# Thermal Investigations on Carbon Nanotubes by Spectroscopic Techniques
## 1 Introduction
In particular, GigaPascal [GPa] is the unit of measurement of the tensile strength, TeraPascal [TPa] is the unit of measurement of the tensile strength Young's Modulus. Siemens/meter [S/m] represents the unit of measurement of the Electrical Conductivity while Watt/meter Kelvin [W/mK] is the unit of measurement the thermal conductivity. The degree Celsius [\({}^{\circ}\)C] is associated to the charge mobility. The unit of measurement of Charge Mobility is [cm\({}^{2}\)/V-s] where V is volt and s represents the second, finally the unit of measurement of the surface area is [m\({}^{2}\)/g] where m is the meter ang is the gram. In order to improve the electronic properties of CNTs, different methods of functionalization of carbon nanotubes have recently been developed by replacing the carbon atoms on the walls with other elements such as nitrogen N [33; 34; 35; 36] and boron B [37; 38; 39; 40; 41]. It is well known that because of their properties, such as high flexibility, mechanical strength, aspect ratio, as well as high thermal and high electrical conductivity, CNTs are employed for many applications, to mention a few; CNTs catalyst supports, CNTs conductive properties and CNTs energy storage. Regarding this latter application, thanks to their intrinsic properties, CNTs are the favorite materials for electrodes in batteries and capacitors and find applications in various fuel cell components [42]. Furthermore, due to the high capacity of heat and electrical conductivity and mechanical properties, CNTs are considered to be efficient electron field-emitters. As for the techniques concerned for these systems, both the FTIR method and Raman spectroscopy have been employed [43; 44; 45; 46; 47]. It is well known that FTIR and Raman techniques are non-destructive and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Experimental Measurements** & **Computational Calculations** \\ \hline Tensile Strength [GPa] & 150 & 300 \\ Young’s Modulus [TPa] & 2.8–3.6 & 1.5–5 \\ Electrical Conductivity [S/m] & \(6.6\times 10^{3}\) & \(1\times 10^{7}\) \\ Thermal Conductivity [W/mK] & 3500 & 80–9500 \\ Thermal Stability in air [\({}^{\circ}\)C] & 420 & 750 \\ Charge Mobility [cm\({}^{2}\)/V-s] & \(1\times 10^{3}\) & \(1.2\times 10^{5}\) \\ Surface Area [m\({}^{2}\)/g] & 619.1 & 50–1315 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of carbon nanotubes (CNTs). not invasive. In particular, FTIR allows nanoscale structure changes to be revealed while Raman spectroscopy obtains information about their interaction with adsorbate molecules. For the characterization of CNTs thermal properties, two innovative methods have been applied. The first, Spectral Distance, refers to the deviation from the spectrum at the lowest temperature, of T = 25 \({}^{\circ}\)C [48; 49]. The second method, Cross Correlation Wavelet (XWT) by means of the coefficient of XWT (\(r_{XWT}\)), is based on the similarity degree of several spectra, taking as reference spectrum at the lowest temperature, of T = 25 \({}^{\circ}\)C [50; 51; 52]. Both the procedures reveal the same result.