# Magnetic Nanoparticles as Mediators for Magnetic Hyperthermia Therapy Applications: A Status Review
## 3 Results and Discussion
### X-ray Diffraction Analysis
Sample (a) in Figure 3 shows as-prepared Ni\({}_{0.725}\)Cu\({}_{0.275}\) MNPs (microemulsion method) and sample (b) in Figure 3 shows the particles thermally homogenized in the NaCl matrix. Figure 3 (a) shows the as-prepared nanoparticles synthesized by the microemulsion method. It can be seen that the peaks are broad and therefore were further homogenized under a reducing atmosphere (Ar/H\({}_{2}\)). Figure 3 (b) clearly shows crystalline peaks that are extremely narrow. Homogenization in a reducing atmosphere also resulted in the growth of nanoparticles. As-prepared nanoparticles were about 7 nm in size, while the homogenized nanoparticles were about 28 nm in size. Thus, the average size of nanoparticles increased at the expense of elevated temperature (750 \({}^{\circ}\)C, 5 h) and reduced atmosphere. The 2\(\theta\) diffraction angles in Figure 4 correspond to the (111), (200), and (220) planes of the Ni\({}_{1-x}\)Cu\({}_{x}\) alloy crystallites after reduction in a silica matrix, single-phase composition [103]. The samples are A (Ni\({}_{67.5}\)Cu\({}_{32.5}\)), B (Ni\({}_{62.5}\)Cu\({}_{37.5}\)), and C (Ni\({}_{60}\)Cu\({}_{40}\)). The silica matrix is manifested by a small peak of cristobalite at 2\(\theta\) = 28\({}^{\circ}\). Using sol-gel synthesis, we first achieved the formation of copper and nickel oxides [52], which were then heated to 850 \({}^{\circ}\)C. Namely, in the silica matrix, the nanoparticles could not agglomerate but only grew accordingly, and the reducing atmosphere (H\({}_{2}\)/Ar) ensured the formation of Ni\({}_{1-x}\)Cu\({}_{x}\) alloy nanoparticles. Compared with the microemulsion technique, the sol-gel method has \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Name** & **Figure** & \(\mathbf{d_{\text{XRD }}}\) **[nm]** & **References** \\ \hline As prepared maghemite particles (A) & Figure 1 & 11.8 & \\ Maghemite MNPs covered with CM-dextran (B) & Figure 1 & 16.0 & [27] \\ (Mg, Ti)-ferrite MNPs (nanocrystallites) & Figure 2 & 20.0 & [26] \\ (Mg, Ti)-ferrite MNPs (crystalline spinel) & Figure 2 & 200 & \\ As-prepared Ni\({}_{0.725}\)Cu\({}_{0.275}\) MNPs & Figure 3 & 7.0 & [41] \\ Ni\({}_{0.725}\)Cu\({}_{0.275}\) MNPs thermally homogenized in & Figure 3 & 28.0 & \\ Ni\({}_{67.5}\)Cu\({}_{32.5}\) (A) & Figure 4 & 19.0 & \\ Ni\({}_{62.5}\)Cu\({}_{37.5}\) (B) & Figure 4 & 17.0 & [50; 103] \\ Ni\({}_{60}\)Cu\({}_{40}\) (C) & Figure 4 & 17.0 & \\ Cu\({}_{x}\)Ni\({}_{1-x}\) (A–F) & Figure 5 & 10.0–12.0 & [55] \\ Cr\({}_{20}\)Ni\({}_{80}\) & Figure 6 & 5.0–25.0 & [107] \\ Cr\({}_{x}\)Ni\({}_{1-x}\) (S–S7) & Figure 7 & 12.0–18.0 & [107] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average particle diameters of different samples were obtained using the Sherrer equation. [108]. the advantage that the homogenization of nanoparticles does not cause agglomeration and uncontrolled size of nanoparticles. Figure 4 clearly shows that the nanoparticles are crystalline and have a size between 17 and 19 nm, which was estimated using the Sherrer equation. Moreover, the analysis of TEM shows that the particles are not agglomerated in the silica matrix using the sol-gel method and subsequent homogenization. In Figure 5, we see the characteristic peaks corresponding to the (100) and (200) planes of bulk FCC metals, 43.47 \({}^{\circ}\), 50.38 \({}^{\circ}\) (Cu), and 44.6 \({}^{\circ}\), and 51.91 \({}^{\circ}\) (Ni) (PDF files 001-1241 and 001-1260). Using EDS analysis, we confirmed that the composition of Cu-Ni MNPs is consistent with the [Cu\({}^{2+}\)]-[Ni\({}^{2+}\)] molar ratio used in the synthesis. Figure 5 shows samples that were milled for 20 h, as this time was found to be optimal for the formation of the CuNi alloy. It is clear from the X-ray diffraction patterns that as the copper content increases, the \(d_{111}\) spacing also increases. For samples A through F, we estimated particle size between 10 and 12 nm using Sherrer's equation, and the size was consistent with the size of nanoparticles estimated by magnetic measurements [55].