Phase Change Materials - From Structures to Kinetics

2006 ◽  
Vol 918 ◽  
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.

Phase change materials: From structures to kinetics

2007 ◽  
Vol 22 (9) ◽  
pp. 2368-2375 ◽  
Author(s):  
Wojciech Wełnic ◽  
Johannes A. Kalb ◽  
Daniel Wamwangi ◽  
Christoph Steimer ◽  
Matthias Wuttig
Keyword(s):  
Phase Change ◽  
Crystalline State ◽  
Phase Change Materials ◽  
Vacancy Concentration ◽  
Amorphous State ◽  
Structural Difference ◽  
Relative Difference ◽  
Crystal Nucleation ◽  
Optical Contrast ◽  
Entropy Of Fusion

Phase change materials possess a unique combination of properties, which includes a pronounced property contrast between the amorphous and crystalline state, i.e., high electrical and optical contrast. In particular, the latter observation is indicative of a considerable structural difference between the amorphous and crystalline state, which furthermore is characterized by a very high vacancy concentration unknown from common semiconductors. Through the use of ab initio calculations, this work shows how the electric and optical contrast is correlated with structural differences between the crystalline and the amorphous state and how the vacancy concentration controls the optical properties. Furthermore, crystal nucleation rates and crystal growth velocities of various phase change materials have been determined by atomic force microscopy and differential thermal analysis. In particular, the observation of different recrystallization mechanisms upon laser heating of amorphous marks is explained by the relative difference of just three basic parameters among these alloys, namely, the melt-crystalline interfacial energy, the entropy of fusion, and the glass transition temperature.

scholarly journals Thermodynamics and kinetics of glassy and liquid phase-change materials

2021 ◽  
Vol 135 ◽  
pp. 106094
Author(s):  
Narges Amini ◽  
Julian Pries ◽  
Yudong Cheng ◽  
Christoph Persch ◽  
Matthias Wuttig ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermodynamics And Kinetics ◽  
Kinetics Of

scholarly journals Cement-Based Renders Manufactured with Phase-Change Materials: Applications and Feasibility

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Luigi Coppola ◽  
Denny Coffetti ◽  
Sergio Lorenzi
Keyword(s):  
Compressive Strength ◽  
Phase Change ◽  
Phase Change Materials ◽  
Residential Buildings ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Hydration Kinetics ◽  
Mechanical Performances ◽  
Entrapped Air ◽  
Kinetics Of

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.

scholarly journals The Effect of Channel Length on Phase Transition of Phase Change Memory

2018 ◽  
Vol 7 (3.11) ◽  
pp. 25
Author(s):  
M S. A.Aziz ◽  
F H. M.Fauzi ◽  
Z Mohamad ◽  
R I. Alip
Keyword(s):  
Phase Transition ◽  
Silicon Carbide ◽  
Phase Change ◽  
Pulse Width ◽  
Crystalline State ◽  
Phase Change Memory ◽  
Amorphous State ◽  
Channel Length ◽  
Change Memory

The phase transition of germanium antimony tellurium (GST) and the temperature of GST were investigated using COMSOL Multiphysic 5.0 software. Silicon carbide was using as a heater layer in the separate heater structure of PCM. These simulations have a different channel of SiC. The temperature of GST and the phase transition of GST can be obtained from the simulation. From the simulation, the 300 nm channel of SiC can change the GST from amorphous to crystalline state at 0.7V with 100 ns pulse width. The 800 nm channel of SiC can change the GST from amorphous to crystalline state at 1.1V with 100 ns pulse width. Results demonstrated that the channel of SIC can affecting the temperature of GST and the GST changes from amorphous state to crystalline state. As the channel of SiC decreased, the temperature of GST was increased and the GST was change to crystalline state quickly.  

The role of structural order and stiffness in the simultaneous enhancement of optical contrast and thermal stability in phase change materials

2019 ◽  
Vol 7 (14) ◽  
pp. 4132-4142 ◽  
Author(s):  
Qian Li ◽  
Kaicheng Xu ◽  
Xiaoyi Wang ◽  
Haihua Huang ◽  
Liang Ma ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Phase Change ◽  
Energy Saving ◽  
Phase Change Materials ◽  
Photonic Devices ◽  
Optical Contrast ◽  
The Past ◽  
Structural Order ◽  
Perfect Absorbers

In the past several years, phase change materials (PCMs) have been widely applied in energy-saving non-volatile photonic devices, such as active perfect absorbers, nanopixel displays and all-photonic memories.

Origin of the Optical Contrast in Phase-Change Materials

2007 ◽  
Vol 98 (23) ◽  
Author(s):  
Wojciech Wełnic ◽  
Silvana Botti ◽  
Lucia Reining ◽  
Matthias Wuttig
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Optical Contrast

The Origin of Optical Contrast in Sb 2 Te 3 ‐Based Phase‐Change Materials

2019 ◽  
Vol 257 (1) ◽  
pp. 1900289 ◽  
Author(s):  
Jose C. Martinez ◽  
Li Lu ◽  
Jing Ning ◽  
Weiling Dong ◽  
Tun Cao ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Optical Contrast
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