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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75 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 Vibrational spectroscopy of the borate mineral olshanskyite Ca3[B(OH)4]4(OH)2.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Pereira, Matheus da Costa AlvesThe mineral olshanskyite is one of many calcium borate minerals which has never been studied using vibrational spectroscopy. The mineral is unstable and decomposes upon exposure to an electron beam. This makes the elemental analysis using EDX techniques difficult. Both the Raman and infrared spectra show complexity due to the complexity of the structure. Intense Raman bands are found at 989, 1,003, 1,025 and 1,069 cm-1 with a shoulder at 961 cm-1 and are assigned to trigonal borate units. The Raman bands at 1,141, 1,206 and 1,365 cm-1 are assigned to OH in-plane bending of BOH units. A series of Raman bands are observed in the 2,900–3,621 cm-1 spectral range and are assigned to the stretching vibrations of OH and water. This complexity is also reflected in the infrared spectra. Vibrational spectroscopy enables aspects of the structure of olshanskyite to be elucidated.Item Infrared and Raman spectroscopic characterization of the phosphate mineral kosnarite KZr2(PO4)3 in comparison with other pegmatitic phosphates.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda MariaIn this research, we have used vibrational spectroscopy to study the phosphate mineral kosnarite KZr2(PO4)3. Interest in this mineral rests with the ability of zirconium phosphates (ZP) to lock in radioactive elements. ZP have the capacity to concentrate and immobilize the actinide fraction of radioactive phases in homogeneous zirconium phosphate phases. The Raman spectrum of kosnarite is characterized by a very intense band at 1,026 cm-1 assigned to the symmetric stretching vibration of the PO4 3- m1 symmetric stretching vibration. The series of bands at 561, 595 and 638 cm-1 are assigned to the m4 out-of-plane bending modes of the PO4 3- units. The intense band at 437 cm-1 with other bands of lower wavenumber at 387, 405 and 421 cm-1 is assigned to the m2 in-plane bending modes of the PO4 3- units. The number of bands in the antisymmetric stretching region supports the concept that the symmetry of the phosphate anion in the kosnarite structure is preserved. The width of the infrared spectral profile and its complexity in contrast to the wellresolved Raman spectrum show that the pegmatitic phosphates are better studied with Raman spectroscopy.Item Chemistry, Raman and infrared spectroscopic characterization of the phosphate mineral reddingite : (MnFe)3(PO4)2(H2O,OH)3, a mineral found in lithium-bearing pegmatite.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Lagoeiro, Leonardo EvangelistaDetailed investigation of an intermediate member of the reddingite–phosphoferrite series, using infrared and Raman spectroscopy, scanning electron microcopy and electron microprobe analysis, has been carried out on a homogeneous sample from a lithium-bearing pegmatite named Cigana mine, near Conselheiro Pena, Minas Gerais, Brazil. The determined formula is ðMn1:60Fe1:21Ca0:01 Mg0:01ÞP2:83ðPO4Þ2:12 ðH2O2:85F0:01ÞP2:86, indicating predominance in the reddingite member. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of reddingite-phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of reddingite– phosphoferrite.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 copper bearing silicate mineral luddenite.(2015) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzThe molecular structure of the copper–lead silicate mineral luddenite has been analysed using vibrational spectroscopy. The mineral is only one of many silicate minerals containing copper. The intense Raman band at 978 cm 1 is assigned to the m1 (A1g) symmetric stretching vibration of Si5O14 units. Raman bands at 1122, 1148 and 1160 cm 1 are attributed to the m3 SiO4 antisymmetric stretching vibrations. The bands in the 678–799 cm 1 are assigned to OSiO bending modes of the (SiO3)n chains. Raman bands at 3317 and 3329 cm 1 are attributed to water stretching bands. Bands at 3595 and 3629 cm 1 are associated with the stretching vibrations of hydroxyl units suggesting that hydroxyl units exist in the structure of luddenite.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 A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe23+(AsO4)2(OH)4-H2O.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Lana, Cristiano de Carvalho; Xi, YunfeiWe have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)3_ stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)3_ bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers.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.