Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:09Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:25Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-06-20T14:23:37Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) / Made available in DSpace on 2018-06-20T14:23:37Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Paola- Dissertacao.pdf: 1239637 bytes, checksum: 85c1de7a05b461f7f506a5ad3652d878 (MD5) Previous issue date: 2018-05-18 / The study of the Half-Heusler alloy has drawn a lot of attention among the researchers due to their characteristics and applications, in general, to characterize as ferromagnetic alloys, constituted by non-magnetic elements. In this research, the TiNiSn alloy was produced by the Mechanical Alloyng in two routes, the first in 3h with analysis done at each hour, and the second at 4h straight. The structure and its thermal behavior were investigated by the following techniques: X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermal Treatment (TT) and Rietveld refinement. According to results obtained, respectively, it was seen that the TiNiSn alloy was produced in 4h grinding by the mechanical alloying method, its diffractograms were verified in order to discover the phases formed in the synthesized alloy in 4h, and by the analysis of differential calorimetry of scanning was seen the thermal behavior of the sample at varied temperatures in a temperature range of 30 °C and 500 °C, so it was possible to analyze the sample by the Thermal Treatment technique. / O estudo da liga Half-Heusler tem chamado muita atenção entres os pesquisadores devido as suas características e aplicações, de uma maneira geral, por caracterizarem-se como ligas ferromagnéticas, constituídas por elementos não magnéticos. Neste trabalho foi produzida e a liga TiNiSn, do tipo Half-Heusler, a fim de analisar sua estrutura. Nesta pesquisa, a liga TiNiSn foi produzida pela técnica de Moagem Mecânica de Alta Energia em dois tempos de moagem, a primeira em 3h com análise feita a cada uma hora, e a segunda em 4h sem pausas. A estrutura e seu comportamento térmico foram investigados pelas seguintes técnicas: Difração de raios X (DRX), Calorimetria Diferencial de Varredura (DSC), Tratamento Térmico (TT) e método de refinamento estrutural de Rietveld (MR). De acordo com os resultados obtidos, respectivamente, foi visto que a liga TiNiSn foi produzida em 4 h de moagem pelo método de mechanical alloying, seus difratogramas foram verificados afim de descobrir as fases formadas na liga sintetizada em 4 h, e pela análise de calorimetria diferencial de varredura (DSC) foi visto o comportamento térmico da amostra em temperaturas variadas, em uma faixa de 30 °C à 500 °C, subsequentemente, foi possível analisar a amostra pela técnica de tratamento térmico.

Thermoelectric (TE) ZrNiSn samples with a half-Heusler atomic structure were synthesized by mechanical alloying (MA) and consolidation by either Spark Plasma Sintering (SPS) or hot pressing (HP). X-Ray diffraction patterns of as milled powders and consolidated samples were compared and analyzed for phase purity. Thermal conductivity, electrical conductivity and Seebeck coefficient are measured as a function of temperature in the range 300 K to 800 K and compared with measurements reported for high temperature solid state reaction synthesis of this compound. HP samples, compared to SPS samples, demonstrate increased grain growth due to longer heating times. Reduced grain size achieved by MA and SPS causes increased phonon scattering due to the increased number of grain boundaries, which lowers the thermal conductivity without doping the base system with addition phonon scattering centers. Mechanical characterization of the samples by microindentation and depth sensing indentation for hardness and elastic modulus will be discussed.