such as large specific surface area and strong chemical activity, and have important applications in catalysis, energy storage and other fields.

[0003] Currently, the main methods for preparing porous metals include chemical dealloying, electrochemical dealloying, liquid-phase dealloying, and gas-phase dealloying. Chemical and electrochemical dealloying are the mainstream methods for preparing porous metal materials. Their principle is to selectively remove relatively reactive sacrificial elements by utilizing the differences in chemical activity of different components in the alloy and the standard electrode potential difference, thereby obtaining porous metals. However, these two methods are only suitable for preparing porous structures of inactive metals, such as Cu, Ag, Pt, Au, and Pd. Liquid-phase dealloying utilizes the differences in miscibility between the alloy components and the molten metal. For example, Nb has very low solubility in Mg melt, while Ni has very high solubility in Mg melt. Therefore, porous Nb can be achieved through liquid-phase dealloying of Nb-Ni alloys in Mg melt. However, after liquid-phase dealloying, acidic chemical reagents are needed to remove residual melt in the porous channels, and this method is also applicable to a limited number of elements. Vapor-phase dealloying utilizes the difference in saturated vapor pressure between different components in an alloy. For example, heating a Co-Zn alloy under low pressure causes Zn to volatilize from the alloy, thereby obtaining nanoporous Co. While this method can achieve dealloying of reactive metals, it requires an expensive vacuum system, increasing the cost of use. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a dealloying method, a method and system for preparing porous metals, which utilizes atmospheric pressure radio frequency plasma to dealloy alloys to obtain porous metals, thereby solving the technical problems of complex operation and high cost in existing dealloying methods for preparing porous metals.

[0005] To achieve the above objectives, the present invention provides a dealloying method, wherein radio frequency power is applied to an alloy precursor to generate atmospheric pressure radio frequency plasma through protective gas discharge; the alloy phase diagram of the alloy precursor contains a solid-liquid coexistence region; the temperature of the atmospheric pressure radio frequency plasma generated under the radio frequency power is within the temperature range corresponding to the solid-liquid coexistence region of the alloy; the alloy precursor is dealloyed using the atmospheric pressure radio frequency plasma; during the dealloying process, on the one hand, the alloy precursor is heated by the atmospheric pressure radio frequency plasma to partially melt the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted portion of the alloy precursor from the alloy precursor.

[0006] According to another aspect of the present invention, a method for preparing porous metal is provided, wherein radio frequency power is applied to an alloy precursor to generate atmospheric pressure radio frequency plasma through protective gas discharge; the alloy phase diagram of the alloy precursor contains a solid-liquid coexistence region; the temperature of the atmospheric pressure radio frequency plasma generated under the radio frequency power is within the temperature range corresponding to the solid-liquid coexistence region of the alloy; the alloy precursor is subjected to dealloying treatment using the atmospheric pressure radio frequency plasma to obtain porous metal; during the dealloying process, on the one hand, the alloy precursor is rapidly heated by the atmospheric pressure radio frequency plasma to partially melt the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor; the remaining unmelted part in the alloy precursor will form porous metal.

[0007] Preferably, the temperature range corresponding to the solid-liquid coexistence region of the alloy precursor has an upper limit and a lower limit that are greater than or equal to 80°C, and more preferably greater than or equal to 100°C.

[0008] Preferably, the alloy precursor is denoted as SM, where S is a sacrificial element and M is the metal remaining after dealloying, wherein S is a low-melting-point metal element, more preferably Zn, Sn, Mg, Sn, Cd, Pb, In or Al; and M is a high-melting-point metal, more preferably an alloy formed from one or more of Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ti, V, Au, Ag, Pt, Pd, Ru, Rh, Ir, W, Os, Ta and Hf.

[0009] Preferably, the alloy precursor is prepared by magnetron sputtering, electroplating, powder metallurgy, or quenching and spinning.

[0010] Preferably, the alloy precursor is in the form of a thin film, filament, block, or strip.

[0011] Preferably, the radio frequency power is 50-150W, more preferably 60-120W, and the time for the dealloying process is 10s-5min, more preferably 1-2min.

[0012] Preferably, the protective gas is a non-oxidizing gas, and more preferably contains a reducing gas, wherein the volume percentage of the reducing gas in the protective gas is 1% to 5%, and the flow rate of the protective gas is controlled at 80 to 1000 mL / min, more preferably 100 to 800 mL / min.

[0013] According to another aspect of the present invention, a dealloying system is provided, comprising an atmospheric pressure radio frequency plasma generator and an alloy precursor disposed within the atmospheric pressure radio frequency plasma generator; the atmospheric pressure radio frequency plasma generator includes an atmospheric pressure radio frequency plasma generating tube, a radio frequency electrode, a radio frequency power supply, a radio frequency matching device, a grounding electrode, a protective gas storage tank, a gas flow meter, and a liquid sealing device; wherein, the atmospheric pressure radio frequency plasma generating tube is a three-way tube, the three-way tube being provided with a first sealing port, a second sealing port, and a third sealing port; the alloy precursor is disposed inside the atmospheric pressure radio frequency plasma generating tube, one end of the radio frequency electrode is connected to the alloy precursor inside the atmospheric pressure radio frequency plasma generating tube, and the other end passes through the first sealing port and is connected to the radio frequency matching device; The radio frequency matching device is connected to the radio frequency power supply, which provides power to the radio frequency matching device. The second sealing port is connected to the protective gas storage tank through a gas flow meter, and is used to introduce protective discharge gas into the atmospheric pressure radio frequency plasma generating tube. The third sealing port extends into the liquid sealing device to act as a liquid seal. The grounding electrode is arranged around the outer wall of the atmospheric pressure radio frequency plasma generating tube at a position corresponding to the position of the alloy precursor inside the tube. During operation, on the one hand, the atmospheric pressure radio frequency plasma heats the alloy precursor, causing it to partially melt. On the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor separates the melted part of the alloy precursor from the alloy precursor.

[0014] According to another aspect of the present invention, a porous metal preparation system is provided, comprising an atmospheric pressure radio frequency plasma generator and an alloy precursor disposed in the atmospheric pressure radio frequency plasma generator; the atmospheric pressure radio frequency plasma generator includes an atmospheric pressure radio frequency plasma generating tube, a radio frequency electrode, a radio frequency power supply, a radio frequency matching device, a grounding electrode, a protective gas storage tank, a gas flow meter, and a liquid sealing device; wherein, the atmospheric pressure radio frequency plasma generating tube is a three-way tube, the three-way tube being provided with a first sealing port, a second sealing port, and a third sealing port; the alloy precursor is disposed inside the atmospheric pressure radio frequency plasma generating tube, one end of the radio frequency electrode is connected to the alloy precursor inside the atmospheric pressure radio frequency plasma generating tube, and the other end passes through the first sealing port and is connected to the radio frequency matching device; the radio frequency matching device and the radio frequency electrode... The source is connected, and the radio frequency power supply is used to provide power to the radio frequency matching device; the second sealing port is connected to the protective gas storage tank through a gas flow meter, and is used to introduce protective discharge gas into the atmospheric pressure radio frequency plasma generating tube; the third sealing port extends into the liquid sealing device to play a liquid sealing role; the grounding electrode is arranged around the outer wall of the atmospheric pressure radio frequency plasma generating tube at a position corresponding to the position of the alloy precursor inside the tube; during operation, on the one hand, the atmospheric pressure radio frequency plasma rapidly heats the alloy precursor, causing the alloy precursor to partially melt; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor; the remaining unmelted part in the alloy precursor will form a porous metal.

[0015] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0016] (1) The present invention provides a dealloying method, wherein radio frequency power is applied to an alloy precursor to generate atmospheric pressure radio frequency plasma by protective gas discharge, and the alloy precursor is dealloyed using atmospheric pressure radio frequency plasma; during the dealloying process, on the one hand, the alloy precursor is rapidly heated by the atmospheric pressure radio frequency plasma to cause non-equilibrium melting of the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor, thereby achieving the purpose of dealloying.

[0017] (2) The dealloying method of the present invention removes one alloy component from the alloy precursor, and the remaining alloy component can form porous metal or even nanoporous metal. Therefore, the present invention is essentially equivalent to proposing a method for preparing porous metal / nanoporous metal. By applying radio frequency power to the alloy precursor, protective gas discharge is generated to form atmospheric pressure radio frequency plasma. The atmospheric pressure radio frequency plasma is used to perform dealloying treatment on the alloy precursor to obtain porous metal.

[0018] (3) The method of this invention employs a novel dealloying mechanism. In this method, the alloy electrode is in direct contact with the radio frequency plasma. The radio frequency plasma can rapidly rise to its maximum temperature after the discharge begins, quickly achieving the dealloying process in a short time. The operation is simple, easy to implement, time-saving, and efficient.

[0019] (4) This method does not require any polluting and complex expensive devices such as chemical reagents, vacuum systems, heating systems, and atmosphere protection systems, which greatly reduces equipment costs.

[0020] (5) The porous metal prepared by this method has a uniform pore distribution and pore size, and the pore structure can be controlled by adjusting the original alloy composition and plasma discharge parameters. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the porous metal preparation apparatus provided by the present invention;

[0022] Figure 2 This is a scanning electron microscope image of the sample surface after 1 minute of radio frequency plasma treatment in Example 1;

[0023] Figure 3 The image shows the X-ray diffraction pattern of the sample after 1 minute of radio frequency plasma treatment in Example 1.

[0024] Figure 4 This is a scanning electron microscope image of the sample surface after 2 minutes of radio frequency plasma treatment in Example 1;

[0025] Figure 5 This is a scanning electron microscope image of the sample surface after 5 minutes of radio frequency plasma treatment in Example 1;

[0026] Figure 6 This is a graph showing the relationship between residual zinc content and plasma treatment time.

[0027] Figure 7 This is a scanning electron microscope image of the sample surface after 1 minute of radio frequency plasma treatment in Example 2;

[0028] Figure 8 The X-ray diffraction pattern of the sample after 1 minute of radio frequency plasma treatment in Example 2;

[0029] Figure 9 This is a scanning electron microscope image of the sample surface after 1 minute of radio frequency plasma treatment in Example 3;

[0030] Figure 10 This is a scanning electron microscope image of the sample surface after 2 minutes of radio frequency plasma treatment in Example 4;

[0031] Figure 11 This is a scanning electron microscope image of the sample surface after 2 minutes of radio frequency plasma treatment in Example 5.

[0032] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0033] 1-Protective gas storage tank; 2-Gas flow meter; 3-RF power supply; 4-RF matching unit; 5-RF electrode; 6-T-shaped quartz tube; 61-First sealing port; 62-Second sealing port; 63-Third sealing port; 7-Grounding electrode; 8-Liquid sealing device; 9-Alloy precursor. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This invention provides a dealloying method in which radio frequency power is applied to an alloy precursor to generate atmospheric pressure radio frequency plasma through protective gas discharge. The alloy phase diagram of the alloy precursor contains a solid-liquid coexistence region. The temperature of the atmospheric pressure radio frequency plasma generated under the radio frequency power is within the temperature range corresponding to the solid-liquid coexistence region of the alloy. The atmospheric pressure radio frequency plasma is used to perform dealloying treatment on the alloy precursor. During the dealloying process, on the one hand, the atmospheric pressure radio frequency plasma rapidly heats the alloy precursor, causing it to undergo non-equilibrium melting. On the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted portion of the alloy precursor from the alloy precursor.

[0036] The atmospheric pressure radio frequency plasma temperature generated under the radio frequency power is located within the temperature range corresponding to the solid-liquid coexistence region of the alloy. The temperature range corresponding to the solid-liquid coexistence region of the alloy represents the alloy with a specific composition corresponding to the alloy precursor of the present invention. The temperatures corresponding to the liquidus line and solidus line in the alloy phase diagram are respectively used as the upper and lower limits to form the temperature range.

[0037] The alloy precursor of this invention includes multiple alloying components, i.e., alloying elements, such as the binary alloy Fe-Zn, which includes Fe and Zn components; and the ternary alloy Fe-Ni-Zn, which includes Fe, Ni, and Zn components. Different alloying components have different melting points. During the experiment, it was found that after the dealloying method of this invention removes one alloying component (which has a lower melting point) from the alloy precursor as a sacrificial component, the remaining alloying component can form porous metal or nanoporous metal. Therefore, this invention is essentially equivalent to proposing a method for preparing porous metal. By applying radio frequency power to the alloy precursor, protective gas discharge is generated to form atmospheric pressure radio frequency plasma. The atmospheric pressure radio frequency plasma is used to perform dealloying treatment on the alloy precursor to obtain porous metal. During the dealloying process, on the one hand, the atmospheric pressure radio frequency plasma rapidly heats the alloy precursor, causing it to melt non-equilibrium. On the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor. In this way, the remaining unmelted part in the alloy precursor will form a porous structure, which can be a nanoporous structure or a microporous structure.

[0038] According to multi-component alloy phase diagrams, most alloys, except for infinitely miscible metallic alloys, exhibit a solid-liquid coexistence region. Multi-component alloys with specific compositions undergo non-equilibrium melting during rapid heating, forming a solid-liquid coexistence state. This invention utilizes this characteristic. When atmospheric pressure radio frequency plasma is used to rapidly heat the alloy precursor, non-equilibrium melting occurs, forming a solid-liquid coexistence state. Simultaneously, at the plasma boundary, due to the "instantaneous" electric field generated by the radio frequency power supply, mobile electrons undergo periodic motion within a space charge cloud composed of positive ions. High-mass ions are only affected by the time-averaged electric field. The periodic motion of the electron cloud generates a sheath near the electrode. Within this sheath, the average number of positive charges per cycle exceeds the number of negative charges, resulting in a net positive charge within the sheath region. This net charge generates a strong oscillating electric field in the sheath, pointing from the plasma towards the electrode. This electric field causes electrohydrodynamic instability fluctuations in the negatively charged molten liquid. The electric field of the sheath layer on the surface of the alloy precursor can be modulated by the applied radio frequency voltage: Where V0 is the amplitude of the radio frequency voltage, and ω is the angular frequency of the radio frequency voltage. The sheath voltage is used. Secondly, the plasma temperature can be controlled by the radio frequency power and gas flow rate; at the same power, a higher gas flow rate results in a lower temperature. Therefore, the plasma temperature can be made the same for different excitation powers by changing the gas flow rate. Adjusting the excitation voltage while simultaneously regulating the gas flow rate ensures that the alloy does not completely melt. When the electric field strength is sufficiently high, this instability fluctuation will be broken, and the liquid will overcome surface tension under the action of the electric field force and leave the electrode. That is, the molten portion in the alloy precursor will separate from the alloy precursor, thereby achieving dealloying.

[0039] To facilitate the preparation of porous metals, in a preferred embodiment, the temperature range corresponding to the solid-liquid coexistence region of the alloy precursor of the present invention has an upper limit (temperature corresponding to the liquidus line) and a lower limit (temperature corresponding to the solidus line) that is greater than or equal to 80°C, more preferably greater than or equal to 100°C, and most preferably greater than or equal to 200°C.

[0040] This invention utilizes atmospheric pressure radio frequency plasma to dealloy alloy precursors, preparing porous metals. For any alloy precursor, during the heating and melting process, when the temperature rises above the melting point (solid line), the alloy transitions from a solid state to a solid-liquid coexistence state. If this temperature is maintained for a prolonged period, the unmelted portion will coarsen, thus failing to form a porous structure. In this invention, the radio frequency plasma itself can rapidly rise to its maximum temperature after excitation, causing the alloy to undergo non-equilibrium melting (the unmelted portion does not have time to diffuse or coarsen). Simultaneously, the molten portion (electrolyte) is immediately separated under the influence of a strong sheath electric field, thereby ensuring that the unmelted portion retains its porous structure.

[0041] The mechanism utilized in this invention differs from vacuum dealloying. First, the operating temperatures differ. Vacuum dealloying is a slow diffusion and evaporation process below the alloy's melting point, while this invention utilizes the rapid heating effect of atmospheric pressure radio frequency plasma and the synergistic effect of the plasma sheath electric field to achieve rapid solid-liquid separation above the alloy's melting point (solid line). Second, the operating pressures differ. Vacuum dealloying typically requires a high vacuum environment to achieve the separation of elements with lower saturated vapor pressures, while the operating pressure of this invention is slightly higher than atmospheric pressure (water-sealed). Furthermore, the sacrificial elements collected in vacuum dealloying are particulate elements, while the sacrificial elements collected in this invention typically contain a small amount of the target component. This is because the molten portion is actually an alloy or solid solution dominated by the sacrificial element. Additionally, simple heating in a He / H2 atmosphere at atmospheric pressure (above the alloy's melting point) does not cause the alloy to form a porous morphology, while heating with radio frequency plasma does, indicating that the sheath electric field plays a decisive role (driving force of the dealloying process) in the dealloying process of this invention.

[0042] The dealloying method or porous metal preparation method of this invention is applicable to any alloy precursor that has a solid-liquid coexistence region in the phase diagram. The alloy precursor includes, but is not limited to, binary alloys, ternary alloys, quaternary alloys, pentagonal alloys, etc. The alloy precursor of this invention is represented as a combination of the target metal M (target metal M includes elemental metals and multi-metal alloys) remaining after dealloying the sacrificial element S+. The S component is preferably a low-melting-point metal element such as Zn, Sn, Mg, Sn, Cd, Pb, In, Al, etc., and the M component is an alloy formed by one or more of the high-melting-point metal elements such as Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ti, V, Au, Ag, Pt, Pd, Ru, Rh, Ir, W, Os, Ta, Hf, etc. As long as there is a wide solid-liquid coexistence region in its alloy phase diagram, the dealloying and porous metal preparation methods of this invention can be used to perform dealloying and prepare porous metal.

[0043] The alloy precursor of this invention can be prepared by any conventional method existing in the art. In some embodiments, the alloy precursor is prepared by magnetron sputtering, electroplating, powder metallurgy, or induction melting followed by rapid cooling and strip spinning. Accordingly, the alloy precursor can be in the form of a thin film, filament, bulk material, or strip. In a preferred embodiment, the alloy precursor is a thin film or strip sample prepared by magnetron sputtering or induction melting followed by rapid cooling and strip spinning. Theoretically, the thickness of the alloy precursor can be any thickness, as long as it is lower than the thickness of the outer shell of the RF power generator. Of course, the thinner the thickness, the more beneficial it is to obtain porous metal in a short time. To ensure the dealloying efficiency, the preferred alloy precursor thickness is no more than 5 mm, the next best alloy precursor thickness is no more than 2 mm, and the most preferred precursor thickness is no more than 500 μm.

[0044] Correspondingly, the present invention also provides a dealloying system, which is also a porous metal preparation system, including an atmospheric pressure radio frequency plasma generator and an alloy precursor disposed in the atmospheric pressure radio frequency plasma generator; the atmospheric pressure radio frequency plasma generator includes an atmospheric pressure radio frequency plasma generating tube, a radio frequency electrode, a radio frequency power supply, a radio frequency matching device, a grounding electrode, a protective gas storage tank, a gas flow meter, and a liquid sealing device; wherein, the atmospheric pressure radio frequency plasma generating tube is a three-way tube, and the three-way tube is provided with a first sealing port, a second sealing port, and a third sealing port; the alloy precursor is disposed inside the atmospheric pressure radio frequency plasma generating tube, and one end of the radio frequency electrode is disposed in the atmospheric pressure radio frequency plasma generator. The plasma generating tube is connected to the alloy precursor at its interior, and its other end passes through the first sealed port and is connected to the radio frequency matching device. The radio frequency matching device is connected to the radio frequency power supply, which provides power to the radio frequency matching device. The second sealed port is connected to the protective gas storage tank via a gas flow meter, and is used to introduce protective discharge gas into the atmospheric pressure radio frequency plasma generating tube. The third sealed port extends into the liquid sealing device to act as a liquid seal. The grounding electrode is arranged around the outer wall of the atmospheric pressure radio frequency plasma generating tube at a position corresponding to the position of the alloy precursor inside the tube (i.e., on the outer wall corresponding to the position of the alloy precursor). During operation, the atmospheric pressure radio frequency plasma heats the alloy precursor, causing it to partially melt. Simultaneously, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor separates the melted portion from the alloy precursor, and the remaining unmelted portion forms a porous metal.

[0045] For different alloy precursors, the material of the atmospheric pressure radio frequency plasma generator tube can be selected according to the melting point temperature of the alloy components. The key is to ensure that atmospheric pressure radio frequency plasma can be generated, and that the temperature of the generated atmospheric pressure radio frequency plasma is between the melting temperature of the alloy precursor and the highest melting point temperature of the alloy components, and that this temperature does not melt the outer shell of the atmospheric pressure radio frequency plasma generator tube. In some embodiments, materials such as... Figure 1The aforementioned dealloying / porous metal preparation system comprises an atmospheric pressure radio frequency plasma generator housed in a three-way quartz tube. All three ports are sealed during operation. One port connects to a radio frequency matching unit and a radio frequency power supply. A grounding electrode surrounds the outer side of the quartz tube corresponding to the alloy precursor. A protective discharge gas is introduced into a branch of the quartz tube through one port, and the gas flow rate is controlled. The third port extends directly into a liquid-sealing device; in some embodiments, the liquid-sealing device is a water-sealing device. Radio frequency power is applied to the alloy precursor to discharge the protective discharge gas, forming atmospheric pressure radio frequency plasma. After a certain processing time, dealloying yields a porous metal.

[0046] This invention enables the production of porous metals by controlling the radio frequency power, the type and flow rate of the protective gas, and the processing time. Furthermore, the pore size of the obtained porous metals can be controlled by adjusting these parameters. The alloy precursor of this invention, through appropriate process parameters, can achieve a porous structure with pore sizes ranging from 100 nm to 5 μm.

[0047] By adjusting the appropriate radio frequency (RF) power, the RF plasma discharge can rapidly reach a suitable temperature. At this temperature, the plasma sheath on the alloy electrode surface can generate a strong electric field that separates the molten portion of the electrode from the electrode, while the temperature does not become so high as to melt all the alloy components. For metal alloys, the protective gas cannot be a purely inert gas. To avoid metal oxidation, the protective gas is a non-oxidizing gas, and preferably, a reducing gas such as hydrogen is added to the protective gas. In some embodiments, the RF power is 50–150 W, preferably 60–120 W, and the dealloying time is 10 s–5 min, preferably 1–2 min. The protective gas is a mixture of He and H2, wherein the volume percentage of H2 is 1%–5%, and the flow rate of the protective gas is controlled at 80–1000 mL / min, preferably 100–800 mL / min, and more preferably 100–400 mL / min.

[0048] The following is an example:

[0049] The following embodiments employ, for example Figure 1 The shown dealloying / porous metal preparation system is used for dealloying and preparing porous metals. The system includes an atmospheric pressure radio frequency plasma generator and an alloy precursor 9 disposed within the atmospheric pressure radio frequency plasma generator. The atmospheric pressure radio frequency plasma generator includes an atmospheric pressure radio frequency plasma generating tube, radio frequency electrodes, a radio frequency power supply, a radio frequency matching device, a grounding electrode, a protective gas storage tank, a gas flow meter, and a liquid sealing device. The atmospheric pressure radio frequency plasma generating tube is... Figure 1The three-way quartz tube 6 has a first sealing port 61, a second sealing port 62, and a third sealing port 63. The alloy precursor is disposed inside the atmospheric pressure radio frequency plasma generating tube, i.e., the three-way quartz tube 1. One end of the radio frequency electrode 5 is connected to the alloy precursor 9 inside the three-way quartz tube 6, and the other end passes through the first sealing port 61 and is connected to the radio frequency matching device 4. The radio frequency matching device 4 is connected to the radio frequency power supply 3, which provides power to the radio frequency matching device 4. The second sealing port 62 is connected to the protective gas storage tank 1 through the gas flow meter 2, and is used to introduce protective discharge gas into the three-way quartz tube. The third sealing port 63 extends into the liquid sealing device 8, and is used to perform a liquid sealing function. A grounding electrode 7 is arranged around the outer wall corresponding to the location of the alloy precursor 9. Among them, the protective gas storage tank 1 is a He / H2 mixed gas tank, the gas flow meter 2 is a mass flow meter, the grounding electrode 7 is a grounding tantalum foil electrode, and the liquid sealing device 8 is a water sealing device. When using the above system for dealloying / porous metal preparation, the following steps are included:

[0050] (1) Alloy precursors were prepared by magnetron sputtering, induction melting and rapid cooling strip spinning.

[0051] (2) Insert the above-mentioned alloy precursor as an electrode into a three-way quartz tube and seal the tube opening. Connect the RF matching device and the RF power supply. The outside of the quartz tube is surrounded by tantalum foil of the same length as carbon cloth as a grounding electrode. The inner diameter of the three-way quartz tube is 1.5-8 mm and the wall thickness of the quartz tube is 0.5-2 mm.

[0052] (3) He / H2 mixture is introduced into the three-way quartz tube through the second sealing port. The H2 ratio is 1% to 5%, and the gas flow rate is controlled at 100 to 400 mL / min. The outlet connecting pipe is then sealed in water.

[0053] (4) Apply 60-100W of radio frequency power to the electrode to discharge the He / H2 mixed gas to form atmospheric pressure radio frequency plasma. After a processing time of 1-5 minutes, a porous metal is obtained.

[0054] Example 1

[0055] Fe-Zn alloy thin films were sputtered onto carbon cloth using magnetron sputtering. The sputtering power, time, and pressure were 100 W, 1 hour, and 1 Pa, respectively. The resulting Fe-Zn alloy film was approximately 1.74 μm thick, with an Fe:Zn atomic ratio of approximately 1:2. The Fe-Zn alloy-coated carbon cloth was cut into 5.5 mm x 5 cm pieces and connected as follows: Figure 1The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 2%.

[0056] Turn on the RF power supply and adjust the RF power to 80W. RF plasma is generated near the alloy electrode (the carbon cloth coated with Fe-Zn alloy). After 1 minute, the sample is removed, yielding carbon cloth-loaded nanoporous iron. Its scanning electron microscope image is shown below. Figure 2 As shown, its pore size distribution is uniform, and the pore size distribution is consistent, with a pore size of approximately 200 nm.

[0057] X-ray diffraction analysis of the above samples revealed that the diffraction peak positions of the obtained porous material correspond to those of iron with a body-centered cubic (BCC) structure, such as... Figure 3 As shown, these peaks correspond to the (110), (200), and (211) diffraction peaks of BCC iron, respectively. The original sample was also a Fe-Zn alloy with a BCC structure.

[0058] Increasing the plasma treatment time, samples treated for 2 minutes and 5 minutes were obtained, and their scanning electron microscope images were as follows: Figure 4 and Figure 5 As shown; Figure 6 The graph shows the relationship between residual zinc content and plasma treatment time. It can be seen that the zinc content is almost zero after 1 minute of treatment, indicating the high efficiency of this method.

[0059] Example 2

[0060] Fe-Ni-Zn alloy thin films were sputtered onto carbon cloth using magnetron sputtering. The sputtering power, time, and gas pressure were 100 W, 1 hour, and 1 Pa, respectively. The resulting Fe-Ni-Zn alloy film had a thickness of approximately 1.85 μm, with an atomic ratio of Fe, Ni, and Zn of approximately 1:2:4. The carbon cloth coated with the Fe-Ni-Zn alloy was cut into pieces measuring 5.5 mm * 5 cm and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 2%.

[0061] Turn on the RF power supply and adjust the RF power to 80W. RF plasma is generated near the alloy electrode (the carbon cloth coated with Fe-Ni-Zn alloy). After 1 minute, the sample is removed, yielding a carbon cloth-loaded nanoporous Fe-Ni alloy. Its scanning electron microscope image is shown below. Figure 7As shown, its pore size distribution is uniform, and the pore size distribution is consistent, with a pore size of approximately 200 nm.

[0062] X-ray diffraction analysis was performed on the above samples, such as... Figure 8 As shown, the obtained porous material is a nanoporous Fe-Ni alloy.

[0063] Example 3

[0064] A Ni-Zn alloy thin film was sputtered onto carbon cloth using magnetron sputtering. The sputtering power, time, and pressure were 100 W, 1 hour, and 1 Pa, respectively. The resulting Ni-Zn alloy film had a thickness of approximately 2.1 μm and an atomic ratio of Ni to Zn of approximately 1:2. The carbon cloth coated with the Ni-Zn alloy was cut into pieces measuring 5.5 mm * 5 cm and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 2%.

[0065] Turn on the RF power supply and adjust the RF power to 80W. RF plasma is generated near the alloy electrode (the aforementioned carbon cloth plated with Ni-Zn alloy). After 1 minute, the sample is removed, yielding carbon cloth-loaded nanoporous nickel. Its scanning electron microscope image is shown below. Figure 9 As shown, its pore size distribution is uniform, and the pore size distribution is uniform, with a pore size of approximately 150 nm.

[0066] Example 4

[0067] Cu-Zn alloy strips were prepared using a rapid cooling and spinning method. The resulting Cu-Zn alloy strips had a thickness of approximately 140 μm and an atomic ratio of Cu to Zn of approximately 1:5. The Cu-Zn alloy strips were cut into 5.5 mm * 2 cm pieces and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 2%.

[0068] Turn on the RF power supply and adjust the RF power to 90W. RF plasma is generated near the Cu-Zn alloy electrode. After 2 minutes, the sample is removed, yielding porous copper. Its scanning electron microscope image is shown below. Figure 10 As shown, its pore size distribution is uniform, and the pore size distribution is consistent, with a pore size of approximately 3 μm.

[0069] Example 5

[0070] Cu-Al alloy strips were prepared using a rapid cooling and spinning method. The resulting Cu-Al alloy strips were approximately 120 μm thick, with a Cu to Al atomic ratio of approximately 1:1. The Cu-Al alloy strips were cut into 5.5 mm x 2 cm pieces and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 2%.

[0071] Turn on the RF power supply and adjust the RF power to 95W. RF plasma is generated near the Cu-Al alloy electrode. After 2 minutes, the sample is removed, yielding porous copper. Its scanning electron microscope image is shown below. Figure 11 As shown, its pore size distribution is uniform, and the pore size distribution is consistent, with a pore size of approximately 1 μm.

[0072] Example 6

[0073] Co-Zn alloy strips were prepared using a rapid cooling and spinning method. The resulting Co-Zn alloy strips were approximately 100 μm thick, with a Co:Zn atomic ratio of approximately 1:4. The Co-Zn alloy strips were cut into 5.5 mm * 2 cm pieces and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 300 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 3%.

[0074] Turn on the RF power supply and adjust the RF power to 95W. RF plasma is generated near the Co-Zn alloy electrode. After 2 minutes, the sample is taken out and porous cobalt is obtained. The pore size distribution is uniform and the pore size is approximately 500nm.

[0075] Example 7

[0076] A FeMoMnCoZn alloy thin film was sputtered onto carbon cloth using magnetron sputtering. The sputtering power, time, and gas pressure were 100 W, 1.5 h, and 1 Pa, respectively. The resulting FeMoMnCoZn alloy thin film had a thickness of approximately 3.5 μm, with an atomic ratio of Fe, Mo, Mn, Co, and Zn of approximately 1:1:1:1:3. The carbon cloth coated with the FeMoMnCoZn alloy was cut into pieces measuring 5.5 mm * 5 cm and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 200 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 4%.

[0077] Turn on the RF power supply and adjust the RF power to 85W. RF plasma is generated near the alloy electrode (the carbon cloth coated with FeMoMnCoZn alloy). After 1 minute, the sample is taken out, and carbon cloth-loaded nanoporous FeMoMnCo is obtained. Its pore size distribution is uniform, and the pore size is about 200nm.

[0078] Example 8

[0079] A NiMoCoMg alloy thin film was sputtered onto carbon cloth using magnetron sputtering. The sputtering power, time, and pressure were 100 W, 1.5 h, and 1 Pa, respectively. The resulting NiMoCoMg alloy film had a thickness of approximately 3.2 μm, with an atomic ratio of Ni, Mo, Co, and Mg of approximately 1:1:1:3. The carbon cloth coated with the NiMoCoMg alloy was cut into pieces measuring 5.5 mm * 5 cm and connected as follows: Figure 1 The radio frequency matching unit shown is placed inside a quartz tube with an inner diameter of 6 mm and a wall thickness of 1 mm and sealed. The mass flow meter is turned on and the gas flow rate is adjusted to 300 mL / min. The gas is ventilated for 2 minutes to remove air from the device. The proportion of H2 in the He / H2 mixture is 3%.

[0080] Turn on the RF power supply and adjust the RF power to 80W. RF plasma is generated near the alloy electrode (the carbon cloth coated with NiMoCoMg alloy). After 1 minute, the sample is taken out, and carbon cloth-loaded nanoporous NiMoCo is obtained. Its pore size distribution is uniform, and the pore size is about 200nm.

[0081] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dealloying method, characterized in that, Radio frequency power is applied to the alloy precursor to generate atmospheric pressure radio frequency plasma through protective gas discharge; the alloy phase diagram of the alloy precursor contains a solid-liquid coexistence region; the temperature of the atmospheric pressure radio frequency plasma generated under the radio frequency power is within the temperature range corresponding to the solid-liquid coexistence region of the alloy; the alloy precursor is subjected to dealloying treatment using the atmospheric pressure radio frequency plasma. The alloy precursor is denoted as SM, where S is the sacrificial element and M is the metal element remaining after dealloying; the temperature range corresponding to the solid-liquid coexistence region of the alloy precursor has an upper limit and a lower limit that are greater than or equal to 80°C. During the dealloying process, on the one hand, the alloy precursor is heated by the atmospheric pressure radio frequency plasma, causing partial melting of the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor.

2. A method for preparing porous metal, characterized in that, Radio frequency power is applied to the alloy precursor to generate atmospheric pressure radio frequency plasma through protective gas discharge; the alloy phase diagram of the alloy precursor contains a solid-liquid coexistence region; the temperature of the atmospheric pressure radio frequency plasma generated under the radio frequency power is within the temperature range corresponding to the solid-liquid coexistence region of the alloy; the alloy precursor is dealloyed using the atmospheric pressure radio frequency plasma to obtain a porous metal. The alloy precursor is denoted as SM, where S is the sacrificial element and M is the metal element remaining after dealloying; the temperature range corresponding to the solid-liquid coexistence region of the alloy precursor has an upper limit and a lower limit that are greater than or equal to 80°C. During the dealloying process, on the one hand, the alloy precursor is rapidly heated by the atmospheric pressure radio frequency plasma, causing partial melting of the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor. The remaining unmelted portion in the alloy precursor forms a porous metal.

3. The method as described in claim 1 or 2, characterized in that, In the alloy precursor, S is a low-melting-point metal element, which is Zn, Sn, Mg, Sn, Cd, Pb, In or Al; M is a high-melting-point metal, which is an alloy formed from one or more of Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ti, V, Au, Ag, Pt, Pd, Ru, Rh, Ir, W, Os, Ta and Hf.

4. The method as described in claim 1 or 2, characterized in that, The alloy precursor is prepared by magnetron sputtering, electroplating, powder metallurgy, or quenching and spinning.

5. The method as described in claim 1 or 2, characterized in that, The alloy precursor is in the form of a thin film, filament, block, or strip.

6. The method as described in claim 1 or 2, characterized in that, The radio frequency power is 50~150 W, and the time for the dealloying process is 10 s~5 min.

7. The method as described in claim 1 or 2, characterized in that, The protective gas is a non-oxidizing gas, and the flow rate of the protective gas is controlled at 80~1000 mL / min.

8. The method as described in claim 7, characterized in that, The protective gas contains a reducing gas, wherein the volume percentage of the reducing gas in the protective gas is 1% to 5%, and the flow rate of the protective gas is 100 to 800 mL / min.

9. A dealloying system, characterized in that, It includes an atmospheric pressure radio frequency plasma generator and an alloy precursor disposed in the atmospheric pressure radio frequency plasma generator; The atmospheric pressure radio frequency plasma generator includes an atmospheric pressure radio frequency plasma generating tube, radio frequency electrodes, a radio frequency power supply, a radio frequency matching unit, a grounding electrode, a protective gas storage tank, a gas flow meter, and a liquid sealing device. The atmospheric pressure radio frequency plasma generating tube is a three-way tube, which is provided with a first sealing port, a second sealing port and a third sealing port. During operation, the alloy precursor is disposed inside the atmospheric pressure radio frequency plasma generating tube. One end of the radio frequency electrode is connected to the alloy precursor inside the atmospheric pressure radio frequency plasma generating tube, and the other end passes through the first sealed tube opening and is connected to the radio frequency matching device. The radio frequency matching device is connected to the radio frequency power supply, and the radio frequency power supply is used to provide power to the radio frequency matching device. The second sealing port is connected to the protective gas storage tank via a gas flow meter, and is used to introduce protective gas into the atmospheric pressure radio frequency plasma generating tube; The third sealing port extends into the interior of the liquid sealing device to serve as a liquid seal. The grounding electrode is arranged around the outer wall of the atmospheric pressure radio frequency plasma generating tube at a position corresponding to the position of the alloy precursor inside the tube. During operation, on the one hand, the alloy precursor is heated by the atmospheric pressure radio frequency plasma, causing partial melting of the alloy precursor; on the other hand, the strong electric field generated by the plasma sheath layer on the surface of the alloy precursor is used to separate the melted part of the alloy precursor from the alloy precursor.

Images