共查询到20条相似文献,搜索用时 15 毫秒
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K. Wang P. Donnadieu P. Garoche 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):279-287
We report on grain growth and related structure change in single phased Al-Li-Cu quasicrystals. The icosahedral phase grains
have been investigated using scanning ion microscopy and transmission electron microscopy. Regular boundaries between large
grains have been observed both before and after high temperature annealing. The electron diffraction study shows that the
grain growth is accompanied by a reduction of the phason-strains. The orientation relation between grains sets the 2-fold
icosahedral axes parallel, and the coincidence of the planes depends on the phason strain-field. The effect of phason-strain
field on these boundaries is discussed. It is proposed that the phason strain elimination can play a role in the grain growth.
Received 1 February 1999 and Received in final form 12 May 1999 相似文献
3.
E. Bonnetier C. Misbah F. Renard R. Toussaint J.-P. Gratier 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):121-131
Non-planar solid-fluid-solid interfaces under stress are very common in many industrial and natural materials. For example,
in the Earth’s crust, many rough and wavy interfaces can be observed in rocks in a wide range of spatial scales, from undulate
grain boundaries at the micrometer scale, to stylolite dissolution planes at the meter scale. It is proposed here that these
initially flat solid-fluid-solid interfaces become rough by a morphological instability triggered by elastic stress. A model
for the formation of these unstable patterns at all scales is thus presented. It is shown that such instability is inherently
present due to the uniaxial stress that promotes them, owing to the gain in the total elastic energy: the intrinsic elastic
energy plus the work of the external forces. This is shown explicitly by solving the elastic problem in a linear stability
analysis, and proved more generally without having resort to the computation of the elastic field. 相似文献
4.
A simplified version of the model by Elser and Joseph for the process of growth of an entropically stabilized, two-dimensional
quasicrystal with no dynamics in the bulk, is proposed. The phason fluctuations are modeled by a scalar field on a periodic
lattice. The choice of the master equation for the growth is restricted by the requirement that its detailed balance solution
describes the equilibrium fluctuations of the field with a quadratic Hamiltonian. The model is parametrized by the chemical
potential bias and the microscopic surface tension coefficient . The phase diagram of the system on the plane (, ) shows several distinct regimes of growth, separated by relatively narrow transition zones. Within the regions corresponding
to these regimes, the phason fluctuations do not depend on and . Analytic expressions for the spectra of phason fluctuations are obtained and confirmed by numerical simulation.
Received 30 June 2000 相似文献
5.
Scattering mechanisms of charge carriers in Transparent Conducting Oxide (TCO) films have been analyzed theoretically. For the degenerate polycrystalline TCO films with relatively large crystallite sizes and high carrier concentrations (higher than 5 × 1018 cm–3), the depletion layers between crystallites are very thin compared to the crystallite sizes, and the grain boundary scattering on electrical carriers makes a small contribution to limit the mobility of the films. Instead of thermionic emission current, a tunneling current dominates the electron transport over grain boundaries. The Petritz model which is based on thermionic emission and extensively quoted in literature should not be applicable. The main scattering mechanisms for the TCO films are ionized impurity scattering in the low-temperature range and lattice vibration scattering in the high-temperature range. The ionized impurity scattering mobility is independent of temperature and the mobility due to thermal lattice vibration scattering is inversely proportional to the temperature. The results obtained from Hall measurements on our ZnO, ITO, SnO2 and SnO2:F films prepared with various methods supports the analysis. 相似文献
6.
M. Belhadi O. Rafil R. Tigrine A. Khater J. Hardy A. Virlouvet K. Maschke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):435-443
The influence of linear defect boundaries on the transmission and scattering of elastic waves in quasi-two-dimensional wave-guides
is studied using the matching method. A linear defect boundary separating two wave-guide crystalline lattice domains is characterised
here by a linear chain of defect masses and by modified elastic constants in the boundary, different from their values in
the bulk of the domains. In particular a square lattice is considered to model the domains of the two-dimensional planar wave-guide
containing the linear defect. The reflection and transmission probabilities, and the total transmission probabilities are
calculated numerically and presented for the scattering processes in a variety of cases. We show that the interaction between
the localised modes introduced by the defect boundary and the propagating modes of the system leads to Fano resonances. These
resonances shift to higher (lower) frequencies for smaller (larger) defect masses, and for the same mass as function of the
angle of the incident wave. Other spectral features shown to exist are due to interference effects especially at oblique incidence
and when modifying the boundary elastic constants.
Received 8 November 1999 and Received in final form 14 January 2000 相似文献
7.
B.M. Letfulov 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):195-203
This paper gives a simplified model of the double exchange which is a kind of indirect exchange interaction between localized
magnetic moments. The presented model is solved exactly in the case of infinite - dimensional space. Equations for single-particle
Green's function and magnetization of the localized spins subsystem are obtained. It is shown that our simple double exchange
model reveals an instability to the ferromagnetic ordering of localized moments. Magnetic and electric properties of this
system on Bethe lattice with are investigated in detail.
Received: 24 January 1997 / Revised: 14 February 1997 / Received in final form: 18 August 1997 / Accepted: 25 August 1997 相似文献
8.
The strength of polycrystals is largely controlled by the interaction between lattice dislocations and grain boundaries. The atomistic details of these interactions are difficult to discern even by advanced high-resolution microscopy methods. In this paper we present results of atomistic simulations of interactions between an edge dislocation and three symmetric tilt grain boundaries in body-centred cubic tungsten. Our simulations reveal that the outcome of the dislocation–grain-boundary interaction depends sensitively on the grain boundary structure, the geometry of the slip systems in neighbouring grains, and the precise location of the interaction within the grain boundary. A detailed analysis of the evolution of the grain boundary structures and local stress fields during dislocation absorption and transmission is provided. 相似文献
9.
基于采用晶体有序化程度参量ψ和晶体学取向θ来表示多晶粒结构的相场模型,利用自适应有限元方法模拟了多晶材料等温过程中的晶粒粗化现象.模拟结果显示,在曲率作用下,通过晶界迁移弯曲晶界逐渐平直化,小晶粒逐渐被大晶粒吞并,当晶界之间的取向差较小时,满足一定能量和几何条件的两晶粒在界面能作用下会发生转动,合并为单个晶粒.模拟结果与实验结果符合较好.因此,该相场模型可以很好地用来模拟固态相变中多晶材料的生长粗化等现象.
关键词:
相场
晶界迁移
晶粒转动
粗化 相似文献
10.
F. Nieto C. Uebing 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):523-531
In this work the diffusion of non-interacting adsorbates on a random AB alloy surface is considered. For this purpose a simple
cubic (sc), body-centered cubic (bcc) or face-centered cubic (fcc) auxiliary metal lattice is introduced. The auxiliary lattice
is truncated parallel to its (100) plane in such a way that the fourfold hollow positions of the metal surface form a regular
net of adsorption sites with square symmetry. The adsorption energy of each adsorption site is determined by its own environment,
i.e. by the numbers of direct A or B neighbors. The Monte-Carlo method has been utilized to simulate surface diffusion of adsorbates
on such energetically heterogeneous alloy surfaces and to calculate the tracer, jump and chemical diffusion coefficients.
The chemical diffusion coefficient was calculated via two different approaches: the fluctuation and the Kubo-Green method. The influence of energetical heterogeneities on the
surface diffusion is largely pronounced at low temperatures and low surface coverages, where most of the adatoms are trapped
by deep adsorption sites. It was found that at low temperatures the sequential occupation of the different types of adsorption
sites can be observed.
Received: 24 October 1997 / Accepted: 17 December 1997 相似文献
11.
(001)-oriented strontium bismuth tantalate thin films have been grown on Pt/TiO2/SiO2/Si (100) substrates by pulsed laser deposition. The room-temperature current–electric field dependence of the films has been
investigated, which revealed a space-charge-limited conduction mechanism. The microstructures of grain boundaries and structural
defects in these films were also examined by transmission electron microscopy and high-resolution transmission electron microscopy,
respectively. The grains of the films deposited at 550 °C exhibited polyhedral morphologies, and the average grain size was
about 50 nm in length and 35 nm in width. At a small misorientation angle (8.2°) tilt boundary, a regular array of edge dislocations
with about 3-nm periodic distance was observed, and localized strain contrast near the dislocation cores was also observed.
The Burgers vector b of the edge dislocation was determined to be [110]. At a high misorientation angle (39.0°) tilt grain boundary lattice strain contrast associated with the distortion of
lattice planes was observed, and the mismatching lattice images occurred at about 2 nm along the boundary. The relationship
between microstructural defects at grain boundaries and leakage currents of these films is also discussed.
Received: 8 September 2000 / Accepted: 18 December 2000 / Published online: 28 February 2001 相似文献
12.
M. Pleimling W. Selke 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):385-391
The effect of imperfections on surface critical properties is studied for Ising models with nearest-neighbour ferromagnetic
couplings on simple cubic lattices. In particular, results of Monte Carlo simulations for flat, perfect surfaces are compared
to those for flat surfaces with random, “weak” or “strong”, interactions between neighbouring spins in the surface layer,
and for surfaces with steps of monoatomic height. Surface critical exponents at the ordinary transition, in particular ,are found to be robust against these perturbations.
Received: 7 October 1997 / Accepted: 19 November 1997 相似文献
13.
Elastohydrodynamic problems of decagonal quasicrystals are analysed where the phonon field obeys wave equation and the phason field obeys diffusive wave equation. Basic equations are solved in the quasiperiodic plane and periodic plane, respectively. Final governing equations of dynamic behaviours of decagonal quasicrystals are obtained. A general solution is derived in terms of introduced three auxiliary functions, where two individually satisfy a fourth-order partial differential equation and one satisfies a second-order hyperbolic diffusion equation. Using the derived governing equations, elastic waves propagating in the quasiperiodic plane and a plane containing the period axis are analysed. Secular equations are obtained. It is found that differing from conventional crystals, at least four branches of elastic waves exist when the phonon–phason coupling is present. Moreover, acoustic waves have attenuation during wave propagation. Phason fluctuations exhibit exponential decaying behaviour due to kinematic viscosity and damping. The phase speeds are isotropic in the quasiperiodic plane and anisotropic in a plane with the periodic axis. The section of the slowness surfaces is plotted. 相似文献
14.
E. Rastelli A. Tassi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):341-347
Ferromagnetic spin chains of a hexagonal lattice coupled by a weak antiferromagnetic interaction J1 develop a helix arrangement if the intrachain antiferromagnetic NNN exchange J2 is sufficiently large. We show that the classical minimum energy spin configuration is an umbrella when an external magnetic field is applied. The scenario is dramatically changed by quantum fluctuations. Indeed we find
that the zero point motion forces the spins in a plane containing the magnetic field so that classical expectation is deceptive
for our model. Our result is obtained by controlled expansion in the low field-long wavelength modulation limit.
Received: 9 September 1997 / Revised: 15 October 1997 / Accepted: 17 November 1997 相似文献
15.
Diffusion processes are studied near triple joints of special grain boundaries, whose dilatation field is modeled by a wedge
disclination. An exact analytic solution of the diffusion equation in the stress field produced by the structural defect considered
is obtained. The results of the theoretical analysis are used to determine the concentration field of point defects near triple
joints of special grain boundaries in a polycrystal.
Fiz. Tverd. Tela (St. Petersburg) 41, 64–67 (January 1999) 相似文献
16.
I. H. Arita R. Hernández V. M. Castaño 《Applied Physics A: Materials Science & Processing》1988,47(4):413-417
A recently proposed technique for preparing, in a very simple way, thin film tilt grain boundaries is described and analyzed.
Some electron microscopy characterization of the bicrystals is presented and a comparison between this new method and some
of the standard techniques is made from a critical point of view. Some new applications of grain boundary research using this
technique are also proposed. 相似文献
17.
R. Nassif Y. Boughaleb A. Hekkouri J.F. Gouyet M. Kolb 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(4):453-464
We examine the behaviour of the concentration profiles of particles with repulsive interactions diffusing on a host lattice.
At low temperature, the diffusion process is strongly influenced by the presence of ordered domains. We use mean field equations
and Monte-Carlo simulations to describe the various effects which influence the kinetic behaviour. An effective diffusion
coefficient is determined analytically and is compared with the simulations. Finite gradient effects on the ordered domains
and on the diffusion are discussed. The kinetics studied is relevant for superionic conductors, for intercalation and also
for the diffusion of particles adsorbed on a substrate.
Received: 26 June 1997 / Revised: 18 September 1997 / Accepted: 10 November 1997 相似文献
18.
In recent studies, many groups have investigated the interaction of dislocations and grain boundaries by bi-crystals and micro-specimen experiments. Partially, these experiments were combined with supplementary simulations by discrete dislocation dynamics, but quantitative data for the grain boundary resistance against slip transfer is still missing. In this feasibility study with first results, we use stage-I-fatigue cracks as highly localised sources for dislocations with well-known Burgers vectors to study the interaction between dislocations in the plastic zone in front of the crack tip and selected grain boundaries. The stress concentration at the grain boundary is calculated with the dislocation-free zone model of fracture using the dislocation density distribution in the plastic zone from slip trace height profile measurements by atomic force microscopy. The grain boundary resistance values calculated from common geometric models are compared to the local stress distribution at the grain boundaries. Hence, it is possible to quantify the grain boundary resistance and to combine geometric and stress approach for grain boundary resistance against slip transfer to a self-contained concept. As a result, the prediction of the grain boundary resistance effect based on a critical stress concept is possible with knowledge of the geometric parameters of the grain boundary only, namely the orientations of both participating grains and the orientation of the grain boundary plane. 相似文献
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A.A. Tarasenko F. Nieto L. Jastrabík C. Uebing 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):311-322
A two-dimensional lattice-gas model with square symmetry is investigated by using the real-space renormalization group (RSRG)
approach with blocks of different size and symmetries. It has been shown that the precision of the method depends strongly
not only on the number of sites in the block but also on its symmetry. In general, the accuracy of the method increases with
the number of sites in the block. The minimal relative error in determining the critical values of the interaction parameters
is equal to . Using the RSRG method, we have explored phase diagrams of both a two-dimensional Ising spin model and of a square lattice
gas with lateral interactions between adparticles. We also have investigated the influence of the attractive and repulsive
interactions on both the thermodynamic properties of the lattice gas and the diffusion of adsorbed particles over surface.
We have calculated adsorption isotherms and coverage dependences of the pair correlation function, isothermal susceptibility
and the chemical diffusion coefficient. In addition, we have included in our analysis the interaction of the activated particle
in the saddle point with its nearest neighbors. We have also used Monte Carlo (MC) technique to calculate these dependences.
Despite the fact that both methods constitute very different approaches, the correspondence of the numerical data is surprisingly
good. Therefore, we conclude that the RSRG approach can be applied to characterize the thermodynamic and kinetic properties
of systems of particles with strong lateral interactions.
Received 1st September 1998 and Received in final form 8 March 2000 相似文献