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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12 resultados
Resultados da Pesquisa
Item A vibrational spectroscopic study of the silicate mineral kornerupine.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have studied the mineral kornerupine a boro-silicate mineral by using a combination of scanning electron microscopy with energy dispersive analysis and Raman and infrared spectroscopy. Qualitative chemical analysis of kornerupine shows a magnesium-aluminium silicate. Strong Raman bands at 925, 995 and 1051 cm-1 with bands of lesser intensity at 1035 and 1084 cm-1 are assigned to the silicon-oxygen stretching vibrations of the siloxane units. Raman bands at 923 and 947 cm-1 are attributed to the symmetrical stretching vibrations of trigonal boron. Infrared spectra show greater complexity and the infrared bands are more difficult to assign. Two intense Raman bands at 3547 and 3612 cm-1 are assigned to the stretching vibrations of hydroxyl units. In the infrared bands are observed at 3544 and 3610 cm-1. Water is also identified in the spectra of kornerupine.Item A vibrational spectroscopic study of the silicate mineral harmotome – (Ba,Na,K)1-2(Si,Al)8O16 6H2O – a natural zeolite.(2015) Frost, Ray Leslie; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Cipriano, Ricardo Augusto ScholzThe mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16 6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm 1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm 1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm 1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm 1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm 1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.Item SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Theiss, Frederick L.; Romano, Antônio WilsonThe mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH) H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm 1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm 1. A very sharp band is observed at 3668 cm 1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm 1 are assigned to water stretching vibrations.Item Scanning electron microscopy with energy dispersive spectroscopy and Raman and infrared spectroscopic study of tilleyite Ca5Si2O7(CO3)2-Y.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Oliveira, Fernando A. N. deThe mineral tilleyite-Y, a carbonate-silicate of calcium, has been studied by scanning electron microscopy 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 tilleyite structure. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water in different molecular environments in the structure of tilleyite. Vibrational spectroscopy offers new information on the mineral tilleyite.Item A vibrational spectroscopic study of the silicate mineral normandite – NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2.(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Cipriano, Ricardo Augusto Scholz; Romano, Antônio WilsonWe have studied the mineral normandite using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral normandite NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2 is a crystalline sodium calcium silicate which contains rare earth elements. Chemical analysis shows the mineral contains a range of elements including Na, Mn2+, Ca, Fe2+ and the rare earth element niobium. No Raman bands are observed above 1100 cm 1. The mineral is characterised by Raman bands observed at 724, 748, 782 and 813 cm 1. Infrared bands are broad; nevertheless bands may be resolved at 723, 860, 910, 958, 933, 1057 and 1073 cm 1. Intense Raman bands at 454, 477 and 513 cm 1 are attributed to OSiO bending modes. No Raman bands are observed in the hydroxyl stretching region, but low intensity infrared bands are observed at 3191 and 3450 cm 1. This observation brings into question the true formula of the mineral.Item A vibrational spectroscopic study of the silicate mineral pectolite – NaCa2Si3O8(OH).(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Cipriano, Ricardo Augusto ScholzThe mineral pectolite NaCa2Si3O8(OH) is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and in other industrial applications. Raman bands at 974 and 1026 cm 1 are assigned to the SiO stretching vibrations of linked units of Si3O8 units. Raman bands at 974 and 998 cm 1 serve to identify Si3O8 units. The broad Raman band at around 936 cm 1 is attributed to hydroxyl deformation modes. Intense Raman band at 653 cm 1 is assigned to OSiO bending vibration. Intense Raman bands in the 2700–3000 cm 1 spectral range are assigned to OH stretching vibrations of the OH units in pectolite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the silicate mineral pectolite.Item Vibrational spectroscopic study of poldervaartite CaCa[SiO3(OH)(OH)].(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena FernandesWe have studied the mineral poldervaartite CaCa[SiO3(OH)(OH)] which forms a series with its manganese analogue olmiite CaMn[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485 _C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852 cm_1 is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm_1 are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547 cm_1 are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of poldervaartiteItem A vibrational spectroscopic study of the silicate mineral ardennite-(As).(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Gandini, Antônio LucianoWe have used a combination of scanning electron microscopy with EDX and vibrational spectroscopy to study the mineral ardennite-(As). The mineral ardennite-(As) of accepted formula Mn4(2+)(Al,Mg)6(Si3O10)(SiO4)2(AsO4,VO4)(OH)6 is a silicate mineral which may contain arsenate and/or vanadates anions. Because of the oxyanions present, the mineral lends itself to analysis by Raman and infrared spectroscopy. Qualitative chemical analysis shows a homogeneous phase, composed by Si, Mn, Al and As. Ca and V were also observed in partial substitution for Mn and As. Raman bands at 1197, 1225, 1287 and 1394 cm(-1) are assigned to SiO stretching vibrations. The strong Raman bands at 779 and 877 cm(-1) are assigned to the AsO4(3-) antisymmetric and symmetric stretching vibrations. The Raman band at 352 cm(-1) is assigned to the ν2 symmetric bending vibration. The series of Raman bands between 414 and 471 cm(-1)are assigned to the ν4 out of plane bending modes of the AsO4(3-) units. Intense Raman bands observed at 301 and 314 cm(-1) are attributed to the MnO stretching and bending vibrations. Raman bands at 3041, 3149, 3211 and 3298 cm(-1) are attributed to the stretching vibrations of OH units. There is vibrational spectroscopic evidence for the presence of water adsorbed on the ardennite-(As) surfaces.Item A vibrational spectroscopic study of the silicate mineral inesite Ca2(Mn,Fe)7Si10O28(OH)-5H2O.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzWe have studied the hydrated hydroxyl silicate mineral inesite of formula Ca2(Mn,Fe)7Si10O28(OH)_5H2O using a combination of scanning electron microscopy with EDX and Raman and infrared spectroscopy. SEM analysis shows the mineral to be a pure monomineral with no impurities. Semiquantitative analysis shows a homogeneous phase, composed by Ca, Mn2+, Si and P, with minor amounts of Mg and Fe. Raman spectrum shows well resolved component bands at 997, 1031, 1051, and 1067 cm_1 attributed to a range of SiO symmetric stretching vibrations of [Si10O28] units. Infrared bands found at 896, 928, 959 and 985 cm_1 are attributed to the OSiO antisymmetric stretching vibrations. An intense broad band at 653 cm_1 with shoulder bands at 608, 631 and 684 cm_1 are associated with the bending modes of the OSiO units of the 6- and 8-membered rings of the [Si10O28] units. The sharp band at 3642 cm_1 with shoulder bands at 3612 and 3662 cm_1 are assigned to the OH stretching vibrations of the hydroxyl units. The broad Raman band at 3420 cm_1 with shoulder bands at 3362 and 3496 cm_1 are assigned to the water stretching vibrations. The application of vibrational spectroscopy has enabled an assessment of the molecular structure of inesite to be undertaken.Item Thermal analysis and vibrational spectroscopic characterization of the boro silicate mineral datolite - CaBSiO4(OH).(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Horta, Laura Frota Campos; López, AndrésThe objective of this work is to determine the thermal stability and vibrational spectra of datolite CaBSiO4(OH) and relate these properties to the structure of the mineral. The thermal analysis of datolite shows a mass loss of 5.83% over a 700–775 °C temperature range. This mass loss corresponds to 1 water (H2O) molecules pfu. A quantitative chemical analysis using electron probe was undertaken. The Raman spectrum of datolite is characterized by bands at 917 and 1077 cm^-1 assigned to the symmetric stretching modes of BO and SiO tetrahedra. A very intense Raman band is observed at 3498 cm^-1 assigned to the stretching vibration of the OH units in the structure of datolite. BOH out-of-plane vibrations are characterized by the infrared band at 782 cm^-1. The vibrational spectra are based upon the structure of datolite based on sheets of four- and eight-membered rings of alternating SiO4 and BO3(OH) tetrahedra with the sheets bonded together by calcium atoms.