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Abstract: Superhydrophobic alkyl ketene dimer (AKD) layers were successfully produced on top of untreated paper surfaces by a rapid expansion of supercritical CO2 solution (RESS) process. The new method resulted in a degree of hydrophobicity, as measured by contact angles of water droplets on AKD surfaces, dramatically higher, up to 173°, compared to a conventional method consisting in melting AKD granules directly on the paper substrate, giving contact angles of around 109°. Experiments were conducted to investigate the effects of varying pre-expansion pressure (100–300bar), pre-expansion temperature (40 and 60°C) and spraying distance (10 and 50mm) on the properties of the treated surfaces. The surfaces were analyzed regarding AKD particle size, surface morphology and hydrophobicity with the aid of scanning electron microscopy (SEM) and contact angle measurements. The average AKD particle size after RESS processing was between 1 and 2μm depending upon the experimental conditions used, being slightly smaller when using higher pre-expansion pressure and temperature as well as shorter spraying distance. [Copyright &y& Elsevier]

Paper samples were rendered superhydrophobic with Alkyl Ketene Dimer using (1) Airblasting with cryo ground micro particles, (2) crystallizing from organic solvents and (3) spraying with Rapid Expansion of Supercritical Solutions (RESS) technique. The papers were characterized using Scanning Electron Microscopy, contact angle to water measurements and X-ray Photoelectron Spectroscopy (XPS). Advancing contact angles were in the region of 150°–160° and receding contact angles were in the region of 110°–130°. Diagrams showing the drop base diameter vs. the contact angle when water is pumped into, and then withdrawn from, a sessile drop show that a stick slip pattern is present in the advancing phase for a non coated internally sized paper. Papers rendered superhydrophobic with the RESS technique showed a much less pronounced stick slip pattern in the advancing phase but still a stick slip pattern in the receding phase. [ABSTRACT FROM AUTHOR]

Abstract: Graphene oxide (GO) paper was treated in supercritical ethanol as a green route for its reduction, which was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis and conductivity measurements. The reduced GO paper showed good electrochemical properties. As a sole component of the anode in lithium ion batteries, its specific capacity was comparable to those of free standing GO papers reduced by hydrazine or carbon nanotube paper. The GO paper reduced by supercritical ethanol can be a potential candidate for a binder-free anode in high performance lithium batteries. [Copyright &y& Elsevier]

This paper describes the chemistry of green materials synthesized with supercritical fluids. First, the properties and some specific features of supercritical water are summarized. Then, supercritical hydrothermal synthesis of nanoparticles is explained, and various applications of green materials are described. The surface control of nanoparticles in supercritical water is also explained. Green processes involving chemical recycling of waste polymers and a combination of hydrothermal synthesis and supercritical water oxidation are also discussed. Finally, commercialization of supercritical water processes is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Low-cost sensors were developed in two steps: (i) using a negative template to print graphite electrodes on vellum paper and (ii) coating with conductive polymers. Thin films of polyaniline (PANI) in the emeraldine oxidation state were investigated as active layers, after being synthesized by two routes: (a) polyaniline doped with dodecylbenzenesulfonic acid (DBSA) deposited by supercritical fluid (SC CO2) and (b) PANI doped with hydrochloric acid (HCl) by the in situ polymerization method. The electrical response (mV) was measured with dedicated circuitry, both in static laboratory air and with a flow of dry nitrogen gas (N2) at room pressure and temperature in a closed chamber, to assess the sensors for their sensitivity and reversibility. The phase morphology (microfiber structure) was characterized by FE-SEM. Results showed a difference in behavior between the sensors obtained by SC CO2 coating with PANI and by in situ polymerization. The voltage in the SC CO2 sensor decreased when it was exposed to the flow of dry nitrogen, whereas the opposite effect was observed in the other sensor. [Copyright &y& Elsevier]

Cirsium yildizianum stalks were liquefied in organic solvents under supercritical conditions with and without catalyst in a cylindrical reactor at temperatures of 260, 280 and 300 °C. The effects of liquefaction temperature, catalyst type and solvent on product yields were investigated. The liquid products (bio-oils) were extracted with diethyl ether and benzene using an extraction procedure. The liquid yields in supercritical methanol, ethanol and acetone were found to as 45.66%, 49.34% and 60.05% in the non-catalytical runs at 300 °C, respectively. The highest conversion (liquid + gaseous products) was obtained in acetone with 10% ferric chloride at 300 °C in the catalytic runs. The produced liquids at 300 °C were analyzed and characterized by elemental, GC–MS and FT-IR. 85, 79 and 60 different types of compounds were identified by GC–MS obtained in methanol, ethanol and acetone, respectively. The liquid products were composed of various organics including aromatics, nitrogenated and oxygenated compounds. [ABSTRACT FROM AUTHOR]

Continuous-flow rhodium-catalysed hydroformylation of long chain alkenes has been achieved with selectivities to the desired linear aldehyde of 92% and minimum rhodium loss, using a xantphos-derived ligand attached to an imidazolium salt in a supercritical fluid–ionic liquid system. The effect of oxygen in the system can be ameliorated to some extent by adding a simple sulfonated triphenylphosphine to the catalytic solution. [ABSTRACT FROM AUTHOR]

The kinetic resolution (KR) and dynamic kinetic resolution (DKR) of racemic 1-phenylethanol with the acyl donor vinyl acetate catalysed by Pseudomonas cepacialipase ATCC 21808 (PCL) (this has recently been reclassified as Burholderia cepacialipase), either as the suspended native protein (PCL) or immobilised on ceramic particles (commercial lipase Amano PS CI) has been examined, as batch reactions, in supercritical carbon dioxide (scCO2). The yields and enantioselectivities achieved in these reactions were comparable to experiments conducted in hexane. The immobilised lipase PS CI displayed excellent yields (48–49%) and enantioselectivities (98–99%) to give (R)-phenylethyl acetate after 2.5 hours reaction at 40 °C in scCO2. The acylated product was obtained in higher yield in scCO2compared to the reaction carried out in hexane (yield 30–35%; ee 98–99%) under comparable conditions. Unlike PCL, the immobilised lipase PS CI could then be successfully reused with no loss of activity or selectivity observed over four reaction cycles. Combining lipase PS CI with a chemical catalyst (either the metal catalyst [Ru(p-cymene)Cl2]2or the acid catalyst Nafion SAC 13) to catalyse the racemisation of the unreacted alcohol caused an increase in the yield of the (R)-acyl phenylethanol product to 70 and 85%, respectively, in scCO2indicating a viable dynamic kinetic resolution system had been established. The enantioselectivities of the products in these reactions were slightly higher in scCO2(96% Ru-catalyst; 85% Nafion) compared to those observed in hexane (91%; 81%). The lower enantioselectivity with the acidic Nafion SAC 13 catalyses indicates that some non-enzymic acid catalysed esterification was occurring. [ABSTRACT FROM AUTHOR]

This paper provides a detailed description of the development and experimental results of the supercritical flow experiment payload carried on the TZ-6 cargo spacecraft, as well as a systematic verification of the out-of-cabin deployment experiment. The technical and engineering indicators of the payload deployment experiment are analyzed, and the functional modules of the payload are shown. The paper provides a detailed description of the design, installation location, size, weight, temperature, illumination, pressure, radiation, control, command reception, telemetry data, downlink data, and experimental procedures for the out-of-cabin payload in the extreme conditions of space. The paper presents the annular liquid surface state and temperature oscillation signals obtained from the space experiment and conducts ground matching experiments to verify the results, providing scientific references for the design and condition setting of space experiments and comparisons for the experimental results to obtain the flow field structure under supercritical conditions. The paper provides a specific summary and discussion of the space fluid science experiment project, providing useful references for future long-term in-orbit scientific research using cargo spacecraft. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of current and prospective technologies for recycling carbon fiber reinforced polymer (CFRP), addressing the growing need for sustainable disposal and resource recovery driven by increasing CFRP applications. Four primary recycling methods are discussed: incineration, physical recycling, chemical recycling, and thermal recycling. Incineration, while offering energy recovery, is unsustainable due to limited material recovery and environmental pollution. Physical recycling, utilizing mechanical processes, is cost-effective but results in significant fiber degradation, restricting applications to low-value fillers. Chemical recycling, involving solvent or acid-based resin decomposition, can yield high-quality fibers but faces challenges regarding environmental impact, process efficiency, and economic viability. Thermal recycling, encompassing pyrolysis in various configurations (conventional, fluidized bed, and microwave), emerges as the most promising approach, offering reasonable recovery rates and acceptable fiber properties, albeit with concerns about energy consumption and potential fiber damage. The review critically evaluates each method based on recovery efficiency, recovered fiber quality, environmental impact, and economic feasibility. It highlights the need for future research focusing on developing greener chemical solvents and catalysts, optimizing thermal processes and exploring product valorization, and investigating novel recycling technologies such as supercritical fluids, bio-based methods, and electrochemical approaches. Furthermore, it emphasizes the importance of establishing comprehensive performance evaluation standards for recycled fibers, exploring surface modification techniques, and expanding application possibilities. Life cycle assessment, economic analysis, and strengthened collaborations among academia, industry, and government are also crucial for advancing CFRP recycling towards industrialization and promoting a circular economy within the composites sector. [ABSTRACT FROM AUTHOR]

In this paper, we apply a theoretical model for fluid state thermodynamics to investigate simulated water in supercooled conditions. This model, which we recently proposed and applied to sub- and super-critical fluid water [Zanetti-Polzi et al., J. Chem. Phys. 156(4), 44506 (2022)], is based on a combination of the moment-generating functions of the enthalpy and volume fluctuations as provided by two gamma distributions and provides the free energy of the system as well as other relevant thermodynamic quantities. The application we make here provides a thermodynamic description of supercooled water fully consistent with that expected by crossing the liquid–liquid Widom line, indicating the presence of two distinct liquid states. In particular, the present model accurately reproduces the Widom line temperatures estimated with other two-state models and well describes the heat capacity anomalies. Differently from previous models, according to our description, a cluster of molecules that extends beyond the first hydration shell is necessary to discriminate between the statistical fluctuation regimes typical of the two liquid states. [ABSTRACT FROM AUTHOR]

The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO2RR) process, but with great challenges in achieving a uniform distribution of catalytic active sites and rapid mass transfer properties. Hierarchical porous materials with a porous hierarchy show great promise for application in CO2RRs owing to the high specific surface area and superior porous connection. Plenty of breakthroughs in recent CO2RR studies have been recently achieved regarding hierarchical porous materials, indicating that a summary of hierarchical porous materials for carbon dioxide reduction reactions is highly desired and significant. In this paper, we summarize the recent breakthroughs of hierarchical porous materials in CO2RRs, including classical synthesis methods, advanced characterization technologies, and novel CO2RR strategies. Moreover, by highlighting several significant works, the advantages of hierarchical porous materials for CO2RRs are analyzed and revealed. Additionally, a perspective on hierarchical porous materials for CO2RRs (e.g., challenges, potential catalysts, promising strategies, etc.) for future study is also presented. It can be anticipated that this comprehensive review will provide valuable insights for further developing efficient alternative hierarchical porous catalysts for CO2 reduction reactions. [ABSTRACT FROM AUTHOR]

High-performance fibers have been widely used due to their special properties such as high strength, high modulus and high temperature resistance, and supercritical CO2 fluid technology provides new ideas and methods for ecological and low-carbon processing of high-performance fiber materials due to its low viscosity, high diffusivity, and significant plasticizing effect.This paper briefly describes the principles and advantages of supercritical CO2 fluid processing technology, reviews the research progress on the modification, dyeing, and functional finishing of high performance fibers such as aramid, ultra-high relative molecular mass polyethylene (UHMWPE), polyimide (PI), and polyphenylene sulfide (PPS) in supercritical CO2, and the challenges of supercritical CO2 fluid processing technology for high performance fibers were discussed. It is pointed out that the main trend of supercritical fluid processing technique for high-performance fiber is to explore novel principles and methods by multi-disciplinary cross-research, develop intelligent supercritical fluid processing equipment and supporting procedures, and design new types of dyeing and finishing agents and multi-functional technologies suitable for the supercritical CO2 fluid system. [ABSTRACT FROM AUTHOR]

CO2 dry fracturing technology, as a new waterless fracturing technique, has become an important research direction in tight oil and gas development in recent years. However, based on literature research, it is found that CO2 dry fracturing technology is not yet mature, mainly due to the low viscosity of liquid carbon dioxide or supercritical CO2, which leads to significant fluid loss and poor proppant carrying capacity. It requires thickening agents to significantly increase the viscosity of CO2. Considering the limitations of silicone-based thickeners that require a large amount of co-solvent and other thickeners with unsatisfactory thickening effects, as well as poor temperature and pressure adaptability, this paper provides an overview of the research progress on thickeners for CO2 fracturing fluids, focusing on branched silicone-based thickeners (with little or no co-solvent) and fluorinated thickeners from the perspectives of thickening mechanisms and thickening characteristics. In the thickening characteristics section, the structural and performance characteristics of these two types of thickeners are summarized. Additionally, the paper reviews the application of liquid CO2 and supercritical CO2 dry fracturing technology in China. Finally, the future research directions for CO2 thickeners and fracturing fluid systems in dry fracturing, including thickening mechanisms, thickening performance, and field applications, are discussed. [ABSTRACT FROM AUTHOR]

Nanotechnology plays a pivotal role in the biomedical field, especially in the synthesis and regulation of drug particle size. Reducing drug particles to the micron or nanometer scale can enhance bioavailability. Supercritical fluid technology, as a green drug development strategy, is expected to resolve the challenges of thermal degradation, uneven particle size, and organic solvent residue faced by traditional methods such as milling and crystallization. This paper provides an insight into the application of super-stable homogeneous intermix formulating technology (SHIFT) and super-table pure-nanomedicine formulation technology (SPFT) developed based on supercritical fluids for drug dispersion and micronization. These technologies significantly enhance the solubility and permeability of hydrophobic drugs by controlling the particle size and morphology, and the modified drugs show excellent therapeutic efficacy in the treatment of hepatocellular carcinoma, pathological scarring, and corneal neovascularization, and their performance and efficacy are highlighted when administered through multiple routes of administration. Overall, supercritical fluids have opened a green and efficient pathway for clinical drug development, which is expected to reduce side effects and enhance therapeutic efficacy. [ABSTRACT FROM AUTHOR]

Nanotechnology is an emerging field with diverse applications, wherein materials ranging in size from 1 to 100 nm, referred to as nanoparticles (NPs), are utilized. Traditional methods for producing metallic NPs primarily involve chemical processes, which can result in unintended outcomes. To overcome these challenges, a greener alternative, known as green synthesis, has been developed. Green synthesis of metallic nanoparticles has emerged as an innovative and environmentally friendly approach in nanotechnology. Utilizing plant extracts, microorganisms, and biopolymers as reducing and stabilizing agents, researchers have successfully prepared various metallic nanoparticles, such as silver, copper, gold, platinum, and palladium nanoparticles. These green methods offer advantages like cost-effectiveness, reduced environmental impact, and facile scalability. This method ensures eco-friendliness by implementing techniques such as the use of safe, nontoxic solvents (such as supercritical fluids and water) and additives like polysaccharides. Different reaction conditions and energy-saving growth methods are also employed to enhance sustainability. Nanoparticles synthesized through green methods exhibit unique properties, rendering them highly suitable for diverse applications, including catalysis, medicine, and energy technologies. This review paper explores recent advances in the biosynthesis of various metallic nanoparticles at the nanoscale and also highlights the different factors that affect their synthesis and possible applications of these nanoparticles. [ABSTRACT FROM AUTHOR]

Indapamide (Indp) and certain other diuretics have been abused in sports, therefore, having sensitive methods for its detection and assay in biological fluids (whole blood, plasma, serum, and urine) is of significant importance. The racemic mixture of Indp is being used as an active pharmaceutical ingredient among other commonly prescribed diuretics. The regulatory authorities and pharmaceutical industries demand analytical methods for successful enantioseparation of such molecules. The paper presents a critical overview of the scientific issues of the application of contemporary techniques involving various chromatographic approaches (with liquid or supercritical fluid as mobile phases) and capillary electrophoresis and method development, for drug screening, assay, bioequivalence studies and enantioseparation of indapamide with their results. It also covers the historical developments that led to significant breakthroughs in research and concise evaluations of research in the area. Different types of chromatographic methods (HPLC, CEC, SFC etc) discussed herein provide an insight and a choice to select a method to (i) screen Indp for drug abuse, (ii) separate, isolate and quantify the enantiomers of Indp and (iii) investigate their pharmacokinetics as markedly different species and not as a total drug. The article evaluates the field's status with a broad base and practical oriented approach so that the underlying principles are easily understood to help chemists and non-specialists gain useful insights into the field outside their specialization and provide experts with summaries of key developments. To the best of authors' knowledge there has been no attempt to review such methods for analysis of Indp and this is the first report of its kind. [ABSTRACT FROM AUTHOR]

Extralow-permeability reservoirs have emerged as a significant area of focus for CO2 geological sequestration due to their stable subterranean structure and expansive storage capacity, offering substantial potential in addressing global climate change. However, the full extent of CO2 geological sequestration potential within these extralow-permeability reservoirs remains largely unexplored. To address this gap, this paper utilizes the Shahejie Formation (Es1 member) of the Shuang 229 block in the Liaohe oilfield, Bohai Bay Basin, as a case study. This section is characterized by its abundant oil-gas reserves and serves as an exemplar for conducting experimental research on CO2 storage within extralow-permeability reservoirs. The results demonstrate that the reservoir lithology of the Es1 member is fine sandstone and siltstone, with high compositional and structural maturity. Moreover, the average porosity is 14.8%, the average permeability is 1.48 mD, and the coefficient of variation of the reservoir is approximately 0.5, which indicates a low- to extralow-permeability homogeneous reservoir. In addition, the overburden pressure is >2.0 MPa, the fault can withstand a maximum gas column height of >200 m, and the reservoir exhibits favorable overburden and fault sealing characteristics. Notably, stepwise increasing gas injection in the Shuang 229-36-62 well reveals that the injected liquid CO2 near the wellhead exhibits a relatively high density, close to 1.0 g/cm3, which gradually decreases to approximately 0.78 g/cm3 near a depth of 2000 m underground. The injected fluid changes into a supercritical state upon entering the formation, and the CO2 injection speed is optimal, at 0.08 HCPV/a. According to these findings, it is predicted that the highest burial CO2 volume via the injection of 1.5 HCPVs in the Wa 128 block area is 1.11 × 105 t/year, and the cumulative burial volume reaches approximately 2.16 × 106 t. This shows that the CO2 sequestration potential of extralow-permeability reservoirs is considerable, providing confidence for similar instances worldwide. [ABSTRACT FROM AUTHOR]

Supercritical drying is the only effective method for producing aerogels. Aerogels are innovative materials that found various applications in the range of industries. At the same time, supercritical drying is a technologically complex and expensive process, and an important goal is to optimize the production process to reduce costs and energy consumption. In this paper, the following aspects are considered: Investigation of the influence of parameters on the supercritical drying of silica aerogels on a laboratory scale; Modeling and simulation of the supercritical drying process; Developing a methodology for calculating the cost of manufacturing of silica aerogels; Creating a software module for calculating the cost of manufacturing of silica aerogels and performing techno-economic optimization of the supercritical drying process; Techno-economical optimization of the supercritical drying of silica aerogels on a pilot scale. With the aid of the developed software, techno-economic optimization of the pilot plant of silica aerogels was carried out. The developed mathematical model, optimization approach, and studies of the intensification of the supercritical drying process make it possible to reduce the cost of manufacturing in the existing production of aerogels by 26.4%. [ABSTRACT FROM AUTHOR]

Azo dyes are synthetic organic dyes used in the textile, leather, and paper industries. They pose environmental problems due to their toxic and persistent nature. The toxicity is due to the presence of azo groups in the dye molecule that can break down into aromatic amines, which are highly toxic to aquatic organisms and humans. Various treatment methods have been developed to remove azo dyes from wastewater. Conventional wastewater treatments have some drawbacks, such as high operating costs, long processing times, generation of sludge, and the formation of toxic by-products. For these reasons, a valid alternative is constituted by advanced oxidation processes. Good results have been obtained using heterogeneous photocatalysis and supercritical water oxidation. In the former method, a photocatalyst is in contact with wastewater, a suitable light activates the catalyst, and generated reactive oxygen species that react with pollutants through oxidative reactions to their complete mineralization; the latter involves pressurizing and heating wastewater to supercritical conditions in a reactor vessel, adding an oxidizing agent to the supercritical water, and allowing the mixture to react. In this review paper, works in the literature that deal with processing wastewater containing azo dyes through photocatalysts immobilized on macroscopic supports (structured photocatalysts) and the supercritical water oxidation technique have been critically analyzed. In particular, advancement in the formulation of structured photocatalysts for the degradation of azo dyes has been shown, underlying different important features, such as the type of support for the photoactive phase, reactor configuration, and photocatalytic efficiency in terms of dye degradation and photocatalyst stability. In the case of supercritical water oxidation, the main results regarding COD and TOC removal from wastewater containing azo dyes have been reported, taking into account the reactor type, operating pressure, and temperature, as well as the reaction time. [ABSTRACT FROM AUTHOR]

We propose in this paper a theoretical model for fluid state thermodynamics based on modeling the fluctuation distributions and, hence, the corresponding moment generating functions providing the free energy of the system. Using the relatively simple and physically coherent gamma model for the fluctuation distributions, we obtain a complete theoretical equation of state, also giving insight into the statistical/molecular organization and phase or pseudo-phase transitions occurring under the sub- and super-critical conditions, respectively. Application to sub- and super-critical fluid water and a comparison with the experimental data show that this model provides an accurate description of fluid water thermodynamics, except close to the critical point region where limited but significant deviations from the experimental data occur. We obtain quantitative evidence of the correspondence between the sub- and super-critical thermodynamic behaviors, with the super-critical water pseudo-liquid and pseudo-gas phases being the evolution of the sub-critical water liquid and gas phases, respectively. Remarkably, according to our model, we find that for fluid water the minimal subsystem corresponding to either the liquid-like or the gas-like condition includes an infinite number of molecules in the sub-critical regime (providing the expected singularities due to macroscopic phase transitions) but only five molecules in the super-critical regime (coinciding with the minimal possible hydrogen-bonding cluster), thus suggesting that the super-critical regime be characterized by the coexistence of nanoscopic subsystems in either the pseudo-liquid or the pseudo-gas phase with each subsystem fluctuating between forming and disrupting the minimal hydrogen-bonding network. [ABSTRACT FROM AUTHOR]

This perspective paper aims to spark a fundamental debate on the key laws that would combine the nano- to micro-scale flow dynamics of resident contaminants in soil systems under supercritical phase-assisted transportation. The rank of supercritical solvents (SCFs) for hazardous polycyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene, and xylenes is deeply discussed beside its confines to meet the current requests of in situ/ex situ fields. The scaling behaviors during soil–pollutants–SCFs interactions are highlighted to underline the hidden laws behind the basic transportation under flooding remediation. A new strategy based on artificial intelligence learning is emphasized with a demonstrative sample to predict the solubility behavior of this kind of contaminants during a spatiotemporal mechanism. This debate illustrates the conjugate experimental and numerical pathways to deal with the complex nano-remediation dynamics and sheds the light on the current trends and future outlook with techno-economic concerns to promote the faith of a clean and sustainable environment. [ABSTRACT FROM AUTHOR]

This paper presents an application of mean force kinetic theory (MFT) to the calculation of the self-diffusivity of CO2 in the supercritical fluid regime. Two modifications to the typical application of MFT are employed to allow its application to a system of molecular species. The first is the assumption that the inter-particle potential of mean force can be obtained from the molecule center-of-mass pair correlation function, which in the case of CO2 is the C–C pair correlation function. The second is a new definition of the Enskog factor that describes the effect of correlations at the surface of the collision volume. The new definition retains the physical picture that this quantity represents a local density increase, resulting from particle correlations, relative to that in the zero density homogeneous fluid limit. These calculations are facilitated by the calculation of pair correlation functions from molecular dynamics (MD) simulations using the FEPM2 molecular CO2 model. The self-diffusivity calculated from theory is in good agreement with that from MD simulations up to and slightly beyond the density at the location of the Frenkel line. The calculation is compared with and is found to perform similarly well to other commonly used models but has a greater potential for application to systems of mixed species and to systems of particles with long range interatomic potentials due to electrostatic interactions. [ABSTRACT FROM AUTHOR]

The editorial in the journal "Pharmaceutics" discusses the use of supercritical fluid technology in pharmaceutical applications. The technology offers a way to reduce the use of harmful chemicals in drug formulations, with supercritical carbon dioxide being the most commonly used solvent due to its economic and non-toxic properties. Various techniques, such as aerogels and drug micronization, are explored in the pharmaceutical sector to enhance drug stability, dissolution rates, and bioavailability. The research presented in the editorial highlights the potential of supercritical techniques in pharmaceutical manufacturing, focusing on areas like colonic delivery, tissue engineering, anticancer therapies, and pulmonary treatments. [Extracted from the article]

With the proposal of replacing toxic solvents with non-toxic solvents in the concept of green chemistry, the development and utilization of new green extraction techniques have become a research hotspot. Phenolic compounds in edible oils have good antioxidant activity, but due to their low content and complex matrix, it is difficult to achieve a high extraction rate in a green and efficient way. This paper reviews the current research status of novel extraction materials in solid-phase extraction, including carbon nanotubes, graphene and metal–organic frameworks, as well as the application of green chemical materials in liquid-phase extraction, including deep eutectic solvents, ionic liquids, supercritical fluids and supramolecular solvents. The aim is to provide a more specific reference for realizing the green and efficient extraction of polyphenolic compounds from edible oils, as well as another possibility for the future research trend of green extraction technology. [ABSTRACT FROM AUTHOR]

Supercritical fluids have been widely used in a variety of applications, in which heat transfer under supercritical pressure is of great importance. This paper presents a critical review on supercritical heat transfer, including a summary on the past work focusing on in-tube heat transfer and the pseudo-boiling concept, the understanding of the mechanisms of supercritical heat transfer, and suggestions for future work. For supercritical fluids heated in tubes, the typical characteristics, the effects of various parameters, the buoyancy and flow acceleration effects, and the heat transfer deterioration phenomenon are all discussed, and the heat transfer correlations and numerical methodologies are summarized. For supercritical fluids cooled in tubes, the experimental observations and explanations, the proposed heat transfer correlations, and the numerical results are summarized and discussed. More importantly, this review provides a comprehensive review of the supercritical pseudo-boiling concept, including the experimentally observed pseudo-boiling phenomenon, the theoretical studies for supercritical fluids to reveal their heterogenous two-phase features, and the progress in the application of the pseudo-boiling concept on supercritical heat transfer. Finally, suggestions for future research are provided to further advance the understanding and enable accurate prediction of supercritical heat transfer. [ABSTRACT FROM AUTHOR]

Nanocomposites based on ferromagnetic nickel nanoparticles and graphene-related materials are actively used in various practical applications such as catalysis, sensors, sorption, etc. Therefore, maintaining their dispersity and homogeneity during deposition onto the reduced graphene oxide substrate surface is of crucial importance to provide the required product characteristics. This paper demonstrates a new, reproducible method for preparing a tailored composite based on nickel nanoparticles on the reduced graphene oxide surface using supercritical isopropanol treatment. It has been shown that when a graphene oxide film with previously incorporated Ni2+ salt is treated with isopropanol at supercritical conditions, nickel (2+) is reduced to Ni (0), with simultaneous deoxygenation of the graphene oxide substrate. The resulting composite is a solid film exhibiting magnetic properties. XRD, FTIR, Raman, TEM, and HRTEM methods were used to study all the obtained materials. It was shown that nickel nanoparticles on the surface of the reduced graphene oxide had an average diameter of 27 nm and were gradually distributed on the surface of reduced graphene oxide sheets. The data obtained allowed us to conduct a reconnaissance discussion of the mechanism of composite fabrication in supercritical isopropanol. [ABSTRACT FROM AUTHOR]

The spacer represents an essential part in the nuclear fuel rod. Spacer grid with mixing vanes in fuel rod bundle of nuclear reactor core has a significant impact on heat transfer performance in downstream to grid spacer. Grid Spacers are located on the nuclear fuel rod assembly to hold suitable clearance among the rods in a bundle. The objective of this paper is to study the enhanced heat transfer performance of R134a at supercritical pressure 4.5 MPa near downstream to mixing vane spacer in a vertical channel of annular flow. A spacer of 0.38 blockage ratio with mixing vanes, situated at mid-span of an annular channel is used in the present work. Numerical simulations have been accomplished for spacer with mixing vane and spacer without mixing vane in an annular channel by using commercial CFD (Computational fluid dynamics) code ANSYS Fluent. The present investigation represents the comparative study for spacer with mixing vane and spacer without mixing vane effects on heat transfer and flow field characteristics in a downstream direction for mass flow-rate 0.41469 kg/s and heat flux 160 kW/m². The results indicate that spacer with mixing vane has notable influence on heat transfer performance and flow field characteristics downstream of mixing vane spacer as compared to spacer without mixing vane. Wall temperature fall and increase of coefficient of heat transfer are significantly greater adjacent to spacer downstream. Spacer influence in the improvement of the heat transfer is noted up to distance X/D = 40 downstream and then flow is found as fully developed. [ABSTRACT FROM AUTHOR]

This paper reports the results of high-pressure high-temperature (HPHT) diamonds growing in an Fe–C melt with introduction of 1 wt% sulfur. Experiments were carried out at a pressure of 6.0 GPa and a temperature of 1450 °C. It was found that adding 1 wt% sulfur leads to a significant decrease in the concentration of nitrogen defects in diamonds. As a result, the grown diamonds are near-colorless containing nitrogen in the range of 20–40 ppm. The dominant state of nitrogen impurities in the form of single substitutional atoms was confirmed by intense photoluminescence arising from the nitrogen-vacancy complexes in different charge states (NV0 and NV−). Only a very small number of nitrogen atoms are present as pairs (A and H3 centers). It is suggested that the pronounced effect of sulfur is attributed to the role of supercritical fluid in crystallization medium. Interaction between components of the H–O–C–S–N fluid leads to an increase in the proportion of complex hydrocarbons, including N-containing hydrocarbons. As a result, nitrogen atoms, which are present in the metal melt, are bound within the supercritical fluid. This nitrogen binding keeps dissociated nitrogen from entering the diamond structure. [ABSTRACT FROM AUTHOR]

The injection of cryogenic fluids into environments where the prevailing conditions are supercritical in comparison to the critical point of the injected cryogenic fluid is encountered in cryogenic rocket engines, and novel engine architectures such as the recuperated split cycle engine. The physical characteristics of cryogens injected into supercritical environment are rather unclear. While surface tension is usually assumed to be absent/negligible for supercritical fluids, recent experimental research has identified the existence of surface tension and its effects on liquid hydrocarbons in supercritical environment. This research work proposes an alternative computationally simple adaptive surface tension algorithm for the simulation of a liquid injected into supercritical environment. The numerical simulations presented here correspond to single- and binary-specie cases of iquid nitrogen and liquid methane respectively, undergoing phase transition post their injection into supercritical conditions. Following a critical review of related numerical works, this paper begins with a brief explanation of the physics behind the surface tension effect in a binary-fluid interface in which a supercritical fluid is involved and we present why this effect is of relevance to supercritical cryogenic jets? Then, the rationale and specifics of the the new modelling framework based on adaptive surface tension is discussed along with its implications. The results of the numerical simulations of low-temperature vs near-critical temperature iquid nitrogen and liquid methane injection dynamics revealed the drastically different fluid- and thermo-dynamics at play in these two cases. The role of surface tension at these conditions is also explored. [ABSTRACT FROM AUTHOR]

The quest for sustainable and environmentally friendly fuel feedstocks has led to the exploration of green solvents for the extraction of bio-oil from various biomass sources. This review paper provides a comprehensive analysis of the challenges and future research outlooks for different categories of green extraction solvents, including bio-based solvents, water-based solvents, supercritical fluids, and deep eutectic solvents (DES). The background of each solvent category is discussed, highlighting their potential advantages and limitations. Challenges such as biomass feedstock sourcing, cost fluctuations, solvent properties variability, limited compatibility, solute solubility, high costs, and potential toxicity are identified and examined in detail. To overcome these challenges, future research should focus on alternative and abundant feedstock sources, the development of improved solubility and separation techniques, optimization of process parameters, cost-effective equipment design, standardization of DES compositions, and comprehensive toxicological studies. By addressing these challenges and advancing research in these areas, the potential of green extraction solvents can be further enhanced, promoting their widespread adoption and contributing to more sustainable and environmentally friendly industrial processes. [ABSTRACT FROM AUTHOR]

The paper deals with the methods of modification of polymer composite materials in supercritical fluid medium in order to improve their characteristics. The main advantages and disadvantages of the presented methods are revealed, especially energy efficiency and environmental friendliness of using the supercritical fluids. [ABSTRACT FROM AUTHOR]

Studies on the recovery of trivalent metal ions such as Nd3+Eu3+(taken as homologs of Am(III)) from solid oxide (Nd2O3), Thorium concentrate (obtained from Monazite ore processing), tissue paper/surgical gloves (rubber), and plant samples have been carried out by supercritical fluid extraction (SFE) using supercritical CO2and ethanol/nitric acid.N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was used as the extractant in these studies. The results showed that the recovery of Nd increased with TODGA concentration from 50% (no TODGA) to 70% (10% TODGA) at 3 M HNO3in ethanol. However, the extraction of Nd at 1 M HNO3was invariant with 1-3% (v/v) TODGA concentration (73 ± 4%). Interestingly, REEs recovery from Th concentrate was ˜ 60% even without TODGA using ethanol/3 M HNO3mixture. On the other hand, quantitative recovery of152,154Eu from tissue paper and surgical gloves sample could be achieved using 3 M HNO3/ethanol mixture. This suggested that it would be possible to decontaminate the contaminated laboratory waste papers using SFE technique. [ABSTRACT FROM PUBLISHER]

Modal and non-modal stability analyses are applied to Hagen–Poiseuille flow with a non-ideal fluid. The non-ideal fluid is defined as a fluid close to its vapor–liquid critical point. In this region, properties of the fluid deviate significantly from the assumptions of the ideal gas model. In this paper, the specific example of CO2 near the critical point is taken as a non-ideal fluid. We studied fluids at supercritical pressure and different wall temperatures so that the centerline temperatures can be lower, equal, and higher than the pseudo-critical temperature. Flow instability is characterized by the Reynolds number, and the product of the Prandtl and Eckert numbers. In modal stability analysis, we observe that there is no unstable mode in Hagen–Poiseuille flow with a non-ideal fluid. Regarding the growth rate, as the axial wavenumber increases, another mode becomes the least stable. The non-modal theory is employed to investigate the optimal response to harmonic external force and transient energy growth. The influence of axial and azimuthal wave numbers, Prandtl and Eckert numbers, and thermodynamic states are also taken into account. In this study, we identify an generalized inflection point in the transcritical base profile, causing the transcritical state to be the most unstable. In non-modal instability, we observe that the optimal response mainly occurs at time invariant axisymmetric disturbance. This suggests that the axisymmetric disturbance could potentially initiate the transition to turbulence. [ABSTRACT FROM AUTHOR]