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Structural transformation of layered double hydroxides: an in situ TEM analysis

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Author: Hobbs, C. · Jaskaniec, S. · McCarthy, E.K. · Downing, C. · Opelt, K. · Güth, K. · Shmeliov, A. · Mourad, M.C.D. · Mandel, K. · Nicolosi, V.
Type:article
Date:2018
Publisher: Nature Publishing Group
Source:npj 2D Materials and Applications, 1, 2
Identifier: 844186
doi: doi:10.1038/s41699-018-0048-4
Article number: 4
Keywords: Aluminum alloys · Binary alloys · Catalysts · Electron diffraction · Flame retardants · High resolution transmission electron microscopy · In situ processing · Nanostructured materials · Nickel oxide · Transmission electron microscopy · Energy filtered TEM · Future applications · Heterogeneous structures · High-resolution TEM · In situ transmission electron microscopy · Layered double hydroxides · Selected area electron diffraction · Structural transformation · Magnesium alloys

Abstract

A comprehensive nanoscale understanding of layered double hydroxide thermal evolution is critical for their current and future applications as catalysts, flame retardants and oxygen evolution performers. In this report, we applied in situ transmission electron microscopy to extensively characterise the thermal progressions of nickel-iron containing LDH nanomaterials. The combinative approach of TEM and selected area electron diffraction yielded both a morphological and crystallographic understanding of such processes. As the Ni-Fe LDH nanomaterials are heated in situ, an amorphization occurred at 250 °C, followed by a transition to a heterogeneous structure of NiO particles embedded throughout a NiFe2O4 matrix at 850 °C, confirmed by high-resolution TEM and scanning TEM. Further electron microscopy characterisation methodologies of energy-filtered TEM were utilised to directly observe these mechanistic behaviours in real time, showing an evolution and nucleation to an array of spherical NiO nanoparticles on the platelet surfaces. The versatility of this characterisation approach was verified by the analogous behaviours of Ni-Fe LDH materials heated ex situ as well as parallel in situ TEM and SAED comparisons to that of an akin magnesium-aluminium containing LDH structure. The in situ TEM work hereby discussed allows for a state-of-the-art understanding of the Ni-Fe material thermal evolution. This is an important first, which reveals pivotal information, especially when considering LDH applications as catalysts and flame retardants. © 2018, The Author.