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 characterization of the borate mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O – implications for the molecular structure.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Graça, Leonardo MartinsWe have studied the mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O using electron microscopy and vibrational spectroscopy. Both tetrahedral and trigonal boron units are observed. The nominal resolution of the Raman spectrometer is of the order of 2 cm^-1 and as such is sufficient enough to identify separate bands for the stretching bands of the two boron isotopes. The Raman band at 1039 cm^-1 is assigned to BO stretching vibration. Raman bands at 1144, 1157, 1229, 1318 cm^-1 are attributed to the BOH in-plane bending modes. Raman bands at 825 and 925 cm^-1 are attributed to the antisymmetric stretching modes of tetrahedral boron. The sharp Raman peak at 925 cm^-1 is from the 11-B component such a mode, then it should have a smaller 10-B satellite near (1.03) x (925) = 952 cm^-1, and indeed a small peak at 955 is observed. Four sharp Raman bands observed at 3371, 3507, 3563 and 3632 cm^-1 are attributed to the stretching vibrations of hydroxyl units. The broad Raman bands at 3076, 3138, 3255, 3384 and 3551 cm^-1 are assigned to water stretching vibrations. Infrared bands at 3367, 3505, 3559 and 3631 cm^-1 are assigned to the stretching vibration of the hydroxyl units. Broad infrared bands at 3072 and 3254 cm^-1 are assigned to water stretching vibrations. Infrared bands at 1318, 1349, 1371, 1383 cm^-1 are assigned to the antisymmetric stretching vibrations of trigonal boron.Item Vibrational spectroscopic characterization of the phosphate mineral phosphophyllite – Zn2Fe(PO4)2 4H2O, from Hagendorf Süd, Germany and in comparison with other zinc phosphates.(2013) Cipriano, Ricardo Augusto Scholz; Frost, Ray Leslie; Xi, Yunfei; Graça, Leonardo Martins; Lagoeiro, Leonardo Evangelista; López, AndrésThis research was undertaken on phosphophyllite sample from the Hagendorf Süd pegmatite, Bavaria, Germany. Chemical analysis was carried out by Scanning Electron Microscope in the EDS mode and indicates a zinc and iron phosphate with partial substitution of manganese, which partially replaced iron. The calculated chemical formula of the studied sample was determined to be: Zn2(Fe0.65, Mn0.35)P1.00(PO4)2- .4(H2O). The intense Raman peak at 995 cm^-11 is assigned to the m1 PO4^3- symmetric stretching mode and the two Raman bands at 1073 and 1135 cm^-1 to the m3 PO4^3- antisymmetric stretching modes. The m4 PO4^3- bending modes are observed at 505, 571, 592 and 653 cm^-1 and the m2 PO4^3- bending mode at 415 cm^-1. The sharp Raman band at 3567 cm^-1 attributed to the stretching vibration of OH units brings into question the actual formula of phosphophyllite. Vibrational spectroscopy enables an assessment of the molecular structure of phosphophyllite to be assessed.Item A vibrational spectroscopic study of the silicate mineral lomonosovite Na5Ti2(Si2O7)(PO4)O2.(2014) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Graça, Leonardo Martins; Cipriano, Ricardo Augusto ScholzThe mineral lomonosovite has been studied using a combination of scanning electron microscopy with energy dispersive X-ray analysis and vibrational spectroscopy. Qualitative chemical analysis gave Si, P, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and Al. The mineral lomonosovite has a formula Na5Ti2(Si2O7)(PO4)O2. Raman bands observed at 909, 925 and 939 cm^-1 are associated with phosphate units. Raman bands found at 975, 999, 1070, 1080 and 1084 cm^-1 are attributed to siloxane stretching vibrations. The observation of multiple bands in both the phosphate stretching and bending regions supports the concept that the symmetry of the phosphate anion in the structure of lomonosovite is significantly reduced. Infrared spectroscopy identifies bands in the water stretching and bending regions, thus suggesting that water is involved with the structure of lomonosovite either through adsorption on the surface or by bonding to the phosphate units.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 A vibrational spectroscopic study of the borate mineral takedaite Ca3(BO3)2.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Graça, Leonardo Martins; Cipriano, Ricardo Augusto ScholzWe have studied the mineral takedaite Ca3(BO3)2, a borate mineral of calcium using SEM with EDX and vibrational spectroscopy. Chemical analysis shows a homogeneous phase, composed of Ca. Boron was not detected. A very intense Raman band at 1087 cm^-1 is assigned to the BO stretching vibration of BO3 units. Additional Raman bands may be due to isotopic splitting. In the infrared spectrum, bands at 1218 cm^-1 and at 1163, 1262 and 1295 cm^-1 are assigned to the trigonal borate stretching modes. Raman bands at 712 and 715 cm^-1 are assigned to the in-plane bending modes of the BO3 units. Vibrational spectroscopy enables aspects of the molecular structure of takedaite to be assessed.