Development of semiconducting graphitic carbon nitride nanofluid for heat transfer applications: A mode mismatched thermal lens studyVijayakumar Gokul
, Mohanachandran Nair S. Swapna
, Govind Ambadas
, Sankaranarayana Iyer Sankararaman
, 2023, izvirni znanstveni članek
Ključne besede: graphitic carbon nitride, nanofluid, heat transfer, thermal lens, thermal diffusiivty
Objavljeno v RUNG: 29.09.2023; Ogledov: 306; Prenosov: 5
Celotno besedilo (5,34 MB)
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Accuracy of Measurements of Thermophysical Parameters by Dual-Beam Thermal-Lens SpectrometryVladislav Khabibulin
, Mladen Franko
, Mikhail Proskurnin
, 2023, izvirni znanstveni članek
Opis: Thermal-lens spectrometry is a sensitive technique for determination of physicochemical
properties and thermophysical parameters of various materials including heterogeneous systems
and nanoparticles. In this paper, we consider the issues of the correctness (trueness) of measurements
of the characteristic time of the thermal-lens effect and, thus, of the thermal diffusivity determined
by dual-beam mode-mismatching thermal lensing. As sources of systematic errors, major factors—
radiation sources, sample-cell and detector parameters, and general measurement parameters—are
considered using several configurations of the thermal-lens setups, and their contributions are
quantified or estimated. Furthermore, with aqueous ferroin and Sudan I in ethanol as inert colorants,
the effects of the intermolecular distance of the absorbing substance on the correctness of finding the
thermophysical parameters are considered. The recommendations for checking the operation of the
thermal-lens setup to ensure the maximum accuracy are given. The results obtained help reducing
the impact of each investigated factor on the value of systematic error and correctly measure the
thermophysical parameters using thermal-lens spectrometry.
Ključne besede: thermal-lens spectrometry, accuracy and trueness, mode-mismatched schematic, measurements of thermal diffusivity
Objavljeno v RUNG: 20.01.2023; Ogledov: 802; Prenosov: 9
Celotno besedilo (9,88 MB)
Recent Progress and Applications of Thermal Lens Spectrometry and Photothermal Beam Deflection Techniques in Environmental SensingMladen Franko
, Leja Goljat
, Mingqiang Liu
, Hanna Budasheva
, Mojca Žorž Furlan
, Dorota Korte
, 2023, izvirni znanstveni članek
Opis: This paper presents recent development and applications of thermal lens microscopy (TLM) and beam deflection spectrometry (BDS) for the analysis of water samples and sea ice. Coupling of TLM detection to a microfluidic system for flow injection analysis (µFIA) enables the detection of microcystin-LR in waters with a four samples/min throughput (in triplicate injections) and provides an LOD of 0.08 µg/L which is 12-times lower than the MCL for microcystin-LR in water. µFIA-TLM was also applied for the determination of total Fe and Fe(II) in 3 µL samples of synthetic cloudwater.
The LODs were found to be 100 nM for Fe(II) and 70 nM for total Fe. The application of µFIA-TLM for the determination of ammonium in water resulted in an LOD of 2.3 µM for injection of a 5 µL sample and TLM detection in a 100 µm deep microfluidic channel. For the determination of iron
species in sea ice, the BDS was coupled to a diffusive gradient in the thin film technique (DGT). The 2D distribution of Fe(II) and total Fe on DGT gels provided by the BDS (LOD of 50 nM) reflected the distribution of Fe species in sea ice put in contact with DGT gels.
Ključne besede: thermal lens microscopy, beam deflection spectrometry, microfluidic system, microcystin-LR detection, iron species determination, ammonium detection
Objavljeno v RUNG: 03.01.2023; Ogledov: 842; Prenosov: 18
Celotno besedilo (2,90 MB)
NONDESTRUCTIVE THERMAL, OPTICAL, CHEMICAL AND STRUCTURAL CHARACTERIZATION OF ADVANCED MATERIALS BY OPTOTHERMAL TECHNIQUESHanna 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: 1413; Prenosov: 51
Celotno besedilo (5,46 MB)