In situ investigation of MgO nanocube deformation at room temperature

Abstract

The mechanical behavior of h1 0 0i-oriented MgO nanocubes is investigated using in situ transmission electron microscopy (TEM) compression tests at room temperature and molecular dynamics simulations. Experiments show high strength and ductility, in addition to specific deformation mechanisms interpreted by the simulation. The nucleation and the propagation of 1/2h1 1 0i{1 1 0} dislocations are at the onset of the plastic deformation. The different deformation processes as well as the possible formation of a dislocation network during compression are discussed.

Deformation behavior of nanocrystalline titania particles accessed by complementary in situ electron microscopy techniques

“…However, for all these studies sample preparation artifacts due to focused ion beam (FIB) machining or conventional ion polishing cannot be ruled out: ions (typically Ar + or Ga + ) from the beam used for machining might influence the existing defect structures prior to compression and might thus influence the mechanical behavior. Issa et al 27 prepared 30-200 nm sized <100>-oriented single-crystalline MgO cubes by burning commercial Mg flakes in air. 10,[21][22][23][24] To avoid any structural changes during sample preparation and handling, well defined metal oxide particles from different synthesis routes can be used.…”

“…A perfectly elasticplastic deformation behavior could be identified for the smallest particles, impressively showing the ductility of small ceramic structures. Issa et al 27 prepared 30-200 nm sized <100>-oriented single-crystalline MgO cubes by burning commercial Mg flakes in air. In situ compression experiments in the TEM in conjunction with molecular dynamics (MD) simulations revealed the nucleation of full dislocations at the beginning of plastic yielding.…”

Dislocations and Plastic Deformation in MgO Crystals: A Review

“…However, in some cases, it is possible to produce pristine samples which allow the investigation of this rarely accessible regime [223][224][225]. Issa and colleagues [224] were able to obtain pristine MgO nanocubes from burning Mg chips in air, tested them in-situ in the TEM and compared these results with MD simulations [224,226] (Figure 27). In both simulations and experiments, the expected dislocations on the softer {110} planes are observed and nucleation occurs at the expected locations, i.e., the edges and corners of the cubes.…”

“…In contrast to other tests, the modeled nucleation stress is very high and a substantial curvature of the dislocation lines is observed (especially in the simulation). Thus, the dislocation microstructures observed at the nanoscale, under a compression stress in the GPa range, may therefore appear more similar those found at high temperatures [224]. In this section, we outline how various nano-mechanical methods in conjunction with electron and atomic force microscopy were used to unravel the dominant plastic deformation mechanisms in MgO.…”

Indentation strength of silicon nitride ceramics processed by spark plasma sintering technique

“…Because of the size of the indenter considered by the authors, R 500 nm berk ≃ , only ultra-fine-grained microstructures were tested. Other approaches based on TEM nanoindentation of ceramic nanoparticles [41] or nanocubes [42] and compression of micropillars [43] were also proposed. But in each case, a sophisticated in situ nanomechanical testing system is required and the derivation of behaviour laws at larger scale, relevant for macroscopic products, has not been addressed yet.…”