Thermal Conductivity at Low Temperatures in Semicrystalline Polymers

AbstractTranscrystallization of semicrystalline polymers, such as PEEK, PEKK and PPS, in high performance composites has been investigated. It is found that PPDT aramid fiber and pitch-based carbon fiber induce a transcrystalline interphase in all three polymers, whereas in PAN-based carbon fiber and glass fiber systems, transcrystallization occurs only under specific circumstances. Epitaxy is used to explain the surface-induced transcrystalline interphase in the first case. In the latter case, transcrystallization is probably not due to epitaxy, but may be attributed to the thermal conductivity mismatch. Plasma treatment on the fiber surface showed a negligible effect on inducing transcrystallization, implying that surface-free energy was not important. A microdebonding test was adopted to evaluate the interfacial strength between the fiber and matrix. Our preliminary results did not reveal any effect on the fiber/matrix interfacial strength of transcrystallinity.

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The lattice thermal conductivity of dilute copper alloys at low temperatures

The London Edinburgh and Dublin Philosophical Magazine and Journal of Science ◽

10.1080/14786441208561143 ◽

1954 ◽

Vol 45 (371) ◽

pp. 1343-1345 ◽

Cited By ~ 34

Author(s):

G.K. White ◽

S.B. Woods

Keyword(s):

Thermal Conductivity ◽

Low Temperatures ◽

Lattice Thermal Conductivity ◽

Copper Alloys

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The Evaluation of TiTe2 as a Diffusion Barrier in the Formation of Low Thermal Conductivity Nanolaminates with Bi2Te3 and Sb2Te3

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.74.38 ◽

2010 ◽

Vol 74 ◽

pp. 38-47

Author(s):

Clay Mortensen ◽

Paul Zschack ◽

David C. Johnson

Keyword(s):

Thermal Conductivity ◽

Diffusion Barrier ◽

Self Assembly ◽

Low Temperatures ◽

Annealing Temperature ◽

The Self ◽

High Angle ◽

X Ray Diffraction ◽

Amorphous Precursor ◽

X Ray

The evolution of designed [(Ti-Te)]x[(Sb-Te)]y, [(Bi-Te)]x[(Sb-Te)]y, [(Ti-Te)]w[(Bi-Te)]x[(Sb-Te)]y and [(Ti-Te)]w[(Bi-Te)]x[(Ti-Te)]y[(Sb-Te)]z precursors were followed as a function of annealing temperature and time using both low and high angle x-ray diffraction techniques to probe the self assembly into nanolaminate materials. The [(Bi-Te)]x[(Sb-Te)]y precursors were found to interdiffuse at low temperatures to form a (BixSb1-x)2Te3 alloy. The [(Ti-Te)]x[(Bi-Te)]y and [(Ti-Te)]x[(Sb-Te)]y precursors formed ordered nanolaminates [{(TiTe2)}1.35]x[Bi2Te3]y and [{(TiTe2)}1.35]x[Sb2Te3]y respectively. The [(Ti-Te)]w[(Bi-Te)]x[(Sb-Te)]x precursors formed [{(TiTe2)}1.35]w[(Bi0.5Sb0.5)2Te3]2x nanolaminates on annealing, as the bismuth and antimony layers interdiffused. Over the range of TiTe2 thicknesses used in [(Ti-Te)]w[(Bi-Te)]x[(Ti-Te)]y[(Sb-Te)]z precursors, Bi and Sb were found to interdiffuse through the 2-4 nm thick Ti-Te layers, resulting in the formation of (BixSb1-x)2Te3 alloy layers as part of the final nanolaminated products. When the Bi-Te and Sb-Te thicknesses were equal in the amorphous precursors, symmetric [{(TiTe2)}1.35]m[(Bi0.5Sb0.5)2Te3]n nanolamiantes were formed. When the thicknesses of Bi-Te and Sb-Te layers were not equal in the amorphous precursor, asymmetric [(TiTe2)1.35]m[(BixSb1-x)2Te3]n[(TiTe2)1.35]m[(BixSb1-x)2Te3]p nanolaminates were formed. These results imply that to form (A)w(B)x(C)y nanolaminates using designed layered precursors all three components must be immiscible. To form (A)x(B)y(A)x(C)z nanolaminates, the components must be immiscible or the precursor to the A component and the A component itself must be an effective interdiffusion barrier preventing B and C from mixing.

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Thermal Property Measurements on Biological Materials at Subzero Temperatures

Journal of Biomechanical Engineering ◽

10.1115/1.2895422 ◽

1991 ◽

Vol 113 (4) ◽

pp. 423-429 ◽

Cited By ~ 17

Author(s):

Xuemei Bai ◽

David E. Pegg

Keyword(s):

Thermal Conductivity ◽

Low Temperatures ◽

The Self ◽

Rabbit Kidney ◽

Kidney Cortex ◽

Low Viscosity ◽

Subzero Temperatures ◽

Liquid Samples ◽

Thermal Probes ◽

Low Ionic Strength

The self-heated thermistor technique was used to measure the thermal conductivity and thermal diffusivity of biomaterials at low temperatures. Thermal standards were selected to calibrate the system at temperatures from −10°C to −70°C. The thermal probes were constructed with a convection barrier which eliminates convection inside liquid samples of low viscosity, without affecting the conductivity and diffusivity results. Using this technique, the thermal conductivity and diffusivity of two organ perfusates (HP5 and HP5 + 2M glycerol), one kidney phantom (a low ionic strength gel), as well as rabbit kidney cortex have been measured from −10°C to −70°C.

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