Expansão térmica sintonizável do ZrW2O8
AUTOR(ES)
Jadna Catafesta
DATA DE PUBLICAÇÃO
2007
RESUMO
Zirconium tungstate (a-ZrW2O8) exhibits isotropic negative thermal expansion over a wide range of temperature. Under high-pressures this material transforms to a metastable amorphous phase (a-ZrW2O8). a-ZrW2O8 can be fully recovered by annealing the amorphous phase at temperatures slightly above 600oC, at room pressure. The amorphous phase, in principle, should exhibit positive thermal expansion and, with the progressive recrystallization of the amorphous phase, it could be possible to obtain samples with tunable thermal expansion between the characteristic values of the amorphous and crystalline phases. It was exactly this possibility that was studied in this work. Samples of a-ZrW2O8 prepared at 7,7 GPa in a toroidal chamber in the Laboratório de Altas Pressões e Materiais Avançados at the Instituto de Física, Universidade Federal do Rio Grande do Sul, were submitted to successive heat treatments at different temperatures. X-ray diffraction measurements were performed in order to verify the occurrence of the phase transition (amorphous -->crystalline). The coefficient of thermal expansion of the samples of ZrW2O8 was determined using a thermomechanical analyzer. The results demonstrated the successful obtainment of crystalline-amorphous composites of ZrW2O8 with tunable thermal expansion coefficient between 7.5 x 10-6C-1 and -9 x 10-6C-1.
ASSUNTO(S)
cerâmica tungstato de zircônio materiais cerâmicos expansão térmica negativa expansão térmica
ACESSO AO ARTIGO
http://tede.ucs.br/tde_busca/arquivo.php?codArquivo=76Documentos Relacionados
- Amorfização do ZrW2O8 induzida por altas pressões
- Estrutura e propriedades elásticas das fases alpha e gama do ZrW2O8
- Decomposição térmica de espumas de poliuretano para fabricação de vitrocerâmica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)
- Obtenção do cermet Ni-ZrO2 por moagem de alta energia
- Study of the formation reaction of the turquoise blue ceramic pigment (V-ZrSiO4) FROM SiO2, ZrO2 E V2O5