PSI - Issue 40

M.V. Fedorov et al. / Procedia Structural Integrity 40 (2022) 145–152 Fedorov M.V., Vasilieva M.I. / Structural Integrity Procedia 00 (2022) 000 – 000

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Figure 2. XRD pattern of initial UDP spinel.

Thermal analysis of UPD spinel from room temperature to 600 ○ C is shown in Figure 3. Thermal analysis established endothermic peaks: between room temperature to 100 ○ C, 130 to 200 ○ C and 300 to 400 ○ C. Further, the weight loss of the sample (TG/%) can be attributed: to the removal of physically adsorbed water at room temperature to 200 ○ C (the weight loss was approximately -1.04% wt.); to the removal of interlayer water of layered double hydroxides (LDH) within 200 ‑ 400 ○ C (the weight loss was approximately -4% wt.); according to Forano et al. (2006), Shaskolskaya (1984), Duan (2006), Booking and Drits (1993), Gabelkov et al. (2011) to dehydroxylation of brucite-like layers and removal of interlayer LDH anions in the remaining range. X-ray phase analysis showed that in the XRD pattern of spinel, there is a complete disappearance of reflections related to the LDH structure and an appearance of reflections related to the Mg-O (see Fig.4). It should be noted that at higher calcination temperatures, along with the Mg-O phase, a stoichiometric spinel MgAl 2 O 4 phase occurs. Thermal analysis of UPD spinel from room temperature to 1000 ○ C is shown in Figure 5. There are typical signs of the decay of SDH. The TG curve has four ranges of mass loss: the range from room temperature to 150 ○ C, where the mass loss is 3.3%; the range from 150 to 200 ○ C, where the mass loss is 1.4%, the range from 200 to 400 ○ C, where the mass loss is 4.7 %, the range from 600 to 1000 ○ C, where weight loss is not. The total weight loss was 9.7%. Similar to the results of diffraction patterns after heated to 600 ○ C, the reflections related to the LDH structure disappear entirely. The UPD spinel composition consists of the spinel and periclase phases; the XRD pattern is shown in Figure 6. Figure 7 shows the thermal analysis of spinel UDP from room temperature to 1450 ○ C, wherein the temperature range 900-1000 ○ C; 1000-1100 ○ C; 1100-1250 ○ C; 1390-1450 ○ C, endothermic peaks were found, indicating the decomposition of LDH into phases of stoichiometric spinel and Mg-O. Clear intense peaks of spinel and periclase are observed in the XRD pattern of UDP spinel after being heated to 1450 ○ C (Fig.8). Based on the results obtained, it can be argued that the spinel UDP under study consists of spinel, periclase, and LDH phases. When the temperature rises from room temperature to 1450 ○ C, the decomposition of LDH occurs. As a result, the formation of Mg-O phases and stoichiometric spinel occurs.