Study made of corrosion resistance of stainless steel and nickel alloys in nuclear reactor superheaters

Experiments performed under conditions found in nuclear reactor superheaters determine the corrosion rate of stainless steel and nickel alloys used in them. Electropolishing was the primary surface treatment before the corrosion test. Corrosion is determined by weight loss of specimens after defilming

Electromechanical Reliability Testing of Three-Axial Silicon Force Sensors

This paper reports on the systematic electromechanical characterization of a new three-axial force sensor used in dimensional metrology of micro components. The siliconbased sensor system consists of piezoresistive mechanicalstress transducers integrated in thin membrane hinges supporting a suspended flexible cross structure. The mechanical behavior of the fragile micromechanical structure isanalyzed for both static and dynamic load cases. This work demonstrates that the silicon microstructure withstands static forces of 1.16N applied orthogonally to the front-side of the structure. A statistical Weibull analysis of the measured data shows that these values are significantly reduced if the normal force is applied to the back of the sensor. Improvements of the sensor system design for future development cycles are derived from the measurement results.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Fabrication and properties of a tin-lithium alloy.

A Sn-25 at.% Li alloy has been fabricated by starting with pure Sn and Li. The alloy was cast into various shapes and sent to researchers in several organizations in the United States and abroad for property measurements. The fabrication procedure involved gradual addition of Li from a separate vessel into a vessel that contained Sn; continuous stirring of the mixture during Li addition increased the Li content of the alloy gradually from 0 to the final value of 25 at.%. The melting temperature of the alloy was 334 C; its density was 6.36 g/cm{sup 3}. Results are presented on microstructure, chemical composition, phase distribution, and microhardness of the alloy. Several experiments were conducted to evaluate the chemical reactivity of the alloy with air, water, and steam. Results showed that the alloy undergoes catastrophic oxidation when T >250 C in air and develops an oxide scale in water at temperatures up to 95 C. Exposure in low-pressure steam at 200 C caused significant swelling and cracking of the alloy

Entwicklung eines LIGA-Mikrosystems zur Messung mechanischer Eigenschaften von Mikroproben

Wissenschaftlliche Berichte - FZKA 5986 Bei der Entwicklung der Mikroelektronik standen zunächst nur die elektrischen und thermischen Materialkenndaten im Vordergrund. Im Zuge der Weiterentwicklung zur Mikrosystemtechnik, bei der mikromechanische Komponenten mit der entsprechenden Auswerteelektronik kombiniert werden, ergibt sich die Notwendigkeit, daß auch die mechanischen Materialeigenschaften der verwendeten Werkstoffe bekannt sind. Da diese Kenndaten aufgrund der spezifischen Herstellungsverfahren der Mikrosystemtechnik und charakteristischer Dimensionen nicht ohne weiteres von der Makromechanik auf Dimensionen im Mikrometerbereich übertragen werden können, müssen sie an mikrostrukturierten Proben ermittelt werden. Um die Handhabung der Mikroproben hinsichtlich Montage und Justage bei der Materialprüfung zu erleichtern, wurde in der vorliegenden Arbeit ein Prüfsystem entwickelt, dessen laterale Dimensionen mit denjenigen des Prüflings vergleichbar sind. Mit diesem sog. Mikroprüfsystem wird der Elastizitäts-Modul von Mikrobalken in einem Biegeexperiment ermittelt. Das Prüfsystem besteht aus einem Mikroaktor mit integriertem Kraftsensor auf der Basis von Dehnmeßstreifen (DMS), einer optischen Wegmeßeinheit und einer Probenhalterung. Es stellt das erste nach dem LIGA-Verfahren gefertigte Mikrosystem dar, das fluidische Aktorik mit optischer und elektrischer Sensorik kombiniert. Die Gesamtabmessungen des Systems betragen 6.5 x 4.5 mm2 bei einer Strukturhöhe von ca. 250 µm. Für die Realisierung einer optimierten Fluidankopplung wurde das LIGA-Verfahren mit dem hierfür entwickelten Opferstrukturverfahren kombiniert. Die DMS werden über einen neuen, zum LIGA-Verfahren kompatiblen Herstellungsprozeß gefertigt, bei dem zunächst die DMS auf dem Substrat realisiert und anschließend die Mikrostrukturen auf diesen galvanisch aufgebaut werden. Für das Mikroprüfsystem wurde ein druckbetriebener Mikroaktor entwickelt, der Prüfkräfte im Bereich mehrerer 10 mN auf die Mikrobalken übertragen kann. Er besteht aus einer Aktorkammer und einem beweglichen Kolben, der sich aufgrund einer Druckdifferenz zwischen Kammer und Außenraum parallel zum Substrat bewegen kann. Wesentlicher Vorteil im Vergleich zu bestehenden Mikroaktoren ist, daß die übertragbaren Kräfte unabhängig vom Stellweg des Kolbens sind. Um die am Prüfling angreifenden Kräfte ermitteln zu können, wurden Kraftsensoren auf dem Kolben integriert. Dabei handelt es sich um DMS, die die Relativbewegung einer beweglichen Komponente innerhalb des beweglichen Kolbens detektieren. Die Wegmeßeinheit ermittelt die Balkenverbiegung indirekt über den Stellweg des Kolbens. Ihr Funktionsprinzip beruht auf der Reflexion eines divergenten Lichtstrahls an einem beweglichen Spiegel und der entsprechenden Detektion der reflektierten Lichtintensität als Funktion der Spiegelposition. Die Ankopplung der Mikrostruktur an die erforderliche Lichtquelle und Detektoren erfolgt über Lichtleitfasern. Die Balkenverbiegung kann mit diesem optischen Meßaufnehmer mit einer Genauigkeit von 200 nm bestimmt werden. Alternativ zum Einsatz des druckbetriebenen Mikroaktors im Mikroprüfsystem konnte dessen mögliche Anwendung in der minimal invasiven Chirurgie nachgewiesen werden. Dabei wird der Aktor die Antriebseinheit für ein Schneidwerkzeug auf einem Herzkatheter bilden

Composition of cuticular lipids in the pteromalid wasp Lariophagus distinguendus is host dependent

The insect cuticle is covered by a thin layer of hydrocarbons not only preventing desiccation but also playing an important role in the sexual communication of several species. In the pteromalid wasp Lariophagus distinguendus, a parasitoid of grain infesting beetles, female cuticular hydrocarbons (CHCs) elicit male courtship behaviour. We analyzed the CHC profiles of male and female L. distinguendus wasps reared on different beetle hosts by coupled gas chromatography- mass spectrometry (GC-MS). Statistical analysis of the data revealed significant differences between strains reared on different hosts, while spatially isolated strains reared on the same host produced similar profiles. CHC profiles of parasitoids reared on Stegobium paniceum were statistically distinguishable from those of wasps reared on all other hosts. A host shift from Sitophilus granarius to S. paniceum resulted in distinguishable CHC profiles of L. distinguendus females after only one generation. Considering the role of CHCs as contact sex pheromones, our data suggest that host shifts in parasitic wasps might lead to reproductive isolation of host races due to the modification of the cuticular semiochemistry

Environmentally assisted cracking in light water reactors. Semiannual report, July 1998-December 1998.

This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors from July 1998 to December 1998. Topics that have been investigated include (a) environmental effects on fatigue S-N behavior of primary pressure boundary materials, (b) irradiation-assisted stress corrosion cracking of austenitic stainless steels (SSs), and (c) EAC of Alloys 600 and 690. Fatigue tests have been conducted to determine the crack initiation and crack growth characteristics of austenitic SSs in LWR environments. Procedures are presented for incorporating the effects of reactor coolant environments on the fatigue life of pressure vessel and piping steels. Slow-strain-rate tensile tests and posttest fractographic analyses were conducted on several model SS alloys irradiated to {approx}0.3 and 0.9 x 10{sup 21} n {center_dot} cm{sup -2} (E > 1 MeV) in helium at 289 C in the Halden reactor. The results have been used to determine the influence of alloying and impurity elements on the susceptibility of these steels to irradiation-assisted stress corrosion cracking. Fracture toughness J-R curve tests were also conducted on two heats of Type 304 SS that were irradiated to {approx}0.3 x 10{sup 21} n {center_dot} cm{sup -2} in the Halden reactor. Crack-growth-rate tests have been conducted on compact-tension specimens of Alloys 600 and 690 under constant load to evaluate the resistance of these alloys to stress corrosion cracking in LWR environments

Possibilities of alternative generation II biotests at Artemia

The meaning of alternative biotests is described and discussed. The paper also deals with the possible application of the developmental studies of the sea Artemia franciscana nauplinus. Five-day biotests including the validation criteria are described. The possibilities of the biotests are very wide. Additionally to the standard applications in ecotoxicology, there is a possibility of modelling pharmacological experiments or monitoring the effects of ionizing radiation and the interaction with other chemicals

Multiplexed, High Density Electrophysiology with Nanofabricated Neural Probes

Extracellular electrode arrays can reveal the neuronal network correlates of behavior with single-cell, single-spike, and sub-millisecond resolution. However, implantable electrodes are inherently invasive, and efforts to scale up the number and density of recording sites must compromise on device size in order to connect the electrodes. Here, we report on silicon-based neural probes employing nanofabricated, high-density electrical leads. Furthermore, we address the challenge of reading out multichannel data with an application-specific integrated circuit (ASIC) performing signal amplification, band-pass filtering, and multiplexing functions. We demonstrate high spatial resolution extracellular measurements with a fully integrated, low noise 64-channel system weighing just 330 mg. The on-chip multiplexers make possible recordings with substantially fewer external wires than the number of input channels. By combining nanofabricated probes with ASICs we have implemented a system for performing large-scale, high-density electrophysiology in small, freely behaving animals that is both minimally invasive and highly scalable

Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

Mapped topographic features are important for understanding processes that sculpt the Earth's surface. This paper presents maps that are the primary product of an exercise that brought together 27 researchers with an interest in landform mapping wherein the efficacy and causes of variation in mapping were tested using novel synthetic DEMs containing drumlins. The variation between interpreters (e.g. mapping philosophy, experience) and across the study region (e.g. woodland prevalence) opens these factors up to assessment. A priori known answers in the synthetics increase the number and strength of conclusions that may be drawn with respect to a traditional comparative study. Initial results suggest that overall detection rates are relatively low (34–40%), but reliability of mapping is higher (72–86%). The maps form a reference dataset

Environmentally assisted cracking in light water reactors. Semiannual report, October 1993--March 1994. Volume 18

This report summarizes work performed by Argonne National Laboratory (ANL) on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) during the six months from October 1993 to March 1994. EAC and fatigue of piping, pressure vessels, and core components in LWRs are important concerns in operating plants and as extended reactor lifetimes are envisaged. Topics that have been investigated include (a) fatigue of low-alloy steel used in piping, steam generators, and reactor pressure vessels, (b) EAC of wrought and cast austenitic stainless steels (SSs), and (c) radiation-induced segregation and irradiation-assisted stress corrosion cracking (IASCC) of Type 304 SS after accumulation of relatively high fluence. Fatigue tests have been conducted on A302-Gr B low-alloy steel to verify whether the current predictions of modest decreases of fatigue life in simulated pressurized water reactor water are valid for high-sulfur heats that show environmentally enhanced fatigue crack growth rates. Additional crack growth data were obtained on fracture-mechanics specimens of austenitic SSs to investigate threshold stress intensity factors for EAC in high-purity oxygenated water at 289{degrees}C. The data were compared with predictions based on crack growth correlations for wrought austenitic SS in oxygenated water developed at ANL and rates in air from Section XI of the ASME Code. Microchemical and microstructural changes in high- and commercial-purity Type 304 SS specimens from control-blade absorber tubes and a control-blade sheath from operating boiling water reactors were studied by Auger electron spectroscopy and scanning electron microscopy to determine whether trace impurity elements, which are not specified in the ASTM specifications, may contribute to IASCC of solution-annealed materials