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Loss of oxygen atoms on well-oxidized cobalt by heterogeneous surface recombination
Domen Paul, Miran Mozetič, Rok Zaplotnik, Jernej Ekar, Alenka Vesel, Gregor Primc, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: Calorimetry is a commonly used method in plasma characterization, but the accuracy of the method is tied to the accuracy of the recombination coefficient, which in turn depends on a number of surface effects. Surface effects also govern the kinetics in advanced methods such as atomic layer oxidation of inorganic materials and functionalization of organic materials. The flux of the reactive oxygen atoms for the controlled oxidation of such materials depends on the recombination coefficient of materials placed into the reaction chamber, which in turn depends on the surface morphology, temperature, and pressure in the processing chamber. The recombination coefficient of a well-oxidized cobalt surface was studied systematically in a range of temperatures from 300 to 800 K and pressures from 40 to 200 Pa. The coefficient increased monotonously with decreasing pressure and increasing temperature. The lowest value was about 0.05, and the highest was about 0.30. These values were measured for cobalt foils previously oxidized with oxygen plasma at the temperature of 1300 K. The oxidation caused a rich morphology with an average roughness as deduced from atomic force images of 0.9 µm. The results were compared with literature data, and the discrepancy between results reported by different authors was explained by taking into account the peculiarities of their experimental conditions.
Ključne besede: heterogeneous surface recombination, recombination coefficient, cobalt, cobalt oxide, temperature dependence, pressure dependence, plasma, oxygen
Objavljeno v DKUM: 26.03.2024; Ogledov: 156; Prenosov: 17
.pdf Celotno besedilo (3,59 MB)
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Recombination of oxygen atoms on the surface of oxidized polycrystalline nickel : temperature and pressure dependences
Domen Paul, Miran Mozetič, Rok Zaplotnik, Jernej Ekar, Alenka Vesel, Gregor Primc, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: The recombination of neutral oxygen atoms in the ground state on the oxidized nickel samples was studied experimentally in the range of pressures where the maximum density occurs in weakly ionized low-pressure oxygen plasma, i.e. between 40 and 200 Pa. The recombination coefficient was determined in the flowing afterglow. The source of oxygen atoms was plasma sustained in a quartz tube of inner diameter 4.7 mm by a microwave discharge in the surfatron mode. The recombination coefficient was determined in the afterglow chamber, which was a Pyrex tube with an inner diameter of 36 mm. The density of oxygen atoms in the afterglow chamber was varied by adjusting the discharge power, the gas flow, the pressure, and the position of a recombinator. Such flexibility of the experimental system enabled adjustment of the temperature of the oxidized nickel samples independently from the O-atom density in its vicinity or other parameters. The density of oxygen atoms in the afterglow chamber at various system parameters was determined by the Šorli method, which is reliable, and has an accuracy of about 20%. The recombination coefficient was determined by calorimetry. The coefficient was inversely proportional to the square root of the pressure and exponentially to the sample temperature. Systematic measurements performed at various pressures and temperatures enabled empirical formula, which were explained qualitatively by recombination kinetics.
Ključne besede: heterogenous surface recombination, recombination coefficient, nickel, nickel oxide, temperature
Objavljeno v DKUM: 25.03.2024; Ogledov: 153; Prenosov: 14
.pdf Celotno besedilo (2,44 MB)
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A review of recombination coefficients of neutral oxygen atoms for various materials
Domen Paul, Miran Mozetič, Rok Zaplotnik, Gregor Primc, Denis Đonlagić, Alenka Vesel, 2023, pregledni znanstveni članek

Opis: Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations. Some numerical models for recombination coefficient determination are also examined. Correlations are drawn between the experimental parameters and the reported coefficients. Different materials are examined and categorized according to reported recombination coefficients into catalytic, semi-catalytic, and inert materials. Measurements from the literature of the recombination coefficients for some materials are compiled and compared, along with the possible system pressure and material surface temperature dependence of the materials’ recombination coefficient. A large scattering of results reported by different authors is discussed, and possible explanations are provided.
Ključne besede: heterogeneous surface recombination, recombination coefficient, surface catalicity, catalytic efficiency, atom loss coefficient, oxygen, neutral atoms, plasma
Objavljeno v DKUM: 21.03.2024; Ogledov: 216; Prenosov: 17
.pdf Celotno besedilo (10,51 MB)
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High-Order Fiber Bragg Grating Corrosion Sensor Based on the Detection of a Local Surface Expansion
Vedran Budinski, Matej Njegovec, Simon Pevec, Boris Macuh, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: This paper presents a fiber optic sensor for the detection of corrosion processes that occur on metal surfaces. In the proposed sensor design, a sensing fiber with an inscribed high-order Bragg grating is attached to the observed metal surface. A broadening of high-order Bragg grating spectral characteristics is observed and used to detect small and highly localized longitudinal strain variations that occur along the fiber as a result of corrosive rust flakes' formations beneath the sensing fiber. The proposed approach provides a straightforward fabrication method, the possibility for unobtrusive mounting, including mounting of the sensor beneath the corrosion-protective layers, and consistent corrosion detection yields.
Ključne besede: optical fiber sensors, corrosion, impact of corrosion, optic sensors
Objavljeno v DKUM: 09.02.2024; Ogledov: 229; Prenosov: 17
.pdf Celotno besedilo (1,58 MB)
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An All-Fiber Fabry–Pérot Sensor for Emulsion Concentration Measurements
Simon Pevec, Janez Kunaver, Vedran Budinski, Matej Njegovec, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: This paper describes a Fabry-Perot sensor-based measuring system for measuring fluid composition in demanding industrial applications. The design of the sensor is based on a two-parametric sensor, which enables the simultaneous measurement of temperature and refractive index (RI). The system was tested under real industrial conditions, and enables temperature-compensated online measurement of emulsion concentration with a high resolution of 0.03 Brix. The measuring system was equipped with filtering of the emulsion and automatic cleaning of the sensor, which proved to be essential for successful implementation of a fiber optic RI sensor in machining emulsion monitoring applications.
Ključne besede: optical fiber sensors, Fabry–Pérot interferometer, refractive index, temperature, emulsion concentration
Objavljeno v DKUM: 06.02.2024; Ogledov: 244; Prenosov: 16
.pdf Celotno besedilo (4,44 MB)
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Razvoj modela za spremljanje degradacije površine materiala med dinamičnim obremenjevanjem : doctoral disertation
Marijana Milković, 2023, doktorska disertacija

Opis: The study focuses on the behavior of the AA7075-T6 material, widely used in the aerospace industry, under dynamic loadings. The material undergoes processing, including cold rolling and stretching, resulting in residual stress compressive stresses on its surface. The research centers on monitoring changes in the surface condition during dynamic loaidngs using Fiber Bragg Grating (FBG) sensors and numerical simulations. The dissertation includes experimental testing of AA 7075-T6 material samples, numerical simulations of optical fiber responses to tensile loads, and an investigation of surface condition changes using techniques such as focused ion beam engraving and scanning electron microscope observation. The study has shown that the surface condition of the material changes even under low dynamic loads, including variations in surface roughness, residual stresses, and FBG response. Despite low load levels, changes in FBG sensor spectra are observable. The dissertation concludes that the surface condition of the material changes during dynamic loadings, detectable through FBG sensors. It underscores the effectiveness of FBG sensors in monitoring stress levels throughout the material’s service life, particularly on the side lobes of the spectral response. In summary, the research on the dynamic behavior of the AA7075-T6 alloy offers valuable insight into surface condition changes that can impact the integrity and durability of materials in the aerospace industry.
Ključne besede: fatigue, high cycle load, Fiber Bragg grating
Objavljeno v DKUM: 05.01.2024; Ogledov: 369; Prenosov: 37
.pdf Celotno besedilo (10,61 MB)

All Silica Micro-Fluidic Flow Injection Sensor System for Colorimetric Chemical Sensing
Vedran Budinski, Denis Đonlagić, 2021, izvirni znanstveni članek

Opis: This paper presents a miniature, all-silica, flow-injection sensor. The sensor consists of an optical fiber-coupled microcell for spectral absorption measurements and a microfluidic reagent injection system. The proposed sensor operates in back reflection mode and, with its compact dimensions, (no more than 200 µm in diameter) enables operation in small spaces and at very low flow rates of analyte and reagent, thus allowing for on-line or in-line colorimetric chemical sensing.
Ključne besede: optical fiber sensor, spectral absorption microcell, colorimetry
Objavljeno v DKUM: 31.07.2023; Ogledov: 395; Prenosov: 15
.pdf Celotno besedilo (4,40 MB)
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Miniature magneto-optic angular position sensor
Vedran Budinski, Simon Pevec, Stanislav Čampelj, Alenka Mertelj, Darja Lisjak, Denis Đonlagić, 2022, izvirni znanstveni članek

Opis: This Letter describes a miniature Fabry–Perot, contactless, magneto-optic sensor for angular position measurement. The sensor utilizes a magneto-optic fluid comprising barium hexaferrite nanoplatelets that become birefringent in the presence of an external magnetic field and a compact fiber-optic sensor system for tracking the liquid’s optical axis direction. An efficient temperature compensation system is provided which allows the use of otherwise highly temperature-sensitive magneto-optic liquids. An unambiguous measurement range of 90° and a resolution of better than 0.05° are demonstrated experimentally.
Ključne besede: Fiber optic sensor, magneto-optic sensor, angular position measurement
Objavljeno v DKUM: 12.05.2023; Ogledov: 521; Prenosov: 63
.pdf Celotno besedilo (3,76 MB)
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Mikrofluidna absorpcijska celica z veliko aktivno dolžino : magistrsko delo
Tomaž Gregorec, 2022, magistrsko delo

Opis: V sklopu magistrskega dela je bila zajeta izdelava sistema za izven-osno lasersko varjenje steklenih kapilar in izdelava absorpcijske celice z veliko aktivno dolžino. Varilnik kapilar omogoča izdelavo posebnih struktur, ki ponujajo nove možnosti pri izdelavi optičnih vlakenskih senzorjev. Absorpcijska celica omogoča meritev absorpcije svetlobe v majhnih volumnih tekočin brez uporabe kolorimetričnih reagentov. Delovanje absorpcijske celice je bilo preizkušeno na meritvi deleža izopropanola v vodi in meritvi koncentracije v vodi raztopljenih bakrenih ionov.
Ključne besede: optično vlakno, absorpcija, velika aktivna dolžina, mikrofluidna celica, varjenje steklenih kapilar
Objavljeno v DKUM: 25.10.2022; Ogledov: 590; Prenosov: 67
.pdf Celotno besedilo (3,75 MB)

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