Uniform Melt State process for Ceramics Spray Coatings and Nanopowder Production

Materials processing suffers from compositional nonhomogeneity and thermal variations. A Uniform Melt State Process (UMSP) owed to microwave plasma technology has been used to solve this problem in spray coatings and nanostructured powder production. The compositional homogeneity is achieved through the injection of molecularly mixed, uniform diameter precursor droplets using piezo-driven droplet maker technology. Thermal path uniformity is achieved through axial injection of droplets into an axisymmetric hot zone with uniform temperature profile and laminar entrainment (and cooling?) flows, followed by high quenching rates.  Amastan demonstrated laboratory scale production level of nanocomposite MgO-Y2O3 uniform particles that are porous, spherical with an amorphous microstructure. Pressureless heat treatment of these powders showed moderate growth of composites grain size with homogeneous distribution of composites in the material matrix. Furthermore, spark plasma sintering revealed that these powders sinter at lower than conventional sintering temperature. Spheroidization of spray-dried MgO-Y2O3 used as feedstock was also demonstrated to yield dense and spherical particles. Spray coating with 8YSZ powders demonstrated dense and thick coatings for TBC applications.   USMP has been used to demonstrate splat deposition using MgO-Y2O3, YAG, and YSZ based solution precursors in order to achieve substantial coating using other solution based materials.

The microwave plasma technology is readily scalable, contaminant free and has an energy efficiency of about 85%. It requires low maintenance and is highly robust.