Plasma spray-physical vapor deposition (PS-PVD), called the third-generation method for thermal barrier coatings (TBCs) fabrication, has great potential for their using in gas-turbine engines. Compared to atmospheric plasma spray (APS), called the first-generation TBCs, and electron beam-PVD (EB-PVD), called the second generation, PS-PVD has many interesting features, including non-line sight deposition, high deposition rate, and microstructural flexibility, among others. Such advantages make them a promising approach to prepare thermal barrier coatings for advanced gas-turbine engines. Using PS-PVD, feather-like columnar TBCs with good strain tolerance and low thermal conductivity can be fabricated. However, prior to their application in gas-turbine engines, some disadvantages, such as CMAS (CaO–MgO–Al2O3–SiO2, etc.) corrosion and oxidation resistance, need to be addressed. In this work, a method to develop Al2O3-modified PS-PVD 7YSZ TBCs was proposed. The experimental results demonstrate that the Al2O3-modification process is an effective approach to address the aforementioned weaknesses of traditional PS-PVD 7YSZ TBCs.
7 February 2022 in Journal of Materials Chemistry C
A sandwich Ti 3 C 2 T x /MoS
2−
x P x heterostructure with outstanding HER activity and excellent long-term durability was constructed by a hydrothermal and phosphorization approach. The sandwich heterostructure and P doping promote excellent HER performance.
Tri-layer Si/mullite/Yb2SiO5 environmental barrier coating (EBC) was prepared on the SiCf/SiC ceramic matrix composite (CMC) by plasma spray-physical vapor deposition (PS-PVD). The EBC samples were carried out with water vapor corrosion at 1300 °C for 200 h. After steam corrosion, Yb2SiO5 layer forms a gradient porous structure. This is mainly due to the inclusion of SiO2-rich layer which is precipitated from the gasification inside the coating and existing a small amount of Yb2O3 separately. During the corrosion process, water vapor infiltrates into the coating and reacts with the SiO2 and Yb2O3 to generate volatile substances. This forms a porous structure to make the coating brittle, resulting in mud cracks finally. In addition, the results show that the Yb2SiO5 can react with the water vapor at the coating surface, forming an Yb2Si2O7 top layer.
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.
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.
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.