Show simple item record

dc.contributor.advisorUwakweh, Oswald
dc.contributor.authorCardona-Quintero, Yenny P.
dc.date.accessioned2019-04-15T17:19:20Z
dc.date.available2019-04-15T17:19:20Z
dc.date.issued2009
dc.identifier.urihttps://hdl.handle.net/handle/20.500.11801/2053
dc.description.abstractThe study of 5 at.% MeB2 doped MgB2 (Me = Ta, Ti, Nb and Cr) was carried out using the High Energy Ball Milling (HEBM) technique and Hot Isostatic Press (HIP) process. Each compound was milled separately for 120 min and then they were mixed and milled at 60 min, 120 min, 180 min, 300 min and 600 min. The milled materials were HIPed at 1000°C and 30,000 psi for 24 hours. Both powder and HIPed materials were characterized in the structural properties with X- ray diffraction (XRD); crystallite size, strain, composition and lattice parameter were determined with this technique. The superconducting properties were carried out on the HIPed material with the use of the physical property measurement system (PPMS); critical temperature (Tc), critical magnetic field (Hc2), connectivity and electron scattering were found. In the structural properties of the powder materials, as the milling time increased, reduction in crystallite sizes and increase in strain was observed. Additionally, decomposition of MgB2 in Mg and B elements occurred. Moreover, with the HIP process the increase in crystallite sizes, the decrease in strain and the reorganization of the structure was determined. In the superconducting properties, the MgB2 – 5 at.% TaB2 material had the highest Hc2 (25 K) value at 180 min of milling time with 7.539 T, while the Tc for the same sample was 38.48 K. These results showed that with TaB2 at 5 at.% material, it is possible to increase Hc2 without decreasing Tc in MgB2. However, the MgB2 – 5 at.% CrB2 material showed a decreased in Hc2 and Tc for all milling times, which suggests that CrB2 is not a good dopant material for MgB2. The residual resistivity ratio (RRR) is an indicator of the electron scattering; RRR decreased with the increase in electron scattering approaching to 1 for very high defect concentration. In this research the RRR parameter decreased with the increasing in milling time, while the Hc2 property increased with the increase in RRR.en_US
dc.description.abstractSe llevó a cabo el estudio del dopaje de MgB2 con 5 % at. de MeB2 (Me = Ta, Ti, Nb and Cr) usando la técnica de molienda por alto impacto (HEBM). Cada compuesto fue molido individualmente por 120 min y posteriormente el material base y el dopante fueron mezclados y molidos por 60, 120, 180, 300 y 600 min. Los materiales molidos fueron sinterizados usando el proceso de presión isostática bajo tratamiento térmico (HIP) a 1000°C y 30000 psi por 24 horas. Las propiedades estructurales tamaño de cristal, strain, composición y parámetros de red fueron determinadas al material en polvo y al material sinterizado con la técnica de difracción de rayos- X (XRD) , mientras las propiedades superconductoras temperatura critica (Tc), campo magnético critico (Hc2), conectividad y dispersión electrónica fueron halladas usando un sistema de medida de propiedades físicas (PPMS). Los resultados muestran que al incrementar el tiempo de molienda se genera una reducción en el tamaño de partícula y un aumento en el strain, y ocurre además la disociación de MgB2 en Mg y B. Además, con el proceso de HIP el tamaño de cristal aumenta, el strain disminuye y se produce la reorganización de la estructura. El material MgB2 dopados a 5 % at. con TaB2 tuvo el mayor valor en Hc2 (25 K) con 7.539 T, para 180 min de tiempo de molienda, mientras Tc para la misma muestra tuvo un valor de 38.48 K. Estos resultados demuestran que con el dopaje de MgB2 con TaB2 al 5 % at. es posible incrementar Hc2 sin que se dé la disminución de Tc. Por otra parte, el compuesto MgB2 dopado con CrB2 al 5 % at. mostró una disminución en Hc2 y Tc para todos los tiempos de molienda, lo cual sugiere que CrB2 no es un buen dopante para MgB2. La razón de la resistividad residual (RRR) es un indicador de la dispersión electrónica, RRR decrece con el incremento en la dispersión electrónica aproximándose a 1 para grandes defectos de concentración. En esta investigación el parámetro RRR decrece con el incremento en el tiempo de molienda, mientras Hc2 incrementa con el aumento en RRR.en_US
dc.description.sponsorshipFlorida State University, to National High Magnetic Field Laboratory and the Applied Superconductivity Center. Synergistic Partnership for Research and Education on Functional and Nanostructured Materials (PREM), National Science Foundation (NSF) Award number 0351449 and Focused Research Group on Magnesium Diboride (FRG): two-gap superconductivity in magnesium diboride and its implications for applications, DMR- 0514592, for the support and for this opportunityen_US
dc.language.isoEnglishen_US
dc.titleMgB2 superconductor doped with different boride compounds by high energy ball millingen_US
dc.typeThesisen_US
dc.rights.licenseAll rights reserveden_US
dc.rights.holder(c) 2009 Yenny P. Cardona-Quinteroen_US
dc.contributor.committeeRadovan, Henri
dc.contributor.committeeKim, Yong-Jihm
dc.contributor.committeeHellstrom, Eric E.
dc.contributor.representativeSharma, Anand D.
thesis.degree.levelM.S.en_US
thesis.degree.disciplinePhysicsen_US
dc.contributor.collegeCollege of Arts and Science - Scienceen_US
dc.contributor.departmentDepartment of Physicsen_US
dc.description.graduationYear2009en_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

  • Theses & Dissertations
    Items included under this collection are theses, dissertations, and project reports submitted as a requirement for completing a degree at UPR-Mayagüez.

Show simple item record

All rights reserved
Except where otherwise noted, this item's license is described as All Rights Reserved