Design of (3,2) and (4,2) CNTFET Ternary Counters for Multipliers

The reduction trees of combinational multipliers are widely applying counters. To be able to compare the ternary and the binary approaches, Nanotube Field-Effect Transistor (CNTFET) ternary (3,2) and ternary (4,2) counters have been designed. The ternary (4,2) counter is compared with the binary (7,3) counter as both compute approximately the same amount of information. The binary counter is more efficient. However, comparing counters is not enough: in the Wallace reduction tree of the ternary multiplier, there are two times more lines to reduce compared to the binary one, as a 1-trit multiplier generates both product and carry terms. Comparing the Wallace tree of an 8*8-trit multiplier and a 12*12-bit binary one also shows that the binary implementation is the most efficient

On the decrepitation mechanism of MgNi and LaNi5-based electrodes studied by in situ acoustic emission

cited By 13International audienceIn situ monitoring of the pulverization of amorphous MgNi and crystalline LaNi5-based alloys has been studied during their hydrogen charge by combining acoustic emission and electrochemical measurements. In both alloys, two classes of acoustic signals with specific temporal and energetic characteristics were detected during their charge: a P1 class related to the particle cracking and a P2 class due to the release of H2 bubbles. By comparing the P1 activity on both materials as a function of the charge input, it was shown that the pulverization phenomenon becomes significant at a much lower charge input for the LaNi5-based electrode (∼5-25 mAh g-1) than for the MgNi electrode (∼365 mAh g-1), reflecting the fact that the mechanism responsible of their decrepitation is not similar. Indeed, it was demonstrated that the cracking of the amorphous and porous MgNi material is mainly induced by the hydrogen evolution reaction whereas for the crystalline and denser LaNi5-based material, the α-β lattice expansion is responsible of its decrepitation. It was also shown that the particle size and the charge current density have a major impact on the MgNi decrepitation. The correlation between the MgNi particle cracking and the discharge capacity decay with cycling was established. © 2011 Elsevier B.V

In situ monitoring of the volume change and cracking of a MgTi hydride electrode

cited By 2International audienceMetastable MgTi-10 wt% Pd alloy was synthesized by high-energy ball milling and evaluated as metal hydride electrode for Ni-MH batteries. In situ acoustic emission and generated/relaxed force measurements were performed to monitor the particle cracking and volume expansion/contraction of the electrode occurring during electrochemical charge-discharge cycling. On the basis on these measurements, it was shown that the electrochemical hydrogenation of the MgTi alloy occurs first by an irreversible hydrogenation (corresponding to a charge capacity of 500 mA h g-1) followed by a reversible hydrogenation (resulting in a discharge capacity of 370 mA h g-1). This second step induces MgTi particle cracking and electrode collapse. During the subsequent cycles, a more reversible volume expansion/contraction is observed and the particle cracking becomes progressively less intensive and originates from the hydrogen evolution reaction rather than to the hydrogen absorption reaction. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

New insights into the pulverization of LaNi5-based alloys with different Co contents from electrochemical acoustic emission measurements

cited By 1International audienceThe pulverization (particle cracking) of LaNi5-based electrodes with different Co contents (ca.5, 8 and 10 wt%) is studied by means of electrochemical acoustic emission measurements. Through an appropriate analysis of the acoustic signals detected during electrode cycling, the acoustic events related to particle cracking can be identified and quantified. It is shown that the particle cracking occurs mostly during the first charge. For the 5 and 8 wt% Co alloys, the particle cracking is mainly detected in the early stage of the hydriding reaction, i.e.when the α-to-β phase transition is initiated. In contrast, for the 10 wt% Co alloy, the particle cracking is more progressive during the first charge with the presence of two successive increases of the acoustic activity, which is attributed to the formation of an intermediate γ-phase hydride. On the basis of the number of acoustic events detected during the first charge, the influence of the Co content on the alloy pulverization is quantified with mean values of 13700, 5600 and 1300 events for a Co content in the alloy of 5, 8 and 10 wt%, respectively. © 2015 Elsevier Ltd. All rights reserved

In-situ X-ray tomographic study of the morphological changes of a Si/C paper anode for Li-ion batteries

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In-situ acoustic emission study of Si-based electrodes for Li-ion batteries

cited By 11International audienceThe mechanical degradation of a Si powder (∼2 μm) based electrode is investigated by acoustic emission (AE). AE signals are mainly detected during the first lithiation, suggesting that electrode cracking mainly occurs during this period. The formation of the solid electrolyte interface (SEI) is not very acoustically emissive, in contrast to the Si particle cracking which is initiated in the early stage of the lithiation in accordance with a core - shell lithiation mechanism. An increase of the AE activity is observed at the end of the discharge when the c-Li15Si4 phase is formed and during the charge when the potential reaches ∼0.45 V, corresponding to the delithiation of c-Li15Si4. From a clustering procedure, three types of signals are identi fied: type-1 signals consisting of a succession of very short waveforms with high peak frequency (∼700 kHz) are primarily detected when the Si lithiation is initiated and are ascribed to the nucleation of surface microcracks on the Si particles; type-2 signals (peak frequency ∼400 kHz), present all during the Si lithiation, are attributed to the propagation of cracks through the Si particles and into the composite film; type-3 signals (peak frequency ∼200 kHz), detected when the potential reaches 60 mV, are ascribed to the accentuation of the electrode cracking due to the c-Li15Si4 formation. © 2014 Elsevier B.V. All rights reserved