- 著者
-
桐野 文良
北田 正弘
- 出版者
- 公益社団法人 日本金属学会
- 雑誌
- 日本金属学会誌 (ISSN:00214876)
- 巻号頁・発行日
- vol.79, no.2, pp.57-63, 2015
- 被引用文献数
-
3
The microstructures of a corrosion layer formed on the surface of two Japanese oldest coins, <i>Wadoukaichin</i> (surface color: dark brown and green) were studied. Compositions of these coins are that main element is Cu and Sn and traces are Pb, Fe and As. X-ray diffraction patterns show that copper di-hydroxide (Cu(OH)<sub>2</sub> 2H<sub>2</sub>O), Cu<sub>1.81</sub>S and Cu<sub>2</sub>O are detected on the surface corrosion layer of dark brown sample, and Cu<sub>2</sub>(CO<sub>3</sub>)(OH)<sub>2</sub> (malachite), Cu<sub>3</sub>(CO<sub>3</sub>)<sub>2</sub>(OH)<sub>2</sub> (azurite) and Cu<sub>2</sub>O are detected on the surface corrosion layer of green sample. Optical microscope images show that the surface corrosion layer of dark brown sample is porous, and blue and green grains on the brown layer are existed on that of green sample. From spectrographs of these grains, the peak wavelength of green grains is matched to that of malachite, but this of blue grains is shifted to long wavelength side of about 40 nm at azurite on an influence of trace contaminations. The corrosion layer has two layers, surface layer is plate-like texture, and under layer is aggregation microstructure from TEM observation. The crystal structure of these two layers is matched to azurite from the electron beam diffraction patterns.<br>