Search results for "Rare earth"

Trace element variability in single ostracod valves as a proxy for hydrochemical change in Nam Co, central Tibet, during the Holocene

2014

Ostracod shells, belonging to three taxa (Leucocytherella sinensis Huang, 1982, ?Leucocythere dorsotuberosa Huang, 1982 and ?L. dorsotuberosa f. postilirata sensu Pang, 1985), were collected from two sediment cores from Lake Nam Co, on the central Tibetan Plateau. Two variants of LA–ICP–MS (laser ablation–inductively coupled plasma–mass spectrometry), spot and line-scan analyses, were used to investigate trace element concentrations (Mg, Sr, Ba, U and rare earth elements [REEs]) in single ostracod shells. The results suggest that the line-scan method can provide better precision than the spot analysis and is therefore preferred. No significant difference in trace element composition between…

Adoption of bonded magnets in place of sintered NdFeB: Performance and economic considerations on a small power generator

2015

Bonded magnets are giving promising results when adopted to replace expensive rare earth magnets. The possibility to “modulate” the magnetic characteristics by varying the binder percentage allows the opening of new lines of investigation and to face the problem of rare earths cost. In the paper a small power generator prototype has been equipped with bonded magnets realized in the Authors' Laboratories; it has been tested and compared with the original generator mounting NdFeB sintered magnets. FEM simulations are validated by means of experimental tests. Economic comparisons are proposed.

Rare earth elements in apatite as a monitor of magmatic and metasomatic processes: The Ilímaussaq complex, South Greenland

2015

Abstract Textural and compositional variations of apatite from the plutonic Ilimaussaq complex in South Greenland and its surrounding country rocks track magmatic and metasomatic processes. Detailed back-scattered electron (BSE) imaging reveals various types of apatite textures including (i) growth zonation (concentric, oscillatory as well as sector zonation) formed during magmatic differentiation, (ii) resorption and overgrowth textures due to fluid/melt induced metasomatic overprint of precursor apatite and (iii) replacement textures indicating the destabilization of apatite in favor of monazite. In the least evolved rocks of the Ilimaussaq complex, apatite incorporates rare earth element…

Zirconium, Hafnium and Rare Earths behaviour during the transport in volcanic fluids. Geochemical effects throughout the sublimation and after intera…

This research indicates the fate of Zr, Hf and Rare Earths during their sublimation from the high-temperature gas phase (100° - 420 °C), in volcanic systems associated with different geodynamic regimes, and processes associated with volcanic sublimation representing the last natural “inorganic” interface where a detailed investigation into the behaviour of Rare Earths had never been conducted. The research was carried out in active volcanic systems at Vulcano (Aeolian Islands, Italy), Santorini (Cyclades Islands, Greece), Phlegrean Fields (Italy), Tenerife (Canary Islands, Spain) and Fogo Island (Cape Verde) where both fumaroles and thermal waters from submarine springs and inland wells wer…

Petrography and high-resolution geochemical records of Lower Jurassic manganese-rich deposits from Monte Mangart, Julian Alps

2016

Deposits with unusually high Mn contents sampled at Monte Mangart in the Julian Alps include organic-rich marlstone and black shale with interbedded manganoan and siliceous limestone, which were deposited during the early Toarcian Oceanic Anoxic Event. Mn enrichment during that period has been related to global sea-level change coincident with increasing subsidence rate. The formation of Fe-Mn nodules, marking a hardground at the base of the Monte Mangart section, seems to be triggered by release of Mn from remote hydrothermal vents into a region of relatively elevated submarine topography where oxidizing conditions prevailed. However, very high Mn contents in carbonate phases above the har…

Distribution of REEs in box-core sediments offshore an industrial area in SE Sicily, Ionian Sea: Evidence of anomalous sedimentary inputs

2009

The distribution of rare earth elements and yttrium (REEs+Y) has been investigated in box-core sediments recovered from four stations in the Sicilian coastal zone seawards of Augusta, one of the most industrialized and contaminated areas in the Mediterranean region. Shale-like REE patterns and low Y/Ho ratios (close to the chondritic ratio) suggest a dominant terrigenous (geogenic) source for REE. Slight enrichment of LREE over the HREE is interpreted as due to preferential adsorptive transfer of LREE from seawater to sediment particles. Samples from offshore cores exhibit slightly positive Gd and negative Ce anomalies. It is here hypothesized that main drivers of anthropogenic Gd flux towa…

Multicolor Up-Conversion Luminescence in Rare-Earth Doped NaLaF4

2011

In this work we tried to achieve multicolor up-conversion luminescence in low phonon energy material NaLaF4 doped with different Er3+ Tm3+ and Yb3+ concentrations. Up-conversion luminescence was measured and main luminescence bands from Er3+ and Tm3+ in red, green and blue spectral regions were observed. The relative intensities of the luminescence bands could be changed by changing the doping levels of rare-earth ions. Changes in the up-conversion luminescence color could be achieved by applying different infrared pump power density. The color coordinates of the multicolor up-conversion luminescence depending on doping level as well as on the pump power density were presented in CIE (x, y)…

Giant Magnetoresistance in Rare Earth Compounds

2008

Dimeric Hydrido Complexes of Rare-Earth Metals Containing a Linked Amido−Cyclopentadienyl Ligand:  Synthesis, Characterization, and Monomer−Dimer Equ…

2000

Dimeric hydrido complexes of lutetium, ytterbium, and yttrium containing a linked amido−cyclopentadienyl ligand, [Ln(η5:η1-C5Me4SiMe2NCMe2R)(L)(μ-H)]2 (Ln = Lu, Yb, Y; R = Me, Et; L = THF, PMe3), w...

Phosphogenesis in the Bonarelli Level from northwestern Sicily, Italy: petrographic evidence of microbial mediation and related REE behaviour

2010

Phosphogenesis at the base of the Bonarelli Level from the Calabianca stratigraphic section (northwestern Sicily) was investigated using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and stable-isotope mass spectrometry. The anoxic event onset is marked by high P(2)O(5tot) concentrations related to the presence of authigenic carbonate-fluorapatite. This mineral is poorly crystallized and occurs in three different forms: (i) fish debris locally showing evidence of re-crystallization, (ii) phosphatically cemented layers, and (iii) dense aggregates of microcrystals. Petrographic features are indicative of a microbial genesis for the carbonate-fluorapatite. Conversely, th…