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This paper describes uncertainty ranges of the analytical values by laser-induced breakdown spectrometry (LIBS), in order to realize an element-based sorting of commercial Al alloys whose chemical compositions are varied depending on the kind. For this purpose, calibration factors and their standard errors between the emission intensity and the content of major alloyed elements were estimated using a series of standard reference materials of Al alloys. From the result of LIBS analysis, Al alloy samples, labeled as A1050, A1100, A2017, A2024, A5052, A5083, and A6061, were actually classified into the kinds of Al alloy for which the chemical compositions have been standardized by the Japanese Industrial Standards. The sorting was successfully conducted, although several of them could not be classified into a particular alloy type. This was not due to the analytical precision of LIBS but due to a similarity of the chemical composition between several types of the Al alloy. For comparison, a similar sorting procedure was carried out using the analytical result by ICP-OES, which gave the same conclusion as the LIBS. In fact, ICP-OES requires sample pretreatment and dissolution and thus cannot be applied to on-site/in-line analysis, whereas LIBS can provide a rapid response of analytical values. Accordingly, the LIBS analysis may be actually applied for sorting Al alloy materials in detail.

Introduction To develop highly active and durable cathode electro-catalysts for polymer electrolyte fuel cell (PEFCs), core-shell type nanoparticles (NPs) have been actively studied. It is well known that oxygen reduction reaction (ORR) properties of the core-shell NPs greatly depend on the core-materials (transition metal elements (M) and/or Pt-M alloys). Particularly, deactivation of ORR under the PEFC operating conditions (low pH, electrochemical potential fluctuations) through elution of M is serious issue. Therefore, developments of highly-stable core materials under the operating conditions have been needed for practical applications of the core-shell type NPs. Ham et al. reported that early transition metal carbides, such as TaCx and HfCx, show high thermal stability and high corrosion resistance under the PEFC operating condition [1]. In this study, we prepared Pt/TaCx NPs by using arc-plasma deposition (APD) of TaCx followed by electron-beam deposition of Pt in ultra-high vacuum (UHV; ~10-8Pa) and investigated the ORR properties (initial activity and electrochemical stability) of the Pt/TaCx NPs. Experimental Highly-oriented pyrolytic graphite (HOPG) was used as a substrate. First, HOPG was scraped by Scotch tape in air and cleaned by annealing for 30 min in UHV. TaCx NPs are synthesized by using APD (Advanced RICO; APS-1) of Ta at substrate temperatures of 1173K or 1273K under CH4 partial pressure of 0.05 Pa. Subsequently, Pt was deposited on the TaCx NPs/HOPG at 873K by electron-beam deposition in UHV. As a reference, Pt/Ta NPs was fabricated through APD of Ta followed by the electron-beam deposition of Pt at 873K in UHV. The prepared Pt/TaCx and Pt/Ta NPs samples were transferred from UHV to electrochemical (EC) setup without air exposure to avoid sample oxidation and contamination. Cyclic voltammetry (CV) was performed in N2-purged 0.1 M HClO4. After that, linear sweep voltammetry (LSV) for ORR was conducted by using rotating disc electrode (RDE) method in O2-saturated 0.1 M HClO4. ORR activity was evaluated as j k values at 0.9 V vs. RHE: the j k value was estimated from Koutecky-Levich plots and electrochemical surface area (ECSA) of Pt. The electrochemical stabilities of the samples were discussed based on change in the j k values during applying square-wave potential cycles (PCs) between 0.6 (3 s) and 1.0 V (3 s) in O2-saturated 0.1 M HClO4 at a room temperature. Crystal structures, surface morphologies, and micro-structures of the prepared NPs samples were observed by XRD, scanning tunneling microscopy (STM), and scanning transmission electron microscope (STEM) combined with energy dispersive X-ray spectrometry (EDS), respectively. Results and Discussion STM images of the Pt/Ta and Pt/TaCx (1173K & 1273K) NPs were shown in Fig. 1(a). The NPs with average diameter of ca. 6 nm are synthesized on the HOPG substrate, irrespective of the Ta deposition conditions (with or without CH4 partial pressure during APD). Fig. 1(b) shows CVs for the corresponding NPs. Hydrogen (QH; 0.05 ~ 0.35 V) and OH-related (QOH; 0.6 ~ 1.0 V) charges for both the Pt/TaCx NPs are higher than that for the Pt/Ta NPs. The evaluated specific ORR activities (j k / ECSA) of the samples are summarized in Fig. 1(c). Filled and hatched bars are the activity before and after 10k PCs of each samples, respectively. One might notice that both Pt/TaCx NPs exhibited much higher activity than the Pt/Ta NPs even after the 10k PCs. Especially, the Pt/TaCx - 1173K shows highest ORR activity and durability among the samples: the retention rate after 10k PCs was ca. 85% of the initial activity. The results clearly reveal that, as for the core materials, tantalum carbide is effective for enhancing ORR activity as well as durability of the core-shell type Pt-based NPs. Acknowledgement This study was supported by the new energy and industrial technology development organization (NEDO) of Japan. References [1] D.J.Ham et al., Energies, 2(2009),873. Fig. 1 (a)STM images (100 nm × 100 nm), (b)CVs of the Pt/TaCx model catalysts prepared under CH 4 partial pressure of 0.05 Pa at substrate temperature of 1173K(orange) and 1273K(green). The Pt/Ta model catalyst (black) prepared in UHV at the substrate temperature of 873K is shown as a reference. (c) Specific ORR activity of the samples Figure 1

Single-nanometer-scale Pt Si fine particles (Pt Si NPs) were synthesized via the arc-plasma deposition of Si on a highly oriented pyrolytic graphite at a fixed substrate temperature of 600 °C, followed by electron-beam deposition of Pt at the temperatures between 100 and 600 °C in ultra-high vacuum. X-ray diffraction patterns of the vacuum-synthesized Pt Si NPs showed that a solid solution of Pt Si was the major component of the particles. Minor diffraction peaks, due to the intermetallic compounds (Pt3Si1 and Pt12Si5), at the Pt-deposition temperature (Tsub-Pt) of 500 °C, were also observed. Scanning tunneling microscopic images exhibited that Pt Si NPs with an average diameter less than 10 nm were dispersed in the substrate at Tsub-Pt temperatures up to 500 °C. The Pt Si NPs synthesized at a Tsub-Pt of 300 and 450 °C showed 1.7 times higher initial mass activity for oxygen reduction reaction (ORR) compared to commercial carbon-supported Pt NPs catalysts and showed better electrochemical stability than pure Pt NPs. These results demonstrate that the arc-plasma deposition of Si NPs, followed by e-beam deposition of metal elements (Pt) in ultra-high vacuum is a new class dry-synthesis for the single-nanometer-scale fine particles of Pt Si for electrocatalysis, e.g. ORR.

This paper describes an analytical method to evaluate the kind and the number of inclusion particles on the surface of a recycled Al ingot using laser-induced breakdown spectrometry (LIBS) with scanning laser beam. The surface was observed with scanning electron microscope - energy dispersive X-ray spectrometry (SEM-EDX) as well as scanning LIBS in the same viewing positions, in which inclusion particles of Si and Fe compounds were found. By measuring the emission intensity of the Fe I 358.119-nm and Si I 288.160-nm lines, the lateral distribution of Si and Fe inclusion particles was estimated from 2D intensity maps of these emission lines. The lateral resolution of the scanning LIBS was about 100 μm, which was restricted by the size of an ablated crater and the surrounding area; therefore, it is difficult to evaluate the actual number of fine inclusion particles (one or more particles may be counted to be a single particle). Nevertheless, the scanning LIBS has an advantage that the analysis can be conducted easily and rapidly compared to conventional analytical methods for inclusions. In our LIBS apparatus, the analysis for a sample surface of 4.0 × 5.0 mm2 was finished in about 40 min. and the time would be reduced if the spectrum analysis is automated on a computer. Accordingly, it is expected that the scanning LIBS can be utilized to consult on the quality of recycled Al materials in the recycling sites.