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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2 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 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.