Supercritical Phase Research Articles

Gradient Bounds for Almost Complex Special Lagrangian Equation with Supercritical Phase

Gradient Bounds for Almost Complex Special Lagrangian Equation with Supercritical Phase

Viscosity measurements of CO2-rich; CO2 + N2 and CO2 + H2 mixtures in gas or supercritical phase at temperatures between 273 and 473 K and pressures up to 8.7 MPa

New experimental viscosity data of three binary CO2-rich mixtures with approximate mole fractions of 0.93 CO2 + 0.07 H2, 0.80 CO2 + 0.20 H2, and 0.90 CO2 + 0.10 N2 are reported. The measurements were performed at four different isotherms between 273 K and 473 K. Two independent rotating body viscometers with different pressure range were utilized, suitable for measurement of pressures up to 2 MPa and 20 MPa, respectively. The maximum expanded combined relative uncertainty (k = 2) in viscosity was 0.25% for the data obtained from the low-pressure viscometer and 0.6% for the data measured by the high-pressure viscometer. The experimental data were compared to the data estimated by the extended corresponding states (ECS) model implemented in the NIST REFPROP 10.0 database. The maximum deviation between the model and the new data is 1.86%. The data measured with the two apparatuses agree within the estimated uncertainty.

Performance Improvement for Ge FinFET CMOS Inverter With Supercritical Fluid Treatment

Performance improvement on Ge nFinFET, pFinFET and CMOS inverter can be achieved by using a novel low temperature damage-free supercritical phase fluid (SCF) treatment. Thanks to effective reduction of unstable oxidation states, oxygen vacancies and interface traps, higher on-off current ratios (8×105 for pFinFET and 3.3×105 for nFinFET), lower S.S. (72 mV/dec), higher on current (>45% improvement) and better reliability in Ge FinFETs are achieved with a SCF treatment as compared with a remote plasma post-oxidation (PPO) one. Besides, a higher voltage gain (88 V/V) of Ge FinFET CMOS inverter is obtained with a SCF treatment in comparison with a remote PPO one.

Number of paths in oriented percolation as zero temperature limit of directed polymer

We prove that the free energy of directed polymer in Bernoulli environment converges to the growth rate for the number of open paths in super-critical oriented percolation as the temperature tends to zero. Our proof is based on rate of convergence results which hold uniformly in the temperature. We also prove that the convergence rate is locally uniform in the percolation parameter inside the super-critical phase, which implies that the growth rate depends continuously on the percolation parameter.

Analysis and Development of a Small-Scale Supercritical Carbon Dioxide (sCO2) Brayton Cycle

Carbon dioxide’s (CO2) ability to reach the supercritical phase (7.39 MPa and 304.15 K) with low thermal energy input is an advantageous feature in power generation design, allowing for the use of various heat sources in the cycle. A small-scale supercritical carbon dioxide (sCO2) power cycle operating on the principle of a closed-loop Brayton cycle is currently under construction at The University of Texas at San Antonio, to design and develop a small-scale indirect-fired sCO2 Brayton cycle, acquire validation data of the cycle’s performance, and compare the cycle’s performance to other cycles operating in similar conditions. The power cycle consists of four principal components: A reciprocating piston compressor, a heating source, a reciprocating piston expander to produce power, and a heat exchanger to dissipate excess heat. The work explained in the present manuscript describes the theory and analysis conducted to design the piston expander, heating source, and heat exchanger in the cycle. Theoretical calculations indicate that using sCO2 for the Brayton cycle generates 4.5 kW of power with the inlet pressure and temperature of 17.23 MPa and 358.15 K to the piston expander. Based on the fully isentropic conditions, the thermal efficiency of the system is estimated to be 12.75%.

Evaluation of CO2 Transport Design Via Pipeline in the CCS System with Various Distance Combinations

Carbon dioxide transportation plays an important role in the CCS system. The pipeline is the most economically viable for CO2 transport medium. In this paper, the design of the CO2 pipeline is systematically evaluated from a technical and economic aspect. Four transport process conditions include gaseous transport, liquid transport, dense phase transport, and supercritical transport will be assessed to obtain the most feasible transport design. A supercritical phase has an advantage when to be applied for long-distance and large-scale CO2 transportation. In the CCS network, the distance between source and sink points may vary. The variation in the distance and transport capacity make a supercritical phase not an effective pipeline transport condition. The proposed methods to determine the optimal design of onshore pipelines with a projected CO2 flow rate are presented in this paper. The methods are based on the simple correlations developed from a wide range of generic cases of CO2 transport. The optimum design is identified from the minimum total annual cost. The result shows that the pipeline design in the CCS network can be performed in the liquid phase when the distance is lower than 100 km.

Speed of sound data and acoustic virial coefficients of two binary (N2 + H2) mixtures at temperatures between (260 and 350) K and at pressures between (0.5 and 20) MPa

This work aims to address the technical concerns related to the thermodynamic characterization of gas mixtures blended with hydrogen for the implementation of hydrogen as a new energy vector. For this purpose, new experimental speed of sound measurements have been done in gaseous and supercritical phases of two binary mixtures of nitrogen and hydrogen using the most accurate technique available, i.e., the spherical acoustic resonator, yielding an experimental expanded (k = 2) uncertainty of only 220 parts in 106 (0.022%). The measurements cover the pressure range between (0.5 and 20) MPa, the temperature range between (260 and 350) K, and the composition range with a nominal mole percentage of hydrogen of (5 and 10) mol%, respectively. From the speed of sound data sets, thermophysical properties that are relevant for the characterization of the mixture, namely the second βa and third γa acoustic virial coefficients, are derived. These results are thoroughly compared and discussed with the established reference mixture models valid for mixtures of nitrogen and hydrogen, such as the AGA8-DC92 EoS, the GERG-2008 EoS, and the recently developed adaptation of the GERG-2008 EoS, here denoted GERG-H2_improved EoS. Special attention has been given to the effect of hydrogen concentration on those properties, showing that only the GERG-H2_improved EoS is consistent with the data sets within the experimental uncertainty in most measuring conditions.

Water content trends in K2-138 and other low-mass multi-planetary systems

Context. Both rocky super-Earths and volatile-rich sub-Neptunes have been found simultaneously in multi-planetary systems, suggesting that these systems are appropriate to study different composition and formation pathways within the same environment. Aims. We perform a homogeneous interior structure analysis of five multi-planetary systems to explore compositional trends and their relation with planet formation. For one of these systems, K2-138, we present revised masses and stellar host chemical abundances to improve the constraints on the interior composition of its planets. Methods. We conducted a line-by-line differential spectroscopic analysis on the stellar spectra of K2-138 to obtain its chemical abundances and the planetary parameters. We selected multi-planetary systems with five or more low-mass planets (M < 20 M⊕) that have both mass and radius data available. We carried out a homogeneous interior structure analysis on the planetary systems K2-138, TOI-178, Kepler-11, Kepler-102, and Kepler-80. We estimated the volatile mass fraction of the planets in these systems assuming a volatile layer constituted of water in steam and supercritical phases. Our interior-atmosphere model took the effects of irradiation on the surface conditions into account. Results. K2-138 inner planets present an increasing volatile mass fraction with distance from their host star, while the outer planets present an approximately constant water content. This is similar to the trend observed in TRAPPIST-1 in a previous analysis with the same interior-atmosphere model. The Kepler-102 system could potentially present this trend. In all multi-planetary systems, the low volatile mass fraction of the inner planets could be due to atmospheric escape, while the higher volatile mass fraction of the outer planets can be the result of accretion of ice-rich material in the vicinity of the ice line with later inward migration. Kepler-102 and Kepler-80 present inner planets with high core mass fractions which could be due to mantle evaporation, impacts, or formation in the vicinity of rocklines.

Studies toward the Use of Ionic Liquids and Supercritical CO2 for the Recovery and Separation of Praseodymium from Waste Streams

Waste streams from the incineration of metal-containing materials like such as computer processor boards and batteries may contain critical rare earth elements like praseodymium. Data on the solubility of Pr compounds and on their distribution coefficients in supercritical CO2/ionic liquid two-phase systems are important to determine if an ionic liquid/supercritical CO2 two-phase approach is feasible toward the recovery of a particular metal. This work provides data on the solubility of various praseodymium compounds in butyl-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyTf2N) ionic liquid and on the distribution coefficients of these praseodymium compounds in the supercritical CO2 phase of the two-phase BMPyTf2N ionic liquid/supercritical CO2 system, with and without a tributyl phosphate additive.

Strict inequality for bond percolation on a dilute lattice with columnar disorder

We consider a dilute lattice obtained from the usual Z3 lattice by removing independently each of its columns with probability 1−ρ. In the remaining dilute lattice independent Bernoulli bond percolation with parameter p is performed. Let ρ↦pc(ρ) be the critical curve which divides the subcritical and supercritical phases. We study the behavior of this curve near the disconnection threshold ρc=pcsite(Z2) and prove that, uniformly over ρ it remains strictly below 1/2 (the critical point for bond percolation on the square lattice Z2).

Effects of flow velocity on the corrosion behaviour of super 13Cr stainless steel in ultra-HTHP CO2–H2S coexistence environment

The corrosion behavior of super 13Cr SS under the effect of flow velocity in the ultra-HTHP supercritical CO2–H2S–Cl- environment was investigated. The results show the morphology and composition of the corrosion products of super 13Cr SS samples change with varying flow state. In the static condition, the layer consists of an inner layer of Cr(OH)3, a middle layer of Fe1−xS, and an outer crystalline FeCO3 layer. However, in the dynamic supercritical CO2 phase, a galvanic couple effect exists between the pyrrhotite and uncovered steel. Meanwhile, the velocity delays the deposition of FeCO3 and promotes the development of pitting.

Thermodynamic Properties of Fluids from Speed of Sound: Integration Along Isentropes

The equations connecting speed of sound with other thermodynamic properties of gases and liquids, suitable for numerical integration with respect to temperature, density, and pressure, along isentropes, are derived. Algorithms of their solution are given too. They are tested with several substances (e.g., Ar, N2, O2, CH4, CO2, and H2O) in wide ranges of pressure and temperature. Average absolute deviation of thermal properties is 0.0129% in supercritical gaseous phase, 0.0308% in transcritical gaseous phase, and 0.0009% in liquid phase. Corresponding deviations of caloric properties are 0.1706%, 0.1863%, and 0.0702%, respectively.

An Experimental Study of Chlorite Stability in Varied Subduction Zone Lithologies with Implications for Fluid Production, Melting, and Diapirism in Chlorite-Rich Mélange Rocks

AbstractFour ultramafic bulk compositions comprising only natural minerals were used to constrain the stability field of chlorite in a variety of subducted, chlorite-rich rocks through an examination of key chlorite dehydration reactions relevant to the sub-arc. Seventy-four piston cylinder experiments were conducted at a range of pressures (1.0–5.0 GPa) and temperatures (500°C–1150°C).Bulk 1 represents a chlorite mélange (Mg# = 0.94) typically formed in the subduction channel. This composition was used to examine the terminal chlorite reactions to olivine, orthopyroxene, and spinel at low pressure and to olivine, garnet, and spinel at high pressure. Chlorite achieves a thermal maximum stability at 2.0 GPa, 850°C; at 3.0 GPa, 850°C; and at 5.0 GPa, 760°C. The terminal chlorite breakdown reaction rises at a much steeper Clapeyron slope than shown in previous studies. Bulk 2 contains additionally antigorite and tremolite, to constrain phase relations in more fertile compositions. Chlorite reacts with clinopyroxene at ~100°C lower temperatures and with orthopyroxene at ~20°C–60°C lower temperatures than the terminal chlorite breakdown. The reactions have a subparallel Clapeyron slope and none of the three chlorite dehydration reactions crosses the antigorite breakdown reaction up to 5 GPa. This demonstrates that chlorite is the most stable carrier of H2O to high temperatures in subducted ultramafic rocks. Chlorite mélanges that form at the subduction plate interface will dehydrate at 850°C–800°C, 80–120 km depth for intermediate to hot subduction geotherms and liberate 10–12 wt.% of H2O, triggering wet melting in associated sediments. For cold subduction geotherms, chlorite dehydration occurs at 780°C–740°C, 120–170 km depth. Interaction of such fluids with sediments will likely produce a supercritical fluid phase. No melting in the ultramafic rocks has been observed at the chlorite breakdown reactions. Wet melting of the chlorite mélange at 3 GPa occurred between 1100°C and 1150°C.The stability of chlorite in more Fe-rich mélanges (bulk Mg# = 0.50 and 0.68, respectively) were conducted at 3.0 GPa and revealed thermal maxima at 650°C and 765°C, respectively. Collectively, the thermal stability of chlorite is dependent upon the Mg# of the bulk composition and spans over 200°C at sub-arc depths. The density of run products was calculated to test the validity of the chlorite mélange diapir model. With the progressive breakdown of chlorite, ultramafic chlorite mélanges transform into garnet peridotite, thereby losing any buoyancy they initially possessed. This makes the likelihood of mélange diapirs as a major transport mechanism through the sub-arc unfeasible.

Direct synthesis of dimethyl carbonate from CO2 and methanol in dual supercritical phases over YxFe1−xOδ catalysts

In this study, the dual supercritical phases were proposed and employed to facilitate the synthesis of dimethyl carbonate (DMC) from CO2 and methanol, which may improve the diffusion rate and contact opportunities of reactant molecules. Under the novel reaction conditions, the synthesis temperature was higher than the supercritical temperatures of each reactant (>239 °C), and the partial pressure for each reactant constituent was larger than its partial supercritical pressure (pCO2 > 7.4 MPa & pmethanol > 8.1 MPa), respectively. A series of YxFe1−xOδ-T catalysts with perovskite-structure were applied in the dual supercritical phases, whose surface properties, crystal phase, microstructure, acidic−basic amounts, and the concentration of oxygen vacancies were detected by BET, XRD, SEM, NH3/CO2-TPD, XPS and EPR, respectively. It was evident from the characterization results that the Y0.5Fe0.5Oδ-850 catalyst possessed the largest acidic−basic amounts, which enabled its highest catalytic activity. The experimental results revealed that higher DMC yield could be achieved under the novel dual supercritical phases (240 °C, 16 MPa), and the increased DMC yield without stirring in the autoclave can be obtained in an impressive shorter reaction time of 3 h, surpassing it acquired at the regular synthesis time of 9 h with stirring during the reaction.

Thermodynamics of Kerr-AdS black holes in the restricted phase space

The thermodynamics for Kerr-AdS black hole in four dimensions is revisited using the recently proposed restricted phase space formalism, which includes the central charge C of the dual CFT and the chemical potential mu , but excludes the pressure and the conjugate volume, as thermodynamic variables. The Euler relation holds automatically, and the first order homogeneity of the mass and the zeroth order homogeneity of the intensive variables are made explicit. Thermodynamic processes involving each pair of conjugate variables are studied in some detail, with emphasis on the scaling properties of the equations of states. It turns out that the thermodynamic behavior of the Kerr-AdS black hole is very similar to that of the RN-AdS black hole studied earlier. In particular, it is found that, there is a first order supercritical phase equilibrium in the T-S processes at fixed nonvanishing angular momentum, while at vanishing angular momentum or at fixed angular velocities, there is always a non-equilibrium transition from a small unstable black hole state to a large stable black hole state. Moreover, there is a Hawking–Page phase transition in the mu -C processes. Due to the complicatedness of the Kerr metric, the exact critical point and the Hawking–Page temperature are worked out explicitly only in the slow rotating limit, however the characteristic thermodynamic properties do not rely on the slow rotating approximation.

Interfacial tension of ethanol, water, and their mixtures in high pressure carbon dioxide: Measurements and modeling

Hypothesis.It is particularly noteworthy to study interfacial tension behavior under pressurized carbon dioxide for supercritical processes such as crystallization or fractionation. For the latter, a liquid phase and a supercritical phase are in contact, and interfacial properties influence mass transfer phenomena and hydrodynamics. Ethanol-water mixture is a good theoretical study case also involved in a wide range of applications. ExperimentalInterfacial tensions of ethanol, water and three mixtures, with an ethanol mass fraction from 0.25 to 0.75, under pressurized CO2 were measured for pressures ranging from 0.1 MPa to 15.1 MPa at 313.15 K and 333.15 K. A specific experimental set-up was used for CO2 phase saturation. FindingsThis work brings interfacial tension data of five different solutions including water and ethanol in contact with CO2. Effects of pressure, temperature, carbon dioxide density and ethanol mass fraction are discussed regarding the literature. Significant discrepancies are found with previous literature data for ethanol–water mixtures. The “two-step” decrease observed when pressure or density increase is also discussed regarding both the concept of Widom line, and the polar and dispersive contributions of the surface tension of a component. For the first time, fair accurate interfacial tension modeling involving these contributions is addressed.

Classification Method and Application of Rock Fracture Ability by Supercritical CO2 Blasting

In order to study the fracture ability classification of rock mass under the cracking action of supercritical CO2 phase transition, based on the classification theory of rock mass in blasting engineering, an analytic hierarchy process (AHP)-entropy weight method (EWM) and the cloud model classification method for rock mass cracking under CO2 phase transformation are proposed. In this method, rock density, rock tensile strength, rock wave impedance, and rock mass integrity coefficient are used as the factors to determine the level of rock mass fracturing, and the evaluation index system of rock mass fracturing is established. Through this evaluation method, the rock mass in a reconstruction project section of Nyingchi, Tibet, is classified and evaluated. The results present that this new classification method of rock mass fracture ability uses AHP–EWM to carry out the weight distribution of the classification index. In addition, it is combined with the cloud model for the classification division, overcoming the traditional classification method fixed with appraisal pattern flaw. Therefore, it has validity and feasibility. According to the characteristics of fracture ability, the rock masses in the area to be rebuilt on the Tibet Highway are divided into grade II, grade III, and grade IV, which provides scientific guidance for the construction of the project.

The wired arboreal gas on regular trees

We study the weak limit of the arboreal gas along any exhaustion of a regular tree with wired boundary conditions. We prove that this limit exists, does not depend on the choice of exhaustion, and undergoes a phase transition. Below and at criticality, we prove the model is equivalent to bond percolation. Above criticality, we characterise the model as the superposition of critical bond percolation and a random collection of infinite one-ended paths. This provides a simple example of an arboreal gas model that continues to exhibit critical-like behaviour throughout its supercritical phase.

Recurrence versus transience for weight-dependent random connection models

We investigate random graphs on the points of a Poisson process in d-dimensional space, which combine scale-free degree distributions and long-range effects. Every Poisson point carries an independent random mark and given marks and positions of the points we form an edge between two points independently with a probability depending via a kernel on the two marks and the distance of the points. Different kernels allow the mark to play different roles, like weight, radius or birth time of a vertex. The kernels depend on a parameter γ, which determines the power-law exponent of the degree distributions. A further independent parameter δ characterises the decay of the connection probabilities of vertices as their distance increases. We prove transience of the infinite cluster in the entire supercritical phase in regimes given by the parameters γ and δ, and complement these results by recurrence results if d=2. Our results are particularly interesting for the soft Boolean graph model discussed in the preprint [arXiv:2108:11252] and the age-dependent random connection model recently introduced by Gracar et al. [Queueing Syst. 93.3-4 (2019)]

Development of a novel theory of pressure-induced nucleation in supercritical carbon dioxide

The theory of pressure-induced supercritical phase nucleation for a binary system with a nonvolatile solute and scCO2 is proposed.