Table 1. Summary of data derived from the thermal analysis of uncoated ACC in air.
| ~Wt% range | α | CaCO3: xH2O | Ea (kJ mol−1) |
Dehydration model |
||||
|---|---|---|---|---|---|---|---|---|
| Type | f(α)=kT | R2 | k (°C−1) | |||||
| 25–40 °C | 20 to 14 | 0.0–0.3 | ~1.4–0.98 | 80 | Second-order reaction | [1/(1−α)]−1 | 0.98 | 0.153* |
| 40–140 °C | 14 to 3 | 0.3–0.85 | ~0.98–0.25 | 140 | Contracting volume | 1−(1−α)1/3 | 0.92 | 0.0042 |
| 140–260 °C | 3 to 0.5 | 0.85–0.95 | ~0.25–0.08 | 245 | Second-order nucleation | α1/2 | 0.85 | 0.0031 |
| 25–260 °C | − | − | − | 125 | Contracting volume | 1−(1−α)1/3 | 0.92 | 0.0038 |
α is the degree of dehydration, Ea is the average activation energy associated with water loss for a given temperature range and CaCO3: xH2O shows the number of moles of water associated with 1 CaCO3 formula unit. The best-fit solid-state reaction models (f(α)=kT) are further given together with the associated coefficient of determination R2 and the rate constant, k.
*f(α)=k[min−1]t.