Hollow ceramic microspheres prepared by combining electro-spraying with non-solvent induced phase separation method: A promising feedstock for thermal barrier coatings

Abstract

Hollow microspheres were prepared by a combination method of electro-spraying and non-solvent induced phase separation, using a slurry of polymer with Y 2 O 3-stabilized ZrO 2 powder (YSZ). Subsequent sintering was carried out to obtain porous hollow YSZ microspheres with proper strength aiming to be thermal spraying feedstock. The ESNP particle size and distribution strongly depended on the applied voltage of the electro-spraying process and the jet nozzle diameter. The YSZ microspheres always consisted of a thin spongy shell and highly porous interior structure. The microsphere size decreased from 1000 to 100 μm with increasing voltage (10 ~ 20 kV). The cone-jet mode of electrospray reached steady as the nozzle diameter varied from 0.5 to 0.8 mm. Compared with the coatings made from commercial hollow spherical powder, the coatings prepared by ESNP powder had enhanced resistance to sintering and exhibited a longer life than commercial spray powder. It has demonstrated that the ESNP method provides a versatile way to manipulate the microstructure of ceramic microspheres, and could been used to fabricate high performance thermal barrier coatings by plasma spraying.

Sintering behavior of a nanostructured thermal barrier coating deposited using electro‐sprayed particles

“…The porosity of the ESP particle was ~ 45% measured by Archimedes’ method, 35 slightly lower than that of the HOSP particle (52%) 46 . Since two particles had similar size and density, as well as the same spray parameters, it was reasonable to assume that they have similar in‐flight speed and surface temperature in the plasma jet.…”

“…The slurry was firstly prepared by mixing the milled 8YSZ powder, PES and NMP with the weight ratio of 3:1:6. An optimized voltage of 20 kV and slurry flow rate of 2.5 mL/min were selected in the electro‐spraying process in order to fabricate feedstock powder with appropriate flowability and particle size (35‐85 μm) based on previous works 34,35 . Finally, the ESP feedstock powder was obtained after the sintering at 1200℃ for 2 hours in a muffle furnace to completely remove the organic materials (mainly PES) and achieve robust structures.…”

A highly strain and damage‐tolerant thermal barrier coating fabricated by electro‐sprayed zirconia hollow spheres

“…The submicron YSZ particles were dispersed in the organic solvent (PES/NMP) as the “sphere A.” Then a dense skin layer and a porous core formed due to diffusion rates of the PES into water is different from surface to core, as the solid “sphere B.” The submicron YSZ particles were connected by the PES (solid phase). Detailed mechanism of the phase inversion can be found elsewhere . After 2 hours annealing at 1100°C, the organic (predominantly PES) was burned out.…”

“…Detailed mechanism of the phase inversion can be found elsewhere. 32 After 2 hours annealing at 1100°C, the organic (predominantly PES) was burned out. Only the YSZ was left in "sphere C" ( Figure 1B).…”

Microstructure and Property of Thermal Insulation Coating on the Carbon Fiber Reinforced Epoxy Resin Composites

“…However, the complex sintering process and the unstable effect seriously limited its further application [5] . By introducing the substance with low thermal conductivity, a loose porous structure such as a large amount of convection-free air would be presented in the barrier-type thermal insulation coating, which could significantly reduce the heat transfer efficiency [6] . Yang, et al [7] used hollow glass microsphere (HGM) and phenolic resin to prepare a composite material with a thermal conductivity of 0.1024 W•m -1 •K -1 .…”