Solid-liquid Transition Temperature Research Articles

Effect of Ni addition on the crystallization behaviors of Cr-Co alloy

Optimizing the crystallization kinetics of Cr-Co alloys through doping is of practical significance to their industrial applications. By employing molecular dynamics (MD) simulations, this study investigates the effect of Ni concentration on the solidification process of Cr30Co70-xNix (x=0, 10, 20, 30, 40) alloys, focusing on crystallization behavior during quenching and microstructural characterization. The evolution of potential energy indicates that higher Ni concentrations promote crystallization, resulting in a lower liquid-solid transition temperature and enhanced relaxation. However, Ni doping does not alter the preference for chemical ordering, with Cr-Co bonding predominant across all the compositions. Microstructural analysis reveals a shift towards fcc-dominant ternary alloys with increased Ni content. Furthermore, Ni addition impacts defect distribution, notably reducing "other" types of defects in the Cr-Co binary alloy. These findings provide a quantitative reference for adjusting the crystallization behavior of Cr-Co alloys through doping, with implications for their design, manufacturing, and utilization.

Co-solvent and additive joint engineering enable long-life and wide-temperature Zn metal battery

The dendrite growth and interfacial side reactions pose significant threaten to the practical applications of aqueous zinc metal batteries (AZMBs), especially at subzero temperature environments. To this end, co-solvent and additive joint engineering is proposed to design hybrid electrolyte, which consists of a mixture of 1,2-propanediol (1,2-PG) solvent and H2O with trace amounts of 18-crown-6 molecules, for constructing stable wide-temperature AZMBs. Notably, the 18-crown-6 and 1,2-PG molecules can both disturb the original hydrogen-bond network of H2O molecules. Interestingly, the 18-crown-6 molecules predominantly tends to absorb on the Zn anode surface and form favorable organic-inorganic hybrid SEI layer to regulate Zn deposition behaviors. The 1,2-PG molecules are responsible for reconstructing the solvation structure of Zn2+ and lowering the solid-liquid transition temperature of aqueous electrolyte, suppressing the H2O-induced side reactions and improving the antifreezing capability of electrolyte. Furthermore, the hybrid electrolyte induces the preferential Zn(002) plane deposition under the low temperature environments due to the synergistic effect of 18-crown-6 and 1,2-PG molecules, enhancing the Zn2+ transport and deposition kinetics. Consequently, the hybrid electrolyte endows the assembled cells with enhanced cycling lifespan and reversibility within the wide temperature range from -50 to 25 °C, expanding the application range of AZMBs.

A Universal Additive Design Strategy to Modulate Solvation Structure and Hydrogen Bond Network toward Highly Reversible Fe Anode for Low-Temperature All-Iron Flow Batteries.

Aqueous all-iron redox flow batteries (RFBs) are promising competitors for next-generation grid-scale energy storage applications. However, the high-performance operation of all-iron RFBs in a wider temperature range is greatly hindered by inferior iron plating/stripping reaction and low solid-liquid transition temperature at Fe anode. Herein, a universal electrolyte additive design strategy for all-iron RFBs is reported, which realizes a highly reversible and dendrite-free Fe anode at low temperatures. Quantum chemistry calculations first screen several organic molecules with oxygen-containing functional groups and identify N,N-Dimethylacetmide (DMAc) as a potential candidate with low cost, high solubility, and strong interactions with Fe2+ and H2 O. Combined experimental characterizations and theoretical calculations subsequently demonstrate that adding DMAc into the FeCl2 solution effectively reshapes the primary solvation shell of Fe2+ via the Fe2+ -O (DMAc) bond and breaks hydrogen-bonding network of water through intensified H-bond interaction between DMAc and H2 O, thereby affording the Fe anode with enhanced Fe/Fe2+ reversibility and lower freezing point. Consequently, the assembled all-iron RFB achieves an excellent combination of high power density (25mWcm-2 ), long charge-discharge cycling stability (95.59% capacity retention in 103h), and preeminent battery efficiency at -20°C (95% coulombic efficiency), which promise a future for wider temperature range operation of all-iron RFBs.

Mechanism of slag pellets sticking on the wall of reduction pot in magnesium production by Pidgeon process

In the preparation of magnesium by Pidgeon process, the phenomenon slag pellets sticking on the wall of reduction pot always appear, and the glaze sticking on the inner wall of the reduction pot is difficult to remove. The mechanism of this phenomenon is studied in this work by X-ray fluorescence spectrometer (XRF) measurement, electron probe microanalyzer scanning (EPMA) analysis, differential scanning calorimetry (DSC) analysis, and thermodynamic calculations. The main components of the glaze are MgO, Ca12Al14F2O32, CaF2, CaO, and a small amount of Ca4Si2O7F2. The solid-liquid transition temperature of Ca12Al14F2O32 and CaF2 is close to the production temperature of Pidgeon process, which leads to the bonding between the slag pellets and the pot wall. The loss of CaF2 in glaze layer will reduce the total amount of liquid phase and increase the temperature at which Ca12Al14F2O32 is completely transformed into liquid phase, which causes glaze layer sticking on the inner wall of the reduction pot.

Temperature sensing properties of a Fabry-Perot fiber probe based on agar film

A Fabry-Perot interferometer probe temperature sensor composed of capillary and agar film for temperature detection is proposed. The effect of capillary length and agar concentration on the performance of the sensor are studied that the temperature response obviously improves on condition that the capillary is shorter and the agar concentration is lower. Meanwhile, the sensor has a solid-liquid transition temperature at about 40°C, which can be determined as the boundary point for human body temperature detection below or above 40°C. Sensors adapted to different demands can be prepared by changing the capillary length and the agar concentration. Good repeatability and stability make the proposed sensor reach certain potential in the field of temperature sensing.

Effect of Ti Content on the Microstructure and Properties of CoCrFeNiMnTix High Entropy Alloy.

The aim of this study was to investigate the effects of the Ti element addition on the microstructure and properties of CoCrFeNiMn high entropy alloys. The Ti element modified CoCrFeNiMnTix high entropy alloys were prepared by vacuum arc melting processing. The Ti rich body-centered cubic structure phase was observed in CoCrFeNiMnTi0.25 and CoCrFeNiMnTi0.55 instead of a simple face-centered cubic structure in CoCrFeNiMn. The amount of the Ti-rich phase depicted an increasing trend with increasing Ti content. Simultaneously, the mechanical properties of CoCrFeNiMnTix were obviously improved. When the Ti content is 0, 0.25 and 0.55, the microhardness is 175 HV, 253 HV and 646 HV, which has an obvious increasing trend, while the ductility decreased. The tensile properties show a trend of first strengthening and then decreasing, changing from 461 MPa to 631 MPa and then to 287 MPa. When x was 0.55, the solid–liquid transition temperature of the alloy decreased, and the melting temperature range increased.

Modulating electrolyte structure for ultralow temperature aqueous zinc batteries

Rechargeable aqueous batteries are an up-and-coming system for potential large-scale energy storage due to their high safety and low cost. However, the freeze of aqueous electrolyte limits the low-temperature operation of such batteries. Here, we report the breakage of original hydrogen-bond network in ZnCl2 solution by modulating electrolyte structure, and thus suppressing the freeze of water and depressing the solid-liquid transition temperature of the aqueous electrolyte from 0 to –114 °C. This ZnCl2-based low-temperature electrolyte renders polyaniline||Zn batteries available to operate in an ultra-wide temperature range from –90 to +60 °C, which covers the earth surface temperature in record. Such polyaniline||Zn batteries are robust at –70 °C (84.9 mA h g−1) and stable during over 2000 cycles with ~100% capacity retention. This work significantly provides an effective strategy to propel low-temperature aqueous batteries via tuning the electrolyte structure and widens the application range of temperature adaptation of aqueous batteries.

A promising "metastable" liquid crystal stationary phase for gas chromatography

The liquid crystal state is an ordered physical state between a solid and a liquid. Previous research, in gas chromatography, proved that it provides a geometric selectivity, which allows the separation of geometric position isomers and cis-trans isomers that are difficult to separate on conventional gas chromatography stationary phases (polydimethyl siloxane derived and polyethylene glycol stationary phases). However, their use was generally very limited by the rather high temperature at which they must be operated, normally above the solid-liquid crystal transition temperature. In the present study we are interested in a new synthesized material, 1,4- bis (4-bromohexyloxy benzoate) phenyl (BHOBP). The first characterizations of BHOBP were carried out by thermogravimetric analysis, hot-stage optical microscopy and differential scanning calorimetry to control the thermal stability of the BHOBP as well as the nematic texture of the mesophase highlighted in a well-defined temperature range (120 °C-200 °C). When heated, the solid compound led to a stable liquid crystal state. Its cooling has revealed "a new metastable physical state, which is the supercooled liquid crystal phase". After these first characterizations, the new material was used as a stationary phase for gas chromatography. The BHOBP was deposited in a capillary column by the dynamic method. The inverse gas chromatography study of the column revealed a solid-stable nematic phase transition temperature, in agreement with the first characterization methods. The stable liquid crystal phase showed good resolutions in the analysis of some geometric isomers of low volatility as PAHs. The presence of the supercooled liquid crystal state in the chromatographic column has also been confirmed. This new metastable state is particularly interesting because it enlarged the scope of this material by improving the resolution of several mixtures. Thus, the separation of highly volatile mixtures of geometric isomers (e.g. cis and trans-decalin) was achieved only through this metastable mesophase confirming its unique selectivity. The metastable liquid crystal, used at 80 °C, has also exhibited an original behavior by its stability after several weeks of use at the same temperature, maintaining constant retention factors and selectivity.

Electrowetting of Ionic Liquid on Graphite: Probing via in Situ Electrochemical X-ray Photoelectron Spectroscopy

Thin films of ionic liquid 1-ethyl-3-methylimidazolium bis(fluoromethylsulfonyl)imide ([EMIm][FSI]) vapor-deposited on highly oriented pyrographite (HOPG) were studied by X-ray photoelectron spectroscopy and atomic force microscopy. The results revealed a reversible morphological transition from a "drop-on-layer" structure to a "flat-layer" structure at positive, and not at negative, polarization. The effect is rationalized in terms of electric-field-induced reduction of the liquid-solid transition temperature in the ionic liquid film, when its thickness is comparable to the charge screening length. The observed bias asymmetry of [EMIm][FSI] electrowetting on HOPG is tentatively explained by the bilayer structure at the interface driven by the affinity of the imidazolium ring to the HOPG surface.

Effect of nanopore confinement on the thermal and structural properties of heneicosan

The effect of nano-confinement on the phase transitions of heneicosane (n-C21H44, C21) were investigated using differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (XRD). When C21 is confined within the pores of controlled pore glasses (CPGs), SBA-15 or other mesoporous materials, the solid-solid (Ts) and solid-liquid (Tm) transition temperatures are depressed. The depression of the phase transition temperatures (ΔTs, ΔTm) for C21 in CPGs and SBA-15, the degree of supercooling and enthalpy change (ΔHs, ΔHm) for C21 in CPGs, exhibited a linear dependence on the inverse pore size. The ΔTm values were insensitive to the polarity pore wall but varied with the pore geometry. XRD analysis revealed that the lamellar ordering characteristic for the solid C21 was disturbed in the nanopores, with the extent increasing as the pore size decreased. A new rotator phase RII is found for C21 confined in CPG (12 nm) and SBA-15 (14.4 nm).

Neat Protein-Polymer Surfactant Bioconjugates as Universal Solvents.

Solvents, particularly those having low volatility, are of great interest for the biocatalytic synthesis of utility chemicals and fuels. We show novel and universal solvent-like properties of a neat and water-less polymer surfactant-bovine serum albumin (BSA) conjugated material (WL-PS pBSA). This highly viscous, nonvolatile material behaves as a liquid above its solid-liquid transition temperature (∼25-27 °C) and can be used as a solvent for variety of completely dry solutes of different sizes and surface chemistries. We show using a combination of optical microscopy and steady -state and time-resolved fluorescence spectroscopy that dry and powdered dyes (hydrophobic Coumarin 153 (C153)), enzymes (α-chymotrypsin (α-Chy)), or even 1 μm microparticles (diffusion coefficient ca. three orders slower than C153), can be solubilized and completely dispersed in the WL-PS pBSA solvent above 25 °C. While C153, irrespective of its mode of addition to WL-PS pBSA, binds similarly to BSA, α-Chy can be stabilized and activated to perform its hydrolysis function, even at 100 °C. This work therefore provides insights into the form of universal solvent characteristic property for this new class of nonaqueous, nonvolatile, biodegradable protein-polymer surfactant-based conjugated materials and suggests potential new avenues that can have a huge impact on biocatalysis, bionanotechnology, drug delivery, and other applications.

Application of thermoporometry for characterization of mesoporous silicon: In search for probe liquid aimed at large pores

Characterization of porous samples containing mesopores larger than 10 nm in size is often difficult due to limitations of standard methods. In the present work thermoporometry (TPM) was introduced to address these challenges. Various probe liquids (water, n-heptane, cyclohexane and o-xylene) were previously applied for TPM characterization of mesoporous silicon containing pores of 20–50 nm. The results, obtained with the use of calibration equations, confirmed the necessity of new probe liquid more suitable for characterization of such samples. Octamethylcyclotetrasiloxane was found to be the most appropriate choice. Mesoporous silicon samples were used as model materials in order to establish an empirical equation between the pore sizes, derived from mercury porometry, and the solid-liquid transition temperature depressions derived from differential scanning calorimetry for the octamethylcyclotetrasiloxane confined inside the pores and in bulk phase. The new calibration equations obtained within this work can be successfully used for characterization of the samples with large mesopores.

The solidification and precipitation behaviors of AE42 magnesium alloy

The solidification and precipitation behaviors of AE42 magnesium at different quenching temperatures were studied. The results showed that the liquid–solid transition temperature range of AE42 alloy was from 630[Formula: see text]C to 590[Formula: see text]C. Precipitation of two kinds of rare earth compounds during solidification had been found. One was Al2RE phase at 616[Formula: see text]C. The other was Al[Formula: see text]RE3 phase at 604[Formula: see text]C. The solidification path of AE42 alloy was L [Formula: see text] [Formula: see text]-Mg [Formula: see text] [Formula: see text]-Mg+Al2RE [Formula: see text] Al2RE+[Formula: see text]-Mg+Al[Formula: see text]RE3.

New approach for determining cartilage pore size distribution: NaCl-thermoporometry

It is often challenging to analyse the pore structure of biological samples because they are sensitive to drying or changes in the composition of liquid within the samples. In the present work, a method based on thermoporometry with NaCl solution is introduced to overcome these difficulties. It was observed that the DSC melting profiles of cartilage soaked in 4.5% aqueous NaCl solution exhibit an additional peak due to the melting of the hydrohalite phase inside cartilage pores. In order to establish an empirical equation between pore size and solid-liquid transition temperature, a series of mesoporous SBA-15 model samples was investigated. The results were employed to study the porosity of cartilage tissues before and after degradation procedures. The cartilage pore diameter was found to be 11–14 nm. The calculated pore size distribution of the cartilage tissue corresponded to the pore sizes previously derived for collagen network. The ability to measure the pore structure of cartilage will be beneficial when designing new computed tomography or magnetic resonance imaging contrast agents that can penetrate into cartilage tissue and have diagnostic potential for detecting various joint injuries.

Freezing and Melting Transitions under Mesoscalic Confinement: Application of the Kossel–Stranski Crystal-Growth Model

The Kossel–Stranski model of crystal growth has been adopted to study freezing and melting of fluids in mesoporous materials. The model is found to exhibit the key features observed in the experiments, including shifted solid–liquid and liquid–solid transition temperatures, irreversibility between freezing and melting, and strong impact of the pore geometry. By first analyzing fluids confined to cylindrical pores, we obtain several important insights into the transition mechanisms. In particular, we establish the conditions for the occurrences of equilibrium and metastable transitions and derive exact analytical equations interrelating the transition temperatures, confinement size, and the interaction parameters of the Kossel crystal. Variation of the channel diameter along the channel axis, mimicking disorder in real porous materials, is shown to strongly affect both freezing and melting. The model predicts that the freezing transition in disordered materials is governed by the pore blocking mechanism. The melting transition is found to result as an interplay of two different transition mechanisms.

Liquid–solid phase transition of hydrogen and deuterium in silica aerogel

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H2 and D2 in an ∼85%-porous base-catalyzed silica aerogel. We find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ∼4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H2 and D2 confined inside the aerogel monolith. Results for H2 and D2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

Phase transition behaviours of a single dendritic polymer.

Dendritic polymers with highly branching structures exhibit many unique properties. In this paper, a computational study using the Wang-Landau sampling technique is carried out to reveal the phase transition behaviours of dendritic homopolymers with various branching structures. Two types of dendritic homopolymers, dendrimers/dendrigrafts (D/D) and hyperbranched (HB) polymers are studied. It is found that with increasing degree of branching in the dendritic polymer, the liquid-solid (LS) transition temperature increases and the coil-globule (CG) transition becomes weak. Additionally, under similar degrees of branching and polymerization, D/D polymers have a higher LS transition temperature than HB polymers. The reason is that the D/D polymers have greater regularity in the radial distribution of the branching units, which facilitates monomer packing during the LS transition. The distinctive internal unit distribution at various temperatures is quantitatively analysed. Our results show the importance of dendritic polymer structure regularity in phase transition behaviours and are valuable in guiding the structural design of dendritic macromolecules for functionalization applications.

A modified thermal peak model with the source function dependent on ion velocity for materials bombarded by heavy ions

A modified thermal spike model is proposed. In contrast to the previous model, this scheme involves a source function dependent on ion energy losses determined by the penetration depth of a target and the characteristic time of ion penetration until comes to a complete stop. Such an approach is especially significant for confirming its applicability for track formation processes observed in materials because, as is shown, characteristic times appreciably exceed the periods of phonon oscillations with frequencies of 1013 Hz or more. The performed calculations make it possible to infer that the source function of the modified model describes thermal processes differently than does the commonly used source function. It is established that the temperature of a material exceeds the solid-liquid transition temperature in the cylindrical regions with sizes that are smaller than those calculated without allowance for ion motion.

Novel ice structures in carbon nanopores: pressure enhancement effect of confinement

We report experimental results on the structure and melting behavior of ice confined in multi-walled carbon nanotubes and ordered mesoporous carbon CMK-3, which is the carbon replica of a SBA-15 silica template. The silica template has cylindrical mesopores with micropores connecting the walls of neighboring mesopores. The structure of the carbon replica material CMK-3 consists of carbon rods connected by smaller side-branches, with quasi-cylindrical mesopores of average pore size 4.9 nm and micropores of 0.6 nm. Neutron diffraction and differential scanning calorimetry have been used to determine the structure of the confined ice and the solid-liquid transition temperature. The results are compared with the behavior of water in multi-walled carbon nanotubes of inner diameters of 2.4 nm and 4 nm studied by the same methods. For D(2)O in CMK-3 we find evidence of the existence of nanocrystals of cubic ice and ice IX; the diffraction results also suggest the presence of ice VIII, although this is less conclusive. We find evidence of cubic ice in the case of the carbon nanotubes. For bulk water these crystal forms only occur at temperatures below 170 K in the case of cubic ice, and at pressures of hundreds or thousands of MPa in the case of ice VIII and IX. These phases appear to be stabilized by the confinement.

Liquid−Solid Transition of Confined Water in Silica-Based Mesopores

Cooling and heating curves of water confined in partially filled Vycor porous glass were measured for both adsorption and desorption processes. One endothermic and two exothermic peaks were observed for almost all cases. The peak temperature and the enthalpy of the exothermic peak located below 232 K increased initially and then decreased with further increases in the filling factor. These abnormal changes were analyzed based on the liquid-solid transition of nanoconfined water using a core/shell model, and the initial adsorption process of water in this typical mesoporous material with disordered pores is discussed. In addition, an interesting observation is that different peak temperatures for the endothermic peak and an almost constant peak temperature for the exothermic peak were observed at the same filling factor obtained under different sample preparation conditions, that is, adsorption and desorption processes. To compare with the liquid-solid transition temperatures of confined water in fully filled silica-based mesopores of different pore radius, a parameter of the ratio of pore inner surface area to confined liquid volume is proposed in this paper. Referring to this parameter, the core part of confined water in silica-based nanopores has the same liquid-solid transition temperatures. This suggestion is valid for the freezing process of water confined in either fully filled ordered or fully or partially filled disordered pores. For the melting process, different linear changes of melting temperature with the ratio of pore inner surface area to liquid volume were observed for water in disordered and ordered pores.