Electron-Phonon Umklapp-Scattering Processes in the Low-Temperature Thermal Resistivity of Potassium

1972 ◽  
Vol 6 (2) ◽  
pp. 371-376 ◽  
Author(s):  
J. W. Ekin
Keyword(s):  
Low Temperature ◽  
Thermal Resistivity ◽  
Umklapp Scattering

scholarly journals Investigation of the Thermo-Physical and Mechanical Properties of Coir and Sugarcane Bagasse for Low Temperature Insulation

2021 ◽  
Vol 6 (4) ◽  
pp. 340-356
Author(s):  
Mustapha Ndagi ◽  
Ajiboye Tajudeen Kolawole ◽  
Fabiyi Mustapha Olawale ◽  
Abdulkareem Sulaiman
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Low Temperature ◽  
Sugarcane Bagasse ◽  
Control Sample ◽  
Gum Arabic ◽  
Absorption Capacity ◽  
Thermal Resistivity ◽  
Insulating Materials ◽  
Insulating Material

This research  reports on the suitability of Agricultural bi-products as low temperature thermal insulating materials to replace synthetic insulating materials like polyurethane used in food warmers and ice coolers. Coir and sugarcane bagasse chosen for this research was based on literature review and local availability of materials. Coir was obtained from Badagry, Lagos State and Sugarcane bagasse obtained from Batati, Niger State, the materials were washed, sun dried for three days and cut into smaller pieces before being blended into smaller particles using an electric blender. The blended materials (Coir and Bagasse) were sieved into two different sieve size of 0.5 mm and 1.0 mm respectively.  The particles sizes were then combined into blend ratios of 50/50, 60/40, and 70/30 using Gum Arabic as binder. Thermal conductivity test showed that 1.0 mm particle size coir mixed with sugarcane bagasse has the lowest thermal conductivity of 0.01467 W/mK whilst that of 0.5 mm particle size has thermal conductivity of 0.01472 W/mK this is lower compared to the measured thermal conductivity of the polyurethane control sample of 0.01832 W/mK. Sample F (1.0 mm particle size,70% coir and 30% bagasse) with a thermal diffusivity of 5.15  m²/s, water absorption capacity of 410 %, UTS of 0.219 MPa, Compressive strength of 0.583 MPa, Specific heat capacity of 1141.3 J/kgK and thermal resistivity of 68.16 W/m/K is most suitable replacement for polyurethane as low temperature thermal insulator. This is corroborated by the performance evaluation test with carried out between polyurethane lined food warmer and bio-composite lined food warmer. The two test samples have close ice melt rate values and the polyurethane slightly edge the Bio-composite insulating material by 1.2 % in efficiency. The edge in efficiency can be accepted as all materials used in the development of the bio-composite insulating material are completely bio-degradable and environmentally friendly.

LOW TEMPERATURE RESISTIVITY OF THE TRANSITION ELEMENTS: COBALT, TUNGSTEN, AND RHENIUM

1957 ◽  
Vol 35 (5) ◽  
pp. 656-665 ◽  
Author(s):  
G. K. White ◽  
S. B. Woods
Keyword(s):  
Electrical Resistivity ◽  
Low Temperature ◽  
Thermal Resistance ◽  
High Purity ◽  
Thermal Resistivity ◽  
Superconducting Transition ◽  
Transition Elements ◽  
Experimental Values ◽  
Thermal Vibrations ◽  
Temperature Resistivity

Experimental values are reported for the electrical resistivity from 1.5° to 300° K. and for the thermal resistivity from 2° to 120° K. of high purity cobalt, tungsten, and rhenium. The temperature variation of the components of the electrical and of the thermal resistance due to scattering by thermal vibrations is deduced and the possible evidence for the importance of s–d transitions is discussed briefly. The temperature of the superconducting transition in samples of rhenium is found to be close to 1.70° K., the value reported by Hulm (1954).

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

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