Electro-Deposited PdNi-Si Schottky Barrier Hydrogen Sensors with Improved Time Response

AbstractHydrogen sensor based on electrodeposited PdNi-Si Schottky barriers have been fabricated with a gradient structure in the PdNi concentration in a single electrodeposition run through variation of the deposition potential. By varying the electrodeposition potential after a fixed amount of charge, we are able to create various Schottky barrier structures.The resulting sensors in the back to back diode configuration show very low idle leakage current and high sensitivity to hydrogen. The structure with increased Ni concentration at the PdNi-Si interface shows dramatically improved time response as compared to the sample with uniform PdNi concentration

Optical Fiber Methane Sensor Using Refractometry

One potential application of fiber refractometers is gas detection. In this work, a multimode fiber (MMF) refractomer has been designed as a CH4 sensor by de-cladding 2 cm of the MMF and then functionalizing this region using a polymeric thin film of cryptophane-A supramolecules incorporated within a styrene acrylonitrile (SAN) host. CH4 concentration is subsequently measured by observing the variation of the transmitted optical power along the MMF compared to an unfunctionalized MMF used as reference. This variation is induced by the modification of the refractive index of the functionalized film due to CH4 concentration variation. The proposed sensor is potentially of lower cost than alternative sensors and can detect CH4 concentration with a resolution of 186 ppm at a relatively fast response of ~25 s

Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Microbathymetry data, in situ observations, and sampling along the 138200N and 138200N oceanic core complexes (OCCs) reveal mechanisms of detachment fault denudation at the seafloor, links between tectonic extension and mass wasting, and expose the nature of corrugations, ubiquitous at OCCs. In the initial stages of detachment faulting and high-angle fault, scarps show extensive mass wasting that reduces their slope. Flexural rotation further lowers scarp slope, hinders mass wasting, resulting in morphologically complex chaotic terrain between the breakaway and the denuded corrugated surface. Extension and drag along the fault plane uplifts a wedge of hangingwall material (apron). The detachment surface emerges along a continuous moat that sheds rocks and covers it with unconsolidated rubble, while local slumping emplaces rubble ridges overlying corrugations. The detachment fault zone is a set of anostomosed slip planes, elongated in the alongextension direction. Slip planes bind fault rock bodies defining the corrugations observed in microbathymetry and sonar. Fault planes with extension-parallel stria are exposed along corrugation flanks, where the rubble cover is shed. Detachment fault rocks are primarily basalt fault breccia at 138200N OCC, and gabbro and peridotite at 138300N, demonstrating that brittle strain localization in shallow lithosphere form corrugations, regardless of lithologies in the detachment zone. Finally, faulting and volcanism dismember the 138300N OCC, with widespread present and past hydrothermal activity (Semenov fields), while the Irinovskoe hydrothermal field at the 138200N core complex suggests a magmatic source within the footwall. These results confirm the ubiquitous relationship between hydrothermal activity and oceanic detachment formation and evolution

A geochemical and Nd isotopic study of Barberton komatiites (South Africa): implication for the Archean mantle

The Komati Formation of the Barberton greenstone belt (BGB), South Africa, is composed of both Al-undepleted and -depleted komatiites. The Al-undepleted komatiites are characterised by Al2O3/TiO2 and CaO/Al2O3 ratios of 15–18 and 1.1–1.5, respectively, and exhibit chondritic trace element contents and (Gd/Yb)N ratios. In contrast, the Al-depleted komatiites show significantly lower Al2O3/TiO2 ratios of 8–12, highly variable CaO/Al2O3 (0.19–2.81) ratios combined with (Gd/Yb)N ratios varying from 1.08 to 1.56. A Sm–Nd whole rock isochron for komatiites of the Komati Formation gives an age of 3657±170 Ma. 147Sm/144Nd ratios (0.1704 and 0.1964) are all lower than the chondritic value of 0.1967. The komatiite i,Nd(3.45) values cluster at +1.9±0.7.Trace element distribution indicates that most of the primary geochemical and isotopic features of the komatiites were preserved in line with the conservation of the primary chemical composition of clinopyroxene. High field strength element and rare earth element abundances indicate that crustal contamination and post-crystallisation processes did not disturb the primary features of komatiites.The Sm/Nd and Nb/U ratios of komatiites indicate that the Barberton greenstone belt mantle source has undergone melt extraction prior to komatiite formation. Variations of Al2O3/TiO2, (Gd/Yb)N, Zr/Sm and Sm/Nd ratios of komatiites indicate that a batch melting of slightly depleted mantle source during with garnet and/or clinopyroxene remained in the residue can produce the geochemical isotopic feature of the Barberton greenstone belt komatiites. Typical geochemical fingerprints of subduction-related processes (LILE enrichment, HFSE depletion compared to REE), as known from modern subduction zones, are not observed. Komatiites exhibit Ti/Zr, La/Nb, Nb/U, Sr/Nd and Ba/La ratios comparable to those of oceanic island basalt and mid-ocean ridge basalt. (La/Nb)PMN, (Sm/Yb)PMN, positive Nb values and flat or slightly enriched REE patterns suggest that BGB komatiites are part of an oceanic plateau rather than an oceanic island such as Iceland. Therefore, an oceanic plateau or mid-ocean ridge, in connection with an oceanic plateau, such as Ontong Java plateau or Caribbean–Colombian oceanic plateau, is a suitable tectonic setting for the formation of the BGB komatiites

Multichronometric evidence for an “ in-situ ” origin of the ultra-high pressure metamorphic terrane of Dabieshan,China.

[[sponsorship]]地球科學研究所[[note]]已出版;[SCI];有審查制度;具代表性[[note]]http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Drexel&SrcApp=hagerty_opac&KeyRecord=0022-1376&DestApp=JCR&RQ=IF_CAT_BOXPLO

Hf isotope ratio analysis using multi-collector inductively coupled plasma mass spectrometry: an evaluation of isobaric interference corrections

From measurements of Hf–Yb mixtures, we have found that the correction of isobaric interferences involving accepted Yb isotope ratios and reasonable estimates of mass bias result in a significantly under-corrected 176Hf, which is proportional to the amount of Yb added. This can be explained by (1) a significant difference in the instrumental mass bias between Hf and Yb, and (2) that the accepted values for isotopic ratios within the Yb and/or Hf systems are incorrect. We have evaluated these possibilities by measuring mixed solutions of Yb and Hf on two MC-ICP-MS instruments and undertaking a series of REE fractionation experiments using a thermal ionisation mass spectrometer (TIMS). Our results indicate that the presently accepted abundances of the Yb isotopes are not appropriate. We present new values for Yb isotopic abundances based on the TIMS and MC-ICP-MS results. Using the newly defined Yb values, we demonstrate that Yb and Hf have similar levels of mass bias in plasma ionisation instruments, and that Hf isotope ratios can be used to correct Yb mass bias before subsequent correction of isobaric interference. A laser ablation comparison of Yb and Hf indicates that similar relationships exist, and can be applied to micro-analytical techniques where chemical separation is not possible. <br/

The behaviour of Nd and Pb isotopes during 2.0 Ga migmatization in paragneisses of the central zone of the Limpopo Belt (South Africa and Botswana)

We have carried out major and trace element analyses and Nd–Pb isotope measurements on different components of two migmatite outcrops in the Limpopo Belt (Lose Quarry, Botswana, and Palala, South Africa) in order to assess the effect of migmatization during a high grade metamorphic event on Sm–Nd systematics and Nd model ages. The outcrops studied are located in the Mahalapye–Tshipise Straightening Zone at the south-western part of the Limpopo Central Zone close to its contact with the Kaapvaal Craton. Leucosomes of peraluminous granitic composition were formed by incongruent biotite melting in an Fe-rich metagreywacke (Lose Quarry) and in a metapelite (Palala), respectively. Monazite U–Pb and garnet Sm–Nd ages yield close to 2.0 Ga for the high grade event, confirming other recent work in the Central Zone. The chemical compositions of the main mineral phases (feldspar, biotite and garnet) indicate minimum melt formation at T&gt;750 °C and low pressure. Isocon plots and Pb isotope data indicate that the partial melts are locally derived. However, LIL trace element distribution between the leucosomes and paleosomes indicate the incomplete equilibration of the nascent melts with the residual feldspars and biotite in the paleosomes. Sm–Nd results on leucosomes and paleosomes of the metagreywacke migmatite show considerable scatter. When calculated back to 2.0 Ga, the paleosomes fall in a narrow range of ?Nd=-4 and give TDM model ages between 2.45 and 2.66 Ga. The ?Nd values of leucosomes are on average four units lower, causing them to have apparent TDM ages of 2.7–2.92 Ga, on average 250 Ma older than those of the paleosomes. The REE, Th, P2O5, and Zr budgets of paleosomes and leucosomes indicate dominance of the LREE by monazite and the HREE by apatite. Incorporation of proportionally more monazite than apatite into the melt is inferred as the cause for the Nd isotope discrepancy and hence the uncertainty of the average protolith mantle derivation age. In contrast, Pb–Pb results define an apparent age of 2025±29 Ma, reflecting nearly full Pb isotope exchange. In the case of the Palala metapelitic migmatite, the ?Nd values at 2.0 Ga of all but two migmatitic constituents cluster between -7 and -9.5, pointing out extensive Nd isotope equilibration during migmatization, whereas the Pb isotopes yield an errorchron date of 2311±65 Ma, indicating incomplete Pb isotope exchange. Here, garnet dominates the HREE distribution whereas the LREE are controlled by feldspar and monazite. Considering that Nd isotope equilibration was nearly reached during migmatization, Nd model ages on the whole rocks represent a good approximation of those of the original protolith (3.0–3.2 Ga). In the regional context, the Pb isotope data from the Lose quarry locality combined with the Nd model age (uncertain, but within the range of 2.5–2.9) are reminiscent of the northern Marginal Zone of the Limpopo Belt and the southern Zimbabwe Craton, whereas the Nd and Pb isotope data from the Palala locality are typical for the Limpopo southern Marginal Zone and the Northern Kaapvaal Craton

Sources of REE in sediment cores from the Rainbow vent site (36,14'N, MAR)

A geochemical investigation was carried out on two sediment cores collected at 2 and 5 km from the Rainbow hydrothermal vent site. Bulk sediment compositions indicate that these cores record clear enrichments in Fe, Cu, Mn, V, P and As from hydrothermal plume fallout (Cave et al., 2002) [Cave, R.R., German, C.R., Thomson, J., Nesbitt, R.W., 2002. Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14?N on the Mid-Atlantic Ridge. Geochim. Cosmochim. Acta 66 (11), 1905–1923]. Sequential dissolution of the bulk sediments has been used to discriminate between a leach (biogenic and oxy-hydroxide) component and a residual phase (detrital and sulphide/sulphate fractions). Major element data (Al, Fe, Ti, Mn, Mg, Ca, Si and index%) reveal that the hydrothermal input, as recorded in the leach phase, is much stronger than apparent from bulk sediment analyses alone. REE patterns for the leach phase record contributions from both biogenic carbonate (mimicking seawater REE patterns) and hydrothermal oxy-hydroxides, with the latter exhibiting positive Eu anomalies (hydrothermal derived) and negative Ce anomalies (seawater derived). Based on major element and REE data, the residue contains contributions from aeolian dust input, local MORB material and a hydrothermal component. Ternary REE mixing calculations indicate that most of the REE within the residual fraction (80%) is derived from hydrothermal material, while detrital contributions to the REE budget, as deep-sea clay and volcanic debris, are &lt;20%. By combining bulk and REE data for the various end-member components of the residue, we calculate that the chemical composition of the residue hydrothermal end-member is high in Ca (6–15%) and with a Nd/Sr ratio of 0.004. These characteristics indicate the presence of low-solubility hydrothermal sulphate (rather than sulphide) material within the residue component of Rainbow hydrothermal sediments. <br/