Nickel Oxide Buffer Research Articles

C-O-H-Cl-S-F Volatile Solubilities, Partitioning, and Mixing in Phonolitic-Trachytic Melts and Aqueous-Carbonic Vapor Saline Liquid at 200 MPa

Hydrothermal experiments were conducted at 200MPa and 900^10188C to determine the solubilities, fluid(s)^melt partitioning, and mixing properties of H2O, CO2, S, Cl, and F in phonolitic^trachytic melts saturated in vapor, vapor plus saline liquid, or saline liquid.The bulk compositions and S, Cl, and F concentrations of the run-product glasses were determined by electron microprobe and the H2O and CO2 contents by Fourier-transform infrared spectroscopy (FTIR). A new parameterization was developed to calculate molar absorption coefficients for FTIR analysis of carbonate in glasses and applied to the run-product glasses.The concentrations of volatiles in the fluid(s) were determined by mass-balance calculations and checked with chloridometer analysis and gravimetry.The range in oxygen fugacity of these experiments is NNO to NNOþ 2 (where NNO is nickel^nickel oxide buffer).The phonolitic^trachytic melts dissolved up to 7 5 wt % H2O, 0 94 wt % Cl, 0 73 wt % CO2, 0 75 wt % F, and 0 16 wt % S, and the integrated bulk fluid(s) contained up to 99 mol % H2O, 34 mol % Cl, 82 mol % CO2, 1 7 mol % F, and 3 7 mol % S.The mixing relationships of H2O, CO2, and Cl in melt versus fluid(s) are complex and strongly non-ideal at these pressure^temperature conditions, particularly with two fluid phases stable. The concentrations of H2O and CO2 in melt change with the addition of Cl S to the system, and the solubility of Cl in melt varies with S.The reductions in H2O and CO2 solubility in melt exceed those resulting from simple dilution of the coexisting fluid(s) owing to addition of other volatiles.The partitioning of H2O and CO2 between fluid(s) and melt varies as a function of fluid(s) and melt composition.The experimental data are applied to phonolitic and related magmas of Mt. Somma^ Vesuvius, Italy, Mt. Erebus, Antarctica, and Cripple Creek, USA, to better interpret processes of fluid(s) exsolution in eruptive and mineralizing systems. Application of the experimental results also provides constraints on eruptive and mineralizing fluid(s) compositions.

Lead Lanthanum Zirconate Titanate Ceramic Thin Films for Energy Storage

An acetic-acid-based sol-gel method was used to deposit lead lanthanum zirconate titanate (PLZT, 8/52/48) thin films on either platinized silicon (Pt/Si) or nickel buffered by a lanthanum nickel oxide buffer layer (LNO/Ni). X-ray diffraction and scanning electron microscopy of the samples revealed that dense polycrystalline PLZT thin films formed without apparent defects or secondary phases. The dielectric breakdown strength was greater in PLZT thin films deposited on LNO/Ni compared with those on Pt/Si, leading to better energy storage. Finally, optimized dielectric properties were determined for a 3-μm-thick PLZT/LNO/Ni capacitor for energy storage purposes: DC dielectric breakdown strength of ∼1.6 MV/cm (480 V), energy density of ∼22 J/cc, energy storage efficiency of ∼77%, and permittivity of ∼1100. These values are very stable from room temperature to 150 °C, indicating that cost-effective, volumetrically efficient capacitors can be fabricated for high-power energy storage.

Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe–Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918–968 to ~950 to 845–895 °C). Oxygen fugacity began at nickel–nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite–rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3–4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and CO2 concentrations and solubility models indicate a dominant storage region at 4–7 km (up to 12 km), with drier inclusions that diffusively re-equilibrated and/or were trapped at shallower depths. Boron and Cl (except in the climactic deposit) largely remained in the melt, suggesting vapor–melt partition coefficients and gas fractions were low. Modeled Li, F, and S vapor–melt partition coefficients are higher than those of B and Cl. The decrease in maximum MI CO2 concentration following the earliest dacitic eruptions is interpreted to result from a broadening of the shallow storage region to greater than the diameter of subjacent feeders, so that greater proportions of reservoir magma were to the side of CO2-bearing vapor bubbles ascending vertically from the locus of recharge magma injection, thereby escaping recarbonation by streaming vapor bubbles. The Mazama melt inclusions provide a picture of a growing magma storage region, where chemical variations in melt and magma occur due to changes in the nature and supply rate of magma recharge, the timing of degassing, and the possible degree of equilibration with gases from below.

Petrology and geochemistry of calc-alkaline volcanic and subvolcanic rocks, Dalli porphyry copper–gold deposit, Markazi Province, Iran

Early Miocene igneous rocks associated with the Dalli porphyry ore body are exposed within the Urumieh-Dokhtar Magmatic Arc (UDMA). The Dalli porphyry Cu–Au deposit is hosted by subduction-related subvolcanic plutons with chemical composition from diorite to granodiorite, which intruded andesitic and dacitic volcanic rocks and a variety of sedimentary sequences. 40Ar/39Ar age data indicate a minimum emplacement age of ∼21 million years for a potasically altered porphyritic diorite that hosts the porphyry system. The deposit has a proven reserve of 8 million tonnes of rock containing 0.75 g/t Au and 0.5% Cu. Chondrite-normalized rare earth element (REE) patterns for the subvolcanic rocks are characterized by light REE enrichments [(La/Sm) n = 2.57–6.40] and flat to gently upward-sloping profiles from middle to heavy REEs [(Dy/Yb) n = 0.99–2.78; (Gd/Yb) n = 1.37–3.54], with no significant Eu anomalies. These characteristics are generated by the fractionation of amphibole and the suppression of plagioclase crystallization from hydrous calc-alkaline magmas. In normalized multi-element diagrams, all analysed rocks are characterized by enrichments in large ion lithophile elements and depletions in high field strength elements, and display typical features of subduction-related calc-alkaline magmas. We used igneous mineral compositions to constrain the conditions of crystallization and emplacement. Biotite compositions plot above the nickel–nickel oxide (NNO) buffer and close to oxygen fugacity values defined by the hematite–magnetite (HM) buffer, indicating oxidizing conditions during crystallization. Assuming a minimum crystallization temperature of 775°C, the oxygen (fO2) and water (fH2O) fugacities are estimated to be 10−10.3 bars (∼ΔNNO+4) and ≤748 bars, respectively, during the crystallization of biotite phenocrysts. The temperature and pressure conditions, estimated from temperature–corrected Al-in-hornblende barometry and amphibole-plagioclase thermometry, suggest that the hornblende phenocrysts in Dalli rocks crystallized at around 780 ± 20°C and 3.8 ± 0.4 kbar. An alternative method using the calcic amphibole thermobarometer indicates that the Dalli magmas were, on average, characterized by an H2O content of 4.3 wt.%, a relatively high oxygen fugacity of 10−11.0 bars (ΔNNO+1.3), and a hornblende phenocryst crystallization temperature of 880 ± 68°C and pressure of 2.6 ± 1.7 kbar.

Growth Dynamics of Barium Titanate Thin Films on Polycrystalline Ni Foils Using Polymer-Assisted Deposition Technique

Polymer-assisted deposition (PAD) technique was developed to fabricate ferroelectric BaTiO(3) (BTO) thin films directly on polycrystalline nickel foils. The growth dynamics was systematically studied to optimize the single-phase BTO films with good dielectric properties. It is critical to pretreat nickel foils with hydrogen peroxide (H(2)O(2)) solution to form thin nickel oxide layers on the surfaces for the growth of BTO films. Both the concentration of H(2)O(2) solution and the pretreated time were found to strongly affect the dielectric constant of BTO films, which may be associated with the oxygen diffusion from nickel oxide buffer layers to BTO layers during annealing. The BTO thin films with optimized growth conditions have good crystal structure and electrical properties, suggesting that the as-grown BTO films by PAD technique can be utilized for new devices development and energy storage applications.

Amphibole stability in primitive arc magmas: effects of temperature, H2O content, and oxygen fugacity

The water-saturated phase relations have been determined for a primitive magnesian andesite (57 wt% SiO2, 9 wt% MgO) from the Mt. Shasta, CA region over the pressure range 200–800 MPa, temperature range of 915–1,070 °C, and oxygen fugacities varying from the nickel–nickel oxide (NNO) buffer to three log units above NNO (NNO+3). The phase diagram of a primitive basaltic andesite (52 wt% SiO2, 10.5 wt% MgO) also from the Mt. Shasta region (Grove et al. in Contrib Miner Petrol 145:515–533; 2003) has been supplemented with additional experimental data at 500 MPa. Hydrous phase relations for these compositions allow a comparison of the dramatic effects of dissolved H2O on the crystallization sequence. Liquidus mineral phase stability and appearance temperatures vary sensitively in response to variation in pressure and H2O content, and this information is used to calibrate magmatic barometers-hygrometers for primitive arc magmas. H2O-saturated experiments on both compositions reveal the strong dependence of amphibole stability on the partial pressure of H2O. A narrow stability field is identified where olivine and amphibole are coexisting phases in the primitive andesite composition above 500 MPa and at least until 800 MPa, between 975–1,025 °C. With increasing H2O pressure ( $${P}_{\text {H}_2{\rm O}}$$ ), the temperature difference between the liquidus and amphibole appearance decreases, causing a change in chemical composition of the first amphibole to crystallize. An empirical calibration is proposed for an amphibole first appearance barometer-hygrometer that uses Mg# of the amphibole and $$f_{\text {O}_2}$$ : $$ P_{\text{H}_{2}{\rm O}}({\rm MPa})=\left[{\frac{{\rm Mg\#}}{52.7}}-0.014 * \Updelta {\rm NNO}\right]^{15.12} $$ This barometer gives a minimum $${P}_{\text{H}_{2}{\rm O}}$$ recorded by the first appearance of amphibole in primitive arc basaltic andesite and andesite. We apply this barometer to amphibole antecrysts erupted in mixed andesite and dacite lavas from the Mt. Shasta, CA stratocone. Both high H2O pressures (500–900 MPa) and high pre-eruptive magmatic H2O contents (10–14 wt% H2O) are indicated for the primitive end members of magma mixing that are preserved in the Shasta lavas. We also use these new experimental data to explore and evaluate the empirical hornblende barometer of Larocque and Canil (2010).

Organic solar cells employing electrodeposited nickel oxide nanostructures as the anode buffer layer

In this work, an electrodeposited nickel oxide (NiO) nanostructure used as an anode buffer layer in organic photovoltaic cells has been studied. The structure of NiO films are tailored by current density and electrodeposition time to have nano-islands or interconnecting nano-rods on indium tin oxide surface. When –CF3-modified NiO structures are used as hole transporting and electron blocking layers, the device performance is affected by the structure and electronic properties of NiO films. The best power conversion efficiency (3.05%) is achieved under an illumination of AM 1.5G (100mW/cm2) for a device with the interconnecting nano-rods NiO buffer layer. This electrodepositing of NiO nanostructures provides an inexpensive and facile method to fabricate an efficient anode buffer for high performance photovoltaic device.

Iron in monticellite as an oxygen barometer for kimberlite magmas

Monticellite is a common magmatic mineral in the groundmass of kimberlites. A new oxygen barometer for kimberlite magmas is calibrated based on the Fe content of monticellite, CaMgSiO4, in equilibrium with kimberlite liquids in experiments at 100 kPa from 1,230 to 1,350°C and at logfO2 from NNO-4.1 to NNO+5.3 (where NNO is the nickel–nickel oxide buffer). The XFeMtc/XFeliq was found to decrease with increasing fO2, consistent with only Fe2+ entering the monticellite structure. Although the XFe-in-monticellite varies with temperature and composition, these dependencies are small compared to that with fO2. The experimental data were fitted by weighted least square regression to the following relationship: $$ \Updelta {\text{NNO}} = \frac{{\left\{ {\log \left[ {0.858( \pm 0.021)\frac{{X_{\text{Fe}}^{\text{Liq}} }}{{X_{\text{Fe}}^{\text{Mtc}} }}} \right] - 0.139( \pm 0.022)} \right\}}}{0.193( \pm 0.004)} $$ where ΔNNO is the fO2 relative to that of the Nickel-bunsenite (NNO) buffer and XFeliq/XFeMtc is the ratio of mole fraction of Fe in liquid and Fe-in-monticellite (uncertainties at 2σ). The application of this oxygen barometer to natural kimberlites from both the literature and our own investigations, assuming the bulk rock FeO is that of their liquid FeO, revealed a range in fO2 from NNO-3.5 to NNO+1.7. A range of Mg/(Mg + Fe2+) (Mg#) for kimberlite melts of 0.46–0.88 was derived from the application of the experimentally determined monticellite-liquid Kd Fe2+–Mg to natural monticellites. The range in Mg# is broader and less ultramafic than previous estimates of kimberlites, suggesting an evolution under a wide range of petrologic conditions.

Electrical and Luminescent Properties of OLEDs by Nickel Oxide Buffer Layer with Controlled Thickness Gyu-Chae Choi1,2, Kook-Chae Chung1,*, Young-Kuk Kim1 ,

Electrical and Luminescent Properties of OLEDs by Nickel Oxide Buffer Layer with Controlled Thickness Gyu-Chae Choi1,2, Kook-Chae Chung1,*, Young-Kuk Kim1 ,

Magma mixing/mingling in the Eocene Horoz (Nigde) granitoids, Central southern Turkey: evidence from mafic microgranular enclaves

Mafic microgranular enclaves (MMEs) are widespread in the Horoz pluton with granodiorite and granite units. Rounded to elliptical MMEs have variable size (from a few centimetres up to metres) and are generally fine-grained with typical magmatic textures. The plagioclase compositions of the MMEs range from An18–An64 in the cores to An17–An29 in the rims, while that of the host rocks varies from An17 to An55 in the cores to An07 to An33 in the rims. The biotite is mostly eastonitic, and the calcic-amphibole is magnesio-hornblende and edenite. Oxygen fugacity estimates from both groups’ biotites suggest that the Horoz magma possibly crystallised at fO2 conditions above the nickel–nickel oxide (NNO) buffer. The significance of magma mixing in their genesis is highlighted by various petrographic and mineralogical characteristics such as resorption surfaces in plagioclases and amphibole; quartz ocelli rimmed by biotite and amphibole; sieve and boxy cellular textures, and sharp zoning discontinuities in plagioclase. The importance of magma mixing is also evident in the amphiboles of the host rocks, which are slightly richer in Si, Fe3+ and Mg in comparison with the amphiboles of MMEs. However, the compositional similarity of the plagioclase and biotite phenocrysts from MMEs and their host rocks suggests that the MMEs were predominantly equilibrated with their hosts. Evidence from petrography and mineral chemistry suggests that the adakitic Horoz MMEs could be developed from a mantle-derived, water-rich magma (>3 mass%) affected by a mixing of felsic melt at P >2.3 kbar, T >730°C.

Ultrathin nickel oxide film as a hole buffer layer to enhance the optoelectronic performance of a polymer light-emitting diode

In order to promote a polymer LED (PLED), we fabricated and introduced an ultrathin nickel oxide (NiO) buffer layer (<10 nm) between the indium tin oxide (ITO) anode and the poly (3, 4-ethylenedioxythiophene) hole injection layer in the PLED. The NiO buffer layer was easily formed on the ITO anode by electron-beam deposition of a nickel (Ni) metal source and an oxygen plasma treatment process. As a result, the PLED device with the NiO buffer layer on its ITO anode had the same turn-on voltage as conventional PLED devices without the NiO buffer layer, and the luminance of the PLED device with the NiO buffer layer was doubled, compared with the conventional PLED devices without the NiO buffer layer. Improvement of the optoelectronic performance of the PLED can be attributed to the increase of the current driven into the diode, resulting from the NiO buffer layer, which can enhance the hole injection and balance the injection of the two types of carriers (holes and electrons). Thus it is an excellent choice to introduce the NiO buffer layer onto the ITO anode of the PLED devices in order to enhance the optoelectronic performance of PLED devices.

Dielectric properties and energy storage capability of antiferroelectric Pb0.92La0.08Zr0.95Ti0.05O3 film-on-foil capacitors

Antiferroelectric (AFE) Pb0.92La0.08Zr0.95Ti0.05O3 (PLZT) films were grown on nickel foils with lanthanum nickel oxide buffer by chemical solution deposition. We observed field-induced AFE-to-ferroelectric (FE) phase transition. The electric field for the AFE-to-FE phase transition (EAF ≈ 270 kV/cm) and that for the reverse phase transition (EFA ≈ 230 kV/cm) were measured at room temperature on samples with PLZT films of ≈1-µm thickness. Relative permittivity of ≈560 and dielectric loss of &lt;0.05 were measured near zero DC bias field. Hysteresis loop analysis showed that energy densities of ≈53 and 37 J/cm3 can be stored and recovered from the film-on-foil capacitors at 25 and 150 °C, respectively. Highly accelerated life tests were conducted. The projected mean time to failure is &gt;5000 h when the capacitors are operated at room temperature with an applied field of ≈300 kV/cm.

Experimental constraints on Pt, Pd and Au partitioning and fractionation in silicate melt–sulfide–oxide–aqueous fluid systems at 800 °C, 150 MPa and variable sulfur fugacity

We have performed experiments to constrain the effect of sulfur fugacity ( fS 2) and sulfide saturation on the fractionation and partitioning behavior of Pt, Pd and Au in a silicate melt–sulfide crystal/melt–oxide–supercritical aqueous fluid phase–Pt–Pd–Au system. Experiments were performed at 800 °C, 150 MPa, with oxygen fugacity ( fO 2) fixed at approximately the nickel–nickel oxide buffer (NNO). Sulfur fugacity in the experiments was varied five orders of magnitude from approximately log fS 2 = 0 to log fS 2 = −5 by using two different sulfide phase assemblages. Assemblage one consisted initially of chalcopyrite plus pyrrhotite and assemblage two was loaded with chalcopyrite plus bornite. At run conditions pyrrhotite transformed compositionally to monosulfide solid solution (mss), chalcopyrite to intermediate solid solution (iss), and in assemblage two chalcopyrite and bornite formed a sulfide melt. Run-product silicate glass (i.e., quenched silicate melt) and crystalline materials were analyzed by using both electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry. The measured concentrations of Pt, Pd and Au in quenched silicate melt in runs with log fS 2 values ranging from approximately 0.0 to −5.0 do not exhibit any apparent dependence on fS 2. The measured Pt, Pd and Au concentrations in mss do vary as a function of fS 2. The measured Pt, Pd and Au concentrations in iss do not appear dependent on fS 2. The data suggest that fS 2, working in concert with fO 2, via the determinant role that these variables play in controlling the magmatic sulfide phase assemblage and the solubility of Pt, Pd and Au as lattice bound components in magmatic sulfide phases, is a controlling factor on the budgets of Pt, Pd and Au during the evolution of magmatic systems.

Chlorine partitioning between a basaltic melt and H 2O–CO 2 fluids at Mount Etna

Partitioning experiments between a basaltic melt from Mt. Etna and a low-density hydrous fluid or vapor containing H 2O or H 2O–CO 2 were performed at 1200–1260 °C, at pressures between 1 and 200 MPa, either near the nickel–nickel oxide (NNO) buffer or at two log units above it (NNO + 2), and with different chloride concentrations. Most of the experiments were done at chloride-brine-undersaturated conditions, although at the highest Cl concentrations explored brine saturation might have been reached. The average partition coefficients ( D Cl fluid/melt) over the range of Cl concentrations were derived on a weight basis by plotting the calculated concentrations of Cl in the fluid phase versus the measured ones in the melt. For H 2O–Cl experiments in which the Cl concentration in the melt was ≤ 0.4 wt.%, a negative dependence between D Cl f/m and pressure is observed. D Cl fluid/melt in H 2O + Cl-bearing experiments ranges between 11–14 at 1 and 25 MPa to 6 at 200 MPa at NNO; and between 4 at 50 MPa and 13 at 100 MPa at ΔNNO ≥ 2. Addition of CO 2 at NNO yields lower partition coefficients than in CO 2-free conditions over the pressure range investigated. The negative pressure dependence observed for H 2O–Cl experiments disappears when CO 2 is present in the system. Overall, once CO 2 is introduced in the system, Cl fugacity in the silicate melt tends to increase, thus resulting in a decrease of D Cl f/m. Application to Mt. Etna shows that the composition of the volcanic plume in terms of Cl records very shallow pressures of magma equilibration with its exsolved fluid.

The Titanomagnetite–Ilmenite Equilibrium: New Experimental Data and Thermo-oxybarometric Application to the Crystallization of Basic to Intermediate Rocks†

Although the titanomagnetite^ilmenite thermo-oxybarometer has been widely used to provide information on temperature and oxygen fugacity during magmatic and metamorphic processes, the available formulations yield unsatisfactory results; for example, at high temperature and low to moderate fO2 (i.e. in conditions relevant to crystallization in basic and intermediate rocks).We present a new version of this thermo-oxybarometer based on numerical fits of a large experimental dataset comprising new results in the Fe^Ti^Al^Mg^O system and those of literature studies. Our new subsolidus experimental results at temperatures in the range 1100^13008C under low to moderate fO2 conditions show that the addition of Mg and/or Al in the concentration ranges that are usual in Fe^Ti oxides from basic magmatic rocks can be accommodated by simple projections. We have taken advantage of this fact and performed numerical fits to generate empirical formulations.With the resulting expressions we can retrieve temperature values from Xusp and Xilm (projected mole fractions) of titanomagnetite^ilmenitess pairs and fO2 values from Xusp and T. The present thermooxybarometer model is designed for assemblages of titanomagnetite and hemoilmenite (with the R 3 space group), with the usual low Al2O3, Cr2O3, MgO and MnO contents (less than about 6 wt %), which equilibrated at high temperatures (T 8008C) and low to moderate oxygen fugacities (^45 NNO5þ2, where NNO is the nickel^nickel oxide buffer).Tests of our model by using the compositions of titanomagnetite^ilmenitess pairs in products of liquidus experiments conducted at knownT^fO2 conditions (literature data and new results) show that the calculated values reproduce the experimental ones within 708C, and in most cases within 508C. The estimates of the oxygen fugacity are mostly within 0 4 log units. This is a significant improvement compared with the previous models.

Pre-eruptive Conditions of the Huerto Andesite (Fish Canyon System, San Juan Volcanic Field, Colorado): Influence of Volatiles (C-O-H-S) on Phase Equilibria and Mineral Composition

Crystallization experiments at 400 MPa, oxidized condition (ΔlogfO2 = NNO + 1, where NNO is nickel–nickel oxide buffer) and over a range of temperatures (850–950°C) and fluid composition (XH2Oin = 0·3–1) have been carried out to constrain the storage conditions of the sulphur-rich magma of the Huerto Andesite (an anhydrite, pyrrhotite, and S-rich apatite-bearing, post-Fish Canyon Tuff mafic lava). The results are used to evaluate the role of fluids released from the crystallization of magmas such as the Huerto Andesite on the remobilization of the largely crystallized dacitic Fish Canyon magma body. Experiments were performed using the natural andesitic bulk composition with and without added sulphur. The presence of sulphur slightly affects the phase equilibria by changing the phase proportions, stability fields of plagioclase, pyroxenes and ilmenite, and also affects the plagioclase composition. Phase equilibria and mineral composition data indicate that the magma may have contained 4·5 wt % water in the melt and that the pre-eruptive temperature was 875 ± 25°C. Assuming that the magma was in equilibrium with a fluid phase, the CO2 concentration of the melt is estimated to be in the range 2000–4000 ppm (at 400 MPa). Before eruption, the andesite had an oxidation state very close to, or slightly within, the co-stability field of anhydrite–pyrrhotite at NNO + 1·1. At these conditions, the sulphur content in the melt is ∼500 ppm. Assuming open-system degassing resulting from continuing crystallization at depth, most of the CO2 dissolved in the andesitic melt should be released after the crystallization of <10 vol. % of the magma, corresponding to a cooling from 875 to 825–850°C. Thus, the fluids released owing to crystallization processes should be mainly composed of water at temperatures below 825°C.

Sulfur concentration at sulfide saturation (SCSS) in magmatic silicate melts

The sulfur concentration in silicate melts at sulfide saturation (SCSS) was experimentally investigated in a temperature range from 1150 to 1450 °C and a pressure range from 500 MPa to 1 GPa in a piston–cylinder apparatus. The investigated melt compositions varied from rhyolitic to basaltic and water concentrations varied from 0 to ∼9 wt%. All experiments were saturated with FeS melt or pyrrhotite crystals. Temperature was confirmed to have a positive effect on the SCSS. Experimental oxygen fugacities were either near the carbon–carbon monoxide buffer or one log unit above the nickel–nickel oxide buffer, and found to positively affect the SCSS. Combining our results with data from the literature we constructed a model to predict the SCSS in melts ranging in composition from komatiitic to rhyolitic, with water concentrations from 0 to 9 wt%, at pressures from 1 bar to 9 GPa and oxygen fugacities between ∼2 log units below the fayalite–magnetite–quartz buffer to ∼2 log units above it. The coefficients were obtained by multiple linear regression of experimental data and the best model found for the prediction of the SCSS is: ln ( S in ppm ) SCSS = 11.35251 - 4454.6 T - 0.03190 P T + 0.71006 ln ( MFM ) - 1.98063 [ ( MFM ) ( X H 2 O melt ) ] + 0.21867 ln ( X H 2 O melt ) + 0.36192 ln X FeO melt where P is in bar, T is in K, MFM is a compositional parameter describing the melt based upon cation mole fractions: MFM = Na + K + 2 ( Ca + Mg + Fe 2 + ) Si × ( Al + Fe 3 + ) , X H 2 O melt is the mole fraction of water in the melt, and X FeO melt is the mole fraction of FeO in the melt. This model was independently tested against experiments performed on anhydrous and hydrous melts in the temperature range from 800 to 1800 °C and 1–9 GPa. The model typically predicts the measured values of the natural log of the SCSS (in ppm) for komatiitic to rhyolitic (∼42 to ∼74 wt% SiO 2) melts to within 5% relative, but is less accurate for high-silica (>76 wt% SiO 2) rhyolites, especially those with molar ratios of iron to sulfur below 2. We demonstrate how this model can be used with the MELTS software to calculate the saturation of natural magmas with a sulfide phase and evolution of the SCSS during magmatic differentiation.

Ferric Iron in CaTiO3 Perovskite as an Oxygen Barometer for Kimberlite Magmas II: Applications

We apply an oxygen barometer based on the Fe content of CaTiO3 perovskite to estimate the oxygen fugacity (fO2) during the crystallization and emplacement of kimberlites in different eruptive phases of a single pipe, or between different pipes, clusters or provinces. Mineral chemical data for perovskite were compiled from the literature and obtained in our detailed study of perovskites from 11 kimberlites at Somerset Island and Lac de Gras, Canada. Perovskite compositions in kimberlites record a range in fO2 of many orders of magnitude from NNO 5 to NNOþ 6 [where log fO2 is given relative to the nickel^nickel oxide (NNO) buffer]. The range of fO2 recorded by different parageneses of perovskite within a single pipe can vary up to three orders of magnitude with trends toward both oxidation and reduction during crystallization. Kimberlites record some of the greatest ranges, and the highest known fO2 conditions for any terrestrial magma. This is attributed to the presence of deep and oxidized source regions and the variable interplay of ferric^ferrous vs carbon^fluid equilibria during ascent of kimberlite magmas. Three kimberlite pipes from the Lac de Gras field show that higher fO2 values correlate with higher proportions of more resorbed diamonds, suggesting that this variable has a measurable effect on the physical properties of diamonds in a pipe.

Highly efficient organic light-emitting diodes fabricated utilizing nickel-oxide buffer layers between the anodes and the hole transport layers

The electrical and the optical properties of organic light-emitting diodes (OLEDs) fabricated utilizing nickel-oxide (NiO) buffer layers between the anodes and the hole transport layers were investigated. The NiO layer was formed by using a thermally evaporated nickel thin film and a subsequent oxidation process. The tunneling holes in the OLED were increased due to the existence of the NiO layer between the anode and the hole transport layer, resulting in enhanced efficiency for the OLED. These results indicate that OLEDs with NiO buffer layers hold promise for potential applications in highly-efficient flat-panel displays.

Ferric Iron in CaTiO3 Perovskite as an Oxygen Barometer for Kimberlitic Magmas I: Experimental Calibration

A method to estimate the oxygen fugacity (fO2) during the crystallization of kimberlites is developed using the Fe content of CaTiO3 perovskite (Pv), a common groundmass phase in these rocks. With increasing fO2, more Fe exists in the kimberlitic liquid as Fe3þ, and thus partitions into Pv. Experiments to study the partitioning of Fe between Pv and kimberlite liquid were conducted at 100 kPa on simple and complex anhydrous kimberlite bulk compositions from 1130 to 13008C over a range of fO2 from NNO 5 to NNOþ 4 (where NNO is the nickel^nickel oxide buffer), and atNb and rare earth element (REE) contents in the starting materials of 0^5 wt % and 1500 ppm, respectively.The partitioning of Fe between Pv and kimberlite liquid is influenced mostly by fO2, although the presence of Nb increases the partition of Fe3þ into perovskite at a given T and fO2. Multiple linear regression (MLR) of all the experimental data produces a relationship that describes the variation of Fe andNbinPvwith fO2relative to theNNObuffer: