Search results for "Kaolinite"
showing 10 items of 65 documents
Late Cretaceous palaeoenvironments expressed by the clay mineralogy of Cenomanian–Campanian chalks from the east of the Paris Basin
2005
Abstract The clay fraction of Cenomanian–Campanian chalks cored at Poigny and Sainte-Colombe, close to Provins (east-south-east of Paris), includes variable proportions of smectitic minerals, illite and kaolinite. The smectitic sediments (which constitute the background of low-terrigenous supply throughout the stratigraphic interval) resulted mainly from the warm, humid climate and high sea level that prevailed during Late Cretaceous in this area. During the Late Turonian, the smectitic sedimentation was interrupted by significant detrital inputs of illite and kaolinite. This reflected tectonic rejuvenation of landmasses coeval with an explosive volcanism expressed by the occurrence of bent…
Effect of Morphology and Size of Halloysite Nanotubes on Functional Pectin Bionanocomposites for Food Packaging Applications
2017
Pectin bionanocomposite films filled with various concentrations of two different types of halloysite nanotubes were prepared and characterized in this study as potential films for food packaging applications. The two types of halloysite nanotubes were long and thin (patch) (200-30 000 nm length) and short and stubby (Matauri Bay) (50-3000 nm length) with different morphological, physical, and dispersibility properties. Both matrix (pectin) and reinforcer (halloysite nanotubes) used in this study are considered as biocompatible, natural, and low-cost materials. Various characterization tests including Fourier transform infrared spectroscopy, field emission scanning electron microscopy, rele…
Chemical weathering of volcanic rocks at the island of Pantelleria, Italy: Information from soil profile and soil solution investigations
2007
Abstract Concentrations of major, minor and trace elements were determined in soil profiles and soil solutions from the island of Pantelleria, Sicily Channel, to evaluate the weathering extent of soils evolved on trachytic and pantelleritic rocks and the aqueous transport of elements by their soil solutions. The chemical index of alteration (CIA) indicates a low-to-moderate degree of weathering; consistently, the mineralogical and geochemical imprints of the parent rocks are generally preserved. The chemical weathering appears to be incongruent, owing to primary minerals and glass dissolving to a variable degree while secondary minerals have formed. Based on the calculated saturation state …
Photoluminescent hybrid nanomaterials from modified halloysite nanotubes
2018
The synthesis of photoluminescent nanomaterials based on halloysite nanotubes is described. The obtained hybrid was characterized by means of TGA, FT-IR, DLS and XPS measurements; in addition its morphology was imaged by TEM and HR-TEM. The HNT hybrid also exhibited photoluminescent properties, both in solution and in the solid state, and white-light emission (0.24, 0.36; CIE coordinates) was observed. This work could be pioneering as a new strategy for manufacturing both LEDs and fluorescent tags based on HNT nanomaterials. © 2018 The Royal Society of Chemistry.
Role of clays in protecting adsorbed DNA against X-ray radiation
2004
The X-ray emission of the young Sun was much harder and intense than today and might have played a significant role in the evolution of complex organics in protoplanetary environments. We investigate the effects of soft X-rays on tryptophan molecules in aqueous solutions at room temperature. As results of the irradiation experiments we detect several light species indicative of fragmentation, together with large molecular structures such as tryptophan dipeptide and tripeptide. Complexification is more evident in H2O solution than in D2O, probably due to isotopic effects. The abundances of peptides depend on the irradiation dose and decrease with increasing energy deposition. Radicals such a…
An assembly of organic-inorganic composites using halloysite clay nanotubes
2018
Halloysite is natural tubular clay suitable as a component of biocompatible nanosystems with specific functionalities. The selective modification of halloysite inner/outer surfaces can be achieved by exploiting supramolecular and covalent interactions resulting in controlled colloidal stability adjusted to the solvent polarity. The functionalized halloysite nanotubes can be employed as reinforcing filler for polymers as well as carriers for the sustained release of active molecules, such as antioxidants, flame-retardants, corrosion inhibitors, biocides and drugs. The tubular morphology makes halloysite a perspective template for core-shell metal supports for mesoporous catalysts. The cataly…
Modeling of the Halloysite Spiral Nanotube
2015
A computational SCC-DFTB investigation dealing with the structure of hydrated and anhydrous halloysite nanotubes with a spiral geometry is reported. The peculiar characteristics of these systems are described in terms of tetrahedral and octahedral distortions, of hydrogen bonds geometries involving water molecules and the surfaces in the hydrated nanotube, and of the interlayer interactions in the anhydrous one. When the properties of the spiral nanotube are compared with those of the kaolinite sheet, a certain degree of intrinsic disorder in the halloysite systems is revealed, due to the intrinsic nature of the spiral folding. This is particularly evident in the hydrogen bonds network occu…
Float glass colouring by ion exchange
2008
Abstract Back in the Middle Ages, glass artists used to produce yellowish colorations in soda-lime glasses using mixtures that contained silver salts, clay composites and natural oils. The resulting colour was a characteristic pale yellow known as silver-stain. This coloration is mainly caused by the extinction – absorption and, to a lesser extent, scattering – of light occasioned by silver nanoparticles formed inside the glass. This colouring technique comprises a heat treatment divided in two stages: in the first one, an ion exchange between the silver ions in the mixture and the alkali ions in the glass takes place. This process is called nucleation of silver nanoparticles. The second st…
Capturing digital data of rock magnetic, gamma-ray and IR spectrometry for in-situ quality control and for the study of the physical–chemical regime …
2014
Abstract Residual kaolin deposits are operated on a worldwide basis. The majority of them is derived from chemical weathering of felsic rocks during the Cenozoic. This is true for the kaolin deposits on the western edge of the Bohemian Massif. Here this type of deposit provides industrial minerals for the ceramic industry in SE Germany. This raw material formed under tropical climatic conditions during the Miocene and Pliocene across a vast peneplain. Only within the Naab-Wondreb Depression, however, were economic accumulations preserved from erosion. Here near Tirschenreuth, kaolin has been mined since its discovery in 1830. The semi-consolidated regolith is composed of quartz and opaline …
Halloysite nanotubes filled with salicylic acid and sodium diclofenac: effects of vacuum pumping on loading and release properties
2021
AbstractIn this work, we investigated the effects of the vacuum pumping on both the loading efficiencies and the release kinetics of halloysite nanotubes filled with drug molecules dissolved in ethanol. As model drugs, salicylic acid and sodium diclofenac were selected. For comparison, the loading of the drug molecules was conducted on platy kaolinite to explore the key role of the hollow tubular morphology on the filling mechanism of halloysite. The effects of the pressure conditions used in the loading protocol were interpreted and discussed on the basis of the thermodynamic results provided by Knudsen thermogravimetry, which demonstrated the ethanol confinement inside the halloysite cavi…