Study on preparation and heat treatment process of LaMgAl₁₁O₁₉ spray powder

Lanthanide magnesium hexaaluminate (LaMgAl₁₁O₁₉) synthesized successfully by solid-state reaction. LaMgAl₁₁O₁₉ powder was prepared by centrifugal spray-drying, and the powder was heat treated. The LaMgAl₁₁O₁₉ coating was prepared with unheated treatment powder and heat treatment powder by plasma spraying and oxidized at 1100℃ for 1h. The flowability and apparent density, microstructure and phase of LaMgAl₁₁O₁₉ powder were analyzed by Hall flowmeter, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that centrifugal spray-drying obtained the uniform particle size and good fluidity LaMgAl₁₁O₁₉ spherical powder, and the internal structure of the powder was loose and not dense. The heat treatment of LaMgAl₁₁O₁₉ powder can improve the fluidity and relative density, and can avoid the decomposition of the coating effectively. The optimal temperature of heat treatment is 1450℃ in this test. Compared with the unheated treatment powder, the fluidity of the powder after heat treatment at 1450℃ is 12.1 s·50 g^-1, the flow time is shortened by 19.9%, and the apparent density is increased by 83.4%. The coating prepared by the heat treatment powders have a lower porosity and a more compact structure, and reduces the formation of the amorphous phase during the spraying process effectively.