bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and Microstructure of Sulfonitriding of Die-Steels
Authors: Nanko Makoto , Horie Kazuya , Nakagane Ryosuke , Kadowaki Satoru , Kuwabara Yoshihiro 
Published: February 2020

Sulfonitriding is one of the surface treatments of die made of steels for forging and casting. In this surface treatment, annealing under NH3 and H2S containing atmosphere provides the formation of top sulfide layer on the nitrided zone. The surface sulfide zone has anti-seizure and lubrication effects during forging and casting processes. In this study, microstructure development and its kinetics in sulfonitriding of die-steels.
Commercial die-steels, JIS-SKT4 and JIS-SKD61, were used. Those steels were annealed under gas-mixture of N2 and H2S at 520°C for 0.5 h and NH3for 2.5 h. Microstructure of the samples was observed by using scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA). Phase identification of the samples was conducted with X-ray diffraction (XRD). Chemical profile from the surface was obtained by using glow discharge spectroscopy (GDS).
A thin continuous layer with 2 -3 μm in thickness was developed on the surface of die-steels. XRD revealed the formation of FeS after sulfonitriding process. The FeS layer was so dense without significant pore network. Results of GDS and EPMA shows that the surface FeS layer include nitrogen and Cr. Inner nitrided zone consisted of mainly Fe3N. Repeating the sulfonitriding process, thickness of the top FeS layer and Fe3N zone increase parabolically. As a result of the marker experiments with Al2O3 particles, top FeS layer was developed by the outward diffusion of Fe and Fe3N zone was grown with inward diffusion of N. Because open pore network in the top FeS layer was not observed, inward diffuses of nitrogen passing through the top FeS layer occurs during sulfonitriding process.
High Temperature Corrosion of High Strength Materials for Boiler Applications in the Temperature Range from 550 C to 750 C
Authors: Singheiser Lorenz , Zurek Joanna , Huczkowski Pawel , Müller Michael , Quadakkers Joe 
Published: February 2020

Since more than 10 years boiler concepts up to 750 °C using ferritic-martensitic and austenitic steels as well as nickel base alloys above 650 °C have been developed to increase power plant efficiency and to reduce CO2- emissions by post combustion as well as oxyfuel processes.
The paper summarizes the influence of temperature and Cr- concentration on the steam oxidation behavior of ferritic martensitic steels as well as of austenitic steels and their limits for long-term high temperature applications, which are mainly determined in conventional boiler applications by steam oxidation. For temperatures well above 650 °C nickel base alloys have to be used, which have good steam oxidation resistance, if Cr- contents are high enough. At temperatures above 670 °C nickel base alloys are prone to type II hot corrosion on the fireside of superheaters, if deposits with high NaSO4 and sulfur content are formed as a consequence of Na- and sulfur rich coal combustion. The maximum of hot corrosion attack is at 750 °C, in good agreement with similar results obtained from gas turbine experience. The susceptibility to hot corrosion can be calculated using Calphad based simulation, if coal composition and combustion conditions are known.
Oxyfuel processes exhibit high CO2- concentrations between 60 to 70 % and approx. 30 % H2O. Due to recirculation of dust free exhaust gas to increase heat transfer within the boiler and superheater, impurities like SO2, NOX and HCl may result in increased oxidation and sulfidation rate. The high CO2- content result in extended internal carburization of ferritic martensitic steels, if water vapor contents are low. With increasing water vapor content, carburization rate decreases due to reduced carbon activity according to the water gas shift reaction. Formation of chromia scales on austenitic steels as well as nickel base alloys prevents carbon uptake in the base alloys. The higher SO2- contents in the oxyfuel flue gas power plants do not significantly accelerate corrosion rates of ferritic martensitic steels at temperatures below 600 °C, which are currently considered for oxyfuel power plants.
Environmental Degradation of Au-Nanoparticle Incorporated Oxides By Reactive Evaporation of AuH(g)
Authors: Holcomb Gordon R , Tylczak Joseph , Baltrus John P , Ohodnicki Paul R 
Published: February 2020

Au-nanoparticle incorporated metal oxide based sensing layers show significant promise for high temperature remote optical sensing applications at temperatures approaching 800°C—or higher depending upon the base oxide material. Simultaneous measurements of temperature and gas composition are possible. Simplified specimens of Au-nanoparticles on SiO2 substrates were exposed to N2 and N2-H2 environments for one week at 700 to 800°C. Loss of Au, as measured by X-ray Photoelectron Spectroscopy (XPS), was detected after exposure in N2-H2 environments with both low (1%) and significant (29%) amounts of H2, and not detected after exposure in pure N2. Thermodynamic and kinetic calculations were made of reactive evaporation reactions of Au to form AuH(g), which were consistent with the observed results.
Molten Salt Corrosion of SiC Fibers
Authors: Opila Elizabeth J. , Herweyer Lucas 
Published: February 2020

The Na2SO4-assisted hot corrosion resistance of Hi-Nicalon, Hi-Nicalon S, Sylramic and Sylramic iBN SiC fibers was characterized as a function of time and temperature. Na2SO4-loaded fibers were exposed in a tube furnace with 0.1% SO2/O2 flowing gas for times between 45 minutes and 24 hours, at temperatures between 900 and 1100C. Fibers were characterized after hot corrosion exposure, and after 24 hour water and HF soaks, by weight change measurements, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. Inductively Coupled Plasma Optical Emission Spectroscopy was used to determine the elemental composition and concentration of dissolved corrosion products found in the water and HF soaks. It was observed across all fiber types that hot corrosion attack was rapid and severe, with fiber fusion, surface pitting and non-uniform scale build-up as common microstructural features. Differences in hot corrosion reactions were observed in surface morphologies and weight change measurements. Time dependence revealed that Hi Nicalon fibers exhibited the largest weight gain, while Sylramic, Sylramic iBN and Hi Nicalon S fibers had similar weight gains.
Soaking Experiments for Understanding Corrosion Behavior of Zircaloy with Molten Stainless Steel−B4c at Elevated Temperatures
Authors: Matsuura Suguru , Nanko Makoto , Kurata Masaki 
Published: February 2020

Abstract:

Recently nuclear power reactors have been commonly used for generation of electricity as well as thermal power generation and hydroelectric generation. Boiling water-type nuclear reactors include fuel rods consisting of uranium pellet fuels cladded with Zircaloy (Zrc) tube and control rods consisting of boron carbide (B4C) powder cladded with stainless steel (SS) plates in the pressure vessel..
When severe accident occurs, water coolant circulation is halted, leading to increase temperature of these fuel rods. Thermal radiation from the fuel rods results in melting the control rods comprised of SS and B4C. The SS-B4C melts can react with Zrc cladding of the fuel rods. Nuclear fuels will be exposed into the ambient atmosphere. However reaction behavior of Zrc cladding with SS-B4C melts has not been researched. Previous study were mainly on solid state reaction of Zrc cladding and control rods [1-3].　In order to study corrosion behavior of Zrc cladding with molten control rods, the soaking experiments of Zrc into molten SS-B4C were conducted.
A powder mixture of SS and 5mol%B4C was heated at 1400°C for 12 h to synthesize the melt. After decreasing temperature to test temperature of 1175, 1200, 1225 and 1250°C, plates made of Zircaloy-4 were soaked to melted SS-B4C for 0 to 60 min. After soaking, the plates were removed from the melt. Thickness of the plates was measured by using an optical microscope. Reaction products on the plates were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD).
The value of thickness reduction of Zrc was increased linearly with increasing the soaking time. The reduction rate of Zrc was increased with increasing temperature. The value of apparent activation energy on the thickness reduction rate was equal to 333 kJ/mol.

References:

[1] Steinbruck M., J. Nuclear Material 400 (2010) 138.
[2] Hofmann P., Markiewicz M., Spino J., KfK 4598, Kernforschungszentrum Karlsruhe GmbH,Karlsruhe, Germany, (1989).
[3] Nagase F., Uetsuka H. and Otomo T., JAERI-Research 95-085 (1995).

Acknowledgements

This study is performed in “Advanced Multi-scale Modeling and Experimental Tests on Fuel Degradation in Severe Accident Conditions", Ministry of Economy, Trade and Industry.
(Invited) Preparation of Ordered Anodic Porous Alumina Through-Hole Membrane and Its Applications
Authors: Yanagishita Takashi , Masuda Hideki 
Published: February 2020

Anodic porous alumina, which is a typical self-ordered nanohole array material formed by anodization of Al in an appropriate acid solution, has recently attracted increasing interest as a key material for the fabrication of functional devices1,2). For the various applications of ordered anodic porous alumina, the preparation of through-hole membranes is important. The fabrication process for porous alumina through-hole membranes has been investigated for a long time3). However, a facile and reliable process that does not require special techniques has not yet been established. To overcome this problem, we have been developing a new high-throughput process for fabricating through-hole alumina membranes4). This process is based on the new finding that through-hole membranes can be easily obtained by dissolving a two-layered sample in an appropriate etchant, which was formed by a first anodization under standard anodizing conditions and a subsequent anodization in concentrated H2SO4. This is because the oxide layer formed in the concentrated H2SO4 can be easily dissolved in an appropriate etchant. After the detachment of the membrane, the residual Al substrate could be repeatedly used for the preparation of ordered through-hole membranes. In this report, recent results of the preparation of ordered anodic porous alumina through-hole membranes and its applications will be presented.

References

1) T. Yanagishita and T. Hidaka, M. Suzuki, and H. Masuda, J. Vac. Sci. Technol. B, 34, 021804 (2016).
2) H. Masuda and K. Fukuda, Science, 268, 1466 (1995).
3) H. Masuda and M. Satoh, Hpn. J. Appl/ Phys., 35, L126 (1996).
4) T. Yanagishita and H. Masuda, Electrochim. Acta, 184, 80 (2015).
Control of the Magnetic Properties of a Magnetic Field Guidable Biocompatible Nanovehicle
Authors: Granitzer Petra , Rumpf Klemens , Reissner Michael , Poelt Peter 
Published: February 2020

Within this work a biocompatible magnetic nanovehicle which is movable in aqueous solutions by a magnetic field is presented. The nanovehicle consists of a porous silicon template and encapsulated iron oxide nanostructures. Both materials employed, porous silicon (PSi) as well as iron oxide are known to be biocompatible (1, 2). Mainly the synthesis of the nanocomposite as well as the magnetic properties of the systems will be discussed.
Two routes are employed to produce various iron oxide phases of the embedded nanostructures within PSi. On the one hand, readily synthesized magnetite nanoparticles (NPs) which are superparamagnetic (SPM) due to their size, are infiltrated into the pores. On the other hand chemical deposition of iron oxide inside the PSi templates is used. The loading process of the templates depends not only on the pore-diameter/particle-size ratio but also on the particle-template interactions due to different surface treatments (e.g. as etched or oxidized PSi). Considering the chemically grown iron oxide, it does not form monodisperse particles but mainly clusters of particles. An increase of the temperature during the deposition resulted in a decrease of the coercivity which can be due to an iron oxide phase modification or due to a modification of the shape of the deposits.
An adjustability of the magnetic properties of the system is achieved by a variation of the iron oxide loading within the PSi. An investigation of the iron oxide deposition dependent on the template and on the chemical parameters as well as of the magnetic properties in dependence on the particle size and on the template morphology of the nanocomposite will be presented.
Temperature dependent magnetization measurements give information about the nature of the particle filling (packing density, spatial distribution), from field dependent magnetization measurements characteristics such as saturation magnetization, coercivity and remanence can be evaluated.
For a sample containing a moderate filling with 8 nm Fe3O4 NPs the saturation magnetization has been estimated in using the measured hysteresis curves and considering the 1/H approach to be in the order of 6×10-3 emu/cm2. The amount of iron oxide particles inside the pores of the PSi matrices has been estimated in taking the magnetic moment of an individual iron oxide NP which is about 1.49 × 10-18 emu. In this case this leads to a number of about 1.3 × 1019 particles/cm3. The coercivity HC of the nanocomposite systems below TBdecreases with decreasing particle size which is due to SPM relaxation effects.
The fabricated magnetic nanovehicles can be tuned in its magnetic behavior (e.g. coercivity, TB) due to the morphology of the template, the particle size and the filling conditions. The resulting magnetic moment of the samples is high enough to be moved within aqueous surroundings by a magnetic field of 0.1 T.
(1) D. Ling, T. Hyeon, Small 9, 2013.
(2) L.T. Canham, Adv. Mater. 7, 1033, 1995.
Dealloying Mechanism of Bulk-AlCu Intermetallic Phases (Al2Cu, Al7Cu2Fe, Al2CuMg) : Effect of Crystallographic Structure and Electrolyte
Authors: Rocca Emmanuel , Tardelli Joffrey 
Published: February 2020

The aluminum alloys with high mechanical properties, the 2xxx and 7xxx series, are very sensible to corrosion because of the presence of numerous coarse intermetallic phases in the aluminum matrix. These phases are often responsible of the formation of pits in corrosion conditions, or the formation of defects in the anticorrosion coatings such as anodized layers.
The objective of this work is to study the behavior of different AlCu intermetallic phases (Al2Cu, Al7Cu2Fe, Al2CuMg) in the 7XXX and 2XXX alloys in NaCl electrolyte and H2SO4 electrolyte.
Firstly, bulk-samples of phases (centimeter size) were synthesized by quick melting in an induction furnace followed by several annealing steps under argon. The electrochemical behavior of the three phases was characterized by stationary electrochemical measurements and electrochemical impedance spectroscopy in function of immersion time at open-circuit potential. The surface layers on each phase were observed on surface and metallographic cross-section by FEG-SEM, EDX spectroscopy and X-ray Photoelectron Spectroscopy.
In NaCl electrolyte, all the studied intermetallic phases undergo a dealloying phenomenon which leads to the formation of a pure copper nanometer sponge. On the surface, the copper sponge can be partially embedded and covered in an aluminum hydroxide gel according to the hydrodynamic conditions. In sulfuric acid, the dealloying phenomenon depends on the copper content in the intermetallic phase and on its crystallographic structure. According to the density of the Cu plan, some phases can form a compact layer of copper that passivate the phase, some others form a nanometer sponge of copper.
In conclusion, after the dissolution of aluminum, magnesium or iron atoms, copper atoms diffuse on the surface of phases to form either crystalline copper nanometer particles, or compact copper layer according to the electrolyte properties and their crystallographic structure.
Enhanced Electrocatalytic Activity on Water Splitting with Niox Nanoflakes Electrode Fabricated Via Selective Etching and Reconstruction of Niw Amorphous Films
Authors: Ling Yunhan , Qin Fei , Yu Siqi , Gu Yanhong 
Published: February 2020

Hydrogen is now widely regarded as most suitable to replace fossil fuels for it burns clean, producing only water and has the highest energy density per unit mass. However, hydrogen is not freely available in nature and needs to be produced, either from water or other compounds. Alkaline water electrolysis offers a simple method for mass production of hydrogen but suffers from the sluggish kinetics of the anodic oxygen evolution reaction, calling for the development of low-cost and durable oxygen evolution electrocatalysts with high activity.
In this work, we report an enhanced electrocatalytic activity on water splitting with NiOx nanoflakes electrode fabricated via selective etching and reconstruction of NiW amorphous films. It was found that the highly electrocatalytic activity was attributed to the increase of specific surface area of the electrode as well as the change of valence states of nickel. It is anticipated that the modification of as-fabricated nanostructured electrodes with bandgap engineering which is under way will further improve the efficiency and prolong the durability, making them potential and more attractive in addressing the pressed technological issues.
Atmospheric Corrosion Monitoring of Carbon Steel in Snowy Cold Region
Authors: Katayama Hideki 
Published: February 2020

Atmospheric corrosion is a complex phenomenon that proceeds under thin water film while influencing a variety of environmental factors. Most of atmospheric corrosion researches generally have been conducted by exposure test. However, the sampling after exposure test are regularly carried out, so it is not possible to catch the changes in the corrosion resistance of samples to environmental factors continuously. In addition, many results are obtained from the data of atmospheric corrosion test in the subtropical region, and there is not much corrosion data in the cold snowy regions. In this study, atmospheric corrosion rate of carbon steel has been monitored in snowy cold region.
Concentric ring type corrosion sensors were used for the corrosion monitoring. The sensor consists of two carbon steel electrodes embedded concentrically in epoxy resin. The exposed areas of both electrodes are the same. Two test racks for outdoor exposure test were placed in Ishikari exposure test site. The height of the test rack was adjusted in consideration of the average snow accumulation, in order to investigate the influence of snow. The exposure test was started in December 2015. There was little snow at the start of the exposure test in Ishikari because snowfall in 2015 was less by the mild winter. The corrosion sensors were set on the test rack at an inclination of 45 degree to the south. The impedances at two different frequencies of 10kHz and 10mHz were measured continuously for corrosion monitoring. The impedances at 10kHz and 10mHz correspond to the solution resistance and the sum of the solution resistance and the corrosion resistance, respectively.
Relationship between snowfall and the solution resistance was investigated in the initial process of exposure test. The solution resistance during snowfall showed a low value, which suggests that the surface was getting wet by snowfall. Further, the solution resistance of a few hundred ohms was obtained during wetting. This means the electrical conductivity of the snow is relatively high. The test site is away only about 500 meters from the sea. Therefore, the electrical conductivity is attributed to airborne sea salt in snow. On the other hand, the corrosion sensor also gave a high corrosion rate during snowfall, indicating that the corrosion is in progress. Although the temperature is very low during snowfall, even the wetting of the surface by snow causes corrosion.
AE Monitoring of Hydrogen Embrittlement Crack in Maraging Steel
Authors: Shinozaki Ippei , Nakayama Gen , Sakakibara Yohei 
Published: February 2020

AE (Acoustic Emission) result from initiation and propagation of cracks in materials. Then AE monitoring can detect the micro cracks.
Maraging steels witch have superior strength are used as structural materials. However, these have hydrogen embrittlement problem under humid air.
Hydrogen embrittlement resistance of maraging steels is usually estimated by visual testing (VT) which checks whether rupture or not in laboratory. However the testing method is batch style testing. Then it is difficult to estimate the exact rupture time through VT. Then the AE monitoring applied to detect hydrogen embrittlement of maraging steel.
Hydrogen embrittlement crack accelerated by a droplet of NaCl solution that was set on the center of the maraging steel thin plate. In this case, the droplet was too small to determine the hydrogen embrittlement crack through the electrochemistry method.AE sensor also set on the plate and detected AE signals.AE signals were classified as to amplitude, frequency, and wave form. AE event rate was also focused. The surface crack propagation was also recorded by digital camera. Crack growth was confirmed from the pictures.
AE event counts separate 3 regions. At first region, AE event counts detect before surface cracks were able to be observed. In this region, cracks may initiate under the droplet. At Second region, AE event counts were constantly increased. In this region it was observed that increment by crack growth was constant by digital camera. It shows that means the second region was the crack growth stage. At third region, AE event rate was increased twice. The second crack growth was observed in digital camera images. Then AE event rate reflected the number of cracks. There was good relation between crack propagation and AE event rate. AE event rates were difference between types of steels. The other steel which has high hydrogen embrittlement resistance tend to have low AE events rate.