Navegando por Autor "Theiss, Frederick L."

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An SEM, EDS and vibrational spectroscopic study of the silicate mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)].
(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Cipriano, Ricardo Augusto Scholz
The mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] is a crystalline sodium calcium beryllium silicate which has the potential to be used as piezoelectric material and for other ferroelectric applications. The mineral has been characterized by a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and vibrational spectroscopy. EDS analysis shows a material with high concentrations of Si and Ca and low amounts of Na, Al and F. Beryllium was not detected. Raman bands at 1016 and 1050 cm 1 are assigned to the SiO and AlOH stretching vibrations of three dimensional siloxane units. The infrared spectrum of meliphanite is very broad in comparison with the Raman spectrum. Raman bands at 472 and 510 cm 1 are assigned to OSiO bending modes. Raman spectroscopy identifies bands in the OH stretching region. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral meliphanite.
A SEM, EDS and vibrational spectroscopic study of the clay mineral fraipontite.
(2015) Theiss, Frederick L.; López, Andrés; Cipriano, Ricardo Augusto Scholz; Frost, Ray Leslie
The mineral fraipontite has been studied by using a combination of scanning electron microscopy with energy dispersive analysis and vibrational spectroscopy (infrared and Raman). Fraipontite is a member of the 1:1 clay minerals of the kaolinite-serpentine group. The mineral contains Zn and Cu and is of formula (Cu,Zn,Al)3(Si,Al)2O5(OH)4. Qualitative chemical analysis of fraipontite shows an aluminium silicate mineral with amounts of Cu and Zn. This kaolinite type mineral has been characterised by Raman and infrared spectroscopy; in this way aspects about the molecular structure of fraipontite clay are elucidated.
SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite.
(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Theiss, Frederick L.; Romano, Antônio Wilson
The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH) H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm 1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm 1. A very sharp band is observed at 3668 cm 1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm 1 are assigned to water stretching vibrations.
Structural characterization of the borate mineral inyoite – CaB3O3(OH)5_4(H2O).
(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Theiss, Frederick L.; Costa, Geraldo Magela da
We have studied the mineral Ca(H4B3O7)(OH)_4(H2O) or CaB3O3(OH)5_4(H2O) using electron microscopy and vibrational spectroscopy. The mineral has been characterized by a range of techniques including X-ray diffraction, thermal analysis, electron microscopy with EDX and vibrational spectroscopy. Electron microscopy shows a pure phase and the chemical analysis shows the presence of calcium only. 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. Raman and infrared bands are assigned to the stretching and bending modes of trigonal and tetrahedral boron and the stretching modes of the hydroxyl and water units. By using a combination of techniques we have characterized the borate mineral inyoite.
Vibrational spectroscopic study of the natural layered double hydroxide manasseite now defined as hydrotalcite-2H - Mg6Al2(OH)16[CO3]-4H2O.
(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Theiss, Frederick L.
Raman and thermo-Raman spectroscopy have been applied to study the mineral formerly known as manasseite now simply renamed as hydrotalcite-2H Mg6Al2(OH)16[CO3]_4H2O. The mineral is a member of the homonymous hydrotalcite supergroup. Hydrogen bond distances calculated using a Libowitzky-type empirical function varied between 2.61 and 3.00 Å. Stronger hydrogen bonds were formed by water units as compared to the hydroxyl units. Raman spectroscopy enabled the identification of bands attributed to the hydroxyl units. Two Raman bands at 1059 and 1064 cm_1 are assigned to symmetric stretching modes of the carbonate anion. Thermal treatment shifts these bands to higher wavenumbers indicating a change in the strength of the carbonate bonding.
A vibrational spectroscopic study of the phosphate mineral vantasselite Al4(PO4)3(OH)3 9H2O.
(2015) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; López, Andrés; Theiss, Frederick L.
We have studied the phosphate mineral vantasselite Al4(PO4)3(OH)3 9H2O using a combination of SEM with EDX and Raman and infrared spectroscopy. Qualitative chemical analysis shows Al, Fe and P. Raman bands at 1013 and 1027 cm 1 are assigned to the PO43 m1 symmetric stretching mode. The observation of two bands suggests the non-equivalence of the phosphate units in the vantasselite structure. Raman bands at 1051, 1076 and 1090 cm 1 are attributed to the PO43 m3 antisymmetric stretching vibration. A comparison is made with the spectroscopy of wardite. Strong infrared bands at 1044, 1078, 1092, 1112, 1133, 1180 and 1210 cm 1 are attributed to the PO4 3 m3 antisymmetric stretching mode. Some of these bands may be due to dAl2OH deformation modes. Vibrational spectroscopy offers a mechanism for the study of the molecular structure of vantasselite.
A vibrational spectroscopic study of the silicate mineral lomonosovite Na5Ti2(Si2O7)(PO4)O2.
(2014) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Graça, Leonardo Martins; Cipriano, Ricardo Augusto Scholz
The mineral lomonosovite has been studied using a combination of scanning electron microscopy with energy dispersive X-ray analysis and vibrational spectroscopy. Qualitative chemical analysis gave Si, P, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and Al. The mineral lomonosovite has a formula Na5Ti2(Si2O7)(PO4)O2. Raman bands observed at 909, 925 and 939 cm^-1 are associated with phosphate units. Raman bands found at 975, 999, 1070, 1080 and 1084 cm^-1 are attributed to siloxane stretching vibrations. The observation of multiple bands in both the phosphate stretching and bending regions supports the concept that the symmetry of the phosphate anion in the structure of lomonosovite is significantly reduced. Infrared spectroscopy identifies bands in the water stretching and bending regions, thus suggesting that water is involved with the structure of lomonosovite either through adsorption on the surface or by bonding to the phosphate units.
A vibrational spectroscopic study of the silicate mineral normandite – NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2.
(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Cipriano, Ricardo Augusto Scholz; Romano, Antônio Wilson
We have studied the mineral normandite using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral normandite NaCa(Mn2+,Fe2+)(Ti,Nb,Zr)Si2O7(O,F)2 is a crystalline sodium calcium silicate which contains rare earth elements. Chemical analysis shows the mineral contains a range of elements including Na, Mn2+, Ca, Fe2+ and the rare earth element niobium. No Raman bands are observed above 1100 cm 1. The mineral is characterised by Raman bands observed at 724, 748, 782 and 813 cm 1. Infrared bands are broad; nevertheless bands may be resolved at 723, 860, 910, 958, 933, 1057 and 1073 cm 1. Intense Raman bands at 454, 477 and 513 cm 1 are attributed to OSiO bending modes. No Raman bands are observed in the hydroxyl stretching region, but low intensity infrared bands are observed at 3191 and 3450 cm 1. This observation brings into question the true formula of the mineral.
A vibrational spectroscopic study of the silicate mineral pectolite – NaCa2Si3O8(OH).
(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Cipriano, Ricardo Augusto Scholz
The mineral pectolite NaCa2Si3O8(OH) is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and in other industrial applications. Raman bands at 974 and 1026 cm 1 are assigned to the SiO stretching vibrations of linked units of Si3O8 units. Raman bands at 974 and 998 cm 1 serve to identify Si3O8 units. The broad Raman band at around 936 cm 1 is attributed to hydroxyl deformation modes. Intense Raman band at 653 cm 1 is assigned to OSiO bending vibration. Intense Raman bands in the 2700–3000 cm 1 spectral range are assigned to OH stretching vibrations of the OH units in pectolite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the silicate mineral pectolite.
Vibrational spectroscopic study of the sulphate mineral glaucocerinite (Zn,Cu)10Al6(SO4)3(OH)32-18H2O - a natural layered double hydroxide.
(2014) Frost, Ray Leslie; Theiss, Frederick L.; López, Andrés; Cipriano, Ricardo Augusto Scholz
We have studied the molecular structure of the mineral glaucocerinite (Zn,Cu)5Al3(SO4)1.5(OH)16_9(H2O) using a combination of Raman and infrared spectroscopy. The mineral is one of the hydrotalcite supergroup of natural layered double hydroxides. The Raman spectrum is characterised by an intense Raman band at 982 cm_1 with a low intensity band at 1083 cm_1. These bands are attributed to the sulphate symmetric and antisymmetric stretching mode. The infrared spectrum is quite broad with a peak at 1020 cm_1. A series of Raman bands at 546, 584, 602, 625 and 651 cm_1 are assigned to the m4 (SO4)2_ bending modes. The observation of multiple bands provides evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 762 cm_1 is attributed to a hydroxyl deformation mode associated with AlOH units. Vibrational spectroscopy enables aspects of the molecular structure of glaucocerinite to be determined.
Vibrational spectroscopic study of the uranyl selenite mineral derriksite Cu4UO2(SeO3)2(OH)6-H2O.
(2014) Frost, Ray Leslie; Čejka, Jiři; Cipriano, Ricardo Augusto Scholz; López, Andrés; Theiss, Frederick L.; Xi, Yunfei
Raman spectrum of the mineral derriksite Cu4UO2(SeO3)2(OH)6_H2O was studied and complemented by the infrared spectrum of this mineral. Both spectra were interpreted and partly compared with the spectra of demesmaekerite, marthozite, larisaite, haynesite and piretite. Observed Raman and infrared bands were attributed to the (UO2)2+, (SeO3)2_, (OH)_ and H2O vibrations. The presence of symmetrically distinct hydrogen bonded molecule of water of crystallization and hydrogen bonded symmetrically distinct hydroxyl ions was inferred from the spectra in the derriksite unit cell. Approximate U–O bond lengths in uranyl and O–H_ _ _O hydrogen bond lengths were calculated from the Raman and infrared spectra of derriksite.