Point triple

thumb|upright=1.2|Diagramme de phase de l'eau. Le point triple de l'eau est à (soit ) et (soit ). right|thumb|Diagramme de phase du silicate d'aluminium à l'état solide. (Cyanite est un anglicisme pour Disthène.) Un point triple est un point du diagramme de phase température-pression d'une substance chimique pure où peuvent coexister trois phases différentes. Ce point est unique, c'est-à-dire que les trois phases ne peuvent coexister qu'à une température et une pression bien précises, dénommées « la température et la pression du point triple ». Quand les trois phases sont effectivement présentes, la variance du système est nulle. La notion de point triple s'applique principalement aux diagrammes de phase des corps purs :

le point triple d'un corps pur est le point du diagramme de phase température-pression où peuvent coexister les trois phases liquide, solide et gaz ;
comme un corps pur solide peut souvent présenter plusieurs formes allotropiques, il existe d'autres points tr

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (8)

Publications associées

Chargement

Personnes associées

Chargement

Unités associées

Chargement

Concepts associés (71)

Concepts associés

Chargement

Cours associés (33)

Cours associés

Chargement

Séances de cours associées (50)

Afficher plus

Séances de cours associées

Chargement

Development of high band gap protocrystalline material for p-i-n thin film silicon solar cells

Fabio Maurizio

High band gap thin film silicon solar cells are of high interest for the use as top cell in triple junctions solar cells. Protocrystalline silicon, in the transition phase between amorphous and microcrystalline silicon, is such a high band gap material. During this project, protocrystalline intrinsic layers have been developed and optimized in p-i-n single junction solar cells by plasma-enhanced chemical vapour deposition (PECVD) in a new multi-chamber deposition system. In the first series, cells and layers were deposited with different dilutions going from silane to hydrogen flux ratios of 1:1 to 1:64. At the dilutions 1:16 and 1:32, protocrystalline ma-terial was obtained which showed amorphous characteristics only up to a certain thickness, where crystallites started to evolve. With dilution 1:16, a second cell series has been deposited with variation of the intrinsic layer thick-ness. The best cells in terms of open-circuit voltage and fill factor product were obtained with an i-layer thickness of 100 nm. These cells have open-circuit voltages and fill factors up to 0.975 V and 75.8 % (0.932 V and 69.9 %) for the initial (degraded) state. These are promising values for the use of this material in top cells. However, the low current density means that the optimum i-layer thickness is probably higher for triple cell application. Further cells have been deposited at different temperatures. These results imply that there is still room for further optimization, when current limitations of the heating system will be overcome.

2012

Chargement

Emergent transport in a many-body open system driven by interacting quantum baths

Eduardo Carlo Mascarenhas Moraes, Juris Reisons, Vincenzo Savona

We analyze an open many-body system that is strongly coupled at its boundaries to interacting quantum baths. We show that the two-body interactions inside the baths induce emergent phenomena in the spin transport. The system and baths are modeled as independent spin chains resulting in a global nonhomogeneous XXZ model. The evolution of the system-bath state is simulated using matrix-product-states methods. We present two phase transitions induced by bath interactions. For weak bath interactions we observe ballistic and insulating phases. However, for strong bath interactions a diffusive phase emerges with a distinct power-law decay of the time-dependent spin current Q alpha t(-alpha). Furthermore, we investigate long-lasting current oscillations arising from the non-Markovian dynamics in the homogeneous case and find a sharp change in their frequency scaling coinciding with the triple point of the phase diagram.

Amer Physical Soc2017

Chargement

Fundamental aspects to localize self-catalyzed III-V nanowires on silicon

William Craig Carter, Anna Fontcuberta i Morral, Martin George Friedl, Lea Ghisalberti, Wonjong Kim, Heidi Andrea Potts, Jelena Vukajlovic Plestina

III-V semiconductor nanowires deterministically placed on top of silicon electronic platform would open many avenues in silicon-based photonics, quantum technologies and energy harvesting. For this to become a reality, gold-free site-selected growth is necessary. Here, we propose a mechanism which gives a clear route for maximizing the nanowire yield in the self-catalyzed growth fashion. It is widely accepted that growth of nanowires occurs on a layerby-layer basis, starting at the triple-phase line. Contrary to common understanding, we find that vertical growth of nanowires starts at the oxide-substrate line interface, forming a ring-like structure several layers thick. This is granted by optimizing the diameter/height aspect ratio and cylindrical symmetry of holes, which impacts the diffusion flux of the group V element through the well-positioned group III droplet. This work provides clear grounds for realistic integration of III-Vs on silicon and for the organized growth of nanowires in other material systems.

2019

Chargement

Azote

L'azote est l'élément chimique de numéro atomique 7, de symbole N (du latin nitrogenium). C'est la tête de file du groupe des pnictogènes. Dans le langage courant, l'azote désigne le corps simple N

Eau

L'eau est une substance chimique constituée de molécules . Ce composé, très stable, mais aussi très réactif, est un excellent solvant à l'état liquide. Dans de nombreux contextes, le terme eau est e

Kelvin

Le 'kelvin' (du nom de William Thomson, dit Lord Kelvin), de symbole K, est l'unité de base SI de température thermodynamique. Jusqu’au , le kelvin était défini comme l

PHYS-105: Advanced physics II (thermodynamics)

Ce cours présente la thermodynamique en tant que théorie permettant une description d'un grand nombre de phénomènes importants en physique, chimie et ingéniere, et d'effets de transport. Une introduction à la physique statistique renforce les notions acquises grâce à une modélisation microscopique.

MSE-234: Mechanical behaviour of materials

Ce cours est une introduction au comportement mécanique, à l'élaboration, à la structure et au cycle de vie des grandes classes de matériaux de structure (métaux, polymères, céramiques et composites)

ENV-200: Environmental chemistry

This course provides students with an overview over the basics of environmental chemistry. This includes the chemistry of natural systems, as well as the fate of anthropogenic chemicals in natural systems. It enables students to apply general chemical concepts to natural systems.