Solid Phase Transition Research Articles

Utilizing reversible solid–liquid phase transition to tune phononic bandgaps

Phononic crystals (PCs) are periodic synthetic materials that can manipulate the propagation of elastic waves and acoustic waves. However, for traditional phononic crystals, once the structure is identified, only a certain bandgap frequency can exist. Here, a supersaturated sodium acetate solution (SSAS) is introduced to realize a reversible liquid–solid phase transition by heating/cooling, which is utilized to tune the low-frequency bandgaps of elastic waves. Based on local resonance, we designed a one-dimensional (1D) PC, which consists of a 1D assembly of a series of goblets filled with the SSAS and heater pasted on the wall of the goblet. Low-amplitude transmission testing was conducted in both the liquid and solid states of the SSAS. An analytical model was proposed to calculate the first bandgap of the PC and to verify the testing results. In addition, numerical simulations were conducted to explore more bandgap zones. The results indicate that the phase transition induces tunable bandgaps of elastic waves. The underlying mechanism is that the phase transition leads to a unit cell stiffness and local heterogeneity. The bandgap from the solid to the liquid state is broadened by 20%. The findings reported here provide a new routine for designing architected metamaterial systems with broad and wide bandgaps for a wide range of potential applications in seismic, vibration, and acoustic wave control and guiding.

Measurement of shock velocity and temperature in laser-shocked carbon disulphide using time-resolved Raman spectroscopy

High-resolution time-resolved Raman spectroscopy of laser-shocked liquid carbon disulfide (CS2) is reported. The symmetric stretching mode (ν1) and first overtone of the bending mode (2 ν2) of CS2 at 656 cm−1 and 802 cm−1 wavenumbers respectively are analyzed to monitor the possible phase transitions occurring in the sample during shock wave propagation in the pressure range 0.4 – 4.4 GPa by varying the laser intensity on target from 0.2 GW/cm2 (40 mJ) to 6.4 GW / cm2 (1300 mJ). A liquid to solid phase transition is observed at 1.5 GPa, as compared to 0.8 GPa in static compression. The difference in these measurements is thought to be due to the high temperatures involved in the dynamic compression experiments described. The shock wave velocities in CS2 at 1.5 GPa and 2.6 GPa are calculated by measuring the intensity ratio of Raman modes emerging from the shocked region to that of the whole sample. 1D radiation-hydrodynamic simulations are performed to corroborate the experimental data. Enhancement of the Raman cross-section of carbon disulfide is observed from 2.5 GPa, which is much lower than the previously reported threshold of 8 GPa as reported by Yoo et al., [24]. This discrepancy in results is thought to be due to the significant contribution of temperature along with the pressure in laser-driven nanosecond single shock experiment.

Reliable and recyclable dynamically combinatorial epoxy networks for thermal energy storage

To overcome the leakage of phase change materials (PCMs) above melting temperature, PCMs are commonly encapsuled by chemically crosslinked networks, which bring the issues of reparability, reprocess-ability and recyclability making for the environment pollution and resource waste. Herein, a reversible aromatic disulfide is adopted to form dynamic epoxy networks which not only encapsulate polyethylene glycol (PEG) as the shape-stabilized PCMs (SSPCMs) but also address the issues about the un-recyclability of traditional SSPCMs. The PEG was well encapsulated and uniformly dispersed in disulfide-based epoxy due to the elaborate molecular design. The obtained SSPCMs (named EXAP2) shows typical solid–solid phase transitions characteristic and thermal reliability with high latent heat value of 82.7 J/g. Besides, the EXAP2 exhibit dynamic performance and can be reprocessed by hot press via the disulfide bonds exchange reaction above topology freezing temperature (Tv). And the reprocessed EXAP2 exhibits close phase change properties with the original sample, implying the reprocessing does not affect the crystalline structure and encapsuling capability of disulfide crosslinked networks. This strategy prove a significant way for fabricating the novel SSPCM with recyclability, reprocessability and reliability.

Template Engineering of Metal-to-Insulator Transitions in Epitaxial Bilayer Nickelate Thin Films.

Understanding metal-to-insulator phase transitions in solids has been a keystone not only for discovering novel physical phenomena in condensed matter physics but also for achieving scientific breakthroughs in materials science. In this work, we demonstrate that the transport properties (i.e., resistivity and transition temperature) in the metal-to-insulator transitions of perovskite nickelates are tunable via the epitaxial heterojunctions of LaNiO3 and NdNiO3 thin films. A mismatch in the oxygen coordination environment and interfacial octahedral coupling at the oxide heterointerface allows us to realize an exotic phase that is unattainable in the parent compound. With oxygen vacancy formation for strain accommodation, the topmost LaNiO3 layer in LaNiO3/NdNiO3 bilayer thin films is structurally engineered and it electrically undergoes a metal-to-insulator transition that does not appear in metallic LaNiO3. Modification of the NdNiO3 template layer thickness provides an additional knob for tailoring the tilting angles of corner-connected NiO6 octahedra and the linked transport characteristics further. Our approaches can be harnessed to tune physical properties in complex oxides and to realize exotic physical phenomena through oxide thin-film heterostructuring.

Deuterium NMR Studies of the Solid–Liquid Phase Transition of Octanol-d17 Confined in SBA-15

Deuterium NMR Studies of the Solid–Liquid Phase Transition of Octanol-<i>d</i>₁₇ Confined in SBA-15

Efficient Phase-Change Polymer Composite Film from Emulsion Gels Stabilized by Cellulose Nanofiber-Based Amphiphiles

Phase-change polymers (PCPs), exhibiting solid–solid phase transition, bring advancement to the conventional solid–liquid system for thermal energy storage. Such a system obtained as an aqueous dispersion is recommended for application as a surface coating. However, achieving good colloidal stability with efficient energy-storage performance requires precise process designing. Herein, we developed a film-forming PCP that was synthesized from emulsion gels stabilized by cellulose nanofiber-based amphiphiles (CLAm’s). The CLAm was obtained by grafting an amphiphile at a significantly higher degree (0.2–2.4). Depending on the degree of substitution and type of oil, the CLAm was able to efficiently stabilize o/w emulsion gels containing a very high oil phase (>90.0%) at a concentration of about 0.1 wt %. The PCPs were produced by the copolymerization of stearyl methacrylate (SMA) and methyl methacrylate used as the oil phase in emulsion gels. The composite film obtained from the colloidal dispersion of P(SMA-co-MMA) exhibited a solid–solid (crystalline–amorphous) phase transition involving high latent heat of upto ∼98 J/g for the melting and crystallization of SMA segments at ∼35 and ∼25 °C, respectively. This approach provides significant advancement in designing an efficient energy-storage material using plant-derived biocompatible nanomaterials.

Quantum Monte Carlo study of topological phases on a spin analogue of Benalcazar–Bernevig–Hughes model

We study the higher-order topological spin phases based on a spin analogue of Benalcazar–Bernevig–Hughes model in two dimensions using large-scale quantum Monte Carlo simulations. A continuous Néel-valence bond solid quantum phase transition is revealed by tuning the ratio between dimerized spin couplings, namely, the weak and strong exchange couplings. Through the finite-size scaling analysis, we identify the phase critical points, and consequently, map out the full phase diagrams in related parameter spaces. Particularly, we find that the valence bond solid phase can be a higher-order topological spin phase, which has a gap for spin excitations in the bulk while demonstrates characteristic gapless spin modes at corners of open lattices. We further discuss the connection between the higher-order topological spin phases and the electronic correlated higher-order phases, and find both of them possess gapless spin corner modes that are protected by higher-order topology. Our result exemplifies higher-order physics in the correlated spin systems and will contribute to further understandings of the many-body higher-order topological phenomena.

Simultaneous derivatization and liquid-solid phase transition microextraction of six biogenic amines in foods followed by narrowbore liquid chromatography-ultraviolet detection

Biogenic amines are quality control criteria for foods that are potentially toxic to humans. In this study, amidation derivatization for biogenic amines and liquid–solid phase transition microextraction were carried out simultaneously for food sample pretreatment. The derivatization reaction was executed in one pot with coumarin-3-carboxylic acid as the derivatizing reagent and (1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate as the coupling agent. Liquid–solid phase transition microextraction was achieved by the salting-out effect, using a phase change salt (1 M disodium hydrogen phosphate) solution. The combined derivatization and microextraction process was completed within 3 min at 30 °C, and the liquid top phase was easily obtained by placing the tube in an ice bath. Finally, a narrowbore liquid chromatograph coupled with a UV detector was used to determine the levels of six biogenic amines. The coupling agent-assisted derivatization and liquid–solid phase transition microextraction parameters were also investigated. The quantitative linear ranges were 3–400 μM for histamine, putrescine, spermidine, cadaverine, and tyramine and 5–400 μM for spermine, and the detection limit was 1 μM. The relative standard deviations of the intra- and inter-batches were <5.3% and 8.4%, respectively, while the relative error was <4.5% for both. We successfully applied this simultaneous derivatization–microextraction method to determine the biogenic amines in fermented foods.

Revisiting the Mechanism of the Meso-to-α Transition of Isotactic Polypropylene and Ethylene–Propylene Random Copolymers

In this work, we have conducted in situ simultaneous small- and wide-angle X-ray scattering and Raman spectroscopy experiments to investigate the fundamental differences in the mechanism of the mesomorphic to α phase transition of the isotactic polypropylene homopolymer and the random ethylene–propylene copolymer. Via quantitative analysis of the results coming from the three techniques, we found that in the homopolymer, chain interlock and chain extension occur during the transition. However, these processes are not necessary for the transition to occur. Indeed, the presence of randomly distributed ethylene co-units hinders the chain interlock process in the early stages of the phase transition (T > 60 °C) and suppresses the chain elongation process at the later stages (T > 90 °C). Consequently, the mesomorphic to α-phase transition in the random copolymer occurs with inclusion of the ethylene co-units inside the crystal lattice, causing increased lateral interchain distance and larger crystalline sizes. Our results show how differences exist in the way solid phase transitions occur at the molecular scale when co-monomers are included into the macromolecular chains, leading to a better understanding of the thermal behavior of semi-crystalline polymers.

A Narrow Bandgap of 2D Ruddlesden-Popper Bilayer Perovskite with Giant Entropy Change and Photoluminescence.

The multifunctional two-dimensional (2D) organic-inorganic hybrid perovskites have potential applications in many fields, such as, semiconductor, energy storage and fluorescent device etc. Here, a 2D Ruddlesden-Popper (RP) perovskite (IPA)2 (FA)Pb2 I7 (1, IPA+ =C3 H9 NI+ , FA+ =CN2 H5 + ) is determined for its photophysical properties. Strikingly, 1 reveals a solid reversible phase transition with Tc of 382 K accompanied by giant entropy change of 40 J mol-1 K-1 . Further optical investigations indicate that 1 reveals a narrow direct bandgap (2.024 eV) attributed to the slight bending of I-Pb-I edge and inorganic [Pb2 I7 ]n layer and a superior photoluminescence (PL) emission with super long lifetime of 0.1607 ms. It is believed that this work will pave an avenue to further design multifunctional semiconductors that combines energy storage and photoelectric materials.

Entropy of simple fluids with repulsive interactions near freezing

Among different thermodynamic properties of liquids, the entropy is one of the hardest quantities to estimate. Therefore, the development of models allowing accurate estimations of the entropy for different mechanisms of interatomic interactions represents an important problem. Here, we propose a method for estimating the excess entropy of simple liquids not too far from the liquid-solid phase transition. The method represents a variant of cell theory, which particularly emphasizes relations between liquid state thermodynamics and collective modes properties. The method is applied to calculate the excess entropy of inverse-power-law fluids with ∝r-n repulsive interactions. The covered range of potential softness is extremely wide, including the very soft Coulomb (n = 1) case, much steeper n = 6 and n = 12 cases, and the opposite hard-sphere interaction limit (n = ∞). An overall reasonably good agreement between the method's outcome and existing "exact" results is documented at sufficiently high fluid densities. Its applicability condition can be conveniently formulated in terms of the excess entropy itself. The method is also applied to the Lennard-Jones potential but demonstrates considerably lower accuracy in this case. Our results should be relevant to a broad range of liquid systems that can be described with isotropic repulsive interactions, including liquid metals, macromolecular systems, globular proteins, and colloidal suspensions.

Thermal transport and phase transitions of zirconia by on-the-fly machine-learned interatomic potentials

Machine-learned interatomic potentials enable realistic finite temperature calculations of complex materials properties with first-principles accuracy. It is not yet clear, however, how accurately they describe anharmonic properties, which are crucial for predicting the lattice thermal conductivity and phase transitions in solids and, thus, shape their technological applications. Here we employ a recently developed on-the-fly learning technique based on molecular dynamics and Bayesian inference in order to generate an interatomic potential capable to describe the thermodynamic properties of zirconia, an important transition metal oxide. This machine-learned potential accurately captures the temperature-induced phase transitions below the melting point. We further showcase the predictive power of the potential by calculating the heat transport on the basis of Green–Kubo theory, which allows to account for anharmonic effects to all orders. This study indicates that machine-learned potentials trained on the fly offer a routine solution for accurate and efficient simulations of the thermodynamic properties of a vast class of anharmonic materials.

One Hundred Years of Ferroelectrics

The brief history of ferroelectrics and related piezoelectrics and pyroelectrics is reviewed in terms of basic science and application. In 1920, J. Valasek discovered the ferroelectricity of Rochelle salt. Since then ferroelectrics have been widely used for sensors, actuators, and electronic and optical devices. Also, phase transitions in solids and hysteretic switching dynamics have been studied in ferroelectrics.

Ab initio phase diagram of silver

Silver has been considered as one of the simple one-phase materials that do not exhibit high pressure or high temperature polymorphism. The solid phase of Ag at ambient conditions is face-centered cubic (fcc) one. However, very recently another solid phase of silver, body-centered cubic (bcc) one, was detected in shock-wave (SW) experiments, and a more sophisticated phase diagram of Ag with the two solid phases was published by Smirnov. In this work, using a suite of ab initio quantum molecular dynamics (QMD) simulations based on the Z methodology which combines both direct Z method for the simulation of melting curves and inverse Z method for the calculation of solid–solid phase boundaries, we refine the phase diagram of Smirnov. We calculate the melting curves of both fcc-Ag and bcc-Ag and obtain an equation for the fcc–bcc solid–solid phase transition boundary. We also obtain the thermal equation of state of Ag which is in agreement with experimental data and QMD simulations. We argue that, despite being a polymorphic rather than a simple one-phase material, silver can be considered as an SW standard.

Logarithmic wave-mechanical effects in polycrystalline metals: theory and experiment

Schrodinger-type wave equations with logarithmic nonlinearity occur in hydrodynamic models of Korteweg-type materials with capillarity and surface tension, which can undergo liquid-solid or liquid-gas phase transitions. One of the predictions of the theory is a periodic pattern of density inhomogeneities occurring in the form of either bubbles (topological phase), or cells (non-topological phase). Such inhomogeneities are described by solitonic solutions of a logarithmic wave equation, gaussons and kinks, in the vicinity of the liquid-solid phase transition. During the solidification process, these inhomogeneities become centers of nucleation, thus shaping the polycrystalline structure of the metal grains. The theory predicts a Gaussian profile of material density inside such a cell, which should manifest in a Gaussian-like profile of microhardness inside a grain. We report experimental evidence of large-scale periodicity in the structure of grains in the ferrite steel S235/A570, copper C-Cu/C14200, austenite in steel X10CrNiTi18-10/AISI 321, and aluminium-magnesium alloy 5083/5056; and also Gaussian-like profiles of microhardness inside an averaged grain in these materials.

Crystal structure and heat capacity study of (C12H25NH3)2CoCl4(s) phase change material

Crystal structure of a novel complex (C12H25NH3)2CoCl4(s) has been determined by X-ray crystallography. Crystal system of the compound is monoclinic, and space group is P2(1)/c. Unit cell dimensions are a = (0.73492 ± 0.00010) nm, b = (1.02115 ± 0.00013) nm, and c = (4.2486 ± 0.0003) nm; α = 90°, β = (94.061 ± 0.002)°, γ = 90°, and Z = 4. Low-temperature heat capacities of the title compound are measured by an improved precision automated adiabatic calorimeter in the temperature range from 77 to 396 K. A solid to solid phase transition process occurs in the temperature range of 330 ∼ 365 K in the heat capacity curve, and peak temperature, molar transition enthalpy and entropy from three series of heat capacity measurements of the title compound are determined. The average phase transition temperature Ttrs, phase transition enthalpy ∆trsHm and phase transition entropy ∆trsSm from three series of experiments are (363.06 ± 0.54) K, (83.119 ± 0.197) kJ•mol−1 and (228.94 ± 0.34) J•K−1•mol−1, respectively. Experimental values of molar heat capacities in the temperature regions of 77–327 K and 367–396 K are, respectively fitted to two polynomial equations. Polynomial fitted values of molar heat capacities and fundamental thermodynamic functions of the sample relative to standard reference temperature 298.15 K are calculated and tabulated at an interval of 5 K.

Preparation and characterization of phase-change energy storage nonwoven fabric

In this work, a phase-change energy storage nonwoven fabric was made of polyurethane phase-change material (PUPCM) by a non-woven melt-blown machine. Polyethylene glycol 2000 was used as the phase transition unit and diphenyl-methane-diisocyanate as the hard segment to prepare PUPCM. Thermal stability of the PUPCM was evaluated through thermal stability analysis. The performance of pristine PUPCM was determined by Fourier transform infrared spectroscopy and differential scanning calorimetry to analyze the spinning technology of spinning temperature and the stretching process. Phase-change energy storage nonwoven fabric (413.22 g/m2) was prepared, and the morphology, solid–solid exothermic phase transition, mechanical properties, and the structures were characterized. The enthalpy of solid–solid exothermic phase transition reached 60.17 mJ/mg (peaked at 23.14°C). The enthalpy of solid–solid endothermic phase transition reached 67.09 mJ/mg (peaked at 34.34°C). The strength and elongation of phase-change energy storage nonwoven fabric were found suitable for garments and tent fabrics.

Mechanistic insights into lepidocrocite conversion to hematite from variable temperature Raman microscopy

The consistent fabrication of high performance α-Fe2O3 photoanodes for the oxygen evolution reaction remains a challenge. We work towards resolving this issue by developing in situ variable temperature Raman spectroscopy as a means to better understand the formation of α-Fe2O3, using the conversion of γ-FeOOH to α-Fe2O3 under varied gaseous environments as a model case. The sensitivity of Raman spectroscopy to structural changes provides mechanistic insights that are not readily available in more conventional approaches, such as thermal gravimetric analysis and differential scanning calorimetry. The Raman spectra are combined with conventional thermal analyses to interpret the photoelectrocatalytic performance of a series of α-Fe2O3 photoanodes prepared by systematic variation of a three-stage annealing protocol. The combined results suggest that protohematite, a form of α-Fe2O3 where trapped hydroxyl ligands are balanced by Fe(III) vacancies, forms between 200 °C and 400 °C in a reaction environment-dependent fashion. This protohematite is shown to be remarkably persistent once formed, degrading photoelectrocatalytic performance. This research advances understanding of the γ-FeOOH to α-Fe2O3 structural transformation, illustrates a powerful method to study solid state phase transitions, and provides guidance for the synthesis of high quality α-Fe2O3 from a convenient precursor.

Solid–solid phase transition in adenine riboswitch crystals driven by large conformational changes induced by ligand

Solid–solid phase transition in adenine riboswitch crystals driven by large conformational changes induced by ligand

Polymorphic Crystallization Design to Prevent the Degradation of the β-Lactam Structure of a Carbapenem

The cooling crystallization of carbapenem CS-023 was performed at 25 °C in an aqueous solution. Tetrahydrate crystals (form H) were obtained. Hydrate crystals are promising drugs, but there has been problems in manufacturing such crystals. During cooling crystallization, a dissolution process at a high temperature of 70 °C was utilized. The main problem in manufacturing was that the degradation rate of CS-023 at 70 °C was high, as expressed in the half-life period of 2.97 h. Poor solvent crystallization using ethanol was observed at 25 °C. Thus, a different polymorph (Form A) was obtained. Form A comprised CS-023, 5/2 ethanol, and 1/2 H2O. Form A, containing ethanol, is not suitable as a drug. Form A was then transformed to another polymorph of hydrate crystals or tetrahydrate Form H. Another hydrate polymorph, Form B, was obtained through the solid phase transformation of Form A and further transformed to the tetrahydrate Form H, at high humidity over 80% RH. This process, which proceeded at the low temperature of 25 °C, helped to prevent the degradation of CS-023, thereby avoiding wastage. Furthermore, the solid-phase transition could be controlled with vapor composition.