X.H. Zhong

Failure Behavior of Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings Under Three-Point Bending Test via Acoustic Emission Technique

In this paper, the failure behavior of plasma-sprayed yttria-stabilized zirconia thermal barrier coatings fabricated by atmospheric plasma spraying (APS-TBCs) under three-point bending (3PB) test has been characterized via acoustic emission (AE) technique. Linear positioning method has been adopted to monitor dynamic failure process of the APS-TBCs under 3PB test. The investigation results indicate that the variation of AE parameters (AE event counts, amplitudes and AE energy) corresponds well with the change of stress–strain curve of the loading processes. The failure mechanism was analyzed based on the characteristics of AE parameters. The distribution of frequency of crack propagation has been obtained. The AE signals came from two aspects: i.e., plastic deformation of substrates, initiation and propagation of the cracks in the coatings. The AE analysis combined with cross-sectional observation has indicated that many critical cracks initiate at the surface of the top-coat. And some main cracks tend to propagate toward the substrate/bond-coat interface. The actual failure mechanism of the APS-TBCs under 3PB test is attributed to the debonding of metallic coating from the substrates and the propagation of the horizontal crack along the substrate/bond-coat interface under the action of flexural moment.

Hydrophobic modification of poly(aryl ether ketone ketone) aerogel via poly(dimethylsiloxane)

Property and structure of aerogels with polar groups almost suffer from their high hydrophilicity. In this study, in order to improve the hydrophobicity of poly(aryl ether ketone ketone) aerogel prepared from poly(aryl ether ketone ketone) containing trimethoxysilane side groups, hydroxy-terminated poly(dimethylsiloxane) was added. During gelation, hydroxy-terminated poly(dimethylsiloxane) condensed with the methoxy groups or the hydrolyzed methoxy groups of the trimethoxysilane side groups. It was found that the hydrophobicity of poly(aryl ether ketone ketone) aerogel improved significantly even though only 5 wt% hydroxy-terminated poly(dimethylsiloxane) was added, and the hydrophobicity of the modified poly(aryl ether ketone ketone) aerogel showed an increase trend with increasing the content of hydroxy-terminated poly(dimethylsiloxane).Graphical Abstract