Research Article Issue
High-precision nondestructive evaluation of a thermal barrier coating based on perovskite quantum dot anion exchange
Nano Research 2024, 17 (5): 4582-4592
Published: 12 January 2024

Thermal barrier coatings (TBCs) in gas turbine engines are used in expressly harsh environments; thus, assessing TBC integrity status is critical for safety and reliability. However, traditional periodic maintenance involves visual inspections of the TBCs, requiring the gas turbine to be decommissioned and partially dismantled. Most importantly, tiny defects or internal damages that easily cause coating failure cannot be identified. In this work, a new nondestructive evaluation (NDE) technique of TBCs based on quantum dot (QD) anion exchange is first explored internationally. By exchanging anions between the Cl ions and the CsPbBr3 QDs, the degrees of salt corrosion of the TBCs are evaluated. The resultant NDE technique shows that the colour of the TBCs obviously changes from green to blue, accompanied by a large blueshift (~ 100 nm) of the photoluminescence (PL) peak position. In addition, the relationship between the PL peak position and coating thermophysical properties indicates that the precision of this NDE technique may easily identify the μm-level of the thermal growth oxide (TGO) changes inside the TBCs.

Open Access Research Article Issue
Al-modification for PS-PVD 7YSZ TBCs to improve particle erosion and thermal cycle performances
Journal of Advanced Ceramics 2022, 11 (7): 1093-1103
Published: 04 May 2022

Plasma spray-physical vapor deposition (PS-PVD) as a novel process was used to prepare feather-like columnar thermal barrier coatings (TBCs). This special microstructure shows good strain tolerance and non-line-of-sight (NLOS) deposition, giving great potential application in aero-engine. However, due to serious service environment of aero-engine, particle erosion performance is a weakness for PS-PVD 7YSZ TBCs. As a solution, an Al-modification approach was proposed in this investigation. Through in-situ reaction of Al and ZrO2, an α-Al2O3 overlay can be formed on the surface of 7YSZ columnar coating. The results demonstrate that this approach can improve particle erosion resistance since hardness improvement of Al-modified TBCs. Meanwhile, as another important performance of thermal cycle, it has a better optimization with 350-cycle water-quenching, compared with the as-sprayed TBCs.

Open Access Research Article Issue
Coupling of ultrasmall and small CoxP nanoparticles confined in porous SiO2 matrix for a robust oxygen evolution reaction
Nano Materials Science 2022, 4 (4): 393-399
Published: 14 April 2022

Rational design of electrocatalysts is important for a sustainable oxygen evolution reaction (OER). It is still a huge challenge to engineer active sites in multi-sizes and multi-components simultaneously. Here, a series of CoP nanoparticles (NPs) confined in an SiO2 matrix (SiO2/CoxP) is designed and synthesized as OER electrocatalysts. The phosphorization of the hydrolyzed Co-phyllosilicate promotes the formation of ultrasmall and small Co2P and CoP. These are firmly confined in the SiO2 matrix. The coupling of multi-size and multi-component CoP catalysts can regulate reaction kinetics and electron transfer ability, enrich the active sites, and eventually promote the intrinsic OER activity. The SiO2 matrix provides abundant porous structure and oxygen vacancies, and these facilitate the exposure of active sites and improve conductivity. Because of the synergy and interplay of multi-sized/component CoxP NPs and the porous SiO2 matrix, the unique SiO2/CoP heterostructure exhibits low overpotential (293 ​mV@10 ​mA ​cm-2), and robust stability (decay 12 ​mV after 5000 CV cycles, 97.4% of initial current after 100 ​h chronoamperometric) for the OER process, exceeding many advanced metal phosphide electrocatalysts. This work provides a novel tactic to design low-cost, simple, and highly efficient OER electrocatalysts.

Open Access Research Article Issue
Pressure infiltration of molten aluminum for densification of environmental barrier coatings
Journal of Advanced Ceramics 2022, 11 (1): 145-157
Published: 10 November 2021

Environmental barrier coatings (EBCs) effectively protect the ceramic matrix composites (CMCs) from harsh engine environments, especially steam and molten salts. However, open pores inevitably formed during the deposition process provide the transport channels for oxidants and corrosives, and lead to premature failure of EBCs. This research work proposed a method of pressure infiltration densification which blocked these open pores in the coatings. These results showed that it was difficult for aluminum to infiltrate spontaneously, but with the increase of external gas pressure and internal vacuum simultaneously, the molten aluminum obviously moved forward, and finally stopped infiltrating at a depth of a specific geometry. Based on the wrinkled zigzag pore model, a mathematical relationship between the critical pressure with the infiltration depth and the pore intrinsic geometry was established. The infiltration results confirmed this relationship, indicating that for a given coating, a dense thick film can be obtained by adjusting the internal and external gas pressures to drive a melt infiltration.

Open Access Research Article Issue
Structural evolution of plasma sprayed amorphous Li4Ti5O12 electrode and ceramic/polymer composite electrolyte during electrochemical cycle of quasi-solid-state lithium battery
Journal of Advanced Ceramics 2021, 10 (2): 347-354
Published: 06 February 2021

A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li4Ti5O12 (LTO) electrode and ceramic/polymer composite electrolyte with a little liquid electrolyte (10 μL/cm2) to provide the outstanding electrochemical stability and better normal interface contact. Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectrometer (EDS) were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments. By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode, the electrochemical behavior of different electrodes is studied. The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8 μm. After 200 electrochemical cycles, the structure of the electrode evolved, and the inside of the electrode fractured and cracks expanded, because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode. Similarly, the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles. The electrochemical cycle results show that the cycle stability, capacity retention rate, coulomb efficiency, and internal impedance of amorphous LTO electrode are better than traditional LTO electrode. This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery, shedding light on the development of next-generation high-performance solid-state lithium batteries.

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