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We have used high‐pressure methods to synthesize CaMnTi2O6 single crystals with edge lengths of up to 70 μm. Compared to previously reported synthetic pathways, we were able to use gold capsules and smaller pressures of 4 GPa. X‐ray diffraction analysis of the single crystals at low temperatures between 100 and 230 K confirmed that no phase transitions occur in this temperature range. We found square planar‐coordinated Mn ions to shift further out of the plane with lower temperatures which could lead to a higher polarization. The measured Raman spectrum of CaMnTi2O6 has been compared with quantum chemically calculated Raman spectrum to assign the vibrational modes. Calculated single‐crystal Raman spectrum has also been also analyzed from the point of view of direction dependency of the Raman intensities. [ABSTRACT FROM AUTHOR]

Local continuity is established for locally bounded, weak solutions to a doubly non-linear parabolic equation that models the temperature of a material undergoing a multi-phase transition. The enthalpy, as a maximal monotone graph of the temperature, is allowed to possess several jumps and/or infinite derivatives at the transition temperatures. The effect of the p-Laplacian-type diffusion is also considered. As an application, we demonstrate a continuity result for the saturation in the flow of two immiscible fluids through a porous medium, when irreducible saturation is present. [ABSTRACT FROM AUTHOR]

Multiferroic materials can realize the mutual coupling between force, electricity, magnetism and other physical fields, and have important application prospects in the field of small size, fast response and low power consumption of magnetoelectric devices. GaFeO3 is a highly promising multiferroic material featuring high spontaneous magnetization and polarization beyond room temperature. In this study, Ferroelectric Mgx Ga1 - x FeO3 (x = 0. 02, 0. 05, 0. 07 and 0. 10) single crystals with a diameter of about 7 mm were grown by light floating zone method. The effect of Mg2 + on the saturation magnetization and magnetic transition temperature of GaFeO3 (GFO) crystals were studied. The structure and phase of the crystal were analyzed through XRD, the results show that all the prepared samples correspond to the diffraction characteristics of the standard crystal card library GFO (PDF#76-1005), and no other heterophase appears. The XRD refinement results indicate that, the crystal structure is orthogonal and its space group is Pna21. As the concentration of Mg2 + rises, the lattice constant and cell volume initially increase and subsequently decrease. Additionlly, the magnetic properties of the crystal were studied through a comprehensive physical property measurement system, the magnetic transition temperature and saturation magnetization of the grown crytals also increase firstly and then decrease with the increase of Mg2 + doping content. When the Mg2 + doping amount is 0. 07, the magnetic transition temperature and saturation magnetization reach the maximum values of 187. 82 K and 8. 75 emu/g, respectively, which achieves the purpose of doping modification. [ABSTRACT FROM AUTHOR]

We have synthesized (G d 0.2 Y 0.2 N d 0.2 D y 0.2 R 0.2) 3 F e 5 O 12 (R = E r , S m and Pr) high entropy garnet ceramic samples via solid-state reaction route for the first time. All the samples are formed in a single phase and exhibit a simple cubic crystal structure with an I a 3 ‾ d space group. The lattice constant of these samples varies as per the ionic radii of the substituted element and ranges in between 12.4458 Å to 12.5062 Å. The morphology and elemental contributions are also investigated for all the high entropy samples. Additionally, magnetization data reveal a similar value of room temperature saturation magnetization i.e., ∼ 16 e m u / g for (G d 0.2 Y 0.2 N d 0.2 D y 0.2 R 0.2) 3 F e 5 O 12 (R = S m and Pr) samples and it becomes 13.67 e m u / g for Er doped sample. This variation is understood with Dionne's sublattice magnetization model where the molecular weight of the substituent will affect the saturation magnetization. Furthermore, a deviation from ideal Debye-type relaxation behavior is noticed in room temperature Nyquist plots for all three samples. An anomaly in the dielectric plot around ferrimagnetic transition temperature indicates the multiferroic behavior of these high entropy ceramic materials. [ABSTRACT FROM AUTHOR]

Vitrimers, possessing associative covalent adaptable networks, are cross‐linked polymers exhibiting malleable (glass‐like) feature and recyclable and reprocessable (thermoplastics‐like) properties. The dynamic behaviors of vitrimer are dependent on both chain/molecular mobility (glass transition temperature, Tg) and dynamic bond‐exchanging reaction rate (topology freezing transition temperature, Tv). This work aims on probing the effect of high Tg on the stress relaxation and physical recyclability of vitrimers, employing a polyimide cross‐linked with dynamic ester bonds (Tg: 310 °C) as the example. Due to its high Tg and chain rigidity, the cross‐linked polyimide does not exhibit a high extent of stress relaxation behavior at 320 °C (10 °C above its Tg), even though the temperature is much higher than the hypothetical Tv. While raising the processing temperature to 345 °C, the cross‐linked polyimide exhibits a stress relaxation time of about 3300 s and physical malleability. Nevertheless, side reactions may occur in the recycling and reprocessing process under the harsh condition (high temperature and high pressure) to alter the thermal properties of the recycled sample. The diffusion control plays a critical role on the topography transition of a vitrimer having a high Tg. The Tg ceiling is noticeable for developments of vitrimers. [ABSTRACT FROM AUTHOR]

The study investigates the absorption spectra of [NH2(C2H5)2]2CuCl4 (DEACC) microcrystals incorporated into a polystyrene matrix. It further explores the influence of low-energy X-ray radiation on the thermochromic properties of this microcomposite. This composite, with an average microcrystal size of 200 µm, was found to possess thermochromic properties similar to those of the bulk crystal, although its discontinuous thermochromic phase transition is shifted to higher temperatures in comparison wi- th a single crystal. Such a shift is explained by surface strains that occur at the interface between the polystyrene matrix and the microcrystal. Ionizing radiation causes much more noticeable changes in the thermochromic properties of microcomposites compared to a single crystal when subjected to equivalent doses of irradiation. This influence consists in the non-trivial dependence of the thermochromic phase transition temperature obtained from the hysteresis loops D(T) on the irradiation dose. At relatively small doses of X-radiation, the phase transition temperature increases due to a mechanism similar to that of a single crystal. Specifically, this mechanism involves the breaking and rearrangement of hydrogen bonds facilitated by anionic tetrahedral complexes, resulting in their reconfiguration into a planar-square shape. Upon reaching certain critical values of the radiation dose, the radiation-induced changes become irreversible. They are primarily caused by the breaking of chemical bonds at the interface between the matrix and the microcrystal, leading to a decrease in the temperature of the thermochromic phase transi- tion. The obtained material is non-hygroscopic, mechanically stable and technological. The very simple production technology of the composites makes them suitable for creating cheap individual ionizing X-ray dose sensors. [ABSTRACT FROM AUTHOR]

Tetragonal tungsten bronzes allow for broader compositional engineering compared to perovskites. Here we investigate solid solutions between Ba 4 Na 2 Nb 10 O 30 (BNN) and K 4 Bi 2 Nb 10 O 30 (KBiN). A transition from orthorhombic to tetragonal symmetry was observed at 30–35 % KBiN. An expansion of the in-plane and a contraction of the out-of-plane parameter were observed with increasing KBiN content. Ferroelectricity, shown by a maximum in permittivity, was observed up to 20–35 % KBiN, while diffuse dielectric behaviour was exhibited from 40 % KBiN. Non-linear P-E loops are evident up to 35 % KBiN, and vaguely present for 40 % KBiN. The most prominent ferroelectric character, assigned by large remanent polarisation and opening of the strain hysteresis response was exhibited at 35 % KBiN. A ferroelastic-paraelastic phase transition between 30 % and 35 % KBiN and a ferroelectric-paraelectric phase transition around ∼40 % KBiN were inferred. Thus, the two distinct phase transitions mimic the temperature dependent structural evolution observed for BNN. [ABSTRACT FROM AUTHOR]

Owing to the ferroelectric-ferroelectric phase transition and macrodomains switching during the polarization process, it is challenging to achieve both large strain with low hysteresis in ferroelectric ceramics, which severely limits their usefulness for practical applications. In this work, an effective strategy of constructing multiple local polarization configurations is designed in lead-free (100-x)Na 0.52 K 0.48 Nb 0.9 Sb 0.1 O 3 -xBaZrO 3 (NKNS-xBZ) ceramics. The incorporation of BZ regulates both the polymorphic phase transition temperature and relaxor behavior of the NKNS matrix, leading to the coexistence of nanoscaled rhombohedral, orthorhombic, and tetragonal phases with ergodic relaxor at room temperature. Consequently, these polar nanodomains with multiple symmetries significantly decrease the polarization and strain hysteresis, leading to the high electrostrictive-like strain (∼0.2 %) and extremely low strain hysteresis (∼7.4 %) with good thermal stability (strain decrease < 10 % from 20 °C to 160 °C) at x = 4. This work provides effective guidance for obtaining high strain with low hysteresis in relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

The critical behavior and the magnetocaloric effect have been researched in rare-earth perovskite EuTiO 3 . Using classical Monte Carlo method, we simulate the phase transition behavior of EuTiO 3 on the Heisenberg model with uniaxial anisotropy and obtain the phase transition temperature T n = 5.4 K, which is almost consistent with the experimental results. The entropy change under isothermal Δ S and temperature change under adiabatic Δ T ad are calculated for different external magnetic fields. The results of the relative cooling power (RCP) are linear with the magnetic field. The critical exponents β =0.269, γ =1.250, and δ =5.602 are obtained by the power laws. These results are almost identical to those calculated using the MCE scaling law. [ABSTRACT FROM AUTHOR]

A comparative specific heat (C P ) study of GdPdAl and TbPdAl compounds crystallizing in hexagonal ZrNiAl-type crystal-structure (space group P 6 ¯ 2 m) is presented. Consistent with earlier reports both the compounds show the signature of two magnetic transitions in magnetization data. The magnitude of the jump in C P at the high-temperature transition at T N 1 (∼ 47 K) in GdPdAl indicates ordering into an amplitude-modulated magnetic structure. The analysis of magnetic entropy change (S 4 f ) showed that about one-half of total S 4 f occurs below low temperature transition at T N 2 . This is in contrast to that seen in TbPdAl, where only one-third of the entropy of transition occurs below T N 2 . For both the compounds S 4 f tends to saturate to about 84% (for T > T N 1 ) of that expected for complete ordering of the rare earth moments, indicating incomplete removal of geometrical frustration. [ABSTRACT FROM AUTHOR]

77 Se NMR measurements confirm that in Fe(Se,Te) a change in the type of nematic transition is observed near its complete suppression. We present the studies of structural phase transitions in FeSe 0.675 Te 0.3 S 0.025 crystals. The data obtained indicate a significant change in the behavior of many characteristics during the transition in this composition compared to the case of the unsubstituted FeSe. Similar to Fe(Se,Te) with a close tellurium content, the resistivity at low temperatures for the studied FeSe 0.675 Te 0.3 S 0.025 is proportional to the square of the temperature, while for pure FeSe below the structural transition it depends almost linearly on temperature. 77 Se NMR proves that these changes are associated with changes in the type of ordering. The NMR data showed a noticeable line broadening below the structural transition and an anomaly in the temperature dependence of the relaxation rate, which was not observed in FeSe. Our results confirm existence of the nematicity change point (NCP) in Fe(Se,Te) at a low Te content and make the phase diagram of quasi-binary Fe(Se,Te) compounds generally consistent with the phase diagram of FeSe under pressure. Thus, in terms of chemical pressure, the effect of isovalent substitution in the series of Fe(Te,Se,S) compounds on the type of ordering can be caused by the anisotropic part of the deformation. [ABSTRACT FROM AUTHOR]

The tempering process is applied in marine 10Ni5CrMoV steel to study microstructure, and mechanical properties by multi‐scale characterizations, strain hardening behavior, and cryogenic toughening mechanism are further investigated. As the tempering temperature increases from 590 to 630 °C, the dislocation density decreases by up to 25% and the austenite volume fraction decreases by up to 35%. Additionally, the morphology of austenite changes from strip to bulk, which weakened the pinning effect on the laths, leading to a coarsened martensite and an increase in the equivalent grain size. Based on the modified Crussard–Jaoul analysis, the specimens at different tempering temperatures exhibit a single‐stage strain hardening behavior during plastic deformation. The increase in strength is attributed to the continuous transformation‐induced plasticity effect and the increasing dislocation density. Furthermore, high austenite volume fraction and the proportion of grain boundary misorientation above 45° promote the release of stress concentration and hinder the propagation of cracks. This results in an increase in the ductile–brittle transition temperature (DBTT) of the specimens from −105 to −135 °C. At a tempering temperature of 610 °C, the specimen demonstrates an outstanding balance between yield strength (868 MPa) and cryogenic toughness (DBTT of −135 °C). [ABSTRACT FROM AUTHOR]

Uninterrupted breakthroughs in the room temperature piezoelectric properties of KNN-based piezoceramics have been witnessed over the past two decades; however, poor temperature stability presents a major challenge for KNN-based piezoelectric ceramics in their effort to replace their lead-based counterparts. Herein, to enhance temperature stability in KNN-based ceramics while preserving the high piezoelectric response, multilayer composite ceramics were fabricated using textured thick films with distinct polymorphic phase transition temperatures. The results demonstrated that the composite ceramics exhibited both outstanding piezoelectric performance (d33~467 ± 16 pC/N; S~0.17% at 40 kV/cm) and excellent temperature stability with d33 and strain variations of 9.1% and 2.9%, respectively, over a broad temperature range of 25–180 °C. This superior piezoelectric temperature stability is attributed to the inter-inhibitive piezoelectric fluctuations between the component layers, the diffused phase transition, and the stable phase structure with a rising temperature, as well as the permanent contribution of crystal orientation to piezoelectric performance over the studied temperature range. This novel strategy, which addresses the piezoelectric and strain temperature sensitivity while maintaining high performance, is well-positioned to advance the commercial application of KNN-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

The influence of ionizing irradiation on the thermochromic properties of [NH2(C2H5)2]2CuCl4 (DEACC) microcrystals incorporated into a polystyrene matrix was investigated. This composite was found to possess thermochromic properties very similar to those in a bulk crystal although its thermochromic phase transition was shifted toward higher temperatures due to the tensions arising within the interface between the polystyrene matrix and the microcrystal. The similar doses of ionizing radiation cause much more pronounced changes in the thermochromic properties of the microcrystals in comparison with a bulk crystal. The main impact consists in the considerable shift of the phase transition temperature derived from the D(T) hysteresis loops toward lower values that were explained by the breaking of the chemical bonds between the polymer matrix and the microcrystals and the corresponding diminishing of the surface strains. The transformation of the discontinuous phase transition into the continuous one under the influence of irradiation was also discussed. [ABSTRACT FROM AUTHOR]

Background: The combination of multiple polymers is anticipated to serve as a means to diversify the physical properties and functionalities of dissolving microneedles. The mixing state of components is considered as a crucial factor in determining their suitability. Objectives: The purpose of this study was to elucidate whether thermal analysis of frozen aqueous solutions can appropriately predict the miscibility of hyaluronic acid (HA) and other polymers used for dissolving microneedles prepared by a micromolding method. Methods: Aliquots of aqueous polymer solutions were applied for thermal analysis by heating the samples from −70 °C at 5 °C/min to obtain the transition temperature of amorphous polymers and/or the crystallization/melting peaks of polymers (e.g., polyethylene glycol (PEG)). Films and dissolving microneedles were prepared by air-drying of the aqueous polymer solutions to assess the polymer miscibility in the solids. Results: The frozen aqueous single-solute HA solutions exhibited a clear Tg′ (the glass transition temperature of maximally freeze-concentrated solutes) at approximately −20 °C. The combination of HA with several polymers (e.g., dextran FP40, DEAE-dextran, dextran sulfate, and gelatin) showed a single Tg′ transition at temperatures that shifted according to their mass ratio, which strongly suggested the mixing of the freeze-concentrated solutes. By contrast, the observation of two Tg′ transitions in a scan strongly suggested the separation of HA and polyvinylpyrrolidone (PVP) or HA and polyacrylic acid (PAA) into different freeze-concentrated phases, each of which was rich in an amorphous polymer. The combination of HA and PEG exhibited the individual physical changes of the polymers. The polymer combinations that showed phase separation in the frozen solution formed opaque films and microneedles upon their preparation by air-drying. Coacervation occurring in certain polymer combinations was also suggested as a factor contributing to the formation of cloudy films. Conclusions: Freezing aqueous polymer solutions creates a highly concentrated polymer environment that mimics the matrix of dissolving microneedles prepared through air drying. This study demonstrated that thermal analysis of the frozen solution offers insights into the mixing state of condensed polymers, which can be useful for predicting the physical properties of microneedles. [ABSTRACT FROM AUTHOR]

Crystal polymers or liquid crystal elastomers undergo a phase transition that results in a change in the corresponding optical properties, which has the potential to be applied in areas such as information encryption and anti-counterfeiting. The utilization of these materials for patterning purposes requires different phase transition temperatures. However, once prepared, altering the phase transition temperature of them presents significant challenges. Herein, a poly(oxime-ester) (POE) network is developed to achieve high-resolution and multilevel patterning by photo-induced isomerization. The as-prepared POE exhibits the ability to transition from an opaque state to a transparent state under temperature stimuli, with the transition temperature and kinetics dependent on UV light exposure time. Thus, complex patterns and information can be encrypted through different selective regional exposure time and decrypted under specific temperature or cooling time. Furthermore, we illustrate an example of temporal communication, where cooling time or temperature serves as the encoded information. This research expands the application scope of advanced encryption materials, showcasing the potential of POE in dynamic information encryption and decryption processes. [ABSTRACT FROM AUTHOR]

Thermochromic polymers with tunable thermochromism, high stretchability and mechanical strength are of interests for optical information storage and encryption. In this work, we demonstrate a new design of thermo-fluorochromic carboxylated nitrile butadiene rubber (XNBR) elastomer cross-linked by Eu3+-COOH dynamic coordination with deprotonated imidazole (DPIm) as the ancillary ligand. The presence of DPIm not only improves the mechanical strength and stretchability, but also dramatically intensifies the fluorescence emission and lifetime of the Eu-containing elastomer. The elastomer behaves reversible thermo-fluorochromism with easily tunable transition temperature and emission intensity by the simple change of the deprotonation degree of imidazole. The facile tunable thermo-fluorochromism, exceptional mechanical strength, and high stretchability (up to about 5000%) enable the Eu-containing XNBR elastomer with potential applications in soft electronics where optical information storage and encryption are required. [ABSTRACT FROM AUTHOR]

Ferroelastic materials with high phase transition temperature have broad application prospects in information conversion and storage, shape memory, energy conversion, hyperelasticity, etc. However, most of the current reports focus on inorganic ferroelastic materials. Inorganic ferroelastic materials have the disadvantages of high energy consumption and harmful metals, which limit their application in practical work. In contrast, organic ferroelastic materials have the advantages of structural adjustability, environmental protection, easy processing, low cost, mechanical flexibility, and so on, which have great development potential in new ferroelastic materials. Here, we have successfully designed and synthesized a pair of homochiral enantiomers [(R/S)‐4‐fluorobenzoic acid‐2‐amino‐2‐phenylethanol] (R‐ and S‐F) using the chemical design strategy of H/F substitution. Compared with the non‐F substitution [(R/S)‐benzoic acid‐2‐amino‐2‐phenylethanol] (R‐ and S‐H), they undergo 2F1‐type ferroelastic phase transitions at 370 K. Notably, the ferroelastic domains of R/S‐F can be controlled through two physical channels that are temperature and stress, showing great potential in dual‐channel switches. [ABSTRACT FROM AUTHOR]

Separation of equally sized particles distinguished solely by interfacial properties remains a highly challenging task. Herein, a particle fractioning method is proposed, which is suitable to differentiate between polymer‐grafted microparticles that are equal in size. The separation relies on the combination of a pressure driven microfluidic flow, together with simultaneous light illumination and temperature control. Heating the solution forces thermo‐responsive surface grafts to undergo a volume phase transition and therefore locally changing the interfacial properties of the microparticles. Light illumination induces the phoretic/osmotic activity of the microparticles and lifts them into a higher plane, where hovering particles experience a different shear stress proportional to the height. The light‐induced hovering height depends on the interfacial properties, and this complex interaction leads to different movements of the microparticles as a function of their surface grafting. The concepts are visualized in experimental studies, where the complex physical principle provides a simple method for fractioning a binary mixture with at least one thermo‐responsive polymer graft. [ABSTRACT FROM AUTHOR]

This attempt covers an investigation of cutting temperature at interfaces of Fiber Metal Laminates (FMLs) made of glass fiber-reinforced polymer (GFRP) stacked with an Al2020 alloy. GFRP/Al/GFRP and Al/GFRP/Al composite stacks are both investigated to highlight the effect of stacking arrangement on thermal behavior within the interfaces. In a first test series, temperature history is recorded within the metal/composite stack interfaces using preinstalled thermocouples. In a second test series, a wireless telemetry system connected to K-type thermocouples implanted adjacent to the cutting edge of the solid carbide drill is used to record temperature evolution at the tool tip. Focus is put on the effects of cutting speed and stacking arrangement on the thrust force, drilling temperature, and delamination. From findings, the temperature histories show high sensitivity to the cutting speed. When cutting Al/GFRP/Al, the peak temperature is found to be much higher than that recorded in GFRP/Al/GFRP and exceeds the glass transition point of the GFRP matrix under critical cutting speeds. However, thrust force obtained at constitutive phases exhibits close magnitude when the stacking arrangement varies, regardless of cutting speed. Damage analysis is also discussed through the delamination factor at different stages of FML thickness. [ABSTRACT FROM AUTHOR]

The development of poly(lactic acid) (PLA) nanocomposites incorporating urchin-like WO3 particles through a cost-effective solution-casting method has led to significant enhancements in structural, thermal, optical, and rheological properties. The incorporation of these WO3 particles up to 7 wt% resulted in the formation of an irregular honeycomb-like morphology with broad pore sizes ranging from 14.1 to 24.7 µm, as confirmed by SEM and EDX analysis. The urchin-like WO3 particles acted as effective nucleating agents, increasing the crystallinity of PLA from 40% to 50% and achieving an impressive overall crystallinity rate of 97%. Differential scanning calorimetry (DSC) revealed an 11 K reduction in the crystalline phase transition temperature while maintaining stable melting (Tm) and glass transition (Tg) temperatures. Thermal analysis indicated a significant decrease in the onset of degradation and maximum thermal stability (Tmax), with a reduction of 21 K due to the incorporation of the WO3 particles. Optical measurements showed enhancement of UV-blocking properties from 9% to 55% with the WO3 particle loading. Rheological tests demonstrated substantial improvements in viscoelastic properties, including a remarkable 30-fold increase in storage modulus, suggesting enhanced gel formation. Although the nanocomposites showed minimal antibacterial activity against Escherichia coli and Staphylococcus aureus, they exhibited significant antifungal activity against Candida albicans. These results underscore the potential of the PLA/WO3 nanocomposites for advanced material applications, particularly where enhanced mechanical, thermal, optical, and antifungal performance is required. [ABSTRACT FROM AUTHOR]

We synthesized thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) colloidal microgel particles of different stiffnesses by controlling the concentration of a polar crosslinker in a precipitation polymerization synthesis method. When suspended in an aqueous medium, the particles collapsed by expelling water as the temperature was raised toward the volume phase transition temperature (VPTT) of ≈ 34 °C. We noted that the sizes of the stiffer particles, synthesized with higher crosslinker concentration, collapsed less abruptly. Using Fourier transform infrared spectroscopy, we observed enhanced particle dehydration with increasing temperature and decreasing particle stiffness. Oscillatory rheology experiments on dense aqueous PNIPAM suspensions, prepared at a fixed particle effective volume fraction ϕ eff = 1.5 at 25°C, revealed that suspensions constituted by the stiffest particles are the most elastic over a broad temperature range. Above the VPTT, suspensions of particles of intermediate stiffnesses exhibited two-step yielding, a typical signature of fragile gel formation. Zeta potential measurements showed that PNIPAM particles of lower stiffnesses are rendered electrostatically unstable in aqueous suspension. Combining cryogenic scanning electron microscopy and rheology, we noted a glass–glass transition when the temperature of a dense suspension of stiff PNIPAM particles was raised across the VPTT. In contrast, suspensions of particles of the lowest stiffnesses showed a gel-viscoelastic liquid–gel transition during an identical temperature ramp experiment. Our study reveals that temperature-induced phase transformations in dense PNIPAM suspensions depend sensitively on the stiffness of the constituent particles and can be explained by considering amphiphilicity-driven morphological changes in the suspension microstructures. [ABSTRACT FROM AUTHOR]

Fracturing of rocks subjected to cryogenic treatment significantly impacts the stability and permeability of underground storage facilities for liquefied natural gas (LNG). However, existing fracturing damage models lack coverage across the entire spectrum of practical engineering conditions, spanning potential temperature ranges from room temperature to − 160 °C and saturation levels from 0 to 100%. Addressing this gap, this study utilizes cracked sandstone disks to investigate the fracture toughness of sandstone following cryogenic treatment to − 160 °C using the Brazilian splitting test. In the experimental setup, treatment temperatures are specified at 15, − 40, − 80, − 120, and − 160 °C, while saturations range from 0 to 100%. The experimental findings reveal that ultralow temperatures reduce the fracture toughness of saturated sandstone by approximately 30%, whereas for dry sandstone, this reduction is approximately 7.4%. This suggests a significant influence of different pore saturations on fracture toughness. A damage model, based on the Boltzmann function, is established to incorporate the effects of both temperature and saturation. This model accurately predicts the damage variable concerning treatment temperature and saturation. Generally, as temperature decreases, the damage variable also decreases, exhibiting two stages: rapid decrease followed by gradual decrease. The transition temperature, marking the division between these stages, tends to be lower in sandstone with higher saturation levels. The experimental results are further discussed within the context of the mineral compositions present in the sandstone, elucidating the thermal–mechanical mechanisms at play. Although the current damage model is specific to sandstone, the methodological approach is generalizable to generic rock types. The damage model's adaptability allows for testing fitting parameters for specific rock types or adjusting the relevant thermal coefficients. These findings and the developed model offer valuable insights for the reliable analysis of stability and permeability in LNG storage facilities or similar geologic engineering projects. Highlights: The Mode-I fracture toughness of sandstone under variable saturation conditions subjected to cryogenic temperatures of − 160 °C is investigated. Saturated sandstone experiences more than four times the amount of damage compared to dry sandstone under ultralow temperatures. A damage model is developed to incorporate the influences of both temperature and saturation. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the nonlinear dynamics of convection flow using the thermodynamic variational principle, focusing on scenarios where multiple external forces, such as a thermal gradient and rotational field, are applied to a shallow annular pool. We observed that with the increase in the thermal gradient, the flow changed from an axial flow to a rotational oscillatory flow with the wave amplitudes aligned. Further increasing the temperature difference led to a rotational oscillatory flow characterized by alternating wave generation and annihilation. Our analysis of the flow, considering heat fluxes orthogonal to the thermal gradient, allowed us to describe the flow state as a phase at equilibrium. The state transition of the flow was accompanied by a discontinuous jump in the heat flux, which occurred at the intersection of the entropy production curves. The first transition occurred at a temperature difference Δ T = 12.4   K   M a r a n g o n i   n u m b e r , M a = 1716 and the second at ΔT = 16.3 K M a = 2255 . Analysis based on entropy production could accurately predict the observed transition points. [ABSTRACT FROM AUTHOR]

Heat storage is an emerging field of research, and, therefore, new materials with enhanced properties are being developed. Examples of phase change materials that provide high heat storage are inorganic salts and salt mixtures. They are commonly used for industrial applications due to their high operational temperature and latent heat. These parameters can be modified by combining different types of salts. This paper presents the experimental study of the impact of the composition of binary salts on their thermophysical properties. Unlike the literature data, this article provides a detailed analysis of the phase change process in both directions: solid–liquid and liquid–solid. The results indicate that the highest latent heat was observed for a 70% NaNO3 content in the NaNO3–KNO3 mixture. Therefore, when this salt is used for heat storage, the most favorable choice is a 70:30 ratio, which provides the highest heat storage density and the lowest phase transition temperature. In the case of the NaNO3–NaNO2 mixture, the highest value of latent heat occurs for a ratio of 80:20, resulting in phase transition temperatures of 267.0 °C for the solid–liquid transition, and 253.5 °C for the liquid–solid transition. For heat storage applications, it is recommended to use pure NaNO2 salt instead of the NaNO3–NaNO2 mixture. [ABSTRACT FROM AUTHOR]

With the growing demand for high‐performance smart windows, the discover of a class of thermochromic materials with reversible cycling and rapid response characteristics has become urgent. In this work, we have uncovered a two‐dimensional (2D) Ruddlesden‐Popper (RP) phase halide perovskite, (PMA)2MAPb2I7−xClx, where PMA=C6H5CH2NH3 and MA=CH3NH3, exhibiting exceptional reversible thermochromic properties. The 2D RP phase perovskite thin film features a low transition temperature (Tc=30 °C from the hydrated state to the hot state, along with a fast transition time of 40 s. Furthermore, the addition of 0.5 times excess MAI significantly enhances the visible light transmittance of the hydrated state. Characteristic hydration peaks in X‐ray diffraction patterns and O−H bond absorption peaks Fourier‐transform infrared spectra are observed in the thin film in its hydrated state, which disappear in the hot state, validating its reversible thermochromic properties. Additionally, a solar cell based on the thermochromic 2D RP phase thin film achieves a power conversion efficiency of 2.31 %, offering a promising solution for advanced smart window technologies. [ABSTRACT FROM AUTHOR]

The study investigates the absorption spectra of [NH2(C2H5)2]2CuCl4 (DEACC) microcrystals incorporated into a polystyrene matrix. It further explores the influence of low-energy X-ray radiation on the thermochromic properties of this microcomposite. This composite, with an average microcrystal size of 200 µm, was found to possess thermochromic properties similar to those of the bulk crystal, although its discontinuous thermochromic phase transition is shifted to higher temperatures in comparison wi- th a single crystal. Such a shift is explained by surface strains that occur at the interface between the polystyrene matrix and the microcrystal. Ionizing radiation causes much more noticeable changes in the thermochromic properties of microcomposites compared to a single crystal when subjected to equivalent doses of irradiation. This influence consists in the non-trivial dependence of the thermochromic phase transition temperature obtained from the hysteresis loops D(T) on the irradiation dose. At relatively small doses of X-radiation, the phase transition temperature increases due to a mechanism similar to that of a single crystal. Specifically, this mechanism involves the breaking and rearrangement of hydrogen bonds facilitated by anionic tetrahedral complexes, resulting in their reconfiguration into a planar-square shape. Upon reaching certain critical values of the radiation dose, the radiation-induced changes become irreversible. They are primarily caused by the breaking of chemical bonds at the interface between the matrix and the microcrystal, leading to a decrease in the temperature of the thermochromic phase transi- tion. The obtained material is non-hygroscopic, mechanically stable and technological. The very simple production technology of the composites makes them suitable for creating cheap individual ionizing X-ray dose sensors. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted to elucidate the impact of cooling rate on the microstructure evolution of boron-containing steel 22MnB5 by in-situ observation using the confocal laser scanning microscope (CLSM). The observations manifested distinct multi-phase formation of reconstructive grain boundary allotriomorphic ferrite (GBA) and pearlite (P) to sympathetic intergranular acicular ferrite (IAF) and bainite (B), as well as the displacive martensite (M) under different predefined cooling rates (1, 10, and 20 °C/s). Notably, as the cooling rate escalated from 1 to 10 or 20 °C/s, the starting and finishing phase transition temperature decreased significantly. For the 22MnB5 steel cooled at 1 °C/s, the solid phase transition sequence followed γ→GBA→P→IAF, while for the steel cooled at 10 and 20 °C/s, the transition sequence shifted to γ→B→M. Additionally, in the sample cooled at 20 °C/s, the bainite lath spacing reduced and more small size martensite appeared as the mechanical stabilization of austenite. Simultaneously, the dislocation density increased compared to the slow cooled samples, primarily due to the elevated nucleation rate from austenite to ferrite and larger internal stress induced by the enhancing cooling intensity. [ABSTRACT FROM AUTHOR]

Thermodynamic data is of great significance to investigate the formation and control mechanisms of solidification defects during the casting process of H13 steel which is high in Si, Cr, Mo, and V elements. It has been proven that the conventional Ueshima model based on the equilibrium phase diagrams of Fe-X (X = C, Si, Mn, P, S, Cr, Mo, and V) binary alloys cannot accurately predict the phase transition in the solidification of H13 steel with multi components. So, the pseudo-binary phase diagrams of Fe-X alloys at different initial concentrations were calculated via Thermo-Calc software. And, the datasets of liquidus and δ/γ phase transition temperatures were obtained. Then, a backpropagation (BP) neural network model was developed to predict the δ/γ phase transition temperature. While, the slopes of liquidus lines were fitted. These updates were implanted into the Ueshima model. And, the BP-Ueshima model was validated with the phase transition temperatures measured via the differential scanning calorimetry (DSC) test. Subsequently, the phase transition and solute micro-segregation behaviors in the solidification of H13 steel were analyzed as well as the influences of solute elements. The results show that the predicted liquidus temperature (TL) and solidus temperature (TS) of H13 steel via BP-Ueshima model agree with the experimental results. As the cooling rate increases from 10 to 20 °C/min, the phase transition temperatures change slightly. Both the solidus and liquidus temperatures decrease with increase of the initial contents of solute elements. Increasing the initial contents of C and Mn can enhance TP and Tδ (the vanishing temperature of δ phase), whereas the trend is reversed for the other solute elements. Changes of the phase transition temperatures depends on the segregation behaviors of solute elements. The micro-segregation ratios of solute elements in the liquid phase at the end of solidification decreases in the order of S, P, Si, Mo, C, V, Mn, and Cr, respectively. It is determined by the redistributive capacity at the solid/liquid interface and the back diffusion in the solid phase of solute elements. [ABSTRACT FROM AUTHOR]

40Cr10Si2Mo steel is widely utilized because of its excellent mechanical properties, with grain size being a critical factor determining subsequent phase transformation processes and material microstructure performance. This paper reports the use of high-temperature laser scanning confocal microscopy (HT-LSCM) for in situ observation experiments to systematically investigate the growth of austenite grains and the martensitic phase transformation mechanism in 40Cr10Si2Mo steel during an 1800-second isothermal hold at temperatures ranging from 900 °C to 1250 °C. A dynamic model of austenite grain growth is established to optimize the parameters of the austenitic process. The results indicate that the austenite grain size increases continuously with increasing temperature and prolonged time. The Dong model predicts grain sizes that align well with experimental values. Austenite grains grow through grain boundary migration and grain annexation, whereas the precipitation and dissolution of M(Cr, Mo)23C6 affect grain growth. With prolonged time, some grain boundaries extend into new boundaries through subgrain rotation. The fine grains at lower temperatures reduce the initial temperature of the martensite transition (Ms), and the primary martensite nucleates along the grain boundaries of the prior austenite. The secondary martensite is attached to the primary martensite nucleus at a certain angle and grows in parallel while inhibiting the phase transition of the surrounding untransformed austenite. [ABSTRACT FROM AUTHOR]

The discovery of the interface‐enhanced superconductivity in the single‐layer film of FeSe epitaxially grown on SrTiO3 substrates has triggered a flurry of activity in the field of superconductivity. It raised the hope to find more conventional high transition temperature (Tc) superconductors that are purely driven by the electron‐phonon interaction at ambient pressure. Here the epitaxial growth of the Pb nano‐sized islands on SrTiO3 (001) substrates with the island volumes ranging from 286 to 4945 nm3 is reported by molecular beam epitaxy, followed by systematic scanning tunneling microscopic/spectroscopic (STM/S) investigation. The observed STS gap for the nanoscale islands highly dependent on the volumes of nano‐sized islands, can be divided into three regions. By performing a detailed spectroscopic investigation, it is founded that superconductivity in the volume above 3700 nm3 (Region I) has a zero temperature energy gap (Δ(0)) and Tc of 6.8 meV and 9.8 K obtained by BCS fitting, showing the largely‐enhanced Δ and slightly‐increased Tc by comparing to the bulk Pb (1.4 meV and 7.2 K). As the volume in the range from 1300 to 3700 nm3 (Region II), a large Coulomb gap induced by electron correlation emerged and shows a volume‐dependent behavior, suggesting the reduced size can enhance electron correlation in Pb islands. As the volume decreases down to Region III, enhanced electron correlation and Coulomb gap become more dominant and superconductivity is totally suppressed. The experiment reveals that an electron‐electron interaction in nano‐sized Pb islands can be significantly enhanced by reducing the island sizes and suppresses the superconductivity, thus demonstrates a competition between superconductivity and electron correlation as the volume varies. [ABSTRACT FROM AUTHOR]

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A series of biobased aliphatic‐aromatic copolyesters, poly(pentylene dodecanoate‐co‐furandicarboxylates) (PPeDFs) were synthesized via an esterification and polycondensation melt process. The copolyesters were characterized using gel permeation chromatography, Fourier transform infrared spectroscopy, 1H NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, wide angle x‐ray scattering, and tensile testing. The thermal transition behavior was strongly dependent on composition, with the melting and glass transition temperatures reaching a minimum at approximately equimolar ratio of D to F. All copolyesters were stable below 300°C with their R600 (the weight of material remaining at 600°C) values increasing with F fraction. PPeD to PPeDF30 (e.g., mole ratio D/F = 7:3) show sharp PPeD crystalline reflections only while broad PPeF reflections are shown in PPeF and PPeDF90. PPeDF40 to PPeDF80 showed both crystal structures. The fractional crystallinity for the PPeD was much higher than PPeF and the fractional crystallinity of the copolymers showed a minimum at D/F ratios closer to the latter. The stress at break and modulus both exhibited maxima at D/F ratios that were either high or low, but somewhat surprisingly a strong maximum in percent elongation at break of over 600% occurs at PPeDF40. For this composition, a typical plastic behavior curve was found including a yield point, high elongation at break, and strain hardening. Highlights: Poly(pentylene dodecanoate‐co‐furandicarboxylates) (PPeDFs) are synthesizedMechanical properties, a function of D:F ratio. High elongation at 40 mol% F.Two melting temperatures/crystal structures, one PPeD, the other PPeFGlass transition temperature minimum at intermediate D:F ratios [ABSTRACT FROM AUTHOR]

The critical behavior and the magnetocaloric effect have been researched in rare-earth perovskite EuTiO 3 . Using classical Monte Carlo method, we simulate the phase transition behavior of EuTiO 3 on the Heisenberg model with uniaxial anisotropy and obtain the phase transition temperature T n = 5.4 K, which is almost consistent with the experimental results. The entropy change under isothermal Δ S and temperature change under adiabatic Δ T ad are calculated for different external magnetic fields. The results of the relative cooling power (RCP) are linear with the magnetic field. The critical exponents β =0.269, γ =1.250, and δ =5.602 are obtained by the power laws. These results are almost identical to those calculated using the MCE scaling law. [ABSTRACT FROM AUTHOR]

Leveraging the unique attributes of functional soft materials to generate force and deformation, significant advancements in soft actuators are driving the evolution of smart robotics. Liquid metals (LMs), known for their high deformability and tunable morphology, demonstrate remarkable actuating capabilities through controllable surface tension. Inspired by the predation method of chameleons, this work introduces a bioinspired LM actuator (BLMA) by modulating the morphology of LM. This BLMA enables high‐strain (up to 170%) actuation by precisely directing LM droplets toward an electrode. Various parameters affecting the BLMA's actuating performance are explored. Notably, the application of a reductive voltage induces rapid solidification of supercooled LM, facilitating phase transition at room temperature. The solidified LM enhances its holding force of BLMA by over 1000 times. To underscore the superior capabilities of the BLMA, diverse applications, such as a complex two‐dimensional plane actuator, a stepper motor with adjustable step intervals, a phase transition‐controlled relay, and a laser code lock actuation gate set, are presented. It is anticipated that the exceptional characteristics of the BLMA will propel advancements in the realms of soft robotics and mechatronics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) van der Waals (vdW) magnets have sparked widespread attention due to their potential in spintronic applications as well as in fundamental physics. Ferromagnetic vdW compound Fe3GeTe2 (FGT) and its Ga variants have garnered significant interest due to their itinerant magnetism, correlated states, and high magnetic transition temperature. Experimental studies have demonstrated the tunability of FGT's Curie temperature, TC, through adjustments in quintuple layer numbers (QL) and carrier concentrations, n. However, the underlying mechanism remains elusive. In this study, we employ molecular beam epitaxy (MBE) to synthesize 2D FGT films down to 1 QL with precise layer control, facilitating an exploration of the band structure and the evolution of itinerant carrier density. Angle-resolved photoemission spectroscopy (ARPES) reveals significant band structure changes at the ultra-thin limit, while first-principles calculations elucidate the band evolution from 1 QL to bulk, largely governed by interlayer coupling. Additionally, we find that n is intrinsically linked to the number of QL and temperature, with a critical value triggering the magnetic phase transition. Our findings underscore the pivotal role of band structure and itinerant electrons in governing magnetic phase transitions in such 2D vdW magnetic materials. [ABSTRACT FROM AUTHOR]

As a common smart hydrogel, thermo‐sensitive hydrogel exhibits significant potential applications in the field of biological engineering due to its unique property of undergoing a substantial volume transition in response to temperature changes. For numerical implementation of thermo‐sensitive hydrogel, many approaches have been developed to simulate the transient deformation during fluid diffusion or heat conduction process. However, the numerical approach for the transient deformation during both fluid diffusion and heat conduction processes is still lacking. To this end, we develop a three‐field coupled finite element framework that can be used to simulate the transient deformation behavior of thermo‐sensitive hydrogel involving large deformation, fluid diffusion, and heat conduction. In the proposed framework, there exist three processes that deal with displacement, concentration, and temperature fields, separately. To realize the coupling of three fields, the separated solving processes are assembled together by using a two‐way coupled approach. Based on the developed finite element framework, the coupling effects between the concentration and temperature can be realized by defining a body flux and a temperature‐dependent diffusion coefficient without solving the complex coupling equations. The finite element framework is implemented in ABAQUS by utilizing several user subroutines. The numerical implementation is validated by comparing the numerical results of a hydrogel disk with experimental results. Furthermore, various numerical examples are simulated to investigate the applicability of the proposed finite element framework under different multi‐field coupling conditions. The proposed finite element scheme is proved to be an efficient and stable tool for numerically simulating the transient behavior of thermo‐sensitive hydrogel incorporating the phase transition effect. [ABSTRACT FROM AUTHOR]

4D printing has attracted widespread attention due to its ability to fabricate complex structures capable of responding to specific stimuli. However, existing smart materials used for 4D printing, such as conventional hydrogels, liquid crystal elastomers, and shape‐memory polymers, are constrained in their ability to fulfill both mechanical ultrastrength and ultrastretchability requirements simultaneously due to their water saturation or uneven network structures. This study presents 4D printing of liquid‐free ionic elastomers (LFIEs) that is achieved through photopolymerization of the acrylic acid‐tetramethylammonium chloride‐polymerizable deep eutectic solvent. The transition temperature (Tt) of the high‐fracture‐strength LFIEs is adjusted by introducing phenylphosphoric acid, harboring multiple hydrogen‐bonds, leading to improved molecular chain mobility through softening of the chains. Consequently, the 4D‐printed LFIEs retain their high strength while achieving ultrastretchable properties even under elevated temperatures during heating. Moreover, the 4D‐printed LFIEs demonstrate both a swift response time and a high fixation rate even after undergoing repeated transformation cycles. These outstanding capabilities exhibit by LFIEs present a reliable strategy for advancing their applications in diverse fields, such as smart furniture, robotics, and intelligent manufacturing with remote monitoring, and beyond. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials have the ability to undergo temperature changes when subjected to varying magnetic fields. These materials are of interest due to their potential for innovative cooling applications. This review article summarizes materials that exhibit magnetic ordering within the temperature range required for gas liquefaction and explores their potential applications through the magnetocaloric effect (MCE). The gas liquefaction temperature range is typically assumed to be 20–77 K, however, this study specifically summarizes materials that have a transition temperature near to the hydrogen liquefaction temperature (≈20K). This review article aims to showcase ongoing research on magnetic materials for hydrogen liquefaction. Driven by the depletion of natural resources and environmental concerns, the search for environmentally sustainable fuels has intensified, making hydrogen a promising alternative. However, the liquefaction of hydrogen is highly energy‐intensive. The investigation focuses on identifying and understanding these materials and assessing their suitability for environmentally friendly and sustainable cooling technologies. By harnessing the magnetocaloric effect, these materials exhibit temperature changes in response to an applied magnetic field, offering advantages over traditional cooling methods that are 20–50% more efficient. The review aims to furnish researchers with essential information that can help modify magnetocaloric effect (MCE) materials, enabling them to achieve the desired magnetic ordering temperature conducive to the liquefaction of hydrogen. [ABSTRACT FROM AUTHOR]

Alkaline earth halides garnered interest in spintronics research due to their longer spin relaxation time. Employing first principles calculations, 3d transition metal (TM)-substituted magnesium bromide (MgBr2) monolayers have been reported for the first time for potential spintronics applicability. Among these systems, Cr-, Cu- and Fe-substituted MgBr2 monolayers showed half-metallicity that can be used in ultra-fast spintronics because of high spin polarization. Bipolar magnetic semiconducting (BMS) nature was observed in Mn-substituted monolayer that enables spin control and manipulation by external bias voltage. The formation energy of TM dopants under Br-rich condition showed the feasibility of TM substitution. The half-metallic TM-substituted systems showed a large spin channel gap which inhibits spin leakage. The spin flip gap in BMS monolayer was feasible for practical device operation. Additionally, significant magnetic anisotropy energy per dopant has been observed with a ferromagnetic coupling in Cr-, Cu- and Fe-substituted systems, while antiferromagnetic coupling was shown by Mn- and V-substituted monolayers. Monte Carlo (MC) simulation revealed a near room temperature magnetic phase transition temperature. Robustness of the half-metallicity and BMS spin flip gap was ascertained with strain-mediated density of states which is of importance while fabrication upon a lattice mismatch between substrate. The magnetic transition temperature tuned by applied either compressive or tensile strain is also performed. Hence, electronic and magnetic studies revealed 3d TM element-substituted monolayer MgBr2 to be a potential system in spintronics applications. [ABSTRACT FROM AUTHOR]

The multiferroics with remarkable magnetoelectric (ME) coupling and technological application have drawn significant attention. Here, we report a chemical doping tunable effect on the magnetic, ferroelectric, and dielectric properties in type-II multiferroic Gd 2 BaCuO 5. The magnetic measurement results show that a long-range antiferromagnetic ordering forms at the Néel temperature (T N1) of ∼12.1 K, and a second magnetization anomaly occurs at a lock-in transition temperature (T N2) of ∼6.4 K. Sharp peaks in the pyroelectric and dielectric curves are observed at the magnetic transition temperatures, indicating intrinsic coupling between magnetic and ferroelectric orderings. The doping of Zn2+ results in a gradual enhancement of magnetization due to the increase of uncompensated spins, and large magnetodielectric (MD) coupling parameter up to ∼7.65 % is obtained in Gd 2 BaCu 0.7 Zn 0.3 O 5 because of strong spin-phonon coupling. The ferroelectric property is weakened in Zn2+ doped samples, suggesting the critical role of the 4 f -3 d magnetic interactions in determining the ME coupling effect. Moreover, an effective manipulation of electric field on magnetization is observed in Gd 2 BaCuO 5. This work helps understand the importance of 4 f -3 d magnetic interactions in inducing ferroelectricity and explore the ME and MD coupling effects with multiple magnetic orderings. [ABSTRACT FROM AUTHOR]

To decipher the effects of replacing alkali with zinc on thermo-mechanical properties, a series of borosilicate glasses with the molar compositions of 70.65SiO 2 ·21.09B 2 O 3 ·1.88Al 2 O 3 ·1Li 2 O·(5.38- x)R 2 O· x ZnO (x = 0, 0.34, 0.67, 1, 1.34, 2.69, 4.04, and 5.38) were prepared. Upon adding a slight quantity of ZnO, a local extreme point for glass transition temperature (T g) appears. This behavior is deciphered to be originated from two opposite factors. On one hand, T g reduces as a characteristic of the colligative properties for a dilute solution; in addition, T g rises due to the higher field strength, bond energy and covalent characteristic of zinc cations compared to that of alkali ions. Otherwise, based on the evolution of intermediate-range clusters revealed by infrared, Raman and NMR spectra, we elucidate the atomic-scale structural origin, which leads to the nonlinear evolution of elastic moduli and coefficient of thermal expansion with the molar ratio of [ZnO]/([R 2 O]+[ZnO]). [ABSTRACT FROM AUTHOR]

Spin crossover (SCO) has long been a hot topic in the field of molecular magnetism owing to its unique bistability character. Rational control of thermal hysteresis and transition temperature (T1/2) is crucial for their practical applications, which rely on precise manipulation of the substituents of SCO coordinating ligands and molecular packing interactions. In this study, we designed two different bridging ligands (2-FDPB: 4,4'-(2-fluoro-1,4-phenylene)dipyridine; 2,3-FDPB: 4,4'-(2,3-difluoro-1,4-phenylene)dipyridine) featuring one and two fluoro substitution on the central benzene ring and applied a Schiff base-like equatorial tetradentate ligand {diethyl(E,E)-2,2'-[4,5-difluoro-1,2-phenyl-bis(iminomethylidyne)]bis(3-oxobutanoate)-(2-)-N,N',O3,O3'} (H2L) to coordinate with the FeII ion. Two FeII-coordination chain polymers [FeII(L)(2,3-FDPB)]·0.25CH2Cl2 (1) and [FeII(L)(2-FDPB)]·0.5CH3OH (2) were obtained. 1 crystallizes in the monoclinic P21/n space group with only one FeII center, while 2 crystallizes in the triclinic P1 space group with two independent FeII centers. Unlike the identical 2D layer stacking in 1, 2 exhibited alternating stacking of the extending 2D layers and meshed chains. Magnetic measurements revealed the typical thermally induced spin crossover behavior (SCO): 1 exhibited a 41 K-wide thermal hysteresis with transition temperatures of T1/2↑ = 245 K and T1/2↓ = 204 K, while 2 showed a higher transition temperature (T1/2 = 330 K) with no thermal hysteresis. Magneto-structural correlation studies suggest that the electron-withdrawing effect present in the fluoro substituents does not have a significant impact on the SCO behaviors. Despite the fluoro substituents having a similar atomic radius of hydrogen atoms, variations in the number of these substituents can alter the crystallization behavior of these complexes, which in turn affects the solvents, molecular stacking patterns, and intermolecular interactions, ultimately influencing the SCO behaviors. [ABSTRACT FROM AUTHOR]

A computational study on the interplay between ligand functionalization and guest effects on the transition temperature (T1/2) in the [Fe2(L1R)3]@X (L1 = 1,3-bis-(3-(pyridin-2-yl)-1H-pyrazol-5-yl)benzene, X = H-, F-, Cl-, Br-, I- and [BF4]-, R = H, F, or CH3) family of metal-organic cages (MOCs) is presented. Our results indicate that ligand functionalization with electron-donating or electron-withdrawing groups can significantly impact the T1/2 as expected, while the guest effect in lowering the T1/2 has a linear correlation with the increasing guest size. More importantly, small guests can move away from the center of the cavity, thus enhancing the two-step characteristic of the transition. All the data can be understood by analyzing the underlying electronic structure of the studied systems in terms of the relevant d-based molecular orbitals. These results can help in the rational design of new MOCs that can operate as sensors at specific temperatures, thus accelerating the discovery of new SCO devices with tailored properties. [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusion Hair fibres possess an inherently porous structure, which is affected by physical and chemical agents from the environment, as well as those from cosmetic treatments. The present work aims to investigate the potential of a calorimetric method for evaluating the changes of hair porosity, in terms of pore size and size distribution.The temperature of the phase transition from solid to liquid is known to be depressed if the liquid is confined within a pore. This shift in temperature can be measured by a calorimetric method like differential scanning calorimetry, DSC. This method is termed thermoporometry and it is the tool used for investigating hair porosity in this work.Virgin and bleached hair fibres are measured by DSC and, by using the equations developed for water behaviour confined in pores of a solid, the size and size distribution of the hair pores are evaluated, and the influence of the cosmetic treatment on the pores is discussed.Thermoporometry measurements of hair produced results in good agreement with those obtained by other methods for measuring hair porosity. The analysis of the data suggests that the fibre pores are mostly of a radius of 4 nm, and that the bleaching process increases the total volume of pores through the addition of smaller pores. A prolonged bleaching process appears to reduce the amount of fine pores produced by the first short process, resulting in fewer, but larger, cavities, most likely through a process of pore‐merging. [ABSTRACT FROM AUTHOR]

Asymmetric carbon molecular sieve (CMS) hollow fiber membranes with tunable micro‐ and macro‐structural morphologies for energy efficient propylene‐propane separation are reported here. A sub‐glass transition temperature (sub‐Tg) thermal oxidative crosslinking strategy enables simultaneous optimization of the intrinsic molecular sieving properties while also reducing the thickness of the CMS “skin” derived from the 6FDA : BPDA/DAM polyimide precursors. Such synergistic tuning of CMS microstructure and macroscopic morphology of CMS hollow fibers enables significantly increased propylene permeance (reaching 186.5 GPU) while maintaining an appealing propylene/propane selectivity of 13.3 for 50/50 propylene/propane mixed gas feeds. Our findings reveal a more refined and versatile tool than available with previous O2‐doping pretreatments. The advanced approach here should be broadly useful to other polyimide precursors and diverse gas pairs. [ABSTRACT FROM AUTHOR]

Ni–Zn–Mg ferrites having the chemical composition Ni0.7-xZnxMg0.3Fe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized using easy and low cost-effective sol–gel autocombustion method. Thermogravimetric and differential thermal analysis (TGA–DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) characterization techniques were used to characterize the synthesized samples. Structural and morphological properties of samples calcined at 500 °C, 600 °C, and 700 °C for 8 h were studied from XRD analysis and SEM analysis. Pure cubic phase along with proper grain growth was observed at calcined temperature 700 °C for 8 h. From TEM study of Ni0.4Zn0.3Mg0.3Fe2O4 average grain size is observed to be in range 50–55 nm that revealed the formation of nanosized particles. Thermoelectric power measurement (TEP) shows the p-type behavior at low temperature and n-type behavior at high temperature. p–n transition temperature for Ni–Zn–Mg ferrite system under investigation lies in the temperature range 90–135 °C. Gas sensing properties of Ni–Zn–Mg ferrite thick films toward NO2 and NH3 gases revealed Ni0.6Zn0.1Mg0.3Fe2O4 ferrite thick film shows good response along with quick response and recovery time as compared to other compositions under investigation. [ABSTRACT FROM AUTHOR]

The crystallographic, microstructural, and dielectric properties of Sr 2.1 Na 0.8-x Ca x Nb 5-x Sn x O 15 (x = 0.00, 0.01, 0.05, 0.10) polycrystalline ceramics have been studied by X-ray diffraction, scanning electron microscopy, dielectric spectroscopy (DS) and impedance spectroscopy (IS). For x = 0.00, 0.05, and 0.10, samples are single phase with P 4 bm symmetry at room temperature with x = 0.01 showing a small quantity of secondary phase(s). All compositions show typical ceramic microstructures and d 50 grain sizes ranging from 5.1 to 26.6 μm. DS shows a clear trend in the high temperature ferroelectric-paraelectric transition with the Curie temperature, T 0 , decreasing from ∼ 160 to ∼ 110 °C, and an additional relaxation at approximately 120 °C with increasing CaSnO 3. IS reveals all samples have a homogeneous electrical microstructure with predominantly electronic conduction. The activation energy of conduction calculated from Arrhenius plots of the conductivity increases with CaSnO 3 content from 1.27 to 1.38 eV likely due to the expansion of the band gap. [ABSTRACT FROM AUTHOR]

Unconventional 1T′ phase transition metal dichalcogenides (TMDs) show great potential for hydrogen evolution reaction (HER). However, they are susceptible to transitioning into the stable 2H phase, which reduces their catalytic activity and stability. Herein, we present a scalable approach for designing thermally stable 1T′‐TMDs hollow structures (HSs) by etching Cu1.94S templates from pre‐synthesized Cu1.94S@TMDs heterostructures, including 1T′‐MoS2, MoSe2, WS2, and WSe2 HSs. Furthermore, taking 1T′‐MoS2 HSs as an example, the etched Cu ions can be firmly adsorbed on their surface in the form of single atoms (SAs) through Cu−S bonds, thereby elevating the phase transition temperature from 149 °C to 373 °C. Due to the advantages conferred by the 1T′ phase, hollow structure, and synergistic effect between Cu SAs and 1T′‐MoS2 supports, the fabricated 1T′‐MoS2 HSs demonstrate superior HER performance. Notably, their high‐phase stability enables continuous operation of designed 1T′‐MoS2 HSs for up to 200 hours at an ampere‐level current density without significant activity decay. This work provides a universal method for synthesizing highly stable 1T′‐TMDs electrocatalysts, with a particular focus on the relationship between their phase and catalytic stability. [ABSTRACT FROM AUTHOR]

A new series of non-linear S-shaped oligomers [bis-6-(2-((4-methoxyphenyl-imino)methyl)-5-(4'-hexyloxy-4-biphenyloxycarbonyl)-phenoxy)alkyl]disulphide have been synthesised and characterised. The present oligomers consist of a central disulphide (S-S) linkage, Schiff base, outer alkyl spacer (n1 = six carbons) and inner alkyl spacer (n2 = six to eleven carbons). Upon cooling, all the oligomers show monotropic nematic phase. The odd–even effect was found at the transition temperature of Cr-I (TCr-I) and temperature range from isotropization to crystallisation (∆TI-Cr). However, the odd–even effect was not observed at the transition temperatures of I-N and N-Cr as the values decrease when n2increases. The representative oligomer with n2 = 7 undergone photoisomerisation behaviour and completed the conversion from trans to cis within a duration of 13 mins and vice versa (up to 1200 min). Optimized molecular structures of oligomers with n2 = 6 and 7 were obtained from TMoleX, and their length-to-breadth ratio can be reasonably employed to explain the odd–even effect in TCr-I, ∆TI-Cr and the reduction of its values in entropy change (∆SI-N/R). [ABSTRACT FROM AUTHOR]