2026-09-22T07:03:38Zhttps://digital.library.adelaide.edu.au/server/oai/request

oai:digital.library.adelaide.edu.au:2440/1383002026-06-14T23:47:55Zcom_2440_14759col_2440_14760

Spooner, Nigel A. Ottaway, David Tsiminis, Georgios Payten, Thomas Bede School of Physical Science 2022 https://hdl.handle.net/2440/138300 Production of critical raw materials such as rare earths and lithium will not meet the projected requirements for either growing world demand or to enable the green energy transition by 2050. Increasing the supply of these materials will require novel technology developments to improve efficiency and unlock resources. One area of improvement is the creation of sensors that convey meaningful information in a meaningful timeframe. Many existing sensor technologies in the mining industry provide limited information on the minerals themselves. Measurement of the minerals is necessary as important elements can have different hosts, and the different hosts can have widely varying properties. The few mineral sensor technologies which exist tend to have long turnaround times – limiting the value of the information. Efficient extraction requires real-time knowledge of the minerals that matter. This research shows real-time detection of minerals of significance using ‘novel’ fluorescence sensing through three regimes that are poorly covered in the existing literature: 1. Visible-light excitation and near infrared emission 2. “Cryogenic” fluorescence 3. Upconversion fluorescence Extending luminescence conditions into visible-light excitation and near infrared emission can allow higher confidence in the identification of signals due to fewer overlapping sources. This excitation/emission regime has had limited investigation to date, possibly due to historic technology limitations. Much of the literature uses specific laser wavelengths of 1064 nm frequency-integers, and detection of emission beyond the capability of silicon detectors (~1000 nm) is infrequently reported. The advent of commercially available optical parametric oscillator laser systems allows thorough examination of excitation wavelengths across broad ranges. Near infrared detection technology has advanced such that Peltier-cooled imaging systems are commercially available. It is well known that reducing the temperature of materials can impact luminescent properties. Minerals previously considered to be non-fluorescent can emit light due to the quenching of thermal phonons (quantised lattice vibrations in a crystalline solid that may enable non-radiative energy relaxation). This opens an additional dimension to mineral fluorescence investigation, and this thesis will report one luminescent response under low-temperature conditions from a mineral previously thought to be nonluminescent. Upconversion fluorescence has been heavily investigated in laser physics and for biological applications, but its application to mineral species is in its infancy. Upconversion from natural rare-earth bearing minerals will be shown and discussed as an alternate or complementary mineral classification technique. This thesis shows critical material sensing using these ‘novel’ fluorescence regimes. Mineral sands systems (sources of titanium and zirconium) will benefit from the demonstrated sensor applications for the minerals zircon, kyanite and rutile. Fluorescence sensing for hard-rock lithium mining (the major source of lithium for battery applications) is shown with detection and discrimination of α and β spodumene using previously unreported luminescence. Discrimination using NIR luminescence of rare earth elements (necessary for advanced materials and electromagnets) in the minerals monazite, xenotime and zircon is investigated. Upconversion from these natural minerals is also shown and is a mineral discriminator. This thesis demonstrates the potential for Novel Fluorescence to achieve real-time mineral discrimination in four critical resources. The results further indicate that Novel Fluorescence will enable many opportunities for future discoveries and applications to minerals and other industries. Thesis (Ph.D.) -- University of Adelaide, School of Physical Science, 2022 en Minerals, Mineral sensors, Critical minerals, Novel Fluorescence, Upconversion, Laser-induced Fluorescence New Fluorescence Sensors for Critical Materials Thesis This thesis is currently under embargo and not available.restricted