bluuebunny/crossref_metadata_2025 huggingface dataset:
Beneficial Changes in the Mechanism of the Cobalt Catalyzed Hydrogen Evolution Reaction, Induced by Corrole Chelation
Authors: Kumar Amit , Fite Shachar , Raslin Arik , Kumar Sachin , Sharma Vinay K , Mizrahi Amir , Mahammed Atif , Gross Zeev
Published: September 2023

Current technologies for mass production of hydrogen gas, needed for fuel cells, synthesis of ammonia and many other purposes, have an enormous carbon footprint. Less than 5% is manufactured by much cleaner water electrolysis, mainly because the electrodes are based on precious platinum. In line with a worldwide effort on replacing platinum by earth abundant metals, the present investigation focuses on electrocatalytic proton reduction by cobalt corroles, via full characterization of a series of complexes and comparison of their properties. The smallest possible and most electron-rich derivative, with H atoms rather than larger and much more electron withdrawing substituents on the macrocycle, provided the best catalytic activity: lowest over potential and largest faradaic efficiency, almost as good as platinum. Mechanism-of-action investigations by experimental and computational analyses exposed that the reason for the superior performance is a new reaction pathway in which protons are activated by singly rather than doubly-reduced cobalt

Figure 1
A New Cancer Therapy with a Resonance Nuclear Reaction between 15n-5-ALA and Proton Beam: iPDT
Authors: Matsui Hirofumi , Ikeda Takafumi , Suzuki Iwane , Iwata Yasushi
Published: September 2023

A super-aged society, the prime example of which is Japan, is being flooded with increasing in numerous numbers of aged cancer patients, who often take anti-coagulant medicines to prevent the attacks of ischemic heart diseases and/ or strokes. Since they have diseases with bleeding tendency induced by the medicines, it’s hard for them to receive surgical operations. Thus, low invasive cancer treatments without bleedings are abundantly desired. In this study, the applicant will establish a new proton therapy, in which a resonance nuclear reaction (RNR) induced by collision of a proton with a stable nitrogen isotope (15N), can be a clue to injure cancer-cells specifically. The LET of the product ions (12C6+, 4He2+) of the 15N RNR is above 50 times in comparison with the LET of proton. To establish the cancer-specific 15N delivery, 15N-aminolevulinic acid (15N-ALA) will be used. This reagent has been already used and obtained regulatory approvals as a diagnostic medicine for the location of the glioblastoma in Japan.

In this study, a pair of rat gastric epithelial cells, one is normal cell, and another is cancerous characteristics cells were used, 15N-ALA treated porphyrin fluorescent intensity of these cells will be compared with 14N-ALA treatment. The cells will be irradiated with a proton beam generated by an electrostatic accelerator and 4.43 MeV gamma-rays will be measured to demonstrate the amount of 15N collected specifically in the tumour cells. Such quantitative analysis of 15N in the tumour cells can be a new pre-diagnosis of iPDT.
Cooperativity at the Solution/Solid Interface: Formation and Reactivity of Self-Assembled Monolayers
Authors: Mazur Ursula , Hipps K. W.
Published: September 2023

Cooperativity is a molecular phenomenon, in which multiple interactions participate synchronously to significantly affect the activity and/or selectivity of the interacting components by accelerating (or impeding) their chemical or physical processes. Cooperative effects are prevalent in biology and can be observed in chemistry and materials science. Synthesis of functional materials frequently requires surfaces and interfaces where cooperative interactions can propagate with substrate assistance. In this context, of great interest is the characterization and control of ligands binding to metal centers, given their rich chemistry and prevalence in functional materials. In addition, self-assembly of compounds on surfaces can be steered by cooperative effects, and supramolecular polymerization can also proceed in a cooperative manner. Essential for these kinds of chemistries is the availability of highly resolving analysis methods to investigate reaction and adsorption outcomes directly at the surface. Scanning tunneling microscopy (STM) is particularly well suited to the study of such processes on surfaces and interfaces by offering both molecular resolution and real time and space information regarding changes in the electronic structure of materials upon adsorption and/or reaction.

In this contribution, we present quantitative STM experimental results and supporting theoretical calculations of the binding dynamics of neutral ligands (heteroaromatics, O2) to metal porphyrins adsorbed on solid substrates as well as self-assembly of polyaromatics on metallic supports. Single molecule level STM imaging was accomplished in-situ under ambient solution conditions. We measured binding affinities and uncovered surface modulated cooperativity both in coordination reactions and in molecular self-assembly -- results essential for understanding adsorbate-surface interactions. Computations corroborate our experimental findings. The high-resolution, quantitative knowledge gained at the molecular level combined with theoretical studies offer not only insights into chelation, adsorption, and cooperativity but also into control parameters for surface-driven synthesis, tunable surface functionalization, and catalysis selectivity control.
Preparation and Characterization of Carbon Nanotubes Enhanced Canola Protein Isolate (CNT/CPI) Bio-Adhesive for Wood Application
Authors: Enemuo Emeka Michael
Published: September 2023

The current wood adhesives technologies rely mainly on formaldehyde-based adhesives produced from petrochemicals. Moreover, these adhesives are derived from non-renewable sources is known to be carcinogenic together with other serious health effects. Therefore, there is an increasing interest in the use of renewable and biodegradable sources for the evolution of an environmentally friendly adhesives for interior wood applications.

The canola meal (the remnant after oil extraction from the canola seed) contains about 36 – 39% (8.5% moisture basis) can be used as a low value feed for the animals. Moreover, its protein content is currently exploring other applications such as in the adhesive technology and it can be used as an alternative to the widely used formaldehyde-based adhesives. Canola proteins (CP) as adhesives have many unique properties such as ease of handling, low cost, low pressing temperatures, and the ability to bind wood with relatively high moisture content. On the other hand, it has relatively low adhesion strength and low water resistance which are the major drawbacks. This study will address these issues by modifying CP adhesive with carbon nanotubes (CNT). CNT are one of the most encouraging strengthening nanofillers with the extraordinary tensile modulus and strength, it has been proved to significantly improve the physical and mechanical properties of the nanocomposites. Generally, this study will intend to improve the water resistance and adhesive strength of the CP adhesive by incorporating different concentrations of the CNT into the protein matrix.

This study is made up of two parts: incorporation of CNT and functionalized CNT (FCNT) into the CP matrix. Incorporation of CNT at 1% (w/w) enhanced the adhesive strength from 5.98, 1.80, and 5.42 to 9.20, 5.64, and 7.44 at percentage increment of 53.85, 213.33, and 37.27% for dry, wet, and soaked strength respectively. The presence of carbonyl group in the CNT after purification as well as the polyvinylpyrrolidone (PVP) helped to attain this improvement in the water resistance and adhesion.

In the second part, functionalization of the CNT greatly improved the shear strength at 1% FCNT concentration to 10.62, 8.10, and 8.13 at 77.59, 350, and 50% increase for dry, wet, and soaked strength respectively. The introduction of the carboxylic group by functionalization significantly improved the mechanical and thermal properties of the CP due to a proper dispersion giving rise for a better hydrophobic and cohesive interactions between the wood and adhesive.

These results proved an enhanced water resistance and adhesion of the CP contributed by the CNT and its functionalization.
(Invited) Novel Materials for Future Li-Ion Batteries
Authors: Yushin Gleb
Published: September 2023

Advancements in the capabilities of lithium-ion batteries have slowed down in the last decade. As conventional electrode materials approach their theoretical limits, substantial gains in battery energy density only come as a trade-off in safety or performance. This talk will discuss how replacing conventional active and inactive materials will significantly improve performance, drastically reduce the cost of Li-ion batteries, and pave the way for renewable energy technologies. For example, Sila's innovative drop-in-replacement nanocomposite silicon-based anode powder offers over five times higher gravimetric capacity than graphite, permits both fast charging and over 20% more energy density today over state-of-the-art lithium-ion, and enables radical product innovation - all without compromising performance. Most importantly, this material has been shipping for over a year and is scaling up for massive electric vehicle (EV) use by mid-decade.

With Sila’s industrialized and scaled scientific innovation, wearables, portable electronics, and EV manufacturers can create breakthrough products today that will minimize our environmental impact tomorrow. This talk will also provide multiple examples of lightweight conversion-type cathodes, flexible ceramic separators, and other technologies that may become instrumental for the transition to a clean and energy-sustainable economy.
(Digital) Kilohertz-Frequency Electrochemical Capacitors Based on Vertical MoS2 Nanoflakes on Carbonized Cellulose Sheets for AC-Line Filtering
Authors: Bal Sourayan , Lin Xueyan , Baranwal Rishav , Fan Zhaoyang
Published: September 2023

Electrochemical capacitors (ECs) with kilohertz frequency response were fabricated by the growth of vertically oriented MoS2 nanoflakes on free-standing carbonized cellulose sheets in a hydrothermal process. The cellulose was carbonized by a rapid pyrolysis process. It was shown that by tuning the MoS2 deposition time on this carbon scaffold, the frequency range and area-specific capacitance of the device can be easily adjusted. Specifically for AC-line filtering application, an EC cell with a characteristic frequency (i.e., the frequency when the phase angle reaches −45°) of 4kHz was made, which shows a specific capacitance density of 1.6mF/cm2 and a phase angle of 79.50 at 120Hz. By increasing MoS2 deposition, EC cells with an areal capacitance of 9.6mF/cm2 and a characteristic frequency of 580Hz were also fabricated.
(Digital Presentation) Preparation and Characterization of PMMA-SWCNT Nanocomposites
Authors: Czapura Łukasz , Stando Grzegorz Jan , Janas Dawid
Published: September 2023

Carbon nanotubes (CNTs) exhibit unique properties such as high tensile strength, excellent electrical conductivity, and resistance to corrosion. Unfortunately, macroscopic objects from these nanostructures do not perform equally well because the individual nanotubes do not transfer electrical charge, phonons, or stress between them sufficiently well. One possible solution to improve the properties of macroscopic ensembles from nanocarbon is to manufacture the composites with other materials like polymers, ceramics, or metals. This connection is usually beneficial. However, the properties depend strongly on the integration degree of the two compounds. For example, nanocomposites with polymers have improved mechanical (Poly(methyl methacrylate), PMMA) or electrical (in the cause of conductive polymers) properties. Many ways lead to PMMA-CNTs, but the most popular are coating (dip-coating, spin-coating, spray-coating) and dispersion methods.

One of the potential applications of these composites is as a membrane for the purification of wastewater from organic residues. Unfortunately, industrial growth in the last century has caused a reduction in the availability of pure water, so the abovementioned application of CNTs would be beneficial. However, the main problem with pristine carbon nanotube films is their structural integrity. The addition of polymer molecules could overcome this problem and lead to a new effective method of removing impurities.

The commercial single-walled carbon nanotubes (TuballTM) were used to create nanocomposites with PMMA using either dip-coating or dispersion method. Scanning Electron Microscopy (SEM), Raman spectroscopy, Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy, and mechanical testing were used to analyze composites. The nanocomposites were used to remove aromatic organic compounds dissolved in water. For model substances methyl orange, methylene blue, and fluorescein were chosen. UV-VIS spectroscopy was used to gauge the concentration of organic compounds before/after the filtration of the aqueous solution dissolved therein. The best results were for SWCNTs and PMMA-SWCNTs membranes as they removed more than 99% of chosen water impurities.
(Digital Presentation) Modification of Physicochemical Properties of Carbon Nanotubes By Chemical Functionalization
Authors: Ćwiertnia Jakub , Stando Grzegorz Jan , Janas Dawid
Published: September 2023

Carbon nanotubes (CNTs) are still one of the most promising nanocarbon materials despite being researched for over 30 years so far. CNTs have magnificent physical and chemical properties such as appreciable tensile strength, high electrical and thermal conductivity, tunable surface character, and chemical activity. However, the amount of structural defects can strongly impact these properties. Nevertheless, from a chemical point of view, these structural damages are often necessary to integrate CNTs with different materials. One of the most popular functionalization strategies is oxidization, which increases the hydrophilicity of the material at the expense of electrical conductivity.

In our research we focused on analysis, how different reduction parameters influence changes in properties of the material. We used modified Hummers method was used to oxidize single-walled carbon nanotubes (SWCNTs) and later reduction was conducted with use of hydrogen in elevated temperature in tube furnace. The process was monitored with Raman spectroscopy, Scanning Electron Microscopy and X-ray photoelectron spectroscopy to track ongoing changes. All materials, obtained in successful synthesis, were characterized to determinate the following properties: water contact angle (WCA), electrical and thermal conductivity and Seebeck coefficient. It was observed that due to reduction Seebeck coefficient increased from 24 μV/K for oxidized material to 39 μV/K after reduction, while WCA changed from 24° to 39°. This method has potential for future modeling of their properties and improved modification process can lead to new field of applications in thermoelectric of carbon nanomaterials.
(Digital Presentation) Deconstructing Proton Transport through Atomically Thin Monolayer CVD Graphene Membranes
Authors: Kidambi Piran
Published: September 2023

Selective proton (H+) permeation through the atomically thin lattice of graphene and other 2D materials offers new opportunities for energy conversion/storage and novel separations. Practical applications necessitate scalable synthesis via approaches such as chemical vapor deposition (CVD) that inevitably introduce sub-nanometer defects, grain boundaries and wrinkles, and understanding their influence on H+ transport and selectivity for large-area membranes is imperative but remains elusive. Using electrically driven transport of H+ and potassium ions (K+) we probe the influence of intrinsic sub-nanometer defects in monolayer CVD graphene across length-scales for the first time. At the micron scale, the areal H+ conductance of CVD graphene (∼4.5–6 mS cm−2) is comparable to that of mechanically exfoliated graphene indicating similarly high crystalline quality within a domain, albeit with K+ transport (∼1.7 mS cm−2). However, centimeter-scale Nafion|graphene|Nafion devices with several graphene domains show areal H+ conductance of ∼339 mS cm−2 and K+ conductance of ∼23.8 mS cm−2 (graphene conductance for H+ is ∼1735 mS cm−2 and for K+ it is ∼47.6 mS cm−2). Using a mathematical-transport-model and Nafion filled polycarbonate track etched supports, we systematically deconstruct the observed orders of magnitude increase in H+ conductance for centimeter-scale CVD graphene. The mitigation of defects (>1.6 nm), wrinkles and tears via interfacial polymerization results in a conductance of ∼1848 mS cm−2 for H+ and ∼75.3 mS cm−2 for K+ (H+/K+ selectivity of ∼24.5) via intrinsic sub-nanometer proton selective defects in CVD graphene. We demonstrate atomically thin membranes with significantly higher ionic selectivity than state-of-the-art proton exchange membranes while maintaining comparable H+ conductance. Our work provides a new framework to assess H+ conductance and selectivity of large-area 2D membranes and highlights the role of intrinsic sub-nanometer proton selective defects for practical applications.

References:

1. Chaturvedi et al. J. Mater. Chem. A, 2022,10, 19797-19810
Fabrication of Anion-Exchanged Electrodeposited Zn-Al Layered Double Hydroxides (LDHs) Coating on ZX21 Mg Alloy
Authors: Hsiao Wei-Lun , Chu Peng-Wei
Published: September 2023

Because of their low density and high specific strength, Mg alloys are considered promising lightweight alloys for various applications. However, due to the high electrochemical activity and poor corrosion resistance, surface modifications of Mg alloys are needed to increase the service life. Hence, an active layered double hydroxides (LDHs) coating was investigated in this study. Owing to the brucite-like layered structure, the weakly bonded interlayer anions can be easily exchanged with other anions in the environment. With the unique anion-exchange mechanism, LDHs coating provides dual protection to the Mg alloy substrate. It can not only act as a physical barrier but also absorb aggressive anions such as Cl- and release corrosion inhibitors to the environment.

Compared to the commonly used hydrothermal method to fabricate LDHs coating, which requires high temperature and long process time, electrochemical deposition has the advantages of high deposition rates, simple experimental setup, and highly controllable process parameters. Therefore, in this study, a three-electrode electrochemical setup was used to fabricate Zn-Al LDHs coatings on a ZX21 Mg alloy. Moreover, different anions are intercalated into the interlayer galleries of the prepared Zn-Al LDHs coating through post anion-exchange processes.

Through electrochemical analysis in a 3.5 wt% NaCl solution, the prepared anion-exchanged electrodeposited Zn-Al LDHs coating improved the corrosion resistance of ZX21 Mg alloy. Electrochemical impedance spectroscopy (EIS) showed that corrosion impedance increases, while potentiodynamic polarization curves revealed that the corrosion current density (i
corr) of the coated sample was an order of magnitude lower than the ZX21 Mg alloy substrate. Besides the improvement of corrosion resistance, the formation mechanism of Zn-Al LDHs coating by electrodeposition was also investigated by electrochemical analysis and in situ optical microscopic (OM) observations. The corrosion behavior and microstructure of Zn-Al LDHs coating and the roles played by different intercalated anions will be discussed based on electrochemical analysis and microstructure characterizations.

Figure 1
Improvement of Adhesion and Corrosion Resistance of TiO2 Nanotubes on Ta6V Alloy
Authors: Eyraud Marielle , Djendel Abderrazak , Ait Ahmed Nadia , Knauth Philippe
Published: September 2023

Titanium and its alloys are used In orthopedic and dental implants due to their good corrosion resistance thanks to the passive native film and biological compatibility. Nevertheless, the increase in life expectancy being higher that the corrosion resistance of such thin layer, several treatments were developped. Among them, electrochemical TiO2 nanotubes allow to increase the corrosion resistance, overcome the bioinert nature of a flat surface that is not favorable for cell development, but suffer of a poor adhesion on Ti surface.

The goal of this communication is to evaluate the corrosion performance as well as the adhesion properties of single and combined electrochemical treatments made on TA6V titanium alloy, including nanostructured (N), compact (C), and dual treated (NC) layers. The influence of potential used for the compact oxidation was evaluated on C and NC systems. The best potential from a corrosion point of view was determined to elaborate an optimal NC film. Given that the hydrophilicity is correlated with cellular adhesion and protein adsorption, water contact angle measurements were realized directly after the treatments and one month later. Since the surfaces became more hydrophobic by ageing, two different ways were tested to recover their initial hydrophilic behavior.
Mechanical Characteristics and Corrosion Behaviour of NiCoCr Medium-Entropy Alloys
Authors: Lu Yu-Sheng , Huang Ching-Chien , Fang Te-Hua
Published: September 2023

In this study, equiatomic NiCoCr medium-entropy alloys (MEAs) were prepared for the experiments using the arc melting method. The cooling rate and annealing effect were analyzed on the microstructure and mechanical properties of the NiCoCr MEAs. The crystal structure, composition changes, surface morphology, and internal defects were explored by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The mechanical characteristics like elasticity modulus, hardness, and cyclic normal compressive loading were determined by a universal testing machine, Vickers hardness tester, and nanoindenter. The results show that the faster the cooling rate, the smaller the grains produced in the sample; otherwise, the larger the grains produced. The AFM results showed that the average surface roughness of the flat area was about 7.23 and 3.73 nm for the low and high cooling rates, respectively. The XRD results showed that the grain sizes determined for the NiCoCr MEAs at annealing temperatures of 300, 450, 600, and 750°C corresponded to 33.68, 18.10, 16.23, and 21.98 nm, respectively. The compression test results showed that the NiCoCr MEAs could withstand an average maximum stress of 45.01 MPa. The average elasticity modulus of the four compression tests was determined to be 2692.33 MPa.The corrosion behavior of the NiCoCr alloy was investigated using electrochemical tests in a NaCl solution.
On the Passive Behavior of the Cantor Alloy in Acidic Environment
Authors: Hou Yaojun , Dou Baojie , Sun Fan , Ogle Kevin , Gharbi Oumaïma , Turmine Mireille , Vivier Vincent
Published: September 2023

High-entropy alloys (HEA) consisting of five or more elements in equimolar or near-equimolar ratios, represent an emerging class of materials showing an exceptional combination of properties such as high strength and ductility, improved fatigue resistance, fracture toughness, and thermal stability. They show considerable potential for use as corrosion resistant alloys to support our infrastructure especially for use in extreme environments. The possibility of high corrosion resistance with single phase HEAs has been demonstrated but the absence of single primary element in the HEA makes the prediction of its corrosion resistance extremely difficult.

EIS was originally developed as a tool for corrosion research and is well suited for the identification of complex mechanism involving adsorption intermediates, and 2D and 3D formation of thin films in the nanometer range. Additionally, EIS can be used for a comprehensive description of the passive film properties. This project focus on the well-defined Cantor alloy to studies its passivation in sulfuric acid solution with various chloride ions contents. EIS and linear wseep voltammetry have been used in order to describe the passive film formation as well as the passive film stability (Fig. 1). A specific attention has been paid in order to finely describe the passive film properties as a function of the applied potential and the chloride contents.

In parallel, the resistance of the passive film was studied using the pumped-micropipette delivery/substrate collection (Pumped-MD/SC) mode of scanning electrochemical microscopy (SECM), which allows to generate a single pitting on the alloy and to study its initiation, propagation and repassivation as a function of the potential and the chloride ion concentration. This approach allows in particular to get rid of the stochastic aspect of the localized corrosion and to perform quantitative analysis of the exchanged charge during the single-pit propagation.

Figure 1: Current potential curve and EIS diagrams measured at different potential for describing the passive film formation on Cantor alloy in chloride containing sulfuric acid solution.

Figure 1
3D Impedance Analysis on Dissolution Behavior of Additive-Manufactured Al-12%Si Alloy
Authors: Hoshi Yoshinao , Miyazawa Ryo , Otani Yuki , Takata Naoki , Kobashi Makoto
Published: September 2023

Laser Powder Bed Fusion (LBPF) is one of the additive manufacturing techniques using a laser beam to melt and fuse layers of metal powder particles forming various metal products with complex shapes. Because the Al-Si alloy manufactured by LPBF has good mechanical properties compared to conventionally cast Al alloys, it is important to investigate the dissolution behavior of Al-Si alloy manufactured by LPBF for wider usage in industry.

In the present study, the film resistance of oxide film formed on additive-manufactured Al-12%Si alloys were investigated by a three-dimensional(3D) impedance spectroscopy1-5. This method allows for the estimation of the film resistance with time information because the impedance is plotted on the 3D diagram whose axes are real, imaginary and time, namely, the instantaneous impedance at arbitrary time can be determined from 3D impedance. To investigate the dissolution behavior of additive-manufactured Al alloys, the non-annealed sample (Al-12Si) and annealed samples at different temperatures ranging from 200 to 350 ℃ (Al-12Si300) and 530 ℃ (Al-12Si530) with arbitrary holding time were used for the electrochemical measurements. The 3D impedance of Al-12Si, Al-12Si300 and Al-12Si530 could be successively measured in the immersion conditions. The 3D impedance of Al-12Si and Al-12Si300 demonstrated that the impedance of both samples was increased with time. The 3D impedance of Al-12Si530 indicated small values during measurement. These results imply that the increase of impedance of Al-12Si and Al-12Si300 is associated with the formation of oxide film on the surface. The film resistance estimated from impedance spectra determined from 3D impedance and the morphology of samples after the measurement were correlated discussed.

References:

Z. B. Stoynov and B. S. Savova-Stoynov, J. Electroanal. Chem., 183 (1985) 133.

M. Itagaki et al., J. Power Sources, 135 (2004) 55.

M. Itagaki et al., J
.
Electroanal
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Chem. 737 (2015) 78.

Y. Hoshi et al., J. Surf. Finish. Soc. Jpn., 67 (2016) 494.

H. Watanabe et al., J. Power Sources, 507 (2021) 230258.
Localized Corrosion and Passive Film Characteristics of Additive Vs. Wrought Al-Zn-Mg-Cu-Based Alloy
Authors: Rajendran Rupesh , Eisenhaure Jeffrey D , Kinsey Alex H , Singh Preet M
Published: September 2023

Al-Zn-Mg-Cu alloys of the 7xxx series have proven to be excellent candidates for the aerospace, defense, and automotive industries due to their high strength to weight ratio, high corrosion resistance, and fatigue performance. For additively manufactured alloys manufactured using laser powder bed fusion (LPBF), the non-conventional microstructures formed as a result of one or more factors like alloy modification, LPBF process, and subsequent thermal treatments can lead to change in corrosion behavior and mechanisms.

Using scanning vibrating electrode technique (SVET) and immersion tests in chloride environments, this work concentrates on understanding the localized corrosion behavior of additively manufactured Al-Zn-Mg-Cu based alloy in comparison with its wrought counterpart. To understand the corrosion mechanisms, microstructures including the precipitates are characterized at different length scales using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the corrosion behavior. The difference in passive film characteristics of additive vs. wrought Al-Zn-Mg-Cu based alloy is studied using electrochemical impedance spectroscopy (EIS) and X-Ray photoelectron spectroscopy (XPS) characterization. Overall, the LPBF-based alloy studied shows better corrosion performance than the wrought counterpart in chloride environments. The microstructural differences and mechanisms responsible for this behavior is proposed.
Kinetic Analysis on Hydrogen Entry into Steel in Aqueous Solutions by Alternating Current Method
Authors: Itagaki Masayuki , Okamoto Nana , Watanabe Hikari , Shitanda Isao
Published: September 2023

Degradation of steels due to the hydrogen embrittlement, which is related to the hydrogen penetration reaction (HPR) into steel, is a serious problem from the standpoint of infrastructure preservation. A Devanathan-Stachurski permeation technique [1, 2] is a well-known method to determine a hydrogen penetration rate in metals. In this technique, two independent electrochemical cells are arranged on right across two surfaces of thin metal sheet and anodic and cathodic polarizations can be performed with each cell using the three-electrode system. The hydrogen penetration rate can be evaluated by measuring the oxidation current of hydrogen atoms diffused in the metal sheet at the anode side. The electrochemical impedance spectroscopy (EIS) was used for electrochemical measurement with the Devanathan cell to investigate HPR mechanisms because the time constants of hydrogen evolution and entry can be discriminated [3-5]. In this study, we used a complex hydrogen penetration ratio (CHPR), which is a transfer function related to hydrogen entry and diffusion in metal sheet, with the Devanathan cell to investigate kinetics of hydrogen entry into metals. The CHPRs of carbon steel sheet immersed in aqueous solution of different pH’s were measured in this study. The rate constant of hydrogen entry was determined by comparing experimental results with the simulated ones according to the theoretical equation, and influence of pH on hydrogen entry was discussed.

References:

[1] M. A. V. Devanathan and Z. Stachurski, Proc. R. Soc. Lond. Ser. A, 270, 90 (1962).

[2] M. A. Devanathan and Z. Stachurski, J. Electrochem. Soc., 111, 619 (1964).

[3] C. Gabrielli, P. P. Grand, A. Lasia, and H. Perrot, J. Electrochem. Soc., 151, A1943 (2004).

[4] A. Tada, E. Nishikata, ISJ internatonal, 56, 424 (2016).

[5] K. Fushimi, M. Jin, T. Nakanishi, Y. Hasegawa, T. Kawano and M. Kimura, ECS Electrochem. Lett., 3, C21 (2014).
Localized Corrosion Behavior and the Relationship to the Second Phases in Biodegradable ZX21 Mg Alloy in Hanks' Balanced Salt Solution
Authors: Fan Chien-Wei , Chu Peng-Wei
Published: September 2023

Mg alloys are considered promising biodegradable implant materials owing to their high activity, which makes Mg alloys degradable in the human body and can avoid second removal surgeries. Also, compared with other biodegradable implant materials, Mg alloy has a similar density and Young’s modulus to human bones, which minimizes the stress shielding effect. ZX series Mg alloys, which contain Zn and Ca, are designed to increase the alloy strength but maintain biocompatibility. However, even with all the advantages, the high degradation rate limits the clinical applications of ZX series Mg alloys. With fast degradation, not only the mechanical properties are affected, but also a large amount of hydrogen gas and hydroxide ions would accumulate around the implant in the patient. Therefore, it is essential to investigate the corrosion mechanism of the ZX series Mg alloys to mitigate the degradation rates.

Localized corrosion is one of the noticeable features in the corrosion process of ZX series Mg alloys, which is the main reason for the low corrosion resistance and high degradation rate of the alloy. However, the origin and detailed mechanism of the initiation and propagation of localized corrosion on ZX series Mg alloys are still unclear. The second phases, which contain Zn and Ca, play complex roles in the corrosion process owing to the inhomogeneous elemental distribution and different electrochemical potentials with respect to the Mg alloy matrix. Thus, this study aims to investigate the microstructure of the localized corrosion sites and the galvanic effects around the second phases in a ZX series Mg alloy.

In this study, an Mg-2 wt%Zn-1 wt%Ca (ZX21) alloy was prepared, and the localized corrosion behavior was investigated in a Hanks’ balanced salt solution (HBSS) at 37°C. By scanning electron microscope (SEM)/focused ion beam (FIB) cross-sectional observations, two kinds of second phases were identified in the ZX21 Mg alloy, one is enriched with Zn and the other is not. After immersion in HBSS, galvanic corrosion sites were found in the Mg alloy matrix next to the second phase enriched with Zn, while the Mg alloy matrix next to the second phase with lower Zn concentration was intact. Furthermore, the second phases in the ZX21 Mg alloy were found to hinder the propagation of localized corrosion. The complex roles of the second phases in the ZX21 Mg alloy on the localized corrosion behavior will be discussed based on electrochemical measurements and microstructure characterizations.

Figure 1
Nd Based Surface Modification to Prevent High Temperature Oxidation of a Ferritic Stainless Steel
Authors: Hong Jong-Eun , Joh Dong Woo , Kim Hye-Sung , Lee Seung-Bok , Lim Tak-Hyoung , Park Seok-Joo , Song Rak-Hyun
Published: September 2023

Fe-Cr stainless steels have experienced a formation of chromia scale when exposed to an oxidising atmosphere at elevated temperatures. The oxidation will reduce the electrical conductivity of the steel for the high resistivity of the Cr oxide layer grown. In addition, the Cr containing scale may result in a poisoning of the air electrode in solid oxide fuel cells (SOFCs), which is led by volatile Cr species released from the surface. Therefore, it is required to avoid or prevent the scale growth to improve the oxidation resistance and electrical conductivity by the application of a protective coating or a surface modification onto the steel surface. In this study, an influence of Nd based surface modification onto a commercial ferrtie stainless steel was examined on the microstructure evolution, high temperature oxidation, and area specific resistance. It was revealed that the Nd modification suppressed chromia scale growth and thus reduced area specific resistance because of the formation of an Nd and Cr containing secondary phase possessing a conductivity than that of the Cr scale.
Probing the Corrosion Rates of Novel Titanium Substrates in a Simulated PEM Fuel Cell Environment
Authors: Yapell David , Alexander David , Borup Rod L. , Rockward Tommy
Published: September 2023

Metallic bipolar plates are often used in proton exchange membrane fuel cells (PEMFCs) due to their facile manufacturing process, high electrical and thermal conductivity, and mechanical strength. [1] Titanium is particularly popular due to its corrosion-resistive properties which come from a naturally occurring passive oxide layer on its surface. However, the naturally occurring passive film cannot fully withstand the acidic environment of an operating PEMFC. And inherently, without this protective layer; corrosion will inevitably occur. [2] Thicker oxide layers can be formed on the surface by exposing the titanium to elevated temperatures in the presence of oxygen

In this study, the corrosion resistance of commercially pure titanium with thermally grown oxidation layers and titanium directly coated with a commercial sub-oxide coating was investigated. The corrosion resistance of the various samples was examined with potentiostatic and potentiodynamic tests in sulfuric acid solution at various temperatures to simulate PEMFC conditions. The samples were also subjected to a novel accelerated stress test to evaluate long term durability under fuel cell vehicle startup and shutdown conditions.

References

[1] Wu, S., Yang, W., Yan, H., Zuo, X., Cao, Z., Li, H., Shi, M., & Chen, H. (2021). A review of modified metal bipolar plates for proton exchange membrane fuel cells. In International Journal of Hydrogen Energy (Vol. 46, Issue 12).

[2] Yu, F., Wang, K., Cui, L., Wang, S., Hou, M., Xiong, F., Zou, R., Gao, P., Peng, H., & Liu, Z. (2022). Vertical-Graphene-Reinforced Titanium Alloy Bipolar Plates in Fuel Cells. Advanced Materials, 34(21).
(Invited) Regimes of Reaction-Diffusion Processes Nearby the Plasma-Liquid Interface
Authors: Uner Necip Berker
Published: September 2023

Plasma-liquid systems are usually comprised of an atmospheric-pressure plasma electrode and a liquid surface, which can have a bubbly and irregular, or a smooth surface. When coupled with a metal counter electrode immersed in the liquid, this configuration has been shown to form capable electrochemical systems that can degrade recalcitrant pollutants, conduct organic chemistry and when reactive gases are used, can create unique gas-liquid reaction pathways for important processes such as N2 fixation and CO2 utilization. Up to date, many different types of plasmas with different frequencies, plasma electrode shapes, gas flow rates and applied powers have been utilized in literature. One common aspect of most plasma sources in plasma-liquid systems is that the current density at the interface is much higher than in conventional electrochemical systems. Consequently, the observed rate constants of some of the plasma-assisted processes mentioned above have been found to fall in a rather narrow range of values, despite the vast differences in plasma sources. This is an indication of mass transport playing a crucial role in the observed kinetics. This argument is supported by experimental results obtained through changing current in continuous plasmas and changing frequency in pulsed plasmas.

When mass transport rate is of the same order with reaction rate or slower, the observed picture for kinetics requires a mathematical description of the interplay of reaction and diffusion to elucidate intrinsic kinetic data. A phenomenological, yet practical and predictive modeling framework has not yet been established for plasma-liquid systems. Despite new kinetics that arise from the unique species produced at the plasma liquid interface, gas-liquid contacting is a well-established field in chemical engineering. In this talk, early chemical engineering studies on gas-liquid contacting will be summarized and the reaction-diffusion models developed through these studies will be applied to plasma-electrochemical systems. According to the theory, multiple regimes of reaction-diffusion processes must exist, and some of these regimes can be reduced to simpler analytical models that allow compact expressions for the observed rate constant and faradaic efficiency. Examples on applying the modeling framework to published experimental data will be given and the criteria that determine the validity of the model equations will be discussed.
Plasma-Synthesis of MOF-Derived Nanoporous Copper Oxides for Solar Thermal Application
Authors: Khalil Sameh , Ganguly Abhijit , Mariotti Davide , Chakrabarti Supriya
Published: September 2023

Nanoporous Metal oxides (P-MOx) have attracted great attention because of their enhanced performances in e.g., energy storage, catalysis, sensors, solar technology, and biomedicine due to large surface area coupled with good thermal and chemical stability. Existing synthesis techniques of P-MOx suffer from major drawbacks such as longer time and limitation in material choices. Plasma assisted synthesis of metal organic framework (MOF) derived P-MOx can be a rapid and sustainable one-step process and allow a higher degree of flexibility in controlling porosity, pore size distribution and surface properties. Herein, synthesis of nanoporous copper oxides (P-CuOx) was carried out by plasma treating copper-based MOF as a precursor. A systematic study of the transformation of MOF to derived P-CuOx has been carried out by varying the plasma treatment time also the formation of different phases of CuO and Cu2O was investigated. Additionally, a comparative study of properties was done between the plasma-synthesised P-CuOx and pyrolytically synthesised P-CuOx. Transformation process of MOF to P-CuOx was studied using x-ray diffraction (XRD) and Raman analysis. Moreover, morphological properties were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally detail optical characterization and solar thermal conversion properties of P-CuOx based nanofluid were studied to test its applicability in solar thermal energy harvesting.
(Digital Presentation) Application of Plasma Cleaning in the Preservation and Restoration of Cultural Heritage
Authors: Fallah Milad , Mohammadhosseini Babak , Khatibi Ali , Ostovarpour Farzaneh , Abbassi Shanbehbazari Mohammad Sadegh , Khani Mohammad Reza , Shokri Babak
Published: September 2023

The chemical reactivity of metals at inappropriate climate conditions can be a threat to metallic cultural heritage. It is known that oxygen plays an important role in the corrosion and decay of metallic objects. Oxide formation is among the most prevalent destructive phenomena in this field. The metallic archaeological objects lose their original shape due to the oxide layer that develops on their surface. Among physical-mechanical and chemical techniques used in the past to remove the oxide layer from these antiques, Cold plasma technology has been proposed as a novel safe method to successfully achieve this goal. In a plasma medium, which can be formed by an electrical discharge, chemically reactive species exhibit a unique behavior in response to the injected gas type, electrical and chemical parameters, etc. This special behavior aids in achieving the user's goal through physicochemical phenomena. In this study, Hydrogen gas, with its reductive character, in the plasma phase provides free radicals of Hydrogen reacting to the copper oxide layer on ancient coins. As a result of this plasma reduction reaction, separation of the oxide layer from the copper surface is achievable. This phenomenon which is called Plasma cleaning, is a type of etching. Plasma cleaning does not destroy surface structure and information contained within metallic heritage artifacts. The feasibility of this non-destructive cleaning method has been investigated for the preservation and restoration of ancient copper coins dating back roughly 300 years ago. These ancient copper coins were exposed to a cold hydrogen plasma for 120 minutes. Results show that Tenorite and Spertiniite formed on the surface of coins have been successfully removed. The black color of Tenorite, a type of copper oxide, gives a dark appearance to copper coins' surface, and Spertitnite, as a copper hydroxide, exhibits a blue-green color on copper coins. According to the results, after 2 hours of hydrogen plasma treatment, not only these green spots have been removed, but also the dark appearance of the entire surface of the coin has been reduced. This amount of clearance is a good result considering the untreated area. Moreover, Figure 1 illustrates the coin's surface using SEM (A) before and (B) after Hydrogen plasma treatment. These images were obtained at a 200x magnification from the surface. In contrast to Figure 1(A), which had heavily polluted surfaces, case B's dark pollution has been removed, reducing the amount of darkness on the coin's surface. This study shows the efficacy of Plasma cleaning for the preservation and restoration of ancient copper coins.

Figure 1
(Invited) Uip-Grade Recycling of Titanium Using Molten Salts
Authors: Okabe Toru H , Ouchi Takanari
Published: September 2023

With the increasing demand for Ti, the amount of Ti scrap is expected to increase. Hence, a new process to efficiently remove oxygen in Ti directly from Ti scrap should be developed to recycle Ti scrap. However, it is difficult to remove oxygen directly from solid Ti, and no effective deoxidation method for Ti scrap has been developed on an industrial scale. In this study, we developed new techniques to remove dissolved oxygen directly from Ti through thermochemical or electrochemical reactions using rare earth metals and/or molten salts. Based on the thermodynamic analysis and experimental verifications, we found that it is possible to remove oxygen in Ti and Ti alloys below 100 mass ppm level directly from high-oxygen-containing metals. This technology is expected to be a new process to remove oxygen directly and efficiently from Ti scrap. Furthermore, the proposed deoxidation technique can be applied to a new smelting process of Ti based on the direct reduction of Ti from oxide feeds.
Anodic Behaviour of NixFeyCu5 and NixFeyCu20 in Potassium-Rich Naf-KF-AlF3-Al2O3 Melts
Authors: Padamata Sai Krishna , Singh Kamaljeet , Haarberg Geir Martin , Saevarsdottir Gudrun
Published: September 2023

Using inert anode technology to produce aluminium would substantially reduce the aluminium industry's carbon footprint. Replacing the Hall-Héroult process with an alternative process based on vertical electrode cell (VEC) design using inert anodes and wettable cathodes is a promising alternative, but must be developed to be economically viable at scale. Three material types have been explored as inert anodes: metals, cermets and ceramics. Metallic anodes have been widely studied for their attractive properties, such as superior mechanical strength, high electrical conductivity and ease of fabrication. Of metallic anodes, Cu-Al, Ni-Fe and Ni-Fe-Cu-based alloys are the most commonly examined alloy systems for anode applications. It is also necessary to use low-temperature melts during the electrolysis process to ensure that the anodes are not damaged. In NaF-KF-AlF3 melts, increasing the KF content in the mixture would reduce the liquidus temperature and increase the alumina solubility in the melt.

In this work, we examine the anodic behaviour of NixFeyCu5 and NixFeyCu20 electrodes, without prior surface treatment, in potassium-rich NaF-KF-AlF3 melts at 770°C. The cryolite ratio (xNaF+xKF/xAlF3) and potassium ratio (xKF/xKF+xNaF) of the melt used for the studies are 1.3 and 0.7, respectively. Electrochemical techniques such as chronopotentiometry, chronoamperometry and linear sweep voltammetry were performed to examine the anodic behaviour of these metallic anodes under an N2 atmosphere.

Figure 1 shows the steady-state anodic polarisation curves on NixFeyCu5 and NixFeyCu20 anodes before and after galvanostatic polarisation with an applied current density of 0.5 Acm-2 for 120 minutes. It can be noted that the anodic potential at the same current density is more for the polarised anode compared to the non-polarised in both cases. This is due to the formation of a stable oxide layer during the galvanostatic polarisation of the anode. Oxidation of the anode is expected instead of fluoridation when the melt is saturated with alumina. The stabilisation of anodic current can be seen between 1.9 and 2.4 V. This stabilisation corresponds to the passivation of anodes due to the oxide layer formation. A rapid increase in the current after 2.4 V is due to the oxygen evolution reaction. The anodic current density in the passive region is much lower in anodes with Cu 20%, meaning a more protective layer is formed. After the galvanostatic polarisation of the anode, anodes were examined using scanning electron microscopy to understand the oxide layer composition. Anodes performed stably in potassium-rich melts, and Cu content plays a vital role in the anode's performance.

Figure 1. Stationary state polarisation curves of NixFeyCu5 and NixFeyCu20 anodes before and after the polarisation at 0.5 A cm-2

Figure 1