Generation of Vacancies in MgO by Deformation

Klein, Mark J.; Gager, W.B.

doi:10.1063/1.1707984

Cited by 21 publications

(4 citation statements)

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“…The value of this charge depends on the different bonding energies of vacancies of negative and positive ions within a dislocation (Klein and Gager 1966;Tyapunina and Belozerova 1988). The value of this charge depends on the different bonding energies of vacancies of negative and positive ions within a dislocation (Klein and Gager 1966;Tyapunina and Belozerova 1988).…”

Section: Theory Of Shock Polarization Of Ionic Monocrystalsmentioning

confidence: 99%

Laboratory Study of Rock Deformation and Fracture

Сурков

Hayakawa

2014

Ultra and Extremely Low Frequency Electromagnetic Fields

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Our primary interest lies in the physics of electromagnetic phenomena associated with deformation and fracture of rocks. We start with a brief review of laboratory study of electromagnetic fields resulted from acoustic waves and shock polarization and magnetization effects in different materials. The vibration of charged dislocations and piezo-galvanic effect are considered to explain this effect in metals whereas the production and mobility of point and linear defects of atomic lattice is treated as a possible cause for the shock polarization effect in dielectrics. We discuss briefly a variety of electromagnetic phenomena caused by rock fracture. Among them are radiowave, optical and -radiation, and electron and ion emissions from fracturing rocks. We study the theories explaining the generation of strong electric fields in cracks and collapsing pores.Keywords Dislocation • Piezo-galvanic effect • Point defect • Rock fracture • Shock magnetization • Shock polarization Electromagnetic Effects Caused by Dynamic Deformation of a SolidIt is common knowledge that the dynamic deformation and fracture of solids are accompanied by a great variety of electromagnetic effects. The basic characteristics of these phenomena depend on the scales of fracture, intensity and duration of stress and strain, and a number of other factors. Such effects as generation of lowfrequency electromagnetic fields and radiowaves, emission of charged particles, light flashes, X -ray emission and micro-discharges inside of cracks have been observed in laboratory experiments (e.g., see Parrot 1995; Surkov 2000). It has been found experimentally that shock compression of different solids gives rise to a jump of electric potential at the shock front in all kinds of materials: metals, semiconductors, and dielectrics (e.g., Mineev and Ivanov 1976; Freund V. Surkov and M. Hayakawa, Ultra and Extremely Low Frequency Electromagnetic Fields, Springer Geophysics, DOI 10.1007/978-4-431-54367-1__9, © Springer Japan 2014 335 336 9 Laboratory Study of Rock Deformation and Fractureand Pilorz 2012). Effects of shock magnetization and demagnetization have been observed in magnetic materials. Fragments of fractured solid, as a rule, carry electric charges. The rock deformation and fracture can explain, in principle, some features of electromagnetic perturbations arising from large-scale tectonic processes such as EQs, volcanic eruptions and deeply buried high-yield detonations. In this section we first review laboratory studies and then examine these electromagnetic phenomena by analyzing the basic physical processes at microscopic level. Sometimes we will need to extend our research field to the frequency range of several MHz to gain a better insight into underlying mechanisms of these phenomena.

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Section: Theory Of Shock Polarization Of Ionic Monocrystalsmentioning

confidence: 99%

Laboratory Study of Rock Deformation and Fracture

Сурков

Hayakawa

2014

Ultra and Extremely Low Frequency Electromagnetic Fields

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“…For example, compression-induced plasticity in bulk MgO materials is related to the nucleation of dislocations, their movement, and intersections. 8 , 9 Enhanced deformation rates and dislocation densities in compressed bulk MgO samples seem to also promote ion vacancy formation 26 and triboemission of charge carriers. 27 Meanwhile, progress in experimental techniques has allowed for addressing plastic deformation and dislocation behavior of MgO at the nanoscale.…”

Section: Introductionmentioning

confidence: 99%

“…Theoretically predicted energies of optical absorptions due to corners, edges, and (100) faces , were found to be in excellent agreement with the experimental values and have even enabled us to isolate spectral contributions from buried interfaces. , Moreover, photoexcitation studies revealed key insights into the energetics of charge separation and subsequent electron and hole trapping at surface defects. − Structural deformation of MgO under loading is also relatively well-understood. For example, compression-induced plasticity in bulk MgO materials is related to the nucleation of dislocations, their movement, and intersections. , Enhanced deformation rates and dislocation densities in compressed bulk MgO samples seem to also promote ion vacancy formation and triboemission of charge carriers . Meanwhile, progress in experimental techniques has allowed for addressing plastic deformation and dislocation behavior of MgO at the nanoscale .…”

Section: Introductionmentioning

confidence: 99%

Rubbing Powders: Direct Spectroscopic Observation of Triboinduced Oxygen Radical Formation in MgO Nanocube Ensembles

et al. 2021

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Powder compaction-induced surface chemistry in metal oxide nanocrystal ensembles is important for very diverse fields such as triboelectrics, tribocatalysts, surface abrasion, and cold sintering of ceramics. Using a range of spectroscopic techniques, we show that MgO nanocube powder compaction with uniaxial pressures that can be achieved by gentle manual rubbing or pressing ( p ≥ 5 MPa) excites energetic electron–hole pairs and generates oxygen radicals at interfacial defect structures. While the identification of paramagnetic O – radicals and their adsorption complexes with O 2 point to the emergence of hole centers, triboemitted electrons become scavenged by molecular oxygen to convert into adsorbed superoxide anions O 2 – as measured by electron paramagnetic resonance (EPR). By means of complementary UV-photoexcitation experiments, we found that photon energies in the range between 3 and 6 eV produce essentially the same EPR spectroscopic fingerprints and optical absorption features. To provide insights into this effect, we performed density functional theory calculations to explore the energetics of charge separation involving the ionization of low-coordinated anions and surface-adsorbed O 2 – radicals at points of contact. For all selected configurations, charge transfer is not spontaneous but requires an additional driving force. We propose that a plausible mechanism for oxygen radical formation is the generation of significant surface potential differences at points of contact under loading as a result of the highly inhomogeneous elastic deformations coupled with the flexoelectric effect.

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“…Large numbers of vacancies have been observed in crystalline metals during plastic flow (Klein and Gager, 1966;Seitz, 1952Seitz, , 1950. It has been pointed out that the average temperature increase due to energy dissipation of dislocation motion is probably not sufficiently high to increase vacancy and interstitial concentrations as a result of thermal effects alone (Seitz, 1952).…”

Section: Introductionmentioning

confidence: 99%