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Dissertations / Theses on the topic 'X-ray Raman scattering'
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Sun, Yu-Ping. "Spontaneous and stimulated X-ray Raman scattering." Doctoral thesis, KTH, Teoretisk kemi (stängd 20110512), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32859.
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The present thesis is devoted to theoretical studies of resonant X-ray scattering and propagation of strong X-ray pulses. In the first part of the thesis the nuclear dynamics of different molecules is studied using resonant X-ray Raman and resonant Auger scattering techniques. We show that the shortening of the scattering duration by the detuning results in a purification of the Raman spectra from overtones and soft vibrational modes. The simulations are in a good agreement with measurements, performed at the MAX-II and the Swiss Light Source with vibrational resolution. We explain why the scattering to the ground state nicely displays the vibrational structure of liquid acetone in contrast to excited final state. Theory of resonant X-ray scattering by liquids is developed. We show that, contrary to aqueous acetone, the environmental broadening in pure liquid acetone is twice smaller than the broadening by soft vibrational modes significantly populated at room temperature. Similar to acetone, the "elastic" band of X-ray Raman spectra of molecular oxygen is strongly affected by the Thomson scattering. The Raman spectrum demonstrates spatial quantum beats caused by two interfering wave packets with different momenta as the oxygen atoms separate. It is found that the vibrational scattering anisotropy caused by the interference of the "inelastic" Thomson and resonant scattering channels in O2. A new spin selection rule is established in inelastic X-ray Raman spectra of O2. It is shown that the breakdown of the symmetry selection rule based on the parity of the core hole, as the core hole and excited electron swap parity. Multimode calculations explain the two thresholds of formation of the resonant Auger spectra of the ethene molecule by the double-edge structure of absorption spectrum caused by the out-of- and in-plane modes. We predict the rotational Doppler effect and related broadening of X-ray photoelectron and resonant Auger spectra, which has the same magnitude as its counterpart-the translational Doppler effect. The second part of the thesis explores the interaction of the medium with strong X-ray free-electron laser (XFEL) fields. We perform simulations of nonlinear propagation of femtosecond XFEL pulses in atomic vapors by solving coupled Maxwell's and density matrix equations. We show that self-seeded stimulated X-ray Raman scattering strongly influences the temporal and spectral structure of the XFEL pulse. The generation of Stokes and four-wave mixing fields starts from the seed field created during pulse propagation due to the formation of extensive ringing pattern with long spectral tail. We demonstrate a compression into the attosecond region and a slowdown of the XFEL pulse up to two orders of magnitude. In the course of pulse propagation, the Auger yield is strongly suppressed due to the competitive channel of stimulated emission. We predict a strong X-ray fluorescence from the two-core-hole states of Ne created in the course of the two-photon X-ray absorption.<br>QC 20110426
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Minkov, Ivaylo. "Nuclear Dynamics in X-ray Absorption and Raman Scattering." Doctoral thesis, Stockholm : Theoretical Chemistry, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3902.
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Feng, Yejun. "Exciton spectroscopy using non-resonant x-ray Raman scattering /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9642.
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Bassi, Andrea Li. "X-ray and light scattering from nanostructured thin films." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4631/.
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The object of this thesis is the study of nanostructured thin films using inelastic fight scattering and elastic x-ray scattering techniques. Their use in combination with other techniques is a powerful tool for the investigation of nanostructured materials. X-ray, Raman and Brillouin characterisation of cluster-assembled carbon films, promising for applications in the field of catalysis, hydrogen storage and field emission, is here presented. X-ray reflectivity (XRR) provided a measure of the density. Raman spectroscopy showed that the local bonding in these amorphous films depends on the size distribution of the clusters and that it is possible to select the cluster size in order to grow films with tailored properties. Brillouin scattering provided a characterisation at the mesoscopic scale and an estimate of the elastic constants, revealing a very soft material. XRR was employed to study density, layering and roughness of a wide range of amorphous carbon films grown with different techniques. Some films possess an internal layering due to plasma instabilities in the deposition apparatus. By comparing XRR with Electron Energy Loss Spectroscopy, a unique value for the electron "effective mass" was deduced and a general relationship between sp(^3)-content and density was found. XRR and H effusion were used to determine the hydrogen content. A study of the size-dependent melting temperature in tin nanoparticle thin films was undertaken with a combined use of X-Ray Diffraction (XRD) and light scattering. A redshift in the position of a Rayleigh peak in the temperature-dependent Brillouin measurements was shown to be related to the melting of the nanoparticles and explained by an effective medium model. XRD also provided information on the low-level of stress in the particles. Low-frequency Raman scattering was used to study the behaviour of the acoustic modes of a single particle as a function of temperature.
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Privalov, Timofei. "Electronic and nuclear dynamics of X-ray processes." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3189.
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Alexandre, Thais Levatti. "Espectrometria de raios-X aliada a quimiometria no estudo de vegetais." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248802.
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Previous issue date: 2006<br>Resumo: O uso da região de espalhamento na espectrometria de raios-X (XRS, do inglês, X-Ray Spectrometry) aliada à quimiometria é uma aplicação recente que tem mostrado bons resultados na discriminação de amostras orgânicas. Nesse trabalho, a proposta de se utilizar XRS para solucionar um problema de classificação taxonômica de Lantana sp, utilizando-se folhas desse vegetal não foi alcançada devido à reconhecida evolução contínua desta espécie. No entanto, o estudo de espécies do gênero Musa e das famílias Polemoniaceae, Asteraceae e Portulacaceae, utilizando-se pseudofrutos e sementes, respectivamente foi bem sucedido. A análise de componentes principais (PCA) realizada com os espectros obtidos da irradiação dos pseudofrutos e das sementes mostrou boa correlação entre a disposição das amostras e a classificação nos níveis gênero, espécies e variedades. Variáveis que poderiam justificar a discriminação obtida desses vegetais foram estudadas como exemplo o estudo envolvendo a utilização de carboidratos. Foram realizadas: a regressão de sacarose, frutose e glicose em solução aquosa e frutose e glicose em suco, com bons coeficientes de linearidade (0,998; 0,995; 0,998; 0,994 e 0,991, respectivamente); a discriminação de carboidratos; a regressão do índice de doçura e a rotação específica da luz polarizada de carboidratos; e a regressão da inversão da sacarose. Além da discriminação dos vegetais e do estudo de carboidratos, esse trabalho também apresenta a fundamentação teórica para explicar o surgimento desta técnica e um provável potencial que ela poderá apresenta para o futuro<br>Abstract: The use of scattering on X-ray Spectrometry (XRS) allied to chemometrics is a new application that is showing good results in discrimination of organics. In the present work the proposal of applying XRS to solve the taxonomic classification of Lantana sp species, using leafs of these plants was not reached due to the evolution process this plant is still undergoing. Nevertheless, this motivated a discrimination study of species of Musa genus (banana) and species of Polemoniaceae, Portulacaceae and Asteraceae families, using fruits and seeds, respectively. Principal component analysis of spectra of fruits and seeds show good correlation between sample arrangement and taxonomic classification in genus, species and varieties. Looking for variables that could justify the discriminations obtained, studies were developed involving carbohydrates. It was realized: sucrose, fructose and glucose regression in aqueous solutions and fructose and glucose calibration in juice solutions with good linear coefficients (0.998; 0.995; 0.998; 0.994 e 0.991, respectively); carbohydrates discrimination; X-ray spectra correlation with sweetness degrees and specific rotation of polarized light of carbohydrates; and regression of kinetics of sucrose inversion. Besides the vegetable classifications and the carbohydrate studies, this work presents a theorical basis to explain the XRS characteristics, the history before the arising of this method and its potentialities for the future<br>Doutorado<br>Quimica Analitica<br>Mestre em Química
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Delhommaye, Steven. "Single-particle modelling of X-ray Absorption and X-ray Raman Scattering spectra : from the impact of vibrations on multipole transition channels to the implementation of L2,3 edges." Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS076.
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Ce travail de thèse porte sur les spectroscopies d’électrons de niveau de cœur ainsi que leur modélisation par la suite de code open source Quantum ESPRESSO. Il porte en particulier sur la Spectroscopie d’Absorption des rayons X (XAS), déjà bien établie, et la Spectroscopie Raman des rayons X (XRS), une alternative au XAS gagnant en popularité, par exemple dans le cas de mesures sous conditions extrêmes. Le premier objectif de cette thèse était l’étude de l’impact des vibrations thermiques des noyaux sur les contributions multipolaires en XAS et en XRS. En effet, le modèle QHA utilisé pour prendre en compte ces effets a déjà fait ses preuves dans le cas d’oxides légers, mais n’a jamais été utilisé pour étudier ces effets sur les canaux quadripolaire en XAS et monopolaire en XRS. L’étude repose sur la comparaison entre calcul et expérience, sur deux composés de référence : TiO2 rutile et α-Al2O3. Par ailleurs, un défaut du modèle QHA concernant la reproduction de subtils effets de dépendance angulaires a été découvert et corrigé par la théorie des groupes. Le second objectif de cette thèse était l’implémentation du calcul des seuils L2,3 en XRS dans le module XSpectra de Quantum ESPRESSO. Cette implémentation est inspirée des précédentes implémentations du calcul de seuils K en XRS et de seuils L2,3 en XAS. L'implémentation comprend les contribution monopolaire et dipolaire jusqu’au premier ordre du développement de l’opérateur de transition XRS. Elle est testée par comparaison entre calcul et expérience pour divers composés du soufre. Un bon accord entre calcul et expérience est obtenu, bien que très sensible à l’approximation du trou de cœur choisie<br>This thesis work focuses on core level spectroscopies and their modelling by Quantum ESPRESSO, an open-source suite of codes. In particular this work focuses on X-Ray absorption spectroscopy (XAS), already well established, and X-Ray Raman Scattering (XRS), proving to be an increasingly popular alternative to XAS, for example under harsh experimental conditions. The first objective of this work was to study the impact of the thermal vibrations of nuclei on the multipole contributions available in XAS and XRS. Indeed, the QHA model used in this work to account for these vibration effects has been used to study light oxides before, but never to assess these effects on the secondary contribution channels of XAS (quadrupole) and XRS (monopole). The study relies on comparison between calculation and experimental data on two well-known reference compounds, rutile TiO2 and α-Al2O3. Moreover, a flaw of the QHA model when trying to reproduce subtle angular dependence signals was discovered and corrected using group theory. The second objective of the thesis was to implement calculation of XRS L2,3 edges in the XSpectra module of Quantum ESPRESSO. It was inspired by the previous implementations of XAS L2,3 edges and XRS K edges calculations in XSpectra. The monopole and dipole contributions were implemented up to the first order of the expansion of the XRS transition operator. It was tested by comparing calculation and measured data on various sulphur compounds. Good agreement with data could be produced, but was found very sensitive to the chosen core hole approximation
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Fürsich, Katrin [Verfasser], and Bernhard [Akademischer Betreuer] Keimer. "X-ray and Raman scattering studies of novel phases in 3d and 4d transition metal oxides / Katrin Fürsich ; Betreuer: Bernhard Keimer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1223928926/34.
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Bizuti, Ariathemis Moreno. "Ordem local na transição a-Si:H - uc-Si." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278123.
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Previous issue date: 2005<br>Resumo: Silício amorfo hidrogenado (a-Si:H) é um material amplamente usado na indústria microeletrônica. Ele é normalmente preparado a partir da decomposição do silano (SiH4). A diluição do silano em hidrogênio (H2) resulta em a-Si:H com propriedades eletrônicas superiores devido ao ataque químico preferencial às ligações mal-formadas. Níveis elevados de diluição resultam na formação de silício microcristalino (µc-Si). O objetivo deste trabalho é estudar o ordenamento da vizinhança química do silício através da transição a-Si:H ® µc-Si por espectroscopia de absorção de raios-X (XAS). Como a maior parte da desordem em a-Si:H manifesta-se na forma de variações nos ângulos de ligação, é necessário estudar o regime de espalhamento múltiplo (XANES), que corresponde às primeiras dezenas de energia (eV) acima da borda de absorção. Filmes finos de silício próximo à transição amorfo-microcristalino foram preparadas por HWCVD a partir de SiH4 diluido em H2. Nas condições utilizadas, a nucleação de µc-Si ocorre a partir de uma espessura crítica de aproximadamente 100 nm. Depositando-se amostras em forma de cunha é possível obter uma superfície de a-Si:H de um lado da amostra e de µc-Si do outro.
Também foram investigadas amostras preparadas por PECVD em condições próximas à formação de pó no reator (chamadas de silício polimorfo, ou seja, entre amorfo e policristalino). Em princípio elas poderiam ter uma estrutura local mais ordenada<br>Abstract: Hydrogenated amorphous silicon (a-Si:H) is a material very used in the microelectronics industry. It is usually prepared starting from the decomposition of the silane (SiH4). Hydrogen dilution of the silane source gas is used to grow a-Si:H with superior electronics properties due to the preferential chemical attack to the bad formed bonding. High hydrogen levels induce the growth of microcrystalline silicon (µc-Si). The objective this work is study the order of the chemical neighborhood of the silicon through the transition a-Si:H ® µc-Si for x-ray-absorption Spectroscopy (XAS). As most of the disorder in the a-Si:H shows in the form of bonding angles variation, it is necessary to study the multiple scattering regime (XANES), that corresponds to the first dozens of energy (eV) above the absorption edge. Thin silicon films close the transition amorphous-microcrystalline was prepared for hot-wire chemical vapor deposition (HWCVD). For these conditions, the nucleation of the µc-Si oc-curs at a critical thickness of approximately 100 nm. Deposited the samples in the wedge form, it is possible to get a-Si:H surface in the one side and µc-Si in the other side.
Also prepared samples were investigated for PECVD in close conditions to the powder formation in the reactor (calls of silicon polymorphous, a silicon sample between amorphous and polycrystalline) with the local order structure<br>Mestrado<br>Física da Matéria Condensada<br>Mestre em Física
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Nyrow, Alexander [Verfasser], Metin [Akademischer Betreuer] Tolan, and Max [Gutachter] Wilke. "Iron containing compounds of the inner earth: X-ray Raman scattering from ambient to extreme conditions / Alexander Nyrow. Betreuer: Metin Tolan. Gutachter: Max Wilke." Dortmund : Universitätsbibliothek Dortmund, 2014. http://d-nb.info/1104947420/34.
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Al-Zein, Ali. "Order and Disorder of Relaxor and Ferroelectric Materials : structural and Vibrational Studies." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20078/document.
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Parmi les matériaux piézo-électriques, les pérovskites ferroélectriques à base de plomb sont connus pour avoir les meilleurs coefficients piézo-électriques et couplage électromécanique. Ils sont largement utilisés dans diverses applications industrielles et technologiques. Les "ferroélectrique relaxeurs" appartiennent à cette famille. Leur structure est caractérisée par la présence de nanorégions polaires orientées de façon aléatoire. Dans cette thèse, nous nous sommes intéressés à l'étude des propriétés structurales et dynamiques de matériaux ferroélectriques et relaxeurs tels que PbTiO3, PbZr0.52Ti0.48O3, PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3, et PbMg1/3Ta2/3O3 (PMT). La structure à longue et courte portée a été étudiée par diffraction de neutrons et spectroscopie d'absorption des rayons X (XAFS), alors que la spectroscopie hyper-Raman (HR) est utilisée pour sonder les vibrations. L'analyse de la structure locale de matériaux pérovskites complexes AB'B''O3 montre que la pression diminue le désordre statique des gros cations occupant le site B, tandis que le champ électrique appliqué a un effet opposé. Cette distortion induite sous champ pourrait être à l'origine des forts coefficient piézoélectrique dans ces matériaux. La diffusion HR dans PMN et PMT a permis d'observer pour la première fois le "mode mou" responsable de la dépendance en température de la constante diélectrique. L'analyse des règles de sélection et la description en modes propres des vibrations actives en HR, permet de rendre compte de l'implication de chaque atome dans le comportement structural en température des ferroélectriques relaxeurs<br>Among piezoelectric materials, lead-based ferroelectric perovskites are known to have the largest piezoelectric coefficients and electromechanical coupling. They are widely used in dfferent industrial and technological applications. The so-called "relaxors" belong to this family. Their structure is characterized by the presence of randomly oriented polar nanoregions. In this thesis, we are interested in studying the structural and dynamical properties of prototypical ferroelectric materials and relaxors such as PbTiO3, PbZr0.52Ti0.48O3, PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3, and PbMg1/3Ta2/3O3 (PMT). The long and short range structure has been investigated by neutron diffraction and X-ray absorption fine structure (XAFS), while hyper-Raman scattering (HRS) is used to probe the vibrations. The local structure analysis of complex perovskite materials AB'B''O3 shows that pressure reduces the static disorder of the large cation occupying the B-site, while an applied electric field has an opposite effect. This field-induced distortion might relate to the large piezoelectric coefficient in such materials. HRS in PMN and PMT allows the first observation of the "primary" soft mode responsible for the temperature dependence of the dielectric constant. The selection rule analysis reveals the nature of the HRS active vibrational bands and enables us to get insights about the involvement of each atom in the structural modifications upon temperature
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Ziegler, Fabian. "Investigation of the Structure and Dynamics of Multiferroic Systems by Inelastic Neutron Scattering and Complementary Methods." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E5A6-5.
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Chaudemanche, Samuel. "Caractérisation in situ de l'endommagement volumique par Spectroscopie Raman et rayons X de différents polypropylènes déformés en traction uniaxiale." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0263/document.
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L'utilisation de matériaux polymères a su s'imposer au cours du 20ième siècle, en remplaçant ou se combinant aux matériaux métalliques, pour des applications mécaniques toujours plus techniques. La grande diversité des propriétés physiques des polymères est intimement lié à leur forte complexité microstructurale, qui malgré leur utilisation massive reste, au demeurant, encore très incomprise. Afin de mieux comprendre les évolutions microstructurales aux échelles nano et micrométrique dont résultent le comportement macroscopique il est nécessaire de développer de nouvelles techniques de caractérisation in situ. Ce travail fait état de l'utilisation de la spectroscopie Raman couplée au système VidéoTractionTM afin d'obtenir des informations microstructurales de la déformation de polymère semi-cristallins. Pour cela, des polypropylènes de formulations diverses ont été étudiés, permettant de souligner le rôle joué par la matrice et les charges organiques et minérales dans le processus de déformation plastique. Des mesures in situ de l'orientation des chaînes macromoléculaires déterminées in situ par Raman ont été confirmées, au synchrotron Petra III d'Hambourg, par une expérience couplant le système VidéoTractionTM-Raman à un dispositif de diffusion des rayons X aux grands angles. L'endommagent volumique des matériaux a été étudié post mortem par Tomographie X et radiographie X. Les améliorations apportées au système VidéoTractionTM-Raman ainsi qu'une étude de la diffusion de la lumière incohérente de nos matériaux au cours de leurs déformations ont permis l'établissement d'un critère de mesure de l'endommagement volumique in situ par Raman<br>The use of polymer materials - replacing or combining with metallic materials - has successfully established itself in the 20th century for increasingly technical mechanical applications. The great diversity of polymers physical properties is closely related to their high microstructural complexity, which is still very misunderstood despite their massive use. The development of new techniques for in situ characterization allows to better understand the microstructural evolutions on nanoscale and micrometer scale which affect the macroscopic behavior. This work report the use of Raman spectroscopy coupled with the VideoTractionTM system in order to obtain information about the microstructural deformation of polymer. Various formulations of polypropylene were studied to highlight the role played by the polypropylene matrix and the organic and mineral fillers in the plastic deformation process. The in situ measures of the macromolecular chains' orientation determined by Raman were confirmed by the performing of an experimental setup coupling the Raman-VideoTractionTM system with a device of Wide angle X-ray scattering. The volume damage of material was studied post mortem using X-ray tomography. The improvements made to VideoTractionTM-Raman system and a study of the incoherent light scattering of our materials enabled the setting of a Raman criterion for measuring in situ the volume damage. The studies carried out to evaluate in situ macromolecular orientation and volume damage highlight the existence of competition between these two processes. The degree of influence of organic and mineral fillers in this competition within the polypropylene matrix was determined
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Genisel, Mustafa Fatih. "Synthesis Of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn Sulfides By Solid-gas Reactions, Investigation Of Structural And Conducting Properties." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12606746/index.pdf.
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In this study some of the first row transition metal oxides were transformed to metal sulfides by new solid gas reaction system.
Transition metal sulfides have wide application area in industry and technology. Several techniques are known for the production of metal sulfides. Such as reactions between metal or metal oxide with H2S, precipitation in several liquid medium, reaction between metal and sulfur in closed vessel, chemical vapor deposition (CVD) technique. These techniques will have some disadvantages<br>for example, reactants are rarely available or expensive materials, their production systems are complicated and hard to set up these systems, products contain oxygen or hydrogen or corresponding metal sulfate as impurities.
In our new sulfidizing system the reactants are metal oxides, carbon and SO2. These materials can be found easily. Especially, SO2 usage in this system is a big advantage of giving possibility of usage the hazardous waste product of SO2 in industry.
The sulfidizing gas mixture was obtained by passing SO2 over activated carbon at 750 OC in a vertical tubular furnace. The obtained gas contains, mainly, CS2, CO and COS. The sulfidizing reactions took place in the horizontal tubular furnace at 450OC-1250 OC. The duration of the reaction, (three hours), and flow rate (60ml/min) of the SO2 gas were kept constant. The products were examined by X-ray powder diffraction and Raman scattering spectroscopy.
All examined metal oxides were transformed to metal sulfides by sulfidizing gas mixture successfully. Ti3S5 was obtained from TiO2. Cr2S3 was obtained from Cr2O3. MnS (Alabandite) was obtained from MnO2. FeS and Fe1-xS (Pyrrhotite) were obtained from Fe2O3. Co9S8 (Cobaltpentlandite) and CoS (Jaipurite) were obtained from Co3O4. NiS was obtained from NiO. Cu7.2S, Cu1.6S (Calcocite-Q), Cu1.81S, Cu7S4 (Anilite) Cu9S5 (Digenite), Cu8S5 (Geerite) were obtained from CuO, ZnS was obtained from ZnO.
The electrical conductivity character of each product obtained by sulfidizing reaction was analyzed in the temperature range of 77 K-300 K. Titanium sulfide, cobalt sulfide and nickel sulfide showed metallic conductivity, cupper sulfide and iron sulfide showed semiconductor behavior in this temperature range.
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Atalay, Ramazan. "Optical and Structural Properties of Indium Nitride Epilayers Grown by High-Pressure Chemical Vapor Deposition and Vibrational Studies of ZGP Single Crystal." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/phy_astr_diss/60.
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The objective of this dissertation is to shed light on the physical properties of InN epilayers grown by High-Pressure Chemical Vapor Deposition (HPCVD) for optical device applications. Physical properties of HPCVD grown InN layers were investigated by X-ray diffraction, Raman scattering, infrared reflection spectroscopies, and atomic force microscopy. The dependencies of physical properties as well as surface morphologies of InN layers grown either directly on sapphire substrates or on GaN/sapphire templates on varied growth conditions were studied. The effect of crucial growth parameters such as growth pressure, V/III molar ratio, precursor pulse separation, substrate material, and mass transport along the flow direction on the optical and structural properties, as well as on the surface morphologies were investigated separately.
At present, growth of high-quality InN material by conventional growth techniques is limited due to low dissociation temperature of InN (~600 ºC) and large difference in the partial pressures of TMI and NH3 precursors. In this research, HPCVD technique, in which ambient nitrogen is injected into reaction zone at super-atmospheric growth pressures, was utilized to suppress surface dissociation of InN at high temperatures.
At high pressures, long-range and short-range orderings indicate that c-lattice constant is shorter and E2(high) mode frequency is higher than those obtained from low-pressure growth techniques, revealing that InN structure compressed either due to a hydrostatic pressure during the growth or thermal contraction during the annealing. Although the influence of varied growth parameters usually exhibit consistent correlation between long-range and short-range crystalline orderings, inconsistent correlation of these indicate inclination of InN anisotropy.
InN layers, grown directly on α-sapphire substrates, exhibit InN (1 0 1) Bragg reflex. This might be due to a high c/a ratio of sapphire-grown InN epilayers compared to that of GaN/sapphire-grown InN epilayers. Optical analysis indicates that free carrier concentration, ne, in the range of 1–50 × 1018 cm–3 exhibits consistent tendency with longitudinal-optic phonon. However, for high ne values, electrostatic forces dominate over inter-atomic forces, and consistent tendency between ne and LO phonon disappears.
Structural results reveal that growth temperature increases ~6.6 ºC/bar and V/III ratio affects indium migration and/or evaporation. The growth temperature and V/III ratio of InN thin films are optimized at ~850 ºC and 2400 molar ratio, respectively. Although high in-plane strain and c/a ratio values are obtained for sapphire-grown epilayers, FWHM values of long-range and short-range orderings and free carrier concentration value are still lower than those of GaN/sapphire-grown epilayers.
Finally, vibrational and optical properties of chalcopyrite ZGP crystal on the (001), (110), and (10) crystalline planes were investigated by Raman scattering and infrared (IR) reflection spectroscopies. Raman scattering exhibits a nonlinear polarizability on the c-plane, and a linear polarizability on the a- and b-planes of ZGP crystal. Also, birefringence of ZGP crystal was calculated from the hydrostatic pressure difference between (110) and (10) crystalline planes for mid-frequency B2(LO) mode.
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Gorce, Jean-Philippe. "Crystallisation and chain conformation of long chain n-alkanes." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19705/.
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Hydrocarbon chains are a basic component in a number of systems as diverse as biological membranes, phospholipids and polymers. A better understanding of the physical properties of n-alkane chains should provide a better understanding of these more complex systems. With this aim, vibrational spectroscopy has been extensively used. This technique, sensitive to molecular details, is the only one able to both identify and quantify conformational disorder present in paraffinic systems. To achieve this, methyl deformations have been widely used as "internal standards" for the normalisation of peak areas. However, in the case of n-alkanes with short chain length, such as n-C[44]H[90] for example, the infrared spectra recorded at liquid nitrogen temperature and reported here show the sensitivity of these latter peaks to the various crystal structures formed. Indeed, the main frequencies of the symmetric methyl bending mode were found between 1384 cm[-1] and 1368 cm[-1] as a function of the crystal form. Changes in the frequency of the first order of the L.A.M. present in the Raman spectra were also observed. At higher temperatures, non all-trans conformers, inferred from different infrared bands present in the wagging mode region, were found to be essentially placed at the end of the n-alkane chains. At the monoclinic phase transition, the concentration of end-gauche conformers, proportional to the area of the infrared band at 1342 cm[-1], increases abruptly. On the contrary, in the spectra recorded at liquid nitrogen temperature no such band is observed. We also studied the degree of disorder in two purely monodisperse long chain n-alkanes, namely n-C[198]H[398] and n-C[246]H[494]. The chain conformation as well as the tilt angle of the chains from the crystal surfaces were determined by means of low frequency Raman spectroscopy and S.A.X.S. measurements on solution-crystallised samples. The increase in the number of end-gauche conformers which was expected to occur with the increase of the tilt angle as a function of the temperature was not detected due to a perfecting of the crystals. Indeed, due to successive heating and cooling to -173°C, the concentration of non all-trans conformers was found to decrease within the crystals. Their numbers were found to be up to six times higher in n-C[198]H[398] crystallised in once folded form than when crystallised in extended form. The C-C stretching mode region of the spectra was used to identify the chain conformation and to estimate the length of the all-trans stem passing through the crystal layers at -173°C. The transition between once folded and extended form crystals was indicated by the presence of additional bands in this region at 1089 cm[-1], 1078 cm[-1] and 1064 cm[-1]. Some of those bands may be related to the fold itself. At the same time, a strong decrease of the intensity of the infrared bands present in the wagging mode region was observed. Finally, the triple layered structure proposed on the basis of X-ray measurements obtained from the crystals of a binary mixture of long chain n-alkanes, namely n-C[162]H[326] and n-C[246]H[494], was confirmed from the study of the C-C stretching mode region of the infrared spectra.
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Combet, Jérôme. "Désordre moléculaire dans les composés d'inclusion du tano : une approche par diffusion des rayons X et diffusion quasi élastique incohérente des neutrons." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10185.
Full textAbstract:
Le nitroxide c#9h#1#6no#2 (tano) forme des composes d'inclusion a canaux avec une grande variete de chaines lineaires (alcanes, monobromo alcanes. . . ). Les molecules de tano (reseau hote) s'organisent de facon a creer des canaux dans lesquels les molecules viennent s'inserer. A temperature ambiante, les molecules de tano et les chaines invitees sont dynamiquement desordonnees. Les cliches de diffraction de rayons x revelent la presence de plans diffus, perpendiculaires a l'axe b, caracteristiques de la nature des molecules incluses et typiques de la diffusion par des chaines de molecules non correlees. L'analyse du profil de diffusion met en evidence l'existence d'un ordre positionnel a courte distance le long des canaux. Les composes monobromes presentent de plus un ordre substitutionnel a courte portee. La projection de la structure parallelement a l'axe des canaux montre un desordre orientationnel des chaines autour de leur axe. Ce phenomene est egalement observe en diffusion quasi elastique incoherente des neutrons. Outre le desordre des molecules incluses, les molecules de tano peuvent adopter l'une ou l'autre des deux formes enantiomeres par inversion dynamique du cycle piperidinique. Chacun des groupements methyles effectue egalement des reorientations de 120 autour de leur position d'equilibre. Cette structure hautement desordonnee est marquee par l'apparition d'une ou deux transitions de phase selon la longueur des molecules incluses. Le mecanisme de transition est relie au blocage simultane des molecules de tano (inversion du cycle) et des molecules incluses, resultant de fortes correlations entre les deux sous reseaux.
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Safoula, Gabriel. "Caracterisation des couches minces polycristallines de selenium dope par un halogene (cl, i) et etude des interfaces metal-selenium (m = cr, bi, te)." Nantes, 1988. http://www.theses.fr/1988NANT2018.
Full textAbstract:
L'effet du dopage a ete analyse par diffraction rx, microscopie electronique a balayage, spectrometrie de masse des ions secondaires, diffusion raman, emission photoelectronique rx, emission electronique auger. On effectue des mesures de conductivite electrique, d'effet hall et de pouvoir thermoelectrique en fonction de la temperature, de la concentration initiale en halogene et du vieillissement. On en deduit que, seule une fraction d'halogene, non uniformement reparti, a un role electriquement actif
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Zschintzsch-Dias, Manuel. "Self organized formation of Ge nanocrystals in multilayers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-86838.
Full textAbstract:
The aim of this work is to create a process which allows the tailored growth of Ge nanocrystals for use in photovoltic applications. The multilayer systems used here provide a reliable method to control the Ge nanocrystal size after phase separation.
In this thesis, the deposition of GeOx/SiO2 and Ge:SiOx~ 2/SiO2 multilayers via reactive dc magnetron sputtering and the self-ordered Ge nanocrystal formation within the GeOx and Ge:SiOx~ 2 sublayers during subsequent annealing is investigated.
Mostly the focus of this work is on the determination of the proper deposition conditions for tuning the composition of the systems investigated. For the GeOx/SiO2 multilayers this involves changing the GeOx composition between elemental Ge (x = 0) and GeO2 (x = 2), whereas for the Ge:SiOx~ 2/SiO2 multilayers this involves changing the stoichiometry of the Ge:SiOx~ 2 sublayers in the vicinity of stochiometric silica (x = 2). The deposition conditions are controlled by the variation of the deposition rate, the deposition temperature and the oxygen partial pressure.
A convenient process window has been found which allows the sequential deposition of GeOx/SiO2 or Ge:SiOx ~2/SiO2 without changing the oxygen partial pressure during deposition. For stoichiometry determination Rutherford back-scattering spectrometry has been applied extensively.
The phase separation in the spatially confined GeOx and Ge:SiOx ~2 sublayers was investigated by X-ray absorption spectroscopy at the Ge K-edge. The Ge sub-oxides content of the as-deposited multilayers diminishes with increasing annealing temperature, showing complete phase separation at approximately 450° C for both systems (using inert N2 at ambient pressure). With the use of chemical reducing H2 in the annealing atmosphere, the temperature regime where the GeOx phase separation occurs is lowered by approximately 100 °C. At temperatures above 400° C the sublayer composition, and thus the density of the Ge nanocrystals, can be altered by making use of the reduction of GeO2 by H2.
The Ge nanocrystal formation after subsequent annealing was investigated with X-ray scattering, Raman spectroscopy and electron microscopy. By these methods the existence of 2 - 5 nm Ge nanocrystals at annealing temperatures of 550 (GeOx) - 700° C (Ge:SiOx ~2) has been confirmed which is within the multilayer stability range.
The technique used allows the production of extended multilayer stacks (50 periods ~ 300 nm) with very smooth interfaces (roughness ~ 0.5 nm). Thus it was possible to produce Ge nanocrystal layers with ultra-thin SiO2 separation layers (thickness ~ 1 nm) which offers interesting possibilities for charge transport via direct tunneling.
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Nguyen, Thi Yen. "Polymorphism of Organic Molecular Crystals." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18812.
Full textAbstract:
Die Kristallisation ist ein wichtiger Teilprozess bei der industriellen Herstellung vieler Materialien und Medikamente. Es ist jedoch ein vielschichtiger, physikalischer Vorgang, der noch nicht vollständig aufgeklärt ist.
Der Schwerpunkt dieser Arbeit liegt auf der Kristallisation von organischen, polymorphen Verbindungen aus unterschiedlichen Lösungsmitteln. Die Kristallisationsstudien wurden in einem akustischen Levitator mit Klimakammer, der den Einfluss von Temperatur, Feuchtigkeit und festen Oberflächen steuert, durchgeführt. Verschiedene analytische in-situ-Methoden und deren Kopplung kamen für die Analyse der Kristallisationsabläufe zum Einsatz. Als Unterstützung für die Interpretation der beobachteten Phänomene wurden unter äquivalenten Bedingungen Moleküldynamik-Simulationen vorgenommen.
Die Kristallisation der Modellverbindungen zeigte verschiedene spezifische Kristallisationspfade, die nicht dem klassischen Kristallisationsmodell entsprachen. Zunächst verdampfte das Lösungsmittel, was mit einer Konzentrationszunahme der Lösung und der Ausbildung von charakteristischen amorphen Phasen (Polyamorphismus) einherging, und schließlich trat die Kristallisation ein. Durch die oberflächenfreie Kristallisation wurde ausschließlich nur ein Polymorph ein- und derselben Verbindung als Kristallisationsprodukt isoliert. Die gezielte Wahl der Ausgangskonzentration und eines Lösungsmittels ermöglichte die Steuerung des Kristallisationsverlaufs hin zu einer gewünschten Kristallstruktur des untersuchten Materials.
Die Ergebnisse dieser Arbeit unterstützen das Verständnis über den komplexen Ablauf des Kristallisationsvorgangs, gleichzeitig zeigen sie weitere Ansätze auf, die Kristallisation zu untersuchen. Die neuen Erkenntnisse sind hilfreich bei der Optimierung der Herstellungsprozesse verschiedener Materialien.<br>Crystallization is a complex process, which is used in different processes in the industrial production of various materials. The limited understanding about its fundamental mechanisms challenges the control of crystallization and influences the quality of the materials. The research of this work concentrates on the crystallization studies of organic model systems (active pharmaceutical ingredients) from different organic solvents in an acoustic levitator. This specific sample environment regulates the influence that solid surfaces, temperature, and humidity have on the crystallization process. The investigations were performed with in situ analytical techniques and theoretical simulations to gain a comprehensive insight into processes, occurring intermediates, and required reaction conditions. The results show that the model systems follow specific crystallization pathways different than those predicted by the classical nucleation theory. The crystallization proceeded via the evaporation of the solvent and the formation of characteristic amorphous phases (polyamorphism) into one crystalline structure of the compound. The targeted choice of the solvent and the concentration enabled the guidance of the pathways, therefore, resulting in the isolation of one desired crystalline structure.
The findings are of great interest and they help explain the crystallization mechanisms on a molecular level, which is a fundamental contribution for the optimization of manufacturing processes.
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Bright, Andrew G. "Mechanistic Insights into the Stabilisation of Biopharmaceuticals using Glycine Derivatives. The Effect of Glycine Derivatives on the Crystallisation, Physical Properties and Behaviour of Commonly used Excipients to Stabilise Antigens, Adjuvants and Proteins in the Solid State." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/15943.
Full textAbstract:
This dissertation has focused on studying the effect of four glycine derivatives on the solid state properties of mannitol, glycine, and sucrose when freeze dried into blended mixtures. The primary goal was to assess their value for use in the stabilisation of vaccines in the solid state, by examining key physical and chemical characteristics, which have been documented to be beneficial to the stabilisation of biopharmaceutical formulations. The novel excipients; dimethyl glycine, and trimethyl glycine, were shown to retard the crystallisation and increase the overall glass transition temperature, of mannitol, when freeze dried as evidenced by DSC and Powder X-ray diffraction. Mannitol’s glass transition temperature increased from 100C to 12.650C and 13.610C when mixed with methyl-glycine and dimethyl glycine respectively. The glycine derivatives did not show the same effect on sucrose which remained amorphous regardless of the concentration of the other excipient. The different behaviour with the sucrose system was thought to be due to relatively high glass transition temperature of sucrose. Conversely glycine remained highly crystalline due it’s relatively low glass transition temperature. The novel excipient formulations were also assessed for their effect on the aggregation of the adjuvant aluminium hydroxide when freeze dried by Dynamic Light Scattering (DLS).The formulations containing the glycine derivatives all caused a decrease in the aggregation size of the adjuvant from ~26 μm, to 185 nm in the presence of methyl glycine. The effects of lysozyme and viral antigen on the adjuvants were also examined showing that the addition of the virus did not affect the size of the aggregates formed, however lysozyme showed significant decreases in the aggregates formed. Examination of the freezing method were also made showing that faster freezing rates produced smaller aggregates of the adjuvant. When investigating the rate at which the excipients lost water during secondary drying there was evidence of the formation of hydrates of glycine, trimethyl glycine, and mannitol has shown that the glycine derivatives have attributes which would be beneficial in stabilising vaccines in the solid state when freeze dried.
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Lachgar, Abdessadek. "Etude cristallographique et spectroscopique de quelques phases nouvelles du systeme k : :(2)o-sb::(2)o::(5)-p::(2)o::(5)." Nantes, 1987. http://www.theses.fr/1987NANT2015.
Full textAbstract:
Identification de cinq phases nouvelles. Determination de la structure pour chacune d'entre elles par diffraction rx sur monocristal. Les edifices covalents sont construits a partir d'octaedres sbo::(6) partageant des sommets ou des aretes, et de tetraedre po::(4) lies aux octaedres par deux, trois ou leurs quatre sommets. Caracterisation par absorption ir, diffusion raman et spectrometre rmn du **(31)p
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Silva, Alessandra dos Santos. "Estudo de propriedades físicas de nanocristais de ZnTe e Zn1-xAxTe (A = Mn; Co) no sistema vítreo P2O5 ZnO Al2O3 BaO PbO." Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/15620.
Full textAbstract:
Fundação de Amparo a Pesquisa do Estado de Minas Gerais<br>In this work, Zn1-xAxTe (A = Mn, Co) diluted magnetic semiconductors (DMS) nanocrystal (NCs) were successfully grown in the P2O5 ZnO Al2O3 BaO PbO glass system synthesized by the method of Fusion-Nucleation, after subjecting to appropriate thermal annealing. Various experimental techniques were used in this study in order to get a comprehensive understanding of the optical, morphological, structural and magnetic properties these NCs. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) images revealed the size of both of Zn1-xMnxTe and Zn1-xCoxTe NCs. From the vibrating sample magnetometer (VSM) technique, there was growth behavior of magnetization and magnetic susceptibility as a function of the Mn concentration in the samples containing Zn1-xMnxTe NCs. At lower Mn concentrations, the sp electrons of ZnTe host semiconductor interact with the d electrons of Mn2+ ions, resulting in the sp-d exchange interaction, which causes a small increase in susceptibility. At higher Mn concentrations, the d-d exchange interaction between Mn atoms dominates over the sp-d exchange interaction, resulting in an abrupt increase in susceptibility. The EPR spectra, in addition to prove the results exhibited the well-known sextet hyperfine lines of Mn2+ ions, since samples with low Mn concentrations revealed the presence of Mn2+ ions within and near the surface of the ZnTe NCs. From the optical absorption spectra (OA) and photoluminescence (PL), analyzed on the basis of crystal field theory (CFT) as well as of the diffraction X-ray (XRD), Raman scattering (RS) and electron microscopy transmission (TEM) techniques, the substitutional incorporation of Mn2+ ions was confirmed up to its solubility limit (x = 0.100) ZnTe NCs. Above this concentration, can observe the formation of manganese oxide NCs such as MnO and MnO2, since the nucleation rate for the formation of these NCs is greater than that of Zn1-xMnxTe NCs, at high concentrations. Furthermore, from the PL spectra, it was found that it is possible to tune the emission of energy related to transition 4T1(4G) → 6A1(6S) of Mn2+ ions, of the spectral orange region to the near infrared, depending on Mn concentration. This is possible due to the variation of the local crystal field, where these ions are inserted. From the OA spectra, analyzed on the basis of CFT, it showed that Co2+ ions are substitutionally incorporated in tetrahedral sites of ZnTe NCs, due to its characteristics transitions in visible and near infrared spectral region. This evidence has been enhanced from MFM images, since NCs doped with magnetic ions, magnetically respond when induced by the magnetization of the probe.<br>Neste trabalho, nanocristais semicondutores magnéticos diluídos (SMD) de Zn1-xAxTe (A = Mn; Co) foram crescidos com sucesso no sistema vítreo P2O5 ZnO Al2O3 BaO PbO, sintetizado pelo método de Fusão-Nucleação, após submetê-lo a tratamento térmico apropriado. Várias técnicas experimentais foram utilizadas neste estudo a fim de obter um entendimento compreensivo das propriedades ópticas, morfológicas, estruturais e magnéticas desses NCs. Imagens de microscopia eletrônica de transmissão (MET) e microscopia de força atômica (MFA) revelaram o tamanho tanto de NCs de Zn1-xMnxTe quanto de Zn1-xCoxTe. A partir da técnica de magnetometria de amostra vibrante (MAV), verificou-se o crescimento da magnetização e o comportamento da susceptibilidade magnética, em função da concentração de Mn, em amostras contendo NCs de Zn1-xMnxTe. Em baixas concentrações de Mn, os elétrons sp do semicondutor hospedeiro ZnTe, interagem com os elétrons d dos íons Mn2+, resultando na interação de troca sp-d, que provoca um pequeno aumento na susceptibilidade magnética. Já, em concentrações mais elevadas de Mn, a interação de troca d-d entre átomos de Mn domina a interação de troca sp-d, o que resulta em um aumento abrupto da susceptibilidade. Os espectros RPE, além de comprovar esses resultados, exibiram o bem conhecido sexteto de linhas hiperfinas de íons Mn2+, uma vez que amostras com baixas concentrações de Mn revelaram a presença de íons Mn2+ no interior e próximos à superfície dos NCs de ZnTe. A partir dos espectros de absorção óptica (AO) e fotoluminescência (FL), analisados com base na teoria do campo cristalino (TCC), bem como das técnicas de difração de raios-X (DRX), espalhamento Raman (ER) e microscopia eletrônica de transmissão (MET), confirmou-se a incorporação substitucional de íons Mn2+ até seu limite de solubilidade nominal (x = 0,100) em NCs de ZnTe. Acima dessa concentração, observa-se a formação de NCs de óxido de manganês, tais como MnO e MnO2, uma vez que a taxa de nucleação para a formação desses NCs é maior que a de NCs de Zn1-xMnxTe, em altas concentrações. Além disso, a partir dos espectros FL, verificou-se que é possível sintonizar a energia de emissão relacionada à transição 4T1(4G) → 6A1(6S) de íons Mn2+, da região espectral laranja ao infravermelho próximo, em função da concentração de Mn. Isso é possível devido à variação do campo cristalino local, onde esses íons estão inseridos. A partir dos espectros AO, analisados com base na TCC, evidenciou-se que íons Co2+ são incorporados substitucionalmente em sítios tetraédricos de NCs de ZnTe, devido às suas transições características na região espectral do visível e infravermelho próximo. Essa evidência foi reforçada a partir de imagens de MFM, uma vez que os NCs, dopados com íons magnéticos, respondem magneticamente quando induzidos pela magnetização da sonda.<br>Doutor em Física
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Lin, Yuhsun, and 林佑勳. "Synthesis of Plasmonic Fluorescent Au-Ag Alloy Nanoparticles by Synchrotron X-ray Irradiation and Their Applications in Surface-Enhanced Raman Scattering and Photoluminescence." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/48010867400564043824.
Full textAbstract:
碩士<br>國立中正大學<br>物理學系暨研究所<br>99<br>In this thesis, Au-Ag alloy nanoparticles have been successfully synthesized via using extremely high intensity Synchrotron x-ray irradiation. Both UV-visible absorption and TEM results indicate that the nanoparticles are with uniform size about 2.2 nm～2.3 nm, and it can be tuned by changing the quantity of PVP.
The surface-enhanced Raman scattering（SERS）spectra of Au-Ag alloy nanoparticles change with the Au-Ag composition ratio, which indicates the nanoparticles are highly crystalline of true alloy instead of core-shell structure. Photoluminescence（PL）measurements show that the fluorescence properties also can be tuned by changing the Au-Ag composition ratio. We have also found the fluorescence resonance energy transfer（FRET）between PVP and silver nanoparticles. The FRET mechanism can enhance PL emission of silver nanoparticles.
From the surface-enhanced Raman scattering（SERS）and Photoluminescence （PL）measurements, Au-Ag Alloy nanoparticles with PVP can be called plasmonic fluorescent nano dots. It simultaneously provides fluorescence and plasma characteristics and should be useful for multimodal bioimaging applications.
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Bianco, Leonardo Martín. "Estudio de procesos (1s, 2p3/2) y (1s 2p1/2) en el espectro Raman resonante de rayos x de alta resolución en Titanio." Bachelor's thesis, 2010. http://hdl.handle.net/11086/30.
Full textAbstract:
Tesis (Lic. en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2010.<br>En este trabajo se estudiaron los procesos de dispersión inelástica resonante de rayos x (RIXS) (1s,2p3/2) y (1s,2p1/2) en Ti. Este estudio se realizó con datos experimentales obtenidos con alta resolución en el Laboratorio Nacional de Luz de Sincrotrón (LNLS) ubicado en Campinas, Brasil. De estos
procesos se estudió la evolución del FWHM (ancho total a media altura), la posición del máximo del espectro y la sección eficaz integrada, cuando la energía de incidencia se aproxima al borde K de absorción. El modelo teórico del electrón independiente se utilizó para la interpretación de los resultados experimentales. El acuerdo entre los resultados experimentales y teóricos resultó muy satisfactorio si se tienen en cuenta los efectos de la resolución instrumental.
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Cheng, Hsiang-Wei, and 鄭翔瑋. "In Situ Raman Spectroscopic and Grazing Incidence Small Angle X-ray Scattering Studies of the Formation Mechanism of MCM-41 at the Air-Water Interface." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/47906383672903594468.
Full textAbstract:
碩士<br>東海大學<br>化學系<br>98<br>The major purpose of this study is use cationic surfactant（cetyltrimethylammonium brombide, C16TAB）as templated, by controlling Tetraethylorthosilicate（TEOS）concentration, acidity and temperature. We used in situ experiment study film formed phase transformation mechanism at the air-water interface.
By using Raman spectroscopic to observe the hydrolysis reaction, and using Grazing incidence small angle x-ray scattering（GISAXS）in air-water interface and Small angle x-ray scattering（SAXS）in bulk solution to observe the phase transformation of C16TAB/TEOS film growth.
Experimental results show Raman spectrometer analysis hydrolysis rate constants（kH）is ca. 8.95× 10-2~ 1.03× 10-1 s-1 ; GISAXS analysis C16TAB /TEOS film is hexagonal structure, route are three main categories: 1. the lamellar route （lamellar phase → hexagonal phase）2. the direct route（isotropic phase → hexagonal phase） and 3. the nematic route（nematic phase → hexagonal phase）; We found out that the routes of SAXS and GISAXS are the same. As compared to films synthesized in bulk solution, the air-water interface exhibit faster kinetics and much better aligned channel domains.
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Robledo, José Ignacio. "Avances en espectroscopía por dispersión inelástica resonante de rayos X en baja y alta resolución." Doctoral thesis, 2019. http://hdl.handle.net/11086/11285.
Full textAbstract:
Tesis (Doctor en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación, 2018.<br>La presente tesis doctoral está centrada en el uso de la Dispersión Inelástica Resonante de Rayos X (RIXS) para la determinación del entorno químico de un átomo emisor a partir de espectros colectados mediante sistemas dispersivos en energía, los cuales pueden obtenerse en laboratorios de rayos X convencionales o en facilidades sincrotrón. En la primera parte de esta tesis se describe la técnica EDIXS (Energy Dispersive Inelastic X-Ray Scattering ) que desarrollamos en base al uso de métodos multivariados para extraer información de espectros RIXS, colectados por un sistema dispersivo en energía y con un haz incidente monocromático. En la segunda parte se describe el diseño, construcción y funcionamiento de un nuevo espectrómetro. Este sistema está basado en un cristal analizador de forma cónica discreta, que selecciona los fotones provenientes de la muestra emisora y los difracta hacia distintas posiciones de la superficie de un detector sensible a la posición.<br>This thesis is focused in the use of Resonant Inelastic X-Ray Scattering (RIXS) in energy dispersive mode for chemical environment characterization of the emitting atoms. These spectra may be easily obtained in synchrotron radiation facilities and also in conventional x-ray laboratories. The thesis is divided in two parts. The first one describes our technique, called Energy Dispersive Inelastic X-Ray Scattering (EDIXS), which is based in the use of multivariate statistical analyses for extracting information from RIXS spectra measured with energy dispersive systems, and a monochromatic beam. The second part is dedicated to the design, construction and fabrication of a new spectrometer, consisting on a crystal analyzer with a "Discrete Conical" shape, that selects photons emitted from the sample and diffracts them towards the surface of a position sensitive detector.
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Walker, Andrew. "Relating the structure of insect silk proteins to function." Phd thesis, 2013. http://hdl.handle.net/1885/140997.
Full textAbstract:
Silks are extracorporeal fibrous protein materials. Classically,
silkworm (Bombyx mori) and orb-spiders (Arachnida: Araneidae)
have served as model organisms in which to investigate silk
protein structure-function relationships. However, silk
production has evolved multiple times in insects. The silk
proteins of many insects do not fold into the beta-sheet
structures found in silkworm and spider silks but into
coiled-coils, collagen helices or polyglycine helices. Therefore,
the structure-function relationships elucidated for silkworm and
spider silk proteins may be too narrow to apply to insect silk
proteins generally. To increase the available data, I examined
silk production by raspy crickets (Orthoptera: Gryllacrididae),
silverfish (order Thysanura), praying mantises (order Mantodea),
glow-worms (Diptera: Keroplatidae), and sawflies (Hymenoptera:
Tenthredinidae). Silk protein primary structures were
investigated using transcriptomics, mass spectrometry, and amino
acid analysis; secondary and tertiary structures were
investigated by infrared and Raman spectroscopy, nuclear magnetic
resonance, circular dichroism spectroscopy, and bioinformatics.
Novel features of silk production were related to idiosyncrasies
of each insect group, while features found in multiple
silk-producing groups were associated with general mechanisms of
silk production. A comparative analysis of silk proteins revealed
a correlation between predominant secondary structure type and
more general architectural features such as length and repeat
regularity: silk proteins that fold into coiled-coils and
collagen helices had low molecular weights and high repeat
regularity, suggesting they fold into short semi-rigid rods;
beta-sheet-forming silk proteins were found to be more variable
in molecular weight and have lower repeat regularity. Based on
these data, I propose three major mechanisms of silk fabrication
by insects: a) mesogenic ordering of short rod-like proteins, a
process for which the coiled-coil and collagen structures are
well-suited; b) molecular extension of long flexible protein
chains to promote intermolecular bonding, which is suitable for
the formation of beta-sheet-rich silks; and c) entanglement of
protein chains, which is suited to silks with a high degree of
disorder. Thus, many features of insect silk proteins are
adaptations for material fabrication. In a few cases, particular
structural motifs constituted adaptations conferring a mechanical
property required for the silk's function in the solid state.
However more often proteins were observed to have features
promoting dense protein packing in a general way. I explain these
data by consideration of how silk mechanical behaviour relates to
the fitness advantage conferred to individual insects by silk
production. Specifically, I suggest protein features ensuring
structural homogeneity and molecular orientation result in silk
materials with mechanical properties sufficient for most
purposes. Further increases in properties such as strength lead
to little or no fitness increase. Local maxima in the fitness
landscape associated with distinct protein secondary structures
or fabrication mechanisms trap silk proteins in one of several
states. Overall, silk protein evolution can to a large extent be
understood as convergence of a number of independently co-opted
proteins of other functions toward one of several distinct
functional archetypes.