Table 3. Quantitative Analysis of Calcium Silicate Thermal Insulation.
| sample/temperature (K) | phases (wt %)a | molar ratio [−] | formation mechanism of new phases |
|---|---|---|---|
| as-received | Ca6Si6O17(OH)2 (87.6), CaCO3 (12.4) | ||
| 1-1/1073 | CaCO3 (5.1), CaSiO3 (17.4), CsAlSiO4 (7.0), Ca2SiO4 (70.5) | CsAlSiO4/Ca2SiO4 = 0.07 | dehydration of xonotlite (eq 3) Ca6Si6O17(OH)2(s) = 6CaSiO3(s) + H2O(g) ΔrG° (900 K) = −188.67 kJ/mol |
| 1-2/1073 | CaCO3 (41.7), CaSiO3 (15.9), CsAlSiO4 (10.9), Ca2SiO4 (31.5) | CsAlSiO4/Ca2SiO4 = 0.24 | |
| 1-3/1073 | CaCO3 (12.7), CaSiO3 (16.2), CsAlSiO4 (9.3), Ca2SiO4 (61.8) | CsAlSiO4/Ca2SiO4 = 0.10 | reaction with CsOH (eq 4) 4CaSiO3(s) + Al2O3(s) + 2CsOH(g) = 2CsAlSiO4(s) + 2Ca2SiO4(s) + H2O(g)ΔrG° (973 – 1073 K) = – 254.38 – –228.75 kJ/mol |
| 2-1/973 | Ca6Si6O17(OH)2 (24.6), CaCO3 (23.1), CsAlSiO4 (12.6),Ca2SiO4 (39.7) | CsAlSiO4/Ca2SiO4 = 0.22 | |
| 2-2/973 | CaCO3 (26.6), CaSiO3 (19.8), CsAlSiO4 (12.9), Ca2SiO4 (40.7) | CsAlSiO4/Ca2SiO4 = 0.22 | reaction with CsOH (eq 5) 2CaSiO3(s) + 2CsOH(g) = Cs2SiO3 (s) + Ca2SiO4(s) + H2O(g) ΔrG° (973–1073 K) = −150.22 – –163.05 kJ/mol |
| 2-3/973 | Ca6Si6O17(OH)2 (12.9), CaCO3 (11.4), CaSiO3 (19.8), CsAlSiO4 (9.9), Ca2SiO4 (65.8) | CsAlSiO4/Ca2SiO4 = 0.10 | |
| 3-1/873 | Ca6Si6O17(OH)2 (13.3), CaCO3 (86.7) | – | reaction with CsOH (eq 6) Ca6Si6O17(OH)2(s) + 6CsOH(l) = 3Cs2SiO3(s) + 3Ca2SiO4(s) + 4H2O(g) ΔrG° (873 K) = −447.47 kJ/mol |
| 3-2/873 | Ca6Si6O17(OH)2 (13.0), CaCO3 (37.3), Ca2SiO4 (49.7) | – | |
| 3-3/873 | Ca6Si6O17(OH)2 (14.2), CaCO3 (85.8) | – |
a
The newly formed phases are shown in bold-typed texts