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Yttria-stabilized zirconia (YSZ) coatings and Al 2 O 3 -YSZ coatings were prepared by atmospheric plasma spraying (APS). Their microstructural changes during thermal cycling were investigated via scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). It was found that the microstructure and microstructure changes of the two coatings were different, including crystallinity, grain orientation, phase, and phase transition. These differences are closely related to the thermal cycle life of the coatings. There is a relationship between crystallinity and crack size. Changes in grain orientation are related to microscopic strain and cracks. Phase transition is the direct cause of coating failure. In this study, the relationship between the changes in the coating microstructure and the thermal cycle life is discussed in detail. The failure mechanism of the coating was comprehensively analyzed from a microscopic perspective.

For decreasing the global cost of corrosion, it is essential to understand the intricate mechanisms of corrosion and enhance the corrosion resistance of materials. However, the ambiguity surrounding the dominant mechanism of calcium‐magnesium aluminosilicate (CMAS) molten salt corrosion in extreme environments hinders the mix‐and‐matching of the key rare earth elements for increasing the resistance of monosilicates against corrosion of CMAS. Herein, an approach based on correlated electron microscopy techniques combined with density functional theory calculations is presented to elucidate the complex interplay of competing mechanisms that control the corrosion of CMAS of monosilicates. These findings reveal a competition between thermodynamics and kinetics that relies on the temperatures and corrosion processes. Innovative medium‐entropy monosilicates with exceptional corrosion resistance even at 1500 °C are developed. This is achieved by precisely modulating the radii of rare earth ions in monosilicates to strike a delicate balance between the competition in thermodynamics and kinetics. After 50 and 100 h of corrosion, the thinnest reactive layers are measured to be only 28.8 and 35.4 µm, respectively. Innovative medium‐entropy monosilicates with exceptional corrosion resistance to CMAS are developed. This is achieved by precisely modulating the radii of RE3+ in monosilicates to strike a delicate balance between the competition in thermodynamics and kinetics. After 50 and 100 h of corrosion, the thinnest reactive layers are measured to be only 28.8 and 35.4 µm, respectively.

It is difficult to obtain a single-phase environmental barrier coating material that simultaneously offers the advantages of low thermal conductivity, a suitable coefficient of thermal expansion, and excellent corrosion resistance. Herein, to synthesize the advantages of single-phase materials, we have developed an effective approach for the design of high-entropy multiphase ceramics of rare earth oxides and silicates. Such a specific design approach is capable of making high-entropy RE 2 SiO 5 /RE 2 O 3 and RE 2 SiO 5 /RE 2 Si 2 O 7 (RE = Lu, Yb, Tm, Er, Ho, and Y) multiphase ceramics as two types of potential environmental barrier coating materials for Al 2 O 3f /Al 2 O 3 and SiC f /SiC ceramic matrix composites.

The ambiguous understanding of calcium‐magnesium aluminosilicate (CMAS) corrosion mechanisms in RETaO4 has hindered performance optimization through rare‐earth compositional engineering. This study systematically investigates the corrosion behavior of 3–10 component RETaO4 systems. In situ X‐ray diffraction/Transmission electron microscope coupled with Electron backscatter diffraction analysis unveils dynamic reaction pathways during the pre‐corrosion heating stage, identifying the crystallization and growth patterns of dominant corrosion product pyrochlore‐structured (Ca2‐a‐bREaAlb)(Ta2‐c‐dMgcSid)O7. A reaction‐diffusion mechanism of CMAS corrosion for RETaO4 is proposed, highlighting the different behaviors of various rare earth elements in the corrosion process. Among eight types of RETaO4, La1/6Nd1/6Sm1/6Eu1/6Gd1/6Dy1/6TaO4 exhibits the best corrosion resistance, with a relatively thin corrosion layer and the ability to avoid element segregation and localized infiltration. These findings establish composition‐property relationships for designing next‐generation corrosion‐resistant thermal barrier coatings. Composition‐property relationships in multi‐component RETaO4 are unveiled. In situ XRD/TEM and EBSD expose dynamic crystallization pathways of the dominant corrosion product (pyrochlore) and reaction‐diffusion corrosion mechanisms. La1/6Nd1/6Sm1/6Eu1/6Gd1/6Dy1/6TaO4 emerges as the optimal composition, combining minimal corrosion layer thickness with suppressed localized infiltration.

Chitosan (CS) is a linear polysaccharide with good biodegradability, biocompatibility and antimicrobial activity, which makes it potentially useful for biomedical applications, including an antimicrobial agent either alone or blended with other polymers. However, the poor solubility of CS in most solvents at neutral or high pH substantially limits its use. Quaternary ammonium CS, which was prepared by introducing a quaternary ammonium group on a dissociative hydroxyl group or amino group of the CS, exhibited improved water solubility and stronger antibacterial activity relative to CS over an entire range of pH values; thus, this quaternary modification increases the potential biomedical applications of CS in the field of anti-infection. This review discusses the current findings on the antimicrobial properties of quaternized CS synthesized using different methods and the mechanisms of its antimicrobial actions. The potential antimicrobial applications in the orthopedic field and perspectives regarding future studies in this field are also considered.

B 4 C coating was fabricated by vacuum plasma spraying and the tribological properties of the coating against WC-Co alloy were evaluated by sliding wear tests. Al 2 O 3 coating, one of the most commonly used wear-resistant coatings, was employed as comparison in the tribological evaluation. The results obtained show that, the B 4 C coating is composed of a large amount of nanostructured particles along with some amorphous phases. Both of the friction coefficient and wear rate of the B 4 C coating are much lower than those of the Al 2 O 3 coating, and the tribological evaluation reveals a decreasing trend for the B 4 C coating in friction coefficient as well as wear rate with increasing normal load, which is explained in terms of the formation of a protective transfer layer on its worn surface. Tribofilm wear is found to be the dominant wear mechanism involved in the B 4 C/WC-Co alloy friction pair.

Yttria-stabilized zirconia (YSZ) and Y 2 O 3 -La 2 O 3 co-stabilized zirconia (La-YSZ) coatings were prepared by atmospheric plasma spraying using identical spray parameters, and their calcium–magnesium–alumina–silicate (CMAS) corrosion behaviors were compared. After CMAS attack, YSZ exhibited a deteriorated microstructure with larger voids and more cracks than La-YSZ. The results revealed that the as-sprayed La-YSZ coatings had a much smaller grain size than YSZ because of La doping but La-YSZ exhibited a better resistance to CMAS than YSZ. Density functional theory calculations showed that the mean square displacement of yttrium in La-YSZ was lower than that of YSZ and the activation energy of CMAS/La-YSZ was higher than that of CMAS/YSZ. EBSD mapping analysis showed La-YSZ coatings have a lower monoclinic/tetragonal ratio than YSZ after corrosion, indicating that the rate of phase transformation in La-YSZ is significantly lower than that in YSZ, which is consistent with calculation results.

The ambiguous understanding of calcium‐magnesium aluminosilicate (CMAS) corrosion mechanisms in RETaO 4 has hindered performance optimization through rare‐earth compositional engineering. This study systematically investigates the corrosion behavior of 3–10 component RETaO 4 systems. In situ X‐ray diffraction/Transmission electron microscope coupled with Electron backscatter diffraction analysis unveils dynamic reaction pathways during the pre‐corrosion heating stage, identifying the crystallization and growth patterns of dominant corrosion product pyrochlore‐structured (Ca 2‐a‐b RE a Al b )(Ta 2‐c‐d Mg c Si d )O 7 . A reaction‐diffusion mechanism of CMAS corrosion for RETaO 4 is proposed, highlighting the different behaviors of various rare earth elements in the corrosion process. Among eight types of RETaO 4 , La 1/6 Nd 1/6 Sm 1/6 Eu 1/6 Gd 1/6 Dy 1/6 TaO 4 exhibits the best corrosion resistance, with a relatively thin corrosion layer and the ability to avoid element segregation and localized infiltration. These findings establish composition‐property relationships for designing next‐generation corrosion‐resistant thermal barrier coatings.

Enhancing the properties of thermal barrier coatings (TBCs) by doping with rare earth elements has been a hot topic for a while. La2O3 and Y2O3 co-doped ZrO2 (La-YSZ) TBCs and yttria-stabilized zirconia (YSZ) TBCs were deposited by atmospheric plasma spraying (APS), and the comprehensive effects of La3+ on the microstructure and property were investigated. The thermal conductivity and microstructure were investigated and were compared with YSZ. The recrystallized fraction components of all TBCs were quantified. It is clearly found that the component of “recrystallized” and “deformed” grains for La-YSZ TBCs is much higher than that for YSZ TBCs. This could be due to La3+ doping enlarging the lattice parameter of YSZ and thus increasing the melting index, which in turns leads to the smaller grain size of La-YSZ TBCs. As a result, the thermal conductivities of La-YSZ TBCs were distinctly lower than those of YSZ TBCs.

Atmospheric plasma spray (APS) yttria-stabilized zirconia coatings have a complex microstructure with a variety of pores that significantly reduce the thermal conductivity. APS thermal barrier coatings (TBCs) with a similar monoclinic phase were prepared. The pore sizes and distributions of the coatings were obtained by scanning their cross-section via SEM; the scanned areas were over 1 mm × 2 mm and more than 23,000 pores for each coating were analyzed. Multiple linear regression was used to analyze the porosity data and then to determine the quantitative relationship between different types of pores and thermal conductivity. Results revealed that the different pores have different effects on decreasing the thermal conductivity. The small, vertical pores have the biggest effect, while the horizontal pores also play a significant role in decreasing the thermal conductivity.