World-leading soft x-ray mineral characterisation developments are providing information for more profitable processing decision making. DAVID SIMPSON reports
Article from resourceful: Issue 12
The demand for high quality commodities is placing pressure on companies to optimise their processes to compete globally.
Iluka Resources, for example, mine heavy mineral sands, processing them in Western Australia to produce zircon, rutile and ilmenite.
Synthetic rutile, or titanium dioxide (TiO2), is used in the manufacture of pigments, ceramics, sunscreens and the production of the metal titanium.
Zircon crystals or "zircons" are used in various forms in applications including ceramics, precision casting, refractories, catalysts, fuel cells, fibre optics, nuclear power generation, water treatment and medical prosthetics.
The commercial value of both synthetic rutile and zircons is directly related to their purity, which in turn, is determined by the processing parameters. The parameters can be optimised by having a detailed understanding of the nature of the feedstock and its transformative states during the process. It's a continuous process that can typically take several days.
Micro-characterisation maximising rutile and zircon production
CSIRO – through its microbeam laboratory – is working with Iluka to apply micro-characterisation methods to better understand this feedstock. They use an electron microprobe-based technique that uses x-rays to characterise both ilmenite and the processing materials during the various steps through the production of synthetic rutile and zircons.
"By combining the chemical information that CSIRO's x-ray analysis provides us, together with structural information from x-ray diffraction, we can set the parameters of the process to ensure we optimise the quality and hence the value of the minerals we produce," Nick Bernard, Iluka Resource's technical development manager, says.
Iluka has worked with CSIRO for more than 40 years on mineral characterisation and development, as well as processes for upgrading titanium minerals. As a major producer of synthetic rutile, this relationship has been pivotal to Iluka's ability to commercialise new resource discoveries.
Information to upgrade titanium production
CSIRO's characterisation work has contributed to Iluka's development of new upgrading technologies and the production of feedstock for their Metalysis titanium metal process.
The micro-characterisation performed by the CSIRO research team uses a custom electron microprobe. This technology was acquired by a consortium comprising CSIRO, Monash University, RMIT University, Swinburne University and The University of Melbourne, together with a Linkage Infrastructure, Equipment and Facilities (LIEF) grant from the Australian Research Council.
"Collaborating with CSIRO to develop this world-leading capability is simultaneously improving our working relationship with the organisation, our ability to conduct research that nobody else can and build upon the strength of having the Australian Synchrotron, the various Monash University and analytical platforms and CSIRO all in one precinct at Clayton, Melbourne," Dr Andy Tomkins, Monash University, says.
CSIRO research group leader, Colin MacRae, says that in the past soft x-ray analysis has generally been the province of synchrotrons, which cannot match the spatial resolution of the probe and require long lead times.
"What we've done, and I believe we are world leaders in doing so, is modified the hardware and software of an electron microscope and associated equipment to enable it to perform a wider range of functions."
By incorporating detectors sensitive to soft x-rays, Mr MacRae's team is able to improve the spatial resolution of their data analyses or maps, enabling features smaller than 100 nanometres to be analysed.
"The soft x-rays carry with them both chemical and structural information and we are developing new analysis strategies to utilise this new information," Mr MacRae says.
"Our characterisation technique takes a small sample – only milligrams to grams of material – we then mount it and polish it to an optical flat. The surface is then examined using the electron microprobe."
The microprobe is a medium to high vacuum instrument that produces a highly focused beam of electrons.
When these electrons impact the specimen they can produce x-rays, light and electrons. All are collected in parallel with the light and x-rays, primarily being used to characterise the sample both through mapping and point analysis.
Mr MacRae's team are continuing to develop the technology to enable high resolution micro-characterisation and mapping in the electron microprobe to provide better solutions to production and analytical problems in the mineral industry.
Mr MacRae also predicted an increasing wide range of applications for the consortium’s world-leading technology.
"We're already looking at using it to investigate gold deportment in sulphide deposits and we anticipate many more mineral applications as we continue to develop and refine the capability and identify our markets.
"Soft x-ray analysis is applicable to materials as well as minerals, and there’s exciting potential in intermetallics and materials like aluminium lithium aerospace alloys," Mr MacRae says.