Single-phase State Research Articles

In-situ growth of high room temperature thermoelectric performance Ag2Se thin films

In this work, well-crystalline Ag2Se thermoelectric thin film with high power factor at room temperature was successfully fabricated at solid substrate by a facile in-situ growth method via co-evaporation deposition. Micro-structure characterizations show that the thin films prepared under proper growth temperature have single α-Ag2Se phase and stable chemical valence states, leading to a high electrical conductivity. Additionally, the carrier concentration is optimized after adjusting growth temperature and further contributes to a high Seebeck coefficient. As a result, a maximum power factor of 15.34 μWcm-1K−2 is achieved, demonstrating that our in-situ growth method is an effective way to fabricate high performance Ag2Se thermoelectric thin films.

ОПТИМИЗАЦИЯ ХИМИЧЕСКОГО СОСТАВА СУПЕРМАРТЕНСИТНОЙ НЕРЖАВЕЮЩЕЙ СТАЛИ С ИСПОЛЬЗОВАНИЕМ ТЕРМОДИНАМИЧЕСКИХ РАСЧЕТОВ

Supermartensitic steels have a unique complex of chemical and mechanical properties, so pipes made of these steels have found their application in the oil and gas industry. However, these steels tend to form a banding structure. The banding structure is the cause of the products properties anisotropy and in addition can lead to the semi-finished products destruction at the production stage. In this work, the steel of the supermartensitic class 10Kh13N3MFB was investigated for its tendency to form a defect “banding” in the structure. For this, thermodynamic calculations and mathematical modeling were carried out using the Thermo-Calc-3.01 software. The following program functions were used: calculation of phase equilibria for the average chemical composition, as well as for compositions with a maximum of austeniteforming elements with a minimum of ferrite-forming elements and with a maximum of ferrite-forming ones with a minimum of austenite-forming elements. An constructed thermodynamic equilibria analysis showed that steel 10Kh13N3MFB tends to form a banded structure. To reduce the likelihood of banding, it is necessary to carry out crystallization and hot rolling of steel only in single-phase states (δ-ferrite and austenite, respectively). Therefore, further calculations in Thermo-Calc were aimed at determining the steel chemical composition, at which the alloy crystallizes in the single-phase δ-region, excluding the appearance of phase segregation, and establishing the temperature range of hot deformation. After analyzing the data obtained, the optimal chemical composition of the steel melting was proposed and the temperature ranges of hot rolling were determined for the average chemical composition with different contents of Ni – 2, 3, 4 wt. %.

Melting and Re-Freezing Leads to Irreversible Changes in the Morphology and Molecular-Level Dynamics of Pfizer-BioNTech COVID-19 Vaccine.

Background and Objectives: As an mRNA-based vaccine, the Pfizer-BioNTech COVID-19 vaccine has stringent cold storage requirements to preserve functionality of the mRNA active ingredient. To this end, lipid components of the vaccine formulation play an important role in stabilizing and protecting the mRNA molecule for long-term storage. The purpose of the current study was to measure molecular-level dynamics as a function of temperature in the Pfizer-BioNTech COVID-19 vaccine to gain microscopic insight into its thermal stability. Materials and Methods: We used quasielastic and inelastic neutron scattering to probe (1) the vaccine extracted from the manufacturer-supplied vials and (2) unperturbed vaccine in the original manufacturer-supplied vials. The latter measurement was possible due to the high penetrative power of neutrons. Results: Upon warming from the low-temperature frozen state, the vaccine in its original form exhibits two-step melting, indicative of a two-phase morphology. Once the melting is completed (above 0 °C), vaccine re-freezing cannot restore its original two-phase state. This observation is corroborated by the changes in the molecular vibrational spectra. The molecular-level mobility measured in the resulting single-phase state of the re-frozen vaccine greatly exceeds the mobility measured in the original vaccine. Conclusions: Even a brief melting (above 0 °C) leads to an irreversible alteration of the two-phase morphology of the original vaccine formulation. Re-freezing of the vaccine results in a one-phase morphology with much increased molecular-level mobility compared to that in the original vaccine, suggesting irreversible deterioration of the vaccine’s in-storage stability. Neutron scattering can be used to distinguish between the vibrational spectra characteristic of the original and deteriorated vaccines contained in the unperturbed original manufacturer-supplied vials.

Experimental and computational study of a low-pressure natural circulation loop

The experimental and analytical study of single-phase flow and heat transfer in natural circulation loop has been carried out. Experiments were performed on water and ethanol that are the liquids with significantly different thermophysical properties. Experimental apparatus was a rectangular shaped loop with vertical flow up leg. The flow up and flow down legs of the loop are joined to the separator-condenser at the top of the loop. The upper limit of heat flux densities in the experiments was set with the consideration for flow regime to remain in single phase state along the whole heated length. Wall temperature time records being registered at different distances from the inlet to the heated zone indicate the occurrence of temperature fluctuations near the exit from heated zone even at relatively low heat flux densities. This fact displaces a complex changing of velocity profiles along the tube with vortex formation and occurrence of flow instability. Experimental data on longitudinal wall temperature distributions of heated section have been used to test a modified method of hydraulic calculation of the loop. It was pointed out that in spite of long year (since early 1950s) experimental, analytical and numerical investigations of natural circulation loops no suitable predicting recommendations for heat transfer and friction have been proposed till today for engineering hydraulic calculations of single-phase natural circulation loops.

Electronic irradiation of TlInSxSe2−x (x = 1): Morphology, structure and raman scattering

It is shown that the replacement of a part of sulfur atoms with selenium atoms in a TlInS2 single crystal stimulates the formation of a single-phase state with a monoclinic structure (space group [Formula: see text]/[Formula: see text] in TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]). Irradiation with 2 MeV electrons and a fluence of [Formula: see text] electron/cm2 of powder TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]) leads to an increase in the crystallite size from 56.5 nm to 65 nm, which is most likely associated with a decrease in the interface. The difference between the surface morphology of the synthesized TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]) single crystal and the surface morphology of the TlInS2 single crystal is established, which consists in a decrease in the height and width of the roughness in TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]). Irradiation of a TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]) single crystal with electrons with a fluence of [Formula: see text] electron/cm2 does not lead to a change in the height of the tubercle on its surface, and the average value of its width increases more than ten-fold. The identity of the peaks in the Raman spectra of the TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]) single crystal before and after its irradiation with electrons with an energy of 2 MeV and upto a fluence of [Formula: see text] electron/cm2, along with the absence of a shift of the peaks, indicates the radiation resistance of the TlInS[Formula: see text]Se[Formula: see text] ([Formula: see text]) single crystal.

Investigation and application of wellbore temperature and pressure field coupling with gas\u2013liquid two-phase flowing

With the development of gas well exploitation, the calculation of wellbore with single-phase state affected by single factor cannot meet the actual needs of engineering. We need to consider the simulation calculation of complex wellbore environment under the coupling of multiphase and multiple factors, so as to better serve the petroleum industry. In view of the problem that the commonly used temperature and pressure model can only be used for single-phase state under complex well conditions, and the error is large. Combined with the wellbore heat transfer mechanism and the calculation method of pipe flow pressure drop gradient, this study analyzes the shortcomings of Ramey model and Hassan & Kabir model through transient analysis. Based on the equations of mass conservation, momentum conservation and energy conservation, and considering the interaction between fluid physical parameters and temperature and pressure, the wellbore pressure coupling model of water-bearing gas well is established, and the Newton Raphael iterative method is used for MATLAB programming. On this basis, the relationship between tubing diameter, gas production, gas–water ratio, and wellbore temperature field and pressure field in high water-bearing gas wells is discussed. The results show that the wellbore temperature pressure coupling model of high water-bearing gas well considering the coupling of gas–liquid two-phase flow wellbore temperature pressure field has higher accuracy than Ramey model and Hassan & Kabir model, and the minimum coefficients of variation of each model are 0.022, 0.037 and 0.042, respectively. Therefore, the model in this study is highly consistent with the field measured data. Therefore, the findings of this study are helpful to better calculate the wellbore temperature and pressure parameters under complex well conditions.

Characterization and Validation of Fatigue Strains for Superelastic Nitinol Using Digital Image Correlation

Abstract Fatigue is a major challenge encountered in cardiovascular implant design. While the properly heat-treated Nitinol can exhibit up to 6–7% recoverable strains allowing for minimally invasive transcatheter delivery of cardiovascular implants, the cyclic in vivo loading can cause premature fracture of the implant if the fatigue strain is too high. Strain-based criteria have been adopted for the development of Nitinol fatigue resistance. Lacking experimental tools to characterize the local material fatigue strain, fatigue testing of Nitinol specimens has largely relied on the finite element analysis to compute the cyclic strain amplitude and mean strain based on experimentally derived constitutive parameters using phenomenological strain energy theory. Without a consistent computational standard, previous works have resulted in controversy and inconsistency in the impact of mean strain on the fatigue resistance of Nitinol in terms of strain amplitude limit at high cycle fatigue regime. In this paper, digital image correlation (DIC) technique is used to experimentally determine local material strains of Nitinol fatigue specimens using monotonic and cyclic loading conditions. These local strains are compared with strains computed from finite element analysis. It was found that strains from DIC and FEA are comparable in the single-phase states (pure austenitic or martensitic), whereas the measured strains can show significant difference from simulation computed strain during the transformation stage where both austenite and martensite phase co-exist. These observations have significant implications to nitinol fatigue testing and implant reliability assessment.

Entropy Landscaping of High-Entropy Carbides.

The entropy landscape of high-entropy carbides can be used to understand and predict their structure, properties, and stability. Using first principles calculations, the individual and temperature-dependent contributions of vibrational, electronic, and configurational entropies are analyzed, and compare them qualitatively to the enthalpies of mixing. As an experimental complement, high-entropy carbide thin films are synthesized with high power impulse magnetron sputtering to assess structure and properties. All compositions can be stabilized in the single-phase state despite finite positive, and in some cases substantial, enthalpies of mixing. Density functional theory calculations reveal that configurational entropy dominates the free energy landscape and compensates for the enthalpic penalty, whereas the vibrational and electronic entropies offer negligible contributions. The calculations predict that in many compositions, the single-phase state becomes stable at extremely high temperatures (>3000 K). Consequently, rapid quenching rates are needed to preserve solubility at room temperature and facilitate physical characterization. Physical vapor deposition provides this experimental validation opportunity. The computation/experimental data set generated in this work identifies "valence electron concentration" as an effective descriptor to predict structural and thermodynamic properties of multicomponent carbides and educate new formulation selections.

Effect of structure of high entropy CrFeCoNiCu alloys produced by EB PVD on their strength and dissipative properties

Thin (up to 100 µm) foils and coatings of high-entropy CrFeCoNiCux (x = 0...3.0) alloys (HEAs) were produced at different temperatures in the 525…1275 K range by electron-beam evaporation of ingots. It is shown that CrFeCoNiCux (where x > 0.3) condensates deposited at a temperature above 925 K have a dual-phase structure consisting of two FCC phases, while those deposited at a temperature below this value exhibit a single-FCC structure. It is also found that annealing of the deposited single-phase CrFeCoNiCux (x = 0.3…3.0) condensates at temperatures above 925 K results in the transition into a dual-FCC phase state. Yet, condensates with the copper content x < 0.3 remain stable at heating up to high temperatures (up to 1300 K). The transition from single-phase condensates into dual-phase condensates occurs through the formation of the metastable Cr-enriched phase. The effect of the condensate structure on their mechanical and dissipative properties is considered. The single-phase condensates exhibit increased microhardness, as compared to the cast alloy. The microhardness of the two-phase condensates is lower than in single-phase ones but still higher than in the cast ingot. HEA-based vacuum condensates in both single-phase and two-phase states show high values of damping capacity, which are comparable with those of highly damping materials, such as AZ31B-F magnesium alloys.

Experimental research on flow boiling characteristics of micro pin-fin arrays with different hydrophobic coatings

Experimental investigations have been conducted on flow and thermal performance of coolant flow boiling in diamond micro arrays with different contact angles (90°, 120° and 150°). Working fluid circulating under mass flow rates in the scope of 21.54–962.75 kg/(m2·s). Images captured by high-speed camera with 500fps showed the coolant flow pattern in these micro pin-fin arrays. Comparative experiments of thermal performance of four micro pin-fins were performed at inlet temperature of 30 °C. The flow patterns of flow boiling could be divided into four states: film boiling state, transition state, nucleate boiling state and single-phase state. The pressure drop of hydrophobic surface is 90% lower than that of bare copper surface as the mass flow rate is 215 kg/(m2·s) The flow resistance is reduced after being covered with hydrophobic coatings. With the increase of contact angles, the micro arrays' thermal characteristics becomes deteriorated rapidly. The flow and thermal performance of diamond micro arrays is better than other three shapes, as the structure of diamond pin-fins plays a significant role in separation and migration of vapor film and bubbles. When the mass flow rate reaches 448 kg/(m2·s), the heat transfer coefficient of diamond is 76% higher than that of triangle.

УЛУЧШЕНИЕ ЭФФЕКТИВНОСТИ ФУНКЦИОНИРОВАНИЯ ГАЗОПРОВОДОВ С УЧЕТОМ СТРУКТУРНЫХ ОСОБЕННОСТЕЙ ТЕЧЕНИЯ ГАЗА

The multi-phase and different composition of gas flows during the development of offshore oil and gas-condensate fields leads to high costs of energy in the system of in-field storage and transportation of well products. The analysis of the existing storage and transportation systems of gas-condensate mixtures shows that the geophysical nature and complexity of the internal structure of the transported fluids must be taken into account when choosing the mode parameters and calculation schemes of the pipelines. High-speed gas lines can be operated in a so-called "dry" mode, in which the liquid is carried along with the gas, the pipeline profile is relatively straight, without ups and downs. In this case, the formation of so-called "stagnant zones" in the pipeline is excluded. However, if the processing depth of the gas does not allow it to be transported in a single-phase state, then the condensing gas factor manifests itself. The hydraulic characteristics of vertical ups and downs on offshore pipelines are complicated, and pipelines are often filled with water and condensate. As a result, the pressure in the pipeline increases and the location of the collection point for condensing gases away from the production site can cause major problems. If we characterize oil and gas-condensate flows as a dynamic system in which alternating structural changes take place, the question of whether these systems are fractal is of great scientific interest. Based on the change in the fractal value, it is possible to diagnose structural changes during the transportation of various systems, including condensing gases in the pipelines. In this article the modes of change of basic parameters of a gas flow (pressure, flow rate and temperature) on various lines of a gas pipeline for the purpose of the producing of diagnostic criterion for revealing of liquid inclusions as a part of transported gas are investigated in this article. It is established, that in the presence of liquid inclusions at movement of gas flows there are the structural changes peculiar to fluid systems, systems which can be identified by variations of fractal dimensions of flowcharacteristics. Studies have shown that the study of the dynamics of structural changes in gas flows can play a role in diagnosing the formation of liquid phase embryos in gas pipelines. For this purpose, diagnostics for the movement of gas streams accompanied by liquid deposits in the pipelines has been proposed.

Correlation between chemical composition, electrical, magnetic and microwave properties in Dy-substituted Ni-Cu-Zn ferrites

Dy3+ ion-substituted nanoferrites Ni0.4Cu0.2Zn0.4Fe2−xDyxO4 (x ≤ 0.04) were produced via sol-gel method. Correlation between chemical composition, crystal structure, electrical, magnetic and microwave properties was investigated. All samples were characterized by single-phase state. It was observed that the increase of the Dy content leads to a decrease in the average crystallite size. The bandgap (Eg) was deduced to be between 1.83 and 1.86 eV. The measurements of magnetization versus applied magnetic field (M-H) and magnetization versus temperature (M-T) were investigated by vibrating sample magnetometer (VSM). Magnetic measurements revealed superparamagnetic character at room temperature. The magnetization was increased initially with doping Dy3+ in the ratio of x = 0.01 compering to the un-doped sample and thereafter dropped as Dy3+ ions content further increases. Microwave properties were discussed in terms of electromagnetic absorption in the frequency range 1–20 GHz. The occurrences of the intensive electromagnetic absorption in the frequency ranged from 1.6 to 2.7 GHz were observed. The changes in the amplitude-frequency characteristics correlated well with the level of chemical substitution (x) with Dy ions concentration.

Study of the influence of electronic radiation on the surface, structure and Raman spectrum of a TlInS2 single crystal

The effect of electrons on the surface, Raman spectra, structure and phase transition in a TlInS2 single crystal was studied. Irradiation of TlInS2 with electrons with an energy of 2 MeV and a fluency of 2 × 1017 electron/cm2 leads to an increase in the height of the bump and its width on the sample surface. Radiation treatment of TlInS2 with electrons indicates the appearance of new peaks at 204 cm−1, 224 cm−1 in the Raman spectra and stimulates the formation of a single-phase state with a hexagonal structure (space group P63/mmc).

Cryogenic and hybrid induction-assisted machining strategies as alternatives for conventional machining of refractory tungsten and niobium

Tungsten (W) and niobium (Nb) belong to the refractory metal group and are used as alloying elements in steels and superalloys for high demand products. These metals are also used in a high purity single-phase state for products within nuclear, space, military and research facilities.In the current study, tool wear development and surface quality at different cutting conditions have been evaluated when machining high purity W 99.95% and Nb 99.7% in longitudinal turning. Cryogenic LN2 cooling and hybrid induction-assisted machining strategies were applied in order to alter W and Nb material state with respect to the ductile-to-brittle transformation temperature, and thus to attempt controlling their machinability. These advanced machining strategies were benchmarked against the more conventional machining solutions of dry, flood and high pressure cooling.It was found that the use of LN2 cooling demonstrated the best result in terms of tool life when machining W followed by induction-assisted heating, dry and flood. All machining strategies provided similar surface quality which is related to strong build-up edge formation and respective surface alteration. When machining Nb, high pressure coolant results in best performance in terms of tool life and surface quality, then followed by flood and cryogenic strategies. Overall, substantial improvement of surface quality (Ra = 0.4–0.6 μm) was observed for high cutting speeds vc ≥ 225 m/min.

B2 precipitates formation in Al-containing CoCrFeMnNi-type high entropy alloy

The non-equiatomic Al7.5Co21.75Cr5.5Fe21.75Mn21.75Ni21.75 high entropy alloy was studied. After cold rolling and annealing at 700-900 °C, a dual-phase ultrafine-grained structure composed of the partially recrystallized fcc matrix and B2 particles was produced; complete recrystallization of the fcc phase was observed after annealing at 1000 °C. The B2 precipitates formation provided a significant strengthening of the alloy in comparison with the single-phase state. The alloy demonstrated an attractive combination of mechanical properties, presenting yield and ultimate tensile strengths of 900 MPa and 1200 MPa, respectively, along with a ductility of 22%.

&amp;lt;i&amp;gt;HydrothermalFoam&amp;lt;/i&amp;gt; v1.0: a 3-D hydrothermal transport model for natural submarine hydrothermal systems

Abstract. Herein, we introduce HydrothermalFoam, a three-dimensional hydro-thermo-transport model designed to resolve fluid flow within submarine hydrothermal circulation systems. HydrothermalFoam has been developed on the OpenFOAM platform, which is a finite-volume-based C++ toolbox for fluid-dynamic simulations and for developing customized numerical models that provides access to state-of-the-art parallelized solvers and to a wide range of pre- and post-processing tools. We have implemented a porous media Darcy flow model with associated boundary conditions designed to facilitate numerical simulations of submarine hydrothermal systems. The current implementation is valid for single-phase fluid states and uses a pure-water equation of state (IAPWS-97). We here present the model formulation; OpenFOAM implementation details; and a sequence of 1-D, 2-D, and 3-D benchmark tests. The source code repository further includes a number of tutorials that can be used as starting points for building specialized hydrothermal flow models. The model is published under the GNU General Public License v3.0.

Symmetrical Components Based State Estimator for Power Distribution Systems

Real-time monitoring of distribution systems gains importance day by day, as the number of distributed energy resources populate across the system. Distribution System State Estimation (DSSE) will constitute the core of real-time monitoring in modern distribution management systems, serving as a basis for many applications whose effectiveness relies on fast and accurate computations of the system state. This paper presents a three-phase weighted least squares state estimation method based on symmetrical components for distribution systems. In the proposed formulation, the three-phase DSSE problem is decomposed into three single-phase problems which can be solved sequentially or simultaneously by single-phase state estimators. As a result, the implementation complexity and computational times required for DSSE solutions are considerably reduced. The effectiveness and validity of the proposed method are demonstrated on distribution feeders of different sizes and topologies, considering statistical criteria, and computational efficiency. Results show that the proposed method estimates the state of large distribution systems significantly faster and with comparable accuracy as a well-established DSSE method.

On the peridynamic effective force state and multiphase constitutive correspondence principle

This article concerns modeling unsaturated deformable porous media as an equivalent single-phase and single-force state peridynamic material through the effective force state. The balance equations of linear momentum and mass of unsaturated porous media are presented by defining relevant peridynamic states. The energy balance of unsaturated porous media is utilized to derive the effective force state for the solid skeleton that is an energy conjugate to the nonlocal deformation state of the solid, and the suction force state. Through an energy equivalence, a multiphase constitutive correspondence principle is built between classical unsaturated poromechanics and peridynamic unsaturated poromechanics. The multiphase correspondence principle provides a means to incorporate advanced constitutive models in classical unsaturated porous theory directly into unsaturated peridynamic poromechanics. Numerical simulations of localized failure in unsaturated porous media under different matric suctions are presented to demonstrate the feasibility of modeling the mechanical behavior of such three-phase materials as an equivalent single-phase peridynamic material through the effective force state concept.

INFLUENCE OF THE MAGNITUDE OF THE BIAS POTENTIAL AND THICKNESS OF THE LAYERS ON THE STRUCTURE, SUBSTRUCTURE, STRESS-DEFORMED STATE AND MECHANICAL CHARACTERISTICS OF VACUUM-ARC MULTI-LAYERED (TiMo)N/(TiSi)N COATINGS

Layers based on titanium nitride doped with molybdenum and silicon were used to create a multilayer composite. In this case, the mismatch between the lattice periods of (TiMo)N and (TiSi)N layers was about 1%. It was found that in the (TiMo)N/(TiSi)N multilayer composite, such a mismatch of the periods in the constituent layers does not change the single-phase state of the composite even at relatively large layer thicknesses (about 350 nm). The creation of a (TiMo)N/(TiSi)N composite with a nanometer layer thickness allows one to reduce the magnitude of macrostresses (a large value of which is characteristic of single-layer (TiMo)N coatings) and change the substructural characteristics in a wide range of values. It has been established that the use of multi-element (TiMo)N and (TiSi)N layers in a multilayer coating design allows one to achieve a high-hard state with high adhesive strength and good tribological characteristics. The highest properties (hardness – 34.8 GPa and adhesive strength - 166.09 N) were achieved in coatings obtained at Ub = -200 V and a layer thickness of 80 nm, which are characterized by compression macrostresses of 7.85 GPa and microstrains - 0.75%.

Efficient and robust phase-split computations in the internal energy, volume, and moles (UVN) space

Phase-split computations in an isolated system, which in general may be defined as one where the total internal energy (U), volume (V), and the number of moles (N=N1,N2,…,Nn) of the components are fixed at some specified set of values, involves the determination of the temperature (T), pressure (P), plus the amount and composition of the various phases that constitute the system. A simpler, but analogous problem is one where T, P, and N are specified instead. In TPN space, one may first perform a stability analysis to determine whether the system is stable, meaning whether at equilibrium it will split up into multiple phases or remain in single phase. If the single-phase state is unstable, the stability analysis reliably provides a good set of initial guesses in the subsequent phase-split computations. In UVN space, however, we demonstrate that the stability analysis (which is the main subject of our earlier study [1]) may not in general provide good enough initial guesses; we offer alternative strategies for setting up good initial guesses. Furthermore, we show that a combination of successive substitution iteration (SSI) and Newton's method---two iterative methods that are prevalent in the literature in TPN space---facilitates a robust and efficient algorithm for phase-split computations in isolated systems. This combination has so far not been applied in UVN space.