The influence of morphological and structural aspects of synthetic graphites used in the aerospace area on their electrical and mechanical properties

Abstract

Synthetic graphite presents unique and differentiated properties (low coefficient of thermal expansion, low modulus, low density, and especially increased mechanical strength) at high temperatures (up to 2700 °C), which makes it suitable for use in the aerospace area. To meet these strict requirements, the importance of synthetic graphite increases as the working temperature becomes more severe and the characteristics of other materials are not adequate. In the present study, three different samples of synthetic graphite were characterized by structural, electrical, morphological, and mechanical analyses. The correlation of the results shows that the graphite with lower crystallographic ordering, smaller pores, and regions richer in mosaic and isotropic structures had both the highest compression strength and electrical resistivity, when it was evaluated by Raman spectroscopy, x-ray diffraction, polarized light optical microscopy, and scanning electron microscopy analyses. These results lead to the conclusion that graphite with smaller pores and richer particles with lower structural ordering is more suitable for aerospace application. The other samples (with better structural ordering and less electrically resistive) have potential application in devices that require better electrical characteristics. The correlation of morphological, structural, electrical, and mechanical results of this study supports graphite selection for aerospace application.