bluuebunny/crossref_metadata_2025 huggingface dataset:
Impurity and Defect Monitoring in Hexagonal Si and SiGe Nanocrystals
Authors: Koelling Sebastian , Plantenga Rianne C. , Hauge Hakon I.T. , Ren Yizhen , Li Ang , Verheijen Marcel A. , Conesa Boj Sonia , Assali Simone , Koenraad Paul M. , Bakkers Erik P.A.M.
Published: September 2016

Silicon-Germanium in a hexagonal crystal-structure is a candidate material for a direct band-gap group IV semiconductor that can be integrated into the CMOS process. It has recently been synthesized as a crystalline shell grown epitaxial around a nanowire core of hexagonal Gallium-Phosphide. In order to study the optical properties of this newly generated material and evaluate its potential for building optical devices it is necessary to grow defect and impurity free hexagonal Silicon-Germanium. Impurity detection and mapping in nano-structures is however challenging as most bulk and thin film characterization methods cannot be used. Here we show that Atom Probe Tomography can be used to map the impurities in hexagonal shells of Silicon-Germanium and Silicon. This will allow to optimize growth of hexagonal Silicon-Germanium nanocrystals towards impurity free, optically active crystals.
Analysis of Microscopic Strain and Crystalline Structure in Ge/Ge1−X
Sn
x
Fine Structures by Using Synchrotron X-ray Microdiffraction
Authors: Ike Shinichi , Nakatsuka Osamu , Inuzuka Yuki , Washizu Tomoya , Takeuchi Wakana , Imai Yasuhiko , Kimura Shigeru , Zaima Shigeaki
Published: September 2016

We examined the formation of locally strained Ge nanostructures sandwiched between Ge1−x
Sn
x
stressors using metal-organic chemical vapor deposition method. We have investigated the microscopic local strain and stress in the Ge/Ge1−x
Sn
x
heterostructures using synchrotron microdiffraction and finite element method calculation. The microdiffraction measurement for an asymmetric lattice plane enables directly quantitative evaluation of the strain value of an individual Ge fine line structure with a few tens of nanometers width. An in-plane compressive strain value of 0.9% is achieved for a 30 nm-width Ge line with Ge1−x
Sn
x
stressors, which corresponds to a compressive stress of 1.2 GPa.
Au / SiO2 Hybrid Bonding with 6-μm-Pitch Au Electrodes for 3D Structured Image Sensors
Authors: Honda Yuki , Hagiwara Kei , Goto Masahide , Watabe Toshihisa , Nanba Masakazu , Iguchi Yoshinori , Saraya Takuya , Kobayashi Masaharu , Toshiyoshi Hiroshi , Higurashi Eiji , Hiramoto Toshiro
Published: September 2016

A 3D structured CMOS image sensor that can process signals pixel-wise in parallel is investigated as a means to simultaneously increase the pixel count and the frame rate. To make the pixel pitch finer, the Au electrode dimension is reduced to a 6-μm pitch that is electrically interconnected using a direct-bonding technique. We also develop a daisy-chain test device to examine the numerous interconnections. The experimental results show that the series of electrical interconnections exceeds 230,000 contacts, with the Au contact resistance for a single connection being ~23.6 mΩ.
Edge Water Penetration in Direct Bonding Interface
Authors: Rieutord François , Tardif Samuel , Landru Didier , Kononchuk Oleg , Larrey Vincent , Moriceau Hubert , Tedjini Marwan , Fournel Frank
Published: September 2016

We report here on measurements demonstrating that water is able to enter a hydrophilic wafer bonding assembly from the edge. The driving forces for water entry are capillary forces driven by the negative Laplace pressure. The characteristic time for water to penetrate the interface is consistent with standard values for water viscosity and gap width.
(Invited) Locally Measuring the Adhesion of InP Membranes Directly Bonded on Silicon
Authors: Patriarche Gilles , Pantzas Konstantinos , Le Bourhis Eric , Beaudoin Gregoire , Talneau Anne
Published: September 2016

Instrumented nano-indentation is combined ex situ with Atomic Force Microscopy and Scanning Transmission Electron Microscopy in a nano-scale analog of the Double-Cantilever Beam experiment to evaluate the adhesion of InP mebranes directly bonded on Silicon. This method is shown to provide reliable and highly localized measurements of the surface bonding energy of InP on Si. The localized nature of the measurements is taken advantage of to investigate the strength of the bonded interface on areas of the Si substrate that include nano-patterned features typically found in advanced Photonic Integrated Circuits.
(Invited) Unseeded Growth of Poly-Crystalline Ge with (111) Surface Orientation on Insulator by Pulsed Green Laser Annealing
Authors: Horita Masahiro , Takao Toru , Nieda Yoshiaki , Ishikawa Yasuaki , Sasaki Nobuo , Uraoka Yukiharu
Published: September 2016

We investigated unseeded growth of poly-crystalline Ge with well-oriented large-size grains on insulator from amorphous Ge by scanning pulsed green laser annealing. The Ge was patterned to 2-µm-wide stripes and then annealed by laser irradiation. The annealed Ge stripes were crystallized with well-oriented (111) surface and the grain size was 2 µm wide and ~10 µm long, where the maximum length was 20 µm. Crystallization process was discussed from dependence of the laser fluence on the crystal states of Ge stripes as well as temperature simulations.
(Invited) Low-Temperature Growth of Orientation-Controlled Large-Grain Ge-Rich SiGe on Insulator at Controlled-Position for Flexible Electronics
Authors: Sadoh Taizoh , Aoki Rikuta , Tanaka Takahiro , Park Jong-Hyeok , Miyao Masanobu
Published: September 2016

A technique for low-temperature (≤300°C) formation of large-grain (≥10 μm) Ge-rich SiGe crystals on insulator, whose orientation and position are controlled, should be developed to realize flexible electronics. To achieve this, the gold-induced layer-exchange crystallization technique using a-SiGe/Au stacked structures has been investigated. By introduction of diffusion control layers into the a-SiGe/Au interface, (111)-oriented large-grain Ge-rich SiGe crystals are achieved on insulating substrates at low temperatures (≤300°C). Moreover, position control of large-grain crystals becomes possible by patterning the diffusion control layers. This low-temperature growth technique is expected to be useful to realize flexible electronics.
(Invited) Low-Temperature Sol-Gel Derived Ultra-Flexible Metal-Oxide Thin-Film-Transistors and Their Applications
Authors: Jo Jeong-Wan , Heo Jae Sang , Kim Kyung-Tae , Kim Jaehyun , Kim Myung-Gil , Park Sung Kyu
Published: September 2016

Solution-processed metal-oxide thin-film transistors (TFTs) were fabricated for flexible integrated circuits. As gate dielectric layer, a transparent insulating oxide, ZAO (Zirconium incorporated aluminum oxide) has been employed instead of using pristine AlOx (Aluminum oxide). Using the ZAO gate dielectric, field-effect mobility of 6.21 cm2/Vs and hysteresis-free property have achieved by improving the interface between the gate dielectric and the IGZO (Indium gallium zinc oxide) semiconductor layer. For the surface modification, a heterogeneous ZAO gate dielectric has been used. With the IGZO TFTs employing ZAO gate dielectric, an ultra-flexible 7-stage ring-oscillator array was fabricated.
Highly Stable Zinc Oxynitride Thin-Film Transistors with Field-Effect Mobility Exceeding 100 cm2/Vs
Authors: Kim Yang Soo , Kim Hyun-Suk
Published: September 2016

A recent work on a relatively new type of semiconductor, namely zinc oxynitride (ZnON) as a promising candidate for the next-generation display applications, will be presented.(1) High mobility ZnON thin films were deposited by RF sputtering. In order to enhance the mobility and stability of ZnON TFTs, thickness and annealing conditions of ZnON thin films were optimized. Using ZnON films grown using the optimum conditions, the fabrication of high performance devices with field effect mobility exceeding 120 cm2/Vs is demonstrated, based on simple reactive RF sputtering methods.
High Aspect Ratio Single Crystal of Cesium Iodide Column
Authors: Chen Chien Chon , Chen Shih Hsun , Yang Jheng En , Huang Ker Jer , Jheng Wern Dare
Published: September 2016

Cesium iodide (CsI), which is used in the phosphor layer of a scintillator plate, exhibits a relatively high conversion rate of X- or g-rays to visible light. Important requirements for the scintillator materials used in the applications include high light output, transparency to the light it produces, high stopping efficiency, fast response, good proportionality, low cost, and availability in large volume In order to simplify and reduce the cost of the scintillator deposition process, we deposit the scintillator of a CsI into a high aspect ratio anodic aluminum oxide (AAO) template to produce CsI columns of nano and submicron sizes. The scintillator material of CsI columns were formed in the AAO template by a non-vacuum method. When the CsI melt is injected a confined to an AAO channel with a high aspect ratio, it grows as a stable single-crystal column with smooth surfaces, free of dendrites and grain boundaries. In this research, we design a novel cooling-function of electrochemical mold for a high quality AAO fabrication and compare the CsI wire and column formation by non-vacuum injection method in a AAO template.
GaN MISIM Diode with High-k Dielectrics of ZrO2 and Al2O3 for UV Sensing
Authors: Lee Gil-Ho , Seol Jeong-Hoon , An Jong-Ki , Yun Ju-Young , Hahm Sung-Ho
Published: September 2016

We fabricated a GaN MISIM (metal-insulator-semiconductor-insulator-metal) UV photodiode using two high-k dielectrics of ZrO2 and Al2O3. The fabricated UV photodiode using ZrO2 showed better photo-electronic properties than that using Al2O3. The dark and photo-responsive current density ratios of the device with ZrO2 and Al2O3 were 250 and 196 at 10 V bias. Their UV/visible rejection ratios (UVRRs) were 1.65 × 102 and 1.34 × 102 for 365 nm wavelength at 1 V bias, respectively. The noise spectral density of the device with ZrO2 was 1.3 × 102 A2/Hz for 10 Hz at 3 V bias which has lower noise value than that with Al2O3. The GaN MISIM UV photodiode with ZrO2 has over 20 % improved photo-electronic properties and lower noise than that with Al2O3.
Ultra Large Scale Manufacturing Challenges of Silicon Carbide and Gallium Nitride Based Power Devices and Systems
Authors: Singh Rajendra , Asif Amir A
Published: September 2016

Both silicon carbide (SiC) and gallium nitride (GaN) have the potential of developing transformative power electronics for future needs. The defect density of current devices is quite high and only niche applications will continue to evolve unless major changes are made in the manufacturing process. In this paper we have proposed advanced process control (APC) based single wafer processing (SWP) tools for manufacturing SiC and GaN power devices. New manufacturing tools have the potential of realizing full potential of these materials.
(Invited) Simulation of the Effects of As-Grown Defects on GaN-Based Power HEMTs
Authors: Mukherjee Shrijit , Patrick Erin , Law Mark E , Ren Fan , Pearton Stephen J.
Published: September 2016

Recent developments in identification of as-grown defects and impurities in the GaN buffer region of AlGaN/GaN High Electron Mobility Transistors (HEMTs) provide an opportunity to identify their role in degradation of dynamic switching behavior. Using TCAD simulation, effect of capture-emission by electron and hole traps on drain current transients during drain lag switching experiments is presented which is otherwise difficult to predict analytically.
Characterization and Comparison of Planar and Trench Silicon Carbide (SiC) Power MOSFETs
Authors: Wang Zhiqiang , Chinthavali Madhu , Campbell Steven
Published: September 2016

This paper presents a comprehensive evaluation and experimental comparison of silicon carbide power MOSFETs through double pulse test. First, a universal hardware platform is designed and developed to test power semiconductor devices with various device packages and measuring requirements. Using the developed platform, the static characteristics and switching performance of the two types of SiC MOSFETs (one planar and one trench type) are evaluated under different case temperatures from 25 oC to 175 oC. Based on the evaluation data, a comparison of both SiC MOSFETs is conducted in terms of their on-state resistance, switching loss, and temperature dependent behavior. It is found that the latest trench SiC MOSFETs present similar switching loss while much lower conduction loss compared to existing commercial planar SiC MOSFETs. Moreover, the trench devices show a nearly temperature independent switching loss, which is beneficial to suppress the potential thermal runaway issue under high temperature continuous operation.
(Invited) Schematic Description of the Internal Stress Distribution Responsible for Defect Generation in Larger-Diameter PVT-Grown 4H-SiC Single Crystals
Authors: Fujimoto Tatsuo , Nakabayashi Masashi , Ushio Shohji , Tani Komomo , Katsuno Masakazu , Sato Shinya , Tsuge Hiroshi
Published: September 2016

Growth stability necessary for the realization of larger-diameter PVT-grown SiC crystals with higher crystallinity was discussed from thermoelastic and thermodynamic viewpoints of SiC-PVT single crystal growth phenomena. A schematic interpretation based upon the equilibrium equations was presented for approximated estimation of thermoelastic stresses, and the effects of reactions between the vapor and carbon sources on the SiC growth were examined in the frame work of thermodynamic description for PVT-SiC growth.
4H-SiC V-Groove Trench MOSFETs with Low Specific On-State Resistance and High Reliability
Authors: Mikamura Yasuki , Uchida Kosuke , Saitoh Yu , Hiyoshi Toru , Masuda Takeyoshi , Tsuno Takashi
Published: September 2016

The originally structured 4H-SiC V-groove trench MOSFET with {0-33-8} face for the trench sidewalls has been proposed. The inclined trench structure can be fabricated by the thermochemical chlorine etching, resulting in the smooth low damage surface. Consequently, the low specific on-state resistance of the VMOSFET was attained. Thus a large current of 150A was obtained with a single 6-mm-square chip. High Temperature Gate Bias (HTGB) test was performed under a gate bias of +20V or -10V at 175oC. After the 2500 hour test, the threshold voltage kept stable only within ±0.2 V voltage shifts. Due to these advantages, the VMOSFETs are suitable for use in automotive electronic devices and the regenerative energy generation system applications.
(Invited) Highly Functional Graphene Nano-Electromechanical (GNEM) Devices for Advanced Switch and Sensor Applications
Authors: Mizuta Hiroshi , Sun Jian , Schmidt Marek E. , Muruganathan Manoharan
Published: September 2016

Novel graphene nano-electro-mechanical (GNEM) devices are developed for low-voltage switching and ultra-sensitive chemical gas sensing applications. Doubly-clamped and cantilever GNEM switches with a local top actuation electrode are developed, and a pull-in voltage less than 5 V is realized. A naturally formed chromium oxide, introduced at the graphene-electrode contact interface, prevents the formation of C-Au chemical bonds, and the reversible switching operation was achieved. The 15-nm patterning of suspended graphene by helium ion beam milling is demonstrated. The reduction of the graphene nanoribbon width leads to the enhancement of temporal resistance change with the molecules adsorption on the graphene channel, which is beneficial for high-resolution sensing. We furthermore develop a GNEM chemical gas sensor device by using a bilayer graphene (BLG) beam suspended above a local bottom gold electrode, which features a slanted BLG channel with built-in tensile strain. By applying a substrate bias voltage of ± 15 V the adsorption processes of dilute CO2 gas molecules is accelerated, and we observe ‘quantized’ increments in the temporal resistance for the slanted BLG channel, which signifies single CO2 molecule adsorption / desorption events onto the BLG channel surface.
Current Transport in Graphene/Copper Hybrid Nano Ribbon Interconnect: A First Principle Study
Authors: Mohsin K M , Srivastava Ashok , Sharma Ashwani K , Mayberry Clay , Fahad Md S
Published: September 2016

Recent studies have shown superior thermal transport of graphene on copper as a potential candidate for the next generation interconnects. Using density function theory (DFT) we have studied the current transport of graphene/copper (G/Cu) hybrid-nano wire interconnect system and compared with graphene interconnect. From the first principle calculation, band structure and density of states have been calculated. Using Landauer-Buttiker (LB) formalism, electrical transport is calculated. For this presented G/Cu system, we found resistivity as 1.25x10-6 Ω-m, which is one tenth of Cu-bulk resistivity. G/Cu hybrid interconnect shows more conductive than graphene only interconnect for low bias applications.
High-Performance Photodetectors Using Transition Metal Dichalcogenide (TMD)-based Hybrid Structures
Authors: Jo Seo-Hyeon , Park Jin-Hong
Published: September 2016

We demonstrate the high-performance TMD (WSe2 and ReSe2) photodetectors with a high responsivity (1.3×106 A/W for WSe2 and 1.2×106 A/W for ReSe2) and fast temporal photoresponse (rising/decaying time: 2.8/20.8 ms for WSe2 and 58/263 ms for ReSe2). These were achieved by (i) applying PPh3 n-doping technique and (ii) inserting passivating layers (h-BN or APTES layers). Through the PPh3-based n-doping process, we significantly increased the photoresponsivity of the both WSe2 and ReSe2 photodetectors (2.7×103 → 4.3×105 A/W for WSe2 and 4.0×103 → 3.7×104 A/W for ReSe2). In particular, by inserting a h-BN layer at the WSe2/SiO2 interface and an APTES layer at the ReSe2/SiO2 interface, respectively, we further enhanced fast temporal photoresponse (rising/decaying time: 97/827 → 2.8/20.8 ms for WSe2) and high responsivity (3.7×104 → 1.2×106 A/W for ReSe2).
(Plenary) Electrochemical Diagnostics and Modeling in Developing the PEMFC Cathode
Authors: Kongkanand Anusorn , Yarlagadda Venkata , Garrick Taylor Reed , Moylan Thomas E , Gu Wenbin
Published: September 2016

Reducing the use of precious metal in a proton exchange membrane fuel cell is a key challenge in mass commercialization of fuel cell electric vehicles. However, as Pt loadings are reduced, fuel cell performance losses due to mass transport phenomena become more localized to the Pt and ionomer interface. In this paper, we provide an overview of how we use in-situ electrochemical diagnostics and modeling to understand the performance of low-Pt electrodes, identify their key limiting factors, and guide our catalyst layer development. In particular, diagnostics used to quantify the local-Pt oxygen transport resistance and the ionomer adsorption on the Pt surface will be discussed.
(Invited) Polymer Electrolyte Fuel Cells Lifetime Prediction By a Full Multi-Scale Modeling Approach
Authors: Gerard Mathias , Robin Christophe , Chandesris Marion , Schott Pascal
Published: September 2016

The objective of this communication is to provide a multi-scale modeling framework for fuel cells lifetime estimation. The methodology is based on a bottom-up approach to calculate the loss of active surface area based on the Ostwald ripening mechanism model developed at the micro-scale with a double layer model (called EDMOND model). By a direct coupling, the Ostwald module is incorporated in the 2D+0D dynamic fuel cell stack model (called PS++ model). Moreover, an original methodology is applied to extrapolate from a durability test the equivalent surface area loss taking into account both catalyst dissolution and oxidation (irreversible and reversible mechanisms). Two 2000-h durability tests validate the methodology and results. In particular, the effects of the dynamic operating conditions and the degradation heterogeneities along the surface of the cell are highlighted.
Dimensionless Model Analysis of PEFC Cathode
Authors: Kawase Motoaki , Yamaguchi Kazuhiro , Kageyama Miho , Sato Kazuyuki , Inoue Gen
Published: September 2016

By investigating a dimensionless form of equations describing the cathode catalyst layer (CL) of a PEFC, the isothermal one-dimensional cathode model was simplified and it was demonstrated that four intrinsic dimensionless moduli control the dimensionless local current profile in the cathode CL and therefore determines the effectiveness factor that is an integral of the current profile over the whole cathode CL. In this study, the effects of convection in the cathode layer on the oxygen reduction reaction (ORR) rate is focused on. In addition, case studies in which dimensional values were estimated from the dimensionless solutions for varying the CL thickness or the CL composition are presented.
A Monte Carlo Study on the Effect of Structural and Operating Parameters on the Water Distribution within the Microporous Layer and the Catalyst Layer of PEM Fuel Cells
Authors: Pournemat Anahid , Wilhelm Florian , Haußmann Jan , Vierrath Severin , Thiele Simon , Scholta Joachim
Published: September 2016

Liquid water agglomerations in the catalyst layer and microporouslayer of PEM fuel cells are simulated with a 3D Monte Carlomodel. The simulations are based on real material structures andlocally resolved operating conditions. The 3D material images areobtained from advanced experimental techniques capable of nm-scale imaging. The temperature and the relative humidity profilesare provided by a computational fluid dynamics simulation, basedon a single channel fuel cell model taking into account all relevanttransport and electrochemical processes. The results of this MonteCarlo study confirm the strong dependency of the water saturationin the catalyst layer and microporous layer on the structuralparameters and operating conditions, such as: wettability, pore sizeand local temperature and relative humidity.
Effect of Gdl(+MPL) Compression on the PEM Fuel Cell Performance
Authors: Carcadea Elena , Varlam Mihai , Ingham Derek B. , Patularu Laurentiu G , Marinoiu Adriana , Ion-Ebrasu Daniela , Stefanescu Ioan
Published: September 2016

Numerical simulations based on ANSYS Fluent software were carried out in order to investigate the effect of the clamping force and MPL addition on the fuel cell performance. The influence of the required gas diffusion layer (GDL) compression, during assembly process, onto fuel cell performance is investigated by considering four cases (0%, 15.7 %, 31.5%, 47.4%) and the optimum compression ratio was obtained (31.5%). The study revealed that the GDL compression and intrusion into the channels affect the fuel cell performance and some aspects related to its influence on liquid saturation are presented. Then, our study analyzed the role of the micro porous layer (MPL) inserted between catalyst layer (CL) and GDL and it found that an improvement in the cell performance can be achieved since it can help to reduce the ohmic and the concentration polarization losses.
RRDE Analysis of Ethylene Glycol and Caprolactam Effects on the ORR
Authors: Qi Jing , Zhai Yunfeng , St-Pierre Jean
Published: September 2016

The contamination impacts of ethylene glycol (EG) and caprolactam on the electro-catalytic behavior of a Pt/C catalyst toward the oxygen reduction reaction (ORR) were investigated in acid media using a rotating ring/disk electrode (RRDE). The Pt surface coverage increased whereas the ORR diffusion-limited and kinetic currents decreased with larger EG and caprolactam concentrations. The poisoning effect of caprolactam on the ORR was more severe than EG. The Tafel slope was unchanged for EG but higher values were observed when the caprolactam concentration increased to 10-1 M. The H2O2 yield greatly increased for both contaminants. The ORR performance loss due to EG was attributed to Pt active sites blocked by COad species and EG oxidation by-products. The adsorption of aminocaproic acid resulting from a caprolactam ring-opening reaction onto Pt active sites was responsible for the ORR activity and selectivity effects.
Effect of Flow-Field Structure on the Performance of Hydrogen/Bromine Redox Flow Batteries
Authors: Oh Kyeongmin , Ju Hyunchul
Published: September 2016

To scale up a lab-scale cell (a few cm2) to practical large-scale cell for grid-level energy storage applications (several hundred cm2), three-dimensional modeling and real-scale simulations are needed to fully elucidate complex electrochemical and transport phenomena occurring in the real-scale cells. This understanding is key to successful design and operation of hydrogen/bromine RFB systems. In this study, a three-dimensional, transient hydrogen/bromine RFB model developed in the previous study (1) is applied to a real-scale cell with an active area of 10 cm2. In order to reduce the computational turnaround time involved in a large numerical mesh with millions of grid points, the 3-D hydrogen/bromine RFB code is parallelized for parallel computing. Particular emphasis is placed on exploring the effects of electrolyte flow mode in the bromine electrode (i.e. flow-by and flow-through modes) on multi-dimensional hydrobromide distribution, and resultant membrane dehydration and cell performance. Such an elaborate simulation tool to predict electrochemical performance and transport phenomena is highly desirable in design and engineering of large-size hydrogen/bromine RFBs.
Hydrogen Fuel Cells for Unmanned Undersea Vehicle Propulsion
Authors: Swider-Lyons Karen , Deitz Daniel
Published: September 2016

The high efficiency of fuel cells combined with the high energy of hydrogen can be used to create energy systems for long endurance vehicles. As the automotive sector has developed fuel cells for this purpose, the same technology might enable long endurance unmanned undersea vehicles (UUVs). This paper describes fuel cell technologies for long endurance UUVs and issues related to integrating hydrogen fuel cells into large UUVs. We also describe an Office of Naval Research program with the U.S. Naval Research Laboratory, Naval Surface Warfare Center Carderock Division, University of Hawaii, and General Motors (GM) to integrate an automotive fuel cell from GM into a UUV. Hydrogen and oxygen storage technologies are also discussed.
Advances in Electrochemical Hydrogen Compression and Purification
Authors: Bouwman Peter Jaime
Published: September 2016

Electrochemical Hydrogen Compression (EHC) delivers pure gas at pressure on demand, with additional features such as single stage compression, no moving parts, silent operation and dynamic (reversible) flow control and low sensitivity to input pressure. Fast kinetics of hydrogen HOR/HER benefit the pump rate capability at the catalyst interface on the impermeable membrane. Here, we developed superior proton conductivity properties in combination with minimal hydrogen back-diffusion characteristics, to be able to compress to pressures as high as 100 MPa with competitive energy consumption. Results are shown at single cell and stack level pumping 2 kg hydrogen per day (also in the field), where relevant models indicate contributions from different processes and influence of operating conditions to the overall energy requirement (kWh/kg). This work will connect the inherent working principles behind this potentially disruptive technology, and its latest achievements, with the status quo of competing technologies, bringing forward near-future applications and energy scenarios.
Evaluation of Acid Accelerators for an Off-Grid PEM Fuel Cell Power Station Utilizing Solid Sodium Borohydride for Hydrogen Storage
Authors: Hsu Lewis , Huang Mindy , Anderson Greg , Rubio Arthur , Kerber Maxwell , Putnam Michael , Phipps Alex
Published: September 2016

Sodium borohydride was once looked at as a promising way to store hydrogen for use in polymer electrolyte membrane (PEM) fuel cells. Concerns regarding hydrogen storage capacity and sustainability of the reactants resulted in its disqualification as a viable hydrogen source in transportation vehicles. Sodium borohydride is still a promising hydrogen storage medium to meet power demands for applications such as remote sensor networks and off-grid communications. In this paper, we discuss the use of acid accelerators to enhance the borohydride hydrolysis reaction when combined with solid borohydride and liquid water. Specifically, we report results for hydrochloric acid, sulfuric acid, citric acid, and acetic acid. As a first approximation, yield of the reaction is above 90% for all these acids and a zero-order dependence on pH was observed.
Amino-Functionalized Mesoporous Silica Based Polyethersuflone-Polyvinylpyrrolidone Composite Membrane for Elevated Temperature Fuel Cells
Authors: Zhang Jin , Lu Shanfu , Zhu Haijin , Chen Kongfa , Liu Jian , Xiang Yan , Forsyth Maria , Jiang San Ping
Published: September 2016

Inorganic-organic nanostructured hybrid membranes based on polyethersulfone (PES)-polyvinylpyrrolidone (PVP) were prepared with mesoporous silica materials. All the hybrid membranes showed the similar phosphoric acid (PA) uptake. However, the proton conductivity of the PA-PES-PVP membrane was significantly increased after the addition of the inorganic fillers, especially for the amino-functionalized hollow mesoporous silica (NH2-HMS). The cell performance test also confirmed the superiority of the PES-PVP membranes with the inorganic fillers. The highest peak power density at 180 oC reached up to 480 mW cm-2 for the NH2-HMS based composite membrane fuel cell, which is 92.7 % higher than that of the PA-PES-PVP membrane fuel cell at the identical condition. The outstanding performance of the inorganic-organic hybrid membranes might be due to the facilitated proton transportation in the ordered mesoporous channels, and the great water retention of the inorganic fillers.
Heteropolyacids - Chitosan Membranes for H2/O2 Low Temperature Fuel Cells
Authors: Santamaria Monica , Pecoraro Claudio Maria , Di Franco Francesco , Di Quarto Francesco
Published: September 2016

Flat, free-standing phosphomolybdic acid and mixed phosphotungstic/phosphomolybdic acid chitosan membranes were prepared by in-situ ionotropic gelation process at room temperature on porous alumina support firstly impregnated by heteropolyacid. The polymeric films were tested as proton conductor in low temperature H2 – O2 fuel cell. Chitosan/phosphomolybdic acid membranes allowed to get peak power of 60 mW cm-2, while better results were obtained with mixed membranes, reticulated and functionalized in 30% H3PMo12O40, - 70% H3PW12O40 aqueous solution, allowing to measure a peak power of 140 mW cm-2 with a proton conductivity of ~ 2.5 mS cm-1.
Reduced Titanium Oxide as Carbon-Free Support of Non-Precious Metal Oxide-Based Cathodes for PEFCs
Authors: Igarashi Hikaru , Ishihara Akimitsu , Nagai Takaaki , Tominaka Satoshi , Matsuzawa Koichi , Napporn Teko W. , Mitsushima Shigenori , Ota Ken-ichiro
Published: September 2016

Development of carbon-free electro-conductive supports for non-noble metal oxygen reduction catalysts is required for wide spread of polymer electrolyte fuel cells. As alternative materials of carbon, we focused on Magnéli phase titanium sub-oxides (TinO2n-1; 4≦n≦10), particularly Ti4O7, because of its high conductivity and stability. In general, Magnéli Ti4O7 phase can be formed by reduction of TiO2 in H2 atmosphere at 1050oC. However, such a high temperature treatment causes the drastic particle growth and morphology destruction. Thus, we applied solid-phase reduction at low temperature by using NaBH4. The solid-phase reduction indicated that rutile-type and anatase-type TiO2 reduced to Ti2O3 and Ti4.5O5, respectively.
On the Design of a Comb-Shaped, Poly(phenylene oxide)-Based Anodic Binder for Anion-Exchange Membrane Direct Methanol Fuel Cell (AEM-DMFC)
Authors: Jurzinsky Tilman , Bär Robin , Heppe Nils , Kübler Markus , Jung Florina , Cremers Carsten , Tübke Jens
Published: September 2016

In this study, we present the synthesis of a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) based comb-like ionomer and the characterization of this ionomer. The ionomer consists of a PPO backbone and a partially fluorinated cationic sidechain. The comb-like ionomer showed high stability regarding ionic conductivity and ion exchange capacity in alkaline media. Besides this, a low swelling ratio for 4M methanol anodic fuel was found for the ionomer making it a suitable candidate for an application in the anodic catalyst layer in AEM-DMFCs. Evaluation of the methanol diffusion with a mass exchanger unit coupled to a mass spectrometer showed that the partially fluorinated sidechain lowers methanol diffusion compared to a non-fluorinated ionomer. Nevertheless, the comb-like ionomer was implemented in single cells as a catalyst binder and provided strong enhancement in single cell performance when the cell was run with KOH-free anodic fuel.
Method for Studying High Temperature Aqueous Electrochemical Systems: A Self Pressurized Autoclave
Authors: Holm Thomas , Dahlstrøm Per Kristian , Sunde Svein , Harrington David A. , Seland Frode
Published: September 2016

A detailed description of a method using a self-pressurized autoclave to run aqueous electrochemical experiments at temperatures above the normal boiling point of water is given. Relevant challenges with studying electrochemical reactions at high current densities in such systems are identified, and potential methods for solving these challenges are provided. The method is demonstrated for a three-electrode setup in sulfuric acid electrolyte up to 140°C.
Analysing Gas-Liquid Flow in PEM Electrolyser Micro-Channels
Authors: Sadeghi Lafmejani Saeed , Olesen Anders Christian , Kær Søren Knudsen
Published: September 2016

PEM water electrolysis is a key component for closing the loop of the renewable energy eco-system. In particular, these high response water electrolysers are suitable for fluctuating power sources. Conventional PEM water electrolysers are typically operated at a current density of around 1 A/cm2 and are fairly expensive. One means of increasing the hydrogen yield to cost ratio of such systems, is to increase the operating current density. However, at high current densities, management of heat and mass transfer in the anode current collector and channel becomes crucial. This entails that further understanding of the gas-liquid flow in both the porous media and the channel is necessary for insuring proper oxygen, water and heat management of the electrolysis cell. In this work, the patterns of vertical upward gas-liquid flow in a 5×1×94 mm micro-channel are experimentally analysed. A sheet of titanium felt is used as a permeable wall for permeation of air through a column of water similar to the phenomenon encountered at the anode. The transparent setup is operated ex-situ and the gas-liquid flow regimes are identified using a camera.
Cobalt Phosphide Based Nanostructures as Bifunctional Electrocatalysts for Low Temperature Alkaline Water Splitting
Authors: Lambert Timothy N. , Vigil Julian A. , Christensen Ben
Published: September 2016

Cobalt phosphide based thin films and nanoparticles were prepared by the thermal phosphidation of spinel Co3O4 precursor films and nanoparticles, respectively. CoP films were prepared with overall retention of the Co3O4 nanoplatelet morphology while the spherical/cubic Co3O4 and Ni0.15Co2.85O4 nanoparticles were converted to nanorods or nanoparticles, respectively. The inclusion of nickel in the nanoparticles resulted in a 2.5 fold higher surface area leading to higher gravimetric performance. In each case high surface area structures were obtained with CoP as the primary phase. All materials were found to act as effective bifunctional electrocatalysts for both the HER and the OER and compared well to commercial precious metal benchmark materials in alkaline electrolyte. A symmetrical water electrolysis cell prepared from the CoP-based film operated at a low overpotential of 0.41-0.51 V.
Electrochemical Measurement of Li2O in Molten LiCl Salt
Authors: Burak Adam J , Simpson Michael Forrest
Published: September 2016

Methods to prepare and condition a reference electrode for precise potential measurements in molten LiCl-Li2O are discussed in this paper. The Ni/NiO redox couple is commonly encased in MgO tubes containing porous, low-density MgO plugs that support ionic transport. Open circuit potential measurement between a source of fixed lithium activity and these reference electrodes is a promising approach to achieving real time Li2O concentration measurement in the salt. But the reference potentials must be extremely stable and reproducible in order for concentration correlations to be accurate for any given reference electrode. It was found in our study that pre-soaking of the reference electrodes is needed to eliminate transient effects. And equalizing the length of the porous MgO plugs is also critical to minimizing variability between different reference electrodes.
Electrochemical Reduction of UO2 to U in LiCl-KCl Molten Salt Eutectic Using the Fluidized Cathode Process
Authors: Abdulaziz Rema , Brown Leon D , Inman Douglas , Sharrad Clint , Shearing Paul R. , Brett Daniel J.L
Published: September 2016

The electrochemical reduction of UO2 to U metal using a fluidised cathode process has been investigated. Voltammetry studies were conducted with reduction observed over the range of -1.7 V to -2.2 V (vs. Ag/Ag+ reference electrode) which may be the consequence of a distribution of partial and full reduction. When performing chronoamperometry, an induction period is observed in which delayed reduction of UO2 to U occurs (compared to WO3 reduction onto W substrate), which may be due to a ‘seeding’ step onto the dissimilar W current collector. Spalling off of the product was observed as well, with associated reduction in current. The reduced product can be collected from two areas, the deposit on the current collector and the bottom of the reactor crucible.
Influence of Cathode Potential on Ti Electrodeposition in Molten Fluoride
Authors: Nishikawa Kazuyoshi , Humiya Sawada , Morishige Taiki , Takenaka Toshihide
Published: September 2016

The electrolysis condition of Ti electrodeposition in CaF2-MgF2 with CaO and TiO2 has been studied at 1573K. It was shown by cyclic voltammetry that cathodic current increased below 0.8V (vs. Mg/Mg2+) with CaO and TiO2 addition and that three reduction steps of Ti was suggested. Based on results of cyclic voltammetry, potentio-staic electrolysis was carried out between 0.2V and 0.7V. The particles containing Ti were obtained by potentio-static electrolysis. Particles containing Ti in electrodeposits were found by SEM-EDX. Ti oxide particles were detected by the electrolysis above 0.5V, while Ti metal particles did by the electrolysis below 0.4V. This result indicates that Ti metal can be electrodeposited below 0.4V (vs. Mg/Mg2+).
Effect of Electrode Shape on Lithium Metal Fog in LiCl-KCl
Authors: Akimura Shogo , Morishige Taiki , Takenaka Toshihide
Published: September 2016

The so-called metal fog sometimes formed during the molten salt electrolysis. In this paper, the effect of the surface shape of electrode on the metal fog formation was investigated in LiCl-KCl. Cyclic voltammetry and potentiostatic electrolysis were carried out at Mo wire electrode with/without screw cutting. The dark blue metal fog was formed at both types of electrodes, while the gray metal fog was generated only at the screw-cut electrode. The gray fog formation also depended on the diameter of the electrode; the formation was intenser at a small electrode than at a large electrode. It is concluded that the shape of electrode strongly affects the gray metal fog formation, and it is suggested that the current concentration at the edge causes the formation.
Electrochemical Formation of RE-Sn (RE=Dy, Nd) Alloys Using Liquid Sn Electrodes in a Molten LiCl-KCl System
Authors: Kuriyama Atsushi , Hosokawa Kohei , Konishi Hirokazu , Ono Hideki , Takeuchi Eiichi , Nohira Toshiyuki , Oishi Tetsuo
Published: September 2016

We proposed new separation and recovery process for Dy metals from Nd magnet scraps using molten salt electrolysis and liquid metals. As the first step, electrochemical formation of RE-Sn (RE=Dy, Nd) alloys were investigated in LiCl-KCl eutectic melts added DyCl3(0.50 mol%) and NdCl3(0.50 mol%). The samples of Nd-Sn alloys were prepared by potentiostatic electrolysis at 0.60, 0.70, 0.80, 1.00 V(vs. Li+/Li) for 0.50 h using liquid Sn electrodes in LiCl-KCl eutectic melts added NdCl3(0.50 mol%). The formation of Nd-Sn alloys were confirmed by the XRF analysis of all samples. Moreover, potentiostatic electrolysis were conducted at 0.60 V and 0.70 V for 0.50 h in LiCl-KCl eutectic melts added DyCl3(0.50 mol%) and NdCl3(0.50 mol%). The formation of Dy-Nd-Sn alloys were confirmed in the bottom portion of liquid Sn electrodes. The atomic ratios of Nd/Dy in both alloy samples were 3.50.
Electrochemical Synthesis of Tantalum Carbide in the NaCl-KCl-K2TaF7-K2CO3 Melt
Authors: Dolmatov Vladimir S. , Kuznetsov Sergey A.
Published: September 2016

The conditions of electrochemical synthesis of tantalum carbide in the NaCl-KCl-K2TaF7-K2CO3 melt have been determined. These conditions are following: potentiostatic electrolysis at discharge potentials of CO3
2--ions during 40-50 min after addition of K2CO3 to the melt and the molar ratio of K2CO3/K2TaF7 = 1:1.
Solubility of Calcium and Zirconium Oxides in Melts CaO-(CaCl2-MCl)eut and CaO-CaCl2-MCl (M - Li, Na, K)
Authors: Savchuk Ruslan N , Gritsai Larisa V. , Omel'chuk Anatolii A
Published: September 2016

The behaviour of calcium oxide in eutectics of CaCl2–MCl and zirconium dioxide in polythermal sections of the ternary systems CaO–CaCl2–MCl (where M = Li, Na, K) has been investigation used methods of thermal and X-Ray analysis. It has been shown that equilibrium content of calcium oxide in the melt CaO–CaCl2–LiCl is much higher than similar melt composition CaO–CaCl2–MCl (M = Na, K). It has been established that the solubility of zirconium dioxide in the test melts rises with increasing acidity of the appropriate melt.
Electrochemical Synthesis of LaSi2 from a NaCl-Naf-LaF3-K2SiF6 Melt at 1023 K
Authors: Kochetova Svetlana , Savchuk Ruslan N , Pisanenko Alexandr Dmitrievich , Devyatkin Sergei Vladimirovich
Published: September 2016

The aim of this work was to examine the possibility of producing lanthanum silicides by the electrolysis of molten salts, containing lanthanum and silicon ions, on a nickel cathode. The electrochemical behavior of the NaCl–NaF–LaF3-K2SiF6 molten salts system was studied by cyclic voltammetry. The electrolysis was carried out in a NaCl–NaF–LaF3-K2SiF6 melt in a glassy carbon crucible at 1023 K in argon atmosphere; a nickel plate was used as the cathode. Cathodic products were analyzed by X-ray and JEM-2100F SEM. Coatings of lanthanum disilicide were deposited from NaCl-NaF- LaF3-K2SiF6 melts on a Ni cathode at 1023 K in argon atmosphere.
Double Salt Ionic Liquids Containing the Trihexyl(tetradecyl)phosphonium Cation: The Ability to Tune the Solubility of Aromatics, Ethers, and Lipophilic Compounds
Authors: Wang Hui , Berton Paula , Myerson Allan S. , Rogers Robin Don
Published: September 2016

The chemical and physical properties of an ionic liquid (IL) can be tuned with the addition of a second IL, forming a Double Salt Ionic Liquid (DSIL). Here, the solubilities of lipophilic solutes with long alkyl chains (e.g., heptane, methyl palmitate) were tuned in the DSIL [C4mim]x[P66614](1-x)[NTf2] ([C4mim]+ = 1-butyl-3-methylimidazolium, [P66614]+ = trihexyl(tetradecyl)phosphonium, [NTf2]- = bis(trifluoromethylsulfonyl)imide) by increasing the [P66614]+ concentration. Additionally, density and viscosity of the DSILs were also modified with the [P66614]+ concentration. The solubility of solvents totally miscible with [P66614][NTf2], such as benzene and toluene, could only be tuned in the DSILs when [P66614]+/[NTf2]- ≤ 0.33, since at higher ratios these solutes were totally miscible with the DSILs. The interactions between the ions account for the different solvent behaviors in the DSILs. Using 1H NMR, 19F NMR, and FT-IR spectroscopy, a preferential interaction was observed between the [NTf2]- anion with [C4mim]+ compared to that with [P66614]+. Also, interactions between [C4mim]+ and [P66614]+ through alkyl chain aggregations were demonstrated.
(Invited) Electrochemical Properties of Ionic Liquids Containing Aprotic Heterocyclic Anions (AHA ILs) and Their Mixtures with Lithium Salts
Authors: Sun Liyuan , Xia Han , Morales-Collazo Oscar , Brennecke Joan F
Published: September 2016

We have previously studied a series of room temperature ionic liquids (RTILs) based on 1-ethyl-3-methylimidazolium ([emim]+) and tetra-alkylphosphonium ([P222n]+) cations with different aprotic heterocyclic anions (AHAs). It has been found that many of the AHA ILs exhibit very good conductivity for their viscosities. The results provide insight into the design of ILs with enhanced dynamics that may be suitable for electrolyte applications (1, 2). Lithium salts based on the bis(trifluoromethylsulfonyl)imide ([TFSI]-), bis(fluorosulfonyl)imide ([FSI]-) and tetrafluoroborate ([BF4]-) anions have been extensively studied in lithium salt/IL mixtures for such applications (3-18). Here we will further explore how the addition of lithium AHA salts, compared to the popular [TFSI]-, [FSI]- and [BF4]--based ones, affects the transport properties of the RTILs in order to evaluate the feasibility of using these AHA ILs for lithium-ion battery applications. In particular, we investigate the viscosity and ionic conductivity, as well as anion, cation and lithium diffusivity, as measured by Pulse-Gradient-Spin-Echo NMR spectroscopy.
Electrochemical Reaction of Bis(acetylacetonato)Palladium in an Amide-Type Ionic Liquid
Authors: Yoshii Kazuki , Oshino Yosuke , Tachikawa Naoki , Toshima Kazunobu , Katayama Yasushi
Published: September 2016

The electrochemical reaction of bis(acetylacetonato)palladium (Pd(acac)2) was investigated in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide using a rotating ring-disk electrode. Metallic palladium was deposited on the electrode after potentiostatic cathodic reduction at −1.9 V vs. Ag|Ag(I). When the linear sweep voltammetry with maintaining the ring potential at −1.25 V was conducted, the anodic current of ring electrode was detected at −1.9 V with the cathodic disk current which is attributed to the reduction of Pd(acac)2. This result suggested that the metallic palladium may be formed by the disproportionation reaction of [Pd(acac)2]−. In addition, Pd nanoparticle was synthesized by the electrochemical reduction in 1-hexyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (HMPTFSA) and 1-decyl-1-methylpyrrolidinium (DMPTFSA) in order to compare the sizes of Pd nanoparticles with that prepared in BMPTFSA. The particle size became small with increasing the alkyl chain length in the cation of ionic liquid.
Anodic Reaction Mechanisms in Direct Carbon Fuel Cells Using Carbon Particles Dispersed in Molten Carbonate
Authors: Watanabe Hirotatsu , Umehara Daisuke
Published: September 2016

This study aims to investigate the anodic reaction mechanisms in direct carbon fuel cell using a carbon/carbonate slurry stirred by Ar bubbling. CO2 and CO production rates were measured during the constant discharge. Gas products were calculated based on complete (C+2CO3
2-→3CO2+4e-) and partial electrochemical oxidation (C+1/2CO3
2-→3/2CO+e-). The impact of Boudouard reaction (C+CO2→2CO) on CO production was also discussed. As a result, an amount of CO was formed without Ar bubbling, whereas CO was not formed with Ar bubbling. The impact of CO2 bubbling on CO formation was insignificant, and calculations of gas products almost agreed with experiments of those. These indicated that CO was formed through not Boudouard reaction but the partial electrochemical oxidation. Moreover, partial electrochemical oxidation helped to explain the trends of open circuit voltages. It was shown that the anodic reactions consisted of complete and partial electrochemical oxidations.