Ferroelectric films with a composition gradient have attracted much attention because of their large polarization offset present in the hysteresis loops. Lead Zirconate Titanate (PZT) films were deposited on Pt/TiO2/SiO2/Si substrates by Pulsed Laser Deposition (PLD) technique, using a Nd:YAG laser (Surelite) with a source pulse wavelength of 1064 nm and duration of 5-7 ns delivering an energy of 320 mJ per pulse and a laser fluence energy about 20 J/cm2. The film growth is performed in O2 atmosphere (0,40 mbar) while the substrate is heated at 600°C by a quartz lamp. Starting from ceramic targets based on PZT compositions and containing 5% mol. of excess of PbO to compensate the lead evaporation during heat treatment, three films with different compositions Zr/Ti 55/45, 65/35 and 92/8, and two types of complex structures were produced. These complex structures are in the case of the up-graded structure (UpG), with PZT (92/8) at the bottom, PZT (65/35) on middle and PZT (55/45) on the top, and for down-graded (DoG) one, that order is reversed.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

The study of old mortars composition, using physical-chemical, mineralogical and microstructural characterization has an important role in the preservation of architectural heritage, allowing a deep knowledge about the materials used, construction techniques, possible repairs and degradation processes.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Ge NCs have attracted considerable attention because of their potential applications in nonvolatile memory and integrated optoelectronics. A number of groups have already proposed integrate flash memories based on Ge NCs embedded SiO2 matrix. Since Al2O3 presents a high dielectric constant comparatively to SiO2, it is a good candidate to replace silica in flash memory systems, and therefore improve their performances. Moreover, Al2O3 presents good mechanical properties, and supports high temperature, which leads it to be an ideal material for Si processing conditions. However, a few studies have been reported on Ge NCs embedded in Al2O3 matrix.

Recently, porous polymer-ceramic composites have been developed and represent promising scaffolds to be used as synthetic extracellular matrix in bone tissue engineering since they combine the advantages of these two types of materials. On the other hand bioactive glasses (BG) have been used as ceramic fillers to promote bioactivity and to enhance mechanical properties and osteoblast functions. Among all the requirements, these 3D porous structures should have a controllable average pore size larger than 100 μm as well as good pore interconnectivity to allow vascularization and tissue ingrowth. The goal of this study is to investigate the effect of the addition of a bioactive glass on the porous structure development of the scaffolds prepared by thermally induced phase-separation and also to test the bioactivity of these composite scaffolds. Poly (L-lactic) acid (PLLA) was chosen as the polymer matrix because of its well-known biocompatibility and adjustable physical and mechanical properties. Micron-sized (<10 μm) glass from the 3CaO.P2O5-MgO-SiO2 system was produced in our laboratory and used as the bioactive ceramic filler.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Owing to its chemical similarity to the mineral phase of human bone and to its biological performance, synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) has long been recognized as an important bone substitute material in orthopaedics, dentistry and artificial implants. HA ceramics have also been studied as drug delivery systems components where an appropriate porosity for ensuring a high ability forcarryingand delivering drugs in a controlled manner is required. For some emerging applications demanding nanoscale structured systems endowed with novel potentialities HA nanoparticles may be addressed as alternative components ensuring a large surface area for adsorbing the pharmacological substance of interest. Moreover particle porosity may offer new possibilities for drug or nutrient delivery, or for biocompatible and bioresobable structural reinforcements in osteologic implants, coatings and adhesives. Mesostructured porous calcium phosphate based systems have been synthesized at macro- and micro-scale, but well established methods for the specific synthesis of porous HA nanoparticles have not been reported so far. Yao et al. reported a successful synthesis of HA mesoporous micron-sized rods 0.5-1 μm in length and 50-100 nm in thickness but having low porosity. A new synthesis challenge for producing nano-sized particles of high surface area and having ordered mesopores is thus addressed.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

The importance of surface analysis of materials has been increasing. The available techniques are complementary. Nuclear techniques, which are non-destructive, provide analysis for a few microns near the surface. Using low energy ion beams of a few MeV, applications have been made to several areas. Nuclear reactions and elastic scattering are the more precise nuclear techniques for obtaining absolute values of concentrations in surface analysis. Nuclear reactions provide, not only high sensitivities for detection of light elements in heavy substrates, but also discrimination of isotopes. We consider the “energy analysis method”, where a spectrum is acquired of ions from the target for a single energy of an incident ion beam. The spectrum inherently contains target composition and concentration profile information. A computational procedure has been developed for predicting such energy spectra, where elastic scattering is a particular and important case. The model mainly accounts for: target parameters, such as composition and concentration profiles; energy spread of the incident ion beam; geometric factors and target rotation; stopping power; differential cross section; energy straggling; detector resolution. An option permits inclusion of effects such as: multiple scattering; incident beam size and angular divergence; detector angular aperture. Computer simulated spectra are compared to experimental data. The chi-square is calculated, to evaluate the goodness of fit. Through variation of target parameters, so as to fit experimental data, target composition and concentration profiles are obtained.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Laser ablation has been extensively studied in polymers because of their considerable utility in diverse fields such as medicine, microelectronics, photonics, etc. As a result, laser ablation of polymers has generated considerable interest in research during the past two decades. Among the many aspects of laser ablation of polymers, several authors have reported the formation and growth of conical structures during laser processing with UV laser radiation. Although this aspect of laser ablation has been investigated since the 1980s, only a few applications of these structures have been reported. In the present paper, we study the development of conical structures on polyimide treated with KrF laser radiation as a function of the radiation fluence, and its effect on the wettability of the polymer.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Mortars are common and essential elements of masonry historical buildings and are composed by a binder, aggregates and eventually, some additives. The binder provides consistency to this composite material, and until the emergence of Portland cement in the 19th century, lime was the main binder used. The aggregates are normally sand or rock fragments with variable sizes. The whole set is morphologically very similar to a sedimentary clastic rock with carbonate cementing. Following an old tradition of microscope use in this kind of rocks, it is not surprising the application of optical microscopy to mortars as also happened with concrete.