Editor’s Note: We are dedicating each Tuesday in July and August to Copper, number 29 on the periodic table.
Our previous post, Copper Compendium, Part 3: Primary Copper Production, discussed the extraction, smelting, and alloying of copper (Cu). Determining the purity of the copper and percentages of any alloying elements present is a very important quality control step all throughout the manufacturing process in order to ensure the integrity of the finished product.
When smelting Cu, it is vital to understand the complex morphology of the various compounds in the raw material. This detailed understanding of the complex morphology is necessary to improve the refining efficiency of each element. In order to get that understanding, we analyzed Cu-compound raw material by phase analysis using the multivariate statistical analysis of EDS spectral imaging data.
We evaluated Cu compounds which were generated in the initial process of copper lead smelting after the extraction of coarse lead. The distribution of the elements and the phase morphology were analyzed using a field emission scanning electron microscope (FESEM) and EDS. The analyzed area (a 230 × 180 µm rectangle) was observed by reflected light optical microscopy for metallic components. EDS data acquisition was done by Silicon Drift Detectors (SDD) and real time multivariate statistical phase analysis was performed during the data acquisition. The sample was polished and coated with carbon for the EDS analysis in the field emission scanning electron microscope (FESEM).
From the results, it became clear that the Cu compounds evaluated in this study have the following morphology of the elements and the distributions.
- The main phase is a Cu-Sn alloy phase.
- A Cu-Sn alloy phase exists as an associated phase with the Pb metal phase.
- A combination phase consisting of oxides of Cu-Sn-Pb and Cu-sulfide exist as a nucleus which is encased by Pb-sulfide.
- The glass component phase (C-9) and calcium fluoride phase (C-16) were easily distinguished. These components are very difficult to detect by EPMA if their presence was not expected.
- S in Pb was identified which is very difficult to evaluate by conventional EDS element mapping. The typical distributions of small amounts of As, Se, In, Sb included in Cu-Sn alloy were clearly identified.
The evaluation of these results plays a key part in identifying and improving the processing steps to improve the efficiency of refining Cu compounds. Although the data acquisition time was only 30 minutes, the analytical data is complete. These rapid results ensure an improved throughput to the refining process. Furthermore by evaluating materials produced in each refining process with this analysis method, the verification work of the material becomes very easy and simple.
By using multivariate statistical analysis software, the morphology, distribution and chemistry of each distinct compound generated in the initial process of copper lead smelting was easily determined. This led to adjustment of the refining process and a cost savings to the smelting process.
Read the application note Rapid Evaluation of Smelting Copper Compounds Using Automated Multivariate Statistical Phase Analysis of EDS Spectral Imaging Data for details on the acquisition conditions, experimental details, electron images, the cumulative spectrum, elemental distributions, spectral details of overlapping peaks, and component maps.