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While thermodynamic reference electrodes with known and stable potentials are common in traditional aqueous systems, the high temperature and corrosive environment of a molten fluoride salt makes achieving long term stability with a thermodynamic reference electrode challenging, especially at temperatures of 600°C or higher. In this work, a thermodynamic reference electrode consisting of U(IV)/U(III) in a boron nitride compartment was evaluated for use in FLiBe at temperatures ≥ 600°C. FLiBe used in the study was purified by AlphaTech's proprietary process and characterized by ICP-MS and square wave voltammetry. The free oxide concentration was <2 ppm. Using the purified FLiBe, the U(IV)/U(III) thermodynamic reference electrode was shown to provide a stable, well-defined, and reproducible potential for more than 600+ hours of use in different tests. Moreover, the thermodynamic reference electrode showed a consistent potential with no signs of failure, even after being cooled between tests and then reheated for reuse. Thus, the U(IV)/U(III) reference electrode is suitable for use in rigorous electrochemical studies in molten fluoride salts. As a result, it may be useful as a common standard, facilitating the advancement of nuclear applications such as isotope separation or online monitoring of reactor systems through improved certainty in the measurement of thermodynamic potentials.

Abstract The realization of low thermal conductivity at high temperatures (0.11 W m ⁻¹ K ⁻¹ 800 °C) in ambient air in a porous solid thermal insulation material, using stable packed nanoparticles of high‐entropy spinel oxide with 8 cations (HESO‐8 NPs) with a relatively high packing density of ≈50%, is reported. The high‐density HESO‐8 NP pellets possess around 1000‐fold lower thermal diffusivity than that of air, resulting in much slower heat propagation when subjected to a transient heat flux. The low thermal conductivity and diffusivity are realized by suppressing all three modes of heat transfer, namely solid conduction, gas conduction, and thermal radiation, via stable nanoconstriction and infrared‐absorbing nature of the HESO‐8 NPs, which are enabled by remarkable microstructural stability against coarsening at high temperatures due to the high entropy. This work can elucidate the design of the next‐generation high‐temperature thermal insulation materials using high‐entropy ceramic nanostructures.

We report the performance of coplanar, multifilament waveguides manufactured from crystalline films of a well-known HTS compound, YBCO, transferred to a low-loss dielectric substrate, such as E-Kapton. The coplanar two-line waveguide delivers low cross-talk, below 20 dB level, and low attenuation, below 4 dB/m at 6 GHz, 77 K. Controlled-impedance 50 Ω waveguides would require a method for reliable patterning narrow, less than 100-micron wide, YBCO traces over a meter length. We report a lithography-etching approach that minimizes the difference in the etching rate of YBCO and the metallization layers of Ag and Cu. An array of metalized vias isolates the traces. Here, we describe the via metallization process that is not damaging to YBCO and compatible with dense, 2 mm period, arrays of vias.

Embedding fiber optic sensors in critical components is a key step for real-time monitoring of structural conditions during service and supporting autonomous system operations. Successful integration of these sensors necessitates effective interfacial bonding between the fiber and matrix, good integrity and functionality of the embedded sensors, robust mechanical strength of the matrix materials, and the ability to retain these properties during transient thermal and stress events. This study demonstrates the encapsulation of fused silica optical fibers in stainless steel and nickel through the electric field-assisted sintering (EFAS) process. Copper-coated and gold-coated single mode optical fibers were embedded under different EFAS conditions. The resulting components with embedded sensors were evaluated using advanced microscopy and optical frequency domain reflectometry (OFDR) to assess the aforementioned critical aspects of embedding. The results indicate that both copper- and gold-coated fibers can be successfully embedded in stainless steel and nickel with good fiber integrity and fiber-matrix bonding. Samples fabricated under optimal conditions passed helium leak testing, confirming effective interfacial bonding. Microstructural characterization revealed excellent fiber-matrix adhesion and interdiffusion of elements across the interface. The functionality of the embedded fibers was evaluated through OFDR scans, which revealed signal insertion loss of 0.43–0.52 dB for nickel samples and 0–0.75 dB for stainless steel samples at the embedding sites. Additionally, the embedded fibers underwent cyclic thermal treatment between 500 °C and 700 °C. The fibers maintained good integrity and interfacial characteristics, demonstrating their ability to survive cyclic thermal events for sensing in harsh environments.

Silicon-based microelectronics are limited to ~150°C and therefore not suitable for the extremely high temperatures in aerospace, energy, and space applications. While wide-band-gap semiconductors can provide high-temperature logic, nonvolatile memory devices at high temperatures have been challenging. In this work, we develop a nonvolatile electrochemical memory cell that stores and retains analog and digital information at temperatures as high as 600°C. Through correlative scanning transmission electron microscopy, we show that this high-temperature information retention is a result of composition phase separation between the oxidized and reduced forms of amorphous tantalum oxide. This result demonstrates a memory concept that is resilient at extreme temperatures and reveals phase separation as the principal mechanism that enables nonvolatile information storage in these electrochemical memory cells.

Numerous high-value applications within the energy sector involve environmental conditions that are incompatible with traditional sensor technology due to degradation of electrical interconnects, packaging, or the sensors themselves. These can include chemically harsh conditions, high temperature operation, or the presence of electromagnetic interference due to high voltage. The fiber optic platform, constructed of robust, electrically insulating glass or single crystal oxides, offers a versatile and often low cost per node solution to this problem, especially with the integration of distributed sensing techniques such as optical time-domain and frequency-domain reflectometry (OTDR, OFDR). A major challenge of gas and chemical sensing on the optical fiber platform is the fabrication of robust and stable sensing materials that interact quickly and reversibly to the presence of the target analytes. In this work, we discuss the utilization of nickel-incorporated oxides on evanescent-field optical fiber sensors for gas sensing under harsh conditions relevant to multiple energy infrastructure applications. This paper will discuss a Ni/GDC (Ni / Gd-doped ceria) based sensing layer targeting conditions relevant for high-temperature (up to at least 800oC) hydrogen sensing applications (e.g., for operation within a solid oxide fuel cell or electrolyzer). The impact of hydrogen at elevated temperatures on the optical properties of Ni/GDC will be shown and the material mechanisms for the optical response will be discussed.

Recent strategy updates by the international particle physics community have confirmed strong interest in a next-generation energy frontier collider after completion of the High-Luminosity LHC program and construction of a e⁺e^- Higgs factory. Both hadron and muon colliders provide a path toward the highest energies, and both require significant and sustained development to achieve technical readiness and optimize the design. For hadron colliders, the energy reach is determined by machine circumference and the strength of the guiding magnetic field. To achieve a collision energy of 100 TeV while limiting the circumference to 100 km, a dipole field of 16 T is required and is within the reach of niobium–tin magnets operating at 1.9 K. Magnets based on high-temperature superconductors may enable a range of alternatives, including a more compact footprint, a reduction of the cooling power, or a further increase of the collision energy to 150 TeV. The feasibility and cost of the magnet system will determine the possible options and optimal configurations. In this article, I review the historical milestones and recent progress in superconducting materials, design concepts, magnet fabrication, and test results and emphasize current developments that have the potential to address the most significant challenges and shape future directions.

Steady-state deuterium plasma exposures were performed on ultra-high temperature ceramics titanium diboride (TiB₂) and zirconium diboride (ZrB₂) using the PISCES-RF linear plasma device (LPD) as early screening for first wall, plasma-facing applications. Deuterium plasma exposures were performed using 40 eV ion energies at 240, 525, and 800 °C sample temperatures and 90 eV ion energies at 240 °C sample temperatures to analyze TiB₂ and ZrB₂ surface morphology and chemistry evolution behavior. Post-plasma exposure chemistry characterization of the near surface (<50 nm) region of the samples all show transition metal enrichment, indicating boron preferential erosion. Transition metal to boron fractions vary with plasma exposure temperature under the 40 eV ion energy; metal enrichment is maximized at 800 °C and then minimized at 525 °C. SEM micrographs of all plasma exposed sample surfaces show no significant or noticeable plasma induced damage from cracking or blistering.

Motivated by the recently reported signatures of superconductivity in trilayer La₄⁢Ni₃⁢O₁₀ under pressure, here we comprehensively study this system using ab initio and random-phase approximation techniques. Without electronic interactions, the Ni d_3z²–r² orbitals show a bonding-antibonding and nonbonding splitting behavior via the O p_z orbitals inducing a “trimer” lattice in La_4⁢Ni₃⁢O₁₀, analogous to the dimers of La₃⁢Ni₂⁢O₇. The Fermi surface consists of three electron sheets with mixed e_g orbitals, and a hole and an electron pocket made up of the d_{3⁢z²–r²} orbital, suggesting a Ni two-orbital minimum model. In addition, we find that superconducting pairing is induced in the s^±-wave channel due to partial nesting between the M = (π,π) centered pockets and portions of the Fermi surface centered at the Γ = (0,0) point. With changing electronic density n, the s^± instability remains leading and its pairing strength shows a domelike behavior with a maximum around n = 4.2 ( ~6.7% electron doping). The superconducting instability disappears at the same electronic density as that in the new 1313 stacking La₃⁢Ni₂⁢O₇, correlated with the vanishing of the hole pocket that arises from the trilayer sublattice, suggesting that the high-T_c superconductivity of La_3⁢Ni₂⁢O₇ does not originate from a trilayer and monolayer structure. Furthermore, we confirm the experimentally proposed spin state in La₄⁢Ni₃⁢O₁₀ with an in-plane (π, π) order and antiferromagnetic coupling between the top and bottom Ni layers, and spin zero in the middle layer.

The development of space and water heating combination heat pumps capable of generating water temperatures high enough for convective heat emitters will enable more cost-effective and equitable decarbonization solutions for electrifying multifamily buildings. Here, in this paper, multifamily building models and a charge-sensitive mechanistic cycle model of a combination heat pump are developed, and the system performance is predicted based on the models. Unlike other state-of-the-art residential heat pumping equipment, the modeled combination heat pump using an economized, fluid-injected variable-speed compressor can achieve higher temperature lifts of 40° - 85°C, with lower installation costs and complexity. The model predicted heating coefficient of performance (COP_h) is 2.1 at an ambient temperature of -15°C with a high-temperature lift of nearly 85°C, and a seasonal coefficient of performance in heating mode (SCOP_h) ranges from 2 - 4 for different locations. The system shows 30% - 90% lower CO₂eq emissions over a condensing gas boiler and 9% - 13% lower projected installation costs than two separate space and water heat pumping appliances.