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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3 resultados
Resultados da Pesquisa
Item Infrared and Raman spectroscopic characterization of the carbonate mineral huanghoite - and in comparison with selected rare earth carbonates.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Belotti, Fernanda MariaRaman spectroscopy complimented with infrared spectroscopy has been used to study the rare earth based mineral huanghoite with possible formula given as BaCe(CO3)2F and compared with the Raman spectra of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of huanghoite displays three bands are at 1072, 1084 and 1091 cm^-1 attributed to the (CO3)^2- symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of (CO3)^2- symmetric stretching vibration varies with mineral composition. Infrared spectroscopy of huanghoite show bands at 1319, 1382, 1422 and 1470 1091 cm^-1. No Raman bands of huanghoite were observed in these positions. Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554 1091 cm^-1 assigned to the m3 (CO3)^2- antisymmetric stretching mode. The observation of additional Raman bands for the m3 modes for some halogenated carbonates is significant in that it shows distortion of the carbonate anion in the mineral structure. Four Raman bands for huanghoite are observed at 687, 704, 718 and 730 1091 cm^-1 and assigned to the (CO3)^2- m2 bending modes. Raman bands are observed for huanghoite at around 627 1091 cm^-1 and are assigned to the (CO3)^2- m4 bending modes. Raman bands are observed for the carbonate m4 in phase bending modes at 722 1091 cm^-1 for bastnasite, 736 and 684 1091 cm^-1 for parisite, 714 1091 cm^-1 for northupite. Raman bands for huanghoite observed at 3259, 3484 and 3589 1091 cm^-1 are attributed to water stretching bands. Multiple bands are observed in the OH stretching region for bastnasite and parisite indicating the presence of water and OH units in their mineral structure. Vibrational spectroscopy enables new information on the structure of huanghoite to be assessed.Item Infrared and Raman spectroscopic characterization of the carbonate mineral weloganite - Sr3Na2Zr(CO3)6 3H2O and in comparison with selected carbonates.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, MauroThe mineral weloganite Na2Sr3Zr(CO3)6_3H2O has been studied by using vibrational spectroscopy and a comparison is made with the spectra of weloganite with other carbonate minerals. Weloganite is member of the mckelveyite group that includes donnayite-(Y) and mckelveyite-(Y). The Raman spectrum of weloganite is characterized by an intense band at 1082 cm_1 with shoulder bands at 1061 and 1073 cm_1, attributed to the CO2_ 3 symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of CO2_ 3 symmetric stretching vibration varies with mineral composition. The Raman bands at 1350, 1371, 1385, 1417, 1526, 1546, and 1563 cm_1 are assigned to the m3 (CO3)2_ antisymmetric stretching mode. The observation of additional Raman bands for the m3 modes for weloganite is significant in that it shows distortion of the carbonate anion in the mineral structure. The Raman band observed at 870 cm_1 is assigned to the (CO3)2_ m2 bending mode. Raman bands observed for weloganite at 679, 682, 696, 728, 736, 749, and 762 cm_1 are assigned to the (CO3)2_ m4 bending modes. A comparison of the vibrational spectra is made with that of the rare earth carbonates decrespignyite, bastnasite, hydroxybastnasite, parisite, and northupite.Item Infrared and Raman spectroscopic characterization of the silicate-carbonate mineral carletonite - KNa4Ca4Si8O18(CO3)4(OH,F) H2O.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda MariaAn assessment of the molecular structure of carletonite a rare phyllosilicate mineral with general chemical formula given as KNa4Ca4Si8O18(CO3)4(OH,F).H2O has been undertaken using vibrational spectroscopy. Carletonite has a complex layered structure. Within one period of c, it contains a silicate layer of composition NaKSi8O18 H2O, a carbonate layer of composition NaCO3 0.5H2O and two carbonate layers of composition NaCa2CO3(F,OH)0.5. Raman bands are observed at 1066, 1075 and 1086 cm 1. Whether these bands are due to the CO2 3 m1 symmetric stretching mode or to an SiO stretching vibration is open to question. Multiple bands are observed in the 300–800 cm 1 spectral region, making the attribution of these bands difficult. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate and carbonate surfaces.