Hafnium silicate and hafnium silicon oxynitride gate dielectrics for strained Si_xGe_1-x: Interface stabilityĪddepalli, Swarna Sivasubramani, Prasanna El-Bouanani, Mohamed Kim, Moon Gnade, Bruce Wallace, Robert These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. High temperature ablation resistant ceramic composites have been made. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.Īblation Resistant Zirconium and Hafnium Ceramicsīull, Jeffrey (Inventor) White, Michael J. Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes.
Hafnium radioisotope recovery from irradiated tantalum