bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method to Improve Quantum Efficiency of Phosphors in the Submicron Size Regime Using a Flux for Solid State Lighting Applications
Authors: Ha Jungmin , Novitskaya Ekaterina , Hirata Gustavo , Zhou Chenhui , Ridley Robyn , Graeve Olivia A , Wang Zhenbin , Ong Shyue Ping , McKittrick Joanna 
Published: February 2020

Micron sized phosphors have been widely studied by using a solid-state reaction method for application in near UV-emitting LEDs. This method produces large crystallite size powders, but have higher quantum efficiencies than smaller crystallite size powders. For the phosphor configuration, the packing density of these large particles on the device is thus low and generates substantial light-scattering. To overcome this issue, phosphors with a small, narrow size distribution are required. If the particle radii are < ~400 nm, scattering from these particles will be negligible on visible and UV radiation. However, submicron-sized phosphors with nano-sized crystallites have poor quantum efficiency compared to micron-sized phosphors with micron-sized crystallites.
An addition of flux (NH4F, NH4Cl, or H3BO3) to the CaMgSi2O6:Eu2+ phosphors during synthesis was performed and the effect of the flux on the crystallite size and quantum efficiency of nanocrystalline and submicron phosphors particles was examined. The use of NH4F or NH4Cl increased the crystallite size in the submicron sized particles, which yielded an increase in emission intensity and quantum efficiency. Adding the H3BO3 flux crystallized SiO2 and changed lattice parameters, degrading the luminescent properties. Excessive NH4Cl was also examined and it resulted in nucleation of a second phase and changed lattice parameters with no improvement in luminescent properties. These results demonstrate that a careful selection and use of a flux is a method to improve the quantum efficiency of submicron particles sized phosphors. This work is supported by the National Science Foundation, Ceramics Program Grant (DMR-1411192).
(Invited) Strain Assisted Band Gap Engineering of SiGe Core–Shell Nanowires using Low-Temperature Condensation Process
Authors: Berbezier Isabelle , David Thomas , Ronda Antoine , Favre Luc , Gailhanou Marc , Gentile Pascal , Buttard Denis , Calvo Vincent , Amato Michele , Aqua Jean-Noël 
Published: February 2020

Selective oxidation of the silicon element of silicon germanium (SiGe) alloys during thermal oxidation is a very important and technologically relevant mechanism used to fabricate a variety of microelectronic devices. We show a two-step epitaxy/condensation process at low temperature to produce atomically flat Ge rich layer fully strained and free of defects. We demonstrate that the condensation based process enables the total inhibition of the classical ATG morphological instability, together with the hindering of dislocations for critical thickness much greater than those commonly obtained by direct deposition. Those behaviors could be explained by the injection of self-interstitials in the Ge-rich layers during condensation.
An integrative approach involving vapor–liquid–solid (VLS) growth followed by selective oxidation steps to the construction of core–shell nanowires and higher-level ordered systems with scalable configurations is used. We contrast this strategy that uses reaction-diffusion-segregation mechanisms to produce coherently strained structures with highly configurable geometry and abrupt interfaces with growth-based processes which lead to low strained systems with non uniform composition, three-dimensional morphology, and broad core–shell interface. We specially focus on SiGe small core–shell nanowires and demonstrate that they can have up to 70% Ge-rich shell and 2% homogeneous strain with core diameter as small as 14 nm. Key elements of the building process associated with this approach are identified with regard to existing theoretical models. Moreover, starting from results of ab initio calculations, we discuss the electronic structure of these novel nanostructures as well as their wide potential for advanced device applications. Similar core-shell structures can be formed around small nanocrystals for photonic applications.
Atomic Layer Deposition of ZnO and Doped ZnO As Alternative Transparent Conducting Oxides for Photovoltaics
Authors: Ryan Louise P , Walsh Adrian , McCarthy Melissa M. , Monaghan Scott , Modreanu M , Romanitan Cosmin , Chaix-Pluchery Odette , O'Brien S , Pemble Martyn E , Povey Ian M 
Published: February 2020

Organometallic halide perovskite solar cells have gained considerable interest in recent times, with low cost and high power conversion efficiencies [1]. However, such cells are not without problems such as, stability, scalability and the need for a low thermal budget in the fabrication of tandem structures. In this work, we examine the transparent conducting electrode where the current materials of choice are FTO and ITO which require a higher process temperature (>450oC).
Zinc oxide thin films have attracted significant attention as transparent conducting oxides due to their diverse electrical and optical properties. ZnO is an n-type semiconductor with a direct band gap of 3.3 eV. It is optically transparent in the UV/visible and infrared spectra and exhibits promising electrical properties.
ALD has distinct characteristics that make it a prospective deposition method of ZnO and doped ZnO, low temperature, conformal and large surface area coating capabilities. The deposition of ZnO and doped ZnO has previously been reported. In this work, an ALD process has been developed to deposit ZnO as a potential TCO in solar cells.
ZnO was deposited using low temperature atomic layer deposition (ALD). Subsequently, zinc oxide was doped with Al, Ti and Hf and the electrical, optical and structural properties were analyzed to determine the effect of doping on ZnO. The presented results revealed that Ti-doped ZnO was the suitable TCO candidate with a sheet resistance value of 41 Ω/□ and electron mobility of 12.8 cm2/Vs. In addition to promising electrical properties, Ti-doped ZnO also exhibited high optical transparency of >80% in the UV/ visible and IR ranges. We demonstrate that ALD of Ti-doped ZnO could be a viable alternative to ITO and FTO for TCO materials in photovoltaics. Preliminary data from perovskite solar cells fabricated with a ZnO based transparent conducting electrode are presented and discussed.
[1] https://www.nrel.gov/pv/assets/images/efficiency-chart.png
Electroless Encapsulation of C-Cloth with Sn and Sn-Cu Alloy for Li-Ion Battery Anode
Authors: Watson Venroy George , Kalu Egwu Eric , Yeboah Yaw D. , Weatherspoon Mark H. , Zheng Jim P 
Published: February 2020

Over the last few decades a vast number of researchers have investigated various methods for the synthesis of tin alloy anode materials capable of repeated cycling, reduced tin pulverization, and capacity retention when used in lithium ion batteries (LIBs).1-3 In this study, we report the use of woven carbon cloth as high surface area template for the deposition of Cu and subsequent encapsulation with Sn via facile electroless coating method without the use of external power supply. The resulting material Sn-Cu@C-cloth was annealed at 200 OC and 400 OC and used as electrodes in LIB half-cells with Li metal as anode. Charge/discharge study at current density of 227 mAh/g indicated that Sn-Cu@C-cloth annealed at 200OC and 400 OC exhibited first cycle capacities of 745 mAh/g, and 1075 mAh/g, respectively, while the C-cloth substrate exhibited only 340 mAh/g. Preliminary results after fifty cycles indicated that the annealed Sn-Cu@C-cloth exhibited capacity retention of ~413 mAh/g. These results indicate that facile electroless encapsulation of carbon cloth as a cost effective approach can potentially be used to fabricate Sn and CuSn alloys anode materials.

References

[1] M. Winter, J.O. Besenhard, Electrochemical lithiation of tin and tin-based intermetallics and composites, Electrochimica Acta 45 (1999) 31.
[2] A.R. Kamali, D.J. Fray, tin-based materials materials as advanced anode materials for lithium ion batteries: A review, Rev. Adv. Mater. Sci. 27 (2011) 14.
[3] H. Kim, G.O. Park, Y. Kim, S. Muhammad, J. Yoo, M. Balasubramanian, Y.-H. Cho, M-G. Kim, B. Lee, K. Kang, H. Kim, J. M. Kim, W.-S. Yoon, New insight into the reaction mechanism for exceptional capacity of ordered mesoporous SnO2 electrodes via synchrotron-based x-ray analysis, Chem. Mater. 26 (2014) 6361.

Figure 1
(Invited) Electrochemical Manufacturing and Characterisation of Nanostructured Electrodes for Lithium Based Batteries
Authors: Rehnlund David , Ihrfors Charlotte , Nyholm Leif 
Published: February 2020

Due to their high energy and power densities, lithium-ion batteries are the primary choice for application in consumer electronics. Although new electrode materials for Li-ion batteries are developed continuously, relatively little attention has so far been paid to the use of electrochemical methods in the manufacturing of battery materials. In the field of microbatteries, electrodeposition has, nevertheless, become an important technique for the manufacturing of current collectors, electrode materials and electrolytes [1]. During the last few years it has also been shown that electrochemically nanostructured electrodes lacking binders and other additives can facilitate the attainment of an improved understanding of the electrochemical reactions taking place in lithium based batteries.
This presentation will focus on the development of electrochemical approaches for the manufacturing and study of nanostructured electrode materials for lithium based batteries. It will be shown that electrodeposition can be used for the manufacturing of 3-D copper and aluminium [1] current collectors as well as the coating of these with thin layers of anode or cathode materials. Electrochemical manufacturing and characterisation of materials such as multilayered Cu/Cu2O nanorods [2], Sn/SnO2 particles [3] and TiO2 nanotubes (see Figure 1) will be discussed, as well as a new approach for the manufacturing of TiO2 nanotube size gradient based electrodes [4]. Some fundamental issues regarding the electrochemical processes in the electrochemically manufactured materials, including the formation of “cathodic passive layers” and “trapping of lithium” in current collectors and alloy forming electrode materials [5] and the electrodeposition of homogeneous lithium films on lithium electrodes (see Figure 1) will likewise be discussed.

References

[1] K. Edström, D. Brandell, T. Gustafsson, L. Nyholm, Electrodeposition as a tool for 3D Microbattery Fabrication, Electrochem. Soc. Interface, 20 (2011) 41.
[2] D. Rehnlund, M. Valvo, C. –W. Tai, J. Ångström, M. Sahlberg, K. Edström, L. Nyholm, Electrochemical fabrication and characterization of Cu/Cu2O multi-layered micro and nanorods in Li-ion batteries, Nanoscale, 7 (2015) 13591.
[3] S. Böhme, K. Edström, L. Nyholm, Overlapping and Rate Controlling Electrochemical Reactions for Tin(IV) Oxide Electrodes in Lithium-Ion Batteries, J. Electroanal. Chem., 797 (2017) 47.
[4] W. Wei, F. Björefors, L. Nyholm, Hybrid energy storage devices based on monolithic electrodes containing well-defined TiO2 nanotube size gradients, Electrochim. Acta, 176 (2015) 1393.
[5] D. Rehnlund, F. Lindgren, S. Böhme, T. Nordh, Y. Zou, J. Pettersson, U. Bexell, M. Boman, K. Edström, L. Nyholm, Lithium Trapping in Alloy forming Electrodes and Current Collectors for Lithium based Batteries, Energy Environ. Sci., 10 (2017) 1350.

Figure 1
(Invited) Electrochemical Synthesis of Nanostructured Materials Using Ionic Liquids for Metal-Ion Batteries
Authors: Lahiri Abhishek , Endres Frank 
Published: February 2020

In the last two decades ionic liquids have evolved to be good electrolytes for the electrodeposition of metals and semiconductors, primarily due to their large electrochemical windows of up to ± 3V. However, only in the last couple of years significant interest in using electrodeposited materials from ionic liquids for applications in batteries has evolved, showing promising and versatile routes for electrode material synthesis.
In this lecture we will give an overview on the electrodeposition of metals such as Al, Zn [1, 2] and semiconductors such as Si, Ge [3, 4] from ionic liquids which have been applied to different metal-ion batteries. In the case of metals such as Zn, we will show how the addition of dopant salts and ionic liquid mixtures makes it possible to inhibit the formation of dendrites during Zn deposition/stripping. Also, electrodeposition of various silicon and germanium macroporous structures as well as nanotubes which have been used as anodes in Li-ion batteries will be shown [5, 6].
Lastly, we will give an insight into the less investigated subject of electroless deposition in ionic liquids [3, 7] and how it can be used to develop battery electrodes as well as to modify Si and Ge deposits for battery applications.

References

S. Zein El Abedin, A. Garsuch, F. Endres, Aus. J. Chem., 2012, 65, 1529-1533

Z. Liu, T. Cui, G. Pulletikurthi, A. Lahiri, T. Carstens, M. Olschewski, F. Endres, Angew. Chem. Int. Ed., 2016, 55, 2889-2893

A. Lahiri, T. Lu, N. Behrens, N. Borisenko, G. Li, F. Endres, ACS Appl. Mater. Interfaces., 2017, 9, 11350-11355

A. Lahiri, G. Li, M. Olschewski, F. Endres, ACS Appl. Mater. Interfaces., 2016, 8, 34143-34150

A. Lahiri, A. Willert, S. Zein El Abedin, F. Endres, Electrochim. Acta., 2014, 121, 154-158

X. Liu, J. Hao, X. Liu, C. Chi, F. Endres, Y. Zhang, Y. Li, J. Zhao, Chem. Commun., 2015, 51, 2064-2067

A. Lahiri, M. Olschewski, R. Gustus, N. Borisenko, F. Endres, Phys. Chem. Chem. Phys, 2016, 18, 14782-14786
(Invited) Tracking Hydrodynamic Signatures of Metal Nucleation Events Via Lateral Molecular Force Microscopy
Authors: Fermin David , Plana Daniela , Harniman Robert , Miles Mervyn 
Published: February 2020

The direct visualization of local events leading to the formation of a critical nucleus remains as one of the most formidable challenges in electrodeposition. Recently, state-of-the-art video-rate scanning tunnelling microscopy has been able to follow lateral growth of Bi deposits with exquisite atomic resolution [1]. However, strong local potential bias between tip and substrate often leads to ‘shielding effects’, significantly decreasing local nucleation rates. Substrate-tip interactions in conventional atomic force microscopy also have a strong effect in local nucleation rate. In this contribution, we shall demonstrate a new approach to monitor individual nucleation events based on tracking local perturbations of hydration shells employing high-speed lateral molecular force microscopy (HS-LMFM).
A unique optical feedback mechanism lies at the center of the operating mode of HS-LMFM [2,3]. Under this configuration, the position of a vertically oriented probe (VOP) is tracked by measuring the scattering of the evanescent wave of a laser impinging under total internal reflection from the back of an optically transparent electrode. As the tip approaches the surface oscillating close to its resonant frequency, the oscillation frequency is affected by the visco-elastic properties of the various hydration layers. Changes in the VOP oscillations are optically detected by the scattering evanescent field. This approach enables monitoring interaction with individual hydration layers simultaneously with, but independent of, the optical feedback.
In these experiments, the tip is positioned at a distance in which shear force interactions with hydration layers of an In-doped SnO2 electrode (approximately 2.9 nm roughness level) become negligible [4]. As nucleation events are triggered, the hydration layers around individual nuclei move into a detectable range of the VOP, leading to changes in the oscillation frequency. Shear force maps uncover a highly dynamic landscape prior to the formation of stable nucleus. At constant potential, the stochastic formation and dissolution of nuclei can be observed in the sub-second time scale. The growth of a stable nucleus is also followed in real-time, illustrating the potential of this technique for probing complex phase formation phenomena at electrode surfaces.
References

Matsushima, H. et al.
Faraday Discuss.
193, 171-185 (2016).

Fletcher, J. M. et al.
Science
340, 595-599 (2013).

Antognozzi, M. et al.
Nat.
Phys.
12, 731-735 (2016).

Harniman, R.L. et al. Nat.
Commun.
8, 971 (2017)
Multivalent Metal Ions As Efficient Reducing Agents for Electroless Metal Deposition Processes
Authors: Norkus Eugenijus , Tamasauskaite-Tamasiunaite Loreta 
Published: February 2020

In this study the possibility and conditions to use lower oxidation state metal ions as reducing agents for autocatalytic electroless metal deposition are discussed.
The theoretical background of such kind reactions is presented in the view of thermodynamics.
Kinetic data on electroless silver, copper, palladium and platinum deposition using Co(II)/Co(III) redox systems with different ligands are presented and discussed.
Ti(III)/Ti(IV) redox systems with different ligands were shown also to be suitable reducing agents for reducing of Pt(IV), Pd(II), Ni(II) and Co(II) to metallic state and formation of continuous metal layer on the surface to be plated.
The morphology of metal layers deposited using above-mentioned reducing agents was characterized by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of metal deposition rate was investigated by means of the gravimetry or Electrochemical Quartz Crystal Microgravimetry (EQCM).
Redox Flow Batteries for Fast EV Charging and for Hydrogen Production for FCEVs
Authors: Girault Hubert H , Dennison Christopher R , Ligen Yorick , Vrubel Heron , Zanzola Elena , Reynard Danick , Amstutz Véronique , Peljo Pekka 
Published: February 2020

A service station for electric vehicles (EVs) and fuel cell EVs (FCEVs) has been constructed based on a vanadium redox flow battery (200kW-400kWh). This battery is used to fast charge EVs using a DC-DC converter operating at 80kW.
We also operate two electrolyzers (one alkaline 50kW, one PEM 25 kW) to produce hydrogen. This hydrogen is dried, purified and stored at 200 bars. A service station for hydrogen has been built with reservoirs at 500 bars to fill a car (Renault Kangoo/Swiss hydrogen) operating at 350 bars and at 900 bars to fill a car operating at 700 bars (Hyundai).
We shall discuss the figures of merit of electric and hydrogen mobility and our experience to run a service station in the Alps.
We shall also present a new technology to produce hydrogen on demand and under pressure directly from a Vanadium (III)/(II) solution from the redox flow battery using a Mo2C catalyst. We shall also discuss the use of solid boosters to enhance the storage in the tanks of a redox flow battery.
High Performance Reversible Hydrogen-Vanadium Fuel Cell for Electrical Energy Storage
Authors: Nguyen Trung Van , Verma Ankit 
Published: February 2020

The hybrid reversible hydrogen-vanadium fuel cell [1,2] offers a feasible solution for storing electrical energy from the grid or intermittent renewable energy sources such as wind and solar. This system is an attractive alternative to the all-vanadium system due to the 50% reduction in the amount of vanadium solution required. This two-phase hybrid system also allows cross-over species to be separated and reused. In this presentation, the performance (cell voltage and power density versus current density and self-discharge rate) of this system at elevated temperatures (40oC and 50oC) will be discussed.
References:

Yufit, B. Hale, M. Matian, P. Mazur and N. Brandon, J. Electrochem. Soc., 160, A856 (2013).

Regis P. Dowd Jr., Vikram Lakhanpal, and Trung Van Nguyen, Electrochem. Soc., 164, F564 (2017).

Figure 1
Probing the Effects of Various Electrocatalysts on Aqueous Vanadium Redox Flow Battery Performance
Authors: Shah Andrew , Pierson Meghan , Joo Yong Lak 
Published: February 2020

It has become increasing clear that renewable electricity can be generated on a large scale through a variety of different methods. While this progress has begun to decarbonize baseload electricity generation, the intermittent nature of the required resources has proven difficult to incorporate into regional electrical grids. Grid-scale electricity storage methods are a promising solution to the inefficiencies associated with unpredictable electricity generation. Redox flow batteries have demonstrated the ability to be used as a reasonably low-cost, long-term electrical storage method. Specifically, vanadium redox flow batteries (VRBs) have been of special interest due to their chemical stability, long life cyclability, and potential for high capacity electrical storage. One of the main factors limiting market penetration of redox flow batteries in energy storage portfolios is the high capital cost associated with this comparatively low energy density technology. To this end, many current research efforts focus on improving the energy density of VRBs to warrant this cost in the long term.
This work focuses on improving the energy density of VRBs by probing the effects of a variety of different metal electrocatalysts. This process uses metal salts to form catalytically active nanoparticles on the surface of the anode to improve the kinetics of the anodic reaction in the VRB. The systems of interest in this study involved using tin, copper, and lead metals deposited on the surface of the anode using a variety of techniques. The direct reduction of metal salts results in the formation of nano-scale and micron-scale electroplated particles on the surface of the anode, which can be used to improve the kinetics of the sluggish anodic reaction in VRBs. This work shows that when as little as 0.02 M concentrations of tin chloride are added to 1.0 M vanadium electrolyte, electrochemically reduced tin nanoparticles have excellent catalytic properties toward the anodic reaction, improving current densities by over 30% and improving the overall capacity of the battery. There were also some synergistic effects observed when the tin salts were coupled with copper salts, further improving the capacity of the battery. A series of methods were used to probe the effects of synthesized lead particles as well. We will present how these processes can have a dramatic effect on increasing both capacity and energy density of aqueous vanadium redox flow batteries.
Improving Electrochemical Performance of The Layer-Structured Ncm Cathode Materials For Large-Scale Lithium Ion Batteries
Authors: Kim Hyun-Soo , Sim Sungju , Jin Bong-Soo 
Published: February 2020

Ni-rich layered LiNixCoyMn(1-x-y)O2 (x≥0.8) has been considered as promising candidate cathodes due to their large specific capacity, high rate capability and low cost. However, Ni-rich materials suffer from severe capacity fading, especially, when cycled at high temperatures due to the formation of highly reactive Ni4+ at charge state. Ni4+ has strong oxidizing property and the reaction between Ni4+ and the electrolyte will be accompanied by gas evolution, which causes severe swelling of the cell. Moreover, the formation LiOH and Li2CO3 on the surface is prone because of residual lithium on the surface, which is remained dut to an excess of lithium to creat a well ordered layered phase. The reaction with electroytes negatively impact the cycling performance by decomposing electrolytes. Therefore, it is necessary to improve the structure and interfacial stability, and many studies have indicated coating and doping approach. The coating for NCM materials is often used with stable metal oxides such as ZrO2, Al2O3, TiO2, SiO2 and Li2ZrO, and the commonly used dopant elements are Al, Mg, Ti, Zr and Fe.
In this work, TiO2 coated and Ti doped LiNi0.8Co0.1Mn0.1O2 were synthesized at the same time to improve the structure stability and suppress the side reaction with electrolytes. TiO2 nano-powder as a raw material was used to coating and doping through a convenient solid state synthesis process. As a result, the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode was enhanced.