scholarly journals Abnormal Effect of Phase Transition on Thermal Transport in Soft Porous Crystals

2021 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Zheng Zhong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermal Transport ◽  
Structural Integrity ◽  
Gas Adsorption ◽  
Phonon Scattering ◽  
Current Knowledge ◽  
Parent Phase ◽  
Mechanical Pressure ◽  
Thermal Transport Property

<p></p><p>Soft porous crystals (SPCs) can undergo large-amplitude phase transitions under external stimulus such as mechanical pressure, gas adsorption, and temperature while retaining their structural integrity. During the gas adsorption process, the generated latent heat is needed to be effectively removed. Thus, understanding the effect of phase transition on the thermal transport in SPCs becomes extremely important for their applications in storage and separation applications. </p> <p>In this paper, taking isorecticular DUT series as an example, the evolution of the thermal transport in SPCs during the phase transition from the large pore (lp) phase to the narrow pore (np) phase is comprehensively investigated by molecular dynamics (MD) simulations together with the Green-Kubo method. After the phase transition, an abnormal thermal transport property is found in the np phase of DUT materials. We find that although the transformed np phase of DUT-48 has a density much larger than its parent phase, the thermal conductivity of its np phase is smaller than its lp phase. This result is in contrast to the previous finding that SPCs with larger density possess a larger thermal conductivity. However, as for other DUT crystals including DUT-47, DUT-49, DUT-50, and DUT-151, the np phase is found to have a higher thermal conductivity than their lp phase counterpart, which is in accordance with the previous finding. This complicated effect of phase transition on thermal transport in SPCs can be explained by the porosity-dominated competition mechanism between the increased volumetric heat capacity and the aggravated phonon scattering during the phase transition process. Overall, the finding extracted from the present study can greatly expand current knowledge about the thermal conductivity of metal-organic frameworks that is previously found to grow usually with increasing porosity.</p><br><p></p>

scholarly journals Abnormal Effect of Phase Transition on Thermal Transport in Soft Porous Crystals

2021 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Zheng Zhong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermal Transport ◽  
Work Performance ◽  
Structural Integrity ◽  
Phonon Scattering ◽  
Dynamic Features ◽  
Mechanical Pressure ◽  
Wide Range ◽  
Abnormal Effect

<p>Soft porous crystals (SPCs) have attracted a lot of attention recently due to their great potential for a wide range of gas storage and separation applications. They can undergo large-amplitude phase transitions under external stimulus such as mechanical pressure, gas adsorption, and temperature while retaining their structural integrity. However, the thermal conductivity of SPCs is usually very low, owing to the porous structure and weak coordination bond, which would heavily influence their work performance. Hence, understanding the thermal transport in SPCs especially considering their dynamic features becomes extremely crucial. </p> <p>In this paper, taking the isorecticular DUT series as an example, the effect of phase transition from the large pore (lp) phase to narrow pore phase (np) on thermal transport in SPCs is comprehensively investigated by molecular dynamics (MDs) simulation together with the Green-Kubo method. According to our calculations, all DUT structures exhibit an ultralow thermal conductivity (). Specifically, we demonstrate here that the np phase of DUT-48 crystal after phase transition has a larger density but owns a smaller thermal conductivity. This abnormal effect of phase transition is in contrast to the previous finding that the SPCs with larger density possess a larger thermal conductivity. For other DUT crystals including DUT-47, DUT-49, DUT-50, and DUT-151, the np phase is found to have a higher thermal conductivity than their lp phase counterpart, which are as expected. This complicated effect of phase transition on thermal transport in SPCs can be explained by a porosity-dominated competition mechanism between the increased volumetric heat capacity and the aggravated phonon scattering during the phase transition process. This finding is expected to fill the gap in understanding the complicated effect of phase transition on the thermal transport in SPCs.</p>

scholarly journals Abnormal Effect of Phase Transition on Thermal Transport in Soft Porous Crystals

2021 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Zheng Zhong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermal Transport ◽  
Work Performance ◽  
Structural Integrity ◽  
Phonon Scattering ◽  
Dynamic Features ◽  
Mechanical Pressure ◽  
Wide Range ◽  
Abnormal Effect

<p>Soft porous crystals (SPCs) have attracted a lot of attention recently due to their great potential for a wide range of gas storage and separation applications. They can undergo large-amplitude phase transitions under external stimulus such as mechanical pressure, gas adsorption, and temperature while retaining their structural integrity. However, the thermal conductivity of SPCs is usually very low, owing to the porous structure and weak coordination bond, which would heavily influence their work performance. Hence, understanding the thermal transport in SPCs especially considering their dynamic features becomes extremely crucial. </p> <p>In this paper, taking the isorecticular DUT series as an example, the effect of phase transition from the large pore (lp) phase to narrow pore phase (np) on thermal transport in SPCs is comprehensively investigated by molecular dynamics (MDs) simulation together with the Green-Kubo method. According to our calculations, all DUT structures exhibit an ultralow thermal conductivity (). Specifically, we demonstrate here that the np phase of DUT-48 crystal after phase transition has a larger density but owns a smaller thermal conductivity. This abnormal effect of phase transition is in contrast to the previous finding that the SPCs with larger density possess a larger thermal conductivity. For other DUT crystals including DUT-47, DUT-49, DUT-50, and DUT-151, the np phase is found to have a higher thermal conductivity than their lp phase counterpart, which are as expected. This complicated effect of phase transition on thermal transport in SPCs can be explained by a porosity-dominated competition mechanism between the increased volumetric heat capacity and the aggravated phonon scattering during the phase transition process. This finding is expected to fill the gap in understanding the complicated effect of phase transition on the thermal transport in SPCs.</p>

scholarly journals Effect of Phase Transition on the Thermal Transport in Isoreticular DUT Materials

2021 ◽  
Author(s):  
Penghua Ying ◽  
Jin Zhang ◽  
Zheng Zhong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Transport Property ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Transition Process ◽  
Thermal Transport Property ◽  
Potential Applications ◽  
Flexible Metal ◽  
Dynamics Simulations

<p></p><p>Soft porous crystals (SPCs) or flexible metal-organic frameworks have great potential applications in gas storage and separation, in which SPCs can undergo phase transition due to external stimuli. Thus, understanding the effect of phase transition on the thermal transport in SPCs becomes extremely crucial, because the latent heat generated in aforementioned applications is needed to be effectively removed. In this paper, taking the isorecticular DUT series as an example, the thermal transport property of SPCs during the phase transition from the large pore (lp) phase to the narrow pore (np) phase is comprehensively investigated by molecular dynamics simulations together with the Green-Kubo method. According to our calculations, all DUT structures exhibit an ultralow thermal conductivity smaller than 0.2 Wm<sup>-1</sup>K<sup>-1</sup>. In addition, we find that the effect of phase transition on the thermal transport property of different DUT materials considered here strongly depends on their porosity. As for DUT-48, its lp phase has a thermal conductivity larger than that of its np phase. However, in other DUT materials, i.e, DUT-47, DUT-49, DUT-50, and DUT-151 the thermal transport property of their lp phase is found to be weaker than that of their np phase. This complicated effect of phase transition on the thermal transport in SPCs can be explained by a porosity-dominated competition mechanism between the increased volumetric heat capacity and the aggravated phonon scattering during the phase transition process.</p><p></p>

scholarly journals Reduction of Lattice Thermal Conductivity in PbTe Induced by Artificially Generated Pores

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Jae-Yeol Hwang ◽  
Eun Sung Kim ◽  
Syed Waqar Hasan ◽  
Soon-Mok Choi ◽  
Kyu Hyoung Lee ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Structure ◽  
Transport Properties ◽  
Thermoelectric Materials ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Phonon Modes ◽  
Thermal Transport Properties

Highly dense pore structure was generated by simple sequential routes using NaCl and PVA as porogens in conventional PbTe thermoelectric materials, and the effect of pores on thermal transport properties was investigated. Compared with the pristine PbTe, the lattice thermal conductivity values of pore-generated PbTe polycrystalline bulks were significantly reduced due to the enhanced phonon scattering by mismatched phonon modes in the presence of pores (200 nm–2 μm) in the PbTe matrix. We obtained extremely low lattice thermal conductivity (~0.56 W m−1 K−1at 773 K) in pore-embedded PbTe bulk after sonication for the elimination of NaCl residue.

scholarly journals Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Lina Yang ◽  
Austin J. Minnich
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Ab Initio ◽  
Grain Boundaries ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Computational Study ◽  
Phonon Transport ◽  
Nanocrystalline Si

Abstract Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Optimized Design of Composite Materials for Heat Transport Applications

2011 ◽  
Author(s):  
Babak Kouchmeshky ◽  
Peter Kroll ◽  
Ibukun Olubanjo
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Thermal Transport ◽  
Elevated Temperatures ◽  
Phonon Scattering ◽  
Optimized Design ◽  
Individual Contributions ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Individual

Careful design of composite materials offers a chance for engineering phonon band gaps and controlling phonon scattering. Taking advantage of this strategy, we study properties of SiC composite materials for engineering applications in which the control of thermal transport is important. In particular, knowledge of the individual contributions of phonons on thermal transport provides us the necessary information to focus on most significant phonon frequencies. In our study, we select a series of candidate model geometries and use a virtual testing method for elevated temperatures to support the design process. Integrating atomistic non-equilibrium molecular dynamics simulations to determine thermal conductivity we provide a proof-of-concept study and deliver best design scenarios of SiC composite materials with very low-thermal conductivity.

Thermal Transport in Few-Quintuple Bi2Te3 Thin Films and Nanoribbons

2011 ◽  
Author(s):  
Bo Qiu ◽  
Xiulin Ruan
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Thermal Transport ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Md Simulations ◽  
Boundary Scattering ◽  
Nanoporous Films

In this work, thermal conductivity of perfect and nanoporous few-quintuple Bi2Te3 thin films as well as nanoribbons with perfect and zig-zag edges is investigated using molecular dynamics (MD) simulations with Green-Kubo method. We find minimum thermal conductivity of perfect Bi2Te3 thin films with three quintuple layers (QLs) at room temperature, and we believe it originates from the interplay between inter-quintuple coupling and phonon boundary scattering. Nanoporous films and nanoribbons are studied for additional phonon scattering channels in suppressing thermal conductivity. With 5% porosity in Bi2Te3 thin films, the thermal conductivity is found to decrease by a factor of 4–6, depending on temperature, comparing to perfect single QL. For nanoribbons, width and edge shape are found to strongly affect the temperature dependence as well as values of thermal conductivity.

scholarly journals Influence of Te Vacancies on the Thermoelectric Properties of n-type Cu0.008Bi2Te2.7-xSe0.3

2020 ◽  
Vol 58 (10) ◽  
pp. 721-727
Author(s):  
Yerim Yang ◽  
TaeWan Kim ◽  
Seokown Hong ◽  
Jiwoo An ◽  
Sang-il Kim
Keyword(s):  
Thermal Conductivity ◽  
Transport Properties ◽  
Point Defect ◽  
Thermoelectric Properties ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Band Model ◽  
Total Thermal Conductivity ◽  
Thermal Transport Properties ◽  
Callaway Model

In this study, we report the influence of Te vacancy formation on the thermoelectric properties of n-type Cu0.008Bi2Te2.7Se0.3 alloys, including their electronic and thermal transport properties. Te-deficient Cu0.008Bi2Te2.7-xSe0.3 (x = 0, 0.005, 0.01 and 0.02) samples were systematically synthesized and characterized. Regarding electronic transport properties, carrier concentration was increased with Te vacancies, while carrier mobility was maintained. As a result, the electrical conductivity significantly increased while the Seebeck coefficient reduced moderately, thus, the power factor was enhanced from 3.04 mW/mK<sup>2</sup> (pristine) to 3.22 mW/mK<sup>2</sup> (x = 0.02) at 300 K. Further analysis based on a single parabolic band model revealed that the weighted mobility of the conduction band increased, which is favorable for electron transport, as Te vacancies were generated. Regarding thermal transport properties, lattice thermal conductivity decreased with Te vacancies due to additional point defect phonon scattering, however, total thermal conductivity increased due to larger electronic contribution as Te vacancies increased. Analysis using the Debye-Callaway model suggests that the phonon scattering by the Te vacancies is as efficient as the substitution point defect scattering. Consequently, the thermoelectric figure of merit zT increased at all temperatures for x = 0.005 and 0.01. The maximum zT of 0.95 was achieved for Te-deficient Cu0.008Bi2Te2.69Se0.3 (x = 0.01) at 400 K.

Thermal Transport Properties and Interface Effects of Carbon Nanostructures

2017 ◽  
Author(s):  
Sushan Nakarmi ◽  
V. U. Unnikrishnan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Heat Bath ◽  
Md Simulations ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Intrinsic Properties ◽  
Thermal Transport Property

The variations in thermal conductivity of nanocomposites are found to depend not only the intrinsic properties of the fiber and matrix phases but also on the interfacial resistance of the reinforcing phase. As we go down the length scales, the interfacial thermal resistance due to size of the nanoparticle becomes significant. In order to address the effect of size (length and diameter) of nanotube on the thermal transport property of nanotube composites, thermal conductivity of different nanotube samples varying in length and diameter will be estimated first using molecular dynamic (MD) simulations with AIREBO potentials. This will be carried out using the ‘Heat-Bath’ method - non-equilibrium molecular dynamics (NEMD) approach. In the heat bath method, constant amount of heat is added to and removed from the hot and cold regions and the resulting temperature gradient is measured and the thermal conductivity is calculated using the Fourier Law. This will be followed by the study of interfacial thermal resistance of these nanostructures. These intrinsic properties are then used with continuum based mathematical formulations to study the effect of size of the nanoparticle on the overall thermal conductivity of the nanocomposite.

scholarly journals First-Principles Study on Lattice Dynamics and Thermal Conductivity of Thermoelectric Intermetallics Fe3Al2Si3

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 388
Author(s):  
Naoki Sato ◽  
Yoshiki Takagiwa
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Microscopic Mechanism ◽  
Practical Applications ◽  
Scattering Rate ◽  
Fine Microstructure ◽  
Thermal Displacements

Thermoelectric materials have been expected as a critical underlying technology for developing an autonomous power generation system driven at near room temperature. For this sake, Fe3Al2Si3 intermetallic compound is a promising candidate, though its high lattice thermal conductivity is a bottleneck toward practical applications. Herein, we have performed the first-principles calculations to clarify the microscopic mechanism of thermal transport and establish effective ways to reduce the lattice thermal conductivity of Fe3Al2Si3. Our calculations show that the lowest-lying optical mode has a significant contribution from Al atom vibration. It should correspond to large thermal displacements Al atoms. However, these behaviors do not directly cause an increase of the 3-phonon scattering rate. The calculated lattice thermal conductivity shows a typical temperature dependence and moderate magnitude. From the calculated thermal conductivity spectrum and cumulative thermal conductivity, we can see that there is much room to reduce the lattice thermal conductivity. We can expect that heavy-element doping on Al site and controlling fine microstructure are effective strategies to decrease the lattice thermal conductivity. This work suggests useful information to manipulate the thermal transport of Fe3Al2Si3, which will make this material closer to practical use.

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