Thermal conduction in glasses and polymers at low temperatures

Morgan, G J; Smith, David A.

doi:10.1088/0022-3719/7/4/004

Cited by 57 publications

(32 citation statements)

References 9 publications

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“…( [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] in good functional agreement with experimental data and a previous handwaving derivation. The total tunneling Gruneisen parameter (Equa tion (1-13)) can be evaluated using the mean-value theorem as…”

Section: Gruneisen Theorysupporting

confidence: 81%

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Thermal expansion of glasses at low temperatures

Lyon

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INFORMATION TO USERSThis material was produced from a microfilm copy of the original document. White the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted.The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction.

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Section: Gruneisen Theorysupporting

confidence: 81%

“…Several theories (5)(6)(7)(8)(9)(10)(11)(12)(13) have been proposed to explain the unusual thermal behavior of glasses at low temperature, with the simple postulate of a slowly varying continuous distribution in energy of two level states (14)(15)(16)(17) giving the best agreement with existing experimental data.…”

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confidence: 99%

Thermal expansion of glasses at low temperatures

Lyon

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“…In fact, there are substantial distinctions in the values of thermal conductivity and heat capacity between amorphous, semicrystalline and crystalline polymers, due to the diversity of their inner structure. This aspect has been exhaustively discussed in a number of papers [14][15][16][17][18] and they were also used in a recent study on the change of optical constants as a function of temperature [13]. In this context cryogenic data were obtained from literature for both PP [19,20] and pPTFE [21,22].…”

Section: B Polymers Physical Propertiesmentioning

confidence: 99%

Heating of large format filters in sub-mm and fir space optics

Baccichet

Savini

2017

International Conference on Space Optics — ICSO 2014

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Most FIR and sub-mm space borne observatories use polymer-based quasi-optical elements like filters and lenses, due to their high transparency and low absorption in such wavelength ranges. Nevertheless, data from those missions have proven that thermal imbalances in the instrument (not caused by filters) can complicate the data analysis. Consequently, for future, higher precision instrumentation, further investigation is required on any thermal imbalances embedded in such polymer-based filters. Particularly, in this paper the heating of polymers when operating at cryogenic temperature in space will be studied. Such phenomenon is an important aspect of their functioning since the transient emission of unwanted thermal radiation may affect the scientific measurements. To assess this effect, a computer model was developed for polypropylene based filters and PTFE-based coatings. Specifically, a theoretical model of their thermal properties was created and used into a multi-physics simulation that accounts for conductive and radiative heating effects of large optical elements, the geometry of which was suggested by the large format array instruments designed for future space missions. It was found that in the simulated conditions, the filters temperature was characterized by a time-dependent behaviour, modulated by a small scale fluctuation. Moreover, it was noticed that thermalization was reached only when a low power input was present.

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“…The main of them concern the nature of TS and the source of their universality (see, e.g., discussion in [3,7]). Since 1972 there have been many attempts to explain the experimental data in terms of propagating thermal phonons scattered by TS [3,[8][9][10][11] (in different modifications), density fluctuations (Rayleigh scattering) [1,3,10,[12][13][14], and the like. Some papers invoked nonpropagating vibrational modes as well [3].…”

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confidence: 99%

Disclination dipoles as the basic structural elements of dielectric glasses

Osipov

Krasavin

1998

Physics Letters A

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We show that the experimentally observed behavior of thermal conductivity of dielectric glasses over a wide temperature range can be explained by a combination of two scattering processes. The first one comes from the phonon scattering due to biaxial dipoles of wedge disclinations while the second one is the Rayleigh type scattering. The results obtained support the cluster picture suggested earlier for glassy materials.Physics of glassy systems has been attracting a considerable interest for a long period. Since the discovery of the anomalous low-temperature behavior of amorphous dielectrics [1] there were many attempts to explain this unusual phenomenon. And yet, in 1986 Freeman and Anderson [2] reviewing both numerous empirical results and theoretical models made a rather drastic conclusion that the thermal conductivity of amorphous dielectrics "is not understood in any temperature range". While at first glance this conclusion looks too pessimistic, it reflects an actual situation existed in glassy physics at that time. It has been found experimentally that the low-temperature anomaly in thermal conductivity, κ, observed by Zeller and Pohl for some noncrystalline solids [1] is universal. In particular, a T 2 dependence of κ below 1K together with the following characteristic plateau region have been found in the most of glassy materials (see, e.g., review [3]) as well as in some quasicrystalline alloys [4]. This finding allows to assume that a realistic theoretical model for description of the thermal conductivity should capture the very essence of these materials, their microstructure. Thus the conclusion of Freeman and Anderson actually suggests that this problem still remains to be solved.The most widely used model which explains glassy physics below 1K has been proposed by Phillips [5] and Anderson, Halperin, and Varma [6]. In this temperature region, thermal transport takes place via propagating acoustic modes. Thus, κ depends on the scattering of the phonons by the structure. Within the model [5,6], the principal scatterers were proposed to be the tunneling states (TS) in the glass. However, in spite of the success achieved in interpreting experimental data, some important questions were left unanswered. The main of them concern the nature of TS and the source of their universality (see, e.g., discussion in [3,7]).Since 1972 there have been many attempts to explain the experimental data in terms of propagating thermal phonons scattered by TS [3,[8][9][10][11] (in different modifications), density fluctuations (Rayleigh scattering) [1,3,10,[12][13][14], and the like. Some papers invoked nonpropagating vibrational modes as well [3]. The most successful approach includes a combination of TS and the Rayleigh scattering [10]. Notice that there were attempts to go beyond the TS approximation (see Ref.[15] and the references therein) as well as to do without TS at all. For example, an interesting phenomenological approach was discussed in Ref. [3] where a combination of the structure scattering together with a...

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Thermal conduction in glasses and polymers at low temperatures

Cited by 57 publications

References 9 publications

Thermal expansion of glasses at low temperatures

Thermal expansion of glasses at low temperatures

Heating of large format filters in sub-mm and fir space optics

Disclination dipoles as the basic structural elements of dielectric glasses

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