scholarly journals A Phase-Change Mechanism of GST-SL Based Superlattices upon Sb Flipping

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 360
Author(s):  
Teng Sun ◽  
Furong Liu ◽  
Jicheng Guo ◽  
Gang Han ◽  
Yongzhi Zhang
Keyword(s):  
Phase Change ◽  
Length Distribution ◽  
Melting Process ◽  
Ab Initio Molecular Dynamics ◽  
Electron Localization ◽  
Switching Model ◽  
Change Mechanism ◽  
Fast Switching ◽  
Reversible Phase ◽  
Bond Length Distribution

Reversible phase-change behaviors of Ge–Sb–Te based superlattices (GST-SL) were studied by ab initio molecular dynamics (AIMD) simulations based on three models containing Ge/Sb intermixing, namely the Petrov-mix, Ferro-mix, and Kooi-mix models. The flipping behavior of Sb atoms was found in all the three GST-SL models in the melting process. Among them the Kooi-mix model exhibited the best stability, and the analyses of bond length distribution and electron localization function provided a better explanation on the phase transition of GST-SL. Finally, we proposed a fast switching model for GST-SL based on Sb flipping.

scholarly journals Numerical simulation of paraffin melting in circular tube using LBM

2021 ◽  
pp. 279-279
Author(s):  
Xiao-Yan Liu ◽  
Nan-Di Zhang ◽  
Xiao-Qing Li ◽  
Cong Li ◽  
Peng Yu ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Circular Tube ◽  
Melting Process ◽  
Melting Rate ◽  
Lattice Boltzmann Model ◽  
Storage Device ◽  
Change Mechanism ◽  
Boltzmann Model ◽  
Change Material

Paraffin melting is widely used in the fields of phase change materials (PCMs) energy storage, gathering and transportation pipeline paraffin removal, etc. Analysis of the phase change mechanism and influencing factors of paraffin melting in the circular tube deeply has important guiding significance for improving the heat storage capacity by changing the structure of phase change material storage device and ensuring the safe transportation of crude oil in the pipeline. A double distribution lattice Boltzmann model based on enthalpy method is established to simulate the temperature field and the flow field of paraffin melting in a circular tube in this paper. The influence of different Rayleigh (Ra) number and Prandtl (Pr) number on the paraffin melting process in a circular tube is analyzed. The results show that the natural convection process is strengthened with the increase of the Ra number, and the decrease of the average Nusselt (Nu) number on the wall is smooth in the transition stage of wax melting due to the existence of fuzzy zone. The melting rate of paraffin can be accelerated or reduced by controlling the number Pr, so as to meet the relevant requirements of engineering.

scholarly journals Ab initio molecular dynamics and materials design for embedded phase-change memory

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Liang Sun ◽  
Yu-Xing Zhou ◽  
Xu-Dong Wang ◽  
Yu-Han Chen ◽  
Volker L. Deringer ◽  
...  
Keyword(s):  
Phase Change ◽  
High Performance ◽  
Materials Design ◽  
Atomic Scale ◽  
Ab Initio Molecular Dynamics ◽  
Core Material ◽  
Structure Property ◽  
Switching Speed ◽  
Atomic Structures ◽  
Memory Applications

AbstractThe Ge2Sb2Te5 alloy has served as the core material in phase-change memories with high switching speed and persistent storage capability at room temperature. However widely used, this composition is not suitable for embedded memories—for example, for automotive applications, which require very high working temperatures above 300 °C. Ge–Sb–Te alloys with higher Ge content, most prominently Ge2Sb1Te2 (‘212’), have been studied as suitable alternatives, but their atomic structures and structure–property relationships have remained widely unexplored. Here, we report comprehensive first-principles simulations that give insight into those emerging materials, located on the compositional tie-line between Ge2Sb1Te2 and elemental Ge, allowing for a direct comparison with the established Ge2Sb2Te5 material. Electronic-structure computations and smooth overlap of atomic positions (SOAP) similarity analyses explain the role of excess Ge content in the amorphous phases. Together with energetic analyses, a compositional threshold is identified for the viability of a homogeneous amorphous phase (‘zero bit’), which is required for memory applications. Based on the acquired knowledge at the atomic scale, we provide a materials design strategy for high-performance embedded phase-change memories with balanced speed and stability, as well as potentially good cycling capability.

The Lattice Boltzmann Investigation for the Melting Process of Phase Change Material in an Inclined Cavity

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Zhonghao Rao ◽  
Yutao Huo ◽  
Yimin Li
Keyword(s):  
Heat Flux ◽  
Phase Change ◽  
Lattice Boltzmann ◽  
Melting Process ◽  
Clockwise Rotation ◽  
Linear Distribution ◽  
Left Wall ◽  
Inclined Cavity ◽  
Solid Liquid ◽  
Change Material

The solid–liquid phase change process is of importance in the usage of phase change material (PCM). In this paper, the phase change lattice Boltzmann (LB) model has been used to investigate the solid–liquid phase change in an inclined cavity. Three heat flux distributions applied to the left wall are investigated: uniform distribution, linear distribution, and parabolic symmetry distribution. The results show that for all the heat flux distributions, the slight clockwise rotation of the cavity can accelerate the melting process. Furthermore, when more heat is transferred to the cavity through the middle part (parabolic symmetry distribution) or bottom part (linear distribution) of left wall, clockwise rotation of cavity leads to larger temperature of PCM.

Preparation of PVA/PEG Phase Change Composite Nanofibers by Electrospinning

2011 ◽  
Vol 306-307 ◽  
pp. 37-40 ◽  
Author(s):  
Da Hui Sun ◽  
Tian Yu Xu ◽  
Yong Jia Liu ◽  
Mei Zhang
Keyword(s):  
Phase Transition ◽  
Phase Change ◽  
Composite Nanofibers ◽  
Diameter Distribution ◽  
Weight Percentage ◽  
Weight Content ◽  
Reversible Phase Transition ◽  
Change Characteristics ◽  
Micro Morphology ◽  
Reversible Phase

Phase change PVA / PEG composite nanofibers were prepared by electrospinning, micro-morphology of PVA / PEG fibers with different weight content were analyzed, the phase change characteristics were also analyzed. The result showed that well distributed composite nanofibers which composed by PVA/PEG blend solution can be obtained by electrospinning.PVA fibreforming were influenced because of the existence of PEG, including bond, irregular block, small rough, uneven diameter distribution in fibers. PVA/PEG blend solution of 4:6 weight content was well fibreforming compared with other different weight content.The continuity of spinneret flow in electrospinning would directly affected by polymer solution consentrition and viscosity. Further research about which and the influence in fibers diameter and morphology will be explored. Composite nanofibers possessed reversible phase transition characteristics,Tm Essentially unchanged ,Tcwere related to the weight percentage of PEG/PVA, at the same time, the enthalpy will increase along with the gradually increase in weight percentage of PEG.

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