| 1. |
- Cemin, Felipe, et al.
(författare)
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Low-energy ion irradiation in HiPIMS to enable anataseTiO(2) selective growth
- 2018
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Ingår i: Journal of Physics D. - : IOP PUBLISHING LTD. - 0022-3727 .- 1361-6463. ; 51:23
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Tidskriftsartikel (refereegranskat)abstract
- High power impulse magnetron sputtering (HiPIMS) has already demonstrated great potential for synthesizing the high-energy crystalline phase of titanium dioxide (rutile Ti-O2) due to large quantities of highly energetic ions present in the discharge. In this work, it is shown that the metastable anatase phase can also be obtained by HiPIMS. The required deposition conditions have been identified by systematically studying the phase formation, microstructure and chemical composition as a function of mode of target operation as well as of substrate temperature, working pressure, and peak current density. It is found that films deposited in the metal and transition modes are predominantly amorphous and contain substoichiometric TiOx compounds, while in compound mode they are well-crystallized and present only O2- ions bound to Ti4+, i.e. pure TiO2. Anatase TiO2 films are obtained for working pressures between 1 and 2 Pa, a peak current density of similar to 1 A cm(-2) and deposition temperatures lower than 300 degrees C. Rutile is favored at lower pressures (amp;lt; 1 Pa) and higher peak current densities (amp;gt;2 A cm(-2)), while amorphous films are obtained at higher pressures (greater than or similar to 5 Pa). Microstructural characterization of selected films is also presented.
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| 2. |
- Singh, Digvijay, et al.
(författare)
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High-temperature oxidation behaviour of nanostructure surface layered austenitic stainless steel
- 2022
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 581
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the high-temperature oxidation behaviour of nanostructure surface layered AISI 304L stainless steel. A severely deformed layer of ∼300 μm thickness, consisting of nanoscale grains (∼40 nm size) in the topmost region, is successfully developed using the surface mechanical attrition treatment (SMAT) process. The SMATed layer is substantially stable up to 700 °C; however, the surface hardness is reduced by ∼37% at 800 °C for 25 h oxidation duration. Glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy analysis revealed the considerable difference in the chemistry and elemental distribution across the oxide scale of SMATed and non-SMATed specimens. Adherent, denser, and thinner scale, dominated by nanocrystals of Cr- and Mn-rich oxides, is formed on the SMATed steel. However, the Fe-oxide dominated scale containing micro-crystals is found on the non-SMATed specimens, which shows noticeable exfoliation. A high density of grain boundaries and lattice defects in the SMATed layer display admirable reactive diffusion properties of Cr and Mn during oxidation of steel, instigating the formation of a protective oxide scale. The SMATed specimens exhibit multiple zones in the oxide scale: (i) Cr/Mn depleted outer layer, (ii) Cr-/Mn-rich inner layer, and (iii) gradually decreasing Cr/Mn region.
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