## 4 Synthesis and Characterizations of Ball Milled Variants
### Synthesis of Magnetic Nanocomposites  
High energy ball milling not enhances the surface properties like active surface area, pore size, pore volume, and bulk density, as well as the magnetic properties of nanocomposites. The magnetic property of nanocomposite depends upon the coupling of the soft and hard phases of the material. It not only depends upon these intrinsic properties, but also on the microstructure and grain size. This helps in achieving high remanence and coercivity. Multiferroic systems can also be obtained by mechanochemical milling [92]. High energy  
Figure 9: Hardness of Al/CNT nanocomposite [88]. (Permissions to use this Figure is granted since the source article is an open access distributed under the terms and conditions of the Creative Commons Attribution (CC By) license ([[http://Creativecommons.org/license/by/4.0/](http://Creativecommons.org/license/by/4.0/)]([http://Creativecommons.org/license/by/4.0/](http://Creativecommons.org/license/by/4.0/)) (accessed on 26 July 2022)).  
ball milling and spark plasma sintering methods were utilized by [PERSON] et al. [93] to prepare SmCo\({}_{7}\)/\(\alpha\)-Fe magnetic nanocomposite. \(\alpha\)-Fe nanoflakes were mixed with Sm\({}_{2}\)Co\({}_{7}\) ribbons and were subjected to high energy milling, and then hot-pressed using spark plasma sintering. To investigate the effect of inter-granular exchange in magnetic properties, the hard (SmCo\({}_{7}\)) and soft phases (SmCo\({}_{5}\)) were compared and found that the hard phase showed a better exchange coupling effect as it increases the exchange length. It was found that magnetic field heating after high energy balling, improves the remanence and coercivity of SmCo/\(\alpha\)-Fe nanocomposite magnets. The remanence and coercivity were improved by 17% and 23%, respectively [94]. SiO\({}_{2}\), Fe\({}_{2}\)O\({}_{3}\), NiO, and ZnO have been milled together to synthesize NiZn ferrite/SiO\({}_{2}\) nanocomposites at 10:1 ball to powder ratio and at a speed of 200 rpm for 1 to 250 h, and heat treatments have been performed to obtain nanocomposites having highest saturation magnetization and coercivity [95]. The NiZn Ferriite/SiO\({}_{2}\) are at least two orders of magnitudes superior to their pristine counterparts.  
[PERSON] et al. [96] reported the preparation of SmCo\({}_{5}\)/\(\alpha\)-Fe magnetic nanocomposite with different La/Ce substitution concentration by high energy ball milling followed by calcining at 450 \({}^{\circ}\)C to 650 \({}^{\circ}\)C for 30 min. The powder to ball weight ratio was 1:25. The X-ray diffraction (XRD) pattern was used to estimate the phase structure of La and Ce doped nanocomposite magnet at different dopant content and annealing temperatures (Figure 10). There was no change in the hard phase with the increased Ce content and elevated temperature in the magnetic nanocomposites, while a transition change was observed with the higher La content and annealing temperature. The magnetic property was studied using a vibrating sample magnetometer. In fact, the increase in La or Ce dopants decrease the magnetization performances of the host material, SmCo\({}_{5}\)/\(\alpha\)-Fe. The hysteresis loop (Figure 11) exhibited strong ferromagnetism for both Ce and La-doped nanocomposite. Additionally, the magnetic performance was found to be higher for the La-doped, SmCo\({}_{5}\)/\(\alpha\)-Fe nanocomposite compared to that of the Ce-doped magnetic nanocomposite.  
Figure 10: _Cont._