Nanostruktuursete oksiidkatete kõvaduse määramine

https://www.ester.ee/record=b5163525*es

Nanostruktuurne kaitsekate alumiiniumsulamile AA6082

https://www.ester.ee/record=b5381731*es

Nanostructured Coating for Aluminum Alloys Used in Aerospace Applications

The authors would like to acknowledge the Estonian Ministry of Education and Research by granting the projects IUT2–24, TLTFY14054T, PSG448, PRG4, SLTFY16134T and by the EU through the European Regional Development Fund under project TK141 (2014-2020.4.01.15-00). The atomic oxygen testing was performed in the framework of the “Announcement of opportunity for atomic oxygen in the ESTEC Materials and Electrical Components Laboratory/ESA-TECQE-AO-013375),” through a collaboration with Picosun Oy. The authors also thank Dr. Elo Kibena-Põldsepp for the electrodeposition of Ag onto the anodized substrates.A thin industrial corrosion-protection nanostructured coating for the Al alloy AA2024-T3 is demonstrated. The coating is prepared in a two-step process utilizing hard anodizing as a pre-treatment, followed by sealing and coating by atomic layer deposition (ALD). In the first step, anodizing in sulfuric acid at a low temperature converts the alloy surface into a low-porosity anodic oxide. In the second step, the pores are sealed and coated by low-temperature ALD using different metal oxides. The resulting nanostructured ceramic coatings are thoroughly characterized by cross-sectioning using a focused ion beam, followed by scanning electron microscopy, transmission electron microscopy, X-ray microanalysis, and nanoindentation and are tested via linear sweep voltammetry, electrochemical impedance spectroscopy, salt spray, and energetic atomic oxygen flow. The best thin corrosion protection coating, made by anodizing at 20 V, 1 °C and sealing and coating with amorphous Al2O3/TiO2 nanolaminate, exhibits no signs of corrosion after a 1000 h ISO 9227 salt spray test and demonstrates a maximum surface hardness of 5.5 GPa. The same coating also suffers negligible damage in an atomic oxygen test, which is comparable to 1 year of exposure to space in low Earth orbit. © 2022 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.Estonian Ministry of Education and Research by granting the projects IUT2–24, TLTFY14054T, PSG448, PRG4, SLTFY16134T; ERDF TK141 (2014-2020.4.01.15-00); Institute of Solid State Physics, University of Latvia as the Center of Excellence acknowledges funding from the European Union’s Horizon 2020 Framework Programme H2020- WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Structure and behavior of ZrO2-graphene-ZrO2 stacks

Producción CientíficaZrO2-graphene-ZrO2 layered structures were built and their crystallinity was characterized before resistive switching measurements. Thin nanocrystalline ZrO2 dielectric films were grown by atomic layer deposition on chemical vapor deposited graphene. Graphene was transferred, prior to the growth of the ZrO2 overlayer, to the ZrO2 film pre-grown on titanium nitride. Nucleation and growth of the top ZrO2 layer was improved after growing an amorphous Al2O3 interface layer on graphene at lowered temperatures. Studies on resistive switching in such structures revealed that the exploitation of graphene interlayers could modify the operational voltage ranges and somewhat increase the ratio between high and low resistance states.Fondo Europeo de Desarrollo Regional (project TK134)Estonian Research Agency (grants PRG753 and PRG4)Ministerio de Economía, Industria y Competitividad (grant TEC2017-84321-C4-2-R

Influence to Hardness of Alternating Sequence of Atomic Layer Deposited Harder Alumina and Softer Tantala Nanolaminates

Atomic layer deposited amorphous 70 nm thick Al2O3-Ta2O5 double- and triple-layered films were investigated with the nanoindentation method. The sequence of the oxides from surface to substrate along with the layer thickness had an influence on the hardness causing rises and declines in hardness along the depth yet did not affect the elastic modulus. Hardness varied from 8 to 11 GPa for the laminates having higher dependence on the structure near the surface than at higher depths. Triple-layered Al2O3/Ta2O5/Al2O3 laminate possessed the most even rise of hardness along the depth and possessed the highest hardness out of the laminates (11 GPa at 40 nm). Elastic modulus had steady values along the depth of the films between 145 and 155 GPa

Atomic-Layer-Deposition-Made Very Thin Layer of Al₂O₃, Improves the Young’s Modulus of Graphene

Nanostructures with graphene make them highly promising for nanoelectronics, memristor devices, nanosensors and electrodes for energy storage. In some devices the mechanical properties of graphene are important. Therefore, nanoindentation has been used to measure the mechanical properties of polycrystalline graphene in a nanostructure containing metal oxide and graphene. In this study the graphene was transferred, prior to the deposition of the metal oxide overlayers, to the Si/SiO2 substrate were SiO2 thickness was 300 nm. The atomic layer deposition (ALD) process for making a very thin film of Al2O3 (thickness comparable with graphene) was applied to improve the elasticity of graphene. For the alumina film the Al(CH3)3 and H2O were used as the precursors. According to the micro-Raman analysis, after the Al2O3 deposition process, the G-and 2D-bands of graphene slightly broadened but the overall quality did not change (D-band was mostly absent). The chosen process did not decrease the graphene quality and the improvement in elastic modulus is significant. In case the load was 10 mN, the Young’s modulus of Si/SiO2/Graphene nanostructure was 96 GPa and after 5 ALD cycles of Al2O3 on graphene (Si/SiO2/Graphene/Al2O3) it increased up to 125 GPa. Our work highlights the correlation between nanoindentation and defects appearance in graphene

Influence of Annealing on Mechanical Behavior of Alumina-Tantala Nanolaminates

Mechanical properties of thin films are significant for the applicability of nanodevices. Amorphous Al2O3-Ta2O5 double and triple layers were atomic layer-deposited to the thickness of 70 nm with constituent single-layer thicknesses varying from 40 to 23 nm. The sequence of layers was alternated and rapid thermal annealing (700 and 800 °C) was implemented on all deposited nanolaminates. Annealing caused changes in the microstructure of laminates dependent on their layered structure. Various shapes of crystalline grains of orthorhombic Ta2O5 were formed. Annealing at 800 °C resulted in hardening up to 16 GPa (~11 GPa prior to annealing) in double-layered laminate with top Ta2O5 and bottom Al2O3 layers, while the hardness of all other laminates remained below 15 GPa. The elastic modulus of annealed laminates depended on the sequence of layers and reached up to 169 GPa. The layered structure of the laminate had a significant influence on the mechanical behavior after annealing treatments

Atomic-Layer-Deposition-Made Very Thin Layer of Al2O3, Improves the Young’s Modulus of Graphene

Nanostructures with graphene make them highly promising for nanoelectronics, memristor devices, nanosensors and electrodes for energy storage. In some devices the mechanical properties of graphene are important. Therefore, nanoindentation has been used to measure the mechanical properties of polycrystalline graphene in a nanostructure containing metal oxide and graphene. In this study the graphene was transferred, prior to the deposition of the metal oxide overlayers, to the Si/SiO2 substrate were SiO2 thickness was 300 nm. The atomic layer deposition (ALD) process for making a very thin film of Al2O3 (thickness comparable with graphene) was applied to improve the elasticity of graphene. For the alumina film the Al(CH3)3 and H2O were used as the precursors. According to the micro-Raman analysis, after the Al2O3 deposition process, the G-and 2D-bands of graphene slightly broadened but the overall quality did not change (D-band was mostly absent). The chosen process did not decrease the graphene quality and the improvement in elastic modulus is significant. In case the load was 10 mN, the Young’s modulus of Si/SiO2/Graphene nanostructure was 96 GPa and after 5 ALD cycles of Al2O3 on graphene (Si/SiO2/Graphene/Al2O3) it increased up to 125 GPa. Our work highlights the correlation between nanoindentation and defects appearance in graphene

Effects of Al and Co Promoters on CuO/SBA-15/Kaolinite Catalyst Properties and CO

CuO on mesoporous silica catalyst was prepared with post synthesis impregnation method, and the effects of Al and Co promoters on CuO/SBA-15/kaolinite catalyst properties and CO2 hydrogenation were studied. The mixing technology with kaolinite clay (containing Al2O3) was used to obtain the granules and to enhance the CO2 conversion to methanol as a product. The performance of all catalysts for catalytic hydrogenation of CO2 was evaluated on a fixed-bed tubular micro-activity reactor at 20 bar and 250°C with H2/CO2 molar ratio 3:1. XRD analysis, N2 adsorption-desorption analysis and SEM-EDX analysis indicated that the mesoporous structure of SBA-15 remains after loading with CuO and promoters, and after mixing with kaolinite clay. Results were compared with results obtained with commercial CuO/Al2O3 catalyst, which showed high MeOH selectivity (78%) during CO2 hydrogenation reaction

Mechanical and Magnetic Properties of Double Layered Nanostructures of Tin and Zirconium Oxides Grown by Atomic Layer Deposition

Double layered stacks of ZrO2 and SnO2 films, aiming at the synthesis of thin magnetic and elastic material layers, were grown by atomic layer deposition to thicknesses in the range of 20–25 nm at 300 °C from ZrCl4, SnI4, H2O, and O3 as precursors. The as-deposited nanostructures consisted of a metastable tetragonal polymorph of ZrO2, and a stable tetragonal phase of SnO2, with complementary minor reflections from the orthorhombic polymorph of SnO2. The hardness and elastic modulus of the stacks depended on the order of the constituent oxide films, reaching 15 and 171 GPa, respectively, in the case of top SnO2 layers. Nonlinear saturative magnetization could be induced in the stacks with coercive fields up to 130 Oe