bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Photogenerated Charge Transport By TiO2 Modification of WO3/BiVO4 Core-Shell Heterojunction
Authors: Park Eunoak , Lee Kiyoung
Published: December 2020

Photoelectrochemical (PEC) water oxidation is a promising approach to generate hydrogen using solar light. For the purpose, several candidate materials are considered that are mostly semiconductive materials including metal oxide. Among various metal oxides, WO3 has been regarded as a prospective resource because of their suitable band position, relatively higher photocorrosion resistance, and low cost. WO3 allows photogenerated electrons and provide easy electron pathway to current collector through the conduction band. Furthermore, BiVO4 deposition on WO3 can attract hole from WO3 that plays a key role for oxygen evolution reaction. Nevertheless, BiVO4 has a drawback to be solved with respect to stability. For this reason, blocking layers with high band gap energy are suggested to protect the unstability. In particular, TiO2 has not only high band gap energy but also chemical/physical stability. Moreover, TiO2 blocks solution-mediated recombination at surface of WO3/BiVO4 core-shell heterojunction, which helps to improve PEC efficiency.

In the present work, we achieve facile approach to modify WO3/BiVO4 with TiO2 deposition. As a result, photoinduced current density is recorded as 0.59 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination. This value makes 78.8µL cm-2 of H2 evolution, which indicates almost 1.5 times higher than the WO3/BiVO4 core-shell heterojunction.

Figure 1
Enhancement of Photoelectrochemical Properties through α-Fe2O3 Deposition on a Modified Fluorine-Doped Tin Oxide
Authors: Choi Yongseon , Lee Kiyoung
Published: December 2020

Hydrogen is attractive energy resource for renewable energy. In order to produce H2, several approaches are suggested. In particular, water splitting is well-known as an eco-friendly production approach. Moreover, electrochemical water splitting has a challenge that noble metal based catalyst. For this reason, photoelectrochemical (PEC) water splitting has been studied for a long time but not yet to reach a goal of society demand.

For PEC water splitting, there are several materials has been considered such as Fe2O3, WO3, TiO2, BiVO4 etc. Among them, Fe2O3 is the most attractive material due to cheap, abundant resources and smaller bandgap than other material. However, it has a demerits of short life time owing to short diffusion length.

In this research, we investigated enhancement of PEC performance with electrodeposited Fe2O3 on surface modified fluorine-doped tin oxide (FTO). The roughness of FTO substrates were increased with various electrochemistry method in acidic electrolyte. The modified FTO substrate area which leads to increasing electric conductivity. Under optimum condition photocurrent could be enhance with 20% in compare with α–Fe2O3 on pristine FTO substrate. Moreover, over-potential was also reduced with 100 mV.

Figure 1
Best Practice for Evaluating Electrocatalysts for the Hydrogen Economy
Authors: Bird Matthew , Goodwin Sean E , Walsh Darren Anthony
Published: December 2020

Making accurate measurements of electrocatalytic activity is of paramount importance for the development of new earth-abundant electrocatalysts. In a typical three-electrode setup Pt or Au is often used as the counter electrode material. These metals can dissolve during testing and subsequently deposit on the test electrocatalyst surface, artificially increasing the measured activity. A Nafion membrane is sometimes used to separate the counter electrode from the test electrocatalyst to minimise this, though no work has conclusively proved this to be effective. The work presented here uses X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis, mass spectrometry, and voltammetry to demonstrate the issues with using metallic counter electrodes and the ineffectiveness of Nafion to mitigate this during constant-current testing of electrocatalysts for the hydrogen evolution reaction. It is further shown that a carbon counter electrode can deactivate electrocatalyst surfaces, and that a glass frit should be used to separate the test surface from the counter electrode in these cases.
Exploring the Optoelectronic Properties of Solution Processed 2D TMD Nanoflakes Exfoliated Via Large Molecule Electrointercalation
Authors: Wells Rebekah , Caretti Marina , Cho Han-Hee , Sivula Kevin
Published: December 2020

The remarkable semiconducting properties of 2D transition metal dicalcogenides (TMDs) are of great interest to researchers hoping to harness such traits for optoelectronic and photoelectrochemical (PEC) applications. 2D MoS2, WSe2, and related materials have been incorporated in ultrathin devices including transistors1, LEDs2, solar cells3, and photoelectrodes4,5. While typical approaches like chemical vapor deposition produce pristine monolayer or few-layer 2D TMD sheets and flakes, these methods are expensive and energy intensive making them unsuitable for large scale implementation. Thus, developing scalable solution processable methods to prepare high-quality 2D TMD materials is crucial.

Typical solution-based production approaches have historically yielded TMDs with poor semiconducting behavior. Recently a novel electrointercalation technique was reported by Lin et al. wherein large organic cations are inserted in between MoS2 layers in a bulk single crystal thereby exfoliating it to thin nanoflakes while maintaining benchmark semiconducting performance. Despite this advance, there remains a lack of information concerning the optoelectronic properties of these flakes and their ability to be used in solar energy conversion devices.

Herein we use the electrointercalation of large cation tetraheptylammonium bromide (THAB) to exfoliate a variety of bulk TMDs, investigate their optoelectronic properties, and process them into photoelectrodes for solar-to-chemical energy conversion. When compared to alternative solution processing methods such as ultrasonication and shear-mixing exfoliation, these THAB-assisted exfoliated flakes show increased photocurrents, photovoltages, and internal quantum efficiencies. We show that this is, in part, a result of thinner 2D flakes with larger lateral dimensions. Raman, photoluminescence, and X-ray spectroscopy suggest that this technique results in a lower defect density when compared to traditional methods. These results suggest that THAB-intercalated 2D TMDs are promising for scalable solar energy applications.

References:

1. Lin, Z.; Liu, Y.; Halim, U.; Ding, M.; Liu, Y.; Wang, Y.; Jia, C.; Chen, P.; Duan, X.; Wang, C.; Song, F.; Li, M.; Wan, C.; Huang, Y.; Duan, X. Nature
2018, 562 (7726), 254–258.

2. Palacios-Berraquero, C.; Barbone, M.; Kara, D. M.; Chen, X.; Goykhman, I.; Yoon, D.; Ott, A. K.; Beitner, J.; Watanabe, K.; Taniguchi, T.; Ferrari, A. C.; Atatüre, M. Nat. Commun.
2016, 7 (1), 12978.

3. Akama, T.; Okita, W.; Nagai, R.; Li, C.; Kaneko, T.; Kato, T. Sci. Rep.
2017, 7 (1), 11967.

4. Wells, R. A.; Johnson, H.; Lhermitte, C. R.; Kinge, S.; Sivula, K. ACS Appl. Nano Mater.
2019, 2 (12), 7705–7712.

5. Yu, X.; Prévot, M. S.; Guijarro, N.; Sivula, K. Nat. Commun.
2015, 6, 7596.
Welcome Remarks - Z01: General Student Poster Session
Authors: Suroviec Alice
Published: December 2020

Welcome to Z01: General Student Poster Session! Take a moment to listen to welcome remarks from the lead organizer, Alice Suroviec.
(Invited) Skin-Mimic Hydrogel Materials with Water-Perspiration Control for Soft Robots Developed by 3D Printing
Authors: Kanai Shuma , Watanabe Yosuke , Shiblee MD Nahin Islam , Khosla Ajit , Ogawa Jun , Kawakami Masaru , Furukawa Hidemitsu
Published: December 2020

In medical and welfare fields, the developments of robots and prosthesis with the touch close to the human skin are required. For those developments, the use of materials with a touch, softness, temperature, and moisture close to human skin is necessary. Hydrogels are materials with their high water content (90 ~ 95%) and softness (kPa to hundreds of kPa). However, hydrogels have some technical drawbacks such as high water evaporation rate, their touch and temperature different from that of human skin.

We designed a flow channel inside the hydrogel to mitigate the mass loss due to drying of the gel by supplying and circulating warm water with a perista pump. The water absorption and evaporation of the gel were investigated for designing the optimum water channel dimensions. With this mechanism mass loss due to drying was decreased by 43%.

We also fabricated a hydrogel hand using 3D printer. Inside the gel hand, bone parts printed with poly lactic acid are embedded. We are planning to make water channel in the gel hand and adjust the composition of the hydrogel to finally create a gel hand with a touch similar to the human skin.

Figure 1
(Invited) Fabrication of Polymer Gels with Double Network Using Multi-Material 2/3D Printing
Authors: Watanabe Yosuke , Shiga Fumiya , Shiblee MD Nahin Islam , Ogawa Jun , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: December 2020

Multi-material systems for additive manufacturing, also known as 3D printing, are used to fabricate the functional objects with different color materials or with the position dependent material properties such as elastic modulus or solubility. The previous work for Fused Deposition Modeling (FDM) method have demonstrated that the multiple print heads or a single head with the mixed-material systems can extrude the complex and composite materials with piling up the multi-material layers connected with the physical bonds between layers.However, few studies have focused on the fabrication of 3D printed gel materials with different materials, and the creation of chemical bonds on the interface between the multi-material layers.

In our previous work, 3D printed hollow objects made of gel materials were fabricated with a customized optical 3D printing system, and the 3D printed objects of multifunctional ionic gels incorporating ionic liquid (IL) in the thiol–ene network of thiol-based end-crosslinker and acrylate monomers were fabricated using commercial stereolithography (SLA) system. It was found that optical 3D printing system utilized to fabricate gel materials could create the microscale objects.

This study report the design and fabrication of 3D printed polymer gels containing two types of gels using 3D gel printer named “SWIMER”. The double network technique for hydrogels is used for the creation of chemical bonds between two types of gels. Figure shows one of examples of 3D printed gel.This gel consists of two parts: the soft body frame for structural support which is made of nonionic polymer gels and the part which is made of the ionic polymer gels. The nonionic gels with an ordered structure are synthesized by the polymerization of the monomer, N,N-Dimethylacrylamide (DMAAm), and the crosslinker, N, N'-Methylenebisacrylamide (MBAA). The ionic gels are synthesized by the polymerization of the monomer, N-(1,1-Dimethyl-2-(sodiosulfo)ethyl)acrylamide and the same chemicals as the nonionic gels. Chemicals as the ultraviolet (UV) initiator are depending on the wavelength of laser source in the process of how we fabricate the gels.The significant difference in the swelling behavior between the two parts enabled them to be actuated in one direction. We found that by controlling the ion concentration in water they enlarged the solvent-induced strains to 108% in water which is comparable to the polymer actuators driven with high voltage.

Figure 1
TiO2/Activated Biochar Hybrid Material Prepared By Ultrasonication and Heat Treatment for Capacitive Deionization
Authors: Stephanie Hellen , Wipf David O
Published: December 2020

TiO2-doped activated biochar was successfully prepared as a hybrid electrode material for capacitive deionization. The introduction of TiO2 has the advantages of low cost, high chemical stability, hydrophilicity, and eco-friendliness. Activated biochar was treated with titanium isopropoxide (TTIP) and isopropyl alcohol solution by an ultrasound assisted process followed by calcination at 400 °C. The physical and chemical properties of the resulting material was characterized by XPS, XRD, SEM, and TEM. Cyclic voltammetry was performed to analyze the electrochemical properties of the prepared electrodes. Furthermore, the performance of TiO2-biochar electrode was evaluated in a 3D-printed CDI cell and the salt removal capacity was examined using a chloride ion-selective electrode. It was shown that the removal capacity was enhanced from 5.1 mg/g NaCl (activated biochar) to 8.6 mg/g NaCl. The increase in capacity is associated with a better wettability of the electrode, which increases the number of surface-active sites and promotes a more efficient ion diffusion inside the biochar pores. This result is beneficial to improve biochar application as an inexpensive alternative electrode material with metal oxide modification.
Biomolecule Exchange Dynamics on Carbon Nanotubes Via Multiplexed Fluorophore Quenching
Authors: Pinals Rebecca , Yang Darwin , Lui Alison , Cao Wendy , Landry Markita P
Published: December 2020

Adsorption of biomolecules on single-walled carbon nanotubes (SWCNTs) has enabled developments in molecular sensing, in vivo imaging, and gene delivery applications.1,2 This noncovalent functionalization of SWCNTs preserves the pristine SWCNT atomic structure, thus retaining the intrinsic near-infrared fluorescence for sensing or imaging functions, and offers a reversible binding mode for cargo delivery. However, biomolecule adsorption is an inherently dynamic process, where exchange occurs between molecules in the bulk solution and molecules on the nanoparticle surface, into what is known as the corona phase. The nature, strength, and kinetics of both the biomolecule binding and unbinding processes on SWCNTs are important contributors to the success of SWCNT-based technologies. Understanding this binding process is especially important for intended uses of functionalized SWCNTs in biological environments, where native biomolecules such as proteins compete with the original biomolecule to occupy the SWCNT surface. Such biofouling of the SWCNT surface disrupts the intended functionality of the nanoparticle and can further lead to adverse biocompatibility outcomes.

We present a generalizable method to study the corona exchange dynamics between solution-phase and corona-phase biomolecules on SWCNTs in real-time.3 This approach exploits the quenching property of fluorophores proximal to the SWCNT surface to monitor ligand binding and unbinding events. Real-time tracking of adsorption and desorption events on the SWCNT surface are conducted with systematic variation of the molecular entities and solution conditions, with a specific focus on DNA (as the sensing moiety) and protein (as the biofouling agent). Binding profiles are extracted from the experimental assay and used to inform a kinetic model of the system. The work presented herein develops an understanding of the fundamental corona exchange mechanism and provides insight into performance of these designed SWCNT-based systems in biologically relevant, protein-rich conditions.

References

Demirer, G. S. et al. High aspect ratio nanomaterials enable delivery of functional genetic material without DNA integration in mature plants. Nature Nanotechnology 1 (2019) doi:10.1038/s41565-019-0382-5.

Beyene, A. G. et al. Imaging striatal dopamine release using a nongenetically encoded near infrared fluorescent catecholamine nanosensor. Science Advances
5, eaaw3108 (2019).

Pinals, R. L., Yang, D., Lui, A., Cao, W. & Landry, M. P. Corona Exchange Dynamics on Carbon Nanotubes by Multiplexed Fluorescence Monitoring. J. Am. Chem. Soc. (2019) doi:10.1021/jacs.9b09617.

Figure 1
Chemical Isolation of Nanotubular Fullerenes (FullerTubes)
Authors: Koenig Ryan M. , Seeler Tiffany L. , Tepper Katelyn R. , Franklin Hannah M. , Stevenson Steven
Published: December 2020

Much literature exists for empty-cage fullerenes with a spheroidal shape. With increasing numbers of carbon atoms, two cage shapes become possible: “tubes” and “balls.” However, little is reported for these nanotubular fullerenes (FullerTubes). This is due to their extremely low yield in typical arc-generated soot extract. Their low abundance renders their isolation quite difficult. HPLC alone is rather challenging using this classical separation method. With our approach, we have discovered a chemical-based approach to selectively react and remove spheroidal fullerenes. In doing so, we obtain samples enriched in FullerTubes by several orders of magnitude. In this presentation, we will discuss the synthesis and separation strategies needed to isolate Fullertubes in macroscopic quantities.
Electrophoretic Deposition of Carbon Nanotubes for Anti-Reflective Coatings
Authors: Wang Dan , Fuqua Peter , Hopkins Alan , Hennessy Amber , Hall Timothy , Snyder Stephen , Inman Maria , Taylor E. J.
Published: December 2020

Space observatory missions requires the development of low-reflectivity surfaces for space-borne instruments, such as seeker telescopes, optical sensors, etc., to minimize stray and reflected light across the visible and infrared wavebands for facilitating the direct exoplanet detection and characterization. For example, in order to improve the sensitivity of missile-defense sensors and seekers, baffles are used within optical telescopes to reduce stray light. Some materials (e.g., aluminum, beryllium, etc.) are too reflective to use as absorptive baffles without surface processing, although they have lightweight and good thermo-structural properties, and survive harsh environments. Black surface coating treatments have been demonstrated as effective approaches to obtain low reflective surfaces. The surface features and intrinsic properties of the coating materials play an important role for scattering, absorbing, or trapping light. The excellent optical absorption performance and light weight of carbon nanotubes (CNTs) make them as ideal coating materials for obtaining low reflectivity surfaces. In this presentation, we will discuss the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition technology. The low-reflectivity CNT coatings have been successfully deposited on various surfaces, including flat, bent, and sharp substrates. The CNT coatings show the reflectance of 0.4% ~ 0.8% across visible to near infrared (NIR) wavebands.

Within this context, Faraday Technology Inc. demonstrated the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition. As shown in Figure 1, the uniform CNT coatings are formed on an aluminum (Figure 1, Inset (Right)), and the diffuse reflectance of the CNT coatings is ~ 0.5% over the visible range. We also demonstrated the potential to apply CNT coating on the internal diameter of cylinders at room temperature (Figure 1, Inset (Lef)t). Faraday are currently working on developing CNT coatings on the surface of absorptive baffle materials, such as beryllium and aluminum. The developed economic and scalable technology for producing CNT black coatings on desired substrates can not only be used for minimizing stray and reflected light for space-borne instruments, but also offer potential applications in other optical related devices which request low reflective surfaces, such as solar cells.

Acknowledgements: The financial support of NASA SBIR/STTR program through contracts No. 80NNSC18P2062 & 80NSSC19C0177 is acknowledged.

Figure 1
Influence of Operating Conditions on Graphene Properties Synthesized from Two-Step Electrochemical Exfoliation
Authors: Momodu Damilola , Madito Moshawe Jack , Singh Ashutosh Kumar , Sharif Farbod , Karan Kunal , Trifkovic Milana , Roberts Edward P.L.
Published: December 2020

Effective exfoliation of relatively high-quality graphene with good yield from graphite is critical for its extensive exploitation in several emerging technologies. Two-step electrochemical exfoliation of graphene offers a route towards achieving such high-quality graphene and tailoring of its properties for nanotechnology-related applications. A precise control of the intercalation and exfoliation conditions provides an additional dimension for tuning these graphene properties.

Here, we report a systematic evaluation of the nature of defects induced in graphene with respect to varying intercalation times and intercalant composition using an acid-blend containing sulphuric acid (H2SO4) and phosphoric acid (H3PO4). A few-layer, exfoliated graphene (eG) is obtained by incorporating relevant functional groups in the main matrix during the intercalation step. Structural analysis by Raman and X-ray microscopy indicates a multi-atom-doped graphene with primarily “boundary
-type” defect signature and n-type charge carriers synthesized for an optimized intercalation time of 1600 s. The average ratio of the defect-activated modes (I

D

/
I

G
and I

D

/
I

D′
) showed a unique defect feature at 1600 s irrespective of the intercalating electrolyte composition. This indicates the need for careful selection of intercalation times to control the nature of defects. The phosphorus and nitrogen-doping content in the eG increased with increasing phosphoric acid content which influences the thermal and electrical conductivity respectively.

Most interesting, by using various intercalation times, we show that increasing intercalation times in the presence of high phosphoric acid content beyond 1600 s results in deteriorating electrical conductivity but enhanced thermal stability. A trade-off in conductivity and thermal stability shows competing factors influence these properties. We attribute this to loss of the sp2 graphitic structure at higher intercalation times which dominates over any contributions from the dopants. The highest electrical conductivity of ~14,000 S m-1 was recorded which is a two orders magnitude increase from the eG intercalated in pure H2SO4. The energy consumption (kWh kg-1) required for exfoliation was reduced by up to 50% and the exfoliation efficiency was enhanced with the incorporation of phosphoric acid into the intercalating electrolyte blend. This study thus provides a facile and energy-efficient recipe for synthesizing graphene nanostructures with unique defects relevant for use in specific applications related to energy storage and water treatment.

Figure 1
Metallic Ni-Fe-Co Nanoparticles Doped with Ultrathin Carbon Nanosheets: A Highly Efficient Electrocatalyst for Overall Water Splitting
Authors: Yaseen Waleed , Ullah Nabi , Xie Meng , Xu Yuanguo , Zhou Minjing , Jing Liquan , Adegbemiga Yusuf Bashir , Xie Jimin
Published: December 2020

Consistent design and cost-effective multifunctional electrocatalyst that comprises of highly abundant earth elements are greatly need for sustainable energy conversion applications. The present study reports a facile single-step strategy for in-situ growth of NiFeCo nanoparticles doped-ultrathin carbon nanosheets (NFC@CNSs) with hierarchical like structure by pyrolysis method. NFC@CNSs catalyst at optimum condition exhibits an outstanding activity with a low overpotential 124 and 256 mV to achieve a current density of 10 mA cm-2 with a small tafel slope 119.22 and 67.83 mV dec-1 for hydrogen and oxygen evolution reactions, respectively, in 1.0 M KOH. Furthermore, NFC@CNSs exhibits the large electrochemical active surface area of 21.30 mF cm-2, highly specific SBET surface area 145.39 m² g-1, low charge transfer resistance 46.87 ohms which forms the superior catalytic performance. The two-electrode system constructed as anode and cathode in an alkaline electrolyzer can achieve a current density of 10 mA cm-2 by a fairly low applied cell-voltage of 1.566 V under the real water splitting condition. The result revealed that, the strong coupling between NiFeCo alloy nanoparticles and carbon nanosheets might have been responsible for formulating such a remarkable electrochemical performances, electronic structure, and robust stability toward overall water splitting. Additionally, ultrathin porous carbon nanosheets structure does not only provides substantial active sites, but also facilitates the charge transfer process during diffusion and saturation of electrolytes which ultimately boost-up catalytic performances. This work provides a facile single-pot approach to construct metal-doped nanostructured materials with earth-abundant elements for sustainable industrial applications.
Relationship between Carbon Structure-Electrical Conductivity By Cluster Analysis for Li-Ion Battery Application
Authors: Moon J.M. , Chae S.W. , Pornaroontham P. , Naraprawatphong R. , Wang X. , Saito N.
Published: December 2020

Carbon materials are widely used as anode on Li-ion battery (LIB). In particular, the effect of electrical conductivity (EC) on the anode is related to capacity and retention, which are important factors for LIB performance. However, the relationship between carbon properties and battery performance is still unclear. This uncertainty is due to the sp3 and sp2 bond states, the diversity of carbon like amorphous structures, and impurities.

In this study, we investigate the structure-EC relationship from over 50 carbon samples. The carbon used was graphite, carbon nanotube (CNT), carbon black (CB), hetero atom doped carbon, and the ones synthesized by solution plasma. The carbon materials are evaluated by X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX), and four-point probe (FPP) measurement. The characterized values were extracted from the results and analyzed by Cluster analysis (CA) with JMP software. CA was used to classify how carbons are related to each other.

The clusters were divided into 3 big groups according to the presence of 002 peak and the degree of defects. Some clusters have been shown high conductivity when they have high crystallinity. It was also found that the heteroatomic effect was higher than the crystallinity in the part showing low EC range. However overall correlation with EC is still unclear. This is because XRD and Raman can only provide information of symmetric or periodic structures rather than the effect of disorder or amorphous parts, sizes and shapes are not considered. Thus, analysis of shapes and sizes such as SEM and BET, and additional measurements related to amorphous structures may be helpful to clarifying the correlation.

Figure 1
Effects of Sulfates on Corrosion of 430 Ferritic Steel in CO2-Saturated Water Containing Oxygen
Authors: Repukaiti Reyixiati , Doğan Ömer N. , Ziomek-Moroz Malgorzata , Oleksak Richard P. , Thomas Randal B. , Baltrus John P , Tucker Julie
Published: December 2020

Aqueous corrosion can be an issue for structural materials in direct supercritical CO2 power cycles, especially in low temperature components such as water separators and coolers where aqueous condensation appears as supercritical CO2 working fluid containing impurities (SOx, O2, H2O) cools down. This study aims at testing 430 ferritic steel as a material of construction for the low temperature components. Immersion experiments were carried out in an aqueous solution with and without H2SO4 (pH was 3 and 4, respectively) in an autoclave pressurized to 8 MPa with 99% CO2 and 1% O2 gas mixture. Temperature of each solution was 50°C. Immersion tests lasted up to 500 hours. Post-corrosion surface characterization techniques included X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The characterization indicated that general corrosion took place in both cases with and without H2SO4. The corrosion rate of samples was calculated based on the mass loss. The corrosion rate values for 430 steel in solutions with and without H2SO4 were very low and similar after 96 hours of immersion. These initial results indicated that the presence of SO4
2- in CO2 -saturated water containing O2 did not have a detrimental effect on the corrosion resistance of 430 steel.
Effects of Pulse Current on Proliferation Behavior and Activity of Osteoblast-like Cells on Pure Titanium
Authors: Sasaki Yusuke , Miyabe Sayaka , Fujimoto Shinji
Published: December 2020

Titanium and its alloys are widely used as metallic biomaterial because they exhibit superior mechanical properties, biocompatibility and corrosion resistance. The excellent corrosion resistance of titanium based materials is essentially attributed to passive films. Therefore, structure and properties of passive films have been extensively examined by electrochemical approaches as well as surface analytical techniques. Biological factors such as protein and cells have been reported to affect the corrosion behavior of titanium and titanium alloys. On the other hand, it has been reported that electrochemical reactions occurred on metallic substrates also cause some impacts on cell activities. In the present work, we focus on effects of cathodic reactions on proliferation behavior and activity of osteoblast-like cells on pure titanium.
Development of Complex Hydrogen Penetration Ratio As a New Transfer Function for Analysis on Hydrogen Penetration Mechanisms into Metals
Authors: Fukada Haruka , Hoshi Yoshinao , Watanabe Hikari , Shitanda Isao , Itagaki Masayuki
Published: December 2020

Degradation of steels related to the hydrogen embrittlement is a serious problem from the standpoint of infrastructure preservation. The hydrogen embrittlement is related to the hydrogen penetration reaction (HPR) into steel. Some electrochemical methods [1-4] were employed to investigate the HPR mechanisms. One of the major electrochemical methods is electrochemical impedance spectroscopy (EIS). The EIS was applied to the investigation of HPR mechanisms because the time constants observed in impedance spectrum can be discriminated [5]. Another one is Devanatnan-Stachurski permeation technique [6, 7]. In this technique, two independent electrochemical cells are arranged on two surfaces of metal sheet and anodic and cathodic polarizations can be performed with each cell using the three-electrode system. The amount of hydrogen penetration rate can be evaluated by measuring the oxidation current of hydrogen atoms diffused in the metal sheet at the anode side. In this study, we proposed a new transfer function based on the electrochemical reactions and mass transfer during HPR by combining EIS and Devanatnan-Stachurski permeation technique. The complex hydrogen penetration ratio (CHPR), ι, as a new transfer function is defined from ratio of ΔI
per and ΔI
ent.

ι = ΔI
per / ΔI
ent (1)

In this equation, the ΔI
per is the current response related to the hydrogen penetrated through metal sheet at anode (detection) side, and the ΔI
ent is the current response of cathode (entry) side. The equation (1) can be expressed by the following equation as the theoretical equations for ΔI
per and ΔI
ent were derived based on Fick's 2nd law,.

ι = 1 / K
ab exp (-h (jω / D)1 / 2) (2)

In the equation (2), K
ab is the hydrogen entry ratio against the total cathodic reaction rate, h is the thickness of metal sheet, j is imaginary number unit, and D is the hydrogen diffusion coefficient.

The simulations of ι were conducted with the equation (2) assuming arbitrary values of D. The simulation results indicated that the phase shift of ι became large with the decrease of D. The new method to determine the value of D from the phase shift of CHPR was developed.

References:

[1] J. O'M. Bockris, J. McBreen, and L. Nanis, J. Electrochem. Soc, 112, 1025 (1965).

[2] A. Komatu, A. Nishikata, T. Tsuru, Zairyo-to-kankyo, 58, 269 (2009).

[3] A. Tada, E. Nishikata, ISJ internatonal, 56, 424 (2016).

[4] K. Fushimi, M. Jin, T. Nakanishi, Y. Hasegawa, T. Kawano and M. Kimura, ECS Electrochem. Lett., 3, C21 (2014).

[5] C. Gabrielli, P. P. Grand, A. Lasia, and H. Perrot, J. Electrochem. Soc., 151, A1943 (2004).

[6] M. A. V. Devanathan and Z. Stachurski, Proc. R. Soc. Lond. Ser. A, 270, 90 (1962).

[7] M. A. Devanathan and Z. Stachurski, J. Electrochem. Soc., 111, 619 (1964).
Detection Condition to Improve the Reliabilty of Coating Flaw Detection on Pipes Buried in the Soil
Authors: Lim Bu Taek , Kim Min Gi , Kim Ki Tae , Chang Hyun Young , Kim Young Sik
Published: December 2020

Generally, indirect assessment of external corrosion of pipe has been undertaken as a 2 step process using a close interval potential survey (CIPS) performed to determine the level of cathodic polarization and a direct current voltage gradient (DCVG) survey to determine the location of coating defects on the pipes buried in the soil. Usually, two techniques are used separately, but there are several advantages to undertaking a combined CIPS and DCVG survey. However, since detection conditions depend upon the experience skill of the experts, the reliability to detect the coating flaw on pipes buried in the soil was low level. This work focused on the deduction of detection voltage to get 100% reliabilty of coating flaw detection on pipes buried in the soil. Test bed with 3 layered pipelines was constructed, and cathodic protection system was real-time monitored. The material of buried pipe was one kind of ‘polyken coated steel pipe’. The burial depths of pipes were from 1 to 3 meters and coating flaws on the pipes were intentionally formed. The effect of applied voltage on the detection reliability of coating flaw on buried pipe in soil was elucidated. The applied voltage to detect the coating flaws is dependent upon the amount of buried pipes and soil condition etc. The detection potential to get 100 % detection reliability can be calculated using the newly proposed equation. (This work was supported by the Nuclear Power Core Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20171520000350))
(Invited) New Insights into the Formation and Failure Modes of Alumina Scales
Authors: Mortazavi Anna N. , Esmaily Mohsen , Geers Christine , Sattari Mohammad , Lindgren Kristina , Malmberg Per , Babic Vedad , Panas Itai , Svensson Jan-Erik , Halvarsson Mats , Johansson Lars-Gunnar
Published: December 2020

Alloys forming external alumina scales can be used at very high temperature because of the excellent ability of alumina to protect against further reaction with the environment. Traces, ~0.1 at. %, of the so-called reactive elements (REs) are added into alumina- (and chromia-) forming alloys in order to enhance their oxidation performance. In this talk, the formation mechanism of protective alumina scales on several FeCrAl and FeNiCrAl alloys for high temperature application will be first discussed. As demostrated in our paper [1], the interaction between water and REs faciliates the formation of the ”protective” alumina scales via the formation of a nanocrystalline alumina layer with yttrium-decorated grain boundaries at the early stages of oxidation. Using state-of-the-art analytical tools such as STEM-EDXS-EELS and NanoSIMS, it has also been revealed that the water/REs interplay leads to the formation of hydride- and hydroxide-nanodomains in the alumina scale. In this context, findings of our latest research on the failure modes of alumina scales will be also presented with the emphasis on the key role of RE particle size distribution and the alloy grain orientation in the protective charactrestics of the oxide scales. Controlled high-temperature oxidation exposures in conjunction with quasi-in-situ experiments revealed that failure of the protective oxide scale occurs at specific, predictable (deterministic) sites on the alloy surface. The new undrestaning that will be discussed in this talk are expected to open up new avenues of research on the development of the next generation of high temperature alloys with superiour properties.
Internal Oxidation of High Strength Steels during Short-Term Annealing: Observation of Significant Enhancement of the Internal Oxidation in Fe-Mn-Si Ternary Alloys
Authors: Zhang Xue , Correa da Silva Caue , Rohwerder Michael
Published: December 2020

In different production steps steels are exposed for short times, from a few minutes to up to a few hours, to high temperatures, either under reducing conditions for iron (e.g. N2-H2 during recrystallization annealing) or in oxidizing environments (e.g. during hot rolling and cooling after hot rolling). These processes are accompanied by external and internal oxidation, which can affect further processing steps. For example, during cooling after hot rolling of high strength steels especially grain boundary oxidation can lead to significant problems during pickling and cold rolling. For some alloys, e.g in the Fe-Mn-Si system, a surprisingly pronounced and deep grain boundary oxidation is observed.

In this paper a fundamental investigation of grain boundary oxidation during annealing under model atmospheres simulating the oxygen partial pressure beneath the scale and also under significant lower partial pressure will be addressed, based on model alloys which are relevant to industrial high strength steel grades. The focus will be on questions such as how the different alloying elements and different annealing conditions influence the internal selective oxidation.

In order to develop a fundamental understanding, the internal oxidation of dedicated binary and ternary model alloys (Fe-Mn, Fe-Si, Fe-Mn-Si, of different composition) was investigated in depth. Besides a thorough analysis of the oxide morphology, one important focus was on monitoring the mass gain in-situ during isothermal oxidation for short term exposures of up to 2h. The partial pressure of oxygen during the experiments was kept just below the equilibrium pressure for FeO/Fe and for comparison also at much lower partial pressure. As the mass changes during internal oxidation are very low, errors from buoyancy effects in a standard set-up are in the same range as the mass change to be investigated. Hence, a novel under-pressure TG set-up was developed and applied here. Furthermore, in-operando photoelectron spectroscopy of the oxide evolution at the surface by Ambient Pressure Photoelectron Spectroscopy (APXPS) was carried out, which provided important additional information for achieving a fundamental understanding of the observed oxidation kinetics. Based on the results the enhancing effect of the combination of Si and Mn on internal oxidation will be discussed.
Oxidation and Hot Corrosion Type I of Alternative Bond Coats for SiC/SiC Ceramic Matrix Composites
Authors: König Till , Galetz Mathias C.
Published: December 2020

With the goal of increasing the combustion temperature and decreasing the weight of todays aero engines, the application of SiC/SiC ceramic matrix composites is widely investigated and first parts are in service. Besides the many advantages of SiC/SiC ceramic matrix composites, some challenges are encountered and have to be overcome to ensure a reliable operation. One of these challenges is the protection of the ceramic matrix composites from oxidation and volatilization. The oxidation of silicon carbide results in the formation of silicon dioxide, which is generally considered protective. The combustion atmosphere, however, contains water vapor and other contaminations. The water vapor results in the formation of volatile silicon hydroxide, while contaminations, like CMAS or Na2SO4, can result in spallation or an increase in oxidation rates. Also, the fiber matrix interface coatings are more prone to oxidation and need to be protected to avoid loss in mechanical properties. Therefore, a coatings system, consisting of an outer environmental barrier coating and an inner bond coat, is applied to SiC/SiC ceramic matrix composite when used in turbine engines.

Within this study alternative bond coats are developed mainly based on aluminum oxide formers, which are in itself less prone to volatilization at the designated temperature of 1200°C. The coating process is realized via chemical vapor deposition, which can coat complex parts cost effectively and without the need for a line-of-sight. The coatings provide a reservoir of the oxide forming species and therefore the oxide scale is able to heal upon crack formation or spallation. One of the developed coatings is based on an oriented aluminum nitride layer, which is in contrast to bulk AlN resistant to high temperature oxidation in humid air. The influence of the orientation and the chlorine content, which is present due to the coating procedure, on the increased oxidation resistance is investigated. Cyclic exposures are done to investigated spallation and cracking behavior due to mismatches in thermal expansion. Further, the resistance to hot corrosion type I is compared to other materials used or investigated for the hottest sections of turbine engines. The microstructure of the coatings was examined before and after the exposures using X-ray diffraction, scanning electron microscopy and electron beam microanalysis.
Influences of Farming Practices on Soil Properties and the 2-Acetyl-1-pyrroline Content of Khao Dawk Mali 105 Rice Grains
Authors: Chinachanta Kawiporn , Herrmann Laetitia , Lesueur Didier , Jongkaewwattana Sakda , Santasup Choochad , Shutsrirung Arawan
Published: December 2020

Khao Dawk Mali 105 (KDML105) is a premium fragrant rice variety and is widely grown in Thung Kula Rong Hai (TKR), northeast Thailand. In the present study, the influence of organic and conventional rice farming (ORF and CRF, respectively) in TKR farmers’ paddy fields on soil properties and their relationship with 2-acetyl-1-pyrroline (2AP) in KDML105 rice grains were investigated. The results indicated that the ORF system had a strong positive effect on major soil quality indicators and the 2AP content in the rice grains. The soil organic matter (SOM) was approximately twice as much in the ORF than in the CRF system, thus leading to much higher total nitrogen (TN), humic acid (HA), and microbial populations in the ORF system. The higher SOM in the ORF system not only enhanced the soil quality indicators but also contributed to approximately 3.5 times higher 2AP than in the CRF system. Principle component analysis indicated a close correlation among SOM, TN, HA, and microbial population under the ORF system; these variables exhibited strong correlations with the 2AP contents in KDML105 rice grains.
Prestige Goods from Élite Burials as Markers of Self-Identity and Networking of the Élites
Authors: Mordvintseva Valentina I.
Published: December 2020

The author proposes an approach to determine self-identities, boundaries, internal political organization and foreign relations of ancient societies using materials of burials of élites in the lack of representative written sources.
A Prodigy Child of the Dutch Revolt: Immediate ‘Precursors’ to Grotius on Just Revolt
Authors: Kubben Raymond
Published: December 2020

One of the odd things about Grotius’s thought is that he – advocate of a rebellious regime – was not very supportive of the right of resistance. Justifying the revolt at the time not only meant legitimizing the new regime he was serving; it also meant ruling out opposition against it. That posed an intricate puzzle; a puzzle Grotius solved by drawing on the theorizing on just revolt of the previous decades. This paper purports to show the connection between Grotius’s thought on just revolt and the intellectual and political environment in which Grotius came of age. It also sets out to show that the solution to the puzzle lies in the element of authority and the particular view taken on the constitutional position of the States in the Low Countries.1
Tales of Antifascism: International Survivors’ Organizations during the Cold War
Authors: Becker Maximilian
Published: December 2020

During the Cold War, international associations of resistance veterans were important transnational actors. Split along the political fault lines, an ‘antifascist’ stance was crucial to them, both in their memories of resistance against Nazi Germany and in their involvement in the propaganda campaigns of the Cold War. Due to its manifold activities, the pro-communist Fédération Internationale des Résistants (fir) was the most important of these international associations. Liberal and anti-communist organizations, like the Fédération Internationale Libre des Déportés et Internés de la Résistance (fildir), formed the counterpart to the fir. These organizations will serve as a point of comparison. This study transcends the prevailing national perspective, instead investigating the transnational memory of the survivors. It goes on to examine the consequences of the political changes in the ussr after Stalin’s death in March 1953, and Khrushchev’s ‘secret speech’ as well as the Hungarian Uprising and its suppression in 1956.
Students as Partners: A New Ethos for the Transformation of Teacher and Student Identities in Chinese Higher Education
Authors: Liang Yifei , Dai Kun , Matthews Kelly E.
Published: December 2020

Engaging students as partners (SaP) in teaching and learning is a growing arena of practice that shapes the mutually beneficial student-teacher relationship. Redefining student-teacher identities in pedagogical practice is one of the key implications of SaP. In the past decade, Chinese higher education institutions have paid increasing attention to student-centred pedagogies. Understanding and investigating new interpretations of student-teacher identities underpins the shift toward such pedagogical practices. In this theoretical discussion paper, based on the recent trends associated with Chinese higher education reform efforts revealed by large-scale and systematic survey results, we interrogate the concept of Chinese student-teacher identities as a learning partnership by drawing on the theorisations of SaP. Our intention is to contribute to the ongoing process of identity transformation within Chinese higher education. By calling for adapting SaP to the unique Chinese educational and cultural features, we provide a future vision for the cultivation of the teacher-student relationship.
Is the Surface Salinity Difference between the Atlantic and Indo-Pacific a Signature of the Atlantic Meridional Overturning Circulation?
Authors: Nilsson Johan , Ferreira David , Schneider Tapio , Wills Robert C. J.
Published: December 2020

The high Atlantic surface salinity has sometimes been interpreted as a signature of the Atlantic meridional overturning circulation and an associated salt advection feedback. Here, the role of oceanic and atmospheric processes for creating the surface salinity difference between the Atlantic and Indo-Pacific is examined using observations and a conceptual model. In each basin, zonally averaged data are represented in diagrams relating net evaporation and surface salinity S. The data-pair curves in the –S plane share common features in both basins. However, the slopes of the curves are generally smaller in the Atlantic than in the Indo-Pacific, indicating a weaker sensitivity of the Atlantic surface salinity to net evaporation variations. To interpret these observations, a conceptual advective–diffusive model of the upper-ocean salinity is constructed. Notably, the –S relations can be qualitatively reproduced with only meridional diffusive salt transport. In this limit, the interbasin difference in salinity is caused by the spatial structure of net evaporation, which in the Indo-Pacific oceans contains lower meridional wavenumbers that are weakly damped by the diffusive transport. The observed Atlantic –S relationship at the surface reveals no clear influence of northward advection associated with the meridional overturning circulation; however, a signature of northward advection emerges in the relationship when the salinity is vertically averaged over the upper kilometer. The results indicate that the zonal-mean near-surface salinity is shaped primarily by the spatial pattern of net evaporation and the diffusive meridional salt transport due to wind-driven gyres and mesoscale ocean eddies, rather than by salt advection within the meridional overturning circulation.