bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalytic and Spectroscopic Studies on Cytochrome Bd Oxidase, a Highly Diverse Bacterial Defense Factor
Authors: Makarchuk Iryna , Kaegi Jan , Melin Frederic , Friedrich Thorsten , Hellwig Petra
Published: September 2023

The selective reduction of oxygen to water is crucial to life and a central process in aerobic organisms. It is catalyzed by several different enzymes, including cytochrome bd oxidases that are solely present in prokaryotes, including several pathogens. In addition, these enzymes play a crucial role in protection against oxidative stress, in virulence, adaptability and antibiotics resistance. The reduction of O2 occurs at the high spin D-type heme in all cytochrome bd oxidases, that is also the binding site for several ligands from signaling processes, including NO, H2S and CO.

Here we present the electrocatalytic study of the cytochrome bd I and bd II oxidases from Escherichia coli
(1,2) as well on other related bd oxidases. Structural parameters that are crucial for the reactivity towards oxygen are analyzed. The pH dependency of the binding and release of NO, an important signaling factor is presented. The influence of mutants in the proton channel on the NO release is discussed.

(1) Grauel, A. Kägi, J. Rasmussen, T. Makarchuk, I. Oppermann, S. Moumbock, A., Wohlwend, D., Müller, R., Melin, F., Günther, S., Hellwig, P., Böttcher, B., and Friedrich, T., ‘Structure of Escherichia coli cytochrome bd-II type oxidase with bound aurachin D’ (2021) Nat. Commun., 12:6498.

(2) Nikolaev, A., Safarian, S., Thesseling, A., Wohlwend, D., Friedrich, T., Michel, H., Kusumoto, T., Sakamoto, J., Melin, F., Hellwig P. ‘Electrocatalytic evidence of the diversity of the oxygen reaction in the bacterial bd oxidase from different organisms’ (2021) Biochim. Biophys. Acta 1862, 148436.
Ring-Closing Reactions of Porphyrins on Noble Metal Surfaces
Authors: Auwarter Wilhelm
Published: September 2023

On-surface chemistry protocols provide elegant routes to individual molecular complexes, oligomers, and hybrid structures at confining interfaces, yielding distinct chemical, physical, and structural properties [1]. In this context, porphyrins and other tetrapyrroles represent versatile precursors that can undergo metalation, ring-opening, and ring-closing reactions. Furthermore, they are often used as functional tectons for self-assembled molecular films, metal-organic coordination networks, and covalent architectures at interfaces [2].

We will report on temperature-induced ring-closing reactions of porphyrins on single crystalline Ag and Au surfaces in an ultrahigh vacuum environment. Examples covered include dehydrogenative homocoupling as well as intramolecular ring-closing. Specifically, distinct oligomers including square-type porphyrin tetramers featuring a planar, central antiaromatic cyclooctatetraene (COT) moiety were achieved on a Ag(100) support by employing unsubstituted Zn- and free-base porphines (see Figure) as precursors [3]. Low-temperature scanning tunnelling microscopy (STM), spectroscopy (STS), and bond-resolved atomic force microscopy (AFM) supported by complementary theoretical modelling were used to comprehensively characterize chemical structure and electronic properties of the square-type tetramers with sub-molecular resolution. Furthermore, the synthesis of π-extended oxygen-embedded porphyrins via O-annulation on Au(111) will be discussed. This surface chemical approach yields high selectivity and yield for planar porphyrin products with distinct symmetries and oxygen content that is not achieved by solution chemistry. The bond-resolved AFM characterization is complemented by X-ray photoelectron spectroscopy measurements. These studies thus give access, and insights, to novel porphyrinoids with distinct properties on noble metal supports.

References

[1] L. Grill, S. Hecht, Nat. Chem. 12, 115 (2020)

[2] W. Auwärter et al., Nature Chem. 7, 105 (2015)

[3] E. Corral Rascon et al., J. Am. Chem. Soc., accepted

Figure 1
(Invited) Catalytic Growth of Width-Controlled Single Atomic Layer MoS2 Sub-10nm Nanoribbons
Authors: Harutyunyan Avetik R. , Li Xufan
Published: September 2023

For the next generation materials for optoelectronics, quantum computing, communication and sensing, single atomic layer semiconducting nanoribbons offer additional degree of freedoms for engineering their properties. However, direct width-controlling synthesis of TMD nanoribbons, especially for the appealing width range below 30 nm, remains challenge. Therefore, developing facile methods for their direct and controllable synthesis is of central importance. We present a new growth method for single and double atomic layer of MoS2 nanoribbons with width down to sub-10 nm. Nanoribbons are grown via precipitation from the Ni-contained composite nanoparticles via vapor-liquid-solid mechanism in which the nanoparticle diameter also controls the width of nanoribbon. We also present preliminarily studies on width-dependent properties of the nanoribbons, which evidence their potential application in the quantum electronics, particularly as a single electron transistor and single photon emitter.
(Invited) Xtalic: Building an Advanced Material Technology Company from Scientific Breakthroughs at MIT
Authors: Clay Tom , Legg Rob
Published: September 2023

Xtalic first commercialized their flagship nanostructured metal alloy XTRONIC with Amphenol in 2008. Since then XTRONIC has scaled to 70% of high-speed internet connections and more than 2 billion smartphones, saving more than $100 million in gold and 78 Million kg of CO2through reduced mining and refining.

As our world continues to electrify, miniaturize, and push for the next generation of product features we will need new sustainable material solutions to pave the path. Building on a strong relationship with MIT, Xtalic has expanded their capabilities to quickly design, engineer and commercialize advanced material technologies across new products and applications.

As a case study in building a company from scientific breakthroughs at MIT, this talk will cover the trials and successes from initial customer engagements through mass production deployments with some of the largest OEMs in the world.
(Invited) NSF Advanced Manufacturing Program and Nanomanufacturing Research
Authors: Cooper Khershed
Published: September 2023

NSF’s Advanced Manufacturing (AM) program supports transformative advances in materials engineering, processing and manufacturing and fosters multidisciplinary research that applies innovative manufacturing approaches to accelerate new product development, customize products, increase production efficiency and reduce production cost. AM is a basic research program the outcomes of which could lead to applications of interest to Industry. The AM program engages industry participation through the GOALI mechanism and through collaborations with the Manufacturing USA Institutes. The AM portfolio includes the entire spectrum of manufacturing processes including nanomanufacturing. Nanomanufacturing is the fabrication of nanoscale (1-100 nm) building-blocks, their assembly into higher-order structures, and the integration of these into larger scale systems. Nanomanufacturing research is the study of processes to manipulate and control matter at the nanoscale in 1-, 2-, and 3-dimensions, reproducibly. This presentation describes the AM program with a focus on Nanomanufacturing research and its role in cross-cutting initiatives.
(Invited) Opportunities for Lab-to-Market and Innovation Support at the National Science Foundation
Authors: Schrag Ben
Published: September 2023

The National Science Foundation offers support for translation of research into the market via a number of innovation programs, now housed in the new Technology, Innovation, and Partnerships (TIP) Directorate. These programs will be discussed at a high level, with a focus toward understanding how stakeholders from academia, industry, and government can engage with these programs. Programs covered will include Small Business Innovation Research, Small Business Technology Transfer, Innovation Corps, Pathways to Enable Open-Source Ecosystems, Partnerships for Innovation, and other NSF opportunities. The talk will also briefly touch on the societal and economic impacts of these programs over the past decades, with some examples of success stories that have benefitted from multiple of these opportunities. Finally, the talk will discuss the motivations for the creation of the TIP Directorate as well as potential concepts that might inform the future expansion of TIP.
Electrochemical Study of Zinc Adsorption on Yttria-Stabilized Zirconia-Water Interfaces
Authors: Brown Austin , Hou Binyang
Published: September 2023

Research has shown that zinc ions can mitigate the corrosion of the alloy materials in nuclear power plants in addition to reducing radiation contaminations. Understanding how zinc ions alter the interfacial structure of the alloy surface is therefore important in improving the life cycle of the materials and achieving higher burnups of the nuclear fuels. While the corrosion mitigation of zinc on nickel and stainless-steel alloys has been widely studied and reported, its effect on zirconium oxide surfaces, i.e. the oxide layer of zirconium alloys exposed to the aqueous solution, has rarely been reported. Meanwhile, zirconium oxide also serves as the solid oxide fuel cell electrolyte in energy storage. The study of the corrosion mitigation mechanism on zirconia could also contribute to the successful commercialization of SOFC technologies as cleaner and more efficient energy conversion electrochemical systems. In this work, we utilize the electrochemical techniques to study the interfacial structure changes under the influence of zinc ions on the yttria-stabilized zirconia (YSZ) surfaces on the (100), (110), and (111) orientations in contact with aqueous solution with and without externally applied electric potentials. The experimental measurements indicated the modification of the interfacial structures by zinc on (100) and (111) surfaces is strongly influenced by the applied external electric fields, while the modification of surface structure by zinc ions is not as evident on the (110) surface. Our study also showed that the Zn2+ adsorption layers on the oxide surfaces could be better preserved by tuning the electric potential on the oxide substrates towards the negative potentials.
Interplay between Anodizing Parameters and Corrosion Resistance of Aluminum-Silicon Alloys
Authors: Bandiera Marco , Abello Mary Angel , Pavesi Arianna , Trombetta Valentina , Valota Giorgio , Bonfanti Andrea , Bertasi Federico
Published: September 2023

Aluminum alloys are widely used in the automotive, aerospace and construction fields due to their excellent physico-mechanical properties. Nevertheless, the corrosion resistance of bare Al alloys is often insufficient to meet the requirements of several industrial applications and protection strategies are needed. Among these, anodizing is particularly effective since it can lead to the formation of a compact and thick dielectric oxide layer with barrier and corrosion protection capabilities.

However, anodizing of highly alloyed Aluminum alloys (e.g. those with an alloy element concentration higher than 5%wt) can be particularly challenging due to the presence of intermetallic precipitates within the Al matrix which generates micro-galvanic coupling events with an associated thickness inhomogeneity of the obtained anodic layer [1].

In this context, the work investigates ten new current waveforms for anodizing of Aluminum Silicon alloys (AlSix). Particular attention is devoted to the interplay among waveform parameters (e.g. duty cycle, peak and rest step intensities), oxide layer morphology and corrosion resistance. In particular, metallography, voltammetry and contact angle methods are used in order to correlate different figures of merit with the anodic layer morphological features.

It is concluded that a careful optimization of the current waveform parameters can modulate the: a) corrosion current; b) corrosion potential; c) breakdown potential; and d) polarization resistance; of coated specimens. In conclusion, the most effective waveforms are identified and coated Aluminum alloy specimens with a remarkable corrosion resistance are obtained.

[1] M Bandiera, A Bonfanti, M Bestetti, F Bertasi, SAE International Journal of Advances and Current Practices in Mobility 3 (2), 973-979.
The Electrochemical Impedance Study of Corrosion Protection of Bronze by Waterborne Organic Coating/Phosphonic Acid Protective System
Authors: Otmacic Curkovic Helena , Kapitanovic Angela
Published: September 2023

The use of organic coatings is the most common method for corrosion protection of metals. However, the majority of the organic coatings are solvent borne. Nowadays, there is a great interest for their replacement by more environmentally friendly waterborne coatings. Unfortunately, their application poses practical problems due to their poor surface wetting, lower level of protection as well as the corrosion of metal substrate. This problem is especially pronounced in protection of bronze cultural heritage due to the requirement that coating does not change the visual appearance of the substrate, which limits the use of protective pigments in the coating. In addition, coating must successfully protect, not only the bronze substrate, but the adhering patina as well.

This work examines the use of waterborne acrylic coating in combination with pretreatment by a long-chain phosphonic acid as a solution for protection of bare and patinated bronze surface. Electrochemical impedance spectroscopy studies are conducted on bare and chemically patinated bronze protected by waterborne coating or by combined protection system phosphonic acid/waterborne coating. In this way it is possible to evaluate the influence of phosphonic acid pretreatment on overall coating protection. Studies are conducted under various aging conditions, including the continuous immersion into artificial acid rainwater, climatic chamber with NO2 introduction and outdoor exposure. The obtained results show that phosphonic acid pretreatment improves the overall corrosion protection level of acrylic coating as the phosphonic acid acts as a corrosion inhibitor. However, some differences in the EIS spectra evolution in time are observed when comparing the results from different aging conditions. This differences are related to the coating swelling and underlying patina transformation under studied corrosion conditions.

Acknowledgment: This work was fully supported funded by the Croatian Science Foundation under the project IP-2019-04-5030
Effect of Ti Corrostion on Separation of Electro-Deposited Cu Foil
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Li Zih-Jhun , Chou Hsing-Mei
Published: September 2023

Cu foils by electroplating are known for many industrial applications such as PCB and Li ion batteries. Ti metal is commonly used as the cathode for the Cu reduction from sulfate solution. Under an acidic and high temperature environment, the passivation layer on the surface of the titanium metal tends to react with acidic solution. As a result, the corrosion of the active titanium metal was observed. In this study, the corrosion behavior of commercial pure titanium in acid copper sulfate baths was investigated, and several surface treatments were used to improve the corrosion resistance of titanium passive layer. The microstructure of titanium metal after immersion in acid copper sulfate solution was examined by using SEM and FIB. The pitting corrosion of Ti was clearly observed using SEM. The corrosion mechanism of the titanium metal in the sulfuric acid solution was discussed. In addition, the electrochemical characteristics of commercial pure titanium metal in sulfuric acid solution were also analyzed using the three-pole potential measurement method.
Plasma-Catalytic Methane Pyrolysis for Hydrogen and Valuable Carbons
Authors: Noudari Abhinav , Pathak Shailesh , Mcginley William , Gupta Gautam , Upadhyayula Sreedevi , Sunkara Mahendra
Published: September 2023

Current technologies for hydrogen production are based primarily on reforming of fossil fuels using steam, which produces large amount of carbon dioxide emissions (> 9 tons of CO2 per ton of hydrogen produced). Majority of refineries, ammonia producers, and fuel cell power plants utilize steam methane reforming for production of hydrogen at scale.

In this paper, we discuss an approach for activating methane and pyrolyzing using molten metal based alloys that includes Gallium. Sunkara’s group had developed this process earlier for making carbon micro-tubes with tunable morphology.[1, 2] Here, experiments were performed using pure methane, acetylene suggests a potential pathway for complete pyrolysis through recycle to produce hydrogen and carbons. The carbons produced are high surface area and are also do not contain any impurities. Majority of the carbons produced contain graphene sheets in random manner along with onion morphologies.

The mechanism of methane pyrolysis involves a similar mechanism as that of silicon dissolution from silanes into molten Gallium. The activated species dissolve into molten Ga [3] and then undergo dehydrogenation reactions resulting in carbon nucleation and growth on molten Ga surface. The immiscibility of carbon and molten Ga allows for easier separation of resulting carbons through simple scraping from the surface.

Techno-economic analysis suggests that the cost of hydrogen produced using the proposed catalytic technology could be less than $1/kg if the carbon by-product has value > $3/kg. Such low cost of hydrogen production is only possible if the following technical specifications are met: methane conversion is greater than 90%; scalable to 100 tons per year; and reduced loss and re-use of catalyst.

Bhimarasetti, G., J.M. Cowley, and M.K. Sunkara, Carbon microtubes: tuning internal diameters and conical angles. Nanotechnology, 2005. 16(7): p. S362.

Bhimarasetti, G., et al., Morphological Control of Tapered and Multi‐Junctioned Carbon Tubular Structures.Advanced Materials, 2003. 15(19): p. 1629-1632.

Carreon, M.L., et al., Synergistic interactions of H2 and N2 with molten gallium in the presence of plasma. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2018. 36(2): p. 021303.
(Invited) Plasma Catalysis: An Emerging Electrification Technology for Sustainable Production of Fuels and Chemicals
Authors: Tu Xin
Published: September 2023

The conversion of inert molecules (e.g., CO2, CH4, and N2) with strong chemical bonds for the synthesis of value-added synthetic fuels and platform chemicals has attracted significant interest. However, the activation of these molecules remains a great challenge as they are thermodynamically stable and require a significant amount of energy for activation. Non-thermal plasma (NTP) is an emerging and attractive technology for gas conversions under ambient conditions. The combination of NTP with heterogeneous catalysis has great potential to generate a synergistic effect from interactions between the plasma and catalysts, which can activate catalysts at low temperatures and improve the activity and stability of the catalysts, resulting in a remarkable increase in conversion, selectivity, and yield of end-products, as well as the energy efficiency of the process. Moreover, plasma processes can be switched on and off instantly, allowing for great flexibility in decentralised chemical production using renewable energy sources, particularly intermittent renewable energy. The potential of plasma-catalytic technologies for the synthesis of fuels and chemicals via various chemical processes such as CH4 activation, CO2 conversion, and ammonia synthesis will be discussed in this presentation.
(Invited) Visualization of Charge Density Distribution in Parallel-Plate Dielectric Barrier Discharge Under Atmospheric-Pressure Air
Authors: Komuro Atsushi
Published: September 2023

Dielectric barrier discharge (DBD) is one of the atmospheric nonequilibrium plasma and is typically driven by sinusoidal or pulse voltage with electrodes that dielectric is inserted. DBD has been used in some industries such as plasma medicine and material processing. However, the fundamental process of DBD has not been elucidated yet. When a parallel plate DBD is driven by sinusoidal voltage under atmospheric pressure, numerous filamentary discharges called microdischarges (MDs) are observed. The surface charge deposited on the dielectric after the discharge plays a major role in the behavior of these MDs. As the MD develops during the gap and reaches the dielectric surface, a surface discharge occurs and deposits the charge on the dielectric surface.

We performed dielectric surface charge measurements using Bi4Ge3O12, a Pockels crystal, in a short-gap, parallel-plate DBD of 0.5 and 0.3 mm driven by a sinusoidal high voltage. The high-speed camera enabled measurement of the spatio-temporal distribution of surface charge and estimation of the net electric field and the characteristics of microdischarges (MDs).

The net electric field strength in the gap was estimated from the measurement results. The axial reduced electric field strength generated by the surface charge was found to be equivalent to 50-60% of the peak value of the applied electric field with all the voltage amplitude and gap length in this study, and the gap electric field after discharge was suppressed to less than 100 Td. Such a strong field keeps the MDs in a nonequilibrium plasma and also prevents re-discharge in the same position at the half cycle. On the other hand, the lateral electric field strength generated by the surface charge is largely characterized by the charge distribution—i.e., the voltage amplitude, gap length, and charge polarity—as mentioned above. Higher amplitude of applied voltage leads to an increase in the area of high lateral electric field strength above 100 Td. Compared to the gap length of 0.5 mm, the lateral electric field weakened, while the axial electric field generated by the surface charge was stronger in the gap length of 0.3 mm. As for the relationship between the charge polarity and the lateral electric field, the lateral field at the anodic dielectric, which the negative charge is deposited on, is dominant in the region of less than 100 Td. Meanwhile, on the cathodic dielectric, which the positive charge is deposited on, the area of above 100 Td is larger. That is, the strong lateral electric field can be observed near the cathodic dielectric, rather than the anodic dielectric. Thus, different chemical reactions may occur in the vicinity of the anodic and cathodic dielectrics, respectively, because of the difference in the drifting charged particles and the lateral field strength.
Plasma-Designed Multifunctional Carbon Electrodes for High-Frequency Line Filtering Applications
Authors: Marath Santhosh Neelakandan , Zavašnik Janez , Cvelbar Uros
Published: September 2023

Demand for higher power efficiency devices to be used in the various miniatured and portable equipment has increased and led to significant growth in the electrochemical capacitors. Currently, different available electrochemical capacitors mostly deliver the highest performance at low frequencies (less than 1 Hz) due to the microporous electrode structures and configurations. Due to these reasons, the use of such capacitors is still not commercialized because of the insufficient supply of direct current at a higher frequency range (between 100 and 200 Hz). Considering the large-scale electricity applications mainly carried with alternating current (AC), it is important to develop electronic devices that work on AC power sources. At the same time, high-power energy devices require a constant DC supply for large-scale applications. Therefore, an advanced device that can sufficiently convert AC to DC has stimulated contemporary research and designing filtering capacitors is gaining research attention. For such capacitors, it is important to design electrode architectures with high electrical conductivity, minimum contact resistance and a thickness between 1 and 10 μm, which can be achieved by depositing active material directly on the current collector. Plasma-enabled techniques have the key advantage of designing electrode architectures directly on the nanostructures and providing the desired morphology and orientation, which is favorable to maximize material–electrolyte interaction and ion transport. In this work, structure-controlled carbon nanostructures were designed using a plasma-enabled deposition approach using the advantage of the plasma catalysis effect. The nanostructures were used in the electrochemistry applications as electrodes in the filtering capacitor for the AC to DC conversion. The deposited nanostructures were vertical carbon nanoforests composed of multiple carbon nanotubes. The plasma-designed electrodes delivered a high capacitance of 430 μF in the high-frequency range (100 Hz) with a phase angle of ∼ -80°, which is excellent for filtering applications. Using such electrode architectures, a prismatic prototype was designed to test the capability of the capacitor to efficiently convert AC to DC, and the designed prototype delivered a capacitance of 12 mF at 100 Hz with long-term filtering stability (above 3 h). This excellent capacitance performance and filtering capabilities of plasma-designed carbon nanostructures open future pathways to replace conventional aluminum electrolytic capacitors for line frequency applications.
(Invited) Thermodynamic Properties of Rare-Earth Alloys Relevant for Efficient Rare-Earth Recovery in Molten Salts
Authors: Kim Hojong , Im Sanghyeok
Published: September 2023

Electrode materials of Fe, liquid Bi, and Sn were investigated to enhance the electrochemical recovery of rare-earth elements in molten salts (eutectic LiCl-KCl) at 500‒700 °C, leveraging their chemical interactions with rare-earth elements. Using Nd as a prototypical example, the degree of interactions was quantified based on electromotive force (emf) measurements of Nd alloys (Nd-Fe, Nd-Bi, and Nd-Sn). Temperature-dependent emf values of the Nd alloys were used to determine the thermodynamic properties such as the partial molar Gibbs energy (chemical potential), entropy, and enthalpy of Nd. In addition, the phase behavior of Nd alloys was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) to determine transition temperatures and microstructures of Nd alloy electrodes. Based on these fundamental properties of Nd alloys, the Nd-Sn alloy at mole fraction, x
Nd = 0.10 was selected as the reference electrode and employed for electrochemical measurements in three-electrode cells in molten chloride salt (LiCl-KCl-NdCl3). The stability of Nd-Sn reference electrode was maintained less than 1 mV deviation between identical constructs during entire measurements, originating from the two phase (liquid + NdSn3) stability of the binary Nd-Sn alloy at 500‒700 °C. Finally, electrodeposition of Nd onto these interacting electrode materials was conducted to assess the recovery efficiency of Nd from molten chloride salt.
(Invited) Electrowinning of Aluminium and Carbon Footprint
Authors: Haarberg Geir Martin , Awayssa Omar , Saevarsdottir Gudrun
Published: September 2023

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na3AlF6-AlF3, at ~960 oC in which the raw material alumina is dissolved and decomposed into pure aluminium and CO2 gas due to the use of carbon anodes. The current efficiency with respect to aluminium can be as high as 96 % in Hall-Heroult cells. The total cell reaction is:

Al2O3 (diss) + 3/2 C (s) = 2 Al (l) + 3/2 CO2 (g)

The electrical energy consumption is around 12 - 15 kWh/kg Al, which corresponds to an energy efficiency of about 50 - 60 %. The main losses are due to a large ohmic voltage drop in the electrolyte and high anodic overvoltage. There are considerable emissions of CO2 from generation of electricity and the anode reaction. In addition there are emissions of CF4 and C2F6 (PFC gases) during so-called anode effect. Several efforts are under way to reduce the carbon footprint of the electrolysis process. One approach is to develop inert anodes to produce oxygen to eliminate the direct emissions of CO2 and PFC. The most promising inert anode candidates are based on alloys (Fe, Ni, Cu) in an electrolyte rich in KF with a lower liquidus temperature. Another idea is to produce aluminium based alloys directly during electrolysis by adding metal oxides in order to co-deposit alloying elements such as silicon, titanium and manganese. Such a method may give significant savings also in terms of carbon footprint since the current method for producing alloys is to add pure metals to liquid aluminium before casting. These alloying metals are associated with high emissions of CO2 durning their primary production processes.
Anodic Overpotential on Metallic Oxygen Evolving Anodes for Aluminum Electrolysis in Low Temperature Electrolyte of KF-Naf-AlF₃-Al₂O₃
Authors: Singh Kamaljeet , Padamata Sai Krishna , Gunnarsson Gudmundur , Haarberg Geir Martin , Saevarsdottir Gudrun
Published: September 2023

To eliminate climate gas emissions from aluminum electrolysis, significant research and development efforts focus on non-consumable oxygen evolving anodes to replace the carbon anodes used in the Hall Héroult process. Modifying the cryolite-based electrolyte currently used, by partly replacing Na with K in the molten fluoride, opens up a range of metallic alloys as feasible materials for inert anodes. In this work, the performance of Cu-Ni-Fe anodes, with or without surface treatment, is benchmarked against Pt and the pure components of the alloy.

Anodic overpotential using an inert anode with low-temperature electrolyte, 750–800 ⁰C, for aluminum reduction should be low to compensate for ~1.10 V higher reversible potential for O₂ evolution than in conventional Hall-Héroult process at 960 ⁰C. In this study, voltammetry methods were applied in a low-temperature electrolyte mixture of KF-NaF-AlF₃-Al₂O₃ at 800 ⁰C. Oxygen evolution overpotential on pure Pt anode was measured using steady-state polarization. Tafel plots were obtained, and kinetic parameters were derived in the form of Tafel coefficients and exchange current density. A theoretical treatment for anodic process on Pt electrode with a two-step electron transfer mechanism is developed.

Some anodic polarization curves were obtained for pure metals of Cu, Ni, Fe, and alloy of Cu-Ni-Fe in KF-NaF-AlF₃-Al₂O₃ at 800 ⁰C. Prior to use, some anodes of Cu-Ni-Fe alloy were oxidized in air at 800 ⁰C for 8 h and found to perform relatively better than an untreated alloy of the same composition. Anodes following electrochemical measurements were characterized by scanning electron microscope (SEM) coupled energy dispersive spectroscopy (EDS).
Electrical Conductivity of Low-Temperature KF-Naf-AlF3 Melts with CaF2 and Al2O3 Addition
Authors: Saevarsdottir Gudrun , Singh Kamaljeet , Haarberg Geir , Padamata Sai Krishna
Published: September 2023

Replacing consumable carbon anodes with oxygen evolving inert anodes, in aluminium reduction cells, has long been a goal for the aluminium industry. Using inert anodes would have several advantages, one of them being the elimination of greenhouse gas emission during the electrolysis process. Metallic alloys have proven to be a promising category of material candidates for inert anodes. The industrial electrolyte is a cryolite based fluoride, and the process temperature is around 960°C. This is a very corrosive environment for the anodes, which have failed to be inert. Lowering the electrolysis temperature is key to improving anode performance. The liquidus can be lowered by reducing the NaF ratio, often termed Cryolite Ratio (CR), of the NaF-AlF3 melt, but that is not feasible as it drastically reduces the alumina solubility. If some, or all, of the NaF in the melt is replaced by KF, acceptable alumina solubility is maintained even at the low CR necessary for melting point down to 700°C. Replacing NaF with KF is known to reduce the electrical conductivity, and therefore it is of interest to determine the electrical conductivity of KF-NaF-AlF3-Al2O3 melts with different parameters.

In the present study, we determine the electrical conductivity of KF-NaF-AlF3 melt at different parameters such as temperature, cryolite ratio (CR = xNaF+xKF/xAlF3), potassium ratio (xKF/xKF+xNaF) and composition of CaF2 and Al2O3 additives. Continuously varying cell constant (CVCC) technique is used to determine the electrical conductivity of the melt, which is governed by equation (1).

(1)

Here κ is the electrical conductivity of the melt in S cm−1, A is the cross-sectional area of the conductivity cell in cm2, l is the length of the cell in cm, and Rm

is the melt resistance in Ω. The experiments are performed at various cell geometries, as shown in figure 1a.

Electrochemical impedance spectroscopy (EIS) is used to determine the resistance (R) of the conductivity cell. AC-technique with a small amplitude of 10 mV and high frequencies ranging from 100 Hz to 100 kHz is used.

R = Rm + Rp + Rc
(2)

Rm

is the melt resistance, Rp

is the polarisation resistance, and Rc

is the resistance related to electrical connections. When EIS is performed at different l values, Rp

and Rc
remain constant while Rm

changes. Thus, the Rp+Rc
value can be estimated by extrapolating the line plotted between R and cell constant to 0 (cell constant value) (see figure 1b).

Figure 1a. Conductivity cell: 1: Stainless steel rod, 2: Alumina tube, 3: BN tube, 4: Molten electrolyte, 5: Counter electrode electrical connector, 6: Graphite working electrodes, 7: Graphite crucible/counter electrode, 8: k-type thermocouple. 1b. An example graph plotted between the cell resistance and cell constant to estimate the melt resistance.

Figure 1
(Invited) Magnesium Production By MgO Reduction in Molten CaF2-MgF2 Salt with Reactive Liquid Metal Cathode and Consumable Carbon Anode or Nonconsumable Zirconia Solid Oxide Membrane
Authors: Telgerafchi Armaghan Ehsani , Espinosa Gabriel , Sehar Daniel McArthur , Rutherford Madison , Powell Adam Clayton
Published: September 2023

A process for magnesium production is proposed beginning with MgO electrolysis in molten MgF2-CaF2 salt with a reactive liquid metal cathode, followed by efficient multiple effect distillation to separate the magnesium from the cathode. Experiments with a liquid tin cathode and carbon anode show over 90% current efficiency; with a yttria-stabilized zirconia (YSZ) solid oxide membrane (SOM) between the bath and anode, current efficiency is above 80%. A detailed mass balance estimates the amount of MgF2 and tin required to maintain steady bath and cathode chemistry with CaO and other impurities in the MgO feedstock. A detailed energy balance describes the relationship between applied potential and cell thermal balance over a range of process temperatures, including minimum energy losses through cell leads. Emissions analysis shows a range of greenhouse emissions depending on the raw material type, MgO separation and calcination method, anode type (carbon or YSZ SOM), and electrical energy source.
MD Simulation and Transport Property Analysis of Silicon in High-Temperature Molten Fluoride Salts Electrolyte
Authors: Zhang Yifan , Chahal Rajni , Gao Michael , Ludwig Karl , Pal Uday , Powell Adam Clayton , Lam Stephen , Zhong Yu
Published: September 2023

Silicon is the dominant solar material because of its abundance, low cost, and high solar efficiency. But manufacturing high-purity silicon required for solar energy is very complex, hard to scale, and unsafe since it involves dealing with toxic flammable gases. Therefore, a new solar silicon production technology based on molten salt electrolysis has been proposed. To comprehensively study the self-diffusion and deposition mechanism of silicon ions in high-temperature molten salt electrolyte and their composition and temperature dependence, both interatomic potential molecular dynamics (IPMD) and ab-initio molecular dynamics (AIMD) are introduced. Thermodynamics and transport properties of molten salt electrolyte such as density, heat capacity, viscosity etc. are investigated and compared to the existed experimental results. Also, local structural information and coordination number analysis are obtained and discussed.
Study of Lithium-Silicon Anode Materials for Thermal Batteries
Authors: Azad Atia , Gover Richard K. B. , Irvine John Thomas Sirr
Published: September 2023

Thermal batteries are constructed from a molten salt electrolyte which is solid at room temperature, a FeS2 positive electrode and a lithium-silicon negative electrode. The typical operating temperature of the battery is between 350 to 500°C. Thermal batteries use an inorganic salt as the electrolyte such as binary or ternary alkali halide eutectics. For example, LiCl-KCl and LiF-LiCl-LiBr. At a composition of 44.8 LiCl and 55.2 KCl wt%, the melting point is around 353°C for LiCl-KCl. Molten salts have a very high electrical conductivity, so thermal batteries have a higher power density than room temperature batteries. In this work, LiCl-KCl eutectic was used for electrochemical testing. The performance of an electrode can be studied in single-cell discharge tests where a discharge profile is obtained. The tests were carried out in a cell testing rig inside an argon glovebox. The cells were made from pellets which were placed in a Swagelok casing. The cells were made from 0.15g of FeS2 mixed with 0.05g LiCl-KCl as the positive electrode, 0.2g of LiCl-KCl with 35% wt MgO as the electrolyte and 0.2g of Li13Si4 as the negative electrode. Lithium silicides were made using solid state synthesis in a tube furnace. The electrochemical tests show that the Li13Si4 is a better negative electrode material than Li7Si3 (Figure 1). In addition, powder neutron diffraction was used to probe the lithium silicides with increasing temperature. The high-temperature behaviour of Li13Si4 and Li7Si3 was studied in March 2020 by the JTSI group at the ISIS neutron source, Rutherford Appleton Laboratory, UK. The data gives information on structural changes in Li13Si4 and Li7Si3. The results indicate that Li13Si4 and Li7Si3 remain remarkably stable at 500°C. There are no phase transitions in the materials from room temperature to 500°C and the materials remain crystalline. These findings give a clearer understanding of thermal battery discharge processes.

Figure 1
Tape Casting for Development of Thermal Batteries
Authors: Jose Josin , Irvine John T.S. , Brousse Thierry
Published: September 2023

Thermal (thermally activated) batteries are primary batteries which operate at temperatures ranging from 350°C to 650°C. Due to its long shelf life and high power density (up to 8kW kg-1)1, thermal batteries have been used reliably for military applications such as providing back up power for aircraft hydraulics, missiles and even the Galileo probe.2 Currently, thermal batteries are manufactured by a labour intensive pellet pressing method which limits the design and thickness of the batteries. To improve the power density of thermal batteries, tape casting has been examined. Tape casting is a common method of manufacturing commercial secondary lithium-ion batteries. Tape casting enables relatively thin films of battery components to be utilized which minimises the thickness of the battery components and gives the option to alter the design of the battery itself.

Despite its many years in operation for important military applications, processing of thermal batteries into functional cast films has not been achieved so far due to the high operational temperatures of thermal batteries which negate the use of standard polymers. To counter this issue, high temperature polymers, inorganic binders and carbon nanotubes have been examined for their use as binders for thermal battery component inks. Their thermal stability was examined using STA and the oxidation of pyrite was analysed through EDS and PXRD. Successful processing of the constituent battery components is hoped to drastically improve the electrochemical performance of the cell and decrease the manufacturing cost of the batteries.

R. A. Guidotti, G. L. Scharrer, E. Binasiewicz and F. W. Reinhardt, 1998.

R. A. Guidotti and P. Masset, J. Power Sources, 2006, 161, 1443-1449.
A Semi-Differentiated Model for the Potential-Sweep Voltammograms of Electrochemical Deposition Reactions
Authors: Williams Tyler , Vann Cameron , Fuller Ranon , Rappleye Devin
Published: September 2023

Molten salt processes commonly occur in melts containing multiple electroactive analytes. A sensor’s voltammogram signals for these analytes may overlap, leading to inaccurate measurements. Semi-differentiation transforms the overlapping signals into more narrow, individually distinguishable peaks that can be analyzed accurately. Because some characteristics of these transforms are non-intuitive, this technique has been misapplied and misunderstood in the literature. For instance, the semi-differentiated peak current has been used to measure concentration without regard to the peak’s dependence on adsorption processes. Here, some non-intuitive characteristics of semi-derivatives are explored, the derived analytical expression is validated against experimental data from high-temperature molten salt systems, and best-practices for semi-differentiation are discussed.
Electrodeposition of Microfabricated Rhenium-Filaments
Authors: Soule Luke , Coleman Jonathan , Pomerene Andrew , Arrington Christian L. , Petersen Steven
Published: September 2023

Metallic filaments comprised of refractory materials are a necessary part of mass spectrometers used to measure isotopes. The current state-of-the-art material, rhenium, is formed into filaments using a mechanical crimper, limiting the accuracy, speed, and quantity of filaments that can be fabricated. The current work describes the development of wafer-scale, microfabricated Re filaments using silicon molds followed by electrodeposition of Re. The goal is to develop filaments with tight dimensional tolerances, high purity, and mechanical rigidity for the desired application and offer the ability to create 100’s-1000’s of filaments on a single silicon wafer.

Electrodeposition of Re is notoriously difficult as the reduction potential of rhenium is close to the hydrogen evolution reaction in aqueous solutions.1 While rhenium has been successfully deposited from alkaline, acid, and concentrated lithium chemistries,2 the films are often thin, porous, and contain many impurities such as hydrogen and oxygen. Rhenium oxide is susceptible to reaction with moisture in the air, resulting in poor quality films with short functional lifetimes. To electroform precise, pure rhenium structures, hardier chemistries must be developed.

The current work seeks to address this challenge using a water-in-salt chemistry (WISE) comprised of up to 4M lithium salts, complexing agents, reducing agents, and oxygen scavengers. Numerous physical agitation techniques were utilized to improve the quality of the film. Solutions were analyzed using various electrochemical techniques, UV-VIS, and Raman spectroscopy. The optimized chemistry was used to electrodeposit bulk batches of microfabricated 2mm x 300 um x 300 um filaments. The filaments were analyzed using microscopy, XRF, XRD, SEM, and EDS with a goal of use in high temperature mass spectrometry experiments.

References

(1) Naor, A.; Eliaz, N.; Burstein, L.; Gileadi, E. Direct Experimental Support for the Catalytic Effect of Iron-Group Metals on Electrodeposition of Rhenium. Electrochemical and Solid-State Letters
2010, 13 (12), D91. DOI: 10.1149/1.3489532.

(2) Pappas, D. P.; David, D. E.; Lake, R. E.; Bal, M.; Goldfarb, R. B.; Hite, D. A.; Kim, E.; Ku, H.-S.; Long, J.; McRae, C. Enhanced superconducting transition temperature in electroplated rhenium. Applied Physics Letters
2018, 112 (18), 182601.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-*****
Electrodeposition of Thin Films for Jewels and Fashion Accessories
Authors: Innocenti Massimo , Giurlani Walter , De Luca Antonio , Bonechi Marco , Comparini Andrea , Vorobyova Mariya Vorobyova , Verrucchi Margherita , Fontanesi Claudio , Caneschi Andrea
Published: September 2023

The interest in scientific research within the metal finishing sector is growing. The demand for durable metals and adaptable manufacturing processes is increasing across a wide range of applications, from aerospace and automotive to machinery and jewelry. An essential step in the production line is the surface engineering of metals, as this determines the final appearance and functionality of a product. Therein electroplating is recognized as a mature technology allowing the low-cost fabrication of defined surfaces with extensive property profiles. Galvanic electrodeposition accounts today for almost 40% of the global market value share with North America and Western Europe leading the scenery. Although technological and processing advancements occurred in the past forty years, industrial firms are still struggling to provide solutions to corrosion protection as well as the reduction of toxic wastes. Specifically, large-scale industrialization of electroplating techniques will continue to be limited by strict environmental regulations. Due to adverse ecological impacts, the adoption of plating processes involving toxic metals such as lead or cadmium is prohibited. Moreover, price volatility of the highly demanding electroplated materials gold, copper, and nickel is expected to impact the market share by more than 60% by 2026.

In that respect, alloy plating offers better answers in terms of economic growth and environmental sustainability due to fine-tuning composition, morphology, and crystallinity [1]. Here, current trends in alloy electrodeposition research are reviewed highlighting open challenges and process innovations from an industrial perspective. The main categories of alloy compounds are presented and the most important properties of the manufacturing process are discussed. Particular attention is devoted to advances in industrial quality control and viable solutions for the reduction of precious metal content in electroplated accessories as well as the replacement of cyanide and nickel baths with non-toxic compounds.

The authors acknowledge Regione Toscana POR CreO FESR 2014-2020 – azione 1.1.5 sub-azione A1 – Bando 1 “Progetti Strategici di ricerca e sviluppo” which made possible the project:

“RAM-PVD” (CUP 3647.04032020.157000057_1225).

References

[1] W. Giurlani, M. Innocenti et all. , Electroplating for Decorative Applications: Recent Trends in Research and Development, Review, Coatings 2018, 8(8), 260.