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A la lumiere de recentes decouvertes archeologiques en Chine, on a examine un pectoral de jade et d'or dans la collection de la Freer Gallery of Art datant de la dynastie Zhou orientale, afin de determiner si l'assemblage actuel est correct. Le pectoral consiste en dix jades attaches a une chaine en or, et on presume qu'il provient du site Zhou oriental de Jincun, pres de Luoyang, province de Henan, Chine. L'analyse par fluorescence X a revele que les memes incrustations de terre etaient presentes sur les jades et que les dix jades avaient la meme composition en terme d'elements majeurs et mineurs. Cependant, une etude au microscope electronique a balayage (MEB) des fils d'or attachant les jades a la chaine a montre que ceux-ci etaient de quatre types differents. Le pectoral Freer s'est revele etre un nouvel assemblage de jades originaux sur la chaine d'or, probablement effectue peu de temps apres les fouilles de la fin des annees 1920. Le pectoral Freer a ete compare a un collier en jade et en or qui proviendrait egalement du site de Jincun de la dynastie Zhou orientale. Les deux objets ont des chaines de styles differents, mais tous deux pourraient avoir ete fabriques en Chine ou dans la region des steppes de l'Ouest durant l'antiquite.

Many ancient Chinese bronze mirrors have survived with a patina that leaves the delicate surface decorations intact. The microstructure of these mirrors is two-phase: Cu-rich α and Sn-rich δ. Although the mirrors have been labeled ‘corrosion-resistant’, the smooth surface includes a corroded layer up to 100 µm thick. In this ‘altered’ layer, there is selective attack of the α phase; the α-phase regions are replaced by tin oxide with the δ phase remaining metallic. Here, electrochemical polarization has been used to drive the dealloying process in modern, cast bronze duplicating the microstructure on ancient bronzes. Timed experiments were performed to investigate the growth of the ‘altered’ region on the model samples. The altered layer forms quickly but the rate of growth slows over time. Theoretical calculations show that dissolution of copper from the α phase leaves a large volume for the tin oxide corrosion product permitting retention of the smooth surface.

Many ancient Chinese bronze mirrors have a smooth patina. An ingress of corrosion to a depth of approximately 100 μm is found beneath the patina. The corrosion selectively replaces the Cu-rich α phase leaving the Sn-rich σ phase intact. Previous work by x-ray diffraction has shown that the a-phase replacement product is poorly crystallized or nanocrystalline SnO2. Transmission electron microscopy was employed to further characterize the replacement product in both ancient mirror and replication samples. Nanocrystalline SnO, in the form of small spheroids has been found. Remnants of an original alloy phase appear to be interspersed with the tin oxide.

Many ancient Chinese bronze mirrors have survived with a patina that leaves the delicate relief surface decorations intact. The microstructure of these ancient mirrors is two-phase and consists of acicular α-phase (Cu-rich) regions encased in a δ-phase (Sn-rich) matrix. At the surface, there is evidence of selective dissolution of the α-phase; the α-phase regions are replaced pseudomorphically by a mineral product with the δ -phase remaining metallic. Electrochemical polarization has been used to drive the copper dealloying process in modern, cast bronze. Synchrotron x-ray diffraction was employed to compare the ancient samples with those that were prepared potentiostatically. Poorly crystallized tin oxide (SnO2) was found in the α - replacement products of both sample types. The corrosion-resistance of the potentiostatically-treated bronze samples was tested by atmospheric exposure. Comparison with exposed, untreated samples indicated that the treatment was protective.

Many ancient Chinese bronze mirrors have survived with their original surface decorationsintact, particularly those with “glassy” black surface coatings. The microstructures and compositions of cross-sectional samples from ancient mirrors have been analyzed with optical and electron microscopy and synchrotron x-ray fluorescence. The core has a two-phase metal structure while the surface shows evidence of selective dissolution of copper from the α (Curich) phase. The ci phase regions are replaced pseudomorphically by a mineral product with the δ (Sn-rich) phase remaining metallic. A fundamental study of the electrochemistry of the copper-tin system has given information on theconditions under which selective dissolution of copper takes place. Electrochemical polarization has been used to drive the copper dealloying process in cast high-tin bronze. Theresulting microstructure is similar to the dealloyed microstructure observed in the ancient samples.