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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99 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 The application of high-temperature X-ray diffraction and infrared emission spectroscopy to the thermal decomposition of krohnkite.(2016) Testasicca, Leonardo Pena; Frost, Ray Leslie; Ruan, Xiuxiu; Lim, Jéssica; Belotti, Fernanda Maria; Cipriano, Ricardo Augusto ScholzHigh-temperature X-ray diffraction and infrared emission spectroscopy have been applied to measure the thermal stability of the sulphate mineral kro¨hnkite Na2Cu(SO4)2 2H2O. Kro¨hnkite shows a low thermal stability. The mineral decomposes into a complex mixture of sulphates below 500 C and sulphides below 650 C, before melting. Broad emission infrared bands at 3350 and 3105 cm-1 are assigned to the stretching vibration of the water units. The intensity of these two bands decreases as the temperature is raised. The intensity of these bands is lost by 250 C. The sharp IES band at 992 cm-1 is assigned to the m1 SO4 2- symmetric stretching vibration. Intensity in this band is lost by 200 C. New IES bands are noted. The important aspect of this work is the use of hightemperature X-ray diffraction to determine the thermal decomposition of a mineral, in this case krohnkite.Item Vibrational spectroscopic study of the phosphate mineral kryzhanovskite and in comparison with reddingite-implications for the molecular structure.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; Wang, LinaWe have studied the phosphate mineral kryzhanovskite (Fe3þ,Mn2þ)3(PO4)2(OH,H2O) which is a member of the phosphoferrite mineral group using a combination of scanning electron microscopy with energy dispersive spectroscopy and Raman and infrared spectroscopy. Chemical analysis shows the presence of P, Mn and Fe and confirms the formula given above. The presence of hydroxyl units in the structure is indicative of ferric iron in the formula that is an oxidised product. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of kryzhanovskite -phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of kryzhanovskite -phosphoferrite.Item A vibrational spectroscopic study of the silicate mineral kornerupine.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have studied the mineral kornerupine a boro-silicate mineral by using a combination of scanning electron microscopy with energy dispersive analysis and Raman and infrared spectroscopy. Qualitative chemical analysis of kornerupine shows a magnesium-aluminium silicate. Strong Raman bands at 925, 995 and 1051 cm-1 with bands of lesser intensity at 1035 and 1084 cm-1 are assigned to the silicon-oxygen stretching vibrations of the siloxane units. Raman bands at 923 and 947 cm-1 are attributed to the symmetrical stretching vibrations of trigonal boron. Infrared spectra show greater complexity and the infrared bands are more difficult to assign. Two intense Raman bands at 3547 and 3612 cm-1 are assigned to the stretching vibrations of hydroxyl units. In the infrared bands are observed at 3544 and 3610 cm-1. Water is also identified in the spectra of kornerupine.Item Raman and infrared spectroscopic characterization of the arsenate-bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, AndrésTheminerals clinotyrolite and fuxiaotuite are discredited in terms of the mineral tangdanite. Themixed anionmineral tangdanite Ca2Cu9(AsO4)4(SO4)0.5(OH)9 9H2O has been studied using a combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. These bands are assigned to water and hydroxyl stretching vibrations. Two intense Raman bands at 837 and approximately 734 cm 1 are assigned to the ν1 (AsO4)3 symmetric stretching and ν3 (AsO4)3 antisymmetric stretching modes. Infrared bands at 1023 cm 1 are assigned to the (SO4)2 ν1 symmetric stretching mode, and infrared bands at 1052, 1110 and 1132 cm 1 assigned to (SO4)2 ν3 antisymmetric stretching modes, confirming the presence of the sulphate anion in the tangdanite structure. Raman bands at 593 and 628 cm 1 are attributed to the (SO4)2 ν4 bending modes. Low-intensity Raman bands found at 457 and 472cm 1 are assigned to the (AsO4)3 ν2 bending modes. A comparison is made with the previously obtained spectral data on the discredited mineral clinotyrolite.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 Thermal analysis and infrared emission spectroscopy of the borate mineral colemanite (CaB3O4(OH)3H2O) : implications for thermal stability.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; Ruan, Xiuxiu; Lima, Rosa Malena FernandesColemanite CaB3O4(OH)3H2O 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. We have studied the thermal decomposition of colemanite by using a combination of thermal analysis (TG/DTG) and infrared emission spectroscopy (IES). Thermogravimetric analysis of the colemanite mineral was obtained by using TA Instruments Inc. Q50 high-resolution TGA operating at a 10 C min-1 ramp with data sample interval of 0.50 s pt-1 from room temperature to 1000 C in a high-purity flowing nitrogen atmosphere (100 cm3 min-1 ). Thermogravimetric analysis shows a sharp mass loss at 400.9 C. Only a single mass loss is observed. IES shows a sharp band at 3610 cm-1 assigned to the stretching vibration of hydroxyl units. Intensity in this band is lost by 350 C. A broad spectral feature is observed at 3274 cm-1 attributed to water stretching vibrations. Intensity in this band is lost by 300 C. A combination of thermogravimetry and IES is used to study the thermal stability of the borate mineral colemanite. 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 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.