EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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5 resultados
Resultados da Pesquisa
Item Infrared and Raman spectroscopic characterisation of the sulphate mineral creedite - Ca3Al2SO4(F,OH) 2H2O - and in comparison with the alums.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Granja, AmandaThe mineral creedite is afluorinatedhydroxy hydrated sulphate of alumini um and calcium of formula Ca3Al2SO4(F,OH) _2H2O. The mineral has been studied by acombination of electron probe analysis to determine the molecular formula of the mineral and the structure assessed by vibrational spectroscopy. The spectroscopy of creedite may be compared with that of the alums. The Raman spectrum of creedite is characterised by an intense sharp band at 986 cm _1 assigned to the SO 24 _ m1 (Ag) symmetric stretching mode. Multiple bands of creedite in the antisymmetric stretching region support the concept of areduc- tion in symmetry of the sulphate anion. Multiple ban ds are also observed in the bending region with the three bands at 601, 629 and 663 cm _1 assigned to the SO 24 _ m4 (Ag) bending modes. The observation of multiple bands at 440, 457 and 483 cm _1 attributed to the SO 24 _ m2 (Bg) bending modes supports the con- cept that the symmetry of the sulphate is reduced by coordination to the water bonded to the Al 3+ in the creedite structure. The splitting of the m2, m3 and m4 modes is attributed to the reduction of symmetry of the SO 4 and it is proposed that the sulphate coordinates to water in the hydrated aluminium in bidentate chelation.Item Characterization of the sulphate mineral amarantite - using infrared, Raman spectroscopy and thermogravimetry.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Silveira, Aléssio Jordan da; Lima, Rosa Malena FernandesThe mineral amarantite Fe3þ 2 (SO4)O _ 7H2O has been studied using a combination of techniques including thermogravimetry, electron probe analyses and vibrational spectroscopy. Thermal analysis shows decomposition steps at 77.63, 192.2, 550 and 641.4 _C. The Raman spectrum of amarantite is dominated by an intense band at 1017 cm_1 assigned to the SO2_ 4 m1 symmetric stretching mode. Raman bands at 1039, 1054, 1098, 1131, 1195 and 1233 cm_1 are attributed to the SO2_ 4 m3 antisymmetric stretching modes. Very intense Raman band is observed at 409 cm_1 with shoulder bands at 399, 451 and 491 cm_1 are assigned to the m2 bending modes. A series of low intensity Raman bands are found at 543, 602, 622 and 650 cm_1 are assigned to the m4 bending modes. A very sharp Raman band at 3529 cm_1 is assigned to the stretching vibration of OH units. A series of Raman bands observed at 3025, 3089, 3227, 3340, 3401 and 3480 cm_1 are assigned to water bands. Vibrational spectroscopy enables aspects of the molecular structure of the mineral amarantite to be ascertained.Item Vibrational spectroscopic characterization of the sulphate mineral khademite Al(SO4)F-5(H2O).(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, YunfeiVibrational spectroscopy has been used to characterize the sulphate mineral khademite Al(SO4)F_5(H2O). Raman band at 991 cm^-1 with a shoulder at 975 cm^-1 is assigned to the m1 (SO4)2_ symmetric stretching mode. The observation of two symmetric stretching modes suggests that the sulphate units are not equivalent. Two low intensity Raman bands at 1104 and 1132 cm^-1 are assigned to the m3 (SO4)2_ antisymmetric stretching mode. The broad Raman band at 618 cm^-1 is assigned to the m4 (SO4)2_ bending modes. Raman bands at 455, 505 and 534 cm_1 are attributable to the doubly degenerate m2 (SO4)2_bending modes. Raman bands at 2991, 3146 and 3380 cm^-1 are assigned to the OH stretching bands of water. Five infrared bands are noted at 2458, 2896, 3203, 3348 and 3489 cm^-1 are also due to water stretching bands. The observation of multiple water stretching vibrations gives credence to the nonequivalence of water units in the khademite structure. Vibrational spectroscopy enables an assessment of the structure of khademite.Item Vibrational spectroscopic characterization of the sulphate mineral leightonite K2Ca2Cu(SO4)4 2H2O : implications for the molecular structure.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Graça, Leonardo Martins; Lagoeiro, Leonardo EvangelistaThe mineral leightonite, a rare sulphate mineral of formula K2Ca2Cu(SO4)4.2H2O, has been studied using a combination of electron probe and vibrational spectroscopy. The mineral is characterized by an intense Raman band at 991 cm^-1 attributed to the SO4^-2 m1 symmetric stretching mode. A series of Raman bands at 1047, 1120, 1137, 1163 and 1177 cm^-1 assigned to the SO4^-2 m3 antisymmetric stretching modes. The observation of multiple bands shows that the symmetry of the sulphate anion is reduced. Multiple Raman and infrared bands in the OH stretching region shows that water in the structure of leightonite is in a range of molecular environments.Item Characterization of the sulphate mineral coquimbite, a secondary iron sulphate from Javier Ortega mine, Lucanas Province, Peru – Using infrared, Raman spectroscopy and thermogravimetry.(2014) Frost, Ray Leslie; Gobac, Željka Žigovečki; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Lana, Cristiano de Carvalho; Lima, Rosa Malena FernandesThe mineral coquimbite has been analysed using a range of techniques including SEM with EDX, thermal analytical techniques and Raman and infrared spectroscopy. The mineral originated from the Javier Ortega mine, Lucanas Province, Peru. The chemical formula was determined as (Fe1.37^3+; Al0.63)Σ2.00(SO4)3. 9H2O. Thermal analysis showed a total mass loss of ~73.4% on heating to 1000 °C. A mass loss of 30.43% at 641.4 °C is attributed to the loss of SO3. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of sulphate tetrahedra, aluminium oxide/hydroxide octahedra, water molecules and hydroxyl ions. The Raman spectrum shows well resolved bands at 2994, 3176, 3327, 3422 and 3580 cm^-1 attributed to water stretching vibrations. Vibrational spectroscopy combined with thermal analysis provides insight into the structure of coquimbite.