Thursday, February 25, 2010

Process for Plasma Sprayable Yttria Stabilized Zirconia for Improved Solid Oxide Fuel Cells Detailed by Indian Scientists

An improved process for the production of plasma sprayable yttria stabilized zirconia (YSZ) powders for solid oxide fuel cells has been developed by Indian inventors Aruna Singanahalli Thippareddy,  Balaj Narayanawamy and Rajam Karaikudi Sankaranarayana  (Bangalore, IN).   The plasma process results in smaller more uniform YSZ powders. The process is detailed in U.S. Patent Application 20100048379.  

Most widely used commercial zirconia powders are composed of porous particles 10-105 microns and 45-75 microns in size. Furthermore, these powders are mixtures of tetragonal, cubic, and monoclinic modifications, which indicate the heterogeneous distribution of the stabilizing yttria dopant in finished powder is not suitable for solid oxide fuel cell applications.

Most of the methods reported in the prior art employs an additional agglomeration step which makes the process more expensive and laborious, The three inventors provide a simple and economical process for the preparation of plasma grade yttria stabilized zirconia powder useful for applications in solid oxide fuel cells (SOFC) and thermal barrier coatings without the agglomeration step. Plasma grade yttria stabilized zirconia powders are prepared at different mole % of yttria varying from 3 to 12%. Finished powder has particle size varying between 33-51 .mu.m and flowabilty of 30-54 seconds per 50 gm of powder having particle morphology ranging from almost spherical to blocky angular shape

The production process is a simple and economical process for the preparation of plasma grade yttria stabilized zirconia (YSZ) powder useful for applications in solid oxide fuel cells (SOFC) and thermal barrier coatings (TBC) without the agglomeration step. The process is particularly suitable for the manufacture of plasma sprayable 3 to 12 mol % yttria stabilized zirconia (YSZ) powders without any agglomeration process.

Although extensive studies have been carried out on the chemical synthesis of ceramic oxide powders, only few efforts have been directed towards preparing chemically uniform oxide powders for plasma spray coatings. Zirconia powder is useful in many advanced structural and electrical ceramics application. Because of its good ionic conductivity, it is used as an electrolyte in solid oxide fuel cells and because of its low thermal conductivity and relatively high thermal expansion coefficient it has been used as good thermal barrier coating in heat engines. Addition of yttrium oxide to zirconia provides the phase stability to finished powder product. Thus, plasma sprayable yttria stabilized zirconia powder finds applications as electrolyte in solid oxide fuel cells, as oxygen sensor and also as a thermal barrier coating. The powder is also typically coated on the engine parts by plasma spray techniques

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