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The optical absorption and fluorescence of Pr 3ϩ ions in yttria-stabilized zirconia single crystals are investigated. Fluorescence emissions from the 1 D 2 level are clearly dominant and low intensity emission lines from the 3 P 0 and 1 G 4 states are also observed. Analysis with the Judd-Ofelt theory of the absorption intensities has been made assuming that only ϳ40% of the praseodymium ions contribute to the optical absorption bands.Quantum efficiency values of ( 3 P 0 )ϳ0.2 and ( 1 D 2 )ϳ 1 are obtained at room temperature. 1 D 2 fluorescence quenching has been observed in heavily-doped samples due to cross relaxation processes among neighboring Pr 3ϩ ions. Analysis using the Inokuti-Hirayama model shows that electric dipole-dipole interactions are mainly responsible for the quenching effect. Pr 3ϩ ions are present in seven and sixfold configurations with a statistical distribution. The energy position of the 4 f 5d configuration is very different for each center. The fluorescence dynamics is explained by a mechanism involving thermally assisted population of the 3 P 1,2 ϩ 1 I 6 upper levels and fast relaxation to the 1 D 2 level via states of the excited 4 f 5d configuration.

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W and W V alloys reinforced with La 2 O 3 particles have been produced by MA and subsequent HIP at 1573 K and 195 MPa. The microstructure of the consolidated alloys has been characterized by scanning electron microscopy, energy dispersive spectroscopy analyses and X ray diffraction. The mechanical properties were studied by nanoindentation measurements. The results show that practically full dense billets of W V, W V La 2 O 3 and W La 2 O 3 alloys can be produced. The microstructure analysis has shown that islands of V are present in W V and W V 1La 2 O 3 alloys. In W 1La 2 O 3 islands of La 2 O 3 are also pres ent. The nanohardness of the W matrix increases with the addition of V, while decreases with the addi tion of La 2 O 3 .

Titanium Hydrostatic extrusion Texture Uni-axial deformation behavior Bi-axial deformation behavior Anisotropy Coarse-grained commercially pure (CP) Titanium is subjected to hydrostatic extrusion resulting in the formation of ultrafine lamellar-type microstructure having very strong fiber texture. Uni-axial tensile tests of longitudinal and transverse specimens are carried out to study anisotropy of uni-axial deformation behavior of hydrostatically extruded CP Titanium. Small punch testing of longitudinal and transverse specimens is performed to study the anisotropy of its bi-axial deformation behavior. It is demonstrated that there is significant anisotropy of both uni-axial and bi-axial deformation of CP Titanium after hydrostatic extrusion which is related to the specific microstructure and texture developed in the material during hydrostatic extrusion.

Highlights:-W-2V and ODS W-2V-0.5Y 2 O 3 alloys have been produced following a powder metallurgy route.-Grain microstructure and microhardness have been studied after isothermal treatments in vacuum.-Both alloys exhibit a duplex grain size population: a submicron-sized grain and a coarse grained one. Keywords: W alloys, Oxide dispersion strengthened W alloys, Grain growth, Recovery, Microhardness Abstract: W-2V and ODS W-2V-0.5Y 2 O 3 alloys have been produced following a powder metallurgy route consisting of mechanical alloying and a subsequent high isostatic pressing HIP at 1573 K. The grain microstruc-ture and microhardness recovery of the alloys have been studied in samples subjected to isothermal treatments in vacuum in temperature range 1073-1973 K. Both alloys exhibit a duplex grain size distri-bution consisting of a submicron-sized grain and a coarse-grained population. It has been found that the Y 2 O 3 addition inhibits growth of the coarse grains at T < 1973 K. Submicron grain growth, with activa-tion enthalpy of 1.9 and 2.49 eV for W-2V and W-2V-0.5Y 2 O 3 , respectively, was observed at T ≥ 1573 K. It resulted that the rate constant for grain growth is 30 times higher in W-2V-0.5Y 2 O 3 than in W-2V. The considerable enhancement of the microhardness in the W-2V-0.5Y 2 O 3 appears to be associated to dispersion strengthening.

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Abstract:The capability of the colloidal method to produce yttria (Y 2 O 3 ) dispersed hydroxyapatite (HA) has been in vestigated as an alternative method to the conventional method of mechanical mixing and sintering for de veloping HA based materials that could exhibit controllable and enhanced functional properties. A water based colloidal route to produce HA materials with highly dispersed Y 2 O 3 has been applied, and the effect of 10 wt.% Y 2 O 3 addition to HA investigated by thermal analysis, X ray diffraction and Fourier transform in frared spectroscopy. These measurements evidence a remarkable effect of this Y 2 O 3 addition on decomposi tion mechanisms of synthetic HA. Results show that incorporation of Y 2 O 3 as dispersed second phase is beneficial because it hinders the decomposition mechanisms of HA into calcium phosphates. This retardation will allow the control of the sintering conditions for developing HA implants with improved properties. Be sides, substitution of Ca 2+ with Y 3+ ions appears to promote the formation of OH − vacancies, which could improve the conductive properties of HA favorable to osseointegration.