Relevant bibliographies by topics / Allotropie

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
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Academic literature on the topic 'Allotropie'

Author: Grafiati
Published: 4 June 2021
Last updated: 4 March 2023

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Journal articles on the topic "Allotropie"

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Pezoldt, Jörg. "Formation of Different Carbon Phases on SiC." Materials Science Forum 615-617 (March 2009): 227–30. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.227.

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Carbon is able to crystallise in different allotrope modifications. They mainly differ in the dominating bindings formed in dependence on the hybridization sp, sp2 and sp3 of the carbon atoms. The present work demonstrates the formation of two different forms of car¬bon allotropes by heating both polar surfaces of on axis 6H-SiC(0001) and 6H-SiC(000 ) crystals to temperatures above 1600°C. In consequence of the structural evolution graphite-like (sp2-hybridised) and carbine-like (sp-hybridised) allotropic carbon modifications were obtained.
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Wynnyckyj, J. R., and C. G. Morris. "A shear-type allotropie transformation in alumina." Metallurgical Transactions B 16, no. 2 (June 1985): 345–53. http://dx.doi.org/10.1007/bf02679726.

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Deinum, H. W. "Zur Frage der Allotropie des Flüssigen Benzols." Recueil des Travaux Chimiques des Pays-Bas 53, no. 11 (September 3, 2010): 1061–63. http://dx.doi.org/10.1002/recl.19340531109.

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Sokołowski, M., A. Sokołowska, M. Wronikowski, and T. Kosik. "Allotropie phase transformation induced by UV power laser irradiation of boron nitride." Journal of Materials Science 25, no. 1 (January 1990): 263–67. http://dx.doi.org/10.1007/bf00544218.

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Gnanaraj, Leena Rosalind Mary, and Deepa Ganesan. "Topological Study of 6.82 D Carbon Allotrope Structure." Symmetry 14, no. 5 (May 18, 2022): 1037. http://dx.doi.org/10.3390/sym14051037.

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Carbonallotropes are widely available and can be found in the atmosphere, the earth’s crust, and in living creatures in myriad forms. Allotropes are also used in several fields, including for medicinal and biological applications, due to their intriguing properties such as low resistance, high electron mobility, abnormal quantum hall effect, unconventional superconductivity in graphene, and so on. The theoretical analysis of carbon allotropes can hence be quite useful as it leads to a better understanding of the nature and behavior of these ubiquitous materials and also opens the door for even better applications. The objective of this research is to theoretically analyze the carbon allotrope by using four kinds of vertex degree based (VDB) topological indices (Tis), namely VDB multiplicative topological indices, VDB indices using M-Polynomial, VDB entropy measures, and irregularity indices. This analysis will extend the current body of knowledge available for this allotrope and help future researchers in the synthesis of new allotropes.
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Impellizzeri, A., A. A. Vorfolomeeva, N. V. Surovtsev, A. V. Okotrub, C. P. Ewels, and D. V. Rybkovskiy. "Simulated Raman spectra of bulk and low-dimensional phosphorus allotropes." Physical Chemistry Chemical Physics 23, no. 31 (2021): 16611–22. http://dx.doi.org/10.1039/d1cp02636d.

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The Placzek approximation with DFT accurately reproduces experimental Raman spectra for phosphorus allotropes. We explain bulk allotrope spectral features in black and white phosphorus, and predict spectra for phosphorus nanostructures.
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Sakai, Hiroshi, Hiroshi Sera, and Satoru Nakashima. "Mössbauer and X-ray diffraction studies of an allotropie form of tin, “α2-Sn”." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 76, no. 1-4 (April 1993): 350–51. http://dx.doi.org/10.1016/0168-583x(93)95234-v.

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Shawki, E. E., S. N. Flengas, and D. R. Sadoway. "Drop calorimetry of the compounds NbCl5, TaCl5, RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6." Canadian Journal of Chemistry 67, no. 7 (July 1, 1989): 1193–99. http://dx.doi.org/10.1139/v89-180.

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Enthalpy contents for NbCl5, TaCl5, RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6 were measured as functions of temperature using a high temperature aluminum block drop calorimeter. It was found that the solid compounds RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6 undergo allotropie solid–solid transformations and the enthalpies and entropies associated with these phase changes, as well as from fusion, have been evaluated.Molar heat capacities for the systems investigated are reported as linear functions of temperature.The molar heat capacities for solid and molten NbCl5 or TaCl5 were used together with available vapour pressure data to express enthalpies and free energies of vaporization for these compounds as functions of temperature through the third law calculation method. Keywords: calorimetry, heat capacities, transition enthalpies, niobium compounds, tantalum compounds.
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Rickhaus, Michel, Marcel Mayor, and Michal Juríček. "Chirality in curved polyaromatic systems." Chemical Society Reviews 46, no. 6 (2017): 1643–60. http://dx.doi.org/10.1039/c6cs00623j.

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Chiral non-planar polyaromatic systems that display zero, positive or negative Gaussian curvature are analysed and their potential to ‘encode’ chirality of larger sp2-carbon allotropes is evaluated. Shown is a hypothetical peanut-shaped carbon allotrope, where helical chirality results from the interplay of various curvature types.
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Yap, Stephanie Hui Kit, Kok Ken Chan, Swee Chuan Tjin, and Ken-Tye Yong. "Carbon Allotrope-Based Optical Fibers for Environmental and Biological Sensing: A Review." Sensors 20, no. 7 (April 5, 2020): 2046. http://dx.doi.org/10.3390/s20072046.

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Recently, carbon allotropes have received tremendous research interest and paved a new avenue for optical fiber sensing technology. Carbon allotropes exhibit unique sensing properties such as large surface to volume ratios, biocompatibility, and they can serve as molecule enrichers. Meanwhile, optical fibers possess a high degree of surface modification versatility that enables the incorporation of carbon allotropes as the functional coating for a wide range of detection tasks. Moreover, the combination of carbon allotropes and optical fibers also yields high sensitivity and specificity to monitor target molecules in the vicinity of the nanocoating surface. In this review, the development of carbon allotropes-based optical fiber sensors is studied. The first section provides an overview of four different types of carbon allotropes, including carbon nanotubes, carbon dots, graphene, and nanodiamonds. The second section discusses the synthesis approaches used to prepare these carbon allotropes, followed by some deposition techniques to functionalize the surface of the optical fiber, and the associated sensing mechanisms. Numerous applications that have benefitted from carbon allotrope-based optical fiber sensors such as temperature, strain, volatile organic compounds and biosensing applications are reviewed and summarized. Finally, a concluding section highlighting the technological deficiencies, challenges, and suggestions to overcome them is presented.
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Dissertations / Theses on the topic "Allotropie"

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Bouslama, Mohamed. "Elaboration de nouveaux catalyseurs nanostructurés à base de sol de TiO₂ immobilisés dans un matériau monolithique ultraporeux d'alumine." Paris 13, 2013. http://scbd-sto.univ-paris13.fr/secure/edgalilee_th_2012_bouslama.pdf.

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Ce travail de thèse a pour objectif d’étudier la possibilité d’immobilisation de nanoparticules de TiO₂ dans différentes classes de substrats d’alumine monolithique poreuse et d’inspecter leurs activités en photocatalyse. Les monolithes d’alumine sont obtenus par oxydation à l’air atmosphérique et à la température ambiante, d’une surface d’aluminium amalgamée. Après élaboration et consolidation par traitement chimique et/ou thermique, différents substrats sont obtenus, qui différent par leurs propriétés allotropiques, microstructurales, et leur surface spécifique. L’élaboration du photocatalyseur est réalisée selon un procédé sol-gel à partir du précurseur, tétraisopropoxyde de titane (TTIP) dans un réacteur sol-gel à micromélange rapide. L’immobilisation d’oxo-nanoparticules de TiO₂ est réalisée dans le même réacteur par imprégnation des monolithes d’alumine. Des traitements thermiques ultérieurs permettent d’obtenir des nanoparticules de dioxyde de titane en phase anatase. Les caractéristiques structurales des nanodépôts ont été quantifiées par diffraction des rayons X, adsorption de N₂, microscopie électronique à balayage et à transmission. La décomposition photocatalytique d’un polluant modèle (l’éthylène) a été effectuée dans un réacteur tubulaire à lit fixe. Des études sur l’influence de la température de traitement des dépôts sur la taille et la variété allotropique du TiO₂ immobilisé sur les différents types de supports sont détaillées dans ce travail. La répercussion des propriétés structurales et cristallochimiques sur l’activité photocatalytique est discutée mettant en évidence le rôle du substrat alumineux dans la stabilisation de la phase de TiO₂ la plus active en photocatalyse : la phase anatase
This PhD work aims to explore the possibility of immobilization of TiO₂nanoparticles in different classes of ultraporous monolithic alumina and inspect their photocatalytic activities. The alumina monoliths are obtained by oxidation of alumina with atmospheric air and at room temperature. After development and consolidation by chemical and / or thermal treatments different substrates are obtained which differby their allotropic properties, microstructure and specific area. The preparation of photocatalyst is made according to a sol-gel process from the precursor: titanium tetra-isopropoxyde (TTIP). It is performed by a sol-gel reactor with rapid micromixing and in-situ particules granulometry contol. Immobilization of oxo-TiO₂ nanoparticles is carried out in the same reactor by impregnating alumina monoliths. Subsequent heat treatments lead to anatase nanoparticles of titanium dioxide. The structural characteristics of nanocoatings were studied by X-ray diffraction, N₂ adsorption, scanning and transmission electron microscopy. The photocatalytic decomposition of a model pollutant (ethylene) was carried out in a fixed bed tubular reactor. Studies of influence of processing temperature on size and allotropic form of TiO₂ immobilized on different types of substrates are detailed in this work. The impact of structural and allotropic properties on the photocatalytic activity is discussed, highlighting the role of the alumina substrates in the stabilization of the most active TiO₂ polymorph in photocatalysis: anatase
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Valance, Stéphane Borst René de. "Aspects mécaniques du changement de phase allotropique à l'échelle mésoscopique." Villeurbanne : Doc'INSA, 2008. http://docinsa.insa-lyon.fr/these/pont.php?id=valance.

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Valance, Stéphane. "Aspects mécaniques du changement de phase allotropique à l'échelle mésoscopique." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0101/these.pdf.

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La prédiction de l’état mécanique de structures en acier soumises à des chargements thermiques ne peut se faire sans modélisation du phénomène de changement de phase allotropique. En effet, le changement de phase induit, pour les aciers, un mécanisme appelé plasticité de transformation conduisant à une déformation irréversible pour des chargements inférieurs à la limite élastique des phases. De nombreux modèles analytiques ont proposé une approche homogénéisée pour la prédiction de l’état mécanique. Mais, pour des chargements complexes, ces modèles se révèlent inadéquates. Prenant acte de ces lacunes, nous présentons une modélisation plus proche de sa description heuristique. L’échelle mésoscopique retenue pour ce travail est de l’ordre de la taille de grain. A cette échelle, nous considérons le comportement de chaque phase comme homogène au sens de la mécanique des milieux continus, par contre, le front de changement de phase est modélisé explicitement. Cette approche mésoscopique du phénomène s’est faite expérimentalement et numériquement. Expérimentalement, nous avons mis au point et utilisé une manipulation permettant la traction et le chauffage sous vide partiel d’une éprouvette. L’acquisition de la surface de l’échantillon pendant la transformation martensitique a conduit, sous certaines hypothèses et grâce à la corrélation numérique d’image, à l’identification partielle des zones affectées localement par la transformation. Numériquement, l’utilisation de la méthode des éléments finis étendus appliquée à des champs de déplacement faiblement discontinus. L’utilisation de cette méthode nécessite la modélisation du support de discontinuité -le front. Pour cela, en s’aidant de la méthode level set, nous avons créé des schémas numériques éléments finis permettant la représentation du support et sa propagation. En sus, nous nous sommes intéressés au calcul des forces motrices définies sur le front à partir du tenseur d’Eshelby et représentatives de sa vitesse locale
The prediction of the mechanical state of steel structures submit to thermo-mechanical loading must take into account consequences of allotropic phase change. Indeed, phase change induce, at least for steels, a mechanism of TRansformation Induced Plasticity (TRIP) leading to irreversible deformation even for loading less than elastic yield limit. Homogeneized analytical models generally fail to achieve a correct prediction for complex loading. In order to overcome these difficulties, we present a model achieving a sharper description of the phenomenon. The mesoscopic working scale we adopt here is the grain scale size. Hence, we consider that the behaviour of each phase is homogenous in the sense of continuous media mechanic, whereas the front is explicitly described. We work both experimentally and numerically. Experimentally, we designed a test facility enabling thermo mechanical loading of the sample under partial vacuum. Acquisition of sample surface while martensitic transformation is happening leads, under some hypothesis and thanks to Digital Image Correlation, to the partial identification of area affected by transformation. Numerically, the eXtended Finite ElementMethod is applied for weakly discontinuous displacement fields. Used of this method needs to numerically track the transformation front -discontinuity support. In that goal, based on level set method, we develop FEM numerical scheme enabling recognition and propagation of discontinuity support. Finally, this work is complete by an approach of driving forces introduced through Eshelbian mechanics which are dual of front velocity. Keywords : allotropic phase change, TRansformation Induced Plasticity, eXtended Finite Element Method (X-FEM), Level set method
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Wosylus, Aron. "Synthese und in-situ Untersuchungen dreidimensionaler Silicium- und Germaniumnetzwerke unter Druck." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1243954160355-12727.

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Schwerpunkte der Arbeit waren die Synthese und in-situ Charakterisierung metastabiler Modifikationen der Elemente Silicium und Germanium, sowie die Darstellung binärer Silicide und Germanide der Erdalkali- und Seltenerdmetalle unter Druck (bis 20 GPa) und bei hoher Temperatur (bis 2200 K). Dabei konnten die Phasenbeziehungen von Allotropen des Germaniums näher beleuchtet werden und es gelang, eine neue Germaniummodifikation, Ge(hR8), in-situ strukturell zu charakterisieren. Die neu dargestellten metastabilen binären Silicide und Germanide unterteilen sich strukturell in solche, die clathratartige Tetrel-Netzwerke mit einer Koordinationszahl von drei und vier enthalten und in jene, bei denen die Anzahl benachbarter Tetrelatome vier übersteigt. So konnten beispielsweise Netzwerke dargestellt werden, die acht homonukleare Silicium oder Germanium Kontakte im Netzwerk aufweisen. Neben der strukturellen Charakterisierung standen die Bestimmungen der elektrischen Leitfähigkeit und des Magnetismus, sowie die Ermittlung der thermischen Eigenschaften im Focus der Arbeit
Key aspects of the present work were the synthesis and in-situ characterization of metastable modifications of elemental silicon and germanium as well as the preparation of binary silicides and germanides of the alkaline earth and rare earth metals under pressure (up to 20 GPa) and at elevated temperatures (up to 2200 K). In that process the phase relations of germanium allotropes could be examined more closely and led to the preparation of a new germanium modification, Ge(hR8), which could be structurally characterized by in-situ experiments. The prepared silicides and germanides can be structurally separated in those containing clathrate-like networks with a coordination number of three and four and those which contain more neighbors in the network than four e.g., eight homonuclear silicon or germanium contacts in the network of CeSi5 and CeGe5. Beside the structural characterization the determination of the electrical resistivity and the magnetical properties as well as the analysis of the thermal behavior were in focus of the work
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Bruzy, Nicolas. "Couplage entre plasticité et transformation de phase dans le Fer : Étude par corrélation d’images et modélisation." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0056/document.

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Les propriétés mécaniques des alliages de fer sont largement conditionnées par leur microstructure et la population de défauts locaux qu’elle contient. Comme il s'agit d'un moment de forte interaction entre ces deux éléments, l'étude des transformations α-γ et γ-α du fer mérite une attention particulière. Outre le passage d'une structure cristalline cubique centrée à une structure cubique faces centrées – donc de compacités différentes –,elles sont associées à une réduction des paramètres de maille. Le changement de volume correspondant est responsable de déformations mécaniques locales autour des sites de germination. La technique de corrélation d'images numériques(CIN) s'est montrée fiable pour ce qui est de calculer des champs cinématiques à l'échelle de quelques grains. Dans ce travail, elle est adaptée à la capture de localisations de la déformation pendant les transformations allotropiques. Un banc expérimental est conçu pour obtenir des images haute résolution avec un contrôle fin des sollicitations thermiques. Des essais de validation sont d'abord effectués sur du fer industriel. Puis des échantillons de fer haute pureté sont ensuite soumis à des cycles de transformation α-γ-α et les champs de déformation correspondant sont calculés par CIN. Associés à l'acquisition des orientations initiales et finales, ils sont utilisés pour valider les mécanismes de transformation proposés dans la littérature. En parallèle, un modèle, écrit en petites déformations, est construit en incorporant des composants liés à la transformation dans une fonctionnelle dont les conditions de stationnarité sont équivalentes au problème thermomécanique à résoudre. Les incréments des variables internes, incluant glissements plastiques et fractions volumique transformées, sont obtenus en minimisant cette fonctionnelle
Mechanical properties of iron-based alloys are largely conditioned by their microstructure and the population of local defects inside this microstructure. As it is a moment of massive interplay between these two elements, the study of the α-γ and γ-α transformations in iron is of particular interest. Besides a change from a body-centered cubic to a face-centered cubic crystal structure – and thus a change in compacity –, they lead to a lattice parameter reduction. The corresponding change in volume is responsible for local mechanical deformations around transformation sites. Digital Image Correlation (DIC) technique has been proven reliable to compute kinematic fields at the scale of a few grains. In the present work, an adaptation of this technique to the observation of strain localizations induced by the formation of a new phase is proposed. A home-made device is designed to obtain high resolution images and to control heating and cooling. Tests are first conducted on industrial iron to assess the viability of the procedure. High-purity iron samples are then submitted to α-γ-α transformation cycles and the associated strain fields are computed. In combination with the acquisition of initial and final orientations they are used to validate transformation mechanisms proposed in the literature. In parallel, a model, written under the small strain format, is built by incorporating transformation related components into a power functional whose stationarity conditions are equivalent to the thermomechanical problem. In accordance with variational principles, the evolution of internal variables,including plastic slip increments and fraction of the material locally transformed, are computed through the minimization of the functional
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Leste-Lasserre, Pierre. "Sulfur allotrope chemistry." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38218.

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The synthesis of the sulfur homocycles S6, S9, S10, S12 and S20, which belong to the group of sulfur allotropes, has been achieved based on existing procedures. Polymeric sulfur Smu was also prepared.
The parameters of a small scale model reaction between 2,3-diphenyl-1,3-butadiene and S10 were optimized. Products were identified and 1H-NMR yields were calculated by comparison with an internal standard. The experimental parameters of this model served as a base for further reactions of S 10 with a variety of simple or conjugated olefins. The products of these reactions were fully isolated and characterized using standard spectroscopic techniques. The structures of a new bis-sulfurated compound having a norbornane framework and of the product obtained from the dimerization of norborn-5-ene-2,3-dithiol were also confirmed by single crystal X-ray crystallography.
The sulfur homocycles S9, S12 and S20 were also found to react with norbornene and two different 1,3-dienes. Products were identified and 1H-NMR yields for these small scale reactions were calculated by internal standard comparison. Differences and similarities with the products obtained with S10 are discussed. Sulfuration efficiencies of the different allotropes towards selected substrates are also compared.
A mechanistic study was carried out. The implication of sulfur radicals in the thermal decomposition of S10 has been suggested. Reaction mechanisms accounting for the formation of the different products observed are proposed.
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Wosylus, Aron. "Synthese und in-situ Untersuchungen dreidimensionaler Silicium- und Germaniumnetzwerke unter Druck." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23730.

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Schwerpunkte der Arbeit waren die Synthese und in-situ Charakterisierung metastabiler Modifikationen der Elemente Silicium und Germanium, sowie die Darstellung binärer Silicide und Germanide der Erdalkali- und Seltenerdmetalle unter Druck (bis 20 GPa) und bei hoher Temperatur (bis 2200 K). Dabei konnten die Phasenbeziehungen von Allotropen des Germaniums näher beleuchtet werden und es gelang, eine neue Germaniummodifikation, Ge(hR8), in-situ strukturell zu charakterisieren. Die neu dargestellten metastabilen binären Silicide und Germanide unterteilen sich strukturell in solche, die clathratartige Tetrel-Netzwerke mit einer Koordinationszahl von drei und vier enthalten und in jene, bei denen die Anzahl benachbarter Tetrelatome vier übersteigt. So konnten beispielsweise Netzwerke dargestellt werden, die acht homonukleare Silicium oder Germanium Kontakte im Netzwerk aufweisen. Neben der strukturellen Charakterisierung standen die Bestimmungen der elektrischen Leitfähigkeit und des Magnetismus, sowie die Ermittlung der thermischen Eigenschaften im Focus der Arbeit.
Key aspects of the present work were the synthesis and in-situ characterization of metastable modifications of elemental silicon and germanium as well as the preparation of binary silicides and germanides of the alkaline earth and rare earth metals under pressure (up to 20 GPa) and at elevated temperatures (up to 2200 K). In that process the phase relations of germanium allotropes could be examined more closely and led to the preparation of a new germanium modification, Ge(hR8), which could be structurally characterized by in-situ experiments. The prepared silicides and germanides can be structurally separated in those containing clathrate-like networks with a coordination number of three and four and those which contain more neighbors in the network than four e.g., eight homonuclear silicon or germanium contacts in the network of CeSi5 and CeGe5. Beside the structural characterization the determination of the electrical resistivity and the magnetical properties as well as the analysis of the thermal behavior were in focus of the work.
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Pierce, Benjamin Thomas. "Search for Superconductivity in Defect Enhanced Allotropic Carbon Systems." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384850067.

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Ewh, Ashley Elizabeth. "Effects of Allotropic Transformations on Interdiffusion Behavior in Binary Systems." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5201.

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Diffusion plays a significant role in most materials systems by controlling microstructural development. Consequently, the overall properties of a material can be largely dependent upon diffusion. This study investigated the interdiffusion behavior of three binary systems, namely, Mo-Zr, Fe-Mo, and Fe-Zr. The main interest in these particular metals is for application in nuclear fuel assemblies. Nuclear fuel plates generally consist of two main components which are the fuel and the cladding. Due to diffusional interactions that can occur between these two components, a third is sometimes added between the fuel and cladding to serve as a diffusion barrier layer. Fe, Mo, and Zr can act as either cladding or barrier layer constituents and both Mo and Zr also serve as alloying additions in uranium based metallic fuels. Therefore, a fundamental understanding of the diffusional interactions in these systems is critical in predicting the performance and lifetime of these fuels. In order to study this diffusion behavior, a series of solid-to-solid diffusion couples were assembled between Fe, Mo, and Zr. These couples were then diffusion annealed isothermally for various predetermined times over a range of temperatures, including some both above and below the allotropic transformation temperatures for Fe and Zr. Following the diffusion anneal, the couples were water quenched, cross-sectioned, and prepared for microstructural and compositional characterization. A combination of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron probe microanalysis (EPMA) were used to obtain micrographs showing the microstructure and to collect compositional data for identifying intermediate phases and determining concentration profiles across the interdiffusion zone. Based on this characterization, the phases that developed in the diffusion zones were identified. In the Mo-Zr system, a large Zr solid solution layer developed in the couples annealed at and above 850[degrees]C and a thin (~1-2 [micro]m) layer of Mo2Zr formed in all couples. Growth constants and concentration dependent interdiffusion coefficients were calculated for the Mo2Zr and Zr solid solution phases, respectively. In the Fe-Mo system, both the [lambda]-Fe2Mo and [micro]-Fe7Mo6 phases were observed in couples annealed at 900[degrees]C and below while [micro]-Fe7Mo6 and [alpha]-Fe solid solution layers were observed in couples annealed above 900[degrees]C. The relevant growth constants and activation energies for growth were calculated. In the Fe-Zr system, the couple annealed at 750[degrees]C developed an FeZr2 and an FeZr3 layer while the couple annealed at 850[degrees]C developed an Fe2Zr and Fe23Zr6 layer in the diffusion zone. The results of this analysis were then compared to available information from literature and the corresponding binary phase diagrams for each system. The results are discussed with respect to the effects of the allotropic transformations of Fe and Zr on the interdiffusion behavior in these systems.
ID: 031001410; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Yongho Sohn.; Title from PDF title page (viewed June 13, 2013).; Thesis (M.S.M.S.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 84-89).
M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering; Accelerated BS to MS
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Bojdys, Michael Janus. "On new allotropes and nanostructures of carbon nitrides." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2010/4123/.

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In the first section of the thesis graphitic carbon nitride was for the first time synthesised using the high-temperature condensation of dicyandiamide (DCDA) – a simple molecular precursor – in a eutectic salt melt of lithium chloride and potassium chloride. The extent of condensation, namely next to complete conversion of all reactive end groups, was verified by elemental microanalysis and vibrational spectroscopy. TEM- and SEM-measurements gave detailed insight into the well-defined morphology of these organic crystals, which are not based on 0D or 1D constituents like known molecular or short-chain polymeric crystals but on the packing motif of extended 2D frameworks. The proposed crystal structure of this g-C3N4 species was derived in analogy to graphite by means of extensive powder XRD studies, indexing and refinement. It is based on sheets of hexagonally arranged s-heptazine (C6N7) units that are held together by covalent bonds between C and N atoms. These sheets stack in a graphitic, staggered fashion adopting an AB-motif, as corroborated by powder X-ray diffractometry and high-resolution transmission electron microscopy. This study was contrasted with one of many popular – yet unsuccessful – approaches in the last 30 years of scientific literature to perform the condensation of an extended carbon nitride species through synthesis in the bulk. The second section expands the repertoire of available salt melts introducing the lithium bromide and potassium bromide eutectic as an excellent medium to obtain a new phase of graphitic carbon nitride. The combination of SEM, TEM, PXRD and electron diffraction reveals that the new graphitic carbon nitride phase stacks in an ABA’ motif forming unprecedentedly large crystals. This section seizes the notion of the preceding chapter, that condensation in a eutectic salt melt is the key to obtain a high degree of conversion mainly through a solvatory effect. At the close of this chapter ionothermal synthesis is seen established as a powerful tool to overcome the inherent kinetic problems of solid state reactions such as incomplete polymerisation and condensation in the bulk especially when the temperature requirement of the reaction in question falls into the proverbial “no man’s land” of classical solvents, i.e. above 250 to 300 °C. The following section puts the claim to the test, that the crystalline carbon nitrides obtained from a salt melt are indeed graphitic. A typical property of graphite – namely the accessibility of its interplanar space for guest molecules – is transferred to the graphitic carbon nitride system. Metallic potassium and graphitic carbon nitride are converted to give the potassium intercalation compound, K(C6N8)3 designated according to its stoichiometry and proposed crystal structure. Reaction of the intercalate with aqueous solvents triggers the exfoliation of the graphitic carbon nitride material and – for the first time – enables the access of singular (or multiple) carbon nitride sheets analogous to graphene as seen in the formation of sheets, bundles and scrolls of carbon nitride in TEM imaging. The thus exfoliated sheets form a stable, strongly fluorescent solution in aqueous media, which shows no sign in UV/Vis spectroscopy that the aromaticity of individual sheets was subject to degradation. The final section expands on the mechanism underlying the formation of graphitic carbon nitride by literally expanding the distance between the covalently linked heptazine units which constitute these materials. A close examination of all proposed reaction mechanisms to-date in the light of exhaustive DSC/MS experiments highlights the possibility that the heptazine unit can be formed from smaller molecules, even if some of the designated leaving groups (such as ammonia) are substituted by an element, R, which later on remains linked to the nascent heptazine. Furthermore, it is suggested that the key functional groups in the process are the triazine- (Tz) and the carbonitrile- (CN) group. On the basis of these assumptions, molecular precursors are tailored which encompass all necessary functional groups to form a central heptazine unit of threefold, planar symmetry and then still retain outward functionalities for self-propagated condensation in all three directions. Two model systems based on a para-aryl (ArCNTz) and para-biphenyl (BiPhCNTz) precursors are devised via a facile synthetic procedure and then condensed in an ionothermal process to yield the heptazine based frameworks, HBF-1 and HBF-2. Due to the structural motifs of their molecular precursors, individual sheets of HBF-1 and HBF-2 span cavities of 14.2 Å and 23.0 Å respectively which makes both materials attractive as potential organic zeolites. Crystallographic analysis confirms the formation of ABA’ layered, graphitic systems, and the extent of condensation is confirmed as next-to-perfect by elemental analysis and vibrational spectroscopy.
Die vorliegende Arbeit befasst sich mit der Synthese und Charakterisierung neuer Allotropen und Nanostrukturen von Karbonitriden und berührt einige ihrer möglichen Anwendungen. Alle gezeigten, ausgedehnten, kovalent verbundenen Karbonitridgerüste wurden in einem ionothermalen Syntheseprozess – einer Hochtemperaturbehandlung in einem eutektischen Salzgemisch als ungewöhnlichem Lösungsmittel – aus einfachen Präkursormolkülen erzeugt. Der Kondensationsmechanismus folgt einer temperaturinduzierten Deaminierung und Bildung einer ausgedehnten, aromatischen Einheit; des dreifach substituierten Heptazines. Die Dissertation folgt vier übergreifenden Themen, beginnend mit der Einleitung in Karbonitridsysteme und der Suche nach einem Material, welches einzig aus Kohlenstoff und Stickstoff aufgebaut ist – einer Suche, die 1834 mit den Beobachtungen Justus von Liebigs „über einige Stickstoffverbindungen“ begann. Der erste Abschnitt zeigt die erfolgreiche Synthese von graphitischem Karbonitrid (g-C3N4); einer Spezies, welche auf Schichten hexagonal angeordneter s-Heptazineinheiten beruht, die durch kovalente Bindungen zwischen C- und N-Atomen zusammengehalten werden, und welche in einer graphitischen, verschobenen Art und Weise gestapelt sind. Der zweite Abschnitt berührt die Vielfalt von Salzschmelzensystemen, die für die Ionothermalsynthese geeignet sind und zeigt auf, dass die bloße Veränderung der Salzschmelze eine andere Kristallphase des graphitischen Karbonitrides ergibt – das g-C3N4-mod2. Im dritten Abschnitt wird vom Graphit bekannte Interkallationschemie auf das g-C3N4 angewendet, um eine Kalliuminterkallationsverbindung des graphitischen Karbonitirdes zu erhalten (K(C6N8)3). Diese Verbindung kann in Analogie zum graphitischen System leicht exfoliiert werden, um Bündel von Karbonitridnanoschichten zu erhalten, und weist darüberhinaus interessante optische Eigenschaften auf. Der vierte und letzte Abschnitt handelt von der Einführung von Aryl- und Biphenylbrücken in das Karbonitridmaterial durch rationale Synthese der Präkursormoleküle. Diese ergeben die heptazinbasierten Frameworks, HBF-1 und HBF-2 – zwei kovalente, organische Gerüste.
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Books on the topic "Allotropie"

1

Smolegovskiĭ, A. M. Istorii︠a︡ izuchenii︠a︡ poliformizma: Khimicheskiĭ aspekt : istorii︠a︡ izuchenii︠a︡ allotropii ugleroda. Moskva: In-t istorii estestvoznanii︠a︡ i tekhniki RAN, 2010.

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Kharisov, Boris Ildusovich, and Oxana Vasilievna Kharissova. Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-03505-1.

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Khokhlov, A. F. Allotropii︠a︡ kremnii︠a︡: Monografii︠a︡. Nizhniĭ Novgorod: Izd-vo Nizhegorodskogo gos. im. N.I. Lobachevskogo, 2002.

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Graphene: Carbon in two dimensions. New York: Cambridge University Press, 2012.

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Poole, Jackie M. Results of field surveys for Allotropa virgata in the Beaverhead and Deerlodge National Forests. Helena, Mont: Montana Natural Heritage Program, 1992.

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Roe, Lisa Schassberger. Status review of Allotropa virgata, U.S.D.A. Forest Service, Region 1, Bitterroot and Deerlodge National Forests, Montana. Helena, Mont: Montana Natural Heritage Program, 1992.

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Dahners, Laurence E. Allotropes. CreateSpace Independent Publishing Platform, 2013.

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Aslam, Jeenat, Chandrabhan Verma, Dakeshwar Kumar Verma, and Ruby Aslam, eds. Carbon Allotropes. De Gruyter, 2022. http://dx.doi.org/10.1515/9783110782820.

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Fisher, David. Diffusion in Carbon Allotropes. Trans Tech Publications, Limited, 2013.

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Fisher, David. Diffusion in Carbon Allotropes: A Compilation. Trans Tech Publications, Limited, 2013.

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Book chapters on the topic "Allotropie"

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Gooch, Jan W. "Allotropes." In Encyclopedic Dictionary of Polymers, 29. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_456.

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Scherrmann, Jean-Michel, Kim Wolff, Christine A. Franco, Marc N. Potenza, Tayfun Uzbay, Lisiane Bizarro, David C. S. Roberts, et al. "Allotropy." In Encyclopedia of Psychopharmacology, 66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-68706-1_4047.

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Gooch, Jan W. "Allotropy." In Encyclopedic Dictionary of Polymers, 29. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_457.

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Sun, Chang Q. "Carbon Allotropes." In Electron and Phonon Spectrometrics, 143–62. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3176-7_7.

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Kharisov, Boris Ildusovich, and Oxana Vasilievna Kharissova. "Conventional Carbon Allotropes." In Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications, 9–33. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-03505-1_2.

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Sun, Ya-Ping. "Nanoscale Carbon Allotropes." In Carbon Dots, 7–46. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-41184-8_2.

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Sisler, H. H. "In Phosphorus Allotropes." In Inorganic Reactions and Methods, 18. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470145210.ch6.

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Mathiasch, B. "Allotropy of Tin." In Inorganic Reactions and Methods, 76–77. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470145234.ch47.

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Sokołowska, A., J. Szmidt, J. Konwerska-Hrabowska, A. Werbowy, A. Olszyna, K. Zdunek, and S. Mitura. "Allotropic Forms of Carbon Nitride." In Diamond Based Composites, 151–59. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5592-2_11.

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Diudea, Mircea V., Beata Szefler, Csaba L. Nagy, and Attila Bende. "Exotic Allotropes of Carbon." In Exotic Properties of Carbon Nanomatter, 185–201. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-9567-8_8.

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Conference papers on the topic "Allotropie"

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Saleev, Vladimir A., and Alexandra V. Shipilova. "Ab initio modeling of optical properties of the new sp3 silicon and germanium allotropes." In Information Technology and Nanotechnology-2017. IP Zaitsev V.D., 2017. http://dx.doi.org/10.18287/1613-0073-2017-1966-10-15.

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The application of the hybrid topological-quantum-mechanical method to the search of new allotropes of 14th group elements is demonstrated for silicon and germanium. Starting from the databases of hypothetical and real zeolite nets and subsequently apllying the geometrical and energetic selection criteria, we extract the most energetically favourable structures for the allotropic modifications of silicon and germanium, and study their optical properties. In the framework of density functional theory we calculate the frequency-dependent complex dielectric tensors, refraction and absorption coefficients of the selected allotropes and their electronic band gaps.
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Shukla, B., N. V. Chandra Shekar, and P. Ch Sahu. "URe2-A compressibility study of allotropic phases." In SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872491.

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Pérez-Bernal, Francisco, and Lorenzo Fortunato. "A tale of two allotropes." In Symmetries and Order: Algebraic Methods in Many Body Systems: A symposium in celebration of the career of Professor Francesco Iachello. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5124578.

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Kumar, Gagnesh, and Sunil Agrawal. "CMOS limitations and futuristic carbon allotropes." In 2017 8th IEEE Annual Information Technology, Electronics and Mobile Communication Conference (IEMCON). IEEE, 2017. http://dx.doi.org/10.1109/iemcon.2017.8117151.

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Wei, Wei, Saiyu Qi, Yong Qi, Wei Wang, and Min Xi. "Allotropy Programming Paradigm for Ubiquitous Computing Environment." In 2007 International Conference on Convergence Information Technology (ICCIT 2007). IEEE, 2007. http://dx.doi.org/10.1109/iccit.2007.414.

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Wei, Wei, Saiyu Qi, Yong Qi, Wei Wang, and Min Xi. "Allotropy Programming Paradigm for Ubiquitous Computing Environment." In 2007 International Conference on Convergence Information Technology (ICCIT 2007). IEEE, 2007. http://dx.doi.org/10.1109/iccit.2007.4420311.

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Mufthas, M. R. M., and C. S. Rupasinghe. "3D Modelling of Carbon Allotropes Used in Nanotechnology." In 2010 Fourth Asia International Conference on Mathematical/Analytical Modelling and Computer Simulation. IEEE, 2010. http://dx.doi.org/10.1109/ams.2010.97.

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Jakhar, Mukesh, Ashok Kumar, Sunita Srivastava, Prakash Parida, and K. Tankeshwar. "Adsorption of nucleobases on different allotropes of phosphorene." In DAE SOLID STATE PHYSICS SYMPOSIUM 2018. AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5113200.

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Wang, Zhanyu, S. Y. Wang, R. J. Zhang, Y. X. Zheng, L. Y. Chen, C. Z. Wang, K. M. Ho, and W. S. Su. "Electronic and optical properties of novel carbon allotropes." In Optical Nanostructures and Advanced Materials for Photovoltaics. Washington, D.C.: OSA, 2015. http://dx.doi.org/10.1364/pv.2015.jtu5a.14.

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Krauland, Christine M., S. Zhang, F. Beg, Mingsheng Wei, Wolfgang Theobald, and Joao J. Santos. "Fast electron transport in different allotropes of shock-heated carbon." In 2016 IEEE International Conference on Plasma Science (ICOPS). IEEE, 2016. http://dx.doi.org/10.1109/plasma.2016.7534170.

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Reports on the topic "Allotropie"

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Lopez, P. C., J. R. Cost, and K. M. Axler. Martensitic nature of {delta} {yields} {gamma} allotropic transformation in plutonium. Office of Scientific and Technical Information (OSTI), September 1996. http://dx.doi.org/10.2172/378831.

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Stevens, Michael Francis. Mechanical Metallurgy of Plutonium Metal, Alloys, and Allotropes. Office of Scientific and Technical Information (OSTI), April 2020. http://dx.doi.org/10.2172/1617338.

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Story, Natasha Claire. Polymer Composites Reinforced by Carbon-Allotrope Fillers for Selective Laser Sintering (SLS) - A Review. Office of Scientific and Technical Information (OSTI), March 2020. http://dx.doi.org/10.2172/1603967.

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Partee, Jonathan. Optically detected magnetic resonance studies on π-conjugate polymers and novel carbon allotropes. Office of Scientific and Technical Information (OSTI), February 1999. http://dx.doi.org/10.2172/348885.

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