Thermal Expansion Behavior Research Articles

Effect of Aggregation Structure on Thermal Expansion Behavior of Polyimide Films with Different Thickness

Effect of Aggregation Structure on Thermal Expansion Behavior of Polyimide Films with Different Thickness

Structural, electronic, mechanical and thermodynamic properties of antiperovskites Ti3InX (X=C and N) ceramics: A first-principles study

The mechanical and thermodynamic properties of Ti3InX (X = C and N) ceramics are investigated by the first-principles calculations. The structural and mechanical parameters are in good agreement with the available theoretical and experimental results. The results show that Ti3InX ceramics are thermodynamics stable. The stiffness and hardness of Ti3InC ceramics are higher than those of Ti3InN ceramics, but its strength is weaker than that of Ti3InN ceramics at 0K. Ti3InC and Ti3InN ceramics belong to brittle phase and ductile phase, respectively. Ti3InC and Ti3InN ceramics exhibit normal thermal expansion behavior at 0–1830K and 0–1640K, respectively, and belong to medium expansion materials and high expansion materials, respectively. The Grüneisen constants of Ti3InC and Ti3InN ceramics are 1.49–1.67 and 1.49–1.88, respectively. The thermal conductivity of Ti3InN ceramics is obviously lower than that of Ti3InC ceramics. The adsorption energy of O on Ti3InC(100) surface is lower than that on Ti3InN(100) surface, indicating that Ti3InC(100) surface is more sensitive to oxygen. Meanwhile, the melting temperature, hardness and Debye temperature of Ti3InX ceramics are also estimated.

Suppression of phase-transition temperature in aluminium indium tungstate and aluminium indium molybdate

Aluminium indium tungstate (AlInW3O12) and aluminium indium molybdate (Al0.84In1.16Mo3O12) were synthesized by non-hydrolytic sol–gel chemistry, and their crystal structures, phase transition and thermal expansion behavior were studied using variable-temperature synchrotron powder diffraction. AlInW3O12 adopts an orthorhombic phase above 260 K and gradually transitions to a monoclinic polymorph below this temperature. Al0.84In1.16Mo3O12 also shows a gradual transition between the monoclinic and orthorhombic structures between 330 and 445 K. Both materials display much lower phase-transition temperatures than predicted on the basis of the parent compounds and Vegard's law. This suppression is attributed to the large size difference between Al3+ and In3+. Interestingly, both samples display positive thermal expansion along all unit-cell axes instead of the typically observed negative expansion of orthorhombic A 2 M 3O12 compositions.

Flower-like Sc2Mo3O12 nanosheet clusters: Synthesis, thermal expansion and photocatalytic properties

In this work, Sc2Mo3O12 has been synthesized via one-pot hydrothermal reaction. The effects of process conditions on the crystal structure, morphology, photocatalytic activity and negative thermal expansion (NTE) behaviors of flower-like Sc2Mo3O12 were systematically investigated. Results indicate that orthorhombic flower-like Sc2Mo3O12 assembled by nano-size flaky crystal grains can be synthesized by one-pot hydrothermal reaction at a temperature as low as 120 °C for 2 h. The hydrothermal reaction temperature and time have no obvious effects on the crystal structure and morphology. However, the photocatalytic property of synthesized Sc2Mo3O12 is sensitive to the above parameters. The sample synthesized at 200 °C for 2 h shows the best photocatalytic degradation of methyl orange, and the degradation rate is 73.32% in 2 h 1The coefficient of thermal expansion (CTE) of Sc2Mo3O12 is −1.99 × 10−6 °C−1 in 50–500 °C tested using TMA. The high-temperature XRD analysis reveals that Sc2Mo3O12 exhibits anisotropic NTE and the intrinsic CTE is measured to be −2.09 × 10−6 °C−1 in 25–800 °C.

Grain size, coefficient of thermal expansion and corrosion behavior of eggshell and rice husk ash reinforced composite material

PurposeThe purpose of this study to find an alternate method to minimize waste i.e., eggshell and rice husk ash. In this paper, eggshell (ES) and rice husk ash (RHA) particles are used as reinforcements for examining their effect on the coefficient of thermal expansion (CTE), grain size (GS) and corrosion behavior for developed composite material.Design/methodology/approachIn this investigation, 5 Wt.% each of ES and RHA reinforcement particles have been introduced. To investigate the microstructures of the developed composite material, scanning electron microscope was used. Physical and mechanical properties of composite material are tensile strength and hardness that have been examined.FindingsThe result of this paper shows that number of grains per square inch for composition Al/5% ES/5% RHA composite was found to be 1,243. Minimum value of the volume CTE was found to be 6.67 × 10–6/°C for Al/5% ES/5% RHA composite. The distribution of hard phases of ES particles in metal matrix is responsible for improvements in tensile strength and hardness. These findings demonstrated that using carbonized ES as reinforcement provides superior mechanical and physical properties than using uncarbonized ES particles.Originality/valueThere are several articles examining the impact of varying Wt.% of carbonized ES and rice husk reinforcement on the microstructures and mechanical characteristics of metal composites. CTE, GS and corrosion behavior are among of the features that are examined in this paper.

Investigating negative thermal expansion property of decahedral Sc2Mo3O12 prepared via hydrothermal method

Orthorhombic Sc2Mo3O12 with decahedral structure have been prepared via hydrothermal method. The phase evolution, morphology and negative thermal expansion (NTE) behavior of the decahedral Sc2Mo3O12 were investigated using XRD, SEM, TMA and high-temperature XRD. XRD and SEM analyses indicate that orthorhombic Sc2Mo3O12 particles with decahedral structure were obtained after annealing at 800 °C. The decahedral Sc2Mo3O12 particles are uniform and regular with a size of about 20 μm × 20 μm × 5 μm. Decahedral Sc2Mo3O12 shows stable NTE. TMA analysis shows the coefficient of thermal expansion (CTE) of decahedral Sc2Mo3O12 is −4.12 × 10−6 K−1 in 25–700 °C. High-temperature XRD analysis reveals that it displays anisotropic NTE at the same temperature range. The axial CTEs of decahedral Sc2Mo3O12 are αa = −4.37 × 10−6 K−1, αb = 3.61 × 10−6 K−1 and αc = −2.96 × 10−6 K−1, respectively. The linear CTE is −1.22 × 10−6 K−1.

Thermal and mechanical properties of the clathrate-II Na24Si136

Thermal expansion, lattice dynamics, heat capacity, compressibility, and pressure stability of the intermetallic clathrate ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$ have been investigated by a combination of first-principles calculations and experimentation. Direct comparison of the properties of ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$ with those of the low-density elemental modification ${\mathrm{Si}}_{136}$ provide insight into the effects of filling the silicon clathrate framework cages with Na on these properties. Calculations of the phonon dispersion only yield sensible results if the Na atoms in the large cages of the structure are displaced from the cage centers, but the exact nature of off-centering is difficult to elucidate conclusively. Pronounced peaks in the calculated phonon density of states for ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$, absent for ${\mathrm{Si}}_{136}$, reflect the presence of low-energy vibrational modes associated with the guest atoms, in agreement with prior inelastic neutron-scattering experiments and reflected in marked temperature dependence of the guest atom atomic displacement parameters determined by single-crystal x-ray diffraction. The bulk modulus is only weakly influenced by filling the Si framework cages with Na, whereas the phase stability under pressure is significantly enhanced. The room-temperature linear coefficient of thermal expansion (CTE) is nearly a factor of 3 greater for ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$ compared to ${\mathrm{Si}}_{136}$. Negative thermal expansion (NTE), observed in ${\mathrm{Si}}_{136}$ below 100 K, is noticeably absent in ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$. In contrast to ${\mathrm{Si}}_{136}$, the thermal expansion behavior in ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$ is relatively well described by the conventional Gr\"uneisen-Debye model in the temperature range of 10--700 K. First-principles calculations in the quasiharmonic approximation correctly predict an increase in high-temperature CTE with Na loading, although the increase is less than observed in experiment. The calculations also fail to capture the absence of NTE in ${\mathrm{Na}}_{24}{\mathrm{Si}}_{136}$, perhaps due to anharmonic effects and/or inadequateness of the ordered structural model.

Effects of Nb and o Contents on the Negative Linear Thermal Expansion Behaviors of Cold Rolled Ti-34Nb Alloys

In this study, the effects of Nb and O contents on the negative thermal expansion behaviors including the coefficient of negative thermal expansion and matensite (α) stability of cold rolled (CR) Ti-34Nb alloys was investigated by optical microscopy, X-ray diffraction and Thermomechanical analysis. Results show that texture strength of CR-Ti-xNb-xO alloys is related to β stability, the addition of Nb and O (β stabilizers) enhances the texture strength. XRD results indicate that Nb and O inhibit the formation of α. The coefficient of negative thermal expansion of CR-Ti-xNb-xO alloys decrease with the increase of Nb and O contents. Moreover, cyclic thermal expansion results reveal that Nb and O promote the decomposition of α.

Thermal expansion behaviour of Invar 36 alloy parts fabricated by wire-arc additive manufacturing

Invar 36 alloy is of high interest in various industrial sectors, due to its reduced thermal expansion properties. This study aims to validate Wire-Arc Additive Manufacturing (WAAM) technology as a valid method for manufacturing aerospace tooling in Invar 36. The main novelty and the objective of this work is to study the properties of Invar deposited by WAAM technology and to provide guidelines for the manufacture of parts using this technology. To do so, the thermal expansion behaviour of Invar specimens manufactured using Gas Metal Arc Welding (GMAW)-based WAAM technology and Plasma Arc Welding (PAW)-based WAAM technology is analyzed for subsequent comparison with the values obtained from the laminated Invar sample used as the reference specimen. A wall is manufactured with each technology, for comparative purposes, from which specimens were extracted for the dilatometry test and metallographic analysis. The results of these analyses show the advantages of GMAW technology for the manufacture of Invar alloy parts, as it presents the same thermal expansion behaviour as the laminated reference material with less presence of precipitates and no macrostructural failures such as pores, cracks and lacks of fusion. Furthermore, to conclude, an aeronautical tooling that has been manufactured within this work demonstrated the potential of this technology to manufacture specialized aeronautical parts.

Phase evolution and thermal stability of novel high-entropy (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si2 ceramics

Owing to the high melting points and high-temperature stability, transition-metal disilicides are potential components for aerospace, automotive, and industrial engineering applications. However, unwanted oxidation known as PEST oxidation severely limits their application owing to the formation of volatile transition metal oxides, especially in the temperature range of 500–1000 °C. To overcome this problem, a new class of high-entropy disilicides, (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si2, was selected by first-principles calculations and then successfully fabricated using a hot-pressing sintering technique. Furthermore, the phase evolution, thermal expansion behavior, thermal conductivity, and oxidation behavior were systematically investigated. Compared with MoSi2, (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si2 possessed a lower thermal conductivity (10.9–14.7 W·m−1·K−1) at 25–1000 °C, higher thermal expansion coefficients (8.6 ± 1.3–6 K–1) at 50–1200 °C, and especially an excellent thermal stability at 500–1000 °C owing to slow diffusion and selective oxidation. This work provides a strong foundation for the synthesis and application of high-entropy disilicides.

Abrupt change from moderate positive to colossal negative thermal expansion caused by imidazolate composite formation

This work describes temperature-induced crystallization processes and reaction mechanisms occurring in the borohydride-imidazolate system. In the course of thermal evolution, crystal structures of two novel bimetallic imidazolates AMnIm3 (A = Na, K) were solved using synchrotron radiation powder diffraction data. Both the alkali metal cation and the Mn cations exhibit distorted octahedral coordination while each imidazolate is surrounded by two alkali metal and two manganese atoms. Extensive study of the thermal expansion behaviour revealed that the expansion of the bimetallic imidazolates does not proceed uniformly over the entire temperature range but rather abruptly changes from a colossal negative to a moderate positive volume expansion. Such behaviour is caused by the coherent intergrowth of the coexisting phases which form a composite, a positive lattice mismatch and a tensile strain during the coexistence of NaMIm3 (M = Mg and Mn) and NaIm or HT-NaIm. Such coherent coalescence of two materials opens the possibility for targeted design of zero thermal expansion materials.Graphical abstractCrystal structures of AMnIm3 (A = Na, K) were determined. Coherently intergrown NaMIm3/NaIm (M = Mg, Mn) present colossal negative thermal expansion.

Predicting the thermal expansion of body-centred cubic (BCC) high entropy alloys in the Mo–Nb–Ta–Ti–W system

In this study, the thermal expansion behaviour of equiatomic alloys in the Mo–Nb–Ta–Ti–W system is studied to provide a predictive method to assess the behaviour of this and other high entropy alloy systems. The simulations used are based on first principles density functional perturbation theory and the quasi-harmonic approximation. Calculations have been used to predict the stability and phonon properties of increasingly complex alloys in the Mo–Nb–Ta–Ti–W system and their thermal expansion coefficients have been predicted. These are benchmarked against rule-of-mixtures predictions and experimental observations, where available. We have shown that atomic-scale modelling techniques can be used to reliably predict the thermal expansion of a range of body-centred cubic high entropy alloys and concentrated solid solutions.

Molecular Motion and Ligand Stacking Influence Thermal Expansion Behavior and Argentophilic Forces in Silver Coordination Complexes

We designed a series of metal–organic solids using ligands with similar molecular structures that were expected to afford coordination complexes with similar solid-state structures. The metal component is silver(I) p-toluenesulfonate, and the ligands differ in their ability to undergo dynamic molecular motion. Although the ligands are similar in their molecular structure, the metal complexes exhibit different solid-state structures because of differences in π-stacking arrangements and the presence or lack of Ag···Ag interactions. The coordination units (ligand-Ag-ligand) in each complex respond differently to temperature changes, which results in thermal expansion behaviors ranging from negative to zero to positive within the series. Two unique complexes were obtained with the azo-containing ligand, and preparation of each complex in bulk was controlled by synthetic conditions. Two polymorphs were obtained with the olefin-containing ligand, and both complexes undergo dynamic molecular motion, although the supramolecular structures differed dramatically. Overall, we show that simple modifications to the ligand structure can significantly affect solid-state structure, crystal form, and subsequent thermal expansion behavior.

Experimental investigation of lattice thermal expansion and specific heat capacity of C15–Cr2Zr Laves phase intermetallic compound by HTXRD and DSC

The lattice thermal expansion and specific heat capacity of the C15–Cr2Zr Laves phase intermetallic compound were investigated using high temperature X-ray diffraction (HTXRD) and differential scanning calorimetry (DSC). All these alloys were prepared by arc melting. Through various heat treatments, the intermetallic compound Cr2Zr with both C14/C36–Cr2Zr and cubic C15–Cr2Zr Laves phase structure was obtained from these ingots. Room temperature XRD profile and scanning electron microscope (SEM) along with energy-dispersive X-ray (EDX) experiments on 1573 K/8h homogenized samples have confirmed the homogeneity and C15 (Fd-3m) crystal structure of Cr2Zr. The lattice parameters and relative phase fraction of the constituent phases were evaluated by using Rietveld refinement. The lattice thermal expansion behaviour of the compound was investigated in the temperature range 298 K–1073 K, and the result shows that its unit cell parameters increased exponentially when the temperature increased. The average thermal expansion coefficients were found to be αai = 1.03 × 10−5 K−1 and αvi = 3.08 × 10−5 K−1. The specific heat capacity of the Laves phase Cr2Zr has been measured by using heat-flux DSC by employing the classical three-step method and is being reported for the first time. The heat capacity data obtained in this study have been compared with the theoretical model using quasi-harmonic Debye Grüneisen formalism in the temperature range 0–860 K and shown the various contributions to total heat capacity. The measured heat capacity data was used to obtain enthalpy increment as a function of temperature, which was effectively modelled by first principles based quasi-harmonic approximation and revealed different contributions to total enthalpy. To the best of our knowledge, this is the first experimental report on the thermal expansion and specific heat capacity of C15–Cr2Zr. A comprehensive set of thermodynamic parameters for C15–Cr2Zr has been established using a combination of measurement and modelling.

Novel approach in analyzing phase transitions in Na0.5Bi0.5TiO3—Comparison with 0.95Na0.5Bi0.5TiO3–0.05CaTiO3

Recently, Na0.5Bi0.5TiO3 and its solid solutions are receiving intensive study as one of the most perspective lead-free ferroelectrics. Not only physical properties, but also the structure and nature of phase transitions of these compositions are of great interest, as their previous studies contain many uncertainties. In the present research, Na0.5Bi0.5TiO3 and 0.95Na0.5Bi0.5TiO3–0.05CaTiO3 solid solutions were thoroughly studied focusing on the elastic and thermal expansion characteristics, accompanying the obtained results by x-ray diffraction, scanning electron microscopy, differential calorimetry, and second harmonic generation measurements. Temperature-frequency dependences of dielectric permittivity were observed to be similar for both compositions. In spite of this, the experimentally obtained temperature dependences of thermal expansion and Young's modulus in Na0.5Bi0.5TiO3 and 0.95Na0.5Bi0.5TiO3–0.05CaTiO3 reveal unambiguous differences in the temperature range of the observed or expected (as in the case of Na0.5Bi0.5TiO3) phase transitions. X-ray diffraction patterns are fitted using Pnma symmetry. This allows us to distinguish the temperature regions with different behaviors of lattice parameters, which correlate with the observed behavior of thermal expansion and Young's modulus. A reduction in the intensity of second optical harmonic was observed upon increasing the temperature in the whole studied temperature range. This encourages us to reconsider the mechanism responsible for the temperature dependence of dielectric permittivity.

Sintering and thermal expansion behaviors of glass and glass–YSZ composites as self‐repairable seals for SOFC

AbstractGlass and glass–ceramics are used as sealants in solid oxide fuel cell (SOFC) because their thermophysical properties can be tailored to meet the stringent requirements of the SOFC stack. The processing, sintering, and thermal expansion behaviors of self‐healing and non‐crystallizing glass and glass containing 10%–30 wt.% non‐reacting yttria‐stabilized zirconia (YSZ) are studied. The addition of inert YSZ to glass significantly retarded the sintering behavior. Thermal expansion behaviors of glass and glass–YSZ are also measured to study the role of YSZ addition on the glass transition, softening point, and coefficient of thermal expansion (CTE). It is shown that the densification is controlled by the viscous sintering mechanism, in which the addition of YSZ increased the effective viscosity of the glass–YSZ as evident from higher glass transition and softening temperatures and decreased CTE. These results demonstrated that the addition of YSZ to glass is promising for achieving optimum thermophysical properties useful as seals for SOFC.

Concurrent enhancement of dimensional stability and thermal conductivity of thermoplastic polyamide 12T/Boron nitride composites by constructing oriented structure

Excellent thermal management property and high-temperature dimensional stability are very important for the materials applied in the electronic devices. In this study, high temperature resistant PA12T was applied as the matrix, and PA12T/BN composites with oriented structure were fabricated by the injection molding method. Morphology, thermal conductivity, thermal expansion property and mechanical properties of the composite were systematically investigated. Results demonstrate that when the content of BN is 40 wt%, the in-plane thermal conductivity and thermal expansion coefficient of the composites are 6.5 W/(m·K) and 36 ppm/°C, respectively, which are 4 times higher and 80% lower than those along the through-plane direction. Meanwhile, the thermal expansion behavior and mechanism of the composite with oriented filler structure are well revealed by finite element analysis, and the simulated results will provide important guidance for the design and application of the composite. Furthermore, by using the PA12T/BN composite with oriented structure as the substrate of printed circuit board, temperature gradient as well as thermal stress inside the device can be well controlled. Therefore, the PA12T/BN composite has great potential in the application as the substrate or packaging materials of electronic devices.

The Effects of Heat Treatment on Tensile and Thermal Expansion Behavior of Laser Powder-Bed Fusion Invar36

The Effects of Heat Treatment on Tensile and Thermal Expansion Behavior of Laser Powder-Bed Fusion Invar36

The effect of interface reaction on the thermal and mechanical properties of Mn3.2Zn0.5Sn0.3N/Al composites

The salient feature of low-expansion metal matrix composites is their dimensional stability. Due to the limitation of the performance of the reinforcement, the current low-expansion metal matrix composite materials cannot achieve both low expansion and high mechanical strength at the same time. With its extremely negative thermal expansion behavior and metallic characteristics, the anti-perovskite manganese nitrogen compound can be used as an ideal thermal expansion inhibitor to prepare high mechanical strength low-expansion composite materials. In the present work, fully-dense Mn3.2Zn0.5Sn0.3N/Al composites with low thermal expansion and high strength have been successfully fabricated by pressure infiltration. The effects of fabricating temperature on the microstructure, thermal expansion and mechanical properties of the Mn3.2Zn0.5Sn0.3N/Al composites have been discussed. Several interfacial reactions were caused by the high fabrication temperature (750 °C and 800 °C). Lower fabrication temperature (700 °C) was used to obtain a well-controlled interface composite with low thermal expansion (α = 6.5 × 10−6 K−1), high compression strength (481 MPa) and hardness (612 HV). A modified theoretical model has also been used to analyze the thermal expansion behavior of the composites.

Study on the anomalous thermal expansion behavior of cold-rolled Ti-34 Nb alloy and its novel tailoring strategy

In this study, we have investigated the anisotropic in-plane thermal expansion behavior of cold-rolled (CR) Ti-34 Nb alloy and its relationship with temperature by means of continuous heating and cyclic heating-cooling thermal expansion measurement methods. A new microscopic model including the morphology of β and martensite (α″) phases, cold rolled textures and α″ content is proposed, which successfully explains the mechanism of anomalous positive thermal expansion of transverse direction (TD) and negative thermal expansion of rolling direction (RD). It is found that the coefficient of thermal expansion (CTE) of CR-Ti-34 Nb alloy is controlled by α″ content. The instantaneous CTEs of TD and RD (absolute value) both increase first and then decrease (nonlinearity) within the temperature range of anomalous thermal expansion, which is attributed to the increase of α″→β transformation rate (temperature increases by 1 °C) with increasing temperature and the significant decomposition of α″ phase above 260 °C. Moreover, we have excluded the influence of the anisotropy of α″ and internal stress on CTE. According to the abovementioned findings, α″ content is adjusted by pre-aging treatment for the first time, and a wide range of CTEs (−33.0 × 10−6 k−1 ~ 0.4 × 10−6 k−1) are obtained in CR-Ti-34 Nb alloy, including a variety of low (−6.3 × 10−6 k−1, −3.3 × 10−6 k−1) and zero (−1.5 × 10−6 k−1, −0.9 × 10−6 k−1, 0.4 × 10−6 k−1) CTEs with a wide temperature window of 275 °C (25 °C ~ 300 °C).