Solid Phase Transition Research Articles

Effect of Cooling Rate on Phase Transformation and Strain Response of SA508-3 Steel by Numerical and Experimental Study

Abstract The key to accurately predict welding residual stress is to explore the solid-phase transition law of SA508-3 steel and establish the phase transition model under continuous cooling conditions. The effects of cooling rate on phase transformation and strain response of SA508-3 steel were investigated in this paper. The established programs accurately predict the evolution of microstructure at different cooling rates, the relationship between the bainite volume fraction and temperature is fitted by a modified bainite transformation model and is validated by optical microscopy and dilatometric test. The strain evolution of SA508-3 steel is predicted at different cooling rates and is verified by the dilatometric test. In addition, the effects of bainite transformation and martensite transformation on the strain response of SA508-3 steel are intensively discussed. This work casts light on the simulation of metallurgical effects at different cooling region during welding.

Solvent-free preparation of α-Fe2O3 nanoparticles from metallurgical iron sludge for the treatment of Cr(VI)-contaminated wastewater

Metallurgical iron sludge (MIS) is an industrial by-product that needs high value-added utilization without harmless to the environment. Here, α-Fe2O3 nanoparticles were successfully prepared from MIS via a novel solvent-free method (SN-α-Fe2O3) and applied to Cr(VI) ions removal. Compared to conventional methods using pure reagents, the as-prepared SN-α-Fe2O3 aggregated into uniform cake-like mesoporous structures with a higher specific surface area (115.03 m2/g) and smaller crystal size (32.87 nm), thus providing a large number of active adsorption sites. Therefore, SN-α-Fe2O3 exhibited superior Cr(VI) removal performance (removal efficiency 98.21%) in Cr(VI)-contaminated wastewater compared to previous studies. Furthermore, Cr(VI)-saturated SN-α-Fe2O3 exhibited great stability under acidic conditions and maintained excellent adsorption performance after five cycles. The proposed SN-α-Fe2O3 preparation process forwent the use of water solvent or organic solvents, thus improving reactor efficiency and avoiding wastewater generation. Particularly, the growth mechanism of SN-α-Fe2O3 crystal followed the solid-phase transition mechanism, whereby small amounts of crystal water contained in pretreated MIS was sufficient for SN-α-Fe2O3 crystallization. Furthermore, SN-α-Fe2O3-mediated Cr(VI) adsorption was attributed to the electrostatic interaction and reduction of hydroxyl group on the surface of SN-α-Fe2O3. This study thus provides a win-win strategy for the conversion of industrial by-products into valuable nanoparticles for the cost-efficient treatment of heavy metal-polluted wastewater.

Crystallization Behavior of Isotactic Polybutene Blended with Polyethylene.

In this work, the melt crystallization behavior and the solid phase transition of isotactic polybutene (PB) were studied in the polybutene/high-density polyethylene (PB/PE) blends covering the whole composition range. For the dynamic cooling crystallization, PE exhibits almost the same crystallization temperature in all blends, whereas PB exhibits a distinct non-monotonic dependence on the composition ratio. Combining the ex situ X-ray diffraction and in situ Fourier transform infrared spectroscope, it was demonstrated that during cooling at 10 °C/min, the presence of at least 70 wt% PE can induce the formation of form I′ directly from the amorphous melt. The detailed relations of polymorphism with temperature were systematically investigated for the PB/PE blends. Different from the formation of the sole tetragonal phase with ≤50 wt% PE, the trigonal form I′ could crystallize directly from amorphous melt with ≥60 wt% PE, which can be further enhanced by elevating the temperature of isothermal crystallization. Interestingly, the critical lowest temperature of obtaining pure form I′ was 85 °C with 70 wt% PE and decreased to 80 °C as the PE fraction was increased to 80 wt%. On the other hand, the spontaneous phase transition from the kinetically favored form II into the thermodynamically stable form I was also explored with X-ray diffraction methods. It was found that at the room temperature, phase transition kinetics can be significantly accelerated by blending at least 70 wt% PE.

Z-α1-antitrypsin polymers impose molecular filtration in the endoplasmic reticulum after undergoing phase transition to a solid state.

Misfolding of secretory proteins in the endoplasmic reticulum (ER) features in many human diseases. In α1-antitrypsin deficiency, the pathogenic Z variant aberrantly assembles into polymers in the hepatocyte ER, leading to cirrhosis. We show that α1-antitrypsin polymers undergo a liquid:solid phase transition, forming a protein matrix that retards mobility of ER proteins by size-dependent molecular filtration. The Z-α1-antitrypsin phase transition is promoted during ER stress by an ATF6-mediated unfolded protein response. Furthermore, the ER chaperone calreticulin promotes Z-α1-antitrypsin solidification and increases protein matrix stiffness. Single-particle tracking reveals that solidification initiates in cells with normal ER morphology, previously assumed to represent a healthy pool. We show that Z-α1-antitrypsin–induced hypersensitivity to ER stress can be explained by immobilization of ER chaperones within the polymer matrix. This previously unidentified mechanism of ER dysfunction provides a template for understanding a diverse group of related proteinopathies and identifies ER chaperones as potential therapeutic targets.

Crystallization and Phase Transition of 1‐Butene Copolymers with Distinct Cyclic Co‐Units

Comprehensive SummaryThe dimethylpyridylamidohafnium catalyst was used to synthesize 1‐butene/cyclohexene and 1‐butene/vinylcyclohexane random copolymers, which have extra six‐membered cyclic co‐units in main chain and side chain, respectively. For the obtained copolymers of different incorporations, the crystallization from amorphous melt and the solid phase transition from tetragonal to trigonal phases were investigated with differential scanning calorimetry. Both of the incorporated cyclic co‐units decrease the crystallization kinetics, but the presence of cyclohexene keeps the melting temperature of copolymers constant. Interestingly, the strong memory effect of crystallization can appear at the elevated temperature even above the equilibrium melting temperature, as the content of co‐units was increased. The 1‐butene/vinylcyclohexane copolymer with 1.52 mol% co‐units exhibits a rather strong memory effect with the broad Domain IIa width of 43°C and the crystallization temperature raising of 24°C. Furthermore, the transition of tetragonal phase into trigonal phase was also explored for different co‐units and incorporations. It was found that both of the cyclohexene co‐units and vinylcyclohexane co‐units effectively slow down the kinetics of phase transition. However, the vinylcyclohexane co‐units have a much higher efficiency in suppressing phase transition than the cyclohexene co‐units, where 0.53 mol% vinylcyclohexane can completely stop phase transition within 1320 h. Considering the fact that copolymers with vinylcyclohexane co‐units actually have lower glass transition temperatures, it was indicated that the suppression of phase transition is also largely influenced by the steric co‐units in the side chain for the helical and positional adjustments, not only by the segmental mobility.

Mechanochemical assisted hydrogenation of Mg-CNTs-Ni:kinetics modeling and reaction mechanism

MgH2, as one of the most potential hydrogen storage materials, has received considerable attention. However, its development has been plagued by its slow hydriding kinetics. Mechanochemical milling is an effective and convenient method for producing MgH2@CNTs-Ni through a solid–gas reaction between Mg-CNTs-Ni and H2. However, the hydriding kinetics and the corresponding mechanism during the milling have not been mentioned. Thus, hydriding kinetics of Mg-CNTs-Ni was researched for the purpose of gaining insights into the reaction mechanism and obtaining the best milling parameters. Also, phase transition during the milling was analyzed using XRD and TEM. It is apparent that the Avrami-Erofeev (AE) model can well describe the mechanochemical process, which contains solid solution, phase transition and growth-controlled regime. Besides, kinetics of hydrogenation is limited by nucleation and growth of MgH2. By fitting with the Arrhenius equation, average apparent activation energy for the hydrogenation of Mg-CNTs-Ni is estimated to be 47.8 kJ mol−1.

Failure model with phase transition for ceramics under shock loading

An explicit failure model for ceramics undergoing a solid–solid phase transition under shock compression is developed and tested on silicon carbide and aluminum nitride. This model enhances the applicability of our failure model recently developed for boron carbide. Smoothed particle hydrodynamics simulations of ceramics under shock loading are performed to optimize the model parameters using the velocity profiles obtained in available shock-wave experiments. It is demonstrated that the inclusion of a phase transition with hysteresis is essential for agreement between simulations and experiments. Evolution of damage spreading in samples with propagation of the failure wave front is discussed. We show that it changes from a homogeneous damage pattern to regular structures of failure bands, where growth is guided by distributions of equivalent stress and shear strength of material within the band tips.

Measurement of the Hugoniot and shock-induced phase transition stress in wrought 17-4 PH H1025 stainless steel

Uniaxial strain, reverse-ballistic impact experiments were performed on wrought 17-4 PH H1025 stainless steel, and the resulting Hugoniot was determined to a peak stress of 25 GPa through impedance matching to known standard materials. The measured Hugoniot showed evidence of a solid–solid phase transition, consistent with other martensitic Fe-alloys. The phase transition stress in the wrought 17-4 PH H1025 stainless steel was measured in a uniaxial strain, forward-ballistic impact experiment to be 11.4 GPa. Linear fits to the Hugoniot for both the low and high pressure phase are presented with corresponding uncertainty. The low pressure martensitic phase exhibits a shock velocity that is weakly dependent on the particle velocity, consistent with other martensitic Fe-alloys.

Observation of an Intermediate State in the Solid–Solid Phase Transition of a Single Crystal of Perylene

Observation of an Intermediate State in the Solid–Solid Phase Transition of a Single Crystal of Perylene

Soft Liquid Metal Infused Conductive Sponges

AbstractLiquid metal droplets of gallium (Ga) and Ga‐based alloys are traditionally incorporated as deformable additives into soft elastomers to make them conductive. However, such a strategy has not been implemented to develop conductive sponges with real sponge‐like characteristics. Herein, polyurethane‐based sponges with Ga microdroplets embedded inside the polyurethane walls are developed. The liquid phase (at 45 °C) and solid phase (at room temperature) transition of the Ga fillers shows the temperature‐dependent functional variations in the mechanical, thermal, and electrical properties on the prepared composite sponges, which are investigated in detail. Unlike elastomers, the sponge possesses excellent elastic recovery, at ≈90%, and conductivity durability without sacrificing structural integrity. The reversible change of resistivity range is remarkable. When the Ga fillers account for 18% of the total sponge volume, the electrical resistivity varies from infinite values (insulator) under no applied pressure to 39.0 Ω m for the solid phase and 3.8 Ω m for the liquid phase under 386.8 kPa. New opportunities in developing flexible electrically conductive composite sponges with tunable mechanical and electrical properties that can be implemented for a variety of future applications are proposed.

Microstructure and Pitting Corrosion Resistance of AISI 430 Ferritic Stainless Steel Joints Fabricated by Ultrasonic Vibration Assisted Cold Metal Transfer Technique

The influences of ultrasonic vibration during cold metal transfer welding process on the microstructure, element distribution and pitting resistance of AISI 430 ferritic stainless steel joints with ER 308L as filler metal were investigated. The combined effects of mechanical vibration, acoustic streaming and cavitation of ultrasonic vibration significantly refined the primary ferrite grain in the weld metal and then impacted the subsequent solid-phase transition process, leading to the ~45% reduction of ferrite content in the weld metal. Moreover, these effects also resulted in the homogenization of alloying elements in the weld metal. The pitting corrosion resistance of the welded joints with ultrasonic vibration was increased compared with that of without ultrasonic vibration, but lower than the base metal. The pitting resistance of the weld metal with ultrasonic vibration was higher than that of the weld metal without ultrasonic vibration and base metal, while that of the one without ultrasonic vibration was lower than the base metal.

Tetramethyl Succinonitrile as a Solid Plasticizer in a Poly(ethylene oxide)8 -LiI-I2 Solid Polymer Electrolyte.

Dye-sensitized solar cell (DSSC) is a promising alternative to the commercially available amorphous silicon-based solar cell because of several advantageous properties. A DSSC with a fast ion conducting solid polymer electrolyte is required for the arid atmosphere of Gulf countries. In this work, a new matrix, poly(ethylene oxide)-tetramethyl succinonitrile blend to synthesize a blend-LiI-I2 solid polymer electrolyte for the DSSC application has been proposed. The tetramethyl succinonitrile is a member of plastic crystal with a solid-solid phase transition temperature (Tpc ) of ≈71°C and melting temperature (Tm ) of ≈170.5°C. Its molar fraction, 0.1-0.15 is sufficient enough for synthesizing a polymer electrolyte with electrical conductivity of >10-4 S cm-1 at room temperature. This electrolyte shows Vogel-Tamman-Fulcher type behavior with a low value (≈0.083eV) of pseudo-activation energy for easy ion transport. The results of Fourier-transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry studies reveal the plasticizing effect of tetramethyl succinonitrile to form an amorphous phase. This electrolyte results in a ≈661% gain in short-circuit current density and thereby a ≈552% gain in the cell efficiency (≈3.5%) with respect to the DSSC prepared with the tetramethyl succinonitrile-free electrolyte.

Unconventional Hysteretic Transition in a Charge Density Wave.

Hysteresis underlies a large number of phase transitions in solids, giving rise to exotic metastable states that are otherwise inaccessible. Here, we report an unconventional hysteretic transition in a quasi-2D material, EuTe_{4}. By combining transport, photoemission, diffraction, and x-ray absorption measurements, we observe that the hysteresis loop has a temperature width of more than 400K, setting a record among crystalline solids. The transition has an origin distinct from known mechanisms, lying entirely within the incommensurate charge density wave (CDW) phase of EuTe_{4} with no change in the CDW modulation periodicity. We interpret the hysteresis as an unusual switching of the relative CDW phases in different layers, a phenomenon unique to quasi-2D compounds that is not present in either purely 2D or strongly coupled 3D systems. Our findings challenge the established theories on metastable states in density wave systems, pushing the boundary of understanding hysteretic transitions in a broken-symmetry state.

Between Harmonic Crystal and Glass: Solids with Dimpled Potential-Energy Surfaces Having Multiple Local Energy Minima

Solids with dimpled potential-energy surfaces are ubiquitous in nature and, typically, exhibit structural (elastic or phonon) instabilities. Dimpled potentials are not harmonic; thus, the conventional quasiharmonic approximation at finite temperatures fails to describe anharmonic vibrations in such solids. At sufficiently high temperatures, their crystal structure is stabilized by entropy; in this phase, a diffraction pattern of a periodic crystal is combined with vibrational properties of a phonon glass. As temperature is lowered, the solid undergoes a symmetry-breaking transition and transforms into a lower-symmetry phase with lower lattice entropy. Here, we identify specific features in the potential-energy surface that lead to such polymorphic behavior; we establish reliable estimates for the relative energies and temperatures associated with the anharmonic vibrations and the solid–solid symmetry-breaking phase transitions. We show that computational phonon methods can be applied to address anharmonic vibrations in a polymorphic solid at fixed temperature. To illustrate the ubiquity of this class of materials, we present a range of examples (elemental metals, a shape-memory alloy, and a layered charge-density-wave system); we show that our theoretical predictions compare well with known experimental data.

Phase separation mechanism for a unified understanding of dissipative pattern formation in a Liesegang system.

Dissipative patterns with solid-phase transitions are ubiquitous in nature. Despite their ubiquitous nature, there is no unified understanding of the non-equilibrium self-assembly mechanisms of such pattern formation. The Liesegang pattern (LP) is a typical model that has the potential to describe dissipative pattern formation arising from the nonlinear coupling of directional mass transport of water-soluble substances into a porous media with their solid-phase transition processes. However, the conventional mechanism in a Liesegang system lacks practicality because most of the existing studies have focused only on the transition mechanism of nucleation from the molecular to the solid state. In this study, we demonstrate a novel experimental system based on a phase transition and separation mechanism that does not require nucleation, namely, the pH-induced aggregation of gold nanoparticles modified with 11-mercaptoundecanoic acid (MUA-Au NPs) by H+ diffusion in a solid hydrogel. Combined experiments and numerical simulations reveal that pattern formation is driven by the macroscopic phase-separation mechanism. Furthermore, the pattern periodicity obtained from both experiments and simulations follows the classical spacing law of LP, namely, the LP morphology is determined without the need for nucleation. Therefore, we can show that the formation of LPs can be described in a unified mechanism, regardless of whether nucleation occurs. This finding opens the possibility that the chemical Liesegang system can be applied as a practical model for proving the mechanisms of similar dissipative pattern formation.

Photo-induced phase-transitions in complex solids.

Photo-induced phase-transitions (PIPTs) driven by highly cooperative interactions are of fundamental interest as they offer a way to tune and control material properties on ultrafast timescales. Due to strong correlations and interactions, complex quantum materials host several fascinating PIPTs such as light-induced charge density waves and ferroelectricity and have become a desirable setting for studying these PIPTs. A central issue in this field is the proper understanding of the underlying mechanisms driving the PIPTs. As these PIPTs are highly nonlinear processes and often involve multiple time and length scales, different theoretical approaches are often needed to understand the underlying mechanisms. In this review, we present a brief overview of PIPTs realized in complex materials, followed by a discussion of the available theoretical methods with selected examples of recent progress in understanding of the nonequilibrium pathways of PIPTs.

On the colossal barocaloric effect in higher n-alkanes

Long-chain n-alkanes exhibit a remarkable barocaloric effect in a wide range of temperatures, enhanced by the onset of a liquid–solid pressure-induced phase transition, and are promising candidates for the development of solid-state cooling systems.

Polymorphism and solid–solid phase transitions of hydrogen bonded 2-adamantanol and 2-methyl-2-adamantanol compounds

The polymorphic behavior at normal pressure as a function of temperature of 2-adamantanol (C10H16O) and 2-methyl-2-adamantanol (C11H18O) has been investigated by single-crystal and powder X-ray diffraction as well as differential scanning calorimetry.

Giant barocaloric effects with a wide refrigeration temperature range in ethylene vinyl acetate copolymers.

Solid-state cooling technology based on the caloric effects of phase-transition materials has been a research hotspot due to its environmental friendliness and high efficiency, but limited for practical applications due to its narrow working temperature region. Here, we report giant barocaloric effects based on pressure-driven liquid-solid phase transitions in elastic copolymers of ethylene and vinyl acetate. Giant adiabatic temperature changes of up to 29.6/-26.9 K are directly observed under rapid compressions/decompressions of 400 MPa near the liquid-solid phase transition points. Strikingly, since both the solid and the liquid sides can show giant barocaloric effects, a very broad refrigeration temperature region of more than 110 K is achieved in these copolymers. Furthermore, a cooling prototype is designed to demonstrate the potential applications of these liquid/elastic barocaloric materials. Our study sheds light on exploring liquid-solid phase transition materials for the next-generation refrigerators.

Biochemical and biophysical characterization of pathological aggregation of amyloid proteins.

Protein amyloid fibrillation, a process of liquid to solid phase transition, is involved in the pathogenesis of a variety of human diseases. Several amyloid proteins including α-synuclein (α-syn), Tau, amyloid β (Aβ) protein, and TAR DNA-binding protein 43 kDa (TDP-43) form pathological fibrils and deposit in patient brains of different neurodegenerative diseases (NDs) such as Parkinson's disease (PD), Alzheimer's disease (AD) and Amyotrophic lateral sclerosis (ALS). Preparation and characterization of amyloid fibrils in vitro are essential for studying the molecular mechanism underlying the dynamic amyloid aggregation and its pathogenesis in diseases. In this protocol, we take PD-associated α-syn as an example, and describe amyloid protein purification and fibrillation approaches. We then introduce biochemical and biophysical characterization of amyloid fibrils by Thioflavin-T (ThT) fluorescence kinetics assay, transmission electron microscopy (TEM), atomic force microscopy (AFM) and multiple fibril stability measurement assays. The approaches described here are applicable to different amyloid proteins, and are of importance for further study on the structure determination of amyloid fibrils and their pathological function in cells and animal models.