Thermal Conductivity in Zeolites Studied by Non-equilibrium Molecular Dynamics Simulations

Schnell, Sondre K.; Vlugt, Thijs J. H.

doi:10.1007/s10765-013-1467-2

Cited by 15 publications

(16 citation statements)

References 53 publications

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“…In addition, given the good agreement between experimental and simulated thermal conductivity values for crystalline ZIF-8, the observed discrepancies may also be due to the entrapped air between the particles in the pressed powder pellets as well as structural defects and inhomogeneities in the experimental bulk glass, which should lower the thermal conductivity. The smaller κ of powder pellets relative to simulated samples has been noted previously in zeolites. − Indeed, defects and entrapped air between the particles are easier to avoid in the thin films (as in the case of ZIF-8) compared to the present powder pellets. This could explain the better agreement in thermal conductivity among simulations and experiments for crystalline ZIF-8 …”

Section: Results and Discussionsupporting

confidence: 52%

Metal–Organic Framework Glasses Possess Higher Thermal Conductivity than Their Crystalline Counterparts

Sørensen

Østergaard

Stępniewska

et al. 2020

ACS Appl. Mater. Interfaces

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The thermal conductivity (κ) of glasses is known to always be lower than that of their corresponding crystals due to the stronger phonon–phonon scattering in the former. However, it is unknown whether this relation holds for metal–organic frameworks. Here, we report our discovery of an inverse relation in κ between glass and crystal for two zeolitic imidazolate frameworks (ZIFs), ZIF-4 and ZIF-62, that is, melt-quenched ZIF-4 and ZIF-62 glasses possess higher thermal conductivities than their crystalline counterparts. We find that the ZIF crystal pellets exhibit ultralow κ (∼0.1 W m–1 K–1) and that the higher κ of the ZIF glasses is due to the collapse of internal cavities and higher atomic number density in the latter. For other systems like oxides, vitrification causes higher free volume, but the opposite is found for the ZIFs, that is, lower free volume owing to the partial collapse of the crystalline framework upon melting.

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Section: Results and Discussionsupporting

confidence: 52%

Metal–Organic Framework Glasses Possess Higher Thermal Conductivity than Their Crystalline Counterparts

Sørensen

Østergaard

Stępniewska

et al. 2020

ACS Appl. Mater. Interfaces

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“…The thermal conductivity of some zeolites are around 0.030 Wm −1 K −1 for powder samples. 14,15 Metal− organic frameworks (MOFs) are porous coordination polymers, formed by the union of metallic agglomerates and organic linkers. There are only a few examples of their thermal properties; for instance, the thermal conductivity of a single crystal of MOF-5 was measured to be 0.32 Wm −1 K −1 .…”

Section: ■ Introductionmentioning

confidence: 99%

“…For example, aerogels have very low values of thermal conductivity, k , (0.010 W m –1 K –1 ), , since more than 95% of their volume consists of empty spaces. , Other classes of porous solids have been developed and include zeolites and, more recently, metal–organic frameworks (MOFs). − Zeolites are porous aluminosilicates, , normally used in adsorption, ion exchange, catalysis, etc. The thermal conductivity of some zeolites are around 0.030 Wm –1 K –1 for powder samples. , Metal–organic frameworks (MOFs) are porous coordination polymers, formed by the union of metallic agglomerates and organic linkers. There are only a few examples of their thermal properties; for instance, the thermal conductivity of a single crystal of MOF-5 was measured to be 0.32 Wm –1 K –1 . , …”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity of Covalent Organic Frameworks as a Function of Their Pore Size

Freitas

Borges²,

Merlini

et al. 2017

J. Phys. Chem. C

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Covalent organic frameworks (COFs) are a relatively new class of organic nanostructured porous materials, formed by covalent bonds between light elements, with high surface area. The thermal conductivity values (k) for some COFs (COF-300, RIO-1, RIO-4, RIO-20) were measured using the modified transient plane source (MTPS) technique. Values ranging from 0.038 to 0.048 W m–1 K–1 were measured depending on the COF pore structure and surface area. Thermal conductivities correlate linearly with the inverse of the cross-sectional area of the pores.

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“…The main different types of damage mechanism are knock-on damage, thermal heating, electrostatic charging and radiolysis [14]. For the thermal heating, the thermal diffusion constants of zeolites are reported to be in the order of 10 11 nm 2 /s which is not comparable with the estimated diffusion constant indicating that heat is not expected to be the cause for the induced damage in the current sample [15,16]. For knock-on damage, atoms are displaced via the interaction of the incoming beam with the nucleus.…”

Section: Discussionmentioning

confidence: 75%

Reducing electron beam damage through alternative STEM scanning strategies. Part II -- Attempt towards an empirical model describing the damage process

Jannis¹,

Velazco²,

Béché³

et al. 2021

Preprint

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In this second part of a series we attempt to construct an empirical model that can mimick all experimental observations made regarding the role of an alternative interleaved scan pattern in STEM imaging on the beam damage in a specific zeolite sample. We make use of a 2D diffusion model that describes the dissipation of the deposited beam energy in the sequence of probe positions that are visited during the scan pattern. The diffusion process allows for the concept of trying to 'outrun' the beam damage by carefully tuning the dwell time and distance between consecutively visited probe positions. We add a non linear function to include a threshold effect and evaluate the accumulated damage in each part of the image as a function of scan pattern details. Together, these ingredients are able to describe qualitatively all aspects of the experimental data and provide us with a model that could guide a further optimisation towards even lower beam damage without lowering the applied electron dose. We deliberately remain vague on what is diffusing here which avoids introducing too many sample specific details. This provides hope that the model can be applied also in sample classes that were not yet studied in such great detail by adjusting higher level parameters: a sample dependent diffusion constant and damage threshold.

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Thermal Conductivity in Zeolites Studied by Non-equilibrium Molecular Dynamics Simulations

Cited by 15 publications

References 53 publications

Metal–Organic Framework Glasses Possess Higher Thermal Conductivity than Their Crystalline Counterparts

Metal–Organic Framework Glasses Possess Higher Thermal Conductivity than Their Crystalline Counterparts

Thermal Conductivity of Covalent Organic Frameworks as a Function of Their Pore Size

Reducing electron beam damage through alternative STEM scanning strategies. Part II -- Attempt towards an empirical model describing the damage process

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