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Ageing Tests (ageing + test)

Distribution by Scientific Domains

Engineering	85%

Selected Abstracts

Long-term Reliability Prediction of 935 nm LEDs Using Failure Laws and Low Acceleration Factor Ageing Tests

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2005
Y. Deshayes
Abstract Numerous papers have already reported various results on electrical and optical performances of GaAs-based materials for optoelectronic applications. Other papers have proposed some methodologies for a classical estimation of reliability of GaAs compounds using life testing methods on a few thousand samples over 10,000 hours of testing. In contrast, fewer papers have studied the complete relation between degradation laws in relation to failure mechanisms and the estimation of lifetime distribution using accelerated ageing tests considering a short test duration, low acceleration factor and analytical extrapolation. In this paper, we report the results for commercial InGaAs/GaAs 935 nm packaged light emitting diodes (LEDs) using electrical and optical measurements versus ageing time. Cumulative failure distributions are calculated using degradation laws and process distribution data of optical power. A complete methodology is described proposing an accurate reliability model from experimental determination of the failure mechanisms (defect diffusion) for this technology. Electrical and optical characterizations are used with temperature dependence, short-duration accelerated tests (less than 1500 h) with an increase in bias current (up to 50%), a small number of samples (less than 20) and weak acceleration factors (up to 240). Copyright © 2005 John Wiley & Sons, Ltd. [source]

Patterns of damage in igneous and sedimentary rocks under conditions simulating sea-salt weathering

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2003
C. Cardell
Abstract A saline-spray artificial ageing test was used to simulate the effects produced in granites and sedimentary rocks (calcarenites, micrites and breccia) under conditions in coastal environments. Three main points were addressed in this study: the durability of the different kinds of rock to salt decay, the resulting weathering forms and the rock properties involved in the weathering processes. For this, mineralogical and textural characterization of each of the different rocks was carried out before and after the test. The soluble salt content at different depths from the exposed surfaces was also determined. Two different weathering mechanisms were observed in the granite and calcareous rocks. Physical processes were involved in the weathering of granite samples, whereas dissolution of calcite was also involved in the deterioration of the calcareous rocks. We also showed that microstructural characteristics (e.g. pore size distribution), play a key role in salt damage, because of their influence on saline solution transport and on the pressures developed within rocks during crystallization. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Extending the retention of friction-reducing capability in low-phosphorus engine oils

LUBRICATION SCIENCE, Issue 2 2005
R. Jensen
Abstract In advanced fuel-efficient engine oils containing molybdenum dialkyldithiocarbamate, Mo(dtc)2, as a friction-reducing additive, the friction-reducing capability is gradually depleted with mileage accumulation and is dependent on the presence of other additives, such as zinc dialkyldithiophosphate, Zn(dtp)2. Indeed, it has been shown that the loss of the friction-reducing capability of Mo(dtc)2 coincides with the depletion of Zn(dtp)2. The next generation of oils will specify a lower phosphorus content (e.g., 0.08% in ILSAC GF-4 and even lower in the specification after GF-4) to reduce the detrimental effects of phosphorus on catalyst systems. This will necessitate the use of less Zn(dtp)2, which could have an adverse effect on the retention of friction-reducing capability. The aim of this study was to determine if the retention of friction-reducing capability could be maintained or even increased at 0.05% phosphorus with newer molybdenum trinuclear, Mo3S7(dtc)4, additives. To facilitate the study, a modified laboratory-based ageing test was developed which correlated with the loss of friction-reducing capability in the Sequence VIB engine test. This ageing test was used to evaluate model blends of Mo3S7(dtc)4 with Zn(dtp)2 at 0.05% phosphorus and added antioxidants. The results indicate that it is possible to extend the retention of friction-reducing capability. However, whether or not it can be extended beyond the current drain intervals is still an open question. [source]

New interdigital design for large area dye solar modules using a lead-free glass frit sealing

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2006
R. Sastrawan
Abstract A new interdigital design for large area dye solar modules is developed for an area of 30×30,cm2. This design requires fewer holes in the glass substrate for electrolyte filling, than the conventional strip design. A complete manufacturing process of this module,ranging from screen printed layers to semi-automated colouring and electrolyte filling,in a laboratory-scale baseline is illustrated. As primary sealing method, a durable glass frit sealing is used. It is shown, that the lead (Pb) content present in many glass frit powders contaminates the catalytic platinum electrode during the sintering process, resulting in a lowering of the fill factor. A screen printable lead-free glass frit paste is developed, which solves this problem. Long term stability tests are presented on 2·5,cm2 dye solar cells, which have been completely sealed with glass frit. In consecutively performed accelerated ageing tests under 85°C in the dark (about 1400,h) and continuous illumination with visible light (1 sun, about 1700,h), a 2·5,cm2 dye solar cell with an electrolyte based on propylmethylimidazolium iodide showed an overall degradation of less than 5% in conversion efficiency. In a subsequently performed thermal cycling test (,40°C to +85°C, 50 cycles) a 2·5,cm2 dye solar cell with the same electrolyte composition also showed only a slight degradation of less than 5% in conversion efficiency. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Identification of degradation mechanisms in field-tested CdTe modules

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2006
Thomas Carlsson
Abstract Field 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. [source]

Long-term stability of dye-sensitised solar cells

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2001
A. Hinsch
Accelerated ageing tests on large numbers of nanocrystalline dye-sensitised solar cells (nc-DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye-sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd. [source]