Phase Evolution of SiO₂–Al₂O₃–ZnO–CaO–ZrO₂–TiO₂‐Based Glass with Added Y‐PSZ Particles

Abstract

Yttria partially stabilized zirconia Y‐PSZ/glass‐ceramic composites were prepared by reaction sintering using powder mixtures of a SiO2–Al2O3–ZnO–CaO–ZrO2–TiO2‐based glass and yttria partially stabilized zirconia (Y‐PSZ). The glass crystallized during sintering at temperatures of 1173, 1273, and 1373 K to give a glass‐ceramic matrix for high‐temperature protecting coatings. With the increasing firing time, the added zirconia reacted with the base glass and a glass‐ceramic material with dispersed zircon particles was prepared in situ. Furthermore, the added zirconia changed the crystallization behavior of the base glass, affecting the shape, amount, and distribution of zircon in the microstructure. The bipyramid‐like zircon grains with imbedded residual zirconia particles turned out to have two growth mechanisms: the inward growth and the outward growth, and its rapid growth was mainly dominated by the later one. For comparison, the referenced glass‐ceramic was prepared by sintering using exclusive glass granules and its crystallization behavior at 1173–1373 K was examined as well. Scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM), and X‐ray diffraction (XRD) were used to characterize the crystallization behavior of the base glass and the phase evolution of the Y‐PSZ/glass‐ceramic composites.

Microstructure stabilization of a novel glass/YSZ composite coating material by adding alumina particles

“…Crystallization behavior of the base glass and phase evolution of the YSZ/glass composites at temperatures of 900 1C, 1000 1C and 1100 1C can be found in detail in our previous papers [33,41]. Fig.…”

“…Firstly, the dissolution of alumina inclusions makes the composite more refractory, e.g., raising the softening temperature or even eliminating the softening phenomenon when the alumina content is high enough [35]. As stated in our precious study [33], YSZ particles firstly dissolved into the base glass in the YSZ/glass composite at high temperatures, supplying Zr 4 þ for the rapid outward growth of zircon. Accordingly, increasing the viscosity of the base glass by adding α-Al 2 O 3 may decrease the dissolution rate of YSZ and then slow down the growth rate of zircon.…”

“…The nominal composition and preparation process of the glass frit has been described in detail elsewhere [33]. The obtained glass frit was dry milled using an agate jar and balls for 100 h. The mean size of the frit granules was below 10 μm.…”

“…Furthermore, this glass coating reinforced by the alumina inclusions was proved to provide enough oxidation resistance for Ni-based superalloy at 1000 1C and even higher temperatures [28][29][30][31][32]. More recently, a YSZ-particle-reinforced glass-ceramic matrix composite was prepared by reaction sintering using the powder mixtures of the glass and YSZ (8 wt% yttria partially stabilized zirconia) [33]. This YSZ/glass-ceramic composite can be used as a promising environmental barrier coating (EBC) material for intermetallics and superalloys.…”

Characterization of thermally stable gamma alumina fibres biomimicking sisal

“…It has been described that aluminas generated from polyaluminium species, in particular from basic aluminium chlorides, have lower transition temperatures than usual [59,60]. Furthermore, the local temperature increase due to the combustion process of the carbonaceous matrix can help to overcome the energy barrier necessary for the formation of alpha phase [61,62] Two signals centred at 7 and 64 ppm are observable in the spectrum of AFh fibres shown in not being perceptible the alpha phase contribution, characterized by an octahedral environment around 13 ppm [40]. It has been estimated that the proportion of Al VI is close to 70%, which suggests that both phases remain even after a reheating cycle with humid air.…”