Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Self-propagating exothermic reactions are known to occur in multilayer films with alternating layers of a transition metal and a light element. The high velocity of these reactions, associated with high heat release rate, convert these systems in a unique heat source. The possibility of tailoring such a heat source to meet the needs of a particular process is very attractive to applications such as brazing or solid-state diffusion bonding. The solid state reactions occurring in Ni and Al multilayer thin films, produced by d.c. magnetron sputtering with bilayer thickness (period) of 5, 14 and 30 nm, were studied by differential scanning calorimetry (DSC). DSC results demonstrated that reaction temperature and heat released increase with the period of Ni/Al multilayer thin films.

From a biomaterials perspective, it is now understood that success in the osseointegration of a dental implant is conditioned by its “macro”, “micro” and “nano” scale features. Macro-scale roughness is necessary to improve primary stabilization in the post-surgical phase inducing a peri-implant thin fibrous layer. However, the more complex process in the true cell-material interaction is dependent on micro and nano scale phenomena. There is clear evidence that cell adhesion, proliferation, organization and phenotype are modulated at the micro-scale and that protein absorption is fundamentally a process conditioned at nano-scale.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Several attempts have been made in the last few years for joining similar pure copper and brass alloys using the solid state friction stir welding (FSW) process. For both material types, all the works performed reported that the production of defect free welds is largely dependent on the correct choice of process parameters. It was also observed that, despite grain refinement occurred in the centre of all the welds, the welds in copper showed a slight reduction in strength, when compared to that of the base material, as opposed to welds in brass alloys, for which an increase in strength was observed. Regardless of the encouraging results obtained in similar FWS of these materials, in the knowledge of the authors, few reports exist concerning dissimilar joints between them. In his work, dissimilar welds between Cu DHP cooper plates and Cu-Zn 37 brass plates, both of 1 mm thickness, with the brass plate positioned in the advancing side of the tool, were analysed. Welds were carried out with a solid tool made of high speed steel. Tool geometry was characterized by a tool shoulder of 10 mm in diameter, containing a conical cavity of 6 degrees, and a threaded probe of 3 mm in diameter. Welds were done in a milling machine, in position control, using the working parameters indicated in table 1.

The environmentally friendly friction stir welding (FSW) process is being increasingly used in joining similar and dissimilar aluminium and copper alloys and other soft materials. In this process a rotating tool promotes significant shear strain and frictional heating of the base materials, in order to stir them into a highly plasticized weld region, at the trailing side of the tool. Due to the intense plastic deformation, complex material flow patterns, such as vortices, swirls and whorls occur during welding. In dissimilar welds, these patterns are readily revealed by differential etching and the respective microstructures characterized. However, in similar welds, such as the welds between plates of AA 5182-H111 aluminium alloy, it is hard to distinguish the different features in the welds and characterize their microstructures. Fig. 1 illustrates optical and TEM micrographs of a weld in this alloy. In the optical image of the weld, at the top of the image, it is possible to distinguish three main areas signalized by numbers: the weld nugget (1), with a very fine grain structure with 2.8 um mean grain size, and a transition region (2) between the nugget and the base material (3), which is usually called the Thermomechanical Affected Zone (TMAZ).

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

From the application point of view, the most interesting compositions in the lead zirconate titanate solid solutions, PbZrxTi1-xO3 (PZT), are those near the centre of the phase diagram, where tetragonal and rhombohedral phases are separated by a boundary nearly independent on temperature. The composition of this so-called morphotropic phase boundary (MPB) is approximately 52/48 at room temperature. The piezoelectric coefficients, electromechanical coupling coefficients, dielectric permittivity and remnant polarization measured on ceramic samples reach a maximum in this region, not necessarily at the same composition, which explains why these compositions are technologically so interesting.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Calcium phosphate (CaP) particles aimed at specific applications including dental defect filling, bone tissue engineering and drug delivery may be engineered by different methods based on solution chemical precipitation. The understanding of CaP particle morphology evolution during precipitation is of great scientific interest not only from a fundamental point of view but also because morphology directly or indirectly determines the applicability of the particle. Citrate ion, widely known as a minor bone component, plays an important role as crystal habit modifier and crystal growth inhibitor. However the prediction of CaP growth morphologies in presence of citrate ion is still a challenging issue because the mechanism of citrate and CaP interactions is not yet clearly understood.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Material analysis, specially surface analysis of materials, has been increasingly important. A wide range of surface analysis techniques is available. The techniques are, generally, complementary. There are nuclear and non-nuclear techniques, e.g. microscopy. Nuclear techniques, which are nondestructive, permit analysis for a few microns near the surface. They have been applied to areas such as scientific, technologic, industry, arts and medicine, using MeV ion beams. Nuclear reactions permit to achieve high sensitivities for detection of light elements in heavy substrates and also discrimination of isotopes. We use ion-ion nuclear reactions, elastic scattering and the energy analysis method, where an energy spectrum is obtained of ions from the target for a chosen energy of the incident ion beam. The target composition and concentration profile information contained in the spectrum is computationally obtained through a computer program that has been developed for predicting such energy spectra. Predicted spectra obtained for variations of target parameters are compared with experimental data, giving that information. SEM and TEM are also used.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

This work investigates the dispersion of nanoclays in polymer/montmorillonite (MMT) nanocomposites. Nanocomposites were prepared in a twin screw extruder and the collected samples were analyzed by SEM and TEM. It was possible to study the dispersion of the nanoclays and moreover understand its effect as compatibilizer.

Morphology development during phase inversion is a very complex and not well understood process. EPDM/PP -based TPVs were prepared and characterize by different electronic microscopy techniques. Using a low Mw-EPDM, morphology development during phase inversion was successfully followed by scanning electron microscopy with a back scattered electron detector.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009