Video Experimental Relacionado
Updated: Jul 2, 2026
06:26
Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Transición estructural reversible en el MIL-53 con histeresis a gran temperatura
Yun Liu1, Jae-Hyuk Her, Anne Dailly
1NIST Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland, USA. yunliu@nist.gov.
Journal of the American Chemical Society
|August 13, 2008
Resumen
Las estructuras metal-orgánicas (MOF) como MIL-53 muestran una transición estructural reversible de "respiración". Este estudio revela que esta transición ocurre con cambios de temperatura, incluso sin moléculas invitadas, y exhibe una significativa histeresis térmica.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Química Química es la química.
- Física Física es la física de las cosas.
Sus antecedentes:
- Las estructuras metal-orgánicas (MOF) exhiben flexibilidad estructural, a menudo desencadenada por la adsorción de moléculas invitadas, lo que lleva a un fenómeno conocido como adsorción de moléculas invitadas.
Objetivo del estudio:
- Investigar las transiciones estructurales inducidas por la temperatura en los MOF MIL-53.
- Determinar si las moléculas invitadas son esenciales para el
Principales métodos:
- La difracción del polvo de neutrones por difracción.
- La dispersión inelástica de neutrones es una dispersión inelástica de neutrones.
- Ab initio simulaciones por computadora de las simulaciones.
Principales resultados:
- MIL-53 sufre una transición estructural reversible entre los estados de poro abierto y poro cerrado basado únicamente en la temperatura.
- Se observó una histeresis térmica significativa: transición abierta a cerrada a 125-150 K y transición cerrada a abierta a 325-375 K.
- La transición de la estructura abierta a la cerrada a bajas temperaturas exhibe una cinética lenta.
Conclusiones:
- Las moléculas huéspedes no son necesarias para el proceso.
Videos de Conceptos Relacionados
01:14Reversible and Irreversible Processes
The thermodynamic processes can be classified into reversible and irreversible processes. The processes that can be restored to their initial state are called reversible processes. It is only possible if the process is in quasi-static equilibrium, i.e., it takes place in infinitesimally small steps, and the system remains at equilibrium However, these are ideal processes and do not occur naturally. An ideal system undergoing a reversible process is always in thermodynamic equilibrium within...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:31Phase Transitions
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...
01:21Phase Transitions
A phase transition is the process in which a substance changes from one state of matter to another, like from a solid to a liquid, liquid to gas, or vice versa, at a specific temperature and under given pressure conditions. This change is spontaneous and is affected by alterations in temperature and pressure. These parameters impact the strength of the forces between molecules (intermolecular forces) in the substance.During a phase transition, both the initial and final phases of the substance...
01:10Entropy Change in Reversible Processes
In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
01:12Temperature Dependent Deformation
In a nonhomogeneous rod made up of steel and brass, restrained at both ends and subjected to a temperature change, several steps are involved in calculating the stress and compressive load. Due to the problem's static indeterminacy, one end support is disconnected, allowing the rod to experience the temperature change freely. Next, an unknown force is applied at the free end, triggering deformations in the rod's steel and brass portions. These deformations are then calculated and added together...