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Nagae T.,University of Toyama | Hadano A.,Archaeological Institute of Kashihara
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2010

The microstructure of a copper bowl excavated from an Edo-period grave in Mukaiyama Ruins in Nara prefecture has been investigated. The sample was subjected to optical microscopy, scanning electron microscopy, electron probe microanalysis and X-ray diffraction analysis to obtain information about the microstructure of both the base metal and the corroded layers. The bowl was made of copper containing 0.9% lead. Annealing twins were observed in the α-Cu phase, which establishes that the bowl was forged and annealed. The corroded layers were composed mainly of cuprite, malachite and copper phosphate. It is thought that the copper phosphate acted as an inhibitor to corrosion. © 2010 The Japan Institute of Metals. Source

Okuyama M.,Archaeological Institute of Kashihara | Sato M.,Nara National Research Institute for Cultural Properties | Akada M.,Kyoto Institute of Technology
Sen'i Gakkaishi | Year: 2012

To preserve excavated archaeological textile fibers, a preliminary investigation of materials and the degraded state of samples is indispensable. The excavated samples are valuable because the remaining amounts are usually scarce and often heavily degraded. In the past, infrared microscopic analysis has been used to overcome the above-mentioned limitation and has sufficient sensitivity for the analysis. However, the identification of bast fibers, such as hemp and ramie, using FT-IR, is rather difficult because their infrared spectra resemble each other. In this report, we investigated a procedure using a polarized radiation beam for the FT-IR microscope at JASRI (SPring-8) Beamline BL43IR for the identification of bast fibers. A minute amount of sample fibers was pressed by diamond plates to make a flat thin layer. The polarized absorbance spectrum of the sample on the diamond plate was measured. The polarizer was rotated from 0° to 90°, measuring the spectrum at 15° intervals. Both of the bast fibers, hemp and ramie, showed a decrease in the absorption peaks at 1428,1371,1160,1110, and 1060cm -1 with increase in the rotation angle of polarizer. Since the absorption peak intensity at 2900cm -1 of both fibers remained constants, the decreases were expressed as the ratios to the 2900cm -1 values of hemp and ramie. The plotted curves showing the relation between peak intensity versus polarizer angle are distinctly different between hemp and ramie. The infrared dichroism could be due to the difference in molecular orientation of the fiber components (cellulose and hemicelluloses) of hemp and ramie. Source

Okuyama M.,Archaeological Institute of Kashihara | Sato M.,Nara National Research Institute for Cultural Properties | Akada M.,Kyoto Institute of Technology
Sen'i Gakkaishi | Year: 2012

The scientific identification of excavated bast fibers (mainly hemp and ramie) is one of the important procedures for the conservation of textile cultural properties. In this paper, the new procedure to distinguish the kind of excavated bast fibers was proposed. Though excavated bast fibers are usually degraded by the long-term preservative environment, it was confirmed that they show still dichroism in infrared spectroscopy. Since the allowed amount of sampling for scientific analysis is severely limited in archaeology or in cultural properties, the authors used polarized synchrotron FT-IR Micro-spectroscopy. All of the bast fibers showed peaks at 1160, 1110, 1060, 670, 620 and 560cm -1. The corresponding modern reference bast fibers also show similar dichroism in polarized FT-IR Micro-spectroscopy. Though SEM images of excavated bast fibers indicate the degraded appearance, the results of polarized FT-IR spectrum show that a part of the molecular orientation of cellulose and hemicelluloses are still remained in fiber structure. The authors are continuing the research for the identification of excavated bast fibers using polarized FT-IR Micro-spectroscopy. Source

Nagae T.,University of Toyama | Srinivasan S.,National Institute of Advanced Studies | Ranganathan S.,National Institute of Advanced Studies | Pillai R.M.,John Cox Memorial CSI Institute of Technology | And 2 more authors.
ISIJ International | Year: 2014

Additions of large amounts of tin to copper lead to high tin bronzes with interesting combination of properties. Such high tin bronzes need to be carefully processed to avoid brittleness in compositions corresponding to beta and delta phases. The latter has been used in China, India, Korea and Japan to produce distortion free mirror images. This investigation is concerned with the bronze mirror from India where the tradition has survived in the village Aranmula in Kerala. The alloy has an exceptionally high tin content consisting almost entirely of the delta phase, which is an intermetallic compound (Cu31Sn8) of composition 32.6% tin. This is an ideal alloy to be polished into a mirror due to the silvery white color and high hardness. Its high brittleness is offset by an ingenious casting and polishing process. In addition to studying the composition and the casting involving a mould cum crucible method, thermographic analysis has been employed to follow the solidification sequence by looking at the thermal profile. It is correlated with the actual composition, processing parameters and the resultant microstructure, due to the cooling rate the alloy solidifies with a mild departure from the equilibrium phase diagram. Some observations regarding the structure of the delta phase which is a Hume-Rothery phase will be provided about its optical and mechanical properties. Source

Okuyama M.,Archaeological Institute of Kashihara | Sato M.,Nara National Research Institute for Cultural Properties
Sen'i Gakkaishi | Year: 2015

It is already known that the infrared spectroscopy is one of the most useful method for the identification of cultural properties, especially for organic materials. However usual analytical procedure, such as Transmission (TR) or Attenuated Total Reflection measurement (ATR), requires preliminary treatment of sampling, and sometimes give damages to valuable samples by mixing or pressing. Contrary to this, Photoacaustic Spectroscopy (PAS) uses totally non-destructive procedures. To clarify the advantage of PAS compared with other procedures, some kinds of natural fibers (processed silk, hemp and ramie) were investigated in this study using PAS, TR or ATR. As a results, we confirmed that PA spectra of these samples were almost identical with that of other procedures (TR or ATR), and PAS could measure using very small amount of samples. We are further continuing the PAS study using various kind of organic cultural properties. Source

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