Phase Transition Temperature Research Articles

Sustained Delivery of Liraglutide Using Multivesicular Liposome Based on Mixed Phospholipids

Background: Although peptides are widely used in the clinical treatment of various diseases due to their strong biological activity, they usually require frequent injections owing to their poor in vivo half-life. Therefore, there is a strong clinical need for sustained peptide formulations. Methods: In this study, liraglutide (Lir) and biocompatible multivesicular liposomes (MVLs) were utilized as the model drug and sustained-release carriers, respectively. The drug release rate of Lir-MVLs was controlled by changing the ratio of SPC and DEPC with different phase transition temperatures (PTT, PTTSPC = −20 °C, PTTDEPC = 13 °C). Results: As the SPC ratio increased, Lir-MVLs had more flexible lipid membranes, poorer structural stabilization, and fewer internal vesicles with larger particle sizes, contributing to faster release of Lir. After subcutaneous injection of Lir-MVLs, the blood glucose concentration (BGC) of db/db mice decreased to different levels. When the SPC-DEPC ratio was greater than 85:15, the drug release rate was too fast; the BGC remained below 16 mM for only 2–4 days, while when the drug release rate was too slow, was the case when the SPC-DEPC ratio was less than 50:50, the BGC also remained below 16 mM for only 2–3 days. However, when the SPC-DEPC ratio was 75:25, the BGC could be maintained below 16 mM for 8 days, indicating that the release properties of this ratio best met the pharmacological requirements of Lir. Conclusions: This study investigated the effects of phospholipids with different PTT on the release characteristics of Lir-MVLs, and provided ideas for the design of sustained-release peptide preparations.

Sustainable thermal buffering of microencapsulated bio-phase change materials through an engineered biochar dopant

Climate change and unbalanced energy demand and consumption require innovative approaches to the development of sustainable and renewable energy technologies. Phase change materials (PCMs) present exceptional solutions for zero-energy thermal management due to their outstanding energy storage density at an isothermal phase transition. However, the low thermal transport and thermal stability of bulk PCMs, as well as the expensive and complex synthesis of additive materials, hinder their large-scale utilization. In this study, food-waste-derived engineered biochar (FW) is produced via slow pyrolysis to improve the thermal properties of a microencapsulated bio-PCM (B28). The thermal performance of biochar-PCM composites is evaluated based on two biochar preparation systems: varying activation temperatures (carbonized at 400 °C followed by KOH activation at different temperatures (500–800 °C)) and varying mass ratios between KOH and biochar. The introduction of a low (0.63 wt%) engineered biochar dopant significantly improves the thermal diffusivity of B28 by more than 1.3-fold. The biochar-PCM microcapsule composites present fusion and crystalline isothermal phase transition temperatures of 29.4 ± 0.38 °C and 16.7 ± 0.13 °C, respectively. Moreover, the bio-PCM exhibits a highly efficient energy per unit mass of 61.6 kJ kg–1, which is 101.7% of the energy storage capacity of bulk B28. Additionally, the composite demonstrates high thermal stability with decomposition occurring above 195 °C, thus enabling an increase of > 20 °C in the onset decomposition point compared with pristine B28. Further analysis reveals the impact of the KOH/biochar mass ratio on the thermal properties of bio-PCM. Sample FW6PCM, in which the biochar is activated at 600 °C with a KOH/biochar mass ratio of 1, exhibits the highest enthalpy storage capacity. This study suggests a promising strategy for designing high-performance, eco-friendly, and scalable bio-based composite PCMs by overcoming the long-standing bottleneck of microcapsules, which is crucial for advanced thermal management applications such as cooling and green buildings.Graphical

Deconfinement and chiral restoration phase transition under rotation from holography in an anisotropic gravitational background

We investigate the effects of rotation on deconfinement and chiral phase transitions in the framework of the dynamical holographic QCD model. Instead of transforming to the rotating system by Lorentz boost, we construct an anisotropic gravitational background by incorporating the rotating boundary current. We first investigate the pure gluon system under rotation to extract deconfinement phase transition from the Polyakov loop then add two-flavor probe for chiral restoration phase transition from the chiral condensate. It is observed that at low chemical potentials, the deconfinement phase transition of pure gluon system is of first order and the chiral phase transition of a two-flavor system is of crossover. Both the critical temperatures of deconfinement and chiral phase transitions decrease/increase with imaginary/real angular velocity (ΩI/Ω) as T/Tc∼1−C2ΩI2 and T/Tc∼1+C2Ω2, which is consistent with lattice QCD results. In the temperature-chemical potential T−μ phase diagram, the critical end point moves toward regions of higher temperature and chemical potential with real angular velocity. Published by the American Physical Society 2025

Unveiling A-site substituent’s influence on magnetocaloric response in La2-xNaxNiMnO6 (0.0 ≤ x ≤ 1.0) double perovskite manganite materials

Abstract In this study, the compounds of La2-xNaxNiMnO6 (x = 0.0, 0.1, 0.2, 0.3, 0.5, and 1.0) double perovskite manganites have been produced by employing the sol-gel method to investigate their magnetocaloric effect. From X-Ray Diffraction analysis, all compounds crystallized in rhombohedral structure form with the $${\rm{R}}\bar{3}{\rm{c}}$$ R 3 ¯ c space group confirmed using the Rietveld refinement technique. The compounds show a magnetic phase transition from ferromagnetic to paramagnetic according to the temperature-dependent magnetization measurement. The phase transition temperatures sharply increased with Na doping (x = 0.1) to 277.8 K which can be considered as under room temperature level and then slowly decreased with further Na concentration to 262.3 K. Using an external magnetic field-dependent magnetization measurements, the isothermal magnetization curves were obtained, and these curves used to find the magnetic entropy change values, which give info about compounds’ characteristics of magnetic cooling performance. Under 5 T magnetic field change, the maximum magnetic entropy change value increased 10 times with a small amount of Na doping (x = 0.1), and compounds’ values changed from 0.21 to 1.29 Jkg−1K−1 for x = 0.0 to 1.0 compounds, respectively. Arrott plots were graphed by using isothermal magnetization curves to demonstrate all the compounds have a 2nd order magnetic phase transition which supports that these compounds can be candidates as magnetic refrigerants. Graphical Abstract

Atomistic analysis of nematic phase transition in 4-cyano-4'-n-alkyl biphenyl liquid crystals: Sampling for the first-order phase transition and the free-energy decomposition.

Molecular dynamics simulations were conducted using the generalized replica exchange method (gREM) on the 4-cyano-4'-n-alkyl biphenyl (nCB) system with n = 5, 6, 7, and 8, which exhibits a nematic-isotropic (NI) phase transition. Sampling near the phase transition temperature in systems undergoing first-order phase transitions, such as the NI phase transition, is demanding due to the substantial energy gap between the two phases. To address this, gREM, specifically designed for first-order phase transitions, was utilized to enhance sampling near the NI phase transition temperature. Free-energy calculations based on the energy representation (ER) theory were employed to characterize the NI phase transition. ER evaluates the insertion free energy of the nCB molecule for both nematic and isotropic phases, revealing a change in the temperature dependence across the NI phase transition. Further decomposition into energetic and entropic terms quantitatively shows the balance between these contributions at the NI phase transition temperature.

Core-Only Calamitic Liquid Crystals: Molecular Design and Optoelectronic Properties.

Thermotropic liquid crystals are typically thought of as requiring a rigid core and flexible side-chains to exhibit liquid crystallinity, but precedent does exist for retaining liquid crystalline nature without these side-chains in highly conjugated, para-substituted aromatic structures, albeit at relatively high temperatures (> 300 °C). Hence, this work aims to establish molecular design criteria for promoting liquid crystallinity in heteroaromatic, fully conjugated, core-only calamitic liquid crystals at sufficiently low phase transition temperatures. The synthesis and characterization of an extensive library of calamitic target structures (32) has been accomplished, where primarily enantiotropic smectic A and nematic phases were observed. Comparison of the mesomorphic properties between different cores and with different terminal functional groups was done and rationalization of the observed differences is attempted through single crystal and computational data. These all-aromatic compounds also display strong fluorescence in solution and in the solid-state that extends over most of the visible spectrum and displays quantum yields between 3% and 95%.

Dilution of dark matter relic abundance due to first order electroweak phase transition in the singlet scalar extended type-II seesaw model

We investigate the effect of a first-order electroweak phase transition (FOEWPT), which is one of the prerequisites for electroweak baryogenesis, on the thermal relic abundance of the dark matter (DM) that freezes out before the occurrence of the phase transition in the complex singlet scalar extended Z3-invariant type-II seesaw model that can simultaneously provide a DM candidate, explain the nonvanishing neutrino masses and the baryon asymmetry of the Universe. Such a phase transition around the electroweak scale leaves an impact on the relic density due to the release of entropy, particularly for a TeV-scale DM. We thus concentrate on the region of parameter space of the said model, which favors an FOEWPT in the early Universe and for which the DM is heavy such that its freeze-out temperature turns out to be larger than the phase transition temperature. We further study the dependencies of the dilution factor of the DM relic density on the model parameters, the nucleation temperature, the strength and the duration of the phase transition. Such a dilution might retrieve some of the regions of parameter space that were previously ruled out by the measured value of the DM relic density and/or the latest constraints from the DM direct-detection experiments. Furthermore, a direct connection is drawn between the dilution factor and the generation of stochastic gravitational waves as a result of an FOEWPT. Published by the American Physical Society 2025

Rheological Behavior and Improved Swelling of Porous Semi-IPN Hydrogels Based on Poly(isopropylacrylamide-co-itaconic Acid)/Sodium Alginate – In Vitro Theophylline Release Analysis

A series of semi-interpenetrating networks (semi-IPN) hydrogels composed of temperature sensitive poly(N-isopropylacrylamide) (PNIPAAm) and pH sensitive itaconic acid (IA) and sodium alginate (SA) were prepared by radical copolymerization/crosslinking reaction. The structures, morphology, thermal, rheological and swelling behaviors of the hydrogels were studied. The evidence for successful synthesis was confirmed by infrared spectroscopy. In thermal analysis, all prepared semi-IPN samples showed a clear endotherm corresponding to a volume phase transition temperature. Morphological aspects of the samples displayed highly porous structure and expanded network depending on alginate content. Rheological analysis showed that all measured viscoelastic properties were influenced by gel composition and temperature; a sharp transition to higher values of the storage modulus G' was observed above the transition temperature. The swelling behavior revealed the high sensitivity of samples for temperature and pH: higher swelling was observed in simulated intestinal fluid (SIF) than in gastric one (SGF). Moreover, the swelling drops radically as the temperature rises up to 37 °C. In both fluids at 20 °C and 37 °C, the swelling is diffusion-controlled mechanism with a Fickian transport. From in vitro degradation study, the hydrogels were degradable in pancreatin-containing SIF solution at 37 °C and samples with higher alginate ratio showed high degradation rate. The high cumulative release of theophylline observed in SIF provides a significant improvement for drug delivery from these hydrogels to intestinal regions; the release profile displays close fitting to Korsmeyer-Peppas model with Fickian transport.

Electrochromic Encryption and Decryption Smart Films Fabricated by Selective Photopolymerization of Polarization‐Dependent Triphenylamine‐Based Thin Films

AbstractThe newly designed triphenylamine (TPA) based asymmetric monomer (TPA‐A) is synthesized for the development of a high‐security information encryption system. TPA‐A exhibits photoluminescence (PL) emission and redox‐active electrochromic (EC) properties, highlighting its potential as a smart encryptable ink. Introducing a methyl group to one side branch of the TPA‐A induces a steric hindrance effect, enabling TPA‐A to form a self‐assembled lamello‐columnar structure. This structural modification reduces the phase transition temperature and simultaneously allows for the uniaxial orientation of TPA‐A by a simple shear‐coating process. The uniaxially oriented and self‐assembled TPA‐A thin films exhibits polarization‐dependent PL properties and electrofluorochromic (EFC) characteristics combined with redox‐responsive EC properties. The selective photopolymerization of polarization‐dependent TPA‐A thin film generates a dual‐mode information encryption system. The newly developed EC smart film can open a new door for optoelectronic information encryption and anti‐counterfeiting technologies.

String tension and Polyakov loop in a rotating background

We study the influence of a rotation on the string tension and the temperature of the confinement-deconfinement phase transition of gluodynamics by gauge/gravity duality. We explore two distinct approaches, global transformation and local transformation, to introduce rotation and compare the results. It is shown that the string tension extracted from the free energy in the presence of a heavy quarkonium decreases with increasing angular velocity, while the transition temperature determined by the Polyakov loop increases with increasing angular velocity, which is in line with lattice simulations. Published by the American Physical Society 2025

Nanoscale insights on phase transition dynamics of doped VO2 for memristor devices

This study utilized co-sputtering to fabricate Mo-doped VO2 films and identified an optimal concentration exhibiting a lower phase transition temperature (Th = 55.8 °C) and a broader hysteresis window (Δ T = 13.6 °C). At the atomistic scale, it is demonstrated that Mo dopant-induced localized strain accelerates the phase transition, which leads to the relaxation of the tetragonal structure. Furthermore, the effects of Mo doping on the phase transition process and electrical properties are characterized at the nanoscale using conductive atomic force microscopy and Kelvin probe force microscopy, and the potential application in selectors can be evaluated. The results indicated that Mo doping destabilizes the M1 phase by introducing a high density of electrons, thereby significantly reducing the electron–electron interactions as per the Mott model. Moreover, the device exhibited stable threshold and memristive properties at room temperature, quickly switching from high to low-resistance states at a threshold voltage of 2.37 V and maintaining stability over more than 1000 cycles with a selectivity >102. The present work not only highlights the role of Mo doping in enhancing the functional properties of VO2 but also demonstrates its feasibility in high-performance selectors devices.

Adaptive Phase Change Microcapsules for Efficient Sustainable Cooling.

Passive radiative cooling has recently gained significant attention as a highly promising technology that offers a zero-energy and electricity-free solution to tackle the pressing issue of global warming. Nevertheless, research efforts have predominantly focused on enhancing daytime and hot-day radiative cooling efficacy, often neglecting the potential downsides associated with excessive cooling and the consequent increased heating expenses during cold nights and winter days. Herein, we demonstrate a micro-nanostructured engineered composite film that synergistically integrates room-temperature adaptive silica-shell/oil-core phase change microcapsules (S-PCMs) with commercially available cellulose fibers. The resultant composite film exhibits a solar reflectance of 0.92 and a mid-infrared emissivity of 0.96, achieving a remarkable average daytime subambient cooling of 7.5 °C under direct sunlight in hot conditions. Encouragingly, upon reaching the phase transition temperature, the heat previously absorbed and stored by S-PCMs is released, resulting in a temperature elevation of the composite film with an average temperature differential of merely 3.0 °C compared to surrounding air. The exceptional latent heat storage capability of our S-PCMs/cellulose composite film mitigates the radiative overcooling effect and substantially diminishes the heating demand, particularly across a diverse array of environmental conditions.

Study of the thermolysis process of copper (II) sulfate pentahydrate by thermovolumometric method

When studying mixtures of minerals, composites of complex composition, and selecting powder catalysts, problems often arise for which the small masses of samples used in thermogravimetry do not provide sample representativeness. This requires the use of other methods of analysis that allow the use of samples ten times larger in mass. The paper presents the results of a study of the thermolysis process of copper (II) sulfate pentahydrate using a thermovolumometric method. During the tests, a sealed container with the analyzed substance and a thermoelectric converter was placed in a tubular furnace. The gas released during thermolysis entered the bubbling tank through the capillary. SoundForge13 and TableCurve 2D programs were used to process experimental data. The sources of error in the thermovolumometric analysis technique are analyzed. Dependencies that can be used to improve its accuracy are given. It was revealed that the value of the repeatability index obtained as a result of assessing the repeatability of the method is 3 °C; in the range of densities of the evolved gases 1. 25 – 1. 43 kg/m3, the resolution of the method in terms of the mass of the substance is 12 – 13 μg. The results obtained can be used to determine the temperatures of phase transitions when studying processes occurring during heating of mineral compositions, as well as the temperatures of decomposition reactions of substances. The accuracy of measurements can be increased by careful sample preparation, reducing the heating rate of the sample and introducing corrections to the measurement result based on the obtained dependencies.

Conserved charge susceptibilities in the relativistic mean-field hadron resonance gas model: Constraints on hadronic repulsive interactions

In this paper, we investigate the effect of repulsive interaction between hadrons on the susceptibilities of conserved charges, namely baryon number (B), electric charge (Q) and strangeness (S). We estimate second-, fourth- and sixth-order susceptibilities of conserved charges, their differences, ratios and correlations within ambit of mean-field hadron resonance gas (MFHRG) model. We consider repulsive mean-field interaction among meson pairs, baryon pairs and antibaryon pairs separately and constrain them by confronting the results of various susceptibilities with the recent lattice quantum chromodynamics (LQCD) data. We find that the repulsive interactions between baryon–baryon pairs and antibaryon–antibaryon pairs are sufficient to describe the baryon susceptibilities of hadronic matter at temperatures below QCD transition temperature. However, small but finite mesonic repulsive interaction is needed to describe electric charge and strangeness susceptibilities. We finally conclude that the repulsive interaction between hadrons play a very important role in describing the thermodynamic properties of hadronic matter, especially near the quark–hadron phase transition temperature ([Formula: see text]). The mean-field parameter for baryons ([Formula: see text]) should be constrained in the range [Formula: see text] to get a good agreement of baryon susceptibilities with the LQCD results, whereas meson mean-field parameter [Formula: see text] must be included with [Formula: see text] to get a reasonable agreement of MFHRG model with the LQCD results for electric charge and strangeness susceptibilities.

Ultrasound-assisted efficient targeting of doxorubicin to the tumor microenvironment by lyso-thermosensitive liposomes of varying phase transition temperatures.

Premature drug release is the primary hindrance to the effective function of the lyso-thermosensitive liposomes (LTSLs) of doxorubicin (Dox), known as ThermoDox® for the treatment of cancer. Herein, we have optimized LTSLs by using a combination of phospholipids (PLs) with high transition temperatures (Tm) to improve the therapeutic outcome in an assisted ultrasound approach. For this, several Dox LTSLs were prepared using the remote loading method at varying molar ratios (0 to 90%) of DPPC (Tm 41°C) and HSPC (Tm 54.5°C), as well as a constant molar ratio of MSPC (10%), DSPE-mPEG2000 (4%). The treatment efficacy was explored by using ultrasound as external hyperthermia (HT) (40-42℃) in mice bearing C26 murine colon carcinoma. All the formulations had an average diameter of around 110 nm, PDI ≤ 0.15, zeta potential of around -12 mV, and Dox encapsulation of >90%. The cytotoxicity results indicated a higher IC50 value of Dox-LTSLs compared to the ThermoDox® (F0: DPPC:MSPC:DSPE-mPEG2000, 90:10:4), attributed to the faster Dox release in F0 formulation devoid of HSPC. Among various formulations, F25 (DPPC: MSPC: DSPE-mPEG2000: HSPC, 65:10:4:25) showed the highest cellular uptake at 42℃ and significantly improved the antitumor and survival efficacy in mice bearing C26 colon carcinoma in combination with ultrasonic HT compared to F0. Collectively, results demonstrated that optimizing the rigidity of the liposomal bilayers through the combinatorial selection of PLs of different transition temperatures could improve the plasma stability of the liposome, and hence ameliorate the outcome of therapy in assistance with an effective HT approach.

Interaction Analysis between Cationic Lipid and Oligonucleotide with a Lipid Membrane-Immobilized Monolith Silica Column: A High-Performance Liquid Chromatography Approach.

Understanding the interactions between lipid membranes and nucleotide drugs is crucial for nucleic acid therapy. Although several methods have been employed to evaluate nucleotide-lipid membrane interactions, these interactions can be complex; this complexity arises from how external factors, such as ionic strength or temperature, influence the lipid membrane's overall properties. In this study, we prepared a lipid membrane-immobilized monolithic silica (LMiMS) column for high-performance liquid chromatography (HPLC) analysis to understand interactions between the lipid membrane and nucleic acid. First, the Raman shift, zeta potential, fluidity, and polarity of the LMiMS-column membrane were analyzed and compared to dispersed liposomes (not immobilized) with the same lipid composition. The results indicated that the column can effectively imitate the temperature-dependent properties of the lipid membrane, suggesting that the immobilized lipid membrane can be used as a model of dispersed liposomal membranes. Subsequently, HPLC was performed to analyze the interaction between the lipid membrane and oligonucleotides. The retention factor k was determined as an interaction factor between the LMiMS column and nucleic acid models (poly 10, 25, and 50mer dC) at various temperatures and mobile phase salt concentrations. The results revealed that changes in membrane interaction were significant by the phase state and salt concentration. Further analysis of the retention factor k showed that the interaction is weak below the phase transition temperature but strong above the phase transition temperature. The results indicate that membrane properties (rigidity and polarity) are also related to membrane interaction, which can be evaluated with the LMiMS column. This analytical method can provide a new perspective on estimating the interactions between target molecules and the lipid membrane through their temperature-induced dynamics. From these results, our method could be useful for analyzing lipid membrane-oligonucleotide interactions.

Liquid Crystal Polycaprolactone Copolymer Elastomer With Low Autonomous Driving Temperature

ABSTRACTLiquid crystal elastomers (LCEs) are liquid crystal polymers with moderate crosslinking that exhibit elasticity in both their isotropic and liquid crystal states. These materials can be programmed through chemical design and geometric configuration to achieve autonomous actuation at specific temperatures. Typically, the autonomous actuation temperature of LCEs exceeds the phase transition temperature of their isotropic states, with most reported LCEs requiring temperatures above 100°C. Such high temperatures pose challenges for use in soft robotics due to increased energy consumption and limited operational flexibility. In this study, we introduce a small amount of polycaprolactone (PCL) into the main chain of LCEs, effectively lowering their phase transition temperature while maintaining over 90% of the reversible shrinkage strain characteristic of pure LCEs. By adjusting the PCL content, the number of twists, and the helix density, we successfully obtained an LCE‐PCL actuator with improved autonomous actuation performance at temperatures ranging from 45°C to 105°C. Moreover, by modulating the degree of torsion and the operating temperature, the LCE‐PCL autonomous actuator demonstrates the ability to perform complex motions, such as reversing and parking. This work offers new insights into the design and application of LCEs with reduced phase transition temperatures and enhanced self‐driving capabilities.

Solar Evaporator with Dual Gradient Heating Effect for Sustained and Efficient Desalination.

Solar desalination shows promise in tackling freshwater shortages, but challenges arise from the trade-off between water transportation and heat supply, affecting evaporators' efficiency and salt resistance. Additionally, intermittent nature of solar radiation significantly diminishes overall evaporative performance. This study presents dual-gradient heating solar evaporator for efficient desalination. Dual-gradient heating is enabled through wettability difference (hydrophilicity aerogel and hydrophobicity film) and difference in phase transition temperature of phase change material, thus, effective heat supply can be provided to evaporation layer consisting of vertically oriented phase-change aerogel by surrounding heating layer consisting of phase-change film, with and without solar radiation. Employing this design, evaporator demonstrates industry-leading comprehensive performance in practical use. Under one sun illumination, evaporation rate achieves 6.84 kgm-2h-1 in 5.0 wt% salinity, with efficiency of 90.9%. In darkness, evaporation rate remains high at 2.61 kgm-2h-1 (30 minutes). Moreover, evaporator exhibits outstanding solar energy storage capacity and long-term stabe evaporative performance and salt resistance for 7-day testing. Furthermore, evaporator successfully produces freshwater from real Bohai Sea water under weak outdoor lighting, addressing recommended daily intake of water for 2.5 households. This work introduces new perspective for maximizing utilization of solar energy for seawater desalination and overcoming intermittent solar radiation.

BKT transitions of the XY and six-state clock models on the various two-dimensional lattices

Abstract In a two-dimensional (2D) spin system, the XY model, characterized by planar rotational symmetry, exhibits a unique phenomenon known as the Berezinskii-Kosterlitz-Thouless (BKT) transition. In contrast, the clock model, which introduces discrete rotational symmetry, exhibits the BKT transition at two different temperatures due to this discreteness.
In this study, we numerically investigate the BKT transition for XY and six-state clock models over various two-dimensional lattices. We employ two primary methods: the Monte Carlo method, which analyzes the size dependence of the ratio of the correlation functions for two different distances, and a machine-learning approach to classify the different phases --- namely, the low-temperature ordered phase, the intermediate BKT phase, and the high-temperature disordered phase.
We identify the BKT transition temperatures for the XY and six-state models on honeycomb, kagome, and diced lattices. 
Combined with the previously calculated data for the triangular lattice, we then compare these values with the second-order phase transition temperatures of the 2D Ising model, for which exact solutions are known. 
Our results indicate that the ratio of the BKT transition temperatures for each lattice relative to the Ising model transition temperatures are close, although the values are not universal. 

Pressure and temperature response and phase transition path during small hole leakage in a near-industrial scale CO2 pipe

ABSTRACT As a large-scale CO2 migration method, pipelines play a crucial role in the CCUS industry chain. Small hole leakage caused by self defects, fatigue and corrosion, and natural disasters is a common accident in CO2 pipelines. When leaked CO2 is sprayed out through a small hole, the temperature inside the pipeline drops sharply under the Joule Thomson effect. This sudden temperature drop significantly reduces the toughness of the material, increases the risk of brittle fracture. In order to improve the CO2 pipeline release database, a new industrial scale CO2 pipeline has been built. The CO2 release experiments were carried out by using this experimental device. The experimental results showed that the pressure drop rate was fast under high pressure and then slowed down when the pressure dropped below the critical pressure, with the coexistence of gas and liquid. Rapid pressure drop and slight rebound occur during the leakage process, and low initial pressure leads to a more pronounced pressure plateau effect. Dense-phase CO2 leakage produced more dry ice than supercritical state, and the far field sublimation effect was more significant. In practice, particular attention should be paid to safety far from the leakage end.