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Master theses

3D chemical imaging inside materials (Id 230)

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Foto: 3D visualization of a sulfide vein with disseminated gold ©Copyright: HZDR/ Jose Godinho2-dimensional imaging of surfaces is the preferred method to analyse the microstructure of rocks for industrial and academic research. The main advantages of 2D imaging are the high resolution and the possibility to analyse the chemical and mineral composition of surfaces. 3D imaging of mineral phases inside a material is also possible using tomographic techniques although the resolution is often lower than surface techniques and no elemental information can be derived. A new energy detector capable of identifying the elements inside rocks is being tested. The student will use the new detector to identify chemical elements and mineral phases inside samples in order to develop new analytical techniques to answer questions important to research and to industry.

Different cases studies are possible:

Project 1: Gold and galena are very dense minerals with similar spatial distribution in porphyritic deposits, which makes them indistinguishable using normal CT. The goal is to optimize the scanning conditions, using the new detector, to identify the valuable gold particles. These particles will be characterized using 3D imaging to estimate the potential value of the deposit and to help defining the mining and mineral processing strategy. Important 3D characteristics include mineral association (pirite/ chalcopyrite/ quartz), particle size distribution. 3D results will be compared to 2D mineral liberation analysis. Due to the small size of gold particles calibration using larger particles may be required.

Project 2: Tin and gold are important technological components of electronic devices (e.g. up to 3 g of Sn in each iphone). To meet their increasing demand mining lower grade deposits and recycling obsolete electronics are necessary. Common to mining and recycling are the steps of grading the elemental content of either rocks or scrap so that the material can be sorted and processed efficiently. A radiographic technique using the new detector will be tested to grade the content of tin and gold. The project aims to determine the suitability of the technique for larger scale application by optimizing the experimental conditions and assessing the spatial resolution, particle size limits, sample environment effect (rock vs scrap), and other factors. Ultimately, the concentration of other minor elements (Bi, Ag, Pb, In) may be detectable, which could be good or could interfere with the measurement of Au and Sn.

Project 3: Rare earth elements, fundamental to HiTec applications, are usually mined as a mixture of lanthanides present in a mixture of primary and secondary minerals, such as xenotime (YPO4), monazite (CePO4) as well as parasite (Ca(Ce,La)2(CO3)3F2) or bastnaesite (Ce(CO3)F). The presence of some lanthanides and their relative abundance, especially the economic extremely important ratio of HREE (Y + Gd - Lu) to LREE (La - Gd) can vary significantly even within the same deposit depending on the ore formation mechanism. This work aims to define the principal analytical parameters necessary to estimate the LREE/HREE value in a sample with other minerals with similar densities present.

Most experimental work is similar to all projects
- Preparation of calibration samples with known properties to evaluate the resolution of the technique.
- Optimization of scanning conditions to maximize resolution and contrast between phases.
- Characterize the 3D mineralogical properties of a material using 3D image processing techniques.
- Correlate 3D chemical imaging to 2D SEM imaging, XRD and XRF to compare and validate the new technique.

Expected learning outcomes
– Hands on experience with CT and 3D image processing techniques
– Knowledge of laboratory procedures and analytical techniques used in raw materials research and industry
– Experience developing analytical methods
– Work in an international collaboration project

Institute: Helmholtz Institute Freiberg for Resource Technology

Contact: Dr. da Assuncao Godinho, Jose Ricardo, Dr. Renno, Axel

Requirements

This project is part of a collaboration between UoG, HIF and industry so that collaboration with a partner's research activities is desirable.
Requirements:
- Good spoken and written English
- Enthusiasm for experimental and analytical laboratory work
- Creativity and desire to do new things
- Studying a subject related to Earth or materials sciences

Conditions

- Start anytime
- Indicate the prefered topic in your application

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