bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Light Enhanced Metal Assisted Chemical Etching of Silicon
Authors: Quiroga-González Enrique , Juárez-Estrada Miguel Ángel , Gómez-Barojas Estela
Published: February 2020

The study of electrochemicl porosification of silicon has allowed the production of different kinds of porosities in it, ranging from micropores to macropores, and directed by cristallographic planes, or electrical current lines. Additional studies have been on the use of different kinds of electrolytes, to etch faster, or with lower branching. Pore modulation has been also an important development, for a range of applications from photonics to energy storage devices. The modulation can be of either different porosities or different pore diameters, and has been accomplished by the use of different current densities [1], or by the use of different light intensities (mainly for n-type Si) [2].

In particular, the use of light allows the production of electron-hole pairs in semiconductors. This is necessary in n-type Si, since electronic holes are part of the etching reaction, and they are scarce in n-type wafers. Having the availability of more of fewer electronic holes, one can etch wider or narrower pores respectively [1].

Metal Assisted Chemical Etching (MACE) is an alternative etching method, which does not use a power source (it is an electroless method). Nobel metal (commonly Au, Ag or Pt) particles or films are deposited on the surface of Si, and the metallized samples are immersed in an etching solution afterwards. The regions with metal are commonly etched much faster, thus they work as a catalyst [3]. At the metal-semiconductor interface, space-charge-region (SCR) is formed, accelerating electronic holes formed at the electrolyte-metal interface. In this way, there is a higher availability of holes for etching in (or close to) the regions where the metal is present.

Having an internal electric field (given by the SCR) in MACE, which is external in the case of electrochemical etching, it is strightforward to think that light may work in a similar way in both etching methods. However, there are just a few reports on the use of light for MACE, and it has been used just at the front-side (the etched face). There are no reports on the use of back-side illumination for MACE. In the present work, evidences of pore modulation or etching conditions through the use of alternating illumination at the back-side will be presented. Illumination induces either lateral or vertical etching, depending on the doping type of Si.

[1] E. Quiroga-González, J. Carstensen, C. Glynn, C. O’Dwyer, H. Föll, Phys.Chem.Chem.Phys., 16, 255 (2014).

[2] S. Matthias, F. Müller, J. Schilling, U. Gösele, Appl. Phys. A, 80(7), 1391 (2005).

[3] X. Li and P.W. Bohn, Appl. Phys. Lett.77, 2572 (2000).
(Invited) 3D Multifunctional Carbon Nanotube Networks
Authors: Scarselli Manuela
Published: February 2020

In the field of nanomaterials research, carbon nanotubes (CNTs), proved to possess unique physicochemical properties, owing to their nanoscale dimensions, that have been applied to improve the performance of existing processes or even design novel technologies.

Recently, there has been a growing interest in obtaining natural and synthetic three-dimensional (3D) architectures instead of two-dimensional ones to increase the active surface-to-volume ratio throughout the entire 3D structure, which proves to be advantageous in several applications. The 3D macroscopic structures can be obtained from the assembly of nanomaterials like graphene, carbon nanotubes, polymers and similar others, following chemical and physical routes and the resulting properties derive from the combination of those of the nano-constituents and those due to the complex architecture (like porosity, lightweight and others).

In this paper, we show that is possible to promote a direct self-assembly of CNTs to obtain 3D networks following a chemical vapor deposition route. The self-supporting internal structure consist of interconnected CNTs and to lesser extent of carbon fibers that form a random skeleton with micrometer-size open pores. The porous nature of the network is directly responsible for its lightweight and the hydrophobic and lipophilic behavior, therefore the material is called CNT-sponge (figure 1). In addition, the macroscopic assembly shows high structural stability and good electrical conductivity, and mechanical response. The experimental results obtained in our laboratory, demonstrate that this 3D new material can be successfully applied in different applications. In particular, they can be applied as active material to address some environmental challenges involving water treatment, energy production, and contaminant sensing. Other potential applications include their use as pressure-sensors, in photon-energy conversion devices and as guides in reconnection of segregated spinal explants.

References

Scarselli M., et al. Beilstein J. Nanotechnol.
6 (2015) 792–798;

Camilli L., Scarselli, M. et al., Appl. Phys. Lett.
102, (2013) 183117;

Camilli, L.; Scarselli, M. et al., Nanotechnology 25, (2014) 065701.

Figure 1
Corrosion Behavior of Thermally Sprayed WC-Co-VC Coatings in NaCl Aqueous Solution
Authors: Rocha Reséndez Rodolfo , Cabral José Angel , Tiburcio Citlalli Gaona , Poblano Carlos , Estupiñan-Lopez Francisco , Zambrano Patricia , Almeraya Facundo
Published: February 2020

WC-17Co coatings are used to protect components against wear, high temperature and corrosion. WC based cermet coatings have been considered as alternative replacements to traditional hard chrome plating for improve surface properties of aircraft landing gear. This coatings are used in engineering applications requiring superior hardness and improved wear resistance, little is known about the corrosion resistance. In this study, four WC-17Co based composite coatings were deposited onto austenitic stainless steel substrates using high velocity oxygen fuel (HVOF) spraying at different concentrations of VC. The corrosion behavior was performed by linear polarization resistance test, potentiodynamic polarization curves and electrochemical impedance spectroscopy in saline environment. Characterization of the coating structure, morphology and composition, was carried out, prior to and after corrosion testing, using scanning electron microscopy and EDX elemental analysis. It was determined that the anodic branches present a tendency to passivation this more pronounced in sodium chloride. The results showed the addition of nanostructured WC-17Co particles improved corrosion resistance in H2O and NaCl. The addition of VC did not affect the corrosion behavior of the bimodal thermal spray coating. The electrochemical data showed that sample with 50 % of nanoparticles of WC-17Co presented higher corrosion resistance than the others in chloride solutions.
Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors
Authors: Hall Timothy D , Vijapur Santosh H. , Wang Dan , Taylor E. J. , Inman Maria , Snyder Stephen , Brady Michael
Published: February 2020

Biomass embodies tremendous potential as a renewable energy resource. According to the biomass thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion,[1] representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors (Figure 1) which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments which include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cookstoves must improve burning efficiency, must be able operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments. Within this context, Faraday Technology Inc. is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 60 wt% Ni – 40 wt% Cr (NiCr) binary and 25 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~1 mg/cm2 every 100 hours). When compared to the 441 SS base material the NiCoCr coating exhibited an significant lifetime improvement over its base material and other alloys.

Acknowledgements: The financial support of DOE Contract No. DE-SC0013870 is acknowledged.

[1] Biomass Production Now 10 Percent of World Energy, http://www.realclearenergy.org/charticles/2013/09/26/biomass_production_now_10_percent_of_world_energy_107257.html. Accessed 12 Jan 2015.

Figure 1
Increasing Acid Dew POINT Corrosion Resistance with Thin Coating Layer on STEEL
Authors: Choi Changhoon , Lee Byoung Ho , Jo Minho , Kim Myung Soo
Published: February 2020

Acid dew point corrosion is a common phenomenon for industrial equipments such as duct, stack, gas gas heater (GGH) in plants using fossil fuels. During the burning process, sulfur in fossil fuel is oxidized to produce sulfuric dioxide (SO2) and further oxidized to sulfuric trioxide (SO3). Under the dew point temperature, water drops form on the surface of equipments along with sulfuric trioxide to develop sulfuric acid (H2O+SO3àH2SO4). Sulfuric acid causes severe damages to equipments and special steel products that are strong against acid dew point corrosion are on the market in the form of cold rolled (CR) or hot rolled (HR) steel. Although these products have stronger corrosion resistance than normal steel to sulfuric acid, life span is still short and further increase of corrosion resistance is required. In this research, we applied thin coating layer to steel and studied how corrosion resistance is changed. Concentration of sulfuric acid on steel equipments is varied according to temperature. A couple of test coupons with 38 mm diameter were immersed in controlled sulfuric acid solutions and weight differences were measured before and after corrosion test. Different types of coatings were applied and tested. Inorganic type coating seems to provide efficient protection against sulfuric acid corrosion but localized corrosion occurrs. We propose a possible solution for localized corrosion as well. Bar coating was used to prepare coating steels and spark erosion was used to make coin type test coupons. Coating layers were observed by various analytical tools including FT-IR, SEM, EPMA, GDS etc.
Stress Corrosion Cracking of Aeronautical Alloys Al6061-T6
Authors: Almeraya Facundo , Tiburcio Citlalli Gaona , Zambrano Patricia , Estupiñan-Lopez Francisco , Cabral José Angel , Treviño Morales Raul , Bastidas Jose Maria
Published: February 2020

For the aeronautical industry corrosion has always been an important problem, especially within the aircraft maintenance, falling into great expenses to study and prevent the formation of it on some elements that are indispensable for the aircraft’s service. The external stresses or the existing loads joined with the atmospheric environment can promote degrading mechanisms that combined cause cracking on the material by means of tension and early failures. This phenomenon, called Stress Corrosion Cracking (SCC), produce a great loss of mechanical strength, without evidence of the material’s damage and loss, but it can produce fast mechanical fracture and catastrophic failures. In this study the objective was to evaluate the used in aeronautical industry, Al6061-T6, to identify which one presents a better resistance to SCC in salt, caustic and acid environments. Mechanical tests were performed using low speeds on a CERT (Constant Extension Rate Test) machine, varying the environment, its pH and concentration. Simultaneously, the electrochemical noise tests were also performed to determine the corrosion rate and link the Stress-Deformation plots with the electrochemical patters recorded, giving results more complete and accurate to the behavior of the materials when in service.
Chemical Conversion Treatment on Stainless Steel 316L By Using TiO2 Thin Films Via Sol-Gel Technique and Adding Niobium and Vanadium As Inhibitors to Enhance Corrosion Resistance
Authors: Herrera-Hidalgo Alan Damian , Rodriguez-Gomez Francisco Javier
Published: February 2020

Stainless steel has been used in a wide variety of industries due to its mechanical, anticorrosion and biocompatibility properties. However, its passive layer can be compromised under aggressive environments leading to corrosion. There are several chemical conversion treatments that are applied on the steel’s surface to improve its corrosion resistance. The most commonly used conversion coatings are based on hexavalent chromium, a compound that is carcinogenic and very hazardous pollutant. The new researches are looking for alternatives that achieve the same or better corrosion inhibition. As an alternative less toxic method, this work presents the use of the sol-gel as a chemical conversion treatment to obtain TiO2 thin films on a stainless steel 316L..

The sol-gel was prepared with titanium butoxide as a precursor; adding niobium and vanadium salts as corrosion inhibitors. Once prepared, the sol-gel was aged for 24 hours. The substrate (stainless steel 316L) was cut in 5x2cm pieces to be ground and polished. Each piece was rinsed with water and finally with acetone. The method dip-coating was used to apply the sol-gel on the surface of the substrate. The dipping was done at three different speeds using a device previously designed and built in the laboratory. After the sol-gel is applied, the pieces are heat treated at different temperatures: 300°C, 500°C and 700°C. The films were characterized by X- Ray Fluorescence and Raman Spectroscopy. These techniques showed the presence of TiO2, with different structures depending on the thermal treatment temperature: amorphous, anatase and rutile. The corrosion behavior was studied in a 3% NaCl solution by Potentiodynamic Polarization Curves and Electrochemical Impedance Spectroscopy. The effect of the dipping speed and the actual TiO2 structures on the anticorrosive properties were reported.
Corrosion Protection of Three Patinas Formed on Copper Alloys As an Alternative of Conservation of Historical Metal Heritage: Effects of Pollutants
Authors: Campechano Clarisa , Galván-Martínez Ricardo , Jimenez Tania , Arguelles David , Orozco-Cruz Ricardo
Published: February 2020

The conservation of archaeological pieces is a stage, sometimes essential, in the study of objects protected in historical sites. When in addition to natural agents such as water, air and temperature, there is the presence of atmospheric pollutants, the degradation processes are accelerated to such a degree that the total loss of a historical vestige can be had. These agents induce even deterioration in metal parts through aggressive corrosion processes.

The evaluation of the patinas by means of electrochemical techniques in the copper-based metallic materials of the historical heritage will allow to acquire knowledge about the formation of the corrosion products and the protective coating that the superficial film provides to the material. In this work, sulphate patina are synthesized by using an aqueous solution of copper sulphate, chloride patina using an aqueous solution of ammonium chloride and electrochemical patinas immersed in a sulphate / carbonate solution. The morphological and structural characterization of each of the patinas was carried out through scanning electron microscopy, X-ray and Raman energy dispersion spectrometry.

The main characteristic of the patinas formed is the blue-green coloration, since it facilitates the identification of corrosion products such as brochantite, in sulphate patinas, atacamita in the chloride patinas and malachite in the electrochemical patinas. In analysis by means of electrochemical techniques and having variations of contaminants in the test medium indicate that the best behavior for protection against corrosion is presented by the patina formed with sulphates.
Electrochemical Evaluation of Epicatechin Gallate (EG) As Corrosion Inhibitor in Bronze in a Saline Medium
Authors: Espinoza Vazquez Araceli , Rodríguez-Gómez Francisco Javier , Angeles Beltrán D. , perez Vazquez Araceli , Mata R.
Published: February 2020

Epicatechine gallate (Figure 1), isolated from green tea, has been tested as corrosion inhibitor in a bronze in a corrosive solution of 3% of NaCl and using electrochemical techniques as electrochemical impedance spectroscopy, polarization curves, and scanning electron microscopy. The results showed that 10 ppm is the best concentration to protect the metallic surface of bronze. The measurements of the different immersion times showed that the epicatechin gallate is stable for 28 days. Afterwards, the adsorption of this compound follows the Langmuir isotherm with a process of physisorption. Finally, it was proved with the use of SEM-EDS that the presence of the inhibitor film diminishes the corrosion process.

Figure 1
Rust Control and Corrosion Prevention of Steel Using Metal Salts
Authors: Yamashita Masato , Kim Kyung-Tae , Fujimoto Shinji
Published: February 2020

Steel materials are basic structural components of social structures. An inherent property of the steel is its high reactivity with oxygen and water existing abundantly in a terrestrial environment. Thus, the steel is easily corroded with the cathodic reaction due to reduction of oxygen from the environing air causing degradation of the steel structures. To ensure long-term reliable service of the steel structures, some measures to inhibit corrosion degradation must be applied.

Rust layer comprised of iron oxides such as α-FeOOH (goethite), β-FeOOH (akaganeite), γ-FeOOH (lepidocrocite), and Fe3O4 (magnetite) forms on the steel surface as a result of corrosion. The rust layer is generally recognized as a surface oxide layer that accelerates the steel corrosion since the reduction of the rust itself is superimposed on the reduction of oxygen, thus accelerating the cathodic reaction. But in some cases, the rust layer is believed to work as a kind of protective coating.

The protective function of the rust layer might vary depending on the crystal structure of the rust. We have examined the influence of water-soluble metal salts, which supply ionic species to the aqueous corrosion environment, on the rust structure and corrosion protection or acceleration by the rust layer formed on the steel surface.

It is shown that some of the metal salts lead to preferential formation of a goethite structure and some form magnetite. Depending on those variety of rust phase, electrochemical reaction is affected by the rust structure. The goethite formation especially suppresses the cathodic reaction on the rusted steel surface and resultantly retards the corrosion reaction of the rusted steel in the atmospheric corrosion environment.
Opuntia Ficus indica Slime As a Natural Corrosion Inhibitor of Steel in Cement Based Materials in Marine Environment
Authors: Torres-Acosta Andres Antonio , Díaz-Cruz Lilia Alejandra
Published: February 2020

This research includes results on the electrochemical performance of carbon steel in cement-based mortar when Opuntia Ficus Indica (OFI) slime was used as an addition in the mortar water mixture. Two were the OFI slimes used: cooked and exudate. The cooked OFI slime was produced from boiling cladodes with water in a 1:1 mass ratio, during 1 hour. The exudate OFI slime was extracted by placing OFI cladodes in water, same 1:1 ratio, during 48 hours. The OFI slime addition was mixed at different concentrations (4%, 8%, 15%, and 30% by water content). Half-cell potentials (E) and linear polarization resistance (LPR) measurements were performed at different time periods to characterize the possible corrosion inhibiting effect of the tested addition concentrations. Results showed better corrosion inhibiting effect of the cooked OFI slime for carbon steel, as compared with exudate OFI slime additions.
Electrochemical Corrosion of the Stainless Steel 15-5PH and 17-4PH Passivation in Citric Acid
Authors: Almeraya Facundo , Lara María , Bernal Ponce Vanessa , Tiburcio Citlalli Gaona , Cabral José Angel , Perez Ortiz Dafne , Zambrano Patricia , Bastidas David M.
Published: February 2020

Corrosion, the product of the oxidation-reduction reactions of a metallic material with its environment, generates in modern military aircraft manufactured mainly with titanium and stainless steels: deterioration, maintenance and even impact on safety. Within the methods of protection against corrosion are the coatings. The passivation is a conversion coating for stainless steels to increase the surface oxide layer that reduces the effects of corrosion. The objective of this work is to study the formation of a passive layer in steels 15-5 and 17-4PH using the electrochemical technique of potentiodynamic polarization curves (PPC), using as a passivating agent citric acid at a temperature of 25 ° C with a time of immersion of 30, 60 and 90 min and exposed in a sodium chloride medium. The passive layer was evaluated by the technique of X-ray photoelectron spectroscopy (XPS). The results obtained by PPC indicate a mixed activation control for both steels. Passive layers with corrosion current density (Icorr) of the order of 10-5mA / cm2 for 15-5PH while for the 17-4PH the passive layer presents Icorr 10-4mA / cm2 at a time immersion of 30min. The corrosion kinetics indicates a passivation mechanism for the 15-5PH steel while for the 17-4PH passivation-pseudopassivation, which indicates less stable passive layers for the latter steel. The XPS technique allows to define passive layers of up to 12.5nm, constituted by Cr2O3.
Transient Response of Chemical-Electrochemical (CE) Processes in Rotating Disk Electrode (RDE) Systems: Diffusion and Electrohydrodynamic Impedances
Authors: Leal Pedro Henrique Moura , Barcia Oswaldo Esteves , Mattos Oscar Rosa
Published: February 2020

We present a transient treatment of chemical-electrochemical (CE) processes in rotating disk electrode systems as an extension to a steady-state analysis already initiated by our group (results have been submitted to the Journal of the Electrochemical Society). Our numerical procedure can investigate systems with different diffusion coefficients over a wide range of homogenous reaction rate constants and was used to investigate both diffusion and electrohydrodynamic impedance responses. Two sets of rate constants (termed “slow kinetics” and “fast kinetics”) were used to assess the impact of the chemical step on both impedances behavior. For diffusion impedances, slow kinetic systems displayed two impedance loops, one associated with the homogenous reaction and the other to the convective diffusion. As the value of the electroactive species rate constant grew relative to its chemical counterpart, the homogenous reaction loop started to dominate the overall impedance. For systems with fast kinetics, only the loop corresponding to the convective diffusion was visible (for frequencies up to 100 Hz) and the overall impedance decreased rapidly with an increase on the reaction rate of the electroactive species. Results for electrohydrodynamic impedance corroborated the previous findings: two time constants could be observed for slow kinetic systems, but only one in the case of fast kinetics. These findings show that impedance techniques can be of great help on establishing reaction mechanisms for complex systems, since they are sensitive to the presence of non-electrochemical activities as long as they interfere with the concentration profile of the electroactive species.
Corrosion Measurement on Reinforced STEEL Concrete after Exposure to Marine Environment By Electrochemical Noise Technique with Artificial Inteligence
Authors: von Putlitz Guillermo Sosa
Published: February 2020

One of the most important effects of corrosion in concrete structures is the reduction of the mechanical properties of steel-reinforcement. This is why structural steels with corrosion resistance characteristics are commonly used to extend the service life of the concrete structure, since it is not appropriate to have a structure that only satisfies characteristics of mechanical resistance if a suitable durability is not guaranteed. The ability to evaluate and control the phenomena of electrochemical corrosion by sophisticated techniques remains a research topic of great interest at worldwide level.

So, in this research work is intended to evaluate the electrochemical behavior of the reinforcing steel embedded in concrete by using the electrochemical noise EN technique with artificial intelligence AI theory. To carry out the electrochemical evaluation, specimens of reinforced concrete were manufactured with standard steel rods and different c/w ratio, and exposing in a tropical marine atmosphere for a several time. EN is performed using stochastic oscillation measurements of the corrosion potential Ecorr
and current I of two identical working electrodes with respect to a reference electrode. In this type of technique plots of I and E vs. time are obtained. The EN data will be analyzed using statistical and mathematical methods such as variance, standard deviation, rapid Fourier transform (FFT), Wavelet transform (WT) and also a neuronal network has been obtained to predict the corrosion damage on reinforced-steel concrete.
Evalution of Corrosion Performance of Coated Steels Using Surface Potential Measurement
Authors: Ono Yuichi , Katayama Hideki , Akashi Takaya
Published: February 2020

Coated steels have been widely used for structures and industrial products, but the coating film deteriorates due to environmental factors such as suneshine and rain, and eventually under-film corrosion occurs. Conventional methods such as tape peeling test for evaluating corrosion deterioration of coated steels are destructive and also the quantitativeness is not high. On the other hand, non-contact type surface potential measurement was proposed for degradation evaluation of coated steels. The masurement method gave the information on the position and size of the deteriorated region. However, the method is applied just for the coated steel with the coating film of under 20 цm, and it is unknown whether it is applicapable for the coated steel with thick coating film which is practically used.

The principle of surface potential measurement used in this study is almost the same as that of the Kelvin method. The contact potential difference between the measurement probe and the sample corresponding to the work function occurs by electrical connection of the both. An AC signal proportional to the charge amount is obtained by opening / closing the shutter attached between the sample and the detection electrode, and the surface potential of the sample is measured using that signal.

Carbon steels of 4 cm × 4 cm was used as a steel substrate, and coated steels with a variety of coating thicknesses were prepared by spraying transparent acrylic lacquer. Corrosion test was conducted by alternating of wet and drying using 100 μL droplet of NaCl solution. After washing away of NaCl precipitated on the surface, the surface potential distribution was measured and the surface was observed by a digital microscope. The potential of 100 µm coated steel went down to 0.1 from 0.2 V after 38 cycles. The potential became further lower with an increase of the number of cycles, and the potential change region also expanded. This means that the deteriorated position and size of the coated steels can be detected by measurement of surface potential distribution. The surface potential measurement is a powerful tool as a deterioration evaluation method of coated steels.
(Invited) Open-Software Tools for the Analysis of Electrochemical Impedance Spectra
Authors: Murbach Matthew D. , Schwartz Daniel T.
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is a powerful technique for noninvasively probing the internal state of many electrochemical systems. Unlocking the full capabilities of EIS requires the extraction of physically meaningful parameters from experimental spectra. Typically, this quantitative analysis is done by fitting equivalent circuit models (ECM). However, despite the widespread use of ECMs in the quantitative analysis of EIS spectra, huge opportunities exist for improving the physical interpretability, robustness, and reproducibility in the EIS analysis workflow. Combining physics-based models and experimental data, we explore the assumptions that determine equivalent circuit applicability and tradeoffs in circuit complexity vs. interpretability. We discuss approaches to improve the accuracy of impedance analysis including physics-based impedance models for lithium-ion batteries, confidence intervals and interactive visualization for ECM analysis, and encouraging best-practices through community-driven software. A web-based tool for analyzing experimental EIS spectra as well as a Python package for model fitting will also be presented.
(Invited) Tip – Surface Electrode Interactions and the Effects of These Interactions on Scanning Electrochemical Microscopy Response
Authors: Mirabal Alex , Calabrese Barton Scott
Published: February 2020

In operando studies of heterogenous active sites using Scanning Electrochemical Microscopy (SECM) can be hindered by non-planar active sites interacting with non-apex portions of the SECM electrode tip. Concentration field distortion can result from surface sites approaching the tip size. We aim to remove these effects via finite-element modeling for a higher-fidelity depiction of surrounding concentration fields.

Experimental concentration fields near ~100 nm Pt nanoparticles are compared to a parallel, steady-state model of the identical system at varying tip-surface separations to extract kinetic and transport parameters, the concentration profile surrounding the particle, and the effective tip radius in relation to tip-surface separation. Differences between the model based on the tip presence is used to correct the experimental data for the presence of the tip.

This approach increases the measurement quality of SECM and improves understanding of heterogeneous reaction mechanisms.
(Invited) Detailed Chemistry Modeling via Cantera: A Pathway to Understanding Battery Degradation Mechanisms
Authors: DeCaluwe Steven C. , Korff Daniel , LeBar Amy , LeBar Amy , Lee Christopher H.
Published: February 2020

In lithium-ion batteries (LIBs), the solid electrolyte interphase (SEI) is a passivation layer that grows at the anode-electrolyte interface. While this layer reduces battery performance, it is a necessary feature of most LIBs, because of electrolyte instability. However, engineering a better SEI is challenging, due to the difficulty in characterizing and modeling its chemical composition and microstructure. The SEI chemistry is incredibly complex, but to date there are essentially no general purpose modeling capabilities which facilitate this electrochemical complexity to support SEI optimization.

Herein, we will use the SEI as a framework to discuss Cantera software as a means to model electrochemical complexity. Cantera is an open-source, object oriented software package which supports thermodynamic, chemical kinetic, and transport calculations in a generalize manner. We will discuss the use of Cantera as part of a computational-experimental framework to understand the SEI, and also its application to electrochemical systems, in general.
(Invited) Open Science Strategy to Accelerate Adoption of Nonlinear Electrochemical Impedance Spectroscopy as a Battery Diagnostic
Authors: Hu Victor Waiman , Murbach Matthew D. , Schwartz Daniel T.
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is a widely adopted diagnostic tool for batteries because of its ability to easily probe different physicochemical processes.1 In contrast, physics-based models are not as widely adopted for analysis of traditional (linear) EIS experiments, nor are the inherent limitations of linearizing the behavior of a battery widely appreciated.2-4 Nonlinear EIS (NLEIS) is an emerging experimental method that addresses the limitation of linearization in EIS,5 but not the challenge of using physics-based models for interpretation. We believe an open science strategy will accelerate this field, but today there are few open data and software platforms to build from,6 so simple equivalent-circuits are mostly used to interpret experiments.7 Here we explore the experimental and theoretical capabilities of NLEIS for sensitively detecting changes in kinetic, transport, and thermodynamic behavior of commercial batteries, including new physics that is invisible to linearized EIS methods. The NLEIS experimental data, software, and computational tools we present are freely available on ECSarXiv as an open science framework project supplement.5 In addition to laying out the experiments and analysis for NLEIS, we demonstrate how to access and use our open source tools, with the goal of expediting the adoption of this exciting analysis method in battery research.

References

M. E. Orazem and B. Tribollet, Electrochemical impedance spectroscopy, p. 523, Wiley, Hoboken, N.J, (2008)

J.R. Wilson, D.T. Schwartz and S.B. Adler, Electrochimica Acta, 51, 1389–1402 (2006).

M. Doyle, J. P. Meyers, and J. Newman, J. Electrochem. Soc., 147, 99–110 (2000).

J. P. Meyers, M. Doyle, R. M. Darling, and J. Newman, J. Electrochem. Soc., 147, 2930–2940 (2000).

M. D. Murbach, V. Hu, and D. T. Schwartz, ECSarXiv (2018) https://ecsarxiv.org/t635x/.

M. D. Murbach and D. T. Schwartz, J. Electrochem. Soc., 165, A297–A304 (2018).

T. Osaka, D. Mukoyama, and H. Nara, Electrochem Soc.,
162, A2529–A2537 (2015).
(Invited) Open Software for Electrochemical Battery Modeling, Estimation, and Control
Authors: Moura Scott , Perez Hector , Gima Zach , Park Saehong , Zhang Dong
Published: February 2020

Batteries are ubiquitous. However, today’s batteries are expensive, range-limited, power-restricted, die too quickly, charge too slowly, and susceptible to safety issues. For this reason, model-based battery management systems (BMS) are of extreme interest. In this talk, we discuss eCAL’s open code for electrochemical-thermal battery models. Specifically, we also discuss applications of this code for (i) parameter identification, and (ii) optimal charging control. Finally, we close with exciting new perspectives for next-generation battery systems.
TiN/Al2O3 Interface Study through ALD Process Modulations
Authors: Leménager Maxime , Voiron Frédéric , El Sabahy Julien , Lallemand Florent , Allard Bruno
Published: February 2020

Integration and miniaturization of highly reliable electronic devices are the basis of advanced technologies used for the manufacturing of implantable medical systems such as pacemakers or neuronal stimulators. Among these components, passive devices and more particularly capacitors have a key role in signal filtering and power energy management. In this context, the capacitance density improvement is a way to enable smaller components, thus increasing the final device miniaturization. Currently, Murata Integrated Passive Solutions is running in production a technology called “PICS™” enabling the 3D structuring of the silicon substrate that dramatically enhances its specific area (i.e. capacitance density) when combined with highly reliable low-k dielectric stacks such as silicon dioxide/nitride/dioxide (ONO).

In order to significantly increase the capacitance density, two points are critical: first the 3D structures need to evolve toward a more aggressive template with a higher aspect ratio, so as to increase much more the dielectric specific area. The second point is the change of dielectric toward materials with higher dielectric constant such as Al2O3 or HfO2. Atomic Layer Deposition (ALD) technique is a key requirement here, as it is a method enabling conformal deposition of various materials, dielectrics or conductors, such as TiN, on high aspect ratio structures. In parallel of the integration and the optimization of such materials within 3D structures, planar ALD based Metal/Insulator(s)/Metal (MIM) capacitors need to be studied to serve as a reference point.

The aim of our investigations is to link the electrical properties of MIM capacitors with the parameters applied during a batch ALD process such as temperature, pulse and purge times, with the support of physico-chemical characterizations (X-ray Photoelectron Spectrometry (XPS), Secondary Ion Mass Spectrometry (SIMS), Scanning Transmission Electron Microscopy (STEM)…). We will focus on the dielectric/electrode interfaces analysis through leakage current mechanism modeling and interpretations. Especially, the amount of O3 used in the Al2O3 deposition process has an important impact on the electrical properties of the MIM by impacting both TiN/Al2O3 interfaces in different ways. An optimization of the O3 dose is proposed.
(Invited) Sub-Nm Quantification of Point Defects in Ceramics and Semiconductors Using Atom Probe Tomography
Authors: Gorman Brian P , Diercks David R
Published: February 2020

Many material properties are dependent upon local defect chemistry and associated charge compensations. Properties such as electronic and ionic transport, intergranular fracture, dielectric constant, and electrical breakdown are dependent upon the accumulation of point defects at internal interfaces such as grain boundaries and heterojunctions. Quantification of these point defect accumulations has been difficult, either due to light element sensitivity, detectability limits, or the 3-D nature of the internal interfaces.

Recent work has shown that Atom Probe Tomography (APT) has the requisite counting statistics, 3-dimensionality, detectability limits, and spatial resolution to quantify point defect accumulations at grain boundaries and heterojunctions. Utilizing the 3-D atom by atom nature of APT data has enabled the conversion of analytical characterization data directly into space charge voltages and band alignments, ultimately enabling the direct relationship between materials characterization and materials or device properties.

The ability of APT to quantify point defect distributions in 3-D has limitations that are dependent upon the type of defect. Individual vacancies on either oxygen or metal cation sites (Vo
** or Vm
’) have been quantified with APT at grain boundaries and heterojunctions. Quantification of vacancies are heavily dependent upon the detection efficiency of the APT experiment and upon the volume being sampled. Interstitial oxygen or metal cations (Oi
” or Mi
*) can be observed but again is limited to the counting statistics of the volume being analyzed. However, their exact location can not be determined at this point as APT is limited in the necessary spatial resolution. Substitutional cations and defect pairs (MN
’) can be quantified as long as the cations are distinguishable in the mass spectrum. Substitutional defects coupled with vacancies (common ordered defect pairs) have been quantified at individual grain boundaries and, in some cases, allow for the calculation of electronic energy levels at interfaces. Schottky defects (Vo
** + Vm
’’) may be quantified using APT, as these defect pairs result in a change in atomic density, however, their quantification is limited by the detection efficiency of the APT instrument. Frenkel pairs on either the oxygen or metal cation sites (Vo
** + Oi
”) do not result in a change in atomic density and are only dependent upon site occupancies. Similar to interstitials, APT does not have the spatial resolution or detection efficiency necessary to identify individual Frenkel pairs. Such analyses will have to wait for Atomic Scale Tomography, of which APT may play a part. Ultimately, the combination of APT’s 3-D spatial and chemical resolution combined with analytical techniques such as EELS that allows for cation valence and free carrier energy levels to be determined will be the most complete solution to defect chemistry quantification.
(Invited) Ferroelectric Oxides and Negative Capacitance for Ultra-low Power Computing
Authors: Khan Asif
Published: February 2020

Thanks to the sub-60 mV/decade switching characteristics, negative capacitance transistors based on ferroelectric gate oxides can enable the reduction of power supply voltage and the power dissipation in future nodes. This talk will give an overview of the exciting developments in the field of negative capacitance over the past nine years starting from the theoretical prediction in 2008 to the clean experimental demonstration of this phenomenon in ferroelectric materials and transistors recently. All three aspects of this technology: physics, materials and devices will be discussed.
(Invited) High Efficiency and Low Hysteresis Solar Cells Based on Perovskite with Triple Cation and Mixed Pb-Sn
Authors: Ji Long , Wang Yafei , Liu Detao , Zhang Peng , Chen Hao , Wang Feng , Zheng Hualin , Chen Zhi David , Li Shibin
Published: February 2020

Perovskite solar cells (PSCs) based on organometallic halide have received wide attention and been developed rapidly in recent years, the highest power conversion efficiency (PCE) have reached 22.1%. However, these materials contain lead (Pb), which is toxic. It is of critical importance to find new elements for partially or completely replacing Pb to reduce the Pb contents. Most works carried out focused on CsSnX3 (X=I, Br), FASnX3 (X=I, Br), (FASnI3)1-x(MAPbI3)x (x=0-1), MASnxPb1-xI3 (x=0.25, 0.5), FA0.75Cs0.25Pb0.5Sn0.5I3, etc. We substitute PbI2 with SnI2 in Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 material for the first time, through changing the ratio of Pb and Sn, which can regulate the size of grains. By optimizing the ratio of PbI2 and SnI2 to achieve the best energy band matching, a power conversion efficiency of 16.10% is achieved by using Cs0.05FA0.79(Pb0.6Sn0.4)0.84I2.5MA0.16Pb0.16Br0.5 as perovskite light absorption layers. With bandgap changing, the hysteresis of the PSCs showed regular variation. Under the optimal bandgap matching, the planar heterojunction PSCs exhibit J-V curves with negligible hysteresis.

Figure 1. a)-f) The reverse and forward voltage scans of Cs0.05FA0.79(Pb1-xSnx)0.84I2.5MA0.16Pb0.16Br0.5 (x=0, x=0.1, x=0.2, x=0.3, x=0.4, x=0.5) perovskite solar cells.

Figure 1
Radiative Annealing of Perovskite Thin Films with Alkyl Halides
Authors: Druffel Thad
Published: February 2020

The performance of the perovskite material in solar cells has garnered a fair amount of interest because it is solution processable and thus a prime target for roll-to-roll coating. The precursor materials are typically prepared in solutions and deposited using common evaporative techniques, some that can be adapted to roll-to-roll manufacturing. The deposited films then must be annealed, a process that is typically accomplished in an oven. The economics of manufacturing improve with increased web speed, which traditional deposition and ovens can handle. However, with a long anneal time the length of the ovens becomes prohibitive, thus processes that can reduce the annealing time are desired. Radiative annealing techniques are often used in the manufacture of solar cells and involve the absorption of intense light energies to induce a thermal response. Our group has been involved in the use of intense pulses of light that can effectively anneal a thin film in under a second.

In this work, we report on solution engineering that enables both the deposition of the perovskite in ambient environments using roll-to-roll applicable technologies. The annealing of these thin films is accomplished using 1-5 millisecond flashes of light. The inks formulation includes an alkyl halide that interacts with the light and improving the overall morphology of the perovskite films. Scanning electron microscopy and X-ray diffraction analysis shows that the films achieve consistent morphology and crystallinity and perform well in solar cell devices. Results of several chemistries and processes will be presented.
Sustainable Recycling of Wafer-Silicon Solar Modules
Authors: Tao Meng , Huang Wen-Hsi , Ebin Burcak , Steenari Britt-Maria
Published: February 2020

A major obstacle to solar module recycling is the cost associated with collecting and processing end-of-life modules. We recently reported a multi-step recycling process to breakdown wafer-silicon modules and recover all the valuable, bulky and toxic materials including solar-grade silicon, silver, aluminum frame, glass, copper, tin and lead. This paper presents a study on the financial and environmental sustainability of our recycling process. At today’s prices for silver and solar-grade silicon, this process can produce at least $15/module from the recovered materials and potentially enable a profitable recycling business for silicon modules without any government support. The risk in recycling revenue is future silver-free modules and lower solar-grade silicon prices, but additional revenues can be generated by recovering the glass unbroken and clean, resulting in $17.50/module in revenue. A network for collecting end-of-life modules is proposed based on the current distribution network for solar modules to contain the collection cost. To avoid hydrofluoric wastes from the recycling process, alternatives need to be found for the fluoropolymer backsheet and silicon nitride layer in silicon modules.
(Invited) Photo-Polymerized Organic Host Network of Ionogels for Lithium Batteries: Effects of Mesh Size and of Ethylene Oxide Content
Authors: Le Bideau Jean , Aidoud Djamel , Guy-Bouyssou Delphine , Guyomard Dominique , Lestriez Bernard
Published: February 2020

Solid ionogel electrolytes are rather competitive compared to liquid carbonates based electrolyte regarding ionic conductivity but they show much better safety. It is striking that the ionogels presented here are obtained within few minutes by UV curing which triggers the formation of the polymer host network confining N-methyl,N-propylpyrrolidinium bis-(trifluoromethyl)sulfonylimide with lithium bis-(trifluoromethyl)sulfonylimide salt at the concentration of 1M. This fast and easy process allows to obtained all-solid like micro-batteries.

Herein the effect of mesh size and ethylene content of various host networks is deciphered. An optimum balance between mesh size, ethylene oxide and lithium content is identified. The ionogel formed from trimethylolpropane ethoxylate triacrylate and 1,6-hexanediol diacrylate confining 90 %wt of ionic liquid shows a mesh size close to 5 nm, with an enhanced fragility of the confined ionic liquid, as referred to that of the bulk one. Along with these last features, its ethylene oxide content allows a very good lithium ion diffusion. At room temperature and at C/5 cycling rate, prototype batteries LiFePO4 | ionogel | Li metal battery can restitute 70% of the initial capacity during up to 1200 cycles.

Figure 1