bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anodizing of Aluminum in Etidronic Acid Solution
Authors: Kikuchi Tatsuya , Takenaga Akimasa , Nishinaga Osamu , Natsui Shungo , Suzuki Ryosuke O. 
Published: February 2020

Introduction

Anodizing of aluminum under appropriate conditions allows the formation of self-ordered porous alumina (porous type oxide film). Ordered porous alumina with large-scale cell sizes and pores is required for expanding the application field in nanotechnology. In the present investigation, we demonstrated anodizing at various conditions in a new electrolyte, etidronic acid, for large-scale ordered porous alumina.

Experimental

High-purity aluminum plates (99.999 wt%) were ultrasonically degreased and electropolished. The electropolished specimens were immersed in 0.2-4.2 M etidronic acid solutions at 288-323 K and then anodized at a constant cell voltage of 145-310 V for up to 24 h. After anodizing, the anodic oxide was selectively dissolved in a 0.2 M CrO3/0.51 M H3PO4 solution at 353 K to expose the aluminum substrate, and then two-step anodizing was carried out for the formation of highly ordered porous alumina. The specimens were examined by field emission scanning electron microscopy (FE-SEM) and image-aberration-corrected scanning transmission electron microscopy (STEM).

Results

Etidronic acid anodizing at 165-270 V and the appropriate temperature caused the self-ordering of porous alumina measuring 400-670 nm in cell diameter. Figure 1 shows an ordered aluminum dimple array fabricated in a 0.2 M etidronic acid solution at 298 K and 260 V for 24 h, and an ideal dimple array was successfully fabricated via etidronic acid anodizing. Ordered porous alumina through the vertical cross-section could be fabricated via two-step etidronic acid anodizing. Phosphorus-free oxide cell boundaries with a honeycomb configuration were measured by STEM-energy dispersive X-ray spectrometry (EDS).

Figure 1. An SEM image of the aluminum dimple array fabricated via 0.2 M etidronic acid anodizing at 260 V for 24 h.

Figure 1
Quantifying the Role of Transition Metal (Re)Plating in the Cathodic Activation of Corroding Magnesium
Authors: Michailidou Emmanouela , McMurray Hamilton Neil , Williams Geraint 
Published: February 2020

Magnesium (Mg) and magnesium-based alloys as biodegradable implants form a distinct pole of attraction for the scientific world due to their advantages over conventional biodegradable metallic materials. Regardless, though, of the promising properties that magnesium offers, its extensive use in vivo is restricted with the main limiting factor to be its high rate of degradation. This paper examines the effect that the transition metals, which have been intentionally or unintentionally added as traces within the metal bulk composition, have on the corrosion properties of commercially high purity magnesium. Furthermore, a series of experiments provide an indication regarding the ability of the selected transition metals to accelerate corrosion through the process of (re)plating aiming to gain an insight on the Mg corrosion activation described in recent publications. Consequently, the current research presents the kinetics involved behind the role of the transition metals in the cathodic activation of corroding magnesium.
During the experimental procedure, high purity magnesium samples containing <80ppm Fe were used, while the kinetics of the effect of Fe2+, Cu2+, Zn2+ and Mn2+ transition metal ions were studied as these are the most common traces of addition alloying or impurities found within the bulk composition of magnesium and magnesium alloys. The transition metals were either added into a corrosive electrolyte of 5% aqueous NaCl at near neutral pH at concentrations ranging from 10-6M to 8·10-3M or they were injected in solid form directly on the immediate vicinity of the corroding surface at a weight range of 5mg to 50mg. Following this step was the volumetrically recording of the evolution of hydrogen gas over a constant period of time in order to follow the kinetics of magnesium corrosion.
The results indicate that the presence of transition metal ions within the solution leads to transition metal (re)plating and to an increase of the magnesium corrosion rate. Furthermore, by systematically varying the transition metal ion concentration it was possible to determine the relative efficiencies of the selected metal cations. During the experiment, it was also observed that the metal (re)plating process and the efficiency of the cathodic activation were limited by the formation of insoluble transition metal (hydr)oxide precipitates and the time-dependent hydrolysis. It was possible, though, to minimize the negative effect of hydrolysis by introducing the metal cations directly on the magnesium surface as it may be assumed then that both the diffusion path length and the time period during which hydrolysis can initiate are shorter.
Does Hydrogen Affect Oxygen Permeability in Alloys?
Authors: Shemet Vladimir 
Published: February 2020

Water vapour and/or steam are well known to accelerate breakaway oxidation of chromia-forming alloys. Some authors have proposed that hydrogen promotes internal oxidation of chromium, resulting in breakaway oxidation. We tested this hypothesis by directly measuring oxygen permeability after oxidation in high pO2
pO2 atmospheres containing water vapour. Palladium with 1 wt% chromium alloy was oxidized in dry and wet Ar-1%O2 at 850 °C. The internal oxidation in all cases obeyed parabolic kinetics. The oxygen permeability deduced from Wagner's diffusion model showed small differences in the internal oxidation of the Pd-1Cr alloy in these gases. We conclude that hydrogen has no influence on oxygen permeability in chromium-containing alloys.
High-Temperature Reactions of Cesium Molybdate on 304 Stainless Steel
Authors: Do Thi-Mai-Dung , Sujatanond Supamard , Ogawa Toru 
Published: February 2020

During a severe accident in a Boiling Water Reactor (BWR), cesium is one of fission products that could be released from nuclear fuel to the reactor vessel and to deposit on the reactor coolant system that is made of stainless steel (SUS). Recently, it has been informed that the released form of cesium is predominantly cesium molybdate. (Cs2MoO4). Under vapor pressure, at high temperature, the deposition of Cs2MoO4 on the surface of oxide SUS could cause some chemical reactions. However, the type of reactions as well as the thermodynamics have not been confimed yet. The aim of this work is to clarify the possible reactions of Cs2MoO4 on the SUS surface at high temperatures. Cs2MoO4 powder was placed in a platinum boat and heated at 1573 K. Either SUS304 or platinum plates were placed downstream at different distances corresponding to temperatures ranging from 1554 to 547 K. The carrier gas was pure argon or argon saturated with steam at 70°C. The flow rate is 100 ml/min. The deposits on SUS304 and platinum plates were examined by X-Ray diffraction equipment (XRD), the micro-Raman spectroscopy and the electron probe micro analyzer (EPMA). The exit gas was passed through the (1%wt HNO3 + H2O) solution. The solution was analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). In dry argon, the obtained deposits on Pt were Cs2MoO4. But on SUS304, the deposits were mainly Mo metal at ~1500 K, then Cs2MoO4 and Cs2Mo2O7 at ~1220K. At further downstream, the deposit were mainly Cs2MoO4. In Ar+steam, on Pt surface, at temperature higher than 1500 K, the deposit could not be obtained, this was probably due to the Cs2MoO4 prefered to stay in gas phase at this stage, but at the temperature below 1200 K, which is close to the melting point (1213 K) of Cs2MoO4, the deposits were predominantly Cs2MoO4. On the surface of SUS304 in Ar+steam, various reactions happened, depending on the temperature. The reaction became even complicated due to the vaporization of CrO2(OH)2. Molybdenum-containing species were found at higher temperatures. But there was no sign of cesium-containing species in SUS304, except for those found on the plates at the low temperatures below ~730 K, where Cs was found as Cs2MoO4.
"Drop-n-Catch" Approach to Calorimetry of Laser Heated Levitated Alumina and Yttria Above 2000 °C
Authors: Kapush Denys , Ushakov Sergey V. , Navrotsky Alexandra 
Published: February 2020

Design and processing of ultra-high-temperature materials (aerospace and nuclear applications) demand detailed understanding of thermodynamic properties of their constituents. Nevertheless there is a lack of experimental thermodynamic data above 2000 °C. Even for La2O3, Y2O3, HfO2, and ZrO2binary oxides, high temperature data are often missing and evaluated with a number of assumptions. Among the rare earth oxides, fusion enthalpy data are largely missing.
A recently modified commercial Setaram Setsys DTA instrument working up to 2500 °C allows observation of phase transitions but the lack of reliable enthalpy standards above the melting temperature of Al2O3 (2054 °C) has posed a major problem caused by the absence of reliable sensitivity calibration in the 2100–2500 oC range.
A newly designed "drop-n-catch" (DnC) calorimeter utilizing laser heated levitated samples significantly complement thermal analysis above 2000 °C and makes it possible to measure enthalpies of phase transitions and fusion in variable atmospheres at temperatures limited by the sample only.
Enthalpy increments measured on DnC experiments give the fusion enthalpy in Al2O3 as 117 ± 10 kJ/mol, compared to 120 kJ/mol from FactSage database. The sum of premelting phase transition (cubic-to-hexagonal) and fusion enthalpies in Y2O3 has been estimated as ~ 155 kJ/mol. These first results open the door to measurements previously inaccessible in terms of temperature range, controllable atmosphere, and lack of sample-container interactions. The instrument and future directions will be discussed.
Synthesis and Characterization of Fullerene Derivatives with Alkyl Spacers and Alkyl Chains in Organic Photovoltaic Devices
Authors: Moriyama Hiroshi , Igawa Mizuki , Kuda Yuki 
Published: February 2020

Bulk heterojunction-type organic photovoltaic (OPV) cells have attracted attention because of their light weight, flexibility and solution-process construction. In our ongoing work in preparing a series of the PCBM analogues, we prepared Methyl-C61-phenyl carboxylic acid methyl ester (MPCM) as well as its C70derivatives and fabricated OPV devices with poly(3-hexylthiophene) (P3HT) as the donor. The performance of devices with [60]MPCM and [70]MPCM was compared, [70]MPCM showing a higher PCE than [60]MPCM.
However, because of the high aggregated property of MPCM, the OPV device performance using MPCM and P3HT gave often morphology problem; thus we also prepared new fullerene derivatives with an alkyl spacer as the modification of MPCM and fabricated OPV devices with P3HT as the donor.
The performance of OPV devices of these fullerene derivatives with an alkyl spacer was investigated, some of them showing higher PCE than that of PCBM.
Furthermore, we synthesized novel fullerene derivatives with different carboxylic acid esters, e.g., hexyl ester; methyl-C61-phenyl carboxylic acid hexyl ester (MPCH). These derivatives have the merit of higher solubility because of the long alkyl chain. Organic photovoltaic devices were fabricated using these fullerene derivatives as an electron acceptor and P3HT as an electron donor. MPCH showed PCE that is higher than that of PCBM.

Figure 1
Arrays of Single-Domain Nanomagnets As Memory- Logic-Hybrid Device - a Nonvolatile Magnetic Memory That Can Perform Logical Operations
Authors: Wanzenboeck Heinz , Bertagnolli Emmerich 
Published: February 2020

With nonvolatile NAND flash memory becoming the dominant memory type the former champion for mass data storage – magnetic memory – has now become a niche player. This is – at least to some extent – unjustified, as magnetic data storage has still its advantages such as radiation-hardness, and long data storage time. In this work we celebrate a renaissance of magnetic data storage with a new concept that allows not only storing of information but also data processing with nanomagnets. We use focused electron beam induced deposition of single domain nanomagnets to fabricate arrays of magnetic nanowires and magnetic nanopillars. If the single nanomagnets are in close vicinity, then the stray fields allow to influence neighboring nanomagnets.
With a majority gate such a nanomagnet assembly can even perform logical calculations. In this work we will present the fabrication process for such nanomagnetic devices, characterize their magnetic properties by magnetic force microscop, and design and fabricate nanomagnet arrays.
With this dual functionality as memory and as logic unit these directly-written nanomagnet devices promise a promising future potential. Further applications of advanced device structures based on single domain nanomagnetswill be discussed.
We will report on the optimization of the device fabrication process and chemical and structural analysis of nanomagnets. The functional characteristics of these hybrid devices will be described and future system applications will be discussed.

Figure 1
Compliance-Free Picosecond Smart Pulse Programming for Rram
Authors: Nminibapiel David Malien , Shrestha Pragya , Kim J. H. , Campbell J P , Baumgart Helmut , Cheung K. P. 
Published: February 2020

RRAM is generally considered as the next generation of nonvolatile memory due to its simple structure, low power consumption, high-speed, high density and its compatibility with conventional CMOS processing. Another attractive feature of RRAM is its tunable resistance with applied voltage, making it a promising candidate for multi-level cell (MLC) storage and for neuromorphic computing. However, reliability and variability issues limit the potential of RRAM. Particular for MLC and neuromorphic application, poor uniformity poses as a severe hindrance. This variability is related to the stochastic nature of, filament formation, resistance switching and poor control of switching energies. While material engineering and structural optimization techniques are employed to reduce the intrinsic randomness in RRAM, these strategies are ineffective when programming energy is not under control. In this work, we propose a Compliance-free Ultra-Short Smart Pulse Programming (CUSPP) technique which offers improved control of FORMING/SET/RESET energies. This technique can potentially lead to tighter distribution of critical RRAM parameters, such as RON and ROFF, resulting in well-defined resistance window during extended cycling.
CUSPP is a custom-built fast pulse-train programming and measurement system with real-time resistance sensing and automatic cycling between SET and RESET when specific resistance is reached. An ultra-short (~100 ps) pulse generator with controllable repetition rate and pulse height (up to 6V) is our source. The custom-built circuit continuously monitors the device resistance using a low DC sensing voltage to determine if the SET/RESET resistance is achieved, and to automatically change the pulse train’s height and/or polarity to enable rapidly cycling up to 2.5 million cycles per second. Unique to CUSPP measurement setup is the absence of a current limiting element such as a series resistor or transistor. The ultra-short pulse width limits the duration of current flow through the device and provide a tight control of switching energies. In the current version of the CUSPP, resistance programming is solely achieved by repetitive pulsing the device with constant pulse amplitude and pulse width. This is in contrast to many reported programming protocols where pulse amplitude and/or width are incrementally increased to reach the target resistance state. In targeting RON/ROFF, higher precision can be achieved by lowering the pulse amplitude and a concomitant higher number of pulses. Thus, high precision comes at a cost of programming speed. With the pulse repetition rate up to a few MHz this cost is entirely acceptable for mechanism studies. CUSPP is a versatile tool that can perform all essential programming of the RRAM with precision and speed while allowing the experimenter to look at the filament kinetics in details.
Electrodeposition of Magnetic SmCo Films from Deep Eutectic Solvents
Authors: Panzeri Gabriele , Magagnin Luca 
Published: February 2020

SmCo alloys have attracted attention for their high Curie temperature, magnetic anisotropy and relatively high saturation magnetization[1]. Because of the very negative reduction potential of Sm (<-2.3V) in aqueous solution its electrodeposition is problematic due to strong hydrogen evolution at the cathode surface[2,3]. Ionic liquids represents a useful alternative to the aqueous solution because of limited quantity of water present and thus wider potential window[4]. Deep eutectic solvent solution of 1 choline chloride: 2 ethylene glycol at T=70°C is studied for the electrodeposition of SmCo deposit. The interest relies in the preparation of homogeneous film and nanowires having magnetic properties. Electrochemical characterization of the solution is performed for different bath composition. Deposits with variable Sm% content are obtained depending on the experimental conditions e.g. current density; both potentiostatic and galvanostatic deposition are performed. XRD analysis is carried out to evaluate the phase deposited. Magnetic properties of the film are analysed. SmCo nanowires are obtained using alumina template; magnetic performances are compared to the film deposit.
[1] YQ Guo, W Li, J Luo, WC Feng, JK Liang. Structure and magnetic characteristics of novel SmCo-based hard magnetic alloys, J Magn Magn Mater. 303 (2006) e367.
[2] J Zhang, P Evans, G Zangari. Electrodeposition of Sm–Co nanoparticles from aqueous solutions, J Magn Magn Mater. 283 (2004) 89-94.
[3] X Long, G Guo, X Li, Q Xia, J Zhang. Electrodeposition of Sm–Co film with high Sm content from aqueous solution, Thin Solid Films. 548 (2013) 259-262.
[4] AP Abbott, KJ McKenzie. Application of ionic liquids to the electrodeposition of metals, Physical Chemistry Chemical Physics. 8 (2006) 4265-4279.
Electrochemical Synthesis and Characterization of Fe-Ni-Pt Alloy Films
Authors: Ge Siyuan , Wodarz Siggi , Hashimoto Shougo , Saitou Manabu , Homma Takayuki , Zangari Giovanni 
Published: February 2020

Fe-Pt alloy films and nanopatterns have been intensively investigated for magnetic recording applications, but their practical use may be limited by the maximum magnetic field available from the write head. Heat Assisted Magnetic Recording (HAMR)1 overcomes this limitation by locally heating the magnetic medium close at or above the Curie temperature to decrease its anisotropy, thus overcoming the limitations brought by the write field. The possibility to modulate magnetic anisotropy by tailoring composition on the other hand could provide close control over coercivity, which could then be matched to the available write field.
Partial substitution of Ni for Fe, leading to Fe50-xNixPt50 alloys, could modulate the magnetic anisotropy in a wide range, varying ideally from the full Fe-Pt value (6.6 MJ/m3) down to zero. Fe-Ni-Pt films were grown using an electrolyte modified from a slightly alkaline citrate-glycinate electrolyte previously used for Fe-Pt synthesis2, with the addition of NiSO4. Electrodeposition was performed at 75°C onto Ru films sputtered on Si wafers; the thickness of Fe-Ni-Pt was kept between 10 and 80 nm. In order to achieve a wide range of Ni fractions in the alloy while maintaining a sufficiently fast deposition rate, it was necessary to use different Ni++ concentrations in the electrolyte (2- 20 mM). For a given [Ni++], the Ni fraction in the alloy generally decreased with increasing overvoltage. On the other hand, the Ni fraction at a given potential did not increase monotonously with [Ni++], suggesting the occurrence of an anomalous deposition process3.
Annealing in forming gas (5% H2, 95% Ar) at 650°-700°C was necessary to observe the (100) reflection of the L10 phase, evidencing the phase transformation. The resulting films were unoriented and showed an approximately isotropic magnetic behavior. Film coercivity after annealing increased with Fe fraction, from about 2 to 10 kOe, demonstrating the possibility to tailor coercivity via composition. Finally, temperature-dependent magnetic measurements between 100-300 K showed a monotonous increase both in magnetization and coercivity, as expected.

References

[1] M.H. Kryder, E.C. Gage, T.W. McDaniel, W.A. Challener, et al. Proc. IEEE 96, 1810 (2008)
[2] D. Liang, J.J. Mallett, G. Zangari, J. electrochem. Soc. 158, D149 (2011)
[3] M. Matlosz, J. electrochem. Soc. 140, 2272 (1993)
Optimized Cofeb Alloy Films for Electroformed Resonators
Authors: Pillars Jamin Ryan , Langlois Eric Donald , Arrington Christian L. , Monson Todd , Staruch Margo , Finkel Peter 
Published: February 2020

Magnetostrictive CoFe films were investigated for use as magnetoelastic tags or sensors. The ability to electrodeposit these films enables batch fabrication processes to pattern a variety of geometries while controlling the film stoichiometry and crystallography. Previous research developed a chemistry and plating parameters to maximize magnetostriction with a stoichiometry range of Co0.7-0.75Fe0.3-0.25 and 20-30nm grain size. A bimorph test structure with electrodeposited CoFe was used in a DC magnetic field to measure the magnetostriction. Resonators were then electroformed into photo definable molds and testing showed no signal in an AC magnetic field. The impedance of the films was analyzed and to minimize attenuation, the resistivity of the films was increased by introducing boron into the films. Dimethylamine borane was added incrementally to the electrochemistry bath and ternary alloy films were produced with boron concentrations of 1-10 atomic %. The stoichiometry of the alloy films were confirmed using inductively coupled plasma mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS). The resistivity of the films and the crystal structure were analyzed as a function of the boron concentration. The magnetic properties of the films and the strength of the resonant signal were also correlated with the film composition.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.