bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Observations of Anodic Alumina Nanopore Growth and Self-Organisation
Authors: Harlow Gary Steven , Vinogradov Nikolay , Evertsson Jonas , Linpe Weronica , Carlà Francesco , Felici Roberto , Lundgren Edvin 
Published: February 2020

Traditional surface science studies have been quite successful in determining several surface structures for alumina films, in particular those grown on NiAl, where the bulk structure consists of a combination of several building blocks but the surface Al atoms are found to occupy sites with either tetrahedral or pyramidal coordination [1]. However, the naturally forming ‘native oxide’ layers are found to be largely amorphous. The thickness of this layer can be increased electrochemically, i.e. by the industrial process of anodization, and to some extent the degree of crystallinity found depends on the applied voltage [2]. This type of oxide layer is called an anodic barrier layer and forms in neutral type electrolytes. In acidic electrolytes a porous oxide film is found, in which case the oxide has many nanometer sized pores and forms the base of most industrial aluminum coloring processes. Furthermore, under certain conditions these pores are found to be self-ordering [3]. They form hexagonal arrays and the pore diameter can be tuned by changes in potential, making excellent nanoscale templates.
We have investigated the formation and self-ordering behavior of porous type anodic alumina films in situ using Grazing Transmission Small-Angle X-Ray Scattering (GTSAXS) [5]. We observe the that the in-plane arrangement of the nanopores is independent of substrate crystallographic orientation whereas the oxide growth rate is not. The self-ordering behavior is studied in a variety of electrolytes and at several potentials in-order to explore the dynamics of self-ordering both below and above the breakdown potential (UB) at which optimal ordering is achieved [4]. It is also possible to follow the chemical etching of the oxide (pore widening) and subsequent metal deposition within the nanopores. The experimental approach presented can be applied to the study of a large variety of electrochemically produced materials such as magnetic nanowires, novel solar cell designs and catalysts.
[1] G. Prevot, et al. Phys. Rev. B, 85, 205450 (2012)
[2] J.W. Diggle, et al. Chem. Revs., 69(3), 365 (1969)
[3] H. Masuda, K. Fukuda, Science. 268, 1466–1468 (1995)
[4] Chu S.Z, et al. A. J. Electrochem Soc., 153, B384 (2006)
[5] Vinogradov, N.Am et al. ACS Applied Nano Materials, Article ASAP, (2018)

Figure 1: GTSAXS pattern during a 2nd anodoization of PAA. The oscillations correspond to the height of the pores.

Figure 1
Degradation Behavior of High-Phosphorus Ni-P Coating for Application in Oil and Gas Industry
Authors: Sun Chong , Fattahpour Vahid , Zeng Hongbo , Luo Jing-Li 
Published: February 2020

Carbon steel casing and tubing, utilized for oil and gas production, may potentially experience severe corrosion due to the presence of corrosive gases (e.g., CO2 and H2S) and chlorine compounds in the production wells. To mitigate the corrosion of carbon steel, the Ni-P coating has been applied to the carbon steel surface using electroless deposition method. The extensive studies have suggested that Ni-P coating can effectively protect the substrate through isolating the substrate from the corrosive environment, and exhibits good corrosion resistance in the environment containing brine, acid, CO2 or even H2S. However, some internal microdefects derived from the deposition process as well as some external defects originated from the mechanical effect during the production process will inevitably be present in the coating. These defects are likely to pose great risks to the reliability of the coating and negatively affect its durability in the corrosive environments, especially in the coexistence of CO2 and Cl-.
In this work, the degradation behavior of a high-phosphorus Ni-P coating with microdefects or an artificial defect in CO2/Cl- environments was systematically investigated using electrochemical methods and surface characterizations. The results show that although the corrosion occurs at the microdefects and extends towards the inside of Ni-P coating, the coating has a good resistance to corrosion disbonding in the CO2/Cl- environment, even with an artificial defect in the coating. Under the cathodic polarization condition (to accelerate the corrosion process), the defects in the coating provide effective pathways for the electrolyte to transport through the coating and along the coating/substrate interface laterally from the defects, thereby, causing the localized corrosion and disbonding of the coating. Finally, a corrosion model is proposed to well interpret the degradation process of the coating with microdefects in CO2/Cl- environment. The electrolyte penetrates into the micropores and causes the corrosion of coating at the micropores, promoting the initiation of the pits. As the corrosion proceeds, the accumulation of corrosive species in the pits increases the localized corrosion rate. After the pits penetrate through the entire coating, the corrosion process is governed by the substrate dissolution and the mass diffusion between the substrate interface and the electrolyte. The corrosion of the substrate propagates along the coating/substrate interface laterally and towards the depth direction due to the accumulation of the electrolyte at the exposed substrate surface, which causes local corrosion disbonding of the coating.
Effect of Fe3+ Ion on Corrosion Behavior of 5083 Aluminum Alloy in Neutral Environment
Authors: Shinozaki Ippei 
Published: February 2020

5000 series aluminum alloys are wildly used as high corrosion resistance aluminum alloys for Marine structures. As atmospheric corrosion test, iron powder and artificial sea water were spread on 5083 Aluminum alloy plate. A plate with only artificial sea water was also prepared. And the plates were kept in a humid environment for one week. After testing, pitting corrosion was only observed in plate with iron powder and artificial sea water. However, Fe3+ that is stable Fe ion was reported not to effect on corrosion of aluminum alloys.Cations derived from salts such as Na and Mg are investigated in detail as their effect on the corrosion resistance of aluminum alloys. On the other hand, the effect of Fe ions derived from steel materials, which are often used together in structural materials, on aluminum alloys is not clear. So, this study focused on effect of Fe ion on corrosion behavior of 5000 series aluminum alloy.
Then, the effect of Fe ion on the corrosion resistance of aluminum alloys was investigated through electrochemical method in beaker test. Open circuit potential in Fe3+ and Cl- solution was measured. FeCl3 aq which contained 0.53% Fe3+ and 1.0%Cl- was prepared. Its pH was adjusted to 7.0 with NaOH. NaCl aq (1%Cl-) was also prepared. OCP of 5083 Aluminum alloy in NaCl aq was -0.8 V vs SCE. However, OCP of FeCl3 aq was gradually lowered and -1.2V at last. Comparing the surfaces after 500hrs in FeCl3 aq and NaCl aq, Surface of 5083 Aluminum alloy in FeCl3 aq showed general corrosion. Surfaces at 0.5 hrs, 30 hrs, and 160 hrs in FeCl3 aq were also observed. The matrix arounds precipitations were dissolved at 0.5hrs. Dissolved area expanded after 30hrs. At last, Discoloration appeared at free surface after 160hrs. Al and O were detected at discoloration area by EDS. It implied that aluminum oxide likely was produced as corrosion product.
Anodic polarization curve in Fe3+ and Cl- solution was measured. The anodic polarization curve in FeCl 3 aq after 0.5hrs was the same as in the NaCl aq.However, OCP lowered after 24hrs. Anode current increment is necessary to lower the OCP. Then, activation of precedence dissolution caused OCP lowering as anodic reaction.Anodic polarization curve in 160 hrs had slightly higher activation potential and lower passivity current than that of 24hrs. So, Al oxide on the surface might possibly protect matrix from corrosion. However OCP kept lower and it did not return to the potential after 0.5hrs.So, the anode reaction was probably kept active even after the oxide was formed on the surface.
Therefore Fe3+ ion accelerated anode reaction that caused OCP lowering and corrosion acceleration of 5083 Aluminum alloy.
Effect of Inhibitor Modifications on Initial Localized Dealloying of Metallic Alloy Surfaces
Authors: Neupane Shova , Losada-Perez Patricia , Renner Frank Uwe 
Published: February 2020

Despite a substantial number of reports on corrosion testing is available, only a few projects aim to understand the basic processes driving materials degradation. A special type of corrosion, localized dealloying, takes place on metallic alloy surfaces modified with self-assembled monolayers (SAMs) of organic inhibitors[1-2]. Corrosion initiation at the nanoscale can be addressed by controlling the spatial distribution and molecular organization of inhibitor-molecule SAMs at nano and micro length scales. We use micro-contact printing on model ultra-flat gold surfaces and obtain well-defined complex organic layers following a multi-step approach [3]. This approach was applied on locally atomically flat Cu3Au (100) surfaces to study initial localized dealloying which results in the initiation of localized dealloying being strongly dependent on the nanoscale surface morphology (Figure 1) [4]. In addition, different organic inhibitors containing -SH (thiol end) films were subsequently applied on polycrystalline Cu and CuZn alloys to analyse inhibitor film stabilities. Force Spectroscopy of Atomic Force Microscopy (FS-AFM) provides a stability status of such inhibitor layers by analysing AFM tip sample force interaction on inhibitor-modified metallic surfaces.
References:
[1] B. R. Shrestha et al, Farad. Discuss. 180 (2015) 191–204.
[2] F. U. Renner et al, Adv. Mater. 27 (2015) 4877–4882.
[3] S. Neupane et al, Langmuir. 34 (2018) 66–72.
[4] S. Neupane et al, to be published.

Figure 1
Single Event Experiment: A Powerful Approach for Studying Passivity Breakdown and Pitting Corrosion
Authors: Heurtault Stéphane , Joiret Suzanne , Vivier Vincent , Rouillard Fabien 
Published: February 2020

Prediction of material lifetime such as stainless steels requires a clear understanding of passivation, corrosion, and pitting mechanisms. Despite its ubiquity and its history, the mechanisms of pitting are poorly understood, mainly because the stochastic behavior of the phenomenon, which results in many individual processes occurring simultaneously on the material surface. It is thus necessary to devise experiments which allow to work on a single pit for a better understanding of mechanisms governing pitting from its initiation to the propagation or its repassivation. Different experimental setup allowing the local injection of aggressive species such as chloride ions, have thus been developed [1-3], including a flow micro-device allowing a single pit to be initiated and then propagated over long time [4-6].
In this work, we show that we were able to reproduce, at will, the pitting of 316L stainless steel in order to study its propagation at various stages and to revisit the different parameters involved in the pitting process. Thanks to a statistical analysis performed on identical experiments, it was possible to build some zone diagrams showing the stability of pits as a function of the chloride concentration, the pit dimensions, and the electrode potential. Interestingly, the chemistry inside the pit was also studied as a function of the electrode potential. These experiments were performed with a specific experimental setup in order to measure the pitting current of a single pit simultaneously with the Raman spectrum thus opening new insight in the identification of species inside the pit. It was also possible to link the sulphate concentration (and thus the pH variation) inside the pit to the current as a function of time.
[1] K. Fushimi, K. Azumi, M. Seo, Use of a liquid-phase ion gun for local breakdown of the passive film on iron, J. Electrochem. Soc., 147 (2000) 552-557.
[2] K. Fushimi, M. Seo, Initiation of a local breakdown of passive film on iron due to chloride ions generated by a liquid-phase ion gun, J. Electrochem. Soc., 148 (2001) B450-B456.
[3] C. Gabrielli, S. Joiret, M. Keddam, H. Perrot, N. Portail, P. Rousseau, V. Vivier, Development of a Coupled SECM-EQCM Technique for the Study of Pitting Corrosion on Iron, J. Electrochem. Soc., 153 (2006) B68-B74.
[4] N. Aouina, F. Balbaud-Celerier, F. Huet, S. Joiret, H. Perrot, F. Rouillard, V. Vivier, A flow microdevice for studying the initiation and propagation of a single pit, Corros. Sci., 62 (2012) 1-4.
[5] S. Heurtault, R. Robin, F. Rouillard, V. Vivier, Initiation and propagation of a single pit on stainless steel using a local probe technique, Faraday Discuss., 180 (2015) 267-282.
[6] S. Heurtault, R. Robin, F. Rouillard, V. Vivier, On the Propagation of Open and Covered Pit in 316l Stainless Steel, Electrochim. Acta, 203 (2016) 316-325.
Effect of Environment Variables and Material Properties on the Limiting Current Density for Oxygen Reduction
Authors: Anderson Rachel , Hangarter Carlos , Policastro Steve 
Published: February 2020

For aircraft alloys that have received surface treatments, primers, and topcoats to control self-corrosion due to precipitate phases, high-strength fasteners made of stainless steel or titanium alloys are the most obvious point of attack due to galvanic mismatches between the materials. However, the electrolytes that form from atmospheric processes can differ widely in composition and thickness. Dissolved oxygen concentrations vary due to temperature and salinity changes in the electrolyte. Recent attempts to model atmospheric corrosion have suggested that, at high salt loadings on the surface, electrolytes can form that have water layer thicknesses that appear as bulk electrolytes in terms of oxygen transport1. Experiments using rotating disk electrode (RDE) measurements and polarization curve data,2 have suggested an upper bound of approximately 800 mm on the diffusion layer thickness for oxygen that can be expected to form in a thin film of water. At distances beyond this thickness, convective flow is expected to dominate oxygen transport. In this report, we compare the results of RDE experiments that simulate thin film behavior on different substrate materials in different electrolytes with polarization data obtained under actual electrolyte thin films equilibrated at different relative humidity values, and bulk polarization measurements, as shown in Figure 1, in order to determine the effects of ohmic drop on the measurements and isolate relevant kinetic parameters. Isolating these effects is important in order to accurately model the corrosion currents arising from galvanic couples in which the oxides at which the reduction reactions are occurring can be changing in response to the changes in the electrolyte as the environment changes.

Figure 1. Bulk cathodic polarization curves in 0.6M NaCl at 25◦C for Pt, UNS S31600, and UNS R56400.

This work was sponsored by the Office of Naval Research, ONR, under grant/contract number N0001418WX00826; the views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Office of Naval Research, the U.S. Navy or the U.S. government.

References

1 Van den Steen, N., Simillion, H., Dolgikh, O., Terryn, H. & Deconinck, J. An integrated modeling approach for atmospheric corrosion in presence of a varying electrolyte film. Electrochimica Acta
187, 714-723, doi:10.1016/j.electacta.2015.11.010 (2016).
2 Liu, C., Srinivasan, J. & Kelly, R. G. Electrolyte Film Thickness Effects on the Cathodic Current Availability in a Galvanic Couple. J Electrochem Soc
164, C845-C855, doi:10.1149/2.1641713jes (2017).

Figure 1
Investigation of the Nanomechanical Properties of Titanium Oxide Films Synthesized Using Atomic Layer Deposition
Authors: Mohammed Yousuf , Zhang Kai , Baumgart Helmut , Elmustafa A A 
Published: February 2020

Titanium oxides thin films are used in artificial heart valves due to their superb biocompatibility. They are used as photocatalysts in solar cells for the production of hydrogen and electric energy due to their stability, nontoxicity, and excellent photocatalytic properties [1]. TiO2 films are also used in heterogeneous catalysis, as a corrosion protective coating [2] and as electrode material in lithium rechargeable batteries. Above all TiO2 is utilized in massive amounts as white pigments in paints and toothpaste and cosmetic products.
It is reported that TiO2 exists in three different crystalline structures: rutile, anatase (both tetragonal) and brookite (rhombohedral). Many of the properties in these applications are strongly dependent on titanium oxide’s crystal morphology, surface area, and mechanical properties. TiO2 films of 500 nm thickness were synthesized using atomic layer deposition (ALD) on p-type Si (100). The films are tested for surface morphology, crystal structure and nanomechanical properties. The nanomechanical properties are tested using a nanoindenter from Keysight equipped with a three sided Berkovich diamond tip. The crystalline structure is verified using X-ray diffraction. The surface morphology is examined using atomic force microscopy (AFM) and the film thickness was verified using field emission scanning electron microscopy (FE-SEM) as indicated by the cross sectional FE-SEM image, shown in Figure 1.
We will discuss the structural and mechanical properties of the films citing the superiority of the ALD technique that is particularly used in the fabrication of the films that are presented in this study.

References

-Q. Hou, D.-M. Zhuang, G. Zhang, M. Zhao, and M.-S. Wu, Applied Surface Science, 218, 97 (2003).

Diebold, Surface Science reports, 48, 53 (2003).

X. Feng,G. Q.Xu, J. Lv,Q. M. Huang, Z. X. Zheng, andY. C.Wu, J. Electrochem. Soc, 160, H727 (2013).

Figure 1
Synaptic Weight Modulation By Controlling Metal Oxide Rram Switching
Authors: Veksler Dmitry , Bersuker Gennadi , Shrestha Pragya Rasmi , Cheung Kin P. , Ayvazian Talin , Bushmaker Adam 
Published: February 2020

Device technologies developed to address specific needs for neuromorphic systems include non-volatile memory (NVM), which can serve as microelectronic "synapses" for low-power mobile computing applications. Desirable memory stack characteristics include, among others, scalability, fast programming, low voltage and power operations, high retention and endurance, multi-state operation and 3D integration capability. Metal-oxide RRAM meets most of these requirements [1]; however, the critical capabilities such as symmetric and gradual conductance update, and potentiation and depression in spike-timing-dependent-plasticity scheme have not been demonstrated. In this study, we show that hafnia-based filamental RRAM devices are capable of gradual multi-level switching at ultra-fast (ps) time scale at low operation voltages (< 1V). This enables high frequency/bandwidth operations with extremely low energy switching.
RRAM devices are formed by crossbar 50x50 nm MIM capacitors fabricated with an ALD polycrystalline 5nm HfO2 film and TiN electrodes. An ultra-fast pulse setup (Fig. 1) provides precise control over the power delivered to the cell and removes the need for a current compliance control (1R configuration). Resistance is shown to stepwise increase or decrease depending on voltage value and polarity (Fig. 2).
To evaluate how synaptic weight can be modulated by the time between the incoming signals, we investigated dependency of the RRAM resistance on time between the consequent pulses (Fig. 3). Reducing the time interval between pulses below 2 ns results in significant amplification of their effect on resistance. It’s consistent with theoretical expectations that, by briefly increasing local temperature [2], the first pulse magnifies the structural changes inducing by the subsequent pulse.
To emulate the effect of time window between the pulses from pre- and post- synaptic neurons, a pair of pulses of positive (pre-synaptic) and negative (post-synaptic) polarity was applied to the same electrode (Fig. 4). In bi-polar switching, a negative polarity pulse induces resistance change in the same direction as a positive pulse applied to the opposite electrode. Potentiation or depression were observed depending on a positive pulse preceding or following the negative one, consistent with the reported brain-inspired operations. A very short time interval between incoming signals enabling potentiation/depression processes implies extremely fast neuromorphic system operations capabilities.

G. Bersuker et al., J. Comput. Electron. 16, 1085, 2017

D. M. Nminibapiel et al., EDL 38, 326, 2017

Figure 1
(Invited) The Non-Volatile Redox Memory for Neuromorphic Computing
Authors: Talin Albert Alec 
Published: February 2020

Inspired by the efficiency of the brain, CMOS-based neural architectures and memristors are being developed for pattern recognition and machine learning. However, the volatility, design complexity and high supply voltages for CMOS architectures, and the stochastic and energy-costly switching of memristors complicate the path to achieve the interconnectivity, information density, and energy efficiency of the brain using either approach. In my talk, I will review the latest advances in neuromorphic computing architectures based on deep neural networks implemented using CMOS and memristors and describe the challenges in achieving both high accuracy and energy efficiency using these devices. I will then discuss an alternative approach based on the non-volatile redox memory (NVRM): a device with a resistance switching mechanism fundamentally different from existing memristors, involving the reversible, electrochemical reduction/oxidation of a material to tune its electronic conductivity. The first type of NVRM that I will describe is based upon the intercalation of Li-ion dopants into a channel of Li1−xCoO2. This Li-ion synaptic transistor for analog computing (LISTA) switches at low voltage (mVs) and energy, displays hundreds of distinct, non-volatile conductance states within a 1V range, and achieves high classification accuracy when implemented in neural network simulations1. The second type of NVRM I will describe operates on a similar principle but is based on the polymer system PEDOT:PSS, and which we call the electrochemical neuromorphic organic device (ENODe) 2. Plastic ENODes are fabricated on flexible substrates enabling the integration of neuromorphic functionality in stretchable electronic systems. Mechanical flexibility makes ENODes compatible with three-dimensional architectures, opening a path towards extreme interconnectivity comparable to the human brain.
(1) E. J. Fuller, F. El Gabaly, F. Léonard, S. Agarwal, S. J. Plimpton, R. B. Jacobs-Gedrim, C. D. James, M. J. Marinella and A. A. Talin, Advanced Materials 29, 1604310 2017.
(2) Y. B. van de Burgt, E. Lubberman, E. J. Fuller, S.T. Keene, G. C. Faria, S. Agarwal, M. J. Marinella, A. A. Talin* and A. Salleo*, Nature Materials 16, 414 2017.