Liquid-solid Transformation Research Articles

A Modified Solid-Liquid-Gas Phase Equation of State.

The solid–liquid–gas equation of state (SLV-EOS) is based on the initial cubic equation of state, the van der Waals equation. Since the van der Waals equation is not accurate enough to predict gas–liquid properties, SLV-EOS cannot better predict the gas–liquid properties of hydrocarbons in actual gas reservoirs. Therefore, a modified solid–liquid–gas unified equation of state was constructed inthis paper, which was developed using the material’s actual critical compressibility factor Zc. The minimum liquid-phase volume at the triple point is also introduced to limit the value of c in the equation, which effectively avoids the solution of Maxwell’s equal-area rule in the solid–liquid transformation process. The model extends the classical Peng–Robinson equation of state for fluid-only (liquid and vapor) states. The predicted p-T and p-ρ phase transition diagrams are reported in this paper for methane, ethane, propane, carbon dioxide, hydrogen sulfide, and sulfur, and they are in good agreement with the experimental data. This methodology is suitable for any substance for which the density of the solid phase is higher than that of the liquid phase. Additionally, the modified SLV equation can be used to estimate the solubility of solid sulfur in the absence of relevant experimental data.

Facile prepared tropinone-based enone dyes with visible-light induced photothermal liquefaction and cold crystallization properties for reusable and switchable adhesive

The solid-liquid phase transition of adhesives triggered by two different wavelength light stimuli enables the switchable and reusable character. The adhesive which could be liquified by photothermal effect by single-wavelength light stimulus and solidified by natural cooling is much easier to operate but little developed. In this work, a class of tropinone-based enone dyes (TPs), prepared by one-pot Claisen-Schmidt condensation, were explored as a novel kind of single-wavelength light-switchable adhesives. TPs could absorption visible light and are non-fluorescent. By changing the length of alkoxy groups, the melting point and crystallization behavior were regulated. Especially, TP6 and TP8 could form overcooled liquid during the cooling process, thus enabling a proper adhesion operation window. Under 405 nm LED irradiation, the rapid solid-liquid transformation was achieved for some of TPs due to the high thermal conversion ability. TPs presented good adhesion strength toward glass plates. Among them, TP8 could work as a reusable and light-switchable adhesive.

A temperature-dependent atomistic-informed phase-field model to study dendritic growth

The effects of solid–liquid interface anisotropy and kinetics on crystallization of highly undercooled titanium melts are studied by coupling molecular dynamics and phase-field simulations. Unlike previous models and to consider the actual physics of crystal growth, the phase-field parameters, representing interface mobility, solid–liquid transformation barrier, and interfacial energy gradient, are temperature dependent. The parameters are determined by a combination of molecular dynamics simulations and classical thermodynamic calculations based on the temperature-dependent solid–liquid interface properties and kinetic coefficient. We investigated Ti dendritic growth as a benchmark example to demonstrate that the phase-field model presented in this work is more compatible with the experimental data and theoretical models in comparison to the earlier models with constant model parameters. The capillary fluctuation method is used to determine the solid–liquid interface energy and its anisotropy for undercoolings up to 400 K. Similar to theoretical models, the average solid–liquid interface energy decreases with temperature, and the preferred dendrite growth direction shifts from 〈100〉 to 〈110〉 direction as the undercooling increases. Phase-field simulations also show other favorite growth directions, implying that there is a competition between the interface anisotropy and kinetics of the solid–liquid interface.

Quantitatively regulating defects of 2D tungsten selenide to enhance catalytic ability for polysulfide conversion in a lithium sulfur battery

Introducing defects into 2D materials can increase the coordinatively unsaturated sites that are usually also catalytically active sites. How does the level of defects influence catalytic performance and how to take advantage of defects to optimize the 2D materials? In this work, anionic Se vacancies and edge dislocations are regulated in 2D WSe2 as a model of transition metal dichalcogenide host material for the sulfur cathode. The defective 2D WSe2 with different W/Se ratios are quantitatively investigated the influence of the defects on enhancing the cathodic process in lithium sulfur (Li-S) batteries. With a moderate level of defects, WSe1.51 shows the optimal performance for adsorbing polysulfides, catalysing polysulfides conversion, and promoting liquid-solid transformation, all of which are crucial steps for Li-S battery. The corresponding sulfur cathode delivers a high initial areal capacity of 11.3 mAh cm −2, and excellent cycle stability with a decay rate of 0.025% during 1000 cycles at 1C rate. Even in a pouch cell, the excellent cyclability and flexibility are still available. The results show the feasibility of enhancing the catalytic ability of 2D transition metal dichalcogenide by controlling the level of defects by which a long-cycle and high-energy Li-S rechargeable battery can be achieved.

Microstructure design and strengthening of mechanical properties in Al–Si alloy through 0.05 wt % Ni-base amorphous alloy

In this work, it was found that nanocrystals (NiTi) can be formed in Ni-base amorphous alloys at a certain temperature. Lattice matching calculations indicated that NiTi matched perfectly with α-Al and Si. In solid-liquid transformation, NiTi nanocrystals promoted heterogeneous nucleation of α-Al, meanwhile hindered the growth of α-Al and Si. After the manipulation, the α-Al and eutectic Si were refined by 87.0% and 27.7%, respectively. The quantity of primary Si went down. The average size of Al2Cu and Mg2Si was with the significant refinement levels of 57.7% and 90.6%, respectively. Based on the comprehensively optimized microstructure configuration, the yield strength (σy), ultimate tensile strength (σU), elongation (δ) and fracture strain (ε) at room temperature were increased by 17.8%, 17.8%, 100.4% and 73.3%, respectively, after the manipulation. The manipulated σy and σU were increased by 21.5% and 14.4%, respectively. The improvement mechanisms of mechanical properties were discussed.

Hierarchical grain refinement during the laser additive manufacturing of Ti-6Al-4V alloys by the addition of micron-sized refractory particles

Ti-6Al-4V alloys mad by additive manufacturing (AM) with slower cooling rate (e. g., direct energy deposition (DED)) generally have the problem of severe coarsening of α phase. This study presents a method to refine the microstructure of the primary β phase formed during the solid–liquid transformation, microstructures formed during the β → α + β transformation, and recrystallized microstructures formed during the repeated heating cycles encountered in AM processes. This is accomplished by the in situ precipitation of nano-sized dispersed high-melting-point yttria Y2O3 particles. The addition of micron-sized particles with high melting points can refine primary crystallized grains and transformed grains corresponding to the secondary phase in Ti-6Al-4V alloys. In addition, they can effectively inhibit the recrystallization and growth of prior-deposited metal grains. The microstructural and tensile properties of laser additive manufactured with filler wire Ti-6Al-4V components with different amounts of Y2O3 (0, 0.12, and 0.22 wt%) were investigated. The refining effect of Y2O3 was significant and the tensile strength of Ti-6Al-4V containing 0.22 wt% Y2O3 in the longitudinal and transverse directions was greater than that of Ti-6Al-4V by approximately 12% and 9%, respectively. Concurrently, there was no loss in the elongation of the material in either direction. The strategy of using micron-sized refractory particles to control phase transformation (primary crystallization, solid-state phase transformation, and recrystallization) can be applied to the AM of different metals, in which microstructures are susceptible to coarsening.

Preparation of polypropylene with high melt strength by wet reaction blending of lignin

AbstractIn this paper, the melt strength of polypropylene is shown to be significantly improved by lignin‐cooperative construction of heterophase network structure and the evolution mechanism of lignin on the topology of polypropylene is investigated. Electron paramagnetic resonance (EPR) analysis shows that the free radicals generated by polypropylene irradiation can remain active for 2 weeks; rheological studies show that lignin promotes the formation of heterogeneous network structures in polypropylene, and its melt is characterized by long‐chain branching. Phase angle‐complex modulus, complex viscosity‐complex modulus, Han's, and Cole–Cole curves are used to analyze the liquid–solid transformation, and the results indicate that the enhanced interfacial action is due to the formation of the heterogeneous network structures. The mechanical properties show that the impact strength is increased by 1.8 times due to the synergistic effect of lignin and acrylamide. SEM shows the formation of a fibrous network structure around the lignin, which undergoes interfacial yielding, improving the interfacial interaction between the components.

Fluorescent thermochromic wood-based composite phase change materials based on aggregation-induced emission carbon dots for visual solar-thermal energy conversion and storage

Efficient solar-thermal energy conversion and storage is significant to overcome current energy shortage problems. Monitoring solar-thermal energy storage process by an evident and convenient display is conducive to improving energy utilization. Herein, fluorescent thermochromic wood-based composite phase change materials (WPCMs) were constructed for visual solar-thermal energy conversion and storage. It was fabricated by encapsulating polyethylene glycol (PEG) and aggregation-induced emission carbon dots (AIE-CDs) showing blue dispersed emission and red aggregation-induced emission into delignified wood (DW). The DW well-preserved the distinctive anisotropic porous structure and prevented the leakage problem of PEG. The WPCMs possessed great solar-thermal conversion capacity benefitting from strong and broad solar light absorption behaviors of AIE-CDs. Additionally, WPCMs showed real-time and visual fluorescent thermochromic property, it exhibited red AIE, and the fluorescence (FL) decreased and shifted into the blue emission band under solar radiation. The solar-thermal energy conversion and storage led to solid–liquid transformation of WPCMs, which promoted AIE-CDs’ dispersion, thereby changing the FL. It also exhibited a high latent heat of fusion (160.8 J·g−1), favorable stability over 150 heating–cooling cycles, thermal stability below 210 °C and good shape stability. The WPCMs can be extended to applications in energy-saving buildings and optical lighting materials with visual thermal regulation capability.

Role of trace nanoparticles in establishing fully optimized microstructure configuration of cold-rolled Al alloy

In this paper, we took cold-rolled Al-Cu5.0-Mg0.5-Si0.5 alloy as the research object. The roles of 0.1 wt% in-situ nano-TiC and nano-TiC-TiB2 in solid–liquid and solid-state transformations (solution plus aging precipitation) were systematically investigated and compared. We found that trace in-situ nanoparticles can stimulate the nucleation of α-Al dendrites and hinder their growth, meanwhile serving as the heat storage and heat sustained-release carriers during solid–liquid transformation. In the process of solid-state transformation, recrystallization nucleation is promoted, and grain boundaries are pinned by nanoparticles. Meanwhile, the nucleation of Al2Cu is accelerated, and refined Al2Cu distributes more uniformly. Besides, similarities and differences in the manipulation mechanisms of nano-TiC and nano-TiC-TiB2 during solid–liquid and solid-state transformations were analyzed. The mechanical properties and the responsible strengthening mechanisms were discussed in detail.

Structure and defects in melting process of quasi-two-dimensional wet particle system

The study of structural defects in particle systems is of great value for studying solid-liquid melting. The volume fraction is a key parameter that can be used to accurately quantify the phase-transition process. The collective behavior and interaction form in a wet particle system are much more complex than that of a dry particle material because of the existence of liquid bridge force between the wet particles. In this paper, the structural defects and the critical value of solid-liquid transformation in the monolayer wet particles during solid-liquid melting under vertical vibration are experimentally studied. The contact model of the wet particle system is constructed according to experimental and theoretical analysis, and the structural changes of the particles in the melting process of the quasi-two-dimensional wet particle system are quantified. The Voronoi tessellation is established to study the phase transition of the particle system, and the local volume fraction is adopted to determine the state of structural defect change during melting. The experimental results indicate that the phase-transition process is caused by structural defects in the solid. The defects appear from the edge of the particle system, and the chain defect pairs spread to the center. The reason for structural defects at the edge of the cluster is that the particles at the edge of the cluster are subjected to less liquid bridge force, and the kinetic energy brought by the collision between the particles and the bottom wall makes the particles become active and begin to explore the available space. The chain defects are caused by the force chain generated by the fluid bridge force, which makes the particles tend to move together in rows. In addition, the local volume fraction of seven-phase defective particles decreases significantly and is much smaller than that of five-phase defective particles and six-phase defective particles when defects occur. Therefore, the evolution and the critical state of the structural defects can be quantified by measuring the change in the minimum local volume fraction (the local volume fraction of particles with 7-fold defects) in the particle system. The local volume fraction of the analysis shows that when the minimum local volume fraction <i>ϕ</i> ≤ 0.6652 defects occur, and when <i>ϕ</i> ≤ 0.4872 particle system transforms from solid to liquid.

Simulation of electromagnetic field and its effect during electromagnetic stirring in continuous casting mold

A mathematical model of in-mold electromagnetic stirrer has been developed to calculate the three-dimensional time-varying magnetic field for electromagnetic stirring in the continuous casting mold. The calculated magnetic field is coupled with the magneto-hydrodynamic and solidification model to analyze the effect of stirrer width at different current and frequency applied to the stirrer. The enthalpy porosity technique is used to track the liquid-solid transformation while the realizable k-ε turbulence model is used to account the turbulence in the fluid flow. The coupling of the time-varying electromagnetic field with solidification model makes the model complicate which leads to having divergence problem and large computation time. The model efficiently computes the electromagnetic field, fluid flow, solidification behavior of an electromagnetically stirred continuous casting mold, which have been validated against the reported results. From the initial results it is observed that magnetic flux density significantly increases with increase in stirrer width and current while, frequency has a marginal effect on magnetic flux density. The result obtained from coupled model shows that increase in frequency has a large influence on stirring intensity and hence on solidification behavior. However, stirrer width and current marginally affect the stirring intensity and solidification behavior.

A Creative “Spark” for High-Entropy Alloys

In this issue of Matter, Feng et al. make a breakthrough understanding of an aerosol system for manufacturing unprecedented alloys with excellent catalytic properties. This work will inspire improved 3D nanoprinting techniques for creating new matter forms for broad applications, including additive manufacturing, catalysts, and metallurgy.

Unconventional Alloys Confined in Nanoparticles: Building Blocks for New Matter

•Unprecedented alloys (e.g., HEAs) are formed via vapor-crystal transformation •Brief oscillatory sparks mix vapors that are quenched to create 55 distinct alloys •Miscibility limits for mixing bulk-immiscible systems are broken at the nanoscale •Mixing abilities diversify materials for additive manufacturing and catalysis Manufacturing unconventional alloys remains challenging owing to the seamless interplay between kinetics and thermodynamics. High-entropy alloys (HEAs), for example, enable paradigm shifts in materials science but these shifts are hindered by traditional liquid-solid transformations. In contrast, vapor–crystal transformations offer the most kinetically efficient pathways to form alloys. Here, a well-mixed vapor is quenched to create 55 distinct alloys confined in nanoparticles (NPs), including unprecedented ones. This confinement is found to stabilize their alloyed states. Unlike precursor feeding, a microseconds-long oscillatory spark mixes the vapors and determines the composition of the alloy NPs. To epitomize practicalities, we apply the NPs as integral building blocks for high-performance catalysts and to nanoscale additive manufacturing. The resulting HEA nanostructures cannot be fabricated by other additive manufacturing techniques. The present work breaks the miscibility limits, thereby providing a powerful roadmap to uncharted territories in metallurgy, catalysis, and additive manufacturing. Manufacturing unconventional alloys remains challenging owing to the seamless interplay between kinetics and thermodynamics. High-entropy alloys (HEAs), for example, enable paradigm shifts in materials science but these shifts are hindered by traditional liquid-solid transformations. In contrast, vapor–crystal transformations offer the most kinetically efficient pathways to form alloys. Here, a well-mixed vapor is quenched to create 55 distinct alloys confined in nanoparticles (NPs), including unprecedented ones. This confinement is found to stabilize their alloyed states. Unlike precursor feeding, a microseconds-long oscillatory spark mixes the vapors and determines the composition of the alloy NPs. To epitomize practicalities, we apply the NPs as integral building blocks for high-performance catalysts and to nanoscale additive manufacturing. The resulting HEA nanostructures cannot be fabricated by other additive manufacturing techniques. The present work breaks the miscibility limits, thereby providing a powerful roadmap to uncharted territories in metallurgy, catalysis, and additive manufacturing.

Evolution of cellular morphology in pure materials

The evolution of cellular morphology during interfacial instability for liquid–solid transition for pure unary material systems is studied using the maximum entropy production (generation) rate principle (MEPR) for steady-state directional solidification. This approach is dependent on a quantity called maximum entropy production rate density which inherently contains key solidification parameters that governs cellular evolution for liquid–solid transformation. The maximum entropy production rate density is computationally measured from the solid–liquid interface in diffuse form and considers steady-state solidification at low velocities for both near and far from equilibrium conditions. The results are presented in mathematical expressions for morphological instability that corresponding to the evolution of a cellular morphology which emanates from the solid–liquid interface. The model is formulated to evaluate the solid–liquid interface thickness, the solidification velocity, grain boundary energy, and the size of the cellular morphological at instability. The results are tested with a number of pure single element materials at different temperature gradients which compare well with available experimental data.

In Vitro Assessment of Arsenic Release and Transformation from As(V)-Sorbed Goethite and Jarosite: The Influence of Human Gut Microbiota.

The importance of arsenic metabolism by gut microbiota has been evidenced in risk characterization from As exposures. In this study, we evaluated the metabolic potency of human gut microbiota toward As(V)-sorbed goethite and jarosite, presenting different behaviors of As release, and the solid-liquid transformation and partitioning. The release of As occurred mainly in the small intestinal phase for jarosite and in the colon phase for goethite, respectively. We found higher degree of As(V) and Fe(III) reduction by human gut microbiota in the colon digests of goethite than jarosite. Speciation analysis using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry and X-ray absorption near-edge spectroscopy, revealed that 43.2% and 8.5% of total As was present as As(III) in the liquid and solid phase, respectively, after goethite incubation, whereas almost all generated As(III) was in the colon digests of jarosite. Therefore, As bioaccessibility in human gastrointestinal tract was predominantly contributed to Fe(III) dissolution in jarosite, and to microbial reduction of Fe(III) and As(V) in goethite. It expanded our knowledge on the role of Fe minerals in human health risk assessment associated with soil As exposures.

Mechanisms and modelling of phosphorus solid–liquid transformation during the hydrothermal processing of swine manure

Influence of exogenous and endogenous factors on phosphorus solid–liquid transformation during the hydrothermal processing of swine manure.

Vibration transfer characteristic of gradient-like structure based on magnetorheological fluid

In this paper, a gradient-like structure composed of magnetorheological (MR) fluids is proposed, and its vibration transfer characteristic is studied through the modeling, numerical calculation and experimental test. Under the action of an externally applied magnetic field, the MR fluid exhibits the liquid-solid transformation property: the process of transformation between solid and liquid in fact is the change of vibration-transfer impedance. Therefore, based on this property, the gradient-like structure is constructed by controlling the external magnetic field. Based on the wave equation of one-dimensional elastic wave propagation, the wave equation of elastic wave transfer in the gradient-like structure is established. In order to describe the relationship between the complex shear modulus and Lame constant of MR fluid and magnetic field intensity in the wave equation, the equivalent parameter model of MR fluid is established based on the theory of elasticity and viscoelastic materials. Then, the experimental set-up is built to modify this model through experiments. Afterward, the discretization method of continuous medium and transfer matrix method are adopted to solve the wave equation, and the expression of vibration level drop is obtained. Through the numerical calculation, the trend of vibration level drop varying with the frequency of incident elastic wave and the intensity of magnetic field for the gradient-like structure is obtained. Finally, the vibration transfer characteristic of the gradient-like structure is studied experimentally, and the influence of magnetic field intensity on the vibration transfer characteristic of the gradient-like structure is analyzed. The results show that the numerical results are in good accordance with the experimental results, thereby verifying that the numerical model is accurate. And the gradient-like structure has a better attenuation effect on the elastic wave than the MR fluid under the action of a uniform magnetic field, and has an excellent tunable property as well.

Structural transformations including melting and recrystallization during shock compression and release of germanium up to 45 GPa

Solid-solid and solid-liquid transformations were examined in Ge(100), using in situ x-ray diffraction measurements during uniaxial strain compression and release. For final stresses above 15.7 GPa, the Ge transformed to a highly textured tetragonal $\ensuremath{\beta}$-Sn phase. At 31.5 GPa and above, Ge transformed to the molten phase. Full stress release (uniaxial strain) from the $\ensuremath{\beta}$-Sn phase, from the melt boundary, and from the completely molten phase, resulted in reversion to an untextured cubic diamond (cd) phase. These findings demonstrate that the cd to $\ensuremath{\beta}$-Sn phase change is reversible, and that recrystallization from the liquid phase occurs on nanosecond timescales during release.

Low-temperature pseudomorphic transformation of polyhedral MIL-88A to lithium ferrite (LiFe3O5) in aqueous LiOH medium toward high Li storage.

The ability to develop novel nanomaterials, and to precisely manufacture their functional structures at the nano- and microscales would benefit many emerging device applications. Herein, as a first example, we describe the exploration of feasibility for the morphological replacement of an iron-based MOF bearing trimeric FeIII-O clusters, MIL-88A preform, with a polyhedral architecture of around 0.4 × 1.2 μm by a lithium ferrite (LiFe3O5) phase via solid-liquid pseudomorphic transformation reactions in biologically and environmentally favourable aqueous lithium hydroxide (LiOH). The reaction proceeds at 170 °C, and the overall reaction can be described as Fe3O(H2O)2(FMA)3(OH)·nH2O (MIL-88A) + 7OH- + Li+ → LiFe3O5 + 3FMA2- + (n + 6) H2O (FMA = fumarate). It was proposed that through the coordination substitution of a MOF ligand by OH-, follow-up dehydration and dehydroxylation, and final H+/Li+ ionic exchange, the monolithiated iron oxides formed thermodynamically at comparatively low temperatures, which transcribe the global nanostructure morphologies of the polyhedral MOF preforms with the hexagonal symmetry, but were composed of interconnected LiFe3O5 particles (about 16 nm) that crystallize in a typical magnetite-type cubic (Fd3[combining macron]m) structure. Given the characteristic texture and structure of the Li-Fe oxide replica, cubic LiFe3O5 was preferentially employed as a new type of electrode material in rechargeable lithium cells. Notably, from the electrochemical evaluation, this metal oxide system exhibits decent anodic performances by undergoing a nine-electron conversion reaction, showing a substantially high specific capacity with an average potential of 0.8 V versus lithium metal, a long service life (700 cycles), and exceptional high-rate capability (up to 2.0 A g-1). The synthetic paradigms demonstrated that the MIL-88A to LiFe3O5 conversion may be transferable to other advanced inorganic-based electrodes from the parent metal compound such as LiFeO2, LiMn2O4 or LiCoO2 toward sustainable energy fields.

Self-healable polysiloxane/graphene nanocomposite and its application in pressure sensor

Polysiloxane is an ideal material for the preparation of wearable and flexible electronic devices. The preparation of pressure sensor using polysiloxane with both self-healing properties and excellent mechanical properties remains a key challenge. This work reports a self-healable pressure sensor based on polysiloxane network cross-linked by dynamic Diels–Alder bonds. The self-healable polysiloxane underwent a solid–liquid–solid transformation during a self-healing process, which has been confirmed by rheology. Depending on the amount of the linear reactive polydimethylsiloxane, mechanical performance and stretchability of the self-healable polysiloxane were tunable. By incorporating graphene nanosheets into polysiloxane elastomer, we fabricated a self-healable nanocomposite with significantly improved tensile stress and excellent electromechanical property. The tensile stress of nanocomposite containing 35 wt% graphene was 1.09 MPa that was improved by more than 1700% compared to that of the elastomer, indicating a significant improvement of the tensile stress with stretchability. The prepared self-healable pressure sensor exhibits a high sensitivity of 0.765 kPa−1 and a gauge factor of 4.87, demonstrating a promising potential use in the pressure sensors.