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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6 resultados
Resultados da Pesquisa
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.Item A Raman and infrared spectroscopic characterisation of the phosphate mineral phosphohedyphane Ca2Pb3(PO4)3Cl from the Roote mine, Nevada, USA.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Souza, Bárbara Emilly Vieira Firmino e; Lana, Cristiano de Carvalho; Xi, YunfeiPhosphohedyphane Ca2Pb3(PO4)3Cl is rare Ca and Pb phosphate mineral that belongs to the apatite supergroup. We have analysed phosphohedyphane using SEM with EDX, and Raman and infrared spectroscopy. The chemical analysis shows the presence of Pb, Ca, P and Cl and the chemical formula is expressed as Ca2Pb3(PO4)3Cl. The very sharp Raman band at 975 cm^-1 is assigned to the PO4^3- v1 symmetric stretching mode. Raman bands noted at 1073, 1188 and 1226 cm^-1 are to the attributed to the PO4^3- v3 antisymmetric stretching modes. The two Raman bands at 835 and 812 cm^-1 assigned to the AsO4^3- v1 symmetric stretching vibration and AsO4^3- v3 antisymmetric stretching modes prove the substitution of As for P in the structure of phosphohedyphane. A series of bands at 557, 577 and 595 cm^-1 are attributed to the v4 out of plane bending modes of the PO4 units. The multiplicity of bands in the v2, v3 and v4 spectral regions provides evidence for the loss of symmetry of the phosphate anion in the phosphohedyphane structure. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra. Some Raman bands attributable to OH stretching bands were observed, indicating the presence of water and/or OH units in the structure.