Search results for "MINERALOGY"
showing 10 items of 1516 documents
The use of tree-rings and foliage as an archive of volcanogenic cation deposition.
2007
Tree cores (Pinus nigra ssp. laricio) and leaves (Castanea sativa) from the flanks of Mount Etna, Sicily were analysed by ICP-MS to investigate whether volcanogenic cations within plant material provide an archive of a volcano's temporal and spatial depositional influence. There is significant compositional variability both within and between trees, but no systematic dendrochemical correlation with periods of effusive, explosive or increased degassing activity. Dendrochemistry does not provide a record of persistent but fluctuating volcanic activity. Foliar levels of bioaccumulated cations correspond to modelled plume transport patterns, and map short-term volcanic fumigation. Around the fl…
Investigation of surface properties of lunar regolith: Part I
2007
This paper describes an initial investigation of the surface properties of three lunar soil samples from the Apollo 11, 12 and 16 missions, respectively. We report on density measurements using a helium pycnometer, adsorption isotherms of krypton applied for the determination of specific surface area of the samples and gravimetric measurement of the isotherms of water, heptane and octane. Electron-microscopic photographs are described and discussed.
Synthesis and characterization of ZnS nanoparticles in water/AOT/n-heptane microemulsions
1999
ZnS nanoparticles were synthetized using water-containing AOT reversed micelles as nanoreactors and characterized by UV-Vis spectrophotometry, HRTEM (high-resolution transmission electron microscopy), SAED (selected-area electron diffraction), and digital image processing. The experimental data evidence a slow growing process of fractal-like ZnS nanoparticles’ coupled with a change of their photophysical properties. Both these processes are well described by power laws. The nanoparticles size is mainly controlled by the micellar size. After evaporation of the organic solvent, it has been found that the deposit is constituted by smaller and more stable ZnS nanoparticles bathed in a surfactan…
The role of pore topology on the behaviour of FCC zeolite additives
1999
Abstract A large variety of zeolite topologies including: large pore tridirectional (Beta), large pore unidirectional (Mordenite, SSZ-24), bidirectional 10 member ring pores (MRP) (ZSM-5), bidirectional 10 × 8 MRP (Ferrierite), tridirectional with connected 12 and 10 MRP (CIT-1), bidirectional with 12 MRP connected by 10 MRP (NU-87), tridirectional with 10 × 11 × 12 MRP (NU-86), and finally 10 MRP, and independent 12 MR cavities connected by 10 MR windows (MCM-22), have been studied as catalysts for the cracking of a gasoline range model molecule ( n -heptane). Kinetic and decay constants as well as selectivity parameters such as paraffin/olefin, i -C 4 / n -C 4 , i -C 5 / n -C 5 , C 3 /C 4…
Structural and conductivity study of the proton conductor BaCe(0.9−x)ZrxY0.1O(3−ı) at intermediate temperatures.
2009
International audience; The perovskite BaCe(0.9−x)ZrxY0.1O(3−ı) is prepared by solid-state reaction at 1400 ◦C and sintering at 1700 ◦C. It is characterised using X-ray diffraction, Raman spectroscopy and electrical measurements. A distortion fromthe cubic structure at roomtemperature is noticeable in the Raman spectra for 0.2 < x < 0.8, but not in the X-ray diffraction patterns. This work points out the rhombohedral nature of this distortion. Phase transitions are studied up to 600 ◦C. The direct current conductivity is measured as a function of oxygen partial pressure, and at a water vapour partial pressure of 0.015 atm. The total conductivity is resolved into an ionic and a p-type compon…
Reconstruction of 3D grain boundaries from rock thin sections, using an advanced polarised-light microscopy method
2017
Grain boundaries play a significant role in materials by initiating reactions and collecting impurities. Here we present FAGO (Fabric Analyser Grain boundary recOnstruction), a first step towards the automatic determination of three-dimensional (3D) grain boundary geometry using polarised light. The trace of the grain boundaries from 2D rock thin sections are determined primarily from data acquired using an automatic fabric analyser microscope and the FAME software (fabric analyser-based microstructure evaluation; Peternell and colleagues and Hammes and Peternell). Based on the Fabric Analyser G50's unique arrangement of nine differently oriented light sources the retardation can be determi…
Imaging connected porosity of crystalline rock by contrast agent-aided X-ray microtomography and scanning electron microscopy
2017
We set out to study connected porosity of crystalline rock using X-ray microtomography and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) with caesium chloride as a contrast agent. Caesium is an important radionuclide regarding the final deposition of nuclear waste and also forms dense phases that can be readily distinguished by X-ray microtomography and SEM-EDS. Six samples from two sites, Olkiluoto (Finland) and Grimsel (Switzerland), where transport properties of crystalline rock are being studied in situ, were investigated using X-ray microtomography and SEM-EDS. The samples were imaged with X-ray microtomography, immersed in a saturated caesium chlorid…
Time-Resolved Luminescence of Nanocrystalline Inorganic Complex Oxides
2007
Two types of complex nanosized oxides – cerium doped Y3Al5O12 (YAG) and CaWO4– have been studied by means of time-resolved luminescence spectroscopy. Comparative study of time-resolve luminescence characteristics of cerium doped YAG single crystal, nanopowders and nanoceramic as well as for CaWO4 macro- and nanocrystals has been done. Two components in the decay kinetic of Ce3+ related emission in YAG nanocrystals were detected and it was suggested that a different energy transfer rate to volume and surface Ce3+ ions takes place. It is shown that the segregation of Ce3+ ions near nanoparticles surface and/or dislocation lines plays a crucial role in degradation of light yield of cerium rela…
Mechanical properties of materials obtained via alkaline activation of illite-based clays of Latvia
2015
Materials has been synthesized in the temperature range from 60-100 °C from two illite based clays of Latvia under activation of KOH and NaOH solutions (4-6 M). Compressive strength and apparent porosity were measured. The effect of concentration of KOH and NaOH solutions on the material mechanical properties was investigated by means of infrared spectroscopy (IR). Compressive strength data of the materials showed that via such activation could obtain building materials with good quality.
Up-conversion process in erbium doped lithium fluoride bulk crystal, lithium borate glass and glass ceramics
2007
In our research the up-conversion processes in Er doped bulk LiF crystal, lithium borate oxyfluoride glass and lithium borate oxyfluoride glass ceramics were studied: up- conversion and traditional photoluminescence spectra, the up-converted signal as a function of the laser power are presented. It was found that sharp luminescence bands in the visible part of the spectrum appear when the bulk crystal is subjected to IR irradiation at 980 nm by a laser diode. After the heat treatment of the glass submicron crystallites were detected by SEM technique. The presence of LiF crystalline phase in the oxyfluoride glass ceramics was proved by XRD method. The questions about the synthesis of the oxy…