Method Of Mechanical Spectroscopy Research Articles

Investigation of relaxation processes and phase transitions in the silica gel-undecylenic acid system using IR spectra in a wide temperature range

The study of relaxation processes in porous inhomogeneous systems via dielectric and mechanical spectroscopy methods is associated with methodological difficulties. To understand how IR spectroscopy can be used to elucidate the temperature-dependent changes that take place in the undecylenic acid - porous silica gel systems, such as phase transition and relaxation processes, we compare IR spectroscopic data with previously obtained dielectric spectroscopy data for the bulk undecylenic acid and undecylenic acid embedded in silica gel matrices of different pore sizes. We demonstrate that the topological soliton model can be used for both bulk undecylenic acid, and the undecylenic acid in nanoporous silica gel matrices.

Mechanical spectroscopy of metal/polymer composite membranes for hydrogen separation

In the present work, mechanical properties of metal-polymer composite membranes for hydrogen separation have been investigated by tensile test and mechanical spectroscopy methods. The membranes were prepared by high-energy ball milling and subsequent thermal pressing of a powder mixture of polyethylene with 10 wt% hydride-forming intermetallic compound LaNi2.5Co2.4Mn0.1. The membranes were then subjected to activation by long exposure in a hydrogen atmosphere. The static tensile test showed a slight decrease in membrane tensile strength after hydrogen activation that may be explained by intermetallic particle embrittlement. Mechanical spectroscopy study reveals a shift of the internal friction peak of the activated membrane by 22 K towards lower temperatures and a small decrease of the activation energy of polyethylene viscoelastic transformation from 144 kJ/mol to 138 kJ/mol.

Effects of thermomechanical treatment on the microstructure, precipitation strengthening, internal friction, and thermal stability of Al–Er-Yb-Sc alloys with good electrical conductivity

Rare-earth elements improve the mechanical properties of aluminum owing to the formation of the L12-structured nanoprecipitates providing the precipitation strengthening effect. The precipitates type, size, and number density depend on the alloy chemical composition and a thermomechanical treatment regime. It is essential to develop the alloys and treatments, providing a combination of the enhanced mechanical strength and a high level of electrical conductivity. This study investigates the influence of thermomechanical treatments on the microstructure, precipitation strengthening, mechanical properties, and electrical conductivity of Al–Er-Yb-Sc alloys with differing Sc content. An as-cast structure of the alloys studied consists of a supersaturated aluminum solid solution and Al3(Er,Yb) phase particles of eutectic origin with the particle thickness of 50–200 nm. A significant strengthening during post-deformation annealing is achieved by precipitation of L12-Al3(Sc,Er,Yb) phase dispersoids of 4–8 nm in size. The mechanical spectroscopy method is successfully used to understand the precipitation kinetics of the studied alloys in comparison with analogous Al-Yb-Y-Sc alloys. This method is highly sensitive to lattice defects parameters, i.e., recrystallization and precipitation kinetics. High-scandium alloys demonstrate an increase of the hardness and tensile strength and insignificant changes in the internal friction background level during post-deformation annealing of cold-worked samples at 300 °C. The yield strength of the Al–Er-Yb-Sc alloys after post-deformation annealing is 142–231 MPa, elongation-to-failure is 3.6–13.5%, and electrical conductivity is 54.8–60.9% IACS, dependent on scandium content and annealing parameters. The studied alloys exhibit high thermal stability of the tensile properties, which remains unchanged during annealing at 300 °C for 100 h.

Revealing the ultra-low-temperature relaxation peak in a model metallic glass

By systematically investigating the relaxation behavior of a model metallic glass based on the extensive molecular dynamics (MD) simulations combined with the dynamic mechanical spectroscopy method, a pronounced ultra-low temperature peak on the loss modulus spectrum was discovered for the first time in MD simulations. It was found that the relaxation peak occurs at a much lower temperature than the typical temperature for the conventional β relation peak as reported in the literature. According to the atomic displacement analysis, we unravel that the reversible atomic motions, rather than the thermal vibrations or local structural rearrangements, mainly contribute to this relaxation peak. We further identify the atomic level mechanism of this fast relaxation process by characterizing the local geometrical anisotropy. Furthermore, by tracing the dynamic behaviors of these “reversible” atoms, we demonstrate the intrinsic hierarchy of the relaxation modes, which are triggered by atomic vibrations and gradually developed to include the reversible and irreversible atomic movements. Our findings provide an important piece of the puzzle about the holistic picture of the rich relaxation processes in metallic glasses.

Revealing the Low-Temperature Fast Relaxation Peak in a Model Metallic Glass

By systematically investigating the relaxation behavior of a model metallic glass based on the extensive molecular dynamics (MD) simulations combined with the dynamic mechanical spectroscopy method, a pronounced ultra-low temperature peak on the loss modulus spectrum was discovered for the first time in MD simulations. It was found that the relation peak occurs at a much lower temperature than the typical temperature for the conventional β relation peak as reported in the literature. According to the atomic displacement analysis, we unravel that the atomic motions, rather than the thermal vibrations or local structural rearrangements, mainly contribute to this relaxation peak. We further identify the atomic level mechanism of this fast relaxation process by characterizing the local geometrical anisotropy. Furthermore, by tracing the dynamic behaviors of these reversible atoms, we demonstrate the intrinsic hierarchy of the local relaxation modes, which are triggered by atomic vibrations and gradually developed to the and irreversible atomic movements. Our findings shed light on a general picture of the relaxation processes in metallic glasses.

Dislocation mechanisms of low-temperature acoustic relaxation in iron

An integrated approach to the study of the mechanisms of low-temperature dislocation relaxation during low-temperature cyclic deformations of crystalline materials has been developed and tested. The approach is based on the combined use of experimental methods of mechanical spectroscopy in wide frequency-temperature ranges and theoretical methods of statistical and thermoactivation analysis of experimental results. The efficiency of this approach was demonstrated by studying low-temperature relaxation resonances in iron crystals whose dislocation structure was varied by preliminary plastic deformation. In this study, the previous mechanical spectroscopy results for iron in the temperature range of 4 K < T < 150 K at vibrational frequencies of about 1 Hz and 105 Hz were supplemented by a detailed study of the temperature spectra of internal friction and the Young’s modulus of a single-crystal iron plate at intermediate frequencies of about 103 Hz. A two-mode dislocation relaxator model was suggested for interpreting the entire set of experimental results. Its first component is a linear segment of a dislocation line in a first-kind Peierls relief whose relaxation properties are determined by thermal activation of kink pairs. The second component is a chain of geometric kinks capable of thermally activated diffusion movement in a second-kind Peierls relief. Empirical estimates of the energy, force, inertial, and geometric characteristics of both components of such a relaxator have been obtained. This study complements the earlier analysis of the processes of mechanical relaxation in crystals caused by nucleation and movements of kinks on dislocation lines [a review: A. Seeger and C. Wüthrich, Nuovo Cimento B 33, 38 (1976)].

Control of Gelation and Network Properties of Cationically Copolymerized Mono- and Diglycidyl Ethers

The development of low temperature curing systems has become a major objective in thermoset technologies for both environmental and economic reasons. The use of protic and chelating additives have recently been underlined for the control of the cationic ring-opening polymerization of epoxies, a curing mode that is very efficient at temperatures close from the ambient but that can easily runaway. In this paper, we propose to use this strategy to control the kinetics of the cationic copolymerization of a diepoxy monomer (diglycidyl ether of bisphenol A, DGEBA) with a monoepoxy monomer (phenyl glycidyl ether, PGE). The purpose of the study is to tune the cross-link density (νe) in order to control the mechanical properties of the materials. The sol–gel transition was first investigated in details at several frequencies by using the Fourier transform mechanical spectroscopy method (FTMS). We found that the gel time (tgel) and the critical conversion (αgel) can be controlled to a great extent by promoting tran...

Arrhenius activation of Zr65Cu18Ni7Al10 bulk metallic glass in the supercooled liquid region

In the current research, the dynamic mechanical spectrum and compressive deformation of Zr65Cu18Ni7Al10 bulk metallic glass in the supercooled liquid region (SLR) are investigated. The experimental results prove the existence of transition from Newtonian flow to non-Newtonian flow in the metallic glasses. In addition, we found that the characteristic stress σtc, which is obtained by a stretched exponential function based on the normalized viscosity, can be regarded as a transition point from Newtonian to non-Newtonian flow. The correlation between strain rate sensitivity exponent and corresponding strain rate was obtained at a certain temperature. It is noted that the variation of transition strain rate from Newtonian to non-Newtonian flow with different absolute temperatures follows the Arrhenius equation. The activation energy is in good accordance with that using the mechanical spectroscopy method.

Martensitic anelasticity in 40Mn60Cu alloy

The martensite anelasticity effects such as internal friction and the shape memory effect in 40Mn60Cu alloy were studied. The kinetics of spinodal decomposition in the 40Mn60Cu alloy after during aging (400, 440 and 540°C) was studied by the mechanical spectroscopy methods. It is shown that the temperature of the martensitic transformation depends on temperature and time of aging within the metastable miscibility gap. The characteristics of the shape memory effect were determined at different pre-strains. It is shown that the extent of shape recovery K decreases exponentially with the increase of pre-strain (γr=1…5%). This is due to the increase of the proportion of irreversible slip deformation.

МЕТОД МЕХАНИЧЕСКОЙ СПЕКТРОСКОПИИ ПОЛИЭТИЛЕНА ТРУБНЫХ МАРОК

МЕТОД МЕХАНИЧЕСКОЙ СПЕКТРОСКОПИИ ПОЛИЭТИЛЕНА ТРУБНЫХ МАРОК

Applications of Transient Grating Spectroscopy to Radiation Materials Science

The ability to study radiation damage in situ will directly enable the rapid innovation and qualification of materials for nuclear applications by allowing direct observation of the effects of radiation damage accumulation. This is a challenging task, as the measurement technique must be noncontact, nondestructive, rapid, and still allow for online irradiation without interference. Applicable methods of mechanical spectroscopy are surveyed, noting their potential usefulness for characterizing radiation-induced microstructural changes in situ. The transient grating (TG) spectroscopy technique appears most suited for these studies, due to its noncontact, nondestructive nature, its ability to rapidly probe materials to the depth of ion irradiation, and the large number of deconvolvable components extractable from its signal. Work is proposed to separate the individual mechanisms of irradiation damage using in situ and ex situ TG spectroscopy, through a suite of single-effect and integrated experiments.

The Effect of Spinodal Decomposition on Martensitic Transformation and Shape Memory Effect in Mn-Cu Alloys

Mechanical spectroscopy methods and X-ray analysis were used to study the effect of aging in the gap of the spinodal decomposition on the structure and properties (shape memory effect) of the Mn-Cu alloys. It is shown that martensitic transformation and shape memory effect in the Mn40Cu60 alloy has been made possible due to spinodal decomposition of γ-solid solution at aging, so the left boundary of the spinodal decomposition extends to a concentration of 40 at. % Mn.

New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies.

Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively.

Effect of thermal cycling on martensitic γ↔ε-transformation in alloy Fe – 22% Mn – 3% Si

Methods of mechanical spectroscopy and differential scanning calorimetry demonstrate the effect of thermal cycling for a specimen of alloy Fe – 22% Mn – 3% Si through the martensitic transformation range on martensitic transformation parameters: points for the start and end of transformation, amount of thermal hysteresis, and transformation development kinetics.

Study of martensitic transformation in the Fe-22 Mn-3 Si alloy by mechanical spectroscopy

Methods of mechanical spectroscopy (determination of the internal-energy dissipation and the elasticity modulus), X-Ray diffraction, and calorimetry have been used to study the specific features of the reversible martensitic transformation in the Fe—22Mn—3Si alloy (wt %). A detailed study has been given to the specific features of the internal-energy dissipatio n during the direct and reverse martensitic transformations in a wide range of heating rates, frequencies, and deformation amplitudes. Particular emphasis has been placed on multiple thermal cycling of the sample through the martensitic-transformation range and its effect on the martensitic-transformation parameters, such as the transformation start and finish temperatures, the value of the thermal hysteresis, and the transformation kinetics.

A method to study the crack healing process of glassformers

A mechanical spectroscopy method of quantitatively monitoring the healing of stress-induced microcracks in small glass samples is described. Whereas the cracks are generated catastrophically at some unpredictable interval below the glass temperature Tg the healing process proves to be highly reproducible and a characteristic temperature for the crack healing process, the temperature of maximum healing rate Tch coincides with Tg.

High-sensitivity tool for studying phonon related mechanical losses in low loss materials

Fundamental mechanical loss mechanisms exist even in very pure materials, for instance, due to the interactions of excited acoustic waves with thermal phonons. A reduction of these losses in a certain frequency range is desired in high precision instruments like gravitational wave detectors. Systematic analyses of the mechanical losses in those low loss materials are essential for this aim, performed in a highly sensitive experimental set-up. Our novel method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy), is well suited to systematically determine losses at the resonant frequencies of the samples of less than 10-9 in the wide temperature range from 5 to 300 K. A high precision set-up in a specially built cryostat allows contactless excitation and readout of the oscillations of the sample. The experimental set-up and measuring procedure are described. Limitations to our experiment due to external loss mechanisms are analysed. The influence of the suspension system as well as the sample preparation is explained.

Mechanical losses in low loss materials studied by cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy)

Mechanical losses of crystalline silicon and calcium fluoride have been analyzed in the temperature range from 5 to 300 K by our novel mechanical spectroscopy method, cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectrocopy). The focus lies on the interpretation of the measured data according to phonon-phonon interactions and defect induced losses in consideration of the excited mode shape.

Cryogenic resonant acoustic spectroscopy of bulk materials (CRA spectroscopy)

The capability to measure Q factors at cryogenic temperatures enhances the ability to study relaxation processes in solids. Here we present a high-precision cryogenic setup with the ability to measure Q factors of at least 10(9). This level of sensitivity offers new potential for analyzing relaxation processes in solids and for correlating mode shape and relaxation strength. Our improved method of mechanical spectroscopy, cryogenic resonant acoustic spectroscopy of bulk materials, is verified by identifying relaxation processes in low-loss quartz crystals. For the first time, we observe additional damping peaks. The mechanical Q factors of different modes of cylindrical crystalline quartz substrates were measured from 300 down to 6 K. Resonant modes with frequencies between 10 and 325 kHz were excited without contact to the substrates and the ring down of the amplitudes was recorded using an interferometric vibration readout.

Mechanical spectroscopy methods for the quantitative analysis of intergranular glass viscosity in polycrystalline ceramics

Mechanical spectroscopy methods for the analysis of viscous behavior of grain boundaries are described and applied to glass-bonded polycrystalline ceramics. Emphasis is placed on the analysis of a high-temperature peak, which originates from grain-boundary sliding relaxation, with respect to: (i) peak shift with damping frequency change; (ii) peak intensity for a given testing geometry and amount of glassy phase; and, (iii) peak morphology characteristics. According to analyses (i) and (ii), an activation energy for intergranular viscous flow and the magnitude of glass-phase viscosity are quantitatively determined. The morphology of the peak depends on the activation energy for intergranular viscous flow, but it is also affected by the volume fraction of intergranular glass and by the presence of chemical gradients at grain boundaries. In addition microstructural inhomogeneities, such as grain size distribution and grain texture, can affect the peak morphology. Chemical and microstructural inhomogeneities generate spectra of activation energies and relaxation times, respectively. With inherently different characteristics, they both contribute to peak broadening. Internal friction experiments as a function of glass volume fraction and chemical composition experimentally confirmed that the above features are actually represented in the internal friction curve of a ceramic polycrystal as a function of temperature.