Caracteriza????o estrutural, t??rmica e ??ptica da liga nanoestruturada snse2 produzida por Mechanical alloying

Submitted by Kamila Costa (kamilavasconceloscosta@gmail.com) on 2015-08-06T14:48:56Z No. of bitstreams: 1 Disserta????o - Zeane V Borges.pdf: 2189307 bytes, checksum: 3fce099edb43ceed11ff4ab744e1f3f5 (MD5) Approved for entry into archive by Divis??o de Documenta????o/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-08-07T14:07:07Z (GMT) No. of bitstreams: 1 Disserta????o - Zeane V Borges.pdf: 2189307 bytes, checksum: 3fce099edb43ceed11ff4ab744e1f3f5 (MD5) Approved for entry into archive by Divis??o de Documenta????o/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-08-07T14:08:30Z (GMT) No. of bitstreams: 1 Disserta????o - Zeane V Borges.pdf: 2189307 bytes, checksum: 3fce099edb43ceed11ff4ab744e1f3f5 (MD5) Made available in DSpace on 2015-08-07T14:08:30Z (GMT). No. of bitstreams: 1 Disserta????o - Zeane V Borges.pdf: 2189307 bytes, checksum: 3fce099edb43ceed11ff4ab744e1f3f5 (MD5) Previous issue date: 2015-06-08 FAPEAM - Funda????o de Amparo ?? Pesquisa do Estado do Amazonas The nanostructured SnSe2 alloy was produced by Mechanical Alloying technique and their structural, thermal and optical properties were investigated by x-ray diffraction (XRD) combined with Rietveld Method (RM), differential scanning calorimetry (DSC), absorbance measurements and photoacoustic absorption spectroscopy (PAS). After characterized in the as milled conditions, the sample was annealed at 450??C in order to evaluate the influence of the interfacial component in their physical properties. The XRD measurements allowed structurally characterize the samples, as well quantify the volume fractions occupied by crystalline and interfacial components. The DSC measurements showed that the melting process of SnSe2 phase, occurs in two-step for both samples. The UV???Vis absorption spectrum showed direct allowed transitions for milled and annealed samples, with band gap of 1.02 eV and 1.48 eV, respectively. Moreover, electronic transition of type direct forbidden was found in the sample annealed with optical band gap of 0.94 eV. PAS measurements provided the thermal diffusivity (????????) for both samples. A reduction of 45% in the thermal diffusivity value of milled sample was observed, when compared with the annealed sample. A liga nanoestruturada SnSe2 foi produzida pela t??cnica Mechanical Alloying e suas propriedades estruturais, t??rmicas e ??pticas foram investigadas por difra????o de Raios X (DRX) combinado com o M??todo de Rietveld (MR), calorimetria diferencial de varredura (DSC), medidas de absorb??ncia ??ptica e espectroscopia de absor????o fotoac??stica (PAS). Ap??s caracterizada nas condi????es como mo??da, a amostra foi tratada termicamente na temperatura de 450??C a fim de avaliar, a influ??ncia da componente interfacial nas suas propriedades f??sicas. As medidas de DRX permitiram caracterizar estruturalmente as amostras, bem como quantificar as fra????es volum??tricas ocupadas pelas componentes cristalina e interfacial. Medidas de DSC mostraram que o processo de fus??o da fase SnSe2, ocorre em duas etapas para ambas as amostras. Os espectros de absor????o UV-Vis mostraram transi????es diretas permitidas para as amostras mo??da e tratada termicamente, com energias de band gap de 1.02 eV e 1.48 eV, respectivamente. Al??m disso, transi????o eletr??nica do tipo proibida direta foi encontrada na amostra tratada com energia de band gap de 0.94 eV. Medidas de PAS forneceram o valor da difusividade t??rmica (????) para ambas as amostras. Uma redu????o de aproximadamente 45% no valor da difusividade t??rmica da amostra mo??da, quando comparada com a amostra tratada termicamente, foi observada.