# Smart Nanocomposites for Nanosecond Signal Control: The Nano4 waves Approach
## 2 Materials and Methods
### Synthesis of MNPs(Magnetic Nanoparticles)@NCS(Nanocarbon Supports) Nanocomposites  
During the project, we were able to decorate five types of NCS with nine different types of MNPs. The origin of the various NCS is listed in Table 1, while Table 2 details the types of MNPs. The desired nanocomposite materials were successfully obtained in all cases by diverse synthetic approaches that can be divided into two main categories: (1) wet-chemical techniques at atmospheric pressure, including sol-gel, usually followed by thermal treatment in dry form and (2) solvothermal methods carried out in an autoclave under high pressure and temperature. Ni@GO was synthesized using a one-pot solvothermal method described in [16]. The preparation of zero valence Iron (ZVI) as well as FeNi, CoNi, and FeCoNi alloyed nanoparticles supported on GO was performed using a Pechini-type sol-gel method fully described in ref. [17]. Direct co-precipitation and covalent linkage were also used, and compared in our previous paper [16], for the synthesis of magnetite Fe\({}_{3}\)O\({}_{4}\) on various NCS. The influence of each method on the obtained nanocomposites most relevant characteristics was studied, such as chemical identity, size of particles, loading rate and spatial distribution of the MNPs over the NCS, as will be illustrated in Section 3.1. The impact of the variables controlling the solvothermal decoration of a wide variety of NCSs was investigated in more detail, such as the nature of the iron precursor and the NCS (type and oxidation state), the reaction temperature, time, and water content. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Name**} & **Specification** & **Company** & **Country** \\ \hline \multirow{3}{*}{Multi-walled carbon nanotubes (MWCNTs)} & NC7000, 90\%C purity & \multirow{3}{*}{Nanocyl} & \multirow{3}{*}{Belgium} \\  & NC3100, 95\%C purity & & & \\ \cline{1-1} \cline{3-5} \multirow{2}{*}{Graphene oxide (GO)} & - & & \\ \cline{1-1} \cline{3-5} \multirow{2}{*}{Reduced graphene oxide (rGO)} & - & & \\ \cline{1-1} \cline{3-5} \multirow{2}{*}{Graphene nanoplatelets (GNP)} & TIMREX C-Therm 002 & \multirow{2}{*}{Imreys} & \multirow{2}{*}{Switzerland} \\  & and TIMREX BNB90 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Nanocarbon supports used in the project. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Type of NPs**} & **NCS \({}^{*}\)** & **Procedure** & \multicolumn{2}{c}{**Studied Synthetic Parameters**} \\ \hline \hline
**INVERSE** & NiFe\({}_{2}\)O\({}_{4}\) & GO & & & Type and concentration of metal precursor. \\ \cline{1-1} \cline{3-5}
**SPINELS** & Fe\({}_{3}\)O\({}_{4}\) & GO & & Type, concentration and molecular weight of capping agent. \\ \hline \multirow{4}{*}{**METALS**} & \multirow{4}{*}{Ni} & GNPs & \multirow{4}{*}{Solvothermal} & \multirow{4}{*}{Reaction temperature. \\  & ox-MWCNTs} & & & Reaction time. \\  & & MWCNTs & & & Reducing agent. \\ \cline{1-1} \cline{3-5} \multirow{2}{*}{**METALS**} & \multirow{2}{*}{Co} & GO & & & \\ \cline{1-1} \cline{3-5}  & & MWCNTs & & & \\ \cline{1-1} \cline{3-5} \multirow{2}{*}{Fe(ZVI)} & \multirow{2}{*}{Ge} & GO & Solution (S) & S & Solvent. \\  & rGO & & Over (O) & & Reaction temperature. \\  & & GNPs & Sol-gel (SG) & & Influence of capping agent. \\  & & ox-MWCNTs & & & Reaction time. \\  & & MWCNTs & & & Reaction temperature. \\ \hline \multirow{4}{*}{**ALLOYS**} & FeCo & \multirow{4}{*}{GO} & \multirow{4}{*}{Sol-gel (SG)} & \multirow{4}{*}{SG} & \multirow{4}{*}{Reaction temperature. \\  & FeNi & & & & Reaction temperature. \\ \cline{1-1}  & CoNi & & & & Composition of reaction atmosphere. \\ \cline{1-1}  & FeCoNi & & & & Proportions of the sol-gel reactants. \\ \hline \multicolumn{5}{l}{\({}^{*}\) GO: graphene oxide, rGO: reduced graphene oxide. GNPs: graphene nanoplatelets. MWCNTs: multiwalled carbon nanotubes. ox-MWCNTs: oxidized multiwalled carbon nanotubes. ZVI: zero valence iron.} \\ \end{tabular}
\end{table}