MgAl2O4 Spinel Research Articles

Highly efficient semi-hydrogenation of acetylene over Ni supported mesoporous MgAl2O4 spinel derived from aluminate-intercalated layered double hydroxide

Even though Ni catalysts have shown promising performance in the semi-hydrogenation of ethylene, the selectivity and stability remain to be improved so that they may be used to replace expensive noble metal catalysts. Herein, an aluminate-intercalated NiMgAl-layered double hydroxide (LDH) was prepared through a facile co-precipitation approach, and then a topotactic transformation strategy was employed to convert the tailored LDH precursor to the spinel catalyst. More than 99% of the Ni/MgAl2O4 catalyst's conversion was achieved toward the semi-hydrogenation of acetylene at 140 °C, with a selectivity of more than 80%. Additionally, due to high specific surface area (309 m2/g) with tuned acidity, this catalyst showed outstanding resistance to the deposition of carbonaceous compounds and satisfactory long-term stability during a 28 hr test. It is hoped that this study will inspire the design of supported non-noble metal materials with high activity and efficiency towards organic or organo-thermal reactions, as well as provide a basic understanding of the role and impacts of intercalated aluminates in LDH.

Dissolution mechanism of magnesium aluminate spinel in copper smelting slag based on the shrinking core reaction models of corrosion

MgAl2O4 spinel is a critical raw material in spinel refractory production. However, the dissolution behavior of the spinel and its interactions with Cu smelting slag have not been previously studied in detail in terms of thermodynamics and kinetics. Therefore, to investigate the interactions of MgAl2O4 spinel in Cu smelting slag, MgAl2O4 spinel was simulated in Cu smelting slag using FactSage. Additionally, the dissolution mechanism of MgAl2O4 spinel in Cu smelting slag was studied via a slag immersion method. It was found that the Fe ions of the Cu smelting slag diffused mutually with the Mg2+ and Al3+ in the spinel, and the final products of the spinel reaction with the slag were ASpinel (Mg1-xFexAl2-yFeyO4) solid solution and liquid slag phases. The dissolution mechanism was consistent with the shrinking core reaction models. In the early stage of dissolution, ASpinel (Mg1-xFexAl2-yFeyO4) was generated at the interface, and the dissolution mechanism was controlled by the rate of solid solution phase generation, with an activation energy of E1 = 153.17 kJ/mol. At the later stage of dissolution, the Fe ions continued to diffuse into the spinel through the solid solution phase, while the spinel dissolved into the slag, and the dissolution mechanism was controlled by the rate of boundary migration of the solid solution phase, with an activation energy of E2 = 110.84 kJ/mol. Meanwhile, this interdiffusion behavior led to an increased liquid viscosity compared to that of the original slag that could further slow slag infiltration. The spinel could absorb Fe ions, rendering it a promising candidate for use in the Cu industry in the field of chromium-free refractories.

Crystallization and pyrolysis of nitric acid pressure leach liquor of limonitic laterite and separation of valuable metals

Based on the advantages of nitric acid pressure process (NAPL) for laterite nickel ores, this study innovatively proposes nitric acid pressure leach liquor crystallization pyrolysis-mixed metal oxides separation process. Firstly, the feasibility and the possible reactions of mixed nitrate pyrolysis were confirmed by thermodynamic analysis. Subsequently, the optimal pyrolysis temperature was experimentally investigated. Then, the pyrolysis process of combined nitrate was thermodynamically analyzed, and the phase composition of mixed metal oxides was determined by X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS). The Pourbaix diagram shows that using NaOH as leaching agent can selectively separate aluminum from mixed metal oxides, and the variables influencing aluminum's leaching rate are investigated. The experimental results are as follows: the optimal pyrolysis temperature of mixed nitrate crystals is 600 °C; the pyrolysis products are mainly oxides with the formation of NiAl2O4 and MgAl2O4 spinel phases; the aluminum leaching rate is 81.9% under the optimal alkali leaching conditions. The presence of spinel phase is not favorable for aluminum leaching. After leaching, an enriched residue of 15.8% Ni, 1.9% Co and 0.19% Sc was obtained.

Non-spherical plasmonic copper nanoparticles in a transparent MgAl2O4 ceramic matrix: Optical spectroscopy and conceptional models

Ion-beam synthesis of plasmonic copper nanoparticles in the surface layer of nanocrystalline ceramics MgAl2O4 spinel was performed. Stepwise annealing of modified ceramics was carried out with simultaneous analysis of optical absorption. It is established that ellipsoidal plasmon nanoparticles are synthesized during the ion-beam bombardment. The use of polarized light to analyze the optical characteristics of irradiated ceramics allowed us to establish that plasmon nanoparticles are drawn in the direction of the incident ion flux during implantation. A mathematical model of the formation of ellipsoidal plasmon nanoparticles was developed, due to the implementation of competing processes of ion diffusion and increased activity of chemical bonds on the curved surface of the nanoparticle.

A highly porous MgAl2O4 spinel-supported Mn3O4 as a reusable catalyst for glycolysis of postconsumer PET waste

A porous MgAl2O4 spinel-supported Mn3O4 catalyst, which is an efficient and robust catalyst for polyethylene terephthalate (PET) glycolysis, was synthesized from MgAl-layered double hydroxide (LDH) as a template via thermal and chemical treatment, followed by Mn oxide loading. A mesoporous structure in the MgAl2O4 spinel provided a high surface area (278 m2/g) and defects in which Mn3O4 was highly dispersed and strongly stabilized by the substitution of Al3+ and incorporation of Mn cation into the defects. The strong interaction of Mn oxide and the porous MgAl2O4 spinel support led to a dramatic increase of moderate acidic and basic properties, and to high resistance for Mn leaching during glycolysis. Using the Mn3O4/p-spMgAl800 catalyst, a yield of bis(2-hydroxyethyl) terephthalate > 95 % was achieved within 3 h at 190 °C. Despite eleven recycling times with regeneration, the catalytic activity remained without significant deactivation and was completely recovered after thermal regeneration at 500 °C.

A new method of obtaining potassium magnesium sulfate and magnesium aluminate spinel from synnyrite, a potassium-rich aluminosilicate raw material

This article is devoted to the study of deep processing of synnyrite, a potassium-rich aluminosilicate raw material of the Kalyumnoye deposit of the Synnyr alkalic rock massif (theRepublic of Buryatia, Russia) to produce valuable agricultural (potassium magnesium sulfate) and technical (magnesium aluminate spinel) products. The study demonstrated the promise of this method of processing synnyrite, based on thermochemical activation of the original ore with magnesite instead of limestone, followed by sulfuric acid leaching. This approach significantly reduces the cost of the thermochemical process and provides an additional useful product MgSO4·6H2O, which recuperates the initial magnesium additive and minimizes solid waste generation. This paper also presents a new method of processing alum KAl(SO4)2 obtained from synnyrite, based on sintering with potassium carbonate K2CO3 and brucite Mg(OH)2 (or magnesium oxide) to produce potassium magnesium sulfate K2Mg(SO4)2 and magnesium aluminate spinel MgAl2O4. The samples were characterized by DSC, chemical analysis, and XRD using the Rietveld method in TOPAS 4.2 software.

Improved microwave dielectric properties of MgAl2O4 spinel ceramics through (Li1/3Ti2/3)3+ doping

A series of nominal compositions MgAl2−x (Li1/3Ti2/3) x O4 (x = 0, 0.04, 0.08, 0.12, 0.16, and 0.20) ceramics were successfully prepared via the conventional solid-state reaction route. The phase compositions, microstructures, and microwave dielectric properties were investigated. The results of x-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that a single phase of MgAl2−x (Li1/3Ti2/3) x O4 ceramics with a spinel structure was obtained at x ≤ 0.12, whereas the second phase of MgTi2O5 appeared when x > 0.12. The cell parameters were obtained by XRD refinement. As the x values increased, the unit cell volume kept expanding. This phenomenon could be attributed to the partial substitution of (Li1/3Ti2/3)3+ for Al3+. Results showed that (Li1/3Ti2/3)3+ doping into MgAl2O4 spinel ceramics effectively reduced the sintering temperature and improved the quality factor (Q f) values. Good microwave dielectric properties were achieved for a sample at x = 0.20 sintering at 1500 °C in air for 4 h: dielectric constant ε r = 8.78, temperature coefficient of resonant frequency τ f = −85 ppm/°C, and Q f = 62 300 GHz. The Q f value of the x = 0.20 sample was about 2 times higher than that of pure MgAl2O4 ceramics (31600 GHz). Thus, MgAl2−x (Li1/3Ti2/3) x O4 ceramics with excellent microwave dielectric properties can be applied to 5G communications.

Photocatalytic activity under visible light illumination of organic dyes over g-C3N4/MgAl2O4 nanocomposite

Using a grinding method, nanocomposites of graphitic carbon nitride (g-C3N4) and magnesium aluminate (MgAl2O4) spinel were successfully synthesized for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Variously formulated g-C3N4/MgAl2O4 nanocomposites were characterized by thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and surface area and micropore analysis (BET surface area). The g-C3N4 powder exhibited a nanosheet structure whereas the MgAl2O4 spinel comprised agglomerated nanoparticles. The optical properties of the g-C3N4/MgAl2O4 nanocomposites were investigated by diffuse reflectance spectroscopy (DRS). As the g-C3N4 loading content increased from 0 to 30%, the optical band gap energy of the nanocomposite decreased from 3.84 to 2.86 eV, the specific surface area decreased from 153.78 to 114.45 m2/g, and the porosity decreased from 0.447 to 0.347 cm3/g. A 20%g-C3N4/MgAl2O4 nanocomposite proved to be the most effective photocatalyst and degraded MB faster and more completely than MO. The degradation rates of both MO (0.0107 min−1) and MB (0.0386 min−1) in a mixed MO-MB system were greater than the degradation rates in their single systems. The key factor that improved the photocatalytic degradation of MO was the synergistic effect whereas the synergistic effect and photosensitization were the key factors that enhanced the photocatalytic degradation of MB. The g-C3N4/MgAl2O4 nanocomposite is suitable for the photocatalytic degradation of mixed dyes because its point of zero charge is neutral and it is stable and recyclable.

Interfacial perpendicular magnetic anisotropy in Co2FeSi alloy films sandwiched by Pt and MgAl2O4

Co2FeSi (CFS) alloy film is one of promising ferromagnetic electrodes and MgAl2O4 (MAO) spinel is an attractive oxide barrier. In this work, we fabricate a series of Pt/CFS/MAO/Pt stacks using sputtering method. For the as-deposited stacks the easy axis lies in the in sample plane. After annealing at 350 °C perpendicular magnetic anisotropy is shown to build in the stacks with CFS thickness ranged from 3.5 to 5.5 nm. A high saturation magnetization of 908 emu/cm3, close to the bulk CFS, is achieved. The perpendicular magnetic anisotropy constant of 105 erg/cm3 in the order of magnitude is witnessed. A large interfacial perpendicular magnetic anisotropy of 1.32 ± 0.18 erg/cm2 is obtained in the annealed stacks. Positive contributions to the PMA from the Pt/CFS and CFS/MAO/Pt interfaces are experimentally confirmed. Significantly improved crystallinity of Pt layers and (111)-oriented CoPt alloy were revealed by X-ray diffractometry measurements on the annealed stacks, which may be additionally responsible for the PMA.

Restraining deactivation of β-zeolite by modifying with MgAl2O4 spinel in gas-phase glycerol dehydration

MgAl2O4 dispersed on HBEA zeolite with different spinel contents were successfully synthesized and their glycerol dehydration performances were presented. The different solids were characterized by XRD, infrared (IR) and Raman spectroscopy, N2 physisorption, SEM-FEG, acidity by TPD-NH3 and DRIFTS-pyridine adsorption. It was not possible to observe the spinel phase in the diffractograms due to its high dispersion, while the reflections of the HBEA were evidenced in the different samples. The Raman and infrared spectra suggested the presence of stretches concerning the MgAl2O4 spinel. N2 isotherms and low-angle XRD indicated that the pore structure and textural properties were altered after impregnation, but the micro-mesoporosity of zeolite was maintained. The HBEA morphology did not undergo significant changes by modification with spinel and the metals are evenly distributed according to SEM and EDS spectral mapping. The addition of spinel on zeolite caused a change in the acidic properties of HBEA related to the type, number and strength of the sites according to the TPD profiles and the DRIFTS spectra. The 2% of MgAl2O4 on HBEA catalyst exhibited the best catalytic performance due to the effects of its acidic and textural properties, reaching 60% of glycerol conversion, 66% of acrolein selectivity in 6 h and 16% of coke deposited in 10 h, restricting deactivation compared to pure zeolite. The reaction pathway for the different products formed depending on the type of acid site were detailed in the proposed mechanism and correlated with electrostatic potential maps as well as the reactions for coke formation were described according to compounds identified by GC-MS after coke extraction.

Precipitation and sintering behaviour of non-stoichiometric MgAl2O4 solid solution powder prepared by combustion synthesis

In this work, non-stoichiometric MgAl2O4 spinel solid solution powders with excess magnesia or alumina were synthesized by combustion synthesis, and their precipitation and sintering behaviour were investigated. The dissolution of MgO or Al2O3 in the lattice of spinel formed interstitial or vacancy solid solutions, respectively. During annealing, the powders with different solid solubility exhibited various precipitation and phase transition behaviour. After hot-press sintering with the as-prepared powders, there were many spheres with 100 nm evenly precipitated in the MgAl2O4 ceramic matrix, which improved mechanical performance. This work can not only provide comprehensive information about the precipitation of magnesia- and alumina-rich MgAl2O4 spinel solid solutions during annealing or sintering, but also offer an easy and convenient way for the industrial preparation of nanocomposite MgAl2O4 ceramics.

Influence of inversion level on the optical absorption spectra of Ti‐doped transparent MgGa2O4 ceramics

AbstractTi‐doped (0.08, 0.30, and 1.00 atomic% [at.%]) transparent MgGa2O4 ceramics (possessing a high inversion level; i up to 0.8) were fabricated by pulsed electric current sintering, at 950°C, under vacuum for 30–90 min. Optical transmission, emission, and electron paramagnetic resonance spectra were recorded. The maximal transmission level was ∼70% (820 nm), for a thickness of ∼1 mm, which, while not very high, permitted the observation of the optical absorption bands location and profile.Interpretation of the fluorescence spectra suggests that some Ti4+ cations (mostly hexacoordinated) were accommodated by the host despite the scarcity of oxygen in the atmosphere during the sintering process. The Ti3+ cations substitute native ions located in tetrahedral sites, distorting the original Td symmetry toward a D2d symmetry. Comparing the Ti‐doped MgGa2O4 (high inversion) and MgAl2O4 (low inversion) spinels, spectral characteristics revealed that a significant increase in the inversion level drives Ti3+ cations from octahedral toward tetrahedral sites. This is reflected in the optical absorption spectra by the disappearance of the band at ∼20 000 cm−1 (detectable in MgAl2O4) in MgGa2O4; the two d–d bands, of MgA2O4, in MgGa2O4 are reduced to a single one, located at 11 800 cm−1. These results, for MgGa2O4, strongly support a similar assignment—of the strong band at 12 800 cm−1, in Ti‐doped MgAl2O4—to a tetracoordinated Ti3+. Thus, while in MgAl2O4, Ti3+ appears in both octahedral and tetrahedral coordination and in MgGa2O4 only the latter state is stable. In both spinels, Ti dopant speciates into Ti3+ and Ti4+ cations.

Defect induced emission of MgAl2O4 sintered at high temperature

MgAl2O4 (MAO) spinel has been considered as one of the excellent optoelectronic material due to its excellent mechanical strength and transparency in visible region to IR region. Many studies reported that MAO has F centers generated due to high temperature sintering which resulted in visible emission. The aim of present study is to explore MAO sintered at high temperature for white light emission. MAO was synthesized by sol-gel method sintered at 1400°C high temperature for 4hrs. Prepared MAO was characterized by various characterization techniques; Fourier transfer infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) with the energy dispersive X-ray spectroscopy (EDX) and Fluorescence spectroscopy (FS). Peak at 674cm-1 in FTIR confirmed the formation of MAO. SEM Images showed the agglomeration of particles due to high temperature sintering Emission properties of MAO was studied by Florescence spectroscopy. MAO was excited by UV light. The emission spectra showed multicolor emission in visible region due to generation of F centers in the bandgap proving MAO as excellent material for white light emission.

Electrochemical Synthesis of Precursors of Al2O3-ZrO2 Ceramic Stabilized with Cerium Oxide and Magnesium Aluminate

This article presents a new approach to preparing the precursors of complex oxide systems Al2O3-ZrO2-MXOY (M = Mg, Ce). The approach is based on the electrogeneration and interaction of reagents with electrolyte components in a coaxial electrochemical reactor. The design of the electrolyzer provides the suspension homogenization due to the turbulence induced by the intensive hydrogen bubbles and electrolyte movement in opposite directions relative to the central electrode in a closed space. Hydrogen evolution leads to the mixing of the solution. The transfer of OH− ions generated at the cathode into the electrolyte and interaction with metal ions (Zr, Al, Ce, Mg) leads to the formation of hydroxoaqua complexes of these metals. They participate in the polycondensation reaction, forming polymerized hydroxides and oxyhydroxides, which are the basis of the primary particles. The process of hydroxylation of nanoparticle surface of the formed precursors of oxide systems stabilizes the dispersion and prevents particle aggregation. The stabilized tetragonal t-ZrO2 was obtained by sintering the precursor of the synthesized oxide system at 1100 °C with the formation of an alumina phase (γ-Al2O3, or an aluminum–magnesium spinel MgAl2O4) with a low CeO2 content (2–3 wt%).

Heterostructured lithium-rich layered oxides core@ spinel- MgAl2O4 shell as high-performance cathode for lithium-ion batteries

Lithium-rich layered oxides (LLO) with ultra-high specific capacity are one of the most promising cathodes for the next-generation lithium-ion batteries. However, the irreversible release of lattice oxygen will cause LLO surface reconstruction and electrolyte decomposition, resulting in low initial coulombic efficiency (ICE), high interface resistance as well as severe voltage and capacity degradation. Herein, a facile and effective strategy is proposed to stabilize the cathode materials by coating the LLO with spinel MgAl2O4. It is found that the robust MgAl2O4 (MAO) decoration layer can not only alleviate the lattice mismatch to sustain the structure integrity, but also inhibit the side reactions with electrolyte during long-term cycles. Furthermore, density functional theory calculations show that the surface oxygen release energy barrier is increased with the surface decoration of MAO. Accordingly, the coated LLO-based hetero-structured cathode exhibits a higher ICE (80.14%) and lower interface resistance than that of LLO electrode. Moreover, a reversible capacity of 176.6 mAh g−1 (with a capacity retention as high as 78.1%) and small voltage drop of 0.27 V are achieved even after 200 cycles at 1 C. This work sheds new light on the facile preparation and modification of lithium-rich layered oxides-related cathode for high-energy density lithium-ion batteries.

Erosion mechanism of tabular alumina of various microstructures under different basicity of blast furnace slag

In this study, three types of commercial tabular alumina aggregates with different microstructural characteristics were selected for corrosion tests on blast furnace slags with varying basicities. A corrosion mechanism with different microstructural characteristics is proposed, and the dominant microstructures in high- and low-basicity environments are evaluated. The pore structure was found to have a crucial influence on the dissolution of tabular alumina aggregates in the blast furnace slag. Under low-basicity (0.5–0.7) conditions, a small amount of clustered pore structure was beneficial for obtaining the maximum thickness (40–60 μm) of the isolation layer between the tabular alumina aggregate and slag. Under high-basicity (0.9–1.1) conditions, the circular pore structure tended to form a uniform and stable double-layer isolation structure of calcium hexaaluminate and MgAl2O4 spinel.

Corrosion resistance of modified YSZ coatings subjected to CMAS attacks

ABSTRACT The deterioration of thermal barrier coatings in reaction engines due to Ca–Mg-Al–Si (CMAS) attacks has been an important issue in recent years. Al2O3–20 wt-% TiO2 (AT) powder was mechanically doped into yttria-stabilized zirconia (YSZ). The corresponding coatings were fabricated using APS to modify the CMAS corrosion resistance. The corrosion-induced microstructure evolution and the composition development in the YSZ and AT-YSZ coatings were investigated. The AT-YSZ coating contained smaller voids and fewer cracks with a much more obvious laminated structure in contrast with the YSZ coatings. After CMAS attack, the YSZ coating flaked off, while the AT-YSZ coating was strongly bonded to the substrate. Phases from tetragonal (t’-ZrO2) to monoclinic (m-ZrO2) were detected, while the MgAl2O4 spinel and gehlenite Ca2Al2Si2O8 phases were formed after the CMAS corrosion. AT20 exists independently in the AT-YSZ coating, which readily causes Al2O3 to accumulate in the CMAS and effectively arrests its infiltration.

Oxygen fugacity buffering in high-pressure solid media assemblies from IW-6.5 to IW+4.5 and application to the VK-edge oxybarometer

AbstractControl of oxygen fugacity during high-temperature phase equilibrium experiments is required to simulate the conditions that exist in natural systems. At high pressures, oxygen fugacity may be imposed using solid buffer equilibria via the classic “double capsule” technique. This design becomes untenable, however, at temperatures above the melting points of commonly used noble metal capsule materials and/or where buffer assemblages may alloy with the capsule or contaminate the sample. Here we introduce and test a modified double capsule approach that includes a solid metal-oxide buffer in close proximity to but separate from the sample of interest. Buffers used include (in order of most oxidized to reduced) Ni-NiO, Co-CoO, W-WO3, Fe-FeO, Mo-MoO2, Cr-Cr2O3, V-V2O3, Ta-Ta2O5, and Nb-NbO. At a fixed temperature, these buffers span a wide range—up to 10 log fO2 units. To demonstrate the buffering capacity of this double capsule approach, secondary redox equilibria and V-doped CaO-MgO-Al2O3-SiO2 system glasses were studied in experiments using the double capsule geometry. The secondary equilibria provide an independent verification of the oxygen fugacity established in the double capsule environment. The glasses proved difficult to interpret, and our results provide guidance to future efforts to utilize the glass oxybarometer at reducing conditions. Application of this modified double capsule technique to studies of V valence in MgAl2O4 spinels led to the recognition of several factors that will affect V valence in this system: temperature of equilibration, duration of experiment, and spinel bulk composition. We have synthesized V-bearing MgAl2O4 spinel at the reduced conditions of the Cr-Cr2O3, (IW-3.51), Ta-Ta2O5, (IW-5.37), and Nb-NbO buffers (IW-5.44). This spinel exhibits a very small V3+ pre-edge peak consistent with its reduced nature. The absence of evidence for V2+ suggests that MgAl2O4 spinel excludes V2+ due to the preference of V for octahedral sites. This finding is supported by DFT calculations for spinels of variable composition, and in agreement with some other indirect evidence for preference for V3+ in aluminous spinels (Bosi et al. 2016; Paque et al. 2013).

INVESTIGATION OF THIN FILMS MGAL2O4, DEPOSITED ON THE SI SUBSTRATES BY VACUUM THERMAL EVAPORATION

The article presents data on the study of X-ray structural and microstructural characteristics of thin films of aluminum-magnesium spinel MgAl2O4 deposited on Si substrates by vacuum thermal evaporation. MgAl2O4 films have a polycrystalline rhombic structure. The values of the unit cell parameters of MgAl2O4 are calculated. Scanning electron and atomic force microscopy showed that MgAl2O4 films have a densely packed structure without cracks. Physical characteristics and good adhesion of MgAl2O4 thin films to silicon substrates indicate their possibility of using in devices of opto- and microelectronics.

Mechanical and optical properties of MgAl2O4 ceramics and ballistic efficiency of spinel based armour

This study was devoted to the understanding of the influence of MgAl2O4 ceramic properties on their ballistic performances. By modifying the processing parameters, ceramics with different microstructures were obtained. Among them, a transparent MgAl2O4 spinel with an in-line transmission between 77% and 83% in the visible range, an average grain size of 8.6 μm and good mechanical properties (11.3 GPa in Knoop hardness and 2.5 MPa√m in fracture toughness) was produced. A thorough characterisation of the ceramics was accomplished in order to establish a link between microstructure, mechanical properties and ballistic protective performances against an armour piercing projectile of calibre 7.62x51 mm. The ballistic evaluation demonstrated the advantage of using a spinel layer as the strike face to stop a threat, while reducing drastically the thickness and the areal density of the transparent multilayer, compared to a simple glass armour. MgAl2O4 spinel with fine grains presented a better combination of mechanical properties compared to coarser microstructures, hence a better potential to damage a projectile at the impact.