Papers by Author: Giovanni Berti

Abstract: The early stage diagnoses of material lattices is becoming a crucial requirement where investigation methods and technologies are faced with both aging of components and materials. The mixing effects of wear, fatigue, temperature variation and environment conditions translate into variations of the atomic flux rate and internal rearrangement of grain size and boundaries of lattices. The related lattice measurements (e.g. the d-.spacing is one important among others) become the only one usable for early stage diagnoses of the lattice structural integrity. When such a diagnoses are the base to identify the qualification of material for the use or the re-qualification for the maintenance in the use, new technologies are required, with methods and appropriate concepts shall be used. The authors bid here to describe shortly the historical evolution of methods and techniques since the 70’s, along with the basic tests performed during the early 90’s of the past century. The technological follow up from those tests is reported along with some results which indicate the significant step up of the most recent technology toward the early stage diagnosis of material via on site x-ray diffraction. Further foreseeable development and advances are also mentioned.

Abstract: Three blocks of silicon have been crashed in this experiment in order to verify the crashing effects on specimens having distinct original micro-structural arrangements. One of them comes from a rod bar of mono-crystal silicon, two others were from polycrystalline silicon manufactured by two distinct manufacturers with distinct growing process. Several specimens of powders, differing in type and grain size, were obtained by treating these source samples. This paper reports on data collected from synchrotron and conventional radiation and the results show that powders obtained from mono-crystalline silicon provide diffraction profiles, where the structural contribution is smaller than for polycrystalline silicon specimens. The peaks from the 'mono-crystal powder' resulted even narrower than peaks from SRM Silicon 640b by NIST.

Abstract: This paper outlines the standardisation process for the XRPD method that is currently being considered by a Working Group (WG10) of Technical Committee 138 "Non-destructive Testing" of the European Committee for Standardisation CEN. Several Standard Documents are on the verge of being released. These documents concern the general principles of (X-ray) diffraction, its terminology, and the basic procedures applied. Another document concerns the instruments used and it offers procedures to characterise and control the performance of an X-ray diffractometer properly. It is intended to issue Standard Documents on specific methods, e.g. determination of residual stresses. In fact work is in progress on this subject. The Standard Documents can be used by industry, government organisations, and research centres with activities related to safety, health and the environment, as well as for educational purposes.

Abstract: Reproducibility of diffraction experiments provides an indication of data consistency with respect to different variables. The level of reproducibility and accuracy of the diffraction measurements is increased when using calibrated instruments. The paper presents most significant results of the 'Calibration Monitoring of Diffractometers', a project using a systematic approach to the Round Robin tests. At the present stage, the results suggest that instrumental performances and other related experimental effects in a diffraction the experiment can be summarised through 'characteristic curves'.