bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Induced Natural Fiber Welding of Cellulosic Substrates
Authors: Brown E. Kathryn , Dennis Kathleen , Haverhals Luke M. , Sweely Kurt D. , De Long Hugh C. , Trulove Paul C. 
Published: February 2020

As excellent solvents for cellulose and silk, certain ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium acetate (EMIAc),1,2 can be used for biopolymer modification and manipulation. Full dissolution and regeneration using IL solvents often results in biomaterials with inferior properties compared to the native material. When natural substrates are only partially dissolved and regenerated through a process we call Natural Fiber Welding (NFW), much of the native biomaterial structure can be maintained while still allowing for significant material modification. NFW enables the structural modification of the surface and incorporation of functional materials through the binding capability of the portion of dissolved biopolymer3-5.
In the present work we have employed a laser as the heat source to initiate partial dissolution of a cellulose substrate causing NFW in a spatially-specific manner. By using a non-solvent for cellulose (e.g., water) with the ionic liquid as a means of inhibiting the dissolution process, heat becomes the controlling factor necessary to obtain significant biopolymer dissolution and mobilization. A CO2 laser was used to raster a specific pattern onto a cellulosic paper substrate coated with IL solution. Raster power, concentration of the ionic liquid and the number of laser passes affect the amount of heat absorbed into the biopolymer and the level of NFW. Through tensile testing, confocal microscopy, ATR-IR, and SEM imaging, the resulting modification of the biopolymers was characterized.

References

Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am Chem Soc, 2002, 124, 4974.

Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350.

Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425.

Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13.

Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417.
Porous Carbon Anodes for the Supply of Methane during Electrowinning of Aluminium
Authors: Khalaghi Babak , Mokkelbost Tommy , Kjos Ole Sigmund , Gudbrandsen Henrik , Haarberg Geir Martin 
Published: February 2020

Currently consumable carbon anodes are utilized in the aluminium production process. The major drawback of this type of anodes is the high amount of CO2 emissions. Furthermore, due to the consumption of the anodes during the electrolysis it is necessary to adjust the anode – cathode distance continuously and finally replace the anode. Introduction of hydrogen or natural gas through the anode can decrease the CO2 emissions significantly and reduce the consumption of the anode. The use of inert porous anodes is interesting since the energy demand will be reduced due to natural gas/hydrogen participating in the anode reaction. However, due to unavailability of a sufficiently inert anode for aluminium electrolysis until now, carbon anodes seem to be more attractive. When natural gas/hydrogen is purged through the porous carbon anode, there will be competing anodic reactions depending on whether carbon from the anode or the CH4/H2 reacts with the oxygen ions from the bath. Previous studies using porous carbon anodes showed 0.3 V depolarization as well as 20% decrease in carbon anode consumption using methane compared to passing argon through the anode1. On the other hand, using CH4/H2 can lead to the formation and evolution of additional hydrogen fluoride. This was studied before and some ideas on how to deal with this extra HF evolution were presented2. In this study, further laboratory experiments were performed and the effect of carbon anodes with different porosities and designs were studied. Besides, off-gas analysis was performed and HF evolution will be discussed.
References:

S. Xiao, T. Mokkelbost, O. Paulsen, A.P. Ratvik, and G.M. Haarberg, Metallurgical and Materials Transactions, 44B, (2013) 1311.

T. Mokkelbost, O. Kjos, O. Paulsen, B. Øye, H. Gudbrandsen, A.P. Ratvik, and G.M. Haarberg, Light metals (2014), 756.
Catalysis of the Oxygen Reduction Reaction: Thin Layer Sonoelectrochemistry
Authors: Duda Chester G , Leddy Johna 
Published: February 2020

The oxygen reduction reaction (ORR) is a multi-electron and -proton transfer mechanism. In acidic solution, the slow step is typically taken as the first electron transfer.
O2 + e + H+ ⇌HO2

Even with platinum electrocatalysts, ORR kinetics impose parasitic losses of ~30 % in proton exchange membrane (PEM) H2|O2 fuel cells. Because of poor O2 reduction kinetics, H2is generated by steam reforming of natural gas rather than by water electrolysis.
Typically, catalysis is achieved by chemical manipulation of the catalyst materials. Physical means, such as increased temperature and pressure, can also increase rates. One means to increase temperature and pressure is irradiation of a fluid with ultrasound so as to induce cavitation. Acoustic energy is carried by a wave that first compresses the fluid, then rarefies the fluid to form microscopic voids, and then compresses the fluid to collapse the voids. On collapse at the thin interface between the fluid and void, extreme temperature (T > 5000 K) and pressure (P > 103 atm) are generated.1

Ultrasound has been applied to electrochemical systems with the first studies undertaken by Coury, et. al.2 In these studies, cavitation was generated in a bulk electrolyte where electrodes were placed at a distance from a sonic horn or other ultrasound source. Large transport enhancements were observed, but effects on heterogeneous reactions were not observed. Bubbles introduced noise in the voltammetry and the distance between the ultrasound source and the electrodes allowed energy to dissipate. See Scheme 1.
Here, the ORR is investigated by sonoelectrochemistry undertaken in a thin layer electrochemical cell,3,4where:

Acoustic energy attenuates less in the thin layer and so impacts the electrode processes..

Acoustic energy is reflected back into the condensed phases rather than pass into the less dense air phase.

Frank cavitation is not observed and not necessary to the enhanced rate of the ORR.

ORR rate is increased to the mass transport limit.

As shown in Figure 1, on sonication in a thin layer, O2reduction proceeds at the mass transport limited rate. The experimental set up is shown in Figure 2.
In general, sonication in a thin layer increases interfacial rates without significant impact on transport3,4 and provides a general, physical means to effect catalysis.

References and Acknowledgments: Support of the National Science Foundation and the University of Iowa is gratefully acknowledged.
[1] K.S. Suslick, Y. Didenko, M.M. Fang, T. Hyeon, K.J. Kolbeck, M.M. Mdleleni, and M. Wong, Acoustic Cavitation, Phil. Trans. Royal Soc. A 1999.
[2] C.R.S Hagan R. S. and L.A. Coury Jr. Anal. Chem., 1994, 66(3), 399–405.
[3] Chester G. Duda, Ph.D. dissertation, University of Iowa, 2012.
[4] J. Leddy, C.G. Duda, and W.J. Leddy III, U.S. Patent application, 2013.
Synergy in the Hydrazine Assisted Electro-Oxidation of Formic Acid
Authors: Machado Eduardo Giangrossi , Varela Hamilton 
Published: February 2020

In a recent paper, Schlogl have discussed thoroughly [1] the importance of chemistry on the energy scenario. It was pointed out that hydrogen could be an interesting source of energy, as long as storage problems could be fixed. Molecules such as formic acid and hydrazine are interesting hydrogen-carrier molecules, thus relevant in these energy-related systems. The mechanism by which the electro-oxidation of these molecules takes place was largely studied individually [2, 3]. However, few studies [4] have been done on the interaction present when these fuels are mixed. The present work aims at exploring the oscillatory instabilities present in the formic acid + hydrazine system to deepen the current understanding of surface reactions underlying these mixed fuels. The synergy in the electro-oxidation of mixtures of these two fuels is explored in this work. The electrochemical response obtained by the mixture is greater than the one obtained by the sum of the individual parts, as can be observed from the different oscillatory features in the separate and the complete system. The separate systems present limitations inherent to the characteristics of each fuel. For instance, formic acid has a self-poisoning process caused by the accumulation of oxygenated species that pulls the system away from the oscillatory condition in short times. On the other hand, hydrazine presents a deactivation of the electrode surface during time, as an effect of pH. When the two fuels are combined, long-last oscillations prevail, similarly to recently reported in our Group [5]. Additionally, the morphology of the time-series is different for the complete system comparing to the separate ones. Those evidences suggest that there is an intricate superficial interaction between the fuels, a synergy, to produce an unexpected oscillatory behavior.

Acknowledgements

EGM and HV acknowledge São Paulo Research Foundation (FAPESP) for financial support (grants #2009/07629-6, #2012/07313-1, #2012/24152-1, and # 12/21204-0). HV (#306151/2010-3) acknowledges Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support.

References

1. Schlogl, R., The role of chemistry in the energy challenge. ChemSusChem, 2010. 3(2): p. 209-22.
2. Aldous, L. and R.G. Compton, The mechanism of hydrazine electro-oxidation revealed by platinum microelectrodes: role of residual oxides. Phys Chem Chem Phys, 2011. 13(12): p. 5279-87.
3. Joo, J., et al., Importance of acid-base equilibrium in electrocatalytic oxidation of formic acid on platinum. J Am Chem Soc, 2013. 135(27): p. 9991-4.
4. Aldous, L. and R.G. Compton, Towards Mixed Fuels: The Electrochemistry of Hydrazine in the Presence of Methanol and Formic Acid. ChemPhysChem, 2011. 12(7): p. 1280-1287.
5. Perini, N.B., B. C.; Angelo, A. C. D.; Epstein, I. R.; Varela, H., Long-lasting oscillations in the electro-oxidation of formic acid on PtSn intermetallic surfaces. ChemPhysChem - in press., 2014.
Spatiotemporal Patterns Formed on p-Type Silicon Electrodes during Electrochemical Dissolution
Authors: Suzuki Yuya , Urata Tomoko , Fukami Kazuhiro , Kitada Atsushi , Murase Kuniaki 
Published: February 2020

Formation of spatiotemporal patterns has been reported in many electrochemical systems [1]. Applications of spatiotemporal patterns to other fields such as materials science and biological science are important for further progress of nonlinear dynamical systems. Since there are lots of parameters for the emergence of the patterns, it is difficult to understand the mechanisms for pattern formation.
Spatiotemporal patterns are often observed in electrochemical systems that show negative differential resistance (NDR) on their current density vs. potential curves. We have found that an S-shaped NDR was observed when a p-type silicon (p-Si) electrode was anodized in an HF solution containing organic solvents. A well-aligned microgroove array was formed after electrochemical dissolution at a potential in the S-shaped NDR. Although the spatial pattern was formed at the S-shaped NDR region, oscillatory instability in current or potential was not observed. In the present study, we report that an oscillatory instability in current is observed at the S-shaped NDR region.
For the electrochemical measurements, p-Si (100) with a resistivity of 1-4.5 W cm was used as the working electrode. Platinum (Pt) rods were used not only as the counter electrode, but also as the indicator electrode. Electrolyte solution was a mixture of aqueous HF (47 wt.%), ultrapure water and methanol (MeOH) with a composition of 5:6:29 in volume. Since the resistance of the solution is significant to estimate the potential applied at the electric double layer, the resistance was measured by impedance spectroscopy. Temperature of the solution was controlled by a water bath.
Figure 1 depicts current density vs. potential (j-U) curves together with current density vs. iR-corrected potential (j-
f) curves measured in the solution at 20°C and 30°C. When using the solution at 20°C, an S-shaped NDR is observed after correcting the iR-drop in the solution. We have confirmed that an array of microgrooves is spontaneously formed at potentials on the NDR branch. No oscillatory instability is observed in the curves. In the solution at 30°C, a fluctuation in current is observed on the j-U curve. After the correction of iR-drop in the solution, a clear oscillatory instability is observed in the region where the S-shaped NDR is detected in the solution at 20°C.
Time developments of current measured at a constant potential in the NDR region was plotted in Figure 2. Clear current oscillations are not observed in the solution at 20°C although the current fluctuates with time. In contrast, a current oscillation whose period is roughly 1 min is observed. This difference suggests that a bifurcation from the Turing to Turing-Hopf occurs by changing the temperature of the solution from 20 °C to 30°C.
[1] K. Krischer, N. Mazouz, P. Grauel, Angew. Chem. Int. Ed.
40, 850 (2001).
Supercapacitors Based on Propylene Carbonate with Addition of Sulfur Containing Organic Solvents
Authors: Eskusson Jaanus , Jänes Alar , Thomberg Thomas , Lust Enn 
Published: February 2020

The widely used mixed electrolytes for supercapacitors are composed of tetraalkyl ammonium salts and mixed solvents such as propylene carbonate (PC), ethylene carbonate (EC) and ethyl methyl carbonate. Cyclic PC and EC have a high dielectric constant, good compatibility with carbon electrodes enabling the dissolution of salts to sufficient concentrations. However, it is highly viscous and gives poor conductivity even at ambient temperatures. When PC or EC is mixed with linear alkyl carbonates, such as diethyl carbonate (DEC), dimethyl carbonate (DMC), or EMC, more rapid ion transport is achieved as a result of lower viscosity and subsequently higher ionic conductivity is observed. The resulting binary or ternary mixed solutions are widely used in commercially available lithium ion batteries. The choice of co-solvent is a critical issue that significantly affects not only the conductivity, but also the electrochemical performance, including the physicochemical properties of solid electrolyte interface (SEI) formation. In recent years, sulfites such as dimethyl sulfite, glycol sulfite, butylene sulfite, and diethyl sulfite have been studied as a film forming and high temperature additives for electrolytes in lithium ion batteries. It should be mentioned that diethyl sulfite (DES) is used as a film forming agent and high temperature additive for electrolytes in lithium ion batteries improving decomposition resistance of the carbonate-based electrolyte. Propylene sulfite (PS) is used as high temperature additive for electrolytes in lithium ion batteries and it improves the decomposition resistance of the electrolyte.
The main aim of this paper is to establish the electrochemical characteristics of the supercapacitors consisting of the two identical mainly microporous titanium carbide derived carbon (TiC-CDC) electrodes in 1 M (C2H5)3CH3NBF4 solutions in propylene carbonate (PC) and mixtures of PC with diethyl sulphite (DES), and propylene sulfite (PS) at different volume ratios. Electrochemical analysis has been made for PC:DES or PC:PS mixtures based electrolytes using cyclic voltammetry, electrochemical impedance spectroscopy, constant current charge/discharge and constant power methods. The limiting capacitance, characteristic time constants and complex power values calculated depend noticeably on the solvent composition and on temperature applied, i.e., on the viscosity and specific conductivity of electrolyte solution used.

Acknowledgements

The present study was supported by The Estonian Centers of Excellence in Science: High Technology Materials for Sustainable Development, ETF Project 9184, European Regional Development Fund Project SLOKT10209T and Project IUT20-13. Authors of the paper would like to thank Ph.D. Tavo Romann for depositing Al on the electrodes.
Nanomechanical Properties of Titanium Oxide (TiO2) Grown by Atomic Layer Deposition
Authors: Mamun M A , Baumgart Helmut , Elmustafa A A 
Published: February 2020

Titanium oxide (TiO2) materials experienced increased attention and growth because of their use as electrode material in lithium rechargeable batteries and they also offer excellent photocatalytic properties due to their stability, nontoxicity, and superb photo catalytic activity. However their absorption of the visible light is restricted due to their wide band gap (3.2 eV). One way of improving their absorption capabilities to the visible light is by doping such wide band gaps semiconducting oxides. The N-doped TiO2 films prepared by sputtering showed noticeable visible light absorption at wavelengths of less than 500 nm due to the bandgap narrowing by mixing of N 2p states with O 2p states [1-3]. Many of the properties in these applications are strongly dependent on titanium oxide’s crystal morphology, surface area, and mechanical properties.
TiO2 films of 200, 300, and 500, ALD cycles were deposited on p-type Si (100) substrates using Atomic layer deposition (ALD) technology. These films have been tested for structural, surface morphology, and nanomechanical properties using nanoindentation. The structural and surface properties will be explored using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). We will discuss the influence of the deposition technique on the structure and properties of the films citing the superiority of the ALD technique that is particularly used in the fabrication of the films that are presented in this study. A field emission scanning electron microscopy (FE-SEM) image is shown in Figure 1.

References

1- R. Asahi, T. Morikawa, T. Ohwaki, K. Aoki, and Y. Taga, Science, 293, 269 (2001).
2- J. Li, Y. Qin, C. Jin, Y. Li, D. Shi, L. Schmidt-Mende, L. H. Gan, and J. H. Yang,bNanoscale, 5, 5009 (2013).
3- C. X. Feng,G. Q.Xu, J. Lv,Q. M. Huang, Z. X. Zheng, andY. C.Wu, J. Electrochem. Soc, 160, H727 (2013).
Anisotropic Magnetoresistance of Ferromagnetic Conductive Filament in Resistive Switching Memory
Authors: Otsuka Shintaro , Hamada Yoshifumi , Shimizu Tomohiro , Shingubara Shoso 
Published: February 2020

A resistive switching (RS) memory has been expected to be a next-generation memory owing to its high density, low power consumption, and high switching speed. The mechanism of the reversible RS phenomenon has been considered in terms of the formation and rupture of conductive filaments (CF). Recently, it has been reported that a ferromagnetic CF was formed in NiO-based RS memory. This suggested the possibility of the new device that has both RS memory and spintronics device functions. The presence of a ferromagnetic CF in the NiO layer was confirmed by measuring the magnetization of the large number of CFs at room temperature using a SQUID magnetometer. Although, it is not yet confirmed that a single ferromagnetic CF is formed by the SET process. The purpose of this study is to understand the physical properties of a single ferromagnetic CF by focusing on magnetoresistance (MR).
We prepared Ni/HfO2/Pt memory device, having ferromagnetic Ni electrode and the oxide of a non-magnetic metal. The fabricated RS memory devices have a cross-bar structure. The crossed electrode size is 1×1 mm2.
RS characteristic was measured with the bipolar operation mode. When current limit is 5 mA, the anisotropic magnetoresistance (AMR) was observed in the low resistance state. The direction of the external magnetic field is in-plane to the substrate, and the current is perpendicular to the magnetic field. The AMR showed a convex behavior with magnetic field, and the MR ratio was approximately 0.15%. It is strongly suggested that AMR came from a ferromagnetic CF formed in the oxide layer. Further discussions will be shown in the workshop.
Random Walk Numerical Simulation of Disordered Semiconductor Heterojunctions
Authors: Mandujano-Ramírez Humberto julián , Oskam Gerko , Gonzalez-Vazquez José Pablo , Anta Juan Antonio 
Published: February 2020

Many recent advances in novel solar cell technologies are based on charge separation in disordered semiconductor heterojunctions. In this work we use the Random Walk Numerical Simulation (RWNS) method to model the dynamics of electrons and holes in two disordered semiconductors in contact. Calculations are performed by simultaneously moving electrons and holes in two semiconductors in contact, according to Miller-Abrahams hopping rates, also we have implemented the Marcus hopping model. Recombination is taken into account by implementing a tunnelling distance-dependent recombination mechanism across the interface. This way, charge separation for specific heterostructures with energy distributions of surface traps in the two semiconductors involved can be adequately simulated.
We show that several fundamental features of bulk heterojunction (BHJ) and quantum dot (QD) sensitised solar cells can be accounted for by this model. The dependence of the open-circuit voltage on the HOMO energy of the donor material in BHJ solar cells is accurately predicted assuming short recombination distances and a diffusion mechanism of transport. In addition, the variation of the voltage with temperature is adequately reproduced. The linearity and recombination order in electron density for both types of solar cell can be extracted in two ways: (1) the behaviour of the open-circuit voltage as a function of the illumination intensity, and (2) from the variation of the recombination current with respect to the open-circuit photovoltage. The RWNS model in combination with exponential disorder and an activated tunnelling mechanism for transport and recombination is shown to reproduce correctly experimental charge separation. This provides a theoretical basis to study relevant features of novel solar cell technologies. This allows for the interpretation of impedance spectroscopy measurements [1].

References.

1. Mandujano-Ramírez, H. J.; González-Vázquez, J. P.; Oskam, G.; Dittrich, T.; Garcia-Belmonte, G.; Mora-Seró, I.; Bisquert, J.; Anta, J. A. Charge separation at disordered semiconductor heterojunctions from random walk numerical simulations. Phys. Chem. Chem. Phys., 2014, doi. 10.1039/C3CP54237H, in press.