masterThesis
Síntese e caracterização do Ca3Co4O9 como material termoelétrico
Fecha
2019-02-27Registro en:
EMERENCIANO, Aline Alencar. Síntese e caracterização do Ca3Co4O9 como material termoelétrico. 2019. 70f. Dissertação (Mestrado em Ciência e Engenharia de Materiais) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2019.
Autor
Emerenciano, Aline Alencar
Resumen
Faced with the requirement for cleaner and higher energy efficiency technologies, we have
noticed a significant focus on the research of thermoelectric materials, capable of converting
thermal energy into electric energy. The Ca3Co4O9 metal oxide is a great alternative, since its
specific properties added to the improvement of its microstructure allow the production of a
compound with considerable thermoelectric characteristics in relation to others reported in the
literature. The stable phase Ca 3 Co 4 O 9, present in a very restricted range in the CaO-CoO
phase diagram, can be obtained by controlling the composition and the temperature. In order to
improve the production of calcium cobalt (C349) three different synthesis techniques were
implemented in this project followed by thermal treatment (precalcination at 350 ° C / 2h,
calcination at 900 ° C / 2h and sintering at 900 / 24h) . The synthesis by the amorphous citrate
method without the use of dispersant, the synthesis by the Sol gel protein method and the
synthesis by Solid State Reaction (with mechanical activation by high energy grinding) using
CaCO3 from shellfish, which reinforces the motivation environmental protection. In all
samples, the subsystem [Ca2CoO3-δ] q [CoO2] was identified, identified by Rietveld
refinement X-ray diffraction; the secondary Ca3Co2O6 phase was present in samples from the
Citrate method. Its microstructures were analyzed by Scanning Mode Scanning Electron
Microscopy (STEM) and Energy Scattering X-ray Spectroscopy (EDS) and the electrical
characterization was evaluated by measurements of Seebeck Coefficient, electrical conductivity
and Power Factor. The microstructures of the sintered samples presented grains in the form of
plates with dimensions in micro and nanometric scales. In the three different methods, with
relative densities around 66%, the highest value of the Power Factor at 700 ° C (0.21 mW /
mK2) was obtained for the sample synthesized by the Sol-gel Proteic method.