Microprobe Research Articles

Rare Occurrence of Bastnaesite, Yttro-columbite and Chevkinite from Podili Granite, Prakasam Alkaline Province within Nellore Schist Belt, Southern India: Insights from Field, Petrography, Geochemistry and Mineral Chemistry

ABSTRACT This work reports the occurrence of Bastnaesite, Yttro-columbite, and Chevkinite for the first time from Podili alkali pluton, Andhra Pradesh. Podili granite is an A-type Mesoproterozoic alkali granite situated within the Prakasam Alkaline Province (PAP), emplaced within the Neoarchaean Nellore schist belt (NSB) towards its northern part. Petrography, SEM-EDS and Electron Probe Micro Analyser (EPMA) confirm the occurrence of bastnaesite [Ce, La (CO3) F] as discrete euhedral hexagonal crystal forming at the interstitial spaces of plagioclase feldspar at times, indicating its magmatic origin. Yttro-columbite [Y(Fe)Nb2O] occurs as inclusion within the zircon. Chevkinite [(Ce, Nd, Ca)4(Fe)2(Ti, Fe)3Si4O22] appear as euhedral grains disseminated in the feldspar-rich matrix. The presence of bastnaesite, yttro-columbite and chevkinite is responsible for the enrichment of ΣLREE (Max.1645ppm) over ΣHREE (Max.129ppm) in Podili syenite evolved through volatile enriched Podili alkali granite. Enrichment of fluorocarbonate bastnaesite indicates the presence of halogen F- in the melt, which substitutes hydroxyl ion (OH-) and facilitates late-stage REE mineral crystallisation. The halogen-bearing late-stage injection of CO2-rich melt affected the initial volatile enriched host alkali granite that evolved the granite and enriched the pluton with the LREE-dominated fluorocarbonate with significant REE mineral precipitation due to fluid-rock interactions.

EPMA and EBSD observations of unirradiated MIMAS-MOX fuels for the study of fission gas release and thermal conductivity

ABSTRACT MOX fuel fabricated through the micronized master blend process (MIMAS) is used in light water reactors. The MIMAS-MOX fuel is characterized by a non-uniform plutonium distribution with plutonium-rich agglomerates. The distributions of plutonium and crystal grains can, respectively, influence the fuel properties and behaviors during irradiation. However, it was difficult to examine the correlation between the distributions of plutonium and crystal grains in an unirradiated MIMAS-MOX fuel because chemical etching for the grain boundary had little effect on the plutonium-rich agglomerates. In this study, the analytical techniques of electron probe micro analyzer and electron backscattered diffraction were applied to the observation of unirradiated MIMAS-MOX fuels. The observation using the two analytical techniques revealed crystal grain distributions in the phases with different concentrations of plutonium, including plutonium-rich agglomerates. In addition to the observation, the fission product gas release and thermal conductivity of MIMAS-MOX fuels were briefly discussed as initial approaches aiming to model them based on the results of the observation using the techniques of electron probe micro analyzer and electron backscattered diffraction.

Microstructural design opportunities and phase stability in the spray-formed AlCoCr0.75Cu0.5FeNi high entropy alloy

Designing a microstructure with controlled morphology is one of the determining factors for the optimum performance of a material. High entropy alloys (HEAs) have gained significant attention due to their enhanced mechanical and functional properties compared to conventional alloys, particularly based on opportunities for microstructural design. In this fast-developing field, varied thermal treatments can be applied to engineer a material as per the requirements. In the present work, we have studied the effect of thermal treatment on the microstructural modifications in the spray-formed AlCoCr0.75Cu0.5FeNi HEA. The alloy was characterized by using a light microscope, scanning electron microscope equipped with EDS detector and electron probe micro analyzer (EPMA). The elemental distribution and microstructural evolution of the alloy were studied by giving the heat treatments at different time-temperature spaces. The evolution of phases and their composition were correlated with the CALPHAD predicted property diagram and phase composition. It is observed that at a higher temperature of 1300°C, the alloy shows the simple solid solution phases to be more stable due to the high entropy effect, which brings down the Gibbs free energy of the system. The formation of the disordered BCC, FCC and their derivatives along with the sigma phase were observed in the temperature range of 600-1000°C. This work also draws attention to why understanding the microstructural evolution and solidification behaviour is important in designing the HEAs to meet the industrial promises and the role of entropy, enthalpy and slow diffusion kinetics are discussed.

Phase equilibria of CaO-Al2O3-Ti2O3 system at 1500 °C and 1600 °C in C/CO equilibrium atmosphere

The phase diagram of CaO-Al2O3-Ti2O3 system has significant implications for the metallurgical slag design of Al-Ti alloy steel. In this work, the high-temperature equilibrium experiments were conducted at 1500 °C and 1600 °C in C/CO equilibrium atmosphere, respectively. The types and compositions of the equilibrium phases were determined by Electron Probe Micro Analysis (EPMA) and X-ray diffraction (XRD). The isothermal section of CaO-Al2O3-Ti2O3 system in the low w(TiOx) region at 1500 °C was constructed for the first time, in which there are 6 three-phase fields, 7 two-phase fields, and a liquid phase field. The isothermal section of CaO-Al2O3-Ti2O3 system in the low w(TiOx) region at 1600 °C was constructed and revised, including 3 three-phase fields, 6 two-phase fields, and a liquid phase field. Additionally, under the current experimental condition, the reasons for the formation of TiC in the high w(TiOx) region of this slag system were analyzed, further discussing the effect of carbon on the phase equilibria of CaO-Al2O3-Ti2O3 system.

Cellular targets of cytotoxic copper phenanthroline complexes: a multimodal imaging quantitative approach in single PC3 cells.

Metal complexes are emerging as promising alternatives to traditional platinum-based cancer treatments, offering reduced side effects. However, understanding their cellular uptake and distribution and quantifying their presence at the single cell level remains challenging. Advanced imaging techniques, including transmission electron microscopy, synchrotron radiation X-ray fluorescence, and energetic ion beam-based nuclear microscopy (scanning transmission ion microscopy, particle-induced X-ray emission, elastic backscattering spectrometry), allow detailed high-resolution visualization of structure and morphology, high sensitivity for elemental detection with quantification within single cells, and the construction of 3D models of metal distribution, positioning them as powerful tools for assessing the cellular uptake and compartmentalization of complexes. Three Cu(II) complexes [Cu(phen)2(H2O)](NO3)2 (1), [Cu(Me2phen)2(NO3)]NO3 (2) and [Cu(amphen)2(H2O)](NO3)2 (3), (phen = 1,10-phenanthroline, Me2phen = 4,7-dimethyl-1,10-phen, amphen = 5-amino-phen) were investigated for Cu uptake and distribution in PC3 prostate cancer cells. All complexes show significant Cu uptake regardless of media concentration. Cu concentrations in the cytoplasm and nucleus are similar between treatments. Complexes 1 and 3 concentrate Cu in the nuclear region and show a vesicle-like pattern around the nucleus, while 2 shows a dispersed cytoplasmic pattern with large vesicles. The 3D models confirm that Cu is not retained at the plasma membrane, with complex 1 targeting the nucleus and 2 remaining in the cytoplasm. These results highlight the importance of quantifying metal distribution and correlating it with structural changes to understand the relevance of the ligand in the mechanisms of cellular uptake and targeting, crucial for the development of effective metal-based cancer therapies.

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCrx porous high-entropy alloys

FeCoNiMnCr porous high-entropy alloys were prepared using the activation reaction sintering method with Fe, Co, Ni, Mn, and Cr as raw materials. The oxidation behaviors of FeCoNiMnCrx porous high-entropy alloys with different Cr contents, such as pore structure, the surface oxide film phase composition, structure, and morphology, were characterized by X-ray diffraction (XRD), electron probe micro analysis (EPMA), energy dispersive X-ray spectroscopy (EDS), and pore tester after high-temperature oxidation at 800–1000 °C. The results indicate that the initial porous high-entropy alloy comprises a single FCC solid solution phase. With the increase in Cr content, the average pore diameter, average porosity, and air permeability of the porous high-entropy alloy also increase. The oxidation kinetics of the porous high-entropy alloy after exposure to temperatures between 800 °C and 1000 °C follows a single-stage parabolic evolution law. At the same oxidation temperature, With the increase of Cr content, the oxidation gains gradually increased, at the same Cr content at different temperatures, the antioxidant performance of 1000 °C was the weakest, followed by 800 °C, and 900 °C showed excellent antioxidant performance. The oxidation products are mainly Mn2O3, Mn3O4, (Mn, Cr)3O4, Cr2O3and Fe2O3.

A supervised machine learning procedure for EPMA classification and plotting of mineral groups

An analytical method to automatically characterize rock samples for geological or petrological purposes is here proposed, by applying machine learning approach (ML) as a protocol for saving experimental times and costs.Proper machine learning algorithms, applied to automatically acquired microanalytical data (i.e., Electron Probe Micro Analysis, EPMA), carried out with a SEM-EDS microprobe on randomly selected areas from a petrographic polished thin section, are trained, used, tested, and reported.Learning and Validation phases are developed with literature mineral databases of electron microprobe analyses on 15 main rock-forming mineral groups. The Prediction phase is tested using an eclogite rock from the Western Alps, considered as an unknown sample: randomly selected areas are acquired as backscattered images whose intervals of gray levels, appropriately set in the gray level histogram, allow the automated particle mineral separation: automated separating Oxford Instruments Aztec Feature ® packages and a mineral plotting software are applied for mineral particle separation, crystal chemical formula calculation and plotting.Finally, a microanalytical analysis is performed on each separated mineral particle. The crystal chemical formula is calculated, and the final classification plots are automatically produced for any determined mineral. The final results show good accuracy and analytical ease and assess the proper nature of the unknown eclogite rock sample. Therefore, the proposed analytical protocol is especially recommended in those scenarios where a large flow of microanalytical data is automatically acquired and needs to be processed.

Hot corrosion behavior of Mo–Si–Ti alloys

AbstractThe hot corrosion behavior of two ternary Mo–Si–Ti alloys (eutectic Mo–20.0Si–52.8Ti (at.%) and eutectoid Mo–21.0Si–34.0Ti (at.%)) was investigated at C and C for up to 100 h. Both Mo‐based alloys evidenced a hot corrosion attack, resulting in a uniform attack of the substrate surface. The higher Ti content of the eutectic alloy significantly reduced the formation of solid and volatile Mo oxides compared with the eutectoid alloy. After 24 h at C, the corrosion products formed on the eutectic alloy were only one‐tenth the thickness of the layers formed on the eutectoid alloy. The corrosion products were examined with optical and electron microscopy. Semiquantitative electron probe micro analysis and X‐ray diffraction measurements were used to identify the formed phases. The underlying corrosion mechanisms comprising not only hot corrosion‐induced fluxing but also oxidation‐induced pesting are discussed in detail.

Alteration and Non-Formula Elements Uptake of Zircon from Um Ara Granite, South Eastern Desert, Egypt

The Um Ara granites are a suite of granitoid rocks located in the southern part of the Eastern Desert of Egypt. The integration of various electron probe micro analyzer (EPMA) techniques, such as backscattered electron (BSE) imaging, X-ray compositional mapping, and wavelength dispersive spectrometry (WDS), has provided valuable insights into the alteration process of zircon in the Um Ara granite. The zircon exhibits high concentrations of non-formula elements such as P, Al, Ca, Fe, Ti, and REEs, suggesting that the alteration involved coupled dissolution-reprecipitation processes influenced by aqueous fluids. The negative correlations between Zr and the non-formula elements indicate that these elements were incorporated into zircon at the expense of Zr and Si, significantly affecting the distribution and fractionation of REEs in the original zircon. Based on the presented data and literature knowledge, the sequence of alteration events is proposed as follows: (1) initial zircon crystallization around 603 Ma accompanied by the formation of other U- and Th-bearing minerals like xenotime, thorite, monazite, and apatite; (2) long-term metamictization leading to fractures and cracks that facilitated fluid circulation and chemical changes; (3) a major hydrothermal event around 20 Ma that released a suite of non-formula elements from the metamicted zircon and associated minerals, with the enriched hydrothermal fluids subsequently incorporating these elements into the modified zircon structure; and (4) further low-temperature alteration during subsequent pluvial periods (around 50,000–159,000 years ago), facilitated by the shear zones in the Um Ara granites, may have allowed further uptake of non-formula elements. The interplay between hydrothermal fluids, meteoric water, and the shear zone environments appears to have been a key driver for the uptake of non-formula elements into the altered zircon.

Investigation of microstructure and thermal expansion behaviour of a functionally graded YSZ/IN718 composite produced by laser-powder bed fusion

Yttria-stabilized zirconia (YSZ) has been extensively used as a thermal barrier coating (TBC) for high-temperature alloys. In this research, the microstructural attributes and thermal expansion behavior of an additively manufactured functionally graded composite (YSZ/IN718 FGC) were investigated. First, a powder mixture of IN718 and YSZ (ranging from 1 wt% to 4 wt%) was achieved via low-energy ball-milling at 100 rpm. Differential scanning calorimetry (DSC) analysis depicted the melting behaviour of the powder mixtures of different YSZ content. The endothermic peaks in the DSC curve, at ∼1360 ℃, suggested that the energy needed to melt the powder mixture increases with increasing YSZ content. These varying powder compositions were used to fabricate FGC samples using L-PBF. The study investigated the effects of laser power variation along the YSZ gradient, successfully mitigating the fusion defects that had been initially observed in FGC samples. Microscopic analyses, comprising scanning electron microscopy (SEM) and transmission electron microscopy (TEM), depicted the elemental segregation of Nb and Mo at the solidification subgrain boundaries (SSBs). Furthermore, the electron backscattered diffraction (EBSD) results demonstrated the refinement of grains and a reduction in textural intensity, particularly along the YSZ gradient. Energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA) were used to validate the uniform dispersion of YSZ particles throughout the composite matrix, with the EPMA line scan affirming a predominantly linear YSZ content variation. Lastly, the coefficients of thermal expansion (CTEs) were evaluated, both parallel and perpendicular to the build direction. A decrease of approximately ∼6 % in CTE was noted along the building or gradation direction. Notably, perpendicular to the building direction, the CTE values for specimens containing 4 wt% and 2 wt% YSZ witnessed significant reductions of ∼32 % and ∼12 %, respectively. This research significantly contributes to the understanding of the microstructural intricacies and thermal behavior of YSZ/IN718 FGC produced by L-PBF process.

Phase equilibria of CaO–Al2O3–CaO·TiO2 system at 1500 °C in hydrogen atmosphere

The phase diagram of CaO–Al2O3-TiOx system is of great importance in guiding the design of metallurgical slag systems for Al–Ti alloy steel, controlling Ti-bearing inclusions in molten steel, and regulating the mineral phase of vanadium-titanium magnetite. In the present work, the high temperature equilibration-quench technique was adopted, and the types and compositions of equilibrium phases were identified by Electron Probe Micro Analysis (EPMA) and X-ray diffraction (XRD). The isothermal section of CaO–Al2O3–CaO·TiO2 system at 1500 °C in H2 atmosphere was constructed for the first time. There are 7 three-phase fields, 10 two-phase fields, and a single liquid phase field. On this basis, according to the theoretical analysis of the crystal structure, the formation energy analysis based on first-principles calculations, and the related theories of defect chemistry, the formation mechanisms of CaTiO3 and Ca3Ti2O7 solid solution with were determined, respectively. Additionally, the experimental phase diagram was utilized to discuss the dissolution type and the equilibrium solubility of typical inclusions (Al2O3, Ti3O5, and CaO·TiO2) in Al–Ti alloy steel.

Phase structure and electrochemical properties of A5B19 La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) hydrogen storage alloy anode material

The La0.8-xPrxMg0.2Ni3.8 (x = 0, 0.05, 0.1, 0.2, 0.3) alloy were synthesized useing the induction melting method. X-ray diffraction, scanning electron microscope, electron probe micro analyzer, and electrochemical tests were used to analyze the structure and electrochemical performance of the La0.8-xPrxMg0.2Ni3.8 (x = 0–0.3) alloy. It was studied how the Pr element affected the electrochemical characteristics and microstructure of the A5B19 La-Mg-Ni based hydrogen storage alloy. The results show that the alloy consists of the CaCu5-LaNi5 phase, 2 H-Pr5Co19 phase, and 3R-Ce5Co19 phase. The abundance of the A5B19 phase increase with the increase of Pr content, while the abundance of the LaNi5 phase decrease, and the addition of Pr promotes the formation of the 2 H-Pr5Co19 phase. According to the results of the electrochemical test, every sample has good activation qualities, and the activation can be completed in 3–4 times. The activation properties are not significantly altered by the addition of Pr. The maximum discharge capacity increases at first, then decreases, reaching the highest 371.15 mAh g−1 at x = 0.2. The cyclic stability gradually improves with increasing content of Pr, and the maximum capacity retention rate reaches 85.80 % after 100 cycles. The primary factor influencing the alloy's high rate discharge ability is the exchange current density. With the increase of the exchange current density, the high rate discharge performance is gradually enhanced.

Biomineralization reaction from nanosized calcium silicate: A new method for reducing dentin hypersensitivity

Background/purposeThis study assessed the ability of experimental materials consisting of dicalcium silicate (DCS) and tricalcium silicate (TCS) with nanosized particles to form intratubular crystals under phosphate-buffered saline (PBS) and the effect on dentin permeability reduction. Materials and methodsBy isolating the cervical part of the extracted premolars, 195 specimens were obtained. Two experimental materials (DCS/TCS and TCS) were applied to the dentin surface by brushing and stored in PBS (n = 65). Another 65 specimens were not treated. Each group was randomly divided into five subgroups based on the PBS immersion period (1, 15, 30, 60, and 90 days, n = 10). The dentin permeability was measured, and the hydraulic conductance, Lp (%), was calculated. After acid challenge with 1 M acetic acid, Lp (%) was remeasured. Data were analyzed using two-way analysis of variance and Fisher's least significant difference test (α = 0.05). Three specimens of each subgroup were longitudinally sectioned and examined using scanning electron microscopy and a field emission-electron probe micro analyzer. ResultsThe Lp (%) of the experimental groups gradually decreased over time (P < 0.05). The hydroxyapatite-like crystals that grew were observed and found to have a Ca/P ratio similar to that of hydroxyapatite. The crystals remained after the acid challenge, and the Lp (%) was not significantly different from that before acid treatment. ConclusionIntratubular crystals formed from the experimental materials consisted of DCS and TCS and were resistant to acid. These crystals significantly reduced dentin permeability.

Quality circle implementation to reduce defects in cast steel products in the heavy equipment industry

Steel products produced from the metal casting process or commonly called cast steel are still very much needed in the industrial world, as components for production machines, power plants, automotives, heavy equipment and other needs. PT KX is a company that produces cast steel products, the products produced are targeted to be able to meet customer needs both for domestic needs and for export needs abroad. One of the problems currently faced by this company is the high defect ratio in several products currently produced. The defects that occur are porosity, gas holes, sand inclusions, cracks, and misruns. This company's good culture in implementing continuous improvement is well developed in all lines and all members of the organization so that this company continuously makes efforts to reduce defects that occur in products. The aim of this research is to analyze the causes of problems and make improvements to reduce the defect ratio. The method used by Quality Circle (QC) is as a method for making continuous improvements in reducing defects. One of the ways in which the verification process is carried out is by utilizing Electron Probe Micro Analyzer (EPMA) machine technology. This aims to make the analysis results more in-depth so that ultimately the defects that occur in a product can be reduced significantly.

Analysis of microscopy techniques to measure segregation in continuous-cast steel slabs.

The accurate characterisation of centreline segregation requires precise measurements of composition variations over large length scales (10 ) across the centreline of the cast product, while having high resolution, sufficient to quantify the significant composition variations between dendrites due to microsegregation at very small length scales (10 ). This study investigates the potential of a novel microscopy technique, named Synchrotron Micro X-ray Flurorescence (SMXRF), to generate large-scale high-resolution segregation maps from a steel sample taken from a thin slab caster. Two methods, Point Analysis and Regression Analysis, are proposed for SMXRF data calibration. By comparing with the traditional Laser-Induced Breakdown Spectroscopy (LIBS), and Electron Probe Micro Analyser (EPMA) techniques, we show that SMXRF is successful in quantitative characterisation of centreline segregation. Over large areas (e.g. 12 16 ) and at high resolution (10-50 pixel size) various techniques yield comparable outcomes in terms of composition maps and solute profiles. The findings also highlight the importance of both high spatial resolution and large field of view to have a quantitative, accurate, and efficient measurement tool to investigate segregationphenomena.

A New Nephrite Occurrence in Jiangxi Province, China: Its Characterization and Gemological Significance

Nephrite is a very precious gemstone material. As a non-renewable resource, the discovery of new nephrite deposits and the study of the genesis of nephrite have aroused great interest. A new occurrence of nephrite known as Xinyu nephrite was discovered in Xinyu Country, Jiangxi province, China. Field investigations reveal that nephrite appears in a contact zone between the Mengshan composite granitic pluton and Permian carbonate rock. The carbonate rock is calcic marble that underwent diopsidization and tremolitization. Nephrites have a light yellow-green color, weak greasy luster, are slightly-translucent to translucent, and are fine-grained. Their refractive index (RI) ranges from 1.60 to 1.61, and their specific gravity (SG) value ranges from 2.90 to 2.91, falling within the range of nephrites from Xinjiang, China. Their Mohs hardness (Hm) ranges from 5.78 to 5.83. Petrographic observations and electron probe micro analyzer (EPMA) data indicated that analyzed nephrites mainly comprise tremolite, with minor diopside, calcite, quartz, and apatite. Tremolite has a ratio of Mg/(Mg + Fe2+) greater than 0.99. The tremolite grains show microscopic fibrous-felted and columnar textures. Scanning electron microscope (SEM) images show some tremolite fibers interwoven in different crystallographic orientations, and some arranged in parallel. Fourier transform infrared and Raman spectroscopy features reveal the bands of minerals typical for nephrite composition. The petrographic characteristics and geological background of the Mengshan area indicate that nephrite formed through a replacement of calcic marble, which differs from the two known types (D-type: dolomite-related; S-type: serpentinite-related). Mineral replacements were common in nephrite, including diopside by tremolite, calcite by tremolite, and recrystallization of coarse by fine tremolite grains. The discovery of Xinyu nephrite occurrence complements the resource and provides an updated case for the in-depth study of the diversity of nephrite deposits.

Simultaneous removal of caesium and strontium using different removal mechanisms of probiotic bacteria

When radioactive materials are released into the environment due to nuclear power plant accidents, they may enter into the body, and exposing it to internal radiation for long periods of time. Although several agents have been developed that help excrete radioactive elements from the digestive tract, only one type of radioactive element can be removed using a single agent. Therefore, we considered the simultaneous removal of caesium (Cs) and strontium (Sr) by utilising the multiple metal removal mechanisms of probiotic bacteria. In this study, the Cs and Sr removal capacities of lactobacilli and bifidobacteria were investigated. Observation using an electron probe micro analyser suggested that Cs was accumulated within the bacterial cells. Since Sr was removed non metabolically, it is likely that it was removed by a mechanism different from that of Cs. The amount of Cs and Sr that the cells could simultaneously retain decreased when compared to that for each element alone, but some strains showed only a slight reduction in removal. For example, Bifidobacterium adolescentis JCM1275 could simultaneously retain 55.7 mg-Cs/g-dry cell and 8.1 mg-Sr/g-dry cell. These results demonstrated the potentials of utilizing complex biological system in simultaneous removal of multiple metal species.

Analysis of Er3+ diffusion within transparent YAG ceramics manufactured through various routes by SPS

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 μm, 63 μm and 140 μm respectively for fully dense, powder and pre-sintered assembly approaches.

Association and textural-compositional evolution of pyrite-organic matter in coals of the Tarakan, Barito, and Pasir Basins, Kalimantan, Indonesia

The Barito, Pasir, and Tarakan Basins in Kalimantan Island is the most extensive coal-bearing sedimentary basin in Indonesia, mined since 1989. The coal is notable in having high sulfur coal content, exceeding >10% in some cases, contributed by the presence of pyrite. The latter issue contributed to interest in the coal, forming economic mineral deposits hosted by the sedimentary pyrite and organic matter. Novel findings of this research providing valuable information of trace element behavior during the diagenetic conditions. This paper documents the textural and compositional evolution of pyrite-organic matter of coals using coal petrographic, proximate, ultimate, total sulfur content, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), electron probe micro analyser (EPMA), and Raman spectroscopy. Coals from Kalimantan are mainly characterized by medium-high sulfur content (>3%) and the maximum temperatures reached by organic matter during diagenesis are 166 ± 10 °C for the Pasir Basin, 136 ± 11 °C for the Barito Basin, and 132 ± 12 °C for the Tarakan Basin. Pyrite is mainly found as large size framboids (mostly >5 μm), indicating formation in the sedimentary layer with dysoxic bottom water conditions during early–late diagenetic stages. The framboidal pyrite was likely formed in detrovitrinite and gelovitrinite under topogenous mire conditions, due to the degradation of macerals and biochemical gelification, which provided the organic templates. High concentrations of trace elements (TE) of framboidal pyrite, such as 1) Cu, Ni, and Co in the Pasir Basin and 2) As in the Barito Basin, likely reflect the local sedimentary provenance and underlying basement rocks. Pyrite texture evolved with increasing diagenetic temperatures from 1) framboidal pyrite, 2) recrystallized framboidal pyrite rims, and 3) anhedral, anhedral-euhedral pyrite transition, and euhedral massive pyrite. This study shows a similar average TE concentrations of various pyrite texture, suggesting that the TEs are not remobilized during the evolution of pyrite at the diagenetic stages.

Experimental investigation of the CaO-Al2O3-TiO2 system: Isothermal section of 1500 °C and liquidus projection

The CaO-Al2O3-TiO2 phase diagram is of great guiding significance for the comprehensive utilization of Ti-bearing mineral resources and the design of metallurgical slag for Al-Ti alloy steel. In this paper, the high-temperature phase equilibrium experimental method was adopted; the types and compositions of phases were identified by Electron Probe Micro Analysis (EPMA) and X-ray diffraction (XRD). A total of 12 equilibrium phases were determined, including CaO, Al2O3, TiO2, 3CaO2TiO2, 4CaO3TiO2, CaOTiO2, Al2O3TiO2, 3CaOAl2O3, CaOAl2O3, CaO2Al2O3, CaO6Al2O3, and Liquid; they formed a total of 16 phase equilibrium relations. The isothermal section of CaO-Al2O3-TiO2 system at 1500 °C in atmosphere was constructed for the first time. There are 10 three-phase fields (Liquid+CaO+3CaO2TiO2, Liquid+3CaO2TiO2+4CaO3TiO2, CaOTiO2+CaOAl2O3+CaO2Al2O3, CaO2Al2O3+CaOTiO2+CaO6Al2O3, Liquid+CaOTiO2+ CaO6Al2O3, Liquid+CaO6Al2O3+Al2O3, Liquid+Al2O3+Al2O3TiO2, Liquid+TiO2+Al2O3TiO2, Liquid+CaOAl2O3+4CaO3TiO2, 4CaO3TiO2(ss)+CaOTiO2(ss)+CaOAl2O3), 13 two-phase fields (Liquid+CaO, CaO+3CaO2TiO2, Liquid+3CaO2TiO2, Liquid+4CaO3TiO2, Liquid+TiO2, Liquid+CaOTiO2, Liquid+Al2O3TiO2, Liquid+Al2O3, Liquid+CaO6Al2O3, Liquid+CaOAl2O3, CaOTiO2(ss)+CaO2Al2O3, 4CaO3TiO2(ss)+CaOTiO2(ss), 4CaO3TiO2(ss)+3CaO2TiO2(ss)), 2 single-phase solid solution fields (4CaO3TiO2(ss), 3CaO2TiO2(ss)), and 2 disconnected single liquid phase fields. On this basis, the liquidus projection of the CaO-Al2O3-TiO2 system was revised. The types of relevant invariant reactions were identified by the Lever Rule; the types of relevant univariant reactions were determined by the original method proposed in this paper.