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Vermiculite

About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.


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Journal ArticleDOI
30 Sep 1977-Gff
TL;DR: The role of iron impurities in the analyses of the spectra is also discussed, and a search scheme for Mossbauer investigations of clay minerals is given in this article, where it is shown that iron occupies the octahedral positions and in rare cases also the tetrahedral position.
Abstract: Mossbauer spectroscopy has been used to study iron in clay and related minerals at room temperature. The investigated minerals are kaolinite, montmorillonite, beidellite, bentonite, muscovite, illite, vermiculite, hectorite, biotite and chlorite and, in all, 19 different minerals have been studied. It is shown that iron occupies the octahedral positions and in rare cases also the tetrahedral position. The Fe3+/Fe2+ ratios are determined and compared with the results of chemical analyses. The role of iron impurities in the analyses of the spectra is also discussed, and a search scheme for Mossbauer investigations of clay minerals is given.

34 citations

Journal ArticleDOI
TL;DR: The orientation dependence of intercalated oligothiophene derivatives in vermiculite and metal disulfides MS 2 (M=Mo, Ti and Zr) on the pendant group on the thiophene ring and the host material was studied by X-ray diffraction and solid state nuclear magnetic resonance spectroscopy as mentioned in this paper.

34 citations

Journal ArticleDOI
TL;DR: Ferrous iron in the layers increased 2-fold or more on deferration of coarser fractions of micaceous vermiculite naturally weathered from biotite (Colorado and Transvaal sources) as discussed by the authors.
Abstract: Ferrous iron in the layers increased 2-fold or more on deferration of coarser fractions of micaceous vermiculite naturally weathered from biotite (Colorado and Transvaal sources) The ferric iron content of the layers was decreased by the deferration treatment but the original content was restored by subsequent H2O2 treatment Sesquioxide coatings on micaceous vermiculite from Colorado, examined electron microscopically, were composed predominantly of Fe2O3 (80 to 85 percent), along with Al2O2 and SiO2 The CEC increased from 64 to 95 meq per 100 g in the fraction coarser than 1000 microns and 50 to 64 meq per 100 g in the fraction 2–02, microns in diameter, as a result of removal by deferration of positively charged sesquioxide coating which had originally blocked a portion of the CEC Although treatment with H2O2 after deferration restored the Fe3+ content to approximately the original value, the CEC was not affected probably because of deprotonation OH− O2− + H+ occurring simultaneous with Fe2+ Fe3+

33 citations

Journal ArticleDOI
TL;DR: The ultrasound-assisted exfoliation and shear-mixing of a multi-phasic vermiculite in mild acidic aqueous solutions were employed to successfully obtain dispersions of mono- and few-layer thick clay nanosheets, which may enable in the future the generation of patterns of thermal insulators onto different surfaces by applying verMiculite nanOSheets in the form of dispersions and printable inks.
Abstract: Phyllosilicates are layered materials possessing unique thermal properties, commonly exploited in their multilayered crystalline form as refractory insulators and heating elements. A more versatile use of such materials, however, would require their existence in the form of inks and dispersions ready to be patterned. Within this framework, the liquid-phase exfoliation of low-cost, low-purity materials such as bulk multiphasic minerals and powders represents an economically advantageous approach for the production of 2D nano-sized objects with a defined composition, size and morphology. Here, ultrasound-assisted exfoliation and shear-mixing of a multi-phasic vermiculite in mild acidic aqueous solutions were employed to successfully obtain dispersions of mono- and few-layer thick clay nanosheets. The exfoliated materials were thoroughly investigated through granulometry, X-Ray Diffraction (XRD), specific surface area measurements and AFM imaging. Despite the fact that the lateral size and the thickness distribution of exfoliated flakes obtained with the two approaches appear similar, the ultrasound-assisted exfoliation process yielded a larger amount of mono- and bi-layer thick flakes as well as materials with a higher specific surface area. XRD analysis revealed that the use of ultrasound waves in an acidic environment results in the complete exfoliation of the vermiculite layer, whereas the use of shear forces under the same conditions results in the exfoliation of hydrobiotite and mica crystalline phases. Thermal conductivity measurements provided clear evidence on how the structural changes - arising from the exfoliation process - have a direct impact on the properties of the exfoliated clay. Remarkably, compared to the raw material, the thermal conductivity of the exfoliated material decreases by 25%, reaching the ultra-low thermal conductivity regime (<0.1 W m-1 K-1). Our approach may enable in the future the generation of patterns of thermal insulators onto different surfaces by applying vermiculite nanosheets in the form of dispersions and printable inks.

33 citations

Journal ArticleDOI
TL;DR: In this article, the dissolution of phlogopite with 0.01 N HCl solution containing 0.1 M NaCl at 50°, 80° and 120°C have been carried out to aid in the understanding of the dissolution process of mica and the formation of secondary phases such as vermiculite and interstratified mica/vermiculites.
Abstract: The alteration experiments of phlogopite with 0.01 N HCl solution containing 0.1 M NaCl at 50°, 80° and 120°C have been carried out to aid in the understanding of the dissolution process of mica and the formation of secondary phases such as vermiculite and interstratified mica/vermiculite. Twenty milligrams of phlogopite samples were suspended in 20 ml or 100 ml of leaching solution. In these experiments, the dissolution ofphlogopite occurred incongruently, where the preferential release of K occurred in almost all stages of the alteration reaction. In the 100 ml experiments, the priority in dissolution in the initial stage was in the order; K > Fe > Mg, Al > Si. This supports that phlogopite leaching is controlled by the mineral structure. At 80° and 50°C in the 20 ml experiments, the release of all elements except for K was nearly congruent. At 120°C in the 20 ml experiments, the dissolution was outwardly incongruent, which Fe decreased remarkably after six days and Al was released most slowly compared with all other elements in phlogopite. This is probably due to the precipitation of secondary phases such as aluminum and iron oxides and/or hydroxides. Vermiculite and R1-type interstratified mica/vermiculite, containing 70 ∼ 50% mica, were formed in the alteration process of phlogopite. The following two processes were confirmed for the formation of interstratified structure: Interstratified structure was formed (1) directly from phlogopite or (2) from vermiculite which was produced earlier from phlogopite by regaining of K from the ambient solution. It may depend on the release rate of K from phlogopite whether mica-vermiculite layer sequences develop or vermiculite-vermiculite sequences do.

33 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202395
2022223
202163
202068
2019104
2018101