bluuebunny/crossref_metadata_2025 huggingface dataset:
Manganese Oxides As Anode Catalysts for Electrolysis: In Situ Raman and Corrosion Studies
Authors: Ranjan Chinmoy
Published: February 2020

Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting (electrolysis) on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved. MnO2 is earth abundant and well known for catalyzing oxygen evolution. A form of MnOx cluster is known to catalyze water oxidation in photosynthesis. These catalysts although with immense potential remain a long way from successful implementation within electrolysers. Catalyst stability remains an extreme challenge. MnO2-x naturally exists in various polymorphs, with various amounts of defects each of which is known to have a different electrocatalytic performance. In such a scenario the true nature of the electrocatalyst needs to be well established.

In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ. Setup for in situ Surface Enhanced Raman Spectroscopy is used for tracking the structural changes of hydrous MnOx. Electrodeposition of MnOx on the surface of Au was achieved by passing an anodic current of 50 mC/cm2 at 1,6V. Besides in-situ study of catalyst structure, ex situ analysis of corrosion using flow cells combined with Inductively Coupled Plasma-Optical Emission Spectroscopy and explicit oxygen detection using Rotating Ring Disc Electrode allows us to develop.

The structural integrity of the MnOx was studied by following the Mn-O-Mn stretching various potential ranges in various electrolytes. Onset of phase changes and corrosion could be clearly established. Beside this, other methods such as XRD, SEM, TEM were applied to study these thin films.

Figure 1
Exploring Phase-Change-Induced Flow in Fuel Cells through X-Ray Computed Tomography
Authors: Shum Andrew , Hatzell Kelsey B. , Connolly Liam G , Burheim Odne Stokke , Parkinson Dilworth Y. , Weber Adam Z , Zenyuk Iryna V
Published: February 2020

Effective liquid-water management is critical for optimal polymer-electrolyte fuel-cell (PEFC) operation. At lower operating temperatures and during startup, there is a need to remove liquid water from the cathode electrode to ensure reactant delivery1. At higher operating temperatures, large thermal gradients from catalyst layer to flow-field channel in the system promote water removal in the vapor phase due to the exponential dependence of water vapor pressure on temperature (i.e., phase-change-induced (PCI) flow). To achieve maximum water permeation and consequently higher current densities, it is necessary to understand the interplay between PCI flow, capillary-driven liquid water transport, and evaporation/condensation in PEFC porous diffusion media. PCI flow causes the liquid water to evaporate in hotter locations (electrode) and condense in cooler locations (PEFC’s land). Simultaneously, the heat redistribution occurs because heat is consumed during evaporation and released during condensation.

Currently there is little understanding of how water is redistributed under PCI flow. Although water transport in diffusion media has been investigated with modeling and experiments,2-3 evaporation and PCI flow are poorly understood. The basic fundamental knowledge is lacking primarily due to a challenge of experimental measurements and visualization of the evaporating water front within these porous materials. In this talk, we will examine the water distribution and quantify local evaporation/condensation within diffusion media subjected to thermal gradients using synchrotron-based X-ray micro computed tomography (XCT). The novel experimental in-situ setup is presented that allows for precise temperature control and simultaneous water injection. Conditions studied include varying liquid pressure, thermal gradients, and GDL materials.

Acknowledgments

We thank Prof. Jeff Gostick for helpful insights and discussions. We thank Dr. Felix Büchi, Dr. Jens Eller and Dr. Adrien Lamibrac for experimental concept of evaporation experiment. This work was supported by EERE, Fuel-Cell Technologies Office, of the U.S. DOE under contract number DE-AC02-05CH11231. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

References

1.          Weber, A. Z., et al., A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells. J Electrochem Soc
2014, 161, F1254-F1299.

2.          Zenyuk, I. V.; Parkinson, D. Y.; Hwang, G.; Weber, A. Z., Probing Water Distribution in Compressed Fuel-Cell Gas-Diffusion Layers Using X-Ray Computed Tomography. Electrochemistry Communications
2015, 53, 24-28.

3.          Zenyuk, I. V.; Weber, A. Z., Understanding Liquid-Water Management in Pefcs Using X-Ray Computed Tomography and Modeling. ECS Transactions
2015, 69, 1253-1265.
Furfuryl Alcohol-Derived Vitreous Carbon Coating on Si/ Silicide Nanocomposite Anode of Li-Ion Batteries:
Authors: Jang Juyoung , Kang Inyeong , Kim Moon-Soo , Kim Jae-Hun , Yi Kyung-Woo , Cho Young Whan
Published: February 2020

Silicon has been widely studied as an anode material for lithium ion batteries because of high gravimetric and volumetric capacity. However, lithium ion insertion and extraction results in a volumetric expansion of about 400%, which leads to pulverization of the silicon anode during electrochemical cycling. One of the methods to mitigate this problem is to coat a thin carbon layer on silicon particles. It can effectively increase the electrical conductivity, improve the chemical and/or physical properties of the surface layer. In addition, the anode particles can be protected from direct contact with electrolyte, leading to enhanced cycle life. Most of the carbon coating layer tried so far is graphitic starting from different types of aromatic hydrocarbon sources.

Here, we have adopted a new carbon coating with vitreous carbon derived from furfuryl alcohol. The vitreous carbon structure, formed after carbonization heat treatment at relatively lower temperatures, with inherently higher strength, hardness, resistance to chemical reaction, as well as lower porosity and permeability may result in better carbon coating layer. For the anode material, we combined chemically inert phase such as silicides with silicon into nanostructured composite particles which should have a much lower volumetric expansion after lithiation than pure silicon particles.

The specific surface area which would affect the irreversible capacity and charge retention ratio of the cell could be controlled by change of the heat treatment condition. The specific surface area was changed between 7m2/g and 70m2/g after coating of the alloy powder with the specific surface area of 3m2/g. By optimizing heat treatment conditions, we could obtained much improved initial capacity as well as significantly better charge retention ratio after 20 cycles.
Hydrocarbon Blended Membrane for Redox Flow Battery
Authors: Kim Haekyoung , Park Su Mi
Published: February 2020

With the expanding need for large electrical energy storage systems in connection with renewable energy sources, flow batteries, have been enormously considered due to their high flexibility in upgrade and low cost associated with scale-up. Of all the flow batteries, vanadium redox flow battery (VRFB) use of same element in both half-cell solutions that overcomes the inherent issue of cross contamination by diffusion of different ions across the membrane. Together with the absence of any toxic emissions, the vanadium redox flow battery has demonstrated its uniqueness in terms of safety and long life cycle. Typical charge-discharge reactions of a VRFB involve two vanadium redox couples, V(II)/V(III) and V(IV)/V(V), in the negative and positive half-cells, respectively. In a fashion similar to most batteries, electrons are transferred between the two electrodes through the external circuit during the charge and discharge processes. In a VRFB, the ion exchange membrane is a key component as an ionic conductor and separator: it not only provides an ionic conduction pathway between the two electrolytes but also prevents mixing of the negative and positive electrolytes. The crossover of ions through the membrane, with the diffusion of vanadium ions from one half-cell to the other due to the concentration gradients between the two electrolytes, will result in self-discharge and thus the loss of the chemical energy.

In this study, the blended membrane of hydrocarbon polymer with perfluorinated organic membrane were fabricated and characterized in terms of ionic conductivity and permeability. The ionic conductivity was measured with four point probe method and the permeability was measured with UV spectroscopy. The blended membrane exhibited comparable ionic conductivity with perfluorinated organic membrane and 30 – 40 % lower permeability than perfluorinated organic membrane. With performances of VRFBs, the energy efficiencies of VRFBs will be discussed.
Advanced Lead Batteries for Automotive and Storage Applications
Authors: Monahov Boris North Carolina , Ellis Timothy
Published: February 2020

In the steadily growing battery market, low emission hybrid electric vehicles (HEV) and energy storage systems (ESS) for supporting utility and decentralized grids linked to renewable energy power are supposed to form the major segments in the coming decade or two. In these applications the requirements to the batteries (which have to be cycled by increasingly high currents and at partial state of charge (HRPSoC)) are challenging for every chemistry. Like other advanced power sources, lead batteries are steadily improving and are matching today to the requirements of the advanced applications. Performance parameters like charge acceptance and dynamic charge acceptance, specific energy and specific power, cranking ability and energy efficiency, as well as cycle life at HRPSoC and deep cycling are subject of steady enhancement by the lead battery community. The ALABC members are achieving this by optimizing the design of the cells or by adding various forms of carbon to the negative and to the positive plates.   

Carbon is added as micro or nano sized particles of graphite, carbon black, activated carbon, nano tubes or graphene; as separate plates operating in parallel to the negative plate, or as a replacement of the grids. Efficient cell design optimization includes thin plates, height to footprint aspect ratio, bipolar and pseudo bipolar design, electrolyte concentration and a variety of additives. Optimizing of the recharge profiles at HRPSoC is another method of significantly prolonging the life of the battery.

A number of companies in the US, in Europe, Asia, Australia and New Zeeland are offering batteries with the above enhancements, following the first lead-carbon battery – the Ultrabattery - which is now available by several battery manufacturers in Japan, USA, Europe and China. Along with lowest production costs and full safety, advanced lead batteries have the lowest carbon dioxide prodution footprint and are fully recycled, what makes them the most environmentally friendly battery chemistry on the market.  

The presentation reviews these innovations and provides a summary of the new program of the ALABC for further basic battery electrochemistry research and technology advancements.
Rational Design of Size-Selective Membranes for Next-Generation Electrochemical Energy Storage
Authors: Doris Sean E. , Ward Ashleigh L. , Frischmann Peter D. , Helms Brett A.
Published: February 2020

Next-generation electrochemical energy storage (EES) devices, including Li-S and non-aqueous redox flow batteries, require selective membranes capable of allowing lithium transport while blocking crossover of active-species. If not properly controlled, this crossover often leads to capacity fade and cell death. In this presentation, I will discuss our work with a new class of size-selective membranes capable of blocking active-species crossover while allowing high ionic conductivity. These membranes are cast from polymers of intrinsic microporosity (PIMs), which exhibit permanent micropores in the solid-state due to frustrated packing of polymer chains. The design rules and structure-property relationships for achieving high selectivity and long membrane lifetime in this exciting new class of materials will be presented.
Study of Room Temperature Solid Polymer Electrolyte for Lithium Sulfur Battery
Authors: Liu Jin , Lin Yue , Zhang Cheng , Liu Yexiang
Published: February 2020

All-solid-state polymer electrolyte lithium sulfur batteries have shown technical and commercial values due to both high energy density and safety. However, room temperature application of the batteries is limited mainly by low lithium ionic transportation efficiency of the electrolyte. In this study, crosslinked polymer hosted solid electrolyte is developed to address the current issues. Results show that the flexible electrolyte possesses not only high ionic conductivity but also high lithium ion transference number at 25 oC. Lithium sulfur batteries fabricated with the electrolyte deliver initial discharge capacity of 1374 mAh g-1 at room temperature. Additionally, mechanisms for such enhancements are studied by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and thermo-gravimetric analysis techniques.
Enhanced High-Temperature Performance of LiNixCoyMn1-x-y
O2 Cathode by

Polymeric Artificial Solid Electrolyte Interphases
Authors: Shao Pei-Sian , Wu Nae-Lih
Published: February 2020

Layered Li ternary transition metal oxides, LiNixCoyMn1-x-yO2 (denoted as NCM) is an important cathode material for lithium ion batteries because of its high capacity, good thermal stability, low cost, and low toxicity. However, its cycle life deteriorates rapidly with increasing operating temperature, because of strong interaction at the solid-electrolyte interface (SEI) causing rapid SEI formation and dissolution of the transitional metal ions. To solve these problems, some of researchers proposed to partially substituting the transitional metals of NCM with different metals, such as Mg2+, Al3+, etc., to stabilize a cation disordered structure after the transitional metals dissolve from the material. However, during long-term cycling, particularly at elevated temperatures, the LiPF6 based electrolyte can readily decompose and reacts with residual water in the electrolyte to generate hydrofluoric acid (HF). The acidic attacking from HF and other side reactions from electrolyte would still deteriorate the active material. On this account, surface coating with metal oxides such as MgO, TiO2, ZrO2, ZnO, Al2O3, etc., had been employed to prevent direct contact with the electrolyte solution. Unfortunately, these approaches also lead to additional drawbacks, such as cracking of the oxide layers, decrease of ion-conductivity and increase of production costs from additional complex steps. In this research, a simple approach using polymeric artificial SEIs to modify the surface of cathode materials to enhance the cyclic and rate performance of the Li-ion batteries at elevated temperatures is proposed. Various polymeric blends were employed for modification of the cathode surface. The results show that the polymeric SEIs can substantially suppress the deteriorating reactions between the electrolyte and electrode, improve the structural stability and decrease the polarization of the material during the electrochemical operations. Comparing to the pristine cell, the modified cells show better performances in both cycle life and rate capability, maintaining lower cell impedance due to the reduced electrolyte decomposition and enhanced structure stability. The underlying mechanism is discussed.

Figure 1
Capacitance Improvement of Semiconductor Electrode By LbL Modification
Authors: Gonzalez Zoilo , Ferrari Begoña , Sanchez-Herencia Antonio , Caballero Alvaro , Morales Julian
Published: February 2020

In the last decades, supercapacitors have been considered as one of the most promising energy storage devices due to their large power density and their long cycle life. Carbon and binder-free technologies have been recently proposed based on the consolidation of semiconductor nanostructures to use as device electrodes [1, 2] due to its wider mechanical and thermal stability. Among oxide films, NiO has been intensively investigated in supercapacitors based on their high theoretical specific capacity values (2584 F/g), high chemical stability, ready availability and lower cost. Electrodes requirements of a supercapacitor, and consequently their delivered capacitance, are largely dependent on the microstructure characteristics. In particular, it strongly depends on the increase of the active surface area avoiding electronic conductivity fall. In fact, a well-connected mesoporous structure, with a high and narrow pore size distribution exhibits greatly improved electrochemical performance. The processing of those ceramic films through inexpensive and ecofriendly powder technologies is challenging. Among different approaches, the use of the colloidal techniques allows nanostructures tailoring, strengthening the control over the specific final properties.

In this work, colloidal routes have been explored to improve the electrochemical response of a pseudocapacitor electrode based on a NiO nanostructure consolidated at low temperature (325°C) [3]. At this time, we have considered the surface modification of Ni(OH)2 nanoplatelets synthesized by ultrasound through the addition of polyelectrolytes to the suspension. The formation of different layers with polycationic and polyanionic electrolytes was studied. Polyethylenimine (PEI) and Polyacrylic Acid (PAA) were used as polyelectrolytes to form a Layer by Layer system. As a result the modified Ni(OH)2 nanoplatelets were stabilized in suspension and shaped by Electrophoretic Deposition (EPD) on Ni substrates, for later sinterization of films which were electrochemically tested.

[1] D.-H. Ha, M.A. Islam and R.D. Robinson, Binder-free and carbon-free nanoparticle batteries: A method for nanoparticle electrodes without polymeric binders or carbon black, Nano Lett .12, 2012, 5122–5130.

[2] S.Cabanas-Polo, Z. González, A.J. Sanchez-Herencia, B.Ferrari, A.Caballero, L.Hernan and J.Morales. Cyclability of binder-free β-Ni(OH)2  anodes shapes by EPD for Li-ion batteries, J. Eu. Cer. Soc., 35, 2015, 573-584

[3]  Z. González, B.Ferrari, A.J. Sanchez-Herencia, , A.Caballero and J.Morales. A One-Step and Binder-Free Method to CoatStructures with NiO nanoplatelets. Influence of the Particle Packing in Supercapacitor Electrodes. J. Electrochem. Soc.
Enhanced Cycle Life and Capacity Retention of Ultrathin Film Coated SnO2 Nanoparticles at High Current Densities
Authors: Liang Xinhua , Palaparty Sai Abhishek , Patel Rajankumar L.
Published: February 2020

Tin oxide (SnO2) has a high theoretical capacity (~782 mAh/g) but, it experiences large volume changes during charge and discharge cycles that causes rapid capacity fade, which limits its practical use as an anode material. In an attempt to solve this, we coated these particles with ultrathin conductive metal oxide films that act as artificial solid electrolyte interphase layer, thus stabilizing the SnO2 particles for better longevity of significantly improved performance at high current densities in a practical voltage window. Since there exists a tradeoff between species transport and protection of particles (expecting long life), a film with an optimum thickness was achieved by atomic layer deposition (ALD) on SnO2 particles. The conductive film coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated samples. With an optimum thickness, an initial capacity of ~ 646 mAh/g was achieved at a high current density of 1,250 mA/g. After 1,000 cycles of charge/discharge at 1,250 mA/g, the coated sample showed a capacity retention of 95% as compared to 24% of the uncoated sample when cycled at room temperature; at 55 ºC, the capacity retention of the coated sample was 97% compared to 34% of the uncoated sample.
(Invited) Charge Generation in Bulk-Heterojunctions Based on Fullerene Heterodimers
Authors: Dyakonov Vladimir , Sperlich Andreas , Poluektov Oleg G. , Niklas Jens , Delgado Juan Luis , Martin Nazario
Published: February 2020

Organic photovoltaic (OPV) cells remain to be one of the most attractive approaches for utilization of solar energy showing gradually increasing conversion efficiency of 11%. Significant efforts were directed to the improvement of the electron donating (polymer) part of the bulk-heterojunction (BHJ) solar cells.  On the other hand, less advancement has been made on the acceptor side. Recently, a few examples of soluble fullerene hetero- and homodimers based on C60 and C70 linked through chemical bridges have been developed and were shown to competitively perform in solar cells. However, the electronic structure of these fullerene dimers is not well understood. Thus, it is not known how those two fullerene molecules are electronically coupled in the dimer, i.e., whether the excited neutral state or anion state of the dimer is delocalized over the whole dimer or still localized only on one fullerene cage. We have experimentally shown that fullerene molecules in the C60-C70-heterodimer in solid films are strongly electronically coupled and the spin densities of the anion and excited triplet states are delocalized over the whole molecular dimer. However, in the frozen diluted solutions the fullerene cages in heterodimers are instead weakly coupled. The anion and triplet states of the dimers show the signature of individual C60 or C70 molecules. We explain this phenomenon by the presence of two different conformers in the solid-state films and in frozen solutions. Since the electronic coupling between fullerene molecules in the dimers is influenced by their packing in the blends, our observation provides insight into how to tune the electronic properties of the fullerene acceptors by proper adjustment of molecular bridge structures between fullerene cages to fix the desired conformation, which in turn may have an impact on the charge carrier generation efficiency in organic solar cells.
(Invited) DNA As Supramolecular Template for the Assembly of Porphyrin Arrays
Authors: Stulz Eugen , Mames Iwona
Published: February 2020

DNA has become very attractive as scaffold for functional molecules on the nanometre scale.1 The sequence specific insertion of modified nucleotides using automated DNA synthesis allows for the creation of new designer molecules with a wide range of potential applications. We have established a general synthetic route to porphyrin-nucleosides and their subsequent site specific incorporation into oligonucleotides to create multiporphyrin arrays. Up to eleven consecutive porphyrins could be incorporated into DNA giving access to a multiporphyrin array of approximately 10 nm in length, which corresponds to the highest amount of DNA modification with a large hydrophobic metal complex.2 The spectroscopic data and structure calculations indicate the formation of a stable helical array in the single strand porphyrin-DNA. The π-stack of the porphyrins leads to strong electronic interaction between the chromophores. A zipper array with induced stability and energy transfer properties has recently been realised, providing access to the first reversible photonic wire based on a DNA scaffold.3

We will present our latest results in terms of structure analysis of porphyrin modified DNA, which includes the stepwise built up of a porphyrin-DNA system and its detailed analysis using CD spectroscop and thermal analysis with absorption and fluorescence spectroscopy. In addition, a novel LNA derived porphyrin building block will be discussed which shows large differences in excitonic coupling depending on the DNA sequence.4 Several applications of porphyrin-DNA will also be described, including highly sensitive genosensors5 and DNA origami nanopores.6

References

1.   T. J. Bandy, A. Brewer, J. R. Burns, G. Marth, T. Nguyen and E. Stulz, Chem. Soc. Rev., 2011, 40, 138-148.

2.   L. A. Fendt, I. Bouamaied, S. Thöni, N. Amiot and E. Stulz, J. Am. Chem. Soc., 2007, 129, 15319-15329.

3.   T. Nguyen, A. Brewer and E. Stulz, Angew. Chem. Int. Ed., 2009, 48, 1974-1977.

4.   D. G. Singleton, R. Hussain, G. Siligardi, P. Kumar, P. J. Hrdlicka, N. Berova, E. Stulz, Org. Biomol. Chem., 2016, in print; DOI: 10.1039/C5OB01681A

5.   I. Grabowska, D. G. Singleton, A. Stachyra, A. Gora-Sochacka, A. Sirko, W. Zagorski-Ostoja, H. Radecka, E. Stulz, J. Radecki, Chem. Commun., 2014, 50, 4196-4199.

6.   a) J. R. Burns, E. Stulz and S. Howorka, Nano Lett., 2013, 13, 2351-2356; b) J. R. Burns, K. Gopfrich, J. W. Wood, V. V. Thacker, E. Stulz, U. F. Keyser and S. Howorka, Angew. Chem.-Int. Edit., 2013, 52, 12069-12072.

Figure 1
Corrosion of an Aluminum Alloy (AA2024) Influenced By Microorganisms of a Bacterial Consortium
Authors: Paez Maritza Angelica
Published: February 2020

In this work, corrosion of an aluminum alloy for aeronautical applications, AA-2024, influenced by a consortium of microorganisms was studied.

Microorganisms were isolated through environmental sampling, which was carried out in the auxiliary fuel in a Twin-Otter aircraft in Antarctic climate conditions. The identification of microorganisms was performed by sequencing of the 16S gene of ribosomal DNA (rDNA), which allowed distinguish a number of bacteria belonging to the genera Staphylococcus, Kocuria, Nosocomiicoccus and Tersicoccus. For all microroganismos, catalase test was positive.

Electrochemical measurements and morphological characterization of the surfaces was performed before,  and after, different immersion times (1, 2, 3, 7 and 14 days) in minimum culture media, Twin (MMT), sterile and inoculated with the consortium and also, with each microorganism isolated.

Impedance diagrams for all immersion times showed a capacitive behavior characterized by a single time constant. Although short exposure times no corrosion process was evident, for longer times the resistance of aluminum oxide (Rox) decreased significantly, suggesting the occurrence of corrosion process, possibly mediated by microorganisms. Morphological changes of surfaces exposed to different media were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM).

The mechanism of corrosion, particularly that associated with Enzyme approach was studied performing potentiostatic measurements pyrocarbon electrodes modified with cobalt phthalocyanine. The latter compound catalyses the reduction of oxygen via two electrons, ie via hydrogen peroxide. Measurements were made in sterile and inoculated media and in the presence of oxygen. Electrochemical results show that the presence of microorganisms significantly alter the mechanism of oxygen reduction, particularly the reduction of oxygen to hydrogen peroxide. This would confirm the mechanism of the enzymatic approach in microbiologically influenced corrosion.
Self-Organizing Anodization in Pure Molten O-H3PO4
Authors: Altomare Marco , Nguyen Nhat Truong , Schmuki P.
Published: February 2020

In 1995 Masuda et al. reported on a straightforward anodization approach that allowed for the growth of self-organized vertically-aligned alumina nanopores.1 Since then, electrochemical anodization has been widely investigated as a most suitable way to fabricate one dimensional (1D) functional oxide structures.2 Highly-ordered architectures of several metal oxides were successfully formed by anodizing in aqueous acidic solutions (e.g., Al2O3),1 fluoride containing aqueous or organic solvents (e.g., TiO2, Ta2O5, ZrO2, HfO2, etc.),3,4 and hot glycerol electrolytes (e.g., Al2O3, Ta2O5, TiO2).5-7

With this contribution we introduce a class of anodizing electrolytes, based on pure ortho-phosphoric acid (i.e., o-H3PO4), that provides high aspect-ratio highly-ordered oxide nanostructures on some of the most challenging elements such as W, as well as on more common elements such as Al, Ti, Nb.8

We describe how to tailor the structure of the formed anodic oxides by adjusting a set of key electrochemical parameters such as the electrolyte temperature, its water content, the applied voltage, and the anodization time. We show that under suitable conditions, an ideal equilibrium is established between field-assisted passivation of the metal and oxide dissolution, this leading to the growth of the anodic oxide layers in a highly ordered fashion.

Not only pure molten ortho-phosphoric acid but also other phosphorus-containing acids, namely, hot pure pyro- and poly-phosphoric acids, are able to establish the required self-organizing electrochemical conditions for the growth of ordered oxide structures. We propose that the role of the molten phosphate electrolyte is two-fold: i) it provides an environment with controlled and limited water content (that is the key oxidant), and ii) it provides phosphate ions that protect the anodic oxide from rapid dissolution, this allowing for a controlled growth of the metal oxide nanostructures.

(1) Masuda, H.; Fukuda, K. Science
1995, 268, 1466; (2) Roy, P.; Berger, S.; Schmuki, P. Angew. Chem. Int. Ed.
2011, 50, 2904; (3) Assefpour-Dezfuly, M. J. Mater. Sci.
1984, 19, 3626; (4) Kowalski, D.; Kim, D.; Schmuki, P. Nano Today
2013, 8, 235; (5) Melody, B.; Kinard, T.; Lessner, P. Electrochem. Solid-State Lett.
1999, 1, 126; (6) Lu, Q.; Alcalá, G.; Skeldon, P.; Thompson, G.; Graham, M. .; Masheder, D.; Shimizu, K.; Habazaki, H. Electrochim. Acta
2002, 48, 37; (7) Kim, D.; Lee, K.; Roy, P.; Birajdar, B.; Spiecker, E.; Schmuki, P. Angew. Chemie Int. Ed.
2009, 48, 9326; (8) Altomare, M.; Pfoch, O.; Tighineanu, A.; Kirchgeorg, R.; Lee, K.; Selli, E.; Schmuki, P. J. Am. Chem. Soc.
2015, 137, 5646.

Figure 1
Corrosion Behavior of Structural Materials for Use in Solar Thermal Molten Salt Power Plants
Authors: Summers Kodi , Chidambaram Dev
Published: February 2020

Introduction

Increasing greenhouse gas emissions and electricity demands coupled with decreasing fossil fuel reserves has dramatically increased the need for alternative energy sources. Solar energy continues to be the most promising carbon-neutral source with more energy incident on the Earth in 1 hour than is consumed in an entire year (1). Concentrated solar plants (CSPs) have been gaining interest due to their relatively high efficiencies of 37-42% (2). Molten salt CSPs have been of particular interest because these designs can achieve the highest temperatures and efficiencies (1). Solar technologies also need to account for periods without sun that can only be solved by developing a method of storing excess energy produced during peak producing time. Concentrated solar plants that use a molten salt heat transfer fluid (HTF) have the ability to store sensible heat for up to 15 hours (3).

Experimental

Experiments were conducted at operating temperatures of a typical CSP using a molten nitrate salt HTF of 300 - 500°C in a static, atmospheric environment. The molten salt working fluid studied was an off-eutectic 40/60 wt.% KNO3/NaNO3 mixture. The alloys studied were stainless steel 316, super-austenitic Incoloy 800H, and carbon steel. Each of these alloys was exposed to the salt for 100 hour exposures and galvanic couples at 300, 400 and 500°C. The alloys were studied electrochemically to simulate long-term exposures analogous of plant operation. The oxide film that is formed on each sample was then characterized to correlate the surface chemistry to the corrosive behavior of the salt on each alloy. The surface characterizations are performed using X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The salt was also studied by dissolving in deionized water and analyzing the solution by inductively coupled plasma optical emission.

Results

Figure 1 shows Raman spectra for SS 316 exposed at 300°C molten KNO3/NaNO3salt mixture for 100 hours. Based on the Raman shift, hematite and magnetite features can be observed on the surface (4). Similarly, the surface chemistry of all alloys are correlated to their corrosion behavior.

Figure
1
: Raman spectrum obtain from SS316 exposed to molten nitrate salt at 300C for 100 hours.

Acknowledgements

This material is based upon work supported by the National Science Foundation under Grant No. IIA-1301726.

References

1.            D. Barlev, R. Vidu and P. Stroeve, Solar Energy Materials and Solar Cells, 95, 2703 (2011).

2.             M. T. Dunham and B. D. Iverson, Renewable and Sustainable Energy Reviews, 30, 758 (2014).

3.             H. L. Zhang, J. Baeyens, J. Degrève and G. Cacères, Renewable and Sustainable Energy Reviews, 22, 466 (2013).

4.             RDSS - A Raman spectra library software using peaks postion for fast and accurate identification of unknown inorganic compounds, in.

Figure 1
(Invited) Process and Integration of Dielectrics Required for 10nm and Beyond Scaling
Authors: Clark Robert D. , Tapily Kandabara , Consiglio Steven , Hakamata Takahiro , O'Meara David , Newman Daniel , Collings Michael , Szymanski Dennis , Wajda Cory S. , Leusink Gert J.
Published: February 2020

Over the past decade traditional scaling by simple linear shrinking has effectively ceased as IC makers have adopted new 3-dimensional device structures, complex integration schemes and new processes and materials for an expanding number of applications in order to overcome fundamental physical limits. This trend will accelerate as devices are scaled to a level approaching atomic dimensions.  Dielectric materials with tailored properties are required to meet future device needs.  And deposition processes that are self-limited (e.g. Atomic Layer Deposition (ALD)), or self-directed (e.g. selective deposition) will enable those materials to be used in scaled 3D devices.  Highly tailored ALD processes are being investigated to fabricate functional material layers. Interspersed treatments and doping to make ternary materials may be used to modify the physical and electrical properties of ALD films further in order to optimize the resulting physical or electrical properties. To improve device contacts, ultra-thin dielectrics and metal layers may be deposited inside of high aspect ratio contact structures in order to provide lower contact resistivity- or may be used to provide solutions for integration of new contact structures. Selective deposition processes can be used to deposit functional materials only where they are needed, thus reducing the patterning burden during IC manufacturing. Future use of new transistor channel materials, such as III-V and Ge, will require the use of ALD gate dielectrics with compatible treatment schemes in order to passivate defects and provide EOT scaling inside of ultra-high ratio replacement gate structures.  Examples of these and similar processes will be described and discussed with the goal of discerning a path beyond 10nm devices.
Dual ICP Si Etching and Vapor Deposition Polymerization Liner for Backside Via-Last TSV Packaging Process Integration
Authors: Morikawa Yasuhiro
Published: February 2020

Smart ICT (Information and Communication Technology) such as “Big Data”, “Cloud computing” and Smart Functionalities such as Stand-alone Self-activating MEMS/Sensors construct Smart Systems which enable IoT (Internet of Things), IoE (Internet of Everything) thus Smart Society. To realize above-mentioned Smart Technologies, high-density, low-power consumption, wide-bandwidth, fast-operation semiconductor devices as well as smart functional devices enabled by integrating functionalities with advanced semiconductor technologies including CMOS technologies are necessary. High-density Packaging technologies such as 3D, 2.5D packaging scheme basing on TSV (through-Si via) technology and 2.1D PCB packaging are among key technologies to satisfy the requirements from the both smart semiconductor devices and smart functional devices. "Hetero 3D stacked" technologies are gathering the most attention from now on. These technologies can make a high density packaging interconnection by using TSV on the each function devises. Heterogynous 3D Si integration has great advantages over conventional 2D devices such as high packaging density, small wire length, high-speed operation, low power consumption, and high feasibility for parallel processing. But, the radical problem about the cost of TSV fabrication is not still solved. In particular, the management of barrier metal film deposition on the smooth surface is most important technology for Cu diffuse protection [1]. On the other hand, TSV isolation liner materials with high step coverage and lower temperature deposition on the smooth surface for high frequency devices will be necessary in the future. “Scallop-free” etching process has developed for TSV fabrication [2]. In this paper, our high-density packaging technologies including scallop-free, low-temperature processed TSV solution for via-last packaging scheme and 2.1D packaging solutions on large panel build-up board by semiconductor manufacturer tools will be introduced. Especially, backside Via-last TSV process integration was proposed by “A Novel Dual ICP Plasma” Si etching and low-temperature "Vapor Deposition Polymerization (VDP)" liner (< 200 degree ) for lower-cost and low-stress hetero 3D chip stacked. “A Novel Dual ICP Plasma” is using 2 RF modes mixed ICP plasma. One is high frequency RF mode. And, another is low frequency RF mode. This plasma is able to generate high-density plasma (High etch rate), and also “Scallop-free” smooth etching. This is a kind of “Non-Bosch” process. On the other hand, this dual ICP plasma can carry out “Bosch” process at the same module. This system is very unique etching tool that can use for distinguishing between "Bosch" and "non-Bosch" to TSV cost reduction.
The Study on Keeping the Pad Surface Condition in W CMP Process
Authors: Oh Dong Won
Published: February 2020

Chemical Mechanical Polishing (CMP) is the most effective planarization process in the integrated circuit fabrication. CMP Process has been applied in various purposes. Different types of surfaces are polished for each object, including oxides, Cu, W and others. 

The performance of each CMP Process depends on ability of tools and limitation of its consumables. Materials of CMP Process are roughly separated slurry, pad, conditioning disk, above all, it is a difficult problem to extend its life time of pad and conditioning disk for mass fabrication.

We were motivated to improve its change period. In this work, we focused on improvement of life time of pad and disk of W CMP Process in NAND FLASH Devices. Because that is less than half the change period to another CMP Processes, the improvement of efficiency of mass fabrication is greatly required. The W CMP Process consists of two step processes, the first step is polishing bulk W film and the second step is polishing oxide mold which was patterned by W film. In the first step for removing bulk W film, it is limited by increasing the polishing time according as accumulation processing wafer counts. On the other hand, in the last step for removing oxide mold which was patterned by w film, it is limited by decreasing the pad groove depth because the pad wear rate is extremely high than other CMP Process.  

In this work, we studied characteristics of each step in W CMP Process to extend the life time. We focused on the ability improvement of diamond disk to keep the steady removal rate and to reduce the lower pad wear rate. We developed the novel diamond disk as controlling the shape and height of protrusion of diamonds.
Mixed Strategy Combination of Pressure and Velocity Control for Chemical Mechanical Planarization of Patterned Wafers
Authors: Chandra Abhijit , Bastawros Ashraf , Wu Kuan-Chuen , Karra Pavan
Published: February 2020

The Preston equation suggests interoperability of material removal rate (MRR) by either pressure or velocity.  Traditionally, planarization is pursued by pressure control.  A novel velocity control strategy for a single step on a blanket wafer is recently proposed.  The effectiveness of both strategies on patterned wafers is numerically investigated here, using the MIT Mask layout.  Superiority is observed to be pattern dependent, scaling with MRR and material choice.  However, improved quality at feature scale induces deterioration at the die scale.  Scratch generation propensity, which is a micro- or even nano-scale phenomenon, is typically invariant to macro-level control strategies.  A mixed control strategy produces better results in terms of finish quality and productivity, by attaining the targeted local and global planarization in less polishing time, compared to individual strategies.
Surface Characterization Driven CMP Optimization for GaN
Authors: Karagoz Ayse , Siebert Max , Leunissen Peter , Basim G. Bahar
Published: February 2020

III-V nitride semiconductors are widely used for optoelectronic devices such as blue lasers diodes (LDs), light-emitting diodes (LEDs), and high power, high frequency field effect transistor (FET) devices [1]. Among these, GaN has exceptional characteristics such as providing direct and wide band-gap energy and high electron mobility and hence is typically used for the high power applications and LEDs [2]. The performance and quality of the optical devices directly correlate to the level of surface defectivity and planarization.  Consequently, application of Chemical Mechanical Planarization (CMP) with minimal defectivity is required. However, introducing CMP on a film that is poorly grown due to epitaxial challenges such as GaN [3], in addition to GaN being a very robust film to effectively remove material limits the CMP performance.

In this study, a systematic experimental approach is followed to determine the conditions to enhance material removal rate while controlling surface defectivity for GaN CMP. Two different crystallographic orientations of the GaN are characterized and compared to a commercial 2” GaN wafer to optimize the CMP material removal rate performances on the basis of the surface electrical, topographic and crystallographic properties. Silica based slurries were used as a function of pH, type of polishing pad and conditioning. CMP responses of Ga reach orientation (Face A) and N reach orientation (Face B) were different while the commercial 2” GaN wafer with unknown surface crystallographic structure was observed to have similar behavior with the Face A bulk wafer. The optimized CMP conditions as a function of surface characteristics helped in increasing the very limited material removal rates of GaN while minimizing defect formation and enhancing the selectivity against silica.

References:

 

Hua Gonga, Guoshun Pana, Yan Zhoua, Xiaolei Shi, Chunli Zoua, Suman Zhanga,“Investigation on the surface characterization of Ga-faced GaN after chemical-mechanical polishing”Applied Surface Science, Volume 338, Pages 85–91, (2015).

Hideo A., Hidetoshi T.,  Koji K., Haruji K., Kazuhiko S.,and Toshiro D., Chemical Mechanical Polishing of Gallium Nitride with Colloidal Silica, Journal of The Electrochemical Society, 158 (12) H1206-H1212, (2011).

Tavernier P. R., Margalith T., Coldren L.A.,DenBaars S.P., and Clarke D.R., Chemical Mechanical Polishing of Gallium Nitride, Electrochemical and Solid-State Letters, 5,(8),G61-G64 (2002).
Plasma Spray Pyrolysis: A Rapid, Scalable Method for Making Mixed Metal Oxide Alloys for Enabling Accelerated Materials Discovery
Authors: Sunkara Mahendra Kumar , Ajayi Babajide , Kumari Sudhesh , Spurgeon Joshua M , Jasinski Jacek B , Jaramillo-Cabanzo Daniel Felipe
Published: February 2020

Many grand challenges in energy conversion and storage need discovery of new materials. However, there are not too many reported synthesis approaches that could easily be implemented for screening and rational understanding of structure-behavior relationships. Specifically, the challenges include semiconductors for photoelectrochemical water splitting, stable electrocatalysts for oxygen evolution and reduction, and nitrogen reduction and for many heterogeneous gas-solid reactions including carbon dioxide reduction. Many of the above challenges require synthesis of multi-element alloys with composition over entire range regardless of phases present.  

Here, we report a new synthesis technique that can be used to accelerate the discovery of materials for various energy conversion and storage applications. Specifically, this technique allows a rapid and controlled synthesis of mixed metal oxide particles using plasma oxidation of liquid droplets containing mixed metal precursors. The conventional wet chemical methods for synthesis of multi-metal oxide alloys often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control.  The concept is demonstrated by synthesizing binary and ternary transition metal oxide alloys with control over entire composition range using metal precursor solution droplets oxidized using atmospheric oxygen plasma. The results show the selective formation of metastable spinel and the rocksalt solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMnzFe2-
zO4 (01), exhibits considerable electrocatalytic activity towards oxygen evolution reaction (OER), achieving an overpotential of 0.39V at a benchmarking current density of 10 mAcm-2 for a low manganese content of z = 0.20.
SEM Analysis of Electrophoretically-Deposited Cobalt Ferrite Films
Authors: Verma Neil , Talbot J. B.
Published: February 2020

Cobalt ferrite nanoparticles (20 nm) were synthesized and electrophoretically deposited onto aluminum foil, graphite paper, and carbon felt (3 mm thickness) from a 100% ethanol bath.  Linear sweep voltammetry was used to test the electrocatalytic activity of the deposits relative to blank substrates for the oxidation of ammonium sulfite to ammonium sulfate in a proposed sulfur ammonia (SA) water-splitting solar thermochemical cycle.  Subsequently, scanning electron microscopy (SEM) was used to study the morphology of the cobalt ferrite films.

The effects of electrophoretic deposition conditions on deposit morphology and the effects of deposit morphology on electrochemical activity in 2 M ammonium sulfite were investigated.  EPD on aluminum and graphite paper was performed such that particles were deposited on only one side of the substrate.  For the 3 mm thick carbon felt, particles were deposited on both sides of the substrate to improve deposit uniformity throughout the sample.  Both deposition time (0-10 minutes) and deposition current (0-16 mA) were varied to analyze their effects on the resulting deposit films for all substrates.

For the EPD conditions studied, a critical deposit thickness was found for graphite paper and carbon felt for maximum electrochemical current density, where additional deposited particles reduced the electrocatalytic activity of the deposits.  This thickness was estimated to be 3 particle layers for the graphite paper substrate.  At this thickness, the deposit had a 5.5 fold increase in activity relative to a blank graphite paper substrate.  SEM micrographs showed that the deposit uniformly covered the substrate and had noticeable cracking.  For the carbon felt, the critical deposit thickness was observed to be approximately 1-2 particle layers via SEM analysis.  Moreover, SEM images showed that the deposit was a uniform film with no cracking.  At this thickness, the deposit had a 4.3 fold increase in activity compared to a blank carbon felt substrate.