Sintering effect of calcium carbonate in high-alumina refractory castables

Luz, A.P.; Consoni, L.B.; Pagliosa, C.; Aneziris, Christos G.; Pandolfelli, V. C.

doi:10.1016/j.ceramint.2018.03.066

Cited by 29 publications

(22 citation statements)

References 19 publications

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“…Considering the phenomenon reported by Luz et al [10], the effect of Ca On the other hand, calcium carbonate, calcium hydroxide and calcium oxide were able to decrease this temperature closer to 700ºC, which are in accordance with the results presented by Consoni et al for dense alumina-based refractory systems [9].…”

Section: Figuresupporting

confidence: 91%

“…Distinct Ca 2+ sources can be used to produce CA6 in situ [6], such as calcined calcium oxide (CaO), calcium carbonate (CaCO3), calcium hydroxide [Ca(OH)2] and calcium aluminate cement (CAC). Besides promoting CA6 formation when heated up to 1400 ºC in the presence of Al 3+ sources, recent studies have shown that CaCO3 and Ca(OH)2 induced lower strengthening temperature in dense alumina-based refractories when compared to samples containing just CAC as Ca 2+ source [9,10], as can be seen in Figure 1.…”

Section: Introductionmentioning

confidence: 91%

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Macroporous high-temperature insulators physical properties by in situ CA6 formation: Does the calcium source matter?

Borges

Santos

Oliveira

et al. 2020

Journal of the European Ceramic Society

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Aiming the in situ formation of CA6 (CaO•6Al2O3) at alumina-based macroporous insulators, distinct Ca 2+ sources and contents were used and their effect on some of the refractories properties were investigated. Adding CaCO3, Ca(OH)2 or CaO resulted in the decrease of the strengthening onset temperature (TS) and also of the linear shrinkage. However, a higher amount of Ca(OH)2 and CaO could not be used because of their effect on reducing the insulator total porosity. The composition prepared with 12.9wt% of CaCO3 was the most promising one, leading to an expansion of 0.81% after firing at 1600ºC for 5h, TS of 680ºC and low thermal conductivity. These results point out the potential reduction of sintering temperatures and to the possibility of in situ firing the ceramic insulator. These features enable the development of a macroporous refractory composition with a higher thermal insulating effectiveness, which can help industries to decrease their energy demand.

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Section: Figuresupporting

confidence: 91%

Section: Introductionmentioning

confidence: 91%

Macroporous high-temperature insulators physical properties by in situ CA6 formation: Does the calcium source matter?

Borges

Santos

Oliveira

et al. 2020

Journal of the European Ceramic Society

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“…These data might induce the correlation between the effect reported by Luz et al [14] for dense refractories with those related to hydrocalumite-like phase formation at the interface among the ceramic particles, which results in CaO and C12A7 during thermal treatment. In addition, this hypothesis can predict that other Ca 2+ sources will also be able to generate such an effect, anticipating the onset strengthening temperature, as long as they form hydrocalumite-like phases during the processing.…”

Section: Figurementioning

confidence: 52%

“…These results are in agreement with those obtained by DRIFT and suggest that hydrocalumitelike phases could be formed during the processing of macroporous alumina-based refractories containing CaCO3, Ca(OH)2 or CaO as Ca 2+ sources and produced by direct foaming. to analyze the effect of CaCO3 on the initial E increase temperature, as previously reported by Luz et al [14] for dense refractory castables. The results can be seen in Figure 4.…”

Section: Figurementioning

confidence: 97%

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Al2O3–CaO macroporous ceramics containing hydrocalumite-like phases

Borges

Santos

Salvini

et al. 2020

Ceramics International

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A mechanism to explain the lower onset strengthening temperature induced by CaCO3 in alumina-based macroporous ceramics is proposed, which relies on hydrocalumite-like phase formation during processing. Close to 600 °C, such phases are decomposed to lime and mayenite (12CaO·7Al2O3), where the latter, due to its intrinsic nanoporosity and high thermal reactivity, generates bonds between the ceramic particles at ~700ºC, resulting in microstructure strengthening. Based on this premise, the authors concluded that other Ca 2+ sources could act similarly. Indeed, compositions containing Ca(OH)2 or CaO showed the same effect on the onset strengthening temperature, which reinforces the proposed mechanism. The results attained indicated that macroporous insulators could be thermally treated at lower temperatures, just to acquire enough mechanical strength for installation, finishing in-situ their firing process. Besides that, lower sintering temperatures could be used to produce macroporous ceramics that would be applied in low thermal demand environments, e.g. aluminum industries.

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Effects of Heating Rate on the Thermal and Mechanical Properties of the Bauxite-Based Low-Cement Refractory Castables

Moghadam

Arab

2020

J. of Materi Eng and Perform

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Sintering effect of calcium carbonate in high-alumina refractory castables

Cited by 29 publications

References 19 publications

Macroporous high-temperature insulators physical properties by in situ CA6 formation: Does the calcium source matter?

Macroporous high-temperature insulators physical properties by in situ CA6 formation: Does the calcium source matter?

Al2O3–CaO macroporous ceramics containing hydrocalumite-like phases

Effects of Heating Rate on the Thermal and Mechanical Properties of the Bauxite-Based Low-Cement Refractory Castables

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