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A common and straightforward method for the standardisation in electron-probe microanalysis (EPMA) is the use of homogeneous reference materials prepared by various techniques such as by melting, sintering, high-temperature annealing and hot-pressing. The reference materials have to be analysed by independent methods accurately in order to define their “true” composition. For some compounds the preparation techniques are difficult because of their specific thermo-chemical properties (e.g. low diffusivities, high equilibrium nitrogen pressure, incongruent melting). In addition, many compounds show large homogeneity ranges with an a priori existing uncertainty in composition, contrary to what is generally preferred: to use compounds with a narrow homogeneity range (“line compounds”). For the latter, diffusional preparation techniques can be applied to yield diffusion layers instead of massive samples for standardisation. However, also single-phase samples with narrow homogeneity ranges can be prepared by diffusion, depending on the phase equilibria in the corresponding system. The presentation summarises efforts that have been made in order to prepare various reference materials for carbon and nitrogen standardisation of EPMA by various techniques. The boundary conditions such as phase stabilities, phase compositions and diffusion kinetics, which are important for their preparation to obtain well-defined reference samples are discussed. These samples were applied to various WDS/EPMA-based studies of phase diagrams and diffusion kinetics by means of Cameca SX 50 and SX 100 microprobes.

Abstract: The Antique ophiolite, located in Panay island (west‐central Philippines), corresponds to several tectonic slices within the suture zone between the Philippine Mobile Belt (PMB) and the North Palawan Block (NPB). It includes dismembered fragments of a basaltic sequence, dominantly pillow‐lavas with minor sheet flows, rare exposures of sheeted dikes, isotropic gabbros, subordinate layered mafic and ultramafic rock sequences and serpentinites. Most of the ophiolite units commonly occur as clasts and blocks within the serpentinites, which intrude the whole ophiolitic body, as well as, the basal conglomerate of the overlying Middle Miocene sedimentary formation.

Abstract.:  WDS-EPMA and GDOES measurements were applied for the characterization of the in-situ surface modification process of (Ti, W)C-based hardmetals by in-diffusion of carbon and nitrogen leading to complicated microstructures composed by layers and/or gradients. The calibration of the analytical techniques was performed with chemically characterized specimens prepared by diffusional techniques or hot-pressing. In addition, for the GDOES method, certified reference materials (CRMs) have been used. The work was started from a re-investigation of the W-C and Mo-C systems in order to measure homogeneity regions of the various phases prepared by use of diffusion couples. Subsequently, the metal and non-metal contents of various sequences of layers and/or gradients in functional-gradient hardmetals (FGHs) were measured. Both methods were employed as complementary tools to get information about the element-concentration distribution in FGHs so that a better understanding of the influence of process parameters for fabrication of special hardmetals is possible.

Abstract: Phase relations in the ternary system N-Ni-Ti have been established experimentally for the 900 °C isothermal section assisted by thermodynamic modeling. Phase equilibria are characterized by an appreciable amount of up to ≅11 at. % N dissolved in the octahedral interstices of the crystal structure of Ti2Ni. Two-phase equilibria are formed at 900 °C among the pairs Ti2N + Ti2NiNx, TiN1-x + Ti2NiNx, TiN1-x + TiNi1-x, and TiN1-x + Ni(Ti)x. The investigation is based on X-ray powder diffraction, metallography, scanning electron microscopy, and electron probe microanalysis techniques on about 50 alloys, which were prepared by arc melting or high-frequency levitation melting of appropriate blends of Ti,Ni-powders with TiN used to introduce nitrogen. Key experiments related to the N solubility in the Ti2Ni phase have been triggered by an interactively performed thermodynamic modeling. The experimental results are in fine agreement with the thermodynamic calculation.