Synthesis and White-Light Emission of ZnO/HfO2: Eu Nanocables

ZnO/HfO2:Eu nanocables were prepared by radio frequency sputtering with electrospun ZnO nanofibers as cores. The well-crystallized ZnO/HfO2:Eu nanocables showed a uniform intact core–shell structure, which consisted of a hexagonal ZnO core and a monoclinic HfO2 shell. The photoluminescence properties of the samples were characterized. A white-light band emission consisted of blue, green, and red emissions was observed in the nanocables. The blue and green emissions can be attributed to the zinc vacancy and oxygen vacancy defects in ZnO/HfO2:Eu nanocables, and the yellow–red emissions are derived from the inner 4f-shell transitions of corresponding Eu3+ ions in HfO2:Eu shells. Enhanced white-light emission was observed in the nanocables. The enhancement of the emission is ascribed to the structural changes after coaxial synthesis

Calculation of CO 2 activities using scapolite equilibria: constraints on the presence and composition of a fluid phase during high grade metamorphism

Thermodynamic and phase equilibrium data for scapolite have been used to calculate CO 2 activities ( a CO 2 ) and to evaluate the presence or absence of a fluid phase in high-grade scapolite bearing meta-anorthosite, granulites, calc-silicates, and mafix xenoliths. The assemblage scapolite-plagioclase-garnet±quartz may be used to calculate or limit a CO 2 by the reaction Meionite+Quartz = Grossular+Anorthite+CO 2 . Granulites from four high-grade terranes (Grenville Province, Canada; Sargut Belt, India; Furua Complex, Tanzania; Bergen Arcs, Norway) yield a CO 2 =0.4-1, with most >0.7. For scapolite-bearing granulites from the Furua Complex, in which a CO 2 ≥0.9, calculated H 2 O activities ( a H 2 O) based on phlogopite dehydration equilibria are uniformly low (0.1–0.2). The a CO 2 calculated for meta-anorthosite from the Grenville Province, Ontario, ranges from 0.2 to 0.8. For Grenville meta-anorthosite also containing epidote, the a H 2 O calculated from clinozoisite dehydration ranges from 0.2 to 0.6. Calc-silicates from the Grenville, Sargur, and Furua terranes mostly yield a CO 2 1). The calculated fluid activities are consistent with metamorphism (1) in the presence of a mixed CO 2 −H 2 O fluid phase in which CO 2 is the dominant fluid species but other C−O−H−S species are minor, (2) in the absence of a bulk fluid phase (“fluid-absent metamorphism”), or (3) in the presence of a fluid-bearing melt phase. The results for many granulites and Grenville meta-anorthosite are consistent with the presence of a CO 2 -rich, mixed CO 2 −H 2 O fluid phase. In contrast the relatively restricted and low values of a CO 2 for calc-silicates require an H 2 O-rich fluid or absence of a fluid phase during metamorphism. The range of values for xenoliths are most consistent with absence of a fluid phase. The primary implication of these results is that a CO 2 -rich fluid accounts for the reduced a H2 O in scapolite-bearing granulites. However, scapolite may be stable with a wide range of fluid compositions or in the absence of a fluid phase, and the presence of scapolite is not a priori evidence of a CO 2 -rich fluid phase. In addition, close association of scapolite-free mafic granulites with scapolite-bearing granulites having identical mineral compositions in the Furua Complex, and the absence of scapolite from most granulite terranes implies that a CO 2 -rich fluid phase is not pervasive on an outcrop scale or common to all granulite terranes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47295/1/410_2004_Article_BF00307340.pd

Calculation and application of clinopyroxene-garnet-plagioclase-quartz geobarometers

Recently published thermodynamic and experimental data in a variety of chemical systems have been evaluated to derive Gibbs free energies for hedenbergite and pyrope. These were used to calculate the geobarometric equilibriaPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47284/1/410_2004_Article_BF00399441.pd