Magnetic-field-induced supercurrent enhancement in hybrid superconductor/magnetic metal structures

The dc transport properties of the (S/M)I(M/S) tunnel structure - proximity coupled superconductor (S) and magnetic (M) layers separated by an insulator (I) - in a parallel magnetic field have been investigated. We choose for the M metal the one in which the effective magnetic interaction, whether it arises from direct exchange interaction or due to configuration mixing, aligns spins of the conducting electrons antiparallel to the localized spins of magnetic ions. For tunnel structures under consideration, we predict that there are the conditions when the destructive action of the internal and applied magnetic fields on Cooper pairs is weakened and the increase of the applied magnetic field causes the field-induced enhancement of the tunnel critical current. The experimental realization of the novel interesting effect of the interplay between superconducting and magnetic orders is also discussed.Comment: 6 pages 2 figure

Tribological behavior of superhard amorphous carbon films

Due to their unique combination of low adhesion, high abrasive resistance and chemical inertness, the amorphous carbon films are increasingly becoming established as optimum tribological coatings for many applications. The breakthrough for protective carbon coatings on components was achieved by their application in Diesel injection systems. Application on tools is limited at higher temperatures, especially in the case of steel machining, because of the high solubility of carbon in steel. Hence, carbon coated tools are preferably to be used for machining of non-iron materials and for forming processes. Up to now only hydrogenated carbon films (a-C:H and related systems), are commercially available. A great potential for future applications is offered by the ta-C films with their markedly higher hardness and their specific interaction with lubricants. Fraunhofer IWS has developed coating technology for deposition of ta-C films in the industrial scale. The tribological behavior of amorphous carbon films is determined by monomolecular covering layers strongly attached to the surface. They cause the very low friction in normal humid air, their absence in dry air or vacuums leads to high friction. Lubricants usually do not improve the tribological behavior in comparison to air. However with non-hydrogenated ta-C films a marked reduction of friction is possible by attaching specially adapted lubricants

Differential and integral hardness - new aspects of quantifying load-depth-alpha in depth-sensing nanoindentation experiments

The Meyer hardness H as load F over contact area AC: H=F/AC, has the physical meaning of the mean pressure inside the contact area. In addition to this we introduce a differential hardness Hd as Hd=dF/dAC. This quantity provides more information on the pressure, required to initiate plastic flow, than the conventional hardness does. Furthermore, an integral or energetic hardness is considered being the plastic work Wp divided by the volume Vp of irreversibly displaced material: He=Wp/Vp. Since the plastic work is the area encircled by the loading and the unloading curve, information from the entire loading curve is involved in the calculation of He, i.e. He integrates over the deformation states from the very beginning of loading up to the unloading procedure. It turns out that He is more surface sensitive than H, whereas Hd proves more sensitive to the material properties of the bulk. H, Hd and He are determined as continuous functions of penetration depth h derived from nanoindentations into fused quartz, single-crystalline CdS and amorphous diamond-like-carbon layers (DLC) onto silicon substrates. The calculation takes advantage of a newly developed iterative procedure to calculate the contact depth hC for every point of the loading curve of a single indent

Lightning safe rotor blade monitoring using an optical power supply for ultrasonic techniques

To provide a safe and reliable technique for rotor blade inspection, the lightning damages caused by any metal equipment inserted into the blade have to be eliminated. This paper, therefore, deals with an approach that consequently avoids any metal cables by applying optical fibers both for data communication as well as for the power supply. The used sensor network is specialized in acoustic emission and acousto ultrasonic techniques. The sensors are located in areas of the blade where failure often occurs. The acoustic signals caused by failures in the blade are constantly recorded and evaluated regarding criteria like energy content and travel time. The optical power supply is realized by a laser source, an optical fiber for the energy transfer, an optical receiver and a communication fiber with receiver and transmitter. The optical power transmitted over one fiber equals approx. 1W

Ölfreie Getriebe

Dargestellt werden unterschiedliche Möglichkeiten zum ölfreien Betrieb von leistungsübertragenden Zahnradgetrieben. Zum Untersuchungsspektrum gehören Beschichtungen (DLC (Diamond-Like Carbon), thermische Spritzschichten) sowie alternative Schmierstoffe (Polymermikropulver). Ausgehend von Analogieversuchen werden die Resultate für Untersuchungen an realen Getrieben unter praxisnahen Bedingungen vorgestellt. Die grundlegende Funktionsfähigkeit einer Polymerpulverschmierung konnte nachgewiesen werden. Aufgrund der fehlenden Wärmeableitung sind die sich einstellenden Zahnmassentemperaturen höher als bei ölgeschmierten Getrieben. Dieses Verhaften ist jedoch unkritisch, solange dauerhaft keine Temperaturen über 150 Grad C (Anlasseffekte bei einsatzgehärteten Stählen) erreicht werden. Es steht somit ein im Betrieb umweltfreundlicher und physiologisch unbedenklicher Schmierstoff zur Verfügung. Die Problematik einer weiter verbesserten Schmierstoffzirkulation sollte jedoch vertiefend untersucht werden. Versuche mit PTFE-geschmierten Zahnkupplungen verliefen nicht erfolgreich, da kein regenerierender Schmierfilm erzeugt werden konnte. Ein zeitlich unbegrenzter Trockenlauf beschichteter Zahnräder mit Standardgeometrie konnte nicht erreicht werden. Eine Kombination von verlustoptimierter Verzahnung und einer verschleißfesten und reibungsarmen DLC-Beschichtung bei geringer Oberflächenrauheit der Zahnflanke Ist jedoch, wie die Versuchsergebnisse beweisen, eine aussichtsreiche Variante um technische relevante Laufzeiten zu erreichen. Eine Kombination mit der PTFE- Pulverschmierung würde die Vorteile beider Schmierungsvarianten kombinieren und die Lebensdauer in den Dauerfestigkeitsbereich anheben, denn die Senkung des Reibkoeffizienten durch die Beschichtung könnte geringere Massentemperaturen durch verringerte Verluste zur Folge haben

Innovative Reaktoren und in-situ-Analytik fuer ultraduenne Schutzschichten. Teilvorhaben: Herstellung und Untersuchung superharter Nanometer-Kohlenstoffschichten abgeschieden mit dem gefilterten Pulsbogen Abschlussbericht

IWS-project no. 120 987Available from TIB Hannover: F03B1501 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Innovative Reaktoren und in-situ-Analytik fuer ultraduenne Schutzschichten. Teilvorhaben: Herstellung und Untersuchung superharter Nanometer-Kohlenstoffschichten abgeschieden mit dem gefilterten Pulsbogen Abschlussbericht

IWS-project no. 120 987Available from TIB Hannover: F03B1501 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman