scholarly journals Anelastic Behavior of Small Dimensioned Aluminum

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 549 ◽  
Author(s):  
Enrico Gianfranco Campari ◽  
Stefano Amadori ◽  
Ennio Bonetti ◽  
Raffaele Berti ◽  
Roberto Montanari
Keyword(s):  
Film Thickness ◽  
Pure Aluminum ◽  
Relaxation Processes ◽  
Specimen Thickness ◽  
Mechanical Spectroscopy ◽  
Free Standing ◽  
Thermally Activated ◽  
Anelastic Behavior ◽  
Vibrating Reed ◽  
Two Peaks

In the present research, results are presented regarding the anelasticity of 99.999% pure aluminum thin films, either deposited on silica substrates or as free-standing sheets obtained by cold rolling. Mechanical Spectroscopy (MS) tests, namely measurements of dynamic modulus and damping vs. temperature, were performed using a vibrating reed analyzer under vacuum. The damping vs. temperature curves of deposited films exhibit two peaks which tend to merge into a single peak as the specimen thickness increases above 0.2 µm. The thermally activated anelastic relaxation processes observed on free-standing films are strongly dependent on film thickness, and below a critical value of about 20 µm two anelastic relaxation peaks can be observed; both their activation energy and relaxation strength are affected by film thickness. These results, together with those observed on bulk specimens, are indicative of specific dislocation and grain boundary dynamics, constrained by the critical values of the ratio of film thickness to grain size.

Mechanical Properties of Free-Standing Porous Anodic Alumina Films

2013 ◽  
Vol 200 ◽  
pp. 54-59
Author(s):  
Eugene Ignashev ◽  
Vladimir Shulgov
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Film Thickness ◽  
Pure Aluminum ◽  
Heat Removal ◽  
Anodic Alumina ◽  
Porous Anodic Alumina ◽  
Free Standing ◽  
Alumina Films ◽  
The One

The flexural strength and microhardness of free-standing anodic alumina films obtained from the one-sided anodization of aluminum are discussed. The films formed of high-pure aluminum were shown to have maximum flexural strength. Even a small amount of impurities decreases the flexural strength of the resulting free-standing anodic alumina films to be associated with their higher defectiveness. The microhardness of thick films of anodic alumina measured on the side of a barrier layer is independent of the film thickness, and this measured on the side of the porous layer decreases continuosly from 5.39-5.88 GPa to 2.94 GPa when the film thickness increases from 50 to 500 μm. The microhardness of thin (<100 μm) films of porous anodic alumina was studied as well. When the samples were immovable in the electrolyte during the anodization, the microhardness of the resulting films is low and varies from 0.93 to 1.86 GPa. When the samples moved in the electrolyte occasionally during the anodization, the microhardness of the resulting films increases to 1.67 – 2.45 GPa. When the samples moved in the electrolyte continuously during the anodization, the microhardness of the resulting films increases to 2.45 - 3.43 GPa. This is associated with the rate of the heat removal from the sample (the oxidation rate) during the anodization. The microhardness of the free-standing porous anodic alumina films formed of low binary alloys of aluminum is lower than one of films formed of high-pure aluminum.

Low Frequency Mechanical Spectroscopy of High Damping Mg-3wt.%Ni Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1761-1764
Author(s):  
Di Qing Wan ◽  
Ya Juan Liu
Keyword(s):  
Grain Boundary ◽  
Low Frequency ◽  
Mechanical Analysis ◽  
Mechanical Spectroscopy ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Ni Alloy ◽  
Dislocation Movement ◽  
Boundary Relaxation ◽  
Two Peaks

The Dynamic Mechanical Analysis (DMA) was applied to investigate the low frequency mechanical spectroscopy response of as-cast high damping Mg-3wt.%Ni hypoeutectic alloys. There are two peaks appearing on the temperature dependent damping spectrum (-100 - 420 °C). The broad peak P1 is overlapped by some small peaks due to the thermally activated dislocation movement, while the P2 peak is a solute grain boundary relaxation peak.

scholarly journals Tetragonal–Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4215
Author(s):  
Roxana E. Patru ◽  
Hamidreza Khassaf ◽  
Iuliana Pasuk ◽  
Mihaela Botea ◽  
Lucian Trupina ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Current Knowledge ◽  
Cubic Phase ◽  
Relaxation Processes ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Low Field ◽  
Conduction Mechanisms ◽  
Temperature Ranges ◽  
Nyquist Plots

The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes’ interfaces.

Strain Analysis in Thin La1−xCaxMnO3 Films by Grazing Incidence X-ray Scattering

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Petit ◽  
L. J. Martinez-Miranda ◽  
M. Rajeswari ◽  
A. Biswas ◽  
D. J. Kang ◽  
...  
Keyword(s):  
Film Thickness ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Strain Analysis ◽  
Grazing Incidence ◽  
Relaxation Processes ◽  
Near Surface ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractWe have performed depth profile analyses of the lattice parameters in epitaxial thin films of La1−xCaxMno3 (LCMO), where x = 0.33 or 0.3, to understand the evolution of strain relaxation processes in these materials. The analyses were done using Grazing Incidence X-ray Scattering (GIXS) on films of different thicnesses on two different substrates, (100) oriented LaAlO3 (LAO), with a lattice mismatch of ∼2% and (110) oriented NGO, with a lattice mismatch of less than 0.1%. Films grown on LAO can exhibit up to three in-plane strained lattice constants, corresponding to a slight orthorhombic distortion of the crystal, as well as near-surface and columnar lattice relaxation. As a function of film thickness, a crossover from a strained film to a mixture of strained and relaxed regions in the film occurs in the range of 700 Å. The structural evolution at this thickness coincides with a change in the resistivity curve near the metalinsulator transition. The in-plane compressive strain has a range of 0.2 – 1.5%, depending on the film thickness for filsm in the range of 400 - 1500 A.

Diffusion Phenomena of the Oxygen and Nitrogen in Niobium by Mechanical Spectroscopy

2010 ◽  
Vol 297-301 ◽  
pp. 1346-1353
Author(s):  
Odila Florêncio ◽  
Paulo Sergio Silva ◽  
Carlos Roberto Grandini
Keyword(s):  
Diffusion Coefficients ◽  
Short Range ◽  
Annealed Sample ◽  
Relaxation Processes ◽  
Torsion Pendulum ◽  
Mechanical Spectroscopy ◽  
Interstitial Diffusion ◽  
Relaxation Parameters ◽  
Low Concentrations ◽  
Diffusion Phenomena

The short-range diffusion phenomenon (Snoek Effect) was investigated by mechanical spectroscopy measurements between 300 K and 650 K, in a polycrystalline niobium sample, containing oxygen and nitrogen, using a torsion pendulum. Experimental spectra of anelastic relaxation were obtained under three conditions: as-received sample; annealed sample and subsequently annealed in an oxygen atmosphere for three hours at 1170 K in partial pressure of 5x10-5mbar. The experimental spectra obtained were decomposed in elementary Debye peaks and the anelastic relaxation processes were identified. With anelastic relaxation parameters and the lattice parameters, the interstitial diffusion coefficients of the oxygen and nitrogen in niobium were calculated for each kind of preferential occupation (octahedral and tetrahedral). The results were compared with the literature data, and confirmed that the best adjustment is for the preferential occupation octahedral model for low concentrations of interstitial solutes, but at higher concentration of oxygen were observed deviations of experimental data for the interstitial diffusion coefficients of oxygen in niobium when compared with the literature data, this could be related to the possible occurrence of a double occupation of interstitial sites in the niobium lattice by oxygen interstitials.

Static Recovery Activation Energy of Pure Aluminum at Room Temperature

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yeh An-Chou ◽  
Chuang Ho-Chieh ◽  
Kuo Chen-Ming
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Pure Aluminum ◽  
Pure Copper ◽  
Tensile Tests ◽  
Engineering Strain ◽  
Static Recovery ◽  
Thermally Activated ◽  
Recovered Strain ◽  
Dislocation Annihilation

Thermally activated energy, which varies linearly with static recovered strain, is calculated from static recovery experiments of pure aluminum initially plastically deformed by strain-rate-controlled tensile tests up to 10% engineering strain at room temperature. The activation energy at the initial static recovery is 20 kJ mol−1, which is much less than that of pure copper and attributed to the dislocation annihilation by glide or cross-slip as well as higher stacking fault energy. Once dislocation annihilation processes are exhausted, more energy is required for subgrains to form and then grow. Eventually the recovered strain is slowed down and gradually saturated.

Magnetic field and dilution effects on the slow relaxation of {Er3} triangle-based arsenotungstate single-molecule magnets

2020 ◽  
Vol 49 (35) ◽  
pp. 12458-12465 ◽  
Author(s):  
Hanhan Chen ◽  
Lin Sun ◽  
Jinpeng Zhang ◽  
Zikang Xiao ◽  
Pengtao Ma ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Molecule ◽  
Magnetic Relaxation ◽  
Slow Relaxation ◽  
Relaxation Processes ◽  
Single Molecule Magnets ◽  
Thermally Activated ◽  
Slow Magnetic Relaxation ◽  
Dilution Effects

Triangular {Er3} cluster containing POM exhibits field-induced two thermally activated relaxation processes. Whereas, the diamagnetic dilution sample indicates slow magnetic relaxation with the QTM being partially suppressed.

scholarly journals Uncovering β-relaxations in amorphous phase-change materials

2020 ◽  
Vol 6 (2) ◽  
pp. eaay6726 ◽  
Author(s):  
Si-Xu Peng ◽  
Yudong Cheng ◽  
Julian Pries ◽  
Shuai Wei ◽  
Hai-Bin Yu ◽  
...  
Keyword(s):  
Phase Change ◽  
Amorphous Phase ◽  
Amorphous Materials ◽  
Phase Change Materials ◽  
Special Kind ◽  
Relaxation Processes ◽  
Glass Transitions ◽  
Mechanical Spectroscopy ◽  
Characteristic Features ◽  
Β Relaxation

Relaxation processes are decisive for many physical properties of amorphous materials. For amorphous phase-change materials (PCMs) used in nonvolatile memories, relaxation processes are, however, difficult to characterize because of the lack of bulk samples. Here, instead of bulk samples, we use powder mechanical spectroscopy for powder samples to detect the prominent excess wings—a characteristic feature of β-relaxations—in a series of amorphous PCMs at temperatures below glass transitions. By contrast, β-relaxations are vanishingly small in amorphous chalcogenides of similar composition, which lack the characteristic features of PCMs. This conclusion is corroborated upon crossing the border from PCMs to non-PCMs, where β-relaxations drop substantially. Such a distinction implies that amorphous PCMs belong to a special kind of covalent glasses whose locally fast atomic motions are preserved even below the glass transitions. These findings suggest a correlation between β-relaxation and crystallization kinetics of PCMs, which have technological implications for phase-change memory functionalities.

Anelastic Behavior due to Interstitial Oxygen in SmBa2Cu3O7-δ

2006 ◽  
Vol 530-531 ◽  
pp. 557-561
Author(s):  
Rubens Maribondo Nascimento ◽  
Juliana Maria de Albuquerque Gimenez ◽  
Carlos Roberto Grandini ◽  
Alfredo Gonçalves da Cunha
Keyword(s):  
Internal Friction ◽  
Oscillation Frequency ◽  
Orthorhombic Phase ◽  
Precise Determination ◽  
Relaxation Processes ◽  
Interstitial Oxygen ◽  
X Ray Diffraction ◽  
Critical Temperatures ◽  
Thermally Activated ◽  
Relaxation Structure

The composite SmBa2Cu3O7-δ (Sm-123), obtained by the substitution of the ion Y for Sm in the very well known and studied YBa2Cu3O7-δ (Y-123), is potentially attractive for better understanding superconductivity mechanisms and for its applications as electronic devices. Sm-123 samples show higher critical temperatures than Y-123 ones do and a larger solubility of Sm in Ba-Cu-O solvent, which makes their growth process faster. When oxygen is present interstitially, it strongly affects the physical properties of the material. The dynamics of oxygen can be investigated by anelastic spectroscopy measurements, a powerful technique for the precise determination of the oscillation frequency and the internal friction when atomic jumps are possible. Anelastic spectroscopy allows determining the elasticity modulus (related to the oscillation frequency) and the elastic energy loss (related to the internal friction) as a function of the temperature. The sample was also investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), and electric resistivity. The results obtained show a thermally activated relaxation structure composed by at least 3 relaxation processes. These processes may be attributed to the jumps of oxygen atoms present of the Cu-O plane in the orthorhombic phase.

Influence of Heat Treatment on the Anelastic Properties of MgB2

2010 ◽  
Vol 660-661 ◽  
pp. 832-836
Author(s):  
Marcos Ribeiro da Silva ◽  
Carlos Roberto Grandini
Keyword(s):  
Heat Treatment ◽  
Grain Boundaries ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Crystalline Lattice ◽  
Relaxation Processes ◽  
Mechanical Spectroscopy ◽  
Critical Temperatures ◽  
Dislocation Movement ◽  
Binary Compounds

The discovery of the superconductivity of MgB2 was of great importance, because this material is one of the few known binary compounds and has one of the highest critical temperatures (39° K). As MgB2 is a granular compound, it is fundamentally important to understand the mechanisms of the interaction of the defects and the crystalline lattice, in addition to the eventual processes involving the grain boundaries that compose the material. In this sense, the mechanical spectroscopy measurements constitute a powerful tool for this study, because through them we can obtain important information about phase transitions, the behavior of interstitial or substitutional elements, dislocations, grain boundaries, diffusion, instabilities, and other imperfections of the lattice. For this paper, the samples were prepared using the PIT method and were characterized by density, X-ray diffraction, scanning electron microscopy, electric resistivity, magnetization, and mechanical spectroscopy. The samples were measured in their as-cast condition and after an ultra-high-vacuum heat treatment. The results showed complex spectra, in which were identified relaxation processes due to dislocation movement, interaction among interstitial elements and dislocations, auto-diffusion, and movement of grain boundaries. Some of these processes disappeared with the heat treatment.

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