bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photocathodic Protection of TiO2 Composite Material on 304 Stainless Steel
Authors: Wang Xiutong , Li Hong , Wei Qinyi , Zhang Qiaoxia , Hou Baorong 
Published: February 2020

TiO2 and other semiconductor materials were found to have photocathodic protection effect for the metal coupled with these semiconductors film, as the potential of the metal shifted to a more negative value than its corrosion potential and the corrosion of the metal was prevented. TiO2 has been one of the most important semiconductors because of its good environmental friendliness and chemical stability. However, due to the wide band gap of TiO2 (3.2 eV) and the recombination of the photogenerated electron-hole (e–-h+) pairs, it can only absorb the light with the wavelength less than 380 nm, and it is hard to maintain the cathodic protection in the dark. In this paper, CdSe and other materials were applied to improve the photocathodic protection property.
TiO2 nanotubes was prepared by anodization method, and CdSe was deposited on the TiO2 nanotube arrays by cyclic voltammetry method, and the optimum condition was selected from different cycles. The surface morphology and crystal phase of the composite was investigated by scanning electron microscopy (SEM), X ray diffraction (XRD) method.
The photocathodic protection property of the composite material for 304 stainless steel in seawater was investigated by the electrochemical method including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and the tafel polarization curves method. The experimental results showed that open circuit potential of 304 stainless steel decreased from -190mV to -500mV when the light was turned on, and the electrode potential slowly rises to about -250mV after the light was turned off. The composite material still could maintain the protective effect on stainless steel after the light was turned off.
The work was supported by the Project of National Development and Reform Commission, the Nantong Science Project (BK2014008), and National Basic Research Program of China (2014CB643304).
Hydrogen Evolution Behavior of Dissolving Magnesium Investigated By EIS and Gas Chromatography
Authors: Takemiya Rie , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki 
Published: February 2020

An air battery is expected as a power source for the automobile and disaster battery because it has a high energy density and charge voltage. Since the magnesium is the less noble material, it is expected as a negative electrode active material of air battery. It is well known that the cathodic reaction of hydrogen evolution was occurred at magnesium surface during anodic polarization measurement of magnesium (1). Petty et. al (1) suggested that the fraction of dissolving magnesium enters the solution as univalent magnesium (Mg+), where it is oxidized by water. Samaniego et. al (2) reproduced the experiment performed by Petty et. al (1) and supplemented with modern in situ Raman spectroscopy. They concluded that the existence of univalent magnesium was not established by Petty et. al (1). Frankel et. al (3) suggested that the ability of magnesium to support the cathodic reaction is enhanced during the anodic dissolution as the result of an increase on the exchange current density for the hydrogen reaction. Although the mechanisms of hydrogen evolution on the magnesium surface have been suggested, reactions of the hydrogen evolution have not been clarified in detail yet. In this study, the relation between the anodic dissolution of magnesium and the hydrogen evolution occurred during anodic polarization of magnesium is investigated by the simultaneous measurements of electrochemical measurement and gas chromatography. The hydrogen evolution of the dissolving magnesium was examined by the 3D impedance measurement in 0.5 M NaCl. The amount of the hydrogen gas during anodic polarization of magnesium was detected by the gas chromatography.
References:
1. R. L. Petty, A. W. Davidson and J. Kleinberg, Journal of the American Chemical Society, 76, 363 (1954).
2. A. Samaniego, B. L. Hurley and G. S. Frankel, Journal of Electroanalytical Chemistry, 737, 123 (2015).
3. G. S. Frankel, A. Samaniego and N. Birbilis, Corrosion Science, 70, 104 (2013).
Dealloying of Magnesium Alloys
Authors: Wingersky Ashlee , Handler Allison , Fisher Julia , Weiss Anna , Sieradzki Karl 
Published: February 2020

The corrosion behavior of cast Mg-Al alloys such as AZ91D and AM60B is strongly dependent on the alloy composition and microstructure. Alloy grain size, area fraction of phases and spatial distribution of the phases are important factors governing both full immersion and atmospheric corrosion behavior. Mg-Al alloy systems can be broadly characterized as being composed of a primary a-Mg matrix (grains) containing Al in solid solution and b-phase intermetallic particles mainly distributed within and adjacent to grain boundaries. Heat treatment of the as-cast alloys significantly modifies the microstructure altering grain size, phase amounts and distribution as well as the a-Mg phase composition.
The general scenario that we envision evolving during corrosion of cast Mg-Al alloys is the following. In near-neutral electrolytes containing chloride, second phase particles such as the Mg17Al12 b-phase serve as cathodes for water reduction resulting in increases in pH. The corresponding dissolution reaction involves the dealloying of Mg from a-matrix grains resulting in enrichment and redistribution of solid solution Al as well as impurities (such as Fe) that may be present within the grains. The redistributed Al will form Al clusters on the surface of the now dealloyed a-phase that can also serve as cathodes. If the pH rises to ~ 9-9.5, the a-phase will begin to passivate and the b-phase can in principle dealloy (selective dissolution of Al) since the corrosion potential (~1.5V vs. SCE) is high enough for this to occur. At this elevated pH, aluminum may dissolve as the soluble aluminate and will tend to precipitate on to the dissolving alloy surface. Thus, owing to these pH changes local cathodes can become anodes and vice versa. The degree to which these processes affect corrosion behaviors depends on the spatial density (mean separation) of existing and evolving surface cathodes and how this length scale compares to the thickness of a electrolyte diffusion boundary layer or condensed liquid layer (atmospheric corrosion) and grain size.
Given this hypothesis for corrosion behavior, we have been examining dealloying of AZ91D and AM60B as well the constituent a- and b-phases. Instead of relying on a technique such as EDS to characterize the time-dependent change in Al concentration on a corroding surface we developed an electrochemical assay involving Li underpotential deposition (UPD) that measures the electrochemically active surface area (ECSA) of Al. We show results comparing the new assay protocol yielding the ECSA of Al to that obtained from EDS. Anodic dissolution behaviors of the alloys and constituent phases have been measured in an ionic liquid electrolyte (neat1:2 molar ratio of choline chloride:urea) which allows for accurate determination of the evolving surface composition as a function of well-defined anodic dealloying rates. We discuss these results together with some preliminary Kinetic Monte Carlo modeling of corrosion processes of the constituent a-phase.
Influence of Proteins and Cells on Corrosion of Mg
Authors: Virtanen Sannakaisa 
Published: February 2020

Mg based materials have been in the focus of increasing interest for temporary biomedical implants, where the device is only required for a certain time of healing. In spite of the large amount of work carried out in the field, many critical issues still remain, such as limited understanding of the interactions between the corroding Mg (alloy) surface and the biological environment. Results concerning the effects of biomolecules, proteins (and/or) cells on Mg corrosion are scarce and somewhat controversial. For instance, both acceleration or inhibition of Mg corrosion has been reported by proteins in the electrolyte. As the different observations are related to different experimental approaches, it is not straightforward to elucidate the reasons for the seeming discrepancies or the underlying mechanisms.
The presentation will discuss some recent findings on interactions between Mg, proteins (mainly bovine serum albumin), and cells. Protein effects on corrosion were studied by electrochemical techniques on commercially-pure Mg and the Mg alloy AZ91. Surface analysis by XPS and ToF-SIMS indicate that proteins indeed adsorb on Mg surfaces and can inhibit corrosion but the effects are time- and material-dependent. In addition, the presence of proteins in solution change the composition of corrosion layers on the surface. Impedance spectroscopy investigations combined with in vitro cell culturing on Mg demonstrate a significant decrease of dissolution rate after certain time of cell growth.
Study of Single Al Corrosion Pit Growth By Electrochemical Techniques
Authors: Zhang Weilong , Kryzman Mike A , Jaworowski Mark R , Zafiris George S 
Published: February 2020

Electrochemical techniques are commonly used for the study of localized corrosion growth [1]. However, pit growth at open circuit is hard to study by electrochemical techniques because of its difficulty of measuring current at open circuit while pit growth under potentiostatic or galvanostatic condition may be totally different from the open circuit.
For stable Al pit growth, it is widely accepted that local pit chemistry and environment are critical; or a critical value of the stability product (x.i), where x the pit depth, and i the current density, must be maintained for pit survival [2-6].
Several techniques have been proposed for studying pit growth rates, including (1) Use of artificial pit (“lead-in-pencil”) electrode[7]; (2) Single pit formed by implantation[8]; laser irradiation[9]; (3) Think film electrode [10] ; (4) The foil penetration technique [11].
In this work, we propose to employ a single Al wire (~100um dia.) mounted in epoxy with different initial pit depth d, which is produced by anodic dissolution, for singe Al corrosion pit growth by coupling with a large Al foil ring as its remote cathode through a zero resistance ammeter (ZRA), as schematically shown in Fig.1. The purpose of this study is, in combined with in-situ scanning vibrating electrode technique (SVET, Fig. 2), to determine quantitatively whether the single Al corrosion pit growth follows a depth-dependent growth model as often predicted.

Acknowledgements

This work was performed under United Technologies Corporate R&D funding.
Fig. 1 Schematic geometry of single al corrosion pit formed by an Al wire mounted in epoxy, by coupling with a large Al foil ring as its remote cathode through a zero resistance ammeter (ZRA).
Fig. 2 In-situ SVE images of single Al corrosion pit growth, showing transition from (a) open circuit condition (before coupled) to (b) galvanically coupled condition.

References

G. S. Frankel, Corros. Sci., 30, 1203 (1990).

J. R. Galvele, J. Electrochem. Soc., 123,464 (1976).

J. R. Galvele, Corros. Set, 21, 551 (1981).

Streblow H.H., Ives M.B., Corr.Sci. 16, 317 (1976).

T.R. Beck, Electrochimica Acta, 29, 485 (1984).

S.T. Pride, J.R. Scully J.R., Hudson J.L., J. Electrochem. Soc. 141, 3028(1994).

H. S. Isaacs and R. C. Newman, Corrosion Chemistry within Pits, Crevices and Cracks, A. Turnbull, Editor, HMSO Books, London (1987).

K. P. Wong and R. C. Alkire, J. Electrochem. Soc., 137, 3010 (1990).

D. W. Buzza and R. C. Alkire, J. Electrochem. Soc., 142, 1104 (1995).

G. S. Frankel, Mat. Sci. For., 247, 1 (1997).

F. Hunkeler and H. Bohni, Corrosion (Houston),
37, 645 (1981).

Figure 1
Modeling Aircraft Galvanic Stress Controlled By Kinetic Limitations
Authors: Lee Jason S 
Published: February 2020

Repair and replacement of structural components due to galvanic corrosion degradation are high cost drivers in aircraft maintenance. Sea-based aviation platforms experience one of the most corrosive operational environments in the Navy. Platform designs are not typically optimized for corrosion performance due to poor materials selection, lack of isolation of dissimilar materials, and geometric features which enhance susceptibility to corrosion. A technological gap exists in the capability of lifetime predictions for galvanically coupled airframe components. While traditional galvanic corrosion models evaluate galvanic stress based on the thermodynamic differences in potential, environmentally-dependent kinetic surface reactions are often not taken into account. The models that do consider kinetic influences use theoretical estimates with little relevance to the exposure environment. A computational model has been designed to develop a basic understanding of the kinetic mechanisms controlling galvanic stress for different aerospace alloy combinations exposed in marine environments. The novelty of the model is that electrochemical boundary conditions are a function of electrolyte chemistry. Regression analysis of the critical boundary condition factors will be used to examine the effects of kinetic limitation on galvanic stress damage.
(Invited) Silicon Electrochemical Micromachining Technology: The Good, the Bad and the Future
Authors: Barillaro Giuseppe 
Published: February 2020

Silicon electrochemical micromachining technology (ECM) has come a long way since the pioneering paper of Lehmann and Foll, dated 1990, which firstly reported about the possibility of controlling the electrochemical dissolution of silicon in HF-aqueous electrolytes by back-side illumination etching for the formation of nicely ordered array of macropores. Currently, ECM is routinely used in different laboratories around the world to fabricate silicon microstructures (e.g. microtips, spirals) and microsystems (e.g. microgrippers, microneedles) of much higher complexity than macropores, with application ranging from (bio)sensing to nanomedicine, from photonics to microelectronics.
ECM technology capitalizes on the experimental and theoretical results reported in the literature over the last two decades on the electrochemical dissolution of silicon in HF-aqueous electrolytes. Among others (e.g. aspect-ratio>100, verticality≈90°, surface roughness<10 nm), it is worth mentioning the peculiarity of dynamically controlling the electrochemical etching anisotropy from 1 to 0 in real-time, which has greatly advanced such a technology with respect to state-of-the-art etching technology. Nonetheless, a number of important limitations either remain unsolved or need to be improved towards future industrial applications of ECM technology (e.g. minimum and maximum etching features, etching rate).
In this paper, basic and advanced features as well as main limitations of silicon microfabrication by ECM technology are thoroughly reviewed and discussed, both from theoretical and experimental points of view, also with reference to future industrial applications. As case studies, fabrication by ECM technology (and characterization) of all-silicon, integrated microstructures and microsystems for different (bio)-sensing/medical applications will be detailed and discussed, with particular emphasis on (though not limited to): i) photonic crystal optofluidic microsystems for (bio)sensing applications, ii) microneedle-based chips for transdermal glycemic control; iii) electrically-actuable silicon microgrippers for biology/medicine applications; iv) 3D microincubators for selection of cancer cells on the basis of their metastatic potential.
Low Doped n-type Localized Porous Silicon Made by Hole Injection from Back-side p+/n Junction for Power Switches Application
Authors: Fèvre Angélique , Menard Samuel , Defforge Thomas , Gautier Gael 
Published: February 2020

Power switches are often present in electrical domestic environment directly connected to the mains supply. This kind of component operates in two principal modes, i.e. ON-mode and OFF-mode. The OFF-mode depends on the device periphery insulation capacity. Glass passivated grooves in the silicon are currently used giving good performances for reasonable cost. Changing this technology would permit higher wafer diameter and packaging simplification. Porous silicon (PS) is a potential candidate thanks to its electrical insulating behavior [1]. However, the usual substrate type and doping for such devices are n-type silicon and 1.1014 cm-3 respectively. At this doping level, porous silicon formation needs hole supply from an external source to avoid breakdown mechanism [1]. This can be achieved by either electron-hole pairs generation by illumination [2] or hole injection from a back-side p+/n junction [3][4]. This study focused on the second technique, which is easier to integrate in an industrial microelectronic process. Indeed, the presence in the active area (ON-mode) of a p+ region on the rear side could be used as a hole source. This junction is realized by boron implantation followed by an annealing. During the electrochemical etching, the p+/n junction needs to be forward biased to inject holes toward the anodic surface (Fig 1). Then, carrier lifetime must be sufficient to let holes cross n-type bulk silicon, featured by its thickness d (Fig 1).
First, a simplified case of non-localized p+/n junction is investigated (Fig 1). The influence of anodization parameters such as the current density and the electrolyte composition (additives) is presented for high HF concentration. A comparison with illumination technique is also discussed. Whatever the process case, the resulting PS morphology consists of a double layer (Fig 2): with a nucleation layer composed of mesopores and a macroporous layer filled with mesopores. To the best of our knowledge, this morphology has not been analyzed for low doped n-type silicon in the literature though it was mentioned in [5].
Electrical transverse characterization in DC (-10 to 10 V) of an Aluminum/PS/Si/Aluminum stack shows a gain in resistivity of 106Ω.cm compared to bulk silicon which is promising for the application.
As PS will be only present in the device periphery, a study of its localization is investigated. The resulting masking issues are analyzed.
1. M. Bouaïcha, M. Khardani and B. Bessaïs, Material Science and Engineering,
C26, 486 (2006).
2. V. Lehmann, J. Electrochem. Soc., 140, 2836 (1993).

3. X. Badel , J. Linnros and P. Kleimann,, Electrochem. and solid-state letters, 6, C79 (2003).
4. L. Coudron, G. Gautier, B. Morillon, S. Kouassi, T. Defforge and L. Ventura, Electrochem. and solid-state letters, 14, H24 (2011).
5. X.Q. Bao, D.H. Ge, S. Zhang, L. Zhao, J.W. Jiao and Y.L. Wang, Chinese Science Bulletin, 54 (7), 1143 (2009).

Figure 1
Morphological and Optical Properties of Stain Etched Silicon in Vanadium Oxide (V2O5) / Hydrofluoric Acid (HF) Solution
Authors: Ayat Maha , Gabouze Noureddine , Sam Sabrina , Boarino Luca , Boukherroub Rabah 
Published: February 2020

In the current semiconductor industry, silicon (Si) nanostructures represent the basic material for the conception of several devices in the field of nanoelectronics, optoelectronics, energy conversion, energy storage, and also (bio) chemical sensors.Various methods have been developed to fabricate Si nanostructures such as reactive ion etching (RIE), electrochemical etching, metal-assisted etching or stain etching. This last one is an electroless method to form porous silicon (PSi) in a mixture based on hydrofluoric acid (HF) and an oxidant.
In this work we report the fabrication of ordered macroporous silicion structures by chemical etching of silicon in vanadium oxide (V2O5) and hydrofluoric acid (HF) solution. The effects of the different etching parameters, including the etching time and the presence of metal catalyst film deposition (Pd, Ag), on the morphologies and the optical properties of the etched Si surfaces were studied. Scanning Electron Microscopy (SEM) was carried out to explore the morphologies of the as etched surfaces with and without the presence of catalyst. The obtained structures were characterized by Fourier Transform Infrared Spectroscopy (FTIR). A spectrophotometer UV-Vis-NIR was used to study the reflectance of the obtained structures.
It has been found that the morphology depends on the etching time and on the presence and the type of the catalyst. The results show that the attack of the silicon surface coated with Palladium or Silver deposit begins by creating circular pores. Moreover the pore diameter can be easily varied by changing the etching parameters such as the concentration and the etching time. In addition, long etching time leads to the formation of porous pyramidal structures at the bottom of the pore silicon. Finally,the presence of metal catalyst (Pd or Ag) does not only accelerate the etch rate but also creates pyramidal structures within the macropores.
A reflectance around 1,78% for the Ag/Si structures and about 4% for Pd/Si structures was obtained after 60 min etching. The surface hydrophobicity was also studied for the obtained structures and we observe a contact angle of 145°.

Figure 1
(Invited) Ultrafine Porous Polyimide Membrane for Rechargeable Lithium Batteries
Authors: Kanamura Kiyoshi , Miyahara Kazuhei , Aoyama Yohei , Ouchi Kenya , Haibara Masaki , Munakata Hirokazu 
Published: February 2020

Porous membranes have been used in various fields as key materials for separation. Their functionalities strongly depend on their structures such as pore size, pore distribution and porosity. Thus, the structure design of porous membranes has been focused over the years. Particularly, the research and development of ultrafine porous membranes has been intensively engaged. In the research field of battery, porous membranes are used as separators, whose role is to prevent electrical short circuits between anode and cathode but easy permeation of ions. Thus, the safety and power of batteries is strongly dependent on the porous separator, and many advanced porous membranes have been developed for batteries. In this study, we have developed an ultrafine porous polyimide membrane illustrated in Fig. 1, and investigated its performance as a battery separator. This structure is so-called three-dimensionally ordered macroporous (3DOM) structure and has an ideal porosity of 74%. The pores are in a hexagonal close-packed arrangement, so that uniform current distribution is expected during battery charge and discharge.
3DOM polyimide membrane for a battery separator was prepared by using a colloidal crystal template composed of mono-disperse spherical particles [1]. Fig. 1 shows the characteristics of 3DOM polyimide separator with the pore size of ~300 nm. The uniformly ordered structure with a high porosity of ~ 70% resulted in a very low Gurley value (32 sec), which is about 1/20 of conventional polyolefin separators [2]. The smaller Gurley value leads to the smoother Li+-ion transport in the separator. Actually, the 3DOM polyimide separator provided uniform current distribution for rechargeable lithium batteries, and was particularly effective to lithium metal anode which has a serious problem to be used in rechargeable batteries due to dendrite-formed deposition during battery charge process (Fig. 3). This is very advantageous for realizing high capacity rechargeable batteries using lithium metal anode.
References
[1] H. Munakata, D. Yamamoto and K. Kanamura, J. Power Sources, 178(2008) 596-602.
[2] S. S. Zhang, J. Power Sources, 164 (2007) 351-364.

Figure 1