The Crystal Structures Of Three New Vanadium Oxide Minerals

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The Crystal Structures Of Three New Vanadium Oxide Minerals

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Author : Howard T. Evans
language : en
Publisher:
Release Date : 1957

The Crystal Structures Of Three New Vanadium Oxide Minerals written by Howard T. Evans and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1957 with Doloresite categories.

The Crystal Chemistry And Mineralogy Of Vanadium

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Author : Howard T. Evans (Jr.)
language : en
Publisher:
Release Date : 1956

The Crystal Chemistry And Mineralogy Of Vanadium written by Howard T. Evans (Jr.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1956 with Oxidation categories.

Doloresite A New Vanadium Oxide Mineral From The Colorado Plateau

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Author : T. W. Stern
language : en
Publisher:
Release Date : 1957

Doloresite A New Vanadium Oxide Mineral From The Colorado Plateau written by T. W. Stern and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1957 with Vanadium ores categories.

Guidebook Of The Albuquerque Country

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Author : New Mexico Geological Society
language : en
Publisher:
Release Date : 1961

Guidebook Of The Albuquerque Country written by New Mexico Geological Society and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1961 with Albuquerque (N.M.) categories.

Geological Survey Professional Paper

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Author :
language : en
Publisher:
Release Date : 1961

Geological Survey Professional Paper written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1961 with Geology categories.

Field Conference

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Author : New Mexico Geological Society
language : en
Publisher:
Release Date : 2003

Field Conference written by New Mexico Geological Society and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Geology categories.

The American Mineralogist

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Author : Walter Fred Hunt
language : en
Publisher:
Release Date : 1968

The American Mineralogist written by Walter Fred Hunt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1968 with Mineralogy categories.

Vols. 6- include Proceedings of the 1st- 1920- annual meeting of the society.

Phase Stability And Transformations In Vanadium Oxide Nanocrystals

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Author : Amy Jo Bergerud
language : en
Publisher:
Release Date : 2016

Phase Stability And Transformations In Vanadium Oxide Nanocrystals written by Amy Jo Bergerud and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.

Vanadium oxides are both fascinating and complex, due in part to the many compounds and phases that can be stabilized as well as the phase transformations which occur between them. The metal to insulator transitions (MITs) that take place in vanadium oxides are particularly interesting for both fundamental and applied study as they can be induced by a variety of stimuli (i.e., temperature, pressure, doping) and utilized in many applications (i.e., smart windows, sensors, phase change memory). Nanocrystals also tend to demonstrate interesting phase behavior, due in part to the enhanced influence of surface energy on material thermodynamics. Vanadium oxide nanocrystals are thus expected to demonstrate very interesting properties in regard to phase stability and phase transformations, although synthesizing vanadium oxides in nanocrystal form remains a challenge. Vanadium sesquioxide (V2O3) is an example of a material that undergoes a MIT. For decades, the low temperature monoclinic phase and high temperature corundum phase were the only known crystal structures of V2O3. However, in 2011, a new metastable polymorph of V2O3 was reported with a cubic, bixbyite crystal structure. In Chapter 2, a colloidal route to bixbyite V2O3 nanocrystals is presented. In addition to being one of the first reported observations of the bixbyite phase in V2O3, it is also one of the first successful colloidal syntheses of any of the vanadium oxides. The nanocrystals possess a flower-like morphology, the size and shape of which are dependent on synthesis time and temperature, respectively. An aminolysis reaction mechanism is determined from Fourier transform infrared spectroscopy data and the bixbyite crystal structure is confirmed by Rietveld refinement of X-ray diffraction (XRD) data. Phase stability is assessed in both air and inert environments, confirming the metastable nature of the material. Upon heating in an inert atmosphere above 700 C, the nanocrystals irreversibly transform to the bulk stable corundum phase of V2O3 with concurrent particle coarsening. This, in combination with the enhanced stability of the nanocrystals over bulk, suggests that the bixbyite phase may be stabilized due to surface energy effects, a well-known phenomenon in nanocrystal research. In Chapter 3, the reversible incorporation of oxygen in bixbyite V2O3 is reported, which can be controlled by varying temperature and oxygen partial pressure. Based on XRD and thermogravimetric analysis, it is found that oxygen occupies interstitial sites in the bixbyite lattice. Two oxygen atoms per unit cell can be incorporated rapidly and with minimal changes to the structure while the addition of three or more oxygen atoms destabilizes the structure, resulting in a phase change that can be reversed upon oxygen removal. Density functional theory (DFT) supports the reversible occupation of interstitial sites in bixbyite by oxygen and the 1.1 eV barrier to oxygen diffusion predicted by DFT matches the activation energy of the oxidation process derived from observations by in situ XRD. The observed rapid oxidation kinetics are thus facilitated by short diffusion paths through the bixbyite nanocrystals. Due to the exceptionally low temperatures of oxidation and reduction, this material, made from earth-abundant atoms, is proposed for use in oxygen storage applications, where oxygen is reversibly stored and released. Further oxidation of bixbyite V2O3 under controlled oxygen partial pressure can lead to the formation of nanocrystalline vanadium dioxide (VO2), a material that is studied for its MIT that occurs at 68 C in the bulk. This transformation is accompanied by a change in crystal structure, from monoclinic to rutile phase, and a change in optical properties, from infrared transparent to infrared blocking. Because of this, VO2 is promising for thermochromic smart window applications, where optical properties vary with temperature. Recently, alternative stimuli have been utilized to trigger MITs in VO2, including electrochemical gating. Rather than inducing the expected monoclinic to rutile phase transition as originally proposed, electrochemical gating of the insulating phase was recently shown to induce oxygen vacancy formation in VO2, thereby inducing metallization, while the characteristic V-V dimerization of the monoclinic phase was retained. In Chapter 4, the preparation and electrochemical reduction of VO2 nanocrystal films is presented. The nanocrystalline morphology allows for the study of transformations under conditions that enhance the gating effect by creating a large VO2-electrolyte interfacial area and by reducing the path length for diffusion. The resulting transitions are observed optically, from insulator to metal to insulator and back, with in situ visible-near infrared spectroelectrochemistry and correlated with structural changes monitored by Raman and X-ray absorption spectroscopies. The never-before-seen transition to an insulating phase under progressive electrochemical reduction is attributed to an oxygen defect induced phase transition to a new phase. This is likely enabled by the nanocrystalline nature of the sample, which may enhance the kinetics of oxygen diffusion, support a higher degree of lattice expansion-induced strain, or simply alter the thermodynamics of the system.

Geological Survey Bulletin

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Author :
language : en
Publisher:
Release Date : 1971

Geological Survey Bulletin written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1971 with Geology categories.

Geological Survey Professional Paper

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Author : Geological Survey (U.S.)
language : en
Publisher:
Release Date : 1960

Geological Survey Professional Paper written by Geological Survey (U.S.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1960 with categories.