# CO\({}_{2}\) Adsorption Reactions of Synthetic Calcium Aluminum Ferrite (CAF)
## 3 Result and Discussion
### Characteristics of Carbo Reaction of SCAF
#### 3.2.3 Image Analysis of SCAF  
Figure 7 shows the results of the SEM analysis according to the carbonation reaction time and sintering temperature. As a result of the analysis of SCAF compounds fired at sintering temperatures of 1000 \({}^{\circ}\)C and 1100 \({}^{\circ}\)C, (a) is the CAF compound in the powder state before hydration, and (b), (c), and (d) show the state of hydrates after reaction times of 1 h, 3 h, and 6 h of carbonation with the wet method. In the case of (a), the synthetic CAF compound in the powder state before hydration, a typical crystal state of CAF compound is observed in glassy form. However, in (b), the crystal after 1 h of hydration, a needle shape is observed, but also the crystals of calcium aluminate hydrate (C-A-H) and calcium aluminate-ferrite hydrate in a plate shape can be seen. In the case of (c), which is hydrate after 3 h of hydration with the transition to calcium carbo aluminate (CAC) compounds, calcium carbo ferrite (CFC) compounds, and CaCO\({}_{3}\) crystals, the hexahydrate is observed [13]. The same pattern can be seen in (d), the result after 6 h of hydration, and a large amount of CaCO\({}_{3}\) crystals can be observed.  
On the other hand, the results of SCAF fired at 1100 \({}^{\circ}\)C were similar to those of SCAF fired at 1000 \({}^{\circ}\)C. In the synthesis of SCAF, conditions of sintering temperature of 1000 \({}^{\circ}\)C or 1100 \({}^{\circ}\)C are considered to not be significant in the production of compounds.  
In the case of carbonation with the wet method, CAH and CAFH, the hydrates, were formed up to the reaction time of 1 h, but after 3 h of reaction time, carbo compounds, which are calcium carbo aluminate and calcium carbo alumino-ferrite compounds, were produced by carbonation.  
The calcium aluminate ferrite compound (4 CaO Al\({}_{2}\)O\({}_{3}\):Fe\({}_{2}\)O\({}_{3}\)-C\({}_{4}\)AF), one of the representative clinker minerals in the cement industry, is the interstitial phase and accounts for about 10% of cement composition. When Fe\({}_{2}\)O\({}_{3}\) is added to the CaO-Al\({}_{2}\)O\({}_{3}\) system to form the ternary system of CaO-Al\({}_{2}\)O\({}_{3}\)-Fe\({}_{2}\)O\({}_{3}\), C2F is first generated around the temperature of 800 \({}^{\circ}\)C, and Al\({}_{2}\)O\({}_{3}\) is combined at 1100 to 1200 \({}^{\circ}\)C to form C\({}_{4}\)AF. As such, the calcium aluminate ferrite compound is formed at a temperature lower than the cement sintering temperature of 1450 \({}^{\circ}\)C. If the SCAF compound, the synthetic product of this study, is synthesized at 1000 \({}^{\circ}\)C or 1100 \({}^{\circ}\)C and then used as partial replacement of the OPC clinker, an energy-saving effect can be expected because the material is fired at a temperature lower  
Figure 6: XRD patterns carbonation with wet method. (a) 1000 \({}^{\circ}\)C; (b) 1100 \({}^{\circ}\)C.  
than the cement sintering temperature by the amount of SCAF replacement. Furthermore, the SCAF compound with CO2 capture performance can be utilized to implement the effect of CO2 capture when used as an OPC clinker replacement.