bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning Kelvin Probe Force Microscopy as Tool for the Investigation of Localized Corrosion
Authors: Rohwerder Michael
Published: February 2020

In this presentation it will be shown that the Scanning Kelvin Probe Force Microscopy (SKPFM) is a powerful tool for the characterization of corrosion processes at the microscopic level, especially underneath organic coatings, see e.g. [1-3], but also on the uncoated surface, see e.g. [4].

Recently it was developed also to detect hydrogen activity in metal alloys at high resolution and sensitivity and [5-7] and it will be shown that it thus can be applied for the investigation also of hydrogen induced corrosion phenomena.

[1] M. Rohwerder, E. Hornung, M. Stratmann, Electrochim. Acta 48 (2003) 1235

[2] C. Senöz, M. Rohwerder, Electrochim. Acta 56 (2011) 9588

[3] C. Senöz, S. Borodin, M. Stratmann, M. Rohwerder, Corros. Sci. 58 (2012) 307

[4] D.B. Blucher, J.E. Svensson, L.G. Johansson, M. Rohwerder, M. Stratmann, J. Electrochem. Soc. 151 (2004) B621

[5] C. Senöz, S. Evers, M. Stratmann and M. Rohwerder, Electrochem. Commun. 13 (2012)1542

[6] S. Evers, M. Rohwerder, Electrochem. Commun. 24 (2012) 85

[7] S. Evers, S. Ceylan, M. Rohwerder, Science and Technology of Advanced Materials 14 (2013) 014201
Volta Potential on Stainless Steel Under Mechanical Stress Conditions
Authors: Casals Nuria , Nazarov Andrej , Thierry Dominique
Published: February 2020

It is well documented fact that mechanical work or surface treatment creates stresses in the metal. In corrosive environment the stress can lead to stress corrosion cracking and failure of the metal construction. It is often supposed that stress influences the properties of the surface oxide film by creating defects like metal vacancies and thus activating the anodic dissolution. On the other hand, the kinetic of the partial corrosion reactions is determined by the local electrochemical potential. Thus it is important to know how the stress influences on the surface potential.

The aim of the present study was to measure the influence of stress on the electrochemical potential of stainless steel 301 grade in situ under loading using Scanning Kelvin Probe. The measurements were carried out in the laboratory air at 50%RH and the measured Volta potential was related to the potential of the steel in the passive state. Previously this kind of measurements was carried out elsewhere [A. Nazarov, D. Thierry "Application of Volta potential mapping to determine metal surface defects",Electrochimica Acta 52 (2007) 7689-7696.].

In this work a constant load cell was applied on the sample with notches that concentrates the stress in a particular location. The load was measured and it was in the elastic or plastic deformation range. It was found that elastic deformation resulted in rather low potential changes whereas plastic deformation decreased the surface potential.

Figure 1: A: Potential profile in the notched area, B: Impact of the compressive stress produced by indentation.

Figure 1A shows the potential profile for the steel surface in the notched area under tensile stress conditions. Figure B shows the impact of the compressive stress produced by indentation.

It is possible to conclude that stress decreased the surface potential of the steel by about 200-300 mV. Thus the stress decreased the level of metal passivity that can facilitate the local anodic dissolution. After unloading under residual stress conditions the surface very slowly shifted the potential to the initial level. The effect of the plastic deformation on the steel potential is explained on the basis of the formation of dislocations and defective oxide film. The surface analytical studies are in progress.
Influence of Altered Surface Layer on Corrosion Inhibition of AA5083
Authors: Seong Jinwook , Frankel Gerald , Sridhar Narasi
Published: February 2020

The 5XXX series aluminum alloys are well known lightweight materials that provide excellent properties for marine applications. However, alloys with Mg concentration greater than 3.5% can sensitize, even at elevated service temperatures, by precipitation of β phase (Mg2Al3) along grain boundaries. Preferential dissolution of β phase on sensitized AA5XXX makes the alloy susceptible to intergranular corrosion (IGC) and stress corrosion cracking. Recent studies of sensitized AA5083 found that sustained β phase dissolution and IGC are not observed even at potentials well above the Eb of bulk β phase. High resolution TEM characterization of polished surfaces on sensitized AA5083 indicated the presence of an altered surface layer (ASL) with smaller grains and no grain boundary β phase. The corrosion behavior in chloride solution was different for samples that were etched to remove the ASL and the behavior of solutionized and sensitized AA5083 were clearly different after etching. Furthermore, corrosion inhibition with K2CrO4 was significantly influenced by removal of the ASL. Chromate acted as strong cathodic inhibitor on solutionized AA5083 samples both before and after etching to remove the ASL. Chromate was also a cathodic inhibitor for sensitized AA5083 with the ASL. However, mixed inhibition was observed for the AA5083 after etching, as a strong anodic inhibition was also observed on this sample on which β phase was apparently exposed at the surface.
Investigating the Initial Stages of KCl-Induced Corrosion of a Chromia Stainless Steel Using ESEM in-Situ and Well-Controlled Ex-Situ Exposures at 450°c
Authors: Mortazavi Nooshin , Intiso Luciana , Halvarsson Mats , Johansson Lars-Gunnar
Published: February 2020

The oxidation behavior of stainless steels is principally affected by the early stages of the oxidation process. In this study, the initial corrosion behavior of a high-alloy stainless steel (Snicro25, 25Ni-22Cr) was investigated through Environmental Scanning Electron Microscopy (ESEM) exposure. The corrosion coupons were first contaminated by KCl(s) and then exposed in-situ for one hour at 450°C. The ESEM in-situ experiment provided continuous imaging during the early stages of the degradation process. Ex-situ exposures were also carried out using well-controlled reference exposures to substantiate the ESEM in-situ experiment and in order to evaluate the effect of the presence of electron beam and the lower pressure in the ESEM chamber. The post-exposure analyses were conducted on the surface and on the cross section of the exposed samples using high-resolution Transmission Electron Backscatter Diffraction (t-EBSD) technique, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Focused Ion Beam milling (FIB). TEM and SEM observations were coupled with the chemical concentration analysis using the energy dispersive X-ray spectroscopy (EDX) technique. Ultrafine grain sized oxide scale was formed with the thickness of around 50 to 100 nm further away from the salt particles. The t-EBSD analysis revealed the changes in the crystallographic orientation of the substrate and also the detection of high misorientation regions (HMRs) beneath the oxide layer and in the depletion zones.
Formation, Segregation, and Degradation of Nanostructured Catalysts for Electrochemical Conversion and Storage
Authors: Strasser Peter
Published: February 2020

We present recent progress in the development of nanostructured catalysts for electrochemical conversion and storage of electrical energy. We will address atomic scale insights in the synthesis, segregation, and degradation of shaped Pt bimetallic catalysts using ex-site and in-situ aberration-correction microscopy. We also highlight the use of CO as a size confining agent in the synthesis of bimetallic nanoparticles. Finally, we will discuss the structure, morphology and surface chemistry during the formation and catalysis of bimetallic Ir-Ni core shell particles for the electrolytic splitting of water in acidic media.
Template-Assisted Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Ge Nanowires
Authors: Ma Luyao , Gu Junsi , Fahrenkrug Eli , Maldonado Stephen
Published: February 2020

Electrodeposition of crystalline Ge nanowires from GeO2 aqueous solutions through an electrochemical liquid-liquid-solid (ec-LLS) process using Ga nano/microdroplets of various sizes has been demonstrated. A silica template featuring regularly spaced opening with defined sizes was prepared on Si substrates by a modified nanosphere lithography patterning process. These platforms were used to electrodeposit Ga droplet arrays with defined sizes and pitch. The Ga nano/microdroplets subsequently enabled growth of crystalline Ge nanowires through ec-LLS in aqueous electrolyte as a function of droplet size. Scanning electron micrographs of the as-produced Ge nanowires showed the base size of the Ge nanowires tracks the Ga droplet diameter. All nanowires featured a consistent taper, with a cone angle of approximately 10°. For the Ga droplets larger than 1 µm in diameter, no nanowires were observed under the employed ec-LLS conditions, but a large isotropic Ge deposit was formed. These cumulative results demonstrate effects that liquid metal size(volume) have on electrodeposition by ec-LLS.
Copper-Nanolaminate Composites – a New and Promising Material for Electrical Contacts in High Voltage and High Current Applications
Authors: Grieseler Rolf , Camargo Magali Karina , Hopfeld Marcus , Bund Andreas , Schaaf Peter
Published: February 2020

Nanolaminate Mn+1AXn phases [1], [2] are materials that show interesting properties. They exhibit high hardness as well as good thermal and chemical stability, which is commonly a ceramic like behavior. On the other hand, they are good conducting materials near the range of metals.

Electrical contacts used in high voltage and high current applications are commonly based on silver-tin dioxid (Ag-SnO) where the SnO is used to increase the durability of the silver contact [3]. Futhermore the silver might be doped or alloyed with other materials such as tungsten or cadmium. The contact material is produced by powder metallurgical approach.

Lately the prices of noble metals are increasing and therefore, the pursuit of finding alternative possibilities is leading to new approaches and materials.

A promising approach is the electrochemical deposition of copper – nanolaminate composites. Two different types of Mn+1AXn phase were chosen as hard particles. One was Ti2AlC from the 211 Mn+1AXn phase family and the second was Ti3SiC2 from the 312 Mn+1AXn phase group. Particles of these two materials (mean size: aprox. 2 µm) were co-deposited with copper to form an electrical conductive surface with higher hardness than common copper. The distribution of the particles was determined using Focused Ion Beam cross section. The behavior at high currents and high voltages as well as in electrical discharges was investigated.

References:

[1] M. W. Barsoum, “The MN+1AXN phases: A new class of solids,” Prog. Solid State Chem., vol. 28, no. 1–4, pp. 201–281, Jan. 2000.

[2] R. Grieseler, T. Kups, M. Wilke, M. Hopfeld, and P. Schaaf, “Formation of Ti2AlN nanolaminate films by multilayer-deposition and subsequent rapid thermal annealing,” Mater. Lett., vol. 82, pp. 74–77, Sep. 2012.

[3] N. Jeanvoine, C. Selzner, F. Soldera, and F. Muecklich, “In situ FIB-Surface Preparation of Ag/SnO Composites for EBSD Measurements,” Microsc. Microanal., vol. 13, no. S02, Aug. 2007.
Electrodeposition of Nanoscale Manganese Oxide for Electrochemical Energy Storage Devices
Authors: Clark Michael Patrick , Ivey Douglas G , Qu Wei
Published: February 2020

As society moves away from fossil fuels towards renewable energy sources, energy storage is becoming increasingly important. Manganese oxide is a good candidate material for multiple energy storage applications (e.g., rechargeable batteries and supercapacitors) because it is environmentally benign and has good catalytic and electrochemical properties. When used as a supercapacitor, manganese oxide stores charge through electric double layer and redox effects. To maximize these effects, the structure of manganese oxide deposits needs to be optimized; this means increasing the effective surface area of the deposit. In addition to the effective surface area, the crystal structure of the deposit also greatly affects both catalytic and electrochemical performance. Manganese oxide is polymorphic and it is important to understand the crystallography of the manganese oxide within a device, in order to optimize its properties.

In this work, nickel foam is coated with high surface area manganese oxide through a simple anodic electrodeposition procedure. Nickel foam is an excellent substrate for many energy storage devices because in addition to nickel’s good conductivity, the porosity of the foam increases surface area and also facilitates fluid flow through the substrate. The latter is important for applications where manganese oxide is being used as a catalyst.

The electrolyte used for deposition of manganese oxide contains manganese acetate, ammonium acetate and dimethyl sulfoxide. By varying deposition and post deposition annealing conditions, different microstructures are obtained. The microstructure, crystallography and chemical state of the manganese oxide deposits are characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS analysis has been used to determine that manganese oxide is in the form of MnO2. Preliminary XRD and TEM results indicate that the deposits obtained in this work are nanocrystalline with grains less than 20 nm in size.

Electrochemical tests such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are used to determine performance (e.g., capacitance and cyclability) and to optimize the morphology and structure of the manganese oxide deposits. Preliminary CV measurements suggest that the manganese oxide deposits on nickel foam exhibit good areal and specific capacitance.
LiCoO2 Thin Film Deposition Using a Low-Temperature Electrochemical-Hydrothermal Route
Authors: Azib Tahar , Lecras Frédérique , Porthault Hélène
Published: February 2020

The increasing miniaturization of electronic devices and the demand for stand-alone systems require adapted power sources in terms of dimensions and energy. All-solid-state microbatteries are an interesting solution for new applications (secured smart cards, medical implants, sensors, etc.). They are obtained by successive deposition of thin films of electrode active materials and solid electrolyte. However, these batteries have a rather low capacity (50-200 µAh/cm²) due to the difficulty to use electrodes thicker than 5µm (electronic conductivity, lithium diffusion and mechanical stress issues). Most of commercially available microbatteries use a LiCoO2 positive electrode due to its interesting properties: a 4V/Li+/Li nominal voltage, an excellent cycle life and a high electronic conductivity [1] . Thin films of LiCoO2 are mainly obtained by sputtering [2, 3] , followed by an annealing (500-700°C) necessary to obtain the electrochemically active phase of LiCoO2 (R-3m). This latter step then limits the possible substrates. Moreover the low deposition rate (10nm/mn) and the required equipments and facilities make this process quite costly.

To circumvent these drawbacks, thin films of LiCoO2 were synthesized by a novel single-step route: the electrochemical-hydrothermal deposition. This technique combines the effects of the hydrothermal conditions (temperature and pressure) with a galvanostatic electrodeposition. Using ethanol as co-solvent in the aqueous media, we succeded in obtaining a pure and highly-crystalline LiCoO2 films, without any Co3O4 impurity. Moreover, the surface roughness is greatly decreased (fig.1) compared with films obtained in pure aqueous media. The obtained thickness can be increased up to 30µm, equal to a deposition rate of 200nm/mn. Galvanostatic cycling and linear sweep voltammetry experiments were carried out on these electrodes using CR2032 coin cells. The electrochemical properties of these films are very promising and clearly evidence the influence of each deposition parameter (temperature, current density, water/ethanol ratio, etc.) (fig2).

[1] Reimers, J.N. and J.R. Dahn, Journal of the Electrochemical Society, 1992. 139(8): p. 2091-2097.

[2] Wei, G., T.E. Haas, and R.B. Goldner, Solid State Ionics, 1992. 58(1-2): p. 115-122.

[3] Wang, B., et al., Journal of the Electrochemical Society, 1996. 143(10): p. 3203-3213.
The 14 Year Path of Lithium-Ion Stacking Power Battery at Amita Technologies
Authors: Cherng Jing-Yih
Published: February 2020

Since the commercialization of lithium-ion batteries in 1990, the applications of lithium-ion batteries have spread in a speed faster than any other battery systems. Pouch lithium-ion cells are becoming popular since the year of 2000. In the beginning, the Bellcore type design and process were used and troubled by internal short circuit and other problems. Afterwards, regular winding designs were used for most of pouch cells for 3C applications. Latest, the stacking design and process were introduced to the pouch cells for the high power applications, especially, the EV applications.

Amita technologies is one of the companies, who introduced the stacking pouch lithium-ion cells into the power applications in the year of 2000. In order to make thinner and safer lithium-ion stacking power cells, quite a few processes are different from the winding processes. Since the new process manufacturing equipments were not available in the year of 2000, Amita not only need to verify the cell design and process also need to design her own manufacturing equipment. From electrode cutting machine, stacking machine, welding machine, electrolyte injection machine, to the conveyor formation system. The development of an automation manufacturing system was completed in 2010. In 2014, the 2nd generation automation system is being designed and will be set up with a higher efficiency and a better consistency in 2015.

Because of the development of EV and renewable energy, it is the interest of many countries to set up its own lithium-ion battery industry. Amita has developed an unique manufacturing model (PDCA, post dry-cell assembly) , by utilizing her own patented design and processes, through which dry cells can be easily made and stored and shipped. PDCA can greatly reduce the difficulties of setting up a lithium-ion battery factory. Since all the materials except the electrolyte have been included in the dry cells, not only the dry cells can be easily made into real cells in the customer side, also the dry cells are perfectly safe to ship and store. Plus, the investment of PDCA becomes less than one fifth of the total production line, and has many other advantages. Unique features of PDCA will be illustrated and explained in details during the presentation.
Electrolyte Circulation in Copper Refinery
Authors: Fukunaka Yasuhiro
Published: February 2020

The importance of natural convection accompanied with electrochemical reactions along vertical electrodes has been recognized in the field of industrial electrochemical engineering as well as electrodeposition. Brenner applied a freezing method to analyze the concentration distribution[1]. Wagner demonstrated that the limiting current density distribution along the vertical cathode was governed by natural convection, based on the boundary layer theory [2, 3]. Wilke, Eisenberg and Tobias described a similarity between the natural convection caused by electrodeposition and by heat transfer [4]. Ibl and Muller examined the ionic mass transfer rate by the interferometry technique [5]. Since then, numerous studies have been carried out on the ionic mass transfer rate associated with natural convection caused by the electrochemical deposition and dissolution of copper in unstirred CuSO4-H2SO4aqueous electrolyte solutions [6-15]. However, most studies have focused on the steady state phenomena along a relatively short electrode at most 15 cm high confined in semi-infinite electrolyte media and have neglected the effects caused by the existence of the counter electrode.

In industrial scale of copper refinery, vertical impure casted anode and starting sheet of electrolytic copper cathode are installed in the tank. Significant electrolyte stratification may frequently cause various troubles to induce poor cathode quality. Each refinery designs their own electrolyte circulation system with their confidence. Additive control technique is a key technology. Sometime a slightly different circulation system is introduced even in one refinery in the same company. It is simply because the principle of electrolyte circulation has been never discussed from the fundamental electrochemical engineering point. It may be a starting point for this problem in such a modernized computational technology.
Maintaining the Momentum in Electrochemical Energy and Power Conversion
Authors: Brodd Ralph
Published: February 2020

Battery technology has reached goals that were considered by many as impossible only 15 years ago. The pace of new developments has accelerated along with the entrance of people with exceptional skills who have been drawn into the technology. I would like to take you back in time to when I entered the arena and relate some of my observations as a means to encourage you to keep up the momentum and remarkable growth that has lead to the use of electrochemical energy and power conversion in our every day personal life. We’ve seen the promise of electric cars fulfilled, solar, and wind power to replace coal fired power plants in order to control global warming. In many respects electrochemical energy conversion (batteries, fuel cells, flow batteries, capacitors, etc.) has become the hope of the future in maintaining our world as we know it.

My journey started at the University of Texas with, Professor, Dr. Norman Hackerman, in 1950. While at the university, The Corrosion Division of the ECS sponsored an essay contest. I entered, and won first place and membership in the ECS in 1952. (the rest is history, so to speak)

My PhD thesis was on the relationship of capacitance and surface area of electrodes. This work continued at the National Bureau of Standards (now NIST) using impedance as a function of frequency to determine the characteristics (rate constants, exchange current, activation energy, etc.) of battery electrode reactions. Today, impedance is being used to sort cells in a production environment and to identify and remove individual problem cells in large array Li-Ion cell systems to prevent an “incident”. Lithium ion batteries are an essential part of our lives and also offer the promise of lowering greenhouse emissions in transportation and utility applications.

A word about lessons learned in my career during the development of the alkaline Zn-MnO2 cell and the birth of lithium technology. I pushed very hard to increase funding for lithium exploration over that for alkaline as a key for the future. We re-engineered the alkaline technology with new MnO2 materials, a new separator, a new anode current collector, and a new seal to prevent leakage. These were all ready for implementation. Finally, the company President said, “Ralph I understand your enthusiasm and outlook, but we need to have a viable and continuing income from alkaline cells to ensure our future.” The new current collector was adopted because it would instantly because it lowered cost and instantly saved over a million dollars annually. The MnO2 research work continued and eventually resulted in new cathode materials for Li-Ion cells.
Voltammetric and Electrochemical Impedance Study of Sm3+ Effect onto the Nickel Electrodeposition Process
Authors: Meas Y. , López J. R. , Méndez P. F. , Perez J. J. , Trejo G. , Ortega R. , Stremsdoerfer G.
Published: February 2020

In this work, cyclic voltammetry and electrochemical impedance techniques were used to study the effect of Sm+3 dissolved in the electrolytic bath, on nickel reduction process. The results obtained by cyclic voltammetry showed that, during nickel electroplating without Sm+3, three reduction processes were observed and they may be related to the adsorption and/or reduction of H2, H3BO3 and Ni+2. On the other hand in presence of samarium, the Ni electroplating process is clearly affected; an additional reduction process and overpotential for Ni reduction can be observed. With the purpose of elucidating the processes attributed to the electroactive species of Sm+3,cyclic voltammetry studies were carried out employing a solution of sulfamic acid + samarium. These results shows the presence of a reduction process in a potential window of -0.77 to -0.82 V vs. SCE and the corresponding oxidation process (-0.54 to -0.57 V vs. SCE), indicating the presence of the redox couple Sm+3/Sm+2. Finally, the results obtained by electrochemical impedance technique indicate that during the electrodeposition of Ni, in the presence of samarium, resistance to charge transfer increases considerably. This increase can be attributed to the formation of a film of oxide or hydroxide of samarium.
Influence of Temperature on Electroless Copper Deposition from Formaldehyde-Containing Solutions Using 2-Hydroxy-1,2,3-Propanetricarboxylic Acid As Cu(II) Ligand
Authors: Kepeniene Virginija , Stagniunaite Raminta , Stalnioniene Irena , Norkus Eugenijus
Published: February 2020

Electroless coating technique is one of the ways to obtain metallic coatings in which there is no usage of electric current. The industrial electroless copper plating solution containing formaldehyde as reducing agent are known from the middle of the last century and are widespread in the practice up to now. Electroless copper coatings are deposited on plastics, ceramics, polymers and other non-conductig materials. However many chemical compounds used in technological processes are hazardous for total environment, therefore the efforts are made to displace those substances with less hazardous or purely harmless compounds. Citric acid (2-hydroxy-1,2,3-propanetricarboxylic acid), forming sufficiently stable complexes with copper (II) ions in alkaline solutions, was found to be a suitable ligand for copper(II) chelating in alkaline (pH > 12) electroless copper deposition solutions.

The substrate was a smooth Pt sheet (1´1 cm) electroplated with Cu for 20 min from acid copper solution (1.0 mol l-1 CuSO4 + 0.5 mol l-1 H2SO4) at 1.5 A dm-2. Before the electroless plating the electroplated substrate was activated for 30 s in acid PdCl2 solution (1 g l-1). The main electroless copper plating experiments were carried out for 30 or 60 min. in 50 ml of the solution containing (mol l-1): CuSO4×5H2O – 0.05; citrate – 0.3; formaldehyde – 0.15.

Our studies were carried out in electroless plating solutions at pH 12.0 – 13.0 and 10 – 30 °C temperature. It was found that the autocatalytic reduction of Cu(II) by formaldehyde from Cu(II)-citrate solutions containing begins at pH above 12 and accelerates with a further increase in pH and temperature. The thickness of the compact copper coatings obtained under optimal operating conditions in 1 h can reach ca. 3 μm. From Cu(II)-citrate solutions deposited copper coatings real surface areas (R
f) vary widely, i. e. from ca. 2.5 up to 15.0. The maximum R
f values were obtained at pH 12.5 solution at 20 °C temperature. Results were compared with those for systems operating with other copper (II) ligands.
Fabrication of FePt and CoPt Magnetic Nanodot Arrays by Electrodeposition Process
Authors: Homma Takayuki , Wodarz Siggi , Nishiie Daiki , Otani Tomohiro , Ge Siyuan , Zangari Giovanni
Published: February 2020

Electrodeposition processes have been extensively used to fabricate various magnetic thin films and micro/nano structures. We have attempted to utilize these processes to form magnetic nanodot arrays for use in bit patterned media (BPM) applications [1,2] for ultra-high density magnetic recording. In this paper, we will discuss our recent results on the synthesis of magnetic nanodot arrays using electrochemical deposition, focusing on FePt and CoPt.

Patterned substrates with nanopore arrays were prepared by electron beam lithography (EBL), which has the capability to form smaller-scale patterns, as well as by UV-nanoimprint lithography (UV-NIL), with larger size but high throughput. N-Si(100) wafer covered with sputter deposited Cu or Ru was used as a substrate. Electrodeposition of CoPt [3] was successfully carried out into the patterned nanopores to form arrays with 20 nm diameter dots, and fabrication of even smaller dots with <10 nm diameter has been performed. In order to achieve precise control of growth, the initial stage of the deposition process was investigated in detail, and correlation between deposition conditions such as applied potential and microstructure of the deposited dots were studied. Based upon these results, we attempted to fabricate nanodot arrays using electrodeposition of FePt, which is expected to exhibit higher perpendicular coercivity, Hc, due to the formation of the fct L10 structure. Application of FePt to BPM has been widely studied, mainly using arrays of discrete nanoparticles [2]. Based upon the bath described in previous studies [4,5], deposition conditions were optimized. It was found that layered deposition of Fe-rich and Pt-rich regions, followed by RTA (rapid thermal annealing) process was most effective in forming the L10 structure, resulting in higher Hc at thinner thickness region; in particular, a Hc of 12 kOe was obtained at < 20 nm thick films. By using this method, the patterned deposition of FePt was attempted and the array with 15 nm diameter dots was formed, the structure of which has been maintained after the annealing process.

This work was financially supported in part by Grant-in-Aid for Scientific Research, MEXT, Japan and by The Storage Research Consortium.

[1] D. Weller et. al, Appl. Phys. Lett. 88, 222512 (2006).

[2] B. D. Terris, T. Thomson, J. Phys. D: Appl. Phys., 38, R199 (2005).

[3] T. Ouchi, Y. Arikawa, Y. Konishi, T. Homma, Electrochim. Acta, 55, 8081 (2010).

[4] D. Liang, J. J. Mallett, G. Zangari, J. Electrochem. Soc., 158,149 (2011).

[5] S. Wodarz, Y. Maniwa, H. Hagiwara, T. Otani, D. Nishiie, G. Zangari, T. Homma, IEICE Tech. Rep., MR2013-20, 7 (2013).
Advancements in Electroplated Co-Pt Thick Film Micromagnets
Authors: Oniku Ololade D. , Garraud Alexandra , Arnold David P
Published: February 2020

There are enormous opportunities to employ permanent magnets to establish strong magnetic fields or field gradients in microsystem applications such as microactuators, microsensors, biological cell manipulation, micro power generators, etc. [1]. These applications motivate the development of microfabrication methods to realize high-remanence, high-coercivity magnetic structures in a dimensional “gap” between traditional bulk materials (usually >1 mm) and thin films (usually <1 mm).

In this work, we summarize advancements in electroplated Co-Pt alloys as candidate materials for wafer-level integration into magnetic microsystems. As a fabrication technology, electrodeposition offers advantages of speed, cost, and process integrability. Compared to other magnetic materials, Co-Pt alloys offer good energy density, high Curie temperature, and high corrosion-resistance. Specific attention is focused on the Co-rich composition (Co80Pt20) as well as the equiatomic composition (Co50Pt50) in the ordered L10phase, as shown in Figure 1.

Electroplated Co80Pt20 affords hard magnetic properties in the as-deposited magnetic state, without the need for any high-temperature processing steps. The material exhibits an hcp structure with large magnetocrystalline anisotropy, and by careful selection of the seed layer, significant out-of-plane texture (perpendicular anisotropy) can be achieved. For example, we have shown films up to 18 mm thick with Hci = 330 kA/m (4 kOe), Br = 1.0 T, and BHmax = 130 kJ/m3(16 MGOe) [2]. One potential drawback of this material is high sensitivity to temperature [3].

In contrast, L10 CoPt requires a high-temperature annealing step (~700°C) to induce a transformation from a disordered fcc atomic arrangement to an ordered L10 structure. This transformation results in strong magnetocrystalline anisotropy, but the material exhibits an overall isotropic behavior due to the random arrangement of the polycrystalline grains. For example, we have demonstrated 15-mm-thick photolithographically patterned magnets with Hci = 800 kA/m (10 kOe), Br = 0.8 T, and BHmax = 150 kJ/m3(19 MGOe) [4].

This talk will expound on the electrodeposition of these two alloys and the resultant magnetic properties. The usage of these films in example microsystem applications will also be presented.

[1] O. Cugat, J. Delamare, and G. Reyne, “Magnetic micro-actuators and systems (MAGMAS),” IEEE Trans. Magn., 39, 3607-3612 (2003)

[2] O. D. Oniku and D. P. Arnold, “Microfabrication of high-performance thick Co80Pt20 permanent magnets for microsystems applications,” ECS Trans., 50(10), 167-174 (2012)

[3] A. Garraud, E. Shorman, O. D. Oniku, B. Qi, and D. P. Arnold, “Influence of temperature on the magnetic properties of electroplated Co-rich Co–Pt thick films,” J. Micromech. Microeng., 24(1), 017002 (2014)

[4] O. D. Oniku, B. Qi, and D. P. Arnold, “Electroplated L10 CoPt thick-film permanent magnets,” J. Appl. Phys., 115(17), 17E521 (2014)
Magnetic Properties of Cobalt Nanowires and Nanotubes
Authors: Lu Jia Grace , Bergmann Gerd , Thompson Richard
Published: February 2020

Development of novel magnetic materials has played an important role in modern day science and technology. Nanomagnetism research not only sparks interests in fundamental physics, but also renders promising technological applications. Ferromagnetic Co nanowires, synthesized via low voltage electrodeposition method. High resolution transmission electron microscopy and x-ray diffraction results show that the nanowires are uniform in size, and consist predominantly hcp structure with the magnetocrystalline easy axis (c-axis) perpendicular to the wire axis. SQUID measurement illustrates the dominance of shape anisotropy, manifested by the weak temperature dependence of the enhanced coercive field along the wire axis. Furthermore, the magnetic domain structures of individual, segmented or multiple nanowires are studied via magnetic force microscopy. It shows a strong dipole at the ends of the wire, together with a spatial magnetization modulation along the wire with a period around 700 nm. Based on theoretical modeling, such intrinsic modulation originates from the competition between the magnetocrystalline polarization along the easy axis and the shape anisotropy along the wire axis. Low temperature magnetoresistance measurement shows irreversible magnetization switching in addition to the anisotropic behavior due to magnetization orientation dependent electron scattering.

On the other hand, Cobalt nanotube arrays embedded in hexagonally ordered anodic aluminum oxide templates are fabricated by direct electrodeposition with low current density under several mA/cm2. The wall thickness is about 15 nm and outer diameters are in accordance with pore diameter around 80 nm. Nearly 100% filling rate is achieved which benefits from the through pores which enable the efficient penetration of electrolyte. Transmission electron microscopy and selected-area electron diffraction are performed to show that the nanotubes are predominantly hcp single crystals with c-axis (easy axis) perpendicular to the tube axis. SQUID and MFM results indicate that the magnetization follows a circumferential direction around the tube, which is manifested in the weak magnetic signal in the MFM imaging as well as a sheared hysteresis dependence for field applied along the tube axis. This phenomenon has been confirmed by theoretical modeling taking into account the magnetocrystalline, shape demagnetization and magnetic exchange energies.
Biocompatibility and Biofunctionality of Magnetic Nanoparticles
Authors: Takemura Yasushi
Published: February 2020

Superparamagnetic nanoparticles are used as an imaging agent. Magnetic particle imaging (MPI) is applicable to not only diagnostics but therapy such as hyperthermia and drug delivery. Integrative therapeutic and diagnostic application is called as theranostics. In particular, magnetic relaxation is one of the most important factors for both imaging and hyperthermia treatment. The evaluation of magnetic relaxation property is necessary to design the materials and instrument applying an external magnetic field. Magnetic relaxation is characterized by two distinct modes. Brownian relaxation is occurred by rotation of the particles. Néel relaxation is induced by rotation of the magnetic moment. The mechanism of magnetic relaxation is influenced by the primary and secondary size of magnetic nanoparticles, surface coating agent, state of materials, viscosity of medium. In this study, the magnetic relaxation properties of Resovist and other commercial magnetic nanoparticles were measured at frequency of several kiro heltz up to 500 kHz and high magnetic field up to 50 Oe. The commercial iron oxide nanoparticles of both of superparamagnetic and ferrimagnetic features were used for the measurements. The hysteresis loop under an applied alternating magnetic field was measured for estimating magnetic loss and effective magnetic relaxation time. The materials were prepared in powder form, dispersed state in medium, or fixed state by agarose / epoxy bond. Magnetic nanoparticles dispersed in medium were rotated by an alternating magnetic field, and both Brownian and Néel relaxation could occur. In contrast, fixation regulated rotation of the particles and only Néel relaxation could occur. Therefore, hysteresis loop of alternating magnetic field in dispersed and fixed samples directly indicated the magnetic relaxation mechanisms of measured materials. The dependency of area of the hysteresis loop on the frequency of magnetic field indicated the effective frequency of Brownian and Néel relaxation. Relaxation time was also calculated. Experimental estimation of effective relaxation time confirms the influence of size distribution, concentration, state, surface coating agent and medium. Thus, evaluation of magnetic loss and magnetic relaxation time measured under the alternating field condition which is used for MPI is the effective method to evaluate the mechanisms of magnetic relaxation and optimum material property.
Studies on Magnetic, Transport and Dielectric Properties of Ni0.65Zn0.35Fe2O4 Thin Films Grown by Pulsed Laser Deposition
Authors: Pradhan Dhiren Kumar , Misra Pankaj , Puli Venkata S , Katiyar Ram S.
Published: February 2020

The ferrimagnetic material Ni1-xZnxFe2O4 (NZFO) has drawn tremendous attention in recent years due to its potential applications in radio frequency coils, transformer cores, rod antennas, magnetic cores of read write heads for high-speed digital tape or disk recording and microwave devices owing to its remarkable magnetic properties, high resistivity and low eddy current. Other than these the NZFO is also considered as potential candidate for multiferroic composite structures. We have chosen Ni0.65Zn0.35Fe2O4 for the present investigation as this composition exhibits the highest saturation magnetization in the entire Ni–Zn family along with high magnetic curie temperature which is ~ 575 K. NZFO thin films were grown by pulsed laser deposition (PLD) at different substrate temperatures in the range of 500-800oC using a KrF excimer laser (λ=248 nm) on LaNiO3 buffered (001) oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates under oxygen pressure of 150 mTorr. These films were subsequently annealed at their respective growth temperature for 30 min in oxygen ambient at a partial pressure of ~ 300 Torr. The highly c-axis oriented growth containing only (004) diffraction peak of NZFO films along with in-plane epitaxial relationship was confirmed by high resolution X-ray diffraction measurements.From the atomic force micrographs it was observed that all the films were densely packed, smooth, free from microcrack and particulates with uniform grain-size distributions. X-ray Photoelectron Spectroscopy measurements confirmed that in all films the Ni, Zn and Fe elements retain their same oxidation states as in bulk target irrespective of growth temperature. The saturation magnetization (Ms
) of NZFO film was found to enhance systematically with increasing growth temperature. The resistance of NZFO films was found to decrease with increasing temperature indicating insulating behaviour. These films showed positive magneto resistance at low magnetic fields. Detailed dielectric, magnetic, magneto resistance and transport characterizations are currently underway and results will be discussed at the meeting.
X-Ray, Dielectric, and Ferroelectric Properties of La0.67Sr0.33MnO3/ Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 Artificial Multilayers and Superlattices structures
Authors: Kumari Shalini , Ortega Nora Patricia , Kumar Ashok , Katiyar Ram S.
Published: February 2020

Superlattice (SLs) is an artificial periodic structure consisting of alternate layers of two different material. Multiferroic SLs exhibit superior properties like low loss, high dielectric constant, very good ferroelectric and magnetic properties which make them attractive candidates for thin film devices applications. Multilayers (MLs) and SLs of the colossal magnetoresistive La0.67Sr0.33MnO3 (LSMO) and low loss multiferroic Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 (PZTFT) materials have been grown by pulsed laser deposition on (100) (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrate with LSMO or LaNiO3 as bottom electrode. Depositions were performed at 600 oC in 150 mTorr oxygen pressure with an energy density of ~3 J/cm2, and a laser repetition rate of 5 Hz. X-ray diffraction revealed well oriented (00l) perovskite structure in all structures, in case of MLs two peaks correspond for LSMO and PZTFT were observed, while in SLs the so-called satellite peaks typical of modulated structures were present. The computed modulation period (Λ) by Bragg’s condition revealed that the SLs structure was observed below of Λ ~ 20 nm. The atomic Force Microscopy studies showed a systematic decrease in grain size with increase in number of layers in PZTFT/LSMO structures. All thin film structures were found to be densely packed, smooth and free of cracks. Piezo force microscopy showed that most of the ferroelectric domains are switching under ± 9 V external bias field in both MLs and SLs films. PZTFT/LSMO bilayer strcuture showed a dielectric constant of ~835 at 1kHz, while the ferroelectric loop showed saturation and remanent polarization of ~ 34 μC/cm2 and 6 μC/cm2 respectively, with a coercive field of 60 kV/cm. The saturation magnetization of LSMO/PZTFT structure grown on LSMO/LSAT was found to be ~45 emu/cm3. A systematic study of the effect of modulation period on dielectric, ferroelectric and magetic properties of the MLs and SLs structures will be discussed.
Polymeric Gel Electrolyte Based on a Rotaxane-Networked Polymer with Alkyl Magnesium Bromide and Ionic Liquid for Rechargeable Mg Batteries
Authors: Yoshimoto Nobuko , Yamabuki Kazuhiro , Kim Intae , Shigematsu Ryou , Tsutsumi Hiromori
Published: February 2020

Rechargeable magnesium (Mg) battery that uses metal Mg as the negative electrode is a potential candidate of the next-generation power sources for electric vehicles (EV) and other large scale applications. We previously reported that Mg is reversibly deposited and dissolved on a metal substrate in mixed solutions containing ionic liquid and alkyl magnesium bromide [1]. However, as the electrolyte system contains high vapor pressure THF, the resulting battery will have still practical problems in safety and reliability. Recently, we have synthesized a novel network polymer with a rotaxane structure, a complex consisting of secondary ammonium salt and 24-membered crown ether component [2]. In this study, a novel gel electrolyte based on a rotaxane-networked polymer has been prepared, in which ethyl magnesium bromide dissolved in triethylene glycol dimethyl ether (C2H5MgBr/Triglyme) and N,N-diethyl-N-methyl- N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl) imide (DEMETFSI) were included. The ionic conductance behavior and electrochemical behavior of the resulting gel electrolytes were investigated.

A “rotaxane network” was synthesized in the same manner as our previous report [2] (Fig.1). The gel electrolytes were prepared by an impregnation method: the polymer film was immersed in the mixed solution of C2H5MgBr/Triglyme and DEMETFSI for 24 h. The resulting network polymer maintained the stable shape without decomposing after a month’s impregnation in 1M C2H5MgBr/Triglyme.

The “rotaxane network” polymeric gel electrolyte impregnated in C2H5MgBr/ Triglyme + DEMETFSI exhibited an ionic conductivity of 2.8×10-4 S cm-1 at 20°C (swelling degree = ca. 60%). Highly reversible behavior was observed for cathodic deposition and anodic dissolution of Mg in this polymeric gel electrolyte system.

Acknowledgment

This research was financially supported by the Japan Science and Technology Agency (JST), Advanced Low Carbon Technology Research and Development Program (ALCA).

References

[1] N. Yoshimoto, M. Matsumoto, M. Egashira, and M. Morita, J. Power Sources, 195, 2096(2010).

[2] K. Yamabuki, K. Onimura, and T. Oishi, Polymer Journal, 40, 205(2008).
Application of Al-Doped LLTO Solid Electrolyte Prepared By Sol-Gel Method in Lithium-Oxygen Batteries
Authors: Le Hang T.T. , Jadhav Harsharaj S. , Kalubarme Ramchandra S. , Jang Seong-Yong , Park Chan-Jin
Published: February 2020

To date, lithium lanthanum titanate (LLTO) of the nominal formula Li3xLa2/3-x
1/3-2xTiO3 with perovskite structure have been considered to be promising solid electrolyte materials for lithium-oxygen battery due to a numerous outstanding advantages such as: (i) a high lithium conductivity at room temperature, (ii) a high lithium diffusion coefficient, (iii) a low electronic conductivity, and (iv) an electrochemical window larger than 4 V. However, the LLTO materials have also suffered from a few disadvantages such as insufficient total conductivity due to the large grain boundary resistance and difficulty in controlling Li+ content and Li+ conductivity of the materials especially after exposure to high annealing temperature. In addition, when the LLTO contacts directly with Li metal, Ti4+ in LLTO can be reduced into Ti3+ by metallic Li leading to increase in the electron conductivity of LLTO.

In this study, we investigated the feasibility of application of Al-doped LLTO ceramics with nominal formula of (Li1/3La5/9)1.005Ti0.99Al0.01O3 (denoted as A-LLTO) in Li–O2 batteries. A-LLTO was synthesized using sol-gel modified Pechini method in the aim of (i) reducing the synthesis temperature (up to 300-400 oC compared to the conventional solid state reaction method); (ii) lessening loss of lithium and gaining homogeneous mixture easily. As referred above, since LLTO cannot contacts directly with Li metal, prior to being assembled in organic- type Li-O2 battery as an electrolyte separator On the A-LLTO ceramics with 16 mm diameter and 200 m thickness, a thin protective layer of LiPON of 200 nm in thickness was sputtered for separation of A-LLTO from the Li metal anode. The perovskite material was used as catalyst for cathode material of the batteries.

The XRD patterns of A-LLTO ceramics obtained after annealing were compared and matched with Li0.33La0.56TiO3 (Code: 01-087-0935; Tetragonal) confirming purely the tetragonal crystalline structure P4/mmm space group of perovskite phase without secondary phases. After polished and heat etched at, the surface of the ceramics was observed using SEM. T ceramics was composed of grains of typical rectangle shape connected together closely. The largest grain size reached 100 m.

Ionic conductivity of A-LLTO measured using electrochemical impedance spectroscopy (EIS) exhibited the relatively high conductivity of 3.17 10-4 S/cm. This is attributed to the low total activation energy of 0.358 eV and the somewhat large crystal grain size compared with ceramics prepared at the same temperature.

The Li-O2 cells employing the A-LLTO ceramic electrolytes were tested in galvanostatic and constant capacity mode. Effect of current density and operating temperature on the charge-discharge behavior of Li-O2 cell was investigated. The Li-O2 cell employing A-LLTO electrolyte layer exhibited the satisfactory performance.