Modulus Expansion Research Articles

Thermodynamic properties of LiNiO2, LiCoO2, and LiMnO2 using density-functional theory.

The formation energies of LiCoO2, LiNiO2 and LiMnO2 were calculated using a combination of adequately selected Hess cycles and DFT computations. Several exchange-correlation functionals were tested and PBE for solids (PBEsol) turned out to be the most accurate. The enthalpies of formation at 0 K are -168.0 kJ mol at-1 for LiCoO2, -173.2 kJ mol at-1 for LiNiO2, -209.9 kJ mol at-1 for o-LiMnO2 and -208.8 kJ mol at-1 for r-LiMnO2. In comparison to experimental formation energy data, a difference of 1.6 and 0.01 kJ mol at-1 was obtained for LiCoO2 and LiMnO2, respectively. By contrast, a much larger discrepancy, around 24 kJ mol at-1, was obtained for LiNiO2 and confirmed by using an additional and independent Hess cycle. The influence of slight crystallographic distortions associated with magnetism and/or the Jahn-Teller effect on energy was carefully searched for and taken into account, as well as corrections arising from vibrational contributions. Hence, these results should motivate future measurements of the thermodynamic properties of LiNiO2, which are currently scarce. Vibrational contributions to the structural and energetic properties were computed within the harmonic and the quasi-harmonic approximations. The LiCoO2 heat capacity at constant pressure is in excellent agreement with experimental data, with a difference of only 3.3% at 300 K. In the case of LiNiO2 the difference reaches 17% at 300 K, which could also motivate further investigation. The Cp(T) value for the orthorhombic phase o-LiMnO2, for which no previous data were available, was computed. Structural properties such as specific mass, bulk modulus and coefficient of thermal expansion are presented.

On the rumpling mechanism in nanocrystalline coatings: Improved by reactive magnetron sputtering with oxygen

• The O dopped nanocrystalline coating is prepared by reactive magnetron sputtering. • The doping of O significantly improves the oxidation resistance of the coating. • The surface rumpling behaviors on coatings is retarded by oxygen. Surface rumpling is detrimental to high temperature protective coatings as it shortens their lifetime and leads to adhesion losses and unexpected corrosion degradation. The driving force and mass transport mechanism behind of rumpling remains to be clarified. In the present investigation, we subjected two types of nanocrystalline coating systems to avoid the influence of interdiffusion on rumpling study. One group was an ordinary nanocrystalline coating, and the other group was designed and prepared with trace oxygen by reactive magnetron sputtering. Systematic cyclic oxidation test at 1100 °C was also carried out. Results show the ordinary nanocrystalline coating oxidized rapidly, which leads to the fast consumption of Al and the acceleration of phase transition in the coating. Meanwhile, severe surface rumpling is observed due to the stress release of nanocrystals through plastic deformation. Besides, the reactive doping of oxygen can significantly reduce the consumption process of Al in nanocrystalline coating. The rumpling is controlled due to the improvement of coefficient of thermal expansion and Young's modulus of the coating. Thereafter, the cyclic oxidation resistance is improved.

Effects of pile and soil properties on thermally induced mechanical responses of energy piles

Energy piles, having the dual roles of exploiting geothermal energy and providing structural stability, are creating large worldwide interest. This paper aims to provide knowledge on the potential effects of pile and soil properties on the thermally induced mechanical behavior of energy piles. It presents the results from in-situ experimental investigations conducted on an energy pile. Three-dimensional numerical models were developed and validated to evaluate the behavior of energy piles equipped with various U-pipe configurations from the viewpoint of energy efficiency and structural safety. The results indicated that although increasing the pipe length could improve the thermal exchange capabilities of energy piles, it introduced more significant mechanical effects on the piles, which should be considered during the design. Moreover, parametric studies were performed to explore the potential effects of the soil thermal expansion and elastic modulus on the thermomechanical response of energy piles. The comparative analysis showed that the soil thermal expansion after heating would reduce the thermal compressive stress induced in the energy piles. The soil thermal expansion effects were time-variable and became more significant with the operating time of the energy piles. The thermal stress increased and approached the theoretical maximum value as the soil elastic modulus increased.

Thermal expansion and Young's modulus evolution of fused silica and crystalline silica‐containing materials

AbstractFused silica bricks (FSBs) with exceptional thermal shock resistance are frequently used to repair localized damage in coke ovens and are hold promising candidates for the efficient construction of new coke ovens. To maximize their utilization, the effects of thermal history on the thermal expansion and Young's modulus evolution of FSBs were investigated in comparison to crystalline silica bricks (CSBs). Due to the gradual phase transformation of fused silica into cristobalite, the thermal expansion of FSBs are sensitive to the thermal cycle; both silica materials exhibit an increase in thermal expansion after five cycles at 1200°C, whereas the thermal expansion of CSBs is five times greater than that of FSBs. When the testing temperature is less than 1000°C, Young's modulus of CSBs is more sensitive to the thermal history, which is caused by phase transformation‐induced microcracks. This sensitivity reduces when the testing temperature is 1200°C, as microcracks healed by liquid phase as well as the softening of residual glass phase. By contrast, when the testing temperature is 1200°C, Young's modulus of fused silica specimens is sensitive to the thermal history owing to the microcracks caused by the gradual phase transformation of fused silica to cristobalite.

Mechanical properties of mixed modified oxide glasses

Mixed modifier effect refers to the nonlinear variations of glass properties when mixing different types of modifier ions. The effect plays an important role since it can be applied to design glasses with controlled properties and it is also related to the raw materials selection. In this review, we will summarize the recent important progress on the mixed modifier effect in oxide glasses. The effect has been found in various properties, but we mainly focus on glass transition temperature ( T g ), hardness ( H ), elastic modulus ( E ), and coefficient of thermal expansion ( α ) since these properties are critical in glass manufacture and products performance. Different properties exhibit unique features and many theories are proposed to account for the effect. The compositional dependence of these properties is reviewed and the theories proposed to explain this effect are discussed. Moreover, we suggest some future directions for the further work on the mixed modifier effect. • The progress on the mixed modifier effect in oxide glasses has been reviewed. • Various theories to account for the effects have been summarized. • Future directions for the further work in this field have been suggested.

Rancidity-induced protein oxidation affects the interfacial dynamic properties and the emulsion rheological behavior of rice bran protein

To improve the practical application of rice bran protein (RBP) prepared from rice bran (RB) with different degrees of rancidity as a stabilizer in emulsion, fresh RB was stored for 0, 1, 5, 7, and 10 d (temperature of 25 °C, relative humidity of 85%) to investigate the effects of RB rancidity on the interfacial dynamic properties and structures of RBP, rheological properties of the O/W emulsion prepared by RBP. RB rancidity-induced moderate oxidation of RBP (prepared from RB storage for 1 d) reduced the particle size (24.36–18.17 nm) and Zeta potential (−13.57 ∼ −14.97 mV) of RBP, while excessive RBP oxidation (prepared from RB storage for 5–10 d) increased the particle size (37.84–68.06 nm) and Zeta potential (−13.40 ∼ −10.6 mV) of RBP. In addition, moderate protein oxidation increased the interfacial pressure, diffusion rate, interfacial expansion modulus of RBP, and emulsion viscoelasticity, while excessive protein oxidation improved the permeability rate and rearrangement rate of RBP. Overall, this study demonstrated that moderate protein oxidation had positive effects on interfacial properties (interfacial dynamic properties and dilatational rheology of interfacial layers) of RBP, which could provide a theoretical basis for mediating the stability and rheology of RBP emulsions by adjusting the degrees of RB rancidity. • Rancidity-induced RBP oxidation changed the K diff , K p and K r of RBP. • RBP oxidation changed the viscoelasticity of interfacial adsorption layers. • RBP oxidation changed the viscosity, G′ and G″ of RBP emulsions.

Building block design for composite metamaterial with an ultra-low thermal expansion and high-level specific modulus

The metamaterials with unique thermal expansions are attracting increasing interest in a broad range of applications. Despite numerous metamaterials with unique thermal expansions have been demonstrated, none of them is without inherent laminations, either in terms of their limited design freedom, the immutability feature of the specimen once fabricated, and the low specific modulus. Inspired by the building block (e.g., Lego toys), this paper introduces a generalized design strategy for reconfigurable mechanical metamaterials with unique thermal/mechanical performances. The triangle metamaterial constructed by the specific collection of structural building blocks shows the capability of this design for achieving an unprecedented low effective CTE (i.e., 0.07 ppm/°C), high-level lightweight (i.e., 0.549 g/cm3), and a remarkable relative specific modulus (i.e., 41385.55 kN∙mm/kg). More specifically, the assembly method with well-designed connectors presented here promises the mechanical robustness and reconfigurable feature of metamaterials. Additionally, the thermal–mechanical factor Φ is adopted for accurately characterizing compatibility of thermal deformation and mechanical properties of the metamaterial. Finally, the comparison of the absolute value of CTE and the comprehensive thermal–mechanical property serves a quantitative comparison of the mechanical metamaterials demonstrated here to the previous reported results, indicating the capability of our designs for their practical engineering applications.

Temperature Responsive PBT Bicomponent Fibers for Dynamic Thermal Insulation.

Thermoresponsive self-crimping polybutylene terephtlate (PBT)-based bicomponent fibers were fabricated by melt-spinning to serve as primary constituents for textiles, such as nonwoven battings, for an adaptive single insulting layer. Due to the intrinsically mismatching modulus and coefficient of thermal expansion (CTE), the fibers curl or straighten with temperature, similar to the concept of Timoshenko’s bimetallic strip. Maximizing the curvature is driven by an optimum of fiber diameter, overall CTE, and fiber moduli, which are all affected by drawing ratio and, consequently, fiber’s microstructure. A draw ratio of 2.33 yielded the best combination of mechanical and thermal properties; it was observed that increasing the draw ratio does not necessarily increase the self-crimping behavior. Tests performed on non-woven battings of these fibers exhibited comparable thermoreponsive behaviors to polypropylene-based thermoresponsive fibers from previous studies in the −20 °C to 20 °C temperature range, which has potential for wearable insulations for both commercial and defense sectors alike.

Thermal deformation and stress of alkali-activated slag concrete under semi-adiabatic condition: Experiments and simulations

This study investigates the deformation of free and stress of restrained alkali-activated slag concrete (AASC), respectively, under semi-adiabatic condition. The concrete shows first thermal expansion, which is compensated soon by autogenous shrinkage. The subsequent cooling down of the concrete aggravates shrinkage and development of tensile stress, which eventually results in early cracking of the concrete. The results show that semi-adiabatic condition is severer for AASC than isothermal condition in view of cracking tendency. The evolutions of coefficient of thermal expansion (CTE) and elastic modulus are measured by elaborated experimental methods. Simulating the deformation of AASC by summing thermal and autogenous deformations appears feasible. With the consideration of relaxation, the stress evolution in restrained AASC can be predicted pretty well by the model used in this paper. This study provides insights into the thermal deformation and cracking tendency of AASC in practical circumstances.

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.

Improvement of the comprehensive properties of polymer templates via a novel dry blending method for fabricating OTFT electrodes

Polymer template is widely used in the fabrication of organic thin-film transistor (OTFT) electrodes. However, the mechanical/thermal properties of the polymer template are generally poor owing to their low Young’s modulus (E) and high coefficient of thermal expansion (CTE), resulting in the formation of massive wrinkles and cracks on the OTFT electrodes, as well as the electrodes incomplete transfer, which seriously affects the fabrication of the electrodes. Here, a novel dry blending method is described in which SiO2 nanoparticles are filled into a grooved silicon template, followed by permeation of polydimethylsiloxane (PDMS) into the SiO2 nanoparticle gaps. The SiO2 nanoparticles in the groove are extracted by curing and peeling off PDMS, affording a PDMS/SiO2 composite template with a nanoparticle content of 83.8 wt% and good transparency. The composite template has a Young’s modulus of 16.58 MPa and a CTE of 96 ppm/°C, which constitutes an increase of 91.56 % and a reduction of 69.23 %, respectively, compared with the original PDMS template. Finally, the high performance OTFT electrodes were fabricated using the composite template with good comprehensive properties.

Expanded vermiculite and polyvinyl acetate composite as gap filler for wooden objects conservation

• Gap fillers are composites used to fill the gaps caused by deterioration processes in wooden objects. • A gap filler composite of expanded vermiculite and polyvinyl acetate was studied for the conservation of wooden objects. • Vermiculite is an inert micaceous mineral. It can also act as a pH buffer. • The mechanical properties, shrinkage and expansion with varying relative humidity of the gap filler indicated the potential use of expanded vermiculite for the conservation of wooden objects stored indoors. Gap fillers are composites used to fill the gaps caused by deterioration processes in wooden objects. The materials commonly used in gap fillers are acrylic, vinyl, cellulosic, and epoxy resins mixed with fillers such as sawdust, glass microspheres, and paper. In this work, a gap filler composite of expanded vermiculite and polyvinyl acetate was studied for the conservation of wooden objects. Expanded vermiculite is a stable material that meets some criteria for gap filler composites. This study evaluated the properties of the proposed gap filler by comparing it to a model gap filler containing sawdust as a filler. The particle size distribution of the filler materials was measured, and the pH, modulus of elasticity, yield point, and expansion and contraction behavior as a function of the relative humidity of the air were measured. The proposed composite showed comparable properties to those of the sawdust and polyvinyl acetate composite; in some tests, the properties were better than those of the model. These data suggest potential use of expanded vermiculite as a filler in gap filler for the conservation of wooden objects.

A micromechanical framework for thermo-elastic properties of multiphase cementitious composites with different saturation

• A micromechanical framework is devised for thermo-elastic properties of CC . • The framework accurately predicts the thermo-elastic properties of CC. • Increasing saturation degree improves the thermo-elastic properties of CC. • CTE monotonically increases with the increase of porosity. Abstract: Understanding of the thermo-elastic properties of cementitious composites (CC) with different saturation degrees is of great importance for the design of CC durability in various hydraulic environments. This work devises a generic micromechanical framework to predict the effective thermo-elastic properties involving the elastic modulus, thermal conductivity, and coefficient of thermal expansion (CTE) of multiphase CC with different saturation degrees, composed of spheroidal aggregates and their surrounding interfacial transition zones (ITZs), water-pores, air-pores and homogeneous bulk paste at a microscopic scale. Comparisons against experimental measurements and theoretical bounds suggest that the micromechanical framework is a reliable means to accurately estimate the effective thermo-elastic properties of multiphase CC under different saturation conditions. The proposed model sheds light on the quantitative effects of saturation degree, porosity, pore shape, and aggregate shape and volume fraction, and ITZ thickness on the thermo-elastic properties of CC, which can provide insights for the design of “tailor-to-demand” thermo-elasticity performance of CC.

Board Level Reliability of Automotive Grade WLCSP for Radar Applications

Wafer-Level Chip Scale Packages (WLCSPs) are becoming commonplace in the industry due to their small form factor. Applications include industrial and automotive which demand high reliability performance. Additionally, WLCSPs may be superior in some implementations to other package options for RF performance in the mmWave spectrum, which is desired for automotive radar application. But board level reliability can be a challenge for some WLCSP package due to CTE mismatch between Si and PCB. Variety of factors including PCB materials, sphere alloys, and board level underfills can influence the board level reliability of WLCSP packages. In this study the industry’s first auto grade 1 capable large WLCSP package. (~ 72 mm2 body size, 18x15 BGA array, 0.5 mm pitch) is presented. Board level underfill application was utilized to achieve automotive grade board level reliability. Underfills are typically selected based on thermomechanical properties of unaged materials. An understanding of the evolution of underfill material properties under thermal aging is important for selecting a stable material capable of meeting the reliability requirements.
 This study evaluates board level underfills and edge bond materials in the form of stand-alone samples and applied to a large daisy-chain WLCSP. The underfilled daisy-chain WLCSPs and the stand-alone samples are placed in a ‑40/125C air cycling chamber (1 cycle/hour). Glass transition temperature (Tg), elastic modulus (E), and coefficient of thermal expansion (CTE) are measured using Dynamic Mechanical Analysis (DMA) and Thermomechanical Analysis (TMA) on the stand-alone samples at various intervals to monitor the evolution of material properties. Simultaneously, the underfilled daisy chain WLCSPs are monitored electrically using an event detector. The combination of material property measurements and cycles to electrical failure can be used to correlate underfill material properties and WLCSP board-level reliability. The results of this study can provide material property guidance for underfill selection.

Physical mechanism interpretation of polycrystalline metals’ yield strength via a data-driven method: A novel Hall–Petch relationship

The Hall–Petch relationship σy=σ0+kyd−0.5 is widely used to describe the relationship between yield strength and grain size of polycrystalline metals, and the material constants σ0 and ky fitted by experimental data are interpreted as lattice friction resistance and coefficient of grain boundary resistance, respectively. The frequent deviations from the Hall–Petch relationship between σy and d in coarser or finer grains, as well as the physical essence of σ0 and ky, have always been the focus of material scientists. In this study, intrinsic factors of the fitted constants σ0 and ky in the traditional Hall–Petch relationship are mined via a data-driven machine learning method, which reveals that the key physical quantities affecting σ0 are valence electron distance (S), cohesive energy (W), and coefficient of linear thermal expansion (lt); meanwhile, the key physical quantities affecting ky are grain boundary interface energy (γ), Young's modulus (E) and coefficient of linear thermal expansion (lt). Then, a novel Hall–Petch model σy=79W/(S3lt)+1.2γE/ltd−0.5 with satisfying prediction accuracy is constructed by symbolic regression methods. There is no experimental fitting constant term in the novel model, which can directly predict the yield strength of polycrystalline metals by key physical quantities. The novel Hall–Petch model has an excellent generalization ability and can be extended to the correlation calculation between the composition, grain structure and mechanical properties of single-phase alloys, which provides a theoretical method for the trans-scale calculation of metallic materials.

Thermal Properties of Solids Under Varying Conditions of Pressure and Temperature

A simple theoretical method is developed to study the properties of solids under varying conditions of pressure and temperature. We have considered different types of materials viz. metallic, hydrides, sulphides and coesites. Unit cell volume, coefficient of volume thermal expansion and bulk modulus have been investigated under varying conditions of pressures and temperatures. The results obtained are compared with the available experimental data. A good agreement between theory and experiment demonstrates the suitability of the model used. It is realized that due to simplicity and applicability, it may be used to a large number of materials and may be of current interest to the researchers working in thehigh pressure and temperature science.

Polyunsaturated fatty acids differentially modulate membrane elasticity in membranes containing high cholesterol

Membrane composition is important for the function of membrane proteins including ion channels and membrane-embedded receptors. One class of proteins that are especially sensitive to membrane composition are mechanosensitive channels, which activate in response to changes in membrane tension. Recently, polyunsaturated fatty acids (PUFAs) were demonstrated to alter mechanosensitive channel behavior, but the mechanism for these observations remains unknown. Mechanosensitive channel behavior is expected to be dependent on membrane mechanical properties such as the membrane area expansion modulus (Ka), which measures the extent to which membrane tension exerts a change in bilayer area.

Effects of Cr/Ni ratio on physical properties of Cr-Mn-Fe-Co-Ni high-entropy alloys

Physical properties of ten single-phase FCC CrxMn20Fe20Co20Ni40-x high-entropy alloys (HEAs) were investigated for 0 ≤ x ≤ 26 at%. The lattice parameters of these alloys were nearly independent of composition while solidus temperatures increased linearly by ∼30 K as x increased from 0 to 26 at.%. For x ≥ 10 at.%, the alloys are not ferromagnetic between 100 and 673 K and the temperature dependencies of their coefficients of thermal expansion and elastic moduli are independent of composition. Magnetic transitions and associated magnetostriction were detected below ∼200 K and ∼440 K in Cr5Mn20Fe20Co20Ni35 and Mn20Fe20Co20Ni40, respectively. These composition and temperature dependencies could be qualitatively reproduced by ab initio simulations that took into account a ferrimagnetic ↔ paramagnetic transition. Transmission electron microscopy revealed that plastic deformation occurs initially by the glide of perfect dislocations dissociated into Shockley partials on {111} planes. From their separations, the stacking fault energy (SFE) was determined, which decreases linearly from 69 to 23 mJ·m−2 as x increases from 14 to 26 at.%. Ab initio simulations were performed to calculate stable and unstable SFEs and estimate the partial separation distances using the Peierls-Nabarro model. While the compositional trends were reasonably well reproduced, the calculated intrinsic SFEs were systematically lower than the experimental ones. Our ab initio simulations show that, individually, atomic relaxations, finite temperatures, and magnetism strongly increase the intrinsic SFE. If these factors can be simultaneously included in future computations, calculated SFEs will likely better match experimentally determined SFEs.

Effect of SiC Nanoparticles on AZ31 Magnesium Alloy.

Magnesium alloys are attractive for the production of lightweight parts in modern automobile and aerospace industries due to their advanced properties. Their mechanical properties are usually enhanced by the incorporation with reinforcement particles. In the current study, reinforced AZ31 magnesium alloy was fabricated through the addition of bulk Al and the incorporation of SiC nanoparticles using a stir casting process to obtain AZ31-SiC nanocomposites. Scanning electron microscope (SEM) investigations revealed the formation of Mg17Al12 lamellar intermetallic structures and SiC clusters in the nanocomposites. Energy dispersive spectroscopy (EDS) detected the uniform distribution of SiC nanoparticles in the AZ31-SiC nanocomposites. Enhancements in hardness and yield strength (YS) were detected in the fabricated nanocomposites. This behavior was referred to a joint strengthening mechanisms which showed matrix-reinforcement coefficient of thermal expansion (CTE) and elastic modulus mismatches, Orowan strengthening, and load transfer mechanism. The mechanical properties and wear resistance were gradually increased with an increase in SiC content in the nanocomposite. The maximum values were obtained from nanocomposites containing 1 wt% of SiC (AZ31-1SiC). AZ31-1SiC nanocomposite YS and hardness were improved by 27% and 30%, respectively, compared to AZ31 alloy. This nanocomposite also exhibited the highest wear resistance; its wear mass loss and depth of the worn surface decreased by 26% and 15%, respectively, compared to AZ31 alloy.

Study on the influence of heavy oil group components on the formation and stability of W/O emulsion

In view of heavy oil B which was easy to form W/O emulsion by water flooding, this paper studied the effect of the group components of heavy oil B on the formation and stability of W/O emulsion from the separation of four-component, the characterization of group components, the determination of interface property and the evaluation of emulsion performance. The structure of the group components of heavy oil B was characterized by infrared spectroscopy and synchronous fluorescence spectroscopy. Compared with the other three group components, the asphaltene had strong polarity and high degree of association between molecules. The results of interfacial property measurement showed that asphaltene could reduce the interfacial tension of simulated oil and formation water to 10° orders of magnitude and increase the interfacial expansion modulus by about 1.4–2.6 times compared with the other three group components. This was because asphaltene had strong polarity and complex aromatic structure. In order to further verify the influence of crude oil group components on the formation and stability of W/O emulsion, this paper systematically evaluated the particle size distribution and stability of emulsion formed by different group components. Compared with the saturated and aromatic, the emulsion droplets formed by resin and asphaltene simulation oil were smaller and concentrated, and the demulsification time of emulsion was prolonged by about 1.5–8 times. In summary, the influence of crude oil group components on the formation and stability of W/O emulsion was as follows: asphaltene > resin > aromatic > saturated.