Ar Gas Stream Research Articles

Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

A new analytical technique was developed for determination of metallic impurities in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small, enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with a particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). The air was exchanged by Ar gas and the particles came out from GED in Ar gas stream. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. This paper describes how the new analytical technique works for ultra-trace level of metallic impurities in wafers.

Continuous measurement of K and S release by means of ETV-ICP OES for high-temperature coal conversion processes

To estimate the fouling, slagging and corrosion potential of an energy feedstock during thermal carbon conversion processes, it is necessary to determine the temperature-dependent release behavior of relevant elements such as potassium and sulfur. For this purpose, this study employed electrothermal evaporation with inductively coupled plasma and optical emission spectroscopy (ETV-ICPOES) to investigate the element release in atmospheres containing oxygen both qualitatively and quantitatively. Using three different coal samples, it is shown that different heating rates (5–350 K/s) and gas atmospheres (0–10 vol-% O2 in the Ar gas stream) lead to differences in the release behavior. More sulfur is released when the oxygen content increases, whatever the sample. The release of potassium, on the other hand, depends on the sample matrix and the secondary reactions that occur. In two of the samples investigated, K is bound to silicates. These samples tend to form slags in which the potassium can bind. In the third sample, the potassium is organically bound or is bound to exchange sites on clay minerals and is released almost completely during the analyses.

Cold Gas-Dynamic Spray for Catalyzation of Plastically Deformed Mg-Strips with Ni Powder.

Magnesium hydride (MgH2) has received significant attention due to its potential applications as solid-state hydrogen storage media for useful fuel cell applications. Even though MgH2 possesses several attractive hydrogen storage properties, it cannot be utilized in fuel cell applications due to its high thermal stability and poor hydrogen uptake/release kinetics. High-energy ball milling, and mechanically-induced cold-rolling processes are the most common techniques to introduce severe plastic deformation and lattice imperfection in the Mg/MgH2. Furthermore, using one or more catalytic agents is considered a practical solution to improve both the de-/rehydrogenation process of MgH2.These treatments are usually dedicated to enhance its hydrogen storage properties and deduce its thermal stability. However, catalyzation of Mg/MgH2 powders with a desired catalytic agent using ball milling process has shown some disadvantages due to the uncontrolled distribution of the agent particles in the MgH2 powder matrix. The present study has been undertaken to employ a cold gas-dynamic spray process for catalyzing the fresh surfaces of mechanically-induced cold-rolled Mg ribbons with Ni powder particles. The starting Mg-rods were firstly heat treated and forged 200 times before cold rolling for 300 passes. The as-treated ribbons were then catalyzed by Ni particles, using cold gas-dynamic spray process. In this catalyzation approach, the Ni particles were carried by a stream of Ar gas via a high-velocity jet at a supersonic velocity. Accordingly, the pelted Ni particles penetrated the Mg-substrate ribbons, and hence created numerous micropores into the Mg, allowed the Ni particles to form a homogeneous network of catalytic active sites in Mg substrate. As the number of coating time increased to three times, the Ni concentration increased (5.28 wt.%), and this led to significant enhancement of the Mg-hydrogen storage capacity, as well as improving the de-/rehydrogenation kinetics. This is evidenced by the high value of hydrogen storage capacity (6.1 wt.% hydrogen) and the fast gas uptake kinetics (5.1 min) under moderate pressure (10 bar) and temperature (200 °C). The fabricated nanocomposite MgH2/5.28 wt.% Ni strips have shown good dehydrogenation behavior, indicated by their capability to desorb 6.1 wt.% of hydrogen gas within 11 min at 200 °C under 200 mbar of hydrogen pressure. Moreover, this system possessed long cycle-life-time, which extended to 350 h with a minimal degradation in the storage and kinetics behavior.

PI/NCC- based carbon molecular sieve membranes for Hydrogen purification: Effect of aging times

In this study, the effect of stabilization temperature on the performance of tubular carbon Upgrade the gas separation performance of the resultant carbon molecular sieve (CMS) membrane, a synthesized nanocrystalline cellulose (NCC) utilizing tissue paper as an added substance was included into the simpleton arrangement at pyrolysis temperatures of 800°C. This paper shows the inference of CMSs from BTDA-TDI/MDI polyimide (PI) arranged by means of a dip-coating strategy on an inorganic cylindrical help surface, trailed by a heat treatment (adjustment and carbonization) under Ar gas stream. Extraordinary consideration was given to the physicochemical attributes of the subsequent PI/NCC-based CMS and its comparing gas permeation properties. Pure gas permeation tests were performed utilizing H2, and N2 at room temperature. The gas permeation information showed that the CMS displayed an amazing performance contrasted with the polymeric membrane. Upgrade in the two gas permeance and selectivity were watched arranged with fresh CMS membrane, with H2N2 selectivity of 434.68±1.39, regarding the neat CMS. By controlling different aging times (fresh, 1 day, multi week, and 3 months), CMSs with various structures and properties were gotten.

Electrochemical investigation of novel reference electrode Ni/Ni(OH)₂ in comparison with silver and platinum inert quasi-reference electrodes for electrolysis in eutectic molten hydroxide

An efficient and green energy carrier hydrogen (H2) generation via water splitting reaction has become a major area of focus to meet the demand of clean and sustainable energy sources. In this research, the splitting steam via eutectic molten hydroxide (NaOH–KOH; 49–51 mol%) electrolysis for hydrogen gas production has been electrochemically investigated at 250–300 °C. Three types of reference electrodes such as a high-temperature mullite membrane Ni/Ni(OH)2, quasi-silver and quasi-platinum types were used. The primary purpose of this electrode investigation was to find a suitable, stable, reproducible and reusable reference electrode in a molten hydroxide electrolyte. Cyclic voltammetry was performed to examine the effect on reaction kinetics and stability to control the working electrode at different scan rate and molten salt temperature. The effect of introducing water to the eutectic molten hydroxide via the Ar gas stream was also investigated. When the potential scan rate was changed from 50 to 150 mV s−1, the reduction current for the platinum wire working electrode was not changed with newly prepared nickel reference electrode that designates its stability and reproducibility. Furthermore, increasing the operating temperature of molten hydroxides from 250 to 300 °C the reduction potential of the prepared nickel reference electrode is slightly positive shifted about 0.02 V. This suggests that it has good stability with temperature variations. The prepared nickel and Pt reference electrode exhibited stable and reliable cyclic voltammetry results with and without the presence of steam in the eutectic molten hydroxide while Ag reference electrode exposed positive shifts of up to 0.1 V in the reduction potential. The designed reference electrode had a more stable and effective performance towards controlling the platinum working electrode as compared to the other quasi-reference electrodes. Consequently, splitting steam via molten hydroxides for hydrogen has shown a promising alternative to current technology for hydrogen production that can be used for thermal and electricity generation.

Effect of Steel Substrates on the Formation and Deuterium Permeation Resistance of Aluminide Coatings

The effect of steel substrates on the formation and deuterium permeation resistance of aluminide coatings for tritium permeation barrier applications was investigated. It was found that the average thickness and crystal structure of electrodeposited Al coatings varied with Cr steel substrates. After aluminization in vacuum, significant differences existed in the composition and thickness of (Fe,Cr)2Al5-type aluminide layers formed on different Cr steel substrates, in which the alloying element Cr from steel substrates was involved. Thereafter, the scale microstructural feature and thickness also changed with the Cr steel substrate after selective oxidation in an Ar gas stream. Consequently, the deuterium permeation resistance of the formed aluminide tritium permeation barriers (TPBs) differed by steel substrates, indicating that the substrate effect existed in aluminide TPB coatings and thus could have a significant influence on the formation and eventual performance of aluminide TPBs.

Electrochemical quartz crystal microbalance, X-ray photoelectron spectroscopy, and Raman spectroscopy analysis of SiCl4 reduction in ionic liquids

The reaction mechanism of Si electrodeposition in the ionic liquid trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) with SiCl4 was investigated using an electrochemical quartz crystal microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). The deposited films were further characterized by Raman spectroscopy. The EQCM method measured the frequency change in situ during electrodeposition, whereas XPS provided the Si mass concentration in the electrodeposited films. By combining these results, the mass change due to SiCl4 reduction was estimated. Then, the current efficiency for Si electrodeposition at various potentials was evaluated. The calculated current efficiency was almost 100% when it was assumed that SiCl4 reduction progressed by four-electron electroreduction. The XPS and Raman results showed that the deposited films were composed primarily of amorphous Si with Si–Si bonds. Crystalline Si thin films were obtained after annealing in an Ar gas stream.

Dissolution of Platinum Single Crystal Surfaces under Potential Cycling in Sulfuric Acid Solution

Pt dissolution is one of the most important topics in Polymer Electrolyte Fuel Cell (PEFC) field because of the origin of the Pt nanoparticle growth, which results in a cell performance loss of PEFC.1 Recent reports showed a submonolayer of Pt dissolution occurs under potential cycling conditions simulating the PEFC operation in acidic environments.2Surface structural controls of Pt nanoparticles against Pt dissolution under potential cycling are a key point to improve the corrosion resistance of Pt surface. We investigated the effect of crystal orientations on the dissolution of Pt surface using Pt(100), Pt(110), and Pt(111) single crystal electrode. Commercial Pt(100), Pt(110) and Pt(111) single crystal electrodes were used as the specimen. The specimens were polished down to 0.25 mm diamond paste, annealed with an oxygen-hydrogen burner for 2 h, and cooled in a stream of Ar gas, prior to the electrochemical measurements. Cyclic voltammetry (CV) at single crystal surfaces was conducted for 100 cycles to examine Pt dissolution. The potential range of CV was from 0.5 to 1.0, 1.2, and 1.4 V. 0.5 M H2SO4solution at 298 K open to air was used as the electrolyte. After 100 cycles of CV, the solutions were analyzed with ICP-MS for the quantification of amount of dissolved Pt. The surface morphology of Pt single crystal electrodes was observed by electrochemical STM measurements. Figure 1 shows STM images of Pt(100), Pt(110), and Pt(111) single crystal surfaces after the anealing, and the cross section height profiles along the white arrows. The surfaces of Pt(100), Pt(110), and Pt(111) single crystal electrodes were composed of atomic height steps and smooth terraces. The saw-like step structures were observed at Pt(100) and Pt(110) surface. In addition, Pt(110) surface was relatively roughened. CVs at Pt(100), Pt(110), Pt(111) single crystal, and polycrystalline Pt surfaces were shown in Fig. 2. The voltammograms of single crystal electrodes exhibited characteristic hydrogen adsorption/desorption peaks between 0.05 and 0.4 V. These peaks were not sharp because of a exposure in air atmosphere during the setup of electrochemical measurements but similar to those reported in the literatures.3This demonstrates well-controlled surface structures of single crystal electrodes were obtained. Figure 3 shows the amount of Pt ions dissolved from single crystal surfaces under 100 cycles of CV in 0.5 M H2SO4solution. The horizontal axis means the upper potential limit of CV. The dissolved amount at Pt(100) and Pt(110) surfaces was almost the same, and increased with rising the upper potential limit. Pt(111) surface hardly dissolved at potentials below 1.2 V, and the amount of dissolution at this surface in the potential range of 0.5–1.4 V was about a half of that at Pt(100) and Pt(110) surfaces. This result indicates Pt(111) surface has the highest corrosion resistance among the three single crystal electrodes examined.1. Y. Shao-Horn, W. C. Sheng, S. Chen, P. J. Ferreira, E. F. Holby, and D. Morgan, Top Catal, 46, 285 (2007).2. Y. Sugawara, T. Okayasu, A. P. Yadav, A. Nishikata, and T. Tsuru, J. Electrochem. Soc., 159(11), F779 (2012).3. N. M. Marković, and P. N. Ross, Surf. Sci. Rep., 45, 117(2002).Caption list:Figure 1 STM images of Pt(100), Pt(110), and Pt(111) single crystal surfaces after the anealing treatment.Figure 2 CVs at Pt(100), Pt(110), Pt(111) single crystal, and polycrystalline Pt surfaces at 10 mVs-1 in 0.5 M H2SO4solution.Figure 3 Amount of Pt ions dissolved from single crystal surfaces as a function of the upper potential limit of CVs. The CVs were carried out for 100 cycles at 10 mVs-1 in 0.5 M H2SO4 solution.

O2-releasing reactivity of ceria-based reactive ceramics on irradiation of artificial concentrated solar beam for solar hydrogen production

In the present paper, different types of metal doped ceria CeO2–MOx (M = Sc, Y, Dy, Zr and Hf) with fluorite structure have been prepared with a complex polymerization method. The O2-releasing potential of prepared samples was evaluated at 1500 °C for a two-step water splitting process. The partially oxygen defected CeO2–MO1.5 (M = Sc3+, Y3+ or Dy3+) mixed oxide exhibited an enhancement of the O2 evolution on CeO2–ScO1.5 owing to the crystal-chemical effect that cation with smaller ionic radius (Sc3+) compensates the volume expansion of crystal lattice resulted in the reduction of Ce4+ with smaller ionic radius into Ce3+ with larger ionic radius. The CeO2–MO2 (M = Zr4+ and Hf4+) produced larger amount of O2 than that for CeO2–MO1.5 mixed oxides, since CeO2–MO2 has no oxygen vacancy initially. While the ionic radii of Zr4+ and Hf4+ are almost equal, the higher O2-releasing reactivity of Ce0.9Hf0.1O2 than that of Ce0.9Zr0.1O2 is explained in terms of ionicity of M–O bond. Also, the weight losses of CeO2, Ce0.9Zr0.1O2 and Ce0.9Hf0.1O2 in the mitigation process from high PO2 (O2 gas stream) to low PO2 (Ar gas stream) atmosphere were determined. The quasi activation energies in the initial period of the O2-release for CeO2, Ce0.9Zr0.1O2 and Ce0.9Hf0.1O2 were evaluated 105, 84.2 and 75.0 kJ/mol, respectively. The O2-releasing reactivity is considered from the standpoint of an activation energy.

Porous Materials with Hybrid Structure Produced by Nitriding Partially-Sintered Silicon

New porous materials with hybrid pore structure “Fibers-In-Pores” structure were produced by developing Si3N4 whiskers in pores of partially-sintered silicon by nitriding. Because silicon and Si3N4 have excellent heat resistance, the proposed porous materials are expected to utilize high-temperature applications such as gas filters. Porous silicon was produced by sintering Si powder at 1300°C for 1 h in a stream of Ar gas. Porous Si bodies were nitrided at 1300°C for 1 h with N2 gas to develop long Si3N4 whiskers in pores of partially-sintered silicon. Specific surface area was increased and gas permeability was decreased by applying the nitridation process at 1300°C.

SURFACE PROPERTIES AND CATALYTIC PERFORMANCE OF ACTIVATED CARBON FIBERS SUPPORTED TiO2 PHOTOCATALYST

Activated carbon fibers supported TiO 2 photocatalyst ( TiO 2/ACF) in felt-form was successfully prepared with a dip-coating process using organic silicon modified acrylate copolymer as a binder followed by calcination at 500°C in a stream of Ar gas. The photocatalyst was characterized by SEM, XRD, XPS, FTIR, and BET surface area. Most of carbon fibers were coated with uniformly distributed TiO 2 clusters of nearly 100 nm. The loaded TiO 2 layer was particulate for the organic binder in the compact film was carbonized. According to XPS and FTIR analysis, amorphous silica in carbon grains was synthesized after carbonizing organic silicon groups, and the Ti – O – Si bond was formed between the interface of loaded TiO 2 and silica. Additionally, the space between adjacent carbon fibers still remained unfilled after TiO 2 coating, into which both UV light and polluted solutions could penetrate to form a three-dimensional environment for photocatalytic reactions. While loaded TiO 2 amount increased to 456 mg TiO 2/1 g ACF, the TiO 2/ACF catalyst showed its highest photocatalytic activity, and this activity only dropped about 10% after 12 successive runs, exhibiting its high fixing stability of coated TiO 2.

Reaction Behavior during Heating Waste Plastic Materials and Iron Oxide Composites

Effective utilization of waste plastic materials is one of key technologies for environmental protection. In this work, we conducted fundamental researches on production techniques of reduced iron and H2 and CO gases from waste plastic materials (polyethylene and Refuse Derived Fuel) and iron oxide mixtures. The mixtures were heated up at the temperatures of 1000–1300°C in Ar gas stream. Concentrations of generated gases from samples were continuously measured by a quad-pole mass spectrometer.Conversion ratios into H2 from waste plastic materials reached 60–70% at 1300°C both in thermal decomposition of the waste plastic materials and reduction of the mixture samples. In the reduction of the mixture samples, conversion ratios into CO reached 70–80% at 1300°C. Final fractional reductions of samples containing RDF at 1200°C and 1300°C were 100%. When waste plastic materials are used as a reducing agent, plastics which contain large amount of fixed carbon are suitable to obtain a high fractional reduction.

Ba 3Fe 2WO 9−δ: Effect of oxygen non-stoichiometry on structural and magnetic properties

The magnetic and structural properties of oxygen-deficient perovskites with composition Ba 3Fe 2WO 9− δ (BFWO) have been systematically studied for two different oxygen contents corresponding to δ = 0.00 and 0.55 in the chemical formula in order to determine and correlate their chemical composition, structural and magnetic properties. The evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature the stoichiometric compound ( δ = 0.00 ) adopts a hexagonal 6H-perovskite structure (space group P 6 3 / mmc ). This phase, when heated at high temperature under a stream of Ar gas, transforms to an oxygen-deficient phase δ = 0.55 ), which is an ordered cubic perovskite structure (space group Fm – 3 m ). The crystallographic and magnetic properties of the obtained phases are compared, and it is clear that the magnetic properties are significantly affected by oxygen non-stoichiometry. These changes of magnetic properties for such a slight decrease in oxygen content are interpreted as a result of structural transformations. Together with the experimental results based on neutron powder diffraction data a discussion of some aspects of the structural transformation ( P 6 3 / mmc → Fm – 3 m ) is presented.

Preparation of activated carbon fibers supported TiO2 photocatalyst and evaluation of its photocatalytic reactivity

Activated carbon fibers (ACFs) supported TiO2 photocatalyst was successfully prepared by a molecular adsorption–deposition (MAD) method followed by calcination in a stream of Ar gas. The photocatalyst developed was characterized by SEM, XRD, XPS, BET surface area and UV–vis adsorption spectroscopy. SEM observation showed TiO2 was deposited on almost each carbon fiber with a coating thickness of about 100 nm, and the space between adjacent fibers was remained unfilled to allow UV light to penetrate into the felt-form photocatalyst to a certain depth. Anatase-form TiO2 was uniquely developed even as calcination temperatures rose up to 900 °C. Tight contact of thin TiO2 coating to carbon fibers surfaces was supposed to suppress phase transformation of TiO2 from anatase to rutile, and to keep high crystallinity of anatase. As confirmed by XRD and XPS examinations, the micrographic structure and surface properties of ACFs had not been damaged by the deposition process and calcination at high temperatures. The present photocatalyst showed high photocatalytic reactivity in photodegradation of highly concentrated methylene blue (MB) solutions. The comparative experiments indicated the photocatalyst produced had a combined effect of photocatalytic reactivity of anatase-type TiO2 with adsorptive property of activated carbon fibers. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed.

Feasibility of TFEL application of Ce-doped CaGa 2S 4 and SrGa 2S 4 films prepared by flash evaporation method

Ce-doped CaGa 2S 4 and SrGa 2S 4 thin films were prepared for the first time by the flash evaporation method. The films were characterized before and after annealing in H 2S(10%)+Ar gas stream by measuring photoluminescence and absorption spectra, X-ray diffraction and electron probe micro analyses. X-ray diffraction curves and absorption spectra before annealing show amorphous behaviour, whereas the annealing leads to a significant crystallization and improves the stoichiometry of the films. Based on the performance data obtained from dispersive type EL cells using CaGa 2S 4:Eu powder together with photoluminescence property comparison between CaGa 2S 4:Eu and CaGa 2S 4:Ce powders, the annealed films prepared by flash evaporation can be considered to become one of the candidates for TFEL flat panel devices.

Structure of metal doped TiO 2 particles produced by RF plasma

Titanium metal powder mixed with 2–5.5 wt.% iron powder was flowed on Ar gas stream and evaporated in the RF plasma with gas mixture of Ar and O 2. The spherical iron doped TiO 2 powder with colour of pinkish white was obtained. Transmission electron microscope (TEM) analysis of the doped particles showed the periodic planer arrangement of iron atoms at empty space of TiO 2 crystals. In the case of Al doped particles, the lattice image presenting the mosaic-like structure is predominantly seen at the (110) lattice image. The difference of the segregation of Fe and Al in rutile particles has been discussed as the intrinsic nature of Fe and Al atoms.

Grain boundary effects on the magneto-transport properties of Sr 2FeMoO 6 induced by variation of the ambient H 2–Ar mixture ratio during annealing

Using the sol–gel method, polycrystalline double perovskites Sr 2FeMoO 6 with nanometer-scale grain size have been synthesized in the ambience of a controlled stream of different gaseous H 2–Ar mixtures during annealing. X-ray diffraction (XRD) results indicated that with an increasing proportion of H 2, the component of the SrMoO 4 impurity present in the crystallites first decreased, but then increased again with further increase of the H 2 proportion. The XRD results were further supported by independent sample analysis using Raman spectroscopy. Systematic investigation of the transport properties of the samples indicated that the SrMoO 4 impurity at the grain boundary played a key role in determining the measured resistance and magnetoresistance of Sr 2FeMoO 6. This impurity effect was found to be correlated to the variation of the mixture ratio of the ambient H 2–Ar gas stream surrounding the sample during annealing.

Improving the Wear Resistance of a Magnesium Alloy by Laser Melt Injection

The objective of this study is to improve the sliding wear resistance of the AZ91 E magnesium alloy, by means of dispersion of hard particles on its surface. Two kinds of powder and injection methods were applied. SiC powder, fed by Ar gas stream, was injected directly into a melt pool formed by laser beam. And the hypereutectic aluminum-silicon alloy was also injected in order to crystallize the fine Mg 2 Si intermetallic compound. These modified surfaces were evaluated by sliding wear test. SiC powder is dispersed uniformly at the surface of the AZ91E alloy, in proportion to the powder feeding rate. In the case of hypereutectic aluminum-silicon alloy, fine dendritic Mg 2 Si compound is crystallized uniformly. The matrixes of the modified layers changes from Mg solid solution to Al solid solution according to the powder feeding rate. And hardness of the layers are also changed. The wear depth of the SiC injected layer is almost zero, while that of the pin is increased by the sliding wear test. The modified layer using Al-30Si powder with the high powder feeding rate shows shallow wear depth and wear depth in the pin is also low.

Rapid determination of Os isotopic composition by sparging OsO 4 into a magnetic-sector ICP-MS

We present a method for the rapid determination of Os isotopic compositions and platinum group element (PGE) concentrations using ICP-MS on the same sample split. The method makes use of transfer of volatile OsO 4 by an Ar gas stream into the torch of a magnetic sector ICP-MS for analysis. A variety of partial or complete sample dissolution methods can be used, namely (1) microwave oven digestion of samples in pressurized Teflon vessels under oxidizing acidic conditions, (2) NiS fire assay for complete sample dissolution and PGE preconcentration, (3) acid leaching techniques to extract labile PGE fractions, and (4) Carius tube digestion. Microwave oven sample digestion with HF–HNO 3–HCl in an all-Teflon system as well as Carius tube digestion also allows the determination of Os isotopic composition and Os and Re concentrations on the same sample split. Spike–sample equilibration can be monitored on-line during sparging into the ICP-MS. The elimination of a nebulizer for Os isotope ratio measurements minimizes memory problems that are often associated with the determination of Os isotope ratios in liquid samples by ICP-MS. The external reproducibility of 187 Os/ 188Os measurements of an in-house Os standard solution using a single-collector, magnetic sector ICP-MS (Finnigan ELEMENT) is 0.78% (1 S.D., n=13) for analyte amounts ranging from 81 pg to 1.22 ng total Os. The ion yield for 7-min data acquisitions is ∼5×10 −5. Compared to negative thermal ionization mass spectrometry (N-TIMS), sample throughput is about on an order of magnitude higher. If NiS fire assay is used for PGE preconcentration, complementary PGE can be determined in the liquid residue by ICP-MS using a microconcentric nebulizer after the extraction of OsO 4.

Formation of LaNi<SUB>5</SUB> by Reduction-Diffusion Process with CaH<SUB>2</SUB>

To clarify the mechanism of formation of La–Ni compounds by the reduction-diffusion (R-D) process, the reduction of La2O3 by CaH2 and the R-D reaction to form La–Ni compounds were carried out at 1200, 1300 and 1400 K. In the reduction experiment, pellets of mixed La2O3 and CaH2 powders were heated in a deoxygenated Ar gas stream and the reduction rate was estimated from the diffraction intensity measured by XRD. In the R-D experiment, La2O3 and CaH2 were mixed with Ni powder or Ni wires and pressed into pellets, and the reacted samples were then examined by XRD, SEM and EPMA.The reduction with CaH2 of 1.7 times the chemical equivalent for the reduction of La2O3 showed that the reduction rate was considerably higher, and that the reaction was completed in about 1 ks from the start of the reaction at 1300 or 1400 K. In the R-D reaction, LaNi5, La2Ni7 and CaNi5 were formed, and the amount of CaNi5 at 1300 K and 1400 K diminished as the reaction proceeded. It was also shown in the R-D reaction for pellets containing Ni wires that a double-layer of CaNi5 and LaNi5 was formed on the surface of each Ni wire, and that La diffused into the CaNi5 layer to form LaNi5. When the amount of CaH2 mixed in a pellet was three times the chemical equivalent for reduction, Ni wires in the pellet were dissolved in Ca melt and their original shapes were not retained. However, with the amount of CaH2 at the chemical equivalent required for reduction, the reaction rate was reduced and the reaction products were LaNi5 and La7Ni16, although no formation of CaNi5 was observed.