Effect of Alumina on Crystallization Behavior of Calcium Ferrite in Fe2O3-CaO-SiO2-Al2O3 System
Abstract
:1. Introduction
2. Experimental Procedures
2.1. Preparation of Samples
2.2. Sinter Process
2.3. Phase Determination
3. Results and Discussion
3.1. Effect of Al2O3
- (1)
- When Al2O3 was not added, Ca2+ reacted with Fe3+ and O2− to form C4F14 and CF, while Ca2+ reacted with Si4+ and O2− to form γ-C2S;
- (2)
- When Al2O3 reached 0.5 mass pct, C4F14 disappeared, and CF had gradually increased, indicating that the preferentially crystallized C4F14 reacted with Al3+ and Si4+ to form SFCA-I;
- (3)
- When Al2O3 reached 2.0 mass pct, CF and Fe2O3 had gradually decreased, γ-C2S had not changed significantly, and SFCA-I increased gradually. It shows that CF also participated in the generation of SFCA-I.
- (4)
- When Al2O3 reached 2.5 mass pct, the iron-rich SFCA-I was transformed into SFCA (high Si, high Al). Simultaneously, it promoted the precipitation of Fe2O3. Fe2O3 and CF increased, and Si4+ was mainly involved in generating SFCA, resulting in the decrease of γ-C2S.
- (5)
- When Al2O3 reached 3.0 mass pct, CF and SFCA continued to increase, while γ-C2S decreased and Fe2O3 disappeared.
3.2. The Sequence of Crystallization Phase
- (1)
- When Al2O3 was not added, the crystalline phase of quenched samples was Fe2O3 and C4F14 at 1350 °C, while Fe2O3 and C4F14 increased at 1300 °C, simultaneously CF appeared; Fe2O3 and C4F14 increased at 1280 °C, while Fe2O3 decreased. CF increased at 1250 °C, simultaneously SFC and γ-C2S appeared while Fe2O3 disappeared; CF increased at 1200 °C, and CF, SFC, and γ-C2S increased at 1150 °C. So it can be considered the crystallization sequence was (Fe2O3, C4F14) → CF → (SFC, γ-C2S).
- (2)
- When Al2O3 reached 1.5 mass pct, the crystalline phase of quenched samples was Fe2O3 and C4F14 at 1350 °C; SFCA-I appeared, simultaneously Fe2O3 increased at 1300 °C, but C4F14 disappeared; Fe2O3 and SFCA-I increased at 1280 °C; SFCA and CF appeared at 1250 °C, simultaneously Fe2O3 and SFCA-I decreased. At this time, SFCA was formed by the preferentially precipitated SFCA-I and Al3+ and Si4+ in the melt; CF and SFCA increased at 1200 °C, simultaneously γ-C2S appeared; CF, SFCA, and γ-C2S increased at 1150 °C. So it can be considered the crystallization sequence was (Fe2O3, C4F14) → SFCA-I → CF → SFCA → γ-C2S.
- (3)
- When Al2O3 reached 3.0 mass pct, the crystalline phase of quenched samples was Fe2O3 and SFCA-I at 1350 °C; SFCA-I increased while Fe2O3 decreased, simultaneously CF appeared at 1300 °C; Fe2O3 and SFCA-I decreased at 1280 °C while CF increased, simultaneously SFCA appeared; CF and SFCA increased at 1250 °C while SFCA-I decreased, simultaneously Fe2O3 disappeared; SFCA-I decreased at 1200 °C while CF and SFCA increased, simultaneously γ-C2S appeared; SFCA-I decreased at 1150 °C while CF, SFCA, and γ-C2S increased. So it can be considered the crystallization sequence was (Fe2O3, SFCA-I) → CF → SFCA → γ-C2S.
3.3. Effect of Cooling Rate on Crystallization
3.4. Discussion on Crystallization Mechanism
- η—solid-liquid mixing viscosity;
- η0—viscosity of pure liquid phase;
- c—a mass fraction of solid phase.
4. Conclusions
- (1)
- Al2O3 has an important effect on the composition of the crystal phase of the Fe2O3-CaO-SiO2-Al2O3 system. Adding alumina promoted the crystallization of Fe2O3, γ-C2S, SFCA-I, and SFCA, while it inhibited the crystallization of C4F14 and SFC. However, the content of CF first decreased and then increased. This is mainly because of the formation of complex calcium ferrite and the transformation of SFCA-I to SFCA.
- (2)
- The crystallization sequence in Fe2O3-CaO-SiO2-Al2O3 melt under different Al2O3 content was investigated, where the corresponding crystalline order is (Fe2O3, C4F14) → CF → (SFC, γ-C2S), (Fe2O3, C4F14) → SFCA-I → CF → SFCA → γ-C2S, and (Fe2O3, SFCA-I) → CF → SFCA → γ-C2S under the Al2O3 content of 0 mass pct, 1.5 mass pct, and 3.0 mass pct respectively. It can be concluded that the C4F14 reacts with Si4+ and Al3+ in the melt to form SFCA-I (C4F14 + Si4+ + Al3+ → SFCA-I), and then SFCA-I reacts with Si4+ and Al3+ to form SFCA (SFCA-I + Si4+ + Al3+ → SFCA).
- (3)
- As the cooling rate increase, C4F14, SFCA-I, Fe2O3, β-C2S, and the amorphous phases are increased while CF and SFCA are reduced, and the crystal transformation from β-C2S to γ-C2S can be effectively inhibited. However, when the cooling rate was increased from 15 °C/s to 65 °C/s, C4F14 was found to crystallize before Fe2O3.
- (4)
- The crystal size of complex calcium ferrite first increases and then decreases by an increase of Al2O3 content, and the order of crystal morphology evolved is from the strip, columnar to needle-shaped. When Al2O3 content reached or exceeded 2.5 mass pct, the viscosity of Fe2O3-CaO-SiO2-Al2O3 melt increased sharply, resulting in the decrease in the crystalline size of calcium ferrite.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Samples | Fe2O3 | CaO | SiO2 | Al2O3 | LT (°C) |
---|---|---|---|---|---|
No. 1 | 75.64 | 20.36 | 4 | 0 | 1261 |
No. 2 | 75.45 | 20.31 | 3.99 | 0.25 | 1259 |
No. 3 | 75.26 | 20.26 | 3.98 | 0.50 | 1257 |
No.4 | 75.07 | 20.21 | 3.97 | 0.75 | 1256 |
No.5 | 74.88 | 20.16 | 3.96 | 1.00 | 1254 |
No.6 | 74.51 | 20.05 | 3.94 | 1.50 | 1250 |
No.7 | 74.13 | 19.95 | 3.92 | 2.00 | 1256 |
No.8 | 73.75 | 19.85 | 3.90 | 2.50 | 1276 |
No.9 | 73.37 | 19.75 | 3.88 | 3.00 | 1293 |
Sample No. | Marked Points | Crystal Phase | Elements (at Pct) | ||||
---|---|---|---|---|---|---|---|
Fe | Ca | Si | Al | O | |||
0mass% | P1 | C4F14 | 46.20 | 13.54 | 1.79 | 0.74 | 37.72 |
P2 | CF | 39.38 | 21.93 | 1.38 | 0.94 | 36.37 | |
P3 | γ-C2S | 0.61 | 40.07 | 20.33 | 0.24 | 38.75 | |
P4 | Fe2O3 | 62.63 | 0.06 | 1.45 | 0.95 | 34.91 | |
1.0mass% | P2 | CF | 41.42 | 23.82 | 0.00 | 0.10 | 34.67 |
P3 | γ-C2S | 0.48 | 41.01 | 19.91 | 0.31 | 38.29 | |
P4 | Fe2O3 | 67.98 | 0.14 | 0.42 | 0.91 | 30.54 | |
P5 | SFCA-I | 47.64 | 14.79 | 2.42 | 2.15 | 33.01 | |
1.5mass% | P2 | CF | 38.51 | 22.76 | 0.31 | 0.29 | 38.12 |
P3 | γ-C2S | 0.86 | 37.95 | 17.98 | 0.26 | 42.96 | |
P4 | Fe2O3 | 64.33 | 0.27 | 0.00 | 0.72 | 34.67 | |
P5 | SFCA-I | 43.01 | 14.34 | 3.83 | 3.65 | 35.16 | |
2.0mass% | P2 | CF | 41.02 | 24.77 | 1.40 | 1.32 | 31.49 |
P3 | γ-C2S | 0.64 | 42.53 | 21.15 | 0.35 | 35.33 | |
P4 | Fe2O3 | 68.94 | 0.00 | 0.04 | 0.92 | 30.10 | |
P5 | SFCA-I | 47.06 | 14.56 | 3.20 | 3.20 | 31.98 | |
2.5mass% | P2 | CF | 39.31 | 24.09 | 0.01 | 0.28 | 36.31 |
P3 | γ-C2S | 0.35 | 39.08 | 19.78 | 0.16 | 40.63 | |
P4 | Fe2O3 | 62.79 | 0.28 | 0.00 | 0.84 | 36.09 | |
P6 | SFCA | 41.35 | 13.26 | 3.83 | 5.00 | 36.56 | |
3.0mass% | P2 | CF | 41.32 | 26.74 | 0.00 | 0.40 | 31.53 |
P3 | γ-C2S | 0.94 | 45.13 | 17.11 | 0.00 | 36.82 | |
P6 | SFCA | 42.86 | 13.37 | 4.17 | 7.19 | 32.41 |
Sample No. | Marked Points | Phase | Elements | ||||
---|---|---|---|---|---|---|---|
Fe | Ca | Si | Al | O | |||
0mass% | P1 | Fe2O3 | 68.63 | 0.49 | 1.36 | 0 | 28.94 |
P2 | C4F14 | 51.13 | 14.23 | 1.16 | 0 | 33.48 | |
P3 | Slag phase | 35.81 | 22.88 | 5.90 | 0 | 35.41 | |
1.5mass% | P1 | C4F14 | 47.25 | 12.37 | 0.00 | 1.08 | 39.30 |
P2 | SFCA-I | 44.04 | 12.68 | 1.08 | 2.20 | 39.99 | |
P3 | Slag phase | 44.52 | 15.88 | 2.71 | 2.55 | 34.34 | |
3.0mass% | P1 | Fe2O3 | 54.96 | 0.62 | 0.00 | 1.10 | 43.32 |
P2 | SFCA-I | 39.52 | 11.80 | 2.31 | 4.84 | 41.53 | |
P3 | Slag phase | 36.85 | 15.91 | 3.18 | 4.12 | 39.95 |
Cooling Rate (°C/s) | Al2O3 (Mass Pct) | ||||||
---|---|---|---|---|---|---|---|
0 | 0.5 | 1 | 1.5 | 2 | 2.5 | 3 | |
5 | CF | CF | CF | CF | CF | CF | CF |
C4F14 | SFCA-I | SFCA-I | SFCA-I | SFCA | SFCA | SFCA | |
Fe2O3 | Fe2O3 | ||||||
β-C2S | |||||||
15 | CF | CF | CF | CF | CF | CF | CF |
C4F14 | SFCA-I | SFCA-I | SFCA-I | SFCA-I | SFCA-I | SFCA-I | |
Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | |
β-C2S | β-C2S | β-C2S | |||||
65 | CF | CF | CF | CF | CF | ||
C4F14 | C4F14 | C4F14 | C4F14 | SFCA-I | SFCA-I | SFCA-I | |
Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | Fe2O3 | |||
β-C2S | β-C2S | β-C2S | β-C2S | β-C2S | β-C2S | β-C2S |
Al2O3 (Mass Pct) | Marked Points | Phase | Elements (at Pct) | ||||
---|---|---|---|---|---|---|---|
Fe | Ca | Si | Al | O | |||
0 | P1 | C4F14 | 52.06 | 12.37 | 0.79 | 0 | 34.78 |
P2 | CF | 40.74 | 19.59 | 3.96 | 0 | 35.72 | |
P3 | Slag phase | 37.10 | 20.93 | 6.93 | 0 | 35.04 | |
1.0 | P2 | CF | 40.49 | 21.60 | 4.95 | 1.77 | 31.20 |
P4 | SFCA-I | 48.28 | 14.24 | 2.09 | 0.92 | 34.48 | |
1.5 | P2 | CF | 42.16 | 19.75 | 4.89 | 2.06 | 31.14 |
P4 | SFCA-I | 49.19 | 14.77 | 2.94 | 2.77 | 30.33 | |
2.0 | P2 | CF | 43.43 | 26.11 | 0 | 0.69 | 29.77 |
P5 | SFCA | 47.35 | 14.22 | 3.40 | 4.42 | 30.62 | |
2.5 | P2 | CF | 39.39 | 21.58 | 4.51 | 3.94 | 30.58 |
P5 | SFCA | 43.77 | 12.73 | 4.28 | 6.27 | 32.95 | |
3.0 | P2 | CF | 39.39 | 21.58 | 4.51 | 3.94 | 30.58 |
P5 | SFCA | 40.10 | 13.17 | 4.26 | 6.25 | 36.22 |
Al2O3 Content (Mass Pct) | Primary Phase | Primary Crystallization Temperature (°C) |
---|---|---|
0 | M2O3 | 1261 |
0.5 | M2O3 | 1258 |
1.0 | M2O3 | 1253 |
1.5 | M2O3 | 1250 |
2.0 | α’-C2S | 1251 |
2.5 | α’-C2S | 1252 |
3.0 | α’-C2S | 1253 |
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Xin, R.-F.; Du, Y.; Guo, X.-M. Effect of Alumina on Crystallization Behavior of Calcium Ferrite in Fe2O3-CaO-SiO2-Al2O3 System. Materials 2022, 15, 5257. https://doi.org/10.3390/ma15155257
Xin R-F, Du Y, Guo X-M. Effect of Alumina on Crystallization Behavior of Calcium Ferrite in Fe2O3-CaO-SiO2-Al2O3 System. Materials. 2022; 15(15):5257. https://doi.org/10.3390/ma15155257
Chicago/Turabian StyleXin, Rui-Feng, Yu Du, and Xing-Min Guo. 2022. "Effect of Alumina on Crystallization Behavior of Calcium Ferrite in Fe2O3-CaO-SiO2-Al2O3 System" Materials 15, no. 15: 5257. https://doi.org/10.3390/ma15155257