TheĬalculated results are compared to previously reported response values obtained We also calculated the heat capacity and time constantįor various materials with Debye temperatures in the range of 600-1400K. The finite-size scaling method for different Debye temperatures and micron size Variation of the specific heat per unit volume and the heat conductivity using The investigation is based on the calculation of the Response of the freestanding-membrane type of superconductor transition-edgeĭetectors is investigated. The effect of substrate thickness and its Debye temperature on the bolometric This work advances the state-of-art of phase change materials for capacitive cooling of handheld devices.
Furthermore design of a microfabricated calorimeter to measure such enhancements is explained in detail.
Using fundamental thermodynamics of phase transition, calculations regarding the enhancement resulting from superheating in such thin film systems is conducted. In this thesis I propose novel nanostructured thin-film materials that can potentially exhibit significantly enhanced volumetric enthalpy change. However, such capacitive management becomes feasible only if there is a significant enhancement in the enthalpy change per unit volume of the phase change material since existing bulk materials such as paraffin fall short of requirements.
Capacitive thermal management based on phase change materials potentially offers a fan-less thermal management for such transient profiles. Transient power dissipation profiles in handheld electronic devices alternate between high and low power states depending on usage. The present results establish a lower bound for the heat capacity of suspended mesoscopic structures and indicate the emergence of the quantum mechanical regime in the dynamics of bounded phonon cavities. It is also demonstrated that the heat capacity of the suspended phonon cavities is invariant under the product of the temperature (T) with a characteristic lateral dimension (L) of the sample. The behavior is more pronounced for the thinnest cavities, but takes place also for moderately thick structures, with thickness-to-side ratios $\gamma$=0.1 to 0.2. The calculations demonstrate that the heat capacity of realistic quasi-2D phonon cavities approach the linear dependence on T at sub-Kelvin temperatures. The vibrational modes of the suspended cavity are accurately obtained from the three-dimensional (3D) elastic equations in the small strain limit and their frequencies assigned to the cavity phonon modes. We present a detailed analysis of the vibrational spectrum and heat capacity of suspended mesoscopic dielectric plates, for various thickness-to-side ratios at sub-Kelvin temperatures. C'est ce que nous cherchons à faire dans ce travail. En revanche les propriétés thermiques et thermodynamiques restent relativement mal comprises et ce pour plusieurs raisons: il est très difficile de contrôler les flux de chaleur à très petite échelle, les énergies mises en jeu pour des systèmes peu massiques sont très faibles et donc délicates à mesurer, et enfin la manipulation et la fragilité de ces petits systèmes transforme leur mesure en un défi expérimental.
Depuis vingt ans de belles illustrations expérimentales de variations de propriétés électriques (magnétiques) ont été obtenues en physique mésoscopique, en matériau ou en magnétisme. Avec l'engouement pour les nanosciences et en particulier pour la nanophysique, les physiciens et chimistes ont cherché à savoir si la matière possédait les mêmes propriétés à petite échelle que dans les échantillons massifs. La réduction des dimensionnalités de systèmes physiques implique des modifications substantielles des propriétés thermiques.