Characteristics, Thermodynamics, and Preparation of Nanocaged 12CaO·7Al₂O₃ and Its Derivatives

Abstract

Crystal structures, characteristics, and preparations of 12CaO·7Al2O3 family and CaO–Al2O3 (C–A) system have been reviewed in detail with relevant thermodynamic parameters being assessed or recalculated. 12CaO·7Al2O3 (shortened as C12A7) can form several derivatives of type C12A7:Mn− or C12A7–Mn− through replacing so‐called “free oxygen ion” by many anions including OH−, H−, O−, O2−, F−, Cl−, and e− in their cages, or being adopted by rare earth metals or alkaline earth metal oxides at cation sites (Ca2+ or Al3+). These doped C12A7 derivatives show unique material properties of transparent conduction, catalysis, and antibacterial with potential applications in fast ion conductors, optoelectronics, oxidants, and catalysts etc.

In-Situ Kinetic Investigation of Calcium Aluminate Formation

“…Furthermore, the literature thoroughly establishes that the C12A7 structure is thermodynamically unfavored in non-humid atmospheres (e.g., dry or vacuum conditions) at elevated temperatures (>1050 • C). This includes both thermodynamically-calculated phase diagrams and experimental results [2,4]. The kinetic characterization for dry (~150 ppm H 2 O) and vacuum atmospheres reported herein supports the instability of C12A7 under non-humid atmospheres but details a formation pathway contrary to that reported in thermodynamic studies.…”

“…The high interconnectivity of the cages in the clathrate structure leads to high occluded anion mobility. The functionality of the structure is derived from the mobility and diversity of occluded chemical species leading to a wide range of applications [1,2]. The C12A7 structure, occluded anion speciation, lattice parameter, and kinetic formation are all heavily correlated to processing conditions [3][4][5].…”

Preparation of calcium aluminate cement by combustion synthesis and application for corundum‐based castables

“…Calcium peroxide powder (CaO 2 : particle size<25 μm, the purity was 88.08%, its XRD pattern as shown in Figure ), aluminum (Al: particle size<25 μm, purity>99.0%) and alumina powder (Al 2 O 3 : particle size<74 μm, purity>99.9%) were used as raw materials for combustion synthesis of calcium aluminate. The CaO 2 /Al molar ratio remained constant, while the amount of Al 2 O 3 was changed to adjust the C/A molar ratio, which located in the phase diagram of CaO‐Al 2 O 3 was shown in Figure . The considered reaction equations in this study can be expressed by Eq.…”

Structure Property Relationships and Cationic Doping in [Ca24Al28O64]4+ Framework: A Review

“…C12A7 research has prompted reviews spanning thermodynamics and synthesis [42], single crystal and thin film growth and the associated electrical properties [2,43], structural disorder and compositional analogs based on the mineral mayenite supergroup [44], and applications in display devices [45]. The goal of this review is to consolidate the structure-physical property relationships, illuminate discrepancies due to the complicated nature of the compound, suggest areas for future research, and investigate the effects of cation doping into the C12A7 clathrate cage framework.…”