scholarly journals Direct measurements ofquasi-zero grain boundary energies in ceramics

2016 ◽  
Vol 32 (1) ◽  
pp. 166-173 ◽  
Author(s):  
Nazia Nafsin ◽  
Ricardo H.R. Castro
Keyword(s):  
Grain Boundary ◽  
Direct Measurements ◽  
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Abstract

Quantitative Valence-Loss Spectroscopy of Carbon Nanostructures

1999 ◽  
Vol 5 (S2) ◽  
pp. 690-691
Author(s):  
T. Stöeckli ◽  
Z.L. Wang ◽  
J.-M. Bonard ◽  
P. Stadelmann ◽  
A. Châtelain
Keyword(s):  
Dielectric Function ◽  
Carbon Nanostructures ◽  
Arc Discharge ◽  
Spherical Geometry ◽  
Dielectric Medium ◽  
Graphitic Carbon ◽  
Dielectric Tensor ◽  
Carbon Sphere ◽  
Direct Measurements ◽  
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Carbon tubes or spheres synthesized by arc-discharge are usually mixed with other byproducts, prohibiting direct measurements of their physical properties by the well established optical techniques because a large quantity of pure specimen is required. Electron energy-loss spectroscopy (EELS) is a unique technique that can be applied to probe the electronic structure of a single carbon tube or sphere. In this paper, the classical dielectric response theory is applied to calculate the EELS spectra acquired from a graphitic carbon sphere at various impact parameters. Graphite is an anisotropic dielectric medium whose dielectric function is described by a tensor. A graphitic carbon sphere is composed of concentric graphitic shells whose dielectric tensor in the spherical geometry, under the local response approximation, is given by (Figure 1)where are the dielectric function of graphite for an electric field perpendicular and parallel, respectively, to the c axis. In the non-relativistic approximation, the surface excitation is calculated by [1]

Quantification Of Segregation Levels Using Xeds In The Stem

1999 ◽  
Vol 5 (S2) ◽  
pp. 146-147
Author(s):  
V. J. Keast ◽  
D. B. Williams
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Scanning Transmission Electron Microscope ◽  
Factor V ◽  
X Ray ◽  
Interaction Volume ◽  
Probe Size ◽  
Scanning Transmission ◽  
The Matrix ◽  
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The quantification of grain boundary segregation levels, as measured with X-ray energy dispersive spectroscopy (XEDS) in a scanning transmission electron microscope (STEM), is dependent on the size and shape of the interaction volume. The segregation level T (in atoms/nm2) is related to the intensities of the characteristic peaks in the X-ray spectrum, Is and Im, bywhere ρ is the density of the matrix in atoms/nm3, Am and As are the atomic masses of the matrix and segregant respectively and ksm is the usual k-factor. The geometric factor, V/A, is the ratio of the volume of interaction to the area of the grain boundary inside in the interaction volume. Different models have been used to describe the interaction volume and these are illustrated in Fig. 1 and the appropriate expression for V/A is given in each case. In the simplest case, beam broadening is neglected and the interaction volume can be described as a cylinder with diameter equal to the probe size, d.

An energy analysis of nanovoid nucleation in nanocrystalline materials with grain boundary sliding accommodations

2014 ◽  
Vol 29 (2) ◽  
pp. 277-287 ◽  
Author(s):  
Lu Wang ◽  
Jianqiu Zhou ◽  
Shu Zhang ◽  
Yingguang Liu ◽  
Hongxi Liu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Energy Analysis ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
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Abstract

Recent trends and open questions in grain boundary segregation

2018 ◽  
Vol 33 (18) ◽  
pp. 2647-2660 ◽  
Author(s):  
Pavel Lejček ◽  
Monika Všianská ◽  
Mojmír Šob
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Open Questions ◽  
Recent Trends ◽  
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Abstract

scholarly journals The Creep Activation Energies of Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 429-444 ◽  
Author(s):  
D. R. Homer ◽  
J. W. Glen
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Creep Deformation ◽  
Tensile Axis ◽  
Strain Rates ◽  
Boundary Slip ◽  
Creep Tests ◽  
Creep Activation Energy ◽  
Single Grain ◽  
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AbstractMonocrystals and bicrystals of ice have been creep tested at temperatures between 4 and — 30°C. The bicrystals had a single grain boundary running parallel to the tensile axis; this configuration inhibited grain-boundary slip between the two grains. The creep tests, which were carried out at constant stress σ and temperature T, yielded data of strain ϵ for time elapsed since the start of the test. These data showed accelerating creep for both monocrystals and bicrystals at all strain levels. Strain-rates were derived at strains of 0.01, 0.05. and 0.10, and these rates were fitted to the expressionk is Boltzmann’s constant and E is the creep activation energy. Derived values of n were 1.9 for monocrystals and 2.9 for bicrystals. The creep activation energy was found to be 78 kJ/mol for monocrystals and 75 kJ/mol for bicrystals. The processes of creep deformation in mono-, bi- and polycrystals are discussed.

scholarly journals Measurement of Grain Boundary Properties in Cu(ln,Ga)Se2 Thin Films

2018 ◽  
Vol 26 (3) ◽  
pp. 32-39
Author(s):  
S. Rozeveld ◽  
C. Reinhardt ◽  
E. Bykov ◽  
A. Wall
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Boundary Properties ◽  
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Abstract

Fabrication and strengthening of porous Si3N4 ceramics by replacement of oxide phase with Si3N4 at grain boundary through carbothermal nitridation

2017 ◽  
Vol 32 (17) ◽  
pp. 3344-3352
Author(s):  
Qiang Zhi ◽  
Zhaoyun Xu ◽  
Huan Pan ◽  
Jianfeng Yang ◽  
Yuchen Deng ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Oxide Phase ◽  
Porous Si3n4 ◽  
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Si3n4 Ceramics ◽  
Porous Si3n4 Ceramics

Abstract

Effect of initial grain sizes on the grain boundary network during grain boundary engineering in Alloy 690

2013 ◽  
Vol 28 (9) ◽  
pp. 1165-1176 ◽  
Author(s):  
Tingguang Liu ◽  
Shuang Xia ◽  
Hui li ◽  
Bangxin Zhou ◽  
Qin Bai ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Engineering ◽  
Grain Sizes ◽  
Alloy 690 ◽  
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Abstract

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