bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Functionalization of Carbon Nanotubes in a Micellar Environment
Authors: Delport Géraud , Orcin-Chaix Lucile , Campidelli Stephane , Voisin Christophe , Lauret Jean-Sébastien
Published: February 2020

A key issue for the use of colloidal nanoobjects concerns their solubility, especially in water. Indeed, they tend to aggregate, resulting in the deterioration of their intrinsic properties. In order to overcome this bottleneck, many strategies have been developed. As far as carbon nanotubes are concerned, the best way to solubilize them in water while preserving their pristine properties is to use a micellar environment. One consequence is that the chemistry of carbon nanotubes in micelles is currently developing. For instance, people have doped nanotubes with diazonium, have grafted photoswitches on the wall of nanotubes, or even performed polymerization around nanotubes in micelles [1-4].

In this presentation, we will show how a simple mixing technique can lead to the functionalization of carbon nanotubes with free base tetraphenyl porphyrins. The role of the stability of the micelles containing the molecules will be investigated. Moreover, we will see how the control of the stability of the micelles can lead to a full control of the kinetics of the functionalization process [5]. Finally, we will discuss the possibility of extending the functionalization of nanotubes in micelles to other molecules with the aim, for instance, of building core-shell nanostructures [6].

References

[1] AJ. Hilmer et al. Langmuir 28(2), 1309-1321 (2012)

[2]S. Kreft et al., J.Phys.Chem.C,119.27 (2015): 15731-15734

[3] G. Clavé, et al, Chem. of Mat. 25.13 (2013): 2700-2707

[4] Y. Tsutsumi RSC Advances 4, 6318 (2014)

[5] G. Delport et al, submitted

[6] L. Orcin-Chaix et al, in preparation
(Invited) Autonomous Experimentation Applied to Carbon Nanotube Synthesis
Authors: Maruyama Benji , Decker Kevin , Nikolaev Pavel , Krein Michael , Poleski Jason , Barto Rick
Published: February 2020

Carbon nanotubes have an exciting array of applications which span mechanical, electrical, thermal and chemical/sensing. However, full exploitation is slowed by a lack of control over synthesis. Despite the two decades since the explosion of work in the area, progress in controlled production of nanotubes is impeded by our lack of understanding of the fundamental mechanisms of nucleation and growth. Our group has endeavored to develop a method that addresses the critical bottlenecks impeding the speed of research by taking advantage of advances in robotics, artificial intelligence, data sciences and in-situ/in-operando characterization.

Our Autonomous Research System, ARES, is capable of designing, executing and evaluating its own CNT growth experiments. Artificial intelligence module based on random tree / genetic algorithm statistical approach analyses experimentally obtained kinetic parameters (rate, time constant, etc.) and proposes new experiments to achieve user-defined objective. These are then executed by ARES automatically and without human intervention, and fed back into the AI module to ensure machine learning.

Recent experiments utilized maximum growth rate as an objective. The normalized difference between the objective and experimentally observed growth rates behaves in a fashion similar to what is typically seen in the control systems, with experimentally observed growth rate oscillating around the target. The convergence can be expressed via cumulative root mean square (RMS) of the rate difference. RMS increases initially (divergence), followed by consistent decrease after ~50 experiments, indicating convergence. That is, after some unsuccessful experimentation, ARES was better able to supply experimental conditions that achieved the objective growth rate. We take this as a clear demonstration of autonomous AI learning: convergence on the objective via closed-loop iterative experimentation without human intervention.
(Invited) Recent Progress Toward Single Crystals of Single-Wall Carbon Nanotubes
Authors: Gao Weilu , Kono Junichiro
Published: February 2020

Despite many years of worldwide efforts, there is presently no established method for producing large-area single-domain films of highly aligned, densely packed, and chirality-enriched single-wall carbon nanotubes (SWCNTs). If developed, such a method can eventually lead to the realization of a SWCNT crystal – i.e., a 3D object consisting of a period array of SWCNTs that maintains the extraordinary properties of individual nanotubes. Here, we report a new, promising method for achieving this long-standing goal. Utilizing spontaneous alignment that occurs during vacuum filtration, we have produced a wafer-scale (i.e., inch-size) film of aligned SWCNTs [1]. This method is universally applicable to SWCNTs synthesized by different methods and can be scaled up in all three dimensions. We characterized the produced large-area films using a variety of microscopy, spectroscopy, and electronic transport techniques, demonstrating nearly perfect global alignment with a single domain. The strikingly high degree of alignment of our films with a nematic order parameter of ~ 1 and a thickness of ~100 nm distinguishes our method from previously reported 2D and 3D postgrowth assembly techniques. We investigated the mechanisms underlying the observed global spontaneous alignment, based on a proposed model of 2D confinement induced phase transitions. We discuss how the degree of alignment depends on the filtration speed, the SWCNT concentration, the surfactant concentration, the hydrophilicity of the filter membrane surface, the SWCNT length, and the SWCNT diameter.

1. X. He, W. Gao, L. Xie, B. Li, Q. Zhang, S. Lei, J. M. Robinson, E. H. Hároz, S. K. Doorn, R. Vajtai, P. M. Ajayan, W. W. Adams, R. H. Hauge, and J. Kono, “Wafer-Scale Monodomain Films of Spontaneously Aligned Single-Walled Carbon Nanotubes,” Nature Nanotechnology 11, 633 (2016).
(Invited) Modulation of Nanotube Optical Properties By Controlling the Dielectric Environment inside of Single-Wall Carbon Nanotubes
Authors: Campo Jochen , Botka Bea , Cambre Sofie , van Werveke Wouter , Wenseleers Wim , Fagan Jeffrey A.
Published: February 2020

Specific and tunable modification to the optical properties of single-wall carbon nanotubes is demonstrated through the direct encapsulation into the nanotube interior of guest molecules with measured static dielectric constants. Optical measurements on SWCNT populations containing over thirty distinct simple compounds of varying static dielectric from 1.8 to 109 in large diameter nanotubes, and 15 compounds in small diameter nanotubes demonstrate for the first time experimentally the general effect of filler static dielectric on the nanotube optical properties. Comparison to effective medium theory predictions is presented, and guest molecules are identified that lead to effects disobeying the general trend and theory. These results both demonstrate a new degree of exploitable modulation in the optical properties of SWCNTs, and provide a foundation for examining higher order effects in host-guest interactions in well controlled pore size materials.
Organic Anolyte Species for Aqueous Redox Flow Batteries
Authors: Hollas Aaron , Wei Xiaoliang , Li Bin , Duan Wentao , Nie Zimin , Murugesan Vijayakumar , Kizewski James , Reed David , Wang Wei , Sprenkle Vincent
Published: February 2020

The incorporation of energy storage devices into the grid has garnered increased attention for their potential to mediate energy supply from intermittent renewable sources like solar and wind and also to balance peak power demand. Redox flow batteries are promising candidates for grid-scale energy storage given their simpler scalability relative to traditional secondary batteries based on solid-state electroactive materials. However, current state-of-the-art vanadium based systems are hindered by high material cost.1 The use of low cost organic electrolytes has emerged as a potential alternative to vanadium based systems.2,3

Presented will be our recent efforts in developing water soluble organic anolyte materials for aqueous flow battery systems. For a family of structurally related molecules, substituent effects on solubilities, electrochemical properties, and chemical stability for a select promising candidate will be discussed. Rational optimization of flow cell conditions including the membrane and electrodes has been achieved for performance improvement. The final anolyte candidate exhibits high solubility in the supporting electrolyte, undergoes two electron redox chemistry, and demonstrates good stability. When coupled with the well-established ferricyanide/ferrocyanide catholyte, the flow battery possesses a high OCV of 1.35 V at 50% SOC and yields stable long-term cyclability.

References

Zhang, M.; Moore, M.; Watson, J.S.; Zawodzinski, T.A.; Counce, R.M. J. Electrochem. Soc.
2012, 159, A1183.

Park, M.; Ryu, J.; Wang, W.; Cho, J. Nat. Rev. Mater.
2016,
2, 16080.

Soloveichik, G.L. Chem. Rev.
2015, 115, 11533.
(Battery Division Student Research Award Address) A Guide to Ethylene Carbonate-Free Electrolyte Making for Li-ion Cells
Authors: Ma Lin , Petibon Remi , Dahn Jeff R
Published: February 2020

The next generation of lithium ion cells for electric vehicles (EVs) requires longer lifetime and higher energy density. The use of electrolyte additives is one of the most effective ways of improving cell performance1–3. In this work, Li[Ni0.42Mn0.42Co0.16]O2 (NMC442)/graphite pouch cells demonstrate superb performance at high voltage when ethylene carbonate (EC)-free electrolytes, using a solvent mixture that is > 95% ethyl methyl carbonate (EMC) and between 2 and 5% of an “enabler”, are used.

The “enablers”, required to passivate graphite during formation, can be vinylene carbonate (VC), methylene-ethylene carbonate (MEC), fluoroethylene carbonate (FEC) or difluoro ethylene carbonate (DiFEC) among others. In order to optimize the amount of “enabler” added to EMC, gas chromatography coupled with mass spectrometry (GC-MS) was used to track the consumption of “enabler” during the formation step. Storage tests, electrochemical impedance spectroscopy (EIS), ultrahigh precision coulometry (UHPC), long-term cycling, differential voltage analysis and isothermal microcalorimetry were used to determine the optimum amount of enabler to add to the cells. It was found that the graphite negative electrode cannot be fully passivated when the amount of “enabler” is too low resulting in gas production and capacity fade. Using excess “enabler” can cause large impedance and gas production in most cases. The choice of “enabler” also impacts cell performance.

Figures 1a and 1b show the amount of enabler left and the percentage of EMC trans-esterification as a function of the initial enabler content after the first cycle (formation) of cells at 40°C with a current of C/20 up to 4.4 V. The dashed blue line in Figure 1a is a line of slope 1. Comparing the data for cells with FEC in Figure 1a to the dashed blue line shows that only 2% FEC was consumed during formation even if the initial FEC content was 3, 4 or 5%. By contrast when MEC is used, the amount of MEC consumed increases with the initial MEC content, since only about 0.5% MEC is left when the initial MEC content was 5%. Figure 1b shows the percentage of EMC that underwent trans-esterification producing dimethyl carbonate (DMC) and diethyl carbonate (DEC) 4,
5. The presence of lithium alkoxides caused by the reduction of linear alkyl carbonates results causes these trans-esterification reactions. Therefore, when trans-esterification of EMC occurs it is a signal that EMC was reduced at the graphite negative electrode during formation.

References:

1. M. Nie, J. Xia, L. Ma, and J. R. Dahn, J. Electrochem. Soc., 162, A2066–A2074 (2015).

2. D. Aurbach, K. Gamolsky, B. Markovsky, Y. Gofer, M. Schmidt, and U. Heider, Electrochimica Acta, 47, 1423–1439 (2002).

3. K. Xu, Chem. Rev., 114, 11503–11618 (2014).

4. J.-Y. Eom, I.-H. Jung, and J.-H. Lee, J. Power Sources, 196, 9810–9814 (2011).

5. K. Kumai, H. Miyashiro, Y. Kobayashi, K. Takei, and R. Ishikawa, J. Power Sources, 81–82, 715–719 (1999).

Figure 1
State of Health Battery Estimator Enabling Degradation Diagnosis
Authors: Dubarry Matthieu , Berecibar Maitane , Baure George , Omar Noshin , Villarreal Igor
Published: February 2020

The state-of-health (SOH) estimation is of extreme importance for the reliability and safety of battery operation in large scale energy storage systems. How to estimate SOH for an assembly of cells in a battery pack remains a subject of great interest.

In this work, a new approach for state of health (SOH) estimation via an automated diagnosis method that could be implemented directly into a battery management system (BMS) is introduced. The approach proposed in this work is a multi-step method that improves the accuracy of the estimation and only requires a multidimensional look-up table to be embedded into the BMS. The embedded look-up table enables a robust diagnosis of the battery degradation with a low computing cost.

The first step of the methodology is the emulation [1] of a cell from its half-cell data. The second step is the selection of features of interest (FOI) [2] from its voltage response. Next, the variations of these FOIs due to different degradation paths are compiled into a multidimensional look-up table. Lastly, SOH diagnosis is performed by comparing the experimental FOI values to the look-up table. The novelty of this approach resides in the consideration of the variations of all FOIs concurrently by using detection in an n-D space for n FOIs. This simultaneous analysis of multiple parameters provides accurate predictions even when each FOI taken separately cannot provide a conclusive diagnosis.

Our study presents a method which was very light on calculation at the BMS level and was accurate for 90% of all the possible degradation paths for commercial GIC//LFP and LTO//NMC cells. Moreover, the area where the method was not accurate can be identified and correlated with the data resolution and thus reduced the probability of an erroneous diagnosis in the field. This poster will present the methodology and its limitations.

Figure 1: Diagnosis error as a function of the LLI/LAMPE/LAMNE split at 10% capacity loss for the GIC//LFP cell (top) and the LTO//NMC cell (bottom). Diagnosis error on LLI, LAMPE and LAMNEestimations are respectively in the left, middle and right columns.

References

[1] M. Dubarry, C. Truchot, B.Y. Liaw, J. Power Sources, 219(2012) 204-216.

[2] M. Berecibar, F. Devriendt, M. Dubarry, I. Villarreal, N. Omar, W. Verbeke, J. Van Mierlo, J. Power Sources, 320(2016) 239-250.

Figure 1
Effect of Cathodic Kinetics on Intergranular Corrosion of AA5083 Under Atmospheric Conditions
Authors: Khullar Piyush , Kelly Robert G.
Published: February 2020

Al-Mg 5XXX series alloys are widely used for marine applications due to their corrosion resistance. However, alloys containing more than 3 wt% Mg, when exposed to standard service temperatures for extended periods of time are known to become sensitized and susceptible to localized corrosion; particularly intergranular corrosion (IGC). Many studies have investigated this IGC phenomenon in AA5XXX and attribute it to precipitation of a more anodic β-phase (Al3Mg2) along grain boundaries after exposure to environments during service in which the surface temperatures can exceed 60 C repeatedly. The majority of the electrochemical studies to understand IGC for AA5083 have been conducted in full immersion under potentiostatic or galvanostatic conditions, but much of the marine infrastructure is exposed to atmospheric conditions/thin films.

This study aims to develop a quantitative understanding of the effect of cathodic kinetics on IGC propagation at open circuit conditions. A new experimental setup using a sintered Ag/AgCl electrode as a combined reference and counter electrode was used to measure cathodic kinetics in thin films. This setup avoided the counter electrode products usually associated with a platinum electrode (H+ or OH-) and maintained uniform current density by placing the electrode right above and parallel to the sample.

Preliminary results indicate that under open circuit conditions (as experienced during service), the cathodic kinetics govern the IGC behavior under droplets/thin films. Different oxidizers like ozone (introduced in the gas phase) and potassium persulfate (introduced in solution) were used to increase cathodic kinetics. AA5083 samples were also coupled to carbon steel, which acted effectively as a galvanostat by suppling the cathodic current required to sustain the anodic activity on AA5083.

Initial thin film electrochemical results agree well with the existing corrosion framework for IGC in full immersion. An understanding of IGC in thin films/atmospheric exposures will provide a basis for developing a framework for IGC in service conditions.
Superhydrophilic and Superhydrophobic Aluminum Alloys Fabricated By Pyrophosphoric Acid Anodizing
Authors: Kikuchi Tatsuya , Kondo Ryunosuke , Nakajima Daiki , Natsui Shungo , Suzuki Ryosuke O.
Published: February 2020

Introduction

Recently, we demonstrated the fabrication of anodic alumina nanofibers via anodizing in a new electrolyte, pyrophosphoric acid (H4P2O7). Interestingly, the aluminum surface covered by the anodic alumina nanofibers exhibited a superhydrophilic behavior with a contact angle measuring less than 10°. In the present investigation, we described the fabrication of superhydrophilic and superhydrophobic aluminum alloys via pyrophosphoric acid anodizing and subsequent SAM modification.

Experimental

Two kinds of aluminum specimens (5N aluminum and 3004/1N30/8021 aluminum alloys) were ultrasonically degreased and chemically polished. The specimens were anodized in a concentrated pyrophosphoric acid solution at a constant cell voltage of 25-75 V for 60 min. The anodized specimens were immersed in a 0.5 mM fluorinated phosphoric acid SAM (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid: FOPA)/ethanol solution at 293-323 K for 48 h. anodized specimens were examined by field emission scanning electron microscopy (FE-SEM). The water contact angles were measured by an optical contact angle meter (2 µL in water volume for hydrophilic measurements and 4 µL for hydrophobic measurements).

Results

Anodizing of aluminum and its alloys in a pyrophosphoric acid solution caused the formation of numerous anodic alumina nanofibers on the aluminum surface. During anodizing of aluminum alloys, many intermetallic compounds were exposed to the surface with anodizing time increase, and the nanofiber-tangled intermetallic particles were formed on the surface. The contact angle decreased with the anodizing time, and the nanofiber-covered aluminum alloys exhibited a superhydrophilic behavior measuring less than 3° in the contact angle (Figure 1, anodizing voltage: Ua = 75 V). As the surface of the nanofiber-covered aluminum alloys was modified with fluorinated phosphoric acid SAMs (solution temperature: Tim = 293-313 K), the contact angle drastically increased with the immersion time and temperature. These aluminum alloys exhibited a superhydrophobic behavior measuring more than 150° (Figure 2).

Figure 1. Changes in the water contact angle, θ, with the anodizing time, ta, on the 5N aluminum and 3004 aluminum alloy surfaces after anodizing in a pyrophosphoric acid solution (293 K) at 75 V.

Figure 2. Changes in the water contact angle, θ, with the immersion time, tim, on the nanofiber-covered aluminum alloys (3004). The specimens were anodized at 75 V for 10 min, and then were immersed in a 0.5 mM FOPA-SAM/ethanol solution.

Figure 1
Influence of Major Alloying Elements on the Corrosion Resistance of Trivalent Chromium Conversion Layer Coated AA 2024
Authors: Saillard Romain , Viguier Bernard , Odemer Gregory , Zanna Sandrine , Seyeux Antoine , Marcus Philippe , Fori Benoît , Blanc Christine
Published: February 2020

This work was performed in the framework of the NEPAL FUI project. CIRIMAT was financially supported by the French Ministry of Economy and industry (BPI-France), the Région Occitanie/Pyrénées-Méditerranée and the European Union (FEDER/ERDF).

This work is a part of the NEPAL project (NEw Protections for ALuminum) that aims to replace hexavalent chromium treatments largely used in aeronautic industry by new trivalent chromium conversion layer. We studied here the influence of major alloying elements of the alloy on the growth on the conversion layer and therefore its corrosion properties.

The study was carried out on an AA 2024 cold rolled 3 mm thin sheet. Three microstructures were studied: i) a T3 metallurgical state ii) a T3 state followed by a tempering at 190°C for 12 h to induce Cu precipitation (aged sample) and iii) a T3 state followed by a prolonged solution heat treatment at 494°C for 40 minutes to induce the formation of a Mg-depleted zone on the near surface of the alloy (solution heat treated sample). The microstructures were characterized by transmission electron microscopy (TEM).

The corrosion behavior of both uncoated and coated samples was evaluated by corrosion potential (Ecorr) measurements, plotting of polarization curves and electrochemical impedance spectroscopy (EIS) measurements performed at Ecorr for various immersion times. For a better understanding of the conversion layer coated alloy corrosion properties, surface analyses of the AA 2024 samples at each step of the conversion layer process were performed by combining X-ray photoelectron spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and cyclic voltammetry measurements.

Results showed the growth of a thick Mg-rich naturally formed oxide for the solution heat treated sample leading to a widening of the passivity plateau observed on the polarization curve for the uncoated sample compared to T3 uncoated sample. This was associated with the formation of a Mg-depleted zone on the near surface of the alloy; however, preferential dissolution of Mg occurred during the pre-treatment (degreasing and deoxidation) for both the T3 and solution heat treated samples so that the kinetics and mechanisms of the conversion layer growth and its corrosion properties were similar for both samples. For the aged alloy, TEM observations showed a dense precipitation of intergranular and intragranular Al2CuMg. These precipitates were assumed to contribute significantly to the Cu enrichment observed on the sample surface after degreasing and deoxidation leading to a Cu-rich conversion layer with a lower corrosion resistance compared to that formed on the T3 sample.
Depth Profiling of TiO2 Nanotubes in Morphology, Composition and Structure
Authors: Schmuki Patrik
Published: February 2020

Depth profiling of TiO2 nanotubes in morphology, composition and structure

Shiva Mohajernia, Anca Mazare, Patrik Schmuki

Department of Materials Science WW-4, LKO, University of Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany

In the past decade, anodically formed self-organized TiO2 nanotube layers attracted considerable scientific interest (see e.g. reviews [1,2]). This is mainly due to the fact that these layers combine the defined nanotubular geometry with a broad range of functional features inherent to TiO2. Particularly in photoelectrochemical and photocatalytic applications nanotubular layers have shown remarkable results.

In this work, we compare composition, structure and morphology of the tube layers using depth profiling techniques (GDOES, TOF-SIMS), sectioning techniques (ion milling), TEM, and integral methods (thermal desorption), to achieve an understanding of how key functional features are and can be embedded in TiO2nanotube arrays.

REFERENCES

P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed. (2011), 2904

K. Lee, A. Mazare, P. Schmuki, CHEMICAL REVIEWS, 114 (2014) 9385
In Situ Raman Spectroscopy for Nuclear Material Monitoring in Molten Salt Systems
Authors: Singh Vickram , Chidambaram Dev
Published: February 2020

Molten salt systems are under consideration for both energy generation and used fuel processing as part of the nuclear fuel cycle. Generation IV nuclear reactor designs use molten salts as both coolants and fuel media. Advanced reprocessing technologies, such as the pyrochemical reprocessing of used nuclear fuel, rely on molten chloride melts as the electrolyte during electrochemical processing of used nuclear fuel. Before any of these technologies can reach the industrial scale, techniques for the monitoring of nuclear material in a nondestructive and in situ manner must be further developed for molten salt systems. Real-time monitoring of nuclear material allows for process optimization, along with addressing nuclear security concerns associated with the diversion of actinide materials. In this study, we explore the use of Raman spectroscopy, employed using a fiber-coupled system, as a method for the in situ­ analysis of molten salt. We present the development of an automated, in situ­ Raman system for analysis of electroactive species in molten LiCl-KCl. The Raman modes of lanthanide chlorides, serving as actinide surrogates, were investigated in LiCl-KCl eutectic at 500°C and compared with the available literature. This work was performed under the auspices of the US Department of Energy (DOE) under contracts DE-NE0008262, DE-NE0008236 and DE-NE0008572, and the US Nuclear Regulatory Commission (NRC) under contract NRC-HQ-13-G-38-0027. Dr. Kenny Osborne serves as the program manager for the DOE awards and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC award.
(Invited) Charge Traps, Temperature- and Bias-Stress Stability of Alumina Dielectric / Indium Gallium Arsenide Gate Stacks
Authors: McIntyre Paul C.
Published: February 2020

Both interface defects and border traps - charge traps in the gate oxide - influence the behavior of InGaAs metal-oxide-semiconductor (MOS) devices. This presentation will summarize the different effects of interface and border traps on the temperature- and bias-stress behavior of aluminum oxide/InGaAs MOS gate stacks, with particular emphasis on threshold voltage stability. The influence of local interface chemistry and the complex role of hydrogen as a defect passivant are highlighted.

In one set of experiments, a temperature dependent border trap response for Al2O3 gate dielectrics is investigated. This behavior is unexpected for defects that have typically been reported to charge and discharge through direct tunneling of electrons from the n-type substrate. Temperature dependent border trap frequency dispersion of the accumulation capacitance and conductance is found to be correlated with the presence of a defective interfacial layer, which can be intentionally produced either by excessive exposure to hydrating or oxidizing species during atomic layer deposition of Al2O3 or by use of a previously-reported aqueous HCl wet clean of the InGaAs surface prior to ALD. These results point out the sensitivity of the temperature dependence of the border trap response in metal oxide/III-V MOS gate stacks to the presence of processing-induced interface oxide layers, which alter the dynamics of carrier trapping at defects that are not located at the semiconductor interface.

We also report on the effects of pre- and post-atomic layer deposition (ALD) defect passivation with hydrogen on the trap density and reliability of Al2O3/InGaAs gate stacks. Reliability is characterized by capacitance-voltage hysteresis measurements on samples prepared using different fabrication procedures and having different initial trap densities. Despite its beneficial ability to passivate both interface and border traps, a final forming gas (H2/N2) anneal (FGA) step is found to induce a significant hysteresis. This is caused by hydrogen depassivation of defects in the gate stack under bias stress, supported by the observed bias stress-induced increase of interface trap density, and strong hydrogen isotope effects on the measured hysteresis. Additional strategies, beyond hydrogen annealing, for more stable interface defect passivation on InGaAs will be discussed briefly.
(Invited) Electrodeposition at Solid and Liquid Electrodes: In Operando Surface X-Ray Scattering Studies of the Atomic-Scale Structure Evolution
Authors: Magnussen Olaf M.
Published: February 2020

Development of modern electrodeposition processes requires better insight into the atomic-scale mechanisms, in particular into the initial stages of nucleation and growth. With state-of-the art synchrotron-based X-ray scattering techniques, detailed structural data can be obtained in operando during deposition. These measurements allow monitoring simultaneously various structural properties, such as the epitaxial relationship, the horizontal and vertical grain size, and the strain, with high temporal and spatial resolution and in parallel with electrochemical and optical data. Moreover, studies of a wide range of electrodeposition processes are feasible. This includes deposition on single crystal electrodes, on technical samples and even at liquid-liquid interfaces – a topic of renewed interest. In this talk, characteristic examples will be given that demonstrate the level of detail, obtainable by such in operando X-ray scattering measurements. In particular, the initial stages of growth from monolayers to thicknesses of several ten nanometers will be discussed.
An Ex-Situ Study of Epitaxial Growth of Nickle on Copper Substrate in Electrodeposition
Authors: Huang Yan-Chin , Hou Ying-Chun , Chang Liuwen , Yan Tao
Published: February 2020

An ex-situ method was used to study the anisotropy of the epitaxial growth of electrodeposited nickel on polycrystalline copper substrate. The orientation of the substrate grain was characterized by electron backscatter diffraction (EBSD) technique prior to the electrodeposition. Nickel films of approximately 1 um thick were then deposited onto the polished substrates in a sulfamate bath under various current densities. The orientation of the Ni deposits located in the prior-analyzed area was characterized again by EBSD to reveal the orientation relationship between the deposit and the substrate. EBSD analysis was also carried out for thick deposits from a transverse direction to clarify the growth behavior and microstructural evolution of the deposits on grains of different orientations. Results indicate that epitaxial growth is allowed solely on grains having an orientation of <100>//ND at a low current density. On the contrary, the nickel deposits grow epitaxially on almost all grains no matter the orientation as the current density is in a range of 1-10 A/dm2. However, the surface topology of the deposits on substrate grains of different orientations is very different. Accordingly, the microstructure evolution of the <100>//ND and non-<100>//ND deposits are very different and detail will be presented.
Development of Environmentally Conscious Electrodeposition Process "Solid Electrodeposition (SED)"
Authors: Yanagimoto Hiroshi , Hiraoka Motoki , Sato Yuki , Iisaka Hirohumi , Murai Jyunya , Itagaki Masayuki , Akamatsu Kensuke
Published: February 2020

Conventional electrodeposition process is widely used for various kinds of functional parts such as electronics, anti-corrosion, decoration and so on. However, this process has serious problem due to a large quantity of waste fluid including toxic substance. Recently, environmental regulation has been strengthened, so that the production line may be needed to be closed system for recycling the waste fluids. Moreover, the additionl processes such as masking and etching is indispensable in producing the patterned circuit board, leading to high cost for final products. We have developed the novel electrodeposition process to solve the environmental and cost problems of a conventional electrodeposition. As shown in Fig. 1, the novel deposition system is simply composed of electrodes, metal solution and polyelectrolyte. By applying potential between two electrodes, metal films are deposited at solid-solid interface, i.e., cathode electrode and polyelectrolyte; electrolyte solution is separated from cathode electrode by polyelectrolyte in which metallic ions can be diffused through ion-exchange reaction. Therefore, when this system is accumulated into small probe system, this process enables electrodeposition of metals only by attaching polyelectrolyte surface into cathode surface in a serial patterning manner, whereas conventional electrodeposition process is based on immersing the substrate of interest into electrolyte solution. We call this novel system, “solid electrodeposition (SED)”. The characteristics of the process are as follows.

1) The system needs only small amount of electrolyte solution, and washing of the cathode substrate after metal deposition is not necessary because of growth of the films at solid-solid interface, leading to much small amount of waste solution.

2) Site-selective deposition can be achieved only by controlling the contact area of the polyelectrolyte used for deposition (Fig. 2a).

3) Since the deposition can proceed through diffusion of metal ions through fine, large amount of ion channels in polyelectrolytes, metal films constructing of tiny crystallites are deposited (Fig. 2b).

Electrical resistivity of the copper films deposited by SED process is comparable with that of bulk copper, indicating high purity, well-defined copper films are deposited on the substrates. From these results, this process offers an effective, environmentally friendly methodology for fabricating metal films in atmospheric conditions and can be, therefore, applied for various microelectronic applications.

Figure 1
Discovery to Product – an Engineer's Perspective
Authors: Mah Dennie T
Published: February 2020

Electrochemical science and technology has been both a rewarding and intriguing challenge for engineers from all disciplines. Conventional chemistry and chemical engineering curricula do not fully prepare future practitioners to take advantage of the potential money making opportunities lying in this area, After 40 years of working in the chemical industry, many involving electrochemical technology, I have encountered and accumulated some practical tips, traps and heuristics that are not guaranteed to be optimal or perfect, but sufficient for the immediate goals of meeting business objectives. Discussion will include a global outlook of the necessary steps to accomplish a viable commercial scale electrochemical application starting from laboratory bench scale studies, through intermediate pilot plant scale demonstration and finally operation of a industrial facility. Whether the business objective is the production of chemicals trough the use of electrochemistry or the production and storage of energy, many basic principles apply. Commercialization requires a multidisciplinary approach and the earlier a comprehensive engineering work plan is formulate the smoother will be the transition from laboratory to plant. Hopefully, the insights presented will enable current and future practitioners of electrochemical technology to achieve their business goals and expand the utility of this area of science and technology.
(Invited) Initially Placed Solid Particle Deposition for Super Efficient Systems and Possible Additive Manufacturing Applications
Authors: Cihangir Salih , Abbott Andrew P. , Ryder Karl Scott
Published: February 2020

Electrodeposition is commonly used for the deposition of metallic and composite coatings. It is useful as it can coat complex 3D structures and can be used for the deposition of alloys. There are a few disadvantages; it is relatively slow to build up thick coatings and in some cases the current efficiency can be low. In this study a fundamentally different method for carrying out electrodeposition is demonstrated. Here instead of dissolving metal from the anode and depositing it on the cathode a powder of the coating metal is put in contact with the cathode and pulse plating sequentially dissolves metal from the powder and then deposits it between the powder grains. A single metal grain used for initial experiments as schematically shown in Figure 1. By this method super-efficient deposition (efficiency >100%) can be achieved, and thick layers can quickly be deposited. This can in principle be carried out in any media but in this study ionic liquids were used to increase the current efficiency of the process. The method is demonstrated using both zinc and copper. It is shown that using these media certain crystal planes can be promoted and ordered deposits are obtained. The morphology of the surfaces was characterized using SEM, X-ray diffraction, and 3D optical microscopy techniques.

Figure 1
Mechanics of Ultrasonic Wave Propagation in Cycling Li-Ion Batteries & Applications for SOC Determination
Authors: Davies Greg , Biswas Shaurjo , Knehr Kevin William , Hodson Thomas , Steingart Daniel A
Published: February 2020

There has been recent interest in applying ultrasonic methods to ‘image’ a variety of battery geometries and chemistries. We demonstrate some results of applying MHz ultrasonics to help accurately determine lithium-ion state of charge (SOC) and state of health (SOH). The propagation of elastic waves through a material is directly related to its material properties. As the electrochemical and mechanical properties of a material are inherently coupled, incorporating some simple ultrasonic metrics into SOC determination allows for significantly improved accuracy over traditional direct-measurement SOC methods. We propose a simple physical model to explain the changes in ultrasonic signals with respect to the electrochemical changes.
(Invited) Multiscale Raman Imaging Applied to High Capacity Battery Materials and Electrodes
Authors: Nanda Jagjit , Kostecki Robert
Published: February 2020

Electrochemical transport across lithium-ion composite electrodes are highly heterogeneous and non-uniform. Origins of such inhomogeneities are both due to intrinsic nature of the electrode active material as well as extrinsic factors such as composition (binder and conductive diluents) and processing conditions. The talk will provide an overview of two decades of work applying conventional as well as micro-Raman spectroscopy to obtain the chemical and morphological information on pristine and cycled lithium-ion battery electrodes1-2. Topics to be presented include micro-Raman imaging of cycled Li1-xNi0.80Co0.15Al0.05 (NCA) electrodes highlighting the observation of a phenomenon called “carbon retreat” that eventually leads to capacity loss and degradation.1-2 Further, based on the metal-oxygen vibrational modes of transition metal oxide cathodes, Raman spectroscopy has been used to measure the spectroscopic state of charge (SOC) of the electrode. The variation of this local spectroscopic SOC is sensitive to local lithium content and defects.3-4 Using a SOC parameter that is based on both the area and intensity of the cathode Raman bands, we observed SOC gradients within cathode secondary particles on the electrode surfaces.4

In situ and ex-situ confocal Raman imaging has been applied to multi-lithium cathode systems Li2MnO3
4 and Li2Cu0.5Ni0.5O2
5 to understand formation of secondary phases and structural transitions during delithiation and its correlation with oxidative stability. Finally, the talk will discuss on recent progress in Surface Enhanced Raman (SERS) and Tip Enhanced Raman Spectroscopy (TERS) applied to battery electrolytes and anodes.

Acknowledgement

Research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy.

References

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R. Kostecki, J. Lei, F. McLarnon, J. Shim , K. Striebel , J. Electrochem.
Soc. 153 , A669 (2006)

Y. Luo, W. B. Cai, X. Xing, D. A. Scherson, Electrochem. Solid-State
Lett. 7, E1. (2004).

J. Nanda et al. Adv. Func. Mater. 21, 3282 2011

R. Ruther et al. J. Phys. Chem. C

J. Phys. Chem C 119, (2015)

R. Ruther et al. Chem. Mater. 227, 6746, (2015).
Effect of MPL Properties on Temperature and Liquid Water Distribution in a GDL
Authors: Hashimura Sota , Minami Ryotaro , Tamada Yusuke , Hasegawa Noriyoshi , Araki Takuto
Published: February 2020

Proton exchange membrane fuel cell (PEMFC) is expected to be used as a power source of next-generation automobiles and household cogeneration systems, because of its high power density, fast startability, high efficiency and clean power source. There are many problems for the practical use of the PEMFC. One of the important problems is difficulty to optimization of water and heat management within PEMFC. Proper water management of the PEMFC is important to achieve high power density and durability of components. At the high current density operation, gas transport is blocked by liquid water remaining in a GDL and a gas channel, causing a performance decline with increasing concentration overpotential. Water condition is influenced by temperature in the cell. In particular, at the high current density, temperature gradient strongly affects the water transport. Therefore, it is important to grasp the mechanism of water and heat transport inside the PEMFC. In this study, we investigated the effect of a MPL properties on temperature and liquid water distribution.

In order to visualize the liquid water in the PEMFC, an X-ray CT apparatus was used. The resin impregnated graphite was used as the material of a separator, because its X-ray permeability is close to liquid water. The separetor temperature was controlled by a thermocouple and a cartridge heater inserted in the separator. For the temperature measurement at the CL / GDL interface, an Au - Ni thin film thermocouple with a thickness of about 9 μm was fabricated using MEMS technology.

Differences between with and without MPL in liquid water distribution was observed. The presence of a MPL reduce the amount of liquid water near the CL.
Investigation of Microstructure and Pt Distribution in Catalyst Layer after Accelerated Degradation Test in PEMFC
Authors: Zeng Rong , Zhang Hongyu , Jiang Lijun , Liu Xiaopeng
Published: February 2020

The membrane electrode assembly (MEA) is the key part of the Proton Exchange Membrane Fuel Cell (PEMFC). Except applying the high efficiency catalyst, to improve the Pt efficiency for oxygen reduction reaction (ORR) by optimizing the microstructure of MEA is also a key point to achieve the high performance and longevity of the low Pt loading MEA. However, it is still difficult to correlate the microstructure of the MEA, especially the microstructure of the catalyst layer (CL) and the performance of the MEA due to the complex physical and chemical processes in the catalyst layer.

In this study, we reported our work on the low Pt loading MEA and the preliminary results of the accelerated degradation test (ADT) of the MEA. The ADT test was conducted under the DOE’s ADT protocol. SEM, associated with back scattered electron imaging (BSE), EDX mapping, EDX linear scan technique, was applied. The spatial distribution of aggregated Pt particles at cathode of our self-made MEAs (Pt loading at anode is kept at 0.05mg/cm2, the Pt loading at cathode is 0.05, 0.15, 0.55mg/cm2 respectively.) was revealed. It suggested three different region of Pt accumulation – the interface between the membrane and the catalyst layer, the main part of the catalyst layer, and the interface between the catalyst layer and the micro porous carbon layer. The significant Pt aggregation happened at the two interface area of the catalyst layer. This implies the different spatial utilization of the Pt catalyst in the catalyst layer. For clarity, Fig 1 shows the BSE images of MEA cathode with Pt loading of 0.1mg/cm2 and the voltage degradation of the MEA during the ADT test. The detailed discussion of the spatial distribution of aggregated Pt particles will be presented at the symposium.

Figure 1
Membrane/Electrode Assembly Water Content Measured with 2 µm Spatial Resolution Neutron Imaging
Authors: Hussey Daniel S , LaManna Jacob M , Baltic Elias , Jacobson David L , Stariha Sarah , Spernjak Dusan , Mukundan Rangachary , Borup Rod L.
Published: February 2020

Neutron imaging is a completely non-destructive probe of the water content in operating fuel cells. However, the spatial and temporal resolution of the method limits the application range. We report on our continued imaging detector resolution improvements, where we have achieved a spatial resolution of 2 µm. We applied this new detector capability to measure the water content of two different membrane/electrode assemblies where the ionomer to carbon mass ratio (I/C) was the only variable. A 1 cm2active area test section with parallel flow channels was operated as a differential cell at 80 °C at constant voltage. Shown in the figure are the imaged water content at 0.4 V, 100% inlet relative humidity for the I/C = 0.9 and I/C = 1.1.

Figure Caption: Neutron images of the water content of an operating fuel cell at 0.4 V; a) I/C of 1.1, b) 2I/C of 0.9. In both cases, the cathode is toward the top of the image and the anode toward the bottom.

The authors from LANL are supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos. The authors from NIST are supported by the U.S. Department of Commerce, the NIST Radiation and Physics Division, the Director's office of NIST, the NIST Center for Neutron Research, and the Department of Energy interagency agreement No. DE_AI01-01EE50660, program manager: Nancy Garland.

Figure 1