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High efficiency and valuable energy distributed generation could be achieved with the coupling of solid oxide fuel cells and biomass processing technologies. This coupling would take advantage of the high operating temperature of the fuel cell and the efficient recovery of its waste high temperature irreversible heat for processes' integration (i.e. thermal integration) and system's performance enhancement. However, different biomass processing technologies lead to bio-fuels of different behaviour in terms of degradation phenomena at the anode side, fuel cell system thermal balance and impact on the performance of the overall system. This paper investigates the utilization of different biogases from anaerobic digestion in solid oxide fuel cells. Two different fermentation paths will be investigated. A first path leads to the production of bio-methane mixtures characterized by the presence of CH4/CO2 (typical 60/40 vol%); a second and innovative path leads to the production of bio-hydrogen mixtures which consist of H2/CO2 (typical 50/50 vol%).

In the second part of the paper series on a noninvasive method to determine the local high frequency resistance (HFR) distribution in polymer electrolyte fuel cells (PEFC), the method is applied to an operating PEFC stack. While in the first part of this paper series the approach of using multiple surface attached electrodes to locally inject 1 kHz AC currents into a cell and to measure the resulting voltage amplitudes at the flow field's surface was introduced. Its sensitivity was assessed using a stack fed only by nitrogen at different humidification levels. Here, it is confirmed that the approach works also during electrochemical operation. First, the method's spatial resolution is further explored and improved by using multiple stimulation patterns after examining the local sensitivity of the different electrode combinations to changes in membrane conductivity by finite element model simulations of the current injection. The method is then applied to a stack operated at different current densities, inlet humidities and gas flow configurations. The HFR distributions are in good agreement with literature data and compare well with the global cell HFR. Finally, the method's transient capabilities are highlighted by measuring the HFR distribution during a current jump and cell drying., Journal of the Electrochemical Society, 169 (12), ISSN:0013-4651, ISSN:1945-7111

In the first paper of this series, the bulk, surface and transport properties of porous transport layer materials (PTL) for polymer electrolyte water electrolysis cells (PEWE) are characterized. A systematic PTL matrix of Ti fiber materials with 3 fiber diameters and 2 nominal porosities as well as a state of the art sintered powder material are investigated to get a better understanding of the governing parameters in electrolysis cells. X-ray tomographic microscopy analysis of ex situ PTL structures and post operando membrane electrode assemblies is performed. On the tomographic structures, bulk (porosity, pore/solid size distributions, fiber orientation), mass transport (diffusivity, permeability, conductivities) and surface parameters (roughness, membrane deformation, PTL surface area and interfacial contact area) are determined. The second paper of this series will correlate the structural parameters with in-depth electrochemical analysis. The new insights into the effect of PTL properties on PEWE performance allow to isolate governing key parameters. From know-how obtained on the fiber based materials fundamental design guidelines for optimization of PTL structures are deduced., Journal of the Electrochemical Society, 166 (4), ISSN:0013-4651, ISSN:1945-7111

This work focuses on the performance and stability of selected commercial carbon electrode materials before and after heat-treatment in an operating all-vanadium redox flow battery (VRB). Heat treatment results in improved cell performance for all tested materials, with SGL 39 AA carbon papers and SIGRACELL GFD4.6 EA carbon felt showing the best performance. Further investigation of these two materials by in situ reference electrode measurements reveal improvements after heat-treatment that originate mainly from the negative electrode or V2+/V3+ side of the cell. Upon extended cycling, carbon felt is found to be stable. Carbon papers however, show significant performance losses originating from the negative electrode side. The potential limit during charging and the exposure to very negative potentials appears to be a critical issue at the negative electrode in the VRB. Analysis of both materials after cycling by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy reveal significant differences in their surface chemistry, structure and morphology. These differences give valuable insights into the behavior and degradation of different carbon materials used in VRBs., Journal of the Electrochemical Society, 164 (7), ISSN:0013-4651, ISSN:1945-7111

GaN devices are promising candidates for the next generation power devices for energy efficient applications. Although astounding performance is already proven by many research papers, the widespread adoption of GaN power devices in the market is still hampered by (1) yield and reproducibility ; (2) cost ; (3) reliability. All three factors are to be considered, but to convince customers to adopt GaN power devices in their next generation products, proven device and product reliability is a must. Cost is kept acceptably low by growing the GaN epi stack on 6inch and 8inch Si substrates, and by processing the GaN power device technology in standard CMOS production lines, with a proper contamination control protocol in place. This paper will focus on the most important intrinsic reliability mechanisms for GaN power devices. It will cover gate dielectric reliability, Ohmic contact reliability, accelerated drain stress testing (high temperature reverse bias--HTRB) and high voltage device wear-out testing (high voltage off-state stress--HVOS). The need to do reliability investigations based on statistical data on large area power transistors (100+ mm gate width) instead of small test structures will be emphasized. Acceleration models and statistical distribution models (Weibull, lognormal) are discussed. The correlation between the GaN buffer stack vertical leakage and the parametric drift in prime device parameters under accelerated stress will be highlighted. Furthermore, since the MOCVD epi layers of the GaN-on-Si buffer stack are key to the device performance, a measurement strategy to extract valuable information about the physical properties of the buffer layers (e.g. activation energies of the traps, conduction mechanisms, …) based on simple transmission line structures, is outlined. This information will also be linked to the so-called “dynamic Ron”, a recoverable reduction in on-state current due to the trapping of charges in the buffer stack and/or the interface. Finally, it will be shown that through proper engineering of the epi buffer stack, device layout and device passivation scheme, dynamic Ron-free power transistors can be obtained.

The overall performance of concrete patch repair systems depends on the durability of and compatibility between the concrete substrate and the repair material. This paper investigates the performance of a new type of SHCC material with embedded bacteria as a repair material. The bacteria are a healing agent to enhance the durability of the repair system. The bonding strength between the repair material and the concrete was studied by means of both pullout tests and flexural tests. Restrained shrinkage was measured in layered systems with the concrete substrate, whereas the durability of the layered systems was measured by means of rapid chloride migration tests and thermal compatibility tests. Detailed results reported in this paper show the potential of SHCC with bacteria as a concrete patch repair material with improved bonding and durability.

This paper aims to better understand the temperature profile of a turbulence inducing grid if pre-heating of the incoming air in the cathode channel is required when the stack is operating under freezing conditions. The goal of this study is to design the grid by changing its thickness and the number of pores. A three-dimensional, steady-state computational fluid dynamic model was developed and validated for a baseline case of a single cathode channel of an air-cooled cell. The computational domain consists of the cathode flow channel, a gas diffusion layer, and the turbulence inducing grid. Four different grid designs were analyzed and compared, and in the best case heating of the turbulence grid was achieved where the temperature of the grid will be 236 °C and the power consumption will be around 30 % of the total power produced by the fuel cell stack. It is concluded that 2 mm thickness is not sufficient, leading to too high temperatures, and a multitude of staggered grids might be required.

This paper describes a systematic study into the role of chromium and chromium (III) oxide thickness in preventing corrosion driven coating disbondment of organically coated packaging steel. A graded wedge of chromium and chromium (III) oxide is applied to steel using physical vapour deposition (PVD). A polyvinyl butyral (PVB) overcoat is applied and corrosion is initiated from an artificial defect using NaCl. Scanning Kelvin probe (SKP) potentiometry is used to monitor coating delamination. Wedge thickness variation allows for high throughput investigations into the effect of both metallic chromium and chromium (III) oxide thickness, on coating disbondment rate. A linear reciprocal relationship is observed between chromium metal thickness and disbondment rate. Increasing chromium (III) oxide thickness (applied over chromium metal) results in a decrease in delamination rate. This work highlights the ability of PVD to produce chromium/chromium (III) oxide corrosion resistant coatings to use as alternatives to hexavalent chromium-based systems.

Tiny optical fiber sensor was applied to realize non-destructive measurement of oxygen concentration on PEFC catalyst layer. Insufficient supply of oxygen to the cathode catalyst layer caused by transport resistance is critical issue. Fundamental study in order to achieve efficient oxygen transport is required, however; non-destructive and in-situ measurement of oxygen concentration on the catalyst layer was not achieved. In this study, oxygen concentration on the catalyst layer under operating condition was measured by using a tiny optical fiber and oxygen indicator. Figure 1 shows experimental setup. Platinum tetrakis pentrafluoropheny porphine (PtTFPP) was employed as oxygen indicator[1]. When the PtTFPP is exposed to excitation light (l = 405 nm), phosphorescence emission (l = 650 nm) is produced. Phosphorescence intensity is determined by oxygen partial pressure. Thus, quantitative oxygen concentration can be obtained by measuring phosphorescence intensity and using calibration data. In this study, PtTFPP was painted at the edge of fused silica optical fiber of which diameter was 110 mm. In order to measure the phosphorescence intensity, bifurcated optical fibers were connected to excitation light source and spectrometer, respectively. The cell has an active area of 4 cm2 (2 × 2 cm) with straight channels. The channel width and depth were 1.0 and 1.0 mm, respectively, and the rib-to-channel ratio was 1. The carbon paper GDL without MPL (SIGRACET®24BA, SGL Group, USA) was used for both the anode and the cathode side. In order to measure the oxygen concentration on the catalyst layer with reducing insertion effect, optical fiber was inserted from the intrinsic large pore of GDL without boring a hole, and the edge of the fiber was touched on the catalyst layer surface. Flow rates of hydrogen and air were 50NmL/min and 125 NmL/min, respectively. Cell was operated under 33 °C because phosphorescence intensity becomes low under high temperature. Bubbler temperature was 22 °C (relative humidity was 50%) In the experiment, cell voltage was varied from 0.9 V to 0.2 V, and change of current density and oxygen concentration were measured. Figure 2 shows current-voltage (IV) characteristics. In the higher current density condition, variation of plots suggests emergence of flooding in the cathode. Since the flooding decreased gas diffusivity in the cathode catalyst layer, IV characteristics fluctuate at high current density and low cell voltage condition. As shown in Figure 3, change of oxygen concentration on the catalyst layer was measured successfully. Oxygen concentration decreases monotonically with decreasing cell voltage. Minimum value of the concentration was below 2 % at 0.2 V cell voltage. Figure 2 indicated that total cell performance was declined by flooding. On the other hand, local oxygen concentration of the catalyst layer was able to be measured by using a tiny optical fiber. Figure 3 shows large amount of oxygen was still consumed under high current density and it means that power generation concentrated on local surface of the catalyst layer where surface not covered with the liquid water. As discussed above, oxygen concentration on cathode catalyst layer was measured non-destructively. This technique holds further potential to measure oxygen transport phenomena on the catalyst layer under 60-80 °C cell operation by improving optical oxygen sensor sensitivity. Acknowledgement This study is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Experimental setup in present study was assisted by Yoshihiko Aoki (Tokyo Institute of Technology). Reference [1] CS Chu., CA Lin, Sensors and Actuators B: Chemica, 2014, 195, 259-265. Figure 1

In the first paper of this series the bulk and surface structural properties of Ti-fiber based porous transport layers (PTL) were characterized and described. In this second part the correlation of structure to the performance in polymer electrolyte water electrolysis cells is analyzed by determination of the three main overpotentials of ohmic, kinetics and mass transport losses. The strongest correlation between the PTL bulk transport properties and cell performance is obtained for heat transport. The current density dependent temperature gradients show good agreement with ex situ determined heat conductivity from part one. However, surface properties of the PTL materials, have a stronger influence on cell performance than the bulk properties. Catalyst layer utilization and ohmic interfacial resistances correlate with the interfacial contact areas reported in part one and performance increases with increasing contact area. This is due to a local mass transport resistance decreasing with increasing catalyst layer utilization., Journal of the Electrochemical Society, 166 (10), ISSN:0013-4651, ISSN:1945-7111

The availability of laboratory grade equipment for battery tests is usually limited due to high costs of the hardware. Especially for lithium-sulfur (Li-S) batteries these experiments can be time intensive since the cells need to be precycled and are usually cycled with relatively low loads. To improve the availability of test hardware, this paper conducts a study to design and test a low cost solution for cycling and testing batteries for tasks that do not necessarily need the high precision of professional hardware. While the described solution is in principle independent of the cell chemistry, here it is specifically optimized to fit to Li-S batteries. To evaluate the accuracy of the presented battery cycler, the hardware is tested and compared with a professional Kepco bipolar power source. The results indicate the usefulness for application oriented battery tests with real life cycles, although inaccuracies occur in the current measurements.

Lithium-Sulfur (Li-S) batteries are an emerging energy storage technology, which is technically-attractive due to its high theoretical limits; practically, it is expected that Li-S batteries will result into lighter energy storage devices with higher capacities than traditional Lithium-ion batteries. One of the actual disadvantages for this technology is the highly pronounced rate capacity effect, which reduces the available capacity to be discharged when high currents are used. This drawback might be addressed by the use of the capacity recovery effect, which by introducing relaxation periods between consecutive pulse discharges of the battery, increases the available discharge capacity of the cell. The capacity recovery effect of the Li-S cell is studied in this paper using the pulse discharge technique, considering its dependence on the applied current, discharge step length, temperature, and on the length of the relaxation period between the discharging pulses.

Neutron radiography was applied to image the water-gas distribution in an operating small scale PEM electrolyser, building up on the anisotropic resolution improvements previously developed for fuel cell imaging. The ability of neutrons to image this distribution across porous materials made of titanium was demonstrated for the first time. This paper presents the procedure's description and limitations, focusing on water content in the porous layers as a function of distance from electrode. A surprising pattern of water content in anodic porous material was observed, which sheds light on the topic of mass transport limitations in PEM electrolysers., Journal of the Electrochemical Society, 163 (11), ISSN:0013-4651, ISSN:1945-7111

In this paper, we present an experimental study on the development of gas diffusion layer (GDL) materials for fuel cells with dedicated water removal pathways generated using radiation induced grafting of hydrophilic compounds onto the hydrophobic polymer coating. The impact of several material parameters was studied: the carbon substrate type, the coating load, the grafted chemical compound and the pattern design (width and separation of the hydrophilic pathways). The corresponding materials were characterized for their capillary pressure characteristic during water imbibition experiments, in which we also evidenced the differences between injection from a narrow distribution channel in the center of the material (and thus strongly relying on lateral transport) and homogeneous injection from one face of the material. All materials parameters were observed to have a significant influence on the water distribution. In particular, the type of substrate has a dramatic impact, with results ranging from a nearly perfect separation of water between hydrophilic and hydrophobic domains for substrates having a narrow pore size distribution to a fully random imbibition of the material for substrates having a broad pore size distribution., Journal of the Electrochemical Society, 163 (9), ISSN:0013-4651, ISSN:1945-7111

The market penetration of fuel and electrolysis cell energy systems in Europe requires the development of reliable assessment, testing and prediction of performance and durability of solid oxide cells and stacks (SOC). To advance in this field the EU-project “SOCTESQA” was launched in May 2014. Partners from different countries in Europe and one external party from Singapore are working together to develop uniform and industry wide test procedures and protocols for SOC cell/stack assembly. In this project new application fields which are based on the operation of the SOC cell/stack assembly in the fuel cell (SOFC), in the electrolysis (SOEC) and in the reversible SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems. The paper presents the results which have been achieved so far in the SOCTESQA project. Besides a summary of existing test procedures a so called “test matrix” was created. This document includes generic test modules, e.g. current-voltage curves, electrochemical impedance spectroscopy, thermal cycling, electrical current cycling and long term tests both under steady state and dynamic operating conditions. The application specific test programs are created by combining several of these test modules. In a next step defined test modules will be applied for the initial test bench validation, which will be improved by several validation loops. The final test protocols will be confirmed by round robin tests.

This paper discusses feasibility of design and future implementation of ultrasmall-size and ultra-low-power digital logic systems by a hexagonal BDD (binary-decision diagram) quantum circuit approach. The discussion is based on various circuits formed on GaAs-based hexagonal nanowire networks controlled by nanometer scale Schottky wrap gates (WPGs). Starting from basic node devices and elementary logic function blocks, fabrication technology of hexagonal BDD quantum circuits up to 8-bit adders with node densities over 45 million nodes/cm2 has been successfully developed. Their correct operations at low temperatures and room temperature have been confirmed by experiments and simulation. Various circuit components in logic processors, including arithmetic logic unit (ALU), controller and decoders have been successfully designed as hexagonal BDD layouts without nanowire crossover. For sequential circuits, WPG-controlled nanowire FETs on hexagonal networks have been investigated, and registers and counters have been implemented using these nanowire FETs showing correct operation. Hexagonal BDD-based static 2-bit nano-processor unit (NPU) has been successfully designed completely on hexagonal nanowire network. Ultra high-density GaAs hexagonal nanowire networks with much smaller wire sizes than those of etched nanowire networks have been successfully formed by selective MBE growth, showing great promise for room temperature operation in quantum regime as well as reduction of system area and power consumption.

Batteries based on alkali-ions, such as lithium, sodium and potassium are considered the energy storage systems of choice for the next generation applications, such as electrified mobility and supply for renewable energy storage [1]. These systems are, in principle, light, efficient and potentially capable to meet several of the targets characterizing the emerging markets [2]. However, the use of the alkali-metal anode is definitely hindered by severe safety issues, including extreme reactivity with the electrolyte, eventual dendrite formation and cell short-circuit, leading to possible heating, thermal runway and fire [3,4]. Therefore, the severe requirements of the modern society triggered the replacement of the metallic anode by alternative materials characterized by higher safety content, in particular based on carbon [5], alloys [6] and metal oxides [7]. This radical change, partially succeeding in particular for lithium [6], is however still limited to few examples of efficient systems, employed for practical energy storage [1,3], such as Graphite/LCO, Graphite/LFP and Graphite/LNMC. Within this paper we developed a series of lithium-ion and sodium-ion batteries, including metal alloying [8], conversion [9] and graphene [10] anodes, high voltage spinel [11], olivine [12], sulfur [13,14] and oxygen [15] cathodes, and ionic liquid electrolyte [10,16] considered of interest for practical employment as alternative, safe and high energy storage systems for next generation applications. Figure: examples of various sodium and lithium ion cells in which the metal anode has been replaced by alternative materials References [1] D. Larcher, J-M. Tarascon, Nature Chemistry, 2015, 7, 19. [2] J. B. Goodenough, K.-S. Park, JACS, 2013, 135, 116. [3] J.-M. Tarascon, M. Armand, Nature, 2001, 414, 359. [4] V. L. Chevrier, G. Ceder, J. Electrochem. Soc., 2011, 158, 9, A1011. [5] M. Winter, J. O. Besenhard, M. E. Spahr, P. Novak, Adv. Mater., 1998, 10, 725. [6] J. Hassoun, P. Reale, B. Scrosati, J. Mater. Chem, 2007, 17, 3668. [7] J. Cabana, L. Monconduit, D. Larcher, M. R. Palacìn, Adv. Energy Mater., 2010, 22, E170. [8] J. Hassoun, S. Panero, P. Reale, and B. Scrosati, Adv. Mater., 2009, 21, 4808 [9] R. Verrelli, J. Hassoun, A. Farkas, T. Jacob, B. Scrosati, J. Mater. Chem. A, 2013, 1, 15329 [10] J. Hassoun, F. Bonaccorso, M. Agostini, M. Angelucci, M.G. Betti, R. Cingolani, M. Gemmi, C. Mariani, S. Panero, V. Pellegrini, B. Scrosati, Nano Letters, 2014, 14, 4901 [11] R. Verrelli, B. Scrosati, Y.-K. Sun, J. Hassoun, ACS Appl. Mater. Interfaces, 2014, 6, 5206 [12] I. Hasa, J. Hassoun, Y.-K. Sun, B. Scrosati, ChemPhysChem, 2014, 15, 2152 [13] M. Agostini, J. Hassoun, Scientific Reports, 20155, 7591 [14] D.-J. Lee, J.-W. Park, I. Hasa, Y.-K. Sun, B. Scrosati, J. Hassoun, J. Mater. Chem. A, 2013, 1, 5256 [15] G.A. Elia, R. Bernhard, J. Hassoun, RSC Advances, DOI: 10.1039/c4ra17277a [16] D. Di Lecce, S. Brutti, S. Panero, J. Hassoun, Materials Letters, 2015, 139, 329 Figure 1

The lithium-ion batteries are energy storage systems of high performance and low cost. They are employed in multiple portable devices and these require the use of increasingly smaller and lighter batteries with high energy and power density, fast charging and long service life. Moreover, these systems are promising for use in electric or hybrid vehicles. However, the lithium-ion battery still requires to improve the electrode materials properties, such as cost, energy density, cycle life, safety, and environmental compatibility. These batteries use carbon as anode material, usually synthetic graphite, because of its high coulombic efficiency and acceptable specific capacity for the formation of intercalation compounds (LiC6). In this paper the methodology used to prepare and characterize the reversible and irreversible capacity and, cyclic stability of graphite materials as anodes in lithium-ion batteries of commercial carbon and Sungite carbon, is presented. The results obtained using electrochemical techniques, are discussed. Fil: Humana, Rita. INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) CONICET; Argentina. Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Catamarca, Argentina. Fil: Ortiz, Mariela. UTN (Universidad Tecnológica Nacional); Argentina. INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) CONICET; Argentina Fil: Thomas, Jorge. INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) CONICET; Argentina Fil: Real, Silvia. UTN (Universidad Tecnológica Nacional); Argentina. INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) CONICET; Argentina Fil: Sedlarikovad, Marie. Faculty of Electrical Engineering and Communication (Brno University of Technology); Czech Republic Fil: Vondrakd, Jiri. Faculty of Electrical Engineering and Communication (Brno University of Technology); Czech Republic Fil: Visintin, Arnaldo. INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) CONICET; Argentina

In order to achieve reliable data regarding high temperature polymer electrolyte fuel cell (HT-PEFC) electrode degradation novel diagnostic techniques for the determination of the electrochemically active surface area (ECSA) were developed. Cyclovoltammetric CO-monolayer oxidation (CO stripping) charge measurements were combined with real-time CO2 exhaust gas analysis. Different evaluating methods were developed to overcome the problem of side reactions during CO stripping. Furthermore, a calibration curve for absolute ECSA determination via CO stripping was established, eliminating the temperature dependency of CO adsorption. In addition, these methods were successfully extended and implemented to locally resolved ECSA measurements. In summary, this paper introduces novel fundamental HT-PEFC electrode diagnostics for improved understanding of degradation phenomena., Journal of the Electrochemical Society, 161 (4), ISSN:0013-4651, ISSN:1945-7111

In this paper, an analytical model is established to describe the deposition kinetics and the deposition chamber characteristics that determine the deposition rates of PureB-layers grown by chemical-vapor deposition (CVD) from diborane (B2H6) as gas source on a non-rotating silicon wafer. The model takes into consideration the diffusion mechanism of the diborane species through the stationary boundary layer over the wafer, the gas phase processes and the related surface reactions. This model is based on a wide range of input parameters, such as initial diborane partial pressure, total gas flow, axial position on the wafer, deposition temperature, activation energy of PureB deposition from diborane, surface H-coverage and reactor dimensions. The model's predictive capabilities have been verified by experiments performed at 700 ºC in these two different ASM CVD reactors.

This paper presents the influence of operation conditions including steam levels, current density and operating time on the performance of Solid Oxide Fuel Cells (SOFCs) fuelled by tar- containing biosyngas. The performance of SOFCs was evaluated by means of recording impedance spectra and polarization curves of the cells before and after tar exposure. The biosyngas composition and the tar concentration used in the measurements were experimentally measured from a commercial gasifier. The results show that increases steam level and current load would reduce the risk of carbon deposition arising from the tar-containing biosyngas. Deposited carbon was found by the change in impedance and by Scanning Electron Microscopy. SOFCs fed by the biosyngas with a high tar level are not expected to be operated for a long term, because this operation resulted in a severe carbon deposition on the anodes.

Source-gated transistors (SGTs) comprise a blocking contact or potential barrier at the source, which control the current. The paper describes how SGTs can be optimized for particular applications and for specific semiconductor material systems. It is shown how the saturation voltage can be designed to be an order of magnitude smaller than in equivalent FETs to give power savings of over 50% for the same current output. The SGT also achieves a better saturation regime, with lower output conductance over a larger range of drain voltages. Flat-panel lighting, remote sensing and signal processing and large-area circuits made using inexpensive but imprecise patterning techniques are some of the applications which could benefit from incorporating these devices.

International audience; The corrosion behavior of a 2024 T351 aluminum alloy exposed to a chloride solution was studied in the present paper. The work was focused on the effect of an environmental and thermal cyclic exposure to corrosive media and aimed to identify the main parameters explaining the changes observed between continuous and cyclic immersion tests. Optical and scanning electron microscope observations showed an increase of the intergranular corrosion damage with the extension of the corrosion from the grain boundaries to the subgrain boundaries for samples exposed to cyclic tests. An experimental set-up, including a laser beam, allowed mechanical stresses induced by the solidification of the electrolyte trapped in the corrosion damage during exposure to negative temperatures to be revealed and the chloride concentration of the electrolyte to be determined. Results were helpful in proposing corrosion mechanism during thermal and environmental cyclic exposure to chloride solutions.

Due to copyright restrictions, the access to the full text of this article is only available via subscription. The conventional demands for development in semiconductor industry are changing as the Moore's Law is approaching to its limits. This paper demonstrates a theoretical optimization approach for the planarization of metal films by Chemical Mechanical Polishing (CMP) process. Optimal removal rate and a smooth surface finish post CMP can be achieved by the combined effect of the chemical and mechanical components of the process. Metal CMP necessitates a protective oxide film formation in the presence of surface active agents, corrosives, pH regulators etc' to achieve global planarization. Formation and mechanical properties of the chemically modified films determine the stresses develop in the film structure delineating the stability of the chemically altered films on the surface of the metal wafer. The balance between the stresses built in the film structure versus the mechanical actions provided during the process can be used to optimize the process variables and furthermore help define new planarization techniques for the next generation microelectronic device manufacturing which is expected to deal with atomic level structures.

This paper proposes a method for electroless plating by combining supercritical fluid technology and electroless plating in a hybrid technique. The electroless plating reactions are carried out in an emulsion of supercritical carbon dioxide and an electroless plating solution with surfactant. The Ni-P film obtained by this proposed technique was a uniform and conformal film without the pinholes that form from the hydrogen bubbles produced by the electrolysis of water, and without the nodules that form from the nuclear growth on the electroless plating reaction. The dissolution of the hydrogen bubbles in the dense CO 2 particles of the emulsion prevented the pinholes from forming. The formation of nodules might have been prevented by the transport properties of the emulsion with the diffusive dense CO 2 and the suppression of the dissolved oxygen concentration when the oxygen dissolved in the dense CO 2 particles of the emulsion. The Ni-P film fabricated by our technique was smoother and more uniform than the substrate. The roughness of the plated film was constant during film growth, whereas the surface of the film fabricated by conventional electroless plating tended to roughen as the reaction time increased.

In this paper, we report on the studies of the local corrosion behaviour of chromium-coated ultra low carbon steel in NaCl solution using polarization, electrochemical impedance spectroscopy (EIS) and SVET.

Novel solid-state electrochemical sensors have been designed using the Mg2+ cation conductors incorporating novel solid-state reference electrodes for in-line monitoring of Mg in molten Al during the refining process and also for in-line monitoring of Mg content in molten Al in the alloying process. In this paper we report the preparation of Mg2+ ion conductors, MgAl2O4 and MgZr4(PO4)6, by the solid state ceramic synthesis route, measurement of their electrical properties using ac-impedance spectroscopy and application of the above cation conductors for designing novel electrochemical sensors for monitoring Mg dissolved in molten Al. The activation energy for Mg2+ ion conduction in MgAl2O4 is 2.08 eV and in MgZr4(PO4)6 is 1.7 eV, respectively. The sensors have been found to respond rapidly to change in Mg content in molten aluminium around 1000 K.

Nickel-iron, and especially Permalloy, plating has been known and used for more than 40 years, but there are still several problems related to stability and maintenance that should be resolved. This paper presents a saccharine-free pulse reversal plating Permalloy electrolyte, which gives low-stress deposits. We demonstrate selected MEMS applications of the electrolyte. The use of the strong complexing agent 5-sulfosalicylic acid allows for a photometric determination of the Fe3+-level in the bath and eliminate precipitates. This makes the electrolyte suitable as a Permalloy plating process used on an irregular basis.

Anodic etching of n-type InP in KOH electrolytes under suitable conditions leads to the formation of a nanoporous region beneath a ~40 nm dense near-surface layer [1]. The early stages of the process involve the formation of square-based pyramidal porous domains [2] and a mechanism is proposed based on directional selectivity of pore growth along the directions. A numerical model of this mechanism is described in this paper. In the algorithm used the growth is limited to the directions and the probability of growth at any pore tip is controlled by the potential and the concentration of electrolyte at the pore tip as well as the suitability of the pore tip to support further growth. The simulated porous structures and their corresponding current versus time curves are in good agreement with experimental data. The results of the simulation also suggest that, after an initial increase in current caused by the spreading out of the porous domains from their origins, growth is limited by the diffusion rate of electrolyte along the pores with the final fall-off in current being caused by irreversible processes such as the formation of a passivating film at the tips or some other modification of the state of the pore tip.

The results of a study into the dependency of SAM coverage, subsequent post-etch pattern definition and minimum feature size on the quality of the Au substrate used in both physical mask and optical mask atomic nanolithographic experiments are presented in this paper. In comparison, sputtered Au substrates yield much smoother surfaces and a higher density of {111} oriented grains than evaporated Au surfaces. Phase imaging with an atomic force microscope shows that the quality and percentage coverage of uniform alkanethiol monolayer adsorption was much greater for sputtered Au surfaces. Exposure of the monolayer with a laser-cooled Cs beam allowed determination of the minimum Cs dose (2 monolayers) to expose the SAM with lateral force microscopy. Suitable wet-etching, with etch rates of 2.2 nm min-1, results in optimized pattern definition. Utilizing these optimizations, features as small as 50 nm were achieved using both a sub-100 nm physical mask and optical standing wave mask.

In Italy the research on lithium batteries has been active since two decades and several projects involving Universities, the ENEA government energy agency and the Arcotronics Italia SpA Company have been carried out with success. At present, in the framework of a project of national interest “Electrode and Electrolyte Nanostructured Materials for Advanced Lithium Batteries” funded by the Minister of Education, University and Research, six Academic groups have been involving in the effort to develop new electrode materials, characterized by high values of specific capacity and suitable morphology, and of new nanocomposite polymer electrolytes. The morphological conversion towards nanostructures is the strategy pursued in this project to achieve its main goal, i.e. the quantum jump in term of battery specific energy and power. In addition to improvement in specific capacity, also cost reduction and environmental compatibility are important goals. As concerns the positive electrode materials the strategy that has been following is that of replacing LiCoO2 with a less expensive and environmentally compatible materials. Accordingly, LiFePO4 has been considered very promising, although its high resistance reduces the operative capacity to fractions much below the theoretical value. To overcome this drawback the dispersion of nanometric conducting powders during the LiFePO4 synthesis process has been performed. The dispersion of nano-sized ceramic powders into the polymeric matrix is the approach which has been pursuing to obtain nanocomposite polymer electrolytes having optimized performance. As concerns negative electrode materials, research efforts have been focusing on the effect of nanometric metal powder additive on commercial graphite and on the graphite substitution with metals alloying Li, such as Sn, which have specific capacity much higher than graphite. However, these metals suffer of a limited cycle life due to the large volume changes accompanying their electrochemical process in lithium-ion batteries. To overcome this drawback the approach of reducing the metal particle size to nanometric values and of substituting the metal with intermetallic compounds or with metal oxides have been pursuing. The results confirm that the strategy to reduce the particle size to the nano scale, particularly improves the cycling stability of the electrode materials. More than 100 galvanostatic cycles without capacity loss and with near 100% coulombic efficiency have been achieved with nanometric Cu6Sn5 alloy hosted in a carbon paper current collector, which is new for this application and may be a suitable alternative to the conventional copper in that it may accommodate submicrometric particles of Cu6Sn5 in a tridimensional matrix. With the aim to give a view of the present research activity on lithium-ion batteries in Italy, the contribution of the Universities of Bologna, Camerino, Chieti, Roma “La Sapienza”, Sassari and of the Torino Politecnico, involved in the outstanding project, are reported with particular details on the results obtained at Bologna University on the negative electrode materials.

The photoelectrode kinetics of the hydrogen evolution reaction is considered, using the WKB approximation for the penetra t ion of the barr ier at the semiconductor-solut ion interface. The absorption characteristics of photons in the eIectrode are introduced and the n u m b e r of electrons produced at the surface is obtained as a function of the semiconductor statistics, and also diffusion and field effects. The model makes use of the conclusion that the photo-produced electrons have been deactivated to the bottom of the conduction band by the t ime they have diffused from the point of photon absorption to the surface. Image energy and the potential difference in the double layer at the semiconductor-solut ion interface are taken into account. The expression obtained for the photo hydrogen current density is tested in its abil i ty to predict the photo-current -potent ia l curves at the gal l ium phosphide cathode. Agreement with exper iment is fair. Discrepancies are discussed. Al though photoeffects on electrochemical reactions at semiconductor-solut ion interfaces have been studied intensively (1-3), few theoretical analyses have been given (4-6). These all have the substant ia l defect that they consider the activation of electrons arising from interactions wi th in the semiconductor and neglect an analysis of t ransfer through the electric double layer at the semiconductor-solut ion interface. Photoeffects on electron t ransfer reactions at the metal /solut ion interfaces have been studied by Brodsky et al. (7). Bockris et al. (8) have treated photoeffects in hydrogen evolut ion reaction at metals, using the WKB approximation for electron tunne l ing through the double layer (9, 10). In the present paper, we apply this approach to photoeffects in the hydrogen evolution reaction at p~type semiconductors, taking into account the activat ion and t ransport of photogenerated electrons to the electrode surface. The approach made is quasiphenomenological and does not a t tempt a general solution, independent o f any assumption as to a ra tede termining step. OHP. Energy levels are counted as zero in value at the bottom of the conduction band. In ptype electrodes, the absorption of photons activates electrons in the conduction band where they are available for cathodic reactions. (Contrast thermal electrochemical reactions at the semiconductor-solut ion interface, where ptype electrodes usual ly function as anodes). The val idi ty of the use of the WKB approximation was examined by Sen and Bockris (9), who compared the approach with that of the t ime-dependent per tur bation theory, the results showing that the WKB approximat ion does not differ in order of magni tude from a t ime-dependent per turba t ion calculation for electron transfer (though there are significant discrepancies for proton transfer calculations). Photon Absorption and Electron Excitation The number of photons, the energy of which is h~, absorbed by the semiconductor between x and x + dx from the surface, Nph (x)dx, is given by