The second weight loss of the MgO-OA precursor of about 47.9% between 400°C and 510°C is attributed to the decomposition this website of MgC2O4 to MgO. A broad endothermic peak at about 500°C is evidence of the reaction occurring resulting in the formation of MgO nanostructures.
The weight loss for the formation of MgO-OA is calculated as shown in chemical reaction (4) and found to be 48.5% which is very close to the experimental value of 47.9%. The whole reaction mechanisms are shown below. (3) (4) Thermal gravimetric analysis (TGA) curve of the MgO-TA precursor shows two pronounced weight losses as shown in Figure 1b. The first weight loss occurs at 380°C to 410°C which is 40.4% corresponding to the removal of the two additional carbons within MgC4H4O6. This reaction started with the absorption of heat, but the decomposition is accompanied by the release of heat energy as can be observed by the endothermic and exothermic peaks at 400°C and 430°C respectively shown in the DSC curve. A mixture of MgC2O4 and MgO is believed to have been formed at this point. To confirm this, the MgO-TA precursor is 4EGI-1 mw heated at 400°C for 30 min and the obtained products examined by XRD. Figure 2 shows the XRD pattern of the material, and the phases MgC2O4 (ICDD reference number 00-026-1222) and MgO (ICDD reference number 01-0178-0430)
are confirmed to exist in the sample as indexed in the dataset shown. SRT2104 mouse This validates the proposed chemical reaction as can be seen in Equation 5. The second weight loss of 32.9% occurring
at a starting temperature of 410°C to 500°C accompanied by a broad endothermic peak approximately at 450°C can be ascribed to the decomposition of the intermediate product, MgC2O4 to MgO. These weight losses are in good agreement with the calculated values proposed in the chemical reactions (5) and (6). The whole reaction mechanisms are shown below. (5) (6) Figure 2 XRD patterns of the intermediate products. They are formed when MgC4H4O6 is annealed at 400°C for 30 min. For both MgO-OA and MgO-TA precursors, the TGs show a horizontal line after 500°C indicating that the MgO stable phase is formed at this temperature. These are confirmed by the XRD results shown in Figure 3. Methane monooxygenase The XRD patterns for both samples are indexed according to ICDD reference number 01-0178-0430 showing a MgO cubic crystal structure of space group Fm-3 m. All the fingerprint peaks (111), (200), (220), (311) and (222) are clearly observable. The samples are pure and single phase with no impurities present. Figure 3 XRD patterns of the MgO samples. They are prepared using (a) oxalic acid and (b) tartaric acid, as a complexing agent. Since the decomposition of the MgO-TA precursor starts at a lower temperature (380°C) compared to the MgO-OA precursor (420°C), the rate of MgO crystal growth will not be the same when identical thermal conditions are used on the precursors (950°C, 36 h).