Sc Phase Research Articles

Thermodynamics of the α-FeOOH (goethite)-ScOOH solid solution

Scandium (Sc) is a rare element that finds uses in modern technologies. Thermodynamic properties of Sc phases could help in the development of innovative technologies to extract Sc from mining waste. In this work, we investigated the FeOOH–ScOOH solid solution with the goethite structure. The end members and five intermediate compositions were synthesized and characterized. The lattice parameters show that the solid solution is non-ideal, with complex behavior induced by the Fe–Sc substitution. The excess unit-cell volume deviates negatively for the Sc-rich region, and positively for the Fe-rich region from the ideal behavior (Vegard’s law). Enthalpies of dissolution were determined by acid-solution calorimetry in 5 mol·dm-3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot \\hbox {dm}^{-3}$$\\end{document} HCl at T = 343.15 K. Enthalpies of mixing (ΔmixH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _{mix}H$$\\end{document}), calculated from the experimental data, are small and positive. The available data allow for fitting the data as ΔmixH=Wx(1-x)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _{mix}H = W x (1-x)$$\\end{document}, with the mixing parameter W=15.2±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W = 15.2\\pm$$\\end{document}1.0 kJ·mol-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot \\hbox {mol}^{-1}$$\\end{document}. Using ΔfGo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta _fG^o$$\\end{document} of ScOOH from earlier literature, we calculated a Lippmann diagram that shows that Sc should strongly partition into the aqueous phase upon goethite precipitation. The field observations from lateritic profiles show that Sc is primarily harbored by goethite via adsorption. It seems that under weathering conditions, thermodynamically driven partitioning of Sc3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Sc}^{3+}$$\\end{document} into the aqueous phases and its subsequent adsorption onto goethite surfaces controls the mobility of Sc in the weathering profiles.

Study of engineering developing decagonal-like rational approximant structure of Al–Ni–Cu–Fe–Mn–Cr senary system in aluminum alloy through additive manufacturing

Quasi-periodic materials hold unique properties, but mass-producing bulk materials with such structures remains challenging. The rational approximant phase belongs to the Bravais crystal system but exhibits irrational cut features and diffraction symmetries, which are similar to quasicrystals. This study uses additive manufacturing (AM) and prolonged annealing to create an aluminum-based alloy featuring a quasicrystal-like rational approximant phase, Al6(Cu, Ni)1(Cr, Mn, Fe)1, overcoming the production limitations of reproducible quasi-periodic materials. This phase transformation occurs at the Al–Al9FeNi interface, resulting in a monoclinic periodic structure with long-range translational symmetry. The structure comprises sublattices of stars and compressed hexagons, forming tile mode coverings with pseudo-five-fold decagonal shield-like tiles (SLTs) through transition-element atoms. Furthermore, HAADF imaging reveals clear dark monoclinic rhombic patterns with long-range ordered translational symmetry, free from atomic defects. The rational approximant phase has been verified crystallography through X-ray diffraction, confirming its translational symmetry. Additionally, the Al3(Zr, Sc) phase facilitates the phase transformation process through lattice interactions. These findings introduce a novel perspective on the phase transformation in decagonal-like rational approximants and broaden the realm for future engineering applications.

An Assessment of Solar Cycle 25 progress through observation of SRBs and associated Geomagnetic Storms

Geomagnetic storms are severe aspects of Space Weather. They originate due to solar transient emissions such as coronal mass ejections (CMEs), whose energetic materials propagate in the Interplanetary medium and are coupled with the magnetosphere system. CME driven Geomagnetic storms are often associated with solar radio bursts (SRBs), particularly type II and type IV bursts. In this study, we present the preliminary results of solar radio observations and their associated geomagnetic activity during solar cycle 25 (SC 25) from January 2020 to June 2023, focusing on the cycle’s first four intense geomagnetic storms. The study used various radio telescopes, mainly the compound astronomical low-frequency low-cost instrument for spectroscopy and transportable observatory (CALLISTO), as well as OMNI data and the World Data Center for Geomagnetism. During the study period, it was found that 23 solar radio bursts diagnosed the geomagnetic storms with Dst <-50nT from 35 reported, including three severe storms of the SC 25. The time delay between the solar radio bursts and the arrival of CMEs and/or HSS near the Earth’s magnetosphere is estimated with an average value of 79 h within the [48–120 h] range for 23 geomagnetic storms associated with solar radio bursts. Among 35 geomagnetic storms recorded, five are recurring geomagnetic storms associated with coronal high-speed streams (HSS), while CMEs cause the rest with average speeds of 750 km/s. The current SC 25 recognizes four major storms within the scope of the study. On 21 April 2023, a type II radio burst followed by a type IV burst diagnosed the first severe geomagnetic storm on 24 April 2023. The second severe storm was unusual and detected in the absence of the precursor as a solar radio burst. The SRBs of type II burst and type IV burst extending in IP medium on 1 November 2021 tracked the third major storm of the cycle while the group of type III radio bursts, type II and type IV bursts on 24 February 2023, predicted the major storm on 27 February 2023. These major geomagnetic storms are linked to CMEs that show expanding flux ropes, which are signatures of type II and moving type IV radio bursts identified. Furthermore, the detected SRBs and related major geomagnetic storms are proof of high solar and magnetic activity of the ascending phase of SC 25. The SC 25 has been characterized overall, and its current progress is being tracked using observations of SRBs and magnetic activity during its rising phase.

Effect of Low-Temperature Plasma Carburization on Fretting Wear Behavior of AISI 316L Stainless Steel

AISI 316L stainless steel has received considerable attention as a common material for key ball valve components; however, its properties cannot be improved through traditional phase transformation, and fretting wears the contact interface between valve parts. A carburized layer was prepared on the surface of AISI 316L stainless steel by using double-glow low-temperature plasma carburization technology. This study reveals the effect of double-glow low-temperature plasma carburization technology on the fretting wear mechanism of AISI 316L steel under different normal loads and displacements. The fretting wear behavior and energy dissipation of the AISI 316L steel and the carburized layer were studied on an SRV-V fretting friction and wear machine with ball–plane contact. The wear mark morphology was analyzed by using scanning electron microscopy (SEM), the phase structure of the carburized layer was characterized with X-ray diffractometry (XRD), and the wear profile and wear volume were evaluated with laser confocal microscopy. The carburized layer contains a single Sc phase, a uniform and dense structure, and a metallurgically combined matrix. After plasma carburizing, the sample exhibited a maximum surface hardness of 897 ± 18 HV0.2, which is approximately four times higher than that of the matrix (273 ± 33 HV0.2). Moreover, the surface roughness was approximately doubled. The wear depth, wear rate, and frictional dissipation energy coefficient of the carburized layer were significantly reduced by up to approximately an order of magnitude compared with the matrix, while the wear resistance and fretting wear stability of the carburized layer were significantly improved. Under different load conditions, the wear mechanism of the AISI 316L steel changed from adhesive wear and abrasive wear to adhesive wear, fatigue delamination, and abrasive wear. Meanwhile, the wear mechanism of the carburized layer changed from adhesive wear to adhesive wear and fatigue delamination, accompanied by a furrowing effect. Under variable displacement conditions, both the AISI 316L steel and carburized layer mainly exhibited adhesive wear and fatigue peeling. Oxygen elements accumulated in the wear marks of the AISI 316L steel and carburized layer, indicating oxidative wear. The fretting wear properties of the AISI 316L steel and carburized layer were determined using the coupled competition between mechanical factors and thermochemical factors. Low-temperature plasma carburization technology improved the stability of the fretting wear process and changed the fretting regime of the AISI 316L steel and could be considered as anti-wearing coatings of ball valves.

Simultaneously Improving Strength and Plasticity of Al–Cu Alloy by Introducing Spherical Precipitates

The trade‐off relation between strength and plasticity is the bottleneck that limits the development of high‐strength and high‐plasticity Al–Cu alloys. Inspired from the influence of precipitate shape on the work‐hardening behavior of Al–Cu alloys, an Al–Cu–Zr–Sc alloy containing a mixed microstructure of spherical‐shaped Al3(Zr, Sc) phases and disk‐shaped θ′ phases is successfully designed and fabricated. Surprisingly, it is found that the strength and plasticity of the Al–Cu–Zr–Sc alloy are synchronously improved compared to the Al–Cu alloy with only disk‐shaped θ′ phases. The introduction of spherical‐shaped Al3(Zr, Sc) phases can increase the yield strength without sacrificing the work‐hardening ability of the Al–Cu–Zr–Sc alloy, which is mainly attributed to the extremely small strain‐hardening exponent of the Al alloy with spherical‐shaped precipitates. Besides, the predicted strength–elongation relation of the Al–Cu alloy is established based on the exponential strain‐hardening model.

The Effect of Point Defects on Young’s Modulus of the Off-Stoichiometric Al3X (X = Li, Sc, and Zr) Phases: A First-Principles Study

L12-Al3X (X = Li, Sc, and Zr) precipitates are the main strengthened phases of high-strength aluminum alloys and are critical for aerospace structural materials. Point defects and substitutional ternary elements change the mechanical properties of Al3X. In this paper, the effect of point defects, including vacancy, antisite, and substitutional element addition defects on the elastic modulus of the off-stoichiometric Al3X (X = Li, Sc, and Zr) phase were investigated by using first-principle calculations. The formation enthalpies of the defective Al3X alloy and isolated point defects in Al3X were calculated, and the results showed that the defects have an effect on the structure and elasticity of the off-stoichiometric Al3X phases. The lattice distortion, elastic constants, and elastic moduli were further investigated. It was found that the point defects increased the Young’s modulus for Al3Zr, and the doping of Er improved the Young’s modulus for off-stoichiometric Al3Li and Al3Sc. Adjusting the position of vacancies can improve the elastic modulus. In addition, the doping of substitutional elements (especially Sc, Ti, Zr, Hf, Ta, Mn, Ir, and Cf) can greatly increase the Young’s modulus of off-stoichiometric Al3Li.

Ab initio investigation on the ordering mechanism of L12 phase in Al–Zr–Y(Sc) alloy

The L12-Al3Y(Sc) phase promotes the precipitation kinetics of Al3Zr. However, although Al3Y and Al3Sc are both with L12 structures, the mechanisms are not entirely the same due to different structures of the compound composites: Al3(Zr, Sc) has a core-shell structure, while Al3(Zr, Y) does not. Formation mechanisms of core-shell and non-core-shell structures were revealed in this work through analyzing surface energy, interface binding energy, and interface energy. The results showed that the interface energy and the lattice mismatch of Al/Al3Sc and Al/Al3Y are 0.011 J/m2,1.9% and 0.512 J/m2 and 5% respectively. During the growth of Al3(Zr, Sc) with Al3Sc as the heterogeneous core, the interface energy decreased linearly with increasing Zr contents at the interface and eventually a Zr rich shell formed. However, during the formation of Al3(Zr, Y), the interface energy fluctuated with changes in the composition and Zr(Y) content at the interface, eventually forming a composite phase shell of Al3Y(Zr). The diffusion migration energy for Zr atoms in pure Al was 1.102 eV, and it increased by at least 2% near the Al/Al3Sc interface, while it decreased by up to 46.3% near the Al/Al3Y interface. The impact of the L12-Al3Y(Sc) heterogeneous core on the diffusion ability of Zr atoms is crucial for its influence on the kinetics of Al3Zr precipitation.

The formation of (Al, Si)3(Ti, Sc) through microalloying and solidification control synergy in Al-7Si-0.7Mg refines α-Al greatly

The grain refinement mechanism of Al-7Si-0.7Mg alloy by Sc and Ti have been systematically investigated at different cooling rate. The Si-poisoning effect have been avoided by synergistic inoculation of Sc and Ti at special where slow cooling rate before solidification is required. The inoculation of Sc and Ti avoid the Si-poisoning effect by forming a new phase of (Al, Si)3(Ti, Sc). The gradient solidification is adopted to make the (Al, Si)3(Ti, Sc) phase reappear at fast cooling rate to avoid Si-poisoning. The average grain size of Al-7Si-0.7Mg-0.15Ti-0.5Sc alloy solidified through gradient solidification is refined to 131 µm decreased 45 % compared with traditional cast. The mechanism for anti Si-poisoning is also investigated using first-principles calculation and High-Angle Annular Dark-Field STEM. Data availabilityData will be made available on request.

Gypsum, crop rotation, and cover crop impacts on soil organic carbon and biological dynamics in rainfed transitional no-till corn-soybean systems.

Soil organic carbon (SOC), a core soil quality indicator, is influenced by management practices. The objective of our 2012-2016 study was to elucidate the impact of gypsum, crop rotation, and cover crop on SOC and several of its biological indicators under no-till in Alabama (Shorter), Indiana (Farmland), and Ohio (Hoytville and Piketon) in the USA. A randomized complete block design in factorial arrangement with gypsum (at 0, 1.1, and 2.2 Mg/ha annually), rye (Secale cereal L.) vs no cover crop, and rotation (continuous soybean [Glycine max (L) Merr., SS] vs corn [Zea mays, L.]-soybean, both the CS and SC phases) was conducted. Composite soils were collected (0-15 cm and 15-30 cm) in 2016 to analyze microbial biomass C (SMBC), SOC, total N, active C, cold and hot-water extractable C, C and N pool indices (CPI and NPI), and C management index (CMI). Results varied for main effects of gypsum, crop rotation, and cover crop on SOC pools, total N, and SOC lability within and across the sites. Gypsum at 2.2 Mg/ha increased SMBC within sites and by 41% averaged across sites. Likewise, gypsum increased SMBC:SOC, active C, and hot-water C (as indicators of labile SOC) averaged across sites. CS rotation increased SOC, active C, CPI, and CMI compared to SS, but decreased SMBC and SMBC:SOC within and across sites. CPI had a significant relationship with NPI across all sites (R2 = 0.90). Management sensitive SOC pools that responded to the combined gypsum (2.2 Mg/ha), crop rotation (CS), and cover crop (rye) were SMBC, SMBC:SOC, active C, and CMI via SMBC. These variables can provide an early indication of management-induced changes in SOC storage and its lability. Our results show that when SOC accumulates, its lability has decreased, presumably because the SMBC has processed all readily available C into a less labile form.

Stability of damping capacity and mechanical properties of high-Zn-concentration Al–Zn–Mg–Sc alloy

The microstructure, damping capacity, mechanical properties, and the performance stability of high-Zn-concentration Al–Zn–Mg–Sc alloys after annealing treatment were studied. The Al–20Zn–0.5 Mg–0.5Sc alloy contained fine grains, a high number of solution atoms, Zn phases, Al 3 Sc phases, and high-density fine η and η' phases. Decreasing the Zn content led to the disappearance of the Zn phases and the decrease of intragranular η phases density and solution atom number. Increasing the Mg content did not increase the number of solution atoms but increased the size of the intragranular η phases. The Al–20Zn–0.5 Mg–0.5Sc alloy exhibited higher internal friction value and higher strength than the other two alloys because of its satisfactory grain boundaries and Al/Zn interface sliding ability at high temperature, as well as its high solid solution and second phase strengthening effects at room temperature. All annealed Al–Zn–Mg–Sc alloys exhibited excellent damping capacity and mechanical properties stability during the DMA test at the highest temperature of 360 °C due to their high structural stability. • A novel Al alloy with excellent damping capacity, mechanical properties, and performances stability was obtained. • The satisfactory GB and Al/Zn interface sliding ability led to the Al–Zn–Mg–Sc alloy exhibited well damping capacity. • The high solid solution and second phase strengthening effects led to the Al–Zn–Mg–Sc alloy exhibited high strength. • Sc addition and annealing led to the Al–Zn–Mg–Sc alloy exhibited excellent structural and properties stabilit.

The study of phase change properties of Sb70Se30 thin film with scandium and aluminum doping

The scandium (Sc) and aluminum (Al) co-doped antimony-selenium (Sb45Se25Sc7Al23) thin film was fabricated and systematically investigated in this study. The results reveal that our examined Sb45Se25Sc7Al23 thin film has good thermal stability (the failure temperature for ten years data retention ∼103 °C) and the fast phase change speed (5 ns) at same time. Besides, the Sb45Se25Sc7Al23 thin film shows no multiple phase change, which derives from the fact that no formation of new Sc or Al related phases that are able to trigger multiple states in the thin film. However, it is found that more Sb precipitation is formed by the increase of dopants, which may increase the tendency of multiple phase change. All results suggest Sb45Se25Sc7Al23 thin film would be a good candidate used for phase change random access memory applications.

Fluctuation conductivity and vortex state in a superconductor with strong paramagnetic pair breaking

The fluctuation conductivity of a moderately clean type II superconductor with strong Pauli paramagnetic pair-breaking (PPB) is studied by focusing on the quantum regime at low temperatures and in high magnetic fields. First, it is pointed out that, as the PPB effect becomes stronger, the quantum superconducting fluctuation is generally enhanced so that the Aslamasov-Larkin (AL) fluctuation conductivity tends to vanish upon cooling. Further, by examining other (the DOS and the Maki-Thompson (MT)) terms of the fluctuation conductivity, the field dependence of the resulting total conductivity is found to depend significantly on the type of the vortex lattice (or, glass) ordered state at low temperatures where the strong PPB plays important roles. By comparing the present theoretical results with the fluctuation-induced negative magnetoresistance behavior upon entering a PPB-induced novel SC phase of Iron selenide (FeSe), it is argued that the vortex matter states of the superconducting order parameter in the second lowest ($n=1$) Landau level are realized in FeSe in the parallel field configuration in high fields and at low temperatures

Combination of pasireotide and octreotide: effects on GH and IGF-I secretion and glucose metabolism in healthy volunteers.

To assess the pharmacokinetics, pharmacodynamics and tolerability of different doses of octreotide and pasireotide (subcutaneous [sc] and long-acting release [LAR]) when co-administered in healthy volunteers. This was an exploratory, Phase I, single-centre study. Healthy adults were enrolled in a staggered approach into seven cohorts to receive octreotide and pasireotide (sc and LAR formulations), alone or in combination. Plasma drug concentrations, growth hormone (GH), insulin-like growth factor I (IGF-I), and plasma glucose were assessed at baseline, immediately after sc treatment, and 21 and 28 days after LAR treatment. Of 88 enrolled subjects, 52 and 82 participated in sc and LAR dosing phases, respectively. There were no relevant pharmacokinetic interactions between octreotide and pasireotide. In combination, pasireotide sc (150 µg) and octreotide sc (100/300 µg) resulted in numerically greater reductions in insulin levels and a higher incidence of AEs than either single agent; the rapid (within 1 h) increase in plasma glucose after pasireotide was delayed with combination treatment. Octreotide sc and pasireotide sc, alone or in combination, reduced IGF-I levels and led to undetectable GH levels in most subjects. During the LAR phase, addition of a low dose of pasireotide (5 mg) to a standard dose of octreotide (20 mg) resulted in an ~2-fold reduction in median IGF-I versus octreotide 20 mg 21 days post-dose; this effect was numerically greater than seen for pasireotide 20 mg alone. Peak plasma glucose was substantially lower after LAR than sc dosing. Interestingly, glucose levels were also numerically lower in the pasireotide 5 mg plus octreotide 20 mg group than for 20 mg of octreotide or pasireotide alone. AEs were less frequent after LAR than sc dosing. Combined low doses of pasireotide LAR (5 mg) and octreotide LAR (10-30 mg) provided greater suppression of IGF-I than either single agent and did not increase blood glucose or incidence of AEs versus either agent alone.

Effect of A‐site atom on static corrosion behavior and irradiation damage of Ti2SC phases

AbstractMAX phases are a large family of damage‐tolerant structural materials for the nuclear energy industry. The anti‐corrosive property to the tritium fluoride (TF) produced by the neutron irradiation of FLiBe is an issue for the MAX phases applied to the molten salt reactors (MSRs). Herein, the Ti2SC phase was used for the first time to evaluate the corrosion resistance to the concentrated hydrofluoric acid as the simulated service condition. The comprehensive characterizations including weight‐loss curves, X‐ray diffraction, field emission scanning electron microscopy, and energy dispersive spectroscopy were employed to analyze the corrosion behavior and mechanism of Ti2SC in comparison with Ti3AlC2 and Ti3SiC2. The good intrinsic anti‐corrosive property of Ti2SC was originated from the strong Ti‐S bond. Considering the acceptable preliminary performance at low displacement per atom (dpa), the Ti2SC probably has a potential to be used as the structural material in the MSRs.

Influence of Adding Modifying Elements and Homogenization Annealing on Laser Melting Process of the Modified AlZnMgCu with 4%Si Alloys.

AlZnMgCu, the high-strength aluminum alloy, is unsuitable for laser melting applications due to its high hot cracking sensitivity and large solidification temperature range. Adapting this alloy for laser melting processing is a high-demand research issue for extending its use. Thus, this paper investigates the effect of adding 4%Si, 4%Si-Sc+Zr, 4%Si-Ti+B, and homogenization annealing on the laser melting process (LMP) of AlZnMgCu alloy. Homogenization annealing at 500 °C for 6.5 h was selected to dissolve most of the low melting temperature phases into the grain matrix and perform stable alloys for the LMP. The pulsed laser melting process (PLM) was performed on the as-casted and the homogenized samples. The microstructures of the as-casted, the homogenized alloys, and after the LMP were evaluated. In addition, the hardness of the base metal (BM) and laser melted zone (LMZ) were measured. The results revealed that the microstructure was enhanced and refined in the as-cast state by adding the modifiers due to the increasing nucleation potency of solidification sites and the formation of primary Al3(Ti, Zr, Sc) phases. The average grain size was decreased by 15.6 times when adding 4%Si + 0.4%Zr + 0.29%Sc, while it decreased by 10.2 times when adding 4%Si + 1%Ti + 0.2%B. The LMZ of the as-casted samples exhibited a non-uniform distribution of the grains and the elements after the LMP. This was attributed to the evaporation of Zn, Mg during the high laser power process besides the non-uniform distribution of elements and phases in samples during casting. After the laser treating of the homogenized samples with 4%Si-Sc + Zr, uniform columnar grains were formed in the direction of the laser. The presence of Ti and B changed the crystallization nature, resulting in the LMZ with very fine and equiaxed grains due to forming many nucleation centers during solidification. The hardness values have positively increased due to Si addition and adding a combination of Ti + B and Sc + Zr. The maximum hardness was 153.9 ± 5 HV achieved in the LMZ of the homogenized samples of 4%Si + 1%Ti + 0.2%B.

Electric-field-induced crossover of polarization reversal mechanisms in Al1−x Sc x N ferroelectrics

Scandium-doped aluminum nitride, Al1−x Sc x N, represents a new class of displacive ferroelectric materials with high polarization and sharp hysteresis along with high-temperature resilience, facile synthesizability and compatibility with standard CMOS fabrication techniques. The fundamental physics behind the transformation of unswitchable piezoelectric AlN into switchable Al–Sc–N ferroelectrics depends upon important atomic properties such as local structure, dopant distributions and the presence of competing mechanism of polarization switching in the presence of an applied electric-field that have not been understood. We computationally synthesize Al1−x Sc x N to quantify the inhomogeneity of Sc distribution and phase segregation, and characterize its crystal and electronic structure as a function of Sc-doping. Nudged elastic band calculations of the potential energy surface and quantum molecular dynamics simulations of direct electric-field-driven ferroelectric switching reveal a crossover between two polarization reversal mechanisms—inhomogeneous nucleation-and-growth mechanism originating near Sc-rich regions in the limit of low applied fields and nucleation-limited-switching in the high-field regime. Understanding polarization reversal pathways for these two mechanisms as well as the role of local Sc concentration on activation barriers provides design rules to identify other combinations of dopant elements, such as Zr, Mg etc. to synthesize superior AlN-based ferroelectric materials.

Structure formation and processability of the Al—Zn—Mg—Ca—Fe—Zr—Sc alloy at hot rolling and TIG welding

Process conditions are suggested for manufacturing wrought semi-finished products (2 and 1 mm sheets) from the Al-4.5%Zn-2.5%Mg-2.5%Ca-0.5%Fe-0.2%Zr-0.1%Sc experimental alloy including thermomechanical processing at t = 400450 °С and reduction ratios up to 98 %, as well as softening annealing of the sheet metal at t = 350400 °C for 1—2 hours. It was found that the as-cast structure consists of eutectic phases (Al, Zn)4Ca, Al10CaFe2 5 to 25 gm in size, and a Al2Mg5Zn5 nonequilibrium T-phase located along the boundaries of dendritic cells (Al). Zirconium and scandium form a solid solution with aluminum as a result of solidification. After hot rolling, the structure of 2 mm sheets consists of lineage-oriented discrete intermetallic particles and their conglomerates up to 40 gm in size in the (Al) matrix. The structure of 1 mm sheets features by greater fineness and structure uniformity. The fine structure of deformed semi-finished products was analyzed using transmission electron microscopy (TEM), and this analysis showed that nanoparticles in the Al3(Zr, Sc) phase of the L12 structural type are maximum 20 nm in cross-section. The following level of mechanical properties was achieved in wrought semi-finished products: ultimate strength σв ~ 310330 MPa, yield strength σ0,2 ~ 250280 MPa with relative elongation δ ~ 4.57.0 %. The possibility of TIG welding using standard AMg5 wire as a filler material was studied. It was shown that the new alloy demonstrated no tendency to form hot cracks. According to the results of X-ray tomography, the percentage of porosity in the weld was 1.27 vol.%. The prevalent pore diameter did not exceed 0.2 mm. In general, the resulting structural and qualitative parameters of weld joints contribute to obtaining a strength of 75 % of the strength index of the initial wrought semi-finished products (sheets) achieved by stabilizing annealing at t = 350 °С for 3 hours.

Effect of Controlled Artificial Disorder on the Magnetic Properties of EuFe2(As1-xPx)2 Ferromagnetic Superconductor.

Static (DC) and dynamic (AC, at 14 MHz and 8 GHz) magnetic susceptibilities of single crystals of a ferromagnetic superconductor, (x = 0.23), were measured in pristine state and after different doses of 2.5 MeV electron or 3.5 MeV proton irradiation. The superconducting transition temperature, , shows an extraordinarily large decrease. It starts at in the pristine sample for both AC and DC measurements, but moves to almost half of that value after moderate irradiation dose. Remarkably, after the irradiation not only moves significantly below the FM transition, its values differ drastically for measurements at different frequencies, ≈16 K in AC measurements and ≈12 K in a DC regime. We attribute such a large difference in to the appearance of the spontaneous internal magnetic field below the FM transition, so that the superconductivity develops directly into the mixed spontaneous vortex-antivortex state where the onset of diamagnetism is known to be frequency-dependent. We also examined the response to the applied DC magnetic fields and studied the annealing of irradiated samples, which almost completely restores the superconducting transition. Overall, our results suggest that in superconductivity is affected by local-moment ferromagnetism mostly via the spontaneous internal magnetic fields induced by the FM subsystem. Another mechanism is revealed upon irradiation where magnetic defects created in ordered lattice act as efficient pairbreakers leading to a significant reduction upon irradiation compared to other 122 compounds. On the other hand, the exchange interactions seem to be weakly screened by the superconducting phase leading to a modest increase of (less than 1 K) after the irradiation drives to below . Our results suggest that FM and SC phases coexist microscopically in the same volume.

Properties of stream interaction regions at Earth and Mars during the declining phase of SC 24

Aims.We inspect the evolution of stream interaction regions (SIRs) from Earth to Mars, covering the distance range 1–1.5 AU, over the declining phase of solar cycle 24 (2014–2018). So far, studies only analyzed SIRs measured at Earth and Mars at different times. We compare existing catalogs for both heliospheric distances and arrive at a clean dataset for the identical time range. This allows a well-sampled statistical analysis and for the opposition phases of the planets an in-depth analysis of SIRs as they evolve with distance.Methods.We use in situ solar wind data from OMNI and the Mars Atmosphere and Volatile EvolutioN spacecraft as well as remote sensing data from Solar Dynamics Observatory. A superposed epoch analysis is performed for bulk speed, proton density, temperature, magnetic field magnitude and total perpendicular pressure. Additionally, a study of events during the two opposition phases of Earth and Mars in the years 2016 and 2018 is conducted. SIR related coronal holes with their area as well as their latitudinal and longitudinal extent are extracted and correlated to the maximum bulk speed and duration of the corresponding high speed solar wind streams following the stream interaction regions.Results.We find that while the entire solar wind high speed stream shows no expansion as it evolves from Earth to Mars, the crest of the high speed stream profile broadens by about 17%, and the magnetic field and total pressure by about 45% around the stream interface. The difference between the maximum and minimum values in the normalized superposed profiles increases slightly or stagnates from 1–1.5 AU for all parameters, except for the temperature. A sharp drop at zero epoch time is observed in the superposed profiles for the magnetic field strength at both heliospheric distances. The two opposition phases reveal similar correlations of in situ data with coronal hole parameters for both planets. Maximum solar wind speed has a stronger dependence on the latitudinal extent of the respective coronal hole than on its longitudinal extent. We arrive at an occurrence rate of fast forward shocks three times higher at Mars than at Earth.

The precipitation behaviours and strengthening mechanism of a Cu-0.4 wt% Sc alloy

The phase transformation sequence of the precipitation in Cu-Sc alloy is found as: supersaturated solid solution→Sc-rich atomic clusters→coherent metastable phase→Cu 4 Sc phase. The tetragonal structured lamellar Cu 4 Sc precipitates with orientation relationships of 0 2 ¯ 2 α / / 211 and 011 α / / [ 11 3 ¯ ] are homogenously distributed in the matrix. A combined process of cryogenic rolling and aging is designed for optimization of the mechanical and electric properties. An excellent integration of yield strength (695.8 MPa) and electrical conductivity (62.84% IACS) is achieved by cryogenic rolling and subsequent aging at 400 °C for 4 h. This high effective strengthening effect of Cu-0.4 wt% Sc alloy is probably due to the superposition of coherent strengthening and Orowan strengthening. • A new type binary copper alloy with scandium addition is designed. • The process of cryogenic rolling and aging is designed for properties optimization. • Lamellar Cu 4 Sc precipitates of tetragonal structure are found in the matrix. • Precipitation strengthening effect attributes to the mechanism superposition. The precipitation behaviours during the aging process and the corresponding strengthening mechanism of a Cu-0.4 wt% Sc alloy were systematically investigated in this study. The phase transformation sequence of the precipitation in the aging process of the Cu-0.4 wt% Sc alloy was found to be: supersaturated solid solution→ Sc-enriched atomic clusters→ metastable phase→Cu 4 Sc phase. The tetragonal structured lamellar Cu 4 Sc precipitates, with a habit plane parallel to the {111} plane of the Cu matrix and orientation relationships of 0 2 ¯ 2 α / / 211 Cu4Sc and 011 α / / [ 11 3 ¯ ] Cu4Sc , are found homogeneously distributed in the matrix. A combined process of cryogenic rolling (CR) and aging was designed for optimization of the mechanical and electrical properties. Excellent integration of yield strength (696 MPa) and electrical conductivity (62.8 % IACS) of this alloy was achieved by cryogenic rolling and subsequent aging process at 400 °C for 4 h. The significant precipitation strengthening effect of this alloy is attributed to the Cu 4 Sc precipitates with an extremely small size of only 1.5–3 nm. The leading strengthening mechanism is considered as the superposition of both coherent strengthening and Orowan strengthening effects.