Wyniki wyszukiwania - Biblioteka Nauki

1

Electrochemical behavior of Co-Cr-W-Ni alloy with passive layer

100%

Walke W. , Paszenda Z. , Tyrlik-Held J.

Advances in Materials Science

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2007

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tom Vol. 7, nr 2(12)

179-188

EN

In the paper the results of corrosion resistance and chemical composition investigations of passive layer formed on the im-plants surface made of Co-Cr-W-Ni alloy used in interventional cardiology have been presented. Corrosion resistance has been tested in the solution simulating environment of human blood at temperature 37+-1°C. Particularly, the investigations of crevice and pitting corrosion resistance have been realized with taking into account the implantation technique of vascular stents. Chemical composition investigations of the passive layer have been carried out with the use of X-ray Photoelectron Spectroscopy (XPS). The results of preliminary tests pointed out on the usefulness of surface treatment of stents made of Co-Cr-W-Ni alloy.

2

On the turbulent boundary layer of a dry granular avalanche down an incline. II – closure model and numerical simulations

100%

Fang C.

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tom Vol. 54 nr 4

1245--1256

EN

Dynamic responses of the closure relations, specific turbulent Helmholtz free energy and turbulent viscosity are postulated followed by experimental calibrations. The established closure model is applied to analyses of a gravity-driven stationary avalanche with incompressible grains down an incline. While the mean velocity and volume fraction increase from their minimum values on the plane toward maximum values on the free surface exponentially, two-fold turbulent kinetic energies and dissipations evolve in a reverse manner. Most two-fold turbulent kinetic energies and dissipations are confined within the thin turbulent boundary layer immediately above the plane, with nearly vanishing two-fold turbulent kinetic energies and finite two-fold turbulent dissipations in the passive layer. The two layers are similar to those of Newtonian fluids in turbulent boundary layer flows, and are preferable recognized by the distributions of turbulent kinetic energies and dissipations.

3

Badanie procesu trawienia stali wysokostopowej za pomocą spektroskopii impedancyjnej

75%

Ślepski P. , Darowicki K. , Krakowiak S.

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2011

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tom nr 7

482-484

PL

Przeprowadzono badania trawienia stali wysokostopowej w mieszaninie kwasu HF i HNO3, wykorzystując elektrochemiczną spektroskopie impedancyjną. W celu odwzorowania warunków naturalnych, eksperyment przeprowadzono przy użyciu deis w trybie galwanostatycznym z wypadkowym prądem równym zero. Wyznaczone zostały zmiany parametrów elektrycznych opisujących układ w czasie. Zaobserwowano wpływ stężenia HF na czas trwania procesu.

EN

Pickling of stainless steel in mixed acid of HF-HNO3 was investigated based on impedance measurements. Experiment was carried out in the galvanostatic mode to reflect real conditions by means of DEIS technique. Changes of particular equivalent circuit parameters have been determined as a function of time. As a result significant effect of the HF concentration on duration time of the investigated process has been observed.

4

Electrochemical impedance spectroscopy of Ni–Mo alloy coatings in 0.5 M NaCl solution

63%

Laszczyńska A. , Winiarski J. , Szczygieł I. , Szczygieł B.

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2017

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tom nr 4

84--87

EN

The corrosion resistance of Ni–Mo (11÷32 wt% Mo) alloy coatings during 72 h exposure in 0.5 mol·dm−3 solution of NaCl was investigated by means of EIS method. The highest corrosion resistance (charge transfer resistance >12 kΩ·cm2) among all investigated coatings was measured for Ni–Mo coatings with higher molybdenum content (21÷32 wt%). However, after 48-60 h of immersion, visible micro cracks appeared in Ni–28 wt% Mo and Ni–32 wt% Mo alloy coatings, probably due to the significant internal stresses. This phenomenon was observed especially for Ni–32 wt% Mo coating, and it was accompanied by an abrupt decrease in a charge transfer resistance from 8.7 to 2.7 kΩ·cmThe corrosion resistance of Ni–Mo (11÷32 wt% Mo) alloy coatings during 72 h exposure in 0.5 mol·dm−3 solution of NaCl was investigated by means of EIS method. The highest corrosion resistance (charge transfer resistance >12 kΩ·cm2) among all investigated coatings was measured for Ni–Mo coatings with higher molybdenum content (21÷32 wt%). However, after 48-60 h of immersion, visible micro cracks appeared in Ni–28 wt% Mo and Ni–32 wt% Mo alloy coatings, probably due to the significant internal stresses. This phenomenon was observed especially for Ni–32 wt% Mo coating, and it was accompanied by an abrupt decrease in a charge transfer resistance from 8.7 to 2.7 kΩ·cm2 after 5 and 24 h, respectively. According to EIS results, coating containing 21 wt% Mo offers the best protective properties towards steel substrate. This may be associated with the existence of a compact, tight and very thin passive layer which does not undergo damage during exposure. after 5 and 24 h, respectively. According to EIS results, coating containing 21 wt% Mo offers the best protective properties towards steel substrate. This may be associated with the existence of a compact, tight and very thin passive layer which does not undergo damage during exposure.

PL

Metodą EIS zbadano odporność na korozję powłok Ni–Mo (11÷32% mas. Mo) w czasie 72 h ekspozycji w 0,5 mol·dm−3 roztworze NaCl. Najwyższą odpornością na korozję (rezystancja przeniesienia ładunku >12 kΩ·cm2), spośród wszystkich zbadanych powłok, charakteryzowały się powłoki Ni–Mo o zawartości 21÷32% mas. molibdenu. Zauważono jednak, że po 36÷60 h ekspozycji, na powierzchni powłok Ni–28% mas. Mo oraz Ni–32% mas. Mo pojawiły się widoczne pęknięcia, których przyczyną są najprawdopodobniej duże naprężenia wewnątrz powłok. To zjawisko było szczególnie wyraźne w przypadku powłoki Ni–32% mas. Mo, bowiem towarzyszył mu gwałtowny spadek rezystancji przeniesienia ładunku z 8,7 do 2,7 kΩ·cm2 po odpowiednio 5 i 24 h ekspozycji. Zgodnie z wynikami pomiarów metodą EIS, powłoka Ni–Mo zawierająca 21% mas. Mo zapewnia najlepsze właściwości ochronne podłoża stalowego, pomimo nieznacznie niższej od powłoki Ni–28% mas. Mo rezystancji przeniesienia ładunku. Można to powiązać z wytworzeniem na jej powierzchni zwartej i bardzo cienkiej warstwy pasywnej, która nie ulega uszkodzeniu w trakcie ekspozycji w roztworze NaCl.

5

Novel method of the initiation stage of stress corrosion cracking monitoring with respect to marine constructions

51%

Darowicki K. , Orlikowski J. , Arutunow A. , Jurczak W.

Polish Journal of Environmental Studies

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2005

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tom 14

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nr Suppl.1

EN

Corrosion of marine constructions and vessels is a very important issue in relation to the safety aspects. It is connected with the fact that many marine constructions are exposed to the aggressive corrosion environment. As a result it leads to vessels collisions and unexpected accidents. The following paper presents the application of dynamic electrochemical impedance spectroscopy (DEIS) for the examination of the initiation stage of stress corrosion fracking (SCC) of aluminum A91050 immersed in 0.1M NaCl solution at room temperature. This paper presents instantaneous impedance spectra obtained at different potential values. The results obtained indicate that the process of the passive layer cracking can be considered as the initiation stage of the SCC and depends on tensile stresses, whereas further evolution of corrosion processes depends on electrochemical conditions.