In this work, the synthetic hydroxyapatite (HAP) was studied using different preparation routes to decrease the crystal size and to study the temperature effect on the HAP nano-sized hydroxyapatite crystallization. X-ray diffraction (XRD) analysis indicated that all samples were composed by crystalline and amorphous phases . The sample with greater quantity of amorphous phase (40% of total mass) was studied. The nano-sized hydroxyapatite powder was heated and studied at 300, 500, 700, 900 and 1150 °C. All samples were characterized by XRD and their XRD patterns refined using the Rietveld method. The crystallites presented an anisotropic form, being larger in the [001] direction. It was observed that the crystallite size increased continuously with the heating temperature and the eccentricity of the ellipsoidal shape changed from 2.75 at 300 °C to 1.94, 1.43, 1.04 and 1.00 respectively at 500, 700, 900 and 1150 °C. In order to better characterize the morphology of the HAP the samples were also examined using atomic force microscopy (AFM), infrared spectrometry (IR) and thermogravimetric analysis (TGA).

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH = 3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasione dimensional variable range hopping (VRH) mechanism.

Nanostructured carbonated hydroxyapatite (nCHA) is a promising biomaterial for bone tissue engineering due to its chemical properties, similar to those of the bone mineral phase and its enhanced in vivo bioresorption. However, the biological effects of nCHA nanoparticles on cells and tissues are not sufficiently known. This study assessed the impact of exposing pre‐osteoblasts to suspensions with high doses of nCHA nanoparticles with high or low crystallinity. MC3T3‐E1 pre‐osteoblasts were cultured for 1 or 7 days in a culture medium previously exposed to CHA nanoparticles for 1 day. Control groups were produced by centrifugation for removal of bigger nCHA aggregates before exposure. Interaction of nanoparticles with the culture medium drastically changed medium composition, promoting Ca, P, and protein adsorption. Transmission Electron microscopy revealed that exposed cells were able to internalize both materials, which seemed concentrated inside endosomes. No cytotoxicity was observed for both materials, regardless of centrifugation, and the exposure did not induce alterations in the release of pro‐and anti‐inflammatory cytokines. Morphological analysis revealed strong interactions of nCHA aggregates with cell surfaces, however without marked alterations in morphological features and cytoskeleton ultrastructure. The overall in vitro biocompatibility of nCHA materials, regardless of physicochemical characteristics such as crystallinity, encourages further studies on their clinical applications.

Ion conducting yttria-stabilized tetragonal zirconia (3YTZ) and Er 3+ -, Nd 3+-and Hf 4+ -doped 3YTZ ceramics were prepared and studied in this work. It is noted that dopant-induced structural effects, associated with free lattice volume for bulk conduction, may still be dominant over charge carrier density effects, even for variations of these latter by up to about 30%. In that way, dopant ion size-modified charge (oxygen vacancy) mobility varied to about +25% in Er 3+ -doped 3YTZ and about −45% in Nd 3+ -doped 3YTZ, with respect to original 3YTZ. Meanwhile, the behavior of grain-boundary electrical properties appeared to adapt well with Frenkel's space-charge model. In both bulk and grain-boundary cases, the electrical response of Hf 4+ -doped 3YTZ remained close to that from 3YTZ, a fact which is also discussed in this report.