bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective Synthesis of Large-Diameter, High-Quality and Metallic Single-Walled Carbon Nanotubes Via Thiophene-Assisted Method
Authors: Li Jinghua , Liu Jie
Published: February 2020

We developed a method that produces enriched metallic nanotubes (m-SWNTs) with large diameter, high quality and high yield. In our research, it was observed that m-SWNTs are dominant species when their diameters are larger than 3 nm under most growth conditions we have tested, which implies that catalyst nanoparticles with larger sizes might have a preference to nucleate m-SWNTs. Based on this observation, a thiophene-assisted CVD method was developed to selectively synthesize metallic carbon nanotubes with large diameters (> 3 nm). It is believed that the up-shift in diameter distribution is sourced from the higher capability of thiophene for carbon supply which can activate larger catalyst particles. Back-gate FETs were fabricated based on individual SWNTs to characterize the as-prepared SWNTs and it was determined that the ratio of m-SWNTs is ~95%. Clearly, the SWNTs synthesized with thiophene in the precursor have a higher percentage of metallic nanotubes. This result is consistent with the rules for selective growth reported in our previous study and provides a facile method for the synthesis of m-SWNTs which can be applied to fabricate transparent conductive films. This is a strong evidence that the growth conditions play an important role in determining the types of nanotubes grown in a CVD process.
An Expanded Family of Dysprosium-Scandium Mixed-Metal Nitride Clusterfullerenes
Authors: Yang Shangfeng
Published: February 2020

Metallic nitride clusterfullerene (NCF) is the most rapidly-growing branch of endohedral fullerenes because of its extraordinarily high yield and peculiar electronic structure with six-electron transfer from the encapsulated trimetallic nitride cluster to the outer carbon cage. A large family of dysprosium-scandium (Dy-Sc) mixed-metal nitride clusterfullerenes (MMNCFs), DyxSc3-xN@C2n (x=1, 2, 2n=68, 70, 76 - 86) have been successfully synthesized and isolated, among which the C70 and C82-based MMNCFs represent two new cages that have never been isolated for MMNCFs. Synthesis of DyxSc3-xN@C2n was accomplished by the “selective organic solid” route using guanidinium thiocyanate as the nitrogen source, and their isolation was fulfilled by recycling HPLC. UV-vis-NIR spectroscopic study indicates that almost all DyxSc3-xN@C2n MMNCFs are kinetically stable fullerenes with optical band-gaps beyond 1 eV. This feature is distinctly different to their counterparts Dy3N@C2n (78≤2n≤88), for which those with relatively large cages such as C84 and C86 have optical band-gaps below 1 eV. FTIR spectroscopic study in combination with DFT calculation enables successful assignments of the cage isomeric structures of all DyxSc3-xN@C2n (x=1, 2, 2n=68, 70, 76 - 86) MMNCFs. The carbon cage size distribution of DyxSc3-xN@C2n (2n=68, 70, 76 - 86) is compared to the reported Dy3N@C2n (78≤2n≤88) homogeneous NCF and GdxSc3-xN@C2n (78≤2n≤88) MMNCF families, revealing that the medium-sized Dy metal plays a crucial role on the expanded size distribution of MMNCFs. As a result, DyxSc3-xN@C2n MMNCFs represent the largest MMNCF family reported to date.
Chiral Fullerenes from Asymmetric Catalysis
Authors: Martin Nazario
Published: February 2020

Chirality is an important and fascinating aspect which, however, has not been properly addressed in fullerenes science.[1] Recent results from our group support the basic idea that the chemistry of fullerenes is not completely developed and that a variety of fundamental reactions, mainly involving transition metals and organocatalysts are helpful in order to address issues such as the regio- and the stereo-selectivity, so far unsolved in the fullerene functionalization.

We have recently reported on the synthesis of enantiomerically pure fullerenes with a total control of the stereochemical outcome. The suitable choice of the chiral metal catalyst ([Cu(II) or Ag(I)] in combination with a variety of different chiral ligands) directs the 1,3-dipolar cycloaddition of N-metalated azomethyne ylides on C60, on C70 and on endohedral metallofullerenes with high levels of site-, regio-, diastereo- and enantio-selectivity.[2] Furthermore, we have also shown that chiral fullerenes can be efficiently prepared by using organocatalysis.[3] In this communication, the most recent synthetic results involving endohedral fullerenes as well as their cis-transisomerization will be discussed.

References:

[1] E. E. Maroto, M. Izquierdo, S. Reboredo, J. Marco-Martínez, S. Filippone, N. Martín "Chiral Fullerenes from Asymmetric Catalysis" Acc. Chem. Res. 2014, 47, 2660−2670.

[2] (a) Filippone, S., Maroto, E.E., Martín-Domenech, A., Suarez, M. and Martín, N., Nature Chem., 2009, 1, 578; (b) Maroto, E. E.; de Cozar, A.; Filippone, S.; Martin-Domenech, A.; Suarez, M.; Cossio, F. P.; Martín, N. Angew. Chem. Int. Ed., 2011, 50, 6060; (c) Sawai, K.; Takano, Y.; Izquierdo, M.; Filippone, S.; Martín, N.; Slanina, Z.; Mizorogi, N.; Waelchli, M.; Tsuchiya, T.; Akasaka, T.; Nagase, S. J. Am. Chem. Soc.,
2011, 133, 17746; (d) Maroto, E.E., Filippone, S., Martín-Domenech, A., Suarez, M. and Martín, N., J. Am.
Chem. Soc.
2012, 134, 12936; (e) E. E. Maroto, S. Filippone, M. Suárez, R. Martínez-Álvarez, A. de Cózar, F. P. Cossío, N. Martín, J. Am.
Chem. Soc., 2014, 136, 705.

[3] (a) J. Marco-Martinez, V. Marcos, S. Reboredo, S. Filippone, N. Martín, Angew. Chem. Int. Ed., 2013, 52, 5115. (b) J. Marco-Martínez, S. Reboredo, M. Izquierdo, V. Marcos, J. L. López, S. Filippone, N. Martín, J. Am.
Chem. Soc., 2014, 136, 2897.

Figure 1
Cycloaddition of Nitrile Imines to Graphene. a Theoretical and Experimental Approach
Authors: Barrejon Myriam , Rodriguez Antonio , Gomez-Escalonilla María J. , Carrillo Jose Ramon , Prieto Maria Pilar , Langa Fernando
Published: February 2020

Graphene is a unique material with outstanding mechanical and electronic properties.1 The modulation of the electronic properties of graphene by chemical functionalization as well as the control over the opening of its band gap are of great interest, because of the potential of this material for a wide range of applications.2

Due to the lower reactivity of graphene, compared to other carbon nanostructures, the range of reactions available for functionalization of this material is smaller than in the case of other carbon nanostructures as fullerene or carbon nanotubes.

Although most of the studies involving graphene functionalization has been performed by amidation of the carboxylic groups at the edges or by using diazonium salts,3 examples of 1,3-dipolar cycloaddition of azomethine ylide have been also described,4 but there are not examples in the literature of cycloaddition of other less reactive dipoles as nitrile imines or nitrile oxides.

In most cycloaddition reactions to [60]fullerene, the LUMO of the fullerene cage is shifted to higher values by 0.15 eV. Nevertheless, we have previously demonstrated that, in the cycloaddition of nitrile imines to fullerenes, affording pyrazolinofullerenes, the LUMO of C60 is not shifted to higher values due to the electron-acceptor character of the pyrazoline ring.5,6 So, cycloaddition of nitrile imines to graphene, if the reaction works, can be useful to modulate the band-gap in a different way than other cycloaddition reactions.

We present here the theoretical and experimental studies on the 1,3-dipolar cycloaddition  of nitrile imines to graphene.

References:

[1]V. Georgakilas, M. Otyepka, B. Bourlinos, V. Chandra, N. Kim, K. C. Kemp, P. Hobza, R. Zboril and K. S. Kim Chem. Soc. Rev.
2012, 112, 6156.

[2] F. M. Koehler and W. J. Stark, Acc. Chem. Res. 2013, 46, 2297.

[3] L. Rodriguez, M. A. Herranz and N. Martin, Chem.
Commun. 2013, 49, 3721.

[4] M. Quintana, E.  Vazquez and M. Prato, Acc.
Chem. Res. 2013, 46, 138.

[5] M. Álvaro, P. Atienzar, P. de la Cruz, J. L. Delgado, H. García and F. Langa, J. Phys. Chem. B
2004, 108, 12691;

[6] J. L. Delgado, N. Martín, P. de la Cruz and F. Langa, Chem. Soc. Rev. 2011, 40, 5253.
Non-Equilibrium Thermodynamics Approach for QED Heat Conductance Between Graphene and SiC Substrate
Authors: You Dan , Rotkin Slava V.
Published: February 2020

Our study aims to explore heat transfer mechanism between graphene and polar insulator substrate. We develop a thermodynamic theory of heat transfer between graphene and SiC substrate based on master equation method and establish the difference of our model to the results obtain earlier by Fischetti (Ref.[1]), their equilibrium theory will be compared with the steady state solution of our non-eqilibrium model.

Graphene has attracted much attention due to potential applications in thermoelectric and photoelectric devices. Thermal properties of graphene have been extensively studied both experimentally and theoretically: graphene has very high in-plane thermal conductivity. Thus the thermal applications might be likely limited by the out-of-plane heat transfer [2]. In this context, integration of graphene with a polar substrate, such as SiC, can modify the thermal properties of former [3].  

In this paper, we consider strong coupling between the surface plasmon- and phonon-polaritons in graphene and the substrate, respectively. These modes were assumed to provide the efficient QED heat flux channels. Fig.1 (a) shows dispersion relations of two (infinite lifetime) eigenstates E1and E2strongly mixed due to the quasi-electrostatic interaction between surface plasmon- and phonon-polaritons.  Such localized surface modes are, in fact, dissipated into reservoir modes representing the bulk of materials, which can be calculated via the corresponding self-energy terms. This interaction between surface modes and their couterparts in the reservoirs (environmental modes) leads to the loss of the quantum coherence and the dissipation of their energy, when driven out of their equilibrium (with the reservoirs). Assuming weak system-reservoir interactions and a short reservoir correlation time, Markovian quantum master equations can be used to describe relaxation dynamics of our system.

Time evolution of the system was theoretically obtained. Assuming different temperatures for substrate and graphene, the coupled system is out of equilibrium which creates an non-zero net heat flux. The dynamics of the system towards the steady state can simulated. The average occupation shows an oscillatory behavior (Fig.1 d and e), here we consider the substrate being at a higher temperature. The heat flow from the surface optical phonon-like modes to graphene and from the substrate into the surface plasmon-like modes are shown in Fig.1b and c. In the steady state (long-time limit), the solution of our model does not coincide with thermal equilibrium state.

This work is supported by AFOSR (#FA9550-11-1-0185).

[1] Z. Y. Ong and Massimo V. Fischetti, Phys. Rev. B 86, 165422 (2011)

[2] A. A. Balandin, S. Ghosh, W. Z. Bao, I. Calizo, D. Teweldebrhan, F. Miao, and C. N. Lau, Nano Lett. 8, 902 (2008)

[3] J. H. Seol, I. Jo, A. L. Moore, L. Lindsay, Z. H. Aitken, M. T. Pettes, X. Li, Z. Yao, R. Huang, D. Broido, N. Mingo, R. S. Ruoff, and L. Shi, Science 328, 213 (2010).

Figure 1
1/F Noise in MoS2 Field Effect Transistors with Channel Length Variation
Authors: Das Suprem Ranjan , Kwon Jiseok , Claussen Jonathan , Hu Shan , Janes David B
Published: February 2020

Field effect transistors (FETs) based on emerging nanoscale channel materials have numerous applications including post-CMOS logic for digital computing, communication and biochemical sensing. However, in fundamental level each of these applications requires tight scrutiny of carrier transport as the device operates in the desired regime and in the proposed environment. One of the important characteristics is to analyze the 1/f noise spectroscopy of the electronic device. In this paper we fabricate multilayer (15 atomic layer) MoS2 transistors of two different channel lengths (1µm and 2µm) and study the flicker noise in the devices at room temperature and ambient conditions; both devices being fabricated following the same process flows on a single micro-mechanically exfoliated flake of MoS2; thereby eliminating variability of 1/f noise from fabrication standpoints. Channel dominated 1/f noise with Hooge’s mobility fluctuation model for the devices were extracted from the bias dependent noise spectra. The noise characteristics of the devices are stable over several months of exposure to ambient. The robustness of the channel to its ambient and stability of current fluctuations reveal MoS2as an emerging candidate for reliable sensing.

Figure shows 1/f noise spectra of MoS2 FET with 15 atomic layer thick back-gated channels with Cr/Au source and drain electrodes. Channel lengths of 1µm and 2µm were compared for this study.   

Key words: 1/f noise, MoS2 FETs, biochemical sensing

Figure 1
Pi-Extended 2D-Networks of Heteroaromatic Compounds - Towards Two-Dimensional Nanostructured Materials
Authors: Ryan Aoife A. , Berner Nina C. , Cafolla Attilo A. , Duesberg Georg S. , Senge Mathias O.
Published: February 2020

Graphene and other two-dimensional (2D) materials such as inorganic transition metal dichalchogenides (TMDs) represent key nanostructural materials for use in a range of functional devices including gas and biosensors. The functionalization of nanomaterials is a critical factor for tailoring their surface properties, enhancing their potential applicability in optoelectronics and catalysis to name but a few. Porphyrins can easily be used for the construction of π-extended systems using well-established synthetic chemistry methodologies. [1] These range from organometallic C-C bond forming reactions to introduce tailored substituents at the porphyrin periphery and the construction of porphyrin arrays connected conjugated linkers, to porphyrin tape-like oligomers through oxidative meso-meso and meso-β-fusing reactions. The selective functionalization of these heteroaromatic systems now opens the possibility to combine them with carbon-based aromatic systems to yield mixed π-extended systems with unique photophysical properties. Present studies reveal the emergence of a surface chemistry of such systems where specific reactions, e.g., metallation, remetallation and C-C–coupling can be induced on surfaces. [2] Surface/macrocycle interactions alter the chemical properties of porphyrins and the adsorption of tailored macrocycles onto 2D surfaces could generate novel platform systems for, e.g., the attachment of biomarkers for use as biosensors. Additionally, TMDs, e.g., MoS2, represent a growing area of research due to their fascinating electronic and optoelectronic properties. [3] Through chemical modification of these surfaces it is hoped that attachment of large heteroaromatic systems will further tailor these materials for functional use.

References

[1] A. A. Ryan, M. O. Senge Eur. J. Org. Chem. 3700 (2013).

[2] S. Krasnikov, C. Doyle, N. Sergeeva, A. Preobrajenski, N. Vinogradov, Y. Sergeeva, A. Zakharov, M. Senge, A. Cafolla Nano Res. 4, 376 (2011).

[3] G. S. Duesberg Nat. Mater. 13, 1075 (2014).
(Invited) Microfluidic Wet Chemical Functionalization of Graphene
Authors: Maggini Michele , Silvestrini Simone , Menna Enzo , Lobo Hyacintha , Carofiglio Tommaso , De Filippo Christian , Vicentini Nicola
Published: February 2020

Microfluidics is a powerful tool for the smart management of chemical reactions. It has been shown that the flow chemistry approach allows for precise control over process parameters, ease of optimization and even simplified scale-up from lab-scale to production modules. These features come in especially handy when dealing with complex systems, where reagents are not molecular in nature. Such is the case of many materials, like metal nanoparticles, carbon nanotubes and graphene, whose chemical functionalization represents a way to produce nano-sized components for a wide range of applications. After our previous experience with the development of flow chemistry method for the functionalization of fullerenes and carbon nanotubes, we have extended our study to graphene-like materials. In the presentation we will propose a general method to control the functionalization of graphene materials, as a mean to prepare derivatives with tailored properties.
(Invited) Synthesis, Characterization, and Applications of Single- and Double-Layer Graphene Grown on Epitaxial Metal Films
Authors: Ago Hiroki
Published: February 2020

To develop graphene’s excellent and unique properties for future electronic devices, the synthesis of large area, high-quality graphene sheets with a controlled number of layers and well-defined structure is important.  Here, we present our work to grow high-quality graphene with controlled orientation.  Our method is based on heteroepitaxial CVD using highly crystalline metal catalyst deposited on single crystalline substrates, such as sapphire and MgO [1-6].  We investigated the CVD growth of single-layer graphene on Cu(111) and Cu(100) and found that the orientation of the graphene is strongly influenced by the underlying Cu lattice [2-4].  Large hexagonal graphene domains with a lateral size of 50-100 μm are aligned on the Cu(111) surface [5].  On the other hand, the orientation of graphene on Cu(100) has two main domain orientations, reflecting the symmetry mismatch between graphene and Cu(100) lattice.  The carrier transport across the neighboring domains merged with the same orientation was investigated.  We found a higher carrier mobility for devices inside one domain (mean value is 7,200 cm2/Vs at 280 K) than those with a domain interface in the channel (2,000 cm2/Vs), suggesting that the domain interface acts as a scattering site even when they merged with the same orientation [6]. 

Moreover, we have realized the selective growth of double-layer graphene on the heteroepitaxial metal films, which is expected to be applicable to semiconductor devices.  The growth mechanism and the stacking order of the double-layer graphene will be discussed.  Finally, our recent progress on the synthesis of two-dimensional heterostructures, such as graphene-MoS2 and graphene-NbS2hybrid structures, will be also presented [7,8].

[1] H. Ago et al., ACS Nano, 4, 7407 (2010). [2] B. Hu et al., Carbon
50, 57 (2012). [3] C. M. Orofeo et al., Carbon, 50, 2189 (2012). [4] Y. Ogawa et al., J. Phys. Chem. Lett., 3, 219 (2012). [5] H. Ago et al., Appl. Phys. Exp., 6, 75101 (2013). [6] Y. Ogawa et al., Nanoscale, 6, 7288 (2014). [7] W. Ge et al., Nanoscale, 5, 5773 (2013). [8] H. Ago et al., submitted.
Preparation and Photoelectrochemical Properties of Multilayered WS2 Coated Titanium Dioxide Nanocomposites
Authors: Lu Rongteng , Du Kang , Liu Guohua , Yang Changping , Wang Kaiying
Published: February 2020

Since TiO2 was discovered for water-splitting to generate hydrogen under UV light, plenty of techniques have been explored to obtain suitable sensitizers for visible-light adsorption in order to increase the activity of water-splitting reaction for hydrogen generation [1-3]. Among them, dispersing a 2D graphene andsimilar layered material on TiO2 nanoparticle exhibits highly photocatalytic activities (i.e. MoS2) [2].

In this paper, graphene-liked WS2 was chosen due to its activity as HER (hydrogen evolution reaction) catalyst and relatively abundant storage [4]. The expected composite was formed through high energy ball milling technique which makes WS2 disperse on the surface of TiO2nanoparticles [5].

The composites consist of 99.5% TiO2 and 0.5% WS2and were prepared by high energy ball milling for five different periods of time-2hours, 4hours, 8hours, 16hours and 32hours. To identify phase evolution of the as-prepared nanocomposites during high energy ball milling procedure, X-ray diffraction (XRD) was performed to examine phase transition, which is shown in Fig.1. It can be seen that, with increasing milling time, the crystallization decrease at first and increase after further milling.

To further study the photoelectrochemical (PEC) characterization of composites after ball milling, a three-electrode setup was used, which is shown in inset of Fig. 2. This three-electrode device consists of a reference electrode (Ag/AgCl), a Pt wire counter electrode, a quartz container filled of 0.5M Na2SO4 aqueous solution and a working electrode. Sintered composites on indium-tin-oxide (ITO) glass substrate acts as the working electrode. Fig.2 shows the PEC measurement results of pure TiO2 and milled composites with milling time for 2hours, 8hours and 32hours. As can be seen, composite reaches the best photocurrent response with 8 hours milling. It is obvious that compared to pure TiO2 sample, adding of WS2and high energy ball milling make positive effect to composites.

In summary, the structure of TiO2 and WS2 nanocomposites through high energy ball milling has been studied by X-ray diffraction. Photoelectrochemical properties of the TiO2 coated with few layered WS2 shows the optimization photochemical response for 8 hours milled nanocomposites. This work provides a facile and low cost process for large amount production of few layer doped TiO2nanocomposites.

References

[1] A. Fujishima, K. Honda, Nature, 238 (1972) 37.

[2] Q. Liu, Z. Pu, A. M. Asiri, A. H. Qusti, A. Q. Al-Youbi, X. Sun,. J Nanopart Res 15 (2013) 1.

[3] W. Zhou, Z. Yin, Y. Du, X. Huang, Z. Zeng, Z. Fan, & H. Zhang, Small, 9(2013) 140.

[4] D. Merki, X. Hu, Energ Environ Sci, 4 (2011) 3878.

[5] H. C. Nazareno, Y. Zhao, K. Wang, IEEE Nano (2014)

Figure 1
Numerical Simulation of Single Solid Oxide Fuel Cell Performance By Coupling Dynamics of Electrochemical Flows with Thermal Impact on Solid Electrolytes
Authors: Chaudhary Tariq Nawaz , Chen Baixin
Published: February 2020

It has been recognized that the thermal impact is the major concern for the electrolyte of Solid Oxide fuel cells (SOFC) due to the high temperature operating conditions. Therefore, it is necessary for engineering design to understand the mechanism of heat transfer from fuel/air reacting to the anode and cathode for cell designs. A numerical model has been developed for a single solid oxide fuel cell by coupling dynamics of electrochemical reacting flows, heat transfer, and thermal strengths of solid porous electrodes for analysing the cell performance. The Finite element method (FEM) is used for numerically solving the set of transportation equations. The developed model is applied to simulate the bench mark case of International Energy Agency (IEA) for both the co-flow and counter flow. The comparison shows a good agreement with the errors of 13% in current density value and 4% in maximum temperature with those of bench mark case. In case of co-flow the maximum temperature about 1109 °C is found at fuel outlet side. In case of counter flow the maximum temperature is 1118 °C and is observed at fuel inlet side.  Predicted temperature distribution is applied to estimate the thermal stresses developed in the cell. Modelling results from simulations of a single unit of the SOFC cell operated at temperature of 900 °C, pressure of 1.01 bar, and the Reynolds number of 44.7 and 0.646 for air and fuel flows under adiabatic boundary condition, show that the maximum thermal stress produced in the cell is about 2600 MPa in the electrolyte at about 5mm away from the fuel inlet. Another case is simulated by considering convective heat flux boundary condition at top and bottom of the cell. The maximum thermal stress produced in this case is about 1820 MPa. The details of model development and the more results from the simulations will be reported in the full paper for predicting the effects of the thermal deformation of anode and cathode on the performance of a SOFC.
A New Cathode Additive to Compensate the Irreversible Lithium Loss at the Anode for a Lithium-Ion Battery
Authors: Park Kyusung , Yu Byeong-Chul , Goodenough John B.
Published: February 2020

Silicon-based anode materials have been considered as high energy-density anodes for a next generation lithium-ion battery. However, it exhibits serious lithium loss owing to the SEI formation and mechanical degradation. To compensate the lithium loss at the anode side, several cathode additives that can feed extra lithium to the anode have been proposed and demonstrated. Li2NiO2 and Li2MoO3 are examples for this purpose. However, Li2NiO2 (i) doesn’t have enough capacity for this purpose: the maximum charge capacity in the literature is about 400 mAh/g, (ii) shows significant oxygen evolution during charge, and (iii) reduce thermal stability of a cell. Li2MoO3 (i) doesn’t have enough capacity for this purpose: the maximum charge capacity in the literature is about 250 mAh/g and (ii) shows a serious molybdenum dissolution issue in a liquid electrolyte. We will propose a new material as a cathode additive that has a very high charging capacity and doesn’t deteriorate any cathode properties.
Challenges for Li-Ion Batteries Working at High Temperatures
Authors: Oltean Gabriel , Gustafsson Torbjörn
Published: February 2020

Li-ion batteries working at high temperatures (from 80 to 110 ºC) are thought to be implemented in hybrid electric heavy vehicles. The high working temperature of the battery would facilitate faster charge and discharge rates, allowing the power demands of such an application to be easily reached. Furthermore, sharing a cooling system between the battery pack and other drive train components, such as power electronics, would simplify the thermal management in the hybrid electric vehicle.

Working at higher temperatures could potentially open the possibility of using electrode materials that do not normally work at room temperature due to kinetic limitations. Solid polymer and ionic liquid electrolytes could also be used, as the ionic conductivity and viscosity are improved at high temperatures. Unfortunately, increasing the working temperature of the battery will also present drawbacks. Secondary reactions kinetics are also improved when increasing the temperature, affecting the coulombic efficiency of the cell. Due to safety considerations, liquid electrolytes that are normally used in ambient temperature Li-ion batteries would have to be replaced by safer solid polymer or ionic liquid electrolytes. Finally, issues like the cold-start of hybrid vehicles and prediction of batteries life-time also need to be addressed.

We will present the work done at Uppsala University on high temperatures Li-ion batteries within the Swedish HT-LIB project. Different materials have been tested in half-cells in order to study their cycling performance at 80 ºC. Iron-based cathode materials (LiFePO4 and Li2FeSIO4) were chosen as they are cheap and environmentally friendly, while titanium-based anode materials (Li4Ti5O12 and TiO2) were chosen due to their high working potential versus lithium. The later is beneficial as there is less solid electrolyte interphase formation at those potentials and there is no risk for lithium plating. Finally, cycling of Li-ion whole cells at 80 ºC will be presented.

High Temperature Lithium-ion Batteries (HT-LIB) is a project funded by the Swedish Energy Agency and the collaboration between Chalmers University of Technology, Lund University, Uppsala University and Scania CV AB was created within the Swedish Hybrid Vehicle Centre.
Electrochemical Properties of SnO2 Electrode Fabricated By Liquid Phase Deposition Method
Authors: Mizuhata Minoru , Shibata Yuya , Maki Hideshi
Published: February 2020

SnO2 nanoparticles which is a wide band gap semiconducting materials has been applied as gas sensor and anode in lithium-ion batteries. SnO2 has larger molecular weight than carbon materials. Compared to carbon materials, SnO2 has less effect of weight change in Li+ ion and Na+ ion, and this is the advantage of weight energy density for SnO2. SnO2 performs a two-stage reaction with Li+ ion and Na+ ion, hence the higher charge/discharge capacity is expected than Sn. Liquid phase deposition (LPD) method is a mild solution process for depositing various metal oxide thin films on the surfaces on various substrates. Moreover this method has been applied synthesis of metal oxide nanoparticles(NPs) by using polymer solution.

The synthesis of SnO2 NPs was carried out as following process: Aqueous [SnF6]2- / HF solution and aqueous H3BO3 solution added into polyethyleneglycol (PEG) and continuously stirred for 10 minutes. The mixed solution was kept at 30 ºC for 24 h. After the LPD reaction time, the mixture was centrifuged and sample was obtained. The synthesized two types of samples were characterized by various characterization tools such as X-ray diffraction (XRD), TEM, SEM, XPS Electrochemical measurement.

In NPs system, All XRD patterns can be assigned to SnO2 rutile. The crystallite size increased with calcination temperature more than 400 ºC. From a TEM observation, a change in morphology by calcination was not confirmed, but it was confirmed that particle size increased because of thermal fusion.  In the first CV scans for all samples in Na+ ion systems, the reduction peak value at 0.01 V, which is thought that alloy reaction of Sn with Na is occurred, increased with increase in crystallite size as shown in Fig.1. However, in all samples the integrated reduction area was larger than the integrated oxidation area and the integrated reduction and oxidation area decreased depending on an increase in the cycle number. These results suggested irreversible reaction of Sn with Na. In XPS measurement, Na 1s peak intensity increased with charge, however it remained at fully discharge, and this showed irreversible reaction. Sn 3d5/2 peak shifted higher energy and this is one of the reasons to cause irreversible reaction. In Li+ ion system, charge – discharge measurement on sample as-deposition was carried out at 0.1 C(current density : 78.3 mAh¥g-1). This electrode gave a first cycle discharge capacity of 1015 mAh¥g-1, which is higher capacity than the theoretical discharge capacity of Sn(783 mAh¥g-1). This result indicated that not only alloy reaction described as Sn + xLi+ + xe- ↔ LixSn, but also redox reaction described as Sn + 2Li2O ↔ SnO2 + 4Li+ + 4e- attributed to charge – discharge property. For the results stated above, alloy type metal oxide electrode has advantage of capacity.

Figure 1
Ternary Metal Fluorides As High-Energy Cathodes with Low Cycling Hysteresis
Authors: Wang Feng , Kim Sung-Wook , Graetz Jason
Published: February 2020

Transition metal fluorides (MFx) are promising for use as high-capacity cathodes in rechargeable lithium batteries for large-scale applications, such as electric vehicles and grid-scale storage, but energy-efficiency and kinetics related issues remain a major hurdle to their commercial use. Cu based fluorides are particularly attractive due to the 3.55 V redox potential and extraordinarily high specific energy (1874 Wh/kg). Here we report on the synthesis, structural and electrochemical properties of new ternary metal fluorides (M1yM21-yFx: M1, M2 = Fe, Cu), which may overcome these issues. By substituting Cu into the Fe lattice, forming the solid solution CuyFe1-yF2, reversible Cu and Fe redox reactions were achieved with surprisingly small hysteresis (<150 mV; Figure 1). This finding indicates that cation substitution may provide a new pathway for tailoring electrochemical properties of conversion electrodes.

The Li storage/release mechanisms and limits to cycling stability of CuyFe1-yF2 were investigated by combining electrochemical measurement with comprehensive structural and chemical analysis using in-situ X-ray absorption spectroscopy, X-ray diffraction, and transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS). The lithium reaction process is much more complicated in CuyFe1-yF2 than the binary metal counterparts (i.e. FeF2, CuF2) [2-4]. Some of the recent results on synthesis, structural and electrochemical characterization of the ternary metal fluorides will be presented. Detailed lithium reaction mechanisms, and Cu-loss related issues along with possible remedy solutions in the CuyFe1-yF2system, will be discussed.

 [1] Wang et al., “Ternary Metal Fluorides as High-Energy Cathodes with Low Cycling Hysteresis”, Nat. Commun.6:6668 (2015).

[2] Wang et al., “Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes”, J. Am. Chem. Soc., 133, 18828 (2011).

[3] Wang et al., “Tracking Li Transport and Electrochemical Reaction in Nanoparticles”, Nat. Commun., 3, 1201(2012).

[4] Hua et al., “Comprehensive Study of the CuF2 Conversion Reaction Mechanism in a Lithium Ion Battery”, J. Phys. Chem. C 118, 15169 (2014).

Figure 1
Long-Term Stability of Quinone Electrolytes in Aqueous Flow Batteries
Authors: Gerhardt Michael R. , Tong Liuchuan , Marshak Michael P. , Gordon Roy G. , Aziz Michael J.
Published: February 2020

Quinone-based flow batteries are attractive candidates for large-scale electrical energy storage, as quinones can be inexpensive, exhibit rapid redox kinetics, and require no electrocatalyst [1-3]. We present the evaluation of several quinone negative electrolyte materials for use in a flow battery with a positive electrolyte containing bromine and hydrobromic acid. Several substituted quinones are shown to undergo reversible two-electron reduction and oxidation in acidic aqueous solution, with tunable reduction potentials. Some are found to be stable in the presence of bromine, while others undergo decomposition reactions. One stable substituted quinone is currently being tested in a quinone-bromide flow battery. As of writing this abstract, the cell exhibits a peak galvanic power density above 700 mW/cm2, an average round-trip energy efficiency of 70%, and current efficiency of 95% as tested to 30 constant-current charge-discharge cycles at 0.25 A/cm2. Further cycling will be reported.

[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature 505, 195 (2014), http://dx.doi.org/10.1038/nature12909

[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans. 61, 27 (2014)

[3]  B. Yang, L. Hoober-Burkhardt, F. Wang, G.K. Surya Prakash, and S.R. Narayanan, J. Electrochem. Soc. 161, A1371 (2014).

Figure 1.
a. Polarization curves and b. galvanic power density as a function of current density for a substituted quinone – bromide flow battery at three different states of charge (SoC). The peak galvanic power density exceeds 0.7 W/cm2at 90% SoC.

Figure 2. Cell voltage during constant current charge-discharge cycling of a substituted quinone-bromide flow battery at ± 0.25 A/cm2. Voltage cutoffs were set at 1.3 V and 0.3 V. The time window chosen shows cycles 14-24 of a 30-cycle experiment.

Figure 1
Manipulating the Polarity of Conductive Polymer Binders for Si-Based Anodes in Lithium-Ion Batteries
Authors: Jia Zhe , Wu Mingyan , Song Xiangyun , Liu Xiaosong , Battaglia Vince , Yang Wanli , Liu Gao
Published: February 2020

Si-based anodes continue to draw tremendous interest for lithium-ion batteries due to their large specific capacity for lithium. However, maintaining the stability while extracting high capacity from Si anodes remains a challenge because of significant volume changes during their electrochemical alloying and de-alloying with lithium. Polymer binder selection and optimization may allow dramatic improvements in the performance of Si-based anodes. Most studies of polymer binders of Si anodes have involved the use of insulating poly(vinylidene fluoride) (PVDF) and carboxyl group containing carboxymethylcellulose (CMC) or poly(acrylic acid) (PAA). Herein, we report for the first time the systematic studies on manipulating the polarity by adjusting the molar ratio of polar triethyleneoxide side chains, therefore the electrolyte up-taking properties change systematically for conductive polyfluorene-based polymer binders. The results show that through optimizing the polarity of polymer binders, superior performance as a binder for Si anodes may be obtained. This study could be used as a model system and may open new avenues to explore a novel series of binders for both insulating and conductive polymer binder families
Non-Chromatographic Isolation of Mixed-Metal Nitride Clusters in Larger Carbon Cages
Authors: Stevenson Steven
Published: February 2020

There is a growing interest in mixed-metal nitride metallofullerenes.  Prior to exploring their properties and applications, these mixed-metal endohedrals must first be purified.  To date, their isolation has been difficult.  Hurdles to overcome include their (1) low abundance in soot extract, (2) their co-synthesis with a complex mixture of many types of fullerenes and metallofullerenes, and (3) their HPLC co-elution with contaminant species.  In this presentation, we reveal a separation methodology to minimize and/or avoid HPLC (e.g., recycling HPLC), which is the conventional (i.e., literature) method for isolating mixed-metal nitride endohedral metallofullerenes.  We also discuss strategies and details of our purification approach, which exploits differences in their reactivity with Lewis acids and aminosilica for their selective removal from extracts and subsequent isolation.
Resonant Raman Scattering Studies of SWCNT Templated Extreme Nanowires of Hgte and Pbi
Authors: Smith David Christopher , Spencer Joe , Sloan Jeremy , Faulques Eric
Published: February 2020

By filling the central pore of a single walled carbon nanotube (SWCNT) it is possible to form nanowires of a wide range of inorganic materials that are one unit cell in diameter. These are extreme nanowires, i.e. at the limit of miniaturisation of nanowires. Nanowires of these diameters show extreme quantum confinement effects and in some cases have crystal structures which cannot be stabilised as 3D crystals. Wide ranges of scientifically and technologically interesting materials have already been used to produce such nanowires. These include ferromagnetic materials, e.g. Fe and Co, phase change materials, e.g. GeTe, ferroelectric materials, e.g. SbSeI, and semiconductors, e.g. HgTe. It is likely that extreme nanowires will have entirely new properties, not just modified versions of the properties of the materials from which they are formed. Such properties would be interesting both fundamentally and technologically.  However, as yet there has only been very limited characterisation of the properties of nanowires formed inside single walled carbon nanotubes and the fundamental physics is not yet really understood.

We will present a comprehensive study of the Raman spectra of the vibrational modes of HgTe extreme nanowires inside single walled carbon nanotubes alongside atomic resolution TEM of the samples. Both TEM and the vibrational spectra clearly indicate that HgTe forms nanowires with an entirely new crystal structure when infiltrated into 1.3-1.4nm diameter SWCNTs. The strength of the Raman scattering is strongly dependent on incoming photon energy, with a strong resonance centred at 1.77eV which tails off more slowly to low energy than to high. Whilst all of the fundamental and combination modes are resonant at the same basic energy, the shape of the resonance varies for different features. It is clear that the form of the resonance has a lot to tell us about the electron-phonon coupling in these 1-Dimensional structures.  We will present the dependence of the Raman scattering on excitation and scattered polarisation, which is entirely in line with what would be expected for nanowires. However the temperature dependence of the Raman scattering is anomalous, showing a decrease in scattering intensity by a factor of ten with increasing temperature from 4K to 300K. We will also present results of electrochemically gated Raman scattering from HgTe nanowires which allow us to determine the band alignment of the template tubes and extreme nanowire. In addition to a comprehensive discussion of Raman scattering from HgTe nanowires, we will also present Raman scattering from PbI2 and CoI2 nanowires formed in SWCNTs and prove that the physics demonstrated by the HgTe nanowires is more generally applicable.

Figure 1
The Origins and Characteristics of the Threshold Voltage Variability of Quasi-Ballistic Single-Walled Carbon Nanotube Field-Effect Transistors
Authors: Cao Qing
Published: February 2020

Ultra-scaled transistors based on single-walled carbon nanotubes are identified as one of the top candidates for future microprocessor chips as they provide significantly better device performance and scaling properties than conventional silicon technologies.  From the perspective of the chip performance, the device variability is as important as the device performance for practical applications.  Here we presents a systematic investigation on the origins and characteristics of the threshold voltage (V
T) variability of scaled quasi-ballistic nanotube transistors.   Analysis of experimental results from variable temperature measurement as well as gate oxide thickness scaling studies shows that the random variation from fixed charges present on the oxide surface close to nanotubes dominates the V
T variability of nanotube transistors.  The V
T variability of single-tube transistors has a figure of merit that is quantitatively comparable with that of current silicon devices; and it could be reduced with the adoption of improved device passivation schemes, which might be necessary  for practical devices incorporating multiple nanotubes, whose area normalized V
T variability becomes worse due to the synergic effects from the limited surface coverage of nanotubes and the nonlinearity of the device off-state leakage current, as predicted by the Monte Carlo simulation.
Nondestructive Production of Magnetic Graphene Towards Energy Applications
Authors: Imae Toyoko , Ahmed Mahmoud Mohamed Mahmoud , Ujihara Masaki
Published: February 2020

Graphene can be prepared from a graphite intercalation compound (GIC)1 with acceptor-type intercalator, FeCl3.2 When the FeCl3–GIC is treated with primary amines at 90 °C for 6 h, the GIC expands to a few layers.3 The expansion is further facilitated, as the alkyl chain of primary amines becomes longer, while tertiary amines cannot penetrate inside the GIC because of their structural steric hindrance. The primary amine adsorbed in the GIC is oriented to form a bilayer by an indirect reactions among FeCl3–graphene–amine, and this process plays an important role in the expansion of the GIC, in contrast to the reaction of primary amines with donor-type GICs.4 Then the expanded-GIC is sonicated to exfoliate the graphene sheets. The obtained material exhibited a superparamagnetic property due to the remaining iron compounds. This approach using FeCl3–GIC and primary amine is preferable for the mass production of graphene because of the mild reaction conditions and the short treatment time for exfoliation from the chemically stable FeCl3–GIC. Moreover, the magnetization of graphene nano-composites could be useful for magnetic-recovery processes, electromagnetic heating, and the other electrochemical applications

References:

1. Zhao, W.; Tan, P. H.; Liu, J.; Ferrari, A. C., Intercalation of few-layer graphite flakes with FeCl3: Raman determination of Fermi level, layer by layer decoupling, and stability. Journal of the American Chemical Society 2011, 133 (15), 5941-5946.

2. Zhan, D.; Sun, L.; Ni, Z. H.; Liu, L.; Fan, X. F.; Wang, Y.; Yu, T.; Lam, Y. M.; Huang, W.; Shen, Z. X., FeCl3‐Based Few‐Layer Graphene Intercalation Compounds: Single Linear Dispersion Electronic Band Structure and Strong Charge Transfer Doping. Advanced Functional Materials 2010, 20 (20), 3504-3509.

3. M. Ujihara, M. M. M. Ahmed, T. Imae and Y. Yamauchi, Massive-exfoliation of magnetic graphene from acceptor-type GIC by long-chain alkyl amine. J. Mater. Chem. A, 2014, (2), 4244 - 4250.

4. Maluangnont, T.; Bui, G. T.; Huntington, B. A.; Lerner, M. M., Preparation of a homologous series of graphite alkylamine intercalation compounds including an unusual parallel bilayer intercalate arrangement. Chemistry of Materials 2011, 23 (5), 1091-1095.
Corrosion Behavior of Casing Steels in Cement Synthetic Pore Solution Exposed to High Pressure CO2 and H2S
Authors: Feng Ruishu , Beck Justin , Hall Derek M. , Buyuksagis Aysel , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: February 2020

As deeper wells drilled for oil and gas extraction encounter higher pressures, temperatures, and concentrations in the downhole environment, it becomes increasingly important to consider the integrity of the casing that provides both support and isolation of the well. These casings are commonly cemented to provide better sealing, and the alkaline environment provided by the pore water at the cement-casing interface typically puts the steel in a passive region. However, exposure to acid gases can cause degradation of the cement and thus lower the pH at the steel surface. Further, many formation waters are brines containing high concentration of chlorides. This increases the risk of corrosion and failure of the well casing. With these issues in mind, a corrosion study was initiated to investigate the corrosion behavior of grade L-80 casing steel in cement synthetic pore solutions in contact with CO2 and H2S. Experimental approaches consisted of two stages. In the first stage, a Class H well cement was exposed to a 5 wt% NaCl brine in contact with CO2 and H2S at 85 °C for 200 hours. At the end of the exposure time, the pore water of the exposed cement was sampled and analyzed qualitatively and quantitatively.  This chemical analysis was used for preparing a cement synthetic pore solution (CSPS) for corrosion testing. In situ electrochemical measurements, performed for the L-80 steel samples in the CSPS at 85 °C, included linear polarization resistance, electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel analysis. Additionally, ex situ surface analyses using scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffraction were performed for the corroded samples. Mass loss measurement coupons were also used to confirm the electrochemical results.
Effect of Tropical Atmosphere on Corrosion of Different Metals: Corrosivity Measurements of Singapore
Authors: Wijesinghe Sudesh Lakshitha , Tan Zixi
Published: February 2020

Corrosion influences and intrudes many parts of our lives. It can cause dangerous and expensive damages. Singapore obviously faces corrosion consequences though there is no direct evidence or record to justify how aggressive and diverse Singapore atmosphere is in terms of corrosion.  However, now there is some light to shed these doubts as standardised atmospheric exposure tests have been established in Singapore. Atmospheric exposure test sites were setup at three locations of Singapore to represent marine, industrial and urban atmospheres or their mixtures. Salient atmospheric constituents or parameters like time of wetness, Cl-, SO2, NO2, O3, HNO3 have been measured in all sites over a period of time to categorise corrosivities of particular atmospheres. The effect of atmosphere on corrosion of Fe, Cu, Al and Zn also has been investigated and quantified. Subsequently, “estimated” and “determined” corrosivity values of Singapore according to ISO 9223:2012 were measured and recorded.