# An Insight into a Shang Dynasty Bronze Vessel by Nuclear Techniques
## 4 Results
### Particle-Induced X-ray Emission--PIXE Analysis  
We investigated the elemental composition of the surface corrosion products and attempted to obtain some qualitative indications about the alloy constituents by investigating a flake (2 mm \(\times\) 10 mm in size), which had fallen off from the leg position, with PIXE microscopy. Figure 9 shows elemental distribution maps 2 mm \(\times\) 2 mm in size from different areas of the flake. Assuming that the positions rich in copper correspond to the main bronze material, the calculated elemental content of bronze is Cu (13.6 \(\pm\) 1.5)%, Sn (71.9 \(\pm\) 0.7)%, Pb (11.6 \(\pm\) 0.1)%, As (1.6 \(\pm\) 0.2)%, Fe (0.7 \(\pm\) 0.1)%, and Ni (0.17 \(\pm\) 0.02)%.  
Figure 8: (**a**) An xy cross-section of the neutron tomography from the vase top; the scale on the left side indicates the correspondence between grey tone and neutron attenuation coefficients. (**b**) An xy orthogonal view of the 3D model showing the repair in blue. The vase is rendered with a semi-transparent surface. (**c**) The profile of the neutron attenuation coefficients plotted at the correspondence of the red marker reported in (**a**).  
Figure 7: (**a**) An xy cross-section of the neutron tomography from the legs of the object; the scale on the left side indicates the correspondence between grey tone and neutron attenuation coefficients experimentally imaged. (**b**) The profile is plotted at the correspondence of the marker reported in (**a**).  
As reported in the literature [12], binary (copper-tin bronze or leaded copper) and ternary (leaded bronze) alloys were commonly employed in early dynastic China ([PERSON] and [PERSON] dynasties). Chinese craftsmen were conscious of the relationship between alloy formulation and functionality; they deliberately modified the alloy with tin and lead to increase the fluidity of the melt for easier casting or to obtain the desired mechanical properties, such as hardness, colour, or toughness. However, in the investigated sample, the relative content of the alloying elements Cu, Sn, and Pb appears to be strongly affected by corrosion mechanisms such as decuprification phenomena causing enrichment in Sn. Although the exact composition of the bulk metal cannot be reliably quantified, the analysis cannot be disregarded, as it suggests the use of a ternary alloy.  
Some observations can be made about the patina. The bronze appears to be covered by a mixture of different minerals rich in iron, calcium, and potassium. The qualitative analysis of elemental distributions suggests that the iron-rich regions are intertwined with a mixture of calcium-potassium-rich regions. Areas rich in Ca, K, and Fe can be related to contaminants from the soil of the burial contest, i.e., calcite, iron oxides, potassium carbonate, or potassium oxide. Further details on the composition of the associated minerals could be potentially ascertained by complementing PIXE analysis with other non-invasive methods. For example, Mossbauer \({}^{119}\)Sn spectroscopy has been applied for the detection of corrosion products to determine the degree of oxidation on the surfaces of and in the interior of tin bronzes [32; 33]. Although additional analysis will be beneficial, constraints are imposed by the possibility to move the sample and the availability of analytical techniques that are in proximity to the museum collection.