Thermodynamics and kinetics of glassy and liquid phase-change materials

The paper focuses on the evaluation of the rheological and mechanical performances of cement-based renders manufactured with phase-change materials (PCM) in form of microencapsulated paraffin for innovative and ecofriendly residential buildings. Specifically, cement-based renders were manufactured by incorporating different amount of paraffin microcapsules—ranging from 5% to 20% by weight with respect to binder. Specific mass, entrained or entrapped air, and setting time were evaluated on fresh mortars. Compressive strength was measured over time to evaluate the effect of the PCM addition on the hydration kinetics of cement. Drying shrinkage was also evaluated. Experimental results confirmed that the compressive strength decreases as the amount of PCM increases. Furthermore, the higher the PCM content, the higher the drying shrinkage. The results confirm the possibility of manufacturing cement-based renders containing up to 20% by weight of PCM microcapsules with respect to binder.

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Microstructural properties, thermodynamics and kinetics of Al-Si semi-solid billet fabricated by liquid phase reaction sintering

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.160932 ◽

2021 ◽

pp. 160932

Author(s):

Wenchao Liu ◽

Lianxi Hu ◽

Yu Sun ◽

Shangqing Sun ◽

Jingyuan Shen ◽

...

Keyword(s):

Liquid Phase ◽

Phase Reaction ◽

Reaction Sintering ◽

Microstructural Properties ◽

Thermodynamics And Kinetics ◽

Semi Solid ◽

Kinetics Of ◽

Liquid Phase Reaction

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Phase Change Materials - From Structures to Kinetics

MRS Proceedings ◽

10.1557/proc-0918-h04-03 ◽

2006 ◽

Vol 918 ◽

Cited By ~ 1

Author(s):

Matthias Wuttig ◽

Wojciech Welnic ◽

Ralf Detemple ◽

Henning Dieker ◽

Johannes Kalb ◽

...

Keyword(s):

Phase Change ◽

Crystalline State ◽

Phase Change Materials ◽

Amorphous State ◽

Structural Difference ◽

Fast Time ◽

Optical Contrast ◽

Fast Time Scale ◽

Kinetics Of ◽

Structure Properties

AbstractPhase change materials possess a unique combination of properties which include a pronounced property contrast between the amorphous and crystalline state, i.e. a high electrical and optical contrast. In particular the latter observation is indicative for a considerable structural difference between the amorphous and crystalline state. At the same time the crystallization of the amorphous state proceeds on a fast time scale. This raises the question how structure, properties and kinetics are related in phase change alloys. It will be demonstrated that only a small group of covalent semiconductors with octahedral-like coordination has the required property combination. This is related to their thermodynamic properties which govern the kinetics of crystallization.

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Breakdown of the Stokes-Einstein relation above the melting temperature in a liquid phase-change material

Science Advances ◽

10.1126/sciadv.aat8632 ◽

2018 ◽

Vol 4 (11) ◽

pp. eaat8632 ◽

Cited By ~ 22

Author(s):

Shuai Wei ◽

Zach Evenson ◽

Moritz Stolpe ◽

Pierre Lucas ◽

C. Austen Angell

Keyword(s):

Liquid Phase ◽

Phase Change ◽

Melting Temperature ◽

Phase Change Materials ◽

Dynamic Properties ◽

Switching Behavior ◽

Einstein Relation ◽

Elastic Neutron ◽

Phase Switching ◽

Memory Applications

The dynamic properties of liquid phase-change materials (PCMs), such as viscosity η and the atomic self-diffusion coefficientD, play an essential role in the ultrafast phase switching behavior of novel nonvolatile phase-change memory applications. To connect η toD, the Stokes-Einstein relation (SER) is commonly assumed to be valid at high temperatures near or above the melting temperatureTmand is often used for assessing liquid fragility (or crystal growth velocity) of technologically important PCMs. However, using quasi-elastic neutron scattering, we provide experimental evidence for a breakdown of the SER even at temperatures aboveTmin the high–atomic mobility state of a PCM, Ge1Sb2Te4. This implies that although viscosity may have strongly increased during cooling, diffusivity can remain high owing to early decoupling, being a favorable feature for the fast phase switching behavior of the high-fluidity PCM. We discuss the origin of the observation and propose the possible connection to a metal-semiconductor and fragile-strong transition hidden belowTm.

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Selection of Solid-Liquid Phase-Change Materials for Spacecraft Thermal Control

Heat Transfer and Spacecraft Thermal Control ◽

10.2514/5.9781600864988.0547.0565 ◽

1971 ◽

pp. 547-565 ◽

Cited By ~ 1

Keyword(s):

Liquid Phase ◽

Phase Change ◽

Phase Change Materials ◽

Thermal Control ◽

Solid Liquid ◽

Spacecraft Thermal Control ◽

Selection Of

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Metal Nanocrystal Formation during Liquid Phase Transmission Electron Microscopy: Thermodynamics and Kinetics of Precursor Conversion, Nucleation, and Growth

Chemistry of Materials ◽

10.1021/acs.chemmater.0c01360 ◽

2020 ◽

Vol 32 (18) ◽

pp. 7569-7581 ◽

Cited By ~ 1

Author(s):

Taylor J. Woehl

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Liquid Phase ◽

Nucleation And Growth ◽

Thermodynamics And Kinetics ◽

Transmission Electron ◽

Nanocrystal Formation ◽

Phase Transmission ◽

Kinetics Of

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Integral Solution of Two-Region Solid–Liquid Phase Change in Annular Geometries and Application to Phase Change Materials–Air Heat Exchangers

Energies ◽

10.3390/en12234474 ◽

2019 ◽

Vol 12 (23) ◽

pp. 4474 ◽

Cited By ~ 3

Author(s):

Hamidreza Shabgard ◽

Weiwei Zhu ◽

Amir Faghri

Keyword(s):

Liquid Phase ◽

Boundary Conditions ◽

Phase Change ◽

Phase Change Materials ◽

Volume Fraction ◽

Control Volume ◽

Solid Volume Fraction ◽

Solidification Time ◽

Design And Optimization ◽

Solid Liquid

A mathematical model based on the integral method is developed to solve the problem of conduction-controlled solid–liquid phase change in annular geometries with temperature gradients in both phases. The inner and outer boundaries of the annulus were subject to convective, constant temperature or adiabatic boundary conditions. The developed model was validated by comparison with control volume-based computational results using the temperature-transforming phase change model, and an excellent agreement was achieved. The model was used to conduct parametric studies on the effect of annuli geometry, thermophysical properties of the phase change materials (PCM), and thermal boundary conditions on the dynamics of phase change. For an initially liquid PCM, it was found that increasing the radii ratio increased the total solidification time. Also, increasing the Biot number at the cooled (heated) boundary and Stefan number of the solid (liquid) PCM, decreased (increased) the solidification time and resulted in a greater (smaller) solid volume fraction at steady state. The application of the developed method was demonstrated by design and analysis of a PCM–air heat exchanger for HVAC systems. The model can also be easily employed for design and optimization of annular PCM systems for all associated applications in a fraction of time needed for computational simulations.

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