Contribution To Thermal Expansion Research Articles

Dual-Wave ZnO Film Ultrasonic Transducers for Temperature and Stress Measurements.

ZnO film ultrasonic transducers for temperature and stress measurements with dual-mode wave excitation (longitudinal and shear) were deposited using the reactive RF magnetron sputtering technique on Si and stainless steel substrates and construction steel bolts. It was found that the position in the substrate plane had a significant effect on the structure and ultrasonic performance of the transducers. The transducers deposited at the center of the deposition zone demonstrated a straight columnar structure with a c-axis parallel to the substrate normal and the generation of longitudinal waves. The transducers deposited at the edge of the deposition zone demonstrated inclined columnar structures and the generation of dominant shear or longitudinal shear waves. Transducers deposited on the bolts with dual-wave excitation were used to study the effects of high temperatures in the range from 25 to 525 °C and tensile stress in the range from 0 to 268 MPa on ultrasonic response. Dependencies between changes in the relative time of flight and temperature or axial stress were obtained. The dependencies can be described by second-order functions of temperature and stress. An analysis of the contributions of thermal expansion, strain, and the speed of sound to changes in the time of flight was performed. At high temperatures, a decrease in the signal amplitude was observed due to the decreasing resistivity of the transducer. The ZnO ultrasonic transducers can be used up to temperatures of ~500 °C.

Phonon Thermal Transport in UO_{2} via Self-Consistent Perturbation Theory.

Computing thermal transport from first-principles in UO_{2} is complicated due to the challenges associated with Mott physics. Here, we use irreducible derivative approaches to compute the cubic and quartic phonon interactions in UO_{2} from first principles, and we perform enhanced thermal transport computations by evaluating the phonon Green's function via self-consistent diagrammatic perturbation theory. Our predicted phonon lifetimes at T=600 K agree well with our inelastic neutron scattering measurements across the entire Brillouin zone, and our thermal conductivity predictions agree well with previous measurements. Both the changes due to thermal expansion and self-consistent contributions are nontrivial at high temperatures, though the effects tend to cancel, and interband transitions yield a substantial contribution.

Thermal and magnetoelastic properties of the van der Waals ferromagnet Fe3−δGeTe2 : Anisotropic spontaneous magnetostriction and ferromagnetic magnon excitations

By determining the lattice parameters as a function of temperature of the hexagonal van der Waals ferromagnet Fe2.92(1)Ge1.02(3)Te2 we obtain the temperature dependence of the spontaneous in-plane magnetostriction in the ferromagnetic and the linear thermal expansion coefficients in the paramagnetic state. The spontaneous magnetostriction is clearly seen in the temperature dependence of the in-plane lattice parameter a(T), but less well pronounced perpendicular to the planes along c. Below TC the spontaneous magnetostriction follows a power law M(T)3/2 of the magnetization and leads to an expansion of the hexagonal layers. Extrapolating to T→ 0 K we obtain a spontaneous in-plane saturation magnetostriction of λsp,a(T→0)≈−220×10−6. In the paramagnetic state the linear thermal expansion coefficients amount to 13.9(1)×10−6K−1 and to 23.2(2)×10−6K−1 for the in-plane and out-of-plane direction, respectively, indicating a linear volume thermal expansion coefficient of 50.8(4)×10−6K−1 which we use to estimate the volume thermal expansion contribution to the heat capacity determined at constant pressure. A Sommerfeld-type linear term in the low-temperature heat capacities can be quantitatively ascribed to two-dimensional (2D) ferromagnetic magnon excitations. Published by the American Physical Society 2024

Carrier–phonon interaction and anharmonic phonon decay in ZnS thin film studied by resonance Raman scattering

AbstractResonance Raman scattering was carried out on polycrystalline zinc sulfide (ZnS) thin film. The resonance Raman spectra revealed strong carrier–phonon interaction where longitudinal optical phonon (LO) with overtones up to the fourth order and its combination phonons with transverse acoustic (TA) phonons were observed, namely, nLO + mTA (where n and m are integers). The resonance Raman scattering processes were well explained within the framework of the cascade scattering model. The wavenumber of the LO phonon with increased temperature was dominated by anharmonic phonon decay. Detailed experimental data fittings showed that thermal expansion contribution to the nLO phonon overtones differed from the fundamental LO phonon due to the involvement of the scattering of the LO phonons at the Brillion zone edge. The negative value of the mode‐Grüneisen parameter for the TA phonon slowed down the wavenumber shift of the combination nLO + mTA phonon modes with increasing temperature compared to the nLO phonons. The anharmonic phonon decay of combination nLO + mTA phonons were dominated by anharmonic phonon decay of nLO phonons.

Quadratic versus linear models to estimate the mean scattering spacing as a function of temperature in ex-vivo tissue

Previous works have shown the feasibility of temperature estimation during ultrasonic therapy using pulse-echo diagnostic ultrasound. These methods are based on the measurement of thermally induced changes in backscattered RF echoes due to thermal expansion and changes in ultrasonic velocity. They assume a joint contribution of these two parameters and a linear dependence with temperature. In this work, the contributions of velocity changes and thermal expansion to the evolution of the mean scatterer spacing of ex vivo bovine skeletal muscle tissue samples were decoupled. This was achieved by employing an experimental setup which allows measuring the absolute velocity value, using the through-transmission technique in a direct transmission configuration. The mean-scatterer spacing was estimated from spectral analysis of the backscattered signals obtained in pulse-echo mode. We propose a quadratic model of the thermal expansion coefficient to fit the evolution of the mean-scatterer spacing with temperature. The temperature increase estimated by the linear model, in the range of 29.5–47 °C, presents a percentage error (mean square error) of 11 %, while for the quadratic model the error is 4.8 %.

Constitutive equations for thermo-elasto-plastic metallic materials undergoing large temperature variations

In the present work, a framework for the development of constitutive models for metallic materials in a thermomechanical context is proposed. Such a framework provides some guidelines to deal with processes involving large temperature variations, which is typical of manufacturing operations or severe service situations. The proposed framework relies on the additive decomposition of the logarithmic strain tensor to include the contributions of elasticity, plasticity and thermal expansion to deformation. Also, the classical internal variable concept is used to describe the history effects (e.g., hardening and recovery) associated with the development of plasticity. Particular attention is given to considering the impact of temperature on thermophysical properties. For the purpose of illustration, the proposed framework is used to build a constitutive model for polycrystalline copper. The resulting set of constitutive equations allows investigating the thermomechanical behavior of this specific material for some simple deformation histories. The corresponding results are finally used to evaluate the temperature-dependence of common thermophysical properties. The importance of the different heat sources that contribute to the heat diffusion equation is also discussed.

Optical properties of AgxCu1–xI alloy thin films

We report on the excitonic transition energy E0 and spin–orbit split-off energy Δ0 of γ-AgxCu1–xI alloy thin films studied by using reflectivity measurements at temperatures between 20 K and 290 K. The observed bowing behavior of the E0 transition as a function of the alloy composition is explained based on first-principles band structure calculations in terms of different physical and chemical contributions within the description of ordered alloys. The spin–orbit coupling is found to increase from a value of 640 meV for CuI to approximately 790 meV for AgI. Furthermore, we show that the temperature-dependent bandgap shift between 20 K and 290 K decreases with increasing Ag-content from 25 meV for CuI to 6 meV for AgI. We attribute this behavior mostly to changes in the contribution of thermal lattice expansion to the bandgap shift.

Process-based estimate of global-mean sea-level changes in the Common Era

Abstract. Although the global-mean sea level (GMSL) rose over the twentieth century with a positive contribution from thermosteric and barystatic (ice sheets and glaciers) sources, the driving processes of GMSL changes during the pre-industrial Common Era (PCE; 1–1850 CE) are largely unknown. Here, the contributions of glacier and ice sheet mass variations and ocean thermal expansion to GMSL in the Common Era (1–2000 CE) are estimated based on simulations with different physical models. Although the twentieth century global-mean thermosteric sea level (GMTSL) is mainly associated with temperature variations in the upper 700 m (86 % in reconstruction and 74 ± 8 % in model), GMTSL in the PCE is equally controlled by temperature changes below 700 m. The GMTSL does not vary more than ±2 cm during the PCE. GMSL contributions from the Antarctic and Greenland ice sheets tend to cancel each other out during the PCE owing to the differing response of the two ice sheets to atmospheric conditions. The uncertainties of sea-level contribution from land-ice mass variations are large, especially over the first millennium. Despite underestimating the twentieth century model GMSL, there is a general agreement between the model and proxy-based GMSL reconstructions in the CE. Although the uncertainties remain large over the first millennium, model simulations point to glaciers as the dominant source of GMSL changes during the PCE.

Effect of deuteration on the barocaloric properties of complex vanadates (NH4)3VOxF6−x (x: 1, 2)

We report on the analysis of intensive and extensive barocaloric properties and their sensitivity to deuteration of complex oxyfluorides (NH4)3VOxF6−x (x: 1, 2) undergoing a similar sequence of structural phase transitions. Due to the high sensitivity to hydrostatic pressure and the strong disordering of six-coordinated anionic fluoro-oxygen species, (NH4)3VO2F4 and (ND4)3VO2F4 crystals demonstrate the highest barocaloric efficiency at low pressure, p = 0.1 GPa, during the phase transition from the initial cubic phase: barocaloric coefficients reach large values |ΔSBCE|/p ≈ 400 J/(kg K GPa) and ΔTAD/p ≈ 80 K/GPa. Anionic, [VOF5] → [VO2F4], and cationic, [ND4] → [NH4] substitutions are accompanied by a decrease in the disorder of structural units in the cubic phase, which leads to a decrease in changes in entropy and temperature under pressure. The contribution of thermal expansion of the crystal lattice to the total intensive and extensive barocaloric effects is large and amounts to about 30–40%.

Contribution of thermal expansion on gas adsorption to coal sorption-induced swelling

Adsorption of gases such as methane and carbon dioxide in coal is an exothermic process. Under isentropic conditions (fully insulated condition), the ejected heat results in an additive transient thermal expansion in addition to the sorption-induced swelling. The magnitude of thermal expansion and its feedback on methane adsorption remains ill-defined. We explore this response in high volatile bituminous coal by measuring the exothermal release of heat (integral heat of adsorption) via temperature change during methane adsorption and use these calorimetric data to define the thermodynamic response. These data link thermal expansion directly to adsorption and adsorption swelling. The results show that methane adsorption can lead to the elevation of coal temperature by more than 10 °C. The resulting thermal expansion is consistent with adsorption swelling and related to adsorption capacity and pressure. The decline of surface potential energy resulting from adsorption is usually considered to be the reason for adsorption swelling. However, the results of this study show that thermal expansion due to the heat of adsorption may account for up to 35% of the total adsorption strain under ideal isentropic conditions. In non-isentropic laboratory experiments of adsorption swelling (approaching isothermal conditions), thermal expansion during adsorption cannot be measured accurately due to the rapid heat loss. However, in-situ within coalbed reservoirs, reduced heat dissipation may retain thermal deformation for longer and impact short-term permeability evolution.

Thermal processes contributions to the temperature dependence of the energy gap in dilute bismuth III-V alloys

This paper presents a methodological analysis of the gap energy temperature dependence of GaAsBi, GaSbBi, InSbBi, and InAsBi. The temperature dependence of the gap energy in these alloys has been analyzed by considering separately the contributions due to thermal expansion and electron-phonon interaction based on Varshni, Viňa, and Pässler models. For the thermal expansion contribution, we use a term that explicitly takes into account the temperature variation of the thermal expansion coefficient and the pressure variation of the bandgap. The thermal expansion coefficient of semi-metallic compounds X–Bi (X = Ga or In) and III-V-Bi alloys is estimated on the basis of the physical properties of material atomic constitution. The overview of different results indicates the competition between the two processes in the temperature sensitivity of bandgap energy referring to a critical temperature of about100K. The coexistence of Bi and Sb has a particular influence on the fitting physical parameters issuing from different fits.

Experimental study of the performance of a 32 m deep excavation in the suburbs of Paris

Fort d'Issy-Vanves-Clamart metro station is a 32 m deep excavation part of the new subway line 15 of the Grand Paris Express project. The performance of the support system is assessed through a wide monitoring programme covering wall displacements, bending moments, strut loads, ground settlements and earth pressure. Classical instrumentation was set up in redundancy to consolidate field measurements. Advanced devices were used to provide accurate measurement data, in particular fibre optic was installed along the retaining wall with total pressure and pore-water pressure cells placed at the soil–wall interface at four in-depth locations. The aim of the present paper is to provide a full description of deep excavation behaviour through a complete monitoring system. Bending moments captured with fibre optic are more accurate than those derived from inclinometers. An analysis methodology is proposed to address the temperature effect on strut load measurements in order to separate the thermal expansion contribution on the strut loading from the excavation process contribution. The stress redistribution behind the wall was observed with the lateral earth pressure increase of top cells while excavating deep levels. The comprehensive field measurements provided in this paper can supply further back-analysis to improve numerical modelling prediction.

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis

Thermal expansion characterization of thin films using harmonic Joule heating combined with atomic force microscopy

Characterizing coefficient of thermal expansion (CTE) for thin films is often challenging as the experimental signal is asymptotically reduced with decreasing thickness. Here, we present a method to measure CTE of thin films by locally confining an active thermal volume using harmonic Joule heating. Importantly, we simultaneously probe the harmonic expansion at atomic-scale thickness resolution using atomic force microscopy. We use a differential method on lithographically patterned thin films to isolate the topographical and harmonic thermal expansion contributions of the thin films. Based on the measured thermal expansion, we use numerical simulations to extract the CTE considering the stress induced from neighboring layers. We demonstrate our method using poly(methyl methacrylate), and the measured CTE of 55.0 × 10−6 ± 6.4 × 10−6 K−1 shows agreement with previous works. This work paves an avenue for investigating thermo-mechanical characterization in numerous materials systems, including both organic and inorganic media.

Low-temperature photoluminescence study of SnV centers in HPHT diamond

Here we report on the study of temperature shift and broadening of the zero phonon line (ZPL) of SnV center in HPHT microcrystalline diamond in the temperature range of 80-300 K. To separate contributions of lattice thermal expansion and electron-phonon coupling, the study of the pressure effect on the ZPL was conducted. A strong nonlinearity observed in the electron-phonon part of the ZPL temperature shift appeared to be in good agreement with well-known polynomial law ∆E(T) = cT^2-dT^4 and, therefore, can be related to the effect of the strong softening of elastic springs.

Is the online global mean sea level information reliable

The purpose of the work is to assess the reliability of satellite altimeter global mean sea level information through consistency, with other products such as ocean temperatures from thermometers or relative mean sea level records from tidal gauges, and stability of the proposed time series. The satellite altimeter global mean sea level is a mostly computational product. The result is unstable, as characterised by significant changes for the past results introduced in subsequent reconstructions. The result is conflicting with the measurements of ocean temperature, which indicates a smaller thermal expansion contribution. The result also is conflicting with the tide gauge records indicating local sea level stability.

A global mean sea surface temperature dataset for the Last Interglacial (129–116 ka) and contribution of thermal expansion to sea level change

Abstract. A valuable analogue for assessing Earth's sensitivity to warming is the Last Interglacial (LIG; 129–116 ka), when global temperatures (0 to +2 ∘C) and mean sea level (+6 to 11 m) were higher than today. The direct contribution of warmer conditions to global sea level (thermosteric) is uncertain. We report here a global network of LIG sea surface temperatures (SST) obtained from various published temperature proxies (e.g. faunal and floral plankton assemblages, Mg ∕ Ca ratios of calcareous organisms, and alkenone U37K′). We summarize the current limitations of SST reconstructions for the LIG and the spatial temperature features of a naturally warmer world. Because of local δ18O seawater changes, uncertainty in the age models of marine cores, and differences in sampling resolution and/or sedimentation rates, the reconstructions are restricted to mean conditions. To avoid bias towards individual LIG SSTs based on only a single (and potentially erroneous) measurement or a single interpolated data point, here we report average values across the entire LIG. Each site reconstruction is given as an anomaly relative to 1981–2010, corrected for ocean drift, and where available seasonal estimates are provided (189 annual, 99 December–February, and 92 June–August records). To investigate the sensitivity of the reconstruction to high temperatures, we also report maximum values during the first 5 millennia of the LIG (129–124 ka). We find mean global annual SST anomalies of 0.2 ± 0.1 ∘C averaged across the LIG and an early maximum peak of 0.9 ± 0.1 ∘C, respectively. The global dataset provides a remarkably coherent pattern of higher SST increases at polar latitudes than in the tropics (demonstrating the polar amplification of surface temperatures during the LIG), with comparable estimates between different proxies. Polewards of 45∘ latitude, we observe annual SST anomalies averaged across the full LIG of > 0.8 ± 0.3 ∘C in both hemispheres with an early maximum peak of > 2.1 ± 0.3 ∘C. Using the reconstructed SSTs suggests a mean LIG global thermosteric sea level rise of 0.08 ± 0.1 m and a peak contribution of 0.39 ± 0.1 m, respectively (assuming warming penetrated to 2000 m depth). The data provide an important natural baseline for a warmer world, constraining the contributions of Greenland and Antarctic ice sheets to global sea level during a geographically widespread expression of high sea level, and can be used to test the next inter-comparison of models for projecting future climate change. The dataset described in this paper, including summary temperature and thermosteric sea level reconstructions, is available at https://doi.org/10.1594/PANGAEA.904381 (Turney et al., 2019).

Structural stability of Sc3CrO6: A Raman spectroscopic study

AbstractStructural stability of the mixed rare earth‐transition metal oxide Sc3CrO6 (space group ) is investigated at high pressures using Raman spectroscopy up to 23.8 GPa, at ambient temperature. Results indicate that the compound transforms reversibly to a lower symmetry phase above 18 GPa. Lattice dynamical calculations carried out using a shell model were used to obtain the bulk modulus and to estimate mode Grüneisen parameters from Raman spectroscopic data. From the nature of changes in the vibrational spectra and from the trends in iso‐structural compounds, we speculate the high pressure phase to be a monoclinic phase. On the other hand, temperature dependent Raman scattering studies in the temperature range 77–1,273 K, indicate disappearance of a few vibrational modes indicating increase in symmetry. From the pressure and temperature dependence of the Raman modes, using calculated bulk modulus and thermal expansion coefficient, anharmonicity of the modes is estimated. It is found that anharmonicity due to phonon–phonon decay is more dominant and the contribution of thermal expansion is small for all of the Raman modes.

Thermodynamic stability and vibrational anharmonicity of black phosphorene—beyond quasi-harmonic analysis

Thermodynamic stability and vibrational anharmonicity of single layer black phosphorene (SLBP) are studied using a spectral energy density (SED) method. At finite temperatures, SLBP sheet undergoes structural deformation due to the formation of thermally excited ripples. Thermal stability of deformed SLBP sheet is analyzed by computing finite temperature phonon dispersion, which shows that SLBP sheet is thermodynamically stable and survives the crumpling transition. To analyze the vibrational anharmonicity, temperature evolution of all zone center optic phonon modes are extracted, including experimentally forbidden IR and Raman active modes. Mode resolved phonon spectra exhibits red-shift in mode frequencies with temperature. The strong anharmonic phonon–phonon coupling is the predominant reason for the observed red-shift of phonon modes, the contribution of thermal expansion is marginal. Further, temperature sensitivity of all optic modes are analyzed by computing their first order temperature co-efficient (χ), and it can be expressed as B 2g > > > > B 1g > & B 2u > B 1u for Raman and IR active modes, respectively. The quasi-harmonic χ values are much smaller than the SED and experimental values; which substantiate that quasi-harmonic methods are inadequate, and a full anharmonic analysis is essential to explain structure and dynamics of SLBP at finite temperatures.

Temperature dependence of Raman scattering in GeSn films

AbstractTemperature dependence of Raman scattering from Ge0.95Sn0.05 and Ge0.92Sn0.08 films, grown on Ge (001) substrates by low temperature molecular beam epitaxy, was studied over the temperature range of 90 to 850 K. Nonlinear temperature dependencies in the Raman shift of Ge‐Ge and Ge‐Sn modes have been observed. Although they could be well described by an empirical formula, much different values were found in first‐order temperature coefficient of the Raman shift for the Ge‐Ge mode in bulk Ge, the Ge0.95Sn0.05, and Ge0.92Sn0.08 films, being 1.7, 2.4, and 2.7 × 10−2 cm−1/K, respectively. Two factors, phonon–phonon coupling and thermal expansion, contribute to the temperature dependence of Raman shift. Detailed analysis shows that the thermal expansion contribution increases slightly with the Sn content, whereas the phonon–phonon coupling contribution increases markedly with the Sn content. In other words, the anharmonic decay process is much enhanced by the alloy perturbation in GeSn alloys. In addition, an abrupt change was observed at temperature of 650 K in Raman shift and linewidth of Ge‐Ge mode for the Ge0.92Sn0.08 film, which is caused by Sn segregation, concomitant lattice relaxation, and crystallization as well.