Repozitorij Univerze v Novi Gorici

Iskanje po repozitoriju
A+ | A- | Pomoč | SLO | ENG

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju


1 - 10 / 33
Na začetekNa prejšnjo stran1234Na naslednjo stranNa konec
Growth of MoSe2 thin films and use in electrochemical hydrogen evolution : abstract
Takwa Chouki, Borjana Donkova, Burhan can Aktarla, Plamen Stefanov, Saim Emin, 2020, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: We present the chemical vapor deposition (CVD) approach to grow MoSe2 thin films using colloidal molybdenum nanoparticles (Mo NPs). The synthetic protocol of Mo NPs was achieved using a wet-chemical method. The obtained Mo NPs were spin-coated on graphite substrates and heat-treated in the presence of selenium vapors at several temperatures (≥750 °C). The electrocatalytic activities of heat-treated MoSe2 thin films were studied for hydrogen evolution reaction (HER) in 0.5 M sulfuric acid (H2SO4). The lowest recorded overpotential of 218 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with MoSe2−800°C catalyst. In addition, electrochemical impedance spectroscopy (EIS) was performed to access the charge-transfer resistance of the MoSe2 films. The colloidal approach combined with CVD is a promising route to produce carbon supported MoSe2 electrocatalyst for HER.
Ključne besede: MoSe2 thin films CVD HER
Objavljeno v RUNG: 06.02.2023; Ogledov: 487; Prenosov: 0
Gradivo ima več datotek! Več...

Hanna Budasheva, doktorska disertacija

Opis: Advanced materials are promising ones in application in fields where it is necessary to decrease energy consumption and ensure better performance at a lower cost. They are materials, which have enhanced properties compared to conventional materials in the field of their applications.1 The huge group of them contributes significantly to every aspect of our lives. Among them, chosen for the present study, are resins for passive sampling of iron species in natural water and sediments, anticorrosive coatings, and multilayered polysaccharide aerogels for medical applications. The composition and structure of each material determine its chemical, mechanical and physical properties, consequently their performance.2 The ability to use advanced materials in areas where their impact will be significant is largely dependent on the ability to precisely determine their characteristics to identify their properties that are either unique or has a better value. Therefore, the development of new methods or improvement of already known ones will make a great contribution to the development of the fields of application of the selected materials. The present study is focused on the examination of the chosen materials by determining their optical, chemical, thermal and structural properties for applying them further in the desired applications. To provide the needed characterization, optothermal techniques such as optothermal beam deflection spectrometry (BDS) and thermal lens spectrometry (TLS) are developed and applied. This dissertation is composed of the following chapters: introduction, theoretical background, optothermal techniques, research goal, part I (gels for passive sampling of iron species in natural water and sediments), part II (anticorrosive coatings), part II (polysaccharide aerogels), references. The core of this dissertation is presented in chapters 5 to 7. Each of the chapters separately covers the information about a selected group of advanced materials, including the sections describing sample preparation, developing the required characterization method, results, and conclusion. The connection link of these chapters is the study of the diffusion process of iron into different types of binding gels in passive samplers; external composites through the anticorrosive layers; drugs into the surrounding during the drug delivery process. In Part I, the BDS method for the study was chosen, it was optimized, and a detailed protocol was developed for the determination of iron in passive sampler gels. The iron residues in the initial solutions were checked by a suitably tuned TLS method. The developed technique was applied to get the iron species distribution in the gel samples deposited in the sediments in the Vrtojbica River. The method was applied to the gels applied on ice from Antarctica in order to obtain the iron species distribution on its surface as well. The obtained results were validated using the TLS, UV-Vis and ICP-MS methods. The chapter contains the analysis of the Fe diffusion depth into the resin sampler, which is presented for the first time. The information is obtained by using the mathematical model and applying it to the obtained practical results by frequency scanning of the gels. The crucial information about the thermal properties of their layers containing Fe-ions from the fitting procedure was extracted. On the basis of these results, information about the diffusion depth of Fe inside the gels was obtained, which has not been previously described in the literature. In Part II, the porosity in the anticorrosion coatings on the basis of their thermal parameters was determined. For the first time, the opened porosity was extracted from the total one. The analysis of Si/Zr-based hybrid sol-gel coatings has shown that the addition of cerium salts into the sol-gel matrix produces changes in its physical, chemical and corrosion properties. And it was found that the sample with the biggest amount of incorporated zirconium and loaded with cerium has the lowest values of porosity and, hence, the best barrier properties of the coating. The obtained thermal parameters of the Si/Zr-based hybrid sol-gel coatings by BDS were validated by the use of the photothermal radiometry method. On the other hand, the analysis of siloxane methacrylate coating has shown that the sol-gel hybrid methodology offers an important route for modification of thermal properties by a combination of inorganic to organic contents where the former than as an integral part of the coating network affects the thermal properties without the need for introducing fillers or nanoparticles. In Part III, the multilayered structure of the samples, containing hyaluronic acid, amoxicillin and fucoidan layers deposited on stainless support has been analyzed by the use of the BDS technique. The thermal parameters of each layer were determined, as well as their thickness. The results revealed the diffusion between neighboring layers and followed changes in the properties of the whole sample, which is reflected in its thermal properties. Such data for multilayered materials, which potentially can be used for drug delivery systems, are presented for the first time. Presented results indicated the ability of the BDS system for the chemical characterisation of the solid materials, the detection of their thermal parameters; investigation of total, opened and closed porosity; determining the thickness of layers in multilayered structures. The TLS method served as the validating one for the purpose of getting comprehensive information in liquid samples about their chemical composition. In summary, this dissertation explores alternative ways to apply optothermal methods to various areas of advanced materials to characterize them in order to improve their initial properties.
Ključne besede: optothermal beam deflection spectrometry, thermal lens spectrometry, diffusive gradients in thin films, iron species, anticorrosive layers, porosity, polysaccharide aerogels, multilayered structures
Objavljeno v RUNG: 29.08.2022; Ogledov: 1181; Prenosov: 50
.pdf Celotno besedilo (5,46 MB)

Nondestructive Evaluation of Surface Roughness of Thin Films through Fractal Analysis, S Soumya
Swapna Mohanachandran Nair Sindhu, 2017, izvirni znanstveni članek

Ključne besede: Nondestructive Evaluation, Surface Roughness, Thin Films, Fractal Analysis
Objavljeno v RUNG: 05.07.2022; Ogledov: 698; Prenosov: 0
Gradivo ima več datotek! Več...

RF sputtered boron carbide thin film for UVB and UVC shielding: A greener approach
Swapna Mohanachandran Nair Sindhu, 2022, izvirni znanstveni članek

Opis: The paper reports the development of RF sputtered boron carbide coatings as refractory and UV-shielder for high-temperature goggles and spacecraft applications. The advancement in the design and fabrication of machinery and UV optics necessitates the development of low-cost, eco-friendly preparation of wear-resistant refractory coatings with strong absorption in the UV region. Boron carbide coatings have proven their potential as abrasives besides their electronic applications. In the present work, boron carbide coatings are prepared by RF sputtering technique using the target prepared by low-temperature hydrothermal synthesis using cotton as carbon precursor. The sample synthesized and the film prepared are subjected to structure, morphological, and optical characterizations. The X-ray diffraction, Fourier transform infrared, micro-Raman and X-ray photoelectron studies confirm the formation of boron-rich boron carbide with the thermal stability of 87% at 800 C, revealed through the thermogravimetric analysis. The Tauc plot analysis gives the bandgap energy of the boron carbide target and film as 2.66 eV and 2.70 eV, respectively. The UV–Vis spectroscopic study also reveals the potential of the sample and the film in blocking UVB and UVC. The CIE plot from the photoluminescence study suggests the sample to be a blue light emitter.
Ključne besede: Boron carbide, RF sputtering, uv shielding, thin films
Objavljeno v RUNG: 30.06.2022; Ogledov: 665; Prenosov: 0
Gradivo ima več datotek! Več...

Towards a novel method for iron species determination in Antarctic sea ice
Hanna Budasheva, Arne Bratkič, Dorota Korte, Mladen Franko, 2021, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Sea-ice borne iron has been found to be an important factor controlling Southern Ocean phytoplankton growth [1]. Knowing the amount and chemical speciation of its labile fraction in sea ice would advance our understanding of the involved processes. Unfortunately, it is rather difficult to perform their measurement because of limited access to the Antarctic. Thus there is a strong need for the development of a quick, simple and reliable technique for determination of iron and its speciation in sea-ice that ensures also low enough limits of detection. Recently, diffusive gradients in thin films (DGT) have been widely used as passive samplers for collecting time-averaged data on the concentrations of transition metals in different media [2]. DGTs are further coupled to an analytical technique that in case of detecting metals in passive sampler films primarily requires their extraction [3], which may potentially lead to changes of the metal specification. In the present study, the beam deflection spectrometry (BDS) is coupled to DGT and used to determine the average concentration of iron in the sea ice samples collected at the Davis Station in the Antarctic. Such a combined technique has been already successfully applied for detecting labile iron species in freshwater sediments [4]. The obtained BDS data were validated by thermal lens spectrometry (TLS) and UV-Vis spectrophotometry (SPEC). The distribution of iron species over a given ice surface area using the DGT-BDS technique revealed total iron concentrations in the range of 0.6 – 5.3 μgL-1, whereas the Fe2+ content was found to be in the range of 0.1 – 1.5 μgL-1. The range taking into account all of the measurement points (5×4), the precision of a single measured point is 0.2 μgL-1. The calculated 24 h-average concentration of total Fe labile species in the ice by using BDS is 2.3 ± 0.5 μgL-1, which coincides with data obtained by SPEC (2.5 ± 0.4 μgL-1) and TLS (2.39 ± 0.02 μgL-1). Our results indicate that it is possible to develop a robust, contamination-resilient detection method for measuring the labile iron species concentration in the sea ice. In opposite to TLS and SPEC, BDS-DGT provides reliable information not only about the speciation of iron but also about their distribution on the ice surface.
Ključne besede: beam deflection spectrometry, diffusive gradients, thin films, iron species, photothermal techniques, Antarctic sea ice
Objavljeno v RUNG: 30.11.2021; Ogledov: 1584; Prenosov: 0
Gradivo ima več datotek! Več...

Improved photocatalytic activity of SnO[sub]2-TiO[sub]2 nanocomposite thin films prepared by low-temperature sol-gel method
Ksenija Maver, Iztok Arčon, Mattia Fanetti, Samar Al Jitan, Giovanni Palmisano, Matjaž Valant, Urška Lavrenčič Štangar, 2021, izvirni znanstveni članek

Opis: The objective of this research was to investigate how the photocatalytic activity of pure TiO2 can be improved by SnO2 modification. Different molar ratios of tin to titanium were prepared. The correlation between tin concentration and structural properties was investigated to explain the mechanism of photocatalytic efficiency and to optimize the synthesis conditions to obtain enhanced activity of the SnO2-modified TiO2 photocatalysts under UV-irradiation. The SnO2-modified TiO2 photocatalysts were prepared by a low-temperature sol-gel method based on organic tin and titanium precursors. The precursors underwent sol-gel reactions separately to form SnO2-TiO2 sol. The sol-gels were deposited on a glass substrate by a dip-coating technique and dried at 150 ◦C to obtain the photocatalysts in the form of a thin film. To test the thermal stability of the material, an additional set of photocatalysts was prepared by calcining the dried samples in air at 500 ◦C. The photocatalytic activity of the samples was determined by measuring the degradation rate of an azo dye. An increase of up to 30% in the photocatalytic activity of the air-dried samples was obtained when the TiO2 was modified with the SnO2 in a concentration range of 0.1–1 mol.%. At higher SnO2 loadings, the photocatalytic activity of the photocatalyst was reduced compared to the unmodified TiO2. The calcined samples showed an overall reduced photocatalytic activity compared to the air-dried samples. Various characterization techniques (UV-Vis, XRD, N2-physisorption, TEM, EDX, SEM, XAS and photoelectrochemical characterization) were used to explain the mechanism for the enhanced and hindered photocatalytic performances of the SnO2-modified TiO2 photocatalysts. The results showed that the nanocrystalline cassiterite SnO2 is attached to the TiO2 nanocrystallites through the Sn-O-Ti bonds. In this way, the coupling of two semiconductors, SnO2 and TiO2, was demonstrated. Compared to single-phase photocatalysts, the coupling of semiconductors has a beneficial effect on the separation of charge carriers, which prolongs their lifetime for accessibility to participate in the redox reactions. The maximum increase in activity of the thin films was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases is achieved for the given physical parameters such as particle size, shape and specific surface area of the catalyst.
Ključne besede: photocatalytic activity, Sn-modified TiO2, low-temperature, thin films, XAS analysis
Objavljeno v RUNG: 05.07.2021; Ogledov: 1659; Prenosov: 0
Gradivo ima več datotek! Več...

Iskanje izvedeno v 0.06 sek.
Na vrh