The sample displayed in the materials library is lead whose exact processing technique is unknown, the only thing can be determined is that it contains high levels of lead, but it may contain little oxidation or even impurities. In general, the composition and microstructure are two kinds of important characteristics for material, on this page, SEM and XRD are used to get the characterization of this sample.

SEM is one of the most universally used characterization methods to observe the material. This technology SEM can observe and analyze the microstructure of the material and analyze the composition of the micro-zone. It will analyze the secondary electrons and back-scattered electrons produced in the interaction between the sample and the fine-focused electron beam to observe and analyze the sample surface or the fracture morphology. From the SEM picture, it is clear for us to observe the microstructure and defect conditions which assist us to analyze the properties and performance of the sample or make a judgement of the sample.

• Minimum imaging range 1~100nm. (different machines have different minimum detection length)
• The gap between imaging and reality in nanoscale smaller than ±5%.

The SEM image of the pure lead block is hard to find. Here are two kinds of the lead coating prepared by an electroplating method. Its surface has similar microstructure and properties to which on the surface of the lead block, to some extent, the materials of our group can be analogized according to the analysis of this surface image.

As can be seen from figure 1, at low current density, deposited particles on its surface have large size than that at higher current density, relatively clear boundaries of blocks can be found, and extent and range of the protrusion are larger than the other one, at the same time, from the right images, the surface of the block is also smoother than the other at the scale of 5 μm; at high current density, it is difficult to see the fixed shape of the surface, the sedimentary particles are smaller and powder-like, and the shape of its surface is more irregular and fragmentary at the scale of 5 μm.

Compared with the two cases, at high current density (2A/dm²), the surface protrusion is low with the relatively flat surface, so its surface is smoother on the macro level which is more consistent with the surface properties of our sample. For the sample with low current density (1A/dm²), although its structure is more regular, there are still some lumps with side length more than 20 μm, which will affect the smoothness of the sample surface to some extent.

The principle of X-ray diffraction detection is to record the scattering interference when X-ray photons collide with atoms which have periodic structure. Bragg diffraction principle can be used to measure the diffraction intensity of an X-ray at a certain angle to the incident beam. Then the diffraction pattern produced by the X-ray on the crystal is obtained. From the diffraction pattern, the crystal surface index of lead in the sample and the diffraction intensity of different crystal surface at different X-ray grazing angles can be obtained. And the crystallinity and diffraction spacing of different substances in the sample can be calculated. The composition of the sample can be obtained by scaring lattice constants of different crystalline forms in a sample.

• Measurement error less than 1%
• Reading accuracy is better than 0.006%

The table 1 and figure 3 are from a paper on lead, lead alloys, and bronze alloys. The data used were derived from the XRD test of pure lead. In this paper, several kinds of high purity lead were characterized, and these test objects were very close to our samples, or even higher purity.

In table 1, subtle differences in the lattice constants may reveal information about the purity of the sample, but they do not directly reveal information about the purity of the material. In the XRD test results, the peak strength, quantity and location of different substances are different, which can be used as the direct basis to distinguish the species of substances.

The diffraction angle fo Pb (200) and Pb (220) is 18.1° and 26.2° respectively. Combing with the X-ray wavelength,  the lattice constant can be calculated, which is the data in Table 1.

However, the quantitative analysis and processing of samples require specialized software similar to Jade, such as the calculation of dot matrix parameters of polycrystalline materials, which will not be described here.

[1] Y Rui, Analytical methods for polymer characterization, CRC press. 2018.

[2] Tang Shenzhi. Research on lead and lead-tin alloy electroplating on titanium matrix of bipolar lead-acid battery. Diss. Harbin Institute of Technology, 2014.

[3] S. Shilstein, A. Berner, Y. Feldman, S. Shalev & Yu. Rosenberg, Distinguishability between ancient and modern leaded tin bronzes by the composition of their lead inclusions[J], STAR: Science & Technology of Archaeological Research, 07 Aug 2019.