Advances in Quantitative X-Ray Mineralogy: Mixed Crystals in Bauxite

Knorr, K.; Neumann, Reiner

doi:10.1007/978-3-642-27682-8_45

Cited by 10 publications

(11 citation statements)

References 7 publications

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“…Quantitative analyzes were performed by refinement of the total multiphase spectrum method, known as the Rietveld method [11][12][13], with Bruker-AXS Diffrac.Topas 5.0 software. The crystal structure files of the phases were sourced from the Bruker-AXS and COD (Crystallographic Open Database) databases, with implementation for the restricted refinement of isomorphic substitutions in goethite [12][13][14], hematite [13][14][15] and the solid solution magnetite-maghemite [3].…”

Section: Methodsmentioning

confidence: 99%

“…The polished blocks were analyzed on reflected light microscope (Zeiss Axioimager M2.m) and Raman microprobe. A Horiba Jobin-Yvon LabRam 800HR spectrometer coupled to an Olympus BX-41 polarizing microscope was employed, using a 632.8 nm excitation laser with neutral density filters to reduce the laser power to 0.7 mW in order to avoid oxidation [14][15][16]. Even reducing the laser power, the spectra had to be measured quickly, for three accumulations of 2 s each, since the decrease in the intensity of the maghemite diagnostic vibrations was observed for longer measurement times.…”

Section: Methodsmentioning

confidence: 99%

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Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by X-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods

Hiraga¹,

Gomes²,

Neumann³

2021

Preprint

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Maghemite (γ-Fe2O3) is a mineral formed from magnetite oxidation at low temperatures, an intermediate metastable term of the magnetite to hematite oxidation and could be mixed with both. It has magnetic susceptibility similar to magnetite, crystal structure close to magnetite with which it forms a solid solution, while compositionally it equals hematite. Maghemite is thus easily misidentified as magnetite by X-ray diffraction and/or as hematite by spot chemical analysis in iron ore characterization routines. Nonstoichiometric magnetite could be quantified in samples of Brazilian soils and iron ores by the Rietveld method using a constrained refinement of the X-ray patterns. The results were confirmed by reflected light microscopy and Raman spectroscopy, thus qualitatively validating the method. X-ray diffraction with the refinement of the isomorphic substitution of Fe2+ by Fe3+ along the magnetite-maghemite solid solution could help to suitably characterize maghemite in iron ores, allowing for the evaluation of its ultimate influence on mineral processing, by affecting its surface and breakage properties.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by X-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods

Hiraga¹,

Gomes²,

Neumann³

2021

Preprint

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“…The results are fast and reliable. 24 The elemental chemical composition was determined by X-ray fluorescence (Shimadzu XRF 800HS). Calibration curves (0.1-1000 mg kg −1 ) for fluorine, aluminum, sodium, silicon, iron, calcium, potassium, magnesium and zirconium were employed for the quantitative analyses of these elements.…”

Section: Characterization Of Ore Samplesmentioning

confidence: 99%

“…The low content in silicates, however, tends to increase the uncertainties related to the quantification by the XRD/Rietveld method. 24 Elemental analysis of fluorine in fluorine-rich minerals by XRF appears thus to be possible.…”

Section: Characterization Of the Ore Samplesmentioning

confidence: 99%

Evaluation of Cryolite From Pitinga (Amazonas-Brazil) as a Source of Hydrogen Fluoride

Paulino¹,

Neumann²,

Afonso³

2016

Química Nova

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This paper reports the use of cryolite from the Pitinga Mine (Amazonas state, Brazil) as raw material in hydrogen fluoride production. Samples were initially characterized by chemical and mineralogical analyses. They presented low silica content (< 4 wt.%). After milling, cryolite samples were digested with concentrated sulfuric acid under stirring (200 rpm) and variable temperature, time and liquid to solid ratio conditions. Under the best experimental conditions (140 °C, 3-5 h), 96 wt.% of fluorine was recovered as hydrogen fluoride. The application of a 2 3 full factorial design showed that temperature and reaction time were relevant parameters during leaching, whereas liquid to solid ratio was not statistically significant.

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“…The procedure was elegantly included in the Rietveld refinement procedure by Knorr andNeumann (2011) andNeumann et al (2014).…”

Section: Lattice Constant Refinement For the Evaluation Of Hematite Amentioning

confidence: 99%

XRD analysis and evaluation of iron ores and sinters

Villiers

Lü

2015

Iron Ore

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Advances in Quantitative X-Ray Mineralogy: Mixed Crystals in Bauxite

Cited by 10 publications

References 7 publications

Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by X-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods

Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by X-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods

Evaluation of Cryolite From Pitinga (Amazonas-Brazil) as a Source of Hydrogen Fluoride

XRD analysis and evaluation of iron ores and sinters

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