C Pareige | PubMed Health

PubMed2001

Imaging the three orientation variants of the DO22 phase by 3D atom probe microscopy.

Three-phase NiAlV alloys were investigated using a three-dimensional atom probe. Ageing at 800 degrees C gives rise to the precipitation of two ordered phases within the supersaturated FCC solid solution, namely Ni3Al (L1(2) structure) and Ni3V (DO22 structure). The DO22 phase has three orientation variants which need to be identified in 3DAP images. It is shown that an appropriate choice of analysis site enables us to image the chemical order within both L1(2) and DO22 ordered phases and to distinguish the three orientation variants of the DO22 phase in reconstructed images. The lateral resolution of 3DAP in these experimental conditions was estimated through simple considerations to be less than 0.3 nm.

Journal Article↗

PubMed1999

Tomographic Atom Probe: New Dimension in Materials Analysis.

: Materials science requires the use of increasingly powerful tools in materials analysis. The last 20 years have witnessed the development of a number of analytical techniques. However, among these techniques, only a few allow observation and analysis of materials at the nanometer level. The tomographic atom probe (TAP) is a three-dimensional atom-probe (3-DAP) developed at the University of Rouen. In this instrument, the specimen is field evaporated, atomic layer by atomic layer, and the use of a position-sensing system makes it possible to map out the chemical identity of individual atoms within each field-evaporated layer on a nearly atomic scale. After analysis, the volume of matter removed from the specimen can be reconstructed atom by atom in the three dimensions of real space. The main advantages of the 3-DAP is its single-atom sensitivity and very high spatial resolution. In addition to 3-D visual information on chemical heterogeneity, 3-D images give an accurate measurement of the composition of any feature without any convolution bias. This study first describes the history of the 3-DAP technique. Its main features and the latest developments of the TAP are then detailed. The performance of this instrument is illustrated through two recent applications in materials science. Possible ways to further improve the technique are also discussed.

Journal Article↗