Temperature-induced Phase Transition Research Articles

An improved methodology to quantify the temperature-induced phase transition in poly(dimethylsiloxane) elastomer

An improved methodology to quantify the temperature-induced phase transition in poly(dimethylsiloxane) elastomer

Flexible and thermoresponsive AEMR-pNIPAM/Cs0.33WO3 composite hydrogel film with NIR shielding potential for smart windows and smart curtains

Thermoresponsive flexible smart windows and smart curtains having high near-infrared (NIR) shielding and tuned visible light transmittance are essential for improving the energy efficiency of the buildings. The lower critical solution temperature (LCST) of the cross-linked poly(N-isopropylacrylamide) (pNIPAM) hydrogel film was precisely modified to a desired LCST value at 27.4 °C through the free radical copolymerization with 10 wt% of acrylated epoxidized methyl ricinoleate (AEMR). Cs0.33WO3 as NIR shielding nanoparticles (particle size < 200 nm) were synthesized via high energy ball milling method with AEMR as a surfactant for high NIR shielding efficiency and dispersion—the composite flexible hydrogel films with different wt% (0.3, 0.5,0.7, and 0.9 wt%) of Cs0.33WO3 nanoparticles were fabricated to analyze the NIR shielding efficiency and thermal insulation performance. The copolymeric hydrogel film with 0.7 wt% of Cs0.33WO3 nanoparticles (0.7-CWO) demonstrates a significant reduction in the NIR transmittance (15.0 % to 2.3 %) and variation in visible light transmittance from 73.6 % to 15.7 % while undergoing temperature-induced phase transition. The smart window fabricated with composite hydrogel film exhibits good integral luminous transmittance (Tlum, 380–780 nm, 68.7 %, below LCST) and justifiable solar modulation ability (ΔTsol, 300–2500 nm, 53.6 %). A model house was designed to monitor the indoor temperature difference, and a noticeable variation of 7 °C was observed in the house with and without 0.7-CWO film. Further, the developed composite material showed improvement in flexibility, water resistance, and thermal stability, confirming its usage for energy-saving smart windows or smart curtains.

Evaluation of Electronic Structure of Prussian Blue Analogue RbMn[Fe(CN)6] in Temperature-Induced Phase Transition Phenomena

Evaluation of Electronic Structure of Prussian Blue Analogue RbMn[Fe(CN)₆] in Temperature-Induced Phase Transition Phenomena

Raman scattering evolution in temperature-induced ferroelectric phase transition of few-layer NbOCl2

NbOCl2 is an emerging layered ferroelectric (FE) material with unique photoelectric properties. However, the phonons and thermal properties of NbOCl2 have remained elusive. Here, we report measurements of Raman and second harmonic generation spectrum of NbOCl2 flakes as a function of temperature (80–500 K). All observed Raman modes exhibit temperature-dependent shift. The first-order temperature coefficients of P1, P2, P3, P4, and P5 modes are 0.001 58, −0.005 21, −0.006 44, −0.012 56, and 0.036 75 cm−1 K−1, respectively. Interestingly, the frequency of the P1 mode changes directly from 161 to 156 cm−1 with increasing temperature, which is attributed to the switching between two independent Raman modes (P1H and P1L). The P1H mode is mainly contributed by the FE phase, while the P1L mode is mainly contributed by the antiferroelectric phase. Our results provide a fundamental understanding and analysis of the thermal–phonon coupling properties of few-layer NbOCl2 and promote the deep exploration of the basic physical properties of few-layer NbOCl2, which is crucial for the design and application of NbOCl2-based thermal and optoelectronic devices in the future.

A tensor renormalization group analysis of an evolutionary game of competing Ising and Potts subgames

The temperature-induced phase transitions of an evolutionary game of competing Ising- and Potts-type coordination subgames are studied using the tensor renormalization group method proposed by Michael Levin and Cody P. Nave. Depending on the relative strength of the subgames, a continuous Ising order to disorder or a continuous Potts order to disorder or consecutive first-order Potts order to Ising order and continuous Ising order to disorder phase transitions are observed. In the game-theoretic interpretation of the model, these results imply that while both types of coordination can spread in the population at low noise levels, one of them will always be dominant in equilibrium. Under a relatively narrow set of circumstances, a small increase in noise can cause the population to suddenly switch from Ising-type coordination to Potts-type coordination. The results are in general qualitative and quantitative agreement with previous Monte Carlo simulation findings.

Temperature-induced polymorphic phase transitions in gels and aerogels of nylon 11

Understanding the Brill transition behavior in nylons is particularly important in processing, as the thermal and mechanical properties of these polymers are highly dependent on the structural transitions. In this work, we report the preparation of a thermoreversible gel of nylon 11, which was freeze-dried to obtain the nylon 11 aerogel. Both gel and aerogel samples crystallized predominantly into the γ form at room temperature. The temperature-induced structural transitions of the gel and aerogel samples were studied using wide-angle X-ray diffraction measurements. The gel samples showed a reverse Brill transition from γ to α form on heating and the transition temperature showed a linear dependency on the polymer concentration in gels. On the other hand, the nylon 11 aerogel samples showed a structural transition from γ to high-temperature pseudohexagonal form upon heating. Current results demonstrate that the solvent molecules within the gel samples trigger the chain conformation change from gauche to trans on heating to induce a reverse Brill transition behavior. By adjusting the gel concentration, nylon 11 aerogel samples with varying porosities were obtained, which in turn display low dielectric constant values that rely on density/porosity. Further, the aerogels are also found to be suitable for oil-water separation applications due to their highly hydrophobic nature.

Investigation on the condensate gas composition variation and wax deposition mechanism during temperature-induced phase transition process

To explore the impact of temperature changes on the wax precipitation of gas condensate during the ultra-deep condensate reservoir development, this work prepares condensate samples and creates the wellbore environment by using a PVT system. At the reference wellbore pressure, the carbon number distribution of components in condensate samples extracted under different temperature conditions is analyzed, and the proportion and composition of precipitated wax are further characterized. The results indicate that the gaseous condensate system gradually produces liquid oil as the temperature decreases. During this process, the precipitated wax particles aggregate while transferring from gas to liquid, forming solid blocks. The exothermic activity caused by temperature decreasing weakens the molecular motion and particle thermal motion of each component in the system, increasing wax precipitation rate and amount. Since the high carbon number components with lower solubility can precipitate earlier than the low carbon number components, the remaining amount of the former in the condensate system significantly decreases, leading to a decrease in its precipitation rate and proportion in the precipitated wax. The carbon number distribution curve peak of the wax shifts towards the low carbon number interval during the temperature decrease. Moreover, since the solubility of coarse-crystal wax changes more significantly during temperature decrease than that of microcrystalline wax, the precipitation activity of the former is higher in the early stage of the experiment, leading to a decrease in the proportion of the latter in the precipitated wax. However, due to the reduction of its remaining amount in the system, its precipitation rate decreases in the later stage, resulting in a relative increase in the precipitation rate and proportion of microcrystalline wax. This study can provide data reference for the formulation of wax blockage prevention and control plans of the target well section, promoting efficient oil reservoir development.

Actively Tunable "Single Peak/Broadband" Absorbent, Highly Sensitive Terahertz Smart Device Based on VO2.

In recent years, the development of terahertz (THz) technology has attracted significant attention. Various tunable devices for THz waves (0.1 THz-10 THz) have been proposed, including devices that modulate the amplitude, polarization, phase, and absorption. Traditional metal materials are often faced with the problem of non-adjustment, so the designed terahertz devices play a single role and do not have multiple uses, which greatly limits their development. As an excellent phase change material, VO2's properties can be transformed by external temperature stimulation, which provides new inspiration for the development of terahertz devices. To address these issues, this study innovatively combines metamaterials with phase change materials, leveraging their design flexibility and temperature-induced phase transition characteristics. We have designed a THz intelligent absorber that not only enables flexible switching between multiple functionalities but also achieves precise performance tuning through temperature stimulation. Furthermore, we have taken into consideration factors such as the polarization mode, environmental temperature, structural parameters, and incident angle, ensuring the device's process tolerance and environmental adaptability. Additionally, by exploiting the principle of localized surface plasmon resonance (LSPR) accompanied by local field enhancement, we have monitored and analyzed the resonant process through electric field characterization. In summary, the innovative approach and superior performance of this structure provide broader insights and methods for THz device design, contributing to its theoretical research value. Moreover, the proposed absorber holds potential for practical applications in electromagnetic invisibility, shielding, modulation, and detection scenarios.

Hyaluronic Acid-Conjugated Thermoresponsive Polymer-Based Bioformulation Enhanced Wound Healing and Gut Barrier Repair of a TNBS-Induced Colitis Injury Ex Vivo Model in a Dynamic Perfusion Device.

Impairment of intestinal epithelium is a typical feature of inflammatory bowel disease (IBD) that causes leakage of bacteria and antigens from the intestinal lumen and thus results in persistent immune activation. Hence, healing and regeneration of the damaged gut mucosa is a promising therapeutic approach to achieve deep remission in IBD. Currently, available systemic therapies have moderate effects and are often associated with numerous side effects and malignancies. In this study, we aimed to develop a topical therapy by chemically conjugating a temperature-responsive polymer, i.e., poly(N-isopropylacrylamide), along with hyaluronic acid to obtain a sprayable therapeutic formulation that upon colon instillation adheres to the damaged gut mucosa due to its temperature-induced phase transition and mucoadhesive properties. An ex vivo adhesion experiment demonstrates that this therapeutic formulation forms a thin physical coating on the mucosal lining at a physiological temperature within 5 min. Physicochemical characterization of (P(NIPAM-co-NTBAM)-HA) established this formulation to be biocompatible, hemo-compatible, and non-immunogenic. Prednisolone was encapsulated within the polymer formulation to achieve maximum therapeutic efficacy in the case of IBD-like conditions as assessed in a custom-fabricated perfusion-based ex vivo model system. Histological analysis suggests that the prednisolone-encapsulated polymer formulation nearly restored the mucosal architecture after 2,4,6-trinitrobenzenesulfonic acid-induced damage. Furthermore, a significant (p ≤ 0.001) increase in mRNA levels of Muc-2 and ZO-1 in treated groups further confirmed the mucosal epithelial barrier restoration.

Insights into temperature-induced phase transition mechanism of CL-20 using terahertz spectroscopy

Understanding the phase transition mechanism of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is crucial for ensuring its safe applications. In this study, we observed the temperature-induced phase transition of CL-20 using terahertz spectroscopy. Subsequently, quantum chemical calculations were employed to assign the vibrations to experimental absorptions. Finally, the variations of intra- and intermolecular vibrations before and after phase transition were analyzed. The results indicated hydrogen bonds formed by the rotation of 5-nitro promoted hydrogen transfer, resulting in the decrease in thermal stability.

Nanoencapsulation of carotenoid extract via the temperature-induced phase transition of triblock polymer in supercritical carbon dioxide

Abstract Objectives Carotenoids are increasingly explored as nutraceuticals, but their low bioavailability due to poor aqueous solubility limits their applications. This study discusses the development of a novel and organic solvent-free method to develop carotenoid-containing polymeric nanoparticles via temperature-induced phase transition (TIPT) of pluronic F-68 to obtain formulations with the improved dissolution of carotenoids. Methods The nanoencapsulation of carotenoids in pluronic F-68 was performed in supercritical carbon dioxide (scCO2) to avoid oxidative or temperature/solvent-induced degradation. The nanoencapsulates were prepared in scCO2 at 40°C or 60°C and 10 MPa without the aid of any organic solvent. The formulations thereafter were characterised for particle size via dynamic light scattering, particle morphology via scanning electron microscopy and carotenoid content/release via high-performance liquid chromatography (HPLC). Key findings HPLC results showed carotenoid degradation to be negligible in freshly prepared formulations when prepared in scCO2 at 60°C and 10 MPa. The developed particles were spheroidal with sizes ranging between 150 and 250 nm depending on carotenoid content in the preparation. An improvement in the aqueous solubility and storage stability (5°C) of carotenoids was also observed for the formulations prepared in scCO2. Conclusions These results suggest that TIPT under scCO2 can be applied to formulate nanoparticulates with improved dissolution rate and stability of thermosensitive molecules such as carotenoids without causing any degradation during the processing.

Application of upconversion nanoparticles as a thermal sensor for biological tissue

The paper shows the possibility of simultaneous registration of the temperature of nanoparticles embedded in the fat layer and temperature-induced phase transitions in the fat layer. The luminescence spectra of upconversion particles (UCNPs) were measured and analyzed in a wide temperature range: from room to physiological and further to a hyperthermic temperature resulting in tissue morphology change. Typical samples thickness of adipose tissue was 0.5 mm. The sample temperature varied between 25 °C and 60 °C. The temperature dependence of the UCNPs luminescence intensity from UCNPs deposited onto the sample surface (1 layer) and from UCNPs deposited between two layers of abdominal adipose tissue was recorded. In the course of adipocyte heating, lipids of fat droplet first transit from a crystalline form to a liquid crystal form and then to a liquid form, which is characterized by much less scattering. The high-temperature transition is recorded most well. The obtained results confirm a high sensitivity of the luminescent UCNPs to the temperature variations within tissues and show a strong potential for the controllable tissue thermolysis.

Vanadium dioxide thin films-assisted terahertz meta-surface for simultaneous absorption, polarization conversion bi-functional switching, and wavefront operation

Actively switchable metasurfaces are extremely useful for achieving a multifunctional integrated platform. The proposed design enables functional switching through the temperature-induced phase transition features of vanadium dioxide (VO2). The hypothesized metasurface can be considered a broadband absorber when VO2 is in the metallic phase, with an absorption rate approaching 90% in the frequency spectrum of 1.41–2.69 THz, according to numerical simulations. When VO2 is in the insulating phase, the proposed metasurface acts as a half-wave plate with more than 80% polarization conversion rate (PCR) in the frequency range of 0.71–2.72 THz. Furthermore, the dynamic modulation of absorbance and PCR can be achieved when the VO2 conductivity varies within a specific range. Finally, by changing the opening angle of the gold split-ring resonator to introduce an abrupt phase at the interface, the composed metacell can perform arbitrary manipulation of reflected beams in the 1.0–2.2 THz broadband range; we also design 1D and 2D focusing metalenses. Both have good subwavelength focusing characteristics. Therefore, the proposed metasurface can be effectively applied in sixth-generation communication systems, terahertz imaging, and other technologies.

Order-Disorder Phase Transition and Ionic Conductivity in a Li2B12H12 Solid Electrolyte.

Temperature-induced phase transitions and ionic conductivities of Li2B12H12 and LiCB11H12 were simulated with the use of machine learning interatomic potentials based on van der Waals-corrected density functional theory (rev-vdW-DF2 functional). The simulated temperature of order-disorder phase transition, lattice parameters, diffusion, ionic conductivity, and activation energies are in good agreement with experimental data. Our simulations of Li2B12H12 uncover the importance of the reorientational motion of the [B12H12]2- anion. In the ordered α-phase (T < 625 K), these anions have well-defined orientations, while in the disordered β-phase (T > 625 K), their orientations are random. In vacancy-rich systems, its complete rotation was observed, while in the ideal crystal, the anions display limited vabrational motion, indicating the static nature of the phase transition without dynamic disordering. The use of machine learning interatomic potentials has allowed us to study large systems (>2000 atoms) in long (nanosecond-scale) molecular dynamics runs with ab initio quality.

Temperature-dependent Raman spectra and thermal expansion of MgP2O6

The Raman spectra and thermal expansion of MgP2O6 metaphosphate were investigated at various temperatures up to 1073 K at ambient pressure. No temperature-induced phase transition was observed in this study. The effect of temperature on the Raman active vibrations and unit cell parameters was determined. All the observed Raman active bands of MgP2O6 showed linear temperature dependences in the range of −2.61 × 10−2 ∼ −0.49 × 10−2 cm−1 K−1. The thermal expansion coefficient of MgP2O6 was estimated to be 3.21(2) × 10−5 K−1. An axial anisotropic thermal expansion exists and the c-axis shows the smallest thermal expansion. The isobaric mode Grüneisen parameters of MgP2O6 were calculated. The obtained results were compared with other compounds in the MgO-P2O5 system.

Systemic approach in the study of the properties and pressure-induced structural transformations in TaN: First-principles molecular dynamics simulations

First-principles molecular dynamics simulations were used to investigate pressure- and temperature-induced phase transitions in different TaN polymorphs. The driving forces and intermediate structures were established for the CoSn-like TaN (ε phase) to WC-type TaN (θ phase) and ε to NaCl type-TaN (δ phase) structural transformations that were observed in experiments and for the θ to hP4-194, θ to cP2-221, δ to cP2-221 and δ to tP4-129 phase transitions that were predicted in this investigation. Other possible TaN polytypes were systematically investigated and five new prospective phases were found: oP8-25, oP12-25, hP8-194, tP8-105 and tI8-109. All new structures are thermodynamically, dynamically and mechanically stable, and their formation energy is only slightly higher than that of the θ phase (by 0.014–0.032 eV/atom). The relative stability, electronic structure, chemical bonding, vibrational spectra, elastic moduli and their spatial anisotropy, Vickers hardness, fracture toughness, Debye temperature and optical properties (real and imaginary parts of the dielectric function, reflectivity spectrum) of the tantalum mononitrides mentioned above were systematically calculated and discussed. The oP12-25, tP8-105 and tI8-109 novel phases exhibit the Vickers hardness (33.1–34.2 GPa), fracture toughness (5.52–5.59 MPa m1/2) and Debye temperatures (609.7–616.1 K) that are higher compared to those of the known TaN structures. The TaN polytypes with the strong Ta-N bonds with minimal fraction of ionicity were found to possess the best mechanical properties. Further experimental investigations are highly desirable to confirm the results presented in this paper.

Hypo-Osmotic Stress and Pore-Forming Toxins Adjust the Lipid Order in Sheep Red Blood Cell Membranes.

Lipid ordering in cell membranes has been increasingly recognized as an important factor in establishing and regulating a large variety of biological functions. Multiple investigations into lipid organization focused on assessing ordering from temperature-induced phase transitions, which are often well outside the physiological range. However, particular stresses elicited by environmental factors, such as hypo-osmotic stress or protein insertion into membranes, with respect to changes in lipid status and ordering at constant temperature are insufficiently described. To fill these gaps in our knowledge, we exploited the well-established ability of environmentally sensitive membrane probes to detect intramembrane changes at the molecular level. Our steady state fluorescence spectroscopy experiments focused on assessing changes in optical responses of Laurdan and diphenylhexatriene upon exposure of red blood cells to hypo-osmotic stress and pore-forming toxins at room temperature. We verified our utilized experimental systems by a direct comparison of the results with prior reports on artificial membranes and cholesterol-depleted membranes undergoing temperature changes. The significant changes observed in the lipid order after exposure to hypo-osmotic stress or pore-forming toxins resembled phase transitions of lipids in membranes, which we explained by considering the short-range interactions between membrane components and the hydrophobic mismatch between membrane thickness and inserted proteins. Our results suggest that measurements of optical responses from the membrane probes constitute an appropriate method for assessing the status of lipids and phase transitions in target membranes exposed to mechanical stresses or upon the insertion of transmembrane proteins.

Phase-Controlled Cobalt Catalyst Boosting Hydrogenation of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran.

The search for non-noble metal catalysts for chemical transformations is of paramount importance. In this study, an efficient non-noble metal catalyst for hydrogenation, hexagonal close-packed cobalt (HCP-Co), was synthesized through a simple one-step reduction of β-Co(OH)2 nanosheets via a temperature-induced phase transition. The obtained HCP-Co exhibited several-times-higher catalytic efficiency than its face-centered cubic cobalt (FCC-Co) counterpart in the hydrogenation of the C=C/C=O group, especially for the 5-hydroxymethylfurfural (HMF) hydrogenation (8.5-fold enhancement). Density functional theory calculations demonstrated that HMF molecules were adsorbed more firmly on the (112_0) facet of HCP-Co than that on the (111) facet of FCC-Co, favoring the activation of the C=O group in the HMF molecule. The stronger adsorption on the (112_0) facet of HCP-Co also led to lower activation energy than that on the (111) facet of FCC-Co, thereby resulting in high activity and selectivity. Moreover, HCP-Co exhibited outstanding catalytic stability during the hydrogenation of HMF. These results highlight the possibility of fabricating hydrogenation catalysts with satisfactory catalytic properties by precisely tuning their active crystal phase.

Functional properties and shape memory effect of Nitinol manufactured via electron beam powder bed fusion

Ti-rich Nitinol (NiTi) is characterized by its functional properties to restore its original shape after deformation due to a temperature-induced reversible martensitic phase transition. In this study, dense Ti-rich Nitinol free of cracks is successfully produced by means of Electron Beam Powder Bed Fusion (PBF-EB). The martensitic phase transition behavior of the as-built NiTi parts and powder is analyzed using Differential Scanning Calorimetry (DSC) analysis. To gain a deep understanding of the DSC results, segregation during solidification is thermodynamically studied (CALPHAD). The PBF-EB-fabricated NiTi shows a microstructure containing fine columnar grains and numerous precipitates, whose influence on the tensile properties at room temperature is discussed. Furthermore, the one-way and two-way shape memory effects of PBE-EB-produced NiTi are investigated using an innovative experimental setup based on thermomechanical training.

Insight into Eu3+-Doped Phase-Change K3Lu(PO4)2 Phosphate toward Data Encryption.

Adjusting the local coordination environment of lanthanide luminescent ions can modulate their crystal-field splittings and broaden their applications in the relevant optical fields. Here, we introduced Eu3+ ions into the phase-change K3Lu(PO4)2 phosphate and found that the temperature-induced reversible phase transitions of K3Lu(PO4)2 (phase I ⇆ phase II and phase II ⇆ phase III, below room temperature) give rise to an obvious photoluminescence (PL) difference of Eu3+ ions. The Eu3+ emission mainly focused on the 5D0 → 7F1 transition in phase III but manifested comparable 5D0 → 7F1,2 transitions in the two low-temperature phases. On this basis, the change of Eu3+-doped concentration led to the phase evolution in Eu3+:K3Lu(PO4)2, which could stabilize two types of low-temperature polymorphs to the specific temperature by controlling the doping content. Finally, we proposed a feasible information encryption strategy based on the PL modulation of Eu3+:K3Lu(PO4)2 phosphors, which was caused by the temperature hysteresis of the relevant phase transition, exhibiting good stability and reproducibility. Our findings pave an avenue for exploring the optical application of lanthanide-based luminescent materials by introducing phase-change hosts.