Home About us Contact
|
Home About us Contact | ||
|
|
||
Layer Properties (layer + property)
Selected AbstractsEffect of Carbon on the Compound Layer Properties of AISI H13 Tool Steel in Pulsed Plasma NitrocarburizingPLASMA PROCESSES AND POLYMERS, Issue S1 2007Rodrigo L. O. Basso Abstract Due to the mechanical and inertness properties of the , -Fe2-3N phase, its formation as a compact monolayer is most wanted in plasma surface treatments of steels. This phase can be obtained by the inclusion of carbon species in the plasma. In this work, we present a systematic study of the carbon influence on the compound layer in an AISI H13 tool steel by pulsed plasma nitrocarburizing process with different gaseous ratios (0%,,,[CH4]/[N2,+,CH4,+,H2],,,4%). The plasma treatment was carried out for 5 h at 575,°C. The microstructure and phase composition of the modified layers were studied by scanning electron microscopy and X-ray diffraction, respectively. X-Ray photoelectron spectroscopy was used to measure the relative concentration of carbon and nitrogen on the surface. The hardening profile induced by the nitrocarburized process is also reported. [source] Development of InN metalorganic vapor phase epitaxy using in-situ spectroscopic ellipsometryCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005M. Drago Abstract Metalorganic vapor phase epitaxy of InN layers on sapphire was studied in-situ by spectroscopic ellipsometry (SE), ex-situ atomic force microscopy and optical microscopy. Surface morphology has been largely improved by using nitrogen instead of hydrogen as carrier gas during sapphire nitridation. Using the sensitivity of in-situ SE with respect to roughness we established a new growth procedure with low V/III ratio (104) at high temperature (580 °C) and growth rates as high as 350 nm/h, leading to improved electronic layer properties and allowing for growth of comparably thick layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A nonlinear atomization model for computation of drop size distributions and spray simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2005Hongbok Park Abstract A model has been developed to provide a comprehensive simulation of a spray formed by a high-speed liquid jet. The primary atomization process is simulated in a completely nonlinear fashion using the boundary element method under the assumption of axisymmetric, inviscid flow. The presence of the orifice boundary layer is simulated with a ring vortex whose strength and location are uniquely determined from boundary layer properties at the orifice exit plane. Droplet and axisymmetric ligament tracking models have been developed to provide more comprehensive spray simulations. The breakup of the axisymmetric ligaments shed from the parent surface is assessed both in a nonlinear fashion as well as using the linear stability analysis of Ponstein. Using this latter approach, drop size distributions have been generated from first principles and compared with the popular Rosin,Rammler model. Copyright © 2005 John Wiley & Sons, Ltd. [source] Bauteiloberfläche und Schwingfestigkeit , Untersuchungen zum Einfluss der Randschicht auf die Dauerschwingfestigkeit von Bauteilen aus StahlMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2006U. Kleemann Dipl.-Ing. surface; surface layer; fatigue strength; surface stress-concentration factor Abstract Die Berechnung der Schwingfestigkeit hat in den letzten Jahren für die Bauteilentwicklung an Bedeutung gewonnen. Aus Zeit- und Kostengründen wird angestrebt, den experimentellen Festigkeitsnachweis auf die Freigabe von Sicherheitsteilen zu beschränken. Die Schwingfestigkeit von glatten, polierten Werkstoffproben (Spannungs- und Dehnungswöhlerlinie) kann heute mit guter Treffsicherheit abgeschätzt bzw. entsprechenden Katalogen entnommen werden. Die Übertragbarkeit der Schwingfestigkeit von Werkstoffproben auf reale Bauteile ist jedoch mit erheblichen Schwierigkeiten verbunden, da eine Reihe von Einflussgrößen zu berücksichtigen sind wie Geometrie und Größe, Mittelspannung, Beanspruchungsart, Mehrachsigkeit, Randschicht (Oberflächentopographie, Eigenspannungen, Gefüge, Härte), Temperatur, korrosive Medien u.,a.. Der Einfluss dieser Größen ist komplex und lässt sich nur sehr grob durch eine Multiplikation von Einflussfaktoren beschreiben. Der heutige Stand im Technischen Regelwerk zum Oberflächeneinfluss, z.,B. FKM-Richtlinie ,Rechnerischer Festigkeitsnachweis für Maschinenbauteile", basiert auf einem Kenntnisstand, der 50 Jahre zurückliegt. Der Ausgang für das Forschungsvorhaben war die Forderung der Industrie nach einer verbesserten rechnerischen Erfassung des Einflusses der Oberflächenbearbeitung bei Zerspanung. Hierzu wurde auf einen Vorschlag von Liu zurückgegriffen, der die Oberflächentopographie neben der Rauheit durch eine Oberflächenformzahl kennzeichnet. Zur Erfassung des Werkstoffes wird eine charakteristische Strukturlänge eingeführt, die sich aus der Werkstoffwechselfestigkeit und dem Schwellenwert für makroskopischen Rissfortschritt berechnet. Weiterhin wurde überprüft, welche Festigkeitshypothesen in der Lage sind, den biaxialen Eigenspannungszustand an der zerspanten Oberfläche realistisch zu erfassen. Damit kann ein Konzept vorgeschlagen werden, mit dem die Dauerfestigkeit zutreffend berechnet werden kann, wenn die statische Festigkeit, die Oberflächentopographie und die Eigenspannungen bekannt sind. Zur Validierung werden Schwingversuche an drei Stählen und zwei Sphärogusslegierungen bei unterschiedlichen Randschichteigenschaften durchgeführt. Structural component surface and fatigue strength , Investigations on the effect of the surface layer on the fatigue strength of structural steel components For the development of structural components, the importance of calculating the fatigue strength has steadily increased during recent years. In order to save time and cost, efforts are in progress for limiting experimental strength testing to the release of safety components. The fatigue strength of smooth, polished material specimens (stress and strain S-N curve) can now be estimated with high accuracy, or can be obtained from the corresponding catalogs. However, the results of fatigue strength determinations on material specimens cannot be applied to real components without considerable difficulty, since a number of decisive parameters must be taken into account. These factors include the geometry and size, mean stress, type of load, multiaxiality, surface layer (surface topography, residual stresses, structure, hardness), temperature, corrosive media, etc. The effect of these parameters is complex, and a multiplication of the various decisive factors yields only a very rough description. The current state of the art in the catalog of technical rules on surface effects, such as the FKM guideline, "Computational Demonstration of Strength for Machine Components", is based on results which were obtained 50 years ago. The original incentive for the research project was the industrial demand for an improved computational method for determining the effect of surface machining by cutting processes. For this purpose, recourse was made to a proposal by Liu, who characterises the surface topography, besides the roughness, with the use of a surface stress-concentration factor. A characteristic structural length is introduced for describing the material; this length is calculated from the fatigue strength of the material and the threshold value for macroscopic crack propagation. Moreover, a check was made to determine which strength hypotheses are capable of realistically describing the biaxial residual stress state on the machined surface. Thus, a concept can be proposed for accurately calculating the fatigue strength, provided that the static strength, the surface topography, and the residual stresses are known. For validation, alternating-load tests are to be performed on three types of steel and two nodular cast alloys with different surface layer properties. [source] Optimization of Ru intermediate layer in CoCr-based perpendicular magnetic recording mediaPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004Jong Wuk Park Abstract The influence of intermediate layer characteristics on the structural and magnetic properties of CoCr-based perpendicular media has been investigated. CoCrPt-SiO2 stacks were deposited on a 2.5-inch glass substrates. To improve intermediate layer properties without noticeable sacrifice of magnetic and structural properties of recording layer, the conditions of intermediate layer deposition were varied. The recording layer was deposited on the Ru intermediate layer in 20 mTorr Ar pressure to increase coercivity. As a result, coercivity is increased from 2.2 to 3.7 kOe because the interface between Ru intermediate layer and recording layer was rougher than the interface formed at low Ar pressure. Additionally, to increase perpendicular anisotropy of recording layer, the Ru sputtering temperature condition was varied, ranging from 150 °C to 300 °C. However, the perpendicular anisotropy of recording layer was decreased. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microcrystalline silicon n-i-p solar cells prepared with microcrystalline silicon oxide (,c-SiOx:H) n-layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Vladimir Smirnov Abstract N-type hydrogenated microcrystalline silicon oxide (,c-SiOx:H) layers were used as window layers in n-side illuminated microcrystalline silicon n,i,p solar cells. Optical, electrical and structural properties of ,c-SiOx:H films were investigated by Photothermal Deflection Spectroscopy, conductivity and Raman scattering measurements. ,c-SiOx:H layers were prepared over a range of carbon dioxide (CO2) flow and film thickness, and the effects on the solar cell performance were investigated. By optimising the ,c-SiOx:H window layer properties, an improved short-circuit current density of 23.4 mA/cm2 is achieved, leading to an efficiency of 8.0% for 1,m thick absorber layer and Ag back contact. The correlation between cell performance and ,c-SiOx:H layer properties is discussed. The results are compared to the performance of solar cells prepared with alternative optimised window layers. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of the activation process of Mg dopant in GaN:Mg layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006B. Paszkiewicz Abstract GaN:Mg layers with different concentration of Mg dopant were grown by metalorganic vapour phase epitaxy. The incorporation of Mg was verified by secondary ion mass spectroscopy. In order to dissociate Mg-related complexes and thus electrically activate the acceptor dopant, the as-grown layers were annealed in pure N2 at ,800 °C for 30 minutes. The influence of the post-growth annealing on the layer properties was studied by photoluminescence (PL) and impedance spectroscopy. Impedance spectroscopy measurement showed that the annealed samples reveal higher charge concentrations and lower sheet resistance. Moreover, the relaxation time of hole traps decreased in annealed samples by one order of magnitude compared to as-grown samples. The changes in the electrical properties have been correlated with the changes in the PL spectra. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Advances of pulsed laser deposition of ZnO thin filmsANNALEN DER PHYSIK, Issue 1-2 2004M. Lorenz Abstract Advances in Pulsed Laser Deposition (PLD) equipment and process design for the epitaxy of ZnO thin films on a-, and c-oriented sapphire substrates are reported. The achieved improvement of device relevant ZnO layer properties is directly related to our equipment design and novel process schemes. First results on growth and reflectivity of ZnO-MgO based dielectric Bragg resonators for future ZnO-based light emitter devices are shown. [source] | |||||||||||||||||||||||||