Atomic-scale features of phase boundaries in hot deformed Nd–Fe–Co–B–Ga magnets infiltrated with a Nd–Cu eutectic liquid

AbstractInterfacial defects like grain boundaries and phase boundaries play an important role in the mechanical behaviour of engineering alloys. In this work the problem of a crack on a bi-crystal interface is studied at the atomic scale, with the goal of elucidating the effects of varrying interatomic interaction on crack behaviour and to assess the suitability of existing fracture criteria to the anisotropic bi-crystal case. Calculations are performed using the Quasicontinuum (QC) method [1]. Using suitable approximations, some of the existing fracture criteria were used to predict ductile or brittle fracture and compared to the QC results.

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On the formation of anti-phase boundaries and interphase boundaries in Al3Zr precipitates of Al-Cu-Zr alloy studied at atomic scale

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.161442 ◽

2021 ◽

pp. 161442

Author(s):

Lipeng Ding ◽

Mingqi Zhao ◽

Zhihong Jia ◽

Yaoyao Weng ◽

Kaiyun Xiang ◽

...

Keyword(s):

Atomic Scale ◽

Phase Boundaries ◽

Interphase Boundaries ◽

Zr Alloy

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Atom probe as a tool for understanding mineral physics and rock deformation: a case study of deformed wehrlite

10.5194/egusphere-egu21-6581 ◽

2021 ◽

Author(s):

Joseph Cukjati ◽

Reid Cooper ◽

Stephen Parman ◽

Ningli Zhao ◽

Austin Akey ◽

...

Keyword(s):

Plate Tectonics ◽

Shear Zones ◽

Atom Probe ◽

Atomic Scale ◽

Resolving Power ◽

Diffusional Creep ◽

Rock Deformation ◽

Phase Boundaries ◽

Earth Planet ◽

Crystallographic Preferred Orientation

Here we report Atom Probe Tomography (APT) analyses of grain and phase boundaries of laboratory-deformed, fine-grained mixtures of clinopyroxene and olivine (Zhao, et al., 2019).&#160; The experiments show that the mixtures deform much more rapidly than either mineral endmember.&#160; This enhanced deformation in the two-phase material is due to stress-driven reactions at the phase boundaries. Lower effective viscosities of phase mixtures may be critical to the initiation of plate tectonics and the formation of mantle shear zones.The hypothesis presented here is that the &#8216;bulk rock&#8217; &#8211; a wehrlite &#8211; deforms rapidly because conversion of one phase to the other occurs at phase boundaries (e.g., Sundberg & Cooper, 2008).&#160; In this model, grain-scale transport of the shared (slowly-diffusing) mineralogical component Si4+ is not required.&#160; The near-boundary gradients of olivine-insoluble ions are presented as evidence of the phase transformation which either dissolves olivine into clinopyroxene or vice versa. &#160;The resolving power of the APT makes it a promising tool for investigating the microphysics of rock deformation, bridging the atomic scale all the way to the plate-tectonic scale.References: Sundberg M, Cooper RF (2008) Crystallographic preferred orientation produced by diffusional creep of harzburgite: effects of chemical interactions among phases during plastic flow. J Geophys Res Solid Earth 113(12):B12208. Zhao N, Hirth G, Cooper RF, Kruckenberg SC, Cukjati J (2019) Low viscosity of mantle rocks linked to phase boundary sliding. Earth Planet Sci Lett 517:83&#8211;94.

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Structure and migration of planar defects in crystals observed in atomic scale

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108568 ◽

1978 ◽

Vol 36 (1) ◽

pp. 284-285 ◽

Cited By ~ 1

Author(s):

H. Hashimoto ◽

Y. Sugimoto ◽

Y. Takai ◽

H. Endoh

Keyword(s):

Electron Microscope ◽

Rotation Angle ◽

Crystal Surface ◽

Electron Gun ◽

Atomic Scale ◽

Present Observation ◽

Twist Boundary ◽

Optical Magnification ◽

Zinc Crystal ◽

And Migration

As was demonstrated by the present authors that atomic structure of simple crystal can be photographed by the conventional 100 kV electron microscope adjusted at “aberration free focus (AFF)” condition. In order to operate the microscope at AFF condition effectively, highly stabilized electron beams with small energy spread and small beam divergence are necessary. In the present observation, a 120 kV electron microscope with LaB6 electron gun was used. The most of the images were taken with the direct electron optical magnification of 1.3 million times and then magnified photographically.1. Twist boundary of ZnSFig. 1 is the image of wurtzite single crystal with twist boundary grown on the surface of zinc crystal by the reaction of sulphur vapour of 1540 Torr at 500°C. Crystal surface is parallel to (00.1) plane and electron beam is incident along the axis normal to the crystal surface. In the twist boundary there is a dislocation net work between two perfect crystals with a certain rotation angle.

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Resolution in the scanning tunneling microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008674x ◽

1991 ◽

Vol 49 ◽

pp. 488-489

Author(s):

R. J. Wilson ◽

D. D. Chambliss ◽

S. Chiang ◽

V. M. Hallmark

Keyword(s):

Scanning Tunneling Microscope ◽

Fundamental Principle ◽

Atomic Scale ◽

Lateral Resolution ◽

Scanning Tunneling ◽

Electronic Noise ◽

Vertical Resolution ◽

Tunneling Microscopy ◽

Spatial Profile ◽

Theoretical Analyses

Scanning tunneling microscopy (STM) has been used for many atomic scale observations of metal and semiconductor surfaces. The fundamental principle of the microscope involves the tunneling of evanescent electrons through a 10Å gap between a sharp tip and a reasonably conductive sample at energies in the eV range. Lateral and vertical resolution are used to define the minimum detectable width and height of observed features. Theoretical analyses first discussed lateral resolution in idealized cases, and recent work includes more general considerations. In all cases it is concluded that lateral resolution in STM depends upon the spatial profile of electronic states of both the sample and tip at energies near the Fermi level. Vertical resolution is typically limited by mechanical and electronic noise.

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What catalysis needs from the electron microscopist

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105539 ◽

1988 ◽

Vol 46 ◽

pp. 694-695

Author(s):

Alexis T. Bell

Keyword(s):

Active Sites ◽

Heterogeneous Catalysts ◽

Catalyst Deactivation ◽

Surface Composition ◽

Internal Surface ◽

Active Phase ◽

Atomic Scale ◽

Metal Catalyst ◽

Internal Surface Area ◽

Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

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Growth of spinel into alumina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126317 ◽

1987 ◽

Vol 45 ◽

pp. 294-295

Author(s):

Y. Kouh Simpson ◽

C. B. Carter

Keyword(s):

Misfit Dislocations ◽

Phase Boundaries ◽

Large Rotation ◽

Alumina Phase ◽

Metallic Interfaces ◽

Small Rotation

The structure of spinel/alumina phase boundaries has recently been studied using the selected- area diffraction technique. It has been found that there exist several dominant topotactic relationships; of these, the two most common situations are when the {111} plane of spinel is parallel to either the (0001) plane or the {1120} plane of alumina. In both of these cases, it has been found that there is often a small rotation from exact topotaxy (typically 0° to 2° but with larger rotations possible) which partially eliminates the need for misfit dislocations. This rotation is a special phenomenon that may be unique to non-metallic interfaces such as phase boundaries in ceramics. In this report, a special spinel/alumina interface in which a large rotation from the exact topotaxy exists between the (111) plane of spinel and the (OOOl) plane of alumina is discussed.

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