The Structure Of The Nano Al <sub> 2 </ Sub> The O <sub> 3 </ Sub> / Tio <sub> 2 </ Sub> / Sio <sub> 2 </ Sub> Thermal Spray Powders And Coatings,

The normal nanocrystalline powder can not be directly used for plasma spraying because of the single particle's low mass, low density, poor flow ability. This powder should be reprocessed into agglomerated powder with particle size in the range of 10-90um.This study focuses on the heat treatment of the agglomerated Al₂O₃-3%TiO₂-2%SiO₂ powder, the influence of heat treatment on the powder's morphology and properties, and there search on the microstructure of alumina/titania/silica coating. During the experiment the powder's flow ability, free hold density, tap density after heat treatment at different temperatures is surveyed. The transformation process of the particle's shape at high heating temperatures is discussed. The alumina/titania/silica coating is obtained on the stainless steel via plasma spraying with nanostructured agglomerated powder. In this research program, scanning electron microscopy and X-ray diffraction are used to characterize the powder and the coating. When heating temperature exceeds 1250℃ the distinct sintering phenomenon happens in the agglomerated powder and nanocrystalline particle's size reach micron scale.- Thus the temperature of heat treatment should be controlled under 1200℃. After the reasonable heat treatment, the flow ability of the agglomerated powder is improved, tap density enhanced, the nanocrystallines inside the agglomerated powder remained which are fit for thermal spraying. The free surface and the cross section of the coating are examined. It is revealed that the coating consists of nano/micro structure without notable laminar structure. A part of the coating is microstructured derived from melted agglomerated powder in plasma and another part is namostructured from unmelted agglomerated powder.