## 3 Results
The relative content of the phases in each studied sample can be investigated by an XRD analysis by the comparison of the characteristic diffractive lines for each sample. Aluminum oxide has its main diffraction line at 35.137\({}^{\circ}\) 20 (ICSD 01-088-0826) and as the main substrate, can indicate the overall content of the reacted aluminum phases. As it is shown in Figure 5a, sample 2 with citric acid additions has the highest intensity of the diffractive line and associated with it the highest amount of Al2O3, a slightly lower amount is in the sample with tartaric acid and the lowest amount of aluminum oxide in the reference sample. Taking into consideration the spectral lines for other phases, these relationships are also visible. Consequently, for the main diffraction line for boehmite shown in Figure 5b, the intensity changes in opposition to aluminum  
Figure 3: Thermal analysis of studied samples, (**a**) TG-DSC, (**b**) TG-EGA. oxide. Reference sample 1 has the highest intensity, followed by the sample with citric acid and at the end is the sample with tartaric acid. This confirms the findings of the thermal analysis, where losses of mass in the last endothermic effect associated with the decomposition of boehmite were in the same order. In the case of Mg-containing phases, the results also show a strong relationship between the addition of citric and tartaric acids and the composition of each sample. In the case of brucite (due to the overlapping of its main diffractive line with peaks for others phases, the second most intensive diffractive line was utilized), we can observe (Figure 5c) that the addition of acids decreases its content in the samples but simultaneously increases the amount of double magnesium aluminum hydroxide hydrate in relation to the reference sample (Figure 5d). The relation in the case of brucite would be in agreement with both the observed amount of double magnesium aluminum hydroxide hydrate and the traces of MgO in samples with chelates addition revealed in the XRD analysis. Taking into consideration the results from the XRD analysis and thermal analysis, the strong influence of acid additions on the hydration process of the studied samples under hydrothermal conditions can be stated. Figure 4: Thermogravimetric analysis of the studied samples with a loss of mass in a specific range of temperature. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Character of the Effect** & **Temperature of Maximum of the Effect** * (“C) & **Range of Temperatures of the Effect** * (“C) & **Mass Loss Connected with the Effect (\%)** \\ \hline \multirow{2}{*}{\(1\)} & Endothermic & 186.1 & 40–250 & 0.81 \\ \cline{2-5}  & Endothermic & 394.4 & 250–450 & 10.35 \\ \cline{2-5}  & Endothermic & 535.9 & 450–1000 & 3.73 \\ \hline \multirow{2}{*}{\(2\)} & Endothermic & 201.8 & 40–250 & 1.75 \\ \cline{2-5}  & Endothermic & 390.1 & 250–450 & 10.90 \\ \cline{2-5}  & Endothermic & 529.4 & 450–1000 & 2.30 \\ \hline \multirow{3}{*}{\(3\)} & Endothermic & 197.5 & 40–250 & 1.82 \\ \cline{2-5}  & Endothermic & 393.2 & 250–450 & 10.93 \\ \cline{2-5}  & Endothermic & 532.6 & 450–1000 & 2.04 \\ \hline \hline \end{tabular}  
* based on a DSC curve. ** based on a TG curve.  
\end{table} 
Table 3: Summary of the thermal effect and a loss of mass in a specified range of temperature. The spectra of FTIR spectroscopy shown in Figure 6 reveal several bands characteristic for hydrated phases that can confirm the previous results. The broad bands in the range of 3000-3700 cm\({}^{-1}\) are mainly connected with hydroxyl groups (-OH), bonded with the metal hydroxide layers. Worthy of notice is the sharp envelope of this band, which indicates a high degree of crystallinity of the studied samples in this aspect. First of these bands, around 3695 cm\({}^{-1}\) is present in each sample, whichis connected with -OH groups in octahedral brucite layers [9; 26].