## 3 Results and Discussion  
### Synthesis and Characterization  
The fibrous magnetic amphiphilic nanostructured composites were produced by impregnation of chrysotile with iron nitrate (1 and 25 wt% of iron, named hereon as Fe1% and Fe25%) followed by a CVD process to grow carbon nanostructures using ethanol as carbon source according to the Figure 1.  
During the CVD the temperature is increased from 30 up to 800 \({}^{\circ}\)C. The iron precursor impregnated on the chrysotile fibers is initially thermally decomposed to Fe\({}_{2}\)O\({}_{3}\). In the presence of ethanol and as the temperature increases, Fe\({}_{2}\)O\({}_{3}\) is then gradually reduced to form Fe\({}_{3}\)O\({}_{4}\), FeO and finally Fe\({}^{0}\) with the main volatile products CO\({}_{x}\) and H\({}_{2}\)O.  
\[\mathrm{Fe_{2}O_{3}\to Fe_{3}O_{4}\to FeO\to Fe^{0}} \tag{1}\]Figure 1: Preparation of magnetic amphiphilic nanoparticles based on Chrysotile obtained by CVD with ethanol. Figure 2: SEM images of chrysotile and magnetic amphiphilic nanoparticles (Fe1% and Fe25%). Figure 2 shows SEM images for the pure chrysotile and the prepared magnetic nanostructured composites. Fe1% shows the presence of chrysotile with agglomerated spherical particles likely related to metallic iron particles on the mineral surface. It was not possible to clearly visualize carbon structures formed in this sample due to the low carbon deposition. In fact, according to the elemental analysis the produced carbon yield was approximately 3%. Fe25% also shows the chrysotile fibers with agglomerated metallic iron particles. SEM images suggest that most of these particles are in the range 100-500 nm. Moreover, several bundles of carbon nanostructures, e.g., nanoffibers and nanotubes, can be observed over the chrysotile fiber surface. The materials have also been characterized by thermal analysis. Figure 3 shows the TG/DTG for the materials Fe1% and Fe25%. TG curve in air of the material Fe1% showed a weight loss of 3% up to 800 \({}^{\circ}\)C related to carbon oxidation (Equation (2)). On the other hand, the TG curve for the material Fe25% showed initially a weight gain up to 400 \({}^{\circ}\)C associated to the iron oxidation (Equation (3)). After 400 \({}^{\circ}\)C up to 650 \({}^{\circ}\)C the TG curve of the material Fe25% showed a weight loss of 35% that is related to carbon oxidation according to Equation (3). \[\text{C(g)}+\text{O}_{\text{2}}\text{(g)}\rightarrow\text{CO}_{\text{2}}\text{ (g)} \tag{2}\]  
\[2\text{ Fe}^{\text{0}}\text{(s)}+\text{3/2 O}_{\text{2}}\text{(g)}\rightarrow\text{Fe}_{\text{2}}\text{O}_{\text{3}}\text{(s)} \tag{3}\]  
It is interesting to note that carbon oxidation occurs at a maximum of velocity at 580 \({}^{\circ}\)C and in a very narrow temperature range, _i.e._, between 500 and 650 \({}^{\circ}\)C, which is typical for oxidation of carbon nanotubes and nanofibers structures [17]. This content of carbon present in the material Fe25% is very close to the one obtained by carbon elemental analyses of 40%. Raman spectra of the magnetic amphiphilic composites Fe1% and Fe25% (Figure 4) showed a band at approximately 1,350 cm\({}^{-1}\) (D band) which is related to defects in the carbon structures such as graphite or amorphous carbon [18]. The other band in region of 1,500-1,600 cm\({}^{-1}\) (G Band) is associated with the vibrations of C-C bonds in tangential directions observed graphitic materials. The G band can indicate the presence of multiwall nanotubes, nanofibers, nano-  
Figure 3: TG/DTG curves of magnetic amphiphilic nanoparticles Fe1% and Fe25%. that grow on metallic particles [19]. Therefore both materials led to the formation of carbon structures. No RBM modes, typical of small diameter nanotubes [19], were observed for the materials Fe1% or Fe25%. The ratio of the intensities of G and D bands (I\({}_{\textrm{G}}\)/I\({}_{\textrm{D}}\)) is _ca_. 1 for Fe1% and lower than 1 for Fe25%, which indicates that higher concentrations of iron leads to the formation of carbon structures being more defective.