bluuebunny/crossref_metadata_2025_split huggingface dataset:
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) 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.
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
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) 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.
(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
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.