Ion Micro Research Articles

Fast Kinetic Carbon Anode Inherited and Developed from Architectural Designed Porous Aromatic Framework for Flexible Lithium Ion Micro Capacitors

AbstractLithium ion micro capacitors (LIMCs) demonstrate competitive advantages of simultaneously high energy/power densities and long cycle life over many other micro supercapacitors and micro batteries. However, these performances are significantly determined by the carbon anode with fast Li+ storage kinetics. Herein, a design strategy at the precursor side of a typical porous aromatic framework‐5 (PAF‐5) from the carbon bonding levels is proposed, and coupling with the post pyrolysis, the sp2/sp3 domains ratio, interlayer spacing, and pore structure of derived carbons can be synergistically balanced. The inherited sp2 domains and porous structure from PAF‐5 endow the derived carbon with high electron transport capability and fast Li+ adsorption capacity. Meanwhile, the developed sp3 domains and enlarged interlayer spacing also enable abundant and fast Li+ intercalation contribution, giving rise to a superior rate capability (141.9 mAh g−1 at 4 A g−1) that is 13 times better than a commercial graphite anode. A flexible LIMCs based on this carbon anode are fabricated, and simultaneously high energy/power densities (71.1 mWh cm−3/1.9 W cm−3), long cycle life (94.7% after 6,000 cycles), and flexibility are achieved, demonstrating a great feasibility of designed PAFs as the trimmed carbon anode precursors for high performance Li+ storage.

Geological framework of the concealed East Tennant area constrained by SHRIMP U–Pb zircon geochronology: Implications for Paleoproterozoic stratigraphic correlations in northern Australia

The fundamental geological framework of the concealed Paleoproterozoic East Tennant area of northern Australia is very poorly understood, despite its relatively thin veneer of Phanerozoic cover and its position along-strike from significant Au–Cu–Bi mineralisation of the Tennant Creek mining district within the outcropping Warramunga Province. We present 18 new U–Pb dates, obtained via Sensitive High Resolution Ion Micro Probe (SHRIMP), constraining the geological evolution of predominantly Paleoproterozoic metasedimentary and igneous rocks intersected by 10 stratigraphic holes drilled in the East Tennant area. The oldest rocks identified in the East Tennant area are two metasedimentary units with maximum depositional ages of ca. 1970 Ma and ca. 1895 Ma respectively, plus ca. 1870 Ma metagranitic gneiss. These units, which are unknown in the nearby Murphy Province and outcropping Warramunga Province, underlie widespread metasedimentary rocks of the Alroy Formation, which yield maximum depositional ages of 1873–1864 Ma. While parts of this unit appear to be correlative with the ca. 1860 Ma Warramunga Formation of the Warramunga Province, our data suggest that the bulk of the Alroy Formation in the East Tennant area is slightly older, reflecting widespread sedimentation at ca. 1870 Ma. Throughout the East Tennant area, the Alroy Formation was intruded by voluminous 1854–1845 Ma granites, contemporaneous with similar felsic magmatism in the outcropping Warramunga Province (Tennant Creek Supersuite) and Murphy Province (Nicholson Granite Complex). In contrast with the outcropping Warramunga Province, supracrustal rocks equivalent to the 1845–1810 Ma Ooradidgee Group are rare in the East Tennant area. Detrital zircon data from younger sedimentary successions corroborate seismic evidence that at least some of the thick sedimentary sequences intersected along the southern margin of the recently defined Brunette Downs rift corridor are possible age equivalents of the ca. 1670–1600 Ma Isa Superbasin. Our new results strengthen ca. 1870–1860 Ma stratigraphic and ca. 1850 Ma tectono-magmatic affinities between the East Tennant area, the Murphy Province, and the mineralised Warramunga Province around Tennant Creek, with important implications for mineral prospectivity of the East Tennant area.

Dual Active and Kinetically Inter-Promoting Li3VO4/Graphene Anode Enabling Printable High Energy Density Lithium Ion Micro Capacitors

Planar micro-supercapacitors (MSCs) with high energy/power densities and long cycle life are expected to expedite the development of the future wearable miniaturized electronics. However, its low energy density issue always falls short in ever-increasing demands of specific energy consumption. Herein, a dual active and kinetically inter-promoting Li3VO4 (LVO)/graphene composite is designed as the anode for high energy density lithium ion micro capacitors (LIMCs). The LVO nanoparticles are evenly confined on graphene nanosheets through an atomic layer pre-deposition (ALD) technique, which substantially disperses the nucleation site and impedes the coarse grain growth in the successive solid-state formation of LVO. The much-promoted reaction kinetics of LVO and graphene substrate with sufficient diffusion space in the interdigital electrodes of LIMCs synergistically boost the three-dimensional and efficiently lithium ion storage behavior. The LVO/graphene exhibits extraordinary rate capability (98.5 mAh g−1 at 40 A g−1 (100 C)) and long-term stability. All the current collectors and asymmetric interdigital electrodes are spray printed, opening a facile and delicate technique for a large-scale production of LIMCs. The LIMCs deliver a superior volumetric energy density of 51.4 mWh cm−3, excellent flexible and cyclic stability, demonstrating a great potential for the future miniaturized, flexible, and high-performance energy storage devices.

SHRIMP U–Pb Zircon Ages, Geochemistry and Sr–Nd–Hf Isotope Systematics of the Zalute Intrusive Suite in the Southern Great Xing’an Range, NE China: Petrogenesis and Geodynamical Implications

An integrated zircon geochronological, elemental geochemical, and Sr–Nd–Hf isotopic investigation was carried out on a suite of dioritic–granitic rocks at Zalute in the southern Great Xing’an Range (SGXR), NE China, in order to probe the source and petrogenesis of these granitoid rocks and further constrain the geodynamical setting of early Early Cretaceous magmatism. The results of Sensitive High-Resolution Ion Micro Probe (SHRIMP) zircon U–Pb dating reveal that the Zalute dioritic–granitic rocks have a consistent crystallization age of ca. 137–136 Ma, consisting of quartz diorite (136 ± 1.4 Ma), monzogranite (136 ± 0.8 Ma), and granite porphyry (137 ± 1.3 Ma), which record an early Early Cretaceous magmatic intrusion. Geochemically, the quartz diorites, monzogranites, and granite porphyries are mostly high-K calc-alkaline and show features of typical I-type affinity. They possess uniform and depleted Sr–Nd–Hf isotopic compositions (e.g., initial 87Sr/86Sr ratios of 0.7035 to 0.7049, εNd(t) of −0.02 to +2.61, and εHf(t) of +6.8 to +9.6), reflecting a common source, whose parental magma is best explained as resulting from the partial melting of juvenile source rocks in the lower crust produced by underplating of mantle-derived mafic magma, with minor involvement of ancient crustal components. Evidence from their close spatio–temporal relationship, common source, and the compositional trend is consistent with a magmatic differentiation model of the intermediate-felsic intrusive suite, with continued fractional crystallization from quartz diorites, towards monzogranites, then to granite porphyries. Combined with previously published data in the SGXR, our new results indicate that the Zalute intermediate-felsic intrusive suite was formed during the post-collisional extension related to the closure of the Mongol–Okhotsk Ocean and subsequent slab break-off.

Development of a negative ion micro TPC detector with SF6 gas for the directional dark matter search

A negative ion micro time projection chamber (NIμTPC) was developed and its performance studied. An NIμTPC is a novel technology that enables the measurement of absolute z coordinates for self-triggering TPCs. This technology provides full-fiducialization analysis, which is not possible with conventional gaseous TPCs, and is useful for directional dark matter searches in terms of background rejection and the improvement of the angular resolution. The developed NIμTPC prototype had a detection volume of 12.8 × 25.6 × 144 mm3. The absolute z coordinate was determined thanks to the different drift velocities between majority and minority carriers with a location accuracy of 16 mm. Simultaneously, there was a successful reconstruction of the three-dimensional (3D) tracks with a spatial resolution of 130 μm. This is the first demonstration of 3D tracking with the detection of absolute z coordinates, and it is an important step in improving the sensitivity of directional dark matter searches.

Precise U–Pb baddeleyite dating of the Derim Derim Dolerite, McArthur Basin, Northern Territory: old and new SHRIMP and ID-TIMS constraints

The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but exploration has been hampered by poor constraints on its post-depositional history that has compromised understanding of the tectonostratigraphic evolution of the basin. The Derim Derim Dolerite occupies an important position in the event chronology of the McArthur Basin, having intruded the Roper Group prior to post-Roper basin inversion, and it is also a major component of Mesoproterozoic intraplate mafic magmatism in northern Australia. Since 1997, the Derim Derim Dolerite has been assigned a magmatic crystallisation age of 1324 ± 4 Ma (all uncertainties are 95% confidence), based on unpublished sensitive high-resolution ion micro probe (SHRIMP) U–Pb analyses on baddeleyite attributed to a dolerite sample from Bureau of Mineral Resources drill-hole Urapunga 5. Herein, we establish that the SHRIMP sample originated from the type locality of the Derim Derim Dolerite in outcrop 90 km northwest of Urapunga 5 and document the 207Pb/206Pb date interpreted from the 1997 dataset. New U–Pb SHRIMP reanalysis of the same grain-mounts yielded a mean 207Pb/206Pb date of 1320.1 ± 5.3 Ma, confirming the 1997 result, and isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) analysis of baddeleyites plucked from the mounts yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U–Pb ID-TIMS date of ca 1313 Ma recently reported elsewhere from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Previously documented geochemical variation in Mesoproterozoic intraplate mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma Galiwinku Dolerite in the McArthur Basin, 1316 ± 40 Ma phonolites in the Nimbuwah Domain of the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. The timing and geochemistry of Derim Derim-Galiwinku mafic igneous activity is strikingly similar to that of the Yanliao Large Igneous Province (LIP) in the northern North China Craton, and the global paucity of 1330–1300 Ma LIPs suggests that the North Australian Craton and the North China Craton were in relatively close proximity at that time. KEY POINTS We document a previously unpublished U–Pb baddeleyite date of 1324 ± 4 Ma for the Derim Derim Dolerite in the McArthur Basin, obtained via sensitive high-resolution ion micro probe (SHRIMP), and substantiate it with an isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) date of 1327.5 ± 0.6 Ma from the same sample. Our dates are significantly older than a U–Pb baddeleyite ID-TIMS date of ca 1313 Ma from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Contemporaneous intraplate mafic magmatism extended hundreds of kilometres across the Northern Territory, spanning the Tomkinson Province, the McArthur Basin, and the Nimbuwah Domain of the eastern Pine Creek Orogen. The timing and geochemistry of Derim Derim Dolerite magmatism strongly resembles the Yanliao Large Igneous Province (LIP) in the northern North China Craton, which suggests that the North Australian Craton and the North China Craton were in close proximity during the Mesoproterozoic.

SHRIMP U-Pb zircon ages for the synkinematic magmatism in the Dorsal de Canguçu Transcurrent Shear Zone, Dom Feliciano Belt (Brazil): Tectonic implications

The Dorsal de Canguçu Transcurrent Shear Zone (DCTSZ) is the main Neoproterozoic structure of the Dom Feliciano Belt in the Rio Grande do Sul sector (Brazil), developed during the late stages of the Brasilano/Pan-African orogenic cycle. This structure, together with its northern – Major Gercino Transcurrent Shear Zone (Santa Catarina sector, Brazil) – and southern extension – Sierra Ballena Transcurrent Shear Zone (Uruguay), constitute a 1000 km long discontinuous lineament. Synkinematic granitoids are widespread along the DCTSZ. The main units are represented by the porphyritic, calc-alkaline high-K Quitéria granite, and the peraluminous Arroio Francisquinho and Cordilheira granites (Cordilheira Suite). In order to better constrain the time frame of the synkinematic magmatism associated with the DCTSZ, we present in this paper new zircon SHRIMP (Sensitive High Resolution Ion Micro Probe) U-Pb ages for this magmatism. The Quitéria granite yielded a concordia U-Pb age of 618.9 ± 4 Ma, interpreted as the magmatic crystallization age. The Arroio Francisquinho and Cordilheira granites yielded concordia U-Pb ages of, respectively, 615.2 ± 13 Ma and 607.3 ± 12 Ma, interpreted as the magmatic crystallization ages. The latter ages constrain the main phase of synkinematic magmatism in the DCTSZ. Zircon rims of the studied samples yielded U-Pb ages between 585 and 540 Ma might represent the influence of post-magmatic fluids and deformation caused by the transcurrent activity of the shear zone. Zircon crystals interpreted as inherited yielded U-Pb ages ranging from 1800 to 650 Ma for the three studied rocks. These inherited ages are similar to those found in detrital zircon from the regional gneissic basement. The new ages for the earliest synkinematic magmatism in the DCTSZ match those of the Major Gercino and Sierra Ballena Shear Zone, strengthen previous correlation between the shear zones.

Petrography and chronology of lunar meteorite Northwest Africa 6950

Northwest Africa (NWA) 6950 is an olivine-gabbro lunar meteorite that has a distinctly different petrographic texture from other lunar basalts. In this contribution, we report the petrography, mineralogy, and U-Pb geochronology of baddeleyite and phosphate in this lunar meteorite and make a comparison with other NWA 773 paired meteorites. NWA 6950 consists mainly of coarse-grained olivine, pyroxene, and plagioclase, with minor ilmenite, chromite, troilite, baddeleyite, taenite, and apatite. The abundant rounded to euhedral olivine has a limited Fo ranging from 68 to 69. Pyroxenes include both augite and pigeonite, with a narrow range of Mg#=71–80, and composition, respectively, ${\rm~En}_{46\text{-}52}{\rm~Fs}_{12\text{-}16}{\rm~Wo}_{32\text{-}41}$ and ${\rm~En}_{58\text{-}68}{\rm~Fs}_{19\text{-}28}{\rm~Wo}_{7\text{-}20}$. Plagioclase is mainly anhedral, conforming to the crystal margins of olivine and pyroxene. The plagioclase grains are elongated and several hundreds of microns in length. Raman spectra shows that plagioclase has been transformed into maskelynite, which is very calcic (${\rm~An}_{87\text{-}95}$) with low sodium and very low potassium (${\rm~Ab}_{4\text{-}9}{\rm~Or}_{0.6\text{-}3.7}$). The weighted mean $^{207}{\rm~Pb}/^{206}{\rm~Pb}$ ages of baddeleyite and phosphate measured using a sensitive high resolution ion micro probe (SHRIMP II) are $3119\pm16$ Ma ($n=9$, MSWD = 2.5) (meansquared weighted deviates, MSWD) and $3119\pm18$ Ma ($n=15$, MSWD = 2.1), respectively, giving the crystallization age of the meteorite.NWA 6950 has similar mineral compositions, geochemical characteristics, and an almost identical age of crystallization to the magnesian gabbro of the NWA 773 clan. We conclude that NWA 6950 and NWA 773 are paired meteorites, which crystallize at ca. 3119 Ma, and represent magmatic activities in the KREEP (potassium (K), rare earth elements (REE) and phosphorus (P) rich lunar material) region of the Moon.

Selective modification of electrical insulator material by ion micro beam for the fabrication of circuit elements

Two well-established electrical insulators, graphene oxide and poly(methylmethacrylate) (PMMA) have been selectively exposed to controlled energy and fluence of ions. Ion micro beam has been proposed for processing of both graphene-based material and polymeric foils for tailoring of their properties. In a single step, the mask-less production of pattern on graphene-oxide and poly(methylmethacrylate) was realized at the Tandetron Laboratory of the Nuclear Physics Institute (Czech Republic) using a stream of 2.2 MeV alpha particles. Elements of a circuit were written on GO and poly(methylmethacrylate) in a controlled way using a software written in LabVIEW code. The induced deoxygenation, and dehydrogenation change the compositional, structural and electrical properties in the exposed samples. The accuracy of the method has been investigated by Rutherford backscattering spectrometry, elastic recoil detection analysis, Raman microscopy and the electrical standard two points method.

Micro ion beam used to optimize the quality of microstructures based on polydimethylsiloxane

Ion micro beam was employed to fabricate microstructures based on poly(dimethylsiloxane) (PDMS). Carbon ions with energy of 6.0 MeV were used. The ion treatment induces modifications in PDMS surface and on the optical properties as a function of the ion current and fluence. PDMS foils were produced from commercially available two component addition materials. The selective modifications of the polymer were studied for applications in micro-fluids, micro-optics and micro-electronics. The comparison between the unirradiated and irradiated PDMS was investigated in morphology and compactness using the atomic force microscopy. The wetting ability of the PDMS surface was also analyzed as a function of the ion microbeam irradiation. The compositional and optical changes in PDMS were monitored by Rutherford backscattering spectrometry, elastic recoil detection analysis and optical spectroscopy measurements.

Localized deoxygenation of graphene oxide foil by ion microbeam writing

An efficient mask-less production of patterns in insulating foils of graphene-oxide was carried out under impact of 5 MeV alpha particle beams delivered by the Ion Micro Beam system at the Tandetron Laboratory of the Nuclear Physics Institute in Rez (Czech Republic). Graphene-oxide (GO) matrix has been exposed to controlled fluences with the aim of inducing deoxygenation and enhancement of the electrical conductivity in selected areas of the exposed samples. The reported designed patterns and their sharp edge profiles demonstrate the feasibility of the process.The compositional changes in the exposed areas of the GO were investigated by Rutherford backscattering spectrometry, elastic recoil detection analysis, scanning electron microscopy, and correlated with the electrical properties measured by a standard 2-point probe technique.

Comparative analysis of textile metal threads from liturgical vestments and folk costumes in Croatia

Abstract Textile is essential for everyday life in all societies. It is used in clothes for protection and warmth but also to indicate class and position, show wealth and social status. Threads from precious metals have also been used in combination with fibres for decoration in order to create luxury fabrics for secular and religious elites. We performed elemental analysis of 17 th to 20 th century metal threads from various textile articles of liturgical vestments and festive folk costumes collected in the museums of northern, southern and central Croatian regions. In order to determine elemental concentrations in threads we performed comparative X-ray Spectroscopy measurements using: (i) Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX) at the Faculty of Textile Technology, (ii) X-ray Fluorescence Spectroscopy (XRF) at the Croatian Conservation Institute and (iii) Particle Induced X-ray Spectroscopy (PIXE) at the Ruđer Boskovic Institute Tandem Accelerator Facility using ion micro beam. Rutherford Backscattering Spectroscopy (RBS) was performed as well on selected samples. SEM-EDX investigations of cross-sections along with the surfaces were also performed. In this work we report and discuss the results obtained by the three X-ray methods and RBS for major (gold, silver, copper) and minor elements on different threads like stripes, wires and “srma” (metal thread wrapped around textile yarn).

敞开式离子源和微型气泵集成的微型针-柱放电结构芯片设计与实验分析

敞开式离子源和微型气泵集成的微型针-柱放电结构芯片设计与实验分析

Precision measurement of the branching fractions of the5pP1/22state inSr+88with a single ion in a microfabricated surface trap

We measured the branching fractions for the decay of the 5p 2 P 1/2 state of 88 Sr + by applying a recently demonstrated photon-counting sequential method (M. Ramm et al., Phys. Rev. Lett. 111, 023004) to a single ion laser-cooled in a micro fabricated surface trap. The branching fraction for the decay into the 5s 2 S 1/2 ground level was found to be p = 0.9453 +0.0007 --0.0005. This result is in good agreement with recent theoretical calculations but disagrees with previous experimental measurements, however affected by a one order of magnitude larger uncertainty. This experiment also demonstrates the reliability and the performances of ion micro trap technology in the domain of precision measurements and spectroscopy. PACS numbers: 32.70.Cs, 06.30.Ft, 37.10.Ty

Ion Micro Beam, promising methods for interdisciplinary research

An increasing attractiveness of top-down nanotechnology using nuclear microprobe techniques have been gathered to the micro and nano patterning process for polymers. This paper presents the research activity on innovative promising techniques able to produce three- dimensional (3D) micro-structures in polymeric resists as well as to obtain images of fabricated nanostructures at Tandetron Laboratory (LT) of the Nuclear Physics Institute in Rez (Czech Republic). The Proton Beam Writing (PBW) technique was used to irradiate PMMA resist with energy of MeVs protons. The fabricated patterns were developed in chemical bath using different etching rates. An overview of micro-scale structures have been fabricated selecting the beam, the energy, the fluence and the exposition time. The produced structures were investigated by different analysis techniques among which Scanning Transmission Ion Microscopy (STIM). The characterizations of the fabricated microtunnels are presented and discussed.

Combined ion micro probe and SEM analysis of strongly non uniform deposits in fusion devices

Conventional ion beam analysis (IBA) of deposited layers from fusion devices may have insufficient accuracy due to strongly uneven appearance of the layers. Surface roughness and spatial variation of the matrix composition make interpretation of broad beam spectra complex and non obvious. We discuss complications of applied IBA arising for fusion-relevant surfaces and demonstrate how quantification can be improved by employing micro IBA methods. The analysis is bound to pre-defined regions on the sample surface and can be extended by employing beams of several types, scanning electron microscopy (SEM) and stereo SEM techniques.

Structural and spectroscopic studies of water-alkaline earth ion micro clusters: an alternate approach using genetic algorithm in conjunction with quantum chemical methods

We present an approach of using a stochastic optimization technique namely genetic algorithm in association with quantum chemical methods to first elucidate structure and then infrared spectroscopy and thermochemistry of water-alkaline earth metal ion clusters. We show that an initial determination of structure using stochastic techniques and following it up with quantum chemical calculation can lead to much faster convergence to high quality structures for these systems. Infrared spectroscopic, thermochemical calculations and natural population analysis based charges on the central metal ions are done to further ascertain the correctness of the structures using our technique. We have done a comparative study with a pure density functional theory calculation and have shown that even for very poor starting guess geometries genetic algorithm in conjunction with density functional theory indeed converges to global structure while pure density functional theory can encounter problems in certain situations to arrive at global geometry. We have also discussed usefulness of Unimodal Normal distribution crossover for handling situation with real coded variables.

A re-evaluation of the Mn–Cr systematics of olivine from the angrite meteorite D’Orbigny using Secondary Ion Mass Spectrometry

‘Quenched’ angrite meteorites are among the best time markers of igneous activity in early formed planetesimals of the Solar System. They can be precisely dated by the Mn–Cr extinct nuclide decay system because they contain olivine with high Mn/Cr. Nevertheless, there is disagreement between various determinations of the initial 53Mn/55Mn for this meteorite, hindering their use for cross-calibration between chronometric systems and between Secondary Ion Mass Spectrometry (SIMS) and bulk measurement techniques. Here we re-evaluate the Mn–Cr systematics of olivine from the quenched angrite D’Orbigny using Sensitive High-mass Resolution Ion Micro Probe Reverse Geometry (SHRIMP-RG) to search for heterogeneity in isotope systematics and check for inter-laboratory bias. We investigated possible bias arising due to different data reduction methods and have paid careful attention to the relative sensitivities of Mn and Cr by utilising a three-component mixing model to correct for matrix effects associated with Mg, Fe and Ca zoning in angrite olivine. We have determined an initial 53Mn/55Mn of 3.60 (±0.39)×10−6 and 3.44 (±0.29)×10−6 (2σ errors) for D’Orbigny olivine by the Mean of Ratios and Ratio of Total Counts data reduction methods. These values are in agreement with those found by some previous bulk and mineral-scale determinations, and with the generally accepted initial 53Mn/55Mn of this meteorite, but not with previous SIMS work on this material. The source of this discrepancy remains unclear. We can exclude heterogeneity in D’Orbigny as a source of discrepancy because we used the same sample and the meteorite appears to have consistent initial 53Mn/55Mn over both micro- and macro-scales. The discrepancy between this and the previous SIMS study probably reflects an unrecognised systematic analytical bias, possibly associated with relative sensitivities of Mn and Cr or with mass spectrometric backgrounds (isobaric interferences or scattered ions) which may become significant at very low Cr count rates.

Initiation and growth of a single pit on 316L stainless steel: Influence of SO42− and ClO4− anions

In this paper, an ion micro dispenser (IMD) was used to initiate a single pit by generating chloride anions above a 316L stainless steel electrode in either H2SO4 or HClO4 electrolyte. The current variations with respect to time provided an unambiguous characterization of the single pit evolution. Different pit shapes were observed depending on both the nature of the electrolyte and potential applied to the electrode. Substituting SO42− for ClO4− gave smaller (in diameter) but deeper pits at the early stage of pitting. However, when using a different setup that allows the sustaining of the pit propagation with a continuous supply of Cl−, the deeper pits were observed in HClO4 rather than H2SO4. The formation of an iron sulphate salt film at the bottom of the pit by precipitation of dissolution products in H2SO4 slowed down the corrosion rate. At high potentials, the repassivation mechanism outweighed the metal dissolution in the ClO4− containing solution.

Mn–Cr relative sensitivity Factors for Secondary Ion Mass Spectrometry analysis of Mg–Fe–Ca olivine and implications for the Mn–Cr chronology of meteorites

Secondary Ion Mass Spectrometry (SIMS) is used to date meteoritic olivine using the 53Mn–53Cr short-lived decay scheme. This involves simultaneously measuring the Cr-isotope composition and Mn/Cr ratio of a sample, but the relative sensitivity of SIMS to Cr and Mn over a compositionally varying olivine matrix is poorly understood. We have synthesized a range of olivine samples in Mg–Fe–Ca space, suitable for investigating Mn–Cr relative sensitivity with particular application to olivine in angrites and secondary fayalite in oxidised carbonaceous chondrites. These were analysed by SIMS (using Sensitive High-mass Resolution Ion Micro Probe Reverse Geometry; SHRIMP-RG) and Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS) to determine the relative sensitivity factors (RSF) necessary to correct SIMS 55Mn+/52Cr+ to atomic 55Mn/52Cr. We have found that RSF changes systematically as a function of the olivine matrix by several tens of percent, apparently being controlled by Fe content. Additionally, the RSF values found in this study are considerably different from most of those previously reported. A review of the literature shows that RSF for the Mg-rich San Carlos olivine differs widely between studies, and is probably controlled by SIMS instrumental settings. Our results show that the 55Mn/52Cr of olivine in some SIMS Mn–Cr studies has been accurately determined (e.g. for pallasites and angrites) but for secondary fayalite in carbonaceous chondrites it has probably been underestimated. If the relationship observed for our SIMS instrument holds true for others, then the initial 53Mn/55Mn of these materials (the abundance of 53Mn with respect to 55Mn at the time of crystallisation/isotopic closure) should be lower by a factor of ∼1.6 and ages should be ∼2.6Ma younger. This would imply that the initial 53Mn/55Mn for secondary fayalites in carbonaceous chondrites is in the range 0.7–1.7×10−6, equating to an age of 4555.2–4559.9Ma relative to the precisely dated D’Orbigny angrite.