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Showing papers in "Philosophical Magazine Letters in 2000"


Journal ArticleDOI
TL;DR: The structure of microporous carbon prepared by the carbonization of sucrose was examined using high-resolution electron microscopy as discussed by the authors, and it was found to be disordered and isotropic and primarily made up of tightly curved individual carbon layers.
Abstract: The structure of a microporous carbon prepared by the carbonization of sucrose was examined using high-resolution electron microscopy. It was found to be disordered and isotropic and primarily made up of tightly curved individual carbon layers, enclosing pores typically about 1nm in size. Completely closed carbon particles were also present. These observations suggest that the carbon may have a fullerene-related structure, in which pentagons and heptagons are distributed randomly throughout a hexagonal network, producing continuous curvature.

108 citations


Journal ArticleDOI
TL;DR: In this paper, the transformation process of twinned 9R copper precipitates to final stable structures via a 3R structure in a thermally aged Fe-Co model alloy was investigated.
Abstract: High-resolution transmission electron microscopy and conventional transmission electron microscopy have been used to investigate in detail the transformation processes of twinned 9R copper precipitates to final stable structures via a 3R structure in a thermally aged Fe-Co model alloy. In 9R precipitates of size greater than about 13nm, the motion of the twin boundaries and the elimination of the regular stacking faults on every third (009)9R close packed plane were observed to occur nearly simultaneously. Direct evidence was found that 3R is a non-cubic structure obtained when the regular stacking faults on the (009)9R basal planes are removed. In larger precipitates (of size up to about 26 nm), lattice plane rotations and plane spacing changes in 3R variants took place towards stable fcc and fct structures, suggesting the occurrence of lattice relaxation involving the diffusion of atoms. The fct structure had larger lattice constants a=b=0.369 nm and c=0.366 nm than bulk fcc copper (a=0.361 nm). Precipi...

91 citations


Journal ArticleDOI
TL;DR: In this paper, the saddle-point configurations of embryonic dislocation loops and their associated activation energies under stress levels up to the ideal shear strength were determined by using a variational boundary integral method in the Peierls-Nabarro framework.
Abstract: We present an analysis and results on the homogeneous nucleation of a dislocation loop under stress in a perfect crystal. By using a variational boundary integral method in the Peierls-Nabarro framework, we have determined the saddle-point configurations of embryonic dislocation loops and their associated activation energies under stress levels up to the ideal shear strength. The high-energy barriers under the usual levels of applied shear stresses, differing markedly from the ideal shear strength, confirm the widely held view that thermal motion should play no role in such nucleation. The result provides means for more definitive solutions of fundamental problems involving homogeneous nucleation of dislocation loops and has significant implications for models based on the mechanism of nucleation of dislocations from a perfect crystal.

81 citations


Journal ArticleDOI
TL;DR: In this paper, the authors re-examine two important issues within the Peierls-Nabarro model, which are critical in obtaining accurate values for the Peiers stress.
Abstract: We re-examine two important issues within the Peierls-Nabarro model, which are critical in obtaining accurate values for the Peierls stress. The first is related to the sampling scheme (double versus single counting) of the misfit energy across the glide plane and the second is the effect of atomic relaxation on the Peierls stress. We argue that the double-counting scheme is physically more appropriate. An analytical formula is derived for the Peierls stress of dislocations in alternating lattices. The atomic relaxation is shown to play an important role on the Peierls stress for narrow dislocations.

73 citations


Journal ArticleDOI
TL;DR: In this article, the authors provide useful quantitative support for theories of the restitution coefficient for normal impacts involving plastic deformation, especially in the region close to the threshold at which the deformation begins.
Abstract: The aim of this work is to provide useful quantitative support for theories of the restitution coefficient for normal impacts involving plastic deformation, especially in the region close to the threshold at which plastic deformation begins. The impacts were from spheres of 5 mm diameter of aluminium oxide (which deformed elastically), dropped on to thick plates of mild steel or aluminium alloy. Very accurate measurements of impact and rebound velocities were made for drop heights from 1.75 m down to 0.6 mm, covering a range of velocities down to the yield threshold. Most of these results are in the elastic-plastic velocity range over which the indentation pressure varies from its value at initial yield of about 1.1sigmay to the value when full plasticity is established of about 2.8sigmay. The variation in the restitution coefficient with velocity in this range closely fits the rebound model of Tabor, which allows the indentation pressure to vary through the Meyer index n. The fitted values of n take into...

66 citations


Journal ArticleDOI
TL;DR: The first evidence of solid-state amorphization of yttria-stabilized cubic zirconia (YSZ) by 400keV Cs-ion implantation to 1 x 10 21 ions m -2 at room temperature was reported in this paper.
Abstract: Stabilized cubic zirconia is a promising candidate material for use as an inert fuel matrix for burning' excess Pu in light-water nuclear reactors. Zirconia is also considered to be an excellent nuclear waste form for direct geological disposal. Both applications are based on zirconia's high solubility for actinides, high chemical durability and high stability under irradiation. We report the first evidence of solid-state amorphization of yttria-stabilized cubic zirconia (YSZ) by 400keV Cs-ion implantation to 1 x 10 21 ions m -2 at room temperature. Amorphization of YSZ is caused by the large size incompatibility and low mobility of Cs ions in the YSZ structure, reflecting a relatively low solubility of Cs in YSZ. Nevertheless, the Cs concentration at which amorphization of YSZ occurred (about 8 at.%) is well above the value that will typically be reached in an inert fuel matrix.

66 citations


Journal ArticleDOI
TL;DR: In this paper, a monodisperse liquid foam is allowed to coarsen while subject to a constant flow of liquid, and the average bubble size is indirectly monitored by measurement of the velocity of forced drainage waves.
Abstract: A monodisperse liquid foam is allowed to coarsen while subject to a constant flow of liquid. The average bubble size is indirectly monitored by measurement of the velocity of forced drainage waves. After an initial period the average bubble diameter is found to increase with the square root of time. The rate of this increase is a function of the flow rate; coarsening is slower in wet foams. This rate is linked to the variation in the film area in a foam as a function of liquid fraction.

53 citations


Journal ArticleDOI
TL;DR: In this article, a combination of neutron scattering, low-temperature ultrasonic attenuation and thermal conductivity measurements are reported on single crystals of the semiconductors Sr8Ga16Ge30 and Ba8Ga 16Ge30.
Abstract: Semiconducting crystalline materials that are poor conductors of heat are important as thermoelectric materials and for technological applications involving thermal management. A combination of neutron scattering, lowtemperature ultrasonic attenuation and thermal conductivity measurements are reported on single crystals of the semiconductors Sr8Ga16Ge30 and Ba8Ga16Ge30. Taken together, these measurements suggest specific structural features that result in a crystal with the lowest possible thermal conductivity, namely that of a glass with the same chemical composition. Weakly bound atoms that 'rattle' within oversized atomic cages in a crystal result in a low thermal conductivity, but the present data show that both 'rattling' atoms and tunnelling states are necessary to produce a true glass-like thermal conductivity.

52 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that a size dependence of the critical temperature Tc of the miscibility gap in nanocrystalline and nanoscale particle interstitial solid solutions results from stress owing to elastic interaction of the bulk with layers of material at the grain boundaries or surfaces which have a small solute susceptibility at the phase transition.
Abstract: It is shown that a size dependence of the critical temperature Tc of the miscibility gap in nanocrystalline and nanoscale particle interstitial solid solutions results from stress owing to elastic interaction of the bulk with layers of material at the grain boundaries or surfaces which have a small solute susceptibility (i.e. a weak dependence of the concentration on the chemical potential) at the phase transition. When the volume fraction occupied by the interfacial layers is not too large, then the changes in Tc and in the critical concentration xc can be predicted on the basis of a series expansion of the solute chemical potential in the bulk about the critical point. The model can be extended to free-standing thin films and coherent multilayers. The dependence of the pressure on the hydrogen concentration in the crystal lattice of nanocrystalline palladium-hydrogen is measured on the basis of X-ray diffraction data. The result agrees with the predictions of the theory.

50 citations


Journal ArticleDOI
TL;DR: In this article, the slip systems in SrTiO3 were identified as ⟨110⟩-{110] dislocations are dissociated into two partial dislocations.
Abstract: Dislocations have been introduced in SrTiO3 by Vickers indentation at room temperature and analysed by transmission electron microscopy. The slip systems in SrTiO3 were identified as ⟨110⟩-{110}. ⟨110⟩ dislocations are dissociated into two partial dislocations. The stacking-fault energy γSF was determined to be 136 ± 15 mJm-2.

50 citations


Journal ArticleDOI
TL;DR: In this paper, a 304 type austenitic stainless steel has been studied in multiple compression with the loading direction being changed in each pass, and it was concluded that a new grained structure can result from a kind of continuous reaction during deformation, namely continuous dynamic recrystallization.
Abstract: Strain-induced grain evolution in a 304 type austenitic stainless steel has been studied in multiple compression with the loading direction being changed in each pass. The tests were carried out to total strains above 6 at 873 K (0.5 T m) at a strain rate of about 10-3 s-1. Multiple deformation promotes the rapid formation of many mutually crossing subboundaries because various slip systems operate from pass to pass. The gradual rise in misorientations across dislocation subboundaries with increasing strain finally leads to the evolution of very fine grains with large-angle boundaries. It is concluded that a new grained structure can result from a kind of continuous reaction during deformation, namely continuous dynamic recrystallization. Such deformation-induced grains are characterized by relatively low densities of dislocations, and considerable lattice curvatures developed in their interiors. The latter observations suggest that high elastic distortions are developed in the grain interiors and so such...

Journal ArticleDOI
TL;DR: In this article, the impact of solid particles during the erosion of stainless steel by a slurry jet reveals a sequence of anodic current transients due to individual impacts, and it is shown that there is a minimum particle energy below which no transients can be detected.
Abstract: The impact of solid particles during the erosion of stainless steel by a slurry jet reveals a sequence of anodic current transients due to individual impacts. Measurement of these current transients shows that there is a minimum particle energy below which no transients can be detected. The result is interpreted as a threshold energy required to rupture the passivating oxide film on the metal surface. If this energy is exceeded, the current transients arise from electrochemical reaction of the depassivated metal surface after denudation. Below this threshold no rupture occurs and there are no current transients.

Journal ArticleDOI
TL;DR: In this article, a closed-form analytical solution for the stress field of a circular Volterra dislocation loop, having glide and prismatic components, was obtained by line integration of the Peach-Koehler equation.
Abstract: A closed-form analytical solution for the stress field of a circular Volterra dislocation loop, having glide and prismatic components, is obtained. Assuming linear elasticity and infinite isotropic material, the stress field is found by line integration of the Peach-Koehler equation for a circular dislocation loop. The field equations are expressed in terms of complete elliptic integrals of the first and second kinds. The general loop solution is, from the principle of superposition, the additive sum of the prismatic and glide solutions. Finally, the obtained stress solution is compared with the stress calculation results from segmented loops (six to 24 segments) having the same radius. Such comparisons are useful as a benchmarking measure for newly emerging dislocation dynamics codes which discretize a curved dislocation line in some form or another.

Journal ArticleDOI
TL;DR: In this article, the Hartree-Fock method was used to study the atomic and electronic structure of the four compounds Sr2TiO4, Sr3Ti2O7, Sr4Ti3O10 and SrTiO3.
Abstract: We have performed a theoretical study of the atomic and electronic structure of the four compounds Sr2TiO4, Sr3Ti2O7, Sr4Ti3O10 and SrTiO3, by a total energy semiempirical Hartree-Fock method. We show that the intercalation of SrO3 layers in the perovskite structure of SrTiO3 induces lattice distortions modifications of the electronic structure, which are mainly localized close to the stoichiometry defect. They include a contraction of the SrO-TiO2 interplanar distance, a rumpling of the adjacent layers and an increase in the ionicity of the Sr-O bond. As the index n increases, the compounds Sr n+1Ti n O3n+1 become more and more unstable with respect to phase dissociation and we predict a limit of stability for n=3.

Journal ArticleDOI
TL;DR: In this article, the nucleation and growth of a nano-icosahedral phase from a supercooled liquid region of Zr65Al7.5M10 (M = Ag or Pd) glasses have been examined by differential scanning calorimetry and transmission electron microscopy.
Abstract: The nucleation and growth of a nano-icosahedral phase from a supercooled liquid region of Zr65Al7.5Ni10Cu7.5M10 (M = Ag or Pd) glasses have been examined by differential scanning calorimetry and transmission electron microscopy. The growth rate of the icosahedral phase is nearly constant at the initial stage and much slower than that of the Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 metallic glass. The homogeneous nucleation rate has a maximum value of 4.4 x 1020 m-3 s-1 at 695 K in the Zr65Al7.5Ni10Cu7.5Ag10 glass, which is approximately 102 times higher than that for the formation of quasicrystalline phase in the Zr69.5Al7.5Ni11Cu12 glass and 104 times higher than that of the Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 glass. With increasing Pd content, the nucleation rate of the primary phase increases significantly and the growth rate decreases at the crystallization temperature. Thus, the addition of Ag and Pd is effective for an increase in the number of nucleation sites and the suppression of grain growth, ...

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanisms of failure of symmetrical tilt boundaries using an atomistic technique and showed that these boundaries are shown to fail through a combined mechanism involving dislocation emission in certain regions of the structural unit.
Abstract: The mechanisms of failure of symmetrical tilt boundaries have been investigated using an atomistic technique. The fracture process advances in steps that are related to the structural unit of the symmetrical tilt grain boundary. These boundaries are shown to fail through a combined mechanism involving dislocation emission in certain regions of the structural unit, followed by microcleavage, and again dislocation emission. The overall toughness of the boundaries is given by the combination of the toughness of these two processes.

Journal ArticleDOI
TL;DR: In this paper, the coefficients of thermal expansion (CTEs) of complex structures can be calculated precisely from first principles by incorporating the Debye model for acoustic response, taking Mo-Si compounds as model systems.
Abstract: Taking Mo-Si compounds as model systems, we show that the coefficients of thermal expansion (CTEs) of complex structures can be calculated precisely from first principles by incorporating the Debye model for acoustic response. Specifically, we obtain a nearly isotropic CTE in MoSi2 but a highly anisotropic CTE in Mo5Si3. The CTE anisotropy in Mo5Si3 is due to an elastically more rigid basal plane and a higher anharmonicity along the c axis. As the structure of 5-3 compounds is modified from D8m to D8l by boron substitutions (Mo5SiB2), we predict a significant decrease in the CTE anisotropy, which is confirmed by experiments.

Journal ArticleDOI
TL;DR: In this paper, single Al-Pd-Re icosahedral quasicrystals with a maximum diameter of 5mm have been grown by a slow cooling method on the basis of a partial phase diagram determined in the present study.
Abstract: Single Al-Pd-Re icosahedral quasicrystals with a maximum diameter of 5mm have been grown by a slow cooling method on the basis of a partial phase diagram determined in the present study. Laue X-ray and electron diffraction verified the highly ordered structure of the single icosahedral quasicrystals. The electrical resistivity rho of the single quasicrystals was measured to be 2000- 4000muOmegacm at 300K and 3000-6000muOmegacm at 2K, revealing a negative temperature dependence with a rho4.2K/rho300K value smaller than 2.

Journal ArticleDOI
TL;DR: In this paper, the transformation and grain growth behavior of an icosahedral phase from the supercooled liquid region of rapidly quenched Zr 65 Cu 7.5 Al7.5 Ni 10 Ag 10 metallic glass have been examined by transmission electron microscopy.
Abstract: The transformation and grain growth behaviour of an icosahedral phase from the supercooled liquid region of rapidly quenched Zr 65 Cu 7.5 Al 7.5 Ni 10 Ag 10 metallic glass have been examined by transmission electron microscopy. The precipitation of the icosahedral phase proceeds according to a polymorphic reaction without any concentration change. The grain size increases linearly with an increase in annealing time and the growth rate strongly depends on the temperature. An Arrhenius plot of the logarithm of growth rate versus the reciprocal of annealing temperature yields a linear relationship, from which an activation energy for grain growth of 409 kJ mol -1 is obtained. This activation energy is much higher than those in the Al-Cu-V and Al-Mn-Si systems. This activation energy is attributed to the strong bonding among constitutional elements and the necessity of the rearrangement of atoms on a long length scale for grain growth. The kinetic data suggest that the icosahedral phase is stabilized by the difficulty of rearrangement of atoms.

Journal ArticleDOI
TL;DR: In this article, a highly polydisperse foam is subjected to a constant liquid flow from above, and large-scale bubble motion is observed, in the course of which large bubbles rise to the top of the foam until a steady state is reached at which the average bubble size increases smoothly with height.
Abstract: A highly polydisperse foam is subjected to a constant liquid flow from above. For sufficiently high flow rates, large-scale bubble motion is observed, in the course of which large bubbles rise to the top of the foam until a steady state is reached at which the average bubble size increases smoothly with height.

Journal ArticleDOI
TL;DR: In this paper, the existence of a sharp low-temperature (T = 400°C) H evolution peak in compact hydrogenated amorphous silicon (a-Si : H) films deposited 'on the edge of crystallinity' is examined.
Abstract: The puzzling existence of a sharp low-temperature (T = 400°C) H evolution peak in compact hydrogenated amorphous silicon (a-Si : H) films deposited 'on the edge of crystallinity' is examined. From infrared absorption and X-ray diffraction (XRD) measurements, we show that none of the standard methods used to explain the existence of this peak in a-Si : H materials is applicable to the present films. From the Si-H wag-mode peak frequency, we postulate the existence of very small Si crystallites contained within the amorphous matrix. While the crystallite volume fraction is too small to be detected by XRD in the as-grown films, crystallization is observed for this material at anneal temperatures as low as 500°C. It is proposed that these crystallites catalyse the crystallization of the remainder of the amorphous matrix upon moderate annealing, enabling H surface desorption and H2 out-diffusion to the sample surface along newly formed grain boundaries at low anneal temperatures.

Journal ArticleDOI
TL;DR: In this article, a method for determining the exchange-stiffness constant A by analysis of the dependence of the elastic SANS cross-section on the applied magnetic field was proposed.
Abstract: In ferromagnets with a non-uniform magnetocrystalline and/or magnetoelastic anisotropy, such as nanocrystalline or cold-worked polycrystalline materials, the static magnetic microstructure gives rise to elastic magnetic small-angle neutron scattering (SANS). The paper explores a method for determining the exchange-stiffness constant A by analysis of the dependence of the elastic SANS cross-section on the applied magnetic field. Experimental results for A and for the spin-wave stiffness constant D in cold-worked or nanocrystalline Ni and Co are found to agree with literature data obtained by inelastic neutron scattering on single-crystal specimens.

Journal ArticleDOI
TL;DR: In this article, duplex silver films, exhibiting antimicrobial behaviour, have been produced by magnetron sputtering and studied using high-resolution scanning electron microscopy, and it was determined that biologically active films had a nanocrystalline structure consisting of loosely held particles with a grain size of the order of 15nm.
Abstract: Novel duplex silver films, exhibiting antimicrobial behaviour, have been produced by magnetron sputtering and studied using high-resolution scanning electron microscopy. These films were grown under deposition conditions in which the gas composition, process pressure and input power were varied. It was determined that biologically active films had a nanocrystalline structure consisting of loosely held particles with a grain size of the order of 15nm. The importance of oxygen in the sputtering environment and the resultant microstructure are discussed to explain the unique antimicrobial properties of these silver films.

Journal ArticleDOI
TL;DR: In this paper, a high-speed photographic study of low-velocity impact cracking of optically transparent acrylic resin and poly(methyl methacrylate) spheres of 12.7mm diameter is described.
Abstract: Results from a high-speed photographic study of low-velocity impact cracking of optically transparent acrylic resin and poly(methyl methacrylate) spheres of 12.7mm diameter are described. It is shown that, in a sphere undergoing an impact, cracking occurs after the sphere has been plastically deformed. The point of initiation of cracking is shown to be located at the circle of contact between the sphere and the impacting platen. The cracking then develops throughout the sphere, with cracks attaining velocities of 600-800m s -1 . It has been suggested that crack initiation at the contact circle is caused by the tensile circumferential stress, which is generated owing to the plastic flow of the sphere.

Journal ArticleDOI
TL;DR: In this paper, the crystallization process of a Hf 59 Ni 8 Cu 20 Al 10 Ti 3 metallic glass was studied using differential scanning calorimetry (DSC), X-ray diffraction and transmission electron microscopy.
Abstract: The crystallization process of a Hf 59 Ni 8 Cu 20 Al 10 Ti 3 metallic glass was studied using differential scanning calorimetry (DSC), X-ray diffraction and transmission electron microscopy. Two exothermic peaks are observed in the DSC curve of the as-quenched sample. It was revealed that the two reactions correspond to the phase transformations amorphous → icosahedral phase + fcc phase and icosahedral phase + fcc phase → Hf 2 Cu + Al 16 Hf 6 Ni 7 + Hf 3 Al 2 , where a = 0.254 nm for the icosahedral phase and a = 0.53 nm for the fcc phase. Nanobeam electron diffraction patterns corresponding to the fivefold, threefold and twofold symmetries of a quasicrystal were obtained, revealing that the quasicrystal is an icosahedral phase. It is suggested that the present report on a Hf-based icosahedral phase is helpful for understanding the structural relationship between amorphous and icosahedral phases.

Journal ArticleDOI
TL;DR: The temperature dependence of flow stress for polycrystalline titanium silicon carbide (Ti3SiC2) has been investigated from room temperature to 1423 K in this article.
Abstract: The temperature dependence of flow stress for polycrystalline titanium silicon carbide (Ti3SiC2) has been investigated from room temperature to 1423 K. An anomalous positive temperature dependence of flow stress was observed in this ceramic. This anomalous phenomenon is attributed to the change in the mechanism controlling the flow stress. However, it is not in good agreement with the widely accepted Kear-Wilsdorf mechanism.

Journal ArticleDOI
TL;DR: Grain-boundary grooving has been studied on polished surfaces of polycrystalline tungsten annealed at 1350°C as mentioned in this paper, where atomic force microscopy images were taken in the same area for each groove after different annealing times.
Abstract: Grain-boundary grooving has been studied on polished surfaces of polycrystalline tungsten annealed at 1350°C. Atomic force microscopy images were taken in the same area for each groove after different annealing times. Secondary oscillations next to the main groove maxima (predicted for grooving by surface diffusion) were observed, to our knowledge for the first time. The agreement between experimental and calculated groove profiles (using the surface diffusion model of Mullins (1957, J. appl. Phys., 28, 333)) improved when grain-boundary fluxes were introduced.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the magnetic and structural changes occurring at the two steps of the crystallization process of Fe73.5Si13.5B9Cu1Nb1X2 (X = Zr, Nb, Mo and V) alloys.
Abstract: Thermomagnetic measurements have been used to study the magnetic and structural changes occurring at the two steps of the crystallization process of Fe73.5Si13.5B9Cu1Nb1X2 (X = Zr, Nb, Mo and V) alloys. Alloying raises the thermal stability of the amorphous phase against nanocrystallization in the order V < Mo < Nb < Zr and some differences in the final crystalline phases are found. The Curie temperature of the amorphous phase increases (about 15K) during structural relaxation. In the course of nanocrystallization a further increase of about 30K in the Curie temperature of the amorphous intergranular is observed for samples with X = Zr, Nb and Mo, but only of about 15K for samples containing V. The observed increase in the Curie temperature of the Fe-Si phase between the end of the first crystallization process and the end of the second crystallization process is associated with a reduction in the Si content, in agreement with X-ray diffraction results.

Journal ArticleDOI
TL;DR: The structure of an Al-Ni-Co decagonal quasicrystal (called the S1-type superstructure) has been studied by atomic-scale observations of electron microscopy as discussed by the authors.
Abstract: The structure of an Al-Ni-Co decagonal quasicrystal (called the S1-type superstructure), which shows diffraction patterns with superlattice reflections, has been studied by atomic-scale observations of electron microscopy. The structure of the decagonal quasicrystal can be characterized as an ordered arrangement of two kinds of atom columnar cluster with different directions of pentagonal symmetry. A fundamental lattice, which is constructed by connecting all the atom clusters, shows a pentagonal quasiperiodic lattice with a bond length of about 2 nm. The pentagonal lattice is divided into two superlattices, which are constructed by connecting atom clusters with the same directions of pentagonal symmetry, with a bond length of 2

Journal ArticleDOI
TL;DR: In this article, electron microscopy observations of the film surface and of cross-sections reveal that dewetting occurs only if a nickel oxide layer forms at the silver-nickel interface, as a result of oxygen diffusion through the silver film.
Abstract: High-temperature annealing in air of thick crystalline silver films deposited on high-purity nickel foils promotes solid-state dewetting, whereas no hole through the film is produced when annealing under high purity argon. Scanning electron microscopy observations of the film surface and of cross-sections reveal that dewetting occurs only if a nickel oxide layer forms at the silver-nickel interface, as a result of oxygen diffusion through the silver film. The main dewetting mechanism over short times (1h 1120K in air) is observed to be the condensation, at the silver-nickel oxide interface, of vacancies into voids which grow towards the free surface of the silver film.