The influence of grain size and density of yttria-tetragonal zirconia polycrystals (Y-TZPs) ceramics on mechanical properties and on low-temperature aging degradation (LTD) in air and in hot water was investigated. A TZP powder containing 3 mol% Y2O3 was consolidated by slip casting and densified by the sintering/hot isostatic pressing (HIP) method. Only the presintered samples that contained less than 0.15% open porosity reached near full density after HIP. The best conditions to reach full density were found to be attained by presintering and HIP both at 1400 °C. At these conditions, some of the best mechanical properties such as modulus of rupture and Weibull modulus reached 1397 ± 153 MPa and, 10.6, respectively. These values were clearly higher than those obtained from sintered bodies and samples hot isostatically pressed at 1600 °C. Aging degradation of 3Y-TZP materials can be avoided through microstructural design. Fully dense materials with a critical grain size <0.36 μm did not show any evidence of degradation after extreme aging conditions at pressurized autoclaving in hot water at 100, 200, and 260 °C for 8 h. We propose a criterion to predict degradation in air as well as in hot water for the characterized materials based on the microstructure and density control of the samples.

Ferroelectric domain configurations in silver-and lanthanum-doped lead zirconate titanate (PZT) ceramics were characterized by scanning force microscopy using contact as well as piezoelectric response force [i.e., piezoelectric force microscopy (PFM)] modes. Coarse crystallites of hard and soft PZT ceramics (12 m in Ag-PZT and 30 m in La-PZT average grain size, respectively) with surface oriented in the {001} planes were chosen to characterize the domain configuration. Results show the conventional right-angled domain structures, which correspond to the {110} twin-related 90°and 180°domains of homogeneous width from 50 to 150 nm. The ability of PFM to image the orientation of pure in-plane arrays of domains (containing 90°-aa-and 180°-aa-types of domain boundaries) is highlighted, and a more detailed notation for in-plane domains is proposed. In addition to such periodical domain arrays, other ordered domains were found, having a misfit of 26°with respect to the {110} domain walls and the {100} surface. This array of domain walls could not be predicted with a geometrical analysis of the intersection of domain walls at the surface according to the conventional spatial array of {110} crystallographic planes. It could be explained only with {210} planes being the domain walls. The reason for this unconventional domain configuration is explained with the clamped conditions of the investigated crystallites in the polycrystalline material.

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The effect of growing conditions and post treatments in electrodeposited calcium phosphate films on 316 L stainless steel is presented. The concentration and pH of electrolyte solution and the potential values for the electrodeposition process were determined based on a study of cyclic voltammetry curves. The electrolyte concentration was fixed at 0.025 M ((NH4) H2PO4) and 0.042 M (Ca(NO3)2.4H2O), choosing a pH = 5 as the better condition for the films deposition. In addition, the electrolyte temperature was varied between room temperature and 60°C to determine the influence of this parameter on the deposited films. Films were characterized using Fourier Transform Infrared Spectroscopy, X-ray diffraction and Scanning electron microscopy equipped with energy dispersive spectroscopy. The as deposited films at -1.2 V and -1.7 V exhibit the dicalcium phosphate dihydrate phase (Brushite) while thermal post treatment favor the formation of octacalcium phosphate in amorphous phase, and basic treatment tend to produce the Hydroxyapatite phase. The suggested mechanism for the HAp phase formation, after the basic treatment, consists in providing the necessary OH- groups to complete the synthesis process.

The effect of substrate temperature and N2/Ar flow ratio on the stoichiometry, structure and hardness of TaNx coatings prepared on (111) Si substrates by DC reactive sputtering was investigated. For the structural, chemical and morphological analysis, X‐ray diffraction (XRD), Auger electron scanning and atomic force microscopy were respectively used. Hardness values of thin films were determined using the work of indentation model from nanoindentation measurements. TaN stoichiometric coatings were obtained for samples deposited at room temperature. The stoichiometric TaN phase was not obtained by increasing the temperature up to 773 K, even when increasing the N2/Ar flow ratio. Even when a saturation in nitrogen content was achieved, nitrogen vacancies are still present in those samples. For coatings prepared at 773 K and low N2/Ar flow ratio, a phase mixture between TaNx and cubic α‐Ta was observed, while a cubic structure δ‐TaN was formed by increasing the N2/Ar flow ratio. A maximum in hardness and (38 GPa) was obtained for the sample deposited at 773 K and a N2/Ar flow ratio of 0.2, which presented a δ‐TaN cubic crystalline structure and a roughness value of 1.6 nm. Copyright © 2015 John Wiley & Sons, Ltd.