Yoshinori Uwamino

X-ray photoelectron spectroscopy of rare-earth compounds

Abstract A variety of rare-earth (RE) compounds (oxides, sulfates and oxalates) have been studied by X-ray photoelectron spectroscopy. Except for Eu, the binding energies (BEs) of the RE 3 d and 4 d peaks for the sulfates and oxalates are respectively almost equal to and 1.3–3.1 eV higher than those for the oxides. In the Eu 3 d spectrum of europium(II) oxalate, distinct shake-down satellite peaks are present, and the BEs of these peaks are 10 eV lower than the parent ones. For the oxides, appreciable differences are found in the BEs of the O 1 s peaks, and a specific “inclined W” form is observed in plots of BE versus 1/ R (where R is the mean distance from the oxygen atom to the neighboring RE atom) and versus the RE oxidation-reduction potential (ORP). No characteristic differences are seen in the BEs (C 1 s , S 2 s and S 2 p ) of the other ligands.

Charge correction by gold deposition onto non-conducting samples in X-ray photoelectron spectroscopy

Abstract Gold deposited onto sample materials has been used as a calibrant for determining their absolute binding energies, and the optimum thickness of the gold decoration investigated. Polytetrafluoroethylene film and NaF and graphite pellets were used as the substrate materials. A series of depositions of gold layers up to ∼60 A thick was performed on each sample surface. The thickness of gold deposited influences the apparent binding energies, the precision of the charge-corrected binding energies, and the FWHMs of the Au 4f, C 1s and F 1s peaks. It seems that, for the instrument used in this study (which records photoelectrons at 45° to the sample surface), the optimum thickness of gold deposited onto a non-conducting sample surface is ∼ 6 A (ie., ∼9 A path-length through the layer).

Determination of trace inpurities high-purity aluminum oxide by inductively-coupled plasma atomic emission-spectrometry

Abstract Trace impurities (Ca, Cu, Fe, Mg, Mn, Na and Si) in 99.99% aluminum oxide were determined by inductively-coupled plasma atomic emission spectrometry (i.c.p./a.e.s.). The sample was fused with lithium carbonate/boric acid to determine Ca, Cu, Mg, Mn, Na and Si or dissolved in phosphoric/sulphuric acids to determine iron. Matrix effects on the calibration graphs for each element were studied: for accurate determinations, calibration solutions must contain lithium and boric acid (or aluminium and phosphoric and sulphuric acids for iron).

Quantitative Analysis of Powdery Sample by Diffuse Reflectance Infrared Fourier Transform Spectrometry: Determination of the α-Component in Silicon Nitride

An application of diffuse reflectance infrared Fourier transform (DRIFT) spectrometry to determine powdery sample with an unknown particle size has been proposed. The usefulness of this technique has been demonstrated for the analysis of the α-component in Si3N4 powders. The particle size of the α-component in Si3N4 powder could be determined by measuring the peak intensity ratio between two peaks (500 and 690 cm−1) on the DRIFT spectrum, and the concentration could be determined by comparing the peak intensity to that of standard α-Si3N4 with same particle size. The particle sizes and concentrations obtained by the DRIFT method were in good agreement with those obtained by the light-scattering method and x-ray diffractometry, respectively.

Determination of Silicon Dioxide in Silicon Carbide by Diffuse Reflectance Infrared Fourier Transform Spectrometry

Diffuse reflectance infrared Fourier transform spectrometry was applied to the determination of SiO2 in SiC powders. The main peaks of SiO2 were observed in the 1000–1250 cm−1 region. The peak intensities were estimated from the peak height at 1150 cm−1. The intensities were little affected by the particle sizes of SiC powders in the 1–9–μm region. The linear relationship between peak intensity and concentration was obtained in the concentration range of 0–5 wt% SiO2. The analytical curve was successfully used for the determination of SiO2 in a few commercial SiC powders.

Simultaneous separation of common mono- and divalent cations on a zirconium-modified silica gel column by ion chromatography with non-suppressed conductimetric detection and tartaric acid–15-crown-5 as eluent

The application of laboratory-made zirconium-modified silica gels (Zr-silicas) as cation-exchange stationary phases to ion chromatography with conductimetric detection (IC-CD) for common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) was carried out. Zr-silicas were prepared by the reaction of the silanol group on the surface of silica gel with zirconium tetrabutoxide (Zr(OCH2CH2CH2CH3)4) in ethanol. Zr-silica adsorbed on 10 mg zirconium g(-1) silica gel was a suitable cation-exchange stationary phase in IC-CD for the separation of these mono- and divalent cations. Excellent simultaneous separation and highly sensitive detection for these cations were achieved in 10 min by IC-CD using a Zr-silica column (150x4.6 mm I.D.) and 10 mM tartaric acid containing 10 mM 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) as the eluent. The proposed IC-CD method was successfully applied to the determination of major mono- and divalent cations in natural water samples.

Synthesis of titania photocatalysts dispersed with nickel nanosized particles

Titania super fine particle photocatalysts containing dispersed nickel nanosized particles were synthesized. The synthesis method was as follows. First, an W/O type emulsion was made with non-ion surfactant. Titania powder with dispersed nickel oxide or nickel hydroxide was synthesized using a solution of nitric acid, nickel and titanium tetra butoxide (TIB). The titania photocatalyst was formed by reduction caused by heat treatment under a suitable reduction condition. Nickel nano-sized particles were distributed in the titania photocatalysts and the amount of hydrogen generated increased in proportion to the surface area of the distributed nickel. The nickel particles dispersed in titania photocatalysts accelerated the generation of rutile as compared to the photocatalyst without nickel.

Laser ablation in a liquid medium as a technique for solid sampling

A new technique for solid sampling, laser ablation in a liquid medium, has been developed and evaluated. A solid sample was held in a liquid medium contained in a flat-bottomed beaker. Laser pulses from a Q-switched Nd:YAG laser were introduced from the bottom of the beaker and were focused on the surface of the solid sample. Both the vapour and the particles produced by the laser ablation were trapped directly by the surrounding liquid, and a suspension was formed. The technique offers both time and spatial separation of the sampling and introduction and excitation processes in the laser ablation. The morphological observation of trapped particles, the evaluation of trapping efficiency and fractional ablation, and the direct introduction of the suspension into an inductively coupled argon plasma were carried out. Nearly 100% trapping efficiency and the absence of fractional ablation were obtained.

Determination of Silicon Dioxide in Silicon Carbide by Photoacoustic Infrared Fourier Transform Spectrometry

Advanced ceramics are being investigated quite actively. The characterization of the materials used to make the ceramics is important to final product performance. We have previously reported an application of diffuse reflectance infrared Fourier transform (DRIFT) spectrometry to the determination of silicon dioxide (SiO2) in silicon carbide (SiC). The DRIFT technique was found to have a simpler application than that of transmission techniques, for the analysis of powdered solids, because DRIFT does not require the sample preparation of KBr disks or mineral oil mulls. However, the scattering caused by the analyte powder surface requires dilution of the SiC powder with KBr fine powder, to avoid distortion of the diffuse refractance spectrum. For quantitative work, this dilution requires accurate weighing and perfect mixing.

Determination of impurities in titanium carbide and titanium nitride by inductively coupled plasma atomic emission spectrometry

Inductively coupled plasma atomic emission spectrometry was applied to the determination of impurities (Al, Ca, Co, Cr, Fe, Mg, Mn, Mo, Na, Nb, Ni, Si, V, W and Zr) in titanium carbide (TiC) and titanium nitride (TiN). A 0.5-g amount of the powder sample was decomposed with 7.5 ml of nitric acid and 2.5 ml of hydrofluoric acid in a PTFE jar. The matrix effects on the background levels and the emission intensities of the elements were compensated for by using matrix-matched standard solutions for calibration. The results showed that the proposed method was useful for the analysis of TiC and TiN samples.