Study of rapid grain boundary migration in a nanocrystalline Ni thin film

Solute stabilization of nanocrystalline tungsten against abnormal grain growth

“…5(c) revealed a uniform distribution of low-energy CSL boundaries in the unimodal grain structure, which is consistent with prior grain growth studies in nanocrystalline metals. 23,65 Surface energy and nonuniform grain boundary mobility effects thus likely complemented the allotropic phase transformation in driving initial microstructural evolution through abnormal grain growth and its transition to continuous, curvature-driven growth upon convergence to a unimodal nanocrystalline structure.…”

“…(1) and demonstrated that an enhanced grain boundary mobility is accompanied by a reduced activation energy for grain growth. 13,17,20 However, the onset of microstructural evolution in a range of nanocrystalline metals often transpires through an abnormal growth process, which has been observed in copper, 21,22 nickel, 21,23 iron, 24 palladium, 13 and cobalt 15 as well as a number of binary nanocrystalline alloys. [25][26][27] As the average grain size increases from the nanocrystalline to the ultrafine grain regime, abnormal grain growth widely succumbs to curvature-driven mechanisms, 28 thus underscoring the importance of stabilizing the nanostructure collectively against the initial and late stages of grain growth in nanocrystalline metals.…”

Thermal stability of consolidated metallic nanomaterials

“…At the same time, neither the existence of a large number of junctions nor the presence of residual porosity (the initial grain sizes were *5 nm, the porosity of the samples was 4%) or residual hydrogen (0.4 at.%), nitrogen (0.2 at.%) and oxygen (0.1 at.%) could prevent the abnormal growth, due to which the palladium nanostructure was transformed into a conventional microstructure with grain sizes of *10 mm within *2 months at room temperature. 56 The phenomenon of abnormal grain growth at room (or elevated) temperature was experimentally observed for many nanomaterials based on copper, 40, 58 nickel, 55,59,60 iron, 61, 62 hard alloys (WC ± Co) 63 and diamond 64 (see also references to earlier studies in monographs 1, 4 ), in particular, using transmission electron microscopy in situ. 40, 59 ± 61 It is noteworthy that the listed nanomaterials were synthesized using different methods such as pulsed electrodeposition, 55 pressing and sintering, 57, 63 severe plastic deformation (torsion at 4.5 GPa) at liquid nitrogen temperature, 58 pulsed laser deposition, 59, 60 intensive mechanical milling and mixing (mechanosynthesis), 40,61,62 sintering under high pressures (T = 1400 8C, P = 6.8 GPa).…”

Anomalous B diffusion profiles in nanocrystalline Si

“…Thus, the variation of the GB migration rate vs. B concentration can be interpreted as the decrease of GB migration rate when B concentration increases in GBs. GB motion is in fact complex and has been shown to be non-continuous at the nanoscale, consisting of a succession of rapid and long-range displacements between periods of time where it is immobile [26,27]. However, as mentioned earlier, the variation of v gb (i.e.…”