Standardization of experimental procedures for the microstructural and compositional characterization of MgB2 doped with diborides and carbon sources

• Grant number: 13/16604-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2013
• End date: October 31, 2014
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Durval Rodrigues Junior
• Grantee: Guilherme Origo Fulop
• Host Institution: Escola de Engenharia de Lorena (EEL). Universidade de São Paulo (USP). Lorena , SP, Brazil

Abstract

From the practical point of view, the physical, chemical and mechanical properties and characteristics of the materials originate from the crystal structure and the microstructure of phases and defects present in the material. The study of physical and chemical characteristics of the materials is important to define their selection and use in applications. These properties are, mostly, a characteristic of the perfect crystal, while the mechanical properties generally depend on the imperfections which occur in the materials. The internal structures of the materials involve not only atoms, but also the way they collaborate with their neighbors, in crystals, molecules and microstructures.The characterization of the crystalline structure of a material, and also of its microstructure, from the point of view of atomic distribution and compositional distribution, is of utmost importance for the understanding and use of the materials in their possible applications. The introduction of secondary phases and/or doping can lead the materials to present interesting behaviors.The experimental characterizations by X-ray diffraction (XRD) should be carefully performed. The simple fact of not calibrating the goniometers before each measurement can lead to characterizations with errors, which often the researcher try to minimize using a XRD analysis program, such as FullProf or PowderCell. This is not the most appropriate methodology. The simple fact of changing the equipment (moving parts, detectors, X-ray sources, etc.) can significantly alter the results, if the user does not have appropriate care.The present project of Scientific Initiation has the main objective to analyze samples of superconducting MgB2 diborides previously doped with metal diborides and different carbon sources, verifying the effectiveness of doping on the crystal structure and phase formation. The student will perform a complete comparison between the available X-ray diffractometers using samples considered "standards". The analysis and comparison of the diffractograms will be performed by simulating the XRD and refinement of the crystal structures. All this procedure will set analysis methodologies that can be used by all other XRD users. The following work will be carried out through the preparation and microstructural characterization of samples in SEM, and compositional characterization using EDS with internal standardization and WDS with external standards. This stage of development will be of great interest because it will define analysis methodologies that will also be available to other users.