Dissertations / Theses on the topic 'Diamond Anvil Cell (DAC)'
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Hadjikhani, Ali. "Raman Spectroscopy Study of Graphene Under High Pressure." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/656.
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Due to its exceptional mechanical and electrical properties, graphene (one layer sheet of carbon atoms) has attracted a lot of attention since its discovery in 2004. The purpose of this research is to compare the Raman spectra of graphene with plasma treated graphene sheets which have been treated by changing the different parameters affecting the plasma treatment like gas flow, power and pressure and treatment time. The graphene we used for our high pressure studies are 4-5 layer CVD deposited graphene samples prepared by our collaborators in Dr. W. B. Choi’s group. First we report a Raman spectroscopy study of graphene on copper substrate at high pressures. Diamond anvil cell (DAC) was used to generate pressure. In situ Raman spectra were collected at pressures up to 10 GPa. The results indicate that the G band of graphene shifts with pressure significantly (about 5 cm-1/GPa) whereas the 2D band changes very little. The plasma treated samples were loaded into DAC. Raman spectrum was captured. Parts of the spectrum which were not related to the grapheme peak position were eliminated. The background was reduced. Peaks were found and fitted using FITYK software and the shift of each peak compared to its last position was observed when the pressure was increased. Next we studied plasma treated graphene samples treated with different partial pressure treatments under high pressure and compared them to each other using zirconia anvil cell with the same method.
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Begen, Burak. "INFLUENCE OF PRESSURE ON FAST DYNAMICS IN POLYMERS." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1195437587.
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Dzyabura, Vasily. "Pathways to a Metallic Hydrogen." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10737.
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The primary subject of this thesis is the study of warm dense hydrogen by means of pulsed laser heating in the pressure region 1 to 2 Mbar and temperatures above the melting line, where a liquid-liquid phase transition from the insulating molecular fluid to a conducting atomic hydrogen fluid, so called plasma phase transition (PPT), was predicted to take place. The first evidence of the PPT under static compression is reported. The observations are in agreement with the negative slope phase line predicted by ab initio methods.Physics
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Sly, Jonathan L. "High-pressure optical studies of III-V semiconductors using the diamond anvil cell." Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/843077/.
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High pressure photoluminescence techniques have been used to investigate bulk and heterostructure properties in a number of III-V semiconductor materials systems. The results are reported in this thesis along with a description of the experimental procedures. The indirect band-gaps of a series of InxGa1-xSb/GaSb quantum-wells have been measured. The results have been extrapolated to zero indium content to give the indirect band-gaps of bulk GaSb; values quoted in the literature vary widely. We obtain results consistent with accepted values but cannot refine them due to experimental errors arising from using ruby as a pressure gauge. A development of the experimental technique is proposed which would eliminate this source of error. The low-temperature F and X band-gaps have been determined in bulk (AlxGa1-x)0.5In0.5P functions of composition; we obtain E8(T)=(1.985+0.61x)eV and E8(X)=(2.282+0.085x)eV respectively. Lower limits have been put on the position of the L minima in this system and 1% compressively strained Ga0.38,In0.62P. Band offsets have been determined in unstrained (y=0.5) and 1% (y=0.62) compressively strained Ga1-yInyP/(AlxGa1-x)0.5 In0.5P; we obtain Ev(meV)=63x+157x2 and Ec(meV)=547x-157x2 for the unstrained system and Ev(meV)=72+63x+157x2 and Ec(meV)=72+547x-157x2 for the strained system. Effects of atomic ordering on the conduction band of Ga0.5In0.5P have been investigated. An investigation of anomalous pressure coefficients in strained InxGa1-x As has been carried out. A strain-related reduction in pressure coefficients (similar to that reported for InxGa1-xAs/GaAs) is found in In0.67Ga0.33As/InGaAsP quantum-wells grown on [001] substrates, but not in InGaAs/GaAs grown on [111] substrates. Preliminary results from tensile samples show evidence of increased pressure coefficients. A new X-ray powder-diffraction technique is described for direct investigation of the elastic behaviour of strained InGaAs.
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Okuchi, Takuo, George D. Cody, Ho-kwang Mao, and Russell J. Hemley. "Hydrogen bonding and dynamics of methanol by high-pressure diamond-anvil cell NMR." American Institute of Physics, 2005. http://hdl.handle.net/2237/7067.
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Smith, D. "Hydrogenation of monolayer graphene in the diamond anvil cell and supercritical phenomena in methane." Thesis, University of Salford, 2016. http://usir.salford.ac.uk/38156/.
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Functionalisation with hydrogen could allow exploitation of the remarkable electronic properties of graphene by creating tuneable electronic band gaps as well as offering access to its incredibly high surface area-to-volume ratio for uses in advanced materials by opening pathways to conventional organic chemistry on the material. While partially-hydrogenated graphene is regularly produced and its properties studied, the current methods of producing the material – which typically employ bombarding graphene with atomised hydrogen – have not yet shown the potential to synthesise fully-hydrogenated graphene, termed graphane. This thesis describes an alternative method of hydrogenating graphene by heating the material in an atmosphere of molecular hydrogen under high pressure (2.6 – 6.5 GPa) in a diamond anvil cell. The hydrogen content of functionalised samples can be estimated by observing the Raman spectrum and such analysis suggests that the diamond anvil cell method currently hydrogenates samples to an extent that is competitive with existing methods. By tailoring the sample architecture to allow hydrogen direct access to both sides of a graphene crystal, it is feasible that the diamond anvil cell method of hydrogenation could be used to synthesise the first graphane crystal. Also presented in this thesis is a series of experiments probing methane in the supercritical region of its pressure-temperature phase diagram, combining Raman spectroscopy and direct structural measurements through X-ray diffraction. At 298K, we observe discontinuous changes in the vibrational Raman spectrum of methane which are not accompanied by a change in density. This phenomena may be explained by a crossing of the recently-theorised Frenkel line or by critical point proximity effects described by Widom in the 1960s. The Raman discontinuity is not observed at 523 K, suggesting that alternative methods must be employed to conclusively determine the presence (or absence) of the Frenkel line.
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Kondrat'yev, Andreiy I. "Finite element modeling and computer simulation of stresses and strains in diamond anvil cell devices." Birmingham, Ala. : University of Alabama at Birmingham, 2006. https://www.mhsl.uab.edu/dt/2008r/kondratyev.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2006.Additional advisors: Heng Ban, Renato P. Camata, Krishan K. Chawla, Joseph G. Harrison. Description based on contents viewed Feb. 13, 2009; title from PDF t.p. Includes bibliographical references (p. 124-126).
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Nikitin, Sergey. "Laser ultrasonics in a diamond anvil cell for investigation of simple molecular compunds at ultrahigh pressures." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1005/document.
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Le travail que j’ai effectué durant ce doctorat est dédié à l’utilisation de l’ultrason des lasers sous haute pression physique. La recherche est construite en utilisant les récentes techniques de mesure de laser ultrasonique dans une enclume de diamant, conduisant à l’exploration de la propagation du son et de sa détermination suivant la vitesse de l’onde acoustique sous ultra-hautes pressions. La diffusion Brillouin a été appliquée ici pour déterminer l’épaisseur de la glace polycristalline compressée dans l’enclume à diamant sous pressions de mégabars. La technique permet d’examiner les caractéristiques des dimensions des inhomogénéités élastiques et la texture de la glace polycristalline, de ce fait ce processus est commun pour les surfaces de l’enclume à diamant avec des sous micromètres de résolution spatiale via les mesures des variations résolues dans le temps sur la vitesse de propagation du pouls acoustique voyageant dans l’échantillon compressé. Ceci a été appliqué pour mesurer la vitesse acoustique dans du H2O à l’état de glace jusqu’à 84 Gpa. La technique d’imagerie développée contient, pour chaque cristallite (ou groupe de cristallites) dans un ensemble homogène chimique transparent, des informations utiles sur son orientation ainsi que sur sa valeur élastique modulée par rapport à la direction de la propagation du son. Cela répand les bases pour une application réussite sur la déformation de solides sous haut-développement de modèles micromécaniques sous la pression à mégabars. Pour une plus longue durée, ce genre d’expériences répandus sur les minéraux de la terre et avec des températures basses ou hautes, assurerait un progrès important dans la compréhension de la construction de la cape terrestre, son évolution ainsi que celle d’autres planètesThis PhD research work is devoted to the use of laser ultrasound in high-pressure physics. The research is done using the recently established technique of laser ultrasonic measurements in a diamond anvil cell which allows investigation of the sound propagation and determination of the acoustic wave velocities at ultrahigh pressures. Time domain Brillouin scattering was applied here to depth-profiling of polycrystalline aggregate of ice compressed in a diamond anvil cell to megabar pressures. The technique allowed examination of characteristic dimensions of elastic inhomogeneities and texturing of polycrystalline ice in the direction, normal to the diamond anvil surfaces with sub-micrometer spatial resolution via time-resolved measurements of variations in the propagation velocity of the acoustic pulse travelling in the compressed sample. It was applied to measure the acoustic velocities in H2O ice up to 84 Gpa. The developed imaging technique provides, for each crystallite (or a group of crystallites) in chemically homogeneous transparent aggregate, usable information on its orientation as well as on the value of the elastic modulus along the direction of the sound propagation. This extends the basis for a successful application of highly developed micromechanical models of solids deformation at mbar pressure. On long term, such experiments extended to earth’s minerals and high or low temperatures would insure a significant progress in understanding of convection of the earth’s mantle and thus evolution of this and other planets
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Pigott, Jeffrey Scott. "Exploration of Earth's Deep Interior by Merging Nanotechnology, Diamond-Anvil Cell Experiments, and Computational Crystal Chemistry." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1435154850.
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Lord, Oliver T. "Experimental Constraints on the Chemistry of the Earth's Core : Novel approaches using the Laser-Heated Diamond Anvil Cell." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520173.
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Aprilis, Georgios [Verfasser], and Natalia [Akademischer Betreuer] Dubrovinskaia. "Pulsed laser heating in the diamond anvil cell : applications in geo- and material sciences / Georgios Aprilis ; Betreuer: Natalia Dubrovinskaia." Bayreuth : Universität Bayreuth, 2021. http://d-nb.info/1227444648/34.
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Leong, Daniel Nichol. "The technology of electrical feedthroughs into the diamond anvil cell and its applications to high pressure electro-optical spectroscopy." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/844190/.
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A relatively simple and reliable gasket insulation technique for electrical feedthroughs in the Diamond Anvil Cell has been successfuly developed. This involved the use of, easy to use components such as epoxy resins which can be easily obtained, and, the use of simple equipment which are part of any reasonably equiped laboratory. Photoconductivity, demonstrator, experiments on strained layer quantum well material were successfully used to prove the feasibility of these techniques. The pressure coefficient values obtained for strained InGaAs/GaAs, InGaAs/AlGaAs and unstrained InGaAs/InGaAsP were in agreement with that obtained with a photoluminescence technique. Unlike photoluminescence it is also possible to obtain the pressure coefficients of higher energy states with the photoconductivity experiment. In the process, laminated gaskets for electrical measurements were also developed. This has led to a tremendous improvement in the experimental reliability to such an extent that the electrical feedthroughs have become almost as routine as the optical experiments. Further, it is now possible to use ordinary optically cut anvils to conduct electrical feedthroughs without resorting to specially designed ones, such as rounded or multiple bevelled anvils, or, even depositing permanent conducting strips onto the diamond culets. The benefits of this is that obtaining ordinary cut anvils is much simpler than obtaining specialist bevelled or rounded edge anvils.
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Castro, Rosane de Paula. "Avaliação da dependência com a pressão de propriedades estruturais de compostos orgânicos de interesse farmacêutico." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8563.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This thesis presents the structure determination using single crystal x-ray crystallography of four drug candidates under ambient conditions of temperature and pressure, as well as submitted to high pressure. The crystallographic analysis of this type of compound allows to obtain the three-dimensional structure in an unambiguous way. This information is useful for the development process of new drugs in order to achieve the planned properties, such as the study of combinations of the drug with the excipients to be used to guarantee the rate of expected release of the drug in the human body and the optimization of interaction between the drug and the target. Furthermore during the process of drug manufacturing in the pharmaceutical industry polymorphic phases may arise due to the application of pressure, which occurs during grinding and in the preparation of tablets, which may alter the bioavailability, solubility and stability of the medicament. Thus, identifying the conditions under which such modifications may occur guarantees the reliability of the final product. In this sense, the crystallization and crystallographic analysis of drug candidates developed by the Laboratório de Avaliação e Síntese de Substâncias Bioativas (LASSBio) of the Universidade Federal do Rio de Janeiro (UFRJ) was carried out. The compounds analyzed were: LASSBio-1773 and LASSBio-1774, which have hypoglycemic activity, LASSBio-1606, with anti-inflammatory properties, and LASSBio-1735, which has been shown to be active against several types of cancer. For the compounds LASSBio-1774 and LASSBio-1606 X-ray diffraction at high pressures was also performed with Diamond Anvil Cell (DAC), determining their unit cells and analyzing the effects of pressure on the crystalline arrangement. In both compounds reversible phase transitions were observed. The analysis of the structural changes for LASSBio-1774 due to pressure was performed with the aid of strain tensors.
Nesta tese serão apresentados os resultados de determinação estrutural por difração de raios X de monocristais de candidatos a fármacos em condições ambientes de temperatura e pressão, assim como submetidos à altas pressões. A análise cristalográfica desse tipo de composto permite obter a estrutura tridimensional de maneira inequívoca. Essa informação é útil para o processo de desenvolvimento de novos fármacos a fim de se alcançar as propriedades planejadas, tais como o estudo de combinações do fármaco com os excipientes a serem utilizados para garantir a taxa de liberação esperada do fármaco no corpo humano e a otimização da interação entre o fármaco e o alvo. Além disso, durante o processo de produção na indústria farmacêutica, podem surgir fases polimórficas devido à aplicação de pressão, que ocorre durante a moagem e na preparação de comprimidos, podendo alterar a biodisponibilidade, solubilidade e estabilidade do medicamento. Assim, identificar as condições nas quais tais modificações podem ocorrer, garante a confiabilidade do produto final. Nesse sentido, no presente trabalho foram realizadas a cristalização e análise cristalográfica de candidatos à fármacos desenvolvidos pelo Laboratório de Avaliação e Síntese de Substâncias Bioativas (LASSBio) da Universidade Federal do Rio de Janeiro (UFRJ). Os compostos analisados foram: LASSBio-1773 e LASSBio-1774, que possuem atividade hipoglicemiante, LASSBio-1606, com propriedade anti-inflamatória, e LASSBio-1735, que se mostrou ativo contra diversos tipos de câncer. Para os compostos LASSBio-1774 e LASSBio-1606 foi realizada também a difração de raios X em altas pressões, com a Diamond Anvil Cell (DAC), determinando suas células unitárias e analisando os efeitos da pressão sobre o arranjo cristalino. Em ambos os compostos foram observadas transições de fase reversíveis. Para o LASSBio-1774 a análise das mudanças estruturais devidas à pressão foi realizada com o auxílio dos tensores de strain.
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Karandikar, Amol [Verfasser], Björn [Gutachter] Winkler, and Lars [Gutachter] Ehm. "Development of the flash-heating method for measuring melting temperatures in the diamond anvil cell / Amol Karandikar ; Gutachter: Björn Winkler, Lars Ehm." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2016. http://d-nb.info/1116426528/34.
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Najiba, Shah. "High Pressure and Low Temperature Study of Ammonia Borane and Lithium Amidoborane." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1388.
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Hydrogen has been considered as a potentially efficient and environmentally friendly alternative energy solution. However, one of the most important scientific and technical challenges that the “hydrogen economy” faces is the development of safe and economically viable on-board hydrogen storage for fuel cell applications, especially to the transportation sector. Ammonia borane (BH3NH3), a solid state hydrogen storage material, possesses exceptionally high hydrogen content (19.6 wt%).However, a fairly high temperature is required to release all the hydrogen atoms, along with the emission of toxic borazine. Recently research interests are focusing on the improvement of H2 discharge from ammonia borane (AB) including lowering the dehydrogenation temperature and enhancing hydrogen release rate using different techniques. Till now the detailed information about the bonding characteristics of AB is not sufficient to understand details about its phases and structures.
Elemental substitution of ammonia borane produces metal amidoboranes. Introduction of metal atoms to the ammonia borane structure may alter the bonding characteristics. Lithium amidoborane is synthesized by ball milling of ammonia borane and lithium hydride. High pressure study of molecular crystal provides unique insight into the intermolecular bonding forces and phase stability. During this dissertation, Raman spectroscopic study of lithium amidoborane has been carried out at high pressure in a diamond anvil cell. It has been identified that there is no dihydrogen bond in the lithium amidoborane structure, whereas dihydrogen bond is the characteristic bond of the parent compound ammonia borane. It has also been identified that the B-H bond becomes weaker, whereas B-N and N-H bonds become stronger than those in the parent compound ammonia borane. At high pressure up to 15 GPa, Raman spectroscopic study indicates two phase transformations of lithium amidoborane, whereas synchrotron X-ray diffraction data indicates only one phase transformation of this material.
Pressure and temperature has a significant effect on the structural stability of ammonia borane. This dissertation explored the phase transformation behavior of ammonia borane at high pressure and low temperature using in situ Raman spectroscopy. The P-T phase boundary between the tetragonal (I4mm) and orthorhombic (Pmn21) phases of ammonia borane has been determined. The transition has a positive Clapeyron slope which indicates the transition is of exothermic in nature. Influence of nanoconfinemment on the I4mm to Pmn21 phase transition of ammonia borane was also investigated. Mesoporus silica scaffolds SBA-15 with pore size of ~8 nm and MCM-41 with pore size of 2.1-2.7 nm, were used to nanoconfine ammonia borane. During cooling down, the I4mm to Pmn21 phase transition was not observed in MCM-41 nanoconfined ammonia borane, whereas the SBA-15 nanocondfined ammonia borane shows the phase transition at ~195 K. Four new phases of ammonia borane were also identified at high pressure up to 15 GPa and low temperature down to 90 K.
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Pigott, Jeff S. "The Viscosity of Water at High Pressures and High Temperatures: A Random Walk through a Subduction Zone." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299607953.
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Sundberg, Sara Nanna Kristina. "Optical and Raman Spectroscopic Studies on H2O at High Pressure." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5934.
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In this thesis, volumetric, optical and vibrational properties of H2O were studied at high pressures by combining techniques of Raman spectroscopy, interferometry and optical imaging. Pressures up to 7 GPa were generated in the diamond anvil cell (DAC), entering the stability fields of liquid water and ices VI, VII and VIII.
A new integrated system for Raman, interferometric and optical-imaging studies has been built up. Utilizing the interferometric patterns formed between closely-spaced diamond anvils, the system allowed the complete monitoring and control of pVT-conditions of studied ices, as well as the determination of their dispersive properties in the visible range using the Airy equation and Cauchy formulation. This setup and technique thus represent a novel tool for the precise determination of equations of state (EOSs) of transparent materials, including fluids and low-Z materials.
Data-sets on thermal pressure were obtained from heating/cooling experiments carried out on the liquid water and used for checking the mutual consistency between published EOSs. A pVT-EOS for ice VIII and room temperature isotherms for ices VI and VII at 300 K were derived by combined methods of interferometry and imaging. While the agreement with the available EOSs of ices VII and VIII is very good, some inconsistent EOSs of ice VI were identified in the present study.
The technique of micro-Raman spectroscopy was applied for the monitoring of phase transformations, identification of various ice phases and for studying the response of vibrational symmetry modes to varying conditions. Analysis based on the combination of the pT-dependencies of the vibrational frequencies with the pVT-EOSs showed that, in the studied ices, the implicit volume-driven contributions dominate over the explicit phonon effects in the total temperature-induced changes in vibrational frequencies. The results provide valuable insight on the anharmonic effects and interactions in these molecular solids.
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Sundberg, Sara Nanna Kristina. "Optical and Raman Spectroscopic Studies on H2O at High Pressure." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5934.
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In this thesis, volumetric, optical and vibrational properties of H2O were studied at high pressures by combining techniques of Raman spectroscopy, interferometry and optical imaging. Pressures up to 7 GPa were generated in the diamond anvil cell (DAC), entering the stability fields of liquid water and ices VI, VII and VIII. A new integrated system for Raman, interferometric and optical-imaging studies has been built up. Utilizing the interferometric patterns formed between closely-spaced diamond anvils, the system allowed the complete monitoring and control of pVT-conditions of studied ices, as well as the determination of their dispersive properties in the visible range using the Airy equation and Cauchy formulation. This setup and technique thus represent a novel tool for the precise determination of equations of state (EOSs) of transparent materials, including fluids and low-Z materials. Data-sets on thermal pressure were obtained from heating/cooling experiments carried out on the liquid water and used for checking the mutual consistency between published EOSs. A pVT-EOS for ice VIII and room temperature isotherms for ices VI and VII at 300 K were derived by combined methods of interferometry and imaging. While the agreement with the available EOSs of ices VII and VIII is very good, some inconsistent EOSs of ice VI were identified in the present study. The technique of micro-Raman spectroscopy was applied for the monitoring of phase transformations, identification of various ice phases and for studying the response of vibrational symmetry modes to varying conditions. Analysis based on the combination of the pT-dependencies of the vibrational frequencies with the pVT-EOSs showed that, in the studied ices, the implicit volume-driven contributions dominate over the explicit phonon effects in the total temperature-induced changes in vibrational frequencies. The results provide valuable insight on the anharmonic effects and interactions in these molecular solids.
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Boye, Shawn Alexander. "Magnetotransport Measurements of Ni Thin Films." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4653.
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This thesis presents transverse magnetoresistance (MR) and Hall resistivity measurements of nickel thin films at temperatures between 280 and 455 K and pressures up to 6 GPa. An experimental system was developed for conducting precise magnetotransport measurements using the current reversal and van der Pauw techniques in combination with a 10 T superconducting magnet. Polycrystalline Ni0.985O0.015 thin film samples were manufactured with preexisting point contacts allowing highly reproducible magnetotransport measurements at pressure in the diamond anvil cell (DAC).
The magnetic resistivity above the technical saturation of the magnetization was found to decrease linearly to the highest applied fields, 10 T, while the field derivative, 0.010-0.018 µΩ cm T-1 between 280 and 316 K, increased with temperature and decreased with pressure. The decrease in the magnetoresistance is attributed to spin wave damping of electron-magnon scattering processes at high fields. The magnon mass, 535(14) meV Å2 at 0 K and 0 GPa, determined from longitudinal magnetic resistivity theory is a slightly increasing function of pressure. Correlation between the zero field resistivity and the extraordinary Hall coefficient (EHC) confirmed side jump scattering as the dominant diffusion mechanism at 0 GPa, however, skew scattering was found to become increasingly important with pressure.
The effect of oxygen and pressure on the density of states (DOS) at the Fermi level was investigated through total energy band structure calculations using a periodic supercell of 64 atoms to simulate the sample chemistry. The DOS of Ni0.985O0.015 at the Fermi level was found to increase by 27% at 10 GPa relative to 0 GPa. However, when compared to the results for pure Ni, decreases of 60% and 23% occurred for the corresponding calculations at 0 and 10 GPa. The relative differences in the magnetic resistivity are attributed to competing effects between the DOS, average magnetic moment and magnon mass.
The technique developed for conducting magnetotransport measurements at pressure is applicable to the study of electronic diffusion in ferromagnets as well as geophysical problems such as the geodynamo.
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Konôpková, Zuzana. "Thermal Conductivity of Materials under Conditions of Planetary Interiors." Doctoral thesis, Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-150396.
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The presented thesis focuses on study of transport and thermoelastic properties of materials under conditions of planetary interiors by means of high-pressure experimental tools and finite element modeling, and their role in the dynamics and states of cores of terrestrial planets. Experiments in laser-heated diamond anvil cell (LHDAC) in combination with numerical simulations of heat transfer in DAC are shown to yield information on thermal conductivity of a pressurized sample. The novel technique consists of one-sided laser heating and double-sided temperature measurements and utilizes a precise determination of several parameters in course of the experiment, including the sample geometry, laser beam power distribution, and optical properties of employed materials. The pressure-temperature conditions at the probed portion of the sample are, however, not uniform. To address this problem, thermal pressure in the laser-heated diamond anvil cell and anisotropic thermal conductivity originating from the texture development upon uniaxial compression have been studied by means of numerical simulations. The method for determination of thermal conductivity is applied to iron at pressures up to 70 GPa and temperatures of 2000 K, meeting the Earth’s lower mantle conditions and covering Mercury’s entire core. The obtained results are extrapolated to the conditions of the Earth’s core-mantle boundary using a theoretical model of the density dependence of thermal conductivity of metals and published values on Grüneisen parameter and bulk modulus. After considering the effect of minor core elements, the obtained value at these conditions supports case for the downward revision of the thermal conductivity in the core. From the point of view of core dynamics and energy budget, the lower thermal conductivity implies more favorable conditions to drive the dynamo. Similar scenario applies for Mercury where, for high values of thermal conductivity, heat flux conducted along the iron-core adiabat exceeds the actual heat flux through the core-mantle boundary. This leads to a negative rate of entropy production in the core that makes it impossible to sustain the dynamo process presumably responsible for the observed magnetic field of Mercury.
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Coleman, Amy Louise. "Studies of dynamically and statically compressed antimony." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31334.
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Physics at extreme conditions is not a young field; there have been decades of developments that have allowed us to generate high-pressure and high-temperature conditions in a vast array of materials. Conventionally, these extreme conditions were generated using static compression techniques; compressing a material in a diamond anvil cell which could then be heated or cooled, with structural information deduced using synchrotron radiation. These techniques are still invaluable for extreme conditions research although the pressures and temperatures that are accessible to them are limited by the strength of the diamond anvil cells and their ability to withstand extreme temperatures. The necessity for access to pressure-temperature states that are beyond the scope of the conventional diamond anvil cell is driven by the need to characterise extreme environments such as planetary interiors. It was long believed that materials in high pressure-temperature states would exhibit relatively simple, high-symmetry crystal structures, but recent research has proven that, conversely, there is an abundance of complex structural behaviour at these extreme conditions. One means of attaining pressure-temperature states beyond those accessible using static compression techniques is to impart a large amount of energy into a material in a comparatively short period of time (milliseconds to nanoseconds); this is known as dynamic compression. Dynamic compression can be generated using impact techniques or, alternatively, via laser ablation. Access to the most extreme conditions is commonly achieved by generating a shockwave which compresses the sample with the fastest achievable compression wave. Not only does this type of compression facilitate access to the most extreme states, it also allows us to explore the physics of impact phenomena and other such situations involving rapid energy transfer. Dynamic compression occurs on short timescales and, as such, there is a considerable challenge in implementing diagnostics to study the behaviour of compressed materials. Furthermore, because complexity is commonplace in extreme conditions, it is vital that any diagnostics should be able to provide data of high enough quality that this complexity may be resolved. The advent of 4th generation light sources (x-ray free electron lasers) has afforded us the opportunity to obtain extraordinarily high quality data on dynamic compression timescales. In the interest of refining analytical techniques when utilising this novel technology, materials exhibiting complex crystal structures should be investigated. Antimony is an element which is known, under static compression, to transform from a Peierls-distorted rhombohedral phase (R-3m) to an incommensurately modulated host-guest structure (I'4=mcm(00γ)000s), a structure with an incredibly high level of complexity. The complexity of this host-guest phase, and the relatively low pressure at which it forms, makes antimony an ideal candidate for testing the resolution achievable using these 4th generation light sources. Furthermore, it is interesting to observe whether such a complex phase can form on the short timescales of dynamic compression. In this work antimony is both statically and dynamically compressed and the results of both experiments are compared. A static phase diagram is constructed for antimony up to 31 GPa and 835 K, confirming the location of a previously theorised triple point and suggesting the location of an additional triple point. Three solid phases are characterised and data are found to agree with the pre-existing static compression studies. The nature of the host-guest phase is investigated and the guest 'chains' are found to remain intact even at the highest temperatures and pressures, a result which has not previously been observed in high pressure-temperature host-guest structures. Dynamic data from shock-compression experiments at pressures up to 59.3 GPa are plotted alongside the static data and contrasting phase behaviour is discussed. Four solid phases are identified along with one liquid phase. Observation of the host-guest phase in shock-compressed antimony confirms that highly complex crystal structures are able to form on the nanosecond timescale.
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Toraille, Loïc. "Utilisation de centres NV comme capteurs de champs magnétiques à haute pression dans des cellules à enclumes de diamant." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN056/document.
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La pression est un paramètre physique qui modifie les interactions structurales, électroniques et magnétiques dans les matériaux. Créer une très haute pression permet donc la synthèse de nouveaux matériaux, comme par exemple des supraconducteurs ayant des valeurs de température critique record. Ces pressions peuvent être générées au moyen d’une cellule à enclume de diamant (DAC) qui peut comprimer un matériau jusqu’à des pressions de plusieurs centaines de GPa. Il est cependant difficile de caractériser les propriétés magnétiques de matériaux à l’intérieur d’une DAC à cause du très faible volume occupé par l’échantillon et des contraintes techniques. Dans cette thèse, nous proposons d’utiliser une technique de magnétométrie optique fondée sur la résonance de spin électronique de centres colorés NV du diamant. Ces centres NV sont fabriqués à la surface d’une des deux enclumes de la DAC et sont ainsi au contact de l’échantillon magnétique à caractériser.Dans un premier chapitre, nous rappelons le fonctionnement de la DAC et décrivons les techniques de mesures magnétiques développées pour la physique des hautes pressions. Nous présentons ensuite le principe de la magnétométrie à centres NV et l’appliquons à la mesure de l’aimantation d’un micro-aimant à pression ambiante. La sensibilité de cette mesure atteint celle des magnétomètres à SQUID. Le troisième chapitre discute de la façon dont les contraintes mécaniques modifient la résonance de spin du centre NV, et détaille la manière dont cet effet se combine avec celui dû à un champ magnétique externe. La possibilité de découpler les deux effets nous permet d’observer la transition de phase magnétique du fer autour de 15 à 30 GPa dans le quatrième chapitre. Enfin, le dernier chapitre décrit le contexte et les enjeux liés à la synthèse d’hydrures supraconducteurs à haute température critique. Nous montrons ensuite qu’il est possible de détecter optiquement une phase supraconductrice à l’intérieur d’une DAC en utilisant les centres NV pour observer l’effet Meissner de MgB2 à une pression de 7 GPa et avec une température critique de 30 KPressure is a physical variable that alters structural, electronic and magnetic interactions in all materials. Reaching high pressure is thus a way to create new materials such as superconductors with record critical temperatures. High pressures can be enabled through the use of diamond anvil cells (DAC), which can attain pressures of several hundred of GPa. It is however quite a challenge to measure magnetic properties of materials inside a DAC because of the very small sample volume available and of technical constraints. In this PhD thesis, we demonstrate the use of a magnetometry method based on the electronic spin resonance of NV centers in diamond. These NV centers are fabricated directly on top of one of the DAC anvils, which places them in contact with the magnetic sample.In the first chapter, we describe how the DAC works and we present the different ways of probing magnetic properties that have been developed for high pressure conditions. We then explain the operating principle of NV magnetometry and use this method to measure the magnetization of a micro-magnet at ambient pressure. The sensitivity of this measure is comparable to that of SQUID magnetometry. In the third chapter, we discuss how mechanical constraints modify the spin resonance of the NV center, and describe how this effect combines with the influence of an external magnetic field. By decoupling these two effects, we can observe the magnetic phase transition of iron around 15 to 30 GPa, which is displayed in the fourth chapter. Finally, the last chapter briefly presents the context and stakes associated with the synthesis of superconducting superhydrides with high critical temperature. We perform an optical detection of a superconducting phase inside a DAC with NV centers through the observation of the Meissner effect in MgB2 at a pressure of 7 GPa and with a critical temperature of 30 K
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Marizy, Adrien. "Super-hydrures sous pression pour le stockage de l’hydrogène et la supraconductivité : développement d’outils et résultats sur H3S, CrHx, LiBH4 et NaBHx." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX115/document.
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Récemment, sous des pressions de plusieurs gigapascals, de nouveaux hydrures ont été synthétisés avec des propriétés étonnantes potentiellement porteuses de ruptures technologiques pour le stockage de l’hydrogène ou la supraconductivité. Plusieurs superhydrures sont étudiés expérimentalement et simulés par DFT dans cette thèse. Les diagrammes de phases en pression de LiBH4 et NaBH4, deux composés d’intérêt pour le stockage de l’hydrogène, sont explorés par diffraction de rayons X, spectroscopie Raman et infrarouge jusqu’à des pressions de 300 GPa sans observer de décomposition. L’insertion d’hydrogène dans NaBH4 donne le super-hydrure NaBH4(H2)0.5. Pour éclaircir l’interprétation de la supraconductivité record à 200 K trouvée dans H2S sous pression, le super-hydrure H3S a été synthétisé à partir des éléments S et H. Les résultats de diffraction semblent en désaccord avec l’interprétation communément admise qu’H3S en phase Im-3m est responsable de cette supraconductivité et laisse la porte ouverte à d’autres interprétations. Enfin, les super-hydrures CrHx avec x=1, 1.5 et 2 ont également été synthétisés à partir des éléments et caractérisés par diffraction de rayons X. Si ces hydrures correspondent bien àceux qui avaient été prédits numériquement, l’absence des stoechiométries plus élevées est discutée. Pour mesurer les températures de supraconductivité calculées dans les superhydrures MHx, une cellule à enclumes de diamant miniature permettant une détection de l’effet Meissner a été développéeRecently, under pressures of several gigapascals, new hydrides have been synthesised with striking properties that may herald technological breakthroughs for hydrogen storage and superconductivity. In this PhD thesis, several superhydrides have been studied experimentally and simulated by DFT. The pressure phase diagrams of LiBH4 and NaBH4, two compounds of interest for hydrogen storage, have been explored thanks to X-ray diffraction and Raman and infrared spectroscopy up to pressures of 300 GPa without observing any decomposition. The insertion of hydrogen inside NaBH4 generates the superhydride NaBH4(H2)0.5. To refine the interpretation of the record superconductivity found in H2S under pressure at 200 K, the superhydride H3S has been synthesised from S and H elements. The results of the diffraction study seem to be at odds with the commonly accepted interpretation that Im-3m H3S is responsible for the superconductivity observed and leaves the door open to other interpretations. Finally, CrHx hydrides with x = 1, 1.5 and 2 have also been synthesised from the elements and characterised by X-ray diffraction. Although these hydrides do correspond to the ones that had been numerically predicted, the absence of the expected higher stoichiometries is discussed. To measure the superconductivity temperatures calculated for MHx hydrides, a miniature diamond anvil cell which allows the detection of a Meissner effect has been developed
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Hrubiak, Rostislav. "Exploring Thermal and Mechanical Properties of Selected Transition Elements under Extreme Conditions: Experiments at High Pressures and High Temperatures." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/696.
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Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. New phase diagrams created for Hf, Ti and Zr from experimental data. P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled). All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature). Complete thermodynamic data for selected elements from standard to extreme conditions.
The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included.
Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.
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Schmidt, Christian. "Experimental Study of the PVTX Properties in Part of the Ternary System H₂O-NaCl-CO₂." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30610.
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Phase equilibria and volumetric properties in the system water-sodium chloride-carbon dioxide were determined experimentally for pressures between about 1 to 6 kbar, temperatures of 300° to 800°C, and fluid compositions up to 40 wt% NaCl and 20 mol% carbon dioxide, both relative to water. This was accomplished by using the synthetic fluid inclusion technique in conjunction with conventional microthermometry, a hydrothermal diamond-anvil cell and Raman spectroscopy.
At constant salinity, the high-pressure portion of the solvus migrates to higher pressures and temperatures with increasing carbon dioxide concentration. Immiscibility is possible in this ternary system over almost the entire range of crustal P-T conditions at salinities equal to or in excess of 20 wt% NaCl and carbon dioxide concentrations between about 30 and 70 mol% carbon dioxide. The dP/dT slopes of lines of equal homogenization temperature decrease nonlinearly with increasing homogenization temperature; at constant homogenization temperature, these slopes become steeper (higher) along pseudobinaries with addition of carbon dioxide and particularly with addition of sodium chloride. Up to concentrations of 20 wt% NaCl and 20 mol% carbon dioxide, a sharp rise in the critical temperature was observed with increasing salinity at a fixed water/carbon dioxide ratio. The critical point shifts rapidly towards higher pressures with increasing carbon dioxide concentration. Addition of carbon dioxide to an aqueous 40 wt% NaCl solution results in a slight elevation of the halite dissolution temperature under vapor-saturated conditions.
A significant error can be associated with the calculation of molar volumes from measured densities of the carbonic phase of water-sodium chloride-carbon dioxide inclusions. To avoid such errors, phase diagrams were constructed based on the obtained lines of equal homogenization temperature for salinities between 6 and 40 wt% NaCl and carbon dioxide concentrations between 5 and 20 mol% relative to water. These diagrams are of direct applicability to the interpretation of natural fluid inclusions from a wide variety of geologic environments.Ph. D.
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Meißner, Thomas. "Exploring Nuclear Magnetic Resonance at the Highest Pressures." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-115023.
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Die vorliegende Arbeit beschäftigt sich mit der Entwicklung und Anwendung der Kernmagnetresonanz (NMR) unter extremen Drücken bis 101 kbar. Es wird gezeigt, dass die Empfindlichkeit von NMR Experimenten unter hohen Drücken in Diamantstempel- und ähnlichen Hochdruckzellen im Vergleich zu früheren experimentellen Versuchsanordnungen durch Verwendung von Mikrospulen um mehrere Größenordnungen verbessert werden kann. Die neue Versuchsanordnung wird dann zum einen bei der Untersuchung der Druckabhängigkeit elektronischer Eigenschaften von metallischem Aluminium bis 101 kbar verwendet. Zum anderen wird damit der Pseudogap des Hochtemperatursupraleiters YBa2Cu4O8 bei Drücken bis zu 63 kbar untersucht.
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Gauvin, Mélanie. "Approche analytique in situ du mécanisme anti-usure des phosphates de zinc." Ecully, Ecole centrale de Lyon, 2008. http://www.theses.fr/2008ECDL0021.
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L’élaboration d'additifs de lubrification respectueux de l'environnement nécessite la compréhension du mode d'action d'additifs anti-usure tel que le dithiophosphate de zinc (ZDDP). Le ZDDP a la. Propriété remarquable de former un film mince résistant à l'usure，appelé tribofilm, à l’interface d'un contact en régime de lubrification limite. Les pressions locales de l'ordre de plusieurs giga Pascals (GPa) dans un contact tribologique en régime de lubrification limite sont potentiellement capables de transformer la structure atomique et les propriétés des matériaux à l’interface. Au cours de ces travaux, nous avons mis en évidence les transformations structurales in situ de composés modèles du ZDDP, sous l'effet de hautes pressions hydrostatiques allant jusqu'à 20 GPa. Nous avons choisi de modéliser le ZDDP par les phosphates de zinc (ZP) suite à l' étude de différents lubrifiants composés de Zn3(P04)2, Zn2P207, et Zn(P03)2 dispersés dans une huile de poly-alfa-oléfine utilisés lors de tests tribologiques en régime de lubrification limite, à température ambiante. La formation d'un tribofilm amorphe formé à partir de Zn3(P04)2 a été observée. Ses propriétés mécaniques et topographiques sont comparables à celles du tribofilm de ZDDP. En revanche, la formation d'un tribofilm à l'interface est négligeable dans le cas de Zn2P207 et Zn(P03)2. Les transformations structurales des unités P04 dans différents ZP sous haute pression ，jusqu'à 20 GPa ont été mises en évidence par spectroscopie Raman in situ. Le degré de polymérisation des chaînes de phosphate est conservé sous pression, menant à la conc1usion que la pression n'est pas responsable de la formation de longue chaînes de phosphate dans le tribofilm de ZDDP. Entre 0. 1 MPa et 4 GPa，les spectres Raman de α-Zn3 (P04 )2 montrent une transition de phase de la structure cristalline initiale sous l'effet de la pression. Au-delà de 4 GPa, la signature vibrationnelle de l' échantillon suggère une perte progressive de l'ordre à longue portée sous pression. A la décompression, la structure obtenue est similaire à la forme amorphe du composé Zn3(P04)2. La structure locale sous pression des atomes de Zn dans α-Zn3(P04 )2 a été étudiée par spectroscopies EXAFS et XANES in situ au seuil K du zinc. Entre 0,1 MPa et 3,5 GPa, l’ordre à longue portée autour du zinc disparaît et la distance moyenne Zn-O augmente de 0,046 + 0,005 A. Le nombre de coordination du zinc n’augmente pas significativement sous une pression maximale de 7 GPa. Le désordre structural est acquis irréversiblement. Enfin, un tribomètre alternatif combiné avec un spectromètre Raman nous a permis d’observer in situ les trnasformations structurales du composé Zn3(PO4)2 sous l’effet de contraintes tribologiques. Des tructures similaires à celles formées sous haute pression hydrostatique ont été mises en évidence dans le contact tribologique. La formation d'un tribofilm amorphe composé de Zn3(PO4)2 est observée à l'interfaceEco-friendly lubricant additives are of primary environmental and economical importance. Their design rely on our understanding of anti-wear additives such as the zinc dialkyldithiophosphate (ZDDP). ZDDP has the remarkable property of forming a thin protective coating against wear， called ZDDP-tribofilm ，at the interface of a boundary lubricated contact. However, detailed reactional pathwaγs leading to the ZDDP tribofilm formation and mechanisms responsible for wear inhibition are still unsolved. High local pressures in the range of several giga pascals in a boundary lubricated contact are likely to modify the atomic structure and macroscopic properties of materials at this interface. Our work focuses on an in situ analysis of structural modifications of ZDDP-like model compounds when exposed to high hydrostatic pressures, up to 20 GPa. We chose to model the ZDDP additive by zinc phosphate compounds (ZP) after performing tribological tests under boundary lubrication conditions using colloidal Zn3 (P04)2, ，Zn2P207 and Zn(P03 )2 compounds mixed to a poly-alpha-olefin oil, at ambient temperature formation of a tribofilm is observed at the interface for Zn3(P04)2 while it is negligible for Zn2P207 and Zn(PO3)2 materials. Mechanical and topographical properties of the amorphous film formed from Zn3(P04)z at the interface, show some similarities with ZDDP tribofilm. In situ micro-Raman spectroscopy was used to probe P04 tetrahedra structural modifications in ZP compounds of different phosphate chain lengths, up to 20 GPa. Pressure had no effect on PO4 tetrahedra polymerization in tested materials and cannot account for the formation of long-chain phosphates found in the ZDDP-tribofilm. Between 0. 1 MPa. And 4 GPa, α -Zn3(P04 )2 Raman spectra undergo important modifications which were attributed to a phase transition of the initial crystalline structure. Above 4 GPa，Zn3(P04 )2 Raman spectra show a progressive loss of the long-rang order in the sample. The structure recovered after decompression is similar to an amorphous Zn3(P04 )2 compound. Local environment of Zn atoms in α Zn3(PO4)2 was investigated under' high static pressure by in situ Zn-K edge EXAFS and XANES spectroscopies. Crystalline order around Zn atoms was found to vanish down to the second sphere of coordination and the mean Zn-O bond length is increased by 0. 046 +0. 005. A when pressure increases from 0. 1 MPa to 3. 5 GPa. The coordination number around Zn atoms does not change significantly at a maximal pressure of 7 GPa. The disordered local structure of zinc atoms observed at high pressure is conserve a decompression. Finally, a reciprocating tribometer combined with in situ micro-Raman spectroscopy was used to probe α-Zn3(P04)2 structural transformations occurring under combined shear and pressure constrains at ambient temperature. Tribolocically constrained Zn3(P04)2 structures were found to be identical to high pressure phases formed in static high pressure experiment and led to the formation of an amourphous zinc orthophosphate tribofilm
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Dilner, David. "Behavior of cutting tool coating material Ti1-xAlxN at high pressure and high temperature." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52773.
Full textAbstract:
The high pressure and high temperature (HPHT) behavior of Ti1-xAlxN coatings on cutting tool inserts have been of interest for this diploma work. A literature study of HPHT techniques as well as measurement methods has been done. A diamond anvil cell (DAC) would be a good device to achieve high pressure and high temperature conditions on small samples. Another way to obtain these conditions would be a cutting test, which has been performed on a Ti1-xAlxN coated cutting tool insert with x = 0.67. Also a cubic press could be used to apply HPHT on a Ti1-xAlxN sample or a large volume press on a whole cutting tool insert. To measure hardness on thin coatings a nanoindentor could be used, which have been done on heat-treated Ti0.33Al0.67N and TiN samples. X-ray diffraction (XRD) is a suitable method to measure phase composition of a sample and was performed on the cutting tested insert as well as on an untreated reference insert. Three ways to continue this project have been outlined all starting with more comprehensive cutting tests.
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Dilner, David. "Behavior of cutting tool coating material Ti1-xAlxN at high pressure and high temperature." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-52773.
Full textAbstract:
The high pressure and high temperature (HPHT) behavior of Ti1-xAlxN coatings on cutting tool inserts have been of interest for this diploma work. A literature study of HPHT techniques as well as measurement methods has been done. A diamond anvil cell (DAC) would be a good device to achieve high pressure and high temperature conditions on small samples. Another way to obtain these conditions would be a cutting test, which has been performed on a Ti1-xAlxN coated cutting tool insert with x = 0.67. Also a cubic press could be used to apply HPHT on a Ti1-xAlxN sample or a large volume press on a whole cutting tool insert. To measure hardness on thin coatings a nanoindentor could be used, which have been done on heat-treated Ti0.33Al0.67N and TiN samples. X-ray diffraction (XRD) is a suitable method to measure phase composition of a sample and was performed on the cutting tested insert as well as on an untreated reference insert. Three ways to continue this project have been outlined all starting with more comprehensive cutting tests.
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Kolesnikov, Anton. "Experimental investigation of hydrocarbon formation and transformation under Earth´s upper mantle conditions." Doctoral thesis, KTH, Kraft- och värmeteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27017.
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The theory of the abyssal abiotic petroleum origin considers oil and natural gas to begenerated in the Earth’s upper mantle. Hydrocarbons migrate further through the deep faults into the Earth’s crust, where they can form oil and gas deposits in any kind of rock in any kind of structural position. Until recently one of the main obstacles for further development of this theory has been the lack of the data covering processes of generation and transformations of hydrocarbons. Experimental data, presented in this thesis, confirms the possibility of hydrocarbons formation from mantle inorganic compounds (water, Fe, CaCO3 or graphite) at temperature and pressure of the upper mantle (1500 K and 5 GPa). Experiments were carried out in CONAC high pressure device and multianvil apparatus BARS. Compositions of received gas mixtures were similar to natural gas. Quantity of hydrocarbons depended on the cooling regime of reaction mixture under pressure. Slow cooling favored higher quantity. We found that donor of carbon (CaCO3 or graphite) determines formation of “dry” (methane-rich) gas or “wet” (light hydrocarbons-rich) gas. Experiments in laser-heated diamond anvil cells showed that methane and ethane partially react under upper mantle thermobaric conditions (2-5 GPa, 1000-1500 K) to form mixture of hydrocarbons: methane, ethane, propane and n-butane – main compounds of natural gas. Similarity of final product mixture obtained from methane and ethane means thermodynamic stability of hydrocarbons in the thermobaric conditions of the upper mantle and equilibrium character of the observed processes.QC 20101203
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Biggs, Timothy James. "Studies of crystalline organic molecular materials under extreme conditions." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:51dae806-2954-4ea7-a3cb-1980ecb53e98.
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This thesis describes investigations into the properties of -phase BEDT-TTF charge transfer salts. Charge transfer salts are mainly studied as they are very useful test beds for fundamental physics due to the tuneability of their proper- ties and ground states. The effects of temperature and pressure on such systems have been studied, as these allow access to a wide range of different states and properties. Transport properties of these systems have been studied to obtain information about the Fermi surface and effective mass, and the effect of deuter- ation and also change of pressure media will be discussed. The interaction of infrared radiation with these systems has also been investigated and simultaneous pressure and temperature measurements will be presented, something not greatly studied due to the large technical challenges. The techniques and approaches for overcoming these are also discussed. Chapter 1 provides an introduction to the organic materials themselves with particular emphasis on the actual compounds studied. Chapter 2 provides the necessary theoretical background for studying organic charge transfer salts using magnetic quantum oscillations and their infrared re- ectivity. Chapter 3 covers the experimental techniques and also discusses some of the challenges encountered and their solutions to aid others working in this area. Chapter 4 describes an investigation into the transport properties of - (ET)2Cu(SCN)2 by studying Shubnikov-de Haas oscillations using both deuter- ated and normal samples and using two different pressure media, and comparing it to work done using a third. Chapter 5 presents an investigation into the pressure dependence of selected phonon modes in -(ET)2Cu(SCN)2 using infrared radiation on a deuterated sam- ple. Chapter 6 presents what is believed to be the first pressure and temperature dependent infrared study of an organic molecular material. In this case the or- ganic molecular material is d8--(ET)2Cu[N(CN)2]Br, but the techniques should be readily transferable to other materials.
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Sonneville, Camille. "Étude des propriétés élastiques des verres d’oxydes sous haute pression : implications structurales." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10114/document.
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Le comportement des verres sous pression, lié à leurs structures topologiques, est un enjeu majeur à la fois fondamental et appliqué. L’anomalie élastique de la silice à 2,5GPa est un phénomène connu et son existence est plus que probable dans le verre de GeO2. Il semblait alors légitime de questionner son existence dans des verres plus répandus de compositions chimiques complexes comme les verres alumino sodo silicatés. L’anomalie élastique a été étudiée in situ par Diffusion Brillouin et Raman pour le verre de GeO2 et trois verres alumino sodo silicaté de compositions chimiques : (Al2O3)X(Na2O)25−X(SiO2)75 où X=0, 6 et 12%. Il a été montré que l’existence de l’anomalie de compressibilité dans le domaine élastique n’était pas réduite qu’à la silice uniquement mais au contraire persistait sur un vaste domaine de compositions chimiques et semblait être liée à la présence d’anneaux à 6 tétraèdres. Au delà de la limite élastique, les modifications structurales à l’origine du phénomène de densification permanente ont été étudiées pour la silice, le verre de GeO2 et six verres d’alumino sodo silicatés (contenant X=0, 2, 6, 9, 12 et 16% d’Al2O3). Tout d’abord nous avons observé par diffusion Brillouin la disparition progressive de l’anomalie élastique de la silice avec la densification. Ce phénomène a été interprété en termes de transformations induites par la pression d’une forme amorphe basse densité (LDA) en une forme amorphe haute densité (HDA) : LDA → HDA. Des études in situ et ex situ par Diffusion Brillouin et Raman, Résonance Magnétique Nucléaire (RMN) et aussi de Spectroscopie d’Absorption des Rayons X proche du seuil (XANES) ont montré que les modifications structurales à l’origine de la densification permanente dépendaient grandement de la composition chimique. En particulier la présence de cation sodique semble favoriser les modifications à courte portée comme la formation d’espèces hautement coordonnées d’aluminium ou encore de silicium ainsi que la dépolymérisation du réseau. Au contraire les verres les plus riches en aluminium semblent montrer une densification plus proche structurellement de celle de la silice pure c’est à dire modifiant principalement l’ordre à moyenne distance avec diminution de l’angle inter-tétraèdre et de la taille des anneauxThe structural study of glasses under pressure is of fundamental interest in Physics, Earth Science and is technologically important for the comprehension of industrial material properties. The elastic anomaly at 2.5GPa in pure silica glass is a well known phenomenon and its existence is more than likely in GeO2 glass. In this work the persistence of the elastic anomaly in more complex and more widely glass compositions as sodium alumino silicate glasses was studied. The elastic anomaly was studied in situ in GeO2 and three sodium alumino silicate glasses by Brillouin and Raman scattering. The studied sodium alumino silicate glasses had the following compositions : (Al2O3)X(Na2O)25−X(SiO2)75 where X=0, 6 et 12% and is the molar percentage of Al2O3. The elastic anomaly was shown to persist in a broad domain of chemical compositions thus its existence is not reduced to pure silica glass. Its existence seems to be linked to the presence of 6 membered rings. Beyond the elastic limit, the structural modifications was studied in pure silica, GeO2 glass and sodium alumino silica glasses (with X=0, 2, 6, 9, 12 et 16% of Al2O3) in order to structurally better understand the densification phenomenon. Firstly the elastic anomaly was studied by Brillouin scattering experiments, was shown to progressively disappear with the densification. This progressive disappearance was interpreted in terms of a progressive structure induced transformation from a Low Density Amorphous form (LDA) into a High Density Amorphous form (HDA) : LDA → HDA. In situ and ex situ studies by Brillouin and Raman scattering, Nuclear Magnetic Resonance (NMR) and X-ray Absorption Near Edge Structure (XANES) showed that the pressure induced structural transformation was highly dependent of the glass chemical composition. For instance the presence of sodium cations promotes short range order modifications, such as formation of highly coordinated species (Al, Si) and network depolymerization. On the other hand, glasses with a high aluminum concentration show a densification process closer to that of pure silica glass, with mainly middle range order structural modifications such as a decrease of the inter-tetrahedral angle or ring size decrease
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Medeghini, Fabio. "Optics and acoustics with a single nano-object : environment effects." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1026/document.
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Dans cette thèse, les propriétés d'une nanoparticule unique ont été réglée en modifiant son environnement.Plus spécifiquement, dans la première partie de ce travail, la résonance des plasmons de surface des nanobipyramides d'or individuelles a été étudié expérimentalement dans un milieu sous pression contrôlable et son évolution encadré par modélisations théoriques.Afin d'accéder à l'optique d'une nanoparticule unique tout en générant un environnement sous haute-pression, la combinaison de la spectroscopie par modulation spatial avec la cellule en enclume de diamant a été atteint.Dans la seconde partie de la thèse, les vibrations acoustiques des nanodisques d'or individuels sur a substrat en saphir ont été caractérisé expérimentalement via spectroscopie pump&probe. Une attention particulière a été accordée à leur amortissement en fonction du rapport d'aspect des disques en soulignant la présence des amplifications en factor de qualité.Modélisations numériques ont fourni un aperçu des amplifications observées, montrant que l'hybridations entre modes se produit pour rapport d'aspect spécifiques, potentiellement en atténuant les pertes en énergie acoustique à travers l'interface disque/substratIn this thesis, the properties of a single nanoparticle have been tuned altering its environment. Specifically, in the first part of this work, the surface plasmon resonance of individual gold nanobipyramids has been experimentally studied under a pressure adjustable surrounding and its evolution physically framed thorough theoretical modeling.In order to access to the single nanoparticle optics while generating a hydrostatic high-pressure environment, a challenging combination of the spatial modulation spectroscopy technique with the diamond anvil cell method has been achieved.In the second part of the thesis, the acoustic vibrations of individual gold nanodisks on sapphire substrate has been experimentally characterized via pump&probe spectroscopy. Particular attention has been paid to their damping as a function of the disks aspect-ratio enlightening the presence of quality-factors enhancements.Numeric modeling has provided a physical insight for the observed amplifications, showing that modes hybridizations occur at specific aspect-ratios, potentially reducing the acoustic energy loss towards the interface disk/substrate
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Berkani, Sophia. "Comportement tribologique et analyses in-situ de polyphosphates de zinc : apport de la spectroscopie Raman." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00963748.
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Le dialkyldithiophosphate de zinc ( ZDDP ) est un additif anti-usure habituellement utilisé dans les lubrifiants moteurs. Dans des conditions sévères de frottement, les molécules de ZDDP forment sur les surfaces métalliques un film, appelé tribofilm, qui protège ces surfaces de l'adhésion et de l'abrasion. Les tribofilms sont principalement composés de polyphosphates de zinc dont la longueur des chaînes varie progressivement sur la hauteur du film. On trouve les chaînes de phosphate les plus courtes à la surface du métal et les chaînes de phosphate les plus longues au sommet du film. Plusieurs études ont été menées afin de comprendre le mécanisme par lequel l'additif peut conduire à la formation de ce gradient de phosphate. Pour améliorer la compréhension de ce mécanisme, nous nous concentrons dans cette étude sur l'influence de la pression, du cisaillement, de la nature des surfaces et de la température sur des composés de type orthophosphate de zinc et métaphosphate de zinc, utilisés pour modéliser le tribofilm de ZDDP. Des tests tribologiques ont été réalisés en régime de lubrification limite à partir de dispersions de ces polyphosphates de zinc dans de l'huile de base. L'effet de la pression seule a été étudié à l'aide d'une cellule à enclumes de diamant (CED) afin de découpler son effet de celui du cisaillement. La spectroscopie Raman a été utilisée pour suivre in-situ ou ex-situ, les changements de structures des poudres de polyphosphate de zinc. Ces expériences ont été réalisées sur ces composés afin d'identifier précisément la contrainte qui conduit à ce gradient de phosphate au sein d'un tribofilm. La pression seule, à induit uniquement des désordres structurels au sein des polyphosphates de zinc. Une dimérisation mineure a été observée pour l'orthophosphate de zinc mais, est peu significative pour expliquer les changements structurels observés dans un tribofilm. Lors des tests tribologiques, les phosphates ont montré une capacité à former des tribofilms. Une dépolymérisation du métaphosphate de zinc à été observée a l'issue de ces tests. Les grandes contraintes et conditions de déformation des essais tribologiques sont nécessaires pour induire une réaction tribochimique entre le métaphosphate de zinc et l'oxyde de fer conduisant à une dépolymérisation du phosphate dans le tribofilm. La réaction anti-usure et la formation de tribofilm est favorisée par les hautes températures (120 * C), et par certaines formes d'oxydes de fer.
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Montagnac, Gilles. "Spectroscopie Raman résonnante UV in situ à haute température ou à haute pression." Thesis, Lyon, École normale supérieure, 2012. http://www.theses.fr/2012ENSL0784/document.
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Dans cette thèse, la spectroscopie Raman résonante UV (SRRUV) est appliquée pour la première fois à l'étude ‘in situ’ de matériaux carbonés à très haute température (> 2000 K) ou à haute pression (< 1 GPa).La thèse est constituée de trois parties. La première aborde notre travail de caractérisation en SRRUV (1) de films semi conducteurs de diamants ultra-nano-cristalins, (2) des kérogènes issues de météorites chondritiques et de charbons, et (3) des tholins, échantillons de carbone-hydrogène-azote, synthétisés comme analogues de l'atmosphère de Titan.L’intérêt pour ces phases du carbone en planétologie et en science des matériaux nous a poussé à mettre en œuvre leur étude ‘in situ’ en SRRUV. La seconde partie de la thèse est consacrée au développement d'une platine chauffante, grâce à laquelle les spectres Raman du graphite sous sa forme pyrolitique et HOPG ont été mesurés jusqu'à 2700 K. Ces données valident les modèles anharmoniques théoriques d’interaction électron-phonon et phonon-phonon. Le spectre Raman du graphite a été étalonné en fonction de la température et devient un « thermomètre » à très haute température.Dans la troisième partie de cette thèse, une presse à enclumes opposées a été modifiée pour suivre en SRRUV les changements structuraux de cristaux moléculaires très luminescents. Les vibrations intramoléculaires du cristal de pérylène sont étudiées sous pression par SRRUV. Ce composé est un cristal formé de molécules organiques polyaromatiques, avec des propriétés de semi-conducteur. Les effets de la pression sur certains modes de vibrations sont non linéaires et mettent en évidence des changement structuraux et de planéité de la moléculeI applied UV resonant Raman spectroscopy (UVRRS) to an ‘in situ’ study of carbon materials at very hight temperature (> 2000 K) or at high pressure (< 1 GPa).The advantages of UVRRS are presented in the first part of this PHD thesis, and used to investigate details of the composition and structure of disordered carbon materials such as: (1) n-type nanocrystalline films, (2) carbonaceous matter in chondrites and (3) tholins, HCN synthetic samples of Titan 's atmosphere.‘In situ’ Raman studies are limited to 2000 K by the visible black-body emission. I designed a high temperature cell to perform UVRRS above this limit. The second part of the manuscript presents Raman spectra of pyrolitic graphite and HOPG up to 2700 K. This data are consistent with anharmonic models up to 900 K, and show the coupling effects of electron-phonon and phonon-phonon. The last one dominates the anharmonicity above 1000 K. The Raman spectra was calibrated as a function of temperature and became a “thermometer” up to 2700 K.For high pressure measurements in the third part, I modified an anvil cell to study by UVRRS, the vibrational changes induced by pressure on very luminescent molecular organic crystals. I present an analysis at 244 nm of resonant Raman modes of perylene crystal under hydrostatic pressure up to 0.8 GPa. Some of them have a non linear feature under pressure, revealing structural and planar modifications of the molecules
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Pal, Srishti. "Spectroscopic and Diffraction Signatures of Quantum Spin Liquids, Skyrmion Lattices and Transition Metal Dichalcogenides at Low Temperatures and High Pressures." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5727.
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This thesis presents experimental as well as theoretical studies on several contemporary
systems like quantum spin liquids (QSLs), skyrmion lattices, and transition metal dichalcogenides
(TMDs) under extreme conditions like low temperature (down to 4K) and ultra high
pressures (up to 26 GPa). Temperature-dependent Raman studies are carried out to investigate
Raman signatures of Kitaev quantum spin liquid (QSL) state of Cu2IrO3 and Ag3LiIr2O6 and
orbital ordering in Heisenberg quantum magnet Ca10Cr7O28. High-pressure studies are performed
on Kitaev QSL candidates -RuCl3, Cu2IrO3, kagomé QSL ZnCu3(OH)6Cl2, skyrmion
lattice system Cu2OSeO3, and TMD candidate VSe2. Structural and vibrational evolutions of
these systems under pressure are probed by X-ray diffraction measurements using synchrotron
source and Raman scattering, respectively.
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Jy, Kaohsiung, and 支高雄. "The compressibility of NiO in a diamond anvil cell." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/38897573471432961227.
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楊聖恩. "Raman Spectroscopic Study of CacO3 in Diamond Anvil Cell." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/67034766020003382324.
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碩士國立臺灣大學
地質學研究所
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The high-pressure Raman spectroscopic experiments of calcite were carried out in a diamond anvil cell with methanol-enthanol medium up to 25 GPa at room temperature. We have observed only two relative intense Raman peaks of v4 and v1 in calcite up to 7 GPa and 25 GPa, respectively. The vibrational frequencies of calcite were found to increase linearly under pressure with their slopes, dv/dP, range from 1.73 to 6.81cm-1/GPa. The appearance of new Raman peaks and the change in slope of these observed modes may indicate that calcite undergoes a series of phase transitions, i.e. CaCO3-Ⅰ→CaCO3-Ⅱ and CaCO3-Ⅱ→CaCO3-Ⅲ ; moreover, these changes might also related to the distorted trigonal planar CO3 groups during compression. A new high-pressure phase was found to coexist with CaCO3-Ⅲ above 14 GPa and the complete transformation to the new phase took place at about 18 GPa. We interpret this new high-pressure phase as calcite-Ⅵ. In addition, all of the phase transitions of calcite observed in our experiment are reversible. On the basis of the present Raman spectroscopic observation, no sign of phase transition in aragonite was found up to 22 GPa. In comparison with the Raman data of calcite, it seems that aragonite and calcite-Ⅵ with a simiar Raman vibrational mode above 18 GPa. The vibrational frequency of v1 increases with decreasing C-O interatomic distance during compression in the CaCO3 phases, We also interpret the cause of the frequencies of v1 and v4 decrease with increasing the ionic radii of cations for some carbonate minerals with calcite and aragonite structure. Finally, according to the unit-cell parameters and the relationship of the pressure-induced C-O bond shortening, we inferred the CO3 groups are more compressible than CaO6 octahedra in pressure range from the ambient pressure to 1.8 GPa. However, above 1.8 GPa, CaO6 octahedra become more compressible than CO3 groups. In comparison with previous studies, we found the compressibilities of C-O bonds in CaCO3-III and CaCO3-VI are similar with those of aragonite, dolomite and magnesite above 2 GPa. However, the C-O bonds in calcite are more compressible than the other carbonate minerals below 2 GPa.
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Lin, Jung-Fu, and 林俊孚. "Raman Spectroscopic Studies of Hydrous Minerals in Diamond Anvil Cell." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/19424954032441245526.
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Wright, Andrew Osbourn. "Solid state defect dynamics measured with site selective spectroscopy employing a diamond anvil cell." 1994. http://catalog.hathitrust.org/api/volumes/oclc/31514073.html.
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Mulcahy, Cara Kim. "Hydrothermal diamond anvil cell studies a possible new calibration mineral and applications to the hydrouscarbonate mineral, nesquehonite /." 2006. http://etd.utk.edu/2006/MulcahyCara.pdf.
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Groß, Juliane [Verfasser]. "Mineral solubility measurements at high pressures: Redesigning the hydrothermal diamond anvil cell, crystal volume computations and birefringence mapping / von Juliane Groß." 2009. http://d-nb.info/997264314/34.
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Patterson, Donald Eugene. "Studies involving novel inorganic materials: I. The direct fluorination of diamond, high-temperature superconductors, and selected organic materials. II. The use of gem-cut cubic zirconia in the diamond anvil cell." Thesis, 1989. http://hdl.handle.net/1911/16279.
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The direct reaction of elemental fluorine with diamonds, YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$, and some unique organic materials has been studied. It has been found that diamonds (powder, slabs, and CVD films) can be directly fluorinated to a small extent using elemental fluorine under various reaction conditions. The reaction appears to proceed by fluorine attacking the diamond's more labile surface features such as the hydroxyl group. While the diamond surface is reactive to some extent, it is difficult to fully fluorinate this surface with elemental fluorine. Plasma fluorination seems to lead to the formation of CF terminal bonds on the diamond surface while high temperature direct fluorination leads to the formation of CF$\sb2$ and CF$\sb3$ terminal bonds. In oxidation resistance studies, the CF$\sb2$ and CF$\sb3$ terminal bonds lead to a more stable product than do the CF bonds.
The direct fluorination of the high temperature superconductor, YBa$\sb2$Cu$\sb3$O$\sb{\rm 7-x}$, leads primarily to the formation of a non-superconducting phase. This phase encapsulates the superconducting phase. Thus, there is no significant change in the fluorinated material's onset of critical temperature, but there is a significant decrease in the degree of magnetic shielding for the material as the amount of fluorination is increased. Initial attempts at synthesizing nitrofluorosuperconductors are presented.
We have successfully used direct fluorination techniques to yield improved properties for Velcro (made principally of polypropylene) and have had some success at fluorinating indan and PVC. The fluoro-Velcro shows enhanced lint repellent properties while maintaining its suppleness and other desirable properties. Perfluoroperhydroindan, a potential fluoroblood, has been prepared in small quantities using this novel treatment. PVC has been modestly fluorinated with the potential of carrying the fluorination to completion and should yield a superior product.
The use of cubic zirconia, an inexpensive diamond simulant, as high pressure/high temperature transmitting windows in the diamond anvil optical cell has been shown to be promising. Pressures nearing 20 kbars can be obtained in the cell using cubic zirconia anvils. The optical properties of cubic zirconia open up a region of the mid-IR that has been inaccessible with previous windows at these pressures. An FT-IR study of the high pressure effects on Fe(CO)$\sb6$($\mu$-CO)$\sb2$($\mu$-CH$\sb2$) is presented as proof. (Abstract shortened with permission of author.)
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Gawraczyński, Jakub. "Optical spectroscopy of selected divalent silver compounds." Doctoral thesis, 2019. https://depotuw.ceon.pl/handle/item/3382.
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Niniejsza rozprawa doktorska opisuje badania związków srebra wykonane metodami spektroskopowymi. Główny nacisk został położony na związki srebra dwuwartościowego: fluorek srebra(II) AgF2, siarczan(VI) srebra(II) wraz ze swoim monohydratem, tetrafluoroboran fluorosrebra(II) (AgF)BF4, fluorosrebrzan(II) cezu CsAgF3, rubidu RbAgF3, oraz wysokotemperaturowa forma fluorosrebrzanu(II) potasu, HT-KAgF3 Ponadto zbadane zostały inne związki srebra: fluorek srebra(I) oraz tlenek srebra(I,III) AgO. Wszystkie związki zostały zbadane za pomocą spektroskopii fourierowskiej w zakresie dalekiej podczerwieni. Część związków zbadana została za pomocą spektroskopii ramanowskiej, spektroskopii absorpcyjnej w zakresie średniej i bliskiej podczerwieni, jak również za pomocą spektroskopii elektronowej z zakresu światła widzialnego i ultrafioletu oraz za pomocą nieelastycznego rozpraszania neutronów. Trzy związki, AgO, AgF i AgF2 zostały zbadane metodą spektroskopii Ramana pod zwiększonym ciśnieniem. Głównym celem pracy było zrozumienie struktury oscylacyjnej badanych związków, jak też wniknięcie w naturę ich przemian strukturalnych pod wysokim ciśnieniem (dla wybranych układów). Drugim celem było oszacowanie stałej nadwymiany magnetycznej dla dwuwymiarowego AgF2 z użyciem spektroskopii Ramana, a dla jednowymiarowego AgFBF4 z użyciem spektroskopii absorpcyjnej w zakresie NIR. Celem ubocznym, który wyniknął w trakcie prowadzenia prac badawczych, było zrozumienie rozkładu fotochemicznego AgF2 i AgSO4.
Badania nad fluorkiem srebra(I) pod wysokim ciśnieniem wykazały obecność większej liczby pasm ramanowskich niż przewidywana z obliczeń teorii grup (brak pasm); część z nich prawodpodobnie pochodzi od centrów barwnych lub od nadtonu aktywnego w podczerwieni drgania normalnego T1u. Badania nad fluorkiem srebra(II) wykazały jego wysoką fotoczułość. Produkt indukowanego światłem laserowym fotorozkładu został zbadany w zakresie od ciśnienia atmosferycznego do 47 GPa. Wydaje się, ze rozkład fotochemiczny prowadzi do pochodnej zawierającej aniony Ag(II)F42–, zapewne Ag(I)2Ag(II)F4, który jest pierwszym znanym fluorkiem srebra o mieszanej wartościowości Ag(I)/Ag(II). Wyznaczono zależność ciśnieniową charakterystycznego pasma ramanowskiego tej nowej fazy do ciśnienia 47 GPa.
Ponadto dzięki zastosowaniu spektroskopii rozproszenia ramanowskiego oraz nieelastycznego rozpraszania neutronów z powodzeniem zidentyfikowano i zarejestrowano po raz pierwszy przejścia bimagnonowe w dwuwymiarowym antyferromagnetyku, AgF2, i wyznaczono wartość wewnątrzwarstwowej stałej nadwymiany magnetycznej, J, dla tego związku. Duża wartość J=70 meV plasuje ten związek jako jedyny, poza warstwowymi tlenkami miedzi(II), wykazujący tak silną nadwymianę magnetyczną w dwóch wymiarach.
Fluoroboran fluorosrebra(II) został scharakteryzowany za pomocą spektroskopii rozproszenia ramanowskiego, nieelastycznego rozproszenia neutronów, spektroskopii fourierowskiej w podczerwieni oraz spektroskopii odbiciowej w zakresie średniej podczerwieni. Charakterystyczne pasmo absorpcyjne w zakresie bliskiej podczerwieni pozwolilo na oszacowanie wewnątrzłańcuchowej stałej nadwymiany magnetycznej dla tego związku na około 270 meV, co przekracza najwyższą znaną do tej pory wartość zmierzoną dla Sr2CuO3 (240 meV).
Badania nad tlenkiem srebra(I,III) prowadzone w zakresie wysokich ciśnień wykazały brak indukowanego ciśnieniem rozkładu lub komproporcjonacji tego związku do nie mniej niż 74 GPa. Ponadto, z uwagi na dobrą zgodność pozycji pasm ramanowskich z obliczeniami teoretycznymi dokonanymi na modelach wysokociśnieniowych faz AgO udało się wykazać istnienie dwóch strukturalnych przejść fazowych w przedziale ciśnienia od 0 do 74 GPa.
W trakcie badań przeprowadzonych na trzech fluorosrebrzanach(II) metali alkalicznych: HT-KAgF3, CsAgF3 i RbAgF3 wykazano bardzo duże podobieństwo widm spektroskopii fourierowskiej w zakresie dalekiej podczerwieni tych związków mimo wyraźnych różnic strukturalnych.This doctoral dissertation describes research on silver compounds carried out with a range of spectroscopic methods. The main focus of the thesis was on divalent silver compounds: AgF2, AgSO4, AgSO4∙H2O, (AgF)BF4, CsAgF3, RbAgF3, and high-temperature form of KAgF3. In addition, other silver compounds were investigated, particularly AgF and silver(I, III) oxide AgO. All compounds were studied by FT-FIR spectroscopy, some were also investigated with Raman spectroscopy (at ambient or high pressure), MIR, NIR, as well as UV and visible absorption spectroscopy and by inelastic neutron scattering. The main scope of the work was to get insight into vibrational structure of the studied compounds as well as understand their pressure-induced phase transitions. The second goal was to determine magnetic superexchange constants for 2D AgF2 from Raman scattering spectra, and for 1D AgFBF4 from NIR-absorption spectra. The auxiliary task, dictated by the course of the experimental work, was to understand photochemical decomposition of AgF2 and AgSO4. The spectroscopic measurements of AgIISO4 prepared using the new electrosynthesis method in concentrated H2SO4 showed its similarity with the product of chemical synthesis developed earlier, albeit substantial differences in reactivity to water vapor were also found. In addition, the laser-induced decomposition of AgIISO4 was observed and it was shown that the decomposition product is dependent on the wavelength of the laser used. A similar photosensitivity was observed in AgIISO4∙H2O. The hydrate was also studied spectroscopically from far-infrared to UV, which allowed determination of the orbital splitting parameters as well as has provided the supplementary evidence for the presence of water molecules in its crystal structure. Research on AgF at high pressure showed the presence of several Raman bands in contrast with predictions of group theory (no Raman-active bands), some of them probably originating from color centers or overtone of the IR-active fundamental. Research on AgF2 proved its high photosensitivity to laser light. Laser-induced photodecomposition product has been studied in the range from atmospheric pressure up to 47 GPa. The decomposition product seems to contain Ag(II)F42– anion, notably Ag(I)2Ag(II)F4, which is the first mixed-valence Ag(I)/Ag(II) fluoride known. Pressure dependence of the characteristic Raman band for this phase was measured up to 47 GPa. In addition, using Raman scattering spectroscopy and inelastic neutron scattering, I have successfully identified and measured for the first time the bimagnon transitions in 2D antiferromagnet, AgF2, and determined the value of the intra-sheet magnetic superexchange constant, J. The large value of J=70 meV sets this compound second only to lamellar oxocuprates(II). (AgF)BF4 has been characterized by Raman scattering, inelastic neutron scattering, IR absorption and reflection spectroscopy. The characteristic band appearing in the NIR absorption spectra enabled estimation of the intra-chain magnetic superexchange constant for this compound to be about 270 meV. This value surpasses the largest known superexchange constant ever measured (240 meV for Sr2CuO3). Research on AgO conducted under a high pressure showed no pressure-induced decomposition or comproportionation of this compound to no less than 74 GPa. Due to the good agreement of the experimental Raman band positions with those derived from the theoretical calculations made on the AgO high-pressure models, it was possible to demonstrate the existence of two structural phase transitions in the pressure range from 0 to 74 GPa. The research carried out on three alkali metal fluoroargentates: CsAgF3, RbAgF3, and high-temperature form of KAgF3 has shown that despite clear structural differences between them, the Fourier transmission spectra in the far infrared range of all compounds show substantial similarity.
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Lu, Chang. "Elasticity of single-crystal iron-bearing pyrope to 20 GPa and 750 K." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-05-5456.
Full textAbstract:
Elastic properties of the major constituent minerals in the Earth’s upper mantle at relevant high pressure-temperature (P-T) conditions are crucial for understanding the composition and seismic velocity structures of the region. In this study, we have measured the single-crystal elasticity of natural Fe-bearing pyrope, Mg2.04Fe0.74Ca0.16Mn0.05Al2Si3O12, using in situ Brillouin spectroscopy and X-ray diffraction at simultaneous high P-T conditions up to 20 GPa and 750 K in an externally-heated diamond anvil cell. The derived aggregate adiabatic bulk and shear modulus (KS0, G0) at ambient conditions are 168.2 (±1.8) GPa and 92.1 (±1.1) GPa, respectively, consistent with literature results. Using the third-order Eulerian finite-strain equation to fit the high P-T data, the derived pressure derivative of the bulk and shear moduli at constant temperature are (∂KS/∂P)T=4.4 (±0.1) and (∂G/∂P)T=1.2 (±0.1), respectively. Applying these pressure derivatives, the temperature derivative of these moduli at constant pressure are also calculated, yielding (∂KS/∂T)P=-18.5(±1.3) MPa/K and (∂G/∂T)P=-5.2(±1.1) MPa/K, respectively. Compared to literature values, our results show that addition of 25% Fe in pyrope increases the pressure derivative of the bulk modulus by 7%, but has a negligible effect on other elastic parameters. Extrapolation of our results shows that Fe-bearing pyrope remains almost elastically isotropic at relevant P-T conditions of the upper mantle, indicating that it may not have a significant contribution to seismic Vp and Vs anisotropy in the upper mantle. Together with the elasticity of olivine and pyroxene minerals in the upper mantle, we have constructed new velocity profiles for two representative compositional models, pyrolite and piclogite, along Earth’s upper mantle geotherm. These velocity models show Vs profiles consistent with seismic observations, although Vp profiles are slightly lower than in seismic models.text
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Schauries, Daniel. "Ion Tracks in Apatite and Quartz and Their Behaviour with Temperature and Pressure." Phd thesis, 2016. http://hdl.handle.net/1885/112508.
Full textAbstract:
Interaction between high energetic particles and matter typically
leads to structural damage of the irradiated material. Swift
heavy ions predominantly interact with a solid by exciting its
electrons. The energy transfer from the electrons to the atoms
can lead to the formation of so-called ion tracks. These
represent damage regions of cylindrical shape, which surround the
entire length of the ion trajectory with a radial size of several
nanometres. In materials science, ion tracks are utilised for a
wide range of applications, from the detection of radiation to
the fabrication of nano-pore filters or nano-electronic devices.
In geology, similar tracks occur naturally in minerals from the
spontaneous fission of radioactive impurities. These fission
tracks can partially anneal and shrink in length when exposed to
elevated temperatures. In this way, the thermal history of a rock
can be determined. The length distributions are routinely studied
in the mineral apatite with optical microscopy after the tracks
have been dissolved and enlarged by chemical etching. Fission
tracks within rocks from thousands of metres below the Earth’s
surface have inevitably experienced high pressures of several
thousand atmospheres. However, pressure is generally not taken
into account when studying formation or annealing rates of
fission tracks.
The present work shows a detailed investigation of ion tracks in
apatite and quartz, specifically a characterisation of their
structure, formation, and thermal stability under ambient and
high pressure conditions. All tracks were created under
controlled conditions by irradiation with ions of energies
between 100 MeV to 37.2 GeV in Canberra, Australia, and
Darmstadt, Germany. The tracks were subsequently characterised at
the Australian Synchrotron in Melbourne through small angle x-ray
scattering (SAXS). This allows assessing the track diameter with
sub-nanometre precision and without altering their structure.
Combining the ability to create tracks under well-controlled
conditions with SAXS characterisation, track formation in
high-pressure and high-temperature environments was studied. This
includes a temperature range between -250 and 640 deg C and
elevated pressure conditions up to 4.4 GPa. The size of the track
radii showed a positive correlation with temperature as well as
pressure. This work further presents an anisotropy for the track
radii along different crystallographic axes and a
characterisation of the track’s cross-section and longitudinal
shape. In situ SAXS was used to monitor the size of the ion
tracks, while these were undergoing thermal annealing. For tracks
in quartz, an anisotropic annealing behaviour was found,
depending on the direction of the tracks within the crystal
lattice. To study thermal track annealing at high pressures,
apatite samples were annealed in heatable diamond anvil cells. An
increase in annealing rate was demonstrated and attributed to the
high-pressure environment. The effects of pressure on track
annealing were demonstrated to be negligible when extrapolated to
geological values. Thus, the present results confirm the validity
of current fission track annealing models. Moreover, the present
findings contribute to the field of radiation materials under
extreme conditions and the theoretical modelling of such effects.
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Saouane, Sofiane. "Extending the Search Space for Novel Physical Forms of Pharmaceuticals and Biomolecules using High-Pressure Techniques." Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-878A-D.
Full text
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Meißner, Thomas. "Exploring Nuclear Magnetic Resonance at the Highest Pressures: Closing the Pseudogap under Pressure in a High Temperature Superconductor." Doctoral thesis, 2012. https://ul.qucosa.de/id/qucosa%3A11967.
Full textAbstract:
Die vorliegende Arbeit beschäftigt sich mit der Entwicklung und Anwendung der Kernmagnetresonanz (NMR) unter extremen Drücken bis 101 kbar. Es wird gezeigt, dass die Empfindlichkeit von NMR Experimenten unter hohen Drücken in Diamantstempel- und ähnlichen Hochdruckzellen im Vergleich zu früheren experimentellen Versuchsanordnungen durch Verwendung von Mikrospulen um mehrere Größenordnungen verbessert werden kann. Die neue Versuchsanordnung wird dann zum einen bei der Untersuchung der Druckabhängigkeit elektronischer Eigenschaften von metallischem Aluminium bis 101 kbar verwendet. Zum anderen wird damit der Pseudogap des Hochtemperatursupraleiters YBa2Cu4O8 bei Drücken bis zu 63 kbar untersucht.
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RUELLO, GIOVANNA. "Pressure dependence of the intermediate-range structure and the boson peak in oxide glasses." Doctoral thesis, 2018. http://hdl.handle.net/11570/3120290.
Full textAbstract:
Despite glasses are widely used for several applications, some of their unique structural and dynamical properties are not completely understood.
We present a detailed investigation of the intermediate-range structure of a series of alkaline borate glasses and of densified borate glasses carried out by performing neutron diffraction measurements. Moreover, a comparative study of Raman scattering, inelastic neutron scattering measurements and low temperature specific heat capacity has been performed on densified B2O3 glasses.
Strong differences are observed in the intermediate range order as a function of density, the specific alkaline ion and of its concentration. On these results, we suggest that the first sharp diffraction peak of glasses arises from the periodicity of the boundaries of interstitial voids in the random glassy network. This interpretation provides a general explanation for all the anomalous compositional and pressure dependence of the FSDP in glasses as due to changes in the distribution of the sizes of the voids.
The detailed analysis of the Boson peak in densified B2O3 glasses demonstrates that all the low-energy vibrational modes giving rise to the BP, extended and localized, are coupled and hybridized, determining an overall spectral distribution, whose spectral shape does not depend on the different packing fractions of the systems.
Furthermore, a clear correlation between the boson peak frequency and the transverse sound velocity is found, suggesting a mainly transverse character of the excess vibrational modes in glasses. It is indeed believed that vibrations merging into the boson peak arise from low atomic density regions and that they are strongly influenced by constraints imposed by the densification on transverse displacements of structural units overlooking these voids.
A good accordance between the correlation lengths of densified glasses (estimated from the boson peak in Raman spectra and from the position of the first sharp diffraction peak), shows that the low-frequency excitations are defined by the characteristic length of voids in the glassy structure.
Lastly, a set-up for in-situ high-pressure Raman experiments was developed, allowing to analyse the low energy modes of a sample of α-quartz at increasing pressures up to 26 GPA. The pressurization on the crystalline sample by a Diamond Anvil Cell provokes its amorphyzation.