A method for improving the cycle durability of hydrogen-chromic magnesium-based thin films

Abstract

This invention discloses a method for improving the cycle durability of hydrogen-chromatic magnesium-based thin films. The method includes the following steps: growing a magnesium-X element composite film layer on a substrate using magnetron sputtering co-sputtering; preparing a palladium catalytic layer using magnetron sputtering; and finally preparing a fluorocarbon film using plasma vapor deposition. The magnesium-X element composite film layer is formed by adding an X element to a magnesium substrate. In this invention, Pd exhibits a catalytic effect, promoting the reversible conversion between hydrogen gas and hydrogen atoms during hydrogen absorption and dehydrogenation. The compound phase formed by adding the composite X element and magnesium inhibits the interdiffusion between the Pd layer and the magnesium layer, which helps maintain the catalytic effect of Pd and thus improves the hydrogen absorption and desorption cycle durability of the composite film layer. The dimming film prepared by this method has good cycle performance and a simple process, showing significant application prospects in the field of hydrogen sensing.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen-chromic thin film technology, specifically relating to a method for improving the cycle durability of hydrogen-chromic magnesium-based thin films. Background Technology

[0002] Hydrogen, as a clean energy carrier, will play a key role in a sustainable society in the future. However, when the hydrogen content in the air is between 4% and 75%, it will explode when exposed to an open flame. At the same time, hydrogen has low ignition energy and hydrogen molecules diffuse very easily. Therefore, hydrogen leakage should be avoided during the storage, transportation and use of hydrogen. On the other hand, hydrogen is colorless, odorless and tasteless, and cannot be detected by humans. Therefore, it is imperative to equip hydrogen with a sensitive and reliable hydrogen detection device, namely a hydrogen sensor.

[0003] Previous hydrogen detection methods primarily relied on catalytic resistor detectors or electrochemical devices. However, these devices still have limitations. For example, they require electrical leads, which can cause sparks at the sensing point, leading to safety issues. Furthermore, these detection systems are bulky, expensive, and have limited applications. Therefore, some research groups have turned their attention to optical sensors based on hydrogen-chromic thin films. Currently, the most representative hydrogen-chromic thin film structure is a palladium / magnesium-based composite / quartz glass. Palladium has good gas adsorption properties and can serve as a catalytic layer, while magnesium-based materials have strong hydrogen storage capabilities and can serve as a dimming layer. Existing composite materials include transition metals, rare earth metals, alkaline earth metals, and transition metal oxides. However, the hydrogen absorption / desorption rates and cycle durability of existing magnesium-based hydrogen-chromic thin films need further improvement to meet the response and durability requirements of hydrogen sensors. In addition, palladium has poor hydrophobicity, as water molecules generated during dehydrogenation and water vapor in the air easily accumulate on the palladium layer surface, corroding the dimming film. Therefore, it is necessary to develop new hydrogen-induced dimming film systems with excellent hydrogen absorption and desorption optical conversion characteristics and good cycle durability.

[0004] However, during the hydrogen adsorption and desorption reactions of the hydrogen-chromatic thin film, significant interdiffusion occurs between the palladium and magnesium layers, leading to structural damage after multiple hydrogen adsorption and desorption cycles. This disrupts the catalytic hydrogen adsorption and desorption function of the Pd layer, resulting in the loss of hydrogen sensing performance. Therefore, finding methods to suppress interdiffusion between the palladium and magnesium layers is crucial for the development of high-cycle-durability hydrogen-chromatic thin films. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing hydrogen-chromatic thin films and provide a method to improve the cycle durability of hydrogen-chromatic magnesium-based thin films. The improved film can maintain high sensing performance, including fast hydrogen absorption and desorption reaction rate and large hydrogen response value, during multiple hydrogen absorption and desorption cycles.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for improving the cycle durability of hydrogen-chromatic magnesium-based thin films, comprising the following steps:

[0008] A magnesium-X element composite film was grown on the substrate by magnetron sputtering co-sputtering, then a palladium catalyst layer was prepared by magnetron sputtering, and finally a fluorocarbon film was prepared by plasma vapor deposition.

[0009] The magnesium-X element composite film is a composite film formed by adding element X to a magnesium base.

[0010] In this invention, Pd has a catalytic effect, which can promote the reversible conversion between hydrogen gas and hydrogen atoms during the hydrogen absorption and dehydrogenation stages. The special compound phase formed by adding composite element X and magnesium can inhibit the interdiffusion between Pd layer and magnesium layer, improve the stability of the membrane interface during the hydrogen absorption and desorption cycle, which is beneficial to maintaining the catalytic effect of Pd and thus improving the hydrogen absorption and desorption cycle durability of the composite membrane.

[0011] As a preferred embodiment, the X element includes scandium.

[0012] As a preferred embodiment, the mass percentage of element X in the magnesium-X element composite film is 5% to 50%. The element X added in this invention combines with magnesium, reducing interdiffusion between the magnesium and palladium layers. In the magnesium-X element composite film, if the magnesium content is too high and the element X content is too low, it will lead to poor film cycling performance; conversely, it will lead to a reduction in the film's dimming range. More preferably, the mass percentage of element X is 12% to 25%.

[0013] As a preferred embodiment, the thickness of the magnesium-X element composite film is 10-200 nm. If the composite film is too thick, it will reduce the cycle performance; if the composite film is too thin, it will lead to a higher transmittance of the dehydrogenated film and a narrower dimming range. The thickness of the palladium catalyst layer is 3-10 nm; and the thickness of the fluorocarbon film layer is 20-200 nm.

[0014] As a further preferred embodiment, the thickness of the magnesium-X element composite film is 25-40 nm; the thickness of the palladium catalyst layer is 5-8 nm; and the thickness of the fluorocarbon film layer is 20-100 nm.

[0015] As a preferred embodiment, the substrate includes any one of quartz glass, optical fiber, conductive glass, plexiglass, and flexible glass.

[0016] As a preferred embodiment, in the step of growing a magnesium-X element composite film on the substrate using the magnetron sputtering co-sputtering method, the sputtering power of the magnesium target and the X element target is 20-200W and 20-200W respectively, and the co-sputtering time is 30-200s.

[0017] As a preferred embodiment, in the step of preparing the palladium catalyst layer by magnetron sputtering, the sputtering power of the palladium target is 20-100W and the sputtering time is 14-70s.

[0018] As a preferred embodiment, in the step of preparing fluorocarbon films using plasma vapor deposition, the working gas pressure is 2-6 Pa, the working gas flow rate is 20-50 sccm, the gas excitation power is 400 W-800 W, and the deposition time is 10-100 s.

[0019] As a preferred embodiment, the working gas is C4F8 gas.

[0020] As a preferred embodiment, the method for improving the cycle durability of hydrogen-induced color-changing magnesium-based thin films specifically includes the following steps:

[0021] S1. Soak the substrate in cleaning solution, then rinse the substrate.

[0022] S2. Place the rinsed substrate into the magnetron sputtering reaction chamber and turn on the vacuum system to perform vacuuming.

[0023] S3. Heat the substrate, introduce working gas A and maintain the pressure. After the gas pressure stabilizes, turn on the power supply to the palladium target, magnesium target and X element target, turn off the baffle in front of the target material, and pre-sputter clean the target material.

[0024] S4. After pre-sputtering is completed, open the baffles of the magnesium target and the X element target, load the co-sputtering process program, and deposit the magnesium-X element composite film.

[0025] S5. After the deposition is completed in step S4, while keeping the vacuum level constant, turn on the baffle of the palladium target and load the sputtering process program of the palladium catalyst layer to deposit the palladium catalyst layer.

[0026] S6. After the deposition is completed in step S5, turn off the power supply to all targets, continue to purge the sample with working gas A, then stop the flow of working gas A and take out the sample.

[0027] S7. Place the extracted sample into the reaction chamber of the reactive ion vapor deposition machine, introduce working gas B, load the plasma vapor deposition process program, and deposit a fluorocarbon film on the surface of the palladium catalyst layer; after deposition is completed, remove the sample to obtain a fluorocarbon / palladium / magnesium-X element hydrogen-induced color-changing film.

[0028] As a further preferred embodiment, the X element target material in the X element target is prepared by: using X with a purity (mass fraction) of 99.99% to make the X element target material, and attaching a copper backing plate. Adding a copper backing plate enhances conductivity, ensures uniform heat dissipation from the target material, and protects the target material.

[0029] As a further preferred embodiment, in step S1, the cleaning solution is a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3:1. This effectively removes impurities and contaminants from the substrate surface without affecting the substrate composition, thus improving the film quality.

[0030] As a further preferred embodiment, in step S3, the working gas A is argon. The argon ions generated after ionization of this gas can bombard the target material to excite target ions without reacting with them, thus having no effect on the film composition; the vacuuming to a background vacuum level of 8 × 10⁻⁶ is further specified. -4 ~9×10 -5 Pa;

[0031] As a further preferred embodiment, the substrate temperature is heated to 20–25°C, the maintaining pressure is 0.4–0.6 Pa, and the pre-sputtering time is 5–20 min.

[0032] As a further preferred embodiment, in step S4, the sputtering power of the magnesium target and the scandium target used in the co-sputtering process is 20-100W and 20-100W respectively, and the co-sputtering time is 30-200s. More preferably, the sputtering power of the magnesium target and the scandium target is 40W and 80-150W respectively, and the co-sputtering time is 60s.

[0033] As a further preferred embodiment, in step S5, the sputtering process uses a palladium target with a sputtering power of 20–100 W and a sputtering time of 14–70 s. More preferably, the palladium target has a sputtering power of 80–100 W and a sputtering time of 14 s.

[0034] As a further preferred embodiment, in steps S4 and S5, the front baffle of the target material is opened during sputtering and closed when not sputtering, both controlled by the set sputtering process program.

[0035] As a further preferred embodiment, in step S7, the working gas B is C4F8 gas; the working gas pressure used in the plasma vapor deposition process is 2-6 Pa, the gas B flow rate is 20-50 sccm, the gas excitation power is 400W-800W, and the deposition time is 10-100s. The gas excitation power affects not only the combination mode of fluorocarbons but also the density of the film layer. If the power is too high, the film layer will be too dense, hindering gas passage and reducing the hydrogen adsorption and desorption efficiency; if the power is too low, the film layer will be too porous, weakening the hydrophobic effect and reducing the protective effect on the inner film layer.

[0036] The opening and closing of the target baffle, sputtering power, sputtering time, and deposition parameters of the fluorocarbon film can all be precisely controlled by programming and importing the data, resulting in a high degree of automation. More preferably, the plasma vapor deposition process uses a working gas pressure of 3–4 Pa, a gas B flow rate of 30–40 sccm, a gas excitation power of 400 W–600 W, and a deposition time of 30–60 s.

[0037] This invention first grows a magnesium-X element composite film on a substrate using co-sputtering, then grows a palladium catalyst layer on this film using magnetron sputtering, and finally deposits a fluorocarbon protective layer around the film using plasma vapor deposition. This invention utilizes the chemical reaction between X and magnesium elements to suppress interdiffusion between the palladium and magnesium layers, thereby maintaining the film structure during cycling and improving the film's hydrogen absorption and desorption cycle durability. The fluorocarbon film can disperse product water, effectively resisting corrosion of the inner film by the external environment. This dimming film exhibits good hydrogen absorption and desorption cycle durability and has significant application prospects in the field of hydrogen sensing.

[0038] Secondly, the present invention also provides a high-cycle-durability hydrogen-induced color-changing magnesium-based thin film prepared according to the aforementioned method.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1) This invention synthesizes magnesium-X element composite thin films by magnetron sputtering co-sputtering. The entire process is controlled by a preset program, which is simple to operate, has good stability, and produces uniform film layers.

[0041] 2) This invention utilizes the chemical reaction between element X and element magnesium to suppress the interdiffusion between the palladium layer and the magnesium layer during hydrogen absorption and desorption cycles, thereby maintaining the thin film structure and improving the durability of the thin film during hydrogen absorption and desorption cycles.

[0042] 3) The palladium film used in this invention has strong antioxidant properties. The in-situ growth method makes palladium more comprehensive in protecting the magnesium substrate. Furthermore, palladium can achieve reversible catalysis of hydrogen at room temperature, and the experimental conditions are low.

[0043] 4) The fluorocarbon membrane used in this invention has good permeability to gas molecules and strong hydrophobicity, which is beneficial for the uniform distribution of gas molecules on the membrane surface, accelerates the gas-induced reaction, and also enhances the corrosion resistance of the membrane. Plasma vapor deposition can generate solid membranes at low temperatures, resulting in high membrane adhesion and a fast reaction rate.

[0044] 5) The thin film prepared by the method of the present invention has a large dimming range and high hydrogen absorption and desorption cycle durability, and has important application prospects. Attached Figure Description

[0045] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0046] Figure 1 a is a schematic diagram of the thin film structure with composition CF / Pd / Mg-25%Sc prepared in Example 1 of the present invention. Figure 1 b shows the thin film structure of CF / Pd / Mg-25%Sc prepared in Example 1 of the present invention and the transmittance change curve obtained by testing during the hydrogen absorption and desorption cycle;

[0047] Figure 2 Figure a shows the EDS analysis results of the longitudinal section of the thin film with the composition CF / Pd / Mg-25% Sc obtained in Example 1 of this invention. Figure 2 Figure b shows the EDS analysis results of the longitudinal section of the CF / Pd / Mg thin film. Detailed Implementation

[0048] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0049] Example 1

[0050] This embodiment provides a method for improving the cycle durability of hydrogen-induced color-changing magnesium-based thin films, including the following steps:

[0051] (1) Scandium target material is made from scandium powder with a purity (mass fraction) of 99.99% and a copper backing plate is attached;

[0052] (2) Soak the quartz glass slide in the prepared cleaning solution for 15 minutes, and rinse it with deionized water for 1 minute. The cleaning solution is a mixture of concentrated sulfuric acid and hydrogen peroxide in a ratio of 3:1. Place the cleaned quartz glass substrate into the magnetron sputtering reaction chamber, turn on the vacuum system to evacuate the vacuum until the background vacuum degree is 3×10⁻⁶. -4 Pa;

[0053] (3) Heat the substrate to a temperature of 20-25°C, introduce working gas A (argon), and maintain a pressure of 0.4-0.6 Pa. After the pressure stabilizes, turn on the power supply for the palladium, magnesium, and scandium targets, turn off the baffles in front of each target, and pre-sputter clean the target for 10 minutes. Then set the co-sputtering process program, with sputtering powers of 40W and 150W for the magnesium and scandium targets, respectively, and a co-sputtering time of 60s. Begin depositing a magnesium-scandium thin film (Mg-25%Sc thin film, where 25% is the mass percentage of scandium in the film), with a film thickness of 40nm.

[0054] (4) After deposition, under the condition of maintaining a vacuum of 0.5 Pa, the sputtering process of the palladium catalyst layer is loaded, the sputtering power of the palladium target is adjusted to 100 W, the sputtering time is 14 s, and the film thickness is 8 nm. After the palladium film growth is completed, the power supply of all target materials is turned off, and the sample is purged with working gas A (argon) for 1 min. Then the sample is taken out to obtain a thin film with the composition of Pd / Mg-25%Sc.

[0055] (5) The Pd / Mg-25%Sc thin film was placed in a reactive ion vapor deposition (RIVDC) system. The process parameters for the fluorocarbon film were set as follows: working gas pressure 4 Pa, working gas B flow rate 40 sccm, gas excitation power 600 W, and deposition time 60 s. Working gas B (C4F8) was introduced, the process program was loaded, and the fluorocarbon film was deposited to a thickness of 100 nm. After completion, the sample was removed, yielding a CF / Pd / Mg-25%Sc thin film. The structure of the obtained film is shown below. Figure 1 As shown in Figure a, it includes a magnesium-X element (scandium) composite film layer (Mg-X layer), a palladium catalyst layer (Pd layer), and a fluorocarbon film layer (FC layer) sequentially disposed on a substrate.

[0056] The hydrogen absorption and desorption cycle transmittance curves of the CF / Pd / Mg-25%Sc thin film obtained by the test are shown below. Figure 1 As shown in b, the film can still maintain high sensing performance after 50 hydrogen absorption and desorption cycles, including fast hydrogen response rate and large hydrogen response value.

[0057] The EDS analysis results of the obtained CF / Pd / Mg-25%Sc thin film are as follows: Figure 2 As shown in Figure a, the EDS analysis results of the CF / Pd / Mg thin film without the addition of Sc are as follows: Figure 2 As shown in b. From Figure 2 a and Figure 2 The results in b show that the introduction of Sc makes the interlayer interface of the thin film clearer and significantly reduces the interdiffusion between the magnesium and palladium layers, which is beneficial to improving the durability of hydrogen absorption and desorption cycles.

[0058] Example 2

[0059] This embodiment provides a method for improving the cycle durability of hydrogen-induced color-changing magnesium-based thin films, including the following steps:

[0060] (1) Scandium target material is made from scandium powder with a purity (mass fraction) of 99.99% and a copper backing plate is attached;

[0061] (2) Soak the quartz glass slide in the prepared cleaning solution for 15 minutes, and rinse it with deionized water for 1 minute. The cleaning solution is a mixture of concentrated sulfuric acid and hydrogen peroxide in a ratio of 3:1. Place the cleaned quartz glass substrate into the magnetron sputtering reaction chamber, turn on the vacuum system to evacuate the vacuum until the background vacuum degree is 3×10⁻⁶. -4 Pa;

[0062] (3) Heat the substrate to a temperature of 20-25°C, introduce working gas A (argon), and maintain a pressure of 0.4-0.6 Pa. After the pressure stabilizes, turn on the power supply for the palladium, magnesium, and scandium targets, turn off the baffles in front of each target, and pre-sputter clean the target for 10 min. Then set the co-sputtering process program, with sputtering powers of 40 W and 80 W for the magnesium and scandium targets, respectively, and a co-sputtering time of 60 s. Begin depositing a magnesium-scandium thin film (Mg-12%Sc, where 12% is the mass percentage of scandium in the film), with a film thickness of 25 nm.

[0063] (4) After deposition, under the condition of maintaining a vacuum of 0.5 Pa, the sputtering process of the palladium catalyst layer is loaded, the sputtering power of the palladium target is adjusted to 80 W, the sputtering time is 14 s, and the film thickness is 5 nm. After the palladium film growth is completed, the power supply of all target materials is turned off, and the sample is continued to be purged with working gas A for 1 min. Then the sample is taken out to obtain a thin film with the composition of Pd / Mg-12%Sc.

[0064] (5) The Pd / Mg-12%Sc thin film was placed in a reactive ion vapor deposition (RIVDC) machine. The process parameters for the fluorocarbon film were set as follows: working gas pressure 3 Pa, gas B flow rate 30 sccm, gas excitation power 400 W, and deposition time 30 s. Working gas B (C4F8) was introduced, the process program was loaded, and the fluorocarbon film was deposited with a thickness of 20 nm. After completion, the sample was removed, and a thin film with the composition CF / Pd / Mg-12%Sc was obtained.

[0065] The test results showed that the CF / Pd / Mg-12%Sc thin film maintained high sensing performance throughout 50 hydrogen adsorption / desorption cycles.

[0066] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for improving the cycle durability of hydrogen-chromatic magnesium-based thin films, characterized in that, Includes the following steps: A magnesium-X element composite film was grown on the substrate by magnetron sputtering co-sputtering, then a palladium catalyst layer was prepared by magnetron sputtering, and finally a fluorocarbon film was prepared by plasma vapor deposition. The magnesium-X element composite film is a composite film formed by adding element X to a magnesium base; The element X is scandium; In the magnesium-X element composite film, the mass percentage of element X is 25%. The thickness of the magnesium-X element composite film is 40 nm; the thickness of the palladium catalyst layer is 8 nm; and the thickness of the fluorocarbon film layer is 100 nm.

2. The method for improving the cycle durability of hydrogen-chromic magnesium-based thin films according to claim 1, characterized in that, The substrate includes any one of quartz glass, optical fiber, conductive glass, plexiglass, and flexible glass.

3. The method for improving the cycle durability of hydrogen-chromic magnesium-based thin films according to claim 1, characterized in that, In the step of growing a magnesium-X element composite film on a substrate using the magnetron sputtering co-sputtering method, the sputtering powers of the magnesium target and the X element target are 20-200W and 20-200W, respectively, and the co-sputtering time is 30-200s.

4. The method for improving the cycle durability of hydrogen-chromic magnesium-based thin films according to claim 1, characterized in that, In the step of preparing the palladium catalyst layer by magnetron sputtering, the sputtering power of the palladium target is 20-100W and the sputtering time is 14-70s.

5. The method for improving the cycle durability of hydrogen-chromic magnesium-based thin films according to claim 1, characterized in that, In the process of preparing fluorocarbon films using plasma vapor deposition, the working gas pressure is 2-6 Pa, the working gas flow rate is 20-50 sccm, the gas excitation power is 400 W-800 W, and the deposition time is 10-100 s.

6. The method for improving the cycle durability of hydrogen-chromatic magnesium-based thin films according to claim 5, characterized in that, The working gas is C4F8 gas.

7. A high-cycle-durability hydrogen-chromic magnesium-based thin film prepared by the method according to any one of claims 1 to 6.

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