991 resultados para Sharp
Resumo:
Some minerals are colloidal and show no X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the assessment of the structure of these types of mineral. Among this group of minerals is kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6. The objective of this research is to determine the molecular structure of the mineral kemmlitzite using vibrational spectroscopy. Raman microscopy offers a useful method for the analysis of such colloidal minerals. Raman and infrared bands are attributed to the AsO43- , SO42- and water stretching vibrations. The Raman spectrum is dominated by a very intense sharp band at 984 cm-1 assigned to the SO42- symmetric stretching mode. Raman bands at 690, 772 and 825 cm-1 may be assigned to the AsO43- antisymmetric and symmetric stretching modes. Raman bands observed at 432 and 465 cm-1 are attributable to the doubly degenerate 2 (SO4)2- bending mode. Vibrational spectroscopy is important in the assessment of the molecular structure of the kemmlitzite, especially when the mineral is non-diffracting or poorly diffracting.
Resumo:
Jeremejevite is a borate mineral of aluminium and is of variable colour, making the mineral and important inexpensive jewel. The mineral contains variable amounts of F and OH, depending on origin. A comparison of the vibrational spectroscopic data is made with the published data of borate minerals. Raman spectra were averaged over a range of crystal orientations. Two intense Raman bands observed at 961 and 1067 cm1 are assigned to the symmetric stretching and antisymmetric stretching modes of trigonal boron. Infrared spectrum, bands observed at 1229, 1304, 1350, 1388 and 1448 cm1 are attributed to BOH in-plane bending modes. Intense Raman band found at 372 cm1 with other bands of significant intensity at 327 and 417 cm1 is assigned to trigonal borate bending modes. A quite intense Raman band is found at 3673 cm1 with other sharp Raman bands found at 3521, 3625 and 3703 cm1 are assigned to the stretching modes of OH. Raman and infrared spectroscopy has been used to assess the molecular structure of the mineral jeremejevite. Such research is important in the study of borate based nanomaterials.
Resumo:
Boracite 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 cm1 was assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1121, 1136, 1143 cm1 are attributed to the in-plane bending vibrations of trigonal boron. Four sharp Raman bands observed at 415, 494, 621 and 671 cm1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3405 and 3494 cm1, 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.
Resumo:
The mineral beryllonite has been characterized by the combination of Raman spectroscopy and infrared spectroscopy. SEMEDX was used for the chemical analysis of the mineral. The intense sharp Raman band at 1011 cm-1, was assigned to the phosphate symmetric stretching mode. Raman bands at 1046, 1053, 1068 and the low intensity bands at 1147, 1160 and 1175 cm-1 are attributed to the phosphate antisymmetric stretching vibrations. The number of bands in the antisymmetric stretching region supports the concept of symmetry reduction of the phosphate anion in the beryllonite structure. This concept is supported by the number of bands found in the out-of-plane bending region. Multiple bands are also found in the in-plane bending region with Raman bands at 399, 418, 431 and 466 cm-1. Strong Raman bands at 304 and 354 cm-1 are attributed to metal oxygen vibrations. Vibrational spectroscopy served to determine the molecular structure of the mineral. The pegmatitic phosphate minerals such as beryllonite are more readily studied by Raman spectroscopy than infrared spectroscopy.
Resumo:
Henmilite is a triclinic mineral with the crystal structure consisting of isolated B(OH)4 tetrahedra, planar Cu(OH)4 groups and Ca(OH)3 polyhedra. The structure can also be viewed as having dimers of Ca polyhedra connected to each other through 2B(OH) tetrahedra to form chains parallel to the C axis. The structure of the mineral has been assessed by the combination of Raman and infrared spectra. Raman bands at 902, 922, 951, and 984 cm1 and infrared bands at 912, 955 and 998 cm1 are assigned to stretching vibrations of tetragonal boron. The Raman band at 758 cm1 is assigned to the symmetric stretching mode of tetrahedral boron. The series of bands in the 400600 cm1 region are due to the out-of-plane bending modes of tetrahedral boron. Two very sharp Raman bands are observed at 3559 and 3609 cm1. Two infrared bands are found at 3558 and 3607 cm1. These bands are assigned to the OH stretching vibrations of the OH units in henmilite. A series of Raman bands are observed at 3195, 3269, 3328, 3396, 3424 and 3501 cm1 are assigned to water stretching modes. Infrared spectroscopy also identified water and OH units in the henmilite structure. It is proposed that water is involved in the structure of henmilite. Hydrogen bond distances based upon the OH stretching vibrations using a Libowitzky equation were calculated. The number and variation of water hydrogen bond distances are important for the stability off the mineral.
Resumo:
Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi2O6(OH)3 is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu2+ in square planar coordination. The intense sharp Raman band at 1053 cm1 is assigned to the 1 (A 1g) symmetric stretching vibration of the SiO4 units. The splitting of the 3 vibrational mode offers support to the concept that the SiO4 tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm1 with a shoulder at 644 cm1 is assigned to the 4 vibrational modes. Intense Raman bands at 419 and 460 cm1 are attributed to the 2 bending modes. Intense Raman bands at 3545 and 3573 cm1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi2O6(OH)3 xH2O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.
Resumo:
We have characterized anapaite Ca2Fe2+(PO4)24(H2O), a rare Ca and Fe phosphate, using a combination of electron microscopy and vibrational spectroscopy. The mineral occurs in soils and lacustrine sediments and is usually related to the diagenetic process in phosphorous rich sediments. The phosphate anion is characterized by its Raman spectrum with an intense sharp band at 943 cm-1, attributed to the 1 PO4 3- symmetric stretching mode. Three bands at 992, 1039 and 1071 cm-1 are attributed to 3 PO4 3-antisymmetric stretching modes. The infrared spectrum of anapaite shows complexity with a series of overlapping bands. Water in the structure of anapaite is observed by OH stretching vibrations at 2777, 3022 and 3176 cm-1 (Raman) and 2744, 3014 and 3096 cm-1 (infrared). The position of these bands provides evidence for the strong hydrogen bonding of water in the anapaite structure and contributes to the stability of the mineral.
Resumo:
This research was undertaken on phosphophyllite sample from the Hagendorf Sd pegmatite, Bavaria, Germany. Chemical analysis was carried out by Scanning Electron Microscope in the EDS mode and indicates a zinc and iron phosphate with partial substitution of manganese, which partially replaced iron. The calculated chemical formula of the studied sample was determined to be: Zn2(Fe0.65, Mn0.35)P1.00(PO4)2- 4(H2O). The intense Raman peak at 995 cm1 is assigned to the m1 PO3 4 symmetric stretching mode and the two Raman bands at 1073 and 1135 cm1 to the m3 PO3 4 antisymmetric stretching modes. The m4 PO3 4 bending modes are observed at 505, 571, 592 and 653 cm1 and the m2 PO3 4 bending mode at 415 cm1. The sharp Raman band at 3567 cm1 attributed to the stretching vibration of OH units brings into question the actual formula of phosphophyllite. Vibrational spectroscopy enables an assessment of the molecular structure of phosphophyllite to be assessed.
Resumo:
This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn3.23, Fe1.04, Ca0.19, Mg0.13)(PO4)2.7(HPO4)2.6(OH)4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm1 assigned to PO stretching vibrations of HPO42 units. The Raman band at 989 cm1 is assigned to the PO43 stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm1 are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO42 and PO43 units. A set of Raman bands at 531, 543, 564 and 582 cm1 are assigned to the 4 bending modes of the HPO42 and PO43 units. Raman bands observed at 414, and 455 cm1 are attributed to the 2 HPO42 and PO43 units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.
Resumo:
Vibrational spectroscopy enables subtle details of the molecular structure of cyrilovite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Cyrilovite is the Fe3+ member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of cyrilovite with that of wardite. The Raman spectrum of cyrilovite in the 8001400 cm1 spectral range shows two intense bands at 992 and 1055 cm1 assigned to the 1View the MathML source symmetric stretching vibrations. A series of low intensity bands at 1105, 1136, 1177 and 1184 cm1 are assigned to the 3View the MathML source antisymmetric stretching modes. The infrared spectrum of cyrilovite in the 5001300 cm1 shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 970 and 1007 cm1 and are attributed to the 1View the MathML source symmetric stretching mode. Raman bands are observed at 612 and 631 cm1 and are assigned to the 4 out of plane bending modes of the View the MathML source unit. In the 26003800 cm1 spectral range, intense Raman bands for cyrilovite are found at 3328 and 3452 cm1 with a broad shoulder at 3194 cm1 and are assigned to OH stretching vibrations. Sharp infrared bands are observed at 3485 and 3538 cm1. Raman spectroscopy complimented with infrared spectroscopy has enabled the structure of cyrilovite to be ascertained and compared with that of wardite.
Resumo:
We have analyzed a frondelite mineral sample from the Cigana mine, located in the municipality of Conselheiro Pena, a well-known pegmatite in Brazil. In the Cigana pegmatite, secondary phosphates, namely eosphorite, fairfieldite, fluorapatite, frondelite, gormanite, hureaulite, lithiophilite, reddingite and vivianite are common minerals in miarolitic cavities and in massive blocks after triphylite. The chemical formula was determined as (Mn0.68, Fe0.32)(Fe3+)3,72(PO4)3.17(OH)4.99. The structure of the mineral was assessed using vibrational spectroscopy. Bands attributed to the stretching and bending modes of PO4 3- and HOPO3 3- units were identified. The observation of multiple bands supports the concept of symmetry reduction of the phosphate anion in the frondelite structure. Sharp Raman and infrared bands at 3581 cm1 is assigned to the OH stretching vibration. Broad Raman bands at 3063, 3529 and 3365 cm1 are attributed to water stretching vibrational modes.
Resumo:
The mineral creedite is a fluorinated hydroxy hydrated sulphate of aluminium and calcium of formula Ca3Al2SO4(F,OH)2H2O. The mineral has been studied by a combination of electron probe analysis to determine the molecular formula of the mineral and the structure assessed by vibrational spectroscopy. The spectroscopy of creedite may be compared with that of the alums. The Raman spectrum of creedite is characterised by an intense sharp band at 986 cm1 assigned to the View the MathML source 1 (Ag) symmetric stretching mode. Multiple bands of creedite in the antisymmetric stretching region support the concept of a reduction in symmetry of the sulphate anion. Multiple bands are also observed in the bending region with the three bands at 601, 629 and 663 cm1 assigned to the View the MathML source 4 (Ag) bending modes. The observation of multiple bands at 440, 457 and 483 cm1 attributed to the View the MathML source 2 (Bg) bending modes supports the concept that the symmetry of the sulphate is reduced by coordination to the water bonded to the Al3+ in the creedite structure. The splitting of the 2, 3 and 4 modes is attributed to the reduction of symmetry of the SO4 and it is proposed that the sulphate coordinates to water in the hydrated aluminium in bidentate chelation.
Resumo:
Vision-based SLAM is mostly a solved problem providing clear, sharp images can be obtained. However, in outdoor environments a number of factors such as rough terrain, high speeds and hardware limitations can result in these conditions not being met. High speed transit on rough terrain can lead to image blur and under/over exposure, problems that cannot easily be dealt with using low cost hardware. Furthermore, recently there has been a growth in interest in lifelong autonomy for robots, which brings with it the challenge in outdoor environments of dealing with a moving sun and lack of constant artificial lighting. In this paper, we present a lightweight approach to visual localization and visual odometry that addresses the challenges posed by perceptual change and low cost cameras. The approach combines low resolution imagery with the SLAM algorithm, RatSLAM. We test the system using a cheap consumer camera mounted on a small vehicle in a mixed urban and vegetated environment, at times ranging from dawn to dusk and in conditions ranging from sunny weather to rain. We first show that the system is able to provide reliable mapping and recall over the course of the day and incrementally incorporate new visual scenes from different times into an existing map. We then restrict the system to only learning visual scenes at one time of day, and show that the system is still able to localize and map at other times of day. The results demonstrate the viability of the approach in situations where image quality is poor and environmental or hardware factors preclude the use of visual features.
Resumo:
The mineral amarantite Fe23+(SO4)O7H2O has been studied using a combination of techniques including thermogravimetry, electron probe analyses and vibrational spectroscopy. Thermal analysis shows decomposition steps at 77.63, 192.2, 550 and 641.4C. The Raman spectrum of amarantite is dominated by an intense band at 1017 cm-1 assigned to the SO42- 1 symmetric stretching mode. Raman bands at 1039, 1054, 1098, 1131, 1195 and 1233 cm-1 are attributed to the SO42- 3 antisymmetric stretching modes. Very intense Raman band is observed at 409 cm-1 with shoulder bands at 399, 451 and 491 cm-1 are assigned to the v2 bending modes. A series of low intensity Raman bands are found at 543, 602, 622 and 650 cm-1 are assigned to the v4 bending modes. A very sharp Raman band at 3529 cm-1 is assigned to the stretching vibration of OH units. A series of Raman bands observed at 3025, 3089, 3227, 3340, 3401 and 3480 cm-1 are assigned to water bands. Vibrational spectroscopy enables aspects of the molecular structure of the mineral amarantite to be ascertained.
Resumo:
Meyerhofferite is a calcium hydrated borate mineral with ideal formula: CaB3O3(OH)5H2O 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 cm1 assigned to the symmetric stretching mode of trigonal boron. Broad Raman bands at 1046, 1110, 1135 and 1201 cm1 are attributed to BOH in-plane bending modes. Raman bands in the 9001000 cm1 spectral region are assigned to the antisymmetric stretching of tetrahedral boron. Distinct OH stretching Raman bands are observed at 3400, 3483 and 3608 cm1. 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.
