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Quantitative aspects of ToF-SIMS analysis of metals and alloys in a UHV, O2 and H2 atmosphere
Jernej Ekar, Saša Kos, Janez Kovač, 2024, izvirni znanstveni članek

Povzetek: Although secondary ion mass spectrometry (SIMS) is a versatile method used in the fields of surface analysis, depth profiling and elemental and molecular mapping, it also lacks quantification capabilities. The main reason for this is the matrix effect, which influences the ionization yield of secondary ions with respect to the substrate from which the analyzed compounds originate. There are several approaches to reduce the matrix effect, and gas flooding is one of the easiest methods to apply. In this work, we have investigated the possibilities of the ToF-SIMS method for the quantification of selected metals and alloys containing these metals in different ratios by reducing the matrix effect in the presence of different atmospheres. The measurements were performed in the ultra-high vacuum (UHV) environment, H2 and O2 atmospheres. H2 flooding shows the most significant improvements compared to the UHV analysis, while O2 is also promising but has some limitations. Improvements are most evident for the transition metals Ti, Cr, Fe, Co and Ni employed in our study, while the p-block elements such as Al and Si do not change so extensively. The deviations from the true atomic ratios of selected transition metals in different alloys reach a maximum of only 46 % when analyzed in the H2 atmosphere. In contrast, these values are 66 and 228 % for the O2 atmosphere and UHV environment, respectively. Our results suggest that gas adsorption and consequent formation of a new matrix on the surface, especially in the case of hydrogen, reduces the differences between the different chemical environments and electronic structures of the surface. In this way, the quantitative aspects of the SIMS method can be improved.
Ključne besede: ToF-SIMS quantification, H2 and O2 gas flooding, matrix effect reduction, cluster secondary ions
Objavljeno v DiRROS: 15.05.2024; Ogledov: 102; Prenosov: 74
.pdf Celotno besedilo (1,15 MB)

Influence of laser colour marking on the corrosion properties of low alloyed Ti
Tadeja Kosec, Andraž Legat, Janez Kovač, Damjan Klobčar, 2019, izvirni znanstveni članek

Povzetek: In the field of surface treatment, laser colour marking can be used to produce coloured marks on the surfaces of metals. Laser colour markings can be applied to various materials, but on titanium alloys a wide spectra of vivid colours can be achieved. This study presents an analysis of the corrosion properties of laser treated surfaces that were exposed to aggressive environments. Different samples were prepared with laser light of various power intensities and processing speeds. The samples were prepared on low alloyed Ti. Electrochemical, spectroscopic and microstructural analyses were conducted in order to study the properties of the laser treated surfaces. Corrosion testing showed different effects of laser power and production speed on the properties of the laser treated surfaces. It was shown that a high intensity and slow processing rate affect the surfaces by forming oxides that are relatively stable in a corrosive environment of 0.1 M NaCl. Spectroscopic investigations including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses showed the differences in chemical structure of the surface layer formed after laser treatment. Similarly, microstructural investigations showed different effects on the surface and sub-surface layer of the laser treated samples.
Ključne besede: Ti alloy, laser treatment, XPS, corrosion
Objavljeno v DiRROS: 25.10.2023; Ogledov: 401; Prenosov: 165
.pdf Celotno besedilo (3,16 MB)
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AFM study of roughness development during ToF-SIMS depth profiling of multilayers with a ▫$Cs^+$▫ ion beam in a ▫$H_2$▫ atmosphere
Jernej Ekar, Janez Kovač, 2022, izvirni znanstveni članek

Objavljeno v DiRROS: 18.10.2023; Ogledov: 440; Prenosov: 169
.pdf Celotno besedilo (5,77 MB)
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Depassivation and repassivation of stainless steels by stepwise pH change
Emir Mujanović, Bojan Zajec, Andraž Legat, Tadeja Kosec, Janez Kovač, Gregor Mori, Stefan Hönig, Gerald Zehethofer, 2020, izvirni znanstveni članek

Povzetek: Immersion tests with different stainless steels have been performed, while the pH was stepwise decreased and then increased again. During 8.5-day exposure, the depassivation and repassivation pH values as a function of pitting resistance equivalent number were determined. There is always a gap between both pH values (depassivation and repassivation), indicating that for every steel, there are conditions where an existing passive layer can be maintained but cannot be rebuilt after depassivation. In such environments, the passive layer is thicker, consisting mainly of molybdenum and iron rich oxides, while chromium is dissolved. Usually, depending on conditions, the passive layer is more chromium-rich, especially the inner layer. This is relevant, for example, for acidizing jobs in oil and gas industry, proving that repassivation after acidizing will happen promptly, when the pH is increased again.
Ključne besede: stress corrosion cracking, surface finish impact, tapered tensile specimen, autoclave, accelerated testing, light water nuclear reactor, critical threshold stress
Objavljeno v DiRROS: 30.08.2023; Ogledov: 338; Prenosov: 173
.pdf Celotno besedilo (4,01 MB)
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Effect of laser texturing pattern on Ti6Al4Vtribocorrosion in a physiological solution
Marjetka Conradi, Tadeja Kosec, Bojan Podgornik, Aleksandra Kocijan, Janez Kovač, Damjan Klobčar, 2022, izvirni znanstveni članek

Povzetek: Laser texturing is a process that alters a material’s surface properties by modifying its morphology, which can improve properties like adherence, wettability, thermal and electrical conductivity and friction. Here, the effect of laser texturing was studied on an alpha-beta titanium alloy (Ti6Al4V) biomedical material. Two types of patterned surfaces, cross-hatch with varying scan-line separations, Dx = 100, 180 and 280 μm and dimples of 200 μm size, were prepared on the surface of alpha-beta titanium alloy by laser technology. Prepared samples were characterised for their surface properties, such as corrosion, wear-induced corrosion, friction and wettability. Electrochemical and tribocorrosion properties in a physiological solution were studied on the samples with different texture densities of cross-hatch pattern and dimples and compared to the as-received alpha-beta titanium alloy surface. Corrosion rate decreased for laser-textured samples, especially for cross-hatch texture (down to 1 μm/year for Dx = 180 μm) when compared to the as-received alpha-beta titanium alloy surface due to the changed laser-induced surface film and wetting properties. Friction coefficient slightly decreased for all laser-textured surfaces, most noticeably for cross-hatch patterns, from 0.38 (as-received) down to 0.34 (Dx = 180 and 280 μm). The main contribution to total wear in physiological solution increased due to the mechanical wear, which is governed by the removal of the surface oxide layer induced by laser texturing.
Ključne besede: TiAIV, laser texturing, tribocorrosion, open access
Objavljeno v DiRROS: 17.05.2023; Ogledov: 313; Prenosov: 125
.pdf Celotno besedilo (2,19 MB)
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