Properties of plasma-sprayed freestanding ceramic parts

Plasma spraying can be used for the production of freestanding parts, such as plates, pipes, and crucibles. However, published data on the properties of such freestanding bodies are scarce. White alumina, gray alumina, zircon, and their combinations were plasma sprayed on metallic mandrels using a water-stabilized plasma gun and then stripped off. The resulting tubes were tested for gas permeability, porosity, and elastic properties. Pipes also were made from a mixture of ceramic and aluminum metal powders, and from "sandwich" bodies consisting of ceramic/metal/ceramic layers. Comparison of as-sprayed samples and samples after various posttreatments showed that posttreatments (i.e., sealing with organic and inorganic compounds or with metals, sol-gel technique, calcination, etc.) generally decreases gas permeability and increases elastic properties.