Solid Transition Research Articles

Avalanches in the Athermal Quasistatic Limit of Sheared Amorphous Solids: An Atomistic Perspective

We study the statistical properties of the yielding transition in model amorphous solids in the limit of slow, athermal deformation. Plastic flow occurs via alternating phases of elastic loading punctuated by rapid dissipative events in the form of collective avalanches. We investigate their characterization through energy vs. stress drops and at multiple stages of deformation, thus revealing a change of spatial extent of the avalanches and degree of stress correlations as deformation progresses. We show that the statistics of stress and energy drops only become comparable for large events in the steady flow regime. Results for the critical exponents of the yielding transition are discussed in the context of prior studies of similar type, revealing the influence of model glass and preparation history.

Diatomaceous Earth: Characterization, thermal modification, and application

AbstractThe diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51–0.55 g/cm3, total porosity of 61–63%, and specific gravity of 2.25 g/cm3. The chemical composition is as follows: SiO2,86.03; Al2O3, 3.01; Fe2O3, 2.89; MnO, 0.06; TiO2,0.20; CaO, 0.76; MgO, 0.28; K2O, 0.69; Na2O, 0.19; P2O5, 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, muscovite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000–1,200°C temperature region. At 1,100°C, the entire opal underwent solid–solid transition to cristobalite. Further ramp of the temperature (1,100–1,200°C) induced formation of mullite. Scanning electron microscopy (SEM) and transmission electron microscopy depict the presence of micro- and nanostructures with pores varying from 260 to 650 nm. SEM analysis further determined morphological changes in terms of the pore diameters shrinkage to 120–250 nm in comparison to the larger pores found in the initial material. The results from this investigation improve the understanding of mechanism of silica phase transition and the relevant phase alterations that took place in DE upon calcination temperatures from 500 to 1,200°C.

Rheo-Optical Study on the Viscoelastic Relaxation Modes of a Microgel Particle Suspension around the Liquid–Solid Transition Regime

Dynamic viscoelasticity and dynamic birefringence of a microgel system were investigated around the liquid–solid transition concentration to clarify the molecular origin of the viscoelastic response of the microgel system. The complex modulus showed viscoelastic liquid-like behavior at concentrations, c, below a threshold cⱼₐₘₘᵢₙg for random close packing of the microgels, whereas viscoelastic solid-like behavior at c > cⱼₐₘₘᵢₙg. The imaginary part of the complex strain-optical coefficient changed its sign with increasing angular frequency ω in a liquid-like regime, suggesting that the stress and birefringence involved three relaxation mechanisms. Utilizing the stress-optical rule, SOR, for each relaxation process, the complex shear modulus at c cⱼₐₘₘᵢₙg, the ordinary SOR held well with a single stress-optical coefficient, C, implying that only one stress origin is dominant, which can be attributed to the orientational stress of densely packed microgels in permanent contact. The strain-optical coefficients evaluated using the Onuki–Doi theory reproduced the measurements qualitatively and supported these assignments.

Random copolymer of poly(polyethylene glycol methyl ether)methacrylate as tunable transition temperature solid-solid phase change material for thermal energy storage

Polymer based phase change materials (PCM) for thermal energy storage (TES) applications have gained some attention recently due to their high stability and potential solid to solid phase transition. Here, we are the first to utilize a simple copolymerization strategy for static tunability transition temperature (Tt) of polymeric PCM. The copolymerization between short and long side chain polyethylene glycol based methacrylate polymers was designed to tune Tt with minimum impact on their energy density. Polarized optical microscope and x-ray techniques were also used to understand the relationship between crystal structure and Tt of different copolymer composition which was discussed in the context. The solid to solid transition polymeric PCM were successfully developed with tunable Tt ranged from 18 °C to 35 °C which is suitable toward building envelop applications.

Construction of phase diagrams to estimate phase transitions at high pressures: A critical point at the solid liquid transition for benzene

Phase diagrams are an integral part of the estimation of material properties in the case of high temperature and pressure. The pressure-temperature (P-T) phase diagram is used to determine the state of aggregation (solid, liquid, gaseous) of a substance under given conditions. This article presents a method to reveal new states in the phase diagram, including the possibility of the plasma state. Using the empirical data of benzene, a critical pressure beyond solid-liquid equilibrium was estimated. It is highly probable that beyond these pressures, benzene may ionize and exhibit plasma behavior. The method proposed in this work for benzene could also be applied to create a comprehensive phase diagram of Hydrogen at certain pressure and temperature. Because the complex behavior of hydrogen, as well as the constant discovery of new varieties and the creation of many different phases of hydrogen makes it very difficult to construct a realistic phase diagram.

Consumer preferences for hybrid and electric vehicles and deployment of the charging infrastructure: A case study of Lebanon

This case study investigates consumer preferences and stakeholders’ interests regarding hybrid electric vehicles (HEVs) and electric vehicles (EVs) in the Greater Beirut Area (GBA) in Lebanon where the market for these vehicle types is still nascent. A mixed logit model incorporating financial and technical attributes of common mid-size Internal Combustion Engines (ICE), HEVs, and EVs is estimated then used to compute Willingness to Pay (WTP) measures and evaluate the effectiveness of different monetary incentives in promoting these vehicle types. The study also uses qualitative research methods to capture the perspectives of different stakeholders regarding electric mobility in Lebanon. Data collected in 2018 through a stated preference survey reveals a WTP for a 100-km increase in driving range equal to 705 $ and for a 1 $ reduction in driving costs per 100 km equal to 305 $, values that are generally lower than several values found in the literature. A policy testing exercise suggests that doubling fuel taxes could increase the potential market shares of HEVs and EVs from 9.25% to 9.59% and from 4.98% to 5.84%, respectively. The provision of charging incentives to consumers could raise the market share of EVs up to 6.96%. A combination of both policies could further increase the proportion of EVs to 7.22%. In parallel, a stakeholder analysis draws attention to a multitude of challenges regarding the HEVs and EVs uptake as well as the public charging infrastructure rollout, namely excessive delays in establishing the enabling institutional and regulatory environment and shortcomings in the electricity supply. This research shows that it is more likely for HEVs than EVs to take off in the short term and that a solid transition to electric mobility in Lebanon necessitates further planning, especially in terms of instituting a clear and effective incentives scheme.

Stabilization of Undercooled Metals via Passivating Oxide Layers

AbstractUndercooling metals relies on frustration of liquid–solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7–5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat‐free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.

Stabilization of Undercooled Metals via Passivating Oxide Layers.

Undercooling metals relies on frustration of liquid-solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7-5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat-free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.

Solidification characteristics and as-cast microstructures of a Ru-containing nickel-based single crystal superalloy

The solidification characteristics and as-cast microstructures of a Ru-containing nickel-based single crystal superalloy were systematically investigated through thermal analysis, Thermo-Calc simulation, the planar interface solidification experiment, and the directional solidification quenching experiment. The main solidification transition temperature, segregation behavior, and solidification path were analyzed, and the microstructure evolution and phase formation mechanism were also discussed. The solidification began with the formation of primary γ dendrites (L → γ). Then Ni, Al, Ta, and Ru were enriched in the residual liquid, resulting in the precipitation of β-NiAl phase (L → β-NiAl). As the β-NiAl phase grew, the content of Ta gradually increased while the content of Al gradually decreased. Thus, the peritectic γ′ phases were precipitated on the surface of β-NiAl phase and coarsened by the incomplete peritectic reaction (L + β-NiAl → peritectic γ′ + β-NiAlResidual). The Al content further decreased and the Ta content further increased with the precipitation of the peritectic γ′ phase, leading to the formation of γ/γ′ eutectics on the surface of the γ dendrites or directly from liquid (L → γ/γ′ eutectic). Since the precipitation of β-NiAl phase and the subsequent incomplete peritectic reaction, Cr, Co, Mo, W, and Re were rejected into the residual liquid in the vicinity of β-NiAl phase, providing conditions for the nucleation of the TCP(R) phases (L → R). The wide freezing range of the alloy might be the cause of the severe micro-segregation and the precipitation of some secondary phases in the interdendritic regions.

Solid solutions of flexible host-guest supramolecules for tuning molecular motion and phase transitions.

By utilizing a supramolecular complex rather than an individual molecule as a deformable and elastic substitutional component, we put forward a solid-solution strategy and demonstrate an example of how two related yet non-isostructural crystalline host-guest compounds can form molecular solid solutions. Interestingly, such a strategy can effectively and continuously modulate the molecular motion and phase transition in them, as revealed by the variable-temperature/frequency dielectric responses.

Magnetic-field induced multi-step transitions in ferromagnetic spin-crossover solids within the BEG model

We study by means of the 2D Blume–Emery–Griffiths (BEG) spin-1 model, spin-crossover (SCO) and prussian blue analogs (PBAs) solids. In this model, the spin states, which can be high-spin (HS) or low-spin (LS), interact magnetically and elastically with their nearest neighbors. To account for the volume change, accompanying the spin transition phenomenon, all interactions through the lattice are assumed as temperature-dependent. In addition, the system is subject to a variable magnetic field lifting the degeneracy in the HS state. A stochastic cooperative dynamics of this BEG-like Hamiltonian, describing the equilibrium and nonequilibrium properties of ferromagnetic spin-crossover solids, is derived from the Glauber approach, with appropriate Arrhenius microscopic transition rates. The model generates under the magnetic field, sigmoidal relaxation and a hysteresis phenomenon of the HS fraction, as well as multistep behavior of the magnetization. These behaviors open the way to new route of multi-stable systems, desired in multi-byte electronics.

Solid-state behaviors of imines: colossal biaxial positive thermal expansion, motion capability, and phase transitions

The torsional flexibility of imines affects solid-state packing and properties. Behaviors including colossal thermal expansion, pedal motion, and phase transitions in imine-containing solids are described.

超快激光诱导固体非热相变及其原子机理进展

超快激光诱导固体非热相变及其原子机理进展

How do clusters in phase-separating active matter systems grow? A study for Vicsek activity in systems undergoing vapor-solid transition.

Via molecular dynamics simulations, we have studied the kinetics of vapor-"solid" phase transition in an active matter model in which self-propulsion is introduced via the well-known Vicsek rule. The overall density of the particles is chosen in such a way that the evolution morphology consists of disconnected clusters that are defined as regions of high density of particles. Our focus has been on understanding the influence of the above-mentioned self-propulsion on structure and growth of these clusters by comparing the results with those for the passive limit of the model that also exhibits vapor-"solid" transition. While in the passive case growth occurs due to a standard diffusive mechanism, the Vicsek activity leads to very rapid growth, via a process that is practically equivalent to the ballistic aggregation mechanism. The emerging growth law in the latter case has been accurately estimated and explained by invoking information on velocity and structural aspects of the clusters into a relevant theory. Some of these results are also discussed with reference to a model for active Brownian particles.

Investigating Thermophysical Properties Under Microgravity: A Review

The advancement of metallic alloys is generally driven by alloy development, but furthermore requires the development of suitable production and processing routines. Almost all metallic products are formed through the solidification processing from the liquid phase. Although the solid‐state is not influenced by gravitational effects, the processing of liquids is strongly impacted by earth's gravity—this influences interface phenomena, momentum, heat, and mass transport and, consequently, the solidification events. Experiments on liquid metallic alloys in microgravity avoid these influences and therefore allow benchmark experiments. This allows, for example, to obtain reliable thermophysical properties, improve the understanding of nucleation, phase selection, crystal growth, and other basic features of the liquid phase and the liquid–solid transition. The basic methodology, as well as a number of recent results obtained in the long‐duration microgravity environment on board the international space station, are presented and discussed.

Stereoregular hybrid azobenzene-cyclosiloxanes with photoinduced reversible solid to liquid transition properties

A new type of stereoregular hybrid azobenzene-organocyclosiloxane discrete molecular structures with photoactive azobenzene groups unidirectionally connected to rigid cyclosiloxane frames through alkyl spacers of different lengths were developed for the first time.The kinetics and thermodynamics of nondegradative reversible trans-cis photoisomerization processes of the synthesized azobenzene-cyclosiloxane conjugates investigated using UV/Vis spectroscopy, DSC and XRD methods showed dependency on their molecular structures.It has been observed that room temperature UV (365 nm) irradiation of the synthesized hybrids leads to photoliquefaction effect consisting of a photoinduced phase transition of crystal solids into liquids. The photoliquefaction process was observed and confirmed with DSC, XRD and POM methods. Backward solidification process was generated with visible light and by heating.The tetra-azobenzene substituted cyclosiloxane single molecule compounds described in this work can be regarded as promising candidates for the development of new hybrid smart materials with many potential high-tech applications.

Melting Curve and Isostructural Solid Transition in Superionic Ice.

The phase diagram and melting curve of water ice is investigated up to 45GPa and 1600K by synchrotron x-ray diffraction in the resistively and laser heated diamond anvil cell. Our melting data evidence a triple point at 14.6GPa, 850K. The latter is shown to be related to a first-order solid transition from the dynamically disordered form of ice VII, denoted ice VII^{'}, toward a high-temperature phase with the same bcc oxygen lattice but larger volume and higher entropy. Our experiments are compared to abinitio molecular dynamics simulations, enabling us to identify the high-temperature bcc phase with the predicted superionic ice VII^{''} phase [J.-A. Hernandez and R. Caracas, Phys. Rev. Lett. 117, 135503 (2016).PRLTAO0031-900710.1103/PhysRevLett.117.135503].

Solid−solid phase transition of tungsten induced by high pressure: A molecular dynamics simulation

Abstract The phase transition of tungsten (W) under high pressures was investigated with molecular dynamics simulation. The structure was characterized in terms of the pair distribution function and the largest standard cluster analysis (LSCA). It is found that under 40−100 GPa at a cooling rate of 0.1 K/ps a pure W melt first crystallizes into the body-centred cubic (BCC) crystal, and then transfers into the hexagonal close-packed (HCP) crystal through a series of BCC−HCP coexisting states. The dynamic factors may induce intermediate stages during the liquid−solid transition and the criss-cross grain boundaries cause lots of indistinguishable intermediate states, making the first-order BCC−HCP transition appear to be continuous. Furthermore, LSCA is shown to be a parameter-free method that can effectively analyze both ordered and disordered structures. Therefore, LSCA can detect more details about the evolution of the structure in such structure transition processes with rich intermediate structures.

Solute trapping in rapid solidification

Abstract

Enthalpy based mathematical modelling for thermal energy storage filled with paraffin encapsulated balls as storage material

Numerical modeling of latent heat thermal storage (LHTS) is always complex to solve because of the necessity to tediously track the moving boundary, which happens due to the continuous variation of solid–liquid interface, during the melting or freezing process of phase change materials (PCM). Moreover, when commercial grades of paraffin are employed as Phase change storage materials for thermal energy storage applications, the phase transition will not happen at a particular fixed temperature but in a narrow range. Also, such paraffin exhibits several zones of transitions such as solid–solid and solid–liquid. The enthalpy (or fixed domain) method is one of the convenient methods to model problems involving phase change (or phase change materials) with the above mentioned conditions. In this paper, the mathematical modeling by enthalpy method for a LHTS system filled with ball shaped PCM containers as storage materials and its numerical solution procedures were discussed. The numerical procedure that considers the solid to solid transition of PCM and enthalpy-temperature relationships for PCMs that exhibit unsymmetrical transition zones before and after the peak transition temperature during the solid–solid and solid–liquid transitions were introduced and analysed.