One-step preparation of α-Al2O3/SiO2 composite tritium permeation barrier via slurry spin coating method and performance investigation

One-step preparation of α-Al2O3/SiO2 composite tritium permeation barrier via slurry spin coating method and performance investigation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article One-step preparation of α-Al 2 O 3 /SiO 2 composite tritium permeation barrier via slurry spin coating method and performance investigation Dong-Guang Liu, Jin-Xin Zou, Ting-Ting Yang, Si-Wei Zhou, Lai-Ma Luo, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2936335/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In the fusion reactor, a-Al 2 O 3 and its composite coatings have became the preferred material for tritium permeation barriers. The slurry spin coating method in this study is used to prepare α-Al 2 O 3 /SiO 2 composite coating for one-step at the temperature of 600 °C, 700 °C and 800 °C. The effect of heat treatment temperature on the composite coating's microstructure and adhesion strength is investigated. When the coating prepared temperature is 600 °C, the thermal shock resistance and hydrogen permeation resistance are also studied. The findings demonstrate that as the heat treatment temperature rises, defects such as holes and cracks appear. The surface of the composite coating is continuous and compact when the preparation temperature is 600 °C, and the adhesion strength is 88.7 N. Thermal shock tests demonstrate that the 600 °C-α-Al 2 O 3 /SiO 2 composite coating is still dense and is bonded well to the substrate after 50 times thermal shocks at 500 °C. The hydrogen resistance capability indicate that the 600 °C-α-Al 2 O 3 /SiO 2 composite is 4.6 times greater than the substrate. slurry spin coating method α-Al2O3/SiO2 composite coating one-step thermal shock hydrogen permeation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction In the Test Blanket Module (TBM) of the International Thermonuclear Experimental Reactor (ITER), because of their small atomic radii, deuterium and tritium as nuclear fuel have a high permeability to structural materials [ 1 , 2 ]. As a result, fuel efficiency, steel mechanical properties, and radioactive pollution of the environment all suffer [ 3 – 5 ]. The application of a tritium penetration barrier (TPB) to the surface of steel structure materials is an important way to prevent hydrogen and its isotopes from penetrating [ 6 ]. Ceramic oxide TPBs possessing excellent corrosion and excellent tritium resistance, have received great attention in recent years [ 7 – 9 ]. The ceramic oxide TPBs mainly include Cr 2 O 3 , Al 2 O 3 , Y 2 O 3 , Er 2 O 3 , TiO 2 , ZrO 2 , and SiO 2 and their composite coatings [ 1 , 2 , 7 , 10 – 17 ]. Many countries have chosen the Al 2 O 3 coating as one of the most promising candidates because of its high hydrogen isotope permeation reduction factor (PRF), strong compatibility, high temperature tolerance, and self-repair potential [ 18 , 19 ]. While Al 2 O 3 can have a variety of phase structures (α, δ, γ, and θ), the α state is the most stable. It can effectively prevent tritium permeation and ensure the tritium barrier's excellent capacity [ 10 ]. However, the α-Al 2 O 3 formation temperature is up to 1000°C, which will bring down the mechanical properties of the structural materials. For example, Wang et al. [ 20 ] used sol-gel method to prepare Al 2 O 3 TPBs on Fe-Cr-Al alloy foils, the formation temperature of α-Al 2 O 3 is 1100°C. Meanwhile, Composite coatings may take advantage of the distinct properties of each of their constituent materials to achieve outstanding overall efficiency [ 21 ]. Therefore, the research emphasis mainly on preparing Al 2 O 3 composite coating with high quality at low temperature in recent years. In addition, none of the traditional methods can produce α-Al 2 O 3 by one-step, and they are usually doping with other forms of Al 2 O 3 . The adhesion strength between the coating and substrate is a significant index to evaluate the quality of the coating. Scratch test is widely used to detect the adhesion strengting of hard thin coatings. Rahmati et al. [ 22 ] and Kallel et al. [ 23 ] use scratch tests to measure the adhesion strength and observe the scratch morphology. Thermal shock test is also a common method to test the adhesion strength and stability of the coating under the condition between thermal and cold. Wen et al. [ 24 ] and Qiu et al. [ 25 ] observe the microstructures between the coating and the substrate through thermal cycles experiments. In this work, the slurry spin coating method is used to prepare the α-Al 2 O 3 /SiO 2 composite coating in a single stage. The slurry spin coating method is not only easy to operate but also can avoid the mechanical properties of the matrix be influenced by the high formation temperature of α-Al 2 O 3 . The effect of heat treatment temperature on the microstructure and adhesion strength of the composite coating are studied. When the coating prepared temperature is 600°C, The coatings' thermal shock resistance and hydrogen permeation resistance are also investigated. 2 Experimental 2.1 Preparation of the samples The matrix material is made of 316L stainless steel. The dimension of the matrix samples is 90mm × 60mm × 2mm. After sanding, the samples are washed in acetone and ethanol for 15 minutes before being dried in a drying oven. The modified SiO 2 sol (purity 30.0%, pH ranges from6.5 to 8) and 30 nm α-Al 2 O 3 powder are combined in a 3:5 mass ratio. The thickness and cracks increased proportionally to the sol viscosity [ 26 ], the slurry prepared by this ratio has good fluidity and the slurry is distributed uniformly. The magnetic stirrer was then used to stir the mixture for 2 h at 25°C using a constant temperature magnetic stirrer at a speed of 2000 r/min. The prepared slurry was spun coated onto the substrate at a speed of 3500 r/min. The coated samples are heat-treated in the air atmosphere for 1h at 600°C, 700°C and 800°C to prepared the α-Al 2 O 3 /SiO 2 composite coating, respectively. 2.2 Analysis of the coating's properties To detect the surface and cross-section microstructure of α-Al 2 O 3 /SiO 2 composite coating at different preparation temperatures, a field-emission scanning electron microscope (SEM) is used. At different heat treatment temperatures, the chemical composition of the α-Al 2 O 3 /SiO 2 coating is identified using an energy dispersive spectroscope (EDS). The crystal structure and phase detail of the α-Al 2 O 3 /SiO 2 composite coating was analyzed using an X-ray diffractometer (XRD). The morphology of the α-Al 2 O 3 /SiO 2 coating is examined using a field-emission transmission electron microscope (TEM). The adhesion strength of α-Al 2 O 3 /SiO 2 coatings at different heat treatment temperatures is carried out using the MFT-4000 multifunctional material surface performance testing machine. The change in loading force is used to determine the friction coefficient and friction force of the composite coating's surface. The friction coefficient and friction force change dramatically as the coating fails, and the loading force becomes the critical load force. The corresponding applied loading force in this case is known as the critical failure loading force, and it reflects the coating's adhesion power [ 27 ]. The length of the scratch tests is 5mm, the loading force is increasing at a rate of 100 N/min, and the applied loading force range is 0-100 N. Thermal shock test is used to characterize the resistance stability between thermal and cold of the composite coating. The stability of the thermal shock resistance is evaluated at 500°C. The samples are first sliced into 10 mm×10 mm. After that, the samples are held at 500°C for 15 min. Finally, the sample is removed and immediately immersed in 20°C water for quenching. A self-made electrochemical hydrogen permeation system is used to evaluate the coating's efficiency, which was described in detail from previous studies [ 17 ]. The hydrogen resistance ability between the prepared coating and the matrix is compared by the steady-state permeation current density. 3 Results and discussion 3.1 Microstructure and phase The silica colloidal particles have negative charge [ 28 ], which can absorb the alumina particles [ 29 ]. The silicon sol can form a threedimensional network structure after the silica sol water evaporates, resulting in bonding firmly between the colloidal particles and the substrate. Figure 1 shows the surface SEM images and points scan of the α-Al 2 O 3 /SiO 2 composite coating at different heat treatment temperatures. As shown in Fig. 1 (a,b), the surface of the composite coating is continuous and compact at 600°C. As the heat treatment temperature reaches 700°C (Fig. 1 (d,e)), there are many holes on the surface of the composite coating. At 800°C (Fig. 1 (g,h)), there are not only having holes but also appearing cracks on the surface of the coating. The XRD patterns of the α-Al 2 O 3 /SiO 2 composite coating at different heat treatment temperatures is shown in Fig. 2 . The phases of the three heat treatment temperatures are the same. It includes the diffraction peaks of Fe, α-Al 2 O 3 and SiO 2 . From the Fig. 3 (a), it can be seen that the α-Al 2 O 3 is distributed in the silica sol uniformly. Combined with the Fig. 2 and the Fig. 3 (b), the alkaline silica sol decomposes into amorphous SiO 2 after 600℃ heat treatment. Figure 3 (c) shows the SAED pattern image of the α-Al 2 O 3 /SiO 2 coating, it can be seen that the added α-Al 2 O 3 nanopowder still exist in α-Al 2 O 3 form. The central part of Fig. 3 (c) shows a distinct halo, which indicates the presence of amorphous SiO 2 phase. The silica sol has cohesiveness and it exists in the form of sol, so the bonding force between the coating and the matrix is improved and the alumina particles can be distributed uniformly. Because X-rays are penetrating, the Fe phase appears in the diffraction pattern. 3.2 Scratch tests The adhesive force is tested by scratch tests at different heat treatment temperatures. Figure 4 shows the curves of friction force and friction coefficient and the scratch topography image of α-Al 2 O 3 /SiO 2 composite coating at different heat treatment temperatures in scratch tests. The Fig. 4 (a)(b)(c) show that the friction coefficient increases rapidly at the beginning of the scratch tests, and then decreases rapidly and reaches a stable value. Then, with the increase of load force, the undulating shape of the curve of friction coefficient and friction force change with the microstructure of the sample surface. In addition, when the critical load force of the coating is reached, the friction coefficient and friction force change significantly. From the Table.1, the adhesion strength of α-Al 2 O 3 /SiO 2 composite coating is 88.7 N at 600 ℃, and the adhesion strength of α-Al 2 O 3 /SiO 2 composite coating is 62.6 N at 700 ℃. Combined with the Fig. 4 (d), when the heat treatment temperature is 600 ℃, a small amount of coating is peeled off at the end of the scratch test. The composite coating begins to peel off in the middle of the scratch test at 700 ℃. However, the curve of the friction force and friction coefficient increase without significant changes, and the critical load force cannot be obtained through this curve at 800 ℃. The friction behavior is strongly influenced by the morphology [ 30 ]. From the Fig. 3 (d), we can see that when the heat treatment temperature is 800 ℃, the composite coating is already peeled off at the beginning of the scratch test. Table.1 The adhesion strength between α-Al 2 O 3 /SiO 2 composite coating and 316L stainless steel matrix at different heat treatment temperatures Teat treatment temperatures (℃) 600 ℃ 700 ℃ 800 ℃ Adhesion strength (N) 88.7 N 62.6 N / 3.3 Thermal shock stability Thermal shock test is used to characterize the resistance stability between thermal and cold of the composite coating. The samples prepared at the heat treatment temperature of 600°C (600°C-α-Al 2 O 3 /SiO 2 composite coating), and cut into 10mm × 10mm thermal shock samples, and then these samples are held for 15 min at the temperature of 500°C. The samples are then removed and immediately immersed in water at 20°C for quenching. Finally, thermal shock resistance of the composite coating is determined according to its macroscopic and microscopic morphology. The macroscopic morphologies of original sample and the thermal shock samples after 10, 30, and 50 times thermal shocks at the temperatures of 500°C are shown in Fig. 5 . It can be seen that there is no discernible difference in the coating structure after 50 thermal shocks at 500°C. Figure 6 (a) shows the SEM morphology of the surface of 600°C-α-Al 2 O 3 /SiO 2 composite coating after 50 times thermal shocks at the temperature of 500°C, on the surface of the composite coating, a few holes and cracks can be observed, but the surface is still dense. Combined with the EDS image of Fig. 6 (b), it can be seen that compared with the original composite coating (Fig. 1 (c)), the content of Si element decreases after 50 times thermal shocks, which results in defects such as holes and cracks on the surface of the composite coating. From Fig. 6 (c), there are no visible cracks in the composite coating, and the thickness of the composite coating is approximatelyt 12.5 µm. From the illustration of Fig. 6 (c), the composite coating is bonded well with the substrate without cracking and spalling after 50 times thermal shocks. Combined with the line scan Fig. 6 (d) the line scan of the cross-section of 600°C-α-Al 2 O 3 /SiO 2 composite coating after 50 times thermal shocks, the Si content of the coating near the substrate is higher than far away from the substrate. 3.4 Hydrogen permeation resistance property The hydrogen permeation resistance property of the composite coating is tested by electrochemical hydrogen permeation. Hydrogen permeation test has high requirements on the sample, especially for air tightness. When the heat treatment temperature are 700°C and 800°C, there are holes and cracks on the coating surface. Therefore, the hydrogen permeation tests were carried out only on samples at the heat treatment temperature of 600°C. Figure 7 (b) shows the hydrogen penetration curve at room temperature of the 316L stainless steel matrix. It can be shown that the matrix has a steady-state permeation current density of 1.45×10 − 6 A/cm 2 , with current density difference of 3×10 − 7 A/cm 2 . Figure 7 (c) shows the hydrogen penetration curve at room temperature of the 600°C-α-Al 2 O 3 /SiO 2 composite coating. The composite coating's steady-state permeation current density is 3.12×10 − 7 A/cm 2 , with a current density difference of 1.22×10 − 7 A/cm 2 . The hydrogen resistance capability indicate that the 600°C-α-Al 2 O 3 /SiO 2 composite is 4.6 times greater than the substrate, and the current density difference ratio is 1:2.5. 4 Conclusion The α-Al 2 O 3 /SiO 2 composite coating is prepared for one-step on the 316L stainless steel matrix by the method of slurry spin coating at the heat treatment temperature of 600°C, 700°C, and 800°C, respectively. With the increase of heat treatment temperature, resulting in defects such as holes and cracks. When the heat treatment temperature is 600 ℃, there is having a high adhesion strength between the α-Al 2 O 3 /SiO 2 composite coating and the substrate, and the adhesion strength of coating is 88.7 N. At 700 ℃, the adhesion strength between the α-Al 2 O 3 /SiO 2 composite coating and the substrate decreases, the adhesion strength is 62.6 N. At 800 ℃, there is having a poor adhesion strength between the α-Al 2 O 3 /SiO 2 composite coating and the substrate, the composite coating already peeled off at the beginning of the scratch test. The thermal shock stability of the 600°C-α-Al 2 O 3 /SiO 2 composite coating is explored at the temperature of 500°C. After 50 times thermal shocks, the composite coating appears a few holes and cracks due to the reduction of SiO 2 sol on the coating's surface, but the surface is still dense. And it is well bonded with the substrate. Electrochemical hydrogen permeation is used to measure the hydrogen permeation resistance property of a 600°C-α-Al 2 O 3 /SiO 2 coating. The hydrogen resistance capability indicate that the 600°C-α-Al 2 O 3 /SiO 2 composite is 4.6 times greater than the substrate, the current density difference ratio is 1:2.5. The 600°C-α-Al 2 O 3 /SiO 2 composite coating increases the hydrogen barrier properties of the substrate. Declarations Authorship contribution statement Dong-Guang Liu, Lai-Ma Luo, Chun-Fu Hong: Writing-original draft, Methodology, Investigation. Jin-Xin Zou,Ting-Ting Yang: Formal analysis. Si-Wei Zhou: Formal analysis. Data Availability Data will be made available on request. Declaration of Competing Interest The authors declare that they have no known competing fi-nancial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was supported by the National Natural Science Foundation of China (U22A20110),Anhui Natural Science Foundation (2008085ME128), and Major Science and technology projects of Anhui Province (202103a05020003), Fujian Provincial Key Laboratory of Advanced Materials Processing and Application (E4700014) References W.J. Wang, Q.H. Yu, X.P. Liu, Z. 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Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lai-Ma","middleName":"","lastName":"Luo","suffix":""},{"id":200592174,"identity":"bd34c3a6-424a-4351-b8e8-8c6ff69427f1","order_by":5,"name":"Chun-Fu Hong","email":"","orcid":"","institution":"Fujian University of Technology) FuZhou","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Chun-Fu","middleName":"","lastName":"Hong","suffix":""}],"badges":[],"createdAt":"2023-05-15 08:44:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2936335/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2936335/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":37151896,"identity":"436b8f96-d63b-4a3c-9af3-18ab3dc49725","added_by":"auto","created_at":"2023-05-17 18:33:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":644807,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe surface SEM images and points scan of the α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2 \u003c/em\u003e\u003c/sub\u003e\u003cem\u003ecomposite coating at different heat treatment temperatures: (a)(b)(c) 600℃, (d)(e)(f) 700℃ and (g)(h)(i) 800℃\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/bc8c952381c93725f5db7006.png"},{"id":37152218,"identity":"c92f52c3-de9d-4460-a385-3f64d1a95f2e","added_by":"auto","created_at":"2023-05-17 18:41:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":181486,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe XRD patterns of the α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2 \u003c/em\u003e\u003c/sub\u003e\u003cem\u003ecoating at different heat treatment temperatures\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/c49d4d7d730f0604e1bf00f5.png"},{"id":37151898,"identity":"1f363f8f-3b4e-45a5-8dbf-a0858afd2e5e","added_by":"auto","created_at":"2023-05-17 18:33:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":668511,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe TEM images of the α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2 \u003c/em\u003e\u003c/sub\u003e\u003cem\u003ecoating at the heat treatment temperature of 600℃: (a) the morphology of the coating, (b) High magnification TEM image and (c) SAED \u0026nbsp;pattern\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/c46becd95ad9d28d5d7b0bca.png"},{"id":37152217,"identity":"b8b03d5c-1257-4842-9ae6-3fbcf7388c59","added_by":"auto","created_at":"2023-05-17 18:41:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":500520,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe curves of friction force and friction coefficient and the scratch topography image at different heat treatment in scratch tests: (a), (b) and (c) are the curves of friction force and friction coefficient and (d) is the scratch topography image\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/5ef54c7dc5dd0106af9431e3.png"},{"id":37151899,"identity":"c228e15c-cf8e-4920-a21e-30c46b057b92","added_by":"auto","created_at":"2023-05-17 18:33:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":418382,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe macroscopic morphology of the 600 °C-α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2 \u003c/em\u003e\u003c/sub\u003e\u003cem\u003ecomposite coating before and after thermal shocks: (a) original, (b) 10 times, (c) 30 times and (d) 50 times\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/ce070cc7ca1389ccfc3aab3b.png"},{"id":37151901,"identity":"b8436106-f312-4565-be1f-454ab6830142","added_by":"auto","created_at":"2023-05-17 18:33:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":516461,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe SEM image after 50 times thermal shocks: (a) surface image, (b) point scan in the region of (a), (c) cross section image and (d) line scan in the region of (c)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/6b548b0ec1d416cb3eab3fc3.png"},{"id":37151895,"identity":"2a591046-5829-4198-a5ff-9c20e0ec9d26","added_by":"auto","created_at":"2023-05-17 18:33:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":218525,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eHydrogen penetration curve at room temperature:(a) 316L and 600 °C-α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e, (b) 316L stainless steel matrix and (c) 600 °C-α-Al\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2 \u003c/em\u003e\u003c/sub\u003e\u003cem\u003ecomposite coating\u003c/em\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/56cc8d96596d8cf21bcbe687.png"},{"id":40208824,"identity":"21f6e920-12ed-4f8c-800e-1972c1b97eb4","added_by":"auto","created_at":"2023-07-18 16:29:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3388792,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2936335/v1/faf5d074-e589-43cc-be51-d1643aad2366.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eOne-step preparation of α-Al\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e/SiO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e composite tritium permeation barrier via slurry spin coating method and performance investigation\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eIn the Test Blanket Module (TBM) of the International Thermonuclear Experimental Reactor (ITER), because of their small atomic radii, deuterium and tritium as nuclear fuel have a high permeability to structural materials [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. As a result, fuel efficiency, steel mechanical properties, and radioactive pollution of the environment all suffer [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The application of a tritium penetration barrier (TPB) to the surface of steel structure materials is an important way to prevent hydrogen and its isotopes from penetrating [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCeramic oxide TPBs possessing excellent corrosion and excellent tritium resistance, have received great attention in recent years [\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The ceramic oxide TPBs mainly include Cr\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Er\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e, and SiO\u003csub\u003e2\u003c/sub\u003e and their composite coatings [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan additionalcitationids=\"CR11 CR12 CR13 CR14 CR15 CR16\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Many countries have chosen the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e coating as one of the most promising candidates because of its high hydrogen isotope permeation reduction factor (PRF), strong compatibility, high temperature tolerance, and self-repair potential [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. While Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e can have a variety of phase structures (α, δ, γ, and θ), the α state is the most stable. It can effectively prevent tritium permeation and ensure the tritium barrier's excellent capacity [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. However, the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e formation temperature is up to 1000\u0026deg;C, which will bring down the mechanical properties of the structural materials. For example, Wang et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] used sol-gel method to prepare Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e TPBs on Fe-Cr-Al alloy foils, the formation temperature of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is 1100\u0026deg;C. Meanwhile, Composite coatings may take advantage of the distinct properties of each of their constituent materials to achieve outstanding overall efficiency [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Therefore, the research emphasis mainly on preparing Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e composite coating with high quality at low temperature in recent years. In addition, none of the traditional methods can produce α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e by one-step, and they are usually doping with other forms of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eThe adhesion strength between the coating and substrate is a significant index to evaluate the quality of the coating. Scratch test is widely used to detect the adhesion strengting of hard thin coatings. Rahmati et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] and Kallel et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] use scratch tests to measure the adhesion strength and observe the scratch morphology. Thermal shock test is also a common method to test the adhesion strength and stability of the coating under the condition between thermal and cold. Wen et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] and Qiu et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] observe the microstructures between the coating and the substrate through thermal cycles experiments.\u003c/p\u003e \u003cp\u003eIn this work, the slurry spin coating method is used to prepare the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating in a single stage. The slurry spin coating method is not only easy to operate but also can avoid the mechanical properties of the matrix be influenced by the high formation temperature of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. The effect of heat treatment temperature on the microstructure and adhesion strength of the composite coating are studied. When the coating prepared temperature is 600\u0026deg;C, The coatings' thermal shock resistance and hydrogen permeation resistance are also investigated.\u003c/p\u003e"},{"header":"2 Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation of the samples\u003c/h2\u003e \u003cp\u003eThe matrix material is made of 316L stainless steel. The dimension of the matrix samples is 90mm \u0026times; 60mm \u0026times; 2mm. After sanding, the samples are washed in acetone and ethanol for 15 minutes before being dried in a drying oven.\u003c/p\u003e \u003cp\u003eThe modified SiO\u003csub\u003e2\u003c/sub\u003e sol (purity 30.0%, pH ranges from6.5 to 8) and 30 nm α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e powder are combined in a 3:5 mass ratio. The thickness and cracks increased proportionally to the sol viscosity [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], the slurry prepared by this ratio has good fluidity and the slurry is distributed uniformly. The magnetic stirrer was then used to stir the mixture for 2 h at 25\u0026deg;C using a constant temperature magnetic stirrer at a speed of 2000 r/min. The prepared slurry was spun coated onto the substrate at a speed of 3500 r/min. The coated samples are heat-treated in the air atmosphere for 1h at 600\u0026deg;C, 700\u0026deg;C and 800\u0026deg;C to prepared the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Analysis of the coating's properties\u003c/h2\u003e \u003cp\u003eTo detect the surface and cross-section microstructure of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating at different preparation temperatures, a field-emission scanning electron microscope (SEM) is used. At different heat treatment temperatures, the chemical composition of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e coating is identified using an energy dispersive spectroscope (EDS). The crystal structure and phase detail of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating was analyzed using an X-ray diffractometer (XRD). The morphology of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e coating is examined using a field-emission transmission electron microscope (TEM).\u003c/p\u003e \u003cp\u003eThe adhesion strength of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e coatings at different heat treatment temperatures is carried out using the MFT-4000 multifunctional material surface performance testing machine. The change in loading force is used to determine the friction coefficient and friction force of the composite coating's surface. The friction coefficient and friction force change dramatically as the coating fails, and the loading force becomes the critical load force. The corresponding applied loading force in this case is known as the critical failure loading force, and it reflects the coating's adhesion power [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The length of the scratch tests is 5mm, the loading force is increasing at a rate of 100 N/min, and the applied loading force range is 0-100 N.\u003c/p\u003e \u003cp\u003eThermal shock test is used to characterize the resistance stability between thermal and cold of the composite coating. The stability of the thermal shock resistance is evaluated at 500\u0026deg;C. The samples are first sliced into 10 mm\u0026times;10 mm. After that, the samples are held at 500\u0026deg;C for 15 min. Finally, the sample is removed and immediately immersed in 20\u0026deg;C water for quenching.\u003c/p\u003e \u003cp\u003eA self-made electrochemical hydrogen permeation system is used to evaluate the coating's efficiency, which was described in detail from previous studies [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The hydrogen resistance ability between the prepared coating and the matrix is compared by the steady-state permeation current density.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Microstructure and phase\u003c/h2\u003e \u003cp\u003eThe silica colloidal particles have negative charge [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], which can absorb the alumina particles [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The silicon sol can form a threedimensional network structure after the silica sol water evaporates, resulting in bonding firmly between the colloidal particles and the substrate. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the surface SEM images and points scan of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating at different heat treatment temperatures. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a,b), the surface of the composite coating is continuous and compact at 600\u0026deg;C. As the heat treatment temperature reaches 700\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d,e)), there are many holes on the surface of the composite coating. At 800\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(g,h)), there are not only having holes but also appearing cracks on the surface of the coating.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe XRD patterns of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating at different heat treatment temperatures is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The phases of the three heat treatment temperatures are the same. It includes the diffraction peaks of Fe, α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e. From the Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a), it can be seen that the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is distributed in the silica sol uniformly. Combined with the Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and the Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b), the alkaline silica sol decomposes into amorphous SiO\u003csub\u003e2\u003c/sub\u003e after 600℃ heat treatment. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c) shows the SAED pattern image of the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e coating, it can be seen that the added α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanopowder still exist in α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e form. The central part of Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c) shows a distinct halo, which indicates the presence of amorphous SiO\u003csub\u003e2\u003c/sub\u003e phase. The silica sol has cohesiveness and it exists in the form of sol, so the bonding force between the coating and the matrix is improved and the alumina particles can be distributed uniformly. Because X-rays are penetrating, the Fe phase appears in the diffraction pattern.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Scratch tests\u003c/h2\u003e \u003cp\u003eThe adhesive force is tested by scratch tests at different heat treatment temperatures. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the curves of friction force and friction coefficient and the scratch topography image of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating at different heat treatment temperatures in scratch tests. The Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a)(b)(c) show that the friction coefficient increases rapidly at the beginning of the scratch tests, and then decreases rapidly and reaches a stable value. Then, with the increase of load force, the undulating shape of the curve of friction coefficient and friction force change with the microstructure of the sample surface. In addition, when the critical load force of the coating is reached, the friction coefficient and friction force change significantly.\u003c/p\u003e \u003cp\u003eFrom the Table.1, the adhesion strength of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating is 88.7 N at 600 ℃, and the adhesion strength of α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating is 62.6 N at 700 ℃. Combined with the Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d), when the heat treatment temperature is 600 ℃, a small amount of coating is peeled off at the end of the scratch test. The composite coating begins to peel off in the middle of the scratch test at 700 ℃. However, the curve of the friction force and friction coefficient increase without significant changes, and the critical load force cannot be obtained through this curve at 800 ℃. The friction behavior is strongly influenced by the morphology [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. From the Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d), we can see that when the heat treatment temperature is 800 ℃, the composite coating is already peeled off at the beginning of the scratch test.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eTable.1 The adhesion strength between α-Al\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003eO\u003c/em\u003e \u003csub\u003e \u003cem\u003e3\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e/SiO\u003c/em\u003e \u003csub\u003e \u003cem\u003e2\u003c/em\u003e \u003c/sub\u003e \u003cem\u003ecomposite coating and 316L stainless steel matrix at different heat treatment temperatures\u003c/em\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTeat treatment temperatures (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e600 ℃\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e700 ℃\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e800 ℃\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdhesion strength (N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e88.7 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e62.6 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Thermal shock stability\u003c/h2\u003e \u003cp\u003eThermal shock test is used to characterize the resistance stability between thermal and cold of the composite coating. The samples prepared at the heat treatment temperature of 600\u0026deg;C (600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating), and cut into 10mm \u0026times; 10mm thermal shock samples, and then these samples are held for 15 min at the temperature of 500\u0026deg;C. The samples are then removed and immediately immersed in water at 20\u0026deg;C for quenching. Finally, thermal shock resistance of the composite coating is determined according to its macroscopic and microscopic morphology.\u003c/p\u003e \u003cp\u003eThe macroscopic morphologies of original sample and the thermal shock samples after 10, 30, and 50 times thermal shocks at the temperatures of 500\u0026deg;C are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. It can be seen that there is no discernible difference in the coating structure after 50 thermal shocks at 500\u0026deg;C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a) shows the SEM morphology of the surface of 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating after 50 times thermal shocks at the temperature of 500\u0026deg;C, on the surface of the composite coating, a few holes and cracks can be observed, but the surface is still dense. Combined with the EDS image of Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(b), it can be seen that compared with the original composite coating (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(c)), the content of Si element decreases after 50 times thermal shocks, which results in defects such as holes and cracks on the surface of the composite coating. From Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(c), there are no visible cracks in the composite coating, and the thickness of the composite coating is approximatelyt 12.5 \u0026micro;m. From the illustration of Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(c), the composite coating is bonded well with the substrate without cracking and spalling after 50 times thermal shocks. Combined with the line scan Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(d) the line scan of the cross-section of 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating after 50 times thermal shocks, the Si content of the coating near the substrate is higher than far away from the substrate.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Hydrogen permeation resistance property\u003c/h2\u003e \u003cp\u003eThe hydrogen permeation resistance property of the composite coating is tested by electrochemical hydrogen permeation. Hydrogen permeation test has high requirements on the sample, especially for air tightness. When the heat treatment temperature are 700\u0026deg;C and 800\u0026deg;C, there are holes and cracks on the coating surface. Therefore, the hydrogen permeation tests were carried out only on samples at the heat treatment temperature of 600\u0026deg;C.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b) shows the hydrogen penetration curve at room temperature of the 316L stainless steel matrix. It can be shown that the matrix has a steady-state permeation current density of 1.45\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e A/cm\u003csup\u003e2\u003c/sup\u003e, with current density difference of 3\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e A/cm\u003csup\u003e2\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e(c) shows the hydrogen penetration curve at room temperature of the 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating. The composite coating's steady-state permeation current density is 3.12\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e A/cm\u003csup\u003e2\u003c/sup\u003e, with a current density difference of 1.22\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e A/cm\u003csup\u003e2\u003c/sup\u003e. The hydrogen resistance capability indicate that the 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite is 4.6 times greater than the substrate, and the current density difference ratio is 1:2.5.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eThe α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating is prepared for one-step on the 316L stainless steel matrix by the method of slurry spin coating at the heat treatment temperature of 600\u0026deg;C, 700\u0026deg;C, and 800\u0026deg;C, respectively. With the increase of heat treatment temperature, resulting in defects such as holes and cracks.\u003c/p\u003e \u003cp\u003eWhen the heat treatment temperature is 600 ℃, there is having a high adhesion strength between the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating and the substrate, and the adhesion strength of coating is 88.7 N. At 700 ℃, the adhesion strength between the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating and the substrate decreases, the adhesion strength is 62.6 N. At 800 ℃, there is having a poor adhesion strength between the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating and the substrate, the composite coating already peeled off at the beginning of the scratch test.\u003c/p\u003e \u003cp\u003eThe thermal shock stability of the 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating is explored at the temperature of 500\u0026deg;C. After 50 times thermal shocks, the composite coating appears a few holes and cracks due to the reduction of SiO\u003csub\u003e2\u003c/sub\u003e sol on the coating's surface, but the surface is still dense. And it is well bonded with the substrate.\u003c/p\u003e \u003cp\u003eElectrochemical hydrogen permeation is used to measure the hydrogen permeation resistance property of a 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e coating. The hydrogen resistance capability indicate that the 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite is 4.6 times greater than the substrate, the current density difference ratio is 1:2.5. The 600\u0026deg;C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating increases the hydrogen barrier properties of the substrate.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDong-Guang Liu, Lai-Ma Luo, Chun-Fu Hong: Writing-original draft, Methodology, Investigation. Jin-Xin Zou,Ting-Ting Yang: Formal analysis. Si-Wei Zhou: Formal analysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing fi-nancial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (U22A20110),Anhui Natural Science Foundation (2008085ME128), and Major Science and technology projects of Anhui Province (202103a05020003), Fujian Provincial Key Laboratory of Advanced Materials Processing and Application (E4700014)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eW.J. 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Technol. 270 324-333 (2015).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"slurry spin coating method, α-Al2O3/SiO2 composite coating, one-step, thermal shock, hydrogen permeation","lastPublishedDoi":"10.21203/rs.3.rs-2936335/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2936335/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn the fusion reactor,\u003cstrong\u003e \u003c/strong\u003ea-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003eand its composite coatings have became the preferred material for tritium permeation barriers. The slurry spin coating method in this study is used to prepare α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating for one-step at the temperature of 600 °C, 700 °C and 800 °C. The effect of heat treatment temperature on the composite coating's microstructure and adhesion strength is investigated. When the coating prepared temperature is 600 °C, the thermal shock resistance and hydrogen permeation resistance are also studied. The findings demonstrate that as the heat treatment temperature rises, defects such as holes and cracks appear. The surface of the composite coating is continuous and compact when the preparation temperature is 600 °C, and the adhesion strength is 88.7 N. Thermal shock tests demonstrate that the 600 °C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite coating is still dense and is bonded well to the substrate after 50 times thermal shocks at 500 °C. The hydrogen resistance capability indicate that the 600 °C-α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e/SiO\u003csub\u003e2\u003c/sub\u003e composite is 4.6 times greater than the substrate.\u003c/p\u003e","manuscriptTitle":"One-step preparation of α-Al2O3/SiO2 composite tritium permeation barrier via slurry spin coating method and performance investigation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-05-17 18:32:56","doi":"10.21203/rs.3.rs-2936335/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5e9847a3-ce54-4c14-b0eb-cc8ceda0ac4d","owner":[],"postedDate":"May 17th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-07-18T16:29:16+00:00","versionOfRecord":[],"versionCreatedAt":"2023-05-17 18:32:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2936335","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2936335","identity":"rs-2936335","version":["v1"]},"buildId":"rHA-KDH7Qsr4HCuvH75dn","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}