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 Thermal analysis and infrared emission spectroscopy of the borate mineral colemanite (CaB3O4(OH)3H2O) : implications for thermal stability.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; Ruan, Xiuxiu; Lima, Rosa Malena FernandesColemanite CaB3O4(OH)3H2O is a secondary borate mineral formed from borax and ulexite in evaporate deposits of alkaline lacustrine sediments. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calcium, water and extra hydroxide units interspersed between these chains. We have studied the thermal decomposition of colemanite by using a combination of thermal analysis (TG/DTG) and infrared emission spectroscopy (IES). Thermogravimetric analysis of the colemanite mineral was obtained by using TA Instruments Inc. Q50 high-resolution TGA operating at a 10 C min-1 ramp with data sample interval of 0.50 s pt-1 from room temperature to 1000 C in a high-purity flowing nitrogen atmosphere (100 cm3 min-1 ). Thermogravimetric analysis shows a sharp mass loss at 400.9 C. Only a single mass loss is observed. IES shows a sharp band at 3610 cm-1 assigned to the stretching vibration of hydroxyl units. Intensity in this band is lost by 350 C. A broad spectral feature is observed at 3274 cm-1 attributed to water stretching vibrations. Intensity in this band is lost by 300 C. A combination of thermogravimetry and IES is used to study the thermal stability of the borate mineral colemanite. It is important to characterize the very wide range of borate minerals including colemanite because of the very wide range of applications of boron-containing minerals.Item Vibrational spectroscopy of the borate mineral tunellite SrB6O9(OH)2 3(H2O) - implications for the molecular structure.(2014) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiTunellite is a strontium borate mineral with formula: SrB6O9(OH)2_3(H2O) and occurs as colorless crystals in the monoclinic pyramidal crystal system. An intense Raman band at 994 cm_1 was assigned to the BO stretching vibration of the B2O3 units. Raman bands at 1043, 1063, 1082 and 1113 cm_1 are attributed to the in-plane bending vibrations of trigonal boron. Sharp Raman bands observed at 464, 480, 523, 568 and 639 cm_1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3567 and 3614 cm_1, attributed to OH units. The molecular structure of a natural tunellite has been assessed by using vibrational spectroscopy.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 Infrared and Raman spectroscopic characterization of the borate mineral colemanite CaB3O4(OH)3 H2O - implications for the molecular structure.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, MauroColemanite CaB3O4(OH)3_H2O is a secondary borate mineral formed from borax and ulexite in evaporate deposits of alkaline lacustrine sediments. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calcium, water and extra hydroxide units interspersed between these chains. The Raman spectra of colemanite is characterized by an intense band at 3605 cm_1 assigned to the stretching vibration of OH units and a series of bands at 3182, 3300, 3389 and 3534 cm_1 assigned to water stretching vibrations. Infrared bands are observed in similar positions. The BO stretching vibrations of the trigonal and tetrahedral boron are characterized by Raman bands at 876, 1065 and 1084 cm_1. The OBO bending mode is defined by the Raman band at 611 cm_1. It is important to characterize the very wide range of borate minerals including colemanite because of the very wide range of applications of boron containing minerals.Item Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzBoracite is a magnesium borate mineral with formula: Mg3B7O13Cl and occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic – pyramidal crystal system. An intense Raman band at 1009 cm_1 was assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1121, 1136, 1143 cm_1 are attributed to the in-plane bending vibrations of trigonal boron. Four sharp Raman bands observed at 415, 494, 621 and 671 cm_1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3405 and 3494 cm_1, thus indicating that some Cl anions have been replaced with OH units. The molecular structure of a natural boracite has been assessed by using vibrational spectroscopy.