Characterisation of phases in nanostructured, multilayered titanium alloys by analytical and high-resolution electron microscopy.

Surface processing of a Ti-6Al-4V alloy led to a complex multilayered microstructure containing several phases of the Ni-Ti-P-Al-O system, which improves the mechanical and tribological surface properties. The microstructure, chemical and phase compositions of the hard layer formed on the surface were investigated by LM, XRD, SEM as well as analytical/high-resolution TEM, STEM, EDS, electron diffraction and FIB. Phase identification based on electron diffraction, HRTEM and EDS microanalysis revealed the presence of several binary and ternary phases in the system Ti-Ni-P, sometimes with partial substitution of Ti by Al. However some phases, mainly nanoparticles, still remain not identified satisfactorily. Electron microscopy techniques used for identification of phases present in surface multilayers and some practical limits to their routine application are reminded here.

Analytical transmission electron microscopy and electron diffraction for characterization of multiphase Ni-P-Ti surface layer on Ti-6Al-4V alloy.

The microstructure, chemical and phase composition of the hard Ni-P-Ti layer formed on the Ti-6Al-4V alloy after duplex surface treatment were investigated by light microscopy, X-ray diffraction, scanning electron microscopy and analytical/high-resolution transmission electron microscopy. These investigations showed that the improved mechanical and tribological properties of the surface-treated alloy were related to the presence of a multilayered microstructure containing several phases from the Ni-Ti-P-Al system.

Electron diffraction and high resolution transmission electron microscopy in the characterization of calcium phosphate precipitation from aqueous solutions under biomineralization conditions.

Calcium phosphate precipitation obtained from aqueous solutions at room and body temperature and pH 5.5-7.5 were investigated by high-resolution transmission electron microscopy (HRTEM), transmission electron diffraction, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Supersaturated solutions of calcium phosphates were prepared by different methods of mixing of the stock solutions: diffusion-controlled mixing in space, convection-controlled mixing on earth and forced mixing on earth and with typical physiological parameters (pH and temperature). Concentrations of the stock solutions, rate of solution mixing and duration of precipitation influence very strongly the chemical composition of the precipitation, the phase composition of individual crystals, their sizes, morphology and structure. Microdiffraction and HRTEM techniques showed an incontestable advantage on other techniques like SEM and XRD in the investigation of small particles and mixtures of calcium phosphates (hydroxyapatite and octacalcium phosphate) with different proportions.

Crystallographic orientation assessment by electron backscattered diffraction.

With an angular orientation accuracy of at least 1 , the ability of electron backscattered diffraction (EBSD) to determine and emphasise crystallographic orientation is illustrated. Using the abilities of specially developed software for computing Euler angles derived from the scanned specimen, misorientations are pointed out with acceptable flexibility and graphic output through crystallographic orientation maps or pole figures. This ability is displayed in the particular case of laser cladding of nickel-based superalloy, a process that combines the advantages of a near net-shape manufacturing and a close control of the solidification microstructure (E-LMF: epitaxial laser metal forming).

Urinary fibres in occupational exposure to asbestos.

Urine samples from 10 workers from an asbestos cement factory and from a control group of 10 workers from a foundry, were obtained; drastic precautions were taken to avoid contamination. Each urinary mineral fibre was sized and identified by transmission electron microscopy. Results show that contamination problems encountered by other authors have been overcome and that the workers exposed to chrysotile appear to excrete more chrysotile fibres, but that this difference is not statistically significant. Possibly only a few of the exposed workers are significantly exposed to asbestos, the overall exposure level being very low. The degradability of chrysotile fibres in biological fluids or the retention of fibres in some organ could explain the lack of apparent correlation between exposure and urinary concentration. Unexpectedly high concentrations of crocidolite fibres of unknown origin were detected in both groups of workers.