Development of an assembly for the realization of a transducer able to operate at very high temperatures

Monitoring the operation of the latest-generation nuclear reactor requires ultrasonic transducers able to operate at very high temperatures (> 600°C). To achieve this, CEA has requested from “Institut de Soudure” to help developing a new technology for these transducers compared to the one previously developed. This began with the development of a reliable assembly technique between a lithium niobate piezoelectric disc whose Curie temperature exceeds 1100°C and stainless steel discs. The chosen solution was to braze the niobate disc between two stainless steel discs. Parallel to this development, it was also necessary to develop a NDE procedure to verify the quality of the brazing assemblies. This development began with a simulation of immersion ultrasonic testing of the assemblies. The constraints were to be able to control the two brazed interfaces from the same access face, with the possibility of detecting and dimensioning defects with an equivalent diameter of 0.25 mm. This phase is important to define the optimal transducer with the associated operating conditions. The first assemblies validated the preliminary choices. To exploit the cartographies obtained, a signal processing procedure was developed. This enabled an automatic characterization of the indications observed. However, the analysis of the signals observed proved to be more complex than the one predicted by the simulation. Once the origin of the various observed signals was identified it was then possible to define windows allowing the construction of the cartographies to analyze. In case of a good quality assembly, it was possible to qualify the generated beam and to image it in the focal plane but with an observed signal having a very low damping. These first encouraging results, however, show that there is still some validation and development work to increase the sensitivity of the developed translator and its damping.

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Discussion: “Short-Time Tensile Properties of Type 316 Stainless Steel at Very High Temperatures” (Gibbs, T. W., and Wyatt, H. W., 1961, ASME J. Basic Eng., 83, pp. 481–488)

Journal of Basic Engineering ◽

10.1115/1.3662241 ◽

1961 ◽

Vol 83 (4) ◽

pp. 488-488

Author(s):

Robert A. Bareiss

Keyword(s):

Stainless Steel ◽

Tensile Properties ◽

High Temperatures ◽

316 Stainless Steel ◽

Short Time ◽

Very High

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Time-Dependent Dielectric Breakdown in Thin Intrinsic SiO2 Films

MRS Proceedings ◽

10.1557/proc-386-227 ◽

1995 ◽

Vol 386 ◽

Cited By ~ 2

Author(s):

J. S. Suehle ◽

P. Chaparala

Keyword(s):

Electric Field ◽

Electric Fields ◽

High Temperatures ◽

Dielectric Breakdown ◽

Operating Conditions ◽

Time Dependent ◽

Stress Tests ◽

Time Dependent Dielectric Breakdown ◽

Wide Range ◽

Very High

ABSTRACTTime-Dependent Dielectric Breakdown studies were performed on 6.5-, 9-, 15-, 20-, and 22.5- nm thick SiO2 films over a wide range of stress temperatures and electric fields. Very high temperatures (400 °C) were used to accelerate breakdown so that stress tests could be performed at low electric fields close to those used for device operating conditions. The results indicate that the dependence of TDDB on electric field and temperature is different from that reported in earlier studies. Specifically, the electric-field-acceleration parameter is independent of temperature and the thermal activation energy was determined to be between 0.7 and 0.9 eV for stress fields below 7.0 MV/cm.Failure distributions of high-quality current-generation oxide films are shown to be of single mode and have dispersions that are not sensitive to stress electric field or temperature, unlike distributions observed for oxides examined in earlier studies. These results have implications on the choice of the correct physical model to describe TDDB in thin films. The data also demonstrate for the first time the reliability of silicon dioxide films at very high temperatures.

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Comparing the impacts of 2003 and 2010 heatwaves in NPP over Europe

Biogeosciences Discussions ◽

10.5194/bgd-10-15879-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 15879-15911 ◽

Cited By ~ 5

Author(s):

A. Bastos ◽

C. M. Gouveia ◽

R. M. Trigo ◽

S. W. Running

Keyword(s):

High Temperatures ◽

Crop Production ◽

Western Europe ◽

Net Primary Production ◽

Net Photosynthesis ◽

Large Area ◽

Main Driver ◽

Vegetation Carbon ◽

The One ◽

Very High

Abstract. In the last decade, Europe was stricken by two outstanding heatwaves, the 2003 event in Western Europe and the recent 2010 episode over Russia. Both extreme events were characterised by record-breaking temperatures, and widespread socio-economic impacts, including significant increments on mortality rates, decreases in crop production and in hydroelectric production. This work aims to assess the influence of both mega-heatwaves on vegetation carbon uptake, using yearly Net Primary Production (NPP) and monthly Net Photosynthesis (PsN) data derived from satellite imagery obtained from MODIS for the period 2000–2011. In 2010, markedly low productivity was observed over a very large area in Russia, at monthly, seasonal and yearly scales, falling below 50% of average NPP. This decrease in NPP in 2010 was far more intense than the one affecting Western Europe in 2003, which corresponded to 20–30% of the average, and affected a~much larger extent. Total NPP anomalies reached −19 Tg C for the selected regions in France during 2003 and −94 Tg C for western Russia in 2010, which corresponds almost to the magnitude of total NPP anomaly during 2010 for the whole Europe. Overall, the widespread negative PsN anomalies in both regions match the patterns of very high temperature values preceded by a long period of below-average precipitation, leading to strong soil moisture deficits, stressing the role of soil-atmosphere coupling. In the case of 2003 heatwave, results indicate a strong influence of moisture deficits coupled with high temperatures in the response of vegetation, while for the 2010 event very high temperatures appear to be the main driver of very low NPP.

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Sintered Stainless Steel for Interconnectors for PEM Fuel Cell

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.1047 ◽

2012 ◽

Vol 706-709 ◽

pp. 1047-1051

Author(s):

Renata Włodarczyk

Keyword(s):

Stainless Steel ◽

Fuel Cells ◽

Fuel Cell ◽

New Technology ◽

Bipolar Plate ◽

Operating Conditions ◽

Bipolar Plates ◽

Fuel Cell Performance ◽

Sintered Stainless Steel ◽

Materials Used

Polymer electrolyte membrane fuel cell performance strongly depends on properties of the fuel cell stack bipolar plates (BPs). Bipolar plates are a key component of fuel cells. Functions of materials used for fuel cells include even distribution of gas fuel and air, conduction of electricity between the adjacent cells, heat transfer from the cell as well as prevention of gas leakage and cooldown. Due to multifunctionality of fuel cell plates, choice of materials used for plates is immensely difficult. This paper presents opportunities of application of a new technology of powder sintering for creation of parts for electricity and heat generators. Sintered stainless steel 316LHD was investigated as a candidate material for bipolar plate materials. 316L powders were compacted with the following load: 700MPa, 550MPa, and 200MPa, and then sintered at the temperature of 1250 °C in hydrogen medium. The main criterion for selection of a particular material for components of fuel cells is their corrosion resistance in operating conditions of hydrogen fuel cells. In order to determine resistance to corrosion in the environment of operation of fuel cells, potentiokinetic curves (as a function of temperature) were registered in synthetic solution 0.1M H2SO4 + 2 ppmF- at 80°C. The investigations also covered measurements of mechanical properties and microstructural testing of sinters with austenitic structure.

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Time-Dependent Dielectric Breakdown in Thin Intrinsic SiO2 Films

MRS Proceedings ◽

10.1557/proc-391-123 ◽

1995 ◽

Vol 391 ◽

Cited By ~ 1

Author(s):

J. S. Suehle ◽

P. Chaparala

Keyword(s):

Electric Field ◽

Electric Fields ◽

High Temperatures ◽

Dielectric Breakdown ◽

Operating Conditions ◽

Time Dependent ◽

Stress Tests ◽

Time Dependent Dielectric Breakdown ◽

Wide Range ◽

Very High

AbstractTime-Dependent Dielectric Breakdown studies were performed on 6.5-, 9-, 15-, 20-, and 22.5-nm thick SiO2 films over a wide range of stress temperatures and electric fields. Very high temperatures (400 °C) were used to accelerate breakdown so that stress tests could be performed at low electric fields close to those used for device operating conditions. The results indicate that the dependence of TDDB on electric field and temperature is different from that reported in earlier studies. Specifically, the electric-field-acceleration parameter is independent of temperature and the thermal activation energy was determined to be between 0.7 and 0.9 eV for stress fields below 7.0 MV/cm.Failure distributions of high-quality current-generation oxide films are shown to be of single mode and have dispersions that are not sensitive to stress electric field or temperature, unlike distributions observed for oxides examined in earlier studies. These results have implications on the choice of the correct physical model to describe TDDB in thin films. The data also demonstrate for the first time the reliability of silicon dioxide films at very high temperatures.

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Closure to “Discussion of ‘Short-Time Tensile Properties of Type 316 Stainless Steel at Very High Temperatures’” (1961, ASME J. Basic Eng., 83, p. 488)

Journal of Basic Engineering ◽

10.1115/1.3662242 ◽

1961 ◽

Vol 83 (4) ◽

pp. 488-488

Author(s):

T. W. Gibbs ◽

H. W. Wyatt

Keyword(s):

Stainless Steel ◽

Tensile Properties ◽

High Temperatures ◽

316 Stainless Steel ◽

Short Time ◽

Very High

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Strain hardening analysis of an austenitic stainless steel at high temperatures based on the one-parameter model

Materials Science and Engineering A ◽

10.1016/j.msea.2011.10.108 ◽

2012 ◽

Vol 532 ◽

pp. 381-391 ◽

Cited By ~ 8

Author(s):

G. Angella

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Strain Hardening ◽

High Temperatures ◽

The One

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Some aspects of the defect structure in an austenitic stainless steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108714 ◽

1978 ◽

Vol 36 (1) ◽

pp. 314-315

Author(s):

R. Gonzalez ◽

L. Bru

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Cellular Structures ◽

Total Strain Amplitude ◽

Total Deformation ◽

Density Of Dislocations ◽

Planar Arrays ◽

Stacking Fault Tetrahedra ◽

Distribution Of Dislocations ◽

Very High

The analysis of stacking fault tetrahedra (SFT) in fatigued metals (1,2) is somewhat complicated, due partly to their relatively low density, but principally to the presence of a very high density of dislocations which hides them. In order to overcome this second difficulty, we have used in this work an austenitic stainless steel that deforms in a planar mode and, as expected, examination of the substructure revealed planar arrays of dislocation dipoles rather than the cellular structures which appear both in single and polycrystals of cyclically deformed copper and silver. This more uniform distribution of dislocations allows a better identification of the SFT.The samples were fatigue deformed at the constant total strain amplitude Δε = 0.025 for 5 cycles at three temperatures: 85, 293 and 773 K. One of the samples was tensile strained with a total deformation of 3.5%.

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Preparation of Electron Transparent Metal-Matrix Composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101414 ◽

1968 ◽

Vol 26 ◽

pp. 334-335 ◽

Cited By ~ 2

Author(s):

M. R. Pinnel ◽

A. Lawley

Keyword(s):

Stainless Steel ◽

Load Transfer ◽

Volume Fraction ◽

Steel Wire ◽

Initial Step ◽

Interfacial Region ◽

Matrix Composites ◽

Specific Test ◽

The Matrix ◽

The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

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