## 3 Results  
### Supporting Cobalt Ferrite Nanoparticles over Co-Fe LDH  
X-ray diffraction pattern of Co-Fe LDH is given in Figure 2. It exhibited the typical XRD pattern of the carbonate-form of LDH, which reported in the literature. Symmetric reflections for the basal (003), (006), and (009) planes were observed in Figure 2 exhibiting sharp peaks. Also, Figure 2 showed asymmetric reflections for the non-basal (012), (015), and (018) planes at high two theta indicating that the product has the layered structure of hydrdalcite-like materials (JCPDS file no. 50-0235). The clear arrangement among the symmetric reflections of the basal planes, i.e., d\({}_{003}\) = 2 \(\times\) d\({}_{006}\) = 3 \(\times\) d\({}_{009}\) for Co-Fe LDH, indicated that the Co-Fe layers are highly packed in ordered form along axis c. The lattice parameter \"c\" is estimated as 3 \(\times\) d\({}_{003}\) and is used to determine the thickness of the layer and the interlayer distance. From the XRD analysis, the position of the (110) reflection allowed calculation of  
Figure 1: A pressurized vessel with a temperature controller unit [28]. the parameter 'a' (a = 2 \(\times\) d\({}_{110}\)). The lattice parameter 'a' is used to determine the average distance between cobalt and iron cations inside the brucite-like layer. These lattice parameters were calculated: basal spacing, d\({}_{003}\) = 0.76 nm; a-axis, a = 0.31 nm; and c-axis, c = 2.28 nm. These parameters were similar to that reported for the natural and synthetic hydrolcite in the case of the guests are carbonate and/or cyanate [29]. In addition, weak peaks of cobalt ferrite CoFe\({}_{2}\)O\({}_{4}\) (JCPDS file no. 79-1744) were observed. According to the XRD calculations, the percentage of CoFe\({}_{2}\)O\({}_{4}\) was about 13.2%. It means that some crystals of cobalt ferrite formed at low temperature and supported over the nanolayers of Co-Fe LDH. The symmetry and the nature of the functional groups of Co-Fe LDH were identified through the FT-IR technique as shown in Figure 3. The vibration of the hydroxyl groups of LDH was observed at 3400 cm\({}^{-1}\) as a broad absorption band. The broadness of the OH band was due to existence of hydrogen bonds which was confirmed by observing weak band at 2952 cm\({}^{-1}\) for the OH stretching mode of the hydrogen bonds to the interlayered anions [15; 16]. The insertion of cyanate anions into the Co-Fe LDH structure was verified by the appearance of the \(\
u_{1}\) vibration at 2190 cm\({}^{-1}\)[29]. A close-up of the vibration region of cyanate anions showed that this band is actually split into two bands because of the lowering of the anion's symmetry. This splitting was clear in Figure 3 where, there is another peak at 2124 cm\({}^{-1}\) accompanied with 2190 cm\({}^{-1}\). Also, the presence of the interlayered carbonate anions was confirmed by observing two bands at 1540 cm\({}^{-1}\) and 1351 cm\({}^{-1}\)[17; 18]. This vibration mode \(\
u_{3}\) is recorded at 1450 cm\({}^{-1}\) for free carbonate species, but the  
Figure 3: FT-IR spectrum of the CoFe\({}_{2}\)O\({}_{4}\)-supported Co-Fe LDH. Figure 2: X-ray diffraction pattern of the CoFe\({}_{2}\)O\({}_{4}\)-supported Co-Fe LDH. symmetry lowering of the interlayered carbonate caused splitting and shifting for this band. In addition, the vibration mode \(\
u_{1}\) of carbonate anion was observed at 1072 cm\({}^{-1}\)[18]. The bands at 965 cm\({}^{-1}\) and 836 cm\({}^{-1}\) were attributed to the mode \(\
u_{2}\) of carbonate anion while the mode \(\
u_{4}\) of carbonate anion was clear at 777 cm\({}^{-1}\). Two other bands, located at 597 cm\({}^{-1}\) and 486 cm\({}^{-1}\), could be attributed to the Fe-OH and Co-OH bending vibration; respectively [19]. These results indicated that the prepared Co-Fe LDH has a similar structure to the usual LDH structure. Thermal characteristics of the supported LDH were determined by TG and DSC as shown in Figure 4. The TG diagram of Co-Fe LDH revealed four weight losses as shown in Figure 4a.