Spinel Crystals Research Articles

Preparation of MgCo2O4/graphite composites as cathode materials for magnesium-ion batteries

Magnesium-ion batteries are fabricated with MgCo2O4/graphite composites as the cathode material. MgCo2O4 nanoparticles are prepared using a co-precipitation method. A three-dimensional mixing process is utilized to mechanically decorate MgCo2O4 nanoparticles on graphite particles. The MgCo2O4 spinel crystals of size ranging from 20 to 70 nm on micrometer-sized graphite chunks are analyzed by using X-ray diffraction and scanning electron microscopy. The electrochemical properties of the as-prepared composites are well characterized by cyclic voltammetry, charge and discharge cycling, and electrochemical impedance spectroscopy (EIS). Surprisingly, the MgCo2O4/graphite composite with a relatively low proportion of MgCo2O4, compared with the other as-prepared composites, achieves the highest specific capacity of 180 mAh g−1 at a C rate of 0.05 C. EIS results suggest that the electrical conductivity of the composite material is an increasing function of the graphite proportion. The superior performance of the MgCo2O4/graphite composite could be ascribed to the decoration of nanosized MgCo2O4 particles as well as to the increased conductivity provided by graphite.

Luminescence characteristics of magnesium aluminate spinel crystals of different stoichiometry

Magnesium aluminate spinel single crystals with different stoichiometry, MgAl2O4 (1:1 spinel) and MgO 2.5Al2O3 (1:2.5) were investigated using different optical methods (cathode-, photo- and thermally stimulated luminescence (TSL), optical absorption, “creation spectra” of TSL peaks and phosphorescence by VUV radiation). Low-temperature charge carrier traps and the position of intrinsic UV emission bands depend on the degree of stoichiometry. Antisite defects (ADs), Mg2+ or Al3+ located in a “wrong” cation site (Mg|A1 or Al|Mg) are the main as-grown structural defects, which serve also as efficient traps for electrons and holes as well as seeds for bound excitons. AD concentration is especially high in 1:2.5 spinel. There are several manifestations of ADs (electronic excitations near ADs) in the spectral region of 7–7.5 eV, slightly below the energy gap.

Effect of Basicity on Precipitation of Spinel Crystals in a CaO-SiO2-MgO-Cr2O3-FeO System

Abstract The comprehensive utilization of stainless steel slag is one of major problems to be solved at “green steelworks”. Precipitation of spinel crystals can effectively detoxify residue. The effect of basicity defined by ω(CaO)/ ω(SiO2) ratio on precipitation of spinel crystals in a CaO-SiO2-MgO-Cr2O3-8 wt% FeO system has been determined with such tools as FactSage 7.1, SEM-EDS, IPP 6.0 and XRD. The FactSage 7.1 results showed that the rate of spinel phase enrichment with chromium was about 98% for the system basicity less than 1.4 and about 78% above this value. The precipitation of solid particles in solution appeared to be significantly influenced by basicity. With its increase the solid phase grew, the liquid one reduced, the particle diffusion was limited, and the growth of spinel crystals was inhibited. The spinel crystal size increased rapidly with decrease of basicity. When basicity increased from 0.6 up to 1.0, the crystal size decreased sharply from 12.30 μm down to 6.22 μm, and the reduction constituted as much as 49.43%. When basicity increased from 1.0 up to 2.2, the spinel crystal size moderately decreased from 6.22 μm down to 4.47 μm. Therefore, reduction of basicity is conducive to spinel crystal enrichment with chromium what appears to be a key factor to control basicity at detoxification of the chromium-containing steel slag.

Interfacial structures of spinel crystals with borosilicate nuclear waste glasses from molecular dynamics simulations

AbstractSpinel crystal formation presents a critical issue and glass formulation in nuclear waste glass processing. In this paper, the interfacial structures of the model borosilicate nuclear waste glasses, the international simple glass (ISG), with two types of spinel crystals, namely the MgAl2O4 and NiFe2O4, were studied using classical molecular dynamics simulations with effective partial charge potentials and recently developed composition‐dependent boron‐related parameters. The simulation results revealed the structural features of the borosilicate nuclear waste glasses and their interfaces with the two types of spinel crystals. It was found that there exist notable structural changes of glasses close to the interfacial region, affected by the adjacent crystal structures, terms of preferential segregation and ordering of cations, as well as ctaion coordination numbers. Specifically, the fraction of fourfold coordinated boron (B3) in glass near the interface decreases as compared to the bulk glass. In addition, the amount of fourfold coordinated Al decreases while fivefold Al increases in the glass region close to the glass‐crystal interface, which suggests indication of initial stage of crystal growth as Al adopts higher (sixfold) coordination like in the crystal as compared to majority of fourfold coordination in the glass. These interfacial structure changes obtained from MD simulations provide evidence of the influence of the precipitated crystals on the surrounding melt and glass and the initial stage of crystal growth.

Petrologic nature of the active subarc crust-mantle boundary: Mixed magmatic-metasomatic processes recorded in xenoliths from Sabtang island, Luzon arc

Some arc magmas reside in the uppermost mantle and the lower crust. Their deep-seated behavior determines the composition of magmas that erupt at the surface. Mafic-ultramafic xenoliths newly found in Sabtang island, Batanes group of islands of the Luzon arc record subarc processes. The xenolith suite is comprised mainly of dunites, orthopyroxenites, clinopyroxenites, hornblendites, and gabbros, all hosted in basaltic to andesitic lavas. Petrographic characteristics suggest the metasomatic formation of orthopyroxenites and hornblendites from dunites and clinopyroxenites, respectively. The apparently primary minerals are homogeneous in composition. Olivine is relatively magnesian (Fo82–90) and chromian spinel is rich in Cr# (=Cr/[Cr + Al], around 0.7) in dunites. Clinopyroxene is relatively magnesian (Mg# = Mg/[Mg + Fe2+] = 0.73–0.93) in clinopyroxenites and gabbros, and plagioclase is highly anorthitic (An89–98) in the gabbros. The primary mineral assemblage reflects crystallization of olivine and spinel followed by clinopyroxene all occurring in the uppermost mantle and lower crust of the Luzon arc. The orthopyroxenes and amphiboles were metasomatically produced at the expense of olivine and clinopyroxene, respectively. Clinopyroxene in the xenoliths is in equilibrium with the magmas that formed the Sabtang volcanics. They have relatively elevated contents of large-ion lithophile elements and light-rare-earth elements, which suggest derivation from an enriched mantle. The Sabtang xenoliths evidence the very active modification of the subarc mantle-crust boundary zone by mantle-derived magmas and slab-derived melts/fluids so that the mineral assemblage of the resultant rocks is similar to that of the predominant recent magma.

Raman study of Ming porcelain dark spots: Probing Mn‐rich spinels

AbstractWe report on the analysis of dendritic crystals present in the dark spot areas of blue‐and‐white Ming porcelains. Using Raman spectroscopy and scanning electron microscopy equipped with energy dispersive spectrometer, we were able to evidence Mn‐rich spinels. Small Mn‐based spinel crystals being highly sensitive to laser‐induced heating, we identified proper working conditions, avoiding excessive heating and damage. Local temperatures during Raman measurements were deduced from Stokes/anti‐Stokes intensity ratios. By analysing the behaviour of the A1g mode of Mn‐rich spinels, we were able to identify phases ranging from jacobsite‐like to hausmannite‐like compounds. Polarized Raman scattering was shown to provide a convenient means of discriminating between these two types of phases, as they display different symmetries. Inhomogeneities within the dendritic network, as evidenced by micro‐Raman measurements, highlight its gradual formation during the cooling phase of firing, depending of Fe3+ and Mn3+ availability. The presence of Mn‐based spinels is consistent with the use of a local Chinese Mn‐rich cobalt ore during the middle Ming Dynasty.

New compounds Mg3IV6V8 (IV=Si, Ge, Sn; V=P, As, Sb) and their potential application to photovoltaic materials

A new non-centrosymmetric Mg-based ternary compounds Mg3Si6As8 with bandgap of about 2.0 eV has been recently synthesized [Woo et al., Advanced Functional Materials, 2018, 28, 1801589], which indicates there exists a new class of Mg-based spinel crystals denoted as Mg3IV6V8 in the II-IV-V family. In this work, through substituting the IV and the V elements in Mg3IV6V8, more stable crystals in this new class are theoretically predicted. It is found that the bandgaps of these Mg3IV6V8 (IV=Si, Ge, Sn; V=P, As, Sb) compounds range from 2.5 eV to 0.88 eV, and each of these compounds shows good performance in photovoltaic (PV) efficiencies. Furthermore, multilayer tandem solar cells consisting of these compounds are proposed, and the PV efficiencies of these solar cells are predicted to reach 30%, exceeding that of silicon and Cu(In,Ge)Se2 (CIGS).

Образование высокоэнтропийных октаэдрических кристаллов в многокомпонентных оксидных системах

In the context of the project covering formation of high-entropy crystal phases with the magnetoplumbite structure the chemical composition, crystal structure, and formation conditions have been analyzed for multicomponent crystals with the spinel structure, obtained as by-products or experiment failures, including crystals with the composition not described in the literature previously. The list of chemical elements, which can be major components of phases with such structures, has been determined. Specifically, it has been found that the composition of the obtained spinel crystals can be expressed by the empirical formulas (Ni,Co,Mn 2+ )(Al,Cr,Fe,Ti,Ga,Mn 3+ ) 2 O 4 and (Co,Fe 2+ ,Mn 2+ )(Al,Cr,Ti,V,Ga,Fe 3+ ,Mn 3+ ) 2 O 4 . At that Ba, Sr, Ca, K, Pb, La, and Bi in such phases can exist in the form of minor admixtures; their addition in all probability does not affect stabilization of the spinel-structured phase. Solubility of indium, In, judging from the obtained data, in solid solutions of the described kind can be limited. Important conclusions of great practical significance have been made, concerning the conditions to be created in the process of crystal growing from high-entropy melts. In particular, it has been shown that allowance must be made for additional oxidation during growing a monocrystal from a melt, compared to the level that can be ensured from the composition of the melt and the air atmosphere, in which the experiments were carried out. It is related to the fact that increasing synthesis temperature (specifically, from 1400 to 1600 °С) leads to reduction of the greater part of iron and manganese atoms to oxidation number +2, which favors formation of octahedral phase in great quantities and has a negative impact on formation of crystals with the magnetoplumbite structure.

Non-isothermal crystallization behavior of spinel crystals in FeO-SiO2-TiO2-V2O3-Cr2O3 slag

The growth behaviour of spinel crystals in vanadium slag with high Cr2O3 content was investigated and clarified by statistical analyses based on the Crystal Size Distribution (CSD) theory. The results indicate that low cooling rate and Cr2O3 content benefit the growth of spinel crystals. The chromium spinel crystals firstly precipitated and then acted as the heterogeneous nuclei of vanadium and titanium spinel crystals. The growth mechanisms of the spinel crystals at the cooling rate of 5 K/min consist two regimes: firstly, nucleation control in the temperature range of 1873 to 1773 K, in which the shapes of CSD curves are asymptotic; secondly, surface and supply control within the temperature range of 1773 to 1473 K, in which the shapes of CSD curves are lognormal. The mean diameter of spinel crystals increases from 3.97 to 52.21 µm with the decrease of temperature from 1873 to 1473 K.

Formation and Evolution of Oxide Inclusions in Titanium-Stabilized 18Cr Stainless Steel

During Ti-stabilized stainless steelmaking process, oxide inclusions in steel generally cause the clogging of submerged entry nozzle and surface defects of cold-rolled products. Therefore, the evolution mechanism of oxide inclusions in Ti-stabilized 18Cr stainless steel was investigated by industrial experiments. The characteristics of inclusions in specimens were analyzed by scanning electron microscopy and energy dispersive spectroscopy. After Al deoxidation, the main inclusions were irregular MgO–Al2O3 spinel. After calcium treatment, MgO–Al2O3 inclusions were modified to be spherical multilayer CaO–MgO–Al2O3 inclusions consisting of spinel crystal embedded in CaO–Al2O3 liquid matrix. Thermodynamic calculation indicated that several ppm Ca could significantly expand the liquid oxides phase in Mg–Al–O phase diagram. After Ti addition, multilayer CaO–MgO–Al2O3–TiOx inclusions were formed. The compositions of steel were located close to Al2O3–TiOx liquid oxide phase, which would help to reduce oxide inclusions and increase titanium yield. Titanium addition has modified spinel inclusions to multilayer MgO–Al2O3–Ti3O5 inclusions containing solid spinel inner layer and MgO–Al2O3–Ti3O5 liquid oxide outer layer. As for improving the cleanliness of molten steel, the contents of magnesium, aluminum, and titanium could be considered simultaneously to liquefy oxide inclusions during Ti-stabilized stainless steelmaking process.

Micron-sized spinel crystals in high level waste glass compositions: Determination of crystal size and crystal fraction

The compositions utilized for immobilization of high-level nuclear wastes (HLW) are controlled using glass property models to avoid the deleterious effects of crystallization in the high-level waste (HLW) vitrification melters. The type and size of the crystals that precipitate during melter operations (typically at 1150 °C) and idling (∼1000 °C) are significantly impacted by glass composition and thermal history. This study was conducted to measure the impact of melt composition and heat treatment temperature on crystal size and fraction. A matrix of 31 multi-component glasses canvasing the expected Hanford HLW compositional space was developed and the glasses fabricated and heat treated at 850, 900, and 950 °C. The crystal amounts, as determined by X-ray diffraction, varied from 0.2 to 41.0 wt%. Spinel concentrations ranged from 0.0 to 13.8 wt%. One glass of the matrix did not precipitate spinel and contained 0.2 wt% RuO2, which was assumed to be undissolved from the melting process. All compositions contained crystals in the as-quenched glass. All of the spinel based crystals present in the glasses were less than 10 μm in diameter, as determined by scanning electron microscopy with image analysis. Composition and temperature dependent models were generated using the resulting data and the best model fit was obtained by only considering spinel concentrations (R2 = 0.87). Two glasses were unable to be characterized because of an inability to process the glass under the conditions of this study. Those glasses were utilized to give insight into a potential multi-component constraint to aid in future statistical composition designs.

Spinel assemblages in lunar meteorites Graves Nunataks 06157 and Dhofar 1528: Implications for impact melting and equilibration in the Moon's upper mantle

AbstractMagnesium‐rich spinel assemblages occur in the two lunar vitric breccia meteorites—Dhofar (Dho) 1528 and Graves Nunataks (GRA) 06157. Dho 1528 contains up to ~0.7 mm cumulate Mg‐rich spinel crystals associated with Mg‐rich olivine, Mg‐ and Al‐rich pyroxene, plagioclase, and rare cordierite. Using thermodynamic calculations of these mineral assemblages, we constrain equilibration depths and discuss an origin of these lithologies in the upper mantle of the Moon. In contrast, small, 10 to 20 μm spinel phenocryst assemblages in glassy melt rock clasts in Dho 1528 and GRA 06157 formed from the impact melting of Mg‐rich rocks. Some of these spinel phenocrysts match compositional constraints for spinel associated with “pink spinel anorthosites” inferred from remote sensing data. However, such spinel phenocrysts in meteorites and Apollo samples are typically associated with significant amounts of olivine ± pyroxene that exceed the compositional constraints for pink spinel anorthosites. We conclude that the remotely sensed “pink spinel anorthosites” have not been observed in the collections of lunar rocks. Moreover, we discuss impact‐excavation scenarios for the spinel‐bearing assemblages in Dhofar 1528 and compare the bulk rock composition of Dho 1528 to strikingly similar compositions of Luna 20 samples that contain ejecta from the Crisium impact basin.

Structural transformations and spectroscopic properties of Ni-doped magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2 for broadband near-IR light emission

Ni:MgAl2O4 spinel shows a reversible random Ni2+ site redistribution with increasing temperature. With the aim of determining the influence of the structure evolution induced by heat-treatment on the nature of luminescence centers in NiO-doped spinel-based magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2, the detailed spectroscopic study of the initial glass during its heat-treatments at increasing and decreasing temperatures has been performed and accompanied by an XRD analysis and Raman spectroscopy. The initial glass was X-ray amorphous. Its optical spectrum is mainly formed by absorption of [5]Ni2+ sites with a small amount of [4]Ni2+ ones. Crystals of the nucleating catalyst, ZrTiO4, about 4 nm in size, appear during heat-treatment at 800 °C, while the absorption spectrum of Ni2+ ions remains near unchanged. At 850 °C, spinel crystals with size of about 6 nm precipitate, which is accompanied by a broadband luminescence in the near-IR centered at 1330 nm with a bandwidth of 380 nm. At 950 °C, there is a slight reduction in intensity of absorption bands attributed to [6]Ni2+, which can be explained by a tendency toward random Ni2+ site redistribution with increasing temperature. A decrease in the amount of the [6]Ni2+ luminescent centers is not accompanied by a decrease in the luminescence intensity because of the increased size of spinel crystals. Additional low-temperature heat-treatment does not lead to a redistribution between [6]Ni2+ and [4]Ni2+ sites in spinel crystals in favor of [6]Ni2+ ones. An increase of the luminescence intensity after low-temperature heat-treatment is associated with additional spinel crystallization.

Thermal and Fluid Effects of Granitoid Intrusions on Granulite Complexes: Examples from the Southern Marginal Zone of the Limpopo Complex, South Africa

The paper summarizes data on the petrology of granitoid intrusions in the Southern Marginal Zone (SMZ) of the Neoarchean Limpopo granulite complex, South Africa, and discusses the thermal and fluid effects of these intrusions on the granulites. The intrusions were emplaced in SMZ at 2680–2640 Ma, when the granulite complex was overthrust on the rocks of the adjacent Kaapvaal Craton. The mineral assemblages of the granitoids reflect temperatures above 900°C for the magmas that crystallized under pressures of 6–9 kbar. The granitoid magmas assimilated host rocks and were thereby enriched in MgO, FeO, and Al2O3, which was favorable for the crystallization of garnet, spinel, sillimanite, and corundum in the granitoids. Fluid inclusions in the granitoids and estimates of the fluid composition based on mineral equilibria indicate that the CO2/H2O ratio of the fluids broadly varied. Along with H2O–CO2 fluid, the magmas carried H2O–salt fluids, which penetrated the host rocks and triggered various metasomatic reactions in them. The thermal effects of the intrusions on the host granulites resulted in the development of partial melting zones that host orthopyroxene with >7 wt % Al2O3. Depending on the fluid regime and temperature, the orthopyroxene is found in equilibrium with either garnet and potassic feldspar or with biotite. The ages of the partial melting zones are comparable with those of the intrusions.

Preparation and Electrical Characterization of Zn-Titanate / Borosilicate Glass Composites

A Composite materials from Zn-titanate/borosilicate glass of 10/0(ZT10), 9/1(ZT9), 7/3(ZT7) and 5/5(ZT5) ratios were prepared. Their XRD, SEM / EDX, electrical and dielectric properties were investigated. Willemite, rutile and Zn2TiO4 composite materials were developed through the sintering process. The incorporation of glass enhances the formation of willemite. The SEM micrographs show clear euhedral micro-size crystals of Zn2TiO4 spinel and willemite embedded in glassy groundmass. The EDX microanalysis shows the incorporation of Al- element into the structure of the formed phases. Both conductivity (σac) and dielectric constant ( $\upvarepsilon ^{\prime })$ , measured within frequency range 0.2 kHz -1 MHz, and temperature range 298- 573 (K). Glass-free sample showed the highest σac and $\upvarepsilon ^{\prime }$ . Although, 5/5 sample exhibited relative higher values than those with 9/1 and 7/3. The dielectric constant of 9/1 and 7/3 and 5/5 samples show almost an independent behavior over a wide range of temperatures which was attributed to the micro-sized grains of crystalline phases and restraining effect of rigid glassy matrix. The results of ac conductivity may indicate the dominance of electronic conduction over the ionic transfer one in the studied samples. Therefore they may present good candidates for semiconductor materials in electronic devices.

Architecture of nanoscale ferroelectric domains in GaMo4S8

Local-probe imaging of the ferroelectric domain structure and auxiliary bulk pyroelectric measurements were conducted at low temperatures with the aim to clarify the essential aspects of the orbitally driven phase transition in GaMo4S8, a lacunar spinel crystal that can be viewed as a spin-hole analogue of its GaV4S8 counterpart. We employed multiple scanning probe techniques combined with symmetry and mechanical compatibility analysis to uncover the hierarchical domain structures, developing on the 10-100 nm scale. The identified domain architecture involves a plethora of ferroelectric domain boundaries and junctions, including primary and secondary domain walls in both electrically neutral and charged configurations, and topological line defects transforming neutral secondary walls into two oppositely charged ones.

Color mechanisms in spinel: a multi-analytical investigation of natural crystals with a wide range of coloration

Twenty natural spinel single crystals displaying colors almost representative for the entire spinel variability were investigated by electron microprobe and UV–VIS–NIR–MIR and FTIR spectroscopies. Eight of them, selected among the Fe-bearing ones, were also analyzed by X-ray diffraction, and five by Mossbauer spectroscopy to obtain information on the oxidation state and site distribution of Fe. The adopted multi-analytical approach was successful in revealing that the color displayed by aluminate spinel crystals is due to a combination of two or more minor transition elements acting as chromophore, such as V3+, Cr3+, Fe2+, Fe3+, Mn2+ and Mn3+, variably distributed in the tetrahedrally and octahedrally coordinated sites of the spinel structure. Iron-poor orange, red and magenta spinel crystals owe their color mainly to the presence of V3+ and Cr3+ at the M sites (with predominance of V3+ for orange and of Cr3+ for red color). Iron-rich pink, blue and green spinel crystals, in spite of exhibiting very different colors, have relatively similar optical absorption spectra characterized by a strong UV-edge absorption and a series of weak absorption bands in the visible range. From pink to blue and green spinel samples, color differences depend on the increase of Fetot (primarily) and Fe3+ contents (secondarily), which are responsible for both the intensification of UV-edge absorption and the different intensity, width and position of the prominent absorption bands occurring in the range 18,000−15,000 cm−1. The scarcity in nature of yellow spinel is explained by the rarity of conditions necessary to obtain the yellow color, such as the exclusive presence of Mn acting as a chromophore or at least the absence of Fe2+, to avoid masking of the weak electronic transitions in Fe3+, Mn2+ and Mn3+.

Particle settling in a simulated melter discharge riser

Legacy tank waste from plutonium production at the Hanford site is planned for vitrification at the Waste Treatment and Immobilization Plant (WTP). The accumulation of spinel crystals in the melter, discharge throat and riser is a possible operational concern wherein clogging and/or subsequent failure of the high level waste (HLW) melter may occur. Experiments were conducted in a full-scale, room temperature test platform that is prototypic of the WTP HLW melter to characterize the particle settling in the riser. The experimental system consists of an acrylic discharge riser and throat attached to a feed tank that allows for visual observation of the particle behavior. Silicone oil and magnetite particles were used as simulants for the molten glass and spinel crystals. A set of equations for wall-corrected, cloud settling of particles at low particle concentration is presented that closely matches the experimentally determined settling rate.

Content and diffusion of water and gases in MgAl2O4 spinel crystals synthesized to produce ceramics

Content, evolution and diffusion characteristics of water and gases in fine-crystalline spinel MgAl2O4 were studied by kinetic thermodesoption mass spectrometry. Water is the main volatile component by quantity in the spinel structure. From the spinel crystals with an average size of 0.52 μm, water is released in vacuum in three temperature ranges: at 100–200 °C due to desorption from micropores, at 300–600 °C due to near-surface dehydroxylation and at 500–800 °C due to diffusion of water from the crystal bulk. The content of structural water, diffusively released from the crystals, is about 3000 ppm. The coefficients and activation energy of diffusion of water from spinel crystals in the range 500–700 °C were calculated. This allows us to estimate at any temperature the degassing time of the spinel with a certain degree of dispersion and ceramics made of it, and thereby promote the production of high-quality ceramics.

Post-mortem analysis of alumina-magnesia-carbon refractory bricks used in steelmaking ladles

Post-mortem studies in secondary steelmaking ladles are an important way to determine the factors related to Alumina-Magnesia-Carbon (AMC) refractory corrosion. AMC refractory bricks installed in the impact zone of a steelmaking ladle bottom were analyzed after 100 castings. X-ray diffraction, X-ray fluorescence chemical analysis, reflected optical light microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, density and porosity measurements, and mercury porosimetry were used to analyze the chemical and physical characteristics of the slag, the unused refractory and the slag+steel attacked bricks. The corrosion process produced a specific microstructure characterized by: i) a thick discontinuous slag layer composed by secondary spinel+steel+liquid; ii) a thick dense, cracked, and continuous layer consisting of calcium aluminates+steel+liquid at the slag/refractory interface; iii) next to this layer, a wide densified layer with a uniform microstructure in which corundum aggregates and spinel crystals were linked together by elongated CaAl12O19 crystals.The formation of these reaction layers constituted a barrier that effectively suppressed the massive slag penetration and surely reduced the wear rate. Thermodynamic calculations based on simplified and complex condensed phase equilibrium diagrams, were used to further understanding of the corrosion mechanism.