Effect of segregation on particle size stability and SPS sintering of Li2O-Doped magnesium aluminate spinel

Caliman, Lorena Batista; Muche, Dereck N.F.; Silva, A.; Machado, Izabel Fernanda; Castro, Ricardo H. R.; Gouvêa, Douglas

doi:10.1016/j.jeurceramsoc.2019.04.017

Cited by 12 publications

(17 citation statements)

References 47 publications

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“…Additionally, these cations had different valences, which could have affected the ion coordination and charge balance on the material surface. The amount of excess Li on the MgAl 2 O 4 surface was comparable to previously reported results, but the bulk solubility limit of Li 2 O on the MgAl 2 O 4 was overestimated …”

Section: Resultssupporting

confidence: 89%

“…The hardness is affected by the grain size, as indicated by the Hall–Petch relationship, which suggests that the hardness is inversely related to the square root of the grain diameter . In previous studies, MgAl 2 O 4 hardness values as high as 28.4 GPa were achieved when the grain size was on the nanoscale, in accordance with the Hall–Petch relationship . However, an inverse Hall–Petch relationship was also observed, characterized by a decrease in the hardness with a decrease in the grain size below the 30‐nm, with the mechanical properties following an inverse scaling law.…”

Section: Introductionsupporting

confidence: 54%

“…The low content of Cl in the doped samples, compared with the Li content, indicated that most of the Cl was lost during the synthesis. This is important, as it suggests that all modifications of the MgAl 2 O 4 nanostability were exclusively related to the Li 2 O …”

Section: Resultsmentioning

confidence: 99%

“…Recently, it has been shown that lithium oxide (Li 2 O) is a very interesting additive for producing MgAl 2 O 4 with a high density and translucency, and segregation was observed at the surface and GB interfaces . In another study, the additive reduced the surface and GB energies .…”

Section: Introductionmentioning

confidence: 99%

“…However, the separation of the kinetic and thermodynamic contributions is difficult with the addition of additives to the material, which are usually seen as physical barriers reducing the GB mobility and are mostly studied as kinetic phenomena. With the advancements of calorimetric techniques for the measurement of the interface energy of nanoparticles, it is possible to show that the surface energy does not remain constant with an increase in the doping content; thus, the nanostability is partially attributed to thermodynamic effects …”

Section: Introductionmentioning

confidence: 99%

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Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation

et al. 2019

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Manufacturing nanoceramics is challenging owing to the instability of the grain size resulting from the high driving force toward growth associated with the interfaces. Nanometric ceramics of some oxides have exceptional mechanical and optical properties, eg, magnesium aluminate spinel (MgAl 2 O 4 ). The production of these fully conformed ceramics requires a precursor powder, which generally contains sintering-promoting additives. Li salts are typically used as sintering promoters for MgAl 2 O 4 , but the interface stability associated with the segregation of the additive is poorly understood. In this study, MgAl 2 O 4 samples containing 0-2.86 mol% Li ions were synthesized via a simultaneous-precipitation method in an ethylic medium and subsequently calcined at 800°C in air. The nanopowders exhibited only the MgAl 2 O 4 phase, and the crystallite size was determined by the Li 2 O concentration. The crystallite size was changed via the chemical modification of the interfaces by the segregation of Li ions. The solubility in the bulk material was very low at the fabrication temperature, and small amounts of Li ions saturated the bulk material and segregated to the grain boundaries (GBs), significantly stabilizing the grain-grain interface compared with the surface. The resulting powder was then aggregated further owing to the initial stage of sintering. The surface excess obtained via the selective lixiviation method confirmed that the segregation to the GBs was greater than that to the surface. Energetics calculations confirmed these results, indicating a high enthalpy of segregation at the GBs (ΔH segr GB = −52.0 kJ∕mol) compared with that at the surfaces (ΔH segr s = −31.5 kJ/mol). The enthalpy of segregation together with theinterface excess allowed us to estimate the reduction in the interface energy with Li + segregation of 0.8% to the surface and 11.2% to the GBs. The Li + segregation to the surfaces started by Al 3+ substitution, and for powders with ≥1.8 mol% Li ions, Mg +2 was preferentially substituted at the surfaces.

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Section: Resultssupporting

confidence: 89%

Section: Introductionsupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation

et al. 2019

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Highly enhanced adsorption and photocatalytic performance of TiO2 quantum dots synthesized by microwaves for degradation of reactive red azo dye

et al. 2021

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Tribological and Mechanical Characteristics of Mg–Zn6.0–Y1.2–Zr0.2 alloy by SPS Technique: Natural and Agro-Waste Utilization

Vinod

Suresh²,

Reddy³

et al. 2022

J Bio Tribo Corros

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In India, urban solid waste generation has risen over the last decade. The aspect of waste generation is a large amount of waste materials among all solid waste types. While using ash particles eliminates waste, it also contributes desirable qualities. In this research work, the effects of Himalayan nettle leaf ash (HNLA) bean pod ash (BPA) with molybdenum trioxide (MoO3) on the ZWK611 (Mg-Zn6.0-Y1.2-Zr0.2) alloy is examined. The as-cast alloy exhibits an α-Mg matrix, and cubic γ-phases are formed in addition to MoO3 particles. In this work, an attempt was made to choose a ZWK611 alloy reinforced with HNLA and BPA by varying weight percentages (X = 4, 8, 12, and 15%) with a constant weight percentage of MoO3 (5%) fabricated using spark plasma sintering (SPS) technique. The mechanical and physical properties were tested for both as-cast alloy and magnesium hybrid composites. Surface morphology and XRD are analysed to identify material behaviour. The addition of 12%(HNLA-BPA)/5%(MoO3) hybrid composite exhibits high strength as compared to the as-cast alloy.

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Effect of segregation on particle size stability and SPS sintering of Li2O-Doped magnesium aluminate spinel

Cited by 12 publications

References 47 publications

Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation

Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation

Highly enhanced adsorption and photocatalytic performance of TiO2 quantum dots synthesized by microwaves for degradation of reactive red azo dye

Tribological and Mechanical Characteristics of Mg–Zn6.0–Y1.2–Zr0.2 alloy by SPS Technique: Natural and Agro-Waste Utilization

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Effect of segregation on particle size stability and SPS sintering of Li2O-Doped magnesium aluminate spinel

Cited by 12 publications

References 47 publications

Li2O‐doped MgAl2O4 nanopowders: Energetics of interface segregation

Li2O‐doped MgAl2O4 nanopowders: Energetics of interface segregation

Highly enhanced adsorption and photocatalytic performance of TiO2 quantum dots synthesized by microwaves for degradation of reactive red azo dye

Tribological and Mechanical Characteristics of Mg–Zn6.0–Y1.2–Zr0.2 alloy by SPS Technique: Natural and Agro-Waste Utilization

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Product

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Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation

Li₂O‐doped MgAl₂O₄ nanopowders: Energetics of interface segregation