Effect of Solid-Solution W Addition on the Nanostructure of Electrodeposited Ni

2002 ◽  
Vol 740 ◽  
Author(s):  
Hajime Iwasaki ◽  
Kenji Higashi ◽  
T. G. Nieh
Keyword(s):  
Solid Solution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Nanocrystalline Structure ◽  
Grain Morphology ◽  
Atomic Layer ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Boundary Structure ◽  
Grain Boundary Structure

ABSTRACTElectrodeposition method was employed to produce freestanding Ni-W alloy foils. The foils consist of nanograins. The structure of the foil, e.g. texture, grain morphology, size distribution, and the nature of grain boundaries, were characterized using X-ray diffraction and high-resolution electron microscopy. The deposited foils exhibit an equiaxed nanocrystalline structure having a grain size value of about 6 nm. Two types of grain boundary structure were observed. One type of grain boundary is essentially one atomic layer thin and another type consists of a structureless layer of about 0.5–1 nm in thickness. Angular dark field (Z-contrast) image of the deposited foils showed an inhomogeneous distribution of W solutes. In some local regions, the W content actually exceeds the equilibrium solid solution limit. Many grain boundaries with a structureless layer of about 0.5–1 nm are probably a result of local supersaturation of W.

Grain Boundary Structure and Sliding of Alumina Bicrystals

1999 ◽  
Vol 601 ◽  
Author(s):  
Y. Ikuhara ◽  
T. Watanabe ◽  
T. Yarnamoto ◽  
T. Saito ◽  
H. Yoshida ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Small Angle ◽  
Boundary Energy ◽  
High Resolution Electron Microscopy ◽  
Grain Boundary Sliding ◽  
Boundary Structure ◽  
Grain Boundary Energy ◽  
Grain Boundary Structure ◽  
Boundary Sliding

AbstractAlumina bicrystals were fabricated by a hot joining technique at 1500°C in air to obtain ten kinds of [0001] symmetric tilt grain boundaries which included small angle, CSL and high angle grain boundaries. Their grain boundary structures were investigated by high-resolution electron microscopy (HREM), and the respective grain boundary energies were systematically measured by a thermal grooving technique. It was found that grain boundary energy strongly depended on the grain boundary characters, e.g., there were large energy cusps at low Σ CSL grain boundaries. But, main part of grain boundary energy is likely to be due to the strain energy around the grain boundary, and the contribution of atomic configuration is not so large. Small angle grain boundaries were consisted of an array of partial dislocation with Burgers vector of 1/3[1100] to form the stacking faults between the dislocations. The behavior of grain boundary sliding was also investigated for typical grain boundaries by high-temperature creep test at 1400°C. As the result, the occurrence of grain boundary sliding was found to depend on the grain boundary atomic structure.

Effect of Cu and Al Substitutions on the Microstructure of R-Fe-B Magnets

1991 ◽  
Vol 232 ◽  
Author(s):  
Y. J. Zhang ◽  
L. Withanawasam ◽  
G. C. Hadjipanayis ◽  
A. Kim
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Secondary Phases ◽  
Al Substitution ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Melt Spun

ABSTRACTThe coercivity of melt-spun Pr-Fe-B ribbons was found to increase with the addition of Cu and Al. The change in size and shape of grains with Cu and Al substitution were investigated by transmission eletron microscopy (TEM) and the grain boundary structure was further examined with high resolution electron microscopy (HREM). For small substitutions only “disturbed lattice” regions were observed at most of the grain boundaries. Secondary phases rich in the added elements were observed mostly at tripple grain boundaries and sometimes at grain boundaries in samples with larger amounts of substitution. The grain size in the substituted samples does not decrease much with further substitution. However, the shape of grains changes from polyhexagons to facets. The enhancement in coercivity can be explained by the grain size reduction and the modification of microstructure at the grain boundary regions.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Structural and Mechanical Properties of Nanophase Ni: A Molecular-Dynamics Study of the Influence of Grain-Boundary Structure on Elastic and Plastic Behavior

1997 ◽  
Vol 492 ◽  
Author(s):  
H. Van Swygenhoven ◽  
M. Spaczér ◽  
A. Caro
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Diffusion Mechanism ◽  
Distribution Functions ◽  
Boundary Structure ◽  
Plastic Behavior ◽  
Self Diffusion ◽  
Common Neighbour ◽  
Grain Boundary Structure

ABSTRACTMolecular dynamics computer simulations of high load plastic deformation at temperatures up to 500K of Ni nanophase samples with mean grain size of 5 nm are reported. Two types of samples are considered: a polycrystal nucleated from different seeds, each having random location and random orientation, representing a sample with mainly high angle grain boundaries, and polycrystals with seeds located at the same places as before, but with a limited missorientation representing samples with mainly low angle grain boundaries. The structure of the grain boundaries is studied by means of pair distribution functions, coordination number, atom energetics, and common neighbour analysis. Plastic behaviour is interpreted in terms of grain-boundary viscosity, controlled by a self diffusion mechanism at the disordered interface activated by thermal energy and stress.

Systematic Study of Grain Boundary Structure and Chemical Analysis of [100] and [111] Tilt Grain Boundaries in Yttria-Stabilized Zirconia

2004 ◽  
Vol 10 (S02) ◽  
pp. 304-305 ◽  
Author(s):  
James P Buban ◽  
Katsuyuki Matsunaga ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Chemical Analysis ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Systematic Study ◽  
Yttria Stabilized Zirconia ◽  
Boundary Structure ◽  
Stabilized Zirconia ◽  
Grain Boundary Structure

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

GRAIN BOUNDARIES: PHASE TRANSITIONS AND CRITICAL PHENOMENA

1991 ◽  
Vol 05 (19) ◽  
pp. 2989-3028 ◽  
Author(s):  
E.I. RABKIN ◽  
L.S. SHVINDLERMAN ◽  
B.B. STRAUMAL
Keyword(s):  
Phase Transitions ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Critical Phenomena ◽  
External Surface ◽  
Theoretical Models ◽  
Boundary Structure ◽  
Boundary Phase ◽  
Recent Experimental Data ◽  
Grain Boundary Structure

Recent theories of grain boundary structure have been reviewed briefly. The possibility of existence of the same variety of phase transitions on grain boundaries as that on the crystal external surface has been demonstrated. Recent experimental data and theoretical models concerning grain boundary phase transitions are critically analysed. Grain boundary phase transitions connected with the formation of thin disordered layers on the boundary (prewetting, premelting) are particularly distinguished. Results of recent indirect experiments, which may be treated in terms of prewetting and premelting, have been reviewed. Experimentally observed critical phenomena in the vicinity of the prewetting transition on the tin-germanium interphase boundary have been discussed in terms of the critical exponents theory. Some ideas regarding directions of further research are presented.

Observations and implications of grain boundary dislocation networks in high-angle YBa2Cu3O7−δ grain boundaries

1990 ◽  
Vol 5 (5) ◽  
pp. 919-928 ◽  
Author(s):  
S. E. Babcock ◽  
D. C. Larbalestier
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Boundary Structure ◽  
High Angle ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Regular Networks

Regular networks of localized grain boundary dislocations (GBDs) have been imaged by means of transmission electron microscopy in three different types of high-angle grain boundaries in YBa2Cu3O7-δ, implying that these boundaries possess ordered structures upon which a significant periodic strain field is superimposed. The occurrence of these GBD networks is shown to be consistent with the GBD/Structural Unit and Coincidence Site Lattice (CSL)/Near CSL descriptions for grain boundary structure. Thus, these dislocations appear to be intrinsic features of the boundary structure. The spacing of the observed GBDs ranged from ∼10 nm to ∼100 nm. These GBDs make the grain boundaries heterogeneous on a scale that approaches the coherence length and may contribute to their weak-link character by producing the “superconducting micro-bridge” microstructure which has been suggested on the basis of detailed electromagnetic measurements on similar samples.

Mechanism of Surface Dissolution in Dense Hydroxyapatite

2007 ◽  
Vol 121-123 ◽  
pp. 1241-1244 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Xrd Analysis ◽  
Boundary Structure ◽  
Molar Ratio ◽  
Dissolution Mechanism ◽  
Grain Boundary Structure ◽  
High Resolution Tem ◽  
Moisture Protection

In this study, it was demonstrated how second phases with small amount, which are hardly detected by XRD analysis, affect grain boundary dissolution and related mechanical properties of HA. All HA disks sintered at 1200 oC for 2 h in air with under moisture protection were phase pure and had Ca/P molar ratio of 1.67. Following certain period of exposure to the distilled water, the surface dissolution initiated at grain boundaries and particle loosening, subsequently resulting in decrease in mechanical properties of HA. In order to understand the dissolution mechanism, grain boundary structure of HA was identified by transmission electron microscopy (TEM) and high resolution TEM observation. From the analysis, it was found that the non-stoichiometric phase as α-tricalcium phosphate (TCP) transformed from β-TCP was existed at grain boundaries and caused surface dissolution of HA. From the XRD analysis, it was found that (211) and (112) planes of hydroxyapatite were susceptible to dissolution, whereas (300) plane was relatively stable.

A Highly Reliable Al Line with Controlled Texture and Grain Boundaries

1995 ◽  
Vol 391 ◽  
Author(s):  
M. Hasunuma ◽  
H. Toyoda ◽  
T. Kawanoue ◽  
S. Ito ◽  
H. Kaneko ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Single Crystal ◽  
Grain Boundaries ◽  
Empirical Relation ◽  
Boundary Structure ◽  
Homogeneous Microstructure ◽  
Grain Boundary Structure ◽  
Dislocation Arrays ◽  
Order Of Magnitude ◽  
Individual Grains

AbstractIn order to clarify the relationship between Al line reliability and film microstructure, especially grain boundary structure and crystal texture, we have tested three kinds of highly textured Al lines, namely, single-crystal Al line, quasi-single-crystal Al line and hypertextured Al line, and two kinds of conventional Al lines deposited on TiN/Ti and on SiO2. Consequently, the empirical relation between the electromigration (EM) lifetime of Al line † and the (111) full width at half maximum (FWHM) value ω is described by † ∝ ω-2 [1]. This improvement of Al line reliability results from as following reasons; firstly, homogeneous microstructure and high activation energy of 1.28eV for the single-crystal Al line (ω=0.18°); secondly, sub-grain boundaries which consisted of dislocation arrays found in the quasi-single-crystal Al line (ω=0.26°) has turned out to be no more effective mass transport paths because dislocation lines are perpendicular to the direction of electron wind. Although there exist plural grain boundary diffusion paths in the newly developed hypertextured Al line (ω=0.5°) formed by using an amorphous Ta-Al underlayer {1], the vacancy flux along the line has been suppressed to the same order of magnitude of single crystal line. It has been clarified that the decrease of FWHM value has promoted the formation of sub-grain boundaries and low-angle boundaries with detailed orientation analysis of individual grains in the hypertextured film. The longer EM lifetime for the hypertextured Al line is considered to be due to the small grain boundary diffusivities for these stable grain boundaries, and this diffusivity reduction resulted in the suppression of void/hillock pair in the Al lines. These results have confirmed that controlling texture and/or grain boundary itself is a promising approach to develop reliable Al lines which withstand higher current densities required in future ULSIs.

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