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Microstructural Investigation and Mechanical Testing of an Ultrafine-grained Austenitic Stainless Steel
Chlupová, Alice ; Man, Jiří ; Polák, Jaroslav ; Karjalainen, L. P.
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with considerably enhanced mechanical properties. Two different conditions of the thermomechanical treatment were adopted and resulting microstructures with different grain sizes were characterised by optical and high resolution scanning electron microscopy (SEM-FEG). Hardness measurements and tensile tests were performed to characterize mechanical properties. To reveal structural changes induced during thermomechanical treatment and during tensile tests a magnetic induction method was additionally applied. Experimental study validated the ability of the above special treatment to produce austenitic stainless steel with grain size about 1.4 m which exhibits tensile strength about 1000MPa while ductility remains on level about 60 %. The results obtained for both thermomechanical conditions are compared and the relationship between microstructure refinement, phase content and mechanical properties is discussed.
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Spinnability of PEO solutions with respect to their aging
Zelenková, Jana ; Peer, Petra ; Filip, Petr
Non - negligible portion of pol ymer commodity suffers from ageing that participates in sometimes significant changes of products attributes. Rheology represents a useful tool for a description of this process. The aim of this contribution is to evaluate possible ageing of PEO solution ( polyethylen e oxide ( M w =300,000 g/mol) dissolved in water at 10 wt.% concentration) based both on rheological characterization and on quality of electrospun fibres. Rheological measurements in steady shear and oscillatory modes were carried out using a rota tional rheometer MCR 501 (Anton Paar, Austria) equipped with the concentric cylinders geometry. The electrospinning measurements were executed with the help of a proposed laboratory device. The tip - to - collector distance attained 20 cm, applied voltage rang ed from 20 to 30 kV. The obtained electrospun fibres were analysed using a scanning electron microscope (VEGA 3, Tescan, Czech Republic). Both types of measurements were carried out in the period of several months during which the solution studied was plac ed in a dark and tempered box (25°C). The measurements indicate no ageing impact on rheological characteristics or quality of electrospun fibres. This guarantees more or less the identical quality of non - woven textiles prepared from PEO solutions regardles s of time period during which the solutions are deposited.
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Nanopositioning with detection of a standing wave
Holá, Miroslava ; Hrabina, Jan ; Číp, Ondřej ; Fejfar, A. ; Stuchlík, J. ; Kočka, J. ; Oulehla, Jindřich ; Lazar, Josef
A measuring technique is intended for displacement and position sensing over a limited range with detection of standing-wave pattern inside of a passive Fabry-Perot cavity. In this concept we consider locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Fixing the length of the cavity to e.g. a highly stable mechanical reference allows stabilizing wavelength of the laser in air and thus to eliminate especially the faster fluctuations of refractive index of air due to air flow and inhomogeneity. Detection of the interference maxima and minima within the Fabry-Perot cavity along the beam axis has been tested and proven with a low loss transparent photodetector with very low reflectivity. The transparent photodetector is based on a thin polycrystalline silicon layer. Reduction of losses was achieved thanks to a design as an optimized set of interference layers acting as an antireflection coating. The principle is demonstrated on an experimental setup.
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Interferometric coordinates measurement sytem for local probe microscopy nanometrology
Hrabina, Jan ; Lazar, Josef ; Klepetek, P. ; Číp, Ondřej ; Čížek, Martin ; Holá, Miroslava ; Šerý, Mojmír
We present an overview of new approaches to the design of nanometrology measuring system with a focus on methodology of nanometrology interferometric techniques and associated problems. The design and development of a nanopositioning setup with interferometric multiaxis monitoring and control involved for scanning probe microscopy techniques (primarily atomic force microscopy, AFM) for detection of the sample profile is presented. Coordinate position sensing allows upgrading the imaging microscope techniques up to quantified measuring. Especially imaging techniques in the micro- and nanoworld overcoming the barrier of resolution given by the wavelength of visible light are a suitable basis for design of measuring systems with the best resolution possible. The system is being developed in cooperation with the Czech metrology institute and it is intended to operate as a national nanometrology standard combining local probe microscopy techniques and sample position control with traceability to the primary standard of length.
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