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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11 resultados
Resultados da Pesquisa
Item A Raman and infrared spectroscopic study of the phosphate mineral laueite.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, AndrésA laueite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been studied by vibrational spectroscopy and scanning electron microscopy with EDX. Chemical formula calculated on the basis of semi-quantitative chemical analysis can be expressed as (Mn2+0.85,Fe2+0.10Mg0.05)P1.00(Fe3+1.90,Al0.10)P2.00(PO4)2(OH)2_8H2O. The laueite structure is based on an infinite chains of vertex-linked oxygen octahedra, with Fe3+ occupying the octahedral centers, the chain oriented parallel to the c-axis and linked by PO4 groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 980 and 1045 cm_1 are assigned to the n1 PO43_ symmetric stretching mode. Intense Raman bands are observed at 525 and 551 cm_1 with a shoulder at 542 cm_1 are assigned to the n4 out of plane bending modes of the PO43_. The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Intense Raman bands are observed at 3379 and 3478 cm_1 and are attributed to the OH stretching vibrations of the hydroxyl units. Intense broad infrared bands are observed. Vibrational spectroscopy enables subtle details of the molecular structure of laueite to be determined.Item SEM, EDX and Raman and infrared spectroscopic study of brianyoungite Zn3(CO3,SO4)(OH)4 from Esperanza Mine, Laurion District, Greece.(2015) Frost, Ray Leslie; López, Andrés; Wang, Lina; Cipriano, Ricardo Augusto Scholz; Sampaio, Ney PinheiroThe mineral brianyoungite, a carbonate–sulphate of zinc, has been studied by scanning electron microscopy (SEM) 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 brianyoungite structure. Intense Raman band at 1056 cm_1 with shoulder band at 1038 cm_1 is assigned to the CO32_ m1 symmetric stretching mode. Two intense Raman bands at 973 and 984 cm_1 are assigned to the symmetric stretching modes of the SO4 2_ anion. The observation of two bands supports the concept of the non-equivalence of sulphate units in the brianyoungite structure. Raman bands at 704 and 736 cm_1 are assigned to the CO32_ m4 bending modes and Raman bands at 507, 528, 609 and 638 cm_1 are assigned to the CO32_ m2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water and hydroxyl units in different molecular environments in the structure of brianyoungite. Vibrational spectroscopy enhances our knowledge of the molecular structure of brianyoungite.Item SEM, EDX and vibrational spectroscopic study of the phosphate mineral ushkovite MgFe2 3+(PO4)2(OH)2 8H2O – implications of the molecular structure.(2015) López, Andrés; Cipriano, Ricardo Augusto Scholz; Frost, Ray Leslie; Belotti, Fernanda MariaThe mineral ushkovite has been analyzed using a combination of electron microscopy with EDX and vibrational spectroscopy. Chemical analysis shows the mineral contains P, Mg with very minor Fe. Thus, the formula of the studied ushkovite is Mg3 2+(PO4)2 8H2O. The Raman spectrum shows an intense band at 953 cm 1 assigned to the m1 symmetric stretching mode. In the infrared spectra complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong infrared bands around 827 cm 1 are attributed to water librational modes. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 2881, 2998, 3107, 3203, 3284 and 3457 cm 1. The wavenumber band at 3457 cm 1 is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH bending modes where a strong infrared band centered around 1653 cm 1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH bending bands from strongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. Vibrational spectroscopy enhances our knowledge of the molecular structure of ushkovite.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 Raman and infrared spectroscopic study of kamphaugite-(Y).(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have studied the carbonate mineral kamphaugite-(Y)(CaY(CO3)2(OH) H2O), a mineral which contains yttrium and specific rare earth elements. Chemical analysis shows the presence of Ca, Y and C. Back scattering SEM appears to indicate a single pure phase. The vibrational spectroscopy of kamphaugite-(Y) was obtained using a combination of Raman and infrared spectroscopy. Two distinct Raman bands observed at 1078 and 1088 cm 1 provide evidence for the non-equivalence of the carbonate anion in the kamphaugite-(Y) structure. Such a concept is supported by the number of bands assigned to the carbonate antisymmetric stretching mode. Multiple bands in the m4 region offers further support for the nonequivalence of carbonate anions in the structure. Vibrational spectroscopy enables aspects of the structure of the mineral kamphaugite-(Y) to be assessed.Item A vibrational spectroscopic study of the arsenate mineral bayldonite (Cu,Zn)3Pb(AsO3OH)2(OH)2 - a comparison with other basic arsenates.(2014) Frost, Ray Leslie; López, Andrés; Gonçalves, Guilherme de Oliveira; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiWe have studied the vibrational spectra of the mineral bayldonite, a hydroxy arsenate of copper and lead of formula Cu3Pb(AsO3OH)2(OH)2 from the type locality, the Penberthy Croft Mine, St Hilary, Mount’s Bay District, Cornwall, England and relate the spectra to the mineral structure. Raman bands at 896 and 838 cm_1 are assigned to the ðAsO4Þ3_ m1 symmetric stretching mode and the second to the ðAsO4Þ3_ m3 antisymmetric stretching mode. It is noted that the position of the symmetric stretching mode is at a higher position than the antisymmetric stretching mode. It is proposed that the Raman bands at 889 and 845 cm_1 are symmetric and antisymmetric stretching modes of the (HOAsO3)2_ units. Raman bands of bayldonite at 490 and 500 cm_1 are assigned to the ðAsO4Þ3_ m4 bending modes. Raman bands for bayldonite are noted at 396, 408 and 429 cm_1 and are assigned to the ðAsO4Þ3_ m2 bending modes. A comparison is made with spectra of the other basic copper arsenate minerals, namely cornubite, olivenite, cornwallite.Item A vibrational spectroscopic study of the phosphate mineral minyulite KAl2(OH,F)(PO4)2 4(H2O) and in comparison with wardite.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cardoso, Luiz Henrique; Cipriano, Ricardo Augusto ScholzVibrational spectroscopy enables subtle details of the molecular structure of minyulite KAl2(OH,F)(PO4)2_ 4(H2O). Single crystals of a pure phase from a Brazilian pegmatite were used. Minyulite belongs to the orthorhombic crystal system. This indicates that it has three axes of unequal length, yet all are perpendicular to each other. The infrared and Raman spectroscopy were applied to compare the structure of minyulite with wardite. The reason for the comparison is that both are Al containing phosphate minerals. The Raman spectrum of minyulite shows an intense band at 1012 cm_1 assigned to the m1 PO3_ 4 symmetric stretching vibrations. A series of low intensity Raman bands at 1047, 1077, 1091 and 1105 cm_1 are assigned to the m3 PO3_ 4 antisymmetric stretching modes. The Raman bands at 1136, 1155, 1176 and 1190 cm_1 are assigned to AlOH deformation modes. The infrared band at 1014 cm_1 is ascribed to the PO3_ 4 m1 symmetric stretching vibrational mode. The infrared bands at 1049, 1071, 1091 and 1123 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching vibrations. The infrared bands at 1123, 1146 and 1157 cm_1 are attributed to AlOH deformation modes. Raman bands at 575, 592, 606 and 628 cm_1 are assigned to the m4 out of plane bending modes of the PO3_ 4 unit. In the 2600– 3800 cm_1 spectral range, Raman bands for minyulite are found at 3661, 3669 and 3692 cm_1 are assigned to AlOH/AlF stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm_1. Raman bands at 3225, 3324 cm_1 are assigned to water stretching vibrations. A comparison is made with the vibrational spectra of wardite. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of minyulite to be ascertained and compared with that of other phosphate minerals.Item A study of the phosphate mineral kapundaite NaCa(Fe3+)4(PO4)4(OH)3 5(H2O) using SEM/EDX and vibrational spectroscopic methods.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzVibrational spectroscopy enables subtle details of the molecular structure of kapundaite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Kapundaite is the Fe3+ member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of kapundaite with wardite. The Raman spectrum of kapundaite in the 800–1400 cm_1 spectral range shows two intense bands at 1089 and 1114 cm_1 assigned to the m1 PO3_ 4 symmetric stretching vibrations. The observation of two bands provides evidence for the non-equivalence of the phosphate units in the kapundaite structure. The infrared spectrum of kapundaite in the 500–1300 cm_1 shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 966, 1003 and 1036 cm_1 and are attributed to the m1 PO3_ 4 symmetric stretching mode and m3 PO3_ 4 antisymmetric stretching mode. Raman bands in the m4 out of plane bending modes of the PO3_ 4 unit support the concept of non-equivalent phosphate units in the kapundaite structure. In the 2600–3800 cm_1 spectral range, Raman bands for kapundaite are found at 2905, 3151, 3311, 3449 and 3530 cm_1. These bands are broad and are assigned to OH stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm_1 and are attributed to water. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of kapundaite to be ascertained and compared with that of other phosphate minerals.Item A vibrational spectroscopic study of the phosphate mineral whiteite CaMn++Mg2Al2(PO4)4(OH)2 8(H2O).(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, YunfeiVibrational spectroscopy enables subtle details of the molecular structure of whiteite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. The infrared and Raman spectroscopy were applied to compare the molecular structure of whiteite with that of other phosphate minerals. The Raman spectrum of whiteite shows an intense band at 972 cm_1 assigned to the m1 PO3_ 4 symmetric stretching vibrations. The low intensity Raman bands at 1076 and 1173 cm_1 are assigned to the m3 PO3_ 4 antisymmetric stretching modes. The Raman bands at 1266, 1334 and 1368 cm_1 are assigned to AlOH deformation modes. The infrared band at 967 cm_1 is ascribed to the PO3_ 4 m1 symmetric stretching vibrational mode. The infrared bands at 1024, 1072, 1089 and 1126 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching vibrations. Raman bands at 553, 571 and 586 cm_1 are assigned to the m4 out of plane bending modes of the PO3_ 4 unit. Raman bands at 432, 457, 479 and 500 cm_1 are attributed to the m2 PO4 and H2PO4 bending modes. In the 2600 to 3800 cm_1 spectral range, Raman bands for whiteite are found 3426, 3496 and 3552 cm_1 are assigned to AlOH stretching vibrations. Broad infrared bands are also found at 3186 cm_1. Raman bands at 2939 and 3220 cm_1 are assigned to water stretching vibrations. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of whiteite to be ascertained and compared with that of other phosphate minerals.Item A Raman and infrared spectroscopic analysis of the phosphate mineral wardite NaAl3(PO4)2(OH)4 .2(H2O) from Brazil.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Lana, Cristiano de Carvalho; Xi, YunfeiA wardite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been examined by vibrational spectroscopy. The mineral is unusual in that it belongs to a unique symmetry class, namely the tetragonal-trapezohedral group. The structure of wardite contains layers of corner-linked –OH bridged MO6 octahedra stacked along the tetragonal C-axis in a four-layer sequence and linked by PO4 groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 995 and 1051 cm^-1 are assigned to the m1 PO4^3- symmetric stretching mode. Intense Raman bands are observed at 605 and 618 cm^-1 with shoulders at 578 and 589 cm^-1 are assigned to the m4 out of plane bending modes of the PO4^3- . The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Sharp infrared bands are observed at 3544 and 3611 cm^-1 are attributed to the OH stretching vibrations of the hydroxyl units. Vibrational spectroscopy enables subtle details of the molecular structure of wardite to be determined.