scholarly journals Through-Plane and In-Plane Thermal Diffusivity Determination of Graphene Nanoplatelets by Photothermal Beam Deflection Spectrometry

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7273
Author(s):  
Humberto Cabrera ◽  
Dorota Korte ◽  
Hanna Budasheva ◽  
Behnaz Abbasgholi-NA ◽  
Stefano Bellucci

In this work, in-plane and through-plane thermal diffusivities and conductivities of a freestanding sheet of graphene nanoplatelets are determined using photothermal beam deflection spectrometry. Two experimental methods were employed in order to observe the effect of load pressures on the thermal diffusivity and conductivity of the materials. The in-plane thermal diffusivity was determined by the use of a slope method supported by a new theoretical model, whereas the through-plane thermal diffusivity was determined by a frequency scan method in which the obtained data were processed with a specifically developed least-squares data processing algorithm. On the basis of the determined values, the in-plane and through-plane thermal conductivities and their dependences on the values of thermal diffusivity were found. The results show a significant difference in the character of thermal parameter dependence between the two methods. In the case of the in-plane configuration of the experimental setup, the thermal conductivity decreases with the increase in thermal diffusivity, whereas with the through-plane variant, the thermal conductivity increases with an increase in thermal diffusivity for the whole range of the loading pressure used. This behavior is due to the dependence of heat propagation on changes introduced in the graphene nano-platelets structure by compression.

Cerâmica ◽  
2003 ◽  
Vol 49 (309) ◽  
pp. 29-35 ◽  
Author(s):  
W. N. dos Santos ◽  
R. Gregório

The hot wire technique is considered to be an effective and accurate means of determining the thermal conductivity of ceramic materials. However, specifically for materials of high thermal diffusivity, the appropriate time interval to be considered in calculations is a decisive factor for getting accurate and consistent results. In this work, a numerical simulation model is proposed with the aim of determining the minimum and maximum measuring time for the hot wire parallel technique. The temperature profile generated by this model is in excellent agreement with that one experimentally obtained by this technique, where thermal conductivity, thermal diffusivity and specific heat are simultaneously determined from the same experimental temperature transient. Eighteen different specimens of refractory materials and polymers, with thermal diffusivities ranging from 1x10-7 to 70x10-7 m²/s, in shape of rectangular parallelepipeds, and with different dimensions were employed in the experimental programme. An empirical equation relating minimum and maximum measuring times and the thermal diffusivity of the sample is also obtained.


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