Plasma Reaction Synthesis of Agglomerated Oxide Powders by Axial Injection Torch

Several compositions of agglomerated ZrO₂(Y₂O₃), Al₂O₃ and MgAl₂O₄ powders were plasma sprayed through an axial injection torch into a water quenching chamber in order to obtain a fully melted and homogenized, metastable particle nanostructure. This metastable extended solid solution morphology allows the powder to be subsequently heat treated and superplastically formed into ceramic parts with potentially excellent optical and mechanical properties. Light microscopy, SEM and XRD analyses were used to evaluate the melt-quenched powder properties, and some comparison was made to previous work performed with traditional radial injection plasma torches. Thick build-ups were also sprayed from the melt-quenched powders to test their ability to superplastically flow. Results showed that during a single processing through the torch the axial injection equipment produced powders with a significantly higher fraction of fully homogenized powders than previously attainable. Homogenization of powders comprised of a larger particle size range was also achieved.