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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10 resultados
Resultados da Pesquisa
Item The application of high-temperature X-ray diffraction and infrared emission spectroscopy to the thermal decomposition of krohnkite.(2016) Testasicca, Leonardo Pena; Frost, Ray Leslie; Ruan, Xiuxiu; Lim, Jéssica; Belotti, Fernanda Maria; Cipriano, Ricardo Augusto ScholzHigh-temperature X-ray diffraction and infrared emission spectroscopy have been applied to measure the thermal stability of the sulphate mineral kro¨hnkite Na2Cu(SO4)2 2H2O. Kro¨hnkite shows a low thermal stability. The mineral decomposes into a complex mixture of sulphates below 500 C and sulphides below 650 C, before melting. Broad emission infrared bands at 3350 and 3105 cm-1 are assigned to the stretching vibration of the water units. The intensity of these two bands decreases as the temperature is raised. The intensity of these bands is lost by 250 C. The sharp IES band at 992 cm-1 is assigned to the m1 SO4 2- symmetric stretching vibration. Intensity in this band is lost by 200 C. New IES bands are noted. The important aspect of this work is the use of hightemperature X-ray diffraction to determine the thermal decomposition of a mineral, in this case krohnkite.Item Raman and infrared spectroscopic characterization of the arsenate-bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, AndrésTheminerals clinotyrolite and fuxiaotuite are discredited in terms of the mineral tangdanite. Themixed anionmineral tangdanite Ca2Cu9(AsO4)4(SO4)0.5(OH)9 9H2O has been studied using a combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. These bands are assigned to water and hydroxyl stretching vibrations. Two intense Raman bands at 837 and approximately 734 cm 1 are assigned to the ν1 (AsO4)3 symmetric stretching and ν3 (AsO4)3 antisymmetric stretching modes. Infrared bands at 1023 cm 1 are assigned to the (SO4)2 ν1 symmetric stretching mode, and infrared bands at 1052, 1110 and 1132 cm 1 assigned to (SO4)2 ν3 antisymmetric stretching modes, confirming the presence of the sulphate anion in the tangdanite structure. Raman bands at 593 and 628 cm 1 are attributed to the (SO4)2 ν4 bending modes. Low-intensity Raman bands found at 457 and 472cm 1 are assigned to the (AsO4)3 ν2 bending modes. A comparison is made with the previously obtained spectral data on the discredited mineral clinotyrolite.Item SEM, EDX and Raman and infrared spectroscopic study of brianyoungite Zn3(CO3,SO4)(OH)4 from Esperanza Mine, Laurion District, Greece.(2015) Frost, Ray Leslie; López, Andrés; Wang, Lina; Cipriano, Ricardo Augusto Scholz; Sampaio, Ney PinheiroThe mineral brianyoungite, a carbonate–sulphate of zinc, has been studied by scanning electron microscopy (SEM) with chemical analysis using energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the brianyoungite structure. Intense Raman band at 1056 cm_1 with shoulder band at 1038 cm_1 is assigned to the CO32_ m1 symmetric stretching mode. Two intense Raman bands at 973 and 984 cm_1 are assigned to the symmetric stretching modes of the SO4 2_ anion. The observation of two bands supports the concept of the non-equivalence of sulphate units in the brianyoungite structure. Raman bands at 704 and 736 cm_1 are assigned to the CO32_ m4 bending modes and Raman bands at 507, 528, 609 and 638 cm_1 are assigned to the CO32_ m2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water and hydroxyl units in different molecular environments in the structure of brianyoungite. Vibrational spectroscopy enhances our knowledge of the molecular structure of brianyoungite.Item A Raman and infrared spectroscopic study of the sulphate mineral aluminite Al2(SO4)(OH)4 7H2O.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Wang, LinaThe mineral aluminite has been studied using a number of techniques, including scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a low intensity band at 1069 cm 1 which may be attributed to a carbonate symmetric stretching mode, indicating the presence of thaumasite. The observation of multiple bands in this m4 spectral region offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3588 cm 1 is assigned to the OH unit stretching vibration and the broad feature at around 3439 cm 1 to water stretching bands. Water stretching vibrations are observed at 3157, 3294, 3378 and 3439 cm 1. Vibrational spectroscopy enables an assessment of the molecular structure of aluminite to be made.Item Vibrational spectroscopic study of the sulphate mineral glaucocerinite (Zn,Cu)10Al6(SO4)3(OH)32-18H2O - a natural layered double hydroxide.(2014) Frost, Ray Leslie; Theiss, Frederick L.; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have studied the molecular structure of the mineral glaucocerinite (Zn,Cu)5Al3(SO4)1.5(OH)16_9(H2O) using a combination of Raman and infrared spectroscopy. The mineral is one of the hydrotalcite supergroup of natural layered double hydroxides. The Raman spectrum is characterised by an intense Raman band at 982 cm_1 with a low intensity band at 1083 cm_1. These bands are attributed to the sulphate symmetric and antisymmetric stretching mode. The infrared spectrum is quite broad with a peak at 1020 cm_1. A series of Raman bands at 546, 584, 602, 625 and 651 cm_1 are assigned to the m4 (SO4)2_ bending modes. The observation of multiple bands provides evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 762 cm_1 is attributed to a hydroxyl deformation mode associated with AlOH units. Vibrational spectroscopy enables aspects of the molecular structure of glaucocerinite to be determined.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.