Hardmetals of tungsten carbides in a cobalt matrix have been attempted to weld in similar joints by Nd/YAG laser in continuous wave mode. The combination of mechanical and thermo-physical properties of these materials poses a significant difficulty in welding these materials, especially for grades with low Co content, as 6 to 12% in volume. However, grades with higher Co content also showed a poor weldability. In fact, when welding hardmetals with a Co content of 25% in volume, a large amount of pores was observed on the fracture surface. Analysis under scanning electron microscopy showed these pores were coated with a thin film.Observations with energy dispersive spectroscopy (SEM-EDS) revealed this film is rich in cobalt and is highly unstable. Figure 1 shows the characteristics of the film around a pore evidencing its corrugated aspect originated during rapid cooling conditions verified during laser welding.

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

CVD diamond coated cutting tools are used for machining of abrasive and hard materials such as Al-Si alloys and tungsten carbide. The knowledge of the mechanisms governing the diamond/substrate interfacial strength is crucial in cutting tools design. The most adequate substrate material for maximizing the adhesion of diamond films is the silicon nitride (Si3N4) ceramic that possesses a thermal expansion coefficient similar to that of diamond. Buchkremer-Hermanns and co-workers consider the formation of a SiC interlayer between diamond and Si3N4, which may favour chemical bonding to diamond, although they could not detect it by glazing incidence X-Ray diffraction. They believed that insufficient detection sensitivity for very thin films, texture effects or presence of amorphous layers are possible reasons. In the case of TiN substrates, a graded interlayer of amorphous TiCN of only 8 Å was suggested by Contreras, as observed by HRTEM images and EDS measurements. Due to the difficulty in the detection of such layers, which can be in the order of a few angstrons, a definite evidence of their nature is yet to be demonstrated.

In the decorative field, besides the optical characteristics needed for achieving desired colours, the material should have suitable properties able to assure the daily use of the component without significant degradation. Oxides are well known materials with a high wear and corrosion resistance which make them a preferential choice of coatings for environmental protection. However, the intrinsic colours possible to be achieved in a single oxide system are very limited. For example in W-O system, besides the different tonalities of grey, only the dark blue can be obtained for slightly substochiometric WO3 compound. The pallet of colours exhibited by WO3 coatings is due to interferometric effects. Recently, it was shown that playing with the gradient of the chemical composition of W-O layers it was possible to tune the global colour of the coatings, which made this system an attractive candidate for decorative applications.

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

Bone tissue engineering is a promising area that aims at developing implants capable of repairing and/ or substituting damaged or lost bone tissue. Ceramics are widely used for bone tissue engineering purposes and in this study, hydroxyapatite porous scaffolds were produced using the polymer replication method. With this method, it was possible to obtain scaffolds with specific demands adequate to tissue engineering purposes namely: macroporosity, microporosity and interconnected porosity. Polyurethane sponges were used as templates and impregnated with a ceramic slurry at different ratios being afterwards sintered following a specific thermal cycle. The characteristics of the hydroxyapatite porous scaffolds were investigated by using scanning electron microscopy and micro computer tomography (μ-CT). Human bone marrow cells (HBMC) were isolated and cultured on the scaffolds for 28 days and SEM was used as a tool to assess cell morphology and distribution.

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

Underwear is the most intimate form of dress, and feminine panties are particularly in close contact with genital mucosa, vulvar skin and perineum area. In fact, despite some controversy, the textile material has been pointed out as promoter of vaginal infection, trough changes on the normal skin physiology. The physiology of vulvar skin is very specific in terms of temperature (≈ 34°C), moisture and pH (< 4.7). This region is also colonized by a very specific microflora that is essential either to protect against pathogenic microorganisms, either to maintain healthy conditions of temperature, moisture and pH.

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

This work reports the study of the frescoes from the Casa de Fresco dos Sanches Baena in Vila Viçosa (Southeast Portugal) to allow their material characterisation, to identify the different microorganism populations and to assess their role in the deterioration of these paintings. The Casa de Fresco dos Sanches Baena is a small semi-underground building constructed in a Palace garden over a well and used as a cool refreshing place by the owners. The frescoes that cover the ceilings (composed of 4 panels) present rich mythological scenes and have other decorative elements, which make them an unusual example of this art form. Unfortunately, due to partial abandonment the paintings are in an advanced state of degradation exhibiting partial detachment of paint layers and mortars, salt efflorescences and abundant biological colonisations (Fig.1).

Titanium aluminide alloys based on the γ-TiAl intermetallic compound are emerging as potential materials for high performance applications on aircraft engines components, aerospace vehicles and automotive engines, owing to their low density, high specific stiffness, excellent strength retention at high temperature and good creep and oxidation resistance. The development of adequate techniques to join γ-TiAl alloys, either to themselves or to other materials, is a key issue regarding the effective use of these alloys. Understanding of the reaction mechanisms that promote bonding is mandatory when optimization of the joining procedure is envisaged.

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

Synthesis of nanostructures has triggered continuous interest in the nanoscience field due to their potential application such as catalysis and biomaterials. Among these systems the possibility of producing nano- microporous surfaces with various controlled structures and pore sizes has increased the interest in the field owing to a better control over the particle's size and location.

Aeroengine components operate under particularly severe conditions, including the combination of both high mechanical stresses and elevated temperatures in chemically aggressive environments. These normal operational requirements will eventually promote both cyclic and time dependent failure mechanisms related with creep-fatigue damages. Therefore, the use of adequate preventive inspection techniques is mandatory in order to maximize safety and reliability levels of these components during service. However, there are some occasional and unpredictable material failures which must be conveniently investigated in order to avoid future hazardous situations. Scanning electron microscopy (SEM) can play a major role in the context of evaluation of failed components, allowing the observation of fracture surfaces and other material's features which are essential to the identification of some particular failure mechanisms.

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

The development of joining processes for TiAl alloys is fundamental to integrate them into functional structures and to widen their application field. Diffusion bonding has become the most reported technique for joining TiAl alloys but have the disadvantage of requiring high temperature stages. Diffusion bonding of TiAl at the 950-1200°C temperature range has been reported to produce defect-free bonds. Çam et al., successfully joined TiAl at 950 °C/30 MPa/3 h and 1000 °C/30 MPa/1 h, however, the bond interfaces were clearly visible.

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