Dissertations / Theses on the topic 'Spodumene'

An investigation into the direct leaching of α-spodumene has being warranted due to increasing societal interest in lithium-ion battery technology. The direct leaching of α-spodumene utilising a caustic autoclave process was investigated, in aspirations of leaching significant quantities of lithium from the silicate matrix of α-spodumene. The influence of reagent dosage, temperature, reaction time and particle size on the extraction efficiency of lithium were investigated. From the investigations conducted it became evident that the leaching efficiency of α-spodumene was consistently greater than 40.00% under the optimal conditions. The optimal conditions evaluated throughout the investigation were found to occur at 573.15 kelvin, 14 molar NaOH, a 6 hour residence time and a P80 of 325 μm. The lithium recovered to solution is present as a hydroxide species, of which is in significant demand within the lithium-ion battery production industry. Sodium silicate or ‘water glass’ was also found to be present within the leach products adding a potential valuable by-product to the process investigated.

Spodumene is an important source of lithium, a key element of Li-ion batteries used in mobile communication and entertainment devices, hybrid and all electric cars and electric bikes. Spodumene forms three different crystal structures, the naturally occurred α- spodumene, and y and β-spodumene which are the products of heat treatment at 700 to 1100 °C. Among these three modifications β-spodumene proven suitable for lithium extraction processes, hence the production of these phases should be closely monitored in feed preparation stage. In order to extract lithium from spodumene, β form of the mineral goes through acid roasting with concentrated sulfuric acid at 250 °C. This method remined unchanged for almost 50 years and limited information on the details of the process and effect of key factors is available. This study will investigate the preparation of suitable spodumene phase for extraction process exploiting two different types of heating. Then focuses on traditional acid roasting of spodumene and the key factors of the process and further on proposing a less energy intense method of acid roasting using microwaves. Spodumene concentrate of the highest purity from Greenbushes Western Australia was studied for mineralogical changes with temperature in muffle furnace. The feed sample with particle size of 325 mm was heated at temperatures from 800 to 1100 °C for different durations of time and structural changes were closely monitored. At 950 °C after 30 minutes of heating γ phase appeared on the XRD spectra which detected while β-spodumene was produced, after 2 hours of heating at 1100 °C. The crystal structure altered from monoclinic α to hexagonal γ and finally tetragonal β-spodumene. Physical properties of product heated at different temperatures and times were analyzed. The significant change was related to the particle size. Conversion of α to γ-spodumene is accompanied by shrinkage of the crystal units leading to contraction of particles. Moreover, particles go through substantial expansion with formation of β-spodumene. This leads to cracking of the particles and their dispersion to smaller particles. This phenomenon directly causes the reduction in particle size which increases the specific surface of the sample. Specific gravity of the sample was constantly reduced with order of changes of the crystal structure. All these alterations positively affect the yields of lithium extraction from β over α-spodumene. As an alternative process of calcination, a sample of α-spodumene was subjected tomicrowave and hybrid microwave heating. The sample reached 98 °C after 10 minutes of microwave irradiation with power of 3 kW. This proved that spodumene is categorized in the group of non-absorbers of microwave. Next a hybrid microwave heating set up was designed which applied three SiC sticks to absorb microwave energy and conventionally heat the spodumene sample. After 32 minutes of hybrid microwave heating and temperature increase up to 643 °C a sudden increase in temperature was observed. Due to localized heat some spot of the sample heated up to the melting point of the spodumene and left sintered and/ or melted parts. This suggested that α-spodumene can start absorbing microwave at temperatures above 643 °C. The process was repeated for a sample of synthesized β-spodumene absorption of microwave energy started at 447 °C. This phenomenon made the complete conversion of the sample complicated. As the next part of this study the common method of extraction of lithium from spodumene was studied. Sample of synthesized β-spodumene was mixed with concentrated sulfuric acid and roasted at temperatures between 200 and 300 °C. This process was followed by water leaching at 50 °C for 1 hour. In addition to temperature, the effects of acid dosage and roasting time were investigated. The highest extraction of 98% was achieved after roasting at 250 °C for 1 hour with 80% excess acid to the stoichiometry of the reaction of spodumene and sulfuric acid. Elongated roasting, roasting at temperatures close to boiling point of the acid and very high amount of excess acid negatively affected Li extraction. The residue after water leach was identified as aluminium silicon hydrate (H2O.Al2O3.4SiO2). In order to reduce the energy consumption of the acid roast process application of microwave oven was proposed. Acid roasting of spodumene was replicated in benchtop microwave oven adjusted on 700 W power. Interestingly 96 % of lithium was extracted after 20 second of microwave irradiation in presence of 80% excess acid. After 30 seconds of roasting the extraction reduced and reached 49% after 4 minutes. The residue of the water leach was aluminium silicon hydrate (H2O.Al2O3.4SiO2) for roasting under 30 seconds and after 4 minutes peaks of β-spodumene appeared in the XRD pattern. More studies on the residue showed that the residue has ion exchange properties and at elevated temperatures in presence of lithium the H+ can be replaced with Li+. With slight grinding the excess acid could be reduced to 15%. The energy consumption of microwave acid roasting was 15.4 kJ which was 3 order of magnitude less than the energy consumption of conventional acid roasting. Microwave acid roasting of β-spodumene is a promising method with less energy consumption.

The conventional process of lithium extraction from α-spodumene (LiAlSi2O6) is energy-intensive and associated with high by-product management cost. In this work, we investigate an alternative process route that uses potassium sulfate (K2SO4) to extract lithium while producing leucite (KAlSi2O6), a slow-release fertiliser and potash alum (KAl(SO4)2∙12H2O), which can be used in water purification, and medical drugs. This work presents the first-ever high temperature in situ record of the reaction of α-spodumene with potassium sulfate, using synchrotron X-ray diffraction (S-XRD) and differential scanning calorimetry (DSC) to document the reaction sequence during prograde heating. During in-situ studies, we observe that the reaction of potassium sulfate and spodumene proceeds through ion exchange between lithium and potassium in the spodumene structure, followed by phase conversion of α-(Li,K)-spodumene into leucite. Once conversion of spodumene to leucite reaches 90 %, a lithium sulfate- melt starts to appear. We optimised the potassium sulfate process at a K2SO4:α-SC 7.6 ratio of 0.6:1 (w/w), 1050 oC and 30 min roasting time, achieving 96.3 ± 2 % (w/w) lithium extraction efficiency, similar to the conventional sulfuric acid process (96.7 ± 0.6 % (w/w)). Using OLI systems modelling we found that purification of the leach liquor from the potassium sulfate requires the addition of aluminium sulfate to recover potassium as potash alum. Comparing the two processes based on 200 kt y-1 of spodumene concentrate, we estimate that the operating profit of the potassium sulfate is 5 % lower than that of the sulfuric acid process. Because of its potassium content, leucite can be converted into a slow-release fertiliser through further processing. For the potassium sulfate process to be more profitable than the sulfuric acid process, the fertiliser market price should exceed US$34.5 t-1. This work demonstrates that K2SO4 process could be a feasible alternative to the conventional sulfuric acid process.

The energy intensive extraction of lithium from α-spodumene (LiAlSi2O6) involves decrepitation at 1100 oC followed by sulphuric acid roasting (200 oC) and water leaching. The extraction of lithium from lepidolite (K(Li,Al)3(Al,Si)4O10(F,OH)2) also involves high temperature (750 – 1000 oC) roasting with additives or direct leaching. The leaching in acid or alkaline media is less attractive due to high reagent consumption and complex purification processes. This thesis reports low temperature extraction of lithium from α-spodumene and lepidolite of 3.58% and 2.37% Li (w/w), from Greenbushes (Western Australia) and Minas Gerais (Brazil), respectively. Characterisation of the solids (feed, calcines, residues, and precipitates) was performed using XRD, SEM-EDS, FTIR and Raman spectroscopy. The ICP-MS analysed the elemental composition of the leach liquors and digested solids. Results from thermogravimetric and differential thermal analysis of feed material and XRD scans of solids were justified by thermodynamic modelling of chemical reactions using HSC software package. The roasting of α-spodumene and lepidolite concentrate of particle size range -75+45 μm with NaOH and Ca(OH)2 for 2 h in a muffle furnace at 500 °C, followed by alkaline leaching at 90 oC, resulted in 98.2% and 98.5% Li extraction, respectively after 3 h, with relatively low dissolution of impurities. Alkaline pressure leaching in autoclave removed about 95% Li, 98% K, 96% Rb and 90% Cs from lepidolite at 250 °C with relatively low NaOH consumption. Alternatively, roasting lepidolite at 500 oC and α-spodumene at 1000 oC with NaHSO4 followed by water leaching yielded 96% and 80% of Li extraction, respectively. Precipitation of Li3PO4 by adding phosphoric acid to the purified alkaline and sulphate leach liquors, both by pH adjustments, recovered 83% and 93% of Li, respectively. Addition of lime to Li3PO4 produced 98% LiOH·H2O with 99.7% conversion.

The production of ??-eucryptite [LiAlSiO4] and ??-spodumene [LiAlSi2O6] from topaz [Al2SiO4(F0.64OH0.36)2, containing ~3 wt% quartz impurity] from Torrington, NSW may be of commercial importance since both lithium aluminosilicates have negative or low coefficients of thermal expansion and are used commercially as raw materials in the glass, ceramics, and metallurgical industries. A review of the literature has revealed that the production of ??-eucryptite and ??-spodumene from topaz has not been reported before. The aim of the present work was to determine the kinetics and reaction mechanisms of formation of ??-eucryptite from topaz + lithium carbonate mixtures and ??-spodumene from topaz + lithium carbonate + silica mixtures. To this end, the related reactions and subsolidus phase equilibria of the Li2O-Al2O3-SiO2 ternary system were determined. The subsolidus phase equilibria for the Li2O-Al2O3-SiO2 ternary system were investigated by literature assessment, experimentation, and thermodynamic calculations. The experimentation confirmed the previously published tentative compatibility relations in the Al2O3 and the SiO2 corners. Thermodynamic calculations were used to define the phase relations in the Li2O corner. Thermodynamic calculations also were used to define the phase equilibria for two binary subsystems, Li2SiO3-LiAlO2 and Li4SiO4-LiAlO2. The decomposition of topaz and formation of ??-eucryptite from topaz + lithium carbonate mixtures and ??-spodumene from topaz + lithium carbonate + silica mixtures were investigated experimentally using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman microspectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM). Confirmatory thermodynamic calculations also were done. One significant finding of the present work was the formation of nanofibres from topaz + lithium carbonate mixtures at 1150???C. These fibres were formed by gas-phase reaction of SiF4 and AlOF produced from the reaction between topaz, lithium carbonate and by reaction of SiO2 and Li(OH), which was produced by Li2O volatilisation. These fibres, which were difficult to analyse, most likely consisted of metastable ???-spodumene solid solution or mullite in the incipient stage of formation. Formation of single-phase ???-spodumene from topaz + lithium carbonate + silica mixtures was observed after heating above 950???C for 24 h. Reaction paths for the formation of ??-spodumene over the temperature range 450???-1550???C were proposed. The formation of single-phase ??-spodumene was not simple and straightforward but a complex process involving several precursor phases. Specifically, there were two reaction mechanisms involving the formation of single-phase ???-spodumene by gas-solid reaction and gas-liquid-solid reaction. The reaction kinetics and thermodynamics of the formation of single-phase ??-spodumene at 750???-950???C were assessed. Essential work supplementary to that associated with the Li2O-Al2O3-SiO2 system consisted of determination of the decomposition mechanism of topaz, which was determined to take place in four stages. Reaction paths for the decomposition of topaz also were proposed. Another significant finding of the present work was the formation of transient single-crystal mullite from topaz + lithium carbonate + silica mixtures at ~600???C, which may be contrasted with the normal temperature range of 1000???-1400???C for formation from clay-based raw materials. This phenomenon occurred via a gas-solid growth mechanism. The present observation suggests a potential low-temperature route for the production of high-purity mullite fibres without glass contamination.

With the increase in global lithium consumption, it is vital that lithium refinery processes are optimised to combat this growing need. One of the richest sources of lithium, spodumene, was tested alongside a common gangue material, silica, for its zeta potential. Variables used are namely modifiers iron chloride, magnesium chloride, calcium chloride and calcium alginate. These materials’ concentrations were tested using a zeta probe to identify theoretically optimal conditions to selectively float spodumene from the gangue. The source of spodumene used was a lithia concentrate obtained from Talison Greenbushes mine and refinery, giving a lithia (Li2O) concentration of 7.0%, which is the target of this investigation. Once the zeta potentials for both spodumene and silica were obtained from a range of pH values, flotation tests were performed to test the theory, followed up by XRD analysis to identify an estimated lithia concentration and confirm whether or not there are some applicable uses for zeta potential measurements in the mining industry. It was discovered post experimentation and analysis, that at notable concentrations for certain cations, collectors and pH conditions, namely 250 mg/L of Ca (II) at a pH of 4 with an anionic collector, Fe (III) at concentrations less than 50 mg/L in neutral conditions with a cationic collector and at greater concentrations on ions in acidic conditions with an anionic collector. Further research in ranges of Mg (II) and sodium alginate concentrations would be required to identify their uses to optimise spodumene flotation; or separation from the bulk slurry solution.

This work provides a detailed description of the qualitative and quantitative mineralogical, dynamic, as well as kinetic aspects for the structural transformation of α-spodumene (α-LiAlSi2O6), and advances the industrial processing of spodumene by introducing two novel alternative technologies that are relatively straightforward and potentially cost-effective. Spodumene, the most abundant lithium-containing mineral, usually undergoes calcination at an extreme temperature of about 1100 ºC and strong-acid digestion during industrial processing. The calcination process stimulates the structural transformation of spodumene from its naturally occurring pyroxene-framework α-phase into the relatively more reactive β-spodumene of the keatite (SiO2) structure. On the other hand, the acid digestion approach facilitates the production of water-soluble lithium compounds (mainly lithium sulfate Li2SO4). This study resolves the technical obstacles associated with cheaper (and safer) processing of spodumene concentrates. The project incorporated intensive experiments to analyse the thermally-activated changes during the calcination of spodumene. The combination of hot-stage and high-temperature synchrotron X-ray diffractometry (XRD) enabled in-situ mineralogical analysis of the transformation processes, identifying (and quantifying) the resulting phases at various temperatures. Each of the diffractometry techniques complements the heating rate and temperature limitations of each other. Likewise, accurate calorimetric and thermogravimetric analyses yielded the corresponding thermodynamic and kinetic functions, allowing the precise determination of the minimum energy required for the heat treatment process. Distinctly, the project also involved detailed investigation on roasting of spodumene with the most effective additives, CaO and Na2SO4, for better extraction of lithium. The addition of these chemicals resulted in the formation of water-soluble lithium compounds via the roasting process at a relatively low temperature (800 – 900 ºC). Set of experiments determined the best condition for minimising these additives and maximising the productivity of lithium. Atomic absorption spectrometry (AAS) quantitated the recovered lithium from the roasted spodumene concentrate. Techniques, such as X-ray fluorescence (XRF) and AAS, attested the chemical analyses of the raw spodumene concentrate. The Match! Software allowed phase identification, while HSC 7.1 software facilitated the estimation of energies. The results of this thesis have demonstrated that the transition reaction of spodumene occurs via different pathways, depending on the amorphicity and the thermal history of the mineral. The results have also identified the intermediate species and clarified their appearance as a function of temperature and heating rate, and particle size, relative to the final phase of β-spodumene. For instance, the formation of the recently reported γ-spodumene is initiated by crystallisation of minuscule amorphous materials in the concentrated sample at slow heating conditions, while fast initial heating to 800 ºC prompts the emergence of a newly-identified phase of β-quartzss, at low temperatures of less than 900 ºC. Requiring an operating temperature of above 1000 ºC, the calcination of spodumene concentrate has been elucidated to adopt slow kinetics, with a high activation energy of more than 800 kJ mol-1 and significant dependency on the degree of conversion. The combined outcomes of this study are instrumental in optimising the energy cost of lithium extraction from spodumene mineral in practical operations. In particular, this thesis reveals that, the roasting of spodumene concentrate with a small amount of CaO reduces the transformation temperature by 150 – 200 ºC as determined by in-situ XRD, which translates into important energy saving during the calcination of spodumene in the first step of the commercial acid digestion process. Roasting of spodumene with CaO and Na2SO4 at 882 ºC for 2 h results in producing a water-leachable lithium compound of LiNaSO4 with 94 % lithium recovery. Thus, the roasting of spodumene concentrate with these two additives eliminates the aggressive acidic treatment and decreases the operating temperature of the kiln.

Course of synthesis of Li2O – Al2O3 – SiO2 (LAS) ceramic via sol – gel process made precursor was investigated. Powder precursor containing LAS components in molar ratio 1:1:4 were prepared by polycondensation technique in aqueous medium using lithium chloride (LiCl), hydrated aluminium nitrate (Al(NO3)39H2O) and silica sol (tosil), respectively. Heated sol was transformed into gel. The resulting gel was dried at temperature 105 °C and xerogel was next calcinated at 750°C. Further was evaluated influence of sintering additives (MgO, ZnO, Ca5(PO4)3OH) on the length of sintering interval. All of them have been stabilized spodumene in the solid solution. The properties of ceramic body prepared by sintering of precursor and grinded Li2CO2, Al2O3 a SiO2 powders were compared. Simultaneous thermogravimety and differential thermal analysis (TG-DTA), X-ray diffractions and heating microscopy were used to study sintering process of LAS ceramic.

This work is focused on Li ceramics and glass-ceramics with low thermal expansion. Composition of these material is based on mineralogical composition of ?-spodumene – Li2O•Al2O3•4SiO2. Sol-gel route of preparation was used for preparation of the material. Sol-gel route is profitable because of production of high purity and controlled grain size powder. Lower sintering temperature, higher degree of homogeneity and shorter time of heat treatment in comparison with traditional approach belong among other advantages of sol-gel route of preparation. Influence of Li+ substitution for K+, which has similar atomic radius, is assessed in this work. These ions are localized in the interstitial position of spodumene structure and are able to maintain the charge balance. Li+ ions were substituted with K+ in the amount of 0; 0,5; 1; 2; 5 and 10 wt. % in view of Li+ weight. In the next step influence of adding mineralizer was specified in the material modified this way. The effect of adding mineralizer on phase transformation and heat treatment tendency was considered. K+ were added to the mixture in the form of potash. Due to this addition forming of orthoclase phase next to spodumene, eucryptit and SiO2 (ss) was detected. Decrease in melting temperature and ability of melt to crystallize were consequence of orthoclase forming. No crystallization appears, when more than 1 wt.% of K+ was added.

Le lithium est un composant majeur des batteries Li-ion, utilisées dans la fabrication de nombreux appareils électroniques portables. La transition énergétique entraîne le passage des véhicules thermiques aux véhicules électriques et hybrides, qui repose principalement sur l'utilisation de batteries Li-ion pour le stockage réversible de l'énergie. Le développement des véhicules électriques basés sur la technologie lithium-ion est à l'origine d'une demande record de sel de lithium (principalement carbonate et hydroxyde de lithium). Le spodumène est la principale source de lithium à partir de minerais. Son traitement nécessite une transformation de phase de la forme α à la forme β, suivie d'un grillage conduisant à la formation d'un sel de lithium après des étapes de lixiviation, de purification et de récupération. Dans cette thèse, le concentré de spodumène de la région de Pilbara en Australie occidentale a été caractérisé pour le traitement thermique et hydrométallurgique. Le traitement thermique est responsable de la formation de fissures dans les grains qui deviennent plus visibles avec l'augmentation de la température. La désintégration du matériau, la fusion et l'agglomération avec les minéraux contenus dans la gangue ont également été observées en augmentant la température jusqu'à 1050 °C. Des énergies d'activation apparentes de 655±20 kJ mol-1 ont été calculées pour la transformation de l'α-spodumène, ce qui confirme une forte dépendance à la température pour les transformations polymorphes du spodumène. Par la suite, nous avons étudié une voie alternative aux méthodes conventionnelles (procédé à l'acide sulfurique) pour traiter le concentré de spodumène dans le but de réduire la consommation d'énergie élevée des étapes de transformation de phase et de grillage au sulfate. Pour ce faire, nous avons procédé à la chloration directe de l'α-spodumène avec du chlorure de calcium, suivie d'une lixiviation à l'eau du résidu pour récupérer le chlorure de lithium. L'analyse du résidu obtenu après lixiviation a indiqué que la forme α était le seul polymorphe présent, ce qui suggère que l'extraction se fait directement à partir de la phase α. Dans des conditions optimales, un traitement thermique à 1000 °C pendant 60 minutes du concentré de spodumène en présence de chlorure de calcium à un rapport molaire chlorure de calcium/spodumène de 2,0 est nécessaire pour extraire près de 90 % du lithium et récupérer 85 % dans la liqueur de lixiviation. Une énergie d'activation apparente d'environ 122±6 kJ mol-1 a été calculée pour des températures allant de 800 à 950 ℃. La liqueur obtenue après lixiviation a été purifiée par échange d'ions et extraction par solvant afin de récupérer du chlorure de lithium d'une pureté suffisante pour être considéré comme un précurseur dans la production de matériaux pour batteries au lithium-ion
Lithium is a major component of Li-ion batteries, used in the manufacture of many portable electronic devices. The energy transition is driving the shift from thermal to electric and hybrid vehicles, which relies mainly on the use of Li-ion batteries for reversible energy storage. The development of electric vehicles based on lithium-ion technology is responsible for a record demand for lithium salt (mainly lithium carbonate and hydroxide). Spodumene is the main source of lithium from ores. Its processing requires a phase transformation from α-form to β-form, followed by roasting leading to the formation of a lithium salt after a leaching, purification, and recovery steps. In this thesis, spodumene concentrate from the Pilbara region of Western Australia was characterized for thermal and hydrometallurgical processing. Heat treatment is responsible for the formation of cracks in the grains which become more noticeable with increasing temperature. Disintegration of the material, melting and agglomeration with minerals contained in the gangue have also been observed by increasing the temperature up to 1050 °C. Apparent activation energies of 655±20 kJ mol-1 was calculated for the transformation of α-spodumene which confirms a strong temperature dependence for polymorphic transformations of spodumene. Subsequently, we investigated an alternative route to conventional methods (sulphuric acid process) to treat the spodumene concentrate with the aim of reducing the high energy consumption of the phase transformation and sulphate roasting steps. This was achieved by direct chlorination of α-spodumene with calcium chloride, followed by water leaching of the residue to recover lithium chloride. Analysis of the residue obtained after leaching indicated that the α-form was the only polymorph present, suggesting that extraction occurs directly from the α-phase. Under optimal conditions, heat treatment at 1000 °C for 60 minutes of the spodumene concentrate in the presence of calcium chloride at a calcium chloride/spodumene molar ratio of 2.0 is required to extract nearly 90% of lithium and recover 85% in the leach liquor. An apparent activation energy of about 122±6 kJ mol-1 was calculated for temperatures ranging from 800 to 950 ℃. The liquor obtained after leaching was purified by ion exchange and solvent extraction to recover lithium chloride of sufficient purity for consideration as a precursor in the production of lithium-ion battery materials

This Master of Science project is supervised by Keliber Oy in co-operating with University of Oulu. Lithium rich spodumene pegmatite deposits of Keliber Oy locate in Central Ostrobothnia, Finland. Studied deposits locate in the municipalities of Kaustinen and Kokkola. The study was focusing on mechanical separation of ore and waste rock and spatial modelling of sorting properties of the ore. The aim of the study was a development of index, that is suitable for spodumene pegmatite ores. The index is a spatial estimation of waste rock dilution within the deposit and it is defined during drill core logging. The index is describing the need and benefits for preconcentration of ore and can be used in mine planning and resource modelling. In Kaustinen region, high contrast difference between light coloured spodumene pegmatite ore and dark coloured country rocks is making optical separation methods possible to use in preconcentration. Another aim of the study was to found methods to separate spodumene pegmatite and barren pegmatite, similar in colours, by sensor-based sorting. The index was defined for one spodumene pegmatite dike of the Rapasaari deposit. The index was represented as percentages of ore from drill core interval and was defined during drill core relogging. There was made block models for black country rocks and barren pegmatite from data of relogged drill cores. Block models included the sorting index. Bench-scale sorting test was done for separation of spodumene pegmatite and barren pegmatite. Also, separation potential of sensor systems for ore and country rock was verified. The used samples were from the Syväjärvi and the Länttä deposits and they included spodumene pegmatite pieces with different grades, quartz-albite-muscovite pegmatite pieces, potassium feldspar pieces, and country rock pieces. Hyperspectral imaging test was done to the selected drill cores of the Rapasaari deposit. Hyperspectral study was done for study of mineralogy and features of spodumene pegmatites. According to the sorting index, the determined amount of waste rock within the ore dike was 15 weight percent and amount of barren pegmatite was 14 weight percent. Average lithium oxide grade of studied ore intercepts was 1.16%. In block modelling, the amount of black waste rock was 12.2 wt.% and the amount of barren pegmatite was 13.9 wt.%. The index is suitable for all ores, where ore and waste rock can be positively identified during drill core logging and sorting. In bench-scale sorting test, it was found that all sensor systems are capable to separate pegmatites and country rock. The LASER sensor system was the only one, that could positively identify differences between spodumene pegmatite and barren pegmatite. However, the LASER sensor accepted 88% of ore samples to the product (i.e. preconcentrate) but rejected 12% of the ore samples as reject (i.e. waste)
Opinnäytetyö tehtiin yhteistyössä Keliber Oy:n ja Oulun yliopiston kanssa. Työssä tutkittiin Keliber Oy:n Keski-Pohjanmaalla, Kaustisen ja Kokkolan kuntien alueella sijaitsevien litiumrikkaiden spodumeenipegmatiittien malmin ja sivukiven erottelua ja mallintamista. Työn tavoitteena oli luoda spodumeenipegmatiittimalmeille soveltuva indeksi, jonka avulla voidaan kuvata tarkasti malmin ja sivukiven määrää malmiesiintymässä alueellisesti. Indeksillä voidaan arvioida malmin esirikastamisen tarvetta ja sen tuomia hyötyjä. Se voidaan ottaa avuksi kaivos- ja louhintasuunnitteluun sekä malmiesiintymän mallintamiseen. Kaustisen alueen spodumeenipegmatiittien ja sivukivien väriero mahdollistaa sensoripohjaisten menetelmien käyttämisen esirikastusvaiheessa malmin ja sivukiven erottelussa. Lisäksi työssä tutkittiin mahdollisuutta erottaa litiumpitoinen spodumeenipegmatiitti litiumköyhästä pegmatiitista optisia menetelmiä käyttäen. Työssä määritettiin Rapasaaren spodumeenipegmatiittiesiintymän yhdelle malmijuonelle indeksi, joka kuvaa malmin ja sivukiven lajittelun tarvetta sekä sen tuomaa hyötyä. Indeksi esitettiin prosenttiosuuksina kairasydänmittaväleistä kairasydänten uudelleen raportoinnissa. Kairasydänraportoinnista saadusta tiedosta tehtiin blokkimallit, jossa kokeiltiin indeksin toimivuutta. Laboratoriomittakaavainen tutkimus sensoripohjaisen erottelun toimivuudesta malmin ja sivukiven erottelussa tehtiin Syväjärven ja Läntän spodumeenipegmatiitti- ja sivukivinäytteille. Tutkimuksessa pyrittiin erottamaan myös spodumeenipegmatiitti litiumköyhästä pegmatiitista. Näytteet sisälsivät eri pitoisuuden omaavia spodumeenipegmatiitti- ja kvartsi-albiitti-muskoviittipegmatiittikappaleita, kalimaasälpäkappaleita sekä sivukivikappaleita. Käytetyt sensorit olivat COLOR, NIR, XRT ja LASER. Hyperspektritutkimus tehtiin valituille Rapasaaren esiintymän kairasydämille. Hyperspektritutkimuksella pyrittiin selvittämään spodumeenipegmatiittien mineralogiaa sekä piirteitä, joilla se voidaan optisesti erottaa litiumköyhästä pegmatiitista. Indeksiin perustuen Rapasaaren spodumeenipegmatiittijuonen laskettiin sisältävän 15 prosenttia tummaa sivukiveä ja 14 prosenttia litiumköyhää pegmatiittia. Malmilävistyksien keskiarvoiseksi litiumoksidipitoisuudeksi saatiin 1,16 %. Blokkimallinnuksessa saatu tumman sivukiven määrä oli 12,2 %. Litiumköyhän pegmatiitin määrä oli 13,9 %. Kehitetty indeksi toimii myös muiden malmien yhteydessä. Indeksiä voidaan soveltaa, kun malmi ja sivukivi ovat erotettavissa kairasydänraportointia tehdessä. Sensoripohjaisen lajittelun todettiin erottelevan vaalea malmi ja tumma sivukivi 100 prosentin todennäköisyydellä kaikkia sensoreita käyttäen. LASER oli ainoa sensori, joka havaitsi eroja spodumeenipegmatiitin ja litiumköyhän pegmatiitin välillä. LASER-sensori hyväksyi 88% malmiksi luokitelluista kappaleista tuotteeksi, mutta hylkäsi 12 % malmikappaleista jätteeksi

O espodumênio (LiAl Si IND 2 O IND 6) de cor lilás, chamado kunzita, encontrado no Estado de Minas Gerais, foi investigado no presente trabalho. A análise de fluorescência de raios-X revelou, além das componentes básicas Si 0 IND 2, Al IND 2 O IND 3 e Li IND 2O, várias impurezas, sendo Mn e Fe as principais. Para comparação com o material natural, um policristal \"puro\" de -espodumênio foi produzido pela devitrificação de um vidro obtido da mistura de Si 0 IND 2, Al IND 2 0 IND 3 e Li IND 2 0. Esse método de devitrificação proporciona um processo importante e relativamente simples para produzir um policristal puro que pode ser usado na comparação do material natural. A curva de emissão termoluminescente (TL) da amostra recozida em 600°C por 1h apresentou picos em 145, 215, 350, 370 e 460°C, após uma irradiação com doses entre 10 e 5000Gy. A resposta TL desses picos, acima de 50Gy, é supralinear. A luz TL emitida por amostras naturais recozidas entre 500 e 900°C e, então, irradiadas, mostra que com o tratamento térmico em 900°C a sensibilidade TL aumenta por um fator de 3 comparado com o recozimento entre 500 e 800°C. Esses tratamentos térmicos afetam, também, a estrutura cristalina, mantendo a cristalinidade, mas produzindo um rearranjo nos planos de reflexão e no tamanho dos grãos. O espectro da luz TL da amostra natural apresenta uma banda em torno de 610nm, intensa e larga (-200nm) para todos os picos, embora uma banda muito fraca e larga seja, também, observada em torno de 480nm. Isto significa que, praticamente todos os elétrons que chegam na BC, após o aquecimento para a leitura TL, recombinam-se com um único centro, emitindo luz em torno de 610nm, sendo ele o centro de alumínio [Al O IND 4/h]. As medidas TL do policristal irradiado e não irradiado mostram que, exceto pelos picos TL em 350 e 370°C, todos os outros são devidos à defeitos intrínsecos. Esta conclusão é confirmada pelo espectro de emissão, o qual mostra na amostra artificial a mesma banda em 610nm. A luz UV induz diretamente a termoluminescência. Como a energia dos fótons é bem inferior à largura da banda proibida, a indução de TL foi interpretada como sendo devido à absorção de dois fótons. A resposta TL observada resultantes da irradiação UV de luz syncrotron ou com lâmpadas fluorescentes ou de Hg é diferente da produzida por irradiação gama e diferente entre elas próprias. Ainda não foi encontrada explicação para o fenômeno. No início da irradiação UV, para o pico de 460°C, predomina o acúmulo de transportadores de carga nas armadilhas. Com a longa exposição (>22h) há a diminuição desse pico, prevalecendo o processo de fototransferência acompanhado de fotoesvaziamento. A irradiação intensa cria vacâncias de oxigênio, que recebem em seguida, elétrons da ionização dando origem a centros F. O cristal torna-se predominantemente verde. As bandas de absorção óptica que surgem com irradiação e pertencem a esse centro F, 310, 360, 470 e 630nm, decaem entre 150 e 250°C. Esse comportamento é similar ao do pico TL em 220°C, indicando que esse centro TL está correlacionado ao centro F. Há forte evidência, como no quartzo contendo alumínio como impureza, que o íon de Al POT. 3+ tem a tendência de substituir o íon de Si POT 4+ no tetraedro Si O IND 4, dando origem ao centro [Al O IND 4] Este é neutralizado por um íon alcalino (Li POT. + ou Na POT. +). A irradiação remove M POT.+ e o radical resultante captura um buraco, dando origem ao centro de alumínio [Al O IND 4/h]. Foi aqui proposto, por isso, o seguinte mecanismo de emissão da luz TL em torno de 220°C: i) Durante a irradiação formam-se os centros F e os centros de alumínio. ii) Durante o aquecimento na região de 150°C a 220°C para a leitura TL, tem-se: a. Centro F ---- calor Vacância de O + 2e POT (ou E IND 1+ e POT. ). b. [Al 0 IND 4 /h]+ e POT - [Al O IND 4] POT - + hv IND. TL (pico de 220°C) Foi constatado que a banda de AO em 530nm cresce entre 200 e 300°C, decaindo além de 300°C, para tornar a kunzita incolor em torno de 400°C. Como o Mn POT .3+ é suposto ser o responsável pela cor lilás, ele dá origem à banda em 530nm. Por outro lado, o tratamento térmico isócrono mostra que os picos TL em 350°C e 370°C decaem entre 320 e 375°C, mostrando que há forte correlação entre a banda de absorção em 530nm e os picos TL em 350 e 370°C. Foi, então, proposto que o Mn POT. 4+, presente na amostra, se torna Mn POT. 3+ como aquecimento entre 200 e 300°C, capturando um elétron. Com o aumento da concentração de Mn POT 3+a cor lilás fica mais intensa. Acima de 300°C, tem-se a liberação de um elétron do Mn POT. 3+, que se torna novamente Mn POT 4+. O elétron assim liberado pode recombinar-se com o centro de alumínio e há emissão de luz TL. Comparando-se o comportamento térmico do pico TL em 460°C e um sinal em g= 1,997 pode-se afirmar que os dois centros têm uma relação íntima. Esse centro paramagnético tem semelhança ao centro E IND 1 \', porém, nenhuma indicação definitiva dessa identificação foi encontrada.
Natural spodumene, LiAlSi2O6, of lilac colour, called kunzite, from Minas Gerais State, Brazil, was investigated. An X-ray fluorescence analysis revealed several impurities, Mn and Fe being the principal ones, besides the matrix components SiO2, Al2O3 and Li2O. For comparison a pure policrystal of -spodumene was produced by devitrifying a glass obtained from Si02, Al2O3 and Li2O. The devitrification process has proved to be an important and relatively simple process to produce a \"pure\" polycrystal, which can be used for comparison with a natural sample. The TL glow curves of kunzite annealed at 600°C for 1h presented TL peaks at 145, 215, 350, 370 and 460°C, after gamma-irradiation with doses varying between 10 and 5000Gy. The TL response of these peaks, above 50 Gy, is supralinear. The TL light emitted by samples heated with treatments between 500 and 900°C and, then, irradiated showed that TL sensibility of kunzite is increased for 900°C by a factor of 3. Since X-ray diffraction of all heat treated samples shows changes in diffraction lines, keeping their crystallinity, such heat treatment seems to produce rearrangement of reflection planes, as well as, of grain sizes. The spectrum of TL emission consists of a very large band around 610nm and a very weak one around 480nm. This means that during heating from TL reading, most of the liberated electrons recombine with only one recombination center, with has been identified as the aluminum center, [AlO4/h]. The TL measurements of an irradiated and non-irradiated artificial polycrystal showed that except for the 350 and 370°C TL peaks, the others are due to intrinsic defects. This conclusion is confirmed by the TL emissions spectra, which shows in the artificial sample the same band at 610nm. The UV light from a fluorescence lamp or usual Hg lamp induce thermoluminescence after 3h or longer exposure. Since photon energy from such UV source is about half of spodumene band gap energy or of other silicate crystals, we assume that it is a two-photon absorption process. Under very long time exposure to UV light, the intensity of the TL peak at 460°C decreases, while high energy photons produce an increase in the intensity until it reaches saturation. It is quite possible that, while the irradiation time is less than ~20h the filling traps (relative to 460°C TL peak) predominante, but, as a large number of the traps are filled, phototranfer becomes effetive emptying these traps. Of course, bleaching process also contribute to decrease the 460°C TL peak. The thermoluminescence induced by Hg lamp UV light, as well as by synchrotron VUV light, differs from that induced by high energy photons, for instance X- or y-rays. So far, no explanation was found. A relatively heavy irradiation creates in the crystal oxygen vacancies, which become F-center after capturing electrons released by ionization. The kunzite then becomes green coloured. The optical absorption bands at 630, 470, 360 and 31 O nm belong to this F-center. All of them are annealed out in the 150 to 250°C temperature region. Since the TL peak at 220°C has similar thermal behaviour, this peak is correlated to the F-center. In silica and silicate crystals there is a tendency for substitution of Si4+ by AI3+. The charge neutrality is guaranteed by alkaline ions, in the case of kunzite by Na+ ions, usually present. Then, during irradiation one has: Lattice with O2- --irrad. Vacancy of O2- in the lattice Vac. O2- + 2e- F-center [AlO4 / M] --irrad. [ALO.]- + M+ [ALO4]- + h [AlO4]- /h] = aluminum center During the TL reading (heating): F-center --heat Vac.O + 2e- (or E1\' +e-) [AlO4 / h] + e- [ALO4]- + hv TL (220°C TL peak) The optical absorption band at 530nm is correlated with lilac colour of kunzite, therefore, it is related to Mn3+. Since heating from 200 to 300°C enhances the colour it was assumed that Mn4+ traps an electron becoming Mn3+. The lilac colour of kunzite fades beyond 300°C leaving the kunzite colourless around 400°C. On the other hand, TL peaks at 350 and 370°C decrease similarly between 300 and 400°C, therefore, it was concluded that these TL peaks are correlated with Mn3+ centers responsible for the 530nm OA band. A week EPR signal with g=1.997 was observed, which decays in a very similar way to 460°C TL peak. Hence we conclude that they are one and the same center. Its nature was not identified, although the experimental result show that it is E1 -like center.

Lithium represents one of the strategic elements for the rest of the 21st century due to its increasing demand in technological applications. Therefore, new efforts should be focused on the optimization of mineral characterization processes, which link the ore properties with its behaviour during downstream processes. These efforts should result in reducing operational risks and increasing resources utilization. The methodology presented in this study is based on the application of several classification techniques, aiming the mineral and textural characterization of two spodumene pegmatite deposits within the Keliber Lithium Project. Twelve textural classes have been proposed for the textual classification of the ore, which have been defined through the recognition of the main mineral features at macro- and micro-scale. The textural classification was performed through the application of drill core logging and scanning electron microscopy. Six classes are proposed to describe the characteristics of the spodumene ore. Six additional classes describe the main properties of the rocks surrounding the ore zone. Image analysis was implemented for the generation of mineral maps and the subsequent quantification of spodumene and Li2O within the analysed drill core images. The image segmentation process was executed in Fiji-ImageJ and is based on eight mineral classes and a set of seven feature extraction procedures. Thus, quantification of spodumene and Li2O is estimated by textural class. Hyperspectral images were used as a reference for assessing the estimations made through images analysis. A machine learning model in Weka allowed forecasting the behaviour of the twelve textural classes during spodumene flotation. This model is fed by metallurgical data from previous flotation tests and uses Random Forest classifier. The proposed methodology serves as an inexpensive but powerful approach for the complete textural characterization of the ore at Keliber Lithium Project. It provides information about: (1) mineral features at different scales, (2) spatial distribution of textures within the pegmatite body, (3) quantification of spodumene and Li2O within the drill cores and (4) processing response of each textural class. However, its application requires wide knowledge and expertise in the mineralogy of the studied deposits.

Thesis Presentation.

Textural and Mineralogical Characterization of Li-pegmatite Deposit: Using Microanalytical and Image Analysis to Link Micro and Macro Properties of Spodumene in Drill Cores.  Keliber Lithium Project, Finland.

La région de Bougouni a pour spécificité la présence de pegmatites et d'aplites porteuses de lithium. Le lithium est actuellement un élément stratégique au regard des besoins croissants en cette matière première. Les pegmatites lithinifères font ainsi partie des gisements les plus recherchés pour le lithium.La zone d'étude, située au SE de Bamako (Mali), appartient à la partie sud du craton ouest africain. Les différentes roches de cette zone se sont formées au cours des événements de croissance crustale du Birimien, lors de l'orogenèse éburnéenne, entre ca. 2200 et 1800 Ma. Les formations rencontrées sont des roches métavolcanosédimentaires et plutoniques majoritairement de nature granitoïdique (tonalite à monzogranite à deux micas), structurées dans une direction NNE-SSW par l'existence de grandes zones de cisaillement. Les dykes sont intrusifs dans ces roches encaissantes sous forme de filons d'épaisseur décimétrique à décamétrique depuis des faciès aplitiques à des faciès pegmatitiques. La mise ne place dans un domaine cassant couplé au bas grade métamorphique des métasédiments encaissants indiquent une mise en place des dykes au niveau de la croûte continentale supérieure.La province de Bougouni compte une centaine de dykes riches en lithium (Li2O > 1.00 wt% de la roche totale). Le spodumène, principal phase minérale porteuse de lithium (Li2O = 8 wt%), représente entre 5 et 30 vol.% de la roche, accompagné de feldspath alcalin, plagioclase, quartz et d'une faible quantité de muscovite et de biotite. Sont également présents une centaine de dykes pauvres en lithium (Li2O < 0.05 wt%) caractérisés par le même assemblage minéralogique que les dykes riches en lithium à l'exception du spodumène remplacé par le grenat.Concernant la géochronologie, les âges U-Pb sur zircons pour l'ensemble des granitoïdes (faciès granodioritiques à granitiques à deux micas) s'étendent entre 2100 ± 14 et 2136 ± 19 Ma. Ces âges sont en accord avec les âges d'autres formations plutoniques s'étalant entre 2080 et 2120 Ma à l'échelle du Birimien. Les âges U-Pb sur apatites magmatiques des dykes sont compris entre 2070 - 2000 Ma. La comparaison des données géochronologique à d'autres pegmatites du Birimien permettent de définir la période ca. 2070 - 2000 Ma comme la période de mise en place des dykes pegmatitiques (notamment les pegmatites de la famille LCT) du Birimien. Cette période tardi- à post orogénique représenterait l'étape finale du magmatisme paléoprotérozoïque dans le domaine du Baoulé-Mossi.Concernant la géochimie en éléments majeurs et traces, l'absence d'une évolution géochimique continue depuis les granitoïdes aux dykes ne permettent pas d'expliquer les liquides pegmatitiques comme étant les termes les plus évolués des granitoïdes. Cette conclusion est en accord avec les données géochronologiques qui témoignent d'une différence d'âge beaucoup trop importantes entre ces formations pour qu'elles puissent avoir un lien génétique. Concernant les dykes, bien qu'ils soient contemporains, les différences en termes de signature géochimique ne permettent pas d'expliquer qu'ils puissent avoir évolués depuis un seul et même liquide parent. Cependant, il est fort probable que les liquides à l'origine des deux types de dykes puissent provenir de la fusion du même type de protolithe de nature métapélitique.En somme, les données de terrain, pétrographiques, géochronologiques et géochimiques ne donnent pas de lien génétique entre les dykes et les granitoïdes de Bougouni. Les deux faciès de dykes sont formés à partir de deux liquides distincts issus d'un seul et même protolithe. La différence de composition minéralogique et géochimique, notamment en Li, entre les dykes riches en lithium et ceux pauvres en lithium pourrait être expliquée par le rôle de fluides d'origine sédimentaire ayant pu percoler et interagir avec les roches mères et/ou les liquides pegmatitiques permettant d'enrichir certains liquides en éléments mobiles, tel que le lithium
The Bougouni region in southern Mali is well known for the ore body lithium-bearing pegmatites and aplites. Lithium is currently a strategic element in view of the growing need for this raw material. The lithiniferous pegmatites are thus among the most sought-after deposits for lithium.The study area, located SE of Bamako (Mali), belongs to the southern part of the West African Craton. The various rocks in this area were formed during the Birimian crustal growth events, during the Eburnean oOrogeny, between ca. 2200 and 1800 Ma. The formations encountered are metavolcano sedimentary and plutonic rocks, mostly granitoid (tonalite to two-mica monzogranite), structured in a NNE-SSW direction by the existence of large shear zones. The dykes are intrusive in these host rocks, which occur in the form of decimeter to decameter thick dykes ranging from aplitic to pegmatitic facies. The emplacement in a brittle domain coupled with the low metamorphic grade of the enclosing metasediments indicate a dyke emplacement in the upper continental crust.The Bougouni province has about 100 Li-rich dykes (Li2O > 1.00 wt% of total rock). Spodumene, the main lithium-bearing mineral phase (Li2O = 8 wt%), represents between 5 and 30 vol.% of the rock, accompanied by alkali feldspar, plagioclase, quartz and a small quantity of muscovite and biotite. In addition to, 100 Li-poor dykes (Li2O < 0.05 wt%) that are characterized by the same mineralogical assemblage as the lithium-rich dykes except for spodumene, which is replaced by garnet.Concerning geochronology, U-Pb ages on zircons for all granitoids (granodioritic to granitic facies with two micas) range between 2100 ± 14 and 2136 ± 19 Ma. These ages are in agreement with the ages of other plutonic formations ranging between 2080 and 2120 Ma on the Birimian scale. The U-Pb ages on magmatic apatites of the dykes are between 2070 - 2000 Ma. Comparison of the geochronological data with other pegmatites of the Birimian allow us to define the period ca. 2070 - 2000 Ma as the period of establishment of the pegmatitic dykes (notably the LCT family pegmatites) of the Birimian. This late- to post-Orogenic period would represent the final stage of paleoproterozoic magmatism in the Boulé-Mossi domain.Concerning major and trace elements geochemistry, the absence of a continuous geochemical evolution from granitoids to dykes does not allow to explain the pegmatitic fluids as the most evolved terms of the granitoids. This conclusion is in agreement with the geochronological data that show a much too large age difference between these formations to be genetically related. Concerning the dykes, although they are contemporaneous, the differences in geochemical signature do not allow to explain that they could have evolved from a single parent melt. However, it is very likely that the melts that gave rise to both types of dykes may have been derived from the melting of the same type of metapelitic protolith.In sum, the field, petrographic, geochronological and geochemical data do not provide a genetic link between the Bougouni dykes and granitoids. The two dyke facies are formed from two distinct melts derived from a single protolith. The difference in mineralogical and geochemical composition, particularly in Li, between the Li-rich and Li-poor dykes could be explained by the role of fluids of sedimentary origin that may have percolated and interacted with the source? host rocks and/or the pegmatitic melts, allowing the enrichment of certain fluids in mobile elements such as lithium

Le champ pegmatitique de la sahatany, d'age parafricain, se situe dans un ensemble de metasediments a tendances evaporitiques: les pegmatites potassiques et les pegmatites sodolithiques. Etude microthermometrique des inclusions fluides dans le quartz, la topaze et le spodumene. Ces fluides indiquent des conditions hydrothermales de temperatures elevees autour de 350-500**(o)c pour une pression de 2000-3000 bars. Les inclusions solides peuvent constituer des residus du stage magmatique

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The spodumene (LiAlSi2O6 - LAS) is a silicate that has shown good results for high-dose dosimetry for gamma rays. This silicate may be obtained naturally or synthetically. The synthetic spodumene has been produced by solid state reaction, whose difficulty arises from the need to employ high temperatures. This paper aims to produce LAS through two different production routes: the proteic sol-gel and Pechini methods. The material produced was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetry (TGA) in order to evaluate the structural properties of the material, as well as possible changes in physical or chemical properties depending on the temperature. It was found by XRD and Rietveld refinement was possible to obtain LAS B-spodumene phase by both methods. The thermal analysis showed that the material for both methods suffer considerable loss of weight in the temperature range 20-600 °C. Through thermoluminescent measures, one can observe that the LAS produced by both methods shows thermoluminescent peaks from beta irradiation at a dose of 1 Gy, thus allowing its application dosimetry. It can be concluded therefore that there is the possibility of producing them in large numbers at reduced cost and environmental impact, being viable in dosimetry. It also follows that the sol-gel protein appeared to be the best way to produce the LAS compared with other routes used, such as solid state synthesis or devitrification.
O espodumênio (LiAlSi2O6 LAS) é um silicato que tem demonstrado bons resultados para dosimetria de altas doses para raios gama. Esse silicato pode ser obtido de forma natural ou sintética. O espodumênio sintético tem sido produzido por reação do estado sólido, cuja dificuldade provém da necessidade de se empregar altas temperaturas. O presente trabalho tem o objetivo de produzir o LAS por meio de duas rotas de produção diferentes: a sol-gel proteica e método Pechini. O material produzido foi caracterizado através da difração de raios X (DRX), análises térmica diferencial (DTA) e termogravimétrica (TGA) com o intuito de avaliar as propriedades estruturais do material, bem como as possíveis mudanças de propriedades físicas ou químicas em função da temperatura. Verificou-se através da DRX e do refinamento Rietveld que foi possível se obter LAS na fase B-espodumênio por ambos os métodos. As análises térmicas mostraram que o material, por ambos os métodos, sofre perda considerável de massa no intervalo de temperatura de 20 a 600 °C. Através de medidas termoluminescentes, pode-se observar que o LAS produzido por ambos os métodos apresenta picos termoluminescentes a partir de irradiação beta com dose de 1 Gy, possibilitando sua aplicação dosimétrica. Pode-se concluir, assim, que há possibilidade de produção do LAS em larga escala a um custo e impacto ambiental reduzidos, sendo viável sua utilização em dosimetria. Também se conclui que o método sol-gel proteico se apresentou como sendo a melhor forma de produzir o LAS em comparação com outras rotas utilizadas, tais como síntese de estado sólido ou desvitrificação.

L’α-spodumène, soit α-LiAlSi[indice inférieur 2]O[indice inférieur 6] est un aluminosilicate de lithium qui provient d’une roche magmatique appelée pegmatite. Le minerai de spodumène est traité en industrie afin d’en extraire son contenu en lithium. Après purification, le minerai de spodumène est calciné afin d’activer la conversion irréversible de sa phase α (monoclinique) vers sa phase β (tétragonale), pour en extraire le lithium. Les objectifs de ce projet sont d’étudier dans la conversion α vers β d’un minerai de spodumène dans un four rotatif en fonction des différents paramètres opératoires (température, temps, concentration de spodumène, concentration d’eau), en utilisant les résultats des méthodes de caractérisation de la diffraction de rayons X (DRX) et de la calométrie différentielle à balayage (DSC). Ces méthodes sont rapides, permettent de prédire et suivre le comportement thermique d’un minerai de spodumène lors de son traitement dans un four rotatif. L’analyse par DRX démontre la complexité minéralogique des différents échantillons étudiés avant leur calcination. Les données de DRX du β-spodumène permettent de quantifier le taux de conversion calculé de l’α vers le β spodumène, en utilisant la loi de Beer-Lambert. Les courbes de DSC présente toutes les transformations se déroulant dans les échantillons, ainsi que la conversion du spodumène (vers 1010 °C) et la liquéfaction du matériel (qui débute vers 1060 °C). Les courbes de DSC illustrent convenablement le modèle thermique qu’adopterait un échantillon durant son traitement thermique. À partir des résultats de la caractérisation, une étude thermodynamique sur la pegmatite de spodumène a permis de développer les diagrammes de phases pseudo-binaires. Selon les modèles simplifiés, le système spodumène-albite-quartz atteint un eutectique à 1060°C, le système spodumène-microcline-quartz atteint le sien à 1171°C, tandis que l’eutectique système albite-microcline-quartz est à 930 °C. Un four rotatif d’échelle laboratoire a permis l’étude de l’effet de la température, du temps de résidence, du taux d’humidité et de la concentration de spodumène. Les résultats montrent que le taux de conversion calculé diminue lorsque la concentration d’impureté ou la concentration d’eau dans le système augmente. Aussi, le taux de conversion calculé augmente en fonction de la température et le temps. Cependant, en cas de liquéfaction du matériel durant le traitement thermique, le taux de conversion diminue considérablement avec la liquéfaction du matériel. Ce dernier influence la formation d’agglomérat dans le four rotatif et résulte en une vitrification du matériel. Finalement, les conditions optimales de la conversion d’un minerai de spodumène dans le four rotatif sont à 1050 °C pour un temps de résidence de 15 minutes.

Parmi les matériaux mineraux, les silicates sont d'un grand intérêt de par leurs propriétés physico-chimiques et leurs nombreuses applications industrielles. La natrolite Na2Al2Si3O10. 2H2O et la scolécite CaAl2Si3O10. 3H2O sont des composés aluminosilicatés appartenant à la famille des zéolithes. L'enchaînement des tétraèdres SiO4 et AlO4 par leurs atomes d'oxygène constitue le squelette de ces matériaux de structure analogue et donne naissance à des canaux dans lesquels sont piégés des cations Na+ et Ca2+ ainsi que des molécules d'eau. Le spodumène LiAlSi2O6 est un silicate du type pyroxène dont la structure se compose de chaînes infinies de tétraèdres de silicium reliés entre eux par un seul atome O. Dans l'espace interchaînaire de ce minéral, l'atome Al et l'ion Li+ sont en coordination octaédrique. Dans les expériences de diffraction X haute résolution sur ces matériaux, les intensités ont été mesurées à l'aide de détecteurs ponctuel ou bidimensionnel du type CCD (spodumène) en utilisant les radiations X MoKa et AgKa. Une analyse statistique approfondie des mesures et des paramètres multipolaires (modèle de Hansen-Coppens) de la densité électronique déterminés dans les affinements par moindres carrés a été menée dans cette étude. La méthode des leviers a été appliquée pour tester la validité des charges atomiques de la scolécite. Les liaisons Si-O et Al-O ont été caractérisées par les propriétés topologiques de la densité électronique définies dans la théorie de Bader. Les charges atomiques obtenues expérimentalement par affinement kappa ont été introduites dans le calcul du potentiel de Madelung afin de mettre en évidence les interactions entre les cations (Na+, Ca2+ et Li+) et le squelette aluminosilicaté de ces composés. Les énergies électrostatiques de l'unité formulaire trouvées sont respectivement de -177. 7, -230. 0 et -123. 8 eV pour la natrolite, la scolécite et le spodumène.

碩士
大同工學院
材料工程學系
84
In the present study, Li2O-Al2O3-SiO2(LAS) and MgO-Al2O3-SiO2( MAS) glass powders were mixedand then sintered to form glass ceramics.The effects of LAS/MAS ratio,Li content in the LAS powder,Particle size of LAS/MAS,and sintering temperature on the densification crystallization, and properties of the materials were investigated. The pure LAS and MAS powders showed excellent sinterability,When a s all amount of MAS was added to LAS,diffusion of Mg ion intoLAS particles reduced the crystallization temperature of the LAS particles,resulting in poor densification.On the other hand, densification was not siginficatly affected as MAS was mixed with smallamount of LAS. For the samples contenting > 40 wt% MAS,high sintered densities can be obtained. For C1 system in which the LASc powder has the stoichiometric sopdumene composition(LASc), densification was not significantly affected the sintering temperature rangeof 850 to 950 C. The B-quartz s.s phase could be found when the samples wese heated at 850 C, which transfered to the stable a- cordierite and/or B-spodumene phases when the higher sintering temperature was increated to 900 C and 950 C. Decrease in the particle size of the LASc and/or MAS glass powder enhanced densification.When the Li content in the stoichiometric LASc powder was decrease,the sinterability of the mixed powders was improved, the crystallization temperaturewas increased, and it the phase transfered or mation from thr B-quartz s.s. and/ora- cordierite was limited. Pure LASc sample (in C1 system) sintered at 850-950 C have thedielectrec of 7.5, for the samples containing > 40Wt%MAS, the increasing in the sintering temperature reduced the dielectric constantfrom 7 to 4.0. For pure LASc (k'=7.5) and MAS(k'=5.0), the particle sizes of raw glass powdersshowed little effect on the dielectric constant. For the samples containing >= 40 wt%MAS, the sequence of sinterability an dielectric constant was C4>C3>C1>C2. The dielectricconstant was in the range of 4.1~5.5. For the pure LAS and MAS composition, the sequenceof the dielectric constant was LASc(~7.8)>LASn(~6.2)>LASm(~5.5).For thr samplecontaining >=40 wt% MAS, the dielectric constants were M>C4>N(6.3~5.1).The dielectric losses of the abovr samples were less than 2.5%. For the samples sintered 950 C for 4 hr, the sequence of the coefficient of thermalexpansion (CTE) were pure MAS>LASm>LASc> LASn. For the samples containing >=60 wt%MAS, the CTE were N>C4> M. The samples fabricated by mixing 20 wt% stoichiometric Li2O. Al2O3.4SiO2 with 80 wt% MAS showed excellent sinterability, a CTE value of 2.8 ppm/C,a dielectric constant was 5.3, and a dielectric loss less than 3 %.The pure LASm composition showed excellent sinterability, a CTE value of 2.8 ppm/C, a dielectricconstant of 5.5, and a dielectric loss less than 3%. The above two compositions can be the candiadates for thehigh- performance substrate applications.