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

Comentarios a la legislación tributaria colombiana

Tesis (Abogado) -- Universidad de Cartagena. Facultad de Derecho y Ciencias Políticas. Programa de Derecho, 1973Estudio de las relaciones jurídicas entre el sujeto activo y pasivo de la obligación tributaria, de acuerdo a la capacidad económica del contribuyente

Semiclassical approach to surface plasmons in spheroidal clusters

Artículo de publicación IS

Starting energy dependence of elastic scattering observables in a full-folding model

Artículo de publicación ISIFull-folding model calculations of proton elastic scattering at intermediate energy made using the free off-shell NNt matrix and including the variation of the energy in the NN center of mass as prescribed by the full-folding model are compared with similar calculations using t matrices evaluated at a fixed energy. The fixed energy is chosen on the basis of the incident beam energy ignoring the Fermi momentum of the struck target nucleon. Near 200 MeV, the energy prescription for the NNt matrix is found to be responsible for much of the difference between recently reported fullfolding calculations as well as for the differences between full-folding calculations and conventional tp approximations to them. The sensitivity of the scattering observables to the starting energy suggests that at lower intermediate energies, explicit medium corrections should be included in applications of the full-folding model

Real-time monitoring of the evolving morphology and molecular structure at an organic-inorganic semiconductor interface: SnPc on GaAs(001)

An organic-III-V hybrid semiconductor interface has been studied using real-time photoelectron spectroscopy and x-ray absorption spectroscopy to reveal the evolving morphology and molecular structure within the organic layer during thin film growth. This new approach to in situ characterization has been enabled by electron detection using a direct electron-counting array detector coupled to a hemispherical electron analyzer. The nonplanar tin phthalocyanine (SnPc) molecules initially form a uniform layer within which they have a distinct molecular orientation relative to the S-passivated gallium arsenide substrate surface [GaAs:S(001)]. The critical thickness of 0.9 nm that marks the transition between layered and clustered growth, determined from the photoemission measurements, corresponds to a single molecular layer with the molecules oriented at an angle of (39 ± 2)° to the substrate plane. This value is confirmed by angle-resolved near-edge x-ray absorption fine structure measurements in the same experimental environment. However, the angle is less for the thicker films as the molecule-molecule interaction dominates over the molecule-substrate interaction and the structure is close to that of the bulk triclinic SnPc crystal. © 2010 American Vacuum Society