A surface hydrogen-selective permeation layer for a hydrogen sensor in transformer oil and a method of manufacturing the same

Abstract

The application discloses a hydrogen selective permeation layer of a hydrogen sensor in transformer oil and a manufacturing method thereof, and belongs to the technical field of on-line fault monitoring of oil-immersed transformers. The hydrogen selective permeation layer comprises, from bottom to top, a Si-Al-O stress regulation molecular sieve layer, an organic silicon modified acrylic resin and a PTFE hydrogen permeation protection layer. The application provides a design and a manufacturing method of the selective permeation layer of the Pd alloy resistance type hydrogen sensor for transformer insulating oil, and has the advantages of low stress, strong bonding force, high chemical stability, high temperature stability and the like, and can be applied to the environment in western regions and coastal regions. The application provides a new idea for the design of the selective permeation layer of the Pd alloy resistance type hydrogen sensor for transformer insulating oil.

Description

Technical Field

[0001] This invention belongs to the field of online fault monitoring technology for oil-immersed transformers, and specifically relates to a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil for online monitoring of hydrogen concentration in oil-immersed transformers and its manufacturing method. Background Technology

[0002] As a critical piece of equipment in substations, the stability of transformers is closely related to the safety of the power system. Therefore, it is necessary to monitor and diagnose the operating status of transformers to prevent problems before they occur. Transformers mainly consist of coils, magnetic cores, and insulating oil. The main functions of the insulating oil are cooling, insulation, and arc suppression, ensuring the safe operation of the transformer. Internal faults such as partial discharge, spark discharge, arcing, and overheating can cause the transformer insulating oil to decompose, producing gases such as H2, CO, CH4, C2H4, and C2H2. These gases dissolve in the oil through convection and diffusion, causing sudden changes in gas concentration, typically at the ppm level. Among the gases produced by the decomposition of transformer insulating oil, the concentration of H2 is often used as an important indicator for monitoring the condition of the transformer insulating oil. Online monitoring of the hydrogen concentration in transformer insulating oil is crucial for early detection of latent faults within the equipment and for monitoring their development. This is of great significance for ensuring the safety of the power supply system and promoting the construction of intelligent power systems.

[0003] Currently, the mainstream hydrogen sensors used for detecting hydrogen concentration in oil are thin-film Pd-based alloy hydrogen resistive sensors and Pd-based alloy grating hydrogen sensors. However, the decomposition of transformer insulating oil produces gases such as CO, CH4, C2H4, and C2H2, which can affect the response of Pd-based alloy hydrogen resistive sensors and Pd-based alloy grating hydrogen sensors used for H2 concentration detection. CO can even poison the surface of the Pd-based alloy, affecting the adsorption-desorption process of H2 on the Pd-based alloy surface. Since the dynamic diameter of the H2 molecule is only 0.289 nm, its volume is smaller than that of the interfering gases. Therefore, preparing a hydrogen selective permeation layer on the surface of the Pd-based alloy can effectively prevent interference from impurity gases and resist Pd-based alloy poisoning. Furthermore, the application scenarios of transformer insulating oil are characterized by complex chemical composition and large diurnal temperature variations (especially in western regions). Therefore, a Pd-based alloy surface hydrogen selective permeation layer with high selectivity, strong H2 permeability, and high stability meets the needs of remote online monitoring of transformer insulating oil and undoubtedly has significant engineering application value.

[0004] Chinese patent application CN107076718A discloses a hydrogen sensor with a protective layer, primarily targeting CO, O2, and H2O. However, this method does not consider the bonding force between the protective layer and the substrate, the influence of inter-film stress release under large temperature differences on film stability, the protection against organic gases generated by the decomposition of transformer insulating oil (CH4, C2H4, C2H2), or the corrosion from acidic sulfides present in the insulating oil. The normalized results shown in the embodiments exhibit severe zero-point drift and large, irregular response variations, indicating a design flaw in the protective layer.

[0005] Chinese patent application CN204479506U discloses a hydrogen sensor for online monitoring of hydrogen concentration in oil-immersed transformers. Its hydrogen-specific coating is one or more of SiO2, Al2O3, and Si3N4 films, with a composite film of SiO2, Al2O3, and Si3N4 being the most preferred. However, several domestic and international publications have used Si3N4 films as hydrogen-blocking layers, which significantly hinder hydrogen permeation. Pure inorganic films only act as molecular sieves for organic molecules, offering limited protection against CH4 small molecules. Furthermore, this protective layer does not consider the impact of stress release between films, under large temperature differences, on film stability, or the corrosion from acidic sulfides in the insulating oil. The protective effect of the layer is not demonstrated. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to address the issues of high stress and poor stability of existing hydrogen selective permeable layers in environments with large temperature differences, rapid temperature changes, acidic substances, and various organic compounds, which lead to cracking, detachment, poisoning, and corrosion of the hydrogen selective permeable layer during operation.

[0007] This invention addresses the need for online monitoring of hydrogen concentration in transformer insulating oil. Taking into full account the large temperature variations and complex chemical composition of transformer insulating oil, it cleverly solves the problems of poor selectivity, low stability, and susceptibility to poisoning faced by existing hydrogen sensors in complex transformer oil environments through an innovative sandwich composite film structure. It proposes a high-stability hydrogen selective permeation layer for the surface of a hydrogen concentration sensor in transformer oil and its manufacturing method. Through an innovative composite film structure design, each layer has a specific function, and the layers are strongly bonded together by chemical bonds, working synergistically to achieve selective hydrogen permeation and effective protection against impurity gases in the oil. This meets the requirement of isolating the surface of Pd-based alloy hydrogen resistive hydrogen sensors used in transformer insulating oil from impurity gases. The manufacturing process is simple and easy to mass-produce. Furthermore, because this protective layer is resistant to acid, alkali, salt spray, organic compounds, and cyanide corrosion, it is further suitable for hydrogen-sensitive film protection in corrosive gas environments such as seawater hydrogen production, electroplating processes, and hydrogen leakage in chemical pipelines.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] This invention provides a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil. The hydrogen selective permeation layer is deposited on one side of the Pd-based alloy surface of a Pd-based alloy hydrogen resistive hydrogen sensor. From bottom to top, it includes: a silicon substrate with a Pd-based alloy hydrogen resistive layer deposited on its surface, a Si-Al-O stress-regulated molecular sieve layer, an organic molecular filter layer, and a polytetrafluoroethylene (PTFE) H2 permeability protection layer.

[0010] The Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor includes a Pd-based alloy hydrogen resistive layer and a SiO2 surface oxide layer. The Si-Al-O stress-regulated molecular sieve layer wraps the upper and side surfaces of the Pd-based alloy hydrogen resistive layer and covers the upper surface of the SiO2 surface oxide layer.

[0011] The Si-Al-O stress-regulated molecular sieve layer is a composite material of SiO2 and Al2O3;

[0012] The organic molecular filter layer is an aqueous organosilicon-modified acrylic resin.

[0013] The thickness of the Si-Al-O stress-regulated molecular sieve layer is 2~10nm, the thickness of the organic molecular filter layer is 10~50nm, and the thickness of the PTFE H2 permeability protective layer is 2~10nm.

[0014] The present invention also provides a method for manufacturing a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil, comprising the following steps:

[0015] Step 1: Clean and dry the Pd-based alloy hydrogen resistive hydrogen sensor;

[0016] Step 2: Spin-coating photoresist: On one side of the Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor monolith, a layer of photoresist is spin-coated using a spin coating process, and then a rectangular groove is photolithographically formed on the photoresist.

[0017] Step 3: On the surface of the Pd-based alloy hydrogen resistive hydrogen sensor monolith after the groove pattern has been photolithographically etched, a Si-Al-O stress-regulated molecular sieve layer is prepared by magnetron sputtering or atomic layer deposition, using trimethylsilicon and trimethylaluminum as silicon and aluminum sources, respectively.

[0018] Step 4: Prepare a water-based organosilicon-modified acrylic resin organic molecular filter layer film using the dip-coating or spin-coating method;

[0019] Step 5: Prepare a PTFE H2 permeable protective layer film using magnetron sputtering;

[0020] Step 6: Ultrasonic stripping removes the photoresist and cleans the area.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides a highly stable hydrogen selective permeation layer for the surface of a Pd-based alloy hydrogen resistive hydrogen sensor in transformer insulating oil, and its manufacturing method. The layer exhibits low stress, strong adhesion, high chemical stability, and high temperature stability. It can be applied to environments in western and coastal regions. This invention provides a new approach to the design of selective permeation layers for Pd alloy resistive hydrogen sensors in transformer insulating oil.

[0023] This invention reduces the stress of the molecular sieve layer, Pd-based alloy sensitive layer, and Si-based matrix by adjusting the Si-Al content ratio through membrane material design. It achieves a transition from inorganic to organic membrane layers from bottom to top through the -Si-O bond linkage, resulting in strong direct adhesion between the membrane layers.

[0024] The prepared PTFE / organosilicon-modified acrylic resin / Si-Al-O composite hydrogen selective permeable layer exhibits better selectivity and provides more H2 channels compared to single-layer Al2O3, SiO2, PMMA, and PTFE layers, while having a smaller impact on response-recovery time. Compared to purely inorganic selective permeable layers (such as Al2O3, SiO2, and Al2O3 / SiO2 composite layers), it has better filtration capabilities for organic gases and can absorb them.

[0025] The prepared PTFE / organosilicon-modified acrylic resin / Si-Al-O composite film is designed for transformer insulating oil environment. It has good oleophobic properties and can isolate oil from sensitive layers, avoiding the influence of metal passivation additives in the oil.

[0026] This invention can adjust parameters and incorporate them into the fabrication process of Pd-based alloy resistive hydrogen sensors. It can prepare a highly stable hydrogen selective permeable layer on the surface of such hydrogen sensors on the wafer surface after the functional film layer has been prepared but before it has been cut into individual pieces, thus enabling large-scale manufacturing. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the high-stability hydrogen selective permeation layer on the surface of the hydrogen sensor in transformer oil according to Embodiment 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the preparation process of the high-stability hydrogen selective permeation layer on the surface of the hydrogen sensor in transformer oil according to Embodiment 1 of the present invention;

[0029] Figure 3 This paper compares the performance of a high-stability hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil prepared in Example 1 of the present invention with that of a single SiO2 hydrogen selective permeation layer of the same thickness. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0032] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0033] The photoresist used is Suzhou Ruihong RZJ-30425cp;

[0034] The waterborne silicone-modified acrylic resin used was Guangzhou Wanhua New Materials WH-1000, and diluted with deionized water to 25 cp.

[0035] Example 1:

[0036] A hydrogen selective permeation layer for a transformer oil hydrogen sensor is deposited on one side of the Pd-based alloy surface of a Pd-based alloy hydrogen resistive hydrogen sensor. From bottom to top, the layer comprises: a silicon substrate with a Pd-based alloy hydrogen resistive layer deposited on its surface; a Si-Al-O stress-regulated molecular sieve layer; an organic molecular filter layer; and a PTFE (polytetrafluoroethylene) H2 permeability protection layer. A schematic diagram is shown below. Figure 1 As shown.

[0037] The structure of the silicon substrate with the Pd-based alloy hydrogen sensor layer deposited on its surface, from bottom to top, consists of a Si substrate, a SiO2 surface oxide layer, and a Pd-based alloy hydrogen sensor layer deposited on the upper surface of the SiO2 surface oxide layer. The Si-Al-O stress-regulated molecular sieve layer wraps around the upper and side surfaces of the Pd-based alloy hydrogen sensor layer and covers the upper surface of the SiO2 surface oxide layer.

[0038] The Si-Al-O stress-regulated molecular sieve layer is a composite material of SiO2 and Al2O3. By controlling the injection time of the Si source and Al source, the ratio of Si to Al is adjusted so that its thermal expansion coefficient is between that of Pd metal and SiO2 on the surface oxide layer of SiO2, thereby improving its resistance to temperature shock. At the same time, the Si and O dangling bonds at the interface with the substrate can form chemical bonds with the dangling bonds of SiO2 on the substrate surface, thereby improving its bonding force with the substrate.

[0039] The organic molecular filter layer is an aqueous organosilicon-modified acrylic resin. The pores inside the organic molecular filter layer contain a large number of C, H, and O dangling bonds, which can effectively chemically adsorb organic gas molecules such as CH4, C2H4, and C2H2, thereby achieving the purpose of filtering organic molecules. The organosilicon-modified acrylic resin and the Si-Al-O stress-regulated molecular sieve layer can form chemical bonds through the Si and O suspended on their surfaces, resulting in a strong bond between them.

[0040] The PTFE H2 permeable protective layer utilizes PTFE's excellent physical and chemical stability, oleophobicity, and hydrogen permeability to protect the internal membrane layer and ensure stable operation. Simultaneously, the C, H, and O dangling bonds on its surface can form chemical bonds with the silicone-modified acrylic resin, enhancing their bonding strength. Both PTFE and the silicone-modified acrylic resin are flexible, effectively buffering thermal stress caused by temperature shocks.

[0041] The thickness of the Si-Al-O stress-regulated molecular sieve layer is 2~10nm, the thickness of the organosilicon-modified acrylic resin organic molecular filter layer is 10~50nm, and the thickness of the PTFE H2 permeable protective layer is 2~10nm.

[0042] This embodiment also provides a method for manufacturing a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil, such as... Figure 2 As shown, it includes the following steps:

[0043] Step 1: Pre-treatment of Pd-based alloy hydrogen resistive type hydrogen sensor: Clean the Pd-based alloy hydrogen resistive type hydrogen sensor in sequence with acetone, alcohol and deionized water, 10 min in each solvent. Dry the cleaned Pd-based alloy hydrogen resistive type hydrogen sensor with a hot plate at 60℃ for 5 min.

[0044] Step 2: Spin-coating photoresist: On one side of the Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor monolith, a layer of photoresist is spin-coated using a spin coating process, and then a rectangular groove is photolithographically formed on the photoresist (the depth of the groove is equal to the thickness of the photoresist).

[0045] Step 3: Deposit a Si-Al-O stress-controlled molecular sieve layer using ALD (Atomic Layer Deposition), i.e., a Si-Al-O thin film with stress-controlled molecular sieve layer: On the surface of a Pd-based alloy hydrogen resistive hydrogen sensor monolith after photolithography to create the groove pattern, a Si-Al-O stress-controlled molecular sieve layer is deposited using trimethylsilicon and trimethylaluminum as silicon and aluminum sources, respectively, using atomic layer deposition. The process gas is nitrogen (high-purity nitrogen N2 ≥ 99.999%). The back vacuum is 0.01 torr, the working pressure is 0.15 torr, the heating temperature of the Si and Al source tube sleeves is 120℃, the water tube sleeve heating temperature is 100℃, the bottom heating temperature is 150℃, the pump heating temperature is 100℃, and the heat trap heating temperature is 400℃. The Si and Al source jetting time is 0.01s, the N2 rinsing time is 30s, the water jetting time is 0.15s, and a second N2 rinsing is performed for 60s. The cycle of "source jetting-N2 rinsing-water jetting-N2 rinsing" was repeated 50 times, and the thickness of the prepared Si-Al-O stress-regulated molecular sieve layer was 5 nm.

[0046] Step 4: Spin coating method for preparing waterborne silicone-modified acrylic resin organic molecular filter layer film: The silicone-modified acrylic resin diluted to 50 cp is drop-coated onto the center of the monolayer with Si-Al-O stress-regulated molecular sieve layer, and spin-coated at a rate of 7000 rpm for 20 s. The thickness of the prepared waterborne silicone-modified acrylic resin organic molecular filter layer film is 30 nm.

[0047] Step 5: Preparation of PTFE H2 permeable protective layer film by magnetron sputtering: A layer of PTFE was sputtered onto the surface of the aqueous silicone-modified acrylic resin organic molecular filter layer film using radio frequency magnetron sputtering. The target was a 4-inch PTFE target with a thickness of 3 mm and a purity greater than 99.9%. Ar was used as the working gas with a purity of 99.999 vol.%. The working gas pressure was 1.5 Pa, the sputtering power was 250 W, the substrate temperature was 25 °C, the target-substrate distance was 15 cm, the film deposition rate was 4 nm / min, and the deposition time was 2 min. The thickness of the prepared aqueous silicone-modified acrylic resin organic molecular filter layer film was 8 nm.

[0048] Step 6: Ultrasonic stripping: Acetone is used as the stripping liquid for ultrasonic stripping at a power of 120W. After stripping, step 1 is repeated for wet cleaning, thus obtaining a highly stable hydrogen selective permeable layer on the surface of the Pd-based alloy hydrogen resistive hydrogen sensor.

[0049] like Figure 3As shown, (a) and (b) represent the response performance of the two samples, respectively, and (c) represents their selectivity. The Pd-based alloy hydrogen resistive hydrogen sensor with a PTFE / organosilicon-modified acrylic resin / Si-Al-O composite hydrogen selective permeation layer prepared on the surface according to the above steps exhibits responses of 3.13%, 0.39%, 0.32%, and 0.14% to H2 concentrations of 4%, 800ppm, 500ppm, and 100ppm, respectively, and to a nitrogen-hydrogen mixture. Simultaneously, its responses to 4% concentrations of CO, C2H4, and C2H2 (all mixtures with N2) are 0.0017%, 0.0006%, and 0.0013%, respectively, which is lower than the 1% (0.031%) response to 4% H2. Compared to currently commercially available single-SiO2 hydrogen selective permeation layers, it exhibits better selective permeation characteristics for hydrogen. Its response values ​​for nitrogen-hydrogen mixtures with H2 concentrations of 4%, 800ppm, 500ppm, and 100ppm are 2.14%, 0.35%, 0.29%, and 0.09%, respectively. Its responses for 4% concentrations of CO, C2H4, and C2H2 (all of which are mixtures with N2) are 0.0024%, 0.0096%, and 0.0153%, respectively.

[0050] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil, characterized in that, The hydrogen selective permeation layer is deposited on one side of the Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor. From bottom to top, it includes: a Si-Al-O stress-regulated molecular sieve layer, an organic molecular filter layer, and a polytetrafluoroethylene (PTFE) H2 permeability protection layer. The organic molecular filter layer chemically adsorbs organic gas molecules.

2. The hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil according to claim 1, characterized in that, The Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor includes a Pd-based alloy hydrogen resistive layer and a SiO2 surface oxide layer. The Si-Al-O stress-regulated molecular sieve layer wraps the upper and side surfaces of the Pd-based alloy hydrogen resistive layer and covers the upper surface of the SiO2 surface oxide layer.

3. The hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil according to claim 2, characterized in that, The Si-Al-O stress-regulated molecular sieve layer is a composite material of SiO2 and Al2O3; The organic molecular filter layer is an aqueous organosilicon-modified acrylic resin.

4. The hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil according to claim 3, characterized in that, The thickness of the Si-Al-O stress-regulated molecular sieve layer is 2~10nm, the thickness of the organic molecular filter layer is 10~50nm, and the thickness of the PTFE H2 permeability protective layer is 2~10nm.

5. A method for manufacturing a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil as described in any one of claims 3-4, characterized in that, Includes the following steps: Step 1: Clean and dry the Pd-based alloy hydrogen resistive hydrogen sensor; Step 2: Spin-coating photoresist: On one side of the Pd-based alloy surface of the Pd-based alloy hydrogen resistive hydrogen sensor monolith, a layer of photoresist is spin-coated using a spin coating process, and then a rectangular groove is photolithographically formed on the photoresist. Step 3: On the surface of the Pd-based alloy hydrogen resistive hydrogen sensor monolith after the groove pattern has been photolithographically etched, a Si-Al-O stress-regulated molecular sieve layer is prepared by atomic layer deposition using trimethylsilicon and trimethylaluminum as silicon and aluminum sources, respectively. Step 4: Prepare a water-based organosilicon-modified acrylic resin organic molecular filter layer film using the dip-coating or spin-coating method; Step 5: Prepare a PTFE H2 permeable protective layer film using magnetron sputtering; Step 6: Ultrasonic stripping removes the photoresist and cleans the area.

6. The method for manufacturing a hydrogen selective permeation layer on the surface of a hydrogen sensor in transformer oil according to claim 5, characterized in that, Step 4 is as follows: The organosilicon-modified acrylic resin diluted to 50 cp is drop-coated onto the center of the monolayer with the Si-Al-O stress-regulated molecular sieve layer, and spin-coated at a rate of 7000 rpm.

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