Identification Of Degradation Mechanisms Research Articles

Identification of Degradation Mechanisms by Post-Mortem Analysis for High Power and High Energy Commercial Li-Ion Cells after Electric Vehicle Aging

Driven by the rise of the electric automotive industry, the Li-ion battery market is in strong expansion. This technology does not only fulfill the requirements of electric mobility, but is also found in most portable electric devices. Even though Li-ion batteries are known for their numerous advantages, they undergo serious performance degradation during their aging, and more particularly when used in specific conditions such as at low temperature or high charging current rates. Depending on the operational conditions, different aging mechanisms are favored and can induce physical and chemical modifications of the internal components, leading to performance decay. In this article, the identification of the degradation mechanisms was carried out thanks to an in-depth ante- and post mortem study on three high power and high energy commercial 18,650 cells. Li-ion cells were aged using a battery electric vehicle (BEV) aging profile at −20 °C, 0 °C, 25 °C, and 45 °C in accordance with the international standard IEC 62-660, and in calendar aging mode at 45 °C and SOC 100%. Internal components recovered from fresh and aged cells were investigated through different electrochemical (half-coin cell), chemical (EDX, GD-OES, NMR), and topological (SEM) characterization techniques. The influence of power and energy cells’ internal design and Si content in the negative electrode on cell aging has been highlighted vis-à-vis the capacity and power fade.

Identification of Degradation Mechanisms in Slot-Die-Coated Nonfullerene ITO-Free Organic Solar Cells Using Different Illumination Spectra

In this work, we have studied degradation mechanisms of nonfullerene-based organic solar cells with PET/Ag/ZnO/PBDTB-T:ITIC/PEDOT:PSS/CPP PEDOT:PSS device structure. We compare pristine and degrade...

Health Assessment of Railway Turnouts: A Case Study

Within railway infrastructure, railway point systems are among the most critical equipment, not only due to accidents and delays caused by their failures but also due to maintenance costs. The detection of early signs of degradation and the ability to identify the maintenance actions required to prevent a failure are key aspects of a successful and advantageous health assessment strategy. While studies focusing on the detection and prognostics of railway point systems exist, few or none address the correlation between environment, field layout and the point system behavior. This paper aims to consider the interaction between these factors and the point system behavior, and compare a fleet-based approach to an asset-based approach for the point systems health assessment, highlighting the influence of the field configuration on the effectiveness of the two methods. The proposed methods exploit Self-Organizing Maps (SOMs) to construct a health indicator for both the detection and the diagnosis of railway point systems. The approaches are applied to a case study for the on-line health assessment of 20 electro-mechanical point systems operating on a main line over the course of 6 months. The results show how an asset-based monitoring system is necessary in order to maintain a level of information which enables to achieve an efficient detection of anomalies and a correct identification of degradation mechanisms. In addition, fleet-based health assessment leads to a higher percentage of missed alarms, due to the intrinsic hypothesis of considering all point systems as operating in the same context and mission profile.

Identification of Degradation Mechanisms Based on Thermal Characteristics of InGaN/GaN Laser Diodes

A method of identifying laser degradation mechanism is established based on thermal characteristic analysis of InGaN/GaN laser diodes (LDs). Both steady and transient thermal characteristics of LDs are calculated by the finite-element analysis method, the results show that thermal resistance and thermal time constant of each layer are determined by the corresponding structure and material. Experiments on thermal characteristics of LDs are carried out, degradation induced heat transport irregularities are localized by comparing the transient cooling curves of the virgin, and degraded LDs and further analyses give more information on degradation mechanisms of the LDs. The results confirm that this identification method is an effective method, which gives specific guidance for the analysis of the laser degradation mechanisms.

Identification of degradation mechanisms in coatings for supercritical steam applications

AbstractThe development and qualification of coatings for materials used in modern steam power plants stems from the increased demand for higher efficiency, and hence higher operating temperatures. Within the EU funded project ‘SUPERCOAT’, several coatings, both overlay and diffusion type, were investigated. Seven different coatings are presented in this work. They included two commercially available HVOF coatings (Ni–20Cr and Ni–50Cr), an aluminium‐based slurry coating (IPCOTE), together with two further variations of this slurry coating containing sputter‐coated inter‐layers. An overlay slurry coating consisting of silica particles embedded in a matrix of alumina and chromia was also examined. The final coating to be investigated was a pack‐aluminised sample of P92.All the coating systems examined showed superior oxidation resistance compared to the 9%Cr steel substrate (P91 or P92) in extended exposures to a steam environment at 650 °C. However, in service component lifetime will be limited by degradation of the coating, therefore it is essential that the mechanisms controlling this behaviour are understood. This paper reviews several degradation mechanisms that have been observed during long‐term exposure of these coatings. The mechanisms that have been observed include depletion of active alloying elements, diffusion of aluminium into the substrate from the coating, formation of Kirkendall porosity and mechanical failure of the coatings. Examples of each of these mechanisms will be presented. Possible processing routes to avoid these degradation mechanisms will also be discussed.

Identification of degradation mechanisms in high-power laser bars using by-emitter degradation studies

An investigation into the degradation of an 808 nm AlGaAs/GaAs compressively strained high-power laser bar is performed using a range of experimental techniques that focus on understanding the performance of the individual emitters that make up the laser bar—a so-called by-emitter analysis. We find that thermally induced current runaway, beginning in the edge emitters, is an important factor in the degradation of this bar and its eventual failure. Facet temperature measurements reveal that temperature distributions where the emitters are hotter at the bar edges as compared to those in the bar centre can occur in aged laser bars. This is in contrast to the facet temperature distributions observed in new devices and also in measurements of the bulk temperature.

Real-SOFC - A Joint European Effort in Understanding SOFC Degradation

The Integrated Project Real-SOFC joins 26 partners from throughout Europe active in planar SOFC technology. The project is funded by the European Commission within the Sixth Framework Programme and aims at improving the understanding of degradation in SOFC stacks and extending the durability of planar SOFC devices such that they become viable for stationary applications. The project consortium comprises of universities, research institutions and industrial companies. The project concept is based on improving materials and materials processing by the provision of extensive test results allowing the identification of degradation mechanisms, and then to supply industrial components of enhanced quality for repeated testing analysis. An iterative programme of component development is employed resulting in the production of '2nd' and '3rd' Generations of SOFC components/stacks. This paper offers recent results on the degradation issues and covers selected aspects of other project-related output such as testing conditions, environmental impact assessment and educational activities.

Towards identification of degradation mechanisms in InGaN laser diodes grown on bulk GaN crystals

In this work we present a reliability study of low dislocation density InGaN laser diodes fabricated on high-pressure grown GaN monocrystaline substrates. The aging process was performed under pulse current conditions. Degradation of these devices manifests primarily in the increase of the threshold current. Interestingly, the differential efficiency of lasers remains stable at all times. The aging time dependence of the increase of the threshold current precisely follows a square root dependence. These observations suggest that the degradation results from the enhancement of the nonradiative recombination within the device active layers and is related to point defect diffusion.

Integrated approach to the characterization and conservation of artefacts of the Brazilian colonial period

Several common-use artifacts (coins, faience, cult objects, etc.) coming from two excavations sites near Rio de Janeiro, two sugar farms Historico do Rochedo and Cruzeiro, have been the subject of this investigation, which aimed to integrate physico-chemical characterizations with the identification of degradation mechanisms, and the proposal of innovative conservation methods, such as PECVD deposition of SiO2-like films for protection of metallic artifacts. For the microchemical, micromorphological and microstructural analysis, optical microscopy-OM, X-ray diffraction XRD, X-ray fluorescence-XRF, and scanning electron microscopy equipped with electron microprobe-SEM+EDS have been employed.

Identification of degradation mechanisms in field‐tested CdTe modules

AbstractField tests and accelerated ageing tests were conducted on CdTe photovoltaic modules with Sb‐based back contacts. Significant performance degradation was observed during one and a half years of outdoor exposure. Small‐area samples were prepared from field tested modules and characterized with current–voltage, capacitance–voltage and resistance measurements. Results show that module performance degradation in the field can be partly attributed to a decrease in doping concentration close to the CdS/CdTe junction and an increased resistance in the transparent front contact. A comparison with results in the literature indicates that bias voltage may play a role in the degradation process. Copyright © 2005 John Wiley & Sons, Ltd.

Identification of degradation mechanisms in a bipolar linear voltage comparator through correlation of transistor and circuit response

The input bias current (I/sub IB/) of the National LM111 voltage comparator exhibits a non-monotonic response to total dose irradiations at various dose rates. At low total doses, below 100 krad(SiO/sub 2/), increased I/sub IB/ is due primarily to gain degradation in the circuit's input transistors. At high total doses, above 100 krad(SiO/sub 2/), I/sub IB/ shows a downward trend that indicates the influence of compensating circuit mechanisms. Through correlation of transistor and circuit response, the transistors responsible for these compensating mechanisms are identified. Non-input transistors in the circuit's input stage lower the emitter-base operating point voltage of the input device. Lower emitter-base voltages reduce the base current supplied by the input transistors, causing a moderate recovery in the circuit response.