Search results for "rare-earth"
showing 10 items of 42 documents
The behaviour of REEs in Thailand's Mae Klong estuary: Suggestions from the Y/Ho ratios and lanthanide tetrad effects
2007
Abstract The concentrations of Rare Earth Elements and yttrium (REY) were measured in dissolved phase, in suspended particulate matter (SPM) and in sediments in seven sampling stations in the Mae Klong estuarine system (Inner Thailand Gulf) in order to study their behaviour and distribution pattern. The analysed samples generally show high Rare Earth Element (REE) content in the dissolved phase, with high Medium Rare Earth Elements (MREEs) and Y enrichments in the shale-normalized pattern (versus PAAS). These chemical features are interpreted in terms of direct influences of weathering processes of REE-rich minerals (e.g., phosphates), which abundantly out-crop in the Mae Klong watershed. T…
Role of Ce3+ as sensitizer for the infrared luminescence of phosphosilicate Er/Yb doped glasses
2012
The luminescence properties of the Yb/Er-doped phosphosilicate preforms used for the design of active optical fibers were investigated under a tunable laser excitation from ultraviolet to infrared domain. We demonstrated that codoping the glass matrix with Ce3+ ions strongly influences the infrared emission associated with Er3+ ions, it enhances the energy transfer from Yb3+ to Er3+ ions, and it provides an additional ultraviolet excitation channel for the emission of both Yb3+ and Er3+ ions. The excitation/emission pathways are discussed on the basis of models proposed in literature for other systems.
Rare-earth doped silica optical fibres for ionizing radiation detection
2016
Scintillating silica optical fibre sensors have shown interesting results for ionizing radiation monitoring and therefore can be useful for dosimetry applications in medical field. In fact, they enable a remote, punctual and real-time dose assessment (Mones et al., 2008). In addition, the high radiation hardness that characterizes silica optical fibers, makes these systems promising for radiation detection in high energy physics experiments (Chiodini et al., 2014). This work aims to review the recent progresses in the development and characterization of rare-earth doped silica fibres. The radioluminescent and dosimetric properties of Ce, Eu, Yb and Pr-doped silica matrices are described and…
Soil REE patterns as tracers of the emplacement of metal-rich anthropogenic materials. A case study in Moa (Cuba)
2019
Purpose: Are rare earth element (REE) patterns employable as tracers in human interventions of bulk soil disturbances, when high concentrations of metals are involved in the in situ soil disturbance? In terms of bulk soil disturbance, it is difficult to distinguish between bulk soil disturbances and emplacement of new earthen material. Chemical fingerprinting, in particular REE plus yttrium, is applied across many fields, but predominantlyin tracking the sources of potential environmental contaminants. Materials and methods: The REE normalised patterns (HNO 3 :HF:HCl 3:1:1 digestion, ICP-MS) of two Calcaric Cambisols were compared with those of a Geric Ferralsol (Novic, Technic) originated …
Rare earth elements distribution in seawater and suspended particulate of the Central Mediterranean Sea
2004
Rare earth element (REE) content in suspended and dissolved phases from the Strait of Sicily (Central Mediterranean Sea) has been measured. Vertical profiles of several dissolved REEs along the water column reflect the 3-D oceanographic features of the studied area and identifies the different water masses present there. Shale-normalized REE distribution patterns and derived parameters calculated for the suspended particulate show different atmospheric dust-surface inputs and their interactions with seawater. Finally, combined information from [La/Yb]N, ratios, REE/La ratios and Eu anomalies measured in the suspended particulate suggest an important contribution of volcanic materials from t…
Recognition of water masses according to geochemical signatures in the Central Mediterranean sea: Y/Ho ratio and rare earth element behaviour
2007
This study reports the results of geochemical investigations carried out in the Strait of Sicily (Central Mediterranean Sea) during the oceanographic cruise BANSIC 2000, focusing on the area around the Pantelleria Island. We evaluate the interface processes between dissolved phase and suspended particulate matter in the water columns on the basis of Y/Ho ratio and rare earth elements and yttrium distributions that are suitable to trace the occurrence of different water layers in Central Mediterranean Area. The main source of trace elements to the sea water system was recognized in the atmospheric fallout, while different scavenging mechanisms among Y and rare earth elements occur. Cation ex…
YREE determination in seawater. Standardization and validation of a new method based on preconcentration techniques
2010
The most interesting attraction of using rare-earth elements and yttrium (YREE) to address geochemical and marine chemical problems consists of their chemical coherence as group of trace elements. These characters allow YREE compositions of rocks and minerals to be extensively used in studies of provenance, petrogenesis and chemical evolution of the geological materials (1). Similarly, YREE compositions in the hydrosphere were used in studies of coagulation, particle-solution reactions and oceanic circulation of water masses (2-4). Unfortunately, very low concentrations of YREE (ng l-1 or sub-ng l-1) associated to high ionic strength of seawater always represented the main difficulty to ana…
Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers
2011
We developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, co…
X-ray irradiation influence on prototype Er3+-optical fibers: confocal luminescence study
2010
International audience; The integration of rare-earth doped optical fibers as part of fiber-based systems in space implies the development of waveguides tolerant to the radiation levels associated with the space missions. We report the spatial distribution, the photoluminescence (PL) properties of color centers and the related changes induced by X-rays radiation at different doses (50, 500 and 1000 krad) for two different prototypes of Er-doped optical fibers. Each sample (in the version pristine, X-irradiated and H2 loaded prior to radiation exposure) was characterized by confocal microscopy luminescence (CML) measurements in Visible range with Visible (488 nm) or UV (325 nm) laser light e…