Temperature Dependence Of Structural Properties Research Articles

Nonlinear Reduced Order Modeling of Heated Structures with Temperature-Dependent Properties

This paper focuses on extending coupled structural–thermal reduced order modeling approaches for the prediction of the nonlinear geometric response of heated structures to efficiently account for temperature-dependent structural and thermal properties. Structurally, a linear dependence of the elasticity tensor and thermal expansion coefficient is assumed consistently with typical material behavior. The resulting structural reduced order model (ROM) equations exhibit polynomials of the temperature generalized coordinates, the coefficients of which are readily identified. A different strategy is proposed for conductance and capacitance properties which typically depend nonlinearly on temperature. It relies on splitting the temperature generalized coordinates into a small set of dominant ones having a nonlinear effect on the ROM conductances and capacitances and a much larger set affecting them linearly. The inclusion of uncertainty in the structural ROM is also addressed extending earlier work limited to temperature independent properties. These strategies are exemplified on a representative hypersonic vehicle panel undergoing a full mission profile and with aero-thermal–structural coupling. The ROM predictions are observed to be very close to the full finite element ones for the mean model. Moreover, an uncertainty analysis demonstrates the strong sensitivity of the response to the structural model in the strongly nonlinear regions of the trajectory.

Temperature-Dependent Structural and Optoelectronic Properties of the Layered Perovskite 2-Thiophenemethylammonium Lead Iodide.

Improved knowledge of the influence of temperature upon layered perovskites is essential to enable perovskite-based devices to operate over a broad temperature range and to elucidate the impact of structural changes upon the optoelectronic properties. We examined the Ruddlesden-Popper layered perovskite 2-thiophenemethylammonium lead iodide (ThMA2PbI4) and observed a structural phase transition between a high- and a low-temperature phase at 220 K using temperature-dependent X-ray diffraction, UV-visible absorption, and photoluminescence (PL) spectroscopy. The structural phase transition altered the tilt pattern of the inorganic octahedra layer, modifying the absorption and PL spectra. Further, we found a narrow and intense additional PL peak in the low-temperature phase, which we assigned to radiative emission from a defect-bound exciton state. In both phases we determined the thermal expansion coefficient and found values similar to those of cubic 3D perovskites, i.e., larger than those of typical substrates such as glass. These results demonstrate that the organic spacer plays a critical role in controlling the temperature-dependent structural and optoelectronic properties of layered perovskites and suggests more widely that strain management strategies may be needed to fully utilize layered perovskites in device applications.

Thermal performance of MgCl2–NaCl–KCl eutectic salt for the next generation concentrated solar power and correlation between structure and thermophysical properties: Insights from atomic and electronic levels

MgCl2–NaCl–KCl (MgNaK) eutectic salt has emerged as a highly promising candidate for concentrated solar power (CSP), with extensive research conducted in recent years. However, the thermal property data for the MgNaK eutectic salt are still very limited. Here, we present a novel and accurate many-body potential trained by machine learning (ML) for MgNaK eutectic salt (with mole fractions of 45.4 %, 33 %, and 21.6 % respectively), developed using energies and forces extracted from first-principles molecular dynamics calculations (FPMD). The performance of the potential is well tested. We conduct a detailed investigation on the temperature-dependent structural and corresponding thermal properties, analyzing them from both the atomic and electronic perspectives. The introduction of Na+ or K+ ions disrupts the net structure formed by corner-joint and edge-joint MgClx units, thereby affecting the transport properties. The calculated density (ρ) and constant pressure specific heat capacity (CP) exhibit agreement with experimental data within a margin of 2 %. We observe and discuss the typical λ of negative linear temperature correlation, which is similar to other molten alkali chloride salts. Finally, based on the simulated and experimental values, we provide reliable recommendations for the λ and viscosities (η) of MgNaK eutectic salt across its entire operating temperature range.

Temperature-dependent structural and magnetic properties of mechanically alloyed Ni80Co17Mo3 powder mixture

Nanostructured materials containing nickel improve the effectiveness of several applications. This study examines the preparation and characterization of nanostructured Ni80Co17Mo3 alloy powders using high-energy mechanical alloying and subsequent annealing. A 72 h milling process used pure elemental powders to synthesise nanocrystalline FCC-NiCo(Mo) solid solution. The milled powders were then subjected to annealing at different temperatures:300°C, 500°C, and 750°C. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and vibrating sample magnetometry indicated significant changes in the powdered alloy properties. The particles growth occurred as the annealing temperature increased, while the microstrain decreased significantly; 14.30±0.07 nm up to 56.30±0.28 nm and 0.680±0.003% up to 0.180±0.001%, at 25°C and 750°C respectively. SEM analysis revealed differences in particle size and shape as milling progressed. Surprisingly, the milled powdered alloy displayed improved magnetic properties, manifesting significant magnetic susceptibility and enhanced saturation magnetisation, remanent magnetisation, and coercivity within the temperature range of 300°C to 750°C. These findings indicate the development of a consistent and structured state, accompanied by significant crystal growth due to the annealing temperature. This study highlights the great importance of high-energy mechanical milling and subsequent annealing to tune / tailor the characteristics and subsequently investigate the potential utilization of nanostructured Ni-based alloys.

Temperature-Dependent Structural Properties of Nickel and Cobalt Selenite Hydrates as Solar Water Evaporators.

Solar water evaporation offers a promising solution to address global water scarcity, utilizing renewable energy for purification and desalination. Transition-metal selenite hydrates (specifically nickel and cobalt) have shown potential as solar absorbers with high evaporation rates of 1.83 and 2.34 kg∙m-2∙h-1, but the reported discrepancy in evaporation rate deserves further investigation. This investigation aims to clarify their thermal stability for applications and determine the underlying mechanisms responsible for the differences. Nickel and cobalt selenite hydrate compositions were synthesized and investigated via thermogravimetric analysis, X-ray diffraction, and Raman spectroscopy to assess their temperature-induced structural and compositional variations. The results reveal distinct phase transitions and structural alterations under various temperature conditions for these two photothermal materials, providing valuable insights into the factors influencing water transportation and evaporation rates.

Temperature-Dependent Structural and Elastic Properties of CdS, CdSe, and CdTe Compounds Studied by Statistical Moment Method

The statistical moment method has been applied to investigate the temperature effects on the lattice parameters and elastic properties of the zinc-blende CdX (X = S, Se, Te) compounds. The analytical expressions of thermal-induced atomic displacement, lattice constant, elastic moduli (Young’s modulus, bulk modulus and shear modulus) and elastic constants (including C11,C12 and C44) of the zinc-blende compounds have been derived. We have pointed out that the temperature effects on the elastic properties of CdS and CdSe are almost the same. And the elastic quantities of CdS and CdSe are more strongly dependent on temperature than those of CdTe semiconductor. This phenomenon is caused by the weaker coupling force of Cd-Te bonds compared to those of Cd-S and Cd-Se bonds. Furthermore, from the calculated Debye temperatures of CdX (X = S, Se, Te) compounds we conclude that CdS has higher phonon thermal conductivity and is therefore more thermally conductive among the three semiconductor compounds. The calculations of present work can be used as an appropriate reference for the experiments in future.

Temperature-dependent structural and optical properties of Sb-doped SnO2 nanoparticles and their electrochemical analysis for supercapacitor application

Transparent conducting oxides (TCOs) play an important role in advanced energy harvesting and storage systems, as well as cutting-edge display technology.

Thermally processed phase change behavior on the stoichiometric efficacy of quaternary Se77.5-X Te20 Sn2.5 AgX (X = 2.5, 5, 7.5) thin films

Thin films of the quaternary metal chalcogenide have recently gained attention due to their improved electrical, optical, thermal, and structural properties. The structural, thermal, morphological, optical, and electrical properties of Ag-modified novel quaternary Se–Te–Sn–Ag thin film systems are investigated in this paper. Temperature-dependent structural, electrical, and thermoelectric properties are given special attention. From Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA), the Ag content in this composition induces thermal stability and crystalline phase as well as glass phase transitions. High-temperature X-ray diffraction (HTXRD) patterns were used to investigate the temperature-dependent structural phase transition, grain size, lattice strain, and dislocation density. The morphological observations show that Ag concentration promotes the nucleation and growth processes of nanorod structures in as-deposited thin films. Optical characteristics reveal higher IR transparency in thin films and high refractive indexes in the range of 3.22–3.29. The as-deposited thin films resistivity decreases with increasing temperature and silver content. The Hall measurement corroborates the results obtained from the Seebeck measurements, indicating that the samples are n-type. The phase change switching mechanism of phase change devices is still unclear; there are two possible mechanisms: thermal and electronic models. This work proposes thermally processed phase transition behaviors in structural and electrical studies. The result of the above analyses shows that the quaternary Se–Te–Sn–Ag thin film will be a potential candidate for phase change device applications.

Tuneable Plasmonic Resonances Of A Dynamic Thin Film Of Ultrasmall Nanocrystals Modified In the Anti-Galvanic Reduction Process.

Ultrasmall gold nanoparticles (NPs) have revolutionized nanotechnology as they are an excellent starting substrate for the synthesis of organic-inorganic hybrid materials with photonic or energy conversion applications, often with a responsive nature. However, ultrasmall NPs do not sustain plasmonic resonances, preventing their use in plasmon-related applications. In the presented work, we show a method of chemical modification of ultrasmall gold nanoparticles in order to fabricate dynamically controlled plasmonic thin films. For this purpose, we used the Anti-Galvanic Reduction process (AGR) to modify the surface of small gold nanoparticles, inducing plasmonic properties without notable size increases. Au@Ag NPs are then modified with liquid crystal-like organic ligands. The obtained NPs can assemble into densely packed films with long-range order and temperature-dependent structural properties. Namely, we detect two, fully reversible phase transitions between the hexagonal and cubic symmetries. The combination of AGR and organic surface modifications enabled us to demonstrate the possibility of managing plasmonic properties in the thin film of ~2 nm diameter metallic NPs.

Temperature-dependent dielectric measurements and structural properties of barium stannate (BaSnO3)

Cubic perovskite BaSnO3, synthesized by solid-state reaction method, was structurally characterized using temperature-dependent X-ray and Raman spectroscopy studies along with room temperature neutron diffraction analysis. Here, we report the effect of temperature on the structural parameters of BaSnO3 in correlation with dielectric properties. Sample homogeneity and elemental composition were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy methods. The compound maintains cubic symmetry even at high temperatures and exhibits gradual increase in unit cell volume owing to thermal expansion. To understand high temperature phase transition, if any, and capacitance behavior, high temperature dielectric measurements were carried out. High value of dielectric constant was obtained at low frequencies as the temperature was increased, which may be due to the presence of oxygen vacancies or the lone-pair effect.

Structural and thermal properties of Eu2Ga11Sn35

Clathrates have been reported to form in a variety of different structure types; however, inorganic clathrate-I materials with a low-cation concentration have yet to be investigated. Furthermore, tin-based compositions have been much less investigated as compared to silicon or germanium analogs. We report the temperature-dependent structural and thermal properties of single-crystal Eu2Ga11Sn35 revealing the effect of structure and composition on the thermal properties of this low-cation clathrate-I material. Specifically, low-temperature heat capacity, thermal conductivity, and synchrotron single-crystal x-ray diffraction reveal a departure from Debye-like behavior, a glass-like phonon mean-free path for this crystalline material, and a relatively large Grüneisen parameter due to the dominance of low-frequency Einstein modes. Our analyses indicate thermal properties that are a direct result of the structure and composition of this clathrate-I material.

Temperature-dependent structural, mechanical, and thermodynamic properties of B2-phase Ti2AlNb for aerospace applications

Temperature-dependent structural, mechanical, and thermodynamic properties of B2-phase Ti2AlNb for aerospace applications

Heat Transfer and Structural Characteristics of Dissimilar Joints Joining Ti-64 and NiTi via Laser Welding

This study investigates the thermal-stress characteristics of a bi-metallic Ti-6Al-4V-Nitinol butt joints manufactured via laser welding. Particularly, the thermal profile along the weld interface and the deformation profile of the finished welded workpiece. A decoupled transient thermomechanical simulation model was constructed to recreate the welding process. This decoupled thermomechanical simulation model consisted of two transient simulation models. A transient thermal simulation model and a transient structural simulation model, with the thermal history of the transient thermal model being fed into the transient structural model. Both the thermal and structural portions of the model utilized temperature-dependent thermal and structural properties of Ti-6Al-4V and Nitinol. The temperature profile of the transient thermal-stress model aligns with the experimental thermal profile within 5% error. The deformation profile also matches the experimental results within 5% error. This approach to modeling laser welding can stand as a guide to predict both thermal and deformation profiles generated during the laser welding process.

Temperature-dependent structural, thermal, and mechanical properties of Mo-10Nb joints prepared by SPS

Temperature-dependent structural, thermal, and mechanical properties of Mo-10Nb joints prepared by SPS

Temperature-dependent structure and electromechanical properties of Er doped PMN-PT single crystal grown by modified Bridgman technique

In this work, the Er-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal with a large size was successfully grown by the modified Bridgman technique. The temperature dependent phase structure, domain configuration and electromechanical properties of the single crystal with the composition of 2 wt%Er-0.66PMN-0.34PT (Er-0.66PMN-0.34PT) were investigated in detail. For [001]C oriented Er-0.66PMN-0.34PT single crystal, it is found that the room temperature phase structure is the coexistence of rhombohedral (R) and monoclinic (M) phases and M phase is dominated. The piezoelectric constant d33 through the converse piezoelectric effect is about 2410 pC/N. The phase transition from R+M to tetragonal (T) phase begins at 80 ℃ and finishes at 120 ℃. Between 80 ℃ and 120 ℃, the single crystal belongs to the coexistence of R, M and T phases. At 135 ℃, the T phase and polar nanoregions (PNRs) transform into cubic phase and PNRs. The compliance constantss33Dand s33E, longitudinal coupling factor k33 and piezoelectric constant d33 increase by 32%, 77%, 34% and 133%, respectively, with temperature increasing from 22 ℃ to 80 ℃. The ultrahigh increase of d33 is derived from the increase of dielectric constant due to easier polarization rotation and domain wall movement at elevated temperature. Our results will helpful for the study of rare-earth doped relaxor ferroelectric single crystals.

Direct comparison of the electrical, optical, and structural phase transitions of VO2 on ZnO nanostructures

We examined the temperature-dependent electrical, optical, and structural properties of VO2 on ZnO nanorods with different lengths in the temperature range from 30 to 100 °C. ZnO nanorods with a uniform length were grown on Al2O3 substrates using a metal organic chemical vapor deposition, and subsequently, VO2 was ex-situ deposited on ZnO nanorods/Al2O3 templates using a sputtering deposition. The optical properties of the VO2/ZnO nanorods were measured simultaneously with direct current (DC) resistance using the reflectivity of an infrared (IR) laser beam with a wavelength of 790 nm. The local structural properties around V atoms of VO2/ZnO nanorods were simultaneously measured with the DC resistance using x-ray absorption fine structure at the V K edge. Direct comparison of the temperature-dependent resistance, IR reflectivity, and local structure reveals that an optical phase transition first occurs, a structural phase transition follows, and an insulator-to-metal transition finally appears during heating.

Facile strategy to synthesize cesium gold-based bromide perovskites: an integrated experimental and theoretical approach to study temperature-dependent structural and optical properties

Fine control over different phases of gold perovskites by anion exchange chemistry to study their temperature-dependent structural and optical properties.

Effect of varying Bi content on the temperature-dependent mechanical, dielectric, and structural properties of nominal Na1/2Bi1/2TiO3

Na1/2Bi1/2TiO3 (NBT) with varying Bi content has gained significant interest as a potential new material for solid-oxide fuel cells and oxygen separation membranes because of its excellent oxygen-ion conductivity. In this work, the effect of varying Bi content in NBT ceramics of compositions Na1/2BixTiO2.25+1.5x, where x = 0.485–0.510, on the temperature-dependent mechanical and dielectric properties and the crystal structure has been investigated, as these applications expose the components to high thermal and mechanical fields. The effects of Bi variation on phase compositions and structural transitions were systematically investigated by scanning electron microscopy-energy dispersive x-ray analyses and neutron diffraction at room temperature, in situ high-temperature x-ray diffraction, dielectric permittivity, and mechanical measurements. In-depth analysis of the temperature-dependent data shows that the Bi content of the samples does not alter the average crystal structure of the NBT; however, the temperature-dependent behavior of the latter depend on variations in Bi content and the associated oxygen vacancy concentration. This change in phase transition temperature displays a good correlation with the temperature-dependent ferroelastic response and with the Bi content.

Substrate Temperature-Dependent Structural, Optical, and Electrical Properties of Thermochromic VO2(M) Nanostructured Films Grown by a One-Step Pulsed Laser Deposition Process on Smooth Quartz Substrates

Thermochromic M-phase vanadium dioxide VO2(M) films with different morphologies have been grown directly on smooth fused quartz substrates using low deposition rate pulsed laser deposition without posttreatment. When the substrate temperature was increased in the range 450°C–750°C, better (011) texturization of VO2(M) films was observed along with an enhancement of their crystallinity. Morphology evolved from small-grained and densely packed VO2(M) grains at 450°C to less packed micro/nanowires at 750°C. Mechanisms behind the crystallinity/morphology evolution were discussed and correlated with the effect of the temperature on the diffusion of the adatoms as well as on the V5+ valence states content in VO2(M) films. Resistivity measurements as a function of temperature revealed that the insulator-to-metal transition features of VO2(M) films (i.e., transition temperature (TIMT), resistivity variation (ΔR), hysteresis width (ΔH), and transition sharpness (ΔT)) are strongly dependent on the processing temperature. In terms of optical properties, it was found that the open (i.e., porous) structure of the films achieved at high temperature induced an improvement of their luminous transmittance. Simultaneously, the enhancement of the films crystallinity with the temperature resulted in better IR modulation ability. The present contribution provides a one-step process to control the morphology of VO2(M) films grown on smooth quartz substrates for applications as switches, memory devices, and smart windows.

Temperature-dependent structural fluctuation and its effect on the electronic structure and charge transport in hybrid perovskite CH3 NH3 PbI3.

The recently discovered hybrid organic-inorganic perovskites have been suggested for high-performance optoelectronic applications. Owing to the mechanical flexibility of these compounds, they demonstrate structural fluctuation at finite temperatures that have been widely discussed with respect to their optical properties. However, the effect of temperature-induced structural fluctuation is not clear until now, with respect to the equally important charge transport properties. In the present study, through ab initio molecular dynamics simulations of cubic-phase CH3 NH3 PbI3 at different temperatures, the temperature-dependent electronic structure and charge carrier transport properties are examined. Compared with the significant structural fluctuation of organic cations, the structural change of the inorganic framework is minor. In addition, because the band edge states at R point are mainly influenced by the anti-bonding character of the Pb-I bond, CH3 NH3 PbI3 demonstrates relatively small deformation potentials as well as low temperature dependence of band gaps (ΔEg ≈ 50 meV from 330 K to 400 K) and electron-phonon coupling strengths, despite the large structural fluctuation of organic cations. Furthermore, the effective mass of the valence band increases with the increase of temperature. The predicted mobilities of CH3 NH3 PbI3 can reach above 75 cm2 V-1 s-1 near room temperature, exhibiting an appropriate optoelectronic potential, while the temperature dependence is steeper than T-1.5 of the traditional semiconductors because of the enhanced effective masses.