bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Potential Thresholds of Sacrificial Metallic Coatings for Protection of Al-Mg Alloys in Marine Environments
Authors: Lee Jason S
Published: February 2020

Repair and replacement of ship structures due to material degradation are high cost drivers in naval platform maintenance. Future ship designs and modernization of existing platforms rely on lightweight aluminum-magnesium (Al-Mg) 5XXX series alloys. A technological gap exists in the predictive capability for lifetime predictions of corrosion preventative sacrificial metallic coatings and identification of the underlying electrochemical, chemical and metallurgical mechanisms that control the potential thresholds for intergranular cracking (IGC) and intergranular stress corrosion cracking (IGSCC). Future ships (e.g. Littoral Combat Ship) which plan to use 5XXX alloys extensively will also be at risk. IGC and IGSCC initiation and growth are both strongly controlled by applied potential (regardless of sensitization level). Potential has been shown to significantly determine whether IGC or IGSCC occurs, onset incubation time and subsequent rates of penetration. Metal-rich primer(s) (MRP(s)) can be used as sacrificial metallic coatings that can control the applied potential across a macro defect site could provide protection against IGC of sensitized Al-Mg alloys. It is currently unknown whether a coating can exert sufficient potential control to mitigate IGC. MRPs (as well as pigmented organic coatings) offer the potential to serve as sacrificial anodes capable of performing this function. A multiphysics finite element package was used to computationally model galvanic protection conditions provided by MRPs in electrical contact with Al-Mg alloy AA5456. Primers included Zn-, Al- and Mg-based MRPs. In addition, pure metals including Mg, Al and Zn were evaluated as galvanic protection systems to validate the model against known mixed potential diagrams. Parametric variables included electrolyte thickness (1 micron to 1 meter) and composition (0.6M and 5.45M (sat’d)) NaCl. Primer evaluation was based on its ability to produce a global galvanic couple potential (Ecouple) below the threshold breakdown/pitting potential of the Mg-rich AA5456 beta-phase (beta-Epit). beta-Epit has been shown to be a critical parameter in the susceptibility of AA5456 to IGC. Sacrificial metallic primers with corrosion potentials (Ecorr) greater than Ecorr of AA5456 were predicted to result in the preferential corrosion of AA5456 based on initial boundary conditions. Zn-based primers exhibit the characteristics for providing galvanic protection to sensitized AA5456 without cathodic polarization at high hydrogen evolution overpotentials.
Combined DFT and Molecular Dynamics Study of Ni Dissolution Activation Energy
Authors: Ke Huibin , Taylor Christopher
Published: February 2020

Dissolution is one of the key processes during corrosion. To better understand and quantify dissolution in metallic materials, chemical dissolution activation energy is a key parameter. However, this value is difficult to obtain due to the challenge determining the transition state of dissolution from metal atom on surface to ion in solution. Here, a combined DFT and molecular dynamics (MD) framework has been built to calculate Ni dissolution activation energy in water. First, DFT is used to investigate the dissolution of an adatom from Ni(111) surface with constrained minimization approach, which gives a good picture of the bond breaking process between metal-metal atoms. Then, a MD simulation is applied to calculate hydration process of Ni atom interacting with H2O molecules. Finally, by integrating these two parts together, a complete picture of dissolution process and the value of dissolution activation energy can be obtained. This study will lay foundation for higher scale modeling of dissolution process of pure metal and alloys, and also provides key parameters for pitting theory validation.
First-Principles Investigation of the Effect of Interstitial Carbon on Corrosion Resistance of Martensitic Medium-Carbon Steel
Authors: Kadowaki Mariko , Saengdeejing Arkapol , Muto Izumi , Chen Ying , Masuda Hiroyuki , Katayama Hideki , Doi Takashi , Kawano Kaori , Miura Hideo , Sugawara Yu , Hara Nobuyoshi
Published: February 2020

Martensitic carbon steels with fine grains are used for many industrial applications. Interstitial carbon provides high strength to martensitic structure. Although it has been reported that the interstitial carbon has the beneficial effect on the pitting corrosion resistance of steels,1,2 the role of interstitial carbon is still unclear. In this research, first-principles calculations were applied to the clarification of the effect of interstitial carbon on the anodic dissolution of martensite.

The base specimen was AISI 1045 carbon steel, and the chemical composition of this steel (mass%) was 0.44%C, 0.20%Si, 0.85%Mn, 0.008%P, 0.002%S, <0.01%Ni, <0.01%Cr, <0.01%Mo, <0.01%Cu, <0.001%Ti, <0.002%Nb, 0.035%Al, 0.003%N, and 0.002%O. The specimens were heat-treated at 1123 K for 10 h in air and then, quenched in water. Since the surface of the specimens was decarburized during this heat-treatment, the low carbon martensitic structure was formed in the surface region of the specimens, and high carbon martensitic structure remained in the core area. Potentiodynamic polarization of the low and high carbon martensitic specimens was conducted using boric-borate buffer solution with 1 mM NaCl at pH 8.0. In addition to the electrochemical measurement, the first-principles calculations based on density functional theory (DFT) were carried out. For the calculation, the carbon concentration was varied from 0.40 at.% to 5.88 at.%.

In the potentiodynamic polarization curves of the low and high carbon martensitic specimens in 1mM NaCl containing boric-borate buffer at pH 8.0, the region of active dissolution appeared on both specimens at about -0.5 V. The dissolution current density for high carbon martensitic specimen was lower than that of the low carbon martensitic one, suggesting that the interstitial carbon suppressed the active dissolution.

Next, the effect of interstitial carbon atoms on the electronic structure of the martensitic structure was analyzed. It was clarified that the electronic density of states (DOS) of iron atoms at and near the Fermi level decreased by increasing carbon concentration. This result indicates that the interstitial carbon atom makes weak atomic bonding with the nearest iron atom, and stabilizes the electronic structure of martensite. This change in the energy state of iron atom was, therefore, attributed to the high corrosion resistance of martensitic carbon steels.

References;

M. Kadowaki, I. Muto, Y. Sugawara, T. Doi, K. Kawano, and N. Hara, J. Electrochem. Soc., 164, C962 (2017).

M. Kadowaki, I. Muto, Y. Sugawara, T. Doi, K. Kawano, and N. Hara, J. Electrochem. Soc., 165, C711 (2018).
Manipulation of a Single Crystal Nanowire on an Atomic Level
Authors: Košiček Martin , Filipič Gregor , Zavašnik Janez , Cvelbar Uros
Published: February 2020

In recent years, metal oxide nanostructures (MO) have been intensively studied due to a wide variety of applications on multiple fields, for example in optoelectronics, gas sensing, photovoltaics, field-effect transistors, UV lasers, field emission sources etc. [1]. However, for applications, other types of structures are also interesting such as sulfides and nitrides. Here the question that raises is can we manipulate nanomaterials like nanowires on an atomic level. Knowing the exact mechanism of sulfur-oxygen exchange in the metal oxide crystal lattice can be utilized for the synthesis of metal sulfides with specific morphologies. When compared to metal oxides, single-crystalline metal sulfide nanostructures of specific morphologies are usually harder to produce than MOs. Generally, metal sulfide nanostructures represent unconventional materials in areas such as batteries or photovoltaics with yet unexploited potential, where their efficiency is mainly limited by the purity of crystalline phases and structural defects [2]. A promising path for novel synthesis route is incorporation of the sulfur in the crystal structure of a metal oxide nanoparticle, while during this transition the morphology of the nanostructure does not change. In this way, it is possible to obtain single crystal metal sulfide nanostructures from metal oxide nanostructures in the single crystal to single crystal (SCSC) transformation. A promising method to achieve such transformation in a short period of time is a treatment of metal oxide nanostructures with the plasma of sulfur-containing gas.

In this research, we studied the mechanism of sulfur incorporation in the metal oxide crystal structure. The procedure was carried out by synthesis of ultra-thin metal oxide nanowires, which were then treated with sulfur-containing gases under increased temperature (in thermodynamic equilibrium conditions) and in the plasma of the same gases (under thermodynamically non-equilibrium conditions). Experiments were conducted at different temperatures and pressures to evaluate the influence of plasma on transformation process. Mechanisms involved in the interaction of sulfur-containing species with metal oxides were studied on isolated single ultra-thin metal oxide nanowire. Furthermore, changes in crystal structures and their effect on the material properties before and after sulfurization were studied.

[1] Umar A. & Hahn Y. B. (Eds.). (2010), Metal Oxide Nanostructures and their Applications. American Scientific Publishers, CA, USA

[2] Zavašnik, J., & Rečnik, A. (2013). Electron microscopy study of CVT grown Fe-sulphides. Journal of Crystal Growth, 367, 18-23.
Co-Electroless Deposition of Pt-M Bimetallic Alloyed Catalysts for Methanol Oxidation
Authors: Meekins Benjamin , Tate Gregory , Xiong Wen , Weidner John , Monnier John R.
Published: February 2020

Direct methanol fuel cells exhibit great promise as portable sources of power. A primary issue, however, is that the platinum catalyst used is readily poisoned by CO that is formed during the methanol oxidation reaction. Further, reducing the amount of Pt used is crucial to reducing the cost of direct methanol fuel cells. A straightforward way to address both issues is to synthesize bimetallic catalysts with Pt and a secondary metal that provides the necessary –OH groups to remove CO from Pt.

Co-precipitation and co-impregnation methods have traditionally been used for the synthesis of metallic and bimetallic catalysts. These methods, however, afford little control over nanoparticle composition, size, and spacing. Electroless deposition solves these issues by allowing precise compositional, size, and, when paired with strong electrostatic adsorption, spacing control. The Monnier group has developed a continuous deposition method that produces composition-controlled bimetallic alloyed catalysts on a seeded support.1

Mehrabadi et al.
2 demonstrated previously that Ru deposited by electroless deposition onto a Pt/C support was superior to commercial PtRu catalysts for methanol oxidation. Bimetallic and trimetallic catalyst syntheses have also been demonstrated. In this work, we synthesize Pt-Co and Pt-Ni bimetallic catalysts with controlled compositions. We find that specific compositions (Pt3Ni and Pt2Co) exhibit significantly improved mass activity. This talk will discuss the synthesis and characterization of these bimetallic alloyed catalysts as well as the activity for methanol oxidation observed.

Tate, G., Kenvin, A., Diao, W., Monnier, J. R., “Preparation of Pt-containing bimetallic and trimetallic catalysts using continuous electroless deposition methods,” Catalysis Today, (2018)

Tavakoli Mehrabadi, B.A., Catalysis Today, https://doi.org/10.1016/j.cattod.2018.11.042
Hydrogen Evolution Reaction on Co-Mo Electrodeposits with Nanoscaled TiO2
Authors: Podlaha Elizabeth J. , Wang Cheng
Published: February 2020

Co-Mo alloys are well known as excellent electrocatalysts for hydrogen generation.1-3 In this work, nanoscale TiO2 particles were embedded into Co-Mo alloys during galvanostatic electrodeposition from a citrate-boric acid electrolyte. Following deposition, the deposits were characterized for their HER performance. Enhancements of the exchange current density and of a lower overpotential with the composites compared to the alloy were observed, and interpreted with a Volmer-Tafel/Heyrovsky mechanism.

The HER kinetics depends on both the Mo and TiO2 composition. For example, in an alkaline electrolyte, the exchange current density exhibited a volcano-type behavior with the Mo composition in the deposits. At the maximum value of the exchange current density, the addition of TiO2 further increased its value nearly 3 times higher than the Co-Mo alloys, accounting for the difference in the electroactive surface area. Figure 1 shows polarization curves of deposits with nearly similar Mo:Co ratios with and without TiO2 in a 1 N NaOH electrolyte. The overpotential at -10 mA/cm2 decreased significantly when particles were present in the deposit by 37 mV, in this example, compared to the alloy in Figure 1. Other deposits having different Mo wt % compositions exhibited a variation in the overpotential reduction between 22-55 mV at similar exchange current densities. The Tafel slope absolute value of all deposits with TiO2 having similar Mo:Co ratios were in the range of 70-75 mV/dec. The Tafel slopes of the alloy, without TiO2, and having high Mo content, was comparable to the composite. When the alloy composition contained less Mo the Tafel slope absolute value increased. In acid, an experiment with a Co-Mo alloy verifies a further decrease of the overpotential, but corrosion of the metal and titania places limitations on the pH.

References

C. McCrory, S. Jung, I. M. Ferrer, S. M. Chatman, J. C. Peters, T. F. Jaramillo, J. Amer. Chem. Soc. 137, 4347 (2015).

P.R. Żabiński, H. Nemoto, S. Meguro, K. Asami, K. Hashimoto, J. Electrochem. Soc.
150,C717 (2003).

Y. Zhang, Q. Shao, S. Long, X. Huang, Nano Energy
45, 448 (2018).

Figure 1
Copper Electrodeposition on Textile for Wearable Electronics
Authors: Rosa-Ortiz Sabrina M. , Takshi Arash
Published: February 2020

Two main tasks in fabricating a circuit is to pattern the interconnections and soldering elements to the patterned conductive traces. Using copper growth electrodeposition assisted by hydrogen evolution as a technique for integration of electronic elements and circuits in fabrics and flexible substrates particularly useful for soldering electronic components, representing an advantage over conventional methods and providing a high quality of the deposits requiring relatively inexpensive equipment. This method has shown high rate of deposition and formation of nanostructures, expected to anchor to the fibers of a fabric for enhanced stability of the structure. Moreover, the technique has proven to be reliable for soldering electronic components at room temperature. A copper pattern can be achieved over a MWCNTs coating by the copper growth deposition in the electrochemical cell after electrolysis is reached in the cell with the aqueous solution of Cu2+ and H2SO4. Cu2+ions interact with hydrogen allowing the formation of the reaction product by the application of voltages above 1.0V. The electrodeposition parameters and the quality of the copper being deposited will be analyzed to find the optimum conditions for fast copper deposition and adhesion to the fabric structure and also will be tested for soldering simple electronic elements and it will be studied to be more resilient during laundry.
Insight into Oxidation of Ultra-Fine Lead Powder By Electrodeposition
Authors: Yang Chang-jiang , Zhao Lv-xing , Gu Yu
Published: February 2020

Pure lead powder has multiple application such as oil and gas exploration, X-ray shield, golf club manufacture, paints, lubricating grease and anti-friction products. Electrochemical deposition of lead powder can be obtained from both the acid electrolytes based on fluoroborate, acetate, fluorosilicate, nitrate, etc. and an alkaline solution. Morphological characteristics of lead powder with overpotential have been detailed in previous literatures. Nevertheless, oxidation of lead powder during electrodepositing process was out of view, which actually decreased the purity and quality of lead powders compared to atomized ones.

In this investigation, ultra-fine lead powders with a minimum median diameter of 4.5 μm were electrodeposited in solution consisting of 2 M CH3COONa, 2 mM Pb(CH3COO)2 and pH values adjusted by acetic acid. The degree of as-deposited lead powder was defined as the content of PbO in wt %, and was determined by complexometric titration with EDTA. The morphology of lead powders shown by SEM was a classical dendrite and branches, which resemble a tree. The oxidation of lead powder reached to about 16% when pH value of electrolyte was 1 and decreased abruptly to around 6 % at pH from 3 to 7. The oxidation of lead powder was stable at ~5.5 % with the cathodic current densities from 23 mA cm-2 to 36 mA cm-2 and increased to 9 % and 13% at current densities of 10 and 45 mA cm-2 respectively. The concentration of gelatin as an additive accelerated the oxidation of lead powder. When ultrasonic was applied, the oxidation degree of lead powder became 3-fold larger than that of the stirred one. More importantly, the average sizes of powder have a directly relationship with the degree of oxidation. The smaller median diameter is, the larger degree of oxidation is.

However, the XRD of the lead powder with about 16 % oxidation shows only metallic Pb with strongly preferred orientation in (111) plane, which indicated the amorphous PbO powders. The results of TEM confirmed the amorphous materials around lead particles, which suggested metallic Pb was partly transformed from PbO. Therefore, we suggested a mechanism of lead electrodeposition result in oxidation of lead as follows:

Deprotonation: [Pb(H2O)]2+ → [PbOH]+ + H+

Electrochemical reduction:

Lead reduction—

Directly：[PbOH]+ + H+ + 2e- → Pb + H2O

Indirectly: [PbOH]+ → PbO + H+

PbO + 2H+ + 2e- → Pb + H2O

Hydrogen evolution—

2[PbOH]+ + 2e- → 2PbO + H2

2H+ + 2e- → H2

The reason of forming [PbOH]+ complex is due to the stability constant, lgβ=13.3, which is about 10 order of magnitude large than that of acetate complexes, lgβ=3.60.

Figure 1
Investigation of Metal Ion Diffusion and Reduction Potential in Several Ionic Liquids
Authors: Horwood Corie , Pham Tuan Anh , Maiti Amitesh , Peters Vanessa N. , Stadermann Michael
Published: February 2020

Electrodeposition is proving to be a promising technique for forming metal capsules and other components required for Inertial Confinement Fusion (ICF) experiments performed at the National Ignition Facility. While we have recently demonstrated that non-porous, defect free parts can be electrodeposited from a variety of water-based solutions,1,2 many of the preferred metals for the ICF program (beryllium, uranium, etc.) cannot be deposited because electrolysis of water occurs at the potential required to reduce such metals.

To circumvent this, we are currently investigating Ionic Liquids (ILs) as solvents for metal electrodeposition, as the wide (~ 6 V) electrochemical window of ILs is expected to allow electrodeposition of Be, U, and many other metals.3 We are investigating the key parameters of metal ion diffusion and reduction potential for two model metals, silver and copper, in several different ionic liquids. We use electrochemical measurements along with first principles density functional theory (DFT) simulations to understand how ionic liquids affect diffusion and reduction potential, and this understanding will be applied to selecting appropriate ILs for deposition of metals such as Be and U.

Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 17-ERD-047. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release LLNL-ABS-771850.

(1) Horwood, C.; Stadermann, M.; Bunn, T. L. Fusion Sci. Technol.
2018, 73 (3).

(2) Bunn, T.; Horwood, C.; Stadermann, M. Cathode System for Electrodeposition of Metals on Microspheres. US Patent 16336-000075-US-PS1, 2018.

(3) Electrodeposition from ionic liquids, 2nd ed.; Endres, F., Abbott, A., MacFarlane, D., Eds.; Wiley-VCH: Weinheim, Germany, 2017.
Investigation on Parameters Influencing the Electrodeposition of Niobium-Based Layers
Authors: Endrikat Anna , Ispas Adriana , Bund Andreas
Published: February 2020

The refractory metal niobium is used in technical applications because of its excellent corrosion and wear properties and as alloying element in steel or in superalloys for high temperature applications. In order to open new fields of application with maximum material efficiency, electrochemically produced niobium protective layers are suitable because they can increase the life-time of critical components.

In principle, the electrochemical production of niobium-based layers is possible. However, due the very cathodic standard potential of refractory metals they cannot be electrodeposited from aqueous electrolytes. The ionic liquids (ILs) allows electrochemical deposition of niobium due to its high electrochemical stability (5 – 6 V electrochemical window) and low melting point <100°C.

Usually metal halides (e.g. NbCl5) are used as precursors for electrochemical niobium deposition. The transfer of five electrons in several individual steps results in a complex reduction mechanism that can adversely affect the film formation, e.g. by formation of stable intermediates.

Applying higher temperatures, additives (e.g. [BMP]Cl, LiCl) or pulsed potentials, the electrode/electrolyte interface changes and the deposition of niobium can be specifically influenced. Another possibility for optimizing the niobium-based layers is based on pre- and post-treatment (e.g. anodic etching).

This contribution will discuss the influence of temperature, additives as well as the use of special pulse parameters on electrochemical niobium deposition. The aim is to find suitable deposition, pre- and post-treatment conditions and thus to optimize the resulting niobium-based layers. By means of various techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical quartz microbalance (EQCM), as well as scanning electron microscopy, a better understanding of the reduction mechanism of niobium halides in ILs in the presence of selected additives shall be obtained.
Noble Metals Alloys Deposition from Non-Aqueous Solvents
Authors: Manolova Mila , Böck Reinhard
Published: February 2020

Binary alloys of Pd and Pt were successfully deposited from 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM-BF4-Cl) ionic liquid and from a deep eutectic solvent (DES) based on a mixture of choline chloride and urea (ChCl-UA) at ambient atmosphere conditions. Ag, Ni and Sn were used as alloy components. Cyclic voltammetry experiments on glassy carbon electrode showed the reduction and dissolution of the alloys in the investigated solvents. Pulse plating and potentiostatic deposition techniques were used to deposit PdAg, PdNi, PdSn and PdPt alloys on cylindrical Cu substrate. The composition of the layers could be varied either by the concentration of the metals in the electrolyte solution or by changing the deposition mode (pulsed current or potentiostatic deposition).

In order to determine the surface morphology and the thickness of the electrodeposited noble metal alloy films, a high resolution scanning electron microscope (SEM/EDX) and an energy dispersive X-ray fluorescence spectrometer (XRF) were used. The surface morphology of the layers was remarkable affected by the composition of the alloys. Scanning electron micrographs of the different electrodeposits showed that Pd alloys deposited by pulse current were generally nodular and relatively compact, whereas the films deposited by potentiostatic deposition were less dense and covered with dendrite-like and sharp-edged crystallites.

The addition of a second metal (e.g. Ag+ or Sn2+) to a basic Pd or Pt electrolytes enhanced the overall metal deposition rate in comparison to solutions without alloying components and caused a remarkable increase of the layer thickness of the alloys.

XRD measurements confirm that it was possible to deposit different binary metal alloys from both non-aqueous electrolytes by applying different deposition techniques.

First adhesion tests and measurements of the microhardness of Pd-Ag deposits showed good properties of the produced alloy films. Also the hydrogen embrittlement of selected samples was proved by a hydrogen analyzer. These results confirmed that the quantity of hydrogen was negligible in the Pd alloy films produced from ionic liquids in comparison to films obtained from conventional aqueous solutions.
Structure-Property Relationships in Prototypical Deep Eutectic Solvents
Authors: Spittle Stephanie , Cosby James Tyler , Sangoro Joshua R
Published: February 2020

Deep eutectic solvents (DESs) have shown great promise as alternative materials for electrochemical applications. Two prototypical DESs comprising of choline chloride (ChCl) and glycerol and urea respectively, were studied using broadband dielectric spectroscopy (BDS), dynamic mechanical spectroscopy (DMS), and differential scanning calorimetry (DSC). In ChCl and glycerol (glyceline), slow sub-α relaxations linked to nanoscale heterogeneity between the two species are observed with BDS and DMS spectra. With increasing ChCl concentration, the sub-α dielectric relaxation, that is coupled to ion diffusion, becomes faster relative to the structural relaxation, while the slower mechanical relaxation remains unaffected. In contrast, ChCl and urea (reline) feature a coordinated hydrogen bonded network where the salt ions interact strongly with urea molecules. With increasing salt concentration, an increase in rate of structural dynamics and dc conductivity is observed up to the eutectic composition. However, it is remarkable that just 3mol% more ChCl above the eutectic composition results in slower dynamics by up to one order of magnitude. The differences between glyceline and reline can be attributed to the drastic difference between the nature of the resultant hydrogen bonded networks associated with glycerol and urea. These results will be discussed within the framework of recent models of dynamics and transport in ion conducting liquids.
(Invited) Thoughts on the Viscous Sublayer
Authors: Newman John
Published: February 2020

Years ago people postulated that there is a laminar sublayer near a solid wall in turbulent flow. Murphree (1932) and Levich (1942, 1944) postulated that the turbulence eddies decay only gradually as the solid wall is approached. There are two schools of thought: one says that the eddy diffusivity is proportional to y
3 near the wall; the other says y
4. Which is right?

Perhaps there is some truth in both views. It may be that y
4 prevails near the outer limit of the viscous sublayer, adjacent to the outer turbulent flow, but that y3 prevails very close to the wall.

It has been thought that this was important only for mass transfer in turbulent flow at high Schmidt numbers, that is, for diffusion coefficients much smaller than the kinematic viscosity. However, it is shown that Nikuradse’s data (1932) for pressure drops (or friction factors) in turbulent pipe flow do not agree with his very careful measurements of profiles of the eddy viscosity. In other words, the viscous sublayer cannot be ignored even in fluid flow.

The profile of predicted eddy diffusivity of Wasan, Tien, and Wilke (1963) show regions of y
3 dependence very close to the wall and y dependence in the outer turbulent flow with perhaps a y
4 dependence in the intermediate region.

On this diagram, one can identify the thickness of the diffusion layer as a function of the Schmidt number. As is well known, the diffusion layer gets very thin at high Schmidt numbers. Using this profile, one can show that the y
4 dependence will not show up clearly in mass-transfer data at any Schmidt number. Any region of y
4 dependence of the eddy diffusivity is outside the diffusion layer where the concentration does not change (at high Schmidt numbers).

These thoughts inspire a method of calculating the profiles of eddy diffusivity and eddy viscosity from consideration of fluctuations themselves. Hopefully this can be a subject of future work.
Molten Salt Electrolysis for the Graphitization of Carbon Based Materials
Authors: Bagri Prashant , Luo Huimin , Dai Sheng
Published: February 2020

Carbon based materials play a critical role in the modern economy with widespread application in many energy applications including batteries and nuclear energy. Further, carbon based materials have recently been employed in important structural materials like carbon based composites for use in aircraft components etc. Most of these modern applications require the use of highly crystalline, graphitic carbon. The current process of graphitization requires the precursor amorphous carbon to be heated to temperatures approaching 3000 K for significant time. In this paper, we continue to explore the recently reported low temperature graphitization process that employs molten salt electrochemical approach to achieve graphitization. Herein, we report a new combination of salts that further significantly reduces the temperature to below 750 C. This is achieved by using a combination of salts that enhance the graphitization reaction. Additionally, the graphite thus synthesized were evaluated for important performance properties in their respective applications.
Electrochemistry Enhanced Activation of Ethane for Co-Production of Ethylene and Hydrogen with Low-Thermal-Budget and Low-CO2-Emission
Authors: Wu Wei , Wang Lucun , Ding Dong
Published: February 2020

The shale gas revolution and rapidly increasing demand for hydrogen (for upgrading lower-quality oils and automotive industry), have spurred the development of more energy-efficient and cost-effective approaches to convert natural gas/natural gas liquids into high value-added fuels and chemicals. Ethylene, one of the largest building blocks in petrochemical industry, is mainly manufactured from high temperature steam cracking of ethane or naphtha. This method is energy intensive and represents the single most energy consuming process in the chemical industry. To fully exploit the potential of ethane as feedstock, we demonstrated electrochemistry enhanced co-production of ethylene and hydrogen through non-oxidative dehydrogenation of ethane at temperatures below 600oC with close to theoretical ethane conversion rate and high ethylene yield. Significant reduction in energy consumption and CO2 emission, compared to the commercial ethane steam cracking process was achieved. The remarkable performance is enabled by advanced fabrication of solid oxide proton conducting electrochemical membrane reactors incorporated with highly selective electrocatalysts as well as comprehensive operation optimization.
(Invited) Understanding Role of Li Substitution at Alkali-Site of NaX[Fe0.5Mn0.5]O2 As Cathode for Sodium Ion Batteries
Authors: Wang Ji Eun , Jung Young Hwa , Kim Do Kyung
Published: February 2020

Sodium ion batteries(SIB) have gained significant attention as next generation of rechargeable batteries based on natural abundance and low cost. Transition metal oxides with layered structure is well known electrode material that have been successfully commercialized in LIB system and have been reported to be one of the promising electrode material for SIBs. Extensive studies have been reported about substitution of various foreign element in the layered structure. Substitution of foreign element could be achieved by substitution at either transition metal site or alkali site. Many studies focused on the composition and substitution at the transition metal site of the layered structure. Here, this study focused on the substitution at the alkali site of layered structure as cathode materials for SIBs. Substitution at alkali site could not only affect the properties of layered structure, but also interfere with intercalation of sodium. In this study, Li was substituted on alkali site of NaXFe0.5Mn0.5O2 as cathode material for SIBs. Although Li have been reported to be substituted at transition metal site in previous literature, Li substitution at alkali site was achieved by varying the ratio between Fe and Mn. Rietveld refinement synchrotron XRD and neutron diffraction patterns, XANES analysis, and ICP analysis were conducted in order to confirm the substitution of Li at alkali site. When Li was substituted at alkali site, it showed improved cycle life and rate capability in spite of decreased interlayer spacing. In situ XRD analysis and DFT calculation was conducted in order to understand the role of Li in structure stability and Na intercalation behavior. The result showed that Li substitution at alkali site stabilized layered structure during charge/discharge process and that Li lowered the energy barrier of Na hopping, leading to improved cycle life and rate capability.
(Invited) Synthesis, Characterization, and Investigation of Non-Arrhenius Behavior in Anti-Perovskite Ion Conductors
Authors: Wang Fei , Tsai Ping-chun , Li Yiliang , Eiler Stephanie L. , Son Seoung-Bum , Chiang Yet-Ming
Published: February 2020

Amongst known families of solid electrolytes of potential interest for solid-state batteries, the anti-perovskites (A3BX) are of interest for the high ionic conductivities observed in certain compositions (see Figure), and, like perovskites, the compositional flexibility provided by the possibility for ion substitution onto multiple lattice sites. For example, variations in the relative size of ions A, B and X result in changes in the Goldschmidt tolerance factor, or extent of disorder, that are accompanied by changes in the distribution of lithium migration energies. [1]

In surveying transport in this family of ion conductors, we observed a trend wherein numerous compositions show upwards curvature on an Arrhenius plot (see Figure), indicating a non-constant activation energy. This is unusual as most solids exhibiting non-Arrhenius behavior exhibit a negative deviation. We have synthesized a wide range of Li and Na anti-perovskites, and have confirmed non-Arrhenius conductivity with a positive deviation in compositions such as Na3OBr0.6I0.4. This talk will discuss compositional trends related to this behavior, and our attempts to understand the structural origin(s) of this behavior through temperature-dependent X-ray and neutron scattering, calorimetry, and other methods. Implications for the design of solid electrolytes for solid state batteries will be discussed.

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

[1] Kwangnam Kim and Donald J. Siegel. "Correlating lattice distortions, ion migration barriers, and stability in solid electrolytes." Journal of Materials Chemistry A 7, no. 7 (2019): 3216-3227.

Figure 1
Glucose Oxidation in Viologen-Mediated Fuel Cells Using a Non-Precious-Metal Anode
Authors: Bahari Meisam , Brown Daniel , Roberts Matt , Hawkins Adam , D. Watt Gerald , Lewis Randy , Harb John N.
Published: February 2020

Glucose has a great potential as a renewable source of energy for fuel-cell applications. However, rapid and complete oxidation of glucose in fuel cells has been a challenge. To address these issues, this study examines the use of dimethyl viologen (MV) as an electron mediator. MV has the potential of oxidizing glucose to a large extent at a relatively fast rate. In a MV-mediated glucose fuel cell, MV homogeneously oxidizes glucose. Subsequently, MV oxidized at the anode of an electrochemical cell, generating current. Since the electrochemical reaction of MV does not require a catalyst, MV-mediated fuel cells also offer a potential cost advantage over precious-metal-based fuel cells. This study investigates the efficiency of MV-mediated glucose oxidation. The study also evaluates the rate capability of an MV-mediated glucose fuel cell in terms of current density and power density.

Glucose oxidation efficiency was experimentally investigated in an electrochemical cell. To do so, the impact of various factors including the initial molar ratio of MV to glucose and the rate of the electrochemical reaction were examined. In addition, 13C-NMR was used to identify reaction products in order to obtain insight into the oxidation mechanism. Our experimental results show that the oxidation efficiency depends on the rate of electrochemical reaction and, over a certain range, can be increased by increasing that rate. Moreover, the oxidation efficiency can also be increased by increasing the initial molar ratio of MV to glucose. The maximum oxidation efficiency observed was 22%, which is almost three times larger than that observed in precious-metal-based fuel cells. 13C-NMR results confirmed that the main oxidation product was glycolic acid, consistent with the measured oxidation efficiency.

To investigate the rate capability of a MV-mediated glucose fuel cell, a mathematical model was developed. A fuel cell device was also made and rate experiments were performed. In such a cell, the homogeneous reaction of glucose with the mediator and the electrochemical reaction of the mediator at the anode are coupled, so that both types of reactions contribute to and have the potential to limit the overall rate. The model helped us to better understand the influence of each type of reaction on the overall rate. Methods for enhancing the overall rate were also explored. Based on the model, system optimization has the potential to produce power densities about one order of magnitude larger than values reported to date in the literature.
Effects of Temperature on the Faradaic Efficiency of Hydrogenation and Hydrogenolysis of Furfural
Authors: May Andrew Scott , Biddinger Elizabeth J
Published: February 2020

Alternative sustainable methods for chemical and fuel production are a growing area of interest. One alternative for biomass upgrading, which typically requires high operating temperatures and pressures, as well as externally-supplied hydrogen gas, is to use electrochemistry to undergo the reaction. Using electrochemical methods, the reaction can be run at ambient conditions. In addition, the external hydrogen which comes from energy intensive methods is not necessary because adsorbed hydrogen for biomass conversion can come from the electrolyte. Furfural (FF) reduction to furfuryl alcohol (FA) and 2-methylfuran (MF) is a promising case for the reaction to be performed electrochemically.

Furfural electroreduction requires high overpotentials for appreciable partial current densities to desired products which leads to significant hydrogen evolution (HER). In this work we show that the reactions rates to desired and non-desired products vary differently with temperature between 10 to 45 °C when studied over copper electrocatalysts in 0.5M sulfuric acid. This affects the overall Faradaic efficiency for all products and allows for the shift of Faradaic efficiency of products as a function of temperature. The Faradaic efficiency is shown to be a function of both temperature and overpotential allowing one to target higher FE of desired products by tuning both temperature and potential.
Pulse Reverse Current Surface Finishing of Additively Manufactured Impellers
Authors: Hall Timothy D. , Garich Holly , Liu Danny X. , Snyder Stephen , Taylor E. J.
Published: February 2020

Powder bed methods of additive manufacturing (AM) use either an electron beam (Electron Beam Melting – EBM) or a laser (Selective Beam Melting – SLM) to sequentially melt powder, layer by layer, to build up a 3-dimensional object directly from a powder bed according to a computer aided design (CAD) file. Complexity is free with AM processes, so parts such as the impeller shown in the Figure Left, are natural candidates for AM.

With EBM. there are four steps to build each layer in a build. First, the beam is scanned to preheat the powder bed without melting, second, the contours (outer edge) of the area to be melted is traced and powder melted, third, the hatch (area within the contours) is melted and finally any supports that need to be built to support higher layers of the part being built are added. The side face of a part adjacent to powder after an EBM build is shown in the Figure Right.

With SLM, a similar strategy is used although powder bed preheating is not necessary (the powder bed remains at ambient temperature or is preheated to a low temperature – up to 200°C – with separate heaters). The result of this low temperature processing is that residual stresses are created. The supports which are added to the model to support higher level downward facing surfaces are structural in nature and used to prevent distortion (unlike those supports in the EBM process which are added for thermal management).

The major concerns for incorporation of AM into structural parts are (1) microstructural anisotropy/inhomogeneity, (2) porosity – open near the surface and closed internally and (3) surface finish that is strongly dependent on the orientation of the surface relative to the build direction. Improving the surface finish is critical for certain applications. While finish machining can be used where surfaces are accessible, one benefit of the complexity of part shape is the possibility of building parts with internal channels, inaccessible to machining.

Therefore, this paper will discuss recent developments toward the demonstration of electrochemical processing conditions and tooling that enable electrochemical finishing of complex components like shrouded impellers. Unlike conventional electrochemical surface finishing processes, the pulse reverse process does not require low conductivity/high viscosity electrolytes or the addition of chemical species (like HF) to remove the passive film associated with electropolishing of passive and strongly passive materials like Ti alloys. This paper will focuses on pulse/pulse reverse electrofinishing processes developed by Faraday Technology and the technique to scale this approach to functional parts of interest.

Acknowledgements: The financial support of USAF Contract No. FA8814-15-C-0007 is acknowledged.

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Carbon Dioxide Electroreduction to Multi-Carbon Products Using a Large-Scale Membrane Electrode Assembly
Authors: O'Brien Colin P , Gabardo Christine M. , Edwards Jonathan P. , McCallum Christopher , Xu Yi , Dinh Cao-Thang , Li Jun , Sargent Edward H. , Sinton David
Published: February 2020

Rising atmospheric carbon dioxide (CO2) concentrations has led to an increased focus on electrochemical CO2 reduction using low-cost renewable electricity to produce low-carbon-intensity fuels and chemical feedstocks. The electrosynthesis of multicarbon (C2+) hydrocarbons and oxygenates, such as ethylene and ethanol, from CO2 feedstocks is appealing due to the large global market demand of these high-value products.

Industrial-scale implementation of this technology requires operation at reaction rates above 100 mA/cm2 to minimize electrolyzer capital costs. Gas diffusion electrodes (GDEs) feed CO2 directly to the electrocatalyst surface, alleviating mass transport limitations faced in traditional aqueous environments and enabling operation at industrially relevant reaction rates. However, when implemented in conventional liquid flow cells with alkaline or neutral electrolytes, major challenges emerge in maintaining electrolyte stability with detrimental carbonate and bicarbonate formation, consequently having adverse effects on energy efficiency.

Here we introduce therefore a membrane electrode assembly (MEA) based CO2 electrolyzer for C2+ production. We investigate the extent to which it can overcome the electrolyte stability limitations by eliminating alkaline electrolyte degradation and neutral electrolyte salt precipitation typically observed in the conventional approach. The MEA design maintains its performance while operating at elevated temperatures and low partial pressures of CO2, important considerations for industrial reactors. We further design a copper catalyst that takes advantage of the high CO2 concentrations afforded by the MEA. This catalyst design strategy achieves more than 50% Faradaic efficiency towards ethylene and more than 80% Faradaic efficiency towards C2+ products while operating at more than 300 mA/cm2. We demonstrate the stability of the system design through the continuous generation of ethylene while operating at industrially-relevant currents for more than 100 hours. The outcome is an engineered system that provides the longest stable ethylene production amongst all CO2 electrolyzers at reaction rates greater than 100 mA/cm2. To reduce costs associated with gas product separation from dilute streams, maximizing CO2 utilization is important. We investigate alternative flow field designs for the MEA reactor to achieve uniform reactant distribution, leading to improved current densities and reduced hydrogen evolution by at least 25% each. Finally, we demonstrate the process and system scalability through C2+ production in a large-scale MEA electrolyzer as part of the NRG COSIA Carbon XPRIZE.
Comparison of Inorganic and Organic Acid Etching Processes on Germanium(100)
Authors: Heslop Stacy Lynn , Muscat Anthony J.
Published: February 2020

Germanium is currently used in semiconductor devices alloyed with silicon and shows promise as an alternative material which could eventually replace silicon. One challenge associated with implementing germanium is rapid oxidation after cleaning, which results in degraded electrical performance because germanium oxides contain many defects. Optimization of cleaning and etching processes are critical to the development of devices based on Ge. This study compares the use of inorganic and organic acids to etch germanium oxides, such as Ge(+1)2O, Ge(+2)O and Ge(+4)O2. X-ray photoelectron spectroscopy (XPS) was used to characterize the Ge(100) surface composition after hydrochloric and citric acid treatments. Immersion in concentrated HCl (12 M) completely removed both GeO2 as well as sub-stoichiometric oxides. The surface remained oxide free when etched inside an Ar purged glovebox attached to an XPS chamber, but suboxides were detected within 3 minutes when samples were exposed to air. A short immersion (60 s) in 2.4 M citric acid in ambient conditions yielded a visible film on the surface even after drying. Two rinse strategies were employed to remove residual citric acid from the surface. After a short rinse (30 s) in ethanol peaks attributed to carboxylic acid were detected in the C 1s XPS region. Residual citrate species were minimized by sonication in ethanol, however citrate species were still detected. Germanium surfaces etched in HCl showed less oxide and adsorbed carbon than those etched in citric acid however both surfaces are unstable in air and suboxides form readily. We investigated the two different acid cleans before passivation of the surface with sulfur.
Analysis of Polyethylene Latex Particle Removal Mechanism on SiO2 Wafer Using Ultrasonic Spray Cleaning
Authors: Seike Yoshiyuki , Sawaki Ryoga , Shimizu Ryosuke , Hikida Tomomi , Honda Yuji , Sato Masanori , Mori Tatsuo
Published: February 2020

In single-wafer cleaning of semiconductor chips and flat panel displays, various cleaning methods tailored to the process, such as two-fluid spray cleaning, high-pressure jet spray cleaning, ultrasonic cleaning spray cleaning, and scrub cleaning have been proposed and put to practical use. In this study, Polyethylene Latex (PSL) particles 0.2 µm in diameter and 1 µm in diameter were electro-sprayed on the SiO2 The soil samples, and then cleaning efficiency were measured using two types of ultrasonic sprayers with frequencies of 1 MHz and 3 MHz confirmed. The soil samples are controlled for adhesion by deforming the PSL particles by heating the silicon wafer from 300K to 425K. From the experimental results, it was found that the is determined by factors other than the conventionally reported radiation flow in PSL particles.

Figure 1