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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13 resultados
Resultados da Pesquisa
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 Vibrational spectroscopy of the borate mineral tunellite SrB6O9(OH)2 3(H2O) - implications for the molecular structure.(2014) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiTunellite is a strontium borate mineral with formula: SrB6O9(OH)2_3(H2O) and occurs as colorless crystals in the monoclinic pyramidal crystal system. An intense Raman band at 994 cm_1 was assigned to the BO stretching vibration of the B2O3 units. Raman bands at 1043, 1063, 1082 and 1113 cm_1 are attributed to the in-plane bending vibrations of trigonal boron. Sharp Raman bands observed at 464, 480, 523, 568 and 639 cm_1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3567 and 3614 cm_1, attributed to OH units. The molecular structure of a natural tunellite has been assessed by using vibrational spectroscopy.Item Vibrational spectroscopy of the borate mineral chambersite MnB7O13Cl - implications for the molecular structure.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiChambersite is a manganese borate mineral with formula: MnB7O13Cl and occurs as colorless crystals in the monoclinic pyramidal crystal system. Raman bands at 902, 920, 942 and 963 cm^-1 are assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1027, 1045, 1056, 1075 and 1091 cm^-1 are attributed to the BCl in-plane bending modes. The intense infrared band at 866 cm^-1 is assigned to the trigonal borate stretching modes. The Raman band at 660 cm^-1 together with bands at 597, 642 679, 705 and 721 cm^-1 are assigned to the trigonal and tetrahedral borate bending modes. The molecular structure of a natural chambersite has been assessed using vibrational spectroscopy.Item Vibrational spectroscopy of the mineral meyerhofferite CaB3O3(OH)5 H2O - an assessment of the molecular structure.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Costa, Geraldo Magela da; Belotti, Fernanda Maria; Lima, Rosa Malena FernandesMeyerhofferite is a calcium hydrated borate mineral with ideal formula: CaB3O3(OH)5_H2O and occurs as white complex acicular to crude crystals with length up to _4 cm, in fibrous divergent, radiating aggregates or reticulated and is often found in sedimentary or lake-bed borate deposits. The Raman spectrum of meyerhofferite is dominated by intense sharp band at 880 cm_1 assigned to the symmetric stretching mode of trigonal boron. Broad Raman bands at 1046, 1110, 1135 and 1201 cm_1 are attributed to BOH in-plane bending modes. Raman bands in the 900–1000 cm_1 spectral region are assigned to the antisymmetric stretching of tetrahedral boron. Distinct OH stretching Raman bands are observed at 3400, 3483 and 3608 cm_1. The mineral meyerhofferite has a distinct Raman spectrum which is different from the spectrum of other borate minerals, making Raman spectroscopy a very useful tool for the detection of meyerhofferite in sedimentary and lake bed deposits.Item The molecular structure of the borate mineral inderite Mg(H4B3O7)(OH)-5H2O - a vibrational spectroscopic study.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Lima, Rosa Malena Fernandes; Cipriano, Ricardo Augusto Scholz; Granja, AmandaWe have undertaken a study of the mineral inderite Mg(H4B3O7)(OH)_5H2O a hydrated hydroxy borate mineral of magnesium using scanning electron microscopy, thermogravimetry and vibrational spectroscopic techniques. The structure consists of ½B3O3ðOHÞ5_2_ soroborate groups and Mg(OH)2(H2O)4 octahedra interconnected into discrete molecules by the sharing of two OH groups. Thermogravimetry shows a mass loss of 47.2% at 137.5 _C, proving the mineral is thermally unstable. Raman bands at 954, 1047 and 1116 cm_1 are assigned to the trigonal symmetric stretching mode. The two bands at 880 and 916 cm_1 are attributed to the symmetric stretching mode of the tetrahedral boron. Both the Raman and infrared spectra of inderite show complexity. Raman bands are observed at 3052, 3233, 3330, 3392 attributed to water stretching vibrations and 3459 cm_1 with sharper bands at 3459, 3530 and 3562 cm_1 assigned to OH stretching vibrations. Vibrational spectroscopy is used to assess the molecular structure of inderite.Item Infrared and Raman spectroscopic characterization of the borate mineral colemanite CaB3O4(OH)3 H2O - implications for the molecular structure.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, MauroColemanite CaB3O4(OH)3_H2O is a secondary borate mineral formed from borax and ulexite in evaporate deposits of alkaline lacustrine sediments. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calcium, water and extra hydroxide units interspersed between these chains. The Raman spectra of colemanite is characterized by an intense band at 3605 cm_1 assigned to the stretching vibration of OH units and a series of bands at 3182, 3300, 3389 and 3534 cm_1 assigned to water stretching vibrations. Infrared bands are observed in similar positions. The BO stretching vibrations of the trigonal and tetrahedral boron are characterized by Raman bands at 876, 1065 and 1084 cm_1. The OBO bending mode is defined by the Raman band at 611 cm_1. It is important to characterize the very wide range of borate minerals including colemanite because of the very wide range of applications of boron containing minerals.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.Item Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzBoracite is a magnesium borate mineral with formula: Mg3B7O13Cl and occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic – pyramidal crystal system. An intense Raman band at 1009 cm_1 was assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1121, 1136, 1143 cm_1 are attributed to the in-plane bending vibrations of trigonal boron. Four sharp Raman bands observed at 415, 494, 621 and 671 cm_1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3405 and 3494 cm_1, thus indicating that some Cl anions have been replaced with OH units. The molecular structure of a natural boracite has been assessed by using vibrational spectroscopy.Item Infrared and Raman spectroscopic characterization of the borate mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O – implications for the molecular structure.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Graça, Leonardo MartinsWe have studied the mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O using electron microscopy and vibrational spectroscopy. Both tetrahedral and trigonal boron units are observed. The nominal resolution of the Raman spectrometer is of the order of 2 cm^-1 and as such is sufficient enough to identify separate bands for the stretching bands of the two boron isotopes. The Raman band at 1039 cm^-1 is assigned to BO stretching vibration. Raman bands at 1144, 1157, 1229, 1318 cm^-1 are attributed to the BOH in-plane bending modes. Raman bands at 825 and 925 cm^-1 are attributed to the antisymmetric stretching modes of tetrahedral boron. The sharp Raman peak at 925 cm^-1 is from the 11-B component such a mode, then it should have a smaller 10-B satellite near (1.03) x (925) = 952 cm^-1, and indeed a small peak at 955 is observed. Four sharp Raman bands observed at 3371, 3507, 3563 and 3632 cm^-1 are attributed to the stretching vibrations of hydroxyl units. The broad Raman bands at 3076, 3138, 3255, 3384 and 3551 cm^-1 are assigned to water stretching vibrations. Infrared bands at 3367, 3505, 3559 and 3631 cm^-1 are assigned to the stretching vibration of the hydroxyl units. Broad infrared bands at 3072 and 3254 cm^-1 are assigned to water stretching vibrations. Infrared bands at 1318, 1349, 1371, 1383 cm^-1 are assigned to the antisymmetric stretching vibrations of trigonal boron.Item The molecular structure of the borate mineral rhodizite (K, Cs) Al4Be4(B, Be)12O28 – a vibrational spectroscopic study.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Souza, Larissa; Lana, Cristiano de CarvalhoWe have studied the borate mineral rhodizite (K, Cs)Al4Be4(B, Be)12O28 using a combination of DEM with EDX and vibrational spectroscopic techniques. The mineral occurs as colorless, gray, yellow to white crystals in the triclinic crystal system. The studied sample is from the Antandrokomby Mine, Sahatany valley, Madagascar. The mineral is prized as a semi-precious jewel. Semi-quantitative chemical composition shows a Al, Ca, borate with minor amounts of K, Mg and Cs. The mineral has a characteristic borate Raman spectrum and bands are assigned to the stretching and bending modes of B, Be and Al. No Raman bands in the OH stretching region were observed.