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Unuigbe, David Moweme. "Characterisation of silicon nanoparticles produced by mechanical attrition using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoemission spectroscopy." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12105.
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The establishment of printing technologies, using nanoparticle based inks, promises inexpensive manufacture of electronic devices. However, to produce working devices, nanoparticles have to meet requirements on size, shape, and composition. In the application of silicon nanoparticles in electronics, it is important that a network of interconnecting particles is formed through which charge transport can take place. Of further importance is that there is an absence of surface oxide in order to maintain a direct silicon-silicon connection within the network. In this work, cheap and scalable production of silicon nanoparticles is achieved efficiently with a top-down process of mechanical attrition by high energy milling.
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Owen, G. T. "Scanning tunnelling microscopy/spectroscopy and X-ray photoelectron spectroscopy investigations of nanocrystalline tin dioxide gas sensors." Thesis, Swansea University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638383.
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Gas sensors fabricated from Tin Dioxide (SnO2) nanoparticles were studied in UHV environments using scanning tunnelling microscopy/spectroscopy (STM/S) and x-ray photoelectron spectroscopy in an attempt to mimic real working conditions. The sensor fabrication process was investigated, where it was determined that the optimum condition for the formation of sintering necks between consecutive grains was at a firing temperature of 400oC for 20 minutes. The effect of introducing oxygen and reducing gases (CH4, CO) was studied at both room and elevated temperatures using XPS and resistance measurements; where chemisorption of these gaseous species caused upward bandbending of 0.2eV upon O2 exposure followed by a 0.1eV bandbending decrease as reducing gases were introduced. Respective resistance variations of 50MΩ and 20MΩ were observed upon exposure to these gases. Simultaneous use of STM and STS techniques revealed the apparent surface band gap measured by STS was significantly narrower at nanoparticles boundaries than at centres. Changes in the conduction band edge position were much more pronounced than for the valence band and were mostly responsible for the variation in band gap. The preferential chemisorption of oxygen at sintering necks causing an increase in surface state density has been suggested as a possible interpretation.
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Slater, Thomas Jack Alfred. "Three dimensional chemical analysis of nanoparticles using energy dispersive X-ray spectroscopy." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/three-dimensional-chemical-analysis-of-nanoparticles-using-energy-dispersive-xray-spectroscopy(3eb607a2-eb03-4d45-b9eb-71b0ca45c2db).html.
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The aim of this thesis is to investigate the methodology of three dimensional chemical imaging of nanoparticles through the use of scanning transmission electron microscope (STEM) – energy dispersive X-ray (EDX) spectroscopy. In this thesis, an absorption correction factor is derived for spherical nanoparticles that can correct X-ray absorption effects. Quantification of EDX spectra of nanoparticles usually neglects X-ray absorption within the nanoparticle but may lead to erroneous results, thus an absorption correction is important for accurate compositional quantification. The absorption correction presented is verified through comparison with experimental data of Au X-ray peaks in spherical Au nanoparticles and is found to agree excellently. This absorption correction allows accurate compositional quantification of large ( > 100 nm) particles with STEM-EDX.Three dimensional chemical mapping is achievable through the use of EDX spectroscopy with electron tomography. Here, the methodology of STEM-EDX tomography is fully explored, with a focus on how to avoid artefacts introduced through detector shadowing and low counts per pixel. A varied-time acquisition scheme is proposed to correct for detector shadowing that is shown to provide a more constant intensity over a series of projections, allowing a higher fidelity reconstruction. The STEM-EDX tomography methodology presented is applied to the study of AgAu nanoparticles synthesized by the galvanic replacement reaction. The elemental distribution as a function of the composition of the as-synthesized nanoparticles is characterised and a reversal in the element segregated to the surface of the nanoparticles is found. The composition at which the reversal takes place is shown to correlate with a peak in the catalytic yield of a three component coupling reaction. It is hypothesized that a continuous Au surface results in the optimum catalytic conditions for the reaction studied, which guides the use of galvanically prepared AgAu nanoparticles as catalysts.
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Burgio, Lucia. "Analysis of pigments on art objects by Raman microscopy and other techniques." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369123.
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SOUZA, JULIANA P. de. "Estudo da sinterização de vidros aluminossilicatos por calorimetria exploratória diferencial." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23660.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Saffarini, Ghassan. "X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density study of ternary chalcogenide glasses based on Ge-Se and Ge-S." Thesis, Brunel University, 1991. http://bura.brunel.ac.uk/handle/2438/7396.
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Glasses of the systems Ge-Se-X (X = Ga, Sn, Bi, Sb), Ge-S-Y (Y = Ag, Ga, Sn, Bi) and Se-S have been examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), density and differential scanning calorimetry (DSC). Two of the compositions, GeSe2 and (GeSe2)92Ga8, have also been examined by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). The emphasis of the XPS measurements was on the changes in the binding energies with composition of the core peaks of the glasses, and on the plasmon energy losses from the L3M4,5M4,5 Auger lines of Se and Ge. It was found that there were small shifts in the binding energies of the core peaks on substitution but the plasmon energy changed markedly with composition. For the XRD measurements, the focus was on two features : (a) to ensure that the samples prepared were truely amorphous and (b) to confirm the presence of the first sharp diffraction peak (FSDP) on the interference functions. The density measurements showed that the addition of the third element (X or Y) to the binary resulted in an increase in the relative density except for one system, Ge-Se-Sn, which showed the opposite behaviour. The DSC measurements showed that the addition of the third element to the binary resulted in a decrease in the glass transition temperatures. The EXAFS and XANES measurements of GeSe2 and (GeSe2)92Ga8 glasses showed that there was very little change in the local order around the Ge atom in GeSe2 glass with increase in temperature and that the local order around the Ge atom changes on alloying GeSe2 with Ga. Correlations between parameters and measured properties of the ternary alloys have been investigated. It has been found that the parameter
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Miller, Charles William. "Surface characterization of inductively coupled radio frequency plasma treated glassy carbons by x-ray photoelectron spectroscopy and scanning electron microscopy /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266362335601.
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Shabani, Juvet Malonda. "Synthesis of clay-based catalysts for bioethanol conversion." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2488.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.For decades, clays have been applicable as commercial catalysts mostly for cracking in petroleum industries. Clays are also used for development of useful catalysts for various other industrial applications. Hence, this work was aimed to synthesize clay-based catalysts from clay minerals (Kaolin, bentonite and talc) that will be active for the conversion of bioethanol to fuel hydrocarbons. Catalyst characterisation techniques employed on the samples produced in this work include the Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM) and the X-Ray Diffraction pattern (XRD). All catalytic reactions were carried out in a fixed bed reactor (at fixed reaction condition of 6 hour and 350 ⁰C) and corresponding reaction products (liquid and gaseous) were analysed through a Gas Chromatograph- Flame Ionisation Detector (GC-FID) and Gas Chromatograph Mass Spectrometer (GC/MS). The activity of clays in their non-modified state was studied and they were all found active for bioethanol conversion to hydrocarbons. Bentonite was the most active catalyst with bioethanol of 84.95 % and this through subsequent beneficiation and acid-modification approach, led to increased bioethanol conversion of 87.3 %. EDS/SEM characterisation of the catalyst in line to the above modification and increased catalyst activity, revealed that the structural morphology of bentonite and the concentration of basic structural elements (in terms of Si/Al ratio) was increased.
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Kersell, Heath R. "Alternative Excitation Methods in Scanning Tunneling Microscopy." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1449074449.
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Maringa, Audacity. "Electrode surface modification using metallophthalocyanines and metal nanoparticles : electrocatalytic activity." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017921.
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Metallophthalocyanines and metal nanoparticles were successfully synthesized and applied for the electrooxidation of amitrole, nitrite and hydrazine individually or when employed together. The synthesized materials were characterized using the following techniques: predominantly scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning electrochemical microscopy (SECM). Different electrode modification methods were used to modify the glassy carbon substrates. The methods include adsorption, electrodeposition, electropolymerization and click chemistry. Modifying the glassy carbon substrate with MPc (electropolymerization) followed by metal nanoparticles (electrodeposition) or vice versa, made a hybrid modified surface that had efficient electron transfer. This was confirmed by electrochemical impedance studies with voltammetry measurements having lower detection potentials for the analytes. This work also describes for the first time the micropatterning of the glassy carbon substrate using the SECM tip. The substrate was electrografted with 4-azidobenzenediazonium salt and then the click reaction was performed using ethynylferrocene facilitated by Cu⁺ produced at the SECM tip. The SECM imaging was then used to show the clicked spot.
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Ledung, Greger. "Heterogenization of a Cobalt Porphyrin Catalyst Investigated by Scanning Probe Microscopy and X-Ray Photoelectron Spectroscopy: The Effect on Catalysis of Oxidation Reactions." Doctoral thesis, Västerås : School of sustainable Development of Society and technology, Mälardalen university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-492.
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Fagerland, Steffen Knut. "Investigation of Focused Ion Beam/Scanning Electron Microscope parameters for Slice and View and Energy Dispersive X-ray Spectroscopy of Embedded Brain Tissue." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25765.
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This Thesis investigates the optimization of a Focused Ion Beam/Scanning Electron Microscope (FIB/SEM) Slice and View protocol of brain tissue. Using a Slice and View protocol in a Dualbeam instrument, the ion and electron beams are used in sequence to alternately mill and image the newly exposed surface of a predefined volume. This creates serial section images that may be used for 3D reconstruction. Research questions addressed include finding FIB parameters most beneficial for accurate milling of the tissue, use of different software strategies and image processing for 3D reconstruction of selected subsets enclosed within the volume sectioned, and the use of Energy Dispersive X-ray Spectroscopy for revealing the volume contents \emph{a priori} of the Slice and View. The reults showed that FIB parameters of $30kV$ and $0.9nA$ provided sufficient accuracy and consistency; that the DAB labeling protocol provided characteristics easily identifiable of the morphology of selected interneurons which were reconstructed, but was difficult to use in a generalized semi-automatic reconstruction protocol; and a model created to test EDX tracing did show potential for its use to increase protocol efficiency by narrowing down the regions of interest of the FIB block.
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Halwani, Dina. "Metal-tissue interactions in early stage biocorrosion of metallic stents." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2007m/halwani.pdf.
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Thesis (M.S.)--University of Alabama at Birmingham, 2007.Additional advisors: Peter G. Anderson, Brigitta C. Brott, Jack E. Lemons. Description based on contents viewed Feb. 4, 2008; title from title screen. Includes bibliographical references (p. 69-70).
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NANDENHA, JULIO. "Desenvolvimento de novos sistemas de eletrocatalisadores nano-sispersos 20% Pt-(2%Pt-Cesub(0.9)Wsub(0.1)Osub(2))/C tolerantes ao monóxido de carbono (CO) para ânodos de PEMFC." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10029.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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PESTANA, RAFAEL C. B. "Identificação de assinaturas de urânio em amostras de esfregaços (Swipe samples) para verificação de atividades nucleares para fins de salvaguardas nucleares." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10590.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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HIGASHI, CRISTIANE. "Investigação do processo de obtenção de aluminatos de bário e cálcio para construção e caracterização de catodos termiônicos impregnados para a aplicação em dispositivos de microondas de potência." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11463.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Dehlinger, Mael. "XAS-XEOL and XRF spectroscopies using near field microscope probes for high-resolution photon collection." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4048/document.
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Les microscopes en champ proche permettent d'obtenir la topographie d'un échantillon avec une résolution pouvant atteindre la résolution atomique. Les spectroscopies de rayons-X sont des méthodes de caractérisation qui permettent de déterminer la composition et la structure élémentaire de l'échantillon avec une précision inférieure à l'Ångström. Nous avons choisi de coupler ces deux techniques en collectant localement la luminescence visible issue de l'échantillon par la pointe-sonde d'un microscope à force de cisaillement, constituée d'une fibre optique effilée de faible ouverture. Cette technique a été utilisée pour caractériser des échantillons semiconducteurs micro- et nano-structurés afin d'en obtenir simultanément la topographie et la cartographie de luminescence locale. Afin de pouvoir étendre ce concept à d'autres types de matériaux, la faisabilité de la collecte de la fluorescence X locale a été évaluée avec la microsource. Pour cela la fluorescence X émise par un échantillon a été collectée par un capillaire cylindrique équipant un détecteur EDX. L'influence du diamètre du capillaire sur le niveau de signal a été mesurée. Une simulation numérique a été développée afin d'estimer le niveau de signal obtenu en utilisant un capillaire de 1 µm de diamètre et d'optimiser la géométrie du système. En couplant la microscopie en champ proche et l'analyse XRF, à la lumière de ces résultats, il sera possible d'atteindre 100 nm de résolution latérale en environnement synchrotron et moins de 1 µm à l'aide d'une source de laboratoire. Il serait alors possible de sélectionner un objet particulier sur une surface et d'en faire l'analyse élémentaireScanning Probe Microscopes allow to obtain sample topography up to atomic resolution. X-ray spectroscopies allow elemental and structural analysis of a sample with accuracy better than 1 Å. The lateral resolution is limited by the primary beam diameter, currently a few µm². We have chosen to couple this two technics. Local sample visible luminescence is collected through a low aperture sharp optical fibre, probe of a shear force microscope. This technique was used to characterize microstructured semiconducting samples to achieve simultaneously the surface topography and luminescence mapping. The results were obtained using either synchrotron radiation or a laboratory microsource equipped with a polycapillary lens. To extend this concept to a wider variety of materials, local XRF collection by an EDX detector equipped with a cylindrical X-ray capillary was tested. A cobalt sample irradiated with the microsource was used for technique evaluation. The signal magnitude dependence with the capillary diameter was measured. Modelling and numerical calculations were developed to estimate the signal magnitude that could be detected using a 1 µm diameter capillary. The optimal system geometry was determined. Scanning Probe Microscopy combined to XRF analysis could thereby lead to simultaneous acquisition of sample topography and chemical mapping. The expected lateral resolution using synchrotron radiation is 100 nm while sub 1 µm resolution is realistic with a laboratory source. This technique would allow to point a peculiar micro- or nano-object on the surface and to perform its chemical analysis
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Åhlund, John. "Electronic and Geometrical Structure of Phthalocyanines on Surfaces : An Electron Spectroscopy and Scanning Tunneling Microscopy Study." Doctoral thesis, Uppsala universitet, Fysiska institutionen, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7802.
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Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields. Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films. We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature. Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K.
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Aitchison, Hannah. "Self-assembly of monolayers of aromatic carboxylic acid molecules on silver and copper modified gold surfaces at the liquid-solid interface." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6950.
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Exploiting coordination bonding of aromatic carboxylic acids at metal surfaces, this thesis explores new directions in the design and application of self-assembled monolayers (SAMs). The SAMs are investigated using a multi-technique approach comprising of a complementary combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, the X-ray standing wave technique (XSW) was used to characterise the substrates. The process of layer formation and the final structures of the SAMs are found to be strikingly dependent on the combination of molecule and substrate, which is discussed in terms of the intermolecular and molecule-substrate interactions, bonding geometries and symmetry of the organic molecules. This is illustrated by the dramatic difference between molecular adsorption on Ag and Cu for molecules such as biphenyl-3,4',5-tricarboxylic acid and biphenyl-4-acetic acid. In the case of self-assembly on Cu, the molecule-substrate interactions play a decisive role in the resulting SAM structure, whereas on Ag, the intermolecular interactions dominate over the weaker molecule-substrate binding. This exploration of the balance of interactions that lead to the formation of these SAM structures lays the foundation for a systematic design of the structures and properties of aromatic carboxylic acid based monolayers. Finally, different applications and properties of some SAMs were investigated, namely coordination of a Pd(II) complex to a pyridine/pyrazole terminated molecule adsorbed on Ag. Evidence of coordination of Pd(II) to single molecules was provided by STM, XPS and NEXAFS spectroscopy. Additionally, controlled STM tip induced modification of local areas of a 1,3,5-tris(4-carboxyphenyl)benzene SAM on Ag was performed, opening an exciting prospect for nanoscale molecular manipulation.
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DUVAIZEM, JOSE H. "Estudo das propriedades mecanicas e microestruturais de ligas a base de titanio-niobio-zirconio processados com hidrogenio e metalurgia do po para utilizacao em implantes dentarios." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9429.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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SCHELL, JULIANA. "Investigação de parâmetros hiperfinos dos óxidos semicondutores SnOsub(2) e TiOsub(2) puros e dopados com metais de transição 3d pela espectroscopia de correlação angular gama-gama perturbada." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23699.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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MAEDA, NANCY T. "Avaliação da neoformação óssea em tíbia de coelhos utilizando cúpula de hidroxiapatita associada a diferentes biomateriais." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10542.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Oh, Seung Cheol [Verfasser], Johannes [Akademischer Betreuer] Barth, and Markus [Akademischer Betreuer] Lackinger. "Single layer films of functional molecules on noble metal surfaces visited by scanning tunneling microscopy and X-ray spectroscopy / Seung Cheol Oh. Gutachter: Johannes Barth ; Markus Lackinger. Betreuer: Johannes Barth." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1060825449/34.
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CAPRONI, ERICA. "Eletrolitos sólidos cerâmicos a base de óxido de zircônio para a detecção de oxigênio." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11534.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:03/07331-0
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REIS, SHIRLEY L. dos. "Efeito dos métodos de síntese e sinterização na densificação, estrutura, microestrutura e condutividade elétrica do galato de lantânio." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11809.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Coates, Megan Patricia. "Characterisation of surfaces modified through self-assembled monolayers and click chemistry." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001684.
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Different approaches to surface modification were investigated in this work on gold, glassy carbon, multi-walled carbon nanotube paper and on single-walled carbon nanotubes adsorbed on glassy carbon. These approaches include electrochemical grafting, electropolymerisation, click chemistry, axial ligation, adsorption and self-assembled monolayers. The modified surfaces were characterised using a variety of techniques; predominantly electrochemistry, scanning electrochemical microscopy and X-ray photoelectron spectroscopy. For the formation of self-assembled monolayers on gold, four new manganese(III) phthalocyanines (1a-d), octa-substituted at the peripheral position with pentylthio, decylthio, benzylthio, and phenylthio groups were synthesized and characterised. X-ray photoelectron spectroscopy was used to show the formation of a sulphur-gold bond. A number of approaches using 4-azidoaniline (2a) combined with azide-alkyne click chemistry and electrochemistry were also used to anchor ferrocene and pyridine moieties on to the carbon surfaces, including direct in situ diazotation and grafting, electropolymerisation, and the synthesis of the diazonium salt followed by grafting. Iron phthalocyanine was linked to the pyridine-clicked surfaces through axial ligation, where the strong axial bond formed by the interaction between the central metal and the lone pair of the nitrogen in the pyridine group resulted in stable modified electrodes. The potential of these surfaces for the detection of analytes such as thiocyanate, hydrazine and sulphite are briefly shown as well. This work also describes for the first time the possibility of performing local micro-electrochemical grafting of a gold substrate by 4-azidobenzenediazonium (2b) using scanning electrochemical microscopy in a single and simple one step approach, without complications from adsorption.
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Munktell, Sara. "Bipolar electrochemistry for high throughput screening applications." Doctoral thesis, Uppsala universitet, Strukturkemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-277937.
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Bipolar electrochemistry is an interesting concept for high throughput screening techniques due to the ability to induce gradients in a range of materials and their properties, such as composition, particle size, or dopant levels, among many others. One of the key advantages of the method is the ability to test, create or modify materials without the need for a direct electrical connection. In this thesis, the viability of this method has been explored for a range of possible applications, such as metal recycling, nanoparticle modification and corrosion analysis. In the initial part of the work a process to electrodeposit gradients in metal composition was evaluated, with a view to applying the technique to the extraction and recycling of metals from fly ash. Compositional gradients in the metals under study could be readily obtained from controlled reference solutions, although the spatial resolution of the metals was not sufficient to perform separation. Only copper could be easily deposited from the fly ash solution. Bipolar electrodeposition was also successfully used to modify the particle size across substrates decorated with gold nanoparticles. The approach was demonstrated both for surfaces possessing either a uniform particle density or a gradient in particle density. In the latter case samples with simultaneous, orthogonal gradients in both particle size and density were obtained. A combination of the bipolar approach with rapid image analysis was also evaluated as a method for corrosion screening, using quantitative analysis of gradients in pitting corrosion damage on stainless steels in HCl as a model system. The factors affecting gradient formation and the initiation of corrosion were thoroughly investigated by the use of a scanning droplet cell (SDC) technique and hard x-ray photoelectron spectroscopy (HAXPES). The ability to screen arrays of different materials for corrosion properties was also investigated, and demonstrated for stainless steel and Ti-Al alloys with pre-formed compositional gradients. The technique shows much promise for further studies and for high throughput corrosion screening applications.
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Gaikwad, Kiran Sampat. "Development of a solid electrolyte for hydrogen production." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000571.
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Church, William Travis. "Laser Activated Bonding of Wood." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76888.
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It was found that laser modified wood surfaces can be bonded together to create a wood composite without the need of any additive. This bonding method removes the need of applying adhesive, potentially lowers cost, and eliminates off gassing of petroleum resins, creating a wood product with many eco-friendly attributes. This body of work outlines a) initial chemical analysis of the laser modified surface b) its bond strength and c) the optimization of factors that control the strength of the bond.
Surface chemical analysis on laser modified wood was conducted using photo acoustic Fourier transform infrared spectroscopy (PA-FTIR) and X-Ray photoelectron spectroscopy (XPS). Light microscopy and scanning electron microscopy were utilized for surface topology analysis.Differential scanning calorimetry (DSC) quantified the thermal properties of the modified wood surface. Screening of multiple factors that would contribute to surface modification and adhesion was performed utilizing mechanical testing. Optimization of significant factors that affect bond strength was determined statistically utilizing a design of experiment approach.
Chemical analysis of the laser modified surface revealed changes in the carbonyl and aromatic regions indicating modification of the hemicellulose and lignin components, intensifying with increasing laser modification.The C1/C2 ratios found via XPS revealed that one or more of the following is occurring: more extractives have moved to the surface, condensation reactions among lignin units, and the loss of methoxy and breakage of aryl ether linkages occurred.Microscopy images showed color changes to a darker caramel color with a smoothing of surface topology, suggesting the occurrence of the softening and/or melting of wood polymers. DSC verified chemical and/or physical changes in the wood with the modified material now having a glass transition temperature between 130-150°C.DOE found that laser parameters (power and focus) as well as hot press parameters (temperature and pressure) were significant in optimizing the bond.
The impact of the study is the first documentation of the ability to laser modifies wood surfaces and subsequently bond them together. The ability of the wood polymers at the surface to undergo flow at elevated temperature is implicated in the adhesion mechanism of the laser modified wood.Master of Science
30
Carson, Emma. "Spin coating of passive electroactive ceramic devices." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369951.
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BUSO, SIDNEI J. "Estudos microestruturais e por microanalise para identificacao dos precipitadores presentes em amostras da liga de niquel tipo 600 (nacional) apos processos de soldagem." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10743.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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CARMO, JOÃO R. do. "Síntese, caracterização microestrutural e elétrica de compostos cerâmicos à base de soluções sólidas de titanato de estrôncio, titanato de cálcio e óxido de ferro." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10035.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
33
ASSIS, SERGIO L. de. "Investigação da resistência a corrosão da liga Ti-13Nb-13Zr por meio de técnicas eletroquímicas e de análise de superfície." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11398.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
34
SALUTTE, CAIO de O. "Investigação do óxido semicondutor CeO2 dopado com Fe e La pela espectroscopia de correlação angular gama-gama perturbada." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10556.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:11/05408-2
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FRANCO, EGBERTO G. "Desenvolvimento de novos eletrocatalisadores para celulas a combustivel a membrana polimerica trocadora de protons." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11208.
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Tese (Doutoramento)
IPEN/T
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
36
CRAESMEYER, GABRIEL R. "Tratamento de efluente contendo urânio com zeólita magnética." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10578.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
37
Mandia, David J. "NC-AFM and XPS Investigation of Single-crystal Surfaces Supporting Cobalt (III) Oxide Nanostructures Grown by a Photochemical Method." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23117.
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The work of this thesis comprises extensive Noncontact Atomic Force Microscopy (NC-AFM) characterization of clean metal-oxide (YSZ(100)/(111) and MgO(100)) and graphitic (HOPG) supports as templates for the novel, photochemically induced nucleation of cobalt oxide nanostructures, particularly Cobalt (III) Oxide. The nanostructure-support surfaces were also studied by X-ray Photoelectron Spectroscopy (XPS) to verify the nature of the supported cobalt oxide and to corroborate the surface topographic and phase NC-AFM data. Heteroepitaxial growth of Co2O3 nanostructures proves to exhibit a variety of different growth modes based on the structure of the support surface. On this basis, single-crystal support surfaces ranging from nonpolar to polar and atomically flat to highly defective and reactive were chosen, again, yielding numerous substrate-nanostructure interactions that could be probed by high-performance surface science techniques.
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ALMEIDA, GISELE F. C. "Estudo do comportamento mecânico em temperaturas elevadas da liga Ti-6Al-4V após tratamento superficial de nitretação por plasma." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28044.
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A liga Ti-6Al-4V é uma das ligas de titânio mais suas aplicações estruturais em temperaturas elevadas são limitadas devido a sua afinidade pelo oxigênio. Um tratamento superficial que melhore a resistência à oxidação desta liga permitindo a substituição de peças que atualmente são produzidas com superligas de Ni por este material, poderia reduzir significativamente o peso destes componentes. O objetivo deste trabalho é melhorar a resistência à fluência desta liga utilizando nitretação por plasma. Para homogeneizar a microestrutura do material, foi realizado um tratamento térmico a 1050ºC por 30 minutos para obtenção da microestrutura de Widmanstätten que foi a que apresentou melhor resistência à fluência no material sem tratamento. A nitretação foi realizada variando parâmetros de processo como tempo, temperatura e mistura de gases na atmosfera. A partir dos resultados obtidos, a mistura de gás de Ar:N2:H2 (0,49:0,49:0,03) a 700°C por 4 horas foi a condição escolhida. A caracterização da camada nitretada foi realizada por técnicas de microscopia ótica e eletrônica de varredura, além de difração de raios X. As fases da amostra nitretada detectadas por DRX foram o ε-Ti2N e δ-TiN, além das fases α e β da matriz. A espessura da camada nitretada foi de cerca de 1 μm. Os ensaios de tração a quente foram realizados em temperaturas entre 500°C e 700°C no material com e sem nitretação e mostraram um aumento na resistência da liga nitretada de até 29% nos limites de escoamento e resistência. Os ensaios de fluência foram realizados variando a temperatura também entre 500 e 700ºC e tensão aplicada entre 125 e 319 MPa. O resultado foi um aumento na resistência à fluência do material nitretado. Isto foi evidenciado pela diminuição da taxa de fluência secundária e também pelo aumento do tempo de ruptura do material.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
39
Ozaslan, Mehtap, Wei Liu, Maarten Nachtegaal, Anatoly Frenkel, Bogdan Rutkowski, Matthias Werheid, Anne-Kristin Herrmann, et al. "Homogeneity and Elemental Distribution in Self-Assembled Bimetallic Pd-Pt Aerogels prepared by a spontaneous one-step gelation process." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-210970.
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Multi-metallic aerogels have recently emerged as a novel and promising class of unsupported electrocatalyst materials due to their high catalytic activity and improved durability for various electrochemical reactions. Aerogels can be prepared by a spontaneous one-step gelation process, where the chemical co-reduction of metal precursors and the prompt formation of the nanochain-consisting hydrogels, as a preliminary stage for the preparation of aerogels take place. However, detailed knowledge about the homogeneity and chemical distribution of these three-dimensional Pd-Pt aerogels at the nano-scale as well as at the macro-scale is still unclear to date.
Therefore, we used a combination of spectroscopic and microscopic techniques to obtain a better insight into the structure and elemental distribution of the various Pd-rich Pd-Pt aerogels prepared by the spontaneous one-step gelation process. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDX) were employed in this work to uncover the structural architecture and chemical composition of the various Pd-rich Pd-Pt aerogels over a broad length range. The Pd80Pt20, Pd60Pt40 and Pd50Pt50 aerogels showed heterogeneity in the chemical distribution of the Pt and Pd atoms inside the macroscopic nanochain-network. Features of monometallic clusters were not detected by EXAFS or STEM-EDX, indicating alloyed nanoparticles. However, the local chemical composition of the Pd-Pt alloys strongly varied along the nanochains and thus within a single aerogel. To determine the electrochemically active surface area (ECSA) of the Pd-Pt aerogels for applications in electrocatalysis, we used the electrochemical CO stripping method. Due to high porosity and extended network structure, the resulting values of the ECSA for the Pd-Pt aerogels were higher than that for a commercially available unsupported Pt black catalyst. We show that the Pd-Pt aerogels possess a high utilization of catalytically active centers for electrocatalytic applications based on the nanostructured bimetallic framework.
Knowledge about the homogeneity and chemical distribution of the bimetallic aerogels can help to further optimize their preparation by the spontaneous one-step gelation process and to tune their electrocatalytic reactivity.
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PINHEIRO, LUCAS B. "Síntese e caracterização de compósitos de NiO-YSZ-CeOsub(2) com tratamento hidrotermal assistido por micro-ondas." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10574.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
41
FONTES, ERIC H. "Oxidação eletroquímica do etanol utilizando eletrocatalisadores PtRh/C em meio alcalino e sintetizados via borohidreto de sódio e redução por álcool." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28013.
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Os eletrocatalisadores PtRh/C foram preparados nas seguintes proporções atômicas: (100,0), (0,100), (90,10), (70,30) e (50,50). Os métodos empregados nas sínteses foram redução via borohidreto de sódio e redução por álcool. Os sais metálicos empregados foram H2PtCl6.6H2O e (RhNO3)3 e o suporte de carbono utilizado foi carbon Vulcan XC72, a composição metálica em massa foi de 20%; e o suporte, 80%. Os eletrocatalisadores foram caracterizados por técnicas físico-químicas, espectroeletroquímica e por experimento em célula a combustível, cujo emprego se deu por uma célula unitária direta a álcool com membrana alcalina. Os eletrodos de trabalho foram preparados pela técnica de camada fina porosa. A técnica de difração de raios X permitiu verificar ligas metálicas, fases segregadas e calcular a porcentagem de ligas metálicas, bem como constatar os tipos de fases cristalinas. A técnica de espectroscopia no infravermelho permitiu verificar que a oxidação eletroquímica do etanol se dá pelo mecanismo indireto de oxidação, ou seja, para todos materiais estudados houve a produção de espécies intermediárias, em que PtRh(70:30)/C sintetizado pelo médodo de redução via borohidreto de sódio produziu grandes quantidades de CO2 e C2H4O. Rh/C mostrou-se ativo eletroquimicamente para ambos os métodos de síntese empregados. A técnica de microscopia eletrônica de transmissão permitiu calcular o tamanho médio e a área superficial média dos eletrocatalisadores. As técnicas eletroquímicas permitiram verificar a estabilidade, potencial onset e pares redox dos sistemas considerados.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
42
Zhang, Shuo. "The Performance and Service Life Prediction of High Performance Concrete in Sulfate and Acidic Environments." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2260.
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Concrete substructures are often subjected to environmental deterioration, such as sulfate and acid attack, which leads to severe damage and causes structure degradation or even failure. In order to improve the durability of concrete, the High Performance Concrete (HPC) has become widely used by partially replacing cement with pozzolanic materials. However, HPC degradation mechanisms in sulfate and acidic environments are not completely understood. It is therefore important to evaluate the performance of the HPC in such conditions and predict concrete service life by establishing degradation models.
This study began with a review of available environmental data in the State of Florida. A total of seven bridges have been inspected. Concrete cores were taken from these bridge piles and were subjected for microstructural analysis using Scanning Electron Microscope (SEM). Ettringite is found to be the products of sulfate attack in sulfate and acidic condition.
In order to quantitatively analyze concrete deterioration level, an image processing program is designed using Matlab to obtain quantitative data. Crack percentage (Acrack/Asurface) is used to evaluate concrete deterioration. Thereafter, correlation analysis was performed to find the correlation between five related variables and concrete deterioration. Environmental sulfate concentration and bridge age were found to be positively correlated, while environmental pH level was found to be negatively correlated.
Besides environmental conditions, concrete property factor was also included in the equation. It was derived from laboratory testing data. Experimental tests were carried out implementing accelerated expansion test under controlled environment. Specimens of eight different mix designs were prepared. The effect of pozzolanic replacement rate was taken into consideration in the empirical equation. And the empirical equation was validated with existing bridges.
Results show that the proposed equations compared well with field test results with a maximum deviation of ± 20%. Two examples showing how to use the proposed equations are provided to guide the practical implementation. In conclusion, the proposed approach of relating microcracks to deterioration is a better method than existing diffusion and sorption models since sulfate attack cause cracking in concrete. Imaging technique provided in this study can also be used to quantitatively analyze concrete samples.
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Gonçalves, Ligia Maria Napolitano. "Efeito da radioterapia sobre as propriedades mecânicas, químicas e morfológicas do esmalte e da dentina de dentes permanentes - Estudo in vitro." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/58/58135/tde-23052012-163912/.
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O presente estudo teve como objetivo avaliar, in vitro, os efeitos da radiação com cobalto-60 nas propriedades mecânicas, morfológicas e químicas do esmalte e da dentina de dentes permanentes através da: 1- microdureza longitudinal; 2- microscopia eletrônica de varredura (MEV); e 3- espectroscopia de energia dispersiva de raios X (EDX). A microdureza do esmalte e da dentina (n=12 hemissecções vestibulares) foi avaliada em três profundidades (superficial, média e profunda), antes e a cada 10 Gy de irradiação, até uma dose cumulativa de 60 Gy. A morfologia do esmalte e da dentina foi avaliada por meio de MEV (n=8 hemissecções), em 2 hemissecções vestibulares irradiadas com dose cumulativa de 30 Gy, 2 hemissecções vestibulares irradiadas com dose cumulativa de 60 Gy e 4 hemissecções palatinas não irradiadas. A composição química do esmalte e da dentina foi avaliada por meio de EDX (n=4 hemissecções), utilizando-se as mesmas hemissecções previamente submetidas à MEV (com dose cumulativa de 60 Gy de irradiação, e nas hemissecções não irradiadas). Os dados foram analisados quanto à sua distribuição e submetidos à Análise de Variância a dois critérios. Para a diferenciação das médias, empregou-se o teste de Fisher. O nível de significância adotado foi de 5%. Com relação à microdureza no esmalte, pôde-se observar que houve diferença estatisticamente significante entre os grupos (p < 0,05). A microdureza no esmalte não irradiado não apresentou diferença estatisticamente significante em comparação com a do esmalte após irradiação com doses de 40, 50 e 60 Gy (p > 0,05), e apresentou-se maior que os valores de microdureza nas doses de 10, 20 e 30 Gy (p < 0,05). Com relação à microdureza nas diferentes profundidades pôde-se observar diferença significante (p < 0,05) entre elas, observando-se no esmalte superficial seus maiores valores. Na análise morfológica do esmalte observou-se que os espécimes irradiados apresentaram alterações crescentes, em função do aumento da dose de radiação, em comparação ao esmalte não irradiado. A porção interprismática tornou-se mais evidente após as doses de 30 e 60 Gy. Em relação à microdureza da dentina, pôde-se observar que houve diferença significante entre os grupos (p < 0,05). A microdureza na dentina não irradiada não apresentou diferença estatisticamente significante em comparação com a microdureza na dose de 40 Gy (p > 0,05) e apresentou valores superiores aos observados nas doses de 10, 20, 30, 50 e 60 Gy (p < 0,05). Em relação à microdureza nas diferentes profundidades avaliadas pôde-se observar diferença significante (p < 0,05) entre elas, sendo que a dentina média apresentou seus maiores valores. Na análise morfológica da dentina observou-se a presença de fendas na estrutura dentinária, túbulos dentinários colabados/destruídos e fragmentação das fibras colágenas nas doses de 30 e 60 Gy, sendo as alterações mais intensas com aumento da dose de irradiação, para todas as regiões analisadas, em comparação à dentina não irradiada. Na análise química do esmalte e da dentina irradiados observou-se discreto aumento de oxigênio (O) e diminuição de fósforo (P) e cálcio (Ca), em comparação aos espécimes não irradiados. Os resultados permitiram concluir que a radioterapia não influenciou a microdureza do esmalte, como um todo, entretanto, quando analisou-se nas diferentes profundidades do esmalte, verificou-se um aumento da microdureza na região superficial. Na dentina, a radioterapia ocasionou diminuição da microdureza após praticamente todas as doses de radiação, em comparação à dentina não irradiada, sendo que na região da dentina média observaram-se seus menores dos valores. As alterações morfológicas das estruturas do esmalte e da dentina foram crescentes com o aumento das doses de irradiação observando-se a porção interprismática mais evidente, presença de fendas e túbulos dentinários colabados/destruídos e fragmentação progressiva das fibras colágenas. Quimicamente, após a irradiação, tanto no esmalte como na dentina, observouse um discreto aumento na porcentagem de oxigênio e redução nas porcentagens de fósforo e cálcio.The present study had as objective to evaluate, in vitro, the effect of the radiation of 60 Cobalt (Co 60) in the mechanical, morphological and chemical properties of the enamel and of the dentine of permanent teeth by means of: 1- longitudinal microhardness; 2- scanning electron microscopy (SEM); and 3; energy dispersive X-ray spectroscopy (EDX). The microhardness of the enamel and of the dentine (n = 12 vestibular hemisections) was evaluated in three depths (superficial, medium and deep), before and at each 10 Gy of irradiation, until a total cumulative dose of 60 Gy. The morphology of the enamel and of the dentine was evaluated by means of a SEM (n = 8 hemisections), in 2 irradiated vestibular hemisections with total cumulative dose of 30 Gy, 2 irradiated vestibular hemisections with total cumulative dose of 60 Gy and 4 not irradiated palatine hemisections (control). The chemical composition of the enamel and of the dentine was evaluated by means of EDX (n = 4 hemisections), using the same hemisections previously submitted to SEM (with cumulative dose of 60 Gy of irradiation, and in the not irradiated hemisections). The data were analyzed about their distribution and submitted to the Analysis of Variance at two criteria. For the differentiation of the averages, the test of Fisher was used. The level of significance adopted was of 5%. About the longitudinal microhardness in the enamel, it was possible to be observed that there was no statistically significant difference between the groups (p < 0,05). The microhardness in the not irradiated enamel was similar to the enamel after the irradiation with doses of 40, 50 and 60 Gy (p > 0,05) and higher than the microhardness values in the doses of 10, 20, e 30 Gy (p < 0,05). About the microhardness in the different depths it was observed significant difference (p < 0,05) between them, being observed in the superficial enamel the greatest values of microhardness. In the morphological analysis of the enamel it was observed that the irradiated specimens presented growing alterations, due to the increase of the radiation dose, comparing to the not irradiated enamel. There was no difficulty in observing the prisms and the crystals after the irradiation, however the interprismatic portion became more evident after the radiation doses of 30 and 60 Gy. About the longitudinal microhardness of the dentine, it could be observed that there was significant difference between the groups (p < 0,05). The microhardness of the not irradiated dentine was not statistically significant compared to the microhardness in the dose of 40 Gy (p > 0,05) and it presented higher values to the observed ones in the doses of 10, 20, 30, 50 and 60 Gy (p < 0,05). About the relation to the microhardness in the different evaluated depths it was possible to observe significant difference (p < 0,05) among them, being that the medium dentine presented the highest values of microhardness. In the morphological analysis of the dentine it was observed the presence of cracks in the dentine structure, collapsed/destroyed dentine tubules and fragmentation of the collagen fibers in the doses of 30 and 60 Gy, being the alterations more intense with the increase of the dose of irradiation, for all the analyzed regions, comparing to the not irradiated dentine. In the chemical analysis of the irradiated enamel and the dentine it was observed the slight increase of oxygen (O) and decrease of phosphorus (P) and Calcium (Ca), comparing to the not irradiated specimens. The result allowed to be concluded that the radiotherapy occasioned the decrease of the microhardness of the enamel after the doses from 10 to 30 Gy, but in the following doses there was an increase of the microhardness, which became similar to the not irradiated enamel, being that in the superficial region it was observed the biggest increase of the microhardness. In the dentin, the radiotherapy caused decrease of the microhardness after practically all doses of radiation, comparing to the not irradiated dentine, being that in the region of the medium dentine the lowest values of microhardness were observed. The morphological alterations of the enamel and of the dentine structure were growing with the increase of the radiation doses observing the more evident interprismatic portion, presence of cracks and collapsed/destroyed dentine tubules and progressive fragmentation of collagen fibers. Chemically, after the irradiation, not only in the enamel but also in the dentin, it was observed a slight increase of percentage of the oxygen and decrease in the percentages of phosphorus and calcium.
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Caproni, Érica. "Estudo de eletrólitos sólidos cerâmicos à base de óxido de zircônio para a detecção de oxigênio." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-30032012-101612/.
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Tendo como vantagem a elevada resistência ao choque térmico da zircônia:magnésia e a alta condutividade iônica da zircônia:ítria, compósitos dessas cerâmicas foram preparados por meio da mistura, em diferentes concentrações, de eletrólitos sólidos de ZrO2: 8,6 mol% MgO e de ZrO2: 3 mol% Y2O3, compactação e sinterização. A caracterização microestrutural foi feita por meio de difração de raios X e microscopia eletrônica de varredura. A análise do comportamento térmico foi feita por dilatometria. As propriedades elétricas foram estudadas por meio de espectroscopia de impedância. Foi feita uma montagem experimental para monitorar a resposta elétrica gerada em função do teor de oxigênio a altas temperaturas. Os principais resultados mostram que os compósitos cerâmicos são parcialmente estabilizados nas fases monoclínica, cúbica e tetragonal, e apresentam comportamento térmico similar ao apresentado por eletrólitos sólidos de zircônia:magnésia de dispositivos sensores de oxigênio. Além disso, os resultados de análise de espectroscopia de impedância mostram que a adição da zircônia:ítria melhora o comportamento elétrico da zircônia:magnésia, e que resposta elétrica gerada é dependente do teor de oxigênio a 1000 °C, mostrando ser possível construir sensores de oxigênio utilizando compósitos cerâmicos.Taking advantage of the high thermal shock resistance of zirconia-magnesia ceramics and the high oxide ion conductivity of zirconia-yttria ceramics, composites of these ceramics were prepared by mixing, pressing and sintering different relative concentrations of ZrO2: 8.6 mol% MgO and ZrO2: 3mol% Y2O3 solid electrolytes. Microstructural analysis of the composites was carried out by X-ray diffraction and scanning electron microscopy analyses. The thermal behavior was studied by dilatometric analysis. The electrical behavior was evaluated by the impedance spectroscopy technique. An experimental setup was designed for measurement the electrical signal generated as a function of the amount of oxygen at high temperatures. The main results show that these composites are partially stabilized (monoclinic, cubic and tetragonal) and the thermal behavior is similar to that of ZrO2: 8.6 mol% MgO materials used in disposable high temperature oxygen sensors. Moreover, the results of analysis of impedance spectroscopy show that the electrical conductivity of zirconia:magnesia is improved with zirconia-yttria addition and that the electrical signal depends on the amount of oxygen at 1000 °C, showing that the ceramic composites can be used in oxygen sensors.
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Lagotzky, Stefan, Roman Barday, Andreas Jankowiak, Thorsten Kamps, Carola Klimm, Jens Knobloch, Günter Müller, Boris Senkovsky, and Frank Siewert. "Prevention of electron field emission from molybdenum substrates for photocathodes by the native oxide layer." Cambridge University Press, 2015. https://tud.qucosa.de/id/qucosa%3A39022.
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Comprehensive investigations of the electron field emission (FE) properties of annealed single crystal and polycrystalline molybdenum plugs, which are used as substrates for actual alkali-based photocathodes were performed with a FE scanning microscope. Well-polished and dry-ice cleaned Mo samples with native oxide did not show parasitic FE up to a field level of 50 MV/m required for photoinjector cavities. In situ heat treatments (HT) above 400°C, which are usual before photocathode deposition, activated field emission at lower field strength. Oxygen loading into the Mo surface, however, partially weakened these emitters. X-ray photoelectron spectroscopy of comparable Mo samples showed the dissolution of the native oxide during such heat treatments. These results reveal the suppression of field emission by native Mo oxides. Possible improvements for the photocathode preparation will be discussed.
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Ervin, Clara Ray. "Poultry Litter Ash as an Alternative Fertilizer Source for Corn." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/103199.
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Poultry litter ash (PLA) is a co-product from manure-to-energy systems that originated in response to increased poultry litter (PL) volumes generated in concentrated poultry production regions. Investigating PLA as a crop fertilizer is an alternative solution to balancing poultry and crop regional nutrient cycling in the Commonwealth of Virginia. As the expanding world population places pressure on the poultry industry to meet consumption demands, increased PL production presents an obstacle to identify alternative uses for increased volumes. Currently, Virginia produces 44 million broilers with PL produced predominately in the Shenandoah Valley and Eastern Shore. Likewise, a growing world population places pressure on crop production areas and subsequently finite natural resources used for crop fertilization. Poultry litter ash is an alternative phosphorus (P) and potassium (K) source enhancing transportation logistics, repurposing PL nutrients, and offers dual purpose as a fertilizer and an energy source when compared to PL.
Three PLA products [(fluidized bed bulk (FB Bulk), fluidized bed fly (FB Fly), and combustion Mix (CMix)], two manufactured co-products [(granulated poultry litter ash (GPLA), and ash coated urea (ACU)] were evaluated as P, K, and N sources for corn (Zea Mays L.) production in comparison to industry fertilizers [(PL, triple superphosphate (TSP), muriate of potash (KCL), and urea). A comprehensive examination of elemental composition, P speciation, P and K solubility, improved functionality into granulized forms, and field testing were conducted to discern PLA potential as an alternative fertilizer source.
Poultry litter ash products were evaluated by total elemental analysis, backscatter-electron dispersive (BSED) microscopy, and X-ray absorption near edge structure (XANES) spectroscopy. Poultry litter ash elemental concentrations were highly variable ranging from 50.6 to 102.0 g P kg -1 and 62.6 to 120.0 g K kg -1 and were comparatively higher than PL concentrations. Phosphorus structures that provided and controlled P solubility were Ca and Ca-Mg-phosphate compounds. Spectroscopy confirmed Ca structures as predominately monetite (dicalcium phosphate anhydrous; CaHPO4; log K ̊ 0.30) and brushite (dicalcium phosphate dihydrate; CaHPO4.2H20; 0.63 log K ̊ ) species that were supported by BSED and elemental stoichiometric ratios (Ca:P; 1.12 to 1.71:1). Additionally, GPLA acidified from FB Fly had higher brushite and monetite percentages described by spectra models, translating into a more soluble Ca-phosphate species when compared to FB Fly original P species.
Granulated poultry litter acidulation trials successfully identified a desired granulation point of 29% (14.5 g acid to 50 g PLA) phosphoric acid (75% H3PO4) acidulation. Acidulation dose response relationships created simple linear regression (SLR) equations that sufficiently (R2 > 0.80) described changes in total measurable P and water soluble P, pH, and exothermic reaction temperatures to increasing H3PO4 acidulation. Solubility tests included: sequential extraction, particle size effect on solubility, carbon effect on water soluble P, and Mehlich-1 extraction of PLA sources that confirmed decreased P solubility. A majority PLA P was found in bound plant unavailable fractions (87.7 to 97.7% P of total P). Granulated poultry litter ash had improved P plant available P of 36.0% P of total P. Carbon (C) effects on PLA P were examined by ashing PLA samples in a muffle furnace at 550 ̊C. Differences in total carbon content negatively impacted FB Bulk and CMix total P (1.30 and 4.56 g P kg -1); however, muffle furnace temperatures increased FB Fly total P by 6.74 g P kg -1.
All fertilizer products were investigated under field conditions in separate P, K and N corn studies across Virginia coastal plain soils to determine fertilizer effects on corn plant parameters [(most mature leaf (V6), corn ear leaf (R1), and grain (R6)]. Poultry litter P treatments, averaged over rate, recorded highest yield in both years. At eight of nine field sites, FB Bulk resulted in numerically or significantly higher Mehlich-1 concentrations than other P sources post-harvest. Although Mehlich-1 P increased, yield and plant parameters did not; which leads to the conclusion that PLA sources increased soil residual P that did not translate into immediate plant availability recorded within a growing season. Across plant efficacy parameters examined, PLA K is a comparable nutrient source and improved plant parameters when compared to control. Eighteen out of twenty-one plant parameters examined found similar ACU and urea effects on N concentrations. Therefore, ACU is a comparable N source to urea. When compared to industry fertilizer sources, we concluded that PLA is a slowly available P source, decreased P availability negatively affected early plant growth, K is a comparable nutrient source and improved plant parameters compared to control, and ACU effectively provided N to maintain sufficient corn growth. In conclusion, PLA co-products serve as a densified nutrient source that may provide plant available nutrients if processed to aid in nutrient distribution to grain producing areas.Doctor of Philosophy
Poultry litter ash (PLA) is a co-product from manure-to-energy systems that originated in response to increased poultry litter (PL) volumes generated in concentrated poultry production regions. Investigating PLA as an alternative crop fertilizer is essential to balancing poultry and crop regional nutrient cycling in the Commonwealth of Virginia. As the expanding world population places pressure on the poultry industry to meet consumption demands, heightened PL production presents an obstacle to identify alternative uses for increased volumes. Currently, Virginia produces 44,683,904 broilers with PL produced predominately in the Shenandoah Valley and Eastern Shore. Likewise, a growing world population places pressure on crop production areas and subsequently finite natural resources used for fertilization vital to maintaining crop yields. Poultry litter ash, a co-product from manure-to-energy systems, is an alternative phosphorus (P) and potassium (K) source enhancing transportation logistics, repurposing PL nutrients, and offers dual purpose as a fertilizer and an energy source when compared to PL. In this dissertation, three PLA products [(fluidized bed bulk (FB Bulk), fluidized bed fly (FB Fly), and combustion Mix (CMix)], two manufactured co-products [(granulated poultry litter ash (GPLA), and ash coated urea (ACU)] were evaluated as P, K, and N source for corn (Zea Mays L.) production in comparison to industry fertilizers (PL, triple superphosphate (TSP), muriate of potash (KCL), and urea). Each of the following chapters provides a comprehensive examination of the following topics: elemental composition, P speciation, P and K solubility, improved functionality into granulized forms, and field testing designed to provide parameters to conclude PLA potential as an alternative P, K and N source. In the second chapter, PLA products were evaluated by total elemental analysis, backscatter-electron dispersive (BSED) microscopy, and X-ray absorption near edge structure (XANES) spectroscopy. Poultry litter ash elemental concentrations are highly variable and are comparatively higher than PL concentrations. Phosphorus structure and species identified Ca as the primary element controlling P structure and subsequent solubility. The third component of this dissertation is granulation trials investigating phosphoric acid effects on granulizing and increasing total and water soluble P. Our results identified 29% (14.5 g acid to 50 g PLA) phosphoric acid acidulation for desired granule size. The third dissertation component examines PLA solubility. The results demonstrated PLA decreased P water solubility when compared to industry fertilizer sources. Granulated poultry litter ash demonstrated improved P plant availability due to the granulation process. The final and fourth dissertation components investigated PLA sources under field conditions in separate P, K and N corn studies across Virginia coastal plain soils to determine fertilizer effects on corn plant parameters. Minority of plant parameters tested revealed P control yielded numerically higher P concentrations than PLA P sources tested. Poultry litter P treatments, averaged over rate, recorded highest yield in both years. At eight of nine field sites, FB Bulk resulted in numerically or significantly higher Mehlich-1 concentrations than other P sources post-harvest. Although Mehlich-1 P concentrations increased, yield and plant parameters did not; which leads to the conclusion that PLA sources increased soil residual P that did not translate into immediate plant availability recorded within a growing season. Across plant efficacy parameters examined, PLA K is a comparable nutrient source and improved plant parameters when compared to controls. The majority of plant parameters examined found similar ACU and urea effects on N concentrations. Therefore, ACU is a comparable N source to urea. When compared to industry fertilizer sources, field results concluded that PLA is a slowly available P source, decreased P availability negatively affected early plant growth, K is a comparable nutrient source and improve plant parameters compared to control, ACU effectively provides N to maintain sufficient corn growth. In conclusion, PLA co-products serve as a densified nutrient source that may provide plant available nutrients if processed to aid in nutrient distribution to grain producing areas.
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Auta, Richard. "Purification and characterisation of novel recombinant β-glucosidases from aspergillus with application in biofuel production." Thesis, University of Wolverhampton, 2015. http://hdl.handle.net/2436/606935.
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β-glucosidases are important components of the cellulase enzyme system in which they not only hydrolyse cellobiose to glucose, but also remove the feedback inhibition effects of cellobiose on exoglucanase and endoglucanase thereby increasing the rate of cellulose degradation to fermentable sugars. A total of 166 proteins were identified as β-glucosidases after manual BLASTp search on the Aspergillus comparative database from eight species. Evidence for Horizontal Gene Transfer (HGT) of bacterial origin of some β-glucosidase genes was provided by their lack of introns, absence of some fungal specific amino acid insertions in their sequences and unusual positions in phylogenetic trees showing similarities to bacterial proteins. A rapid plate assay based on Congo red methods was developed to study the optimum parameters such as pH and temperature for growth of strains and activities of the enzymes produced. Bacterial cellulose (BC) was produced by Gluconacetobacter xylinus. For the first time a fully detailed characterization by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), Differential scanning calorimeter (DSC), Thermogravimetric analysis (TGA) and 13Carbon Solid State Nuclear Magnetic Resonance (SSNMR) of pure BC before and after treatment with a commercially available Aspergillus cellulase enzyme was demonstrated. Two encoding sequences for novel Aspergillus nidulans hydrophobin genes ANID_05290.1 and ANID_07327 that do not fall into either the class I or class II category of hydrophobins were successfully cloned. Two encoding sequences for a novel β-glucosidase gene from an Aspergillus niger strain from Nigeria were amplified and cloned from genomic DNA using PCR. Aspergillus nidulans β-glucosidases (AN2227 and AN1804) expressed in Pichia were purified to homogeneity by using ammonium sulphate precipitation and DEAE-Sephadex A-50 chromatography. Both enzymes had a remarkably broad pH and temperature profile. Further experiments on the development of a technology for lignocellulose degradation based on co-production of β-glucosidase with hydrophobin for biofuel production are suggested.
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PAGANINI, PAULA P. "Síntese e caracterização de nanopartículas de óxido misto de estanho/titânio dopadas com lantanídeos para marcação biológica." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10182.
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Made available in DSpace on 2014-10-09T12:35:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:56Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hettiarachchi, Chaminda Lakmal. "Organometal Halide Perovskite Solar Absorbers and Ferroelectric Nanocomposites for Harvesting Solar Energy." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7034.
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Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH3NH3PbI3-xClx), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH3NH3PbI3-xClx perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid and methylamine) are quite expensive. This work describes a novel, single-step, simple, and cost-effective solution approach to prepare CH3NH3PbI3-xClx thin films by the direct reaction of the commercially available CH3NH3Cl (or MACl) and PbI2. A detailed analysis of the structural and optical properties of CH3NH3PbI3-xClx thin films deposited by aerosol assisted chemical vapor deposition is presented. Optimum growth conditions have been identified. It is shown that the deposited thin films are highly crystalline with intense optical absorbance.
Charge carrier separation of these thin films can be enhanced by establishing a local internal electric field that can reduce electron-hole recombination resulting in increased photo current. The intrinsic ferroelectricity in nanoparticles of Barium Titanate (BaTiO3 -BTO) embedded in the solar absorber can generate such an internal field. A hybrid structure of CH3NH3PbI3-xClx perovskite and ferroelectric BTO nanocomposite FTO/TiO2/CH3NH3PbI3-xClx: BTO/P3HT/Cu as a new type of photovoltaic device is investigated. Aerosol assisted chemical vapor deposition process that is scalable to large-scale manufacturing was used for the growth of the multilayer structure. TiO2 and P3HT with additives were used as ETL and HTL respectively. The growth process of the solar absorber layer includes the nebulization of a mixture of PbI2 and CH3NH3Cl perovskite precursors and BTO nanoparticles dissolved in DMF, and injection of the aerosol into the growth chamber and subsequent deposition on TiO2. While high percentage of BTO in the film increases the carrier separation, it also leads to reduced carrier generation. A model was developed to guide the optimum BTO nanoparticle concentration in the nanocomposite films. Characterization of perovskite solar cells indicated that ferroelectric polarization of BTO nanoparticles leads to the increase of the width of depletion regions in the perovskite layer hence the photo current was increased by one order of magnitude after poling the devices. The ferroelectric polarization of BTO nanoparticles within the perovskite solar absorber provides a new perspective for tailoring the working mechanism and photovoltaic performance of perovskite solar cells.
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Kleinhans, Henrik. "Evaluation of the Carbonization of Thermo-Stabilized Lignin Fibers into Carbon Fibers." Thesis, Linköpings universitet, Kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120519.
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Thermo-stabilized lignin fibers from pH-fractionated softwood kraft lignin were carbonized to various temperatures during thermomechanical analysis (TMA) under static and increasing load and different rates of heating. The aim was to optimize the carbonization process to obtain suitable carbon fiber material with good mechanical strength potential (high tensile strength and high E-modulus). The carbon fibers were therefore mainly evaluated of mechanical strength in Dia-Stron uniaxial tensile testing. In addition, chemical composition, in terms of functional groups, and elemental (atomic) composition was studied in Fourier transform infrared spectroscopy (FTIR) and in energy-dispersive X-ray spectroscopy (EDS), respectively. The structure of carbon fibers was imaged in scanning electron microscope (SEM) and light microscopy. Thermogravimetrical analysis was performed on thermo-stabilized lignin fibers to evaluate the loss of mass and to calculate the stress-changes and diameter-changes that occur during carbonization. The TMA-analysis of the deformation showed, for thermo-stabilized lignin fibers, a characteristic behavior of contraction during carbonization. Carbonization temperatures above 1000°C seemed most efficient in terms of E-modulus and tensile strength whereas rate of heating did not matter considerably. The E-modulus for the fibers was improved significantly by slowly increasing the load during the carbonization. The tensile strength remained however unchanged. The FTIR-analysis indicated that many functional groups, mainly oxygen containing, dissociate from the lignin polymers during carbonization. The EDS supported this by showing that the oxygen content decreased. Accordingly, the relative carbon content increased passively to around 90% at 1000°C. Aromatic structures in the carbon fibers are thought to contribute to the mechanical strength and are likely formed during the carbonization. However, the FTIR result showed no evident signs that aromatic structures had been formed, possible due to some difficulties with the KBr-method. In the SEM and light microscopy imaging one could observe that porous formations on the surface of the fibers increased as the temperature increased in the carbonization. These formations may have affected the mechanical strength of the carbon fibers, mainly tensile strength. The carbonization process was optimized in the sense that any heating rate can be used. No restriction in production speed exists. The carbonization should be run to at least 1000°C to achieve maximum mechanical strength, both in E-modulus and tensile strength. To improve the E-modulus further, a slowly increasing load can be applied to the lignin fibers during carbonization. The earlier the force is applied, to counteract the lignin fiber contraction that occurs (namely around 300°C), the better. However, in terms of mechanical performance, the lignin carbon fibers are still far from practical use in the industry.