Phase transitions in mayenite

Шкерин, С. Н.; Tolkacheva, A. S.; Korzun, I. V.; Плаксин, С. В.; Вовкотруб, Э. Г.; Zabolotskaya, E. V.

doi:10.1007/s10973-016-5282-4

Cited by 10 publications

(5 citation statements)

References 29 publications

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“…From Figure , it can be seen that mayenite with excess oxygen (specifically δ > 1) strongly favors the O 2 -clathrate form because its redox energy is considerably lower than that of the O-clathrate mayenite at the same level of nonstoichiometry (as indicated in experiments) . In fact, incorporating O 2 species into O-clathrate mayenite is also associated with a relatively low energy cost.…”

Section: Resultsmentioning

confidence: 79%

“…From Figure 9, it can be seen that mayenite with excess oxygen (specifically δ > 1) strongly favors the O 2 -clathrate form because its redox energy is considerably lower than that of the O-clathrate mayenite at the same level of nonstoichiometry (as indicated in experiments). 56 In fact, incorporating O 2 species into O-clathrate mayenite is also associated with a relatively low energy cost. We performed simulations to evaluate the energy associated with incorporating O 2 species into stoichiometric O-clathrate mayenite (C12A7:1O 2− ) and partially reduced O-clathrate mayenite (C12A7:0.5O 2− ).…”

Section: Methodsmentioning

confidence: 99%

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Understanding Oxygen Nonstoichiometry in Mayenite: From Electride to Oxygen Radical Clathrate

et al. 2019

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Mayenite (Ca12Al14O32+δ) is a unique material that forms an electride stable at room conditions when reduced and shows oxygen storage capability when oxidized. The distinct redox behavior and properties of mayenite are known to originate from its clathrate structure that can host a range of oxygen species as well as anionic electrons. However, the oxygen nonstoichiometry in mayenite remains poorly understood. In this work, we establish, based on ab initio simulations, a systematic understanding of the oxygen nonstoichiometry in mayenite in relation to redox conditions and the speciation of the clathrated oxygen ions. It is found that the nonstoichiometric mayenite can be divided into three regions: (i) electride region (0 < δ < 1), wherein the energetically preferred clathrated species are O2– and anionic electrons, (ii) oxidized region (1 < δ < 4), wherein a mixture of O–, O2–, and O2 – ions can be clathrated in the nanocages, and (iii) strongly oxidized region (4 < δ < 12), wherein the O2-clathrate form is the most stable. The computed redox energetics suggests that the stability of the mayenite electride at room conditions is due to a kinetically limited oxidation process and achieving superstoichiometry is thermodynamically possible in conditions such as in air between 300 and 1000 K. On the basis of the simulation results, the Ellingham diagram for the mayenite electride is computed by considering the different anionic electron concentrations and the chemical potentials for various oxygen species are established to facilitate the development of mayenite as a versatile functional material.

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Section: Resultsmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Understanding Oxygen Nonstoichiometry in Mayenite: From Electride to Oxygen Radical Clathrate

et al. 2019

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“…As previously mentioned, this LDH phase decomposes around 600 ºC resulting in lime and mayenite [17]. The mayenite formed contains intrinsic nanoporosity and undergoes a phase transition at 650 ºC, which makes it even more reactive [20,22].…”

Section: Crushing Strength and Linear Shrinkage Versus Temperaturementioning

confidence: 88%

Section: Figurementioning

confidence: 99%

“…This feature classifies mayenite as an anti-zeolite phase. Recent studies pointed out that mayenite, besides releasing peroxide ions from 350 ºC to 650 ºC, reducing the number of filled cages, undergoes phase transition close to 650 ºC, giving rise to a phase in which the lattice parameter increases more rapidly with the temperature [20,22]. 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.…”

Section: Introductionmentioning

confidence: 99%

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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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Binary Calcia‐Alumina Thin Films: Synthesis and Properties and Applications

Ray

2021

Oxide Electronics

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Phase transitions in mayenite

Cited by 10 publications

References 29 publications

Understanding Oxygen Nonstoichiometry in Mayenite: From Electride to Oxygen Radical Clathrate

Understanding Oxygen Nonstoichiometry in Mayenite: From Electride to Oxygen Radical Clathrate

Al2O3–CaO macroporous ceramics containing hydrocalumite-like phases

Binary Calcia‐Alumina Thin Films: Synthesis and Properties and Applications

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