Оксид железа кальция (CaFe2O4)

Identification

Calcium iron oxide (CaFe2O4) is a mixed oxide of calcium and iron, calcium ferrite. The chemical composition is described by the elements Ca, Fe, O. CAS number 12013-33-1, EC number 234-584-5. English name Calcium iron oxide (CaFe2O4). Synonyms: Ferrate (FeO21-), calcium; Calcium ferrate (CaFe2O4); Calcium ferrite (CaFe2O4); Calcium iron oxide (Ca0.5FeO2); CAS numbers of related forms 730961-48-5 and 160666-48-8 are also found.

Physico-chemical characteristics

• Molecular Weight: 215.7656
• Exact weight: 223.875
• EU number: 234-584-5
• PSA Features: 4
• XLogP3: 0.00000
• Density: 4.620 g/cm3

Substance class

Calcium ferrite CaFe2O4 belongs to mixed oxides of alkaline earth and transition metals with a structure similar to spinels and perovskite-like ferrites. Such compounds are formed in the CaO-Fe2O3 system and are intermediate phases during high-temperature sintering of iron-containing raw materials with lime.

Scope of application

• intermediate and target phase (ferrite C2F/CF/CF2) in the production of cement clinker - calcium aluminum ferrite and related ferrite phases act as a flux that reduces the temperature of formation of the liquid phase during clinker firing
• a component of high-iron sulfoaluminate and special cements that increase the resistance of concrete to chloride corrosion and improve frost resistance by compacting the pore structure
• object of research in metallurgy as a product of the interaction of slag-forming oxides of calcium and iron
• component of ceramic and magnetic materials based on calcium ferrites

Physical properties and firing behavior

At temperatures of 700-900 °C, calcium carbonate reacts endothermically with aluminum and iron oxides to form embryonic aluminate and ferrite; The ferrite phase acts as a flux, facilitating the formation of the liquid phase at a lower temperature and accelerating the binding of the clinker raw materials. The high density of the substance (4.620 g/cm3) reflects the dense packing of calcium and iron cations in the crystal lattice.

Storage and transportation

Store in a closed container in a dry place. Specific hazard codes and transport restrictions for this compound are not given in the sources; When working with powder, you should adhere to the general rules for handling finely dispersed inorganic oxides - use respiratory protection, avoid dust.

Place among calcium ferrites

In the CaO-Fe2O3 system, a number of ferrite phases of different compositions are known: C2F (2CaO Fe2O3), CF (CaO Fe2O3, corresponding to the formula CaFe2O4) and CF2 (CaO 2Fe2O3). All of them are formed at different stages of firing, depending on the local ratio of calcium and iron oxides in the raw material mixture, and in industrial Portland cement clinker, tetracalcium aluminum ferrite C4AF (4CaO Al2O3 Fe2O3) predominates - a solid solution of aluminate and ferrite phases, including the composition CaFe2O4 as one of the limiting members of the series.

Effect on cement properties

Ferritic phases, including C4AF, form ferrous gels and ferrous hydrates during cement hardening; These products compact the pore structure of cement stone, which increases frost resistance and reduces permeability to chloride ions. Sulfoaluminate cements with a high content of ferrite phase demonstrate better resistance to chloride corrosion compared to ordinary Portland cement.