Distribution and Nanostructure of Orange Dyestuff Compound Pb2CrO5 in Cotton Fiber Used for Touzan Fabric Made in the Late Edo Period

The distribution and nanostructure of the orange dyestuff compound. Pb2CrO5, in cotton fiber used for touzan fabric made in the late Edo period have been investigated. Dyed fiber specimens are taken from old touzan fabric. To observe the distribution of nanometer-sized compound grains in the fiber, the cross section of the fiber is flattened by ion milling after mechanical polishing. The macrostructure is observed by X-ray CT. The nanostructure is observed by SEM and TEM. The composition and crystal structure are analyzed by EDS, XRD and ED. The dye compound, Pb2CrO5, is mainly detected by EDS and XRD. Fine acicular precipitates of Pb2CrO5 are aligned along the fiber, forming concentric circles. The Pb2CrO5 needlelike crystals have lengths and widths of 100 similar to 300 nm and 20 similar to 50 nm, respectively. However, the needlelike precipitate consists of an aggregation of many nanometer-size Pb2CrO5 crystals. Preferential precipitation is observed at cracks in the fiber, and precipitation-free zones near the fiber surface, in the area of the fiber lumen and in the area near the crack are also observed. It is thought that the Pb2CrO5 nano-crystals nucleate and grow in the amorphous area in the fiber. A possible nucleation and growth model of the Pb2CrO5 crystal is proposed.