Lattice distortions and oxygen vacancies produced in Au+-irradiated nanocrystalline cubic zirconia

The oxygen ion conductivity, attributed to an oxygen vacancy mechanism, of yttria-stabilized zirconia membranes used in solid oxide fuel cells is restricted due to trapping limitations. In this work, a high concentration of oxygen vacancies has been deliberately introduced into nanocrystalline stabilizer-free zirconia through ion-irradiation. Oxygen vacancies with different charge states can be produced by varying irradiation temperatures. Due to the reduced trapping sites and high oxygen vacancy concentration, this work suggests that the efficiency of solid oxide fuel cells can be improved

Lattice distortions and oxygen vacancies produced in Au+-irradiated nanocrystalline cubic zirconia

The oxygen ion conductivity, attributed to an oxygen vacancy mechanism, of yttria-stabilized zirconia membranes used in solid oxide fuel cells is restricted due to trapping limitations. In this work, a high concentration of oxygen vacancies has been deliberately introduced into nanocrystalline stabilizer-free zirconia through ion-irradiation. Oxygen vacancies with different charge states can be produced by varying irradiation temperatures. Due to the reduced trapping sites and high oxygen vacancy concentration, this work suggests that the efficiency of solid oxide fuel cells can be improved

United States Patent: Nano-Crystalline, Homo-Metallic, Protective Coatings

The present invention provides orthopedic prosthesis having at least one metallic component that includes a metallic substrate on which an integrally formed nano-crystalline coating is formed. The coating and the substrate have at least one metallic constituent in common having an average atomic concentration in the coating that differs from an average atomic concentration in the substrate by less than about 10 percent. Further, the nano-crystalline coatings includes crystalline grains with an average size in a range of about 1 to 999 nanometers, and more preferably in a range of about 10 to 200 nanometers. A transition region that exhibits a graded reduction in average grain size separates the coating from the substrate. The coating advantageously exhibits an enhanced hardness, and a high degree of resistance to corrosion and wear. In one application, the nanocrystalline coatings of the invention are utilized to form articulating surfaces of various orthopedic devices

Nanosized rutile (TiO\u3csub\u3e2\u3c/sub\u3e) thin film upon ion irradiation and thermal annealing

Among three TiO2 polymorphs, rutile is thermodynamically unstable as compared with anatase and brookite when the crystal size is ∼10 nm. In this study, nanocrystalline rutile with an average grain size of ∼6 nm was synthesized in a thin film geometry by ion beam-assisted deposition (IBAD) with an amorphous TiO2 interlayer between the rutile film and Si-substrate. Nonstoichiometry produced by high-intensity ion bombardment during deposition may have stabilized the metastable rutile phase on the nanoscale. The phase stability of nanosized rutile was investigated by irradiation using 1 MeV Kr2+ combined with thermal annealing. In situ transmission electron microscopy (TEM) results indicate that partial amorphization occurred in nanocrystalline rutile when irradiated at room temperature, whereas the nanocrystals remained stable upon irradiation at 573 K. Ion beam-induced recrystallization occurred in the amorphous TiO2 at a 573 K, significantly lower than the temperature for thermally induced recrystallization, which occurs at 673 K. This is an example of radiation-enhanced kinetics of a phase transformation. With a further increase in the irradiation temperature, to 1073 K, the tetragonal rutile transformed to triclinic Ti5O9. © 2011 American Chemical Society

Thermal stability of nanostructurally stabilized zirconium oxide

Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO2) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited films are consistent with cubic phase ZrO2. Rutherford backscattering spectroscopy (RBS) indicated the formation of stoichiometric ZrO2. The phase identity of these optically transparent NSZ films was in agreement with cubic ZrO2, as indicated by the matching elastic modulus values from the calculated results for pure cubic zirconium oxide and results of nanoindentation measurements. Upon annealing in air for 1 h, these NSZ films were found to retain most of their room temperature deposited cubic phase x-ray diffraction signature up to 850 °C. Size effect and vacancy stabilization mechanisms and the IBAD technique are discussed to explain the present results