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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34 resultados
Resultados da Pesquisa
Item Assessment of the molecular structure of an intermediate member of the triplite-zwieselite mineral series : a raman and infrared study.(2014) Frost, Ray Leslie; Xi, Yunfei; López, Andrés; Moreira, Viviane Amaral; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Gandini, Antônio LucianoThe mineral series triplite-zwieselite with theoretical formula (Mn2þ)2(PO4)(F)-(Fe2þ)2(PO4)(F) from the El Criolo granitic pegmatite, located in the Eastern Pampean Ranges of Cordoba Province, was studied using electron microprobe, thermogravimetry, and Raman and infrared spec- troscopy. The analysis of the mineral provided a formula of (Fe1.00, Mn0.85, Ca0.08, Mg0.06)P2.00(PO4)1.00(F0.80, OH0.20)P1.00. An intense Raman band at 981cm1 with a shoulder at 977cm1 is assigned to the PO3 4 n1 symmetric stretching mode. The observation of two bands for the phosphate symmetric stretching mode offers support for the concept that the phosphate units in the structure of triplite-zwieselite are not equivalent. Low-intensity Raman bands at 1012, 1036, 1071, 1087, and 1127 cm1 are assigned to the PO3 4 n3 antisymmetric stretching modes. A set of Raman bands at 572, 604, 639, and 684 cm1 are attributed to the PO3 4 n4 out-of-plane bending modes. A single intense Raman band is found at 3508 cm1 and is assigned to the stretching vibration of hydroxyl units. Infrared bands are observed at 3018, 3125, and 3358 cm1 and are attributed to water stretching vibrations. Supplemental materials are available for this article. Go to the publisher’s online edition of Spectroscopy Letters to view the supplemental file.Item Raman and infrared spectroscopic study of turquoise minerals.(2015) Čejka, Jiři; Sejkora, Jiři; Macek, Ivo; Malíková, Radana; Wang, Lina; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Frost, Ray LeslieRaman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8_4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O–H…O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)2_ units were observed.Item A vibrational spectroscopic study of the anhydrous phosphate mineral sidorenkite Na3Mn(PO4)(CO3).(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Xi, YunfeiSidorenkite is a very rare low-temperature hydrothermal mineral, formed very late in the crystallization of hyperagpaitic pegmatites in a differentiated alkalic massif (Mt. Alluaiv, Kola Peninsula, Russia). Sidorenkite Na3Mn(PO4)(CO3) is a phosphate–carbonate of sodium and manganese. Such a formula with two oxyanions lends itself to vibrational spectroscopy. The sharp Raman band at 959 cm 1 and 1012 cm 1 are assigned to the PO43 stretching modes, whilst the Raman bands at 1044 cm 1 and 1074 cm 1 are attributed to the CO32 stretching modes. It is noted that no Raman bands at around 800 cm 1 for sidorenkite were observed. The infrared spectrum of sidorenkite shows a quite intense band at 868 cm 1 with other resolved component bands at 850 and 862 cm 1. These bands are ascribed to the CO32 out-of-plane bend (m2) bending mode. The series of Raman bands at 622, 635, 645 and 704 cm 1 are assigned to the m4 phosphate bending modes. The observation of multiple bands supports the concept of a reduction in symmetry of the carbonate anion from D3h or even C2v.Item Vibrational spectroscopic characterization of the phosphate mineral althausite Mg2(PO4)(OH,F,O) - implications for the molecular structure.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzNatural single-crystal specimens of althausite from Brazil, with general formula Mg2(PO4)(OH,F,O) were investigated by Raman and infrared spectroscopy. The mineral occurs as a secondary product in granitic pegmatites. The Raman spectrum of althausite is characterized by bands at 1020, 1033 and 1044 cm_1, assigned to m1 symmetric stretching modes of the HOPO3_ 3 and PO3_ 4 units. Raman bands at around 1067, 1083 and 1138 cm_1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 575, 589 and 606 cm_1 are assigned to the m4 out of plane bending modes of the PO4 and H2PO4 units. Raman bands at 439, 461, 475 and 503 cm_1 are attributed to the m2 PO4 and H2PO4 bending modes. Strong Raman bands observed at 312, 346 cm_1 with shoulder bands at 361, 381 and 398 cm_1 are assigned to MgO stretching vibrations. No bands which are attributable to water were found. Vibrational spectroscopy enables aspects of the molecular structure of althausite to be assessed.Item Raman, infrared and near-infrared spectroscopic characterization of the herderite-hydroxylherderite mineral series.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Queiroz, Camila de Siqueira; Belotti, Fernanda Maria; Cândido Filho, MauroNatural single-crystal specimens of the herderite–hydroxylherderite series from Brazil, with general formula CaBePO4(F,OH), were investigated by electron microprobe, Raman, infrared and near-infrared spectroscopies. The minerals occur as secondary products in granitic pegmatites. Herderite and hydroxylherderite minerals show extensive solid solution formation. The Raman spectra of hydroxylherderite are characterized by bands at around 985 and 998 cm_1, assigned to m1 symmetric stretching mode of the HOPO3_ 3 and PO3_ 4 units. Raman bands at around 1085, 1128 and 1138 cm_1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 563, 568, 577, 598, 616 and 633 cm_1 are assigned to the m4 out of plane bending modes of the PO4 and H2PO4 units. The OH Raman stretching vibrations of hydroxylherderite were observed ranging from 3626 cm_1 to 3609 cm_1. The infrared stretching vibrations of hydroxylherderites were observed between 3606 cm_1 and 3599 cm_1. By using a Libowitzky type function, hydrogen bond distances based upon the OH stretching bands were calculated. Characteristic NIR bands at around 6961 and 7054 cm_1 were assigned to the first overtone of the fundamental, whilst NIR bands at 10,194 and 10,329 cm_1 are assigned to the second overtone of the fundamental OH stretching vibration. Insight into the structure of the herderite–hydroxylherderite series is assessed by vibrational spectroscopy.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 Vibrational spectroscopy of the phosphate mineral kovdorskite - Mg2PO4(OH)-3H2O.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Granja, Amanda; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena FernandesThe mineral kovdorskite Mg2PO4(OH)_3H2O was studied by electron microscopy, thermal analysis and vibrational spectroscopy. A comparison of the vibrational spectroscopy of kovdorskite is made with other magnesium bearing phosphate minerals and compounds. Electron probe analysis proves the mineral is very pure. The Raman spectrum is characterized by a band at 965 cm_1 attributed to the PO3_ 4 m1 symmetric stretching mode. Raman bands at 1057 and 1089 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching modes. Raman bands at 412, 454 and 485 cm_1 are assigned to the PO3_ 4 m2 bending modes. Raman bands at 536, 546 and 574 cm_1 are assigned to the PO3_ 4 m4 bending modes. The Raman spectrum in the OH stretching region is dominated by a very sharp intense band at 3681 cm_1 assigned to the stretching vibration of OH units. Infrared bands observed at 2762, 2977, 3204, 3275 and 3394 cm_1 are attributed to water stretching bands. Vibrational spectroscopy shows that no carbonate bands are observed in the spectra; thus confirming the formula of the mineral as Mg2PO4(OH)_3H2O.Item The molecular structure of the phosphate mineral chalcosiderite - a vibrational spectroscopic study.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Ribeiro, Carlos Augusto de BritoThe mineral chalcosiderite with formula CuFe6(PO4)4(OH)8_4H2O has been studied by Raman spectroscopy and by infrared spectroscopy. A comparison of the chalcosiderite spectra is made with the spectra of turquoise. The spectra of the mineral samples are very similar in the 1200–900 cm_1 region but strong differences are observed in the 900–100 cm_1 region. The effect of substitution of Fe for Al in chalcosiderite shifts the bands to lower wavenumbers. Factor group analysis (FGA) implies four OH stretching vibrations for both the water and hydroxyl units. Two bands ascribed to water are observed at 3276 and 3072 cm_1. Three hydroxyl stretching vibrations are observed. Calculations using a Libowitzky type formula show that the hydrogen bond distances of the water molecules are 2.745 and 2.812 Å which are considerably shorter than the values for the hydroxyl units 2.896, 2.917 and 2.978 Å. Two phosphate stretching vibrations at 1042 and 1062 cm_1 in line with the two independent phosphate units in the structure of chalcosiderite. Three bands are observed at 1102, 1159 and 1194 cm_1 assigned to the phosphate antisymmetric stretching vibrations. FGA predicts six bands but only three are observed due to accidental degeneracy. Both the m2 and m4 bending regions are complex. Four Raman bands observed at 536, 580, 598 and 636 cm_1 are assigned to the m4 bending modes. Raman bands at 415, 420, 475 and 484 cm_1are assigned to the phosphate m2 bending modes. Vibrational spectroscopy enables aspects of the molecular structure of chalcosiderite to be assessed.Item A vibrational spectroscopic study of the phosphate mineral lulzacite Sr2Fe2+(Fe2+,Mg)2Al4(PO4)4(OH)10.(2014) Frost, Ray Leslie; López, Andrés; Belotti, Fernanda Maria; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzThe mineral lulzacite from Saint-Aubin des Chateaux mine, France, with theoretical formula Sr2Fe2+(Fe2+,Mg)2Al4(PO4)4(OH)10 has been studied using a combination of electron microscopy with EDX and vibrational spectroscopic techniques. Chemical analysis shows a Sr, Fe, Al phosphate with minor amounts of Ga, Ba and Mg. Raman spectroscopy identifies an intense band at 990 cm_1 with an additional band at 1011 cm_1. These bands are attributed to the PO3_ 4 m1 symmetric stretching mode. The m3 antisymmetric stretching modes are observed by a large number of Raman bands. The Raman bands at 1034, 1051, 1058, 1069 and 1084 together with the Raman bands at 1098, 1116, 1133, 1155 and 1174 cm_1 are assigned to the m3 antisymmetric stretching vibrations of PO3_ 4 and the HOPO2_ 3 units. The observation of these multiple Raman bands in the symmetric and antisymmetric stretching region gives credence to the concept that both phosphate and hydrogen phosphate units exist in the structure of lulzacite. The series of Raman bands at 567, 582, 601, 644, 661, 673 and 687 cm_1 are assigned to the PO3_ 4 m2 bending modes. The series of Raman bands at 437, 468, 478, 491, 503 cm_1 are attributed to the PO3_ 4 and HOPO2_ 3 m4 bending modes. No Raman bands of lulzacite which could be attributed to the hydroxyl stretching unit were observed. Infrared bands at 3511 and 3359 cm_1 are ascribed to the OH stretching vibration of the OH units. Very broad bands at 3022 and 3299 cm_1 are attributed to the OH stretching vibrations of water. Vibrational spectroscopy offers insights into the molecular structure of the phosphate mineral lulzacite.Item Vibrational spectroscopic characterization of the phosphate mineral kulanite Ba(Fe2+,Mn2+,Mg)2(Al,Fe3+)2(PO4)3(OH)3.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Granja, Amanda; Cipriano, Ricardo Augusto ScholzThe mineral kulanite BaFe2Al2(PO4)3(OH)3, a barium iron aluminum phosphate, has been studied by using a combination of electron microscopy and vibrational spectroscopy. Scanning electron microscopy with EDX shows the mineral is homogenous with no other phases present. The Raman spectrum is dominated by an intense band at 1022 cm_1 assigned to the PO3_ 4 m1 symmetric stretching mode. Low intensity Raman bands at 1076, 1110, 1146, 1182 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching vibrations. The infrared spectrum shows a complex spectral profile with overlapping bands. Multiple phosphate bending vibrations supports the concept of a reduction in symmetry of the phosphate anion. Raman spectrum at 3211, 3513 and 3533 cm_1 are assigned to the stretching vibrations of the OH units. Vibrational spectroscopy enables aspects on the molecular structure of kulanite to be assessed.