Estimation of Clay Proportions in Mixtures by X-Ray Diffraction and Computerized Chemical Mass Balance (original) (raw)
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The change of phase composition in kaolinite- and illite-rich clay-based ceramic bodies
Applied Clay Science, 2004
Raw material for ceramics consists mainly of kaolinite, illite, quartz and feldspar. Three representative clays, a high kaolinitic (HB), illitic-and quartz-rich (KW) and naturally mixed kaolinite-illite (P1) clays of Westerwald area, were chosen for this study [Kromer, H., 1980. Tertiary clays in the Westerwald area. Geol. Jb. D. Rhei D Hanover, 69-84]. The largest and oldest clay mining area of Germany is in the Westerwald area. These clays were mixed with each other and also with K, and Ca-Na feldspar. The high temperature phases of the mixed bodies were of three groups: crystalline phase, amorphous/glassy phase and porosity. The aim of this study was to determine: (1) the effect of kaolinite-illite-quartz ratios, (2) the effect of heat treatment and (3) the effect of feldspar on the fired mineralogy of the fired products. The crystalline phases are cristobalite, mullite, quartz, hematite and anatase. The bodies consist of crystalline phases such as quartz, mullite and cristobalite in a composite structure where crystals and pores are often embedded in amorphous/glassy phase. The formation of mullite and cristobalite is very distinctive in kaolinitic clay, and the structure is dominated by the spiky primary mullite. In the illite/sericite-rich mixtures, the high K content causes a large amount of melt superimposed on the mullite formation. The cristobalite formation is completely suppressed in illite/sericite-rich bodies. After dehydroxylation, metakaolinite and illite/sericite anhydride structures are formed. The persistence of illite/sericite anhydride peaks above 950 jC in KW clay indicates the presence of sericite/muscovite mineral. The disappearance temperatures and firing behaviour of K and Ca-Na feldspar observed within the XRD patterns of mixed bodies are different. K feldspar lines disappear earlier in HB bodies than in KW bodies, but Ca-Na feldspar shows a reverse behaviour. While Ca-Na feldspar peak intensity gradually decreases but persists at 1150-1250 jC, K feldspar suddenly disappears at 1150 jC.
Clays and Clay Minerals, 1978
Kaolinites of all kinds (fine, 'fireclay,' "type IV,' etc.), some of which do not expand or expand incompletely with the usual intercalation methods used for comparison, are expanded completely by treatment of dry (110~ clay with dry CsCl salt, followed by contact with hydrazine for 1 day at 65~ and then with DMSO overnight at 90~ Comparison treatments were grinding in KOAc, soaking in hydrazine, and Li-DMSO, as well as combination of these. Following the Cs-hydrazine-DMSO treatment, the 7.2 ,~ spacing of l: 1 dioctahedral layer silicates shifts to I 1.2/~ and the I 1.2/~/(7.2 + 11.2/~) ratio = 1.0. The trioctahedral 1:1 layer silicates and chlorite are not expanded by the Cs-hydrazine-DMSO procedure.
Applied Clay Science, 2016
The thermal transformations processes of kaolinite (K) in kaolinitic clays is known to consist of a dehydroxylation into metakaolin (MK) at ≈600°C, followed by the formation of a spinel type aluminosilicate (SAS) at ≈980°C, and finally the development of mullite (M) at higher temperatures (1200-1300°C). The structural characterization of these materials is generally based on X-ray diffraction (XRD) studies, where the XRD features of K and M are well defined due to their crystalline nature, but as consequence of the low crystallinity of MK and SAS, the precise characterization of these phases is not possible using this technique. In this study the nature of aluminum atoms in the different materials obtained by thermal treatments of a kaolinite is investigated using Al K-XANES and compared with other well-known aluminum containing materials. XRD and SEM characterization were also carried out. The results confirm the potentiality of this synchrotron based techniques for the characterization of natural materials and ceramics especially with low crystallinity. Particularly the mullite aluminums Al K-XANES spectra were not reported before.
The Thermodynamic Status of Compositionally-Variable Clay Minerals: A Discussion
Clays and Clay Minerals, 1992
wide compositional variations and excess enthalpies of mixing calculated with electrostatic models imply that clay minerals of variable composition are disequilibrium solids. However, recent ATEM analyses ofillite samples indicate compositional homogeneity of single illite grains and limited compositional variations in sedimentary basins. Moreover, Lippmann's electrostatic model may be inadequate inasmuch as it neglects polarization energy which is known to be a significant component of lattice energy even in dominantly ionic structures. Contrary to the assumptions of Lippmann, I/S minerals have also been shown to undergo Ostwald ripening. reported that smectites do not reversibly control equilibria and further argued that conceptual and experimental deficiencies inherent in the solubility method prevent the attainment and demonstration of equilibrium in experiments with complex aluminosilicates of variable composition. However, equilibrium may be assumed if: (1) steady states are approached from both under-and oversaturation, (2) the slopes of univariant lines representing mineral-solution equilibria are rational over a wide range of solution compositions and temperature, and (3) results are reproducible in experiments of long duration. Recent solubility studies of smectites, chlorites, and illites meet these criteria indicating that clay minerals of variable composition are true phases capable of attaining equilibrium.
Minerals Engineering, 2011
Hydrothermal transformations and weathering are important mineralizing processes in carbonatiterelated ores. But the transformation products of mafic minerals, such as the clay minerals, vermiculite and interstratified phases, preclude the use of X-ray diffraction, particularly the Rietveld method, for mineral phase quantification. After treatment with KCl, vermiculite and interstratified phases (all peaks roughly at 1.2, 1.4-1.5 and 2.4 nm) are converted to a phlogopite-like structure with d(0 0 1) = 1.0 nm, which can successfully be refined. The method was tested using three carbonatite-derived ores, with a total phlogopite-like phase content ranging from 1.2 to 32.3 wt.%. Comparison of the chemical analyses with the calculated chemical composition, based on the phase quantification and the mineral composition is in good agreement for major elements, such as Si, Fe and Al. For P results were also very good, but Ti and Nb are generally underestimated, and Ba is overestimated. Minerals with lower contents, as pyrochlore, approach the diffraction detection limit. Problems to accurately determine mineral composition for some of the phases also impacts on the reconciliation. The chemical composition of the pyrochlore group minerals changed, but not to an extent to constrain the usefulness of the technique. Cation exchange successfully extended the amenability of the Rietveld method for phase quantification.
6th Eeigm International Conference on Advanced Materials Research, 2012
The aim of this study was to compare the thermal behaviour of clays containing illite and kaolinite in various proportions. The clays contained small amounts of K and Fe, which act as fluxing agents. In order to investigate the phase formations during heating, the samples were examined in a differential scanning calorimeter at temperatures up to 1300ºC. The thermal expansion of the samples was determined by dilatometer measurements from room temperature up to 1150ºC. Phases were identified using x-ray diffraction and scanning electron microscopy. In all samples, most of the kaolinite was transformed into metakaolinite during heating up to 650ºC, while illite remained unchanged up to 950ºC. There was no influence of K and Fe on dehydroxylation. Metakaolinite formed at temperatures above 950ºC leading to a Si-Al spinel. Furthermore, mullite was formed in the temperature interval 1050-1150ºC. In this temperature range, the mechanism of mullite formation depended on the amount of K and Fe in the samples, changing the temperature of formation of mullite. It was observed by x-ray diffraction that most of the illite was transformed into a Si-Al spinel phase at 1050ºC, and during further heating transformed into mullite. An increased amount of illite in the clays slightly decreased the melting temperature. The dilatometer measurements showed expansion and shrinkage for the dehydroxylation and spinel-phase formation, respectively.
Journal of Soils and Sediments, 2017
Purpose Brazilian soils that present extremely hard sub-superficial horizons when dry and friable when humid are similar to the Australian and South African hardsetting horizons whose hardness can be mainly related to low crystallinity. Studies involving refinement by the Rietveld method with X-ray diffraction (RM-XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and their relation have not been carried out in hardsetting horizon soils. Thus, the objective of this study is to obtain information about the kaolinite in the hardsetting horizon of a Yellow Argisol clay fraction, taking into consideration the results of isomorphic substitution, crystallite average size, and microstrains, relating them to particle image analysis regarding their morphology and size. Materials and methods Soil samples were collected in the hardsetting horizon of a Yellow Argisol in the Coastal Tablelands region, which covers the whole Brazilian Northeast coast and part of the Southeast region. The sample was powdered, sieved, and submitted to dispersion and physical fractioning process by sedimentation. The clay fraction was analyzed by RM-XRD, AFM, and SEM techniques. Results and discussion The RM-XRD provided improvement of indices with isomorphic substitutions in the goethite [Fe 0.70 Al 0.30 O(OH)], kaolinite [Al 1.44 Fe 0.56 Si 2 O 5 (OH) 4 ], and halloysite [Al 1.42 Fe 0.58 Si 2 O 5 (OH) 4 ]; 29 nm crystallite average size; 5 × 10 −3 microstrain; and 49.5% kaolinite. AFM analyses indicated particle average size from 80 to 250 nm and average height from 60 to 80 nm. By relating this data, it was possible to estimate that the particles under analysis are kaolinite composed of 3 to 9 crystallites and stacking of 88 to 112 layers. Conclusions The process, analyses, and comparisons such as crystallographic and morphologic information about the kaolinite mineral particles contribute to the comprehension of the hardsetting horizon soil nature as well as other soils that present minerals with a high degree of isomorphic substitution.
Clay Mineralogy: Spectroscopic and Chemical Determinative Methods
Journal of Environmental Quality, 1995
Of the determinative methods used to study clay minerals, chemical analysis is the oldest and most established. Before the development of the earliest instrumental techniques, such as X-ray diffraction and thermal methods, the identification of clay-mineral phases was accomplished by chemical analysis, supplemented where possible by optical data and physical characteristics such as specific gravity, colour, hardness, etc. However, fine-grained materials cannot be characterized reliably using these methods alone, and misidentifications were common. With the routine application of infrared spectroscopy and electron microscopy, in addition to X-ray diffraction and thermal analysis, instrumental techniques are now unquestionably superior to chemical analysis for clay-mineral identification and a clay is often described and identified without recourse to chemical analysis. Nevertheless, for complete characterization, a chemical analysis is still essential, as this is the only way that a structural formula can be calculated and the distribution of cations in the structure defined directly. A full characterization should include the determination of all the major and minor elements (with the proportion of the iron present in the ferrous and ferric forms) and also the determination of the cation-exchange capacity and, if possible, the anion-exchange capacity. Classification of clay minerals has always depended heavily on chemical data, and many clay-mineral groups, such as smectites, illites and chlorites, are subdivided according to composition. The characterization of a clay mineral as 'dioctahedral' or 'trioctahedral' can be determined from a b-dimension measurement using X-ray or electron-diffraction techniques, but these terms also have a chemical connotation, indicating the valency of the cations occupying the octahedral sheets. The type and Clay Mineralogy: Spectroscopic and Chemical Determinative Methods.
Petroleum Science and Technology, 2008
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Plant and Soil, 2008
Potassium (K) is a major element for plant growth. The K + ions fixed in soil 2:1 clay mineral interlayers contribute to plant K nutrition. Such clay minerals are most often the majority in temperate soils. Field and laboratory observations based on Xray diffraction techniques suggest that 2:1 clay minerals behave as a K reservoir. The present work investigated this idea through data from a replicated long term fertilization experiment which allowed one to address the following questions: (1) Do fertilization treatments induce some modifications (as seen from X-ray diffraction measurements) on soil 2:1 clay mineralogy? (2) Are soil 2:1 clay mineral modifications related to soil K budget in the different plots?