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Thick thermal barrier coatings (TBCs) are the main choice in the aviation industry due to their ability to handle elevated temperature exposure in turbines. However, the efficacy of thick TBCs has not been adequate. This study presents a highly durable, thick top-coat (TC) of Lanthanum–gadolinium–yttria stabilized zirconia (La–Gd–YSZ) on high-velocity oxygen fuel (HVOF)-bond coat (HVOF-BC). Crack propagation was quantitatively assessed using a three-dimensional (3D) measuring laser microscope due to higher reliability in calculating the actual crack length of TBC. The findings revealed the HVOF-BC is highly durable with intact structural composition, while the conventional TBC of atmospheric plasma spraying (APS) bond coat (APS-BC) of the same composition and thickness with identical TC was detached at a crack-susceptible zone. The significant enhancement in HVOF-BC is due to the low mixed-oxides growth rate in thermally grown oxide (TGO) with a uniform and dense protective layer of stable Al2O3 which reduces crack propagation. Meanwhile, the failure in APS-BC can be attributed to the high TGO growth rate and thickness with segmented and unstable Al2O3. Furthermore, detrimental mixed oxides such as spinel Ni(Cr,Al)2O4 and NiO lead to disastrous horizontal and compressive cracks. To that end, we study the effect of TGO growth and crack propagation on HVOF-BC TBCs using APS-BC TBCs as a reference.

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Summary Dye‐sensitized solar cells (DSSCs) are more attractive than silicon solar cells due to their low dependency on light intensity so that they can perform both indoor and outdoor with low‐level lightings. DSSC's global revenue exceeded 16 million USD in 2014 for emerging portable charging, solar bags, and wireless keyboards. However, on‐grid DSSC modules are still under R&D for massive commercialization to improve their long‐term stability and safety issues due to the liquid electrolyte leakage. Therefore, quasi‐solid‐state electrolytes (QSE) have been proposed as a novel alternative to overcome the limitations stated above since 2001. Here, we deliver a short outline of the QSE properties, which are linked with the performance of DSSC in terms of different types of QSE structures: gel, hydrogel, and aerogel. Furthermore, these QSE structures are classified under bio and non‐bio materials. Finally, the impact, outlook, and future prospects of QSE‐DSSC are included as a conclusion in this review.

Durability of a thermal barrier coating (TBC) depends strongly on the type of mixed oxide in the thermally grown oxide (TGO) of a TBC. This study aims on discovering the effect of thermal stability in the TGO area containing mixed oxides. Two different bondcoats were studied using high-resolution transmission electron microscopy: high-velocity oxygen fuel (HVOF) and air-plasma spray (APS), under isothermal and thermal cyclic tests at 1400 °C. The HVOF bondcoats were intact until 1079 cycles. In comparison, APS failed at the early stage of thermal cycling at 10 cycles. The phase transformation of topcoat from tetragonal to the undesired monoclinic was observed, leading to TBC failure. The results showed that the presence of transient aluminas found in HVOF bondcoat helps in the slow growth of α-Al2O3. In contrast, the APS bondcoat does not contain transient aluminas and transforms quickly to α-Al2O3 along with spinel and other oxides. This fast growth of mixed oxides causes stress at the interface (topcoat and TGO) and severely affects the TBC durability leading to early failure. Therefore, the mixed oxide with transient aluminas slows down the quick transformation into alpha-aluminas, which provides high thermal stability for a high TBC durability.