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The coordination chemistry of various fission and decay products, such as actinides and lanthanides, are crucial to the commercial deployment of molten salt reactors as they can affect the thermophysical properties. Here, we examined the structure, coordination environment, and physical properties such as the density and the vibrational density of states for three lanthanide species, namely Ce, Eu, and Sm in the LiCl–KCl eutectic system using a combination of quantum mechanics simulations and spectroscopic experiments. Quantum mechanics molecular dynamics (QM-MD) modelling was employed to determine the physical properties of each system resulting in accurate local coordination of each species. Then, the vibrational density of states (DOS) was determined using a two-phase thermodynamic modelling which was then compared to the experimentally obtained Raman spectra of the species in molten LiCl–KCl having the eutectic composition. We find that Ce3+, Eu3+ and Sm3+ all adopt octahedral local coordination environments in the eutectic salt composition in good agreement with experimental results. Ce3+ is found to fluctuate between an octahedral six-coordinated and a seven-coordinated structure due to the increased local proximity of Cl in the eutectic salt, resulting in a lower fluidicity/diffusivity than the other trivalent lanthanides studied. The thermophysical properties of the eutectic composition with trivalent lanthanides were not significantly different from the pure eutectic salt composition, but several changes were noted. [ABSTRACT FROM AUTHOR]

The continued development of molten salt reactors and concentrated solar power plants requires highly efficient and stable instruments that can efficiently monitor the chemical conditions of the molten salt during long‐term operation in both the fuel and coolant/heat transfer fluid loops. Sapphire (Al2O3) fibers have shown tremendous potential due to inherent radiation resistance and a broader operational range of temperature. In this work, computational thermodynamic modeling (CALPHAD) using the ThermoCalc software in conjunction with the SGTE (Scientific Group Thermodata Europe) Molten Salts (SALT1) and Pure Substances (Pure5) databases is applied to understand the compatibility of Al2O3 fibers with NaCl‐MgCl2 eutectic molten salt in the temperature range of 1500–2500 K. The thermodynamic calculations show that sapphire fibers are not expected to be stable over the long‐term when exposed to molten chloride salts at these temperatures. To improve the stability of these diagnostic fibers in molten salt environments, various pure metallic elements were evaluated as potential cladding materials for Al2O3 fibers. Based on the thermodynamic analysis, molybdenum (Mo) and nickel (Ni) could be effective cladding materials to enhance the stability of Al2O3 in NaCl‐MgCl2 chloride salt molten bath in the desired temperature range. Thus, the presence of Mo and Ni cladding can provide a protective coating against the corrosive molten salts, thus improving the stability of Al2O3. Additionally, it is also shown that Al2O3 remains stable up to 2400 K in the presence of preexisting Al2MgO4 and Al2NiO4 in the eutectic molten chloride bath environment. [ABSTRACT FROM AUTHOR]

Electrochemical corrosion testing was used to evaluate the corrosion resistance of four different nickel-based alloys, namely UNS N06230, UNS N06025, UNS N06617, and UNS N06625, in a molten nitrate salt that is used as a heat transfer media and thermal energy storage material in solar-thermal power plants. The tests were conducted at 500 °C to simulate near-maximum service temperature in the 3:2 by weight sodium nitrate: potassium nitrate mixture. All tested samples had corrosion current densities on the order of 10-4 A cm-2 with corrosion potentials varying from -227 mV to -66.2 mV vs Pt. The tested samples exhibited low corrosion current density in the range of 0.225 mA cm-2 to 0.431 mA cm-2. The morphology of the samples surfaces was studied using scanning electron microscopy which showed the formation of a surface film on all samples. Cross-sectional analysis was performed using focused ion beam scanning electron microscopy. The surface chemistry was ascertained using energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Raman spectra paired with XPS suggested the formation of various nickel-chromium-iron spinels on UNS N06625. These results show that UNS N06625 has the potential to be a material for use in solar-thermal plants. [ABSTRACT FROM AUTHOR]

Advances in 3D-printing technology was used to design and develop a customizable flow-type electrochemical microcell with analytical resolution similar to conventional glass capillary-based microcells. The advantages of this design are better and easier reproducibility, increased durability, and better control over design parameters. 3D printing was combined with conventional machining to enable rapid prototyping and testing of various flow designs and apertures sizes. Results from potentiodynamic polarization of copper demonstrated repeatability and accuracy in spatial resolution. Reproducibility of experimental area had 1.9%variation between different spots. The ease of use and endurance of the design was demonstrated through repeated use. [ABSTRACT FROM AUTHOR]

Exposure testing was performed on CoCrFeMnNi equiatomic high entropy alloy (HEA) produced via directed energy deposition additive manufacturing in NaNO3-KNO3 (60-40 wt%) molten salt at 500 °C for 50 h to evaluate the corrosion performance and oxide film chemistry of the HEA. Potentiodynamic electrochemical corrosion testing, scanning electron microscopy, focused ion beam milling coupled with energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectroscopy were used to analyze the corrosion behavior and chemistry of the HEA/nitrate molten salt system. The CoCrFeMnNi HEA exhibited a higher passive current density during potentiodynamic polarization testing than steel alloys SS316L and 4130 and the high-Ni alloy 800 H in identical conditions. The oxide film was primarily composed of a (Mn,Co,Ni)Fe2O4 spinel with a vertical plate-like morphology at the surface. Cr and Ni were found to be totally depleted at the outer surface of the oxide and dissolved in high concentrations in the molten salt. While Cr was expected to dissolve into the molten salt, the high concentration of dissolved Ni has not been observed with traditional alloys, suggesting that Ni is less stable in the spinel when Mn and Co are present. [ABSTRACT FROM AUTHOR]

Electrolytic water splitting offers energy storage and conversion opportunities, yet the slow kinetics of the oxygen evolution reaction requires the incorporation of catalytic materials. Herein, we present a facile method for the synthesis of a low-cost Ni-FeCo material that efficiently catalyzes the oxygen evolution reaction. A mixed transition metal electrocatalyst was synthesized using a nickel-plated iron substrate and a low concentration cobalt reagent. The catalyst was able to achieve competitive current densities (>130 mA cm−2 ) and still exhibit a low overpotential of 0.30 V at the benchmark current density of 10 mA cm−2 . The Ni-Fe-Co catalyst was stable and maintained its activity during 24 h of electrolysis in alkaline media. The catalyst was also stable when maintained in ambient conditions for 90 days. This is the first reported oxygen evolution reaction catalyst that exhibits these competitive characteristics and that was synthesized using an environmentally-conscious, one-step process that can be manufactured on an industrial scale. [ABSTRACT FROM AUTHOR]

• Saccharomyces cerevisiae was immobilized in electrospun polymeric fibers. • Immobilized yeast was used for ethanol production in continuous flow reactor. • Ethanol was continuously produced for 2 weeks at yield >90%. Saccharomyces cerevisiae immobilized in electrospun Pluronic F127 dimethacrylate (FDMA) was successfully employed for the production of ethanol in an immobilized cell reactor. Yeast cells were immobilized into fibers formed through the process of electrospinning and cross-linking. The threads had an average diameter of 0.88 μm and were used in continuous-flow immobilized cell reactors. The immobilized cell reactors were able to maintain a high ethanol yield of >90% from day 4 through to the end of the time course at day 14. The reactor was able to achieve a maximum ethanol yield of 94.3%. This study shows that the use of electrospinning is a promising method for continuous ethanol production through immobilized cell-based continuous flow reactors. [ABSTRACT FROM AUTHOR]

This study explores the surface chemistry of Inconel 625 samples exposed to molten LiCl-Li2O-Li solutions at 650°C for 500 and 1000hr and aims to understand the effect of solvated Li on corrosion behavior in molten LiCl-Li2O-Li. The surfaces of Inconel 625 samples were analyzed using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The oxide films formed on the surface of the samples in the absence of Li is composed of LiCrO2, with small contributions of Li2CrO4 and NiFexCr2-xO4. The presence of Li was observed to destabilize these compounds, resulting in a primarily metallic surface with trace amounts of oxidized Cr, Mo, and Nb present depending on the concentration of Li in solution. [ABSTRACT FROM AUTHOR]

Abstract Exposure testing of Stainless Steel 316L was performed in LiCl-Li 2 O-Li solutions at 650 °C for periods of 500 and 1000 h to investigate the effect of metallic Li on corrosion of materials used to contain the LiCl-Li 2 O electrolyte for the electrolytic reduction of used nuclear fuel. Melt compositions studied consisted of LiCl containing 1 or 2 wt% Li 2 O and 0, 0.3, 0.6, or 1 wt% Li. Post exposure surface analysis was performed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Focused ion beam and mechanical cross sections of the samples and gravimetric analyses were performed to determine the time-averaged corrosion rate for each sample. Lithium metal induced attack rates were found to be as high as 2.91 mm/y. In the absence of solvated Li in the LiCl-Li 2 O system, LiCrO 2 , Li 2 CrO 4 , and NiFe x Cr 2-x O 4 were observed to be the primary corrosion products. When Li was present in the melt, the oxidized alloying elements were only detectable via X-ray photoelectron spectroscopy, and the surface was primarily comprised of bare metal. Highlights • SS316L exposed to molten LiCl-Li 2 O-Li undergoes intergranular attack. • Attack rates as high as 2.9 mm/year were observed in the presence of Li0. • LiCrO 2 , Li 2 CrO 4 , and NiFe x Cr 2-x O 4 were seen on SS316L surfaces in absence of Li0. • In the presence of Li0, no bulk oxide film forms to prevent further corrosion. • A transition between electrochemical and liquid metal attack occurs based on [Li0]. [ABSTRACT FROM AUTHOR]

The corrosion resistance of a Ni-Cu alloy, Monel 400, in molten LiCl-Li2O-Li at 923 K (650 °C) was investigated. Exposure testing of Monel 400 samples submerged in molten LiCl-2 wt pct Li2O solutions with Li concentrations between zero and 1 wt pct was performed at 923 K (650°C) for 20 hours. Post exposure surface analysis was performed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, optical microscopy, micro-Vickers hardness testing, and X-ray photoelectron spectroscopy, while inductively coupled plasma optical emission spectroscopy was used to quantify the rate of material leaching. The extent of material degradation was observed to be strongly correlated to the concentration of metallic Li in the molten LiCl-Li2O system. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic behavior of microbially‐formed palladium nanoparticles using Clostridium pasteurianum BC1 is reported. To our knowledge, this is the first study that evaluates the electrochemical catalytic activity of microbially‐formed palladium nanoparticles. Pd nanoparticles formed using immobilized microbes were found to exhibit an average mass activity of 177 mA mg−1 which was almost twice the activity of the abiotically formed controls (94 mA mg−1). The results of this study aim to support the use of nanoparticles formed using facile and environmentally‐friendly microbial synthesis methods as a suitable alternative as opposed to standard physical and chemical synthesis methods. [ABSTRACT FROM AUTHOR]

A knowledge gap exists in our understanding of corrosion of alloys in molten LiCl-Li 2 O-Li. Coupons of stainless steel alloy 316L were exposed to LiCl-Li 2 O solutions containing up to 1 wt%Li. A protective surface films of LiCrO 2 forms in molten solutions containing up to 0.4 wt%Li. The surfaces of samples exposed to melts containing greater than 0.4 wt% Li were observed to be depleted of Cr and mostly devoid of oxides. Results indicate that material interactions with the LiCl-Li 2 O-Li system are governed by electrochemical oxidation phenomena when the Li concentration is low, while liquid metal effects dominate when the Li concentration is high. [ABSTRACT FROM AUTHOR]

Extensive research and process development has been conducted on the electrolytic reduction of actinide oxides inmolten LiCl-Li2O. It is now accepted that the reduction of these metal oxides occurs via two separate reduction mechanisms: direct electro-chemical reduction and mediated chemical reduction by metallic lithium. The deposition of metallic lithium at the cathode (mediated chemical reduction mechanism) during the process is known to be essential in order to achieve high process throughputs and reduction yields, and yet a knowledge gap exists regarding the nature of metallic lithium in this system. This review summarizes the formation of lithium during the process and its dispersion into the molten salt electrolyte. Previously reported aspects of the physical chemistry of the LiCl-Li2O-Li system are presented with a specific focus on the dispersion of Li in the solution. Finally, issues regarding the effect of the presence of lithium on the electrolytic reduction process are discussed. Evidence shows that electrochemically generated metallic lithium is likely a significant source of experimental uncertainty, low current efficiency and Li2O consumption in the oxide reduction process. [ABSTRACT FROM AUTHOR]

INCONEL alloy 625® (I625) was exposed to molten LiCl-Li2O-Li to evaluate the material reliability for applications involving the electrolytic reduction of uranium oxide. Samples of I625 were exposed to solutions of LiCl with 1 and 2 wt% Li2O, containing either 0, 0.5, or 1 wt% metallic lithium for 20 h at 650°C. Additional experiments exposed samples to LiCl saturated with Li2O to investigate the mechanism of interaction between materials and the melt. Postexposure sample surface morphology and chemistry were studied using scanning electron microscopy and X-ray photoelectron spectroscopy. Additionally, inductively coupled plasma-optical emission spectroscopy was used to analyze the melt to determine the alloy constituents that leached out of the coupon during the exposure. The inclusion of 0.5 wt% metallic lithium in the molten solution was found to increase the stability of chromium-rich surface films and suppress the dissolution rate of alloying elements, compared to melts of LiCl-Li2O containing no metallic Li. Alternatively, samples exposed to solutions containing 1 wt% metallic lithium did not form surface films and demonstrated evidence of chromium depletion. The degradation of materials exposed to solutions containing 1 wt% metallic lithium was observed to be different from samples exposed to solutions saturated with lithium oxide, demonstrating a chemical effect other than, or in addition to, salt basicity. [ABSTRACT FROM AUTHOR]

This work investigates two austenitic stainless steels, Nitronic-50 and stainless steel 316, for use in both subcritical and supercritical water (SCW) conditions. The mechanical characteristics of the materials were investigated using slow strain rate testing in a SCW test loop under the following conditions: nitrogen at ambient temperature and pressure, liquid water at 473 K (200 °C) and 8 MPa, liquid water at 573 K (300 °C) and 15 MPa, and SCW at 698 K (425 °C) and 27 MPa. The surfaces of the failed samples were characterized using Raman spectroscopy, and X-ray photoelectron spectroscopy. Nitronic-50 was found to have superior mechanical strength characteristics at all conditions compared to stainless steel 316. At all elevated temperature conditions, stainless steel 316 was found to have a surface film consisting of iron oxides, while the surface film of Nitronic-50 predominantly consisted of nickel-iron spinel. [ABSTRACT FROM AUTHOR]

Due to its wide gap, WO 3 mostly absorbs only the ultraviolet radiation, resulting into lower charge collection and thus necessitating the coupling (doping or sensitization) of WO 3 with low band gap materials so as to achieve the photoexcitation and charge separation. This study reports the sensitization of WO 3 films with ternary quantum dots (ZnCdSe) using SILAR technique for the first time. The porous WO 3 layer was spray deposited using ammonium metatungstate as precursor. The structural, surface morphological and optical properties of the sensitized WO 3 thin films were studied. Photoelectrochemical (PEC) studies of the sensitized films showed superior performance to that of unmodified WO 3 films. Photocurrent density of 8.53 mA/cm 2 (at 0 V vs Ag/AgCl) was observed for film sensitized with 9 cycles of SILAR deposition annealed at 400 °C under nitrogen atmosphere, which is a 120-fold and 14-fold increase in photocurrent density when compared to unsensitized WO 3 film and WO 3 /TiO 2 film, respectively. Sensitization with ternary quantum dots as ZnCdSe thus offers two advantages: (i) the lower band gap of ZnCdSe allows it to absorb more energy and in turn produce more charge carriers and (ii) the conduction band of ZnCdSe, which lies above the conduction band of TiO 2 , results in a better charge transfer from sensitizer to the substrate material. [ABSTRACT FROM AUTHOR]