bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Properties of Li7La3Zr2O12 and Li0.33La0.57TiO3
Authors: Wolfenstine Jeffrey 
Published: February 2020

Abstract
Many new types of high energy Li batteries may require a solid Li-ion conducting electrolyte. The major requirements for the solid Li-ion electrolyte are; high Li-ion conductivity, low electronic conductivity and good chemical/electrochemical stability. However, in many applications adequate mechanical properties are also relevant. For example, an electrolyte with a high shear modulus is required to prevent dendrite penetration when using a Li anode. At present information on the mechanical properties of two new promising solid Li-ion conductors; Li7La3Zr2O12 (LLZO) and Li0.33La0.57TiO3 (LLTO) is lacking. It is therefore the purpose of this talk to present some of the first information on the room temperature mechanical behavior of high density (>98% relative density) LLZO and LLTO. These include: hardness, elastic modulus, fracture strength, fracture toughness and thermal expansion. The results will compared to existing data for other solid Li-ion conductors and theoretical predictions. In addition, the methods to improve the mechanical behavior of LLZO and LLTO while retaining high ionic conductivity will be presented.
Assessment of Factors Controlling the X-ray Penetration Depth in Studies of 4H-SiC using Monochromatic and White Beam Synchrotron X-ray Topography in Reflection Geometry
Authors: Yang Yu , Guo Jianqiu , Goue Ouloide Yannick , Wu Fangzhen , Raghothamachar Balaji , Dudley Michael 
Published: February 2020

Synchrotron X-ray Topography has been shown to be a vital tool for the nondestructive characterization of defects in 4H-SiC crystals [1-2]. Techniques utilizing reflection geometry are particularly useful for discerning defects at different depths below the crystal surface. For example, in studying defects in SiC pin diode structures, which typically comprise a buffer layer homoepitaxially grown on a substrate, with the drift layer grown on top of the buffer layer, it is important to be able to discriminate the depth at which particular defect configurations reside. This is particularly important for the characterization of defects resulting from relaxation processes such as interfacial dislocations and half loop arrays [3]. Accurate discernment of the depth of a defect requires precise measurement of the effective penetration depth of the X-ray beam in the diffraction geometry in question. This paper provides an assessment of the factors controlling that penetration depth in grazing incidence, reflection and back reflection geometries. There are generally two approaches adopted depending of the level of perfection of the crystal. In deformed regions (such as around dislocation cores) the penetration depth is simply determined by photoelectric absorption. In perfect regions it is determined by extinction. We will present a comparison between measured penetration depths in various diffraction geometries with those calculated using these two approaches and develop an optimized model to explain our observations.
[1] Muller, G.S., et al., Volume production of high quality SiC substrates and epitaxial layers: Defect trends and device applications. Journal of Crystal Growth, 2012. 352(1): p. 39-42.
[2] Dudley, M., et al., Characterization of 100 mm diameter 4H-Silicon carbide crystals with extremely low basal plane dislocation density, Material Science Forum,2001. 65: p. 353-356.
[3] Wang, H., Dudley, M., et al., Studies of the Origins of Half-Loop Arrays and Interfacial Dislocations Observed in Homoepitaxial Layers of 4H-SiC. Journal of Electronic Materials, 2015. 44(5): p. 1268-1274
(Invited) Semiconductor/Oxide Composite Nanowires Supplying White Luminescence
Authors: Ishikawa Fumitaro , Yamamoto Naoki 
Published: February 2020

Integration of semiconductor and oxides within a monolithically synthesized nanowire system would have strong potential for the future functional devices. We then challenge to fabricate semiconductor/oxide heterostructure nanowire with molecular beam epitaxy combined with wet-oxidation of compound semiconductor heterostructure system.
We fabricate oxide heterostructure nanowire by selective wet oxidation of GaAs/AlGaAs core-shell type nanowire grown on Si substrate. Applying adequate oxidation condition, we obtain GaAs/AlGaOx semiconductor-oxide composite nanowire as illustrated in the Figure. At an adequate condition, the shell AlGaAs was selectively oxidized but the core GaAs remained sue to its large contrast of oxidation rate.
The figure also shows the result of cathodoluminescence measurement on the sample. The contrast in the NW (the panchromatic CL image) reflects the core-shell structure of the NWs. The spectrum acquired from the 1×1μm2 area involving the NW is also shown in the figure. The spectrum exhibits a sharp peak at 340 nm and a broad peak extending from approximately 400 nm to 700 nm, probably constituting several overlapped peaks. This spectrum is similar to previously reported spectra of Al2O3 nanoparticles. As seen in the figure, the shell layer emitted strong luminescence at 342 nm and 423 nm. Furthermore, the observed emissions were localized, in consistence with luminescence sourced from nanostructured oxides. This suggests the formation of shell oxides with luminescent properties. The observed spectral range varies from violet to a green-yellow regime, possibly reflecting the different arrangements of molecules responsible for the luminescence. In our case, luminescence is observed from ultraviolet (300 nm) to near infrared (700 nm) wavelengths, including the broadened tail of the spectrum.[1] This broad white luminescence might be sourced from the small Ga constituent within the amorphous AlGaOx shell and the wide nanoscale particle size distribution of the shell.
[1] H. Hibi, M. Yamaguchi, N. Yamamoto, and F. lshikawa, Nano Lett. 14, 7024, 2014.

Figure 1
Design of Supported PtCo Electrocatalysts for Pemfcs
Authors: Stassi Alessandro , Gatto Irene , Saccà Ada , Patti Assunta , Monforte Giuseppe , Baglio Vincenzo , Aricò Antonino S. 
Published: February 2020

Pt-alloy electrocatalysts have been investigated for operation in both hydrogen and methanol-fed polymer electrolyte membrane (PEM) fuel cells with the aim of evaluating their performance and resistance to degradation. Nanosized PtCo catalysts with particle size of about 3 nm were prepared by using a sulphite complex route [1-4]. To achieve a high degree of alloying a carbothermal reduction was used. This caused the occurrence of a primitive cubic ordered structure. The surface properties were investigated by X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectroscopy (LE-ISS, 3He+ at 1kV). The formation of a Pt skin layer on the surface of the alloy electro-catalyst was studied. Oxide supports were evaluated as alternative to carbon black materials with the aim to increase the electrochemical stability. The structural and surface characteristics of the samples as well as the type of catalyst support appear to strongly influence the PtCo catalyst performance and degradation.

References

[1] Aricò, A.S., Stassi, A., Modica, E., Ornelas, R., Gatto, I., Passalacqua, E., Antonucci, V.
Performance and degradation of high temperature polymer electrolyte fuel cell catalysts
Journal of Power Sources, (2008) 178 (2), pp. 525-536.
[2] Aricò, A.S., Stassi, A., Gatto, I., Monforte, Passalacqua, E., Antonucci, V.
Surface Properties of Pt and PtCo Electrocatalysts and Their Influence on the Performance and Degradation of High-Temperature Polymer Electrolyte Fuel Cells,
J. Phys. Chem. C (2010), 114, 15823–15836.
[3] Baglio, V., D'Urso, C., Sebastián, D., Stassi, A., Aricò, A.S.
PtCo catalyst with modulated surface characteristics for the cathode of direct methanol fuel cells
(2014) International Journal of Hydrogen Energy, 39 (10), pp. 5399-5405.
[4] Stassi, A., Gatto, I., Baglio, V., Passalacqua, E., Aricò, A.S.
Oxide-supported PtCo alloy catalyst for intermediate temperature polymer electrolyte fuel cells
(2013) Applied Catalysis B: Environmental, 142-143, pp. 15-24.

Acknowledgement

The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2011-2014) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement Impact n° 303452.
Molecular Engineering of Ion-Conducting Polymers for Fuel Cell Membrane Applications
Authors: Lee Woo-Hyung , Mohanty Angela D , Bae Chulsung 
Published: February 2020

Ion-conducting polymer membranes (cation exchange and anion exchange) are a key component in clean energy conversion devices (e.g., fuel cells and water electrolysis). For example, perfluorinated sulfonic acid polymers such as Nafion are state-of-the-art proton-conducting polymers, but they suffer from high cost, mediocre mechanical strength, and moderate operation temperature. Thus, it is highly desirable to develop readily tunable, high-performance ion-conducting membranes based on low-cost hydrocarbon polymers.
Over the years we have developed a novel polymer functionalization method that allows incorporation of a variety of ionic groups to aromatic polymers. Using the method we synthesized highly proton-conductive fuel cell membranes containing sulfonate groups with different acidity strengths (fluoroalkylsulfonic, arylsulfonic, and alkylsulfonic acid groups) [1-2]. The effect of these different sulfonate groups of polymers on proton transport properties and fuel cell performance will be discussed.
Recently, anion exchange membrane fuel cells (AEMFCs) have gained significant attention because they can efficiently and cleanly convert the chemical energy stored in fuels directly into electrical energy [3]. Since AEMFCs utilize a solid alkaline electrolyte [i.e. anion exchange membrane (AEM)] to transport hydroxide anions, they can avoid issues previously faced with the concentrated aqueous KOH electrolyte in alkaline fuel cells. However, significant shortcomings still remain in AEMFCs such as poor long-term alkaline stability and low hydroxide conductivity. In our continued effort to develop robust, high performance ion-conducting polymers, we prepared styrene-ethylene/butylene-styrene (SEBS)-based AEM materials bearing various ammonium-cation groups. Utilizing our groups’ recently developed metal-catalyzed synthetic strategy, involving C-H borylation followed by Suzuki coupling [4], we successfully introduced chemically stable ammonium-cation species to the aromatic units of SEBS. The synthesis, hydroxide transport properties, alkaline stability, and fuel cell performance of these SEBS-based AEMs will be presented.

References:

[1] Y. Chang, G. F. Brunello, J. Fuller, M. Hawley, Y. S. Kim, M. Disabb-Miller, M. A. Hickner, S. S. Jang, C. Bae, Macromolecules
2011, 44, 8458–8469.
[2] Y. Chang, G. F. Brunello, J. Fuller, M. Disabb-Miller, M. Hawley, Y. S. Kim, M. A. Hickner, S. S. Jang, C. Bae, Polym. Chem.
2013, 4, 272–281
[3] G. Couture, A. Alaaeddine, F. Boschet, and B. Ameduri, Prog. Polym. Sci.,
2011, 36, 1521–1557.
[4] A. D. Mohanty, Y. –B. Lee, Liang, Zhu, M. A. Hickner, C. Bae, Macromolecules, 2014, 47, 1973–1980.
Fast X-Ray Tomographic Imaging: Investigation of Freezing Mechanisms in PEFC during Sub-Zero Start-Ups
Authors: Mayrhuber Immanuel , Marone Federica , Stampanoni Marco , Schmidt Thomas J. , Büchi Felix N 
Published: February 2020

Starting from subfreezing temperatures is a challenge for polymer electrolyte fuel cells. The product water removal is a problem since ice may form, limiting the gas transport in gas diffusion and catalyst layers.
X-ray tomographic imaging is used to investigate the liquid/solid water phase in the GDL and to deduce information on the mechanism of freezing of the water, which induces a performance drop during freeze starts of PEFC. As freeze starts are transient processes tomographic imaging is tuned for fast acquisition while conserving acceptable image quality. Tomographic scans of 4.9 s are recorded.
As freezing of the super-cooled water is a temperature dependent nucleation process [1,2], the time to freezing of the super-cooled water depends on the cell temperature. The figure shows an isothermal freezing experiment with X-ray imaging and a slice through the tomographic scan of the cathode GDL 30 s before performance drop.
[1] Y. Ishikawa, et al., J. Power Sources, 179 (2008), pp. 547-552
[2] T.J. Dursch, et al., Langmuir 28, (2012), pp 1222-1234
Different freezing mechanisms are observed. At low temperatures (i.e. -20 °C) and low current density no water is observed in the GDL. The product water seems to freeze instantly in the catalyst layer (CL) which leads to a slow performance drop with filling of the CL with ice. At the same low temperatures, but higher current densities super-cooled liquid water emerges from the CL and fills part of the macro-porous gas diffusion layer and even penetrates into the channel. In this case the freezing dynamics are different: as long as the water remains liquid, operation continues. Then all water freezes instantly at the same time and operation stops abruptly.

Figure 1
Progress Towards Commercial Solid Hydrogen Storage Systems
Authors: Fisher Allison M , Bennington Stephen 
Published: February 2020

Cella Energy has developed an ammonia borane-poly(ethylene oxide) solid hydrogen storage fuel that is being demonstrated as a lightweight high-performance replacement for batteries in a number of premium markets such as powering unmanned aerial vehicles. Cella’s technology will be suitable for the high energy requirements of “green/electric aircraft” replacing carbon fuels for powering on-board systems with a safety factor that exceeds the capability of compressed hydrogen.
Development of a viable hydrogen storage system will overcome a critical barrier for the widespread commercialization of hydrogen and fuel cells technologies, an emerging renewable, clean energy industry with potential for growth in stationary, portable, and transportation areas. One of the most promising approaches to achieve high energy density system goals is to store hydrogen as a solid chemical hydride and release the hydrogen thermally, ideally between 80-150°C. The process by which the solid hydrogen fuel will be used is conceptually easy: the fuel is packaged as discrete “pellets” that are in contact with an ignition element such as a heater, insulated, and packed into a cartridge-type container. Combined with the appropriate electronic controls and filters, this is a hydrogen storage fuel system.
Several challenges impact the success of these systems significantly. Simply put, in addition to hydrogen, all solid hydrogen fuels release some quantity of toxic impurities on heating, and many fuels expand rapidly and considerably while releasing a large quantity of heat, which imparts mechanical stress on packaging, among other issues. In addition, some volatiles are able to oligomerize in the gas phase, which means that if not trapped before leaving the hydrogen fuel cartridge then there is high probability of clogging fuel lines to the fuel cell based energy conversion system, as well as contamination of the fuel cell stack. This presentation will present an overview of Cella’s efforts to develop solid hydrogen fuel systems, as well as active R&D efforts to understand and optimize solid hydrogen material properties for safe storage and dehydrogenation when fuel is needed.
Platinum Deposited on Boron Doped Diamond Nanoparticles By the Rotating Disc Slurry Electrode (RoDSE) As a Catalyst for Alkaline Fuel Cell
Authors: Acevedo Raul , Cabrera Carlos R 
Published: February 2020

Platinum deposited on boron doped diamond is a robust material for use as an electrode. In this work platinum is deposited on boron doped diamond by a method developed in the laboratory, the Rotating Disc Slurry Electrode (RoDSE).
The synthesized catalyst was characterized by Raman spectroscopy, xray diffraction, transmission electron microscopy, cyclic voltammetry and chronoamperometry in a half cell. The catalyst was used in the anode side of a membrane electrode assembly (MEA) of a direct alkaline fuel cell where power density curves were obtained for hydrogen and ammonia on the anode side, oxygen was used on the cathode side.
Effects of Functionalize Carbon Nanofibers Supported Catalysts on Oxygen Reduction Reaction in Alkaline Medium
Authors: Huang Wenjiao , Ahlfield John M. , Kohl Paul A , Zhang Xinsheng 
Published: February 2020

Fuel cells are attractive because they provide clean and efficient energy for stationary and portable applications. Among the various types of fuel cells, the proton-exchange membrane fuel cells (PEMFC) have a high energy density and a fast start-up, but the cost of noble-metal catalysts and perfluorinated membranes is high. Anion-exchange membrane fuel cells (AEMFC) are attractive because they have enhanced the oxygen reduction and methanol oxidation kinetics at high pH, which makes the use of non-noble catalysts possible.
Carbon nanofibers (CNFs) have outstanding structural, mechanical and electrical properties, and are widely used as catalyst supports in fuel cells. CNFs are also considered to be good material for the oxygen reduction reaction catalysts in alkaline fuel cells because of their high surface area, thermal stability and electrical conductivity.
In this work, we use CNFs as the support for fuel cell catalysts in hybrid fuel cells, which combine alkaline and acidic conditions at the different electrodes. Functional groups were added onto the CNFs, including carboxyl groups (CNF-OX), carbonyl groups (CNF-CO), hydroxyl groups (CNF-OH) and nitrogen-containing groups (CNF-ON). In previous studies, they were tested them in half-cell experiments and it was found that the catalysts supported on CNF-ON have high ORR activity. The CNF-ON electrodes can change the ORR from the two-electron pathway to the four-electron pathway. Pt/CNFs have been tested in hybrid fuel cell and compared with Pt/C.
Gas Crossover in Polymer Electrolyte Membranes
Authors: Jung Aeri , Kim Min Soo 
Published: February 2020

The polymer electrolyte membrane fuel cell system has received a considerable attention as one of powerful candidates for the next generation power sources. Numerous studies have been carried out to develop good performance and high durability systems with PEM fuel cells. As a result, several solutions to enhance the operating characteristics have been formed; however, durability of the system is still required to be improved.
As the durability of the system emerges as one of the critical problem, understanding the degradation mechanism in the fuel cell system is the key step for a better system design. Gas crossover has a great influence on the degradation of the membrane electrode assembly. Thus, it is essential to investigate the crossover of related gases through the membrane gas crossover has a negative effect not only on the performance but also on the durability of the system.
In this study, the novel detecting technique to measure accurate gas crossover rate and the effect of various parameters on gas crossover with different gases are investigated experimentally. Experiments are performed with the unit cell which has active area of 25 cm2 with four flow channels. To distinguish the effect of the specific parameter, it is controlled separately in the experimental setup. For measuring the gas crossover rate, mass spectrometer is used in this experiment. Consequently, the effects of temperature, relative humidity condition, hydrogen pressure, and membrane thickness on gas crossover rate in PEM fuel cells are investigated.
Investigation of Durability of MEAs at Higher Temperature
Authors: Kitamura Masahiko , Noda Zhiyun , Matsuda Junko , Hayashi Akari , Sasaki Kazunari 
Published: February 2020

PEFCs recently attract much more attention owing to the commercialization of fuel cell vehicles (FCVs). We are interested in the operation of PEFC at high temperature to improve overvoltage loss of reactions occurring in PEFC. In this study, extracting problems on catalytic degradation at higher temperature is particularly focused on, and then durability of MEAs at 105 °C is considered.
MEAs were prepared using standard catalyst and electrolyte, Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.) and Nafion. For obtained MEAs, current-voltage (IV) performance and durability were studied. Regarding to durability evaluation, two protocols[1] recommended by Fuel Cell Commercialization of Japan (FCCJ), “load cycles” and “start-stop cycles”, were in use. Three different conditions of operation temperature and humidity (80 °C/RH100%, 105 °C/RH57%, and 80 °C/RH57%) were applied.
Regarding to durability analyses using “start-stop cycles”,[2] the increased loss of IV performance was clearly observed at 105 °C/RH57%. To understand degradation mechanism, the structure change of cathode layers was evaluated using FIB-SEM. The cathode layers became thinner in all the cases, but the condition of 105 °C/RH57% led to the thinnest layer. By further three-dimensional evaluation of cathode layers, increased size of pores constructing the catalyst layer was observed. The condition of 105 °C/RH57% resulted in formation of large pores especially near the Nafion membrane. Therefore, we believe such large pore formation derived by carbon corrosion led to collapsing and finally thinning the cathode layer.
On evaluation of “load cycles” durability tests, the operation at 105 °C/RH57% resulted in lower durability than that at 80 °C/RH100%. However, the difference was much smaller comparing to the case in “stop-start cycles”. Regarding to Pt size evaluated by SEM (Figure 1), the size increase of Pt particles was more pronounced in the case of 80 °C/RH100%. The reason most likely comes from enhanced Pt growth under the higher water content. Thus, the decreased IV performance at 105 °C/RH57% involves additional factors such as Nafion degradation at the low humidity condition.
Possible degradation mechanism using two different durability protocols is discussed with macrostructure change in cathode layers.
Reference
[1] A. Ohma et al., ECS Trans, 41(2011) 755.
[2] M. Kitamura et al., ECS Trans, 64 (2014) 755.

Figure 1
Study of Ionomer Adsorption on Carbon Supported Pt Catalyst By the Quartz-Crystal Microbalance (QCM) Method
Authors: Okuyama Takumi , Kinoshita Shinji , Tanuma Toshihiro 
Published: February 2020

In polymer electrolyte fuel cells, the three-phase interface in a catalyst layer (CL) is considered to be very important as the electrochemical reaction site. The CL is typically formed using a dispersion of carbon supported platinum catalyst (Pt/C) and ionomer, and the interaction between the ionomer and Pt/C particles probably has an impact on the platinum utilization in the electrode and the dispersion stability.
In this study, we focused on the adsorptive property of ionomers onto the Pt/C surface. The amount of adsorbed ionomer on a Pt/C catalyst was measured using the quartz-crystal microbalance (QCM) method. The amount was used as an index of the affinity of the ionomer for the Pt/C catalyst surface.
The Pt/C catalyst particles were immobilized on a QCM sensor. The catalyst-immobilized sensor was placed into a solvent, and was left for a while until the QCM oscillation stabilized. An ionomer solution was then added drop-wise into the QCM cell. The change in resonance frequency of the quatz-crystal before and after adding the ionomer dispersion was recorded. The amount of a perfluorosulfonic acid polymer, Flemion® (Asahi Glass), adsorbed on the Pt/C catalyst surface is plotted against the concentration of the ionomer dispersion in Fig.. The amount was calculated based on the change in the resonance frequency of the QCM sensor. It shows the higher the ionomer concentration, the more ionomer was adsorbed. The relationship between the adsorptive property of various ionomers will be discussed in terms of their chemical properties (IEC, chemical structure etc.). The viscoelastic character of the adsorbed ionomer layers will also be described.

Figure 1