Test and Modelling of Solid Oxide Fuel Cell Durability: A Focus on Interconnect Role on Global Degradation

High-temperature fuel cells are a promising technology due to their high energy efficiency and low environmental impacts compared to conventional engines. Nevertheless, they have a limited lifetime which reduces the use to a few application fields. Among them, Solid Oxide Fuel Cells (SOFCs) have had a recent development at the industrial level in two possible configurations: an-ode-and electrolyte-supported design. Considering the impossibility to experimentally distinguish the effects of every degradation mechanism on global cell performance, each layer should be tested singularly through ex situ tests and then assembled into a virgin cell to evaluate its role on the whole system by in situ tests. However, this procedure results as quite complex, and some further micro-structural changes could occur during cell sintering. In order to overcome these constraints, the proposed approach paired ex situ experimental observations on a single element with modelling results on global SOFC. As a case study, CoMnO/Crofer22 APU and CuMnO/AISI 441 interconnect samples were tested, measuring their resistance variation for some hundreds of hours, followed by a detailed post-mortem microstructural analysis. Based on a previously validated local model, SIMFC (SIMulation of Fuel Cells), the durability of commercial anode-and electrolyte-supported cells was simulated, adding specific degradation functions only for the interconnects in order to highlight their influence on SOFC performance

Surface Induced Order in Liquid Metals and Binary Alloys

Measurements of the surface x-ray scattering from several pure liquid metals (Hg, Ga, and In) and from three alloys (Ga-Bi, Bi-In, and K-Na) with different heteroatomic chemical interactions in the bulk phase are reviewed. Surface-induced layering is found for each elemental liquid metal. The surface structure of the K-Na alloy resembles that of an elemental liquid metal. Bi-In displays pair formation at the surface. Surface segregation and a wetting film are found for Ga-Bi.Comment: 10 pages, 3 fig, published in Journal of Physics: Condensed Matte

ATPG for Dynamic Burn-In Test in Full-Scan Circuits

Yield and reliability are two key factors affecting costs and profits in the semiconductor industry. Stress testing is a technique based on the application of higher than usual levels of stress to speed up the deterioration of electronic devices and increase yield and reliability. One of the standard industrial approaches for stress testing is high temperature burn-in. This work proposes a full-scan circuit ATPG for dynamic burn-in. The goal of the proposed ATPG approach is to generate test patterns able to force transitions into each node of a full scan circuit to guarantee a uniform distribution of the stress during the dynamic burn-in tes

Synthesis of easily sinterable ceramic electrolytes based on Bi-doped 8YSZ for IT-SOFC applications

Ceramic electrolytes formed by Bi (4 mol%)-doped 8YSZ, i.e., Y2O3 (8 mol%)-doped ZrO2, were synthesized by a simple co-precipitation route, using ammonia solution as precipitating agent. The amorphous as-synthesized powders convert into zirconia-based single phase with fluorite structure through a mild calcination step at 500 \ub0C. The calcined powders were sintered at very low temperatures (i.e., 900-1100 \ub0C) achieving in both cases very high values of relative densities (i.e., > 95%); the corresponding microstructures were highly homogeneous and characterized by micrometric grains or sub-micrometric grains for sintering at 1100 \ub0C and 900 \ub0C, respectively. Very interesting electrochemical properties were determined by Electrochemical Impedance Spectroscopy (EIS) in the best samples. In particular, their total ionic conductivity, recorded at 650 \ub0C, are 6.06 7 10-2S/cm and 4.44 7 10-2S/cm for Bi (4 mol%)-doped 8YSZ sintered at 1100 \ub0C and 900 \ub0C, respectively. Therefore, Bi was proved to be an excellent sintering aid dopant for YSZ, highly improving its densification at lower temperatures while increasing its total ionic conductivity

Automatic March Tests Generations for Static Linked Faults in SRAMs

Static linked faults are considered an interesting class of memory faults. Their capability of influencing the behavior of other faults causes the hiding of the fault effect and makes test algorithm design a very complex task. A large number of March tests with different fault coverage have been published and some methodologies have been presented to automatically generate March tests. In this paper we present an approach to automatically generate March tests for static linked faults. The proposed approach generates better test algorithms then previous, by reducing the test lengt

Indirect Detection of Kaluza-Klein Dark Matter from Latticized Universal Dimensions

We consider Kaluza-Klein dark matter from latticized universal dimensions. We motivate and investigate two different lattice models, where the models differ in the choice of boundary conditions. The models reproduce relevant features of the continuum model for Kaluza-Klein dark matter. For the model with simple boundary conditions, this is the case even for a model with only a few lattice sites. We study the effects of the latticization on the differential flux of positrons from Kaluza-Klein dark matter annihilation in the galactic halo. We find that for different choices of the compactification radius, the differential positron flux rapidly converges to the continuum model results as a function of the number of lattice sites. In addition, we consider the prospects for upcoming space-based experiments such as PAMELA and AMS-02 to probe the latticization effect.Comment: 25 pages, 9 figures, LaTeX. Final version published in JCA

A Pressure-Induced Incommensurate Phase in Ammonium Hydrogen Oxalate Hemihydrate

We report evidence for the existence of a new incommensurate phase in a crystal of ammonium hydrogen oxalate hemihydrate. This phase is remarkable in two aspects: it exists only above a critical pressure Pc, and the incommensurate wave vector, which is parallel to the vector c* of the reciprocal lattice, has the largest variation ever reported, varying continuously from 0.147c* at 4.3 kbar to ~ 0.25c* at the maximum pressure (8 kbar) used to date

Peak Power Estimation: A Case Study on CPU Cores

International audienceHigh peak power consumption during test may lead to yield loss. On the other hand, reducing too much test power may lead to test escape. In order to overcome this problem, test power has to mimic the power consumed during functional mode, being as high as possible but not crossing the frontier of over-consumption. Measuring power consumption is a very time consuming activity, therefore many works in the literature focused on the indirect ways to provide power consumption estimation in a fast manner. In this paper we concentrate on a similar issue, concentrating our effort on devising a fast method for the identification and estimation of the peak power produced by test patterns. In particular we provide a detailed discussion on case studies related to peak power estimation of CPU cores when executing functional patterns, the proposed method uses the gate-level description of the CPU to identify a subset of time points over the entire test pattern that are showing the most significant peak power values. The proposed methodology has been validated on two case studies synthesized in a 65nm industrial technology