Transformer cores exhibiting higher operating power and improved efficiency are of great interest to electrical utilities, industry, and the de-carbonization effort. Minnealloy, α″-Fe16(C,N)2, a martensite made only of iron, nitrogen, and carbon, has shown the largest saturation magnetization of any soft ferromagnet, 250 emu/g, and tunable magnetocrystalline anisotropy. Given this represents a significant increase in power transferred per cycle compared to legacy transformer core materials, we investigate three novel, industrially scalable routes for fabricating Minnealloy. The martensite phase content is investigated for each route. Vibrating sample magnetometry is used to investigate the change in saturation magnetization and coercivity with respect to the relative content of the desired phase and other iron, iron-nitride, and iron oxide phase impurities. The relationship between structure and magnetic properties of bulk α″-Fe16(C,N)2 is investigated using LDA, PBE, and PBEsol exchange-correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U).

The magnetostrictive response of a Terfenol-D pellet was measured via a laboratory-based X-ray diffractometer. X-ray diffraction patterns were collected from the pellet sample with and without the presence of an applied magnetic field (~30 mT) generated by placing a large magnet under the pellet. A standard reference material, Silicon 640c, was employed as an internal standard. Magnetostriction values of 323 and 227 ppm Δ l / l were determined for the (104) and (110) indexed peaks, respectively, assuming a rhombohedral structure for Terfenol-D. A threshold noise level value of ~20 to 30 ppm Δ l / l was suggested based on before/after measurements in the absence of the applied field. No clear evidence of domain wall rotation was detected via changes in relative intensities of diffraction peaks in the presence of the applied magnetic field.

Electrical polarization and defect transport are examined in 0.8BaTiO(3)-0.2BiZn(0.5)Ti(0.5)O(3), an attractive capacitor material for high power electronics. Oxygen vacancies are suggested to be the majority charge carrier at or below 250 degrees C with a grain conduction hopping activation energy of 0.97 eV and 0.92 eV for thermally stimulated depolarization current (TSDC) and impedance spectroscopy measurements, respectively. At higher temperature, thermally generated electronic conduction with an activation energy of 1.6 eV is dominant. Significant oxygen vacancy concentration is indicated (up to similar to 1%) due to cation vacancy formation (i.e., acceptor defects) from observed Bi (and likely Zn) volatility. Oxygen vacancy diffusivity is estimated to be 10(-12.8) cm(2)/s at 250 degrees C. Low diffusivity and high activation energies are indicative of significant defect interactions. Dipolar oxygen vacancy defects are also indicated, with an activation energy of 0.59 eV from TSDC measurements. The large oxygen vacancy content leads to a short lifetime during high voltage (30 kV/cm), high temperature (250 degrees C) direct current (DC) electrical measurements.

Phase formation and stability of five component compositionally complex rare earth zirconates (5RE(2)Zr(2)O(7)) were investigated by X-ray diffraction and electron microprobe analysis. Zirconates with different rare earth compositions (LaNdSmEuDy, LaNdSmEuYb, LaNdEuErYb, LaNdDyErYb, SmEuDyYHo, LaYHoErYb, and DyYHoErYb) were synthesized at 1700 & DEG;C and 2000 & DEG;C by the solid-state method to investigate the effect of A-site site disorder (& delta;(A)) on phase stability. Increased site disorder results from mixed cation occupancy with localized crystallographic strain and bond disorder. Compositions LaNdSmEuDy (& delta;(A) = 4.6) and LaNdSmEuYb (& delta;(A) = 6.0) produced a single pyrochlore phase and compositions SmDyYHoErYb (& delta;(A) = 2.8), LaYHoErYb (& delta;(A) = 6.2), and DyYHoErYb (& delta;(A) = 1.7) produced a single fluorite phase. High & delta;(A) compositions LaNdEuErYb (& delta;(A) = 6.9) and LaNdDyErYb (& delta;(A) = 7.2) produced a pyrochlore and fluorite phase mixture at 1700 & DEG;C. Single phase was obtained for the latter composition at 2000 & DEG;C. Of the single phase compositions calcined at 1700 & DEG;C, LaNdSmEuYb and LaYHoErYb (both with largest & delta;(A)) showed decomposition to mixed fluorite and pyrochlore phases during lower temperature anneals, indicating entropic stabilization. Comparison with prior work shows a temperature dependence of the critical & delta;(A) for phase stability, and compositions near it are expected to be entropy stabilized.

Phase transformations under high strain rates (dynamic compression) are examined in situ on ZrW2O8, a negative thermal expansion ternary ceramic displaying polymorphism. Amorphization, consistent with prior quasi-static measurements, was observed at a peak pressure of 3.0 GPa under dynamic conditions, which approximate those expected during fabrication. Evidence of partial amorphization was observed at lower pressure (1.8 GPa) that may be kinetically restrained by the short (<∼150 ns) time scale of the applied high pressure. The impact of kinetics of pressure-induced amorphization from material fabrication methods is briefly discussed.

Low-temperature molten sodium batteries comprising molten sodium anodes, a NaSICON solid-state separator, and molten halide salt catholytes offer promise as low-cost, earth-abundant energy storage technologies. The emergence of a specific, high-voltage, sodium iodide (NaI)-based catholyte chemistry has prompted the evaluation of chemical and electrochemical properties of the molten salts, particularly at critical interfaces with high-performance NaSICON separators. Herein, batteries operated at 110 degrees C with NaI-AlCl3-based catholytes of differing Lewis acidities were evaluated. Batteries with >50 mol % AlCl3 (acidic catholytes) experienced a linear decline in energy efficiency during cycling, whereas batteries with >50 mol % NaI (basic catholytes) maintained >95% energy efficiency for 50 cycles (>80 days) at 2.5 mA cm(-2). A three-electrode cell was developed, enabling identification of the NaSICON-catholyte interface as the source of increased battery impedance. Complementary physical and chemical characterization of the NaSICON exposed to acidic and basic catholytes showed no changes in crystallinity, bulk morphology, or bulk chemical composition, but surface sensitive X-ray photoelectron spectroscopy (XPS), however, revealed subtle changes in local NaSICON surface chemistry. In addition, Raman spectroscopy indicated that stably performing basic catholytes lack the dimer species Al2Cl6I- present in acidic catholytes. Select thermodynamic and formal charge assessments suggest that preferential interactions between these acidic dimeric species and the NaSICON surface may be responsible for the observed increases in electrochemical impedance and degraded battery performance. These results indicate that maintaining a Lewis basic catholyte avoids such potentially deleterious interactions, enabling efficient and stable battery cycling.

A combination of electrodeposition and thermal reduction methods have been utilized for the synthesis of ligand-free FeNiCo alloy nanoparticles through a high-entropy oxide intermediate. These phases are of great interest to the electrocatalysis community, especially when formed by a sustainable chemistry method. This is successfully achieved by first forming a complex five element amorphous FeNiCoCrMn high-entropy oxide (HEO) phase via electrodeposition from a nanodroplet emulsion solution of the metal salt reactants. The amorphous oxide phase is then thermally treated and reduced at 570-600 °C to form the crystalline FeNiCo alloy with a separate CrMnOx cophase. The FeNiCo alloy is fully characterized by scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy elemental analysis and is identified as a face-centered cubic crystal with the lattice constant a = 3.52 Å. The unoptimized, ligand-free FeNiCo NPs activity toward the oxygen evolution reaction is evaluated in alkaline solution and found to have an ∼185 mV more cathodic onset potential than the Pt metal. Beyond being able to synthesize highly crystalline, ligand-free FeNiCo nanoparticles, the demonstrated and relatively simple two-step process is ideal for the synthesis of tailor-made nanoparticles where the desired composition is not easily achieved with classical solution-based chemistries.

The composition and phase fraction of the intergranular phase of 94ND10 ceramic is determined and fabricated ex situ. The fraction of each phase is 85.96 vol% Al2O3 bulk phase, 9.46 vol% Mg-rich intergranular phase, 4.36 vol% Ca/Si-rich intergranular phase, and 0.22 vol% voids. The Ca/Si-rich phase consists of 0.628 at% Mg, 12.59 at% Si, 10.24 at% Ca, 17.23 at% Al, and balance O. The Mgrich phase consists of 14.17 at% Mg, 0.066 at% Si, 0.047 at% Ca, 28.69 at% Al, and balance O. XRD of the ex situ intergranular material made by mixed oxides consisting of the above phase and element fractions yielded 92 vol% MgAl2O4 phase and 8 vol% CaAl2Si2O8 phase. The formation of MgAl2O4 phase is consistent with prior XRD of 94ND10, while the CaAl2Si2O8 phase may exist in 94ND10 but at a concentration not readily detected with XRD. The MgAl2O4 and CaAl2Si2O8 phases determined from XRD are expected to have the elemental compositions for the Mg-rich and Ca/Si-rich phases above by cation substitutions (e.g., some Mg substituted for by Ca in the Mg-rich phase) and impurity phases not detectable with XRD.