Thermal conduction mechanisms absorption coefficient

In the case of solid crystalline oxides, thermal conductivity decreases with increasing temperature but begins to rise above 1500— 1600 °C because transmission of heat by radiation (photons) begins to take a significant part besides the conduction of heat (phonon mechanism). In completely transparent materials (the coefficient of absorption a = O), no interaction with the radiation occurs in an opaque body (a = oo) the heat is transferred by conduction alone. With translucent materials, each element of the substance absorbs some of the incident radiation, and emits simultaneously,This internal radiation mechanism of heat transmission is characteristic for glasses. At high temperatures, a considerable proportion of heat is therefore transmitted by radiation the so-called apparent thermal conductivity is a sum of true conductivity with radiation conductivity ... 

First, the main difference between NC and UNCD films has to be considered. The decrease of the crystal grain size from NC to UNCD films increases the number of grain boundary interfaces. This also results in a decrease of thermal conductivity and an increase of the optical absorption of UNCD films compared to NC films. At the same time, the friction coefficient of UNCD films is lower than that of NC films. Both types of CVD films can be used for MEMS (microelectromechan-ical systems), NEMS (nanoelectromechanical systems), and also for electrochemical applications. " DND is applied as an abrasive for ultrafine mechanical polishing of hard surfaces of materials. Present-day polishing compositions based on detonation ND offer the possibility of obtaining... 

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