Characterisation of Nanocrystalline Magnesium Oxide by X‐Ray Absorption Spectroscopy

Savin, Shelley L. P.; Chadwick, Alan V.; O’Dell, Luke A.; Smith, Mark E.

doi:10.1002/cphc.200600750

Cited by 10 publications

(4 citation statements)

References 73 publications

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“…It should be stressed, however, that the average structure remains the rocksalt one. Similar behaviour has been reported for ball-milled MgO, which shares the same rocksalt structure [13]. Most likely, this disorder is linked to the appearance of point defects, such as vacancies, induced by the ball-milling procedure, which distort the local structure by inducing localized atomic relaxation while retaining the average rocksalt structure.…”

Section: Structural Characterizationsupporting

confidence: 76%

Exchange bias and interface structure in the Ni/NiO nanogranular system

Bianco

Boscherini

Tamisari

et al. 2008

J. Phys. D: Appl. Phys.

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The exchange bias (EB) effect has been studied in Ni/NiO nanogranular samples obtained by annealing in H2, at different temperatures (200 ⩽ Tann ⩽ 300 °C), NiO powder previously ball-milled for 20 h. Typically, the samples consist of Ni nanoparticles (mean size of 10–18 nm) embedded in a nanocrystalline NiO matrix. With increasing Tann, the Ni fraction varies from 4% up to 69%. The exchange field depends on the Ni amount, being maximum (∼600 Oe), at T = 5 K, in the sample with 15% Ni. In all the samples, the EB effect vanishes at T = 200 K. The structural features of the samples have been investigated by x-ray diffraction, electron microscopy and extended x-ray absorption fine structure and the low-temperature magneto-thermal behaviour has been thoroughly analyzed. The results show the existence of a structurally and magnetically disordered NiO component, which plays the key role in the EB mechanism.

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Section: Structural Characterizationsupporting

confidence: 76%

Exchange bias and interface structure in the Ni/NiO nanogranular system

Bianco

Boscherini

Tamisari

et al. 2008

J. Phys. D: Appl. Phys.

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show abstract

“…A similar behavior has been reported for ball-milled MgO, which shares the same rocksalt structure. 23 Most likely, this disorder is linked to the appearance of point defects, such as vacancies, induced by the ball-milling procedure, which distort the local structure by inducing localized atomic relaxation while retaining the average rocksalt structure. In the hydrogenated samples, this disorder persists.…”

Section: Extend X-ray Absorption Fine Structurementioning

confidence: 99%

Exchange bias and structural disorder in the nanogranularNi∕NiOsystem produced by ball milling and hydrogen reduction

et al. 2008

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The exchange bias effect has been studied in Ni/ NiO nanogranular samples prepared by mechanical milling and partial hydrogen reduction of NiO; the Ni weight fraction varied between 4% and 69%. In this procedure, coarse-grained NiO powder has been ball milled in air for 20 h and subsequently subjected to annealing in H 2 ͑at a temperature ranging between 200 and 300°C͒ to induce the formation of metallic Ni. The structural properties of the samples have been studied by x-ray diffraction, electron microscopy, and extended x-ray absorption fine structure. The magnetic properties have been extensively investigated by carrying out hysteresis loops and magnetization measurements in the 5 -300 K temperature range, in zero-field-cooling and fieldcooling conditions. The results indicate that both in the as-milled NiO powder and in the hydrogenated samples, the NiO phase is composed of nanocrystallites ͑having a mean size of ϳ20 nm, structurally and magnetically ordered͒ and of highly disordered regions. The samples with low Ni content ͑up to 15%͒ can be modeled as a collection of Ni nanoparticles ͑mean size of ϳ10 nm͒ dispersed in the NiO phase; with increasing Ni content, the Ni nanoparticles slightly increase in size and tend to arrange in agglomerates. In the Ni/ NiO samples, the exchange field depends on the Ni amount, being maximum ͑ϳ600 Oe͒, at T = 5 K, in the sample with 15% Ni. However, exchange bias is observed also in the as-milled NiO powder, despite the absence of metallic Ni. In all the samples, the exchange bias effect vanishes at ϳ200 K. We propose a mechanism for the phenomenon based on the key role of the disordered NiO component, showing a glassy magnetic character. The exchange bias effect is originated by the exchange interaction between the Ni ferromagnetic moments and the spins of the disordered NiO component ͑in the as-milled NiO powder, the existence of ferromagnetic moments has been connected to chemical inhomogeneities of the NiO phase͒. The thermal dependence of the exchange bias effect reflects the variation of the anisotropy of the NiO disordered component with temperature.

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“…31 In addition, the micro-nanosizing of MH requires resynthesis or grinding. [32][33][34] The mechanochemical method is a green, efficient, solvent-free synthesis method. [35][36][37] Qin et al 38 used oleic acid (OA) to modify magnesium silicate hydroxide (MSH) by mechanochemical methods.…”

Section: Introductionmentioning

confidence: 99%

“…However, due to the inherent nature of solution processing, there are some disadvantages such as the long processing time, complex process and solvent waste 31 . In addition, the micro‐nanosizing of MH requires resynthesis or grinding 32–34 …”

Section: Introductionmentioning

confidence: 99%

Study of the effect of different functionalized magnesium hydroxide prepared by mechanochemical method on the flame retardancy and mechanical properties of styrene‐ethylene‐butadiene‐styrene/polypropylene composites

Wang

Chu

et al. 2022

J of Applied Polymer Sci

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Solvent‐free synthetic methods have received more attention because of their reducing chemical waste and simplifying the process. A series of functionalized magnesium hydroxides (FMHs) were successfully modified with siloxanes containing different functional groups (Octyl: OTES, Octadecyl: OTMS, Phenyl: PTMS, Vinyl: VTEO, and 3‐Aminopropyl: APS) via a solvent‐free mechanochemical method. Ball milling conditions (such as reaction time, siloxane/MH ratio), the morphology, surface properties and particle size of the FMHs were investigated in detail and the results showed that both of the adjustment of particle size and the modification of surface of MH were successfully achieved at one time within 20 min. All FMHs were successfully converted from hydrophilic to hydrophobic except for the sample modified by the silane containing APS group. The influence of the different functional groups and particle size of FMHs on the mechanical properties and flame retardancy of styrene‐ethylene‐butadiene‐styrene (SEBS)/polypropylene (PP) composites were discussed. Compared with original MH/SEBS/PP, the FMHs/SEBS/PP composites have better tensile strength and elongation at break. When 68 wt% of FMHs were added to the SEBS/PP matrix, the composites can pass V‐0 rating of UL‐94 testing, and their limiting oxygen index values are above 32.3%. Meanwhile, the composites also exhibited strong smoke suppression.

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Characterisation of Nanocrystalline Magnesium Oxide by X‐Ray Absorption Spectroscopy

Cited by 10 publications

References 73 publications

Exchange bias and interface structure in the Ni/NiO nanogranular system

Exchange bias and interface structure in the Ni/NiO nanogranular system

Exchange bias and structural disorder in the nanogranularNi∕NiOsystem produced by ball milling and hydrogen reduction

Study of the effect of different functionalized magnesium hydroxide prepared by mechanochemical method on the flame retardancy and mechanical properties of styrene‐ethylene‐butadiene‐styrene/polypropylene composites

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