Kinetics of zircon formation in yttria partially stabilized zirconia as a result of oxidation of embedded molybdenum disilicide

Abstract

This is an author's version published in: http://oatao.univ-toulouse.fr/24028 a b s t r a c t Recently MoSi 2 sacrificial particles embedded in yttria partially stabilized zirconia (YPSZ) have been proposed as attractive healing agents to realize significant extension of the lifetime of the thermally loaded structures. Upon local fracture of the YPSZ, the embedded healing particles in the path and in the vicinity of the crack react with the oxygen atoms transported via the crack and first fill the crack with a viscous glassy silica phase (SiO 2 ). The subsequent reaction between this freshly formed SiO 2 and the existing tetragonal ZrO 2 of the YPSZ leads to the formation of rigid crystalline zircon (ZrSiO 4 ), which is key in the crack-healing mechanism of YPSZ based materials. The isothermal kinetics of the self-healing reaction and the mechanism of zircon formation from the decomposing MoSi 2 and the surrounding YPSZ were assessed via X-ray diffraction (XRD). The obtained results revealed that at 1100 C the reaction between amorphous SiO 2 and YPSZ is completed after about 10 h. For a more accurate determination of the kinetics of the self-healing reaction, bilayer samples of YPSZ e MoSi 2 (with and without boron addition) were annealed in air over a temperature range of 1100e1300 C. This led to the formation of a MoSi 2 /amorphous (boro)silica/zircon/YPSZ multi-layer, which was investigated with scanning electron microscopy (SEM) and electron probe X-ray microanalysis (EPMA). Kinetic modeling of the growth of zircon and silica or borosilicate layers showed that zircon growth was dominated by the diffusion of Si 4þ in zircon whereas the growth of the silica or borosilicate layer was controlled by oxygen diffusion. Moreover, a significant increase in the rate of ZrSiO 4 formation was observed due to the presence of B in the MoSi 2 particles.

Fabrication of mechanically robust nanoporous ZrSiO4 ceramics at low temperature with a low doping level of Mn dopant

“…Theoretically, all the ZrO 2 component should be consumed to form ZrSiO 4 , however, there was still a small amount of residual ZrO 2 (Figure 1). Atomic diffusion plays a significant role in the solid‐state reaction (ZrO 2 +SiO 2 →ZrSiO 4 ) 9,27 . In our previous study, 11 we observed that t‐ZrO 2 grains are surrounded by a shell of ZrSiO 4 .…”

Submicronic spherical inclusion black pigment by double‐shell reaction sintering

“…Meanwhile, the O 1 s XPS spectrum is split into two single‐peaks corresponding to Zr–O bonds (530.8 eV) and Si–O (532.8 eV) bonds, as shown in Figure C . Therefore, according to the formation kinetics of zircon, the as‐synthesized pigments (the main crystal phase is ZrSiO 4 ) was successfully prepared. The optical properties of ceramic pigments depend on the particle scale and morphology .…”

“…Some studies dealt with the actual reaction mechanism of zirconium silicate formation in different model . However, the effect of the reaction mechanism on the core‐shell structure pigments has not been supported yet by experimental evidence.…”

“…Some studies dealt with the actual reaction mechanism of zirconium silicate formation in different model. 30,35 However, the effect of the reaction mechanism on the coreshell structure pigments has not been supported yet by Figure S3) and CSZ pigments to study the influence of shell order (ZrO 2 -SiO 2 and SiO 2 -ZrO 2 ) on the encapsulation rate. The results show that there is a great difference in the encapsulation rate and morphology phenomenon for the two kinds of pigments, as shown in Figure 4.…”

A review on development and application of self-healing thermal barrier composite coatings

“…To prepare TBCs with the self-healing ability, Carnicer et al [121] used an aqueous suspension of Al 2 O 3 and SiCY-TZP. To prevent the SiC oxidation as a self-healing agent, suspension plasma spraying was utilized for the deposition of the coating.…”