bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Sulfur-Melt Infiltration into Electrospun Carbon Nanofibers As Cathodes for Room Temperature Na-S Batteries
Authors: Singh Arvinder , Dillard Caitlin , Kalra Vibha 
Published: February 2020

Room temperature sodium–sulfur (RT Na–S) batteries are gaining attention as an alternative to lithium batteries due to natural abundance and relatively low cost of sodium. Although the cell chemistry of RT Na-S batteries is similar to that of Li-S batteries, Na-based batteries are more challenging due to the larger Na+ ions that results in greater volume expansion and slower kinetics during the charge-discharge processes. This, in turn, leads to shorter cycle life, lower power density and lower sulfur utilization compared to Li-based batteries. Notable progress has been made in the last few years to overcome the aforesaid issues by utilizing various carbon hosts for sulfur such as the multiwall carbon nanotubes, hollow carbon, carbon nanofibers and microporous carbon. However, the powder-based carbon/sulfur (insulating) materials are blended together with binders and conducting additives into a slurry with little control on morphology, which ultimately results in discontinuity in the electron transporting network and low sulfur loading in the final cathodes.
Here, we report a novel approach to develop carbon nanofibers (CNFs)/sulfur cathodes using a rapid sulfur melt-diffusion process (~5 seconds). Rapid impregnation of sulfur into free-standing carbon mats eliminates the use of additional components (binders, current collectors and conducting additives) and other time consuming infiltration processes. It is important to mention that rapid melt infiltration approach used here allows precise control of any sulfur loading regardless of the host matrix and can be used for developing high performance sulfur cathodes. Carbon nanofibers (CNFs) used in the present work are produced by electrospinning polyacrylonitrile/dimethylformamide gel and subsequently carbonizing at 1000°C. CR2032 coin cells were assembled using Na metal as anode, 30µL electrolyte (1.5M NaClO4 and 0.3M NaNO3 in tetraethylene glycol dimethyl ether) and as-prepared free-standing CNFs/sulfur cathodes with ~50 wt% (~0.85 mg/cm2) sulfur loading. These cells were cycled at C/5 rate (1C = 1675 mAh g-1) after conditioning 1st cycle at C/10 rate. The initial discharge capacity was ~231 mAh g-1 at C/5 rate, which reduced to ~137 mAh g-1after 20 cycles. The obtained results are comparable to those reported earlier for room temperature Na-S batteries. Electrochemical performance evaluation of CNFs/sulfur cathodes with higher sulfur loading is under investigation.

Figure 1
Using X-Ray Diffraction and Imaging for the Investigation of Battery Materials: From Bulk Structural Characterization to in Situ and in Operando Measurements
Authors: Masiello Fabio , Nenert Gwilherm , Speakman Scott , Quinn Julie , Sommariva Marco , Gateshki Milen 
Published: February 2020

X-ray diffraction and scattering are powerful tools for the study of battery materials.
We describe here X-ray methods which allows the researcher to combine multiple X-ray techniques to obtain a wealth of information about new materials used in battery applications.
By using X-ray diffraction it is possible to identify the different crystallographic phases and quantify the amount of each phase in the bulk material. Moreover, with the Rietveld method it is possible to refine the crystallographic structures of the different materials.
It is also possible to study the battery in situ and in operando. This can be done either in reflection geometry or in transmission geometry. In order to perform the measurement in transmission geometry, more penetrating radiation is required, e.g. Mo or Ag radiation. A newly developed X-ray detector allows for shorter measurement time and/or better quality data thanks to the higher efficiency of the CdTe sensor material.
Polyvinylidene Fluoride Derived Carbon As High Performance Anode Material for Lithium Ion Batteries
Authors: Suresh Mamidi , Gopalakrishna Karthik Mamandur , Sharma Chandra Shekhar 
Published: February 2020

Introduction

Polyvinylidene fluoride (PVDF) is a fluoropolymer which consists of vinylidene fluoride as a monomer. Conventionally, it is widely used material in electrode preparation as a binder between active carbon material and the current collector. However in this work, we propose the use of PVDF as a polymer precursor to carbon. In literature, PVDF was used as precursor for carbon with ~20% yield.1 However, this yield was increased to ~70% by dehydrofluorination of PVDF prior to pyrolysis.2,3

In our present work, we first carried out dehydrofluorination followed by pyrolysis at different temperatures (900, 1200 and 1400 ⁰C respectively) to obtain the hard carbon as characterization by field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. Later, electrochemical performance of these hard carbons pyrolyzed at different pyrolysis temperature was investigated at different current densities.

Experimental Section:

PVDF powder was dehydrofluorinated in NaOH and Tetra-n-butylammoniumbromide solution. Dehydrofluorinated powder was pyrolyzed in inert atmosphere at different final pyrolysis temperature. Slurry made of this carbon was coated over stainless steel foil and dried for 12 h in a vacuum oven prior to cell packing in argon atmosphere glove box. Electrochemical performance was studied using glavanostat/potentiostat.

Results and discussions:

Figure 1: (a,b) HRTEM images of CDI-1400 at different magnifications; (c) Comparison of cycling behaviour at 0.1 C rate for carbonized samples for different temperature
TEM images (Figure 1a and 1b) clearly reveals that particle size is 290 nm and inside the each spherical particle, there are disordered areas consists of randomly arranged smaller crystallites of graphene. From this, we can conclude that carbon derived from PVDF precursor is a hard carbon.
From Figure 1c, we observe that the sample pyrolyzed at 1400 ⁰C exhibited higher reversible capacity (297 mAh/g) than the other two samples (pyrolyzed at 900 ⁰C and 1200 ⁰C) after 11 cycles of charge-discharge at 0.1 C rate. The coulombic efficiency was found to be more than 94 % after 11 cycles for all three samples. A detailed analysis on dehydroflorination and charge discharge experiments at different current densities will be presented at conference. Cyclic voltammetry and impedance studies will also be presented to support the cyclic stability and capacity retention values.

References:

1. T. Zheng et al.,
Electrochem. Soc.
142, 2581–2590 (1995)
2. Jatuphorn et al., Journal of Metals, Materials and Minerals. 18, 57-62, (2008).

3. Seok-Min Hong et al., RSC Adv.
4
,58956-58963 (2014).

Figure 1
(Invited) Use of Support-Free Amines to Isolate Larger Cage Endohedral Metallofullerenes
Authors: Stevenson Steven , Thompson Hannah R. , Kirkhorn Amelia , Budd Sarah K , Kime Brittany L 
Published: February 2020

Many publications exist for C80 endohedral metallofullerenes (e.g., M3N@C80), but there is little research on larger metallofullerene cages, such as M3N@C88-C112 and M3C98-C102. Our goal is to isolate these larger endohedrals from complex extracts via chemical selectivity. We seek to replace our earlier use of reactive amines that were immobilized on silica gel. Finding a support-free amine with water-soluble groups would remove the need to synthesize aminosilica and save the expenses of chemicals and time. In this presentation, we discuss the feasibility of using amino alcohols as selective reagents. With this approach, we can either chemically isolate a larger cage endohedral (M3N@C88) or delay the use of HPLC by injecting only highly enriched samples obtained from our chemical purification.
Template Effects of Tetrakis(thiadiazole)Porphyrazine to the Structures of Phthalocyanine Thin Films
Authors: Awaga Kunio , Eguchi Keitaro , Heutz Sandrine 
Published: February 2020

Molecular templating is an attractive method to improve the crystallinity of organic thin films and control the molecular orientations in them. Here, we report on the templating effects of an organic n-type semiconductor, tetrakis(thiadiazole)porphyrazine (H2TTDPz), on the structure and optical absorption of a p-type semiconductor, copper phthalocyanine (CuPc). X-ray diffraction measurements for the double layer thin films, CuPc/H2TTDPz, indicate a flat-on structure of CuPc, which is copied by the structure of the H2TTDPz thin films, in spite of that the CuPc thin films usually form edge-on type thin films. The optical absorption measurements show new low-energy transitions in the templated CuPc films.
Hexaphenylbenzene and Hexabenzocoronene Porphyrin Conjugates
Authors: Jux Norbert , Lungerich Dominik , Martin Max 
Published: February 2020

We will present the synthesis, characterization, and properties of some novel hexaphenylbenzene-substituted porphyrins. The oxidation to hexabenzocoronene conjugates will be discussed as well.[1-3]

References

[1] J. M. Englert, J. Malig, V. A. Zamolo, A. Hirsch, N. Jux, Chem. Commun. 2013, 49, 4827 – 4829.
[2] D. Lungerich, J. F. Hitzenberger, M. Marcia, F. Hampel, T. Drewello, N. Jux, Angew. Chem. Int. Ed..
2014,
53, 12231-12235.
[3] D. Lungerich, J. F. Hitzenberger, W. Donaubauer, T. Drewello, N. Jux, Chem. Eur. J. 2016, 22, 16755-16759.

Figure 1
Mediating Charge Shift Reactions in Electron Transport Chains
Authors: Guldi Dirk M. 
Published: February 2020

In Nature, energy and electron transfer processes in the photosynthetic machinery following light absorption have been perfectionated. To mimic the aforementioned, that is, efficiently utilizing light to separate charges and, in turn, to generate solar fuels, a great variety of multicomponent artificial photosynthetic systems have been designed and synthesized. Incentives for the design build around molecules have been taken from Nature: For example, implementing suitable electrochemical gradients across arrays of several molecular building blocks have enabled the unidirectional transformation of solar energy into electrical energy. A key parameter is the right balance between the reduction / oxidation strengths of the individual building blocks and their spatial arrangements. Both affect the thermodynamic driving forces for each step and, in turn, the overall efficiency. Notably, acceptor-donor1-donor2 or acceptor-donor1-donor2-donor3 types of artificial photosynthetic systems have been reported. Besides an initial charge transfer, charge shifts take place via oxidative electron transfers from donor1 to donor2 and, eventually, to donor3.
Considering the effectiveness of multicomponent systems, in which photoexcitation triggers a cascade of short range electron transfers, we report on two sets of novel multicomponent DA1A2s – Figure 2. These DA1A2 types feature electron transport chains with C60 and C70 of different electron acceptor strengths to create an electrochemical gradient. As a complement to electron accepting C60 / C70 either zinc porphyrins (ZnP) and zinc phthalocyanines (ZnPc) were employed. The motivation for our pump-probe investigations was to establish the role of ZnPc or ZnP as light harvester and electron donor to power unidirectional (reductive) charge shift reactions along a variety of electron transport chains.
In summary, we will demonstrate the control over unidirectional charge shift along electron transport chains en route towards highly energetic, long-lived charge separated states. Key is, however, a charge shift mediating state, whose relative energy determines the overall efficiency. If the energy of the mediating state, on one hand, is higher than the charge separated state, resonance conditions enable efficiencies as high as 50%. If the energy, on the other hand, is lower than the charge separated state, deactivation to the ground state limits the efficiency to 10%.
Some Extensions of the Galvele Approach to Localized Corrosion, Including the Effect of Cation Complexation
Authors: Nguyen Van Anh Thi , Ghaznavi Mahmoudreza , Carcea Anatolie G , Newman Roger C. 
Published: February 2020

Analytical and numerical modeling have been used to extend the understanding of pitting corrosion in a one-dimensional geometry. The approach is based on that of Galvele [1] and later experimental studies that supported many of Galvele’s findings [2], but with more detail and new features. We have examined both ideal solutions, and non-ideal solutions where the diffusivity (D) is a function of concentration (c) for any species, as well as cation complexation by chloride.
The essential result that Galvele obtained was:
Epit = A – B log [NaCl],
where Epit is the pitting potential and B should be 0.059 V at 298 K.
Laycock and Newman [2] clarified that the quantity A contained the kinetics of the anodic dissolution reaction, and defined a quantity that they called the transition potential, ET, which is the potential where the anodic current density i becomes equal to the anodic limiting current density, iL.
The origin of Galvele’s equation is an analytical solution of the governing reaction-transport equation (Nernst-Planck equation) considering an unreacting ion such as Cl-. In this solution, as refined by Newman [3], the second term in Galvele’s equation is the IR drop in the pit at the limiting current density iL. Importantly, iL depends on [NaCl] because the contribution of migration to the outward flux of dissolved metal cations increases as [NaCl] decreases.
In the present work, we have examined the following refinements, with the following preliminary outcomes:

The variation of B with [NaCl] – B is constant at 0.059 V over a certain range of [NaCl], but decreases at high [NaCl]. This is easily understood physically. At low [NaCl] there appear to be small deviations from 0.059 V that are still under investigation.

The effect of introducing a D(c) – this turned out to be an intriguing area of study, and new results will be presented at the meeting. Briefly, the effect of varying diffusivity is not as great as might be assumed.

Cation complexation – this is the latest aspect to be investigated. Changes in B with complexation are expected. Such changes may explain the different empirical values of B found in different materials including stainless steels.
References:

Jose R. Galvele, Transport Processes and the Mechanism of Pitting of Metals. J. Electrochem. Soc., 1976, 123(4), 464-474.

N.J. Laycock, R.C. Newman, Localised Dissolution Kinetics, Salt Films and Pitting Potentials. Corrosion Science, 1997, 39(10-11), 1771-1790.

R.C. Newman, Pitting Corrosion of Metals, The Electrochemical Society Interface, 2010, 19(1), 33-38.
Corrosion Performance of New Composite Coatings Onto Carbon Steel By Electrochemical Methods
Authors: Branzoi Florina , Branzoi Viorel , Pahom Zoia 
Published: February 2020

In this study, cyclic voltammetry, galvanostatic and potentiostatic electrodeposition mode was used for the synthesis of new composite (Ppy-AOT/PNEA) coatings onto carbon steel of type OLC 45 for corrosion protection.
monolayer poly (N, ethylaniline) (PNEA), polypyrrole (Ppy), and bilayer PNDMA/ Ppy-AOT and Ppy-SDS/PNDMA coatings have been electropolymerization on carbon steel by cyclic voltammetry, galvanostatic and potentiostatic synthesis techniques from aqueous solutions 0.1 M N, ethylaniline, 0.1M pyrrole, 0.01 M dioctyl sulfosuccinate sodium (AOT) and 0.1 M, 0.3 M and 0.5M oxalic acid. In order to include dioctyl sulfosuccinateions as dopant in the polypyrrole, AOT was also added to the polymerization solution of polypyrrole. Characterization of monolayer and bilayer polymer coatings was carried out by cyclic voltammetry, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) techniques. Corrosion behaviour of PNEA-AOT/PPY coated carbon steel of type OLC 45 was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in 1 M H2SO4 and 1M HCl solutions. The results of the corrosion tests showed that PNEA/PPY-AOT coatings ensure good corrosion protection of carbon steel OLC 45 in aggressive media. Bilayer coatings revealed better corrosion protection efficiencies than monolayer coatings. The new nanocomposite realized by this method is promising and might lead to industrial applications in the protection of the carbon steel substrates against corrosion
The corrosion protection efficiency follows the order: OLC 45/PNEA/PPY-AOT > OLC 45/PPY-AOT/PNEA > OLC 45/PPY- AOT > OLC 45/PNEA because the presence of these coatings causes a significant decrease in corrosion rate.

Keywords: nanocomposite films, electrochemical electrodeposition method, corrosion protection, SEM, EIS, FT-IR
(Invited) Novel Dilute Nitride III/V-Semiconductor Laser System for the Monolithic Integration to Si-Micro- and Nanoelectronics
Authors: Ludewig Peter , Volk Michael , Volz Kerstin , Stolz Wolfgang 
Published: February 2020

In recent years the class of dilute nitride III/V-semiconductors and corresponding heterostructures are gaining increasing interest both from fundamental as well as applied point of view. This is caused by their unique optoelectronic properties and in particular by the novel conduction band formation process leading to an extreme band gap bowing with increasing N-content in the crystal.
The novel material system Ga(NAsP) can be grown lattice-matched to (001) Si-substrate. The incorporation of N in the Ga(NAsP)-material allows for a significant reduction in the lattice constant, which leads on one side to a dislocation free deposition. On the other side the specific conduction band formation process in these materials is used to realize a direct band gap semiconductor. By applying a variety of physical investigation techniques the high crystalline quality as well as the direct band gap character of the novel Ga(NAsP)-material system have been verified. Ga(NAsP)/(BGa)(AsP)-MQWH were grown on exactly oriented (001) Si substrates embedded in thick (BGa)P separate confinement hetero-layers by metalorganic vapour phase epitaxy (MOVPE). The optoelectronic properties and first lasing characteristics of Ga(NAsP)-MQWH on (001) Si-substrate will be presented and possible integration concepts with Si-CMOS-based micro- and nanoelectronics will be discussed.
(Invited) Electronics in Flatland
Authors: Banerjee Sanjay K 
Published: February 2020

2D materials such as graphene, transition metal dichalcogenides and topological insulators have opened up avenues in beyond-CMOS device concepts. We will discuss our work involving single or many-particle 2D-2D tunneling, leading to transistors with negative differential resistance. We also explore spintronics in these systems for novel logic and memory devices. We will also discuss the use of these materials in less esoteric, but more practical high frequency, mechanically flexible FETs for IoT applications.
The work was done in collaboration with H.Movva, A.Sanne, A.Rai, S.Kang, C.Corbet, R.Ghosh, A.Roy, B.Ghosh, S.Majumder, D.Akinwande, E.Tutuc and L.F.Register
Effect of Resistive Switching-Layer Oxygen-Concentration on Nonvolatile Memory Characteristics for Carbon-Oxide Based Reram
Authors: Jin Soo-Min , Kwon Ki-Hyun , Kim Dong Won , Kim Hye-Jee , Kim Do Jun , Park Jea-Gun 
Published: February 2020

Resistive random access memories (ReRAM) are highly promising as one of next-generation memories due to high current density, high speed, simple structure, and low power consumption [1]. Recently, amorphous carbon oxide based ReRAM has been researched due to its strong advantages over typical ReRAM chacacteristics such as large memory margin (Ion/Ioff
> 100), high switching speed (20~50ns) and CMOS compatible process. In this work, we present the electrical features of amorphous carbon oxide, working as a resistive switching layer [2], where tunsten (W) / amorphous carbon oxide / platinum (Pt) configuration with the pattern size of ranging 34 to 1,921 nm. The thickness of carbon oxide, O2 flow rate of RF magnetron sputter, and N2-annealing temperature were varied with the device cell size to optimize the device performance. The device of amorphous carbon oxide based ReRAM demonstrated typical electrical characteristics, i.e., the set voltage of 1.8 V, the reset voltage of –2.0 V, high resistance state current of 4.6×10-11 A at 0.1 V, and low resistance state current of 7.5×10-9 A at 0.1 V. Moreover, stable endurance and retention were observed at 10 nm-thick amorphous carbon oxide after N2-annealing at 400 oC, which were the endurance of 1.0×106 cycles with a margin (Ion/Ioff
) of 3.5×101 and retention of 105 sec with a margin of 6.2×101. In particular, we present the mechanism and memory characteristics on operating behavior of the amorphous carbon-oxide based ReRAM via investigating the effect of amorphous carbon-oxide thickness, O2 flow rate of RF magnetron sputter, and N2-annealing temperature on the electrical characteristics by using auger electron spectroscopy(AES), energy-dispersive X-ray spectroscopy (EDS), cross sectional transmission electron microscopy (TEM) and X-ray diffraction (XRD).

* This material is based upon work supported by the Ministry of Trade, Industry & Energy(MOTIE, Korea) under Industrial Technology Innovation Program (10068055).

[1] Daniele Ielmini, Semicond. Sci. Technol. 31 (2016) 063002
[2] Claudia A. Santini et al, NAT COMMUN, 6:8600 (2015)

Figure 1
Improvements to the Charging Efficiency of an All-Iron Redox-Flow Cell
Authors: Jayathilake Buddhinie Srimali , Manohar Aswin , Plichta Edward J. , Hendrickson Mary A. , Narayanan S. R. 
Published: February 2020

Development of reliable, low cost, durable and ecofriendly energy storage systems for large scale applications is essential to support the intermittent generation from renewable energy sources. Among the different electrochemical energy storage technologies, redox-flow batteries are promising for large-scale applications due to its design, scalability and low cost. [1] In the quest for an inexpensive as well as eco-friendly energy storage system, we have been investigating a novel anion-exchange-membrane-based iron chloride redox flow rechargeable battery with the aqueous electrolytes composed of solution of iron chloride, ammonium chloride, and specific electrolyte additives. [2] Such an all-iron redox-flow battery based on iron chloride with the Fe3+/Fe2+ redox couple at the positive electrode and the Fe2+/Fe0 redox couple at the negative electrode has a cell voltage of 1.21 V and a theoretical specific energy of 170 Wh/ kg. Although we have shown the technical viability of the concept, the development of such a battery into a large-scale system has still remained a challenge due to the parasitic hydrogen evolution reaction at the negative electrode that lowers the efficiency of the charging process. Our efforts have aimed at increasing the efficiency of the charging process at higher charging current densities by minimizing the rate of the hydrogen evolution reaction.

This report, we present the effect of operating parameters on the rate of the parasitic hydrogen evolution reaction and the charging efficiency of the redox flow battery. By increasing the electrolyte pH to 3 in the presence of ascorbic as an electrolyte additive, we have achieved a charging efficiency of 94% at 80 mA cm-2 at the negative electrode (Fig.1a). Elevated plating bath temperature significantly increased the faradaic efficiency during both iron electrodeposition and electro-dissolution achieving 98% charging efficiency at 20 mA cm-2 at 333K at pH 3 (Fig.1b). We will also present results on the electrochemical kinetics for hydrogen evolution and iron deposition studied at iron-plated graphite electrode during charging process of the all iron redox flow cell.
Acknowledgment
Authors acknowledge US Army RDECOM CERDEC CP&I for financial support of this work.
References:
1. F. Pan and Q. Wang, Molecules, 20 19711 (2015).
2. A. K. Manohar, K. M. Kim, E. Plichta, M. Hendrickson, S. Rawlings and S. R. Narayanan, Journal of The Electrochemical Society, 163, A5118 (2016).

Figure 1