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Silicon nitride/carbon nanotube composites: preparation and characterization

Mikuśkiewicz Marta

Bulletin of the Polish Academy of Sciences. Technical Sciences

2021

Vol. 69, nr 5

art. no. e138234

This paper investigates the preparation of silicon nitride composites with multi-walled carbon nanotubes (MWCNTs). Samples containing 1–10 wt% MWCNTs were ultrasonically processed in non-aqueous suspensions, dried, pressed, and then subjected to non-pressure sintering at 1600 °C for 2 h. The preliminary results showed that the mixture of activated silicon nitride and covered MWCNTs could be sintered. The porosity of the obtained samples ranged from 0.27 to 36.94 vol.%. The microstructure was observed by scanning electron microscopy (SEM), and the mechanical properties (hardness and fracture toughness) were also determined. Good hardness values were obtained for samples prepared by sintering the mechanically activated precursor under a flowing nitrogen atmosphere using the lowest fraction of CNTs. Residual activator reduced the densification of the composites.

Degradation of La2Zr2O7+8YSZ composite TBC systems during oxidation at temperature of 1100°C

Jasik Anna, Mikuśkiewicz Marta, Moskal Grzegorz

Ochrona przed Korozją

2019

nr 4

130--134

The degradation process of La2Zr2O7 + 8YSZ composite thermal barrier coatings (TBC) was presented in this paper. These systems were deposited by air plasma spraying (APS) on AMS 5599 alloy and on a NiCrAlY bond-coat. A scope of tests consisting of isothermal oxidation in air atmosphere at 1100°C for 500 h was performed. Detailed microstructural tests were carried out after 2, 10, 48, 175 and 500 hours of exposure. These tests included microstructure evaluation of a ceramic layer in all coating types, while particularly taking into account phenomena, which occur in a TGO (thermally growth oxide) zone. Evaluation of TGO zone growth was worked out and obtained results were compared with data for conventional TBC layers, which were deposited from 8YSZ powders and La2Zr2O7 respectively.

W artykule przedstawiono proces degradacji kompozytowych powłokowych barier cieplnych typu La2Zr2O7 + 8YSZ. Powłoki zostały wykonane metoda natrysku cieplnego w powietrzu na stopie niklu typu AMS 5599 z międzywarstwą typu NiCrAlY. Powłoki poddano badaniom w postaci testu odporności na utlenianie izotermiczne w temperaturze 1100°C przez czas 500 h. Szczegółowe badania mikrostrukturalne wykonano po 2, 10, 48, 175 and 500 godzinach testu. Zakres zastosowanych badan obejmował ocenę mikrostrukturalną wszystkich powłok ze szczególnym uwzględnieniem zjawisk zachodzących w strefie TGO. Rozwój i morfologia strefy TGO została porównane do wyników uzyskanych dla standardowych powłok jednowarstwowych bazujących na ceramice typy 8YSZ i La2Zr2O7 .