Tetsuya Ashino

Determination of trace amounts of selenium and tellurium in high-purity iron by electrothermal atomic absorption spectrometry after reductive coprecipitation with palladium using ascorbic acid

Abstract Trace amounts of selenium and tellurium in high-purity iron were quantitatively separated by a reductive coprecipitation technique with palladium, and determined by electrothermal atomic absorption spectrometry. When ascorbic acid was used as reductant, selenium and tellurium could be simultaneously separated from large quantities of iron. The precipitate was dissolved in HNO3 and HCl, then the sample solution was injected into a graphite furnace with ascorbic acid solution. The atomic absorbance of selenium was increased about 4 times, and the atomic absorbance of tellurium was increased about 3.5 times by the presence of palladium. The detection limits (3σ) of selenium and tellurium were 0.017 μg g−1 and 0.011μg g−1, respectively.

Determination of trace amounts of selenium and tellurium in nickel-based heat-resisting superalloys, steels and several metals by electrothermal atomic absorption spectrometry after reductive coprecipitation with palladium using ascorbic acid

Trace amounts of selenium and tellurium in nickel-based heat-resisting superalloys and constituent metals were separated by a reductive coprecipitation technique with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry. Selenium and tellurium each added in 1 μg amounts to solutions of metals (Ni, Al, Cr, Co, Cu, Mn, Mo, V, Ti, Nb, Ta, W and Zr), were recovered by the proposed method. In all metals, both selenium and tellurium were quantitatively recovered in H2SO4, H2SO4-tartaric acid, H2SO4-oxalic acid or H2SO4-H3PO4 solution. In Ni, Al, Nb, Ta, W and Zr, they were also quantitatively recovered in HF-H2SO4 solution. This proposed method could be adapted to determine trace amounts of selenium and tellurium in several alloys (heat-resisting superalloys, stainless steels and high speed steels).

Determination of elements in lithium potassium niobate and lithium niobate containing vanadium by ICP-AES

The elements in lithium potassium niobate and lithium niobate containing vanadium (such as aluminum, lithium, niobium, potassium and vanadium) were determined by inductively coupled plasma atomic emission spectrometry after fusion of the sample with ammonium hydrogensulfate. The samples were completely decomposed and high precision results were obtained for the metallic elements. Oxygen has been determined by a helium carrier fusion thermal conductivity method using both a nickel capsule and tin as a melting flux in a graphite crucible.

Determination of trace amounts of antimony, germanium and tin in high-purity iron by electrothermal atomic absorption spectrometry after reductive coprecipitation with palladium

Trace amounts of antimony, germanium and tin in high-purity iron were quantitatively separated by a reductive coprecipitation technique with palladium, and determined by electrothermal atomic absorption spectrometry. When sodium phosphinate (NaPH2O2) was used as a reductant, antimony and germanium could be separated simultaneously from large amounts of iron. Similarly, when sodium tetrahydroborate (NaBH4) was used, germanium and tin could also be separated simultaneously. The atomic absorbances of antimony, germanium and tin were increased by about 1.5, 3.7 and 4.5 times, respectively, in the presence of palladium. The limits of detection (corresponding to three times the standard deviation of the blank) of antimony, germanium and tin were 0.019, 0.010 and 0.031µg g–1, respectively.

Effect of carbon on the microstructure, mechanical properties and metal ion release of Ni-free Co-Cr-Mo alloys containing nitrogen.

This paper investigated the effect of carbon addition on the microstructure and tensile properties of Ni-free biomedical Co-29Cr-6Mo (mass%) alloys containing 0.2 mass% nitrogen. The release of metal ions by the alloys was preliminarily evaluated in an aqueous solution of 0.6% sodium chloride (NaCl) and 1% lactic acid, after which samples with different carbon contents were subjected to hot rolling. All specimens were found to primarily consist of a γ-phase matrix due to nitrogen doping, with only the volume fraction of M23C6 increasing with carbon concentration. Owing to the very fine size of these carbide particles (less than 1 μm), which results from fragmentation during hot rolling, the increased formation of M23C6 increased the 0.2% proof stress, but reduced the elongation-to-failure. Carbon addition also increased the amount of Co and Cr released during static immersion; Co and Cr concentrations at the surfaces, which increased with increasing the bulk carbon concentrations, possibly enhanced the metal ion release. However, only a very small change in the Mo concentration was noticed in the solution. Therefore, it is not necessarily considered a suitable means of improving the strength of biomedical Co-Cr-Mo alloys, even though it has only to date been used in this alloy system. The results of this study revealed the limitations of the carbon strengthening and can aid in the design of biomedical Co-Cr-Mo-based alloys that exhibit the high durability needed for their practical application.

Degradation Process of Graphite Furnace Estimated from Atomic Gas Temperature of Iron in Graphite Furnace Atomic Absorption Spectrometry

GF-AAS has been employed for determining several trace impurities in metallic materials. The analytical precision in the continuous analysis tends to worsen due to thermal degradation of the graphite furnace at the atomization stage. Changes of the atomization condition along with increasing the number of measurements were investigated by monitoring the temporal variation in the atomic gas temperature of iron. In a working solution containing low-concentration of acid, the inner wall of the graphite furnace was gradually damaged and then the efficiency for the atomizing process was reduced. In a working solution containing sub-mol/L order of sulfuric acid, thinning or cracking of the graphite furnace progressed more rapidly and the function of it was greatly deteriorated. [doi:10.2320/matertrans.M2010180]

Determination of trace amounts of sulfur in high-purity iron by infrared absorption after combustion: Selection and pre-treatment of reaction accelerators

Pre-treatment procedures for the analysis of trace sulfur amounts in high-purity iron are investigated. The sulfur content of metal samples has been determined with an infrared absorption method after combustion by high-frequency induction. An analytical sample with a tungsten-tin mixture as reaction accelerator in a ceramic crucible is subjected to combustion in an oxygen atmosphere. Sulfur in the sample is extracted with high efficiency as SO 2 by combustion. Accordingly, it is necessary to select the reaction accelerator with the highest performance. Since sulfur contamination in the ceramic crucible and the accelerator cause analytical blank values pre-treatment procedures to decrease and stabilize the blank values are needed. Tungsten and tin were cleaned in HCl. After heating the tungsten at 1003 K for more than 2 h, the mixture of 0.5 g of tungsten and 1.5 g of tin was heated at 1003 K for 28 min. This gave the highest SO 2 extraction, hence the sulfur blank was lowest. Trace amounts of μg/g level sulfur in high-purity iron were determined by the proposed method.

Trace Analysis of Released Metallic Ions in Static Immersion Test for Characterization of Metallic Biomaterials

For characterization of corrosion resistance of metallic biomaterials, determination of trace amounts of metallic ions released from the materials in static immersion into simulated body fluids were investigated. In a pre-treatment method by sulfuric acid, sensitive, precise and accurate determination of the trace metallic elements in simulated body fluids could be performed by an inductively coupled plasma-optical emission spectrometry. For accurate analysis, it was necessary to employ a matrix-matched solution for the calibration. Moreover, usage of a vessel made of tetrafluoro ethylene-perfluoro alkylvinyl ether copolymer in the static immersion test was recommended for the prevention of contamination. Thus, it was possible to determine μg dm-3 order of elements in simulated body fluids and evaluate nano-gram order of the released metallic ions.